Abstract:
A color filter and a method for manufacturing the same are provided. The color filter includes a polarizer matrix ( 202 ), which is patterned in accordance with the pixel arrangement of a liquid crystal display device. The polarizer matrix ( 202 ) is made of a thin crystal film material, which may linearly polarize incident light along one direction. By incorporating with a polarizer film ( 206 ), the polarizer matrix ( 202 ) becomes an effective black matrix. A thinner black matrix may thus be produced, and the manufacturing processes of the color filter are simplified.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention relates generally to color filters and method for manufacturing the same, and more particularly, to color filters and method for manufacturing the same for liquid crystal display devices.  
           [0003]    2. Prior Art  
           [0004]    Liquid crystal display (LCD) devices, especially color LCD devices have many applications. For example, the color LCD devices are applicable in laptop computers, DVD players, cellular phones, personal digital assistants (PDA), etc. In order to make an LCD display colorful, a color filter is needed.  
           [0005]    [0005]FIG. 1 illustrates a conventional color filter  100 , which comprises a substrate  101 , a black matrix (BM)  102 , a red, green and blue color filter layer  103   a ,  103   b  and  103   c , a protection layer  104 , and a transparent conductive layer  105 .  
           [0006]    Methods for manufacturing the color filter  100  include pigment dispersion method, dyeing method, printing method and electrodeposition method. Regardless of which of the above methods is employed, a black matrix (BM) should be formed on a substrate before further processing for preventing leakage of light due to liquid crystal alignment defects.  
           [0007]    Conventionally, a black matrix is formed on a glass substrate by photolithography. The black matrix is generally comprised of a thin metal film, such as a chromium film, with a fine pattern. The black matrix is formed by first sputtering a thin metal film on a substrate in a vacuum environment. Then, a photoresist is applied on the thin metal film. A pattern is formed on the photoresist for defining the pattern of the thin metal film. The thin metal film is then etched in accordance with the pattern formed on the photoresist. The desired black matrix is thus formed after depleting the photoresist on the thin metal film. This photolithography method requires many processing steps, resulting in a higher production cost.  
           [0008]    Another conventional method for forming a black matrix is disclosed by Keijiro Inoue, et al. in U.S. Pat. No. 5,786,042, which is entitled “Resin Black Matrix for Liquid Crystal Display Device”. However, the formation of a resin black matrix on a substrate still requires photolithography processes. In addition, the resin black matrix is approximately 1 μm or more in thickness, which reduces the flatness of a color filter.  
         SUMMARY OF THE INVENTION  
         [0009]    In accordance with the above and other reasons, one objective of the present invention is to provide a color filter having a thinner black matrix.  
           [0010]    Another objective of the present invention is to provide a method for manufacturing a color filter, which requires fewer processing steps.  
           [0011]    Accordingly, to achieve the above objectives, the color filter of the present invention comprises a substrate, a polarizer matrix formed on one surface of the substrate defining a plurality of openings, and a color filter layer formed on the substrate in the openings of the polarizer matrix, wherein the polarizer matrix is made of a thin crystal film material. One may determine the polarization direction of the polarizer matrix by robbing or applying a stress force, or gravitational or electromagnetic fields on the polarizer matrix. The color filter layer formed in each of the openings of the polarizer matrix is a red light filter, a green light filter, or a blue light filter. In order to protect the color filter layer, a protective layer covering the polarizer matrix and the color filter layer may be formed. A transparent conductive material such as indium-tin-oxide (ITO) may further be formed on the protective layer, acting as the common electrode of a liquid crystal display device. On another surface of the substrate, a polarizer film has a polarization direction perpendicular to that of the polarizer matrix is formed. Since the polarization directions of the polarizer film and the polarizer matrix are perpendicular to each other, light transmitted through the polarizer matrix is not permitted to transmit through the polarizer film, thus forming an effective black matrix. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0012]    [0012]FIG. 1 illustrates a cross-sectional view of a conventional color filter.  
         [0013]    [0013]FIG. 2 illustrates a cross-sectional view of a color filter of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0014]    Referring to FIG. 2, a color filter  200  of the present invention is illustrated. The color filter  200  comprises a substrate  201 , a polarizer matrix  202 , red, green and blue color filter layers  203   a ,  203   b  and  203   c , a protective layer  204 , a transparent conductive layer  205 , and a polarizer film  206 .  
