Liquid ejection head

Abstract

To inhibit occurrence of cracks.SOLUTION: A liquid ejection head includes a piezoelectric element and a vibration plate. A first electrode, a piezoelectric layer, and a second electrode of the piezoelectric element are laminated in a lamination direction which is a direction from the vibration plate to the piezoelectric element in a written order. The piezoelectric layer is formed of a piezoelectric material containing lead as a constituent element, and the first electrode has an electrode layer and a lead-containing layer disposed between the electrode layer and the vibration plate and containing lead. When, of two regions arranged in a crossing direction which is a direction crossing the lamination direction, when seen in the lamination direction, a region farther away from a center of the first electrode is referred to as a first region and a region closer to the center of the first electrode is referred to as a second region, a lead content percentage of the lead-containing layer in the first region is higher than a lead content percentage of the lead-containing layer in the second region.SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] The present disclosure relates to a liquid ejection head. [Background technology]

[0002] Liquid ejection devices, such as piezoelectric inkjet printers, use liquid ejection heads that eject liquids such as ink. For example, the head described in Patent Document 1 includes a diaphragm and a piezoelectric element. The piezoelectric element is configured by sequentially laminating a lower electrode, a piezoelectric film, and an upper electrode on a diaphragm. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2002-319714 Summary of the Invention [Problem to be solved by the invention]

[0004] In the head described in Patent Document 1, depending on the lead content in the lower electrode, the stress generated in the lower electrode may become unevenly distributed, which may result in damage such as cracks. [Means for solving the problem]

[0005] In order to solve the above problems, one embodiment of a liquid ejection head of the present disclosure comprises a piezoelectric element having a first electrode, a piezoelectric layer, and a second electrode, and a vibration plate connected to the piezoelectric element, wherein the first electrode, the piezoelectric layer, and the second electrode are stacked in this order in a stacking direction that is a direction from the vibration plate toward the piezoelectric element, the piezoelectric layer is made of a piezoelectric material that contains lead as a constituent element, the first electrode has an electrode layer and a lead-containing layer that is arranged between the electrode layer and the vibration plate and contains lead, when two regions aligned in a cross direction that is a direction that intersects the stacking direction in the stacking direction are defined as a first region and a second region, the second region is positioned closer to the center of the first electrode than the first region, and the lead content of the lead-containing layer in the first region is higher than the lead content of the lead-containing layer in the second region. [Brief explanation of the drawings]

[0006] [Figure 1] 1 is a configuration diagram that schematically illustrates a liquid ejection apparatus that includes a liquid ejection head according to an embodiment. [Figure 2] FIG. 2 is an exploded perspective view of the liquid ejection head according to the embodiment. [Figure 3] FIG. 3 is a cross-sectional view taken along line AA in FIG. 2. [Figure 4] FIG. 2 is a plan view showing a part of the liquid ejection head according to the embodiment. [Figure 5] FIG. 5 is a cross-sectional view taken along line BB in FIG. [Figure 6] FIG. 6 is an enlarged view of a portion Q in FIG. [Figure 7] 10 is a diagram showing the relationship between the state of lead contained in the lead-containing layer and the evaluation of the liquid ejection head. DETAILED DESCRIPTION OF THE INVENTION

[0007] Preferred embodiments of the present disclosure will be described below with reference to the accompanying drawings. Note that the dimensions and scale of each part in the drawings may differ from the actual dimensions and are shown schematically to facilitate understanding. Furthermore, the scope of the present disclosure is not limited to these embodiments unless otherwise specified in the following description to the effect that the present disclosure is limited.

[0008] In the following description, the mutually intersecting X-axis, Y-axis, and Z-axis are used as appropriate. In the following description, one direction along the X-axis is the X1 direction, and the direction opposite the X1 direction is the X2 direction. Similarly, the opposite directions along the Y-axis are the Y1 direction and the Y2 direction. Furthermore, the opposite directions along the Z-axis are the Z1 direction and the Z2 direction. The Z1 direction is an example of a "stacking direction." Furthermore, viewing in the direction along the Z-axis is sometimes referred to as a "planar view."

[0009] Here, the Z axis is typically the vertical axis, and the Z2 direction corresponds to the downward vertical direction. However, the Z axis does not have to be the vertical axis. Furthermore, the X axis, Y axis, and Z axis are typically perpendicular to each other, but are not limited to this. For example, they may intersect at an angle between 80° and 100°.

[0010] 1. Embodiment 1-1. Overall configuration of the liquid ejection device FIG. 1 is a schematic diagram illustrating a liquid ejection device 100 equipped with a liquid ejection head 50 according to an embodiment. The liquid ejection device 100 is an inkjet printing device that ejects ink, an example of a liquid, as droplets onto a medium M. The medium M is typically printing paper. However, the medium M is not limited to printing paper, and may be a printing target made of any material, such as a resin film or fabric.

[0011] As shown in FIG. 1, the liquid ejection device 100 includes a liquid container 10, a control unit 20, a transport mechanism 30, a moving mechanism 40, and a liquid ejection head 50.

[0012] The liquid container 10 is a container that stores ink. Specific examples of the liquid container 10 include a cartridge that is detachable from the liquid ejection device 100, a bag-shaped ink pack made of flexible film, and an ink tank that can be refilled with ink. The type of ink stored in the liquid container 10 is not particularly limited and can be any type.

[0013] The control unit 20 includes a processing circuit such as a CPU (Central Processing Unit) or an FPGA (Field Programmable Gate Array) and a storage circuit such as a semiconductor memory, and controls the operation of each element of the liquid ejection device 100.

[0014] The transport mechanism 30 transports the medium M in the Y2 direction under the control of the control unit 20. The movement mechanism 40 reciprocates the liquid ejection head 50 in the X1 direction and the X2 direction under the control of the control unit 20. In the example shown in FIG. 1, the movement mechanism 40 has a substantially box-shaped carriage 41 that houses the liquid ejection head 50, and a transport belt 42 to which the carriage 41 is fixed. Note that the number of liquid ejection heads 50 mounted on the carriage 41 is not limited to one, and may be multiple. In addition to the liquid ejection head 50, the carriage 41 may also be equipped with the aforementioned liquid container 10.

[0015] The liquid ejection head 50 ejects ink supplied from the liquid container 10 from each of a plurality of nozzles onto the medium M in the Z2 direction under the control of the control unit 20. This ejection is performed in parallel with the transport of the medium M by the transport mechanism 30 and the reciprocating movement of the liquid ejection head 50 by the movement mechanism 40, thereby forming an ink image on the surface of the medium M.

[0016] 1-2. Overall configuration of liquid ejection head Fig. 2 is an exploded perspective view of a liquid ejection head 50 according to an embodiment. Fig. 3 is a cross-sectional view taken along line AA in Fig. 2. As shown in Figs. 2 and 3, the liquid ejection head 50 has a flow path substrate 51, a pressure chamber substrate 52, a nozzle plate 53, a vibration absorber 54, a diaphragm 55, a plurality of piezoelectric elements 56, a sealing plate 57, a case 58, and a wiring substrate 59. The diaphragm 55 and the piezoelectric elements 56 constitute an actuator 1. In this way, the liquid ejection head 50 has the actuator 1 that includes the piezoelectric elements 56 and the diaphragm 55.

[0017] Here, a pressure chamber substrate 52, a vibration plate 55, a plurality of piezoelectric elements 56, a case 58, and a sealing plate 57 are disposed in an area positioned further in the Z1 direction than the flow path substrate 51. On the other hand, a nozzle plate 53 and a vibration absorber 54 are disposed in an area positioned further in the Z2 direction than the flow path substrate 51. Each element of the liquid ejection head 50 is roughly a plate-like member that is elongated in the direction along the Y axis, and is joined to one another by, for example, an adhesive.

