JP2016115702A - Piezoelectric actuator, method for manufacturing the same, inkjet head, and inkjet printer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a piezoelectric actuator capable of, in a piezoelectric layer 25, reducing electrostatic capacitance in a wiring region Rby reducing a dielectric constant, while ensuring high piezoelectric characteristics in a displacement region Rby suppressing generation of crystal defects.SOLUTION: A piezoelectric actuator 21a comprises: a substrate 22; a first electrode (a lower electrode 24, for example); second electrodes (upper electrodes 26, for example); and a piezoelectric layer 25. The piezoelectric layer 25 has: first regions R1; and a second region R2 which is placed so as to surround the first regions R1 with planes thereof perpendicular in a thickness direction. Each of the first regions R1 has a displacement region Rwhich is displaced in accordance with a potential difference between the first electrode and the second electrode. The second region R2 has a wiring region Rwhich becomes a base of wires 51 for pulling out the second electrodes on the displacement regions R. The displacement regions Rhave a polycrystalline film 25a including a plurality of crystals. In the second region R2, at least the wiring region Rhas a modified film 25b where a grain boundary has disappeared because of temporary modification of the plurality of crystals.SELECTED DRAWING: Figure 2

Description

  The present invention includes a piezoelectric actuator having a lower electrode, a piezoelectric layer, and an upper electrode in this order from the substrate side, a method for manufacturing the piezoelectric actuator, an inkjet head including the piezoelectric actuator, and the inkjet head. The present invention relates to an inkjet printer.

  2. Description of the Related Art Conventionally, ink jet printers that print characters and designs by discharging liquid ink onto a recording medium such as paper or cloth are known. By controlling ink ejection while moving an inkjet head having a plurality of channels (ink ejection sections) relative to the recording medium, a two-dimensional image can be output on the recording medium. Ink can be ejected by using an actuator (piezoelectric, electrostatic, thermal deformation, etc.) or by generating bubbles in the ink in the tube by heat. Among them, the piezoelectric actuator has advantages such as high output, modulation, high responsiveness, and choice of ink, and has been frequently used in recent years.

  In addition, piezoelectric actuators include those using a bulk piezoelectric body and those using a thin film piezoelectric body (piezoelectric thin film). Since the former has a large output, large droplets can be discharged, but it is large and expensive. On the other hand, since the latter has a small output, the amount of droplets cannot be increased, but is small and low in cost. In order to realize a small, low-cost printer with high resolution (small droplets may be sufficient), it can be said that it is suitable to configure an actuator using a piezoelectric thin film. In the piezoelectric actuator, whether to use a piezoelectric thin film or a bulk piezoelectric body may be selected depending on the application. Depending on the size of the image to be printed, the printing speed, the size of the apparatus, and the like, the piezoelectric material to be used can be properly used for the bulk type and the thin type.

  FIG. 7 is a plan view showing a schematic configuration of a conventional inkjet head 100 using a piezoelectric actuator, and a cross-sectional view taken along line B-B ′ in the plan view. The inkjet head 100 is configured by sandwiching a support substrate 101 having a plurality of pressure chambers 101a between a diaphragm 102 and a nozzle plate 103, and forming a drive element 104 on the diaphragm 102 above each pressure chamber 101a. ing. The nozzle plate 103 is formed with nozzle holes 103a for discharging the ink in each pressure chamber 101a to the outside.

  The drive element 104 is configured by forming a lower electrode 201, a piezoelectric body 202, and an upper electrode 203 in this order from the support substrate 101 side. The lower electrode 201 is an electrode common to all the drive elements 104. The upper electrode 203 is individually connected to the connection terminal portion 301 via a narrow lead portion 301a. The lead portion 301a and the connection terminal portion 301 are formed on a piezoelectric body 202 that is drawn along the lower electrode 201 from above the pressure chamber 101a. The lower electrode 201 and the connection terminal portion 301 are electrically connected to a drive circuit (not shown) through electric wiring.

  In addition, an ink supply port 105 is formed through the diaphragm 102 and the lower electrode 201. Ink from an ink tank (not shown) passes through the ink supply port 105 and is supplied to the pressure chamber 101 a through the ink flow path 101 b formed in the support substrate 101.

  When a voltage is applied to the lower electrode 201 and the upper electrode 203 from the drive circuit, the piezoelectric body 202 expands and contracts in a direction perpendicular to the thickness direction. Then, due to the difference in length between the piezoelectric body 202 and the diaphragm 102, a curvature occurs in the diaphragm 102, and the diaphragm 102 is displaced (curved) in the thickness direction. By applying pressure to the pressure chamber 101a by such displacement of the vibration plate 102, the ink in the pressure chamber 101a is ejected to the outside through the nozzle hole 103a.

  The piezoelectric body 202 above the pressure chamber 101a expands and contracts as described above by applying a voltage to the lower electrode 201 and the upper electrode 203, but the piezoelectric body 202 serving as the base of the lead-out portion 301a and the connection terminal portion 301 Since the digging portion is not formed in the support substrate 101, it hardly deforms when a voltage is applied, and the vibration plate 102 hardly vibrates. For this reason, stress concentrates on the narrow drawer portion 301a and the piezoelectric body 202 below (particularly near the boundary with the pressure chamber 101a), and the drawer portion 301a may be damaged together with the piezoelectric body 202. In order to alleviate such stress concentration, a digging portion (buffer chamber) narrower than the pressure chamber 101a may be formed in the support substrate 101 below the lead-out portion 301a.

Perovskite-type metal oxides such as barium titanate (BaTiO ₃ ) and lead zirconate titanate (Pb (Ti / Zr) O ₃ ) called PZT are widely used for piezoelectric elements used in driving elements. . When the piezoelectric body is composed of a piezoelectric thin film, for example, PZT is formed on the substrate by film formation. PZT can be formed by various methods such as sputtering, CVD (Chemical Vapor Deposition), and sol-gel. Note that silicon (Si) is often used for the substrate because high temperature is required for crystallization of the piezoelectric material. In the case of using a bulk piezoelectric body separately manufactured by a firing method, this piezoelectric body may be fixed to the substrate by adhesion or screwing.

  In order to realize high-resolution drawing in an ink jet head, it is necessary to narrow the arrangement pitch of driving elements and channels. At this time, it is possible to apparently reduce the pitch by increasing the number of channels and shifting the channels between the columns. In order to realize a high resolution equivalent to that of a printing press such as 600 to 2400 dpi (dot per inch), several to several tens of columns are required.

