JP5240001B2 - Piezoelectric actuator manufacturing method, piezoelectric actuator, and liquid transfer device - Google Patents

Description

  The present invention relates to a method for manufacturing a piezoelectric actuator, a piezoelectric actuator, and a liquid transfer device.

  2. Description of the Related Art Conventionally, a piezoelectric actuator that has a diaphragm and a piezoelectric layer formed on the diaphragm, and drives the driving target by bending the diaphragm due to deformation (piezoelectric strain) of the piezoelectric layer when an electric field is applied. Are known. As a method for manufacturing such a piezoelectric actuator, a method is known in which a manufactured piezoelectric layer is pressed against a diaphragm and bonded. Here, the manufactured piezoelectric layer may have unevenness and waviness in the manufacturing process.

  Therefore, in the piezoelectric actuator described in Patent Document 1, an electrode having a larger shrinkage rate in a direction parallel to the surface than the green sheet is stacked on the green sheet, and is lowered at the firing temperature. Irregularities and undulations in the piezoelectric layer after firing are suppressed.

JP 2004-349688 A

  However, in the piezoelectric actuator described in Patent Document 1, even if the electrode arranged on the piezoelectric layer is used to suppress unevenness and waviness of the piezoelectric layer, this electrode acts on the active portion of the piezoelectric layer. In addition, it is necessary to arrange in a predetermined shape at a predetermined position. As described above, since the position and shape of the electrode are limited in order to fulfill the original purpose and the position and shape cannot be freely determined, the unevenness and the undulation of the piezoelectric layer may not be effectively suppressed. .

  When the piezoelectric layer with the irregularities and undulations is pressed and joined to the diaphragm, the irregularities and undulations are corrected and the piezoelectric layer becomes flat. At this time, a compressive stress acts on one side and a tensile stress acts on the other side with respect to the neutral surface of the piezoelectric layer. Since the active portion of the piezoelectric layer is deformed by the action of an electric field and drives the target, if a stress is applied to the active portion, the deformation of the active portion is constrained and the amount of deformation is reduced. That is, the apparent piezoelectric characteristics of the active part are reduced.

  On the other hand, when the piezoelectric layer and the vibration plate are pressed and heat-bonded with a thermosetting resin or the like, if the linear expansion coefficient of the piezoelectric layer is smaller than the vibration plate, compressive stress remains in the piezoelectric layer after heat-bonding and cooling To do. On the other hand, when manufacturing an electrode made of a piezoelectric layer and a material having a larger linear expansion coefficient than that of the piezoelectric layer, if the green sheet and the electrode that become the piezoelectric layer are integrally fired, Since the electrode having a larger expansion coefficient contracts than the piezoelectric layer, compressive stress remains in the piezoelectric layer. The active portion having the residual compressive stress is restrained from being deformed, and the amount of deformation is reduced. That is, the apparent piezoelectric characteristics of the active part are reduced.

  In this way, the piezoelectric layer with unevenness and waviness is pressed and joined to the diaphragm, and the unevenness and waviness are corrected, whereby compressive stress or tensile stress acts on the piezoelectric layer depending on the position in the thickness direction. . When the position of the active part is a position that receives only the compressive stress, the residual compressive stress described above is added to the compressive stress generated by correcting irregularities and waviness, and the apparent piezoelectric characteristics of the active part are degraded. On the other hand, when the position of the active part is a position where only the tensile stress is received, the tensile stress generated by correcting the unevenness and the undulation and the above-described residual compressive stress are offset, and the apparent piezoelectric characteristics of the active part do not deteriorate. (The apparent piezoelectric characteristics are improved as compared with the case where compressive stress remains). That is, the stress acting on the active portion varies depending on the relationship between the unevenness and waviness of the piezoelectric layer and the position of the active portion, and the piezoelectric characteristics of the active portion deviate from desired characteristics.

  Accordingly, an object of the present invention is to provide a method of manufacturing a piezoelectric actuator, a piezoelectric actuator, and a liquid transfer device that can make the piezoelectric characteristics of an active portion almost desired.

Method for manufacturing a piezoelectric actuator of the present invention, have a first active portion in a part of the thickness direction and a piezoelectric said first active section Ru is disposed so as to overlap the pressure chambers in plan view, the piezoelectric A piezoelectric actuator formed of a material larger than the linear expansion coefficient of the body and bonded to one surface of the piezoelectric body, wherein the first active portion is a neutral of the piezoelectric body A piezoelectric body forming step of forming the piezoelectric body and a region of the piezoelectric body that overlaps the first active portion in plan view, the first body being disposed on one side with respect to the thickness direction with respect to the surface. 1 including a removal step of removing at least a part in the thickness direction of a portion other than the active portion, and a heating and joining step of heating and pressing the piezoelectric body and the vibration plate, the in plan view of the piezoelectric first Neutral plane in the region overlapping with the active portion, so as to be located substantially in the center for the first active portion thickness direction, are disposed on the opposite side to the one side about the thickness direction with respect to the neutral plane of the piezoelectric body In addition, at least a part of the portion other than the first active portion in the region overlapping the first active portion in a plan view is removed from the surface side away from the first active portion. The neutral surface is a surface that is not distorted when a bending moment is applied.

  According to the method for manufacturing a piezoelectric actuator of the present invention, after the heat-bonding step, the piezoelectric body is compressed to an environmental temperature, and thermal distortion occurs due to the difference in the linear expansion coefficient between the piezoelectric body and the diaphragm. Occurs. Further, in the removing step, at least a part in the thickness direction of the portion other than the first active portion in the region overlapping with the first active portion of the piezoelectric body is removed from the surface side away from the first active portion of the piezoelectric body. ing. By removing a part of the piezoelectric body in the region overlapping the first active part in plan view of the piezoelectric body, the neutral surface is displaced in that region and approaches the center of the first active part in the thickness direction. Thereby, when the piezoelectric body and the diaphragm are pressed and joined, if the unevenness and waviness of the piezoelectric body are corrected, the area where the compressive stress acts on the first active portion and the area where the tensile stress acts are almost the same size. It becomes. Here, in the region where the compressive stress acts on the first active portion when the above-described unevenness and undulation are corrected, the compressive stress generated by the thermal strain is added, and only the compressive stress generated by the thermal strain acts. Compared to the case, since a large compressive stress acts on the piezoelectric body, the deformation of the active portion in the region is restrained, so that the apparent piezoelectric characteristics of the active portion are deteriorated. On the other hand, in the region where tensile stress acts on the first active part when correcting the above unevenness and waviness, only the compressive stress caused by thermal strain acts by offsetting the compressive stress caused by thermal strain. Since the compressive stress acting on the piezoelectric body is smaller than in the case where the active portion is present, the deformation of the active portion in that region is not constrained, and the apparent piezoelectric characteristics of the active portion are improved. As a result, as a whole first active portion, it is possible to cancel out the fluctuation of the piezoelectric characteristics between the region where the piezoelectric characteristics are reduced and the region where the piezoelectric properties are improved, and the first active portion is brought to almost the desired piezoelectric characteristics. can do.

