Piezoelectric element, liquid discharge head, and printer

Abstract

To provide a piezoelectric element that can prevent the occurrence of cracks.SOLUTION: A piezoelectric element includes: a first electrode and a second electrode; and a piezoelectric layer that is provided between the first electrode and the second electrode, and has a plurality of layers including a complex oxide with a perovskite-type structure including potassium, sodium, and niobium. When measurement of asymmetrical reflection is performed within a range where sin2ψ is 0 or more and 0.7 or less, where ψ denotes a tilt angle, by using an X-ray diffraction method for the piezoelectric layer, an obtained peak is separated to a high angle-side peak and a low angle-side peak; a lattice constant in a thickness direction of the piezoelectric layer is determined on the basis of the low angle-side peak; and when the plurality of lattice constants are plotted in the range, and linear approximation is performed on the plurality of plots by using the least squares method, the inclination of the approximate straight line is 0.002 or less.SELECTED DRAWING: Figure 8

Description

Technical Field

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

Background Art

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

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

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

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

Means for Solving the Problems

[0006] One aspect of the piezoelectric element according to the present invention is a first electrode and a second electrode, 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, and includes with respect to the piezoelectric layer, using X-ray diffraction method, with the tilt angle as ψ, sin 2Measure the asymmetric reflection in the range where ψ is 0 or more and 0.7 or less, separate the obtained peak into a high-angle side peak and a low-angle side peak, obtain the lattice constant in the thickness direction of the piezoelectric layer based on the low-angle side peak, and when a plurality of the lattice constants are plotted for the range, if the plurality of plots are linearly approximated by the least squares method, the slope of the approximated straight line is 0.002 or less.

[0007] One aspect of the liquid ejection head according to the present invention is the piezoelectric element, a flow path forming substrate in which a pressure generating chamber whose volume changes by the piezoelectric element is formed, a nozzle plate in which a nozzle hole communicating with the pressure generating chamber is formed, and includes.

[0008] One aspect of the printer according to the present invention is the liquid ejection head, a transport mechanism that relatively moves a recording medium with respect to the liquid ejection head, a control unit that controls the liquid ejection head and the transport mechanism, and includes.

Brief Description of Drawings

[0009]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Mode for Carrying Out the Invention

[0010] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. Note that the embodiments described below do not unduly limit the content of the present invention described in the claims. Also, not all of the configurations described below are essential constituent elements of the present invention.

[0011] 1. Piezoelectric Element 1.1. Configuration First, the piezoelectric element according to the present embodiment will be described with reference to the drawings. FIG. 1 is a cross-sectional view schematically showing the piezoelectric element 100 according to the present embodiment.

[0012] As shown in FIG. 1, 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 on a substrate 2.

[0013] 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 in which a plurality of layers are laminated. The substrate 2 is not limited in internal structure as long as the upper surface has a planar shape, and may have a structure in which a space or the like is formed inside.

[0014] The substrate 2 may have a diaphragm that deforms by 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.

[0015] The first electrode 10 is provided on the substrate 2. The first electrode 10 is provided between the substrate 2 and the orientation control layer 20. The shape of the first electrode 10 is, for example, layer-like. 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.

[0016] The first electrode 10 is, for example, a titanium layer, a platinum layer, an iridium layer, etc. The first electrode 10 may be a laminate 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 adhesion 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.

[0017] The orientation control layer 20 is provided on the first electrode 10. The orientation control layer 20 is provided between the first electrode 1 and the piezoelectric layer 30. In the illustrated example, the orientation control layer 20 is further provided on the substrate 2. The thickness of the orientation 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.

[0018] The orientation control layer 20 contains a perovskite-structured composite oxide containing bismuth (Bi), iron (Fe), titanium (Ti), and lead (Pb). The orientation control layer 20 is, for example, a bismuth lead titanate ferrite ((Bi,Pb)(Fe,Ti)O3:BFTP) layer. The orientation control layer 20 may be a BFTP layer to which an additive is added. The orientation control layer 20 controls the orientation of the piezoelectric layer 30.

[0019] The piezoelectric layer 30 is provided on the orientation control layer 20. The piezoelectric layer 30 is provided between the first electrode 10 and the second electrode 40. In the illustrated example, the piezoelectric layer 30 is provided between the orientation 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 nm or less, more preferably 600 nm or more and 2000 nm or less, and still more 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"). The piezoelectric layer 30 deforms when a voltage is applied between the first electrode 10 and the second electrode 40.

[0020] The piezoelectric layer 30 includes a plurality of crystal layers 32. The piezoelectric layer 30 is, for example, composed of 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, preferably 3 or more and 20 or less. In the illustrated example, 5 crystal layers 32 are provided. The thickness of the crystal layer 32 is, for example, 10 nm or more and 200 nm or less, preferably 30 nm or more and 150 nm or less.

