Piezoelectric element, liquid ejection head, and printer

Abstract

The invention provides a piezoelectric element capable of improving piezoelectric characteristics, a liquid ejection head, and a printer. A piezoelectric element includes: a first electrode; a piezoelectric layer provided above the first electrode and having a perovskite-type composite oxide containing potassium, sodium, and niobium; and a second electrode provided above the piezoelectric layer, in which the piezoelectric layer is preferentially oriented in a (100) plane, and the half width of a peak derived from the (100) plane as measured by an X-ray rocking curve method is 3.193 DEG or less.

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 such as a liquid ejection head for an inkjet printer is configured, for example, such that a piezoelectric layer made of a piezoelectric material having an electromechanical conversion function is sandwiched between two electrodes.

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

[0004] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2018-133458

[0005] In a piezoelectric element as described above, improvement in piezoelectric characteristics is desired. Summary of the Invention

[0006] One aspect of the piezoelectric element according to the present invention includes: a first electrode; a piezoelectric layer provided above the first electrode and having a perovskite-type composite oxide containing potassium, sodium, and niobium; and a second electrode provided above the piezoelectric layer, wherein the piezoelectric body is preferentially oriented in the (100) plane, and the half-width of the peak derived from the (100) plane measured by the X-ray rocking curve method is 3.193° or less.

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

[0008] One aspect of the printer according to the present invention includes: the liquid ejection head; a conveyance mechanism that relatively moves a recording medium with respect to the liquid ejection head; and a control unit that controls the liquid ejection head and the conveyance mechanism. Brief Description of the Drawings

[0009] Figure 1 is a cross-sectional view schematically showing the piezoelectric element according to the present embodiment.

[0010] Figure 2 is an exploded perspective view schematically showing the liquid ejection head according to the present embodiment.

[0011] Figure 3 is a top view schematically showing the liquid ejection head according to the present embodiment.

[0012] Figure 4 is a cross-sectional view schematically showing the liquid ejection head according to the present embodiment.

[0013] Figure 5 is a perspective view schematically showing a printer according to this embodiment.

[0014] Figure 6 is the result of proton NMR measurement of niobium 2-ethylhexanoate for the KNN precursor solution.

[0015] Figure 7 is a table showing the experimental results of Examples 1 and 2 and Comparative Examples 1 and 2.

[0016] Explanation of Reference Numerals

[0017] 2: Substrate, 10: First Electrode, 20: Orientation Control Layer, 30: Piezoelectric Layer, 32: Crystal Layer, 40: Second Electrode, 100: Piezoelectric Element, 200: Liquid Nozzle Head, 202: Lead Electrode, 203: Adhesive, 204: Connection Wiring, 210: Flow Path Formation Substrate, 211: Pressure Generation Chamber, 212: Partition Wall, 213: First Communication Channel, 214: Second Communication Channel, 215: Third Communication Channel, 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 Substrate, 260: Plastic Substrate, 262: Sealing Layer, 264: Fixing Plate, 266: Through-Hole, 300: Printer, 310: Head Unit, 312, 314: Cartridge, 316: Carriage, 320: Device Main Body, 322: Carriage Shaft, 330: Driving Motor, 332: Timing Belt, 340: Conveyor Roll, 350: Printer Controller. Detailed Embodiment

[0018] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. It should be noted that the embodiments described below do not unduly limit the content of the present invention recited in the claims. In addition, not all of the configurations described below are essential elements of the present invention.

[0019] 1. Piezoelectric Element

[0020] 1.1. Configuration

[0021] First, the piezoelectric element according to this embodiment will be described with reference to the drawings. Figure 1 is a cross-sectional view schematically showing the piezoelectric element 100 according to this embodiment.

[0022] As Figure 1As 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 disposed on a substrate 2.

[0023] 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 obtained by laminating a plurality of layers. If the upper surface of the substrate 2 has a planar shape, the internal structure thereof is not limited, and it may also be a structure having a space or the like formed therein.

[0024] The substrate 2 may also have a diaphragm that deforms due to the operation of the piezoelectric layer 30. The diaphragm is, for example, a silicon oxide layer, a zirconium oxide layer, or a laminate having a zirconium oxide layer provided on a silicon oxide layer.

[0025] The first electrode 10 is disposed on the substrate 2. The first electrode 10 is disposed between the substrate 2 and the orientation 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.

[0026] The first electrode 10 is, for example, a titanium layer, a platinum layer, an iridium layer, or the like. The first electrode 10 may be obtained by laminating a titanium layer, a platinum layer, and an iridium layer in this order 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 an electrode for applying a voltage to the piezoelectric layer 30.

[0027] The orientation control layer 20 is disposed on the first electrode 10. The orientation control layer 20 is disposed between the first electrode 1 and the piezoelectric layer 30. In the illustrated example, the orientation control layer 20 is also disposed 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.

