Abstract:
A color filter substrate for a liquid crystal display device includes a transparent insulation substrate, a black matrix defining first and second pixel areas on the transparent insulation substrate, and a color filter in the first and second pixel areas for displaying first and second colors, respectively, wherein a surface of the black matrix having recesses at sides thereof adjacent to the first and second pixel areas, respectively, for preventing an overflow of the first color from the first pixel area into the second pixel area.

Description:
This application claims the benefit of the Korean Patent Application No. 10-2006-0034154 filed in Korea on Apr. 14, 2006, which is hereby incorporated by reference in its entirety. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     Embodiments of the present invention relates to a liquid crystal display device, a more particularly, to a color filter substrate for a liquid crystal display device and a manufacturing method thereof. 
     2. Description of the Background Art 
     As society is becoming more and more information-driven, demand has been increasing for diverse forms of display devices. Recently, diverse flat display devices have been studied, which include a liquid crystal display (LCD) device, a plasma display panel (PDP) device, an electro luminescent display (ELD) device, and a vacuum fluorescent display (VFD) device. Some of the flat display devices are currently in use in diverse forms of equipment. 
     In particular, the LCD device is most widely used as a portable display device because it provides an excellent image quality, is thin and light, and consumes low-power. In light of these advantages, the LCD is supplanting cathode ray tube (CRT) as a preferred display device. For example, LCD devices are used as monitors for televisions, desktop computers, and laptop computers. To be used as a general display device, the LCD device should remain thin and light, consume low-power, but also should be able to provide a high-quality image on a wide panel that has a high definition and a high brightness. 
     The LCD includes a liquid crystal display panel with liquid crystal cells in an active matrix arrangement, and driving circuits for driving the liquid crystal panel. The LCD device displays images by controlling the optical transmission rate of liquid crystal cells in accordance with inputted video signals. A color image is formed on a thin-film transistor liquid crystal display (TFT-LCD) device by adjusting the optical transmission rate of an incident white light from a backlight as the incident white light propagates through the liquid crystal pixels, and additively mixing colored light emitted from red (R), green (G), and blue (B) color filter layers, which are arranged in a ratio of 1:1 on the liquid crystal pixels. 
       FIG. 1  shows a cross-sectional view of an LCD panel according to the related art. Referring to  FIG. 1 , the related art LCD panel includes a TFT substrate  10 , a color filter substrate  50  and a liquid crystal material  30  injected between the TFT substrate  10  and the color filter substrate  50 . 
     In the case of a twisted nematic (TN) type LCD panel, the color filter substrate  50  is composed of a black matrix  52 , a color filter  53 , an overcoat  54 , a common electrode  55 , and a first alignment film  56 , which are sequentially formed on a transparent first insulation substrate  51 . Thus, the color filter substrate  50  includes not only the RGB color filter pattern  53  for displaying colors but also an indium titanium oxide (ITO) thin film  55 , which is a common electrode for applying voltage to the liquid crystal pixels, and the black matrix  52  which blocks the light between unit pixels. Also, the TFT substrate  10  may include a TFT pixel electrode  17  and a second alignment film  19  formed on a transparent second insulation substrate  11 . In case of an in-plane switching (IPS) type liquid crystal display panel, both the common electrode  55  and the pixel electrode  17  may be formed on the TFT substrate  11 . 
       FIG. 2  shows a cross-sectional view of a color mixture caused during fabrication of a color filter for the LCD panel according to the related art. Referring to  FIG. 2 , a black matrix  52  defining a pixel area is formed on a transparent insulation substrate  51 , and a color filter  53  for displaying different colors is formed in the pixel area. The color filter uses a color photo resist (PR) including a pigment or a color ink in an ink-jet method. As shown in portion A of  FIG. 2 , dripping ink or color photo resist may cause an overflow in the related art method. The overflow may cause an unintended mixture of colors. 
     SUMMARY OF THE INVENTION 
     Accordingly, the present invention is directed to a color filter substrate for liquid crystal display panel and a method of manufacturing thereof, which substantially obviate one or more problems due to limitations and disadvantages of the related art. 
     An object of the present invention to provide a color filter substrate for a liquid crystal display device that can prevent an unintended mixture of colors due to an overflow of a color filter material. 
     Another object of the present invention to provide method of manufacturing a color filter substrate for a liquid crystal display device that can prevent an overflow of a color filter material due to a dripping of ink or a color photo resist. 