         [0015]    The substrate  201  is a thin transparent slab made of glass or any transparent polymeric material such as acrylic. A layer of polarizer matrix  202  with a pattern is formed on the substrate  201 . In accordance with one embodiment of the present invention, the polarizer matrix  202  is made of a thin crystal film material such as the commercially available Optiva TCF™ material, developed by Optica Inc. of California, with a thickness of 0.5 μm or less. The polarizer matrix  202 , capable of producing linearly polarized light, has a first polarization direction determined by robbing or applying a stress force, or gravitational or electromagnetic fields thereon. In general, the pattern of the polarizer matrix  202  follows the pixel arrangement of the liquid crystal display device. Among them, the most commonly used pixel arrangements include stripe arrangement, delta arrangement, mosaic arrangement, and square arrangement. In this particular embodiment of the present invention, the pixel arrangement is a stripe arrangement. The pattern of the polarizer matrix  202  defines a plurality of openings exposing the first surface  201   a  of the substrate  201 . The method for printing thin crystal film material on the first surface  201   a  of the substrate  201  to form the polarizer matrix  202  is disclosed in, for example, U.S. Pat. No. 6,583,284, a detailed discussion of which is thus omitted. The substrate  201 , on which the polarizer matrix  202  has been formed, is then cured in an oven with a temperature ranging from 180° C. to 250° C.  
         [0016]    The red, green and blue color filter layers  203   a ,  203   b  and  203   c  are subsequently deposited in the corresponding openings of the polarizer matrix  202  on the first surface  201   a  of the substrate  201 . In this particular embodiment of the present invention, the red, green and blue color filter layers  203   a ,  203   b  and  203   c  are deposited by a pigment dispersion method. There are, however, other methods for depositing color filter layers  203   a ,  203   b  and  203   c , such as a dyeing method, a printing method, and an electrodeposition method. Since the present invention is defined in the accompanying claims, any color filter having the disclosed features of the present invention is considered within the scope of the present invention regardless of the manufacturing method of the color filter layers employed.  
         [0017]    The protective layer  204  and the transparent conductive layer  205  are then subsequently formed on the substrate, on which the color filter layers  203   a ,  203   b  and  203   c  have been formed. The transparent conductive layer  205  may be formed directly on the color filter layers  203   a ,  203   b  and  203   c  without the protective layer  204 . In this particular embodiment, the protective layer  204  is made of polymeric material such as epoxy and acrylic, while the transparent conductive layer  205  is made of transparent metallic materials such as indium-tin-oxide (ITO). Since the methods for forming the protective layer  204  and the transparent conductive layer  205  are know in the art, detailed descriptions of which is thus omitted.  
         [0018]    The polarizer film  206  is formed on the second surface  201   b  of the substrate  201 , which is capable of producing linearly polarized light. The polarizer film  206  may be composed of the same thin crystal film material as that of the polarizer matrix  202 . However, other optically anisotropic materials such as polyvinyl alcohol (PVA) may also be employed. In addition, the polarization direction of the polarizer film  206  is chosen to be perpendicular to the polarization direction of the polarizer matrix  202 . Therefore, light incident from direction  207  is partly linearly polarized by the polarizer matrix  202  and partly color filtered to each of the corresponding colors of the color filter layers  203   a ,  203   b  and  203   c . By incorporating with the polarizer film  206 , the linearly polarized part of the incident light is sufficiently blocked by the polarizer film  206 , resulting in an effective black matrix (BM) of the color filter  200 .  
         [0019]    In summary, the method for manufacturing a color filter  200  of the present invention includes the following steps: providing a substrate  201  having a first surface  201   a  and a second surface  201   b ; forming a polarizer matrix  202  on the first surface  201   a  of the substrate  201  and defining a plurality of openings; applying a stress force, or gravitational or electromagnetic fields on the polarizer matrix  202  so as to obtain a first polarization direction of the polarizer matrix  202 ; curing the substrate  201  on which a polarizer matrix  202  has been formed in an oven; forming red, green and blue color filter layers  203   a ,  203   b  and  203   c  on the substrate  201  in the openings of the polarizer matrix  202 ; forming a protective layer  204  covering the color filter layers  203   a ,  203   b  and  203   c , and the polarizer matrix  202 ; forming a transparent conductive layer  205  on the protective layer  204 ; and forming a polarizer film  206  on the second surface  201   b  of the substrate  201 , the polarizer film  206  having a second polarization direction perpendicular to the first polarization direction.  
         [0020]    It is appreciated that the above discussion discloses only a preferred embodiment of the present invention. Any person having ordinary skill in the art may easily find various other embodiments equivalent to the present invention. Therefore, the scope of the present invention is covered by the appended claims as set forth in the following.