Piezoelectric actuator and liquid dispensing head

Abstract

Reduces damage such as cracks. [Solution] The piezoelectric actuator comprises a piezoelectric element and a diaphragm that vibrates when driven by the piezoelectric element. The diaphragm includes a first layer containing zirconium oxide as its main constituent material. When the zirconium oxide contained in the first layer is measured by X-ray diffraction, the intensity related to the cubic crystal (111) is defined as the first intensity, and the intensity related to the monoclinic crystal (111) is defined as the second intensity. In this case, the ratio of the first intensity to the sum of the first and second intensities is 40% or more.

Description

Technical Field

[0001] The present disclosure relates to a piezoelectric actuator and a liquid ejection head.

Background Art

[0002] Patent Document 1 discloses an actuator device including a diaphragm and a piezoelectric element formed on the diaphragm. In Patent Document 1, the diaphragm is formed by forming an insulator film made of monoclinic zirconium oxide that preferentially orientates in (-111) on an elastic film made of silicon oxide.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the technology described in Patent Document 1, cracks may occur depending on the crystallinity or orientation of zirconium oxide.

Means for Solving the Problems

[0005] In order to solve the above problems, a piezoelectric actuator according to a preferred embodiment of the present disclosure includes a piezoelectric element and a diaphragm that vibrates by driving the piezoelectric element, the diaphragm includes a first layer containing zirconium oxide as a main constituent material, and when the zirconium oxide contained in the first layer is measured by X-ray diffraction method, when the intensity related to cubic crystal (111) is defined as the first intensity and the intensity related to monoclinic crystal (111) is defined as the second intensity, the ratio of the first intensity to the sum of the first intensity and the second intensity is 40% or more.

[0006] A liquid ejection head according to a preferred embodiment of the present disclosure has the piezoelectric actuator of the above-described embodiment. [Brief explanation of the drawing]

[0007] [Figure 1] This is a schematic diagram showing an example configuration of a liquid dispensing device. [Figure 2] This is an exploded perspective view of the liquid dispensing head according to the embodiment. [Figure 3] This is a cross-sectional view along line AA in Figure 2. [Figure 4] Figure 2 is a plan view of a portion of the liquid discharge head. [Figure 5] This is a cross-sectional view along line BB in Figure 4. [Figure 6] This is an explanatory diagram of the first and second intensities. [Figure 7] This is an explanatory diagram of the manufacturing method of a piezoelectric actuator according to the embodiment. [Figure 8] This is an explanatory diagram of the manufacturing method of a piezoelectric actuator according to the embodiment. [Figure 9] This figure shows the conditions and evaluation results for each of Examples 1-6 and the comparative example. [Figure 10] This figure shows the additive elements of the Zr targets used in Examples 1-6 and the Comparative Examples. [Figure 11] This figure shows the results of the X-ray analysis of the second layer in Example 1 and the Comparative Example. [Modes for carrying out the invention]

[0008] Preferred embodiments of the present disclosure will be described below with reference to the attached drawings. Note that the dimensions and scale of parts in the drawings may differ from actual dimensions as appropriate, and some parts are shown schematically for ease of understanding. Furthermore, the scope of the present disclosure is not limited to these embodiments unless otherwise stated in the following description.

[0009] For convenience, the following explanation will use the X, Y, and Z axes intersecting each other as appropriate. In the following, one direction along the X axis is the X1 direction, and the direction opposite to the X1 direction is the X2 direction. Similarly, opposite directions along the Y axis are the Y1 and Y2 directions. Also, opposite directions along the Z axis are the Z1 and Z2 directions. The Z1 direction is an example of the "thickness direction of the first layer".

[0010] Here, typically, the Z-axis is the vertical axis, and the Z2 direction corresponds to the downward direction in the vertical. However, the Z-axis does not have to be the vertical axis. Also, the X, Y, and Z axes are typically orthogonal to each other, but are not limited to this; for example, they can intersect at an angle within the range of 80° to 100°.

[0011] 1: Embodiment 1-1: Overall configuration of the liquid dispensing device Figure 1 is a schematic diagram showing an example of the configuration of a liquid ejection device 100 according to an embodiment. The liquid ejection device 100 is an inkjet printing device that ejects ink, which is an example of a "liquid," as droplets toward a recording medium M. The recording medium M is, for example, printing paper. However, the recording medium M is not limited to printing paper, and may be any material to be printed on, for example, a resin film or a cloth.

[0012] As shown in Figure 1, the liquid dispensing device 100 comprises a liquid container 10, a control module 20, a transport mechanism 30, a moving mechanism 40, and a plurality of liquid dispensing heads 50.

[0013] The liquid container 10 stores ink. Specific examples of the liquid container 10 include a cartridge detachable from the liquid dispensing device 100, a bag-shaped ink pack made of flexible film, and an ink tank from which ink can be refilled. The type of ink stored in the liquid container 10 is arbitrary.

[0014] The control module 20 controls the operations of each element of the liquid ejection device 100. The control module 20 includes, for example, 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. Here, the control module 20 outputs a drive signal Com for driving the liquid ejection head 50 and a control signal SI for controlling the driving of the liquid ejection head 50. With such a drive signal Com and control signal SI, the control module 20 controls the ejection operation from the liquid ejection head 50.

[0015] The conveyance mechanism 30 conveys the recording medium M along the Y-axis under the control of the control module 20.

[0016] The moving mechanism 40 reciprocates the liquid ejection head 50 along the X-axis under the control of the control module 20. The moving mechanism 40 has a substantially box-shaped carrier 41 called a carriage that houses the liquid ejection head 50, and an endless conveyor belt 42 to which the carrier 41 is fixed. In addition to the liquid ejection head 50, the aforementioned liquid container 10 may be mounted on the carrier 41.

[0017] Each of the plurality of liquid ejection heads 50 ejects ink supplied from the liquid container 10 onto the recording medium M from each of the plurality of nozzles N under the control of the control module 20. By performing this ejection in parallel with the conveyance of the recording medium M by the conveyance mechanism 30 and the reciprocating movement of the liquid ejection head 50 by the moving mechanism 40, an image with ink is formed on the surface of the recording medium M.

