Abstract:
The present invention relates to a gravure printing method comprising providing a printing substrate where a plurality of recessed cells are formed adjacently each other; filling the recessed cells with ink using an ink jet apparatus which includes a plurality of nozzle heads to jet different colors of inks; and transferring the ink in the recessed cells to an insulating substrate. Thus, the present invention provides a gravure printing method which has a simple process and an improved yield.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application claims the benefit of Korean Patent Application No. 2006-0010807, filed on Feb. 3, 2006, in the Korean Intellectual Property Office, which is hereby incorporated by reference for all purposes as if fully set forth herein.  
       BACKGROUND  
       [0002]     1. Field of the Invention  
         [0003]     The present invention relates to a printing apparatus, a gravure printing method and a method of a manufacturing display device using the same.  
         [0004]     2. Description of the Related Art  
         [0005]     Flat panel display devices have been popular because of their small size and light weight. The flat panel display device includes a liquid crystal display (LCD), and a back lighting unit such as an organic light emitting diode (OLED) or the like. The LCD displays images by controlling the light transmittance of the liquid crystal molecules in a matrix array according to an image signal.  
         [0006]     The LCD panel includes a thin film transistor (TFT) substrate where TFTs are formed, a color filter substrate where color filters are formed, and a liquid crystal layer disposed therebetween.  
         [0007]     The LCD is manufactured by a gravure printing method in which ink is applied to a plurality of recessed cells formed in a printing substrate with a blade. The ink in the recessed cells is transferred to an insulating substrate on which a black matrix is disposed to form a color filter layer.  
         [0008]     In the gravure printing method different colors of ink, such as red, green or blue, fill the respective recessed cells and are transferred to regions between the black matrixes to form the color filter layers. Because, different colors may not formed at the same time since the colors may be mixed with each other thereby making the process complicated and time consuming.  
       SUMMARY  
       [0009]     According to one aspect of the present invention a gravure printing method which is simple process and which results in an improved yield comprising filling the recessed cells of a printing substrate with ink using an ink jet apparatus having a plurality of nozzle heads to jet different colors of ink; and transferring the ink in the recessed cells to an insulating substrate.  
         [0010]     According to another embodiment of the invention, the ink in the recessed cells is transferred to a roller by rolling the roller on the surface of the printing substrate; and transferring the ink on the roller to the insulating substrate.  
         [0011]     According to another embodiment of the invention, the ink jet apparatus comprises a plurality of nozzle units that move over the printing surface to fill the recessed cells with red ink, green ink and blue ink, respectively.  
         [0012]     According to another embodiment of the invention, the gravure printing method further comprises flattening the ink on the surface of the printing substrate after filling the recessed cells with the ink by progressing a flattening plate closely to the surface of the printing substrate.  
         [0013]     According to another embodiment of the invention, the flattening plate progresses parallel with the extending direction of the recessed cells.  
         [0014]     According to another embodiment of the invention, the flattening plate comprises a blade.  
         [0015]     According to another embodiment of the invention, the different colors of inks have such a viscosity as not to mix with each other when filling in the recessed cells.  
         [0016]     According to another embodiment of the invention, the different colors of inks are injected from the plurality of nozzle heads to the recessed cells at such pressure that the different colors of inks do not mix with each other when filling in the recessed cells.  
         [0017]     According to an embodiment of the invention, there is provided a manufacturing method of a display device comprising providing a printing substrate where a plurality of recessed cells are formed adjacently each other; filling the recessed cells with ink using an ink jet apparatus which includes at least one nozzle head; and transferring the ink in the recessed cells to an insulating substrate.  
         [0018]     According to another embodiment of the invention, the recessed cells comprises a first through third recessed cells disposed along a first through third lines respectively, and different colors of inks are filled in the first through third recessed cells at the same time or sequentially.  
         [0019]     According to another embodiment of the invention, a black matrix having an opening pattern is provided on the insulating substrate, and the ink in the recessed cells is transferred to the opening pattern.  
