Piezoelectric element, liquid ejecting head, and liquid ejecting apparatus

Abstract

The present disclosure provides a piezoelectric element, a liquid ejecting head, and a liquid ejecting apparatus, each of which has a first electrode, a piezoelectric layer, and a second electrode stacked on a substrate, and has a good piezoelectric property. The piezoelectric element is formed by sequentially stacking the first electrode, the piezoelectric layer, and the second electrode on the substrate, and has an orientation control layer provided between the piezoelectric layer and the first electrode and configured to control an orientation of the piezoelectric layer, and a titanium layer provided between the first electrode and the orientation control layer and containing at least Ti.

Description

Technical Field

[0001] This disclosure relates to a piezoelectric element, a liquid ejector head, and a liquid ejection device. Background Technology

[0002] Generally, piezoelectric elements have a structure formed by sequentially stacking a lower electrode layer, a piezoelectric body layer, and an upper electrode layer on a substrate. It is known that, for example, when the piezoelectric body layer is composed of lead zirconate titanate (hereinafter, PZT) with a rhombohedral crystal structure, the piezoelectric properties are enhanced when the PZT layer is oriented on the (100) plane. Therefore, a method for oriented the PZT layer on the (100) plane has been proposed (for example, Patent Document 1). Patent Document 1 discloses a structure having an orientation control layer composed of lanthanum nickelate below the PZT layer.

[0003] However, in cases where the substrate is strongly oriented, there are situations where the piezoelectric layer is not sufficiently oriented even when it is formed on the orientation control layer.

[0004] Patent Document 1: Japanese Patent Application Publication No. 2004-66600 Summary of the Invention

[0005] This disclosure can be implemented in the following ways. According to one aspect of this disclosure, a piezoelectric element is provided. The piezoelectric element is formed by sequentially stacking a first electrode, a piezoelectric layer, and a second electrode on a substrate, and has: an orientation control layer disposed between the piezoelectric layer and the first electrode for controlling the orientation of the piezoelectric layer; and a titanium layer disposed between the first electrode and the orientation control layer, and comprising at least Ti.

[0006] Furthermore, according to one aspect of this disclosure, a liquid ejector head is provided. The liquid ejector head includes: the piezoelectric element; and a vibrating plate that is driven by the piezoelectric element to vibrate.

[0007] Furthermore, according to one aspect of this disclosure, a liquid ejection device is provided. This liquid ejection device includes: the liquid ejection head; and a control unit that controls the operation of the liquid ejection head. Attached Figure Description

[0008] Figure 1 This is a schematic diagram illustrating the simplified structure of a liquid ejection device.

[0009] Figure 2 An exploded 3D view of the liquid ejector head.

[0010] Figure 3 for Figure 2 Sectional view along line III-III.

[0011] Figure 4 This is a plan view of a piezoelectric element.

[0012] Figure 5 for Figure 4 VV-line sectional view.

[0013] Figure 6 This is a sampled STEM image.

[0014] Figure 7 A graph showing the results of the sampled EDX.

[0015] Figure 8 The X-ray diffraction pattern is shown in Example 1.

[0016] Figure 9 The X-ray diffraction pattern is shown in Example 2.

[0017] Figure 10 The X-ray diffraction pattern is for comparison.

[0018] Figure 11 A graph representing the results of XPS. Detailed Implementation

[0019] A. Implementation method:

[0020] A1. Overall structure of the liquid ejection device:

[0021] Figure 1 This is a schematic diagram illustrating the simplified structure of the liquid ejection device 100 in this embodiment. The liquid ejection device 100 is an inkjet printing apparatus 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, which are orthogonal to each other, are used. Furthermore, when a specific orientation is specified, a positive direction is designated as "+", a negative direction as "-", and both positive and negative symbols are used on the direction marking. 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 secondary scanning direction, which is the medium transport direction orthogonal to the main scanning direction. The Z direction is the ink ejection direction.

[0022] The liquid ejection device 100 includes a liquid ejection head 26, a head moving mechanism 20, a liquid receiving part 14, a conveying mechanism 16, and a control part 80.

[0023] The liquid collection section 14 collects the ink supplied to the liquid ejector head 26. The liquid collection section 14 can be a bag-shaped liquid pack made of a flexible film, an ink can that can be refilled, or a removable ink cartridge.

[0024] The liquid ejector head 26 has multiple nozzles N for ejecting ink. The multiple nozzles N are arranged along the Y direction. The liquid ejector head 26 ejects ink supplied from the liquid collection section 14 from the multiple nozzles N toward the medium 12.

[0025] The head moving mechanism 20 includes a conveyor belt 21 and a carriage 22 for housing the liquid spray 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.

