Piezoelectric element, liquid discharge head, and printer

Abstract

To provide a piezoelectric element that can improve piezoelectric characteristics.SOLUTION: The piezoelectric element includes: a first electrode; a piezoelectric layer above the first electrode, the piezoelectric layer having a perovskite-type composite oxide containing potassium, sodium, and niobium; and a second electrode above the piezoelectric layer. The piezoelectric layer is preferentially oriented in a (100) plane, and the half width of a peak derived from the (100) plane measured by X-ray rocking curve analysis is 3.193° at a maximum.SELECTED DRAWING: Figure 7

Description

[Technical Field]

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

[0002] Piezoelectric elements used in liquid ejection heads of inkjet printers and the like are configured, for example, by sandwiching a piezoelectric layer made of a piezoelectric material having an electromechanical conversion function between two electrodes.

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

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2018-133458 Summary of the Invention [Problem to be solved by the invention]

[0005] In the above-mentioned piezoelectric element, it is desired to improve the piezoelectric characteristics. [Means for solving the problem]

[0006] One aspect of the piezoelectric element according to the present invention is A first electrode; a piezoelectric layer provided above the first electrode and having a perovskite complex oxide containing potassium, sodium, and niobium; a second electrode provided above the piezoelectric layer; Including, The piezoelectric layer has a (100) preferred orientation, 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 is The piezoelectric element; a flow path forming substrate in which a pressure generating chamber whose volume changes due to the piezoelectric element is formed; a nozzle plate having nozzle holes formed therein that communicate with the pressure generating chambers; Includes:

[0008] One aspect of the printer according to the present invention is the liquid ejection head; a conveying mechanism that moves a recording medium relative to the liquid ejection head; a control unit that controls the liquid ejection head and the transport mechanism; Includes: [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a cross-sectional view schematically showing a piezoelectric element according to an embodiment of the present invention. [Figure 2] FIG. 1 is an exploded perspective view schematically showing a liquid ejection head according to an embodiment of the present invention. [Figure 3] FIG. 1 is a plan view schematically showing a liquid ejection head according to an embodiment of the present invention. [Figure 4] FIG. 1 is a cross-sectional view schematically showing a liquid ejection head according to an embodiment of the present invention. [Figure 5] FIG. 1 is a perspective view schematically illustrating a printer according to an embodiment of the present invention. [Figure 6] Proton NMR measurement results of niobium 2-ethylhexanoate used in the KNN precursor solution. [Figure 7] 1 is a table showing the experimental results of Examples 1 and 2 and Comparative Examples 1 and 2. DETAILED DESCRIPTION OF THE INVENTION

[0010] Preferred embodiments of the present invention will be described in detail below with reference to the drawings. Note that the embodiments described below do not unduly limit the content of the present invention as defined in the claims. Furthermore, not all of the configurations described below are necessarily essential components of the present invention.

[0011] 1. Piezoelectric element Configuration First, the piezoelectric element according to this embodiment will be described with reference to the drawings. Fig. 1 is a cross-sectional view that schematically shows a piezoelectric element 100 according to this embodiment.

[0012] 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 base 2.

[0013] The base 2 is, for example, a flat plate made of a semiconductor, an insulator, or the like. The base 2 may be a single layer or a laminate of multiple layers. The internal structure of the base 2 is not limited as long as the upper surface has a flat shape, and the base 2 may have a structure in which a space or the like is formed inside.

[0014] The base 2 may have a diaphragm that is deformed 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 alignment control layer 20. The first electrode 10 has, for example, a layered shape. The thickness of the first electrode 10 is, for example, 5 nm or more and 300 nm or less, and 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, or the like. The first electrode 10 may be formed by laminating a titanium layer, a platinum layer, and an iridium layer in this order from the base 2 side. The titanium layer, for example, improves adhesion between the base 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 10 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, and preferably 10 nm or more and 50 nm or less.

[0018] The orientation control layer 20 includes, for example, a complex oxide with a perovskite structure containing bismuth (Bi), iron (Fe), titanium (Ti), and lead (Pb). The orientation control layer 20 is, for example, a bismuth lead ferrate titanate ((Bi,Pb)(Fe,Ti)O:BFTP) layer. The orientation control layer 20 may also be a BFTP layer containing an additive. The orientation control layer 20 controls the orientation of the piezoelectric layer 30.

[0019] The piezoelectric layer 30 is provided above the first electrode 10. In the illustrated example, 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 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 of the piezoelectric layer 30 (hereinafter simply referred to as the "thickness direction"). The piezoelectric layer 30 is deformed when a voltage is applied between the first electrode 10 and the second electrode 40.