Further, in another aspect, the method for manufacturing a piezoelectric actuator of the present invention, have a first active portion in a part of the thickness direction, and the first active portion is arranged so as to overlap with the pressure chambers in plan view A piezoelectric body, an electrode made of a material having a larger linear expansion coefficient than the piezoelectric body for applying an electric field to the first active portion, and a diaphragm bonded to one surface of the piezoelectric body. In the method of manufacturing an actuator, the first active portion is arranged to be biased to one side in the thickness direction with respect to the neutral surface of the piezoelectric body, and the piezoelectric body and the electrode are integrally fired. Forming piezoelectric body firing step, removing step of removing at least a part of the piezoelectric body in a thickness direction of a portion other than the first active portion in a region overlapping the first active portion in plan view, Press and bond the piezoelectric body and the diaphragm And covering step comprises a, in the removing step, so that the neutral plane in the region overlapping with the first active portion in plan view of the piezoelectric body is located substantially centrally about the thickness direction of the first active portion Further, the thickness direction of the portion other than the first active part in the region overlapping the first active part in plan view, disposed on the opposite side to the one side in the thickness direction with respect to the neutral surface of the piezoelectric body At least a part of is removed from the surface side away from the first active part.

  According to the method for manufacturing a piezoelectric actuator of the present invention, in the piezoelectric body firing step, the piezoelectric body and the electrode made of a material having a larger linear expansion coefficient than the piezoelectric body are integrally fired to form and fire and cool to the environmental temperature. Then, a compressive stress is generated in the piezoelectric body due to a difference in linear expansion coefficient between the piezoelectric body and the diaphragm. Then, a part of the piezoelectric body in the region overlapping with the first active portion in a plan view of the piezoelectric body is removed, and the neutral surface in the region is vibrated with the piezoelectric body approaching the center in the thickness direction of the first active portion. When the unevenness and waviness of the piezoelectric body are corrected when the plates are joined by pressing, the region where the compressive stress acts on the first active portion and the region where the tensile stress acts become approximately the same size. Here, in the region where the compressive stress acts on the first active portion when the above unevenness and waviness are corrected, the residual compressive stress generated by cooling after firing is added, and only the residual compressive stress acts. Compared to the case, since a large compressive stress acts on the piezoelectric body, the deformation of the active portion in the region is restrained, so that the apparent piezoelectric characteristics of the active portion are deteriorated. On the other hand, in the region where tensile stress acts on the first active part when correcting the above unevenness and waviness, the residual generated by cooling after firing is offset by offsetting the residual compressive stress produced by cooling after firing. Compared to the case where only the compressive stress is applied, the compressive stress acting on the piezoelectric body is reduced, so that the deformation of the active portion in that region is not restricted, and the apparent piezoelectric characteristics of the active portion are improved. . As a result, as a whole first active portion, it is possible to cancel out the fluctuation of the piezoelectric characteristics between the region where the piezoelectric characteristics are reduced and the region where the piezoelectric properties are improved, and the first active portion is brought to almost the desired piezoelectric characteristics. can do.

  Furthermore, it is preferable to further include a filling step for filling the removed portion of the piezoelectric body with an insulating material. In many cases, electrodes are arranged on both surfaces of the first active portion in order to apply an electric field. According to this, even if this electrode is exposed from the side surface of the removed region of the piezoelectric body, By filling the insulating material, a short circuit between the electrodes can be prevented.

  In addition, the first active portion is formed at an end portion on one surface side in the thickness direction of the piezoelectric body, and overlaps the first active portion in a plan view of the piezoelectric body in the removing step. It is preferable to remove all the parts other than the first active part. According to this, since only the first active part exists in the region overlapping the first active part in the plan view of the piezoelectric body, the neutral plane in the region overlapping the first active part in the plan view of the piezoelectric body is the first surface. It passes through the center in the thickness direction of the active part. Then, in the joining process, when the diaphragm is pressed against the piezoelectric body, the first active portion of the piezoelectric body has a region where compressive stress is generated on one side of the neutral surface and tensile stress on the other side. The areas are almost the same size. As a result, it is possible to cancel the fluctuation of the piezoelectric characteristics between the area where the piezoelectric characteristics of the first active part as a whole are reduced and the area where the piezoelectric characteristics are improved, so that the piezoelectric characteristics of the first active part become the desired characteristics. can do.

  The piezoelectric body includes two stacked piezoelectric layers. One of the piezoelectric layers includes a first electrode to which a first potential and a second potential different from the first potential are selectively applied, and the first potential. The first active portion is sandwiched between the first electrode and the first constant potential electrode of the one piezoelectric layer from the region sandwiched between the first constant potential electrode and the first constant potential electrode. Preferably, in the removing step, a region overlapping the first active portion in a plan view of the other piezoelectric layer is removed. According to this, in the case where the first active portion as described above is disposed so as to be biased to one side in the thickness direction with respect to the neutral surface of the piezoelectric body, the piezoelectric characteristics of the first active portion are almost desired. can do.

  The piezoelectric body further includes a second active portion so as to sandwich the first active portion in a plane direction, and the first active portion selectively receives a first potential and a second potential different from the first potential. It is composed of a part of the piezoelectric body sandwiched between a first electrode to be applied and a first constant potential electrode to which the first potential is applied, and the second active portion includes the first electrode, It consists of a part of the piezoelectric body sandwiched between the second constant potential electrode to which the second potential is applied, and overlaps the first active part in the planar view of the piezoelectric body in the removing step. You may remove at least one part regarding the thickness direction of parts other than the said 1st active part in an area | region. According to this, in the case where the first active portion as described above is disposed so as to be biased to one side in the thickness direction with respect to the neutral surface of the piezoelectric body, the piezoelectric characteristics of the first active portion are almost desired. can do.

The piezoelectric actuator of the present invention, possess an active portion in a part of the thickness direction and the piezoelectric element wherein the active portion is Ru is disposed so as to overlap the pressure chambers in plan view, is bonded to one surface of the piezoelectric The active portion is arranged to be biased to one side with respect to the thickness direction of the piezoelectric body, and is in a region overlapping the active portion in plan view of the piezoelectric body, At least in part in the thickness direction of the portion other than the active portion, the neutral surface in the region overlapping with the active portion in a plan view of the piezoelectric body is positioned substantially at the center in the thickness direction of the active portion. A concave portion that is recessed from the surface side away from the active portion in the thickness direction of the piezoelectric body is formed.

  According to the piezoelectric actuator of the present invention, when the diaphragm is pressed and joined to the piezoelectric body in the manufacturing process, the active portion of the piezoelectric body has a region where compressive stress is generated on one side of the neutral surface and the other side. The region where the tensile stress is generated on the side is almost the same size. As a result, the fluctuation of the piezoelectric characteristics can be canceled out between the area where the piezoelectric characteristics of the active part as a whole are reduced and the area where the piezoelectric characteristics are improved, and the piezoelectric characteristics of the active part can be made almost desired. it can.