[0028] The orientation control layer 20 contains, for example, a complex oxide having a perovskite structure, and the complex oxide contains bismuth (Bi), iron (Fe), titanium (Ti), and lead (Pb). The orientation control layer 20 is, for example, a bismuth ferrite-lead titanate ((Bi, Pb)(Fe, Ti)O3: BFTP) layer. The orientation control layer 20 may also be a BFTP layer added with an additive. The orientation control layer 20 controls the orientation of the piezoelectric layer 30.

[0029] The piezoelectric layer 30 is disposed above the first electrode 10. In the illustrated example, the piezoelectric layer 30 is disposed on 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 T 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, and more preferably 600 nm or more and 1000 nm or less. The thickness T of the piezoelectric layer 30 is measured by spectroscopic ellipsometry. The piezoelectric layer 30 has columnar crystals extending in the thickness direction (hereinafter also simply referred to as the "thickness direction") of the piezoelectric layer 30. The piezoelectric layer 30 deforms by applying a voltage between the first electrode 10 and the second electrode 40.

[0030] The piezoelectric layer 30 includes, for example, a plurality of crystal layers 32. The piezoelectric layer 30 is composed of, 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, 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, preferably 30 nm or more and 150 nm or less.

[0031] The crystal layer 32 is a layer of 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 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, preferably 5 mol% or less. The additive may also be concentrated at the grain boundaries of the crystal layer 32.

[0032] The second electrode 40 is disposed above the piezoelectric layer 30. In the illustrated example, the second electrode 40 is disposed on the piezoelectric layer 30. Although not shown, if the second electrode 40 is electrically separated from the first electrode 10, it may also be disposed on the side surface of the piezoelectric layer 30 and the substrate 2. 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.

[0033] The second electrode 40 is, for example, a platinum layer, a titanium layer, or an iridium layer. The second electrode 40 may also be obtained 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.

[0034] 1.2. X-ray diffraction method

[0035] The piezoelectric layer 30 is preferentially oriented on the (100) plane. "Preferential orientation" means that 70% or more, preferably 80% or more, of the crystals are oriented on a specified crystal plane. "Preferentially oriented on the (100) plane" includes the case where all the crystals of the piezoelectric layer 30 are oriented on the (100) plane and the case where 70% or more, preferably 80% or more, of the crystals are oriented on the (100) plane. Whether the piezoelectric layer 30 is preferentially oriented on the (100) plane is confirmed by performing X-ray diffraction method (X-Ray Diffraction: XRD) on the piezoelectric layer 30.

[0036] In the piezoelectric layer 30, the full width at half maximum (FWHM) of the peak derived from the (100) plane measured by the X-ray rocking curve method is 3.193° or less, preferably 3.150° or less, more preferably 3.140° or less, and further more preferably 3.133° or less. If the full width at half maximum of the peak derived from the (100) plane is 3.193° or less, the crystallinity of the piezoelectric layer 30 can be improved. In the piezoelectric layer 30, the full width at half maximum of the peak derived from the (100) plane measured by the X-ray rocking curve method is, for example, 2.0° or more.

[0037] In the piezoelectric layer 30, the integrated intensity of the peak derived from the (100) plane measured by the X-ray rocking curve method is, for example, 2.5×10 4 cps or more, preferably 2.8×10 4 cps or more, more preferably 2.81×10 4 cps or more. If the integrated intensity of the peak derived from the (100) plane is 2.5×10 4 cps or more, the orientation of the (100) plane of the piezoelectric layer 30 can be improved. In the piezoelectric layer 30, the integrated intensity of the peak derived from the (100) plane measured by the X-ray rocking curve method is, for example, 4.0×10 4 cps or less.

[0038] The integrated intensity of the peak derived from the (100) plane measured by the X-ray rocking curve method with respect to the thickness T of the piezoelectric layer 30 is, for example, 70.0 cps / nm or more, preferably 70.5 cps / nm or more, and more preferably 70.65 cps / nm or more. If the integrated intensity of the peak derived from the (100) plane with respect to the thickness T is 70.0 cps / nm or more, the orientation of the (100) plane of the piezoelectric layer 30 can be improved. The integrated intensity of the peak derived from the (100) plane measured by the X-ray rocking curve method with respect to the thickness T is, for example, 100.0 cps / nm or less.

[0039] The crystal structure of the piezoelectric layer 30 is tetragonal. The crystal structure of the piezoelectric layer 30 is measured by X-ray diffraction. The crystal structure of the piezoelectric layer 30 is, for example, a tetragonal crystal represented by a = c ≠ b, a > b when a, b, and c are lattice constants. a / b is, for example, 1.0280 or more, preferably 1.0285 or more. If a / b is 1.0280 or more, the half-width of the peak derived from the (100) plane measured by the X-ray rocking curve method can be reduced. In XRD using Cu as the tube target, two or more peaks are confirmed between 2θ = 44° and 47°, and a / b can be obtained from the ratio when the larger one of the lattice plane spacings obtained from the largest peak and the second largest peak according to the Bragg equation is used as the numerator and the smaller one is used as the denominator.

