Liquid discharge head

Abstract

To reduce variation in characteristics of a plurality of piezoelectric elements, while enhancing reliability on the piezoelectric elements.SOLUTION: A liquid discharge head comprises piezoelectric elements having individual electrodes, a piezoelectric layer and a common electrode in this order, and vibration plates connected to the piezoelectric elements. The individual electrodes are provided on the plurality of piezoelectric elements respectively, the common electrode is commonly provided on the piezoelectric elements, and the piezoelectric layer is constituted of piezoelectric materials including lead as constituent elements. The individual electrodes and the common electrode respectively include lead, where a content rate of lead in the common electrode is lower than a content rate of lead in the individual electrode.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] The head described in Patent Document 1 does not take into consideration the relationship between the lead content of the lower electrode and the upper electrode, and there is room for improvement. [Means for solving the problem]

[0005] In order to solve the above problems, one aspect of the liquid ejection head disclosed herein comprises a piezoelectric element having an individual electrode, a piezoelectric layer, and a common electrode in that order, and a vibration plate connected to the piezoelectric element, wherein the individual electrodes are provided individually for a plurality of the piezoelectric elements, the common electrode is provided in common to a plurality of the piezoelectric elements, the piezoelectric layer is made of a piezoelectric material containing lead as a constituent element, each of the individual electrodes and the common electrode contains lead, and the lead content in the common electrode is lower than the lead content in the individual electrodes. [Brief explanation of the drawings]

[0006] [Figure 1] 1 is a configuration diagram that schematically shows a liquid ejection device that includes a liquid ejection head according to a first embodiment. [Figure 2] FIG. 1 is an exploded perspective view of a liquid ejection head according to a first embodiment. [Figure 3] FIG. 3 is a cross-sectional view taken along line AA in FIG. 2. [Figure 4] FIG. 1 is a plan view showing a part of a liquid ejection head according to a first 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] FIG. 10 is a schematic cross-sectional view of a liquid ejection head according to a second embodiment. [Figure 8] FIG. 8 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 a first 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 the first 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 first embodiment. Fig. 5 is a cross-sectional view taken along line BB in Fig. 4. Below, the pressure chamber substrate 52, piezoelectric element 56, and vibration plate 55 will be described 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 , the piezoelectric element 56 overlaps the pressure chamber C in a plan view. As shown in FIG. 5 , the piezoelectric element 56 includes an individual electrode 56 a, a piezoelectric layer 56 b, and a common electrode 56 c, in this order. In this embodiment, the individual electrode 56 a, the piezoelectric layer 56 b, and the common electrode 56 c are stacked in this order in the Z1 direction. That is, the individual electrode 56 a, the piezoelectric layer 56 b, and the common electrode 56 c 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 includes a first mixed layer 56 d, a second mixed layer 56 e, and a lead diffusion suppression layer 56 f in addition to the individual electrode 56 a, the piezoelectric layer 56 b, and the common electrode 56 c. Hereinafter, in this embodiment, the individual electrode 56 a may be referred to as the “lower electrode” and the common electrode 56 c may be referred to as the “upper electrode.”

[0031] The individual electrodes 56a are electrodes individually provided on the plurality of piezoelectric elements 56. Specifically, the plurality of individual 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 individual electrodes 56a of each piezoelectric element 56.

[0032] The individual electrode 56a may include, for example, a layer made of platinum (Pt), a layer made of iridium (Ir), and a layer made of titanium (Ti). That is, the individual electrode 56a includes platinum, iridium, and titanium. Platinum is an electrode material with excellent conductivity. Therefore, using platinum as a constituent material of the individual electrode 56a can reduce the resistance of the individual 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 enhancing 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.

[0033] As described above, the individual electrodes 56a are mainly made of an electrode material with excellent conductivity, but also contain a small amount of lead. The inclusion of lead in the individual electrodes 56a reduces the Young's modulus of the individual electrodes 56a and improves the adhesion between the individual electrodes 56a and the piezoelectric layer 56b. Note that, hereinafter, the material that constitutes the individual electrodes 56a may be referred to as the "first electrode material."