[0021] The crystal layer 32 is a layer containing a perovskite-type composite oxide containing potassium (K), sodium (Na), and niobium (Nb). The crystal layer 32 is, for example, a potassium sodium niobate ((K,Na)NbO3:KNN) layer. The crystal layer 32 may be a KNN layer to which an additive is added. 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, preferably 5 mol% or less. The additive may be unevenly distributed at the grain boundaries of the crystal layer 32.

[0022] The second electrode 40 is provided on the piezoelectric layer 30. Although not shown, if the second electrode 40 is electrically separated from the first electrode 10, it may be further provided on the side surface of the piezoelectric layer 30 and on the substrate 2. The shape of the second electrode 40 is, for example, layer-like. The thickness of the second electrode 40 is, for example, 15 nm or more and 300 nm or less.

[0023] The second electrode 40 is, for example, a platinum layer, a titanium layer, or an iridium layer. The second electrode 40 may be a laminate of a plurality of the layers exemplified above. The second electrode 40 is the other electrode for applying a voltage to the piezoelectric layer 30.

[0024] 1.2. X-ray Diffraction Method The case of using the X-ray Diffraction (XRD) method for the piezoelectric layer 30 will be described. In XRD, the glancing angle ψ is changed to measure an asymmetric reflection where the incident angle and the reflection angle of the X-ray are different. The measurement range of the asymmetric reflection is in the range where sin 2 ψ is 0 or more and 0.7 or less. Note that if the measurement range includes the range where sin 2 ψ is 0 or more and 0.7 or less, the range where sin 2 ψ is greater than 0.7 may also be included. XRD may be performed by thin film X-ray diffraction. The glancing angle ψ is, for example, 0° or more and 90° or less.

[0025] The peaks obtained by XRD are peak-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 peak-separated peaks. The high-angle side peak is the peak on the higher 2θ side among the two peak-separated peaks. separated peaks.

[0026] Based on the peak position of the low-angle side peak, the longitudinal lattice constant in the thickness direction is obtained. Specifically, the longitudinal lattice constant is obtained from the peak position of the low-angle side peak according to Bragg's equation. The KNN layer has a cubic crystal structure. The longitudinal lattice constant is the lattice constant when the a or c axis, which is longer than the b axis, is along the thickness direction. Similarly, based on the peak position of the high-angle side peak, the lateral lattice constant in the thickness direction is obtained. The lateral lattice constant is the lattice constant when the a and c axes are along the direction orthogonal to the thickness direction.

[0027] The longitudinal lattice constant is sin 2 ψ is measured multiple times in the range where 0 ≤ ψ ≤ 0.7. The number of measurements is, for example, 5 or more and 12 or less, preferably 7 or more and 10 or less. The longitudinal lattice constant is sin 2 ψ is plotted multiple times for the range where 0 ≤ ψ ≤ 0.7. Similarly, the lateral lattice constant is measured multiple times. The lateral lattice constant is plotted multiple times.

[0028] When multiple plots of the longitudinal lattice constant are linearly approximated by the least squares method, the slope of the approximated straight line is 0.002 or less, preferably -0.012 or less, more preferably -0.0121 or less. The slope of the approximated straight line may be -0.03 or more.

[0029] When multiple plots of the lateral lattice constant are linearly approximated by the least squares method, the slope of the approximated straight line is, for example, -0.03 or less, preferably -0.0387 or less. The slope of the approximated straight line may be -0.05 or more.

[0030] When the tilt angle ψ is 0°, the difference between the longitudinal lattice constant and the lateral lattice constant is, for example, 0.080 or more, preferably 0.082 or more. The difference may be 0.10 or less.

[0031] Here, FIG. 2 is a diagram for explaining the relationship between the tilt angle ψ and the inter-plane spacing d of the KNN layer. When the tensile stress F generated in the KNN layer is large, the inter-plane spacing d becomes large. In the illustrated example, the tensile stress F is a stress that pulls the KNN layer in a direction orthogonal to the film thickness direction (hereinafter also referred to as the in-plane direction). The in-plane direction may be the horizontal direction. However, when ψ = 0°, the inter-plane spacing d in the in-plane direction is less likely to be affected by the tensile stress F. On the other hand, for example, as shown in ψ = 30° and 45° in FIG. 2, the plane having an inclination with respect to the tensile stress F has a larger inter-plane spacing d as the inclination is larger. The lattice constant calculated from the inter-plane spacing d becomes larger as ψ becomes larger. Therefore, 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.

