Piezoelectric element, liquid ejection head, and printer

Abstract

To provide a piezoelectric element capable of reducing a leakage current.SOLUTION: A piezoelectric element includes a first electrode and a second electrode, and a piezoelectric layer provided between the first electrode and the second electrode and including a complex oxide with a perovskite structure containing potassium, sodium, and niobium, the piezoelectric layer including lithium, manganese, and an additive element, the additive element being copper or cobalt, and in X-ray photoelectron spectroscopy of the piezoelectric layer, when the binding energy of the peak derived from K2p3 / 2 is normalized at 291.7 eV and the binding energy of the peak derived from Nb3d5 / 2 is normalized at 207.0 eV, the peak derived from Mn2p3 / 2 has a maximum intensity in a range of binding energies of 641.18 eV or less.SELECTED DRAWING: Figure 6

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 including a KNN piezoelectric layer containing potassium, sodium, and niobium as its main components. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-36035 Summary of the Invention [Problem to be solved by the invention]

[0005] In the above-mentioned piezoelectric element, it is desirable to reduce the leakage current. [Means for solving the problem]

[0006] One aspect of the piezoelectric element according to the present invention is a first electrode and a second electrode; a piezoelectric layer provided between the first electrode and the second electrode and including a complex oxide with a perovskite structure containing potassium, sodium, and niobium; Including, the piezoelectric layer contains lithium, manganese, and an additive element; the additional element is copper or cobalt, In X-ray photoelectron spectroscopy of the piezoelectric layer, when the binding energy of the peak derived from K2p3 / 2 is normalized to 291.7 eV and the binding energy of the peak derived from Nb3d5 / 2 is normalized to 207.0 eV, the intensity of the peak derived from Mn2p3 / 2 becomes maximum in the binding energy range of 641.18 eV 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] 1 is a table showing the production conditions and experimental results of Examples 1 and 2 and Comparative Examples 1 to 4. [Figure 7] Graph showing the XPS results of Examples 1 and 2 and Comparative Examples 1 and 2. [Figure 8]2 is a graph showing the results of XPS depth profile analysis of Example 1 and Comparative Example 1. 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, a seed 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 seed 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 seed layer 20 is provided on the first electrode 10. The seed layer 20 is provided between the first electrode 10 and the second electrode 40. Specifically, the seed layer 20 is provided between the first electrode 10 and the piezoelectric layer 30. In the illustrated example, the seed layer 20 is further provided on the base 2. The thickness of the seed layer 20 is, for example, 5 nm to 100 nm, preferably 10 nm to 50 nm, and more preferably 15 nm to 30 nm. The thickness of each layer of the piezoelectric element 100, such as the seed layer 20 and the piezoelectric layer 30, is measured, for example, by a scanning electron microscope (SEM).

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

[0019] The material of the seed layer 20 is not limited to a BFTP layer, but may be a bismuth ferrite titanate (Bi(Fe,Ti)O:BFT) layer, a lanthanum nickelate (LaNiO:LNO) layer, a strontium ruthenate (SrRuO:SRO) layer, or a bismuth ferrite (BiFeO:BFO) layer.

[0020] The piezoelectric layer 30 is provided on the seed 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 seed layer 20 and the second electrode 40. The thickness of the piezoelectric layer 30 is, for example, 100 nm or more and 3000 nm or less, preferably 200 nm or more and 2500 nm or less, and more preferably 300 nm or more and 2000 nm or less. When a voltage is applied between the first electrode 10 and the second electrode 40, the piezoelectric layer 30 is deformed.

[0021] The piezoelectric layer 30 is, for example, preferentially oriented on the (100) plane. The seed layer 20, for example, causes the piezoelectric layer 30 to be oriented on the (100) plane. "Preferential orientation" means that 70% or more, preferably 80% or more of the crystals are oriented on a predetermined 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 (XRD) or electron backscatter diffraction (EBSD) on the piezoelectric layer 30.

[0022] The piezoelectric layer 30 includes a complex oxide having a perovskite structure containing potassium (K), sodium (Na), and niobium (Nb). The piezoelectric layer 30 further includes lithium (Li), manganese (Mn), and an additive element. The additive element is copper (Cu) or cobalt (Co). The piezoelectric layer 30 is, for example, a potassium sodium niobate layer containing lithium, manganese, and the additive element. The complex oxide having a perovskite structure of the piezoelectric layer 30 contains, for example, lithium, manganese, and the additive element. The piezoelectric layer 30 is, for example, a ((K,Na,Li)(Nb,Mn,Cu)O x ) layer (where 0 <x), a ((K,Na,Li)(Nb,Mn,Co)O x ) layer (where 0 <x). Note that x may be 3 or less as well.

