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 first electrode contains a first constituent element as a main component. When, of two regions overlapping the second electrode when viewed in the lamination direction and arranged in a crossing direction which is a direction crossing 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 content percentage of the first constituent element of the first electrode in the first region is higher than a content percentage of the first constituent element of the first electrode 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, there is a risk of cracks occurring at the end of the lower electrode. [Means for solving the problem]

[0005] In order to solve the above problems, one embodiment of a liquid ejection head disclosed herein 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, and the first electrode contains a first constituent element as a main component, and when viewed in the stacking direction, the first electrode overlaps the second electrode and is 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 the first region, and the region closer to the center of the first electrode is defined as the second region, the content of the first constituent element of the first electrode in the first region is higher than the content of the first constituent element of the first electrode 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. 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 C, 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 adhesion layers 56d and 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.

[0032] The first electrode 56a contains a first constituent element as a main component. Here, "main component" means a content of 50 atm% or more. Therefore, the content of the first constituent element in the first electrode 56a is 50 atm% or more. In other words, the first electrode 56a contains the first constituent element at a content of 50 atm% or more. Hereinafter, the main component of the material that constitutes the first electrode 56a will be simply referred to as the "first constituent element."

[0033] Platinum (Pt), for example, is preferably used as the first constituent element. When platinum (Pt) is used as the first constituent element, the first electrode 56a includes, for example, a layer composed of platinum (Pt), a layer composed of iridium (Ir), and a layer composed of titanium (Ti). That is, the first electrode 56a includes platinum, iridium, and titanium. Platinum (Pt) is an electrode material with excellent conductivity. Therefore, using platinum (Pt) as the constituent material of the first electrode 56a can reduce the resistance of the first electrode 56a. Furthermore, when forming the piezoelectric layer 56b, the titanium island-shaped layer serves as a crystal nucleus, controlling the orientation of the piezoelectric layer 56b and improving the crystallinity or orientation of the piezoelectric layer 56b. Note that instead of or in addition to these layers, layers composed 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.

[0034] The first electrode 56a is formed, for example, after the diaphragm 55 and the adhesion layer 56e (described later) are formed, by a known film formation technique such as sputtering, and a known processing technique using photolithography, etching, etc. The thickness of the first electrode 56a is, for example, about 100 nm.

[0035] 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 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 piezoelectric element 56. Note that when viewed in the cross section shown in FIG. 5, the piezoelectric layer 56b may be provided across the plurality of piezoelectric elements 56.

[0036] The piezoelectric layer 56b is a layer made of a piezoelectric material. The piezoelectric material is, for example, a piezoelectric material containing lead as a constituent element. More specifically, the piezoelectric material has a perovskite crystal structure represented by the general composition formula ABO3, and is, for example, lead zirconate titanate (Pb(Zr,Ti)O3). In addition to lead (Pb), the piezoelectric layer 56b may also contain at least one element selected from the group consisting of vanadium (V), niobium (Nb), tantalum (Ta), nitrogen (N), phosphorus (P), arsenic (As), antimony (Sb), and bismuth (Bi).

[0037] Such a piezoelectric layer 56b is formed, for example, by forming the piezoelectric layer 56b and the adhesion layer 56d described below, uniformly forming a piezoelectric precursor layer by a sol-gel method, baking the precursor layer to crystallize it, and then patterning it by etching such as reactive ion etching (RIE) or ion milling.

[0038] 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.

[0039] 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.

[0040] The second electrode 56c is formed, for example, after the piezoelectric layer 56b is formed, by a known film formation technique such as sputtering, and a known processing technique using photolithography, etching, etc. The thickness of the second electrode 56c is, for example, about 100 nm.

[0041] 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.

[0042] 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.

[0043] The elastic layer 55a is a film made of, for example, silicon oxide (SiO2). Note that the material making up the elastic layer 55a is not limited to silicon oxide, 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 an element, oxide, or nitride.

[0044] 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.

[0045] 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 zirconium oxide 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.

[0046] 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.

[0047] 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.

[0048] 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.