The liquid transfer device of the present invention includes a liquid transfer head in which a piezoelectric actuator for transferring a liquid in the pressure chamber is joined to a flow path unit in which a pressure chamber is formed, and a voltage application for applying a voltage to the piezoelectric actuator. The piezoelectric actuator includes a piezoelectric body having an active portion overlapping a central portion of the pressure chamber in a plan view in a part in a thickness direction, and one surface of the piezoelectric body And the active portion is disposed on one side with respect to the thickness direction of the piezoelectric body, and the piezoelectric body overlaps the active portion in plan view. there, a portion relating to the thickness direction of the portion other than the active portion, such that the neutral plane in the region overlapping with the active portion in a plan view of the piezoelectric body is located substantially centrally about the thickness direction of the active portion , Recesses recessed from a remote side from said active portion with respect to the thickness direction of the piezoelectric body is formed.

  When compressive stress is generated in the active portion, the contraction force when a voltage is applied is reduced, and the piezoelectric characteristics of the piezoelectric layer are deteriorated. According to the liquid transfer device of the present invention, when the diaphragm is pressed and joined to the piezoelectric body in the manufacturing process, the active portion of the piezoelectric body includes a region where compressive stress is generated on one side of the neutral surface, and the other side. The regions where the tensile stress on the side of the side is generated are almost the same size. As a result, the fluctuation of the piezoelectric characteristics can be canceled out between the area where the piezoelectric characteristics of the active part as a whole are reduced and the area where the piezoelectric characteristics are improved, and the piezoelectric characteristics of the active part can be made almost desired. it can.

  When the piezoelectric layer with unevenness is pressed and bonded to the diaphragm, there are a region where the compressive stress of the first active portion is generated and the piezoelectric property is lowered, and a region where tensile stress is generated and the piezoelectric property is improved. As a whole, the fluctuation of the piezoelectric characteristics can be almost canceled out as the entire first active portion. As a result, the piezoelectric characteristics of the first active part can be made substantially desired.

1 is a schematic configuration diagram of a printer according to an embodiment. It is a perspective view of an inkjet head. It is a top view of an inkjet head. (A) is the elements on larger scale of FIG. 3, (b)-(d) is a figure of the surface of each piezoelectric layer. It is the VV sectional view taken on the line of Fig.4 (a). It is the VI-VI sectional view taken on the line of Fig.4 (a). It is process drawing which shows the manufacturing process of a piezoelectric actuator, (a) is a lamination process, (b) is a removal process, (c) is a joining process. It is the schematic for demonstrating a joining process, (a) is a schematic sectional drawing of a piezoelectric material, (b) is the elements on larger scale of the A part vicinity after a joining process, (c) is a joining process. It is the elements on larger scale of the back B part vicinity. 6 is a cross-sectional view of a piezoelectric actuator in Modification 1. FIG. 10 is a cross-sectional view of a piezoelectric actuator in Modification 2. FIG. 10 is a cross-sectional view of a piezoelectric actuator according to Modification 3. FIG. 10 is a cross-sectional view of a piezoelectric actuator according to Modification 4. FIG. 10 is a schematic cross-sectional view of a piezoelectric actuator in Modification 5. FIG. 10 is a schematic cross-sectional view of a piezoelectric actuator in Modification 6. FIG.

  Hereinafter, preferred embodiments of the present invention will be described. FIG. 1 is a schematic configuration diagram of a printer according to the present embodiment. As shown in FIG. 1, the printer 1 includes a carriage 2, an inkjet head 3, a transport roller 4, and the like.

  The carriage 2 reciprocates in the scanning direction (left and right direction in FIG. 1). The inkjet head 3 is attached to the lower surface of the carriage 2 and ejects ink from nozzles 15 (see FIG. 3) formed on the lower surface. The transport roller 4 transports the recording paper P in the paper feed direction (front side in FIG. 1). In the printer 1, printing is performed on the recording paper P by ejecting ink onto the recording paper P from the nozzles 15 of the inkjet head 3 that reciprocates in the scanning direction together with the carriage 2. Further, the recording paper P for which printing has been completed is discharged in the paper feeding direction by the transport roller 4.

  Next, the inkjet head 3 will be described in detail. FIG. 2 is an exploded perspective view of the inkjet head of FIG. FIG. 3 is a plan view of the inkjet head of FIG. FIG. 4A is a partially enlarged view of FIG. 4B to 4D are views showing the upper surfaces of a lower piezoelectric layer 40, an intermediate piezoelectric layer 41, and an upper piezoelectric layer 42, which will be described later, in FIG. 4A, respectively. FIG. 5 is a cross-sectional view taken along line VV in FIG. FIG. 6 is a cross-sectional view taken along line VI-VI in FIG.

  In order to make the drawings easier to understand, in FIG. 3 and FIG. 4, the illustration of the ink flow path excluding the pressure chamber 10 and the nozzle 15 of the flow path unit 31 to be described later is omitted, and in FIG. Illustration of the lower electrode 43 and the intermediate electrode 44 is omitted. In FIG. 4A, the lower electrode 43 and the intermediate electrode 44, both of which are to be illustrated by dotted lines, are illustrated by two-dot chain lines and one-dot chain lines, respectively. Further, in FIGS. 4B to 4D, a lower electrode 43, an intermediate electrode 44, and an upper electrode 45, which will be described later, are hatched. Further, in FIG. 6, illustration of a portion below the pressure chamber 10 of the flow path unit 31 is omitted.

  As shown in FIGS. 2 to 6, the inkjet head 3 has a flow path unit 31 and a piezoelectric actuator 32. In the flow path unit 31, a plurality of plates 21 to 27 are stacked on each other, whereby the manifold flow path 11 to which ink is supplied from the ink supply port 9, and the outlet of the manifold flow path 11 through the aperture flow path 12. An ink channel having a plurality of individual ink channels from the pressure chamber 10 to the nozzle 15 through the descender channel 14 is formed. As will be described later, when pressure is applied to the ink in the pressure chamber 10 by the piezoelectric actuator 32, ink is ejected from the nozzle 15 communicating with the pressure chamber 10.

  The plurality of pressure chambers 10 have a substantially elliptical planar shape with the scanning direction (left-right direction in FIG. 3) as the longitudinal direction, and are arranged along the paper feed direction (up-down direction in FIG. 3). Two pressure chamber rows 8 are formed, and such pressure chamber rows 8 are arranged in two rows in the scanning direction to form one pressure chamber group 7. Further, five such pressure chamber groups 7 are arranged along the scanning direction. Here, the pressure chambers 10 constituting the two pressure chamber rows 8 included in one pressure chamber group 7 are arranged so as to be shifted from each other in the paper feeding direction. The plurality of nozzles 15 are also arranged in the same manner as the plurality of pressure chambers 10.