[0018] In the example shown in FIG. 1, the number of liquid ejection heads 50 is four. Note that the number of liquid ejection heads 50 is not limited to the example shown in FIG. 1, and is arbitrary. It may be a single one, or a plurality of three or less or five or more. Also, the arrangement of the plurality of liquid ejection heads 50 is not limited to the example shown in FIG. 1, and is arbitrary.

[0019] 1-2: Liquid ejection head Figure 2 is an exploded perspective view of the liquid dispensing head 50 according to an embodiment. Figure 3 is a cross-sectional view taken along line AA in Figure 2. An example of the configuration of the liquid dispensing head 50 will be described below.

[0020] As shown in Figures 2 and 3, the liquid discharge head 50 has a plurality of nozzles N arranged in the direction along the Y axis.

[0021] The multiple nozzles N of the liquid discharge head 50 are divided into a first nozzle row Ln1 and a second nozzle row Ln2, which are spaced apart from each other in the direction along the X axis. Each of the first nozzle row Ln1 and the second nozzle row Ln2 is a collection of multiple nozzles N arranged linearly in the direction along the Y axis.

[0022] The liquid discharge head 50 has a configuration that is substantially symmetrical with respect to the X-axis. However, the positions of the multiple nozzles N of the first nozzle row Ln1 and the multiple nozzles N of the second nozzle row Ln2 along the Y-axis may coincide or differ. Figures 2 and 3 illustrate a configuration in which the positions of the multiple nozzles N of the first nozzle row Ln1 and the multiple nozzles N of the second nozzle row Ln2 along the Y-axis coincide.

[0023] As shown in Figures 2 and 3, the liquid discharge head 50 includes a communication substrate 510, a pressure chamber substrate 520, a nozzle plate 530, a vibration absorber 540, a diaphragm 550, a plurality of piezoelectric elements 560, a protective substrate 570, a case 580, and a wiring substrate 590. Here, the piezoelectric elements 560 and the diaphragm 550 constitute a piezoelectric actuator 130. Thus, the piezoelectric actuator 130 includes the piezoelectric elements 560 and the diaphragm 550.

[0024] Thus, the device has a liquid discharge head 50 and a piezoelectric actuator 130. As a result, the occurrence of cracks in the piezoelectric actuator 130 is reduced, as described later, and a highly reliable liquid discharge head 50 can be provided.

[0025] The communication substrate 510 and the pressure chamber substrate 520 are stacked in this order in the Z1 direction, forming a flow path for supplying ink to multiple nozzles N. A diaphragm 550, multiple piezoelectric elements 560, a protective substrate 570, a case 580, a wiring board 590, and a drive circuit 600 are installed in the region located in the Z1 direction from the stack consisting of the communication substrate 510 and the pressure chamber substrate 520. On the other hand, a nozzle plate 530 and a vibration absorber 540 are installed in the region located in the Z2 direction from the said stack. Each element of the liquid discharge head 50 is generally a plate-shaped member that is elongated in the Y direction, and is joined to each other, for example, by adhesive. The elements of the liquid discharge head 50 will be described in order below.

[0026] The nozzle plate 530 is a plate-shaped member provided with a plurality of nozzles N in the first nozzle row Ln1 and the second nozzle row Ln2, respectively. Each of the plurality of nozzles N is a through hole through which ink passes. Here, the surface of the nozzle plate 530 facing the Z2 direction is the nozzle surface FN. The nozzle plate 530 is manufactured by processing a silicon single crystal substrate using semiconductor manufacturing technology, such as dry etching or wet etching. However, other known methods and materials may be used in the manufacture of the nozzle plate 530 as appropriate. In addition, the cross-sectional shape of the nozzles N is typically circular, but is not limited to this, and may be non-circular, such as polygonal or elliptical.

[0027] The communication substrate 510 is provided with a flow path R1, a plurality of supply flow paths Ra, and a plurality of communication flow paths Na for each of the first nozzle row Ln1 and the second nozzle row Ln2. Flow path R1 is a flow path provided in common to the plurality of nozzles N, and is a flow path that communicates with the plurality of nozzles N and is upstream of the nozzles N, and is composed of an elongated hole that extends in the direction along the Y axis in a plan view taken in the direction along the Z axis. Each of the supply flow path Ra and communication flow path Na is a flow path composed of a through hole formed for each nozzle N. Each supply flow path Ra communicates with flow path R1.

[0028] The connecting substrate 510 is manufactured, similar to the nozzle plate 530 described above, for example, by processing a silicon single crystal substrate using semiconductor manufacturing technology. However, other known methods and materials may be used in the manufacture of the connecting substrate 510 as appropriate.

[0029] The pressure chamber substrate 520 is a plate-shaped member provided with a plurality of pressure chambers C1, called cavities, for each of the first nozzle row Ln1 and the second nozzle row Ln2. The plurality of pressure chambers C1 are arranged in the direction along the Y axis. Each pressure chamber C1 is formed for each nozzle N and is a long space extending in the direction along the X axis in a plan view. As described above, the pressure chamber substrate 520 has a plurality of pressure chambers C1 arranged in the Y1 direction or the Y2 direction.

[0030] The pressure chamber substrate 520 is manufactured, similar to the nozzle plate 530 described above, for example, by processing a silicon single crystal substrate using semiconductor manufacturing technology. However, other known methods and materials may be used in the manufacture of the pressure chamber substrate 520 as appropriate.

[0031] The pressure chamber C1 is located between the communication substrate 510 and the diaphragm 550. For each of the first nozzle row Ln1 and the second nozzle row Ln2, multiple pressure chambers C1 are arranged in a direction along the Y axis. The pressure chamber C1 also communicates with the communication channel Na and the supply channel Ra, respectively. Therefore, the pressure chamber C1 communicates with the nozzle N via the communication channel Na and with the channel R1 via the supply channel Ra.

[0032] The diaphragm 550 is positioned on the surface of the pressure chamber substrate 520 facing the Z1 direction. The diaphragm 550 is an elastically vibrating plate-shaped member that vibrates when driven by the piezoelectric element 560. The diaphragm 550 will be described in detail later with reference to Figure 5.