[0049] 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 chemical vapor deposition (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 a method using thermal oxidation, and may be, for example, a CVD method or an atomic layer deposition (ALD) method. The diaphragm 55 is not limited to a configuration having the elastic layer 55a and the insulating layer 55b, and may be, for example, a configuration made of single crystal silicon.

[0050] 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.

[0051] The vibration region PV is divided into an active portion RA and a non-active portion RN. The active portion RA is a portion of the actuator 1 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 portion of the actuator 1 that overlaps with the pressure chamber C when viewed along the Z axis, and is a portion different from the active portion RA.

[0052] Fig. 6 is an enlarged view of a portion Q in Fig. 5. As shown in Fig. 6, the active portion RA includes a first region RE1 and a second region RE2.

[0053] The first region RE1 overlaps with the second electrode 56c in the stacking direction DL and is the region farther from the center of the first electrode 56a of two regions aligned in an intersecting direction that intersects with the stacking direction DL, while the second region RE2 is the region closer to the center of the first electrode 56a of the two regions.

[0054] 6, the active portion RA is divided into a first region RE1 and a 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.

[0055] The content of the first constituent element in the first electrode 56a in the first region RE1 is higher than the content of the first constituent element in the first electrode 56a in the second region RE2. As the purity or density of the first constituent element increases, the toughness of the first electrode 56a increases because the properties of the first constituent element approach those of the metal element that is the main component of the first electrode 56a. Therefore, by making the content of the first constituent element in the first region RE1 higher than the content of the first constituent element in the first electrode 56a in the second region RE2, the toughness of the first electrode 56a in the first region RE1 can be made higher than the toughness of the first electrode 56a in the second region RE2. This makes it possible to suppress the occurrence of cracks in the first region RE1.

[0056] Furthermore, because the content of the first constituent element of the first electrode 56a in the second region RE2 is lower than the content of the first constituent element of the first electrode 56a in the first region RE1, the Young's modulus of the first electrode 56a in the second region RE2 can be made smaller than the Young's modulus of the first electrode 56a in the first region RE1. This makes it easier for the first electrode 56a in the active portion RA to expand, making it easier to deform the active portion RA of the piezoelectric element 56.

[0057] For example, if the first constituent element of the first electrode 56a is platinum, the platinum content of the first electrode 56a in the first region RE1 is higher than the platinum content of the first electrode 56a in the second region RE2. This increases the toughness of the first electrode 56a in the first region RE1 and suppresses the occurrence of cracks due to stress generated at the end of the first electrode 56a when the piezoelectric element 56 in the active portion RA is deformed. Furthermore, by including an element with a lower Young's modulus than platinum in the first electrode 56a in the second region RE2, the Young's modulus can be reduced, making it easier for the active portion RA of the piezoelectric element 56 to deform.

[0058] The content of the first constituent element in the first electrode 56a is measured by, for example, secondary ion mass spectrometry or energy dispersive X-ray analysis.

[0059] For example, when the first constituent element of the first electrode 56a is platinum and the content of the first constituent element is measured by secondary ion mass spectrometry, the area of ​​1 mm2 in plan view is 2 The content of two or more elements, including platinum, contained in the first electrode 56a is measured over this range, and the platinum content is normalized by the sum of the contents of platinum and the other elements to calculate the platinum content, which is the first constituent element. When measuring the content of oxygen as an element other than platinum, the platinum content may be normalized by the oxygen content for calculation.

[0060] The comparison of the content of the first constituent element of the first electrode 56a in the first region RE1 and the second region RE2 is performed by comparing the content of the first constituent element at the center of the first electrode 56a in the stacking direction DL. Note that this comparison may be performed using the content of the first constituent element at one end of the first electrode 56a in the stacking direction DL, or may be performed using an average value obtained by averaging the content of the first constituent element at multiple locations of the first electrode 56a in the stacking direction DL.

[0061] When the first electrode 56a contains titanium, the titanium content of the first electrode 56a in the first region RE1 is preferably lower than the titanium content of the first electrode 56a in the second region RE2. This makes it easier to increase the toughness of the first electrode 56a in the first region RE1 compared to the toughness of the first electrode 56a in the second region RE2, thereby preferably suppressing the occurrence of cracks and the like in the first region RE1. The titanium content of the first electrode 56a is measured in the same manner as the content of the first constituent element of the first electrode 56a described above.

