Piezoelectric device, liquid ejection head, and liquid ejection apparatus

Abstract

To provide a piezoelectric device which suppresses burning of a piezoelectric actuator and drive failure of an active part, and provide a liquid jet head, and liquid jet device.SOLUTION: A piezoelectric device includes a substrate 10 having a plurality of recessed parts 12, a diaphragm 50 which is arranged on one surface side of the substrate 10, and a piezoelectric actuator 300 which is formed by laminating a first electrode 60, a piezoelectric layer 70 and a second electrode 80 from a diaphragm 50 side. The piezoelectric actuator 300 includes a plurality of active parts 310 which is formed by sandwiching a piezoelectric layer 70 by the first electrode 60 and the second electrode 80. The first electrode 60 structures an individual electrode independent from each of the active parts 310. The second electrode 80 structures a common electrode common to the plurality of active parts 310. The second electrode 80 includes a first end part 83 as a reference, and a protrusion part 84 which protrudes than the first end part 83 from an end part of the active part 310 toward a connection electrode 82 electrically connected to the first electrode 60.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to a piezoelectric device having a substrate, a vibration plate, and a piezoelectric actuator, a liquid ejection head that ejects liquid from a nozzle, and a liquid ejection apparatus. [Background technology]

[0002] Inkjet recording heads are known as liquid ejection heads, which are one type of electronic device. An inkjet recording head includes a substrate having a plurality of pressure chambers communicating with nozzles, a vibration plate provided on the substrate, and a piezoelectric actuator having a first electrode, a piezoelectric layer, and a second electrode provided on the vibration plate. The piezoelectric actuator for such an inkjet recording head has been proposed to have a plurality of active sections, each of which has a piezoelectric layer sandwiched between a first electrode and a second electrode. The first electrode is an individual electrode independent of each active section, and the second electrode is a common electrode shared by the plurality of active sections (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-166160 Summary of the Invention [Problem to be solved by the invention]

[0004] However, repeated driving of the active section causes stress concentration at the end of the active section, which in turn causes cracks in the piezoelectric layer, leading to current leakage along the cracks, which can easily cause burnout or malfunction of the active section.

[0005] Such problems exist not only in liquid jet heads such as ink jet recording heads, but also in piezoelectric devices. [Means for solving the problem]

[0006] An aspect of the present invention that solves the above problem is a piezoelectric device comprising a substrate having a plurality of recesses, a vibration plate provided on one side of the substrate, and a piezoelectric actuator in which a first electrode, a piezoelectric layer, and a second electrode are stacked from the vibration plate side, the piezoelectric actuator having a plurality of active portions in which the piezoelectric layer is sandwiched between the first electrode and the second electrode, the first electrode forming an individual electrode independent of each of the active portions, the second electrode forming a common electrode common to the plurality of active portions, and the second electrode having a first end serving as a reference, and a convex portion that protrudes beyond the first end from the end of the active portion toward a connection electrode that is electrically connected to the first electrode.

[0007] Another aspect of the present invention is a liquid ejection head comprising: a substrate having a plurality of pressure chambers formed therein, each of which communicates with a nozzle that ejects liquid; a vibration plate provided on one side of the substrate; and a piezoelectric actuator having a first electrode, a piezoelectric layer, and a second electrode stacked from the vibration plate side, the piezoelectric actuator having a plurality of active portions in which the piezoelectric layer is sandwiched between the first electrode and the second electrode, the first electrode forming an individual electrode independent of each of the active portions, the second electrode forming a common electrode common to the plurality of active portions, and the second electrode having a first end portion serving as a reference, and a convex portion that protrudes beyond the first end portion from the end of the active portion toward a connection electrode that is electrically connected to the first electrode.

[0008] Another aspect of the present invention is a liquid-jet apparatus including the liquid-jet head according to the above aspect. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 2 is an exploded perspective view of the recording head according to the first embodiment. [Figure 2] 3 is a plan view of a flow path forming substrate of the recording head according to the first embodiment. FIG. [Figure 3] 1 is a cross-sectional view of a recording head according to a first embodiment. [Figure 4]1 is a cross-sectional view of a recording head according to a first embodiment. [Figure 5] 1A and 1B are a plan view and a cross-sectional view of a main part of a recording head according to a first embodiment. [Figure 6] 10A and 10B are a plan view and a cross-sectional view of a main part of a recording head according to a second embodiment. [Figure 7] FIG. 10 is a plan view of a main portion of a modified example of the recording head according to the second embodiment. [Figure 8] FIG. 10 is a plan view of a main portion of a modified example of the recording head according to the second embodiment. [Figure 9] FIG. 10 is a plan view of a main portion of a modified example of the recording head according to the second embodiment. [Figure 10] FIG. 1 is a schematic diagram of a recording apparatus according to an embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0010] The present invention will be described in detail below based on embodiments. However, the following description illustrates one aspect of the present invention and can be modified as desired within the scope of the present invention. In each drawing, the same reference numerals indicate the same components, and their description will be omitted as appropriate. In each drawing, X, Y, and Z represent three spatial axes that are orthogonal to each other. In this specification, the directions along these axes are referred to as the X direction, Y direction, and Z direction. In each drawing, the direction indicated by the arrow is referred to as the positive (+) direction, and the direction opposite the arrow is referred to as the negative (-) direction. In addition, the three spatial axes X, Y, and Z, which are not limited to the positive and negative directions, will be referred to as the X axis, Y axis, and Z axis.

[0011] (Embodiment 1) FIG. 1 is an exploded perspective view of an ink jet recording head 1, which is an example of a liquid jet head according to this embodiment. FIG. 2 is a plan view of a flow path forming substrate 10 of the recording head 1. FIG. 3 is a cross-sectional view of the recording head 1 taken along line AA' in FIG. 2. FIG. 4 is a cross-sectional view of the recording head 1 taken along line BB' in FIG. 2. FIG. 5 is an enlarged plan view of a main part of FIG. 2 and its cross-sectional view.

[0012] As shown in the figure, the recording head 1 of this embodiment includes a flow path forming substrate 10 as an example of a "substrate." The flow path forming substrate 10 is made of a silicon substrate, a glass substrate, an SOI substrate, or any of various ceramic substrates.

