JP7002026B2 - Piezoelectric actuator, liquid discharge device, and manufacturing method of piezoelectric actuator - Google Patents

Description

The present invention relates to a piezoelectric actuator and a liquid discharge device having a piezoelectric actuator.

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

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

A plurality of electric contact portions are arranged on the upper surface of one end of the piezoelectric film in a direction orthogonal to the nozzle arrangement direction, and a plurality of individual electrodes of the plurality of piezoelectric elements arranged in four rows are used. The drive wiring extends toward the electrical contacts. Of the four piezoelectric element rows, the drive wiring corresponding to the piezoelectric element forming the piezoelectric element row located on the side opposite to the electric contact portion is the piezoelectric element forming the piezoelectric element row located on the electrical contact portion side. It passes between the elements and extends to the electrical contacts. An IC chip for applying a voltage to each piezoelectric element is connected to the electric contact portion.

Japanese Unexamined Patent Publication No. 2000-79683

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

In the above configuration, the distance from the electric contact portion in the orthogonal direction is different between the plurality of piezoelectric element trains arranged in the direction orthogonal to the arrangement direction of the pressure chamber. That is, the distance between the electrode portion of the common electrode for applying voltage to each piezoelectric element facing the individual electrodes with the piezoelectric film sandwiched between the plurality of piezoelectric element rows and the electrical contact portion is It will be different. As a result, in the piezoelectric element row located far from the electric contact portion, the path from the electric contact portion to the electrode portion of the common electrode becomes longer than that in the piezoelectric element row located near the electric contact portion.

Therefore, when the piezoelectric element is driven, the voltage drop in the above path becomes large. In addition, the degree of voltage drop also differs due to the difference in the length of the above-mentioned path among the plurality of piezoelectric element trains. Due to this difference in voltage drop, the voltage applied to the piezoelectric element varies among a plurality of piezoelectric element trains, and the variation in the applied voltage causes a variation in ejection characteristics among a plurality of nozzles. appear.

In order to suppress the variation in the applied voltage between the piezoelectric elements due to the difference in the length of the path, the thickness of the common electrode is increased so that the difference in the voltage drop in the common electrode can be ignored. do it. However, if the common electrode is thick, there is a problem that the deformation of the piezoelectric film in the pressure chamber is hindered and the deformation efficiency is lowered.

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

Means for Solving Problems and Effects of Invention

The piezoelectric actuator of the present invention is arranged on the substrate in the first direction, and the first piezoelectric element row, the first piezoelectric element row, and the second piezoelectric element row arranged in the second direction orthogonal to the first direction. A plurality of piezoelectric elements constituting the above, and a contact portion arranged 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 wirings extending from the plurality of piezoelectric elements toward the contact portion in the second direction, respectively.
Each piezoelectric element has a piezoelectric portion, a first electrode arranged on one side in the thickness direction of the piezoelectric portion, and a second electrode arranged on the other side in the thickness direction of the piezoelectric portion, and each drives. The wiring is connected to the first electrode of each piezoelectric element, and the second electrode of the plurality of piezoelectric elements is electrically connected to each other by an electrode conduction portion arranged between the plurality of second electrodes, and the plurality of first electrodes are connected to each other. A common electrode for the plurality of piezoelectric elements is configured 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 drive wiring of the first piezoelectric element row. It extends between the two adjacent piezoelectric elements in the first direction to the contact portion, and is arranged between the two adjacent piezoelectric elements in the first direction of the second piezoelectric element row. Moreover, it is characterized in that conduction wirings that are electrically connected to the electrode conduction portion of the common electrode are arranged at two positions separated from each other in the second direction.

In the present invention, a plurality of piezoelectric elements are arranged in the first direction to form two rows of piezoelectric elements arranged in the second direction. Further, the drive wiring corresponding to the piezoelectric element of the second piezoelectric element row extends in the second direction through between the piezoelectric elements of the first piezoelectric element row and extends to the contact portion. Here, of the two rows of piezoelectric elements, the second piezoelectric element row located on the opposite side of the contact portion has a longer distance to the contact portion than the first piezoelectric element row. The voltage drop when a current flows from the second electrode of the piezoelectric element to the contact portion becomes large. Therefore, in the present invention, in the second piezoelectric element row located at a position away from the contact portion, conduction wiring that conducts with the common electrode at two positions is arranged between the two adjacent piezoelectric elements. By this conduction wiring, the path through which the current flows between the second electrode of each piezoelectric element in the second piezoelectric element row and the contact portion increases, and the voltage drop can be suppressed.

Further, a drive wiring corresponding to the piezoelectric element of the second piezoelectric element row away from the contact portion passes between the piezoelectric elements of the first piezoelectric element row near the contact portion. On the other hand, since there is a vacant region between the piezoelectric elements of the second piezoelectric element row, it is easier to install the conduction wiring between the piezoelectric elements as compared with the first piezoelectric element row.

