Piezoelectric element, liquid dispensing head, and liquid dispensing device

Abstract

To provide a piezoelectric element in which the degradation of piezoelectric properties is suppressed.SOLUTION: A piezoelectric element consists of a first electrode, a seed layer, a piezoelectric material layer, and a second electrode stacked on a substrate, and the seed layer is a composite oxide containing at least Pb, Bi, Fe, and Ti.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] This disclosure relates to a piezoelectric element, a liquid dispensing head, and a liquid dispensing device. [Background technology]

[0002] Generally, piezoelectric elements have a structure in which a lower electrode layer, a piezoelectric layer, and an upper electrode layer are stacked on a substrate in this order. For example, when the piezoelectric layer is made of lead zirconate titanate (hereinafter referred to as PZT) with a rhombohedral crystal structure, it is known that the piezoelectric properties are improved when the PZT layer is oriented to the (100) plane. Therefore, a method for oriented the PZT layer to the (100) plane has been proposed (for example, Patent Document 1). Patent Document 1 discloses a structure having an orientation control layer made of lanthanum nickelate below the PZT layer. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2004-66600 [Overview of the project] [Problems that the invention aims to solve]

[0004] However, in the piezoelectric element described in Patent Document 1, during processes such as heat treatment in manufacturing, lanthanum or nickel in the orientation control layer may diffuse into the piezoelectric layer, potentially degrading the piezoelectric properties. [Means for solving the problem]

[0005] This disclosure can be implemented in the following forms. According to one embodiment of this disclosure, a piezoelectric element is provided. This piezoelectric element is a piezoelectric element in which a first electrode, a seed layer, a piezoelectric layer, and a second electrode are laminated on a substrate, wherein the seed layer is a composite oxide containing at least Pb, Bi, Fe, and Ti.

[0006] Also, according to one embodiment of the present disclosure, a liquid ejection head is provided. This liquid ejection head includes the piezoelectric element and a drive circuit that drives the piezoelectric element.

[0007] Also, according to one embodiment of the present disclosure, a liquid ejection device is provided, which includes the liquid ejection head and a control unit that controls the operation of the liquid ejection head.

Brief Description of Drawings

[0008] [Figure 1] Schematic diagram showing a schematic configuration of a liquid ejection device. [Figure 2] Exploded perspective view of a liquid ejection head. [Figure 3] Cross-sectional view taken along line III-III in FIG. 2. [Figure 4] Plan view of a piezoelectric element. [Figure 5] Cross-sectional view taken along line V-V in FIG. 4. [Figure 6] Table showing compositions of seed layers of Examples (1) to (8) and Comparative Examples. [Figure 7] X-ray diffraction pattern measured on platinum of a Comparative Example. [Figure 8] X-ray diffraction patterns measured on platinum of Examples (1) to (7). [Figure 9] Enlarged view near the (100) peak of the X-ray diffraction patterns measured on platinum of Examples (1) to (7). [Figure 10] Enlarged view near the (110) peak of the X-ray diffraction patterns measured on platinum of Examples (1) to (7). [Figure 11] Enlarged view near the (111) peak of the X-ray diffraction patterns measured on platinum of Examples (1) to (7). [Figure 12] X-ray diffraction pattern measured on zirconium oxide of a Comparative Example. [Figure 13] X-ray diffraction patterns measured on zirconium oxide of Examples (1) to (7). [Figure 14] Enlarged view near the (100) peak of the X-ray diffraction patterns measured on zirconium oxide of Examples (1) to (7). [Figure 15] Magnified view of the area around the (110) peak of the X-ray diffraction pattern measured on zirconium oxide in Examples (1) to (7). [Figure 16] Magnified view of the area around the (111) peak of the X-ray diffraction pattern measured on zirconium oxide in Examples (1) to (7). [Figure 17] X-ray diffraction pattern measured on iridium in Example (8). [Modes for carrying out the invention]

[0009] A. Embodiments: A1. Overall configuration of the liquid dispensing device Figure 1 is a schematic diagram showing the general configuration of the liquid ejection device 100 in this embodiment. The liquid ejection device 100 is an inkjet printing device that performs printing by ejecting droplets of liquid ink onto a medium 12. The medium 12 can be any material, such as printing paper, resin film, or cloth. In the following description, the X, Y, and Z directions are mutually orthogonal. When specifying the direction, the positive direction is denoted as "+" and the negative direction as "-", and both positive and negative signs are used in the direction notation. In this embodiment, the X direction is the main scanning direction, which is the direction of movement of the liquid ejection head 26. The Y direction is the sub-scanning direction, which is the medium feeding direction perpendicular to the main scanning direction. The Z direction is the ink ejection direction.

[0010] The liquid dispensing device 100 comprises a liquid dispensing head 26, a head moving mechanism 20, a liquid storage section 14, a transport mechanism 16, and a control unit 80.

[0011] The liquid storage section 14 contains the ink supplied to the liquid ejection head 26. The liquid storage section 14 can be a pouch-shaped liquid pack made of a flexible film, an ink tank that allows for ink replenishment, or a removable ink cartridge.

[0012] The liquid ejection head 26 has a plurality of nozzles N for ejecting ink. The plurality of nozzles N are arranged in the Y direction. The liquid ejection head 26 ejects ink supplied from the liquid storage section 14 from the plurality of nozzles N toward the medium 12.

[0013] The head movement mechanism 20 comprises a conveyor belt 21 and a carriage 22 that houses the liquid discharge head 26. The carriage 22 is connected to the conveyor belt 21 and reciprocates in the X direction as the conveyor belt 21 is driven. The conveying mechanism 16 conveys the medium 12 in the +Y direction.