[0013] The flow path forming substrate 10 is provided with two rows in the +Y direction, in which a plurality of pressure chambers 12 are arranged side by side along the +X direction, which is a first direction. The plurality of pressure chambers 12 constituting the rows of pressure chambers 12 are arranged on a straight line along the +X direction so that their positions in the +Y direction are the same. Furthermore, pressure chambers 12 adjacent to each other in the +X direction are partitioned by partition walls 11. Of course, the arrangement of the pressure chambers 12 is not particularly limited to this, and for example, among the pressure chambers 12 arranged side by side in the +X direction, every other pressure chamber 12 may be arranged at a position shifted in the +Y direction, in a so-called staggered arrangement.

[0014] Furthermore, the pressure chamber 12 in this embodiment has a rectangular shape when viewed in the +Z direction. Of course, the shape of the pressure chamber 12 when viewed in the +Z direction is not limited to a rectangle, and may be a parallelogram, a rectangular shape with semicircular longitudinal ends, so-called a rounded rectangle, an oval shape such as an ellipse or an egg shape, a circle, a polygon, or the like. This pressure chamber 12 corresponds to a "recess" provided in the "substrate."

[0015] On the +Z direction side of the flow path forming substrate 10, a communication plate 15 and a nozzle plate 20 are stacked in this order.

[0016] The communication plate 15 is made of a plate-shaped member, and has a nozzle communication passage 16 penetrating therethrough in the +Z direction, which connects the pressure chamber 12 and the nozzle 21 to each other.

[0017] The communication plate 15 is also provided with a first manifold portion 17 and a second manifold portion 18 which constitute a part of a manifold 100 which serves as a common liquid chamber to which the plurality of pressure chambers 12 are commonly connected. The first manifold portion 17 is provided so as to penetrate the communication plate 15 in the +Z direction. The second manifold portion 18 is provided so as to open on the surface on the +Z direction side without penetrating the communication plate 15 in the +Z direction.

[0018] Furthermore, the communication plate 15 is provided with supply communication passages 19 that communicate with the Y-axis ends of the pressure chambers 12, independently for each pressure chamber 12. The supply communication passages 19 communicate between the second manifold portion 18 and the pressure chambers 12, and supply ink from within the manifold 100 to the pressure chambers 12.

[0019] A silicon substrate, a glass substrate, an SOI substrate, various ceramic substrates, a metal substrate such as a stainless steel substrate, or the like can be used as the communicating plate 15. It is preferable that the communicating plate 15 be made of a material having approximately the same thermal expansion coefficient as the flow path forming substrate 10. By using materials having approximately the same thermal expansion coefficient for the flow path forming substrate 10 and the communicating plate 15 in this way, it is possible to reduce the occurrence of warping due to heat caused by the difference in thermal expansion coefficient.

[0020] The nozzle plate 20 is made of a plate-like member and is provided on the side of the communication plate 15 opposite to the flow path forming substrate 10, that is, on the surface on the +Z direction side.

[0021] The nozzle plate 20 has nozzles 21 formed therein, which communicate with each pressure chamber 12 via nozzle communication passages 16. In this embodiment, the nozzles 21 are arranged in two rows spaced apart in the +Y direction, with the nozzles 21 aligned in a line along the +X direction. That is, the nozzles 21 in each row are aligned at the same position in the +Y direction. Of course, the arrangement of the nozzles 21 is not particularly limited thereto. For example, the nozzles 21 may be aligned in a line along the +X direction, with every other nozzle 21 aligned in a line shifted in the +Y direction, in a so-called staggered arrangement. Such a nozzle plate 20 may be made of a silicon substrate, a glass substrate, an SOI substrate, various ceramic substrates, a metal substrate such as a stainless steel substrate, or an organic substrate such as a polyimide resin. It is preferable that the nozzle plate 20 be made of a material having a thermal expansion coefficient substantially identical to that of the communicating plate 15. By using materials having a thermal expansion coefficient substantially identical for the nozzle plate 20 and the communicating plate 15, warping due to heat caused by differences in thermal expansion coefficients can be reduced.

[0022] The vibration plate 50 and the piezoelectric actuator 300 are laminated in this order on the −Z direction side of the flow path forming substrate 10. That is, the flow path forming substrate 10, the vibration plate 50, and the piezoelectric actuator 300 are laminated in this order in the −Z direction.

[0023] The diaphragm 50 has an elastic film 51 made of silicon oxide provided on the flow path forming substrate 10 side, and an insulating film 52 made of zirconium oxide provided on the elastic film 51. Note that the flow paths such as the pressure chambers 12 provided in the flow path forming substrate 10 are formed by anisotropically etching the flow path forming substrate 10 from the surface on the +Z direction side, and the surface of the pressure chambers 12 on the -Z direction side is defined by the elastic film 51. Note that the diaphragm 50 is not limited to the above-described one, and may be composed of only the elastic film 51 or only the insulating film 52, for example. Note that the diaphragm 50 may have other films in addition to the elastic film 51 and the insulating film 52. Note that the material of the diaphragm 50 is not limited to the above-described one.

[0024] The piezoelectric actuator 300 is provided on the -Z direction side of the vibration plate 50 and includes a first electrode 60, a piezoelectric layer 70, and a second electrode 80, which are sequentially stacked from the vibration plate 50 side toward the -Z direction. The piezoelectric actuator 300 serves as a pressure generating means for generating a pressure change in the ink within the pressure chamber 12. Such a piezoelectric actuator 300 is also referred to as a piezoelectric element, and refers to a portion including the first electrode 60, the piezoelectric layer 70, and the second electrode 80. Furthermore, a portion of the piezoelectric layer 70 where piezoelectric strain occurs when a voltage is applied between the first electrode 60 and the second electrode 80 is referred to as an active portion 310. In contrast, a portion of the piezoelectric layer 70 where piezoelectric strain does not occur is referred to as an inactive portion. In other words, the active portion 310 refers to the portion of the piezoelectric layer 70 sandwiched between the first electrode 60 and the second electrode 80. In this embodiment, an active portion 310 is formed for each pressure chamber 12, which is a recess. That is, the piezoelectric actuator 300 is formed with a plurality of active portions 310. In this embodiment, the active portions 310 are arranged in two rows in the +Y direction in accordance with the pressure chambers 12, with the active portions 310 arranged side by side in the +X direction. In this embodiment, the first electrode 60 constitutes an independent individual electrode for each active portion 310, and the second electrode 80 is configured as a common electrode shared by the plurality of active portions 310. In addition, the portion of the piezoelectric actuator 300 that faces the pressure chamber 12 in the direction along the Z axis is a flexible portion, and the outer portion that does not face the pressure chamber 12 in the direction along the Z axis is a non-flexible portion.

