Piezoelectric element, liquid discharge head and liquid discharge 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] The present disclosure relates to a piezoelectric element, a liquid ejection head, and a liquid ejection apparatus. [Background technology]

[0002] In general, a piezoelectric element has a structure in which a lower electrode layer, a piezoelectric layer, and an upper electrode layer are laminated in this order on a substrate. For example, when the piezoelectric layer is made of lead zirconate titanate (hereinafter, PZT) having a rhombohedral crystal structure, it is known that the piezoelectric characteristics are improved if the PZT layer is oriented in the (100) plane. Therefore, a method for orienting the PZT layer in 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 under the PZT layer. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2004-66600 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the piezoelectric element described in Patent Document 1, there is a risk that lanthanum or nickel in the orientation control layer will diffuse into the piezoelectric layer during steps such as heat treatment during production, resulting in a deterioration in the piezoelectric characteristics. [Means for solving the problem]

[0005] The present disclosure can be realized in the following forms. According to one form of the present disclosure, there is provided a piezoelectric element. The 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, and the seed layer is a composite oxide containing at least Pb, Bi, Fe, and Ti.

[0006] According to another aspect of the present disclosure, there is provided a liquid ejection head, the liquid ejection head including the piezoelectric element and a drive circuit for driving the piezoelectric element.

[0007] According to another aspect of the present disclosure, there is provided a liquid ejection device including the liquid ejection head and a control unit that controls an operation of the liquid ejection head. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a schematic diagram showing a schematic configuration of a liquid ejection device. [Diagram 2] FIG. [Diagram 3] Cross-sectional view of line III-III in Figure 2. [Figure 4] FIG. [Diagram 5] Cross-sectional view of line VV in Figure 4. [Figure 6] 1 is a table showing the compositions of seed layers in Examples (1) to (8) and a comparative example. [Figure 7] X-ray diffraction pattern measured on platinum for comparison. [Figure 8] X-ray diffraction patterns measured on platinum for Examples (1) to (7). [Figure 9] FIG. 2 is an enlarged view of the vicinity of the (100) peak in the X-ray diffraction pattern measured on platinum in Examples (1) to (7). [Figure 10] FIG. 2 is an enlarged view of the vicinity of the (110) peak in the X-ray diffraction pattern measured on platinum in Examples (1) to (7). [Figure 11] FIG. 2 is an enlarged view of the vicinity of the (111) peak in the X-ray diffraction pattern measured on platinum in Examples (1) to (7). [Figure 12] 4 is an X-ray diffraction pattern measured on a comparative zirconium oxide. [Figure 13] X-ray diffraction patterns measured on the zirconium oxides of Examples (1) to (7). [Figure 14] FIG. 2 is an enlarged view of the vicinity of the (100) peak in the X-ray diffraction pattern measured on the zirconium oxide of Examples (1) to (7). [Figure 15] FIG. 2 is an enlarged view of the vicinity of the (110) peak in the X-ray diffraction pattern measured on the zirconium oxide of Examples (1) to (7). [Figure 16] FIG. 2 is an enlarged view of the vicinity of the (111) peak in the X-ray diffraction pattern measured on the zirconium oxide of Examples (1) to (7). [Figure 17] X-ray diffraction pattern measured on iridium of Example (8). DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] A. Embodiment: A1. Overall configuration of the liquid ejection device FIG. 1 is a schematic diagram showing a schematic configuration of a liquid ejection device 100 in an embodiment. The liquid ejection device 100 is an inkjet printing device that performs printing by ejecting droplets of ink as a liquid onto a medium 12. The medium 12 can be a printing target of any material, such as printing paper, resin film, or cloth. In the following description, the X direction, Y direction, and Z direction, which are mutually perpendicular, are used. In addition, when specifying a direction, the positive direction is designated as "+" and the negative direction is designated as "-", and positive and negative signs are used in combination to indicate the direction. In this embodiment, the X direction is the main scanning direction, which is the movement direction of the liquid ejection head 26. The Y direction is the sub-scanning direction, which is the medium feed direction perpendicular to the main scanning direction. The -Z direction is the ink ejection direction.

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

[0011] The liquid storage unit 14 stores ink to be supplied to the liquid ejection head 26. As the liquid storage unit 14, a bag-shaped liquid pack formed of a flexible film, an ink tank that can be refilled with ink, a removable ink cartridge, or the like can be used.

[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 unit 14 from the plurality of nozzles N toward the medium 12.

