JP6237238B2 - Piezoelectric actuator, liquid ejection device, and method of manufacturing piezoelectric actuator - Google Patents

Description

  The present invention relates to a piezoelectric actuator.

  Patent Document 1 discloses a piezoelectric actuator for an ink jet head that ejects ink from a nozzle. The piezoelectric actuator is bonded to the flow path unit of the ink jet head, and applies ejection energy to the ink in the plurality of nozzles of the flow path unit. The piezoelectric actuator disclosed in Patent Document 1 includes two stacked piezoelectric bodies (referred to as “diaphragm” and “piezoelectric layer” in Patent Document 1, respectively) and a flow path on the upper surface of the upper piezoelectric body. It has a plurality of individual electrodes provided corresponding to a plurality of nozzles of the unit, and a common electrode provided between two piezoelectric bodies.

  A plurality of extraction electrodes (surface electrodes) that are electrically connected to the common electrode are provided on the upper surface of the upper piezoelectric body. Further, a through hole is formed in the upper piezoelectric body, and each extraction electrode and the common electrode are connected by a conductive material filled in the through hole. Further, the plurality of individual electrodes and the plurality of extraction electrodes arranged on the upper surface of the upper piezoelectric body are each connected to a wiring member. By this wiring member, a ground potential and a driving potential are selectively applied to the individual electrodes. On the other hand, the common electrode is always held at the ground potential by being connected to the wiring member.

JP 2012-206442 A

  Since the piezoelectric body constituting the piezoelectric actuator is formed of piezoelectric ceramic which is a brittle material, cracks may occur during firing or handling in a post-process after firing. . In particular, when a through hole is formed in the upper piezoelectric body, a portion of the lower piezoelectric body exposed in the through hole is locally thin and weak in strength, or stress concentration occurs. For reasons such as being easy, it is known that cracks are likely to occur compared to other parts.

  When the piezoelectric actuator on the lower piezoelectric body is cracked at the exposed portion of the through hole, and the piezoelectric actuator is joined to the flow path unit with an adhesive, a part of the excess adhesive penetrates into the crack, and the through hole Further, there is a possibility of overflowing to the upper surface of the upper piezoelectric body. If the adhesive, which is an insulating material, spreads into the through-holes and the upper surface of the upper piezoelectric body, poor conduction between the extraction electrode and the conductive portion or between the individual electrode and the extraction electrode and the wiring member Cause.

  An object of the present invention is to provide an adhesive in a piezoelectric actuator having a structure in which two or more piezoelectric bodies are laminated, when a crack is generated in an exposed portion of a through-hole of a piezoelectric body to be bonded to another member. Is to prevent cracks from penetrating into the through hole.

Means for Solving the Problems and Effects of the Invention

A piezoelectric actuator according to a first aspect of the present invention is disposed on a surface of a first piezoelectric body, a second piezoelectric body stacked on the first piezoelectric body, and a surface of the first piezoelectric body opposite to the second piezoelectric body. The first electrode, the second electrode disposed between the first piezoelectric body and the second piezoelectric body, and the first piezoelectric body on the surface opposite to the second piezoelectric body, An extraction electrode disposed away from the electrode; and a second hole and the extraction electrode disposed in a through hole penetrating the first piezoelectric body in a region where the extraction electrode of the first piezoelectric body is formed. And a conduction part that conducts,
The conducting portion is formed to overlap the first conductive layer and the first conductive layer provided to cover a portion of the second piezoelectric body exposed from the first piezoelectric body in the through hole. And a second conductive layer.

  In the present invention, the conductive portion in the through hole has a first conductive layer and a second conductive layer. The first conductive layer is provided so as to cover a portion of the second piezoelectric body exposed from the first piezoelectric body in the through hole. In the present invention, “the portion of the second piezoelectric body exposed from the first piezoelectric body in the through hole” means a portion in which the first piezoelectric body is not locally stacked due to the presence of the through hole. Point to. That is, a portion of the second piezoelectric body that is in the through hole and is covered with the second electrode is also included in the “exposed portion”.

  When a crack is generated in the exposed portion of the second piezoelectric body, a part of the conductive material filled in the through hole penetrates into the crack when the first conductive layer is formed. As a result, the crack is closed with the conductive material. Therefore, when the surface on the second piezoelectric body side of the piezoelectric actuator is joined to another member with an adhesive, excess adhesive passes through the cracks, into the through hole, and further to the surface of the first piezoelectric body. Exudation is surely prevented.

  From the above viewpoint, the first conductive layer is preferably formed of a conductive material that easily permeates cracks. On the other hand, only the first conductive layer formed of such a conductive material can pass through the first conductive layer. The reliability of conduction in the hall is low. Therefore, in the present invention, the second conductive layer is formed so as to overlap the first conductive layer, thereby improving the conduction reliability in the through hole. The second conductive layer may be formed of a material different from that of the first conductive layer. However, the second conductive layer is formed of a material different from that of the first conductive layer in a separate process after the formation of the first conductive layer. Also good.

  The piezoelectric actuator according to a second aspect of the present invention is characterized in that, in the first aspect, the first conductive layer is thinner than the second conductive layer.

  In the present invention, the first conductive layer formed in the exposed portion of the second piezoelectric body in the through hole is thinner than the second conductive layer. Such a thin conductive layer is usually formed of a highly fluid conductive material. Since the highly fluid conductive material easily penetrates into the cracks generated in the second piezoelectric body, the cracks are reliably closed. On the other hand, the conduction reliability in the conduction part is low only with the thin first conductive layer. Therefore, the second conductive layer having a thickness larger than that of the first conductive layer is formed so as to improve the conduction reliability in the through hole.

  According to a third aspect of the present invention, in the piezoelectric actuator according to the first or second aspect, the first electrode is provided so as to cover the first electrode layer and the first electrode layer of the first piezoelectric body. The first electrode layer of the first electrode and the first conductive layer of the conductive portion are formed of the same material, the second electrode layer of the first electrode, The second conductive layer of the conduction part is formed of the same material.

  When the first electrode has a configuration including the first electrode layer and the second electrode layer, the first electrode layer of the first electrode and the first conductive layer of the conductive portion are formed of the same material. Can be formed at once. Similarly, since the second electrode layer of the first electrode and the second conductive layer of the conductive portion are formed of the same material, both can be formed at a time.