[0033] On the surface of the diaphragm 550 facing the Z1 direction, multiple piezoelectric elements 560 corresponding to the nozzles N are arranged for each of the first nozzle row Ln1 and the second nozzle row Ln2. Each piezoelectric element 560 is a passive element that deforms when a potential corresponding to the drive signal Com is supplied, causing pressure fluctuations in the ink within the pressure chamber C1. Each piezoelectric element 560 is elongated in shape, extending along the X-axis in a plan view. Multiple piezoelectric elements 560 are arranged along the Y-axis to correspond to multiple pressure chambers C1. In a plan view, the piezoelectric elements 560 overlap the pressure chambers C1. These piezoelectric elements 560 apply pressure to the pressure chambers C1, which are connected to the nozzles N that eject the ink. Details of the piezoelectric elements 560 will be explained later with reference to Figure 5.

[0034] The protective substrate 570 is a plate-shaped member installed on the surface of the diaphragm 550 facing the Z1 direction, protecting the plurality of piezoelectric elements 560 and reinforcing the mechanical strength of the diaphragm 550. Here, the plurality of piezoelectric elements 560 are housed in the space S between the protective substrate 570 and the diaphragm 550. The protective substrate 570 is made of, for example, a resin material.

[0035] Case 580 is a case for storing ink supplied to multiple pressure chambers C1. Case 580 is made of, for example, a resin material. Case 580 is provided with a flow path R2 for each of the first nozzle row Ln1 and the second nozzle row Ln2. Flow path R2 is a space connected to the aforementioned flow path R1 and is composed of an elongated hole extending in the direction along the Y axis in a plan view taken in the direction along the Z axis. Flow path R2 is in communication with the nozzles N and, together with flow path R1, functions as a reservoir R for storing ink supplied to multiple pressure chambers C1. Case 580 is provided with inlets HL for supplying ink to each reservoir R. The ink in each reservoir R is supplied to the pressure chamber C1 via each supply flow path Ra. Note that the position and number of inlets HL for each reservoir R are not limited to the examples in Figures 2 and 3 and are arbitrary.

[0036] The vibration absorber 540, also called the compliance substrate, is a flexible resin film that forms the wall surface of the reservoir R and absorbs pressure fluctuations of the ink in the reservoir R. The vibration absorber 540 may also be a flexible thin plate made of metal. The surface of the vibration absorber 540 facing the Z1 direction is joined to the communication substrate 510 by adhesive or the like.

[0037] The wiring board 590 is mounted on the surface of the diaphragm 550 facing the Z1 direction and is a mounting component for electrically connecting the control module 20 and the liquid discharge head 50. The wiring board 590 is a flexible wiring board such as COF (Chip On Film), FPC (Flexible Printed Circuit), or FFC (Flexible Flat Cable). In this embodiment, a drive circuit 600 is mounted on the wiring board 590. Under the control of the control module 20, the drive circuit 600 switches whether or not to supply pulses included in the drive signal Com output from the control module 20 to each of the plurality of piezoelectric elements 560 of the liquid discharge head 50. As described above, the wiring board 590 supplies the drive signal Com that drives the piezoelectric elements 560. Note that the wiring board 590 may be a rigid board. In this case, the drive circuit 600 is mounted on the rigid board or on a flexible board connected to the rigid board.

[0038] 1-3: Piezoelectric actuator Figure 4 is a plan view of a part of the liquid discharge head 50 shown in Figure 2. Figure 5 is a cross-sectional view taken along line BB in Figure 4. In Figure 4, for ease of viewing, the portion of the second electrode 562 not covered by the second wiring 120 (described later) is indicated by dots.

[0039] First, the configuration of the diaphragm 550 and the piezoelectric element 560 will be explained based on Figures 4 and 5.

[0040] Multiple piezoelectric elements 560 are arranged on the surface of the diaphragm 550 facing the Z1 direction. As shown in Figure 5, each piezoelectric element 560 has a first electrode 561, a second electrode 562, and a piezoelectric layer 563. These are stacked in the Z1 direction in the order of the first electrode 561, the piezoelectric layer 563, and the second electrode 562. Although not shown, a seed layer is provided between the first electrode 561 and the piezoelectric layer 563 as needed to control the orientation of the piezoelectric layer 563.

[0041] In the piezoelectric element 560, when a voltage is applied between the first electrode 561 and the second electrode 562, the piezoelectric layer 563 deforms due to the inverse piezoelectric effect. When the diaphragm 550 vibrates in conjunction with this deformation, the pressure in the pressure chamber C1 fluctuates, causing ink to be ejected from the nozzle N.

[0042] As shown in Figure 4, the first electrode 561 is electrically connected to the first wiring 110, and a drive signal Com is supplied via the first wiring 110. The first wiring 110 is a lead wire provided individually for each piezoelectric element 560 and is electrically connected to the first electrode 561 of the corresponding piezoelectric element 560. On the other hand, the second electrode 562 is electrically connected to the second wiring 120, and a constant potential is supplied via the second wiring 120. The second wiring 120 is a common wiring provided in common to multiple piezoelectric elements 560 and is electrically connected to the second electrode 562.

[0043] In the example shown in Figure 4, the first wiring 110 is connected to the first electrode 561 and is drawn out from the first electrode 561 toward the wiring board 590 for each piezoelectric element 560. On the other hand, the second wiring 120 is drawn out from both ends of the second electrode 562 in the Y1 and Y2 directions toward the wiring board 590 toward the diaphragm 550. Here, the second wiring 120 has strip-shaped conductive layers 121 and 122 extending in the Y1 direction. The conductive layers 121 and 122 are arranged at a predetermined interval in the X1 direction. Such second wiring 120 also functions as a weight to suppress vibration of the diaphragm 550.

[0044] The constituent materials of the first wiring 110 and the second wiring 120 are not particularly limited, but examples include metals such as gold (Au), copper (Cu), titanium (Ti), tungsten (W), nickel (Ni), chromium (Cr), platinum (Pt), and aluminum (Al). Among these, gold (Au) is preferably used as the constituent material for the first wiring 110 and the second wiring 120. Here, for each of the first wiring 110 and the second wiring 120, a structure in which a layer made of gold is laminated as a surface layer on top of a layer made of nickel-chromium or the like is preferably used.

[0045] The first electrode 561 is an individual electrode positioned on the diaphragm 550, spaced apart from each other for each piezoelectric element 560. A drive signal Com is supplied to the first electrode 561. The second electrode 562 is a common strip-shaped electrode positioned on the piezoelectric layer 563, extending along the Y-axis to be continuous across multiple piezoelectric elements 560. A constant potential is supplied to the second electrode 562, for example.

