Piezoelectric device, liquid injection head, and liquid injection device

Abstract

To prevent cracks or burns in a piezoelectric layer caused by a distortion difference from an active part near the end of an active part of a piezoelectric actuator.SOLUTION: A piezoelectric device comprises: a vibration plate 50 provided on one surface side of a substrate 10; a first electrode 60 layered on a side of the vibration plate 50 opposite the substrate 10; and a piezoelectric actuator 300 having a piezoelectric layer 70 and a second electrode 80. The piezoelectric actuator 300 includes an active part 310 in which the piezoelectric layer 70 is held between the first and second electrodes 60 and 80. On the surface of the piezoelectric layer side 70 of the first electrode 60 at the end of the active part 310, an uneven part 63 including a plurality of projected parts 61 and recessed parts 62 formed among the projected parts 61 is provided.SELECTED DRAWING: Figure 7

Description

Technical Field

[0001] The present invention relates to a piezoelectric device, a liquid ejection head, and a liquid ejection apparatus, which include a diaphragm, and a piezoelectric actuator having a first electrode, a piezoelectric layer, and a second electrode.

Background Art

[0002] As a representative example of a liquid ejection head, which is one type of piezoelectric device, there is an inkjet recording head that ejects ink droplets. As an inkjet recording head, for example, it includes a flow path forming substrate in which a pressure chamber communicating with a nozzle is formed, and a piezoelectric actuator provided via a diaphragm on one surface side of the flow path forming substrate. By causing a pressure change in the ink in the pressure chamber by the piezoelectric actuator, an inkjet recording head that ejects ink droplets from the nozzle is known.

[0003] Further, as a piezoelectric actuator, there is known one that includes a first electrode formed on a diaphragm, a piezoelectric layer formed of a piezoelectric material having electro-mechanical conversion characteristics on the first electrode, and a second electrode provided on the piezoelectric layer (see, for example, Patent Document 1).

[0004] This Patent Document 1 discloses a configuration including a plurality of piezoelectric elements as piezoelectric actuators, and these plurality of piezoelectric elements are arranged in parallel in a row. And each piezoelectric element includes an active part (also referred to as an active portion) in which the piezoelectric layer is sandwiched between the first electrode and the second electrode, and in a direction orthogonal to the parallel arrangement direction of the piezoelectric elements, the end of the active part is defined by the end of the second electrode.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] In this configuration, where the end of the active part of the piezoelectric actuator is defined by the end of the second electrode, there is a risk that cracks or burnout may occur in the piezoelectric layer near the end of the active part due to the difference in strain between the active and inactive parts. Specifically, the bending deformation of the piezoelectric actuator may cause minute cracks in the piezoelectric layer, and burnout may occur due to the leakage current value caused by these minute cracks in the piezoelectric layer.

[0007] It should be noted that this problem is not limited to liquid ejection heads, such as those used in inkjet recording heads that eject ink, but also exists in other piezoelectric devices. [Means for solving the problem]

[0008] One aspect of the present invention that solves the above problems is a piezoelectric device comprising a diaphragm provided on one side of a substrate, and a piezoelectric actuator having a first electrode, a piezoelectric layer, and a second electrode laminated on the side of the diaphragm opposite to the substrate, wherein the piezoelectric actuator has an active portion in which the piezoelectric layer is sandwiched between the first electrode and the second electrode, and the surface of the first electrode on the piezoelectric layer side at the end of the active portion has an uneven portion composed of a plurality of protrusions and recesses formed between the protrusions.

[0009] Another aspect of the present invention is a liquid injection head characterized by comprising the piezoelectric device of the above aspect.

[0010] Another aspect of the present invention is a liquid injection device characterized by being equipped with the liquid injection head of the above aspect. [Brief explanation of the drawing]

[0011] [Figure 1] This is an exploded perspective view of the recording head according to Embodiment 1. [Figure 2] This is a plan view of the recording head according to Embodiment 1. [Figure 3]Cross-sectional view of the recording head according to Embodiment 1. [Figure 4] Cross-sectional view of the piezoelectric actuator according to Embodiment 1. [Figure 5] Cross-sectional view of the piezoelectric actuator according to Embodiment 1. [Figure 6] Planar view showing the main part of the piezoelectric actuator according to Embodiment 1. [Figure 7] Cross-sectional view showing the main part of the piezoelectric actuator according to Embodiment 1. [Figure 8] Cross-sectional view showing a modified example of the piezoelectric actuator according to Embodiment 1. [Figure 9] Cross-sectional view showing the main part of the piezoelectric actuator according to Embodiment 2. ​​​​​​​​​​​​​​​​​​​​​​FIG. 1 is an exploded perspective view of an inkjet recording head, which is an example of a liquid ejection head according to Embodiment 1 of the present invention. FIG. 2 is a plan view of the recording head, and FIG. 3 is a cross-sectional view taken along line A-A of FIG. 2. FIG. 4 is an enlarged cross-sectional view of the piezoelectric actuator portion, and FIG. 5 is a cross-sectional view taken along line B-B of FIG. 4. Further, FIG. 6 is an enlarged plan view of the vicinity of the end of the piezoelectric actuator, and FIG. 7 is a cross-sectional view corresponding to line C-C of FIG. 6.

[0015] As shown in FIGS. 1 to 3, an inkjet recording head (hereinafter, also simply referred to as a recording head) 1, which is an example of the liquid ejection head of the present embodiment, ejects ink droplets in the Z-axis direction, which is the first direction, more specifically, the +Z direction.

[0016] The inkjet recording head 1 includes a flow path forming substrate 10 as an example of a substrate. The flow path forming substrate 10 is made of, for example, a silicon substrate, a glass substrate, an SOI substrate, various ceramic substrates, and the like. Note that the flow path forming substrate 10 may be a substrate with (100) plane preferential orientation or a substrate with (110) plane preferential orientation.

[0017] A plurality of pressure chambers 12 are arranged in two rows in the X-axis direction, which is the second direction intersecting the Z-axis direction, which is the first direction, on the flow path forming substrate 10. That is, the plurality of pressure chambers 12 constituting each row are arranged along the Y-axis direction, which is the third direction intersecting the X-axis direction.

[0018] The plurality of pressure chambers 12 constituting each row are arranged on a straight line along the Y-axis direction so that their positions in the X-axis direction are the same. The pressure chambers 12 adjacent to each other in the Y-axis direction are partitioned by a partition wall 11. Of course, the arrangement of the pressure chambers 12 is not particularly limited. For example, the arrangement of the plurality of pressure chambers 12 arranged in the Y-axis direction may be a so-called staggered arrangement in which each pressure chamber 12 is shifted in the X-axis direction at every other position.

