Patent Publication Number: US-8534803-B2

Title: Liquid jet head chip, manufacturing method therefor, liquid jet head, and liquid jet recording apparatus

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a liquid jet head chip, a manufacturing method therefor, a liquid jet head, and a liquid jet recording apparatus having the liquid jet head. 
     2. Description of the Related Art 
     Conventionally, there is used an inkjet recording apparatus (liquid jet recording apparatus), which jets liquid, e.g., ink from nozzle holes (liquid jet holes) of a head chip (liquid jet head chip) so that ink drops are placed on a recording medium, to thereby print characters, images or the like. Each of the nozzle holes of the head chip is coupled to a piezoelectric actuator (liquid feeding portion). The piezoelectric actuator is provided with a plurality of groove portions (channels) in which the ink is filled. When a drive electrode that is provided to a partition for parting the groove portion is energized, the partition is deformed to squeeze out the ink so that the ink drop jets out from the nozzle hole, to thereby perform printing on the recording medium. 
     Here, it is common to use a diamond blade called “dicer” for grinding an actuator plate so as to form the groove portion of the piezoelectric actuator in a dicing step (see, for example, Japanese Patent Application Laid-open No. Hei 05-269995 and Japanese Patent Application Laid-open No. 2005-271305). For instance, as described in Japanese Patent Application Laid-open No. Hei 05-269995, the groove portion of the piezoelectric actuator formed by grinding with the dicer has a width of approximately 60 to 86 μm. 
     Recently, the liquid jet recording apparatus such as the inkjet recording apparatus described above is required to improve resolution of characters and symbols printed on the recording medium so that higher resolution (higher definition) is achieved. 
     Here, in order to increase resolution of the inkjet recording apparatus, it is conceivable, for example, to decrease a pitch of the groove portions of the piezoelectric actuator. In order to decrease a pitch of the groove portion, it is conceivable to use a dicer that is as thin (small width) as possible to grind the actuator plate. 
     However, the thickness (width) of the dicer to be used in the dicing process has a limitation for securing strength or the like of the dicer, and hence there is a limitation in decreasing a pitch of the groove portion. 
     In addition, it is also conceivable to decrease a width of the partition in order to decrease a pitch of the groove portion. 
     However, if the width of the partition is decreased, the partition may be broken. In order to decrease the width of the partition, high accuracy of machining is required, which causes difficulty in machining. As a result, yield cannot be improved, and there may be a case where the machining cannot be performed. 
     Thus, it is difficult to decrease a pitch of the groove portion further in the future. 
     SUMMARY OF THE INVENTION 
     The present invention is created in view of the above-mentioned situation, and it is an object of the present invention to provide a liquid jet head chip in which easiness in machining is improved and a narrow pitch of channels and high resolution are realized, and to a manufacturing method for the liquid head chip, a liquid jet head having the liquid head chip, and a liquid jet recording apparatus having the liquid jet head. 
     In order to solve the above-mentioned problems, the present invention provides the following means. 
     A liquid jet head chip according to the present invention includes: a jet plate in which a plurality of jet holes for jetting liquid are formed; and a liquid feeding portion having channels communicating to the jet holes so as to supply the liquid from the channels to the jet holes, in which: the liquid feeding portion includes a first actuator plate and a second actuator plate; each of the first actuator plate and the second actuator plate has a plurality of partitions formed with predetermined spaces in an arrangement direction of the jet holes and a groove portion formed between neighboring partitions, the first actuator plate and the second actuator plate are superimposed with each other so that the partition of one of the first actuator plate and the second actuator plate is disposed in the groove portion of another of the first actuator plate and the second actuator plate, and each of the channels is formed between the partition of the first actuator plate and the partition of the second actuator plate. 
     With this structure, the first actuator plate and the second actuator plate are superimposed with each other so that the partition of the first actuator plate is disposed in the groove portion of the second actuator plate while the partition of the second actuator plate is disposed in the groove portion of the first actuator plate. In other words, the first actuator plate and the second actuator plate are superimposed with each other so that the partitions of the actuator plates are disposed alternately, and hence the partition of one of the first actuator plate and the second actuator plate divides the space in the groove portion of another of the first actuator plate and the second actuator plate into two parts in the width direction. Thus, one groove portion can form two channels, and hence it is possible to form a channel having smaller width than the conventional channel by using existing machining tools and manufacturing method. 
     Therefore, a small pitch of the channels can be realized while easiness of machining and yield can be improved. Thus, resolution of characters and symbols recorded on the recording medium can be improved so that high resolution can be realized. 
     Further, the first actuator plate and the second actuator plate are formed to have the same shape. 
     With this structure, both the first actuator plate and the second actuator plate can be formed to have the same shape, and hence the first actuator plate and the second actuator plate can be manufactured by using the same machining tools and manufacturing method. Thus, easiness of machining can be improved and manufacturing cost can be reduced. 
     Further, each of the jet holes is formed to have an opening part of an elliptic contour, and is arranged so that a minor axis direction thereof corresponds to a short side direction of each opening part of the channels. 
     With this structure, the minor axis direction of the jet holes and the short side direction of the channels correspond to each other, and hence the area of the opening can be increased compared with a circular jet holes. Thus, even if the liquid is jetted through a channel having a small width, a jet amount of the liquid can be secured. 
     Further, a liquid inlet hole communicating to the channels is formed in one of the first actuator plate and the second actuator plate so that the liquid can be supplied to the channels. 
     With this structure, one of the actuator plates is provided with the liquid inlet hole that can communicate to the channels, and hence the liquid can be filled in the plurality of channels at one time. Thus, the structure can be simplified compared with the case where each channel is provided with a supplying hole for the liquid, for example. 
     Further, a deep groove portion that is formed deeper than the groove portion is formed in the groove portion of one of the first actuator plate and the second actuator plate on one side in a width direction of the partition of another of the first actuator plate and the second actuator plate, and the liquid inlet hole is formed so as to be able to communicate only to the channel in which the deep groove portion is formed. 
