Patent Publication Number: US-7909436-B2

Title: Inkjet head, manufacturing method for the same, and inkjet recording apparatus

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an inkjet head, a manufacturing method for the same, and an inkjet recording apparatus. 
     2. Description of the Related Art 
     There is generally known an inkjet recording apparatus for recording characters or images on a recording medium using an inkjet head including a plurality of nozzles which eject ink (for example, see JP 2004-090492 A and JP 2005-212365 A). In the inkjet head described in JP 2005-212365 A, regions each having a different polarization direction are formed in the poles serving as a driving section of the head, whereby a drive voltage is reduced to realize high efficiency of ejecting operations. 
       FIG. 11  is a flowchart showing in section a manufacturing method for an inkjet head described in JP 2005-212365 A. 
     In manufacturing a conventional inkjet head, first, as shown in  FIG. 11A , a first piezoelectric substrate  543  and a second piezoelectric substrate  544  each having a different polarization direction are prepared, and those piezoelectric substrates are made to be opposite to each other for bonding. Next, as shown in  FIG. 11B , the first piezoelectric substrate  543  having a thickness of about 1 mm is ground so as to have a thickness of about 0.15 mm. Next, as shown in  FIG. 11C , a plurality of groove portions  549  are processed from the first piezoelectric substrate  543  side. Next, drive electrodes  565  are film-formed on side walls of the groove portions  549 , and then a cover plate substrate  550  having an ink supply path  556  formed therein is bonded to the first piezoelectric substrate  543 . 
     As described above, in the manufacturing method for an inkjet head as shown in  FIGS. 11A to 11E , three substrates, that is, the first piezoelectric substrate  543 , the second piezoelectric substrate  544 , and the cover plate substrate  550 , are required. The first piezoelectric substrate  543  is processed thinly to have a thickness of about 1 mm to about 0.15 mm, which leads to an increase in material costs or processing costs. Further, most parts of the first piezoelectric substrate  543  are discarded through grinding, which is a waste of materials. 
     SUMMARY OF THE INVENTION 
     The present invention has been made in view of the aforementioned problems, and an object thereof is to provide an inkjet head, which can be manufactured with ease, and a manufacturing method for the same while saving material costs or processing costs. 
     In order to solve the aforementioned problems, the present invention relates to the inkjet head including: a base substrate, at least a part of the base substrate being formed of a piezoelectric material; a plurality of ink chambers formed in the base substrate; and drive electrodes formed on side walls of the plurality of ink chambers, in which: the base substrate is formed of a first substrate and a second substrate through bonding, at least one of the first substrate and the second substrate being a piezoelectric substrate; the first substrate includes a plurality of first groove portions formed on one surface thereof, and an ink supply path which is connected to the plurality of first groove portions and opens toward another surface thereof; the second substrate includes a plurality of second groove portions, the plurality of second groove portions forming the plurality of ink chambers, on a bonding surface between the first substrate and the second substrate, together with the plurality of first groove portions; and the drive electrodes are formed on at least one of side walls of the plurality of first groove portions and side walls of the plurality of second groove portions, the at least one of side walls of the plurality of first groove portions and side walls of the plurality of second groove portions being the side walls of groove portions of a substrate being the piezoelectric substrate among the first substrate and the second substrate. 
     With this structure, the inkjet head can be formed using two piezoelectric substrates, or one piezoelectric substrate and one substrate made of another material (for example, alumina substrate), and hence the inkjet head can be manufactured using fewer substrates at a lower cost compared with the conventional inkjet head. Besides, most of the initial substrate is not discarded through polishing, and thus waste of materials does not occur. 
     Alternatively, a structure in which both of the first substrate and the second substrate are the piezoelectric substrates may be employed. In this case, though manufacturing costs increase because two piezoelectric substrates are used, there can be realized an inkjet head having a structure in which the side wall partitioning the first groove portion and the side wall partitioning the second groove portion are driven (a shear deformation is generated) to discharge ink. 
     Preferably, a depth of the first groove portion is substantially equal to a depth of the second groove portion. With such a structure, a maximum ink discharge amount can be obtained. 
     Further, there can be employed a structure in which the second groove portion has a width different from a width of the first groove portion. With such a structure, a margin of positioning the first groove portion and the second groove portion increases, which enhances the manufacturability. 
     There can be employed a structure in which: the first piezoelectric substrate and the second piezoelectric substrate are each a piezoelectric substrate and have polarization directions opposite to each other in a thickness direction thereof; a first drive electrode is formed on the sidewall of the first groove portion, and a second drive electrode is formed on the side wall of the second groove portion; and the drive electrode includes the first drive electrode, the second drive electrode, and a conduction member connecting the first drive electrode and the second drive electrode. With this structure, all the side walls of the ink chamber deform in response to a voltage application, and thus the inkjet head can be driven at a low voltage, and power consumption thereof can be reduced. 
     Also with this structure, the width of the second groove portion is preferably larger than the width of the first groove portion. By employing such a structure, a conduction member excellent in reliability can be formed without difficulty, and an inkjet head excellent in reliability can be easily manufactured. 
