Piezoelectric actuator and method for inspecting the same

Abstract

To grasp a degree of warpage at an end part of a piezoelectric actuator.SOLUTION: A vibration plate 41, a first piezoelectric layer 42 and a second piezoelectric layer 43 are arranged from below in this order in a Z-direction which is a vertical direction. A connection part 524 which is a portion of a high-potential electrode is arranged at an end part in a Y-direction of a surface between the first piezoelectric layer 42 and the second piezoelectric layer 43. Second surface electrodes 55a and 55b connected to the connection part 524 and electrodes 62a and 62b for inspection overlapping with the connection part 524 in a Z-direction are arranged at an end part in the Y-direction of an upper surface of the second piezoelectric layer 43.SELECTED DRAWING: Figure 10

Description

[Technical field]

[0001] The present invention relates to a piezoelectric actuator and a method for inspecting a piezoelectric actuator. [Background technology]

[0002] As an example of a piezoelectric actuator, Patent Document 1 describes a piezoelectric actuator that applies pressure to ink in a pressure chamber in an inkjet head. In the piezoelectric actuator described in Patent Document 1, a piezoelectric body is formed by stacking three piezoelectric layers. A plurality of individual electrodes are arranged on the upper surface of the upper piezoelectric layer, which are separate for the plurality of pressure chambers. A first common electrode common to the plurality of individual electrodes is arranged on the surface between the lower piezoelectric layer and the central piezoelectric layer. A second common electrode common to the plurality of individual electrodes is arranged on the surface between the central piezoelectric layer and the upper piezoelectric layer. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2014-189017 A Summary of the Invention [Problem to be solved by the invention]

[0004] When manufacturing the piezoelectric actuator of Patent Document 1, the laminate of the piezoelectric layers and electrodes is heated, and at this time, warping may occur in the piezoelectric actuator due to the difference in linear expansion coefficient between the piezoelectric layers and the electrodes. When warping occurs in the piezoelectric actuator, the capacitance of the portion of the piezoelectric layer sandwiched between the electrodes changes. Therefore, it is conceivable to measure the capacitance by applying a probe to the two electrodes sandwiching the piezoelectric layer, and to grasp the degree of warping of the piezoelectric actuator based on the measured capacitance, for example.

[0005] Here, the central part of the piezoelectric actuator is surrounded by other parts of the piezoelectric actuator all around, and warping is easily restricted by these other parts. In contrast, the ends of the piezoelectric actuator are not restricted in warping because there are no other parts of the piezoelectric actuator on the outside. In addition, the central part and the ends of the piezoelectric actuator experience different atmospheres (temperatures, etc.) when heated. Due to these factors, warping of the piezoelectric actuator is greater at its ends.

[0006] However, the end of the piezoelectric actuator of Patent Document 1 does not have an electrode that can be used to measure the above-mentioned capacitance. At the end of the piezoelectric actuator of Patent Document 1, the first connection terminal and the first common electrode, and the second connection terminal and the second common electrode are arranged with the piezoelectric layer between them, but the first connection terminal and the first common electrode, and the second connection terminal and the second common electrode are each electrically connected via a through hole, and therefore cannot be used to measure the above-mentioned capacitance. As a result, the degree of warping at the end of the piezoelectric actuator cannot be grasped.

[0007] If the degree of warping at the ends of the piezoelectric actuator cannot be grasped, an inkjet head may be manufactured using a piezoelectric actuator with a large warping at the ends. In this case, there is a risk that the piezoelectric layer will be damaged when a flow path member or a wiring member such as a COF is joined to the piezoelectric actuator. There is also a risk of problems such as differences in the ink ejection characteristics from the nozzle between the center and the ends.

[0008] An object of the present invention is to provide a piezoelectric actuator that makes it possible to grasp the degree of warping at the end portion, and a method for inspecting the piezoelectric actuator. [Means for solving the problem]

[0009] The piezoelectric actuator of the present invention has insulating properties on at least one surface in a first direction. Ruthe piezoelectric element includes a vibration plate, a first piezoelectric layer arranged on one surface of the vibration plate in the first direction, a second piezoelectric layer arranged on the one surface of the first piezoelectric layer in the first direction, a plurality of individual electrodes arranged on the one surface of the second piezoelectric layer in the first direction, a first common electrode arranged on a surface between the vibration plate and the first piezoelectric layer and common to the plurality of individual electrodes, a second common electrode arranged on a surface between the first piezoelectric layer and the second piezoelectric layer and common to the plurality of individual electrodes, a first surface electrode arranged on the one surface of the second piezoelectric layer in the first direction and in electrical conduction with the first common electrode, and a second surface electrode arranged on the one surface of the second piezoelectric layer in the first direction and in electrical conduction with the second common electrode, before Second common electrode is a surface between the first piezoelectric layer and the second piezoelectric layer. the end in a second direction perpendicular to the first direction a first common electrode portion located at an end of a surface between the first piezoelectric layer and the second piezoelectric layer in the third direction, extending in a third direction perpendicular to both the first direction and the second direction, overlapping the second surface electrode in the first direction and connected to the second surface electrode, and a second common electrode portion located at an end of a surface between the first piezoelectric layer and the second piezoelectric layer in the third direction, extending in the second direction, and connected to the first common electrode portion, the second piezoelectric layer is disposed on an end portion in the second direction of the surface on the one side in the first direction, Second common electrode The first common electrode portion and a test electrode overlapping the individual electrode in the first direction and not conducting with any of the individual electrode, the first common electrode, and the second common electrode. The length of the first common electrode portion in the second direction is longer than the length of the second common electrode portion in the third direction, and the length of the testing electrode in the second direction is longer than the length in the third direction, and the testing electrode overlaps with the first common electrode portion in the first direction over the entire length in the second direction. . [Brief description of the drawings]

[0010] [Figure 1] 1 is an overall configuration diagram of a printer 1 including a piezoelectric actuator according to a first embodiment of the present invention. [Diagram 2] FIG. 2 is a plan view of the head 3 of FIG. [Diagram 3] FIG. 3 is an enlarged view of region III in FIG. 2. [Figure 4] FIG. 4 is a cross-sectional view taken along line IV-IV in FIG. [Diagram 5] FIG. 4 is a cross-sectional view taken along line VV in FIG. [Figure 6] 4 is a plan view showing the upper surface of a second piezoelectric layer 43. FIG. [Figure 7] 6A is an enlarged view of the inspection electrode 62a in FIG. 6 and some of the electrodes aligned with it in the X direction, and FIG. 6B is an enlarged view of the inspection electrode 62b in FIG. 6 and some of the electrodes aligned with it in the X direction. [Figure 8] 2 is a plan view showing the upper surface of a first piezoelectric layer 42. FIG. [Figure 9] 2 is a plan view showing the upper surface of the diaphragm 41. FIG. [Figure 10] 6A is a cross-sectional view taken along line XA-XA in FIG. 6, FIG. 8, and FIG. 9, and FIG. [Figure 11] 5A shows the state of the actuator section 90 in the cross section of FIG. 5 when a low potential (GND potential) is applied to the individual electrode 51, and FIG. 5B shows the state of the actuator section 90 in the cross section of FIG. 5 when a high potential (VDD potential) is applied to the individual electrode 51. [Figure 12] 10 is a flowchart showing a procedure for inspecting a piezoelectric actuator. [Figure 13] (a) is a diagram for explaining how to apply the two probes 103 when measuring the first capacitance C1a, (b) is a diagram for explaining how to apply the two probes 103 when measuring the second capacitance C2a, (c) is a diagram for explaining how to apply the two probes 103 when measuring the first capacitance C1b, and (d) is a diagram for explaining how to apply the two probes 103 when measuring the second capacitance C2b. [Figure 14] 13(a) is a view from the X direction of the piezoelectric actuator 22 arranged on the suction stage 101 in the state of FIG. 13(a), (b) is a view from the X direction of the piezoelectric actuator 22 arranged on the suction stage 101 in the state of FIG. 13(b), (c) is a view from the X direction of the piezoelectric actuator 22 arranged on the suction stage 101 in the state of FIG. 13(c), and (d) is a view from the X direction of the piezoelectric actuator 22 arranged on the suction stage 101 in the state of FIG. 13(d). [Figure 15] 7(a) is a diagram corresponding to FIG. 7(a) of Modification 1, and FIG. 7(b) is a diagram corresponding to FIG. 7(b) of Modification 1. FIG. [Figure 16] 7(a) is a diagram corresponding to FIG. 7(a) of Modification 2, and FIG. 7(b) is a diagram corresponding to FIG. 7(b) of Modification 2. FIG. [Figure 17] 13 is a flowchart showing a procedure for inspecting a piezoelectric actuator in Modification 3. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] A preferred embodiment of the present invention will be described below. In the following description, the X and Y directions are perpendicular to the Z direction, and the X and Y directions are perpendicular to each other. For example, the Z direction is a vertical direction, and the X and Y directions are horizontal directions. The Z direction corresponds to the "first direction" of the present invention, the Y direction corresponds to the "second direction" of the present invention, and the X direction corresponds to the "third direction" of the present invention. The upper side in the Z direction corresponds to the "one side of the first direction" of the present invention, and the lower side in the Z direction corresponds to the "other side of the first direction" of the present invention. The left side of FIG. 1 in the Y direction corresponds to the "one side of the second direction" of the present invention, and the right side of FIG. 1 corresponds to the "other side of the second direction" of the present invention.

[0012] <Overall configuration of Printer 1> As shown in FIG. 1, a printer 1 according to this embodiment includes a carriage 2, a head 3, and two pairs of transport rollers 4.

[0013] The carriage 2 is supported by two guide rails 5 extending in the Y direction, and is movable along the guide rails 5 in the Y direction.

[0014] The head 3 is of a serial type, is mounted on the carriage 2, and is movable in the Y direction together with the carriage 2. A plurality of nozzles 15 are formed on the bottom surface of the head 3.

[0015] The two transport roller pairs 4 are disposed in the X direction, sandwiching the carriage 2 therebetween. When the transport roller pairs 4 rotate while sandwiching the paper P, the paper P is transported in a transport direction along the X direction.