  Then, among these five pressure chamber groups 7, black ink is ejected from the nozzles 15 corresponding to the pressure chambers 10 constituting the right two in FIG. 3, and the pressure constituting the left three in FIG. From the nozzles 15 corresponding to the chambers 10, yellow, cyan, and magenta inks are ejected in order from the nozzles arranged on the right side of FIG. The configuration of other portions of the ink flow path is the same as that of the conventional one, and therefore detailed description thereof is omitted here.

  The piezoelectric actuator 32 includes a diaphragm 52, a piezoelectric body 55, a lower electrode 43 (second constant potential electrode), an intermediate electrode 44 (first constant potential electrode), an upper electrode 45 (first electrode), and an adhesive 60. ing.

  The diaphragm 52 is made of a metal material such as stainless steel, and is disposed on the upper surface of the flow path unit 31 so as to cover the plurality of pressure chambers 10. Since the vibration plate 52 that comes into contact with the ink in the pressure chamber 10 is made of a metal material, the ink hardly penetrates and prevents the ink in the pressure chamber 10 from coming into contact with the lower piezoelectric layer 40.

  The piezoelectric body 55 is made of a piezoelectric material mainly composed of lead zirconate titanate, which is a mixed crystal of lead titanate and lead zirconate, and the lower piezoelectric layer 40, the intermediate piezoelectric layer 41, and the upper piezoelectric layer 42 are stacked on each other. Has been formed. The piezoelectric body 55 is disposed on the upper surface of the diaphragm 52. A through hole 40a penetrating in the thickness direction is formed in a region of the lower piezoelectric layer 40 that overlaps the facing portion 44a of each intermediate electrode 44 in plan view. A through hole 41a penetrating in the thickness direction is formed in a region of the intermediate piezoelectric layer 41 that overlaps the facing portion 44a of each intermediate electrode 44 in plan view. Since the through holes 40a and 41a are formed in the piezoelectric body 55, the piezoelectric body 55 is formed with a concave portion that is recessed from the surface side away from the first active portion R1 described later in the thickness direction. Furthermore, the thicknesses of the lower piezoelectric layer 40, the intermediate piezoelectric layer 41, and the upper piezoelectric layer 42 are each about 20 μm.

  The lower electrode 43 is formed on the upper surface of the lower piezoelectric layer 40, and is disposed between the lower piezoelectric layer 40 and the intermediate piezoelectric layer 41, except for a region that overlaps the facing portion 44a of each intermediate electrode 44 in plan view. Corresponding to each pressure chamber group 7, the pressure chamber groups 7 are formed so as to extend in the paper feeding direction along the two pressure chamber rows 8 constituting each pressure chamber group 7. Although not shown, the portions extending in the paper feeding direction are connected to each other. The lower electrode 43 is connected to the driver IC 51 via a flexible printed circuit board (FPC) 50 disposed above the piezoelectric actuator 32, and is always held at the ground potential (second potential) by the driver IC 51. .

  The intermediate electrode 44 is formed on the upper surface of the intermediate piezoelectric layer 41, and is disposed between the intermediate piezoelectric layer 41 and the upper piezoelectric layer 42. For each pressure chamber group 7, a plurality of facing portions 44a and connection portions are provided. 44b, 44c. The plurality of facing portions 44 a have a substantially rectangular planar shape whose length in the paper feeding direction is shorter than that of the pressure chamber 10, and is disposed so as to face the central portion of the plurality of pressure chambers 10.

  The connecting portion 44b extends in the paper feeding direction, and among the two pressure chamber rows 8 constituting each pressure chamber group 7, a plurality of pressure chambers 10 constituting the pressure chamber row 8 arranged on the right side in FIG. 4 are connected to each other on the right side in FIG. 4. The connecting portion 44c extends in the paper feeding direction, and among the two pressure chamber rows 8 constituting each pressure chamber group 7, a plurality of pressure chambers 10 constituting the pressure chamber row 8 arranged on the left side in FIG. 4 are connected to each other on the left side in FIG. The intermediate electrode 44 is connected to the driver IC 51 via the FPC 50, and is always held at a predetermined potential (for example, about 20V: the first potential) different from the ground potential by the driver IC 51.

  The plurality of upper electrodes 45 are formed on the upper surface (the surface opposite to the intermediate piezoelectric layer 41) of the upper piezoelectric layer 42 so as to face almost the entire region of the plurality of pressure chambers 10 corresponding to the plurality of pressure chambers 10. And has a substantially rectangular planar shape whose length in the paper feed direction is longer than the facing portion 44a of the intermediate electrode 44. Further, the upper electrode 45 has a portion at the end opposite to the nozzle 15 in the scanning direction extending to a portion not facing the pressure chamber 10 in the scanning direction, and this portion serves as a connection terminal 45 a connected to the FPC 50. Yes. The upper electrode 45 is connected to the driver IC 51 via the FPC 50, and the potential can be selectively switched between the ground potential and the predetermined potential (for example, 20V).

  The adhesive 60 is made of an insulating material, and is defined by the lower surface of the facing portion 44 a of the intermediate electrode 44, the wall surface of the through hole 40 a of the lower piezoelectric layer 40, the wall surface of the through hole 41 a of the intermediate piezoelectric layer 41, and the upper surface of the diaphragm 52. The inside of the space is filled. The adhesive 60 may be extruded and flown when the piezoelectric body 55 and the diaphragm 52 are joined, or may be filled in this space separately from the joining. By filling the through holes 40 a and 41 a with the adhesive 60, it is possible to prevent a short circuit between the lower electrode 43 exposed from the wall surface of the through holes 40 a and 41 a and the facing portion 44 a of the intermediate electrode 44.

  As described above, by arranging the lower electrode 43, the intermediate electrode 44, and the upper electrode 45, the upper electrode 45 and the intermediate electrode 44 are opposed to each other in the portion of the upper piezoelectric layer 42 facing the central portion of the pressure chamber 10. Will be. Then, the region is a first active portion R1 by being polarized upward from the intermediate electrode 44 toward the upper electrode 45. The first active portion R <b> 1 is arranged to be biased to one side with respect to the thickness direction of the piezoelectric body 55.

  Further, in the upper piezoelectric layer 42 and the intermediate piezoelectric layer 41 that face the pressure chamber 10, the upper electrode 45 and the lower electrode in the outer peripheral part (the part that does not face the intermediate electrode 44) than the part that faces the intermediate electrode 44. 43 will be opposed to each other. The region is a second active portion R2 because it is polarized downward from the upper electrode 45 toward the lower electrode 43.

  Here, the operation of the piezoelectric actuator 32 will be described. First, in the standby state before the piezoelectric actuator 32 performs the operation of ejecting ink, as described above, the lower electrode 43 and the intermediate electrode 44 are always set to the ground potential and the predetermined potential (for example, 20 V), respectively. In addition to being held, the potential of the upper electrode 45 is previously held at the ground potential. In this state, the upper electrode 45 has a lower potential than the intermediate electrode 44 and has the same potential as the lower electrode 43.

