JP2019081386A - Piezoelectric actuator, liquid discharge device and manufacturing method of piezoelectric actuator - Google Patents

Abstract

An object of the present invention is to suppress voltage drop by increasing the number of paths of current flowing through a common electrode, thereby suppressing variations in voltage applied to piezoelectric elements among a plurality of piezoelectric element arrays. A drive wiring 35 corresponding to a piezoelectric element 39 constituting piezoelectric element rows 40b to 40d located on the opposite side of a contact portion 43 among four piezoelectric element rows 40 is located on the contact portion 43 side. It extends to the contact portion 43 through between two adjacent piezoelectric elements 39 of the piezoelectric element row 40a. Between two adjacent piezoelectric elements 39 of the piezoelectric element rows 40b to 40d, a common electrode 42 for the plurality of piezoelectric elements 39 and a conducting wire 52 electrically connected at two positions are arranged. [Selection drawing] Fig. 2

Description

  The present invention relates to a piezoelectric actuator and a liquid ejection apparatus having the piezoelectric actuator.

  Patent Document 1 discloses an ink jet head as a liquid discharge device. The inkjet head includes an actuator having a head body in which a plurality of nozzles, a plurality of pressure chambers communicating with the plurality of nozzles are formed, and a plurality of piezoelectric elements respectively corresponding to the plurality of pressure chambers.

  The plurality of pressure chambers of the head main body are respectively arranged corresponding to the plurality of nozzles, and constitute four pressure chamber rows arranged in the direction orthogonal to the nozzle arrangement direction. The actuator includes a diaphragm covering a plurality of pressure chambers, a piezoelectric film disposed on the diaphragm, and a plurality of individual electrodes disposed corresponding to the plurality of pressure chambers on the upper side of the piezoelectric film. And. The portion of the piezoelectric film corresponding to each pressure chamber is one piezoelectric element. That is, according to the arrangement of the plurality of pressure chambers, the plurality of piezoelectric elements are arranged in four rows. Further, the diaphragm is made of Cr or a Cr-based metal, and faces the plurality of individual electrodes with the piezoelectric film interposed therebetween, and the diaphragm also serves as a common electrode for the plurality of piezoelectric elements.

  A plurality of electrical contact portions are disposed on the upper surface of one end of the piezoelectric film in the direction orthogonal to the nozzle arrangement direction. A plurality of individual electrodes of the plurality of piezoelectric elements arranged in four rows are arranged respectively. Drive wires extend towards the electrical contacts. Of the four piezoelectric element rows, the drive wiring corresponding to the piezoelectric element constituting the piezoelectric element row positioned on the opposite side to the electrical contact portion is a piezoelectric element constituting the piezoelectric element row positioned on the electrical contact portion side It passes between the elements and extends to the electrical contact. An IC chip for applying a voltage to each piezoelectric element is connected to the electrical contact portion.

JP 2000-79683 A

  Although there is no clear description in the above-mentioned patent documents, in the electrical contact portion, not only the electrical connection between a plurality of drive wires and the IC chip but also the connection between the common electrode (diaphragm) and the IC chip In many cases, a configuration in which a reference potential (for example, ground) is also applied to the common electrode is employed.

  In the case of the above configuration, the distance between the plurality of piezoelectric element rows arranged in the direction orthogonal to the arrangement direction of the pressure chambers is different from the distance to the electrical contact portion in the orthogonal direction. That is, among the plurality of piezoelectric element rows, an electrode portion for applying a voltage to each of the common electrodes facing the individual electrode with the piezoelectric film interposed therebetween and a distance to the electrical contact portion are It will be different. As a result, in the piezoelectric element row located at a position far from the electrical contact portion, the path from the electrical contact portion to the electrode portion of the common electrode is longer than in the piezoelectric element row located at a position near the electrical contact portion.

  Therefore, when the piezoelectric element is driven, the voltage drop in the above path becomes large. Further, due to the difference in the length of the above-described path among the plurality of piezoelectric element arrays, a difference also occurs in the degree of voltage drop. The difference in voltage drop causes variations in the voltage applied to the piezoelectric element among the plurality of piezoelectric element rows, and further, variations in the applied voltage result in variations in the ejection characteristics among the plurality of nozzles. appear.

  In order to reduce the variation in applied voltage between the piezoelectric elements due to the difference in the path length, the difference in voltage drop in the common electrode can be small enough to be ignored by increasing the thickness of the common electrode. do it. However, when the common electrode is thick, there is a problem that the deformation of the piezoelectric film in the pressure chamber is inhibited and the deformation efficiency is reduced.

  An object of the present invention is to increase a path of current flowing through a common electrode to suppress a voltage drop, and to suppress variation in voltage applied to piezoelectric elements among a plurality of piezoelectric element arrays.

Means for Solving the Problems and Effects of the Invention

The piezoelectric actuator of the present invention is arranged in a first direction on a substrate, and a first piezoelectric element row, and a second piezoelectric element row arranged in a second direction orthogonal to the first piezoelectric element row and the first direction. And a plurality of piezoelectric elements constituting the contact point portion, and a contact portion disposed on the substrate at a position opposite to the second piezoelectric element row in the second direction with respect to the first piezoelectric element row. And a plurality of drive wires respectively extending in the second direction from the plurality of piezoelectric elements toward the contact portion,
Each piezoelectric element includes a piezoelectric portion, a first electrode disposed on one side in the thickness direction of the piezoelectric portion, and a second electrode disposed on the other side in the thickness direction of the piezoelectric portion, A wire is connected to the first electrode of each piezoelectric element, and the second electrodes of the plurality of piezoelectric elements are electrically connected to each other by an electrode conduction portion disposed between the plurality of second electrodes, and the plurality of A common electrode for the plurality of piezoelectric elements is constituted by the two electrodes and the electrode conduction portion, and the drive wiring corresponding to the piezoelectric element constituting the second piezoelectric element row is the one of the first piezoelectric element row. It extends between two adjacent piezoelectric elements in a first direction to the contact portion, and is disposed between the two adjacent piezoelectric elements in the first direction of the second piezoelectric element row, And two separated in the second direction Were respectively conducted with the electrode conducting portion of the common electrode in position, characterized in that the conductive wires are disposed.

  In the present invention, the plurality of piezoelectric elements are arranged in the first direction to form two piezoelectric element arrays arranged in the second direction. Further, drive wires corresponding to the piezoelectric elements of the second piezoelectric element array extend in the second direction between the piezoelectric elements of the first piezoelectric element array and extend to the contact portion. Here, in the second piezoelectric element row located on the opposite side to the contact portion among the two piezoelectric element rows, the distance to the contact portion is longer compared to the first piezoelectric element row, so The voltage drop when current flows from the second electrode of the piezoelectric element to the contact portion is increased. Therefore, in the present invention, in the second piezoelectric element row located at a distance from the contact portion, a conductive wire electrically connected to the common electrode at two positions is disposed between two adjacent piezoelectric elements. By the conductive wiring, a current flow path is increased between the second electrode of each piezoelectric element of the second piezoelectric element row and the contact portion, and the voltage drop can be suppressed.

  Further, between the piezoelectric elements of the first piezoelectric element row close to the contact portion, driving wires corresponding to the piezoelectric elements of the second piezoelectric element row separated from the contact portion pass. On the other hand, since a vacant region exists between the piezoelectric elements of the second piezoelectric element row, it is easy to install the conductive wiring between the piezoelectric elements compared to the first piezoelectric element row.

