Patent Publication Number: US-2012038862-A1

Title: Liquid crystal display panel and color filter substrate

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the priority benefit of Taiwan application serial no. 99126609, filed on Aug. 10, 2010. The entirety of the above-mentioned patent application is hereby incorporated by reference herein and made a part of this specification. 
     BACKGROUND 
     1. Field of the Invention 
     The invention relates to a liquid crystal display panel. Particularly, the invention relates to a color filter substrate of a liquid crystal display panel. 
     2. Description of Related Art 
     As liquid crystal displays (LCDs) are continually developed towards a large size display specification, to overcome a viewing angle problem of large size display, a wide viewing angle technology of LCD panels has to be continually developed. A multi-domain vertical alignment (MVA) LCD panel applies a commonly used wide viewing angle technology. 
     Generally, to improve optical performance of the MVA LCD panel, a horizontal phase compensation film (referred to as an A-plate phase compensation film) and a vertical phase compensation film (referred to as a C-plate phase compensation film) are disposed on a color filter substrate of the MVA LCD panel, i.e. at least a color filter film, the A-plate phase compensation film and the C-plate phase compensation film are disposed on the color filter substrate. Generally, alignment films are respectively disposed between the color filter film, the A-plate phase compensation film and the C-plate phase compensation film. Accordingly, in the conventional MVA LCD panel, layers of thin films on the color filter substrate thereof is relatively more, so that a thickness of the color filter substrate is relatively great. Moreover, since the color filter substrate has relatively more layers of the thin films, a number of fabrication processes thereof is relatively more, which may increase a fabrication cost of the color filter substrate. 
     SUMMARY OF THE INVENTION 
     The invention is directed to a liquid crystal display panel and a color filter substrate thereof, which may have a relatively low fabrication cost. 
     The invention provides a color filter substrate including a substrate, a stacked layer, a phase compensation film and a second alignment film. The stacked layer is disposed on the substrate and includes a first alignment film and a color filter layer having a phase compensation effect, wherein the first alignment film and the color filter layer are stacked on each other. The phase compensation film is disposed on the stacked layer. The second alignment film is disposed on the phase compensation film. 
     In an embodiment of the invention, the first alignment film is disposed between the substrate and the color filter layer having the phase compensation effect. 
     In an embodiment of the invention, a phase retardation of the color filter layer having the phase compensation effect is substantially equivalent to a phase retardation of an A-plate compensation film, and the phase compensation film is a C-plate compensation film. 
     In an embodiment of the invention, a material of the C-plate phase compensation film includes polymer liquid crystal. 
     In an embodiment of the invention, a phase retardation of the color filter layer having the phase compensation effect is substantially equivalent to a phase retardation of a C-plate compensation film, and the phase compensation film is an A-plate compensation film. 
     In an embodiment of the invention, the color filter substrate further includes a third alignment film disposed between the phase compensation film and the color filter layer having the phase compensation effect. 
     In an embodiment of the invention, a material of the A-plate phase compensation film includes polymer liquid crystal. 
     In an embodiment of the invention, a material of the color filter layer having the phase compensation effect includes a pigment, a phase compensation material and a solvent. A weight percentage of the pigment is substantially greater than or equal to 30% and smaller than or equal to 54%. A weight percentage of the phase compensation material is substantially greater than or equal to 5% and smaller than or equal to 20%. A weight percentage of the solvent is substantially greater than or equal to 35% and smaller than or equal to 50%. 