[0025] 2 and 4, the first electrode 60 is separated for each pressure chamber 12 to form an independent individual electrode for each active section 310. The first electrode 60 is formed with a width narrower than the width of the pressure chamber 12 in the +X direction. That is, in the +X direction, an end of the first electrode 60 is located inside a region facing the pressure chamber 12. Also, as shown in FIG. 3, one end of the first electrode 60 on the nozzle 21 side is located outside the pressure chamber 12 in the Y axis. An individual lead electrode 91, which is a lead wiring, is connected to the end of this first electrode 60 located outside the pressure chamber 12 in the Y axis.

[0026] As shown in FIGS. 2, 3, and 4, the piezoelectric layer 70 has a predetermined width in the +Y direction and is continuously provided across the +X direction. The width of the piezoelectric layer 70 in the +Y direction is longer than the length of the pressure chamber 12 in the +Y direction, which is the longitudinal direction of the pressure chamber 12. Therefore, on both sides of the pressure chamber 12 in the +Y direction and the −Y direction, the piezoelectric layer 70 extends to the outside of the region facing the pressure chamber 12. The end of the piezoelectric layer 70 opposite the nozzle 21 in the Y axis is located outside the end of the first electrode 60. In other words, the end of the first electrode 60 opposite the nozzle 21 is covered by the piezoelectric layer 70. Furthermore, the end of the piezoelectric layer 70 on the nozzle 21 side is located inside the end of the first electrode 60, and the end of the first electrode 60 on the nozzle 21 side is not covered by the piezoelectric layer 70. As described above, an individual lead electrode 91 made of gold (Au) or the like is connected to the end of the first electrode 60 on the nozzle 21 side that is not covered with the piezoelectric layer 70.

[0027] Furthermore, recesses 71 corresponding to the partition walls 11 are formed in the piezoelectric layer 70. The width of each recess 71 in the +X direction is the same as or wider than the width of the partition walls 11. In this embodiment, the width of each recess 71 in the +X direction is wider than the width of the partition walls 11. This reduces the rigidity of the portions of the vibration plate 50 facing both ends of the pressure chambers 12 in the +X direction and the -X direction, i.e., the arm portions of the vibration plate 50, thereby improving the displacement efficiency of the piezoelectric actuator 300. The recesses 71 may penetrate the piezoelectric layer 70 in the +Z direction, which is the thickness direction, or may be provided partway through the thickness of the piezoelectric layer 70 without penetrating the piezoelectric layer 70 in the +Z direction. That is, the piezoelectric layer 70 may be completely removed from the bottom surface of each recess 71 in the +Z direction, or a portion of the piezoelectric layer 70 may remain.

[0028] Such a piezoelectric layer 70 is constructed using a piezoelectric material made of a composite oxide with a perovskite structure represented by the general formula ABO3. In this embodiment, lead zirconate titanate (PZT; Pb(Zr,Ti)O3) is used as the piezoelectric material. By using PZT as the piezoelectric material, a piezoelectric layer 70 with a relatively large piezoelectric constant d31 can be obtained. Note that the piezoelectric material used for the piezoelectric layer 70 may be a material with a reduced Pb content, known as a low-lead material, or a material that does not use Pb, known as a lead-free material. Using a low-lead material as the piezoelectric material can reduce the amount of Pb used. Furthermore, using a lead-free material as the piezoelectric material eliminates the need for Pb. Therefore, using low-lead or lead-free materials as the piezoelectric material can reduce the environmental impact.

[0029] As shown in FIGS. 2 to 5 , the second electrode 80 is provided on the −Z direction side of the piezoelectric layer 70, opposite the first electrode 60, and constitutes a common electrode shared by multiple active sections 310. The second electrode 80 is provided on a surface along the XY plane defined by the X and Y axes on the −Z direction side of the piezoelectric layer 70, on a side surface of the piezoelectric layer 70 (i.e., on a surface intersecting the XY plane), and on a portion of the first electrode 60 not covered by the piezoelectric layer 70. The second electrode 80 also has a removed portion 81 that penetrates the second electrode 80 on the piezoelectric layer 70 along the Z axis, which is the thickness direction. The removed portion 81 is provided continuously along the X axis on the nozzle 21 side of the piezoelectric layer 70, and electrically disconnects the portion of the second electrode 80 that is provided on the first electrode 60 along the Y axis from the opposite portion. Hereinafter, the portion cut off by the remover 81 from the portion provided on the first electrode 60 will be referred to as the second electrode 80. Furthermore, the portion made of the same layer as the second electrode 80, but provided from the first electrode 60 not covered by the piezoelectric layer 70 to the −Z direction surface of the piezoelectric layer 70 and electrically cut off from the second electrode 80 by the remover 81 will be referred to as the third electrode 82. In this embodiment, the third electrode 82 corresponds to a “connection electrode” electrically connected to the first electrode 60. In this embodiment, the second electrode 80 and the third electrode 82 are formed in the same layer, but this is not limited thereto, and the second electrode 80 and the third electrode 82 may be formed in different layers. Here, the second electrode 80 and the third electrode 82 being different layers includes both being layers formed at different times using the same material and being layers formed at different times using different materials.

[0030] As shown in FIG. 5 , the third electrodes 82 connected to the first electrodes 60 are separated and provided corresponding to each of the first electrodes 60. That is, the third electrodes 82 are not provided continuously in the +X direction, but are provided in parallel at regular intervals along the +X direction. This prevents electrical conduction between the multiple first electrodes 60 via the third electrodes 82. Specifically, the removal portion 81 of this embodiment includes a first removal portion 81a and a second removal portion 81b. The first removal portion 81a is provided continuously in the +X direction on the −Z direction surface of the piezoelectric layer 70. The first removal portion 81a is also located at a position slightly away from the nozzle 21 end of the piezoelectric layer 70 along the Y axis. The first removal portion 81a separates the third electrode 82 and the second electrode 80 on the first electrode 60, preventing electrical conduction between the first electrode 60 and the second electrode 80.

[0031] The second removed portions 81b are disposed on the −Z direction surface of the piezoelectric layer 70 between adjacent first electrodes 60 in the +X direction, with one end connected to the first removed portion 81a and the other end extending along the Y axis to the end of the piezoelectric layer 70 in the direction along the Y axis. A plurality of second removed portions 81b are disposed at regular intervals along the +X direction. The second removed portions 81b divide the third electrode 82 into each first electrode 60, thereby preventing electrical conduction between the multiple first electrodes 60. In other words, the removed portions 81 are disposed so that the first removed portions 81a and the second removed portions 81b form a substantially comb-like shape when viewed in the +Z direction.