[0014] The control unit 80 includes processing circuits such as one or more CPUs (Central Processing Units) and FPGAs (Field Programmable Gate Arrays), and storage circuits such as semiconductor memory, and controls the operation of the entire liquid dispensing device 100. The control unit 80 is electrically connected to the transport mechanism 16, the head movement mechanism 20, and the liquid dispensing head 26, and controls each part. An image is printed on the medium 12, which is transported by the transport mechanism 16, by dispensing liquid from the nozzle N onto the medium 12.

[0015] A2. Configuration of the liquid dispensing head Figure 2 is an exploded perspective view of the liquid discharge head 26 according to the embodiment. Figure 3 is a cross-sectional view taken along line III-III in Figure 2. Figure 4 is a plan view of the piezoelectric element 44. Figure 5 is a cross-sectional view taken along line VV in Figure 4.

[0016] As shown in Figure 2, the liquid discharge head 26 includes a nozzle plate 62, two vibration absorbers 64, a flow path substrate 32, a pressure chamber substrate 34, a diaphragm 36, a wiring substrate 46, a drive circuit 50, and a housing portion 48. The nozzle plate 62, vibration absorbers 64, flow path substrate 32, pressure chamber substrate 34, diaphragm 36, and wiring substrate 46 are elongated plate-shaped members in the Y direction. Each of the nozzle plate 62, flow path substrate 32, pressure chamber substrate 34, and diaphragm 36 has a structure that is substantially symmetrical with respect to the center line in the X direction. The planar shapes of the pressure chamber substrate 34, diaphragm 36, and wiring substrate 46 are smaller than the planar shapes of the flow path substrate 32 and housing portion 48. During assembly, the nozzle plate 62, the two vibration absorbers 64, the flow path substrate 32, the pressure chamber substrate 34, the diaphragm 36, the wiring substrate 46, and the housing 48 are stacked in this order and bonded to each other, for example, with an adhesive.

[0017] The nozzle plate 62 is a plate-shaped member on which multiple nozzles N are formed. Each nozzle N is a through-hole with a substantially circular planar shape. The multiple nozzles N are arranged along the Y direction. There are two rows of nozzles N, and these two rows are aligned in the X direction. The two vibration absorbers 64 are flexible films and are positioned in the X direction, flanking the nozzle plate 62.

[0018] The flow channel substrate 32 has two first openings 32a, a plurality of second openings 32b, and a plurality of third openings 32c. The planar shape of the first openings 32a is a rectangle that is elongated in the Y direction. The first opening 32a is formed along the edge of the flow channel substrate 32 parallel to the Y direction. Multiple second openings 32b are arranged in the Y direction. Similarly, multiple third openings 32c are arranged in the Y direction. There are two rows of second openings 32b and two rows of third openings 32c. In the X direction, the first opening 32a, one row of second openings 32b, one row of third openings 32c, one row of third openings 32c, one row of second openings 32b, and the first opening 32a are formed in this order. Furthermore, adjacent second openings 32b and third openings 32c in the X direction are formed such that their positions in the Y direction are approximately identical.

[0019] Multiple openings 34a are formed in the pressure chamber substrate 34. The planar shape of the openings 34a is a rectangle that is elongated in the X direction. The multiple openings 34a are arranged in the Y direction. There are two rows in which the multiple openings 34a are arranged, and these two rows are formed side by side in the X direction. The openings 34a are formed in positions that overlap with the adjacent second opening 32b and third opening 32c formed in the flow channel substrate 32 when viewed from the Z direction.

[0020] On the diaphragm 36, a piezoelectric element 44 is formed at a position that overlaps with the opening 34a formed in the pressure chamber substrate 34 when viewed from the Z direction.

[0021] The drive circuit 50 drives the piezoelectric element 44. More specifically, the drive circuit 50 is implemented as an IC (Integrated Circuit) chip that outputs a drive signal and a reference voltage for driving the piezoelectric element 44. The drive circuit 50 is mounted on a wiring board 46. Wiring for the input signal to the drive circuit 50 and the drive signal and reference voltage output from the drive circuit 50 is formed on the wiring board 46. As shown in Figure 3, the wiring board 46 and the piezoelectric element 44 are joined via bump B. Input signals to the drive circuit 50 are input to terminals formed on the wiring board 46 (not shown), for example, via FPCs (Flexible Printed Circuits).

[0022] The housing portion 48 is a case for storing ink and has a frame shape. When stacked, the pressure chamber substrate 34, the diaphragm 36, and the wiring substrate 46 are arranged in the internal space of the housing portion 48. Through holes 48a are formed at each of the ends of the housing portion 48 in the X direction.

[0023] The cross-sectional structure of the liquid discharge head 26 will be explained using Figure 3. At each end of the housing portion 48 in the X direction, a space Rb extending in the Y direction is formed. Space Rb is in communication with the through hole 48a. Space Ra, the supply liquid chamber 26a, and the supply flow path 26b are formed by connecting the flow path substrate 32 and the vibration absorber 64. Space Ra is the internal space of the first opening 32a. The supply liquid chamber 26a is the space surrounded by the partition wall 32d separating the first opening 32a and the second opening 32b, and the vibration absorber 64. The supply flow path 26b is the internal space of the second opening 32b. Space Ra is in communication with space Rb and the supply liquid chamber 26a, and the supply liquid chamber 26a is in communication with the supply flow path 26b. The pressure chamber C is formed by connecting the pressure chamber substrate 34 and the diaphragm 36. The pressure chamber C is a space enclosed by the opening 34a and the diaphragm 36. The pressure chamber C is in communication with the supply channel 26b. The communication channel 26c is formed by the connection between the channel substrate 32 and the nozzle plate 62. The communication channel 26c is the internal space of the third opening 32c. The communication channel 26c is in communication with the pressure chamber C and the nozzle N.