     With this structure, the plurality of channels obtained by dividing the groove portion work as the discharging channel alternately. Therefore, even if conductive liquid, for example, is used, the drive electrode disposed in the discharging channel and the drive electrode disposed in the dummy channel can be used independently in an electrically separated state without being conducted through the liquid. Therefore, the conductive liquid can be used for recording. Thus, additional values can be enhanced because the conductive liquid can be used without a problem. 
     In particular, the deep groove portion is further formed in the groove portion of one of the actuator plates on one side in the width direction, and the liquid inlet hole is formed so as to communicate only to the deep groove portion. In this way, the liquid can be filled only in the discharging channel. Thus, it is possible to provide the piezoelectric actuator that can support the conductive liquid without increasing the machining steps. Therefore, manufacturing cost and manufacturing efficiency can be maintained. 
     Further, a manufacturing method for a liquid jet head chip according to the present invention includes: a jet plate in which a plurality of jet holes for jetting liquid are formed; and a liquid feeding portion having channels communicating to the jet holes so as to supply the liquid from the channels to the jet holes, the liquid feeding portion being constituted by combining a first actuator plate and a second actuator plate, the method comprising: forming a plurality of groove portions that extend in a direction perpendicular to an arrangement direction of the jet holes of the first actuator plate and the second actuator plate, and are arranged with spaces in the arrangement direction of the jet holes of the first actuator plate and the second actuator plate; and superimposing the first actuator plate and the second actuator plate with each other so that the partition of one of the first actuator plate and the second actuator plate is arranged in the groove portion of another of the first actuator plate and the second actuator plate 
     With this structure, the actuator plates are superimposed with each other so that the partitions of the actuator plates are disposed alternately. Thus, the partition of one actuator plate divides the groove portion of the other actuator plate in the width direction into two parts. Therefore, one groove portion can form two channels, and hence it is possible to form a channel having smaller width than the conventional channel by using existing machining tools and manufacturing method. 
     Therefore, a small pitch of the channels can be realized while easiness of machining is improved. Thus, it is possible to provide the liquid jet head chip that can improve resolution of characters and symbols recorded on the recording medium so that high resolution can be realized. 
     Further, a liquid jet head according to the present invention includes: the liquid jet head chip according to the present invention described above; a supply unit for supplying a predetermined amount of the liquid to the liquid inlet hole; and a control unit for applying a drive voltage to a drive electrode. 
     With this structure, the supply unit supplies a predetermined amount of liquid securely to the liquid inlet hole of the liquid jet head chip. Further, the control unit applies the drive voltage appropriately to the drive electrode, and hence the liquid is jet through the jet hole, to thereby perform recording as described above. 
     In particular, there is provided a high quality liquid jet head chip with channels of a narrow pitch, and hence recording can be performed securely, and hence quality of the liquid jet head itself can be increased. 
     Further, a liquid jet recording apparatus according to the present invention includes: the liquid jet head according to the present invention described above; a conveying unit for conveying a recording medium in a predetermined direction; and a moving unit for moving the liquid jet head in a reciprocating manner in a direction perpendicular to a conveying direction of the recording medium. 
     With this structure, the conveying unit conveys the recording medium in a predetermined direction while the moving unit moves the liquid jet head in a reciprocating manner in the direction perpendicular to the conveying direction of the recording medium. Thus, the recording can be performed correctly in a desired area on the recording medium. In particular, there is provided a high quality liquid jet head chip with channels of a narrow pitch, and hence quality of the liquid jet recording apparatus itself can be increased similarly. 
     According to the present invention, the first actuator plate and the second actuator plate are superimposed with each other so that the partition of the first actuator plate is disposed in the groove portion of the second actuator plate while the partition of the second actuator plate is disposed in the groove portion of the first actuator plate. In other words, the first actuator plate and the second actuator plate are superimposed with each other so that the partitions of the actuator plates are disposed alternately, and hence the partition of one actuator plate divides the space in the groove portion of the other actuator plate into two parts in the width direction. Thus, one groove portion can form two channels, and hence it is possible to form a channel having smaller width than the width of the conventional channel by using existing machining tools and manufacturing method. 
     Therefore, a small pitch of the channels can be realized while easiness of machining is improved. Thus, resolution of characters and symbols recorded on the recording medium can be improved so that high resolution can be realized. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the accompanying drawings: 
         FIG. 1  is a perspective view illustrating a general structure of an inkjet printer according to an embodiment of the present invention; 
         FIG. 2  is a perspective view illustrating an appearance of an inkjet head; 
         FIG. 3  is a perspective view of a head chip; 
         FIG. 4  is a side view of a piezoelectric actuator according to a first embodiment of the present invention; 
         FIG. 5A  is a sectional view taken along the line A-A of FIG.  4 , and  FIG. 5B  is a sectional view taken along the line B-B of  FIG. 4 ; 
         FIG. 6  are plan views of an actuator plate, in which  FIG. 6A  is an upper view,  FIG. 6B  is a side view, and  FIG. 6C  is a front view thereof; 
         FIGS. 7A to 7C  are process views illustrating a manufacturing method for the piezoelectric actuator; 
         FIGS. 8A to 8C  are process views illustrating a manufacturing method for the piezoelectric actuator; 
         FIGS. 9A and 9B  are sectional views of the piezoelectric actuator according to a second embodiment of the present invention; and 
         FIG. 10  is a side view of the piezoelectric actuator according to a third embodiment of the present invention; 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     First Embodiment 
     (Inkjet Printer) 
     Next, a first embodiment of the present invention is described with reference to the attached drawings. Note that, in this embodiment, an inkjet printer  1  that uses nonconductive oil ink (liquid) W for printing is described as an example of a liquid jet recording apparatus. 