[0019] Furthermore, the pressure chamber 12 in this embodiment is formed in a rectangular shape, for example, where the length in the X-axis direction is longer than the length in the Y-axis direction when viewed from the +Z direction in a plan view. Of course, the shape of the pressure chamber 12 when viewed from the +Z direction in a plan view is not particularly limited and may be a parallelogram, polygon, circle, oval, etc. Note that the oval shape referred to here is a shape based on a rectangle with semicircular ends in the longitudinal direction, and includes rounded rectangles, ellipses, egg shapes, etc.

[0020] On the +Z direction side of the channel-forming substrate 10, the communication plate 15, the nozzle plate 20, and the compliance substrate 45 are sequentially stacked.

[0021] The communication plate 15 is provided with a nozzle communication passage 16 that connects the pressure chamber 12 and the nozzle 21. The communication plate 15 is also provided with a first manifold section 17 and a second manifold section 18 that constitute part of a manifold 100, which is a common liquid chamber through which multiple pressure chambers 12 are connected. The first manifold section 17 is provided penetrating the communication plate 15 in the Z-axis direction. The second manifold section 18 is provided opening on the +Z side surface without penetrating the communication plate 15 in the Z-axis direction.

[0022] Furthermore, the connecting plate 15 is provided with an independent supply passage 19 for each of the pressure chambers 12, which communicates with one end of the pressure chamber 12 in the X-axis direction. The supply passage 19 connects the second manifold section 18 to each pressure chamber 12, supplying ink from the manifold 100 to each pressure chamber 12.

[0023] As the connecting plate 15, a silicon substrate, glass substrate, SOI substrate, various ceramic substrates, metal substrates, etc., can be used. Examples of metal substrates include stainless steel substrates. It is preferable that the connecting plate 15 be made of a material with a thermal expansion coefficient approximately the same as that of the channel forming substrate 10. This makes it possible to suppress warping of the channel forming substrate 10 and the connecting plate 15 caused by differences in thermal expansion coefficients when the temperatures of the channel forming substrate 10 and the connecting plate 15 change.

[0024] The nozzle plate 20 is provided on the side of the communication plate 15 opposite to the flow path forming substrate 10, that is, on the +Z direction side. Nozzles 21 are formed on the nozzle plate 20, which communicate with each pressure chamber 12 via nozzle communication passages 16.

[0025] In this embodiment, the multiple nozzles 21 are arranged in a line along the Y-axis. The nozzle plate 20 has two rows of nozzles arranged in the X-axis direction, each row containing multiple nozzles 21. That is, the multiple nozzles 21 in each row are arranged so that they are at the same position in the X-axis direction. The arrangement of the nozzles 21 is not particularly limited. For example, the nozzles 21 arranged in a line along the Y-axis direction may be positioned with every other nozzle offset in the X-axis direction.

[0026] The material of the nozzle plate 20 is not particularly limited, and for example, silicon substrates, glass substrates, SOI substrates, various ceramic substrates, and metal substrates can be used. Examples of metal plates include stainless steel substrates. Furthermore, organic materials such as polyimide resin can also be used as the material of the nozzle plate 20. However, it is preferable to use a material for the nozzle plate 20 that has approximately the same thermal expansion coefficient as the communication plate 15. This makes it possible to suppress warping of the nozzle plate 20 and the communication plate 15 caused by differences in thermal expansion coefficients when the temperature of the nozzle plate 20 and the communication plate 15 changes.

[0027] The compliance substrate 45 is provided together with the nozzle plate 20 on the side of the communication plate 15 opposite to the flow path forming substrate 10, i.e., on the +Z direction side. This compliance substrate 45 is provided around the nozzle plate 20 and seals the openings of the first manifold portion 17 and the second manifold portion 18 provided on the communication plate 15. In this embodiment, the compliance substrate 45 comprises 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. Therefore, one side of the manifold 100 is a compliance portion 49 sealed only by the flexible sealing film 46.

[0028] On the other hand, on the side of the flow path forming substrate 10 opposite to the nozzle plate 20, i.e., the side in the -Z direction, a diaphragm 50 and a piezoelectric actuator 300 that causes the diaphragm 50 to bend and deform, thereby creating a pressure change in the ink in the pressure chamber 12, are provided, as will be described in more detail later. Figure 3 is a diagram illustrating the overall configuration of the recording head 1, and the piezoelectric actuator 300 is shown in a simplified manner.

[0029] A protective substrate 30, having approximately the same size as the channel-forming substrate 10, is further bonded to the -Z-direction side of the channel-forming substrate 10 using an adhesive or the like. The protective substrate 30 has a holding portion 31, which is a space for protecting the piezoelectric actuator 300. The holding portion 31 is provided independently for each row of piezoelectric actuators 300 arranged in the Y-axis direction, and two of them are formed side by side in the X-axis direction. In addition, the protective substrate 30 has a through hole 32 that penetrates in the Z-axis direction between the two holding portions 31 arranged side by side in the X-axis direction.

[0030] Furthermore, a case member 40 is fixed to the protective substrate 30, which together defines a manifold 100 communicating with multiple pressure chambers 12, in conjunction with the flow path forming substrate 10. The case member 40 has substantially the same shape as the communication plate 15 described above in plan view, and is joined to the protective substrate 30 as well as to the communication plate 15 described above.

[0031] Such a case member 40 has a housing portion 41 on the side of the protective substrate 30 that is a space with a depth capable of accommodating the flow path forming substrate 10 and the protective substrate 30. This housing portion 41 has an opening area larger than the surface of the protective substrate 30 that is joined to the flow path forming substrate 10. When the flow path forming substrate 10 and the protective substrate 30 are housed in the housing portion 41, the opening surface of the housing portion 41 on the nozzle plate 20 side is sealed by a communication plate 15.

[0032] Furthermore, the case member 40 has third manifold sections 42 defined on both outer sides of the housing section 41 in the X-axis direction. The manifold 100 of this embodiment is composed of the first manifold section 17 and the second manifold section 18 provided on the communication plate 15, and the third manifold section 42. The manifold 100 is provided continuously along the Y-axis direction, and the supply communication passages 19 that connect each pressure chamber 12 to the manifold 100 are arranged side by side in the Y-axis direction.

[0033] Furthermore, the case member 40 is provided with an inlet 44 that communicates with the manifold 100 and supplies ink to each manifold 100. In addition, the case member 40 is provided with a connection port 43 that communicates with the through hole 32 of the protective substrate 30 and through which the wiring substrate 120 is inserted.