[0024] Spaces Ra and Rb function as liquid storage chambers for storing ink supplied to the pressure chamber C. Space Rb communicates with multiple spaces Ra aligned in the Y direction, and the ink supplied through the through-hole 48a is stored in the multiple spaces Ra via space Rb. The ink stored in space Ra flows through the supply liquid chamber 26a and the supply channel 26b and is supplied to the pressure chamber C.

[0025] In a plan view from the Z direction, piezoelectric elements 44 are positioned to overlap with each of the two pressure chambers C, and a wiring board 46 and a drive circuit 50 are arranged to cover the two pressure chambers C. A drive signal and a reference voltage are input from the wiring board 46 to the piezoelectric elements 44 via bumps B. When a drive signal and a reference voltage are input, the piezoelectric element 44 deforms when the voltage is applied, and the diaphragm 36 vibrates in conjunction with the deformation of the piezoelectric element 44, causing the pressure in the pressure chamber C to fluctuate, which in turn causes ink to be ejected from the nozzle N.

[0026] A3. Structure of the piezoelectric element As shown in FIG. 5, the diaphragm 36 as a substrate has a silicon substrate 361 and an insulator layer 362. The piezoelectric element 44 is formed by laminating a first electrode 441, a seed layer 442, a piezoelectric layer 443, and a second electrode 444 on the diaphragm 36 in this order. Here, when viewed from the Z direction, the portion where the first electrode 441, the seed layer 442, the piezoelectric layer 443, and the second electrode 444 overlap is referred to as the active part 440. The active part 440 is a part where the piezoelectric layer 443 is deformed when a voltage is applied between the first electrode 441 and the second electrode 444.

[0027] Located on the +Z direction side of the silicon substrate 361, silicon dioxide is formed on the surface in contact with the insulator layer 362. The insulator layer 362 is made of zirconium oxide (ZrO2). The first electrode 441 is composed of a titanium (Ti) layer and a platinum (Pt) layer.

[0028] Note that the first electrode 441 is not limited to a plurality of layers of a Ti layer and a Pt layer. For example, it may be a single layer of a metal material such as Ti, Pt, iridium (Ir), aluminum (Al), nickel (Ni), gold (Au), copper (Cu), etc., or a plurality of these metal materials may be laminated to form it.

[0029] The seed layer 442 functions as an orientation control layer for controlling the orientation of the piezoelectric layer 443 described later. The seed layer 442 is a composite oxide containing at least lead (Pb), bismuth (Bi), iron (Fe), and titanium (Ti). Specifically, the seed layer 442 is Pb x Bi (a-x) Fe y Ti (b-y) O z It is preferably composed of a composite oxide represented by. However, a > x and b > y. Here, it is preferable that x / (a - x) satisfies the following formula (1). 0.04 < x / (a - x) < 1.40 ··· Formula (1) Furthermore, for the purpose of orienting the piezoelectric layer 443 to the (100) plane, it is preferable that x / (a - x) satisfies the formula (2). x / (a - x) < 0.72 ··· Equation (2) Also, it is preferable that b = 1, and a / b preferably satisfies Equation (3). 0.8 < (a / b) < 1.4 ··· Equation (3) z preferably satisfies Equation (4). 2.8 < z < 3.2 ··· Equation (4) Note that the composition of the seed layer 442 is the molar ratio of each element when preparing a solution of the organic compound of each element by the solution method described later. In this embodiment, a = 1.2, b = 1.0, x = 0.1, and y = 0.5. The seed layer 442 has a perovskite structure. The thickness T of the seed layer 442 is preferably 5 nm or more and 200 nm or less, and more preferably 5 nm or more and 100 nm or less. Also, the dielectric constant of the seed layer 442 is considered to be relatively high. Therefore, the displacement efficiency indicated by the displacement amount of the piezoelectric layer 443 with respect to the applied voltage is good. Note that the seed layer 442 is not limited to the perovskite structure and may have a structure similar to the perovskite structure, such as a bismuth layered structure, having an octahedron in which six oxygens (O) are coordinated to Fe or Ti.

[0030] The piezoelectric layer 443 is made of a composite oxide containing Pb, Zr, and Ti as constituent elements and having a perovskite structure. In this embodiment, the piezoelectric layer 443 is made of lead zirconate titanate (PZT), which has a rhombohedral crystal system and a perovskite structure. However, the piezoelectric layer 443 is not limited to PZT, and for example, lead lanthanum zirconate titanate ((Pb,La)(Zr,Ti)O3), lead zirconium niobate titanate (Pb(Zr,Ti,Nb)O3), lead zirconium magnesium niobate titanate (Pb(Zr,Ti)(Mg,Nb)O3), etc. can be used. Furthermore, the piezoelectric layer 443 does not necessarily have to contain lead. Specifically, as a piezoelectric layer 443 that is substantially free of Pb, a composite oxide containing at least two of K, Na, Nb, Bi, Fe, Ti, and Ba and having a perovskite structure can also be used. More specifically, potassium sodium niobate ((K,Na)NbO3), bismuth sodium titanate ((Bi,Na)TiO3), bismuth ferrite (BiFeO3), barium titanate (BaTiO3), and bismuth potassium titanate ((Bi,K)TiO3) can also be used as the piezoelectric layer 443. Note that "substantially Pb-free" refers to cases where no Pb is present at all, or where only a very small amount of Pb is present as an impurity, without any functional benefit. The particle size of the piezoelectric layer 443 is preferably 2 μm or less, and more preferably 1 μm. It is known that a larger particle size in the piezoelectric layer 443 makes it more prone to cracking. Furthermore, a larger particle size in the piezoelectric layer 443 may reduce its durability. Therefore, by setting the particle size of the piezoelectric layer 443 to 1 μm or less, cracking in the piezoelectric layer 443 can be suppressed, thereby preventing a decrease in durability. In this embodiment, the particle size of the piezoelectric layer 443 is approximately several hundred nanometers.