[0013] The head moving mechanism 20 includes a conveyor belt 21 and a carriage 22 that houses a liquid ejection head 26. The carriage 22 is connected to the conveyor belt 21, and is reciprocated in the X direction as the conveyor belt 21 is driven. The conveyor mechanism 16 conveys the medium 12 in the +Y direction.

[0014] The control unit 80 includes one or more processing circuits such as a CPU (Central Processing Unit) or an FPGA (Field Programmable Gate Array) and a storage circuit such as a semiconductor memory, and controls the operation of the entire liquid ejection device 100. The control unit 80 is electrically connected to the transport mechanism 16, the head moving mechanism 20, and the liquid ejection head 26, and controls each of these components. An image is printed on the medium 12 by ejecting liquid from the nozzles N onto the medium 12 transported by the transport mechanism 16.

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

[0016] 2, the liquid ejection head 26 includes a nozzle plate 62, two vibration absorbers 64, a flow path substrate 32, a pressure chamber substrate 34, a vibration plate 36, a wiring substrate 46, a drive circuit 50, and a housing unit 48. The nozzle plate 62, the vibration absorbers 64, the flow path substrate 32, the pressure chamber substrate 34, the vibration plate 36, and the wiring substrate 46 are plate-like members that are elongated in the Y direction. The nozzle plate 62, the flow path substrate 32, the pressure chamber substrate 34, and the vibration plate 36 each have a structure that is substantially symmetrical with respect to a center line in the X direction. The size of the planar shape of the pressure chamber substrate 34, the vibration plate 36, and the wiring substrate 46 is smaller than the size of the planar shape of the flow path substrate 32 and the housing unit 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 portion 48 are layered in this order and bonded together, for example, with an adhesive.

[0017] The nozzle plate 62 is a plate-like member in which a plurality of nozzles N are formed. The nozzles N are through-holes having a substantially circular planar shape. The plurality of nozzles N are arranged along the Y direction. The plurality of nozzles N are arranged in two rows, and the two rows are aligned in the X direction. The two vibration absorbers 64 are flexible films, and are disposed on either side of the nozzle plate 62 in the X direction.

[0018] The flow path 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 a side of the flow channel substrate 32 parallel to the Y direction. The second openings 32b are arranged in the Y direction. Similarly, the third openings 32c are arranged in the Y direction. There are two rows of the second openings 32b and two rows of the third openings 32c. In the X direction, the first openings 32a, one row of the second openings 32b, one row of the third openings 32c, one row of the third openings 32c, one row of the second openings 32b, and the first openings 32a are formed in this order. In addition, the second openings 32b and the third openings 32c adjacent to each other in the X direction are formed so that their positions in the Y direction are approximately the same.

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

[0020] A piezoelectric element 44 is formed on the vibration plate 36 at a position overlapping with the opening 34a formed in the pressure chamber substrate 34 when viewed from the Z direction.

[0021] The driving circuit 50 drives the piezoelectric element 44. More specifically, the driving circuit 50 is realized by an IC (Integrated Circuit) chip that outputs a driving signal and a reference voltage for driving the piezoelectric element 44. The driving circuit 50 is mounted on a wiring board 46. The wiring board 46 is formed with wiring for an input signal to the driving circuit 50 and a driving signal and a reference voltage output from the driving circuit 50. As shown in FIG. 3, the wiring board 46 and the piezoelectric element 44 are joined via bumps B. An input signal to the driving circuit 50 is input to a terminal (not shown) formed on the wiring board 46 via, for example, an FPC (Flexible Printed Circuits).

[0022] The housing part 48 is a case for storing ink and has a frame shape. When stacked, the pressure chamber substrate 34, the vibration plate 36, and the wiring board 46 are disposed in the internal space of the housing part 48. A through hole 48a is formed in each of both ends of the housing part 48 in the X direction.

[0023] The cross-sectional structure of the liquid ejection head 26 will be described with reference to FIG. 3. A space Rb extending in the Y direction is formed at each of both ends in the X direction of the housing part 48. The space Rb is in communication with the through hole 48a. The flow path substrate 32 and the vibration absorber 64 are connected to form the space Ra, the supply liquid chamber 26a, and the supply flow path 26b. The space Ra is the internal space of the first opening 32a. The supply liquid chamber 26a is a space surrounded by the vibration absorber 64 and the partition wall 32d separating the first opening 32a and the second opening 32b. The supply flow path 26b is the internal space of the second opening 32b. The space Ra is in communication with the 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 substrate 34 is connected to the vibration plate 36 to form a pressure chamber C. The pressure chamber C is a space surrounded by the opening 34a and the vibration plate 36. The pressure chamber C is in communication with the supply flow path 26b. The flow path substrate 32 and the nozzle plate 62 are connected to form a communication flow path 26c. The communication flow path 26c is the internal space of the third opening 32c. The communication flow path 26c is in communication with the pressure chamber C and the nozzle N.