         [0020]     According to another embodiment of the invention, the transferring the ink to the insulating substrate comprises transferring the ink in the recessed cells to a roller by the roller progressing closely to a surface of the printing substrate; and transferring the ink on the roller to the opening pattern.  
         [0021]     According to another embodiment of the invention, the manufacturing method further comprises flattening the ink on the surface of the printing substrate and removing the ink disposed outside of the recessed cells by progressing a flattening plate closely to the surface of the printing substrate after filling the recessed cells with the ink.  
         [0022]     According to an embodiment of the invention, there is provided a printing apparatus comprising a stage including a seating region where a printing substrate with a plurality of recessed cells is seated; an ink jet apparatus including a plurality of nozzle heads to jet ink to the recessed cells; a roller transferring the ink in the recessed cells to an insulating substrate; a first through third driving parts to drive the stage, the ink jet apparatus and the roller respectively; and a controller to control the first through third driving parts.  
         [0023]     According to another embodiment of the invention, the printing apparatus further comprises a flattening plate which flattens the ink in the recessed cells and removes ink overflowed outside the recessed cells; and a fourth driving part to drive the flattening plate, wherein the controller controls the fourth driving part.  
         [0024]     According to another embodiment of the invention, the recessed cells comprises a first through third recessed cells provided along a first through third lines, and the ink jet apparatus jets different colors of inks to the first through third recessed cells at the same time.  
         [0025]     According to another embodiment of the invention, the recessed cells comprises a first through third recessed cells provided along a first through third lines, and the ink jet apparatus jets different colors of inks to the first through third recessed cells in a separate process, respectively.  
         [0026]     According to another embodiment of the invention, the ink jet apparatus jets the ink from the plurality of nozzle heads to the recessed cells at such pressure that the different colors of inks do not mix with each other when filling in the recessed cells.  
         [0027]     According to another embodiment of the invention, the ink jet apparatus jets the ink from the plurality of nozzle heads to the recessed cells at such pressure that the different colors of inks do not mix with each other when filling in the recessed cells.  
         [0028]     Additional features of the invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the invention.  
         [0029]     The scope of the invention is defined by the claims, which are incorporated into this section by reference. A more complete understanding of embodiments of the present invention will be afforded to those skilled in the art, as well as a realization of additional advantages thereof, by a consideration of the following detailed description of one or more embodiments. Reference will be made to the appended sheets of drawings that will first be described briefly. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0030]     The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention.  
         [0031]      FIGS. 1 through 5  illustrate a gravure printing method according to an exemplary embodiment of the present invention.  
         [0032]      FIGS. 6 and 7  illustrate a manufacturing method of a display device according to the exemplary embodiment of the present invention.  
         [0033]      FIGS. 8 and 9  illustrate a printing apparatus according to the exemplary embodiment of the present invention. 
     
    
       [0034]     Embodiments of the present invention and their advantages are best understood by referring to the detailed description that follows. It should be appreciated that like reference numerals are used to identify like elements illustrated in one or more of the figures. It should also be appreciated that the figures may not be necessarily drawn to scale.  
       DETAILED DESCRIPTION  
       [0035]     Hereinafter, a gravure printing apparatus and a gravure printing method according to an exemplary embodiment will be described with reference to  FIGS. 1 through 5 .  
         [0036]     Referring to  FIG. 1 , a printing substrate  10  is prepared. A plurality of recessed cells  11  are arranged in parallel on the printing substrate  10 . The recessed cells  11  are concave having a predetermined depth. The width, the length and the depth of the recessed cells  11  are substantially the same as the width, the length and the height of a pattern to be formed and are arranged to correspond to the arrangement of the pattern.  
         [0037]     Referring to  FIG. 2 , an ink-jet apparatus  20  fills the recessed cells  11  with ink  25   a ,  25   b  and  25   c  from a plurality of nozzle unit heads  21 ,  22  and  23  each jetting a different color inks. For example, nozzle head  21  jets red ink  25   a , nozzle head  22  jets green ink  25   b , and nozzle head  23  jets blue ink  25   c . The recessed cells  11  include first recessed cells disposed along a first line (a), second recessed cells disposed along a second line (b), and third recessed cells disposed along a third line (c). The first through third recessed cells are disposed repeatedly without changing their sequence. The first through third nozzle heads  21 ,  22  and  23  operate along the first through third recessed cells.  