       FIG. 1  is a perspective view illustrating a general structure of the inkjet printer  1 . 
     As illustrated in  FIG. 1 , the inkjet printer  1  of this embodiment includes a plurality of inkjet heads (liquid jet heads)  2  for jetting ink W, a conveying unit  3  for conveying recording paper (recording medium) P in a predetermined conveying direction L 1 , and a moving unit  4  for moving the plurality of inkjet heads  2  in a reciprocating manner in the perpendicular direction L 2  that is perpendicular to the conveying direction L 1 . 
     In other words, the inkjet printer  1  is a so-called shuttle type printer that conveys the recording paper P in the conveying direction L 1  while the inkjet head  2  is moved in the perpendicular direction L 2  that is perpendicular to the conveying direction L 1  for recording characters or images on the recording paper P. Note that this embodiment exemplifies the case where there are disposed four inkjet heads  2  for jetting ink W of different colors (e.g., black, cyan, magenta, and yellow). Note that the four inkjet heads  2  have the same structure. 
     The four inkjet heads  2  are mounted on a carriage  6  that is housed in a casing  5  having a substantially rectangular solid shape. 
     The carriage  6 , which is constituted of a base  6   a  like a flat plate for supporting the plurality of inkjet heads  2  and a wall portion  6   b  rising vertically from the base  6   a , is supported by guide rails  7  arranged along the perpendicular direction L 2  in a reciprocatingly movable manner. In addition, the carriage  6  is supported by the guide rails  7  and is coupled to a carriage belt  9  that is wound around a pair of pulleys  8 . One of the pair of pulleys  8  is coupled to an output shaft of the motor  10 , and hence the pulley can rotate receiving a rotation torque from the motor  10 . Thus, the carriage  6  can move in a reciprocating manner toward the perpendicular direction L 2 . 
     In other words, the pair of guide rails  7 , the pair of pulleys  8 , the carriage belt  9 , and the motor  10  work as the above-mentioned moving unit  4 . 
     In addition, a pair of feed-in rollers  15  and a pair of conveying rollers  16  are disposed in parallel with a space along the perpendicular direction L 2  similarly to the pair of guide rails  7  in the casing  5 . The pair of feed-in rollers  15  are disposed on the rear side of the casing  5  while the pair of conveying rollers  16  are disposed on the front side of the casing  5 . Further, the pair of feed-in rollers  15  and the pair of conveying rollers  16  are adapted to be rotated by a motor (not shown) with the state where the recording paper P is sandwiched between the feed-in rollers  15  and between the conveying rollers  16 . Thus, the recording paper P can be conveyed along the conveying direction L 1  from the rear side to the front side of the casing  5 . 
     In other words, the pair of feed-in rollers  15  and the pair of conveying rollers  16  work as the above-mentioned conveying unit  3 . 
     (Inkjet Head) 
       FIG. 2  is a perspective view illustrating an appearance of the inkjet head  2 . 
     As illustrated in  FIG. 2 , each inkjet head  2  is a so-called shear mode type inkjet head, which includes a rectangular fixing plate  20  that is fixed to the base  6   a  of the carriage  6  with screws (not shown), a head chip  21  fixed to an upper surface of the fixing plate  20 , a supply unit  22  for supplying ink W to an ink inlet hole  40  (see  FIG. 3 ) of the head chip  21  to be described later, and a control unit  23  for applying a drive voltage to a drive electrode  37  to be described later. 
     (Head Chip) 
       FIG. 3  is a perspective view of the head chip  21 . 
     As illustrated in  FIG. 3 , the head chip  21  is mainly constituted of a piezoelectric actuator (liquid feeding portion)  30 , a support plate  32 , and a nozzle plate  33  (jet plate). 
     The support plate  32  supports the piezoelectric actuator  30  as well as the nozzle plate  33 . An engaging hole  32   a  is formed in the lateral width direction (Y direction) of the support plate  32 , and the piezoelectric actuator  30  is fit in the engaging hole  32   a  so as to be supported. In this case, the support plate  32  and the piezoelectric actuator  30  are combined to each other so that the front end surface of the support plate  32  forms a flat surface with the front end surface of the piezoelectric actuator  30 . 
     Then, the nozzle plate  33  is adhered to the end surface of the support plate  32  and the front end surface of the piezoelectric actuator  30  with an adhesive (not shown). 
     The nozzle plate  33  is a sheet-like plate made of a film material such as polyimide having a thickness of approximately 50 μm. Further, one surface of the nozzle plate  33  is an adhesive surface that is adhered to the support plate  32  while the other surface is an opposing surface (surface  33   b ) to be opposed to the recording paper P. Note that the surface  33   b  is coated with a water repellent film having water repellency for preventing the ink W from adhering. 
     In addition, a plurality of nozzle holes (let holes)  33   a  are formed along the lateral width direction (Y direction) of the nozzle plate  33 . In this case, the nozzle holes  33   a  are formed at constant intervals substantially linearly along the lateral width direction (Y direction) of the nozzle plate  33 . 
     In addition, each of the nozzle holes  33   a  is formed to have an ellipse contour. For instance, the nozzle hole  33   a  is formed to have a minor axis of approximately 10 μm and a major axis of approximately 53 μm, and a discharging amount of the nozzle hole  33   a  is set to be approximately 30 pico-litters. Further, the inlet diameter D 1  (e.g., minor axis of the nozzle hole  33   a ) on the adhesive surface side is larger than the outlet diameter D 2  on the surface  33   b  side so that the nozzle hole  33   a  has a tapered cross section. Note that the nozzle holes  33   a  are formed by using an excimer laser apparatus or the like. 