  On the other hand, FIG. 8 is a cross-sectional view showing a schematic configuration of another conventional inkjet head 200. In the ink jet head 200, voltage is applied to the upper electrode 203 of the drive element 104 via the bump 401 and the lead wiring 402. The lead-out wiring 402 is formed on the front and back of the wiring board 404 that is disposed so as to face the support board 101 and the flow path board 403, and is connected to an external drive circuit 405. The support substrate 101 is bonded to the nozzle plate 103 via the glass plate 106.

  As described above, by forming a wiring (lead wiring 402) for applying a voltage to the upper electrode 203 on a substrate (wiring substrate 404) different from the supporting substrate 101, the wiring is formed on the supporting substrate 101. Therefore, the drive element 104 can be arranged with high density.

  Thus, for example, Patent Document 1 discloses a configuration in which the support substrate 101 and the wiring substrate 404 are arranged to face each other and the drive elements 104 are arranged at high density. In Patent Document 1, by using the same silicon as the support substrate 101 as the base material of the wiring substrate 404, the wiring substrate 404 can be finely processed and the processing accuracy is improved.

  In addition, the base material of the wiring board 404 is made of an insulating material so as not to have an excessive capacitance, and there is an example in which glass, polyimide, or the like is used. The lead-out wiring 402 is formed on one side or both sides of such a base material.

  However, when the inkjet head 200 is configured using the wiring board 404 as described above, the cost increases due to an increase in member costs due to the use of the wiring board 404 and an increase in the number of assembly steps. In order to reduce the cost, as described above, it is desirable that the wiring is directly formed on the support substrate on which the driving element is formed.

  In the configuration in which the wiring for driving the driving element is directly formed on the support substrate, a piezoelectric body having high piezoelectric characteristics and high dielectric constant is formed as the piezoelectric body of the driving element in order to achieve excellent ink ejection performance. Is done. Since the piezoelectric body is an insulator, it is possible to directly form a wiring for drawing out the upper electrode on the piezoelectric body. However, since the dielectric constant of the piezoelectric body is high, the wiring portion (the portion sandwiched between the wiring and the lower electrode) The capacitance will also increase. An increase in the capacitance causes an increase in power consumption during driving and a delay of the drive signal, so that the capacitance needs to be reduced.

The dielectric constant of the piezoelectric body (insulator) is εs, the distance between two metal plates (electrodes) sandwiching the piezoelectric body is d (m), the area of the metal plate is S (m ² ), and the dielectric constant of vacuum Is εo (= 8.854 × 10 ⁻¹² F / m) and the capacitance is C (F), C = εo · εs · (S / d). Therefore, when the area S and the distance d are constant, the capacitance C increases as the dielectric constant εs of the piezoelectric body increases.

  Therefore, for example, in Patent Document 2, the capacitance of the wiring portion is reduced by forming a low dielectric film between the piezoelectric body and the upper electrode or the lower electrode in the wiring portion. However, in this configuration, by providing the low dielectric film, a step is generated between the upper electrode above the pressure chamber and the upper electrode (wiring) in the wiring portion, so that the upper electrode is easily broken and the yield is reduced. .

  In this regard, for example, in Patent Document 3, the dielectric constant of the piezoelectric body in the wiring portion is lowered by controlling the crystal structure of the piezoelectric body. More specifically, in the piezoelectric layer, a perovskite type piezoelectric body having good piezoelectric characteristics is formed in the displacement region where the piezoelectric body is displaced, and the wiring region located below the lead-out wiring of the upper electrode is formed in the piezoelectric region. A piezoelectric material having a pyrochlore structure having a dielectric constant lower than that of the displacement region is formed flush with the displacement region. This eliminates the step of the upper electrode on the piezoelectric layer, reduces the disconnection of the wiring due to the step, prevents the yield, and lowers the capacitance by reducing the dielectric constant of the wiring region. I have to.

JP 2011-218641 A (refer to claims 1 to 3, paragraphs [0016] and [0033], FIG. 5 and the like) Japanese Patent Laid-Open No. 9-156099 (see claims 1 and 5, paragraphs [0006], [0007], [0031], [0032], FIG. 4 and the like) JP 2004-104106 A (refer to claims 1 to 3, paragraphs [0007], [0008], [0027], [0036], [0042], [0044] to [0046], FIG. 7, FIG. 8, etc.) )

  However, in Patent Document 3, a crystal control layer (for example, PLT; lanthanum lead titanate) for controlling the crystal structure of the piezoelectric material is used as a base when forming a piezoelectric material having a perovskite structure in the displacement region. It is necessary to form a film. Therefore, additional steps such as film formation, patterning, and etching of the crystal control layer are required. If foreign matter (contamination) or the like is left in the added process, a film having good piezoelectric characteristics cannot be obtained in the film formation in the next process, or crystal defects in the piezoelectric body increase. When crystal defects are taken into the drive element, the reliability of the drive element is deteriorated.

  The present invention has been made to solve the above-described problems, and its purpose is to reduce the dielectric constant in the wiring region while suppressing the generation of crystal defects in the displacement region and maintaining high piezoelectric characteristics. It is an object of the present invention to provide a piezoelectric actuator that can be reduced in size and suppress capacitance, and a manufacturing method thereof, and an inkjet head and an inkjet printer that include the piezoelectric actuator.

  A piezoelectric actuator according to one aspect of the present invention is a piezoelectric actuator having a substrate, a first electrode, a second electrode, and a piezoelectric layer, wherein the piezoelectric layer includes the first electrode and the first electrode. A first region including a displacement region that is displaced in accordance with a potential difference with the second electrode; and a second region positioned so as to surround the first region in a plane perpendicular to the thickness direction. The second region includes a wiring region serving as a base of a wiring for drawing out the second electrode on the displacement region, and the displacement region includes a polycrystalline film including a plurality of crystals, In the second region, at least the wiring region has a deteriorated film in which grain boundaries have disappeared due to integral deterioration of a plurality of crystals.

  According to the above configuration, at least the wiring region of the piezoelectric layer has the altered film. The altered film is a film in which grain boundaries have disappeared due to integral alteration of a plurality of crystals, and has a lower dielectric constant than a polycrystalline film having grain boundaries. Therefore, since the wiring region has the altered film, the dielectric constant of the wiring region can be made smaller than that of the displacement region. Moreover, since the dielectric constant of the wiring region can be reduced without providing a crystal control layer for controlling the crystallinity of the piezoelectric body as in the prior art, the disadvantage caused by the film formation of the crystal control layer, that is, film formation There are no inconveniences such as an increase in crystal defects and a decrease in piezoelectric properties due to contamination with foreign matters.

  Therefore, according to the above configuration, in the piezoelectric layer, the generation of crystal defects can be suppressed in the displacement region and high piezoelectric characteristics can be maintained, while the dielectric constant can be reduced and the capacitance can be suppressed in the wiring region.

