Patent Publication Number: US-2009223398-A1

Title: Printing apparatus and fabricating method thereof

Description:
RELATED APPLICATIONS 
     This application is a Divisional of U.S. patent application Ser. No. 11/304,447 filed on Dec. 14, 2005, which claims the benefit of priority under 35 U.S.C. § 119 to Korean Patent Application No. P2005-58733, filed Jun. 30, 2005, which is incorporated by reference in its entirety herein. 
    
    
     FIELD OF THE INVENTION 
     The present embodiments relate to a printing apparatus, and more particularly to a printing apparatus that is adaptive for enabling to print a pattern of wide line width and a pattern of narrow line width with one printing plate when fabricating a liquid crystal display device, and a fabricating method thereof. 
     BACKGROUND 
     A liquid crystal display device controls light transmittance of a liquid crystal having dielectric anisotropy by using of an electric field to display a picture. A picture is displayed through a liquid crystal display panel having a liquid crystal cell matrix and a drive circuit for driving the liquid crystal display panel. 
     The liquid crystal display panel includes a color filter substrate and a thin film transistor substrate which are bonded with a liquid crystal layer therebetween. The color filter substrate includes a black matrix, a color filter and a common electrode sequentially formed on an upper glass substrate. The thin film transistor substrate includes thin film transistors and pixel electrodes formed at cell areas defined by crossing gate lines and data line in a lower glass substrate. The color filter substrate and the thin film transistor substrate can be formed by photolithography, etching, or use of a printing apparatus. 
       FIGS. 1A to 1C  are diagrams depicting a process for printing a target pattern using a printing apparatus of the related art.  FIG. 1A  depicts a printing apparatus, including a printing roll  3  having a blanket  5  with target pattern forming material  7  spread over the blanket  5  surface. In a first printing step, the printing roll in  FIG. 1A  is used to print pattern forming material onto printing plate patterns  13  in a printing substrate  11  ( FIG. 1B ). When the pattern forming material  7  adheres to a printing plate pattern  13  on the printing substrate  11 , portions of pattern forming material are removed from the printing roll, thereby creating a target pattern  15  on the surface of the printing roll  3  ( FIG. 1B ). Then, in a second printing step, the target pattern  15  on the printing roll is printed onto a target substrate  21 , thereby creating target pattern  15  thereon ( FIG. 1C ). A target pattern  15  can be applied as a pattern to various parts of a liquid crystal display device, including the black matrix, color filter, gate line, data line, etc. 
     A printing plate pattern  13  may be formed using a mask in a photolithography or etching process.  FIG. 2  illustrates an etching process for forming a printing plate pattern  13  in which a mask  29  is arranged on the printing substrate  11 , exposing an exposure area P 2  that can etched to form a desired printing plate pattern  13 . Typically, a wet or dry etching method employing a glass substrate as the printing substrate  11  may be used. In view of the disadvantages associated with dry etching, including long process times, high manufacturing costs, and target pattern limitations regarding wide line width, wet etching processes are often preferred. 
     A fluoric acid solution may be used in a wet etching process. In the isotropic wet etching process depicted in  FIG. 2  where the depth of etching is 10 μm, each side of the printing substrate  11  adjacent to the exposure area P 2  is also etched by 10 μm. For example, if the exposure area has a line width of 10 μm and the depth of the wet etching is 10 μm, the etched area will have a line width of 30 μm. 
     When forming a target pattern  15  with a line width of less than 100 μm, the printing plate pattern  13  is normally formed with a height of about 10 μm. However, when forming a target pattern  15  having a line width of 100 μm or more where the height of the printing plate pattern  13  is 10 μm, the target pattern formed in the second printing step may carry an inappropriate separation or break. 