[0062] When the piezoelectric layer 56b contains lead zirconate titanate, the first electrode 56a preferably contains lead. This improves adhesion between the first electrode 56a and the piezoelectric layer 56b. The lead content of the first electrode 56a in the first region RE1 is preferably lower than the lead content of the first electrode 56a in the second region RE2. This increases the density of the first constituent element in the first region RE1, thereby suppressing the occurrence of cracks in the first region RE1. Furthermore, the lead content of the first electrode 56a in the second region RE2 is higher than the lead content of the first electrode 56a in the first region RE1, thereby improving adhesion between the first electrode 56a and the piezoelectric layer 56b. The lead content of the first electrode 56a is measured in the same manner as the content of the first constituent element of the first electrode 56a described above.

[0063] Furthermore, when the piezoelectric layer 56b contains any one of vanadium (V), niobium (Nb), tantalum (Ta), nitrogen (N), phosphorus (P), arsenic (As), antimony (Sb), and bismuth (Bi), the content of the element in the first electrode 56a in the first region RE1 is preferably lower than the content of the element in the first electrode 56a in the second region RE2. When the piezoelectric layer 56b contains at least one element selected from V, Nb, Ta, N, 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 lowering the content of the element in the first electrode 56a in the first region RE1 compared to the content of the element in the first electrode 56a in the second region RE2, the density of the first constituent element in the first region RE1 can be increased, thereby suppressing the occurrence of cracks and the like in the first region RE1. The content of the element in the first electrode 56a is measured in the same manner as the content of the first constituent element in the first electrode 56a described above.

[0064] In the second region RE2, the content of the first constituent element in the central portion of the first electrode 56a in the stacking direction DL is preferably higher than the content of the first constituent element in the lower portion of the first electrode 56a than in the central portion of the first electrode 56a in the stacking direction DL. This can suitably improve the conductivity of the first electrode 56a. Here, the central portion is a portion including a center line LC that indicates the neutral plane in the thickness direction of the first electrode 56a in the second region RE2. The lower portion is a portion between the central portion and the diaphragm 55.

[0065] 6, the thickness of the first electrode 56a in the second region RE2 is substantially constant, whereas the thickness of the first electrode 56a in the first region RE1 becomes thinner with increasing distance from the second region RE2. Note that the thickness of the first electrode 56a in the first region RE1 may be substantially constant, similar to the thickness of the first electrode 56a in the first region RE1. Furthermore, the thickness of the first electrode 56a in the first region RE1 may be the same as or different from the thickness of the first electrode 56a in the first region RE1.

[0066] The piezoelectric element 56 has the above-mentioned first electrode 56a, piezoelectric layer 56b, and second electrode 56c, as well as an adhesive layer 56d and an adhesive layer 56e.

[0067] The adhesion layer 56d is disposed between the first electrode 56a and the piezoelectric layer 56b in at least the first region RE1 and serves to enhance adhesion between the first electrode 56a and the piezoelectric layer 56b. The adhesion layer 56d contains titanium, which enhances adhesion between the first electrode 56a and the piezoelectric layer 56b and controls the orientation of the piezoelectric layer 56b. The formation of the adhesion layer 56d is not particularly limited, but may be performed, for example, using a film formation method such as ion plating after the formation of the first electrode 56a. The adhesion layer 56d may also contain a metal element other than titanium. The titanium contained in the adhesion layer 56d may exist as a single element or an alloy, or as an oxide, oxynitride, or oxynitride.

[0068] 6, when viewed in the stacking direction DL, a region 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 adhesion layer 56d is provided in a range spanning the first region RE1, the second region RE2, and the third region RE3. The third region RE3 is included in the inactive part RN.