[0020] 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 crystal layers 32 is, for example, 2 to 30, and preferably 3 to 20. In the illustrated example, five crystal layers 32 are provided. The thickness of the crystal layers 32 is, for example, 10 to 200 nm, and preferably 30 to 150 nm.

[0021] The crystal layer 32 is a layer having a complex oxide with a perovskite structure 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, and 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 above the piezoelectric layer 30. In the illustrated example, the second electrode 40 is provided on the piezoelectric layer 30. Although not illustrated, the second electrode 40 may also be provided on the side surface of the piezoelectric layer 30 and on the base 2, as long as it is electrically isolated from the first electrode 10. The second electrode 40 has, for example, a layered shape. 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 formed by stacking 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 piezoelectric layer 30 is preferentially oriented in the (100) plane. "Preferential orientation" means that 70% or more, preferably 80% or more, of the crystals are oriented in a specific crystal plane. "Preferential orientation in the (100) plane" includes cases where all of the crystals in the piezoelectric layer 30 are oriented in the (100) plane, and cases where 70% or more, preferably 80% or more, of the crystals are oriented in the (100) plane. Whether the piezoelectric layer 30 is preferentially oriented in the (100) plane can be confirmed by subjecting the piezoelectric layer 30 to X-ray diffraction (XRD).

[0025] In the piezoelectric layer 30, the full width at half maximum (FWHM) of the peak derived from the (100) plane, measured by X-ray rocking curve spectroscopy, is 3.193° or less, preferably 3.150° or less, more preferably 3.140° or less, and even 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 X-ray rocking curve spectroscopy, is, for example, 2.0° or more.

[0026] In the piezoelectric layer 30, the (100) plane-derived peaks were measured by the X-ray rocking curve method. The integrated intensity of the peak is, for example, 2.5 × 10 4 cps or more, preferably 2.8 × 10 4 cps or more, and more preferably 2.81 × 10 4 The integrated intensity of the peak originating from the (100) plane is 2.5×10 4 If the peak intensity is 4.0×10 cps or more, it is possible to improve the orientation of the (100) plane of the piezoelectric layer 30. 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.

[0027] The integrated intensity of the peak derived from the (100) plane relative to the thickness T of the piezoelectric layer 30, as measured by the X-ray rocking curve method, 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 relative 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 relative to the thickness T, as measured by the X-ray rocking curve method, is, for example, 100.0 cps / nm or less.

[0028] The crystal structure of the piezoelectric layer 30 is tetragonal. The crystal structure of the piezoelectric layer 30 is measured by X-ray diffraction. For example, the crystal structure of the piezoelectric layer 30 is tetragonal, where a = c ≠ b and a > b, where a, b, and c are lattice constants. a / b is, for example, 1.0280 or more, and 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 a Cu tube, two or more peaks are confirmed between 2θ = 44° and 47°. Of the interplanar spacings calculated according to the Bragg equation from the largest and second largest peaks, a / b can be calculated from the ratio of the larger one as the numerator to the smaller one as the denominator.

[0029] Specifically, of the two peaks present at 44° to 47°, the low-angle peak side indicates a lattice with "a" standing in the film thickness direction, and the high-angle peak side indicates a lattice with "b" standing in the film thickness direction.

[0030] When the thickness T of the piezoelectric layer 30 is measured at 16 points, the value calculated for the measured thickness T by (maximum value - minimum value) / arithmetic mean value x 100 is, for example, 2.90 or less, preferably 2.50 or less, and more preferably 2.168 or less. If the value calculated by (maximum value - minimum value) / average value x 100 is 2.90 or less, the variation in 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, the value calculated for the measured thickness T by (maximum value - minimum value) / arithmetic mean value x 100 is, for example, 1.0 or more.

[0031] 1.3. Effects The piezoelectric element 100 includes a first electrode 10, a piezoelectric layer 30 provided above the first electrode 10 and having a perovskite complex oxide containing potassium, sodium, and niobium, and a second electrode 40 provided above the piezoelectric layer 30, wherein 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 more.

[0032] Therefore, the piezoelectric element 100 can have higher crystallinity than when the half-width of the peak derived from the (100) plane measured by, for example, the X-ray rocking curve method is smaller than 3.193°. This can improve the piezoelectric characteristics. Specifically, the piezoelectric constant can be improved.

[0033] In the piezoelectric element 100, the peak originating from the (100) plane with respect to the thickness T of the piezoelectric layer 30 The integrated intensity 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.

[0034] In the piezoelectric element 100, the crystal structure of the perovskite complex oxide is a tetragonal system expressed by a=c≠b, a>b, where a, b, and c are lattice constants, and a / b is 1.0285 or more. Therefore, in the piezoelectric element 100, the half-width of the peak derived from the (100) plane of the piezoelectric layer 30 measured by the X-ray rocking curve method can be reduced.

