Patent Publication Number: US-10786991-B2

Title: Liquid jetting apparatus

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     The present application is a continuation of U.S. patent application Ser. No. 15/919,626, filed Mar. 13, 2018, now U.S. Pat. No. 10,618,282, which claims priority from Japanese Patent Application No. 2017-192192, filed on Sep. 29, 2017, the disclosures of which are incorporated herein by reference in their entirety. 
    
    
     BACKGROUND 
     Field of the Invention 
     The present invention relates to a liquid jetting apparatus. 
     Description of the Related Art 
     Conventionally, there is known a liquid jetting apparatus which includes piezoelectric elements. A conventional liquid jetting apparatus includes individual electrodes provided to correspond individually to the piezoelectric elements, and a common electrode provided commonly for the piezoelectric elements. The common electrode is connected with a wiring member on which a driver IC is mounted to output a drive signal for driving the piezoelectric elements via traces connected to the common electrode. Further, each of the individual electrodes is connected with the wiring member via a trace connected thereto. 
     Because the common electrode is provided commonly for the piezoelectric elements, the electric current flowing through the traces connected to the common electrode is larger than the electric current flowing through the traces connected to the individual electrodes. Therefore, on the way of the route linking the contact points between the traces and the common electrode and the contact points between the traces and the wiring member, if a trace connected to the common electrode becomes thinner, then the electric resistance of that part will become larger. If the electric resistance of the trace for the common electrode becomes larger, then the waveform of the drive signal transmitted to each of the piezoelectric elements is liable to become dull and/or the common electrode is liable to underdo excessive heating. 
     Japanese Patent Application Laid-open No. 2016-185604 discloses an ink-jet head including piezoelectric elements each of which has an upper electrode and a lower electrode facing each other, and a piezoelectric body layer interposed between the upper electrode and the lower electrode. The upper electrode is the common electrode shared among the piezoelectric elements. A common electrode layer is provided as traces on the upper surface of the upper electrode. A sealing plate is provided as a cover on the respective piezoelectric elements, and a common bump electrode provided on the lower surface of the sealing plate is joined with the common electrode layer. Further, an individual electrode layer is laid as traces on the upper surface of the lower electrodes. The individual electrode layer extends from the position laid with the lower electrodes to the upper surface of the piezoelectric layer, passing over the step at the end portion of the piezoelectric body layer. The individual electrode layer is joined with individual bump electrodes provided on the lower surface of the sealing plate at the position of the upper surface of the piezoelectric body layer. 
     According to Japanese Patent Application Laid-open No. 2016-185604, the individual electrode layer is a film formed across the step in the vicinity of the end portion of the piezoelectric layer. Therefore, when forming the film of the individual electrode layer, the individual electrode layer is liable to become thinner than the desired thickness in the vicinity of the end portion of the piezoelectric layer. On the other hand, the common electrode layer extends from the position overlapping with the upper electrode to the position joined with the common bump electrode, without coming down the step of the piezoelectric layer. Therefore, the common electrode layer is less liable to become thinner on the route linking the position overlapping the upper electrode and the position joined with the common bump electrode. Hence, according to the ink-jet head of Japanese Patent Application Laid-open No. 2016-185604, such problems are less likely to happen as the drive signal becoming dull and/or the heating in the common electrode layer which is the traces for the common electrode. 
     SUMMARY 
     However, the sealing plate of Japanese Patent Application Laid-open No. 2016-185604 is used as a substrate to support a pressure chamber formation substrate, in a process of grinding the pressure chamber formation substrate to a desired thickness for forming pressure chambers. In this case, the pressure chamber formation substrate is ground with the common bump electrode and the individual bump electrodes being respectively joined with the common electrode layer and the individual electrode layer. On this occasion, there is a load on the junction part between the common bump electrode and the common electrode layer, and the junction part between the individual bump electrodes and the individual electrode layer. Therefore, in the vicinity of those junction parts, crack is liable to occur in the upper electrode and the piezoelectric body layer. Further, the junction parts are liable to separate due to the load thereon in the grinding process. 
     The present teaching is made in view of such situations, and an object thereof is to provide a liquid jetting apparatus which is capable of joining the wiring member and the traces from the upper electrode and lower electrodes, and which is less likely to give rise to defection in the manufacturing process. 
     According to a first aspect of the present teaching, there is provided a liquid jetting apparatus including: a pressure chamber formation member having first pressure chambers arranged in a first direction, and an insulation film covering the first pressure chambers; a cover joined to the pressure chamber formation member, the cover having a first convex portion and a second convex portion, each of the first convex portion and the second convex portion having a bonding surface to the pressure chamber formation member and extending in the first direction; and a wiring member joined to the pressure chamber formation member, wherein the first pressure chambers have first ends aligned in the first direction, second ends aligned in the first direction, and centers positioned between the first ends and the second ends in a second direction which is along a planar direction of the insulation film and orthogonal to the first direction; the centers of the respective first pressure chambers being positioned between the first convex portion and the second convex portion of the cover in relation to the second direction, the pressure chamber formation member has: first electrodes overlapping respectively with the first pressure chambers in a third direction orthogonal to the planar direction of the insulation film, while sandwiching the insulation film therebetween; a piezoelectric layer overlapping with the insulation film and the first electrodes in the third direction; a second electrode overlapping with the first electrodes in the third direction, while sandwiching the piezoelectric layer therebetween; first traces connected respectively with the first electrodes; and a second trace connected with the second electrode, the piezoelectric layer has a first surface facing the insulation film and the first electrodes, and a second surface on a side opposite to the insulation film and the first electrodes with respect to the first surface, the second trace is connected to the wiring member, the second trace includes an extending portion extending continuously from the second electrode to a contact point with the wiring member, and the piezoelectric layer is positioned between the insulation film and the extending portion of the second trace in relation to the third direction. 