It is a schematic plan view of the printer 1 which concerns on this embodiment. It is a top view of the head unit 16 of the inkjet head 4. It is the X part enlarged view of FIG. FIG. 3 is a sectional view taken along line IV-IV of FIG. It is a figure which shows the manufacturing process of a piezoelectric actuator 23, (a) film formation of a vibrating film 30, (b) formation of a common electrode 42 (lower electrode 31), (c) film formation of a piezoelectric film 32, (d) piezoelectric. Each step of etching the film 32 is shown. It is a figure which shows the manufacturing process of a piezoelectric actuator 23, and shows each process of (a) formation of an upper electrode 33, (b) formation of a protective film 38, and (c) formation of wirings 35, 52. It is a top view of the head unit 16 of a modified form. It is a top view of the head unit 16 of another modified form. It is a partially enlarged view of the piezoelectric actuator 23 of another modified form. It is a partially enlarged view of the piezoelectric actuator 23 of another modified form. FIG. 10 is a sectional view taken along line XI-XI of FIG. It is a top view of the head unit 16 which concerns on embodiment about the disclosed 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, a 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-right direction of the printer 1. Further, the upstream side in the transport direction in FIG. 1 is defined as the rear side of the printer 1, and the downstream side is defined as the front side of the printer 1. Further, a direction orthogonal to the scanning direction and the transport direction (direction orthogonal to the paper surface 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. In the following, each direction word of front, back, left, right, up and down will be described as appropriate.

(Approximate 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 reciprocating in the scanning direction along the two guide rails 10 and 11 in the region facing the platen 2. An endless belt 14 is connected to the carriage 3, and the carriage 3 is driven by the carriage drive motor 15 to move the carriage 3 in the scanning direction.

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

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

The control device 6 includes a ROM (Read Only Memory), a RAM (Random Access Memory), an ASIC (Application Specific Integrated Circuit) including various control circuits, and the like. The control device 6 executes various processes such as printing on the recording paper 100 by the ASIC according to the program stored in the ROM. For example, in the printing process, the control device 6 controls the head unit 16 of the inkjet head 4, the carriage drive motor 15, and the like based on a printing command input from an external device such as a PC, and an image is printed on the recording paper 100. Etc. are printed. Specifically, the ink ejection operation of ejecting ink while moving the inkjet head 4 together with the carriage 3 in the scanning direction and the conveying operation of conveying a predetermined amount of the recording paper 100 in the conveying direction by the conveying rollers 18 and 19 are alternately performed. 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. Since the two head units 16a and 16b have the same structure, the head unit 16a that ejects black and yellow ink will be described below as a representative. FIG. 2 is a top view of the head unit 16 of the inkjet head 4. FIG. 3 is an enlarged view of part X of FIG. FIG. 4 is a 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 board 21, a second flow path board 22, a piezoelectric actuator 23, and the like. In FIG. 2, for the sake of simplification of the drawing, only the outer shape of the protective member 28 located above the first flow path substrate 21 in FIG. 4 is shown by a two-dot chain line. Further, in order to make it easier to understand the configuration of the piezoelectric actuator 23 in FIG. 2, the protective film 38 that completely covers the first flow path substrate 21 shown in FIGS. 3 and 4 is not shown in FIG. It is omitted.

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

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

The second flow path substrate 22 is joined 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 formed in a portion of the second flow path substrate 22 that vertically overlaps the pressure chamber rows 27a and 27b in the right two rows and a portion that vertically overlaps the pressure chambers 26c and 27d in the left two rows. ing. Each manifold 25 extends along a transport direction, which is the arrangement direction of the pressure chambers 26. Each manifold 25 and the pressure chamber 26 belonging to the corresponding two rows of pressure chamber rows 27 are communicated with each other by a communication hole 48. Further, the two manifolds 25 are 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 pressure chambers 26, respectively. 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 and the nozzle 24 formed in the nozzle plate 20. When the ejection energy is applied to the ink in the pressure chamber 26 by the piezoelectric actuator 23 described below, the ink droplets 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 inks in the plurality of pressure chambers 26, respectively. The piezoelectric actuator 23 has a plurality of piezoelectric elements 39 arranged on the upper surface of the vibrating membrane 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, and form four piezoelectric element rows 40 (40a to 40d) arranged 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 that covers a plurality of piezoelectric elements 39 of the piezoelectric actuator 23 is bonded 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 membrane 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 configured to be electrically connected to each other by a portion (electrode conduction portion 41) of the common electrode 42 arranged between the plurality of pressure chambers 26. The material of the common electrode 42 (plurality of lower electrodes 31 and the electrode conduction portion 41) is not particularly limited, but is formed 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 rectangular film in a plan view formed over 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 each other. 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 made of a lead-free piezoelectric material that does not contain lead. The thickness of the piezoelectric film 32 is, for example, 1 μm.

