Patent Publication Number: US-2021191198-A1

Title: Assistant dyes for color conversion in lcd displays

Description:
BACKGROUND OF THE INVENTION 
     1. Technical Field 
     The present invention relates to the field of color conversion films in displays, and more particularly, to color conversion films with fluorescent compounds. 
     2. Discussion of Related Art 
     Improving displays with respect to their energy efficiency and color gamut performance is an ongoing challenge in the industry. While color conversion films are available which use quantum dots to enhance display performance, it is particularly challenging to achieve comparable goals in ways that do not involve heavy metals such as toxic cadmium used in quantum dots. 
     Constant developments in the field of liquid crystal displays concern improvements of optical and visual performance, increasing the displayed intensity while complying to white point requirements. 
     LCDs are continuously being developed, with performance improvements taking place in different components of the displays, such as the backlight units, liquid crystal module, layering of the LCD panel and optimization of optical performance of the displays. 
     SUMMARY OF THE INVENTION 
     The following is a simplified summary providing an initial understanding of the invention. The summary does not necessarily identify key elements nor limit the scope of the invention, but merely serves as an introduction to the following description. 
     One aspect of the present invention provides A LCD (liquid crystal display) comprising: a backlight unit, and a LCD panel receiving illumination radiation from the backlight unit, the LCD panel comprising: a liquid crystal (LC) module, RGB (red, green, blue) color filters (common ranges are Red: 635-700 nm, Green: 520-560 nm and Blue: 450-490 nm, the exact ranges can be tuned according to desired specifications), and at least one color conversion film comprising: at least one red-fluorescent rhodamine-based fluorescent (RBF) compound selected to have at least one R (red) emission peak, at least one green RBF compound selected to have at least one G (green) emission peak, and at least one assistant dye configured to modify a spectrum of received radiation. 
     These, additional, and/or other aspects and/or advantages of the present invention are set forth in the detailed description which follows; possibly inferable from the detailed description; and/or learnable by practice of the present invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       For a better understanding of embodiments of the invention and to show how the same may be carried into effect, reference will now be made, purely by way of example, to the accompanying drawings in which like numerals designate corresponding elements or sections throughout. 
       In the accompanying drawings: 
         FIG. 1A  is a high level schematic overview illustration of disclosed configurations of displays, according to some embodiments of the invention. 
         FIG. 1B  is a high level schematic overview illustration of disclosed film production processes, film configurations and display configurations, according to some embodiments of the invention. 
         FIG. 1C  is a high-level schematic exploded view of a LCD having a collimated backlight unit, according to some embodiments of the invention. 
         FIG. 1D  is a high level schematic block diagram illustrating various configurations of LCD panels and displays, according to some embodiments of the invention. 
         FIGS. 2A-2L  are high level schematic illustrations of configurations of digital displays with color conversion film(s), according to some embodiments of the invention. 
         FIG. 2M  is a high-level schematic illustration of patterned color conversion film(s) with matrix-like crosstalk-reducing layer(s) in an above-LC configuration, according to some embodiments of the invention. 
         FIGS. 2N and 2S  are high-level schematic illustrations of the LCD panel comprising the color conversion and filtering layer above the LC module, with a top optical-elements array, according to some embodiments of the invention. 
         FIGS. 2O-2R  are high-level schematic illustrations of a part of the LCD panel, according to some embodiments of the invention. 
         FIG. 3A  is a high-level schematic layered view of a LCD having a collimated backlight unit, according to some embodiments of the invention. 
         FIGS. 3B and 3C  are high-level schematic illustrations of illumination units with designed serrated lens and an additional lens providing collimated illumination, according to some embodiments of the invention. 
         FIG. 4  is a high-level schematic illustration of a light source layer and illumination units with array of optical elements, configured to provide collimated backlight illumination, according to some embodiments of the invention. 
         FIGS. 5A-5J  are high-level schematic illustrations of illumination units and light source layers, according to some embodiments of the invention. 
         FIG. 6A  is a high-level schematic illustration of a light source layer with lateral illumination source(s) and common internally reflective cavity(ies) having multiple pinpoint openings, configured to provide collimated backlight illumination, according to some embodiments of the invention. 
         FIG. 6B  is a high-level schematic illustration of a light source layer with multiple pinpoint openings and associated optical elements for each illumination source and internally reflective cavity, configured to provide collimated backlight illumination, according to some embodiments of the invention. 
         FIGS. 7A-7F  are high-level schematic illustrations of illumination units, according to some embodiments of the invention. 
         FIGS. 8A-8E  are high level schematic illustrations of configurations of digital displays with color conversion film(s), according to some embodiments of the invention. 
         FIG. 9  is an illustration example of polarization anisotropy of film(s) with RBF (rhodamine-based fluorescent) compound(s), according to some embodiments of the invention. 
         FIGS. 10A and 10B  are high level schematic illustration of spectral enhancements in devices with white illumination, according to some embodiments of the invention. 
         FIGS. 10C-10E  are high level schematic illustrations of spectrum shaping using assistant dyes, according to some embodiments of the invention. 
         FIG. 11  is a high level schematic illustration of multiple film preparation steps and processes, according to some embodiments of the invention. 
         FIG. 12  is a high-level schematic illustration of a backlight unit (BLU) for a liquid crystal display (LCD), according to some embodiments of the invention. 
         FIG. 13  is a high-level schematic illustration of white point adjustment for LCD, according to some embodiments of the invention. 
         FIGS. 14A-F  are high-level schematic illustrations of BLUs with color conversion unit having partly reflective structure(s), according to some embodiments of the invention. 
         FIGS. 15A-15E and 16A-16D  are high-level schematic illustrations of BLUs having color conversion unit in which the color conversion elements receive only part of the overall radiation, according to some embodiments of the invention. 
         FIG. 17  is a high-level flowchart illustrating methods, according to some embodiments of the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     In the following description, various aspects of the present invention are described. For purposes of explanation, specific configurations and details are set forth in order to provide a thorough understanding of the present invention. However, it will also be apparent to one skilled in the art that the present invention may be practiced without the specific details presented herein. Furthermore, well known features may have been omitted or simplified in order not to obscure the present invention. With specific reference to the drawings, it is stressed that the particulars shown are by way of example and for purposes of illustrative discussion of the present invention only, and are presented in the cause of providing what is believed to be the most useful and readily understood description of the principles and conceptual aspects of the invention. In this regard, no attempt is made to show structural details of the invention in more detail than is necessary for a fundamental understanding of the invention, the description taken with the drawings making apparent to those skilled in the art how the several forms of the invention may be embodied in practice. 
     Before at least one embodiment of the invention is explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of the components set forth in the following description or illustrated in the drawings. The invention is applicable to other embodiments that may be practiced or carried out in various ways as well as to combinations of the disclosed embodiments. Also, it is to be understood that the phraseology and terminology employed herein is for the purpose of description and should not be regarded as limiting. 
     LCDs (liquid crystal displays) with improved efficiency and performance, as well as corresponding methods are disclosed. Color conversion films and elements with rhodamine-based fluorescent compounds and/or assistant dyes are used to modify the spectrum of the illumination provided by the backlight unit in either or both the backlight unit itself and the LCD panel, in various configurations. Color conversion may be performed above the LC (liquid crystal) module, possibly by a patterned layer incorporating the color filters, and/or within the backlight unit within a fluorescence-intensifying section in which radiation is recycled to enhance color conversion. Film configuration, positions and optionally supportive structures are provided, to extend the lifetime of the fluorescent compounds. Collimation of backlight illumination may further enhance the optical performance of disclosed LCDs. 
     Facing the challenge of improving the efficiency and color performance of displays without having to rely on compounds involved in displays containing quantum-dot-based technologies (e.g., in color filters, color conversion materials etc.), the inventors have discovered ways of using organic molecules to significantly improve display properties. In the following, display configurations are presented with respect to the use of color conversion films and then sol-gel and UV (ultraviolet) technologies are disclosed for preparing color conversion films as well as for preparing associated protective films or coatings for the color conversion films. 
     Embodiments of the present invention provide efficient and economical methods and mechanisms for constructing and operating LCDs. Backlight units, LCDs and methods are provided, which utilize collimated illumination which improves the performance of the LCDs. Backlight units comprise illumination source(s) configured to provide illumination, reflective cavity(ies) configured to receive the provided illumination, pinpoint openings in the internally reflective cavity(ies), which are arranged in a plane and have opening areas of below a specified size, and an array of optical elements configured to collimate illumination exiting from the pinpoint openings. The collimated illumination improves the spatial accuracy of the LCD and enables efficiency improvements using color conversion films, e.g., in above-panel configurations, with separate or integrated color conversion film and color filters layer consecutive to the LC module, without scattering losses and parallax inaccuracies. Certain embodiments may reduce parallax issues in multilayered LC panels, and enable implementation of local dimming for supporting high dynamic range (HDR) displays. 
     Embodiments of the present invention provide efficient and economical methods and mechanisms for improving LCD backlight units and LCD white points using color conversion elements. Backlight units (BLUs) for liquid crystal displays (LCDs) are provided, as well as methods of enhancing color conversion in BLUs. BLUs comprise color conversion unit(s) having partly reflective structure(s) and color conversion element(s), and illumination source(s) configured to deliver radiation through the color conversion unit(s) to the LCD panel of the LCD. Color conversion element(s) may comprise fluorescent dye(s) configured to convert blue radiation to green and/or red radiation. The partly reflective structure(s) are configured to redirect at least a part of the delivered radiation to pass multiple times through the color conversion element(s) to thereby (and by color conversion elements configuration) set a white point of the delivered radiation according to specified requirements. Some of the blue radiation may be delivered directly to the LCD panel, to enhance the lifetime of the LCD and/or of the fluorescent dyes. 
     Color conversion films for a LCD (liquid crystal display) having RGB (red, green, blue) color filters (having red, green and blue filtering ranges, configured to comply with any of various standards), as well as such displays, formulations, precursors and methods are provided, which improve display performances with respect to color gamut, energy efficiency, materials and costs. The color conversion films absorb backlight illumination and convert the energy to green and/or red emission at high efficiency, specified wavelength ranges and narrow emission peaks. For example, rhodamine-based fluorescent compounds are used in matrices produced by sol gel processes and/or UV (ultraviolet) curing processes which are configured to stabilize the compounds and extend their lifetime—to provide the required emission specifications of the color conversion films. Film integration and display configurations further enhance the display performance with color conversion films utilizing various color conversion elements and possibly patterned and/or integrated with a crosstalk blocking matrix. For example, the color conversion film(s) may be integrated in the LCD panel below the color filters, either before or after the analyzer associated with the liquid crystal film. 
       FIG. 1A  is a high level schematic overview illustration of disclosed configurations of display  100 , according to some embodiments of the invention. Schematically, display  100  comprises a backlight unit  300  (BLU) comprising an illumination source  400  and additional layers  350  (e.g., diffuser(s), prism layer(s) etc., see below), and a LCD panel  200  comprising a LC (liquid crystal) module  210  modifying illumination  120  received from BLU  300  and color filters  220  (e.g., RGB—red, green and blue filtering elements), both LC module  210  and color filters  220  are typically patterned into pixels and subpixels, and additional layers  250  (see examples below). 
     It is noted that while the numerals  300  and  400  are used herein to denote the BLU and the modified illumination sources, respectively, certain embodiments comprise extended illumination sources  400  which may be used as BLUs  300 . In such cases, either numeral,  300  or  400 , is applicable. In other cases, with BLU  300  comprising additional layers  350 , the numerals are clearly distinct. It is further noted that various embodiments may comprise combinations of illumination source  400  and layers  350 , which are disclosed in different embodiments. 
     One or more color conversion layers  130  are introduced herein, which are configured to improve any of a number of display performance parameters such as display energy use efficiency, display lifetime, display color performance (e.g., color gamut) etc. Color conversion layer(s)  130  may be implemented in LCD panel  200  and/or in BLU  300 , possibly in combination with supportive structures, e.g., as a fluorescence-intensifying section  150  which enhances fluorescence output and possibly extends the lifetime of fluorescent molecules in cases color conversion layers  130  are based on fluorescent molecules. In any of the disclosed display configuration, either or both color conversion layer  130  and fluorescence-intensifying section  150  may be used interchangeably, or in combination, according to specified performance requirements. Various embodiments disclosed below may be combined into specified display configurations upon requirement. 
     In certain embodiments, color conversion layer(s)  130  may be used in adjacency or in combination with color filters  220 , either as adjacent layers or an integrated layer, possibly further comprising patterning elements (see, e.g.,  FIGS. 2O, 2P, 2R, 2S ). Color filters  220  with color conversion layer  130  may be positioned above LC module  210  (see, e.g.,  FIGS. 2H and 2K-2N ) or within LC module  210  (see, e.g.,  FIG. 2G ). 
     In certain embodiments, fluorescence-intensifying section  150  (and/or color conversion layer(s)  130 ) may be positioned between LC module  210  and color filters  220 , possibly with additional patterning elements (see, e.g.,  FIGS. 2K-2N ) and possibly upon enhanced collimation of illumination  120  from BLU  300 . 
     In certain embodiments, fluorescence-intensifying section  150  (and/or color conversion layer(s)  130 ) may be positioned within LC module  210 , and configured to maintain the operability of LC module  210 , possibly using additional patterning elements and/or by modifying BLU  300  to enhance the degree of collimation of illumination  120  provided thereby (see, e.g.,  FIGS. 3A-3C ). 
     In certain embodiments, fluorescence-intensifying section  150  (and/or color conversion layer(s)  130 ) may be positioned within BLU  300 , either or both above illumination source  400  or within illumination source  400 , as illustrated e.g., in  FIGS. 2F and 14A-16B . 
     In certain embodiments, illumination source  400  may be modified to deliver collimated illumination  120  (see e.g.  FIGS. 3A-7F ), to improve the performance of LCD panel  200 , possibly compensating for some straying of light which may be caused by the addition of fluorescence-intensifying section  150  and/or color conversion layer(s)  130  in BLU  300  and/or in LCD panel  200 . 
       FIG. 1B  is a high level schematic overview illustration of disclosed film production processes  70 , film configurations  130  and display configurations  100 , according to some embodiments of the invention. Embodiments combine color conversion elements (such as rhodamine-based fluorescent (RBF) compounds  115  and/or other color conversion elements  76  such as fluorescent organic and/or inorganic compounds, quantum dots etc.) into films  130  by various film production processes  70  (such as sol gel processes  600 , UV curing processes  700  and/or other processes  101 ) to yield a variety of film configurations  130  such as color conversion films  130  and/or protective films  131  (which may be also color conversion films  130 ), which are then used in a variety of display configurations  100 . Any of films  130  and  131  and layers  132 ,  133 ,  134  and possibly color conversion element(s)  135  discussed below may be prepared by sol gel processes  600  and/or UV curing processes  700 . Film(s)  130  and  131  and layers  132 ,  133 ,  134  and possibly color conversion element(s)  135  may be used in display(s)  100  in one or more ways, such as any of: positioned in one or more locations in a backlight unit  300  and/or in LCD panel  200  and used as multifunctional films  130  (e.g., configured to function as any of: color conversions films, protective films, diffusers, polarizers etc.). Further display configurations  100  may comprise adjusting film(s)  130  according to the backlight source  400  (see e.g., red enhancement below, possibly also green enhancement) and/or adjusting the display white point  145 , adjustment which may be carried out by modifying any of the color conversion elements, film production processes  70  and/or film configurations  130 . Some embodiments provide integrative approaches to display configuration, which take into account multiple factors at all illustrated levels, as exemplified below. 
     Embodiments of display configurations  100  comprise various combinations of elements of the present disclosure, such as above-panel configurations  201  comprising positions of color conversion layer  130  above LC module  210  (see, e.g.,  FIGS. 2H and 2K-2N ), partly reflective elements implementing fluorescence-intensifying section  150 , and one or more embodiments of color conversion films  130 ; as well as various BLU modifications such as partly reflective elements implementing fluorescence-intensifying section  150  in BLU  300  (see, e.g.,  FIGS. 14A-F ), dye-lifetime enhancing configurations  151  (see, e.g.,  FIGS. 15A-E ) and/or collimating structures  121  (see e.g.  FIGS. 3A-7F ), as illustrated below. 
       FIG. 1C  is a high-level schematic exploded view of a LCD  100  having a collimated backlight unit  300 , according to some embodiments of the invention.  FIG. 1C  provides a schematic example for above-panel configurations  201 , possibly implementing collimating structures  121  in BLU  300 . In certain embodiments, light source  300  may provide blue illumination  120  (from blue illumination source  80 A) which is collimated, composed of parallel beams. LCD panel  200  may comprise LC module  210  having liquid crystal (LC) layer with associated polarizers and control circuitry (not shown), which is configured to control the images of LCD  100 , with a color conversion film  130  and color filter layer  220  (which may be separate or integrated) following, to provide the displayed image. The above-display configuration of color conversion film  130  and color filter layer  220  is enabled by the fact that illumination  120  is collimated, preventing spatial discrepancies (such as scattering and cross talk) between positions of LC elements and positions of color filter elements. 
     It is noted that any of the disclosed embodiments may be implemented in various pixel arrangements (e.g., stripe, mosaic, delta and boomerang arrangements, as non-limiting examples) and with respect to any number of subpixel per pixel (e.g., 1, 2, 3 or more subpixels per pixel, possibly with various color allocations per subpixel), possibly with corresponding spatial adjustments and configurations, and possibly only to some of the sub-pixels in the array. Clearly, the patterning of color conversion film  130  (see e.g., schematic illustration of patterning  520  in  FIG. 11 ) may be configured to follow the patterning of color filter layer  220  and/or be integrated therewith. Elements of color conversion film  130  may be configured to be produced together with color filter layer  220  with minimal or possibly no additional complexity, using same or possibly modified production processes. 
       FIG. 1D  is a high level schematic block diagram illustrating various configurations of LCD panel  200  and display  100 , according to some embodiments of the invention. Various configurations and combinations illustrated in  FIG. 1D  are explained in more detail and demonstrated below. Disclosed configurations may be implemented for backlight units  300  configured to provide white illumination  80 B (e.g., using white LEDs) and/or blue illumination  80 A (e.g., using blue LEDs), as discussed below. 
     For white illumination  80 B, red-fluorescent and green-fluorescent RBF compounds  115  in respective layers  134 ,  132  (or possibly in mixed layer  133 ) may be used to enhance efficiency (illumination intensity of LCD display  100 ) and/or adjust its white point. Efficiency enhancement may be achieved by changing the white illumination spectrum to bring a larger part of the spectrum into the transmission ranges of RGB filters  220 , as illustrated e.g., in  FIGS. 10A-10E  and the respective disclosure sections. White point adjustment may be achieved by changing the ratios between the illumination components in the transmission ranges of RGB filters  220  within the illumination spectrum, as illustrated e.g., in  FIGS. 8A-8E  and the respective disclosure sections. 
     For blue illumination  80 A, red-fluorescent and green-fluorescent RBF compounds  115  in one or more layers  133  may be used to adapt the illumination spectrum to the transmission ranges of RGB filters  220 , as disclosed herein (see also  FIG. 2D ). 
     It is noted that the configuration of red-fluorescent and green-fluorescent RBF compounds  115  in color conversion films  130  or color conversion elements may be applied when using blue illumination  80 A for providing green and red illumination; when using white illumination  80 B for enhancing green and red illumination and adjusting the illumination spectrum; and possibly when using blue and green illumination  80 C (e.g., with blue and green LEDs in backlight units  300 ) for providing red illumination and enhancing red illumination and adjusting the illumination spectrum. 
     In any of the above-disclosed cases, assistant dye compounds  117  may be used as disclosed below (e.g.,  FIGS. 10A-E ,  13 A-B) to enhance any of the efficiency, FWHM, peak shape and/or white point of the illumination reaching RGB filters  220  and the illumination provided by LCD display  100 . Assistant dye compounds  117  may be selected to have specified absorption and emission peaks and/or to have absorption curves and fluorescence curves which change the shape of illumination spectrum  80 A and/or  80 B and/or change the shape and intensity of illumination components in the transmission ranges of RGB filters  220 . Two non-limiting examples for assistant dyes  117  are 5-FAM and 5-Carboxyfluorescein. Another non-limiting example of assistant dye  117  is HPTS; pyranine (8-Hydroxypyrene-1,3,6-Trisulfonic Acid, Trisodium Salt), having an absorption peak at shorter wavelengths than 5-FAM (e.g., at ca. 450 nm vs. 490 nm), with a similar emission peak at 520-530 nm (depending on embedding conditions). Other non-limiting examples of assistant dye  117  are rhodamine 12, rhodamine 101 from Atto-Tec® and perylene dye F300 from Lumogen®. Assistant dye compounds  117  may be integrated in any of disclosed films  130 ,  132 ,  134 ,  133 , and/or in separate film(s). 
     Examples for Assistant Dyes 
     Disclosed assistant dyes  117  are provided, which may be used to modify a received spectrum by absorption of radiation at some spectral regions to reduce their intensity and emission of radiation at other spectral regions to increase their intensity. Disclosed assistant dyes  117  may be used to convert radiation in the LCD display—possibly in combination with other assistant dyes disclosed herein. 
     In some embodiments, assistant dye compounds  117  may be represented by the following structure of Formula (A1): 
     
       
         
         
             
             
         
       
     
     wherein
 
R 109  is H, alkyl, haloalkyl, heterocycloalkyl, cycloalkyl, aryl or benzyl;
 
R 110  and R 110′  are each independently H, alkyl, haloalkyl, cycloalkyl, heterocycloalkyl, aryl, benzyl, halide, NO 2 , OR a , N(R a ) 2 , COR a , CN, CON(R a ) 2 , CO(N-heterocycle) or COOR a ;
 
R 111 , R 111′ , R 112  and R 112′  are each independently absent, H, alkyl, haloalkyl, cycloalkyl, heterocycloalkyl, aryl, benzyl, halide, NO 2 , OR a , N(R a ) 2 , COR a , CN, CON(R a ) 2 , CO(N-heterocycle) or COOR a ;
 
R 113  is H, alkyl, haloalkyl, cycloalkyl, heterocycloalkyl, aryl, benzyl, halide, NO 2 , OR a , N(R a ) 2 , COR a , CN, CON(R a ) 2 , CO(N-heterocycle) or COOR a ;
 
R 114  is H, alkyl, haloalkyl, cycloalkyl, heterocycloalkyl, aryl, benzyl, halide, NO 2 , OR a , N(R a ) 2 , COR a , CN, CON(R a ) 2 , CO(N-heterocycle) or COOR a ;
 
R 115  is H, alkyl, haloalkyl, cycloalkyl, heterocycloalkyl, aryl, benzyl, halide, NO 2 , OR a , N(R a ) 2 , COR a , CN, CON(R a ) 2 , CO(N-heterocycle) or COOR a ;
 
R 116  is H, alkyl, haloalkyl, cycloalkyl, heterocycloalkyl, aryl, benzyl, halide, NO 2 , OR a , N(R a ) 2 , COR a , CN, CON(R a ) 2 , CO(N-heterocycle) or COOR a ;
 
R 117  is H, alkyl, haloalkyl, heterocycloalkyl, cycloalkyl, aryl or benzyl;
 
R 118  and R 119  are each independently H, alkyl, haloalkyl, heterocycloalkyl, cycloalkyl, aryl or benzyl;
 
X 1  is NR a , S or O;
 
X 2  is NR a , S or O
 
Y 1  is N or CR a ;
 
Y 2  is N or CR a ;
 
R a  is H, alkyl, haloalkyl, cycloalkyl, heterocycloalkyl, aryl or benzyl;
 
n is an integer between 0 and 3; and
 
wherein if there is a double bond between the carbons which are substituted by R 111 , R 111′ , R 112  and R 112′ —then one of R 111  and R 111′  is absent and one of R 112  and R 112′  is absent.
 
     In another embodiment, assistant dye compounds  117  may be represented by the following structure of Formula (A1a): 
     
       
         
         
             
             
         
       
     
     wherein
 
R 109  is H, alkyl, haloalkyl, heterocycloalkyl, cycloalkyl, aryl or benzyl;
 
R 110  and R 110′  are each independently H, alkyl, haloalkyl, cycloalkyl, heterocycloalkyl, aryl, benzyl, halide, NO 2 , OR a , N(R a ) 2 , COR a , CN, CON(R a ) 2 , CO(N-heterocycle) or COOR a ;
 
R 111 , R 111′ , R 112  and R 112′  are each independently absent, H, alkyl, haloalkyl, cycloalkyl, heterocycloalkyl, aryl, benzyl, halide, NO 2 , OR a , N(R a ) 2 , COR a , CN, CON(R a ) 2 , CO(N-heterocycle) or COOR a ;
 
R 113  is H, alkyl, haloalkyl, cycloalkyl, heterocycloalkyl, aryl, benzyl, halide, NO 2 , OR a , N(R a ) 2 , COR a , CN, CON(R a ) 2 , CO(N-heterocycle) or COOR a ;
 
R 114  is H, alkyl, haloalkyl, cycloalkyl, heterocycloalkyl, aryl, benzyl, halide, NO 2 , OR a , N(R a ) 2 , COR a , CN, CON(R a ) 2 , CO(N-heterocycle) or COOR a ;
 
R 115  is H, alkyl, haloalkyl, cycloalkyl, heterocycloalkyl, aryl, benzyl, halide, NO 2 , OR a , N(R a ) 2 , COR a , CN, CON(R a ) 2 , CO(N-heterocycle) or COOR a ;
 
R 116  is H, alkyl, haloalkyl, cycloalkyl, heterocycloalkyl, aryl, benzyl, halide, NO 2 , OR a , N(R a ) 2 , COR a , CN, CON(R a ) 2 , CO(N-heterocycle) or COOR a ;
 
R 117  is H, alkyl, haloalkyl, heterocycloalkyl, cycloalkyl, aryl or benzyl;
 
R 118  and R 119  are each independently H, alkyl, haloalkyl, heterocycloalkyl, cycloalkyl, aryl or benzyl;
 
X 1  is NR a , S or O;
 
X 2  is NR a , S or O
 
Y 1  is N or CR a ;
 
Y 2  is N or CR a ;
 
R a  is H, alkyl, haloalkyl, cycloalkyl, heterocycloalkyl, aryl or benzyl; and
 
wherein if there is a double bond between the carbons which are substituted by R 111 , R 111′ , R 112  and R 112′ —then one of R 111  and R 111′  is absent and one of R 112  and R 112′  is absent.
 
