JP2006019718A - Method of manufacturing piezoelectric actuator, the piezoelectric actuator and ink jet head - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing a piezoelectric actuator capable of improving adhesiveness between a piezoelectric layer and an electrode, and to provide the piezoelectric actuator. <P>SOLUTION: A plurality of individual electrodes 32 are formed on the surface of an insulating material layer 31, a recess (through hole 32a) is formed on the surface of each of the individual electrodes 32, a piezoelectric layer 33 is formed on the surface of the individual electrodes 32, and a common electrode 34 is further formed on the surface of the piezoelectric layer 33. Accordingly, since one part of the piezoelectric layer 33 on the surface of the individual electrodes 32 enters the through hole 32a and is adhered to the layer 31, the piezoelectric layer 33 is unlikely to be peeled off from the individual electrodes 32; and the adhesion between the individual electrodes 32 and the piezoelectric layer 33 is improved. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for manufacturing a piezoelectric actuator, a piezoelectric actuator, and an inkjet head having the piezoelectric actuator.

  2. Description of the Related Art Conventionally, piezoelectric actuators that drive an object to be driven by deforming the piezoelectric layer by applying an electric field to the piezoelectric layer are known. As such a piezoelectric actuator, there is one used in an ink jet recording apparatus as described in Patent Document 1. The piezoelectric actuator of Patent Document 1 includes a piezoelectric layer made of lead zirconate titanate (PZT), a plurality of lower electrodes provided on the lower surface of the piezoelectric layer so as to correspond to a plurality of pressure chambers of the inkjet head, and A plurality of upper electrodes provided on the upper surface of the piezoelectric layer respectively corresponding to the plurality of lower electrodes. When a drive voltage is supplied to the piezoelectric actuator, the potentials of the lower electrode and the upper electrode become different, and an electric field acts on the piezoelectric layer sandwiched between the two electrodes, causing the piezoelectric layer to deform, and the diaphragm Pressure is applied to the ink in the pressure chamber through the lower electrode that also serves as

  This piezoelectric actuator is manufactured as follows. First, an upper electrode is formed on a single crystal MgO substrate by sputtering. Next, a PZT layer is formed on the surface of the upper electrode by sputtering, and this layer is subjected to heat treatment to form a piezoelectric layer. Further, a lower electrode is formed on the surface of the piezoelectric layer by sputtering.

Japanese Patent Laying-Open No. 2003-154646 (FIG. 3)

  However, in the piezoelectric actuator described in Patent Document 1, there is a large difference in the thermal expansion coefficient between the conductive material forming the electrode and the PZT forming the piezoelectric layer in contact with the electrode. For this reason, the deformation amount when the PZT is heat-treated to form the piezoelectric layer is greatly different between the PZT and the electrode, so that the interfacial stress between the piezoelectric layer and the electrode is increased, and the piezoelectric layer is easily peeled off from the electrode. . Therefore, the durability of the piezoelectric actuator is lowered, and the yield in the manufacturing stage is also deteriorated.

  An object of the present invention is to provide a piezoelectric actuator manufacturing method and a piezoelectric actuator capable of improving the adhesion between a piezoelectric layer and an electrode.

Means for Solving the Problems and Effects of the Invention

  According to a first aspect of the present invention, there is provided a method for manufacturing a piezoelectric actuator, comprising: forming a first electrode on a surface of an insulating material layer; and forming a recess on the surface of the first electrode; And a third step of forming a second electrode on the surface of the piezoelectric layer. The second step of forming a piezoelectric layer on the surface of the piezoelectric layer and the third step of forming a second electrode on the surface of the piezoelectric layer. In addition, the recessed part formed in the surface of the 1st electrode in this invention also includes the form of the through-hole which penetrates the 1st electrode.

  A method for manufacturing a piezoelectric actuator according to a second invention is characterized in that, in the first invention, the recess is a through-hole penetrating the first electrode.

  According to a third aspect of the present invention, there is provided a method of manufacturing a piezoelectric actuator according to the second aspect, wherein a plurality of the through holes are formed.

  In these piezoelectric actuator manufacturing methods, in the first step, a first electrode is formed on the surface of the insulating material layer, a recess is formed on the surface of the first electrode, and then the second step. In step 3, a piezoelectric layer is formed on the surface of the first electrode, and in the third step, a second electrode is formed on the surface of the piezoelectric layer. For this reason, a part of the piezoelectric layer enters the recess, and the piezoelectric layer is formed to be uneven at the interface between the first electrode and the piezoelectric layer, so that the piezoelectric layer is constrained by the recess. Therefore, the piezoelectric layer is difficult to peel from the surface of the first electrode, and the adhesion between the piezoelectric layer and the first electrode is improved. Accordingly, the durability of the piezoelectric actuator is improved and the yield in the manufacturing stage is also improved. Note that the concave portion formed on the surface of the first electrode may be a through hole penetrating the first electrode, and a plurality of through holes may be formed. According to these cases, since the constraint of the piezoelectric layer is made stronger, the adhesion between the piezoelectric layer and the first electrode is further improved.