FIG. 1 is a schematic plan view of a printer 1 according to the present embodiment. FIG. 3 is a top view of a head unit 16 of the inkjet head 4; It is the X section enlarged view of FIG. FIG. 4 is a cross-sectional view taken along line IV-IV of FIG. 3; FIG. 6A is a view showing a manufacturing process of the piezoelectric actuator 23, and (a) film formation of the vibrating film 30, (b) formation of the common electrode 42 (lower electrode 31), (c) film formation of the piezoelectric film 32, Each step of etching the film 32 is shown. FIG. 7 is a view showing the manufacturing process of the piezoelectric actuator 23, and shows each process of (a) formation of the upper electrode 33, (b) formation of the protective film 38, and (c) formation of the wirings 35 and 52. It is a top view of head unit 16 of a change form. It is a top view of the head unit 16 of another modification. It is a partially enlarged view of the piezoelectric actuator 23 of another modification. It is a partially enlarged view of the piezoelectric actuator 23 of another modification. 11 is a cross-sectional view taken along line XI-XI of FIG. It is a top view of head unit 16 concerning an embodiment about a disclosure invention.

  Next, an embodiment of the present invention will be described. FIG. 1 is a schematic plan view of a printer according to the present embodiment. First, the schematic configuration of the inkjet printer 1 will be described with reference to FIG. The scanning direction shown in FIG. 1 is defined as the left and right direction of the printer 1. Further, the upstream side in the transport direction of FIG. 1 is defined as the rear of the printer 1 and the downstream side is as the front of the printer 1. Furthermore, a direction perpendicular to the scanning direction and the conveyance direction (direction orthogonal to the sheet of FIG. 1) is defined as the vertical direction of the printer. The front side of FIG. 1 is the upper side, and the other side of FIG. 1 is the lower side. Below, each direction word of front and rear, right and left upper and lower sides is used suitably, and is explained.

(Schematic configuration of printer)
As shown in FIG. 1, the inkjet printer 1 includes a platen 2, a carriage 3, an inkjet head 4, a transport mechanism 5, a control device 6 and the like.

  A recording sheet 100, which is a recording medium, is placed on the upper surface of the platen 2. The carriage 3 is configured to be reciprocally movable in the scanning direction along the two guide rails 10 and 11 in a region facing the platen 2. The endless belt 14 is connected to the carriage 3, and the carriage 3 is moved in the scanning direction by driving the endless belt 14 by the carriage drive motor 15.

  The inkjet head 4 is attached to the carriage 3 and moves in the scanning direction together with the carriage 3. The ink jet head 4 is connected to a cartridge holder 7 to which four color (black, yellow, cyan, magenta) ink cartridges 17 are attached, by a tube (not shown). The inkjet head 4 includes two head units 16 (16a, 16b) aligned in the scanning direction. A plurality of nozzles 24 (see FIGS. 2 to 4) that eject ink toward the recording paper 100 placed on the platen 2 on the lower surface (surface opposite to the paper surface of FIG. 1) of each head unit 16 Is formed. Of the two head units 16a, one head unit 16a discharges ink of two colors of black and yellow, and the other head unit 16b discharges ink of two colors of cyan and magenta It is.

  The transport mechanism 5 has two transport rollers 18 and 19 arranged to sandwich the platen 2 in the transport direction. The transport mechanism 5 transports the recording sheet 100 placed on the platen 2 in the transport direction by the two transport rollers 18 and 19.

  The control device 6 includes a read only memory (ROM), a random access memory (RAM), an application specific integrated circuit (ASIC) including various control circuits, and the like. The control device 6 executes various processes such as printing on the recording sheet 100 by the ASIC in accordance with the program stored in the ROM. For example, in the printing process, the control device 6 controls the head unit 16 of the ink jet head 4 and the carriage drive motor 15 based on a print command input from an external device such as a PC to print an image on the recording sheet 100. Print the etc. Specifically, the ink discharge operation of discharging the ink while moving the ink jet head 4 together with the carriage 3 in the scanning direction, and the transporting operation of transporting the recording paper 100 by the transporting rollers 18 and 19 by a predetermined amount in the transporting direction are alternated. Let me do it.

(Details of the head unit of the inkjet head)
Next, the detailed configuration of the head unit 16 of the inkjet head 4 will be described. Incidentally, since the two head units 16a and 16b have the same structure, hereinafter, the head unit 16a which discharges the black and yellow inks will be representatively described. FIG. 2 is a top view of the head unit 16 of the inkjet head 4. FIG. 3 is an enlarged view of a portion X in FIG. FIG. 4 is a cross-sectional view taken along line IV-IV of FIG. As shown in FIGS. 2 to 4, the head unit 16 includes a nozzle plate 20, a first flow path substrate 21, a second flow path substrate 22, a piezoelectric actuator 23 and the like. In FIG. 2, in order to simplify the drawing, the protective member 28 located above the first flow path substrate 21 in FIG. Furthermore, in order to facilitate understanding of the configuration of the piezoelectric actuator 23 in FIG. 2, the protective film 38 covering the entire first flow path substrate 21 shown in FIGS. 3 and 4 is illustrated in FIG. It is omitted.

(Nozzle plate)
The nozzle plate 20 is, for example, a plate formed of silicon or the like. The nozzle plate 20 has a plurality of nozzles 24 formed therein. As shown in FIG. 2, the plurality of nozzles 24 are arranged in the transport direction (the first direction of the present invention) to form four rows of nozzles arranged in the scanning direction (the second direction of the present invention). . The two right nozzle rows are nozzle rows that eject black ink. The position of the nozzles 24 in the transport direction is shifted by half (P / 2) of the arrangement pitch P of each nozzle row between the two nozzle rows on the right side. The left two nozzle rows are nozzle rows that eject yellow ink. Also in the two left nozzle rows, the positions of the nozzles 24 in the transport direction are shifted by P / 2 between the two nozzle rows, similarly to the right two nozzle rows.

(Flow path substrate)
The first flow path substrate 21 and the second flow path substrate 22 are each a silicon single crystal substrate. A plurality of pressure chambers 26 respectively communicating with the plurality of nozzles 24 are formed in the first flow path substrate 21. Each pressure chamber 26 has a rectangular planar shape elongated in the scanning direction. The plurality of pressure chambers 26 are arranged in the transport direction according to the plurality of nozzles 24, and constitute four pressure chamber rows 27 (27a to 27d) aligned in the scanning direction. Pressure chamber rows 27a and 27b on the right two rows are pressure chamber rows 27 for black ink, and pressure chamber rows 27c and 27d on the left two rows are pressure chamber rows 27 for yellow ink. Further, the first flow path substrate 21 has a vibrating film 30 formed on the upper surface thereof and covering the plurality of pressure chambers 26. The vibrating film 30 is a film formed by oxidizing or nitriding the surface of the silicon substrate.

  The second flow path substrate 22 is bonded to the lower surface of the first flow path substrate 21. Further, the nozzle plate 20 described above is joined to the lower surface of the second flow path substrate 22. Two manifolds 25 are respectively formed in a portion of the second flow path substrate 22 vertically overlapping with the right side two rows of pressure chambers 27a and 27b and in a portion vertically overlapping the left two rows of pressure chambers 26c and 27d. ing. Each manifold 25 extends along the transport direction, which is the direction in which the pressure chambers 26 are arranged. The manifolds 25 communicate with the pressure chambers 26 belonging to the two pressure chamber rows 27 corresponding to the manifolds through communication holes 48. Further, the two manifolds 25 are respectively connected to two ink cartridges 17 (see FIG. 1) mounted on the cartridge holder 7 by a tube or the like (not shown).