     Additional features and advantages of the invention will be set forth in the description of exemplary embodiments which follows, and in part will be apparent from the description of the exemplary embodiments, or may be learned by practice of the exemplary embodiments of the invention. These and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description of the exemplary embodiments and claims hereof as well as the appended drawings. 
     To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described, a color filter substrate for a liquid crystal display device includes a transparent insulation substrate, a black matrix defining first and second pixel areas on the transparent insulation substrate, and a color filter in the first and second pixel areas for displaying first and second colors, respectively, wherein a surface of the black matrix having recesses at sides thereof adjacent to the first and second pixel areas, respectively, for preventing an overflow of the first color from the first pixel area into the second pixel area. 
     In another aspect, a method for manufacturing a color filter for a liquid crystal display device including a transparent insulating substrate includes forming a black matrix defining first and second pixel areas on the transparent insulation substrate, forming a color filter in the first and second pixel areas for displaying first and second colors, and forming recesses on a surface of the black matrix at sides thereof adjacent to the first and second pixel areas, respectively, for preventing an overflow of the first color from the first pixel area into the second pixel area. 
     It is to be understood that both the foregoing general description and the following detailed description of the present invention are exemplary and explanatory and are intended to provide further explanation of the invention as claimed. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings, which are included to provide a further understanding of the present invention and are incorporated in and constitute a part of this application, illustrate embodiments of the present invention and together with the description serve to explain the principle of embodiments of the present invention. In the drawings: 
         FIG. 1  shows a cross-sectional view of an LCD panel according to the related art; 
         FIG. 2  shows a cross-sectional view of a color mixture caused during fabrication of a color filter for the LCD panel according to the related art; 
         FIG. 3  shows a cross-sectional view of an exemplary LCD panel in accordance with an embodiment of the present invention; 
         FIGS. 4A and 4B  show the formation of an exemplary black matrix having overflow preventing recesses in a color filter substrate of a LCD panel in accordance with an embodiment of the present invention; and 
         FIGS. 5A to 5E  show the formation of an exemplary color filter substrate for an LCD panel in accordance with an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS 
     Reference will now be made in detail to exemplary embodiments of the present invention, which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts. 
       FIG. 3  shows a cross-sectional view of an exemplary LCD panel in accordance with an embodiment of the present invention. Referring to  FIG. 3 , the exemplary LCD panel includes a TFT substrate  110 , a color filter substrate  150  and a liquid crystal material  130  between the TFT substrate  110  and the color filter substrate  150 . The color filter substrate  150  may include a black matrix  152  and a color filter  153  sequentially formed on a first transparent insulation substrate  151 . The color filter substrate  150  may further include an overcoat layer  154 . 
     The TFT substrate  110  may include a plurality of TFTs, a pixel electrode  117 , and an alignment film  119  on a second transparent insulation substrate  111 . In an exemplary embodiment of the invention, the LCD panel is an IPS type, in which the pixel electrode  117  and the common electrode (not shown) can be formed on the TFT substrate  110 . 
     The black matrix  152  of the color filter substrate  150  is disposed on the first transparent insulation substrate  151  in areas corresponding to TFT areas of the TFT substrate  110 , areas where a plurality of gate lines are formed, and areas where a plurality of data lines are formed. The black matrix  152  defines pixel areas where the color filter  153  is to be formed. Herein, the black matrix  152  improves image quality by preventing the leakage of light and absorbing external light to increase an effective contrast ratio of the LCD panel. 
     In an exemplary embodiment of the invention, a portion of the surface of the black matrix  152  is shaped appropriately to prevent overflow during the formation of the color filter  153 . For example, the surface of the black matrix  152  is provided with well-shaped recesses on each side thereof adjacent to one or more of the pixel areas. Other embodiments of the present invention may include recesses with other shapes. 
     The black matrix  152  may be formed of a resin, which is an organic material, or metal. When the black matrix  152  is formed of a resin, the overflow preventing recess may be formed by light exposure through a plurality of slits. When the black matrix  152  is a metal thin film, it may be formed through dry etching or wet etching. 
     The color filter  153  may be formed over pixel areas separated by the black matrix  153 , and the color filter  153  may be formed for each of the R, G and B areas to display R, G and B colors. The color filter  153  is formed by using a color photo resist containing a pigment or by dripping a color ink in an ink-jet method. Thus, the overflow preventing recess of the black matrix  152  prevent an overflow of the color ink or the color photo resist. 
     The overcoat layer  154  may be formed to cover the color filter  153  to planarize the color filter substrate. In an embodiment, the overcoat layer  154  may not be formed. 