  Also, when the piezoelectric layer is formed of a material that requires heat treatment such as lead zirconate titanate (PZT), the material for forming the piezoelectric layer and the material for forming the first electrode have a thermal expansion coefficient of both. Due to the difference, a difference occurs in the deformation amount during the heat treatment, and accordingly, an interfacial stress occurs between the two. If the interfacial stress is large, the piezoelectric layer is easily peeled off from the first electrode. However, according to the third aspect of the invention, the contact surface between the first electrode and the piezoelectric layer is divided at some places by the plurality of through holes, and the interfacial stress between the two is reduced. Even when is performed, the adhesion between the piezoelectric layer and the first electrode is improved.

  According to a fourth method of manufacturing a piezoelectric actuator, in the second or third invention, the insulating material layer is formed of a material whose thermal expansion coefficient is closer to the piezoelectric layer than the first electrode. It is a feature. Even when the piezoelectric layer is formed of a material requiring heat treatment such as lead zirconate titanate (PZT), the thermal expansion coefficient of the insulating material layer is closer to that of the piezoelectric layer than that of the first electrode. When applied, the difference in deformation between the piezoelectric layer and the insulating material layer is smaller than the difference in deformation between the piezoelectric layer and the first electrode. Therefore, the piezoelectric layer is in close contact with the insulating material layer. The piezoelectric layer is in close contact with the insulating material layer partially through the through hole formed in the first electrode, so that the adhesion between the piezoelectric layer and the first electrode is further improved.

  According to a fifth aspect of the present invention, there is provided a method for manufacturing a piezoelectric actuator according to any one of the second to second aspects, wherein the diameter of the through hole is larger than the thickness of the first electrode. . Therefore, the piezoelectric layer is easily adhered to the insulating material layer through the through hole, and the adhesion between the piezoelectric layer and the first electrode is improved.

  According to a sixth aspect of the present invention, there is provided a method of manufacturing a piezoelectric actuator according to any one of the second to fifth aspects, wherein the diameter of the through hole is smaller than the thickness of the piezoelectric layer. Therefore, it is possible to suppress as much as possible that the electric field applied to the piezoelectric layer is disturbed by the through hole and the deformation efficiency of the piezoelectric layer is reduced.

  The method for manufacturing a piezoelectric actuator according to a seventh aspect of the present invention is the method according to any one of the third to sixth aspects, wherein the arrangement density of the plurality of through holes in the outer peripheral portion of the first electrode is the first electrode. It is characterized by being larger than the arrangement density in the central part. At the interface between the piezoelectric layer and the first electrode, the interface stress increases toward the outer peripheral side of the first electrode, and the piezoelectric layer tends to peel off from the outer peripheral side. However, the arrangement of the through holes in the outer peripheral side portion of the first electrode By making the density larger than the central portion, it is possible to increase the adhesion at the outer peripheral side portion, so that the piezoelectric layer is less likely to be peeled off from the first electrode.

  The method for manufacturing a piezoelectric actuator according to an eighth aspect of the present invention is the method for manufacturing a piezoelectric actuator according to any one of the third to seventh aspects, wherein, in the first step, a driving voltage is applied to the first electrode and extends from the first electrode. For this purpose, a wiring portion is formed, and a plurality of through holes are also formed in this wiring portion. Thus, by forming a plurality of through holes in the wiring portion extending from the first electrode, the adhesion between the first electrode and the wiring portion and the piezoelectric layer can be further improved.

  According to a ninth aspect of the present invention, there is provided a piezoelectric actuator manufacturing method according to any one of the first to eighth aspects, wherein the piezoelectric layer is formed by an aerosol deposition method, a sputtering method, a CVD method, or a sol-gel method in the second step. It is formed by either. When the piezoelectric layer is formed by these methods, since the particles of the material forming the piezoelectric layer easily enter the recess, the adhesion between the piezoelectric layer and the first electrode is improved.

  According to a tenth aspect of the present invention, there is provided a method for manufacturing a piezoelectric actuator according to any one of the first to ninth aspects, wherein the insulating material layer is formed on a surface of a metal diaphragm. Therefore, the vibration plate can be made of a metal material having a high elastic modulus to enhance the responsiveness of the piezoelectric actuator. Furthermore, the metal vibration plate and the first electrode are electrically insulated by the insulating material layer. can do.

  A piezoelectric actuator according to an eleventh aspect of the invention is provided with a first electrode provided on the surface of the insulating material layer and having a recess formed on the surface, a piezoelectric layer formed on the surface of the first electrode, And a second electrode formed on the surface of the piezoelectric layer. In addition, the recessed part formed in the surface of the 1st electrode in this invention includes the form of the through-hole which penetrates the 1st electrode.

  A piezoelectric actuator of a twelfth aspect of the invention is the piezoelectric actuator of the eleventh aspect of the invention, wherein the recess is a through hole that penetrates the first electrode.