[0032] 1.3. Function and Effect In the piezoelectric element 100, the first electrode 10 and the second electrode 40, and a piezoelectric layer 30 including a plurality of crystal layers 32 including a perovskite-type composite oxide containing potassium, sodium, and niobium provided between the first electrode 10 and the second electrode 40. For the piezoelectric layer 30, using the X-ray diffraction method, with the tilt angle as ψ, sin 2 Measurements of asymmetric reflection are performed in the range where ψ is 0 or more and 0.7 or less, and the obtained peaks are separated into a high-angle side peak and a low-angle side peak. Based on the low-angle side peak, the lattice constant in the thickness direction of the piezoelectric layer 30 is obtained. When a plurality of lattice constants are plotted for this range and the plurality of plots are linearly approximated by the least squares method, the slope of the approximate straight line is 0.002 or less.

[0033] 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. Therefore, in the piezoelectric element 100, the occurrence of cracks can be suppressed.

[0034] If the tensile stress F generated in the piezoelectric layer is large, cracks will occur in the piezoelectric layer. On the other hand, if the tensile stress F in the piezoelectric layer is small and the compressive stress is dominant, it becomes difficult for cracks to occur in the piezoelectric layer. The piezoelectric layer 30 of the piezoelectric element 100 has a configuration in which the compressive stress is dominant.

[0035] 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 made smaller.

[0036] 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 occurrence of cracks can be suppressed.

[0037] The piezoelectric element 100 further includes an orientation control layer 20 provided between the first electrode 10 and the piezoelectric layer 30 and containing bismuth, iron, titanium, and lead. Therefore, in the piezoelectric element 100, the orientation of the piezoelectric layer 30 can be controlled.

[0038] 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 occurrence of cracks can be suppressed.

[0039] 2. Manufacturing method of piezoelectric element Next, a method for manufacturing the piezoelectric element 100 according to the present embodiment will be described with reference to the drawings.

[0040] As shown in FIG. 1, a substrate 2 is prepared. Specifically, a silicon oxide layer is formed by thermally oxidizing a silicon substrate. Next, a zirconium layer is formed on the silicon oxide layer by a sputtering method or the like, and a zirconium oxide layer is formed by thermally oxidizing the zirconium layer. Through the above steps, the substrate 2 can be prepared.

[0041] Next, a first electrode 10 is formed on the substrate 2. The first electrode 10 is formed, for example, by a sputtering method or a vacuum evaporation method. Next, the first electrode 10 is patterned, for example, by photolithography and etching.

[0042] Next, an alignment control layer 20 is formed on the first electrode 10 and the substrate 2. The alignment control layer 20 is formed, for example, by a CSD (Chemical Solution Deposition) method such as a sol-gel method or a MOD (Metal Organic Deposition).

[0043] 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. Next, the precursor solution is applied onto the first electrode 10 by a spin coating method to form a precursor layer. Next, the precursor layer is heated at, for example, 130 °C or higher and 250 °C or lower for a certain period of time to be dried, and further, the dried precursor layer is heated at, for example, 300 °C or higher and 450 °C or lower for a certain period of time to be degreased. Next, the degreased precursor layer is crystallized by firing at, for example, 550 °C or higher and 800 °C or lower. Thus, the alignment control layer 20 made of a BFTP layer can be formed.

[0044] Next, a piezoelectric layer 30 is formed on the alignment control layer 20. The piezoelectric layer 30 is formed, for example, by a CS D method.

[0045] 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.

[0046] Examples of the metal complex containing potassium include potassium 2-ethylhexanoate and potassium acetate. Examples of the metal complex containing sodium include sodium 2-ethylhexanoate and sodium acetate.

[0047] Examples of the metal complex containing niobium include niobium 2-ethylhexanoate. The piezoelectric layer 30 is a layer formed using niobium 2-ethylhexanoate in which no peak is confirmed in the range of 3 ppm or more and 5 ppm or less in proton NMR (Nuclear Magnetic Resonance) measurement. Therefore, the impurities in niobium 2-ethylhexanoate are few. Niobium 2-ethylhexanoate may not contain impurities.

[0048] Examples of the solvent include 2-ethylhexanoic acid, decane, or a mixed solvent thereof.

[0049] Next, the prepared precursor solution is applied onto the alignment control layer 20 using a spin coating method or the like to form a precursor layer. Next, the precursor layer is heated at, for example, 130°C or higher and 250°C or lower for a certain period of time to be dried, and further, the dried precursor layer is heated at, for example, 300°C or higher and 450°C or lower for a certain period of time to be degreased. Next, the degreased precursor layer is crystallized by firing at, for example, 550°C or higher and 800°C or lower.

[0050] Thus, the crystal layer 32 of the piezoelectric layer 30 can be formed. Then, a series of steps from the application of the precursor solution to the firing of the precursor layer are repeated a plurality of times. Thereby, the piezoelectric layer 30 composed of a plurality of crystal layers 32 can be formed.