     According to the present invention, there is provided a manufacturing method for an inkjet head including a plurality of ink chambers and drive electrodes, the plurality of ink chambers being formed in a base substrate, at least apart of the base substrate being formed of a piezoelectric material, the drive electrodes being formed on side walls of the plurality of ink chambers, the manufacturing method including: preparing a first substrate and a second substrate, at least one of the first substrate and the second substrate being a piezoelectric substrate, and forming a plurality of first groove portions each serving as a part of each of the plurality of ink chambers on one surface of the first substrate to form, on a surface opposite to the surface formed with the plurality of first groove portions, an ink supply path connected to the plurality of first groove portions; forming, on one surface of the second substrate, a plurality of second groove portions forming of the plurality of ink chambers with the plurality of first groove portions; forming the drive electrodes on side walls of any one of the plurality of first groove portions and the plurality of second groove portions, the side walls of any one of the plurality of first groove portions and the plurality of second groove portions being the side walls of groove portions of a substrate being the piezoelectric substrate among the first substrate and the second substrate; and causing the plurality of first groove portions and the plurality of second groove portions to be opposite to each other to bond the first substrate to the second substrate. 
     According to this manufacturing method, two piezoelectric substrates, or one piezoelectric substrate and one substrate made of another material can be used to manufacture the inkjet head including the ink chamber and the ink supply path, which makes it possible to manufacture the inkjet head at a lower cost compared with a conventional inkjet head. 
     Preferably, a depth of the plurality of first groove portions is substantially equal to a depth of the plurality of second groove portions. According to this manufacturing method, a high-performance inkjet head can be easily manufactured. 
     A width of the plurality of second groove portions may be formed differently from a width of the plurality of first groove portions. According to this manufacturing method, because the margin of positioning of the first piezoelectric substrate and the second piezoelectric substrate is increased, and thus the inkjet head can be easily manufactured. 
     The first piezoelectric substrate and the second piezoelectric substrate may each be the piezoelectric substrate and have polarization directions opposite to each other in a thickness direction thereof, the forming the drive electrodes may include forming first drive electrodes on the side walls of the plurality of the first groove portions and forming second drive electrodes on the side walls of the plurality of second groove portions, and the manufacturing method may further include forming, after bonding the first substrate to the second substrate, a conduction member connecting the first drive electrode and the second drive electrode. With this structure, an inkjet head causing deformation in all the side walls of the ink chamber can be manufactured. 
     The forming a conduction member preferably includes film-forming the conduction members on the sidewalls of the plurality of first groove portions and the side walls of the plurality of second groove portions via the ink supply path. According to this manufacturing method, the first drive electrode and the second electrode are easily made conductive after bonding the first piezoelectric substrate to the second piezoelectric substrate. 
     The width of the plurality of second groove portions is preferably formed larger than the width of the plurality of first groove portions. According to this manufacturing method, a conduction electrode can be easily formed without impairing reliability of the conduction electrode. 
     An inkjet recording apparatus according to the present invention includes the inkjet head according to the present invention. With this structure, the inkjet recording apparatus can be provided at a low cost. 
     According to the present invention, because the inkjet head can be formed using two piezoelectric substrates, the inkjet head can be provided using fewer substrates at a lower cost compared with a conventional inkjet head. Moreover, the inkjet head according to the present invention can be manufactured without waste of the materials since fewer parts thereof are discarded through grinding. Besides, according to the present invention, the inkjet head can be manufactured at a low cost. Further, the inkjet recording apparatus can be manufactured inexpensively. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the accompanying drawings: 
         FIG. 1  is a view showing an inkjet recording apparatus according to a first embodiment of the present invention; 
         FIG. 2  is a view showing a head unit according to the first embodiment; 
         FIG. 3  is a perspective structural view of an inkjet head according to the first embodiment; 
         FIG. 4  is an exploded perspective view of the inkjet head according to the first embodiment; 
         FIGS. 5A and 5B  are sectional views of the inkjet head according to the first embodiment; 
         FIGS. 6A and 6B  are views explaining operations of the inkjet head according to the first embodiment; 
         FIGS. 7A-i  to  7 D-ii are flowcharts showing a manufacturing process of the inkjet head according to the first embodiment; 
         FIGS. 8A-i  to  8 E-ii are flowcharts showing another manufacturing process of the inkjet head according to the first embodiment; 
         FIGS. 9A and 9B  are views showing modifications of the inkjet head according to the first embodiment; 
         FIG. 10  is a sectional view showing an inkjet head according to a second embodiment of the present invention; and 
         FIGS. 11A to 11E  are flowcharts showing a manufacturing process of a conventional inkjet head. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     First Embodiment 
     Hereinafter, an inkjet head according to a first embodiment of the present invention and an inkjet recording apparatus provided with the inkjet head are described with reference to the drawings. 
       FIG. 1  is a view showing the inkjet recording apparatus according to the first embodiment of the present invention.  FIG. 2  is a perspective view showing a head unit provided in the inkjet recording apparatus.  FIG. 3  is a perspective view showing an inkjet head according to this embodiment.  FIG. 4  is an exploded perspective view of the inkjet head shown in  FIG. 3 . 