         [0038]     According to the size of the ejecting hole  24 , the nozzle heads  21 ,  22  and  23  may jet the ink  25   a ,  25   b  and  25   c  in discontinuous droplets or continuously. The size of the ejecting hole  24  may be properly adjusted depending on the viscosity of the ink  25   a ,  25   b  and  25   c  and the jetting pressure. For example, the size of the ejecting hole  24  of the first through third nozzle heads  21 ,  22  and  23  according to the present exemplary embodiment may be larger than that of a nozzle head used for a conventional ink-jet method. In the conventional ink-jet method, the size of an ejecting hole is made small and a small amount of ink is jetted several times. This is necessary since a misplaced or spilled or splashed spot may be recognized on a display panel unless the jetting position of ink and the ejecting amount thereof are properly and accurately controlled. In the present exemplary embodiment, however, the jetting position of the ink  25   a ,  25   b  and  25   c  and the ejected amount thereof need not be precisely controlled because any ink outside of the recessed cells  11  is removed by a blade to form a smooth surface after recessed cells  11  have been filled with ink Thus, the probability of perceiving a splashed or spilled or misplaced spot on the display panel is reduced. Further, in the present exemplary embodiment, the jetting position and the jetting amount are not required to be as accurate as those in the conventional ink-jet method, the jetting speed can be increased to reduce processing time and enhance yield.  
         [0039]     It is preferred that the inks  25   a ,  25   b  and  25   c  should not be in a liquid state but should be in a gel state having a predetermined viscosity so that the inks  25   a ,  25   b  and  25   c  are transferred to fill recessed cells  11  while maintaining a predetermined shape. Accordingly, the viscosity of the inks  25   a ,  25   b  and  25   c  jetted from the nozzle heads  21 ,  22  and  23  is higher than that of the ink used in the conventional ink-jet method in order to minimize the possibility of mixing the different colors of inks that are jetted at the same time. The higher viscosity will prevent the different colors of ink  25   a ,  25   b  and  25   c  jetted from the nozzle heads  21 ,  22  and  23  from splashing or flowing into the wrong ones of recessed cells  11 . Moreover, the high viscosity of the inks  25   a ,  25   b  and  25   c  allows the jetted droplets to maintain their shapes during jetting. Thus, the amount of inks  25   a ,  25   b  and  25   c  that could possibly splash or flow into the improper cells  11  is reduced.  
         [0040]     Further, the different colors of inks  25   a ,  25   b  and  25   c  are preferably jetted to the recessed cells at such pressure that the different colors of inks may not be mixed each other. Jetting pressure may be adjusted according to the size of the ejecting hole  24  and the viscosity of the inks  25   a ,  25   b  and  25   c.    
         [0041]     Referring to  FIG. 3 , a flattening plate  30  is positioned on one side of the printing substrate  10  and moved along the surface of printing substrate  10  to flatten the inks  25   a ,  25   b  and  25   c  and remove any of the ink that may have overflowed from the recessed cells  11 . Thus, the inks  25   a ,  25   b  and  25   c  do not spread or flow into the wrong ones of recessed cells  11  even though the recessed cells  11  are filled close to the surface of the printing substrate. The flattening plate  30  has a rectangular shape wide enough to cover one side of the printing substrate  10  and includes a contacting part  31  having a soft material such as rubber or silicon at contacting portion with the surface of the printing substrate  30 . The contacting part  31  removes any of the ink that may have overflowed the recessed cells  11 .  