[0046] Examples of materials that make up the first electrode 561 and the second electrode 562 include metallic materials such as platinum (Pt), aluminum (Al), iridium (Ir), nickel (Ni), gold (Au), and copper (Cu). Of these, one type can be used alone, or two or more types can be used in combination in the form of an alloy or laminate.

[0047] The piezoelectric layer 563 is positioned between the first electrode 561 and the second electrode 562 and is composed of a piezoelectric material. A composite oxide having a perovskite structure represented by the general composition formula ABO3 is preferably used as the piezoelectric material. Examples of such composite oxides include lead zirconate titanate (Pb(Zr,Ti)O3) and lead magnesium niobate / lead titanate solid solution (Pb(Mg,Nb)O3-PbTiO3). Furthermore, the composite oxide is not limited to the lead-containing compounds mentioned above, but may also be a lead-free compound, such as potassium sodium niobate ((K,Na)NbO3, abbreviated as "KNN"), bismuth ironate ((BiFeO3), abbreviated as "BFO"), potassium sodium lithium niobate ((K,Na,Li)(NbO3)), potassium sodium lithium tantalate niobate ((K,Na,Li)(Nb,Ta)O3), bismuth manganese (BiMnO3, abbreviated as "BM"), etc.

[0048] In the example shown in Figure 4, the piezoelectric layer 563 is a strip-shaped structure extending along the Y-axis so as to be continuous across multiple piezoelectric elements 560. Here, the piezoelectric layer 563 is provided with notches G extending along the X-axis, penetrating the piezoelectric layer 563 in regions corresponding to the gaps between adjacent pressure chambers C1 in a plan view. Note that the piezoelectric layer 563 may be provided individually for each piezoelectric element 560. The notches G may also be closed-end grooves.

[0049] The diaphragm 550 has a third layer 551, a first layer 552, and a second layer 553. These are stacked in the Z1 direction in the order of third layer 551, second layer 553, and first layer 552. That is, the first layer 552 is positioned in the Z1 direction relative to the second layer 553, and the third layer 551 is positioned in the Z2 direction. In this way, the second layer 553 is positioned between the third layer 551 and the first layer 552. In the figure, the interface between the first layer 552 and the second layer 553 is clearly shown, but it does not have to be clear. For example, each layer may be embedded in the other layers, dispersed, or integrated.

[0050] The third layer 551 is an elastic film containing silicon oxide (SiO2) as its main constituent material, and is formed, for example, by thermal oxidation of one side of a silicon single crystal substrate. The third layer 551 may consist solely of silicon oxide, or it may consist of a material in which appropriate elements are added to silicon oxide. Here, the main constituent material refers to the material that makes up 50% or more of the material constituting the layer.

[0051] The thickness t1 of the third layer 551 is determined according to the thickness t and width of the diaphragm 550, and is not particularly limited, but is preferably in the range of 100 nm to 3500 nm, and more preferably in the range of 500 nm to 2500 nm.

[0052] The first layer 552 is an insulating film containing zirconium oxide (ZrO2) as its main constituent material. For example, it is formed by creating a zirconium layer by sputtering and then thermally oxidizing the layer. The first layer 552 may consist solely of zirconium oxide, or it may consist of a material in which appropriate elements are added to zirconium oxide.

[0053] The thickness t2 of the first layer 552 is determined according to the thickness t and width of the diaphragm 55, and is not particularly limited, but is preferably thinner than the thickness t1 of the third layer 551, for example, within the range of 10 nm to 2000 nm. However, the thickness t2 of the first layer 552 may be greater than or equal to the thickness t1 of the third layer 551.

[0054] The second layer 553 is a layer containing additives different from the main constituent materials of the first layer 552. The second layer 553 originates from a layer formed to diffuse the additives into the first layer 552, and is a layer in which the additives and the main constituent materials of the first layer 552 are mixed. Therefore, the content of the additives in the second layer 553 relative to the main constituent elements of the first layer 552 is higher than the content in the first layer 552.

[0055] The thickness t3 of the second layer 553 depends on the diffusivity of the additive, but is in the range of 1 nm to 15 nm. Note that since the additive diffuses into the first layer 552, the interface between the second layer 553 and the first layer 552 may not be clearly defined.

[0056] The additive is a material containing one or more elements selected from carbon (C), aluminum (Al), titanium (Ti), chromium (Cr), iron (Fe), hafnium (Hf), yttrium (Y), cerium (Ce), silicon (Si), tantalum (Ta), and iridium (Ir) in the form of elemental, oxide, or nitride. Preferably, the additive contains one or more elements selected from carbon, titanium, hafnium, and cerium in the form of elemental, oxide, or nitride. For example, if the additive contains titanium, hafnium, and cerium, these elements have the same valence as zirconium contained in the first layer 552, which can reduce leakage current.

[0057] Furthermore, the first layer 552 contains the additives included in the second layer 553. The additives in the first layer 552 are present in a ratio of 0.01% to 1% relative to the main constituent material, zirconium oxide (ZrO2).

[0058] Furthermore, the diaphragm 550 is not limited to the lamination of the third layer 551 and the first layer 552 described above, but may also be composed of a single layer consisting of the first layer 552, or of three or more layers.

[0059] For example, an adhesion layer may be provided on the surface of the third layer 551 facing the Z1 direction to enhance adhesion between it and the first layer 552 or the second layer 553. The adhesion layer is made of a different material from the third layer 551 and the first layer 552. For example, the adhesion layer is made of titanium oxide.

[0060] Furthermore, the arrangement of the second layer 553 is not limited to the arrangement described above, but may also be in the following arrangements. For example, the second layer 553 may be formed on the surface of the first layer 552 facing the Z1 direction. In this case, the additive diffuses inward from the surface of the first layer 552 facing the Z1 direction. Alternatively, the second layer 553 may be formed on both the surface of the first layer 552 facing the Z2 direction and the surface of the first layer 552 facing the Z1 direction.

[0061] Alternatively, a configuration may be one in which no region with a high concentration of additives relative to the main constituent elements is formed, as in the second layer 553, and the concentration of additives is uniform throughout the first layer 552. In this case, the first layer 552 is made to contain additives by doping the target with additives when depositing the first layer 552, or by ion implantation into the first layer 552.