[0051] In the step of forming the crystal layer 32, the heating device used for drying and degreasing the precursor layer is, for example, a hot plate. The heating device used for firing the precursor layer is an infrared lamp annealing device (Rapid Thermal Annealing: RTA) device.

[0052] Next, a second electrode 40 is formed on the piezoelectric layer 30. The second electrode 40 is formed, for example, by a sputtering method, a vacuum evaporation method, or the like. Next, the second electrode 40 and the piezoelectric layer 30 are patterned, for example, by photolithography and etching. Note that the second electrode 40 and the piezoelectric layer 30 may be patterned in separate processes.

[0053] Through the above processes, the piezoelectric element 100 can be manufactured.

[0054] 3. Liquid ejection head Next, the liquid ejection head according to the present embodiment will be described with reference to the drawings. FIG. 3 is an exploded perspective view schematically showing the liquid ejection head 200 according to the present embodiment. FIG. 4 is a plan view schematically showing the liquid ejection head 200 according to the present embodiment. FIG. 5 is a cross-sectional view taken along line V-V of FIG. 4 schematically showing the liquid ejection head 200 according to the present embodiment. In FIGS. 3 to 5, the X-axis, the Y-axis, and the Z-axis are shown as three axes orthogonal to each other. In FIGS. 3 and 5, the piezoelectric element 100 is shown in a simplified manner.

[0055] As shown in FIGS. 3 to 5, the liquid ejection head 200 includes, for example, a substrate 2, a piezoelectric element 100, a nozzle plate 220, a protective substrate 240, a circuit board 250, and a compliance substrate 260. The substrate 2 has a flow path forming substrate 210 and a diaphragm 230. For the sake of convenience, in FIG. 4, the illustration of the circuit board 250 is omitted.

[0056] The flow path forming substrate 210 is, for example, a silicon substrate. A pressure generation chamber 211 is formed in the flow path forming substrate 210. The pressure generation chamber 211 is partitioned by a plurality of partition walls 212. The volume of the pressure generation chamber 211 changes due to the piezoelectric element 100.

[0057] At the +X-axis end of the pressure generation chamber 211 on the flow path forming substrate 210, a first communication path 213 and a second communication path 214 are formed. The first communication path 213 is configured such that its opening area becomes smaller by narrowing the +X-axis end of the pressure generation chamber 211 from the Y-axis direction. The size of the second communication path 214 in the Y-axis direction is, for example, the same as the size of the pressure generation chamber 211 in the Y-axis direction. In the +X-axis direction of the second communication path 214, a third communication path 215 that communicates with a plurality of the second communication paths 214 is formed. The third communication path 215 constitutes a part of the manifold 216. The manifold 216 serves as a common liquid chamber for each pressure generation chamber 211. Thus, in the flow path forming substrate 210, 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 generation chamber 211 are formed. The supply flow path 217 communicates with the pressure generation chamber 211 and supplies liquid to the pressure generation chamber 211.

[0058] The nozzle plate 220 is provided on one surface of the flow path forming substrate 210. The material of the nozzle plate 220 is, for example, SUS (Steel Use Stainless). The nozzle plate 220 is joined to the flow path forming substrate 210 by, for example, an adhesive or a heat welding film. A plurality of nozzle holes 222 are formed along the Y-axis in the nozzle plate 220. The nozzle holes 222 communicate with the pressure generation chamber 211 and discharge liquid.

[0059] The diaphragm 230 is provided on the other surface of the flow path forming substrate 210. The diaphragm 230 is composed of, for example, a silicon oxide layer 232 provided on the flow path forming substrate 210 and a zirconium oxide layer 234 provided on the silicon oxide layer 232.

[0060] The piezoelectric element 100 is provided, for example, on the diaphragm 230. A plurality of piezoelectric elements 100 are provided. The number of piezoelectric elements 100 is not particularly limited. For convenience, in FIG. 4, the illustration of the orientation control layer 20 is omitted.

[0061] In the liquid ejection head 200, the diaphragm 230 and the first electrode 10 are displaced due to the deformation of the piezoelectric layer 30 having electromechanical conversion characteristics. That is, in the liquid ejection head 200, the diaphragm 230 and the first electrode 10 substantially function as a diaphragm. Note that the diaphragm 230 may be omitted and only the first electrode 10 may function as a diaphragm. When the first electrode 10 is directly provided on 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.

[0062] The first electrode 10 is configured as an individual electrode independent for each pressure generation chamber 211. The size of the first electrode 10 in the Y-axis direction is smaller than the size of the pressure generation 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 generation 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 generation chamber 211. A lead electrode 202 is connected to the -X-axis direction end of the first electrode 10.