[0035] 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) / average value×100 for the measured thickness T is 2.168 or less. Therefore, in the piezoelectric element 100, the variation in the thickness T of the piezoelectric layer 30 can be reduced.

[0036] The piezoelectric element 100 further includes an orientation control layer 20 that is provided between the first electrode 10 and the piezoelectric layer 30 and contains bismuth, iron, titanium, and lead. Therefore, in the piezoelectric element 100, the orientation of the piezoelectric layer 30 can be controlled.

[0037] 2. Manufacturing method of piezoelectric element Next, a method for manufacturing the piezoelectric element 100 according to this embodiment will be described with reference to the drawings.

[0038] As shown in Figure 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 the zirconium layer is then thermally oxidized to form a zirconium oxide layer. Through these steps, the substrate 2 can be prepared.

[0039] Next, the first electrode 10 is formed on the base 2. The first electrode 10 is formed by, for example, sputtering or vacuum deposition. Next, the first electrode 10 is patterned by, for example, photolithography and etching.

[0040] Next, the orientation control layer 20 is formed on the first electrode 10 and the base 2. The orientation control layer 20 is formed by, for example, a sol-gel method or a CSD (Chemical Solution Deposition) method such as MOD (Metal Organic Deposition).

[0041] Specifically, a BFTP precursor solution is prepared by dissolving or dispersing a metal complex containing bismuth, an iron, a titanium, and a lead in an organic solvent. The BFTP precursor solution is then applied to the first electrode 10 by spin coating to form a BFTP precursor layer. The BFTP precursor layer is then heated, for example, at 130°C to 250°C and dried for a certain period of time. The dried BFTP precursor layer is then degreased by heating, for example, at 300°C to 450°C and maintaining the temperature for a certain period of time. The degreased BFTP precursor layer is then crystallized by baking, for example, at 550°C to 800°C. This process forms the orientation control layer 20, which is a BFTP layer.

[0042] Next, the piezoelectric layer 30 is formed on the orientation control layer 20. The piezoelectric layer 30 is formed by, for example, the CSD method.

[0043] 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.

[0044] Examples of metal complexes containing potassium include potassium 2-ethylhexanoate, and examples of metal complexes containing sodium include sodium 2-ethylhexanoate.

[0045] An example of a metal complex containing niobium is niobium 2-ethylhexanoate. Specifically, the metal complex containing niobium is niobium 2-ethylhexanoate, which does not show a peak in the range of 3 ppm to 5 ppm in proton NMR (Nuclear Magnetic Resonance) measurement. Therefore, the amount of impurities in niobium 2-ethylhexanoate is small. 2-ethylhexanoate may be free of impurities. Examples of impurities include ethoxy groups derived from the raw materials and by-produced ethanol.

[0046] The organic solvent may be, for example, a mixed solvent of 2-ethylhexanoic acid and decane. The volume ratio of 2-ethylhexanoic acid to the total 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 alkoxide or silicone oil.

[0047] The KNN volume concentration in the KNN precursor solution is, for example, greater than 40% by volume, preferably 42% to 60% by volume, more preferably 44% to 55% by volume, and even more preferably 45% to 50% by volume. A KNN volume concentration of 42% by volume or greater can reduce the proportion of organic solvent, which prevents the formation of crosslinks during the drying and degreasing steps described below and stabilizes the crosslinks in the piezoelectric layer 30. In the KNN layer formed by the CSD method, the organic side chains and solvent surrounding the metal elements K, Na, and Nb are eliminated during the drying, degreasing, and firing processes, forming crosslinks and ultimately becoming crystalline. Therefore, reducing the proportion of organic solvent can stabilize the crosslinks in the piezoelectric layer 30. A KNN volume concentration of 60% by volume or less can prevent the formation of bubbles in the KNN precursor solution.

[0048] The "KNN volume concentration" is the sum of the volume of potassium 2-ethylhexanoate, the volume of sodium 2-ethylhexanoate, and the volume of niobium 2-ethylhexanoate relative to the total volume of the KNN precursor solution.

[0049] The KNN mass concentration 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 KNN mass concentration is 50% by mass or more, crosslinking of the piezoelectric layer 30 can be stabilized. If the KNN mass concentration is 70% by mass or less, generation of bubbles in the KNN precursor solution can be suppressed.

[0050] The "KNN mass concentration" is the sum of the mass of potassium 2-ethylhexanoate, the mass of sodium 2-ethylhexanoate, and the mass of niobium 2-ethylhexanoate relative to the total mass of the KNN precursor solution.

[0051] The KNN molar concentration 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 KNN molar concentration is 10.0 mol / L or more, crosslinking of the piezoelectric layer 30 can be stabilized. If the KNN molar concentration is 15.0 mol / L or less, generation of bubbles in the KNN precursor solution can be suppressed.