[0062] Furthermore, the third layer 551 is not limited to a structure consisting mainly of silicon oxide (SiO2). For example, the third layer 551 may be formed from a single or multiple layer of a material containing one or more elements selected from titanium (Ti), silicon (Si), aluminum (Al), tantalum (Ta), chromium (Cr), iridium (Ir), haunium (Hf), zirconium (Zr), and carbon (C) in any state as elemental, oxide, or nitride. For example, the third layer 551 may be a structure in which multiple layers of silicon oxide (SiO2) and silicon nitride (SiN) are stacked. Alternatively, the third layer 551 may be a structure in which multiple layers of silicon oxide (SiO2) and titanium oxide (TiO2) are stacked.

[0063] Furthermore, the relative thicknesses of the third layer 551 and the first layer 552 are not limited to the illustrated example and are arbitrary.

[0064] In the diaphragm 550 with the above general configuration, the inventors, through diligent research, have discovered that the occurrence of cracks in the first layer 552 is due to the ratio of cubic zirconium oxide to monoclinic layers. One reason why crack occurrence can be suppressed is that in regions where the zirconium oxide crystal grains grow at an angle to the substrate, a force is generated that pushes the film in a planar direction as the crystals grow, compared to when the crystal grains grow perpendicular to the substrate. As a result, the inventors believe that increasing the ratio of cubic crystals reduces the tensile stress in the first layer 552, making it less prone to cracking. It should be noted that, conventionally, the relationship between the ratio of cubic zirconium oxide to monoclinic layers and the reduction of tensile stress was unknown.

[0065] The film stress of a thin film on a substrate is expressed by the following Stoney equation.

number

[0066] As this equation shows, film stress is proportional to Young's modulus. Therefore, the smaller the Young's modulus, the smaller the film stress.

[0067] On the other hand, it is known that the Young's modulus of cubic zirconium oxide (212 GPa) is smaller than that of monoclinic zirconium oxide (249 GPa or 241 GPa).

[0068] Based on the above investigations, when zirconium oxide contained in the first layer 552 was measured by X-ray diffraction, the first intensity P1 was defined as the intensity for cubic crystal (111), and the second intensity P2 was defined as the intensity for monoclinic crystal (111). The ratio of the first intensity P1 to the sum of the first and second intensities (P1+P2), P1 / (P1+P2), was 40% or more. This makes it possible to increase the proportion of cubic crystal (111) zirconium oxide contained in the first layer 552 relative to monoclinic crystal (111). As a result, crack generation can be suppressed.

[0069] Figure 6 is an explanatory diagram of the first intensity P1 and the second intensity P2. Figure 6 shows the results of X-ray analysis of the first layer 552, which has a configuration corresponding to Example 5 described later.

[0070] Here, the first intensity P1 is the difference between the maximum and minimum values ​​of the spectrum in the range where the cubic (111) peak exists. The second intensity P2 is the difference between the maximum and minimum values ​​of the spectrum in the range where the monoclinic (111) peak exists.

[0071] The ratio P1 / (P1+P2) of the first strength P1 to the sum of the first strength P1 and the second strength P2 (P1+P2) is preferably 50% or more, and more preferably 57% or more. When the ratio P1 / (P1+P2) is 50% or more, the displacement of the diaphragm 550 can be increased while suppressing crack occurrence, compared to the configuration where the ratio P1 / (P1+P2) is less than 50%. Furthermore, when the ratio P1 / (P1+P2) is 57% or more, the film stress of the first layer 552 can be reduced to 100 MPa or less. As a result, the occurrence of cracks in the diaphragm 550 can be suitably suppressed. Note that when the ratio P1 / (P1+P2) is 57% or more, the first strength P1 is greater than the second strength P2.

[0072] The tensile stress of the first layer 552 is preferably 100 MPa or less. This suppresses the occurrence of cracks in the diaphragm 550. Conversely, if the tensile stress of the first layer 552 is too high, there is a risk of cracks occurring in the diaphragm 550.

[0073] Compressive stress refers to the internal stress generated in one of two layers when that layer is subjected to a compressive force by the other layer. This internal stress has a repulsive force against the compressive force that the other layer receives from the first layer. On the other hand, tensile stress refers to the internal stress generated in one of two layers when that layer is subjected to a tensile force by the other layer. This internal stress has a repulsive force against the tensile force that the other layer receives from the first layer.

[0074] The first layer 552 preferably contains, in addition to zirconium oxide, at least one element from among carbon, aluminum, titanium, chromium, iron, hafnium, yttrium, and cerium. This allows the first intensity P1 to be preferably greater than the second intensity P2. In other words, the proportion of cubic crystals (111) can be increased.

[0075] The at least one element is included in the first layer 552 as an additive element. Such a first layer 552 is formed by diffusing the additive contained in the second layer 553 into the first layer 552. Alternatively, such a first layer 552 may be formed by sputtering or the like using a target containing the at least one element, or by introducing the at least one element into a zirconium oxide layer deposited by any method, such as by ion implantation.

[0076] In particular, it is preferable that the first layer 552 contains an element with the same valence as zirconium as an additive element. This can improve the insulating properties of the first layer 552 and reduce the leakage current to the diaphragm 550.

[0077] Elements with the same valency as Zr (valency: 4+) include, for example, titanium, hafnium, and cerium.

[0078] Furthermore, it is preferable that the first layer 552 contains carbon. This makes it possible to increase the proportion of cubic crystals (111) while lowering the film stress of the first layer 552.

[0079] When a second layer 553 containing an additive element is formed in the first layer 552, the additive element is present in the first layer 552. By supplying the additive from the second layer 553 to the first layer 552, the first intensity P1 can be preferably made greater than the second intensity P2. As a result, the proportion of cubic crystals (111) can be increased.

[0080] When the second layer 553 contains titanium, the thickness of the second layer 553 is 1 nm or more and 15 nm or less, preferably 1 nm or more and 10 nm or less. By including titanium, which is easily permeable to heat diffusion, in the second layer 553, titanium can be suitably diffused into the first layer 552 as an additive element. However, if the thickness of the second layer 553 is greater than 15 nm, the amount of titanium that diffuses into the first layer 552 increases, resulting in areas with low density in both the second layer 553 and the first layer 552, which may result in the diaphragm 550 becoming brittle. By making the thickness of the second layer 553 15 nm or less, the increase in the brittleness of the diaphragm 550 can be suppressed.