On the upper surface of the piezoelectric film 32, a plurality of upper electrodes 33 corresponding to the plurality of pressure chambers 26 are formed. The upper electrode 33 is an individual electrode individually provided for each pressure chamber 26. The shape of the upper electrode 33 is not particularly limited, but for example, FIG. 3 shows one having a rectangular planar shape smaller than that of the pressure chamber 26. The material of the upper electrode 33 is also not particularly limited, but is formed 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, faces 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 for which the protective film 38 is provided is to prevent the piezoelectric element 39 from becoming damp. The material of the protective film 38 is not particularly limited, but is formed of, for example, silicon nitride, silicon dioxide, alumina, or the like. Further, the protective film 38 may be arranged 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 corresponding to the plurality of piezoelectric elements 39 are formed on the upper surface of the protective film 38. One end of each drive wiring 35 is arranged so as to ride on the upper electrode 33. A through hole 38a is formed in a portion of the protective film 38 that overlaps with one end of the drive wiring 35. The drive wiring 35 and the upper electrode 33 are electrically connected to each other by a conductive portion 46 made of a conductive material arranged in the through hole 38a and provided so as to penetrate 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 wirings 35 connected to the upper electrodes 33 of the plurality of piezoelectric elements 39 extend to the right from the corresponding upper electrodes 33. .. Therefore, the drive wiring 35 drawn from the upper electrode 33 of the three piezoelectric element rows 40 on the left side passes between the two piezoelectric elements 39 belonging to the other piezoelectric element rows 40 located on the right side of the drive wiring 35 and passes to the right. Extends to. For example, as shown in FIG. 2, between the two piezoelectric elements 39 adjacent to each other in the transport direction of the piezoelectric element row 40a located on the rightmost side, three piezoelectric element rows 40b to 40d corresponding to the three piezoelectric element rows 40b to 40d on the left side are respectively. The drive wirings 35b to 35d of the above are arranged. The material of the drive wiring 35 is not particularly limited, but gold (Au) having a low electrical resistivity or an aluminum-based material (for example, Al—Cu alloy) can be preferably 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 that is more prone to migration than gold, when the drive wiring 35 is made of aluminum, a plurality of drive wiring 35 may be covered with an insulating film to prevent migration. preferable. The thickness of the drive wiring 35 is, for example, 1 μm.

As shown in FIG. 2, a contact portion 43 to which the COF 50, which is a wiring member, is joined is provided on the upper surface of the right end portion of the vibrating film 30 of the first flow path substrate 21. A plurality of drive contact portions 44 and two ground contact portions 45 arranged in the transport direction are arranged in the contact portion 43. The drive wiring 35 connected to the upper electrode 33 of each piezoelectric element 39 is connected to the drive contact portion 44 arranged in the contact portion 43. Further, 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, a COF 50 is joined to the contact portion 43, a plurality of drive contact portions 44 arranged in the contact portion 43, and a plurality of signal wirings (not shown) formed in the COF 50. However, they are electrically connected to each other. Further, the two ground contact portions 45 arranged in the contact portion 43 are connected to the 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 wiring of the COF 50, and is further supplied to each upper electrode 33 via the drive wiring 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 a 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, the potential difference between the upper electrode 33 and the lower electrode 31 causes the piezoelectric portion 37 to be in the thickness direction thereof. Parallel electric fields act. Here, in order for the polarization direction of the piezoelectric portion 37 to coincide with the direction of the electric field, the piezoelectric portion 37 extends in the thickness direction, which is the polarization direction, and contracts in the plane direction. As the piezoelectric portion 37 contracts and deforms, the vibrating membrane 30 bends so as to be convex toward the pressure chamber 26. As a result, the volume of the pressure chamber 26 is reduced and a pressure wave is generated in the pressure chamber 26, so that ink droplets are ejected from the nozzle 24 communicating with the pressure chamber 26.

By the way, in the present embodiment, the plurality of piezoelectric elements 39 constitute four piezoelectric element rows 40a to 40d 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 between the four piezoelectric element rows 40a to 40d. In the piezoelectric element row 40d located at a position away 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 that the electric resistance between them is the largest. As a result, when the piezoelectric element 39 is driven, the voltage drop when a current flows from the second electrode 31 toward the ground contact portion 45 becomes large. In particular, when ink is ejected from a large number of nozzles 24 at the same time, many piezoelectric elements 39 are driven at the same time. Therefore, the voltage drop at the common electrode 42 becomes relatively large, and the voltage applied to each piezoelectric element 39 becomes small.