[0018] As shown in FIG. 2, the nozzle plate 53 is a plate-like member provided with a plurality of nozzles N arranged in a direction along the Y-axis. Each nozzle N is a through-hole that allows ink to pass through. In this manner, the nozzle plate 53 has a plurality of nozzles N that eject ink. The nozzle plate 53 is manufactured by processing a silicon single crystal substrate using a semiconductor manufacturing technique that uses processing techniques such as dry etching or wet etching. However, other known methods and materials may also be used as appropriate to manufacture the nozzle plate 53.

[0019] The flow path substrate 51 is a plate-like member for forming ink flow paths. As shown in FIGS. 2 and 3 , the flow path substrate 51 is provided with an opening R1, multiple supply flow paths Ra, and multiple communication flow paths Na. The opening R1 is an elongated through-hole that extends in the direction along the Y-axis in a plan view viewed along the Z-axis so as to be continuous across the multiple nozzles N. On the other hand, the supply flow paths Ra and the communication flow paths Na are through-holes individually provided for each nozzle N. Each of the multiple supply flow paths Ra communicates with the opening R1. Like the nozzle plate 53 described above, the flow path substrate 51 is manufactured by processing a silicon single crystal substrate using semiconductor manufacturing technology, for example. However, other known methods and materials may also be used as appropriate for manufacturing the flow path substrate 51.

[0020] The pressure chamber substrate 52 is a plate-like member in which multiple pressure chambers C corresponding to the multiple nozzles N are formed. The pressure chambers C are located between the flow path substrate 51 and the vibration plate 55 and are spaces known as cavities for applying pressure to the ink filled in the pressure chambers C. The multiple pressure chambers C are arranged in a direction along the Y axis. Each pressure chamber C is formed by a hole 52a that opens on both sides of the pressure chamber substrate 52 and has an elongated shape extending in a direction along the X axis. Thus, the pressure chamber substrate 52 has multiple pressure chambers C that communicate with the nozzles N. The X2-direction end of each pressure chamber C communicates with the corresponding supply flow path Ra. Meanwhile, the X1-direction end of each pressure chamber C communicates with the corresponding communication flow path Na. The pressure chamber substrate 52, like the nozzle plate 53 described above, is manufactured by processing a silicon single crystal substrate using, for example, semiconductor manufacturing technology. However, other known methods and materials may be used as appropriate to manufacture each of the pressure chamber substrates 52.

[0021] A diaphragm 55 is disposed on the surface of the pressure chamber substrate 52 facing the Z1 direction. The diaphragm 55 is an elastically deformable plate-like member, and is connected to a piezoelectric element 56. Details of the diaphragm 55 will be described later with reference to FIG.

[0022] Piezoelectric elements 56 are arranged on the surface of the vibration plate 55 facing the Z1 direction. The piezoelectric elements 56 are passive elements that deform when supplied with a drive signal, and have an elongated shape extending in the direction along the X axis. One piezoelectric element 56 is provided for each pressure chamber, and multiple piezoelectric elements 56 are arranged in the direction along the Y axis so as to correspond to multiple pressure chambers C. When the vibration plate 55 vibrates in conjunction with the deformation of the piezoelectric elements 56, the pressure in the pressure chambers C fluctuates, causing ink to be ejected from the nozzles N. Details of the piezoelectric elements 56 will be described later with reference to Figures 4 to 6.

[0023] The case 58 is a case for storing ink to be supplied to the multiple pressure chambers C, and is bonded to the surface of the flow path substrate 51 facing the Z1 direction with an adhesive or the like. The case 58 is made of, for example, a resin material and manufactured by injection molding. The case 58 is provided with a storage section R2 and an inlet IH. The storage section R2 is a recessed portion whose outer shape corresponds to the opening R1 of the flow path substrate 51. The inlet IH is a through hole that communicates with the storage section R2. The space formed by the opening R1 and the storage section R2 functions as a liquid storage chamber R, which is a reservoir that stores ink. Ink is supplied to the liquid storage chamber R from the liquid container 10 via the inlet IH.

[0024] The vibration absorber 54 is an element for absorbing pressure fluctuations within the liquid storage chamber R. The vibration absorber 54 is, for example, a compliance substrate, which is a flexible sheet member that is elastically deformable. Here, the vibration absorber 54 is disposed on the surface of the flow path substrate 51 facing the Z2 direction so as to close the opening R1 and the multiple supply flow paths Ra of the flow path substrate 51 and form the bottom surface of the liquid storage chamber R.

[0025] The sealing plate 57 is a structure that protects the multiple piezoelectric elements 56 and reinforces the mechanical strength of the pressure chamber substrate 52 and the vibration plate 55. The sealing plate 57 is bonded to the surface of the vibration plate 55 with, for example, an adhesive. The sealing plate 57 has recesses that accommodate the multiple piezoelectric elements 56.

[0026] A wiring board 59 is bonded to the surface of the pressure chamber substrate 52 or the vibration plate 55 facing the Z1 direction. The wiring board 59 is a mounting component on which a plurality of wires are formed for electrically connecting the control unit 20 and the liquid ejection head 50. The wiring board 59 is a flexible wiring board such as an FPC (Flexible Printed Circuit) or an FFC (Flexible Flat Cable). A drive circuit 60 for driving the piezoelectric elements 56 is mounted on the wiring board 59. The drive circuit 60 selectively supplies drive signals for driving each piezoelectric element 56 to each piezoelectric element 56 via the wiring board 59.

[0027] 1-3. Details of the diaphragm and piezoelectric element Fig. 4 is a plan view showing a part of the liquid ejection head 50 according to the embodiment. Fig. 5 is a cross-sectional view taken along line BB in Fig. 4. The pressure chamber substrate 52, the piezoelectric element 56, and the vibration plate 55 will be described below in this order with reference to Figs. 4 and 5.

[0028] As shown in Figures 4 and 5, holes 52a that form pressure chambers C are provided in the pressure chamber substrate 52. Accordingly, wall-like partitions 52b extending in the direction along the X-axis are provided between two adjacent holes 52a in the pressure chamber substrate 52. The pressure chamber substrate 52 is manufactured, for example, by processing a silicon single crystal substrate using semiconductor manufacturing technology. In Figure 4, the dashed line shows the planar shape of the holes 52a when formed by anisotropic etching on a silicon single crystal substrate with a (110) plane orientation. Note that the planar shape of the holes 52a is not limited to the example shown in Figure 4 and may be any shape.

[0029] Here, the pressure chambers C are formed after the piezoelectric elements 56 are formed. The pressure chambers C are formed, for example, by anisotropically etching one of the two surfaces of the silicon single crystal substrate after the piezoelectric elements 56 are formed, opposite the surface on which the piezoelectric elements 56 are formed. At this time, an etchant for the anisotropic etching is, for example, an aqueous potassium hydroxide (KOH) solution. At this time, if the elastic layer 55a is made of silicon oxide, the elastic layer 55a functions as a stopping layer that stops the anisotropic etching. After the pressure chambers C are formed as described above, the flow path substrate 51 and the like are bonded to the pressure chamber substrate 52 with an adhesive. Note that after the piezoelectric elements 56 are formed, the surface of the silicon single crystal substrate opposite the surface on which the piezoelectric elements 56 are formed is ground, as necessary, by CMP (chemical mechanical polishing) or the like to flatten that surface or adjust the thickness of the substrate.

[0030] As shown in Fig. 4, in a plan view, the piezoelectric element 56 overlaps the pressure chamber C. As shown in Fig. 5, the piezoelectric element 56 has a first electrode 56a, a piezoelectric layer 56b, and a second electrode 56c, which are stacked in this order in the Z1 direction. That is, the first electrode 56a, the piezoelectric layer 56b, and the second electrode 56c are stacked in this order in a stacking direction DL, which is the direction from the vibration plate 55 toward the piezoelectric element 56. As will be described later with reference to Fig. 6, the piezoelectric element 56 has a first lead diffusion suppression layer 56d and a second lead diffusion suppression layer 56e in addition to the first electrode 56a, the piezoelectric layer 56b, and the second electrode 56c.