[0024] The spaces Ra and Rb function as liquid storage chambers that store ink to be supplied to the pressure chambers C. The space Rb communicates with the multiple spaces Ra aligned in the Y direction, and ink supplied via the through-holes 48a is stored in the multiple spaces Ra via the spaces Rb. The ink stored in the spaces Ra is supplied to the pressure chambers C through the supply liquid chambers 26a and the supply flow paths 26b.

[0025] In a plan view seen from the Z direction, the piezoelectric element 44 is disposed at a position overlapping with each of the two pressure chambers C, and a wiring board 46 and a drive circuit 50 are disposed so as to cover the two pressure chambers C. A drive signal and a reference voltage are input from the wiring board 46 to the piezoelectric element 44 via the bumps B. A drive signal and a reference voltage are input, and when a voltage is applied, the piezoelectric element 44 deforms. The vibration plate 36 vibrates in conjunction with the deformation of the piezoelectric element 44, and the pressure in the pressure chamber C fluctuates, causing ink to be ejected from the nozzle N.

[0026] A3. Structure of the piezoelectric element As shown in FIG. 5, the diaphragm 36 as the 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 portion 440. The active portion 440 is a portion where the piezoelectric layer 443 deforms 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 (ZrO 2 ). 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 Preferably, it is 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, x / (a - x) preferably satisfies Equation (2) in order to orient the piezoelectric layer 443 on the (100) plane. 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, which has an octahedron in which six oxygen (O) atoms are coordinated to Fe or Ti.

[0030] The piezoelectric layer 443 contains Pb, Zr, and Ti as constituent elements and is composed of a complex oxide having a perovskite structure. In this embodiment, the piezoelectric layer 443 has a rhombohedral crystal system and is composed of lead zirconate titanate (PZT) having a perovskite structure. Note that the piezoelectric layer 443 is not limited to PZT, and for example, lead lanthanum zirconate titanate ((Pb,La)(Zr,Ti)O 3 ), lead zirconium titanate niobate (Pb(Zr,Ti,Nb)O 3 ), lead zirconium titanate magnesium niobate (Pb(Zr,Ti)(Mg,Nb)O 3) or the like can be used. Furthermore, the piezoelectric layer 443 does not necessarily need to contain lead. Specifically, as the piezoelectric layer 443 that does not substantially contain Pb, a composite oxide that contains at least two of K, Na, Nb, Bi, Fe, Ti, and Ba and has a perovskite structure can be used. More specifically, as the piezoelectric layer 443, potassium sodium niobate ((K,Na)NbO 3 ), sodium bismuth titanate ((Bi,Na)TiO 3 ), bismuth ferrite (BiFeO 3 ), barium titanate (BaTiO 3 ), bismuth potassium titanate ((Bi,K)TiO 3 ) can also be used. The phrase "substantially free of Pb" refers to a case where Pb is not contained at all, or a case where only a very small amount of Pb that does not perform any function is contained as an impurity. The grain size of the piezoelectric layer 443 is preferably 2 μm or less, and more preferably 1 μm. It is known that if the grain size of the piezoelectric layer 443 is large, the piezoelectric layer 443 is more likely to crack. In addition, if the grain size of the piezoelectric layer 443 is large, the durability of the piezoelectric layer 443 may decrease. Therefore, by setting the grain size of the piezoelectric layer 443 to 1 μm or less, it is possible to suppress the occurrence of cracks in the piezoelectric layer 443 and suppress the decrease in durability. In this embodiment, the grain size of the piezoelectric layer 443 is about several hundreds of nm.

[0031] When the first electrode 441 formed on the vibration plate 36 and the piezoelectric layer 443 formed on the seed layer 442 are analyzed in the stacking direction by X-ray diffraction, the peak intensity of the (100) plane is higher than the peak intensity of the (110) plane in the X-ray diffraction pattern measured by X-ray diffraction. Also, the peak intensity of the (100) plane is higher than the peak intensity of the (110) plane in the X-ray diffraction pattern measured by X-ray diffraction of the piezoelectric layer 443 formed on the seed layer 442 formed on the vibration plate 36. That is, the piezoelectric layer 443 is strongly oriented in the (100) plane in the stacking direction in the piezoelectric element 44.