In this regard, it is possible to suppress the voltage drop low by increasing the thickness of the common electrode 42 and reducing the electrical resistance of the common electrode 42. However, if the thickness of the common electrode 42 (particularly, the lower electrode 31) is increased, the deformation of the piezoelectric portion 37 is hindered by the thickness. Further, as the material of the common electrode 42, platinum (Pt), which does not easily affect the orientation of the piezoelectric film 32, is suitable, but since platinum is an expensive material, the thickness of the common electrode 42 should be increased from the viewpoint of cost. It's difficult to make it bigger.

For the above reason, there is a difference in the degree of voltage drop between the lower electrode 31 and the ground contact portion 45 depending on the distance from the ground contact portion 45 among the four piezoelectric element trains 40a to 40d. In the piezoelectric element row 40 having a large voltage drop, the voltage applied to the piezoelectric element 39 is substantially reduced. That is, the voltage applied to the piezoelectric element 39 varies among the four piezoelectric element rows 40a to 40d. This variation in the applied voltage appears as a variation in the ejection characteristics of the nozzle 24 among the four nozzle rows, which leads to deterioration of print quality. Therefore, in the present embodiment, it is an object to suppress the voltage drop between the lower electrode 31 of the piezoelectric element 39 constituting the piezoelectric element row 40 away from the contact portion 43 and the ground contact portion 45 of the contact portion 43 to be low. As a result, the following configuration is adopted.

As shown in FIGS. 2 to 4, of the four piezoelectric element rows 40a to 40d, the three piezoelectric element rows 40b to 40d arranged on the left side (opposite to the contact portion 43) are adjacent to each other in the transport direction. A conduction wiring 52 that conducts with the common electrode 42 is provided between the upper electrodes 33 of the two piezoelectric elements 39.

The conductive wiring 52 is made of the same conductive material (gold, aluminum-based material, etc.) as the drive wiring 35, and is arranged on the upper surface of the protective film 38 that covers the plurality of piezoelectric elements 39, similarly to the drive wiring 35 described above. That is, the conduction wiring 52 is arranged 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 rows 40b to 40d, the conduction wiring 52 extends in the scanning direction between the two adjacent piezoelectric element 39s.

The length of the conduction wiring 52 in the scanning direction is longer than the length of the upper electrodes 33 of the two adjacent piezoelectric elements 39 in the scanning direction. More specifically, the length of the conduction wiring 52 in the scanning direction is substantially equal to the length of the pressure chamber 26 in the scanning direction. Further, the thickness of the conduction 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, which is the same as that of the drive wiring 35.

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, and the like. Changes. Therefore, from the viewpoint of reducing the variation in the 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 wiring 52 is made of the same conductive material as the drive wiring 35.

As shown in FIGS. 3 and 4, two through holes 32a are formed in the portions of the piezoelectric film 32 that overlap both ends of the conduction wiring 52. Further, two through holes 38b are also formed in the portion of the protective film 38 that overlaps both ends of the conductive wiring 52. The through hole 32a of the piezoelectric film 32 and the through hole 38b of the protective film 38 are filled with the conductive material constituting the conductive wiring 52, so that the conductive portion 53 penetrating the piezoelectric film 32 and the protective film 38 is arranged. Has been done. Both ends of each conduction wiring 52 are connected to the electrode conduction portion 41 of the common electrode 42 via two conduction portions 53, respectively. The positions of the two conduction portions 53 that conduct the conduction wiring 52 and the common electrode 42 are not limited to both ends of the conduction wiring 52. However, if the conductive portion 53 is located near the central portion of the conductive wiring 52, the length of the conductive wiring 52 that functions as a path for passing a part of the current flowing through the common electrode 42 is substantially shortened. It is preferable that the two conductive portions 53 are provided at both ends of the conductive wiring 52.

In the piezoelectric element row 40b located second from the right, a conduction wiring 52b and two drive wirings 35c and 35d drawn out from the piezoelectric element rows 40c and 40d are provided between two adjacent piezoelectric elements 39, respectively. Have been placed. Further, in the piezoelectric element row 40c located third from the right, a conduction wiring 52c and one drive wiring 35d drawn out from the piezoelectric element row 40d are arranged between two adjacent piezoelectric elements 39. There is. In the piezoelectric element rows 40b and 40c, the conduction wiring 52 is arranged behind the drive wiring 35. Further, in the piezoelectric element row 40d located on the leftmost side, only the conduction wiring 52d is arranged between the two adjacent piezoelectric elements 39.