[0034] The individual electrodes 56a are formed, for example, after the formation of the diaphragm 55, by a known film-forming technique such as sputtering, and a known processing technique using photolithography, etching, etc. The individual electrodes 56a may contain lead, but are not limited to this. For example, lead may be introduced by ion implantation, or a film of a material containing lead may be formed. The thickness of the individual electrodes 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, 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.

[0036] 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 also contain at least one element selected from the group consisting of vanadium (V), niobium (Nb), tantalum (Ta), phosphorus (P), arsenic (As), antimony (Sb), and bismuth (Bi). The lead contained in the piezoelectric material constituting the piezoelectric layer 56b may not be an element that constitutes part of the perovskite crystal structure.

[0037] Such a piezoelectric layer 56b is formed, for example, by forming a piezoelectric precursor layer uniformly by a sol-gel method after the individual electrodes 56a are formed, baking the precursor layer to crystallize it, and then patterning it by etching such as reactive ion etching (RIE), ion milling, etc. In this embodiment, the piezoelectric layer 56b is composed of a plurality of layers LA, as will be described later, and the plurality of layers LA are formed by repeatedly forming and baking the precursor.

[0038] The common electrode 56c is an electrode provided in common to the plurality of piezoelectric elements 56. Specifically, the common electrode 56c has a strip shape extending 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 common electrode 56c.

[0039] The common electrode 56c is made of, for example, iridium (Ir). The material of the common 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 common electrode 56c may be made of one of these metal materials alone, or two or more of them may be combined in a laminated form, for example.

[0040] As described above, the common electrode 56c is mainly composed of an electrode material with excellent conductivity, but also contains a small amount of lead. The inclusion of lead in the common electrode 56c reduces the Young's modulus of the common electrode 56c and improves adhesion between the common electrode 56c and the piezoelectric layer 56b. Note that, hereinafter, the material constituting the common electrode 56c may be referred to as the "second electrode material."

[0041] The common 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 and etching. The common electrode 56c may contain lead, but is not limited to this. For example, lead may be introduced by ion implantation or by forming a film of a material containing lead. The thickness of the common electrode 56c is, for example, about 150 nm.

[0042] In the piezoelectric element 56, when a voltage is applied between the individual electrode 56a and the common 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.

[0043] 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 individual electrode 56a in the thickness direction of the diaphragm 55.

[0044] 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 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), carbon (C), and silicon (Si), in the form of a simple substance, oxide, or nitride.

[0045] 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.

[0046] 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 individual electrode 56a in the thickness direction of the diaphragm 55, it is possible to prevent lead contained in the individual 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), zirconium (Zr), and silicon (Si) in the form of an oxide or nitride.

[0047] 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.

[0048] 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.

[0049] 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.

[0050] The method for forming each of the multiple films constituting diaphragm 55 is not limited to the above-described example, and may be any method. For example, at least a portion of elastic layer 55a may be formed using a chemical vapor deposition (CVD) method or the like. When an adhesive layer is provided between elastic layer 55a and insulating layer 55b, the adhesive layer is formed by forming a layer of chromium, titanium, aluminum, or the like on 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 insulating layer 55b. The method for forming the adhesive layer is not limited to the thermal oxidation method, and may be, for example, a CVD method or an atomic layer deposition (ALD) method.

[0051] 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.

[0052] 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 individual electrode 56a, the piezoelectric layer 56b, and the common 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.

[0053] In the liquid ejection head 50 described above, the individual electrodes 56a and the common electrode 56c each contain lead, as described above.

[0054] When contained in each of the individual electrodes 56a and the common electrode 56c, lead has the effect of improving the adhesion between the individual electrodes 56a and the common electrode 56c and the piezoelectric layer 56b, but it also increases the resistance values ​​of the individual electrodes 56a and the common electrode 56c.