[0032] In general, it is known that when the PZT constituting the piezoelectric layer 443 has a rhombohedral crystal structure, the displacement amount increases, that is, the piezoelectric characteristics improve, if the PZT is oriented in the (100) plane. When the seed layer 442 is the composite oxide of this embodiment, the piezoelectric layer 443 can be oriented in the (100) plane. Therefore, the formation of the seed layer 442 of this embodiment can improve the piezoelectric characteristics of the piezoelectric layer 443. In addition, 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 in the (100) plane while increasing the displacement efficiency of the piezoelectric layer 443. If the thickness of the seed layer 442 is thinner than 5 nm, the seed layer 442 is difficult to form uniformly, and the effect of orienting the piezoelectric layer 443 in the (100) plane decreases. If the thickness of the seed layer 442 is too thick, 200 nm or more, the dielectric constant of PZT is higher than that of the seed layer 442, so that it becomes difficult to apply a voltage to the piezoelectric layer 443, and the displacement efficiency of the piezoelectric layer 443 decreases. In addition, since the constituent elements of the seed layer 442 are close to the constituent elements 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 prevent the piezoelectric characteristics of the piezoelectric element 44 from being reduced. In addition, since the seed layer 442 does not have electrical conductivity, it is possible to adopt the structure of the piezoelectric element 44 of this embodiment in which the seed layer 442 is in contact with the first electrode 441 and the second electrode 444. It is known that, even if it is not PZT, if it has a piezoelectric characteristic and has a structure with a polarization axis in a direction other than the (100) direction, the piezoelectric characteristics are improved if it is oriented in the (100) plane like PZT.

[0033] The second electrode 444 is made of Ir. Note that the second electrode 444 is not limited to Ir, and may be, for example, a single layer of a metal material such as Pt, Al, Ni, Au, or Cu, or may be formed by stacking a plurality of layers of these metal materials.

[0034] As shown in FIG. 4, the first electrode 441 is formed for each pressure chamber C, that is, for each active section 440. The first electrodes 441 are drawn out in the +X direction and are individually electrically connected to the drive circuit 50. In contrast, the second electrodes 444 are formed so as to cover the multiple active sections 440 aligned in the Y direction. That is, the first electrodes 441 are individually provided for the multiple active sections 440, and the second electrodes 444 are commonly provided for the multiple active sections 440. An individual voltage is applied to the first electrodes 441 for each active section 440, and a common voltage is applied to the second electrodes 444 for the multiple active sections 440 aligned in the Y direction. The piezoelectric layer 443 is formed with a through hole 443a between adjacent active sections 440. The through hole 443a is an area where the piezoelectric layer 443 is not formed. The seed layer 442 is formed so as to cover the multiple piezoelectric elements 44 aligned in the Y direction.

[0035] A4.How to make a piezoelectric element First, the diaphragm 36 is fabricated. Specifically, silicon dioxide is formed on the surface in the +Z direction by thermally oxidizing the silicon substrate 361. Next, a Zr layer is formed by a sputtering method, and the Zr is thermally oxidized to form ZrO as the insulator layer 362. 2 A layer is formed.

[0036] Next, the first electrode 441 is formed. Specifically, a Ti layer and a Pt layer are laminated in order by a sputtering method. Next, the Ti layer and the Pt layer are patterned using photolithography. Specifically, a resist is applied onto 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, a seed layer 442 is formed by a MOD (Metal Organic Decomposition) method. Specifically, 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, drying and degreasing are performed at 350°C using a hot plate. Next, heat treatment is performed at 700°C for 5 minutes by RTA (Rapid Thermal Anneal).

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

[0039] Next, the second electrode 444 is formed. Specifically, Ir is laminated by sputtering. 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 section 440, and the second electrode 444 is provided in common to the multiple active sections 440 arranged in the Y direction. In contrast, the first electrode 441 may be provided in common to the multiple active sections 440 arranged in the Y direction, and the second electrode 444 may be provided for each active section 440.

[0041] (B2) The method for producing the piezoelectric element 44 is not limited to the above. For example, the etching for patterning the first electrode 441 may be an etching method other than ion milling. In addition, the method for forming the seed layer 442 is not limited to the MOD method, and may be other methods such as a sol-gel method or a sputtering method.