[0031] The first electrodes 56a are individual electrodes spaced apart from one another and arranged for each piezoelectric element 56. Specifically, a plurality of first electrodes 56a extending in the direction along the X-axis are arranged in the direction along the Y-axis at intervals from one another. A drive signal including a predetermined voltage pulse is supplied from the control unit 20 to the first electrode 56a of each piezoelectric element 56. Details of the first electrodes 56a will be described later with reference to FIG. 6.

[0032] 4 and 5, the piezoelectric layer 56b has a strip shape extending in the direction along the Y-axis so as to be continuous across the plurality of piezoelectric elements 56. In the example shown in FIG. 4, the piezoelectric layer 56b has through-holes 56b1 extending in the direction along the X-axis, penetrating the piezoelectric layer 56b, in regions corresponding in plan view to the gaps between adjacent pressure chambers C. As a result, when viewed in the cross section shown in FIG. 5, the piezoelectric layer 56b is provided individually for each of the piezoelectric elements 56. Note that the piezoelectric layer 56b may be provided individually for each of the plurality of piezoelectric elements 56.

[0033] The piezoelectric layer 56b is made of a piezoelectric material containing lead as a constituent element. The piezoelectric material has a perovskite crystal structure represented by the general composition formula ABO3, such as lead zirconate titanate (Pb(Zr,Ti)O3). In addition to lead (Pb), the piezoelectric layer 56b may contain at least one element selected from the group consisting of vanadium (V), niobium (Nb), tantalum (Ta), nickel (Ni), phosphorus (P), arsenic (As), antimony (Sb), and bismuth (Bi). The lead contained in the piezoelectric material constituting the piezoelectric layer 56b may be an element that does not constitute part of the perovskite crystal structure.

[0034] The second electrode 56c is a strip-shaped common electrode that extends in the direction along the Y-axis so as to be continuous across the plurality of piezoelectric elements 56. A predetermined constant potential is supplied to the second electrode 56c.

[0035] The second electrode 56c is made of, for example, iridium (Ir). The material of the second electrode 56c is not limited to iridium, and may be, for example, a metal material such as titanium (Ti), platinum (Pt), aluminum (Al), nickel (Ni), gold (Au), or copper (Cu), or a conductive oxide such as lanthanum nickel oxide (LaNiO3:LNO) or strontium ruthenium oxide (SrRuO3:SRO). The second electrode 56c may be made of one of these metal materials alone, or two or more of them may be combined in a stacked form, for example.

[0036] In the piezoelectric element 56, when a voltage is applied between the first electrode 56a and the second electrode 56c, the piezoelectric layer 56b is deformed due to the inverse piezoelectric effect. A diaphragm 55 is connected to the piezoelectric element 56, and the diaphragm 55 vibrates in response to the deformation of the piezoelectric layer 56b.

[0037] 5, the diaphragm 55 has an elastic layer 55a and an insulating layer 55b, which are laminated in this order in the Z1 direction. Here, the insulating layer 55b is biased toward a position closer to the first electrode 56a in the thickness direction of the diaphragm 55.

[0038] The elastic layer 55a is a film made of, for example, silicon oxide (SiO2). The material making up the elastic layer 55a is not limited to SiO2, and may be a material containing one or more elements selected from titanium (Ti), silicon (Si), aluminum (Al), tantalum (Ta), chromium (Cr), iridium (Ir), hafnium (Hf), zirconium (Zr), and carbon (C) in the form of a simple substance, oxide, or nitride.

[0039] The thickness of the elastic layer 55a is determined depending on the thickness and width of the diaphragm 55, and is not particularly limited, but is, for example, within the range of 100 nm to 3000 nm.

[0040] The insulating layer 55b is, for example, a film made of zirconium oxide (ZrO2) and contains zirconium (Zr). By disposing the insulating layer 55b containing zirconium in a position closer to the first electrode 56a in the thickness direction of the diaphragm 55, it is possible to prevent lead contained in the first electrode 56a from bonding with the material constituting the elastic layer 55a. Note that the material constituting the insulating layer 55b is not limited to ZrO2 and may be, for example, a material containing one or more elements selected from titanium (Ti), aluminum (Al), tantalum (Ta), chromium (Cr), hafnium (Hf), and zirconium (Zr) in the form of an oxide or nitride.

[0041] The thickness of the insulating layer 55b is determined depending on the thickness and width of the diaphragm 55 and is not particularly limited, but is, for example, within the range of 100 nm to 2000 nm.

[0042] 5, the elastic layer 55a and the insulating layer 55b are in contact with each other. Note that another layer, such as an adhesive layer, may be interposed between the elastic layer 55a and the insulating layer 55b to enhance adhesion between the elastic layer 55a and the insulating layer 55b. The adhesive layer may be made of a material such as TiO X , AlO X , CrO X The thickness of the adhesive layer is determined depending on the thickness and width of the diaphragm 55, and is not particularly limited, but is, for example, in the range of 20 nm to 2000 nm.

[0043] The elastic layer 55a and insulating layer 55b are obtained by being deposited in this order on a silicon single crystal substrate for forming the pressure chamber substrate 52. For example, if the elastic layer 55a is made of silicon oxide, the elastic layer 55a is formed by thermally oxidizing one surface of the silicon single crystal substrate. For example, if the insulating layer 55b is made of zirconium oxide, the insulating layer 55b is formed by forming a zirconium layer on the elastic layer 55a by a sputtering method and then thermally oxidizing the layer.

[0044] The method for forming each of the multiple films constituting the diaphragm 55 is not limited to the above-described example, and may be any method. For example, at least a portion of the elastic layer 55a may be formed using a CVD method or the like. When an adhesive layer is provided between the elastic layer 55a and the insulating layer 55b, the adhesive layer is formed by forming a layer of chromium, titanium, aluminum, or the like on the elastic layer 55a by a sputtering method and then thermally oxidizing the layer. In this case, the thermal oxidation for forming the adhesive layer may be performed simultaneously with the thermal oxidation for forming the insulating layer 55b. The method for forming the adhesive layer is not limited to the method using thermal oxidation, and may be, for example, a CVD method or an atomic layer deposition (ALD) method.

[0045] The actuator 1, which is made up of the diaphragm 55 and piezoelectric element 56, has a vibration region PV that vibrates when driven by the piezoelectric element 56. The vibration region PV is a part of the actuator 1, and is a portion that overlaps with the pressure chamber C in a plan view.

[0046] The vibration region PV is divided into an active portion RA and a non-active portion RN. The active portion RA is a part of the actuator 1 and is a region that overlaps with the pressure chamber C, the first electrode 56a, the piezoelectric layer 56b, and the second electrode 56c when viewed along the Z axis. The non-active portion RN is a part of the actuator 1 and is a region that overlaps with the pressure chamber C when viewed along the Z axis, but is different from the active portion RA. The non-active portion RN is a region where the first electrode 56a is not provided and where at least one of the piezoelectric layer 56b and the second electrode 56c overlaps with the pressure chamber C when viewed along the Z axis.

[0047] Fig. 6 is an enlarged view of a portion Q in Fig. 5. As shown in Fig. 6, the first electrode 56a has an electrode layer 56a1, a lead-containing layer 56a2, a first mixed layer 56a3, and a second mixed layer 56a4.

[0048] The electrode layer 56a1 includes, for example, a layer made of platinum (Pt), a layer made of iridium (Ir), and a layer made of titanium (Ti). That is, the electrode layer 56a1 includes platinum, iridium, and titanium. Platinum (Pt) is an electrode material with excellent conductivity. Therefore, by using platinum (Pt) as a constituent material of the first electrode 56a, the resistance of the first electrode 56a can be reduced. Furthermore, when forming the piezoelectric layer 56b, the titanium layer controls the orientation of the piezoelectric layer 56b by forming islands of Ti as crystal nuclei, thereby improving the crystallinity or orientation of the piezoelectric layer 56b. Note that, instead of or in addition to these layers, layers made of other metal materials or conductive oxides may be provided. Furthermore, the layer may include a layer of a mixture or alloy of multiple metal materials. The thickness of the electrode layer 56a1 is, for example, in the range of 90 nm to 160 nm.