  According to a thirteenth aspect of the present invention, there is provided a piezoelectric actuator according to the twelfth aspect, wherein a plurality of the through holes are formed.

  In these piezoelectric actuators, the piezoelectric layer enters the recess, and the piezoelectric layer is formed to be uneven at the interface between the first electrode and the piezoelectric layer, and the piezoelectric layer is constrained by the recess. It becomes difficult to peel from the surface of the electrode, and the adhesion between the piezoelectric layer and the first electrode is improved. Accordingly, the durability of the piezoelectric actuator is improved and the yield in the manufacturing stage is also improved. Note that the concave portion formed on the surface of the first electrode may be a through hole penetrating the first electrode, and a plurality of through holes may be formed. According to these cases, since the constraint of the piezoelectric layer is made stronger, the adhesion between the piezoelectric layer and the first electrode is further improved.

  According to a fourteenth aspect of the present invention, in the twelfth or thirteenth aspect, the insulating material layer is formed of a material whose thermal expansion coefficient is closer to the piezoelectric layer than the first electrode. The layer is partially adhered to the insulating material layer through the through hole. Even when the piezoelectric layer is formed of a material that requires heat treatment such as lead zirconate titanate (PZT), the thermal expansion coefficient of the insulating material layer is closer to that of the piezoelectric layer than that of the first electrode. When applied, the difference in deformation between the piezoelectric layer and the insulating material layer is smaller than the difference in deformation between the piezoelectric layer and the first electrode. Therefore, the piezoelectric layer adheres closely to the insulating material layer. It becomes easy, and the adhesiveness between the piezoelectric layer and the first electrode is further improved because the piezoelectric layer is partially adhered to the insulating material layer through the through hole formed in the first electrode.

  An ink jet head according to a fifteenth aspect of the present invention includes a flow path unit having a plurality of pressure chambers communicating with nozzles that eject ink, and a piezoelectric actuator that selectively changes the volume of the plurality of pressure chambers. The actuator is formed on the surface of the insulating material layer, the plurality of individual electrodes formed on the surface of the insulating material layer corresponding to the plurality of pressure chambers, and the plurality of individual electrodes straddling the plurality of individual electrodes. A piezoelectric layer and a common electrode formed on the surface of the piezoelectric layer are provided, and a concave portion is provided on the surface of each individual electrode. In addition, the recessed part formed in the surface of the individual electrode in this invention includes the form of the through-hole which penetrates an individual electrode.

  An ink jet head according to a sixteenth aspect is the ink jet head according to the fifteenth aspect, wherein the concave portion is a through-hole penetrating the individual electrode.

  An ink jet head according to a seventeenth aspect is the ink jet head according to the sixteenth aspect, wherein a plurality of the through holes are formed.

  In these ink jet heads, when a driving voltage is selectively supplied to a plurality of individual electrodes of a piezoelectric actuator, an electric field is generated in the piezoelectric layer between the individual electrode and the common electrode, and the piezoelectric layer is deformed. Pressure is applied to the ink in the pressure chamber by the deformation of the piezoelectric layer, and the ink is ejected from the nozzle. Here, in the piezoelectric actuator, since the concave portion is provided on the surface of each individual electrode, the piezoelectric layer is hardly peeled off from the individual electrode, and the adhesion between the individual electrode and the piezoelectric layer is improved. In addition, the recessed part formed in the surface of the individual electrode may be a through hole penetrating the individual electrode, and a plurality of through holes may be formed. According to these cases, the adhesion between the individual electrode and the piezoelectric layer is further improved.

  An ink jet head according to an eighteenth aspect of the present invention is the ink jet head according to the sixteenth or seventeenth aspect, wherein the insulating material layer is formed of a material whose thermal expansion coefficient is closer to the piezoelectric layer than the individual electrode. The insulating material layer is partially adhered to the insulating material layer through the plurality of through holes. According to the eighteenth aspect, as in the fourteenth aspect described above, the piezoelectric layer is in close contact with the insulating material layer through the through hole, so that the adhesion between the piezoelectric layer and the individual electrode is improved.

  Embodiments of the present invention will be described. This embodiment is an example in which the present invention is applied to a piezoelectric actuator used in an inkjet head.

  As shown in FIG. 1, the inkjet head 1 includes a flow path unit 2 in which an ink flow path is formed, and a piezoelectric actuator 3 stacked on the upper surface of the flow path unit 2.

  First, the flow path unit 2 will be described. FIG. 2 is a schematic plan view of the right half of the inkjet head 1 of FIG. 3 is a cross-sectional view taken along line III-III in FIG. 2, and FIG. 4 is a cross-sectional view taken along line IV-IV in FIG. As shown in FIGS. 2 to 4, the flow path unit 2 includes a cavity plate 10, a base plate 11, a manifold plate 12, and a nozzle plate 13, and these four plates 10 to 13 are bonded in a laminated state. Yes. Among these, the cavity plate 10, the base plate 11, and the manifold plate 12 are substantially rectangular stainless steel plates. Therefore, ink flow paths such as a manifold 17 and a pressure chamber 14 described later can be easily formed on these three plates 10 to 12 by etching. The nozzle plate 13 is formed of, for example, a polymer synthetic resin material such as polyimide, and is bonded to the lower surface of the manifold plate 12. Or this nozzle plate 13 may be formed with metal materials, such as stainless steel, similarly to the three plates 10-12.