[0052] The "KNN molar concentration" refers to the ratio of the number of moles of potassium 2-ethylhexanoate, the number of moles of sodium 2-ethylhexanoate, and the number of moles of 2-ethylhexanoate dissolved in 1 L of the KNN precursor solution. The sum of the number of moles of niobium hexanoate and

[0053] Next, the prepared KNN precursor solution is applied onto the orientation control layer 20 using a spin coating method or the like to form a KNN precursor layer. Next, the KNN precursor layer is heated, for example, at 130°C to 250°C and dried for a certain period of time, and the dried KNN precursor layer is degreased by heating, for example, at 300°C to 450°C and holding for a certain period of time. Next, the degreased KNN precursor layer is crystallized by baking, for example, at 550°C to 800°C. The heating rate during baking is, for example, 5°C / s to 15°C / s, preferably 8°C / s to 12°C / s.

[0054] As a result, a crystal layer 32 made of a KNN layer can be formed. Then, the series of steps from applying the KNN precursor solution to firing the KNN precursor layer is repeated multiple times. In this way, a piezoelectric layer 30 made of multiple crystal layers 32 can be formed.

[0055] In the step of forming the crystal layer 32, a heating device used for drying and degreasing the KNN precursor layer is, for example, a hot plate. A heating device used for firing the KNN precursor layer is an infrared lamp annealing (Rapid Thermal Annealing: RTA) device.

[0056] Next, the second electrode 40 is formed on the piezoelectric layer 30. The second electrode 40 is formed by, for example, sputtering or vacuum deposition. Next, the second electrode 40 and the piezoelectric layer 30 are patterned by, for example, photolithography and etching. Note that the second electrode 40 and the piezoelectric layer 30 may be patterned in separate steps.

[0057] Through the above steps, the piezoelectric element 100 can be manufactured.

[0058] 3. Liquid ejection head Next, the liquid ejection head according to this embodiment will be described with reference to the drawings. Fig. 2 is an exploded perspective view that schematically shows the liquid ejection head 200 according to this embodiment. Fig. 3 is a plan view that schematically shows the liquid ejection head 200 according to this embodiment. Fig. 4 is a cross-sectional view taken along line IV-IV in Fig. 3 that schematically shows the liquid ejection head 200 according to this embodiment. Note that Figs. 2 to 4 illustrate an X-axis, a Y-axis, and a Z-axis as three mutually orthogonal axes. Furthermore, Figs. 2 and 4 illustrate a simplified version of the piezoelectric element 100.

[0059] 2 to 4, 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 board 250, and a compliance substrate 260. The base 2 has a flow path forming substrate 210 and a vibration plate 230. For convenience, the circuit board 250 is not shown in FIG.

[0060] The flow path forming substrate 210 is, for example, a silicon substrate. Pressure generating chambers 211 are formed in the flow path forming substrate 210. The pressure generating chambers 211 are partitioned by a plurality of partition walls 212. The volume of the pressure generating chambers 211 changes depending on the piezoelectric element 100.

[0061] A first communication passage 213 and a second communication passage 214 are formed at the end of the pressure generating chamber 211 in the +X-axis direction of the flow path forming substrate 210. The first communication passage 213 is configured so that the opening area thereof is reduced by narrowing the end of the pressure generating chamber 211 in the +X-axis direction from the Y-axis direction. The size of the second communication passage 214 in the Y-axis direction is, for example, the same as the size of the pressure generating chamber 211 in the Y-axis direction. A third communication passage 215 that communicates with the plurality of second communication passages 214 is formed at the +X-axis direction of the second communication passage 214. The third communication passage 215 constitutes a part of a manifold 216. The manifold 216 serves as a common liquid chamber for each pressure generating chamber 211. In this way, the flow path forming substrate 210 is provided with the first communication passage 213, the second communication passage 214, and the third communication passage 215. A supply flow path 217 formed by the passage 215 and a pressure generating chamber 211 are formed. The supply flow path 217 communicates with the pressure generating chamber 211 and supplies the pressure generating chamber 211 with liquid.

[0062] 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-sealed film. A plurality of nozzle holes 222 are formed in the nozzle plate 220 along the Y axis. The nozzle holes 222 communicate with the pressure generating chambers 211 and eject liquid.

[0063] The vibration plate 230 is provided on the other surface of the flow path forming substrate 210. The vibration plate 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.

[0064] The piezoelectric element 100 is provided, for example, on a vibration plate 230. A plurality of piezoelectric elements 100 are provided. The number of piezoelectric elements 100 is not particularly limited. For convenience, the orientation control layer 20 is not shown in FIG. 3.

