Piezoelectric element, liquid jet head, and printer

Abstract

The invention relates to a piezoelectric element, a liquid ejecting head and a printer, and provides a piezoelectric element capable of suppressing generation of cracks. The piezoelectric element comprises a first electrode and a second electrode; and a piezoelectric layer provided between the first electrode and the second electrode and having a plurality of layers including a composite oxide having a perovskite-type structure containing potassium, sodium, and niobium, the piezoelectric layer being subjected to asymmetric reflection measurement using X-ray diffraction at an inclination angle psi in a range of sin2 psi of 0-0.7, when the obtained peak is separated into a high-angle side peak and a low-angle side peak, a lattice constant in the thickness direction of the piezoelectric layer is obtained on the basis of the low-angle side peak, and the lattice constant is drawn into a multipoint diagram for the range, the lattice constant is calculated when the multipoint diagram is linearly approximated by a least square method, and the lattice constant in the thickness direction of the piezoelectric layer is calculated on the basis of the high-angle side peak and the low-angle side peak. The slope of the approximate straight line is 0.002 or less.

Description

Technical Field

[0001] The present invention relates to a piezoelectric element, a liquid ejector head, and a printer. Background Art

[0002] A piezoelectric element used in a liquid ejector head of an inkjet printer or the like is configured, for example, by sandwiching a piezoelectric body layer made of a piezoelectric material exhibiting an electromechanical conversion function between two electrodes.

[0003] For example, Patent Document 1 discloses a piezoelectric body element including a thin-film piezoelectric body layer made of a perovskite-type composite oxide containing potassium, sodium, and niobium.

[0004] Patent Document 1: Japanese Patent Application Laid-Open No. 2018-133458

[0005] In a piezoelectric body element as described above, internal stress may accumulate in the piezoelectric body layer depending on the temperature during formation of the piezoelectric body layer, and cracks may occur in the piezoelectric body layer. Summary of the Invention

[0006] One aspect of the piezoelectric element according to the present invention includes:

[0007] a first electrode and a second electrode; and

[0008] a piezoelectric body layer disposed between the first electrode and the second electrode, having a plurality of layers each containing a perovskite-type structure composite oxide containing potassium, sodium, and niobium,

[0009] When performing an asymmetric reflection measurement on the piezoelectric body layer at an inclination angle ψ in the range of 0 or more and 0.7 or less using X-ray diffraction method, separating the obtained peaks into a high-angle side peak and a low-angle side peak, obtaining a lattice constant in the thickness direction of the piezoelectric body layer based on the low-angle side peak, and plotting the lattice constant as a multi-point graph for the range, when performing a linear approximation on the multi-point graph by the least squares method, the slope of the approximate straight line is 0.002 or less. 2

[0010] One aspect of the liquid ejector head according to the present invention includes:

[0011] the piezoelectric element;

[0012] a flow path forming substrate forming a pressure generating chamber whose volume changes according to the piezoelectric element; and

[0013] a nozzle plate forming a nozzle communicating with the pressure generating chamber.

[0014] One aspect of the printer according to the present invention includes:

[0015] The liquid nozzle;

[0016] A conveying mechanism that relatively moves the recording medium with respect to the liquid nozzle; and

[0017] A control unit that controls the liquid nozzle and the conveying mechanism. Description of the Drawings

[0018] Figure 1 A cross-sectional view schematically showing a piezoelectric element according to the present embodiment.

[0019] Figure 2 A diagram for explaining the relationship between the tilt angle ψ and the interplanar spacing d of the KNN layer.

[0020] Figure 3 An exploded perspective view schematically showing a liquid nozzle according to the present embodiment.

[0021] Figure 4 A top view schematically showing a liquid nozzle according to the present embodiment.

[0022] Figure 5 A cross-sectional view schematically showing a liquid nozzle according to the present embodiment.

[0023] Figure 6 A perspective view schematically showing a printer according to the present embodiment.

[0024] Figure 7 Proton NMR measurement results of niobium 2-ethylhexanoate used in the KNN precursor solution.

[0025] Figure 8 A graph showing the longitudinal lattice constant and the transverse lattice constant calculated at each tilt angle ψ in Example 1 with respect to sin 2 ψ.

[0026] Figure 9 A graph showing the longitudinal lattice constant and the transverse lattice constant calculated at each tilt angle ψ in Comparative Example 1 with respect to sin 2 ψ.

[0027] Figure 10 A table showing the slopes of the approximate straight lines in Examples 1-4 and Comparative Example 1.

[0028] Description of Reference Numerals

[0029] 2: Substrate; 10: First electrode; 20: Orientation control layer; 30: Piezoelectric layer; 32: Crystal layer; 40: Second electrode; 100: Piezoelectric element; 200: Liquid nozzle; 202: Lead electrode; 203: Adhesive; 204: Connection wiring; 210: Flow path forming substrate; 211: Pressure generating chamber; 212: Partition wall; 213: First communication path; 214: Second communication path; 215: Third communication path; 216: Manifold; 217: Supply flow path; 220: Nozzle plate; 222: Nozzle hole; 230: Diaphragm; 232: Silicon oxide layer; 234: Zirconium oxide layer; 240: Protection substrate; 242, 244: Through hole; 246: Opening; 250: Circuit board; 260: Plastic substrate; 262: Sealing layer; 264: Fixing plate; 266: Through hole; 300: Printer; 310: Print head assembly; 312, 314: Ink cartridge; 316: Carriage; 320: Device main body; 322: Carriage shaft; 330: Driving motor; 332: Timing belt; 340: Conveyor roller; 350: Printer controller. Detailed implementation mode

[0030] Next, the preferred implementation modes of the present invention will be described in detail with reference to the accompanying drawings. In addition, the implementation modes described below do not unduly limit the content of the present invention recited in the claims. Furthermore, not all of the configurations described below are necessarily essential components of the present invention.