[0040] It should be noted that specifically, among the two peaks existing at 44° to 47°, the low-angle peak side represents the lattice where "a" takes values in the film thickness direction, and the high-angle peak side represents the lattice where "b" takes values in the film thickness direction.

[0041] When the thickness T of the piezoelectric layer 30 is measured at 16 points, among the measured thicknesses T, the value calculated as (maximum value - minimum value) / arithmetic mean × 100 is, for example, 2.90 or less, preferably 2.50 or less, more preferably 2.168 or less. If the value calculated as (maximum value - minimum value) / arithmetic mean × 100 is 2.90 or less, the deviation of the thickness T of the piezoelectric layer 30 can be reduced. When the thickness T of the piezoelectric layer 30 is measured at 16 points, among the measured thicknesses T, the value calculated as (maximum value - minimum value) / arithmetic mean × 100 is, for example, 1.0 or more.

[0042] 1.3. Effects

[0043] In the piezoelectric element 100, including the first electrode 10, the piezoelectric layer 30, and the second electrode 40, the piezoelectric layer 30 is provided above the first electrode 10 and has a perovskite-type composite oxide containing potassium, sodium, and niobium. The second electrode 40 is provided above the piezoelectric layer 30. The piezoelectric layer 30 is preferentially oriented in the (100) plane, and the half-width of the peak derived from the (100) plane measured by the X-ray rocking curve method is 3.193° or less.

[0044] Therefore, in the piezoelectric element 100, for example, compared with the case where the half-width of the peak derived from the (100) plane measured by the X-ray rocking curve method is greater than 3.193°, it can have high crystallinity. Thus, the piezoelectric characteristics can be improved. Specifically, the piezoelectric constant can be increased.

[0045] In the piezoelectric element 100, the integrated intensity of the peak derived from the (100) plane with respect to the thickness T of the piezoelectric layer 30 is 70.65 cps / nm or more. Therefore, in the piezoelectric element 100, the orientation of the (100) plane of the piezoelectric layer 30 can be improved.

[0046] In the piezoelectric element 100, the crystal structure of the perovskite-type composite oxide is a tetragonal crystal represented by a = c ≠ b, a > b when a, b, and c are lattice constants, and a / b is 1.0285 or more. Therefore, in the piezoelectric element 100, the full width at half maximum of the peak derived from the (100) plane of the piezoelectric layer 30 measured by the X-ray rocking curve method can be reduced.

[0047] In the piezoelectric element 100, when the thickness T of the piezoelectric layer 30 is measured at 16 points, the value calculated by (maximum value - minimum value) / arithmetic mean × 100 for the measured thickness T is 2.168 or less. Therefore, in the piezoelectric element 100, the deviation of the thickness T of the piezoelectric layer 30 can be reduced.

[0048] 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.

[0049] 2. Manufacturing method of piezoelectric element

[0050] Next, a method for manufacturing the piezoelectric element 100 according to the present embodiment will be described with reference to the drawings.

[0051] As Figure 1 shown, 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 sputtering 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.

[0052] Next, a first electrode 10 is formed on the substrate 2. The first electrode 10 is formed, for example, by sputtering, vacuum evaporation, or the like. Next, the first electrode 10 is patterned by photolithography and etching, for example. <(

[0053] Next, an orientation control layer 20 is formed on the first electrode 10 and the substrate 2. The orientation control layer 20 is formed by a CSD (Chemical Solution Deposition) method such as a sol-gel method or MOD (Metal Organic Deposition), for example.

[0054] 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 BFTP precursor solution. Next, the BFTP precursor solution is coated on the first electrode 10 by a spin coating method to form a BFTP precursor layer. Next, the BFTP precursor layer is heated, for example, at a temperature of 130°C or higher and 250°C or lower for a certain period of time to dry it. Further, the dried BFTP precursor layer is heated and held for a certain period of time, for example, at a temperature of 300°C or higher and 450°C or lower to remove grease. Next, the degreased BFTP precursor layer is fired, for example, at a temperature of 550°C or higher and 800°C or lower to crystallize it. Through the above process, an orientation control layer 20 composed of a BFTP layer can be formed.

[0055] Next, a piezoelectric layer 30 is formed on the orientation control layer 20. The piezoelectric layer 30 is formed, for example, by a CSD method.

[0056] 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 KNN precursor solution.

[0057] Examples of the metal complex containing potassium include potassium 2-ethylhexanoate. Examples of the metal complex containing sodium include sodium 2-ethylhexanoate.