The piezoelectric actuator may include a lower electrode as the first electrode, the piezoelectric layer, and an upper electrode as the second electrode in this order from the substrate side. In this case, the above-described effect can be obtained in the configuration in which the piezoelectric layer is driven in the d ₃₁ mode. The d ₃₁ mode refers to a drive mode in which the voltage application direction and the displacement direction are orthogonal to the piezoelectric layer.

  The altered film may have an amorphous structure. By having an amorphous structure (amorphous structure), it is possible to reliably realize a deteriorated film having no grain boundary.

  The wiring region may include a polycrystalline film including a plurality of crystals and the altered film in this order from the substrate side. Even if there is a polycrystalline film on the part (substrate side) in the thickness direction of the wiring region, the remaining altered film (on the wiring side) makes the dielectric constant of the wiring region smaller than that of the displacement region. be able to.

  The thickness of the altered film is preferably thinner than the thickness of the polycrystalline film on the substrate side. The altered film is formed by, for example, altering a plurality of crystals integrally (for example, making them amorphous) by irradiation with laser light, for example. In the case where the altered film is thickened, there is a concern that the lower layer (electrode, substrate) of the polycrystalline film is deteriorated due to the high heat at the time of laser light irradiation. Therefore, the altered film is desirably thinner than the polycrystalline film.

  The first region may further include an intermediate region that is located outside the displacement region and serves as a base of the wiring that draws the second electrode on the displacement region onto the wiring region. The altered film is formed, for example, by irradiating the wiring region with laser light. An intermediate region is located between the displacement region and the wiring region, and the altered film in the wiring region is separated from the displacement region. Therefore, when the altered film is formed, laser light is unintentionally irradiated to the displaced region. Thus, it is possible to reliably avoid the deterioration of the piezoelectric characteristics in the displacement region.

  An inkjet head according to another aspect of the present invention includes the above-described piezoelectric actuator and a nozzle plate having a nozzle hole for ejecting ink, and the displacement region of the piezoelectric layer in the substrate of the piezoelectric actuator. A pressure chamber that accommodates the ink may be formed at a position corresponding to, and the nozzle hole of the nozzle plate may communicate with the pressure chamber. In addition, an ink jet printer according to still another aspect of the present invention may be configured to include the above-described ink jet head and eject ink from the ink jet head toward a recording medium. In this case, it is possible to realize an ink jet head or an ink jet printer that has high performance and high reliability, and that suppresses an increase in power consumption and a delay in driving signals.

  According to still another aspect of the present invention, there is provided a piezoelectric actuator manufacturing method comprising: forming a piezoelectric layer having a polycrystalline film including a plurality of crystals on a substrate including a substrate; and applying a voltage to the piezoelectric layer. At least one of a step of forming a first electrode and a second region located in the piezoelectric layer so as to surround the first region including the displacement region in a plane perpendicular to the thickness direction. The wiring region serving as the base of the wiring for drawing the second electrode formed on the displacement region is heated from the side opposite to the substrate to integrally change the plurality of crystals contained in the polycrystalline film. A step of forming a denatured film in which the grain boundary has disappeared in at least part of the thickness direction of the wiring region; and a step of forming the second electrode on the displacement region of the piezoelectric layer; Pulling the second electrode over the displacement region And, and a step of forming the wiring on the wiring region.

  According to the above manufacturing method, the first electrode, the piezoelectric layer, and the second electrode are formed on the base including the substrate. In the piezoelectric layer, by heating at least the wiring region from the side opposite to the substrate among the second regions positioned so as to surround the first region including the displacement region in a plane perpendicular to the thickness direction. The altered film in which the grain boundaries have disappeared is formed on at least a part of the wiring region in the thickness direction. The second electrode is formed on the displacement region of the piezoelectric layer, and the wiring that pulls out the second electrode is drawn from the displacement region to the wiring region. Note that the second electrode and the wiring may be formed at the same time, or may be formed so as to be shifted back and forth in time.

  The above-mentioned altered film is formed by heating the above-mentioned wiring region and altering a plurality of crystals integrally. An altered film with disappeared grain boundaries has a lower dielectric constant than a polycrystalline film with grain boundaries. By forming such an altered film in the wiring region, the dielectric constant of the wiring region is made smaller than that of the displacement region. can do. In addition, since the conventional crystal control layer for controlling the crystallinity of the piezoelectric material can be formed as a base region of the piezoelectric material layer, a displacement region and a wiring region having a low dielectric constant can be formed. There is no increase in crystal defects or deterioration in piezoelectric properties due to the layer formation.

  Therefore, in the displacement region of the piezoelectric layer, the generation of crystal defects can be suppressed and high piezoelectric characteristics can be maintained, and in the wiring region, the dielectric constant can be reduced to reduce the capacitance.

From the substrate side, a lower electrode as the first electrode, the piezoelectric layer, and an upper electrode as the second electrode may be formed in this order. In this case, a piezoelectric actuator that drives the piezoelectric layer in the d ₃₁ mode can be realized.

  The piezoelectric layer is preferably heated by laser light irradiation. By laser irradiation, the piezoelectric layer (polycrystalline film) is locally heated, that is, a part of the piezoelectric layer in the thickness direction (for example, the surface side) is instantaneously heated to form a modified film. can do. Such local heating can prevent excessive heat from being applied to the substrate or the electrode serving as the base of the piezoelectric layer, so that deterioration of these members can be prevented.

  In the step of forming the deteriorated film, the deteriorated film may be formed by irradiating the wiring region located away from the displacement region with a laser beam. In this case, when the altered film is formed in the wiring region by laser irradiation, it is possible to reliably prevent the laser light from being unintentionally irradiated to the displacement region and the piezoelectric characteristics of the displacement region from being deteriorated.

  The wavelength of the laser beam is preferably such that the transmittance when transmitting through the piezoelectric layer is 50% or less. By irradiating a laser beam having a wavelength that is absorbed by the piezoelectric layer, the piezoelectric layer can be reliably heated locally.

  In the displacement region of the piezoelectric layer, it is possible to suppress the generation of crystal defects in the piezoelectric material and maintain high piezoelectric characteristics, and in the wiring region, it is possible to reduce the dielectric constant and suppress the capacitance.