       FIGS. 3A-3C  illustrate a pattern separation problem that can result when etching e.g., a wide line width patterns (e.g., 100 μm or greater) greatly exceeding the height of the printing plate pattern (e.g., 10 μm). In a case where the gap between printing plate patterns  13  is 100 μm or greater and the height of the printing plate pattern  13  is 10 μm, target pattern forming material  7  may inappropriately adhere to the printing substrate  11  between adjacent printing plate patterns  13  ( FIGS. 3A ,  3 B). As a result, a portion of target pattern forming material  7  of width X which is designated for a wide line width target pattern  15  may become inappropriately displaced on the printing substrate  11  ( FIG. 3B ), so that the resultant target pattern  15  formed in the second printing step carries an inappropriate gap having a width X corresponding to the displaced portion of target pattern forming material ( FIG. 3C ). 
     In view of these limitations, related art approaches may utilize one printing substrate to correctly form a target pattern having a wide line width of 100 μm or greater and a second printing substrate to form a target pattern having a wide line width less than 100 μm. Accordingly, there is a need in the art for a fabrication methodology adapted for printing wide line width patterns and narrow wide line width patterns using one printing substrate. 
     SUMMARY 
     In one aspect, a printing apparatus includes a printing roll having target pattern forming material spread on its surface, a printing substrate, including at least one barrier rib pattern spaced between a pair of adjacent printing plate patterns, and a target substrate configured to receive target pattern forming material remaining on the printing roll following transfer of target forming material to the printing substrate. 
     An exemplary pair of adjacent printing plate patterns may be separated by a distance of at least 100 μm and may contain one or more barrier rib patterns therebetween. The height of a barrier rib pattern may be about 10% to 45% of the gap length between the barrier rib pattern and an adjacent printing plate pattern or barrier rib pattern. In addition, the gap distance between adjacent printing plate and/or barrier rib patterns may be about eightfold to tenfold the height of the printing plate and/or barrier rib patterns defined by the gap therebetween. The line width of a barrier rib pattern may be about 5% to 10% of the length of the gap between the barrier rib pattern and an adjacent printing plate or barrier rib pattern. 
     In another aspect, a method of using a printing apparatus to fabricate a target substrate includes providing a printing substrate including at least one barrier rib pattern disposed between a pair of adjacent printing plate patterns, providing a printing roll having target pattern forming material spread thereon, printing target pattern forming material onto printing plate patterns and barrier rib patterns disposed on the printing substrate, and printing a target pattern on a target substrate from the target pattern forming material remaining on the printing roll after the transfer to the printing substrate. 
     The printing plate patterns and the barrier rib patterns may be formed by wet etching and they may be disposed or formed according to various heights, line widths and spacing therebetween. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIGS. 1A to 1C  are diagrams showing a printing process for forming a pattern according to the related art. 
         FIG. 2  is a diagram showing a related art method for forming a printing plate pattern. 
         FIGS. 3A to 3C  are diagrams illustrating a pattern printing problem according to the related art. 
         FIGS. 4A to 4D  are diagrams showing a method of printing a target pattern according to selected aspects of the present invention. 
         FIG. 5  is a diagram showing a part of a printing plate according to an aspect of the present invention. 
         FIGS. 6A to 6C  are diagrams showing a process of fabricating a portion of a printing plate and a process for printing a target pattern using the printing plate. 
         FIG. 7  is a diagram showing a black matrix pattern. 
     
    
    
     DETAILED DESCRIPTION 
       FIGS. 4A to 4D  depict a printing process adapted for printing wide line width patterns and narrow wide line width patterns on one printing substrate. The printing apparatus depicted in  FIGS. 4A to 4D , includes a printing roll  100  having target pattern forming material  101  printed in a first printing step onto printing plate patterns  43  and barrier rib patterns  45  in a printing substrate  103 . As target pattern forming material  101  is removed from the printing roll, a target pattern  49   a  is formed thereon. The target pattern  49   a  on the printing roll  100  can then be printed onto a target substrate  47  to form a target pattern  49   b  that extends in length as pressure is applied in a second printing step. 