[0016] A control unit (not shown) of the printer 1 alternately controls an ejection operation in which ink is ejected from the nozzles 15 while moving the head 3 in the Y direction together with the carriage 2, and a transport operation in which the transport roller pair 4 transports the paper P a predetermined distance in the transport direction. In this way, an image is recorded on the paper P.

[0017] <Head 3 Configuration> As shown in FIG. 2, the head 3 includes a flow passage unit 21 and a piezoelectric actuator 22.

[0018] <Flow passage unit 21> As shown in FIGS. 2 to 4, the flow path unit 21 has a rectangular shape when projected in the Z direction, and is made up of four plates 31 to 34 stacked in the Z direction.

[0019] A plurality of pressure chambers 10 are formed in the plate 31. A communication passage 12, 13 is formed in the plate 32 for each pressure chamber 10. The communication passages 12, 13 overlap one end and the other end of the corresponding pressure chamber 10 in the Y direction in the Z direction, respectively. A communication passage 14 is formed in the plate 33 for each communication passage 13. The communication passage 14 overlaps the corresponding communication passage 13 in the Z direction. The plate 33 further has 12 manifold channels 11. The manifold channels 11 are provided for each row 10R of the pressure chambers 10 arranged in the X direction. Each manifold channel 11 extends in the X direction and communicates with the plurality of pressure chambers 10 belonging to the corresponding row 10R via the communication passage 12. A plurality of nozzles 15 are formed in the plate 34. Each nozzle 15 overlaps with the communication passage 14 in the Z direction.

[0020] Four ink supply ports 8 are formed on the upper surface of the plate 31 in an area where the piezoelectric actuators 22 are not disposed. Each ink supply port 8 communicates with an ink cartridge (not shown) via a tube (not shown) or the like, and also communicates with three manifold channels 11. Ink supplied from the ink cartridge to each ink supply port 8 is supplied to the three manifold channels 11. Ink is supplied from each manifold channel 11 via a communication channel 12 to a plurality of pressure chambers 10 belonging to each row 10R.

[0021] <Piezoelectric actuator 22> 2 to 5, the piezoelectric actuator 22 is disposed on the upper surface of the flow path unit 21. The piezoelectric actuator 22 includes a vibration plate 41, a first piezoelectric layer 42, and a second piezoelectric layer 43, which are laminated in the Z direction, with the Z direction being the thickness direction, a plurality of individual electrodes 51, a high potential electrode 52 (the "second common electrode" of the present invention), and a low potential electrode 53 (the "first common electrode" of the present invention).

[0022] The diaphragm 41 is disposed on the upper surface of the flow path unit 21 (plate 31). The first piezoelectric layer is disposed on the upper surface of the diaphragm 41. The second piezoelectric layer 43 is disposed on the upper surface of the first piezoelectric layer .

[0023] The vibration plate 41, the first piezoelectric layer 42, and the second piezoelectric layer 43 are made of a piezoelectric material mainly composed of lead zirconate titanate, which is a mixed crystal of titanate and lead zirconate. However, the vibration plate 41 may be made of an insulating material other than a piezoelectric material. Alternatively, the vibration plate 41 may be formed of an ink separation layer made of a metal material such as stainless steel or a synthetic resin material and disposed on the upper surface of the flow path unit 21, and an insulating layer made of an insulating material such as a piezoelectric material and disposed on the upper surface of the ink separation layer. In other words, it is sufficient that at least the portion forming the upper surface of the vibration plate 41 has insulating properties.

[0024] The vibration plate 41, the first piezoelectric layer 42, and the second piezoelectric layer 43 each have a thickness (length in the Z direction) of, for example, about 15 μm. Furthermore, the vibration plate 41, the first piezoelectric layer 42, and the second piezoelectric layer 43 each have a length Ly in the Y direction that is shorter than a length Lx in the X direction. For example, Ly is about 30 to 35 mm, and Lx is about 35 to 40 mm. As a result, the piezoelectric actuator 22 has a length in the Y direction that is shorter than its length in the X direction.

[0025] As shown in FIG. 3, the individual electrodes 51 are arranged on the upper surface of the second piezoelectric layer 43 in correspondence with the pressure chambers 10. Each individual electrode 51 has a main portion 51a and a protruding portion 51b. The main portion 51a overlaps with substantially the entire area of ​​the corresponding pressure chamber 10 in the Z direction. The protruding portion 51b protrudes from the main portion 51a in the Y direction and does not overlap with the corresponding pressure chamber 10 in the Z direction. The protruding portion 51b is provided with a contact point that is electrically connected to a COF (Chip On Film) (not shown). A driver IC (not shown) mounted on the COF selectively applies either a high potential (VDD potential) or a low potential (GND potential) to each individual electrode 51 via the wiring of the COF under the control of the control unit.

[0026] 6, the multiple individual electrodes 51 are arranged in the X direction in an area on the upper surface of the second piezoelectric layer 43 excluding both ends in the X direction and both ends in the Y direction of the second piezoelectric layer 43, forming multiple drive electrode rows 51R corresponding to the rows 10R (see FIG. 2) of the pressure chambers 10. The multiple drive electrode rows 51R are aligned in the Y direction.

[0027] Dummy electrodes 59 are provided on one side (upper side in FIG. 6) and the other side (lower side in FIG. 6) in the X direction of each driving electrode row 51R. The dummy electrodes 59 have the same size and shape as the individual electrodes 51 belonging to the corresponding driving electrode row 51R, and are arranged at equal intervals in the X direction together with the individual electrodes 51. The dummy electrodes 59 are not electrically connected to the COF, and no potential is applied to them. By providing the dummy electrodes 59, even if the thickness of the dummy electrodes 59 at the ends in the X direction becomes small when forming electrodes by screen printing along the X direction, the thickness of the individual electrodes 51 is not affected, and the individual electrodes 51 can be appropriately formed. In addition, the difference in the amount of shrinkage due to electrode formation between the individual electrodes 51 at the center in the X direction and the individual electrodes 51 at the ends in the X direction in each driving electrode row 51R can be suppressed, and thus the variation in the amount of ejection from the multiple nozzles 15 corresponding to each driving electrode row 51R can be suppressed.

[0028] On the upper surface of the second piezoelectric layer 43, in addition to the individual electrodes 51 and the dummy electrodes 59, first surface electrodes 54a, 54b, second surface electrodes 55a, 55b, a plurality of non-conductive electrodes 63a, 63b, and inspection electrodes 62a, 62b are arranged.

[0029] As shown in Figures 6, 7(a), and 10(a), the first surface electrode 54a is disposed at the other end in the X direction (the lower left end in Figure 6) of a region at one end in the Y direction (the left end in Figure 6) of the upper surface of the second piezoelectric layer 43. As shown in Figures 6, 7(b), and 10(b), the first surface electrode 54b is disposed at one end in the X direction (the upper right end in Figure 6) of a region at the other end in the Y direction (the right end in Figure 6) of the upper surface of the second piezoelectric layer 43. The first surface electrodes 54a and 54b extend in the X direction.

[0030] As shown in Figures 6, 7(a), and 10(a), the second surface electrode 55a is disposed at one end in the X direction (upper left end in Figure 6) of a region at one end in the Y direction (left end in Figure 6) of the upper surface of the second piezoelectric layer 43. As shown in Figures 6, 7(b), and 10(b), the second surface electrode 55b is disposed at the other end in the X direction (lower right end in Figure 6) of a region at the other end in the Y direction (right end in Figure 6) of the upper surface of the second piezoelectric layer 43. The second surface electrodes 55a and 55b extend in the X direction.

[0031] Moreover, the first surface electrode 54a and the second surface electrode 55a are located at the same position in the Y direction. The first surface electrode 54a and the second surface electrode 55a are arranged at an interval in the X direction. The first surface electrode 54b and the second surface electrode 55b are located at the same position in the Y direction. The first surface electrode 54b and the second surface electrode 55b are arranged at an interval in the X direction.

[0032] As shown in FIG. 6, FIG. 7(a), and FIG. 10(a), the non-conductive electrodes 63a are arranged between the first surface electrode 54a and the second surface electrode 55a, and are aligned in the X direction. As shown in FIG. 6, FIG. 7(b), and FIG. 10(b), the non-conductive electrodes 63b are arranged between the first surface electrode 54b and the second surface electrode 55b, and are aligned in the X direction. Each non-conductive electrode 63a is divided into two electrode portions 63a1 aligned in the X direction. Each non-conductive electrode 63b is divided into two electrode portions 63b1 aligned in the X direction. The shape of the electrode portions 63a1 and 63b1 projected in the Z direction is a rectangle with the Y direction as the longitudinal direction. The length of the electrode portions 63a1 and 63b1 in the Y direction is approximately the same as the length of the first surface electrode 54a and the second surface electrode 55a in the Y direction. In addition, in the Y direction, the positions of the two electrode portions 63a1 and the positions of the two electrode portions 63a1 are the same. In the X direction, the distance between the electrode portions 63a1 in each non-conductive electrode 63a and the distance between the electrode portions 63b1 in each non-conductive electrode 63b are smaller than the distance between the non-conductive electrodes 63a and the distance between the non-conductive electrodes 63b.

[0033] Here, the reason why the non-conductive electrodes 63a, 63b are each divided into two electrode portions 63a1 and two electrode portions 63b1 is to prevent warping from occurring at the Y-direction end portion of the piezoelectric actuator 22 when the piezoelectric actuator 22 is heated during manufacture of the piezoelectric actuator 22. However, unlike the above, each of the non-conductive electrodes 63a, 63b may be a single electrode that is not divided.

[0034] As shown in Figures 6, 7(a) and 10(a), the inspection electrode 62a is disposed between the non-conductive electrode 63a closest to the second surface electrode 55a (the uppermost electrode in Figure 7(a)) and the second surface electrode 55a. This results in the inspection electrode 62a and the multiple non-conductive electrodes 63a being arranged between the first surface electrode 54a and the second surface electrode 55a. The inspection electrode 62a has two electrode portions 62a1 and 62a2 and a connecting portion 62a3.

