Patent Publication Number: US-7588315-B2

Title: Array printhead and inkjet image forming apparatus having the same

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority under 35 U.S.C. §119 from Korean Patent Application No. 10-2005-0126930, filed on Dec. 21, 2005, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein in its entirety by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present general inventive concept relates to an inkjet image forming apparatus, and more particularly, to an inkjet image forming apparatus having an array printhead including a nozzle unit of a length that corresponds to the width of paper. 
     2. Description of the Related Art 
     An inkjet image forming apparatus is an apparatus which fires ink using a printhead (i.e., a shuttle type printhead) spaced apart a predetermined interval from the front surface of a sheet of paper and which reciprocates in a direction (i.e., the width direction of the sheet of paper) perpendicular to a delivery direction of the sheet of paper to form an image on the sheet of paper. The printhead includes a nozzle unit having a plurality of nozzles to eject ink. 
     Recently, an attempt has been made to realize high-speed printing by using a printhead (i.e., an array printhead) having a nozzle unit of a length that corresponds to the width of the sheet of paper instead of the shuttle type printhead which reciprocates in the width direction of the sheet of paper. Since the printhead is fixed and only the sheet of paper is moved in the array printhead inkjet image forming apparatus, a driving mechanism is simple and high-speed printing may be realized. 
     The array printhead may supply ink of a plurality of colors to form a color image. For that purpose, a plurality of supply channels through which ink of the plurality of colors is supplied may be formed at a length that corresponds to the width of the sheet of paper in a lower surface of the array printhead. 
     However, as described above, since the supply channels which supply ink in the array printhead are formed with a length that corresponds to the width of the sheet of paper, the array printhead is difficult to manufacture and a degree of planarization needs to be managed to properly mount a head chip on the array printhead. 
     SUMMARY OF THE INVENTION 
     The present general inventive concept provides an array printhead having ink supply channels, and an inkjet image forming apparatus having the same, capable of mounting a plurality of head chips in a plurality of lines and allowing ink of four colors to be supplied to each of the plurality of head chips. 
     Additional aspects and advantages of the present general inventive concept will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the general inventive concept. 
     The foregoing and/or other aspects of the present general inventive concept may be achieved by providing an array printhead to print an image on a print medium, the array printhead including a first member to supply ink of different colors, a second member to separately receive the ink of different colors supplied from the first member, a third member having a plurality of supply grooves each corresponding to each of a plurality of head chips, the plurality of supply grooves being formed in one side of the third member where the plurality of head chips are mounted, and having a plurality of supply holes each supplying the ink of different colors supplied from the second member, the plurality of supply holes being formed in corresponding ones of the plurality of supply grooves so as to independently supply the ink of different colors to each of the plurality of head chips, wherein the first, second, and third members sequentially overlap and couple to each other, and each of the plurality of supply holes is located on an axis line different from axis lines of adjacent others of the plurality of supply holes in a direction perpendicular to a width direction of the print medium. 
     The foregoing and/or other aspects of the present general inventive concept may be achieved by providing an inkjet image forming apparatus having a paper feeding element feeding paper in one direction and an array printhead ejecting ink onto the paper to form an image, the array printhead including a first member to supply ink of different colors, a second member to separately receive the ink of different colors supplied from the first member, a third member having a plurality of supply grooves each corresponding to each of a plurality of head chips, the plurality of supply grooves being formed in one side of the third member where the plurality of head chips are mounted, and having a plurality of supply holes each supplying the ink of different colors supplied from the second member, the plurality of supply holes being formed in corresponding ones of the plurality of supply grooves so as to independently supply the ink of different colors to each of the plurality of head chips, wherein the first, second, and third members sequentially overlap and couple to each other, and each of the plurality of supply holes is located on an axis line different from axis lines of adjacent others of the plurality of supply holes in a direction perpendicular to a width direction of the paper. 