[0031] 1. Piezoelectric element

[0032] 1.1. Configuration

[0033] First, the piezoelectric element according to the present implementation mode will be described with reference to the accompanying drawings. Figure 1 FIG. is a cross-sectional view schematically showing the piezoelectric element 100 according to the present implementation mode.

[0034] As Figure 1 shown, the piezoelectric element 100 includes, for example, a first electrode 10, an orientation control layer 20, a piezoelectric layer 30, and a second electrode 40. The piezoelectric element 100 is provided above the substrate 2.

[0035] The substrate 2 is, for example, a flat plate formed of a semiconductor, an insulator, or the like. The substrate 2 may be a single layer or a laminate formed by laminating a plurality of layers. As long as the upper surface of the substrate 2 is a planar shape, the internal structure is not limited, and it may be a structure in which a space or the like is formed inside.

[0036] The substrate 2 may also have a diaphragm that deforms according to the operation of the piezoelectric layer 30. The diaphragm is, for example, a silicon oxide layer, a zirconium oxide layer, or a laminate in which a zirconium oxide layer is provided on a silicon oxide layer.

[0037] The first electrode 10 is disposed above the substrate 2. The first electrode 10 is disposed between the substrate 2 and the alignment control layer 20. The shape of the first electrode 10 is, for example, a layer shape. The thickness of the first electrode 10 is, for example, 5 nm or more and 300 nm or less, preferably 50 nm or more and 200 nm or less.

[0038] The first electrode 10 is, for example, a titanium layer, a platinum layer, an iridium layer, or the like. The first electrode 10 may also be laminated in the order of a titanium layer, a platinum layer, and an iridium layer from the substrate 2 side. The titanium layer, for example, improves the tightness between the substrate 2 and the platinum layer. The first electrode 10 is one of the electrodes for applying a voltage to the piezoelectric layer 30.

[0039] The alignment control layer 20 is disposed above the first electrode 10. The alignment control layer 20 is disposed between the first electrode 10 and the piezoelectric layer 30. In the illustrated example, the alignment control layer 20 is also disposed above the substrate 2. The thickness of the alignment control layer 20 is, for example, 5 nm or more and 100 nm or less, preferably 10 nm or more and 50 nm or less.

[0040] The alignment control layer 20 contains a perovskite-type composite oxide containing bismuth (Bi), iron (Fe), titanium (Ti), and lead (Pb). The alignment control layer 20 is, for example, a lead bismuth titanate ferrite ((Bi,Pb)(Fe,Ti)O3: BFTP) layer. The alignment control layer 20 may also be a BFTP layer added with an additive. The alignment control layer 20 controls the orientation of the piezoelectric layer 30.

[0041] The piezoelectric layer 30 is disposed above the alignment control layer 20. The piezoelectric layer 30 is disposed between the first electrode 10 and the second electrode 40. In the illustrated example, the piezoelectric layer 30 is disposed between the alignment control layer 20 and the second electrode 40. The thickness of the piezoelectric layer 30 is, for example, 100 nm or more and 3000 nm or less, preferably 200 nm or more and 2000 or less, more preferably 600 nm or more and 2000 nm or less, and further preferably greater than 600 nm and 1000 nm or less. The thickness of the piezoelectric layer 30 is measured by SEM (Scanning Electron Microscope). The piezoelectric layer 30 has columnar crystals extending in the thickness direction of the piezoelectric layer 30 (hereinafter also simply referred to as the "thickness direction"). By applying a voltage between the first electrode 10 and the second electrode 40, the piezoelectric layer 30 is deformed.

[0042] The piezoelectric layer 30 includes a plurality of crystal layers 32. The piezoelectric layer 30 is constituted by, for example, a plurality of crystal layers 32. The number of the plurality of crystal layers 32 is, for example, 2 or more and 30 or less, and preferably 3 or more and 20 or less. In the illustrated example, five crystal layers 32 are provided. The thickness of the crystal layer 32 is, for example, 10 nm or more and 200 nm or less, and preferably 30 nm or more and 150 nm or less.

[0043] The crystal layer 32 is a layer including a perovskite-type structure composite oxide containing potassium (K), sodium (Na), and niobium (Nb). The crystal layer 32 is, for example, a sodium potassium niobate ((K,Na)NbO3: KNN) layer. The crystal layer 32 may also be a KNN layer added with an additive. Examples of the additive include lithium (Li), manganese (Mn), and copper (Cu). The content of the additive in the crystal layer 32 is, for example, 10 mol% or less, and preferably 5 mol% or less. The additive may also be present preferentially at the grain boundaries of the crystal layer 32.

[0044] The second electrode 40 is provided above the piezoelectric layer 30. Although not shown, the second electrode 40 may be further provided on the side surface of the piezoelectric layer 30 and above the substrate 2 as long as it can be electrically separated from the first electrode 10. The shape of the second electrode 40 is, for example, a layer shape. The thickness of the second electrode 40 is, for example, 15 nm or more and 300 nm or less.

[0045] The second electrode 40 is, for example, a platinum layer, a titanium layer, or an iridium layer. The second electrode 40 may also be formed by laminating a plurality of the layers exemplified above. The second electrode 40 is another electrode for applying a voltage to the piezoelectric layer 30.

[0046] 1.2. X-ray diffraction method

[0047] A case of using X-ray diffraction (XRD) method for the piezoelectric layer 30 will be described. In XRD, the inclination angle ψ is changed, and an asymmetric reflection with different incident and reflection angles of X-rays is measured. The measurement range of the asymmetric reflection is such that sin 2 ψ is in the range of 0 or more and 0.7 or less. In addition, as long as the measurement range includes the range where sin 2 ψ is in the range of 0 or more and 0.7 or less, it may also include the range where sin 2 ψ is greater than 0.7. XRD can also be performed by thin film X-ray diffraction. The inclination angle ψ is, for example, 0° or more and 90° or less.