[0032] The end of the active portion 310 on the nozzle 21 side in the Y axis is defined by the end formed by the first removed portion 81a of the second electrode 80. In other words, the first electrode 60 is provided along the Y axis, straddling the end of the second electrode 80 on the removed portion 81 side, and the end of the active portion 310 on the nozzle 21 side is defined by the end of the second electrode 80 on the first removed portion 81a side.

[0033] Here, the second electrode 80 has a first end portion 83 that serves as a reference and is formed by the first removed portion 81a, and a protrusion 84 that protrudes further from the first end portion 83 toward the third electrode 82.

[0034] The first end 83 is formed in a straight line along the X-axis. The first end 83 is mainly an end of the non-active section.

[0035] The protrusion 84 is provided from the end of the active section 310 toward the third electrode 82, protruding beyond the first end 83. "Protruding from the end of the active section 310" means that the base of the protrusion 84 is positioned so as to overlap the first electrode 60 when viewed in the +Z direction along the Z axis. The "base of the protrusion 84" refers to the portion that is located at the same position as the first end 83 in the direction along the Y axis. In other words, "positioning the base of the protrusion 84 so as to overlap the first electrode 60 when viewed in the +Z direction" means that the connection portion between the protrusion 84 and the first end 83 overlaps the first electrode 60 when viewed in the +Z direction. In this embodiment, the width of the base of the protrusion 84 is smaller than that of the first electrode 60 in the direction along the X axis.

[0036] Furthermore, the end of the active portion 310 and the third electrode 82 are disposed at positions facing each other in the direction along the Y axis, which is the longitudinal direction of the pressure chamber 12. In other words, the end of the active portion 310 and the third electrode 82 are disposed at the same position in the direction along the X axis. Therefore, the direction in which the convex portion 84 protrudes toward the third electrode 82 coincides with the direction along the Y axis.

[0037] The width of such a protrusion 84 in the direction along the X-axis, which is orthogonal to the protruding direction, gradually decreases toward the third electrode 82. In other words, the protrusion 84 has a so-called tapered shape in which the area per unit length in the direction along the Y-axis decreases toward the tip. However, the protrusion 84 is not limited to this, and may include a linear portion having a linear shape that has the same width in the direction along the X-axis toward the third electrode 82, and a tapered portion having a tapered shape whose width in the direction along the X-axis gradually decreases. When the protrusion 84 is composed of a linear portion and a tapered portion, the linear portion may be provided on the first end portion 83 side and the tapered portion may be provided on the third electrode 82 side, or vice versa.

[0038] Furthermore, the protrusions 84 of this embodiment are arranged in positions where their tips also overlap with the first electrodes 60 when viewed in the +Z direction. In other words, the protrusions 84 are arranged in positions where their entirety overlaps with the first electrodes 60 when viewed in the +Z direction.

[0039] By providing the protrusions 84 on the second electrode 80 in this manner, the electrical resistance value can be gradually increased toward the tip of the protrusions 84. That is, if the inside of the first end 83 of the second electrode 80 shown in FIG. 5 , i.e., the pressure chamber 12 side, is defined as the first region P1 and the first removed portion 81a is defined as the sixth region P6, the electrical resistance value of the protrusions 84 gradually increases along the Y axis from the first region P1 toward the sixth region P6. In this embodiment, the width of the protrusions 84 along the X axis is narrower than the width of the second electrode 80 on the first end 83 side, so the electrical resistance value of the protrusions 84 gradually increases toward the third electrode 82. Furthermore, because the width of the protrusions 84 along the X axis gradually decreases toward the third electrode 82, the cross-sectional area of ​​the protrusions 84 in the protruding direction gradually decreases toward the third electrode 82. This also causes the electrical resistance value of the protrusions 84 to gradually increase toward the third electrode 82. In other words, when the protrusion 84 is divided along the Y axis into four regions, the second region P2, the third region P3, the fourth region P4, and the fifth region P5, the electrical resistance value of the second region P2 is greater than that of the first region P1, and the electrical resistance value of the third region P3 is greater than that of the second region P2. The electrical resistance value of the fourth region P4 is greater than that of the third region P3. The electrical resistance value of the fifth region P5 is greater than that of the fourth region P4. Therefore, the voltage applied to the protrusion 84 gradually decreases from the second region P2 to the fifth region P5 compared to the voltage applied to the first region P1. Therefore, the electric field applied to the active section 310 can be gradually decreased from the second region P2 to the fifth region P5 of the protrusion 84 compared to the first region P1. Therefore, the stress applied to the piezoelectric layer 70 as it tries to deform when the active section 310 is driven gradually decreases from the first region P1 toward the fifth region P5, which is the tip of the convex portion 84, thereby reducing stress concentration on the piezoelectric layer 70. Furthermore, since the electric field applied to the active section 310 in the fifth region P5 is sufficiently lower than that in the first region P1, stress concentration in the boundary between the fifth region P5 and the sixth region P6 can be suppressed when the active section 310 is driven.Therefore, stress concentration at the boundary between the active portion 310 and the inactive portion, i.e., the sixth region P6, is suppressed, which in turn suppresses the occurrence of damage such as cracks in the piezoelectric layer 70 and the occurrence of leakage current along the cracks between the first electrode 60 and the second electrode 80. This makes it possible to suppress driving defects of the active portion 310 caused by damage to the piezoelectric layer 70.

[0040] The end of the active section 310 on the opposite side of the nozzle 21 in the Y axis is defined by the end of the first electrode 60. In other words, the second electrode 80 is provided along the Y axis, straddling the end of the first electrode 60 on the opposite side of the nozzle 21, and the end of the active section 310 on the opposite side of the nozzle 21 is defined by the end of the first electrode 60. The first electrode 60, which defines the end of the active section 310 on the opposite side of the nozzle 21 along the Y axis, is located close to the neutral axis of the vibration plate 50 and the piezoelectric element 300, and the piezoelectric layer 70, the second electrode 80, etc. are formed in the -Z direction, so that stress concentration is unlikely to occur, and the piezoelectric layer 70 is unlikely to be damaged.

[0041] Furthermore, the second electrode 80 of this embodiment is also provided on the side surface of the recess 71 of the piezoelectric layer 70 and on the vibration plate 50, which is the bottom surface of the recess 71. Of course, the second electrode 80 may be provided only on a part of the inner surface of the recess 71, or may not be provided over the entire inner surface of the recess 71.