     An inkjet recording apparatus  1  includes an apparatus main body  2  and a plurality of head units  3  housed in the apparatus main body  2 . The apparatus main body  2  includes a casing  6  having a substantially rectangular parallelepiped shape. In the casing  6 , there are provided a carriage  7 , guide rails  8 , an ink cartridge  17 , carrying-in rollers  21 , and carrying-out rollers  22 . 
     The carriage  7  includes a flat-shaped pedestal  7   a . The head units  3  are fixed to the pedestal  7   a . At an edge of the pedestal  7   a , a pedestal wall portion  7   b  provided to extend upward from the pedestal  7   a  is provided. The pedestal wall portion  7   b  is provided with a wiring board  5 . The wiring board  5  is provided with an electronic component for operating each component of the inkjet recording apparatus  1 . 
     The carriage  7  is supported by a pair of guide rails  8  extending in a width direction (longitudinal direction) W of the casing  6 . The carriage  7  is made to reciprocate in the width direction W of the casing  6  along the guide rails  8 . 
     A timing belt  14  extending along the guide rails  8  is provided between the pair of guide rails  8 . The timing belt  14  is fixed to the carriage  7  and is also made to bridge over pulleys  12  and  13  which are provided at respective ends of the casing  6  in the width direction W thereof. The pulley  12  is coupled to a motor  11 , and the carriage  7  is made to reciprocate in the width direction W via the timing belt  14  by driving the motor  11 . 
     The ink cartage  17  is placed in the vicinity of a side surface of the casing  6 . Flexible ink supply tubes  18  extend from the ink cartridge  17 , and each edge of the ink supply tubes  18  is connected to each of the head units  3  attached to the carriage  7 . Through the ink supply tubes  18 , various inks are supplied from the ink cartridge  17  to the head units  3 . 
     Further, on a front surface (surface at a right side in a D direction of  FIG. 1 ) and a rear surface (surface at a left side in a D direction of  FIG. 1 ) of the casing  6 , apertures (not shown) provided to be opposite to each other are provided. In a position corresponding to the aperture of the front surface among those apertures, the pair of carrying-out rollers  22  extending in the longitudinal direction W are provided. On the other hand, in a position corresponding to the aperture of the rear surface, the pair of carrying-in rollers  21  extending in the longitudinal direction W are provided. When the carrying-in rollers  21  and the carrying-out rollers  22  are driven, a sheet (recording medium) S arranged at the aperture of the rear surface is drawn into the casing  6  and is subjected to a process, and the sheet S subjected to the recording process is delivered from the aperture of the front surface. 
     As shown in  FIG. 2 , the head unit  3  includes a mounting base  25 , an inkjet head  26 , a flow channel substrate  27 , a pressure adjustment portion  38 , a base plate  31 , and a wiring board  35  onto which a control circuit  32  is mounted. 
     At a lower edge of the head unit  3 , the mounting base  25  having a substantially rectangular shape is arranged. The mounting base  25  is attached to the pedestal  7   a  of the carriage  7  via screws (not shown). The inkjet head  26  is attached to a top surface of the mounting base  25 . At one surface side of the inkjet head  26 , the flow channel substrate  27 , which extends over a full length in a longitudinal direction thereof and has a rectangular shape, is provided. A coupling portion  30  is provided in a center of a top surface of the flow channel substrate  27 . 
     The pressure adjustment portion  38  including a reservoir for reserving ink is provided above the flow channel substrate  27 . An ink communicating pipe  39  communicating with the reservoir is provided below the pressure adjustment portion  38 . The ink communicating pipe  39  is coupled to the coupling portion  30  of the flow channel substrate  27  via an O-ring. 
     On the other hand, above the pressure adjustment portion  38 , an ink intake  42  communicating with the reservoir is provided. The ink supply tube  18  is attached to the ink intake  42 . 
     Besides, the base plate  31  which is erected from the mounting base  25  and has a rectangular shape is provided to the mounting base  25 . The base plate  31  is a plate-like material made of aluminum or the like. On one of principal surfaces (principal surface at the inkjet head  26  side) of the base plate  31 , the wiring board  35  is provided. The control circuit  32  which performs various types of control for the inkjet head  26  is mounted onto the wiring board  35 . A supporting portion  37  extending to one principal surface side is provided on an upper edge of the base plate  31 . Through fixation of the pressure adjustment portion  38  to the supporting portion  37 , the head unit incorporating the aforementioned respective members is formed. 
     In the head unit  3  of the aforementioned structure, ink supplied from the ink cartridge  17  via the ink supply tubes  18  is taken from the ink intake  42  to the reservoir within the pressure adjustment portion  38 . Then, a predetermined amount of ink is supplied to the inkjet head  26  via the ink communicating pipe  39  and the flow channel substrate  27 . 
     As shown in  FIG. 3  and  FIG. 4 , the inkjet head  26  includes a substrate formed of a first piezoelectric substrate  43  and a second piezoelectric substrate  44  which are placed to be opposite to each other and have a substantially rectangular shape, and has a structure in which a nozzle plate  51  is bonded to a side edge surface of the substrate. 