  As shown in FIG. 2, the cavity plate 10 is formed with a plurality of pressure chambers 14 arranged along a plane. The plurality of pressure chambers 14 are open on the surface of the flow path unit 2 (the upper surface of the cavity plate 10 to which a diaphragm 30 described later is joined). FIG. 2 shows some (eight) of the plurality of pressure chambers 14. Each pressure chamber 14 is formed in a substantially elliptical shape in plan view, and is arranged so that the major axis direction thereof is parallel to the longitudinal direction of the cavity plate 10.

  Communication holes 15 and 16 are formed at positions overlapping the both ends in the long axis direction of the pressure chamber 14 in plan view of the base plate 11, respectively. The manifold plate 12 is formed with a manifold 17 extending in two rows in the short direction of the manifold plate (vertical direction in FIG. 2) and overlapping the right half of the pressure chamber 14 in FIG. Ink is supplied to the manifold 17 from an ink tank (not shown) through an ink supply port 18 formed in the cavity plate 10. A communication hole 19 is also formed at a position overlapping the left end of the pressure chamber 14 in FIG. Further, the nozzle plate 13 is formed with a plurality of nozzles 20 at positions overlapping the left end portions of the plurality of pressure chambers 14 in plan view. The nozzle 20 is formed, for example, by performing excimer laser processing on a polymer synthetic resin substrate such as polyimide.

  As shown in FIG. 3, the manifold 17 communicates with the pressure chamber 14 through the communication hole 15, and the pressure chamber 14 communicates with the nozzle 20 through the communication holes 16 and 19. As described above, an individual ink flow path from the manifold 17 to the nozzle 20 through the pressure chamber 14 is formed in the flow path unit 2.

  Next, the piezoelectric actuator 3 will be described. As shown in FIGS. 1 to 5, the piezoelectric actuator 3 includes a vibration plate 30 disposed on the surface of the flow path unit 2, an insulating material layer 31 formed on the surface of the vibration plate 30, and a plurality of pressure chambers. 14, a plurality of individual electrodes 32 (first electrodes) formed on the surface of the insulating material layer 31, and a piezoelectric layer 33 formed on these surfaces across the plurality of individual electrodes 32, A common electrode 34 (second electrode) formed on the surface of the piezoelectric layer 33 and provided in common across the plurality of individual electrodes 32 is provided.

  The diaphragm 30 is a plate made of stainless steel having a substantially rectangular shape in plan view, and is joined in a state of being stacked on the upper surface of the cavity plate 10 so as to block the openings of the plurality of pressure chambers 14. Here, since the vibration plate 30 is formed of stainless steel having a relatively high elastic modulus, the rigidity of the vibration plate 30 is increased when the piezoelectric layer 33 is deformed during the ink ejection operation as described later. As a result, the responsiveness of the piezoelectric actuator 3 is increased. Further, the diaphragm 30 is joined to the surface of the cavity plate 10 which is also formed of stainless steel. Therefore, the thermal expansion coefficients of the diaphragm 30 and the cavity plate 10 become equal, and the bonding strength between the two is improved. Furthermore, the ink in the flow path unit 2 comes into contact with the flow path unit 2 and the vibration plate 30 formed of stainless steel having excellent corrosion resistance against the ink. Therefore, no matter what kind of ink is selected, there is no possibility that a local battery is formed in the flow path unit 2 or on the diaphragm 30, and the ink selection is not restricted by the corrosive surface. The degree is increased.

  An insulating material layer 31 made of a ceramic material having a high elastic modulus such as alumina, zirconia, or silicon nitride and having a flat surface is formed on the surface of the vibration plate 30. Thus, since the insulating material layer 31 is formed of a ceramic material having a high elastic modulus, the rigidity of the actuator is increased and the responsiveness is further increased.

  Furthermore, a plurality of individual electrodes 32 having an elliptical planar shape that is slightly smaller than the pressure chamber 14 are formed on the surface of the insulating material layer 31. The individual electrode 32 is formed at a position overlapping the central portion of the corresponding pressure chamber 14 in plan view. The individual electrode 32 is made of a conductive material such as gold. The adjacent individual electrodes 32 are electrically insulated from each other by the insulating material layer 31. As shown in FIGS. 3 to 5, each individual electrode 32 is formed with a plurality of through holes 32 a penetrating the individual electrode 32. The plurality of through holes 32 a are provided in order to improve adhesion between a piezoelectric layer 33 (described later) formed on the surface of the individual electrode 32 and the individual electrode 32. The plurality of through holes 32a will be described in detail later.