[0042] In addition, an individual lead electrode 91 and a common lead electrode 92, which are lead wirings in this embodiment, are connected to the first electrode 60 and the second electrode 80 of the piezoelectric actuator 300, respectively. In this embodiment, the individual lead electrode 91 and the common lead electrode 92 (hereinafter, collectively referred to as the lead electrode 90) are formed from the same layer but are electrically discontinuous. Such a lead electrode 90 is not particularly limited as long as it is made of a conductive material, and examples thereof include gold (Au), platinum (Pt), aluminum (Al), and copper (Cu). The lead electrode 90 may also have an adhesion layer that improves adhesion with the first electrode 60, the second electrode 80, and the diaphragm 50. In this embodiment, gold (Au) is used as the lead electrode 90. In other words, the top layer of the lead electrode 90 contains gold (Au).

[0043] The individual lead electrode 91 extends along the Y-axis from above the first electrode 60, which is provided on the outer side of the piezoelectric layer 70, to above the vibration plate 50. That is, the individual lead electrode 91 extends along the Y-axis from the end of the first electrode 60 on the nozzle 21 side toward above the vibration plate 50. While FIG. 2 shows a portion of the individual lead electrode 91 bent, this is not limitative and the individual lead electrode 91 may be provided linearly along the Y-axis. The individual lead electrode 91 also extends along the Y-axis from above the first electrode 60 to above the third electrode 82. The individual lead electrode 91 is provided only on the third electrode 82 without covering the end of the third electrode 82 on the removed portion 81 side. The individual lead electrode 91 extending over the third electrode 82 aligns the height of the adhesive surface to which the adhesive 130 is adhered by the individual lead electrode 91 with an extension portion 93 (described later) when the protection substrate 30 is bonded to the −Z direction side of the flow path forming substrate 10, thereby suppressing variations in the thickness of the adhesive 130.

[0044] The common lead electrode 92 is drawn out along the Y axis from above the second electrode 80 to above the diaphragm 50 at both ends of the second electrode 80 along the X axis, i.e., at the end in the +X direction and the end in the -X direction.

[0045] The common lead electrode 92 also has an extension portion 93 provided on the wall surface of the pressure chamber 12 along the Y axis, spanning the boundary between the flexible portion and the non-flexible portion. The extension portion 93 is provided continuously in the +X direction on the second electrode 80 relative to the multiple active portions 310, and is continuous with the common lead electrode 92 at both ends along the X axis. That is, the common lead electrode 92 having the extension portion 93 is continuously arranged so as to surround the periphery of the active portion 310 when viewed in plan from the protective substrate 30 side. In other words, the extension portion 93 refers to two portions of the common lead electrode 92 provided along the X axis. The extension portion 93 does not cover the end of the second electrode 80 on the removed portion 81 side, and is provided closer to the pressure chamber 12 along the Y axis than the end of the second electrode 80 on the removed portion 81 side.

[0046] By providing the extension portion 93 on the common lead electrode 92 in this manner, it is possible to suppress a voltage drop in the direction along the X-axis of the second electrode 80, thereby suppressing deterioration and variation in the ejection characteristics of ink ejected from each nozzle 21. In particular, in this embodiment, by providing the extension portion 93 on each of both ends of the active portion 310 in the direction along the Y-axis, it is possible to increase the cross-sectional area of ​​the extension portion 93 along the YZ plane defined by the Y-axis and Z-axis, thereby making the electrical resistance value relatively small and effectively suppressing a voltage drop. Furthermore, by providing the extension portion 93 at a position overlapping the boundary between the flexible portion and the non-flexible portion when viewed in the +Z direction, it is possible to improve the rigidity of the boundary between the flexible portion and the non-flexible portion and suppress damage to the piezoelectric layer 70 due to stress concentration at the boundary between the flexible portion and the non-flexible portion. Furthermore, by providing the extension portions 93 at both end portions of the active portion 310 where the amount of deformation is relatively small in the direction along the Y axis, and not providing them in the central portion where the amount of deformation is relatively large, it is possible to prevent the extension portions 93 from hindering the deformation of the active portion 310 and to prevent a significant decrease in the amount of deformation of the piezoelectric actuator 300. Furthermore, the extension portions 93 can adjust the height when the protection substrate 30 is bonded on the -Z direction side.

[0047] As described above, the flexible wiring board 121 is connected to the ends of the individual lead electrodes 91 and the common lead electrode 92 opposite to the ends connected to the piezoelectric actuator 300. The wiring board 121 has a drive circuit 120 mounted thereon that has a switching element for driving the piezoelectric actuator 300.

[0048] 3, a protective substrate 30 having substantially the same size as the flow path forming substrate 10 is bonded with an adhesive 130 to one surface (the -Z direction side) of the flow path forming substrate 10 on which the piezoelectric actuator 300 is provided. In this embodiment, the protective substrate 30 is bonded to the piezoelectric actuator 300 with the adhesive 130. The adhesive 130 is provided so as to adhere to the extension portion 93, the removed portion 81, etc. of the piezoelectric actuator 300.

[0049] 3, the protective substrate 30 is provided with a through hole 32 penetrating in the +Z direction at a position overlapping between the two rows of piezoelectric actuators 300 when viewed in the +Z direction. The ends of the individual lead electrodes 91 and the common lead electrode 92 drawn from the electrodes of the piezoelectric actuators 300 extend so as to be exposed within the through hole 32, and the individual lead electrodes 91 and the common lead electrode 92 are electrically connected to the wiring substrate 121 within the through hole 32.

[0050] Furthermore, a case member 40 that forms a manifold 100 that communicates with the multiple pressure chambers 12 is fixed to the -Z direction side of the protective substrate 30. The case member 40 has substantially the same shape as the above-mentioned communicating plate 15 in a plan view, and is bonded to the protective substrate 30 as well as to the above-mentioned communicating plate 15.

[0051] The case member 40 has a recess 41 that opens to the surface on the +Z direction side and has a depth that allows the flow-channel-forming substrate 10 and the protective substrate 30 to be accommodated therein. The recess 41 has an opening area larger than the surface of the protective substrate 30 that is joined to the flow-channel-forming substrate 10. With the flow-channel-forming substrate 10, the protective substrate 30, and the like accommodated in the recess 41, the opening of the recess 41 facing the nozzle plate 20 is sealed by a communicating plate 15. The case member 40 also has third manifold portions 42, which are grooves that open in the +Z direction, on both outer sides of the recess 41 in the direction along the Y axis, i.e., on both the +Y direction and the −Y direction. The third manifold portion 42 has approximately the same opening area as the opening on the −Z direction side of the first manifold portion 17 provided in the communicating plate 15. By joining the case member 40 to the communicating plate 15, the third manifold portion 42 and the first manifold portion 17 are in communication with each other. The manifold 100 of this embodiment is configured by the third manifold portion 42 provided in this case member 40, and the first manifold portion 17 and second manifold portion 18 provided in the communication plate 15. The manifold 100 is provided continuously over the +X direction in which the pressure chambers 12 are arranged side by side, and the supply communication passages 19 that connect the pressure chambers 12 and the manifold 100 are arranged side by side in the +X direction.