[0049] The lead-containing layer 56a2 is disposed between the electrode layer 56a1 and the diaphragm 55 and contains lead. In the example shown in FIG. 6, the surface of the lead-containing layer 56a2 facing the Z2 direction constitutes the surface of the first electrode 56a facing the Z2 direction. That is, the lead-containing layer 56a2 constitutes the bottom layer of the first electrode 56a in the stacking direction DL. The thickness of the lead-containing layer 56a2 is, for example, in the range of 5 nm to 25 nm. The lead-containing layer 56a2 has a higher lead content than other portions of the electrode layer 56a1. For example, when the lead content is measured by secondary ion mass spectrometry or energy dispersive X-ray analysis, the lead-containing layer 56a2 has a higher lead content than other portions of the electrode layer 56a1.

[0050] The lead-containing layer 56a2 contains a metal element other than lead. For example, the lead-containing layer 56a2 contains the material contained in the electrode layer 56a1. The lead-containing layer 56a2 may also contain other metal materials. The lead contained in the lead-containing layer 56a2 may exist as an elemental substance or an alloy, or as an oxide, oxynitride, or oxynitride.

[0051] When viewed in the stacking direction DL, of the two regions aligned in the intersecting direction DC, which is a direction intersecting the stacking direction DL, the region farther from the center of the first electrode 56a is defined as the first region RE1, and the region closer to the center of the first electrode 56a is defined as the second region RE2, the lead content of the lead-containing layer 56a2 in the first region RE1 is higher than the lead content of the lead-containing layer 56a2 in the second region RE2.

[0052] The size of the first region RE1 in the cross direction DC is determined depending on the thickness and width of the first electrode 56a, and is not particularly limited, but is within a range of 180 nm to 320 nm, for example. That is, the first region RE1 is a region located within a range of 180 nm to 320 nm from the end of the first electrode 56a toward the center in the cross direction DC.

[0053] Although not shown, first regions RE1 are provided on both ends of the active portion RA in the cross direction DC. Therefore, the second region RE2 is a region sandwiched between the first regions RE1 in the cross direction DC.

[0054] 6, the width of the first electrode 56a is approximately 40 μm, the thickness of the first electrode 56a is approximately 110 nm, and the size of the first region RE1 in the cross direction DC is approximately 240 nm. The size of the first region RE1 may be determined based on the thickness of the first electrode 56a. For example, the size of the first region RE1 is preferably at least two times but less than four times the thickness of the first electrode 56a.

[0055] 6, the first electrode 56a has an inclined surface 56s at the end in the cross direction DC, where the surface facing the Z1 direction is inclined toward the diaphragm 55. In this example, the inclined surface 56s is located in the first region RE1.

[0056] For example, when the lead content is measured by secondary ion mass spectrometry, energy dispersive X-ray analysis, or the like, the lead content of the lead-containing layer 56a2 in the first region RE1 is higher than the lead content of the lead-containing layer 56a2 in the second region RE2. The lead content is calculated, for example, from the ratio to the content of other materials contained in the electrode layer 56a1.

[0057] For example, when measuring the lead content of the lead-containing layer 56a2 by secondary ion mass spectrometry, the content of each of two or more elements, including lead, contained in the lead-containing layer 56a2 is measured over a specific area in a plan view, and the lead content is normalized by the sum of the content of lead and other elements to calculate the lead content. When measuring the content of oxygen as an element other than lead, the lead content may be normalized by the oxygen content for calculation. Alternatively, the lead content may be normalized by the content of a specific material for calculation.

[0058] When calculating the lead content of the lead-containing layer 56a2 in the first region RE1 and the second region RE2, it is preferable to measure the lead content at a center position in the stacking direction DL and the cross direction DC in the lead-containing layer 56a2 in the first region RE1 and the second region RE2. It is also preferable to measure the lead content at a position at the same height in the stacking direction DL. When calculating the lead content, an average value obtained by averaging the lead content at a plurality of locations in the lead-containing layer 56a2 in the stacking direction DL or the cross direction DC may be used.

[0059] The first region RE1 and the second region RE2 are included in the active portion RA. In the example shown in FIG. 6, the active portion RA is divided into the first region RE1 and the second region RE2, and the first region RE1 and the second region RE2 are adjacent to each other. The first region RE1 is adjacent to the inactive portion RN. Here, the second region RE2 is a region located toward the center of the first electrode 56a in the stacking direction DL. The first region RE1 is a region located outside the second region RE2 in the stacking direction DL.

[0060] Thus, the lead content of the lead-containing layer 56a2 in the first region RE1 is higher than the lead content of the lead-containing layer 56a2 in the second region RE2. In other words, the lead content of the center of the first electrode 56a is lower than the lead content of the end of the first electrode 56a. This allows the electrical resistance of the center of the first electrode 56a to be lower than the electrical resistance of the end of the first electrode 56a. Furthermore, the lead in the lead-containing layer 56a2 in the first region RE1 reduces the penetration of lead from the piezoelectric layer 56b into the lead-containing layer 56a2 in the second region RE2 via the lead-containing layer 56a2 in the first region RE1. As a result, a sufficient area can be secured to function as the active portion RA of the piezoelectric element 56.

[0061] When averaged over the entire first electrode 56a, the lead content of the first electrode 56a in the first region RE1 is higher than the lead content of the first electrode 56a in the second region RE2 due to the relationship between the lead-containing layer 56a2 in the first region RE1 and the second region RE2 described above. A high lead content increases electrical resistance and voltage drop.

[0062] Therefore, the voltage drop across the first electrode 56a in the first region RE1 can be made larger than the voltage drop across the first electrode 56a in the second region RE2. Therefore, by positioning the first region RE1 at the boundary between the active portion RA and the non-active portion RN of the piezoelectric element 56, the amount of displacement of the piezoelectric element 56 can be gradually reduced from the active portion RA toward the non-active portion RN of the piezoelectric element 56. This makes it possible to alleviate stress occurring between the active portion RA and the non-active portion RN of the piezoelectric element 56.

[0063] Furthermore, the interface between the first electrode 56a and the diaphragm 55 in the first region RE1 or the interface between the first electrode 56a and the second lead diffusion suppression layer 56e (described later) in the first region RE1 can be roughened. This improves adhesion between the first electrode 56a and the diaphragm 55 or the second lead diffusion suppression layer 56e in the first region RE1 due to an anchor effect. As a result, peeling of the first electrode 56a in the first region RE1 from the diaphragm 55 can be effectively prevented.

[0064] The lead content of the lead-containing layer 56a2 in the first region RE1 preferably decreases toward the second region RE2. This reduces the voltage drop toward the center of the first electrode 56a, thereby ensuring a suitable region that functions as the active portion RA of the piezoelectric element 56. Another advantage is that stress generated between the active portion RA and the non-active portion RN of the piezoelectric element 56 can be easily alleviated.

[0065] The ratio of the lead content of the lead-containing layer 56a2 in the first region RE1 to the lead content of the lead-containing layer 56a2 in the second region RE2 is preferably 1.01 or more. That is, when the lead content of the lead-containing layer 56a2 in the first region RE1 is α and the lead content of the lead-containing layer 56a2 in the second region RE2 is β, α / β is preferably 1.01 or more. This makes it possible to preferably obtain the effect of making the lead content of the lead-containing layer 56a2 in the first region RE1 higher than the lead content of the lead-containing layer 56a2 in the second region RE2.

[0066] 6, the thickness of the lead-containing layer 56a2 in the second region RE2 is substantially constant, whereas the thickness of the lead-containing layer 56a2 in the first region RE1 becomes thinner with increasing distance from the second region RE2. Note that the thickness of the lead-containing layer 56a2 in the first region RE1 may be substantially constant, similar to the thickness of the lead-containing layer 56a2 in the first region RE1.