     In some embodiments, assistant dye compounds  117  may be represented by the following structure of Formula (A2): 
     
       
         
         
             
             
         
       
     
     wherein
 
R 109  is H, alkyl, haloalkyl, heterocycloalkyl, cycloalkyl, aryl or benzyl;
 
R 110  and R 110′  are each independently H, alkyl, haloalkyl, cycloalkyl, heterocycloalkyl, aryl, benzyl, halide, NO 2 , OR a , N(R a ) 2 , COR a , CN, CON(R a ) 2 , CO(N-heterocycle) or COOR a ;
 
R 111 , R 111′ , R 112  and R 112′  are each independently absent, H, alkyl, haloalkyl, cycloalkyl, heterocycloalkyl, aryl, benzyl, halide, NO 2 , OR a , N(R a ) 2 , COR a , CN, CON(R a ) 2 , CO(N-heterocycle) or COOR a ;
 
R 113  is H, alkyl, haloalkyl, cycloalkyl, heterocycloalkyl, aryl, benzyl, halide, NO 2 , OR a , N(R a ) 2 , COR a , CN, CON(R a ) 2 , CO(N-heterocycle) or COOR a ;
 
R 114  is H, alkyl, haloalkyl, cycloalkyl, heterocycloalkyl, aryl, benzyl, halide, NO 2 , OR a , N(R a ) 2 , COR a , CN, CON(R a ) 2 , CO(N-heterocycle) or COOR a ;
 
R 115  is H, alkyl, haloalkyl, cycloalkyl, heterocycloalkyl, aryl, benzyl, halide, NO 2 , OR a , N(R a ) 2 , COR a , CN, CON(R a ) 2 , CO(N-heterocycle) or COOR a ;
 
R 116  is H, alkyl, haloalkyl, cycloalkyl, heterocycloalkyl, aryl, benzyl, halide, NO 2 , OR a , N(R a ) 2 , COR a , CN, CON(R a ) 2 , CO(N-heterocycle) or COOR a ;
 
R 117  is H, alkyl, haloalkyl, heterocycloalkyl, cycloalkyl, aryl or benzyl;
 
R 118  and R 119  are each independently H, alkyl, haloalkyl, heterocycloalkyl, cycloalkyl, aryl or benzyl;
 
X 1  is NR a , S or O;
 
X 2  is NR a , S or O
 
Y 1  is N or CR a ;
 
Y 2  is N or CR a ;
 
R a  is H, alkyl, haloalkyl, cycloalkyl, heterocycloalkyl, aryl or benzyl; and
 
wherein if there is a double bond between the carbons which are substituted by R 111 , R 111′ , R 112  and R 112′ —then one of R 111  and R 111′  is absent and one of R 112  and R 112′  is absent.
 
     In some embodiments, assistant dye compounds  117  may be represented by the following structure of Formula (A3): 
     
       
         
         
             
             
         
       
     
     wherein
 
R 109  and R 109′  are each independently is H, alkyl, haloalkyl, heterocycloalkyl, cycloalkyl, aryl or benzyl;
 
R 113  and R 113′  are each independently is H, alkyl, haloalkyl, cycloalkyl, heterocycloalkyl, aryl, benzyl, halide, NO 2 , OR a , N(R a ) 2 , COR a , CN, CON(R a ) 2 , CO(N-heterocycle) or COOR a ;
 
R 114  is H, alkyl, haloalkyl, cycloalkyl, heterocycloalkyl, aryl, benzyl, halide, NO 2 , OR a , N(R a ) 2 , COR a , CN, CON(R a ) 2 , CO(N-heterocycle) or COOR a ;
 
R 115  is H, alkyl, haloalkyl, cycloalkyl, heterocycloalkyl, aryl, benzyl, halide, NO 2 , OR a , N(R a ) 2 , COR a , CN, CON(R a ) 2 , CO(N-heterocycle) or COOR a ;
 
R 116  is H, alkyl, haloalkyl, cycloalkyl, heterocycloalkyl, aryl, benzyl, halide, NO 2 , OR a , N(R a ) 2 , COR a , CN, CON(R a ) 2 , CO(N-heterocycle) or COOR a ;
 
R 117  is H, alkyl, haloalkyl, heterocycloalkyl, cycloalkyl, aryl or benzyl;
 
R 118  and R 119  are each independently H, alkyl, haloalkyl, heterocycloalkyl, cycloalkyl, aryl or benzyl;
 
X 1  is NR a , S or O;
 
X 2  is NR a , S or O
 
Y 1  is N or CR a ;
 
Y 2  is N or CR a ; and
 
R a  is H, alkyl, haloalkyl, cycloalkyl, heterocycloalkyl, aryl or benzyl.
 
     In some embodiments, assistant dye compounds  117  may be selected from the group consisting of compounds A1-, A1-2, A1-3, A2-1, A2-2 and A3-1, represented by the following structures: 
     
       
         
         
             
             
         
       
     
     In these five non-limiting examples, Compounds A3-1 and A1-3 absorb violet radiation and emits blue radiation, effectively converting radiation from the violet range to the blue range, while the other Compounds A1-, A1-2, A2-1 and A2-2 absorb blue radiation and emit green radiation, effectively converting radiation from the blue range to the green range, as illustrated by the data provided in the following Table 1. 
     
       
         
           
               
             
               
                 TABLE 1 
               
             
            
               
                   
               
               
                 Absorption and emission wavelengths (in EtOH, ethanol), 
               
               
                 quantum yield, and FWHM (Full width at half maximum 
               
               
                 of the emission) for the exemplified compounds. 
               
            
           
           
               
               
               
               
               
            
               
                   
                 Absorbance 
                 Emission 
                 Quantum 
                   
               
               
                   
                 EtOH 
                 EtOH 
                 yield 
                 FWHM 
               
               
                 Compound 
                 [nm] 
                 [nm] 
                 [%] 
                 [nm] 
               
               
                   
               
            
           
           
               
               
               
               
               
            
               
                 Compound A1-1 
                 447 
                 503 
                 0.75 
                 55 
               
               
                 Compound A1-2 
                 446 
                 510 
                 0.72 
                 55 
               
               
                 Compound A1-3 
                 415 
                 494 
                 0.1 
                 68 
               
               
                 Compound A2-1 
                 443 
                 510 
                 0.74 
                 55 
               
               
                 Compound A2-2 
                 440 
                 505 
                 0.75 
                 55 
               
               
                 Compound A3-1 
                 408 
                 473 
                 — 
                 — 
               
               
                   
               
            
           
         
       
     