[0035] The shape of the electrode portion 62a1 projected in the Z direction is a rectangle whose longitudinal direction is in the Y direction and whose length in the Y direction is longer than that of the electrode portion 63a1. In the Y direction, one end of the electrode portion 62a1 (the left side in FIG. 7(a)) is located on one side of one end of the non-conductive electrode 63a. In addition, in the Y direction, the position of the other end of the electrode portion 62a1 (the right side in FIG. 7(a)) is the same as the position of the other end of the non-conductive electrode 63a.

[0036] The electrode portion 62a2 is located on one side of the electrode portion 62a1 in the X direction (upper side in FIG. 7(a)). The shape of the electrode portion 62a2 projected in the Z direction is a rectangle similar to that of the electrode portion 62a1. In the Y direction, the position of the end on one side of the electrode portion 62a2 (left side in FIG. 7(a)) is the same as the position of the end on one side of the non-conductive electrode 63a. In addition, in the Y direction, the end on the other side of the electrode portion 62a2 (right side in FIG. 7(a)) is located on the other side of the other end of the non-conductive electrode 63a.

[0037] And, because the electrode portion 62a1 and the electrode portion 62a2 are arranged in this manner, the electrode portion 62a2 is shifted to the other side in the Y direction (the right side in FIG. 7(a)) with respect to the electrode portion 62a1.

[0038] Furthermore, the electrode portion 62a1 and the electrode portion 62a2 are disposed with a gap therebetween in the X direction. The length of this gap in the X direction is, for example, approximately the same as the distance between the electrode portions 63a1 of the non-conductive electrode 63a. The connecting portion 62a3 is disposed in the gap between the electrode portion 62a1 and the electrode portion 62a2, and connects the electrode portion 62a1 and the electrode portion 62a2.

[0039] Since the inspection electrode 62a is configured in this manner, the length W1a between one end and the other end of the inspection electrode 62a in the Y direction is longer than the length W1b (the length between one end and the other end) of the non-conducting electrode 63a in the Y direction.

[0040] As shown in Figures 6, 7(b) and 10(b), the inspection electrode 62b is disposed between the non-conductive electrode 63b closest to the second surface electrode 55b (the bottommost electrode in Figure 7(b)) and the second surface electrode 55b. This results in the inspection electrode 62b and the multiple non-conductive electrodes 63b being arranged between the first surface electrode 54b and the second surface electrode 55b. The inspection electrode 62b has two electrode portions 62b1 and 62b2 and a connecting portion 62b3.

[0041] The electrode portions 62b1, 62b2 and the connecting portion 62b3 are the same in size and shape as the electrode portions 62a1, 62a2 and the connecting portion 62a3. In the Y direction, the end of one side (the left side in FIG. 7(b)) of the electrode portion 62b1 is located on one side of the end of one side of the non-conductive electrode 63b. In the Y direction, the end of the other side (the right side in FIG. 7(b)) of the electrode portion 62b1 is located on the same side as the end of the other side of the non-conductive electrode 63b. In the Y direction, the end of one side (the left side in FIG. 7(b)) of the electrode portion 62b2 is located on the same side as the end of one side of the non-conductive electrode 63b. In the Y direction, the end of the other side (the right side in FIG. 7(b)) of the electrode portion 62b1 is located on the other side of the end of the other side of the non-conductive electrode 63b.

[0042] Since the electrode portion 62b1 and the electrode portion 62b2 are arranged in this manner, the electrode portion 62b2 is shifted to the other side in the Y direction (the right side in FIG. 7(b)) with respect to the electrode portion 62b1. Furthermore, since the inspection electrode 62b is configured in this manner, the length W2a between one end and the other end of the inspection electrode 62b in the Y direction is longer than the length W2b of the non-conducting electrode 63b in the Y direction (the length between one end and the other end).

[0043] The first surface electrodes 54a, 54b and the second surface electrodes 55a, 55b are electrically connected to the COF (not shown). The driver IC (not shown) applies a low potential (GND potential) to the first surface electrodes 54a, 54b and a high potential (VDD potential) to the second surface electrodes 55a, 55b through the wiring of the COF under the control of the control unit. On the other hand, the non-conductive electrodes 63a, 63b and the inspection electrodes 62a, 62b are not electrically connected to the COF. In addition, the non-conductive electrodes 63a, 63b and the inspection electrodes 62a, 62b are not electrically connected to any of the individual electrodes 52, the high potential electrode 52, and the low potential electrode 53, and no potential is applied to them.

[0044] As shown in FIGS. 4 and 5, the high potential electrode 52 is disposed on the upper surface of the first piezoelectric layer 42 (the surface between the first piezoelectric layer 42 and the second piezoelectric layer 43).

[0045] 8, 10(a) and 10(b), the high potential electrode 52 includes two trunks 521, 522 extending in the Y direction, a plurality of branch portions 523 branching from each of the trunks 521, 522 and extending in the X direction, a plurality of individual portions 52a arranged in the X direction and connected by the branch portions 523, and connection portions 524, 525 ("overlapping portions" of the present invention) overlapping with the second surface electrodes 55a, 55b in the Z direction. Each individual portion 52a corresponds to each pressure chamber 10, and overlaps with the center portion of each pressure chamber 10 in the X direction in the Z direction (see FIG. 5). Each trunk 521, 522 connects the plurality of branch portions 523.

[0046] A stem 521 is disposed on one side in the Y direction (left side in FIG. 8) of one end in the X direction of the first piezoelectric layer 42 (upper end in FIG. 8), and a stem 522 is disposed on the other side in the Y direction (right side in FIG. 8) of the other end in the X direction of the first piezoelectric layer 42 (lower end in FIG. 8). The stems 521 and 522 extend in the Y direction.

[0047] Three branch portions 523 extend in the X direction from the trunk portion 521, from one end (upper end in FIG. 8) in the X direction of the first piezoelectric layer 42 to the other end (lower end in FIG. 8). Four branch portions 523 extend in the X direction from the trunk portion 522, from the other end (lower end in FIG. 8) in the X direction of the first piezoelectric layer 42 to one end (upper end in FIG. 8). The branch portions 523 branching from each of the trunk portions 521, 522 are aligned in the Y direction.

[0048] 8 and 10(a), the connection portion 524 extends in the X direction across the second surface electrode 55a and the inspection electrode 62a at one end portion in the Y direction of the first piezoelectric layer 42 (the left end portion in FIG. 8), and overlaps with the second surface electrode 55a and the inspection electrode 62a in the Z direction. The connection portion 524 is connected to one end portion in the Y direction of the trunk portion 521 (the left end portion in FIG. 8), and is connected to the branch portion 523 located furthest in the Y direction (the left side in FIG. 8) among the multiple branch portions 523 branched off from the trunk portion 521.

[0049] 8 and 10(b), the connection portion 525 extends in the X direction across the second surface electrode 55b and the inspection electrode 62b at the other end in the Y direction of the first piezoelectric layer 42 (the right end in FIG. 8), and overlaps with the second surface electrode 55b and the inspection electrode 62b in the Z direction. The connection portion 524 is connected to the other end in the Y direction of the trunk portion 522 (the right end in FIG. 8), and is connected to the branch portion 523 located furthest in the other direction in the Y direction (the right side in FIG. 8) among the multiple branch portions 523 branched off from the trunk portion 522.

[0050] The connection portions 524 and 525 are electrically connected to the second surface electrodes 55a and 55b via through holes 43x formed in the second piezoelectric layer 43, respectively.

[0051] In addition to the high potential electrode 52, connection electrodes 56A, 56B and a plurality of non-conducting electrodes 64, 65 are disposed on the upper surface of the first piezoelectric layer 42 (the surface between the first piezoelectric layer 42 and the second piezoelectric layer 43).

[0052] As shown in Fig. 8, the connection electrodes 56A and 56B are each L-shaped and have a portion 561 extending in the Y direction and a portion 562 extending in the X direction. The connection electrode 56A is disposed at a corner on one side in the X direction (upper side in Fig. 8) and the other side in the Y direction (right side in Fig. 8) of the first piezoelectric layer 42. The connection electrode 56B is disposed at a corner on the other side in the X direction (lower side in Fig. 8) and one side in the Y direction (left side in Fig. 8) of the first piezoelectric layer 42.

[0053] As shown in FIGS. 8, 10(a) and 10(b), the portions 562 of the connection electrodes 56A and 56B are electrically connected to the first surface electrodes 54a and 54b via through-holes 43y formed in the second piezoelectric layer 43, respectively.

[0054] A portion 561 of the connection electrode 56A overlaps in the X direction with the first and second branch portions 523 from the right in Fig. 8, and also overlaps in the X direction with three columns of the multiple driving electrode columns 51R on the right in Fig. 6. A portion 561 of the connection electrode 56B overlaps in the X direction with the first and second branch portions 523 from the left in Fig. 8, and also overlaps in the X direction with three columns of the multiple driving electrode columns 51R on the left in Fig. 6.

[0055] The non-conductive electrodes 64 are arranged between the connection portion 524 and the portion 562 of the connection electrode 56B, and between the connection portion 525 and the portion 562 of the connection electrode 56A, and are spaced apart in the Y direction. The non-conductive electrodes 64 are provided individually for the non-conductive electrodes 63a, 63b and the testing electrodes 62a, 62b, and overlap the corresponding non-conductive electrodes 63a, 63b or the testing electrodes 62a, 62b in the Z direction. The non-conductive electrodes 64 are electrodes having the same size and shape as the non-conductive electrodes 63a, 63b.

[0056] The non-conducting electrodes 65 are arranged between the portion 561 and the trunk portion 521 of the connection electrode 56A and between the portion 561 and the trunk portion 522 of the connection electrode 56B, and are aligned at intervals in the Y direction.

[0057] The non-conducting electrodes 64 and 65 are not electrically connected to any of the individual electrodes 52, the high potential electrode 52, and the low potential electrode 53, and no potential is applied to them.

[0058] As shown in FIGS. 4 and 5, the low potential electrode 53 is disposed on the upper surface of the diaphragm 41 (the surface between the diaphragm 41 and the first piezoelectric layer 42).

