Piezoelectric actuator, liquid discharge head, and recording device

Abstract

A piezoelectric actuator according to the present disclosure has a piezoelectric element that is transformed when voltage is applied thereto. The piezoelectric element comprises a vibration plate, an internal electrode, a piezoelectric ceramic body, a surface electrode, a connection electrode, and a groove. The internal electrode is disposed on the surface of the vibration plate. The piezoelectric ceramic body is disposed on the surface of the internal electrode. The surface electrode is disposed on the surface of the piezoelectric ceramic body. The connection electrode is disposed on the surface of the piezoelectric ceramic body and is connected to the surface electrode. In a plan view when the piezoelectric element is viewed from a direction perpendicular to the surface of the piezoelectric ceramic body, the groove is located around or on the inner side of the surface electrode, and extends in a shape conforming to the outer shape of the surface electrode. The groove comprises a deep groove part and a shallow groove part. The deep groove part has at least a depth that reaches the internal electrode. The shallow groove part is located closer to the connection electrode than the deep groove part is, and has a depth less than the depth that reaches the internal electrode.

Description

Technical Field

[0001] The disclosed embodiments relate to a piezoelectric actuator, a liquid ejection head, and a recording device.

Background Art

[0002] As a printing device, an inkjet printer or an inkjet plotter using an inkjet recording method is known. Such an inkjet printing device is equipped with a liquid ejection head for ejecting a liquid.

[0003] The liquid ejection head ejects the liquid in the pressure chamber from the nozzle by driving a piezoelectric element located above the pressure chamber to change the pressure in the pressure chamber. The piezoelectric element has a piezoelectric body, an internal electrode located inside the piezoelectric body, and a surface electrode located on the surface of the piezoelectric body.

[0004] Patent Document 1 discloses a piezoelectric element in which a groove portion surrounding the surface electrode is formed around the surface electrode for the purpose of reducing the occurrence of crosstalk between piezoelectric elements. In the thickness direction of the piezoelectric element, the groove portion reaches a position deeper than the internal electrode.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

[0006] A piezoelectric actuator according to one embodiment has a piezoelectric element that deforms upon application of voltage. The piezoelectric element includes a diaphragm, an internal electrode, a piezoelectric ceramic body, a surface electrode, a connecting electrode, and a groove. The internal electrode is located on the surface of the diaphragm. The piezoelectric ceramic body is located on the surface of the internal electrode. The surface electrode is located on the surface of the piezoelectric ceramic body. The connecting electrode is located on the surface of the piezoelectric ceramic body and is connected to the surface electrode. In a plan view of the piezoelectric element from a direction perpendicular to the surface of the piezoelectric ceramic body, the groove is located around or inside the surface electrode and extends in a shape corresponding to the outer shape of the surface electrode. The groove has a deep groove and a shallow groove. The deep groove has a depth greater than or equal to the depth that reaches the internal electrode. The shallow groove is located closer to the connecting electrode than the deep groove and has a depth less than the depth that reaches the internal electrode. [Brief explanation of the drawing]

[0007] [Figure 1] Figure 1 is a schematic front view of a printer according to this embodiment. [Figure 2] Figure 2 is a schematic plan view of the printer according to this embodiment. [Figure 3] Figure 3 is a schematic exploded perspective view of the liquid dispensing head according to this embodiment. [Figure 4] Figure 4 is a schematic plan view showing the main parts of the head body according to the embodiment. [Figure 5] Figure 5 is a schematic enlarged view of region V shown in Figure 4. [Figure 6] Figure 6 is a schematic cross-sectional view taken along the line VI-VI shown in Figure 5. [Figure 7] Figure 7 is a schematic plan view of a piezoelectric element according to an embodiment. [Figure 8] Figure 8 is a schematic cross-sectional view taken along the line VIII-VIII shown in Figure 7. [Figure 9] Figure 9 is a schematic diagram illustrating the location of the boundary between the deep groove and the shallow groove. [Figure 10] Figure 10 is a schematic diagram showing an example of the position of the groove according to the embodiment. [Figure 11]Figure 11 is a schematic diagram showing an example of the position of the groove according to the embodiment. [Figure 12] Figure 12 is a schematic cross-sectional view of a groove according to another embodiment of the first. [Figure 13] Figure 13 is a schematic plan view showing the configuration of a groove according to a second embodiment. [Figure 14] Figure 14 is a schematic cross-sectional view showing the configuration of a groove according to a second embodiment. [Figure 15] Figure 15 is a schematic cross-sectional view showing the configuration of a groove according to a third embodiment. [Figure 16] Figure 16 is a schematic plan view showing the configuration of a piezoelectric element according to a fourth embodiment. [Modes for carrying out the invention]

[0008] Hereinafter, embodiments of the piezoelectric actuator, liquid discharge head, and recording device disclosed in this application will be described in detail with reference to the attached drawings. However, the present invention is not limited to the embodiments described below.

[0009] The conventional liquid dispensing heads described above are susceptible to ion migration. Ion migration is a phenomenon in which the metal on the anode side is ionized by the application of voltage, and the ionized metal moves to the cathode, where it is regenerated as metal again. If the metal generated at the cathode grows and reaches the anode, the anode and cathode may become electrically connected, potentially causing a short circuit.

[0010] This problem is not limited to liquid discharge heads, but is common to piezoelectric actuators having piezoelectric elements driven by the application of voltage, and to devices having such piezoelectric actuators in general.

[0011] Therefore, there is a need for a piezoelectric actuator, a liquid discharge head, and a recording device that can increase the driving displacement of the piezoelectric element while suppressing the risks associated with ion migration.

[0012] <Configuration of Printer> First, referring to FIGS. 1 and 2, an overview of a printer 1, which is an example of a recording apparatus according to an embodiment, will be described. FIG. 1 is a schematic front view of the printer 1 according to the embodiment. FIG. 2 is a schematic plan view of the printer 1 according to the embodiment. The printer 1 according to the embodiment is, for example, a color inkjet printer.

[0013] As shown in FIG. 1, the printer 1 includes a paper feed roller 2, a guide roller 3, an applicator 4, a head case 5, a plurality of transport rollers 6, a plurality of frames 7, a plurality of liquid ejection heads 8, a transport roller 9, a dryer 10, a transport roller 11, a sensor unit 12, and a recovery roller 13. The transport roller 6 is an example of a transport unit.

[0014] Furthermore, the printer 1 has a control unit 14 that controls each part of the printer 1. The control unit 14 controls the operations of the paper feed roller 2, the guide roller 3, the applicator 4, the head case 5, the plurality of transport rollers 6, the plurality of frames 7, the plurality of liquid ejection heads 8, the transport roller 9, the dryer 10, the transport roller 11, the sensor unit 12, and the recovery roller 13.

[0015] The printer 1 records an image, characters, etc. on the printing paper P by landing droplets on the printing paper P. The printing paper P is an example of a recording medium. The printing paper P is in a state of being wound around the paper feed roller 2 before use. The printer 1 transports the printing paper P wound around the paper feed roller 2 into the head case 5 via the guide roller 3 and the applicator 4.

[0016] The applicator 4 uniformly applies a coating agent to the printing paper P. Thereby, since the surface treatment can be performed on the printing paper P, the printing quality of the printer 1 can be improved.