  On the surface of the insulating material layer 31, a plurality of wiring portions 35 extend in parallel with the long axis direction of the individual electrode 32 from one end portion (the right end portion in FIG. 2) of the plurality of individual electrodes 32. Terminal portions 36 are respectively formed at the ends of the wiring portions 35. An output terminal 37a of a driver IC 37 that selectively supplies a drive voltage to the plurality of individual electrodes 32 is formed on a plurality of terminal portions 36 respectively corresponding to the plurality of individual electrodes 32 from a conductive brazing material such as solder. The driver ICs 37 are disposed on the surface of the insulating material layer 31.

  Furthermore, a plurality of connection terminals 40 are also formed on the insulating material layer 31, and the plurality of connection terminals 40 and the input terminals 37b of the driver IC 37 are respectively joined via bumps 39 made of solder or the like. The driver IC 37 and a control device (not shown) that controls the driver IC 37 are connected via the connection terminal 40.

  On the surface of the plurality of individual electrodes 32, a piezoelectric layer 33 mainly composed of lead zirconate titanate (PZT), which is a solid solution and is a ferroelectric substance, of lead titanate and lead zirconate is formed. The piezoelectric layer 33 is formed as one continuous layer over all of the plurality of individual electrodes 32 so as to cover the entire surface of the plurality of individual electrodes 32.

Here, as described above, each individual electrode 32 has a plurality of through holes 32a. As shown in FIGS. 3 and 4, a part of the piezoelectric layer 33 enters the through hole 32 a and the lower surface of the piezoelectric layer 33 is formed in an uneven shape, so that the piezoelectric layer 33 is restrained by the through hole 32. In addition, the adhesion between the individual electrode 32 and the piezoelectric layer 33 is enhanced. Further, as will be described later, the piezoelectric layer 33 is subjected to heat treatment in a state where it is formed on the surface of the individual electrode 32. Here, the thermal expansion coefficient of the conductive material such as gold forming the individual electrode 32 is about 14 × 10 ⁻⁶ , whereas the thermal expansion coefficient of PZT forming the piezoelectric layer 33 is about 3 × 10 ^−6. Therefore, after the heat treatment is performed on the piezoelectric layer 33, an interfacial stress is generated between the individual electrode 32 and the PZT forming the piezoelectric layer 33 due to a difference in thermal deformation amount. When this interfacial stress is large, the piezoelectric layer 33 is easily peeled off from the individual electrode 32, but the contact surface between the individual electrode 32 and the piezoelectric layer 33 is divided at some points by a plurality of through holes 32a, and the interfacial stress between the two is reduced. Therefore, the piezoelectric layer 33 is difficult to peel off from the individual electrode 32. Furthermore, the thermal expansion coefficient of the insulating material layer 31 below the individual electrode 32 is, for example, about 7 × 10 ^{−6 in} the case of alumina, and the thermal expansion coefficient of the piezoelectric layer 33 is higher than the thermal expansion coefficient of the individual electrode 32. Therefore, the piezoelectric layer 33 can easily adhere to the insulating material layer 31 through the plurality of through holes 32a. As described above, the piezoelectric layer 33 is partially adhered to the insulating material layer 31 through the plurality of through holes 32a, so that the piezoelectric layer 33 is more difficult to be separated from the individual electrode 32.

  A common electrode 34 common to the plurality of individual electrodes 32 is formed on the entire surface of the piezoelectric layer 33 on the surface of the piezoelectric layer 33. As shown in FIG. 2, one wiring part 41 extends from the common electrode 34, and this wiring part 41 extends over the surface of the piezoelectric layer 33 and the surface of the insulating material layer 31. Is formed. Further, the terminal portion 42 provided at the end of the wiring portion 41 is in contact with a terminal (not shown) of the driver IC 37. Thereby, the common electrode 34 is grounded via the wiring portion 41 and the driver IC 37 and is held at the ground potential. The common electrode 34 is also made of a conductive material such as gold.

  Next, the operation of the piezoelectric actuator 3 during ink ejection will be described. When a drive voltage is selectively supplied from the driver IC 37 to the plurality of individual electrodes 32 respectively connected to the driver IC 37 via the plurality of wiring sections 35, the lower side of the piezoelectric layer 33 to which the drive voltage is supplied is provided. The electric potentials of the individual electrodes 32 and the common electrode 34 on the upper side of the piezoelectric layer 33 held at the ground potential are different from each other, and an electric field in the vertical direction is generated in the piezoelectric layer 33 sandwiched between the electrodes 32 and 34. Then, a portion of the piezoelectric layer 33 immediately above the individual electrode 32 to which the drive voltage is applied contracts in a horizontal direction orthogonal to the vertical direction that is the polarization direction. Here, since the insulating material layer 31 and the diaphragm 30 below the piezoelectric layer 33 are fixed to the cavity plate 10, the portion of the piezoelectric layer 33 sandwiched between both electrodes 32 and 34 is the pressure chamber. It deforms so as to be convex toward the 14 side, and with the partial deformation of the piezoelectric layer 33, the portion covering the pressure chamber 14 of the diaphragm 30 is also deformed so as to be convex toward the pressure chamber 14 side. Then, since the volume in the pressure chamber 14 decreases, the ink pressure rises, and ink is ejected from the nozzle 20 communicating with the pressure chamber 14.