[0042] (B3) In the above embodiment, the first electrode 441 is formed by laminating a Ti layer and a Pt layer, and the first electrode 441 is drawn in the +X direction to be electrically connected to the drive circuit 50. In contrast, a wiring made of Ir may be included between the first electrode 441 and the seed layer 442, the first electrode 441 is not drawn outward from the active section 440 in a plan view, and the wiring made of Ir may be configured to be conductive to the first electrode 441 and the drive circuit 50. In this configuration, the seed layer 442 may be made of ZrO 2 In this configuration, the first electrode 441 formed on the vibration plate 36, the wiring made of Ir, and the piezoelectric layer 443 formed on the seed layer 442 are formed on the piezoelectric layer 443. In an X-ray diffraction pattern measured by X-ray diffraction method, the peak intensity of the (100) plane is higher than the peak intensity of the (110) plane. 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: Preparation of seed layer and piezoelectric layer The composition ratio of the seed layer, specifically the Pb content, was changed to produce Examples (1) to (8) and a Comparative Example. FIG. 6 shows the composition of the seed layer produced in Examples (1) to (8) and a Comparative Example. The composition of the seed layer in Examples (1) to (8) and a Comparative Example is Pb x Bi (a-x) Fe y Ti (b-y) O zIt is expressed by the above. In the seed layers of Examples (1) to (8), a=1.2, and x is a value of 0.05 or more and 0.9 or less. In the seed layer of the comparative example, x=0, that is, it is a complex oxide that does not contain Pb. In Examples (1) to (7) and the comparative example, the uppermost layer of the first electrode layer is a Pt layer. Example (8) has the configuration of the above-mentioned other embodiment (B3), in which an Ir layer is formed on the first electrode layer, and a seed layer and a piezoelectric layer are formed on the Ir layer. In FIG. 6, x / a, which indicates the substitution rate of Pb, is shown together with the composition of the seed layer. The column "lower layer" in FIG. 6 shows the configuration of the lower layer of the seed layer at the portion where the measurement was performed when the X-ray diffraction pattern described later was measured.

[0044] In each of the experimental examples and comparative examples, a seed layer and a piezoelectric layer were formed on a diaphragm by the same manufacturing method as described above. Specifically, first, a silicon substrate was thermally oxidized to form silicon dioxide. Next, a Zr layer was formed by a sputtering method, and the Zr layer was thermally oxidized to form ZrO 2 In the examples (1) to (7) and the comparative example, a ZrO 2 After the layer is formed, a Ti layer and a Pt layer are laminated in this order by a sputtering method. Next, the Ti layer and the Pt layer are patterned by photolithography. Next, a seed layer and a piezoelectric layer are formed. For Example (8), ZrO 2 After the formation of the layer, a Ti layer, a Pt layer, and an Ir layer are laminated in this order. Next, the Ti layer, the Pt layer, and the Ir layer are patterned using photolithography. Next, a seed layer and a piezoelectric layer are formed.

[0045] In the examples (1) to (8), the seed layer is formed by applying a propionic acid solution of Pb, Bi, Fe, and Ti, each adjusted to have a molar ratio, to a vibration plate by spin coating. Next, drying and degreasing are performed at 350°C using a hot plate. Next, heat treatment is performed at 700°C for 5 minutes by RTA (Rapid Thermal Anneal). In the comparative example, a propionic acid solution not containing Pb is used, and after application, drying, degreasing, and heat treatment are performed to form a 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 in the same manner for Examples (1) to (8) and 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 onto the seed layer by spin coating. Next, drying and degreasing are performed at 200°C and 410°C using a hot plate. Next, heat treatment is performed at 740°C for 5 minutes by RTA (Rapid thermal anneal).

[0047] C2: Evaluation of the piezoelectric layer The X-ray diffraction patterns of Examples (1) to (8) and Comparative Example were measured to evaluate the degree of orientation of the piezoelectric layer. The X-ray diffraction device was a Bruker D8 DISCOVER with GADDS. The measurement conditions were tube voltage: 50 kV, tube current: 100 mA, detector distance: 15 cm, collimator diameter: 0.1 mm, and measurement time: 180 seconds. The two-dimensional data obtained by the measurement was converted into an X-ray diffraction intensity curve with a 2θ range of 20° to 40°, a χ range of -95° to -85°, a step width of 0.02°, and an intensity normalization method of bin normalized. In Examples (1) to (7), the seed layer and piezoelectric layer formed on Pt were patterned by the Ti layer and Pt layer, and the ZrO 2 The X-ray diffraction pattern was measured for the seed layer and piezoelectric layer formed on Pt, and for the ZrO 2Similarly, in Example (8), the seed layer and the piezoelectric layer formed on Ir were measured by patterning the Ti layer, the Pt layer, and the Ir layer, and the ZrO 2 The seed layer and the piezoelectric layer formed on the Ir are included. Of these, in Example (8), the seed layer and the piezoelectric layer formed on the Ir were measured.