[0026] The control unit 80 includes one or more processing circuits such as CPUs (Central Processing Units), FPGAs (Field Programmable Gate Arrays), and storage circuits such as semiconductor memories, and controls the overall operation of the liquid ejection device 100. The control unit 80 is electrically connected to the conveying mechanism 16, the head moving mechanism 20, and the liquid ejection head 26, and controls each part. By ejecting liquid from the nozzle N onto the medium 12 conveyed by the conveying mechanism 16, an image is printed on the medium 12.

[0027] A2. Structure of the liquid ejector head:

[0028] Figure 2 This is an exploded perspective view of the liquid ejector head 26 according to the embodiment. Figure 3 for Figure 2 Sectional view along line III-III. Figure 4 This is a plan view of the piezoelectric element 44. Figure 4 In the image, a shaded line is added to the area where the second electrode 445 is formed, outside the area where the first conductive layer 451 and the second conductive layer 452 are formed. Figure 5 for Figure 4 VV-line sectional view.

[0029] like Figure 2As shown, the liquid ejector head 26 includes a nozzle plate 62, two vibration absorbers 64, a flow channel substrate 32, a pressure chamber substrate 34, a vibrating plate 36, a sealing body 46, a frame portion 48, and a circuit board 50. The nozzle plate 62, vibration absorbers 64, flow channel substrate 32, pressure chamber substrate 34, vibrating plate 36, and sealing body 46 are elongated plate-shaped components along the Y direction. The nozzle plate 62, flow channel substrate 32, pressure chamber substrate 34, vibrating plate 36, and sealing body 46 each have a structure that is approximately linearly symmetrical with respect to a centerline in the X direction. The planar shape of the pressure chamber substrate 34, vibrating plate 36, and sealing body 46 is smaller than the planar shape of the flow channel substrate 32 and the frame portion 48. During assembly, the nozzle plate 62, the two vibration absorbers 64, the flow channel substrate 32, the pressure chamber substrate 34, the vibrating plate 36, the sealing body 46, and the frame portion 48 are stacked in this order and bonded together, for example, by an adhesive.

[0030] Nozzle plate 62 is a plate-shaped component having a plurality of nozzles N. Each nozzle N is a through-hole with a generally circular planar shape. The plurality of nozzles N are arranged along the Y direction. There are two rows of the plurality of nozzles N arranged side-by-side along the X direction. Two vibration absorbers 64 are flexible films and are arranged in the X direction, separated by nozzle plate 62.

[0031] The flow channel substrate 32 has two first openings 32a, a plurality of second openings 32b, and a plurality of third openings 32c. The first openings 32a are rectangular in planar shape, elongated along the Y direction. The first openings 32a are formed along the edge of the flow channel substrate 32 parallel to the Y direction. The plurality of second openings 32b are arranged along the Y direction. Similarly, the plurality of third openings 32c are arranged along the Y direction. There are two columns of second openings 32b and two columns of third openings 32c. The first openings 32a, one column of second openings 32b, one column of third openings 32c, one column of second openings 32b, and the first openings 32a are formed in this order along the X direction. Furthermore, adjacent second openings 32b and third openings 32c in the X direction are formed in a manner that their positions are approximately the same in the Y direction.

[0032] A plurality of openings 34a are formed on the pressure chamber substrate 34. The planar shape of the openings 34a is a rectangle that is elongated along the X direction. The plurality of openings 34a are arranged along the Y direction. There are two columns of the plurality of openings 34a, and the two columns are formed side by side along the X direction. In addition, the openings 34a are formed at positions that overlap with the adjacent second openings 32b and third openings 32c formed on the flow channel substrate 32 when viewed from the Z direction.

[0033] A piezoelectric element 44 is formed on the vibrating plate 36 at a position overlapping with the opening 34a formed on the pressure chamber substrate 34 when viewed from the Z direction. The sealing body 46 strengthens the pressure chamber substrate 34 and the vibrating plate 36, and protects the piezoelectric element 44. The sealing body 46 has a sealing body opening 46a and... Figure 3 The sealing body recess 46b is shown. The sealing body opening 46a has a planar shape that is a rectangle elongated along the Y direction. Figure 3 As shown, the sealing body recess 46b is formed by recessing from the surface of the sealing body 46 opposite to the piezoelectric element 44.

[0034] On the circuit board 50, a drive circuit (not shown) for driving the piezoelectric element 44 is mounted. The drive circuit is implemented by an IC (Integrated Circuit) chip that outputs a drive signal for driving the piezoelectric element 44 and a reference voltage. The drive circuit and the piezoelectric element 44 are connected via... Figure 3 The electrical wiring 51 shown is electrically connected.

[0035] The frame portion 48 is a housing for storing ink and has a frame shape. When stacked, the pressure chamber substrate 34, the vibrating plate 36, and the sealing body 46 are disposed in the internal space of the frame portion 48. Through holes 48a are formed at both ends of the frame portion 48 in the X direction.

