Patent Publication Number: US-11040537-B2

Title: Head chip, liquid jet head and liquid jet recording device

Description:
RELATED APPLICATIONS 
     This application claims priority to Japanese Patent Application Nos. 2018-211471 filed on Nov. 9, 2018, the entire content of which is incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present disclosure relates to a head chip, a liquid jet head and a liquid jet recording device. 
     2. Description of the Related Art 
     As one of liquid jet recording devices, there is provided an inkjet type recording device for ejecting (jetting) ink (liquid) on a recording target medium such as recording paper to perform recording of images, characters, and so on (see, e.g., JP-A-2014-233875). 
     In the liquid jet recording device of this type, it is arranged so that the ink is supplied from an ink tank to an inkjet head (a liquid jet head), and then the ink is ejected from nozzle holes of the inkjet head toward the recording target medium to thereby perform recording of the images, the characters, and so on. Further, such an inkjet head is provided with a head chip for ejecting the ink. 
     In such a head chip or the like, it is desired to prevent, for example, occurrence of short circuit between electrodes different in potential to enhance the reliability. Therefore, it is desirable to provide a head chip, a liquid jet head, and a liquid jet recording device capable of enhancing the reliability. 
     SUMMARY OF THE INVENTION 
     A head chip according to an embodiment of the present disclosure is a head chip adapted to jet liquid including an actuator plate adapted to apply pressure to the liquid, wherein the actuator plate includes a first surface, and a second surface facing to an opposite side to the first surface, ejection channels and non-ejection channels which have an opening on at least one of the first surface and the second surface and are alternately arranged so as to be separated from each other, a common electrode disposed on a sidewall of the ejection channel, an individual electrode electrically separated from the common electrode and disposed on a sidewall of the non-ejection channel, a common electrode pad disposed on the first surface and adapted to electrically connect the common electrode and an external interconnection to each other, and a bypass interconnection adapted to electrically connect the individual electrodes in the non-ejection channels adjacent to each other to each other and failing to be exposed on the first surface. 
     A liquid jet head according to an embodiment of the present disclosure is a liquid jet head adapted to jet liquid including an actuator plate adapted to apply pressure to the liquid, and a wiring board, wherein the actuator plate includes a first surface, and a second surface facing to an opposite side to the first surface, ejection channels and non-ejection channels which have an opening on at least one of the first surface and the second surface and are alternately arranged so as to be separated from each other, a common electrode disposed on a sidewall of the ejection channel, an individual electrode electrically separated from the common electrode, and disposed on a sidewall of the non-ejection channel, a common electrode pad disposed on the first surface and adapted to electrically connect the common electrode and the wiring board to each other, and a bypass interconnection adapted to electrically connect the individual electrodes in the non-ejection channels adjacent to each other and failing to be exposed on the first surface. 
     A liquid jet recording device according to an embodiment of the disclosure is provided with the liquid jet head according to an embodiment of the disclosure, and a containing section adapted to contain the liquid. 
     According to the head chip, the liquid jet head and the liquid jet recording device related to an embodiment of the disclosure, it becomes possible to enhance the reliability. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic perspective view showing a schematic configuration example of a liquid jet recording device according to an embodiment of the present disclosure. 
         FIG. 2  is a schematic diagram showing a schematic configuration example of a liquid jet head and an ink circulation mechanism shown in  FIG. 1 . 
         FIG. 3  is an exploded perspective view of the liquid jet head shown in  FIG. 1 . 
         FIG. 4  is a cross-sectional view of the liquid jet head shown in  FIG. 1 . 
         FIG. 5  is another cross-sectional view of the liquid jet head shown in  FIG. 1 . 
         FIG. 6  is a cross-sectional view showing, in an enlarged manner, a cross-sectional surface perpendicular to an extending direction of an ejection channel in the liquid jet head shown in  FIG. 1 . 
         FIG. 7  is a partially broken perspective view showing, in an enlarged manner, a part of the liquid jet head chip shown in  FIG. 3 . 
         FIG. 8  is a perspective view showing, in an enlarged manner, a cover plate shown in  FIG. 3 . 
         FIG. 9A  is a cross-sectional view showing one process of a method of manufacturing the liquid jet head shown in  FIG. 1 . 
         FIG. 9B  is a cross-sectional view showing one process following the process shown in  FIG. 9A . 
         FIG. 9C  is a cross-sectional view showing one process following the process shown in  FIG. 9B . 
         FIG. 9D  is a cross-sectional view showing one process following the process shown in  FIG. 9C . 
         FIG. 9E  is a cross-sectional view showing one process following the process shown in  FIG. 9D . 
         FIG. 9F  is a cross-sectional view showing one process following the process shown in  FIG. 9E . 
         FIG. 9G  is a cross-sectional view showing one process following the process shown in  FIG. 9F . 
         FIG. 9H  is a cross-sectional view showing one process following the process shown in  FIG. 9G . 
         FIG. 9I  is a cross-sectional view showing one process following the process shown in  FIG. 9H . 
         FIG. 9J  is a cross-sectional view showing one process following the process shown in  FIG. 9I . 
         FIG. 10  is a plan view showing one process for forming the cover plate included in the method of manufacturing the liquid jet head shown in  FIG. 1 . 
         FIG. 11  is a cross-sectional view showing one process following the process shown in  FIG. 10 . 
         FIG. 12  is a plan view showing a process of manufacturing a flow channel plate included in the method of manufacturing the liquid jet head shown in  FIG. 1 . 
         FIG. 13  is a cross-sectional view of a liquid jet head according to Modified Example 1. 
         FIG. 14  is a cross-sectional view of a liquid jet head according to Modified Example 2. 
         FIG. 15  is a cross-sectional view of a liquid jet head according to Modified Example 3. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     An embodiment of the present disclosure will hereinafter be described in detail with reference to the drawings. It should be noted that the description will be presented in the following order: 
     1. Embodiment (an example of an edge-shoot type inkjet head in which a flow channel plate is disposed between a pair of head chips, and which performs ink circulation) 
     2. Modified Examples:
         Modified Example 1 (an example of an edge-shoot type inkjet head in which a flow channel plate is disposed between a pair of head chips, and which does not perform ink circulation)   Modified Example 2 (an example of an edge-shoot type inkjet head in which a head chip is disposed on one side of a flow channel plate, and which performs ink circulation)   Modified Example 3 (an example of an edge-shoot type inkjet head supplied with ink from outside of a pair of head chips)       

     3. Other Modified Examples 
     1. EMBODIMENT 
     [Overall Configuration of Printer  1 ] 
       FIG. 1  is a perspective view schematically showing a schematic configuration example of a printer  1  as a liquid jet recording device according to an embodiment of the present disclosure. The printer  1  is an inkjet printer for performing recording (printing) of images, characters, and the like on recording paper P as a recording target medium using ink. 
     As shown in  FIG. 1 , the printer  1  is provided with a pair of carrying mechanisms  2   a ,  2   b , ink tanks  3 , inkjet heads  4 , supply tubes  50 , a scanning mechanism  6 , and an ink circulation mechanism  8 . These members are housed in a housing  10  having a predetermined shape. It should be noted that the scale size of each of the members is accordingly altered so that the member is shown large enough to recognize in the drawings used in the description of the specification. 
     Here, the printer  1  corresponds to a specific example of the “liquid jet recording device” in the present disclosure, and the inkjet heads  4  (the inkjet heads  4 Y,  4 M,  4 C, and  4 K described later) each correspond to a specific example of the “liquid jet head” in the present disclosure. 
     The carrying mechanisms  2   a ,  2   b  are each a mechanism for carrying the recording paper P along the carrying direction d (an X-axis direction) as shown in  FIG. 1 . These carrying mechanisms  2   a ,  2   b  each have a grit roller  21 , a pinch roller  22  and a drive mechanism (not shown). The grit roller  21  and the pinch roller  22  are each disposed so as to extend along a Y-axis direction (the width direction of the recording paper P). The drive mechanism is a mechanism for rotating (rotating in a Z-X plane) the grit roller  21  around an axis, and is constituted by, for example, a motor. 
     (Ink Tanks  3 ) 
     The ink tanks  3  are each a tank for containing the ink inside. As the ink tanks  3 , there are disposed four types of tanks for individually containing the ink of four colors of yellow (Y), magenta (M), cyan (C), and black (K) in this example as shown in  FIG. 1 . In other words, there are disposed the ink tank  3 Y for containing the yellow ink, the ink tank  3 M for containing the magenta ink, the ink tank  3 C for containing the cyan ink, and the ink tank  3 K for containing the black ink. These ink tanks  3 Y,  3 M,  3 C, and  3 K are arranged side by side along the X-axis direction inside the housing  10 . 
     It should be noted that the ink tanks  3 Y,  3 M,  3 C, and  3 K have the same configuration except the color of the ink contained, and are therefore collectively referred to as ink tanks  3  in the following description. Here, the ink tanks  3  each correspond to a specific example of a “containing section” in the present disclosure. 
     (Inkjet Heads  4 ) 
     The inkjet heads  4  are each a head for jetting (ejecting) the ink having a droplet shape from a plurality of nozzles  78  described later to the recording paper P to thereby perform recording of images, characters, and so on. As the inkjet heads  4 , there are also disposed four types of heads for individually jetting the four colors of ink respectively contained in the ink tanks  3 Y,  3 M,  3 C, and  3 K described above in this example as shown in  FIG. 1 . In other words, there are disposed the inkjet head  4 Y for jetting the yellow ink, the inkjet head  4 M for jetting the magenta ink, the inkjet head  4 C for jetting the cyan ink, and the inkjet head  4 K for jetting the black ink. These inkjet heads  4 Y,  4 M,  4 C and  4 K are arranged side by side along the Y-axis direction inside the housing  10 . 
     It should be noted that the inkjet heads  4 Y,  4 M,  4 C, and  4 K have the same configuration except the color of the ink used, and are therefore collectively referred to as inkjet heads  4  in the following description. Further, the detailed configuration of the inkjet heads  4  will be described later (see  FIG. 2  and so on). 