     In an embodiment of the invention, a weight percentage of the pigment is substantially greater than or equal to 38% and smaller than or equal to 45%. Moreover, the pigment includes at least one of C.I. pigment red 122, C.I. pigment red 177, C.I. pigment red 202, C.I. pigment red 206, C.I. pigment red 209, C.I. pigment red 254, C.I. pigment red 255, C.I. pigment green 7, C.I. pigment green 36, C.I. pigment yellow 13, C.I. pigment yellow 55, C.I. pigment yellow 119, C.I. pigment yellow 138, C.I. pigment yellow 139, C.I. pigment yellow 150, C.I. pigment yellow 168, C.I. pigment violet 23, C.I. pigment orange 71, C.I. pigment blue 15:3, C.I. pigment blue 15:4, C.I. pigment blue 15:6, C.I. pigment black 1, C.I. pigment black 7, titanium oxide, barium sulphate, calcium carbonate, zinc oxide, titanium nitride, lead sulphate, yellow lead, zinc yellow, red iron oxide III, cadmium red, ultramarine blue, Prussian blue, chromium oxide green, cobalt green, amber, titanium black, synthetic iron black, and carbon back, or combinations thereof. 
     In an embodiment of the invention, a weight percentage of the phase compensation material is substantially equal to 10%. Moreover, the phase compensation material includes polymerizable liquid crystal molecules. 
     In an embodiment of the invention, a weight percentage of the solvent is substantially greater than or equal to 41% and smaller than or equal to 50%. Moreover, the solvent includes at least one of N-methylpyrrolidinone, ethylene glycol monobutyl ether, propylene glycol monomethyl ether, and propylene glycol monomethyl ether acetate, or combinations thereof. 
     In an embodiment of the invention, a weight percentage of the N-methyl pyrrolidinone is substantially equal to 1%, a weight percentage of the ethylene glycol monobutyl ether is substantially equal to 3.5%, a weight percentage of the propylene glycol monomethyl ether is substantially equal to 32.5%, and a weight percentage of the propylene glycol monomethyl ether acetate is substantially equal to 10%. 
     In an embodiment of the invention, the color filter layer having the phase compensation effect further includes an initiator, wherein a weight percentage of the initiator is substantially greater than 0% and smaller than or equal to 1%. 
     In an embodiment of the invention, a weight percentage of the initiator is substantially equal to 0.5%. Moreover, the initiator includes at least one of 1-hydroxycyclohexyl phenyl ketone, and 2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropane-1-one, or a combination thereof. 
     In an embodiment of the invention, the color filter layer having the phase compensation effect further includes a dispersant, wherein a weight percentage of the dispersant is substantially greater than 0% and smaller than or equal to 5%. 
     In an embodiment of the invention, a weight percentage of the dispersant is substantially greater than or equal to 1% and smaller than or equal to 3.5%. Moreover, the dispersant includes a polymer dispersant. 
     In an embodiment of the invention, the color filter substrate further includes a common electrode disposed between the phase compensation film and the second alignment film. 
     In an embodiment of the invention, the color filter substrate further includes an overcoat disposed between the common electrode and the phase compensation film. 
     In an embodiment of the invention, the color filter substrate further includes a plurality of spacers disposed between the common electrode and the second alignment film. 
     In an embodiment of the invention, the color filter substrate further includes a plurality of alignment protrusions disposed between the common electrode and the second alignment film. 
     The invention provides a liquid crystal display (LCD) panel including an active device array substrate, a color filter substrate, a liquid crystal layer and a third alignment film. The color filter substrate is disposed above the active device array substrate, and includes a substrate, a stacked layer, a phase compensation film and a second alignment film. The stacked layer is disposed on the substrate and includes a first alignment film and a color filter layer having a phase compensation effect, wherein the first alignment film and the color filter layer are stacked on each other. The phase compensation film is disposed on the stacked layer. The second alignment film is disposed on the phase compensation film. The liquid crystal layer is disposed between the active device array substrate and the second alignment film. The third alignment film is disposed between the active device array substrate and the liquid crystal layer. 
     According to the above descriptions, in the LCD panel and the color filter substrate of the invention, the color filter layer having the phase compensation effect is used to replace the A-plate phase compensation film or the C-plate phase compensation film. In this way, a number of layers of the color filter substrate can be reduced, so as to simplify fabrication processes and reduce a fabrication cost of the color filter substrate. 
     In order to make the aforementioned and other features and advantages of the invention comprehensible, several exemplary embodiments accompanied with figures are described in detail below. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification. The drawings illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention. 