[0023] The lithium contained in the piezoelectric layer 30 may be present in the A site of the perovskite structure, thereby forming the perovskite structure. The additive element such as niobium, manganese, copper, or cobalt contained in the piezoelectric layer 30 may be present in the B site of the perovskite structure, thereby forming the perovskite structure. Note that a portion of the lithium may be present in the B site of the perovskite structure, and the niobium and the additive element may be present in the A site of the perovskite structure.

[0024] The composition of the perovskite structure of the piezoelectric layer 30 may be a stoichiometric composition or may be different from the stoichiometric composition, as in the perovskite structure of the seed layer 20 described above.

[0025] When the amount of all metal elements contained in the piezoelectric layer 30 is 100 at%, the lithium content in the piezoelectric layer 30 is, for example, 1.0 at% or more and 5.0 at% or less, preferably 2.0 at% or more and 4.5 at% or less, and more preferably 3.0 at% or more and 4.0 at% or less.

[0026] When the amount of all metal elements contained in the piezoelectric layer 30 is taken as 100 at%, the manganese content in the piezoelectric layer 30 is, for example, 0.1 at% to 1.5 at%, preferably 0.2 at% to 1.0 at%, and more preferably 0.3 at% to 0.7 at%. In the piezoelectric layer 30, manganese exists in at least a 2+ valence state.

[0027] When the amount of all metal elements contained in the piezoelectric layer 30 is 100 at%, the content of the added elements in the piezoelectric layer 30 is, for example, 0.05 at% or more and 0.5 at% or less, preferably 0.1 at% or more and 0.4 at% or less, and more preferably 0.2 at% or more and 0.3 at% or less.

[0028] When the additive element is copper, all of the metal elements contained in the piezoelectric layer 30 are, for example, potassium, sodium, niobium, lithium, manganese, and copper. When the additive element is cobalt, all of the metal elements contained in the piezoelectric layer 30 are, for example, potassium, sodium, niobium, lithium, manganese, and cobalt. The piezoelectric layer 30 may also contain a very small amount of chromium (Cr). The content of the metal elements contained in the piezoelectric layer 30 is measured, for example, by X-ray photoelectron spectroscopy (XPS).

[0029] The piezoelectric layer 30 is formed, for example, by stacking a plurality of layers 32. The number of the plurality of layers 32 is, for example, 2 to 30, and preferably 3 to 20. In the illustrated example, five layers 32 are provided. The thickness of each layer 32 is, for example, 10 to 300 nm, and preferably 30 to 250 nm. A surface 34 of the piezoelectric layer 30 is the surface on the second electrode 40 side. In the illustrated example, the surface 34 is in contact with the second electrode 40.

[0030] The second electrode 40 is provided on the piezoelectric layer 30. Although not shown, the second electrode 40 may be further provided on the side surface of the piezoelectric layer 30, the side surface of the seed layer 20, and 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, 5 nm or more and 300 nm or less, and preferably 50 nm or more and 200 nm or less.

[0031] 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.

[0032] 1.2. XPS In XPS of the surface 34 of the piezoelectric layer 30, when the binding energy of the peak derived from K2p3 / 2 is normalized to 291.7 eV and the binding energy of the peak derived from Nb3d5 / 2 is normalized to 207.0 eV, the peak derived from Mn2p3 / 2 has the maximum intensity when the binding energy is in the range of 641.28 eV or less. In other words, the binding energy of the peak derived from Mn2p3 / 2 with the maximum intensity (hereinafter also referred to as the "maximum Mn peak") is in the range of 641.18 eV or less. The binding energy of the maximum Mn peak is, for example, 638.0 eV or more, preferably 639.0 eV or more, and more preferably 640.0 eV or more. The peak derived from Mn2p3 / 2 is a peak derived from manganese.

[0033] Piezoelectric layer 30, which includes a composite oxide with a perovskite structure containing potassium, sodium, and niobium, is susceptible to absorbing moisture and dust from the atmosphere. In XPS, normalization based on peaks derived from CC and CH can result in the XPS results being affected by moisture in the atmosphere, making accurate analysis impossible. Therefore, as described above, it is desirable to normalize based on peaks derived from K2p3 / 2 and Nb3d5 / 2.