     The supply tubes  50  are each a tube for supplying the ink from the inside of the ink tank  3  to the inside of the inkjet head  4 . 
     (Scanning Mechanism  6 ) 
     The scanning mechanism  6  is a mechanism for making the inkjet heads  4  perform a scanning operation along the width direction (the Y-axis direction) of the recording paper P. As shown in  FIG. 1 , the scanning mechanism  6  has a pair of guide rails  31 ,  32  disposed so as to extend along the Y-axis direction, a carriage  33  movably supported by these guide rails  31 ,  32 , and a drive mechanism  34  for moving the carriage  33  along the Y-axis direction. Further, the drive mechanism  34  has a pair of pulleys  35 ,  36  disposed between the guide rails  31 ,  32 , an endless belt  37  wound between the pair of pulleys  35 ,  36 , and a drive motor  38  for rotationally driving the pulley  35 . 
     The pulleys  35 ,  36  are respectively disposed in areas corresponding to the vicinities of both ends in each of the guide rails  31 ,  32  along the Y-axis direction. To the endless belt  37 , there is coupled the carriage  33 . The carriage  33  has a base  33   a  having a plate-like shape for mounting the four types of inkjet heads  4 Y,  4 M,  4 C, and  4 K described above, and a wall section  33   b  erected vertically (in the Z-axis direction) from the base  33   a . On the base  33   a , the inkjet heads  4 Y,  4 M,  4 C, and  4 K are arranged side by side along the Y-axis direction. 
     It should be noted that it is arranged that there is constituted a moving mechanism for moving the inkjet heads  4  and the recording paper P relatively to each other by such a scanning mechanism  6  and the carrying mechanisms  2   a ,  2   b  described above. 
     (Ink Circulation Mechanism  8 ) 
       FIG. 2  is a schematic diagram showing a schematic configuration example of the ink circulation mechanism  8 . The ink circulation mechanism  8  is a mechanism for circulating the ink between the ink tank  3  and the inkjet head  4 , and is provided with a circulation flow channel  83  constituted by an ink supply tube  81  and an ink discharge tube  82 , a pressure pump  84  provided to the ink supply tube  81 , and a suction pump  85  provided to the ink discharge tube  82 . The ink supply tube  81  and the ink discharge tube  82  are each formed of, for example, a flexible hose having flexibility to the extent of being capable of following the action of the scanning mechanism  6  for supporting the inkjet heads  4 . 
     The pressure pump  84  is for pressurizing the inside of the ink supply tube  81  to deliver the ink to the inkjet head  4  through the ink supply tube  81 . Due to the function of the pressure pump  84 , the inside of the ink supply tube  81  between the pressure pump  84  and the inkjet head  4  is provided with positive pressure with respect to the inkjet head  4 . 
     The suction pump  85  is for depressurizing the inside of the ink discharge tube  82  to suction the ink from the inkjet head  4  through the ink discharge tube  82 . Due to the function of the suction pump  85 , the inside of the ink discharge tube  82  between the suction pump  85  and the inkjet head  4  is provided with negative pressure with respect to the inkjet head  4 . It is arranged that the ink can circulate between the inkjet head  4  and the ink tank  3  through the circulation flow channel  83  by driving the pressure pump  84  and the suction pump  85 . It should be noted that the ink circulation mechanism  8  is not limited to the configuration described above, but can also be provided with other configurations. 
     [Detailed Configuration of Inkjet Head  4 ] 
     Then, the detailed configuration example of the inkjet head  4  will be described with reference to  FIG. 3  through  FIG. 8  in addition to  FIG. 1 .  FIG. 3  is a perspective view showing the detailed configuration example of the inkjet head  4 .  FIG. 4  is a cross-sectional view showing a configuration example of the Y-Z cross-sectional surface including ejection channels  54  (described later) of a head chip  40 A and dummy channels  55  (described later) of a head chip  40 B in the inkjet head  4 .  FIG. 5  is a cross-sectional view showing a configuration example of the Y-Z cross-sectional surface including the dummy channels  55  (described later) of the head chip  40 A and the ejection channels  54  (described later) of the head chip  40 B in the inkjet head  4 .  FIG. 6  is a cross-sectional view showing, in an enlarged manner, a cross-sectional surface (the X-Y cross-sectional surface) perpendicular to the extending direction (the Z-axis direction) of the ejection channels  54  and the dummy channels  55  in the inkjet head  4 .  FIG. 7  is a partially broken perspective view showing a part of the head chip  40  in an enlarged manner. 
     As shown in  FIG. 3  through  FIG. 5 , the inkjet head  4  is provided with the pair of head chips  40 A,  40 B, a flow channel plate  41 , an entrance manifold  42 , an exit manifold (not shown), a return plate  43 , a nozzle plate (jet plate)  44 , and a wiring board  45 . The inkjet head  4  is of a circulation type (an edge-shoot circulation type) for circulating the ink between the inkjet head  4  and the ink tank  3  out of so-called edge-shoot types for ejecting the ink from a tip part in the extending direction (the Z-axis direction) of the ejection channel  54 . 
     (Head Chips  40 A,  40 B) 
     The pair of head chips  40 A,  40 B have respective configurations substantially the same as each other, and are disposed at substantially symmetrical positions so as to have substantially symmetric postures across the flow channel plate  41  in the Y-axis direction. Hereinafter, the description will be presented collectively referring the pair of head chips  40 A,  40 B as head chips  40  unless the discrimination therebetween is particularly required. It should be noted that the head chip  40  corresponds to a specific example of a “head chip” in the present disclosure. The head chip  40  is provided with a cover plate  52 , an actuator plate  51 , and a sealing plate  53  in this order from a position near to the flow channel plate  41 . It should be noted that the sealing plate  53  corresponds to a specific example of a “sealing plate” in the present disclosure. 
     (Actuator Plate  51 ) 
     The actuator plate  51  is a plate-like member expanding along the X-Z plane having the X-axis direction as the longitudinal direction, and the Z-axis direction as the short-side direction, and has an obverse surface  51   f   1  opposed to the cover plate  52 , and a reverse surface  51   f   2  opposed to the sealing plate  53 . The obverse surface  51   f   1  and the reverse surface  51   f   2  face to respective sides opposite to each other. It should be noted that the “obverse surface  51   f   1 ” is a specific example corresponding to a “second surface” in the present disclosure, and the “reverse surface  51   f   2 ” is a specific example corresponding to a “first surface” in the present disclosure. As shown in  FIG. 7 , the reverse surface  51   f   2  includes an end part region R 1  and a channel forming region R 2 . The end part region R 1  is a part exposed outside without overlapping the sealing plate  53 , and the channel forming region R 2  is a part in which the ejection channels  54  and the dummy channels  55  are formed, and which overlaps the sealing plate  53 . The actuator plate  51  is a laminate substrate of a so-called chevron type obtained by stacking two piezoelectric substrates  51   a ,  51   b  having respective polarization directions different from each other in a thickness direction (the Y-axis direction) and connecting the obverse surface  51   f   1  and the reverse surface  51   f   2  to each other (see  FIG. 6 ). As those piezoelectric substrates  51   a ,  51   b , there are preferably used ceramics substrates formed of a piezoelectric material such as PZT (lead zirconate titanate). 
     The actuator plate  51  has the plurality of ejection channels  54  and the plurality of dummy channels  55  penetrating in the thickness direction (the Y-axis direction). In other words, the plurality of ejection channels  54  and the plurality of dummy channels  55  have openings on the obverse surface  51   f   1  and the reverse surface  51   f   2 . The plurality of ejection channels  54  and the plurality of dummy channels  55  are each disposed so as to linearly extend in the Z-axis direction. The ejection channels  54  and the dummy channels  55  are alternately disposed so as to be separated from each other in the X-axis direction. The discharge channels  54  and the dummy channels  55  are separated by drive walls  56 , respectively. Therefore, the actuator plate  51  has a structure in which channels each having a slit-like shape are arranged in a cross-sectional surface (the X-Y cross-sectional surface) perpendicular to the Z-axis direction (see  FIG. 6 ). It should be noted that the “ejection channels  54 ” and the “dummy channels  55 ” are specific examples corresponding to “ejection channels” and “non-ejection channels” in the present disclosure, respectively, and the “drive wall  56 ” is a specific example corresponding to a “sidewall” in the present disclosure. 
     The ejection channels  54  are each a part functioning as a pressure chamber for applying pressure to the ink, and each have a pair of inner surfaces  541  (the drive walls  56 ) opposed to each other in the X-axis direction. The pair of inner surfaces  541  are each a plane parallel to the Y-Z plane, for example. A lower end part of each of the ejection channels  54  is disposed so as to extend to a lower end surface  511  (a surface opposed to the return plate  43 ) of the actuator plate  51  as shown in  FIG. 7  to form an opening  54 K opposed to the return plate  43 . The opening  54 K is an ejection end from which the ink is ejected. In contrast, an upper end part of each of the ejection channels  54  terminates within the actuator plate  51  without reaching an upper end surface (a surface on an opposite side to the return plate  43 )  512  of the actuator plate  51 . In other words, the vicinity of the upper end part of each of the ejection channels  54  forms a closed end located between the lower end surface  511  and the upper end surface  512 , and including a tilted surface  54   b , and is formed so that the depth (the dimension in the Y-axis direction) gradually decreases in a direction toward the upper end surface  512 . Therefore, a distance L 1  from a crossing position between the tilted surface  54   b  and the reverse surface  51   f   2  to the lower end surface  511  as an ejection end is shorter than a second distance L 2  from a crossing position between the tilted surface  54   b  and the obverse surface  51   f   1  to the lower end surface  511  (see  FIG. 4 ). 