[0059] As shown in Fig. 9, Fig. 10(a) and (b), the low potential electrode 53 includes two trunks 531, 532 extending in the Y direction, a plurality of branch portions 533 branching from each of the trunks 531, 532 and extending in the X direction, a plurality of individual portions 53a arranged in the X direction and connected by the branch portions 533, and connection portions 534, 535 overlapping the first surface electrodes 54a, 54b (see Fig. 6) in the Z direction, respectively. Of the plurality of individual portions 53a arranged in the X direction, each individual portion 53a, except for the individual portions 53a located on the extreme one side and the extreme other side in the X direction, straddles two pressure chambers 10 adjacent to each other in the X direction and has a portion overlapping in the Z direction with the ends of the two pressure chambers 10 in the X direction (see Fig. 5). The individual portions 53a located on the extreme one side and the extreme other side in the X direction have a portion overlapping in the Z direction with the end of one pressure chamber 10 in the X direction. Each of the trunks 531 and 532 connects a plurality of branches 533 .

[0060] A trunk portion 531 is disposed on the other side in the Y direction (the right side in FIG. 9) of one end portion in the X direction of diaphragm 41 (the upper end portion in FIG. 9), and a trunk portion 532 is disposed on the one side in the Y direction (the right side in FIG. 8) of the other end portion in the X direction of diaphragm 41 (the lower end portion in FIG. 9). Trunk portions 531 and 532 extend in the Y direction.

[0061] Four branch portions 533 extend in the X direction from the trunk portion 531, from one end (upper end in FIG. 9) in the X direction of the second piezoelectric layer 43 to the other end (lower end in FIG. 9). Three branch portions 533 extend in the X direction from the trunk portion 532, from the other end (lower end in FIG. 9) in the X direction of the second piezoelectric layer 43 to one end (upper end in FIG. 9).

[0062] Branches 533 branching from each trunk 531, 532 are aligned in the Y direction. Here, among the multiple branches 533 branching from trunk 531, the branch 533X located furthest on one side in the Y direction (left side in FIG. 9) is connected to trunk 532. In other words, among the four branches 533 branching from trunk 531, the branch 533X located furthest on one side in the Y direction (left side in FIG. 9) is the same as the branch 533X located furthest on the other side in the Y direction (right side in FIG. 9) among the three branches 533 branching from trunk 532. One end of the branch 533X in the X direction is connected to trunk 531, and the other end of the branch 533X in the X direction is connected to trunk 532.

[0063] The connection portion 534 extends in the X direction at the other end in the Y direction of the second piezoelectric layer 43 (the right end in FIG. 9). The connection portion 534 is connected to the other end in the Y direction of the trunk portion 531 (the right end in FIG. 9). The connection portion 535 extends in the X direction at one end in the Y direction of the second piezoelectric layer 43 (the left end in FIG. 9). The connection portion 535 is connected to one end in the Y direction of the trunk portion 532 (the left end in FIG. 9).

[0064] 10(a) and 10(b), the connection portions 534 and 535 are electrically connected to the portions 562 of the connection electrodes 56A and 56B via the through holes 42y formed in the first piezoelectric layer 42. As described above, the portions 562 of the connection electrodes 56A and 56B are electrically connected to the first surface electrodes 54a and 54b and further to the COF (not shown) via the through holes 43y formed in the second piezoelectric layer 43. Therefore, the connection portions 534 and 535 are electrically connected to the first surface electrodes 54a and 54b and further to the COF via the portions 562 of the connection electrodes 56A and 56B.

[0065] On the upper surface of the diaphragm 41 (the surface between the diaphragm 41 and the first piezoelectric layer 42), in addition to the low potential electrode 53, connection electrodes 57A and 57B and a plurality of non-conductive electrodes 66 are arranged.

[0066] Connection electrodes 57A and 57B are each L-shaped, and have a portion 571 extending in the Y direction and a portion 572 extending in the X direction. Connection electrode 57A is arranged at a corner on one side in the X direction (upper side in FIG. 9) and one side in the Y direction (left side in FIG. 9) of diaphragm 41. Connection electrode 57B is arranged at a corner on the other side in the X direction (lower side in FIG. 9) and the other side in the Y direction (right side in FIG. 9) of diaphragm 41.

[0067] 10(a) and 10(b), the portions 572 of the connection electrodes 57A and 57B are electrically connected to the connection portions 524 and 525 of the high potential electrode 52 via the through holes 42x formed in the first piezoelectric layer 42. As described above, the connection portions 524 and 525 of the high potential electrode 52 are electrically connected to the second surface electrodes 55a and 55b via the through holes 43x formed in the second piezoelectric layer 43. Therefore, the connection electrodes 57A and 57B are electrically connected to the second surface electrodes 55a and 55b via the connection portions 524 and 525 of the high potential electrode 52.

[0068] Portion 571 of connection electrode 57A overlaps in the X direction with the first and second branch portions 533 from the left in Fig. 9, and also overlaps in the X direction with five columns on the left side of multiple driving electrode columns 51R in Fig. 7. Portion 561 of connection electrode 57B overlaps in the X direction with the first to third branch portions 523 from the right in Fig. 9, and also overlaps in the X direction with seven columns on the right side of multiple driving electrode columns 51R in Fig. 6.

[0069] A portion 571 of the connection electrode 57A overlaps in the Z direction with a trunk portion 521 (see FIG. 8) of the high potential electrode 52. A portion 571 of the connection electrode 57B overlaps in the Z direction with a trunk portion 522 (see FIG. 8) of the high potential electrode 52.

[0070] The non-conductive electrodes 66 are arranged between the connection portion 534 and the portion 572 of the connection electrode 57B, and between the connection portion 535 and the portion 572 of the connection electrode 57A, and are aligned in the X direction. The non-conductive electrodes 64 are provided individually for the non-conductive electrodes 64, and overlap the corresponding non-conductive electrodes 64 in the Z direction. The non-conductive electrodes 66 are electrodes having the same size and shape as the non-conductive electrodes 64.

[0071] The non-conducting electrode 66 is not electrically connected to any of the individual electrodes 51, the high potential electrode 52, and the low potential electrode 53, and no potential is applied to the non-conducting electrode 66.

[0072] Furthermore, the thickness of each of the above-mentioned electrodes arranged on the surface between the vibration plate 41 and the first piezoelectric layer 42, the surface between the first piezoelectric layer 42 and the second piezoelectric layer 43, and the upper surface of the second piezoelectric layer 43 is, for example, approximately 0.5 to 1.5 μm.

[0073] <Actuator section> 5, in the piezoelectric actuator 22, a portion of the second piezoelectric layer 43 sandwiched between the individual electrode 51 and the individual portion 52a of the high potential electrode 52 in the Z direction is a first active portion 91 that is mainly polarized upward. Also, a portion of the first piezoelectric layer 42 and the second piezoelectric layer 43 sandwiched between the individual electrode 51 and the individual portion 53a of the low potential electrode 53 in the Z direction is a second active portion 92 that is mainly polarized downward. The piezoelectric actuator 22 has an actuator portion 90 for each pressure chamber 10, which is composed of one first active portion 91 and two second active portions 92 that sandwich the first active portion 91 in the X direction.

[0074] Here, the operation of the actuator element 90 corresponding to a certain nozzle 15 when ink is ejected from that nozzle 15 will be described.

[0075] 11(a), before ink is ejected from the nozzles 15 in the head 3, a low potential (GND potential) is applied to each individual electrode 51. At this time, due to the potential difference between the individual electrode 51 and the high potential electrode 52, an upward electric field equal to the polarization direction is generated in the first active section 91, and the first active section 91 contracts in the planar direction (directions along the X and Y directions). As a result, the portions of the vibration plate 41, the first piezoelectric layer 42, and the second piezoelectric layer 43 that overlap with the pressure chamber 10 in the Z direction are bent so as to be convex (downward) toward the pressure chamber 10. At this time, the volume of the pressure chamber 10 is smaller than when the first piezoelectric layer 42 and the second piezoelectric layer 43 are flat.

[0076] When ink is ejected from a certain nozzle 15, first, as shown in FIG. 11B, the potential of the individual electrode 51 corresponding to the nozzle 15 is switched from low potential (GND potential) to high potential (VDD potential). At this time, the potential difference between the individual electrode 51 and the high potential electrode 52 disappears, and the contraction of the first active section 91 is eliminated. On the other hand, the potential difference between the individual electrode 51 and the low potential electrode 53 occurs, and a downward electric field equal to the polarization direction is generated in the second active section 92, and the second active section 92 contracts in the planar direction. However, the second active section 92 is intended to suppress crosstalk (a phenomenon in which pressure fluctuations accompanying deformation of the actuator section 90 in a certain pressure chamber 10 are transmitted to another pressure chamber 10 adjacent to the pressure chamber 10 in the X direction), and does not contribute much to the deformation of the actuator section 90. That is, at this time, the first piezoelectric layer 42 and the second piezoelectric layer 43 are in a flat state, with the portions overlapping with the pressure chamber 10 in the Z direction not bending to be convex (upward) away from the pressure chamber 10. As a result, the volume of the pressure chamber 10 becomes larger than in the state of FIG. 11(a).

[0077] 11(a), the potential of the individual electrode 51 corresponding to the nozzle 15 is switched from a high potential (VDD potential) to a low potential (GND potential). Then, in the same manner as described above, the portions of the first piezoelectric layer 42 and the second piezoelectric layer 43 that overlap with the pressure chamber 10 in the Z direction bend so as to become convex (downward) toward the pressure chamber 10. At this time, the volume of the pressure chamber 10 is greatly reduced, so that a large pressure is applied to the ink in the pressure chamber 10, and ink is ejected from the nozzle 15.

[0078] <Inspection of the piezoelectric actuator 22> Next, a method for inspecting the piezoelectric actuator 22 will be described.

[0079] The piezoelectric actuator 22 can be manufactured, for example, by stacking sheets of piezoelectric material that form the vibration plate 41, the first piezoelectric layer 42, and the second piezoelectric layer 43, each having electrodes formed on its surface by screen printing, and then firing the stack.

[0080] When the laminate is heated during firing, warping may occur in the piezoelectric actuator 22 due to the difference in linear expansion coefficient between the piezoelectric material constituting the vibration plate 41, the first piezoelectric layer 42, and the second piezoelectric layer 43, and the metal material constituting the electrodes.