[0048] The peaks obtained by XRD are separated into a high-angle side peak and a low-angle side peak. The peak separation is performed by a Gaussian function. The low-angle side peak is the peak on the lower 2θ side among the two peaks separated from the peak. The high-angle side peak is the peak on the higher 2θ side among the two peaks separated from the peak.

[0049] Based on the peak positions of the low-angle side peaks, the longitudinal lattice constant in the thickness direction is obtained. Specifically, according to the Bragg formula, the longitudinal lattice constant is obtained based on the peak positions of the low-angle side peaks. The KNN layer has a crystal structure of a tetragonal system. The longitudinal lattice constant is the lattice constant when the a-axis or c-axis, which is longer than the b-axis, is along the thickness direction. Similarly, based on the peak positions of the high-angle side peaks, the transverse lattice constant in the thickness direction is obtained. The transverse lattice constant is the lattice constant when the a-axis and c-axis are along the direction orthogonal to the thickness direction.

[0050] At sin 2 ψ is in the range of 0 or more and 0.7 or less, the longitudinal lattice constant is measured multiple times. The number of measurements is, for example, 5 or more and 12 or less, and preferably 7 or more and 10 or less. For sin 2 ψ in the range of 0 or more and 0.7 or less, the longitudinal lattice constant is plotted as a multi-point graph. Similarly, the transverse lattice constant is measured multiple times. The transverse lattice constant is plotted as a multi-point graph.

[0051] When the longitudinal lattice constant is plotted as a multi-point graph, when this multi-point graph is linearly approximated by the least squares method, the slope of the approximate straight line is 0.002 or less, preferably -0.012 or less, and more preferably -0.0121 or less. The slope of the approximate straight line can also be -0.03 or more.

[0052] When the transverse lattice constant is plotted as a multi-point graph, when this multi-point graph is linearly approximated by the least squares method, the slope of the approximate straight line is -0.03 or less, preferably -0.0387 or less. The slope of the approximate straight line can also be -0.05 or more.

[0053] When the inclination angle ψ is 0°, the difference between the longitudinal lattice constant and the transverse lattice constant is, for example, 0.080 or more, preferably 0.082 or more. This difference can also be 0.10 or less.

[0054] Here, Figure 2 is a graph for explaining the relationship between the inclination angle ψ and the interplanar spacing d of the KNN layer. The greater the tensile stress F generated in the KNN layer, the greater the interplanar spacing d. In the illustrated example, the tensile stress F is the stress that stretches the KNN layer in the direction orthogonal to the film thickness direction (also referred to as the "in-plane direction" below). The in-plane direction can also be the horizontal direction. Among them, when ψ = 0°, the interplanar spacing d in the in-plane direction is not easily affected by the tensile stress F. On the other hand, for example, as Figure 2As shown for ψ = 30° and 45°, the larger the inclination of the surface with respect to the tensile stress F, the larger the surface spacing d. The larger ψ is, the larger the lattice constant calculated from this surface spacing d. Thus, the larger the slope of the above approximate straight line, the larger the tensile stress F. Conversely, the smaller the slope of the approximate straight line, the smaller the tensile stress F.

[0055] 1.3. Effect

[0056] The piezoelectric element 100 includes a first electrode 10, a second electrode 40, and a piezoelectric layer 30 disposed between the first electrode 10 and the second electrode 40 and having a plurality of crystal layers 32 containing a perovskite-type composite oxide containing potassium, sodium, and niobium. When performing an asymmetric reflection measurement on the piezoelectric layer 30 at an inclination angle of ψ within the range of 0 or more and 0.7 or less using X-ray diffraction method, and separating the obtained peaks into a high-angle side peak and a low-angle side peak, and calculating the lattice constant in the thickness direction of the piezoelectric layer 30 based on the low-angle side peak and plotting the lattice constant as a multi-point graph for this range, when performing a linear approximation on the multi-point graph by the least squares method, the slope of the approximate straight line is 0.002 or less. 2 As described above, the smaller the slope of the approximate straight line, the smaller the tensile stress F generated in the piezoelectric layer 30. In the piezoelectric element 100, since the slope of the approximate straight line is 0.002 or less, the tensile stress F generated in the piezoelectric layer 30 is small. Thus, in the piezoelectric element 100, the generation of cracks can be suppressed.

[0057] When the tensile stress F generated in the piezoelectric layer is large, cracks are likely to occur in the piezoelectric layer. On the other hand, when the tensile stress F in the piezoelectric layer is small and the compressive stress dominates, cracks are less likely to occur in the piezoelectric layer. The piezoelectric layer 30 of the piezoelectric element 100 is configured such that the compressive stress dominates.

[0058] In the piezoelectric element 100, the slope of the approximate straight line is -0.012 or less. Therefore, in the piezoelectric element 100, the tensile stress F generated in the piezoelectric layer 30 can be further reduced.

[0059] In the piezoelectric element 100, the thickness of the piezoelectric layer 30 is greater than 600 nm and 2000 nm or less. Therefore, in the piezoelectric element 100, the generation of cracks can be suppressed.

[0060] In the piezoelectric element 100, an orientation control layer 20 containing bismuth, iron, titanium, and lead is further provided between the first electrode 10 and the piezoelectric layer 30. Therefore, in the piezoelectric element 100, the orientation of the piezoelectric layer 30 can be controlled.

