Abstract:
A head chip unit comprises a first head chip having a first ink chamber configured to contain first ink and having a first channel in communication with the first ink chamber for receiving the first ink from the first ink chamber and via which the first ink is discharged in an ink supply direction of the head chip unit. A second head chip is laminated with the first head chip along a laminating direction generally orthogonal to the ink supply direction. The second head chip has a second ink chamber with an ink supply part configured to receive second ink different from the first ink, a second channel in communication with the second ink chamber for receiving the second ink from the ink supply part and via which the second ink is discharged in the ink supply direction, and an ink supply hole through which the second ink is supplied into the ink supply part of the second ink chamber, the ink supply hole extending in the laminating direction so that the ink supply hole does not overlap the first ink chamber and the first channel of the first head chip.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a head chip unit and a method of producing the same for performing printing by discharging ink, an inkjet head including the head chip unit, and an inkjet printer including the inkjet head. 
     2. Description of the Related Art 
     Conventionally, as means for recording a character, an image, and the like on a medium such as paper, there has been used an inkjet printer for performing printing by discharging ink. The inkjet printer includes an inkjet head for discharging ink and a carriage for allowing the inkjet head to scan in a direction substantially orthogonal to a medium transport direction. The inkjet head includes a head chip including a plurality of channels each having an electrode formed on a wall surface thereof. A voltage is applied to each electrode from a wiring board connected to the head chip, to thereby change a volume of each of the channels to which ink is supplied. As a result, the ink is discharged from each of the channels through nozzles, thereby making it possible to perform printing. 
     In this case, printing in a plurality of colors can be performed in such a manner that a plurality of inkjet heads corresponding to the kinds of ink are mounted to discharge a plurality of colors of ink. However, there are problems in that the number of inkjet heads to be mounted is increased, a printer including the inkjet heads is increased in size, and costs thereof are increased. In addition, it is necessary to perform positioning of each of the inkjet heads, which makes the carriage having the inkjet heads mounted thereto complicated. For this reason, in recent years, there has been proposed a technology of printing which can be performed using a plurality of kinds of ink with a single inkjet head while achieving both miniaturization and printing in a plurality of colors. Specifically, there is proposed an inkjet head including: a base plate in which channels are formed; a head chip unit in which a plurality of head chips, each of which is formed of a cover plate disposed on the base plate, are laminated; and a wiring board connected to the cover plate of each of the head chips (for example, see JP 10-146974 A). In addition, there is proposed an inkjet head including: a head chip unit having two rows of channels which are formed on both surfaces of a single head chip; and a wiring board connected to the both surfaces (for example, see JP 2001-315353 A). 
     However, in the head chip unit mounted to the inkjet head as described in JP 10-146974 A, the channels arranged in a plurality of rows are disclosed, but means for supplying ink to each of the channels is not disclosed. Accordingly, a plurality of kinds of ink cannot be discharged from the channels in each row. Further, in the head chip unit mounted to the inkjet head as described in JP2001-315353 A, the channels in each row communicate with different ink chambers, thereby enabling discharge of different kinds of ink, but at most two kinds of ink can be discharged in the structure. For this reason, both of the head chip units have not achieved a technique of discharging a plurality of kinds of ink while achieving miniaturization. 
     SUMMARY OF THE INVENTION 
     The present invention has been made in view of the above-mentioned circumstances, and therefore an object of the present invention is to provide a head chip unit and a method of producing the same capable of discharging a plurality of kinds of ink while achieving both miniaturization and printing in a plurality of kinds of ink, an inkjet head including the head chip unit, and an inkjet printer including the inkjet head. 
     In order to achieve the above-mentioned object, the present disclosure discloses the following aspects of the invention. 
     A head chip unit according to the present invention includes: 
     a head chip having a substantially plate shape including:
         a channel extending from one edge side to another edge side to be opened on the another edge side; and   an ink chamber formed in an arrangement direction orthogonal to a supply direction for forming the channel and communication with the channel on the one edge side,       

     the head chip being laminated in multiple, characterized in that: 
     the ink chamber of at least one of the head chip includes a supply part formed until a position where the supply part is not overlapped with the channel and the ink chamber of another head chip in a laminating direction of the head chip, the another head chip being laminated on a surface of the at least one of the head chip; and 
     the another head chip laminated on the surface of at least one of the head chip including the supply part, includes an ink supply hole which is formed so that the ink supply hole is opened on the one side and penetrates the head chip so as to communicate with the supply part. 
     In another aspect, a method of producing a head chip unit according to the present invention includes: 
     a head chip having a substantially plate shape forming step of forming a channel extending from one edge side of the head chip main body to another edge side thereof to be opened on the another edge side, and an ink chamber extending in an arrangement direction orthogonal to a supply direction for forming the channel and communicating with the channel on the one edge side; 
     a lamination step of laminating a plurality of the head chips formed in the head chip forming step; and 
     an ink supply hole forming step of forming an ink supply hole opened on one side of the head chip to be laminated and penetrating in a laminating direction of the head chip, characterized in that: 
     the head chip forming step includes forming as a part of the ink chamber a supply part in at least one of the head chip, which extends until a position where the supply part is not overlapped with the channel and the ink chamber of another head chip in a laminating direction of the head chip, the another head chip being laminated on the surface of the head chip in the lamination step; and 
     the ink supply hole forming step includes forming the ink supply hole corresponding to the supply part at a position where the ink supply hole communicates with the supply part. 