  As a result, a potential difference is generated between the upper electrode 45 and the intermediate electrode 44, and an upward electric field that is the same as the polarization direction acts on the first active part R1, and the first active part R1 is in a horizontal direction orthogonal to the electric field. Shrink to. As a result, the portions of the upper piezoelectric layer 42, the intermediate piezoelectric layer 41, and the lower piezoelectric layer 40 that face the pressure chamber 10 are deformed so as to be convex toward the pressure chamber 10 as a whole. In this state, the volume of the pressure chamber 10 is small as compared with a horizontal state in which the upper piezoelectric layer 42, the intermediate piezoelectric layer 41, and the lower piezoelectric layer 40 are not deformed.

  When the piezoelectric actuator 32 is driven to eject ink, the potential of the upper electrode 45 is once switched to the predetermined potential. When the potential of the upper electrode 45 is switched to the predetermined potential, the upper electrode 45 becomes the same potential as the intermediate electrode 44 and at a higher potential than the lower electrode 43. Thereby, the contraction of the first active part R1 is restored. At the same time, a potential difference is generated between the upper electrode 45 and the lower electrode 43, a downward electric field that is the same as the polarization direction is generated in the second active part R2, and the second active part R2 contracts in the horizontal direction. To do. As a result, the upper piezoelectric layer 42, the intermediate piezoelectric layer 41, and the lower piezoelectric layer 40 as a whole are deformed so as to protrude toward the opposite side of the pressure chamber 10, and the volume of the pressure chamber 10 increases.

  Thereafter, when the potential of the upper electrode 45 is returned to the ground potential, the portions of the upper piezoelectric layer 42, the intermediate piezoelectric layer 41, and the lower piezoelectric layer 40 facing the pressure chamber 10 as a whole become the pressure chamber 10 as described above. The pressure chamber 10 is deformed so as to be convex, and the volume of the pressure chamber 10 is reduced. As a result, the pressure of the ink in the pressure chamber 10 increases (pressure is applied to the ink in the pressure chamber 10), and the ink is ejected from the nozzle 15 communicating with the pressure chamber 10.

  Further, when the piezoelectric actuator 32 is driven as described above, when the potential of the upper electrode 45 is switched from the ground potential to a predetermined potential, the first active portion R1 expands from the contracted state to the pre-contracted state at the same time. Since the second active part R2 contracts, the extension of the first active part R1 is partially absorbed by the contraction of the second active part R2. On the other hand, when the potential of the upper electrode 45 is returned from the predetermined potential to the ground potential, the first active portion R1 contracts and the second active portion R2 expands to the state before contraction. The contraction is partially absorbed by the extension of the second active part R2.

  From the above, the deformations of the portions of the lower piezoelectric layer 40, the intermediate piezoelectric layer 41, and the upper piezoelectric layer 42 facing the pressure chamber 10 are transmitted to the portions facing the other pressure chamber 10 and the other pressure chamber 10 is concerned. In other words, the so-called crosstalk, in which the ink ejection characteristics from the nozzles 15 communicating with the ink fluctuate, is suppressed.

  Next, a method for manufacturing the inkjet head 3 will be described. The inkjet head 3 is manufactured by separately manufacturing the flow path unit 31 and the piezoelectric actuator 32 and joining the manufactured flow path unit 31 and the piezoelectric actuator 32.

(Flow path unit manufacturing process)
First, holes penetrating in the thickness direction constituting the ink flow paths such as the pressure chamber 10, the manifold flow path 11, and the nozzle 15 are formed in the seven plates 21 to 27 constituting the flow path unit 31. These holes are formed by etching or laser processing. Then, the seven plates 21 to 27 are stacked and heated and pressed, and the plates are joined with an adhesive to produce the flow path unit 31. The seven plates 21 to 27 may be joined by metal diffusion bonding or the like when made of a metal material.

(Piezoelectric actuator manufacturing process)
FIGS. 7A and 7B are process diagrams showing the manufacturing process of the piezoelectric actuator, where FIG. 7A is a stacking process, FIG. 7B is a removal process, and FIG. 7C is a joining process. First, the upper electrode 45, the intermediate electrode 44, and the lower electrode 43 are formed by screen printing on one surface of three green sheets of the same outer shape, which are made of piezoelectric ceramics and are formed in advance with the amount of shrinkage caused by firing. . Then, as shown in FIG. 7A, the green sheets with the lower electrode 43, the green sheet with the intermediate electrode 44, and the green sheet with the upper electrode 45 are laminated in order from the bottom. Then, this laminated body is fired at a predetermined temperature (lamination process), and the piezoelectric body 55 is formed. At this time, since the upper electrode 45, the intermediate electrode 44, and the lower electrode 43 are formed of a material having a larger linear expansion coefficient than that of the piezoelectric ceramic, after firing and cooling, due to thermal strain due to the difference between these linear expansion coefficients. The compressive stress remains in the lower piezoelectric layer 40, the intermediate piezoelectric layer 41, and the upper piezoelectric layer.

  Then, as shown in FIG. 7B, the lower piezoelectric layer 40 and the intermediate piezoelectric layer 41 other than the first active portion R1 in the region overlapping the first active portion R1 in a plan view are arranged on the lower piezoelectric layer 40 side (the first piezoelectric layer 40). 1 is removed from the active portion R1 and the through holes 40a and 41a are formed (removal step). As this removal method, a polishing agent mixed with compressed air is sprayed on the surface of the lower piezoelectric layer 40 by sandblasting, and the lower piezoelectric layer 40 and the intermediate piezoelectric layer 41 are scraped off. At this time, the electrodes are less likely to be scraped than the piezoelectric layers. Therefore, the spraying force is increased only when the lower electrode 43 is removed, and during the other periods, the electrode is not scraped but the piezoelectric layer can be scraped so that each piezoelectric layer can be scraped. Thereby, it is possible to scrape and remove only a desired portion without scraping the intermediate electrode 44.

  Next, as shown in FIG. 7C, the diaphragm 52 is pressed against the surface of the lower piezoelectric layer 40 of the piezoelectric body 55 and bonded with an adhesive (bonding process) to manufacture the piezoelectric actuator 32. At this time, the adhesive 60 extruded at the time of joining is filled in the through holes 40a and 41a of the lower piezoelectric layer 40 and the intermediate piezoelectric layer 41 (filling step). That is, the filling process is performed together with the joining process. Note that the adhesive 60 may be filled in the through holes 40a and 41a of the lower piezoelectric layer 40 and the intermediate piezoelectric layer 41 in advance before the bonding step.

