Abstract:
A vibration plate forms a part of a pressure chamber communicated with a nozzle orifice from which a liquid droplet is ejected. The pressure chamber is defined by first edges extending in a first direction with a first dimension and second edges extending in a second direction substantially perpendicular to the first direction with a second dimension shorter than the first dimension. A piezoelectric vibrator is disposed on the vibration plate so as to oppose to the pressure chamber. The piezoelectric vibrator includes a drive electrode extending beyond one of the second edges, a first piezoelectric layer laminated on the drive electrode so as to extend beyond the second edges, and a first common electrode laminated on the first piezoelectric layer. A drive terminal is electrically connected to the drive electrode to supply a drive signal thereto. The drive terminal is overlaid on one of portions of the first piezoelectric layer where is extended beyond the second edges, while being separated from the first common electrode.

Description:
BACKGROUND OF THE INVENTION 
   This invention relates to a liquid jetting head for ejecting a liquid droplet from a nozzle orifice by causing pressure fluctuation to occur in liquid in a pressure chamber as a piezoelectric vibrator becomes deformed. 
   Liquid jetting heads each for ejecting a liquid droplet from a nozzle orifice by causing pressure fluctuation to occur in liquid in a pressure chamber include a recording head, a liquid crystal jetting head, a color material jetting head, and the like, for example. The recording head is installed in an image recording apparatus such as a printer or a plotter for ejecting ink liquid as ink droplets. The liquid crystal jetting head is used with a display manufacturing apparatus for manufacturing liquid crystal displays. In the display manufacturing apparatus, a liquid crystal ejected from the liquid crystal jetting head is poured into a predetermined grid of a display substrate having a large number of grids. The color material jetting head is used with a filter manufacturing apparatus for manufacturing a color filter, and ejects a color material onto the surface of a filter substrate. 
   Various types of liquid jetting heads are available, one of which is a liquid jetting head for ejecting liquid droplets by deflecting and deforming piezoelectric vibrators formed on the surface of a vibration plate. This liquid jetting head is made up of an actuator unit including pressure chambers and piezoelectric vibrators and a flow passage unit including nozzle orifices and a common liquid reservoir, for example. In the liquid jetting head, a piezoelectric vibrator on the vibration plate is deformed, whereby the volume of the corresponding pressure chamber is changed for causing pressure fluctuation to occur in liquid stored in the pressure chamber. Using the pressure fluctuation, a liquid droplet is ejected from the corresponding nozzle orifice. For example, the pressure chamber is contracted, whereby liquid is pressurized for pushing out the liquid from the nozzle orifice. 
   By the way, there is a strong demand for miniaturizing such a liquid jetting head, because the range of uses of the liquid jetting head can be increased as the liquid jetting head is miniaturized. The actuator units are produced, for example, as ceramics are baked. Thus, as the actuator unit is miniaturized, the number of actuator units produced for each lot (for example, from one ceramic sheet) can be increased, leading to cost reduction. 
   SUMMARY OF THE INVENTION 
   It is therefore an object of the invention to provide a liquid jetting head having a structure suited for miniaturization. 
   In order to achieve the above object according to the invention, there is provided a liquid jetting head, comprising: 
   a vibration plate, which forms a part of a pressure chamber communicated with a nozzle orifice from which a liquid droplet is ejected, the pressure chamber being defined by first edges extending in a first direction with a first dimension and second edges extending in a second direction substantially perpendicular to the first direction with a second dimension shorter than the first dimension; 
   a piezoelectric vibrator, disposed on the vibration plate so as to oppose to the pressure chamber, the piezoelectric vibrator comprising: 
   a drive electrode, extending beyond one of the second edges; 
   a first piezoelectric layer, laminated on the drive electrode so as to extend beyond the second edges; and 
   a first common electrode, laminated on the first piezoelectric layer; and 
   a drive terminal, electrically connected to the drive electrode to supply a drive signal thereto, the drive terminal being overlaid on one of portions of the first piezoelectric layer where is extended beyond the second edges, while being separated from the first common electrode. 