[0031] When the first electrode 441 formed on the diaphragm 36 and the piezoelectric layer 443 formed on the seed layer 442 were analyzed from the stacking direction by X-ray diffraction, the peak intensity of the (100) plane in the X-ray diffraction pattern measured by X-ray diffraction was higher than the peak intensity of the (110) plane. Furthermore, in the X-ray diffraction pattern of the piezoelectric layer 443 formed on the seed layer 442 formed on the diaphragm 36, the peak intensity of the (100) plane was higher than the peak intensity of the (110) plane. In other words, the piezoelectric layer 443 is strongly oriented towards the (100) plane in the stacking direction of the piezoelectric element 44.

[0032] Generally, it is known that if the PZT constituting the piezoelectric layer 443 has a rhombohedral crystal structure, oriented to the (100) plane increases the amount of displacement, i.e., improves the piezoelectric properties. If the seed layer 442 is the composite oxide in this embodiment, the piezoelectric layer 443 can be oriented to the (100) plane. Therefore, the piezoelectric properties of the piezoelectric layer 443 can be improved by forming the seed layer 442 in this embodiment. Furthermore, by setting the thickness of the seed layer 442 to 5 nm or more and 200 nm or less, the piezoelectric layer 443 can be well oriented to the (100) plane while increasing the displacement efficiency of the piezoelectric layer 443. If the thickness of the seed layer 442 is less than 5 nm, it becomes difficult to uniformly deposit the seed layer 442, and the effect of oriented the piezoelectric layer 443 to the (100) plane decreases. If the thickness of the seed layer 442 is too thick, exceeding 200 nm, the dielectric constant of the PZT is higher than that of the seed layer 442, making it difficult to apply voltage to the piezoelectric layer 443 and reducing the displacement efficiency of the piezoelectric layer 443. Furthermore, since the constituent elements of the seed layer 442 are similar to those of the piezoelectric layer 443, even if the constituent elements of the seed layer 442 diffuse into the piezoelectric layer 443, it is possible to avoid degrading the piezoelectric properties of the piezoelectric element 44. In addition, since the seed layer 442 is not conductive, the piezoelectric element 44 of this embodiment can be constructed such that the seed layer 442 is in contact with the first electrode 441 and the second electrode 444. It should be noted that even if it is not PZT, if it has piezoelectric properties and a polarization axis in a direction other than the (100) direction, it is known that the piezoelectric properties will improve if it is oriented in the (100) plane, similar to PZT.

[0033] The second electrode 444 is made of Ir. However, the second electrode 444 is not limited to Ir, and may be a single layer of a metallic material such as Pt, Al, Ni, Au, or Cu, or it may be formed by laminating multiple layers of such metallic materials.

[0034] As shown in Figure 4, a first electrode 441 is formed for each pressure chamber C, i.e., for each active part 440. The first electrode 441 is led out in the +X direction and is individually electrically connected to the drive circuit 50. In contrast, the second electrode 444 is formed to cover a plurality of active parts 440 arranged in the Y direction. That is, the first electrode 441 is provided individually for a plurality of active parts 440, while the second electrode 444 is provided in common for a plurality of active parts 440. An individual voltage is applied to the first electrode 441 for each active part 440, and a common voltage is applied to the second electrode 444 for a plurality of active parts 440 arranged in the Y direction. The piezoelectric layer 443 is formed with through holes 443a between adjacent active parts 440. The through holes 443a are regions where the piezoelectric layer 443 is not formed. The seed layer 442 is formed to cover a plurality of piezoelectric elements 44 arranged in the Y direction.

[0035] A4. Method for fabricating piezoelectric elements First, the diaphragm 36 is fabricated. Specifically, silicon dioxide is formed on the +Z direction surface by thermal oxidation of the silicon substrate 361. Next, a Zr layer is formed by sputtering, and a ZrO2 layer, which serves as an insulating layer 362, is formed by thermal oxidation of the Zr.

[0036] Next, the first electrode 441 is formed. Specifically, a Ti layer and a Pt layer are sequentially stacked by sputtering. Next, the Ti layer and Pt layer are patterned using photolithography. Specifically, a resist is applied to the Pt layer, and after exposure, the Ti and Pt are ion-milled. Next, the resist is removed by oxygen plasma ashing, and the substrate is cleaned.

[0037] Next, seed layer 442 is formed using the MOD (Metal Organic Decomposition) method. Specifically, first, a propionic acid solution of Pb, Bi, Fe, and Ti, adjusted to a molar ratio of Pb:Bi:Fe:Ti = 10:110:50:50, is applied to the diaphragm 36 by spin coating. Next, it is dried and degreased at 350°C using a hot plate. Then, it is heat-treated at 700°C for 5 minutes using RTA (Rapid Thermal Annealing).

[0038] Next, the piezoelectric layer 443 is formed by a solution method. Specifically, the formation method involves first applying an acetic acid solution of Pb, Zr, and Ti, adjusted to a molar ratio of Pb:Zr:Ti = 118:52:48, onto the seed layer 442 by spin coating. Next, drying and degreasing are performed using a hot plate at 200°C and 410°C. Then, a heat treatment is performed using RTA (Rapid Thermal Annealing) at 740°C for 5 minutes.

[0039] Next, the second electrode 444 is formed. Specifically, Ir is layered using the sputtering method. Next, the Ir layer is patterned using photolithography.

[0040] B. Other embodiments: (B1) In the above embodiment, the first electrode 441 is formed for each active part 440, and the second electrode 444 is provided in common for a plurality of active parts 440 arranged in the Y direction. Alternatively, the first electrode 441 may be provided in common for a plurality of active parts 440 arranged in the Y direction, and the second electrode 444 may be provided for each active part 440.