[0034] In this embodiment of the recording head 1, ink is drawn in from an inlet 44 connected to an external ink supply means (not shown), and the inside is filled with ink from the manifold 100 to the nozzles 21. Then, according to the recording signal from the drive circuit 121, a voltage is applied to each piezoelectric actuator 300 corresponding to the pressure chamber 12. As a result, the diaphragm 50 flexes and deforms together with the piezoelectric actuator 300, increasing the pressure in each pressure chamber 12, and ink droplets are ejected from each nozzle 21.

[0035] The configuration of the piezoelectric actuator 300 according to this embodiment will now be described. As described above, the piezoelectric actuator 300 is provided on the side of the flow path forming substrate 10 opposite to the nozzle plate 20 via a vibrating plate 50.

[0036] As shown in Figures 4 and 5, the diaphragm 50 is composed of an elastic film 51 made of silicon oxide provided on the channel-forming substrate 10 side, and an insulating film 52 made of zirconium oxide provided on the elastic film 51. Liquid channels such as the pressure chamber 12 are formed by anisotropic etching of the channel-forming substrate 10 from the +Z direction side, and the -Z direction side of the liquid channels such as the pressure chamber 12 is composed of the elastic film 51.

[0037] The composition of the diaphragm 50 is not particularly limited. The diaphragm 50 may be composed of either an elastic film 51 or an insulating film 52, or it may also include other films besides the elastic film 51 and the insulating film 52. Examples of materials for the other films include silicon and silicon nitride.

[0038] The piezoelectric actuator 300 is a pressure generating means that causes a pressure change in the ink in the pressure chamber 12, and is also called a piezoelectric element. This piezoelectric actuator 300 comprises a first electrode 60, a piezoelectric body layer 70, and a second electrode 80, which are sequentially stacked from the +Z direction side (the diaphragm 50 side) toward the -Z direction.

[0039] In the piezoelectric actuator 300, the portion of the piezoelectric layer 70 that experiences piezoelectric strain when a voltage is applied between the first electrode 60 and the second electrode 80 is referred to as the active portion 310. Conversely, the portion of the piezoelectric layer 70 that does not experience piezoelectric strain is referred to as the inactive portion 320. In other words, in the piezoelectric actuator 300, the portion of the piezoelectric layer 70 sandwiched between the first electrode 60 and the second electrode 80 is the active portion 310, and the portion of the piezoelectric layer 70 not sandwiched between the first electrode 60 and the second electrode 80 is the inactive portion 320.

[0040] Furthermore, when the piezoelectric actuator 300 is driven, the part that actually displaces in the Z-axis direction is referred to as the flexible part, and the part that does not displace in the Z-axis direction is referred to as the non-flexible part. In other words, of the active part 310 of the piezoelectric actuator 300, the part facing the pressure chamber 12 in the Z-axis direction is the flexible part, and the part outside the pressure chamber 12 is the non-flexible part.

[0041] Generally, one of the electrodes of the active section 310 is configured as an individual electrode independent of each piezoelectric actuator 300, and the other electrode is configured as a common electrode common to multiple piezoelectric actuators 300. In this embodiment, the first electrode 60 constitutes an individual electrode, and the second electrode 80 constitutes a common electrode.

[0042] Specifically, the first electrode 60 is divided into individual electrodes for each pressure chamber 12, making each active portion 310 independent. The first electrode 60 is formed with a width narrower than the width of the pressure chamber 12 in the Y-axis direction. That is, the end of the first electrode 60 is located inside the region facing the pressure chamber 12 in the Y-axis direction.

[0043] Furthermore, the first electrode 60 extends in the X-axis direction from the region facing the pressure chamber 12 to the outside of the pressure chamber 12, and the +X end 60a and -X end 60b of the first electrode 60 in Figure 4 are located outside the pressure chamber 12. The +X end 60a of the first electrode 60 is located in a position that is more +X than the +X end 12a of the pressure chamber 12, and the -X end 60b of the first electrode 60 is located in a position that is more -X than the -X end 12b of the pressure chamber 12.

[0044] The material of the first electrode 60 is not particularly limited, but conductive materials such as metals like iridium or platinum, or conductive metal oxides such as indium tin oxide (abbreviated as ITO) can be used.

[0045] The piezoelectric layer 70 is provided continuously along the Y-axis direction with a predetermined length in the X-axis direction. That is, the piezoelectric layer 70 is provided continuously along the direction in which the pressure chambers 12 are arranged side by side with a predetermined thickness. The thickness of the piezoelectric layer 70 is not particularly limited, but it is formed to a thickness of about 1 to 4 μm.

[0046] Furthermore, the length of the piezoelectric layer 70 in the X-axis direction is longer than the length of the pressure chamber 12 in the X-axis direction, and the piezoelectric layer 70 extends to both outer sides of the pressure chamber 12 in the X-axis direction. Also, the +X-direction end 70a of the piezoelectric layer 70 in Figure 4 is located outside the +X-direction end 60a of the first electrode 60. That is, the end 60a of the first electrode 60 is covered by the piezoelectric layer 70. On the other hand, the -X-direction end 70b of the piezoelectric layer 70 is located inside the -X-direction end 60b of the first electrode 60, and the end 60b of the first electrode 60 is not covered by the piezoelectric layer 70.

[0047] As shown in Figure 5, grooves 71, which are thinner than other areas, are formed in the piezoelectric layer 70 at positions corresponding to each partition wall 11. In this embodiment, the grooves 71 are formed by completely removing the piezoelectric layer 70 in the Z-axis direction. That is, having a portion of the piezoelectric layer 70 that is thinner than other areas includes areas where the piezoelectric layer 70 has been completely removed in the Z-axis direction. Of course, the piezoelectric layer 70 may remain thinner than other parts at the bottom surface of the grooves 71.

[0048] By providing grooves 71 in the piezoelectric layer 70, the rigidity of the portion of the diaphragm 50 facing the Y-axis end of the pressure chamber 12, the so-called arm portion of the diaphragm 50, is reduced, thereby allowing the piezoelectric actuator 300 to be displaced more effectively.

[0049] Examples of piezoelectric layers 70 include perovskite-structured crystalline films (perovskite-type crystals) made of ferroelectric ceramic material exhibiting electromechanical conversion properties, formed on the first electrode 60. For example, the material for the piezoelectric layer 70 can be a ferroelectric piezoelectric material such as lead zirconate titanate (PZT), or a material to which metal oxides such as niobium oxide, nickel oxide, or magnesium oxide are added. Specifically, lead titanate (PbTiO3), lead zirconate titanate (Pb(Zr,Ti)O3), lead zirconate (PbZrO3), lead lanthanum titanate ((Pb,La),TiO3), lead zirconate titanate lanthanum ((Pb,La)(Zr,Ti)O3), or magnesium zirconium titanate lead (Pb(Zr,Ti)(Mg,Nb)O3). In this embodiment, lead zirconate titanate (PZT) was used as the piezoelectric layer 70.

