Abstract:
An LCD including a color filter substrate, an array substrate, and a liquid crystal layer therebetween is provided. This color filter substrate has a plurality of color filters with overlap regions acting as a black matrix. Subsequently, patterned regions are defined in part of the overlap regions. After formation of a planarization layer and a conductive layer, spacers are formed in the patterned regions. The spacers may not shield the transparent region of the color filters, thereby enhancing the aperture ratio of the color filter substrate. Additionally, the thickness of the planarization layer in the patterned regions is not influenced by the overlap of the color filters, such that the spacers thereon have a uniform height. Furthermore, the at least one spacer of the color filter substrate and at least one data line of the array substrate are overlapped.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a Continuation of pending U.S. patent application Ser. No. 11/759,329, filed Jun. 7, 2007, and entitled “Color Filter Substrate And LCD Utilizing The Same”, which claims priority of Taiwan Patent Application No. 095144656, filed on Dec. 1, 2006, the entirety of which is incorporated by reference herein. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to a liquid crystal display (LCD), and in particular to a color filter substrate thereof. 
     2. Description of the Related Art 
     Conventional LCDs comprise a color filter substrate, an array substrate, and a liquid crystal layer disposed therebetween. Formerly, the distance between the substrates was defined by ball spacers. However, no method existed to regulate distribution thereof, so use of a patterned photoresist layer as a spacer became popular. 
     Conventional large color filter substrates include black matrices between different color filters, with middle or small color filter substrates serving in overlap regions of different color filters as black matrices. As shown in  FIGS. 1A and 1B , the color filter substrate includes red, green, and blue color filters  10 R,  10 G, and  10 B on a substrate  11 , wherein the color filters overlap to form the overlap regions  12 A and  12 B.  FIG. 1B  is a section view of line X-X′ in  FIG. 1A , defining the overlap regions. The thickness of overlap regions  12 A and  12 B is influenced by the overlap of two color filters. To ensure spacers have uniform height, spacers are preferably formed beyond the overlap region. For example, the spacer  14  is formed in the corner of transparent region of the color filter  10 R in  FIG. 1A . Thus, spacer  14  formed in transparent region of any color filter will reduce aperture ratio of the color filter. If the spacer  14  is directly formed in the overlap region  12 A or  12 B, the overlap difference of color filters  12 R,  12 G, and  12 B will result in different heights of spacers  14 . Thus, a method is called for forming uniform height spacers without reducing aperture ratio. 
     BRIEF SUMMARY OF THE INVENTION 
     Accordingly, the invention provides a liquid crystal display, comprising a color filter substrate, comprising: a substrate; a first color filter formed on the substrate; a second color filter formed on the substrate, wherein the first color filter and the second color filter overlap to form an overlap region; a conductive layer on the first and second color filters; and at least one spacer formed in the overlap region; an array substrate, comprising: at least one data line, wherein the at least one spacer and the at least one data line are overlapped; and a liquid crystal layer disposed between the color filter substrate and the array substrate. 
     The invention also provides a liquid crystal display, comprising a color filter substrate, comprising: a substrate; a first color filter formed on the substrate; a second color filter formed on the substrate, wherein the first color filter and the second color filter overlap to form an overlap region, wherein the overlap region comprises a patterned region and an non-patterned region; a conductive layer on the first and second color filters; and at least one spacer formed in the overlap region; an array substrate, comprising: at least one data line, wherein the at least one spacer and the at least one data line are overlapped; and a liquid crystal layer disposed between the color filter substrate and the array substrate. 
     A detailed description is given in the following embodiments with reference to the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention can be more fully understood by reading the subsequent detailed description and examples with references made to the accompanying drawings, wherein: 
         FIG. 1A  is a top view of a conventional color filter substrate; 
         FIG. 1B  is a section view of line X-X′ in  FIG. 1A ; 
         FIGS. 2A-2C ,  4 A- 4 C,  5 A- 5 C,  6 A- 6 D,  7 A- 7 C,  8 A- 8 C, and  9 A- 9 C are section views of manufacture of a color filter substrate in an embodiment of the invention; 
         FIG. 3  is a top view of a color filter substrate in an embodiment of the invention; and 
         FIG. 10  is a section view of a liquid crystal display in an embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The following description is of the best-contemplated mode of carrying out the invention. This description is made for the purpose of illustrating the general principles of the invention and should not be taken in a limiting sense. The scope of the invention is best determined by reference to the appended claims. 