[0041] (B2) The method for fabricating the piezoelectric element 44 is not limited to the above. For example, etching during patterning of the first electrode 441 may be performed by an etching method other than ion milling. Also, the method for forming the seed layer 442 is not limited to the MOD method, but may be other methods such as the sol-gel method or sputtering method.

[0042] (B3) In the above embodiment, the first electrode 441 is formed by laminating a Ti layer and a Pt layer. In order to be electrically connected to the drive circuit 50, the first electrode 441 is drawn out in the +X direction. In contrast, a wiring made of Ir is included between the first electrode 441 and the seed layer 442, and in plan view, the first electrode 441 is not drawn out outward from the active portion 440, and the wiring made of Ir may be configured to be conductive with the first electrode 441 and the drive circuit 50. In the case of this configuration, the seed layer 442 is formed on the ZrO2 layer, the Pt layer, and the Ir layer. In this configuration, in the X-ray diffraction pattern measured by the X-ray diffraction method for the first electrode 441 formed on the diaphragm 36, the wiring made of Ir, and the piezoelectric layer 443 formed on the seed layer 442, the peak intensity of the (100) plane is higher than the peak intensity of the (110) plane. Also, in the above embodiment, the first electrode 441 is formed by laminating a Ti layer and a Pt layer, but the first electrode 441 may be formed by laminating a Ti layer, a Pt layer, and an Ir layer in this order.

[0043] C. Examples and Comparative Examples: C1: Fabrication of Seed Layer and Piezoelectric Layer Examples (1) to (8) and comparative examples were fabricated by changing the composition ratio of the seed layer, specifically the Pb content. FIG. 6 shows the compositions of the fabricated seed layers of Examples (1) to (8) and the comparative examples. The compositions of the seed layers of Examples (1) to (8) and the comparative examples are Pb x Bi (a-x) Fe y Ti (b-y) O zThis is represented by the following. In Examples (1) to (8), the seed layer has a=1.2, and x is a value between 0.05 and 0.9. In the Comparative Example, the seed layer has x=0, meaning it is a composite oxide that does not contain Pb. The uppermost layer of the first electrode layer in Examples (1) to (7) and the Comparative Example is a Pt layer. Example (8) has the same configuration as the other embodiment (B3) described above, with an Ir layer formed on the first electrode layer, and a seed layer and a piezoelectric layer formed on the Ir layer. In Figure 6, the composition of the seed layer is shown along with x / a, which indicates the Pb substitution rate. In the "Lower Layer" column of Figure 6, the composition of the lower layer of the seed layer in the measured portion is shown when measuring the X-ray diffraction pattern described later.

[0044] In each experimental example and comparative example, a seed layer and a piezoelectric layer were formed on the diaphragm using the same manufacturing method as described above. Specifically, first, silicon dioxide was formed by thermal oxidation of a silicon substrate. Next, a Zr layer was formed by sputtering, and a ZrO2 layer was formed by thermal oxidation of the Zr layer. For Examples (1) to (7) and the comparative example, after the formation of the ZrO2 layer, Ti layers and Pt layers were sequentially laminated by sputtering. Next, the Ti layers and Pt layers were patterned using photolithography. Next, the seed layer and piezoelectric layer were formed. For Example (8), after the formation of the ZrO2 layer, Ti layers, Pt layers, and Ir layers were sequentially laminated. Next, the Ti layers, Pt layers, and Ir layers were patterned using photolithography. Next, the seed layer and piezoelectric layer were formed.

[0045] For Examples (1) to (8), the seed layer is formed by applying a propionic acid solution of Pb, Bi, Fe, and Ti, adjusted to the respective molar ratios, onto a diaphragm using a spin-coating method. Next, it is dried and degreased at 350°C using a hot plate. Then, it is heat-treated at 700°C for 5 minutes using an RTA (Rapid Thermal Annealing). For the comparative example, a propionic acid solution without Pb is used, and after application, it is dried, degreased, and heat-treated to form the seed layer. The molar ratio of each element in the propionic acid solution of the comparative example is Bi:Fe:Ti = 120:50:50.

[0046] The piezoelectric layer is made of PZT. The piezoelectric layer is formed similarly for Examples (1) to (8) and the Comparative Example. Specifically, first, an acetic acid solution of Pb, Zr, and Ti, adjusted to a molar ratio of Pb:Zr:Ti = 118:52:48, is applied to the seed layer by spin coating. Next, drying and degreasing are performed using a hot plate at 200°C and 410°C. Then, a heat treatment is performed using RTA (Rapid Thermal Annealing) at 740°C for 5 minutes.

[0047] C2: Evaluation of the piezoelectric layer The X-ray diffraction patterns of Examples (1) to (8) and the Comparative Example were measured to evaluate the degree of orientation of the piezoelectric layer. The X-ray diffraction apparatus used was a Bruker D8 DISCOVER with GADDS. The measurement conditions were: tube voltage: 50kV, tube current: 100mA, detector distance: 15cm, collimator diameter: 0.1mm, and measurement time: 180 seconds. The 2D data obtained from the measurement was converted into an X-ray diffraction intensity curve using a 2θ range of 20° to 40°, a χ range of -95° to -85°, a step size of 0.02°, and an intensity normalization method of Bin normalized. In Examples (1) to (7), the patterning of the Ti and Pt layers resulted in portions of the seed layer and piezoelectric layer formed on Pt and portions of the seed layer and piezoelectric layer formed on ZrO2. In the measurement of the X-ray diffraction patterns, measurements were performed for the portions of the seed layer and piezoelectric layer formed on Pt and for the portions of the seed layer and piezoelectric layer formed on ZrO2. Similarly, Example (8) has a seed layer and piezoelectric layer formed on Ir and a seed layer and piezoelectric layer formed on ZrO2, due to patterning of the Ti layer, Pt layer, and Ir layer. Of these, for Example (8), measurements were taken of the seed layer and piezoelectric layer formed on Ir.