  According to a fourth aspect of the present invention, there is provided the piezoelectric actuator according to any one of the first to third aspects, wherein the first electrode and the extraction electrode are disposed on a surface of the first piezoelectric body opposite to the second piezoelectric body. Are arranged side by side in a predetermined direction, and the extraction electrode is formed at an edge of the through hole on the first electrode side in the predetermined direction, and the first electrode in the predetermined direction of the through hole It is not formed in the edge part of an other side, It is characterized by the above-mentioned.

  The occurrence of cracks in the second piezoelectric body can occur not only during the production of the piezoelectric actuator, such as in the firing step, but also when the completed piezoelectric actuator is bonded to another member while being pressed. At the time of bonding, since the conductive portion in the through hole is already formed, the crack generated at this stage is, as described in the first invention, the conductive material forming the conductive portion. It is not possible to infiltrate and block. Therefore, in the present invention, when excess adhesive oozes through the through-holes through a crack generated during bonding, the adhesive spreads to the first electrode formed on the first piezoelectric body. An object is to avoid adversely affecting the driving of the actuator as much as possible.

  That is, in the present invention, an extraction electrode is formed on the edge of the through hole on the first electrode side, but no extraction electrode is present on the edge on the side opposite to the first electrode. As a result, when the excess adhesive that oozes out from the crack generated in the second piezoelectric body into the through hole further overflows from the through hole, it is formed at the edge of the through hole on the first electrode side. A part of the extraction electrode serves as a dike to prevent the adhesive from flowing to the first electrode. Therefore, the adhesive overflowing from the through hole flows to the opposite side of the first electrode without the bank, and the adhesive is prevented from spreading to the first electrode.

  According to a fifth aspect of the present invention, in the piezoelectric actuator according to the fourth aspect, the first conductive layer is formed to cover the entire exposed portion of the second piezoelectric body in the through hole, and the second conductive layer is The second piezoelectric body is formed only on at least a part of the exposed portion of the second piezoelectric body on the first electrode side.

  In the present invention, since the first conductive layer is formed on the entire exposed portion of the second piezoelectric body in the through hole, the conductive material for forming the first conductive layer in the crack generated in the exposed portion. The cracks can be reliably closed. On the other hand, the second conductive layer suffices if it can be securely connected to the extraction electrode and the common electrode, and from that point of view, the second conductive layer should be formed at least on the first electrode side of the exposed portion. Good. That is, unlike the first conductive layer, the second conductive layer is not necessarily provided on the entire exposed portion of the second piezoelectric body.

  According to a sixth aspect of the present invention, in the fourth or fifth aspect, the through hole has a shape that is long in the predetermined direction when viewed from the stacking direction of the first piezoelectric body and the second piezoelectric body. It is characterized by this.

  Due to misalignment when forming the extraction electrode or misalignment when forming the through hole, the through hole is confined within the region where the extraction electrode is formed, and the entire edge of the through hole is formed. It is conceivable that a configuration in which an extraction electrode exists is formed. In the present invention, the through hole has a shape that is long in the direction in which the extraction electrode and the first electrode are arranged. Therefore, even if the extraction electrode and the through hole are formed in a slightly shifted position in this direction, the through hole is not formed. It does not fall within the region where the extraction electrode is formed.

  According to a seventh aspect of the present invention, in the piezoelectric actuator according to the fourth or fifth aspect, the plurality of first electrodes are arranged in an electrode arrangement direction orthogonal to the predetermined direction, and the extraction electrode is arranged in the electrode arrangement direction. The plurality of through holes are arranged along the electrode arrangement direction, and the positions in the predetermined direction are different among the plurality of through holes.

  In the present invention, since the positions of the plurality of through holes in the arrangement direction of the extraction electrode and the first electrode are different, even if the extraction electrodes and the through holes are formed in a slightly shifted position in this direction, all the through holes are formed. The holes do not fit into the region where the extraction electrode is formed.

A liquid ejection apparatus according to an eighth aspect includes a flow path structure having a liquid flow path including a plurality of nozzles, and a piezoelectric actuator joined to the flow path structure.
The piezoelectric actuator includes a first piezoelectric body, a second piezoelectric body disposed on the flow channel structure side with respect to the first piezoelectric body, and laminated on the first piezoelectric body, and the first piezoelectric body, A first electrode disposed on a surface opposite to the second piezoelectric body, a second electrode disposed between the first piezoelectric body and the second piezoelectric body, and the first piezoelectric body. In a through-hole penetrating the first piezoelectric body in a region where the extraction electrode arranged away from the first electrode and the extraction electrode of the first piezoelectric body are formed on the surface opposite to the two piezoelectric bodies And a conduction portion that conducts the second electrode and the extraction electrode,
The conducting portion is formed so as to overlap the first conductive layer and the first conductive layer provided to cover a portion of the second piezoelectric body exposed from the first piezoelectric body in the through hole. And a second conductive layer.

  In the present invention, when the first conductive layer is formed by injecting a conductive material into the through hole, a part of the conductive material penetrates into the crack, and the crack is closed with the conductive material. Thus, when the surface of the piezoelectric actuator on the second piezoelectric body side is joined to the flow path structure with an adhesive, it is reliably prevented that excessive adhesive penetrates through the crack. Furthermore, since the second conductive layer is formed so as to overlap the first conductive layer, the conduction reliability in the through hole is enhanced.

  A method for manufacturing a piezoelectric actuator according to a ninth aspect of the present invention is the method for manufacturing a piezoelectric actuator according to any one of the first to seventh aspects, wherein the first hole is formed in the through hole that penetrates the first piezoelectric body. After the first conductive layer forming step and the first conductive layer forming step, the second conductive material is filled into the through hole after the first conductive layer is formed. A second conductive layer forming step of forming the second conductive layer, wherein the fluidity of the first conductive material is higher than the fluidity of the second conductive material. Is.

  In the present invention, the through hole is filled with the first conductive material to form the first conductive layer, and then the through hole is filled with the second conductive material to form the second conductive layer. Form. Here, the first conductive material has higher fluidity than the second conductive material. Therefore, the first conductive material can easily penetrate into cracks generated in the exposed portions of the second piezoelectric body in the through holes, and the cracks can be reliably closed.

1 is a schematic plan view of an ink jet printer according to an embodiment. It is a top view of an inkjet head. It is the A section enlarged view of FIG. FIG. 4 is a sectional view taken along line IV-IV in FIG. 3. It is the B section enlarged view of FIG. It is a figure explaining the manufacturing process of a piezoelectric actuator. FIG. 6 is a partially enlarged sectional view corresponding to FIG. 5 of an ink jet head according to a modified embodiment. It is an enlarged view of the circumference | surroundings of the extraction electrode of the inkjet head of another modification. It is an enlarged view of the circumference | surroundings of the extraction electrode of the inkjet head of another modification. It is a partially expanded plan view of the inkjet head of another modification. It is a partially expanded plan view of the inkjet head of another modification. It is a partially expanded sectional view of the ink jet head concerning other indication invention.