[0052] Furthermore, the case member 40 is provided with an inlet 44 on the −Z direction side of the third manifold portion 42, which is in communication with the manifolds 100 and supplies ink to each manifold 100. The case member 40 is also provided with a connection port 43 which is in communication with the through hole 32 of the protection substrate 30 and through which the wiring substrate 121 is inserted.

[0053] Furthermore, a compliance substrate 45 is provided on the surface of the communicating plate 15 on the +Z direction side where the first manifold portion 17 and the second manifold portion 18 open. This compliance substrate 45 seals the openings on the +Z direction side of the first manifold portion 17 and the second manifold portion 18. In this embodiment, such compliance substrate 45 includes a sealing film 46 made of a flexible thin film, and a fixed substrate 47 made of a hard material such as metal. The region of the fixed substrate 47 facing the manifold 100 is an opening 48 that is completely removed in the thickness direction, and therefore one surface of the manifold 100 forms a compliance portion 49 that is a flexible portion sealed only by the flexible sealing film 46.

[0054] In the recording head 1 of this embodiment, ink is taken in from the inlet 44 connected to an external ink supply means (not shown), and the interior is filled with ink from the manifold 100 to the nozzles 21. Then, in accordance with a recording signal from the drive circuit 120, a voltage is applied between each of the first electrodes 60 and second electrodes 80 corresponding to the pressure chambers 12. This causes the vibration plate 50 to bend and deform together with the piezoelectric actuator 300, increasing the pressure inside each pressure chamber 12 and causing ink to be ejected from each nozzle 21.

[0055] As described above, the recording head 1, which is an example of a piezoelectric device according to the present invention, includes a flow channel-forming substrate 10, which is a substrate having a plurality of pressure chambers 12 formed as recesses; a vibration plate 50 provided on one side of the flow channel-forming substrate 10; and a piezoelectric actuator 300, which is formed by stacking a first electrode 60, a piezoelectric layer 70, and a second electrode 80 from the vibration plate 50 side. The piezoelectric actuator 300 also includes a plurality of active sections 310, each of which has a piezoelectric layer 70 sandwiched between the first electrode 60 and the second electrode 80. The first electrode 60 constitutes an independent individual electrode for each active section 310, and the second electrode 80 constitutes a common electrode shared by the plurality of active sections. The second electrode 80 also includes a first end 83 serving as a reference and a protrusion 84 that protrudes beyond the first end 83 from the end of the active section 310 toward a third electrode 82, which is a connection electrode electrically connected to the first electrode 60.

[0056] By providing the convex portion 84 on the second electrode 80 in this manner, the electrical resistance value of the convex portion 84 can be gradually increased toward the tip compared to the electrical resistance value on the first end 83 side. Therefore, the voltage applied to the convex portion 84 can be gradually decreased toward the tip, and the electric field strength applied to the end of the active portion 310 can be gradually decreased toward the tip of the convex portion 84. As a result, the stress applied to the end of the active portion 310 can be dispersed, and it is possible to prevent damage such as cracks in the piezoelectric layer 70 due to stress concentration and to prevent driving defects of the active portion 310 due to leakage current occurring between the first electrode 60 and the second electrode 80 along the cracks.

[0057] Furthermore, in the recording head 1 of this embodiment, it is preferable that the width of the convex portion 84 in the direction along the X axis, which is orthogonal to the protruding direction, gradually narrows toward the third electrode 82, which is the connecting electrode. This allows the electrical resistance value of the convex portion 84 to further gradually increase toward the third electrode 82, thereby effectively suppressing stress concentration at the end of the active portion 310.

[0058] Furthermore, in the recording head 1 of this embodiment, when viewed in the +Z direction, which is the stacking direction of the piezoelectric actuator 300 and the flow path forming substrate 10, which is the substrate, it is preferable that the base of the convex portion 84 overlaps with the first electrode 60. This allows the convex portion 84 to protrude from the end of the active portion 310, and the convex portion 84 can suppress stress concentration at the end of the active portion 310.

[0059] In the present embodiment, the entire convex portion 84 is arranged at a position overlapping the first electrode 60 when viewed in the +Z direction, but this is not particularly limited. The convex portion 84 may be arranged at a position where its tip does not overlap the first electrode 60, as long as it is arranged at a position where at least its base overlaps the first electrode 60 when viewed in the +Z direction. This is because, even if the tip of the convex portion 84 is arranged at a position where it does not overlap the first electrode 60 when viewed in the +Z direction, the electrical resistance value of the convex portion 84 gradually increases toward the tip, and therefore, even in the region where the convex portion 84 overlaps the first electrode 60 when viewed in the +Z direction, the electrical resistance value gradually increases toward the third electrode 82.

[0060] (Embodiment 2) 6 is an enlarged plan view and a cross-sectional view of a main part of a flow path forming substrate 10 of an ink jet recording head 1, which is an example of a liquid jet head according to embodiment 2 of the present invention. Note that the same reference numerals are used to designate the same members as those in the above-described embodiment, and redundant explanations will be omitted.

[0061] The protrusion 84 of the second electrode 80 has a first protrusion 84a and a parallel portion 84b.

[0062] The first protrusion 84a has the same shape as the protrusion 84 of the first embodiment described above. That is, the first protrusion 84a is provided so as to protrude from the end of the active section 310 toward the third electrode 82 beyond the first end 83. The protrusion 84 also has a tapered shape in which the width in the direction along the X-axis, which is a direction perpendicular to the protruding direction, gradually narrows toward the third electrode 82. Furthermore, the protrusion 84 of this embodiment is also arranged at a position where the tip overlaps with the first electrode 60 when viewed in the +Z direction. That is, the protrusion 84 is arranged at a position where the entire protrusion overlaps with the first electrode 60 when viewed in the +Z direction.