     The first piezoelectric substrate  43  is formed of, for example, lead zirconium titanate (PZT). On a lower surface (surface on the second piezoelectric substrate  44  side) of the first piezoelectric substrate  43 , which is shown in  FIG. 3 , a plurality of first groove portions  46  extending in a short side direction of the first piezoelectric substrate  43  are formed in a stripe shape. In other words, the plurality of first groove portions  46  are partitioned from each other by side walls  45  formed therebetween. 
     A bottom surface of the first groove portion  46  is formed of a front planar surface  43   a  extending from a front side of the first piezoelectric substrate  43  to a substantially center portion in the short side direction thereof and an inclined surface  43   b  which is formed such that a depth thereof gradually decreases from a rear portion of the front planar surface  43   a  toward a rear side of the first piezoelectric substrate  43 . First drive electrodes  61  are formed on side wall surfaces of the first groove portion  46 . 
     The first piezoelectric substrate  43  is formed with an ink supply path  56  opening toward a principal surface  43   s  opposite to the first groove portion  46 . The ink supply path  56  is an aperture which extends along a longitudinal direction of the first piezoelectric substrate  43  and has a rectangular shape. The ink supply path  56  pierces the first piezoelectric substrate  43  to reach the first groove portions  46 . In other words, the ink supply path  56  opens on the bottom surface of each of the first groove portions  46 . 
     The second piezoelectric substrate  44  is formed of PZT or the like as in the case of the first piezoelectric substrate  43 . On an upper surface of the second piezoelectric substrate  44 , which is shown in  FIG. 3 , a plurality of second groove portions  48  extending in a short side direction of the second piezoelectric substrate  44  are formed. Those second groove portions  48  are partitioned from each other by side walls  47 . 
     A bottom surface of the second groove portion  48  is formed of a front planar surface  44   a  and an inclined surface  44   b  as in the case of the bottom surface of the first groove portion  46 . Second drive electrodes  62  are formed on side wall surfaces of the second groove portion  48 . 
     The first piezoelectric substrate  43  and the second piezoelectric substrate  44  described above are bonded to each other via an adhesive (not shown) in the state where the first groove portions  46  and the second groove portions  48  are positioned. In other words, the side walls  45  partitioning the first groove portions  46  and the side walls  47  partitioning the second groove portions  48  are bonded to each other on top surfaces thereof. Accordingly, an ink chamber  49  formed of the first groove portion  46  and the second groove portion  48  is formed. The ink supply path  56  is connected to each ink chamber  49 . 
     Here,  FIG. 5A  is a sectional view showing a structure of the ink chamber of the inkjet head, and  FIG. 5B  is a sectional view taken along a line I-I of  FIG. 5A . As shown in  FIGS. 5A and 5B , the ink supply path  56  piercing the first piezoelectric substrate  43  leads to the ink chamber  49 . In regions extending from the ink supply path  56  in a thickness direction thereof among the side wall surfaces of the ink chamber  49 , conduction electrodes (conduction members)  63  are formed. The conduction electrode  63  is formed through the first drive electrode  61  formed on the side wall surface of the first groove portion  46  and the second drive electrode  62  formed on the side wall surface of the second groove portion  48 . The first drive electrode  61 , the second drive electrode  62 , and the conduction electrode  63  form a drive electrode  65  of the inkjet head according to this embodiment. 
     Note that, though not shown, a terminal of the drive electrode  65  formed on both side walls of the ink chamber  49  is drawn outside the ink chamber  49  through a drawing wire formed simultaneously with the first drive electrode  61  or the second drive electrode  62 . The drive electrode  65  is electrically connected to the control circuit  32  via the aforementioned terminal. 
     Arrows  43   z  and  44   z , which are added to the side walls  45  and  47  of  FIG. 5B , respectively, indicate a polarization direction of the first piezoelectric substrate  43  and a polarization direction of the second piezoelectric substrate  44 , respectively. In other words, the first and second piezoelectric substrates are formed of piezoelectric materials having a polarization direction opposite to each other in a thickness direction thereof. 
     A depth of the first groove portion  46  and a depth of the second groove portion  48 , which form the ink chamber  49 , are formed to be substantially the same. With such a structure, a displacement amount of a bonding surface between the side wall  45  and the side wall  47  can be made to be maximum, and thus a maximum ink discharge amount can be obtained. 
     As shown in  FIG. 3  and  FIG. 5A , on a side edge surface of the substrate formed of the first piezoelectric substrate  43  and the second piezoelectric substrate  44  through bonding, the nozzle plate  51  formed of, for example, polyimide is provided. On one principal surface of the nozzle plate  51  is made a bonding surface between the first piezoelectric substrate  43  and the second piezoelectric substrate  44 . On another principal surface (outer surface) of the nozzle plate  51 , a water-repellent film (not shown) having water repellency for preventing adhesion of ink or the like is applied. 