  Next, an embodiment of the present invention will be described. FIG. 1 is a schematic plan view of the ink jet printer of the present embodiment. First, a schematic configuration of the inkjet printer 1 will be described with reference to FIG. In the following, the front side in FIG. 1 is defined as the upper side, and the other side of the page is defined as the lower side, and the explanation will be made using direction words “up” and “down” as appropriate.

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

  On the upper surface of the platen 2, a recording sheet 100 as a recording medium is placed. The carriage 3 is configured to reciprocate in the scanning direction along the two guide rails 10 and 11 in a region facing the platen 2. An endless belt 14 is connected to the carriage 3, and the endless belt 14 is driven by a carriage drive motor 15, whereby the carriage 3 moves in the scanning direction.

  The inkjet head 4 is attached to the carriage 3 and moves in the scanning direction together with the carriage 3. The inkjet head 4 is connected to ink cartridges 17 of four colors (for example, black, yellow, cyan, and magenta) mounted on the printer 1 by a tube (not shown). A plurality of nozzles 25 are formed on the lower surface of the inkjet head 4 (the surface on the opposite side of the paper surface in FIG. 1). The inkjet head 4 ejects the four colors of ink supplied from the ink cartridge 17 to the recording paper 100 placed on the platen 2 from the plurality of nozzles 25.

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

  The control device 6 includes a ROM (Read Only Memory), a RAM (Random Access Memory), an ASIC (Application Specific Integrated Circuit) including various control circuits, and the like. The control device 6 executes various processes such as printing on the recording paper 100 by the ASIC according to the program stored in the ROM. For example, in the printing process, the control device 6 controls the inkjet head 4, the carriage drive motor 15, and the like based on a print command input from an external device such as a PC, and prints an image or the like on the recording paper 100. . Specifically, an ink discharge operation for discharging ink while moving the inkjet head 4 in the scanning direction together with the carriage 3 and a transport operation for transporting the recording paper 100 in the transport direction by the transport rollers 18 and 19 alternately. Let me do it.

(Inkjet head)
Next, the inkjet head 4 will be described. FIG. 2 is a plan view of the inkjet head 4. FIG. 3 is an enlarged view of a portion A in FIG. 4 is a cross-sectional view taken along line IV-IV in FIG. 2 and 4, the COF 63 connected to the piezoelectric actuator 21 of the inkjet head 4 is schematically shown by a two-dot chain line. As shown in FIGS. 2 to 4, the inkjet head 4 includes a flow path unit 20 and a piezoelectric actuator 21.

(Configuration of flow path unit)
As shown in FIG. 4, the flow path unit 20 includes five flow path forming plates 31 to 35 each having a flow path forming hole and an ink sealing film 36 bonded to the upper surface of the flow path forming plate 31. And have. As can be understood from FIG. 2, the five flow path forming plates 31 to 35 have the same planar size. On the other hand, the ink sealing film 36 has a slightly smaller planar size than the flow path forming plates 31 to 35.

  The material of the five flow path forming plates 31 to 35 is not particularly limited. For example, the upper four flow path forming plates 31 to 34 are preferably made of a metal material having high corrosion resistance such as stainless steel. Can be used. The lowermost flow path forming plate 35 is a nozzle plate in which a plurality of nozzles 25 are formed. As the nozzle plate 35, a plate formed of a resin such as polyimide can be preferably used. As the ink sealing film 36, a material having a low ink permeability, for example, a metal material such as stainless steel can be suitably used. When the five flow path forming plates 31 to 35 are stacked, the flow path forming holes communicate with each other, so that the ink flow path as described below is formed in the flow path unit 20.

  As shown in FIG. 2, four ink cartridges 17 (FIG. 1) are disposed in the upstream area in the transport direction where the ink sealing film 36 is not joined on the upper surface of the flow path unit 20 (flow path forming plate 31). Four ink supply holes 23 connected to (see) are formed. Further, four manifolds 24 connected to the four ink supply holes 23 are formed inside the flow path unit 20. The four color inks of the four ink cartridges 17 (see FIG. 1) are supplied to the four manifolds 24 through the four ink supply holes 23, respectively. The four manifolds 24 extend in the transport direction.

  The flow path unit 20 includes a plurality of nozzles 25 formed on the lowermost plate 35 and a plurality of pressures formed on the uppermost plate 31 of the five flow path forming plates 31 to 35. A chamber 26 is provided. As shown in FIG. 2, a plurality of nozzles 25 are arranged along the transport direction on the lower surface of the flow path unit 20 (the surface on the other side in FIG. 3), and four rows corresponding to the four manifolds 24 respectively. A nozzle row is configured. Each pressure chamber 26 is a hole having a substantially rectangular planar shape that is long in the scanning direction.

  The plurality of pressure chambers 26 are arranged in four rows corresponding to the four manifolds 24 and the four nozzle rows. The plurality of pressure chambers 26 are covered from above by an ink sealing film 36 bonded to the upper surface of the flow path forming plate 31. Each pressure chamber 26 has a substantially elliptical planar shape that is long in the scanning direction. As shown in FIG. 4, one longitudinal end of each pressure chamber 26 communicates with the manifold 24, and the other longitudinal end communicates with the nozzle 25. As a result, the flow path unit 20 is formed with a plurality of individual ink flow paths that branch from the manifold 24 and reach the nozzles 25 through the pressure chambers 26.

(Configuration of piezoelectric actuator)
The piezoelectric actuator 21 is disposed on the upper surface of the ink sealing film 36 of the flow path unit 20. As shown in FIGS. 2 to 5, the piezoelectric actuator 21 includes two piezoelectric bodies 41 and 42, a plurality of individual electrodes 44, and a common electrode 45.

  The two piezoelectric bodies 41 and 42 are each made of a piezoelectric material mainly composed of lead zirconate titanate, which is a mixed crystal of lead titanate and lead zirconate. The piezoelectric bodies 41 and 42 are arranged on the upper surface of the ink sealing film 36 in a state where they are laminated. The lower piezoelectric body 42 is bonded to the ink sealing film 36 with an adhesive.