[0055] Therefore, the lead content of the common electrode 56c is lower than that of the individual electrodes 56a. In other words, the lead content of the individual electrodes 56a is higher than that of the common electrode 56c. This makes it possible to reduce variations in the characteristics of the multiple piezoelectric elements 56 while improving the reliability of the liquid ejection head 50.

[0056] Specifically, because the lead content of the common electrode 56c is lower than that of the individual electrodes 56a, an increase in resistance due to the lead content of the common electrode 56c can be suppressed. Unlike the individual electrodes 56a, the common electrode 56c is provided over a wide area in common with multiple piezoelectric elements 56. Therefore, the greater the electrical resistance of the common electrode 56c, the more likely variations in potential among the piezoelectric elements 56 occur. Therefore, by suppressing an increase in resistance due to the lead content of the common electrode 56c, variations in potential among the piezoelectric elements 56 can be reduced. Furthermore, because the lead content of the individual electrodes 56a is higher than that of the common electrode 56c, adhesion between the individual electrodes 56a and the piezoelectric layer 56b can be improved. Because the contact area between the individual electrodes 56a and the piezoelectric layer 56b is smaller than the contact area between the common electrode 56c and the piezoelectric layer 56b, the individual electrodes 56a are more likely to peel off from the piezoelectric layer 56b than the common electrode 56c. Therefore, by improving the adhesion between the individual electrodes 56a and the piezoelectric layers 56b, the reliability of the piezoelectric elements 56 can be suitably improved.

[0057] Furthermore, because the lead content of the common electrode 56c is lower than the lead content of the individual electrodes 56a, the purity of the metal material constituting the common electrode 56c can be higher than the purity of the metal material constituting the individual electrodes 56a. Specifically, the content of the metal material that is the main component of the common electrode 56c is higher than the content of the metal material that is the main component of the individual electrodes 56a. For example, if the common electrode 56c and the individual electrodes 56a are made of platinum, the platinum content of the common electrode 56c is higher than the platinum content of the individual electrodes 56a.

[0058] In this embodiment, the common electrode 56c, which has superior ductility compared to the individual electrodes 56a due to the purity of the metal, is used as the upper electrode, thereby making it possible to make the piezoelectric element 56 more easily deformable.

[0059] When the lead content of the individual electrode 56a is α [atm %] and the lead content of the common electrode 56c is β [atm %,] β / α corresponds to the peak intensity ratio measured by energy dispersive X-ray spectroscopy (EDS) or secondary ion mass spectroscopy (SIMS). Here, the peak intensity ratio is calculated by comparing the peak values ​​indicating lead in the individual electrode 56a and the common electrode 56c. If the individual electrode 56a or the common electrode 56c does not exhibit a peak, the broad shoulder portion of the individual electrode 56a or the common electrode 56c is treated as the peak. If the individual electrode 56a or the common electrode 56c exhibits both a peak and a shoulder, either the shoulder or the peak is treated as the peak.

[0060] Furthermore, when the lead content in each of the piezoelectric layer 56b and the common electrode 56c is measured by energy dispersive X-ray spectroscopy, the peak value indicating lead in the common electrode 56c is smaller than the peak value indicating lead in the piezoelectric layer 56b.

[0061] FIG. 6 is an enlarged view of a portion Q in FIG. 5. As shown in FIG. 6, the piezoelectric layer 56b includes multiple layers LA-1 to LA-5 made of piezoelectric materials. Hereinafter, the layers LA-1 to LA-5 may be referred to as layers LA without distinction. The number of layers LA making up the piezoelectric layer 56b is not limited to the example shown in FIG. 6 and may be four or less or six or more. The thicknesses of the multiple layers LA may be equal to or different from each other. For ease of explanation, FIG. 6 clearly shows the interface between two adjacent layers, but the interface may not be clear due to a gradient material configuration, etc.