     The nozzle plate  51  is formed with a plurality of nozzle apertures  52  at predetermined intervals (at intervals similar to pitches between the ink chambers  49 ) in a longitudinal direction thereof. The nozzle apertures  52  are formed in the nozzle plate  51  made of a polyimide film using, for example, an excimier laser. Each of the nozzle apertures  52  is arranged correspondingly to each of the ink chambers  49 . 
     With such a structure, when a predetermined amount of ink is supplied to the flow channel substrate  27  from the reservoir chamber within the pressure adjustment portion  38  via the ink communicating pipe  39  and the coupling portion  30 , the supplied ink is fed to the respective ink chambers  49  via the ink supply path  56 . Then, the inkjet head  26  vibrates the side walls  45  and  47  to change volumes of the ink chambers  49 , with the result that the ink is discharged from the nozzle apertures  52 . 
       FIGS. 6A and 6B  are operation explanatory views of the inkjet head  26 . Note that, in  FIGS. 6A and 6B , symbols A to F are merely added as reference numerals for distinguishing each structural element. 
     First, when no voltage is applied to any of the drive electrodes  65 , the side walls  45  and  47  of the inkjet head  26  are in upright positions in a substrate thickness direction as shown in  FIG. 5B . 
     Next, as shown in  FIG. 6A , voltage is applied to each of drive electrodes  65 A and  65 B opposing to each other by sandwiching side walls  45 A and  47 A, drive electrodes  65 C and  65 D opposing to each other by sandwiching side walls  45 B and  47 B, and drive electrodes  65 E and  67 F opposing to each other by sandwiching side walls  45 C and  47 C, and thus electric fields in electric field directions E 1  and E 2 , which are indicated by chain line arrows, are made to act on piezoelectric materials forming the side walls  45  and  47 . The electric field directions E 1  and E 2  each are orthogonal to polarization directions  43   z  and  44   z.    
     Accordingly, a shear deformation is generated on a bonding surface of the side walls  45 A and  47 A, and in the same manner, the side walls  45 B and  47 B, and the side walls  45 C and  47 C are deformed such that bonding surfaces thereof are shifted in directions opposite to the electric field directions E 1  and E 2 , respectively. As a result, a volume of an ink chamber  49 A enclosed by the side walls  45 A and  47 A and the side walls  45 B and  47 B is increased, whereas a volume of an ink chamber  49 B adjacent to the ink chamber  49 A is reduced. Then, ink is fed from the ink supply path  56  to the ink chamber  49 A whose volume is increased. 
     Next, when voltage supply to the drive voltages  65  is stopped, the side walls  45  and  47  return to the upright positions shown in  FIG. 5B . Then, as shown in  FIG. 6A , when voltage applied to the drive electrodes  65  is changed to reverse the electric field directions acting on the side walls  45  and  47 , the volume of the ink chamber  49 A holding ink is reduced. As a result, the ink is discharged from the nozzle aperture  52  corresponding to the ink chamber  49 A. Along with the discharge of the ink, the ink is fed to the ink chamber  49 B whose volume is increased. 
     Further, through repetition of the aforementioned operation, ink is succeedingly discharged from the ink chambers  49 A and  49 B via the nozzle apertures  52 . 
     According to this embodiment described above, the inkjet head provided with the ink chambers  49  and the ink supply path  56  is realized using two piezoelectric substrates. Therefore, an amount of the substrate usage is reduced compared with a conventional inkjet head, and there is no waste of materials through grinding of the piezoelectric substrate, which leads to an inkjet head excellent in manufacturability. 
     Besides, the inkjet recording apparatus according to this embodiment includes the inkjet head described above according to the present invention, which realizes the inkjet recording apparatus whose main parts can be manufactured at low costs and which can be provided at a low price. 
     (Manufacturing Method) 
     Next, a manufacturing method for the inkjet head  26  according to the first embodiment is described with reference to  FIGS. 7A-i  to  7 D-ii and  FIGS. 8A-i  to  8 E-ii. Note that, in  FIGS. 7A-i  to  7 D-ii and  FIGS. 8A-i  to  8 E-ii, FIGS. i and ii are drawings corresponding to each other in the same step. More specifically, FIG. i are sectional views corresponding to positions (positions along lines II-II, III-III, and IV-IV) shown in FIG. ii. FIG. ii are sectional views corresponding to positions where the ink chambers are formed in FIG. i. 
     First, a processing step of the first piezoelectric substrate  43  is described with reference to  FIG. 7A-i  to  7 D-ii. 
     As shown in  FIGS. 7A-i  and  7 A-ii, the first piezoelectric substrate  43  is prepared. As the first piezoelectric substrate  43 , a PZT substrate having an upward polarization direction  43   z  as shown in  FIG. 7A-i . 
     Next, as shown in  FIGS. 7B-i  and  7 B-ii, the plurality of first groove portions  46  are formed all over the first piezoelectric substrate  43  (on a bottom surface of  FIGS. 7A-i  and  7 A-ii). In processing the first groove portions  46 , there can be preferably adopted a dicing process which is performed using a dicing blade having a thickness corresponding to a width of the first groove portion  46 . In the case where a disc-shaped dicing blade is used, the inclined surface  43   b  is formed at a back end of the first groove portion  46 . 