[0048] FIG. 7 shows the X-ray diffraction pattern measured on Pt of the comparative example. FIG. 8 shows the X-ray diffraction patterns measured on Pt of Examples (1) to (7). In the X-ray diffraction pattern of the comparative example, the peak intensity of the (100) plane near 22° is low, the peak intensity of the (110) plane near 31° is recognized, and the peak intensity of the (111) plane near 38° is high. On the other hand, in the X-ray diffraction patterns measured on Pt of Examples (1) to (7), generally the peak intensity of the (100) plane is high. FIGS. 9 to 11 are the X-ray diffraction patterns on Pt of Examples (1) to (7) with the vicinity of the peak of the (100) plane, the vicinity of the (110) peak, and the vicinity of the (111) peak magnified, respectively. As shown in FIG. 9, the peak intensity of the (100) plane is low in the order of Example (3), Example (2), Example (4), Example (1), Example (5), Example (6), and Example (7). As shown in FIG. 10, the peaks of the (110) plane are recognized in Example (6) and Example (7). In Example (6) and Example (7), since the peaks of the (110) plane are recognized and the peak intensity of the (100) plane is low, it is considered that the effect of orienting PZT on the (100) plane is low in the seed layer where x / (a - x) indicating the substitution rate of Pb is 1.400 or more and x / a is 0.583 or more. On the other hand, in Examples (1) to (5), since the peaks of the (110) plane are not recognized and the peak intensity of the (100) plane is high, it is considered that the effect of orienting PZT on the (100) plane is high in the seed layer where x / (a - x) is 0.714 or less and x / a is 0.417 or less. From the above, for the seed layer represented by Pb x Bi (a-x) Fe y Ti (b-y) O z when the composition satisfies 0.04 < x / (a - x) < 1.40 and 0.04 < (x / a) < 0.58, PZT can be oriented on the (100) plane. Further, when the composition satisfies x / (a - x) < 0.72 and (x / a) < 0.42, the effect of orienting PZT on the (100) plane can be enhanced. As shown in FIG. 11, for Examples (1) to (7), the peaks of the (111) plane are not recognized.

[0049] Figure 12 shows the X-ray diffraction pattern measured on ZrO₂ of the comparative example. Figure 13 shows the X-ray diffraction patterns measured on ZrO₂ of Examples (1) to (7). The X-ray diffraction patterns measured on ZrO₂ show a similar tendency to those measured on Pt. In the X-ray diffraction pattern of the comparative example, the peak intensity of the (100) plane near 22° is low, and the peak intensity of the (110) plane near 32° is high. On the other hand, in the X-ray diffraction patterns measured on ZrO₂ of Examples (1) to (7), generally the peak intensity of the (100) plane is high. Figures 14 to 16 are the X-ray diffraction patterns on ZrO₂ of Examples (1) to (7), respectively, with the vicinity of the peak of the (100) plane, the vicinity of the peak of the (110) plane, and the vicinity of the peak of the (111) plane enlarged. As shown in Figure 14, the peak intensity of the (100) plane is small in the order of Example (2), Example (1), Example (3), Example (4), and Example (5). Also, in Examples (6) and (7), the peak of the (100) plane is not recognized. As shown in Figure 15, the peak intensity of the (110) plane is high in Example (6) and Example (7). In Examples (6) and (7), since the peak intensity of the (110) plane is high and the peak of the (100) plane is not recognized, it is considered that the effect of orienting PZT on the (100) plane is low in the seed layer where x / a is 0.583 or more. On the other hand, in Examples (1) to (5), the peak of the (110) plane is not recognized or the peak intensity is low, and the peak of the (100) plane is recognized. Therefore, in the seed layer where x / (a - x) is 0.714 or less and x / a is 0.417 or less, it is considered that the effect of orienting PZT on the (100) plane is high. From the above, for the seed layer represented by Pb x Bi (a-x) Fe y Ti (b-y) O z when the composition satisfies 0.04 < x / (a - x) < 1.40 and 0.04 < (x / a) < 0.58, PZT can be oriented on the (100) plane. Further, when the composition satisfies x / (a - x) < 0.72 and (x / a) < 0.42, the effect of orienting PZT on the (100) plane can be enhanced. As shown in Figure 16, for Examples (1) to (7), the peak of the (111) plane is not recognized.

[0050] Figure 17 shows the X-ray diffraction pattern measured on Ir in Example (8). The X-ray diffraction pattern measured on Ir shows a similar trend to the X-ray diffraction pattern measured on Pt. In the X-ray diffraction pattern measured on Ir, the peak intensity of the (100) plane is high, and the peak intensity of the (110) plane and the peak of the (111) plane are not observed. From the above, it can be concluded that Pb stacked on Ir... x Bi (a-x) Fe y Ti (b-y) O z The seed layer represented by can also be oriented to the (100) plane. Furthermore, the X-ray diffraction pattern of Example (8) is similar to the X-ray diffraction pattern on Pt in Example (2), which includes a seed layer with the same composition as Example (8). Therefore, it is considered that piezoelectric layers with compositions other than that of Example (8), formed on a seed layer formed on Ir, also have the effect of being oriented to the (100) plane.