[0017] The head case 5 houses multiple transport rollers 6, multiple frames 7, and multiple liquid discharge heads 8. Inside the head case 5, a space is formed that is isolated from the outside, except for some parts such as the area where the printing paper P enters and exits.

[0018] The internal space of the head case 5 is controlled by the control unit 14, as needed, by at least one of the control factors such as temperature, humidity, and atmospheric pressure. The transport rollers 6 transport the printing paper P within the head case 5 to the vicinity of the liquid ejection head 8.

[0019] The frame 7 is a rectangular flat plate positioned close above the printing paper P being transported by the transport rollers 6. Furthermore, as shown in Figure 2, the frame 7 is positioned so that its longitudinal direction is perpendicular to the transport direction of the printing paper P. Inside the head case 5, multiple (for example, four) frames 7 are positioned at predetermined intervals along the transport direction of the printing paper P.

[0020] The liquid ejection head 8 is supplied with a liquid, such as ink, from a liquid tank (not shown). The liquid ejection head 8 ejects the liquid supplied from the liquid tank.

[0021] The control unit 14 controls the liquid ejection head 8 based on data such as images or characters, and ejects liquid toward the printing paper P. The distance between the liquid ejection head 8 and the printing paper P is, for example, about 0.5 to 20 mm.

[0022] The liquid dispensing head 8 is fixed to the frame 7. The liquid dispensing head 8 is positioned so that its longitudinal direction is perpendicular to the direction in which the printing paper P is transported.

[0023] In other words, the printer 1 according to this embodiment is a so-called line printer in which a liquid ejection head 8 is fixed inside the printer 1. However, the printer 1 according to this embodiment is not limited to a line printer, and may be a so-called serial printer.

[0024] A serial printer is a type of printer that alternates between recording data while moving a liquid ejection head 8 in a direction intersecting the transport direction of the printing paper P, for example, in a nearly perpendicular direction, and transporting the printing paper P.

[0025] As shown in Figure 2, multiple (for example, five) liquid discharge heads 8 are fixed to a single frame 7. Figure 2 shows an example where three liquid discharge heads 8 are located in front of the printing paper P in the transport direction and two are located behind it, and the liquid discharge heads 8 are positioned so that the centers of each liquid discharge head 8 do not overlap in the transport direction of the printing paper P.

[0026] A head group 8A is formed by multiple liquid ejection heads 8 located on a single frame 7. The four head groups 8A are positioned along the transport direction of the printing paper P. Liquid ejection heads 8 belonging to the same head group 8A are supplied with ink of the same color. As a result, the printer 1 can print using four colors of ink with the four head groups 8A.

[0027] The ink colors ejected from each head group 8A are, for example, magenta (M), yellow (Y), cyan (C), and black (K). The control unit 14 controls each head group 8A to eject multiple colors of ink onto the printing paper P, thereby enabling the printing of a color image on the paper P.

[0028] Furthermore, in order to treat the surface of the printing paper P, a coating agent may be dispensed onto the printing paper P from the liquid ejection head 8.

[0029] Furthermore, the number of liquid ejection heads 8 included in one head group 8A and the number of head groups 8A installed in the printer 1 can be changed as appropriate depending on the object to be printed or the printing conditions. For example, if the color to be printed on the printing paper P is a single color and the printing is limited to the area that can be printed with one liquid ejection head 8, then the printer 1 may have as few as one liquid ejection head 8.

[0030] The printed paper P, which has been processed inside the head case 5, is transported to the outside of the head case 5 by the transport roller 9 and passes through the inside of the dryer 10. The dryer 10 dries the printed paper P. The dried printed paper P is transported by the transport roller 11 and collected by the recovery roller 13.

[0031] In printer 1, drying the printing paper P in the dryer 10 reduces the likelihood of overlapping printing paper P sticking together or undried liquid rubbing against each other in the recovery roller 13.

[0032] The sensor unit 12 is composed of a position sensor, a speed sensor, or a temperature sensor, etc. The control unit 14 can determine the state of each part of the printer 1 based on the information from the sensor unit 12 and control each part of the printer 1.

[0033] The printer 1 described so far has shown the case where printing paper P is used as the printing target (i.e., recording medium), but the printing target in printer 1 is not limited to printing paper P; a roll of cloth or other material may also be used as the printing target.

[0034] Alternatively, the printer 1 may transport the printing paper P on a conveyor belt instead of directly transporting it. By using a conveyor belt, the printer 1 can print on sheets of paper, cut cloth, wood, tiles, etc.

[0035] The printer 1 may also print wiring patterns for electronic devices by ejecting a liquid containing conductive particles from the liquid ejection head 8. Alternatively, the printer 1 may produce chemical products by ejecting a predetermined amount of liquid chemical agent or a liquid containing chemical agents, etc., from the liquid ejection head 8 toward a reaction vessel or the like.

[0036] <Configuration of the liquid dispensing head> Next, the configuration of the liquid dispensing head 8 according to the embodiment will be described using Figure 3. Figure 3 is a schematic exploded perspective view of the liquid dispensing head 8 according to the embodiment.

[0037] The liquid discharge head 8 comprises a head body 20, a wiring section 30, a housing 40, and a pair of heat sinks 45. The head body 20 includes a flow path member 21, a piezoelectric actuator 22 (see Figure 4), and a reservoir 23.

[0038] In the following explanation, for convenience, the direction in which the head body 20 is provided in the liquid discharge head 8 may be referred to as "down," and the direction in which the housing 40 is provided relative to the head body 20 may be referred to as "up."

[0039] The flow path member 21 of the head body 20 is substantially flat in shape and has a first surface 21a which is a main surface, and a second surface 21b (see Figure 6) located on the opposite side of the first surface 21a. The first surface 21a has an opening (not shown), and liquid is supplied from the reservoir 23 to the inside of the flow path member 21 through this opening.

[0040] The second surface 21b has multiple discharge holes 163 (see Figure 6) for discharging liquid onto the printing paper P. The flow channel member 21 has a flow channel inside that allows liquid to flow from the first surface 21a to the second surface 21b.

[0041] The piezoelectric actuator 22 is located on the first surface 21a of the flow channel member 21. The piezoelectric actuator 22 has a plurality of piezoelectric elements 170 (see Figure 6). The flexible substrate 31 of the wiring section 30 is electrically connected to the piezoelectric actuator 22.

[0042] A reservoir 23 is located on the piezoelectric actuator 22. The reservoir 23 has openings 23a at both ends in the main scanning direction, which is perpendicular to the sub-scanning direction, which is the transport direction of the printing paper P, and parallel to the printing paper P. The reservoir 23 has a flow path inside, and liquid is supplied from the outside through the openings 23a. The reservoir 23 supplies liquid to the flow path member 21. The reservoir 23 also stores the liquid supplied to the flow path member 21.

[0043] The wiring section 30 includes a flexible substrate 31, a wiring substrate 32, a plurality of driver ICs 33, a pressing member 34, and an elastic member 35. The flexible substrate 31 transmits a predetermined signal sent from the outside to the head body 20. As shown in Figure 3, the liquid discharge head 8 according to this embodiment may have two flexible substrates 31.