[0063] The parallel portion 84b is provided continuously from the tip of the first convex portion 84a and is provided parallel to the end face of the third electrode 82 facing the second electrode 80. In other words, the parallel portion 84b being parallel to the third electrode 82 means that the distance between the parallel portion 84b and the third electrode 82 is constant along the X-axis in the direction along the Y-axis, which is the protruding direction of the convex portion 84. In this embodiment, the end face of the third electrode 82 facing the second electrode 80 along the Y-axis is linearly provided along the X-axis, and therefore the end face of the parallel portion 84b facing the third electrode 82 is linearly provided along the X-axis. Furthermore, the width of the parallel portion 84b in the direction along the Y-axis is constant along the X-axis. In other words, the parallel portion 84b in this embodiment is provided along a straight line along the X-axis with the same width across the X-axis.

[0064] Furthermore, the width W1 of the parallel portion 84b along the X-axis is preferably equal to or greater than the width W2 of the third electrode 82. In other words, the width W1 of the parallel portion 84b and the width W2 of the third electrode 82 preferably satisfy the relationship W1≧W2. The width W1 of the parallel portion 84b is greater than the width of the first convex portion 84a along the X-axis. In other words, the convex portion 84 is thickest at the tip end, that is, the parallel portion 84b.

[0065] As described above, in the recording head 1, which is an example of a piezoelectric device according to this embodiment, the convex portion 84 has a parallel portion 84b at its tip end that is parallel to the third electrode 82, which is a connecting electrode. By providing the parallel portion 84b parallel to the third electrode 82 on the convex portion 84 in this manner, the electric field between the third electrode 82 and the convex portion 84 is applied across the X-axis of the parallel portion 84b. This prevents the electric field between the convex portion 84 and the third electrode 82 from being concentrated at one point on the convex portion 84, thereby preventing a short circuit from occurring between the third electrode 82 and the convex portion 84. Furthermore, the first convex portion 84a of the convex portion 84 increases the electrical resistance toward the tip end. Therefore, even if the electrical resistance of the parallel portion 84b becomes greater than that of the first convex portion 84a, the first convex portion 84a can reduce the voltage applied toward the tip end. This allows the voltage applied to the parallel portion 84b to be sufficiently reduced. That is, the area inside the first end 83 of the second electrode 80, i.e., the area on the pressure chamber 12 side, is defined as the first region P1, the first removed portion 81a is defined as the sixth region P6, the first convex portion 84a of the convex portion 84 is defined as the second region P2, the third region P3, and the fourth region P4 from the first region P1 side, and the region where the parallel portion 84b is provided is defined as the fifth region P5. In this case, the electrical resistance value of the fifth region P5 where the parallel portion 84b of the convex portion 84 is provided is higher than those of the second region P2, the third region P3, and the fourth region P4, but because the voltage is sufficiently reduced in the fourth region P4, the voltage applied to the parallel portion 84b of the fifth region P5 is the same as or lower than that of the fourth region P4. Therefore, even when the parallel portion 84b is provided, the electric field applied to the end of the active portion 310 by the convex portion 84 can be gradually reduced toward the tip of the convex portion 84, thereby suppressing stress concentration at the end of the active portion 310 and suppressing the occurrence of damage such as cracks in the piezoelectric layer 70 and driving defects of the active portion 310 due to leakage current along the cracks. Note that, although the convex portion 84 has the first convex portion 84a and the parallel portion 84b, the width of the first convex portion 84a on the parallel portion 84b side in the direction along the X-axis may be the same as the width of the parallel portion 84b. In other words, the parallel portion may be formed by forming the entire convex portion 84 in a tapered shape whose width in the direction along the X-axis gradually increases.Of course, the protrusion 84 may have a shape having a linear portion formed in part with the same width in the direction along the X axis.

[0066] Furthermore, in the recording head 1 of this embodiment, the width W1 of the parallel portion 84b in the direction along the X-axis, which is a direction perpendicular to the protruding direction of the convex portion 84, is preferably equal to or greater than the width W2 of the third electrode 82, which is a connecting electrode. By making the width W1 of the parallel portion 84b equal to or greater than the width W2 of the third electrode 82 in this way, the electric field applied across the X-axis of the parallel portion 84b can be dispersed, thereby further suppressing the occurrence of a short circuit between the third electrode 82 and the convex portion 84.

[0067] Furthermore, in the recording head 1 of this embodiment, the width in the direction along the X-axis, which is the direction perpendicular to the protrusion direction of the convex portions 84, is preferably widest at the tip. In other words, compared to when the convex portions 84 are composed of only the parallel portions 84b, by configuring the convex portions 84 with the first convex portions 84a and the thicker parallel portions 84b, it is possible to cause a voltage drop toward the tip by the first convex portions 84a and to suppress the occurrence of electric field concentration at the parallel portions 84b, which are the tip portions of the convex portions 84.

[0068] In this embodiment, the first protrusion 84a has a tapered shape in which the width on both sides of the X-axis narrows toward the tip, but is not particularly limited to this. Modified examples of the protrusion 84 are shown in Figures 7 to 9. Figures 7 to 9 are plan views of the main part of the flow path forming substrate 10, illustrating modified examples of the protrusion 84.

[0069] 7, the convex portion 84 has a first convex portion 84a and a parallel portion 84b, and the first convex portion 84a has a tapered shape in which the width on one side of the X-axis narrows toward the tip, that is, the side surface of the first convex portion 84a in the +X direction is provided along the Y-axis, and the side surface in the -X direction is inclined with respect to the Y-axis, resulting in a tapered shape in which the width gradually narrows toward the tip. In this way, even if the first convex portion 84a has a shape in which the width narrows from one side of the X-axis, it can achieve the same effect as that described above.

[0070] 8, the protrusion 84 includes a first protrusion 84a and a parallel portion 84b. The first protrusion 84a has a shape in which the width along the X-axis gradually decreases toward the tip and gradually increases from the middle. Even if the first protrusion 84a has such a shape that the width increases from the middle, the same effect as that described above can be achieved.

[0071] As shown in FIG. 9 , the protrusion 84 includes a first protrusion 84a and a parallel portion 84b. The first protrusion 84a has a width along the X-axis that is constant across the Y-axis. Even with this shape of the first protrusion 84a, the electrical resistance increases less toward the tip compared to the first protrusion 84a shown in FIG. 6 , but the same effect as that shown in FIG. 6 can be achieved. That is, even though the first protrusion 84a has the same width along the Y-axis, the electrical resistance increases toward the tip compared to the first end 83, resulting in a voltage drop toward the tip. Therefore, even if the first protrusion 84a has the same width along the Y-axis, the electric field strength applied to the end of the active portion 310 can be gradually reduced. This suppresses stress concentration at the end of the active portion 310 and suppresses leakage current and burnout due to breakdown of the piezoelectric layer 70.

[0072] Of course, the first protrusions 84a shown in FIGS. 7 to 9 can also be applied to the protrusions 84 of the first embodiment described above.