   Preferably, the piezoelectric vibrator further comprises: a second common electrode, formed on the vibration plate and electrically connected to the first common electrode; and a second piezoelectric layer, interposed between the second common electrode and the drive electrode. 
   In such a configuration, as the end portion of the drive terminal is overlaid, the size in the longitudinal direction of the piezoelectric vibrator can be reduced accordingly, so that head miniaturization can be accomplished. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The above objects and advantages of the present invention will become more apparent by describing in detail preferred exemplary embodiments thereof with reference to the accompanying drawings, wherein: 
       FIG. 1  is an exploded perspective view to show the configuration of a recording head according to one embodiment of the invention; 
       FIG. 2  is a sectional view to show an actuator unit and a flow passage unit in the recording head; 
       FIG. 3  is a partially enlarged view to show a nozzle plate in the recording head; 
       FIG. 4  is a perspective view of the actuator unit viewed from the side of a piezoelectric vibrator; 
       FIGS. 5 and 6  are sectional views to show the structure of the piezoelectric vibrator; 
       FIG. 7  is an enlarged view of A part in  FIG. 6 ; 
       FIG. 8  is an enlarged view of B part in  FIG. 6 ; 
       FIG. 9  is a drawing to show the structure of one end portion of a dummy vibrator of the recording head; and 
       FIG. 10  is a drawing to show the structure of the other end portion of the dummy vibrator. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Referring now to the accompanying drawings, there will be described one preferred embodiment of the invention. In the description that follows, as a liquid jetting head, a recording head  1  installed in an image recording apparatus such as a printer or a plotter is taken as an example, as shown in  FIG. 1 . The recording head  1  is roughly made up of a flow passage unit  2 , actuator units  3 , and a film-like wiring board  4 . The actuator units  3  are joined side by side on the surface of the flow passage unit  2 , and the wiring board  4  is attached to the surfaces of the actuator units  3  on the opposite side to the flow passage unit  2 . 
   For example, as shown in  FIG. 7 , the wiring board  4  is formed with a conductor pattern  4 B on the surface of a base film  4 A and with a contact terminal  20  left, the conductor pattern  4 B is covered with a resist  4 C and thus the contract terminal  20  is soldered to a discrete terminal  19  (described later) for attaching the wiring board  4 . 
   As shown in  FIG. 2  (sectional view), the flow passage unit  2  is made up of a supply port formation substrate  7  formed with through holes used as a part of an ink supply port  5  and a part of each nozzle communication port  6 , an ink chamber formation substrate  9  formed with through holes used as a common ink reservoir  8  and a part of each nozzle communication port  6 , and a nozzle plate  11  having nozzle orifices  10  arranged in a subscanning direction. The supply port formation substrate  7 , the ink chamber formation substrate  9 , and the nozzle plate  11  are produced by pressing a stainless steel plate material, for example. 
     FIG. 2  shows a part of the flow passage unit  2  corresponding to one actuator unit  3 . In the embodiment, three actuator units  3  are joined to one flow passage unit  2  and therefore a total of three sets of the ink supply port  5 , the nozzle communication ports  6 , the supply port formation substrate  7 , the common ink reservoir  8 , etc., are formed in a one-to-one correspondence with the three actuator units  3 . 
   To produce the flow passage unit  2 , the nozzle plate  11  is placed on one surface of the ink chamber formation substrate  9  (the lower side in the figure) and the supply port formation substrate  7  is placed on an opposite surface of the ink chamber formation substrate  9  (the upper side in the figure) and the supply port formation substrate  7 , the ink chamber formation substrate  9 , and the nozzle plate  11  are joined, for example, with a sheet-like adhesive. 