[0062] 6, the piezoelectric element 56 has, in addition to the individual electrodes 56a, piezoelectric layers 56b, and common electrodes 56c, a first mixed layer 56d, a second mixed layer 56e, and a lead diffusion suppression layer 56f. The lead diffusion suppression layer 56f may not be regarded as a component of the piezoelectric element 56 but as a component of the diaphragm 55, or may be regarded as a component separate from the piezoelectric element 56 and the diaphragm 55.

[0063] The first mixed layer 56d is disposed between the individual electrode 56a and the piezoelectric layer 56b and is made of a material obtained by mixing or alloying the first electrode material constituting the individual electrode 56a with lead. By providing this first mixed layer 56d, it is possible to improve the adhesion between the individual electrode 56a and the piezoelectric layer 56b. As a result, the effect of increasing the lead content in the individual electrode 56a compared to the lead content in the common electrode 56c is significantly achieved.

[0064] The first mixed layer 56d contains a first adhesive material that assists in adhesion between the individual electrodes 56a and the piezoelectric layer 56b, and is preferably a mixture or alloy of the first adhesive material, the first electrode material, and lead, thereby improving adhesion between the individual electrodes 56a and the piezoelectric layer 56b.

[0065] The first adhesive material may be, for example, a metal such as Ti or Ir, or TiO X , ZnO X , AlO X , ZrO X , HfO X , TaO X , IrO X , RuO X ,VO X , SrRuO X , SrTaO X , LaTaO X , (LaSr)CoO X and the like metal oxides.

[0066] The first adhesive material contains titanium oxide (TiO X) is preferably contained. This increases the oxygen concentration in the first mixture layer 56d, thereby suppressing the oxidation-reduction reaction in the first mixture layer 56d. As a result, oxygen loss from the piezoelectric layer 56b can be suppressed. Specifically, according to the Ellingham diagram, when Pb and Ti are compared, PbO is more likely to be reduced to Pb, and Ti is more likely to be reduced to TiO. X Therefore, if the titanium concentration in the first mixed layer 56d is high, this oxidation-reduction reaction can be suppressed, and therefore oxygen loss from the piezoelectric layer 56b and reduction of lead zirconate titanate can be suppressed.

[0067] The specific thickness t1 of the first mixed layer 56d is not particularly limited, but is, for example, in the range of 20 nm to 80 nm. The first mixed layer 56d is provided as needed, and may be omitted.

[0068] The second mixed layer 56e is disposed between the common electrode 56c and the piezoelectric layer 56b and is made of a mixed or alloyed material of the second electrode material constituting the common electrode 56c and lead. By providing such a second mixed layer 56e, it is possible to improve the adhesion between the common electrode 56c and the piezoelectric layer 56b.

[0069] The second mixed layer 56e contains a second adhesive material that assists adhesion between the common electrode 56c and the piezoelectric layer 56b, and is preferably a mixture or alloy of the second adhesive material, the second electrode material, and lead, thereby improving adhesion between the common electrode 56c and the piezoelectric layer 56b.

[0070] The second adhesive material may be, similarly to the first adhesive material, a metal such as Ti or Ir, or TiO X , ZnO X , AlO X , ZrO X , HfO X , TaO X , IrO X , RuO X ,VO X , SrRuO X , SrTaO X , LaTaOX , (LaSr)CoO X and the like metal oxides.

[0071] The second adhesive material contains titanium oxide (TiO X ) is preferably contained. This increases the oxygen concentration in the second mixture layer 56e, thereby suppressing the oxidation-reduction reaction in the second mixture layer 56e. As a result, oxygen loss from the piezoelectric layer 56b can be suppressed.

[0072] The specific thickness t2 of the second mixed layer 56e is not particularly limited, but is, for example, in the range of 20 nm to 80 nm. The second mixed layer 56e may be provided as needed or may be omitted. The relationship in magnitude between the thickness t2 of the second mixed layer 56e and the thickness t1 of the first mixed layer 56d is not particularly limited.