     Printing plate patterns may be separated on a printing plate by gap distances greater than, less than, or equal to 100 μm. The printing plate patterns  43  adjacent to the A region depicted in  FIG. 4B  are representative of printing plate patterns separated by gap distances equal to or greater than 100 μm.  FIG. 4B  depicts representative barrier rib patterns  45  formed in an area where the gap length between adjacent printing plate patterns  43  is 100 μm or more. The printing plate patterns  43  and barrier rib patterns  45  may be formed using a mask in a photolithography or etching process, preferably a wet etching process. 
     The barrier rib patterns can facilitate correct formation of a wide line width target pattern as exemplified by target pattern  49   b  depicted in  FIGS. 4C and 4D . As a result, one printing substrate  103  can be used to facilitate printing of a target pattern  49   b  having a wide line width of 100 μm or more, as well as a target pattern  49   c  having a narrow line width of less than 100 μm. 
       FIG. 4A  depicts a target pattern forming material  101  being spread onto a printing roll  100 . The target pattern forming material  101  may include a polymeric solution melted in an organic solvent, forming a viscous, paste-like material capable of deforming under pressure. 
     A first printing step is performed in which the target pattern forming material  101  spread on the printing roll  100  is printed onto printing plate patterns  43  and barrier rib patterns  45  disposed on a printing substrate  103  ( FIG. 4B ). As target pattern forming material  101  on the printing roll  100  adheres to printing plate patterns  43  and barrier rib patterns  45  on the printing substrate  103 , target pattern forming material  101  remaining on the printing roll  100  defines a target pattern  49   a  thereon ( FIG. 4B ). 
     The target pattern  49   a  on the printing roll  100  is then printed onto a target substrate  47  to form an extended target pattern  49   b  as pressure is applied in a second printing step ( FIG. 4C ). In particular, as pressure is applied from the printing roll  100 , portions of the target forming material expand in a manner depicted by the arrows in  FIG. 4D . The extensions denoted by arrows in  FIG. 4D  represent gapped areas in the target pattern  49   a  filled in as pressure is applied. Accordingly, the target pattern  49   b  formed on the target substrate may include designated length extensions of target pattern forming material at gapped ends of the target pattern  49   a , including those defined by target pattern forming material areas printed onto the barrier rib patterns  45  in the first printing step. 
     Target pattern forming material may be extended at each gapped end of target pattern forming material  49   a  by about 5% to 10% of the length between adjacent gaps defined by areas printed onto adjacent printing plate pattern  43  and/or barrier rib patterns  45  on the printing substrate  103 . As a consequence of the extensions, the angle of target pattern forming material at extended end regions relative to a printing substrate  43  or target substrate  47  may vary from e.g., 90 degrees to about 20 degrees, respectively. 
     A barrier rib pattern  45  may be designed to have a width corresponding to 5% to 10% of the gap between adjacent printing plate pattern  43  and/or barrier rib patterns  45 . As depicted in  FIG. 4D , the extension of target pattern forming material  101  in the second printing step allows for gapped target pattern forming material  49   a  from the first printing step to be connected after pressure is applied in the second printing step ( FIG. 4C ). Accordingly, the use of barrier rib patterns  45  enables a desired wide line width target pattern  49   b  to be formed without separation. Exemplary target patterns may be formed in a liquid crystal display device, including those formed in a black matrix, a color filter, a gate line, or data line, etc. 
     The use of barrier rib patterns  45  enable printing of target patterns having both line widths of 100 μm or more and line widths of 100 μm or less using one printing substrate. By incorporating a barrier rib pattern  45  between printing plate patterns  43  separated by 100 μm or more in the first printing step, target pattern forming material  101  adheres to the barrier rib pattern  45  instead of the gap between the printing plate patterns  43  in the first printing step. However, because the width of the barrier rib pattern  45  can match a length by which the target pattern forming material can be extended in the second printing process, a target pattern can be correctly formed having a wide line width. 