     Subsequently, the TFT in the TFT substrate  110  includes a gate electrode  112  formed on the transparent second insulation substrate  111  together with gate lines (not shown), a semiconductor layer  114  overlapped with the gate electrode  112 , a gate insulation layer  113  between the semiconductor layer  114  and the gate electrode  112 , and source/drain electrodes  115  and  116  formed together with data lines (not shown) with the semiconductor layer  114  between them. The TFT supplies a pixel voltage, which is a data signal inputted through the data lines to the pixel electrode  117  in response to a scan signal supplied through the gate lines. 
     The pixel electrode  117  is a transparent conductive material having a high optical transmission rate. The pixel electrode  117  contacts a drain electrode  116  of the TFT with a protective layer  118  between them. The alignment film  119  for alignment of the liquid crystal is formed by applying an alignment material, such as polyimide, and performing rubbing. 
       FIGS. 4A and 4B  show the formation of an exemplary black matrix having overflow preventing recesses in a color filter substrate of a LCD panel in accordance with an embodiment of the present invention. Referring to  FIG. 4A , the black matrix  152  may be formed of a resin, which is an organic material, by light exposure through a mask  160  having a plurality of slits. The amount of light incident onto the surface of the black matrix  152  is controlled by the width of the slits and the distance between the slits. For example, more light propagates through a large opening at first central portion of the mask  160  than at the portion B of the mask where the slits are narrower. The black matrix  152  is solidified by exposure to light. An unexposed portion of the black matrix  152  can be removed in a subsequent process. Thus, referring to the portion C of  FIG. 4B , well-shaped recesses are formed on the surface of the black matrix  152  in the positions scarcely exposed to light transmitted through the slits at portion B (shown in  FIG. 4A ) in the mask  160 . 
       FIGS. 5A to 5E  show the formation of an exemplary color filter substrate for an LCD panel in accordance with an embodiment of the present invention. Referring to  FIG. 5A , an opaque material  152 , such as an opaque resin and an opaque metal, is deposited on an entire surface of the first transparent insulation substrate  151 . 
     Referring to  FIG. 5B , the opaque material  152 , for example an opaque resin, is exposed to light through a mask  160  having slits. The opaque material  152  has a property that it is solidified upon light exposure. 
     Thus, referring to  FIG. 5C , the exposed opaque material  152  is patterned by removing the portion of the opaque material  152  not exposed to light to form the black matrix  152 . Well-shaped patterns are also formed at portions C on each side of the black matrix  152 . The wells are formed on the surface of the black matrix  152  in positions scarcely exposed to light transmitted through the slits at portion B of the mask  160 . Pixel areas are defined by the black matrix  152  including the well-shaped recess thereon. In short, the overflow preventing recesses are formed on each side of a surface of the black matrix  152  to prevent overflow during the formation of the color filter  153 . 
     In another embodiment, opaque material for the black matrix  152  is a thin film of metal, such as chrome (Cr). Then, the overflow preventing recesses may be formed by etching the metal thin film. 
     Subsequently, referring to  FIG. 5D , the color filter  153  is formed in the pixel area to display R, G and B colors. Herein, the color filter  153  is formed by using a color photo resist including a pigment or dripping a color ink in an ink-jet method. When the color filter  153  is formed in the ink-jet method, R, G and B color filters  153  may be concurrently formed. 
     Thus, although overflow may occur due to the color ink or the color photo resist, the overflow preventing recesses can prevent a color ink or a color photo resist from one pixel area from mixing with a color ink or a color photo resist in another pixel area. 
     Referring to  FIG. 5E , an overcoat layer  154  may be formed to planarize the surface of the color filter  153  by depositing an organic material on the entire surface of the black matrix  152  and the color filter  153 . 
     The color filter, which is formed as described above, can be easily applied not only to a TN-type LCD panel but also an IPS-type liquid crystal display panel and a vertical alignment (VA)-type liquid crystal display panel. The color filter substrate  150  prepared as described above goes through inspection and enters a liquid crystal cell preparation process such as a fabrication of a TFT substrate  110 . 
     In accordance with an embodiment of the present invention, the overflow preventing recesses on the surface of the black matrix can prevent the ink or the color photo resist overflowing from a dripping ink or a color photo resist from mixing with one another. 
     It will be apparent to those skilled in the art that various modifications and variations can be made in embodiments of the present invention. Thus, it is intended that embodiments of the present invention cover the modifications and variations of the embodiments described herein provided they come within the scope of the appended claims and their equivalents.