[0069] The adhesion layer 56d includes a third adhesion layer 56d1. The third adhesion layer 56d1 is a portion of the adhesion layer 56d that is disposed between the first electrode 56a and the piezoelectric layer 56b in the first region RE1. The third adhesion layer 56d1 can enhance adhesion between the first electrode 56a and the piezoelectric layer 56b in the first region RE1. In contrast, if the third adhesion layer 56d1 is omitted, the difference in crystal lattice between the first electrode 56a and the piezoelectric layer 56b in the first region RE1 increases as the density of the first constituent element of the first electrode 56a increases. This may result in poor adhesion between the first electrode 56a and the piezoelectric layer 56b or poor orientation of the piezoelectric layer 56b in the first region RE1. Note that the adhesion layer 56d only needs to include the third adhesion layer 56d1 disposed in the first region RE1; the portions in the second region RE2 and the third region RE3 may be omitted.

[0070] As described above, the thickness of the first electrode 56a in the first region RE1 becomes thinner with increasing distance from the second region RE2. As a result, the surface of the adhesion 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.

[0071] Here, the third adhesion layer 56d1 covers the first electrode 56a in the first region RE1. In the first region RE1, the angle θ1 between the surface of the third adhesion layer 56d1 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 third adhesion layer 56d1 becomes thicker in the first region RE1 from the second region RE2 toward the non-active portion RN. This reduces the difference between the orientation controllability of the piezoelectric material by the third adhesion layer 56d1 in the first region RE1 and the orientation controllability of the piezoelectric material by the adhesion layer 56d in the second region RE2. This increases the orientation of the piezoelectric layer 56b in the active portion RA.

[0072] In the first region RE1, the angle θ1 formed between the surface of the first electrode 56a opposite to the diaphragm 55 and the plate surface of the diaphragm 55 is not particularly limited, but is, for example, 10 degrees or more and less than 60 degrees.

[0073] The thickness of the adhesive layer 56d is not particularly limited, but is, for example, in the range of 20 nm to 80 nm. The adhesive layer 56d may be provided as needed, or may be omitted.

[0074] The adhesion 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 is a layer that enhances adhesion between the first electrode 56a and the diaphragm 55. The adhesion layer 56e contains titanium as a second constituent element. This enhances adhesion between the first electrode 56a and the diaphragm 55. The adhesion layer 56e may also contain a metal element other than titanium. Furthermore, the titanium contained in the adhesion layer 56e may exist as a simple substance or an alloy, or as an oxide, oxynitride, or oxynitride. The formation of such an adhesion layer 56e is not particularly limited, but may be performed, for example, using a film formation method such as ion plating after the formation of the diaphragm 55.

[0075] 6, the adhesive layer 56e is provided in a range spanning the first region RE1, the second region RE2, and the third region RE3. The adhesive layer 56e in the third region RE3 may be omitted.

[0076] The adhesion layer 56e has a first adhesion layer 56e1 and a second adhesion layer 56e2. The first adhesion layer 56e1 is a part of the adhesion layer 56e and is a portion disposed between the diaphragm 55 and the first electrode 56a in the first region RE1. The second adhesion layer 56e2 is a part of the adhesion layer 56e and is a portion disposed between the diaphragm 55 and the first electrode 56a in the second region RE2. As described above, the adhesion layer 56e contains titanium as the second constituent element, and therefore each of the first adhesion layer 56e1 and the second adhesion layer 56e2 contains titanium as the second constituent element.

[0077] 6, the first adhesive layer 56e1 and the second adhesive layer 56e2 are integrally formed. However, the first adhesive layer 56e1 and the second adhesive layer 56e2 may be separate from each other.

[0078] The thickness t1 of the first adhesion layer 56e1 is preferably thinner than the thickness t2 of the second adhesion layer 56e2. This increases the density of the first constituent element in the first region RE1. Furthermore, since the thickness t2 of the second adhesion layer 56e2 is thicker than the thickness t1 of the first adhesion layer 56e1, the adhesion between the vibration plate 55 and the first electrode 56a can be improved.