[0063] 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 +X-axis direction end of the piezoelectric layer 30 is, for example, located outside the +X-axis direction end of the first electrode 10. The +X-axis direction end of the first electrode 10 is covered by the piezoelectric layer 30. On the other hand, the -X-axis direction end of the piezoelectric layer 30 is, for example, located inside the -X-axis direction end of the first electrode 10. The -X-axis direction end of the first electrode 10 is not covered by the piezoelectric layer 30.

[0064] The second electrode 40 is, for example, continuously provided on the piezoelectric layer 30 and the diaphragm 230. The second electrode 40 is configured as a common electrode common to a plurality of piezoelectric elements 100.

[0065] The protective substrate 240 is joined to the flow path forming substrate 210 by an adhesive 203. A through hole 242 is formed in the protective substrate 240. In the illustrated example, the through hole 242 penetrates the protective substrate 240 in the Z-axis direction and communicates with the third communication path 215. The through hole 242 and the third communication path 215 constitute a manifold 216 that serves as a common liquid chamber for each pressure generating chamber 211. Further, a through hole 244 that penetrates the protective substrate 240 in the Z-axis direction is formed in the protective substrate 240. The end of the lead electrode 202 is positioned in the through hole 244.

[0066] An opening 246 is formed in the protective substrate 240. The opening 246 is a space for not inhibiting the driving of the piezoelectric element 100. The opening 246 may or may not be sealed.

[0067] The circuit board 250 is provided on the protective substrate 240. The circuit board 250 includes a semiconductor integrated circuit (IC) for driving the piezoelectric element 100. The circuit board 250 and the lead electrode 202 are electrically connected via a connection wiring 204.

[0068] The compliance substrate 260 is provided on the protective substrate 240. The compliance substrate 260 has a sealing layer 262 provided on the protective substrate 240 and a fixing plate 264 provided on the sealing layer 262. The sealing layer 262 is a layer for sealing the manifold 216. The sealing layer 262 has, for example, flexibility. A through hole 266 is formed in the fixing plate 264. The through hole 266 penetrates the fixing plate 264 in the Z-axis direction. The through hole 266 is provided at a position overlapping the manifold 216 when viewed from the Z-axis direction.

[0069] 4. Printer Next, the printer according to the present embodiment will be described with reference to the drawings. FIG. 6 is a perspective view schematically showing a printer 300 according to the present embodiment.

[0070] The printer 300 is an inkjet printer. The printer 300 includes a head unit 310 as shown in FIG. 6. The head unit 310 has, for example, liquid ejection heads 200. The number of liquid ejection heads 200 is not particularly limited. Cartridges 312, 314 constituting a supply means are removably provided on the head unit 310. A carriage 316 carrying the head unit 310 is provided on a carriage shaft 322 attached to the device body 320 so as to be freely movable in the axial direction, and ejects liquid supplied from the liquid supply means.

[0071] Here, the term "liquid" refers to any material in a liquid phase, including liquid-state materials such as sols and gels. In addition to liquids as one state of matter, liquids also include particles of functional materials made of solid matter such as pigments and metal particles dissolved, dispersed, or mixed in a solvent. Representative examples of liquids include inks and liquid crystal emulsifiers. Ink includes various liquid compositions such as general water-based inks and oil-based inks as well as gel inks and hot melt inks.

[0072] In the printer 300, the driving force of the drive motor 330 is transmitted to multiple gears and wheels (not shown). The power is transmitted to the carriage 316 via a moving belt 332, whereby the carriage 316 carrying the head unit 310 is moved along a carriage shaft 322. Meanwhile, the device main body 320 is provided with a transport roller 340 as a transport mechanism for moving a sheet S, which is a recording medium such as paper, relative to the liquid ejection head 200. The transport mechanism for transporting the sheet S is not limited to a transport roller, and may be a belt, a drum, or the like.

[0073] The printer 300 includes a printer controller 350 as a control unit that controls the liquid ejection head 200 and the conveyance roller 340. The printer controller 350 is electrically connected to the circuit board 250 of the liquid ejection head 200. The printer controller 350 includes, for example, a RAM (Random Access Memory) that temporarily stores various data, a ROM (Read Only Memory) that stores a control program and the like, a CPU (Central Processing Unit), and a drive signal generation circuit that generates a drive signal for supplying the liquid ejection head 200.