     The foregoing and/or other aspects of the present general inventive concept may be achieved by providing an array printhead usable in an image forming apparatus, including an array printhead usable in an image forming apparatus, including a member to receive ink of different colors in a first direction, and having a plurality of inlet holes spaced apart from each other in a second direction to receive the corresponding ink of different colors in the first direction, a plurality of ink channels to communicate with corresponding ones of the plurality of the inlet holes and to direct the corresponding ink of the different colors in the second direction, a plurality of channel groove groups disposed in the second direction, each group having channel grooves to communicate with corresponding ones of the plurality of ink channels and to direct the corresponding ink of different colors in a third direction, and a plurality of head chips disposed in the second direction to correspond to respective ones of the channel groove groups, each of the plurality of head chips having a plurality of nozzle lines disposed in the third direction, each nozzle line receiving the corresponding ink of different colors from corresponding ones of the channel groove. 
     The member may include a plurality of supply holes formed on corresponding ones of the channel grooves of the each channel groove group, and a plurality of supply grooves disposed in the second direction to correspond to corresponding nozzle lines to direct the corresponding ink of different colors to the corresponding nozzle lines. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and/or other aspects and advantages of the present general inventive concept will become apparent and more readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which: 
         FIG. 1  is a view illustrating an inkjet image forming apparatus according to an embodiment of the present general inventive concept; 
         FIG. 2  is an exploded perspective view illustrating an array printhead usable with an image forming apparatus according to an embodiment the present general inventive concept; 
         FIG. 3  is an exploded perspective view illustrating a backside of the array printhead of  FIG. 2 ; 
         FIG. 4  is a perspective view illustrating the array printhead of  FIG. 2 ; 
         FIG. 5  is a partial enlarged view illustrating a portion A of  FIG. 2 ; 
         FIG. 6  is a partial enlarged view illustrating a portion B of  FIG. 3 ; 
         FIG. 7  is a partial enlarged view illustrating a modification of the portion B of  FIG. 3 ; 
         FIG. 8  is a partial enlarged view illustrating another modification of the portion B of  FIG. 3 ; and 
         FIG. 9  illustrates a sectional view taken along a line V-V′ of  FIG. 4 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Reference will now be made in detail to the embodiments of the present general inventive concept, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to the like elements throughout. The embodiments are described below in order to explain the present general inventive concept by referring to the figures. 
     Referring to  FIG. 1 , an inkjet image forming apparatus  100  includes a paper feeding element to feed a printing medium, such as a sheet of paper P, in one direction and an array printhead  130  to eject ink onto the paper P to form an image on the paper P. 
     The paper feeding element may include feeding rollers  110  to feed the paper P such that the paper P passes through a paper path below the array printhead  130  and discharge rollers  190  to discharge the paper P on which the image is formed by ejection of the ink to a paper-discharging tray  191 . The paper feeding element may also include a paper pickup roller  105  to pick up the paper P stacked in the paper-supply cassette  101 . 
     Each of the feeding rollers  110  and the discharge rollers  190  has a pair of rollers which may include a drive roller and a driven roller installed to press against each other, and the paper P progresses between contact surfaces where the drive roller and the driven roller of the respective feeding and discharge rollers are pressed to contact each other. A reference numeral  115  is a pair of registration rollers to align the paper P in order to form the image on a desired portion of the paper P. 
     The inkjet image forming apparatus  100  includes the paper-supply cassette  101  in which the paper P on which the image is to be printed is stacked, and the pickup roller  105  to pick up the paper P sheet by sheet stacked in the paper-supply cassette  101 . Also, the inkjet image forming apparatus  100  further includes a dryer  180  to dry the image formed on the paper P by the ejection of ink. Since the inkjet image forming apparatus  100  having the array printhead  130  has a high printing speed, the paper P may not be sufficiently dried as it is successively stacked on the paper-discharging tray  191 , which may cause ink spreading. The drier  180  prevents a printing defect due to the ink spreading by rapidly drying an image. 
     An ink cartridge  120  is located between the registration rollers  115  and the drier  180 . 
     The ink cartridge  120  includes four ink tanks  122 C,  122 M,  122 Y, and  122 K which respectively receive ink of four colors of cyan (C), magenta (M), yellow (Y), and black (K), four negative pressure regulators  125 C,  125 M,  125 Y, and  125 K, and the array printhead  130  therein. 
     The negative pressure regulators  125 C,  125 M,  125 Y, and  125 K regulate negative pressures of ink which flows to the array printhead  130  from the four ink tanks  122 C,  122 M,  122 Y, and  122 K to prevent air bubbles from penetrating into the inside of the array printhead  130  (refer to  FIG. 3 ) or prevent the ink from leaking out unnecessarily. 