[0051] Based on (a) the X-ray diffraction pattern measured on Pt of the comparative example, (b) the X-ray diffraction pattern measured on ZrO2 of the comparative example, (c) the X-ray diffraction pattern measured on Pt of Example (2), and (d) the X-ray diffraction pattern measured on ZrO2 of Example (2), the Lotgering factor was evaluated using JCPDS Card No. 330784. The Lotgering factor is an index indicating the degree of orientation, with a maximum value of 1. The calculated Lotgering factors are as follows. (a) 0.13 (b) 0.21 (c)0.99 (d) 0.99 In both the Pt and ZrO2 environments, the Lot-Gering factor in Example (2) was high, indicating that PZT was strongly oriented in the (100) plane.

[0052] In the manufacturing process of the piezoelectric element 44, after forming the Ti layer and Pt layer as the first electrode 441, patterning is performed using photolithography. During the patterning process, minute irregularities may be formed on the surface of the first electrode 441, for example, due to a small amount of residual resist. If irregularities are formed on the surface of the first electrode 441, the seed layer 442 may not be formed properly, and the piezoelectric layer 443 may not be oriented to the (100) plane. In this regard, as shown by the X-ray diffraction results, the seed layer 442 according to this embodiment can be oriented to the (100) plane even after patterning has been performed.

[0053] Furthermore, as can be seen from Figures 6, 8, 13, and 17, in this embodiment, the piezoelectric layer 443 is oriented to the (100) plane regardless of whether the layer on which the seed layer 442 is laminated is Pt, ZrO2, or Ir. In other words, with the seed layer 442 of this embodiment, the piezoelectric layer 443 can be oriented to the (100) plane regardless of the layer on which the seed layer 442 is laminated.

[0054] Furthermore, the full width at half maximum (FWHM) of the rocking curve on the (100) plane around 22° is preferably 8.4° or less, more preferably 4.0° or less, and particularly preferably 3.2° or less. The rocking curve indicates the degree of variation in crystal orientation, and a smaller FWHM of the rocking curve indicates that the crystal orientations are aligned, which reduces variations in expansion and contraction during crystal growth and thus reduces the occurrence of cracks and other defects.

[0055] Furthermore, it is preferable that the arithmetic mean roughness of the piezoelectric layer 443 in the +Z direction be relatively small, i.e., flat. A flatter surface increases the contact area between the second electrode 444, which is laminated on the +Z side of the piezoelectric layer 443, and the piezoelectric layer 443, thereby improving adhesion and thus enhancing durability. Also, if the surface is very uneven, the contact area between the piezoelectric 443 and the third electrode 444 is limited to the convex portion of the piezoelectric 443, which may cause charge to concentrate on the convex portion. A flat surface can suppress this charge concentration in specific areas. Specifically, it is preferable that the arithmetic mean roughness of the piezoelectric layer 443 in the +Z direction be 2.8 nm or less, and particularly preferable that be 1.0 nm or less.

[0056] D. Other forms This disclosure is not limited to the embodiments described above, and can be implemented in various configurations without departing from its spirit. For example, the technical features of the embodiments corresponding to the technical features in each form described in the summary of the invention can be replaced or combined as appropriate in order to solve some or all of the above-described problems, or to achieve some or all of the above-described effects. Furthermore, if a technical feature is not described as essential in this specification, it can be deleted as appropriate.

[0057] (1) According to one embodiment of the present disclosure, a piezoelectric element is provided. This piezoelectric element comprises a substrate on which a first electrode, a seed layer, a piezoelectric layer, and a second electrode are laminated, wherein the seed layer is a composite oxide containing at least Pb, Bi, Fe, and Ti. According to this embodiment, the piezoelectric layer can be oriented to the (100) plane.

[0058] (2) In the piezoelectric element of the above form, the composite oxide contained in the seed layer is Pb x Bi (a-x) Fe y Ti (b-y) O z It is represented as follows, where a>x and b>y. With this configuration, the piezoelectric layer can be oriented to the (100) plane.

[0059] (3) In the piezoelectric element of the above form, 0.04 < x / (a - x) < 1.40. According to this form, the piezoelectric layer can be oriented on the (100) plane.

[0060] (4) In the piezoelectric element of the above form, x / (a - x) < 0.72. According to this form, the piezoelectric layer can be oriented on the (100) plane.

[0061] (5) In the piezoelectric element of the above form, 0.8 < (a / b) < 1.4. According to this form, the piezoelectric layer can be oriented on the (100) plane.

[0062] (6) In the piezoelectric element of the above form, b = 1. According to this form, the piezoelectric layer can be oriented on the (100) plane.

[0063] (7) In the piezoelectric element of the above form, 2.8 < z < 3.2. According to this form, the piezoelectric layer can be oriented on the (100) plane.

[0064] (8) In the piezoelectric element of the above form, the thickness of the seed layer is 5 nm or more and 200 nm or less. According to this form, the piezoelectric layer can be oriented on the (100) plane. Also, the dielectric properties of the piezoelectric layer can be improved.

[0065] (9) In the piezoelectric element of the above form, the particle size of the piezoelectric layer on the seed layer is 2 μm or less. According to this form, the occurrence of cracks in the piezoelectric layer can be suppressed.

[0066] (10) In the piezoelectric element of the above form, when the piezoelectric layer is analyzed from the stacking direction by X-ray diffraction method, the peak intensity of the (100) plane of the X-ray diffraction pattern is higher than the peak intensity of the (110) plane.

[0067] (11) In the piezoelectric element of the above form, the uppermost layer of the first electrode is made of Pt, and the peak intensity of the (100) plane of the piezoelectric element stacked on the Pt is higher than the peak intensity of the (110) plane.

[0068] (12) In the piezoelectric element of the above form, the uppermost layer of the substrate is made of ZrO2, and the peak intensity of the (100) plane of the piezoelectric element laminated on the ZrO2 is higher than the peak intensity of the (110) plane.