[0074] Note that the piezoelectric element 100 can be used in a wide range of applications, not limited to liquid ejection heads and printers. The piezoelectric element 100 is suitably used, for example, as a piezoelectric actuator such as an ultrasonic motor, a vibration type dust removing device, a piezoelectric transformer, a piezoelectric speaker, a piezoelectric pump, and a pressure-electric conversion device. Further, the piezoelectric element 100 is suitably used, for example, as a piezoelectric type sensor element such as an ultrasonic detector, an angular velocity sensor, an acceleration sensor, a vibration sensor, an inclination sensor, a pressure sensor, a collision sensor, a human sensor, an infrared sensor, a terahertz sensor, a heat detection sensor, a pyroelectric sensor, and a piezoelectric sensor. Further, the piezoelectric element 100 is suitably used as a ferroelectric element such as a ferroelectric memory (FeRAM), a ferroelectric transistor (FeFET), a ferroelectric arithmetic circuit (FeLogic), and a ferroelectric capacitor. Further, the piezoelectric element 100 is suitably used as a voltage control type optical element such as a wavelength converter, an optical waveguide, an optical path modulator, a refractive index control element, and an electronic shutter mechanism.

[0075] 5. Examples and Comparative Examples 5.1. Preparation of Samples 5.1.1. Example 1 By thermally oxidizing the surface of a single crystal silicon substrate, a SiO2 layer with a thickness of 1460 nm was formed. Next, Zr with a thickness of 400 nm was deposited by DC (Direct Current) sputtering, and a ZrO2 layer was formed by heat treatment at 850 °C.

[0076] Next, on the ZrO2 layer, as the first electrode, a Ti layer, a Pt layer, and an Ir layer with thicknesses of 20 nm, 80 nm, and 5 nm respectively were formed by DC sputtering method.

[0077] Next, a BFTP precursor solution was prepared so as to have a molar ratio of Bi:Pb:Fe:Ti = 110:10:50:50. Then, the prepared BFTP precursor solution was applied onto the Ir layer and the ZrO2 layer by spin coating method, followed by drying at 180 °C for 3 minutes, degreasing at 380 °C for 3 minutes, and firing at 650 °C for 3 minutes. Thus, a BFTP layer with a thickness of 20 nm was formed.

[0078] Next, single-solvent solutions composed of potassium 2-ethylhexanoate, sodium 2-ethylhexanoate, and niobium 2-ethylhexanoate were synthesized respectively. As the solvent, a mixed solvent of 2-ethylhexanoic acid and decane was used. The volume ratio of 2-ethylhexanoic acid to the total solvent (hereinafter also referred to as "solvent ratio") is 0.42. These single-solvent solutions were prepared so as to be (K 0.50 Na 0.50 ) 1.015 NbO x (where x is any number greater than 0) to obtain a KNN precursor solution. The concentration of the KNN precursor solution (hereinafter also referred to as "KNN concentration") was set to 45% by volume. Note that the "KNN concentration" refers to the sum of the volume of potassium 2-ethylhexanoate, the volume of sodium 2-ethylhexanoate, and the volume of niobium 2-ethylhexanoate with respect to the total volume of the solution. Here, FIG. 7 shows the results of proton NMR measurement of niobium 2-ethylhexanoate used in the KNN precursor solution. As the NMR apparatus, "Ascend TM 400" manufactured by Bruker was used. For data analysis, "TopSpin4.2.0" manufactured by Bruker was used. As the deuterated solvent, CDCl3 (400 MHz, δ: 7.26 ppm) was used. Specifically, deuterated chloroform was used as both the solvent and the reference substance, and the peak of deuterated chloroform was measured by adjusting it to 7.26 ppm.

[0079] ​

[0080] As in "Example 1" shown in FIG. 7, in the NMR measurement profile of niobium 2-ethylhexanoate, no peak was confirmed in the range of 3 ppm or more and 5 ppm or less. Using such niobium 2-ethylhexanoate, a KNN precursor solution was prepared.

[0081] Next, the prepared KNN precursor solution was applied onto the BFTP layer by the spin coating method, and 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 was 10 °C / second. Thus, a crystal layer with a thickness of 80 nm was formed. Then, a series of steps from the application of the above KNN precursor solution to the firing of the KNN precursor layer were repeated 5 times to form a piezoelectric layer with a thickness of 400 nm composed of 5 crystal layers.

[0082] Next, a Pt layer with a thickness of 50 nm was formed on the piezoelectric layer by DC sputtering. Then, the Pt layer was patterned by photolithography and etching to form the second electrode.

[0083] Thus, the piezoelectric element of Example 1 was formed.

[0084] 5.1.2. Example 2 A piezoelectric element of Example 2 was formed in the same manner as in Example 1, except that the solvent ratio in the KNN precursor solution was set to 0.67.

[0085] 5.1.3. Example 3 A 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 set to 0.30.

[0086] 5.1.4. Example 4 A piezoelectric element of Example 4 was formed in the same manner as in Example 1, except that the concentration of the KNN precursor solution was set to 25% by volume.