[0081] Furthermore, the titanium diffused into the first layer 552 is replaced, for example, at the zirconium sites of zirconium oxide.

[0082] When a second layer 553 containing an additive element to be added to the first layer 552 is formed on top of the first layer 552, the additive element is included in the first layer 552. By supplying the additive from the second layer 553 to the first layer 552, the first intensity P1 can be preferably made greater than the second intensity P2. As a result, the proportion of cubic crystals (111) can be increased.

[0083] 1-4: Method for manufacturing a piezoelectric actuator Figures 7 and 8 are explanatory diagrams of a method for manufacturing a piezoelectric actuator 130 according to an embodiment. The method for manufacturing the piezoelectric actuator 130 includes steps ST1 to ST6 in that order, as shown in Figures 7 and 8. Each step will be described in order below.

[0084] Step ST1 involves preparing the substrate 520A. Substrate 520A is a substrate that will become the pressure chamber substrate 520 through processing, and is, for example, a silicon single crystal substrate.

[0085] Step ST2 is performed after step ST1 to form a third layer 551 on one surface of the substrate 520A. The third layer 551 is formed, for example, by thermal oxidation of one surface of the substrate 520A.

[0086] Step ST3, following step ST2, forms layers 553A and 552A in that order on the third layer 551. Layer 553A is a layer for forming the second layer 553, and is formed, for example, by depositing titanium by sputtering. Layer 552A is a layer for forming the first layer 552, and is formed, for example, by depositing zirconium by sputtering.

[0087] In step ST4, following step ST3, layers 553A and 552A are simultaneously thermally oxidized to form the second layer 553 and the first layer 552. This forms the diaphragm 550.

[0088] In step ST4, at least some of the elements such as titanium contained in layer 553A diffuse into layer 552A. This increases the proportion of cubic (111) zirconium oxide in the first layer 552.

[0089] The heating temperature in step ST4 is preferably, for example, 500°C to 1000°C, and more preferably 500°C to 700°C. This makes it possible to increase the proportion of cubic zirconium oxide (111) in the first layer 552.

[0090] Step ST5, following step ST4, forms a piezoelectric element 560 on the first layer 552. Specifically, step ST5 deposits the first electrode 561, the piezoelectric layer 563, and the second electrode 562 on the diaphragm 55 in that order. Here, the formation of the first electrode 561 and the second electrode 562 is carried out using known film deposition techniques such as sputtering, and known processing techniques such as photolithography and etching. The piezoelectric layer 563 is formed, for example, by forming a piezoelectric precursor layer by a solution process, and then firing the precursor layer to crystallize it. The piezoelectric layer 563 is also subjected to polarization treatment by applying a voltage between the first electrode 561 and the second electrode 562.

[0091] In step ST6, following step ST5, a plurality of pressure chambers C1 are formed in the substrate 520A. This forms the pressure chamber substrate 520. Thus, the piezoelectric actuator 130 is obtained. Furthermore, after step ST6, the liquid discharge head 50 is obtained through a known appropriate process.

[0092] Furthermore, when an adhesion layer is provided on the upper surface of the third layer 551, a step for forming the adhesion layer is provided between steps ST2 and ST3. In this step, for example, a layer for forming the adhesion layer is formed by depositing titanium by sputtering, and the layer is heated to oxidize the titanium and form an adhesion layer composed of titanium oxide. Here, as described above, the process for forming the second layer 553 and the adhesion layer is different.

[0093] 2. Examples The following describes specific examples.

[0094] 2-1. Manufacturing of Piezoelectric Actuators 2-1-1. Example 1 First, a 1500 nm thick first layer composed of silicon oxide was formed by thermal oxidation of one side of a silicon single crystal substrate with a (110) orientation.

[0095] Next, a 10 nm thick titanium film and a 400 nm thick zirconium film were deposited on the first layer in that order by sputtering. Then, the second and third layers were formed by thermal oxidation and firing of these films at an annealing temperature of 600°C. For the deposition of the zirconium film, target B, which contains additive elements, was used as the Zr target, as shown in Figure 9.

[0096] Then, a laminate consisting of a titanium layer, a platinum layer, and an iridium layer was formed on the second layer by sputtering, and the first electrode of the piezoelectric element was formed by processing the laminate using photolithography and dry etching.

[0097] Next, a piezoelectric layer consisting of multiple layers, made of lead zirconate titanate, was formed using a solution process.

[0098] Next, a second electrode, consisting of an iridium layer and a titanium layer, was formed on the piezoelectric layer by sputtering.

[0099] Subsequently, a pressure chamber was formed by anisotropic etching of the other side of the silicon single crystal substrate using an aqueous potassium hydroxide solution (KOH) or the like as an etching solution. A piezoelectric actuator was then manufactured.

[0100] 2-1-2. Example 2 A piezoelectric actuator was manufactured in the same manner as in Example 1, except that the deposition of a titanium film was omitted, that is, the formation of the third layer was omitted.

[0101] 2-1-3. Example 3 A piezoelectric actuator was manufactured in the same manner as in Example 1, except that the thickness of the titanium film was set to 2 nm.

[0102] 2-1-4. Example 4 A piezoelectric actuator was manufactured in the same manner as in Example 1, except that the annealing temperature was set to 900°C.

[0103] 2-1-5. Example 5 A piezoelectric actuator was manufactured in the same manner as in Example 2, except that the annealing temperature was set to 900°C.

[0104] 2-1-6. Example 6 A piezoelectric actuator was manufactured in the same manner as in Example 4, except that target A shown in Figure 9 was used as the Zr target. That is, a piezoelectric actuator was manufactured in the same manner as in Example 1, except that target A shown in Figure 9 was used as the Zr target and the annealing temperature was set to 900°C. Target A is a target with a lower amount of added elements than target B. For example, target A has lower content of C, Al, Cr, and Fe than target B.

[0105] 2-1-7. Comparative Example A piezoelectric actuator was manufactured in the same manner as in Example 6, except that the deposition of a titanium film was omitted, that is, the formation of the third layer was omitted.