[0058] Examples of the metal complex containing niobium include niobium 2-ethylhexanoate and the like. Specifically, as the metal complex containing niobium, 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 is used. For this reason, the impurities in niobium 2-ethylhexanoate are few. Niobium 2-ethylhexanoate may also contain no impurities. Examples of the impurities include ethoxy groups derived from raw materials and by-produced ethanol.

[0059] Examples of the organic solvent include a mixed solvent of 2-ethylhexanoic acid and decane. The volume ratio of 2-ethylhexanoic acid to the entire organic solvent is, for example, 0.30 or more and 0.50 or less, preferably 0.40 or more and 0.45 or less. The KNN precursor solution does not contain, for example, metal alkoxides or silicone oils.

[0060] The volume concentration of KNN in the KNN precursor solution is, for example, greater than 40% by volume, preferably 42% by volume or more and 60% by volume or less, more preferably 44% by volume or more and 55% by volume or less, and even more preferably 45% by volume or more and 50% by volume or less. If the volume concentration of KNN is 42% by volume or more, the proportion of the organic solvent can be reduced, so that the formation of crosslinks in the subsequent drying and debinding processes is not hindered, and the crosslinking of the piezoelectric layer 30 can be stabilized. In the process of drying, debinding, and firing the KNN layer based on the CSD method, the organic side chains and solvents around the respective metal elements of K, Na, and Nb disappear to form crosslinks and finally become crystals. Therefore, by reducing the proportion of the organic solvent, the crosslinking of the piezoelectric layer 30 can be stabilized. If the volume concentration of KNN is 60% by volume or less, the generation of bubbles in the KNN precursor solution can be suppressed.

[0061] It should be noted that the "volume concentration of KNN" refers to the total volume of potassium 2-ethylhexanoate, sodium 2-ethylhexanoate, and niobium 2-ethylhexanoate relative to the total volume of the KNN precursor solution.

[0062] The mass concentration of KNN in the KNN precursor solution is, for example, 50% by mass or more and 70% by mass or less, preferably 52% by mass or more and 60% by mass or less, and more preferably 53.12% by mass or more and 58.08% by mass or less. If the mass concentration of KNN is 50% by mass or more, the crosslinking of the piezoelectric layer 30 can be stabilized. If the mass concentration of KNN is 70% by mass or less, the generation of bubbles in the KNN precursor solution can be suppressed.

[0063] It should be noted that the "mass concentration of KNN" refers to the total mass of potassium 2-ethylhexanoate, sodium 2-ethylhexanoate, and niobium 2-ethylhexanoate relative to the total mass of the KNN precursor solution.

[0064] The molar concentration of KNN in the KNN precursor solution is, for example, 10.0 mol / L or more and 15.0 mol / L or less, preferably 10.5 mol / L or more and 12.0 mol / L or less, and more preferably 10.83 mol / L or more and 11.84 mol / L or less. If the molar concentration of KNN is 10.0 mol / L or more, the crosslinking of the piezoelectric layer 30 can be stabilized. If the molar concentration of KNN is 15.0 mol / L or less, the generation of bubbles in the KNN precursor solution can be suppressed.

[0065] It should be noted that the "molar concentration of KNN" refers to the total number of moles of potassium 2-ethylhexanoate, sodium 2-ethylhexanoate, and niobium 2-ethylhexanoate dissolved in 1 L of the KNN precursor solution.

[0066] Next, the prepared KNN precursor solution is applied onto the alignment control layer 20 by a spin coating method or the like to form a KNN precursor layer. Next, for example, the KNN precursor layer is heated at a temperature of 130 °C or higher and 250 °C or lower for a certain period of time to dry it. Further, for example, the dried KNN precursor layer is heated at a temperature of 300 °C or higher and 450 °C or lower for a certain period of time to degrease it. Next, for example, the degreased KNN precursor layer is fired at a temperature of 550 °C or higher and 800 °C or lower to crystallize it. The heating rate during firing is, for example, 5 °C / second or higher and 15 °C / second or lower, preferably 8 °C / second or higher and 12 °C / second or lower.

[0067] Through the above process, a crystalline layer 32 composed of a KNN layer can be formed. Then, the series of processes from the application of the KNN precursor solution to the firing of the KNN precursor layer are repeated multiple times. Thereby, a piezoelectric layer 30 composed of a plurality of crystalline layers 32 can be formed.

[0068] In the process of forming the crystalline layer 32, the heating device used for drying and degreasing the KNN precursor layer is, for example, a hot plate. The heating device used for firing the KNN precursor layer is an infrared lamp annealing device (Rapid Thermal Annealing (RTA) device).

[0069] 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, for example, the second electrode 40 and the piezoelectric layer 30 are patterned by photolithography and etching. It should be noted that the second electrode 40 and the piezoelectric layer 30 may also be patterned in separate processes.

[0070] Through the above processes, a piezoelectric element 100 can be manufactured.