1 is an explanatory diagram illustrating a schematic configuration of an inkjet printer according to an embodiment of the present invention. FIG. It is the figure which showed together the top view which shows the general | schematic structure of the inkjet head with which the said inkjet printer is provided, and the A-A 'arrow sectional drawing in the top view. It is explanatory drawing which shows typically the microscope image of the polycrystalline film and the altered film which the piezoelectric material layer of the said inkjet head has. It is sectional drawing which shows the manufacturing process of the said inkjet head. It is sectional drawing which shows the manufacturing process of the said inkjet head. It is a graph which shows the spectral transmittance of PZT which is a constituent material of the said piezoelectric material layer. It is the figure which showed together the top view which shows the general | schematic structure of the conventional inkjet head, and the B-B 'arrow sectional drawing in the top view. It is sectional drawing which shows the schematic structure of the other conventional inkjet head.

  An embodiment of the present invention will be described below with reference to the drawings. In the present specification, when the numerical range is expressed as A to B, the numerical value range includes the values of the lower limit A and the upper limit B.

[Configuration of inkjet printer]
FIG. 1 is an explanatory diagram illustrating a schematic configuration of an inkjet printer 1 according to the present embodiment. The ink jet printer 1 is a so-called line head type ink jet recording apparatus in which an ink jet head 21 is provided in a line shape in the width direction of a recording medium in the ink jet head unit 2.

  The ink jet printer 1 includes an ink jet head unit 2, a feed roll 3, a take-up roll 4, two back rolls 5 and 5, an intermediate tank 6, a liquid feed pump 7, a storage tank 8, and a fixing tank. And a mechanism 9.

  The ink jet head unit 2 ejects ink from the ink jet head 21 toward the recording medium P to perform image formation (drawing) based on image data, and is disposed in the vicinity of one back roll 5. Details of the inkjet head 21 will be described later.

  The feed roll 3, the take-up roll 4 and the back rolls 5 are members each having a cylindrical shape that can rotate about its axis. The feeding roll 3 is a roll that feeds the long recording medium P wound around the circumferential surface toward the position facing the inkjet head unit 2. The feeding roll 3 is rotated by driving means (not shown) such as a motor, thereby feeding the recording medium P in the X direction in FIG.

  The take-up roll 4 is taken out from the take-out roll 3 and takes up the recording medium P on which the ink is ejected by the inkjet head unit 2 around the circumferential surface.

  Each back roll 5 is disposed between the feed roll 3 and the take-up roll 4. One back roll 5 located on the upstream side in the conveyance direction of the recording medium P is opposed to the inkjet head unit 2 while winding the recording medium P fed by the feeding roll 3 around and supporting the recording medium P. Transport toward The other back roll 5 conveys the recording medium P from a position facing the inkjet head unit 2 toward the take-up roll 4 while being wound around and supported by a part of the peripheral surface.

  The intermediate tank 6 temporarily stores the ink supplied from the storage tank 8. The intermediate tank 6 is connected to a plurality of ink tubes 10, adjusts the back pressure of ink in each inkjet head 21, and supplies ink to each inkjet head 21.

  The liquid feed pump 7 supplies the ink stored in the storage tank 8 to the intermediate tank 6 and is disposed in the middle of the supply pipe 11. The ink stored in the storage tank 8 is pumped up by the liquid feed pump 7 and supplied to the intermediate tank 6 through the supply pipe 11.

  The fixing mechanism 9 fixes the ink ejected to the recording medium P by the inkjet head unit 2 on the recording medium P. The fixing mechanism 9 includes a heater for heat-fixing the discharged ink on the recording medium P, a UV lamp for curing the ink by irradiating the discharged ink with UV (ultraviolet light), and the like. Yes.

  In the above configuration, the recording medium P fed from the feeding roll 3 is transported to a position facing the inkjet head unit 2 by the back roll 5, and ink is ejected from the inkjet head unit 2 to the recording medium P. Thereafter, the ink ejected onto the recording medium P is fixed by the fixing mechanism 9, and the recording medium P after ink fixing is taken up by the take-up roll 4. As described above, in the line head type inkjet printer 1, ink is ejected while the recording medium P is conveyed while the inkjet head unit 2 is stationary, and an image is formed on the recording medium P.

  The ink jet printer 1 may be configured to form an image on a recording medium by a serial head method. The serial head method is a method of forming an image by ejecting ink by moving an inkjet head in a direction orthogonal to the transport direction while transporting a recording medium.

[Configuration of inkjet head]
Next, the configuration of the inkjet head 21 will be described. FIG. 2 shows a plan view showing a schematic configuration of the inkjet head 21 and a cross-sectional view taken along line AA ′ in the plan view.

  The piezoelectric actuator 21a of the inkjet head 21 has a thermal oxide film 23, a lower electrode 24, a piezoelectric layer 25, and an upper electrode 26 in this order on a substrate 22 having a plurality of pressure chambers 22a (openings). . The substrate 22 and the thermal oxide film 23 constitute a base on which the lower electrode 24 is formed. The nozzle plate 31 is bonded to the opposite side of the substrate 22 from the piezoelectric layer 25 to form the ink jet head 21. The nozzle plate 31 has a nozzle hole 31a communicating with the pressure chamber 22a.

The substrate 22 is configured by a semiconductor substrate made of a single crystal Si (silicon) single-piece having a thickness of, for example, about 100 to 300 μm or an SOI (Silicon on Insulator) substrate. For example, the substrate 22 is prepared by preparing a substrate having a thickness of about 300 to 750 μm, forming a piezoelectric layer 25 described later on the substrate, and then forming a thickness of 100 to 300 μm by polishing or the like. FIG. 2 shows a case where the substrate 22 is configured by an SOI substrate. The SOI substrate is obtained by bonding two Si substrates 42 and 43 through a Box layer 41 made of silicon oxide (SiO ₂ ). The upper wall of the pressure chamber 22 a in the substrate 22, that is, the Si substrate 42 located on the piezoelectric layer 25 side of the pressure chamber 22 a constitutes a vibration plate 22 b serving as a driven film, and drives the piezoelectric layer 25 ( Displacement (vibration) is accompanied with expansion and contraction, and pressure is applied to the ink in the pressure chamber 22a.

The thermal oxide film 23 is made of, for example, SiO ₂ (silicon oxide) having a thickness of about 0.1 μm, and is formed for the purpose of protecting and insulating the substrate 22.

  The lower electrode 24 is a common electrode (first electrode) provided in common to the plurality of pressure chambers 22a, and is configured by laminating a Ti (titanium) layer and a Pt (platinum) layer. The Ti layer is formed in order to improve the adhesion between the thermal oxide film 23 and the Pt layer. The thickness of the Ti layer is, for example, about 0.02 μm, and the thickness of the Pt layer is, for example, about 0.1 μm. Note that a layer made of titanium oxide (TiOx) may be formed instead of the Ti layer.