     As illustrated in  FIG. 2 , the head chip  21  is fixed to the upper surface of the fixing plate  20  as described above. On the upper surface of the fixing plate  20 , the rectangular base plate  24  made of aluminum or the like is fixed so as to rise vertically, and a channel member  22   a  is fixed for supplying ink W to the ink inlet hole  40  of the head chip  21 . Above the channel member  22   a , a pressure buffer  22   b  having a reservoir for reserving the ink W is arranged and supported by the base plate  24 . This pressure buffer  22   b  and the channel member  22   a  are connected to each other via an ink connecting tube  22   c . In addition, a supplying tube  60  for supplying the ink W is disposed above the pressure buffer  22   b.    
     In the inkjet head  2  having the structure described above, the ink W is supplied to the pressure buffer  22   b  via the supplying tube  60 . Then, the ink W is stored temporarily in the reservoir inside the pressure buffer  22   b . Further, the pressure buffer  22   b  is adapted to supply a predetermined amount of the ink W out of the stored ink W to the ink inlet hole  40  of the head chip  21  via the ink connecting tube  22   c  and the channel member  22   a . In other words, the channel member  22   a , the pressure buffer  22   b  and the ink connecting tube  22   c  work as the supply unit  22  described above. 
       FIG. 4  is a side view of the piezoelectric actuator  30 , and  FIGS. 5A and 5B  are sectional views of the piezoelectric actuator  30 , in which  FIG. 5A  is a sectional view taken along the line A-A of  FIG. 4 , and  FIG. 5B  is a sectional view taken along the line B-B of  FIG. 4 . 
     Here, as illustrated in  FIGS. 3 to 5 , the piezoelectric actuator  30  is constituted by superimposing a first actuator plate  41   a  and a second actuator plate  41   b  with each other. Note that the first actuator plate  41   a  and the second actuator plate  41   b  have substantially the same structure, and hence both of them are referred to as an actuator plate  41  except for the case where they should be distinguished from each other in the following description. 
       FIG. 6  are plan views of the actuator plate  41 , in which  FIG. 6A  is an upper view,  FIG. 6B  is a side view, and  FIG. 6C  is a front view thereof. 
     As illustrated in  FIGS. 6A to 6C , the actuator plate  41  is a plate made of a piezoelectric material such as lead zirconate titanate (PZT) having the polarization direction set along the thickness direction. On the surface  42   a  side of the actuator plate  41 , a plurality of groove portions  35  extending in the length direction (direction of the arrow X) are formed at constant intervals in the lateral width direction (direction of the arrow Y) perpendicular to the length direction. The plurality of groove portions  35  are separated from each other by the partition  36 . In this case, the width I 1  of the groove portion  35  is larger than the width I 2  of a partition  36 . For instance, the width I 1  of the groove portion  35  is approximately 50 μm, the width I 2  of the partition  36  is approximately 20 μm, and the pitch  13  of the groove portion  35  is approximately 70 μm (see  FIG. 6C ). 
     Each of the plurality of groove portions  35  works as a discharging channel  50  in which the ink W is filled (see  FIGS. 5A and 5B ) as described later, and each of the plurality of groove portions  35  is formed to have an opening on each end of the actuator plate  41  in the length direction (X direction). 
     In addition, the front side of the partition  36  in the length direction (X direction) is constituted of a front extending portion  36   a  extending from the front end surface  42   b  of the actuator plate  41  to substantially the middle portion in the length direction and an inclining portion  36   b  having the decreasing height of the partition  36  from the rear end of the front extending portion  36   a  toward the rear side. In other words, the partition  36  has a trapezoidal shape in the side view (see  FIG. 6B ), and a plurality of partitions  36  are arranged in the lateral width direction like comb teeth when viewed from the rear end surface  42   c  side of the actuator plate  41  (see  FIG. 6C ). Further, behind the inclining portion  36   b  of the partition  36 , each of the groove portions  35  is opened in the lateral width direction (Y direction) of the actuator plate  41  so as to form a flat surface  38 . 
     The drive electrode  37  made of aluminum, gold, or the like is formed in the length direction on the partition  36  and the flat surface  38  of each of the plurality of groove portions  35  by oblique vapor deposition or the like. The drive electrode  37  includes side face electrodes  37   a  formed on the side surfaces of the partition  36  and flat surface electrodes  37   b  formed on the flat surface  38 . 
     The side face electrode  37   a  is formed along the peripheral portion from the front end side to the rear end side on the side surface of the front extending portion  36   a , specifically from the upper end of the partition  36  to the middle position thereof in the height direction. In addition, the side face electrode  37   a  is formed along the side surface of the inclining portion  36   b , and is formed on the rear end side of a bottom surface  35   a  of the groove portion  35  as the inclining portion  36   b  becomes low. 
     Further, the flat surface electrode  37   b  is formed along the length direction (X direction) on the flat surface  38  in the state of being connected from the rear end side of the groove portion  35  to the side face electrode  37   a , extending to the rear end surface  42   c  of the actuator plate  41 . In other words, each of the drive electrodes  37  is formed from the front end surface  42   b  to the rear end surface  42   c  over the partition  36  and the flat surface  38  in the length direction of the actuator plate  41 . In the lateral width direction, the side face electrodes  37   a  are opposed between the partitions  36 . The flat surface electrodes  37   b  extend in parallel with a predetermined distance in the lateral width direction on the flat surface  38 . 
     Thus, the flat surface electrodes  37   b  of the drive electrodes  37  are connected electrically to lead electrodes (not shown) of the flexible circuit boards  45   a  and  45   b  (see  FIG. 4 ) described later, and hence the control unit  23  can apply the drive voltage individually. Further, the drive electrode  37  has a role of deforming the partition  36  by piezoelectric thickness sliding effect when the drive voltage is applied. 