  The individual electrode 44 is formed on the upper surface of the piezoelectric layer 41 that is the surface opposite to the piezoelectric layer 42. The individual electrode 44 has a first electrode layer 51 and a second electrode layer 52. The first electrode layer 51 is thinly formed on the upper surface of the piezoelectric body 41 using, for example, a conductive material such as gold. The first electrode layer 51 has a main electrode portion 51a and a sub electrode portion 51b. The main electrode portion 51a has a substantially elliptical planar shape that is long in the scanning direction, and faces the central portion of the corresponding pressure chamber 26. The sub electrode portion 51b extends from one end portion in the longitudinal direction of the main electrode portion 51a on the upper surface of the piezoelectric body 41 to a region that does not face the pressure chamber 26 along the scanning direction. The second electrode layer 52 is provided so as to cover the sub electrode portion 51 b of the first electrode layer 51. The second electrode layer 52 is made of a conductive material different from that of the first electrode layer 51, for example, Ag—Pd, and the second electrode layer 52 is thicker than the first electrode layer 51. . For example, the thickness of the first electrode layer 51 is 0.5 μm or less, and the thickness of the second electrode layer 52 is 1.0 μm or more.

  Conductive bumps 53 are provided at the ends of the second electrode layer 52 of the individual electrodes 44. As shown in FIG. 4, a COF 63 that is a wiring member is pressed and bonded to the bump 53. Thereby, the individual electrode 44 is electrically connected to the COF 63 via the bump 53. The COF 63 is connected to the control device 6 (see FIG. 1) of the printer 1. The COF 63 is provided with a driver IC 64. The driver IC 64 switches the potential of each individual electrode 44 between a predetermined drive potential and a ground potential based on the ejection control signal from the control device 6.

  In the present embodiment, the reason why the individual electrode 44 is composed of two layers of the first electrode layer 51 and the second electrode layer 52 is as follows. The portion of the individual electrode 44 that overlaps the pressure chamber 26 is preferably as thin as possible so as not to inhibit the deformation of the piezoelectric bodies 41 and 42 as much as possible. Therefore, only the main electrode portion 51 a of the first electrode layer 51 is disposed in a region facing the central portion of the pressure chamber 26. On the other hand, it is preferable that the portion of the individual electrode 44 joined by the COF 63 and the bump 53 has a certain thickness so as to withstand the pressure when the COF 63 is joined. Further, since the sub electrode portion 51b has a smaller width than the main electrode portion 51a, there is a possibility that the sub electrode portion 51b may be disconnected. Therefore, the sub-electrode part 51b is reinforced by overlapping the second electrode layer 52 on the sub-electrode part 51b that does not face the pressure chamber 26.

  The common electrode 45 is disposed almost entirely between the two piezoelectric bodies 41 and 42. Further, the common electrode 45 faces each of the plurality of individual electrodes 44 with the upper piezoelectric body 41 interposed therebetween. The common electrode 45 is made of a conductive material such as Ag or Ag—Pd, for example.

  As shown in FIG. 2, two extraction electrodes 47 are provided apart from the plurality of individual electrodes 44 at both ends of the upper surface of the upper piezoelectric body 41 in the scanning direction. Further, the two extraction electrodes 47 are arranged side by side in the scanning direction with respect to the plurality of individual electrodes 44 positioned on the center side in the scanning direction. Each extraction electrode 47 extends in the transport direction, which is the arrangement direction of the individual electrodes 44, and is aligned with a part (seven in FIG. 2) of the individual electrodes 44 in the scanning direction.

  These two extraction electrodes 47 are formed of the same conductive material (for example, Ag or Ag—Pd) as the second electrode layer 52 of the individual electrode 44. As will be described later, the two extraction electrodes 47 are electrically connected to a common electrode 45 disposed between the two piezoelectric bodies 41 and 42. In addition, conductive bumps 54 are provided on the extraction electrode 47, and COF 63 is pressed against the bumps 54 to join them. Thereby, the extraction electrode 47 is connected to the ground wiring formed in the COF 63, and the common electrode 45 is held at the ground potential.

  Next, the electrical connection structure between the extraction electrode 47 and the common electrode 45 will be described in detail. FIG. 5 is an enlarged view of a portion B in FIG. As shown in FIG. 2, a through hole 41 a penetrating the piezoelectric body 41 is provided on the upper end of the upper piezoelectric body 41 at the scanning direction end where the extraction electrode 47 is formed. One is formed. As shown in FIGS. 2 and 3, each through hole 41a has a through hole 41a that is more than the outer edge in the scanning direction of the extraction electrode 47 when viewed from the vertical direction that is the stacking direction of the two piezoelectric bodies 41 and. The edges of the bulge protrude a little outside. As a result, as shown in FIG. 5, the lead electrode 47 is formed at the edge of the through hole 41a on the individual electrode 44 side, while at the end of the through hole 41a opposite to the individual electrode 44. The extraction electrode 47 is not formed.

  In the through hole 41a, a conduction portion 46 for conducting the common electrode 45 and the extraction electrode 47 is disposed. The conduction part 46 includes a first conductive layer 55 and a second conductive layer 56.

  The first conductive layer 55 covers the lower piezoelectric body 42 and the entire portion of the common electrode 45 formed on the upper surface of the piezoelectric body 42 that is exposed from the upper piezoelectric body 41 in the through hole 41a. Is provided. Hereinafter, for convenience of explanation, a portion of the lower piezoelectric body 42 exposed from the piezoelectric body 41 in the through hole 41a is particularly referred to as an “exposed portion 42a”. In the present embodiment, the common electrode 45 is formed over the entire upper surface of the exposed portion 42 a of the piezoelectric body 42. The first conductive layer 55 is formed thin with the same material (for example, gold) as the first electrode layer 51 of the individual electrode 44. The first conductive layer 55 is electrically connected to the common electrode 45 by contacting the common electrode 45 disposed on the exposed portion 42 a of the piezoelectric body 42.

  Note that the first conductive layer 55 is not only through the exposed portion 42a of the piezoelectric body 42 that becomes the bottom surface of the through hole 41a, but also from the exposed portion 42a through the side surface of the through hole 41a closer to the individual electrode 44. The hole 41a is formed up to the edge on the individual electrode 44 side.

  The second conductive layer 56 is formed so as to overlap the first conductive layer 55. The second conductive layer 56 is formed of a material different from that of the first conductive layer 55 and the same material as the second electrode layer 52 of the extraction electrode 47 and the individual electrode 44 (for example, Ag or Ag-Pd). Has been. The second conductive layer 56 is thicker than the first conductive layer 55. For example, the thickness of the first conductive layer 55 is 0.5 μm or less, and the thickness of the second conductive layer 56 is 1.0 μm or more. As described above, the extraction electrode 47 is not disposed so as to surround the through hole 41a, but is disposed only at the edge of the through hole 41a on the individual electrode 44 side. The second conductive layer 56 of the conduction portion 46 is formed from the bottom surface of the through hole 41a to the side surface on the individual electrode 44 side, and is electrically connected to the extraction electrode 47 at the edge portion of the through hole 41a on the individual electrode 44 side. Yes.