[0065] In the liquid ejection head 200, the vibration plate 230 and the first electrode 10 are displaced by deformation of the piezoelectric layer 30, which has electromechanical transduction characteristics. That is, in the liquid ejection head 200, the vibration plate 230 and the first electrode 10 essentially function as a vibration plate. Note that the vibration plate 230 may be omitted, and only the first electrode 10 may function as a vibration plate. When the first electrode 10 is provided directly 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.

[0066] The first electrode 10 is configured as an independent individual electrode for each pressure generating chamber 211. The size of the first electrode 10 in the Y-axis direction is smaller than the size of the pressure generating chamber 211 in the Y-axis direction. The size of the first electrode 10 in the X-axis direction is larger than the size of the pressure generating chamber 211 in the X-axis direction. In the X-axis direction, both ends of the first electrode 10 are positioned outside both ends of the pressure generating chamber 211. A lead electrode 202 is connected to the end of the first electrode 10 in the -X-axis direction.

[0067] The size of the piezoelectric layer 30 in the Y-axis direction is larger than the size of the first electrode 10 in the Y-axis direction, for example. The size of the piezoelectric layer 30 in the X-axis direction is larger than the size of the pressure generating chamber 211 in the X-axis direction, for example. The end of the piezoelectric layer 30 in the +X-axis direction is located, for example, outside the end of the first electrode 10 in the +X-axis direction. The end of the first electrode 10 in the +X-axis direction is covered by the piezoelectric layer 30. On the other hand, the end of the piezoelectric layer 30 in the -X-axis direction is located, for example, inside the end of the first electrode 10 in the -X-axis direction. The end of the first electrode 10 in the -X-axis direction is not covered by the piezoelectric layer 30.

[0068] The second electrode 40 is, for example, provided continuously on the piezoelectric layer 30 and the vibration plate 230. The second electrode 40 is configured as a common electrode shared by a plurality of piezoelectric elements 100.

[0069] The protective substrate 240 is bonded to the flow path forming substrate 210 with an adhesive 203. A through hole 242 is formed in the protective substrate 240. In the example shown, the through hole 242 penetrates the protective substrate 240 in the Z-axis direction and communicates with the third communication passage 215. The through hole 242 and the third communication passage 215 form a manifold 216 that serves as a common liquid chamber for each pressure generating chamber 211. Furthermore, a through hole 244 is formed in the protective substrate 240 that penetrates the protective substrate 240 in the Z-axis direction. An end of the lead electrode 202 is positioned in the through hole 244.

[0070] An opening 246 is formed in the protection substrate 240. The opening 246 is a space that does not hinder the driving of the piezoelectric element 100. The opening 246 may or may not be sealed.

[0071] The circuit board 250 is provided on the protection 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.

[0072] The compliance substrate 260 is provided on the protection substrate 240. The compliance substrate 260 has a sealing layer 262 provided on the protection 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 passes through the fixing plate 264 in the Z-axis direction. The through-hole 266 is provided at a position overlapping with the manifold 216 when viewed from the Z-axis direction.

[0073] 4. Printer Next, a printer according to this embodiment will be described with reference to the drawings. Figure 5 is a perspective view that schematically shows a printer 300 according to this embodiment.

[0074] The printer 300 is an inkjet printer. As shown in FIG. 5, the printer 300 includes a head unit 310. The head unit 310 has, for example, liquid ejection heads 200. There is no particular limitation on the number of liquid ejection heads 200. Cartridges 312 and 314, which constitute a supply means, are detachably provided on the head unit 310. A carriage 316 carrying the head unit 310 is axially movable on a carriage shaft 322 attached to the device main body 320, and ejects liquid supplied from the liquid supply means.

[0075] Here, a liquid refers to any material in a liquid phase, including liquid-state materials such as sols and gels. Liquids not only refer to a single state of matter, but also to particles of functional materials made of solids such as pigments and metal particles dissolved, dispersed, or mixed in a solvent. Representative examples of liquids include inks and liquid crystal emulsifiers. Ink encompasses various liquid compositions, such as general water-based inks and oil-based inks, as well as gel inks and hot-melt inks.

[0076] In the printer 300, the driving force of a drive motor 330 is transmitted to a carriage 316 via multiple gears (not shown) and a timing belt 332, causing the carriage 316, which carries the head unit 310, to move along a carriage shaft 322. Meanwhile, the device main body 320 is provided with a transport roller 340 as a transport mechanism that moves a sheet S, which is a recording medium such as paper, relative to the liquid ejection head 200. The transport mechanism that transports the sheet S is not limited to a transport roller, and may be a belt, a drum, or the like.