[0073] The lead diffusion suppression layer 56f is disposed between the individual electrode 56a and the diaphragm 55. By providing such a lead diffusion suppression layer 56f, the penetration of lead into the diaphragm 55 can be suppressed.

[0074] The lead diffusion prevention layer 56f contains an oxide or nitride of at least one element selected from the group consisting of zirconium (Zr), strontium (Sr), ruthenium (Ru), bismuth (Bi), iron (Fe), titanium (Ti), chromium (Cr), Pb, hafnium (Hf), iridium (Ir), rhodium (Rh), osmium (Os), and silicon (Si), thereby preventing lead from penetrating from the lower electrode into the diaphragm 55.

[0075] The lead diffusion suppression layer 56f preferably contains one or both of zirconium and silicon, which has the advantage of making it easier to improve adhesion between the individual electrodes 56a and the diaphragm 55.

[0076] The thickness of the lead diffusion suppression layer 56f is not particularly limited, but is, for example, in the range of 1 nm to 10 nm. The lead diffusion suppression layer 56f is provided as needed, and may be omitted.

[0077] 2. Second embodiment A second embodiment of the present disclosure will be described below. In the following exemplary embodiment, for elements whose actions and functions are similar to those of the first embodiment, the reference numerals used in the description of the first embodiment will be used, and detailed descriptions of each element will be omitted as appropriate.

[0078] Fig. 7 is a schematic cross-sectional view of a liquid ejection head 50A according to the second embodiment. Fig. 8 is an enlarged view of a portion Q in Fig. 7. The liquid ejection head 50A has the same configuration as the liquid ejection head 50 of the first embodiment, except that it includes a piezoelectric element 56A instead of the piezoelectric element 56 of the first embodiment.

[0079] 7 and 8, the piezoelectric element 56A has the same structure as the piezoelectric element 56 of the first embodiment, except that the layer order is reversed and the lead diffusion suppression layer 56f is omitted. For ease of explanation, the first mixed layer 56d and the second mixed layer 56e are not shown in FIG. 7. The piezoelectric element 56A may include the lead diffusion suppression layer 56f.

[0080] 8, in this embodiment, the diaphragm 55, the common electrode 56c, the piezoelectric layer 56b, and the individual electrode 56a are stacked in this order in the stacking direction DL. Here, the first mixed layer 56d is disposed between the individual electrode 56a and the piezoelectric layer 56b. The second mixed layer 56e is disposed between the common electrode 56c and the piezoelectric layer 56b. Hereinafter, in this embodiment, the common electrode 56c may be referred to as the "lower electrode" and the individual electrode 56a may be referred to as the "upper electrode."

[0081] In this configuration, the lead content of the common electrode 56c is also lower than that of the individual electrodes 56a, ie, higher than that of the common electrode 56c.

[0082] Also in this embodiment, the piezoelectric layer 56b is composed of multiple layers LA. As described above, the diaphragm 55, the common electrode 56c, the piezoelectric layer 56b, and the individual electrodes 56a are stacked in this order in the stacking direction DL. This can cause the lead concentration to differ among the multiple layers LA when the piezoelectric layer 56b is formed by film deposition. As a result, excess lead may remain in the uppermost layer LA-5 of the multiple layers LA of the piezoelectric layer 56b, potentially causing the lead to leak out. According to this configuration, the individual electrodes 56a, which are upper electrodes with a high lead content, cover the piezoelectric layer 56b. Therefore, considering the equilibrium state between the piezoelectric layer 56b and the individual electrodes 56a, it is possible to prevent lead from leaking out of the piezoelectric layer 56b during firing.

[0083] As with the first embodiment, the second embodiment described above can also reduce variations in the characteristics of the plurality of piezoelectric elements 56A while increasing the reliability of the piezoelectric elements 56A.

[0084] 3. 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.