       FIGS. 2A-2C  show a manufacture of a color filter substrate in an embodiment of the invention. First, a red color filter  20 R is formed on a substrate  21 . The formation may utilize a photoresist containing red pigment spun on the substrate  21 . In an embodiment, the substrate  21  can be plastic, resin, glass, or the like. The color filter  20 R is then patterned by lithography, for example. As shown in  FIG. 2B , a green color filter  20 G is formed on the substrate  21 . The composition and the formation of the color filter  20 G are similar to color filter  20 R. Similarly, a blue color filter  20 B is then formed on the substrate  21  in  FIG. 2C . As shown in  FIG. 2C , part of the color filter  20 G remains on color filter  20 R to form an overlap region  22 A. Similarly, part of the color filter  20 B remains on the color filter  20 G to form an overlap region  22 B. The formation sequence of color filters is not limited to red, green, and blue. Nor are the color filters limited to the three conventional primary colors, and may include other colors such as cyan, yellow, or magenta. The overlap regions  22 A and  22 B can be the same or different. For example, because mixture of green light and blue light is easier than mixture of green light and red light, the overlap region  22 B is preferably larger than the overlap region  22 A to reduce color mixture. Because the aperture ratio of the overlap region  22 A and  22 B is less than the transparent region of the color filters, the overlap regions  22 A and  22 B serve as black matrices, such that the process of forming additional black matrices may be ignored. 
       FIG. 3  is a top view of the disclosed structure, and  FIG. 2C  a section view of line Y-Y′ in  FIG. 3 . In  FIG. 2C , the overlap regions  22 A and  22 B are formed by left color filters (e.g.  20 G or  20 B) covering right color filters (e.g.  20 R or  20 G). In another embodiment, it is optional that right color filters cover left color filters. In further embodiments, outside color filters (e.g.  20 R and  20 B) can cover middle color filter (e.g.  20 G), and vice versa. Color filters  20 R,  20 G, and  20 B have tilt boundary as shown in  FIG. 2C , however, their boundary can be perpendicular to the substrate if necessary. 
     Unlike the conventional technology, when color filters  20 R,  20 G, and  20 B are patterned, the patterned region  23  is simultaneously formed as shown in  FIG. 3 . Formation of the patterned region  23  preferably first comprises forming a photoresist layer (not shown) on non-patterned color filters. The photoresist layer is then patterned by lithography, for example. Subsequently, the patterned regions  23  of the color filters  23 R,  23 G, and  23 B (not masked by the patterned photoresist layer) are removed. Suitable removal methods comprise dry etching such as reactive ion etching (RIE) or plasma etching. In other embodiments, the patterned regions  23  can be formed by laser ablation, such as direct writing or utilizing a photo mask.  FIG. 4A  shows a section view of line A-A′ in  FIG. 3 , wherein patterned regions  23  are lower than the top surface of the overlap region  22 A. The patterned regions  23  and the top surface of the color filters  20 R,  20 G,  20 B are of the same height. In other embodiments, the patterned regions  23  can be openings in  FIG. 4B  lower than the top surface of the color filters  20 R,  20 G, and  20 B. In further embodiments, the patterned regions  23  can expose the substrate  21 .  FIGS. 5A-5C  show a section view of line B-B′ in  FIG. 3  at about the middle of the overlap region  22 A. As shown in  FIG. 5A , the patterned region  23  and the color filters  20 R are of the same height, such that color filter  20 R is covered by the color filter  20 G in the patterned region  23 . As shown in  FIG. 5B , the patterned region  23  is an opening, and part of the color filter  20 R is exposed in the patterned region  23 . As shown in  FIG. 5C , the patterned region  23  exposes part of the substrate  21 . The described patterned regions  23  and the overlap regions  22 A/ 22 B may be of the same or different widths. Additionally, patterned regions  23  are not formed in all overlap regions  22 A and  22 B, only being formed in part of the overlap regions  22 A and  22 B if necessary. While patterned regions  23  are circular in  FIG. 3 , other shapes such as square, rectangle, rhomb, hexagon, or ellipse are possible. The width of the overlap region  22 A and  22 B can be the same or different. 