  The ink supplied from the ink cartridge 17 is supplied to the manifold 25, and is further supplied from the manifold 25 to the corresponding plurality of pressure chambers 26. Further, the second flow path substrate 22 is also formed with a communication hole 49 for communicating the pressure chamber 26 formed in the first flow path substrate 21 with the nozzle 24 formed in the nozzle plate 20. When ejection energy is applied to the ink in the pressure chamber 26 by the piezoelectric actuator 23 described next, droplets of the ink are ejected from the nozzle 24 communicating with the pressure chamber 26.

(Piezoelectric actuator)
The piezoelectric actuator 23 applies ejection energy for ejecting ink from the nozzles 24 to the ink in the plurality of pressure chambers 26. The piezoelectric actuator 23 has a plurality of piezoelectric elements 39 disposed on the upper surface of the vibrating film 30 of the first flow path substrate 21. The plurality of piezoelectric elements 39 are arranged in the transport direction corresponding to the plurality of pressure chambers 26, respectively, and constitute four piezoelectric element rows 40 (40a to 40d) aligned in the scanning direction. Each piezoelectric element 39 has a piezoelectric portion 37, a lower electrode 31, and an upper electrode 33. A protective member 28 covering a plurality of piezoelectric elements 39 of the piezoelectric actuator 23 is joined to the upper surface of the first flow path substrate 21.

  The configuration of the piezoelectric element 39 will be described in detail. A common electrode 42 is continuously formed on the upper surface of the vibrating film 30 so as to straddle the plurality of pressure chambers 26. The portion of the common electrode 42 facing the pressure chamber 26 is the lower electrode 31 of each piezoelectric element 39. The lower electrodes 31 of the plurality of piezoelectric elements 39 are electrically connected to each other by portions (electrode conductive portions 41) of the common electrode 42 disposed between the plurality of pressure chambers 26. The material of the common electrode 42 (the plurality of lower electrodes 31 and the electrode conduction portion 41) is not particularly limited, but is made of, for example, platinum (Pt). The thickness of the common electrode 42 is, for example, 0.1 μm.

  A piezoelectric film 32 is formed on the upper surface of the vibrating film 30 so as to cover the common electrode 42. The piezoelectric film 32 is a film formed in a rectangular shape in plan view and formed over the four pressure chamber rows 27 on the upper surface of the vibrating film 30. The portion of the piezoelectric film 32 facing each pressure chamber 26 constitutes the piezoelectric portion 37 of one piezoelectric element 39. That is, it can be said that the piezoelectric film 32 is a film formed by connecting the piezoelectric portions 37 of the plurality of piezoelectric elements 39 to one another. The piezoelectric film 32 is made of, for example, a piezoelectric material containing lead zirconate titanate (PZT), which is a mixed crystal of lead titanate and lead zirconate, as a main component. Alternatively, the piezoelectric film 32 may be formed of a lead-free piezoelectric material not containing lead. The thickness of the piezoelectric film 32 is, for example, 1 μm.

  A plurality of upper electrodes 33 corresponding to the plurality of pressure chambers 26 are formed on the upper surface of the piezoelectric film 32. The upper electrode 33 is an individual electrode individually provided for each pressure chamber 26. Although the shape of the upper electrode 33 is not particularly limited, for example, one having a rectangular planar shape smaller than the pressure chamber 26 is shown in FIG. Also, the material of the upper electrode 33 is not particularly limited, but is made of, for example, iridium (Ir). The thickness of the upper electrode 33 is, for example, 0.1 μm.

  The piezoelectric portion 37 of each piezoelectric element 39 which is a portion sandwiched between the lower electrode 31 and the upper electrode 33 of the piezoelectric film 32 is directed downward in the thickness direction, that is, in the direction from the upper electrode 33 toward the lower electrode 31 It is polarized.

  A protective film 38 made of an insulating material is formed on the upper surfaces of the vibrating film 30 and the piezoelectric film 32 so as to cover the plurality of piezoelectric elements 39. The main purpose of the protective film 38 is to prevent the piezoelectric element 39 from being damped. Although the material of the protective film 38 is not particularly limited, it is formed of, for example, silicon nitride, silicon dioxide, alumina or the like. Further, the protective film 38 may be disposed so as to cover only a part of each piezoelectric element 39. For example, the protective film 38 may have an opening for exposing the upper electrode 33, and the upper electrode 33 may not be covered with the protective film 38.

  A plurality of drive wirings 35 respectively corresponding to the plurality of piezoelectric elements 39 are formed on the upper surface of the protective film 38. One end of each drive wire 35 is disposed to run on the upper electrode 33. A through hole 38 a is formed in a portion of the protective film 38 overlapping with one end of the drive wiring 35. The drive wiring 35 and the upper electrode 33 are electrically connected by a conductive portion 46 formed of a conductive material disposed in the through hole 38 a and penetrating the protective film 38. The drive wiring 35 connected to the upper electrode 33 of each piezoelectric element 39 extends to the right on the upper surface of the protective film 38.

In the present embodiment, as shown in FIGS. 2 and 3, all of the plurality of drive wires 35 respectively connected to the upper electrodes 33 of the plurality of piezoelectric elements 39 extend from the corresponding upper electrode 33 to the right. . Therefore, the drive wiring 35 drawn out from the upper electrodes 33 of the left three piezoelectric element rows 40 passes between the two piezoelectric elements 39 belonging to the other piezoelectric element row 40 located on the right side thereof and is then It extends to For example, as shown in FIG. 2, three piezoelectric element arrays 40 b to 40 d corresponding to the left three piezoelectric element arrays 40 a on the right side, between the two adjacent piezoelectric elements 39 in the transport direction. The drive wirings 35b to 35d are disposed. The material of the drive wiring 35 is not particularly limited, but gold (Au) having a low electric resistivity, or an aluminum-based material (for example, an Al-Cu alloy) can be suitably used. The electrical resistivity of gold is 2.2 × 10 ⁻⁸ Ωm, the electrical resistivity of aluminum is 2.7 × 10 ⁻⁸ Ωm, and the electrical resistivity of copper is 1.7 × 10 ⁻⁸ Ωm. On the other hand, the electrical resistivity of platinum, which is a material constituting the common electrode 42, is 1.0 × 10 ⁻⁷ Ωm. However, since aluminum is a material which is more susceptible to migration than gold, when drive wiring 35 is formed of aluminum, a plurality of drive wirings 35 may be covered with an insulating film to prevent migration. preferable. Also, the thickness of the drive wiring 35 is, for example, 1 μm.

  As shown in FIG. 2, on the upper surface of the right end portion of the vibration film 30 of the first flow path substrate 21, a contact portion 43 to which the COF 50 which is a wiring member is bonded is provided. In the contact portion 43, a plurality of drive contact portions 44 and two ground contact portions 45 arranged in the transport direction are disposed. The drive wire 35 connected to the upper electrode 33 of each piezoelectric element 39 is connected to the drive contact portion 44 disposed in the contact portion 43. The common electrode 42 including the plurality of lower electrodes 31 is connected to the two ground contact portions 45 by the wiring 36.

  As shown in FIGS. 2 to 4, the COF 50 is joined to the contact portion 43 described above, and a plurality of drive contact portions 44 disposed in the contact portion 43 and a plurality of signal wires (not shown) formed in the COF 50 Are electrically connected to each other. The two ground contact portions 45 disposed in the contact portion 43 are connected to ground wiring (not shown) formed in the COF 50. Although not shown, the COF 50 is also connected to the control device 6 (see FIG. 1) of the printer 1.