     Here, as illustrated in  FIGS. 3 to 5B , the first actuator plate  41   a  and the second actuator plate  41   b  are superimposed so that the surfaces of the plates  41   a  and  41   b  in which the groove portions are formed (surfaces  42   a ) are opposed to each other. Specifically, the partitions  36  of the first actuator plate  41   a  enter the groove portions  35  of the second actuator plate  41   b  respectively while the partitions  36  of the second actuator plate  41   b  enter the groove portions  35  of the first actuator plate  41   a  respectively. In other words, the partitions  36  of the actuator plates  41   a  and  41   b  are arranged alternately, and hence a partition  36  of one actuator plate divides the space in the groove portion  35  of the other actuator plate into two parts in the lateral width direction (Y direction). Further, the actuator plates  41   a  and  41   b  are adhered and fixed to each other with adhesive (not shown) applied between the upper end surfaces of the partitions  36  of one actuator plate (e.g., first actuator plate  41   a ) and the bottom surfaces  35   a  of the groove portions  35  of the other actuator plate (e.g., second actuator plate  41   b ). Note that the adhesive to be used in this case is preferably an epoxy adhesive. 
     Each of the groove portions  35  divided by the partition  36  into two parts works as the discharging channel  50  in which the ink W is filled. In this case, the width of the discharging channel  50  is approximately 15 μm, and the pitch of the discharging channel  50  is approximately 35 μm. The pitch of the plurality of nozzle holes  33   a  of the nozzle plate  33  described above is also the same value. Note that the nozzle holes  33   a  are arranged so that the minor axis direction of the nozzle hole  33   a  corresponds to the width direction of the discharging channel  50 , and that the center thereof is positioned on the center line of each discharging channel  50  in the lateral width direction. 
     Note that the side face electrodes  37   a  of the actuator plates  41   a  and  41   b  are formed in the peripheral portion of the partition  36 . Therefore, when the actuator plates  41   a  and  41   b  are superimposed with each other, the side face electrodes  37   a  in each discharging channel  50  are arranged to be shifted from each other in the vertical direction (in the state not being opposed to each other). However, the side face electrodes  37   a  to be a pair for deforming the partition  36  are the side face electrodes  37   a  that are formed on the same partition  36 , and hence there is no problem for driving. 
     In addition, the second actuator plate  41   b  is provided with the ink inlet hole  40  that is formed to communicate between the back surface  42   d  thereof and the bottom surface  35   a  of the groove portion  35 . The ink inlet hole  40  is a through hole formed in the lateral width direction of the second actuator plate  41   b  and having a rectangular shape in the plan view, and is formed in the region where the front extending portion  36   a  is formed in the length direction. In other words, the ink inlet hole  40  can communicate with the individual discharging channels  50 , and hence the ink W can be filled in the plurality of discharging channels  50  at one time. Thus, the structure can be simplified compared with the structure in which a supplying hole for the ink W is provided to each of the discharging channels  50 . 
     In addition, as illustrated in  FIG. 2 , an IC substrate  26  is fixed to the piezoelectric actuator  30 , and the driving circuit  25  such as an integrated circuit for driving the head chip  21  is mounted on the IC substrate  26 . The driving circuit  25  and the drive electrodes  37  of the actuator plates  41   a  and  41   b  are electrically connected to each other via the first and second flexible circuit boards  45   a  and  45   b . Specifically, one end of the first flexible circuit board  45   a  is connected to the driving circuit  25  via a wiring pattern (not shown) on the IC substrate  26  at one side, and the other end thereof is led to the flat surface  38  of the first actuator plate  41   a  and is connected to the flat surface electrode  37   b  of the drive electrode  37  formed on the flat surface  38 . 
     On the other hand, one end of the second flexible circuit board  45   b  is connected to the driving circuit  25  via a wiring pattern (not shown) on the IC substrate  26  at the other side, and the other end thereof is led to the flat surface  38  of the second actuator plate  41   b  and is connected to the flat surface electrode  37   b  of the drive electrode  37  formed on the flat surface  38 . In other words, connecting portions of the first flexible circuit board  45   a  and the second flexible circuit board  45   b  on one end are shifted from each other in the width direction of the IC substrate  26  and are connected with each other. Note that the second flexible circuit board  45   b  is a so-called inverted flexible circuit board in which the contact portion (not shown) with the driving circuit  25  is formed on one surface and the contact portion (not shown) with the flat surface electrode  37   b  is formed on the other surface. 
     The driving circuit  25  applies the drive voltage to the drive electrodes  37  via the individual flexible circuit boards  45   a  and  45   b  for jetting the ink W. In other words, the driving circuit  25  and the flexible circuit board  45  work as the above-mentioned control unit  23 . 
     Then, as illustrated in  FIG. 4 , sealing compound  44  is filled between the flat surfaces  38  of the actuator plates  41   a  and  41   b  on the rear side of the piezoelectric actuator  30 . The sealing compound is filled in the lateral width direction of the actuator plates  41   a  and  41   b  so as to prevent the ink W from leaking from the rear end side of the piezoelectric actuator  30  and to secure insulation between the flexible circuit boards  45   a  and  45   b . A material of the sealing compound  44  is preferably a resin material having some elasticity and high resistance to the ink W, e.g., silicon resin. When the material having elasticity is used for the sealing compound  44 , a stress when the partition is deformed can be absorbed so that a breakage or the like of the actuator plate  41  can be prevented. 
     In addition, in this embodiment, there is a gap between the front end side of the sealing compound  44  and the rear end side of each discharging channel  50  in the length direction, the discharging channels  50  being communicated with each other by the gap. Note that when the oil (nonaqueous) ink W is used as in this embodiment, there is no fear that the electric current leaks through the ink W. Therefore, neighboring discharging channels  50  can be communicated with each other. However, the sealing compound  44  may be filled in to reach the rear end side of each discharging channel  50  so that the individual discharging channels  50  are separated from each other. 
     (Manufacturing Method for the Head Chip) 
     Next, a manufacturing method for the above-mentioned head chip  21  is described. Note that a manufacturing method for the piezoelectric actuator  30  is described mainly in the following description.  FIGS. 7 and 8  are process views illustrating the manufacturing method for the piezoelectric actuator  30 . 