     In the head chip unit and the method of producing the head chip unit according to the present invention, the channel and the ink chamber are formed in the head chip main body to thereby produce a head chip in the head chip forming step, and a plurality of the head chips are laminated in the lamination step. As a result, in at least one of the head chips, the supply part is formed as a part of each of the ink chambers at a position where the supply part is not overlapped with the channel and the ink chamber of another head chip, which is laminated on the surface of the head chip. Further, by the ink supply hole forming step, the another head chip, which is laminated on the surface of the head chip having the supply part formed therein, and the ink supply hole opened on the one side are formed so as to communicate with the supply part. For this reason, to the channel of the head chip including the ink chamber having the supply part, the ink different in kind from that of the another head chip can be supplied from the ink supply hole through the ink chamber, and can be discharged from opening formed on the another edge side of the channel. Accordingly, a plurality of kinds of ink can be discharged so as to correspond to the number of ink chambers each having the supply part and the number of ink supply holes to be formed so as to correspond to the supply parts. 
     Further, in the head chip unit, it is preferred that: 
     at least one of the head chip includes a plurality of the channel and a plurality of the ink chamber; 
     the plurality of the ink chambers each include the supply part and communicate with the different channels; and 
     the another head chip laminated on the one side of the head chip including the supply part includes a plurality of the ink supply holes formed therein in correspondence with the supply parts. 
     Further, in the method of producing a head chip unit, it is preferred that the head chip forming step further includes forming a plurality of the channels in at least one of the head chip, and forming a plurality of the ink chambers so that the plurality of ink chambers each include the supply part and communicate with the plurality of different channels; and 
     the ink supply hole forming step further includes forming a plurality of the ink supply holes in correspondence with the respective supply parts of the plurality of the ink chambers. 
     In the head chip unit and the method of producing the head chip unit according to the present invention, the plurality of ink chambers are formed in one head chip in the head chip forming step, the supply part is formed in the respective ink chambers, and the plurality of ink supply holes are formed so as to correspond to the supply parts in the ink supply hole forming step. As a result, with a single head chip, different kinds of ink can be supplied to each of the plurality of channels from each of the ink supply holes through the ink chambers to be discharged. 
     Still further, in the head chip unit, it is preferred that the ink chamber of the head chip includes:
         a main body part formed in the arrangement direction and communicating with the channel; and   an introduction part formed in the supply direction at a position where the introduction part is not overlapped with the channel in the laminating direction to be connected to the main body part; and       

     the supply part is provided to the introduction part. 
     Yet further, in the method of producing a head chip unit, it is preferred that the head chip forming step further includes forming a main body part as the ink chamber in at least one of the head chip, which extends in the arrangement direction and communicates with the channels, and an introduction part, which extends in the supply direction and connects to the main part at a position where the introduction part is not overlapped with the channel in the laminating direction, to thereby form the supply part to the introduction part. 
     In the head chip unit and the method of producing the head chip unit according to the present invention, the main body part and the introduction part are formed and the supply part is formed to the introduction part in the head chip forming step. As a result, a width of the head chip main body in the arrangement direction is set to a minimum size for forming the channels and the introduction part of the ink chambers, and positions of the supply parts and the corresponding ink supply holes can be arbitrarily set in the supply direction in which the channels are formed. Accordingly, even when a plurality of supply parts and the corresponding ink supply holes are formed, the head chip unit is not increased in size with the minimum width in the arrangement direction, thereby making it possible to supply a plurality of kinds of ink to be discharged. 
     Yet further, in the head chip unit, it is preferred that the head chip includes at least four sets of the ink supply part of the ink chamber and the ink supply hole corresponding to the supply part, which are independently provided. 
     In the head chip unit according to the present invention, the supply parts of the ink chambers and the ink supply holes corresponding to the supply parts are independently provided in at least four sets. As a result, four colors of ink, that is, yellow, magenta, cyan, and black can be separately discharged, thereby making it possible to perform printing in various colors according to a discharge amount of each ink. 
     Further, an inkjet head according to the present invention is characterized by including the head chip unit. 
     In the inkjet head according to the present invention, a plurality of kinds of ink can be discharged from a single head chip unit, whereby miniaturization is achieved while printing with a plurality of kinds of ink can be performed. 
     Further, an inkjet printer according to the present invention includes the inkjet head. 
     The inkjet printer according to the present invention includes the above-mentioned inkjet head, whereby miniaturization is achieved while printing with a plurality of kinds of ink can be performed. 
     In the head chip unit according to the present invention, the ink chambers each have the supply part, and the ink supply holes corresponding to the supply parts are formed. As a result, a plurality of kinds of ink can be discharged according to the number of the supply parts and ink supply holes to be formed, so miniaturization is achieved and printing with a plurality of kinds of ink can be performed. 
     Further, the method of producing the head chip unit according to the present invention includes the head chip forming step and the ink supply hole forming step, thereby enabling production of a small-size head chip capable of printing with a plurality of kinds of ink. 
     Further, the inkjet head according to the present invention includes the above-mentioned head chip unit, whereby the size and manufacturing costs of the inkjet head can be reduced and printing with a plurality of kinds of ink can be performed. 