[0036] like Figure 3 As shown, spaces Rb extending in the Y direction are formed at both ends of the frame portion 48 in the X direction. Spaces Rb communicate with through holes 48a. By connecting the flow channel substrate 32 and the vibration absorber 64, spaces Ra, a supply liquid chamber 26a, and a supply flow channel 26b are formed. Space Ra is the internal space of the first opening 32a. The supply liquid chamber 26a is a space surrounded by a partition 32d that separates the first opening 32a and the second opening 32b, and the vibration absorber 64. The supply flow channel 26b is the internal space of the second opening 32b. Space Ra communicates with spaces Rb and the supply liquid chamber 26a, and the supply liquid chamber 26a communicates with the supply flow channel 26b. By connecting the pressure chamber substrate 34 and the vibrating plate 36, a pressure chamber C is formed. The pressure chamber C is a space surrounded by the opening 34a and the vibrating plate 36. The pressure chamber C communicates with the supply flow channel 26b. By connecting the flow channel substrate 32 and the nozzle plate 62, a connecting flow channel 26c is formed. The connecting flow channel 26c is the internal space of the third opening 32c. The connecting flow channel 26c communicates with the pressure chamber C and the nozzle N.

[0037] Spaces Ra and Rb function as liquid storage chambers for storing ink supplied to pressure chamber C. Space Rb communicates with multiple spaces Ra arranged along the Y direction, and ink supplied through through hole 48a is stored in multiple spaces Ra via space Rb. The ink stored in space R flows through supply liquid chamber 26a and supply flow channel 26b and is supplied to pressure chamber C.

[0038] When viewed from a plane in the Z direction, piezoelectric elements 44 are positioned at locations overlapping the two pressure chambers C. A drive signal and a reference voltage are input to the piezoelectric elements 44 from the circuit board 50 via electrical wiring 51. By inputting the drive signal and the reference voltage and applying a voltage, the piezoelectric elements 44 deform, and in conjunction with this deformation, the vibrating plate 36 vibrates, causing a change in pressure within the pressure chambers C, thereby ejecting ink from the nozzles N.

[0039] A3. Structure of piezoelectric elements:

[0040] like Figure 5 As shown, the piezoelectric element 44 is formed by stacking a first electrode 441, a titanium layer 442, an alignment control layer 443, a piezoelectric layer 444, and a second electrode 445 on the vibrating plate 36 in this order. Here, the portion where the first electrode 441, titanium layer 442, alignment control layer 443, piezoelectric layer 444, and second electrode 445 overlap when viewed from the Z direction is referred to as the first region R1. The first region R1 is the portion where the piezoelectric layer 444 deforms when a voltage is applied between the first electrode 441 and the second electrode 445.

[0041] The vibrating plate 36, serving as a substrate, includes a silicon substrate 361 and an insulating layer 362. Silicon dioxide is formed on the surface of the silicon substrate 361 located in the +Z direction and in contact with the insulating layer 362. The insulating layer 362 is composed of zirconium oxide (ZrO2). Alternatively, the insulating layer 362 may also be silicon nitride (SiN) or the like. In this embodiment, the insulating layer 362 is a non-oriented layer. Furthermore, other layers such as metal oxides may be disposed between the silicon substrate 361 and the insulating layer 362.

[0042] The first electrode 441 is composed of a titanium (Ti) layer, a platinum (Pt) layer, and an iridium (Ir) layer. Furthermore, the first electrode 441 is not limited to multiple layers of Ti, Pt, and Ir; it can be a single layer of a metal material such as Ti, Pt, Ir, aluminum (Al), nickel (Ni), gold (Au), or copper (Cu), or it can be formed by stacking multiple layers of these metal materials.

[0043] The titanium layer 442 is a counteracting layer that counteracts the orientation effect from the substrate to the piezoelectric layer 444. In this embodiment, the substrate is the first electrode 441. In this embodiment, since the first electrode 441 is a metal layer containing Pt, it is prone to (111) orientation. Therefore, when the orientation control layer 443 is formed on the first electrode 441 without the titanium layer 442, the orientation control layer 443 may be affected by the (111) orientation of the first electrode 441 and thus cannot be sufficiently (100) oriented. Therefore, in this embodiment, by forming the titanium layer 442 between the first electrode 441 and the orientation control layer 443, the orientation effect of the first electrode 441 can be counteracted, and the orientation control layer 443 can be sufficiently (100) oriented. Furthermore, the piezoelectric layer 444 formed on the orientation control layer 443 can be well (100) oriented. As a result, the piezoelectric characteristics of the piezoelectric element 44 can be improved. The titanium layer 442 is a layer mainly containing Ti. When the amount of metal elements different from Ti contained in the titanium layer 442 is denoted as na and the amount of Ti contained in the titanium layer 442 is denoted as nt, nt satisfies the following equation (1).