[0069] (13) In the piezoelectric element of the above form, a layer made of Ir is included between the first electrode and the piezoelectric element, and the peak intensity of the (100) plane of the piezoelectric element laminated on the Ir is greater than the peak intensity of the (110) plane.

[0070] (14) In the piezoelectric element of the above embodiment, the piezoelectric layer is a composite oxide containing at least Pb, Zi, and Ti and having a perovskite structure. According to this embodiment, the piezoelectric properties of the piezoelectric layer oriented to the (100) plane can be improved.

[0071] (15) In the piezoelectric element of the above form, the composite oxide of the seed layer has a perovskite structure.

[0072] (16) According to one embodiment of the present disclosure, a liquid dispensing head is provided. The liquid dispensing head comprises a piezoelectric element according to the above embodiment and a drive circuit for driving the piezoelectric element. According to this embodiment, a liquid dispensing head can be provided which comprises a piezoelectric element oriented to the (100) plane and having good piezoelectric properties.

[0073] (17) A liquid dispensing head according to the above embodiment, wherein the piezoelectric element includes a plurality of active parts, the first electrode is provided individually on the plurality of active parts, and the second electrode is provided in common on the plurality of active parts. According to this embodiment, a liquid dispensing head can be provided comprising a piezoelectric element having good piezoelectric properties, a first electrode, and a second electrode.

[0074] (18) A liquid dispensing head according to the above embodiment, wherein the piezoelectric element includes a plurality of active parts, the first electrode is provided in common to the plurality of active parts, and the second electrode is provided individually to the plurality of active parts. According to this embodiment, a liquid dispensing head can be provided comprising a piezoelectric element having good piezoelectric properties, a first electrode, and a second electrode.

[0075] (19) According to one embodiment of the present disclosure, a liquid dispensing device is provided. The liquid dispensing device comprises a liquid dispensing head as described above and a control unit for controlling the operation of the liquid dispensing head. According to this embodiment, a liquid dispensing device can be provided that includes a liquid dispensing head comprising a piezoelectric element having good piezoelectric properties, a first electrode, and a second electrode. [Explanation of symbols]

[0076] 12... Medium, 14... Liquid containment section, 16... Conveying mechanism, 20... Head movement mechanism, 21... Conveying belt, 22... Carriage, 26... Liquid discharge head, 26a... Supply liquid chamber, 26b... Supply channel, 26c... Communication channel, 32... Channel substrate, 32a... First opening, 32b... Second opening, 32c... Third opening, 32d... Partition wall, 34... Pressure chamber substrate, 34a... Opening, 36... Vibrating plate, 44... Piezoelectric element Child, 46...Wiring board, 48...Housing, 48a...Through hole, 50...Drive circuit, 62...Nozzle plate, 64...Vibration absorber, 80...Control unit, 100...Liquid discharge device, 361...Silicon substrate, 362...Insulator layer, 440...Active part, 441...First electrode, 442...Seed layer, 443...Piezoelectric layer, 443a...Through hole, 444...Second electrode, B...Bump, C...Pressure chamber, N...Nozzle, Ra,Rb...Space

Claims

1. A method for manufacturing a piezoelectric element in which a seed layer and a piezoelectric layer are stacked on a substrate in the stacking direction, On the aforementioned substrate, A step of forming the seed layer using a solution in which Pb, Bi, Fe, and Ti are mixed, and the ratio of Pb, Bi, Fe, and Ti is Pb:Bi:Fe:Ti = x:a-x;y:b-y (where a>x>0, b>y>0), and 0.04 < x / (a-x) < 1.

40. A method for manufacturing a piezoelectric element, characterized by performing the step of forming the piezoelectric layer after the step of forming the seed layer.

2. The method for manufacturing a piezoelectric element according to claim 1, characterized in that x / (a-x) < 0.

72.

3. A method for manufacturing a piezoelectric element according to claim 1 or 2, characterized in that 0.8 < (a / b) < 1.

4.

4. A method for manufacturing a piezoelectric element according to any one of claims 1 to 3, characterized in that b = 1.

5. The method for manufacturing a piezoelectric element according to any one of claims 1 to 4, characterized in that the solution is a propionic acid solution.

6. A method for manufacturing a piezoelectric element according to any one of claims 1 to 5, characterized in that the seed layer is formed by the MOD method in the step of forming the seed layer.

7. A method for manufacturing a piezoelectric element according to any one of claims 1 to 5, characterized in that the seed layer is formed by a sol-gel method in the step of forming the seed layer.

8. A method for manufacturing a piezoelectric element according to any one of claims 1 to 5, characterized in that the seed layer is formed by sputtering in the step of forming the seed layer.

9. The method for manufacturing a piezoelectric element according to any one of claims 1 to 8, characterized in that the piezoelectric layer comprises at least Pb, Zr, and Ti.

10. The method for manufacturing a piezoelectric element according to any one of claims 1 to 8, characterized in that the piezoelectric layer comprises at least K, Na, and Nb.

11. A method for manufacturing a piezoelectric element according to any one of claims 1 to 10, characterized in that at least a portion of the constituent elements of the piezoelectric layer and the constituent elements of the seed layer are different.

12. On the aforementioned substrate, Prior to the step of forming the seed layer, there is a step of forming the first electrode, A method for manufacturing a piezoelectric element according to any one of claims 1 to 11, characterized in that the step of forming a second electrode is performed after the step of forming the piezoelectric layer.

13. A method for manufacturing a liquid dispensing head, characterized by arranging a piezoelectric element obtained by the manufacturing method described in any one of claims 1 to 12 on a pressure chamber substrate provided with a pressure chamber for applying pressure for dispensing liquid, such that the piezoelectric element is positioned at a location that overlaps with the pressure chamber when viewed from the stacking direction.

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