     In some embodiments, assistant dye compounds  117  may absorb light in the wavelength range of 350-800 nm. In one embodiment, the absorbance range is 350-500 nm. In another embodiment, the absorbance range is 400-500 nm. In another embodiment, compound 27 absorbs light at 408 nm (in Ethanol). In another embodiment, compound 28 absorbs light at 447 nm (in Ethanol). In another embodiment, compound 29 absorbs light at 446 nm (in Ethanol). In another embodiment, compound 30 absorbs light at 443 nm (in Ethanol). Each possibility represents a separate embodiment of this invention. 
     In some embodiments, assistant dye compounds  117  may emit light in the wavelength range of 400-800 nm. In one embodiment, the emission range is 400-550 nm. In another embodiment, compound 27 emits light at 473 nm (in Ethanol). In another embodiment, compound 28 emits light at 503 nm (in Ethanol). In another embodiment, compound 29 emits light at 510 nm (in Ethanol). In another embodiment, compound 30 emits light at 510 nm (in Ethanol). Each possibility represents a separate embodiment of this invention. 
     In some embodiments assistant dye compounds  117  may have a quantum yield (QY) of between 0.5-1. In one embodiment, the QY is 0.7-0.9. In another embodiment, compound 28 has a QY of 0.75. In another embodiment, compound 29 has a QY of 0.72. In another embodiment, compound 30 has a QY of 0.74. Each possibility represents a separate embodiment of this invention. 
     In some embodiments assistant dye compounds  117  may have a Full width at half maximum (FWHM) of emission being between 30-60 nm. In one embodiment, the FWHM is between 50-60 nm. In another embodiment, compound 28 has an FWHM of 55 nm. In another embodiment, compound 29 has an FWHM of 55 nm. In another embodiment, compound 30 has an FWHM of 55 nm. Each possibility represents a separate embodiment of this invention. 
     Display Configurations 
     Film Positions and Optional Patterning 
       FIGS. 2A-2J  are high level schematic illustrations of configurations of digital display  100  with color conversion film(s)  130 , according to some embodiments of the invention. Digital displays  100  are illustrated schematically as comprising a backlight unit  300  and a LCD panel  200 , the former providing RGB illumination  120  to the latter. 
     Backlight unit  300  is illustrated schematically in  FIG. 2A  in a non-limiting manner as comprising a backlight source  400  (e.g., white LEDs  80 B or blue LEDs  80 A), a waveguide  420  with reflector(s) (the latter for side-lit waveguides), a diffuser  406 , prism film(s)  355  (e.g., brightness enhancement film (BEF), dual BDF (DBEF), etc.) and polarizer film(s)  302 , which may be configured in various ways. Films  130  may be applied at various positions in backlight unit  300  such as on either side ( 130 A,  130 B) of diffuser  406 , on either side ( 130 C,  130 D) of at least one of prism film(s)  355 , on either side ( 130 E,  130 F) of at least one polarizer film(s)  302 , etc. In certain embodiments, film  130  may be deposited on any of the film in back light unit  300 . 
     In certain embodiments, films  130  may be used to replace diffuser  406  and/or polarizer film  302  (and possibly prism film(s)  355 ), once appropriate optical characteristics are provided in films  130  as explained herein. 
     The location of film(s)  130  may be optimized with respect to radiation propagation in backlight unit  300 , in both forwards ( 120 A) and backward ( 120 B) directions due to reflections in backlight unit  300 . For example, optimization considerations may comprise fluorescence efficiency, energy efficiency, stability of rhodamine-based fluorescent (RBF) compounds  115  or other color conversion elements in film(s)  130 , and so forth. As a non-limiting example, in the position of the lower film  130 A, B (e.g., on diffuser  406 ) more radiation is expected to excite RBF compounds  115 —increasing its conversion efficiency but increasing losses and reducing the durability of RBF compounds  115 . In the position of the higher film  130 E, F (e.g., on polarizer film  302 ) less radiation is expected to excite RBF compounds  115 —reducing its conversion efficiency but reducing losses and increasing the durability of RBF compounds  115  and/or other color conversion elements in film(s)  130 . 
     Some embodiments of displays  100  comprise a blue light source  80 A (such as blue LEDs—light emitting diodes) with film(s)  130  configured to provide red and green components in RGB illumination  120 , e.g., by using red-fluorescent RBF compound(s) (e.g., with silane precursor(s) such as PhTMOS (trimethoxyphenylsilane) and/or TMOS (trimethoxysilane) with fluorine substituents—see below) and green-fluorescent RBF compound(s) (e.g., with silane precursor(s) such as F 1 TMOS (trimethoxy(3,3,3-trifluoropropyl)silane)—see below). It is emphasized that various silane precursor(s)  104  may be used with either red-fluorescent or green-fluorescent RBF compounds  115  as disclosed below. 
     The red and green fluorescent RBF compound(s) may be provided in a single film layer  133  or in multiple film layers  134 ,  132 . The process may be optimized to provide required absorption and emission characteristics of RBF compounds in film  130 , while maintaining stability thereof during operation of display  100 . Similarly, film(s)  130  with either one or more color conversion elements (e.g., other fluorescent compounds, organic or inorganic, quantum dots etc.) may be integrated in display  100  in a similar way and according to respective considerations. In the following any of the mentioned RBF compound(s) may, in some embodiments, be replaced or augmented by other color conversion elements (e.g., other fluorescent compounds, organic or inorganic, quantum dots etc.). 
     Some embodiments of displays  100  comprise a white light source  80 B (such as white LEDs) with film(s)  130  configured to provide red and green components in RGB illumination  120 , e.g., by using red-fluorescent RBF compound(s) (e.g., with PhTMOS and/or TMOS with fluorine substituents as silane precursor(s)). The red fluorescent RBF compound(s) may be provided in a single film layer or in multiple film layers  134 . The process may be optimized to provide required absorption and emission characteristics of RBF compounds in film  130 , while maintaining stability thereof during operation of display  100 . Red-fluorescent RBF compound(s) may be used to shift some of the yellow region (550-600 nm) in the emission spectrum of white light source  80 B into the red region, to reduce illumination losses in LCD panel  200  while maintaining the balance between B and R+G in RGB illumination  120 . 
       FIG. 2B  illustrates in more details various films and elements in display  100  to which film  130  may be associated or which may be replaced by film  130  in some embodiments. LCD panel  200  is shown to include compensation films  204 ,  254 , glass layers  206 ,  252 , thin film transistors (TFT)  255 , ITO (indium tin oxide) layers  258 ,  262 , liquid crystal cell (LC)  261 , RGB color filters  220 , polarizer film  256  and protective film  266  (e.g., anti-glare, anti-reflection).  FIG. 2B  further illustrates typical illumination transmission in each layer and cumulatively, indicating ca. 40% loss in backlight unit  300  and 90% loss in LCD panel  200 , the latter mainly resulting from RGB color filters  220  and polarizers  202 ,  302  in LCD panel  200  and backlight unit  300 , respectively. One or more film(s)  130  may be attached to or replace any of various layers in backlight unit  300  and/or in LCD panel  200 , depending on considerations of minimizing further illumination losses, film performance and lifetime of the fluorescent dyes (RBF compounds  115 ). As non-limiting examples,  FIG. 2B  illustrates schematically associating on one or more films  130  with any of diffuser and/or light guide  406 , reflector  421 , prism layer(s)  355 , diffusers  360 ,  361 , polarizers  83 A,  83 B (in either or both backlight unit  300  and LCD panel  200 , respectively), LC  261 , ITO  262  and/or color filters  220 . It is emphasized that  FIG. 2B  merely provides a non-limiting example of a display configuration, and films  130  may be applied at various positions and any display configuration. It is noted that in various display configurations, disclosed layers may be to some extent re-ordered and modified. In following disclosed configurations, particularly polarizers and diffusers may be illustrated at different locations, reflecting the diversity of LCD designs. 
     In some embodiments, similar considerations may be used with respect to positioning of any type of color conversion film  130 , which may comprise color conversion elements other than RBF compounds  115 , such as organic (non-rhodamine-based) or inorganic fluorescent compounds, quantum dots etc. Various display  100  configurations may be provided, which optimize illumination loss with film parameters and lifetime of the color converting elements. 
       FIGS. 2C and 2D  schematically illustrate some of the above considerations, by comparing display  100  ( FIG. 2D ) with color conversion film  130  in LCD panel  200  versus display  100  ( FIG. 2C ) with color conversion film  130  in backlight unit  300 . The schematic illustrations depict the illumination intensity as I 0 , and illumination components R, G, B as they are produced in the respective display. In display  100 , color conversion film  130  in backlight unit  300  provides illumination at RGB, assuming in a non-limiting manner no loss on the conversion. In LCD panel  200 , color filters  220  remove two of the three illumination components, leaving ca. 10% of the original illumination at each color component (see also  FIG. 2B , illustrating a more realistic lower rate of less than 5% per color component). When placing color conversion film  130  in LCD panel  200  (e.g., as a patterned film  130 , see e.g., schematic illustration of patterning  520  in  FIG. 11 ), as illustrated for display  100  ( FIG. 2D , assuming blue LED illumination), a blue component may be delivered directly to blue color filter  220  without color conversion or filtering, while R and G may be converted from corresponding blue component just before filters  220 , so that that filters  220  pass most or all of the illumination they receive, which is wavelength-adjusted just before entering color filters  220 —resulting in a much higher efficiency than in display  100  of ca. 30% of the original illumination at each color component (corresponding to 10-15% per color component in terms of  FIG. 2B ). 
     Such gain in efficiency may be achieved by some embodiments having any type of color conversion film  130 , which may comprise color conversion elements other than RBF compounds  115 , such as organic (non-rhodamine-based) or inorganic fluorescent compounds, quantum dots etc. Various display configurations may be provided which increase illumination use efficiency by positioning respective color conversion film  130  in LCD panel  200 , before color filters  220 . Some embodiments comprise respective LCD panels  200  having color conversion film  130  integrated therein and positioned before color filters  220  thereof, as well as corresponding displays  100 . 
       FIG. 2E  illustrates an example for configuration of film  130  folded into a corrugated (e.g., zig-zag folded) form, characterized by an overall length L, overall thickness d 1  and step d 2  between folds. Film  130  may be folded to increase the film thickness through which the illumination passes, without increasing the actual thickness of film  130  (formulated otherwise—to reduce the light flux per area of film  130 ). The folding may increase the lifetime of RBF compounds  115  in film or of any other comprise color conversion elements on which film  130  may be based, such as organic (non-rhodamine-based) or inorganic fluorescent compounds, quantum dots etc. 
       FIGS. 2F-2L  are high level schematic illustrations of configurations of digital display  100  with color conversion film(s)  130 , according to some embodiments of the invention.  FIG. 2F  illustrates, schematically, embodiments in which color conversion film  130  is positioned in backlight unit  300 , e.g., between diffuser  406  and prism  355  or associated therewith, as disclosed above. 
       FIG. 2G  illustrates, schematically, embodiments in which color conversion film  130  is positioned in LCD panel  200  between polarizer  202 / 258  and an analyzer film  262 / 256  (e.g., a corresponding polarizing film), e.g., between liquid crystal layer  261  and analyzer film  262 / 256  and below RGB color filter layer  220 . In such configurations, with LCD panel  200  comprising, sequentially with respect to received illumination  120 : polarizing film  202 / 258 , liquid crystal layer  261 , color conversion film  130 , RGB color filter layer  220  and analyzer film  262 / 256 —the position of color conversion film  130  may be optimized to provide maximal light conversion efficiency while retaining long life time (due to less radiation passing though film  130  after non-polarized illumination has been filtered out by polarizer  202 / 258 ) and maintaining the polarization of the illumination. The latter effect may be achieved by corresponding configuration of color conversion film  130  to maintain or even enhance the respective polarization, e.g., by aligning RBF compounds  115  during preparation of color conversion film  130 , as disclosed herein. One or more color conversion film(s)  130  may be positioned in certain embodiments between polarizer  202 / 258  and liquid crystal layer  261 . 
     It is noted that in both  FIGS. 2F and 2G , LC module  210  may include color filter layer  220  (and possibly color conversion layer  130 ), in addition to LC film  261  and polarizers  262 / 256 . It is noted that in both  FIGS. 2F and 2G , LCD panel  200  may comprise LC module  210  and additional layers, which are not shown in these figures. 
       FIG. 2H  illustrates, schematically, embodiments in which color conversion film  130  is positioned in LCD panel  200  after analyzer film  262 / 256  and below RGB color filter layer  220 . In certain embodiments, RGB color filter layer  220  in LCD panel  200  may be positioned after analyzer film  262 / 256 , and be preceded by color conversion film  130 . In such configurations, with LCD panel  200  comprising, sequentially with respect to received illumination  120 : polarizing film  202 / 258 , liquid crystal layer  261 , analyzer film  262 / 256 , color conversion film  130 , RGB color filter layer  220  and protective film  266 . The position of color conversion film  130  may be optimized to provide maximal light conversion efficiency while retaining long life time (due to less radiation passing though film  130  after non-polarized illumination has been filtered out by polarizer  202 / 258 ). Polarization maintenance is not necessarily required in these embodiments, as color conversion film  130  is positioned after liquid crystal layer  261  and analyzer film  262 / 256 . One or more color conversion film(s)  130  may be positioned in certain embodiments between analyzer film  262 / 256  and protective film  266 . In certain embodiments, multiple films  130  may be used in display  100 , e.g., combining embodiments illustrated in  FIGS. 2F-2H , possibly with different films  130  which are configured each with respect to its position in display  100 . In certain embodiments, color conversion film(s)  130  may be patterned with respect to a patterning of RGB color filter layer  220  to yield a spatial correspondence between film regions with R and G emission peaks and respective R and G color filters, as disclosed herein (see e.g.,  FIG. 2D ). Color conversion film(s)  130  may comprise one or more layers, with corresponding red-fluorescent RBF compound(s) and green-fluorescent RBF compound(s) as disclosed herein. Color conversion film(s)  130  may comprise independent film(s) and/or corresponding layers applied onto any of the LCD panel components disclosed herein, according to their respective position in LCD panel  200 . It is noted that in  FIGS. 2F-2H , LCD panel  200  may comprise additional layers, which are not shown in the figures. 
     In certain embodiments, considerations for positioning color conversion film(s)  130  within LCD panel  200  may be carried out according to estimations of transmission of illumination, similar to the non-limiting example presented in  FIG. 2B . The considerations may comprise minimizing radiation intensity passing through color conversion film(s)  130  with respect to the complexity of modifying LCD panel  200 . Additional considerations may comprise reduction of parallax effects due to film thickness, which may be achieved by close association of film(s)  130  with color filters  220 , applying at least part(s) of film(s)  130  as coatings on color filters  220  or on other films in LCD panel  200 , and possibly providing barriers in film(s)  130  to limit stray light. 
       FIG. 2I  is a high level schematic illustration of an intensity regulating mechanism implemented by a controller  212 , according to some embodiments of the invention. Controller  212  may be configured to regulate transmission through LC module  210 , e.g., by controlling LC layer  261  and/or polarizers  202 / 258 / 262 / 256 ) in relation to the intensity of fluorescence from color conversion film  130 . For example, controller  212  may be configured to tune down transmission through LC module  210  when color conversion film  130  is fresh and provides a high level of fluorescence, and gradually tune up transmission through LC module  210  as color conversion film  130  degrades and provides less fluorescence. Such operation of controller  212  may be configured to provide a constant output from display  100 , even within a given range of degradation of color conversion film  130  to increase the lifetime of display  100 . 
       FIG. 2J  is a high level schematic illustration of a fluorescence-intensifying section  150  with color conversion film  130 , according to some embodiments of the invention. Section  150  may comprise optical elements  152  and optionally  154 , configured to enhance red and green radiation by reflecting fluorescent radiation from green-fluorescent and red-fluorescent RBF compounds  115  (indicated schematically by the arrows) back in direction of color filters  220  (not illustrated). The distribution and density of green-fluorescent and red-fluorescent RBF compounds  115  in color conversion film  130  may be configured to take into account recurring fluorescence to provide the required white point parameters. Section  150  may be configured to pass the blue illumination component without reflections (attenuated only by the absorption by RBF compounds  115 ). For example, optical element  152  may comprise DBEF (Dual Brightness Enhancement Film) film(s) which may be configured to be transparent to blue light and reflective to red and green light. Optical element  154  may also comprise DBEF film(s) configured to be transparent to blue light and reflective to red and green light, to form some back and forth reflections of R and/or G light through color conversion film  130 . Optical element  154  is optional in the sense that fluorescence-intensifying section  150  may comprise only optical elements  152  to enhance R and/or G light by simple reflection. In certain embodiments, fluorescence-intensifying section  150  may be also configured to enhance the degree of polarization of the illumination, by selectively reflecting (by optical element  152 ) and/or transmitting (by optical element  137 ) light with specified polarization properties, in particular red and green light with specified polarization properties. Fluorescence-intensifying section  150  may at least partly compensate for possibly loss of polarization by fluorescence of RBF compounds  115  in color conversion film  130 . Fluorescence-intensifying section  150  may be positioned in either backlight unit  300  and/or LCD panel  200 , and may be combined with any of the disclosed display configurations. As illustrated schematically, fluorescence-intensifying section  150  may be positioned in various, one or more positions in BL  300  and/or in LCD panel  200  (see also  FIG. 1A ). Advantageously, fluorescence-intensifying section  150  may be configured to reduce stray light, compensate for absorption and/or enhance polarization of light passing through color conversion film  130 . 
     In certain embodiments, enhancements may be applied to color conversion film  130  integrated in backlight unit  300  and/or in LCD panel  200 . For example, a short-pass reflector (SPR) layer (see e.g., layer  152  in  FIG. 2L ) may be positioned before color conversion film  130  to reflect backward fluorescent emission of RBF compounds  115  into the forward direction, to prevent absorption loss of the backward fluorescent emission. It is noted that SPR layer  152  may be implemented as any of, e.g., single-edge short-pass dichroic beam splitter(s), bandpass filter(s) and/or blocking single-band bandpass filter(s) or their combinations. In certain embodiments, a layer may be positioned after color conversion film  130  to enhance the fluorescent output of color conversion film  130  by directing more radiation through it; to reduce stray fluorescent emission and possibly to reduce cross talk between RGB color filters  220  (see also crosstalk-reducing layer  160  disclosed below). In certain embodiments, possible polarization scrambling by film  130  may be compensated by a layer positioned before or after film  130 , such as a thin analyzer (polarizer) layer  258 . 
       FIGS. 2K and 2L  are high level schematic illustrations of patterned color conversion films  130  with a matrix-like crosstalk-reducing layer  160 , according to some embodiments of the invention.  FIG. 2K  illustrates schematically a cross section through a part of LCD panel  200 , between polarizer  202  and analyzer  260  of embodiments similar to the illustrated in  FIG. 2G . It is noted that in various display configurations (see e.g.,  FIG. 2B ), disclosed layers may be to some extent re-ordered and modified. In following disclosed configurations, particularly polarizers and diffusers may be illustrated at different locations, reflecting the diversity of LCD designs. 
     In certain embodiments, color conversion film  130  may be patterned and attached to or adjacent to RGB color filters layer  220 . Regions of color conversion film  130  which are adjacent to B (blue) color filter regions of layer  220  may be devoid of RBF compounds  115  and pass all the blue light (see also  FIG. 2D ); regions of color conversion film  130  which are adjacent to G (green) color filter regions of layer  220  may comprise only green-fluorescent RBF compounds  115  to convert blue light to green light; and regions of color conversion film  130  which are adjacent to R (red) color filter regions of layer  220  may comprise both green-fluorescent and red-fluorescent RBF compounds  115  to convert blue light to green light and green light to red light, respectively. The film stack comprising patterned color conversion film  130 , color filters layer  220  and possibly liquid crystal (LC) layer  261 , polarizer  202  and analyzer  260  (indicated as an LC module  210 )—may be produced or processed jointly to achieve exact alignment of patterned color conversion film  130  and color filters layer  220 . 
     Color conversion films  130  may have a crosstalk-reducing layer  160  embedded therein (see also  FIG. 2M  below), and/or patches of color conversion film  130  may be incorporated within the structural framework of crosstalk-reducing layer  160 . Color conversion film  130  with crosstalk-reducing layer  160  may be patterned to comprise compartments of film  130  with green-fluorescent RBF compounds  115 , denoted  130  ( 115 G)—before the G filter regions of RGB filter  220 , compartments of film  130  with both red-fluorescent and green-fluorescent RBF compounds  115 , denoted  130  ( 115 R) and  130  ( 115 G), respectively—before the R filter regions of RGB filter  220  and compartments with blue or no film  130  (e.g., possibly blue emitting film “B”, a diffuser and/or a void, as explained below) before the B filter regions of RGB filter  220 . 
       FIG. 2L  illustrates schematically a cross section through a part of LCD panel  200 , with additional optical elements configured to optimize the LCD output and the radiation movement through the LC panel. For example, SPR layer  152  may be used before layer  130  to recycle backscattered fluorescent light and possibly to increase blue transmission by configuration in the respective polarization; and optical elements  262 ,  264  may be used to control radiation after layer  130 . For example, optical elements  264  may comprise diffuser or concave micro lens configured to correct possible spatial distribution differences in illumination between the B, R and G component from film  130  and filters  220  (e.g., possibly correcting deviations introduced be film  130 ). 
     Optical elements  264  may comprise, in addition or in place of analyzer  260 , and possibly integrated in protective layer  266 , optical elements configured to reflect back and/or absorb ambient light, a black matrix with micro lenses to further improve the LCD output. In certain embodiments, thin analyzer  258  may be positioned before SPR layer  152  to enhance the degree of polarization of the radiation reaching film  130 , optionally to compensate for possible polarization scrambling in film  130 . Thin analyzer  258  and SPR layer  152  (illustrated as stack  259 ) may be replaced by (main) analyzer  260 , a glass substrate and SPR layer  152  in alternative embodiments of stack  259 . 
     Certain embodiments comprise an integrated and patterned layer of color conversion film(s)  130 , RGB color filters  220  and crosstalk-reducing layer  160 , comprising the structural framework configured to reduce cross-talk between patterned pixels of the integrated layer. 
       FIG. 2M  provides a schematic cross section view of a part of LCD panel  200  as well as a perspective view of color conversion films  130  with crosstalk-reducing layer  160 , showing the top compartments thereof ( 130  ( 115 G) of the red compartments are not visible in the image, see in  FIGS. 2K, 2L ). In non-limiting examples, layer  160  may have a honeycomb structure, a rectangular structure or any other structure designed to correspond to patterns of color filters  220  and/or to patterns of color conversion film  130  disclosed above. The combination of color conversion films  130  and crosstalk-reducing layer  160  may be implemented by a range of technologies, such as deposition methods, photolithography, solution-based coating methods and/or by producing a film (such as a white film, a black film, a reflective film etc.) with holes by the corresponding color-conversion materials (patches of film  130  with respective RBF compounds  115 ). Layers  130 ,  160  may be positioned next to LC layer  261  and/or after analyzer  87  (see e.g.,  FIGS. 2G, 2H , respectively), depending on the level pf polarization layers  130 ,  160  are configured to provide. 
       FIG. 2M  further illustrates patterned color conversion film  130  with a matrix-like crosstalk-reducing layer  160  in an above-LC configuration, according to some embodiments of the invention. Collimated illumination  120  may be configured to enable maintaining the direction of illumination exiting the LC module as it propagates through color conversion film  130  to color filters  220  and exits display  100 —to achieve a low level of blurring and high efficiency.  FIG. 2M  is a schematic cross section through a part of LCD panel  200 , including polarizer  202 , LC layer  210 , polarizer (analyzer)  262 , and patterned color conversion film  130  and color filters layer  220  positioned above polarizer (analyzer)  262 . 
       FIGS. 2N and 2S  are high-level schematic illustrations of LCD panel  200  comprising the color conversion and filtering layer above the LC module, with a top optical-elements array  222 , according to some embodiments of the invention. The color conversion and filtering layer may comprise separate color conversion layer  130  and color filters layer  220  or integrated color conversion and filtering layer  230  as shown in  FIGS. 2O and 2P  below. LCD panel  200  may comprise top optical-elements array  222  having e.g., a micro-lens array ( FIG. 2N ), which is placed above color filters  220  and configured to increase the brightness and radiance of LCD  100  at the center of a vertical viewing direction. LCD panel  200  may comprise top optical-elements array  222  having optical elements such as lenslets, encapsulated within a transparent material (typically having a lower refractive index than the lenslets), as illustrated schematically in  FIG. 2S , providing a flat optical element which is placed above color filters  220  and configured to increase the brightness and radiance of LCD  100  at the center of a vertical viewing direction. 
       FIG. 2N  further illustrates schematically blue diffuser elements  161 , which may be applicable to any of the embodiments disclosed herein, configured to provide a similar spatial distribution of blue light as the red and green light spatial distributions, which are affected by color conversion elements  130 R and/or  130 G. In certain embodiments, top optical-elements array  222  may comprise optical elements (e.g., micro-lenses) only over blue sub-pixels (in addition or in place of blue diffuser elements  161 ) to equalize the light spatial distributions of R, G and B light. 
       FIGS. 2O-2Q  are high-level schematic illustrations of apart of LCD panel  200 , according to some embodiments of the invention.  FIG. 2P  is a schematic cross section view,  FIG. 2O  is a schematic side and perspective view. In certain embodiments, crosstalk-reducing layer  160  and color conversion layer  130  may be integrated into single patterned color conversion film  133  and possibly further integrated with color filters layer  220  into a single layer  230  configured to perform both functions of color conversion and filtering. Layer  230  may be pixelated in any pattern of pixels and subpixels, and may have regions B, G+ 130 G and R+ 130 R (possibly with additional colors, e.g., yellow) configured to provide blue, green and red light from collimated blue illumination  120 , through color conversion and color filtering. Corresponding concentrations and amounts of absorptive and fluorescent dyes may be produced into the compartments of layer  230  according to the principles disclosed herein, possibly integrated in a production process which is similar to the current process of producing color filters layer  220 . Supporting elements and/or matrix-like crosstalk-reducing layer  160  may be part of layer  230  to maintain collimation of the provided light and minimize light stray. Integrated layer  230  may comprise any of color conversion layer  130 , RGB filters layer  220  and crosstalk-reducing layer  160 . 
       FIG. 2P  is a high level schematic illustration of an integrated layer  230  of patterned color conversion film  130  with RGB color filters  220 , according to some embodiments of the invention. In certain embodiments, one or more of RGB color filters  220  may be configured to comprise red-fluorescent and/or green-fluorescent RBF compounds  115  and/or assistant dyes  117  and be configured as respective integrated RGB color filters  230 . 
     As illustrated e.g., in  FIG. 2P , certain embodiments comprise LCD  100  comprising backlight unit  300  configured to provide illumination  120  and LCD panel  210  receiving illumination radiation from backlight unit  300  and comprising, sequentially with respect to the received illumination: polarizing film  202 ,  258 , liquid crystal layer  261 , analyzer film  262 , integrated RGB color filter layer  220  which is integrated with color conversion film  130  (possibly patterned), and protective layer  266 , possibly with additional analyzer film  262  between integrated RGB color filter layer  220  and protective layer  266 —as illustrated e.g., in  FIGS. 2K-2M . Integrated RGB color filter layer  220  may comprise rhodamine-based fluorescent (RBF) compounds  115  selected to absorb illumination from backlight unit  300  and have an R emission peak and a G emission peak. 
     Integration of color filters  220  with color conversion layer  130  may simplify the design of display  100  and enhance its efficiency (e.g., reduce losses, further reducing stray light and increasing the efficiency of utilization of illumination  120 ). In certain embodiments, illumination  120  may comprise blue illumination  80 A and integrated RGB color filter layer  220  may comprise RBF compounds  115  having the R emission peak and the G emission peak. In certain embodiments, illumination  120  may comprise white illumination  80 B and integrated RGB color filter layer  220  may comprise RBF compounds  115  having the R emission peak and/or the G emission peak configured to provide red and/or green color enhancement, respectively. In certain embodiments, illumination  120  may comprise blue and green illumination  80 C and integrated RGB color filter layer  220  may comprise RBF compounds  115  having the R emission peak and/or the G emission peak configured to provide red color conversion and possibly red and/or green color enhancement, respectively. In any of the embodiments, assistant dyes  117  may be further integrated in integrated RGB color filter layer  220  and/or possibly used as separate color conversion elements  117 . 
     In certain embodiments, the efficiency of illumination may be determined by a large number of parameters, such as spectrum overlap between illumination  120  from backlight unit  300  and absorption ranges of color conversion and assistant dyes  115 ,  117  respectively, transmission and reflection parameters in the spectral range of optical elements in LCD panel  210  (e.g., optical elements  152  and optionally  154  illustrated in  FIG. 2J ), quantum yields of the dyes and recycling efficiency of the backscattered fluorescent light; and spectrum overlap between the modified spectrum and color filters  220 , e.g., spectrum overlap between the emission spectra of color conversion and assistant dyes  115 ,  117  respectively, and color filters  220 , residual illumination after color conversion, and spatial considerations such as angular dependency of fluorescent radiation, and of optical elements in LCD panel  200 . Optimization of color conversion and assistant dyes  115 ,  117  respectively, of dye integration in color filters  220 , of spectrum shaping (see below) and of crosstalk-reducing layer  160  may be carried out with respect to individual color ranges and specified required gamut parameters. 
       FIG. 2Q  further illustrates schematically red and/or green diffuser elements  161 A, which may be applicable to any of the embodiments disclosed herein, configured to regulate the spatial distribution of red and/or green light, respectively, possibly to compensate for effects of color conversion elements  130 R and/or  130 G, respectively. In certain embodiments, blue diffuser elements  161  may be applied together with red and/or green diffuser elements  161 A. Any of the embodiments may be configured to equalize the light spatial distributions of R, G and B light. 
     In certain embodiments, color conversion film  130  may be patterned and attached to or adjacent to RGB color filters layer  220 . Regions of color conversion film  130  which are adjacent to B (blue) color filter regions of layer  220  may be devoid of color conversion compounds and pass all the blue light; regions of color conversion film  130 G which are adjacent to G (green) color filter regions of layer  220  may comprise only green color conversion compounds, such as green-fluorescent rhodamine-based compounds disclosed in U.S. Patent Publication No. 2018/0057688, included herein by reference in its entirety, to convert blue light to green light; and regions of color conversion film  130 R which are adjacent to R (red) color filter regions of layer  220  may comprise both green and color conversion compounds such as green-fluorescent and red-fluorescent rhodamine-based compounds disclosed in U.S. Patent Publication No. 2018/0057688 and U.S. Pat. No. 9,771,480, included herein by reference in their entirety, to convert blue light to green light and green light to red light, respectively. 
     Color conversion films  130  may comprise crosstalk-reducing layer  160  embedded therein (patterned in squares, hexagons, or other shapes), and/or patches of color conversion film  130  may be incorporated within the structural framework of crosstalk-reducing layer  160 . Color conversion film  130  with crosstalk-reducing layer  160  may be patterned to comprise compartments  130 G of film  130  with green color conversion compounds adjacent and before the G filter regions of RGB filter  220 , compartments  130 R,  130 G (possibly combined or integrated) of film  130  with both green and red color conversion compounds adjacent and before the R filter regions of RGB filter  220  and compartments with blue or no film  130  (e.g., possibly blue emitting film, a diffuser and/or a void) adjacent and before the B filter regions of RGB filter  220 . 
     In certain embodiments, additional layers may be added, such as short-pass reflector (SPR) layer(s) to recycle backscattered fluorescent light and possibly to increase blue transmission by configuration in the respective polarization, optical elements configured to control radiation after color conversion layer  130  such as diffuser(s) or concave micro lenses configured to correct possible spatial distribution differences in illumination between the B, R and G component from color conversion film  130  and filters  220 , to reflect back and/or absorb ambient light, to further improve the LCD output e.g., using a black matrix with micro lenses, etc. In certain embodiments, a thin analyzer layer may be used as polarizer (analyzer)  262  to enhance the degree of polarization of the radiation reaching color conversion film  130 , optionally to compensate for possible polarization scrambling therein. 
       FIG. 2R  is a high level schematic illustration of patterned color conversion films  130  with a layer  117  of assistant dyes, according to some embodiments of the invention. Layer  117  of assistant dyes may be patterned, possibly with different assistant dyes associated with each of R, G and B filters  220 , indicated schematically as assistant dye layers  117 (R, G, B). In certain embodiments (not shown), assistant dye layers  117  may be integrated in one or more of patterned color conversion film(s)  130 . 
     In certain embodiments, an illumination efficiency calculation may be used to adjust the relative amounts of illumination in each spectral range (e.g., R, G, B ranges). First, color conversion factors may be adjusted to provide relative amounts of R, G, B illumination reaching color filters  220  (e.g., green and red color conversion for blue illumination  80 A, red color conversion for blue and green illumination  80 C), second, color conversion dyes (and possibly assistant dyes) may be provided to adjust the illumination spectrum and fine tune the relative amounts of R, G, B illumination reaching color filters  220  (e.g., red and green enhancement for blue illumination  80 A, red and green enhancement for white illumination  80 B, red and possibly green enhancement for blue and green illumination  80 C). Third, conversion efficiencies and adjustment efficiencies may be calculated together with efficiency figures of other components to adjust the relative intensities of R, G, B illumination provided by LCD display  100 . For example, red and green enhancements may be configured to compensate for higher losses through red and green conversion films and possibly for higher losses for R illumination (due to double conversion—to green and then to red) than for G illumination (see also  FIGS. 1D and 2J ). 
     In certain embodiments, assistant dye(s) may comprise phosphorous compound(s) selected to convert blue illumination  80 A to illumination at longer wavelengths, as an assistant component (e.g., in association with R color filters  220  as  117 R). 
     In the case of blue illumination  80 A which is used with quantum dots  76 , red-fluorescent and/or green-fluorescent RBF compounds  115  and/or assistant dyes  117  may be used to enhance any of the efficiency, FWHM, peak shape and/or white point of the illumination reaching RGB filters  220  and the illumination provided by LCD display  100  ( FIG. 1D ). Red-fluorescent and/or green-fluorescent RBF compounds  115  and/or assistant dye compounds  117  may be selected to have specified absorption curves and fluorescence curves which change the shape of illumination spectrum  80 A after it is modified by quantum dots  76  and/or change the shape and intensity of illumination components in the transmission ranges of RGB filters  220 . In particular, red-fluorescent and/or green-fluorescent RBF compounds  115  and/or assistant dye compounds  117  may be selected to correct symmetry issues in the transmission ranges of RGB filters  220  which are prevalent when using certain color conversion technologies (see e.g., WIPO Publication No. WO 2017/085720 and U.S. Pat. No. 9,868,859, incorporated herein by reference in their entirety). 
     As disclosed above and illustrated in  FIG. 2S , a flat optical element  222  may be placed above color filters  220  and configured to increase the brightness and radiance of LCD  100  at the center of a vertical viewing direction. Flat optical element  222  may comprise sub elements  224 A such as micro lenses (shown schematically) embedded within transparent surface  224 B. Optical element  222  may be configured to control the spatial intensity pattern of the radiation emitted by display  100 . 
       FIG. 3A  is a high-level schematic layered view of LCD  100  having collimated backlight unit  300 , according to some embodiments of the invention. Analogously to  FIGS. 1C and 2M-2S ,  FIG. 3A  illustrates, sequentially, collimated backlight unit  300  providing collimated illumination  120 , LC layer  210  with polarizers  202 ,  262 , color conversion film  130  and color filter layer  220 . 
     Backlight unit  300  may comprise at least one illumination source  80  configured to provide illumination, at least one cavity  110  (shown schematically) configured to receive the provided illumination from illumination source(s)  80 , and an array of optical elements  116  (shown schematically) configured to collimate illumination exiting from respective cavities  110 , to provide collimated illumination  120 . Cavity  110  may be produced in different ways, possibly using internal reflective coatings the bottom, and possibly parts of the sides of cavities  110  from within, such as metallic coating, white coatings, highly reflective coatings such as Spectralon®, mirror coatings, possibly narrow-band mirrors (such as dielectric mirrors) or laser line mirrors, etc. In certain embodiments, the internal reflectivity of cavities  110  may be very high only over a narrow spectral band-width which corresponds to the wavelength band of illumination source(s)  80 . In certain embodiments, cavities  110  are not internally reflective in any part thereof. 
     In certain embodiments, illumination sources  80 , cavities  110  and optical elements  116  may be arranged in a light source layer  400  and/or may be arranged into illumination units  122 , each comprising one illumination source  80 , one cavity  110  and one optical element  116 . It is noted that other embodiments may comprise different numeral ratios between the elements. It is further noted that the sizes of illumination units  122  in respective embodiments may be optimized with respect to illumination properties, possibly unrelated to LCD panel parameters such as pixel parameters. 
       FIGS. 3B and 3C  are high-level schematic illustrations of illumination units  122  with designed serrated lens  111  and an additional lens  116  providing collimated illumination  120 , according to some embodiments of the invention. 
     In certain embodiments, designed optical element  111  such as a serrated lens, may be configured to deliver radiation from illumination source(s)  80  to optical elements  116  to be collimated after optical elements  116  as collimated illumination  120 . In certain embodiments, the design of optical element  111  may simulate illumination from a point source such as pinpoint openings  114  of internally reflective cavities  110  disclosed below. Designed optical element  111  may be molded onto illumination source(s)  80  and/or illumination source(s)  80  may be positioned within designed optical element  111 , e.g., during a molding process thereof. Designed optical element  111  may be further configured to provide effective heat dissipation from illumination source(s)  80 . In certain embodiments, designed optical element  111  may be configured to deliver collimated radiation  80  without need for additional optical elements  116 . 
     Optionally, illumination units  122  may further comprise a reflector  111 A configured to reflect radiation towards the LCD panel and possibly support lens  111  mechanically. 
     It is noted that  FIGS. 3A and 4-6B  are not drawn in correct proportions, as typically the dimensions of illumination sources  80  are several orders of magnitude smaller than the dimensions of cavities  110  and optical elements  116 . 
     In certain embodiments, such as illustrated in  FIGS. 4, 5A-5E and 6A-6B , illumination sources  80  (shown with supporting structure), internally reflective cavities  110  and optical elements  116  may be arranged in a light source layer  400  and/or may be arranged into illumination units  122 , each comprising one illumination source  80 , one internally reflective cavity  110  and one optical element  116 . It is noted that other embodiments may comprise different numeral ratios between the elements, as exemplified below. It is further noted that the sizes of illumination units  122  in respective embodiments may be optimized with respect to illumination properties, possibly unrelated to LCD panel parameters such as pixel parameters. 
     It is noted that in any of  FIGS. 4, 5A-5J and 6A-6B , internally reflective cavities  110  may be internally coated, lined and/or produced from any type of reflective coating or material, such as metallic coatings, white coatings, highly reflective coatings such as Spectralon®, mirror coatings, possibly narrow-band mirrors (such as dielectric mirrors) or laser line mirrors, etc. 
       FIG. 4  is a high-level schematic illustration of light source layer  400  and illumination units  122  with array  118  of optical elements  116 , configured to provide collimated backlight illumination  120 , according to some embodiments of the invention. In the non-limiting illustrated example, array  118  of optical elements  116  may comprise array  118  of lenslets  116 , each lenslet  116  positioned to have a corresponding pinpoint opening  114  at its focal point and each lenslet  116  configured to collimate illumination exiting from corresponding pinpoint opening  114 . 
     In certain embodiments, pinpoint openings  114  may be adjacent to the focal points of optical elements  116 , or remote therefrom. In certain embodiments, optical elements  116  may comprise one or more grating(s) configured to collimate radiation from pinpoint openings  114 . It is noted that in certain embodiments, LCD  100  may comprise light source layer  400  without optical elements  116 . 
     Advantageously, internally reflective cavities  110  may be designed to effectively disperse heat generated by illumination source(s)  80  such as LEDs (light emitting diodes). In certain embodiments, materials of cavities  110  may be selected to provide effective heat dispersion. In certain embodiments, cooling means may be associated with cavities  110  and/or with illumination source(s)  80 . 
     The deigns presented in  FIGS. 3A-3C, 4, 5A-5J and 6A-6B  may be modified and optimized with respect to illumination source(s)  80  (concerning parameters such as wavelength, power, size, type etc.), with respect to optical elements  116  (concerning parameters such as their presence, type, optical configuration, dimensions and pitch, coatings etc.), and with respect to cavities  110  (concerning parameters such as dimensions, form and design, pinhole shape and size, internal coatings, spacing or pitch between the cavities etc.). Further optimization may be carried out with respect to overall optical performance (at the LCD level), illumination-use efficiency and other parameters such as dimensions, complexity and costs. 
     In certain embodiments, multiple illumination source(s)  80  may be positioned within respective multiple internally reflective cavities  110 , one illumination source  80  in each internally reflective cavity  110 . Internally reflective cavities  110  may be configured to have any of a range of shapes, possibly determined by efficiency and production configurations. As a non-limiting example,  FIG. 4  illustrates dome shaped internally reflective cavities  110 , having reflective domes  110 A and reflective bases  110 B, with pinpoint openings  114  at the tops of respective domes  110 A. In certain embodiments, internally reflective cavities  110  may have a common base (e.g., corresponding to bases  110 B) on a plane parallel to the plane of pinpoint openings  114 , and possibly parallel to array  118  of optical elements  116  such as array  118  of lenslets  116 . 
     In certain embodiments, internally reflective cavities  110  may be triangularly shaped, with bases  110 B and pinpoint openings  114  at the triangle tops (not shown). In certain embodiments, internally reflective cavities  110  may be box shaped, with bases  110 B and pinpoint openings  114  at the box tops, on a plane parallel to bases  110 B. 
       FIGS. 5A-5J  are high-level schematic illustrations of illumination units  122  and light source layers  400 , according to some embodiments of the invention. Various embodiments comprise internally reflective cavities  110  having different shapes (e.g., dome-shaped in  FIGS. 5A and 5C , spheroid or ellipsoid in  FIG. 5B , rectangular, or box-shaped, in  FIG. 5D , triangular in  FIG. 5E  and various frustal forms such as truncated cones, truncated pyramids or related forms, illustrated schematically in  FIG. 5F-5J ); various configurations of supports  113  configured to mechanically stabilize light source layers  400  (and/or illumination units  122 ), supporting, e.g., each illumination unit  122  ( FIGS. 5A, 5B, 5C, 5D ) or groups of illumination units  122  ( FIG. 5C ). In certain embodiments, supports  113  may be configured to fixate a configured position of array  118  of optical elements  116  with respect to pinpoint openings  114  to optimize performance of backlight unit  300  and/or LCD  100 . Heat dissipation elements  124  may be configured and positioned to remove heat from illumination source  80 , e.g., along bases  110 B of illumination units  122  (see  FIG. 4 ). Pinpoint openings  114  may be designed to have different shapes, such as points (e.g., as illustrated in  FIGS. 5A-5E, 5I and 5J ), elongated tubes (e.g., as illustrated in  FIGS. 5F and 5H ) and/or cone or frustum shaped (e.g., as illustrated in  FIG. 5G ), configured to optimize illumination units  122  with respect to the collimation of illumination provided thereby, in cooperation with optical elements  116 . In certain embodiments, a polarizer  119  may be part of illumination units  122  and configured to regulate collimated illumination using specified polarization directions, and possibly increase the degree of collimation of illumination  120  by removing less collimated radiation in different polarization direction(s). In certain embodiments, polarizer  119  may be configured to supplement or even replace polarizer  202  in LCD panel  200 . Supports  113  may be further configured to support polarizer  119 , which may be common to multiple illumination units  122 , possibly to the whole of light source layer  400 . Polarizer  119  may be set and be control for each one or groups of illumination units  122  (see  FIGS. 5I, 5J , respectively) or one polarizer  119  may be provided for whole of light source layer  400 . Supports  113  may be further configured to stabilize a distance between polarizer  119  and array  118  of lenslets  116 . 
       FIG. 6A  is a high-level schematic illustration of light source layer  400  with lateral illumination source(s)  80  and common internally reflective cavity(ies)  110  having multiple pinpoint openings  114 , configured to provide collimated backlight illumination  120 , according to some embodiments of the invention. At least one illumination source  80  may be positioned on an edge of backlight unit  300 , in optical communication with one or more internally reflective cavity  110 , which may comprise a plurality of pinpoint openings  114 . Array  118  of optical elements  116  (e.g., lenslets) may be set in parallel to one or more internally reflective cavity  110  and/or in parallel to the plane of pinpoint openings  114  (e.g., with pinpoint openings  114  at the focal points of lenslets  116 ) to collimate illumination delivered by lateral illumination source(s)  80  through one or more internally reflective cavity  110  (indicated as internal broken arrows) and out through pinpoint openings  114 . In certain embodiments, one or more internally reflective cavity  110  may comprise single internally reflective cavity  110  with all pinpoint openings  114 . 
       FIG. 6B  is a high-level schematic illustration of light source layer  400  with multiple pinpoint openings  114  and associated optical elements  116  (e.g., lenslets) for each illumination source  80  and internally reflective cavity  110 , configured to provide collimated backlight illumination  120 , according to some embodiments of the invention. Multiple illumination units  122  may each comprise multiple pinpoint openings  114  and associated optical elements  116  (e.g., lenslets) for each illumination source  80  and internally reflective cavity  110 . 
       FIGS. 7A-7F  are high-level schematic illustrations of illumination units  122 , according to some embodiments of the invention. 
     In certain embodiments, a designed optical element  116  such as a serrated lens (see e.g.,  FIG. 7A ), may be configured to deliver collimated radiation  120  by collimating radiation from illumination source(s)  80 , possibly without any additional optical elements such as lenslets. In certain embodiments, a cavity  110 C between illumination source(s)  80  and designed optical element  116  may be at least partly internally reflective, e.g., having a base reflector (not shown). Designed optical element  116  may be molded onto supports  113  of illumination units  122 , e.g., during a molding process thereof. 
     In certain embodiments, a concave lens  111  or another designed optical element  111  may be configured to regulate the radiation distribution within cavity  110 C, which may partly reflective (e.g., using reflector  111 A, see  FIG. 7B ). Cavity  110 C may have top reflective member  110 A (e.g., a flat surface, a dome etc., see e.g.  FIGS. 4 and 5A-6B ) or may be defined directly by optical element(s)  116 , possibly comprising sub elements  116 A such as micro lenses within transparent surface  116 B. Designed optical element  111  may be configured to define the dispersion of radiation within cavity  110 C to optimize collimated illumination  120 . For example, designed optical element  111  may be configured to provide homogeneous illumination to lenslets  116  and/or to provide homogeneous collimated illumination  120 . 
     Certain embodiments, illustrated schematically in  FIGS. 7B-7F  may comprise internally reflecting cavity  110  between reflector  111 A and lenslet  116  and/or optical elements  116  comprising lenslets  116 A within transparent layer  116 B, as illustrated schematically in  FIG. 7B , and/or internally reflecting cavity  110  between reflector  111 A and reflective perforated elements  110 D-G, illustrated schematically in  FIGS. 7C-7F , respectively. 
     In certain embodiments, optical elements  116  may be compound and comprise multiple sub elements  116 A, e.g., micro-lenses produced in different sizes and orientations, possibly with transparent layer  116 B to provide collimation requirements. 
     In certain embodiments, illumination units  122  may comprise reflective perforated elements  110 D-G limiting internally reflecting cavities  110  and having perforations  114 , with element design and perforations design configured to deliver radiation to optical elements  116  in a way which optimizes collimated illumination  120 . 
     Non-limiting examples include  FIG. 7C  illustrating reflective perforated elements  110 D having variable density of perforations  114 , having sparse perforations in a central region  114 A of reflective perforated element  110 D and denser perforations in peripheral regions  114 B of reflective perforated element  110 D. Perforation density may vary continuously and be coordinated with the design of optical elements  116  and their sub elements. 
     Non-limiting examples include  FIG. 7D  illustrating reflective perforated elements  110 E having variable density and size of perforations  114 , having dense and narrow perforations in a central region  114 C of reflective perforated element  110 E and sparser and broader perforations in peripheral regions  114 D of reflective perforated element  110 E. Perforation size and density may vary continuously and be coordinated with the design of optical elements  116  and their sub elements. 
     Non-limiting examples include  FIGS. 7E and 7F  illustrating reflective perforated elements  110 F having variable density of perforations  114  (e.g., in regions  114 E,  114 F), and designed reflective sub-elements of reflective perforated elements  110 F, e.g., having prism or dome shapes (illustrated schematically in  FIGS. 7E and 7F  respectively), possibly being reflective elements to further optimizes collimated illumination  120 , e.g., make it more homogenous and/or increase the efficiency of illumination units  122 . Sub-elements design and perforation size and density may vary continuously and be coordinated with the design of optical elements  116  and their sub elements. 
     Optionally, illumination units  122  may further comprise a reflector  111 A configured to reflect radiation towards the LCD panel and possibly support lens  111  mechanically. 
     In certain embodiments, optical elements  116  may be designed using the Fresnel lens design principle, to yield flat lenslets with facets that provide good collimation of radiation from illumination sources  80  (e.g., in  FIGS. 3A-3C ) and/or openings  114  (e.g., in  FIGS. 4-7F ). 
     In certain embodiments, sub elements  116 A (which are embedded within transparent layer  116 B to form optical elements  116 ) may be designed to have different sizes and different distances from respective pinholes  114 . 
     In any of the disclosed embodiments, diffractive optics may be used to direct collimated illumination  120  directly at specified regions of interest (ROIs) to increase efficiency and brightness substantially. 
     In certain embodiments, the opening area of pinpoint openings  114  may be below a specified size, such as 1 m 2  or much higher, such as 10 mm 2  per opening  114 . 
     In certain embodiments, pinpoint openings  114  may be controlled by shutters (not shown) which are configured to control the extent of illumination from each and/or a group of pinpoint openings  114 , e.g., to implement local dimming for supporting high dynamic range (HDR) displays. Control of pinpoint openings  114  may be carried out locally, e.g., by mechanical, electrical and/or optical shutters; and/or, as illumination  120  is collimated, may be carried out remotely from pinpoint openings  114  e.g., by modulating the operation of LC layer  210  according to required attenuation parameters. 
     In certain embodiments, the sizes of optical elements  116  (e.g., lenslets) may be e.g., 100μ 2 -50 cm 2  per element  116  such as lenslet. 
     In certain embodiments, optical elements  116  may comprise diffractive optics configured to collimate radiation exiting cavities  110  through pinpoint openings  114 . In certain embodiments, pinpoint openings  114  may be set off the focal points of optical elements  116 . 
     In certain embodiments, the volumes of internally reflective cavities  110  may be e.g., 1 mm 3 -200 cm 3 , per single cavity  110  illumination units  122  (see e.g.,  FIG. 4 ). Internally reflective cavities  110  may have much larger volumes when having multiple pinpoint openings  114  and/or associated with multiple optical elements  116  (see e.g.,  FIGS. 6A, 6B ) (100μ 2 -50 cm 2 ). 
     In certain embodiments, any of illumination source  80  may comprise one or more blue LEDs. 
     In certain embodiments, any of internally reflective cavities  110 , pinpoint openings  114 , optical elements  116 , illumination sources  80  and light source layer  400  may be produced by lithographic methods, micromechanical processing, and/or any process applicable to ICs (integrated circuits) and/or MEMS (micro-electro-mechanical systems). 
     Certain embodiments comprise LCD  100  comprising any of disclosed backlight units  300 , possibly with LCD panel  200  thereof comprising, sequentially, LC module  210 , and, separate or integrated, color conversion layer  130  and color filters layer  220  (see  FIGS. 1C and 2M-2S ). 
       FIGS. 8A-E  schematically illustrates white point adjustment  145  that extends a display lifetime of display  100 , according to some embodiments of the invention. Illustration  145 A ( FIG. 8A ) shows an example for EC-154 (Z 3  with JK-71+Z 2  with ES-61, see line 9 in Table 1 of U.S. Pat. No. 9,868,859, incorporated herein by reference) sample color gamut compared to DCI (digital cinema initiatives) P3 cinema standard color gamut over the CIE 1931 color space with a white region indicated by WR and a white point denoted by WP, having a diameter which is denoted by d and may be e.g., 0.01 in the diagram&#39;s x coordinates. The region WP denotes the range within which display  100  is considered to be within the specifications with respect to its color performance. Once the actual white point of display  100  is outside region WP, even when it remains within a possibly larger region WR corresponding to white color, display  100  is considered over its lifetime and not operating according to specifications. In a typical setting, films  130  are configured to provide a white point  141 A at the center of the region WP and as with time RBF compounds  115  or other color conversion elements degrade  141  (indicated in graph  145 C,  FIG. 8C , showing the emission spectrum of film  130  by arrows which are denoted Time) white point  141 A moves until it exits region WP and the display is considered over its lifetime. The degradation in terms of the distance on color diagram  145 A is illustrated in graph  145 B ( FIG. 8B ) using non-limiting experimental data of the distance from point  141 A over the operation time (in arbitrary units, a.u., scaled to 1000) of the display. In some embodiments of display  100  however, film(s)  130  may be fine-tuned to have the exact white point within region WP but at a point  141 B on the edge of it which is opposite to the direction of degradation marked by arrow  141  (illustrations  145 D,  145 E in  FIGS. 8D and 8E , respectively, show an enlarged view of white region WR). Such fine tuning to white point  141 A enables the display characteristics to be changed to ca. double as much as with white point  141 A while staying within the specified region WP, and as a result ca. double the lifetime of display  100 . The semi-quantitative example in graph  145 B illustrates an increase in display lifetime, from ca. 600 a.u. to ca. 900 a.u., when changing the white-point from  141 A to  141 B. As a result of the change, instead of display starting exactly white and becoming somewhat colder white (see graph  145 C, the green and red components decrease with time and correspondingly the blue component increases), display  100  starts a bit warmer, goes through the exact white point and ends a bit colder, with a longer lifetime overall. Setting a higher concentration of RBF compounds  115  or other color conversion elements in film  130  thus enables effective lengthening of the lifetime of display  100 . Examples for increased dye concentrations may be up to 20% for green dyes and up to 40% for red dyes. Some embodiments comprising raising the concentration of one or more types of dyes (such as red-fluorescent and green-fluorescent RBF compounds  115 ), to fine tune the exact white point of display  100 . The increased concentration of dyes may result in a somewhat warmer white within specified region WP. Illustrations  145 D and  145 E ( FIGS. 8D, 8E ) emphasize that white point  141 B may be selected according to known degradation  141  of color conversion film  130  with respect to specified white point WP, for any type of film  130 , including films using organic (non-rhodamine-based) or inorganic fluorescent compounds, quantum dots etc. 
     Polarization 
     Film  130  may comprise at least one layer  134  with red fluorescent RBF compound, or at least one layer  134  with red fluorescent RBF compound and thereupon at least one layer  132  with green fluorescent RBF compound. At least one of the layers of film  130  may be configured to exhibit polarization properties. 
       FIG. 9  is an illustration example of polarization anisotropy of film(s)  130  with RBF compound(s)  115 , according to some embodiments of the invention. The inventors have found out that in certain cases, during the embedding of RBF compound(s)  115  in film  130 , the molecules self-assemble to affect light polarization, providing at least partially polarized light emission. Process parameters may be adjusted to enhance the degree of polarization of light emitted from film  130 , e.g., by providing conditions that cause self-assembly to occur to a larger extent. Without being bound by theory, the inventors suggest that the polarized emission of fluorescence is related to the limitations on rotational motions of the macromolecular fluorophores during the lifetime of the excitation state (limitations relating to their size, shape, degree of aggregation and binding, and local environment parameters such as solvent, local viscosity and phase transition). The inventors have further found out that these limitations may be at least partially controlled by the preparation process of film  130  which may thus be used to enhance illumination polarization in display  100 . 
     For example,  FIG. 9  illustrates polarization and anisotropy measurement of films  130  prepared with red and green fluorescent compounds (specifically, green coumarin 6 dye and rhodamine 101 red molecular dyes, using the sol gel process). In the example, the anisotropy values range between 0.3-0.5 at the emission wavelengths. 
     Films  130  having different red and/or green fluorescent RBF compound  115 , as well as films  130  prepared by UV curing also present polarization properties and may be used in device  100  to enhance or at least partially replace polarizer films (e.g.,  302 ,  202 ,  256  etc. see  FIGS. 2A and 2B ). 
     Some embodiments comprise any type of color conversion film  130 , which may comprise color conversion elements other than RBF compounds  115 , such as organic (non-rhodamine-based) or inorganic fluorescent compounds, quantum dots etc.—configured to provide polarize fluorescent radiation as disclosed above. Such films  130  may be used to enhance or at least partially replace polarizer films in respective displays  100 . 
     Red Enhancement 
       FIG. 10A  is a high level schematic illustration of red (R) enhancement in devices with white illumination, according to some embodiments of the invention.  FIG. 10A  schematically illustrates a typical white light spectrum  80 B- 1  (of white illumination source  80 B), optimized to provide RGB illumination  120  in prior art backlight units, and typical ranges ( 85 R,  85 G,  85 B) of RGB filters  220  in LCD panel  200  (see  FIGS. 2B, 2C and 2D ). The inventors have noticed that while white light spectrum  80 B- 1  is optimized with respect to the ratio between its blue section ( 80 B-B) and its yellow section ( 80 B-Y), it is deficient with respect to the relative position of the yellow region ( 80 B-Y) and G and R ranges  85 G,  85 R, respectively (corresponding, for example, to B, G, R denoted in  FIGS. 2C and 2D ). Indeed, much of the illumination energy in yellow region  80 B-Y is filtered out and thus wasted in the operation of the display and moreover, color cross talk (part of the yellow orange might go to the green filter and some of the green-yellow to the red filter) which degrades the color gamut. The inventors have further found out that using film(s)  130  with red-fluorescent RBF compound(s)  115  (layer(s)  134 ) shifts  132 A at least some of the illumination energy in yellow region  80 B-Y into red region  85 R which is passed by the R (red) filter in LCD panel  200  and is therefore not wasted. Using film(s)  130  thus increases the energy efficiency of display  100  and possibly improves its color gamut. 
     As illustrated in U.S. Provisional Application No. 62/488,767, incorporated herein by reference in its entirety, RGB spectrum  120  improvements may be provided by backlight unit  300  using film(s)  130 . In the specific non-limiting example, films  130  were produced by UV curing process  700 . White light spectrum  80 B- 1  is somewhat different from the one illustrated in  FIG. 10A  due to the difference in white light source  80 B, yet also exhibits a peak in the yellow region. In contrast, emission spectrum  134 - 1  of film  130  (made of layer(s)  134 —specifically—one to three layers with JK32 (0.02-0.3 mg/ml for each layer, spectra shown without LCD color filter effects) in backlight unit  300  splits the yellow peak of white light spectrum  80 B- 1  into a green and a red peak, each within the range of the corresponding G and R filters, thereby increasing the efficiency, reducing the color cross talk and improving the gamut of display  100 , e.g., by providing a more saturated (narrower FWHM, full width at half maximum) red and at longer red wavelength. In the example, the characteristics of the green and red peaks of emission spectrum  134 - 1  of film  130  were 618±5 nm peak with FWHM of ca. 60 nm for the red peak and 518±5 nm peak with FWHM of ca. 50 nm for the green peak; with the quantum yield of film  130  being between 70-90% and the lifetime at device level being between 20,000-50,000 hours for multiple repeats. 
     Some embodiments comprise any type of color conversion film  130 , which may comprise color conversion elements other than RBF compounds  115 , such as organic (non-rhodamine-based) or inorganic fluorescent compounds, quantum dots etc.—configured to provide polarize fluorescent radiation as disclosed above. Such films  130  may be used for RGB spectra  120  by providing shifts  132 A of yellow illumination  80 B-Y into the red region of corresponding R color filters  220  in respective displays  100 . 
     Green Enhancement 
     In some embodiments, films  130  may be configured to provide green enhancement, using only or mostly green-fluorescent compounds. 
       FIG. 10B  is a high level schematic illustration of green (G) and red (R) enhancement in devices with white illumination, according to some embodiments of the invention.  FIG. 10B  schematically illustrates a typical white light spectrum  80 B- 1  (of white illumination source  80 B), optimized to provide RGB illumination  120  in prior art backlight units, and typical ranges ( 86 R,  86 G,  86 B) of RGB filters  220  in LCD panel  210  (see  FIGS. 2B-2D ). In addition to red enhancement illustrated and disclosed in  FIGS. 5A and 5B , the inventors have further found that further enhancement may be achieved by shifting at least some of a cyan component  80 B-C in white illumination  80 B into the green region (and possibly at partly further into the red region), as typically much of the illumination energy in cyan region  80 B-C is filtered out by RGB filters  220  and thus wasted in the operation of the display and moreover, color cross talk (part of the greenish cyan might go to the green filter and some of the bluish cyan to the blue filter) degrades the color gamut. The inventors have further found that using film(s)  130  with green-fluorescent RBF compound(s)  115  (layer(s)  132 ) shifts  132 B at least some of the illumination energy in cyan region  80 B-C into green region  86 G which is passed by G (green) filter  220  in LCD panel  210  and is therefore not wasted. Using film(s)  130  thus increases the energy efficiency of display  100  and possibly improves its color gamut. 
     Certain embodiments comprise LCD  100  comprising backlight unit  300  configured to provide white illumination  80 B and LCD panel  210  receiving illumination (radiation) from backlight unit  300  and comprising, sequentially with respect to the received illumination: polarizing film  202 ,  258 , liquid crystal layer  261 , analyzer film  262 , color conversion film  130  (possibly patterned), RGB color filter layer  220 , and protective layer  266 , possibly with additional analyzer film  256  between RGB color filter layer  220  and protective layer  266 . Color conversion film  130  may comprise rhodamine-based fluorescent (RBF) compounds  115  selected to absorb illumination from backlight unit  300  and have an R emission peak and a G emission peak. In any of the embodiments, assistant dyes  117  may be further integrated in the color conversion film  130  and/or in a separate layer. Green enhancement in white LED applications may improve the efficiency and/or intensity of green and/or red filters  220 . 
     Assistant Dyes and Spectrum Shaping 
       FIGS. 10C-10E  are high level schematic illustrations of spectrum shaping using assistant dyes  117 , according to some embodiments of the invention. One or more assistant dye(s)  117  may be used, independently and/or integrated in color conversion layer(s)  130  (and/or  132 ,  133 ,  134 ) and/or integrated in RGB color filters  220  and/or integrated in integrated RGB color filters  220  (having color conversion compounds  115 ). Assistant dyes  117  are characterized herein by their absorption curve  178  and their emission (e.g., fluorescence, possibly phosphorescence) curve  179 , which are shown in  FIGS. 10C-10E  in a schematic, non-limiting manner as triangles. Clearly realistic curves may be used to optimize displays  100  according to the disclosed principles. It is further noted that absorption and emission curves are used herein interchangeably with the terms absorption and emission peaks, respectively, in a non-limiting manner, to refer to complementary spectral characteristics of disclosed dyes  115  and/or  117 . Examples for assistant dyes  117  are provided above, by Formulas (A1), (A1a), (A2) and (A3) and by compounds A1-, A1-2, A1-3, A2-1, A2-2 and A3-1. 
     Certain embodiments comprise shaping spectral distribution of illumination  80  delivered to RGB filters  220  using fluorescent compound(s) having one or more absorption peaks outside a respective transmission region of one of RGB filters  220  and one or more fluorescence peaks, at least one of which being inside the respective transmission region of the RGB filter.  FIG. 10C  illustrates an example for the R color filter, providing certain embodiments with one assistant dye  117  having an absorption curve  178  outside the transmitted range of the R filter and an intermediate emission curve  179  which partly overlaps absorption curve  178  of RBF compound  115  (in the illustrated case, red-fluorescent RBF compound  115 R) to enhance the illumination absorbed thereby. In certain embodiments, multiple assistant dyes  117  may be used, having a series of absorption and emission curves (each emission curve  179  at least partly overlapping absorption curve  178  of next assistant dye  117  in the series), which form a photon delivery chain from filtered to unfiltered regions of the spectrum. 
     Certain embodiments comprise LCD  100  comprising backlight unit  300  configured to provide illumination  120  and LCD panel  210  receiving illumination  120  from backlight unit  300  and comprising, sequentially with respect to the received illumination: polarizing film  202 ,  258  liquid crystal layer  261 , analyzer film  262 , color conversion film  130  (possibly patterned), RGB color filter layer  220 , and protective layer  266 , possibly with additional analyzer film  256  between RGB color filter layer  220  and protective layer  266 . Color conversion film  130  may comprise a plurality of fluorescent compounds  115 ,  117  selected to have, when embedded in color conversion film  130 , a series of absorption peaks (or curves)  178  outside a respective transmission region of one of RGB filters  220  and respective series of fluorescence (or phosphorescence) peaks (or curves)  179 , one of fluorescence peaks  179  being inside the respective transmission region of RGB filter  220  (e.g., fluorescence peak of RBF compound  115 ) and at least one other fluorescence peak being intermediate between the fluorescence peak inside the respective transmission region and the absorption peaks, forming a photon delivery chain from filtered to unfiltered regions of the spectrum. 
     Certain embodiments comprise shaping a spectral distribution of illumination  120  delivered to RGB filters  220  of LCD  100  by using at least one fluorescent compound  115  in color conversion film  130 , which is selected to have, when embedded in color conversion film  130 , absorption peak  178  outside a respective transmission region of one of RGB filters  220  and fluorescence peak  179  inside the respective transmission region of RGB filter  220 . Correspondingly, certain embodiments comprise LCD  100  comprising backlight unit  300  configured to provide illumination  120  and LCD panel  210  receiving illumination (radiation)  120  from backlight unit  300  and comprising, sequentially with respect to the received illumination: polarizing film  202 ,  258  liquid crystal layer  261 , analyzer film  262 , color conversion film  130  (possibly patterned), RGB color filter layer  220 , and protective layer  266 , possibly with additional analyzer film  256  between RGB color filter layer  220  and protective layer  266 . Color conversion film  130  comprises at least one fluorescent compound  115  selected to have, when embedded in color conversion film  130 , absorption peak  178  outside a respective transmission region of one of RGB filters  220  and fluorescence peak  179  inside the respective transmission region of RGB filter  220 . 
     Certain embodiments comprise shaping a spectral distribution of illumination delivered to RGB filters  220  of LCD  100  by using at least one fluorescent compound  115  and/or at least one assistant dye  117  in color conversion film  130 , selected to have, when embedded in color conversion film  130 , absorption curve  178  and fluorescence curve  179  selected to re-shape a spectral region of illumination  120  within a respective transmission region of at least one of RGB filters  220  to decrease FWHM (full width at half maximum) of the illumination in the respective transmission region. Correspondingly, certain embodiments comprise LCD  100  comprising backlight unit  300  configured to provide illumination  120  and LCD panel  210  receiving illumination  80  from backlight unit  300  and comprising, sequentially with respect to the received illumination: polarizing film  202 ,  258  liquid crystal layer  261 , analyzer film  262 , color conversion film  130  (possibly patterned), RGB color filter layer  220 , and protective layer  266 , possibly with additional analyzer film  256  between RGB color filter layer  220  and protective layer  266 . Color conversion film  130  comprises at least one fluorescent compound  115  and/or at least one assistant dye  117  having, when embedded in color conversion film  130 , absorption curve  178  and fluorescence curve  179 —selected to re-shape a spectral region of illumination  120  within a respective transmission region of at least one of RGB filters  220  to decrease FWHM of the illumination in the respective transmission region. 
     As illustrates e.g., in  FIG. 10E , modified illumination  80 - 1  may comprise components  80 - 1 (B),  80 - 1 (G),  80 - 1 (R) in the transmission regions of B, G, R color filters  220 , respectively, which are shaped according to requirements by one or more fluorescent compound(s)  115  and/or assistant dye(s)  117 , e.g., by removal of spectral sections by absorption (e.g., any of sections  178 A(B),  178 A(G), possibly also a section in the red section (not shown), respectively) and/or by enhancement of spectral sections by emission (e.g., any of sections  179 A(B),  179 A(G),  179 A(R), respectively)—as disclosed above. 
     In certain embodiments, LCD  100  may utilize quantum dot technology, e.g., with color conversion film  130  being based on quantum dots. Similar ideas of assistant dyes and green and red enhancement may be applied to quantum-dots-based display. 
     In certain embodiments, LCD  100  may utilize color conversion films  130  having asymmetric emission spectrum  76 . Color conversion film  130  may further comprise one or more fluorescent compound(s)  115  and/or assistant dye(s)  117  selected to reduce a level of asymmetry in an emission spectrum of color conversion film  130 . For example (see WIPO Publication No. WO 2018/042437 and U.S. Publication Nos. 2018/0072892 and 2018/0039131, incorporated herein by reference in their entirety), absorption spectrum  178  of assistant dye  117  may be selected to be reversely asymmetric, to reduce the level of asymmetry with spectral regions of RGB color filter(s)  220 , e.g., B color filter  220  as illustrated in the non-limiting example. 
     In any of the disclosed embodiments, one or more fluorescent compound(s)  115  and/or one or more assistant dye(s)  117  may be used, independently, and/or integrated in color conversion layer(s)  130  (and/or layers  132 ,  133 ,  134 ) and/or integrated in RGB color filters  220  and/or integrated in integrated RGB color filters  220  (having color conversion compounds  115 ). 
     In any of the disclosed embodiments, one or more fluorescent compound(s)  115  and/or one or more assistant dye(s)  117  may be further be used to adjust the white point of LCD display  100 , as illustrated e.g., in  FIGS. 8C-8E . 
     Spectrum Enhancement and Shaping 
     WIPO Publication No. WO 2018/042437 and U.S. Publication Nos. 2018/0072892 and 2018/0039131, which are incorporated herein by reference in their entirety, provide examples (see e.g.,  FIGS. 14A-14I ) for illumination and absorption spectra, such as white illumination spectrum  80 , absorption spectra  178  of red-fluorescent RBF compound  115  listed above as RS285, absorption spectra  178  of green-fluorescent RBF compound  115  listed above as ES144, absorption spectra  178  and emission spectra  179  of two non-limiting examples for assistant dyes  117 —5-FAM and 5-Carboxyfluorescein (respectively), for which fluorescence enhancement by assistant dyes  117  is illustrated schematically in  FIG. 10D , blue illumination spectrum  80 A, absorption and emission spectra  178 ,  179 , respectively, of assistant dye  117  (e.g., 5-FAM) as well as absorption curve  178  of red-fluorescent RBF compound  115  listed above as RS285. It is noted that in case of blue illumination spectrum  80 A, phosphorous compound(s) (see above) may be selected to enhance the correspondence between the resulting illumination spectrum and absorption spectra  178  of RBF and assistant dyes  115 ,  117  (see also  FIG. 2R  above for spatial adjustment of illumination to red filter  220  only). 
     Various embodiments comprise methods of diverting illumination from unused spectral regions into illumination that passes through color filters  220 , using one or more assistant dyes  117  which absorb unused illumination and emit usable illumination (or illumination which is further absorbed and emitted in a spectral range that is transmitted through color filter  220 ). It is noted that assistant dyes  117  may be selected to provide required absorption and emission spectra while maintaining good integrability in color conversion film  130  and long photostability. For example, HPTS; pyranine (8-Hydroxypyrene-1,3,6-Trisulfonic Acid, Trisodium Salt), may be used as assistant dye  117 , having an absorption peak at shorter wavelengths than 5-FAM (e.g., at ca. 450 nm vs. 490 nm), with a similar emission peak at 520-530 nm (depending on embedding conditions). 
       FIG. 10D  illustrates schematically fluorescence enhancement by assistant dyes  117 , according to some embodiments of the invention. Assistant dyes  117  may be configured and used to transfer radiation from the green region of the spectrum to the red region of the spectrum by absorbing emitted green radiation and emitting the absorbed radiation in the absorption region of the red-fluorescent dye, the transfer is illustrated schematically in  FIG. 10D  by arrow  117 C from overlap region  117 A through overlap region  117 B to the red emission region. 
     For example, relating as a non-limiting example to 5-FAM and 5-Carboxyfluorescein, the inventors estimate their effective quantum yield at ca. 90%, with high absorption coefficients of ca. 100,000/mol/L/gr. Taking RS285 and ES144 as non-limiting examples for green-fluorescent and red-fluorescent RBF compounds  115 (G),  115 (R), respectively, the inventors estimate an overlap area  117 A (illustrated schematically as a broken-line triangle in  FIG. 141 ) between the emission of green dye (for example RS285)  115 (G) with absorbance  178  of 5-FAM  117  as being around 10-30%; and overlap area  117 B (illustrated schematically as a broken-line triangle in  FIG. 141 ) between emission  179  of 5-FAM  117  and absorbance  178  ( 115 R) of red dye (for example ES144)  115 (R) over 80%. Using these estimations, the extent of radiation  117 C (illustrated schematically as an arrow from green to red) transferred from the green region to the red region of the spectrum is at least 10-30% (of the 5-FAM absorbance) times 90% (of the 5-FAM quantum yield) times 80% (of the overlap between 5-FAM emission and red dye absorption)—resulting between 7 and 20%. Moreover, the FWHM of the green fluorescence  115 (G) (e.g., by RS285) becomes narrower by estimated 5-20 nm. The inventors estimate that the intensity of the red fluorescence  115 (R) (e.g., by ES144) may be increased by 10-30% compared to not using assisting dyes  117 . Hence, advantageously, assisting dyes  117  improve the device performance with respect to the color gamut, efficiency and/or intensity. 
     It is noted that 5-FAM and 5-Carboxyfluorescein may be used as assistant dyes  117  in the green region, and compounds such as red rhodamines (e.g., rhodamine 12, rhodamine 101 from Atto-Tec®, perylene dye F300 from Lumogen® etc.) may be used as assistant dyes  117  in the red region. 
     Rhodamine-Based Fluorescent Molecules 
     A wide range of fluorescent organic molecules may be incorporated in films  130 , such as materials of the xanthene dye family like fluorescein, rhodamine derivatives and coumarin family dyes, as well as various inorganic fluorescent materials. In the following, explicit examples of rhodamine-based derivatives, RBF compounds  115 , are presented in detail, in a non-limiting manner. 
     Red-Fluorescent RBF Compounds 
     Some embodiments of red-fluorescent RBF compounds  115  are defined by Formula 1. 
     