  As described above, the common electrode 45 and the extraction electrode 47 are electrically connected by the conductive portion 46 having the first conductive layer 55 and the second conductive layer 56 in the through hole 41a. Here, in the present embodiment, the reason why the conductive portion 46 in the through hole 41a is composed of two layers of the first conductive layer 55 and the second conductive layer 56 is that the piezoelectric layer on the lower side as shown in FIG. When the crack 58 is generated in the exposed portion 42 a of the body 42, the excessive adhesive 57 when the piezoelectric actuator 21 is joined to the flow path unit 20 with the adhesive 57 is prevented from seeping through the crack 58. Because. Details thereof will be described later.

  In addition, the portion of the piezoelectric body 41 sandwiched between the individual electrode 44 and the common electrode 45 shown in FIG. The active part 40 is polarized downward in the thickness direction, that is, in a direction from the individual electrode 44 toward the common electrode 45.

  The operation of the piezoelectric actuator 21 described above when ejecting ink from the nozzle 25 is as follows. It is assumed that the potential of a certain individual electrode 44 is switched from the ground potential to the drive potential by the driver IC 64. At this time, a potential difference is generated between the individual electrode 44 and the common electrode 45 held at the ground potential. Thereby, an electric field in the thickness direction is generated in the active portion 40 of the piezoelectric body 41 shown in FIG. Further, since the polarization direction of the active portion 40 and the direction of the electric field coincide with each other, the active portion 40 extends in the thickness direction, which is the polarization direction, and contracts in the plane direction. As the active portion 40 contracts and deforms, the two piezoelectric bodies 41 and 42 are bent so as to protrude toward the pressure chamber 26. As a result, the volume of the pressure chamber 26 is reduced, pressure is applied to the ink inside the pressure chamber 26, and ink droplets are ejected from the nozzle 25 communicating with the pressure chamber 26.

  Next, the manufacturing process of the piezoelectric actuator 21 described above will be described. FIG. 6 is a diagram for explaining a manufacturing process of the piezoelectric actuator 21.

(Through hole forming process)
First, as shown in FIG. 6A, a through hole 41 a is formed in an unfired green sheet 71 that becomes the upper piezoelectric body 41. The through hole 41a can be formed by a known method such as punching or laser processing.

(Common electrode formation process)
Also, as shown in FIG. 6B, the common electrode 45 is formed on one surface of another unfired green sheet 72 that becomes the lower piezoelectric body 42. The formation of the common electrode 45 can be performed by a known method such as screen printing, vapor deposition, or CVD.

(Lamination process, firing process)
Next, as shown in FIG. 6 (c), the green sheet 71 in which the through hole 41a is formed and the green sheet 72 in which the common electrode 45 is formed are sandwiched between them. Laminate. The two stacked green sheets 71 and 72 are then fired by heating at a predetermined temperature to obtain a stacked body of two piezoelectric bodies 41 and 42.

(Individual electrode, extraction electrode, conductive part formation process)
Next, the individual electrode 44 and the extraction electrode 47 are formed on the upper surface of the piezoelectric body 41, and the conduction portion 46 is formed in the through hole 41a.

  First, as shown in FIG. 6 (d), a plurality of conductive films such as gold are mixed with a predetermined solvent on the upper surface of the piezoelectric body 41 by screen printing or the like using a first conductive paste. The first electrode layer 51 of the individual electrode 44 is formed. At this time, at the same time, the first conductive paste is attached to the edge of the through hole 41a (particularly, the edge on the left side in the drawing on the individual electrode 44 side), and flows into the through hole 41a from this edge, The first conductive paste is filled into the through hole 41a. Thereby, the first conductive layer 55 of the conductive portion 46 is formed in the through hole 41a so as to cover the entire exposed portion 42a of the piezoelectric body 42. Note that the first conductive paste used here has a fairly high fluidity. Since such highly fluid conductive paste spreads quickly on the upper surface of the piezoelectric body, the first electrode layer 51 and the first conductive layer 55 formed by the first conductive paste have a small thickness.

  Next, as shown in FIG. 6E, a second conductive paste obtained by mixing a conductive material such as Ag or Ag-Pd with a predetermined solvent on the upper surface of the piezoelectric body 41 is used. The second electrode layer 52 of the plurality of individual electrodes 44 and the extraction electrode 47 are formed simultaneously by screen printing or the like. The through hole 41a formed in the piezoelectric body 41 is slightly shifted to the opposite side to the individual electrode 44 with respect to the region where the extraction electrode 47 is formed (screen printing printing region when the extraction electrode 47 is formed). ing. Therefore, when the extraction electrode 47 is formed, the second conductive paste adheres only to the edge of the through hole 41a on the individual electrode 44 side, and flows into the through hole 41a from this edge to be filled. This filled second conductive paste becomes the second conductive layer 56 covering the first conductive layer 55. As a result, the extraction electrode 47 is formed at the edge of the through hole 41a on the individual electrode 44 side, but the extraction electrode 47 is not formed at the edge of the through hole 41a opposite to the individual electrode 44.

  Here, the fluidity of the first conductive paste used when forming the first conductive layer 55 of the conductive portion 46 is greater than the fluidity of the second conductive paste used when forming the second conductive layer 56. Is also expensive. That is, the viscosity of the second conductive paste is higher than the viscosity of the first conductive paste, and the second conductive paste is less likely to spread than the first conductive paste. Therefore, the second electrode layer 52 and the second conductive layer 56 formed of the second conductive paste are thicker than the first electrode layer 51 and the second conductive layer 56 formed of the first conductive paste. It will be a thing.

  By the way, cracks may occur in the piezoelectric bodies 41 and 42 that are brittle materials during the firing step, the handling after firing, and the like before the step of forming the individual electrodes 44. In particular, as shown in FIG. 5, a crack 58 is likely to occur in the exposed portion 42 a of the lower piezoelectric body 42. However, when the first conductive paste is filled in the through hole 41a, a part of the conductive paste penetrates into the crack 58 from the exposed portion 42a of the piezoelectric body 42, so that the crack 58 is blocked. In addition, the first conductive paste has higher fluidity than the second conductive paste, so that it easily penetrates into the crack 58 and the crack 58 is surely closed. In addition, since the first conductive layer 55 covers the entire exposed portion 42a of the piezoelectric body 42, the first conductive paste penetrates into the crack 58 regardless of the position of the crack 58 in the exposed portion 42a. Can be closed.

