JP2010069618A - Liquid discharging head and piezoelectric actuator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress warpage caused by electrodes used for driving during calcining, and to inspect the presence of cracks from a pressure room side in a plurality of piezoelectric layers. <P>SOLUTION: An inkjet head 3 includes a cavity unit 11 having a plurality of the pressure rooms 14Aa and a plurality of nozzles communicating with the respective pressure rooms 14Aa, and a lamination type piezoelectric actuator 12 fixed to the cavity unit 11. The piezoelectric actuator 12 is constituted of a plurality of the piezoelectric layers 12a and 12b, drive electrodes 21 and 22 used for driving and a dummy electrode 23 which are laminated in the thickness direction. The dummy electrode 23 is positioned at the pressure room 14Aa side in the laminating direction of the laminated body. The warpage caused by the electrodes 21 and 22 used for driving during calcining is suppressed, and there is the function of inspecting the presence of the cracks from the pressure room 14Aa side of the piezoelectric layer 15. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a liquid discharge head and a piezoelectric actuator.

  An ink jet head as a liquid discharge head is known which includes a cavity unit having a plurality of pressure chambers and a plurality of nozzles respectively communicating with the pressure chambers, and a laminated piezoelectric actuator fixed to the cavity unit. Such a piezoelectric actuator is configured by laminating a plurality of piezoelectric layers and drive electrodes used for driving in the thickness direction.

  Such an actuator is usually formed by laminating and firing a two-layer or three-layer piezoelectric element (PZT) single plate and a drive electrode in the thickness direction, but the arrangement of the drive electrodes is not symmetrical in the thickness direction. Then, so-called warpage occurs in the actuator after firing.

  That is, as shown in FIG. 13, the piezoelectric actuator 101 has the uppermost piezoelectric layer 103 (first layer) when the pressure chamber 14Aa is viewed in plan (when viewed from the stacking direction of the cavity unit 102 and the piezoelectric actuator 101). And an individual electrode 121 corresponding to the central portion of the pressure chamber 102a and a ground electrode 122 formed over the second piezoelectric layer 104 (second layer / vibration plate) from the upper side. Prepare. Since the actuator after firing has different shrinkage rates between the piezoelectric material and the electrode material, so-called warpage occurs as shown in FIG. 14 if the arrangement of the drive electrodes is not symmetrical in the thickness direction.

Therefore, in a structure having a plurality of piezoelectric layers, a driving electrode used for driving and a dummy electrode that does not contribute to driving deformation are formed symmetrically in the thickness direction between them, so that the heat between the piezoelectric element (PZT) and the electrode is increased. It has been proposed to correct the warp of the piezoelectric actuator during firing due to the different shrinkage rates (see, for example, Patent Document 1).
JP 2001-162696 A (Claim 5)

  As in the technique described in Patent Document 1, warpage of the piezoelectric actuator during firing can be corrected by forming the drive electrode and the dummy electrode symmetrically, but unlike the drive electrode that contributes to drive deformation. Since the dummy electrode does not contribute to driving deformation, the dummy electrode becomes useless after firing. In addition to the drive electrode, providing such a dummy electrode also causes an increase in size of the piezoelectric actuator.

  The present invention uses a dummy electrode to not only suppress warping during firing but also to inspect the presence or absence of cracks in the plurality of piezoelectric layers from the pressure chamber side and a piezoelectric actuator The purpose is to provide.

According to a first aspect of the present invention, there is provided a liquid discharge head comprising: a cavity unit having a plurality of pressure chambers and a plurality of nozzles respectively communicating with the pressure chambers; and a stacked piezoelectric actuator fixed to the cavity unit. The laminated piezoelectric actuator is configured by laminating a plurality of piezoelectric layers, a drive electrode used for driving and a dummy electrode in the thickness direction, and the dummy electrode is driven in the stacking direction of the laminate. The dummy electrode is positioned closer to the pressure chamber than the electrode, and the dummy electrode suppresses warping due to the electrode used for driving during firing of the piezoelectric actuator, and the plurality of piezoelectric layers from the pressure chamber side. It has a function of inspecting the presence or absence of cracks. Here, the “driving electrode used for driving” means an electrode used for driving, that is, an electrode that contributes to deformation of the piezoelectric layer by applying an electric field to the piezoelectric layer. “Dummy electrode” means an electrode that is not used for driving, that is, does not apply an electric field to the piezoelectric layer or contribute to deformation of the piezoelectric layer.

  In this way, the laminated piezoelectric actuator is configured by laminating a plurality of piezoelectric layers, drive electrodes used for driving and dummy electrodes in the thickness direction, and the dummy electrodes are arranged in the stacking direction of the laminate. Since it is located closer to the pressure chamber than the drive electrode, the function of the dummy electrode suppresses (or corrects) warpage of the piezoelectric actuator due to the electrode used for the drive during firing. In addition, after firing, the presence or absence of cracks from the pressure chamber side of the plurality of piezoelectric layers can be inspected using dummy electrodes.

  According to a second aspect of the present invention, in the liquid ejection head according to the first aspect, the dummy electrode exists in a region corresponding to each of the pressure chambers and a region corresponding to a space between two adjacent pressure chambers. Can be configured so as not to exist.

  In this case, even if the dummy electrode is formed so as not to exist in a region corresponding to the space between two adjacent pressure chambers, it exists in a region corresponding to each pressure chamber. The dummy electrode can be used for inspection (detection) of the presence or absence of cracks from the pressure chamber side of the plurality of piezoelectric layers.

  According to a third aspect of the present invention, in the liquid discharge head according to the first aspect, the dummy electrode may be formed over the entire area of the piezoelectric layer.

  In this case, since the dummy electrode is formed over the entire area of the piezoelectric layer, it is not necessary to consider the relationship with the pressure chamber, and manufacturing is easy.

  According to a fourth aspect of the present invention, in the liquid discharge head according to any one of the first to third aspects, the amount of warpage during firing of the piezoelectric actuator when only the electrode used for the driving is disposed is used for the driving. It is desirable that the dummy electrode is provided so that the amount of warpage when the piezoelectric actuator is fired when the electrode and the dummy electrode are arranged is small.

  In this case, the provision of the dummy electrode reduces the amount of warping during firing of the piezoelectric actuator, compared to the case where the dummy electrode is not provided.

  The liquid discharge head according to any one of claims 1 to 3, wherein only the electrode used for the drive is disposed, and the amount of warpage during firing of the piezoelectric actuator and the electrode used for the drive In addition, it is preferable that the size of the dummy electrode and the position to be provided are set so that the difference between the amount of warpage when the piezoelectric actuator is fired when only the dummy electrode is disposed is equal to or less than a certain amount. Here, the warpage amount is an absolute value not related to the direction of warpage.