  The piezoelectric layer 25 is composed of a ferroelectric thin film made of, for example, PZT (lead zirconate titanate), and is formed on almost the entire surface of the substrate 22. Hereinafter, the piezoelectric layer 25 will be described with an example using PZT, but is not limited thereto, PLZT in which lanthanum (La) is added to PZT, PNZT in which niobium (Nb) is added to PZT, or other A material having an additive may be used. The film thickness of the piezoelectric layer 25 is, for example, 1 μm or more and 10 μm or less. In the piezoelectric layer 25, a groove G having a shape corresponding to each pressure chamber 22a is formed. Thereby, even when the piezoelectric layer 25 is provided on the entire surface of the substrate 22, the piezoelectric layer 25 can be expanded and contracted corresponding to each pressure chamber 22a. The details of the piezoelectric layer 25 will be described later.

  The upper electrode 26 is an individual electrode (second electrode) provided corresponding to each pressure chamber 22a, and is configured by laminating a Ti layer and a Pt layer. The Ti layer is formed in order to improve the adhesion between the piezoelectric layer 25 and the Pt layer. The thickness of the Ti layer is about 0.02 μm, for example, and the thickness of the Pt layer is about 0.1 to 0.2 μm, for example. The upper electrode 26 is provided so as to sandwich the piezoelectric layer 25 from the film thickness direction with the lower electrode 24. Note that a layer made of gold (Au) may be formed instead of the Pt layer.

  The lower electrode 24, the piezoelectric layer 25, and the upper electrode 26 constitute a thin film piezoelectric element 27 (driving element) for discharging ink in the pressure chamber 22a to the outside. The thin film piezoelectric element 27 is driven based on a voltage (drive signal) applied to the lower electrode 24 and the upper electrode 26 from a drive circuit (not shown). The ink jet head 21 is formed by arranging the thin film piezoelectric element 27 and the pressure chamber 22a vertically and horizontally.

  In addition, an ink supply port 28 is formed in the substrate 22 (particularly the Si substrate 42), the thermal oxide film 23, the lower electrode 24, and the piezoelectric layer 25, and an ink flow path 29 is formed in the substrate 22. . The ink in the intermediate tank 6 is supplied to the pressure chamber 22 a through the ink supply port 28 and the ink flow path 29.

  In the above configuration, when a voltage is applied from the drive circuit to the lower electrode 24 and the upper electrode 26, the piezoelectric layer 25 is in a direction perpendicular to the thickness direction (substrate) according to the potential difference between the lower electrode 24 and the upper electrode 26. (Direction parallel to the surface of 22). Then, due to the difference in length between the piezoelectric layer 25 and the diaphragm 22b, a curvature is generated in the diaphragm 22b, and the diaphragm 22b is displaced (curved or vibrated) in the thickness direction.

  Therefore, if ink is accommodated in the pressure chamber 22a, a pressure wave is propagated to the ink in the pressure chamber 22a by the vibration of the vibration plate 22b described above, and the ink in the pressure chamber 22a drops from the nozzle hole 31a into an ink droplet. Is discharged to the outside.

[Details of piezoelectric layer]
The piezoelectric layer 25 described above has a first region R1 and a second region R2 located so as to surround the first region R1 in a plane perpendicular to the thickness direction.

The first region includes a displacement area R _11, and an intermediate region R _12. Displacement area R ₁₁ is a region where the piezoelectric layer 25 according to the potential difference between the lower electrode 24 and the upper electrode 26 is displaced, are positioned to correspond to the formation area of each of the pressure chambers 22a. The displacement region R ₁₁ is composed of a polycrystalline film 25a made of an aggregate of a plurality of crystals (for example, columnar crystals) having a perovskite structure.

The intermediate region R ₁₂ is constituted by the same polycrystalline film 25a and the displacement area R _11, outside the displacement area R _11, i.e., in a plane perpendicular to the thickness direction, the displacement region R ₁₁ and the outer It is located so as to surround the groove G. Groove G is formed in the piezoelectric layer 25 along substantially the shape of the pressure chamber 22a, thereby, it is possible to displace the piezoelectric layers 25 of the displacement region R _11. The intermediate region R ₁₂ is an upper electrode 26 on the displacement range R _11, also serves as a base of the wiring 51 to draw on the wiring region R ₂₁ of the second region R2.

The second region R2 includes a wiring region R _21, and a remaining region R _22. The wiring region R ₂₁ is a region serving as a base of the wiring 51 that leads the upper electrode 26 on the displacement region R _{11 to} the outside of the pressure chamber 22 a in the piezoelectric layer 25. The wiring 51 includes a lead portion 52 having a width smaller than that of the upper electrode 26, and a connection terminal portion 53 for electrically connecting the lead portion 52 and a drive circuit (not shown). The upper electrode 26 is formed correspondingly.

The wiring region R ₂₁ has, from the substrate 22 side, the same polycrystalline film 25a as the displacement region R ₁₁ and an altered film 25b in this order. The altered film 25b is a film in which grain boundaries have disappeared due to integral alteration of a plurality of crystals (for example, columnar crystals), and is, for example, a film having an amorphous structure (amorphous structure). In general, alteration refers to changing the properties of a substance, but here refers to changing the film quality by integrally changing the crystal structure of a plurality of crystals having grain boundaries. As will be described later, such alteration can be realized by irradiating a laser beam of a predetermined wavelength to a film having a polycrystalline structure and heating it to melt and solidify the irradiated portion.

  FIG. 3 schematically shows horizontal cross sections of the polycrystalline film 25a and the altered film 25b observed with a scanning electron microscope (SEM). As shown in the figure, in the polycrystalline film 25a, there are grain boundaries between the crystals, but in the altered film 25b, there is no grain boundary as seen in the polycrystalline film 25a. It has a crystalline structure.

The remaining region R ₂₂ is a region other than the wiring region R ₂₁ in the second region R 2, but the layer configuration is the same as that of the wiring region R ₂₁ . That is, the remaining region R ₂₂ also includes the polycrystalline film 25a and the altered film 25b in this order from the substrate 22 side. The surface of the remaining region R ₂₂ is exposed because the wiring 51 is not formed thereon.

Incidentally, when the obtaining the effect of this embodiment described below (the effect of reducing the dielectric constant of the wiring area R _21), the remaining area R ₂₂ may or may not have a deteriorated film 25b (polycrystalline film 25a only in may be configured), in order to increase the degree of freedom (flexibility in selection of the formation of the wiring position 51) when the wire 51 is patterned, the entire second region R2 containing the remaining area R ₂₂ It is desirable that the altered film 25b is formed.