     A processing depth of the first groove portion  46  is assumed to be equal to a depth corresponding to substantially a half of a desired height of the ink chamber  49 . 
     Next, as shown in  FIGS. 7C-i  and  7 C-ii, a metal material is obliquely vapor-deposited from a side of the first piezoelectric substrate  43  where the first groove portions  46  are formed. Thus, first drive electrodes  61  are formed on the side wall surfaces of the first groove portions  46 . Note that the first drive electrodes  61  need to be individually formed on the side wall surfaces of the first groove portions  46  at both sides thereof in a width direction, and thus vapor deposition is performed in a direction P shown in  FIG. 7C-i , and then vapor deposition is performed in a direction Q opposite to the direction P. 
     Next, as shown in  FIGS. 7D-i  and  7 D-ii, the first piezoelectric substrate  43  is processed from a surface on an opposite side to the first groove portion  46  of the first piezoelectric substrate  43 , to thereby form the ink supply path  56 . The formed ink supply path  56  passes from the principal surface  43   s  of the first piezoelectric substrate  43  to the inclined surface  43   b  of the first groove portion  46  to open toward a bottom surface of the first groove portion  46 . 
     Through the steps described above, the first piezoelectric substrate  43  formed with the first groove portions  46  and the ink supply path  56  is obtained. Next, a processing step of the second piezoelectric substrate  44 , which is performed separately from the processing step of the first piezoelectric substrate  43 , is described with reference to  FIGS. 8D-i  and  8 E-ii. 
     First, as shown in  FIGS. 8A-i  and  8 A-ii, the second piezoelectric substrate  44  is prepared. As the second piezoelectric substrate  44 , the PZT substrate having an upward polarization direction  44   z  as shown in  FIG. 8A-i  is used. 
     Next, as shown in  FIGS. 8B-i  and  8 B-ii, the plurality of second groove portions  48  are formed all over a surface (bottom surface of  FIGS. 8B-i  and  8 B-ii) of the second piezoelectric substrate  44 . The dicing process can be preferably used in the process of the second groove portions  48  as in the case of the first groove portions  46 . Through this step, the second groove portions  48  including inclined surfaces  44   b  at back sides of the bottom surface thereof are formed. A processing depth of the second groove portions  48  is also substantially a half of the height of the ink chambers  49  to be formed, and is made to be substantially equal to the depth of the first groove portions  46 . In addition, a length of the second groove portions  48  is substantially equal to a length of the first groove portions  46 . 
     Next, as shown in  FIGS. 8B-i  and  8 B-ii, a metal material is obliquely vapor-deposited from a side of the second piezoelectric substrate  44  where the second groove portions  48  are formed. Thus, the second drive electrodes  62  are formed on side wall surfaces of the second groove portions  48 . Note that the second drive electrodes  62  are individually formed on the side wall surfaces of the second groove portions  48  at both sides thereof in a width direction as in the case of the first drive electrodes  61 . 
     Through the steps described above, the second piezoelectric substrate  44  including the second groove portions  48  is obtained. 
     After the completion of the processing of the first piezoelectric substrate  43  and the second piezoelectric substrate  44 , as shown in  FIGS. 8C-i  and  8 C-ii, the first piezoelectric substrate  43  and the second piezoelectric substrate  44  are next bonded to each other. At this time, the first groove portions  46  and the second groove portions  48  are aligned for bonding the substrates. In other words, the first piezoelectric substrate  43  and the second piezoelectric substrate  44  are bonded to each other in the state where top surfaces of the side walls  45  (which correspond to bottom surfaces in  FIG. 8C-i ) partitioning the first groove portions  46  and top surfaces of side walls  47  partitioning the second groove portions  48  are aligned. As a result, the ink chambers  49  each formed of the first groove portion  46  and the second groove portion  48  are formed. 
     Next, as shown in  FIGS. 8D-i  and  8 D-ii, a metal film is vapor-deposited from the ink supply path  56  of the first piezoelectric substrate  43  toward the ink chambers  49 . Accordingly, conduction electrodes  63  are formed on side walls of the ink chambers  49 , whereby the first drive electrode  61  is electrically connected with the second drive electrode  62 . The ink chambers  49  each include the drive electrodes  65  formed of the first drive electrode  61 , the second drive electrode  62 , and the conduction electrode  63  on the side wall surfaces at both sides thereof. 
     Next, as shown in  FIGS. 8E-i  and  8 E-ii, the nozzle plate  51  is bonded to a side edge surface where the apertures of the ink chambers  49  are provided while positioning the nozzle apertures  52  and the ink chambers  49 , with the result that the inkjet head according to the first embodiment is obtained. 
     In the manufacturing method for an inkjet head described above in detail, the first piezoelectric substrate  43  and the second piezoelectric substrate  44  are formed with the first groove portions and the second groove portions  48  which have substantially the same depths, respectively, and the first piezoelectric substrate and the second piezoelectric substrate  44  are bonded to each other, whereby the ink chambers  49  are formed. The first piezoelectric substrate  43  is formed with the ink supply path  56  connected to the plurality of ink chambers  49 . 