         [0042]     Preferably, the flattening plate  30  moves in an extending direction (d) of the recessed cells  11  so that the different colors of inks  25   a ,  25   b  and  25   c  filled in the respective recessed cells  11  may not mix with each other. If the flattening plate  30  moves along the surface of the printing substrate  10  at an angle away from extending direction (d) of the recessed cells there is the possibility that ink disposed in the first line (a) may be driven into the second recessed cells in the second line (b), thereby resulting in the undesirable mixing of different colors of ink. The flattening plate  30  may include a blade.  
         [0043]     Referring to  FIG. 4 , the different colors of inks  25   a ,  25   b  and  25   c  that have been uniformly filled in the recessed cells  11  are transferred to roller  40  that moves closely over the surface of the printing substrate  10 . The transfer of ink to roller  40  obeys the following principle: when the surface tension or frictional force of the surface of the recessed cells  11  is smaller than that of the inks  25   a ,  25   b  and  25   c  and surface tension or frictional force of the roller  40  is larger than the that of the inks  25   a ,  25   b  and  25   c , the inks  25   a ,  25   b  and  25   c  in the recessed cells  11  is transferred to the roller  40 . Alternatively, when the surface of the recessed cells  11  is charged with positive or negative charge and the inks  25   a ,  25   b  and  25   c  are charged with the same charge as the surface of the recessed cells  11 , the repulsive force tends to cause the inks  25   a ,  25   b  and  25   c  to be separated from the surface of the recessed cells  11 . When the roller  40  has a charge that is opposite to the charge on any of inks  25   a ,  25   b  and  25   c , the inks  25   a ,  25   b  and  25   c  are transferred to the roller  40 . Ink will also be transferred to roller  40  if the inks  25   a ,  25   b  and  25   c  and the surface of the recessed cells  11  are charged with the same positive or negative charge and the roller  40  is charged opposite thereto. Ink may be easily transferred to the roller  40  when the inks  25   a ,  25   b  and  25   c  are charged more intensively than the surface of the recessed cells  11  so that force between the inks  25   a ,  25   b  and  25   c  and the roller  40  is stronger than force between the surface of the recessed cells  11  and the roller  40 .  
         [0044]     Referring to  FIG. 5 , the roller  40  with the inks  25   a ,  25   b  and  25   c  thereon moves to transfer the inks  25   a ,  25   b  and  25   c  to a predetermined position on an insulating substrate  50 , thereby forming a pattern. The inks  25   a ,  25   b  and  25   c  may be transferred by the aforementioned principles.  
         [0045]     Accordingly, the different colors of inks  25   a ,  25   b  and  25   c  may easily be transferred to the insulating substrate  50  without mixing with each other, thereby forming the pattern on the insulating substrate  50 . Further, the different colors inks  25   a ,  25   b  and  25   c  are transferred to the insulating substrate  50  at the same time, thereby simplifying the process, reducing processing hour and minimizing color mixing, and thus enhancing a yield of a printing process.  
         [0046]     An LCD panel includes a TFT substrate, a color filter substrate facing the TFT substrate, and a liquid crystal layer disposed therebetween.  
         [0047]     The color filter substrate includes an insulating substrate  210 , a black matrix  220  and a common electrode. The insulating substrate  210  includes insulating materials such as glass, quartz, ceramic or plastic and a color filter layer  230   a  and  230   b . The color filter layers  230   a  and  230   b  have red, green and blue color filters or cyan, magenta and yellow color filters. The black matrix  220  is formed between the color filters  230   a  and  230   b , and the common electrode is formed on the black matrix  220  and the color filter layer  230   a  and  230   b.    
         [0048]     The black matrix  220  is disposed between the color filters  230   a  and  230   b  having different colors such as red, green and blue or cyan, magenta and yellow to divide therebetween.  
         [0049]     Hereinafter, a manufacturing method of a display device using the aforementioned gravure printing method will be described with reference to drawings in detail. It should be noted that the following description will be made to only different features from those of the gravure printing method, and description to the remaining similar features will not be repeated herein. The inks described in  FIGS. 1 through 5  correspond to a color filter ink.  
