Patent Publication Number: US-2007103620-A1

Title: Color filter and liquid crystal display using same

Description:
BACKGROUND  
      1. Technical Field  
      The present invention relates to color filters, and more particularly, to a color filter having a piezoelectric material and a liquid crystal display using the color filter.  
      2. Discussion of Related Art  
      A color filter is one of the most important elements in a liquid crystal display. The color filter is generally used in the liquid crystal display for converting white light beams transmitted therethrough into red light beams, green light beams and blue light beams. The red light beams, the green light beams and the blue light beams are configured to display color images.  
      Referring to  FIG. 6 , a typical color filter  1  generally includes a substrate  10 , a black matrix layer  12 , a color layer, and an indium-tin oxide (ITO) layer  11 . The black matrix layer  12  is formed on the substrate  10  and is used to separate sub-pixels of the color layer from each other. The sub-pixels of the color layer are red pigment  13 , green pigment  14  and blue pigment  15 . The ITO layer  11  is formed on the color layer. When the white light beams transmitting through the color layer are converted into red light beams, green light beams and blue light beams, the red pigment  13 , the green pigment  14  and the blue pigment  15  decrease the brightness of the red light beams, the green light beams and the blue light beams and consequently decrease the brightness of the liquid crystal display.  
      In addition, when the red pigment  13 , the green pigment  14  and the blue pigment  15  are deposited on the substrate  10  using conventional methods the pigments may overlap creating an overlap area  16 . The overlap area  16  can influence uniformity and brightness of light passing therethrough, and the display quality of the liquid crystal display will consequently be influenced.  
      What is needed, therefore, is a color filter and a liquid crystal display with enhanced uniformity and brightness.  
     SUMMARY  
      In one embodiment, a color filter includes a grating including: a base; a black matrix arranged on the base; a grating layer arranged on the base. The grating layer comprising a plurality of grating units separated by the black matrix, the grating units being comprised of a piezoelectric material, the grating unit comprising a plurality of striated (i.e. long parallel lines) microstructures; and a controlling circuit comprising a plurality of controlling units each electrically connected with its respective striated microstructures. Each of the controlling units being configured to apply a voltage to its respective striated microstructure so as to adjust the grating constant associated therewith, thereby allowing light with a predetermined wavelength to be filtered through the grating unit.  
      In another embodiment, a liquid crystal display includes a liquid crystal display panel; a backlight module; a color filter disposed between the liquid crystal display panel and the backlight module, the color filter comprising a base; a black matrix arranged on the base; a grating layer arranged on the base, the grating layer comprising a plurality of grating units separated by the black matrix, the grating units being comprised of a piezoelectric material. The grating unit comprises a plurality of striated microstructures; and a controlling circuit comprising a plurality of controlling units electrically connected with the respective striated microstructures, with each controlling unit being configured to apply a voltage to its corresponding striated microstructure so as to adjust the grating constant associated therewith. Thus allowing light with a predetermined wavelength to be filtered through the grating unit.  
      Other advantages and novel features of the present color filter will become more apparent from the following detailed description of preferred embodiments when taken in conjunction with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      Many aspects of the present color filter and related liquid crystal display can be better understood with reference to the following drawings. The components in the drawings are not necessarily drawn to scale, the emphasis instead being placed upon clearly illustrating the principles of the present color filter and related liquid crystal display.  
       FIG. 1  is a schematic, perspective view of a color filter in accordance with a first embodiment;  
       FIG. 2  is a partly, plan view of the color filter of  FIG. 1 , showing a cross-sectional profile of an arcuate striated microstructure of the color filter;  
       FIG. 3  is a partly, plan view of the color filter of  FIG. 1 , showing that a cross-sectional profile of a striated microstructure of the color filter is a trapezoid;  
       FIG. 4  is a schematic, plan view of a liquid crystal display in accordance with a second embodiment;  
       FIG. 5  is a schematic, plan view of a liquid crystal display in accordance with a third embodiment; and  
       FIG. 6  is a schematic, cross-sectional view of a conventional color filter.  
    