   The nozzle orifices  10  are made like rows at predetermined pitches as shown in  FIG. 3 . The nozzle orifices  10  made like a row make up each nozzle row  12 . For example,  92  nozzle orifices  10  make up one nozzle row  12 . The two nozzle rows  12  are formed for one actuator unit  3 . Thus, a total of six nozzle rows  12  are formed side by side for one flow passage unit  2   
   The actuator unit  3  is also called a head chip and is one type of piezoelectric actuator. As shown in  FIG. 2 , the actuator unit  3  is made up of a pressure chamber formation substrate  14  formed with through holes used as pressure chambers  13 , a vibration plate  15  for defining a part of each pressure chamber  13 , a lid member  17  formed with through holes used as a supply communication port  16  and a part of each nozzle communication port  6 , and piezoelectric vibrators  18 . As for the plate thicknesses of the members, preferably each of the pressure chamber formation substrate  14  and the lid member  17  is 50 μm or more, more preferably 100 μm or more. Preferably, the vibration plate  15  is 50 μm or less, more preferably about 3 to 12 μm. 
   To produce the actuator unit  3 , the lid member  17  is placed on one surface of the pressure chamber formation substrate  14  and the vibration plate  15  is placed on an opposite surface and the members are formed in one piece. That is, the pressure chamber formation substrate  14 , the vibration plate  15 , and the lid member  17  are made of ceramics of alumina, zirconium oxide, etc., and are baked and put into one piece. 
   For example, work of cutting, punching, etc., is performed on a green sheet (unbaked sheet member) to form necessary through holes, etc., for forming each sheet-like precursor of the pressure chamber formation substrate  14 , the vibration plate  15 , and the lid member  17 . The sheet-like precursors are deposited on each other and are baked, whereby they are put into one piece to form one ceramic sheet. In this case, the sheet-like precursors are baked in one piece and therefore a special adhesion treatment is not required. A high sealing property can also be provided on the joint faces of the sheet-like precursors. 
   One ceramic sheet is formed with pressure chambers  13 , nozzle communication ports  6 , etc., of a plurality of units. In other words, a plurality of actuator units (head chips)  3  are produced from one ceramic sheet. For example, a plurality of chip areas each to form one actuator unit  3  are set like a matrix within one ceramic sheet. Necessary members of the piezoelectric vibrators  18 , etc., are formed in each chip area and then the sheet-like member (ceramic sheet) is cut for each chip area, whereby a plurality of actuator units  3  are provided. 
   The pressure chambers  13  are each a hollow elongated in a direction orthogonal to the nozzle row  12  and are formed in a one-to-one correspondence with the nozzle orifices  10 . That is, the pressure chambers  13  are placed like a row in the nozzle row direction, as shown in  FIG. 3 . Each pressure chamber  13  communicates at one end with the common ink reservoir  8  through the supply communication port  16  and the ink supply port  5 . The pressure chamber  13  communicates at an opposite end to the supply communication port  16  with the corresponding nozzle orifice  10  through the nozzle communication port  6 . Further, a part of the pressure chamber  13  (lower surface) is defined by the vibration plate  15 . 
   The piezoelectric vibrators  18  are each a piezoelectric vibrator  18  in deflection vibration mode and are formed in a one-to-one correspondence with the pressure chambers  13  on the vibration plate surface opposite to the pressure chambers  13 . The piezoelectric vibrator  18  is shaped like a block elongated in the longitudinal direction of the pressure chamber. It has a width roughly equal to that of the pressure chamber  13  and a length a little longer than that of the pressure chamber  13 . Further, the piezoelectric vibrator  18  is disposed so that both end portions are beyond the end portions of the pressure chamber  13  in the longitudinal direction thereof. 
   As shown in  FIG. 4 , the piezoelectric vibrators  18  are provided in a one-to-one correspondence with the pressure chambers  13  on the vibration plate surface opposite to the pressure chambers  13 . That is, the piezoelectric vibrators  18  are arranged in the nozzle row direction. The piezoelectric vibrators  18  at the ends of each vibrator row are dummy vibrators  18   a  not involved in ejecting ink droplets (namely, not deformed because no drive signal is supplied). The piezoelectric vibrators  18  other than the dummy vibrators  18   a  serves as drive vibrators  18   b  involved in ejecting ink droplets (namely, deformed as a drive signal is supplied). 
   The discrete terminals  19  are provided in a one-to-one correspondence with the piezoelectric vibrators  18  on one side of the piezoelectric vibrators  18  (drive vibrators  18   b  and dummy vibrators  18   a ) in the longitudinal direction thereof. The above-mentioned contact terminals  20  of the wiring board  4  (see  FIG. 7 ) are electrically connected to the discrete terminals  19 . A linear proximal common electrode  21  forming a part of a common electrode is extended in the nozzle row direction on an opposite side of the piezoelectric vibrators  18  in the longitudinal direction thereof. 