[0087] 5.1.5. Comparative Example 1 As in "Comparative Example 1" shown in FIG. 7, a KNN precursor solution was prepared using 2-ethylhexanoic acid in which peaks were confirmed in the range of 3 ppm or more and 5 ppm or less in the NMR measurement profile. Except for this, a piezoelectric element of Comparative Example 1 was formed in the same manner as in Example 1.

[0088] The peaks in the range of 3 ppm or more and 5 ppm or less confirmed in the "Comparative Example" of FIG. 7 are peaks derived from impurities such as by-produced ethanol and ethoxy groups derived from raw materials. In FIG. 7, the peak is surrounded by a broken line.

[0089] 5.2. XRD XRD measurement was performed using "D8 DISCOVER with GADDS" manufactured by Bruker. While gradually tilting the tilt angle ψ, ω-2θ measurement of asymmetric reflection was performed. The collimator was set to 1 mmΦ. At each ψ, the plane index peaks detected according to Bragg's equation were separated into a high-angle side peak and a low-angle side peak by a solver using a Gaussian function. Then, according to Bragg's equation, the vertical lattice constant was calculated from the peak position 2θ of the low-angle side peak, and the horizontal lattice constant was calculated from the peak position 2θ of the high-angle side peak.

[0090] FIG. 8 is a graph plotting the vertical lattice constant and the horizontal lattice constant calculated at each ψ in Example 1 against sin 2 ψ. In FIG. 8 and FIG. 9 described later, the plot of the vertical lattice constant is indicated by black circles, and the plot of the horizontal lattice constant is indicated by white circles. When linearly approximating the range of sin 2 ψ = 0 to 0.7 by the least squares method, the slope of the approximate straight line was -0.0121 for the vertical lattice constant and -0.0387 for the horizontal lattice constant.

[0091] FIG. 9 is a graph plotting the vertical lattice constant and the horizontal lattice constant calculated at each ψ in Comparative Example 1 against sin 2 ψ. sin 2When linearly approximating in the range of ψ = 0 to 0.7 by the least squares method, the slope of the approximate straight line is 0.0695 for the vertically elongated lattice constant and -0.0015 for the horizontally elongated lattice constant.

[0092] Figure 10 is a table showing the slopes of the approximate straight lines in Examples 1 to 4 and Comparative Example 1. As shown in Figure 10, for both the vertically elongated lattice constant and the horizontally elongated lattice constant, the slopes of the approximate straight lines in Examples 1 to 4 were smaller than the slope of the approximate straight line in Comparative Example 1. From this, it was found that in Examples 1 to 4, the tensile stress generated in the KNN layer was smaller than in Comparative Example 1. In Examples 1 to 4, niobium 2-ethylhexanoate with less impurities was used, so the tensile stress generated in the KNN layer could be reduced.

[0093] 5.3. Observation of KNN layer In Examples 1 to 4 and Comparative Example 1, the thickness of the KNN layer was increased until cracks occurred in the KNN layer. The thickness of the KNN layer at which cracks occurred is shown as the "crack-resistant film thickness" in Figure 10. Observation of cracks was carried out using a metalloscope.

[0094] As shown in Figure 10, in Comparative Example 1, cracks were confirmed at a thickness of 600 nm. On the other hand, in Examples 1 to 4, even when the thickness was increased to 1000 nm, no cracks were confirmed. In Examples 1 to 4, since the tensile stress generated in the KNN layer was small, it was found that cracks were less likely to occur.

[0095] Also, when the cross-sectional morphology of the KNN layer was confirmed by SEM, it was columnar in Examples 1 to 4 and had a random shape in Comparative Example 1.

[0096] The above-described embodiments and modifications are examples and are not necessarily limited thereto. For example, it is also possible to appropriately combine each embodiment and each modification.

[0097] The present invention includes configurations that are substantially the same as the configurations described in the embodiments, for example, configurations having the same functions, methods, and results, or configurations having the same objectives and effects. The present invention also includes configurations in which non-essential portions of the configurations described in the embodiments are replaced. The present invention further includes configurations that exhibit the same operational effects as the configurations described in the embodiments or configurations that can achieve the same objectives. The present invention also includes configurations in which known techniques are added to the configurations described in the embodiments.

[0098] The following content is derived from the above-described embodiments and modifications.

[0099] One aspect of the piezoelectric element is a first electrode and a second electrode, a piezoelectric layer provided between the first electrode and the second electrode and including a plurality of layers containing a complex oxide having a perovskite-type structure containing potassium, sodium, and niobium, and with respect to the piezoelectric layer, using an X-ray diffraction method, with the tilt angle being ψ, performing measurement of asymmetric reflection in a range where sin 2 ψ is 0 or more and 0.7 or less, separating the obtained peak into a high-angle side peak and a low-angle side peak, obtaining the lattice constant in the thickness direction of the piezoelectric layer based on the low-angle side peak, and when a plurality of the lattice constants are plotted for the range and the plurality of plots are linearly approximated by the least squares method, the slope of the approximate straight line is 0.002 or less.