[0106] 2-2. Ratio of intensity Figure 10 shows the results of measuring the ratio P1 / (P1+P2) based on the analysis of the second layer by X-ray for Examples 1-6 and the Comparative Example. Figure 11 shows the results of analyzing the second layer by X-ray for Example 1 and the Comparative Example. In addition to the ratio P1 / (P1+P2), Figure 10 also shows the ratio P2 / P1 and the ratio P2(P1+P2).

[0107] X-ray analysis was performed by thin-film X-ray diffraction using a multi-axis X-ray diffractometer. Here, Cu was used as the X-ray source, and CuKα rays with a wavelength of 1.5418 Å were used as the characteristic X-ray. Out-of-plane measurements were performed by detecting the diffracted X-rays with a two-dimensional detector. The detection angle 2θ of the diffracted X-rays was set from 20 to 50 degrees, and γ (the tilt angle on the secondary detector side) was set to a range of -50° to -130° when the direction perpendicular to the substrate (position perpendicular to the substrate) is set to -90°, and to a range of -40° to +40° when the direction perpendicular to the substrate (position perpendicular to the substrate) is set to 0°.

[0108] As shown in Figure 10, in Examples 1-6, the ratio P1 / (P1+P2) is 40% or more, whereas in the comparative example, the ratio P1 / (P1+P2) is less than 40%. Also, as shown in Figure 11, in Example 1, the cubic (111) peak is larger than in the comparative example, while the monoclinic (111) peak is smaller than in the comparative example. Furthermore, in Example 1, the monoclinic (-111) peak is smaller than in the comparative example.

[0109] 2-2. Evaluation 2-2-1. Crack Figure 10 shows the results of the durability test for Examples 1-6 and Comparative Example 1, specifically regarding the presence or absence of cracks. This durability test measures whether cracks occur within a specified time limit when a high voltage is applied to a piezoelectric element and it is continuously driven in a high-temperature, high-humidity environment. In this test, the occurrence of cracks was judged as "present," and the absence of cracks was judged as "absent."

[0110] As shown in Figure 10, no cracks occurred in Examples 1-6, whereas cracks occurred in the comparative example.

[0111] 2-2-2. Displacement Figure 10 shows the results of measuring the diaphragm displacement for Examples 1-6 and the Comparative Example. This measurement was performed by measuring the diaphragm displacement when a voltage difference of 25V or more was applied to the piezoelectric element. Note that the displacements shown in Figure 10 are relative values, with the displacement in each example and comparative example set to the displacement in the comparative example as the baseline (100%).

[0112] As shown in Figure 10, the displacement of the diaphragm is larger in Examples 1-6 compared to the comparative example.

[0113] 3: Variant Each of the forms exemplified above can be modified in various ways. Specific examples of modifications that can be applied to each of the aforementioned forms are given below. Any form selected from the following examples can be combined as appropriate, provided they do not contradict each other.

[0114] 3-1: Variation 1 In the embodiments described above, an example is shown in which the second electrode 562 is a common electrode. However, the embodiment is not limited to this example, and the second electrode 562 may be an individual electrode for each piezoelectric element 650. In this case, the first electrode 561 may be a common electrode common to multiple piezoelectric elements 560. However, even when the first electrode 561 is a common electrode and the second electrode 562 is an individual electrode, the piezoelectric layer 563 includes a region that does not overlap with the first electrode 561.

[0115] 3-2: Variation 2 In the embodiments described above, a serial-type liquid dispensing device 100 was exemplified, in which a transporter 41 equipped with a liquid dispensing head 50 is moved back and forth. However, this disclosure also applies to a line-type liquid dispensing device in which multiple nozzles N are distributed across the entire width of the recording medium M.

[0116] 3-3: Modification 3 The liquid dispensing device 100 exemplified in the above-described form may be used in various devices such as facsimile machines and photocopiers, in addition to equipment dedicated to printing, and the applications of this disclosure are not particularly limited. However, the applications of the liquid dispensing device are not limited to printing. For example, a liquid dispensing device that dispenses a colorant solution can be used as a manufacturing device for forming color filters for display devices such as liquid crystal display panels. A liquid dispensing device that ejects a conductive material solution can be used as a manufacturing device for forming wiring and electrodes on a wiring board. A liquid dispensing device that ejects a solution of organic matter related to living organisms can be used, for example, as a manufacturing device for producing biochips.

[0117] 4. Addendum A summary of this disclosure is provided below.

[0118] (Note 1) A first embodiment of a piezoelectric actuator of the present disclosure comprises a piezoelectric element and a diaphragm that vibrates by driving the piezoelectric element, wherein the diaphragm includes a first layer containing zirconium oxide as the main constituent material, and when the zirconium oxide contained in the first layer is measured by X-ray diffraction, the intensity for cubic crystal (111) is defined as the first intensity and the intensity for monoclinic crystal (111) is defined as the second intensity, the ratio of the first intensity to the sum of the first and second intensities is 40% or more.

[0119] In the above embodiment, the proportion of cubic (111) zirconium oxide in the first layer can be increased relative to monoclinic (111) zirconium oxide. As a result, crack formation can be suppressed.

[0120] (Note 2) In the second embodiment, which is a preferred example of the first embodiment, the ratio of the first strength to the sum of the first strength and the second strength is 50% or more. In this embodiment, the displacement of the diaphragm can be increased compared to the embodiment in which the ratio is less than 50%. Therefore, the displacement of the diaphragm can be secured while suppressing the occurrence of cracks.

[0121] (Note 3) In the third embodiment, which is a preferred example of the second embodiment, the ratio of the first strength to the sum of the first strength and the second strength is 57% or more. In the above embodiment, the film stress of the first layer can be reduced to 100 MPa or less. As a result, the occurrence of cracks in the diaphragm can be suitably suppressed.

[0122] (Note 4) In the fourth embodiment, which is a preferred example of the third embodiment, the tensile stress of the first layer is 100 MPa or less. In the above embodiments, the occurrence of cracks in the diaphragm can be suppressed. On the other hand, if the tensile stress of the second layer is too high, there is a risk that cracks will occur in the diaphragm.

[0123] (Note 5) In a fifth embodiment, which is a preferred example of any of the first to fourth embodiments, the first layer contains at least one element from carbon, aluminum, titanium, chromium, iron, hafnium, yttrium, and cerium. In the above embodiments, the first intensity can be preferably made greater than the second intensity. That is, the proportion of cubic crystals (111) can be increased.