[0044] na<nt……Equation (1)

[0045] Preferably, nt satisfies the following formula (2), and more preferably, nt satisfies the following formula (3). As a result, the function of counteracting the above-mentioned orientation effect can be further improved.

[0046] na≤0.4×nt……Equation (2)

[0047] na≤0.2×nt……Equation (3)

[0048] The thickness of the titanium layer is preferably 1 nm or more and 30 nm or less. This allows it to effectively counteract the aforementioned orientation effects. Furthermore, the titanium layer 442 is preferably amorphous.

[0049] The Ti content of the titanium layer 442, as measured by EDX (Energy Dispersive X-ray Spectroscopy), is greater than the Ti content of the orientation control layer 443, as measured by EDX analysis. Here, the content is expressed as atomic percentage (atom%). In this embodiment, the orientation control layer 443 contains iron (Fe). Furthermore, the Fe content in the titanium layer 442, as measured by EDX analysis, is less than the Fe content in the orientation control layer 443, as measured by EDX analysis. Additionally, the Fe content in the titanium layer 442, as measured by EDX analysis, is greater than the Fe content in the first electrode 441, as measured by EDX analysis. By including Fe in the titanium layer 442, the adhesion of the orientation control layer 443 can be improved compared to the case where Fe is absent. In this embodiment, the EDX analysis was performed using a JEM-ARM200F analyzer manufactured by Nippon Electronics Corporation. Alternatively, in other embodiments, the titanium layer 442 may be Fe-free.

[0050] The orientation control layer 443 functions to control the orientation of the piezoelectric layer 444. The orientation control layer 443, as a structural element, contains at least one of lead (Pb) and bismuth (Bi). In this embodiment, the orientation control layer 443 contains lead (Pb), bismuth (Bi), iron (Fe), and titanium (Ti). Specifically, the orientation control layer 443 is a composite oxide represented by ((Pb,Bi)(Fe,Ti)Ox). Furthermore, the orientation control layer 443 has a perovskite structure. The thickness of the orientation control layer 443 is preferably 5 nm or more and 200 nm or less. By setting the thickness of the orientation control layer 443 to the aforementioned thickness, it is possible to improve the displacement efficiency, expressed as the displacement of the piezoelectric layer 444 relative to the applied voltage, while maintaining the orientation control function.

[0051] In other embodiments, the orientation control layer 443 may also contain Pb, Fe, and Ti, but not Bi. Alternatively, the orientation control layer 443 may also contain Bi, Fe, and Ti, but not Pb. Furthermore, the orientation control layer 443 may not have a perovskite structure.

[0052] The piezoelectric layer 444 is composed of a composite oxide containing Pb, Zr, and Ti as structural elements. In this embodiment, the piezoelectric layer 444 has a rhombohedral crystal system and is composed of lead zirconate titanate (PZT) having a perovskite structure. Furthermore, the piezoelectric layer 444 is not limited to PZT, and can be, for example, potassium sodium niobate ((K,Na)NbO3), lanthanum lead zirconate titanate ((Pb,La)(Zr,Ti)O3), lead zirconate titanate niobate (Pb(Zr,Ti,Nb)O3), lead zirconate titanate magnesium niobate (Pb(Zr,Ti)(Mg,Nb)O3), lead magnesium niobate / lead titanate solid solution (Pb(Mg,Nb)O3-PbTiO3), sodium bismuth titanate ((Bi,Na)TiO3), etc. Moreover, the crystal structure of the piezoelectric layer 444 is not limited to a perovskite structure; any crystal structure with piezoelectric properties is acceptable.

[0053] The second electrode 445 is composed of Ir. In addition, the second electrode 445 is not limited to Ir, but can be a single layer of metal materials such as Pt, Al, Ni, Au, Cu, etc., or it can be formed by stacking multiple layers of these metal materials.

[0054] like Figure 4 As shown, a first electrode 441 is formed for each pressure chamber C, i.e., for each first region R1. The first electrode 441 is led out in the +X direction and is independently electrically connected to the drive circuit via a first wiring 446 that is conductive to the first electrode 441. The first wiring 446 is formed of a conductive material with lower resistance than the first electrode 441. Specifically, the first wiring 446 is formed, for example, by laminating a conductive film of gold (Au) onto the surface of a conductive film formed of a nickel-chromium alloy (NiCr). In contrast, a second electrode 445 is formed to cover the plurality of first regions R1 arranged in the Y direction. That is, the first electrode 441 is independently disposed in the plurality of first regions R1. In contrast, the second electrode 445 is disposed in a manner shared by the plurality of first regions R1. An independent drive voltage is applied to the first electrode 441 for each first region R1, and a reference voltage shared by the plurality of first regions R1 arranged in the Y direction is applied to the second electrode 445. The piezoelectric layer 444 is formed such that it has a through hole 444a between adjacent first regions R1. The through hole 444a is the region where the piezoelectric layer 44 is not formed.

