CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims priority under 35 U.S.C. §119(a) from Korean Patent Application No. 2006-0116463, filed on Nov. 23, 2006 in the Korean Intellectual Property Office, the disclosure of which is incorporated herein in its entirety by reference. 
       BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present general inventive concept relates to a head chip and ink cartridge and an image forming apparatus having the same, and more particularly, to a head chip and ink cartridge having an improved ink supplying slit structure and an image forming apparatus having the same. 
         [0004]    2. Description of the Related Art 
         [0005]    An image forming apparatus forms image data onto a recording medium according to a printing signal which is applied by a host. Generally, the image forming apparatus is divided into an inkjet type where an image is formed by discharging ink onto a recording medium, an electrophotographic type where the image is formed by selectively applying developer onto the recording medium using electric potential differences among a photosensitive member, the developer, and a transfer roller, and a thermal printing type where the image is formed by contacting an ink ribbon coated with ink with the recording medium and applying heat and pressure to transfer the ink to the recording medium. 
         [0006]    According to the inkjet type image forming apparatus, an ink cartridge in which the ink is stored discharges the ink onto the recording medium to form the image. The inkjet type image forming apparatus is divided into a shuttle type, where the ink cartridge discharges the ink while it shuttles in a direction perpendicular to a feeding direction of the recording medium, and a line head type, where the ink cartridge is provided to have a width to correspond to a width of the recording medium and forms the image by discharging the ink per whole width. 
         [0007]      FIG. 1  is a perspective view illustrating a conventional ink cartridge  10 . As illustrated in  FIG. 1 , the ink cartridge  10  comprises an ink storing part  11  which stores the ink, and a flexible printed circuit board (FPCB)  20 , which is attached to the ink storing part  11  and exchanges an electrical signal with an image forming apparatus main body (not illustrated) through a contact pad  21 . The FPCB  20  comprises a head chip  30  which discharges the ink of the ink storing part  11  onto the recording medium. The head chip  30  is attached to a head chip receiving hollow  13  of the ink cartridge  10 . The head chip  30  is coupled with the head chip receiving hollow  13  by an adhesive. 
         [0008]      FIGS. 2A and 2B  are sectional views illustrating the ink cartridge  10  of  FIG. 1 . Referring to  FIGS. 2A and 2B , the head chip  30  comprises a substrate layer  32  having an ink supplying slit  31  which is supplied with the ink from an ink supplying hole  15  of the ink storing part  11 , a chamber layer  34  having a heater  33  which heats the ink supplied from the ink supplying slit  31 , and a nozzle layer  36  having a nozzle  35  where an ink bubble generated by heat from the heater  33  is used to discharge the ink to an outside. 
         [0009]    To manufacture the conventional ink cartridge having above structure, an adhesive A is applied onto a border surface to couple the head chip  30  with the ink storing part  11 , and then the ink cartridge goes through a heat treatment at about 110° C. Therefore, the head chip  30  and the ink storing part  11  are solidly coupled therebetween. 
         [0010]    However, since the ink storing part  11  of the conventional ink cartridge  10  is made of plastics and the substrate layer  32  of the head chip  30  is made of silicon, a shear stress F is generated on the border surface between the two materials which are of different kinds by a difference in coefficients of thermal expansion while the ink cartridge  10  goes through the heat treatment at about 110° C. In particular, as the coefficient of thermal expansion of the plastics is 50 times greater than that of the silicon, a bending deformation δ is generated in the substrate layer  32  as illustrated in  FIG. 2B . The bending deformation of the substrate layer  32  causes a bending deformation of the nozzle layer  36 , which is provided at an upper side of the substrate  32 . 
         [0011]    If the deformation is generated in the nozzle layer  36 , the ink is discharged through the nozzle  35  obliquely instead of perpendicularly onto the recording medium, so that a printing quality is deteriorated. 
         [0012]    Also, during a wiping process for removing foreign substances or ink which is attached to a surface of the nozzle, the nozzle layer  36  may be damaged due to the bending deformation of the nozzle layer  36 . 
         [0013]    Moreover, the problem caused by the bending deformation of the head chip  36  as described above may be more serious in a case of a line head, where the head chip  30  is plurally provided. 
       SUMMARY OF THE INVENTION 
       [0014]    The present general inventive concept provides a head chip and ink cartridge having a reinforcing bridge to minimize deformation of the head chip when the head chip is coupled with an ink storing part, and an image forming apparatus having the same. 
         [0015]    Additional aspects and utilities 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 present general inventive concept. 