         FIGS. 1A-1G  are schematic diagrams illustrating a fabrication process of a color filter substrate according to an embodiment of the invention. 
         FIG. 2  is a side view of a liquid crystal display panel according to an embodiment of the invention. 
         FIG. 3  is a side view of a color filter substrate according to another embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION OF DISCLOSED EMBODIMENTS 
     First Embodiment 
       FIGS. 1A-1G  are schematic diagrams illustrating a fabrication process of a color filter substrate according to an embodiment of the invention. Referring to  FIG. 1A , an alignment film  120  is formed on a substrate  110 , wherein a material of the alignment film  120  is, for example, polyimide or polymethyl methacrylate. Then, a color filter layer  130  is formed on the alignment film  120 , as that shown in  FIG. 1B . The color filter layer  130  has a phase compensation effect, and in the present embodiment, a phase retardation of the color filter layer  130  is substantially equivalent to a phase retardation of an A-plate phase compensation film. In other words, the color filter layer  130  has both of the phase retardation function and the color filter function. 
     In detail, a process of forming the color filter layer  130  is as follows. A plurality of black matrices  130   d  is formed on the alignment film  120 . Then, a red filter film  130   a , a green filter film  130   b  and a blue filter film  130   c  are disposed between the black matrices  130   d , and the red filter film  130   a , the green filter film  130   b  and the blue filter film  130   c  have a phase retardation substantially equivalent to that of the A-plate phase compensation film. Moreover, thickness of the red filter film  130   a , the green filter film  130   b  and the blue filter film  130   c  can be the same or different. 
     Then, a phase compensation film  140  is formed on the color filter layer  130 , as that shown in  FIG. 1C . In the present embodiment, the phase compensation film  140  is, for example, a C-plate phase compensation film, and a material thereof is, for example, solid state/liquid state polymer liquid crystal. Preferably, the material of C-plate phase compensation film is, for example, solid state polymer liquid crystal. Then, an overcoat  150  is formed on the phase compensation film  140 , as that shown in  FIG. 1D . In the present embodiment, a material of the overcoat  150  is, for example, SiNx, SiOy or SiOxNy. Then, a common electrode  160  is formed on the overcoat  150 , as that shown in  FIG. 1E . A material of the common electrode  160  is, for example, a transparent conductive oxide such as indium tin oxide (ITO) or indium zinc oxide (IZO). 
     Then, a plurality of alignment protrusions  170  and a plurality of spacers  180  are formed on the common electrode  160 , as that shown in  FIG. 1F . After the alignment protrusions  170  and the spacers  180  are fabricated, an alignment film  190  is formed on the common electrode  160 , the alignment protrusions  170  and the spacers  180 , as that shown in  FIG. 1G . After the alignment film  190  is fabricated, fabrication of the color filter substrate  100  of the present embodiment is roughly completed. It should be noticed that the overcoat  150 , the common electrode  160 , the alignment protrusions  170  and the spacers  180  can be optional components. 
     Referring to  FIG. 1G , in the present embodiment, the color filter substrate  100  includes the substrate  110 , the alignment films  120  and  190 , the color filter layer  130 , the phase compensation film  140 , the overcoat  150 , the common electrode  160 , the alignment protrusions  170  and the spacers  180 . The alignment film  120  is disposed on the substrate  110 , the color filter layer  130  is disposed on the alignment film  120 , the phase compensation film  140  is disposed on the color filter layer  130 , the overcoat  150  is disposed on the phase compensation film  140 , the common electrode  160  is disposed on the overcoat  150 , the alignment protrusions  170  and the spacers  180  are disposed on the common electrode  160 , and the alignment film  190  is disposed on the common electrode  160 , the alignment protrusions  170  and the spacers  180 . 
     Further, the alignment film  120  and the color filter layer  130  can be regarded as a stacked layer, and in the present embodiment, the color filter layer  130  is stacked on the alignment film  120 , though in other embodiments, the alignment film  120  can also be stacked on the color filter layer  130 , i.e. positions and a forming sequence of the alignment film  120  and the color filter layer  130  can be exchanged. Moreover, in other applicable embodiments, an alignment film can be further disposed between the color filter layer  130  and the phase compensation film  140  (for example, a position pointed by an arrow P). 