  In this way, by providing a dummy electrode and setting the size of the dummy electrode and the position where the dummy electrode is provided, the difference between the amount of warpage during firing of the piezoelectric actuator when the dummy electrode is not provided is a constant amount. It becomes as follows.

According to a sixth aspect of the present invention, in the liquid discharge head according to the fourth or fifth aspect, the piezoelectric actuator includes an area of each electrode disposed on the pressure chamber side with respect to the intermediate surface in the thickness direction and each electrode from the intermediate surface. So that the sum of the products up to the length is equal to the sum of the product of the area of each electrode arranged on the counter pressure chamber side from the intermediate surface in the thickness direction and the length from the intermediate surface to each electrode. It can be set as the structure by which the electrode used for a drive and the dummy electrode are arrange | positioned.

  In this way, the size (area) and position of the electrode used for driving and the dummy electrode are balanced, and warpage during firing of the piezoelectric actuator is suppressed.

  In the liquid discharge head according to any one of claims 1 to 6, the cavity unit is configured to have conductivity, and the dummy electrode and the cavity unit include: It can be set as the structure which can connect the test | inspection means which test | inspects the continuity state between them.

  In this way, by inspecting the conduction state (for example, the state of electrical resistance and current) between the dummy electrode and the conductive cavity unit with the inspection means, the plurality of piezoelectric layers are The presence or absence of cracks from the pressure chamber side can be inspected.

  The liquid discharge head according to any one of claims 1 to 6, wherein the cavity unit is configured to have conductivity, and the piezoelectric layer on the pressure chamber side and In addition, a dummy electrode or an electrode used for driving is provided on the piezoelectric layer away from the pressure chamber, respectively, and the dummy electrode or the driving electrode and the cavity unit have inspection means for inspecting the conduction state between them. It is desirable to be connectable.

  In this case, the inspection state of the conduction state between the dummy electrode or the drive electrode and the conductive cavity unit is inspected, so that the plurality of piezoelectric layers are separated from the pressure chamber side. The presence or absence of cracks can be inspected.

  In the liquid discharge head according to any one of claims 1 to 6, the piezoelectric layer on the pressure chamber side and the piezoelectric layer further away from the pressure chamber are used for dummy electrodes or driving. It is desirable that each of the electrodes is provided and an inspection means for inspecting a conduction state between them can be connected to the piezoelectric layer on the pressure chamber side and the dummy electrode of the piezoelectric layer on the pressure chamber or the electrode used for driving. .

  In this way, the conduction state between the piezoelectric layer on the pressure chamber side and the dummy electrode or the electrode used for driving on the piezoelectric layer on the upper side of the piezoelectric layer can be determined by the cracks of the plurality of piezoelectric layers from the pressure chamber side. Existence can be checked.

  According to a tenth aspect of the present invention, in the liquid discharge head according to any one of the first to ninth aspects, the piezoelectric actuator is provided so as to be biased to a portion of the thickness direction on the side away from the pressure chamber. The portion is an active portion, and a portion close to the pressure chamber where the driving electrode is not provided is a unimorph type piezoelectric actuator in which the non-active portion is provided, and the dummy electrode is the inactive portion It can be set as the structure provided in the part. Here, the “active part” means a part that changes its shape by applying or not applying a voltage, and becomes a deformed state or a non-deformed state. This means the part where the shape does not change.

  In this way, it is not a part that becomes an active part that changes its form due to liquid discharge (becomes deformed or non-deformed) but a part that becomes an inactive part whose form does not change. Since the electrode is provided, there is no possibility that the dummy electrode affects the liquid ejection.

The liquid ejection head according to any one of claims 1 to 9, wherein the piezoelectric actuator includes a first active portion corresponding to a central portion of the pressure chamber and a central portion of the pressure chamber. A second active portion corresponding to a portion on the outer periphery side, and the electrode used for driving includes a region corresponding to the first active portion and a region corresponding to the second active portion. An individual electrode formed so as to occupy both of these regions across, a first constant potential electrode formed so as to occupy a region corresponding to the first active portion, and at least the second active portion A second constant potential electrode formed so as to occupy a corresponding region can be provided.

  In this way, the deformation of the first active portion is transmitted to the first active portion with respect to the adjacent pressure chamber is canceled by the second active portion, which is advantageous for suppressing so-called crosstalk. Can be realized.

  The invention according to claim 12 is a laminated piezoelectric actuator fixed to a cavity unit having a plurality of pressure chambers and a plurality of nozzles respectively communicating with the pressure chambers, and the plurality of piezoelectric layers and drive electrodes used for driving And the dummy electrode are laminated in the thickness direction, and the dummy electrode is located on the pressure chamber side in the lamination direction of the laminate, and suppresses warping due to the electrode used for driving during firing. In addition, the plurality of piezoelectric layers have a function of inspecting for the presence or absence of cracks from the pressure chamber side.

  In this way, the dummy electrode suppresses (or corrects) the warp of the piezoelectric actuator due to the electrode used for driving during firing, and after firing, the plurality of piezoelectric elements are utilized using the dummy electrode. It is also possible to inspect the layer for cracks from the pressure chamber side.

  As described above, the present invention is configured by laminating a plurality of piezoelectric layers, a drive electrode used for driving, and a dummy electrode in the thickness direction, and the dummy electrode is formed in the pressure chamber in the stacking direction of the laminate. Therefore, the dummy electrode can suppress (or correct) the warp caused by the electrode used for driving during firing. In addition, after firing, the presence or absence of cracks from the pressure chamber side of the plurality of piezoelectric layers can be inspected using dummy electrodes.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
(First embodiment)
FIG. 1A is a schematic configuration diagram showing a schematic configuration of an ink jet printer (droplet ejection apparatus) according to a first embodiment of the present invention, and FIG. 1B is a diagram illustrating a cavity unit, a piezoelectric actuator, and a piezoelectric actuator according to the present invention. It is explanatory drawing which shows the relationship of a flexible wiring board (COP).

  As shown in FIG. 1A, an inkjet printer 1 according to the present invention has an inkjet head for recording on a recording sheet P (recording medium) on a lower surface of a carriage 2 on which an ink cartridge (not shown) is mounted. 3 (droplet discharge head) is provided. The carriage 2 is supported by a carriage shaft 5 provided in the printer frame 4 and a guide plate (not shown), and is configured to reciprocate in a direction B perpendicular to the conveyance direction A of the recording paper P. The recording paper P conveyed in the A direction from a paper supply unit (not shown) is introduced between a platen roller (not shown) and the ink jet head 3 and is ejected from the ink jet head 3 toward the recording paper P. As a result, predetermined recording is performed, and then the paper is discharged by the paper discharge roller 6.