[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 the examples (1) to (7). In the X-ray diffraction pattern of the comparative example, the peak intensity of the (100) plane is low around 22°, the peak intensity of the (110) plane is observed around 31°, and the peak intensity of the (111) plane is high around 38°. In contrast, the X-ray diffraction patterns measured on Pt of the examples (1) to (7) generally show a high peak intensity of the (100) plane. FIG. 9 to FIG. 11 show the X-ray diffraction patterns on Pt of the examples (1) to (7) enlarged around the peak of the (100) plane, the peak of the (110) peak, and the peak of the (111) peak, 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, a peak in the (110) plane is observed in Examples (6) and (7). In Examples (6) and (7), a peak in the (110) plane is observed, and the peak intensity of the (100) plane is low. This suggests that a seed layer in which x / (ax), which indicates the Pb substitution rate, is 1.400 or more and x / a is 0.583 or more has a low effect of orienting PZT in the (100) plane. On the other hand, in Examples (1) to (5), a peak in the (110) plane is not observed, and the peak intensity of the (100) plane is high. This suggests that a seed layer in which x / (ax) is 0.714 or less and x / a is 0.417 or less has a high effect of orienting PZT in the (100) plane. From the above, it can be concluded that the Pb layer laminated on the Pt layer x Bi (a-x) Fe y Ti (b-y) O zRegarding the seed layer represented by [formula], 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. Furthermore, 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), no peak of the (111) plane was observed.

[0049] Fig. 12 shows the X-ray diffraction pattern measured on [substrate of Comparative Example]. 2 Fig. 13 shows the X-ray diffraction pattern measured on [substrate of Examples (1) to (7)]. 2 The X-ray diffraction pattern measured on [substrate] shows a similar trend to the X-ray diffraction pattern measured on Pt. 2 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. In contrast, in the X-ray diffraction pattern measured on [substrate of Examples (1) to (7)], generally the peak intensity of the (100) plane is high. Figs. 14 to 16 respectively show the enlarged views near the peak of the (100) plane, near the peak of the (110) plane, and near the peak of the (111) plane for [substrate of Examples (1) to (7)]. 2 2The above is the X-ray diffraction pattern. As shown in Fig. 14, the peak intensity of the (100) plane decreases in the order of Example (2), Example (1), Example (3), Example (4), and Example (5). Also, in Example (6) and Example (7), no peak of the (100) plane is observed. As shown in Fig. 15, the peak intensity of the (110) plane is high in Example (6) and Example (7). In Example (6) and Example (7), since the peak intensity of the (110) plane is high and no peak of the (100) plane is observed, it is considered that in the seed layer where x / a is 0.583 or more, the effect of orienting PZT on the (100) plane is low. On the other hand, in Examples (1) to (5), no peak of the (110) plane is observed or the peak intensity is low, and a peak of the (100) plane is observed. Therefore, in the seed layer where x / (a - x) is 0.714 or less and x / a is 0.417 or less, the effect of orienting PZT on the (100) plane is considered to be high. From the above, for the seed layer represented by ZrO 2 stacked on top, 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. Furthermore, 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. 16, for Examples (1) to (7), no peak of the (111) plane is observed.

[0050] Fig. 17 shows the X-ray diffraction pattern measured on Ir of Example (8). The X-ray diffraction pattern measured on Ir shows the same tendency as 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 no peak intensity of the (110) plane and the (111) plane is observed. From the above, for Pb x Bi (a-x) Fe y Ti (b-y) O zThe seed layer represented by the formula (100) can also orient PZT to the (100) plane. The X-ray diffraction pattern of Example (8) is similar to the X-ray diffraction pattern on Pt of Example (2) including the seed layer of the same composition as Example (8). Therefore, it is considered that the effect of orienting to the (100) plane is also observed for a piezoelectric layer having a composition other than that of Example (8) formed on a seed layer formed on Ir.

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

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

[0053] As can be seen from FIGS. 6, 8, 13, and 17, the seed layer 442 of this embodiment is made of a material selected from the group consisting of Pt, ZrO 2 Whether the seed layer 442 is made of Ir or Ir, the piezoelectric layer 443 is oriented in the (100) plane. In other words, according to the seed layer 442 of this embodiment, the piezoelectric layer 443 can be oriented in the (100) plane regardless of the layer on which the seed layer 442 is laminated.