[0050] Furthermore, the material for the piezoelectric layer 70 is not limited to lead-based piezoelectric materials containing lead; lead-free piezoelectric materials can also be used. Examples of lead-free piezoelectric materials include bismuth ironate ((BiFeO3), abbreviated as "BFO"), barium titanate ((BaTiO3), abbreviated as "BT"), potassium sodium niobate ((K,Na)(NbO3), abbreviated as "KNN"), potassium sodium lithium niobate ((K,Na,Li)(NbO3)), potassium sodium lithium tantalate niobate ((K,Na,Li)(Nb,Ta)O3), and potassium bismuth titanate ((Bi 1 / 2 K 1 / 2 )TiO3, abbreviated as "BKT"), bismuth sodium titanate ((Bi 1 / 2 Na 1 / 2 (x[(Bi x K 1-x((1-x)[BiFeO3]-x[BaTiO3], abbreviated as "BKT-BF"), a composite oxide having a perovskite structure containing bismuth, iron, barium, and titanium ((1-x)[BiFeO3]-x[BaTiO3], abbreviated as "BFO-BT"), and those to which metals such as manganese, cobalt, and chromium are added ((1-x)[Bi(Fe 1-y M y Examples include )O3]-x[BaTiO3](where M is Mn, Co, or Cr).

[0051] The second electrode 80 is provided on the -Z direction side of the piezoelectric layer 70, opposite to the first electrode 60, and constitutes a common electrode common to multiple active parts 310. The second electrode 80 is provided continuously in the Y direction with a predetermined length in the X direction. This second electrode 80 is also provided on the inner surface of the groove 71, that is, on the side surface of the groove 71 of the piezoelectric layer 70 and on the insulating film 52 which is the bottom surface of the groove 71. Within the groove 71, the second electrode 80 may be provided only on a part of the inner surface of the groove 71, or it may not be provided over the entire inner surface of the groove 71.

[0052] Furthermore, in Figure 4, the +X-direction end 80a of the second electrode 80 is positioned outside the end 60a of the first electrode 60, which is covered by the piezoelectric layer 70. That is, the end 80a of the second electrode 80 is located outside the +X-direction end 12a of the pressure chamber 12 and outside the end 60a of the first electrode 60. Therefore, the +X-direction end of the active portion 310, i.e., the boundary between the active portion 310 and the inactive portion 320, is defined by the end 60a of the first electrode 60.

[0053] On the other hand, in Figure 4, the -X end 80b of the second electrode 80 is located outside the -X end 12b of the pressure chamber 12, but inside the -X end 70b of the piezoelectric layer 70. As described above, the end 70b of the piezoelectric layer 70 is located inside the end 60b of the first electrode 60. Therefore, the end 80b of the second electrode 80 is located on the piezoelectric layer 70 inside the end 60b of the first electrode 60. As a result, there is an exposed surface area of ​​the piezoelectric layer 70 outside the end 80b of the second electrode 80.

[0054] Thus, since the end 80b of the second electrode 80 is positioned in the +X direction more than the -X direction ends 60b,70b of the piezoelectric layer 70 and the first electrode 60, the -X direction end of the active portion 310, i.e., the boundary between the active portion 310 and the inactive portion 320, is defined by the end 80b of the second electrode 80.

[0055] The material of the second electrode 80 is not particularly limited, but, similar to the first electrode 60, conductive materials such as metals like iridium or platinum, or conductive metal oxides such as indium tin oxide are preferably used.

[0056] Furthermore, outside the end 80b of the second electrode 80, that is, in the -X direction from the end 80b of the second electrode 80, a wiring section 85 is provided, which is made up of the same layer as the second electrode 80 but is electrically discontinuous with the second electrode 80. The wiring section 85 is formed on the piezoelectric layer 70 and extends over the first electrode 60, which is extended in the -X direction from the piezoelectric layer 70, with a gap so as not to contact the end 80b of the second electrode 80. The wiring section 85 is provided independently for each active section 310. That is, multiple wiring sections 85 are arranged at predetermined intervals along the Y axis. The wiring section 85 may be formed in a different layer from the second electrode 80, but it is preferable that it be formed in the same layer as the second electrode 80. This simplifies the manufacturing process of the wiring section 85 and reduces costs.

[0057] As shown in Figures 2 and 3, the first electrode 60 and the second electrode 80 constituting the piezoelectric actuator 300 are connected to individual lead electrodes 91 and a common lead electrode 92, which is a common drive electrode, respectively. A flexible wiring board 120 is connected to the ends of the individual lead electrodes 91 and the common lead electrode 92 that are opposite to the ends connected to the piezoelectric actuator 300. In this embodiment, the individual lead electrodes 91 and the common lead electrode 92 extend so as to be exposed within through holes 32 formed in the protective substrate 30, and are electrically connected to the wiring board 120 within these through holes 32. A drive circuit 121 having a switching element for driving the piezoelectric actuator 300 is mounted on the wiring board 120.

[0058] In this embodiment, the individual lead electrodes 91 and the common lead electrode 92 are made of the same layer but are formed to be electrically discontinuous. This simplifies the manufacturing process and reduces costs compared to forming the individual lead electrodes 91 and the common lead electrode 92 separately. Of course, the individual lead electrodes 91 and the common lead electrode 92 may be formed from different layers.

[0059] The material of the individual lead electrodes 91 and the common lead electrode 92 is not particularly limited as long as it is an conductive material, and for example, gold (Au), platinum (Pt), aluminum (Al), copper (Cu), etc. can be used. In this embodiment, gold (Au) was used for the individual lead electrodes 91 and the common lead electrode 92. The individual lead electrodes 91 and the common lead electrode 92 may also have an adhesion layer made of nickel-chromium (NiCr) or the like to improve adhesion with the first electrode 60, the second electrode 80 and the diaphragm 50.

[0060] Individual lead electrodes 91 are provided for each active portion 310, that is, for each first electrode 60. The individual lead electrodes 91 are connected via wiring portions 85 to the vicinity of the -X end 60b of the first electrode 60, which is located outside the piezoelectric layer 70, and are led out in the X-axis direction onto the flow channel forming substrate 10, and in fact onto the diaphragm 50.

[0061] On the other hand, the common lead electrode 92 is drawn out in the X-axis direction from the second electrode 80, which constitutes the common electrode on the piezoelectric layer 70, to the diaphragm 50 at both ends in the Y-axis direction. The common lead electrode 92 also has an extension portion 93 that extends along the Y-axis direction to a region corresponding to one end of the pressure chamber 12 in the X-axis direction. Furthermore, the common lead electrode 92 has an extension portion 94 that extends along the Y-axis direction to a region corresponding to the other end of the pressure chamber 12 in the X-axis direction. These extension portions 93 and 94 are provided continuously along the Y-axis direction to a plurality of active portions 310.