     According to a second aspect of the present teaching, there is provided a liquid jetting apparatus including: a pressure chamber formation member having first pressure chambers arranged along a first direction, and an insulation film covering the first pressure chambers; and a wiring member joined to the pressure chamber formation member, wherein the pressure chamber formation member has: first electrodes overlapping respectively with the first pressure chambers in a third direction orthogonal to the planar direction of the insulation film, while sandwiching the insulation film therebetween; a piezoelectric layer overlapping with the insulation film and the first electrodes in the third direction; a second electrode overlapping with the first electrodes in the third direction while sandwiching the piezoelectric layer therebetween; first traces connected respectively with the first electrodes; and a second trace connected with the second electrode, the piezoelectric layer has a first surface facing the insulation film and the first electrodes, and a second surface on a side opposite to the insulation film and the first electrodes with respect to the first surface, the second trace is connected to the wiring member, the second trace includes an extending portion extending continuously from the second electrode to a contact point with the wiring member, the piezoelectric layer is positioned between the insulation film and the extending portion of the second trace in relation to the third direction, the wiring member has a base material and traces formed in the base material, and the base material of the wiring member has a first part joined to the pressure chamber formation member, a second part drawn out in a direction away from the pressure chamber formation member, and a curved part between the first part and the second part. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic plan view of a printer according to an embodiment of the present teaching. 
         FIGS. 2A to 2C  depict a pressure chamber formation substrate, wherein  FIG. 2A  is a plan view depicting an end side of the pressure chamber formation substrate according to a conveyance direction,  FIG. 2B  is a cross-sectional view along the line IIB-IIB of  FIG. 2A , and  FIG. 2C  is a cross-sectional view along the line IIC-IIC of  FIG. 2A . 
         FIGS. 3A and 3B  are enlarged views of an individual trace, wherein  FIG. 3A  is an enlarged perspective view of the part A of  FIG. 2A , and  FIG. 3B  is an enlarged perspective view of the part B of  FIG. 2A . 
         FIGS. 4A to 4C  depict the pressure chamber formation substrate joined with a cover, wherein  FIG. 4A  is a plan view depicting the end side of the pressure chamber formation substrate joined with the cover according to the conveyance direction,  FIG. 4B  is a cross-sectional view along the line IVB-IVB of  FIG. 4A , and  FIG. 4C  is a cross-sectional view along the line IVC-IVC of  FIG. 4A . 
         FIG. 5  is a bottom view of the cover. 
         FIG. 6  is a flow chart depicting a process of manufacturing a jetting module. 
         FIGS. 7A and 7B  depict the pressure chamber formation substrate and cover of a jetting module according to a first modified embodiment of the present teaching, wherein  FIG. 7A  is a plan view corresponding to  FIG. 4A , and  FIG. 7B  is a cross-sectional view corresponding to  FIG. 4B . 
         FIGS. 8A and 8B  depict the pressure chamber formation substrate and cover of a jetting module according to a second modified embodiment of the present teaching, wherein  FIG. 8A  is a plan view corresponding to  FIG. 4A , and  FIG. 8B  is a cross-sectional view corresponding to  FIG. 4B . 
         FIGS. 9A and 9B  depict the pressure chamber formation substrate and cover of a jetting module according to a third modified embodiment of the present teaching, wherein  FIG. 9A  is a cross-sectional view corresponding to  FIG. 2B , and  FIG. 9B  is a cross-sectional view corresponding to  FIG. 2C . 
         FIG. 10  is a plan view, corresponding to  FIG. 2A , of the pressure chamber formation substrate of a jetting module according to a fourth modified embodiment of the present teaching. 
     
    
    
     DESCRIPTION OF THE EMBODIMENT 
     Next, a preferred embodiment of the present teaching will be explained. First, referring to  FIG. 1 , an explanation will be made about a schematic configuration of an ink-jet printer  1 . Note that each direction of the front, rear, left and right depicted in  FIG. 1  is defined as the “front”, “rear”, “left”, and “right” of the printer. Further, the near side of the page is defined as the “upper” whereas the far side of the page is defined as the “lower”. Hereinbelow, each term of the above front, rear, left, right, upper and lower directions will be used as appropriate for the explanation. 
     &lt;Schematic Configuration of the Printer&gt; 
     As depicted in  FIG. 1 , the ink-jet printer  1  includes a platen  2 , a carriage  3 , an ink-jet head  4 , a conveyance mechanism  5 , a controller  6 , and the like. 
     A recording medium, namely recording paper  100 , is placed on the upper surface of the platen  2 . The carriage  3  is configured to be reciprocatingly movable in a left/right direction (to be referred to below as a scanning direction) along two guide rails  10  and  11 , in an area facing the platen  2 . An endless belt  14  is linked to the carriage  3 . A carriage drive motor  15  drives the endless belt  14  such that the carriage  3  may move in the scanning direction. 