[0071] 3. Liquid ejection head

[0072] Next, the liquid ejection head according to the present embodiment will be described with reference to the drawings. Figure 2 FIG. is an exploded perspective view schematically showing a liquid ejection head 200 according to the present embodiment. Figure 3 FIG. is a plan view schematically showing a liquid ejection head 200 according to the present embodiment. Figure 4 FIG. is a schematic cross-sectional view taken along line IV-IV of the liquid ejection head 200 according to the present embodiment Figure 3 In, as three mutually orthogonal axes, the X-axis, the Y-axis, and the Z-axis are illustrated. In addition, in Figures 2 to 4 simplified piezoelectric elements 100 are illustrated. Figure 2 and Figure 4 In, simplified piezoelectric elements 100 are illustrated.

[0073] As shown inFigures 2 to 4 As shown, the liquid ejection head 200 includes, for example, a base 2, a piezoelectric element 100, a nozzle plate 220, a protective substrate 240, a circuit substrate 250, and a plastic substrate 260. The base 2 has a flow path forming substrate 210 and a diaphragm 230. It should be noted that, for convenience, Figure 3 the illustration of the circuit substrate 250 is omitted in the figure.

[0074] The flow path forming substrate 210 is, for example, a silicon substrate. Pressure generation chambers 211 are formed on the flow path forming substrate 210. The pressure generation chambers 211 are partitioned by a plurality of partition walls 212. The volume of the pressure generation chambers 211 changes by the piezoelectric element 100.

[0075] A first communication channel 213 and a second communication channel 214 are formed at the +X-axis direction end of the pressure generation chamber 211 on the flow path forming substrate 210. The first communication channel 213 is configured such that by narrowing the +X-axis direction end of the pressure generation chamber 211 from the Y-axis direction, its opening area becomes smaller. The size of the second communication channel 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. A third communication channel 215 communicating with the plurality of second communication channels 214 is formed in the +X-axis direction of the second communication channel 214. The third communication channel 215 forms a part of a manifold 216. The manifold 216 becomes a common liquid chamber for each pressure generation chamber 211. In this way, a supply flow path 217 composed of the first communication channel 213, the second communication channel 214, and the third communication channel 215 and the pressure generation chambers 211 are formed on the flow path forming substrate 210. The supply flow path 217 communicates with the pressure generation chambers 211 and supplies liquid to the pressure generation chambers 211.

[0076] 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: stainless steel). The nozzle plate 220 is joined to the flow path forming substrate 210 by, for example, an adhesive, a heat fusion film, etc. 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 generation chambers 211 and eject liquid.

[0077] 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.

[0078] The piezoelectric element 100 is, for example, provided on the diaphragm 230. A plurality of piezoelectric elements 100 are provided. The number of the piezoelectric elements 100 is not particularly limited. It should be noted that, for convenience, Figure 3 the illustration of the orientation control layer 20 is omitted in the figure.

[0079] In the liquid ejection head 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 ejection head 200, the diaphragm 230 and the first electrode 10 substantially function as a diaphragm. It should be noted 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 to prevent the liquid from coming into contact with the first electrode 10.

[0080] The first electrode 10 is configured as an independent individual electrode corresponding to 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 end portions of the first electrode 10 are located at positions more outside than both end portions of the pressure generation chamber 211. The lead electrode 202 is connected to the -X-axis direction end portion of the first electrode 10.

[0081] 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 portion of the piezoelectric layer 30 is, for example, located at a position more outside than the +X-axis direction end portion of the first electrode 10. The +X-axis direction end portion of the first electrode 10 is covered by the piezoelectric layer 30. On the other hand, the -X-axis direction end portion of the piezoelectric layer 30 is, for example, located at a position more inside than the -X-axis direction end portion of the first electrode 10. The -X-axis direction end portion of the first electrode 10 is not covered by the piezoelectric layer 30.

[0082] 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 shared by a plurality of piezoelectric elements 100.

[0083] 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 channel 215. The through holes 242 and the third communication channel 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 hole 244.

[0084] An opening 246 is formed on the protective substrate 240. The opening 246 is a space for not obstructing the driving of the piezoelectric element 100. The opening 246 may or may not be sealed.

[0085] A circuit substrate 250 is provided on the protective substrate 240. The circuit substrate 250 includes a semiconductor integrated circuit (IC) for driving the piezoelectric element 100. The circuit substrate 250 is electrically connected to the lead electrode 202 via a connection wiring 204.

[0086] A plastic substrate 260 is provided on the protective substrate 240. The plastic 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 flexibility, for example. 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. When viewed from the Z-axis direction, the through hole 266 is provided at a position overlapping with the manifold 216.

[0087] 4. Printer

[0088] Next, the printer according to the present embodiment will be described with reference to the drawings. Figure 5 FIG. is a perspective view schematically showing a printer 300 according to the present embodiment.