[0061]

[0062] ​In the piezoelectric element 100, when the tilt angle ψ is 0°, the difference between the lattice constant in the thickness direction obtained based on the low-angle side peak and the lattice constant in the thickness direction obtained based on the high-angle side peak is 0.082 or more. Therefore, in the piezoelectric element 100, the generation of cracks can be suppressed.

[0063] 2. Method for manufacturing a piezoelectric element

[0064] Next, while referring to the attached Figure 1 the method for manufacturing the piezoelectric element 100 according to the present embodiment will be described.

[0065] As Figure 1 shown, a substrate 2 is prepared. Specifically, a silicon oxide layer is formed by thermally oxidizing a silicon substrate. Then, a zirconium layer is formed above the silicon oxide layer by a sputtering method or the like, and a zirconia layer is formed by thermally oxidizing the zirconium layer. Through the above steps, the substrate 2 can be prepared.

[0066] Then, a first electrode 10 is formed above the substrate 2. The first electrode 10 is formed, for example, by a sputtering method or a vacuum deposition method or the like. Then, the first electrode 10 is patterned by, for example, photolithography and etching.

[0067] Then, an orientation control layer 20 is formed above the first electrode 10 and the substrate 2. The orientation control layer 20 is formed, for example, by a sol-gel method or a CSD (Chemical Solution Deposition) method such as MOD (Metal Organic Deposition).

[0068] Specifically, first, a metal complex containing bismuth, a metal complex containing iron, a metal complex containing titanium, and a metal complex containing lead are dissolved or dispersed in an organic solvent to prepare a precursor solution. Then, the precursor solution is coated on the first electrode 10 by a spin coating method to form a precursor layer. Then, the precursor layer is heated and dried at a temperature of, for example, 130°C or higher and 250°C or lower for a certain period of time, and further, the dried precursor layer is heated and held at a temperature of, for example, 300°C or higher and 450°C or lower for a certain period of time to degrease it. Then, the degreased precursor layer is fired at a temperature of, for example, 550°C or higher and 800°C or lower to crystallize it. Through the above steps, the orientation control layer 20 made of a BFTP layer can be formed.

[0069] Then, a piezoelectric layer 30 is formed above the orientation control layer 20. The piezoelectric layer 30 is formed, for example, by a CSD method.

[0070] Specifically, first, for example, a metal complex containing potassium, a metal complex containing sodium, and a metal complex containing niobium are dissolved or dispersed in an organic solvent to prepare a precursor solution.

[0071] Examples of the metal complex containing potassium include potassium 2-ethylhexanoate, potassium acetate, etc. Examples of the metal complex containing sodium include sodium 2-ethylhexanoate, sodium acetate, etc.

[0072] Examples of the metal complex containing niobium include niobium 2-ethylhexanoate, etc. The piezoelectric layer 30 is a layer formed from niobium 2-ethylhexanoate. In proton NMR (Nuclear Magnetic Resonance) measurement of niobium 2-ethylhexanoate, no peak is confirmed in the range of 3 ppm or more and 5 ppm or less. Therefore, niobium 2-ethylhexanoate has few impurities. Niobium 2-ethylhexanoate may also be free of impurities.

[0073] Examples of the solvent include 2-ethylhexanoic acid, decane, or a mixed solvent thereof, etc.

[0074] Then, the prepared precursor solution is coated on the alignment control layer 20 using a spin coating method or the like to form a precursor layer. Then, by heating and drying the precursor layer at a temperature of, for example, 130°C or more and 250°C or less for a certain period of time, and further heating and holding the dried precursor layer at a temperature of, for example, 300°C or more and 450°C or less for a certain period of time, it is defatted. Then, by firing the defatted precursor layer at a temperature of, for example, 550°C or more and 800°C or less, it is crystallized.

[0075] Through the above steps, the crystal layer 32 of the piezoelectric layer 30 can be formed. Subsequently, the series of processes from coating the precursor solution to firing the precursor layer are repeated multiple times. Thereby, the piezoelectric layer 30 composed of multiple crystal layers 32 can be formed.

[0076] In the process of forming the crystal layer 32, the heating device for drying and defatting the precursor layer is, for example, a hot plate. The heating device for firing the precursor layer is an infrared annealing device (Rapid Thermal Annealing: RTA).

[0077] Then, a second electrode 40 is formed above the piezoelectric layer 30. The second electrode 40 is formed, for example, by a sputtering method or a vacuum deposition method, etc. Then, the second electrode 40 and the piezoelectric layer 30 are patterned, for example, by photolithography and etching. In addition, the second electrode 40 and the piezoelectric layer 30 may also be patterned in different processes.

[0078] Through the above processes, the piezoelectric element 100 can be manufactured.

[0079] 3. Liquid nozzle

[0080] Next, while referring to the attached Figure 1 drawings, the liquid nozzle according to this embodiment will be described. Figure 3 FIG. is an exploded perspective view schematically showing the liquid nozzle 200 according to this embodiment. Figure 4 FIG. is a top view schematically showing the liquid nozzle 200 according to this embodiment. Figure 5 FIG. is a cross-sectional view schematically showing the liquid nozzle 200 according to this embodiment, taken along the Figure 4 V-V line. Additionally, in Figures 3 to 5 , as three mutually orthogonal axes, the X-axis, Y-axis, and Z-axis are illustrated. Further, in Figure 3 and Figure 5 , the piezoelectric element 100 is schematically illustrated.

[0081] As Figures 3 to 5 shown, the liquid nozzle 200 includes, for example, a base 2, a piezoelectric element 100, a nozzle plate 220, a protective substrate 240, a circuit board 250, and a compliance substrate 260. The base 2 has a flow path forming substrate 210 and a diaphragm 230. Additionally, for convenience, the illustration of the circuit board 250 is omitted in Figure 4 .