[0077] The printer 300 includes a printer controller 350 as a control unit that controls the liquid ejection head 200 and the transport roller 340. The printer controller 350 is electrically connected to a circuit board 250 of the liquid ejection head 200. The printer controller 350 includes, for example, a random access memory (RAM) that temporarily stores various data, a read only memory (ROM) that stores control programs and the like, a central processing unit (CPU), and a drive signal generating circuit that generates drive signals to be supplied to the liquid ejection head 200.

[0078] 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 preferably used as a piezoelectric actuator in, for example, ultrasonic motors, vibration-type dust removal devices, piezoelectric transformers, piezoelectric speakers, piezoelectric pumps, and pressure-to-electricity conversion devices. The piezoelectric element 100 is also preferably used as a piezoelectric sensor element in, for example, ultrasonic detectors, angular velocity sensors, acceleration sensors, vibration sensors, tilt sensors, pressure sensors, collision sensors, human presence sensors, infrared sensors, terahertz sensors, heat detection sensors, pyroelectric sensors, and piezoelectric sensors. The piezoelectric element 100 is also preferably used as a ferroelectric element in, for example, ferroelectric memories (FeRAMs), ferroelectric transistors (FeFETs), ferroelectric arithmetic circuits (FeLogics), and ferroelectric capacitors. The piezoelectric element 100 is also preferably used as a voltage-controlled optical element in, for example, wavelength converters, optical waveguides, optical path modulators, refractive index control elements, and electronic shutter mechanisms.

[0079] 5. Examples and Comparative Examples 5.1. Sample preparation Example 1 A 1460 nm thick SiO2 layer was formed by thermally oxidizing the surface of a single-crystal silicon substrate. Next, a 400 nm thick Zr film was deposited by DC (Direct Current) sputtering, and a ZrO2 layer was formed by heat treatment at 850°C.

[0080] Next, a Ti layer, a Pt layer, and an Ir layer with thicknesses of 20 nm, 80 nm, and 5 nm, respectively, were formed as first electrodes on the ZrO2 layer by DC sputtering.

[0081] Next, a BFTP precursor solution was prepared with a molar ratio of Bi:Pb:Fe:Ti = 110:10:50:50. The prepared BFTP precursor solution was then applied to the Ir layer and ZrO2 layer by spin coating, followed by drying at 180°C for 3 minutes, degreasing at 380°C for 3 minutes, and baking at 650°C for 3 minutes. This resulted in the formation of a 20 nm thick BFTP layer.

[0082] Next, simple solutions consisting of potassium 2-ethylhexanoate, sodium 2-ethylhexanoate, and niobium 2-ethylhexanoate were synthesized. A mixed solvent of 2-ethylhexanoic acid and decane was used as the organic solvent. The volume ratio of 2-ethylhexanoic acid to the total organic solvent was 0.42. These simple solutions were prepared by (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 KNN volume concentration in the KNN precursor solution was set to 50 volume %, the KNN mass concentration in the KNN precursor solution was set to 58.08 mass %, and the KNN molar concentration in the KNN precursor solution was set to 0.610 mol / L.

[0083] Figure 6 shows the results of proton NMR measurement of niobium 2-ethylhexanoate used in the KNN precursor solution. The NMR instrument used was an Ascend™ 400 manufactured by Bruker. Data analysis was performed using Bruker's TopSpin 4.2.0. CDCl3 (400 MHz, δ: 7.26 ppm) was used as the deuterated solvent. Specifically, deuterated chloroform was used as both the solvent and the reference material, and the deuterated chloroform peak was adjusted to 7.26 ppm for measurement.

[0084] As shown in Figure 6 for "Example 1," no peaks were observed in the range of 3 ppm to 5 ppm in the NMR measurement profile of niobium 2-ethylhexanoate. This indicates that the niobium 2-ethylhexanoate used in Example 1 does not contain impurities such as ethoxy groups derived from the raw materials or by-produced ethanol. A KNN precursor solution was prepared using such niobium 2-ethylhexanoate.

[0085] On the other hand, in the case of niobium 2-ethylhexanoate containing impurities, as in the "Reference Example" shown in Figure 6, a peak is observed in the range of 3 ppm to 5 ppm in the NMR measurement profile. In Figure 6, this peak is surrounded by a dashed line.

[0086] Next, the prepared KNN precursor solution was applied to the BFTP layer by spin coating, followed by drying at 180°C for 3 minutes, degreasing at 380°C for 3 minutes, and baking at 700°C for 3 minutes. The baking temperature was increased at a rate of 10°C / sec. This resulted in the formation of a crystalline layer with a thickness of 80 nm. The series of steps from applying the KNN precursor solution to baking the KNN precursor layer was repeated five times to form a 400 nm thick piezoelectric layer consisting of five crystalline layers.

[0087] Next, a 50 nm thick Pt layer was formed on the piezoelectric layer by DC sputtering, and then the Pt layer was patterned by photolithography and etching to form a second electrode.