  As shown in FIG. 2, the driver IC 51 is mounted on the COF 50. The driver IC 51 generates and outputs a drive signal for driving each piezoelectric element 39 based on the control signal sent from the control device 6. The drive signal output from the driver IC 51 is input to the drive contact portion 44 via the signal line of the COF 50, and is further supplied to each upper electrode 33 via the drive line 35. When a drive signal is supplied to the upper electrode 33, the potential of the upper electrode 33 changes between a predetermined drive potential and a ground potential. Further, by connecting the ground contact portion 45 to the ground wiring of the COF 50, the potential of the lower electrode 31 connected to the ground contact portion 45 is always maintained at the ground potential.

  The operation of each piezoelectric element 39 when the drive signal is supplied from the driver IC 51 will be described. In the state where the drive signal is not supplied, the potential of the upper electrode 33 is the ground potential, which is the same potential as the lower electrode 31. From this state, when a drive signal is supplied to a certain upper electrode 33 and a drive potential is applied to the upper electrode 33, a potential difference between the upper electrode 33 and the lower electrode 31 causes the piezoelectric portion 37 to move in the thickness direction. A parallel electric field acts. Here, since the polarization direction of the piezoelectric portion 37 matches the direction of the electric field, the piezoelectric portion 37 extends in the thickness direction, which is the polarization direction, and contracts in the planar direction. With the contraction and deformation of the piezoelectric portion 37, the vibrating film 30 is bent so as to be convex toward the pressure chamber 26 side. As a result, the volume of the pressure chamber 26 decreases and a pressure wave is generated in the pressure chamber 26, whereby the ink droplets are discharged from the nozzle 24 communicating with the pressure chamber 26.

  By the way, in the present embodiment, the plurality of piezoelectric elements 39 configure four piezoelectric element arrays 40 a to 40 d arranged in the scanning direction. Further, the common electrode 42 including the lower electrodes 31 of the plurality of piezoelectric elements 39 is connected to the ground contact portion 45 of the contact portion 43 located at the right end portion of the first flow path substrate 21. In this configuration, the distance between the lower electrode 31 of the piezoelectric element 39 and the ground contact portion 45 of the contact portion 43 is different among the four piezoelectric element rows 40a to 40d. In the piezoelectric element row 40d located at a distance from the contact portion 43, the distance between the lower electrode 31 of each piezoelectric element 39 and the ground contact portion 45 is the longest, so the electrical resistance between the portions is the largest. As a result, when the piezoelectric element 39 is driven, the voltage drop when current flows from the second electrode 31 toward the ground contact portion 45 is increased. In particular, when ink is ejected from a large number of nozzles 24 simultaneously, a large number of piezoelectric elements 39 are simultaneously driven. Therefore, the voltage drop at the common electrode 42 relatively increases, and the voltage applied to each piezoelectric element 39 decreases.

  In this regard, it is possible to suppress the voltage drop to a low level by increasing the thickness of the common electrode 42 to reduce the electrical resistance of the common electrode 42. However, if the thickness of the common electrode 42 (in particular, the lower electrode 31) is increased, deformation of the piezoelectric portion 37 is inhibited by the thickness. In addition, although platinum (Pt) which hardly affects the orientation of the piezoelectric film 32 is suitable as a material of the common electrode 42, since platinum is an expensive material, the thickness of the common electrode 42 is set also from the viewpoint of cost. It is difficult to make it bigger.

  From the above reason, if there is a difference in the degree of voltage drop between lower electrode 31 and ground contact portion 45 depending on the distance from ground contact portion 45 among four piezoelectric element rows 40a to 40d. In the piezoelectric element array 40 having a large voltage drop, the voltage substantially applied to the piezoelectric element 39 is reduced. That is, the voltage applied to the piezoelectric element 39 varies among the four piezoelectric element arrays 40a to 40d. The variation in the applied voltage appears as variation in the discharge characteristics of the nozzles 24 among the four nozzle rows, which leads to the deterioration of the printing quality. Therefore, in the present embodiment, it is an object to suppress a voltage drop between the lower electrode 31 of the piezoelectric element 39 forming the piezoelectric element array 40 separated from the contact portion 43 and the ground contact portion 45 of the contact portion 43 to a low level. The following configuration is adopted.

  As shown in FIGS. 2 to 4, among the four piezoelectric element arrays 40 a to 40 d, the three piezoelectric element arrays 40 b to 40 d disposed on the left side (the opposite side to the contact portion 43) are adjacent in the transport direction A conductive wire 52 electrically connected to the common electrode 42 is provided between the upper electrodes 33 of the two piezoelectric elements 39.

  The conductive wiring 52 is disposed on the upper surface of the protective film 38 covering the plurality of piezoelectric elements 39 by using the same conductive material (gold, aluminum-based material or the like) as the drive wiring 35 as the drive wiring 35 described above. That is, the conductive wiring 52 is disposed so as to overlap the common electrode 42 with the piezoelectric film 32 and the protective film 38 interposed therebetween. Further, in each of the three piezoelectric element arrays 40b to 40d, the conductive wiring 52 extends in the scanning direction between the two adjacent piezoelectric elements 39.

  The length in the scanning direction of the conductive wiring 52 is longer than the length in the scanning direction of the upper electrodes 33 of the two adjacent piezoelectric elements 39. More specifically, the length of the conductive wire 52 in the scanning direction is approximately equal to the length of the pressure chamber 26 in the scanning direction. Further, the thickness of the conductive wiring 52 is the same as that of the drive wiring 35 and is larger than the thickness of the common electrode 42. For example, when the thickness of the common electrode 42 is 0.1 μm, the thickness of the conduction wiring 52 is 1.0 μm, as in the case of the drive wiring 35.

  Incidentally, by arranging conductors such as the drive wiring 35 and the conductive wiring 52 around the piezoelectric element 39, residual stress generated in the piezoelectric element due to film formation of each film, patterning of the piezoelectric film 32, etc. Changes. Therefore, from the viewpoint of reducing variations in residual stress among the plurality of piezoelectric elements 39, the thickness of the conductive wiring 52 is the same as the thickness of the drive wiring 35. Further, for the same reason, the conductive wire 52 is formed of the same conductive material as the drive wire 35.

  As shown in FIG. 3 and FIG. 4, two through holes 32 a are formed in portions of the piezoelectric film 32 overlapping with both end portions of the respective conductive wires 52. Further, two through holes 38 b are also formed in portions of the protective film 38 overlapping with both end portions of the respective conductive wirings 52. The conductive material constituting conductive wire 52 is filled in through hole 32 a of piezoelectric film 32 and through hole 38 b of protective film 38, whereby conductive portion 53 penetrating piezoelectric film 32 and protective film 38 is disposed. It is done. Then, both end portions of each conductive wire 52 are connected to the electrode conductive portion 41 of the common electrode 42 through the two conductive portions 53, respectively. The positions of the two conducting portions 53 for conducting the conducting wire 52 and the common electrode 42 are not limited to the both end portions of the conducting wire 52. However, if the conductive portion 53 is in a position close to the central portion of the conductive wire 52, the length of the conductive wire 52 which functions as a path for flowing a part of the current flowing through the common electrode 42 becomes substantially short. The two conducting parts 53 are preferably provided at both ends of the conducting wire 52.