Alteration film 25b of the wiring region R ₂₁ is a film grain boundaries disappeared by integral alteration of a plurality of crystals. Since the altered film 25b having an amorphous structure has a lower dielectric constant than the polycrystalline film 25a having a regular crystal structure, the wiring region R ₂₁ has such a modified film 25b, so that the wiring region The dielectric constant of R ₂₁ can be made smaller than that of the displacement region R ₁₁ having the polycrystalline film 25a. In addition, the displacement region R ₁₁ and the wiring region R ₂₁ can be formed without forming a conventional crystal control layer, and the dielectric constant of the wiring region R ₂₁ can be made smaller than that of the displacement region R ₁₁ . There is no increase in crystal defects or deterioration in piezoelectric properties due to the formation of the crystal control layer. Therefore, according to the configuration of this embodiment, the piezoelectric layer 25, the displacement region R ₁₁ in while maintaining a high piezoelectric characteristics by suppressing the generation of crystal defects, to reduce the dielectric constant in the wiring region R _21, wiring portions (wiring 51, wiring area R _21, lower electrode 24) can be suppressed to a low electrostatic capacity.

  Further, since the altered film 25b has an amorphous structure having no grain boundary, the altered film 25b in which the grain boundary disappears can be reliably realized.

Further, the wiring region R ₂₁ has a polycrystalline film 25a and an altered film 25b in this order from the substrate 22 side. Be present polycrystalline film 25a in a part of the thickness direction of the wiring region R _21, by the presence of altered layer 25 to the rest, that the dielectric constant of the wiring area R ₂₁ is smaller than the displacement area R ₁₁ it can.

Here, in the wiring region R ₂₁ , if the altered film 25 b is formed thick by laser light irradiation, the lower layer (lower electrode 24, substrate 22) of the underlying polycrystalline film 25 a is deteriorated by high heat during laser light irradiation. Is concerned. For this reason, it is desirable that the thickness of the altered film 25b is smaller than the thickness of the underlying polycrystalline film 25a.

Incidentally, alteration the film 25b too thin, reduces the effect of reducing the dielectric constant of the wiring area R _21, the effect to reduce the capacitance is reduced. To ensure that smaller the dielectric constant of the wiring region R ₂₁ by the formation of the degraded layer 25, it is desirable thickness of the affected layer 25b is 5nm or more, and more desirably at 20nm or more.

Further, in the wiring region R _21, it may constitute the entire thickness direction alteration film 25b. In this case, the dielectric constant of the wiring region R ₂₁ can be reliably made smaller than that of the displacement region R ₁₁ , and the capacitance can be reliably reduced. In the case where the altered film 25b is formed in the entire thickness direction, there is a concern about deterioration of the lower layer due to high heat during laser light irradiation as described above, but this configuration is effective when emphasizing the effect of reducing capacitance. .

In the present embodiment, the intermediate region R ₁₂ is located between the wiring region R ₂₁ of the second region R 2 and the displacement region R ₁₁ of the first region R 1. ₂₁ and the displacement region R ₁₁ are separated (see FIG. 2). Alteration film 25b, as will be described later, are formed by irradiating a laser beam in the wiring region R _21, since the formation position of the alteration layer 25b is apart from the displacement area R _11, during the formation of the degraded layer 25b can laser light is irradiated to the displacement area R ₁₁ unintentionally, the piezoelectric properties of the displacement area R ₁₁ is reliably prevented from being lowered.

In the present embodiment, the film thickness of the piezoelectric layer 25 is constant from the first region R1 to the second region R2 except for the groove G. For this reason, even when the wiring 51 is drawn from the upper electrode 26 on the displacement region R ₁₁ to the altered film 25 b via the intermediate region R ₁₂ , no step is generated in the upper electrode 26 and the wiring 51.

[Inkjet head manufacturing method]
Next, a method for manufacturing the above-described inkjet head 21 will be described. 4 and 5 are cross-sectional views showing the manufacturing process of the inkjet head 21. FIG.

(1) Substrate preparation step and thermal oxide film formation step First, the substrate 22 is prepared. As the substrate 22, crystalline silicon (Si) often used in MEMS (Micro Electro Mechanical Systems) can be used. Here, two Si substrates 42 and 43 are disposed via a Box layer 41 which is an oxide film. An SOI structure having a bonded structure is used. Then, the substrate 22 is put in a heating furnace and held at about 1500 ° C. for a predetermined time, and thermal oxide films 23a and 23b made of SiO ₂ are formed on the surfaces of the Si substrates 42 and 43, respectively.

(2) Lower Electrode Formation Step, Piezoelectric Layer Formation Step Next, the lower electrode 24 is formed on the base including the substrate 22. That is, each layer of TiO ₂ (eg, thickness 0.02 μm) and Pt (eg, thickness 0.1 μm) is sequentially formed on one thermal oxide film 23a on the substrate 22 by sputtering, and the lower electrode 24 is formed. Form. Subsequently, the substrate 22 is reheated to about 600 ° C., and a piezoelectric layer 25 (for example, having a thickness of 1 to 5 μm) made of PZT is formed on the lower electrode 24 by sputtering. The piezoelectric layer 25 is a polycrystalline film 25a made of an aggregate of a plurality of crystals.

(3) In the laser irradiation step piezoelectric layer 25, the second region R2 located apart from the displacement area R ₁₁ is heated by laser irradiation from the side opposite to the substrate 22, a plurality contained in the polycrystalline film 25a By altering the crystals integrally, the altered film 25b in which the grain boundary disappears is formed in the second region R2. Thus, alteration film 25b is formed on at least a portion of the thickness direction of the wiring region R ₂₁ of the piezoelectric layer 25. In other words, the piezoelectric layer 25 after film formation has a columnar crystal structure (polycrystalline film 25a) having orientation, but the portion irradiated with the laser does not have an amorphous grain boundary. To change. Incidentally, alteration film 25b in the thickness direction is not formed part of the wiring region R ₂₁ remains polycrystalline film 25a. In this step, the at least wiring region R ₂₁ of the second region R2 and the substrate 22 may be formed alteration layer 25b therein by heating from the opposite side, the heating of the residual areas R ₂₂ is not necessarily performed.

(4) Upper electrode formation process Next, each layer of Ti (for example, thickness 0.02 micrometer) and Au (for example, thickness 0.3 micrometer) used as the upper electrode 26 is formed by a vapor deposition method or a sputtering method.

(5) over the displacement area R ₁₁ containing polycrystalline film 25a forming the individual pattern of the upper electrode and the wiring process the piezoelectric layer 25, to form a discrete pattern of the upper electrode 26, upper electrode on displacement area R ₁₁ pull out 26, to form a discrete pattern of the wiring 51 on the intermediate region R ₁₂ above and the wiring region R _21.