[0082] The flow path forming substrate 210 is, for example, a silicon substrate. A pressure generating chamber 211 is formed on the flow path forming substrate 210. The pressure generating chamber 211 is divided by a plurality of partition walls 212. The volume of the pressure generating chamber 211 changes according to the piezoelectric element 100.

[0083] A first communication path 213 and a second communication path 214 are formed at the end of the flow path forming substrate 210 in the +X-axis direction of the pressure generating chamber 211. The first communication path 213 is configured to reduce the opening area by narrowing the end of the pressure generating chamber 211 in the +X-axis direction from the Y-axis direction. The dimension of the second communication path 214 in the Y-axis direction is, for example, the same as the dimension of the pressure generating chamber 211 in the Y-axis direction. A third communication path 215 communicating with a plurality of second communication paths 214 is formed in the +X-axis direction of the second communication path 214. The third communication path 215 forms a part of a manifold 216. The manifold 216 is a liquid chamber shared by each pressure generating chamber 211. In this way, a supply flow path 217 composed of the first communication path 213, the second communication path 214, and the third communication path 215 and the pressure generating chamber 211 are formed on the flow path forming substrate 210. The supply flow path 217 communicates with the pressure generating chamber 211 and supplies liquid to the pressure generating chamber 211.

[0084] The nozzle plate 220 is disposed on the surface of one side of the flow path forming substrate 210. The material of the nozzle plate 220 is, for example, SUS (Steel Use Stainless, stainless steel). The nozzle plate 220 is joined to the flow path forming substrate 210, for example, by an adhesive or a thermal welding film. A plurality of nozzle holes 222 are formed along the Y-axis on the nozzle plate 220. The nozzle holes 222 communicate with the pressure generating chamber 211 to eject a liquid.

[0085] The diaphragm 230 is disposed on the surface of the other side of the flow path forming substrate 210. The diaphragm 230 is composed of, for example, a silicon oxide layer 232 provided above the flow path forming substrate 210 and a zirconium oxide layer 234 provided above the silicon oxide layer 232.

[0086] The piezoelectric elements 100 are, for example, disposed above the diaphragm 230. A plurality of piezoelectric elements 100 are provided. The number of the piezoelectric elements 100 is not particularly limited. In addition, for convenience, the illustration of the alignment control layer 20 is omitted in Figure 4 the figure.

[0087] In the liquid ejector 200, the diaphragm 230 and the first electrode 10 are displaced by the deformation of the piezoelectric layer 30 having electro-mechanical conversion characteristics. That is, in the liquid ejector 200, the diaphragm 230 and the first electrode 10 substantially function as a diaphragm. In addition, the diaphragm 230 may be omitted, and only the first electrode 10 may function as a diaphragm. When the first electrode 10 is directly disposed above the flow path forming substrate 210, it is preferable to protect the first electrode 10 with an insulating protective film or the like so that the liquid does not come into contact with the first electrode 10.

[0088] The first electrode 10 is configured as an individual electrode independent for each pressure generating chamber 211. The size of the first electrode 10 in the Y-axis direction is smaller than the size of the pressure generating chamber 211 in the Y-axis direction. The size of the first electrode 10 in the X-axis direction is larger than the size of the pressure generating chamber 211 in the X-axis direction. In the X-axis direction, both ends of the first electrode 10 are located outside both ends of the pressure generating chamber 211. A lead electrode 202 is connected to the end of the first electrode 10 in the -X axis direction.

[0089] The size of the piezoelectric layer 30 in the Y-axis direction is, for example, larger than the size of the first electrode 10 in the Y-axis direction. The size of the piezoelectric layer 30 in the X-axis direction is, for example, larger than the size of the pressure generation chamber 211 in the X-axis direction. The end portion of the piezoelectric layer 30 in the +X-axis direction is, for example, located outside the end portion of the first electrode 10 in the +X-axis direction. The end portion of the first electrode 10 in the +X-axis direction is covered by the piezoelectric layer 30. On the other hand, the end portion of the piezoelectric layer 30 in the -X-axis direction is, for example, located inside the end portion of the first electrode 10 in the -X-axis direction. The end portion of the first electrode 10 in the -X-axis direction is not covered by the piezoelectric layer 30.

[0090] The second electrode 40 is, for example, continuously provided above the piezoelectric layer 30 and the diaphragm 230. The second electrode 40 is configured as a common electrode shared by a plurality of piezoelectric elements 100.

[0091] The protective substrate 240 is joined to the flow path forming substrate 210 by an adhesive 203. Through holes 242 are formed in the protective substrate 240. In the illustrated example, the through holes 242 penetrate the protective substrate 240 in the Z-axis direction and communicate with the third communication path 215. The through holes 242 and the third communication path 215 constitute a manifold 216 that serves as a common liquid chamber for each pressure generation chamber 211. Further, through holes 244 that penetrate the protective substrate 240 in the Z-axis direction are formed in the protective substrate 240. The end portion of the lead electrode 202 is located in the through holes 244.

[0092] An opening 246 is formed in the protective substrate 240. The opening 246 is a space for not obstructing the driving of the piezoelectric element 100. The opening 246 may be sealed or may not be sealed.

[0093] The circuit board 250 is provided above the protective substrate 240. The circuit board 250 includes a semiconductor integrated circuit (IC) for driving the piezoelectric element 100. The circuit board 250 is electrically connected to the lead electrode 202 via a connection wiring 204.

[0094] The plastic substrate 260 is provided above the protective substrate 240. The plastic substrate 260 has a sealing layer 262 provided above the protective substrate 240 and a fixing plate 264 provided above the sealing layer 262. The sealing layer 262 is a layer for sealing the manifold 216. The sealing layer 262 has, for example, flexibility. Through holes 266 are formed in the fixing plate 264. The through holes 266 penetrate the fixing plate 264 in the Z-axis direction. When viewed from the Z-axis direction, the through holes 266 are provided at positions overlapping the manifold 216.