Further, as shown in FIG. 1B, the ink jet head 3 includes a cavity unit 11.
The piezoelectric actuator 12 is provided in order from the lower side, and a flexible wiring board 13 (signal line) that supplies a drive signal to the upper surface of the piezoelectric actuator 12 is provided.

  As shown in FIG. 2, the cavity unit 11 includes a laminate 14 composed of a plurality of plate members. A piezoelectric layer 15 (top plate) as a vibration plate is provided on the upper side of the laminated body 14, while a nozzle plate 16 having a nozzle hole 16 a and a through hole 17 a corresponding to the nozzle hole 16 a are provided on the lower side. A plate assembly 18 formed by adhering a spacer plate 17 is integrally attached. A piezoelectric actuator 12 for selectively ejecting ink (liquid) in each pressure chamber 14Aa is bonded (fixed) to the upper side of the piezoelectric layer 15. Further, a filter 19 for capturing dust contained in the ink is provided in the opening 11 a of the cavity unit 11. The nozzle plate 16 is a synthetic resin (for example, polyimide resin) plate in which one nozzle hole 16a is provided for each pressure chamber 14Aa of the cavity plate 14A (which constitutes the laminate 14). The nozzle plate 16 may be a metal plate.

  As shown in FIG. 3, the laminate 14 has a cavity plate 14A, a base plate 14B, an aperture plate 14C, two manifold plates 14D and 14E, and a damper plate 14F stacked in order from the upper side and metal diffusion bonded. It is. The six plates 14A to 14F are stacked in alignment with each other so that an ink flow path is individually formed for each nozzle hole 16a. Here, the cavity plate 14A is a metal plate in which openings functioning as a plurality of pressure chambers 14Aa are regularly formed corresponding to the nozzle rows. The base plate 14B is a metal plate provided with communication holes 14Ba from the manifolds 14Da and 14Ea (common ink chambers) to the pressure chambers 14Aa and communication holes 14Bb from the pressure chambers 14Aa to the nozzle holes 16a. On the upper surface of the aperture plate 14C, a communication passage 21 that communicates each pressure chamber 14Aa and the manifolds 14Da, 14Ea is formed as a recessed passage, and from the manifolds 14Da, 14Ea (common ink chamber) to each pressure chamber 14Aa. This is a metal plate provided with a communication hole 14Ca and a communication hole 14Cb from each pressure chamber 14Aa to the nozzle hole 16a. The manifold plates 14D and 14E are metal plates provided with communication holes 14Db and 14Eb from the pressure chambers 14Aa to the nozzle holes 16a in addition to the manifolds 14Da and 14Ea. The damper plate 14F is a metal plate provided with a communication hole 14Fb for communicating each pressure chamber 14Aa with each nozzle hole 16a in addition to a damper chamber 14Fa formed as a recess on the lower surface.

  As described above, the cavity unit 11 includes the plurality of nozzle holes 16a, the plurality of pressure chambers 14Aa communicating with each of the plurality of nozzle holes 16a, and the manifolds 14Da and 14Ea for temporarily storing ink supplied to the pressure chambers 14Aa. The plurality of pressure chambers and 14Aa communicate with the plurality of nozzle holes 16a, respectively.

  As shown in FIG. 4, the piezoelectric actuator 12 is formed by laminating a plurality of piezoelectric layers 12a and 12b in order from the upper side. The piezoelectric layers 12a and 12b are made of a lead zirconate titanate (PZT) ceramic material (piezoelectric sheet) having ferroelectricity, and are polarized in the thickness direction. In this embodiment, the piezoelectric layer 15 is also made of the same material as the piezoelectric layers 12a and 12b, that is, a lead zirconate titanate (PZT) ceramic material (piezoelectric sheet) having ferroelectricity.

The piezoelectric actuator 12 is configured by laminating a plurality of piezoelectric layers 12a and 12b, individual electrodes 21 and constant potential electrodes 22 that are driving electrodes used for driving, and a dummy electrode 23 that does not contribute to driving in the thickness direction. ing. The dummy electrode 23 is located on the pressure chamber 14Aa side in the stacking direction of the stacked body of the piezoelectric layers 12a and 12b and the electrodes 21 to 23. In other words, the dummy electrode 23 is located closer to the pressure chamber 14Aa than the center in the thickness direction of the piezoelectric actuator 12. The dummy electrode 23 is located on the pressure chamber 14Aa side with respect to the individual electrode 21 and the constant potential electrode 22 used for driving.

  That is, as shown in FIG. 4, the individual electrode 21 formed on the upper side of the uppermost piezoelectric layer 12a (first layer) and corresponding to the central portion of the pressure chamber 14Aa, and the second piezoelectric layer 12b (second) from the upper side. The ground electrode 22 is formed over the entire upper side of the layer. Moreover, the dummy electrode 23 formed over the entire upper side of the piezoelectric layer 15 which is the third layer from the upper side is provided. Here, the central portion of the pressure chamber 14Aa is a central portion in the nozzle row direction X in which the nozzle holes 16a are arranged. The electrodes 21 to 23 are made of a metal material such as Ag—Pd.

  Further, the electrodes 21 to 23 of each of the piezoelectric layers 12a and 12b are arranged as shown in FIG. 5 when viewed in plan (when viewed from the stacking direction of the cavity unit 11 and the piezoelectric actuator 12). That is, on the upper surface side of the piezoelectric layer 12a (first layer), the individual electrodes 21 are formed at a constant pitch in the nozzle row direction corresponding to each pressure chamber 14Aa. Adjacent individual electrodes 21 are formed with a half-pitch shift in the nozzle row direction, and between these rows, the individual electrodes 21 are connected to the connection terminals (not shown) of the flexible wiring board 13. Terminal portions 21a are formed in a staggered pattern.

  The dummy electrode 23 has a first function of suppressing (or correcting) warpage due to the electrodes (individual electrodes 21 and constant potential electrodes 22) used for driving during firing. In addition, it has a second function of inspecting the plurality of piezoelectric layers 12a and 12b for cracks from the pressure chamber 14Aa side. In consideration of the first function, the layer thicknesses of the piezoelectric layers 12a and 12b are set.

  A driver IC 90 (see FIG. 1B) that supplies a drive signal is electrically connected to the connection terminal portion 21a of each individual electrode 21 through the flexible wiring board 13 (signal line). The driver IC 90 and the flexible wiring board 13 constitute voltage applying means for applying a driving voltage to the active portion S of the piezoelectric actuator 12.