     Therefore, according to the manufacturing method of this embodiment, a manufacturing process for the inkjet head, in which three substrates are conventionally required, can be realized using two piezoelectric substrates. Thus, the number of substrates is reduced, which leads to a reduction in cost. Moreover, there is no need to make the piezoelectric substrates thinner through grinding, and hence there is no waste of piezoelectric materials. 
     In this embodiment, because the depths of the first groove portions  46  are made substantially equal to the depths of the second groove portions  48 , the heights of the side walls  45  and  47  which become the side walls of the ink chambers  49  are substantially equal to each other, and a displacement amount of the side walls when the head is driven is maximized. As a result, a maximum ink discharge amount can be obtained. 
     Note that, in the conventional inkjet head, in order to align the heights of the side walls of portions where the polarization directions are different from each other, adjustment needs to be made in both the formation depths of the grooves and the grinding thicknesses of the piezoelectric substrates. In contrast, in this embodiment, because the side walls  45  and  47  are formed through processing the groove portions, the heights thereof can be easily aligned with each other, and thus the inkjet head can be manufactured with a good yield. 
     Further, because the conduction electrode  63  electrically connecting the first drive electrode  61  and the second drive electrode  62  is formed by a vapor deposition method performed via the ink supply path  56 , even after the first drive electrode  61  and the second drive electrode  62  are formed on separate substrates and the separate substrates are bonded to each other, both the first drive electrode  61  and the second drive electrode  62  are electrically continuous with each other without difficulty. 
     Note that, in the first embodiment, formation positions and a formation method of the conduction electrodes  63  are not limited to the embodiment described above. In other words, if the first drive electrode  61  can be electrically connected to the second drive electrode  62 , the conduction electrode  63  can be formed at appropriate positions by an appropriate method. 
     For instance, the conduction electrode  63  may be formed by a plating method. For example, in this case, electric field plating in which both of the first drive electrode  61  and the second drive electrode  62  are electrodes is performed. A plated film formed on the first drive electrode  61  and a plated film formed on the second drive electrode  62  are integrated with each other during the growth process of the plated films, whereby the first drive electrode  61  and the second drive electrode  62  can be well conductively connected. 
     Alternatively, after bonding of the first piezoelectric substrate  43  and the second piezoelectric substrate  44 , a conducting film may be obliquely vapor-deposited from an entrance side of the ink chamber  49  opening toward a side edge surface where the nozzle plate  51  is provided. 
     Further alternatively, a wire pulled out from the first drive electrode  61  may be formed outside the first groove portion  46  when the first drive electrode  61  is formed, and a wire may also be pulled outside the second groove portion  48  when the second drive electrode  62  is formed so that those wires (or terminals formed at tips thereof) are electrically connected to each other outside the ink chamber  49 . In the case where the wires are connected to each other as described above, a conductive paste may be used. 
     (Modification) 
     Next, a modification of the inkjet head according to the first embodiment is described with reference to  FIGS. 9A and 9B . 
       FIG. 9A  is an enlarged view showing a vicinity of an ink chamber  49  of the inkjet head according to the modification. 
     As shown in  FIG. 9A , the inkjet head according to this modification is different from the inkjet head according to the first embodiment in the width of the side wall  45  of the first piezoelectric substrate  43  and the width of the side wall  47  of the second piezoelectric substrate  44 . 
     As described above, in the manufacturing method according to the present invention, the first piezoelectric substrate  43  formed with the side walls  45  and the second piezoelectric substrate  44  formed with the side walls  47  are bonded to each other while being adjusted so that the side walls  45  are opposite to the side walls  47 . In this case, if the side wall  45  and the side wall  47  are formed to have a different width, the side wall  45  and the side wall  47  can be reliably bonded to each other even if a position of the side wall  45  and a position of the side wall  47  are misaligned in width directions thereof to some extent. 
     Therefore, adopting the structure of this modification enables a margin of the positioning to increase in the case of bonding the first piezoelectric substrate  43  and the second piezoelectric substrate  44  to each other, while also realizing a simpler manufacturing and enhancement of yield. 
     Note that, in an example shown  FIG. 9A , the width of the side wall  45  is made to be smaller than the width of the side wall  47 , but the width of the side wall  47  may be made to be smaller than the width of the side wall  45 . With any of those structures, the similar effects can be obtained. 
     However, in the inkjet head according to the modification, more advantages can be obtained when the width of the side wall  45  of the first piezoelectric substrate  43  is made to be smaller than the width of the side wall  47 .  FIG. 9B  is a view for explaining such advantages. In  FIG. 9B , the conduction electrode  63  for electrically connecting the first drive electrode  61  and the second drive electrode  62  is formed. 
     As described in the former embodiment, the conduction electrode  63  is film-formed through vapor deposition via the ink supply path  56  of the first piezoelectric substrate  43 . In the case of forming the conduction electrode  63  in this way, if the width of the side wall  45  is made to be smaller than the width of the side wall  47 , a step is formed between the side wall  45  and the side wall  47  as shown in  FIG. 9B . Further, because the step faces the ink supply path  56 , when vapor deposition is performed from the ink supply path  56  side, the conduction electrode  63  is formed along the step. Accordingly, the first drive electrode  61  and the second drive electrode  62  are satisfactorily brought into conduction by means of the conduction electrode  63 . 