[0081] At this time, since the central portion of the piezoelectric actuator 22 is surrounded by other portions of the piezoelectric actuator 22, warping is suppressed by the other portions. In contrast, since the end portions of the piezoelectric actuator 22 are not present on the outer side of the central portion, warping is not easily suppressed by the other portions. In addition, when the piezoelectric actuator 22 is fired, a difference in atmosphere (temperature, etc.) occurs between the central portion and the end portions of the piezoelectric actuator 22. For these reasons, warping is more likely to occur at the end portions of the piezoelectric actuator 22 than at the central portion of the piezoelectric actuator 22. In addition, in this embodiment, the length Ly in the Y direction of the vibration plate 41, the first piezoelectric layer 42, and the second piezoelectric layer 43 is shorter than the length Lx in the X direction. Therefore, warping is particularly likely to occur at the end portions of the piezoelectric actuator 22 in the Y direction.

[0082] If the head 3 is manufactured using a piezoelectric actuator 22 with large warpage at the ends in the Y direction, there is a risk that cracks will occur in the vibration plate 41, the first piezoelectric layer 42, and the second piezoelectric layer 43 due to the force applied to the ends in the Y direction of the piezoelectric actuator 22 when bonding the piezoelectric actuator 22 to the flow path unit 21 or when bonding a COF to the piezoelectric actuator 22. Furthermore, there is a risk that the ejection characteristics of ink from the nozzles 15 will differ between the center and the ends in the Y direction in the manufactured head 3.

[0083] Therefore, in this embodiment, after manufacturing the piezoelectric actuator 22, the piezoelectric actuator 22 is inspected as described below to determine the degree of warping at the Y-direction end of the piezoelectric actuator 22, and based on the results, it is determined whether the piezoelectric actuator 22 is normal or abnormal.

[0084] When inspecting the piezoelectric actuator 22, as shown in FIG. 12, first, the manufactured piezoelectric actuator 22 is attached to an attachment stage 101 (see FIGS. 14(a) to (d), the “base material” of the present invention) (S101).

[0085] A large number of suction holes connected to a negative pressure pump (not shown) are formed on the mounting surface of the suction stage 101 on which the piezoelectric actuator 22 is mounted. The piezoelectric actuator 22 mounted on the suction stage 101 is sucked by the large number of suction holes, and is thereby adhered to the suction stage 101. Note that the suction force of the suction holes is not very large, and if the piezoelectric actuator 22 has a warp at the end in the Y direction, the warp of the piezoelectric actuator 22 will not be corrected to a flat state even if the piezoelectric actuator 22 is sucked by the suction holes, as shown by the dashed lines in Figures 14(a) to (d).

[0086] Next, the first capacitance C1a is measured as the capacitance between the inspection electrode 62a and the high potential electrode 52 (S102). More specifically, in S102, as shown in FIG. 13(a) and FIG. 14(a), two probes 103 connected to the capacitance measuring device 102 are applied to one end in the Y direction of the electrode portion 62a1, which is the portion of the inspection electrode 62a that is the most one side in the Y direction (the left side in FIG. 7(a)), and the second surface electrode 55a. Furthermore, the probe 103 applied to the one end in the Y direction of the electrode portion 62a1 is pressed against the suction stage 101. In this state, as shown by the solid line in FIG. 14(a), the warp of the piezoelectric actuator 22 is corrected in the Y direction at the portion where the one end in the Y direction of the electrode portion 62a1 against which the probe 103 is pressed is located, and at the portion inside the portion is closer to a flat state. In this state, the capacitance measuring device 102 measures the first capacitance C1a.

[0087] Next, the second capacitance C2a is measured as the capacitance between the inspection electrode 62a and the high potential electrode 52 (S103). More specifically, in S103, as shown in FIG. 13(b) and FIG. 14(b), the two probes 103 are applied to the other end in the Y direction of the electrode portion 62a2, which is the part of the inspection electrode 62a that is the other side in the Y direction (the right side in FIG. 7(a)), and the second surface electrode 55a. Furthermore, the probe 103 applied to the other end in the Y direction of the electrode portion 62a2 is pressed against the suction stage 101. In this state, as shown by the solid line in FIG. 14(b), the warp of the piezoelectric actuator 22 is corrected in the Y direction at the part where the other end in the Y direction of the electrode portion 62a2 against which the probe 103 is pressed is located, and at the part inside the part, and the warp is corrected and approaches a flat state. Here, in the Y direction, the other end of electrode portion 62a2 is located more inward of piezoelectric actuator 22 than one end of electrode portion 62a1, and therefore the degree of correction of warpage of piezoelectric actuator 22 in S103 is smaller than the degree of correction of warpage of piezoelectric actuator 22 in S102. Then, in this state, second capacitance C2a is measured by capacitance measuring device 102.

[0088] Next, it is determined whether or not the absolute value |C1a-C2a| of the difference between the measured first capacitance C1a and second capacitance C2a is less than a predetermined value D (S104). If the absolute value |C1a-C2a| is equal to or greater than the predetermined value D (S104: NO), it is determined that the piezoelectric actuator 22 is abnormal (S105).

[0089] If the absolute value |C1a-C2a| is less than the predetermined value D (S104: YES), then the first capacitance C1b is measured as the capacitance between the inspection electrode 62b and the high potential electrode 52 (S106).

[0090] More specifically, in S106, as shown in FIG. 13(c) and FIG. 14(c), the two probes 103 are applied to one end in the Y direction of the electrode portion 62b1, which is the portion of the inspection electrode 62b that is the most one side in the Y direction (the left side in FIG. 7(b)), and the second surface electrode 55a. Furthermore, the probe 103 applied to one end in the Y direction of the electrode portion 62b1 is pressed against the suction stage 101. In this state, as shown by the solid line in FIG. 14(c), the warp of the piezoelectric actuator 22 is corrected in the Y direction at the portion where the one end in the Y direction of the electrode portion 62b1 against which the probe 103 is pressed is located, and at the portion inside the portion, and the warp approaches a flat state. In this state, the first capacitance C1b is measured by the capacitance measuring device 102.

[0091] Next, the second capacitance C2b is measured as the capacitance between the inspection electrode 62b and the high potential electrode 52 (S107). More specifically, in S107, as shown in FIG. 13(d) and FIG. 14(d), the two probes 103 are applied to the other end in the Y direction of the electrode portion 62b2, which is the portion of the inspection electrode 62b that is the other side in the Y direction (the right side in FIG. 7(b)), and the second surface electrode 55a. Furthermore, the probe 103 applied to the other end in the Y direction of the electrode portion 62b2 is pressed against the suction stage 101. In this state, as shown by the solid line in FIG. 14(d), the warp of the piezoelectric actuator 22 is corrected in the Y direction at the portion where the other end in the Y direction of the electrode portion 62b2 against which the probe 103 is pressed is located, and at the portion inside the portion, and the warp is brought closer to a flat state. Here, in the Y direction, the other end of electrode portion 62a2 is located outside piezoelectric actuator 22 relative to one end of electrode portion 62a1, and therefore the degree of correction of warpage of piezoelectric actuator 22 in S107 is greater than the degree of correction of warpage of piezoelectric actuator 22 in S106. Then, in this state, second capacitance C2b is measured by capacitance measuring device 102.

[0092] Next, it is determined whether or not the absolute value |C1b-C2b| of the difference between the measured first capacitance C1b and second capacitance C2b is less than a predetermined value D (S108). If the absolute value |C1b-C2b| is equal to or greater than the predetermined value D (S108: NO), it is determined that the piezoelectric actuator 22 is abnormal (S105). If the absolute value |C1b-C2b| is less than the predetermined value D (S108: YES), it is determined that the piezoelectric actuator 22 is normal (S109).

[0093] <Effects> In the above embodiment, the second surface electrodes 55a, 55b conducting with the high potential electrode 52 and the inspection electrodes 62a, 62b overlapping with the connection parts 524, 525 of the high potential electrode 52 in the Z direction are disposed at the ends of the upper surface of the second piezoelectric layer 43 in the Y direction. Therefore, two probes 103 connected to the capacitance measuring device 102 are applied to the inspection electrode 62a and the second surface electrode 55a, and the inspection electrode 62b and the second surface electrode 55b, respectively, to measure the capacitance between the inspection electrode 62a and the high voltage electrode 52, and the capacitance between the inspection electrode 62b and the high voltage electrode 52, and the degree of warping at the ends of the piezoelectric actuator 22 in the Y direction can be grasped based on the measured capacitance.

[0094] More specifically, the first capacitance C1a is measured while the two probes 103 are placed against an end portion on one side in the Y direction of the inspection electrode 62a and the second surface electrode 55a, and the probes 103 placed against the above-mentioned portion of the inspection electrode 62a are pressed against the suction stage 101. The second capacitance C2a is measured while the two probes 103 are placed against an end portion on the other side in the Y direction of the inspection electrode 62a and the second surface electrode 55a, and the probes 103 placed against the above-mentioned portion of the inspection electrode 62a are pressed against the suction stage 101.

[0095] Similarly, the two probes 103 are brought into contact with one end of the inspection electrode 62b in the Y direction and the second surface electrode 55b, and the first capacitance C1b is measured with the probes 103 brought into contact with the above-mentioned portion of the inspection electrode 62b being pressed against the suction stage 101. Moreover, the two probes 103 are brought into contact with the other end of the inspection electrode 62b in the Y direction and the second surface electrode 55b, and the second capacitance C2b is measured with the probes 103 brought into contact with the above-mentioned portion of the inspection electrode 62b being pressed against the suction stage 101.

[0096] Here, if warping occurs at the Y-direction end of the piezoelectric actuator 22, the more the outer portion of the piezoelectric actuator 22 in the Y direction is pressed toward the suction stage 101, the more the warping is corrected and the closer it becomes to a flat state.