[0062] Furthermore, the extended portions 93 and 94 extend from the inside of the pressure chamber 12 to the outside of the pressure chamber 12 in the X-axis direction. In this embodiment, the active portion 310 of the piezoelectric actuator 300 extends to the outside of the pressure chamber 12 at both ends of the pressure chamber 12 in the X-axis direction, and the extended portions 93 and 94 extend along this active portion 310 from the inside to the outside of the pressure chamber 12 (see Figure 4).

[0063] Incidentally, at the X-axis end of the active portion 310 of such a piezoelectric actuator 300, the surface of the first electrode 60 on the piezoelectric layer 70 side is provided with a surface 63 consisting of a plurality of protrusions 61 and recesses 62 formed between these protrusions 61, as shown in Figures 6 and 7. In this embodiment, the surface of the first electrode 60 is provided with a surface 63 consisting of two protrusions 61 arranged side by side in the Y-axis direction and one recess 62 formed between these two protrusions 61. Each protrusion 61 is formed in a continuous linear shape along the X-axis direction, which is the direction in which the first electrode 60 is pulled out. As a result, the recesses 62 are also formed in a continuous linear shape along the X-axis direction, which is the direction in which the first electrode 60 is pulled out.

[0064] The number of protrusions 61 and recesses 62 constituting the uneven portion 63 is not particularly limited. For example, the uneven portion 63 may be composed of three or more protrusions 61. For example, the uneven portion 63 may be composed of five protrusions 61 and four recesses 62 formed between these five protrusions 61.

[0065] Furthermore, the uneven portion 63 is formed from the same metal material as the first electrode 60. In this embodiment, the uneven portion 63 is formed on the first electrode 60 itself. The first electrode 60 is formed by depositing a film on the entire surface of the channel-forming substrate 10 on an insulating film 52, and then patterning it into a predetermined shape. At that time, the uneven portion 63 is formed on the surface of the first electrode 60 by performing a dry etching process such as laser processing or ion milling. Of course, the method of forming the uneven portion 63 on the surface of the first electrode 60 is not particularly limited.

[0066] Furthermore, each of the protrusions 61 constituting the uneven portion 63 is formed in a mountain shape, and as shown in Figure 7, its cross-section is approximately triangular. Therefore, the surface of each protrusion 61 is an inclined surface that slopes with respect to the surface 10a of the flow channel forming substrate 10. The recesses 62 formed between these protrusions 61 are formed to a depth approximately the same as the thickness of the first electrode 60, but are formed without penetrating the first electrode 60 in the Z-axis direction, which is the thickness direction. For this reason, the surface (inner surface) of the recesses 62 is also an inclined surface. In other words, the first electrode 60 is provided continuously in the Y-axis direction as well.

[0067] The piezoelectric layer 70 is formed on the first electrode 60, which includes the uneven portion 63, with a substantially constant thickness. Therefore, the surface of the piezoelectric layer 70 in the portion corresponding to the uneven portion 63 has an uneven shape that follows the surface shape of the uneven portion 63. Similarly, the surface of the second electrode 80 in the portion corresponding to the uneven portion 63 also has an uneven shape that follows the surface of the uneven portion 63.

[0068] Here, the piezoelectric layer 70 formed on the uneven portion 63 of the first electrode 60 has a lower orientation ratio than the piezoelectric layer 70 formed on the part of the first electrode 60 other than the uneven portion 63. The surfaces of the protrusions 61 and recesses 62 that constitute the uneven portion 63 are inclined surfaces as described above. Due to the influence of the inclined substrate, the piezoelectric layer 70 formed on such an inclined surface of the first electrode 60 has a lower orientation ratio than the piezoelectric layer 70 formed on the flat surface of the first electrode 60 that is parallel to the surface 10a of the channel forming substrate 10. In other words, the piezoelectric layer 70 formed on the uneven portion 63 of the first electrode 60 has a lower orientation ratio than the piezoelectric layer 70 formed on the part of the first electrode 60 other than the uneven portion 63.

[0069] In this embodiment, the piezoelectric layer 70 formed on the first electrode 60 basically has a (100) plane preference orientation, but the (100) plane orientation rate of the piezoelectric layer 70 formed on the uneven portion 63 is lower than the (100) plane orientation rate of the piezoelectric layer 70 formed on portions other than the uneven portion 63.

[0070] In other words, the piezoelectric layer 70 formed on the first electrode 60 basically has a (100) plane preferential orientation, but the portion corresponding to the end of the active portion 310 has a low orientation portion 75 in which the (100) plane orientation ratio is lower than that of other portions due to the formation of the uneven portion 63.

[0071] "Preferential orientation" means that 50% or more, preferably 80% or more, of the crystals are oriented to a predetermined crystal plane. For example, "(100) plane preferential orientation" includes not only the case where all crystals are (100) plane oriented, but also the case where more than half of the crystals (in other words, 50% or more, preferably 80% or more) are (100) plane oriented. Furthermore, the low-orientation portion 75 of the piezoelectric layer 70 only needs to have a (100) plane orientation rate lower than other portions, and of course it may be (100) plane oriented, but it does not have to be (100) plane oriented.

[0072] The piezoelectric layer 70 formed on the uneven portion 63 of the first electrode 60, that is, the low-oriented portion 75 where the (100) plane orientation ratio is lower than that of other parts, causes the piezoelectric strain when voltage is applied to the piezoelectric actuator 300 to be moderately smaller than that of other parts of the active portion 310. For this reason, at the end of the active portion 310 where the uneven portion 63 is provided on the first electrode 60, the deformation of the piezoelectric actuator 300 is moderately suppressed compared to other parts.

[0073] This makes it possible to suppress the occurrence of minute cracks in the piezoelectric layer 70 due to the bending deformation of the piezoelectric actuator 300 at the end of the active part 310, that is, at the boundary between the active part 310 and the inactive part 320. Therefore, it is possible to suppress the occurrence of burnout due to leakage current caused by minute cracks in the piezoelectric layer 70. In other words, it is possible to suppress the occurrence of cracks and burnout in the piezoelectric layer 70 at the end of the active part 310 due to the difference in strain between the active part 310 and the inactive part 320.

[0074] As described above, the piezoelectric device according to the present invention comprises a diaphragm provided on one side of a substrate, and a piezoelectric actuator having a first electrode, a piezoelectric layer, and a second electrode laminated on the side of the diaphragm opposite to the substrate, wherein the piezoelectric actuator has an active portion in which the piezoelectric layer is sandwiched between the first electrode and the second electrode, and the surface of the first electrode on the piezoelectric layer side at the end of the active portion is an uneven portion composed of a plurality of protrusions and recesses formed between the protrusions.