As described above, in the piezoelectric element row 40 (40b to 40d) located at a position away from the contact portion 43 in the scanning direction, a conduction wiring 52 that conducts with the common electrode 42 is provided between the adjacent piezoelectric elements 39. There is. Therefore, the path through which the current flows increases between the lower electrode 31 of the piezoelectric element 39 constituting the piezoelectric element rows 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 element 39 constituting the piezoelectric element rows 40b to 40d located at a position away from the contact portion 43, the lower electrode 31 and the lower electrode 31 when a current flows from the lower electrode 31 toward the ground contact portion 45 of the contact portion 43. The voltage drop between the ground contact portion 45 and the ground contact portion 45 can be suppressed to a small value. By suppressing the voltage drop to be small, the variation in the voltage applied to the piezoelectric element 39 is suppressed among the plurality of piezoelectric elements 39, so that the difference in ejection characteristics among the plurality of nozzles 24 becomes small.

In the first piezoelectric element row 40a near the contact portion 43, three drive wirings 35b corresponding to the other three piezoelectric element rows 40b to 40d are provided between the two piezoelectric element rows 39 adjacent to each other in the transport direction. ~ 35d has passed. Compared to this, in the other three piezoelectric element rows 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 rows 40b to 40c away from the contact portion 43, the area of the vacant region existing between the two adjacent piezoelectric element 39s is larger than that of the piezoelectric element rows 40a, so that the two adjacent piezoelectric element rows 40b to 40c have a larger area. It is easy to install the conduction wiring 52 between the piezoelectric elements 39.

Further, even between the three piezoelectric element rows 40b to 40d provided with the conductive wiring 52, the larger the distance from the contact portion 43, the more the lower electrode 31 of the piezoelectric element 39 and the ground contact portion 45 of the contact portion 43 come into contact with each other. The electrical resistance between them is large, and the voltage drop is also large. Therefore, the electric resistance of the conductive wiring 52 provided in the piezoelectric element row 40 that is far from the contact portion 43 becomes smaller than the electric resistance of the conductive wiring 52 provided in the piezoelectric element row 40 close to the contact portion 43. It is preferable to have. That is, the conduction wiring 52 arranged between the two adjacent piezoelectric elements 39 has (1) a large wiring width, (2) a large number of wirings, or (3) with respect to the drive wiring 35. It is preferably made of a material having a low electrical resistivity.

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

Specific examples of the width of the conductive wiring 52 are given below. When the distance D (see FIG. 3) between the two upper electrodes 33 adjacent to each other 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 of the conduction wiring 52b having the smallest width is the smallest. The width is preferably 2 to 3 μm, which is the same as that of the drive wiring 35. Further, the width of the conductive wiring 52c is preferably 4 to 6 μm, which is twice the width of the conductive wiring 52b. Further, 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 conduction wiring 52 among the plurality of piezoelectric element rows 40 can be generalized by the following equation.
When the width of the conduction wiring 52 located in the nth row from the contact portion 43 is Wn,
Wn = k × (n-1) (where k is a constant)
Will be.

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

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

By adopting these configurations, the electric resistance between 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, and the voltage drop is reduced. It can be suppressed.

Next, the manufacturing process of the head unit 16 of the inkjet head 4 described above, particularly the piezoelectric actuator 23, will be described. In the present embodiment, a piezoelectric actuator 23 including a plurality of piezoelectric elements 39 is manufactured by sequentially forming and patterning various films on the vibration film 30 of the first flow path substrate 21.

FIG. 5 shows each step of (a) film formation of a vibrating film, (b) formation of a common electrode (lower electrode), (c) film formation of a piezoelectric film, and (d) etching of a 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, a common electrode 42 (lower electrode 31) is formed on the vibrating film 30 by forming a film 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, a piezoelectric film 32 is formed on the upper surface of the vibrating film 30 by a sol-gel method, a sputtering method, or the like so as to cover the common electrode 42. Next, as shown in FIG. 5D, the piezoelectric film 32 is patterned by dry etching. At this time, through holes 32a for conducting the conduction wiring 52 described later with the common electrode 42 are formed in the portions of the piezoelectric film 32 corresponding to the three piezoelectric element rows 40b to 40d.

FIG. 6 shows each process of (a) upper electrode formation, (b) protective film formation, and (c) wiring formation. As shown in FIG. 6A, 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. 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 serving as the plurality of piezoelectric elements 39. First, a protective film 38 is formed on the upper surface of the vibrating film 30 so as to cover the piezoelectric film 32 by a film forming method such as sputtering. Next, the portion of the protective film 38 that overlaps with the right end portion of the upper electrode 33 and the portion corresponding to the through hole 32a of the piezoelectric film 32 are removed by etching, and the through holes 38a and 38b are formed in the protective film 38. Form.