     The inner surfaces  541  of the ejection channel  54  each include a part covered with a common electrode  61  continuously from the obverse surface  51   f   1  to the reverse surface  51   f   2 . It should be noted that it is also possible for the common electrode  61  to cover only a part of the inner surface  541  of the ejection channel  54 . However, even in that case, it is preferable for the common electrode  61  to cover the inner surface  541  continuously from the obverse surface  51   f   1  to the reverse surface  51   f   2  in the Y-axis direction. The common electrode  61  is connected to a common electrode pad  62 . The common electrode pad  62  is formed so as to cover a part of the peripheral part of the upper end part of the ejection channel  54  in the reverse surface  51   f   2 . The common electrode pad  62  is disposed so as to extend from the peripheral part to the end part region R 1  of the ejection channel  54  in the reverse surface  51   f   2  ( FIG. 7 ). To the common electrode pad  62 , there is coupled the wiring board  45 . In other words, it is arranged that the drive voltage is applied from the wiring board  45  to the common electrode  61  via the common electrode pad  62 . It should be noted that the common electrode  61  is a specific example corresponding to a “common electrode” in the present disclosure, and the common electrode pad  62  is a specific example corresponding to a “common electrode pad” in the present disclosure. 
     The ejection channels  54  are filled with the ink, while it is arranged that the dummy channels  55  are not filled with the ink. As shown in  FIG. 3 , an upper end part of the dummy channel  55  opens in the upper end surface  512 , and a lower end part of the dummy channel  55  opens in the lower end surface  511 . 
     As shown in  FIG. 6 , the dummy channels  55  each have a pair of inner surfaces  551  (the drive walls  56 ) opposed to each other in the X-axis direction. The pair of inner surfaces  551  are each a plane parallel to the Y-Z plane, for example. The pair of inner surfaces  551  each include a part covered with an individual electrode  63  continuously from the obverse surface  51   f   1  to the reverse surface  51   f   2 . It should be noted that the individual electrode  63  can also be an electrode covering only a part of the inner surface  551  of the dummy channel  55 . Further, the pair of individual electrodes  63  for respectively covering the pair of drive walls  56  in the dummy channel  55  are isolated from each other. The individual electrodes  63  are coupled to individual electrode pads  64  each covering a part of the end part region R 1  of the reverse surface  51   f   2 . It should be noted that in the present embodiment, the individual electrode pads  64  are each disposed so as to extend in a part located above the common electrode pad  62  out of the peripheral part ( FIG. 7 ). The individual electrode pads  64  each couple a pair of individual electrodes  63  adjacent to each other across the ejection channel  54 . Here, the individual electrodes  63  and the individual electrode pad  64  are electrically isolated from the common electrodes  61  and the common electrode pad  62 . To the individual electrode pad  64 , there is coupled the wiring board  45 . In other words, it is arranged that the drive voltage is applied from the wiring board  45  to the pair of individual electrodes  63  via the individual electrode pad  64 . It should be noted that the individual electrode  63  is a specific example corresponding to an “individual electrode” in the present disclosure, and the individual electrode pad  64  is a specific example corresponding to an “individual electrode pad” in the present disclosure. 
     In the present embodiment, in order to couple the pair of individual electrodes  63  adjacent to each other across the ejection channel  54  to each other, the actuator plate  51  is provided with a bypass electrode  64 B in addition to the individual electrode pad  64 . The bypass electrode  64 B is disposed so as to be separated from the individual electrode pad  64 . In other words, the bypass electrode  64 B is disposed at a different position from the individual electrode pad  64 . Although the details will be described later, according to this configuration, even if the individual electrode pad  64  is broken, the pair of individual electrodes  63  are electrically coupled to each other. 
     The bypass electrode  64 B is disposed inside a bypass groove G provided to the obverse surface  51   f   1 , for example. It is sufficient for the bypass electrode  64 B to be disposed at a position not exposed on the reverse surface  51   f   2  on which the common electrode pad  62  is disposed. For example, it is also possible to arrange that the bypass electrode  64 B is disposed on the obverse surface  51   f   1  without disposing the bypass groove G. Alternatively, it is also possible to dispose a tunnel-like hole extending in the X-axis direction between the reverse surface  51   f   2  and the obverse surface  51   f   1 , and then dispose the bypass electrode  64 B in this hole. Although the details will be described later, by disposing the bypass electrode  64 B at the position not exposed on the reverse surface  51   f   2  as described above, occurrence of the short circuit between the wiring board  45  coupled to the common electrode pad  62  and the bypass electrode  64 B can be prevented. 
     The bypass groove G where the bypass electrode  64 B is disposed is disposed in the end part region R 1  of the obverse surface  51   f   1 , and extends in a direction (e.g., the X-axis direction shown in  FIG. 7 ) in which the ejection channels  54  and the dummy channels  55  are arranged. For example, the actuator plate  51  is provided with the single bypass groove G, and the bypass groove G is communicated with all of the dummy channels  55 . It is also possible for the bypass grooves G to be disposed so as to be separated from each other so as to connect the pair of dummy channels  55  adjacent to each other across the ejection channel  54 . The bypass groove G is disposed at a position closer to the channel forming region R 2  than, for example, a position opposed to the individual electrode pad  64  of the reverse surface  51   f   2 . For example, the bypass groove G is disposed at a position opposed to the vicinity of the upper end part of the common electrode pad  62  of the reverse surface  51   f   2 . It is sufficient for the depth (the size in the Y-axis direction) of the bypass groove G to be a level capable of housing the bypass electrode  64 B. 
     The bypass electrode  64 B disposed inside the bypass groove G is coupled to the pair of individual electrodes  63  adjacent to each other across the ejection channel  64 . Inside the bypass groove G, there are disposed two or more bypass electrodes  64 B so as to be separated from each other. The width (the size in the Z-axis direction) of the bypass electrode  64 B is made smaller than, for example, the width of the bypass groove G. The width of the bypass electrode  64 B can also be roughly equal to the width of the bypass groove G. Alternatively, it is also possible for the bypass electrode  64 B to be disposed throughout an area from a bottom surface to a side surface of the bypass groove G. The bypass electrode  64 B is formed of, for example, the same material as the constituent material of the common electrodes  61  and the individual electrodes  63 . 
     (Cover Plate  52 ) 
     The cover plate  52  is a plate-like member having the X-axis direction as the longitudinal direction and the Z-axis direction as the short-side direction, and extending along the X-Z plane. The cover plate  52  has an opposed surface  52   f   1  opposed to the obverse surface  51   f   1  of the actuator plate  51 . 
       FIG. 8  is a perspective view of the cover plate  52  viewed from the flow channel plate  41  side. The cover plate  52  is provided with a liquid supply channel  70  penetrating the cover plate  52  in the Y-axis direction (the thickness direction), and at the same time communicated with the ejection channels  54 . The liquid supply channel  70  is a specific example corresponding to a “liquid flow hole” in the present disclosure. The liquid supply channel  70  includes a common ink chamber  71  opening on the flow channel plate  41  side in the Y-axis direction, and a plurality of slits  72  each communicated with the common ink chamber  71 , and at the same time opening on the actuator plate  51  side in the Y-axis direction. The plurality of slits  72  is disposed at positions corresponding to the plurality of ejection channels  54 . The common ink chamber  71  is disposed commonly to the plurality of slits  72 , and is communicated with the ejection channels  54  through the plurality of slits  72 . The common ink chamber  71  is not communicated with the dummy channels  55 . 
     The common ink chamber  71  is provided to an opposed surface  52   f   2  opposed to the flow channel plate  41  in the cover plate  52 . The common ink chamber  71  is disposed at substantially the same position as the tilted surfaces  54   b  of the ejection channels  54  in the Z-axis direction. The common ink chamber  71  is formed to have a groove-like shape recessed toward the opposed surface  52   f   1 , and at the same time extending in the X-axis direction. It is arranged that the ink inflows into the common ink chamber  71  through the flow channel plate  41 . 
     The plurality of slits  72  is provided to the opposed surface  52   f   1  opposed to the actuator plate  51 . The plurality of slits  72  is arranged at positions each overlapping a part of the common ink chamber  71  in the Y-axis direction. The plurality of slits  72  is communicated with the common ink chamber  71  and the plurality of ejection channels  54 . It is desirable for the width in the X-axis direction of each of the slits  72  to substantially the same as the width in the X-axis direction of each of the ejection channels  54 . 
     It should be noted that it is preferable for the cover plate  52  to be formed of a material having an insulating property, and having thermal conductivity equal to or higher than the thermal conductivity of a material constituting the actuator plate  51 . For example, in the case of forming the actuator plate  51  with PZT, it is preferable for the cover plate  52  to be formed of PZT or silicon. This is because thus the difference between the temperature of the cover plate  52  of the head chip  40 A and the temperature of the cover plate  52  of the head chip  40 B is reduced, and it is possible to achieve the homogenization of the ink temperature inside the inkjet head  4 . As a result, the variation in ejection speed of the ink is reduced, and the printing stability is improved. 
     (Sealing Plate  53 ) 
     The sealing plate  53  is a plate-like member having the X-axis direction as the longitudinal direction and the Z-axis direction as the short-side direction, and extending along the X-Z plane similarly to the cover plate  52 . The sealing plate  53  has a lower end surface  531  coinciding with the lower end surface  511  of the actuator plate  51  and a lower end surface  521  of the cover plate  52  in the Z-axis direction, and an upper end surface  532  located on an opposite side to the lower end surface  531  in the Z-axis direction. The upper end surface  532  is located at a position retracting from the upper end surface  512  and an upper end surface  522  in the Z-axis direction. The sealing plate  53  further has an opposed surface  53   f   1  opposed to the reverse surface  51   f   2  of the actuator plate  51 . The sealing plate  53  is disposed so that the opposed surface  53   f   1  faces the channel forming region R 2  out of the reverse surface  51   f   2  of the actuator plate  51 . Therefore, it is arranged that the plurality of ejection channels  54  and the plurality of dummy channels  55  are closed by the sealing plate  53  and the cover plate  52 . The sealing plate  53  is not required to have an opening, a cutout, a groove, or the like. In other words, since it is sufficient for the sealing plate  53  to be a simple rectangular solid, it is possible to use a functional material difficult to fabricate, or a low-price material difficult to obtain high processing accuracy as the constituent material thereof. Therefore, the degree of freedom of selection of a material type is enhanced. 