     First, as illustrated in  FIG. 7A , the actuator plate  41  is ground (grinding step). Specifically, the flat surface  38  is formed on the rear side of the actuator plate  41  in the length direction, and the inclining portion  36   b  is formed from the flat surface  38  to the front side so that the thickness of the actuator plate  41  is gradually decreased. 
     Next, as illustrated in  FIG. 7B , a laminate  51  is attached onto the surface  42   a  of the actuator plate  41  on the front side in the length direction (mask formation step). Specifically, film-like resist such as dry film resist is attached first to the region (groove portion  35  forming region) on the surface  42   a  of the actuator plate  41  except for the inclining portion  36   b  and the flat surface  38 . Then, using the photolithography technology, the laminate is exposed to light and is developed so that the laminate  51  in the groove portion  35  forming region (see  FIGS. 5A and 5B ) is removed. Thus, a mask pattern for forming the groove portion  35  is formed on the surface  42   a  of the actuator plate  41 . Note that the resist material used for the masking step may be liquid resist or the like instead of the dry film resist. However, when the dry film resist is used as in this embodiment, the thickness of the laminate  51  can be uniform so that the depth of the groove portion  35  can be controlled easily in the dicing step that is described later. 
     Next, as illustrated in  FIG. 7C , the dicing process is performed on the surface  42   a  of the actuator plate  41  so as to form the groove portions  35  (groove portion forming step). Specifically, the diamond blade or other dicer is used for grinding the actuator plate  41  in accordance with the mask pattern of the laminate  51  formed on the actuator plate  41 . Thus, the plurality of groove portions  35  can be formed on the surface  42   a  of the actuator plate  41  with the width and the pitch described above, and the partitions  36  for separating the individual groove portions  35  can be formed like comb teeth. 
     Further, as illustrated in  FIG. 8A , an electrode film  52  to be the drive electrode  37  (see  FIG. 6 ) is formed on the surface  42   a  of the actuator plate  41  (electrode film forming step). Specifically, using a known oblique vapor deposition method or the like, a vapor deposition material is scattered in an oblique direction onto the surface  42   a  of the actuator plate  41  so that the electrode film  52  is formed on the upper surface, the upper half of the side surface, and the flat surface  38  of the partition  36 . In this case, the electrode film  52  is not formed on the side surface of the front extending portion  36   a  of the partition  36  and the bottom surface  35   a  of the groove portion  35  corresponding to the front extending portion  36   a  (see  FIGS. 5A and 5B ). 
     Next, as illustrated in  FIG. 8B , the mask pattern of the laminate  51  (see  FIG. 7C ) attached to the upper surface of the front extending portion  36   a  of the partition  36  is lift off, and is removed together with the electrode film  52  formed on the laminate  51  (lift off step). 
     Then, as illustrated in  FIG. 8C , the electrode film  52  formed on the surface  42   a  of the actuator plate  41  is divided into the plurality of drive electrodes  37  (trimming step). Specifically, laser trimming is performed along the length direction of the actuator plate on the middle portion of the groove portion  35  in the lateral width direction and on the middle portion of the partition  36  in the lateral width direction so that the electrode film  52  is divided into the plurality of drive electrodes  37  with spaces in the lateral width direction. 
     Thus, the first actuator plate  41   a  and the second actuator plate  41   b  described above are completed. 
     After that, as illustrated in  FIGS. 5A and 5B , the ink inlet hole  40  communicating between the back surface  42   d  of the second actuator plate  41   b  and the bottom surface  35   a  of the groove portion  35  is formed along the lateral width direction of the second actuator plate  41   b.    
     Then, the first actuator plate  41   a  and the second actuator plate  41   b  are adhered to each other with adhesive (adhering step). Specifically, the adhesive is applied to the upper end surfaces of the partitions  36  of both the actuator plates  41   a  and  41   b , and the actuator plates  41   a  and  41   b  are superimposed with each other so that the partitions  36  of the actuator plates  41   a  and  41   b  are arranged alternately, and the partition  36  of one actuator plate divides the space in the groove portion  35  of the other actuator plate into two parts in the lateral width direction. Here, the width I 1  of the groove portion  35  is larger than the width I 2  of the partition  36  as described above. Therefore, the partition  36  of the first actuator plate  41   a  can be securely positioned in the groove portion  35  of the second actuator plate  41   b , while the partition  36  of the second actuator plate  41   b  can be securely positioned in the groove portion  35  of the first actuator plate  41   a.    
     Thus, the actuator plates  41   a  and  41   b  are adhered and fixed to each other with adhesive (not shown) applied between the upper end surface of the partition  36  of one actuator plate (e.g., first actuator plate  41   a ) and the bottom surface  35   a  of the groove portion  35  of the other actuator plate (e.g., second actuator plate  41   b ), thereby the piezoelectric actuator  30  is completed. 
     After that, the piezoelectric actuator  30  is fit in the engaging hole  32   a  of the support plate  32 , and the nozzle plate  33  is adhered and fixed to the front end surfaces of the support plate  32  and the piezoelectric actuator  30 . On this occasion, the nozzle plate  33  is adhered to the front end surfaces while the nozzle holes  33   a  of the nozzle plate  33  and the discharging channels  50  of the piezoelectric actuator  30  are aligned so as to be communicated with each other. 
     Thus, the head chip  21  of this embodiment is completed. 
     (Operating Method for the Inkjet Printer) 
     Next, a case of using the inkjet printer  1  having the structure described above for printing characters or graphics on the recording paper P is described below. Note that it is supposed that the four ink tanks  39  are adequately filled with the ink W of different colors as an initial state. In addition, the ink W in the ink tank  39  is supplied to the pressure buffer  22   b  through the supplying tube  60 . Therefore, a predetermined amount of ink W is supplied to the ink inlet hole  40  of the head chip  21  via the ink connecting tube  22   c  and the channel member  22   a  and is filled in the channel via the slit  31   b.    