       FIG. 5  illustrates the area (A) depicted in the printing substrate  103  of  FIG. 4B . The exemplary A area depicted in  FIG. 5  corresponds to region having a gap (L) between adjacent printing plate patterns  43  of 100 μm or more in which barrier rib patterns  45  are formed therebetween. The width (W) of each barrier rib pattern  45  is formed to be 5% to 10% of the gap (I) between adjacent printing plate patterns  43  and barrier rib patterns  45 . Preferably, the height (h) of a printing plate pattern  43  or barrier rib pattern  45  is about 10% to 45% of the gap (I) between adjacent printing plate patterns  43  and barrier rib patterns  45  disposed between the adjacent pair of printing plate patterns  43  separated by a gap (L) of 100 μm or more. 
     If the height (h) of the printing plate pattern and the barrier rib pattern is too low (less than 10%), target pattern forming material may inappropriately adhere to gaps between the printing plate patterns  43  and barrier rib patterns  45  during the first printing process, precluding the above advantages obtained when using barrier rib patterns  45  as described above. The height (h) of the printing plate patterns and the barrier patterns is preferably limited to 45% or less. 
     Preferably, a gap (I) between a barrier rib pattern  45  and an adjacent printing plate pattern  43  or barrier rib pattern  45  is formed where the length of the gap (I) is eightfold to tenfold the height (h) of adjacent printing plate patterns  43  or barrier rib patterns  45  ( FIG. 5 ). If the gap (I) is greater than tenfold the height of the of the printing plate pattern  43  or barrier rib pattern  45 , however, target pattern forming material may adhere to the gap (I) between the barrier rib patterns  45  and an adjacent printing plate pattern  43  or barrier rib pattern  45  in the first printing process, thereby negating the advantages of using a barrier rib pattern  45  as described above. On the other hand, if the gap (I) is less than eightfold the height (h) of the printing plate pattern  43  or barrier rib pattern  45 , it is difficult to use wet etching to accurately form the printing plate pattern  45  and barrier rib pattern  43 . A barrier rib pattern  45  may be formed to have a cross-section according to a variety of shapes, including but not limited to a line, hexagon, lozenge, circle and the like. 
       FIG. 6A  illustrates the use of wet, isotropic etching in conjunction with an exemplary printing methodology. When the height (h) of a printing plate pattern  53   a ,  53   b  or barrier rib pattern  55  is isotropically etched, side surfaces of the printing plate patterns  53   a ,  53   b  and the barrier rib pattern  55  shielded by a mask in non-exposure areas P 1  are similarly etched to a degree matching the depth or height (h) of etching in the exposure areas P 2 . Accordingly, the mask  140  is arranged to facilitate a degree of etching appropriate for desired printing plate pattern and barrier rib pattern widths. 
     The width of the non-exposure areas P 1  extending from the sides of the printing plate patterns  53   a ,  53   b  and the barrier rib pattern  55  are the same as the corresponding height (h) of the printing plate patterns  53   a ,  53   b  and the barrier rib pattern  55 . If the height (h) of the printing plate patterns and the barrier rib pattern were to exceed the above mentioned 45% gap width and the width of the non-exposure areas P 1  extending from of the mask were to similarly extend to match the height (and thereby exceed the above mentioned 45% gap width in both directions), the adjacent non-exposure areas P 1  could become connected so as to preclude the exposure areas P 2  from forming. Accordingly, the height (h) of the printing plate patterns and the barrier rib patterns are limited to 45% or less. 
       FIGS. 6A to 6C  illustrate benefits and characteristics of an exemplary embodiment in which a gap between a first printing plate pattern  53 A and a second printing plate pattern  53 B adjacent thereto is 210 μm. Although not shown, the printing substrate  203  depicted in  FIGS. 6A to 6C  may further include gaps between adjacent printing plate patterns spaced less than 100 μm from one another, as well as gaps elsewhere spaced from one another by 100 μm or more. 