  Next, a method for manufacturing the piezoelectric actuator 3 will be described. First, as shown in FIG. 6, the three stainless steel plates 10 to 12 and the stainless steel diaphragm 30 are joined by diffusion bonding or the like. Here, since the cavity plate 10 and the diaphragm 30 are made of the same stainless steel, the thermal expansion coefficients are equal, and the residual stress on the joint surface is small, so that the joint strength between them is extremely good.

  Next, as shown in FIG. 7, an insulating material layer 31 is formed on the surface of the diaphragm 30 from a ceramic material such as alumina, zirconia, or silicon nitride. As a method of forming the insulating material layer 31, for example, an extremely thin layer can be used by using an aerosol deposition method in which ultrafine particle material is deposited by colliding at high speed. In addition, the insulating material layer 31 can be formed using a sol-gel method, a sputtering method, or a CVD (chemical vapor deposition) method.

  Next, the individual electrodes 32 are formed on the surface of the insulating material layer 31, and a plurality of through holes 32a are formed in each individual electrode (first step). As shown in FIG. 8, a conductive layer 40 is formed on the entire surface of the insulating material layer 31 by plating, sputtering, vapor deposition, or the like. Then, as shown in FIG. The conductive layer 40 is partially removed to form the individual electrode 32 and the plurality of through holes 32a. Alternatively, the individual electrodes 32 and the plurality of through holes 32a may be formed at a time by screen-printing a conductive paste on the surface of the insulating material layer 31.

  Next, as shown in FIG. 10, a piezoelectric layer 33 made of PZT is formed on the surface of the individual electrode 32 using an aerosol deposition method, a sol-gel method, sputtering, or the CVD method (second step). By forming the piezoelectric layer 33 by these methods, the PZT particles forming the piezoelectric layer 33 can easily enter into the plurality of through holes 32a formed in the individual electrode 32, and the piezoelectric layer 33 is formed into the plurality of through holes 32a. It becomes easy to adhere to the insulating material layer 31 partly through. Subsequently, in order to refine the structure of the piezoelectric layer 33, the piezoelectric layer 33 is subjected to heat treatment at about 600 ° C.

  Then, as shown in FIG. 11, a common electrode 34 is formed on the entire surface of the piezoelectric layer 33 using screen printing, vapor deposition, sputtering, or the like (third step). Finally, as shown in FIG. 12, the nozzle plate 13 is bonded to the lower surface of the manifold plate 12.

  In order to make the piezoelectric layer 33 easily adhere to the insulating material layer 31 through the plurality of through holes 32a, the diameter of the plurality of through holes 32a is preferably larger than the thickness of the individual electrode 32. If the hole diameter of the through-hole 32a is such a large size, the portion formed in the through-hole 32a of the piezoelectric layer 33 has a diameter that is sufficiently large with respect to the depth thereof. There is less possibility that the piezoelectric layer 33 in the vicinity thereof is broken. On the other hand, if the hole diameters of the plurality of through holes 32a are too large, the electric field applied to the piezoelectric layer 33 between the individual electrode 32 and the common electrode 34 is disturbed, and the deformation efficiency of the piezoelectric layer 33 is reduced. Since there is a risk of lowering, the hole diameter of the through hole 32 a is preferably smaller than the thickness of the piezoelectric layer 33. For example, when the thickness of the individual electrode 32 is about 2 μm and the thickness of the piezoelectric layer 33 is about 10 μm, the hole diameter of the plurality of through holes 32 a is preferably about 2 to 10 μm.

  When the nozzle plate 13 is formed of a metal material such as stainless steel, the nozzle plate 13 is joined together with the other three plates at the same time to form the flow path unit 2, and then the flow of the nozzle plate 13 is increased. The diaphragm 30, the individual electrode 32, and the piezoelectric layer 33 may be sequentially laminated on the surface of the path unit 2, and the piezoelectric layer 33 may be heat treated.

  According to the inkjet head 1, the piezoelectric actuator 3, and the method for manufacturing the piezoelectric actuator 3 described above, the following effects can be obtained.

  By forming a plurality of through holes 32a in the individual electrode 32, a part of the piezoelectric layer 33 on the surface of the individual electrode 32 enters the through hole 32a, and that part is restrained by the through hole 32a. It becomes difficult to peel off from the electrode 32. In addition, since the contact surface between the individual electrode 32 and the piezoelectric layer 33 is divided by the plurality of through holes 32a, the interfacial stress between the individual electrode 32 and the piezoelectric layer 33 generated after the heat treatment of the piezoelectric layer 33 is small. Thus, the adhesion between the individual electrode 32 and the piezoelectric layer 33 is improved. Further, the insulating material layer 31 below the individual electrode 32 has a thermal expansion coefficient closer to that of the piezoelectric layer 33 than the individual electrode 31, and a part of the piezoelectric layer 33 that has entered the plurality of through holes 32 a is part of the insulating material layer 31. Therefore, the adhesion between the individual electrode 32 and the piezoelectric layer 33 is further improved.