[0088] In this way, the piezoelectric element of Example 1 was formed.

[0089] Example 2 The piezoelectric element of Example 2 was formed in the same manner as in Example 1, except that the KNN volume concentration, KNN mass concentration, and KNN molar concentration in the KNN precursor solution were set to 45% by volume, 53.12% by mass, and 0.549 mol / L, respectively.

[0090] 5.1.3. Comparative Example 1 A piezoelectric element of Comparative Example 1 was formed in the same manner as in Example 1, except that the KNN precursor solution had a volume concentration of 40% by volume, a mass concentration of KNN of 48.02% by mass, and a molar concentration of KNN of 0.488 mol / L.

[0091] 5.1.4. Comparative Example 2 A piezoelectric element of Comparative Example 1 was formed in the same manner as in Example 1, except that the KNN volume concentration, KNN mass concentration, and KNN molar concentration in the KNN precursor solution were set to 35% by volume, 42.73% by mass, and 0.427 mol / L, respectively.

[0092] Experimental conditions The XRD device used was a Bruker "D8 DISCOVER with GADDS." Measurements were performed using a Cu tube and a collimator with a diameter of φ = 0.3 mm under the conditions of 2θ = 20° to 50° and 10 sec / °. Rocking curve measurements were performed under the conditions of 2θ = 21° to 24° and χ = -95° to -85°.

[0093] 5.3. Experimental Results Figure 7 is a table showing the experimental results of Examples 1 and 2 and Comparative Examples 1 and 2. In Figure 7, "KNN mass concentration *1" is the sum of the mass of potassium 2-ethylhexanoate, the mass of sodium 2-ethylhexanoate, and the mass of niobium 2-ethylhexanoate relative to the total mass of the KNN precursor solution. "KNN mass concentration *2" is the sum of the mass of KO in potassium 2-ethylhexanoate, the mass of NaO in sodium 2-ethylhexanoate, and the mass of NbO in niobium 2-ethylhexanoate relative to the total mass of the KNN precursor solution.

[0094] As shown in Fig. 7, Examples 1 and 2 had smaller "KNN(100) rocking curve half-width" than Comparative Examples 1 and 2. That is, Examples 1 and 2 had smaller half-widths of the peaks derived from the (100) plane measured by the X-ray rocking curve method than Comparative Examples 1 and 2. This shows that Examples 1 and 2 have higher crystallinity than Comparative Examples 1 and 2. In Examples 1 and 2, a KNN precursor solution with a higher KNN concentration was used compared to Comparative Examples 1 and 2, and therefore the "KNN(100) rocking curve half-width" could be reduced.

[0095] As shown in Figure 7, Examples 1 and 2 had a larger "KNN (100) rocking curve half-width / thickness" than Comparative Examples 1 and 2. That is, Examples 1 and 2 had a larger peak integrated intensity derived from the (100) plane measured by the X-ray rocking curve method relative to the thickness of the piezoelectric layer than Comparative Examples 1 and 2. This shows that Examples 1 and 2 can improve the orientation of the (100) plane compared to Comparative Examples 1 and 2.

[0096] The thickness of the piezoelectric layer is the average of thicknesses measured at 16 points at 0.5 mm intervals in a region centered at the center of the sample in a plan view, covering 32% of the entire sample area. The measurements were performed using a laser ellipsometer "MARY-102" manufactured by Five Labs.

[0097] As shown in Figure 7, the a / b ratio of the KNN lattice constant was larger in Examples 1 and 2 than in Comparative Examples 1 and 2. Two or more peaks were observed between 2θ = 44° and 47°, and a / b was calculated from the ratio of the larger of the interplanar spacings calculated according to the Bragg equation from the largest and second largest peaks, with the larger peak serving as the numerator and the smaller peak serving as the denominator. The two large peaks observed between 2θ = 44° and 47° were the peak derived from the (200) plane and the peak derived from the (020) plane.

[0098] 7, Examples 1 and 2 had smaller in-plane variations in the piezoelectric layer than Comparative Examples 1 and 2. The thickness of the piezoelectric layer was measured at 16 points at 0.5 mm intervals in a region centered on the center of the sample in a plan view, covering 32% of the entire sample area, and was calculated as (maximum value - minimum value) / average value x 100.

[0099] The above-described embodiment and modifications are merely examples, and the present invention is not limited to these. For example, the embodiments and modifications can be combined as appropriate.

[0100] The present invention includes configurations that are substantially the same as the configurations described in the embodiments, for example, configurations with the same functions, methods, and results, or configurations with the same purpose and effects. The present invention also includes configurations that replace non-essential parts of the configurations described in the embodiments. The present invention also includes configurations that achieve the same effects or purposes as the configurations described in the embodiments. The present invention also includes configurations that add publicly known technology to the configurations described in the embodiments.