     Further, the inkjet printer according to the present invention includes the above-mentioned inkjet head, whereby the size and manufacturing costs of the inkjet head can be reduced and printing with a plurality of kinds of ink can be performed with low cost. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the accompanying drawings: 
         FIG. 1  is a perspective view showing an outline of an inkjet printer according to a first embodiment of the present invention; 
         FIG. 2  is a side view showing the outline of the inkjet head according to the first embodiment of the present invention; 
         FIG. 3  is an exploded perspective view showing a head chip unit according to the first embodiment of the present invention; 
         FIG. 4  is a top view showing the head chip unit according to the first embodiment of the present invention; 
         FIG. 5  is a cross-sectional diagram showing the head chip unit according to the first embodiment of the present invention; 
         FIGS. 6A and 6B  are top views each showing a substrate of one head chip in the head chip unit according to the first embodiment of the present invention; 
         FIGS. 7A and 7B  are top views each showing a substrate of another head chip in the head chip unit according to the first embodiment of the present invention; 
         FIGS. 8A and 8B  are top views each showing a substrate of another head chip in the head chip unit according to the first embodiment of the present invention; 
         FIGS. 9A and 9B  are top views each showing a substrate of another head chip in the head chip unit according to the first embodiment of the present invention; 
         FIG. 10  is a schematic diagram showing electrode wirings in the head chip unit according to the first embodiment of the present invention; 
         FIG. 11  is an explanatory diagram showing a lamination step in a production process for the head chip unit according to the first embodiment of the present invention; 
         FIG. 12  is an explanatory diagram showing a nozzle plate bonded surface treatment step in the production process for the head chip unit according to the first embodiment of the present invention; 
         FIG. 13  is an explanatory diagram showing a nozzle plate bonding step in the production process for the head chip unit according to the first embodiment of the present invention; 
         FIG. 14  an explanatory diagram showing an ink supply hole forming step in the production process for the head chip unit according to the first embodiment of the present invention; 
         FIG. 15  is an explanatory diagram showing a wiring board connecting step in the production process for the inkjet head according to the first embodiment of the present invention; 
         FIG. 16  is a top view showing a modified example of the head chip unit according to the first embodiment of the present invention; 
         FIG. 17  is a partially enlarged cross-sectional diagram showing the modified example of the head chip unit according to the first embodiment of the present invention; 
         FIG. 18  is a top view showing a head chip unit according to a second embodiment of the present invention; 
         FIGS. 19A and 19B  are top views each showing a substrate of one head chip in the head chip unit according to the second embodiment of the present invention; and 
         FIGS. 20A and 20B  are top views each showing a substrate of another head chip in the head chip unit according to the second embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     First Embodiment 
       FIGS. 1 to 15  each show an embodiment of the present invention. As shown in  FIG. 1 , an inkjet printer  1  according to a first embodiment of the present invention includes: a pair of transport means  2  and  3  for transporting a medium M such as paper in a transport direction X; an inkjet head  10  for discharging ink onto the medium M; ink tanks  4  for supplying ink to the inkjet head  10 ; and scanning means  5  for scanning the inkjet head  10  in a width direction Y substantially orthogonal to the transport direction X. The pair of transport means  2  and  3  are formed of a grid roller  2   a  and a pinch roller  2   b , and a grid roller  3   a  and a pinch roller  3   b , respectively. The grid rollers  2   a  and  3   a  are rotated by a drive motor (not shown), thereby enabling transportation of the medium M pinched between the pinch rollers  2   b  and  3   b  in the transport direction X. The scanning means  5  includes a pair of guide rails  5   a  and  5   b  arranged in the width direction Y, and a carriage  6  which is slidable on the pair of guide rails  5   a  and  5   b  in the width direction Y and has the inkjet head  10  mounted thereto. In addition, between the pair of guide rails  5   a  and  5   b , a timing belt  7  to which the carriage  6  is fixed is disposed in the width direction Y and is wound around a pair of pulleys  8   a  and  8   b  at both ends. The pulley  8   a  is coupled to a carriage drive motor  9 , and the carriage drive motor  9  is driven to rotate the pulley  8   a , thereby running the timing belt  7  in the width direction Y so as to advance and retract the carriage  6  in the width direction Y. 
     In the first embodiment of the present invention, as the ink tanks  4 , there are mounted four ink tanks  4 A,  4 B,  4 C, and  4 D which are filled with different kinds of ink so as to be capable of performing printing in four kinds of ink of yellow, magenta, cyan, and black. Note that, in the first embodiment of the present invention, the ink filled in each of the ink tanks  4  is described as aqueous ink. The ink tanks  4  are each connected to the inkjet head  10 , which is mounted to the carriage  6 , via pipings  4   a , thereby enabling supply of the four kinds of ink to the inkjet head  10 . In addition, the pipings  4   a  each have flexibility so as to be capable of following the movement of the carriage  6 . 