[0044] One end of the flexible circuit board 31 is electrically connected to the piezoelectric actuator 22 of the head body 20. The other end of the flexible circuit board 31 is extended upward so as to pass through the slit portion 23b of the reservoir 23 and is electrically connected to the wiring board 32. This allows the piezoelectric actuator 22 of the head body 20 to be electrically connected to the outside.

[0045] The wiring board 32 is located above the head body 20. The wiring board 32 distributes signals to multiple driver ICs 33.

[0046] Multiple driver ICs 33 are located on one main surface of the flexible substrate 31. As shown in Figure 3, in the liquid discharge head 8 according to this embodiment, two driver ICs 33 are provided on each flexible substrate 31, but the number of driver ICs 33 provided on a single flexible substrate 31 is not limited to two.

[0047] The driver IC 33 drives the piezoelectric actuator 22 of the head body 20 based on the drive signal sent from the control unit 14 (see Figure 1). In this way, the driver IC 33 drives the liquid discharge head 8.

[0048] The pressing member 34 has a roughly U-shape in cross-section and presses the driver IC 33 on the flexible substrate 31 toward the heat sink 45 from the inside. In this embodiment, the heat generated when the driver IC 33 is driven can be efficiently dissipated to the outer heat sink 45.

[0049] The elastic member 35 is provided so as to be in contact with the outer wall of a pressing portion (not shown) of the pressing member 34. By providing such an elastic member 35, the possibility of the pressing member 34 damaging the flexible substrate 31 when pressing the driver IC 33 can be reduced.

[0050] The elastic member 35 is made of, for example, foam double-sided tape. Furthermore, by using, for example, a non-silicon thermal conductive sheet as the elastic member 35, the heat dissipation of the driver IC 33 can be improved. Note that the elastic member 35 is not necessarily required.

[0051] The housing 40 is positioned on the head body 20 so as to cover the wiring section 30. This allows the housing 40 to seal the wiring section 30. The housing 40 is made of, for example, resin or metal.

[0052] The housing 40 is a box shape that extends long in the main scanning direction and has a first opening 40a and a second opening 40b on a pair of opposing sides along the main scanning direction. The housing 40 also has a third opening 40c on its bottom surface and a fourth opening 40d on its top surface.

[0053] One side of the heat sink 45 is positioned to block the first opening 40a, and the other side of the heat sink 45 is positioned to block the second opening 40b.

[0054] The heat sink 45 is provided so as to extend in the main scanning direction and is made of a metal or alloy with high heat dissipation properties. The heat sink 45 is provided so as to be in contact with the driver IC 33 and dissipates the heat generated by the driver IC 33.

[0055] The pair of heat sinks 45 are each fixed to the housing 40 by screws (not shown). As a result, the housing 40 to which the heat sinks 45 are fixed has a box shape with the first opening 40a and the second opening 40b closed, and the third opening 40c and the fourth opening 40d open.

[0056] The third opening 40c is positioned opposite the reservoir 23. The flexible substrate 31 and the pressing member 34 are inserted through the third opening 40c.

[0057] The fourth opening 40d is provided for inserting a connector (not shown) provided on the wiring board 32. Sealing the space between the connector and the fourth opening 40d with resin or the like makes it difficult for liquids or dust to enter the inside of the housing 40.

[0058] Furthermore, the housing 40 has a heat insulating section 40e. This heat insulating section 40e is positioned adjacent to the first opening 40a and the second opening 40b, and is provided to protrude outward from the side surface of the housing 40 along the main scanning direction.

[0059] Furthermore, the heat-insulating section 40e is formed to extend in the main scanning direction. That is, the heat-insulating section 40e is located between the heat sink 45 and the head body 20. By providing the heat-insulating section 40e in the housing 40 in this way, heat generated by the driver IC 33 is less likely to be transferred to the head body 20 via the heat sink 45.

[0060] Note that Figure 3 shows an example of the configuration of the liquid dispensing head 8, and may include other components besides those shown in Figure 3.

[0061] <Construction of the head unit> Next, the configuration of the head body 20 according to the embodiment will be described. Figure 4 is a schematic plan view showing the main parts of the head body 20 according to the embodiment.

[0062] As described above, the head body 20 includes a flow channel member 21 and a piezoelectric actuator 22. The flow channel member 21 and the piezoelectric actuator 22 have a flat plate shape, and the piezoelectric actuator 22 is located approximately in the center of the flow channel member 21.

[0063] The piezoelectric actuator 22 has a discharge region 24. Multiple piezoelectric elements 170 are located in the discharge region 24.

[0064] Figure 5 is a schematic enlarged view of region V shown in Figure 4. Figure 5 is a plan view of the piezoelectric element 170 as seen from a direction perpendicular to the surface of the piezoelectric ceramic body 171. Note that the groove 100, which will be described later, is omitted in Figure 5.

[0065] As shown in Figure 5, the multiple piezoelectric elements 170 are positioned to correspond to the multiple pressure chambers 162 of the flow channel member 21. Specifically, the multiple piezoelectric elements 170 are arranged such that the electrode body 174a of the surface electrode 174, which will be described later, is located above the pressure chamber 162.

[0066] Here, the configuration of the flow channel member 21 having a pressure chamber 162 will be described. Figure 6 is a schematic cross-sectional view taken along the line VI-VI shown in Figure 5. The line VI-VI shown in Figure 5 is a straight line passing through the center point P1 of the electrode body 174a of the surface electrode 174, which will be described later, and the center point P2 of the connecting electrode 175, which will be described later.

[0067] As shown in Figure 6, the flow path member 21 has a laminated structure in which multiple plates are stacked. Specifically, the flow path member 21 has a cavity plate 21A, a base plate 21B, an aperture plate 21C, a supply plate 21D, manifold plates 21E, 21F, 21G, a cover plate 21H, and a nozzle plate 21I. These plates are positioned in this order from the first surface 21a side of the flow path member 21. These plates are made of a metal such as stainless steel (SUS).

[0068] The plates constituting the flow channel member 21 have numerous holes formed in them. The thickness of each plate is approximately 10 μm to 300 μm. This allows for high precision in hole formation. The plates are stacked and aligned so that these holes communicate with each other to form individual flow channels 164 and a supply manifold 161.

[0069] In the flow path member 21, the supply manifold 161 and the discharge hole 163 are connected by individual flow paths 164. The supply manifold 161 is located on the second surface 21b side inside the flow path member 21, and the discharge hole 163 is located on the second surface 21b of the flow path member 21.

[0070] The individual flow path 164 has a pressure chamber 162 and an individual supply flow path 165. The pressure chamber 162 is located on the first surface 21a of the flow path member 21, and the individual supply flow path 165 is a flow path connecting the supply manifold 161 and the pressure chamber 162.

[0071] Furthermore, the individual supply channel 165 includes a narrower constriction 166 than the rest of the channel. Because the constriction 166 is narrower than the rest of the individual supply channel 165, it has high flow resistance. Thus, with high flow resistance in the constriction 166, the pressure generated in the pressure chamber 162 has difficulty escaping to the supply manifold 161.