[0085] 3-1. Variation 1 In each of the above-described embodiments, the piezoelectric layer 56b is provided in common to a plurality of pressure chambers C, but this is not limitative. The piezoelectric layer 56b may be divided for each pressure chamber C.

[0086] 3-2. 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.

[0087] 3-3. 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.

[0088] 4. Summary of this disclosure A summary of this disclosure is provided below.

[0089] (Appendix 1) A first aspect, which is a preferred example of a liquid ejection head of the present disclosure, comprises a piezoelectric element having an individual electrode, a piezoelectric layer, and a common electrode in this order, and a vibration plate connected to the piezoelectric element, wherein the individual electrodes are provided individually for a plurality of the piezoelectric elements, the common electrode is provided in common to a plurality of the piezoelectric elements, the piezoelectric layer is made of a piezoelectric material containing lead as a constituent element, each of the individual electrodes and the common electrode contains lead, and the lead content in the common electrode is lower than the lead content in the individual electrodes.

[0090] In the above-described embodiment, the lead content of the common electrode is lower than that of the individual electrodes, thereby suppressing an increase in resistance due to the lead content of the common electrode. Unlike individual electrodes, the common electrode is provided over a wide area in common to multiple piezoelectric elements. Therefore, the greater the electrical resistance of the common electrode, the more likely variations in potential among the piezoelectric elements are to occur. Therefore, suppressing an increase in resistance due to the lead content of the common electrode can effectively reduce variations in potential among the piezoelectric elements. Furthermore, the lead content of the individual electrodes is higher than that of the common electrode, thereby improving adhesion between the individual electrodes and the piezoelectric layer. Because the contact area between the individual electrodes and the piezoelectric layer is smaller than the contact area between the common electrode and the piezoelectric layer, the individual electrodes are more likely to peel off from the piezoelectric layer than the common electrode. Therefore, improving adhesion between the individual electrodes and the piezoelectric layer can favorably improve the reliability of the piezoelectric elements.

[0091] The lead contained in the individual electrodes and the common electrode improves the adhesion between the individual electrodes and the common electrode and the piezoelectric layer, but also increases the resistance of the individual electrodes and the common electrode. Therefore, as described above, by making the lead content in the common electrode lower than the lead content in the individual electrodes, it is possible to increase the reliability of the piezoelectric elements and reduce the variation in the characteristics of multiple piezoelectric elements.

[0092] (Note 2) In a second aspect, which is a preferred example of the first aspect, a first mixed layer is disposed between the individual electrodes and the piezoelectric layer, and is formed by mixing or alloying a first electrode material constituting the individual electrodes with lead. This aspect improves adhesion between the individual electrodes and the piezoelectric layer. As a result, the effect of increasing the lead content in the individual electrodes relative to the lead content in the common electrode is significantly achieved.

[0093] (Note 3) In a third aspect, which is a preferred example of the second aspect, the first mixed layer includes a first adhesion material that assists adhesion between the individual electrodes and the piezoelectric layer, and the first adhesion material, the first electrode material, and lead are mixed or alloyed together. In the above aspect, the adhesion between the individual electrodes and the piezoelectric layer can be improved.

[0094] (Note 4) In a fourth aspect, which is a preferred example of the third aspect, the first adhesive material contains titanium oxide as a constituent element. In this aspect, by increasing the oxygen concentration in the first mixture layer, it is possible to suppress the oxidation-reduction reaction in the first mixture layer. As a result, it is possible to suppress oxygen loss from the piezoelectric layer.

[0095] (Supplementary Note 5) In a fifth aspect, which is a preferred example of any of the first to fourth aspects, the piezoelectric element further comprises a second mixed layer disposed between the common electrode and the piezoelectric layer, the second mixed layer being a mixture or alloy of lead and a second electrode material constituting the common electrode. In the above aspect, the adhesion between the common electrode and the piezoelectric layer can be improved.