     As shown in  FIG. 2 , the inkjet head  10  includes: an outer casing  11  covering a periphery of the inkjet head  10 ; a head chip unit  20  contained in the outer casing  11 ; an IC substrate  12 ; and flexible printed circuit boards (hereinafter, referred to as “FPC”)  13 . The head chip unit  20  is connected to each of the ink tanks  4  via the corresponding pipings  4   a , and a discharge surface  20   a  is allowed to expose from the outer casing  11 . In addition, a part of the IC substrate  12  is exposed from the outer casing  11  so as to be capable of being electrically connected to an outside, and is connected to a control part (not shown) in a state of being mounted to the carriage  6 . The FPCs  13  each electrically connect, as a wiring board, the head chip unit  20  to the IC substrate  12 . In the first embodiment of the present invention, four FPCs  13  are connected so as to correspond to the number of layers of head chips  21  to be described later. Further, in response to electrical signals to be input from the IC substrate  12  via the FPCs  13 , the head chip unit  20  can discharge ink supplied from each of the ink tanks  4  from the discharge surface  20   a . Hereinafter, the head chip unit  20  will be described in detail. 
     As shown in  FIG. 2 , the head chip unit  20  includes: the head chips  21  laminated in a plurality of layers; a head cover  22  for connecting the head chips  21  to the pipings  4   a ; and a nozzle plate  23  having the discharge surface  20   a  formed thereon and having nozzle holes  23   a . As shown in  FIGS. 3 to 5 , the head chips  21  are laminated in four layers, that is, head chips  21 A,  21 B,  21 C, and  21 D so as to correspond to the kinds of ink. The head chips  21  are laminated so as to be stepwise on a side of one edge  21   a  and so as to be aligned with each other on a side of another edge  21   b  so that the nozzle plate  23  can be joined thereto. The head chips  21  are each formed of a substantially plate-like head chip main body  27  in which a cover plate substrate  26  is laminated on one surface  25   a  of an actuator substrate  25 . In this case,  FIG. 6A  is a top view of the cover plate substrate of the head chip  21 A, and  FIG. 6B  shows a top view of the actuator substrate of the head chip  21 A. In a similar manner,  FIGS. 7A and 7B  are top views respectively showing the cover plate substrate and the actuator substrate of the head chip  21 B, FIGS.  8 A and  8 B are top views respectively showing the cover plate substrate and the actuator substrate of the head chip  21 C, and  FIGS. 9A and 9B  are top views respectively showing the cover plate substrate and the actuator substrate of the head chip  21 D. 
     As shown in  FIGS. 3 to 9B , in each of the head chips  21 , the actuator substrate  25  is formed of a substantially plate-like member made of piezoceramic and has a substrate connecting surface  28  on which the FPC  13  is connected to the one surface  25   a  on the one edge  21   a  side. In addition, in the actuator substrate  25 , on the side of the another edge  21   b  of the substrate connecting surface  28 , there are provided a plurality of channels  29  each formed in a groove shape opened in the one surface  25   a . The plurality of channels  29  are each formed so as to extend in a supply direction P from the one edge  21   a  to the another edge  21   b , and are each opened with an opening  29   a  at the another edge  21   b . In addition, the plurality of channels  29  are arranged in an arrangement direction Q substantially orthogonal to the supply direction P with side walls  30  formed between the plurality of channels  29 . In this case, in the plurality of head chips  21 , the plurality of channels  29  each have substantially the same cross-sectional shape and length. In addition, on wall surfaces  29   b  of the plurality of channels  29 , there are formed electrodes  31  each extending to the substrate connecting surface  28 . The electrodes  31  are each formed of a common electrode  31   a  and a drive electrode  31   b . As described later, the common electrodes  31   a  are formed so as to correspond to common grooves  29   c  alternately set in the plurality of channels  29 . In other words, the common electrodes  31   a  are each formed in a substantial I-shape on the substrate connecting surface  28  on a proximal end side of each of the common grooves  29   c , and are each branched and formed to both wall surfaces  29   b  of the corresponding common grooves  29   c . In addition, the drive electrodes  31   b  are formed so as to correspond to active grooves  29   d  each formed between the common grooves  29   c . In other words, the drive electrodes  31   b  are each formed in a substantial U-shape so as to extend to the adjacent active grooves  29   d  at both sides thereof across the common electrode  31   a . The drive electrodes  31   b  extending to the active grooves  29   d  are each continuously formed to the wall surfaces  29   b  on the sides adjacent to the corresponding common grooves  29   c.    
     Further, in each of the head chips  21 , the cover plate substrate  26  is formed of a substantial plate-like member made of ceramic or metal. In view of deformation of the cover plate substrate  26  after being coupled to the actuator substrate  25 , it is preferable that the cover plate substrate  26  be made of ceramic which has substantially the same coefficient of thermal expansion. The cover plate substrate  26  is laminated on the one surface  25   a  of the actuator substrate  25  so that the another edge  21   b  side of the cover plate substrate  26  is formed at substantially the same position as that of the actuator substrate  25  and so that the substrate connecting surface  28  formed on the actuator substrate  25  is allowed to project to the one edge  21   a  side. 