[0067] The lead-containing layer 56a2 may contain at least one element selected from the group consisting of vanadium (V), niobium (Nb), tantalum (Ta), nickel (Ni), phosphorus (P), arsenic (As), antimony (Sb), and bismuth (Bi). For example, when the piezoelectric layer 56b contains at least one element selected from the group consisting of V, Nb, Ta, Ni, P, As, Sb, and Bi, the content of the at least one element in the lead-containing layer 56a2 in the first region RE1 is preferably higher than the content of the at least one element in the lead-containing layer 56a2 in the second region RE2.

[0068] When the piezoelectric layer 56b contains at least one element selected from the group consisting of V, Nb, Ta, Ni, P, As, Sb, and Bi, oxygen vacancies in the piezoelectric layer 56b can be reduced. As a result, the driving speed of the piezoelectric element 56 can be increased. Furthermore, by making the content of the element in the lead-containing layer 56a2 in the first region RE1 higher than the content of the element in the lead-containing layer 56a2 in the second region RE2, it is possible to obtain the same effect as when the lead content of the lead-containing layer 56a2 in the first region RE1 is higher than the lead content of the lead-containing layer 56a2 in the second region RE2.

[0069] The thickness of the lead-containing layer 56a2 is not particularly limited, but is, for example, in the range of 5 nm to 25 nm. The lead-containing layer 56a2 may be a dense layer or a sparse layer in which lead, an alloy, an oxide, a nitride, or an oxynitride is scattered in an island pattern.

[0070] The first mixed layer 56a3 is disposed between the electrode layer 56a1 and the lead-containing layer 56a2 in the first region RE1 and is made of a material obtained by mixing the material constituting the electrode layer 56a1 with lead. By providing the first mixed layer 56a3, it is possible to further improve the adhesion between the first electrode 56a and the diaphragm 55 in the first region RE1. As a result, it is possible to suppress peeling of the first electrode 56a from the diaphragm 55 and the occurrence of cracks. Note that, for convenience of explanation, FIG. 6 clearly shows the interface between the first mixed layer 56a3 and the electrode layer 56a1 and the interface between the first mixed layer 56a3 and the lead-containing layer 56a2, but these interfaces do not need to be clear.

[0071] The thickness t1 of the first mixed layer 56a3 is not particularly limited, but is, for example, in the range of 5 nm to 30 nm.

[0072] The second mixed layer 56a4 is disposed between the electrode layer 56a1 and the lead-containing layer 56a2 in the second region RE2 and is made of a material obtained by mixing the material constituting the electrode layer 56a1 with lead. In the example shown in FIG. 6, the second mixed layer 56a4 is integrated with the first mixed layer 56a3 as the same layer. The second mixed layer 56a4 may be separated from the first mixed layer 56a3. For ease of explanation, FIG. 6 clearly shows the interface between the second mixed layer 56a4 and the electrode layer 56a1 and the interface between the first mixed layer 56a3 and the lead-containing layer 56a2, but these interfaces do not need to be clearly defined.

[0073] The thickness t2 of the second mixed layer 56a4 is preferably thinner than the thickness t1 of the first mixed layer 56a3. That is, the thickness t1 of the first mixed layer 56a3 is preferably thicker than the thickness t2 of the second mixed layer 56a4. This makes it possible to effectively suppress both the occurrence of cracks in the first region RE1 and peeling of the first electrode 56a from the diaphragm 55.

[0074] The thickness t2 of the second mixed layer 56a4 is not particularly limited, but is, for example, in the range of 5 nm to 30 nm.

[0075] The first mixed layer 56a3 and the second mixed layer 56a4 have a lower lead content than the lead-containing layer 56a2. The lead contents of the first mixed layer 56a3 and the second mixed layer 56a4 are measured in the same manner as the lead content described above.

[0076] The first electrode 56a is formed, for example, after the formation of the diaphragm 55, by a film formation technique such as sputtering, and a processing technique using photolithography, etching, and the like. To make the lead-containing layer 56a2 contain lead, for example, lead may be introduced by ion implantation or by depositing a film of a material containing lead. To make the lead content of the lead-containing layer 56a2 in the first region RE1 and the second region RE2 different, the amount of lead introduced by ion implantation may be different, or the film formation conditions and targets may be different for each region.

[0077] The piezoelectric element 56 has the first electrode 56a, the piezoelectric layer 56b, and the second electrode 56c described above, as well as a first lead diffusion suppression layer 56d and a second lead diffusion suppression layer 56e.

[0078] The first lead diffusion suppression layer 56d is disposed between the first electrode 56a and the piezoelectric layer 56b in at least the second region RE2 and suppresses lead diffusion from the piezoelectric layer 56b to the first electrode 56a. This suppresses lead from penetrating from the piezoelectric layer 56b into the first electrode 56a in the second region RE2. The first lead diffusion suppression layer 56d contains titanium. The first lead diffusion suppression layer 56d may contain a metal element other than titanium. The titanium contained in the first lead diffusion suppression layer 56d may exist as an elemental substance or an alloy, or may exist as an oxide, oxynitride, or oxynitride.

[0079] 6, when viewed in the stacking direction DL, a region that is connected to the first region RE1 on the opposite side to the second region RE2 in the cross direction DC is defined as a third region RE3, the first lead diffusion suppression layer 56d is provided in a range that spans the first region RE1, the second region RE2, and the third region RE3. The third region RE3 is included in the inactive part RN.

[0080] The size of the third region RE3 in the cross direction DC is determined depending on the thickness and width of the first electrode 56a, and is not particularly limited, but is, for example, within a range of 90 nm to 320 nm. That is, the third region RE3 is a region located within a range of 90 nm to 320 nm from the end of the first electrode 56a outward in the cross direction DC. In the example shown in FIG. 6, the size of the third region RE3 in the cross direction DC is approximately 240 nm.

[0081] The titanium content of the first lead diffusion suppression layer 56d in the third region RE3 is preferably higher than the titanium content of the first lead diffusion suppression layer 56d in the first region RE1. For example, when the titanium content is measured by secondary ion mass spectrometry, energy dispersive X-ray analysis, or the like, the titanium content of the first lead diffusion suppression layer 56d in the third region RE3 is higher than the titanium content of the first lead diffusion suppression layer 56d in the second region RE2. The titanium content is calculated, for example, from the ratio of the content of other materials contained in the first lead diffusion suppression layer 56d. This allows lead leaking from the piezoelectric layer 56b in the third region RE3 to preferentially bond with titanium in the first lead diffusion suppression layer 56d in the third region RE3, thereby suppressing lead from entering the first region RE1 and the second region RE2. When measuring the titanium content, it is preferable to measure the titanium content at the center of the first lead diffusion suppression layer 56d in the first region RE1 and the third region RE3 in the stacking direction DL and the cross direction DC.

[0082] The first lead diffusion suppression layer 56d also has a function of controlling the orientation of the piezoelectric layer 56b. The piezoelectric layer 56b is in contact with the first lead diffusion suppression layer 56d across the first region RE1 and the second region RE2. This allows the orientation of the piezoelectric layer 56b in the first region RE1 and the second region RE2 to be controlled by the first lead diffusion suppression layer 56d.

[0083] As described above, the thickness of the lead-containing layer 56a2 in the first region RE1 becomes thinner with increasing distance from the second region RE2. As a result, the surface of the first lead diffusion suppression layer 56d opposite to the diaphragm 55 is inclined with respect to the plate surface of the diaphragm 55, and the surface of the first electrode 56a opposite to the diaphragm 55 is inclined with respect to the plate surface of the diaphragm 55.