  That is, in order to change the volume of the pressure chamber 14Aa, the first potential (ground potential) and the second potential (positive potential, for example, 20 V) different from the first potential (ground potential) are selected for the individual electrodes 21 through the flexible wiring board 13. Applied. The constant potential electrode 22 is always applied with a first potential (ground potential). The active portion S is polarized in the same direction (polarization direction) as the voltage applied when the individual electrode 21 is deformed by applying the second potential and applying the first potential to the constant potential electrode 22. Has been. The dummy electrode 23 does not need to be applied with a potential, but the first potential (ground potential) may be always applied similarly to the constant potential electrode 22 so as not to affect driving.

  As described above, the piezoelectric actuator 12 has the individual electrodes 21 corresponding to the respective pressure chambers 14Aa, and the individual electrodes 21 have the first potential (ground potential) and the second potential (positive potential) as drive signals. Is selectively applied to change the volume of the pressure chamber 14Aa to eject ink from the nozzle hole 16a. That is, the active portion S is not deformed even when the first potential is applied to the individual electrode 21, but when the second potential is applied, the active portion S is deformed so as to protrude into the pressure chamber 14Aa. Since the volume of the chamber 14Aa is changed to be small, ink is ejected from the nozzle hole 16a.

In the above-described structure of the piezoelectric actuator 12, the amount of warpage (absolute value) during firing of the piezoelectric actuator when only the electrodes used for driving (drive electrode 21, constant potential electrode 22) are disposed, and the electrodes used for driving (drive electrodes) 21, constant potential electrode 22) and dummy electrode 2
The size of the dummy electrode 23 and the position where the dummy electrode 23 is provided (including the layer thickness of the piezoelectric layer) so that the difference from the warpage amount (absolute value) when firing the piezoelectric actuator 12 when only 3 is disposed is less than a certain amount. ) Is preset. The size and the position of the dummy electrode 23 are obtained in advance by experiment and analysis prior to manufacture for each type of piezoelectric actuator.

  For example, in the piezoelectric actuator 12, the sum of the product of the area of each electrode disposed on the pressure chamber 14Aa side from the intermediate surface in the thickness direction and the length from the intermediate surface to each electrode is greater than the intermediate surface in the thickness direction. Electrodes used for driving (drive electrode 21 and constant potential electrode 22) such that the sum of the product of the area of each electrode arranged on the counter pressure chamber 14Aa side and the length from the intermediate surface to each electrode is substantially equal. And the dummy electrode 23 is arrange | positioned.

  As described above, the piezoelectric actuator 12 is configured by laminating the plurality of piezoelectric layers 12a and 12b, the drive electrode 21, the constant potential electrode 22, and the dummy electrode 23 in the thickness direction. Since the laminate is arranged in a predetermined positional relationship on the pressure chamber 14Aa side in the stacking direction of the stacked body, the dummy electrode 23 is used to drive an electrode (drive electrode 21, constant potential) when the piezoelectric actuator 12 is fired. Warpage that occurs when only the electrode 22) is provided is suppressed.

  Therefore, in the structure of the piezoelectric actuator 12, only the dummy electrode 23 that does not affect driving is provided, and only the electrodes used for driving (individual electrode 21, constant potential electrode 22) are disposed at the time of firing the piezoelectric actuator 12. The amount of warping during firing of the piezoelectric actuator when the electrode used for driving and the dummy electrode are arranged is smaller than the amount of warping (first function of the dummy electrode 23).

  Further, since the cavity unit 11 has a laminated body 14 of metal plates and is configured to have conductivity, the dummy electrode 23 and the cavity unit 11 (cavity plate 14A) have a conductive state between them. A resistance detection circuit 41 is connected as inspection means for inspection. Thereby, based on the conduction state between the dummy electrode 23 and the cavity unit 11, the presence or absence of a crack from the pressure chamber 14Aa side of the piezoelectric layer 15 as a vibration plate, that is, a crack causing discharge failure is inspected. (Second function of the dummy electrode 23).

  Such an inspection is performed in a state where the pressure chamber 14Aa is filled with ink or a test liquid having conductivity. Between the dummy electrode 23 and the cavity unit 11 (cavity plate 14A), there is a piezoelectric layer 15 as a diaphragm having no electrical conductivity. Therefore, the piezoelectric layer 15 penetrates the piezoelectric layer 15 from the pressure chamber 14Aa. If there is no crack extending to the dummy electrode 23, the electrical resistance increases. On the other hand, when the piezoelectric layer 15 has a crack extending from the pressure chamber 14Aa through the piezoelectric layer 15 to the dummy electrode 23, the electric resistance is reduced. This is because an electric current flows through the ink that has entered the crack or the test liquid having conductivity.

  Therefore, by inspecting the electrical resistance between the dummy electrode 23 and the cavity unit 11 in this way, it is easily determined whether the product is a pass product without a crack as described above or a reject product with a crack. can do.

  Next, the electrical configuration of the inkjet printer 1 centering on the control device 51 will be described with reference to the block diagram of FIG.

The control device 51 includes a CPU that is a central processing unit, a ROM that stores various programs and data for controlling the overall operation of the printer 1, and a RAM that temporarily stores data and the like processed by the CPU. And an input / output interface for transmitting / receiving signals to / from an external device.

  And as shown in FIG. 6, the control apparatus 51 is provided with the recording control part 51A. The recording control unit 51A is configured to record the image on a recording sheet based on the data regarding the recording image input from the input device 52, the carriage driving motor 53 that drives the carriage 2, and the transport mechanism 54. The paper feed motor 54A and the paper discharge motor 54B are controlled. Further, the recording control unit 51A displays information related to recording, error messages, and the like on the display 55.

  In addition, the control device 51 includes a crack determination unit 51B that determines whether or not there is a crack from the pressure chamber 14Aa side that causes a discharge failure. The crack determination unit 51B performs determination based on the electrical resistance between the dummy electrode 23 and the cavity unit 11 (cavity plate 14A) detected by the resistance detection circuit 41. Specifically, when the value of the electrical resistance detected by the resistance detection circuit 41 is equal to or greater than a set value, the crack determination unit 51B is normal with no crack extending from the pressure chamber 14Aa to the dummy electrode 23. On the other hand, if the value of the electrical resistance detected by the resistance detection circuit 41 is less than the set value, there is a crack extending from the pressure chamber 14Aa side to the dummy electrode 23. It is determined that the insulation is deteriorated and abnormal. Further, this is displayed on the display 55 to notify the user.