   The piezoelectric vibrator  18  (drive vibrator  18   b ) in the embodiment has a multilayer structure including a piezoelectric layer  22 , a branch common electrode  23 , a drive electrode (discrete electrode)  24 , etc., and the piezoelectric layer  22  is sandwiched between the drive electrode  24  and the branch common electrode  23 , as shown in  FIG. 5 . A supply source (not shown) of a drive signal is electrically connected to the drive electrode  24  through the discrete electrode  19  while the branch common electrode  23  is adjusted to ground potential, for example, through the proximal common electrode  21 , etc. When a drive signal is supplied to the drive electrode  24 , an electric field of the strength responsive to the potential difference is generated between the drive electrode  24  and the branch common electrode  23 . The electric field is given to the piezoelectric layer  22 , which then becomes deformed in response to the strength of the given electric field. 
   That is, the higher the potential of the drive electrode  24 , the more contracted the piezoelectric layer  22  in the direction orthogonal to the electric field, deforming the vibration plate  15  so as to reduce the volume of the pressure chamber  13 . On the other hand, the lower the potential of the drive electrode  24 , the more extended the piezoelectric layer  22  in the direction orthogonal to the electric field, deforming the vibration plate  15  so as to increase the volume of the pressure chamber  13 . 
   The actuator unit  3  and the flow passage unit  2  are joined to each other. For example, a sheet-like adhesive is placed between the supply port formation substrate  7  and the lid member  17  and in this state, the actuator unit  3  is pressed against the flow passage unit  2 , whereby the actuator unit  3  and the flow passage unit  2  are joined. 
   In the described recording head  1 , ink flow passages each from the common ink reservoir  8  through the ink supply port  5 , the supply communication port  16 , the pressure chamber  13 , and the nozzle communication port  6  to the nozzle orifice  10  are formed in a one-to-one correspondence with the nozzle orifices  10 . At the operating time, the ink flow passage fills with ink. As the piezoelectric vibrator  18  is deformed, the corresponding pressure chamber  13  is contracted or expanded and pressure fluctuation occurs in ink in the pressure chamber  13 . As the ink pressure is controlled, an ink droplet can be ejected from the nozzle orifice  10 . For example, if the pressure chamber  13  of a stationary volume is once expanded and then rapidly contracted, the pressure chamber  13  is filled with ink as the pressure chamber  13  is expanded, and then the ink in the pressure chamber  13  is pressurized because of the later rapid contraction of the pressure chamber  13 , ejecting an ink droplet. Further, as an ink droplet is ejected from the nozzle orifice  10 , new ink is supplied from the common ink reservoir  8  into the ink flow passage, so that successively ink droplets can be ejected. 
   To execute high-speed recording, a larger number of ink droplets need to be ejected in a short time. To meet the requirement, it is necessary to consider compliance of the vibration plate  15  of the portion defining the pressure chamber  13  and the deformation amount of the piezoelectric vibrator  18 . The reason why the compliance and the deformation amount need to be considered is that as the compliance of the vibration plate  15  increases, responsibility to the deformation worsens and it becomes difficult to drive at a high frequency and that as the compliance of the vibration plate  15  lessens, the vibration plate  15  becomes hard to deform and the shrinkage amount of the pressure chamber  13  lessens, decreasing the ink amount of one droplet. 
   In the embodiment, the piezoelectric vibrators  18  each of a multilayer structure are used to lessen the compliance of the vibration plate  15  and it is made possible to eject an ink droplet of the necessary amount at a higher frequency than ever. The end portions of the discrete terminals  19  are deposited on the piezoelectric vibrators  18  for miniaturizing the actuator unit  3  in the width direction thereof. Further, a connection electrode for electrically connecting the proximal common electrode  21  and the discrete electrode  19  is placed in each dummy electrode  18   a . These points will be discussed below. 