     According to the above descriptions, since the color filter layer  130  has the phase compensation effect, and the phase retardation of the color filter layer  130  is substantially equivalent to that of the A-plate phase compensation film, the color filter layer  130  can be used to replace the A-plate phase compensation film. In this way, under a premise of maintaining an original optical performance of the color filter substrate  100 , a number of layers of the color filter substrate  100  can be reduced, so that fabrication processes and a fabrication cost of the color filter substrate  100  can be reduced. 
     Moreover, in the present embodiment, the color filter layer  130  includes the aforementioned red filter film  130   a , the green filter film  130   b , the blue filter film  130   c  and the black matrices  130   d , though in other embodiments, the color filter layer  130  may also include color filter films of other colors. It should be noticed that the color filter layer  130  having the phase compensation effect is formed through a suitable reaction (for example, a thermal or an optical process) of a solution having special ingredients. 
     The solution used for fabricating the color filter layer  130  includes a pigment, a phase compensation material and a solvent. In other exemplary embodiments, the solution further includes an initiator and/or a dispersant. The dispersant helps evenly distributing the pigment or other components (for example, the phase compensation material and the initiator, etc.) in the solvent. If the phase compensation material has a polymerizable functional group, the initiator may help accelerating a polymerisation reaction of the polymerizable functional group. Certainly, if the phase compensation material does not have the polymerizable functional group, the initiator is not required. 
     The pigment is mainly used for providing a color filtering effect, i.e. forming a color of the color filter film. Compared to a weight of the whole solution, a weight percentage of the pigment is substantially greater than or equal to 30% and smaller than or equal to 54%, and preferably greater than or equal to 38% and smaller than or equal to 45%. The pigment can be various organic pigments or inorganic pigments having colors. The organic pigments are, for example, C.I. pigment red 122, C.I. pigment red 177, C.I. pigment red 202, C.I. pigment red 206, C.I. pigment red 209, C.I. pigment red 254, C.I. pigment red 255, C.I. pigment green 7, C.I. pigment green 36, C.I. pigment yellow 13, C.I. pigment yellow 55, C.I. pigment yellow 119, C.I. pigment yellow 138, C.I. pigment yellow 139, C.I. pigment yellow 150, C.I. pigment yellow 168, C.I. pigment violet 23, C.I. pigment orange 71, C.I. pigment blue 15:3, C.I. pigment blue 15:4, C.I. pigment blue 15:6, C.I. pigment black 1, C.I. pigment black 7, etc., though the invention is not limited thereto. The inorganic pigments, are for example, titanium oxide, barium sulphate, calcium carbonate, zinc oxide, titanium nitride, lead sulphate, yellow lead, zinc yellow, red iron oxide III, cadmium red, ultramarine blue, Prussian blue, chromium oxide green, cobalt green, amber, titanium black, synthetic iron black, and carbon back, etc., though the invention is not limited thereto. One of the above various pigment components can be selected for utilization, or various pigment components can be arbitrarily combined for utilization, so as to provide the required color filtering effect. It should be noticed that the pigment referred in the present embodiment is differentiated from a dye. A general dye can be dissolved in a solvent, which may influence a phase compensation effect of the phase compensation material. Moreover, the dye has a poor optical stability and is easy to produce a photodecomposition phenomenon. The pigment used in the present embodiment is not dissolved in the solvent used in the present embodiment, but is evenly spread in the solvent in form of particles, so that a better optical stability is provided, and the phase compensation effect is not influenced. 
     The phase compensation material is used for providing a phase compensation function. Compared to the weight of the whole solution, a weight percentage of the phase compensation material is substantially greater than or equal to 5% and smaller than or equal to 20%, and preferably equal to 10%. The phase compensation material is generally a polymerizable liquid crystal (PLC) material, which has a main part and a polymerizable functional group part. For example, a monomer structure of the PLC material can be as follows: 
     