  Here, the detection timing of the electric resistance by the resistance detection circuit 41 is not limited to a specific timing, and may be during the recording operation of the inkjet printer 1 or in a standby state where the recording operation is not performed. Also good. That is, at an arbitrary timing, the resistance detection circuit 41 measures the electrical resistance between the dummy electrode 23 and the cavity unit 11, and based on the result, the crack determination unit 51 </ b> B detects the dummy electrode 23 from the pressure chamber 14 </ b> Aa side. Inspection for the presence or absence of cracks extending up to can be performed.

  The functions of the recording control unit 51A and the crack determination unit 51B described above are realized by the CPU executing various control programs stored in the ROM of the control device 51.

  Further, not only the piezoelectric layer 15 which is the layer closest to the pressure chamber 14Aa but also the piezoelectric layer 12b which is an upper layer thereof can be inspected for cracks from the pressure chamber 14Aa side. That is, since the constant potential electrode 22 (ground potential) is provided in the piezoelectric layer 12b that is further away from the pressure chamber 14Aa than the piezoelectric layer 14Aa on the pressure chamber 14Aa side, although not specifically illustrated, the constant potential electrode Similarly, not only the piezoelectric layer 15 but also the piezoelectric layer 12b is connected by connecting another inspection means (second resistance detection circuit) for inspecting the conduction state between the cavity 22 and the cavity unit 11 (laminated body 14). It is also possible to inspect whether there is a crack from the pressure chamber 14Aa side that also penetrates.

In the embodiment, the dummy electrode 23 is formed over the entire upper side of the piezoelectric layer 15 that is the third layer from the upper side. As shown in FIGS. You may make it form so that it may exist in the area | region corresponding to pressure chamber 14Aa, and it may not exist in the area | region corresponding between two adjacent pressure chambers 14Aa. This is because the dummy electrode 23A is provided in order to suppress warpage during firing of the piezoelectric actuator, and does not need to be formed over the entire surface of the piezoelectric layer 15. The detection of the presence or absence of cracks by the dummy electrode 23 is for checking whether there is a possibility that the ink in the pressure chamber 14Aa may permeate the piezoelectric layer 15 side and hinder the ejection function. Also from this point, the dummy electrode 23A is not particularly required to be provided over the entire upper surface of the piezoelectric layer 15, and may be provided in a region corresponding to each of the plurality of pressure chambers 14Aa. In this embodiment, as shown in FIG. 8, the dummy electrode 23A includes a plurality of first portions 23Aa formed in a region corresponding to each pressure chamber 14Aa and a beam portion 14Ab (see FIG. 8) between the pressure chambers 14Aa. 7) and a second portion 23Ab formed in the nozzle row direction X and connected to each first portion 23Aa. In addition, this 2nd part 23Ab is formed corresponding to the site | part (girder part 14Ab) in which the connection terminal part 21a of the individual electrode 21 is provided.
(Second Embodiment)
In this embodiment, as shown in FIGS. 9 and 10, the piezoelectric actuator 12A is formed by stacking three layers (multiple layers) of piezoelectric layers 12e, 12f, and 12g in order from the upper side. .

  As shown in FIGS. 9 and 10, the piezoelectric actuator 12A includes an individual electrode 31 formed on the upper side of the uppermost piezoelectric layer 12e (first layer) and corresponding to the central portion of the pressure chamber 14Aa, and the second electrode from the upper side. A first constant potential electrode 32 having a first portion 32a formed on the upper side of the piezoelectric layer 12f (second layer) and corresponding to the central portion of the pressure chamber 14Aa, and a third piezoelectric layer 12g (third layer from the upper side) ) And a second constant potential electrode 33 formed over the whole. A dummy electrode 34 is provided over the entire piezoelectric layer 15 which is the fourth layer from the top and functions as a diaphragm. Adjacent individual electrodes 31 are formed with a half-pitch shift in the nozzle row direction, and between these rows, the individual electrodes 31 are connected to the connection terminals (not shown) of the flexible wiring board 13. The point that the terminal portions 31a are formed in a staggered manner is the same as in the first embodiment.

  The first active portion S1 is a portion sandwiched between the individual electrode 31 and the first constant potential electrode 32, and corresponds to the central portion of the pressure chamber 14Aa, while the second active portion S2 includes the individual electrode 31 and the first constant potential electrode 32. It is a portion sandwiched between the two constant potential electrodes 33 and corresponds to a portion on the outer peripheral side with respect to the central portion of the pressure chamber 14Aa. The second active portion S2 includes not only a region corresponding to the spar 14Ab that is a wall that partitions adjacent pressure chambers 14Aa, but also a region corresponding to an inner portion (center portion side) of the outer peripheral edge of the pressure chamber 14Aa. Including. Each individual electrode 31 is shared with respect to the first and second constant potential electrodes 32 and 33, and the electrodes 31 to 33 are made of a metal material such as an Ag-Pd system.

  In the piezoelectric actuator 12A, the electrodes (individual electrodes 31, constant potential electrodes 32, 33) used for driving are provided in a portion on the side away from the pressure chamber 14Aa in the thickness direction of the piezoelectric actuator 12A. And a second active portion S1, S2, and a unimorph type piezoelectric actuator in which the portion (piezoelectric layer 12g and piezoelectric layer 15) on the side close to the pressure chamber 14Aa not provided with the drive electrode is an inactive portion It is. The dummy electrode 34 is provided in the portion serving as the inactive portion, and the warpage amount (absolute value) at the time of firing of the piezoelectric actuator 12A when only the electrode used for driving is disposed, the electrode used for driving, and The size of the dummy electrode 34 and the position where the dummy electrode 34 is provided are set so that the difference from the warpage amount (absolute value) when the piezoelectric actuator 12A is fired when the dummy electrode 34 is disposed is equal to or less than a certain amount.

  Further, since the cavity unit 11 is configured to have conductivity, the resistance detection circuit as an inspection unit that inspects the conduction state between the dummy electrode 34 and the cavity unit 11 (cavity plate 14A). 41 is connected. As a result, as in the first embodiment, based on the conduction state between the dummy electrode 34 and the cavity unit 11, the piezoelectric layer 15 serving as the diaphragm is cracked from the pressure chamber 14Aa side, that is, has a defective discharge. It can be inspected for the presence of cracks.

  As described above, the dummy electrode 34 suppresses warping due to the electrodes (individual electrode 31 and constant potential electrodes 32 and 33) used for driving during firing, and whether or not the piezoelectric layer 15 is cracked from the pressure chamber 14Aa side. It has a function of inspecting.