         [0016]    The foregoing and/or other aspects and utilities of the present general inventive concept can be achieved by providing a head chip usable in an image forming apparatus, the head chip comprising a nozzle layer having a nozzle to discharge ink onto a recording medium, a substrate layer having at least one ink supplying slit provided to be parallel with the nozzle layer to supply the nozzle with the ink, and at least one reinforcing bridge provided along an extending direction of the ink supplying slit and blocks at least one region of the ink supplying slit. 
         [0017]    A thickness of the reinforcing bridge may not greater than the thickness of the substrate layer. 
         [0018]    A width d of the reinforcing bridge may be p×2≦d≦p×6 and p may be a pitch between adjacent nozzles. 
         [0019]    The reinforcing bridge may be provided plurally along the extending direction of the ink supplying slit. 
         [0020]    The substrate layer may comprise a plurality of ink supplying slits which are provided to be parallel therewith. 
         [0021]    Each of the plurality of ink supplying slits may supply the nozzle with ink of a different color. 
         [0022]    A reinforcing bridge of a first ink supplying slit may be aligned with a reinforcing bridge of a neighboring ink supplying slit. 
         [0023]    A reinforcing bridge of a first ink supplying slit may not align with a reinforcing bridge of an adjacent ink supplying slit. 
         [0024]    The foregoing and/or other aspects and utilities of the present invention can also be achieved by providing an ink cartridge usable in an image forming apparatus, the ink cartridge comprising an ink storing part, and a head chip disposed at a lower side of the ink storing part to discharge ink onto a recording medium, the head chip comprising a nozzle layer having a nozzle to discharge ink onto a recording medium, a substrate layer having at least one ink supplying slit provided to be parallel with the nozzle layer and supplies the nozzle with the ink, and at least one reinforcing bridge provided along an extending direction of the ink supplying slit and blocks at least one region of the ink supplying slit. 
         [0025]    The ink storing part may be provided to correspond to a width of a printing medium and may comprise a plurality of head chips. 
         [0026]    The foregoing and/or other aspects and utilities of the present invention can also be achieved by providing an ink cartridge usable in an image forming apparatus, the ink cartridge comprising an ink storing part, and a head chip coupled to the ink storing part, the head chip comprising a substrate, a plurality of ink supplying slits formed in the substrate, a chamber layer formed on the substrate and defining a plurality of ink chambers, a nozzle layer defining a plurality of nozzles to eject ink, an ink discharging device disposed in the ink chamber to provide an energy to eject ink from the ink chamber through the nozzles, and a plurality of reinforcing bridges disposed within the ink supplying slits to strengthen the head chip and prevent a deformation thereof when the head chip is coupled to the ink storing part. 
         [0027]    Each of the plurality of reinforcing bridges may have a thickness equal or less than a thickness of the substrate. 
         [0028]    The plurality of reinforcing bridges may be disposed in an alternating pattern with respect to adjacent ink supplying slits. 
         [0029]    The plurality of reinforcing bridges may be disposed in an aligning pattern with respect to adjacent ink supplying slits. 
         [0030]    A width of each reinforcing bridge may be p×2≦d≦p×6 and p may be a pitch between adjacent nozzles. 
         [0031]    The ink cartridge may be a line printing type head cartridge and the head chip may comprise a plurality of head chips disposed along a length of the ink cartridge corresponding to a width of a printing medium. 
         [0032]    The ink discharging device may be one of a piezoelectric device to apply a deformation pressure to the ink and a heater to heat the ink and generate bubbles in the ink to eject ink through the nozzles. 
         [0033]    The foregoing and/or other aspects and utilities of the present invention can also be achieved by providing a reinforced head chip usable in an image forming apparatus, the head chip comprising a substrate having ink supplying slits formed thereon, a chamber layer formed on the substrate to define an ink chamber, a nozzle layer formed above the chamber layer to define a nozzle, an ink discharging device disposed in the ink chamber to provide an energy to eject ink from the ink chamber through the nozzles, and at least one reinforcing bridge provided in at least one ink supplying slit to strengthen the head chip and prevent a deformation thereof when the head chip is coupled to an ink storing part of an ink cartridge. 
         [0034]    A height of the at least one reinforcing bridge may be equal or less than a height of the substrate where the reinforcing bridge is disposed. 