  Next, modified embodiments in which various modifications are made to the embodiment will be described. However, components having the same configuration as in the above embodiment are given the same reference numerals, and description thereof is omitted as appropriate.

  1] Generally, the interfacial stress between the individual electrode 32 and the piezoelectric layer 33 increases toward the outer peripheral portion of the individual electrode 32, so that the piezoelectric layer 33 is easily peeled off from the outer peripheral side of the individual electrode 32. Therefore, as shown in FIG. 13, the arrangement density of the through holes 32a in the outer peripheral portion of the individual electrode 32 is made larger than that in the central portion, and the adhesion between the individual electrode 32 and the piezoelectric layer 33 in the outer peripheral portion is further increased. This can more reliably prevent the piezoelectric layer 33 from peeling from the individual electrode 32.

  2] As shown in FIG. 14, when the plurality of through holes 32a are formed in the individual electrode 32, the plurality of through holes 35a are also formed in the wiring portion 35 extending from the individual electrode 32, so that the individual electrode 32 and the wiring portion are formed. You may make it improve the adhesiveness of 35 and the piezoelectric layer 33 further.

  3] In the method of manufacturing the piezoelectric actuator of the above embodiment, the insulating material layer 31 is formed on the surface of the metallic diaphragm 30, and the plurality of individual electrodes 32 are formed on the surface of the insulating material layer 31. However, as shown in FIG. 15, a plurality of individual electrodes 32 are formed directly on the surface of a diaphragm 50 (corresponding to the insulating material layer of the present invention) made of an insulating material, and a plurality of individual electrodes 32 are formed on each individual electrode 32. The through hole 32a may be formed. In the piezoelectric actuator 53 thus manufactured, a part of the piezoelectric layer 33 formed on the surface of the individual electrode 32 is in close contact with the diaphragm 50 through the plurality of through holes 32a. In order to improve the responsiveness of the piezoelectric actuator 53, the insulating material constituting the diaphragm 50 may be a material having a high elastic modulus such as a ceramic material such as alumina or zirconia, or a glass material such as borosilicate glass. preferable.

  4] In the above embodiment, the individual electrode 32 is formed on the surface of the insulating material layer 31 (the lower surface of the piezoelectric layer 33), and the common electrode 34 is formed on the surface of the piezoelectric layer 33. The common electrode 34 may be formed on the surface, and the individual electrode 32 may be formed on the surface of the piezoelectric layer 33. In this case, a plurality of through holes for improving the adhesion with the piezoelectric layer 33 are formed in the common electrode 34.

  5] In the above-described embodiment, the plurality of through holes 32a are formed in the individual electrodes 32. For example, as shown conceptually in FIGS. 16 to 19, only one through hole is formed in each individual electrode. It may be formed. In FIG. 16, a single spiral groove (through hole) is formed in the individual electrode 60. Alternatively, as shown in FIG. 17, an S-shaped groove 62 a may be formed in the individual electrode 62. The groove can be formed in an arbitrary shape. Further, in consideration of the fact that the vicinity of the outer periphery of the individual electrode is more likely to be peeled off than the center portion, a U-shaped or substantially annular groove may be formed only in the vicinity of the outer periphery of the individual electrode 64 as shown in FIG. Good. Furthermore, as shown in FIG. 19, a plurality of grooves 66 a and 66 b may be provided in the individual electrode 66.

  6] In the above embodiment, the plurality of through holes 32a are respectively formed in the individual electrode 32. Instead, for example, one is provided on the surface of the individual electrode 132 on the piezoelectric layer 33 side as shown in FIG. You may provide the above recessed part 132a. The individual electrode 132 having the recess 132a can be formed by a plating method, a sputtering method, a vapor deposition method, or the like. The diameter of the recess 132 a is desirably larger than the thickness of the individual electrode 132 and smaller than the thickness of the piezoelectric layer 33 as in the case of the through hole. The depth of the recess 132 a can be selected as appropriate in consideration of the peel resistance of the piezoelectric layer 33 from the individual electrode 132. For example, when the concave portions 132a are provided in the outer peripheral portion and the central portion of the individual electrode 132, the outer peripheral concave portion 132a may be formed deeper than the concave portion 132a in the central portion. Here, a portion defined between the concave portion 132a formed in the individual electrode 132 and the concave portion 132a can be regarded as a convex portion. That is, even when the individual electrode 132 is provided with a protrusion or protrusion protruding from the surface, a recess is formed in a portion sandwiched between the two protrusions. Therefore, the present invention includes a case where a plurality of convex portions are formed. In addition, the planar shape of the concave portion 132a (or the convex portion) is not limited to a circle, and may be a rectangle or various shapes. Further, only one recess 132 a may be formed in the individual electrode 132.