   To begin with, the structure of the drive vibrator  18   b  will be discussed. As shown in  FIG. 5 , the piezoelectric layer  22  is formed like a block elongated in the longitudinal direction of the pressure chamber and is made up of an upper piezoelectric body (outer piezoelectric body)  31  and a lower piezoelectric body (inner piezoelectric body)  32  deposited on each other. The branch common electrode  23  is made up of an upper common electrode (outer common electrode)  33  and a lower common electrode (inner common electrode)  34 . The branch common electrode  23  and the drive electrode  24  make up an electrode layer. 
   The term “upper (outer)” or “lower (inner)” mentioned here is used to indicate the position relationship with the vibration plate  15  as the reference. That is, the term “upper (outer)” is used to indicate the side distant from the vibration plate  15  and the term “lower (inner)” is used to indicate the side near to the vibration plate  15 . 
   The drive electrode  24  is formed on the boundary between the upper piezoelectric body  31  and the lower piezoelectric body  32 . The lower common electrode  34  and the upper common electrode  33  together with the proximal common electrode  21  make up the common electrode. That is, the common electrode is pectinated so as to form a plurality of branch common electrodes  23  (lower common electrode  34  and upper common electrode  33 ) extended from the proximal common electrode  21 . 
   The lower common electrode  34  is formed between the lower piezoelectric body  32  and the vibration plate  15 , and the upper common electrode  33  is formed on the surface of the upper piezoelectric body  31  on the opposite side to the lower piezoelectric body  32 . That is, the drive vibrator  18   b  is of a multilayer structure wherein the lower common electrode  34 , the lower piezoelectric body  32 , the drive electrode  24 , the upper piezoelectric body  31 , and the upper common electrode  33  are deposited in order from the vibration plate  15  side. 
   In the embodiment, the piezoelectric layer  22  has a thickness of about 17 μm (the thickness of the upper piezoelectric body  31  plus the thickness of the lower piezoelectric body  32 ). The total thickness of the piezoelectric vibrator  18  including the branch common electrode  23  is about 20 μm. The related-art piezoelectric vibrator of the single-layer structure has a total thickness of about 15 μm. Therefore, as the thickness of the piezoelectric vibrator  18  increases, the compliance of the vibration plate  15  lessens accordingly. 
   The upper common electrode  33  and the lower common electrode  34  are adjusted to a constant potential, for example, ground potential regardless of a drive signal. The drive electrode  24  is changed in potential in response to the supplied drive signal. Therefore, as the drive signal is supplied, electric fields opposite in direction occur between the drive electrode  24  and the upper common electrode  33  and between the drive electrode  24  and the lower common electrode  34 . 
   As materials forming the electrodes, various conductors of discrete metal, an alloy, a mixture of electric insulating ceramics and metal, and the like can be selected, but it is required that a defective condition of deterioration, etc., should not occur at the baking temperature. In the embodiment, gold is used for the upper common electrode  33  and platinum is used for the lower common electrode  34  and the drive electrode  24 . 
   Both the upper piezoelectric body  31  and the lower piezoelectric body  32  are made of piezoelectric material consisting essentially of lead zirconate titanate (PZT), for example. The upper piezoelectric body  31  and the lower piezoelectric body  32  are opposite in polarization direction. Thus, the upper piezoelectric body  31  and the lower piezoelectric body  32  are identical in the extending or contracting direction when the drive signal is applied, and can deform the vibration plate  15  without a hitch. That is, as the potential of the drive electrode  24  is made higher, the upper piezoelectric body  31  and the lower piezoelectric body  32  deform the vibration plate  15  so as to lessen the volume of the pressure chamber  13 ; as the potential of the drive electrode  24  is made lower, the upper piezoelectric body  31  and the lower piezoelectric body  32  deform the vibration plate  15  so as to increase the volume of the pressure chamber  13 . 
   Next, the structure of one side (common ink reservoir 8 side) of the drive vibrator  18   b  will be discussed. 