[0097] Therefore, the greater the warpage of the Y-direction end of the piezoelectric actuator 22, the greater the absolute value |C1a-C2a| of the difference between the first capacitance C1a and the second capacitance C2a and the absolute value |C1b-C2b| of the difference between the first capacitance C1b and the second capacitance C2b. Therefore, in this embodiment, the degree of warpage at the Y-direction end of the piezoelectric actuator 22 can be grasped based on whether or not the absolute value |C1a-C2a| and the absolute value |C1b-C2b| are less than a predetermined value D, and it can be determined whether or not the piezoelectric actuator 22 is normal.

[0098] Furthermore, in this embodiment, since the length Ly of the piezoelectric actuator 22 in the Y direction is shorter than the length Lx in the X direction, the piezoelectric actuator 22 is prone to warping at its end in the Y direction due to heating during manufacture.

[0099] In contrast to this, in this embodiment, the inspection electrodes 62a, 62b and the second surface electrodes 55a, 55b are arranged at the Y-direction ends of the upper surface of the second piezoelectric layer 43. Therefore, it is possible to grasp the degree of warping at the Y-direction ends of the piezoelectric actuator 22 which is prone to warping.

[0100] Also, unlike this embodiment, the inspection electrode can be arranged so as to overlap with the low potential electrode 53 in the Z direction, and the two probes 103 can be brought into contact with the inspection electrode and the first surface electrodes 54a, 54b that are conductive with the low potential electrode 53, to measure the capacitance between the inspection electrode and the low potential electrode 53. In the same manner as described above, it is also possible to grasp the degree of warping at the Y direction end of the piezoelectric actuator 22.

[0101] However, in this case, the distance between the inspection electrode and the low potential electrode 53 is greater than the distance between the inspection electrodes 62a, 62b and the high potential electrode 52 in the present embodiment, so the measured capacitance is smaller and the change in measured capacitance due to warping at the Y-direction end of the piezoelectric actuator 22 is also smaller.

[0102] Therefore, in this embodiment, as described above, the inspection electrodes 62a, 62b are arranged to overlap the high potential electrode 52 in the Z direction, and the degree of warping at the Y direction end of the piezoelectric actuator 22 is grasped based on the electrostatic capacitance between the inspection electrodes 62a, 62b and the high potential electrode 52. This results in a large change in the measured electrostatic capacitance relative to the degree of warping at the Y direction end of the piezoelectric actuator 22, making it easy to grasp the degree of warping at the Y direction end of the piezoelectric actuator.

[0103] In this embodiment, the first surface electrode 54a and the second surface electrode 55a are spaced apart in the X direction, while the inspection electrode 62a is located between the first surface electrode 54a and the second surface electrode 55a. The first surface electrode 54b and the second surface electrode 55b are spaced apart in the X direction, while the inspection electrode 62b is located between the first surface electrode 54b and the second surface electrode 55b. This increases the rigidity of the piezoelectric actuator 22 at the end in the Y direction compared to when the inspection electrodes 62a and 62b are not located at these positions, making it difficult for warping to occur at the end in the Y direction of the piezoelectric actuator 22.

[0104] Furthermore, in this embodiment, between the first surface electrode 54a and the second surface electrode 55a, the inspection electrode 62a and the multiple non-conductive electrodes 63a are arranged side by side in the X direction. Also, between the first surface electrode 54b and the second surface electrode 55b, the inspection electrode 62b and the multiple non-conductive electrodes 63b are arranged side by side in the X direction. This further increases the rigidity of the Y direction end of the piezoelectric actuator 22, making it more difficult for warping to occur at the Y direction end of the piezoelectric actuator 22.

[0105] Furthermore, in this embodiment, the connection portion 524 overlaps with the second surface electrode 55a in the Z direction and extends in the X direction to a position where it overlaps with the inspection electrode 62a in the Z direction, while the inspection electrode 62a is disposed between the second surface electrode 55a and the non-conductive electrode 63a closest to the second surface electrode 55a. This allows the length of the X direction of the connection portion 524 extending in the X direction to be as short as possible. Similarly, in this embodiment, the connection portion 525 overlaps with the second surface electrode 55b in the Z direction and extends in the X direction to a position where it overlaps with the inspection electrode 62b in the Z direction, while the inspection electrode 62b is disposed between the second surface electrode 55b and the non-conductive electrode 63b closest to the second surface electrode 55b. This allows the length of the X direction of the connection portion 525 extending in the X direction to be as short as possible.

[0106] If an electrode with a long length in the X direction is present at the Y direction end of piezoelectric actuator 22, warping is likely to occur at the Y direction end of piezoelectric actuator 22. However, by shortening the X direction length of connecting parts 524, 525 in this manner, warping can be made less likely to occur at the Y direction end of piezoelectric actuator 22.

[0107] Furthermore, the greater the distance in the Y direction between a portion of the inspection electrode 62a against which the probe 103 is applied when measuring the first capacitance C1a and a portion against which the probe 103 is applied when measuring the second capacitance C2a, the greater the difference in the degree of correction of the warp of the piezoelectric actuator 22 when the probe 103 applied to the inspection electrode 62a is pressed against the suction stage 101. As a result, the absolute value |C1a-C2a| of the difference between the first capacitance C1a and the second capacitance C2a becomes larger for the warp at the end of the piezoelectric actuator 22 in the Y direction.

[0108] Similarly, the greater the distance in the Y direction between a portion of the inspection electrode 62b against which the probe 103 is applied when measuring the first capacitance C1b and a portion against which the probe 103 is applied when measuring the second capacitance C2b, the greater the difference in the degree of correction of the warp of the piezoelectric actuator 22 when the probe 103 applied to the inspection electrode 62b is pressed against the suction stage 101. As a result, the absolute value |C1b-C2b| of the difference between the first capacitance C1b and the second capacitance C2b becomes larger for the warp at the end of the piezoelectric actuator 22 in the Y direction.

[0109] In this embodiment, the length W1a between one end and the other end of the inspection electrode 62a in the Y direction (the length between one end of the electrode portion 62a1 and the other end of the electrode portion 62a2) is longer than the length W1b in the Y direction of the non-conductive electrode 63a. Also, the length W2a between one end and the other end of the inspection electrode 62b in the Y direction (the length between one end of the electrode portion 62b1 and the other end of the electrode portion 62b2) is longer than the length W2b in the Y direction of the non-conductive electrode 63b. As a result, the absolute values ​​|C1a-C2a| and |C1b-C2b| of the capacitance differences with respect to the warpage of the piezoelectric actuator 22 become larger, making it easier to grasp the degree of warpage of the piezoelectric actuator.

[0110] Furthermore, in this embodiment, the inspection electrode 62a has two rectangular electrode portions 62a1, 62a2 whose shape when projected in the Z direction is rectangular with the Y direction as its longitudinal direction, and the inspection electrode 62b has two rectangular electrode portions 62b1, 62b2 whose shape when projected in the Z direction is rectangular with the Y direction as its longitudinal direction, thereby enabling the area of ​​the inspection electrodes 62a, 62b to be secured.

[0111] Further, the force that tends to warp the piezoelectric actuator 22 due to the difference in the linear expansion coefficient between the inspection electrodes 62a, 62b and the second piezoelectric layer 43 is greatest at the center of the inspection electrodes 62a, 62b in the Y direction. In contrast, in the present embodiment, the electrode portion 62a1 and the electrode portion 62a2 are arranged to be shifted in the Y direction in the inspection electrode 62a, and the electrode portion 62b1 and the electrode portion 62b2 are arranged to be shifted in the Y direction in the inspection electrode 62b. Therefore, the portion where the force that tends to warp the piezoelectric actuator 22 due to the difference in the linear expansion coefficient between the electrode portion 62a1 and the second piezoelectric layer 43 is greatest and the portion where the force that tends to warp the piezoelectric actuator 22 due to the difference in the linear expansion coefficient between the electrode portion 62a2 and the second piezoelectric layer 43 is greatest can be shifted in the Y direction. Also, it is possible to shift in the Y direction a portion where the force tending to warp the piezoelectric actuator 22 caused by the difference in the linear expansion coefficient between the electrode portion 62b1 and the second piezoelectric layer 43 is greatest, and a portion where the force tending to warp the piezoelectric actuator 22 caused by the difference in the linear expansion coefficient between the electrode portion 62b2 and the second piezoelectric layer 43 is greatest. As a result, the force tending to warp the piezoelectric actuator 22 is not concentrated in the same portion of the piezoelectric actuator 22 in the Y direction, and the warping generated in the piezoelectric actuator 22 can be reduced.

[0112] <Modification> Although the preferred embodiments of the present invention have been described above, the present invention is not limited to the above-mentioned embodiments, and various modifications are possible within the scope of the claims.

[0113] The shape of the inspection electrodes is not limited to that in the above-described embodiment.

[0114] For example, the positions of the electrode portion 62a1 and the electrode portion 62a2 in the Y direction may be reversed from those in the above embodiment, and the electrode portion 62a2 may be shifted to one side in the Y direction (the left side in FIG. 7(a)) relative to the electrode portion 62a1. In this case, in S102, the probe 103 is brought into contact with an end portion on the other side in the Y direction of the first electrode portion 62a1, and in S103, the probe 103 is brought into contact with an end portion on one side in the Y direction of the second electrode portion 62a2.

[0115] Similarly, the positions of the electrode portion 62b1 and the electrode portion 62b2 in the Y direction may be reversed from those in the above embodiment, and the electrode portion 62b2 may be shifted to one side in the Y direction (the left side in FIG. 7(a)) relative to the electrode portion 62b1. In this case, in S102, the probe 103 is brought into contact with an end portion on the other side in the Y direction of the first electrode portion 62b1, and in S103, the probe 103 is brought into contact with an end portion on one side in the Y direction of the second electrode portion 62b2.

[0116] Alternatively, at least one of the electrode portion 62a1 and the electrode portion 62a2 of the inspection electrode 62a and the electrode portion 62b1 and the electrode portion 62b2 of the inspection electrode 62b may not be misaligned in the X direction. If the electrode portion 62a1 and the electrode portion 62a2 are not misaligned in the X direction, the probe 103 is brought into contact with one end of either the electrode portion 62a1 or 62a2 in the Y direction in the above-mentioned S102. Also, the probe 103 is brought into contact with the other end of either the electrode portion 62a1 or 62a2 in the Y direction in the above-mentioned S103. Also, if the electrode portion 62b1 and the electrode portion 62b2 are not misaligned in the X direction, the probe 103 is brought into contact with one end of either the electrode portion 62b1 or 62b2 in the Y direction in the above-mentioned S106. Also, in the above-mentioned S107, the probe 103 is brought into contact with the end portion on the other side in the Y direction of either the electrode portion 62b1 or 62b2.