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

As described above, since the conductive wiring 52 connected to the common electrode 42 is formed by the same film forming process as the plurality of drive wirings 35 corresponding to the plurality of piezoelectric elements 39, the conductive wiring 52 is formed. No special process is added. Further, since the common electrode 42 and the drive wiring 35 can be electrically separated by the protective film 38, the common electrode 42 can be easily handled, and the voltage drop in the common electrode 42 can be further suppressed.

After the piezoelectric actuator 23 is formed on the vibrating membrane 30 as described above, the protective 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 on the first flow path substrate 21 by etching. Further, the second flow path substrate 22 and the nozzle 24 are joined to the first flow path substrate 21, and the production of the head unit 16 is completed.

In the embodiment described above, the inkjet head 4 corresponds to the "liquid ejection device" of the present invention. The first flow path substrate 21 corresponds to the "substrate" of the present invention. The piezoelectric element row 40a corresponds to the "first piezoelectric element row" of the present invention, the piezoelectric element row 40b corresponds to the "second piezoelectric element row" of the present invention, and the piezoelectric element rows 40c and 40d correspond to the present invention. Corresponds to the "third piezoelectric element sequence" 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" of 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, a modified embodiment in which various modifications are made to the embodiment will be described. However, those having the same configuration as that of the above-described embodiment are designated by the same reference numerals and the description thereof will be omitted as appropriate.

1] As shown in FIG. 7, conduction wirings 62b to 62d provided for each of the three piezoelectric element rows 40b to 40d on the left side are connected portions 60a arranged between the three piezoelectric element rows 40b to 40d. , 60b may be conducted. More specifically, the conductive wiring 62c provided in the piezoelectric element row 40c and the conductive wiring 62d provided in the piezoelectric element row 40d intersect with the scanning direction between the piezoelectric element row 40c and the piezoelectric element row 40d. It is conductive by the connecting portion 60a extending in the direction of Further, the conductive wiring 62b provided in the piezoelectric element row 40b and the conductive wiring 62c provided in the piezoelectric element row 40c are in a direction intersecting the scanning direction between the piezoelectric element row 40b and the piezoelectric element row 40c. It is conducted by the extending connection portion 60b. That is, the conductive wiring 62b to 62d and the connecting portions 60a and 60b constitute one conductive wiring extending over the three piezoelectric element rows 40b to 40d.

According to this configuration, a path different from the common electrode 42 is provided between the lower electrode 31 of the piezoelectric element 39 constituting the piezoelectric element rows 40c and 40d away from the contact portion 43 and the ground contact portion 45 of the contact portion 43. The section where the current flows becomes longer. Therefore, the electric resistance between the piezoelectric elements 39 constituting the piezoelectric element rows 40c and 40d to the contact portion 43 is reduced, and the voltage drop is further suppressed.

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

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

As described above, since the number of conductive wirings 63 provided for the piezoelectric element row 40 that is far from the contact portion 43 is large, the piezoelectric element that is separated from the contact portion 43 is the same as in the above embodiment. The electrical resistance between the lower electrode 31 of the piezoelectric element 39 constituting the row 40 and the ground contact portion 45 of the contact portion 43 is reduced, and the voltage drop between them is suppressed to be small.

Further, in FIG. 8, the total number of the drive wiring 35 and the conduction wiring 63 arranged between the two piezoelectric elements 39 adjacent to each other in the transport direction is equal to each other between the four piezoelectric element rows 40a to 40d. ing. Specifically, in the piezoelectric element row 40a, three drive wirings 35 are arranged between two adjacent piezoelectric elements 39. In the piezoelectric element row 40b, two drive wirings 35 and one conduction wiring 63 are arranged. In the piezoelectric element row 40c, one drive wiring 35 and two conduction wirings 63 are arranged. Further, in the piezoelectric element row 40d, three conduction wirings 63 are arranged. That is, between the piezoelectric elements 39 belonging to each of the four piezoelectric element rows 40, conditions such as the amount of conductors arranged around each piezoelectric element 39 and the place where they are arranged approach each other. As a result, the residual stress generated when forming various thin films and the stress conditions generated in the piezoelectric element 39 due to the patterning of the piezoelectric film 32 can be brought close to each other, so that the variation in the residual stress is minimized. be able to.

From the viewpoint of further suppressing the variation in the residual stress, it is preferable that the widths of the drive wiring 35 and the conduction wiring 63 arranged between the two adjacent piezoelectric elements 39 are all the same. For example, when the distance between the upper electrodes of the two piezoelectric elements 39 adjacent to each other 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 set to 2 to 3 μm, respectively. good. Further, it is preferable that the thickness of the drive wiring 35 and the thickness of the conduction wiring 63 are also the same.