     The ink-jet head  4  is fitted on the carriage  3  to move together with the carriage  3  in the scanning direction. The ink-jet head  4  includes four jetting modules  16  aligning in the scanning direction. The four jetting modules  16  are connected respectively with a cartridge holder  7  installed with four ink cartridges  17  through undepicted tubes. The four ink cartridges retain inks of four colors (black, yellow, cyan, and magenta), respectively. Each of the jetting modules  16  has nozzles  24  (see  FIG. 2A ) formed on its lower surface (the surface on the far side of the page of  FIG. 1 ). The nozzles  24  of each of the jetting modules  16  jet the ink of one color supplied from any one ink cartridge  17  toward the recording paper  100  placed on the platen  2 . 
     The conveyance mechanism  5  has two conveyance rollers  18  and  19  arranged to interpose the platen  2  therebetween in a front/rear direction. With the two conveyance rollers  18  and  19 , the conveyance mechanism  5  conveys the recording paper  100  placed on the platen  2  to the front side (also to be referred to below as in a conveyance direction). 
     The controller  6  includes a ROM (Read Only Memory), a RAM (Random Access Memory), and an ASIC (Application Specific Integrated Circuit) including various control circuits, etc. The controller  6  causes the ASIC to carry out various processes such as printing on the recording paper  100  and the like, according to programs stored in the ROM. For example, in a printing process, the controller  6  controls the ink-jet head  4 , the carriage drive motor  15 , and the like to print image and the like on the recording paper  100 , based on a print command inputted from an external device such as a PC or the like. In particular, the controller  6  causes the relevant members to alternately carry out a jetting operation to jet the inks while moving the ink-jet head  4  together with the carriage  3  in the scanning direction, and a conveying operation to let the conveyance rollers  18  and  19  convey the recording paper  100  through a predetermined distance in the conveyance direction. 
     Next, a detailed explanation will be made about a configuration of the jetting modules  16  of the endless belt  14 . Note that because the four jetting modules  16  have the same configuration with each other, the following explanation will be made about one of the four jetting modules  16 . 
     As depicted in  FIGS. 2A to 4C , the jetting module  16  includes a pressure chamber formation member  22 , a COF (Chip On Film)  50 , a cover  60 , and the like. The pressure chamber formation member  22  includes a nozzle plate  20 , a flow channel substrate  21 , an insulation film  30 , lower electrodes  32 , a piezoelectric film  33 , upper electrodes  34 , individual traces  41 , a common trace  42 , and the like. 
     &lt;Nozzle Plate  20 &gt; 
     The nozzle plate  20  is, for example, a plate formed of silicon or the like. The nozzle plate  20  is formed with nozzles  24 . As depicted in  FIG. 2A , the nozzles  24  are arrayed along the conveyance direction to form two nozzle rows  27  aligning in the scanning direction. Further, if P is taken for the arrayal pitch of the nozzles  24  of one nozzle row  27 , then between the two nozzle rows  27 , the nozzles  24  are positioned to deviate by P/2 in the conveyance direction. 
     &lt;Flow Channel Substrate  21 &gt; 
     The flow channel substrate  21  is formed of substrates  21   a  and  21   b  of a two-layer silicon single crystal. The substrate  21   a  is formed with pressure chambers  26  and part of aftermentioned manifolds  25 . The substrate  21   b  is formed with flow channels for respective communications between the part of the manifolds  25 , the pressure chambers  26  and the nozzles  24 , and flow channels for respective communications between the pressure chambers  26  and the manifolds  25 , etc. Each of the pressure chambers  26  has a rectangular planer shape elongated in the scanning direction. Hereinbelow, the scanning direction will also be referred to as “longitudinal direction (of the pressure chambers)”, and the conveyance direction as “transverse direction (of the pressure chambers)”. The pressure chambers  26  are arranged according to the abovementioned arrangement of the nozzles  24 , to form two pressure chamber rows  28  aligning in the scanning direction. The lower surface of the flow channel substrate  21  is covered by the nozzle plate  20 . As viewed in an up/down direction, one end portion of each pressure chamber  26  according to the longitudinal direction overlaps with the nozzle  24 . The one end portion of each pressure chamber  26  according to the longitudinal direction is the end portion at the central side of the jetting module  16 . 
     In left and right end portions of the flow channel substrate  21 , the two manifolds  25  are formed to extend in the conveyance direction, corresponding respectively to the two pressure chamber rows  28 . Each of the respective pressure chambers  26  forming one pressure chamber row  28  is in communication with the corresponding manifold  25 . 
     Each of the manifolds  25  is connected with the cartridge holder  7  through an ink supply member (not depicted) including a tube or the like. The inks in the ink cartridges  17  installed in the cartridge holder  7  flow into the manifolds  25  via the above ink supply members to supply the respective pressure chambers  26  with the inks from the manifolds  25 . 
     &lt;Insulation Film  30 &gt; 
     As depicted in  FIG. 2B , the insulation film  30  covers the pressure chambers  26  formed in the flow channel substrate  21 . The insulation film  30  of this embodiment is a dioxide silicon film formed by oxidizing a surface of the flow channel substrate  21 , the film being integrated with the flow channel substrate  21 . Note that the insulation film  30  is not limited to such a configuration but may be formed of another material on a surface of the flow channel substrate  21 . The insulation film  30  is, for example, 1 to 2 μm thick. 