[0084] The first lead diffusion suppression layer 56d covers the first electrode 56a in the first region RE1. In the first region RE1, the angle θ1 between the surface of the first lead diffusion suppression layer 56d opposite the diaphragm 55 and the plate surface of the diaphragm 55 is smaller than the angle θ2 between the surface of the first electrode 56a opposite the diaphragm 55 and the plate surface of the diaphragm 55. The thickness of the first lead diffusion suppression layer 56d increases from the first region RE1 toward the non-active section RN. This reduces the difference between the piezoelectric material orientation controllability provided by the first lead diffusion suppression layer 56d in the first region RE1 and the piezoelectric material orientation controllability provided by the first lead diffusion suppression layer 56d in the second region RE2. This improves the orientation of the piezoelectric layer 56b in the active section RA.

[0085] In the first region RE1, the angle θ1 formed between the surface of the first electrode 56a opposite to the vibration plate 55 and the plate surface of the vibration plate 55 is preferably 10 degrees or more and less than 60 degrees. This makes it possible to reduce the size of the liquid ejection head 50 while suppressing the intrusion of lead into the first electrode 56a in the first region RE1.

[0086] The thickness of the first lead diffusion suppression layer 56d is not particularly limited, but is, for example, in the range of 20 nm to 80 nm. The first lead diffusion suppression layer 56d is provided as necessary, and may be omitted.

[0087] The first lead diffusion suppression layer 56d is formed by a film formation technique such as sputtering. To make the titanium content of the first lead diffusion suppression layer 56d different between the first region RE1 and the third region RE3, the film formation conditions and targets may be changed for each region.

[0088] The second lead diffusion suppression layer 56e is disposed between the first electrode 56a and the diaphragm 55 in each of the first region RE1 and the second region RE2, and suppresses lead diffusion from the first electrode 56a to the diaphragm 55. The second lead diffusion suppression layer 56e contains titanium. The second lead diffusion suppression layer 56e may contain a metal element other than titanium. The titanium contained in the second lead diffusion suppression layer 56e may exist as an elemental substance or an alloy, or as an oxide, oxynitride, or oxynitride.

[0089] The titanium content of the second lead diffusion suppression layer 56e in the first region RE1 is preferably higher than the titanium content of the second lead diffusion suppression layer 56e in the second region RE2. For example, when the titanium content is measured by secondary ion mass spectrometry, energy dispersive X-ray analysis, or the like, the titanium content of the second lead diffusion suppression layer 56e in the first region RE1 is higher than the titanium content of the second lead diffusion suppression layer 56e in the second region RE2. The titanium content is calculated, for example, from the ratio to the content of other materials contained in the second lead diffusion suppression layer 56e.

[0090] The titanium in the second lead diffusion suppression layer 56e is bonded to the lead in the lead-containing layer 56a2 to form TiPbO x Therefore, by making the titanium content of the lead-containing layer 56a2 in the first region RE1 higher than the titanium content of the lead-containing layer 56a2 in the second region RE2, it is possible to suppress lead from entering the second region RE2 from the first region RE1.

[0091] The titanium oxide content of the second lead diffusion suppression layer 56e in the first region RE1 is preferably higher than the titanium oxide content of the second lead diffusion suppression layer 56e in the second region RE2. This increases the oxidation degree of the lead-containing layer 56a2 in the first region RE1 compared to the oxidation degree of the lead-containing layer 56a2 in the second region RE2, thereby suppressing oxygen loss from the piezoelectric layer 56b through the first region RE1.

[0092] The TiO2 content of the second lead diffusion suppression layer 56e in the first region RE1 is preferably higher than the TiO2 content of the second lead diffusion suppression layer 56e in the second region RE2. Because TiO2 is more chemically stable than titanium oxides of other oxidation states, making the TiO2 content of the lead-containing layer 56a2 in the first region RE1 higher than the TiO2 content of the lead-containing layer 56a2 in the second region RE2 can suitably suppress oxygen loss from the piezoelectric layer 56b through the first region RE1.

[0093] The thickness of the second lead diffusion suppression layer 56e is not particularly limited, but is, for example, in the range of 1 nm to 10 nm. The second lead diffusion suppression layer 56e is provided as needed, and may be omitted.

[0094] The second lead diffusion suppression layer 56e is formed by a film formation technique such as sputtering. To incorporate titanium or titanium oxide into the second lead diffusion suppression layer 56e, titanium may be introduced by ion implantation, or a material containing titanium or titanium oxide may be deposited. To differentiate the titanium or titanium oxide content of the second lead diffusion suppression layer 56e in the first region RE1 and the second region RE2, different film formation conditions or targets may be used for each region.

[0095] 7 is a diagram showing the relationship between the state of lead content in the lead-containing layer 56a2 and the evaluation of the liquid ejection head 50. FIG. 7 shows the results of evaluating the lifespan and electrical resistance of the liquid ejection head 50 for Samples No. 1-4, which have different lead contents in one or both of the first region RE1 and the second region RE2. The lead content in the lead-containing layer 56a2 is measured using, for example, secondary ion mass spectrometry, and the lead content is measured in each of the first region RE1 and the second region RE2 in an area of ​​1 mm2 in plan view. 2 The oxygen content and lead content are measured at each measurement over the range of 1000 to 15000, and the lead content is normalized by the oxygen content to calculate the lead content.

[0096] In sample No. 1, the lead content α of the lead-containing layer 56a2 in the first region RE1 is 20 atm% or more, and the lead content β of the lead-containing layer 56a2 in the second region RE2 is 1.7 atm%, where α / β is greater than 11.

[0097] In sample No. 2, the lead content α of the lead containing layer 56a2 in the first region RE1 is 20 atm% or more, and the lead content β of the lead containing layer 56a2 in the second region RE2 is 18.7 atm%, where α / β is greater than 1.07.

[0098] In sample No. 3, the lead content α of the lead containing layer 56a2 in the first region RE1 is 1.5 atm% or less, and the lead content β of the lead containing layer 56a2 in the second region RE2 is 1.7 atm%, where α / β is smaller than 0.88.

[0099] In sample No. 4, the lead content α of the lead containing layer 56a2 in the first region RE1 is 1.5 atm% or less, and the lead content β of the lead containing layer 56a2 in the second region RE2 is 18.7 atm%, where α / β is less than 0.08.

[0100] Regarding the lifespan evaluation in Figure 7, P indicates that the active part RA is unlikely to break down, and F indicates that the active part RA is likely to break down. Regarding the electrical resistance evaluation in Figure 7, A indicates that the effect of reducing the electrical resistance of the piezoelectric element 56 is significant, and B indicates that the effect of reducing the electrical resistance of the piezoelectric element 56 is recognized, but only slightly. Regarding the overall evaluation in Figure 7, A, B, C, and D indicate the overall evaluation of lifespan and electrical resistance, from highest to lowest.

[0101] As shown in FIG. 7, in Sample No. 1 and Sample No. 2, destruction of the active portion RA is unlikely to occur, whereas in Sample No. 3 and Sample No. 4, destruction of the active portion RA is likely to occur.

[0102] Furthermore, in samples No. 1 and No. 3, the effect of reducing the electrical resistance of the piezoelectric element 56 is significant, whereas in samples No. 2 and No. 4, the effect of reducing the electrical resistance of the piezoelectric element 56 is noticeable but only slightly.

[0103] From the above, the overall evaluation order from highest to lowest is Sample No. 1, Sample No. 2, Sample No. 3, and Sample No. 4.

[0104] As can be seen from the above, the lead content of the lead-containing layer 56a2 in the first region RE1 is higher than the lead content of the lead-containing layer 56a2 in the second region RE2, thereby making it possible to suitably suppress the occurrence of cracks.

[0105] 2. Variations Each of the above-mentioned exemplary embodiments can be modified in various ways. Specific modified embodiments that can be applied to each of the above-mentioned embodiments are exemplified below. Two or more embodiments arbitrarily selected from the following examples can be appropriately combined within the scope of not contradicting each other.