[0089] The printer 300 is an inkjet printer. As Figure 5 shown, the printer 300 includes a head unit 310. The head unit 310 has, for example, a liquid ejection head 200. The number of liquid ejection heads 200 is not particularly limited. The head unit 310 is detachably provided with cartridges 312 and 314 constituting a supply unit. A carriage 316 carrying the head unit 310 is provided on a carriage shaft 322 mounted on a device main body 320 so as to be movable freely in the axial direction, and ejects the liquid supplied from the liquid supply unit.

[0090] Here, the liquid may be a material in a liquid phase state, and liquid materials such as sols and gels are also included in the liquid. In addition, not only the liquid as a state of matter, but also substances obtained by dissolving, dispersing, or mixing particles of a functional material composed of solids such as pigments and metal particles in a solvent are included in the liquid. Representative examples of the liquid include ink, liquid crystal emulsifiers, etc. Ink includes general aqueous ink, oil-based ink, and various liquid compositions such as gel ink and hot melt ink.

[0091] In printer 300, the driving force of driving motor 330 is transmitted via a plurality of gears (not shown) and timing belt 332 to carriage 316, such that carriage 316 carrying head unit 310 moves along carriage shaft 322. On the other hand, in device main body 320, there is provided a conveyance roller 340 as a conveyance mechanism that relatively moves a sheet S such as paper, which is a recording medium, relative to liquid ejection head 200. The conveyance mechanism for conveying sheet S is not limited to a conveyance roller, and may also be a belt, a drum, or the like.

[0092] Printer 300 includes a printer controller 350 as a control unit that controls liquid ejection head 200 and conveyance roller 340. Printer controller 350 is electrically connected to circuit board 250 of liquid ejection head 200. Printer controller 350 includes, for example: a RAM (Random Access Memory) that temporarily stores various data, a ROM (Read Only Memory) that stores control programs and the like, a CPU (Central Processing Unit), and a drive signal generation circuit that generates a drive signal for supplying to liquid ejection head 200.

[0093] It should be noted that piezoelectric element 100 is not limited to being used in liquid ejection heads and printers, and it can be used for a wide range of applications. Piezoelectric element 100 is, for example, suitable as a piezoelectric actuator for an ultrasonic motor, a vibration type dust removal device, a piezoelectric transformer, a piezoelectric speaker, a piezoelectric pump, a pressure-electric conversion device, etc. In addition, piezoelectric element 100 is, for example, suitable as a piezoelectric type 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 sensor, an infrared sensor, a terahertz sensor, a thermal detection sensor, a thermoelectric sensor, a piezoelectric sensor, etc. In addition, 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, piezoelectric element 100 is suitable as a voltage control type optical element for a wavelength converter, an optical waveguide, an optical path modulator, a refractive index control element, an electronic shutter mechanism, etc.

[0094] 5. Examples and Comparative Examples

[0095] 5.1. Fabrication of Specimens

[0096] 5.1.1. Example 1

[0097] A SiO2 layer with a thickness of 1460 nm was formed by thermally oxidizing the surface of a single-crystalline silicon substrate. Subsequently, 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.

[0098] Subsequently, on the ZrO2 layer, Ti layer, Pt layer, and Ir layer with thicknesses of 20 nm, 80 nm, and 5 nm respectively were formed by DC sputtering method as the first electrode.

[0099] Subsequently, 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 coated on the Ir layer and the ZrO2 layer by spin coating method, 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 process, a BFTP layer with a thickness of 20 nm was formed.

[0100] Subsequently, monomer solutions composed of potassium 2-ethylhexanoate, sodium 2-ethylhexanoate, and niobium 2-ethylhexanoate were synthesized respectively. As the organic solvent, a mixed solvent of 2-ethylhexanoic acid and decane was used. The volume ratio of 2-ethylhexanoic acid to the whole organic solvent was 0.42. These monomer solutions were formulated as (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 volume concentration of KNN in the KNN precursor solution was 50 vol%. The mass concentration of KNN in the KNN precursor solution was 58.08 mass%. The molar concentration of KNN in the KNN precursor solution was 0.610 mol / L.

[0101] Herein, Figure 6 is the result of proton NMR measurement of niobium 2-ethylhexanoate used in the KNN precursor solution. As the NMR apparatus, “Ascend TM400” manufactured by Bruker was used. As the 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 made to coincide with 7.26 ppm for the measurement.

[0102] As Figure 6In the "Example 1" shown, in the NMR measurement spectrum of niobium 2-ethylhexanoate, no peak was confirmed in the range above 3 ppm and below 5 ppm. Therefore, it can be known that the niobium 2-ethylhexanoate used in Example 1 does not contain impurities such as ethoxy groups derived from raw materials and by-produced ethanol. Using such niobium 2-ethylhexanoate, a KNN precursor solution was prepared.