     A platen  165  is located below the array printhead  130  to support the paper P containing the image thereon and to pass the paper P through the paper path below the array printhead  130 . By use of the platen  165 , a uniform interval is maintained between the array printhead  130  and the paper P as it passes through the paper path below the array printhead  130 . 
     Referring to  FIGS. 2 and 3 , the array printhead  130  includes a support member  131 , a first member  140 , a second member  150 , and a third member  160 , which sequentially overlap and couple with each other in a first direction. 
     The first, second, and third members  140 ,  150 , and  160  are respectively formed by molding liquid crystal polymer, which is a polymer resin. The liquid polymer has excellent molding properties, excellent chemical durability, and a high resistance against twisting due to external forces. The liquid polymer is a material having excellent measurement stability and thus is appropriate for the printhead  130  which requires a high degree of planarization and a high degree of accuracy in measurement. 
     The support member  131  includes guide holes  132   a ,  132   b ,  132   c , and  132   d  to receive ink of different colors, and first and second coupling holes  134  and  135 . The guide holes  132   a ,  132   b ,  132   c , and  132   d  are spaced apart by a distance in a second direction having an angle with the first direction. 
     The first member  140  includes four inlet holes  141   a ,  141   b ,  141   c , and  141   d  formed to allow ink of four colors of cyan, magenta, yellow, and black from the four negative pressure regulators  125 C,  125 M,  125 Y, and  125 K (refer to  FIG. 2 ) through the guide holes  132   a ,  132   b ,  132   c , and  132   d  to flow into an inside of the array printhead  130  (i.e., four channels  151   a ,  151   b ,  151   c , and  151   d  of the second member  150 ). In detail, ink of cyan, magenta, yellow, and black may flow through a first inlet hole  141   a , a second inlet hole  141   b , a third inlet hole  141   c , and a fourth inlet hole  141   d , respectively. Four channels  143   a ,  143   b ,  143   c , and  143   d  are formed in a lower surface of the first member  140  to separately receive the ink of four colors of C, M, Y, and K, which have flowed in through the four inlet holes  141   a ,  141   b ,  141   c , and  141   d . Through holes  142   a ,  142   b ,  142   c , and  142   d  are formed in the respective four channels  143   a ,  143   b ,  143   c , and  143   d  to communicate with the four inlet holes  141   a ,  141   b ,  141   c , and  141   d , respectively. 
     The second member  150  includes the four channels  151   a ,  151   b ,  151   c , and  151   d  disposed in a third direction having an angle with the second direction to separately receive ink of four colors of C, M, Y, and K, which has flowed in through the four through holes  142   a ,  142   b ,  142   c , and  142   d , respectively. The channels  151   a ,  151   b ,  151   c , and  151   d  are mutually parallel to the width direction of the paper P, i.e., a length direction of the array printhead  130  or a direction perpendicular to a paper feeding direction of the paper P. The four channels  151   a ,  151   b ,  151   c , and  151   d  may receive cyan ink, magenta ink, yellow ink, and black ink, respectively. The first angle may be 90 degrees with respect to the second and third angles, and the second angle may be 90 degrees with respect to the third angle. 
     The four channels  143   a ,  143   b ,  143   c , and  143   d  are also formed in a lower surface of the first member  140  in a same pattern as the four channels  151   a ,  151   b ,  151   c , and  151   d  formed in an upper surface of the second member  150 . With this construction, the channels  143   a ,  143   b ,  143   c , and  143   d  of the first member  140  face the four channels  151   a ,  151   b ,  151   c , and  151   d  of the second member  150 , so that sufficient ink receiving spaces may be provided for the ink of four colors of C, M, Y, and K, respectively. 
     A rib  156  is protruded from the periphery of the upper surface of the second member  150  and a groove  146  is formed in a periphery of the lower surface of the first member  140  to receive the rib  156  of the second member  150 . The rib  156  and the groove  146  serve as references when the first member  140  and the second member  150  are attached to each other. The rib  156  and the groove  146  may suppress bending and twisting of the first member  140  and the second member  150 , thereby improving sealing between the first member  140  and the second member  150 . 