       
         
         
             
             
         
       
         
         
           
             wherein 
             R 1  is COOR, NO 2 , COR, COSR, CO(N-heterocycle), CON(R) 2 , or CN; 
             R 2  each is independently selected from H, halide, N(R) 2 , COR, CN, CON(R) 2 , CO(N-heterocycle), NCO, NCS, OR, SR, SO 3 H, SO 3 M and COOR; 
             R 3  each is independently selected from H, halide, N(R) 2 , COR, CN, CON(R) 2 , CO(N-heterocycle), NCO, NCS, OR, SR, SO 3 H, SO 3 M and COOR; 
             R 4 -R 16  and R 4′ -R 16′  are each independently selected from H, CF3, alkyl, haloalkyl, cycloalkyl, heterocycloalkyl, alkenyl, alkynyl, aryl, benzyl, halide, NO 2 , OR, N(R) 2 , COR, CN, CON(R) 2 , CO(N-Heterocycle) and COOR; 
             R is H, alkyl, cycloalkyl, heterocycloalkyl, alkenyl, alkynyl, aryl, benzyl, —(CH 2 CH 2 O) r CH 2 CH 2 OH, —(CH 2 ) p OC(O)NH(CH 2 ) q Si(Oalkyl) 3 , —(CH 2 ) p OC(O)CH═CH 2  or —(CH 2 ) p Si(Oalkyl) 3 ; 
             n and m are each independently an integer between 1-4; 
             p and q are each independently an integer between 1-6; 
             r is an integer between 0-10; 
             M is a monovalent cation; and 
             X is an anion. 
           