[0034] The maximum intensity I of the largest peak observed in the binding energy range of 638 eV to 650 eV (hereinafter referred to as the "638-650 eV maximum peak") MAX and the average intensity of the peaks observed in a given range of binding energies, I AVE and the ratio I AVE / I MAXis, for example, 0.50 or more and 0.95 or less, preferably 0.54 or more and 0.90 or less, more preferably 0.70 or more and 0.85 or less, and even more preferably 0.71 or more and 0.80 or less. The range peak observed in a predetermined range of binding energy ranges from the value obtained by subtracting 1.4 eV from the binding energy of the 638 to 650 eV maximum peak to the value obtained by subtracting 1.0 eV from the binding energy of the 638 to 650 eV maximum peak. The 638 to 650 eV maximum peak is, for example, the maximum Mn peak, and hereinafter also referred to as the "maximum Mn peak." The range peak observed in a predetermined range of binding energy is, for example, Mn derived from divalent manganese. 2+ This is the peak, and hereafter referred to as "Mn 2+ The Voigt function is used to separate the peaks in the range of 1.0 eV to 1.4 eV from the binding energy of the maximum Mn peak, and the Mn peak is determined from the intensity of the peaks obtained by the peak separation. 2+ Average peak intensity I AVE For example, if the binding energy of the maximum Mn peak is 641.08 eV, peak separation is performed in the binding energy range of 639.68 eV to 640.08 eV, and the average value I AVE Calculate.

[0035] When XPS depth direction analysis is performed on the piezoelectric layer 30, the manganese content at the surface 34 of the layer 32a, which is the layer closest to the second electrode 40 among the multiple layers 32, is smaller than the maximum manganese content in the depth direction of the piezoelectric layer 30. In the depth direction of the piezoelectric layer 30, the manganese content does not reach a maximum at the surface 34. The depth direction of the piezoelectric layer 30 refers to the thickness direction of the piezoelectric layer 30.

[0036] XPS on the piezoelectric layer 30 may be performed on a portion of the piezoelectric layer 30 that does not overlap the second electrode 40 in a planar view, or may be performed on a portion of the piezoelectric layer 30 that is exposed by removing the second electrode 40 by etching or the like.

[0037] 1.3. Effects The piezoelectric element 100 includes a first electrode 10, a second electrode 40, and a piezoelectric layer 30 disposed between the first electrode 10 and the second electrode 40, the piezoelectric layer 30 including a complex oxide with a perovskite structure containing potassium, sodium, and niobium. The piezoelectric layer 30 includes lithium, manganese, and an additive element, which may be copper or cobalt. In XPS analysis of the piezoelectric layer 30, when the binding energy of the peak derived from K2p3 / 2 is normalized to 291.7 eV and the binding energy of the peak derived from Nb3d5 / 2 is normalized to 207.0 eV, the peak derived from Mn2p3 / 2 exhibits maximum intensity when the binding energy is 641.18 eV or less. Therefore, the piezoelectric element 100 can improve insulation and reduce leakage current, as shown in the "Examples and Comparative Examples" described below.

[0038] In the piezoelectric element 100, the maximum intensity I of the peak with the maximum value of 638 to 650 eV is confirmed in the range of binding energy of 638 eV or more and 650 eV or less. MAX and the average intensity of the peaks observed in a given range of binding energies, I AVE and the ratio I AVE / I MAX is 0.54 or more, and the predetermined range is from the value obtained by subtracting 1.4 eV from the binding energy of the maximum peak between 638 and 650 eV to the value obtained by subtracting 1.0 eV from the binding energy of the maximum peak between 638 and 650 eV. AVE / I MAX The ratio of divalent manganese is higher than when the ratio is less than 0.54. This makes it possible to reduce the leakage current, as will be shown in the "Examples and Comparative Examples" described later.

[0039] In the piezoelectric element 100, when the amount of all metal elements contained in the piezoelectric layer 30 is taken as 100 at%, the lithium content is 5.0 at% or less, the manganese content is 1.5 at% or less, and the additive element content is 0.5 at% or less. Therefore, in the piezoelectric element 100, precipitation due to excessive amounts of lithium, manganese, and additive elements can be suppressed. Furthermore, a decrease in the orientation of the piezoelectric layer 30 can be suppressed.

[0040] In the piezoelectric element 100, the piezoelectric layer 30 is made up of a plurality of layers 32, and the manganese content in the surface 34 of the layer 32a, which is closest to the second electrode 40 among the plurality of layers 32, is smaller than the maximum manganese content in the depth direction of the piezoelectric layer 30. Therefore, in the piezoelectric element 100, it is possible to suppress the deposition of manganese on the surface 34 of the piezoelectric layer 30.

[0041] 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.

[0042] 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.

[0043] 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.

[0044] Next, the seed layer 20 is formed on the first electrode 10 and the base 2. The seed layer 20 is formed by, for example, a sol-gel method or a CSD (Chemical Solution Deposition) method such as MOD (Metal Organic Deposition).

[0045] Specifically, a precursor solution is prepared by dissolving or dispersing a metal complex containing bismuth, a metal complex containing iron, a metal complex containing titanium, and a metal complex containing lead in an organic solvent. The precursor solution is then applied to the first electrode 10 by spin coating to form a precursor layer. The precursor layer is then heated, for example, at 130°C to 450°C for a certain period of time to dry and degrease it. The degreased precursor layer is then crystallized by baking, for example, at 550°C to 800°C. The baking is performed, for example, in an oxygen atmosphere. This completes the formation of the seed layer 20.