  However, the first conductive layer 55 formed of the first fluid paste having high fluidity is thin, and the conduction reliability between the common electrode 45 and the extraction electrode 47 by the conduction part 46 is only with such a thin first conductive layer 55. The nature is low. Therefore, the second conductive layer 56 having a thickness larger than that of the first conductive layer 55 is formed so as to improve the conduction reliability in the through hole 41a.

  In the present embodiment, not only the conduction portion 46 but also the individual electrode 44 is formed of two layers. The first electrode layer 51 of the individual electrode 44 and the first conductive layer 55 of the conduction part 46 are formed of the first conductive paste, and the second electrode layer 52 of the individual electrode 44 and the second conductive layer of the conduction part 46 are formed. 56 is formed by the second conductive paste. Therefore, as described above, the first electrode layer 51 and the first conductive layer 55 are formed at a time by screen printing or the like, and the second electrode layer 52 and the second conductive layer 56 are formed at a time by screen printing. Is possible.

(Joining process)
The piezoelectric actuator 21 manufactured through the processes described above is bonded to the upper surface of the ink sealing film 36 of the flow path unit 20 as shown in FIG. Specifically, first, a thermosetting adhesive 57 is applied to the upper surface of the ink sealing film 36. Next, the piezoelectric body 42 of the piezoelectric actuator 21 is placed on the upper surface of the ink sealing film 36 via the adhesive 57. Then, while heating the piezoelectric actuator 21 with a heater (not shown), the piezoelectric actuator 21 is pressed against and bonded to the flow path unit 20.

  When cracks 58 are generated in the piezoelectric body 41 as shown in FIG. 5 in the process prior to the joining process, excess adhesive 57 passes through the cracks 58 during the joining process and passes through the holes 41a. There is a possibility that it may ooze out to the inside or the surface of the piezoelectric body. However, as described above, when the first conductive layer 55 of the conductive portion 46 is formed, the first conductive paste penetrates the crack 58 and closes the crack 58. Can be prevented.

  Needless to say, cracks 58 are generated in portions other than the exposed portion 42 a of the piezoelectric body 42. However, even if a crack 58 occurs in a portion other than the exposed portion 42a, because another piezoelectric body 41 exists on the crack 58, even if excess adhesive 57 penetrates into the crack 58, The adhesive 57 does not ooze up to the upper surface of the upper piezoelectric body 41.

  However, the generation of the crack 58 in the exposed portion 42a of the piezoelectric body 42 may occur not only during the manufacturing of the piezoelectric actuator 21 such as the firing process but also when the piezoelectric actuator 21 is pressed in the joining process. At the stage of the joining process, since the conductive part 46 in the through hole 41a is already formed, the cracks generated during the joining process are infiltrated with the first conductive paste that forms the conductive part 46. I can't say that. Therefore, even when the adhesive 57 oozes out from the crack generated in the exposed portion 42a of the piezoelectric body into the through hole 41a, the adhesive 57 is applied to the individual electrode 44 formed on the upper surface of the piezoelectric body 41. It is preferable to avoid the adverse effect on the driving of the piezoelectric actuator 21 as much as possible.

  In this regard, in the present embodiment, the extraction electrode 47 is formed on the edge of the through hole 41a on the individual electrode 44 side, but the extraction electrode 47 is formed on the edge opposite to the individual electrode 44. Absent. As a result, the adhesive 57 oozes out from the crack generated in the exposed portion 42a into the through hole 41a, and when the adhesive 57 is about to overflow from the through hole 41a, the through electrode 41 side of the through hole 41a. A part of the extraction electrode 47 formed on the edge of the metal serves as a bank to prevent the adhesive 57 from flowing to the individual electrode 44. Therefore, the excess adhesive 57 overflowing from the through hole 41a mainly flows on the opposite side of the individual electrode 44 without a dike, and the adhesive 57 is prevented from spreading to the individual electrode 44. .

  In the embodiment described above, the inkjet head 4 corresponds to the liquid ejection apparatus of the present invention. The flow path unit 20 corresponds to the flow path structure of the present invention. The upper piezoelectric body 41 corresponds to the first piezoelectric body of the present invention. The lower piezoelectric body 42 corresponds to the second piezoelectric body of the present invention. The individual electrode 44 corresponds to the first electrode of the present invention. The common electrode 45 corresponds to the second electrode of the present invention. The first conductive paste corresponds to the first conductive material of the present invention. The second conductive paste corresponds to the second conductive material of the present invention.

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

1] In the above embodiment, the first conductive layer 55 and the second conductive layer 56 of the conductive portion 46 are formed of different materials, but the first conductive layer 55 and the second conductive layer 56 are formed of the same material. May be. For example, by mixing the same conductive material with two types of solvents having different fluidity, the first conductive paste and the second conductive paste having the same conductive particles but different fluidity are produced. be able to.

  Further, there is no particular problem even if the first conductive layer 55 and the second conductive layer 56 are formed using the same conductive paste. In this case, the first conductive layer 55 and the second conductive layer 56 have substantially the same thickness. The purpose of the second conductive layer 56 is mainly to improve the conduction reliability. In this sense, the second conductive layer 56 is more effective when the thickness is larger. Even if it is thinner than the first conductive layer 55, a certain degree of improvement in conduction reliability can be obtained.

2] In the above embodiment, as shown in FIG. 5, both the first conductive layer 55 and the second conductive layer 56 of the conductive portion 46 cover the entire exposed portion 42 a of the piezoelectric body 42. The first conductive layer 55 is preferably formed so as to cover the entire exposed portion 42a in order to reliably close a crack generated in the exposed portion 42a of the piezoelectric body 42. However, the second conductive layer 56 only needs to be able to reliably connect the extraction electrode 47 and the common electrode 45. From this viewpoint, the second conductive layer 56 is at least on the individual electrode 44 side (extraction electrode) of the exposed portion 42a. 47 side). That is, unlike the first conductive layer 55, the second conductive layer 56 need not be provided on the entire exposed portion 42 a of the piezoelectric body 42. Therefore, as shown in FIG. 7A, the second conductive layer 56 may be formed only on a part of the exposed portion 42a of the piezoelectric body on the individual electrode 44 side.