[0072] Next, the configuration of the piezoelectric element 170 will be described with reference to Figures 5 and 6. As shown in Figures 5 and 6, the piezoelectric element 170 includes a piezoelectric ceramic body 171, a reinforcing plate 172, an internal electrode 173, a surface electrode 174, and a connecting electrode 175.

[0073] The piezoelectric ceramic body 171 has a flat plate shape. The piezoelectric ceramic body 171 is located on the first surface 21a of the flow channel member 21 via the reinforcing plate 172.

[0074] The piezoelectric ceramic body 171 includes, for example, multiple piezoelectric ceramic layers 171a and 171b. Each of the piezoelectric ceramic layers 171a and 171b has a thickness of, for example, about 20 μm. Each of the piezoelectric ceramic layers 171a and 171b extends across multiple pressure chambers 162. Multiple piezoelectric elements 170 share one piezoelectric ceramic body 171.

[0075] As the piezoelectric ceramic layers 171a and 171b, lead zirconate titanate (PZT)-based ceramic materials having ferroelectric properties can be used.

[0076] Here, an example is shown in which the piezoelectric ceramic body 171 includes two piezoelectric ceramic layers 171a and 171b, but the piezoelectric ceramic body 171 may include three or more piezoelectric ceramic layers.

[0077] The piezoelectric ceramic layer 171b is an example of a diaphragm. Note that the diaphragm does not necessarily have to be a piezoelectric ceramic material such as PZT.

[0078] The reinforcing plate 172 has a flat plate shape. The reinforcing plate 172 is located between the first surface 21a of the flow channel member 21 and the back surface of the piezoelectric ceramic body 171 opposite to the surface where the surface electrodes 174 are located. The reinforcing plate 172 extends across multiple pressure chambers 162 and constitutes the ceiling portion of the multiple pressure chambers 162. Multiple piezoelectric elements 170 share one reinforcing plate 172.

[0079] The reinforcing plate 172 is made of a material harder than the piezoelectric ceramic body 171. For example, the reinforcing plate 172 is made of a metal such as stainless steel (SUS). In this case, the piezoelectric ceramic layer 171b is not necessarily required.

[0080] Note that the piezoelectric element 170 does not necessarily need to have a reinforcing plate 172. In this case, the piezoelectric ceramic body 171 constitutes the ceiling portion of the multiple pressure chambers 162.

[0081] The internal electrode 173 is located inside the piezoelectric ceramic body 171. Specifically, the internal electrode 173 is located between the two piezoelectric ceramic layers 171a and 171b. The internal electrode 173 is formed over substantially the entire surface in the planar direction in the region between the piezoelectric ceramic layers 171a and 171b. That is, the internal electrode 173 overlaps with all the pressure chambers 162 in the region facing the piezoelectric actuator 22. Such an internal electrode 173 functions as a common electrode shared by multiple piezoelectric elements 170.

[0082] The internal electrode 173 can be made of a metallic material such as an Ag-Pd system. The thickness of the internal electrode 173 is, for example, about 2 μm.

[0083] The internal electrode 173 is electrically connected to a connecting electrode (not shown) located on the surface of the piezoelectric ceramic body 171 via a via hole formed in the piezoelectric ceramic layer 171a. This connecting electrode for the internal electrode 173 is grounded and maintained at ground potential.

[0084] The surface electrode 174 has an electrode body 174a and an extraction electrode 174b. The electrode body 174a is located in the region opposite the pressure chamber 162. The electrode body 174a is slightly smaller than the pressure chamber 162 and has a shape that is approximately similar to the pressure chamber 162.

[0085] As shown in Figure 5, the embodiment shows an example where the pressure chamber 162 and the electrode body 174a are circular in plan view. However, the shape of the pressure chamber 162 and the electrode body 174a is not limited to this example. This point will be discussed later with reference to Figure 16.

[0086] The lead electrode 174b is drawn out from the electrode body 174a. The lead electrode 174b extends linearly toward the connecting electrode 175, which will be described later. That is, the connecting electrode 175 is located in the portion of the lead electrode 174b that is drawn out outside the region facing the pressure chamber 162 at one end.

[0087] The electrode body 174a and the extraction electrode 174b of the surface electrode 174 can be made of a metallic material such as Au.

[0088] The connecting electrode 175 has a convex shape, for example, with a thickness of about 15 μm. The connecting electrode 175 is located on the surface of the piezoelectric ceramic body 171 and is connected to the surface electrode 174. Specifically, the connecting electrode 175 is located on the extraction electrode 174b and is electrically connected to the electrode body 174a via the extraction electrode 174b. The connecting electrode 175 is electrically joined to an electrode provided on the flexible substrate 31 (see Figure 3).

[0089] The connecting electrode 175 contains a metal that is more likely to cause ion migration than the metal contained in the surface electrode 174 (for example, Au). For example, the connecting electrode 175 may contain Ag, Cu, Sn, Pb, or Ni. Specifically, silver-palladium containing glass frit is used as the connecting electrode 175.

[0090] Multiple surface electrodes 174 are individually electrically connected to a control unit 14 (see Figure 1) via connecting electrodes 175, a flexible substrate 31, and wiring, in order to individually control their potentials. When the surface electrodes 174 and the internal electrodes 173 are set to different potentials and an electric field is applied in the polarization direction of the piezoelectric ceramic layer 171a, the portion of the piezoelectric ceramic layer 171a to which the electric field is applied acts as an active part that deforms due to the piezoelectric effect.

[0091] In other words, the piezoelectric element 170 in the piezoelectric actuator 22 is composed of the surface electrode 174, the piezoelectric ceramic layer 171a, the reinforcing plate 172, and the portion of the internal electrode 173 facing the pressure chamber 162. When this piezoelectric element 170 undergoes unimorph deformation, the pressure chamber 162 is pressed, and liquid is discharged from the discharge hole 163. The discharge hole 163 is an example of a nozzle that penetrates the nozzle plate 21I.

[0092] <Structure of the groove> Figure 7 is a schematic plan view of the piezoelectric element 170 according to the embodiment. Figure 8 is a schematic cross-sectional view taken along the line VIII-VIII shown in Figure 7. Note that in Figure 7, the size of the groove 100 is exaggerated for ease of understanding.

[0093] As shown in Figure 7, the piezoelectric element 170 has a groove 100. In the plan view shown in Figure 7, that is, the plan view of the piezoelectric element 170 from a direction perpendicular to the surface of the piezoelectric ceramic body 171, the groove 100 is located near the surface electrode 174 and extends in a shape corresponding to the outer shape of the electrode body 174a on the surface electrode 174.

[0094] For example, in the example shown in Figure 7, the groove 100 extends in an arc shape along the outer shape of the electrode body 174a so as to surround the circular electrode body 174a. Both ends of the groove 100 in the longitudinal direction extend to the vicinity of the extraction electrode 174b. Specifically, one end of the groove 100 in the longitudinal direction faces one side of the extraction electrode 174b, and the other end faces the other side of the extraction electrode 174b. That is, in the example shown in Figure 7, the groove 100 surrounds almost the entire circumference of the electrode body 174a, specifically the entire circumference of the electrode body 174a excluding the region from which the extraction electrode 174b is drawn out.