     Further, as shown in  FIGS. 5 to 9B , on the cover plate substrate  26 , an ink chamber  32  opened in one surface  26   a  is formed. In the head chips  21  ( 21 A,  21 B,  21 C, and  21 D), the corresponding ink chambers  32  ( 32 A,  32 B,  32 C, and  32 D) each have a main body part  33  formed in the arrangement direction Q at a position corresponding to the one edge  21   a  side of the plurality of channels  29 . In addition, in the head chips  21 B,  21 C, and  21 D other than the head chip  21 A laminated on a surface closest to one side. R 1 , the ink chambers  32  ( 32 B,  32 C, and  32 D) each include introduction parts  34  formed in the supply direction P from both end parts  33   a  and  33   b  of the main body part  33 , and supply parts  35  formed at each end of the introduction parts  34 . In a state where the head chips  21  are laminated, the main body parts  33  of the plurality of head chips  21  are formed at substantially the same position in the supply direction P with the another edge  21   b  as a reference. The main body parts  33  are formed in the arrangement direction Q at positions where the both end parts  33   a  and  33   b  are not overlapped with the plurality of channels  29 , which are arranged in the arrangement direction Q, in a laminating direction R. Thus, the introduction parts  34  each connected to the main body part  33  at the both end parts  33   a  and  33   b  are formed in the supply direction P substantially in parallel with the plurality of channels  29  toward the another edge  21   b  side at positions where the introduction parts  34  are not overlapped with the plurality of channels  29  in the laminating direction R. In this case, lengths of the introduction parts  34  of the head chips  21 B to  21 D in the supply direction P are set to be longer in an order from the head chip  21 B laminated on the one side R 1  to the head chip  21 D laminated on an another side R 2 . Thus, in the ink chamber  32 , the supply parts  35  formed at each end of the introduction parts  34  are formed at positions where the supply parts  35  are not overlapped, in the laminating direction R, with the plurality of channels  29  and the ink chamber  32  of another head chip  21  laminated on the one side R 1  from the subject head chip  21  in which the supply parts  35  are formed. In addition, the main body part  33  of the ink chamber  32  has a plurality of through holes  33   c  formed therein, which alternately communicate with the corresponding the plurality of channels  29 . Accordingly, the plurality of channels  29  of the actuator substrate  25  alternately become the common grooves  29   c  capable of supplying ink from the main body part  33  of the ink chamber  32 . In addition, ink is not supplied between the common grooves  29   c , thereby obtaining the active grooves  29   d  which merely cause a volume change. 
     Then, as shown in  FIGS. 3 to 5 , among the plurality of head chips  21 , the head chips  21  laminated to be adjacent to each other are joined with each other so that a position of one edge of the cover plate substrate  26  of the head chip  21  on the another side R 2  is substantially equal to a position of one edge of the actuator substrate  25  of the head chip  21  on the one side R 1 . As a result, the plurality of head chips  21  are laminated stepwise such that the substrate connecting surface  28  formed on each of the actuator substrates  25  is allowed to project to the one edge  21   a  side toward the one side R 1  in the laminating direction R. Accordingly, on the another edge  21   b  side, the plurality of channels  29  are arranged in four rows in the laminating direction R. Note that the nozzle holes  23   a  of the nozzle plate  23  are formed in four rows in the laminating direction R so as to correspond to the common grooves  29   c  in the plurality of channels  29 . Further, as shown in  FIGS. 3 ,  4 , and  6 A to  9 B, in each of the laminated head chips  21 , ink supply holes  36  ( 36 B,  36 C, and  36 D), which are opened in the head chip  21 A laminated on a surface closest to the one side R 1  and which communicate with the supply parts  35  of the ink chambers  32  ( 32 B,  32 C, and  32 D), are each formed to be penetrated in the laminating direction R. 
     Then, as shown in  FIG. 2 , the four pipings  4   a  each connected to the head cover  22  from the ink tanks  4  are respectively connected to the main body part  33  of the ink chamber  32 A and the ink supply holes  36 B,  36 C, and  36 D in the head chip  21 A laminated on the surface closest to the one side R 1 . In other words, for example, it is assumed that the ink tank  4 A filled with yellow ink is connected to the main body  33  of the ink chamber  32 A, the ink tank  4 B filled with magenta ink is connected to the ink supply hole  36 B, the ink tank  4 C filled with cyan ink is connected to the ink supply hole  36 C, and the ink tank  4 D filled with black ink is connected to the ink supply hole  36 D. In this case, the yellow ink supplied to the main body part  33  of the ink chamber  32 A is supplied to each of the common grooves  29   c  of the head chip  21 A, which communicates with the ink chamber  32 A, in the plurality of channels  29 . By the FPC  13  connected to the substrate connecting surface  28 , the common electrodes  31   a  are grounded with wirings as shown in  FIG. 10 , and a voltage is applied to each of the drive electrodes  31   b  independently with a predetermined pattern, thereby making it possible to continuously change a volume of an inside of each of the plurality of channels  29 . As a result, the yellow ink supplied in each of the common grooves  29   c  can be discharged to the outside through the nozzle holes  23   a  of the nozzle plate  23  from the openings  29   a  of the head chip  21 A. The cyan ink supplied to the ink supply hole  36 B is supplied to the main body part  33  via the introduction parts  34  from the supply parts  35  in the ink chamber  32 B of the head chip  21 B. Then in a similar manner, the cyan ink can be discharged to the outside via the nozzle holes  23   a  of the nozzle plate  23  from the openings  29   a  of the head chip  21 B. In addition, the magenta ink supplied to the ink supply hole  36 C can be discharged to the outside from the openings  29   a  of the head chip  21 C, and the black ink supplied to the ink supply hole  36 D can be discharged to the outside from the openings  29   a  of the head chip  21 D. In other words, in a single head chip unit  20 , the ink of four colors, that is, yellow, cyan, magenta, and black can be simultaneously discharged from the plurality of channels  29  in each row. In this case, the plurality of channels  29  of each of the head chips  21  have substantially the same cross-sectional shape and length, with the result that the ink can be discharged from the plurality of channels  29  in four rows with the same discharge performance for each color. 