     &lt;Lower Electrodes  32 &gt; 
     The lower electrodes  32  are arranged in such areas of the upper surface of the insulation film  30  as overlapping respectively with the pressure chambers  26 . That is, the lower electrodes  32  are arranged in two rows in the scanning direction to correspond respectively to the two pressure chamber rows  28 . In this embodiment, each lower electrode  32  has a first part  32   a  extending in the scanning direction, and a second part  32   b  further extending in the scanning direction from one end of the first part  32   a  in the scanning direction (the end at the central side of the jetting module  16 ). The first part  32   a  has a rectangular shape one size smaller than the planar shape of each pressure chamber  26 , and the entire first part  32   a  overlaps with one pressure chamber  26 . The width of the second part  32   b  along the conveyance direction is smaller than the width of the first part  32   a  along the conveyance direction. The lower electrodes  32  are supplied individually with a drive signal from an aftermentioned driver IC  53  through the individual traces  41 . That is, the lower electrodes  32  are so-called individual electrodes each provided individually for the pressure chambers  26 . The lower electrodes  32  are formed of, for example, platinum (Pt). Further, the lower electrodes  32  are, for example, 0.05 to 0.30 μm thick. 
     &lt;Piezoelectric Film  33 &gt; 
     The piezoelectric film  33  is formed on the insulation film  30  and lower electrodes  32 . The piezoelectric film  33  is formed of, for example, a piezoelectric material such as lead zirconate titanate (also PZT: Piezoelectric Zirconate Titanate) or the like. Alternatively, the piezoelectric film  33  may be formed of a piezoelectric material not containing lead. The piezoelectric film  33  is, for example, 1 to 2 μm thick. 
     The piezoelectric film  33  is formed with two through holes  38  aligning in the scanning direction. Each of the through holes  38  extends in the conveyance direction within the two opposite ends of the piezoelectric film  33  in the conveyance direction. The two through holes  38  are positioned within the two pressure chamber rows  28  in the scanning direction. In more detail, as depicted in  FIG. 2A , the two through holes  38  are positioned between right end portions of the respective pressure chambers  26  forming the left pressure chamber row  28 , and left end portions of the respective pressure chambers  26  forming the right pressure chamber row  28 . As depicted in  FIGS. 2A and 2B , the second part  32   b  of each lower electrode  32  extends in the scanning direction to the inside of the through hole  38 . That is, a leading end portion of the second part  32   b  of each lower electrode  32  is exposed from the through hole  38 . Note that in the following explanation, for the sake of convenience, the term “active portion” will be used to refer to such a part of the piezoelectric film  33  as at the outside of the two through holes  38  in the scanning direction, whereas the term “junction portion” will be used to refer to such a part of the piezoelectric film  33  as at the inside of the two through holes  38  in the scanning direction. Then, the term “intermediate portion” will be used to refer to such a part of the piezoelectric film  33  as between the active portion and the junction portion in the scanning direction where no through hole  38  is formed. 
     &lt;Upper Electrodes  34 &gt; 
     An upper surface  33   b  of the piezoelectric film  33  is formed with the two upper electrodes  34  aligning in the scanning direction to correspond respectively to the two pressure chamber rows  28 . Each of the upper electrodes  34  has a rectangular shape elongated in the conveyance direction to overlap entirely with the pressure chambers  26  forming the corresponding pressure chamber row  28  in the up/down direction. In more detail, all the pressure chambers  26  forming the corresponding pressure chamber row  28  are arranged within the two opposite ends of each upper electrode  34  in the scanning direction. That is, the two opposite ends of each pressure chamber  26  are positioned within the two opposite ends of the corresponding upper electrode  34  in the scanning direction. Further, the two upper electrodes  34  overlap respectively with the two rows of the lower electrodes  32  across the piezoelectric film  33 . The upper electrodes  34  are formed of, for example, iridium. The upper electrodes  34  are, for example, 0.01 to 0.10 μm thick. 
     &lt;Individual Traces  41 &gt; 
     Next, referring to  FIGS. 2A, 2B, 3A and 3B , the individual traces  41  will be explained. The lower electrodes  32  aligning in the two rows are connected respectively with the individual traces  41 . Each of the individual traces  41  extends from the upper surface of the active portion to the upper surface of the junction portion of the piezoelectric film  33  across the through hole  38 . Each individual trace  41  is connected to the leading end portion, exposed from the through hole  38 , of the second part  32   b  of the corresponding lower electrode  32 . 
     Each individual trace  41  is formed from a conductive portion  41   a , a first extending portion  41   b  continuing from the conductive portion  41   a , a second extending portion  41   c  continuing from the first extending portion  41   b , and a third extending portion  41   d  continuing from the second extending portion  41   c . The conductive portion  41   a  is formed along the upper surface of the active portion of the piezoelectric film  33  and an inner surface  33   c  formed due to the through hole  38  at the active portion side. The first extending portion  41   b  is formed along the upper surface of the insulation film  30  to overlap with the part, exposed from the through hole  38 , of the second part  32   b  of the lower electrode  32 . The second extending portion  41   c  is formed along an inner surface  33   d  formed due to the through hole  38  at the junction portion side. The third extending portion  41   d  is formed along the upper surface of the junction portion of the piezoelectric film  33 . 