         [0035]    A width of each reinforcing bridge may be p×2≦d≦p×6 and p may be a pitch between adjacent nozzles. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0036]    These and/or other aspects and utilities 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: 
           [0037]      FIG. 1  is an exploded perspective view illustrating a conventional ink cartridge; 
           [0038]      FIG. 2A  and  FIG. 2B  are sectional views illustrating the conventional ink cartridge of  FIG. 1  before deformation and after deformation, respectively; 
           [0039]      FIG. 3A  and  FIG. 3B  illustrate a plan view and a sectional view, respectively, of a substrate layer of a head chip according to an exemplary embodiment of the present general inventive concept; 
           [0040]      FIG. 4A  and  FIG. 4B  are sectional views illustrating the head chip according to the exemplary embodiment of the present general inventive concept; 
           [0041]      FIG. 5  is an expanded plan view illustrating a reinforcing bridge of the head chip according to an exemplary embodiment of the present general inventive concept; 
           [0042]      FIG. 6A  and  FIG. 6B  illustrate experimental results about a strength of the head chip according to an exemplary embodiment of the present general inventive concept; and 
           [0043]      FIG. 7  is a plan view illustrating an ink cartridge according to an exemplary embodiment of the present general inventive concept. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0044]    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 like elements throughout. The embodiments are described below so as to explain the present general inventive concept by referring to the figures. 
         [0045]      FIG. 3A  and  FIG. 3B  are a plan view and a sectional view, respectively, illustrating a substrate layer of a head chip according to an exemplary embodiment of the present general inventive concept.  FIG. 4A  is a sectional view illustrating the head chip of  FIGS. 3A and 3B . 
         [0046]    As illustrated in  FIG. 3A ,  FIG. 3B , and  FIG. 4A , an ink cartridge  100  according to the exemplary embodiment of the present general inventive concept may comprise an ink storing part  200  to store ink, and a head chip  300  which is provided at a lower side of the ink storing part  200  to discharge the ink from the ink storing part  200  onto a recording medium. 
         [0047]    The ink storing part  200  may comprise an ink chamber (not illustrated) in which the ink is stored, a foam chamber (not illustrated) to discharge the ink into the head chip  300  by a predetermined negative pressure, and a partitioning wall (not illustrated) to separate the ink chamber (not illustrated) from the foam chamber (not illustrated). A connecting opening part (not illustrated) may be provided at a lower end part of the partitioning wall (not illustrated) to allow the ink to flow from the ink chamber (not illustrated) to the foam chamber (not illustrated). 
         [0048]    A flexible printed circuit board (similar to FPCB  20  of  FIG. 1 ) can be combined to a lower part of the ink storing part  200  to exchange an electrical signal with an image forming part main body (not illustrated) through a contact pad (similar to contact pad  21  of  FIG. 1 ). The ink storing part  200  may store ink of one color or ink of a plurality of colors. That is, the ink storing part  200  may comprise only a black ink storing part, or may comprise a plurality of ink storing parts  200  to correspond to each color of yellow, magenta, cyan, black and/or other known ink colors, respectively. 
         [0049]    The ink storing part  200  may be provided integrally with the head chip  300 . Alternatively, the head chip  300  may also be provided on the image forming apparatus main body (not illustrated) and only the ink storing part  200  may be detachably provided. 
         [0050]    Since a structure of the ink storing part  200  is similar to that illustrated in  FIG. 1 , a detailed description thereof is omitted. 
         [0051]    As illustrated in  FIG. 3A  and  FIG. 4A , the head chip  300  may comprise a substrate layer  310  having an ink supplying slit  311  having a reinforcing bridge  313 , a nozzle layer  330  having a nozzle  333  to discharge an ink droplet onto the recording medium, and a chamber layer  320  having an ink discharging device  321  to supply an energy to discharge the ink through the nozzle  333 . 
         [0052]    The substrate layer  310  may comprise the ink supplying slit  311  which guides the ink in the ink storing part  200  to the nozzle layer  330 , and the reinforcing bridge  313  which is provided in the ink supplying slit  311  to partially block an ink supply and to reinforce a strength of the substrate layer  310 . The substrate layer  310  may be provided as a silicon wafer which is generally used in a manufacture of an integrated circuit. 
         [0053]    The ink supplying slit  311  is filled with the ink, which is supplied from the ink storing part  200 , and supplies the ink to the chamber layer  320 . As illustrated in  FIG. 3A , the ink supplying slit  311  can be provided to have a predetermined length l. The ink supplying slit  311  may be formed by etching a surface of a substrate  315  which is exposed through the nozzle  333 . Alternatively, the ink supplying slit  311  may be formed by etching the surface of the substrate  315  prior to formation of the nozzle layer  330 , or may be formed by etching a lower surface of the substrate  315  prior to coupling the substrate to the ink storing part  200 . 