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

5] In the above embodiment, the plurality of drive contact portions 44 and the ground contact portion 45 of the contact portion 43 are arranged side by side in the transport direction. Therefore, the distance from the ground contact portion 45 is different even among the plurality of piezoelectric elements 39 constituting each of the three piezoelectric element rows 40b to 40d. Therefore, the width of the plurality of conduction wirings provided for each of the three piezoelectric element rows 40b to 40d may be wider as the distance from the ground contact portion 45 is longer. In FIG. 9, the upper side in the figure indicated by the arrow A is the direction toward the ground contact portion 45 in the transport direction, and the lower side in the figure indicated by the arrow B is the direction away from the ground contact portion 45. The width of the conduction wiring 64 provided in each piezoelectric element row 40 is larger as it is arranged on the lower side in the drawing, that is, on the side farther from the ground contact portion 45. That is, in the transport direction, the width of the conduction wiring 64 increases as the distance from the ground contact portion 45 increases. With this configuration, the voltage drop between the lower electrode 31 and the ground contact portion 45 can be kept small even for the piezoelectric element 39 located at a position far from the ground contact portion 45 in one piezoelectric element row 40. Can be done. The drive contact portion 44 in the above embodiment corresponds to the "first contact portion" of the present invention, and the ground contact portion 45 corresponds to the "second contact portion" of the present invention.

6] As in the above-described embodiment and the above-mentioned modification (FIG. 8 and the like), the conduction wiring arranged between the two piezoelectric elements 39 adjacent to each other in the transport direction between the three piezoelectric element rows 40b to 40d. It is not always necessary to have different widths and numbers. That is, the width and the number of conduction wirings may be equal among the three piezoelectric element rows 40b to 40d.

7] In the above embodiment, as shown in FIGS. 2 and 3, the piezoelectric film 32 is arranged on the vibrating film 30 so as to cover the plurality of pressure chambers 26, and the piezoelectric portions of the plurality of piezoelectric elements 39 are arranged. 37 are connected to each other. The drive wiring 35 and the conduction wiring 52 are arranged in the portion of the piezoelectric film 32 between the piezoelectric portions 37 of the adjacent piezoelectric elements 39. On the other hand, the present invention can be applied 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 arranged so as to cover the common electrode 42. An opening 72a is formed in the region of the piezoelectric film 72 between two piezoelectric elements 39 adjacent to each other in the transport direction by etching. In each opening 72a, the common electrode 42 is exposed from the piezoelectric film 72, but the protective film 38 formed after the formation of the upper electrode 33 covers the common electrode 42 exposed from the opening 72a. ..

On top of that, between the two adjacent piezoelectric elements 39 of each piezoelectric element row 40, the drive wiring 35 and the conduction wiring 82 are arranged on the protective film 38 covering the opening 72a. In FIG. 4 of the embodiment, the piezoelectric film 32 and the protective film 38 are arranged between the drive wiring 35 and the conduction wiring 52 and the common electrode 42, but in FIG. 11, the opening 72a is formed. In this region, only the protective film 38 is arranged between the drive wiring 35 and the conduction wiring 82 and the common electrode 42. The conduction wiring 82 is electrically connected to the common electrode 42 by two conduction portions 83 arranged so as to penetrate the protective film 38.

Further, 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 size of the piezoelectric portion 37 and the upper electrode 33 are almost the same, or the upper electrode 33 is slightly smaller than the piezoelectric portion 37.

8] In the above embodiment, the protective film 38 is provided so as to cover the plurality of piezoelectric elements 39, but 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 a 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 above embodiment, a plurality of piezoelectric elements 39 form 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 rows 40.

11] In the piezoelectric actuator 23 of the above embodiment, the conduction 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 conduction wiring 52 may also be provided for the piezoelectric element row 40a closest to the contact portion 43.

Contrary to the above, it is not always necessary to provide the conductive wiring 52 for all three piezoelectric element rows 40b to 40d, and the conductive wiring 52 is provided only for any one of the three piezoelectric element rows 40b to 40d. May be done.

13] In the above embodiment, the COF 50, which is a wiring member, is joined to the contact portion 43 provided on the first flow path board 21, but the contact portion 43 is electrically connected to a component other than the wiring member such as an IC chip. May be connected.