         
       
    
     Alternatively, or complementarily, some embodiments of red-fluorescent RBF compounds  115  are defined by Formula 1, wherein 
     R 1  is halide, alkyl, haloalkyl, COOR, NO 2 , COR, COSR, CON(R) 2 , CO(N-heterocycle) or CN;
 
R 2  each is independently selected from H, halide, N(R) 2 , COR, CN, CON(R) 2 , CO(N-heterocycle), NCO, NCS, OR, SR, SO 3 H, SO 3 M and COOZ;
 
R 3  each is independently selected from H, halide, N(R) 2 , COR, CN, CON(R) 2 , CO(N-heterocycle), NCO, NCS, OR, SR, SO 3 H, SO 3 M and COOZ;
 
R 4 -R 7 , R 13 -R 16 , R 4′ -R 7′  and R 13′ -R 16′  are each independently selected from H, alkyl, alkenyl, alkynyl, epoxide, alkylated epoxide, azide, cycloalkyl, heterocycloalkyl, aryl, benzyl, halide, NO 2 , SR, OR, N(R) 2 , COR, CN, CON(R) 2 , CO(N-heterocycle) and COOR;
 
R 8 -R 9 , R 11 -R 12 , R 8′ -R 9′  and R 11′ -R 12′  are each independently selected from absent, H, alkyl, alkenyl, alkynyl, epoxide, alkylated epoxide, azide, cycloalkyl, heterocycloalkyl, aryl, benzyl, halide, NO 2 , SR, OR, N(R) 2 , COR, CN, CON(R) 2 , CO(N-heterocycle) and COOR;
 
R 10  and R 10′  are each independently selected from H, alkyl, alkenyl, alkynyl, epoxide, alkylated epoxide, alkylated azide, azide, SO 3 H, SO 3 M, cycloalkyl, heterocycloalkyl, aryl, benzyl, halide, NO 2 , SR, OR, N(R) 2 , COR, CN, CON(R) 2 , CO(N-heterocycle) and COOR;
 
R is H, haloalkyl, alkyl, cycloalkyl, heterocycloalkyl, aryl, benzyl, —(CH 2 CH 2 O) r CH 2 CH 2 OH, —(CH 2 ) p OC(O)NH(CH 2 ) q Si(Oalkyl) 3 , (CH 2 ) p OC(O)NH(CH 2 ) q Si(halide) 3 , —(CH 2 ) p OC(O)CH═CH 2 , —(CH 2 ) p OC(O)C(CH 3 )═CH 2 , —(CH 2 ) p Si(halide) 3 , alkenyl, alkynyl, alkylated epoxide, alkylated azide, azide, or —(CH 2 ) p Si(Oalkyl) 3 ;
 
Z is alkyl, haloalkyl, alkenyl, alkynyl, alkylated epoxide, cycloalkyl, heterocycloalkyl, aryl, benzyl, —(CH 2 CH 2 O) r CH 2 CH 2 OH, —(CH 2 ) p OC(O)NH(CH 2 ) q Si(Oalkyl) 3 , —(CH 2 ) p OC(O)CH═CH 2 , —(CH 2 ) p OC(O)C(CH 3 )═CH 2 , or —(CH 2 ) p Si(Oalkyl) 3 ;
 
Z 101  is O or C(CH 3 ) 2 ;
 
M is a monovalent cation;
 
n and m are each independently an integer between 1-4;
 
p and q are each independently an integer between 1-6;
 
r is an integer between 0-10;
 
X is an anion;
 
wherein if there is a double bond between the carbons which are substituted by R 8 , R 8′ , R 9  and R 9′ —then R 8  and R 9  are absent or R 8  and R 9′  are absent or R 8′  and R 9  are absent or R 8′  and R 9′  are absent; and
 
wherein if there is a double bond between the carbons which are substituted by R 11 , R 11′ , R 12  and R 12′ —then R 11  and R 12  are absent or R 11  and R 12′  are absent or R 11′  and R 12  are absent or R 11′  and R 12′  are absent.
 
     Additional chemical species which are based on Formula 1 are provided in WIPO Publication No. WO 2018/042437 and U.S. Publication Nos. 2018/0072892 and 2018/0039131, which are incorporated herein by reference in their entirety. 
     The positions of R 1 , (R 2 ) n  and (R 3 ) m  may be selected to be any feasible position with respect to the indicated ring. Any of R 1 , (R 2 ) n  and (R 3 ) m  may be positioned at ortho, meta or para positions with respect to the rest of the molecule, as long as the resulting structure is chemically feasible. Precursors  72  and formulation  74  may be adapted to accommodate and support embodiments of the selected red-fluorescent RBF compound(s) according to the principles disclosed herein. 
     Specific, non-limiting, examples of red-fluorescent RBF compounds  115  which were tested below include compounds denoted ES61, JK32 (shown as JK-32A and/or JK-32B), RS56 (shown as RS56A and/or RS56B), RS106 and RS130, ES118 and ES144. 
     
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
     
     Some embodiments of red-fluorescent RBF compounds are presented in more detail in U.S. Publication Nos. 2018/0072892 and 2018/0039131, and U.S. Pat. No. 9,771,480 and are considered likewise part of the present disclosure. Non-limiting examples are provided in the following variants, numbered 1-11, 9a, 10a, 11a, 20 and 23-26. 
     
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
     
     Green-Fluorescent RBF Compounds 
     Some embodiments of green-fluorescent RBF compounds are defined by Formula 2. 
     
       
         
         
             
             
         
       
     
     wherein
 
R 101  each is independently H, Q 101 , Q 101 , C(O)Q 101 , NQ 101 Q 102 , NO 2 , CN, SQ 101 , —NQ 101 Q 102 CONQ 103 Q 104 , NCO, NCS, —OC(O)OQ 1  or halide;
 
R 102  each is independently H, Q 101 , Q 101 , C(O)Q 101 , NQ 101 Q 102 , NO 2 , CN, SQ 101 , —NQ 101 Q 102 CONQ 103 Q 104 , NCO, NCS, —OC(O)OQ 101  or halide;
 
R 103  each is independently H, Q 101 , Q 101 , C(O)Q 101 , NQ 101 Q 102 , NO 2 , CN, SQ 101 , —NQ 101 Q 102 CONQ 103 Q 104 , NCO, NCS, —OC(O)OQ 101  or halide;
 
R 104 , R 104′ , R 108  and R 108′  are each independently selected from H, alkyl, haloalkyl, heterocycloalkyl, cycloalkyl, aryl and benzyl;
 
R 105  and R 105′  are each independently selected from H, Z′, OQ 101 , C(O)Q 101 , COOQ 101 , CON(Q 101 ) 2 , NQ 101 Q 102 , NO 2 , CN, SO 3   − , SO 3 M, SO 3 H, SQ 101 , —NQ 101 Q 102 CONQ 103 Q 104 , NCO, NCS, alkenyl, alkynyl, epoxide, alkylated epoxide, alkylated azide, azide and halide;
 
R 106 , R 106′ , R 107  and R 107′  are each independently selected from H, Q 101 , Q 101 , C(O)Q 101 , COOQ 101 , CON(Q 101 ) 2 , NQ 101 Q 102 , NO 2 , CN, SO 3   − , SO 3 M, SO 3 H, SQ 101 , —NQ 101 Q 102 CONQ 103 Q 104 , NCO, NCS, alkenyl, alkynyl, epoxide, alkylated epoxide, alkylated azide, azide and halide;
 
R 104  and R 105 , R 104′  and R 105′ , R 104  and R 108  or R 104′  and R 108′  may form together an N-heterocyclic ring wherein said ring is optionally substituted;
 
Q 101  and Q 102  are each independently selected from H, alkyl, haloalkyl, heterocycloalkyl, cycloalkyl, aryl, benzyl, —(CH 2 ) p OC(O)NH(CH 2 ) q Si(Oalkyl) 3 , —(CH 2 ) p OC(O)CH═CH 2 , —(CH 2 ) p OC(O)C(CH 3 )═CH 2 , —(CH 2 ) p Si(Oalkyl) 3 , —(CH 2 ) p OC(O)NH(CH 2 ) q Si(halide) 3 , —(CH 2 ) p Si(halide) 3 , —OC(O)N(H)Q 104 , —OC(S)N(H)Q 104 , —N(H)C(O)N(Q 103 ) 2  and —N(H)C(S)N(Q 103 ).
 
Z 101  is O or C(CH 3 ) 2 ;
 
Z′ is selected from alkyl, haloalkyl, heterocycloalkyl, cycloalkyl, aryl, benzyl, —(CH 2 ) p OC(O)NH(CH 2 ) q Si(Oalkyl) 3 , —(CH 2 ) p OC(O)CH═CH 2 , —(CH 2 ) p OC(O)C(CH 3 )═CH 2 , —(CH 2 ) p Si(Oalkyl) 3 , —(CH 2 ) p OC(O)NH(CH 2 ) q Si(halide) 3 , —(CH 2 ) p Si(halide) 3 , —OC(O)N(H)Q 104 , —OC(S)N(H)Q 104 , —N(H)C(O)N(Q 103 ) 2  and —N(H)C(S)N(Q 103 ).
 
Q 103  and Q 104  are each independently selected from H, alkyl, haloalkyl, heterocycloalkyl, cycloalkyl, aryl and benzyl;
 
M is a monovalent cation;
 
n, m and l are independently an integer between 1-5;
 
p and q are independently an integer between 1-6; and
 
X is an anion.
 
     Additional chemical species which are based on Formula 2 are provided in WIPO Publication No. WO 2018/042437 and U.S. Publication Nos. 2018/0072892 and 2018/0039131, which are incorporated herein by reference in their entirety. For example, certain embodiments having R 108 ═H are provided in these applications and are incorporated herein by reference in their entirety. Also, certain embodiments having R 106 , R 106′ , R 107 , R 107′ , R 108  and R 108′  as H are provided in these applications and are incorporated herein by reference in their entirety, as well as embodiments with R 105  and R 105′  being F, R 104  and R 104′  being CF 3 , and various examples. 
     Specific, non-limiting, examples of green-fluorescent RBF compounds  115  of the invention include compounds represented by the structures below, denoted as JK71 and RS285. 
     
       
         
         
             
             
         
       
     
     (Z)—N-(2,7-difluoro-9-phenyl-6-((2,2,2-trifluoroethyl)amino)-3H-xanthen-3-ylidene)-2,2,2-trifluoroethan-1-aminium methanesulfonate 
     
       
         
         
             
             
         
       
     
     Some embodiments of green-fluorescent RBF compounds are presented in more detail in U.S. Publication Nos. 2018/0057688, 2018/0072892 and 2018/0039131 and are considered likewise part of the present disclosure. Non-limiting examples are provided in the following variants, numbered 12-19 and 21-22. 
     
       
         
         
             
             
         
       
       
         
         
             
             
         
       
     
     An “alkyl” group refers, in some embodiments, to a saturated aliphatic hydrocarbon, including straight-chain or branched-chain. In some embodiments, alkyl is linear or branched. In another embodiment, alkyl is optionally substituted linear or branched. In another embodiment, alkyl is methyl. In another embodiment alkyl is ethyl. In some embodiments, the alkyl group has 1-20 carbons. In another embodiment, the alkyl group has 1-8 carbons. In another embodiment, the alkyl group has 1-7 carbons. In another embodiment, the alkyl group has 1-6 carbons. In another embodiment, non-limiting examples of alkyl groups include methyl, ethyl, propyl, isobutyl, butyl, pentyl or hexyl. In another embodiment, the alkyl group has 1-4 carbons. In another embodiment, the alkyl group may be optionally substituted by one or more groups selected from halide, hydroxy, alkoxy, carboxylic acid, aldehyde, carbonyl, amido, cyano, nitro, amino, alkenyl, alkynyl, aryl. azide, epoxide, ester, acyl chloride and thiol. Each possibility represents a separate embodiment of this invention. 
     A “cycloalkyl” group refers, in some embodiments, to a ring structure comprising carbon atoms as ring atoms, which are saturated, substituted or unsubstituted. In another embodiment, the cycloalkyl is a 3-12 membered ring. In another embodiment, the cycloalkyl is a 6 membered ring. In another embodiment, the cycloalkyl is a 5-7 membered ring. In another embodiment, the cycloalkyl is a 3-8 membered ring. In another embodiment, the cycloalkyl group may be unsubstituted or substituted by a halogen, alkyl, haloalkyl, hydroxyl, alkoxy, carbonyl, amido, alkylamido, dialkylamido, cyano, nitro, CO 2 H, amino, alkylamino, dialkylamino, carboxyl, thio and/or thioalkyl. In another embodiment, the cycloalkyl ring may be fused to another saturated or unsaturated 3-8 membered ring. In another embodiment, the cycloalkyl ring is an unsaturated ring. Non limiting examples of a cycloalkyl group comprise cyclohexyl, cyclohexenyl, cyclopropyl, cyclopropenyl, cyclopentyl, cyclopentenyl, cyclobutyl, cyclobutenyl, cycloctyl, cycloctadienyl (COD), cycloctaene (COE) etc. Each possibility represents a separate embodiment of this invention. 
     A “heterocycloalkyl” group refers in some embodiments, to a ring structure of a cycloalkyl as described herein comprising in addition to carbon atoms, sulfur, oxygen, nitrogen or any combination thereof, as part of the ring. In some embodiments, non-limiting examples of heterocycloalkyl include pyrrolidine, pyrrole, tetrahydrofuran, furan, thiolane, thiophene, imidazole, pyrazole, pyrazolidine, oxazolidine, oxazole, isoxazole, thiazole, isothiazole, thiazolidine, dioxolane, dithiolane, triazole, furazan, oxadiazole, thiadiazole, dithiazole, tetrazole, piperidine, oxane, thiane, pyridine, pyran, thiopyran, piperazine, morpholine, thiomorpholine, dioxane, dithiane, diazine, oxazine, thiazine, dioxine, triazine, and trioxane. Each possibility represents a separate embodiment of this invention. 
     As used herein, the term “aryl” refers to any aromatic ring that is directly bonded to another group and can be either substituted or unsubstituted. The aryl group can be a sole substituent, or the aryl group can be a component of a larger substituent, such as in an arylalkyl, arylamino, arylamido, etc. Exemplary aryl groups include, without limitation, phenyl, tolyl, xylyl, furanyl, naphthyl, pyridinyl, pyrimidinyl, pyridazinyl, pyrazinyl, triazinyl, thiazolyl, oxazolyl, isooxazolyl, pyrazolyl, imidazolyl, thiophene-yl, pyrrolyl, phenylmethyl, phenylethyl, phenylamino, phenylamido, etc. Substitutions include but are not limited to: F, Cl, Br, I, C 1 -C 5  linear or branched alkyl, C 1 -C 5  linear or branched haloalkyl, C 1 -C 5  linear or branched alkoxy, C 1 -C 5  linear or branched haloalkoxy, CF 3 , CN, NO 2 , —CH 2 CN, NH 2 , NH-alkyl, N(alkyl) 2 , hydroxyl, —OC(O)CF 3 , —OCH 2 Ph, —NHCO-alkyl, COOH, —C(O)Ph, C(O)O-alkyl, C(O)H, or - or —C(O)NH 2 . Each possibility represents a separate embodiment of this invention. 
     N-heterocycle refers to in some embodiments, to a ring structure comprising in addition to carbon atoms, a nitrogen atom, as part of the ring. In another embodiment, the N-heterocycle is a 3-12 membered ring. In another embodiment, the N-heterocycle is a 6 membered ring. In another embodiment, the N-heterocycle is a 5-7 membered ring. In another embodiment, the N-heterocycle is a 3-8 membered ring. In another embodiment, the N-heterocycle group may be unsubstituted or substituted by a halogen, alkyl, haloalkyl, hydroxyl, alkoxy, carbonyl, amido, alkylamido, dialkylamido, cyano, nitro, CO 2 H, amino, alkylamino, dialkylamino, carboxyl, thio and/or thioalkyl. In another embodiment, the heterocycle ring may be fused to another saturated or unsaturated cycloalkyl or heterocyclic 3-8 membered ring. In another embodiment, the N-heterocyclic ring is a saturated ring. In another embodiment, the N-heterocyclic ring is an unsaturated ring. Non limiting examples of N-heterocycle comprise pyridine, piperidine, morpholine, piperazine, pyrrolidine, pyrrole, imidazole, pyrazole, pyrazolidine, triazole, tetrazole, piperazine, diazine, or triazine. Each possibility represents a separate embodiment of this invention. 
     In some embodiments, the term “halide” used herein refers to any substituent of the halogen group (group 17). In another embodiment, halide is fluoride, chloride, bromide or iodide. In another embodiment, halide is fluoride. In another embodiment, halide is chloride. In another embodiment, halide is bromide. In another embodiment, halide is iodide. Each possibility represents a separate embodiment of this invention. 
     In some embodiments, haloalkyl is partially halogenated alkyl. In another embodiment haloalkyl is perhalogenated alkyl (completely halogenated, no C—H bonds). In another embodiment, haloalkyl refers to alkyl, alkenyl, alkynyl or cycloalkyl substituted with one or more halide atoms. In another embodiment, haloalkyl is CH 2 CF 3 . In another embodiment. haloalkyl is CH 2 CCl 3 . In another embodiment, haloalkyl is CH 2 CBr 3 . In another embodiment, haloalkyl is CH 2 CI 3 . In another embodiment, haloalkyl is CF 2 CF 3 . In another embodiment, haloalkyl is CH 2 CH 2 CF 3 . In another embodiment, haloalkyl is CH 2 CF 2 CF 3 . In another embodiment, haloalkyl is CF 2 CF 2 CF 3 . Each possibility represents a separate embodiment of this invention. 
     In some embodiments, the term “alkenyl” used herein refers to any alkyl group wherein at least one carbon-carbon double bond (C═C) is found. In another embodiment, the carbon-carbon double bond is found in one terminal of the alkenyl group. In another embodiment, the carbon-carbon double bond is found in the middle of the alkenyl group. In another embodiment, more than one carbon-carbon double bond is found in the alkenyl group. In another embodiment, three carbon-carbon double bonds are found in the alkenyl group. In another embodiment, four carbon-carbon double bonds are found in the alkenyl group. In another embodiment, five carbon-carbon double bonds are found in the alkenyl group. In another embodiment, the alkenyl group comprises a conjugated system of adjacent alternating single and double carbon-carbon bonds. In another embodiment, the alkenyl group is a cycloalkenyl, wherein “cycloalkenyl” refers to a cycloalkyl comprising at least one double bond. Each possibility represents a separate embodiment of this invention. 
     In some embodiments, the term “alkynyl” used herein refers to any alkyl group wherein at least one carbon-carbon triple bond (C≡C) is found. In another embodiment, the carbon-carbon triple bond is found in one terminal of the alkynyl group. In another embodiment, the carbon-carbon triple bond is found in the middle of the alkynyl group. In another embodiment, more than one carbon-carbon triple bond is found in the alkynyl group. In another embodiment, three carbon-carbon triple bonds are found in the alkynyl group. In another embodiment, four carbon-carbon triple bonds are found in the alkynyl group. In another embodiment, five carbon-carbon triple bonds are found in the alkynyl group. In another embodiment, the alkynyl group comprises a conjugated system. In another embodiment, the conjugated system is of adjacent alternating single and triple carbon-carbon bonds. In another embodiment, the conjugated system is of adjacent alternating double and triple carbon-carbon bonds. In another embodiment, the alkynyl group is a cycloalkynyl, wherein “cycloalkynyl” refers to a cycloalkyl comprising at least one triple bond. Each possibility represents a separate embodiment of this invention. 
     In some embodiments, the term “alkylated azide” used herein refers to any alkylated substituent comprising an azide group (—N 3 ). In another embodiment, the azide is in one terminal of the alkyl. In another embodiment, the alkyl is a cycloalkyl. In another embodiment, the alkyl is an alkenyl. In another embodiment, the alkyl is an alkynyl. In another embodiment, the epoxide is monoalkylated. 
     In some embodiments, the term “alkylated epoxide” used herein refers to any alkylated substituent comprising an epoxide group (a 3-membered ring consisting of oxygen and two carbon atoms). In another embodiment, the epoxide group is in the middle of the alkyl. In another embodiment, the epoxide group is in one terminal of the alkyl. In another embodiment, the alkyl is a cycloalkyl. In another embodiment, the alkyl is an alkenyl. In another embodiment, the alkyl is an alkynyl. In another embodiment, the epoxide is monoalkylated. In another embodiment, the epoxide is dialkylated. In another embodiment, the epoxide is trialkylated. In another embodiment, the epoxide is tetraalkylated. 
     In some embodiments, the notion of “ ” of a bond within any of the disclosed structures of the current invention refers to a carbon-carbon on single bond (“ ”) or a carbon-carbon double bond (“ ”). In some embodiments, each structure in any of the disclosed structures of the current invention comprise two   bonds. In another embodiment, each structure comprises two   bonds that are selected to be two single bonds, two double bonds, one single and one double bond or one double and one single bond, each represents a separate embodiment of this invention. 
     Referring back to  FIGS. 1A-1D and 2A, 2B , some embodiments comprise color conversion films  130  for LCD&#39;s  100  having RGB color filters  220  which comprise color conversion element(s) such as RBF compound(s)  115  or other compounds  76  selected to absorb illumination from backlight source  80  of LCD  100  and have a R emission peak and/or a G emission peak (see non-limiting examples below). For example, color conversion films  130  for LCD&#39;s with backlight source  80  providing blue illumination may comprise both R and G peaks provided by corresponding RBF compounds having Formula 1 and Formula 2. In another example, color conversion films  130  for LCD&#39;s with backlight source  80  providing white illumination may comprise R peak provided by corresponding RBF compound(s) having Formula 1. Color conversion film(s)  130  may be set in either or both backlight unit  300  and LCD panel  200 ; and may be attached to other film(s) in LCD  100  or replace other film(s) in LCD  100 , e.g. being multifunctional as both color conversion films and polarizers, diffusers, etc., as demonstrated above. Color conversion film(s)  130  may be produced by various methods, such as sol gel and/or UV curing processes, may include respective dyes at the same or different layers, and may be protected by any of a protective film, a protective coating and/or protective components in the respective sol gel or UV cured matrices which may convey enhanced flexibility, mechanical strength and/or less susceptibility to humidity and cracking. Color conversion film(s)  130  may comprise various color conversion elements such as organic or inorganic fluorescent molecules, quantum dots and so forth. 
     Film Production Embodiments 
       FIG. 11  is a high level schematic illustration of multiple film preparation steps and processes, according to some embodiments of the invention; mostly referring to sol gel processes  600 , but also including UV curing processes  700 , combined processes (sol gel+UV) and auxiliary processes (e.g., patterning), as well as multiple options for dye incorporation in the films (various RBF compounds  115  and their combinations, assistant dyes, protective films without dyes, etc.). 
     Sol-Gel Processes 
     Some embodiments of fluorescent film production  70  were developed on the basis of sol gel technology in a different field of laser dyes. Reisfeld 2006 (Doped polymeric systems produced by sol-gel technology: optical properties and potential industrial applications, Polimery 2006, 51(2): 95-103) reviews sol-gel technology based on hydrolysis and subsequent polycondensation of precursors, such as organo-silicon alkoxides, leading to formation of amorphous and porous glass. The matrices for incorporation of organically active dopants are the glass/polymer composites, organically modified silicates (ORMOSIL) or hybrid materials zirconia-silica-polyurethane (ZSUR). However, the matrices taught by Reisfeld 2006 do not yield films with photo-stable fluorescent compounds that are necessary for color conversion films. 
     Starting from Reisfeld 2006, the inventors have found out that sol gel technology may be modified and adapted for producing films of fluorescent optical compounds which may be used in displays, with surprisingly good performance with respect to emission spectra and stability of the fluorescent compounds. The inventors have found out that multiple modifications to technologies discussed in Reisfeld 2006 enable using them in a completely different field of implementation and moreover, enable to enhance the stability of the fluorescent compounds and to tune their emission spectra (e.g., peak wavelengths and widths of peaks to enable wide color gamut illuminance from the display backlight) using process parameters. Hybrid sol-gel precursor formulations, formulations with rhodamine-based fluorescent compounds, films, displays and methods are provided, in which the fluorescent compounds are stabilized and tuned to modify display backlight illumination in a manner that increases the display&#39;s efficiency and widens its color gamut. Silane precursors are used with silica nanoparticles and zirconia to provide fluorescent films that may be applied in various ways in the backlight unit and/or in the LCD panel and improve the display&#39;s performance. The sol-gel precursor and film forming procedures may be optimized and adjusted to provide a high photostability of the fluorescent compounds and narrow emission peaks of the backlight unit. 
     A main, yet non-limiting, section of  FIG. 11  illustrates precursors  72  and formulations  74  for sol gel films, as well as a schematic illustration of films  130  and displays  100  according to some embodiments of the invention. 
     WIPO Publication Nos. WO 2017/085720 and WO 2018/042437, and U.S. Publication Nos. 2018/0072892 and 2018/0039131, and U.S. Pat. No. 9,868,859 provide additional details as well as comparison to the prior art and are incorporated herein by reference in their entirety. 
     Hybrid sol-gel precursor formulations  72  comprise an epoxy silica ormosil solution  106  prepared from TEOS (tetraethyl orthosilicate)  102 , at least one silane precursor  104  and/or MTMOS (methyltrimethoxysilane)  91 B, and GLYMO  91 C; a nanoparticles powder  109  prepared from isocyanate-functionalized silica nanoparticles  111 , or non-functionalized silica nanoparticles  111 , and ethylene glycol  108 ; and a transition metal(s) alkoxide matrix solution  103  (based on e.g., zirconia, titania or other transition metal(s) alkoxides). The ratios (wt/vol/vol (mg/ml/ml)) of nanoparticles powder/epoxy silica ormosil solution/transition metal(s) alkoxide matrix solution may be in the range 15-25/1-3/1, with each of the components possibly deviating by up to 50% from the stated proportions. Additional variants  107  are provided below.  FIG. 11  presents non-limiting examples of process  600 . 
     In a non-limiting example, the epoxy silica ormosil solution and the transition metal(s) alkoxide matrix solution may be mixed at ratio of between 1:1 and 3:1 (e.g., 2:1) followed by adding the nanoparticles powder at a concentration of 5-10 mg/1 ml mixed (e.g., epoxy silica ormosil solution and zirconia) solution—resulting in ratios (wt/vol/vol (mg/ml/ml)) of nanoparticles powder/epoxy silica ormosil solution/transition metal(s) alkoxide matrix solution of 15-30/2/1 in the non-limiting example, wherein any of the components may deviate by up to ±50% from the stated proportions. The solution may then be mixed (e.g., for one hour) and then filtered (e.g., using a syringe with a 1 μm filter). The fluorophore may then be added to form formulation  74  from precursor  72 , and the mixing may be continued for another hour. Formulation  74  may then be evaporated and heated (e.g., in a non-limiting example, using a rotovap under pressure of 60-100 mbar and temperature of 40-60° C.) to achieve increased photo-stability as found out by the inventors and explained below. 
     Epoxy Silica Ormosil Solution 
     Specifically, compared to the process of Reisfeld 2006, the inventors have found out that replacing TMOS by TEOS  102  and using different silane precursors  104  provide epoxy silica ormosil solution  106  which enables association of rhodamine-based fluorescent (RBF) compounds  115  in resulting films  130  which are usable in displays  100 , which prior art ESOR does not enable. In particular, the inventors have used various silane precursors  104  to enhance stability of and provide emission spectrum tunability to RBF compounds  115  in produced film  130 , as shown in detail below. 
     For example, silane precursors  104  may comprise any of: MTMOS (methyltrimethoxysilane), PhTMOS, a TMOS with fluorine substituents, e.g., F 1 TMOS (trimethoxy(3,3,3-trifluoropropyl)silane), F 0 TEOS (Fluorotriethoxysilane) or F 2 TMOS (tridecafluoro-1,1,2,2-tetrahydrooctyl)trimethoxysilane, 1,2-bis(triethoxysilyl)ethane, trimethoxy(propyl)silane, octadecyltrimethoxysilane, fluorotriethoxysilane, and ammonium(propyl)trimethoxysilane. The first three options are illustrated below. 
     