       
         
         
             
             
         
       
     
     wherein R 1  and R 2  are dissimilar, and are chain segments containing heteroatoms, so that reactivity of an ethylene double bond having R 3  is higher than that of an ethylene double bond having R 4 . R 1  and R 2  respectively contain a following structure: 
     
       
         
         
             
             
         
       
     
     etc. 
     wherein R is an alkyl of C 1 -C 12 . R 3  and R 4  are respectively independent, and are respectively selected from H or CH 3 . Ar is an aromatic ring, which can be a Phenyl, naphthyl, anthryl, or heterocyclic aromatic ring. Taiwan Patent No. 1323278 can be referred for a detailed implementation of the polymerizable liquid crystal molecules of the present embodiment, and in other embodiments, the phase compensation material can be other non-liquid crystal materials, though the phase compensation function can still be achieved. 
     If the phase compensation material has the polymerizable functional group, the initiator can be added to accelerate the polymerisation reaction of the polymerizable functional group. The initiator can be various optical initiators or thermal initiators. Compared to the weight of the whole solution, a weight percentage of the initiator is substantially greater than 0% and smaller than or equal to 1%, and preferably equal to 0.5%. The initiator is, for example, 1-hydroxycyclohexyl phenyl ketone, or 2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropane-1-one, though the invention is not limited thereto. 
     The dispersant helps evenly distributing the phase compensation material or other components (for example, the pigment and the initiator, etc.) in the solution. Compared to the weight of the whole solution, a weight percentage of the dispersant is substantially greater than 0% and smaller than or equal to 5%, and preferably greater than or equal to 1% and smaller than or equal to 3.5%. The dispersant can be an anionic dispersant, a cationic dispersant, a non-ionic surfactant or a polymer dispersant, and is preferably the polymer dispersant. 
     A weight percentage of the solvent is substantially greater than or equal to 35% and smaller than or equal to 50%, and preferably greater than or equal to 41% and smaller than or equal to 50%. The solvent of the present embodiment includes alcohols, ketones, ethers, esters or combinations thereof. The alcohol solvent is, for example, N-butanol, 2-butanol, tertiary butyl alcohol, or isopropyl alcohol. The ketone solvent is, for example, N-methylpyrrole ketone, cyclohexanone, methyl ethyl ketone, or methyl tertiary butyl ketone. The ether solvent is, for example, glycol ethers, glycol ether, ethylene glycol monobutyl ether, or propylene glycol monomethyl ether. The ester solvent is, for example, propylene glycol monomethyl ether acetate, propylene glycol monomethyl ether acetate, ethyl-2-ethoxyethanol acetate, 3-ethoxy ethyl propionate, or isoamyl acetate, though the invention is not limited thereto. In an exemplary embodiment, the solvent is formed by mixing N-methylpyrrole ketone, ethylene glycol monobutyl ether, propylene glycol monomethyl ether, and propylene glycol monomethyl ether acetate according to a certain proportion. For example, compared to the weight of the whole solution, a weight percentage of the N-methyl pyrrole ketone is substantially equal to 1%, a weight percentage of the ethylene glycol monobutyl ether is substantially equal to 3.5%, a weight percentage of the propylene glycol monomethyl ether is substantially equal to 32.5%, and a weight percentage of the propylene glycol monomethyl ether acetate is substantially equal to 10%. 
     Moreover, other additives can be added to the solution used for fabricating the color filter layer  130  according to an actual design requirement, for example, catalysts, sensitizers, stabilizers, chain transfer agents, inhibitors, common reactive monomers, interface active compounds, lubricants, wetting agents, hydrophobic agents, adhesives, flow improving agents, defoamers, degassing agents, diluents, reactive diluents, auxiliary agents, and coloring agents, etc., though the invention is not limited thereto. It should be noticed that the above solution components can also be evenly distributed in the solvent with assistant of the dispersant. 
     Second Embodiment 