  Here, the joining process will be described in detail. FIG. 8 is a schematic diagram for explaining the joining process, (a) is a schematic cross-sectional view of the piezoelectric body, (b) is a partially enlarged view in the vicinity of part A after the joining process, (c ) Is a partially enlarged view in the vicinity of part B after the joining step. As shown in FIG. 8A, the piezoelectric body 55 produced by firing in a state where three green sheets are laminated in the lamination process may have irregularities and undulations. When the piezoelectric body 55 having such irregularities and undulations is pressed and joined to the diaphragm 52, the irregularities and undulations are corrected, but at this time, on one side of the neutral surface of the piezoelectric layer, A compressive stress acts, and a tensile stress acts on the other side.

  At this time, if the lower piezoelectric layer 40 and the intermediate piezoelectric layer 41 are not formed with the through-holes 40a and 41a and the PZT is disposed, the first active portion R1 and the first active portion R1 are viewed in a plan view of the piezoelectric body 55. If the overlapping region is convex on the side opposite to the side to be joined to the diaphragm 52, the convex region is flattened by pressing and joining the piezoelectric body 55 and the diaphragm 52. Compressive stress acts on the first active portion R1 disposed on the side that is convex with respect to the neutral surface. That is, the compressive stress further acts on the residual compressive stress due to the thermal strain in the cooling after firing the green sheet. When compressive stress is applied to the active part, deformation of the active part is constrained, and the apparent piezoelectric characteristics of the active part are degraded. Therefore, the apparent piezoelectric characteristics of the first active portion R1 are lower than when only the residual compressive stress due to thermal strain in cooling after firing the green sheet is acting.

  On the other hand, when the region overlapping the first active portion R1 in a plan view of the piezoelectric body 55 is convex on the side to be joined to the diaphragm 52, the piezoelectric body 55 and the diaphragm 52 are pressed and joined. Although the convex region is flat, a tensile stress acts on the first active portion R1 disposed on the side opposite to the convex side with respect to the neutral surface. That is, the residual compressive stress due to the thermal strain in the cooling after firing the green sheet described above and the tensile stress are offset. Therefore, the apparent piezoelectric characteristics of the first active portion R1 are improved as compared with the case where only the residual compressive stress due to the thermal strain in the cooling after firing the green sheet is acting on the first active portion R1. As described above, the first active portion R1 is disposed in a region that is convex on the side of the piezoelectric body 55 that is bonded to the diaphragm 52, or is opposite to the side of the piezoelectric body 55 that is bonded to the diaphragm 52. Depending on whether it is arranged in a region that is convex, the apparent piezoelectric characteristics are different.

  Therefore, in the present embodiment, the lower piezoelectric layer 40 and the intermediate piezoelectric layer 41 other than the first active portion R1 in the region overlapping the first active portion R1 in plan view of the piezoelectric body 55 are removed. Thereby, the neutral surface in this area | region is the approximate center regarding the thickness direction of 1st active part R1. Then, when the piezoelectric body 55 is pressed and joined to the diaphragm 52, the first active portion R1 has a region where the compressive stress acts and a region where the tensile stress acts equally.

  For example, as shown in part A of FIG. 8A, when the first active part R1 is formed on a part of the piezoelectric body 55 that is convex on the side opposite to the side to be joined to the diaphragm 52. As shown in FIG. 8B, when the irregularities are corrected, compressive stress is generated on the side opposite to the side to be joined with the diaphragm 52 of the neutral surface, and the diaphragm 52 is joined with the neutral surface. Tensile stress is generated on the side. 8A, when the first active portion R1 is formed on a portion of the piezoelectric body 55 that protrudes toward the side to be joined to the vibration plate 52, FIG. As shown in (c), when the unevenness is corrected, tensile stress is generated on the side opposite to the side joined to the diaphragm 52 on the neutral surface, and compression is performed on the side joined to the diaphragm 52 on the neutral surface. Stress is generated. That is, in any case, the compressive stress and the tensile stress act on regions having substantially the same size in the thickness direction of the first active portion R1.

  Here, only the residual compressive stress due to the thermal strain in the cooling after firing the green sheet acts on the first active part R1. And the area | region which receives the compressive stress of 1st active part R1 is added to the said compressive residual stress, and the apparent piezoelectric characteristic falls compared with the case where only the residual compressive stress is acting. On the other hand, the portion receiving the tensile stress of the first active portion R1 is offset with the residual compressive stress, and the apparent piezoelectric characteristics are improved as compared with the case where only the residual compressive stress is acting.

  However, when viewed as a whole of the first active part R1, this apparent decrease in piezoelectric characteristics and the improvement are offset, and the first active part R1 is flat as shown in part C of FIG. 8 (a). The apparent piezoelectric characteristics are almost the same as when formed in the portion. Thus, even if the first active portion R1 is formed on the portion of the piezoelectric body 55 that protrudes to the side joined to the diaphragm 52, the first active portion R1 is convex on the side opposite to the side joined to the diaphragm 52. Even if the first active portion R1 is formed in a flat portion or a flat portion, the piezoelectric characteristics of the first active portion R1 can be made almost desired.

  Then, the inkjet head 3 is completed by bonding the diaphragm 52 of the piezoelectric actuator 32 to the plate 21 of the flow path unit 31 with an adhesive or the like.

  Next, modified examples in which various changes are made to the present 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.

  The present invention is also applicable to a piezoelectric actuator having the following configuration. This will be described with reference to FIG. FIG. 9 is a cross-sectional view of the piezoelectric actuator in the first modification. As shown in FIG. 9, the piezoelectric actuator 150 includes a diaphragm 52, two piezoelectric layers 140 and 141, a plurality of individual electrodes 144, and a common electrode 145. The individual electrode 144 is disposed on the upper surface of the piezoelectric layer 140 at a position overlapping the substantially central portion of the plurality of pressure chambers 10 in a plan view, and one of two types of potentials, a driving potential and a ground potential. A potential is selectively applied. The common electrode 145 is formed on the upper surface of the piezoelectric layer 141 and is always given a ground potential.

  The two piezoelectric layers 140 and 141 are made of a piezoelectric material containing PZT as a main component, like the piezoelectric layers 41 and 42 in the present embodiment. The piezoelectric layer 140 is polarized in the thickness direction in advance, and a region sandwiched between the individual electrode 144 and the common electrode 145 is an active portion R10. The piezoelectric layer 141 is bonded to the vibration plate 52. A through hole 141a is formed in a region overlapping the individual electrode 144 in plan view of the piezoelectric layer 141, and the adhesive 60 is filled in the through hole 141a.

  In the piezoelectric actuator 150, when ink is ejected from a certain nozzle 15, a driving potential is applied to the individual electrode 144 corresponding to the nozzle 15, thereby the common electrode held at the ground potential with the individual electrode 144. A potential difference is generated between the active portion R145 and the active portion R10 sandwiched between the two, and an electric field parallel to the thickness direction is generated. The piezoelectric layer 140 polarized in the thickness direction contracts in the horizontal direction orthogonal to the direction of the electric field. As a result, the portion of the diaphragm 52 that faces the pressure chamber 10 is deformed so as to protrude toward the pressure chamber 10 (unimorph deformation). At this time, the volume of the pressure chamber 10 is reduced, the ink pressure inside the pressure chamber 10 is increased, and ink is ejected from the nozzle 15 communicating with the pressure chamber 104.