[0075] This makes it possible to suppress the occurrence of minute cracks in the piezoelectric layer 70 due to the bending deformation of the piezoelectric actuator 300 at the end of the active part 310, that is, at the boundary between the active part 310 and the inactive part 320. Therefore, it is possible to suppress the occurrence of burnout due to leakage current caused by minute cracks in the piezoelectric layer 70.

[0076] Here, it is preferable that the uneven portion 63 is formed over as wide an area as possible in the non-flexible portion of the active portion 310 of the piezoelectric actuator 300, that is, in the portion extending outside the pressure chamber 12. In other words, it is preferable that the low-oriented portion 75 of the piezoelectric layer 70 is formed over as wide an area as possible in the non-flexible portion of the active portion 310 of the piezoelectric actuator 300. This makes it easier to further suppress the occurrence of cracks and burnout in the piezoelectric layer 70.

[0077] Furthermore, it is preferable that the protrusions 61 and recesses 62 constituting the uneven portion 63 are formed linearly along the direction in which the first electrode 60 is drawn out. By making the protrusions 61 and recesses 62 in this shape, the uneven portion 63 can be formed relatively easily by patterning the surface of the first electrode 60. Also, even if the uneven portion 63 is formed on the first electrode 60 itself, the first electrode 60 remains electrically continuous through the uneven portion 63, making it easier to ensure the function of the first electrode 60.

[0078] Furthermore, it is preferable that the uneven portion 63 is formed of the same metal material as the first electrode 60. In this embodiment, the uneven portion 63 is formed on the first electrode 60 itself. This makes it possible to form the uneven portion 63 relatively easily by patterning after the first electrode 60 has been formed. The uneven portion 63 may also be formed on a layer separate from the first electrode 60. For example, an additional layer made of the same metal material as the first electrode 60 may be formed on the piezoelectric layer 70 side of the first electrode 60, and the uneven portion 63 may be formed by patterning this additional layer.

[0079] Furthermore, it is preferable that the uneven portion 63 is provided continuously from the active portion 310 to the inactive portion 320 of the piezoelectric actuator 300, as in this embodiment. For example, in Figure 4, it is preferable that the -X-direction end 63a of the uneven portion 63 is located outside the -X-direction end 80b of the second electrode 80. That is, in Figure 4, it is preferable that the -X-direction end 75a of the low-oriented portion 75 of the piezoelectric layer 70 is located outside the end 80b of the second electrode 80.

[0080] The end portion 80b of the second electrode 80 defines the boundary between an active portion 310 where piezoelectric strain occurs when voltage is applied and an inactive portion 320 where piezoelectric strain does not occur. For this reason, minute cracks are likely to occur in the piezoelectric layer 70 near the end portion 80b of the second electrode 80 when voltage is applied.

[0081] However, because the uneven portion 63 is continuously provided from the active portion 310 to the inactive portion 320, that is, because the uneven portion 63 extends beyond the end 80b of the second electrode 80, the piezoelectric strain at the boundary between the active portion 310 and the inactive portion 320 is kept to a moderately small level. Therefore, it becomes easier to further suppress the occurrence of cracks in the piezoelectric layer 70 near the end of the active portion 310.

[0082] Furthermore, the shape of the uneven portion 63 is not particularly limited. In this embodiment, the protrusions 61 are formed continuously along the Y-axis direction, but for example, as shown in Figure 8, each protrusion 61 may be provided with a gap between them. In other words, each recess 62 may be provided penetrating the first electrode 60 in the thickness direction. The surface of each recess 62 may be formed of an inclined surface that is tilted with respect to the surface 10a of the flow channel forming substrate 10 and a side portion 62a composed of the first electrode 60 and a bottom portion 62b composed of an insulating film 52.

[0083] In the example shown in Figure 8, the bottom surface 62b of the recess 62 is a flat surface substantially parallel to the surface 10a of the channel-forming substrate 10. However, as described above, this bottom surface 62b is composed of an insulating film 52. Therefore, the orientation ratio of the piezoelectric layer 70 formed on the bottom surface 62b is lower than that of the piezoelectric layer 70 formed on the side surface 62a, and is lower than that of the piezoelectric layer 70 formed on parts other than the uneven portion 63. In other words, even in this configuration, the piezoelectric layer 70 formed on the uneven portion 63 becomes a low-orientation portion 75 with a lower orientation ratio than other parts.

[0084] Therefore, even with this configuration, the occurrence of minute cracks in the piezoelectric layer 70 due to the bending deformation of the piezoelectric actuator 300 can be suppressed at the end of the active part 310. Consequently, the occurrence of burnout due to leakage current caused by minute cracks in the piezoelectric layer 70 can be suppressed.

[0085] Furthermore, since the recess 62 is provided penetrating the first electrode 60, product inspection when forming the uneven portion 63 becomes easier. In other words, since the insulating film 52 is exposed within the recess 62, it becomes easier to determine during product inspection whether or not the recess 62 has been properly formed.

[0086] (Embodiment 2) Figure 9 is a cross-sectional view of an inkjet recording head, which is an example of a liquid jet head according to Embodiment 2 of the present invention, and is a cross-sectional view corresponding to the CC line in Figure 6. The same reference numerals are used for the same components as in Embodiment 1, and redundant explanations are omitted.

[0087] This embodiment is a modified example of the uneven portion 63 formed on the surface of the first electrode 60, and the other configurations are the same as in Embodiment 1.

[0088] In this embodiment, the surface of the underlying layer that serves as the base for the first electrode is also provided with an uneven surface composed of multiple protrusions and recesses formed between the protrusions. Specifically, as shown in Figure 9, the surface of the insulating film 52, which is the base layer for the first electrode 60, is provided with an uneven surface 55 in the portion corresponding to the uneven surface 63 of the first electrode 60, which is composed of two protrusions 53 and one recess 54 formed between these two protrusions 53.

[0089] The first electrode 60 is formed on an insulating film 52 having the uneven surface 55 in this manner, with a substantially constant thickness. As a result, an uneven surface 63, consisting of two protrusions 61 and one recess 62, is formed on the piezoelectric layer 70 side of the first electrode 60.

[0090] In this embodiment, the surface of the base layer that serves as the base for the first electrode at the end of the active portion is also provided with an uneven surface composed of multiple protrusions and recesses formed between the protrusions. Even with this configuration, the piezoelectric layer 70 formed on the uneven surface 63 has a lower orientation ratio than the piezoelectric layer 70 formed on the parts of the first electrode 60 other than the uneven surface 63. Therefore, the occurrence of minute cracks in the piezoelectric layer 70 due to the bending deformation of the piezoelectric actuator 300 can be suppressed at the end of the active portion 310. Consequently, the occurrence of burnout due to leakage current caused by minute cracks in the piezoelectric layer 70 can be suppressed. Furthermore, since the first electrode 60 has a substantially constant thickness even on the uneven surface 63, it is easier to ensure its function as the first electrode 60.