       FIG. 2  is a side view of an LCD panel according to an embodiment of the invention. Referring to  FIG. 2 , after fabrication of the color filter substrate  100  is completed, the color filter substrate  100  and an active device array substrate  60  can be assembled to form an LCD panel  50 , and liquid crystal is filled between the color filter substrate  100  and the active device array substrate  60  to form a liquid crystal layer  80 . In the present embodiment, an alignment film  70  can be formed on the active device array substrate  60 . According to the above descriptions, the LCD panel  50  of the present embodiment includes the active device array substrate  60 , the alignment film  70 , the liquid crystal layer  80  and the color filter substrate  100 , wherein the color filter substrate  100  is as that described with reference of  FIGS. 1A-1G , so that a detailed description thereof is not repeated. In the present embodiment, the alignment film  70  is disposed on the active device array substrate  60 , the liquid crystal layer  80  is disposed on the alignment film  70 , and the color filter substrate  100  is disposed on the liquid crystal layer  80 . 
     When a driving voltage is applied between the assembled active device array substrate  60  and the color filter substrate  100 , if the alignment protrusions  170  are optionally disposed, the liquid crystal molecules in the liquid crystal layer  80  can lean towards different directions to form a plurality of domains, so as to achieve a wide viewing angle display effect, though the invention is not limited thereto, and according to an actual design requirement, the invention can also be applied to a transmissive display panel, a trans-reflective display panel, a reflective display panel, a double-sided display panel, a vertical alignment (VA) display panel, an in plane switch (IPS) display panel, a multi-domain vertical alignment (MVA) display panel, a twist nematic (TN) display panel, a super twist nematic (STN) display panel, a patterned-silt vertical alignment (PVA) display panel, a super patterned-silt vertical alignment (S-PVA) display panel, an advance super view (ASV) display panel, a fringe field switching (FFS) display panel, a continuous pinwheel alignment (CPA) display panel, an axially symmetric aligned micro-cell mode (ASM) display panel, an optical compensation banded (OCB) display panel, a super in plane switching (S-IPS) display panel, an advanced super in plane switching (AS-IPS) display panel, an ultra-fringe field switching (UFFS) display panel, a polymer stabilized alignment (PSA) display panel, a dual-view display panel, a triple-view display panels, or other types of display panels or combinations thereof, or an organic light-emitting device according to a material (for example, a liquid crystal layer, an organic light-emitting layer (for example, small molecules, polymer, or a combination thereof), a blue phase material, a ferro-electric material, or combinations thereof) electrically contacting at least one of a pixel electrode and a drain electrode thereof. 
     Third Embodiment 
       FIG. 3  is a side view of a color filter substrate according to another embodiment of the invention. Referring to  FIG. 1G  and  FIG. 3 , a structure of the color filter substrate  300  is similar to that of the color filter substrate  100 , and a difference there between lies in a color filter layer  310  and a phase compensation film  320 , wherein the same reference numerals refer to the same components. In the present embodiment, a phase retardation of the color filter layer  310  is substantially equivalent to the phase retardation of the C-plate phase compensation film, i.e. phase retardations of a red filter film  310   a , a green filter film  310   b  and a blue filter film  310   c  are all substantially equivalent to the phase retardation of the C-plate phase compensation film. Moreover, the phase compensation film  320  is, for example, the A-plate phase compensation film, and a material thereof is, for example, polymer liquid crystal. Preferably, the material of A-plate phase compensation film is, for example, solid state polymer liquid crystal. Therefore, under a premise of maintaining the optical performance of the color filter substrate  100 , the number of layers of the color filter substrate  100  can also be reduced, so that fabrication processes and a fabrication cost of the color filter substrate  100  can be reduced. 
     In summary, in the LCD panel and the color filter substrate of the invention, the color filter layer having the phase compensation effect is used to replace the A-plate phase compensation film or the C-plate phase compensation film. In this way, the number of layers of the color filter substrate can be reduced, so as to simplify the fabrication processes and reduce a fabrication cost of the color filter substrate. 
     It will be apparent to those skilled in the art that various modifications and variations can be made to the structure of the invention without departing from the scope or spirit of the invention. In view of the foregoing, it is intended that the invention cover modifications and variations of this invention provided they fall within the scope of the following claims and their equivalents.