  Further, as shown in FIG. 7B, when the thickness of the first conductive layer 55 is thinner than the second conductive layer 56, the first conductive layer 55 is opposite to the individual electrode 44 of the through hole 41a. It may rest on the side edge. When the first conductive layer 55 is formed, the first conductive paste is attached to both the edge of the through hole 41a on the individual electrode 44 side and the edge on the opposite side of the individual electrode 44, so that the through hole 41a is formed. On the other hand, the first conductive paste can be introduced from both sides, and the first conductive layer 55 can be formed so as to reliably cover the entire exposed portion 42a of the piezoelectric body. On the other hand, in this configuration, the first conductive layer 55 is formed on both the edge on the individual electrode 44 side of the through hole 41 a and the edge on the opposite side to the individual electrode 44. However, since the second conductive layer 56 having a large thickness exists at the edge portion on the individual electrode 44 side, the adhesive that has oozed into the through hole 41a is difficult to flow out to the individual electrode 44 side.

3] The through-hole 41a is unintentionally formed by the positional displacement when the through-hole 41a is formed in the piezoelectric body 41 or the positional displacement when the extraction electrode 47 is formed on the piezoelectric body 41 by printing or the like. It is conceivable that 41 falls within the region where the extraction electrode 47 is formed. In this case, the extraction electrode 47 is arranged over the entire circumference of the edge of the through hole 41a. In this case, when the adhesive 57 oozes out into the through hole 41a through the crack, the adhesive 57 can flow out from the through hole 41a in any direction. That is, it is difficult to escape the adhesive 57 only to the side opposite to the individual electrode 44 and prevent the adhesive 57 from flowing to the individual electrode 44 side.

  In this regard, the through hole 41a may be formed in a shape that is long in the scanning direction, which is the direction in which the individual electrode 44 and the extraction electrode 47 are arranged. For example, in FIG. 8, the through hole 41a has a long hole shape that is long in the scanning direction. In this embodiment, even if the positions of the through hole 41a and the extraction electrode 47 are slightly shifted in the scanning direction, the through hole 41a does not fall within the region where the extraction electrode 47 is formed.

  Alternatively, as shown in FIG. 9, even if the positions in the scanning direction, which is the arrangement direction of the individual electrodes 44 and the extraction electrodes 47, are different between the plurality of through holes 41 a provided for one extraction electrode 47. Good. In this embodiment, since the positions of the plurality of through holes 41a in the arrangement direction of the individual electrodes 44 and the extraction electrodes 47 are different, the extraction electrodes 47 and the through holes 41a may be formed with a slight shift in this direction. This does not mean that all the through holes 41a are accommodated in the region where the extraction electrode 47 is formed.

4] In the above embodiment, the through hole 41a is formed so as to partially overlap the region of the upper surface of the piezoelectric body 41 where the extraction electrode 47 is formed. However, as shown in FIG. May be disposed so as to be within the region where the extraction electrode 47 is formed. In this case, exudation of the adhesive 57 due to cracks generated during the joining process cannot be prevented, but if the cracks occurred before the joining process, they can be blocked during the formation of the first conductive layer 55 of the conductive portion 46. it can.

5] The arrangement of the first electrode layer 51 and the second electrode layer 52 constituting the individual electrode 44 is not limited to the arrangement relationship as in the above embodiment. That is, the individual electrode 44 can be changed as appropriate according to the purpose of configuring the individual electrode 44 with two layers. For example, if the reinforcement of the joint portion with the COF 63 where pressing force acts when joining with the COF 63 is mainly considered, the second electrode layer 52 is formed only at the distal end portion of the sub electrode portion 51b of the first electrode layer 51. May be. Further, from the viewpoint of reinforcement (improvement of durability) of the main electrode portion 51a that is deformed immediately above the pressure chamber 26, as shown in FIG. Layer 52 may be overlaid.

  In addition, the individual electrode 44 is not necessarily configured by the two electrode layers 51 and 52, and the individual electrode 44 may be formed by one electrode layer.

6] The number of stacked piezoelectric bodies is not limited to two, and the present invention can also be applied to a piezoelectric actuator in which three or more piezoelectric bodies are stacked.

  In the above-described embodiment and its modifications, the present invention is applied to an inkjet head that prints an image or the like by ejecting ink onto a recording sheet. The present invention can also be applied to a liquid ejection apparatus that is used. For example, the present invention can also be applied to a liquid ejection device that ejects a conductive liquid onto a substrate to form a conductive pattern on the substrate surface. Furthermore, the piezoelectric actuator of the present invention is not limited to those used for liquid ejection applications, and the present invention can be applied to piezoelectric actuators used for other applications.

Next, disclosed inventions other than the inventions according to claims 1 to 8 described in the claims at the beginning of the application will be described.
That is, a first piezoelectric body, a second piezoelectric body stacked on the first piezoelectric body, a first electrode disposed on a surface of the first piezoelectric body opposite to the second piezoelectric body, A second electrode disposed between the first piezoelectric body and the second piezoelectric body; and a surface of the first piezoelectric body opposite to the second piezoelectric body and disposed away from the first electrode. An extraction electrode; and a conductive portion that is disposed in a through hole that penetrates the first piezoelectric body in a region where the extraction electrode of the first piezoelectric body is formed, and that electrically connects the second electrode and the extraction electrode; Have
On the surface of the first piezoelectric body opposite to the second piezoelectric body, the first electrode and the extraction electrode are arranged side by side in a predetermined direction, and the first piezoelectric body and the second piezoelectric body On the opposite surface, the first electrode and the extraction electrode are arranged side by side in a predetermined direction, and the extraction electrode is formed at an edge of the through hole on the first electrode side in the predetermined direction, It is an invention of a piezoelectric actuator characterized in that it is not formed at the edge of the through hole opposite to the first electrode in the predetermined direction.

  The disclosed invention corresponds to claim 4 of the scope of claims at the beginning of the application, but the technical scope of the disclosed invention includes those not premised on the configuration of claim 1. That is, the conductive portion disposed in the through hole is not premised on the configuration having the first conductive layer and the second conductive layer, and the conductive portion includes only one conductive layer. included.