       
         
         
             
             
         
       
     
     In certain embodiments, silane precursors  104  may comprise any alkoxysilane, with R 1 , R 2 , R 3  typically consisting of methyl or ethyl groups (e.g., R 4 —OSi(Me) 3 ), and R 4  may consist of a branched or unbranched carbon chain, possibly with any number of halogen substituents, as illustrated below. 
     
       
         
         
             
             
         
       
     
     In certain embodiments, silane precursors  104  may comprise any of: tetraalkoxysilane (e.g., tetraethoxysilane), alkyltrialkoxysilane, aryltrialkoxysilane, haloalkyltrialkoxysilane, heterocycloalkyltrialkoxysilane, N-heterocycletrialkoxysilane, (3-Glycidyloxypropyl)trialkoxysilane, haloalkyltrialkoxysilane, heterocycloalkyltrialkoxysilane, N-heterocycletrialkoxysilane, and cycloalkyltrialkoxysilane. 
     In certain embodiments, silane precursors  104  may be selected from any of the following structures: 
     
       
         
         
             
             
         
       
     
     wherein T101 is an alkyl, T102 an aryl, T103 an haloalkyl, T104 an heterocycloalkyl (including a N-heterocycle) and T105 an cycloalkyl, as defined herein. 
     In certain embodiments, silane precursors  104  may comprise, in addition or in place of silane precursor  104  disclosed above, at least one of: 1,2-bis(triethoxysilyl)ethane, trimethoxy(propyl)silane, octadecyltrimethoxysilane, fluorotriethoxysilane, ammonium(propyl)trimethoxysilane (illustrated below) and any further varieties of any of disclosed silane precursor  104 . 
     
       
         
         
             
             
         
       
     
     In certain embodiments, epoxy silica ormosil solution may be prepared by first mixing the TEOS and the at least one silane precursor(s) under acidic conditions and then adding the GLYMO. The acidic conditions may be adjusted by adding acetic acid, followed by adding water and alcohol(s) such as ethanol, propanol, 2-propanol or butanol. 
     In certain embodiments, the volumetric ratio between TEOS:MTMOS or other silane precursor(s):GLYMO may be between 1:1:1.5-2; and the volumetric ratio between TEOS:silane precursor(s):acetic acid:alcohol:water may be between 1:1:0.01-1:1-10:4-8. Epoxy silica ormosil solution mixing time may be reduced to five minutes. Any of the components may deviate by up to ±50% from the stated proportions. 
     In some embodiments (e.g., additional variants  107 ), ethanol and/or water are not used, to simplify the process. For example, diphenylsilanediol (DPSD) may be used to provide a water-free matrix, avoiding the first hydrolysis step in the condensation. 
     In some embodiments (e.g., additional variants  107 ), citric acid and/or ascorbic acid may replace or be added to the acetic acid. 
     Nanoparticles Powder 
     Nanoparticles powder  109  is prepared from ethylene glycol  108  and isocyanate-functionalized silica nanoparticles (IC-Si NP)  111  or non-functionalized silica nanoparticles  111 . 
     The inventors have found out that using ethylene glycol  108  for nanoparticles powder  109  instead of polyethylene glycol for DURS (diurethane siloxane) (as in Reisfeld 2006) enables better control of the film production and better films  130  than prior art sol-gel precursors, as explained below. 
     IC-Si NP  111  are multi-functional nanoparticles which have many active sites and specifically many more then prior art 3-isocyanatopropyltriethoxysilane (ICTEOS)  94 B which is not multi-functionalized. ICTEOS has a single isocyanate group and when two ICTEOS molecules bind to PEG they create diuretane silane (DURS); while IC-Si NP has many active sites which may form significantly different matrix structures. 
     
       
         
         
             
             
         
       
     
     IC-Si NP have hydroxide groups on their surface which participate in the condensation step (detailed below), and accordingly increase the actual functionality of the IC-Si NP. 
     The inventors have found that using IC-Si NP  111  for nanoparticles powder  109  instead of prior art 3-isocyanatopropyltriethoxysilane (ICTEOS) may produce films with a tighter matrix and may limit the diffusion of the RBF compound and inhibit reactive molecules from reaching the RBF compound. The matrix may also absorb residue solvents and unreacted precursors thereby protecting RBF compound from potential reactions that may occur with the residue solvents and unreacted precursors. 
     The isocyanate-functionalized silica nanoparticles (IC-Si NP) may comprise (isocyanato)alkylfunctionalized silica nanoparticles and/or 3-(isocyanato)propyl-functionalized silica nanoparticles, which may be prepared from precursors (isocyanato)alkylfunctionalized trialkoxysilane and/or 3-(isocyanato)propyltrietoxysilane, respectively. 
     In some embodiments, nanoparticles  111  may comprise non-functionalized silica nanoparticles. The non-functionalized silica nanoparticles  111  may be comprised of any silica nanoparticles. In some embodiments, the non-functionalized silica nanoparticles  111  may comprise standard silica gel (CAS 7631-86-9). 
     The nanoparticles powder may be prepared by mixing and refluxing the silicon (e.g. IC-Si NP) and glycolated precursors. In some embodiments, the ethylene glycol may be added in excess. In some embodiments, the reflux may be followed by cooling and filtration steps. In some embodiments, chlorobenzene (C 6 HCl) may be added to the mixture before the reflux step. In some embodiments, the chlorobenzene (C 6 H 5 Cl) may be evaporated prior to the cooling step. In an example, nanoparticles powder was prepared by refluxing 3-isocyanatopropyl functionalized nanoparticles and ethylene glycol. In one embodiment, about 50-150 mg of 3-isocyanatopropyl functionalized silica nanoparticles (with 200-400 mesh, 1.2 mmol/g loading) and 16-320 μl of ethylene glycol were refluxed in chlorobenzene for about 2-6 hours. The functionalized silica nanoparticles were then separated from the chlorobenzene by a rotary evaporator. 
     In various embodiments, the size of the silica nanoparticles may be any of between about 1-500 nm, between about 1-400 nm, between about 1-100 nm, between about 50-300 nm, between about 50-200 nm, between about 100-200 nm, between about 100-160 nm and/or between about 110-140 nm. 
     U.S. Provisional Patent Application Nos. 62/593,936 and 62/613,085, incorporated herein by reference in their entirety, provide a high-resolution SEM image of a sol-gel film prepared with IC-Si NP which clearly shows there are nanoparticles within the sol-gel matrix. In certain embodiments, using IC-silica NP, as opposed to ICTEOS, increases the photostablity of the film from one day with ICTOS to three days with IC-silica NP. In this example both films were prepared using JK71 as the RBF molecule in a Z3 matrix and the measurements were done by a Fluorimeter, FluoroMax-4 Horiba, the excitation was: 452 nm, the temperature was: 70° C. and the flux 70 mW/cm. 
     In some embodiments, the non-functionalized nanoparticles  111  may replace the functionalized nanoparticles in both Z2 and Z3 matrix using the same concentration by weight of the particles per volume of the solution. 
     U.S. Provisional Patent Application Nos. 62/593,936 and 62/613,085, incorporated herein by reference in their entirety, also show a photo-stability comparison between a device with functionalized silica NP and non-functionalized silica NP, with the latter, in some embodiments, providing at least the same photostability. Nanoparticles powder  109  may be prepared from a mixture of functionalized and non-functionalized silica NP. In some embodiments the ratio of functionalized and non-functionalized silica NP in the mixture may be any of 50:50, 40:60, 20:80, 10:90, 60:40, 70:30, 80:20 and 90:10. In some embodiments, the size of the functionalized NP is between about 1-400 nm and the size of the non-functionalized NP is between about 1-100 nm. In some embodiments, the size of the functionalized NP is between about 50-300 nm and the size of the non-functionalized NP is between about 50-200 nm. In some embodiments, the size of the functionalized NP is between about 100-200 nm and the size of the non-functionalized NP is between about 100-160 nm. In some embodiments, the size of the functionalized NP is between about 110-140 nm and the size of the non-functionalized NP is between about 1-400 nm. Any of the above embodiments may be combined together. In some embodiments (e.g., additional variants  107 ), all nanoparticles may be functionalized, or all nanoparticles may be non-functionalized. 
     In some embodiments (e.g., additional variants  107 ), nanoparticles powder is not used, to simplify the process. 
     Transition Metal(s) Alkoxide Matrix Solution 
     Transition metalalkoxide matrix solution  103  may comprise alkoxides of one or more transition metals. For example, a zirconia (ZrO 2 ) matrix solution may be prepared from zirconium tetraalkoxide, e.g., Zr(OPr) 4  and/or zirconium, mixed with alcohol (e.g., propanol) under acidic conditions (e.g., in the presence of acetic acid, citric acid and/or ascorbic acid). Various transition metals alkoxides may be used in place or in addition to zirconia. 
     In certain embodiments, the epoxy silica ormosil solution may be mixed with the zirconia matrix solution at a 2:1 volumetric ratio, and the nanoparticles powder may then be added to the mixture to provide, after mixing (e.g., for 1-5 hours) and filtering, hybrid sol-gel precursor formulations. The zirconia matrix solution may be configured to catalyze the epoxy polymerization of the epoxy silica ormosil solution. In some embodiments, the zirconia matrix solution may be added to the epoxy silica ormosil solution after e.g., 15, 30, 45 minutes. The subsequent mixing time may be decreased down to 10 minutes. 
     In some embodiments, other metal oxide matrix may be used instead or in addition to zirconia matrix during the sol-gel process, such as titania using titanium isopropoxide or boron oxide using boric acid. Zirconia and/or alkoxides from transition metals such as boron alkoxide  103  may be used in preparing sol-gel precursor  72 . 
     Formulation 
     Formulations  74  comprise hybrid sol-gel precursor formulations  72  and at least one RBF compound  115  such as red-fluorescent RBF compound(s) and green-fluorescent RBF compound(s) which may be configured to emit the R and G components of the required RGB illumination, provided by the display&#39;s backlight unit (red-fluorescent RBF compounds emit radiation with an emission peak in the red region while green-fluorescent RBF compounds emit radiation with an emission peak in the green region). It is emphasized that formulations  74  are very different from prior art laser dye formulation as laser dye usage as gain medium is very different from the operation of fluorescent films in the backlight unit, e.g., concerning stability, emission spectra and additional performance requirement as well as operation conditions. 
     Stages of methods  600 —namely preparing hybrid sol-gel precursor formulation  72  (stage  610 ), mixing in RBF compound(s)  115  to form formulation  74  (stage  620 ), forming film  130  (stage  630 ) and optionally evaporating alcohols prior to film formation (stage  625 )—are shown schematically and explained in more detail below. 
     The mixture of the hybrid sol-gel precursor formulation and the RBF compound(s) may be stirred and then evaporated and heated (e.g., in a non-limiting example, stirred for between 20 minutes and three hours, evaporated at 60-100 mbar and heated to 40-60° C.) to increase the photo-stability of the RBF compound(s) (see additional process details below). Process parameters may be adjusted to avoid damage to the fluorescent dyes, control parameters of the sol gel process and optimize the productivity in the process. 
     The evaporation of alcohols from the sol-gel prior to the coating of the substrate may form a denser matrix which provides a tight packaging for the RBF compound. The tighter packaging may result in higher photostablity as can be seen in FIG. 7C of U.S. Publication No. 2018/0072892 incorporated herein by reference. The figure is a graph showing the normalized intensity, with and without an evaporation step, of a film of Z1 formulation (detailed below) with RS130 as the RBF molecule. As can be seen the stability of the layer with evaporation (dark color line) is almost twice that of the layer without evaporation (light color line). Details of the measurement are: Fluorimeter, FluoroMax-4 Horiba, Excitation: 540 nm; Detail of acceleration: Excitation: 452 nm; Temperature: 70° C.; Flux: 70 mW/cm 2 . 
     The concentration of the RBF compound(s) may be adjusted to determine the final peak emission intensity excited by the chosen backlight unit and may range e.g., between 0.005-0.5 mg/ml. It is noted that multiple fluorescent molecules having different emission peaks may be used in a single formulation  74 . The processes may be optimized to achieve required relations between the RBF compound(s) and the other components of the film, e.g., to achieve any of supramolecular encapsulation of the RBF compound(s) in the sol gel matrix, covalent embedding of the RBF compound(s) in the sol gel matrix (e.g., via siloxane bonds), and/or incorporation of the RBF compound(s) in the sol gel matrix. 
     Silane precursors  104  may be selected according to the used RBF compound. For example, the inventors have found out that PhTMOS may be used to stabilize red-fluorescent RBF compounds. In another example, the inventors have found out that TMOS with fluorine substituents may be used to stabilize red-fluorescent RBF compounds. Modifying and adjusting parameters of the substituents was found to enable control of the photostability and emission characteristics of the fluorescent compounds. In yet another example, the inventors have found out that F 1 TMOS may be used to stabilize green-fluorescent RBF compounds. These and more findings are presented below in detail. 
     Optimizing the Silane Precursors in the Epoxy Silica Ormosil Solution to Stabilize and Tune the Fluorescent Molecules 
     Films  130  prepared from formulation  74  may comprise epoxy silica ormosil solution  106  prepared from TEOS  102 , at least one silane precursor  104  (and/or MTMOS  91 B), and GLYMO  91 C; nanoparticles powder  109  prepared from isocyanate-functionalized silica nanoparticles  111  or non-functionalized silica nanoparticles  111  and ethylene glycol  108 ; a transition metal(s) alkoxide matrix solution  103 ; and at least one RBF compound  115 , selected to emit green and/or red light and being supramolecularly encapsulated and/or covalently embedded within film  130 . Silane precursors  104  may comprise any of MTMOS, PhTMOS, a TMOS with fluorine substituents, F 1 TMOS, F 2 TMOS (tridecafluoro-1,1,2,2-tetrahydrooctyl)trimethoxysilane, 1,2-bis(triethoxysilyl)ethane, trimethoxy(propyl)silane, octadecyltrimethoxysilane, fluorotriethoxysilane, and ammonium(propyl)trimethoxysilane. For example, for film  130  and/or film layer  134  with red-fluorescent RBF compound, silane precursor  104  may comprise PhTMOS and/or a TMOS with fluorine substituents. In another example, for film  130  and/or film layer  132  with green-fluorescent RBF compound, silane precursor  104  may comprise F 1 TMOS. 
     Examples are provided below for four matrix compositions (Z 1 , Z 2 , Z 3 , Z 4 ) for mixtures of epoxy silica ormosil solution and zirconia matrix solution having the components Zr(PrO) 4 :GLYMO:TEOS:silane precursor at n=0.011:0.022:0.013:0.021 (moles), with the silane precursor being MTMOS in Z 1 , PhTMOS in Z 2 , F 1 TMOS in Z 3 , and F 2 TMOS in Z 4 , as illustrated below. 
     
       
         
         
             
             
         
       
     
     These matrices were mixed with several dyes and tested, as corresponding films  130 , for quantum yield and lifetime, as presented in detail below, with results presented in WIPO Publication No. WO 2017/085720 and U.S. Pat. No. 9,868,859, which are incorporated herein by reference in their entirety, and demonstrate the capabilities of the disclosed technology to increase the lifetime of RBF compound(s) in film  130  multiple times over, reach high quantum yields, tune the emission peak wavelength of the RBF compound(s) significantly and provide tuned multi-layered films  130 . Specifically, intercalating the red fluorescent compound(s) in the Z 2  matrix resulted in increased photo-stability, intercalating the green fluorescent compound(s) in the Z 3  matrix resulted in increased photo-stability and improved the QY (quantum yield) compare to the Z 1  matrix. When combining the precursor of Z 2  and Z 3  together, changing the PhTMOS:F 1 TMOS ratio can provide tuning of the green wavelength. 
     The inventors have also found out that the length of the carbon chain of the silane precursor(s) may contribute to the stability of the red-fluorescent RBF compounds; in certain embodiments the carbon chain may consist of 8, 9, 10, 12 or more carbon atoms, possibly with corresponding fluorine atom as hydrogen substituents. In certain embodiments, some or all fluorine atoms may be replaced by another halogen such as chlorine. Moreover, the inventors have found out that modifying the length and hydrophobic\hydrophilic degree of the chain may be used to further tune and adjust the emission peak (beyond the data exemplified above), according to requirements. 
     The inventors have used various silane precursors  104  to provide emission spectrum tunability to film  130 . In some embodiments tuning of the wavelength may be achieved by adjusting the ratio of the silane precursors  104 . In some embodiments, the ratio of silane precursors is adjusted within each layer; such as a 1:1 ratio of PhTMOS and F 1 TMOS in a single sol-gel matrix layer. In some embodiments, the ratio of the silane precursors is adjusted between layers; such as a 1:1 ratio of layers—for example one layer with PhTMOS and one layer with F 1 TMOS one on top of each other. 
     U.S. Pat. No. 9,868,859 and U.S. Publication No. 2018/0072892, incorporated herein by reference in their entirety, further provide an example of a peak shift due to the change in molar ratio of two silane precursors PhTMOS (Z3 matrix detailed below): F 1 TMOS (Z2 matrix detailed below). As can be seen (in FIG. 8F of U.S. Publication No. 2018/0072892) the first peak with just Z3 is at 535 nm and as Z2 is added and the ratio changes the peak shifts to higher wave lengths up to 545 nm when the ratio is 3:1. The wavelengths for each ratio can be found in rows 5-8 in Table 1 of U.S. Pat. No. 9,868,859. In this example JK71, a green RBF molecule, was used in a concentration of 0.15 mg/ml, in a single layer of ˜40 μm thickness. 
     In some embodiments, the GLYMO precursor is polymerized  107 C (poly-GLYMO) before it is used in the epoxy silica ormosil solution preparation. See example below: 
     
       
         
         
             
             
         
       
     
     Using poly-GLYMO  107 C in the preparation of the hybrid sol-gel matrix may result in an increase of the crosslinking density. 
     In some embodiments GLYMO is polymerized in the presence of at least one RBF compound. This may provide a polymer cage which limits the diffusion of the RBF compound and inhibits reactive molecules from reaching the RBF compound. 
     In some embodiments, the RBF compound has epoxide groups which enable it to covalently bind to the sol-gel&#39;s polymer back bone thus further limiting the RBF diffusion. In some embodiments, the RBF compound is ES-118 according to the following formula: 
     
       
         
         
             
             
         
       
     
     In some embodiments (3-Glycidyloxypropyl)trimethoxysilane (Glymo CAS: 2530-83-8) was dissolved in ethanol in concentration of 1-10 mM. Then to initiate the polymerization 1-methylimidazole (CAS: 616-47-7) was added, in concentration of 0.05%-5% (w/w), the solution was then maintained under reflux for three (3) hours. 
     In some embodiments, the poly-glymo:TEOS ratio is about 1:1-3:1 (v/v). 
     Epoxy Silica Ormosil Solution Additives 
     There is a positive relation between the crosslinking density of a matrix and the photo-stability of the trapped fluorophore. Additives  107 , described below, increase the crosslinking density of the hybrid sol-gel matrix and have additional advantages detailed below. 
     In some embodiments one or more additional additives  107  may be added to the epoxy silica ormosil solution. In some embodiments, the additives are added during the preparation of the epoxy silica ormosil solution and specifically following the addition of the silane precursors. 
     Polydimethylsiloxane Hydroxy Terminated 
     In some embodiments additive  107  may be polydimethylsiloxane hydroxy terminated (PDMS-hydroxy CAS: 70131-67-8) as illustrated below. PDMS is highly flexible (has a very low Tg) and highly hydrophobic. The PDMS&#39;s hydroxyl groups on both sides of the main chain allow covalent linkage to the sol-gel matrix and act as flexible crosslinkers. 
     