     Because the second extending portion  41   c  is formed along an inner surface  38   b  of the through hole  38  at the junction portion side, the second extending portion  41   c  is likely to become thinner than the first extending portion  41   b  formed on the upper surface of the insulation film  30 . Therefore, in this embodiment, the width d 2  of the second extending portion  41   c  along the conveyance direction is larger than the width d 1  of the first extending portion  41   b  along the conveyance direction in a central portion along the scanning direction. By virtue of this, in the second extending portion  41   c , the individual trace  41  is prevented from decrease in electric resistance. From the same reason, the width d 5  of the conductive portion  41   a  along the conveyance direction is larger than the width d 1  of the first extending portion  41   b  along the conveyance direction in the central portion along the scanning direction. 
     The third extending portion  41   d  has a wide part  41   d   1  and a narrow part  41   d   2  which are continuous in the scanning direction. The width d 3  of the wide part  41   d   1  along the conveyance direction is larger than the width d 4  of the narrow part  41   d   2  along the conveyance direction. 
     In this embodiment, the first extending portion  41   b  and the third extending portion  41   d  are inclined respectively at different angles to the scanning direction. That is, when viewed from above, each individual trace  41  extends in the scanning direction while inflecting at a plurality of places. Each individual trace  41  is formed of, for example, gold (Au). The conductive portion  41   a  is, for example, 0.5 to 2.0 μm thick. The first extending portion  41   b  is, for example, also 0.5 to 2.0 μm thick. The second extending portion  41   c  is, for example, 0.3 to 1.5 μm thick. The third extending portion  41   d  is, for example, 0.5 to 2.0 μm thick. 
     As depicted in  FIGS. 2A and 2B , on the junction portion of the piezoelectric film  33 , there are aligned alternately in the conveyance direction the third extending portions  41   d  corresponding respectively to the lower electrodes  32  on the left, and the third extending portions  41   d  corresponding respectively to the lower electrodes  32  on the right. The third extending portions  41   d  are joined with an aftermentioned COF  50 . That is, each of the third extending portions  41   d  has a drive contact point  46  as a contact point with the COF  50 . 
     &lt;Common Trace  42 &gt; 
     The common trace  42  is constructed from two circular portions  42   a  formed respectively on the upper surfaces of the two upper electrodes  34 , and two extending portions  42   b  connecting the two circular portions  42   a  in their respective leading end portions along the conveyance direction. 
     As depicted in  FIGS. 2A to 2C , the circular portions  42   a  of the common trace  42  are formed on the upper surfaces of the respective upper electrodes  34 . A rectangular opening  42   c  elongated in the conveyance direction is formed in a central portion of each circular portion  42   a  along the scanning direction and along the conveyance direction. The two opposite ends of each opening  42   c  along the conveyance direction are positioned outside the pressure chambers  26  positioned at the two opposite ends along the conveyance direction among the pressure chambers  26  forming the corresponding pressure chamber row  28 . The part of the upper electrode  34 , exposed from the opening  42   c , overlaps with the all corresponding pressure chambers  26 . 
     As depicted in  FIG. 2A , each of the two extending portions  42   b  of the common trace  42  is formed in such a part of the piezoelectric film  33  as outside the two through holes  38  along the conveyance direction. In other words, each of the two extending portions  42   b  of the common trace  42  is formed in such a part of the piezoelectric film  33  as without the through hole  38  at one or the other of the two opposite end sides along the conveyance direction. Further, as depicted in  FIG. 2C , each extending portion  42   b  extends while being inclined with respect to the scanning direction along the upper surfaces of the active portion, intermediate portion and junction portion of the piezoelectric film  33 . Then, the two opposite ends of each extending portion  42   b  along the scanning direction are connected to the two circular portions  42   a . That is, each extending portion  42   b  overlaps entirely with the upper surface  33   b  of the piezoelectric film  33 . In other words, the piezoelectric film  33  is positioned between the insulation film  30  and each extending portion  42   b  along the up/down direction. The aftermentioned COF  50  is joined to such a part of each extending portion  42   b  as overlapping with the junction portion of the piezoelectric film  33 . That is, there is a ground contact point  48  as the contact point with the COF  50 , in the part of each extending portion  42   b  overlapping with the junction portion of the piezoelectric film  33 . 
     The common trace  42  is formed of, for example, gold (Au). The circular portions  42   a  of the common trace  42  are, for example, 0.5 to 2.0 μm thick, while the extending portions  42   b  are, for example, also 0.5 to 2.0 μm thick. 
     &lt;COF  50 &gt; 
     The COF  50  includes a base material  51 , traces  52  formed in the base material  51 , a driver IC  53  mounted on the base material  51 , and the like. As depicted in  FIGS. 4B and 4C  with the broken lines, the base material  51  has a junction portion  51   a  joined to the pressure chamber formation member  22  and arranged along the upper surface of the piezoelectric film  33 , a draw-out portion  51   b  drawn out upward to be away from the pressure chamber formation member  22 , and a curved portion  51   c  between the junction portion  51   a  and the draw-out portion  51   b . Further, the COF  50  is inserted into a through hole  62  of the aftermentioned cover  60  to join to the third extending portion  41   d  of each individual trace  41  and the extending portions  42   b  of the common trace  42 . 
     As depicted in  FIGS. 4B and 4C , the junction portion  51   a  of the base material  51  is joined to the upper surface of the junction portion of the piezoelectric film  33 , where the drive contact points  46  and the two ground contact points  48  are arranged. The driver IC  53  is mounted on the draw-out portion  51   b  of the base material  51 . Further, while illustration is omitted, the other end of the COF  50  is connected to the controller  6  of the ink-jet printer  1  (see  FIG. 1 ). When the COF  50  is joined to the pressure chamber formation member  22 , the end portions of the traces  52  formed on the base material  51  are connected electrically with the drive contact points  46  and the two ground contact points  48 . 