     In such the initial state, the recording paper P is inserted from the opening part of the casing  5  on the rear side, and the inkjet printer  1  is activated. Then, as illustrated in  FIG. 1 , the pair of feed-in rollers  15  and the pair of conveying rollers  16  are first rotated so as to convey the recording paper P in the conveying direction L 1 . In addition, at the same time, the motor  10  rotates the pulley  8  so as to make the carriage belt  9  turn. Thus, the carriage  6  moves in a reciprocating manner in the perpendicular direction L 2  with being guided by the guide rail  7 . 
     Then, in this period, the head chips  21  of the individual inkjet heads  2  jet four color ink W appropriately to the recording paper P so that characters or images can be recorded. In particular, the inkjet printer  1  of this embodiment is the shuttle type, and hence recording can be performed correctly in a desired range on the recording paper P. 
     Here, the operation of each inkjet head  2  is described in detail below. 
     When the carriage  6  starts the reciprocating movement, the driving circuit  25  applies the drive voltage to the drive electrode  37  via the flexible circuit boards  45   a  and  45   b . The piezoelectric actuator  30  of this embodiment has one polarization direction of the actuator plate  41 , and the side face electrode  37   a  is formed only in the region extending to the middle position on the side surface of the partition  36  in the height direction. Therefore, when the drive voltage is applied, the partition  36  is bent and deformed in a V-shape with the center at the middle position in the height direction. Thus, the volumetric capacity of the discharging channel  50  is increased so that the ink W is led into the discharging channel  50  through the ink inlet hole  40 . Then, the drive voltage applied to the drive electrode  37  is made to be zero at the timing when a pressure wave due to the ink W reaches a vicinity of the nozzle hole  33   a , and the deformation of the partition  36  is reset so that the increased volumetric capacity of the discharging channel  50  is reset to be the original volumetric capacity. By this operation, the pressure inside the discharging channel  50  increases so that the ink W is pressurized. As a result, the ink W is discharged from the discharging channel  50  as being pushed out by the partition  36 . 
     The discharged ink W passes through the nozzle hole  33   a  and is discharged to the outside. Further, the ink W becomes like a drop, i.e., an ink drop when the ink W passes through the nozzle hole  33   a , and is discharged. As a result, recording can be performed correctly in a desired range on the recording paper P. 
     In this way, this embodiment has the structure in which the first actuator plate  41   a  and the second actuator plate  41   b  are superimposed with each other so that the partitions  36  thereof are arranged alternately, and the discharging channel  50  in which the ink W is filled is formed between the partition  36  of the first actuator plate  41   a  and the partition  36  of the second actuator plate  41   b.    
     With this structure, the partitions  36  of the actuator plates  41   a  and  41   b  are arranged alternately, and hence the partition  36  of one actuator plate divides the space in the groove portion  35  of the other actuator plate into two parts in the width direction. Thus, one groove portion  35  can form two discharging channels  50 , and hence the discharging channel  50  having a width smaller than that of the conventional discharging channel  50  can be formed by using the existing machining tools and manufacturing method. 
     Therefore, the pitch of the discharging channels  50  can be decreased while easiness in machining and yield are improved. Thus, resolution of characters and symbols printed on the recording paper P can be increased so that high resolution can be realized. As a result, high quality of the inkjet printer  1  itself can be realized. 
     Further, in this embodiment, the actuator plates  41  having the same shape are used so that the actuator plates  41   a  and  41   b  can be manufactured by using the same machining tools and manufacturing method. Therefore, the easiness in machining can be further improved, and manufacturing cost can be reduced. 
     In addition, the minor axis direction of the nozzle hole  33   a  corresponds to the width direction of the discharging channel  50  so that the nozzle hole  33   a  and the discharging channel  50  are communicated to each other. Therefore, the opening area can be larger than a nozzle hole having a circular shape, for example. Thus, even if the ink W is jet through the discharging channel  50  having a small width, the discharging amount of the ink W can be secured. 
     Second Embodiment 
     Next, a second embodiment of the present invention is described.  FIGS. 9A and 9B  are sectional views of a piezoelectric actuator  130  in the second embodiment, which correspond to  FIGS. 5A and 5B . Note that the same structure as in the first embodiment described above is denoted by the same reference symbol so that overlapping description is omitted. The inkjet printer of this embodiment has a structure of mainly using conductive aqueous ink for recording. 
     As illustrated in  FIGS. 9A and 9B , the piezoelectric actuator  130  of a head chip  121  according to this embodiment has the groove portion  35  that is divided into two channels. One channel constitutes a discharging channel  150  in which the ink W is filled, while the other channel constitutes a dummy channel  151  in which the ink W is not filled. In other words, the channels of this embodiment include the discharging channels  150  and the dummy channels  151  that are arranged alternately. 
     A deep groove portion  100  that is ground deeper than the bottom surface  35   a  of the groove portion  35  is formed in the discharging channel  150  of the groove portion  35  of the second actuator plate  41   b . The deep groove portion  100  is formed after the dicing step described above, by using a dicer having a thickness (blade width) smaller than (approximately a half of) that of the dicer used in the dicing step, and by grinding the region where the discharging channel  150  of the groove portion  35  is formed. Note that the deep groove portion  100  is separated from the dummy channel  151  by the partition  36  of the first actuator plate  41   a.    
     Here, the second actuator plate  41   b  is provided with an ink inlet hole  140  communicating only between the back surface  42   d  thereof and a bottom surface  100   a  of the deep groove portion  100 . The ink inlet hole  140  is a through hole formed in the lateral width direction of the second actuator plate  41   b  and having a rectangular shape in the plan view. In other words, the ink inlet hole  140  communicates to the discharging channel  150  via the deep groove portion  100  so that the ink W can be filled in the discharging channel  150 . In contrast, the ink inlet hole  140  does not communicate to the dummy channel  151 , and hence the ink W is not filled in the dummy channel  151 . 