       FIG. 6A  depicts a process for fabricating a printing substrate  203  having printing plate patterns  53 A,  53 B and a barrier rib pattern  55  disposed thereon. The patterns may be fabricated by a photolithography process employing a glass substrate and a mask  140  having a light shielding part P 1  and a light transmission part P 2 . The printing substrate may then be etching using a fluoric acid solution in an area corresponding to the light transmission part P 2 . Preferably, the etching is performed to a depth of 10% to 45% of the narrowest gap (100 μm) within a gap between printing plate patterns  53   a ,  53   b  separated by 100 μm or more. In  FIG. 6A , the substrate  203  is etched to depth of 10 μm which is 10% of the 100 μm. The 10 μm depth further corresponds to the non-exposed side surfaces of patterns  53 A,  53 B,  55  adjacent to the light transmission part P 2  which are similarly etched by 10 μm. Accordingly, the mask  140  is arranged so that the width of the light shielding parts P 1  is extended by 10 μm on each side surface relative to desired patterns  53 A,  53 B,  55 . Of course, the mask arrangement is varied according to the depth of the etching. 
       FIG. 6B  depicts the first printing step in which target pattern forming material on the printing roll  153  is printed onto the printing plate patterns  53 A,  53 B and the barrier rib pattern  55  disposed on the printing substrate  203 . The target pattern forming material retained on the printing roll  153  thereafter includes gaps corresponding to target pattern forming material area printed onto the barrier rib pattern  55  and the printing plate patterns  53 A,  53 B. The target pattern forming material retained on the printing roll  153  defines a target pattern  63  that can be subsequently printed onto a target substrate  61  in a second printing step ( FIG. 6C ). 
     The target pattern  63  formed on the printing material can be extended when pressure is applied in the second printing step. As a result, the resulting extensions can produce line width increases of 5% to 10% at side surfaces corresponding to where the printing plate patterns  53   a ,  53   b  and the barrier rib pattern  55  are closely adhered ( FIGS. 6B ,  6 C). Accordingly, even though there is a barrier rib pattern  55  between a first printing plate pattern  53   a  and a second printing plate pattern  53 B, extension of the target pattern forming material can fill in the gap produced by the barrier rib pattern  55  in the first printing step. As exemplified in  FIG. 6C , the line width extensions can account for a wide line width pattern  63  of 220 μm without gaps on a substrate  61 . In other words, an appropriate target pattern  63  can be formed by connecting target pattern forming material through line width extensions produced in the second printing step to form a wide line width target pattern  63  according to a desired pattern or shape. 
     The use of barrier rib patterns can accurately enable wide line width target patterns from printing plate patterns separated by 100 μm or more. In the embodiment exemplified in  FIG. 6B , the width of the barrier rib pattern  55  (10 μm) is 10% of the gap between the barrier rib pattern  55  and the adjacent printing plate patterns  53 A,  53 B. However, the width of the barrier rib pattern  55  may be varied according to the desired characteristics of the target pattern  63  and according to characteristics of the target pattern forming material. 
     In a representative embodiment, a black matrix pattern  72  may be formed on a color filter substrate of the liquid crystal display device as depicted in  FIG. 7 . The black matrix  72  includes areas X 1 , X 2  of wide line width (measured in millimeters) formed at the border of the color filter substrate, and areas Y 1 , Y 2  of narrow line width (measured in micrometers) formed between color filters  71 . The wide line width areas X 1 , X 2  and the narrow line width areas Y 1 , Y 2  may be formed using a printing substrate with barrier rib patterns disposed at locations requiring a wide line pattern. Since the wide line width areas X 1 , X 2  and the narrow line width areas Y 1 , Y 2  can be formed using one printing substrate, the use of barrier rib patterns facilitates more efficient fabrication of liquid crystal display devices. 
     The above described printing apparatus makes it possible to print a target pattern of wide line width and the target pattern of narrow line width with one printing substrate. Moreover, incorporation of the above described barrier rib patterns between the printing plate patterns separated from one another 100 μm or more can prevent formation of target patterns carrying inappropriate gaps therein. 
     Although the present invention has been explained by the embodiments shown in the drawings described above, it should be understood that the invention is not limited to the embodiments, and that various changes or modifications are possible without departing from the spirit or scope of the invention. Accordingly, it is intended that the present invention cover such modifications and variations provided they come within the scope of the appended claims and their equivalents.