[0054] In addition, the half-width of the rocking curve in the (100) plane at about 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 it is believed that when the half-width of the rocking curve is small, the crystal orientation is uniform, so that the variation in expansion and contraction during crystal growth is also small, and the occurrence of cracks, etc. can be reduced.

[0055] In addition, it is preferable that the arithmetic mean roughness of the piezoelectric layer 443 in the +Z direction is small to a certain extent, that is, flat. The flat surface increases the contact area between the second electrode 444, which is laminated on the +Z direction side of the piezoelectric layer 443, and the piezoelectric layer 443, thereby improving adhesion and thereby improving durability. In addition, if the unevenness is large, the contact portion between the piezoelectric body 443 and the third electrode 444 is limited to the convex portion of the piezoelectric body 443, and there is a risk that electric charges will concentrate on the convex portion. If the surface is flat, it is possible to suppress the electric charge concentration on this specific portion. Specifically, it is preferable that the arithmetic mean roughness of the piezoelectric layer 443 in the +Z direction is 2.8 nm or less, and it is particularly preferable that it is 1.0 nm or less.

[0056] D. Other forms The present disclosure is not limited to the above-described embodiments, and can be realized in various configurations without departing from the gist thereof. 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 appropriately replaced or combined in order to solve some or all of the above-described problems, or to achieve some or all of the above-described effects. Further, if the technical feature is not described as essential in this specification, it can be appropriately deleted.

[0057] (1) According to one embodiment of the present 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, and 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 in the (100) plane.

[0058] (2) In the piezoelectric element of the above embodiment, the composite oxide contained in the seed layer is Pb x Bi (a-x) Fe y Ti (b-y) O z represented by However, a > x and b > y. According to this embodiment, the piezoelectric layer can be oriented in the (100) plane.

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

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

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

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

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

[0064] (8) In the piezoelectric element of the above-described embodiment, the thickness of the seed layer is 5 nm or more and 200 nm or less. According to this embodiment, 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-described embodiment, the particle size of the piezoelectric layer on the seed layer is 2 μm or less. According to this embodiment, it is possible to suppress the formation of cracks in the piezoelectric layer.

[0066] (10) In the piezoelectric element of the above-described embodiment, 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-described embodiment, the uppermost layer of the first electrode is made of Pt, and the peak intensity of the (100) plane of the piezoelectric element laminated on the Pt is higher than the peak intensity of the (110) plane.

[0068] (12) In the piezoelectric element of the above-described embodiment, the uppermost layer of the substrate is ZrO 2 and the peak intensity of the (100) plane of the piezoelectric element laminated on the ZrO 2 is higher than the peak intensity of the (110) plane.

[0069] (13) In the piezoelectric element of the above-described embodiment, 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, Zr, and Ti and having a perovskite structure. According to this embodiment, the piezoelectric characteristics of the piezoelectric layer oriented in the (100) plane can be improved.

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

[0072] (16) According to one aspect of the present disclosure, there is provided a liquid ejection head. The liquid ejection head includes the piezoelectric element of the above aspect and a drive circuit for driving the piezoelectric element. According to this aspect, it is possible to provide a liquid ejection head including a piezoelectric element oriented in the (100) plane and having good piezoelectric characteristics.

[0073] (17) In the liquid ejection head of the above aspect, the piezoelectric element includes a plurality of active parts, the first electrode is provided individually for the plurality of active parts, and the second electrode is provided commonly for the plurality of active parts. According to this aspect, it is possible to provide a liquid ejection head including a piezoelectric element having good piezoelectric characteristics, a first electrode, and a second electrode.

[0074] (18) In the liquid ejection head of the above aspect, the piezoelectric element includes a plurality of active parts, the first electrode is provided commonly to the plurality of active parts, and the second electrode is provided individually to the plurality of active parts. According to this aspect, it is possible to provide a liquid ejection head including a piezoelectric element having good piezoelectric characteristics, a first electrode, and a second electrode.