[0095] Furthermore, the groove 100 does not necessarily have to strictly follow the outer shape of the electrode body 174a. For example, the groove 100 may meander with respect to the outer shape of the electrode body 174a, or it may be partially interrupted.

[0096] In the example shown in Figure 7, the groove 100 is located around (outside) the electrode body 174a of the surface electrode 174, but it is not limited to this and may be located inside the electrode body 174a. This point will be explained later with reference to Figure 11.

[0097] In this way, by providing grooves 100 near the surface electrodes 174, the rigidity of the piezoelectric ceramic body 171 can be reduced, and the driving displacement of the piezoelectric element 170 can be increased compared to the case where grooves 100 are not provided.

[0098] Here, if the depth of the groove 100 is set to a relatively shallow depth such that it does not reach the internal electrode 173, the driving displacement of the piezoelectric element 170 cannot be sufficiently large. For this reason, from the viewpoint of increasing the driving displacement of the piezoelectric element 170, it is preferable that the depth of the groove 100 be greater than or equal to the depth that reaches the internal electrode 173. Note that "depth" refers to the distance in the thickness direction of the piezoelectric ceramic body 171.

[0099] On the other hand, if the depth of the groove 100 is made greater than or equal to the depth reaching the internal electrode 173, the internal electrode will be exposed on the wall surface of the groove 100. This creates a risk of ion migration occurring between the connecting electrode 175 and the internal electrode 173. Ion migration is known to occur easily with Ag, Pb, Cu, etc. As mentioned above, the connecting electrode 175 and the internal electrode 173 are composed of Ag. Therefore, ion migration is likely to occur between the connecting electrode 175 and the internal electrode 173. It should be noted that ion migration is less likely to occur with Au, Fe, Pt, etc. The surface electrode 174 is composed of a metal other than Ag, specifically Au. Therefore, ion migration is relatively unlikely to occur between the surface electrode 174 and the internal electrode 173.

[0100] The groove 100 has a deep groove 101 and two shallow grooves 102. One of the two shallow grooves 102 is connected to one end of the deep groove 101, and the other of the two shallow grooves 102 is connected to the other end of the deep groove 101. These deep groove 101 and the two shallow grooves 102 form a continuous groove 100.

[0101] As shown in Figure 8, the deep groove 101 has a depth greater than or equal to the depth to reach the internal electrode 173. In contrast, the shallow groove 102 has a depth less than the depth to reach the internal electrode 173. Furthermore, the shallow groove 102 is located closer to the connecting electrode 175 than the deep groove 101.

[0102] As described above, in the piezoelectric element 170 according to this embodiment, the depth of the shallow groove portion 102 in the groove portion 100 that is close to the connecting electrode 175 is made shallower than that of the internal electrode 173. This allows the distance between the exposed position of the internal electrode 173 and the connecting electrode 175 to be increased compared to the case where groove portions with a depth greater than or equal to the depth reaching the internal electrode 173 are provided over the entire longitudinal area. The greater the distance between the exposed position of the internal electrode 173 and the connecting electrode 175, the longer the distance that metal generated by ion migration in the exposed portion of the internal electrode 173 travels to reach the connecting electrode 175. In other words, short circuits between the internal electrode 173 and the connecting electrode 175 become less likely to occur.

[0103] Thus, according to the piezoelectric actuator 22 of this embodiment, the driving displacement of the piezoelectric element 170 can be increased while suppressing the risk of ion migration.

[0104] For example, the depth of the shallow groove 102 may be 15 μm or more and 20 μm or less, and the width of the shallow groove 102 may be 25 μm or more and 150 μm or less. Also, for example, the depth of the deep groove 101 may be 25 μm or more and 45 μm or less, and the width of the deep groove 101 may be 25 μm or more and 150 μm or less. Also, for example, if the depth of the shallow groove 102 is D1 and the depth of the deep groove 101 is D2, then D1 / D2 may be 0.33 or more and 0.80 or less. In other words, in a two-travel piezoelectric actuator 22 having internal electrodes, it is preferable that the depth of the shallow groove 102 be 50% or more and less than 80% of the thickness of the upper layer (piezoelectric ceramic layer 171a), and the depth of the deep groove 101 be greater than the thickness of the upper layer and smaller than the total thickness (total thickness of piezoelectric ceramic layer 171a, internal electrode 173, and piezoelectric ceramic layer 171b). By setting the range in this manner, the driving displacement of the piezoelectric element 170 can be suitably increased while suitably suppressing the risks associated with ion migration.

[0105] Furthermore, the liquid discharge head 8 having the piezoelectric actuator 22 according to the embodiment allows for the discharge of higher viscosity liquids due to the large driving displacement of the piezoelectric element 170, and is highly reliable because it is less prone to risks due to ion migration.

[0106] The groove portion 100, which has a deep groove portion 101 and a shallow groove portion 102, can be formed, for example, by laser processing. Specifically, the groove portion 100 can be formed by changing the laser processing conditions for the deep groove portion 101 and the shallow groove portion 102. For example, the groove portion 100 may be formed by making the laser output or pulse frequency different for the deep groove portion 101 and the shallow groove portion 102. Alternatively, the groove portion 100 may be formed by keeping the laser output or pulse frequency constant while making the movement speed of the laser irradiation position or the laser irradiation time different for the deep groove portion 101 and the shallow groove portion 102.

[0107] As shown in Figure 8, the deep groove 101 may penetrate the internal electrode 173. In this configuration, the rigidity of the piezoelectric ceramic body 171 can be made lower compared to the case where the deep groove 101 does not penetrate the internal electrode 173, thereby allowing for a larger driving displacement of the piezoelectric element 170. Note that the deep groove 101 only needs to reach the internal electrode 173, and does not necessarily need to penetrate the internal electrode 173.

[0108] Furthermore, the deep groove 101 may have a depth that reaches the reinforcing plate 172. As described above, the reinforcing plate 172 is made of a metal such as SUS that is harder than the piezoelectric ceramic body 171, and is less likely to be abraded by a laser than the piezoelectric ceramic body 171. In other words, the reinforcing plate 172 should be made of a material that has lower laser processing efficiency than the piezoelectric ceramic body 171 for the selected laser light source. Therefore, compared to the case where the depth of the deep groove 101 is set to a depth that does not reach the reinforcing plate 172, it is possible to reduce the variation in the depth of the deep groove 101 among the multiple piezoelectric elements 170. This makes it possible to reduce the variation in drive displacement among the multiple piezoelectric elements 170. In addition, by reducing the variation in drive displacement among the multiple piezoelectric elements 170, it is possible to reduce the variation in liquid discharge performance among the multiple piezoelectric elements 170.

[0109] Furthermore, the deep groove 101 may have a depth greater than or equal to the depth that reaches the reinforcing plate 172, not limited to the example in Figure 8.

[0110] The boundary portion 103 between the deep groove portion 101 and the shallow groove portion 102 may have a stepped shape. That is, the end face of the deep groove portion 101 in the longitudinal direction may be cut vertically. With this configuration, for example, the variation in the exposed position of the internal electrodes 173 among the multiple piezoelectric elements 170 can be reduced compared to the case where the shallow groove portion 102 has a slope shape. This makes it possible to more reliably reduce the risk due to ion migration.