  In the piezoelectric actuator 12A, as shown in FIG. 9, the individual electrode 31 corresponds to the region corresponding to the first active portion S1 and the second active portion S2 in the direction Y orthogonal to the nozzle row direction X. The two regions are formed so as to occupy both regions. The first constant potential electrode 32 is formed so as to occupy a region corresponding to the first active portion S1. The second constant potential electrode 33 is formed so as to occupy at least a region corresponding to the second active portion S2. The first active part S1 has the same direction as the direction of the voltage applied when the first electrode is applied with the first electric potential and the second electric potential is applied to the first constant potential electrode 32 to be deformed. It is polarized in (polarization direction). On the other hand, the second active portion S2 has the same direction as the direction of the voltage applied when the second potential is applied to the individual electrode 31 and the first potential is applied to the second constant potential electrode 33 to be deformed. Is polarized. That is, the polarization is performed so that the direction in which the voltage is applied and the polarization direction are the same.

  The first constant potential electrode 32 is always set to the second potential (positive potential), and the second constant potential electrode 33 is always set to the first potential (ground potential). The individual electrode 31 is selectively given a first potential (ground potential) and a second potential (positive potential) in order to change the volume of the pressure chamber 14Aa. . An example is shown in Table 1 below. That is, the direction of voltage application is the same during polarization and during driving, but the first constant potential electrode 32 is always set to a positive potential (20 V: constant), and the second constant potential electrode 33 is always grounded. The potential (0 V: constant) is applied, and a positive potential (20 V: constant) is applied to the individual electrode 31 or the application is canceled. Therefore, when the individual electrode 31 is set to the ground potential, a voltage is applied to the first active portion S1, but no voltage is applied to the second active portion S2, while the individual electrode 31 is at the ground potential. When the potential is positive, the voltage is not applied to the first active part S1, but the voltage is applied to the second active part S2. Here, as shown in Table 1, the voltage applied between the electrodes at the time of driving is smaller than the voltage applied at the time of polarization, so that deterioration due to repeated application of voltage between the electrodes is suppressed. .

このように電極３１〜３３を配置することで、前記電圧印加手段により、個別電極３１に第２の電位（正の電位：２０Ｖ）を付与する、第１の活性部Ｓ１への電圧の非印加時（待機時）では、第１の活性部Ｓ１は、第１及び第２の方向Ｚ，Ｘにおいて伸縮しない、変形しない状態となる。このとき、第２の活性部Ｓ２は、電圧印加状態となり、圧力室１４Ａａに向かう積層方向Ｚ（第１の方向）に伸張し、その積層方向Ｚと直交するノズル列方向Ｘ（第２の方向）に収縮しようとするので、圧電層１２ｇ及び振動板としての圧電層１５の働きによって、ノズル列方向側部に位置する第２の活性部Ｓ２が、圧力室１４Ａａから離れる方向に反るように変形する。この第２の活性都Ｓ２の変形が、圧力室１４Ａａの容積変化を大きくするのに寄与し、マニホールド１４Ｄａ，１４Ｅａから圧力室１４Ａａにインクを多く吸い込むのに貢献する。

By disposing the electrodes 31 to 33 in this way, the voltage application unit applies a second potential (positive potential: 20 V) to the individual electrode 31 and does not apply a voltage to the first active portion S1. At the time (standby), the first active part S1 is not expanded and contracted in the first and second directions Z and X, and is not deformed. At this time, the second active portion S2 is in a voltage application state, extends in the stacking direction Z (first direction) toward the pressure chamber 14Aa, and extends in the nozzle row direction X (second direction) perpendicular to the stacking direction Z. Therefore, the second active portion S2 located on the side in the nozzle row direction is warped in the direction away from the pressure chamber 14Aa by the action of the piezoelectric layer 12g and the piezoelectric layer 15 as a vibration plate. Deform. The deformation of the second active city S2 contributes to increasing the volume change of the pressure chamber 14Aa, and contributes to sucking a large amount of ink from the manifolds 14Da and 14Ea into the pressure chamber 14Aa.

On the other hand, when a voltage is applied to the first active portion S1 that applies a first potential (ground potential) to the individual electrode 31 (during driving), the first active portion S1 has the same direction as the polarization direction. A voltage is applied to the electrode, and the piezoelectric lateral effect expands in the stacking direction Z toward the pressure chamber 14Aa, contracts in the nozzle row direction X orthogonal to the stacking direction Z, and protrudes and deforms in the direction of the pressure chamber 14Aa. It becomes. On the other hand, since the piezoelectric layers 12g and 15 are not affected by the electric field and therefore do not spontaneously contract, the polarization direction between the piezoelectric layers 12e and 12f located on the upper side and the piezoelectric layers 12g and 15 located on the lower side is reduced. A difference is produced in the distortion in the vertical direction. Combined with this, the piezoelectric layer 15 is fixed to the cavity plate 14, and the piezoelectric layers 12e and 12f try to deform so as to protrude toward the pressure chamber 14Aa (unimorph deformation). For this reason, the volume of the pressure chamber 14Aa decreases, the ink pressure increases, and ink is ejected from the nozzle holes 16a.

  When the voltage is applied to the first active portion S1, the second active portion S2 is in a voltage non-applied state, and thus returns to a state where it does not expand and contract in the first and second directions Z and X. It will be. Therefore, when the first active part S1 is projecting and deforming in the direction of the pressure chamber 14Aa, the second active part S2 returns to a state in which it does not deform, and therefore the influence of the deformation of the first active part S1 is the first. 2 is canceled by the second active portion S2, hardly reaching the adjacent pressure chamber 14Aa, and crosstalk is suppressed. That is, the second active portion S2 is controlled so that the deformation of the first active portion S1 due to the switching between the application and non-application of the voltage to the first active portion S1 is prevented from propagating to the adjacent pressure chamber 14Aa. Switching between application and non-application of a voltage is performed.

  Thereafter, when the individual electrode 31 is returned to the same potential (ground potential) as that of the first constant potential electrode 32, as described above, the first active portion S1 is not deformed, and the second active portion S2 is Since the pressure chamber 14Aa is deformed so as to warp away from the pressure chamber 14Aa and the volume of the pressure chamber 14Aa returns to the original volume, ink is sucked into the pressure chamber 14Aa from the manifolds 14Da and 14Ea.

  Due to such deformation of the first active portion S1 and the second active portion S2, the ink discharge operation is repeated, and in each discharge operation, the volume change of the pressure chamber 14Aa is increased to increase the discharge efficiency and the crosstalk. Is suppressed.

  In addition, the state where the first potential is applied to the individual electrode 31 is set to the standby state, and then the ink is ejected by once applying the second potential and then returning to the first electricity again, so-called striking control. A method is also possible.