     It is preferable for the sealing plate  53  to be formed of a material high in thermal conductivity. The sealing plate  53  is formed of, for example, PZT or silicon. When the sealing plate  53  formed of the material high in thermal conductivity is bonded to the reverse surface  51   f   2  of the actuator plate  51 , unevenness of the heat in the actuator plate  51  caused when driving decreases. Thus, the difference between the temperature of the actuator plate  51  of the head chip  40 A and the temperature of the actuator plate  51  of the head chip  40 B is reduced, and it is possible to achieve the homogenization of the ink temperature inside the inkjet head  4 . As a result, the variation in ejection speed of the ink is reduced, and the printing stability is improved. 
     (Arrangement Relationship Between Pair of Head Chips  40 A,  40 B) 
     As shown in  FIG. 3 , the pair of head chips  40 A,  40 B are disposed across the flow channel plate  41  in the Y-axis direction in the state in which the respective opposed surfaces  52   f   2  are opposed to each other in the Y-axis direction. 
     The ejection channels  54  and the dummy channels  55  of the head chip  40 B are arranged so as to be shifted as much as a half pitch in the X-axis direction with respect to the arrangement pitch of the ejection channels  54  and the dummy channels  55  of the head chip  40 A. In other words, the ejection channels  54  and the dummy channels  55  of the head chip  40 A and the ejection channels  54  and the dummy channels  55  of the head chip  40 B are arranged in a zigzag manner. 
     Therefore, as shown in  FIG. 4 , the ejection channels  54  of the head chip  40 A and the dummy channels  55  of the head chip  40 B are opposed to each other in the Y-axis direction. Similarly, as shown in  FIG. 5 , the dummy channels  55  of the head chip  40 A and the ejection channels  54  of the head chip  40 B are opposed to each other in the Y-axis direction. It should be noted that the pitch of the ejection channels  54  and the dummy channels  55  in each of the head chips  40 A,  40 B can arbitrarily be changed. 
     (Flow Channel Plate  41 ) 
     The flow channel plate  41  is sandwiched between the head chip  40 A and the head chip  40 B in the Y-axis direction. It is preferable for the flow channel plate  41  to be integrally formed of the same member. As shown in  FIG. 3 , the flow channel plate  41  has a rectangular plate-like shape having the X-axis direction as the longitudinal direction, and the Y-axis direction as the short-side direction. When viewed from the Y-axis direction, the outer shape of the flow channel plate  41  is substantially the same as the outer shape of the cover plate  52 . 
     To a principal surface  41   f   1  (a surface facing the head chip  40 A) in the Y-axis direction of the flow channel plate  41 , there is bonded the opposed surface  52   f   2  in the head chip  40 A. To a principal surface  41   f   2  (a surface facing the head chip  40 B) in the Y-axis direction of the flow channel plate  41 , there is bonded the opposed surface  52   f   2  in the head chip  40 B. 
     As shown in  FIG. 4  and  FIG. 5 , to the principal surfaces  41   f   1 ,  41   f   2  of the flow channel plate  41 , there are respectively provided entrance flow channels  74  individually communicated with the common ink chamber  71 , and exit flow channels  75  individually communicated with circulation channels  76  of the return plate  43 . It should be noted that the entrance flow channel  74  corresponds to a specific example of a “liquid supply flow channel” in the present disclosure, and the exit flow channel  75  corresponds to a specific example of a “liquid discharge flow channel” in the present disclosure. 
     As shown in  FIG. 3 , the exit flow channel  75  is recessed from each of the principal surfaces  41   f   1 ,  41   f   2  of the flow channel plate  41  inward in the Y-axis direction, and at the same time, recessed from the lower end surface  411  of the flow channel plate  41  toward the upper end surface  412 . One end part of each of the exit flow channels  75  opens in the other end surface in the X-axis direction of the flow channel plate  41 . Each of the exit flow channels  75  bends downward from the other end surface in the X-axis direction of the flow channel plate  41  so as to have a crank-like shape, and then extends linearly toward the one end side in the X-axis direction. It is preferable for the width in the Z-axis direction of the exit flow channel  75  to be smaller than the width in the Z-axis direction of the entrance flow channel  74  as shown in  FIG. 4 . Further, the depth in the Y-axis direction of the exit flow channel  75  is substantially the same as the depth in the Y-axis direction of the entrance flow channel  74 . The exit flow channels  75  are coupled to an exit manifold (not shown) on the other end surface in the X-axis direction of the flow channel plate  41 . The exit manifold is coupled to the ink discharge tube  82  (see  FIG. 1 ). 
     (Entrance Manifold  42 ) 
     As shown in  FIG. 3 , the entrance manifold  42  is bonded to one end surfaces in the X-axis direction of the head chips  40 A,  40 B and the flow channel plate  41 . The entrance manifold  42  is provided with a supply channel  77  communicated with the pair of entrance flow channels  74 . An end part on the opposite side to the flow channel plate  41  in the supply channel  77  is coupled to the ink supply tube  81  (see  FIG. 1 ). 
     (Return Plate  43 ) 
     The return plate  43  has a rectangular plate-like shape having the X-axis direction as the longitudinal direction, and the Y-axis direction as the short-side direction. The return plate  43  is collectively bonded to the lower end surfaces  511 ,  521 , and  531  of the head chips  40 A,  40 B and the lower end surface  411  of the flow channel plate  41 . In other words, the return plate  43  is disposed on the opening  54 K side of each of the ejection channels  54  in the head chip  40 A and the head chip  40 B. The return plate  43  is a spacer plate intervening between the openings  54 K of the ejection channels  54  in the head chip  40 A and the head chip  40 B, and an upper surface of the nozzle plate  44 . The return plate  43  is provided with a plurality of circulation channels  76  for coupling the ejection channels  54  of the head chips  40 A,  40 B and the exit flow channels  75  to each other. The plurality of circulation channels  76  includes first circulation channels  76   a  and second circulation channels  76   b . The plurality of circulation channels  76  penetrates the return plate  43  in the Z-axis direction. 
     (Nozzle Plate  44 ) 
     As shown in  FIG. 3 , an outer shape of the nozzle plate  44  has a rectangular plate-like shape having the X-axis direction as the longitudinal direction, and the Y-axis direction as the short-side direction. The nozzle plate  44  is bonded to a lower end surface of the return plate  43 . In the nozzle plate  44 , there are arranged a plurality of nozzles  78  (jet holes) penetrating the nozzle plate  44  in the Z-axis direction. The plurality of nozzles  78  includes first nozzles  78   a  and second nozzles  78   b . The plurality of nozzles  78  penetrates the nozzle plate  44  in the Z-axis direction. 
     As shown in  FIG. 4 , in the nozzle plate  44 , the first nozzles  78   a  are each formed in a part opposed in the Z-axis direction to the first circulation channel  76   a  of the return plate  43 . In other words, the first nozzles  78   a  are arranged on a straight line at intervals in the X-axis direction at the same pitch as that of the first circulation channels  76   a . The first nozzles  78   a  are each communicated with the first circulation channel  76   a  in an outer end part in the Y-axis direction in the first circulation channel  76   a . Thus, the first nozzles  78   a  are communicated with the corresponding ejection channels  54  of the head chip  40 A via the first circulation channels  76   a , respectively. 
     As shown in  FIG. 5 , in the nozzle plate  44 , the second nozzles  78   b  are each formed in a part opposed in the Z-axis direction to the second circulation channel  76   b  of the return plate  43 . In other words, the second nozzles  78   b  are arranged on a straight line at intervals in the X-axis direction at the same pitch as that of the second circulation channels  76   b . The second nozzles  78   b  are each communicated with the second circulation channel  76   b  in an outer end part in the Y-axis direction in the second circulation channel  76   b . Thus, the second nozzles  78   b  are communicated with the corresponding ejection channels  54  of the head chip  40 B via the second circulation channels  76   b , respectively. The dummy channels  55  are not communicated with the first nozzles  78   a  and the second nozzles  78   b , and are covered with the return plate  43  from below. 
     (Wiring Board  45 ) 
     The wiring board  45  electrically connects each of the common electrode pads  62  and the individual electrode pads  64  to a drive circuit. The wiring board  45  is provided with, for example, a plurality of extraction electrodes respectively connected to the plurality of common electrode pads  62 , and a plurality of extraction electrodes respectively connected to the plurality of individual electrode pads  64 . The drive circuit is formed of, for example, an integrated circuit (IC). The integrated circuit can also be mounted on the wiring board  45 . It should be noted that the “wiring board  45 ” is a specific example corresponding to a “wiring board” or an “external interconnection” in the present disclosure. 
     [Method of Manufacturing Inkjet Head  4 ] 
     Then, a method of manufacturing the inkjet head  4  will be described. The method of manufacturing the inkjet head  4  according to the present embodiment includes a head chip manufacturing process, a flow channel manufacturing process, a plate bonding process, and a return plate and so on-bonding process. It should be noted that the head chip manufacturing process can be performed by substantially the same methods for the head chip  40 A and the head chip  40 B. Therefore, in the following description, the head chip manufacturing process in the head chip  40 A will be described. 
     (Head Chip Manufacturing Process) 
     The head chip manufacturing process in the method of manufacturing the inkjet head  4  according to the present embodiment mainly includes a process related to the actuator plate  51 , and a process related to the cover plate  52 . Among these processes, the process related to the actuator plate  51  includes, for example, a wafer preparation process, a mask pattern formation process, a channel formation process, and an electrode formation process. Hereinafter, with reference to  FIG. 9A  through  FIG. 9J , the process related mainly to the actuator plate  51  will be described. 
     In the wafer preparation process, two piezoelectric wafers  51   a Z,  51   b Z on which the polarization treatment has been performed in the thickness direction (the Y-axis direction) are prepared, and are stacked on one another so that the polarization directions thereof become opposite to each other as shown in  FIG. 9A . Subsequently, grinding work is performed on the piezoelectric wafer  51   a Z as needed to adjust the thickness of the piezoelectric wafer  51   a Z. The obverse surface of the piezoelectric wafer  51   a Z on this occasion becomes the obverse surface  51   f   1 . Thus, the actuator wafer  51 Z is formed. 