[0073] (Other embodiments) Although one embodiment of the present invention has been described above, the basic configuration of the present invention is not limited to the above.

[0074] For example, in each of the above-described embodiments, the protrusion 84 is formed as part of the second electrode 80, but this is not particularly limited, and the protrusion 84 may be formed on a layer different from the second electrode 80, for example, on the common lead electrode 92 or on another layer. In other words, as long as the protrusion 84 is electrically connected to the second electrode 80, the protrusion 84 essentially becomes part of the second electrode 80.

[0075] Furthermore, for example, the convex portion 84 in the above-described first embodiment and the first convex portion 84a shown in FIGS. 6 to 8 in the second embodiment have a tapered shape in which the width along the X-axis gradually narrows toward the tip, but this is not particularly limited thereto, and the convex portion 84 may have a so-called staircase shape in which the width along the X-axis narrows in stages toward the tip.

[0076] The recording head 1 of the first embodiment is mounted on an ink jet recording apparatus I. FIG.

[0077] In the inkjet recording device I shown in Figure 10, a recording head 1 is provided with a detachable cartridge 2 constituting a liquid supply means, and a carriage 3 carrying this recording head 1 is provided on a carriage shaft 5 attached to the device main body 4 so as to be movable in the axial direction.

[0078] The driving force of the drive motor 6 is transmitted to the carriage 3 via multiple gears and a timing belt 7 (not shown), causing the carriage 3 carrying the recording head 1 to move along the carriage shaft 5. Meanwhile, the device body 4 is provided with a transport roller 8 as a transport means, and a recording sheet S, which is a recording medium such as paper, is transported by the transport roller 8. Note that the transport means for transporting the recording sheet S is not limited to a transport roller, and may be a belt, a drum, or the like.

[0079] Furthermore, in the inkjet recording device I described above, the recording head 1 is mounted on a carriage 3 and moves in the main scanning direction, but this is not particularly limited to this, and the present invention can also be applied to, for example, a so-called line-type recording device in which the recording head 1 is fixed and printing is performed simply by moving a recording sheet S such as paper in the sub-scanning direction.

[0080] In the above embodiment, an inkjet recording head is used as an example of a liquid jet head, and an inkjet recording device is used as an example of a liquid jet device. However, the present invention is directed to a wide range of liquid jet heads and liquid jet devices, and can of course be applied to liquid jet heads and liquid jet devices that jet liquids other than ink. Examples of other liquid jet heads include various recording heads used in image recording devices such as printers, colorant jet heads used in manufacturing color filters for liquid crystal displays, electrode material jet heads used in forming electrodes for organic EL displays, FEDs (field emission displays), and bioorganic material jet heads used in manufacturing biochips, and the present invention can also be applied to liquid jet devices equipped with such liquid jet heads.

[0081] Furthermore, the present invention is not limited to liquid jet heads typified by ink jet recording heads, but can also be applied to ultrasonic devices, motors, pressure sensors, pyroelectric elements, ferroelectric elements, and other piezoelectric devices. Also included in the piezoelectric device are finished products that utilize these piezoelectric devices, such as a liquid jetting apparatus that utilizes the liquid jetting head, an ultrasonic sensor that utilizes the ultrasonic device, a robot that utilizes the motor as a drive source, an IR sensor that utilizes the pyroelectric element, and a ferroelectric memory that utilizes a ferroelectric element. [Explanation of symbols]

[0082] I...inkjet recording apparatus (liquid ejection apparatus), 1...inkjet recording head (liquid ejection head), 2...cartridge, 3...carriage, 4...apparatus main body, 5...carriage shaft, 6...drive motor, 7...timing belt, 8...transport roller, 10...flow path forming substrate, 12...pressure chamber, 15...communicating plate, 16...nozzle communicating passage, 17...first manifold portion, 18...second manifold portion, 19...supply communicating passage, 20...nozzle plate, 21...nozzle, 30...protective substrate, 32...through hole, 40...case member, 41...recess, 42...third manifold portion, 43...connecting port, 44...inlet, 45...comply 1. An insulating film having a first end, a second end, a piezoelectric layer, a first recess, a first convex portion, a first convex portion, a first convex portion, a first convex portion, a first parallel portion, a first end ...

Claims

1. a substrate having a plurality of recesses; a diaphragm provided on one surface of the substrate; a piezoelectric actuator in which a first electrode, a piezoelectric layer, and a second electrode are stacked from the vibration plate side; Equipped with the piezoelectric actuator has a plurality of active portions in which the piezoelectric layer is sandwiched between the first electrode and the second electrode, the first electrode constitutes an independent individual electrode for each of the active portions; the second electrode constitutes a common electrode common to a plurality of the active portions, A piezoelectric device characterized in that the second electrode has a first end portion that serves as a reference, and a convex portion that protrudes beyond the first end portion from the end of the active portion toward a connection electrode that is electrically connected to the first electrode.

2. 2. The piezoelectric device according to claim 1, wherein the width of the protrusion in a direction perpendicular to the protruding direction gradually decreases toward the connection electrode.

3. 3. The piezoelectric device according to claim 1, wherein the protrusion has a parallel portion at a tip end thereof that is parallel to the connection electrode.

4. 4. The piezoelectric device according to claim 3, wherein the width of the parallel portion in a direction perpendicular to the direction in which the convex portion protrudes is equal to or greater than the width of the connection electrode.

5. 5. The piezoelectric device according to claim 1, wherein a base of the protrusion overlaps with the first electrode when viewed in a stacking direction of the piezoelectric actuator and the substrate.

6. 6. The piezoelectric device according to claim 1, wherein the width of the convex portion in a direction perpendicular to the protruding direction is greatest at the tip end.

7. a substrate in which a plurality of pressure chambers communicating with nozzles that eject liquid are formed; a diaphragm provided on one surface of the substrate; a piezoelectric actuator in which a first electrode, a piezoelectric layer, and a second electrode are stacked from the vibration plate side; Equipped with the piezoelectric actuator has a plurality of active portions in which the piezoelectric layer is sandwiched between the first electrode and the second electrode, the first electrode constitutes an independent individual electrode for each of the active portions; the second electrode constitutes a common electrode common to a plurality of the active portions, The liquid jet head is characterized in that the second electrode has a first end portion that serves as a reference, and a convex portion that protrudes beyond the first end portion from the end of the active portion toward a connection electrode that is electrically connected to the first electrode.

8. A liquid ejection apparatus comprising the liquid ejection head according to claim 7.

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