     Next, a description is given of the head chip unit  20  and a production method for the inkjet head  10  including the head chip unit  20  with reference to  FIGS. 11 to 15 . First, as a head chip forming step, the head chip main body  27 , which forms each of the head chips  21 , is processed, thereby forming the substrate connecting surface  28 , the plurality of channels  29 , the electrodes  31 , and the ink chamber  32 . Specifically, as an actuator substrate forming step, the plurality of channels  29  are formed through a dicing process or the like on the actuator substrate  25  in the head chip main body  27 . Then, in a range from the substrate connecting surface  28  on the one surface  25   a  of the actuator substrate  25  to the wall surfaces  29   b  of the plurality of channels  29 , metal films serving as the electrodes  31  are formed with a predetermined pattern by deposition or the like. Further, as a cover plate substrate forming step, the ink chamber  32  is similarly formed in the cover plate substrate  26  through a dicing process or the like. Note that, as described above, the plurality of channels  29  of the head chips  21  in each layer are formed with substantially the same cross-sectional shape and length, and the ink chambers are formed such that the main body parts  33  of the ink chambers  32  with the another edge as a reference are formed at substantially the same positions. 
     Then, as a lamination step, as shown in  FIG. 11 , the actuator substrate  25  and the cover plate substrate  26 , which form each of the head chips  21 , are laminated on each other. First, the actuator substrate  25  forming the head chip  21 D which projects to the side closest to the one edge  21   a , is joined with the cover plate substrate  26 . In this case, the both substrates are joined with each other by setting the another edge  21   b  side of each of the substrates to substantially the same position. As a result, the substrate connecting surface  28  is allowed to project to the one edge  21   a  side. Then, the adjacent actuator substrate  25  of the head chip  21 C is joined to the one surface  26   a  of the cover plate substrate  26  of the head chip  21 D. In this case, the both substrates are joined with each other by setting the respective another edge  21   b  sides to substantially the same positions, whereby the both substrates are joined with each other by setting the one edge  21   a  side of each of the substrates to substantially the same position. Then, the cover plate substrate  26  of the head chip  21 C is joined to the one surface  25   a  of the actuator substrate  25 . After that, by repeating the process, the four head chips  21 A,  21 B,  21 C, and  21 D are laminated such that the substrate connecting surfaces  28  are each allowed to project to the one edge  21   a  side stepwise, and the positions of the head chips at the another edge  21   b  are set to be substantially equal to each other. In this case, in the head chip forming step for each of the head chips  21 , the positions of the main body parts  33  of the ink chambers  32  are set to be substantially equal to each other in the supply direction P, whereby the main body parts  33  are arranged in the laminating direction R. In addition, the supply parts  35  of the ink chambers  32  are arranged at positions where the supply parts  35  are not overlapped, in the laminating direction R, with the plurality of channels  29  and the ink chambers  32  of another head chip  21  laminated on the one side R 1 . 
     Next, as shown in  FIG. 12 , as a nozzle plate bonded surface treatment step, the head chips  21  are cut at the another edge  21   b  side to which the nozzle plate  23  is to be bonded, thereby forming a flat surface. Then, as shown in  FIG. 13 , as a nozzle plate bonding step, the nozzle plate  23  is bonded to the another edge  21   b  side of the head chips  21 . Then, as an ink supply hole forming step, the ink supply holes  36  are formed. Specifically, as shown in  FIG. 14 , from the one surface  26   a  of the cover plate substrate  26  of the head chip  21 A on the one side R 1 , through holes are formed so as to reach the corresponding supply parts  35  of the ink chambers  32 . Thus, the one surface  26   a  of the cover plate substrate  26  of the head chip  21 A is opened, thereby forming the ink supply holes  36  ( 36 B,  36 C, and  36 D) communicating with the supply parts  35  of each of the ink chambers  32 . In addition, the head cover  22 , which is omitted, is mounted in a similar manner, thereby producing the head chip unit  20 . 
     Next, by the use of the head chip unit  20  thus produced, the inkjet head  10  is produced. First, as a wiring board connecting step, the FPCs  13  are connected to the head chip unit  20 . Specifically, the FPCs  13  are connected to each of the substrate connecting surfaces  28  in an order from the head chip  21 D, which projects to the side closest to the one edge  21   a , toward the one side R 1 , among the head chips  21  forming the head chip unit  20 . In other words, an anisotropic conductive film  38  is bonded to the substrate connecting surface  28 , and a connecting part of the FPC  13  is brought, into contact thereon. In this state, a heat chip  40  is brought into contact with the FPC  13  from the one side R 1  while being heated at about 280° C. to be pressurized. As a result, the FPC  13  is electrically connected to the electrode  31  on the substrate connecting surface  28 . In this case, the head chips  21 , as described above, are laminated stepwise such that the substrate connecting surfaces  28  are each allowed to project to the one edge  21   a  side. Thus, by connecting the FPC  13  to each of the substrate connecting surfaces  28  in the order from the head chip  21 D having the substrate connecting surface  28  allowed to project to the side closest to the one edge  21   a , pressurization and heating by the heat chip  40  can be performed while other head chips  21  or other FPCs  13  previously connected do not interfere with the pressurization and heating, and the FPCs  13  can be connected with ease and reliability. In addition, the head chips  21  are laminated such that the position of the one edge of the cover plate  26  of the adjacent head chip  21  is set to be substantially equal to the position of the one edge of the actuator substrate  25  of each of the head chips  21 . As a result, a force acting by the heat chip  40  in the pressurization process can be reliably supported by the laminated head chips  21 , and the FPCs  13  can be connected with higher reliability. Finally, the head chip unit  20  and the IC substrate  12  are accommodated in the outer casing  11 , and the FPCs  13  each connected to the head chip unit  20  are connected to the IC substrate  12 , thereby completing the inkjet head  10 . 