         [0054]    The ink supplying slit  311  may be provided as a single slit or may be provided plurally as illustrated in  FIG. 3A . If the ink supplying slit  311  is provided plurally, each ink supplying slit  311  ( 311 M,  311 Y,  311 C, and  311 K in  FIG. 3A ) may supply ink of the same color or ink of different color with respect to the other ink supplying slits  311 . For example, each ink supplying slit  311 Y,  311 M,  311 C, and  311 K may supply yellow, magenta, cyan, and black ink, respectively. 
         [0055]    The reinforcing bridge  313  is provided at the ink supplying slit  311  to prevent a bending deformation of the substrate layer  310 , which may be generated when the head chip  300  is coupled with the ink storing part  200 . As illustrated in  FIG. 4A , the reinforcing bridge  313  may partially block the ink supplying slit  311  and reinforces the substrate layer  310  so that the substrate layer  310  may not be deformed by a shear stress F which may be generated by a difference in coefficients of thermal expansion between materials of the substrate  315  and the ink storing part  200 . As a length of a part of the ink supplying slit  311  where the bending deformation may occur is decreased due to the reinforcing bridge  313 , a maximum bending deformation amount may also be decreased. 
         [0056]    For example, a thickness h 1  of the reinforcing bridge  313  may be provided not to be greater than a thickness h of the substrate  315 . That is, the thickness h 1  of the reinforcing bridge  313  may be provided to be smaller than the thickness h of the substrate  315  as illustrated in  FIG. 4A  or a thickness h 2  may be provided same as the thickness h of the substrate  315  as illustrated in  FIG. 4B . The ink, which surrounds the reinforcing bridge  313 , may be more easily supplied to the chamber layer  320  when the thickness h 1  of the reinforcing bridge  313  is provided to be smaller than the thickness h of the substrate  315  than when the thickness h 2  of the reinforcing bridge  313  is provided to be the same as the thickness h of the substrate  315 . 
         [0057]    However, the amount of the deformation which is generated if the ink storing part  200  is combined with the head chip  300  is small when the thickness h 2  of the reinforcing bridge  313  is provided to be the same as the thickness h of the substrate  315 . Therefore, the thickness of the reinforcing bridge  313  may be provided properly by considering the ink supply to the nozzle  333  and the amount of the deformation of the substrate layer  310 . 
         [0058]    On the other hand, a width d of the reinforcing bridge  313  may be provided not to obstruct the flow of the ink which is supplied to the nozzle  333 . Experimentally, as illustrated in  FIG. 5 , the width d of the reinforcing bridge  313  may be 2 to 6 times as large as a distance p between adjacent nozzles  333 . If the width d of the reinforcing bridge  313  is smaller than twice the distance p, the ink may not be smoothly supplied to the nozzle  333  which surrounds the reinforcing bridge  313 . Also, if the width d of the reinforcing bridge  313  is larger than six times the distance p, the ink may not be smoothly supplied to the nozzle  333  which is disposed at a center of the plurality of the nozzles  333  surrounding the reinforcing bridge  313 . 
         [0059]    Also, if a distance between adjacent reinforcing bridges  313  provided at the ink supplying slit  311  is small, deformation of the substrate layer can be reduced. However, the small distance between adjacent reinforcing bridges  313  may be an influence upon the smooth supply of the ink. Therefore, the distance between adjacent reinforcing bridges  313  may be properly provided by considering a width w and the thickness h of the ink supplying slit  311 . 
         [0060]    The reinforcing bridge  313  may be provided at each of the plurality of the ink supplying slits  311 . In this case, as illustrated in  FIG. 3A , the reinforcing bridges  313  may be provided in an alternating pattern so as to not align with a reinforcing bridge of an adjacent ink supplying slit  311 . For example, as illustrated in  FIG. 3A , reinforcing bridge  313 A of ink supplying slit  311 Y is provided to alternate with reinforcing bridges  313  of the ink supplying slit  311 M. Alternatively, as illustrated in  FIG. 6A , the reinforcing bridges  313  may be provided to align with reinforcing bridges  313 B which are provided at an adjacent ink supplying slit  311 . 
         [0061]    The reinforcing bridge  313  may be formed by not etching a part of the substrate  315  to correspond to the thickness h 1  and the width d of the reinforcing bridge  313  when the substrate  315  is etched to form the ink supplying slit  311 . In this case, the reinforcing bridge  313  is provided integrally with the substrate  315 . Alternatively, the reinforcing bridge  313  may be provided by attaching an additional member in the ink supplying slit  311  formed by etching. 