       
         
         
             
             
         
       
     
     In some embodiments PDMS was added in a molecular weight of 0.1-20 (kDa) and in a concentration of 5%-20% (w/w). The resulting hybrid sol-gel had a higher viscosity, enabled more uniform spreading, increased flexibility, reduction of bubbles, better resistant to thermal shock, less splintering during cutting and better resistance toward humidity compared to the hybrid sol-gel without PDMS. 
     WIPO Publication No. WO 2018/042437 and U.S. Publication Nos. 2018/0072892 and 2018/0039131, incorporated herein by reference in their entirety, provides a comparison of a film with and without PDMS-hydroxyl, which demonstrates how the addition of PDMS-hydroxyl advantageously prevents the bubbling effect and produces a smoother surface. 
     Dendritic Polyol 
     In some embodiments additive  107  may be a dendritic polyol. Dendritic polyols have a large number of active chemical sites and a flexible backbone. The dendritic polyols also have many hydroxyl groups which allow covalent linkage to the sol-gel matrix and act as highly functional crosslinkers. 
     In some embodiments, the dendritic polyol is Boltorn™ H2004 (CAS: 462113-22-0, Propanoic acid, 3-hydroxy-2-(hydroxymethyl)-2-methyl-,1,1′-[2-[[3-hydroxy-2-(hydroxymethyl)-2-methyl-1-oxopropoxy]methyl]-2-methyl-1,3-propanediyl] ester), as illustrated below: 
     
       
         
         
             
             
         
       
     
     In some embodiments Boltorn H2004 was added in a concentration of 1%-10% (w/w). The resulting hybrid sol-gel film had improved adhesion and flexibility compared to the hybrid sol-gel without Boltorn H2004. 
     Dendritic polyols may also be used when preparing a matrix using UV as detailed below. 
     Polyvinylpyrrolidone 
     In some embodiments additive  107  may be Polyvinylpyrrolidone (PVP CAS: 9003-39-8) as illustrated below: 
     
       
         
         
             
             
         
       
     
     In some embodiments PVP was added in a molecular weight of 10 kDa and in a concentration of 5%-20% (w/w). The resulting hybrid sol-gel had improved adhesion and flexibility compared to the hybrid sol-gel without PVP. 
     In some embodiments a combination of two or more of PDMS, dendritic polyol and PVP may be used in the preparation of the epoxy silica ormosil solution. 
     In some embodiments, the combination is tuned to receive certain desired characteristics. 
     Sol Gel and UV 
     In some embodiments, the sol-gel process may be followed by a UV curing process, with respect to some or all layers of film  130  (stage  626  in  FIG. 11 ). In some embodiments a substrate is coated with the sol-gel solution followed by irradiation with UV light for curing. In some embodiments the coated substrate is then placed in an oven. In some embodiments the coated substrate is then cooled and is irradiated again with UV light for a final curing. UV curing following the sol-gel process may be faster than thermal curing and may allow an easier path to patterning. 
     In some embodiments, the UV process may be followed by thermal curing process, with respect to some or all layers of film  130 . In some embodiments film  130  may comprise multiple layers wherein each layer may be cured by UV, by thermal curing or by a combination thereof; first by thermal curing followed by UV curing or first by UV curing followed by thermal curing. In some embodiments film  130  comprises 1-10 layers. In some embodiments film  130  comprises 1-100 layers. In some embodiments film  130  comprises 1-5 layers. In some embodiments film  130  comprises 10-20 layers. In some embodiments film  130  comprises 20-30 layers. U.S. Provisional Patent Application Nos. 62/593,936 and 62/613,085, and WIPO Publication No. WO 2018/042437 and U.S. Publication Nos. 2018/0072892 and 2018/0039131, incorporated herein by reference in their entirety, provide examples for illustrations of characteristics of formulations and films according to some embodiments of the invention—exemplifying the tuning of the emission spectrum (tuning of the emission peak is indicated by J) by adjusting formulation  74  and exemplifying the implementation of formulation  74  with two fluorescent compounds and different respective precursors. 
     Film Preparation 
     Films  130  may be prepared from formulations  74  using a transparent substrate (e.g., glass, polyethylene terephthalate (PET), polycarbonate, poly-methyl-methacrylate (PMMA) etc.) or as stand-alone films (after solidification) and be used as color-conversion films in backlight units of displays. The substrate may be scrubbed to increase the surface roughness or be laminated to provide diffuser properties—in order to increase scattering or diffusing of blue light from the backlight unit. 
     In some embodiments, the surface of the substrate may be treated prior to applying the film. Treating the surface may improve the adhesion of the film and may prevent delamination and cracks at extreme conditions. 
     In some embodiments, the surface is treated by covalently binding aminosilanes. In one embodiment, the aminosilane is (aminoprpyl)triethoxysilane (APTES). The aminosilanes and APTES provide an anchoring active site for alkoxy condensation within the sol-gel reaction thus covalently binding the sol-gel matrix to the substrate and resulting in a strong adhesion between the film and the substrate. U.S. Provisional Patent Application Nos. 62/593,936 and 62/613,085, incorporated herein by reference in their entirety, provide examples for films prepared with pretreatment of the substrate with APTES. 
     In non-limiting examples, 0.1%-10% v/v of APTES were mixed with toluene. The mixture was then poured in to a bath. The substrate was dried with hot air and then placed in the bath with the mixture. The bath was then hermetically sealed (to prevent moisture absorbance) and the substrate was soaked for 3 hours. The substrate was then removed from the bath, washed with toluene and dried before coating. 
     The evaporation of alcohols  625  prior to the layer application may result in a denser sol-gel matrix which provides tight packaging of the RBF compound and accordingly may result in higher photostablity and therefore may reduce the number of layers. U.S. Provisional Patent Application Nos. 62/593,936 and 62/613,085, incorporated herein by reference in their entirety, provide a comparison of the normalized intensity in a single-color layer with and without evaporation. 
     Spreading formulation  74  may be carried out by any of manual coating (blade or spiral bar), automatic coting (blade or spiral bar), spin coating, deep coating, spray coating or molding; and the coatings may be applied on either side or both sides of the transparent substrate. Multiple layers of formulation  74  may be applied consecutively to film  130  (film thickness may range between 10-100 μm). 
     Concerning the drying, or curing process of formulation  74 , it may be a two-step process comprising an initial short-term curing at a high reaction rate for determining the formation of the sol-gel matrix and a long-term curing at a lower reaction rate for determining the completion of the reaction (the temperature and duration of this step may be set to determine and adjust the reaction results). The initial short-term curing (drying) maybe carried out by a hot plate, an oven, a drier and/or an IR (infrared) lamp. In a non-limiting example, film  130  on glass may be placed on top of a hot plate or in an oven and undergo a heating profile: constant temperature (e.g., 60-100° C. for 1-3 hours) followed by step-wise temperature increments (e.g., 3-5 steps of 20-40° C. increase for 15-90 minutes each). In another non-limiting example, films may be cured by a drier or an IR lamp, e.g., being set on a conveyor (moving e.g., in 0.1-5 m/min) and heated to temperatures between 60-100° C. The curing may be configured to avoid film annealing and provide a required mesh size, while maintaining and promoting the stability of the RBF compound(s)  115 . Curing parameters may be optimized with respect to a tradeoff between photostability and brightness, which relate to the film density resulting from the curing. In case of films with multiple layers (e.g., up to twenty layers), additional curing may be carried out between layer depositions (e.g., 50-90° C. for 1-3 hours) and a final curing may be applied after deposition of the last layer (e.g., 100-200° C. for 2-72 hours). In some embodiments, lower curing temperatures may be applied for longer times, e.g., the curing may be carried out for a week in 50° C. In some embodiments, curing temperatures may be raised stepwise, possibly with variable durations, e.g., the curing may be carried out stepwise at 30° C., 60° C., 90° C., two hours at each step. Optionally a final curing stage (e.g., at 130° C.) may be applied. 
     For example, green-fluorescent RBF compound in Z 3  (F 1 TMOS) matrix was cured under different heat transport regimes: IR only (IR intensity 10%; 25 min on the conveyor moving at 0.1 m/min) dryer only (at consecutive 15 min steps of 30° C., 50° C., 70° C., 90° C., 110° C.) and a combination of IR followed by dryer, with a final curing of  24   h  in an oven at 130° C. The samples maintained their emission peaks, FWHM (full width at half maximum) and QY and exhibited the following reduction of emission intensity after eight days with respect to the initial intensity (measured by a fluorimeter): IR only—54%, dryer only—79%, IR and dryer—73%, showing the efficiency of the latter two methods. 
     The process may be further adjusted to yield encapsulation or bonding of the RBF compound(s)  115  in the matrix which narrows the FWHM of the emission band by adjusting the micro-environment of the fluorescent molecules. The process may be monitored and optimized using any of quantum yield measurements, fluorescent measurements, photometric measurements, photostability (lifetime) testing and others. 
     Concerning display properties, it is noted that emission peaks may be related to the display hue property and the FWHM may be related to the display saturation property. The adjustment of the hue and saturation properties may be carried out by corresponding adjustments in one or more components of formulation  74  and/or in the film production process described above. It is further noted that additional display properties such as intensity/lightness and brightness/LED power may be adjusted with respect to the designed film properties. 
     Preparation and Measurement Details—Examples 
     The following illustrates some experimental procedures used to derive the results presented above (see  FIG. 11  for overview). These experimental procedures are not limiting the application of the disclosed invention. 
     In a first example, film  130  was prepared by applying ten layers of formulation  74  with green-fluorescent RBF compound at a concentration of 0.1 mg/ml in the formulation, layer by layer, onto a transparent substrate and then applying two layers of formulation  74  with red-fluorescent RBF compound at a concentration of 0.05 mg/ml in the formulation, layer by layer, onto the former, green emitting layers. The inventors later found out that the multiple green-fluorescent layers may be replaced by fewer or even a single layer when evaporation of the alcohols is carried out prior to the layer application. 
     WIPO Publication No. WO 2018/042437 and U.S. Publication Nos. 2018/0072892 and 2018/0039131, incorporated herein by reference in their entirety, provide examples for the resulting spectrum and its emission peaks; examples for the larger color gamut range of film  130  in display  100  with respect to the standard LCD (sRGB) gamut and is in the range of the NTSC standard gamut; examples for multi-layered films  130  and their influence on the resulting spectrum, to demonstrate that the white point position may be tuned as desired by changing the structure of film  130 , e.g., by adjusting the number of layers and/or concentration in formulation  74  of either RBF compound; and examples for various film compositions, such as 5- and 6-Carboxy X-rhodamine-Silylated illustrated below, as a non-limiting example. Similar covalent binding of RBF compounds  115  to the sol gel matrix may be achieved with other RBF compounds in similar ways. 
     5- and 6-Carboxy X-Rhodamine-Silylated 
     
       
         
         
             
             
         
       
     
     WIPO Publication No. WO 2018/042437 and U.S. Publication Nos. 2018/0072892 and 2018/0039131 provide multiple examples for film compositions and preparations methods, which are incorporated herein by reference in their entirety.
 
Cross-Linking with PMMA
 
     Some embodiments comprise fluorescent compounds which are bonded to PMMA and have Si linkers to bond the PMMA-bonded compounds to the sol-gel matrix. 
     The following non-limiting examples illustrate binding RBF compounds to PMMA by showing the preparation of RBF compound ES-87 and cross-linking it with PMMA and linker of Si to be bonded to the sol-gel matrix. ES-86 was prepared as a precursor by dissolving 3-bromopropanol (0.65 ml, 7.19 mmol, 1 eq) in dry DCM (dichloromethane) under N 2  atmosphere. NEt 3  (0.58 ml, 7.91 mmol, 1.1 eq) was added and the mixture was cooled to 0° C. Acryloyl chloride (1.1 ml, 7.19 mmol, 1 eq) was added dropwise and the mixture was heated to room temperature and stirred at this temperature for 2 h. Upon completion, the mixture was quenched with 0.4 ml MeOH, diluted with DCM and was washed with saturated NaHCO 3 . The organic layer was separated, dried with Na 2 SO 4 , filtered and the solvent was removed under reduced pressure. The crude product was purified by column chromatography (SiO 2 , 10% EtOAc/Hex) to give the product as a colorless oil (943 mg, 68% yield). 
     
       
         
         
             
             
         
       
     
     ES-87 was then prepared by dissolving RS-106 (see below, 150 mg, 0.26 mmol, 1 eq) in 3 ml dry DMF (dimethylformamide) under N 2  atmosphere. K 2 CO 3  (55 mg, 0.4 mmol, 1.5 eq) was added and the mixture was stirred for 5 min before ES-86 (154 mg, 0.8 mmol, 3 eq) was added. The mixture was stirred for 3 hours at room temperature. Upon completion, the mixture was diluted with DCM and was washed with brine. The organic layer was separated, dried with Na 2 SO 4 , filtered and the solvents were removed under reduced pressure. The crude product was purified by column chromatography (SiO 2 , DCM to 10% MeOH/DCM) to give the product as a blue powder (147 mg, 75% yield). 
     
       
         
         
             
             
         
       
     