     A planarization layer  30  is then formed overlying the described structure, as shown in  FIGS. 6A-6C .  FIGS. 6A-6C  correspond to line A-A′ in  FIG. 3 . The planarization layer  30  can be transparent material, organic material, or combinations thereof. The openings in  FIGS. 4B-4C  are filled by the planarization layer  30  to complete a smooth top surface.  FIG. 6D  shows the structure, after formation of the planarization layer  30 , continued from  FIG. 2C  corresponding to line Y-Y′ in  FIG. 3 . Overlap regions  22 A and  22 B have a higher top surface than color filters  20 R,  20 G  20 B other than the overlap regions, however, the top surface of the planarization layer  30  can be planarized to be uniformly smooth by back etching.  FIGS. 7A-7C  show the structure, after formation of the planarization layer  30 , continued from the  FIGS. 5A-5C  corresponding to line B-B′ in  FIG. 3 . Irrespective of whether or not the patterned regions  23  are of the same height as shown in  FIGS. 4A and 5A , openings as in  FIGS. 4B and 5B , or exposed substrate  21  as in  FIGS. 4C and 5C , the planarization layer  30  has a smooth top surface. It is clearly shown in figures that the planarization layer  30  is thickest on patterned region  30 , thinner on color filters  20 R,  20 G, and  20 B, and thinnest (can be zero) on the overlap regions  22 A and  22 B. In an embodiment, the planarization layer  30  has a thickness of about 0 μm to 10 μm, and more preferably of about 0.5μm to 4 μm. 
     After formation of a conductive layer  40  on the structure, spacers  50  are formed in the patterned region  23 . Generally, the conductive layer  40  can be indium tin oxide (ITO), indium zinc oxide (IZO), or aluminum zinc oxide (AZO), and have a thickness of about 400 Å to 2000 Å. Suitable spacers  50  include positive or negative photoresist.  FIGS. 8A-8C  continue from  FIGS. 6A-6C , and  FIGS. 9A-9C  continue from  FIGS. 7A-7C , respectively. Compared to the conventional technology, the patterned regions  23  of the present embodiments unlike the overlap regions  22 A and  22 B influenced by the overlap of the color filters  20 R,  20 G, and  20 B, such that the spacers  50  formed overlying the patterned regions  23  have uniform height. Especially in  FIG. 8C , since only planarization layer  30  and conductive layer  40  formed on the exposed substrate  21  in the patterned regions  23 , the influence from color filters  20 R,  20 G, and  20 B to spacers  50  can be totally eliminated. In addition, the spacers  50  are not formed in the transparent regions of the color filters, thereby retaining the aperture ratio. Note that while spacers  50  have a rectangular cross section in illustration, they may be ladder-shaped with narrow top and wide bottom, conical, or other suitable shape.  FIGS. 8A-8C  show two spacers in three color filters, but the spacer density is not limited thereto. In other words, part of the patterned regions  23  may be free of spacer  50 . If color filters  20 R,  20 G, and  20 B are large, dense spacers are needed. If color filters  20 R,  20 G, and  20 B are small, it is possible that several sets of color filters  20 R,  20 G and  20 B need only one spacer  50 . As long as the support is sufficient, the skilled may optionally tune the spacer  50  factors such as density, shape, color, size, material, and number. 
     Using the color filter substrate in  FIG. 8C  as an example, a liquid crystal layer is disposed between the color filter substrate and an array substrate to form a liquid crystal display. As shown in  FIG. 10 , the bottom substrate is color filter substrate  90 A with description thereof omitted for brevity. The top substrate is the array substrate  90 C. The substrate  25  of the array substrate  90 C is similar to substrate  21 . In the multi-layered structure  27 , data lines  60  are preferably wider than the patterned regions  23  or overlap regions  22 A and  22 B (please referring to  FIG. 10 ). The liquid crystal layer  90 B is disposed between the color filter substrate  90 A and the array substrate  90 C to complete the liquid crystal display  100  of the present embodiments. 
     While the invention has been described by way of example and in terms of preferred embodiments, it is to be understood that the invention is not limited thereto. To the contrary, it is intended to cover various modifications and similar arrangements (as would be apparent to those skilled in the art). Therefore, the scope of the appended claims should be accorded the broadest interpretation so as to encompass all such modifications and similar arrangements.