     As described above, in the head chip unit  20  according to the first embodiment of the present invention, with respect to the head chips  21  other than the head chip  21 A laminated on the surface closest to the one side R 1 , the supply parts  35 ′ are formed, as a part of the ink chamber  32 , at the positions where the supply parts  35  are not overlapped with the plurality of channels  29  and the ink chambers  32  of the other head chip  21  laminated on the one side R 1  from the subject head chip  21  in the laminating direction R. In addition, the ink supply holes  36  opened in the head chip  21 A are formed so as to communicate with the corresponding supply parts  35 . As a result, to the plurality of channels  29  of each of the head chips  21 , the ink different in kind from that of the other head chips  21  can be supplied from the corresponding ink supply hole  36  through the ink chamber  32 , and the ink can be discharged from the openings  29   a  on the another edge  21   b  side of the plurality of channels  29 . In particular, as in the first embodiment of the present invention, the head chips  21  are formed in four layers, and four sets of the supply parts  35  and of the ink supply holes  36  communicating with the supply parts  35  are provided so as to correspond to the layers. As a result, four different colors of ink can be discharged from the layers, and printing can be performed in various colors with a single head chip unit  20  according to a discharge amount of each ink. 
     Further, each of the ink chambers  32  includes the main body part  33  and the introduction parts  34 , and the supply parts  35  are formed to the introduction parts  34 . Accordingly, the width of the head chip main body  27 , which forms each of the head chips  21 , in the arrangement direction Q can be set to a minimum size for forming the plurality of channels  29  and the introduction parts  34  of the ink chamber  32 . In addition, within a range in which the plurality of channels  29  are formed, the positions of the supply parts  35  and of the ink supply holes  26  corresponding to the supply parts  35  can be arbitrarily set in the supply direction P. For this reason, even when the plurality of head chips  21  are laminated and the multiple supply parts  35  and the ink supply holes  36  corresponding to the supply parts  35  are formed, the minimum width in the arrangement direction Q can be set without increasing the size, and a plurality of kinds of ink can be supplied and discharged. 
     Further, in the inkjet head  10  including the head chip unit  20 , a plurality of kinds of ink can be discharged from a single head chip unit  20 , thereby achieving miniaturization while enabling printing with the plurality of kinds of ink. In the inkjet printer  1 , there is no need to provide a plurality of inkjet heads  10 , thereby reducing the size of the entire apparatus and costs thereof, and enabling printing in the plurality of kinds of ink. 
     Note that, in the first embodiment of the present invention, the ink chambers  32  of the head chips  21  excluding the head chip  21 A laminated on the surface closest to the one side R 1  each include the supply parts  35 , and are each provided with the corresponding ink supply holes  36 . However, the present invention is not limited thereto. In at least one head chip  21 , when the ink chamber  32  includes the supply parts  35 , the ink different from that supplied to the ink chamber  32  of the head chip  21 A laminated on the surface closest to the one side. R 1  can be supplied. Note that, in this case, when through holes communicating with the ink chambers  32  are formed in the other head chips  21 , the same kind of ink can be supplied and discharged. Further, the ink supply holes  36  are each formed on both sides of a single ink chamber  32  in the arrangement direction Q. However, the present invention is not limited thereto. Alternatively, even when the ink supply hole  36  is formed on only one side, the ink can be supplied to each of the ink chambers  32 . 
     Further, in the lamination step, the actuator substrates  25  and the cover plate substrates  26 , which form each of the head chips  21 , are alternately laminated, but the present invention is not limited thereto. Alternatively, after the actuator substrate  25  and the cover plate substrate  26  are joined with each other for each head chip  21 , each of the head chips  21  may be laminated. Further, the actuator substrate  25  of one head chip  21  and the cover plate substrate  26  of another head chip  21  are joined with each other so that the positions of each one edge thereof are set to be substantially equal to each other, but the present invention is not limited thereto. Alternatively, even when the cover plate  26  of the another head chip  21  projects to the one edge side, the force acting when the FPC  13  is connected to the substrate connecting surface  28  can be reliably supported. In addition, the head chip main body  27  is formed of the actuator substrate  25  and the cover plate substrate  26 , but the present invention is not limited thereto. Alternatively, the head chip main body  27  may be formed of a single substrate and the substrate may be provided with the substrate connecting surface  28 , the plurality of channels  29 , the electrodes  31 , and the ink chamber  32 . Further, the ink supply hole forming step is performed after the lamination step. Alternatively, in the head chip forming step, after the through holes, which becomes the ink supply holes, are formed in each of the head chips  21 , the head chips  21  may be laminated so that the through holes can communicate with each other. 