[0103] On the other hand, as Figure 6 shown in the "Reference Example", in the case of niobium 2-ethylhexanoate containing impurities, in the NMR measurement spectrum, a peak was confirmed in the range above 3 ppm and below 5 ppm. In Figure 6 , this peak is circled with a dashed line.

[0104] Next, the prepared KNN precursor solution was 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 of the firing was 10 °C / second. Through the above process, a crystalline layer with a thickness of 80 nm was formed. Then, the above series of processes from the coating of the KNN precursor solution to the firing of the KNN precursor layer were repeated five times to form a piezoelectric layer with a thickness of 400 nm composed of five crystalline layers.

[0105] 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.

[0106] Through the above process, the piezoelectric element of Example 1 was formed.

[0107] 5.1.2. Example 2

[0108] Except that the KNN volume concentration in the KNN precursor solution was 45 vol%, the KNN mass concentration was 53.12 mass%, and the KNN molar concentration was 0.549 mol / L, a piezoelectric element of Example 2 was formed by the same method as in Example 1 above.

[0109] 5.1.3. Comparative Example 1

[0110] Except that the KNN volume concentration in the KNN precursor solution was 40 vol%, the KNN mass concentration was 48.02 mass%, and the KNN molar concentration was 0.488 mol / L, a piezoelectric element of Comparative Example 1 was formed by the same method as in Example 1 above.

[0111] 5.1.4. Comparative Example 2

[0112] A piezoelectric element of Comparative Example 2 was formed by the same method as in Example 1 above, except that the volume concentration of KNN in the KNN precursor solution was 35% by volume, the mass concentration of KNN was 42.73% by mass, and the molar concentration of KNN was 0.427 mol / L.

[0113] 5.2. Experimental conditions

[0114] The XRD apparatus used "D8 DISCOVER with GADDS" manufactured by Bruker Corporation. Cu was used as the tube target, the diameter of the collimator was φ = 0.3 mm, and the measurement was carried out under the conditions of 2θ = 20° to 50° and 10 sec / °. The rocking curve measurement was carried out at 2θ = 21° to 24° and χ = -95° to -85°.

[0115] 5.3. Experimental results

[0116] Figure 7 is a table showing the experimental results of Examples 1 and 2 and Comparative Examples 1 and 2. It should be noted that in Figure 7 "KNN mass concentration ※1" is the total mass of potassium 2-ethylhexanoate, sodium 2-ethylhexanoate, and niobium 2-ethylhexanoate relative to the total mass of the KNN precursor solution. "KNN mass concentration ※2" is the total mass of K2O in potassium 2-ethylhexanoate, Na2O in sodium 2-ethylhexanoate, and Nb2O5 in niobium 2-ethylhexanoate relative to the total mass of the KNN precursor solution.

[0117] As Figure 7 shown, the "KNN (100) rocking curve half-width" of Examples 1 and 2 is smaller than that of Comparative Examples 1 and 2. That is, the half-width of the peak derived from the (100) plane measured by the X-ray rocking curve method in Examples 1 and 2 is smaller than that of Comparative Examples 1 and 2. From this, it can be seen that Examples 1 and 2 have higher crystallinity compared to Comparative Examples 1 and 2. In Examples 1 and 2, compared with Comparative Examples 1 and 2, since a KNN precursor solution with a high KNN concentration is used, the "KNN (100) rocking curve half-width" can be reduced.

[0118] As Figure 7 shown, the "KNN (100) rocking curve half-width / thickness" of Examples 1 and 2 is larger than that of Comparative Examples 1 and 2. That is, the integrated intensity of the peak derived from the (100) plane measured by the X-ray rocking curve method with respect to the thickness of the piezoelectric layer in Examples 1 and 2 is larger than that of Comparative Examples 1 and 2. From this, it can be seen that Examples 1 and 2 can improve the orientation of the (100) plane compared to Comparative Examples 1 and 2.

[0119] It should be noted that the thickness of the piezoelectric layer is the average of the thicknesses measured at 16 points at intervals of 0.5 mm in a region centered on the center of the sample and having an area of 32% relative to the entire sample when viewed from above. The measurement was performed using the laser ellipsometer "MARY-102" manufactured by Five Lab Co., Ltd.

[0120] As Figure 7 shown, compared with Comparative Examples 1 and 2, the a / b of the lattice constant of KNN in Examples 1 and 2 is larger. a / b is obtained by identifying two or more peaks between 2θ = 44° and 47°, and calculating the ratio with the larger one of the lattice plane spacings obtained from the largest peak and the second largest peak according to Bragg's equation as the numerator and the smaller one as the denominator. The two large peaks identified between 2θ = 44° and 47° are the peaks originating from the (200) plane and the peaks originating from the (020) plane.