[0055] like Figure 5As shown, the region where the piezoelectric layer 444 is sandwiched between the first electrode 441 and the second electrode 445 is designated as the first region R1. Conversely, the region where the piezoelectric layer 444 is not sandwiched between the first electrode 441 and the second electrode 445 is designated as the second region R2. The thickness T1 of the titanium layer 442 in the first region R1 is thicker than the thickness T2 of the titanium layer 442 in the second region R2. Since the piezoelectric layer 444 in the second region R2 has a smaller impact on ejection performance, its piezoelectric properties are not required compared to the titanium layer 442 in the first region R1. Therefore, its thickness T2 can be thinner than its thickness T1. Furthermore, by also forming a titanium layer 442 in the second region R2, the occurrence of cracks in the piezoelectric layer 444 at the boundary between the first region R1 and the second region R2 can be suppressed compared to the case where no titanium layer 442 is formed in the second region R2. This is because, although a difference in the orientation of the piezoelectric layer 444 may occur at the boundary between the first region R1 and the second region R2 if the titanium layer 442 is not formed in the second region R2, the formation of the titanium layer 442 in the second region R2 makes it difficult for the difference in orientation to occur.

[0056] like Figure 4 As shown, a strip-shaped first conductive layer 451 and a second conductive layer 452 extending in the Y direction are formed above the second electrode 445. The first conductive layer 451 and the second conductive layer 452 are electrically connected to the second electrode 445. The first conductive layer 451 and the second conductive layer 452 are arranged opposite each other in the X direction with a piezoelectric element 44 in between. The first conductive layer 451 and the second conductive layer 452 are, for example, conductive patterns formed by stacking a gold conductive film on the surface of a conductive film formed of a nickel-chromium alloy. The first conductive layer 451 and the second conductive layer 452 also function as counterweights for suppressing the vibration of the vibrating plate 36.

[0057] A4. Method for manufacturing piezoelectric elements:

[0058] First, a vibratory plate 36 is fabricated. Specifically, silicon dioxide is formed on the surface in the +Z direction by thermally oxidizing a silicon substrate 361. Next, a Zr layer is formed by sputtering, and a ZrO2 layer as an insulating layer 362 is formed by thermally oxidizing the Zr.

[0059] Next, the first electrode 441 is formed. Specifically, a Ti layer and a Pt layer are sequentially stacked by sputtering. Next, an Ir layer is stacked by sputtering. Next, the Ti layer, Pt layer, and Ir layer are patterned using photolithography. Specifically, a photoresist is applied to the Ir layer, and after exposure, the Ti, Pt, and Ir layers are ion-milled. Next, the photoresist is removed by oxygen plasma ashing polishing, and the substrate is cleaned.

[0060] Next, a titanium layer 442 is formed. For example, it can be formed using sputtering. Alternatively, the titanium layer 442 can be formed using CVD (Chemical Vapor Deposition) or MOD (Metal-Organic Decomposition). Next, an orientation control layer 443 is formed using MOD (Metal-Organic Decomposition). Specifically, first, a propionic acid solution of Pb, Bi, Fe, and Ti, prepared in a molar ratio of Bi:Pb:Fe:Ti = 110:10:50:50, is spin-coated onto a vibrating plate 36. Next, drying and degreasing are performed at 350°C using a hot plate. Next, a heat treatment is performed at 700°C for five minutes using RTA (Rapid Thermal Annealing).

[0061] Next, the piezoelectric layer 444 is formed using a solution method. Specifically, the formation method involves first applying an acetic acid solution of Pb, Zr, and Ti, prepared in a molar ratio of Pb:Zr:Ti = 118:52:48, onto the orientation control layer 443 via spin coating. Next, drying and degreasing are performed using a hot plate at 200°C and 410°C. Finally, a heat treatment is performed at 740°C for five minutes using RTA (Rapid Thermal Anneal).

[0062] Next, the second electrode 445 is formed. Specifically, Ir is deposited by sputtering. Then, the Ir layer is patterned using photolithography.

[0063] According to the above method, the piezoelectric element 44, by having a titanium layer 442, can counteract the influence of the orientation of the first electrode 441, thereby ensuring that the orientation control layer 443 is sufficiently (100) oriented. Furthermore, the piezoelectric layer 444 formed on the orientation control layer 443 can be well (100) oriented. Therefore, the piezoelectric characteristics of the piezoelectric element 44 can be improved.

[0064] B. Other implementation methods:

[0065] (B1) In the above embodiment, the first electrode 441 is formed for each first region R1, and the second electrode 445 is provided in a manner shared by a plurality of first regions R1 arranged in the Y direction. Alternatively, the first electrode 441 may be provided in a manner shared by a plurality of first regions R1 arranged in the Y direction, and the second electrode 445 may be provided for each first region R1.