  Further, based on the conduction state between the dummy electrode 34 and the cavity unit 11, the inspection of the piezoelectric layer 15 for cracks from the pressure chamber 14Aa side, that is, cracks that cause ejection failure, is performed in the first embodiment. As in the embodiment, the pressure chamber 14Aa is filled with ink or a test liquid having conductivity, and the piezoelectric layer 15 has no crack extending from the pressure chamber 14Aa to the dummy electrode 34 through the piezoelectric layer 15 The electrical resistance increases. On the other hand, when the piezoelectric layer 15 has a crack extending from the pressure chamber 14Aa through the piezoelectric layer 15 to the dummy electrode 34, the electric resistance is reduced. Therefore, by checking the electrical resistance between the dummy electrode 23 and the cavity unit 11, it is possible to easily determine whether the product is a pass product without a crack as described above or a reject product with a crack. it can.

  In the second embodiment, the first constant potential electrode 32 has a portion corresponding to the central portion of the pressure chamber 14Aa. However, as shown in FIGS. It is also possible to use the first constant potential electrode 32A in which the portion corresponding to the central portion becomes the opening 32c ′. In this case, the first active portion S1 ′ is sandwiched between the individual electrode 31 and the first constant potential electrode 32A by the piezoelectric layers 12e and 12f sandwiched between the individual electrode 31 and the second constant potential electrode 33. The second active portion S2 ′ is formed by the piezoelectric layer 12e. The first constant potential electrode 32A is always set to the second potential (positive potential), and the second constant potential electrode 33 is always set to the first potential (ground potential). A first potential (ground potential) and a second potential (positive potential) are selectively applied to the individual electrode 31 in order to change the volume of the pressure chamber 14Aa.

  The first constant potential electrode 32A is formed to occupy a region corresponding to the second active portion S2 ′ and a region corresponding to the beam portion 14Ab between the pressure chambers 14Aa adjacent in the direction orthogonal to the nozzle row direction. ing. In other words, the second constant potential electrode 33 extends to a region corresponding to the nozzle row direction side portion of the pressure chamber 14Aa including the region corresponding to the beam portion 14Ab, and is adjacent to the two pressures in the nozzle row direction of the pressure chamber 14Aa. The chambers 14Aa and 14Aa are shared.

  Also in this embodiment, since the cavity unit 11 has conductivity, a resistance detection circuit 41 is connected between the dummy electrode 34 and the cavity unit 11 (cavity plate 14A). Similarly to the above, based on the conduction state between the dummy electrode 34 and the cavity unit 11, it is possible to inspect the presence or absence of cracks in the piezoelectric layer 15 from the pressure chamber 14 </ b> Aa side, that is, cracks that cause ejection failure.

  Therefore, the dummy electrode 34 has a function of suppressing warping due to the electrode used for driving during firing and inspecting the piezoelectric layer 15 for cracks from the pressure chamber 14Aa side.

  Also in this embodiment, since the second constant potential electrode 33 (ground potential) is provided in the piezoelectric layer 12g farther from the pressure chamber 14Aa than the piezoelectric layer 14Aa on the pressure chamber 14Aa side, Although not shown in the figure, by connecting another inspection means (second resistance detection circuit) for inspecting the conduction state between the second constant potential electrode 33 and the cavity unit 11, similarly, It is also possible to inspect whether there is a crack from the pressure chamber 14Aa side that penetrates not only the layer 15 but also the piezoelectric layer 12g. That is, the presence or absence of cracks from the pressure chamber 14Aa side of the plurality of piezoelectric layers 15 and 12g can be inspected.

  The piezoelectric actuator operates in the same manner as in the above-described embodiment. That is, when the second electrode (ground potential) is applied to the individual electrode 31 and the voltage is not applied to the first active part S1 ′ (during standby), the first active part S1 ′ In the second directions Z and X, it does not expand and contract and does not deform, but the second active portion S2 ′ located on the side in the nozzle row direction is in a voltage application state and warps in a direction away from the pressure chamber 14Aa. Deform. The deformation of the second active city S2 'contributes to increasing the volume change of the pressure chamber 14Aa, and contributes to sucking a large amount of ink from the manifolds 14Da and 14Ea into the pressure chamber 14Aa.

  On the other hand, when a voltage is applied to the first active part S1 ′ that applies a first potential (positive potential: 20V) to the individual electrode 31 (during driving), the first active part S1 ′ The piezoelectric lateral effect expands in the stacking direction Z toward the pressure chamber 14Aa, contracts in the nozzle row direction X orthogonal to the stacking direction Z, and enters a state in which the pressure chamber 14Aa protrudes and deforms. The volume decreases, the ink pressure increases, and ink is ejected from the nozzle holes 16a. At this time, since the second active part S2 'is in a voltage non-application state, the second active part S2' returns to a state where it does not expand and contract in the first and second directions Z and X. Therefore, the influence of the deformation of the first active part S1 'is canceled by the second active part S2', hardly reaching the adjacent pressure chamber 14Aa, and crosstalk is suppressed.

  Thereafter, when the individual electrode 31 is returned to the same potential (ground potential) as that of the first constant potential electrode 32, as described above, the first active portion S1 ′ is not deformed, and the second active portion S2 ′. Is deformed so as to warp away from the pressure chamber 14Aa, and the volume of the pressure chamber 14Aa returns to the original volume, so that ink is sucked into the pressure chamber 14Aa from the manifolds 14Da and 14Ea.

The deformation of the first active part S1 ′ and the second active part S2 ′ as described above causes the ink ejection operation to be repeated. In each ejection operation, the volume change of the pressure chamber 14Aa is increased to increase the ejection efficiency, Crosstalk is suppressed.

  In addition to the above, the present invention can be implemented with the following modifications.

(i) In the above-described embodiment, the inkjet printer 1 includes the resistance detection circuit 41 that detects the electrical resistance between the dummy electrodes 23 and 34 and the cavity unit 11. Only at the time of inspection for detecting the presence or absence of cracks, a resistance detector as a resistance detection circuit is connected to the dummy electrodes 23 and 34 of the printer 1 and the cavity unit 11 so that the electrical resistance can be measured. It is also possible to configure. That is, the printer 1 is not always provided with a resistance detection circuit, but can be configured such that a resistance detector (resistance detection circuit) can be connected to the printer 1 when necessary.

  (ii) Although the cavity unit is configured to have conductivity, when the cavity unit does not have conductivity, dummy electrodes 23, 23A, 34 provided on the piezoelectric layer 15 which is a layer on the pressure chamber 14Aa side, and more It is also possible to connect an inspection means for inspecting the conduction state between the electrodes 22 and 33 used for driving provided on the piezoelectric layers 12b and 12g on the side away from the pressure chamber 14Aa. It is.