  In the piezoelectric element row 40b positioned second from the right, the conductive wire 52b and the two drive wires 35c and 35d drawn from the piezoelectric element rows 40c and 40d are disposed between two adjacent piezoelectric elements 39. It is arranged. Further, in the piezoelectric element row 40c positioned third from the right, the conductive wiring 52c and one drive wiring 35d drawn from the piezoelectric element row 40d are disposed between two adjacent piezoelectric elements 39. There is. In the piezoelectric element arrays 40 b and 40 c, the conduction wiring 52 is disposed rearward of the drive wiring 35. Furthermore, in the piezoelectric element row 40d located on the leftmost side, only the conductive wire 52d is disposed between two adjacent piezoelectric elements 39.

  As described above, in the piezoelectric element row 40 (40b to 40d) located at a distance from the contact portion 43 in the scanning direction, the conductive wiring 52 electrically connected to the common electrode 42 is provided between the adjacent piezoelectric elements 39. There is. Therefore, a current flow path is increased between the lower electrode 31 of the piezoelectric element 39 constituting the piezoelectric element arrays 40b to 40d and the ground contact portion 45 of the contact portion 43. As a result, the electrical resistance between the lower electrode 31 and the ground contact portion 45 is substantially reduced. Therefore, in the piezoelectric elements 39 forming the piezoelectric element arrays 40 b to 40 d at positions away from the contact portion 43, the lower electrode 31 and the lower electrode 31 when current flows from the lower electrode 31 to the ground contact portion 45 of the contact portion 43 The voltage drop to the ground contact portion 45 can be suppressed to a low level. By suppressing the voltage drop as described above, the variation in voltage applied to the piezoelectric element 39 is suppressed among the plurality of piezoelectric elements 39, and the difference in ejection characteristics among the plurality of nozzles 24 is reduced.

  In the first piezoelectric element row 40a close to the contact portion 43, three drive wirings 35b respectively corresponding to the other three piezoelectric element rows 40b to 40d between the two piezoelectric elements 39 adjacent in the transport direction. ~ 35d is passing. In comparison with this, in the other three piezoelectric element arrays 40b to 40d, the number of drive wirings 35 passing between the two adjacent piezoelectric elements 39 is small. That is, in the piezoelectric element arrays 40b to 40c apart from the contact portion 43, the area of the vacant region existing between two adjacent piezoelectric elements 39 is larger than that of the piezoelectric element array 40a. It is easy to install the conductive wire 52 between the piezoelectric elements 39.

  In addition, as the distance from the contact portion 43 increases, the lower electrode 31 of the piezoelectric element 39 and the ground contact portion 45 of the contact portion 43 also increase as the distance between the contact portion 43 increases. The electrical resistance between them is large and the voltage drop is also large. Therefore, the electrical resistance of the conducting wire 52 provided in the piezoelectric element row 40 at a distance from the contact portion 43 is smaller than the electrical resistance of the conducting wire 52 provided in the piezoelectric element row 40 near the contact portion 43 Is preferred. That is, the conductive wire 52 disposed between two adjacent piezoelectric elements 39 has (1) a large wire width, (2) a large number of wires, or (3) with respect to the drive wire 35. It is preferable that it is formed of a material having a low electrical resistivity.

  As an example, in the present embodiment, as the distance between the piezoelectric element array 40 and the contact portion 43 increases, the width in the transport direction of the conductive wiring 52 provided in the piezoelectric element array 40 increases. That is, the width of the conductive wiring 52 d of the piezoelectric element row 40 d is the largest, next, the width of the conductive wiring 52 c of the piezoelectric element row 40 c is the largest, and the width of the conductive wiring 52 b of the piezoelectric element row 40 b is the smallest.

  The specific example of the width | variety of the conduction wiring 52 is given below. The distance D (see FIG. 3) between two upper electrodes 33 adjacent in the transport direction is 15 to 20 μm, and the width of the drive wiring 35 in the scanning direction is 2 to 3 μm. The width is preferably 2 to 3 μm as in the case of the drive wiring 35. The width of the conductive wiring 52c is preferably 4 to 6 μm, which is twice that of the conductive wiring 52b. Furthermore, the width of the conductive wiring 52d is preferably 6 to 9 μm, which is three times the width of the conductive wiring 52b.

The relationship between the widths of the conductive wires 52 among the plurality of piezoelectric element rows 40 can be generalized by the following equation.
Assuming that the width of the conductive wiring 52 located in the n-th column from the contact portion 43 is Wn,
Wn = k × (n−1) (where k is a constant)
It becomes.

  Moreover, it is preferable that the electrical resistance of the conductive wiring 52 itself be as small as possible. Therefore, the conductive wiring 52 is formed of a conductive material having a smaller electric resistance than the common electrode 42. Specifically, when the common electrode 42 is formed of platinum, it may be formed of gold or aluminum, which has an electrical resistivity lower than that of platinum, like the drive wiring 35. If the same conductive material is used for the conductive wire 52 and the drive wire 35, the drive wire 35 and the conductive wire 52 can be formed in the same film formation process. Furthermore, as shown in FIG. 4, the thickness of the conductive wiring 52 is larger than the thickness of the common electrode 42.

  Further, the length in the scanning direction of the conductive wiring 52 is longer than the length in the scanning direction of the upper electrode 33. By increasing the length of the conductive wire 52, the electric resistance of the conductive wire 52 itself does not necessarily decrease, but between the lower electrode 31 and the ground contact portion 45 of the contact portion 43, the common electrode 42 Since the section in which the current flows in another path becomes longer, there is an effect that the overall electrical resistance between the lower electrode 31 and the ground contact portion 45 is lowered.

  By adopting these configurations, the electric resistance from the lower electrode 31 of the piezoelectric element 39 constituting the piezoelectric element rows 40b to 40d to the ground contact portion 45 of the contact portion 43 is lowered to reduce the voltage drop. It can be suppressed.

  Next, the manufacturing process of the piezoelectric actuator 23 of the head unit 16 of the inkjet head 4 described above, particularly, will be described. In the present embodiment, various films are sequentially formed and patterned on the vibrating film 30 of the first flow path substrate 21 to manufacture the piezoelectric actuator 23 including the plurality of piezoelectric elements 39.

  FIG. 5 shows each process of (a) film deposition of vibrating film, (b) formation of common electrode (lower electrode), (c) film deposition of piezoelectric film, and (d) etching of piezoelectric film.

  First, as shown in FIG. 5A, a vibrating film 30 such as silicon dioxide is formed on the surface of the first flow path substrate 21 by thermal oxidation or the like. Next, as shown in FIG. 5B, the common electrode 42 (lower electrode 31) is formed on the vibrating film 30 by film formation by sputtering or the like and patterning by etching.

  Next, the piezoelectric film 32 is formed on the common electrode 42. First, as shown in FIG. 5C, the piezoelectric film 32 is formed on the upper surface of the vibrating film 30 so as to cover the common electrode 42 by a sol-gel method, a sputtering method, or the like. Next, as shown in FIG. 5D, the piezoelectric film 32 is patterned by dry etching. At this time, through holes 32 a for electrically connecting a conductive wire 52 to be described later to the common electrode 42 are formed in portions of the piezoelectric film 32 corresponding to the three piezoelectric element arrays 40 b to 40 d.