[0066] (B2) The fabrication method of the piezoelectric element 44 is not limited to the above. For example, the etching during the pattern formation of the first electrode 441 can be an etching method other than ion milling. Furthermore, the formation method of the orientation control layer 443 is not limited to the MOD method, but can also be other methods such as sol-gel method and sputtering method.

[0067] (B3) In the above embodiment, the first electrode 441 is formed by stacking a Ti layer, a Pt layer, and an Ir layer. Furthermore, in order to be electrically connected to the driving circuit, the Ti layer, Pt layer, and Ir layer are led out in the +X direction. Alternatively, it can be configured such that only the Ir layer is led out in the +X direction, thereby enabling the first electrode 441 and the circuit board 50 to conduct electricity.

[0068] C. Examples and Comparative Examples:

[0069] C1. Preparation of Examples and Comparative Examples:

[0070] The following Examples 1, 2, and Comparative Examples were prepared.

[0071] As an example 1, the following structure was used: a titanium layer and an orientation control layer were sequentially stacked on the first electrode, and lead zirconate titanate was formed on the orientation control layer as a piezoelectric layer.

[0072] As an example 2, the following structure was used: a titanium layer and an orientation control layer were sequentially stacked on the first electrode, and sodium potassium niobate was formed on the orientation control layer as a piezoelectric layer.

[0073] As a comparative example, a structure was used in which a titanium layer is not present, but an orientation control layer is stacked on the first electrode, and lead zirconate titanate is formed on the orientation control layer as a piezoelectric layer.

[0074] C2. Evaluation of the titanium layer and orientation control layer:

[0075] A portion of the sample from Example 1 was cut off. A focused ion beam (FIB) was used to expose the cross-section of the sample, and the STEM-EDS (Scanning Transmission Electron Microscope-Energy-Dispersive-Spectroscopy) spectral profile along the depth direction of the cross-section was observed. The spherical aberration scanning transmission analytical electron microscope used was a JEM-ARM200F manufactured by Nippon Electron Ltd.

[0076] Figure 6 This is a sampled STEM image. Figure 7This is a graph representing the results of the sampled EDX. For example... Figure 6 As shown, titanium layers with varying contrast can be identified between the alignment control layer and the first electrode. Figure 7 As shown, the titanium layer between the orientation control layer and the first electrode contains a large amount of Ti. The titanium layer is considered to be amorphous titanium oxide (TiOx).

[0077] C3. Evaluation of the piezoelectric layer:

[0078] X-ray diffraction patterns of Examples 1, 2, and the Comparative Example were measured, and the degree of orientation of the piezoelectric layer was evaluated. The X-ray diffraction apparatus was a Bruker D8DISCOVER with GADDS. Measurement conditions were: tube voltage: 50 kV, tube current: 100 mA, detector distance: 15 cm, collimating tube diameter: 0.1 mm, and measurement time: 180 seconds. The two-dimensional data obtained by measurement were transformed into X-ray diffraction intensity curves using a 2θ range of 20° to 50°, a χ range of -95° to -85°, a step size of 0.02°, and a bin normalized intensity method. Furthermore, for samples from Example 1 before piezoelectric layer formation and from the Comparative Example before piezoelectric layer formation, depth-direction composition analysis was performed using X-ray photoelectron spectroscopy (XPS) during backsputtering. The X-ray photoelectron spectroscopy apparatus used was a ThermoFisher Scientific ESCALAB 250.

[0079] Figure 8 The X-ray diffraction pattern is shown in Example 1. Figure 9 The X-ray diffraction pattern is shown in Example 2. Figure 10 The X-ray diffraction pattern is for a comparative example. In the X-ray diffraction pattern of the comparative example, the peak intensities of the (100) plane near 22° and the (110) plane near 31° are high, and the peak intensity of the (111) plane near 38° is also identified. In contrast, the peak intensity of the (100) plane is high in the X-ray diffraction patterns of Examples 1 and 2. That is, in the comparative example, the piezoelectric layer is not (100) oriented, while in Examples 1 and 2, the piezoelectric layer is (100) oriented.

[0080] Figure 11 The results of XPS compositional analysis of Ti in the film thickness direction are shown for samples from Example 1 before piezoelectric layer formation and for samples from a comparative example before piezoelectric layer formation. Figure 11 At the location indicated by the circle, a peak was identified in Example 1, while no peak was identified in the Comparative Example. That is, in the Comparative Example, it can be confirmed that no titanium layer was formed.

[0081] Based on the above results, in Examples 1 and 2 where a titanium layer is formed beneath the orientation control layer, the piezoelectric layer is oriented at (100). In contrast, in the comparative example, no titanium layer is formed, and the piezoelectric layer is not oriented at (100). This is believed to be because the orientation state of the underlying layer, i.e., the substrate information, is canceled out by the titanium layer, thus allowing the piezoelectric layer to be oriented by forming the titanium layer.