     The driver IC  53  generates a drive signal based on a control signal fed from the controller  6 . The drive signal is inputted to a drive contact point  46  via the trace  52  and, furthermore, supplied to the corresponding lower electrode  32  via the individual trace  41 . On this occasion, the lower electrode  32  changes between a predetermined drive potential and the ground potential. On the other hand, the ground potential is applied to the upper electrode  34  connected with the ground contact point  48  through the common trace  42 . 
     Next, an explanation will be made about an interaction between the pressure chamber  26  and the insulation film  30 , lower electrode  32 , piezoelectric film  33  and upper electrode  34 , when the drive signal is supplied from the driver IC  53 . 
     If the drive signal is not yet inputted, then the lower electrode  32  is at the ground potential, being the same as the upper electrode  34 . From this state, if the drive signal is inputted to the lower electrode  32 , then due to the potential difference between the lower electrode  32  and the upper electrode  34 , an electric field is acting in the thickness direction on such a part of the piezoelectric film  33  as nipped between the lower electrode  32  and the upper electrode  34 . On this occasion, due to the inverse piezoelectric effect, that part of the piezoelectric film  33  being nipped between the lower electrode  32  and the upper electrode  34  contracts in the planar direction. 
     On this occasion, those parts overlapping with the pressure chamber  26 , of the insulation film  30 , the lower electrode  32 , the piezoelectric film  33 , and the upper electrode  34 , bend to project toward the pressure chamber  26 , such that the pressure chamber  26  decreases in volume. By virtue of this, a pressure wave occurs in the pressure chamber  26  to jet ink droplets from the nozzle  24  in communication with the pressure chamber  26 . In the following explanation, the term “piezoelectric element  31 ” will be used to refer to the part of the lower electrode  32 , piezoelectric film  33  and upper electrode  34  overlapping with one pressure chamber  26 . That is, piezoelectric elements  31  are arranged to correspond respectively to the pressure chambers  26 . Then, the piezoelectric elements  31  are arranged in two rows along the scanning direction to correspond respectively to the two pressure chamber rows  28 . 
     &lt;Cover  60 &gt; 
     As depicted in  FIGS. 4A to 4C , the cover  60  is joined to the pressure chamber formation member  22  with an adhesive. The outer circumference of the cover  60  has a rectangular shape elongated in the conveyance direction, and a rectangular through hole  62  elongated in the conveyance direction is formed in a central portion along the conveyance direction and along the scanning direction. As depicted in  FIG. 5 , two concave portions  60   a  are formed in the lower surface of the cover  60  to align in the scanning direction across the through hole  62 . Each of the concave portions  60   a  has an outer edge in a rectangular shape elongated in the conveyance direction. Each concave portion  60   a  is as deep as not impeding the drive of each piezoelectric element  31  in the up/down direction. On the other hand, a convex portion  61  is formed in such a part of the lower surface of the cover  60  as without the through hole  62  and the concave portions  60   a , to project downward from the bottom surface of each concave portion  60   a . In the following explanation, the name “first convex portions  61   a ” will be used to refer to such parts of the convex portion  61  as extending along the long side of one of the concave portions  60   a  to the two short sides of that concave portion  60   a , while the name “second convex portions  61   b ” will be used to refer to such parts of the convex portion  61  as extending along the long side of the other of the concave portions  60   a  to the two short sides of that concave portion  60   a . Further, the name “third convex portions  61   c ” will be used to refer to such parts of the convex portion  61  as other than the first convex portions  61   a  and second convex portions  61   b.    
     The cover  60  is joined with the pressure chamber formation member  22  on the lower surfaces of the first convex portions  61   a , the lower surfaces of second convex portions  61   b , and the lower surfaces of third convex portions  61   c . In more detail, the lower surfaces of the first convex portions  61   a  are joined with the circular portions  42   a  of the common trace  42  and such a part of the conductive portion  41   a  of each individual trace  41  as formed on the upper surface of the piezoelectric film  33 . The circular portions  42   a  of the common trace  42  are joined to the lower surfaces of the second convex portions  61   b  and the lower surfaces of the third convex portions  61   c.    
     The respective pressure chambers  26  forming the left pressure chamber row  28  are positioned between the left first convex portion  61   a  and the left second convex portion  61   b  in the scanning direction. In more detail, the two opposite ends of the pressure chambers  26  forming the left pressure chamber row  28  along the scanning direction are positioned between the left first convex portion  61   a  and the left second convex portion  61   b  in the scanning direction, such that the respective pressure chambers  26  do not overlap with the left first convex portion  61   a  and the left second convex portion  61   b . As depicted in  FIG. 4B , the left first convex portion  61   a  is positioned between the left through hole  38  of the piezoelectric film  33  and the right ends of the left respective pressure chambers  26 , in the scanning direction. In more detail, the two opposite ends of the junction surface along the scanning direction between the left first convex portion  61   a  and the pressure chamber formation member  22  are positioned between the right ends of the left respective pressure chambers  26  and an angular portion  33   e  formed by the upper surface  33   b  of the piezoelectric film  33  and the left inner surface  33   c  at the active portion side. Further, in the following explanation, the angular portion  33   e  will be used to refer to such a part of the outer surface with the smallest curvature radius as formed by the upper surface  33   b  of the piezoelectric film  33  and the inner surface  33   c  at the active portion side. Further, the name “angular portion  33   f ” will be used to refer to such a part of the outer surface with the smallest curvature radius as formed by the upper surface  33   b  of the piezoelectric film  33  and the inner surface  33   d  at the junction portion side. 