  FIG. 6 shows each process of (a) upper electrode formation, (b) protective film formation, and (c) wiring formation. As shown in FIG. 6A, on the upper surface of the piezoelectric film 32, a plurality of upper electrodes 33 respectively corresponding to the plurality of pressure chambers 26 are formed. Specifically, a conductive film is formed by sputtering or the like, and then the conductive film is patterned by etching to form the upper electrode 33.

  Next, as shown in FIG. 6B, a protective film 38 is formed on the upper surface of the vibrating film 30 so as to cover the piezoelectric films 32 to be the plurality of piezoelectric elements 39. First, the protective film 38 is formed on the upper surface of the vibrating film 30 by a film forming method such as sputtering so as to cover the piezoelectric film 32. Next, portions of the protective film 38 overlapping with the right end of the upper electrode 33 and portions corresponding to the through holes 32 a of the piezoelectric film 32 are respectively removed by etching, and the through holes 38 a and 38 b are formed in the protective film 38. Form.

  Next, as shown in FIG. 6C, the drive wiring 35 made of a material such as gold or aluminum and the conduction wiring 52 are formed in the same film formation process on the upper surface of the protective film 38 (wiring formation process). The process for forming the wiring is not particularly limited, but the preferred method differs somewhat depending on the material used. For example, in the case of forming by gold, first, a mask by a photoresist is formed so as to partially cover the piezoelectric film 32, and a film of gold is formed in a region not covered by the mask by plating. Thus, the drive wiring 35 and the conductive wiring 52 may be formed. Further, in the case of forming with an aluminum-based material, first, a film of an aluminum-based material is formed on the entire upper surface of the protective film 38 by sputtering or the like. Next, a part of the above film is partially removed by wet etching to simultaneously form the drive wiring 35 and the conduction wiring 52.

  As described above, since the conductive wire 52 connected to the common electrode 42 is formed in the same film formation process as the plurality of drive wires 35 respectively corresponding to the plurality of piezoelectric elements 39, the conductive wire 52 is formed. There is no increase in special processes. Further, since the common electrode 42 and the drive wiring 35 can be electrically separated by the protective film 38, the arrangement of the common electrode 42 becomes easy, and the voltage drop in the common electrode 42 can be further suppressed.

  As described above, when the piezoelectric actuator 23 is formed on the vibrating film 30, the protection member 28 (see FIG. 4) is joined to the first flow path substrate 21 so as to cover the plurality of piezoelectric elements 39 of the piezoelectric actuator 23. Do. Further, a plurality of pressure chambers 26 are formed in the first flow path substrate 21 by etching. Further, the second flow path substrate 22 and the nozzle 24 are bonded to the first flow path substrate 21 to complete the manufacture of the head unit 16.

  In the embodiment described above, the inkjet head 4 corresponds to the “liquid discharge device” of the present invention. The first flow path substrate 21 corresponds to the “substrate” in the present invention. The piezoelectric element array 40a corresponds to the "first piezoelectric element array" of the present invention, the piezoelectric element array 40b corresponds to the "second piezoelectric element array" of the present invention, and the piezoelectric element arrays 40c and 40d are the present invention. Corresponds to the “third piezoelectric element array” of The lower electrode 31 corresponds to the "first electrode" of the present invention, and the upper electrode 33 corresponds to the "second electrode" of the present invention. The protective film 38 corresponds to the "insulating film" in the present invention. The conductive portion 46 corresponds to the "first conductive portion" of the present invention, and the conductive portion 53 corresponds to the "second conductive portion" of the present invention.

  Next, modified embodiments in which various modifications are added to the embodiment will be described. However, about what has the same structure as the said embodiment, the same code | symbol is attached | subjected and the description is abbreviate | omitted suitably.

1] As shown in FIG. 7, connecting portions 60a provided between the three piezoelectric element rows 40b to 40d are provided with the conductive wires 62b to 62d respectively provided for the three piezoelectric element rows 40b to 40d on the left side. , 60b. More specifically, the conductive wire 62c provided in the piezoelectric element row 40c and the conductive wire 62d provided in the piezoelectric element row 40d intersect the scanning direction between the piezoelectric element row 40c and the piezoelectric element row 40d. The connection portion 60a extends in the direction of FIG. In addition, the conductive wire 62b provided in the piezoelectric element row 40b and the conductive wire 62c provided in the piezoelectric element row 40c cross the scanning direction between the piezoelectric element row 40b and the piezoelectric element row 40c. Conduction is achieved by the extending connection portion 60b. That is, one conduction wiring extending over the three piezoelectric element rows 40 b to 40 d is configured by the conduction wirings 62 b to 62 d and the connection portions 60 a and 60 b.

  According to this configuration, a path separate from the common electrode 42 between the lower electrode 31 of the piezoelectric element 39 forming the piezoelectric element arrays 40c and 40d separated from the contact portion 43 and the ground contact portion 45 of the contact portion 43 Section where the current flows is longer. Therefore, the electric resistance between the piezoelectric elements 39 constituting the piezoelectric element arrays 40c and 40d to the contact portion 43 is reduced, and the voltage drop can be further suppressed.

2) In the embodiment, from the viewpoint of reducing the electrical resistance of the conductive wire 52 corresponding to the piezoelectric element row 40 far from the contact portion 43, the piezoelectric element row 40 increases as the distance between the piezoelectric element row 40 and the contact portion 43 increases. The width in the scanning direction of the conductive wiring 52 provided on the On the other hand, as the distance between the piezoelectric element array 40 and the contact portion 43 increases, the number of conductive wires provided between two adjacent piezoelectric elements 39 may increase.

  As shown in FIG. 8, the three piezoelectric element rows 40 b to 40 d are provided between two piezoelectric elements 39 constituting the piezoelectric element row 40 as the distance between the piezoelectric element row 40 and the contact portion 43 increases. The number of conductive wires 63 to be formed is increased. Specifically, the number of the conductive wirings 63d provided in the piezoelectric element array 40d is the largest, and three conductive wirings 63d are disposed between the two piezoelectric elements 39 of the piezoelectric element array 40d. Next, the number of the conductive wirings 63c provided in the piezoelectric element array 40c is large, and two conductive wirings 63c are disposed between the two piezoelectric elements 39 of the piezoelectric element array 40c. The number of the conductive wirings 63b provided in the piezoelectric element array 40b is the smallest, and only one conductive wiring 63b is disposed between the two piezoelectric elements 39 of the piezoelectric element array 40b.

  As described above, since the number of conductive wires 63 provided for the piezoelectric element array 40 at a distance from the contact portion 43 is large, the piezoelectric element separated from the contact portion 43 is the same as in the above embodiment. The electric resistance to the lower electrode 31 of the piezoelectric element 39 constituting the column 40 and the ground contact portion 45 of the contact portion 43 is reduced, and the voltage drop between them is suppressed to a small value.

  Further, in FIG. 8, the total number of drive wires 35 and conductive wires 63 which are disposed between two piezoelectric elements 39 adjacent in the transport direction among the four piezoelectric element rows 40 a to 40 d is equal to each other. ing. Specifically, in the piezoelectric element array 40 a, three drive wirings 35 are disposed between two adjacent piezoelectric elements 39. In the piezoelectric element array 40b, two drive wires 35 and one conductive wire 63 are disposed. In the piezoelectric element array 40c, one drive wire 35 and two conductive wires 63 are disposed. Furthermore, in the piezoelectric element row 40d, three conductive wires 63 are arranged. That is, among the piezoelectric elements 39 belonging to the four piezoelectric element rows 40, conditions such as the amount of the conductor disposed around each piezoelectric element 39 and the place where the elements are disposed are closer. As a result, the residual stress generated when forming various thin films, the stress condition generated in the piezoelectric element 39 due to the patterning of the piezoelectric film 32, and the like can be approximated, so the variation in residual stress is minimized. be able to.