     The array printhead  130  may include a plurality of head chips  163  arranged in a zigzag with respect to the width direction of paper (i.e., the length direction of the array printhead  130 ), so that the head chips  163  form a plurality of head chip lines. 
     A plurality of head chip mounting parts  1641  and  1642  each constituting the plurality of head chip lines may also be formed in a zigzag in a backside of the third member  160  so that each of the plurality of head chips  163  may be mounted on each of the plurality of head chip mounting parts  1641  and  1642 . 
     A plurality of channel groove groups  161  and  162 , each channel groove group serving as a flowing passage of ink that has flowed from the second member  150 , may be formed in an upper surface of the third member  160 . 
     To supply ink to the head chip mounting parts  1641  and  1642 , respectively, the plurality of channel groove groups  161  and  162  of the third member  160  may be repeatedly formed in the length direction of the array printhead  130  to correspond to the arrangement of the head chips  163 . That is, the plurality of channel groove groups  161  and  162  may be formed in the zigzag. Therefore, cyan ink, magenta ink, yellow ink, and black ink may be respectively supplied to a first nozzle line  163   a , a second nozzle line  163   b , a third nozzle line  163   c , and a fourth nozzle line  163   d  formed on the head chip  163  in the second direction. The ink of four colors may be supplied to one chip, so that “1-head chip 4-colors” can be achieved. 
     A plurality of second channel groove groups  152  and  153  may also be formed on the lower surface of the second member  150  in a same pattern as a pattern of the channel groove groups  161  and  162  of the third member  160 . 
     A rib  166  may protrude from a periphery of the upper surface of the third member  160  and a second groove  157  may be formed in a periphery of the lower surface of the second member  150  to receive the rib  166 . The second rib  166  and the second groove  157  serve as references when the second member  150  and the third member  160  are attached to each other. The second rib  166  and the second groove  157  suppress bending and twisting of the second member  150  and the third member  160 , thereby improving sealing between the second member  150  and the third member  160 . 
     Referring to  FIGS. 2 ,  3 , and  5 , the channel groove group  162  includes four channel grooves  1621 ,  1622 ,  1623 , and  1624 . The channel grooves  1621 ,  1622 ,  1623 , and  1624  may have a same width W and different lengths. Supply holes  162   a ,  162   b ,  162   c , and  162   d , respectively, which supply ink of four colors to a head chip mounting part  1642 , may be formed at ends of the channel grooves  1621 ,  1622 ,  1623 , and  1624 , respectively, to pass through the head chip mounting part  1642 . The supply holes  162   a ,  162   b ,  162   c , and  162   d  correspond to the first, second, third, and fourth nozzle lines  163   a ,  163   b ,  163   c , and  163   d , respectively. 
     As illustrated in  FIG. 5 , assuming that the supply holes  162   b  and  162   d  are first supply holes and the supply holes  162   a  and  162   c  are second supply holes, the first supply holes  162   b  and  162   d  may be spaced apart from each other by a distance L 1  in a direction (third direction) perpendicular to a width (second direction) of paper P and located on a same vertical axis line C. The first supply hole  162   b  may be a horizontal distance L 2  away from either of the second supply holes  162   a  or  162   c  in the second direction. The first supply hole  162   b  may also be a vertical distance L 3  (where L 3 =[1/3]*[L 1 ]) away from the second supply hole  162   a  in the third direction, and may also be the vertical distance L 3  from the second supply hole  162   c  in the third direction. The first supply hole  162   d  may also be the vertical distance L 3  away from the second supply hole  162   a  and the second supply hole  162   c  in the third direction. That is, the first supply holes  162   b  and  162   d  may be located to face each other on the vertical axis line C (third direction) and may be spaced apart by the distance L 1  which is greater than the horizontal distance L 2  between either of the second supply holes  162   a  and  162   c  and the axis line C in the second direction. The distance L 1  between the first supply holes  162   b  and  162   d  may also be greater than the vertical distance L 3  between individual ones of the second supply holes  162   a  and  162   c  and the first supply holes  162   b  and  162   d  in the third direction. In other words, the distance L 1  may be greater than the horizontal distance L 2  in the second direction or the vertical distance L 3  in the third direction. The horizontal distance L 2  and the vertical distance L 3  may be less than the width W. 