[0095] 4. Printer

[0096] Next, the printer according to this embodiment will be described with reference to the accompanying drawings. Figure 6 FIG. is a perspective view schematically showing the printer 300 according to this embodiment.

[0097] The printer 300 is an inkjet printer. As Figure 6 shown, the printer 300 includes a print head assembly 310. The print head assembly 310 has, for example, a liquid nozzle 200. The number of the liquid nozzles 200 is not particularly limited. The print head assembly 310 is detachably provided with ink cartridges 312 and 314 constituting a supply device. The carriage 316 carrying the print head assembly 310 is provided on a carriage shaft 322 mounted on the device main body 320 so as to be movable freely in the axial direction, and ejects the liquid supplied from the liquid supply device.

[0098] Here, the liquid may be a material in a liquid phase state, and the liquid also includes liquid materials such as sols and gels. In addition, the liquid includes not only a liquid as a state of matter, but also a substance obtained by dissolving, dispersing, or mixing particles of a functional material composed of solid substances such as pigments or metal particles in a solvent. As representative examples of the liquid, ink or a liquid crystal emulsifier can be cited. The ink covers various liquid compositions such as general water-based ink, oil-based ink, gel ink, and hot melt ink.

[0099] In the printer 300, the driving force of the driving motor 330 is transmitted to the carriage 316 via a plurality of gears and a timing belt 332 (not shown), so that the carriage 316 carrying the print head assembly 310 moves along the carriage shaft 322. On the other hand, a conveying roller 340 as a conveying mechanism is provided on the device main body 320, and this conveying mechanism relatively moves a sheet S such as paper as a recording medium with respect to the liquid nozzle 200. The conveying mechanism for conveying the sheet S is not limited to a conveying roller, and may also be a conveyor belt or a drum.

[0100] The printer 300 includes a printer controller 350 as a control unit for controlling the liquid nozzle 200 and the conveying roller 340. The printer controller 350 is electrically connected to the circuit board 250 of the liquid nozzle 200. The printer controller 350 includes, for example, a RAM (Random Access Memory) for temporarily storing various data, a ROM (Read Only Memory) storing a control program and the like, a CPU (Central Processing Unit), and a drive signal generation circuit for generating a drive signal to be supplied to the liquid nozzle 200.

[0101] In addition, the piezoelectric element 100 is not limited to being used in liquid nozzles and printers, and can be used in a wide range of applications. For example, the piezoelectric element 100 is suitable as a piezoelectric actuator for an ultrasonic motor, a vibration type dust removing device, a piezoelectric transformer, a piezoelectric speaker, a piezoelectric pump, a pressure-electric conversion device, etc. In addition, the piezoelectric element 100 is suitable as a piezoelectric sensor element for an ultrasonic detector, an angular velocity sensor, an acceleration sensor, a vibration sensor, an inclination sensor, a pressure sensor, a collision sensor, a human body sensing sensor, an infrared sensor, a terahertz sensor, a thermal detection sensor, a pyroelectric sensor, a piezoelectric sensor, etc. In addition, the piezoelectric element 100 is suitable as a ferroelectric element for a ferroelectric memory (FeRAM), a ferroelectric transistor (FeFET), a ferroelectric arithmetic circuit (FeLogic), a ferroelectric capacitor, etc. In addition, the piezoelectric element 100 is suitable as a voltage-controlled optical element for a wavelength converter, an optical waveguide, an optical path modulator, a refractive index control element, an electronic shutter mechanism, etc.

[0102] 5. Examples and Comparative Examples

[0103] 5.1. Fabrication of Samples

[0104] 5.1.1. Example 1

[0105] By thermally oxidizing the surface of a single crystal silicon substrate, a SiO2 layer with a thickness of 1460 nm was formed. Then, a Zr film with a thickness of 400 nm was formed by DC (Direct Current) sputtering method, and a ZrO2 layer was formed by heat treatment at 850 °C.

[0106] Then, Ti layer, Pt layer, and Ir layer with thicknesses of 20 nm, 80 nm, and 5 nm respectively were formed as the first electrode on the ZrO2 layer by DC sputtering method.

[0107] Then, a BFTP precursor solution was prepared with a molar ratio of Bi:Pb:Fe:Ti = 110:10:50:50. Subsequently, the prepared BFTP precursor solution was spin-coated on the Ir layer and the ZrO2 layer, dried at 180 °C for 3 minutes, degreased at 380 °C for 3 minutes, and fired at 650 °C for 3 minutes. Through the above steps, a BFTP layer with a thickness of 20 nm was formed.

[0108] Then, monomer solutions composed of potassium 2-ethylhexanoate, sodium 2-ethylhexanoate, and niobium 2-ethylhexanoate were synthesized respectively. A mixed solvent of 2-ethylhexanoic acid and decane was used as the solvent. The volume ratio of 2-ethylhexanoic acid to the whole solvent (hereinafter also referred to as "solvent ratio") was 0.42. These monomer solutions were prepared into (K 0.50 Na 0.50 ) 1.015 NbOx (where x is any value greater than 0), a KNN precursor solution is obtained. The concentration of the KNN precursor solution (hereinafter also referred to as "KNN concentration") is 45 vol%. In addition, the "KNN concentration" refers to the sum of the volumes of potassium 2-ethylhexanoate, sodium 2-ethylhexanoate, and niobium 2-ethylhexanoate relative to the volume of the entire solution.