[0117] In the first modification, as shown in FIGS. 15(a) and 15(b), the shapes of the testing electrodes 111a and 111b projected in the Z direction are each parallelograms having a pair of opposing sides 112 parallel to the X direction.

[0118] The corner of the inspection electrode 111a on one side in the Y direction and the other side in the X direction (the lower left corner in FIG. 15(a)) is located on the furthest side in the Y direction (the left side in FIG. 15(a)). In addition, in the Y direction, this corner of the inspection electrode 111a is located on one side (the left side in FIG. 15(a)) of the end on one side of the non-conducting electrode 63a (the left end in FIG. 15(a)).

[0119] Also, the corner of the inspection electrode 111a on the other side in the Y direction and one side in the X direction (the upper right corner in FIG. 15(a)) is located on the other side in the Y direction (the right side in FIG. 15(a)). In addition, in the Y direction, this corner of the inspection electrode 111b is located on the other side (the right side in FIG. 15(a)) of the end on the other side of the non-conducting electrode 63a (the right end in FIG. 15(a)).

[0120] Also, the corner of the inspection electrode 111b on one side in the Y direction and the other side in the X direction (the lower left corner in FIG. 15(a)) is located on the furthest side in the Y direction (the left side in FIG. 15(a)). In addition, in the Y direction, this corner of the inspection electrode 111b is located on one side (the left side in FIG. 15(b)) of the end on one side of the non-conducting electrode 63b (the left end in FIG. 15(b)).

[0121] Also, the corner of the inspection electrode 111b on the other side in the Y direction and one side in the X direction (the upper right corner in FIG. 15(a)) is located on the other side in the Y direction (the right side in FIG. 15(a)). In addition, in the Y direction, this corner of the inspection electrode 111b is located on the other side (the right side in FIG. 15(b)) of the end on the other side of the non-conductive electrode 63b (the right end in FIG. 15(b)).

[0122] In the first variant, since the inspection electrodes 111a, 111b have this shape, the lengths W3a, W4a between one end and the other end of the inspection electrodes 111a, 111b in the Y direction are longer than the lengths W3b, W4b of the non-conducting electrodes 63a, 63b in the Y direction.

[0123] In the first modification, in the above-mentioned S102 and S106, the probe 103 is brought into contact with the lower left corners of the inspection electrodes 111a and 111b in Figs. 15(a) and 15(b), respectively. In addition, in the above-mentioned S103 and S107, the probe 103 is brought into contact with the upper right corners of the inspection electrodes 111a and 111b in Figs. 15(a) and 15(b), respectively.

[0124] In the first modification, the shape of the testing electrodes 111a, 111b projected in the Z direction is a parallelogram having a pair of opposing sides 112 parallel to the Y direction, so that the length between one end and the other end of the testing electrodes 111a, 111b in the Y direction can be increased.

[0125] In the second modification, as shown in Fig. 16(a), the testing electrode 121a has a first electrode portion 122a, a second electrode portion 122b, and a third electrode portion 122c. The first electrode portion 122a extends in the Y direction. In addition, in the Y direction, one end (the left end in Fig. 16(a)) of the first electrode portion 122a is located on one side (the left side in Fig. 16(a)) of one end (the left end in Fig. 16(a)) of the non-conducting electrode 63a.

[0126] The second electrode portion 122b extends in the Y direction. In addition, in the Y direction, the other end of the second electrode portion 122b (the right end in FIG. 16(a)) is located on the other side (the right end in FIG. 16(a)) of the other end of the non-conductive electrode 63b (the right end in FIG. 16(a)). The third electrode portion 122c is located between the first electrode portion 122a and the second electrode portion 122b, and connects the other end of the first electrode portion 122a in the Y direction (the right end in FIG. 16(a)) and one end of the second electrode portion 122b in the Y direction (the left end in FIG. 16(a)).

[0127] 16(b), the testing electrode 121b has a first electrode portion 123a, a second electrode portion 123b, and a third electrode portion 123c. The first electrode portion 123a, the second electrode portion 123b, and the third electrode portion 123c are the same in size and shape as the first electrode portion 122a, the second electrode portion 122b, and the third electrode portion 122c, respectively.

[0128] In the second variant, since the inspection electrodes 121a, 121b are configured in this manner, the lengths W5a, W6a between one end and the other end of the inspection electrodes 121a, 121b in the Y direction are longer than the lengths W5b, W6b of the non-conducting electrodes 63a, 63b in the Y direction.

[0129] In the second modification, in the above-mentioned S102, the probe 103 is brought into contact with an end portion on one side in the Y direction (the left side in FIG. 16(a)) of the first electrode portion 122a of the inspection electrode 121a. In addition, in the above-mentioned S103, the probe 103 is brought into contact with an end portion on the other side in the Y direction (the right side in FIG. 16(a)) of the second electrode portion 122b of the inspection electrode 121a. In addition, in the above-mentioned S106, the probe 103 is brought into contact with an end portion on one side in the Y direction (the left side in FIG. 16(b)) of the first electrode portion 123a of the inspection electrode 121b. In addition, in the above-mentioned S107, the probe 103 is brought into contact with an end portion on the other side in the Y direction (the right side in FIG. 16(b)) of the second electrode portion 123b of the inspection electrode 121b.

[0130] In the second modification, the testing electrodes 121a, 121b have the first to third electrode portions 122a-122c and the first to third electrode portions 123a-123c as described above, respectively, so that the length between one end and the other end of the testing electrodes 121a, 121b in the Y direction can be increased.

[0131] In addition, by making the shape of the inspection electrode projected in the Z direction different from that described above, the length in the Y direction between one end and the other end in the Y direction may be longer than the length in the Y direction of the non-conducting electrodes 63a, 63b.

[0132] Furthermore, the length in the Y direction between one end and the other end of the testing electrode in the Y direction is not limited to being longer than the length in the Y direction of the non-conductive electrodes 63a, 63b. The length in the Y direction between one end and the other end of the testing electrode in the Y direction may be equal to or shorter than the length in the Y direction of the non-conductive electrodes 63a, 63b.

[0133] In the above embodiment, the connection portion 524 overlapping the second surface electrode 55a in the Z direction extends to a position overlapping the inspection electrode 62a in the Z direction, and the inspection electrode 62a is disposed between the second surface electrode 55a and the non-conductive electrode 63a closest to the second surface electrode 55a. In addition, the connection portion 525 overlapping the second surface electrode 55b in the Z direction extends to a position overlapping the inspection electrode 62b in the Z direction, and the inspection electrode 62b is disposed between the second surface electrode 55b and the non-conductive electrode 63b closest to the second surface electrode 55b. However, the present invention is not limited to this.

[0134] For example, in a configuration in which the connection portion 524 overlapping the second surface electrode 55a in the Z direction extends to a position overlapping the inspection electrode 62a in the Z direction, the inspection electrode 62a may be disposed between two non-conductive electrodes 63a, or between the first surface electrode 54a and the non-conductive electrode 63a closest to the first surface electrode 54a.

[0135] Similarly, in a configuration in which the connection portion 525 overlapping with the second surface electrode 55b in the Z direction extends to a position overlapping with the testing electrode 62b in the Z direction, the testing electrode 62b may be arranged between two non-conducting electrodes 63b, or between the first surface electrode 54b and the non-conducting electrode 63b closest to the first surface electrode 54b.

[0136] In the above embodiment, the inspection electrode 62a and the multiple non-conductive electrodes 63a are arranged in the X direction between the first surface electrode 54a and the second surface electrode 55a. In addition, the inspection electrode 62b and the multiple non-conductive electrodes 63b are arranged in the X direction between the first surface electrode 54b and the second surface electrode 55b. However, the present invention is not limited to this.

[0137] For example, there may be only one non-conducting electrode disposed between at least one of the first surface electrode 54a and the second surface electrode 55a and the first surface electrode 54b and the second surface electrode 55b. Also, for example, there may be no non-conducting electrode disposed between at least one of the first surface electrode 54a and the second surface electrode 55a and the first surface electrode 54b and the second surface electrode 55b.

[0138] In the above embodiment, the inspection electrode 62a is disposed between the first surface electrode 54a and the second surface electrode 55a. The inspection electrode 62b is disposed between the first surface electrode 54b and the second surface electrode 55b. However, the present invention is not limited to this.

[0139] For example, the inspection electrode 62a may be disposed outside the first surface electrode 54a or outside the second surface electrode 55a in the X direction. Similarly, for example, the inspection electrode 62b may be disposed outside the first surface electrode 54b or outside the second surface electrode 55b in the X direction.

[0140] In addition, in the above embodiment, the inspection electrodes 62a, 62b overlap in the Z direction with the high-voltage electrode 52 arranged on the surface between the first piezoelectric layer 42 and the second piezoelectric layer 43, but this is not limited to the above. The inspection electrodes may overlap in the Z direction with the low-voltage electrode 51 arranged on the surface between the vibration plate 41 and the first piezoelectric layer 42.

[0141] In the above embodiment, the length Ly of the piezoelectric actuator in the Y direction is shorter than the length Lx of the piezoelectric actuator in the X direction, but this is not limited to the above. The length Ly may be equal to or greater than the length Lx.

[0142] Furthermore, the method of inspecting the piezoelectric actuator is not limited to that described in the above embodiment. In Modification 3, the piezoelectric actuator is inspected according to the flow of Fig. 17. Note that, although the following description will be given taking an example of inspecting the piezoelectric actuator 22, the other piezoelectric actuators described above can also be inspected in a similar manner to that described below.

[0143] 17, in the third modification, as in the above-described embodiment, the piezoelectric actuator 22 is adsorbed to the adsorption stage 101 (S201). Then, the two probes 103 are brought into contact with the inspection electrode 62a and the second surface electrode 55a to measure the capacitance C3a between the inspection electrode 62a and the high-voltage electrode 52 (S202).