    
      Corresponding reference characters indicate corresponding parts throughout the drawing. The exemplifications set out herein illustrate at least one preferred embodiment of the present invention, in one form, and such exemplifications are not to be construed as limiting the scope of the invention in any manner.  
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
      Reference will now be made to the drawings to describe embodiments of the present color filter and liquid crystal display.  
      Referring to  FIG. 1 , a color filter  2  in accordance with a first embodiment of the present invention is shown. The color filter  2  includes a base  21  and a grating layer  22  formed on the base  21 . The grating layer  22  includes a plurality of grating units  221  being comprised of a piezoelectric material. Each grating unit  221  may be a phase grating. Each grating unit  221  includes a plurality of striated microstructures  221 ′. A control circuit  23  includes a plurality of controlling units where each controlling unit is electrically connected to its respective striated microstructure  221 ′. It is recognized that if a piezoelectric material is subjected to a voltage differential, it mechanically deforms. The controlling units are configured to apply a voltage to the respective striated microstructure  221 ′ so as to adjust a grating constant associated with the corresponding grating unit, thereby allowing light with a predetermined wavelength to be filtered through the grating unit. A black matrix  24  is arranged on the base  21 , and is used for separating the grating units  221  from each other.  
      The base  21  is made from a transparent material such as an insulated glass. Preferably, the grating layer  22  is comprised of a piezoelectric material, such as plumbozirconium titania (PZT), lithium niobate (LiNbO.sub.3), lithium tantalate (LiTaO.sub.3), and zinc oxide (ZnO). A base film such as polyvinyl chloride (PVC) can be optionally arranged between the grating layer  22  and the base  21 . The base film is used for connecting grating layer  22  and the base  21 .  
      The grating layer  22  is used to provide the light of a given color for example, R(ed)-light, G(reen)-light, and B(lue)-light. An energy distribution of the R-light, the G-light, and the B-light is determined by the configuration of the striated microstructure of the grating. The striated microstructure can be of any suitable structure such as grooves or protrusions. For instance, as shown in  FIG. 2 , a striated microstructure  321 ′ has an arcuate surface  2211 ′. As shown in  FIG. 3 , the cross-section of the striated microstructure  421 ′ is a trapezoid. The cross-section of the striated microstructure can be rectangular or triangle-shaped etc.  
      Because the piezoelectric material deforms under a voltage differential, the controlling unit can control the grating constant of the striated microstructure  221 ′ connected therewith through applying the voltage differential to the striated microstructure  221 ′. The relationship between the grating constant and the light wavelength obeys the following equation: d(sin θ−sin θ1)=mλ, where d is the grating constant, θ is angle of emergence, θ1 is angle of incidence, λ is optical wavelength, and m is an integer, the grating constant d is independently variable and the angle of emergence θ is dependently variable when the angle of incidence θ1 of white light is known. In the illustrated embodiment, the striated microstructures  221 ′ can cooperatively separate the incident white light into, for example, the R-light, the G-light, or the B-light and control angle of emergence of the light separated by adjusting of the grating constant of the grating unit  221 .  
      The grating units  221  are configured to spatially correspond to the sub-pixel of the liquid crystal display panel. For example, every three adjacent grating units  221  are configured to correspond to one pixel that consists of R sub-pixels G sub-pixels and B sub-pixels of the liquid crystal display panel. The R-light, the G-light, and the B-light separated by the grating units  221  is directed to the corresponding sub-pixels.  
       FIG. 4  shows a schematic view of a liquid crystal display in accordance with a second embodiment. The liquid crystal display  5  includes a light source  51 , a wedge-shaped light guide plate  53 , a color filter  54 , and a liquid crystal display panel  55 . The wedge-shaped light guide plate  53  includes a light incidence surface  532 , a light-emitting surface  531  connecting with the light incidence surface  532 , and a bottom surface  533  opposite to the light-emitting surface  531 . The light source  51  faces the light incidence surface  532 . The liquid crystal display  5  further includes a reflector plate  52  facing the bottom surface  533 . The wedge-shaped light guide plate  53  can provide a uniform surface light source. The color filter  54  of the second embodiment is similar to the color filter  2  of the first embodiment.  
      In this embodiment, each sub-pixel of the liquid crystal display panel  55  corresponds to a grating unit of the color filter  54 . Each pixel consists of an R sub-pixel a G sub-pixel and a B sub-pixel. In other words, every three adjacent grating units correspond to a common pixel.  
       FIG. 5  shows a schematic view of a liquid crystal display in accordance with a third embodiment. The liquid crystal display  6  is similar to that of the second embodiment, except that a collective lens  66  is positioned between the color filter  64  and the liquid crystal display panel  55 . The R-light, the G-light, and the B-light can be converged onto a respective pixel of the liquid crystal display panel  55 .  
      It is to be understood that the above-described embodiment is intended to illustrate rather than limit the invention. Variations may be made to the embodiment without departing from the spirit of the invention as claimed. The above-described embodiments are intended to illustrate the scope of the invention and not restrict the scope of the invention.