1 is a perspective view of an inkjet head according to an embodiment of the present invention. It is a top view of the right half part of the inkjet head in FIG. It is the III-III sectional view taken on the line of FIG. It is the IV-IV sectional view taken on the line of FIG. FIG. 3 is a partially enlarged view of FIG. 2. It is a figure which shows the process of joining a flow path unit and a diaphragm. It is a figure which shows the process of forming an insulating layer. It is a figure which shows the process of forming an individual electrode. It is a figure which shows the process of forming a several through-hole. It is a figure which shows the process of forming a piezoelectric layer. It is a figure which shows the process of forming a common electrode. It is a figure which shows the process of joining a nozzle plate. FIG. 6 is a diagram corresponding to FIG. FIG. 6 is a diagram corresponding to FIG. 5 in another modified form. FIG. 6 is a view corresponding to FIG. 3 in still another modified form. It is a conceptual diagram which shows another modification. It is a conceptual diagram which shows another modification. It is a conceptual diagram which shows another modification. It is a conceptual diagram which shows another modification. It is a figure which shows another modification.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Inkjet head 2 Flow path unit 3,53 Piezoelectric actuator 14 Pressure chamber 30,50 Diaphragm 31 Insulating material layer 32,60,62,64,66,132 Individual electrode 32a Through hole 33 Piezoelectric layer 34 Common electrode 35 Wiring part 35a Through hole

Claims (18)

Forming a first electrode on the surface of the insulating material layer and forming a recess on the surface of the first electrode;
A second step of forming a piezoelectric layer on the surface of the first electrode;
And a third step of forming a second electrode on the surface of the piezoelectric layer.   The method for manufacturing a piezoelectric actuator according to claim 1, wherein the concave portion is a through-hole penetrating the first electrode.   The method for manufacturing a piezoelectric actuator according to claim 2, wherein a plurality of the through holes are formed.   4. The method of manufacturing a piezoelectric actuator according to claim 2, wherein the insulating material layer is formed of a material having a thermal expansion coefficient closer to that of the piezoelectric layer than that of the first electrode.   5. The method of manufacturing a piezoelectric actuator according to claim 2, wherein a diameter of the through hole is larger than a thickness of the first electrode.   The method for manufacturing a piezoelectric actuator according to claim 2, wherein a diameter of the through hole is smaller than a thickness of the piezoelectric layer.   7. The arrangement density according to claim 3, wherein an arrangement density of the plurality of through holes in an outer peripheral side portion of the first electrode is larger than an arrangement density in a central portion of the first electrode. A method for manufacturing a piezoelectric actuator.   In the first step, a wiring portion that extends from the first electrode and applies a driving voltage to the first electrode is formed, and a plurality of through holes are formed in the wiring portion. The manufacturing method of the piezoelectric actuator in any one of Claims 3-7.   The piezoelectric actuator according to claim 1, wherein in the second step, the piezoelectric layer is formed by any one of an aerosol deposition method, a sputtering method, a CVD method, and a sol-gel method. Method.   The method for manufacturing a piezoelectric actuator according to claim 1, wherein the insulating material layer is formed on a surface of a metal diaphragm. A first electrode provided on the surface of the insulating material layer and having a recess formed on the surface;
A piezoelectric layer formed on the surface of the first electrode;
And a second electrode formed on the surface of the piezoelectric layer.   The piezoelectric actuator according to claim 11, wherein the concave portion is a through-hole penetrating the first electrode.   The piezoelectric actuator according to claim 12, wherein a plurality of the through holes are formed. The insulating material layer is formed of a material having a thermal expansion coefficient closer to that of the piezoelectric layer than the first electrode, and the piezoelectric layer is partially adhered to the insulating material layer through the through hole. The piezoelectric actuator according to claim 12 or 13, characterized in that: A flow path unit having a plurality of pressure chambers communicating with a nozzle for discharging ink, and a piezoelectric actuator for selectively changing the volume of the plurality of pressure chambers,
The piezoelectric actuator is
An insulating material layer;
A plurality of individual electrodes formed on the surface of the insulating material layer corresponding to the plurality of pressure chambers;
A piezoelectric layer formed on the surface of the plurality of individual electrodes,
A common electrode formed on the surface of the piezoelectric layer,
An ink jet head, wherein the surface of each individual electrode is provided with a recess.   The inkjet head according to claim 15, wherein the recess is a through-hole penetrating the individual electrode.   The inkjet head according to claim 16, wherein a plurality of the through holes are formed. The insulating material layer is formed of a material having a thermal expansion coefficient closer to that of the piezoelectric layer than the individual electrode, and the piezoelectric layer is partially adhered to the insulating material layer through the plurality of through holes. The inkjet head according to claim 16 or 17, wherein

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