         [0062]    The chamber layer  320  may comprise the ink discharging device  321  which supplies the ink with the energy to discharge the ink through the nozzles  333 , which is supplied through the ink supplying slit  311 , onto the recording medium, and a chamber wall  323  which accommodates the ink discharging device  321 . In this case, the ink discharging device  321  may be provided as a piezoelectric device or an electricity-heat transforming device, such as a heater. The chamber wall  323  can be made of epoxy resin. However, the chamber wall  323  may also be made of a photoresist resin of a silicon base, an acryl base, or an imide base. 
         [0063]    An electrode  340  can be provided at an outer side of the chamber layer  320  to apply a current to the ink discharging device  321 . The electrode  340  may be made of aluminum or aluminum alloy which has a superior conductivity and may be easily patterned. Additionally, the electrode  340  can be provided as a layer formed over the ink discharging device  321  to supply a current thereto. 
         [0064]    The nozzle layer  330  may comprise the plurality of the nozzles  333  to discharge ink by the energy supplied by the ink discharging device  321  of the chamber layer  320 . In this case, the more nozzles  333  that are provided, the more a printing quality is improved. Therefore, the nozzles  333  may be provided to be disposed in their maximum number per unit area. 
         [0065]    Hereinafter, an operating process of the ink cartridge  100  according to the present general inventive concept is described. First, the ink which is supplied from the ink storing part  200  flows through the ink supplying slit  311  of the substrate layer  310  and into the chamber layer  320 . The ink which fills the chamber layer  320  is discharged to the outside through the nozzle  333  by the energy supplied by the ink discharging device. For example, by an abrupt heating or vibration of the ink discharging device  321 . That is, if the ink discharging device  321  is heated, an ink bubble is generated in the ink in the chamber layer  320 . Then, the generated bubble pushes the ink via an expanding force of the bubble, so that the ink can be discharged through the nozzle  333 . 
         [0066]      FIG. 6B  illustrates an experimental result of an analysis through ANSYS on the deformation amount of the substrate layer  310  when the shear stress F of 20 [MPa] is applied to the head chip  300  of the ink cartridge  100  according to the present general inventive concept. 
         [0067]    According to the experimental result, when there is no reinforcing bridges, the maximum deformation amount of the ink supplying slit  311  of the substrate layer  310  was 6.57 [μm]. On the other hand, as illustrated in  FIG. 6A , in the head chip  300  according to the present general inventive concept having five reinforcing bridges  313  each with a respective width of 84 [μm] for each ink supplying slit  311 , the maximum deformation amount due to the same shear stress F was estimated to be 0.276 [μm]. Therefore, it can be seen that a hardness of the head chip  300  according to the present general inventive concept is increased by about 24 times as much as that of the head chip lacking reinforcing bridges. 
         [0068]    As described above, as the head chip according to embodiments of the present general inventive concept and the ink cartridge having the head chip comprise the plurality of the reinforcing bridges in the ink supplying slit, the bending deformation, which is generated when the ink storing part is combined with the head chip, can be minimized. 
         [0069]    Also, as described above, the bending deformation of the head chip can be minimized by the reinforcing bridge, so that an ink discharging direction can be uniformly maintained, thus enhancing the printing quality. 
         [0070]    Also, as a degree of the bending deformation is small, a surface of the nozzle can be maintained undamaged during a wiping process. 
         [0071]    In the above description, the ink cartridge according to the exemplary embodiment of the present general inventive concept is a shuttle type ink cartridge which comprises only one head chip. However, the present general inventive concept is not limited thereto, and as illustrated in  FIG. 7 , the ink cartridge according to the present general inventive concept is applicable to a line head type ink cartridge with a width that corresponds to a width of the printing medium and comprising a plurality of the head chips. 
         [0072]    As described above, according to the present general inventive concept, the head chip and the ink cartridge, where the bending deformation of the substrate layer can be minimized, may be provided by having the reinforcing bridge in the ink supplying slit to reinforce the strength of the substrate layer. 
         [0073]    Although a few exemplary 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.
A head chip usable in an image forming apparatus, the head chip includes a nozzle layer having a nozzle to discharge ink onto a recording medium, a substrate layer having an ink supplying slit provided to be parallel with the nozzle layer to supply the nozzle with the ink, and a reinforcing bridge provided along an extending direction of the ink supplying slit and blocks at least one region of the ink supplying slit.