     The second supply holes  162   a  and  162   c  may be spaced apart from the first supply holes  162   b  and  162   d  by as much as the distance L 2  on both sides of the vertical axis line C of the first supply holes  162   b  and  162   d , in a direction (second direction) of the width of the paper P and perpendicular to the vertical axis line C (third direction). 
     Referring again to  FIGS. 2 ,  3 , and  5 , the channel grooves  1621 ,  1622 ,  1623 , and  1624  may be spaced apart from one another by as much as distances L 1  and L 2  without overlapping one another. Sealant may be coated on spaced portions of the third member  160  between the channel grooves  1621 ,  1622 ,  1623 , and  1624  in order for coupling of the third member  160  with the second member  150 . Since the spaced portions between the channel grooves  1621 ,  1622 ,  1623 , and  1624  may be symmetrically formed with respect to the first supply holes  162   b  and  162   d , it is possible to uniformly coat the sealant between the channel grooves  1621 ,  1622 ,  1623 , and  1624 . Accordingly, the channel grooves  1621 ,  1622 ,  1623 , and  1624  and the supply holes  162   a ,  162   b ,  162   c , and  162   d  may form supply passages between the second member  150  and the third member  160  which supply the ink of four colors to head chip  163 . 
     As described above, it is possible to provide the supply passages through which ink of different colors may be supplied securely and without being mixed by providing the above arrangement with respect to the supply holes  162   a ,  162   b ,  162   c , and  162   d  and the channel grooves  1621 ,  1622 ,  1623 , and  1624 . Also, it is possible to stably secure a bonding space in which an adhesive may be coated so that the third member  160  may be coupled to the second member  150 . 
     Referring to  FIGS. 2 and 3 , the head chip  163  includes four nozzle lines  163   a ,  163   b ,  163   c , and  163   d  formed in parallel to the width direction (second direction) of the paper P to eject the ink of different colors. In detail, cyan ink, magenta ink, yellow ink, and black ink may be respectively supplied to a nozzle line  163   a , a nozzle line  163   b , a nozzle line  163   c , and a nozzle line  163   d  formed on the head chip  163 . Therefore, the ink of four colors is supplied to one chip, so that ‘1-head chip 4-colors’ is achieved. 
     Referring to  FIGS. 3 ,  6  and  9 , an embodiment of the present general inventive concept with respect to an arrangement of the portion B of  FIG. 3  will be explained. A head mounting part  1642  ( FIG. 3 ) includes a plurality of supply grooves  1643 ,  1644 ,  1645 , and  1646  formed in parallel to a width direction of paper P. The supply grooves  1643 ,  1644 ,  1645 , and  1646  supply ink of different colors to corresponding nozzle lines  163   a ,  163   b ,  163   c , and  163   d  of the head chip  163  mounted on the head mounting part  1642 . 
     Each of the plurality of supply grooves  1643 ,  1644 ,  1645 , and  1646  communicates with each of plural channel grooves  1621 ,  1622 ,  1623 , and  1624  through supply holes  162   a ,  162   b ,  162   c , and  162   d.    
     The plurality of supply grooves  1643 ,  1644 ,  1645 , and  1646  may have slopes  1680  formed to be inclined on both sides of the supply holes  162   a ,  162   b ,  162   c , and  162   d  along a direction from the supply holes  162   a ,  162   b ,  162   c , and  162   d  to a lower surface of the head chip mounting part  1642  (i.e., a direction toward the head chip  163  in  FIG. 3 ). Therefore, as illustrated in  FIG. 9  which is a sectional view taken along a line V-V′ of  FIG. 4 , ink may be supplied through an inlet hole  141   d  of a first member  140  and through ink supply passages formed by a second member  150  and a third member  160 . Then, the ink that has flowed into the supply grooves  1643 ,  1644 ,  1645 , and  1646  through the supply holes  162   a ,  162   b ,  162   c , and  162   d  may be uniformly supplied along inclined portions of the supply grooves  1643 ,  1644 ,  1645 , and  1646  to the nozzle lines  163   a ,  163   b ,  163   c , and  163   d  of the head chip  163 . 