[0079] The second adhesion layer 56e2 preferably contains the first constituent element and the second constituent element. In this case, at least a portion of the second adhesion layer 56e2 in the thickness direction functions as a mixed layer in which the first constituent element and the second constituent element are mixed or alloyed. That is, in this case, the second adhesion layer 56e2 has a mixed layer in which the first constituent element and the second constituent element are mixed or alloyed. This can further improve the adhesion between the first electrode 56a and the diaphragm 55. Note that the first adhesion layer 56e1 may have a mixed layer similar to that of the second adhesion layer 56e2. Furthermore, the material constituting the mixed layer may be a material in which other elements are mixed or alloyed in addition to the first constituent element and the second constituent element.

[0080] The thickness of the adhesive layer 56e is not particularly limited, but is, for example, in the range of 1 nm to 20 nm. The adhesive layer 56e may be provided as needed, or may be omitted.

[0081] 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.

[0082] 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.

[0083] 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.

[0084] 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.

[0085] 3. Summary of this disclosure A summary of this disclosure is provided below.

[0086] (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, and the first electrode contains a first constituent element as a main component, and of two regions that overlap the second electrode in the stacking direction and are aligned in an intersecting direction that intersects the stacking direction, the region farther from the center of the first electrode is defined as the first region, and the region closer to the center of the first electrode is defined as the second region, the content of the first constituent element of the first electrode in the first region is higher than the content of the first constituent element of the first electrode in the second region.

[0087] In the above-described embodiment, the content of the first constituent element of the first electrode in the first region is higher than the content of the first constituent element of the first electrode in the second region, thereby making the toughness of the first electrode in the first region higher than that of the first electrode in the second region. This makes it possible to suppress the occurrence of cracks and the like in the first region. Here, the reason why the toughness of the first electrode in the first region is higher than that of the first electrode in the second region is that the higher the purity or density of the first constituent element, the closer the toughness of the first electrode is to the properties of the metal element that is the main component of the first electrode. Furthermore, the content of the first constituent element of the first electrode in the second region is lower than the content of the first constituent element of the first electrode in the first region, making the Young's modulus of the first electrode in the second region smaller than that of the first electrode in the first region. This makes it easier to deform the active portion of the piezoelectric element.

[0088] (Supplementary Note 2) In a second aspect, which is a preferred example of the first aspect, the first electrode contains titanium, and the titanium content of the first electrode in the first region is lower than the titanium content of the first electrode in the second region. In this aspect, the toughness of the first electrode in the first region is easier to increase than the toughness of the first electrode in the second region, so that the occurrence of cracks and the like in the first region can be suitably suppressed.

[0089] (Supplementary Note 3) In a third aspect, which is a preferred example of the second aspect, the piezoelectric element includes a first adhesion layer disposed between the diaphragm and the first electrode in the first region, and a second adhesion layer disposed between the diaphragm and the first electrode in the second region, wherein each of the first adhesion layer and the second adhesion layer contains titanium as a second constituent element, and the thickness of the first adhesion layer is thinner than the thickness of the second adhesion layer. In the above aspect, the thickness of the first adhesion layer is thinner than the thickness of the second adhesion layer, thereby increasing the density of the first constituent element in the first region. Furthermore, the thickness of the second adhesion layer is thicker than the thickness of the first adhesion layer, thereby increasing the adhesion between the diaphragm and the first electrode.

[0090] (Supplementary Note 4) In a fourth aspect, which is a preferred example of the third aspect, the second adhesion layer has a mixed layer in which the first constituent element and the second constituent element are mixed or alloyed. In the above aspect, the adhesion between the first electrode and the diaphragm can be further improved.

[0091] (Appendix 5) In a fifth aspect, which is a preferred example of any of the first to fourth aspects, a third adhesion layer is disposed between the first electrode and the piezoelectric layer in the first region. In the above aspects, the adhesion between the first electrode and the piezoelectric layer in the first region can be improved. In contrast, if the third adhesion layer is omitted, the higher the density of the first constituent element of the first electrode in the first region, the greater the difference in crystal lattice between the first electrode and the piezoelectric layer, which may result in poor adhesion between the first electrode and the piezoelectric layer or poor orientation of the piezoelectric layer in the first region.