[0096] (Appendix 6) In a sixth aspect, which is a preferred example of any of the first to fifth aspects, a lead diffusion suppression layer is further provided between the individual electrode and the diaphragm, and the diaphragm, the individual electrode, the piezoelectric layer, and the common electrode are stacked in this order in the stacking direction. In the above aspect, it is possible to suppress the penetration of lead into the diaphragm. Furthermore, by using a common electrode, which has superior ductility compared to the individual electrodes due to its metal purity, as the upper electrode, it is possible to make the piezoelectric element more easily deformable.

[0097] (Supplementary Note 7) In a seventh aspect, which is a preferred example of the sixth aspect, the lead diffusion suppression layer contains one or both of zirconium and silicon. This aspect has the advantage of easily improving adhesion between the individual electrodes and the diaphragm.

[0098] (Appendix 9) In a ninth aspect, which is a preferred example of any of the first to fifth aspects, the diaphragm, the common electrode, the piezoelectric layer, and the individual electrodes are stacked in this order in the stacking direction, and the piezoelectric layer includes multiple layers made of the piezoelectric material. In the above aspect, since the upper electrode with a high lead content covers the piezoelectric layer, considering the equilibrium state between the piezoelectric layer and the upper electrode, it is possible to prevent lead from escaping from the piezoelectric layer to the outside during firing. [Explanation of symbols]

[0099] 1...actuator, 10...liquid container, 20...control unit, 30...transport mechanism, 40...movement mechanism, 41...carriage, 42...transport belt, 50...liquid ejection head, 50A...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...piezoelectric element, 56a...individual electrode, 56b...piezoelectric layer, 56b1...through hole, 5 6c...common electrode, 56d...first mixed layer, 56e...second mixed layer, 56f...lead diffusion suppression layer, 57...sealing plate, 58...case, 59...wiring board, 60...drive circuit, 100...liquid ejection device, C...pressure chamber, DL...stacking direction, IH...inlet, LA-1 to LA-5...layers, 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, RN...non-active part, Ra...supply flow path, t1...thickness, t2...thickness.

Claims

1. a piezoelectric element having an individual electrode, a piezoelectric layer, and a common electrode in this order; a vibration plate connected to the piezoelectric element, the individual electrodes are provided individually for the plurality of piezoelectric elements, the common electrode is provided in common to the plurality of piezoelectric elements, the piezoelectric layer is made of a piezoelectric material containing lead as a constituent element, each of the individual electrodes and the common electrode contains lead; the lead content of the common electrode is lower than the lead content of the individual electrodes; A liquid ejection head characterized by:

2. a first mixed layer disposed between the individual electrodes and the piezoelectric layer, the first mixed layer being a mixture or alloy of a first electrode material constituting the individual electrodes and lead; The liquid ejection head according to claim 1 .

3. the first mixed layer includes a first adhesion material that assists adhesion between the individual electrode and the piezoelectric layer, and the first adhesion material, the first electrode material, and lead are mixed or alloyed together; The liquid ejection head according to claim 2 .

4. the first adhesive material contains titanium oxide as a constituent element; The liquid ejection head according to claim 3 .

5. a second mixed layer disposed between the common electrode and the piezoelectric layer, the second mixed layer being a mixture or alloy of a second electrode material constituting the common electrode and lead; The liquid ejection head according to claim 2 .

6. a lead diffusion suppression layer disposed between the individual electrode and the diaphragm; the vibration plate, the individual electrode, the piezoelectric layer, and the common electrode are stacked in this order in the stacking direction; The liquid ejection head according to claim 1 .

7. the lead diffusion suppression layer contains one or both of zirconium and silicon; The liquid ejection head according to claim 6 .

8. the vibration plate, the common electrode, the piezoelectric layer, and the individual electrodes are stacked in this order in the stacking direction; the piezoelectric layer includes a plurality of layers made of the piezoelectric material; The liquid ejection head according to claim 1 .

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