     Likewise, the respective pressure chambers  26  forming the right pressure chamber row  28  are positioned between the right first convex portion  61   a  and the right second convex portion  61   b  in the scanning direction. In more detail, the two opposite ends of the pressure chambers  26  forming the right pressure chamber row  28  along the scanning direction are positioned between the right first convex portion  61   a  and the right second convex portion  61   b  in the scanning direction, such that the respective pressure chambers  26  do not overlap with the right first convex portion  61   a  and the right second convex portion  61   b . As depicted in  FIG. 4B , the right first convex portion  61   a  is positioned between the right through hole  38  of the piezoelectric film  33  and the left ends of the right respective pressure chambers  26 , in the scanning direction. In more detail, the two opposite ends of the junction surface along the scanning direction between the right first convex portion  61   a  and the pressure chamber formation member  22  are positioned between the left ends of the right respective pressure chambers  26  and another angular portion  33   e  formed by the upper surface  33   b  of the piezoelectric film  33  and the right inner surface  33   c  at the active portion side. 
     Next, referring to  FIG. 6 , an explanation will be made about a process for manufacturing the aforementioned jetting module  16 . 
     First, the insulation film  30  is formed on a surface of a silicon single crystal substrate, which will become the substrate  21   a  of the flow channel substrate  21 , by a method such as thermal oxidation or the like (step S 11 ). Next, a conductive film for the lower electrodes  32  is formed on the insulation film  30  by way of sputtering or the like. The conductive film for the lower electrodes  32  is patterned by way of etching, to form the lower electrodes  32  having the first parts  32   a  and the second parts  32   b  (step S 12 ). 
     Next, on the insulation film  30  formed with the lower electrodes  32 , the piezoelectric film  33  is formed by the sol-gel or sputtering method. The through holes  38  are formed in the piezoelectric film  33  by way of etching (step S 13 ). 
     Next, on the piezoelectric film  33 , a conductive film for the upper electrodes  34  is formed by way of sputtering or the like. The conductive film for the upper electrodes  34  is patterned by way of etching, to form the upper electrodes  34  (step S 14 ). 
     Next, the method of plating is used to form the individual traces  41  in the aforementioned shape and the common trace  42  in the aforementioned shape (step S 15 ). 
     Next, the cover  60  is joined with an adhesive to the above position of the pressure chamber formation member  22  (step S 16 ). 
     Next, the pressure chamber formation member  22  joined with the cover  60  is tuned back and, with the pressure chamber formation member  22  being supported with the cover  60 , the substrate  21   a  is ground which will become part of the flow channel substrate  21 . After the substrate  21   a  is ground to a predetermined thickness, the ground surface of the substrate  21   a  is etched to form the pressure chambers  26 . After the pressure chambers  26  are formed, the ground surface of the substrate  21   a  is attached to the substrate  21   b  where various flow channels are formed by etching beforehand to communicate with the pressure chambers  26  (step S 17 ). 
     After the substrate  21   a  is attached to the substrate  21   b , the nozzle plate  20  is joined to the substrate  21   b  (step S 18 ). Finally, the COF  50  is joined to the above position of the pressure chamber formation member  22  (step S 19 ). 
     According to the above embodiment, the third extending portion  41   d  of each individual trace  41  and the extending portion  42   b  of the common trace  42  are all arranged on the junction portion of the piezoelectric film  33 . Then, the COF  50  is joined with the third extending portion  41   d  of each individual trace  41  and the extending portion  42   b  of the common trace  42 , upon the junction portion of the piezoelectric film  33 . Because the third extending portion  41   d  of each individual trace  41  and the extending portion  42   b  of the common trace  42  are positioned at the same height, it is possible to join the COF  50 , each individual trace  41  and the common trace  42  with high reliability. 
     Further, according to the above embodiment, the drive contact points  46  and the ground contact points  48  are not covered by the cover  60 . Therefore, even though the substrate  21   a  is ground with the pressure chamber formation member  22  being supported with the cover  60 , there is still no load on the drive contact points  46  and the ground contact points  48 . Hence, defection is less likely to arise in the process for manufacturing the jetting module  16 . 
     Further, according to the above embodiment, the left first convex portion  61   a  is positioned on the left of the through hole  38  at the left side of the piezoelectric film  33  according to the scanning direction, while the right first convex portion  61   a  is positioned on the right of the through hole  38  at the right side of the piezoelectric film  33  according to the scanning direction. That is, the left first convex portion  61   a  and the right first convex portion  61   a  are positioned on the outside of the two through holes  38  of the piezoelectric film  33  according to the scanning direction. Therefore, it is possible to secure a sufficient area of the pressure chamber formation member  22  for joining the COF  50 . 
     In the above embodiment, the jetting modules  16  correspond to the “liquid jetting apparatus” of the present teaching. The lower electrodes  32  correspond to the “first electrodes” of the present teaching. The upper electrodes  34  correspond to the “second electrode” of the present teaching. The conveyance direction (the transverse direction of the pressure chambers) corresponds to the “first direction” of the present teaching, while the scanning direction (the longitudinal direction of the pressure chambers) corresponds to the “second direction” of the present teaching. Further, the up/down direction corresponds to the “third direction” of the present teaching. The inner surface  33   c  of the piezoelectric film  33  corresponds to the “first inner surface” of the present teaching, while the inner surface  33   d  corresponds to the “second inner surface” of the present teaching. The angular portion  33   e  corresponds to the “first angular portion” of the present teaching, while the angular portion  33   f  corresponds to the “second angular portion” of the present teaching. 