[0082] D. Other methods:

[0083] This disclosure is not limited to the embodiments described above, and various structures can be implemented without departing from its spirit. For example, in order to solve some or all of the above-described problems, or to achieve some or all of the above-described effects, the technical features of the embodiments corresponding to the technical features of the various methods described in the Summary of the Invention section can be appropriately replaced or combined. Furthermore, if a technical feature is not described as essential in this specification, it can be appropriately deleted.

[0084] (1) According to one aspect of this disclosure, a piezoelectric element is provided in which a first electrode, a piezoelectric layer, and a second electrode are sequentially stacked on a substrate. The piezoelectric element includes: an orientation control layer disposed between the piezoelectric layer and the first electrode, for controlling the orientation of the piezoelectric layer; and a titanium layer disposed between the first electrode and the orientation control layer, comprising at least Ti. According to this approach, by having the titanium layer, the piezoelectric element can counteract the influence of the orientation of the first electrode, thereby ensuring sufficient orientation of the orientation control layer. Furthermore, the piezoelectric layer formed on the orientation control layer can be well oriented. Thus, the piezoelectric characteristics of the piezoelectric element can be improved.

[0085] (2) Alternatively, in the piezoelectric element described above, the titanium layer has the function of counteracting the influence of orientation from the first electrode to the piezoelectric layer. According to this method, the orientation control layer can be sufficiently oriented.

[0086] (3) Alternatively, in the piezoelectric element described above, when the amount of a metal element different from Ti contained in the titanium layer is set as na and the amount of Ti contained in the titanium layer is set as nt, na < nt is satisfied.

[0087] (4) Alternatively, the following method can be used, namely, in the piezoelectric element of the above method, na≤0.4×nt is satisfied.

[0088] (5) Alternatively, the following method can be used, namely, in the piezoelectric element of the above method, na≤0.2×nt is satisfied.

[0089] (6) Alternatively, in the piezoelectric element described above, the orientation control layer may contain at least one of Pb and Bi.

[0090] (7) Alternatively, the orientation control layer in the piezoelectric element described above may contain Pb, Bi, Fe, and Ti.

[0091] (8) Alternatively, in the piezoelectric element described above, the orientation control layer may contain Pb, Fe, and Ti, but not Bi.

[0092] (9) Alternatively, in the piezoelectric element described above, the orientation control layer contains Bi, Fe, and Ti, but not Pb.

[0093] (10) Alternatively, in the piezoelectric element described above, the Ti content in the titanium layer as measured by EDX analysis is greater than the Ti content in the orientation control layer as measured by EDX analysis.

[0094] (11) Alternatively, in the piezoelectric element described above, the titanium layer contains Fe, and the Fe content in the titanium layer, as measured by EDX analysis, is less than the Fe content in the orientation control layer, as measured by EDX analysis.

[0095] (12) Alternatively, in the piezoelectric element described above, the Fe content in the titanium layer as measured by EDX analysis is greater than the Fe content in the first electrode as measured by EDX analysis.

[0096] (13) Alternatively, in the piezoelectric element described above, when the region where the piezoelectric layer is sandwiched between the first electrode and the second electrode is designated as the first region and the region where the piezoelectric layer is not sandwiched between the first electrode and the second electrode is designated as the second region, the thickness of the titanium layer in the first region is greater than the thickness of the titanium layer in the second region.

[0097] (14) Alternatively, in the piezoelectric element described above, the orientation control layer is a composite oxide with a perovskite structure.

[0098] (15) Alternatively, in the piezoelectric element described above, the titanium layer is 1 nm or more and 30 nm or less, and the orientation control layer is 5 nm or more and 200 nm or less.

[0099] (16) According to one aspect of this disclosure, a piezoelectric element is provided in which a first electrode, a piezoelectric layer, and a second electrode are sequentially stacked on a substrate. The piezoelectric element includes: an alignment control layer disposed between the piezoelectric layer and the first electrode, for controlling the alignment of the piezoelectric layer; and a counteracting layer disposed between the first electrode and the alignment control layer, for counteracting the influence of the alignment from the first electrode to the piezoelectric layer. According to this approach, the influence of the first electrode's alignment can be counteracted, thereby ensuring sufficient alignment of the alignment control layer.

[0100] (17) Alternatively, the piezoelectric element in the above manner may be provided with a piezoelectric layer containing Pb, Zr, and Ti.

[0101] (18) Alternatively, in the piezoelectric element described above, the piezoelectric layer contains K, Na, and Nb.

[0102] (19) According to one aspect of this disclosure, a liquid ejector head is provided. This liquid ejector head may also have a piezoelectric element as described above and a vibrating plate driven by the piezoelectric element to vibrate. According to this approach, a liquid ejector head having an oriented piezoelectric element with good piezoelectric properties can be provided.