     Referring to  FIGS. 7 and 8 , the supply holes  162   a ,  162   b ,  162   c , and  162   d  are arranged differently from those in  FIGS. 5 and 6 . That is, referring to  FIG. 7 , the second supply holes  162   a  and  162   c  are arranged to a right side of the first supply holes  162   b  and  162   d . Referring to  FIG. 8 , the second supply holes  162   a  and  162   c  are arranged to a left side of the first supply holes  162   b  and  162   d.    
     It is possible to stably secure a space on which sealant is coated between the supply holes  162   a ,  162   b ,  162   c , and  162   d  with an arrangement where a spaced distance (L 71  in  FIG. 7  or L 81  in  FIG. 8 ) between the first supply holes  162   b  and  162   d  is set to be equal to a spaced distance (L 72  in  FIG. 7  or L 82  in  FIG. 8 ) between the second supply holes  162   a  and  162   c.    
     When the sealant is hardened at a predetermined temperature with the sealant coated between the channel grooves  1621 ,  1622 ,  1623 , and  1624  of  FIG. 5  and the head chip  163  of  FIGS. 2 ,  3 , and  9  mounted on the head chip mounting part  1642  of  FIG. 3 , a gas of high temperature and high pressure is generated. At this point, when the generated gas remains without being exhausted, the gas exerts stress on the head chip  163 . Furthermore, stress is added to the head chip  163  due to a difference in linear expansion coefficients during contraction. 
     Referring to  FIGS. 5 ,  6 ,  7 , and  8 , it is possible to prevent the stress from being concentrated on only one portion of the head chip  163  by providing the supply holes  162   a ,  162   b ,  162   c , and  162   d  to uniformly distribute the stress due to the gas generated when the sealant is hardened over the entire head chip  163 . 
     Referring to  FIGS. 2 ,  3 , and  4 , channel groove groups  152  and  153  may also be formed in a lower surface of the second member  150  in a same pattern as a pattern of the channel groove groups  161  and  162  formed in an upper surface of the third member  160 . 
     A rib  166  ( FIG. 2 ) protrudes from a periphery of the upper surface of the third member  160  and a groove  157  ( FIG. 3 ) to receive the rib  166  may be formed in a periphery of the lower surface of the second member  150 . The rib  166  and the groove  157  allow the second member  150  and the third member  160  to be cooperatively bonded to each other. When the sealant is coated on a space between the channel groove groups  161  and  162  of the third member  160  and the channel groove groups  152  and  153  of the second member  150  to bond the third member  160  to the second member  150 , the third member  160  and the second member  150  are closely attached to each other and the channel groove groups  161  and  162  of the third member  160  and the channel groove groups  152  and  153  of the second member  150  constitute ink supply channels or supply passages. 
     The first, second, and third members  140 ,  150 , and  160  are vertically coupled to a support member  131  using a coupling element. For that purpose, as illustrated in  FIGS. 2 ,  3 , and  4 , the coupling element may include the first coupling parts  174  that sequentially couple the support member  131 , the first member  140 , and the second member  150  vertically from a first side of the support member  131 , and second coupling parts  175  that sequentially couple the third member  160 , the second member  150 , the first member  140 , and the support member  131  vertically from a second side of the support member  131 . 
     The support member  131  includes the first and second coupling holes  134  and  135 . The first member  140  includes first and second coupling holes  144  and  145 , the second member  150  includes first and second coupling holes  154  and  155 , and the third member  160  includes second coupling holes  165 . Accordingly, the first coupling part  174  is coupled in the first coupling holes  134 ,  144 , and  154 , and the second coupling part  175  is coupled in the second coupling holes  135 ,  145 ,  155 , and  165 . 
     As described above, the array printhead according to the present general inventive concept has the following effects. 
     The present general inventive concept may provide a uniform width of a channel groove for each color to swiftly supply ink. 
     The present general inventive concept may provide maximum adhesive area to enhance adhesive force when bonding is performed with an adhesive. 
     A plurality of supply holes may be arranged such that stress is not concentrated only at one portion of a head chip. 
     Since adhesive force is reinforced, mixing of colors and leakage of ink may be prevented. 
     An adhesive surface is formed in a uniform pattern, so that an adhesive process may be easily performed. 
     Although a few embodiments of the present general inventive concept have been shown and described, it will be appreciated by those skilled in the art that changes may be made in these embodiments without departing from the principles and spirit of the general inventive concept, the scope of which is defined in the appended claims and their equivalents.