[0109] Here, Figure 7 is the proton NMR measurement result of niobium 2-ethylhexanoate used in the KNN precursor solution. "Ascend TM 400" manufactured by Bruker is used as the NMR device. Data analysis is performed using "TopSpin 4.2.0" manufactured by Bruker. CDCl3 (400 MHz, δ: 7.26 ppm) is used as the deuterated solvent. Specifically, deuterated chloroform is used as both the solvent and the reference substance, and the peak of deuterated chloroform is adjusted to 7.26 ppm for measurement.

[0110] As Figure 7 shown in "Example 1", in the NMR measurement curve of niobium 2-ethylhexanoate, no peak is confirmed in the range of 3 ppm or more and 5 ppm or less. The KNN precursor solution is prepared using such niobium 2-ethylhexanoate.

[0111] Then, the prepared KNN precursor solution is coated on the BFTP layer by spin coating, dried at 180 °C for 3 minutes, degreased at 380 °C for 3 minutes, and fired at 700 °C for 3 minutes. The heating rate during firing is 10 °C / second. Through the above steps, a crystal layer with a thickness of 80 nm is formed. Subsequently, the above series of processes from coating the KNN precursor solution to firing the KNN precursor layer is repeated 5 times to form a piezoelectric layer with a thickness of 400 nm composed of 5 crystal layers.

[0112] Then, a Pt layer with a thickness of 50 nm is formed on the piezoelectric layer by DC sputtering. Thereafter, the Pt layer is patterned by photolithography and etching to form the second electrode.

[0113] Through the above steps, the piezoelectric element of Example 1 is formed.

[0114] 5.1.2. Example 2

[0115] Except that the solvent ratio in the KNN precursor solution is 0.67, the piezoelectric element of Example 2 is formed in the same manner as in Example 1.

[0116] 5.1.3. Example 3

[0117] The piezoelectric element of Example 3 was formed in the same manner as in Example 1, except that the solvent ratio in the KNN precursor solution was 0.30.

[0118] 5.1.4. Example 4

[0119] The piezoelectric element of Example 4 was formed in the same manner as in Example 1, except that the concentration of the KNN precursor solution in the KNN precursor solution was 25% by volume.

[0120] 5.1.5. Comparative Example 1

[0121] As Figure 7 shown in "Comparative Example 1", a KNN precursor solution was prepared using niobium 2-ethylhexanoate that showed a peak in the range of 3 ppm to 5 ppm in the NMR measurement curve. Except for this, the piezoelectric element of Comparative Example 1 was formed in the same manner as in Example 1.

[0122] In Figure 7 the "Comparative Example", the peaks in the range of 3 ppm to 5 ppm confirmed are peaks derived from by-products such as ethanol and ethoxy groups from the raw materials. In Figure 7 this, the peak is circled by a dotted line.

[0123] 5.2. XRD

[0124] XRD measurements were performed using "D8 DISCOVER with GADDS" manufactured by Bruker. While gradually tilting the inclination angle ψ, ω-2θ measurements of asymmetric reflection were carried out. The collimator was 1 mm Φ. For each ψ, the peak positions of the crystal plane indices detected according to Bragg's formula were separated into high-angle side peaks and low-angle side peaks using a Gaussian function through a solver. Subsequently, according to Bragg's formula, the longitudinal lattice constant was calculated from the peak position 2θ of the low-angle side peak, and the transverse lattice constant was calculated from the peak position 2θ of the high-angle side peak.

[0125] Figure 8 Fig. is a graph showing the longitudinal lattice constant and the transverse lattice constant calculated for each inclination angle ψ in Example 1 plotted against sin 2 ψ. In Figure 8 and the following Figure 9 , the plot of the longitudinal lattice constant is represented by black circles, and the plot of the transverse lattice constant is represented by white circles. For the range of sin 2 ψ = 0 to 0.7, when linear approximation was performed by the least squares method, the slope of the approximate straight line of the longitudinal lattice constant was -0.0121, and the slope of the approximate straight line of the transverse lattice constant was -0.0387.

[0126] Figure 9The graph showing the longitudinal lattice constant and the transverse lattice constant calculated at each inclination angle ψ in Comparative Example 1 plotted against sin 2 ψ. For the range of sin 2 ψ = 0 to 0.7, when performing linear approximation by the least squares method, the slope of the approximate straight line for the longitudinal lattice constant is 0.0695, and the slope of the approximate straight line for the transverse lattice constant is -0.0015.

[0127] Figure 10 A table showing the slopes of the approximate straight lines in Examples 1 - 4 and Comparative Example 1. As Figure 10 shown, for both the longitudinal lattice constant and the transverse lattice constant, the slopes of the approximate straight lines in Examples 1 - 4 are smaller than those in Comparative Example 1. Thus, it can be seen that in Examples 1 - 4, compared with Comparative Example 1, the tensile stress generated in the KNN layer is small. In Examples 1 - 4, since niobium 2 - ethylhexanoate with less impurities is used, the tensile stress generated in the KNN layer can be reduced.

[0128] 5.3. Observation of the KNN layer

[0129] In Examples 1 - 4 and Comparative Example 1, the thickness of the KNN layer was increased until cracks occurred in the KNN layer. Figure 10 shows the thickness of the KNN layer where cracks occurred, as the "crack - resistant film thickness". A metallurgical microscope was used to observe the cracks.

[0130] As Figure 10 shown, in Comparative Example 1, cracks were confirmed at a thickness of 600 nm. On the other hand, in Examples 1 - 4, even when the thickness was 1000 nm, no cracks were confirmed. It can be seen that in Examples 1 - 4, due to the small tensile stress generated in the KNN layer, cracks are not easily generated.

[0131] In addition, the cross - sectional morphology of the KNN layer was confirmed by SEM. It was columnar in Examples 1 - 4, while it was random in shape in Comparative Example 1.