[0106] 2-1. Variation 1 In each of the above-described embodiments, the piezoelectric layer 56b is provided in common to the multiple pressure chambers C, but this is not limiting, and the piezoelectric layer 56b may be divided for each pressure chamber C. Furthermore, the second electrode 56c may be an individual electrode, in which case the first electrode 56a may be a common electrode, or both the first electrode 56a and the second electrode 56c may be individual electrodes.

[0107] 2-2. Variation 2 In each of the above-mentioned embodiments, a serial-type liquid ejection device 100 is exemplified, in which a carriage 41 carrying a liquid ejection head 50 moves back and forth, but the present disclosure can also be applied to a line-type liquid ejection device in which multiple nozzles N are distributed across the entire width of the medium M.

[0108] 2-3. Variation 3 The liquid ejection device 100 exemplified in each of the above-described embodiments can be employed in various devices, such as facsimile machines and copiers, as well as devices dedicated to printing. However, the use of the liquid ejection device of the present disclosure is not limited to printing. For example, a liquid ejection device that ejects a solution of a color material is used as a manufacturing device for forming color filters for liquid crystal display devices. Furthermore, a liquid ejection device that ejects a solution of a conductive material is used as a manufacturing device for forming wiring and electrodes on a wiring board.

[0109] 3. Summary of this disclosure A summary of this disclosure is provided below.

[0110] (Appendix 1) A first aspect, which is a preferred example of a liquid ejection head of the present disclosure, comprises a piezoelectric element having a first electrode, a piezoelectric layer, and a second electrode, and a vibration plate connected to the piezoelectric element, wherein the first electrode, the piezoelectric layer, and the second electrode are stacked in this order in a stacking direction that is a direction from the vibration plate toward the piezoelectric element, the piezoelectric layer is made of a piezoelectric material that contains lead as a constituent element, the first electrode has an electrode layer and a lead-containing layer that is disposed between the electrode layer and the vibration plate and contains lead, and when, as viewed in the stacking direction, two regions are aligned in an intersecting direction that is a direction intersecting the stacking direction, the region farther from the center of the first electrode is defined as a first region, and the region closer to the center of the first electrode is defined as a second region, the lead content of the lead-containing layer in the first region is higher than the lead content of the lead-containing layer in the second region.

[0111] In the above embodiment, the lead content of the lead-containing layer in the first region is higher than the lead content of the lead-containing layer in the second region. That is, the lead content of the center portion of the first electrode is lower than the lead content of the edge portion of the first electrode. This allows the electrical resistance of the center portion of the first electrode to be lower than the electrical resistance of the edge portion of the first electrode. Furthermore, the lead in the lead-containing layer in the first region can reduce the intrusion of lead from the piezoelectric layer into the second region. As a result, a sufficient area can be secured to function as the active portion of the piezoelectric element.

[0112] Furthermore, the voltage drop across the first electrode in the first region can be made larger than the voltage drop across the first electrode in the second region. Therefore, by positioning the first region at the boundary between the active and inactive portions of the piezoelectric element, the amount of displacement of the piezoelectric element can be gradually reduced from the active portion to the inactive portion of the piezoelectric element. This can alleviate stress occurring between the active and inactive portions of the piezoelectric element.

[0113] Furthermore, the interface between the first electrode and the diaphragm in the first region can be roughened, thereby improving the adhesion between the first electrode and the diaphragm in the first region through an anchor effect, thereby effectively preventing the first electrode from peeling off from the diaphragm.

[0114] (Note 2) In the second aspect, which is a preferred example of the first aspect, the lead content of the lead-containing layer in the first region decreases toward the second region. This aspect can ensure a region that functions as the active part of the piezoelectric element. Another advantage is that it is easy to alleviate stress that occurs between the active and non-active parts of the piezoelectric element.

[0115] (Supplementary Note 3) In a third aspect, which is a preferred example of the first or second aspect, the ratio of the lead content of the lead-containing layer in the first region to the lead content of the lead-containing layer in the second region is 1.01 or more. In this aspect, the effect of making the lead content of the lead-containing layer in the first region higher than the lead content of the lead-containing layer in the second region can be suitably obtained.

[0116] (Appendix 4) In a fourth aspect, which is a preferred example of any of the first to third aspects, the first electrode has a first mixed layer disposed between the electrode layer and the lead-containing layer in the first region and composed of a material obtained by mixing the material constituting the electrode layer with lead. In this aspect, the adhesion between the first electrode and the diaphragm in the first region can be further improved. As a result, the occurrence of cracks in the first region can be suppressed.

[0117] (Appendix 5) In a fifth aspect, which is a preferred example of any of the first to fourth aspects, the first electrode has a second mixed layer disposed between the electrode layer and the lead-containing layer in the second region and made of a material obtained by mixing the material constituting the electrode layer with lead, the first mixed layer having a thickness greater than that of the second mixed layer. In the above aspect, it is possible to preferably suppress both the occurrence of cracks in the first region and peeling of the first electrode from the diaphragm.

[0118] (Appendix 6) In a sixth aspect which is a preferred example of any of the first to fifth aspects, the piezoelectric element further includes a first lead diffusion suppression layer disposed between the first electrode and the piezoelectric layer in at least the second region, the first lead diffusion suppression layer suppressing lead diffusion from the piezoelectric layer to the first electrode. In the above aspect, lead can be prevented from penetrating from the piezoelectric layer into the first electrode in the second region.

[0119] (Supplementary Note 7) In a seventh aspect, which is a preferred example of any of the first to sixth aspects, the piezoelectric element further includes a second lead diffusion suppression layer disposed between the first electrode and the diaphragm in each of the first and second areas, and configured to suppress diffusion of lead from the first electrode to the diaphragm, the second lead diffusion suppression layer containing titanium, and the titanium content of the second lead diffusion suppression layer in the first area being higher than the titanium content of the second lead diffusion suppression layer in the second area. In the above aspect, titanium in the lead-containing layer is bonded to lead to form TiPbO x Therefore, by making the titanium content of the lead-containing layer in the first region higher than the titanium content of the lead-containing layer in the second region, the lead in the piezoelectric layer can penetrate into the second region via the first region.

[0120] (Supplementary Note 8) In an eighth aspect, which is a preferred example of the seventh aspect, the titanium oxide content of the second lead diffusion suppression layer in the first region is higher than the titanium oxide content of the second lead diffusion suppression layer in the second region. In this aspect, the oxidation degree of the lead-containing layer in the first region is higher than the oxidation degree of the lead-containing layer in the second region, so that oxygen loss from the piezoelectric layer through the first region can be suppressed.

[0121] (Supplementary Note 9) In a ninth aspect, which is a preferred example of the eighth aspect, the TiO2 content of the second lead diffusion suppression layer in the first region is higher than the TiO2 content of the second lead diffusion suppression layer in the second region. In the above aspect, since TiO2 is more chemically stable than titanium oxides of other oxidation states, by making the TiO2 content of the lead-containing layer in the first region higher than the TiO2 content of the lead-containing layer in the second region, oxygen loss from the piezoelectric layer through the first region can be suitably suppressed.

[0122] (Supplementary Note 10) In a tenth aspect, which is a preferred example of any of the sixth to ninth aspects, when a region connected to the first region on the opposite side of the second region in the intersecting direction in the stacking direction is defined as a third region, the first lead diffusion suppressing layer is provided in a range spanning the first region, the second region, and the third region, and the titanium content of the first lead diffusion suppressing layer in the third region is higher than the titanium content of the first lead diffusion suppressing layer in the first region. In the above aspect, lead that escapes from the piezoelectric layer preferentially bonds to titanium in the third region, thereby suppressing lead from entering the first and second regions.

[0123] (Appendix 11) In an eleventh aspect, which is a preferred example of any of the sixth to tenth aspects, the first lead diffusion suppression layer covers the first electrode in the first region, and the angle between the surface of the first lead diffusion suppression layer opposite the diaphragm and the plate surface of the diaphragm in the first region is smaller than the angle between the surface of the first electrode opposite the diaphragm and the plate surface of the diaphragm. In the above aspect, it is possible to reduce the difference between the orientation controllability of the piezoelectric material by the first lead diffusion suppression layer in the first region and the orientation controllability of the piezoelectric material by the first lead diffusion suppression layer in the first region. This allows for improved orientation of the piezoelectric layer.