  More specifically, a photosensitive resin material is applied onto the upper electrode 26 by spin coating, and unnecessary portions of the photosensitive resin material are removed by exposure and etching through a mask, corresponding to each pressure chamber 22a. The shape of the individual upper electrode 26 to be transferred and the shape of the wiring 51 for drawing out the individual upper electrode 26 along the lower piezoelectric layer 25 are transferred. Then, using the photosensitive resin material as a mask, an unnecessary portion of the metal layer (upper electrode 26) is removed using a reactive ion etching method, and a pattern of individual upper electrode 26 and wiring 51 is formed.

(6) Piezoelectric layer pattern forming step Next, a photosensitive resin material is applied onto the piezoelectric layer 25 by a spin coat method, exposed through a mask, and etched to remove unnecessary portions of the photosensitive resin material. The pattern shape of the piezoelectric layer 25 is transferred. Then, using the photosensitive resin material as a mask, the unnecessary portion of the piezoelectric layer 25 is removed by reactive ion etching. Thus, the groove G is formed around the piezoelectric layer 25 of the displacement region R _11, the pattern of the piezoelectric layer 25 of the displacement region R ₁₁ is formed.

(7) Substrate Polishing Step Next, the thermal oxide film 23b on the back surface of the substrate 22 is removed and polishing is performed to adjust to a desired thickness.

(8) Pressure chamber and ink flow path forming step A photosensitive resin material is applied to the back surface of the substrate 22 by spin coating, and exposed and etched through a mask to remove unnecessary portions of the photosensitive resin material. The shape of the pressure chamber 22a and the ink flow path 29 to be formed is transferred. Then, using the photosensitive resin material as a mask, the substrate 22 is removed using a reactive ion etching method to form a pressure chamber 22a and the like to form the piezoelectric actuator 21a. At this time, the ink supply port 28 is formed by performing the same processing from the piezoelectric layer 25 side of the substrate 22.

(9) Nozzle plate joining process Then, the board | substrate 22 of the piezoelectric actuator 21a and the nozzle plate 31 which has the nozzle hole 31a are joined using an adhesive agent. Thereby, the inkjet head 21 is completed. Note that an intermediate glass having a through hole at a position corresponding to the nozzle hole 31a may be used, and the substrate 22 and the intermediate glass, and the intermediate glass and the nozzle plate 31 may be anodically bonded. In this case, the three parties (substrate 22, intermediate glass, nozzle plate 31) can be joined without using an adhesive.

In this way, by heating at least the wiring region R ₂₁ of the piezoelectric layer 25 to form the altered film 25b in which the grain boundaries disappear, the dielectric constant of the wiring region R ₂₁ is made smaller than that of the displacement region R _11. Can do. In addition, since it is not necessary to form a crystal control layer as a base for the piezoelectric layer 25 as in the prior art, an increase in crystal defects and a decrease in piezoelectric characteristics due to the formation of the crystal control layer do not occur. Therefore, while maintaining a high piezoelectric characteristics by suppressing the crystal defects in the displacement area R ₁₁ of the piezoelectric layer 25, to reduce the dielectric constant in the wiring region R _21, to realize a small restrained piezoelectric actuator 21a capacitance Can do.

  Further, since the piezoelectric layer 25 is heated by laser light irradiation, the altered film 25b can be formed by instantaneously heating a part of the piezoelectric layer 25 in the thickness direction with the laser light. Such local heating can prevent the substrate 22 and the lower electrode 24, which are constituent members, from being exposed to excessively high heat, so that deterioration of these members can be prevented.

Further, in the wiring region R ₂₁ , the modified film 25 b is formed by irradiating the piezoelectric layer 25 at a position distant from the displacement region R ₁₁ to form the modified film 25 b, so that the laser light is displaced when the modified film 25 b is formed. ₁₁ can be reliably avoided. As a result, the unintentional irradiation of a laser beam, the piezoelectric properties of the displacement area R ₁₁ can be reliably prevented from being lowered.

  Here, FIG. 6 is a graph showing the spectral transmittance of PZT which is a constituent material of the piezoelectric layer 25. The laser beam used for local heating of the piezoelectric layer 25 may be any wavelength that does not transmit PZT but can be absorbed by PZT and heat its surface. Note that when laser light having a wavelength that passes through the piezoelectric layer 25 is irradiated, the laser light may pass through the piezoelectric layer 25 and damage the base (the lower electrode 24 and the substrate 22). From this viewpoint, the wavelength of the laser beam to be used is desirably a wavelength at which the transmittance when transmitting through the piezoelectric layer 25 is 50% or less. Therefore, when heating PZT, as shown in FIG. 6, it is preferable to use laser light having a wavelength of 400 nm or less, and it is more preferable to use laser light having a wavelength of 360 nm or less. Note that it is better to use a laser beam for an oven or a hot plate because instantaneous local heating is difficult.

〔Example〕
Next, a specific example of forming the altered film 25b will be described.

The lower electrode 24 and the piezoelectric layer 25 are sequentially formed on the substrate 22 by the method shown in FIGS. 4 and 5, and then the altered region 25 b is formed by irradiating the wiring region R ₂₁ of the piezoelectric layer 25 with laser light. After that, the upper electrode 26 and the wiring 51 were formed to manufacture the piezoelectric actuator 21a. At this time, the thickness of the diaphragm 22b (Si substrate 32) made of Si is 5 μm, the thickness of the lower electrode 24 containing Pt is 0.1 μm, the thickness of the piezoelectric layer 25 made of PZT is 5 μm, and contains Au. The thickness of the upper electrode was 0.3 μm.

The piezoelectric layer 25 formed on the lower electrode 24 by sputtering is a polycrystalline film 25a in which columnar crystals extending upward from the lower electrode 24 are gathered (grain size: about several tens of nm to 1 μm, crystal orientation: <100> direction), and in the wiring region R ₂₁ of the piezoelectric layer 25, amorphous PZT, that is, a region having no grain boundary (modified film 25b) is formed. It was confirmed from SEM images. In addition, the thickness of the altered film 25b was 20 nm.

  Here, the altered film 25b is formed by locally heating the polycrystalline film 25a of PZT (only the surface is heated). The local heating at this time is performed by a YAG laser irradiator (LR-3100SUV) manufactured by HOYA. Was performed by irradiating a pulse laser. The wavelength of the laser beam was 266 nm, the pulse width was 5 nsec, and the light amount was 0.1 mJ. The melting point of PZT is generally said to be 1300 to 1600 ° C. However, by using the above laser beam, the PZT surface is surely melted and solidified by local heating, and the grain boundary on the PZT surface is changed. I was able to lose it.