   On the one side, the discrete terminal  19  is formed as described above. The discrete terminal  19  of the drive vibrator  18   b  is a drive potential supply terminal for supplying a drive signal (drive potential), and is electrically connected to the contact terminal  20  of the wiring board  4 . The discrete terminal  19  is electrically connected to the drive electrode  24  extended in the longitudinal direction of the pressure chamber  13 . That is, a part of the discrete terminal  19  is deposited on an end portion of the drive electrode  24 . 
   The embodiment is characterized by the fact that the end portion of the discrete terminal  19  is overlaid on the surface of the vibrator end portion (upper piezoelectric body) which is not superposed on the pressure chamber  13 , and further the discrete terminal  19  is formed away from the upper common electrode  33  (branch common electrode  23 ). 
   That is, as shown in  FIGS. 6 and 7 , the one end portion of the piezoelectric vibrator  18  is extended beyond the end portion of the pressure chamber  13 , in other words, to a non-superposition area outside the superposition area on the pressure chamber  13 . The vibrator-side end portion of the discrete terminal  19  is deposited on the upper surface of the piezoelectric vibrator  18  in the non-superposition area. The end portion of the discrete terminal  19  formed on the piezoelectric vibrator  18  becomes an electric connection (conduction) part with the wiring board  4  (contact terminal  20 ), which will be hereinafter also called conduction part  19   a . On the other hand, the end portion of the upper common electrode  33  is formed to a point before the discrete terminal  19 , but an isolation area X from the discrete terminal  19  is provided and therefore they are not electrically connected. 
   Such a structure makes it possible to miniaturize the actuator unit  3 . That is, the end portion of the discrete terminal  19  is positively overlaid on the surface of the piezoelectric vibrator  18 , so that the discrete terminal  19  can be formed leaning to the piezoelectric vibrator side as a whole. Thus, as for the discrete terminal  19 , while the length required for electric connection (namely, the necessary length for joint to the contact terminal  20 ) is ensured, the width of the actuator unit  3 , particularly, the width in the longitudinal direction of the pressure chamber can be shortened. 
   As the actuator unit  3  is miniaturized, at the manufacturing time, a larger number of actuator units  3  can be laid out on a ceramic sheet of the same area as the ceramic sheet in the related art. Therefore, in a case where the same process as that in the related art is applied, a larger number of actuator units  3  can be manufactured so that the manufacturing efficiency can be improved. The raw material can also be saved. Since the manufacturing efficiency can be improved and the raw material can be saved, cost reduction in the actuator unit  3  is also made possible. 
   At the connecting time to the wiring board  4 , with the contact terminal  20  of the wiring board  4  put on the discrete terminal  19 , a heating terminal (not shown) is pressed from the wiring board surface on the opposite side to the discrete terminal  19  for soldering the discrete terminal  19  and the contact terminal  20 , as shown in  FIG. 7 . In this case, the conduction part  19   a  of the discrete terminal  19  is positioned above the piezoelectric vibrator  18  and is at the highest position in the actuator unit  3  and therefore is most strongly pressurized by the heating terminal. Thus, reliable soldering can be accomplished. 
   Further, the conduction part  19   a  is formed on the piezoelectric vibrator  18  and thus the member below the conduction part  19   a  is thickened as much as the piezoelectric vibrator  18 , so that the member is enhanced in rigidity and can also receive reliably the press force from the heating terminal. 
   Next, the structure of an opposite side (nozzle orifice  10  side) of the drive vibrator  18   b  will be discussed. 
   As shown in  FIGS. 6 and 8 , on the opposite side of the drive vibrator  18   b , the upper common electrode  33  and the lower common electrode  34  are extended in the longitudinal direction of the pressure chamber  13 . That is, the lower common electrode  34  is formed through the top of the vibrator plate  15  to the lower face of the proximal common electrode  21 . The upper common electrode  33  is formed through a side end face of the piezoelectric layer  22  to the surface of the lower common electrode  34 . Further, the upper common electrode  33  is also formed to the lower face of the proximal common electrode  21 . Therefore, both the upper common electrode  33  and the lower common electrode  34  are electrically connected to the proximal common electrode  21 . 