[0132] The above - mentioned implementation forms and modification examples are only examples and are not limited thereto. For example, each implementation manner and each modification example can also be appropriately combined.

[0133] The present invention includes a configuration that is substantially the same as the configuration described in the embodiment, for example, a configuration with the same function, method, and result, or a configuration with the same purpose and effect. In addition, the present invention includes a configuration obtained by replacing non - essential parts of the configuration described in the embodiment. In addition, the present invention includes a configuration that achieves the same effect as the configuration described in the embodiment or can achieve the same purpose. In addition, the present invention includes a configuration obtained by adding known technologies to the configuration described in the embodiment.

[0134] The following contents can be derived from the above-mentioned embodiments and modifications.

[0135] One aspect of piezoelectric elements includes:

[0136] a first electrode and a second electrode; and

[0137] The piezoelectric layer is provided between the first electrode and the second electrode and has a plurality of layers including a composite oxide having a perovskite structure containing potassium, sodium and niobium.

[0138] In the X-ray diffraction method, the inclination angle is ψ in the sin 2 The piezoelectric layer is measured for asymmetric reflection when ψ is in the range of not less than 0 and not more than 0.7, and the obtained peak is separated into a high-angle side peak and a low-angle side peak. The lattice constant in the thickness direction of the piezoelectric layer is calculated based on the low-angle side peak, and the lattice constant is plotted as a multi-point diagram for the range. When the multi-point diagram is linearly approximated by the least squares method, the slope of the approximate straight line is less than 0.002.

[0139] According to this piezoelectric element, the occurrence of cracks can be suppressed.

[0140] In one aspect of a piezoelectric element,

[0141] The slope may be -0.012 or less.

[0142] According to this piezoelectric element, the tensile stress generated in the piezoelectric layer can be further reduced.

[0143] In one aspect of a piezoelectric element,

[0144] The thickness of the piezoelectric layer may be greater than 600 nm and less than or equal to 2000 nm.

[0145] According to this piezoelectric element, the occurrence of cracks can be suppressed.

[0146] In one aspect of a piezoelectric element,

[0147] The piezoelectric element may further include an orientation control layer provided between the first electrode and the piezoelectric layer, and containing bismuth, iron, titanium, and lead.

[0148] According to this piezoelectric element, the orientation of the piezoelectric layer can be controlled.

[0149] In one aspect of a piezoelectric element,

[0150] When the inclination angle is 0°, a difference between the lattice constant in the thickness direction obtained based on the low-angle side peak and the lattice constant in the thickness direction obtained based on the high-angle side peak may be 0.082 or more.

[0151] According to this piezoelectric element, generation of cracks can be suppressed.

[0152] In one aspect of the piezoelectric element,

[0153] The piezoelectric layer may be a layer formed from niobium 2-ethylhexanoate which shows no peak in the range of 3 ppm or more and 5 ppm or less in proton NMR measurement.

[0154] According to this piezoelectric element, niobium 2-ethylhexanoate with few impurities can be used as a raw material.

[0155] One aspect of a liquid ejector includes:

[0156] One aspect of the piezoelectric element;

[0157] A flow path forming substrate having a pressure generating chamber whose volume changes according to the piezoelectric element; and

[0158] A nozzle plate having a nozzle communicating with the pressure generating chamber.

[0159] One aspect of a printer includes:

[0160] One aspect of the liquid ejector;

[0161] A conveyance mechanism that relatively moves a recording medium with respect to the liquid ejector; and

[0162] A control unit that controls the liquid ejector and the conveyance mechanism.

Claims

1. A piezoelectric element, characterized in that: The piezoelectric element comprises: a first electrode and a second electrode; and a piezoelectric layer provided between the first electrode and the second electrode and including a plurality of layers containing a composite oxide having a perovskite structure containing potassium, sodium and niobium, In the X-ray diffraction method, the inclination angle is ψ in the sin 2 The piezoelectric layer is measured for asymmetric reflection when ψ is in the range of not less than 0 and not more than 0.7, and the obtained peak is separated into a high-angle side peak and a low-angle side peak. The lattice constant in the thickness direction of the piezoelectric layer is calculated based on the low-angle side peak, and the lattice constant is plotted as a multi-point diagram for the range. When the multi-point diagram is linearly approximated by the least squares method, the slope of the approximate straight line is less than 0.

002.

2. The piezoelectric element according to claim 1, wherein The slope is less than -0.

012.

3. The piezoelectric element according to claim 1, wherein The thickness of the piezoelectric layer is greater than 600 nm and less than or equal to 2000 nm.

4. The piezoelectric element according to claim 1, wherein: The piezoelectric element further includes an orientation control layer provided between the first electrode and the piezoelectric layer and containing bismuth, iron, titanium and lead.

5. The piezoelectric element according to claim 1, wherein: When the inclination angle is 0°, a difference between the lattice constant in the thickness direction obtained based on the low-angle side peak and the lattice constant in the thickness direction obtained based on the high-angle side peak is 0.082 or more.

6. The piezoelectric element according to claim 1, wherein: The piezoelectric layer is a layer formed using niobium 2-ethylhexanoate as a raw material, and no peak is confirmed in the range of 3 ppm to 5 ppm in proton NMR measurement of the niobium 2-ethylhexanoate.

7. A liquid ejector, characterized in that: The liquid ejector comprises: The piezoelectric element according to any one of claims 1 to 6; a flow path forming substrate having a pressure generating chamber whose volume varies according to the piezoelectric element; and The nozzle plate is formed with a nozzle communicating with the pressure generating chamber.

8. A printer, characterized in that: The printer comprises: The liquid ejecting head according to claim 7; A conveying mechanism for moving the recording medium relative to the liquid ejecting head; and The control unit controls the liquid ejecting head and the conveying mechanism.

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