[0111] As shown in Figure 7, the external shape formed by the surface electrode 174 and the connecting electrode 175 in a plan view is symmetrical with respect to a line L1 passing through the center point P1 of the electrode body 174a of the surface electrode 174 and the center point P2 of the connecting electrode 175. Note that "the external shape formed by the surface electrode 174 and the connecting electrode 175" refers to the single silhouette formed by the surface electrode 174 and the connecting electrode 175.

[0112] The groove 100 may be symmetrical in a plan view with respect to the line passing through the centroid of the surface electrode 174, specifically, the centroid of the electrode body 174a on the surface electrode 174.

[0113] For example, in the example shown in Figure 7, the centroid of the electrode body 174a is assumed to coincide with the center point P1 of the electrode body 174a. In this case, the groove 100 may be symmetric with respect to the straight line L1, which is the axis of symmetry of the outer shape formed by the surface electrode 174 and the connecting electrode 175. Specifically, the deep groove 101 may be symmetric with respect to the straight line L1, and the two shallow grooves 102 may also be symmetric with respect to the straight line L1.

[0114] With this configuration, the point where the displacement of the electrode body 174a is maximum can be positioned on or near the line passing through the center of gravity of the electrode body 174a. The closer the point where the displacement of the electrode body 174a is maximum is to the center of gravity of the electrode body 174a, the more efficiently the energy due to the displacement of the electrode body 174a can be transmitted to the pressure chamber 162. Therefore, with this configuration, pressure can be efficiently transmitted to the pressure chamber 162.

[0115] <Regarding the location of the boundary between the deep groove and the shallow groove> Figure 9 is a schematic diagram illustrating the location of the boundary between the deep groove and the shallow groove. In Figure 9, three adjacent piezoelectric elements 170_1, 170_2, and 170_3 are shown among the multiple piezoelectric elements 170 of the piezoelectric actuator 22. Note that the groove 100 is omitted in Figure 9.

[0116] The position of the boundary 103 between the deep groove 101 and the shallow groove 102 in the groove 100 may be defined, for example, by the circle C1 and the straight line L2 shown in Figure 9.

[0117] Specifically, as shown in Figure 9, the surface electrode 174 of piezoelectric element 170_1 is designated as the first surface electrode 174_1, and the surface electrode 174 of the other piezoelectric element 170_2 closest to the connection electrode 175 of piezoelectric element 170_1 is designated as the second surface electrode 174_2. Note that this example shows two piezoelectric elements 170_2 located equidistant from piezoelectric element 170_1, but there may be only one other piezoelectric element 170_2 closest to the connection electrode 175 of piezoelectric element 170_1.

[0118] Circle C1 is a virtual circle in a plan view that is centered at the center point P2 of the connecting electrode 175 of the piezoelectric element 170_1 and tangent to the second surface electrode 174_2. The boundary 103 between the deep groove 101 and the shallow groove 102 in the groove 100 of the piezoelectric element 170_1 may be located outside of this circle C1.

[0119] This configuration allows for a sufficiently large distance between the exposed internal electrode 173 and the connecting electrode 175. Therefore, the risk of ion migration between the connecting electrode 175 and the internal electrode 173 can be significantly reduced.

[0120] Here, circle C1 is assumed to be a virtual circle tangent to the second surface electrode 174_2, but more specifically, it may be a virtual circle tangent to the outer edge of the groove 100 of the piezoelectric element 170_2. By adopting such a configuration, the risk of ion migration between the connecting electrode 175 and the internal electrode 173 can be reduced more reliably.

[0121] Furthermore, in a plan view, the straight line L2 is a straight line that passes through the center point P1 of the electrode body 174a of the first surface electrode 174_1, and is a straight line perpendicular to the straight line L1 that passes through the center point P1 of the electrode body 174a and the center point P2 of the connecting electrode 175.

[0122] The boundary portion 103 between the deep groove portion 101 and the shallow groove portion 102 in the groove portion 100 of the piezoelectric element 170_1 may be located closer to the connecting electrode 175 than the intersection point P3 of the straight line L2 and the electrode body 174a.

[0123] From the viewpoint of increasing the driving displacement of the piezoelectric element 170, it is desirable to increase the proportion of the deep groove portion 101 in the groove portion 100. Therefore, by providing the deep groove portion 101 in the surface electrode 174 so as to occupy at least half of the outer edge of the electrode body 174a, it is possible to make it difficult to reduce the driving displacement caused by providing the shallow groove portion 102.

[0124] Thus, it is preferable that the boundary portion 103 between the deep groove portion 101 and the shallow groove portion 102 is located closer to the connecting electrode 175 than the intersection point P3 of the straight line L2 and the electrode body 174a, and further from the connecting electrode 175 than the intersection point P4 of the circle C1 and the electrode body 174a.

[0125] Furthermore, the boundary 103 between the deep groove 101 and the shallow groove 102 can be described as the position where the internal electrode 173 is exposed. Alternatively, the boundary 103 between the deep groove 101 and the shallow groove 102 can be described as both ends of the deep groove 101 in its longitudinal direction.

[0126] <Location of the groove> Figures 10 and 11 are schematic diagrams showing an example of the location of the groove 100 according to the embodiment. Figures 10 and 11 show cross-sectional views obtained by cutting the piezoelectric element 170 along the straight line L2 shown in Figure 9, for example.

[0127] As shown in Figure 10, the groove 100 may be located inside the pressure chamber 162 and outside the surface electrode 174 (electrode body 174a) in a cross-sectional view.

[0128] With this configuration, even if the position of the electrode body 174a relative to the pressure chamber 162 is misaligned among the multiple piezoelectric elements 170, it is possible to reduce variations in the drive displacement among the multiple piezoelectric elements 170 due to such misalignment. Therefore, it is possible to reduce variations in discharge performance among multiple nozzles.

[0129] Furthermore, as shown in Figure 11, the groove 100 may be located inside the pressure chamber 162 and inside the surface electrode 174 (electrode body 174a) in a cross-sectional view.

[0130] In this configuration, the outer periphery of the electrode body 174a is cut off by the laser when forming the groove 100. Therefore, even if the position of the electrode body 174a relative to the pressure chamber 162 is misaligned among the multiple piezoelectric elements 170 before being cut off by the laser, this misalignment can be reduced by cutting off by the laser. As a result, variations in drive displacement among the multiple piezoelectric elements 170 are less likely to occur, and variations in discharge performance among the multiple nozzles can be reduced.

[0131] <Another embodiment of the first part: Regarding the shape of the groove> Figure 12 is a schematic cross-sectional view of the groove 100 according to another embodiment of the first. As shown in Figure 12, the shallow groove 102 may have a slope shape that deepens towards the deep groove 101. This slope may continue into the deep groove 101. That is, the groove 100 may have a slope (inclined surface) that deepens from the end of the shallow groove 102 on the side of the connecting electrode 175 toward the bottom surface of the deep groove 101. In this case, the portion of the slope to which the internal electrode 173 is exposed is the boundary portion 103 between the deep groove 101 and the shallow groove 102.