[0100] According to this piezoelectric element, the generation of cracks can be suppressed.

[0101] In one aspect of the piezoelectric element, the slope may be -0.012 or less.

[0102] According to this piezoelectric element, the tensile stress generated in the piezoelectric layer can be made smaller.

[0103] In one aspect of the piezoelectric element, The thickness of the piezoelectric layer may be greater than 600 nm and equal to or less than 2000 nm.

[0104] According to this piezoelectric element, the generation of cracks can be suppressed.

[0105] In one aspect of the piezoelectric element, An orientation control layer containing bismuth, iron, titanium, and lead may be further provided between the first electrode and the piezoelectric layer.

[0106] According to this piezoelectric element, the orientation of the piezoelectric layer can be controlled.

[0107] In one aspect of the piezoelectric element, When the tilt angle is 0°, the difference between the lattice constant in the thickness direction determined based on the low-angle side peak and the lattice constant in the thickness direction determined based on the high-angle side peak may be 0.082 or more.

[0108] According to this piezoelectric element, the generation of cracks can be suppressed.

[0109] In one aspect of the piezoelectric element, The piezoelectric layer may be a layer formed using niobium 2-ethylhexanoate in which no peak is confirmed in the range of 3 ppm or more and 5 ppm or less in proton NMR measurement as a raw material.

[0110] According to this piezoelectric element, niobium 2-ethylhexanoate with few impurities can be used as a raw material.

[0111] One aspect of the liquid ejection head is One aspect of the piezoelectric element and A flow path forming substrate in which a pressure generating chamber whose volume changes by the piezoelectric element is formed, A nozzle plate in which nozzle holes communicating with the pressure generating chamber are formed, and includes.

[0112] One aspect of the printer is One aspect of the liquid ejection head, a conveyance mechanism that relatively moves a recording medium with respect to the liquid ejection head, a control unit that controls the liquid ejection head and the conveyance mechanism, and includes.

Explanation of Reference Numerals

[0113] 2... Substrate, 10... First electrode, 20... Alignment control layer, 30... Piezoelectric layer, 32... Crystal layer, 40... Second electrode, 100... Piezoelectric element, 200... Liquid ejection head, 202... Lead electrode, 203... Adhesive, 204... Connection wiring, 210... Flow path formation substrate, 211... Pressure generation 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... Compliance substrate, 262... Sealing layer, 264... Fixed plate, 266... Through hole, 300... Printer, 310... Head unit, 312, 314... Cartridge, 316... Carriage, 320... Apparatus main body, 322... Carriage shaft, 330... Drive motor, 332... Timing belt, 340... Conveyance roller, 350... Printer controller

Claims

1. a first electrode and a second electrode, a piezoelectric layer provided between the first electrode and the second electrode and having a plurality of layers including a complex oxide having a perovskite structure containing potassium, sodium, and niobium, comprising, For the piezoelectric layer, using the X-ray diffraction method, with the tilt angle as ψ, sin ２ Asymmetric reflection is measured in the range where ψ is 0 or more and 0.7 or less, 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 obtained based on the low-angle side peak, and when a plurality of the lattice constants are plotted for the range, if the plurality of plots are linearly approximated by the least squares method, the slope of the approximate straight line is 0.002 or less, a piezoelectric element.

2. In Claim 1, the piezoelectric element in which the inclination is -0.012 or less.

3. In Claim 1, the piezoelectric element in which the thickness of the piezoelectric layer is greater than 600 nm and 2000 nm or less.

4. In Claim 1, the piezoelectric element further comprising an orientation control layer provided between the first electrode and the piezoelectric layer and containing bismuth, iron, titanium, and lead.

5. In Claim 1, when the skew angle is 0°, the difference between the lattice constant in the thickness direction determined based on the low-angle side peak and the lattice constant in the thickness direction determined based on the high-angle side peak is 0.082 or more, the piezoelectric element.

6. In Claim 1, the piezoelectric element in which the piezoelectric layer is a layer formed using niobium 2-ethylhexanoate in which no peak is confirmed in the range of 3 ppm or more and 5 ppm or less in proton NMR measurement.

7. the piezoelectric element according to any one of Claims 1 to 6, a flow path forming substrate in which a pressure generating chamber whose volume changes by the piezoelectric element is formed, a nozzle plate in which a nozzle hole communicating with the pressure generating chamber is formed, comprising a liquid ejection head.

8. the liquid ejection head according to Claim 7, a conveyance mechanism for relatively moving a recording medium with respect to the liquid ejection head, a control unit for controlling the liquid ejection head and the conveyance mechanism, comprising a printer.

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