[0101] The following can be derived from the above-described embodiment and modifications.

[0102] One aspect of the piezoelectric element is A first electrode; a piezoelectric layer provided above the first electrode and having a perovskite complex oxide containing potassium, sodium, and niobium; a second electrode provided above the piezoelectric layer; Including, The piezoelectric layer has a (100) preferred orientation, The half-width of the peak derived from the (100) plane measured by the X-ray rocking curve method is 3.193° or less.

[0103] This piezoelectric element can improve the piezoelectric characteristics.

[0104] In one embodiment of the piezoelectric element, The integrated intensity of the peak derived from the (100) plane with respect to the thickness of the piezoelectric layer may be 70.65 cps / nm or more.

[0105] This piezoelectric element can improve the orientation of the (100) plane of the piezoelectric layer.

[0106] In one embodiment of the piezoelectric element, The crystal structure of the perovskite complex oxide is a tetragonal crystal expressed by a=c≠b and a>b, where a, b, and c are lattice constants, a / b may be 1.0285 or greater.

[0107] This piezoelectric element can reduce the half-value width of the peak derived from the (100) plane of the piezoelectric layer measured by the X-ray rocking curve method.

[0108] In one embodiment of the piezoelectric element, When the thickness of the piezoelectric layer is measured at 16 points, the value calculated by (maximum value-minimum value) / arithmetic mean value×100 for the measured thickness may be 2.168 or less.

[0109] This piezoelectric element can reduce variations in the thickness of the piezoelectric layer.

[0110] In one embodiment of the piezoelectric element, The piezoelectric element may further include an orientation control layer provided between the first electrode and the piezoelectric layer and containing bismuth, iron, titanium, and lead.

[0111] This piezoelectric element allows the orientation of the piezoelectric layer to be controlled.

[0112] One aspect of the liquid ejection head is One aspect of the piezoelectric element; a flow path forming substrate in which a pressure generating chamber whose volume changes due to the piezoelectric element is formed; a nozzle plate having nozzle holes formed therein that communicate with the pressure generating chambers; Includes:

[0113] One aspect of the printer is One aspect of the liquid ejection head; a conveying mechanism that moves a recording medium relative to the liquid ejection head; a control unit that controls the liquid ejection head and the transport mechanism; Includes: [Explanation of symbols]

[0114] 2...base, 10...first electrode, 20...orientation control layer, 30...piezoelectric layer, 32...crystalline layer, 40...second electrode, 100...piezoelectric element, 200...liquid ejection head, 202...lead electrode, 203...adhesive, 204...connecting wiring, 210...flow path forming substrate, 211...pressure generating chamber, 212...partition wall, 213...first communication path, 214...second communication path, 215...third communication path, 216...manifold, 217...supply path, 220...nozzle plate, 222...nozzle hole, 230...vibration plate, 232...silicon oxide layer, 234...zirconium oxide layer, 240...protective substrate, 242, 244...through hole, 246...opening, 250...circuit board, 260...compliance 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...drive motor, 332...timing belt, 340...conveyor Roller, 350... Printer controller

Claims

1. A first electrode; a piezoelectric layer provided above the first electrode and having a perovskite complex oxide containing potassium, sodium, and niobium; a second electrode provided above the piezoelectric layer; Including, the piezoelectric layer is preferentially oriented in the (100) plane; A piezoelectric element, wherein the half-width of the peak derived from the (100) plane measured by an X-ray rocking curve method is 3.193° or less.

2. In claim 1, A piezoelectric element, 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. In claim 1, The crystal structure of the perovskite complex oxide is a tetragonal crystal expressed as a=c≠b and a>b, where a, b, and c are lattice constants, A piezoelectric element in which a / b is 1.0285 or greater.

4. In claim 1, A piezoelectric element, wherein when the thickness of the piezoelectric layer is measured at 16 points, the value calculated by (maximum value - minimum value) / arithmetic mean value x 100 for the measured thicknesses is 2.168 or less.

5. In claim 1, The piezoelectric element further includes an orientation control layer provided between the first electrode and the piezoelectric layer, the orientation control layer including bismuth, iron, titanium, and lead.

6. The piezoelectric element according to any one of claims 1 to 5, a flow path forming substrate in which a pressure generating chamber whose volume changes due to the piezoelectric element is formed; a nozzle plate having nozzle holes formed therein that communicate with the pressure generating chambers; A liquid ejection head comprising:

7. The liquid ejection head according to claim 6, a conveying mechanism that moves a recording medium relative to the liquid ejection head; a control unit that controls the liquid ejection head and the transport mechanism; Including the printer.

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