         [0050]     A manufacturing method of a color filter layer  230   a ,  230   b  and  230   c  using the gravure printing method will be described with reference to  FIGS. 2 through 4  and  FIGS. 8 and 9 .  
         [0051]     Referring to  FIG. 2 , the ink-jet apparatus  20  fills the plurality of recessed cells  11  on the printing substrate  10  with the color filter inks  25   a ,  25   b  and  25   c . The different colors of color filter inks  25   a ,  25   b  and  25   c  may be filled in the recessed cells  11  at the same time, or independently by separate ink-jet processes (see  FIG. 4 ).  
         [0052]     Referring to  FIG. 3 , the flattening plate  30  flattens the color filter inks  25   a ,  25   b  and  25   c  on the surface of the printing substrate (see  FIG. 4 ).  
         [0053]     Referring to  FIG. 4 , the roller  40  rolls to transfer the color filter inks  25   a ,  25   b  and  25   c  on the surface of the printing substrate  10  to the roller  40 .  
         [0054]     The width of the recessed cells  11  on the printing substrate  10  (see  FIG. 1 ) is provided to be the same as or larger than a space between the black matrixes  220  on the insulating substrate  210  so that the color filter inks  25   a ,  25   b  and  25   c  filled in the recessed cells  11  may be transferred to fill the space between the black matrixes  220 , thereby obtaining a clear image.  
         [0055]     The total length of the recessed cells  11  in the first through third lines may depend on the size of the LCD panel, i.e., the total length of the recessed cells  11  becomes long as the size of the LCD panel becomes big. Likewise, the number of the recessed cells  11  is proportional to the size of the LCD panel. The depth of the recessed cells  11  is the same or a little higher than the black matrix  220  on the insulating substrate  210  so that the color filter inks  25   a ,  25   b  and  25   c  may be formed. In the present exemplary embodiment, the different colors of color filter inks  25   a ,  25   b  and  25   c  may be filled in the recessed cells  11  by an ink-jet method at the same time, thereby simplifying a process and reducing processing hour.  
         [0056]     Referring to  FIG. 8 , the roller  40  with the color filter inks  25   a ,  25   b  and  25   c  thereon rolls on the insulating substrate  210  where the black matrix  220  is formed to transfer the color filter inks  25   a ,  25   b  and  25   c  to a space between the black matrixes  220 . Accordingly, referring to  FIG. 9 , the color filter layer  230   a ,  230   b  and  230   c  having three different colors of filters is formed. The three different colors of filters  230   a ,  230   b  and  230   c  are formed at the same time, thereby reducing processing hour and improving a yield.  
         [0057]     Then, the color filter substrate are fabricated by a known method and joined with the TFT substrate, and the liquid crystal layer is interposed therebetween, thereby completing the LCD panel.  
         [0058]     Hereinafter, a printing apparatus according to the exemplary embodiment will be described with reference to  FIGS. 2, 10  and  11 .  
         [0059]     A printing apparatus  500  according to the exemplary embodiment includes a stage  510  where a printing substrate with a plurality of recessed cells  11  is seated; an ink jet apparatus  20  having a plurality of nozzle heads  21 ,  22  and  23  to jet ink to the recessed cells  11 ; a flattening plate  30  to flatten the ink in the recessed cells  11 ; a roller  40  transferring the inks  40  in the recessed cells  11  to an insulating substrate  50  (see  FIG. 5 ); a first through fourth driving parts  520 ,  530 ,  540  and  550  to drive the stage  510 , the ink jet apparatus  20 , the flattening plate  30  and the roller  40 ; and a controller  560  to control the first through fourth driving parts  520 ,  530 ,  540  and  550 .  
         [0060]     The stage  510  has a seating region (g) where the printing substrate  10  is seated and may move in a first direction (h). The ink jet apparatus  20  moves relatively to the stage  510  to jet and fill in the recessed cells  11  with the ink. The ink jet apparatus  20  may move in a second direction (i) relatively to the first direction in which the stage  510  moves. Alternatively, one of the stage  510  and the ink jet apparatus  20  may be fixed and the other thereof may move in the first direction (h) or in the second direction (i). The stage  510  and the ink jet apparatus  20  moves according to operations of the first and second driving parts  520  and  530 . The controller  560  controls the first and second driving parts  520  and  530  to accurately jet the ink in the recessed cells  11 .  