     In contrast, when the width of the side wall  45  is formed to be larger than the width of the side wall  47 , the step between the side wall  45  and the side wall  47  becomes a step facing a bottom surface of the second groove portion  48 . Thus, even if vapor deposition is performed from the ink supply path side  56 , a break is likely to occur in conduction electrode  63 . 
     Therefore, in the case of forming the conduction electrode  63  by vapor deposition from the ink supply path side  56 , when the width of the side wall  45  is made to be smaller than the width of the side wall  47 , the effect of easily positioning the first piezoelectric substrate  43  and the second piezoelectric substrate  44  can be obtained without impairing the reliability of the conduction electrode  63 . 
     Second Embodiment 
     Next, a second embodiment of the present invention is described with reference to  FIG. 10 . 
       FIG. 10  is a sectional view showing an inkjet head  126  provided in an inkjet recording apparatus according to the second embodiment, which corresponds to  FIG. 5B  referenced in the first embodiment. 
     Note that constitutional elements common to the first embodiment are denoted by the same symbols in  FIG. 10 , and detailed descriptions thereof are omitted. 
     As shown in  FIG. 10 , in the inkjet head  126  according to this embodiment, drive electrodes  161  are formed only on side wall surfaces of the first groove portions  46  among the first groove portions  46  and the second groove portions  48  which form the ink chamber  49 . Besides, the polarization direction  43   z  of the first piezoelectric substrate  43  is the same as the polarization direction  44   z  of the second piezoelectric substrate  44  in a substrate thickness direction. 
     In the inkjet head  126  according to this embodiment, the drive electrodes  161  are formed only on a part of the side wall surfaces of the ink chambers  49 . When voltage is applied to those drive electrodes  161  and an electric field is made to act on the side walls  45 , the inkjet head  126  can be operated as in the case of the first embodiment. 
     However, the shear deformation is generated owing to the electric field only on the side walls  45 , and thus the drive voltage needs to be larger compared with the first embodiment. 
     In the case where the drive electrode is formed only in a part of the ink chamber  49 , in order to obtain a large amount of deformation, the drive electrodes need to be accurately formed in a half region of side surfaces of the ink chamber  49  in a height direction thereof. In this regard, conventionally, a groove portion having a depth corresponding to a height of the ink chamber is formed in the piezoelectric substrate, and oblique vapor deposition in which an angle thereof is adjusted is performed on the groove portion, to thereby form the drive electrode. In such a formation method, forming regions of the drive electrodes differ from each other depending on a positional relationship between a vapor deposition source and the groove portion, which makes it difficult to accurately form a metal film only in a part of the side wall. 
     When the structure according to this embodiment is adopted, the drive electrodes  161  are formed in advance in the first groove portion  46  of the first piezoelectric substrate  43 , and thus the forming region of the drive electrode  161  is accurately defined by merely aligning a processing depth of the first groove portion  46  and a processing depth of the second groove portion  46 . Hence, this embodiment has a structure which can contribute to improvements of the performance and yield of the inkjet head including drive electrodes only in a part of the side walls of the ink chamber. 
     Note that this embodiment has the structure in which the drive electrodes  161  are formed only on the side wall surfaces of the first groove portion  46 , but may have the structure in which the drive electrodes  161  are formed only on the side wall surfaces of the second groove portion  48  of the second piezoelectric substrate  44 . Also in this case, similar operation and effect can be obtained. Further, the polarization directions  43   z  and  44   z  are the same direction in this embodiment, but may be opposite to each other as in the first embodiment. This is because the shear deformation does not occur in the side walls where the drive electrodes are not formed. 
     Further, the structure in which two piezoelectric substrates are provided is described in this embodiment. However, the inkjet head  126  according to this embodiment requires that only the first piezoelectric substrate  43  be a piezoelectric substrate, and a substrate made of other material can be used in place of the second piezoelectric substrate  44 . For instance, in place of the second piezoelectric substrate  44 , a ceramic substrate such as an alumina substrate can be used. This is because, in the structure where the drive electrodes  161  are formed only in the first groove portion  46  as in this embodiment, only the side wall  45  is deformed owing to the electric field, and the side wall  47  merely deforms following the side wall  45 . In addition, the alumina substrate or the like available at a few tenths of the cost for the piezoelectric substrate is used in place of the piezoelectric substrate, with the result that costs can be greatly reduced. 
     It goes without saying that there can be employed a structure where the ceramic substrate is used in place of the first piezoelectric substrate  43 , and the drive electrodes are formed in the second groove portion  48  of the second piezoelectric substrate  44 . If the ceramic substrate is used in place of the first piezoelectric substrate  43  whose processing amount is increased because of the formation of the ink supply path  56 , an amount of the piezoelectric material discarded through processing is reduced. Accordingly, waste of the material can be reduced.