[0132] In this way, by smoothly changing the depth of the groove 100, it is possible to reduce the likelihood of cracks or other damage caused by stress concentration when the piezoelectric element 170 is displaced.

[0133] <A second embodiment: Regarding the positional relationship between the deep groove and the shallow groove> Figure 13 is a schematic plan view showing the configuration of the groove 100 according to a second embodiment. Figure 14 is a schematic cross-sectional view showing the configuration of the groove 100 according to a second embodiment.

[0134] As shown in Figures 13 and 14, the deep groove 101 and the shallow groove 102 may be separated. In this case, the deep groove 101 and the shallow groove 102 are separated by the piezoelectric ceramic body 171. In other words, the wall of the piezoelectric ceramic body 171 is located at the boundary 103 between the deep groove 101 and the shallow groove 102.

[0135] This configuration allows for an even longer distance for the metal generated by ion migration to reach the connecting electrode 175 at the exposed position of the internal electrode 173. Therefore, the risks associated with ion migration can be further reduced.

[0136] <Third alternative embodiment: Regarding the configuration of the shallow groove section> Figure 15 is a schematic cross-sectional view showing the configuration of the groove 100 according to a third embodiment. As shown in Figure 15, the shallow groove 102 may have a plurality of protrusions 121. Each protrusion 121 includes a portion 121a that becomes shallower and a portion 121b that becomes deeper toward the connecting electrode 175 from the deep groove 101.

[0137] This configuration allows for an even longer distance for the metal generated by ion migration to reach the connecting electrode 175 at the exposed position of the internal electrode 173. Therefore, the risks associated with ion migration can be further reduced.

[0138] The height of the protrusion 121 may be, for example, at least 1 / 3 of the depth of the shallow groove 102. Preferably, the height of the protrusion 121 may be half or more of the depth of the shallow groove 102.

[0139] <Fourth alternative embodiment: Regarding the shape of the piezoelectric element> Figure 16 is a schematic plan view showing the configuration of a piezoelectric element 170 according to a fourth embodiment. The shape of the piezoelectric element 170 is not limited to the shape shown in Figure 5. For example, as shown in Figure 16, the shape of the piezoelectric element 170 may be bowling pin-shaped.

[0140] Specifically, in a plan view, the pressure chamber 162 may have a rhombic shape with rounded corners. In this case, the electrode body 174a of the surface electrode 174 also has a rhombic shape with rounded corners in a plan view, matching the shape of the pressure chamber 162. The lead electrode 174b extends linearly from one of the acute corners of the electrode body 174a toward the connecting electrode 175. The connecting electrode 175 is circular in a plan view.

[0141] Similarly in this case, the piezoelectric element 170 may have a groove 100 (not shown here) located around or inside the electrode body 174a on the surface electrode 174, extending in a shape corresponding to the outer shape of the electrode body 174a. Similarly in this case as well, it is preferable that the boundary portion 103 between the deep groove portion 101 and the shallow groove portion 102 in the groove portion 100 is located closer to the connecting electrode 175 than the intersection point P3 of the straight line L2 and the electrode body 174a, and further from the connecting electrode 175 than the intersection point P4 of the circle C1 and the electrode body 174a.

[0142] As described above, the piezoelectric actuator according to the embodiment (for example, piezoelectric actuator 22) has a piezoelectric element (for example, piezoelectric element 170) that deforms when a voltage is applied. The piezoelectric element has a diaphragm (for example, piezoelectric ceramic layer 171b), an internal electrode (for example, internal electrode 173), a piezoelectric ceramic body (for example, piezoelectric ceramic layer 171a), a surface electrode (for example, surface electrode 174), a connecting electrode (for example, connecting electrode 175), and a groove (for example, groove 100). The internal electrode is located on the surface of the diaphragm. The piezoelectric ceramic body is located on the surface of the internal electrode. The surface electrode is located on the surface of the piezoelectric ceramic body. The connecting electrode is located on the surface of the piezoelectric ceramic body and is connected to the surface electrode. In a plan view of the piezoelectric element from a direction perpendicular to the surface of the piezoelectric ceramic body, the groove is located around or inside the surface electrode and extends in a shape corresponding to the outer shape of the surface electrode. The groove section has a deep groove section (for example, deep groove section 101) and a shallow groove section (for example, shallow groove section 102). The deep groove section has a depth greater than or equal to the depth to reach the internal electrode. The shallow groove section is located closer to the connecting electrode than the deep groove section and has a depth less than the depth to reach the internal electrode.

[0143] Therefore, according to the piezoelectric actuator of this embodiment, the driving displacement of the piezoelectric element can be increased while suppressing the risk of ion migration.

[0144] Although embodiments of the present disclosure have been described above, the present disclosure is not limited to the above embodiments, and various modifications are possible without departing from the spirit thereof. For example, in the above embodiments, an example was shown in which the flow channel member 21 is composed of a plurality of stacked plates, but the flow channel member 21 is not limited to the case in which it is composed of a plurality of stacked plates.

[0145] For example, the flow channel member 21 may be constructed by etching a supply manifold 161 or individual flow channels 164, etc.

[0146] The recording device may also be a vehicle body painting apparatus. In this case, the recording device may include a liquid discharge head having a nozzle surface for dispensing paint material, an arm for holding the liquid discharge head, and a control unit for controlling the movement of the head via the arm. The arm may be, for example, a multi-joint robot driven by multiple motors.

[0147] Further effects and modifications can be readily derived by those skilled in the art. Therefore, broader aspects of the present invention are not limited to the specific details and representative embodiments expressed and described above. Accordingly, various modifications are possible without departing from the spirit or scope of the overall concept of the invention as defined by the appended claims and their equivalents. [Explanation of Symbols]

[0148] 1. Printer 2 Paper feed rollers 3 Guide rollers 4. Coating machine 5 Head Cases 6 Conveyor rollers 7 frames 8 liquid dispensing heads 9 Conveyor rollers 10 Dryer 11 Conveyor rollers 12 Sensor section 13 Recovery Roller 14 Control Unit 20 Head Body 21 Flow channel member 22 Piezoelectric Actuator 23 Reservoir 24 Discharge area 30 Wiring section 31 Flexible circuit board 32 Wiring board 34 Pressing member 35 Elastic members 40 cabinets 45 Heat sink 100 groove section 101 Deep groove part 102 Shallow groove section 103 Boundary 121 Convex part 161 Supply Manifold 162 Pressure Chamber 163 Discharge hole 164 Individual channel 165 Individual supply channels 170 Piezoelectric element 171 Piezoelectric ceramic body 171a Piezoelectric ceramic layer 171b Piezoelectric ceramic layer 172 Reinforcement Plate 173 Internal electrode 174 Surface electrode 174 _1 1st surface electrode 174 _2 2nd surface electrode 174a Electrode body 174b Extraction electrode 175 Connecting electrodes

Claims

1. It has a piezoelectric element that deforms when a voltage is applied, The piezoelectric element is The diaphragm and The internal electrode located on the surface of the diaphragm, A piezoelectric ceramic body located on the surface of the internal electrode, A surface electrode located on the surface of the piezoelectric ceramic body, A connecting electrode located on the surface of the piezoelectric ceramic body and connected to the surface electrode, In a plan view of the piezoelectric element from a direction perpendicular to the surface of the piezoelectric ceramic body, a groove is located outside the surface electrode and extends in a shape corresponding to the outer shape of the surface electrode. It has, The groove portion is A deep groove having a depth greater than or equal to the depth reaching the internal electrode, A shallow groove portion located closer to the connecting electrode than the deep groove portion, and having a depth less than the depth to reach the internal electrode. It has, A piezoelectric actuator in which the deep groove and the shallow groove are formed continuously.