     Further, in the wiring board connecting step, the FPCs  13  are each connected to the substrate connecting surfaces  28  of the head chips  21  with the anisotropic conductive film  38 , but the present invention is not limited thereto. For example, the FPCs  13  may be connected by wire bonding. Also in this case, the FPCs  13  can be each wire bonded onto the substrate connecting surfaces  28  with ease and reliability by using a capillary for bonding while the other head chips  21  and the other FPCs  13  do not interfere the connection. Moreover, in the first embodiment of the present invention, aqueous ink is used, but the present invention is not limited thereto. Alternatively, oil-based ink, solvent-based ink, UV-based ink, and the like may be used. 
     Further, in the first embodiment of the present invention, in the plurality of channels  29 , the common grooves  29   c  capable of discharging ink are alternately formed and the active grooves  29   d  which do not discharge ink are formed therebetween, but the present invention is not limited thereto. In other words, as shown in  FIGS. 16 and 17 , in the cover plate substrate  26  of each of the head chips  21 , instead of forming the plurality of through holes  33   c , the entire main body part  33  of the ink chamber  32  may be penetrated so as to communicate with all the channels  29 . Note that, in this case, in can be discharged from all the channels  29 . As a result, the nozzle holes  23   a  are formed in the nozzle plate  23  so as to correspond to all the channels  29 . 
     Second Embodiment 
       FIGS. 18 to 20B  each show a second embodiment of the present invention. In the second embodiment of the present invention, components common to the components used in the above-mentioned embodiment are denoted by the same reference symbols, and descriptions thereof are omitted. 
     As shown in  FIGS. 18 to 20B , a head chip unit  50  according to the second embodiment of the present invention includes head chips  51  ( 51 A and  51 B) laminated in two layers. The head chips  51 A and  51 B each include the actuator substrate  25  and the cover plate substrate  26 , as the head chip main body  27 . In this case,  FIG. 19A  shows the cover plate substrate  26  of the head chip  51 A,  FIG. 19B  shows the actuator substrate  25  of the head chip  51 A,  FIG. 20A  shows the cover plate substrate  26  of the head chip  51 B, and  FIG. 20B  shows the actuator substrate  25  of the head chip  51 B. The actuator substrate  25  of each of the head chips  51  has the substrate connecting surface  28 , the plurality of channels  29 , and the electrodes  31  formed therein as in the first embodiment. In the head chip  51 A in which the cover plate substrate  26  is allowed to expose to one side, the cover plate substrate  26  includes only the main body part  33  as the ink chamber  32 . In the head chip  51 B, the cover plate  26  includes a first ink chamber  52 , a second ink chamber  53 , a third ink chamber  54 , and a plurality of ink chambers which do not interfere with each other. The first ink chamber  52  includes a main body part  55   a , an introduction part  56   a , and a supply part  57   a . The second ink chamber  53  includes a main body part  55   b , an introduction part  56   b , and a supply part  57   b . The third ink chamber  54  includes a main body part  55   c , an introduction part  56   c , and a supply part  57   c . The main body part  55   a  of the first ink chamber  52  is formed on a side of one side edge  51   a  in the arrangement direction Q, and has a through hole  55   d  formed therein so as to communicate with the plurality of channels  29  on the one side edge  51   a  side. The main body part  55   c  of the third ink chamber  54  is formed on a side of another side edge  51   b  in the arrangement direction Q, and has the through hole  55   d  formed therein so as to communicate with the plurality of channels  29  on the another side edge  51   b  side. The main body  55   b  of the second ink chamber  53  is formed between the main body part  55   a  of the first ink chamber  52  and the main body part  55   c  of the third ink chamber  54  in the arrangement direction Q, and has the through hole  55   d  formed therein so as to communicate with the plurality of channels  29  formed at a central portion. In addition, the introduction parts  56   a ,  56   b , and  56   c  are connected to the corresponding main body parts  55   a ,  55   b , and  55   c , respectively, and extend to positions where the introduction parts  56   a ,  56   b , and  56   c  are not overlapped with the plurality of channels  29  and the ink chambers  32  of the head chip  51 A on the one side, and the supply parts  57   a ,  57   b , and  57   c  are formed. Further, ink supply holes  58   a ,  58   b , and  58   c  communicating with the supply parts  57   a ,  57   b , and  57   c , respectively, are formed so as to be opened in the cover plate substrate  26  of the head chip  51 A. 
     In the head chip unit  50  according to the second embodiment of the present invention, a plurality of ink chambers are formed in a single head chip  51 B, the supply parts  57   a ,  57   b , and  57   c  are respectively formed in the plurality of ink chambers, and the ink supply holes  58   a ,  58   b , and  58   c  are formed so as to correspond to the supply parts, thereby making it possible to supply different ink to be discharged with a single head chip  51 B. In addition, in the second embodiment of the present invention, different ink is also supplied to the head chip  51 A, thereby discharging four colors of ink from one head chip unit  50 , thereby enabling printing. Note that, in the second embodiment of the present invention, the head chip is formed in two layers. Alternatively, the head chip having a plurality of ink chambers may be laminated in a plurality of layers. 
     As described above, the embodiments of the present invention are described with reference to the drawings. The detailed structures of the present invention are not limited to those embodiments, and various design modifications and the like can be made within a range without departing from the gist of the present invention.