[0091] In this embodiment, the insulator film 52 is provided with irregularities 55 as the underlying layer for the first electrode 60, but the irregularities 55 do not necessarily have to be provided on the insulator film 52. The irregularities 55 may be provided on, for example, the elastic film 51, or, if the diaphragm 50 includes other films besides the elastic film 51 and the insulator film 52, the irregularities 55 may be provided on the other films.

[0092] (Embodiment 3) Figure 10 is a cross-sectional view showing the main parts of the inkjet recording head according to Embodiment 3, and is a cross-sectional view corresponding to the CC line in Figure 6. The same reference numerals are used for the same components, and redundant explanations are omitted.

[0093] This embodiment is a modified example of the uneven portion 63 formed on the surface of the first electrode 60, and the other configurations are the same as in Embodiment 1.

[0094] Specifically, as shown in Figure 10, in this embodiment, the protrusions 61A constituting the uneven portion 63A are formed of a different material from the first electrode 60. That is, the protrusions 61A are formed by an additional layer 65 made of a different material from the first electrode 60, which is formed on the piezoelectric layer 70 side of the first electrode 60.

[0095] The protrusion 61A is formed, for example, with a substantially trapezoidal cross-section and is linearly formed along the pulling direction of the first electrode 60, similar to the embodiment described above. Each recess 62A constituting the uneven portion 63A is formed to a depth approximately the same as the thickness of the additional layer 65, but without penetrating the additional layer 65 in the Z-axis direction. In other words, the additional layer 65 is continuously provided in the Y-axis direction as well. Therefore, the first electrode 60 is covered by the additional layer 65 without its surface being exposed within the uneven portion 63.

[0096] As the protrusions 61A constituting the uneven portion 63A are formed of a different material from the first electrode 60, the orientation of the piezoelectric layer 70 formed on the protrusions 61A is easily inhibited. Therefore, as in the first embodiment, the piezoelectric layer 70 formed on the uneven portion 63A of the first electrode 60 has a lower orientation than the piezoelectric layer 70 formed on parts of the first electrode 60 other than the uneven portion 63A. Consequently, in this embodiment as well, the occurrence of minute cracks in the piezoelectric layer 70 due to bending deformation at the end of the active portion 310 can be suppressed. Therefore, the occurrence of burnout due to leakage current caused by minute cracks in the piezoelectric layer 70 can be suppressed.

[0097] The material of the protrusion 61A may be different from that of the first electrode 60, but it is preferable that it be made of a material that contributes little to the orientation of the piezoelectric layer 70, that is, a material that easily inhibits the orientation of the piezoelectric layer 70. In other words, it is preferable that the additional layer 65 functions as an orientation inhibiting layer that inhibits the orientation of the piezoelectric layer 70. Furthermore, it is preferable that the material of the protrusion 61A be an insulating material that inhibits the orientation of the piezoelectric layer 70, such as aluminum oxide (Al2O3). This makes it possible to moderately suppress the piezoelectric strain at the end of the active part 310, and further makes it easier to suppress the occurrence of cracks in the piezoelectric layer 70.

[0098] The method for forming the uneven portion 63A is not particularly limited, but it can be formed by forming an additional layer 65 over the entire surface of the first electrode 60 and then patterning the additional layer 65. For example, the uneven portion 63A, which consists of a convex portion 61A and a concave portion 62A, can be formed relatively easily by removing the portion of the additional layer 65 corresponding to the concave portion 62A by laser processing.

[0099] (Other embodiments) Although various embodiments of the present invention have been described above, the basic configuration of the present invention is not limited to those described above.

[0100] For example, in the above-described embodiment, a configuration in which each protrusion 61 is formed only of an inclined surface was illustrated, but each protrusion 61 may also include a small flat surface that is substantially parallel to the surface 10a of the flow channel forming substrate 10. In such a configuration, the effect may be smaller compared to the configuration in which the protrusion 61 is formed only of an inclined surface as described above, but it can be expected to have the effect of suppressing the occurrence of burnout due to leakage current caused by minute cracks in the piezoelectric layer 70 compared to the conventional configuration.

[0101] For example, in the embodiments described above, the first electrode 60 constitutes an individual electrode for each active part 310, and the second electrode 80 constitutes a common electrode for multiple active parts 310. However, the first electrode 60 may constitute a common electrode for multiple active parts 310, and the second electrode 80 may constitute an individual electrode for each active part 310. Even in this case, the same effects as in the embodiments described above can be obtained.

[0102] Furthermore, the recording head 1 of each of these embodiments is mounted on an inkjet recording device, which is an example of a liquid jet device. Figure 11 is a schematic diagram showing an example of an inkjet recording device, which is an example of a liquid jet device according to one embodiment.

[0103] In the inkjet recording device I shown in Figure 11, the recording head 1 is mounted on a carriage 3 and is equipped with a detachable cartridge 2 that constitutes the ink supply means. The carriage 3 on which the recording head 1 is mounted is movably mounted in the axial direction of the carriage shaft 5 attached to the main body of the device 4.

[0104] The driving force of the drive motor 6 is transmitted to the carriage 3 via multiple gears (not shown) and a timing belt 7, causing the carriage 3, on which the recording head 1 is mounted, to move along the carriage axis 5. Meanwhile, the main body of the device 4 is provided with transport rollers 8 as a transport means, and the recording sheet S, which is a recording medium such as paper, is transported by the transport rollers 8. Note that the transport means for transporting the recording sheet S is not limited to transport rollers, but may also be a belt or a drum.

[0105] In this type of inkjet recording device I, the recording sheet S is transported in the X-axis direction relative to the recording head 1, while the carriage 3 is moved back and forth in the Y-axis direction relative to the recording sheet S. During this movement, ink droplets are ejected from the recording head 1, causing ink droplets to land on almost the entire surface of the recording sheet S, thus performing what is known as printing.

[0106] Furthermore, in the above-described embodiment, an example was given of an inkjet recording device I in which the recording head 1 is mounted on a carriage 3 and moves back and forth in the X-axis direction, which is the main scanning direction. However, the configuration of the inkjet recording head I is not limited to this. The inkjet recording device I may also be a so-called line-type recording device in which, for example, the recording head 1 is fixed and printing is performed simply by moving a recording sheet S such as paper in the Y-axis direction, which is the sub-scanning direction.