(iii) The present invention is not limited to the case where the liquid discharge head is an ink jet head, and other liquids such as applying a colored liquid as fine droplets or forming a wiring pattern by discharging a conductive liquid. It can also be applied to a discharge head.

  (iv) Not only recording paper but also various materials such as resin and cloth can be used as the recording medium, and not only ink but also various materials such as colored liquid and functional liquid are used as the liquid to be ejected. be able to.

FIG. 1A is a schematic configuration diagram showing a schematic configuration of an ink jet printer (droplet ejection apparatus) according to a first embodiment of the present invention, and FIG. 1B is a diagram illustrating a cavity unit, a piezoelectric actuator, and a piezoelectric actuator according to the present invention. It is explanatory drawing which shows the relationship of a flexible wiring board (COP). It is a perspective view which shows the state which affixed the piezoelectric actuator on the upper side of the cavity unit. It is a figure which decomposes | disassembles a cavity unit into each plate which is a component, and shows them with a diaphragm. It is a schematic sectional drawing of 1st Embodiment. It is explanatory drawing of arrangement | positioning of the electrode in each piezoelectric layer of a piezoelectric actuator about 1st Embodiment. FIG. 2 is a block diagram schematically showing an electrical configuration of the inkjet printer. It is a figure similar to FIG. 4 about the modification of 1st Embodiment. It is a figure similar to FIG. 5 about the modification of 1st Embodiment. It is a figure similar to FIG. 4 about 2nd Embodiment. It is a figure similar to FIG. 5 about 2nd Embodiment. It is a figure similar to FIG. 4 about the modification of 2nd Embodiment. It is a figure similar to FIG. 5 about the modification of 2nd Embodiment. It is a figure similar to FIG. 4 about a prior art example. It is a figure similar to FIG. 5 about a prior art example.

Explanation of symbols

1 Inkjet printer 3 Inkjet head (liquid ejection head)
12, 12A Piezoelectric actuators 12a, 12b, 12e-12g Piezoelectric layer 15 Piezoelectric layers 21, 31 Individual electrodes 22, 32, 32A, 33 Constant potential electrodes 23, 34 Dummy electrodes 41 Electrical resistance detection circuit 51B Crack determination section

Claims (12)

A cavity unit having a plurality of pressure chambers and a plurality of nozzles respectively communicating with the pressure chambers;
A laminated piezoelectric actuator fixed to the cavity unit;
A liquid ejection head comprising:
The laminated piezoelectric actuator is
A plurality of piezoelectric layers, a driving electrode used for driving, and a dummy electrode are stacked in the thickness direction, and the dummy electrode is positioned closer to the pressure chamber than the driving electrode in the stacking direction of the stacked body. And
The dummy electrode has a function of suppressing warping due to the electrode used for driving during firing of the piezoelectric actuator and inspecting the plurality of piezoelectric layers for cracks from the pressure chamber side. Liquid discharge head.   2. The dummy electrode is formed so as to exist in a region corresponding to each of the pressure chambers, and not to exist in a region corresponding to between two adjacent pressure chambers. Liquid discharge head.   The liquid ejection head according to claim 1, wherein the dummy electrode is formed over the entire area of the piezoelectric layer.   The amount of warping during firing of the piezoelectric actuator when the electrodes used for driving and the dummy electrode are disposed is smaller than the amount of warping during firing of the piezoelectric actuator when only the electrodes used for driving are disposed. The liquid discharge head according to claim 1, wherein the dummy electrode is provided.   There is a difference between the amount of warping when firing the piezoelectric actuator when only the electrodes used for driving are disposed and the amount of warping when firing the piezoelectric actuator when only the electrodes used for driving and the dummy electrodes are disposed. The liquid ejection head according to claim 1, wherein a size of the dummy electrode and a position where the dummy electrode is provided are set so as to be a certain amount or less.   In the piezoelectric actuator, the sum of the product of the area of each electrode disposed on the pressure chamber side from the intermediate surface in the thickness direction and the length from the intermediate surface to each electrode is greater than the counter pressure chamber from the intermediate surface in the thickness direction. 5. The electrode used for driving and the dummy electrode are arranged so as to be equal to the sum of the product of the area of each electrode arranged on the side and the length from the intermediate surface to each electrode. Or the liquid discharge head of 5. The cavity unit is configured to have conductivity,
The liquid discharge head according to claim 1, wherein an inspection unit for inspecting a conduction state between the dummy electrode and the cavity unit is connectable. The cavity unit is configured to have conductivity,
A dummy electrode or an electrode used for driving is provided in each of the piezoelectric layer on the pressure chamber side and the piezoelectric layer further away from the pressure chamber,
The liquid discharge head according to claim 1, wherein an inspection unit for inspecting a conduction state between the dummy electrode or the drive electrode and the cavity unit can be connected thereto. . A dummy electrode or an electrode used for driving is provided in each of the piezoelectric layer on the pressure chamber side and the piezoelectric layer further away from the pressure chamber,
An inspection means for inspecting a conduction state between the piezoelectric layer on the pressure chamber side and the dummy electrode on the piezoelectric layer on the pressure chamber side or an electrode used for driving can be connected. 6. The liquid discharge head according to any one of 6. In the piezoelectric actuator, the drive electrode is provided in a portion on the side away from the pressure chamber in the thickness direction, and this portion becomes an active portion, and the side close to the pressure chamber where the drive electrode is not provided Is a unimorph type piezoelectric actuator in which the part becomes an inactive part,
The liquid ejection head according to claim 1, wherein the dummy electrode is provided in a portion that becomes the inactive portion. The piezoelectric actuator includes a first active portion corresponding to a central portion of the pressure chamber, and a second active portion corresponding to a portion on the outer peripheral side of the central portion of the pressure chamber,
The electrode used for the drive includes an individual electrode formed so as to occupy both the region corresponding to the first active part and the region corresponding to the second active part, and the first electrode Comprising a first constant potential electrode formed so as to occupy a region corresponding to the active portion of the first active electrode and a second constant potential electrode formed so as to occupy a region corresponding to at least the second active portion. The liquid discharge head according to claim 1, wherein the liquid discharge head is a liquid discharge head. A laminated piezoelectric actuator fixed to a cavity unit having a plurality of pressure chambers and a plurality of nozzles respectively communicating with the pressure chambers,
A plurality of piezoelectric layers and a drive electrode used for driving and a dummy electrode are stacked in the thickness direction, and the dummy electrode is positioned on the pressure chamber side in the stacking direction of the stacked body,
A piezoelectric actuator characterized by suppressing warping due to an electrode used for driving during firing and having a function of inspecting the plurality of piezoelectric layers for cracks from the pressure chamber side.

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