The embodiment described above and the modified embodiment thereof apply the present invention to a piezoelectric actuator of an inkjet head that ejects ink onto recording paper to print an image or the like, but has various uses other than printing of an image or the like. The present invention can also be applied to the liquid discharge device used in the above. For example, the present invention can be applied to a liquid discharge device that discharges a conductive liquid onto a substrate to form a conductive pattern on the surface of the substrate. Further, the piezoelectric actuator of the present invention is not limited to the 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 the inventions according to claims 1 to 17 described in the claims at the time of filing will be described.
The present invention comprises a first piezoelectric element array arranged in the first direction on the substrate, and a second piezoelectric element array arranged in the second direction orthogonal to the first piezoelectric element array and the first piezoelectric element array. With multiple piezoelectric elements
A contact portion on the substrate, which is arranged 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 wirings extending from the plurality of piezoelectric elements toward the contact portion in the second direction are provided.
Each piezoelectric element has a piezoelectric portion, a first electrode arranged on one side in the thickness direction of the piezoelectric portion, and a second electrode arranged on the other side in the thickness direction of the piezoelectric portion.
Each drive wiring 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 an electrode conduction portion arranged between the plurality of second electrodes, and the plurality of second electrodes and the electrode conduction portion are provided with respect to the plurality of piezoelectric elements. Common electrodes are configured,
Further having a piezoelectric connecting portion for connecting the piezoelectric portions of a plurality of piezoelectric elements constituting each piezoelectric element row to each other.
The drive wiring corresponding to the piezoelectric element of the second piezoelectric element row extends to the contact portion of the first piezoelectric element row through between two adjacent piezoelectric elements in the first direction. ,
A piezoelectric actuator of the second piezoelectric element row, characterized in that a dummy wiring is arranged between two adjacent piezoelectric elements in the first direction and separated from the drive wiring. It is an invention.

An embodiment of the disclosed invention will be described with reference to FIG. The piezoelectric actuator 103 has a plurality of piezoelectric elements 39 constituting four piezoelectric element rows 40a to 40d corresponding to the four pressure chamber rows 27a to 27d, respectively. 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 connected to each other by the piezoelectric connecting portions 111 arranged between the adjacent pressure chambers 26 in the piezoelectric film 32. It has become.

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

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

Further, the number of drive wirings 35 passing between the two adjacent piezoelectric elements 39 differs between the three piezoelectric element rows 40a to 40c on the right side. Therefore, in FIG. 12, dummy wirings 110b and 110c are provided for the piezoelectric element rows 40b and 40c, which have a small number of drive wirings 35 to pass through, as well as the piezoelectric element rows 40d. However, the width of the dummy wiring 110c of the piezoelectric element row 40c is smaller than the width of the dummy wiring 110d of the piezoelectric element row 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 1st flow path substrate 23 Piezoelectric actuator 24 Nozzle 26 Pressure chamber 27 Pressure chamber row 30 Vibration film 31 Lower electrode 32 Piezoelectric film 33 Upper electrode 35 Drive wiring 37 Piezoelectric part 38 Protective film 39 Piezoelectric element 40 Piezoelectric element row 41 Electrode conduction part 42 Common electrode 43 Contact part 44 Drive contact part 45 Ground contact part 46 Conduction part 52 Conduction wiring 53 Conduction part 60a, 60b Connection part 62 Conduction wiring 63 Conduction wiring 64 Conduction wiring 72 Piezoelectric film 82 Conduction wiring 83 Conduction part

Claims (3)

A first piezoelectric element row arranged in the first direction on the substrate, a second piezoelectric element row arranged in the second direction orthogonal to the first piezoelectric element row and the first direction, and a second piezoelectric element row arranged in the second direction. A plurality of piezoelectric elements constituting the third piezoelectric element row arranged on the opposite side of the first piezoelectric element row with respect to the second piezoelectric element row.
A contact portion on the substrate arranged 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 wirings extending from the plurality of piezoelectric elements toward the contact portion in the second direction are provided.
Each piezoelectric element has a piezoelectric portion, a first electrode arranged on one side in the thickness direction of the piezoelectric portion, and a second electrode arranged on the other side in the thickness direction of the piezoelectric portion.
Each drive wiring is connected to the first electrode of each piezoelectric element.
The second electrode of the plurality of piezoelectric elements conducts with the conduction wiring,
The drive wiring corresponding to the piezoelectric element constituting the second piezoelectric element train extends to the contact portion of the first piezoelectric element train through between two adjacent piezoelectric elements in the first direction. And
The conduction wiring is
The first conduction wiring arranged between the two adjacent piezoelectric elements in the first direction of the second piezoelectric element row,
The third piezoelectric element train has a second conductive wiring arranged between two adjacent piezoelectric elements in the first direction.
A piezoelectric actuator characterized in that the electrical resistance of the second conductive wiring is lower than the electrical resistance of the first conductive wiring. The piezoelectric actuator according to claim 1, wherein the width of the second conductive wiring is larger than the width of the first conductive wiring. The conduction wiring is
Claim 1 or 2 is characterized by having a connecting portion arranged between the second piezoelectric element row and the third piezoelectric element row and connecting the first conductive wiring and the second conductive wiring. The piezoelectric actuator described.

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