     Due to the subsequent mask pattern formation process, as shown in  FIG. 9B , a resist pattern RP 1  to be used as a mask when forming the common electrodes  61  and so on is formed on the obverse surface  51   f   1  of the actuator wafer  51 Z described above. It is also possible for the resist pattern RP 1  to have a plurality of openings corresponding to the plurality of ejection channels  54  and the plurality of dummy channels  55  at predetermined positions where the plurality of ejection channels  54  and the plurality of dummy channels  55  are to be formed. It should be noted that the resist pattern RP 1  can be formed of dry resist, or can also be formed of wet resist. 
     In the subsequent channel formation process, cutting work is performed from the obverse surface  51   f   1  of the actuator wafer  51 Z described above with a dicing blade not shown or the like. Specifically, by digging down an exposed part which is not covered with the resist pattern RP 1  out of the actuator wafer  51 Z, a plurality of trenches  54 U and a plurality of trenches  55 U are formed so as to be arranged in parallel to each other at intervals in the X-axis direction, and at the same time arranged alternately (see  FIG. 9B ). It should be noted that the trenches  54 U and the trenches  55 U are parts which turn to the ejection channels  54  and the dummy channels  55  later, respectively. 
     For example, it is possible to provide the bypass groove G to the obverse surface  51   f   1  in the same process as the channel formation process. For example, in the resist pattern RP 1 , an opening is disposed in advance at a predetermined position where the bypass groove G is to be formed. Subsequently, the opening part is cut by a dicing blade or the like. Thus, it is possible to form the bypass groove G (not shown in  FIG. 9B ) in the same process as the process of forming the plurality of trenches  54 U and the plurality of trenches  55 U. 
     In the subsequent first electrode formation process, metal coatings MF 1  are formed with, for example, an evaporation method so as to cover inner surfaces  541 U of the plurality of trenches  54 U, inner surfaces  551 U of the plurality of trenches  55 U, and the resist pattern RP 1  as shown in  FIG. 9C . On this occasion, for example, the metal coating MF 1  is also formed in the bypass groove G (not shown in  FIG. 9C ). Thus, the bypass electrodes  64 B are formed. In the first electrode formation process, it is preferable to perform oblique vapor deposition for making the constituent material of the metal coating MF 1  adhere to the inner surfaces  541 U,  551 U from an oblique direction to thereby cover the inner surfaces  541 U of each of the trenches  54 U and the inner surfaces  551 U of each of the trenches  55 U to positions as deep as possible in the Y-axis direction. It should be noted that it is also possible to perform a descumming treatment for removing residues such as the resist adhering to the inner surfaces  541 U of each of the trenches  54 U and the inner surfaces  551 U of each of the trenches  55 U as needed in an anterior stage to the formation of the metal coatings MF 1 . 
     Subsequently, the resist pattern RP 1  is removed to thereby expose the obverse surface  51   f   1  of the actuator wafer  51 Z, and then, the cover plate  52  is bonded so that the opposed surface  52   f   1  overlaps the obverse surface  51   f   1  as shown in  FIG. 9D . On that occasion, the opposed surface  52   f   1  of the cover plate  52  is bonded to the obverse surface  51   f   1  so that the liquid supply channel  70  is opposed to the trenches  54 U. Here, by removing the resist pattern RP 1 , there remain only the parts covering the inner surfaces  541 U of the trenches  54 U and the inner surfaces  551 U of the trenches  55 U out of the metal coatings MF 1 . 
     Then, as shown in  FIG. 9E , the grinding work is performed on the piezoelectric wafer  51   b Z from a reverse surface (a surface on the opposite side to the piezoelectric wafer  51   a Z) to adjust the thickness of the piezoelectric wafer  51   b Z. On that occasion, the plurality of trenches  54 U and the plurality of trenches  55 U are exposed, and thus, the plurality of ejection channels  54  and the plurality of dummy channels  55  are formed. The reverse surface of the piezoelectric wafer  51   b Z on this occasion becomes the reverse surface  51   f   2 . Thus, a so-called chevron type actuator plate  51  is formed. 
     In the subsequent second electrode formation process, metal coatings MF 2  covering the inner surfaces of the plurality of ejection channels  54  and the inner surfaces of the plurality of dummy channels  55  are formed with, for example, an evaporation method as shown in  FIG. 9F . On this occasion, it is preferable to make the metal coating MF 2  have contact with the metal coating MF 1 , or make a part of the metal coating MF 2  overlap a part of the metal coating MF 1 . 
     Then, as shown in  FIG. 9G , the part of the metal coating MF 2  covering the second surface  51   f   2  is removed to thereby expose the reverse surface  51   f   2 , and then, a resist pattern RP 2  is selectively formed on the reverse surface  51   f   2 . Here, by selectively removing the part covering the reverse surface  51   f   2  out of the metal coatings MF 2 , there remain only the parts covering the inner surfaces  541  of the ejection channels  54  and the inner surfaces  551  of the dummy channels  55  out of the metal coatings MF 2 . As a result, the common electrode  61  including the metal coatings MF 1 , MF 2  is formed on each of the inner surfaces  541  of the ejection channels  54 , and the individual electrode  63  including the metal coatings MF 1 , MF 2  is formed on each of the inner surfaces  551  of the dummy channels  55 . 
     Subsequently, as shown in  FIG. 9H , metal coatings MF 3  are formed using, for example, an evaporation method so as to cover the reverse surface  51   f   2  and the resist pattern RP 2  as the third electrode formation process. On this occasion, it is preferable to make the metal coating MF 3  have contact with the common electrode  61  and the individual electrode  63 , or make a part of the metal coating MF 3  overlap a part of the common electrode  61  and the individual electrode  63 . 
     Then, as shown in  FIG. 9I , by removing the resist pattern RP 2 , some parts of the metal coatings MF 3  remain on the reverse surface  51   f   2  to form the common electrode pads  62  and the individual electrode pads  64 . 
     Lastly, as shown in  FIG. 9J , by bonding the opposed surface  53   f   1  of the sealing plate  53  to the reverse surface  51   f   2 , the actuator plate  51  and the sealing plate  53  are bonded to each other. According to the above, manufacturing of the head chip  40 A is completed. The head chip  40 B can also be manufactured in a similar manner. 
     Here, the process related to the cover plate  52  will be described with reference mainly to  FIG. 10  and  FIG. 11 .  FIG. 10  is a plan view showing a formation process of the common ink chamber  71 , and  FIG. 11  is a cross-sectional view showing a formation process of the slits  72  following the process shown in  FIG. 10 . It should be noted that  FIG. 11  shows a cross-sectional surface in the arrow direction along the cutting line XI-XI shown in  FIG. 10 . 
     As shown in  FIG. 10 , in the formation process of the common ink chamber  71 , firstly, sandblasting or the like is performed on a cover wafer  120  prepared from the obverse surface side through a mask not shown to form the common ink chamber  71 . Subsequently, as shown in  FIG. 11 , in the slit formation process, sandblasting or the like is performed on the cover wafer  120  from the reverse surface side through a mask not shown to form the slits  72  individually communicated with the common ink chamber  71 . It should be noted that each of the formation process of the common ink chamber  71  and the formation process of the slits  72  is not limited to sandblasting, but can also be performed using dicing, cutting, or the like. Lastly, the cover wafer  120  is segmentalized along the dashed-dotted lines extending in the X-axis direction shown in  FIG. 10 . Thus, the cover plate  52  is completed. 
     (Flow Channel Plate Manufacturing Process) 
     The flow channel manufacturing process in the method of manufacturing the inkjet head  4  according to the present embodiment includes a flow channel formation process and a segmentalizing process. 
       FIG. 12  is a plan view showing the flow channel plate manufacturing process. As shown in  FIG. 12 , in the flow channel formation process, firstly, sandblasting or the like is performed on a flow channel wafer  130  from the obverse surface side through a mask not shown to form each of the entrance flow channels  74  on the obverse surface side and the exit flow channels  75  on the obverse surface side. 
     In addition, in the flow channel formation process, sandblasting or the like is performed on the flow channel wafer  130  from the reverse surface side through a mask not shown to form the entrance flow channels  74  on the reverse surface side and the exit flow channels  75  on the reverse surface side. It should be noted that each process in the flow channel formation process is not limited to sandblasting, but can also be performed using dicing, cutting, or the like. 
     In the segmentalizing process following the flow channel formation process, the flow channel wafer  130  is segmentalized along the axis lines (the imaginary lines D shown in  FIG. 13 ) of straight line parts in the X-axis direction in the exit flow channels  75  using a dicer or the like. Thus, the flow channel plate  41  (see  FIG. 3 ) is completed. 
     (Various-Plate Bonding Process) 
     As shown in  FIG. 3 , in the various-plate bonding process, each of the cover plate  52  of the head chip  40 A and the cover plate  52  of the head chip  40 B is bonded to the flow channel plate  41 . Specifically, the principal surface  41   f   1  of the flow channel plate  41  is bonded to the opposed surface  52   f   2  of the head chip  40 A, and at the same time, the principal surface  41   f   2  of the flow channel plate  41  is bonded to the opposed surface  52   f   2  of the head chip  40 B. Thus, a plate bonded body is manufactured. It should be noted that it is also possible to arrange that the plate bonded body obtained by sequentially bonding the cover plate  52  of the head chip  40 A and the cover plate  52  of the head chip  40 B to each other is manufactured by bonding one cover wafer  120  to each of the both surfaces of the flow channel wafer  130 , and then performing chip separation (segmentalization). 
     (Return Plate and so On-Bonding Process) 
     Subsequently, the return plate  43  and the nozzle plate  44  are bonded to the plate bonded body described above. Subsequently, the wiring board  45  is mounted on the common electrode pads  62  and the individual electrode pads  64  (see  FIG. 4 ,  FIG. 5 ). 
     According to the above, the inkjet head  4  according to the present embodiment is completed. 