[0092] (Appendix 6) In a sixth aspect, which is a preferred example of any of the first to fifth aspects, the piezoelectric layer contains lead zirconate titanate, the first electrode contains lead, and the lead content of the first electrode in the first region is lower than the lead content of the first electrode in the second region. In the above aspect, the lead content of the first electrode in the first region is lower than the lead content of the first electrode in the second region, thereby increasing the density of the first constituent element in the first region and suppressing the occurrence of cracks, etc. in the first region. Furthermore, the lead content of the first electrode in the second region is higher than the lead content of the first electrode in the first region, thereby favorably increasing adhesion between the first electrode and the piezoelectric layer.

[0093] (Supplementary Note 7) In a seventh aspect, which is a preferred example of any one of the first to sixth aspects, the piezoelectric layer contains one of V, Nb, Ta, N, P, As, Sb, and Bi, and the content of that element in the first electrode in the first region is lower than the content of that element in the first electrode in the second region. In the above aspects, when the piezoelectric layer contains at least one element from V, Nb, Ta, N, P, As, Sb, and Bi, oxygen vacancies in the piezoelectric layer can be reduced. As a result, the driving speed of the piezoelectric element can be increased. Furthermore, by making the content of that element in the first electrode in the first region lower than the content of that element in the first electrode in the second region, the same effect as when the lead content of the first electrode in the first region is higher than the lead content of the first electrode in the second region can be obtained.

[0094] (Supplementary Note 8) In an eighth aspect which is a preferred example of any of the first to seventh aspects, in the second region, the content of the first constituent element in a central part of the first electrode in the stacking direction is higher than the content of the first constituent element in a part below the central part of the first electrode in the stacking direction. In the above aspect, the conductivity of the first electrode can be suitably increased. [Explanation of symbols]

[0095] 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...vibration plate, 55a...elastic layer, 55b...insulating layer, 56...piezoelectric element, 56a...first electrode, 56b...piezoelectric layer, 56b1...through hole, 56c...second electrode, 56d...adhesion layer, 56d1...third adhesion layer, 56e...adhesion layer, 56e1... First adhesion layer, 56e2...second adhesion layer, 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, LC...center line, M...medium, N...nozzle, Na...communicating flow path, PV...vibration area, Q...portion, R...liquid storage chamber, R1...opening, R2...accommodation section, RA...active section, RE1...first region, RE2...second region, RE3...third region, RN...non-active section, Ra...supply flow path, t1...thickness, t2...thickness, 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 first electrode contains a first constituent element as a main component, When two regions overlap the second electrode in the stacking direction and are arranged in an intersecting direction that intersects 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 content rate of the first constituent element of the first electrode in the first region is higher than a content rate of the first constituent element of the first electrode in the second region; A liquid ejection head characterized by:

2. the first electrode comprises titanium; the titanium content of the first electrode in the first region is lower than the titanium content of the first electrode in the second region; The liquid ejection head according to claim 1 .

3. a first adhesion layer disposed between the vibration plate and the first electrode in the first region; a second adhesive layer disposed between the vibration plate and the first electrode in the second region; each of the first adhesion layer and the second adhesion layer contains titanium as a second constituent element; The thickness of the first adhesive layer is thinner than the thickness of the second adhesive layer. The liquid ejection head according to claim 2 .

4. the second adhesion layer has a mixed layer in which the first constituent element and the second constituent element are mixed or alloyed; The liquid ejection head according to claim 3 .

5. a third adhesive layer disposed between the first electrode and the piezoelectric layer in the first region; The liquid ejection head according to claim 2 .

6. the piezoelectric layer contains lead zirconate titanate, the first electrode comprises lead; the lead content of the first electrode in the first region is lower than the lead content of the first electrode in the second region; The liquid ejection head according to claim 1 .

7. the piezoelectric layer contains any one element selected from the group consisting of V, Nb, Ta, N, P, As, Sb, and Bi; a content of the element in the first electrode in the first region is lower than a content of the element in the first electrode in the second region; The liquid ejection head according to claim 1 .

8. In the second region, a content rate of the first constituent element at a central portion of the first electrode in the stacking direction is higher than a content rate of the first constituent element at a portion below the central portion of the first electrode in the stacking direction. The liquid ejection head according to claim 1 .

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