[0107] In the above embodiments, an inkjet recording head was described as an example of a liquid ejection head, and an inkjet recording device as an example of a liquid ejection device. However, the present invention broadly applies to liquid ejection heads and liquid ejection devices in general, and can of course be applied to liquid ejection heads and liquid ejection devices that eject liquids other than ink. Other examples of liquid ejection heads include various recording heads used in image recording devices such as printers, colorant ejection heads used in the manufacture of color filters for liquid crystal displays, electrode material ejection heads used in electrode formation for organic EL displays and FEDs (field emission displays), and bio-organic material ejection heads used in biochip manufacturing. The present invention can also be applied to liquid ejection devices equipped with such liquid ejection heads.

[0108] Furthermore, the present invention can be applied not only to liquid ejection heads, such as those found in inkjet recording heads, but also to ultrasonic devices such as ultrasonic transmitters, ultrasonic motors, pressure sensors, pyroelectric sensors, and other piezoelectric devices. [Explanation of symbols]

[0109] I... Inkjet recording device, 1... Inkjet recording head (recording head), 2... Cartridge, 3... Carriage, 4... Device body, 5... Carriage shaft, 6... Drive motor, 7... Timing belt, 8... Conveyor roller, 10... Flow path forming substrate, 11... Partition wall, 12... Pressure chamber, 15... Communication plate, 16... Nozzle communication passage, 17... First manifold section, 18... Second manifold section, 19... Supply communication passage, 20... Nozzle plate, 21... Nozzle, 30... Protective substrate, 31... Holding section, 32... Through hole, 40... Case member, 41... Housing section, 42... Third manifold section, 43... Connection port, 44... Inlet, 45... Compliance substrate, 46... Sealing film, 47... Fixing substrate, 48... Opening, 49... Compliance section, 50... Diaphragm 51…Elastic film, 52…Insulator film, 53…Convex portion, 54…Concave portion, 55…Rough portion, 60…First electrode, 61…Convex portion, 62…Concave portion, 63…Rough portion, 65…Additional layer, 70…Piezoelectric layer, 71…Groove portion, 75…Low orientation portion, 80…Second electrode, 85…Wiring portion, 91…Individual lead electrode, 92…Common lead electrode, 93,94…Extended portion, 100…Manifold, 120…Wiring board, 121…Drive circuit, 300…Piezoelectric actuator, 310…Active portion, 320…Inactive portion, S…Recording sheet

Claims

1. A diaphragm provided on one side of the substrate, A piezoelectric device comprising a piezoelectric actuator having a first electrode, a piezoelectric layer, and a second electrode laminated on the side of the diaphragm opposite to the substrate, The piezoelectric actuator comprises an active portion in which the piezoelectric layer is sandwiched between the first electrode and the second electrode, The surface of the first electrode on the piezoelectric layer side at the end of the active portion has an uneven surface composed of a plurality of protrusions and recesses formed between the protrusions, The surface of the first electrode on the piezoelectric layer side, other than the end of the active portion, does not have the aforementioned uneven portion. A piezoelectric device characterized by the following features.

2. A diaphragm provided on one side of the substrate, A piezoelectric device comprising a piezoelectric actuator having a first electrode, a piezoelectric layer, and a second electrode laminated on the side of the diaphragm opposite to the substrate, The piezoelectric actuator comprises an active portion in which the piezoelectric layer is sandwiched between the first electrode and the second electrode, The surface of the first electrode on the piezoelectric layer side at the end of the active portion has an uneven surface composed of a plurality of protrusions and recesses formed between the protrusions, The convex portion and the concave portion are provided linearly along the extraction direction of the first electrode. A piezoelectric device characterized by the following features.

3. A piezoelectric device according to claim 1 or 2, The aforementioned uneven portion is formed from the same metal material as the first electrode. A piezoelectric device characterized by the following features.

4. A diaphragm provided on one side of the substrate, A piezoelectric device comprising a piezoelectric actuator having a first electrode, a piezoelectric layer, and a second electrode laminated on the side of the diaphragm opposite to the substrate, The piezoelectric actuator comprises an active portion in which the piezoelectric layer is sandwiched between the first electrode and the second electrode, The surface of the first electrode on the piezoelectric layer side at the end of the active portion has an uneven surface composed of a plurality of protrusions and recesses formed between the protrusions, The aforementioned uneven portion is formed of the same metal material as the first electrode, The recess is provided so as to penetrate the first electrode in the thickness direction. A piezoelectric device characterized by the following features.

5. A diaphragm provided on one side of the substrate, A piezoelectric device comprising a piezoelectric actuator having a first electrode, a piezoelectric layer, and a second electrode laminated on the side of the diaphragm opposite to the substrate, The piezoelectric actuator comprises an active portion in which the piezoelectric layer is sandwiched between the first electrode and the second electrode, The surface of the first electrode on the piezoelectric layer side at the end of the active portion has an uneven surface composed of a plurality of protrusions and recesses formed between the protrusions, The aforementioned uneven portion is formed of a material different from that of the first electrode. A piezoelectric device characterized by the following features.

6. A diaphragm provided on one side of the substrate, A piezoelectric device comprising a piezoelectric actuator having a first electrode, a piezoelectric layer, and a second electrode laminated on the side of the diaphragm opposite to the substrate, The piezoelectric actuator comprises an active portion in which the piezoelectric layer is sandwiched between the first electrode and the second electrode, The surface of the first electrode on the piezoelectric layer side at the end of the active portion has an uneven surface composed of a plurality of protrusions and recesses formed between the protrusions, The aforementioned uneven portion is provided continuously from the active portion to the inactive portion. A piezoelectric device characterized by the following features.

7. A diaphragm provided on one side of the substrate, A piezoelectric device comprising a piezoelectric actuator having a first electrode, a piezoelectric layer, and a second electrode laminated on the side of the diaphragm opposite to the substrate, The piezoelectric actuator comprises an active portion in which the piezoelectric layer is sandwiched between the first electrode and the second electrode, The surface of the first electrode on the piezoelectric layer side at the end of the active portion has an uneven surface composed of a plurality of protrusions and recesses formed between the protrusions, The surface of the base layer that serves as the base for the first electrode at the end of the active portion is also provided with an uneven surface consisting of a plurality of protrusions and recesses formed between the protrusions. A piezoelectric device characterized by the following features.

8. A piezoelectric device according to any one of claims 1 to 7, The first electrode is an individual electrode independent of each piezoelectric actuator, and the second electrode is a common electrode common to a plurality of piezoelectric actuators. A piezoelectric device characterized by the following features.

9. The piezoelectric device is provided according to any one of claims 1 to 8. A liquid spray head characterized by the following features.

10. The liquid spray head described in claim 9 is mounted A liquid injection device characterized by the following features.

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