     [Operations and Functions/Advantages] 
     (A. Basic Operation of Printer  1 ) 
     In the printer  1 , the recording operation (a printing operation) of images, characters, and so on to the recording paper P is performed in the following manner. It should be noted that as an initial state, it is assumed that the four types of ink tanks  3  ( 3 Y,  3 M,  3 C, and  3 K) shown in  FIG. 1  are sufficiently filled with the ink of the corresponding colors (the four colors), respectively. Further, there is achieved the state in which the inkjet heads  4  are filled with the ink in the ink tanks  3  via the ink circulation mechanism  8 , respectively. More specifically, there is achieved the state in which a predetermined amount of ink is supplied to the head chips  40  via the ink supply tube  81  and the flow channel plate  41  to fill the ejection channels  54  via the liquid supply channels  70 . 
     In such an initial state, when operating the printer  1 , the grit rollers  21  in the carrying mechanisms  2   a ,  2   b  each rotate to thereby carry the recording paper P along the carrying direction d (the X-axis direction) while being held between the grit rollers  21  and the pinch rollers  22 . Further, at the same time as such a carrying operation, the drive motor  38  in the drive mechanism  34  rotates each of the pulleys  35 ,  36  to thereby operate the endless belt  37 . Thus, the carriage  33  reciprocates along the width direction (the Y-axis direction) of the recording paper P while being guided by the guide rails  31 ,  32 . Then, on this occasion, the four colors of ink are appropriately ejected on the recording paper P by the respective inkjet heads  4  ( 4 Y,  4 M,  4 C, and  4 K) to thereby perform the recording operation of images, characters, and so on to the recording paper P. 
     (B. Detailed Operation in Inkjet Head  4 ) 
     Then, the detailed operation (the jet operation of the ink) in the inkjet head  4  will be described with reference to  FIG. 1  through  FIG. 8 . Specifically, in the inkjet head  4  (edge-shoot type) according to the present embodiment, the jet operation of the ink using a shear mode is performed in the following manner. It should be noted that the following jet operation is performed by a drive circuit (not shown) mounted on the inkjet head  4 . 
     In such an inkjet head  4  which is the edge-shoot type, and is the circulation type as in the present embodiment, firstly, the pressure pump  84  and the suction pump  85  shown in  FIG. 2  are operated to thereby make the ink flow through the circulation flow channel  83 . On this occasion, the ink flowing through the ink supply tube  81  passes through the supply channel  77  of the entrance manifold  42  shown in  FIG. 3 , and inflows into the entrance flow channels  74  of the flow channel plate  41 . The ink having flowed into the entrance flow channels  74  passes through the common ink chambers  71 , and is then supplied to the ejection channels  54  through the slits  72 . The ink having flowed into the ejection channels  54  reaggregates in the exit flow channels  75  via the circulation channels  76  of the return plate  43 , then passes through the exit manifold, and is then discharged to the ink discharge tube  82  shown in  FIG. 2 . The ink discharged to the ink discharge tube  82  is returned to the ink tank  3 , and is then supplied to the ink supply tube  81  again. Thus, the ink is circulated between the inkjet head  4  and the ink tank  3 . 
     Then, when the reciprocation is started by the carriage  33  (see  FIG. 1 ), drive voltages are applied between the common electrodes  61  and the individual electrodes  63  via the wiring board  45 . On this occasion, for example, the individual electrode  63  is set to a drive potential Vdd, and the common electrode  61  is set to a reference potential GND. When applying the drive voltage between the common electrode  61  and the individual electrode  63 , a thickness-shear deformation occurs in the two drive walls  56  for defining the ejection channel  54 , and the two drive walls  56  deform so as to protrude toward the dummy channels  55 . Specifically, since the actuator plate  51  has a structure in which the two piezoelectric substrates  51   a ,  51   b  on which the polarization treatment has been performed in the thickness direction (the Y-axis direction) are stacked on one another, by applying the drive voltage described above, the actuator plate  51  makes a flexural deformation to have a V-shape centered on the intermediate position in the Y-axis direction in the drive walls  56 . Thus, the ejection channel  54  deforms as if it bulges. 
     When the capacity of the ejection channel  54  increases due to the deformation of the two drive walls  56  defining the ejection channel  54 , the ink in the common ink chamber  71  is induced into the ejection channel  54  through the slit  72 . Then, the ink having been induced into the ejection channel  54  propagates inside the ejection channel  54  as a pressure wave. The drive voltage between the common electrode  61  and the individual electrode  63  is vanished at the timing at which the pressure wave has reached the nozzle  78 . Thus, the shapes of the two drive walls  56  are restored, and the capacity of the ejection channel  54  having once increased is restored to the original capacity. Due to this operation, the internal pressure of the ejection channel  54  increases to pressurize the ink in the ejection channel  54 . As a result, it is possible to eject the ink from the nozzle  78 . On this occasion, the ink becomes an ink droplet having a droplet shape when passing through the nozzle  78 , and is then ejected. Thus, it is possible to record characters, images, and the like on the recording paper P as described above. 
     It should be noted that the operation method of the inkjet head  4  is not limited to the content described above. For example, it is also possible to adopt a configuration in which the drive walls  56  in the normal state are deformed toward the inside of the ejection channel  54  as if the ejection channel  54  gives inward. This case can be realized by setting the drive voltage to be applied between the common electrode  61  and the individual electrode  63  to the voltage having an opposite polarity to that of the voltage described above, or by reversing the polarization direction of the actuator plate  51  without changing the polarity of the voltage. Further, it is also possible to deform the ejection channel  54  so as to bulge outward, and then deform the ejection channel  54  so as to give inward to thereby increase the pressurizing force of the ink when ejecting the ink. 
     (C. Functions/Advantages) 
     Then, the functions and the advantages in the head chips  40 , the inkjet head  4 , and the printer  1  according to the present embodiment will be described in detail. 
     In the head chips  40  according to the present embodiment, the actuator plate  51  is provided with the bypass electrodes  64 B in addition to the individual electrode pads  64 , and the bypass electrodes  64 B are disposed at the positions closer to the channel forming region R 2  than the individual electrode pads  64 . Thus, it is possible to more surely maintain the connection of the pair of individual electrodes  63  adjacent to each other across the ejection channel  54 . Hereinafter, the function and the advantages will be described. 
     The piezoelectric material such as PZT constituting the actuator plate  51  is relatively low in mechanical strength, and breakage, a crack, or the like easily occurs. An external impact is apt to act in particular on the vicinity of the upper end surface  512  and the lower end surface  511  of the actuator plate  51 , and therefore, the breakage, the crack, or the like easily occurs. If the breakage, the crack, or the like occurs in the vicinity of the upper end surface  512  of the actuator plate  51  in the stages of fabrication, distribution, and so on of the head chips  40 , the individual electrode pads  64  is broken, and thus, a conduction failure occurs. Specifically, the electrical connection between the pair of individual electrodes  63  adjacent to each other across the ejection channel  54  cannot be maintained, and the pair of individual electrodes  63  cannot be commonalized. Therefore, there is a possibility that the yield drops. 
     In contrast, in the head chips  40  (the actuator plate  51 ) according to the present embodiment, there are disposed the bypass electrodes  64 B for electrically connecting the pair of individual electrodes  63  adjacent to each other across the ejection channel  54  to each other separately from the individual electrode pads  64 . Further, the bypass electrodes  64 B are disposed at the positions closer to the channel forming region R 2  than the individual electrode pads  64 . Therefore, even if the breakage, the crack, or the like occurs in the vicinity of the upper end surface  512  of the actuator plate  51 , and thus, the individual electrode pads  64  are broken, the pair of individual electrodes  63  adjacent to each other across the ejection channel  54  are electrically connected to each other. Specifically, even in the case in which the breakage, the crack, or the like of the actuator plate  51  occurs, it is possible to commonalize the pair of individual electrodes  63  adjacent to each other across the ejection channel  54 . Therefore, it is possible to suppress the drop of the yield of the head chips  40  due to the conduction failure. 
     Further, the bypass electrodes  64 B are disposed inside the bypass groove G provided to the obverse surface  51   f   1 . Thus, it is possible to prevent the short circuit between the bypass electrodes  64 B and the wiring board  45  connected to the common electrode pads  62  from occurring. Hereinafter, the function and the advantages will be described. 
     For example, it is conceivable to dispose the bypass electrodes  64 B on the reverse surface  51   f   2  side. In this case, the bypass electrodes  64 B and the common electrode pads  62  are both disposed on the reverse surface  51   f   2  side of the actuator plate  51 . To the common electrode pads  62 , there is coupled the wiring board  45 . Therefore, there is a possibility that when connecting the wiring board  45  to the common electrode pads  62 , the wiring board  45  is deflected, and thus, the short circuit occurs between the wiring board  45  and the bypass electrode  64 B. Therefore, there is a possibility that the reliability of the head chips  40  is damaged. 
     It is conceivable to provide a groove on the reverse surface  51   f   2  side to dispose the bypass electrodes  64 B in the groove. However, in this case, since the bypass electrodes  64 B are exposed on the reverse surface  51   f   2 , the short circuit between the wiring board  45  and the bypass electrodes  64 B can occur. Further, if the depth of the groove is small, it becomes easier for the short circuit to occur, and therefore, it becomes necessary to form a deep groove. Therefore, it becomes difficult to reduce the thickness (the size in the Y-axis direction) of the actuator plate  51 . 
     In contrast, in the head chips  40  (the actuator plate  51 ) according to the present embodiment, since the bypass electrodes  64 B are disposed at the positions not exposed on the reverse surface  51   f   2  provided with the common electrode pads  62 , even when the wiring board  45  is deflected when connecting the wiring board  45  to the common electrode pads  62 , it is possible to prevent the short circuit between the wiring board  45  and the bypass electrodes  64 B from occurring. Therefore, it becomes possible to enhance the reliability of the head chips  40 . 
     Here, such bypass electrodes  64 B are disposed inside the bypass groove G provided to the obverse surface  51   f   1 . It is also possible to dispose the bypass electrodes  64 B on the obverse surface  51   f   1  without disposing the bypass groove G. Alternatively, it is also possible to dispose a tunnel-like hole extending in the X-axis direction between the reverse surface  51   f   2  and the obverse surface  51   f   1 . However, by disposing the bypass electrodes  64 B inside the bypass groove G, the bypass electrodes  64 B are surrounded by the sidewalls of the bypass groove G, and are protected. Therefore, the broken line and so on of the bypass electrodes  64 B due to, for example, a failure in the manufacturing process can be prevented from occurring. Further, the bypass groove G can easily be formed compared to the tunnel-like hole disposed between the reverse surface  51   f   2  and the obverse surface  51   f   1 . 