[0144] Next, it is determined whether the absolute value |C3a-C0| of the difference between the measured capacitance C3a and the reference capacitance C0 is less than a predetermined value E (S203). If the absolute value |C3a-C0| is equal to or greater than the predetermined value E (S203: NO), it is determined that the piezoelectric actuator 22 is abnormal (S204).

[0145] If the absolute value |C3a-C0| is less than the predetermined value E (S203: YES), then the two probes 103 are placed against the inspection electrode 62b and the second surface electrode 55b to measure the capacitance C3b between the inspection electrode 62b and the high voltage electrode 52 (S205).

[0146] Next, it is determined whether the absolute value |C3b-C0| of the difference between the measured capacitance C3b and the reference value C0 is less than a predetermined value E (S206). If the absolute value |C3b-C0| is equal to or greater than the predetermined value E (S206: NO), it is determined that the piezoelectric actuator 22 is abnormal (S204). If the absolute value |C3b-C0| is less than the predetermined value E (S206: YES), it is determined that the piezoelectric actuator 22 is normal (S207).

[0147] As described above, in the third modification, the degree of warping of the end portion of the piezoelectric actuator 22 in the Y direction can be grasped based on the absolute value of the difference between the capacitance C3a between the inspection electrodes 62a, 62b and the high potential electrode 52 and the reference value C0, and it can be determined whether the piezoelectric actuator 22 is normal or abnormal.

[0148] In the above, an example has been described in which the present invention is applied to a piezoelectric actuator that constitutes a head that ejects ink from a nozzle and to its inspection, but the present invention is not limited to this. It is also possible to apply the present invention to a piezoelectric actuator that constitutes a device other than a head and to its inspection. [Explanation of symbols]

[0149] 22 Piezoelectric Actuator 41 Vibration plate 42 First piezoelectric layer 43 Second piezoelectric layer 51 Individual electrodes 52 High potential electrode 53 Low potential electrode 54a,54b 1st surface electrode 55a,55b 2nd surface electrode 62a, 62b Inspection electrodes 62a1,62a2,62b1,62b2 Electrode part 63a,63b Non-conducting electrode 111a, 111b Inspection electrodes 121a, 121b Inspection electrodes 122a, 123a 1st electrode part 122b, 123b 2nd electrode part 122c, 123c 3rd electrode part 524,525 Connection

Claims

1. a vibration plate having insulation on at least one surface in a first direction; a first piezoelectric layer disposed on the one surface of the vibration plate in the first direction; a second piezoelectric layer disposed on the one surface of the first piezoelectric layer in the first direction; a plurality of individual electrodes disposed on a surface of the second piezoelectric layer on the one side in the first direction; a first common electrode that is common to the plurality of individual electrodes and that is disposed on a surface between the vibration plate and the first piezoelectric layer; a second common electrode that is common to the plurality of individual electrodes and that is disposed on a surface between the first piezoelectric layer and the second piezoelectric layer; a first surface electrode disposed on the one surface of the second piezoelectric layer in the first direction and electrically connected to the first common electrode; a second surface electrode disposed on the one surface of the second piezoelectric layer in the first direction and electrically connected to the second common electrode; The second common electrode is a first common electrode portion located at an end of a surface between the first piezoelectric layer and the second piezoelectric layer in a second direction perpendicular to the first direction, extending in a third direction perpendicular to both the first direction and the second direction, overlapping with the second surface electrode in the first direction and connected to the second surface electrode; a second common electrode portion located at an end in the third direction of a surface between the first piezoelectric layer and the second piezoelectric layer, extending in the second direction, and connected to the first common electrode portion; a testing electrode that is disposed on an end portion in the second direction of the one surface of the second piezoelectric layer in the first direction, overlaps with the first common electrode portion of the second common electrode in the first direction, and is not electrically connected to any of the individual electrodes, the first common electrode, and the second common electrode, a length of the first common electrode portion in the second direction is longer than a length of the second common electrode portion in the third direction; The inspection electrode is A piezoelectric actuator, characterized in that the length in the second direction is longer than the length in the third direction, and the piezoelectric actuator overlaps with the first common electrode portion in the first direction over the entire length in the second direction.

2. 2 . The piezoelectric actuator according to claim 1 , wherein the vibration plate, the first piezoelectric layer, and the second piezoelectric layer have lengths in the second direction that are shorter than their lengths in the third direction.

3. a vibration plate having insulation on at least one surface in a first direction; a first piezoelectric layer disposed on the one surface of the vibration plate in the first direction; a second piezoelectric layer disposed on the one surface of the first piezoelectric layer in the first direction; a plurality of individual electrodes disposed on a surface of the second piezoelectric layer on the one side in the first direction; a first common electrode that is common to the plurality of individual electrodes and that is disposed on a surface between the vibration plate and the first piezoelectric layer; a second common electrode that is common to the plurality of individual electrodes and that is disposed on a surface between the first piezoelectric layer and the second piezoelectric layer; a first surface electrode disposed on the one surface of the second piezoelectric layer in the first direction and electrically connected to the first common electrode; a second surface electrode disposed on the one surface of the second piezoelectric layer in the first direction and electrically connected to the second common electrode; one of the first common electrode and the second common electrode extends to an end of a surface on which the other common electrode is disposed, in a second direction perpendicular to the first direction; a testing electrode that is disposed at an end in the second direction of the one surface of the second piezoelectric layer in the first direction, overlaps one of the common electrodes in the first direction, and is not electrically connected to any of the individual electrodes, the first common electrode, and the second common electrode; the first surface electrode is disposed on an end portion, in the second direction, of the one surface, in the first direction, of the second piezoelectric layer; the second surface electrode is disposed at an end, in the second direction, of the one surface of the second piezoelectric layer in the first direction, at a distance from the first surface electrode in a third direction perpendicular to both the first direction and the second direction; A piezoelectric actuator, characterized in that the inspection electrode is disposed on the surface of the second piezoelectric layer on one side in the first direction, in a portion between the first surface electrode and the second surface electrode.

4. a portion of the surface of the second piezoelectric layer on the one side in the first direction between the first surface electrode and the second surface electrode, the portion including at least one non-conductive electrode that is not conductive to any of the individual electrodes, the first common electrode, the second common electrode, and the testing electrode, and is different from the testing electrode; 4. The piezoelectric actuator according to claim 3, wherein the at least one non-conducting electrode and the testing electrode are arranged side by side in the third direction.

5. The one common electrode is an overlapping portion extending in the first direction to a position overlapping one of the first surface electrode and the second surface electrode that is electrically connected to the one common electrode, the overlapping portion extends in the third direction to a position where it overlaps with the testing electrode in the first direction; 5. The piezoelectric actuator according to claim 4, wherein the inspection electrode is disposed on the one surface of the second piezoelectric layer in the first direction, in a portion between the one surface electrode and the non-conducting electrode.

6. 6. The piezoelectric actuator according to claim 4, wherein the testing electrode has a length in the second direction between one end and the other end in the second direction that is longer than that of the non-conducting electrode.

7. The inspection electrode is 7. The piezoelectric actuator according to claim 6, characterized in that it has two electrode portions that are connected to each other side by side in the third direction and whose shape when projected in the first direction is a rectangle with the second direction as its longitudinal direction.

8. 8. The piezoelectric actuator according to claim 7, wherein the two electrode portions are offset in the second direction.

9. 7. The piezoelectric actuator according to claim 6, wherein the shape of the testing electrode projected in the first direction is a parallelogram having a pair of opposing sides parallel to the second direction.

10. The inspection electrode is a first electrode portion extending in the second direction; a second electrode portion disposed apart from the first electrode portion in the third direction, extending in the second direction, and shifted toward the other side in the second direction with respect to the first electrode portion; a third electrode portion connecting an end portion of the first electrode portion on the other side in the second direction and an end portion of the second electrode portion on the one side in the second direction, 7. The piezoelectric actuator according to claim 6, wherein a length in the second direction between an end of the first electrode portion on one side in the second direction and an end of the second electrode portion on the other side in the second direction is longer than a length in the second direction of the non-conducting electrode.

11. A diaphragm having insulation on at least one side in a first direction; a first piezoelectric layer disposed on the one surface of the vibration plate in the first direction; a second piezoelectric layer disposed on the one surface of the first piezoelectric layer in the first direction; a plurality of individual electrodes disposed on a surface of the second piezoelectric layer on the one side in the first direction; a first common electrode that is common to the plurality of individual electrodes and that is disposed on a surface between the vibration plate and the first piezoelectric layer; a second common electrode that is common to the plurality of individual electrodes and that is disposed on a surface between the first piezoelectric layer and the second piezoelectric layer; a first surface electrode disposed on the one surface of the second piezoelectric layer in the first direction and electrically connected to the first common electrode; a second surface electrode disposed on the one surface of the second piezoelectric layer in the first direction and electrically connected to the second common electrode; one of the first common electrode and the second common electrode extends to an end of a surface on which the other common electrode is disposed, in a second direction perpendicular to the first direction; a test electrode that is disposed at an end in the second direction of one surface of the second piezoelectric layer in the first direction, overlaps one of the common electrodes in the first direction, and is not electrically connected to any of the individual electrodes, the first common electrode, and the second common electrode, The piezoelectric actuator is attached to a substrate; a probe is applied to one end of the testing electrode in the second direction and to the one common electrode, and the probe applied to the testing electrode is pressed against the base material, and a first capacitance is measured as a capacitance between the testing electrode and the one common electrode; a probe is applied to the other end of the testing electrode in the second direction and to one of the common electrodes, and the probe applied to the testing electrode is pressed against the base material, and a second capacitance is measured as a capacitance between the testing electrode and one of the common electrodes; When the difference between the first capacitance and the second capacitance is less than a predetermined value, the piezoelectric actuator is determined to be normal; A method for inspecting a piezoelectric actuator, comprising the steps of: determining that the piezoelectric actuator is abnormal when a difference between the first capacitance and the second capacitance is equal to or greater than a predetermined value.

12. The method for inspecting a piezoelectric actuator according to claim 11, wherein the piezoelectric actuator is the piezoelectric actuator according to any one of claims 7 to 11.

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