   Next, the structure of the dummy electrode  18   a  will be discussed. The basic structure of the dummy electrode  18   a  is the same as that of the drive vibrator  18   b  described above. That is, as shown in  FIGS. 9 and 10 , the dummy electrode  18   a  also has a piezoelectric layer  22  including an upper piezoelectric body  31  and a lower piezoelectric body  32  and formed like a block elongated in the pressure chamber longitudinal direction and is formed with an electrode layer between the vibration plate  15  and the lower piezoelectric body  32 , an electrode layer on the boundary between the upper piezoelectric body  31  and the lower piezoelectric body  32 , and an electrode layer on the surface of the upper piezoelectric body  31  opposite to the lower piezoelectric body  32 . 
   In the embodiment, the electrode layer between the vibration plate  15  and the lower piezoelectric body  32 , which will be hereinafter referred to as a first connection electrode  35 , and the electrode layer on the boundary between the upper piezoelectric body  31  and the lower piezoelectric body  32 , which will be hereinafter referred to as a second connection electrode  36 , are extended to both sides in the longitudinal direction of the pressure chamber  13  for electrically connecting the proximal common electrode  21  and the discrete terminal  19 . 
   That is, the first connection electrode  35  is formed from the proximal common electrode  21  through the lower side of the lower piezoelectric body  32  to the discrete terminal  19 , and the second connection electrode  36  is formed from the proximal common electrode  21  through the lower side of the upper piezoelectric body  31  to the discrete terminal  19 . In the embodiment, the connection electrodes are formed with the same electrode material as the lower common electrode  34  and the drive electrode  24 . 
   In the structure, the discrete terminal  19  provided on the dummy electrode  18   a  and the proximal common electrode  21  are electrically connected through the connection electrodes  35 ,  36 , so that the discrete terminal  19  can be used as a supply terminal to supply common potential (for example, ground potential). Since the discrete terminal  19  is formed in the same row as the discrete terminal  19  for the drive vibrator  18   b , the actuator unit  3  can be miniaturized. To electrically connect the wiring board  4  and each discrete terminal  19 , the discrete terminal  19  for the dummy vibrator  18   a  and the discrete terminal  19  for the drive vibrator  18   b  can be electrically connected collectively, so that the work efficiency can be improved. 
   The connection electrodes are placed on the lower side of the piezoelectric layer  22 , no burr-like parts occur. Thus, defective conditions of breaking or short-circuiting the wiring due to a burr-like part after the wiring board  4  is mounted can be prevented reliably. Therefore, full use of the stable performance of the recording head  1  with less trouble can be made. 
   Further, the connection electrodes  35  and  36  are separated into two layers and thus a sufficient thickness can be ensured, so that the resistance value of the electrode can be suppressed to a low value. In addition, the connection electrodes  35  and  36  are formed with the same electrode material as the lower common electrode  34  and the drive electrode  24  and thus can be manufactured at the same time as the lower common electrode  34  and the drive electrode  24 . That is, the first connection electrode  35  can be manufactured at the same time as the lower common electrode  34 , and the second connection electrode  36  can be manufactured at the same time as the drive electrode  24 . This eliminates the need for executing the specific process for forming the connection electrodes, and the manufacturing efficiency can be enhanced. 
   It is to be understood that the invention is not limited to the specific embodiment and the combination and arrangement of parts may be resorted to without departing from the spirit and the scope of the invention as claimed. 
   For example, in the embodiment, the piezoelectric vibrator  18  is of the multilayer structure wherein the upper and lower piezoelectric bodies  31  and  32  and the like are deposited, but the invention can also be applied to the piezoelectric vibrator of a single-layer structure including a single layer of piezoelectric layer. For example, for the drive vibrator  18   b , the drive electrode  24  is formed between the piezoelectric layer  22  and the vibration plate  15 , and the upper common electrode  33  and the discrete electrode  19  are formed on the piezoelectric layer surface opposite to the vibration plate  15 . For the dummy vibrator  18   a , the connection electrode is formed between the piezoelectric layer  22  and the vibration plate  15 . 
   Although the liquid jetting head has been described by taking the recording head  1 , one type of liquid jetting head, as an example, the invention can also be applied to other liquid jetting heads such as a liquid crystal jetting head and a color material jetting head.