     Further, it is sufficient for the bypass groove G to be capable of housing the bypass electrodes  64 B, and therefore, the depth of the bypass groove G can be made smaller. Therefore, it is possible to reduce the thickness of the actuator plate  51  to reduce the size of the head chip  40 . 
     Further, although the ejection channels  54  and the dummy channels  55  each have the openings on the surfaces  51   f   1 ,  51   f   2 , the openings on the reverse surface  51   f   2  are closed by the sealing plate  53 . In other words, it is arranged that the actuator plate  51  is supplied with the ink from the obverse surface  51   f   1  side. By providing the bypass groove G to the obverse surface  51   f   1  on the ink supply side, it becomes possible to form the bypass groove G in the same process as the formation process of the ejection channels  54  and the dummy channels  55  as described above. Therefore, it is possible to form the bypass groove G in a simplified process compared to the case (e.g., an inkjet head  4 C shown in  FIG. 15  described later) of disposing the bypass groove G on the opposite surface to the surface on the ink supply side. 
     Further, in the head chips  40  according to the present embodiment, the common electrode pads  62  electrically connected to the common electrodes  61  covering the inner surfaces of the ejection channels  54  are disposed on the reverse surface  51   f   2  on the opposite side to the cover plate  52  for supplying the ink to the ejection channels  54  out of the actuator plate  51 . Therefore, the external device for supplying the voltage to the common electrodes  61  can easily be coupled to the common electrode pads  62 . Further, in the head chips  40 , the nozzle plate  44  is disposed so as to be opposed to the lower end surface  511  including the openings  54 K through which the ink is ejected, and it is arranged that the actuator plate  51  and the cover plate  52  are stacked on one another in the thickness direction (the Y-axis direction) perpendicular to the extending direction (the Z-axis direction) of the ejection channels  54 . Therefore, in the head chips  40 , the connection to the external device becomes possible on the reverse surface  51   f   2  on the opposite side to the cover plate  52  out of the actuator plate  51 . As a result, the paths of the common electrode pads  62  provided to the actuator plate  51  and to be coupled to the common electrodes  61  are simplified, and moreover, the path length of each of the common electrode pads  62  is shortened. Therefore, broken lines of the common electrode pads  62  are difficult to occur. Further, since the resistance value of the common electrode pad  62  can be reduced due to the reduction in path length of the common electrode pad  62 , it is possible to reduce the heat generation amount when driving the head chips  40 . 
     In the head chips  40 , a plating method can be selected as the formation method of the common electrodes  61 , and moreover, since the ejection channels  54  penetrate the actuator plate  51  in the Y-axis direction, it is also possible to select a two-sided evaporation process. Specifically, using the two-sided evaporation process of forming the metal coatings MF 1  by the evaporation from the obverse surface  51   f   1  side as shown in  FIG. 9C , and then forming the metal coatings MF 2  by the evaporation from the reverse surface  51   f   2  side as shown in  FIG. 9F , it is possible to form the common electrodes  61 . Therefore, in the head chips  40 , the degree of freedom of the formation method of the common electrodes  61  increases. In contrast, in the case in which the ejection channels do not penetrate the actuator plate in the thickness direction, naturally, the two-sided evaporation process cannot be applied. It should be noted that in the case in which the actuator plate  51  is the chevron type stacked substrate as shown in  FIG. 6 , it is desirable to form the common electrodes  61  using the two-sided evaporation process described above. However, in the case in which the actuator plate  51  is not the chevron type stacked substrate, it is desirable to form the common electrodes  61  by performing only the evaporation from one side, for example, by performing only the evaporation from the obverse surface  51   f   1  without performing the evaporation from the reverse surface  51   f   2  side. 
     Further, in the head chips  40 , among the three parts, namely the actuator plate  51 , the cover plate  52 , and the sealing plate  53 , the shape of the sealing plate  53  is simplified. Therefore, since the high processing accuracy becomes unnecessary when manufacturing the sealing plate  53 , it is possible to form the sealing plate  53  using a material which is difficult to process with high accuracy. In other words, the degree of freedom of selection of the constituent material of the sealing plate  53  is increased. 
     Further, in the inkjet head  4  according to the present embodiment, since it is arranged that the common flow channel plate  41  is disposed between the two head chips  40 A,  40 B, a part of the ink flow channel can be used in common. However, in the inkjet head described in, for example, JP-A-2007-50687, it is arranged that ink chamber plates  7 ,  10  including an ink chamber are disposed on the outer side of piezoelectric ceramic plates  2 ,  5  including grooves through which the ink flows. In other words, the flow channel of the ink for supplying the ink to the piezoelectric ceramic plate  2  and the flow channel of the ink for supplying the ink to the piezoelectric ceramic plate  5  are separated from each other. Therefore, the dimension in the stacking direction of the piezoelectric ceramic plates  2 ,  5  and the ink chamber plates  7 ,  10 , namely the thickness is apt to increase. Alternatively, as the inkjet head described in the specification of U.S. Pat. No. 8,091,987, since two systems of ink flow channels become necessary also in the structure in which the ink having ejected from the ejection ends of the pair of actuator plates arranged so as to be adjacent to each other is discharged outside the pair of actuator plates, the thickness is also apt to increase. In contrast, in the inkjet head  4  according to the present embodiment, since the flow channels for supplying the ink to the two head chips  40 A,  40 B can be consolidated, it is possible to realize the inkjet head  4  in which a simpler structure compared to the related art is realized, the thickness in the Y-axis direction is reduced, and the weight is reduced. 
     The head chips  40  according to the present embodiment is arranged to be further provided with the individual electrodes  63  disposed on the inner surfaces of the dummy channels  55 , and the individual electrode pads  64  disposed on the reverse surface  51   f   2 . Therefore, by applying the drive voltage between the common electrode  61  and the individual electrode  63 , it is possible to cause the thickness-shear deformation in the two drive walls  56  for defining the ejection channel  54  to introduce the ink into the ejection channel  54 , and by vanishing the drive voltage between the common electrode  61  and the individual electrode  63 , it is possible to restore the drive walls  56  to eject the ink from the ejection channel  54 . In particular, since the actuator plate  51  is formed of the chevron substrate having the structure in which the two piezoelectric substrates  51   a ,  51   b  on which the polarization treatment has been performed in the thickness direction are stacked on one another, it is possible to decrease the drive voltage of the actuator plate  51  compared to the case of using a monopole substrate as the actuator plate  51 . 
     Further, in the head chips  40  according to the present embodiment, the lower end part of each of the ejection channels  54  forms the opening  54 K exposed on the lower end surface  511  of the actuator plate  51 , and the upper end part of each of the ejection channels  54  forms the closed end including the tilted surface  54   b  terminated within the actuator plate  51 . Therefore, the ink supplied from the liquid supply channel  70  of the cover plate  52  to the ejection channel  54  is guided by the tilted surface  54   b  of the closed end so as to proceed toward the opening  54 K. Therefore, since the ink can smoothly move inside the ejection channel  54 , the stable ejection operation can be realized. 
     2. MODIFIED EXAMPLES 
     Then, some modified examples (Modified Examples 1 through 3) of the embodiment described above will be described. It should be noted that substantially the same constituents as those in the embodiment are denoted by the same reference symbols, and the description thereof will arbitrarily be omitted. 
     Modified Example 1 
       FIG. 13  shows a cross-sectional surface along the extending direction of the ejection channels  54  in an inkjet head  4 A according to Modified Example 1.  FIG. 13  corresponds to  FIG. 4  showing the inkjet head  4  according to the embodiment described above. The inkjet head  4  according to the embodiment described above has the structure in which the return plate  43  is inserted between the head chips  40  and the nozzle plate  44  to perform the ink circulation between the ink tank  3  and the inkjet head  4 . In contrast, the inkjet head  4 A according to Modified Example 1 shown in  FIG. 13  does not have the return plate  43 . Specifically, the nozzle plate  44  is bonded to the lower end surfaces  511 ,  521 , and  531  of the head chips  40 A,  40 B and the lower end surface  411  of the flow channel plate  41  with an adhesive or the like. Further, the flow channel plate  41  is provided with the entrance flow channels  74 , but is not provided with the exit flow channels  75 . Therefore, in the inkjet head  4 A, it is arranged that the ink circulation in the inside is not performed, and the ink to be ejected from the opening  54 K of the ejection channel  54  proceeds toward the nozzle plate  44 , and is then ejected from the nozzle  78 . The inkjet head  4 A according to Modified Example 1 has substantially the same configuration as that of the inkjet head  4  according to the embodiment described above in other points except the point described above, and can therefore be provided with substantially the same advantages as in the inkjet head  4  according to the embodiment described above. 
     Modified Example 2 
       FIG. 14  shows a cross-sectional surface along the extending direction of the ejection channels  54  in an inkjet head  4 B according to Modified Example 2.  FIG. 14  corresponds to  FIG. 4  showing the inkjet head  4  according to the embodiment described above. The inkjet head  4  according to the embodiment described above has the structure in which the head chip  40 A and the head chip  40 B are disposed on both sides of one flow channel plate  41 . In contrast, the inkjet head  4 B according to Modified Example 2 shown in  FIG. 14  has a structure in which the head chip  40  is disposed only on one side of one flow channel plate  41 B. The inkjet head  4 B according to Modified Example 2 has substantially the same configuration as that of the inkjet head  4  according to the embodiment described above in other points than the point described above. 