  Hereinafter, exemplary embodiments of the disclosed invention will be described. As shown in FIG. 12, the piezoelectric actuator 81 has a conducting portion 96 that is disposed in the through hole 91 a of the piezoelectric body 91 and conducts the common electrode 95 and the extraction electrode 97. Unlike the above-described embodiment, the conductive portion 96 is composed of only one conductive layer. On the upper surface of the piezoelectric body 91, the individual electrode 94 and the extraction electrode 97 are arranged side by side in the scanning direction. Further, the through hole 91a is arranged so as to be shifted to the opposite side to the individual electrode 94 with respect to the region where the extraction electrode 97 is formed. Therefore, the lead electrode 97 is formed on the edge of the through hole 91a on the individual electrode 94 side, but the lead electrode 97 is not formed on the edge on the opposite side of the individual electrode 94.

  Therefore, when the piezoelectric actuator 81 is joined to the flow path unit 80, the adhesive 87 has oozed out into the through hole 91a through the crack 88 generated in the exposed portion 92a of the piezoelectric body 92 in the through hole 91a. Even in this case, the adhesive 87 flows to the side opposite to the individual electrode 94 where the extraction electrode 97 is not present. Therefore, the adhesive 87 is prevented from spreading to the individual electrode 94.

4 Ink-jet head 20 Flow path unit 21 Piezoelectric actuator 41 Piezoelectric body 41a Through hole 42 Piezoelectric body 42a Exposed portion 44 Individual electrode 45 Common electrode 46 Conducting portion 47 Extraction electrode 51 First electrode layer 52 Second electrode layer 55 First conductive layer 56 Second conductive layer 57 Adhesive 58 Crack

Claims (9)

A first piezoelectric body;
A second piezoelectric body laminated on the first piezoelectric body;
A first electrode disposed on a surface of the first piezoelectric body opposite to the second piezoelectric body;
A second electrode disposed between the first piezoelectric body and the second piezoelectric body;
An extraction electrode disposed on the surface of the first piezoelectric body opposite to the second piezoelectric body and spaced apart from the first electrode;
A conductive portion that is disposed in a through hole that penetrates the first piezoelectric body in a region where the extraction electrode of the first piezoelectric body is formed, and that conducts the second electrode and the extraction electrode;
The conduction part is
A first conductive layer provided so as to cover a portion of the second piezoelectric body exposed from the first piezoelectric body in the through hole;
A second conductive layer formed overlying the first conductive layer;
Have
On the surface of the first piezoelectric body opposite to the second piezoelectric body, the first electrode and the extraction electrode are arranged side by side in a predetermined direction,
The extraction electrode is formed at the edge of the through hole on the first electrode side in the predetermined direction, and is formed at the edge of the through hole on the opposite side of the first electrode in the predetermined direction. Piezoelectric actuator characterized by not.   The piezoelectric actuator according to claim 1, wherein the first conductive layer is thinner than the second conductive layer. The first electrode has a first electrode layer and a second electrode layer provided so as to cover the first electrode layer,
The first electrode layer of the first electrode and the first conductive layer of the conduction portion are formed of the same material,
3. The piezoelectric actuator according to claim 1, wherein the second electrode layer of the first electrode and the second conductive layer of the conducting portion are formed of the same material. The first conductive layer is formed to cover the entire exposed portion of the second piezoelectric body in the through hole,
The said 2nd conductive layer is formed only in the at least one part by the side of the said 1st electrode among the said exposed parts of the said 2nd piezoelectric material, The Claim 1 characterized by the above-mentioned. Piezoelectric actuator.   5. The piezoelectric actuator according to claim 1, wherein the through hole has a shape that is long in the predetermined direction when viewed from the stacking direction of the first piezoelectric body and the second piezoelectric body. A plurality of the first electrodes are arranged in an electrode arrangement direction orthogonal to the predetermined direction,
The extraction electrode extends along the electrode arrangement direction,
The plurality of through holes are arranged along the electrode arrangement direction,
The piezoelectric actuator according to claim 1, wherein positions in the predetermined direction are different among the plurality of through holes. A first piezoelectric body;
A second piezoelectric body laminated on the first piezoelectric body;
A first electrode disposed on a surface of the first piezoelectric body opposite to the second piezoelectric body;
A second electrode disposed between the first piezoelectric body and the second piezoelectric body;
An extraction electrode disposed on the surface of the first piezoelectric body opposite to the second piezoelectric body and spaced apart from the first electrode;
A conductive portion that is disposed in a through hole that penetrates the first piezoelectric body in a region where the extraction electrode of the first piezoelectric body is formed, and that conducts the second electrode and the extraction electrode;
On the surface of the first piezoelectric body opposite to the second piezoelectric body, the first electrode and the extraction electrode are arranged side by side in a predetermined direction ,
Before SL lead electrode, the through hole, wherein the edge of the first electrode side in a predetermined direction is formed, the through-hole, the edge opposite to the first electrode in the predetermined direction is formed A piezoelectric actuator characterized by not being provided. A flow path structure having a liquid flow path including a plurality of nozzles, and a piezoelectric actuator joined to the flow path structure,
The piezoelectric actuator is
A first piezoelectric body;
A second piezoelectric body disposed on the flow path structure side with respect to the first piezoelectric body and laminated on the first piezoelectric body;
A first electrode disposed on a surface of the first piezoelectric body opposite to the second piezoelectric body;
A second electrode disposed between the first piezoelectric body and the second piezoelectric body;
An extraction electrode disposed on the surface of the first piezoelectric body opposite to the second piezoelectric body and spaced apart from the first electrode;
A conductive portion that is disposed in a through hole that penetrates the first piezoelectric body in a region where the extraction electrode of the first piezoelectric body is formed, and that conducts the second electrode and the extraction electrode;
The conduction part is
A first conductive layer provided so as to cover a portion of the second piezoelectric body exposed from the first piezoelectric body in the through hole;
A second conductive layer formed overlying the first conductive layer;
Have
On the surface of the first piezoelectric body opposite to the second piezoelectric body, the first electrode and the extraction electrode are arranged side by side in a predetermined direction,
The extraction electrode is formed at the edge of the through hole on the first electrode side in the predetermined direction, and is formed at the edge of the through hole on the opposite side of the first electrode in the predetermined direction. A liquid ejection device characterized by not having the above. A method of manufacturing a piezoelectric actuator according to any one of claims 1 to 6,
A first conductive layer forming step of forming the first conductive layer by filling a first conductive material into the through hole penetrating the first piezoelectric body;
A second conductive layer forming step of forming the second conductive layer by filling the through hole with a second conductive material after the first conductive layer forming step;
The fluidity of the first conductive material is higher than the fluidity of the second conductive material,
The extraction electrode is formed on the edge of the through hole on the first electrode side in the predetermined direction, and is not formed on the edge of the through hole on the opposite side of the first electrode in the predetermined direction. A method for manufacturing a piezoelectric actuator.

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