2. The piezoelectric actuator according to claim 1, wherein the connecting electrode contains a metal that is more likely to cause ion migration than the metal contained in the surface electrode.

3. The piezoelectric actuator according to claim 2, wherein the connecting electrode contains Ag.

4. It has a piezoelectric element that deforms when a voltage is applied, The piezoelectric element is The diaphragm and The internal electrode located on the surface of the diaphragm, A piezoelectric ceramic body located on the surface of the internal electrode, A surface electrode located on the surface of the piezoelectric ceramic body, A connecting electrode located on the surface of the piezoelectric ceramic body and connected to the surface electrode, In a plan view of the piezoelectric element as seen from a direction perpendicular to the surface of the piezoelectric ceramic body, a groove portion is located around or inside the surface electrode and extends in a shape corresponding to the outer shape of the surface electrode. It has, The groove portion is A deep groove having a depth greater than or equal to the depth reaching the internal electrode, A shallow groove portion located closer to the connecting electrode than the deep groove portion, and having a depth less than the depth to reach the internal electrode. It has, The diaphragm, the piezoelectric ceramic body, and the plurality of piezoelectric elements sharing the internal electrodes are provided. The groove portion of one of the piezoelectric elements is A piezoelectric actuator having a boundary between a deep groove and a shallow groove, in a plan view, where the surface electrode of one piezoelectric element is designated as the first surface electrode, and the surface electrode of another piezoelectric element closest to the first piezoelectric element is designated as the second surface electrode.

5. Having a piezoelectric element that deforms when a voltage is applied, The piezoelectric element is The diaphragm and The internal electrode located on the surface of the diaphragm, A piezoelectric ceramic body located on the surface of the internal electrode, A surface electrode located on the surface of the piezoelectric ceramic body, A connecting electrode located on the surface of the piezoelectric ceramic body and connected to the surface electrode, In a plan view of the piezoelectric element from a direction perpendicular to the surface of the piezoelectric ceramic body, a groove is located outside the surface electrode and extends in a shape corresponding to the outer shape of the surface electrode. It has, The groove portion is A deep groove having a depth greater than or equal to the depth reaching the internal electrode, A shallow groove portion located closer to the connecting electrode than the deep groove portion, and having a depth less than the depth to reach the internal electrode. It has, The surface electrode is Electrode body and A lead-out portion extending from the electrode body toward the connecting electrode and It has, The groove portion is In the plan view, the piezoelectric actuator has a boundary between the deep groove and the shallow groove at a position closer to the connecting electrode than the intersection of the electrode body with a straight line passing through the center point of the electrode body and the center point of the connecting electrode, which is perpendicular to the straight line passing through the center point of the electrode body and the center point of the connecting electrode.

6. It has a piezoelectric element that deforms when a voltage is applied, The piezoelectric element is The diaphragm and The internal electrode located on the surface of the diaphragm, A piezoelectric ceramic body located on the surface of the internal electrode, A surface electrode located on the surface of the piezoelectric ceramic body, A connecting electrode located on the surface of the piezoelectric ceramic body and connected to the surface electrode, In a plan view of the piezoelectric element as seen from a direction perpendicular to the surface of the piezoelectric ceramic body, a groove portion is located around or inside the surface electrode and extends in a shape corresponding to the outer shape of the surface electrode. It has, The groove portion is A deep groove having a depth greater than or equal to the depth reaching the internal electrode, A shallow groove portion located closer to the connecting electrode than the deep groove portion, and having a depth less than the depth to reach the internal electrode. It has, The deep groove portion is Penetrating the aforementioned internal electrode, A reinforcing plate located on the back surface opposite to the surface where the internal electrodes are located on the diaphragm, and which is harder than the diaphragm. It has, The deep groove portion has a depth greater than or equal to the depth to reach the reinforcing plate, wherein the piezoelectric actuator.

7. The groove portion is The piezoelectric actuator according to claim 1, wherein, in the plan view, it is symmetrical with respect to a line passing through the centroid of the surface electrode.

8. Having a piezoelectric element that deforms when a voltage is applied, The piezoelectric element is The diaphragm and The internal electrode located on the surface of the diaphragm, A piezoelectric ceramic body located on the surface of the internal electrode, A surface electrode located on the surface of the piezoelectric ceramic body, A connecting electrode located on the surface of the piezoelectric ceramic body and connected to the surface electrode, In a plan view of the piezoelectric element from a direction perpendicular to the surface of the piezoelectric ceramic body, a groove is located outside the surface electrode and extends in a shape corresponding to the outer shape of the surface electrode. It has, The groove portion is A deep groove having a depth greater than or equal to the depth reaching the internal electrode, A shallow groove portion located closer to the connecting electrode than the deep groove portion, and having a depth less than the depth to reach the internal electrode. It has, A piezoelectric actuator having a stepped shape at the boundary between the deep groove and the shallow groove.

9. Having a piezoelectric element that deforms when a voltage is applied, The piezoelectric element is The diaphragm and The internal electrode located on the surface of the diaphragm, A piezoelectric ceramic body located on the surface of the internal electrode, A surface electrode located on the surface of the piezoelectric ceramic body, A connecting electrode located on the surface of the piezoelectric ceramic body and connected to the surface electrode, In a plan view of the piezoelectric element from a direction perpendicular to the surface of the piezoelectric ceramic body, a groove is located outside the surface electrode and extends in a shape corresponding to the outer shape of the surface electrode. It has, The groove portion is A deep groove having a depth greater than or equal to the depth reaching the internal electrode, A shallow groove portion located closer to the connecting electrode than the deep groove portion, and having a depth less than the depth to reach the internal electrode. It has, A piezoelectric actuator wherein the shallow groove portion has a slope shape that becomes deeper towards the deep groove portion.

10. The aforementioned shallow groove portion is Having multiple protrusions, Each of the aforementioned protrusions is The piezoelectric actuator according to claim 1, having a portion where the depth decreases toward the connecting electrode from the deep groove and a portion where the depth increases toward the deep groove from the connecting electrode.

11. A nozzle that dispenses liquid droplets, A pressure chamber connected to the nozzle, A piezoelectric actuator according to any one of claims 1 to 10, which deforms by the application of voltage and deforms the pressure chamber, A liquid dispensing head having a liquid dispensing head.

12. The pressure chamber is provided in a position that overlaps with the piezoelectric element in the plan view. The liquid discharge head according to claim 11, wherein the groove is located inside the pressure chamber and outside the surface electrode.

13. The pressure chamber is provided in a position that overlaps with the piezoelectric element in the plan view. The liquid discharge head according to claim 11, wherein the groove is located inside the pressure chamber and inside the surface electrode.

14. A recording device having a liquid dispensing head as described in claim 11.

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