[0124] (Supplementary Note 12) In a twelfth aspect which is a preferred example of the eleventh aspect, the first lead diffusion suppression layer has a function of controlling the orientation of the piezoelectric layer, and the piezoelectric layer is in contact with the first lead diffusion suppression layer across the first region and the second region. In the above aspect, the orientation of the piezoelectric layer in the first region and the second region can be controlled by the first lead diffusion suppression layer.

[0125] (Supplementary Note 13) In a thirteenth aspect, which is a preferred example of any one of the first to twelfth aspects, the diaphragm has an insulating layer containing zirconium, and the insulating layer is biased toward a position closer to the first electrode in the thickness direction of the diaphragm. In the above aspect, it is possible to prevent lead contained in the first electrode from bonding with the material constituting the diaphragm.

[0126] (Supplementary Note 14) In a fourteenth aspect, which is a preferred example of any one of the first to thirteenth aspects, the piezoelectric layer contains at least one element selected from the group consisting of V, Nb, Ta, Ni, P, As, Sb, and Bi, and the content of the at least one element in the lead-containing layer in the first region is higher than the content of the at least one element in the lead-containing layer in the second region. In the above aspects, when the piezoelectric layer contains at least one element selected from the group consisting of V, Nb, Ta, Ni, P, As, Sb, and Bi, oxygen deficiency in the piezoelectric layer can be reduced. As a result, the driving speed of the piezoelectric element can be increased. Furthermore, by increasing the content of the element in the lead-containing layer in the first region compared to the content of the element in the lead-containing layer in the second region, the same effect as when the lead content in the lead-containing layer in the first region is increased compared to the content in the lead-containing layer in the second region can be achieved.

[0127] (Supplementary Note 15) In a fifteenth aspect which is a preferred example of any of the first to fourteenth aspects, in the first region, the angle formed between the surface of the first electrode opposite the vibration plate and the plate surface of the vibration plate is 10 degrees or more and less than 60 degrees. In this aspect, it is possible to reduce the size of the liquid ejection head while suppressing the intrusion of lead into the second region. [Explanation of symbols]

[0128] 1...actuator, 10...liquid container, 20...control unit, 30...transport mechanism, 40...movement mechanism, 41...carriage, 42...transport belt, 50...liquid ejection head, 51...flow path substrate, 52...pressure chamber substrate, 52a...hole, 52b...partition wall, 53...nozzle plate, 54...vibration absorber, 55...diaphragm, 55a...elastic layer, 55b...insulating layer, 56...piezoelectric element, 56a...first electrode, 56a1...electrode layer, 56a2...lead-containing layer, 56a3...first mixed layer, 56a4...second mixed layer, 56b...piezoelectric layer, 56b1...through hole, 56c...second electrode, 56d...first lead Diffusion suppression layer, 56e...second lead diffusion suppression layer, 56s...inclined surface, 57...sealing plate, 58...case, 59...wiring board, 60...drive circuit, 100...liquid ejection device, C...pressure chamber, DC...cross direction, DL...stacking direction, IH...inlet, M...medium, N...nozzle, Na...communicating flow path, PV...vibration area, Q...part, R...liquid storage chamber, R1...opening, R2...accommodation part, RA...active part, RE1...first area, RE2...second area, RE3...third area, RN...non-active part, Ra...supply flow path, t1...thickness, t2...thickness, α...content, β...content, θ1...angle, θ2...angle.

Claims

1. a piezoelectric element having a first electrode, a piezoelectric layer, and a second electrode; a vibration plate connected to the piezoelectric element, the first electrode, the piezoelectric layer, and the second electrode are stacked in this order in a stacking direction that is a direction from the vibration plate toward the piezoelectric element, the piezoelectric layer is made of a piezoelectric material containing lead as a constituent element, The first electrode is an electrode layer; a lead-containing layer that is disposed between the electrode layer and the diaphragm and contains lead; When viewed in the stacking direction, of two regions aligned in an intersecting direction that is a direction intersecting the stacking direction, the region farther from the center of the first electrode is defined as a first region, and the region closer to the center of the first electrode is defined as a second region, a lead content of the lead-containing layer in the first region is higher than a lead content of the lead-containing layer in the second region; A liquid ejection head characterized by:

2. the lead content of the lead-containing layer in the first region decreases toward the second region; The liquid ejection head according to claim 1 .

3. a ratio of the lead content of the lead-containing layer in the first region to the lead content of the lead-containing layer in the second region is 1.01 or more; The liquid ejection head according to claim 1 .

4. The first electrode is a first mixed layer disposed between the electrode layer and the lead-containing layer in the first region and made of a material obtained by mixing the material constituting the electrode layer with lead; The liquid ejection head according to claim 1 .

5. The first electrode is a second mixed layer disposed between the electrode layer and the lead-containing layer in the second region and made of a material obtained by mixing the material constituting the electrode layer with lead; The thickness of the first mixed layer is greater than the thickness of the second mixed layer. The liquid ejection head according to claim 4 .

6. The piezoelectric element is a first lead diffusion suppression layer disposed between the first electrode and the piezoelectric layer in at least the second region, the first lead diffusion suppression layer suppressing lead diffusion from the piezoelectric layer to the first electrode; The liquid ejection head according to claim 1 .

7. The piezoelectric element is a second lead diffusion suppression layer disposed between the first electrode and the diaphragm in each of the first region and the second region, the second lead diffusion suppression layer suppressing lead diffusion from the first electrode to the diaphragm; the second lead diffusion suppression layer contains titanium, the titanium content of the second lead diffusion suppression layer in the first region is higher than the titanium content of the second lead diffusion suppression layer in the second region; The liquid ejection head according to claim 1 .

8. the titanium oxide content of the second lead diffusion suppression layer in the first region is higher than the titanium oxide content of the second lead diffusion suppression layer in the second region; The liquid ejection head according to claim 7 .

9. TiO of the second lead diffusion suppression layer in the first region 2 The content of TiO in the second lead diffusion suppressing layer in the second region is 2 Higher than the content of The liquid ejection head according to claim 8 .

10. When a region connected to the first region on the opposite side to the second region in the intersecting direction in the stacking direction is defined as a third region, the first lead diffusion suppression layer is provided in a range spanning the first region, the second region, and the third region, the titanium content of the first lead diffusion suppression layer in the third region is higher than the titanium content of the first lead diffusion suppression layer in the first region; The liquid ejection head according to claim 6 .

11. the first lead diffusion suppression layer covers the first electrode in the first region, In the first region, an angle formed between a surface of the first lead diffusion suppression layer opposite to the vibration plate and a plate surface of the vibration plate is smaller than an angle formed between a surface of the first electrode opposite to the vibration plate and the plate surface of the vibration plate. The liquid ejection head according to claim 6 .

12. the first lead diffusion suppression layer has a function of controlling the orientation of the piezoelectric layer, the piezoelectric layer is in contact with the first lead diffusion suppression layer across the first region and the second region; The liquid ejection head according to claim 11.

13. the diaphragm has an insulating layer containing zirconium; The liquid ejection head according to claim 1 , wherein the insulating layer is biased toward a position closer to the first electrode in the thickness direction of the vibration plate.

14. the piezoelectric layer contains at least one element selected from the group consisting of V, Nb, Ta, Ni, P, As, Sb, and Bi; a content of the at least one element in the lead-containing layer in the first region is higher than a content of the at least one element in the lead-containing layer in the second region; The liquid ejection head according to claim 1 .

15. In the first region, an angle formed between a surface of the first electrode opposite to the diaphragm and a plate surface of the diaphragm is equal to or greater than 10 degrees and less than 60 degrees. The liquid ejection head according to claim 1 .

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