  From the viewpoint of further suppressing the variation in residual stress, it is preferable that the widths of the drive wiring 35 and the conductive wiring 63 disposed between two adjacent piezoelectric elements 39 be all equal. For example, when the distance between the upper electrodes of two piezoelectric elements 39 adjacent in the transport direction is 15 to 20 μm, the width of the drive wiring 35 and the width of the conduction wiring 63 are each 2 to 3 μm. Good. Moreover, it is preferable that the thickness of the drive wiring 35 and the thickness of the conduction wiring 63 be equal.

4) In order to lower the electrical resistance from the ground contact portion 45 of the contact portion 43 to the lower electrode 31 of the piezoelectric element 39, it is preferable that the conductive wiring be formed of a conductive material with a low electrical resistivity as much as possible. . Therefore, the conductive wire may be formed of a conductive material having a lower electrical resistivity than the drive wire 35. For example, in FIGS. 2 and 3 of the embodiment, when the drive wiring 35 is formed of a relatively inexpensive aluminum-based material, the conductive wiring 52 is more expensive than the aluminum-based material, but the electrical resistivity It may be formed of low gold.

5) In the embodiment, the plurality of drive contact portions 44 of the contact portion 43 and the ground contact portion 45 are arranged side by side in the transport direction. Therefore, the distance from the ground contact portion 45 is different among the plurality of piezoelectric elements 39 constituting each of the three piezoelectric element rows 40b to 40d. Therefore, the plurality of conductive wirings provided for each of the three piezoelectric element arrays 40b to 40d may be wider as the distance from the ground contact portion 45 is larger. In FIG. 9, the upper side in the drawing shown by the arrow A is a direction approaching the ground contact portion 45 in the transport direction, and the lower side in the drawing shown by the arrow B is a direction separating from the ground contact portion 45. The conductive wiring 64 provided in each piezoelectric element row 40 has a larger width as it is disposed on the lower side in the drawing, that is, the side farther from the ground contact portion 45. That is, in the transport direction, the width of the conductive wiring 64 is larger as the distance from the ground contact portion 45 is increased. With this configuration, the voltage drop between the lower electrode 31 and the ground contact portion 45 can be suppressed to a low level also for the piezoelectric element 39 in a position far from the ground contact portion 45 in one piezoelectric element row 40. Can. The drive contact portion 44 in the above embodiment corresponds to the "first contact portion" in the present invention, and the ground contact portion 45 corresponds to the "second contact portion" in the present invention.

6) As in the embodiment and the modified embodiment (FIG. 8 and the like) described above, the conductive wire disposed between two piezoelectric elements 39 adjacent in the transport direction among the three piezoelectric element rows 40b to 40d. It is not necessary to make the width and the number different. That is, the width and number of the conductive wires may be equal among the three piezoelectric element arrays 40b to 40d.

7) In the embodiment, as shown in FIGS. 2 and 3, the piezoelectric film 32 is disposed on the vibrating film 30 so as to cover the plurality of pressure chambers 26, and the piezoelectric portion of the plurality of piezoelectric elements 39 37 are connected to each other. The drive wiring 35 and the conduction wiring 52 are disposed in a portion between the piezoelectric portions 37 of the adjacent piezoelectric elements 39 in the piezoelectric film 32. On the other hand, it is possible to apply the present invention even when the piezoelectric portions of the plurality of piezoelectric elements 39 are separated in the transport direction.

  As shown in FIGS. 10 and 11, the piezoelectric film 72 is disposed so as to cover the common electrode. An opening 72 a is formed by etching in a region between the two piezoelectric elements 39 adjacent to each other in the transport direction of the piezoelectric film 72. In each opening 72 a, the common electrode 42 is exposed from the piezoelectric film 72, but the common electrode 42 exposed from the opening 72 a is covered by the protective film 38 formed after the formation of the upper electrode 33. .

  Further, between the adjacent two piezoelectric elements 39 of each piezoelectric element row 40, the drive wiring 35 and the conduction wiring 82 are disposed on the protective film 38 covering the opening 72a. Although the piezoelectric film 32 and the protective film 38 are disposed between the drive wiring 35 and the conduction wiring 52, and the common electrode 42 in FIG. 4 of the embodiment, the opening 72a is formed in FIG. In the above region, only the protective film 38 is disposed between the drive wire 35 and the conductive wire 82 and the common electrode 42. The conductive wiring 82 is electrically connected to the common electrode 42 by two conductive parts 83 disposed so as to penetrate the protective film 38.

  Alternatively, the piezoelectric film 32 may be patterned for each pressure chamber 26, and the piezoelectric portion 37 may be completely separated between the plurality of pressure chambers 26. In this case, the sizes of the piezoelectric portion 37 and the upper electrode 33 are approximately the same, or the upper electrode 33 is slightly smaller than the piezoelectric portion 37.

8) In the embodiment described above, the protective film 38 is provided to cover the plurality of piezoelectric elements 39. However, the protective film 38 can be omitted.

9) In the above embodiment, the plurality of lower electrodes 31 are electrically connected to each other by the electrode conduction portion 41 to form the common electrode 42 for the plurality of piezoelectric elements 39, while each upper electrode 33 is an individual electrode. The lower electrode may be an individual electrode, and the upper electrode may be a common electrode.

10] In the piezoelectric actuator 23 of the embodiment, the plurality of piezoelectric elements 39 constitute four piezoelectric element rows 40, but the number of piezoelectric element rows is not limited to four. That is, the present invention is applicable to a piezoelectric actuator having two or more piezoelectric element arrays 40.

11] In the piezoelectric actuator 23 according to the embodiment, the conductive wiring 52 is provided for the three piezoelectric element rows 40b to 40d on the opposite side of the contact portion 43 among the four piezoelectric element rows 40, The conductive wiring 52 may be provided also for the piezoelectric element array 40 a closest to the contact portion 43.

  Contrary to the above, the conductive wires 52 do not necessarily have to be provided for all the three piezoelectric element rows 40 b to 40 d, and the conductive wires 52 are provided for only one of the three piezoelectric element rows 40 b to 40 d. It may be done.

13) In the above embodiment, the COF 50 as a wiring member is joined to the contact portion 43 provided on the first flow path substrate 21. However, the contact portion 43 is electrically connected to components other than the wiring member such as an IC chip. May be connected.

  Although the embodiment described above and the modification form apply the present invention to the piezoelectric actuator of the ink jet head which discharges ink on recording paper and prints an image etc., various uses other than printing of an image etc. The present invention can also be applied to the liquid discharge device used in For example, the present invention can be applied to a liquid discharge apparatus that discharges a conductive liquid onto a substrate to form a conductive pattern on the surface of the substrate. Moreover, the piezoelectric actuator of the present invention is not limited to one used for the purpose of applying pressure to a liquid. For example, the present invention can be applied to an actuator that moves a solid object, an actuator that pressurizes a gas, and the like.