         [0061]     The flattening plate  30  is provided as a plate member extending in one direction and disposed at a side of the printing substrate  10 . The flattening plate  30  moves closely on the surface of the printing substrate  10  to flatten the ink in the recessed cells  11  and to remove the ink overflowed outside from the recessed cells  11 . The flattening plate  30  includes a blade and may move upward, downward and in the second direction (i).  
         [0062]     The circumference of the roller  40  is substantially the same as the length of the printing substrate  10  in a moving direction of the roller  40 , and the width of the roller  40  is substantially the same as the of the width of the printing substrate  10  in a transverse direction to the moving direction of the roller  40 . The roller  40  rolls closely on the surface of the printing substrate  10  so that the ink in the recessed cells  11  may be transferred to the roller  40 . The roller  40  may move upward, downward and in the second direction (i).  
         [0063]     Hereinafter, a driving method of the printing apparatus  20  will be described. When the printing substrate  10  is seated on the stage  510 , the ink jet apparatus  20  is disposed close to a side of the printing substrate  10 . Here, the first through third nozzle heads  21 ,  22  and  23  are disposed corresponding to the recessed cells  11  where the ink is jetted.  
         [0064]     The first through third nozzle heads  21 ,  22  and  23  move over the surface of the printing substrate  10  in the second direction (i) to fill the recessed cells  11  disposed in the different lines (a), (b) and (c) with the ink. For example, as shown in  FIG. 2 , the first recessed cells  11  disposed in the first line (a) is filled with red ink  25   a , the second recessed cells  11  disposed in the second line (b) is filled with green ink  25   b , and the third recessed cells  11  disposed in the third line (c) is filled with blue ink  25   c.    
         [0065]     Alternatively, the stage  510  may move in the first direction (h) or second direction (i) to fill the recessed cells  11  with the ink, without moving the ink jet apparatus  20 . The ink jet apparatus  20  may fill the first through third recessed cells  11  with different colors of inks  25   a ,  25   b  and  25   c , respectively in independent processes. As described above, the jetting position and the jetting amount are not required to be as accurate as those in the conventional ink-jet method, and thus an increased jetting speed reduces a processing hour and enhances a yield.  
         [0066]     When the recessed cells  11  are filled with the ink, the second driving part  530  moves the ink jet apparatus  20  out of a processing space.  
         [0067]     Referring to  FIG. 3 , the controller  560  controls the fourth driving part  550  so that the flattening plate  30  moves closely on the surface of the printing substrate to flatten the ink in the recessed cells  11  and to remove the ink overflowed outside from the recessed cells  11 .  
         [0068]     Subsequently, the controller  560  controls the third driving part  540  so that the roller  40  rolls closely on the surface of the printing substrate  10 . Accordingly, referring to  FIG. 4 , the ink in the recessed cells  11  is transferred to the roller  40 . When the ink is transferred to the roller  40 , the controller  560  controls the third driving part  540  to transport the roller  40  over the insulating substrate  50  to which the ink transferred. The roller  40  rolls on the insulating substrate  50  to transfer the ink to the insulating substrate  50 , thereby forming a pattern on the insulating substrate  50  (see  FIG. 5 ). Accordingly, the printing apparatus can simplify a process and improve a yield.  
         [0069]     The aforementioned exemplary embodiment is described with a manufacturing method of a color filter substrate of an LCD panel as an example, but it is not limited thereto. The present exemplary embodiment may be employed to form an organic material or a polymer of an organic light emitting diodes (OLED) on predetermined regions between electrodes. Further, the present exemplary embodiment may also be employed to form a color filter layer on a TFT substrate, which is a color on array (COA).  
         [0070]     It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the invention. Thus it is intended that the present invention cover the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.