     Next, explanations will be made about modified embodiments applying various changes and/or modifications to the above embodiment. However, the same numeral or alphanumeral is assigned to each component having the same configuration as that in the above embodiment, and explanation therefor will be omitted as appropriate. 
     In the above embodiment, the two opposite ends of the pressure chambers  26  forming the left pressure chamber row  28  along the scanning direction are positioned between the left first convex portion  61   a  and the left second convex portion  61   b  in the scanning direction. However, without being limited to that, it is allowable for the centers of the pressure chambers  26  forming the left pressure chamber row  28  along the scanning direction to be positioned between the left first convex portion  61   a  and the left second convex portion  61   b  in the scanning direction. Likewise, it is allowable for the centers of the pressure chambers  26  forming the right pressure chamber row  28  along the scanning direction to be positioned between the right first convex portion  61   a  and the right second convex portion  61   b  in the scanning direction. 
     The left first convex portion  61   a  and the right first convex portion  61   a  may not be positioned on the outside of the two through holes  38  of the piezoelectric film  33  according to the scanning direction. For example, as depicted in  FIGS. 7A and 7B , a left first convex portion  161   a  and a right first convex portion  161   a  may be positioned on the inside of the two through holes  38  of the piezoelectric film  33  according to the scanning direction (a first modified embodiment). That is, the left first convex portion  161   a  and the right first convex portion  161   a  may be positioned on the outside of the left second angular portion  33   f  and the right second angular portion  33   f  according to the scanning direction. In this case, because the junction portion between each first convex portion  161   a  and the pressure chamber formation member  22  is away from the respective piezoelectric elements  31 , it is possible to prevent the adhesive from flowing out to any of the piezoelectric elements  31  to give rise to variation in the displacement feature of the piezoelectric elements  31 . 
     Alternatively, as depicted in  FIGS. 8A and 8B , a left first convex portion  261   a  and a right first convex portion  261   a  may overlap respectively with the two through holes  38  of the piezoelectric film  33  (a second modified embodiment). That is, each first convex portion  261   a  may have a larger width along the scanning direction than the distance along the scanning direction between the angular portion  33   e  and the angular portion  33   f , i.e., the width of each through hole  38  along the scanning direction. In this case, when a cover  260  is joined to the pressure chamber formation member  22 , the angular portion of each first convex portion  261   a  comes into the through hole  38  such that it is possible to prevent giving damage to such a part of each individual trace  41  as formed inside the through hole  38 . 
     As depicted in  FIGS. 9A and 9B , a film  39  may be formed of the same material as the lower electrodes  32 , between the junction portion of the piezoelectric film  33  and the insulation film  30  (a third modified embodiment). This film  39  may be patterned together with the lower electrodes  32  after the conductive film for the lower electrodes  32  is formed. By virtue of this, steps are formed at the upper surface of the junction portion of the piezoelectric film  33 , and at the extending portion  42   b  of the common trace  42  and the third extending portion  41   d  of each individual trace  41  which are formed on the upper surface of the junction portion of the piezoelectric film  33 . Therefore, it is possible to join the COF  50  more reliably with the extending portion  42   b  of the common trace  42  and the third extending portion  41   d  of each individual trace  41 . 
     As depicted in  FIG. 10 , such a slit  138  may be formed as circularly continuous along the planar direction of the piezoelectric film  33 , in a central portion of the piezoelectric film  33  according to the scanning direction and the conveyance direction. By virtue of this, the piezoelectric film  33  may be defined as a first part inside the inner circumference of the circularly continuous slit  138  in the planar direction of the piezoelectric film  33 , and a second part outside the inner circumference of the circularly continuous slit  138  in the planar direction of the piezoelectric film  33  but inside the outer edge of the piezoelectric film  33  in the planar direction of the piezoelectric film  33  (a fourth modified embodiment). 
     The two upper electrodes  34  may connected in the corresponding end portions according to the conveyance direction with the same material as the upper electrodes  34 , along the scanning direction. 
     The cover  60  may be formed as two different covers each of which has one concave portion  60   a.    
     The COF  50  is merely an example of the wiring member of the present teaching, and the wiring member of the present teaching may include a flexible base material and traces formed in the base material. 
     An additional layer may be included, as far as without impeding the drive of the piezoelectric elements  31 , between the insulation film  30  and the lower electrodes  32 , between the lower electrodes  32  and the piezoelectric film  33 , between the piezoelectric film  33  and the upper electrodes  34 , between the upper electrodes  34  and the common trace  42 , between the piezoelectric film  33  and the common trace  42 , between each individual trace  41  and the insulation film  30 , between each individual trace  41  and the piezoelectric film  33 , and/or the like. 
     In the embodiment explained above, the present teaching is applied to an ink-jet head for jetting ink to recording paper to print image and the like. However, the present teaching is also applicable to liquid jetting apparatuses used for various purposes other than printing image and the like. For example, it is also possible to apply the present teaching to liquid jetting apparatuses for jetting a conductive liquid to a substrate, for example, to form a conductive pattern on a surface of the substrate.