     ES-87 was used to prepare cross-linked dyes as explained below in three non-limiting examples. 
     ES-91 was prepared by charging a 50 ml round-bottom flask with dry EtOH (9 ml) and N 2  was bubbled through for 20 min. Methyl methacrylate (0.3 ml, 2.8 mmol, 1 eq), ES-87 (4 mg, 0.0056 mmol, 0.002 eq) and AIBN (azobisisobutyronitrile, 10 mg, 0.056 mmol, 0.02 eq) were added and N 2  was bubbled through for 10 min. The reaction mixture was heated to reflux under N 2  atmosphere for 24 h. Upon completion, the mixture was cooled to room temperature and was evaporated to dryness under reduced pressure. The crude product was dissolved in 3 ml of DCM and then was added dropwise to 50 ml of Hex. The precipitate was filtered and the purification process was repeated again to give the product as a blue powder. 
     ES-99 was prepared by charging a 50 ml round-bottomed flask with dry EtOH (9 ml) and N 2  was bubbled through for 20 min. Methyl methacrylate (0.3 ml, 2.8 mmol, 1 eq), 3-methacryloxypropyl trimethoxysilane (34 μl, 0.14 mmol, 0.05 eq), ES-87 (8 mg, 0.01 mmol, 0.002 eq) and AIBN (10 mg, 0.056 mmol, 0.02 eq) were added and N 2  was bubbled through for 10 min. The reaction mixture was heated to reflux under N 2  atmosphere for 24 h. Upon completion, the mixture was cooled to room temperature and was evaporated to dryness under reduced pressure. The crude product was dissolved in 3 ml of DCM and then was added dropwise to 50 ml of Hex. The precipitate was filtered and the purification process was repeated again to give the product as a blue powder. 
     ES-113 and ES-110 were prepared similarly to ES-99, but using higher concentration of the linker 3-methacryloxypropyl trimethoxysilane, namely 50% and 100% linker respectively, compared with 5% in ES-99. WIPO Publication No. WO 2017/085720 and U.S. Pat. No. 9,868,859, incorporated herein by reference in their entirety, some embodiments of PMMA cross-linked dyes, according to some embodiments of the invention. Any of disclosed RBF compounds  115 , as well as other dyes such as assistant dyes  117  may be cross linked to one or more polymers in color conversion film  130 . 
     Protective Films 
     Some embodiments comprise applying a protective film  131  to color conversion film  130  and/or configuring color conversion film  130  to have protective properties which prevent humidity damages and cracking. Any type of color conversion film  130  may be protected and/or enhanced as described in the following, e.g., RBF-compounds-based films  130  as well as films  130  based on other organic or inorganic fluorescent molecules and quantum-dot-based color conversion films  130 . 
     For example, protective film  131  may be formed using zirconium-phenyl siloxane hybrid material (ZPH), a transparent, clear and flexible polymer, based on the description in Kim et al. 2014 (“Sol-gel derived transparent zirconium-phenyl siloxane hybrid for robust high refractive index led encapsulant”, ACS Appl. Mater. Interfaces 2014, 6, 3115-3121), with the following modifications, found by the inventors to isolate films  130  from the surroundings, provide the film mechanical support and prevent cracks. 
     ZPH is a silica based polymer gel, cured in a hydrosilylation addition reaction. The polymer comprises two resin components: HZPO (a Si—H functionalized silica) and VZPO (a vinyl functionalized silica). Both components are synthesized in a sol-gel reaction separately and then mixed in the proper ratio into formulation  74  and cured to yield a semi-solid form. HZPO was mixed from 3.2 ml Methyldiethoxysilane (MDES), 6.5 g diphenylsilanediol (DPSD) and 25 mg amberlite IRC76 for 1 hour at 100° C. and then, while stirring, 673 μL zirconium propoxide (ZP) 70% in 1-propanol was added slowly and the reaction continued overnight. VZPO was mixed from 3.1 g vinyltrimethylsilane (VTMS), 4.4 g DPSD and 7.7 mg barium hydroxide monohydrate in 0.86 ml p-xylene at 80° C. and then, while stirring, ZP was added slowly, with the reaction time being four hours. ZPH was prepared by mixing VZPO and HZPO in a ratio of 1:1 mol/mol and 10 ml of a platinum catalyst was added to the viscous liquid, which was then stirred vigorously for one minute and applied on the substrate using a coating rod. Protective film  131  was inserted into the oven in 150° C. for three hours for curing. 
     Additional examples for protective films  131  include using polymerized MMA (methyl-methacrylate) as protection, by allowing MMA to diffuse into the sol-gel pores. Color conversion films  130  may be coated with additional MMA monomers that penetrate the sol-gel pores and then polymerize inside, thereby improving the life time of film  130 . The preparation procedure may be modified to provide such polymerization conditions. 
     Some embodiments comprise using a trimethoxysilane derivative as coating, e.g., an R-TMOS coating with R being e.g., phenyl, methyl, CH 2 CH 2 CF 3  or other groups, with proper process adaptations which provide the coating conditions for forming protective film  131  and/or protective characteristics of film  130 . 
     Some embodiments comprise using as epoxy silica ormosil solution layer as protective coating  131 , such as epoxy silica ormosil solution with no dye as protective layer  131  applied on cured film  130 . Other protective coatings  131  of film  130  may comprise an acetic anhydride surface treatment derived from acetic acid with ending —OH groups changed to -Ac groups to enhance life time and/or chlorotrimethoxysilane protective layer  131  having endings with —OH groups modified to -trimethylsilane to enhance life time. 
     In certain embodiments, disclosed protective films  131  may be used in a range of applications for protective respective films from humidity and mechanical damages. For example, disclosed protective films  131  may be used to coat various plastic films (made of e.g., PEI (polyethylenimine), acrylic polymers, polycarbonate, PET, PDMS (polydimethylsiloxane) and related siloxanes, as well as other polymers), glass and metals/metal oxide films or surfaces (e.g., of copper, silicon, silicon oxides, aluminum, titanium and other transition metals and their oxides). Protective films  131  may be configured to have corresponding good adhesion to the respective films. 
     In some embodiments, protective films  131  may be used to coat diffusers, polarizers, glasses or any other film that needs temperature and humidity protection (e.g., up to 85° C., 95% relative humidity). 
     In some embodiments, protective films  131  and/or formulations thereof may be used as fillers in porous films. 
     UV Curing Processes 
     UV curing processes  740  may be used additionally or in place of sol gel processes to provide the color conversion films. Formulations with and without rhodamine-based fluorescent compounds, films, displays and methods are provided, in which the fluorescent compounds are stabilized and tuned to modify display backlight illumination in a manner that increases the display&#39;s efficiency and widens its color gamut. UV cured formulations may be used to provide fluorescent films that may be applied in various ways in the backlight unit and/or in the LCD panel and improve the display&#39;s performance. The formulation, curing process and film forming procedures may be optimized and adjusted to provide a high photostability of the fluorescent compounds and narrow emission peaks of the backlight unit. 
     In certain embodiments, the sol gel process may be replaced by a UV curing process, with respect to some or all layers of film  130 . Similar or different RBF compounds  115  may be used in UV cured layers, such as RBF compounds disclosed above, and films  130  produced by UV curing may replace (or complement) films  130  (or layers  132  and/or  134 ) produced by the sol gel processes in the configurations of backlight unit  300  and display  100  which are illustrated herein. Other organic or inorganic fluorescent dyes as well as quantum dots may be embedded in disclosed UV cured films  130  or modifications thereof as well. Also, configurations of film  130  disclosed above in relation to display configurations, polarizing films and red enhanced films may be implemented with UV cured films  130  or layers  132 ,  134 . In the following, examples for applicable UV processes are presented. 
     In some embodiments, UV curing is advantageous due to the wide range of UV curable materials, which provide an opportunity to create polymeric matrices which are compatible with the incorporated dyes, such as RBF compounds  115 . In order to achieve maximal life time and QY, the structure and the crosslinking density may be optimized and the interaction between the dye and the matrix may be minimized. The use done in UV curing of highly reactive components may significantly reduce the amount of non-crosslinked material even at low UV exposure and short retention time—thereby enabling to minimize damage to the dye molecules while providing required matrices for the dye, e.g., matrices which provide high photostability, narrow FWHM (e.g., 40-60 nm) and high QY in the green and red regions (e.g., due to less occupied vibration levels), for RBF compounds  115  or other fluorescent molecules). The cross-linking degree may be optimized per dye material in order to obtain high QY (too much cross linking may degrade the QY). 
     Various examples are presented below for formulations  74  which are then UV cured after being applied to transparent PET (polyethylene terephthalate) substrate or diffuser films (PET coated with PMMA coating) by drawing using coating rods for providing films with widths ranging  20 - 100  which are then irradiated once under “H” UV lamp at conveyor speed 2-7 m/min. Color conversion films  130  may comprise multiple layers which may be applied one on top of the other. Resulting color conversion films  130  (or protective films  131 , see below) may be used as explained above by themselves or in combination with films  130  produced by sol gel processes  600 . Formulations  74  for UV cured films  130  may comprise RBF compounds  115  as described above. Life times of fluorescent dyes in UV cured matrix are different for different dyes and depend on the cured formulation and on the curing conditions. Generally, the stability of RBF compounds  115  under continued blue light excitation provides a long life time. 
     UV cured films  130 , in particular UV cured color conversion films  130 , may be prepared from formulations  74  comprising 65-70% monomers, 25-30% oligomers, and 1-5% photoinitiator; as well as color conversion elements such as RBF compounds at low concentration (e.g., 0.005-0.05%), in weight percentages of the total formulation. Following are non-limiting examples for such formulations  74 , which are UV cured to yield respective films  130 . 
     WIPO Publication No. WO 2018/042437 and U.S. Publication Nos. 2018/0072892 and 2018/0039131 provide examples for UV cured films, their preparation methods and resulting film performance, and are incorporated herein by reference in their entirety. 
     The produced films may be combined and optimized to form film  130 , for example a non-limiting example of film  130  was optimized to operate with a blue backlight source  80 A of about 10 mW/cm 2  of optical power and provided a red emission peak at 616 nm with FWHM of 60 nm and a green emission peak at 535 nm with FWHM of 45 nm, with a white point at (0.30, 0.27) CIE 1931 coordinates (white point adjustment may also be carried out as disclosed above). WIPO Publication No. WO 2018/042437 and U.S. Publication Nos. 2018/0072892 and 2018/0039131, which are incorporated herein by reference in their entirety, further provide examples for the resulting absorption and emission spectra of film  130  and example for color gamut ranges which are comparable or surpass respect to sRGB, NTSC and quantum-dots-based displays in performance parameters. 
     Protective Films 
     Some embodiments comprise applying a protective film  131  to color conversion film  130  and/or configuring color conversion film  130  to have protective properties which prevent humidity damages and cracking. Any type of color conversion film  130  may be protected and/or enhanced as described in the following, e.g., RBF-compounds-based films  130  as well as films  130  based on other organic or inorganic fluorescent molecules and quantum-dot-based color conversion films  130 . 
     For example, UV cured protective film  131  may be formed using a mixture of 3,4-epoxycyclohexylmethyl 3,4-epoxycyclohexanecarboxylate, triarylsulfonium hexafluoroantimonate salts, mixed-50 wt % in propylene carbonate, polyether modified polydimethylsiloxane and 3-ethyloxetane-3-methanol, which is UV cured on a conveyor. 
     In another example, UV cured protective film  131  may be formed by mixing 76.8% 3,4-epoxycyclohexylmethyl 3,4-epoxycyclohexanecarboxylate, 19.2% trimethylolpropane (TMP) oxetane (TMPO), 3.8% triarylsulfonium hexafluoroantimonate salts, mixed-50 wt % in propylene carbonate and 0.2% polyether-modified polydimethylsiloxane (in this order) and stirring the mixture at room temperature. The sample was applied to a sol-gel layer (e.g., color conversion film  130  produced by a sol gel process disclosed above) by drawing using a coating rod to form a 50 μm layer and then irradiated once under H UV lamp at conveyor speed 7 m/min. The sol-gel layer was cleaned with ethanol and air dried before coating. 
     BLU Modifications and Configurations 
       FIG. 12  is a high-level schematic illustration of a backlight unit (BLU)  300  for a liquid crystal display (LCD)  100 , according to some embodiments of the invention. BLU  300  comprises at least one color conversion unit  150  and at least one illumination source  80 . 
     Color conversion unit(s)  150  comprises at least one partly reflective structure  155  and at least one color conversion element  135 . Color conversion element(s)  135  comprises at least one fluorescent dye (e.g., RBF compound(s)  115 ) configured to convert blue radiation to green and/or red radiation. Illumination source(s)  80  is configured to deliver radiation through color conversion unit(s)  150  to a LCD panel  200  of LCD  100 . Partly reflective structure(s)  155  is configured to redirect at least a part of the delivered radiation to pass multiple times through color conversion element(s)  135 . Radiation (denoted by  120 A) is delivered by illumination source(s)  80  through partly reflective structure(s)  155  which redirects (e.g., any of reflects, scatters, disperses, etc.) radiation through color conversion element(s)  135 , denoted as radiation  120 B,  120 C (for multiple, two or more passes through color conversion element(s)  135 ) before radiation  120  is delivered to LCD panel  200 . Partly reflective structure(s)  155  may be configured to recycle blue radiation through color conversion unit(s)  150  to enhance color conversion efficiency and/or flux, and/or to increase the lifetime of color conversion element(s)  135 . Advantageously, the inventors have found out that passing the radiation from illumination source(s)  80  multiple times through color conversion element(s)  135  provides illumination radiation  120 , modifies the white point of LCD  100  in a controllable manner, and one color conversion unit(s) may be configured to set a white point of delivered radiation  120  and LCD  100  according to specified requirements. 
       FIG. 13  is a high-level schematic illustration of white point adjustment for LCD  100 , according to some embodiments of the invention.  FIG. 13  illustrates schematically a prior art spectrum  82  of delivered radiation, and a spectrum  122  of delivered radiation  120  to LCD panel  200 , according to some embodiments of the invention of delivered radiation. Spectra  82 ,  122  have a relatively large blue peak (e.g., between 440-460 nm) and smaller green and red peaks (e.g., between 520-540 nm and between 610-630 nm, respectively). However, multiple passing of the delivered radiation resulting in spectrum  122  has a lower blue peak and higher green and/or red peaks than prior art spectrum  82 , due to enhanced color conversion resulting from the multiple passes. Lowering the blue peak (indicated schematically by ΔB) and raising the green and/or red peaks (indicated schematically by ΔG and ΔR, respectively) changes the white point (indicated schematically as wp on the schematic color space diagram) of LCD  100  with respect to prior art LCDs, and configuration of partly reflective structure(s)  155  and color conversion element(s)  135  provides required or specified settings of the white point by increasing or decreasing ΔB, ΔG and ΔR according to specifications (indicated schematically by the arrows). 
       FIGS. 14A-F  are high-level schematic illustrations of BLUs  300 , according to some embodiments of the invention. One or more illumination source(s)  80 , such as blue LEDs  80 A and/or white LEDs  80 B in various configurations may be used with a waveguide  420  for guiding the radiation from illumination source(s)  80  towards partly reflective structure(s)  155  and/or towards optical element(s)  410  guiding delivered radiation  120  towards LCD panel  200 . For example, optical element(s)  410  may comprise polarizer(s), dual brightness enhancement film(s) (BEF), possibly dual brightness enhancement film(s) (DBEF) etc. 
     It is noted that while the numerals  300  and  400  are used herein to denote the BLU and the modified illumination sources, respectively, certain embodiments comprise extended illumination sources  400  which may be used as BLUs  300 . In such cases, either numeral,  300  or  400 , is applicable. In other cases, with BLU  300  comprising additional layers  350 , the numerals are clearly distinct. It is further noted that various embodiments may comprise combinations of illumination source  400  and layers  350 , which are disclosed in different embodiments. 
     Partly reflective structure(s)  155  may be configured in different ways, e.g., comprising a top reflector  154  configured to re-introduce at least part of radiation  120 A back into color conversion element(s)  135  as radiation  120 B (see  FIG. 12 ) and possibly comprising a bottom reflector  152  configured to re-direct at least part of radiation  120 B towards LCD panel  200  as radiation  120 C, possibly back through color conversion element(s)  135 . Top reflector  154  is partly reflective, comprising e.g., a perforated reflector  158  (e.g., as illustrated schematically in  FIG. 14A ), a spectral filter having specified transmittance and reflectance curves configured to pass and/or reflect part of the blue radiation into partly reflective structure(s)  155  and partly pass red and/or green radiation out of partly reflective structure(s)  155 . The parts of radiation in different wavelength ranges may be configured according to required intensity of B, G and R and according to the geometric configuration of BLU  300  and of partly reflective structure(s)  155 . For example, top reflector  154  may comprise one or more short pass filter(s) (SPFs), long pass filter(s) (LPFs). In certain embodiments, top reflector  154  may further comprise diffusing elements such as diffuser layer(s) and/or may be patterned to control and homogeneity of radiation  120 . In certain embodiments, intermediate filter layers  156  may be further introduced between color conversion element(s)  135  to regulate radiation passing therebetween (see e.g.,  FIG. 14D ). In certain embodiments, multiple lateral illumination sources  80 A may be used (see e.g.,  FIG. 14B ), with only some of the illumination radiation passing through color conversion element(s)  135 , e.g.,  135 R and  135 G, in order to increase their lifetime. For example, blue light from upper illumination source  80 A may be provided without any color conversion, while blue light from bottom illumination source  80 A may be mostly converted into red and green light. Additional reflectors and/or diffusers  445 ,  447  may be positioned, e.g., below partly reflective structure(s)  155  such as in association with waveguide  420  (e.g., see  FIG. 14C ) and/or on sides of waveguide  420  and/or color conversion unit(s)  150  (e.g., see  FIGS. 14A-F ). BLU  300  may further comprise additional reflectors  440  (see e.g.,  FIGS. 14C, 14D ) as well as sides of waveguide  420  and/or sides of partly reflective structure(s)  155 , which may be configured to control the dispersal of radiation within BLU  300 , to yield required illumination parameters for delivered radiation  120 . In certain embodiments, no diffusers are used in color conversion unit(s)  150 . 
     Color conversion element(s)  135  may comprise one or more layers, e.g., color conversion element(s)  135 G configured to convert blue radiation into green radiation, color conversion element(s)  135 R configured to convert blue and/or green radiation into red radiation, in various spatial configurations, such as one or more layers of each, combined layers, separate elements within partly reflective structure(s)  155  etc. In various embodiments, color conversion element(s)  135 G may be set between color conversion element(s)  135 R (see e.g.,  FIG. 14A ) and/or color conversion element(s)  135 R may be set between color conversion element(s)  135 G and/or color conversion elements  135 R,  135 G may be integrated into a single layer (see e.g.,  FIG. 14E ). Color conversion element(s)  135  may use rhodamine-based fluorescent dyes, embedded in various matrices such as sol-gel based matrices, UV cured matrices, etc.—as disclosed e.g., in WO 2018/042437 and U.S. Publication Nos. 2018/0072892, 2018/0037738 and 2018/0039131, or may be based on other color conversion elements, such as quantum dots. For example, the fluorescent dye(s) may be configured to convert blue radiation to green radiation, green radiation to red radiation and/or blue radiation to red radiation. 
     In certain embodiments, color conversion element(s)  135  may comprise assistant dyes configured to modify the radiation spectrum by absorbing radiation in one specified wavelengths range and emitting radiation at another one specified wavelengths range, which is typically lower the absorption range, at efficiencies typically ranging between 70-90%. For example, assistant dyes may be selected or configured to absorb radiation outside the range of the LCD filters (B, G and R) and emit radiation within such range, to enhance display efficiency, as disclosed, e.g., in U.S. Publication No. 2018/0039131. For example, the fluorescent dye(s) may be configured to convert radiation outside a wavelength range of a color filter of the LCD into radiation inside the wavelength range of the color filter of the LCD. 
     Illumination source(s)  80  may comprise any of blue LEDs  80 A and/or white LEDs  80 B (see e.g.,  FIG. 14E ), combinations thereof, as well as illumination source(s)  80  having any other combination of colors. 
       FIGS. 15A-15E and 16A-16D  are high-level schematic illustrations of BLUs  300  having color conversion unit(s)  150  in which color conversion elements  135  receive only part of the overall radiation, according to some embodiments of the invention. In certain embodiments, illumination source(s)  80  may be further configured to deliver only some of the radiation through color conversion unit(s)  150  to LCD panel  200 , and deliver a part of the radiation directly to LCD panel  200 . Embodiments illustrated in  FIGS. 15E and 16A-16D  may comprise color conversion unit(s)  150  disclosed above. 
     For example,  FIG. 15A  illustrates schematically BLU  300  having one or more illumination source(s)  80 B configured to deliver radiation to LCD panel  200  through color conversion unit(s)  150  (shown very schematically) and one or more illumination source(s)  80 A configured to deliver radiation directly to LCD panel  200 . 
     In various embodiments, illustrated schematically in  FIGS. 15B and 15C , dedicated illumination source(s)  80 A,  80 B may be configured to deliver radiation through separate paths to provide delivered radiation  120  (e.g., through different waveguides  420 ,  430  as illustrated schematically in  FIG. 15B ) and/or illumination source(s)  80  may be configured to deliver radiation which is then split in waveguide  420  so that some of the radiation is delivered directly to LCD panel  200  and some is delivered through corresponding color conversion elements  135 R,  135 G, possibly through corresponding elements  403 R,  403 G (radiation indicated by  80 A,  80 B, respectively, in schematic illustration  FIG. 15C ), which may comprise any of color filters, reflectors, diffusers etc. Such elements are optional and may be set above and/or below respective color conversion elements  135 R,  135 G. 
       FIGS. 15D and 15E  illustrate schematically separation of radiation from illumination source(s)  80 A,  80  into direct radiation  120 D and color converted radiation  120 E in two conceptual configurations, which may be used separately or be combined. In the configuration illustrated schematically in  FIG. 15D , the splitting of the delivered radiation into direct radiation  120 D and color converted radiation  120 E is carried out globally at the BLU level, e.g., by directing only some of the radiation into color conversion unit(s)  150  and letting a part of the radiation exit BLU  300  directly. Any configuration of BLU  300  illustrated e.g., in  FIG. 14A-F  may be used for such configurations. In the configuration illustrated schematically in  FIG. 15E , the splitting of the delivered radiation into direct radiation  120 D and color converted radiation  120 E is carried out locally, by configuring color conversion elements  135  to spatially intercept only part of the radiation  120 E delivered by illumination source(s)  80 , and not affecting some of the delivered radiation  120 D at all. For example, in the side walls configuration illustrated schematically in  FIG. 15E , color conversion elements  135  intercept only side lobes of radiation emitted from illumination source(s)  80 , the amount of which is geometrically controlled and also depends on the configuration of illumination source(s)  80  and the radiation distribution they emit. 
     In certain embodiments, direct illumination (as illustrated schematically in  FIG. 15E ) and indirect illumination (as illustrated schematically in  FIG. 15D , e.g., using diffusive elements) may be combined in BLU  300  to optimize performance such as color conversion efficiency and lifetime. 
       FIGS. 16A-16D  illustrate schematically various configurations of BLUs  300  with color conversion elements  135  that intercept only side lobes  120 E of radiation emitted from illumination source(s)  80 , leaving a predefined part  120 D of the illumination to be delivered without passing through any color conversion elements  135 . For example,  FIG. 16A  illustrates schematically color conversion elements  135  as lateral walls, which may be configured to have various thicknesses and heights according to the required amount of color conversion and radiation side lobes  120 E. It is noted that in  FIGS. 15E and 16A  color conversion elements  135  may receive and convert radiation coming from either side of the respective walls, enhancing color conversion efficiency. Color conversion elements  135  may further comprise reflectors  450  to enhance color conversion efficiency. 
     In certain embodiments, illustrated schematically in  FIGS. 16B-16D , color conversion elements  135  may be designed in various geometric and spatial configurations, to determine and control the relative part of the radiation which passes therethrough, and at least partly converted to green and/or red radiation by respective dyes in color conversion elements  135 . For example, color conversion elements  135  may be designed as truncated triangles, or zig-zags (illustrated e.g., in  FIGS. 16B and 16C ), as truncated domes (illustrated e.g., in  FIG. 16D ) or any other shape having openings or perforations through which part  120 D of the radiation may be delivered to LCD panel  200  in radiation  120  without passing through color conversion elements  135 . The size and arrangement of the openings between color conversion elements  135  and the spatial design of color conversion elements  135  may be configured to control the radiation flux directed to color conversion elements  135  to optimize performance such as color conversion efficiency and lifetime. 
     In any of the disclosed embodiments, optical element(s)  410  such as BEF(s), DBEF(s), diffuser(s), polarizer(s) etc., may be used on top of BLU  300  to further configure delivered radiation  120  according to given requirements (e.g., have a Lambertian distribution with specified parameters). In any of the disclosed embodiments, illumination source(s)  80  may comprise any of multiple LEDs and/or multiple dispersive and/or diffusive elements in optical communication with waveguide  420  delivering radiation from LED(s). Illumination source(s)  80  may comprise scattering spots configured to deliver radiation received from edge LEDS through the waveguide—in the direction of the color conversion elements and eventually the LCD panel. The dispersive and/or diffusive elements may be set at a top and/or at a bottom layer of waveguide  420  (see e.g.,  FIGS. 16C and 16D , respectively), and may be configured to deliver a given profile of radiation, to control and determine parts  120 D,  120 E thereof. In any of the disclosed embodiments, dispersion of the fluorescent dyes through color conversion elements  135  may be configured to enhance lifetime, e.g., change gradually in fluorescent dye concentration. 
     The inventors have found out that when color conversion efficiency is high, it may be advantageous to reduce the radiation flux passing through color conversion elements  135 , in order to increase their lifetime, and/or to reduce the overall flux of radiation used in LCD  100 , to increase the lifetime thereof and of elements in LCD panel  200 . Enhanced color conversion efficiency may be used to reduce the clue radiation flux delivered to color conversion unit(s)  150 , and to deliver blue radiation separately from color converted radiation to improve efficiency, lifetime and enhance the ability to control the white point of LCD  100 . In certain embodiments, the inventors have noted that recycled blue radiation, passing multiple times through color conversion unit(s)  150 , degrades color conversion elements  135  less than a larger flux of non-recycled radiation. Combining shaped color conversion elements  135  with elements of partly reflective structure(s)  155  may be used to simultaneously enhance color conversion efficiency, increase lifetime and provide controllable white point of delivered radiation  120  and of LCD  100 . 
     In any of the embodiments disclosed in  FIGS. 15A-15C, 15E and 16A-16D , partly reflective structure(s)  155  are not illustrated for simplicity reasons and may well be integrated in the illustrated BLUs according to the principles outlined above (see e.g.,  FIGS. 13A, 14A -F and  15 D). 
     Various embodiments of disclosed methods are presented in  FIG. 17  below, the stages of which may be combined into various embodiments. 
       FIG. 17  is a high-level flowchart illustrating a method  500 , according to some embodiments of the invention. The stages of method  500  may be carried out with respect to various aspects of precursors  72 , formulations  74 , films  130  and displays  100  described above, which may optionally be configured to implement method  500 , irrespective of the order of the stages. 
     In some embodiments, method  500  comprises configuring a LCD with RGB color filters to have at least one color conversion film prepared to have a R emission peak and/or a G emission peak (stage  510 ), patterning the at least one color conversion film with respect to a patterning of the RGB color filters to yield a spatial correspondence between film regions with R and G emission peaks and respective R and G color filter (stage  520 ), and positioning the color conversion film in an LCD panel of the LCD, possibly above the LC module (stage  525 ). 
     In some embodiments, method  500  comprises configuring a LCD with RGB color filters to have at least one color conversion film prepared to have a R emission peak and a G emission peak (stage  510 ), and adjusting an intensity of the R and G emission peaks of the at least one color conversion film to fine tune a white point of the LCD to be at a center of an expected line of deterioration of the intensity within given LCD specifications (stage  530 ). 
     In some embodiments, method  500  comprises configuring a LCD with RGB color filters to have at least one color conversion film prepared to have a R emission peak and a G emission peak (stage  510 ), preparing the at least one color conversion film using a matrix and a process which direct self-assembly of molecules of color conversion molecules of the at least one color conversion film to yield polarization of at least part of illumination emitted by the color conversion film (stage  540 ), and replacing at least one polarizer in the LCD by the at least one color conversion film (stage  545 ). 
     In some embodiments, method  500  comprises configuring a LCD with RGB color filters and white backlight illumination to have at least one color conversion film prepared to have a R emission peak (stage  550 ). 
     In some embodiments, method  500  further comprises applying a protective layer to the color conversion film (stage  555 ). For example, method  500  may further comprise any of: preparing the protective layer by a sol gel process with at least one of: zirconium-phenyl siloxane hybrid material (ZPH), methyl methacrylate (MMA), trimethoxysilane derivative and an epoxy silica ormosil solution; preparing the protective layer by an acetic anhydride surface treatment and/or a trimethylsilane surface treatment; and/or preparing the protective layer by a UV curing process using a mixture of 3,4-epoxycyclohexylmethyl 3,4-epoxycyclohexanecarboxylate and triarylsulfonium hexafluoroantimonate salts, mixed in propylene carbonate. 
     The at least one color conversion film may comprise at least one RBF compound defined by Formula 1 and/or Formula 2. 
     Method  500  may further comprise embedding the at least one color conversion film in a fluorescence-intensifying section which comprises at least one supportive structure configured to redirect radiation to the at least one color conversion film (stage  560 ). 
     Method  500  may further comprise integrating the at least one color conversion film with the RGB color filters and/or with a crosstalk-reducing layer comprising a structural framework which is patterned according to a pixel structure of the RGB color filters (stage  570 ). 
     Method  500  may further comprise patterning the at least one color conversion film to yield a spatial correspondence between film regions with R and G emission peaks of the at least one color conversion film and respective R and G color filters (stage  580 ). 
     Method  500  may further comprise regulating transmission through the LC module according to an intensity of fluorescence from the at least one color conversion film, by tuning down the transmission through the LC module when the at least one color conversion film is fresh and provides a high level of fluorescence, and gradually tuning up the transmission through the LC nodule as the at least one color conversion film degrades and provides less fluorescence, to yield a constant output from the LCD (stage  590 ). 
     In method  500 , the at least one color conversion film may be prepared by at least one corresponding sol-gel process (stages and method  600 ) and/or UV curing process (stage and method  700 ), which are presented in more detail below. 
       FIG. 17  is further a high-level flowchart illustrating a method  600  which may be part of method  500 , according to some embodiments of the invention. The stages of method  600  may be carried out with respect to various aspects of precursors  72 , formulations  74 , films  130  and displays  100  described above, which may optionally be configured to implement method  600 . Method  600  may comprise stages for producing, preparing and/or using precursors  72 , formulations  74 , films  130  and displays  100 , such as any of the following stages, irrespective of their order. 
     Method  600  may comprise preparing a hybrid sol-gel precursor formulation from: an epoxy silica ormosil solution prepared from TEOS, at least one MTMOS or TMOS derivative, and GLYMO; a nanoparticles powder prepared from isocyanate-functionalized silica nanoparticles and ethylene glycol; and a metal(s) alkoxide matrix solution (stage  610 ), mixing the prepared hybrid sol-gel precursor with at least one RBF compound (stage  620 ); and spreading the mixture and drying the spread mixture to form a film (stage  630 ). 
     Method  600  may comprise comprising evaporating alcohols from the mixture prior to spreading  630  (stage  625 ). The inventors have found out that using ethylene glycol  108  in the preparation of nanoparticles powder  109  and evaporating  625  the alcohols prior to spreading improve film properties, and, for example, enable reducing the number of required green-fluorescent RBF layers  132  due to the increased viscosity of formulation  74 . Possibly, the number of required green-fluorescent RBF layers  132  may be reduced to one by substantial or complete evaporation of the alcohols in formulation  74  prior to spreading  630 . 
     Preparing  610  of the hybrid sol-gel precursor formulation may be carried out under acidic conditions (stage  612 ), mixing  620  may comprise adjusting types and amounts of the TMOS derivatives to tune emission wavelengths of the fluorophores (stage  615 ), spreading and drying  630  may be carried out respectively by bar coating and by at least one of convective heating, evaporating and infrared radiation (stage  640 ). 
     As explained above, the RBF compound may be a red-fluorescent RBF compound and the TMOS derivative(s) may comprise for example PhTMOS and/or a TMOS with fluorine substituents; and/or the RBF compound may be a green-fluorescent RBF compound and the TMOS derivative(s) may comprise PhTMOS and/or F 1 TMOS with the PhTMOS:FiTMOS ratio being adjusted to tune emission properties of the green-fluorescent RBF compound. Other TMOS derivatives may comprise F 2 TMOS (tridecafluoro-1,1,2,2-tetrahydrooctyl)trimethoxysilane, 1,2-bis(triethoxysilyl)ethane, trimethoxy(propyl)silane, octadecyltrimethoxysilane, fluorotriethoxysilane, and ammonium(propyl)trimethoxysilane. 
     Method  600  may comprise forming the film from at least one red fluorescent RBF compound and/or from at least one green fluorescent RBF compound (stage  650 ). The RBF compound(s) may be supramoleculary encapsulated and/or covalently embedded in one or more layers. As non-limiting examples, method  600  may comprise forming the film from at least one red fluorescent RBF compound to enhance a red illumination component in displays using a white light source (stage  680 ), such as a white-LED-based display. Alternatively or complementarily films may be formed to have both red and green fluorescent RBF compounds and be used for enhancing red and green illumination components in displays using a blue light source (blue LEDs). 
     Method  600  may comprise associating the film with any of diffuser(s), prism film(s) and polarizer film(s) in a display backlight unit (stage  660 ), e.g. attaching one or more films onto any of the elements in the display backlight unit or possibly replacing one or more of these elements by the formed film(s). For example, method  600  may comprise configuring the film to exhibit polarization properties (stage  670 ) and using the polarizing film to enhance or replace polarizer film(s) in the display backlight unit. 
       FIG. 17  is further a high-level flowchart illustrating a method  700  which may be part of method  500 , according to some embodiments of the invention. The stages of method  700  may be carried out with respect to various aspects of formulations  74 , films  130  and displays  100  described above, which may optionally be configured to implement method  700 . Method  700  may comprise stages for producing, preparing and/or using formulations  74 , films  130  and displays  100 , such as any of the following stages, irrespective of their order. 
     Method  700  may comprise preparing a formulation from 65-70% monomers, 25-30% oligomers, 1-5% photoinitiator and at least one RBF compound (stage  710 ), in weight percentages of the total formulation, spreading the formulation to form a film (stage  730 ), and UV curing the formulation (stage  740 ). Method  700  may comprise any of: selecting the monomers from: dipropylene glycol diacrylate, ditrimethylolpropane tetraacrylate, dipentaerythritol hexaacrylate, ethoxylated pentaerythritol tetraacrylate, propoxylated (3) glyceryl acrylate and trimethylolpropane triacrylate; selecting the oligomers from: polyester acrylate, modified polyester resin diluted with dipropyleneglycol diacrylate and aliphatic urethane hexaacrylate; and selecting the photoinitiator from: alpha-hydroxy-cyclohexyl-phenyl-ketone and alpha-hydroxy ketone (possibly difunctional). 
     Method  700  may further comprise configuring the formulation and the film to yield a color conversion film and determining UV curing parameters to avoid damage to the color conversion elements, such as RBF compound(s) (stage  745 ). Method  700  may further comprise forming the color conversion film with at least one red fluorescent RBF compound and with at least one green fluorescent RBF compound (stage  750 ). 
     In some embodiments, method  700  may comprise configuring the color conversion film to exhibit polarization properties (stage  770 ), e.g., by directing self-assembly of molecules of the RBF compound(s) into at least partial alignment. Method  700  may further comprise associating the color conversion film with any of: a diffuser, a prism film and a polarizer film in a display backlight unit (stage  760 ). 
     In some embodiments, method  700  may comprise forming the color conversion film with at least one red fluorescent RBF compound to enhance a red illumination component in a white-LED-based display (stage  780 ) by shifting some of the yellow region in the emission spectrum of the white light source into the red region, namely into the R transmission region of the R color filter, to reduce illumination losses in the LCD panel while maintaining the balance between B and R+G regions in the RGB illumination (stage  782 ). 
       FIG. 17  is further a high-level flowchart further illustrating a method  800  of preparing BLUs with color conversion film(s) and/or elements(s), according to some embodiments of the invention. The method stages may be carried out with respect to LCDs  100  and BLUs  300  described above, which may optionally be configured to implement method  800 . Method  800  may comprise stages for producing, preparing and/or using LCDs  100  and BLUs  300 , such as any of the following stages, irrespective of their order. 
     Method  800  may comprise enhancing color conversion in a BLU, (stage  805 ) by incorporating at least one color conversion element, comprising at least one fluorescent dye configured to convert blue radiation to green and/or red radiation, within at least one partly reflective structure (stage  810 ) which is configured to redirect at least a part of radiation delivered from at least one illumination source of the BLU to a LCD—to pass multiple times through the at least one color conversion element (stage  820 )—to set a white point of the delivered radiation according to specified requirements (stage  840 ). Method  800  may further comprise redirecting delivered radiation to pass multiple times through the at least one color conversion element (stage  825 ) as well as converting blue radiation to green and/or red radiation by fluorescent dyes (stage  830 ) to provide, with respect to the multiple passes of radiation therethrough, the required white point parameters as well as other illumination parameters such as intensity and spatial pattern, as disclosed above. 
     In certain embodiments, method  800  may further comprise delivering only some of the radiation through the at least one color conversion unit to the LCD panel, and delivering a part of the radiation directly to the LCD panel (stage  850 ), either globally, by redirecting part of the radiation directly toward the LCD panel, or locally, by designing illumination units to deliver only part of the radiation to the color conversion elements. Method  800  may further comprise configuring the part of the radiation directly to the LCD panel to increase a lifetime of the LCD, with respect to color conversion enhancement achieved by using the at least one partly reflective structure (stage  855 ). 
       FIG. 17  is further a high-level flowchart further illustrating a method  900  of modifying the BLU design to improve LCD performance, according to some embodiments of the invention. The method stages may be carried out with respect to LCD  100  and/or collimated backlight unit  300  described above, which may optionally be configured to implement method  900 . Method  900  may comprise stages for producing, preparing and/or using LCD  100  and/or collimated backlight unit  300 , such as any of the following stages, irrespective of their order. 
     Method  900  comprises providing collimated illumination to a LCD panel of a LCD (stage  910 ) by introducing illumination into at least one internally reflective cavity with a plurality of pinpoint openings (stage  920 ), and collimating illumination exiting the pinpoint openings by a corresponding of optical elements (stage  940 ). 
     In certain embodiments, method  900  may comprise configuring a plurality of internally reflective cavities, each with a corresponding one of the pinpoint openings at a focus point of a corresponding one of the optical elements (stage  930 ). 
     In certain embodiments, method  900  may comprise configuring one internally reflective cavity to receive illumination laterally and have the plurality of pinpoint openings at corresponding focus points of the optical elements (stage  935 ). Method  900  may further comprise perforating the cavity tops to provide multiple pinholes per cavity, to regulate the distribution of emitted radiation, and designing the optical elements accordingly (stage  937 ), e.g., to have multiple sub elements per each cavity, designed with respect to the multiple pinholes in each cavity. Possibly, method  900  may further comprise encapsulating the optical elements and/or sub elements within flat transparent material, to provide a flat optical element (stage  939 ). 
     In certain embodiments, method  900  may comprise designing one or more lenses (per illumination source) to collimate illumination from illumination sources (stage  950 ) and possibly molding the illumination sources in the designed lenses to collimate illumination therefrom (stage  955 ). 
     Method  900  may further comprise positioning lenslets of a lenslets array at a plane parallel to a plane defined by the pinpoint openings, with the pinpoint openings at the focus points of corresponding lenslets (stage  960 ). Method  900  may further comprise designing the optical elements and/or sub elements thereof to be encapsulated within flat transparent material, to provide a flat optical element (stage  965 ). 
     Method  900  may further comprise integrating the color conversion layer and the color filter layer (stage  970 ). 
     In certain embodiments, method  900  may comprise configuring the LCD to have the color conversion layer and the color filter layer above the LC module (stage  980 ). 
     In certain embodiments, method  900  may comprise setting a top optical-elements array on the LCD panel, configured to increase the brightness and radiance of the LCD (stage  990 ). In certain embodiments, method  900  may comprise designing the top optical-elements array to be encapsulated within flat transparent material, to provide a flat optical element (stage  992 ). In certain embodiments, method  900  may comprise using diffuser elements in any of R, G, B regions of the color conversion layer (stage  995 ). 
     In the above description, an embodiment is an example or implementation of the invention. The various appearances of “one embodiment”, “an embodiment”, “certain embodiments” or “some embodiments” do not necessarily all refer to the same embodiments. Although various features of the invention may be described in the context of a single embodiment, the features may also be provided separately or in any suitable combination. Conversely, although the invention may be described herein in the context of separate embodiments for clarity, the invention may also be implemented in a single embodiment. Certain embodiments of the invention may include features from different embodiments disclosed above, and certain embodiments may incorporate elements from other embodiments disclosed above. The disclosure of elements of the invention in the context of a specific embodiment is not to be taken as limiting their use in the specific embodiment alone. Furthermore, it is to be understood that the invention can be carried out or practiced in various ways and that the invention can be implemented in certain embodiments other than the ones outlined in the description above. 
     The invention is not limited to those diagrams or to the corresponding descriptions. For example, flow need not move through each illustrated box or state, or in exactly the same order as illustrated and described. Meanings of technical and scientific terms used herein are to be commonly understood as by one of ordinary skill in the art to which the invention belongs, unless otherwise defined. While the invention has been described with respect to a limited number of embodiments, these should not be construed as limitations on the scope of the invention, but rather as exemplifications of some of the preferred embodiments. Other possible variations, modifications, and applications are also within the scope of the invention. Accordingly, the scope of the invention should not be limited by what has thus far been described, but by the appended claims and their legal equivalents.