Processing at a wavelength with a high PZT transmittance (a wavelength with little absorption) is not preferable because most of the light passes through the PZT and the heat applied to the surface of the PZT becomes very small. The wavelength of laser light that can be used for local heating of PZT is desirably 400 nm or less as described above. Examples of such laser light include the following.
(1) YAG laser (a type of solid-state laser with a fundamental wavelength of 1064 nm)
YAG third harmonic: Wavelength 355 nm (YAG fundamental wave converted to 1/3 wavelength)
YAG fourth harmonic: wavelength 266 nm (YAG fundamental wave converted to a quarter wavelength)
YAG fifth harmonic: Wavelength 213 nm (YAG fundamental wave converted to 1/5 wavelength)
(2) Excimer laser (a type of gas laser with different wavelengths depending on the medium used)
Medium N ₂ : wavelength 337 nm
Medium XeCl: wavelength 308 nm
Medium KrF: wavelength 248 nm
Medium KrCl: wavelength 222 nm
Medium ArF: wavelength 193 nm

  Further, when the amount of irradiation light is increased so that sufficient heat is applied to the PZT surface, not only the PZT surface but also the base (the lower electrode 24, the diaphragm 22b, etc.) and the periphery of the irradiation area are affected by heating, Performance may be degraded. For this reason, it is necessary to appropriately set the irradiation light quantity.

In the piezoelectric actuator 21a fabricated in this manner, as compared with the configuration having no deterioration film 25b in the wiring region R _21, the capacitance of the wiring part including the wiring region R ₂₁ was able to be reduced to 1/10 or less .

The example in which the piezoelectric actuator 21a is configured by forming the lower electrode 24 as the first electrode, the piezoelectric layer 25, and the upper electrode 26 as the second electrode in this order from the substrate 22 side has been described above. In such a piezoelectric actuator 21a, the piezoelectric layer 25 is driven by a d ₃₁ mode. That is, the direction in which the voltage is applied to the piezoelectric layer 25 (for example, the thickness direction of the substrate 22) and the displacement direction of the piezoelectric layer 21 (for example, the direction perpendicular to the thickness direction of the substrate 22) are orthogonal to each other. However, the configuration and manufacturing method described in the present embodiment is also applicable to a piezoelectric actuator 21a driven by a driving mode other than the d ₃₁ mode. For example, a piezoelectric actuator that drives electrodes in a driving mode (d ₁₅ mode) that uses electrodes on the outer and inner sides of an annular piezoelectric layer and uses sliding deformation (shear deformation) of the piezoelectric layer, The configuration of the present embodiment in which a deteriorated film is formed in a region serving as a base of wiring in the piezoelectric layer can be applied, and thereby the same effect as in the present embodiment can be obtained.

  The piezoelectric actuator of the present invention can be used for an inkjet head and an inkjet printer.

DESCRIPTION OF SYMBOLS 1 Inkjet printer 21 Inkjet head 21a Piezoelectric actuator 22 Substrate 22a Pressure chamber 24 Lower electrode (first electrode)
25 Piezoelectric layer 25a Polycrystalline film 25b Altered film 26 Upper electrode (second electrode)
31 nozzle plate 31a nozzle hole 51 lines P recording medium R1 first region R2 second region R ₁₁ displacement area R ₁₂ intermediate region R ₂₁ wiring region

Claims (13)

A piezoelectric actuator having a substrate, a first electrode, a second electrode, and a piezoelectric layer,
The piezoelectric layer is
A first region including a displacement region that is displaced according to a potential difference between the first electrode and the second electrode;
A second region positioned so as to surround the first region in a plane perpendicular to the thickness direction,
The second region includes a wiring region serving as a base of a wiring for drawing out the second electrode on the displacement region,
The displacement region has a polycrystalline film including a plurality of crystals,
In the second region, at least the wiring region has a modified film in which grain boundaries disappear due to integral modification of a plurality of crystals.   2. The piezoelectric device according to claim 1, further comprising a lower electrode as the first electrode, the piezoelectric layer, and an upper electrode as the second electrode in this order from the substrate side. Actuator.   The piezoelectric actuator according to claim 1, wherein the altered film has an amorphous structure.   4. The piezoelectric actuator according to claim 1, wherein the wiring region includes a polycrystalline film including a plurality of crystals and the altered film in this order from the substrate side. 5. .   The piezoelectric actuator according to claim 4, wherein the thickness of the altered film is smaller than the thickness of the polycrystalline film on the substrate side.   The first region further includes an intermediate region that is located outside the displacement region and serves as a base of the wiring that draws the second electrode on the displacement region onto the wiring region. The piezoelectric actuator according to any one of claims 1 to 5. A piezoelectric actuator according to any one of claims 1 to 6,
A nozzle plate having nozzle holes for discharging ink,
In the substrate of the piezoelectric actuator, a pressure chamber containing the ink is formed at a position corresponding to the displacement region of the piezoelectric layer,
The inkjet head according to claim 1, wherein the nozzle hole of the nozzle plate communicates with the pressure chamber.   An ink jet printer comprising the ink jet head according to claim 7, wherein ink is ejected from the ink jet head toward a recording medium. Forming a piezoelectric layer having a polycrystalline film including a plurality of crystals on a substrate including a substrate;
Forming a first electrode for applying a voltage to the piezoelectric layer;
In the piezoelectric layer, a second electrode formed on at least the displacement region of the second region located so as to surround the first region including the displacement region in a plane perpendicular to the thickness direction. By heating the wiring region that is the base of the wiring that draws out from the side opposite to the substrate, the plurality of crystals contained in the polycrystalline film are integrally altered, thereby the altered film in which the grain boundaries disappeared, Forming at least part of the thickness direction of the wiring region;
Forming the second electrode on the displacement region of the piezoelectric layer;
Extracting the second electrode on the displacement region, and forming the wiring on the wiring region. A method of manufacturing a piezoelectric actuator, comprising:   The piezoelectric actuator according to claim 9, wherein a lower electrode as the first electrode, the piezoelectric layer, and an upper electrode as the second electrode are formed in this order from the substrate side. Production method.   The method for manufacturing a piezoelectric actuator according to claim 9 or 10, wherein the piezoelectric layer is heated by laser light irradiation.   12. The method of manufacturing a piezoelectric actuator according to claim 11, wherein, in the step of forming the altered film, the altered film is formed by irradiating the wiring region positioned away from the displacement region with a laser beam. Method.   13. The method of manufacturing a piezoelectric actuator according to claim 11, wherein the wavelength of the laser light is a wavelength at which the transmittance when transmitting through the piezoelectric layer is 50% or less.

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