  In the case of forming the piezoelectric body composed of the piezoelectric layers 140 and 141 of the piezoelectric actuator 150 as described above, the electrodes are stacked on two green sheets and fired as in the present embodiment. At this time, compressive stress remains in the piezoelectric body due to cooling after firing. Then, by removing the portion that overlaps the active portion R10 in plan view of the piezoelectric body, that is, the portion that overlaps the active portion R10 in plan view of the piezoelectric layer 141, the approximate center of the active portion R10 becomes a neutral surface. Therefore, when unevenness and undulation are corrected by pressing and bonding the piezoelectric body to the diaphragm 52, the regions where the compressive stress and the tensile stress act are approximately the same in the thickness direction of the active portion R10. . As a whole, the residual compression stress and the compressive stress at the time of joining to the vibration plate 52 decrease the apparent piezoelectric characteristics of the active part R10, and the tensile stress at the time of joining to the vibration plate 52 is offset. Thus, it is possible to substantially cancel the improvement of the apparent piezoelectric characteristics. As a result, the piezoelectric characteristics of the active part R10 can be made substantially desired (Modification 1).

  In addition, the arrangement of the electrode to which the driving potential is applied, the electrode to which the ground potential is applied, and the electrode to which one of the driving potential and the ground potential is selectively applied is an electrode arrangement different from the present embodiment. Thus, even when the configurations of the first active part and the second active part sandwiching the first active part in the plane direction are different, the portion overlapping the first active part in plan view other than the first active part of the piezoelectric body is removed. By doing so, the neutral surface in the region overlapping the first active part in plan view of the piezoelectric body becomes the center of the first active part, and the effect of the present invention is exhibited. Hereinafter, an example will be described with reference to FIGS.

  1) As shown in FIG. 10, when the first active part R20 and the second active part R21 are formed, a portion overlapping the first active part R20 of the piezoelectric layer 120 which is a part of the piezoelectric body is removed. (Modification 2). Thereby, the neutral surface in the region overlapping the first active part R20 in the plan view of the piezoelectric body approaches the center of the first active part R20.

  2) As shown in FIG. 11, when the first active portion R30 and the second active portion R31 are formed, the portions of the piezoelectric layers 130 and 131 that are part of the piezoelectric body overlap with the first active portion R30. Is removed (Modification 3). Thereby, the neutral surface in the region overlapping the first active part R30 in the plan view of the piezoelectric body becomes the center of the first active part R30.

  3) As shown in FIG. 12, when the first active part R40 and the second active part R41 are formed, a portion overlapping the first active part R40 of the piezoelectric layer 140 which is a part of the piezoelectric body is removed. (Modification 4). Thereby, the neutral surface in the region overlapping the first active part R40 in plan view of the piezoelectric body becomes the center of the first active part R40.

  In the present embodiment, the through hole 40a of the lower piezoelectric layer 40 and the through hole 41a of the intermediate piezoelectric layer 41 are filled with the adhesive 60 pushed out when the piezoelectric body 55 and the diaphragm 52 are joined. The through hole 40a of the lower piezoelectric layer 40 and the through hole 41a of the intermediate piezoelectric layer 41 may be filled with the adhesive 60 in advance. At this time, since the adhesive 60 filled in the through holes 40a of the lower piezoelectric layer 40 and the through holes 41a of the intermediate piezoelectric layer 41 has low rigidity, the through holes 40a and the intermediate piezoelectric layer 41 of the lower piezoelectric layer 40 are low. By forming the through-hole 41a, the neutral surface in that region becomes substantially the center of the first active portion R1.

  Further, the filler filled in the through hole 40a of the lower piezoelectric layer 40 and the through hole 41a of the intermediate piezoelectric layer 41 is not limited to an adhesive but may be any insulating material such as resin or ceramics as long as it is an insulating material. .

  Furthermore, in the present embodiment, in the removal step, all the parts other than the first active part R1 in the region overlapping the first active part R1 of the piezoelectric body 55 are removed, but only a part is removed. Also good. For example, as shown in FIG. 13A, when the first active portion R50 is not formed on one surface end portion of the piezoelectric body but is formed inside, the first active portion R50 of the piezoelectric body 155 is formed. A portion of the region overlapping the portion R50 other than the first active portion R50 may be removed from the side away from the first active portion R50 in the thickness direction of the piezoelectric body 155 to form a through hole 155a (deformation) Example 5). As a result, the neutral surface in the region overlapping with the first active portion R50 in plan view of the piezoelectric body 155 passes through the center of the first active portion R50, and the first active portion R50 as a whole is subjected to residual compression during firing of the piezoelectric body. The apparent piezoelectric characteristics are deteriorated by the stress and the compressive stress at the time of joining to the diaphragm 52, and the residual compressive stress at the time of firing the piezoelectric body and the tensile stress at the time of joining to the diaphragm 52 are offset. The improvement in the piezoelectric characteristics can be almost offset. At this time, as shown in FIG. 13B, in the removing process, the piezoelectric member 155 has a piezoelectric element so that the neutral surface in the region overlapping the first active part R50 in a plan view is displaced from the center of the first active part R50. Only a part other than the first active part R1 in the region overlapping the first active part R1 of the body 55 may be removed.

  At this time, as shown in FIG. 14, all the portions other than the first active portion R50 in the region overlapping the first active portion R50 of the piezoelectric body 155 are removed from both sides in the thickness direction of the piezoelectric body 155. The through holes 155b and 155c may be formed (Modification 6). Even in this case, the neutral surface in the region overlapping the first active portion R50 of the piezoelectric body 155 passes through the center of the first active portion R50, and the residual compressive stress and vibration during the firing of the piezoelectric body as the entire first active portion R50. The apparent piezoelectric characteristics are deteriorated by the compressive stress at the time of joining to the plate 52, and the residual compressive stress at the time of firing the piezoelectric body and the tensile stress at the time of joining to the vibration plate 52 are offset, resulting in an apparent piezoelectric characteristic. The improvement can be almost offset.

  In the present embodiment, since the first active portion R1 is formed on the side away from the diaphragm 52 of the piezoelectric body 55 in the thickness direction, the piezoelectric layer is removed from the diaphragm 52 side. When the active portion R1 is formed on the side close to the diaphragm 52 in the thickness direction of the piezoelectric body 55, the piezoelectric layer may be removed from the side away from the diaphragm 52. That is, the piezoelectric layer may be removed from the side away from the first active portion R1 in the thickness direction of the piezoelectric body 55.