Next, disclosed inventions other than inventions according to claims 1 to 17 described in the original claim will be described.
The present invention constitutes a first piezoelectric element row arranged in a first direction on a substrate, and a second piezoelectric element row arranged in a second direction orthogonal to the first piezoelectric element row and the first direction. Multiple piezoelectric elements,
A contact portion disposed on the substrate at a position opposite to the second piezoelectric element row in the second direction with respect to the first piezoelectric element row, and to which a wiring member is joined;
A plurality of drive wires extending in the second direction from the plurality of piezoelectric elements toward the contact portion;
Each piezoelectric element includes a piezoelectric portion, a first electrode disposed on one side in the thickness direction of the piezoelectric portion, and a second electrode disposed on the other side in the thickness direction of the piezoelectric portion.
Each drive wire is connected to the first electrode of the corresponding piezoelectric element,
The second electrodes of the plurality of piezoelectric elements are electrically connected to each other by the electrode conduction portion disposed between the plurality of second electrodes, and the plurality of piezoelectric elements are electrically connected by the plurality of second electrodes and the electrode conduction portion. Common electrode of the
The piezoelectric device further includes a piezoelectric connecting portion connecting the piezoelectric portions of the plurality of piezoelectric elements constituting each piezoelectric element row,
The drive wiring corresponding to the piezoelectric element of the second piezoelectric element line extends between the two piezoelectric elements adjacent in the first direction of the first piezoelectric element line to the contact portion. ,
A piezoelectric actuator is disposed between two adjacent piezoelectric elements in the first direction of the second piezoelectric element row, and a dummy interconnection separated from the drive interconnection is disposed. It is an invention.

  An embodiment of the above disclosed invention will be described with reference to FIG. The piezoelectric actuator 103 has a plurality of piezoelectric elements 39 constituting four piezoelectric element arrays 40 a to 40 d respectively corresponding to the four pressure chamber arrays 27 a to 27 d. Similar to the above embodiment, the piezoelectric film 32 is formed across the four pressure chamber rows 27. That is, the piezoelectric portions 37 of the plurality of piezoelectric elements 39 constituting the four piezoelectric element rows 40 are mutually connected by the piezoelectric connecting portions 111 disposed between the adjacent pressure chambers 26 of the piezoelectric film 32. It has become.

  From the plurality of piezoelectric elements 39 constituting the four piezoelectric element arrays 40, corresponding drive wires 35 are drawn to the right toward the contact portion 43. Therefore, in the three piezoelectric element arrays 40a to 40c on the right side, the drive wiring 35 from the other piezoelectric element array 40 passes between the two piezoelectric elements 39 adjacent in the transport direction. On the other hand, in the piezoelectric element row 40d positioned on the leftmost side, the drive wiring 35 of the other piezoelectric element row 40 is not disposed between the two piezoelectric elements 39 adjacent in the transport direction.

  The residual stress in each piezoelectric element 39 changes depending on whether or not a conductive film such as the drive wiring 35 is present on the piezoelectric film 32 between two adjacent piezoelectric elements 39. As a result, the residual stress of the piezoelectric element 39 varies among the four piezoelectric element arrays 40. Therefore, in FIG. 12, in the leftmost piezoelectric element row 40d, the dummy wiring 110d is disposed between two piezoelectric elements 39 adjacent in the transport direction. The dummy wiring 110d does not conduct to the upper electrode 33 or the drive wiring 35, and unlike the conducting wiring 52 (see FIGS. 2 and 3) in the embodiment, does not conduct to the common electrode 42, It is an electrode placed in isolation. By arranging the dummy wiring 110 between two adjacent piezoelectric elements 39 of the piezoelectric element row 40d, variation in residual stress with the piezoelectric elements 39 of the other piezoelectric element rows 40 can be suppressed to a small level.

  Further, among the three piezoelectric element arrays 40a to 40c on the right side, the number of drive wires 35 passing between the two adjacent piezoelectric elements 39 is different. Therefore, in FIG. 12, dummy wirings 110b and 110c are provided also for the piezoelectric element arrays 40b and 40c having a small number of drive wirings 35 passing therethrough, similarly to the piezoelectric element array 40d. However, the width of the dummy wiring 110c of the piezoelectric element array 40c is smaller than the width of the dummy wiring 110d of the piezoelectric element array 40d. Further, the width of the dummy wiring 110b of the piezoelectric element row 40b is further smaller than the width of the dummy wiring 110c of the piezoelectric element row 40c.

4 inkjet head 21 first flow path substrate 23 piezoelectric actuator 24 nozzle 26 pressure chamber 27 pressure chamber row 30 vibrating film 31 lower electrode 32 piezoelectric film 33 upper electrode 35 drive wiring 37 piezoelectric section 38 protective film 39 piezoelectric element 40 piezoelectric element array 41 Electrode conduction portion 42 common electrode 43 contact portion 44 drive contact portion 45 ground contact portion 46 conduction portion 52 conduction wiring 53 conduction portion 60a, 60b connection portion 62 conduction wiring 63 conduction wiring 64 conduction wiring 72 piezoelectric film 82 conduction wiring 83 conduction portion

Claims (4)

A plurality of piezoelectric elements constituting a first piezoelectric element array arranged in a first direction on a substrate and a second piezoelectric element array arranged in a second direction intersecting the first piezoelectric element array and the first direction When,
A contact portion disposed on the substrate at a position opposite to the second piezoelectric element row in the second direction with respect to the first piezoelectric element row;
A plurality of drive wires extending in the second direction from the plurality of piezoelectric elements toward the contact portion;
Each piezoelectric element includes a piezoelectric portion, a first electrode disposed on one side in the thickness direction of the piezoelectric portion, and a second electrode disposed on the other side in the thickness direction of the piezoelectric portion.
Each drive wire is connected to the first electrode of the corresponding piezoelectric element,
The second electrodes of the plurality of piezoelectric elements are mutually conducted by an electrode conduction portion,
The drive wiring corresponding to the piezoelectric element of the second piezoelectric element line extends between the two piezoelectric elements adjacent in the first direction of the first piezoelectric element line to the contact portion. ,
A dummy wiring is disposed between the two piezoelectric elements adjacent in the first direction of the second piezoelectric element row, and is separated from the drive wiring.
The thickness of the dummy wiring is the same as the thickness of the drive wiring. The piezoelectric actuator according to claim 1, wherein the dummy wiring is formed of the same conductive material as the drive wiring.   The piezoelectric actuator according to claim 1, wherein the dummy wiring and the drive wiring do not overlap. A substrate,
A plurality of piezoelectric elements constituting a first piezoelectric element row arranged in a first direction and a second piezoelectric element row arranged in a second direction intersecting the first direction with the first piezoelectric element row on the substrate Element,
A contact portion disposed on the substrate at a position opposite to the second piezoelectric element row in the second direction with respect to the first piezoelectric element row;
A plurality of drive wires extending in the second direction from the plurality of piezoelectric elements toward the contact portion;
Each piezoelectric element includes a piezoelectric portion, a first electrode disposed on one side in the thickness direction of the piezoelectric portion, and a second electrode disposed on the other side in the thickness direction of the piezoelectric portion.
Each drive wire is connected to the first electrode of the corresponding piezoelectric element,
The second electrodes of the plurality of piezoelectric elements are mutually conducted by an electrode conduction portion,
The drive wiring corresponding to the piezoelectric element of the second piezoelectric element line extends between the two piezoelectric elements adjacent in the first direction of the first piezoelectric element line to the contact portion. ,
A dummy wiring is disposed between the two piezoelectric elements adjacent in the first direction of the second piezoelectric element row, and is separated from the drive wiring.
The substrate corresponds to the plurality of piezoelectric elements, and has a plurality of pressure chambers arranged in the first direction,
The liquid discharge head, wherein the dummy wiring is formed on a girder between the pressure chambers adjacent in the first direction.

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