[0124] (Note 6) In the sixth embodiment, which is a preferred example of any of the first to fifth embodiments, the first layer has an element with the same valence as zirconium. In the above embodiments, the insulating properties of the first layer can be increased, and the leakage current to the diaphragm can be reduced.

[0125] (Note 7) In the seventh embodiment, which is a preferred example of the fifth embodiment, the first layer contains carbon. In the above embodiments, the film stress of the first layer can be reduced while increasing the proportion of cubic crystals (111).

[0126] (Note 8) In the eighth embodiment, which is a preferred example of any of the first to seventh embodiments, the diaphragm further comprises a third layer containing silicon oxide located below the first layer in the thickness direction of the first layer, and a second layer provided between the first layer and the third layer in the thickness direction and containing an element different from zirconium, wherein the element different from zirconium is included in the first layer. In the above embodiments, the first intensity can be preferably made greater than the second intensity by supplying additives from the second layer to the first layer. As a result, the proportion of cubic crystals (111) can be increased.

[0127] (Note 9) In the ninth embodiment, which is a preferred example of the eighth embodiment, the second layer contains titanium, and the thickness of the second layer is 10 nm or less. In the above embodiments, by including titanium in the second layer, which is easily thermally diffused, titanium can be suitably diffused into the first layer. Furthermore, by having a second layer thickness of 10 nm or less, the reduction in the strength of the diaphragm can be reduced.

[0128] (Note 10) In the tenth embodiment, which is a preferred example of any of the first to ninth embodiments, the diaphragm has a second layer above the first layer in the thickness direction of the first layer, the second layer containing an element different from zirconium, and the element different from zirconium is included in the first layer. In the above embodiments, by supplying impurities from the second layer to the first layer, the first intensity can be preferably made greater than the second intensity. As a result, the proportion of cubic crystals (111) can be increased.

[0129] (Note 11) In the 11th embodiment, which is a preferred example of any of the first to tenth embodiments, the diaphragm includes a layer containing silicon oxide below the first layer in the thickness direction of the first layer. The layer containing silicon oxide has compressive stress. On the other hand, the first layer has tensile stress. Therefore, since the directions of the internal stress in the layer containing silicon oxide and the first layer are opposite, the internal stresses generated in the diaphragm cancel each other out, and the overall internal stress of the diaphragm can be reduced.

[0130] (Note 12) An eleventh embodiment, which is a preferred example of the liquid dispensing head of the present disclosure, has a piezoelectric actuator according to any of the first to tenth embodiments. In these embodiments, a liquid dispensing head with excellent reliability can be provided. [Explanation of symbols]

[0131] 10...Liquid container, 20...Control module, 30...Transport mechanism, 40...Moving mechanism, 41...Transport body, 42...Transport belt, 50...Liquid discharge head, 53...Third layer, 55...Diaphragm, 100...Liquid discharge device, 110...First wiring, 120...Second wiring, 121...Conductive layer, 122...Conductive layer, 130...Piezoelectric actuator, 510...Communicating substrate, 511...First layer, 520...Pressure chamber substrate, 520A...Substrate, 530...Nozzle plate, 540...Vibration absorber, 550...Diaphragm, 551...First layer, 552...Second layer, 552A...Layer, 553...Third layer, 553A...Layer, 560...Piezoelectric element, 561...First electrode, 56 2...Second electrode, 563...Piezoelectric layer, 570...Protective substrate, 580...Case, 590...Wiring board, 600...Drive circuit, 650...Piezoelectric element, C1...Pressure chamber, Com...Drive signal, FN...Nozzle surface, G...Notch, HL...Inlet, Ln1...First nozzle row, Ln2...Second nozzle row, M...Recording medium, N...Nozzle, Na...Communication channel, P1...First intensity, P2...Second intensity, R...Reservoir, R1...Channel, R2...Channel, Ra...Supply channel, S...Space, SI...Control signal, ST1...Process, ST2...Process, ST3...Process, ST4...Process, ST5...Process, ST6...Process, t1...Thickness, t2...Thickness, t3...Thickness.

Claims

1. Piezoelectric element and The system comprises a diaphragm that vibrates when driven by the piezoelectric element, The diaphragm includes a first layer containing zirconium oxide as its main constituent material. When the zirconium oxide contained in the first layer is measured by X-ray diffraction, the intensity for the cubic crystal (111) is defined as the first intensity, and the intensity for the monoclinic crystal (111) is defined as the second intensity, The ratio of the first intensity to the sum of the first and second intensities is 40% or more. A piezoelectric actuator characterized by the following features.

2. The ratio of the first intensity to the sum of the first and second intensities is 50% or more. The piezoelectric actuator according to feature 1.

3. The ratio of the first intensity to the sum of the first and second intensities is 57% or more. The piezoelectric actuator according to feature 2.

4. The tensile stress of the first layer is 100 MPa or less. The piezoelectric actuator according to feature 3.

5. The first layer contains at least one element from carbon, aluminum, titanium, chromium, iron, hafnium, yttrium, and cerium. A piezoelectric actuator according to any one of claims 1 to 4.

6. The first layer has an element with the same valence as zirconium, A piezoelectric actuator according to any one of claims 1 to 4.

7. The first layer contains carbon, The piezoelectric actuator according to feature 5.

8. The diaphragm is located below the first layer in the thickness direction of the first layer, A third layer containing silicon oxide, The present invention further comprises a second layer provided between the first and third layers in the thickness direction, and containing an element different from zirconium. The elements different from zirconium are included in the first layer. A piezoelectric actuator according to any one of claims 1 to 4.

9. The aforementioned second layer contains titanium, The thickness of the second layer is 10 nm or less. The piezoelectric actuator according to feature 8.

10. The diaphragm has a second layer containing an element different from zirconium, located above the first layer in the thickness direction of the first layer. The elements different from zirconium are included in the first layer. A piezoelectric actuator according to any one of claims 1 to 4.

11. The diaphragm includes a layer containing silicon oxide below the first layer in the thickness direction of the first layer. A piezoelectric actuator according to any one of claims 1 to 4.

12. A piezoelectric actuator according to any one of claims 1 to 4, A liquid dispensing head characterized by the following features.

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