[0121] As Figure 7 shown, compared with Comparative Examples 1 and 2, the in-plane deviation of the piezoelectric layer in Examples 1 and 2 is smaller. The thickness of the piezoelectric layer is a value calculated as (maximum value - minimum value) / average value × 100 by measuring at 16 points at intervals of 0.5 mm in a region centered on the center of the sample and having an area of 32% relative to the entire sample when viewed from above.

[0122] The above embodiments and modifications are just examples and are not limited thereto. For example, the various embodiments and modifications can be appropriately combined.

[0123] The present invention includes configurations that are substantially the same as those described in the embodiments, such as configurations having the same functions, methods, and results, or configurations having the same purposes and effects. In addition, the present invention includes configurations obtained by replacing non-essential parts of the configurations described in the embodiments. In addition, the present invention includes configurations that achieve the same effects as those of the configurations described in the embodiments or can achieve the same purposes. In addition, the present invention includes configurations obtained by adding well-known technologies to the configurations described in the embodiments.

[0124] The following is derived from the above embodiments and modifications.

[0125] One aspect of the piezoelectric element includes: a first electrode; a piezoelectric layer disposed above the first electrode and having a perovskite-type composite oxide containing potassium, sodium, and niobium; and a second electrode disposed above the piezoelectric layer, wherein the piezoelectric layer is preferentially oriented in the (100) plane, and the half-width of the peak originating from the (100) plane measured by the X-ray rocking curve method is 3.193° or less.

[0126] According to this piezoelectric element, the piezoelectric characteristics can be improved.

[0127] In one aspect of the piezoelectric element, it is also possible that the integrated intensity of the peak derived from the (100) plane with respect to the thickness of the piezoelectric layer is 70.65 cps / nm or more.

[0128] According to this piezoelectric element, the orientation of the (100) plane of the piezoelectric layer can be improved.

[0129] In one aspect of the piezoelectric element, it is also possible that the crystal structure of the perovskite-type composite oxide is a tetragonal crystal represented by a = c ≠ b, a > b when a, b, and c are lattice constants, and a / b is 1.0285 or more.

[0130] According to this piezoelectric element, the full width at half maximum of the peak derived from the (100) plane of the piezoelectric layer measured by the X-ray rocking curve method can be reduced.

[0131] In one aspect of the piezoelectric element, it is also possible that when the thickness of the piezoelectric layer is measured at 16 points, the value calculated as (maximum value - minimum value) / arithmetic mean × 100 in the measured thickness is 2.168 or less.

[0132] According to this piezoelectric element, the deviation in the thickness of the piezoelectric layer can be reduced.

[0133] In one aspect of the piezoelectric element, it may further include an orientation control layer disposed between the first electrode and the piezoelectric layer and containing bismuth, iron, titanium, and lead.

[0134] According to this piezoelectric element, the orientation of the piezoelectric layer can be controlled.

[0135] One aspect of the liquid ejection head includes: one aspect of the piezoelectric element; a flow path forming substrate on which a pressure generating chamber whose volume changes by the piezoelectric element is formed; and a nozzle plate on which nozzle holes communicating with the pressure generating chamber are formed.

[0136] One aspect of the printer includes: one aspect of the liquid ejection head; a conveyance mechanism that relatively moves a recording medium with respect to the liquid ejection head; and a control unit that controls the liquid ejection head and the conveyance mechanism.

Claims

1. A piezoelectric element, characterized in that, Comprising: A first electrode; A piezoelectric layer disposed above the first electrode and having a perovskite-type composite oxide containing potassium, sodium, and niobium; And A second electrode disposed above the piezoelectric layer, The piezoelectric layer is preferentially oriented in the (100) plane, The half-width of the peak derived from the (100) plane measured by the X-ray rocking curve method is 3.193° or less.

2. The piezoelectric element according to claim 1, wherein: The integrated intensity of the peak derived from the (100) plane with respect to the thickness of the piezoelectric layer is 70.65 cps / nm or more.

3. The piezoelectric element according to claim 1, wherein: The crystal structure of the perovskite-type composite oxide is a tetragonal crystal represented by a = c ≠ b, a > b when a, b, and c are lattice constants, a / b is 1.0285 or more.

4. The piezoelectric element according to claim 1, wherein: When the thickness of the piezoelectric layer is measured at 16 points, among the measured thicknesses, the value calculated by (maximum value - minimum value) / arithmetic mean × 100 is 2.168 or less.

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

6. A liquid ejection head, characterized in that, Comprising: The piezoelectric element according to any one of claims 1 to 5; A flow path forming substrate having a pressure generating chamber whose volume changes by the piezoelectric element; And A nozzle plate having nozzle holes communicating with the pressure generating chamber.

7. A printer, characterized in that, Comprising: The liquid ejection head according to claim 6; A conveyance mechanism that relatively moves a recording medium with respect to the liquid ejection head; And A control unit that controls the liquid ejection head and the conveyance mechanism.

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