  Further, in the present embodiment, it has been described that the compressive stress remains in the piezoelectric body in the cooling after firing the piezoelectric body. However, the compressive stress remains not limited thereto. Even when a piezoelectric body and a diaphragm having a linear expansion coefficient larger than that of the piezoelectric body are heated, pressed and thermally bonded with a thermosetting resin, compressive stress remains in the piezoelectric body during cooling after bonding. To do. Even in this case, as in the above-described example, at least a part other than the first active portion of the region overlapping the first active portion in plan view of the piezoelectric body is removed, and the neutral surface of the region is removed. May approach the center of the first active part.

  In the present embodiment, the piezoelectric body having a plurality of first active portions has been described. However, the present invention is not limited to this. Even when there is only one first active part, the first active part can have desired piezoelectric characteristics by adopting the above-described configuration.

  The present invention is not limited to the piezoelectric actuator that applies pressure to the liquid in the pressure chamber and the manufacturing method thereof, and the present invention can also be applied to a piezoelectric actuator that drives a predetermined moving portion and a manufacturing method thereof. Further, the present invention is applied to a liquid transfer device that transfers liquid in a liquid transfer channel including a pressure chamber by applying pressure to the liquid in the pressure chamber, such as a liquid discharge head that discharges liquid other than ink from a nozzle. It is also possible.

DESCRIPTION OF SYMBOLS 1 Printer 3 Inkjet head 31 Flow path unit 32 Piezoelectric actuator 40a, 41a Through-hole 52 Diaphragm 55 Piezoelectric body R1 1st active part R2 2nd active part

Claims (8)

It has a first active portion in a part of the thickness direction and the piezoelectric element that will be arranged so as to overlap the pressure chamber first active portion in plan view, formed in larger material than the linear expansion coefficient of the piezoelectric And a diaphragm bonded to one surface of the piezoelectric body, and a method of manufacturing a piezoelectric actuator comprising:
The first active portion is arranged to be biased to one side in the thickness direction with respect to the neutral surface of the piezoelectric body,
A piezoelectric body forming step for forming the piezoelectric body;
A removing step of removing at least a part of the piezoelectric body in a thickness direction of a portion other than the first active portion in a region overlapping the first active portion in a plan view;
A heating and bonding step of heating and pressing the piezoelectric body and the diaphragm, and comprising:
In the removing step, the neutral surface of the piezoelectric body is such that a neutral surface in a region overlapping with the first active portion in a plan view of the piezoelectric body is located approximately in the center in the thickness direction of the first active portion. At least a part of the first active part in the thickness direction of the part other than the first active part in a region overlapping the first active part in a plan view disposed on the opposite side to the one side with respect to the thickness direction A method for manufacturing a piezoelectric actuator, wherein the piezoelectric actuator is removed from a surface side away from the part. It has a first active portion in a part of the thickness direction, and the first active portion and the piezoelectric body that will be arranged to overlap the pressure chambers in plan view, for imparting an electric field to the first active portion A method for manufacturing a piezoelectric actuator, comprising: an electrode made of a material having a larger linear expansion coefficient than the piezoelectric body; and a diaphragm bonded to one surface of the piezoelectric body,
The first active portion is arranged to be biased to one side in the thickness direction with respect to the neutral surface of the piezoelectric body,
A piezoelectric body firing step in which the piezoelectric body and the electrode are integrally fired;
A removing step of removing at least a part of the piezoelectric body in a thickness direction of a portion other than the first active portion in a region overlapping the first active portion in a plan view;
A bonding step of pressing and bonding the piezoelectric body and the diaphragm, and
In the removing step, the neutral surface of the piezoelectric body is such that a neutral surface in a region overlapping with the first active portion in a plan view of the piezoelectric body is located approximately in the center in the thickness direction of the first active portion. At least a part of the first active part in the thickness direction of the part other than the first active part in a region overlapping the first active part in a plan view disposed on the opposite side to the one side with respect to the thickness direction A method for manufacturing a piezoelectric actuator, wherein the piezoelectric actuator is removed from a surface side away from the part. Method for manufacturing a piezoelectric actuator according to claim 1 or 2, characterized in that it further comprises a filling step of filling an insulating material in the removed portion of the piezoelectric body. The first active portion is formed at an end on one surface side in the thickness direction of the piezoelectric body,
In the removing step, in a region overlapping with the first active portion in plan view of the piezoelectric any of claims 1-3, characterized in that the removal of all portions other than the first active portion 1 A method for manufacturing the piezoelectric actuator according to Item. The piezoelectric body is composed of two stacked piezoelectric layers,
One of the piezoelectric layers is sandwiched between a first electrode to which a first potential and a second potential different from the first potential are selectively applied, and a first constant potential electrode to which the first potential is applied,
The first active part is composed of a region sandwiched between the first electrode and the first constant potential electrode of the one piezoelectric layer,
It said removing method for manufacturing a piezoelectric actuator according to any one of claims 1 to 4, characterized in that removing a region overlapping with the other of the piezoelectric layer of the first active portion in plan view of the. The piezoelectric body further includes a second active portion so as to sandwich the first active portion in the surface direction,
The first active portion includes the piezoelectric member sandwiched between a first electrode to which a first potential and a second potential different from the first potential are selectively applied, and a first constant potential electrode to which the first potential is applied. Composed of parts of the body,
The second active portion is composed of a part of the piezoelectric body sandwiched between the first electrode and a second constant potential electrode to which the second potential is applied,
2. The removal step includes removing at least a part of the portion other than the first active portion in a region overlapping the first active portion in a plan view of the piezoelectric body in a thickness direction. 6. A method for manufacturing a piezoelectric actuator according to claim 5 . The active portion possess a part in the thickness direction and a piezoelectric body in which the active portion is Ru is disposed so as to overlap the pressure chambers in plan view,
A diaphragm bonded to one surface of the piezoelectric body,
The active portion is arranged to be biased to one side with respect to the thickness direction of the piezoelectric body,
At least a part in the thickness direction of the portion other than the active portion in the region overlapping the active portion in plan view of the piezoelectric body is a neutral surface in the region overlapping the active portion in plan view of the piezoelectric body. However, a concave portion that is recessed from the surface side away from the active portion in the thickness direction of the piezoelectric body is formed so as to be positioned substantially in the center in the thickness direction of the active portion. A liquid transfer comprising: a liquid transfer head in which a piezoelectric actuator for transferring a liquid in the pressure chamber is joined to a flow path unit in which a pressure chamber is formed; and a voltage applying means for applying a voltage to the piezoelectric actuator. A device,
The piezoelectric actuator is
A piezoelectric body having an active portion overlapping a central portion of the pressure chamber in a plan view in a part of the thickness direction;
A diaphragm bonded to one surface of the piezoelectric body,
The active portion is arranged to be biased to one side with respect to the thickness direction of the piezoelectric body,
A part of the piezoelectric body in a region overlapping with the active part in a plan view has a neutral surface in a region overlapping with the active part in a plan view of the piezoelectric body. The liquid transfer device is characterized in that a concave portion that is recessed from the surface side away from the active portion in the thickness direction of the piezoelectric body is formed so as to be positioned substantially in the center in the thickness direction of the active portion.

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