     Modified Example 3 
       FIG. 15  shows a cross-sectional surface along the extending direction of the ejection channels  54  in an inkjet head  4 C according to Modified Example 3.  FIG. 15  corresponds to  FIG. 4  showing the inkjet head  4  according to the embodiment described above. The inkjet head  4  according to the embodiment described above has the structure in which the common electrode pads  62  and the individual electrode pads  64  are disposed on the reverse surface  51   f   2  of the actuator plate  51 . In contrast, the inkjet head  4 C according to Modified Example 3 shown in  FIG. 15  has a structure in which the common electrode pads  62  and the individual electrode pads  64  are disposed on the obverse surface  51   f   1  of the actuator plate  51 . The inkjet head  4 C according to Modified Example 3 has substantially the same configuration as that of the inkjet head  4  according to the embodiment described above in other points than the point described above. 
     The pair of head chips  40 A,  40 B are disposed so that the sealing plates  53  of the pair of head chips  40 A,  40 B are adjacent to each other in the Y-axis direction, and the cover plate  52  of the head chip  40 A and the cover plate  52  of the head chip  40 B are opposed to each other across the sealing plates  53  and the actuator plates  51  of the pair of head chips  40 A,  40 B. 
     In the inkjet head  4 C, the common electrode pads  62  and the individual electrode pads  64  are disposed on the obverse surface  51   f   1  to be the ink supply side of the actuator plate  51 , and the bypass groove G and the bypass electrodes  64 B are disposed on the reverse surface  51   f   2  with the sealing plate  53 . Here, the “obverse surface  51   f   1 ” is a specific example corresponding to the “first surface” of the present disclosure, and the “reverse surface  51   f   2 ” is a specific example corresponding to the “second surface” of the present disclosure. In the inkjet head  4 C, for example, it is sufficient to form the reverse surface  51   f   2  of the actuator plate  51  (the process shown in  FIG. 9E ), and then form the bypass groove G and the bypass electrodes  64 B. 
     It is not required for the inkjet head  4 C to have the return plate  43  similarly to the case described in the inkjet head  4 A according to Modified Example 1 described above. It is also possible for the inkjet head  4 C to have a single head chip  40  similarly to the case described in the inkjet head  4 B according to Modified Example 2 described above. 
     3. OTHER MODIFIED EXAMPLES 
     The present disclosure is described hereinabove citing the embodiment and some modified examples, but the present disclosure is not limited to the embodiment and so on, and a variety of modifications can be adopted. 
     For example, in the embodiment described above, the description is presented specifically citing the configuration examples (the shapes, the arrangements, the number and so on) of each of the members in the printer, the inkjet head, and the head chip, but those described in the above embodiment and so on are not limitations, and it is possible to adopt other shapes, arrangements, numbers and so on. 
     In the embodiment and so on described above, the description is presented illustrating the so-called edge-shoot type inkjet head for ejecting the ink from the ejection end (the opening  54 K) as an end part in the extending direction of the ejection channels, but the liquid jet head according to the present disclosure is not limited to the illustration. Specifically, it is also possible to adopt a so-called side-shoot type inkjet head in which the ink passes in the thickness direction of the actuator plate, namely the depth direction of the ejection channels. 
     Further, the method of forming the liquid jet head chip according to the present disclosure is not limited to the procedure explained in the embodiment described above. For example, after the processes shown in  FIG. 9A  through  FIG. 9E , it is also possible to form the metal coatings MF 2  and the metal coatings MF 3  in a lump as described below. Specifically, as shown in  FIG. 9E , the grinding work is performed on the piezoelectric wafer  51   b Z from the reverse surface to expose the plurality of ejection channels  54  and the plurality of dummy channels  55 . Then, unlike the resist pattern RP 2  shown in  FIG. 9G , the resist pattern is selectively formed on the reverse surface  51   f   2  so as not to close the plurality of dummy channels  55 . Specifically, the resist pattern is selectively formed on the reverse surface  51   f   2  of the parts where the ejection channels  54  or the dummy channels  55  are not formed out of the piezoelectric substrate  51   b , namely the parts eventually turn to the drive walls  56 , in the piezoelectric substrate  51   b . Subsequently, the metal coatings MF 2  covering the inner surfaces  541  of the plurality of the ejection channels  54  and the inner surfaces  551  of the plurality of dummy channels  55 , and the metal coatings MF 3  covering the reverse surface  51   f   2  and the resist pattern using, for example, an evaporation method in a lump. Subsequently, the resist pattern is removed. As a result, there remain only the parts covering the inner surfaces  541  of the ejection channels  54  or the inner surfaces  551  of the dummy channels  55  out of the metal coatings MF 2 , and thus, the common electrodes  61  and the individual electrodes  63  are formed. In addition, some parts of the metal coatings MF 3  remain in the reverse surface  51   f   2  to form the common electrode pads  62  and the individual electrode pads  64 . 
     Further, although in the embodiment and so on described above, there is described the example in which the ejection channels and the dummy channels each have the openings on the two opposed surfaces (the surfaces  51   f   1 ,  51   f   2 ) of the actuator plate, it is also possible for each of the ejection channels and the dummy channels to have the opening on either one of the opposed surfaces of the actuator plate. 
     Further, in the embodiment and so on described above, there is illustrated the chevron type actuator plate in which the two piezoelectric substrates having the respective polarization directions different from each other are stacked on one another, but it is also possible for the inkjet head according to the present disclosure to be an inkjet head having a so-called cantilever type (monopole type) actuator plate. The cantilever type actuator plate is formed of a single piezoelectric substrate having the polarization direction set to one direction along the thickness direction. It should be noted that in the cantilever type actuator plate, for example, the drive electrode is attached to the upper half in the depth direction with the oblique vapor deposition. Therefore, by the drive force acting only on the part provided with the drive electrode, the drive walls make the flexural deformation. As a result, even in this case, since the drive walls make the flexural deformation to have the V-shape, it results in that the ejection channel deforms as if the ejection channel bulges. 
     Further, in the embodiment and so on described above, the description is presented citing the printer  1  (the inkjet printer) as a specific example of the “liquid jet recording device” in the present disclosure, but this example is not a limitation, and it is also possible to apply the present disclosure to other devices than the inkjet printer. In other words, it is also possible to arrange that the “head chip” (the head chips  40 A,  40 B) and the “liquid jet head” (the inkjet head  4 ) of the present disclosure are applied to other devices than the inkjet printer. Specifically, it is also possible to arrange that the “head chip” and the “liquid jet head” of the present disclosure are applied to a device such as a facsimile or an on-demand printer. 
     It should be noted that the advantages described in the specification are illustrative only but are not a limitation, and other advantages can also be provided. 
     Further, the present disclosure can also take the following configurations. 
     &lt;1&gt; 
     A liquid jet head adapted to jet liquid, comprising an actuator plate adapted to apply pressure to the liquid; and a wiring board, wherein the actuator plate includes a first surface, and a second surface facing to an opposite side to the first surface, ejection channels and non-ejection channels which have an opening on at least one of the first surface and the second surface and are alternately arranged so as to be separated from each other, a common electrode disposed on a sidewall of the ejection channel, an individual electrode electrically separated from the common electrode and disposed on a sidewall of the non-ejection channel, a common electrode pad disposed on the first surface and adapted to electrically connect the common electrode and the wiring board to each other, and a bypass interconnection adapted to electrically connect the individual electrodes in the non-ejection channels adjacent to each other and failing to be exposed on the first surface. 
     &lt;2&gt; 
     The liquid jet head according to &lt;1&gt;, wherein the bypass interconnection is disposed on the second surface. 
     &lt;3&gt; 
     The liquid jet head according to &lt;1&gt; or &lt;2&gt;, wherein a bypass groove extending in a direction in which the ejection channels and the non-ejection channels are arranged is provided to the second surface, and the bypass interconnection is disposed in the bypass groove. 
     &lt;4&gt; 
     The liquid jet head according to any one of &lt;1&gt; to &lt;3&gt;, wherein the actuator plate further includes an individual electrode pad which electrically connects the individual electrodes in the non-ejection channels adjacent to each other and which is provided to the first surface. 
     &lt;5&gt; 
     The liquid jet head according to any one of &lt;1&gt; to &lt;4&gt;, further comprising a sealing plate opposed to the actuator plate; and a cover plate which includes a liquid flow hole communicated with the ejection channel, and which is disposed so as to be opposed to the sealing plate across the actuator plate, wherein the ejection channels and the non-ejection channels have the opening on both of the first surface and the second surface, and the sealing plate closes the opening on the first surface of the ejection channels and the non-ejection channels. 
     &lt;6&gt; 
     The liquid jet head according to &lt;5&gt;, further comprising a return plate which is disposed in a direction crossing the actuator plate, and has a circulation channel communicated with the ejection channels; a first actuator plate and a second actuator plate respectively corresponding to the actuator plate; a first cover plate and a second cover plate respectively corresponding to the cover plate; a first sealing plate and a second sealing plate respectively corresponding to the sealing plate; and a flow channel plate disposed between the first sealing plate and the second sealing plate, wherein the first actuator plate is disposed between the first sealing plate and the flow channel plate, the second actuator plate is disposed between the second sealing plate and the flow channel plate, the first cover plate is disposed between the first actuator plate and the flow channel plate, the second cover plate is disposed between the second actuator plate and the flow channel plate, and the flow channel plate includes a liquid supply flow channel communicated with the liquid flow hole of the first cover plate and the liquid flow hole of the second cover plate, and a liquid discharge flow channel communicated with the circulation channel. 
     &lt;7&gt; 
     A liquid jet recording device comprising the liquid jet head according to any one of &lt;1&gt; to &lt;6&gt;; and a containing section adapted to contain the liquid. 
     &lt;8&gt; 
     A head chip adapted to jet liquid, comprising an actuator plate adapted to apply pressure to the liquid, wherein the actuator plate includes a first surface, and a second surface facing to an opposite side to the first surface; ejection channels and non-ejection channels which have an opening on at least one of the first surface and the second surface and are alternately arranged so as to be separated from each other; a common electrode disposed on a sidewall of the ejection channel; an individual electrode electrically separated from the common electrode and disposed on a sidewall of the non-ejection channel; a common electrode pad disposed on the first surface and adapted to electrically connect the common electrode and an external interconnection to each other; and a bypass interconnection adapted to electrically connect the individual electrodes in the non-ejection channels adjacent to each other and failing to be exposed on the first surface.