[0075] According to one aspect of the present disclosure, there is provided a liquid ejection device, the liquid ejection device including the liquid ejection head of the above aspect and a control unit that controls an operation of the liquid ejection head. According to this aspect, it is possible to provide a liquid ejection device that includes a liquid ejection head that includes a piezoelectric element having good piezoelectric characteristics, a first electrode, and a second electrode. [Explanation of symbols]

[0076] Reference Signs List 12...medium, 14...liquid storage section, 16...transport mechanism, 20...head moving mechanism, 21...transport belt, 22...carriage, 26...liquid ejection head, 26a...supply liquid chamber, 26b...supply flow path, 26c...communicating flow path, 32...flow path substrate, 32a...first opening, 32b...second opening, 32c...third opening, 32d...partition wall, 34...pressure chamber substrate, 34a...opening, 36...diaphragm, 44...piezoelectric element element, 46...wiring board, 48...casing portion, 48a...through hole, 50...driving circuit, 62...nozzle plate, 64...vibration absorber, 80...control portion, 100...liquid ejection device, 361...silicon substrate, 362...insulator layer, 440...active portion, 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 piezoelectric element in which a first electrode, a seed layer, a piezoelectric layer, and a second electrode are laminated on a substrate, The seed layer is a composite oxide containing at least Pb, Bi, Fe, and Ti.

2. 2. The piezoelectric element according to claim 1, The composite oxide contained in the seed layer is Pb x Bi (a-x) Fe y Ti (b-y) O z A piezoelectric element represented by the formula: However, a>x and b>y.

3. 3. The piezoelectric element according to claim 2, A piezoelectric element, wherein 0.04<x / (ax)<1.

40.

4. 4. The piezoelectric element according to claim 3, A piezoelectric element, wherein x / (ax)<0.

72.

5. 5. The piezoelectric element according to claim 2, A piezoelectric element, wherein 0.8<(a / b)<1.

4.

6. 6. The piezoelectric element according to claim 2, A piezoelectric element, where b=1.

7. 7. The piezoelectric element according to claim 2, A piezoelectric element, wherein 2.8<z<3.

2.

8. 8. The piezoelectric element according to claim 1, A piezoelectric element, wherein the seed layer has a thickness of 5 nm or more and 200 nm or less.

9. 9. The piezoelectric element according to claim 1, A piezoelectric element, wherein the grain size of the piezoelectric layer on the seed layer is 2 μm or less.

10. 10. The piezoelectric element according to claim 1 , A piezoelectric element, wherein when the piezoelectric layer is analyzed in the stacking direction of the piezoelectric layer by X-ray diffraction, the peak intensity of the (100) plane in the X-ray diffraction pattern is greater than the peak intensity of the (110) plane.

11. The piezoelectric element according to claim 10, A piezoelectric element, wherein the uppermost layer of the first electrode is made of Pt, and the peak intensity of the (100) plane of the piezoelectric element laminated on the Pt is higher than the peak intensity of the (110) plane.

12. 12. The piezoelectric element according to claim 10, The top layer of the substrate is ZrO 2 The ZrO 2 A piezoelectric element, the peak intensity of the (100) plane of the piezoelectric element laminated thereon being higher than the peak intensity of the (110) plane.

13. 13. The piezoelectric element according to claim 10, A piezoelectric element including wiring made of Ir between the first electrode and the piezoelectric element, wherein the peak intensity of the (100) plane of the piezoelectric element stacked on the Ir is higher than the peak intensity of the (110) plane.

14. 14. The piezoelectric element according to claim 1, The piezoelectric element, wherein the piezoelectric layer is a complex oxide containing at least Pb, Zr, and Ti and having a perovskite structure.

15. 14. The piezoelectric element according to claim 1, A piezoelectric element, wherein the piezoelectric layer is a complex oxide containing at least two of K, Na, Nb, Bi, Fe, Ti, and Ba and having a perovskite structure.

16. 16. A piezoelectric element according to claim 1, A piezoelectric element, wherein the composite oxide of the seed layer has a perovskite structure.

17. 17. A piezoelectric element according to claim 1, A piezoelectric element, wherein when the piezoelectric layer is analyzed in the stacking direction of the piezoelectric layer by X-ray diffraction, the half-width of a rocking curve in a (100) plane by X-ray diffraction is 4.0° or less.

18. A piezoelectric element according to any one of claims 1 to 17, A liquid ejection head having a drive circuit for driving the piezoelectric element.

19. 20. The liquid ejection head according to claim 18, The piezoelectric element includes a plurality of active portions, the first electrodes are provided individually on the active portions, The second electrode is provided in common to the plurality of active portions.

20. 20. The liquid ejection head according to claim 18, The piezoelectric element includes a plurality of active portions, the first electrode is provided in common to the plurality of active portions, The second electrode is provided individually on each of the active portions.

21. A liquid ejection head according to any one of claims 18 to 20, A control unit that controls the operation of the liquid ejection head.

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