     Therefore, according to this embodiment, in addition to the same effect of the first embodiment described above, the plurality of channels formed by dividing the groove portion  35  work as discharging channels  150  alternately. Therefore, even if conductive aqueous ink W is used, the drive electrode  37  disposed in the discharging channel  150  and the drive electrode  37  disposed in the dummy channel  151  can be used independently in an insulated manner from each other without being conducted through the ink W. Therefore, the aqueous ink W can be used for recording. Thus, the conductive ink W can be used without a problem, and hence additional values of the inkjet printer  1  can be enhanced. 
     In this case, the deep groove portion  100  is further formed in the groove portion  35  of the second actuator plate  41   b , and the ink inlet hole  140  that communicates only to the deep groove portion  100  is formed so that the ink W can be filled only in the discharging channel  150 . Thus, it is possible to provide the piezoelectric actuator  130  that can support aqueous ink W without increasing machining steps compared with the case of using the oil ink W. Therefore, manufacturing cost and manufacturing efficiency can be maintained. 
     Third Embodiment 
     Next, a third embodiment of the present invention is described.  FIG. 10  is a side view of a piezoelectric actuator  230  in the third embodiment. Note that the same structure as in the first embodiment described above is denoted by the same reference symbol so that overlapping description is omitted. 
     As illustrated in  FIG. 10 , the piezoelectric actuator  230  of a head chip  221  of this embodiment is different from that of the first embodiment described above concerning a shape of a first actuator plate  241   a . As illustrated in  FIG. 10 , the first actuator plate  241   a  is a plate made of a piezoelectric material such as PZT similarly to the first actuator plate  41   a  (see  FIG. 4 ) of the first embodiment described above. A plurality of groove portions  235  extending in the length direction (direction of the arrow X) are formed on the upper surface of the first actuator plate  241   a  and arranged in the lateral width direction (direction of the arrow Y) with predetermined spaces. Further, the plurality of groove portions  235  are separated from each other by a plurality of partitions  236  formed like comb teeth. 
     The plurality of groove portions  235  are formed so as to have openings on a front end surface  242   b  side of the first actuator plate  241   a  and to have the depth decreasing gradually toward a rear end surface  242   c . In other words, the bottom surface of each groove portion  235  is constituted of a front flat surface  235   a  extending from the front end surface  242   b  of the first actuator plate  241   a  to substantially the middle portion in the length direction, an inclined surface  235   b  having a groove depth decreasing from the rear end of the front flat surface  235   a  toward the rear side, and a rear flat surface  235   c  extending from the rear end of the inclined surface  235   b  toward the rear side. 
     On the opening side of the groove portion  235  on each side surface of each partition  236 , a drive electrode  237  for applying the drive voltage is formed to extend along the length direction of the first actuator plate  241   a . The drive electrode  237  is formed by the oblique vapor deposition or the like, and the rear end thereof is connected to the lead electrode (not shown) of the flexible circuit board  45   a.    
     Further, the first actuator plate  241   a  and the second actuator plate  41   b  are superimposed with each other so that the rear flat surface  235   c  of the first actuator plate  241   a  and the flat surface  38  of the second actuator plate  41   b  are opposed to each other and that the partitions  236  and  36  of the actuator plates  241   a  and  41   b  are arranged alternately. Thus, the partition  236  or  36  of one actuator plate divides the groove portion  35  or  235  of the other actuator plate into two parts in the lateral width direction. Further, the actuator plates  241   a  and  41   b  are adhered and fixed to each other with adhesive (not shown) applied between the upper end surface of the partition  236  of one actuator plate (e.g., first actuator plate  241   a ) and the bottom surface  35   a  of the groove portion  35  of the other actuator plate (e.g., second actuator plate  41   b ). Thus, the groove portions  235  and  35  divided by the partitions  236  and  36  into two parts each constitute the discharging channel  250  in which the ink W is filled. 
     According to this embodiment, the first actuator plate  241   a  having the groove portion  235  is simply superimposed with the second actuator plate  41   b  having the same structure as the first embodiment, and thus the same effect as in the first embodiment can be obtained. Therefore, flexibility in design can be improved because different types of actuator plates  241   a  and  41   b  can be combined. 
     Note that the present invention is not limited to the embodiments described above, which can be modified variously within the scope of the present invention without deviating from the spirit thereof. 
     For instance, the inkjet printer  1  is exemplified as an example of the liquid jet recording apparatus in the embodiments described above, but the present invention is not limited to the printer. For instance, the present invention can be applied to a facsimile or an on-demand printer. 
     In addition, in the embodiments described above, there is described the case where the actuator plate  41  having one polarization direction is used, and the drive electrode  37  is formed in the area extending to the middle portion in the height direction of the partition  36  so that the partition  36  can be bent and deformed. However, the polarization direction of the actuator plate may have two directions, i.e., the upward and the downward direction (so-called chevron type). In this case, the drive electrode may be formed on the entire surface of the side surface of the partition, and hence the partition is bent and deformed by the piezoelectric sliding effect in a V-shape with the center at the middle position in the height direction. Therefore, the partition can be deformed with a low voltage. 
     In addition, widths of the groove portion and the partition of the actuator plate, the pitch of the discharging channels, and the like can be modified in design appropriately if necessary. 
     In addition, the connecting portions of the first flexible circuit board  45   a  and the second flexible circuit board  45   b  at one end are shifted from each other in the width direction of the IC substrate  26  for connection in the embodiment described above. However, the flexible circuit boards having different lengths may be used so that the connecting portions thereof are shifted from each other in the length direction of the IC substrate  26  for connection.