[0103] (20) According to one aspect of this disclosure, a liquid ejection device is provided. This liquid ejection device may also include the liquid ejection head and a control unit for controlling the operation of the liquid ejection head. According to this approach, a liquid ejection device having a liquid ejection head with a piezoelectric element can be provided, and the piezoelectric element has good piezoelectric characteristics.

[0104] Symbol Explanation

[0105] 12…medium; 14…liquid receiving section; 16…conveying mechanism; 20…head moving mechanism; 21…conveyor belt; 22…carriage; 26…liquid nozzle; 26a…supply chamber; 26b…supply channel; 26c…connecting channel; 32…channel substrate; 32a…first opening; 32b…second opening; 32c…third opening; 32d…partition; 34…pressure chamber substrate; 34a…opening; 36…vibrating plate; 44…piezoelectric element; 46…sealing body; 46a…sealing body opening; 46b…sealing body recess; 48…frame section; 4 8a, 444a… Through hole; 50… Drive circuit; 51… Electrical wiring; 62… Nozzle plate; 64… Vibration absorber; 80… Control unit; 100… Liquid ejection device; 361… Silicon substrate; 362… Insulator layer; 441… First electrode; 442… Titanium layer; 443… Orientation control layer; 444… Piezoelectric layer; 445… Second electrode; 446… First wiring; 451… First conductive layer; 452… Second conductive layer; C… Pressure chamber; N… Nozzle; R1… First region; R2… Second region; Ra, Rb… Space; T1, T2… Thickness.

Claims

1. A piezoelectric element, which is formed by sequentially stacking a first electrode, a piezoelectric layer, and a second electrode on a substrate, and has: an orientation control layer provided between the piezoelectric layer and the first electrode, and configured to control an orientation of the piezoelectric layer; and a titanium layer provided between the first electrode and the orientation control layer, and containing at least Ti, the titanium layer having a function of canceling an influence on the orientation of the piezoelectric layer from the first electrode, the orientation control layer being provided above the titanium layer in a manner so as to be adjacent to the titanium layer.

2. The piezoelectric element according to claim 1, wherein, when a substance amount of a metal element other than Ti contained in the titanium layer is set as na, and a substance amount of Ti contained in the titanium layer is set as nt, na < nt is satisfied.

3. The piezoelectric element according to claim 2, wherein, na ≤ 0.4 x nt is satisfied.

4. The piezoelectric element according to claim 2, wherein, na ≤ 0.2 x nt is satisfied.

5. The piezoelectric element according to claim 1, wherein, the orientation control layer contains at least any one of Pb and Bi.

6. The piezoelectric element according to claim 5, wherein, the orientation control layer contains Pb, Bi, Fe, and Ti.

7. The piezoelectric element according to claim 5, wherein, the orientation control layer contains Pb, Fe, and Ti, and does not contain Bi.

8. The piezoelectric element according to claim 5, wherein, the orientation control layer contains Bi, Fe, and Ti, and does not contain Pb.

9. The piezoelectric element according to any one of claims 6 to 8, wherein, a content of Ti in the titanium layer measured by energy dispersive X-ray spectroscopy (EDX) is larger than a content of Ti in the orientation control layer measured by EDX.

10. The piezoelectric element according to claim 6, wherein, the titanium layer contains Fe, a content of Fe in the titanium layer measured by EDX is smaller than a content of Fe in the orientation control layer measured by EDX.

11. The piezoelectric element according to claim 10, wherein, a content of Fe in the titanium layer measured by EDX is larger than a content of Fe in the first electrode measured by EDX.

12. The piezoelectric element according to claim 1, wherein, when a region in which the piezoelectric layer is sandwiched between the first electrode and the second electrode is set as a first region, and a region in which the piezoelectric layer is not sandwiched between the first electrode and the second electrode is set as a second region, a thickness of the titanium layer in the first region is thicker than a thickness of the titanium layer in the second region.

13. The piezoelectric element according to claim 1, wherein, the orientation control layer is a composite oxide having a perovskite structure.

14. The piezoelectric element according to claim 1, wherein, the titanium layer is 1 nm or more and 30 nm or less, and the orientation control layer is 5 nm or more and 200 nm or less.

15. The piezoelectric element according to claim 1, wherein, ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ The piezoelectric layer contains Pb, Zr, and Ti.

16. The piezoelectric element as claimed in claim 1, wherein, The piezoelectric layer contains K, Na, and Nb.

17. A liquid ejector head, comprising: The piezoelectric element according to any one of claims 1 to 16; A vibrating plate, which is driven by the piezoelectric element to vibrate.

18. A liquid ejection device, comprising: The liquid ejector head as described in claim 17; The control unit controls the movement of the liquid nozzle.

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