[0046] In the step of forming the seed layer 20, a heating device used for drying and degreasing the precursor layer is, for example, a hot plate. A heating device used for firing the precursor layer is, for example, an infrared lamp annealing device that uses high-temperature, short-time annealing (RTA).

[0047] Next, the piezoelectric layer 30 is formed on the seed layer 20. The piezoelectric layer 30 is formed by, for example, the CSD method.

[0048] Specifically, first, a precursor solution is prepared by dissolving or dispersing, in an organic solvent, a metal complex containing potassium, a metal complex containing sodium, a metal complex containing niobium, a metal complex containing lithium, a metal complex containing manganese, and a metal complex containing an additive element such as copper or cobalt.

[0049] An example of a metal complex containing potassium is potassium 2-ethylhexanoate. An example of a metal complex containing sodium is sodium 2-ethylhexanoate. An example of a metal complex containing niobium is niobium 2-ethylhexanoate. An example of a metal complex containing lithium is lithium 2-ethylhexanoate. An example of a metal complex containing manganese is manganese 2-ethylhexanoate. An example of a metal complex containing copper is copper 2-ethylhexanoate. An example of a metal complex containing cobalt is cobalt 2-ethylhexanoate.

[0050] Examples of the organic solvent include 2-ethylhexanoic acid, decane, and a mixed solvent thereof. When a mixed solvent of 2-ethylhexanoic acid and decane is used as the organic solvent, the volume ratio of 2-ethylhexanoic acid to the total organic solvent is, for example, 0.30 or more and 0.50 or less, and preferably 0.40 or more and 0.45 or less.

[0051] Next, the prepared precursor solution is applied onto the seed layer 20 using a spin coating method or the like to form a precursor layer. Next, the precursor layer is heated, for example, at a temperature of 130°C to 250°C and dried for a certain period of time, and the dried precursor layer is further degreased by heating, for example, at a temperature of 300°C to 450°C and holding the temperature for a certain period of time. Next, the degreased precursor layer is crystallized by baking. The baking temperature is, for example, 600°C to 800°C. The temperature rise rate during baking is, for example, 5°C / sec to 15°C / sec. Baking is performed, for example, in an oxygen atmosphere.

[0052] In this way, the layer 32 can be formed. Then, the series of steps from applying the precursor solution to firing the precursor layer is repeated multiple times. In this way, the piezoelectric layer 30 made up of multiple layers 32 can be formed.

[0053] In the step of forming the piezoelectric layer 30, a heating device used for drying and degreasing the precursor layer is, for example, a hot plate. A heating device used for firing the precursor layer is, for example, an infrared lamp annealing device using RTA.

[0054] 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, the piezoelectric layer 30, and the seed layer 20 are patterned by, for example, photolithography and etching. Note that the second electrode 40, the piezoelectric layer 30, and the seed layer 20 may be patterned in separate steps.

[0055] Through the above steps, the piezoelectric element 100 can be manufactured.

[0056] 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.

[0057] 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.

[0058] 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 elements 100.

[0059] 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 its opening area 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 multiple second communication passages 214 is formed at the +X-axis direction of the second communication passage 214. The third communication passage 215 forms a part of the 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 formed with a supply flow passage 217 consisting of the first communication passage 213, the second communication passage 214, and the third communication passage 215, and the pressure generating chambers 211. The supply flow path 217 communicates with the pressure generating chamber 211 and supplies the liquid to the pressure generating chamber 211 .

[0060] 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, stainless steel (Steel Use Stainless: SUS). 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.

[0061] 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.

[0062] 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 seed layer 20 is not shown in FIG. 4.

[0063] 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.

[0064] 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.

[0065] 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.

[0066] 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.

[0067] 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.

[0068] 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.

[0069] 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.

[0070] 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.

[0071] 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.

[0072] 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.

[0073] 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.

[0074] 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.

[0075] 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.

[0076] 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.

[0077] 5. Examples and Comparative Examples 5.1. Sample preparation Example 1 A silicon dioxide layer was formed on the silicon substrate by thermal oxidation. Next, a zirconium layer was formed on the silicon dioxide layer by sputtering, and then thermally oxidized to form a zirconium oxide layer. Next, a platinum layer was formed as the first electrode on the zirconium oxide layer by sputtering.

[0078] Next, a propionic acid solution of bismuth, iron, titanium, and lead was prepared in a molar ratio of Bi:Pb:Fe:Ti = 110:10:50:50. The prepared precursor solution was then applied to the platinum layer and the zirconium oxide layer by spin coating. The layers were then dried and degreased at 350°C using a hot plate, and then heated at 650°C for 3 minutes using an RTA. This resulted in the formation of a BFTP layer as a seed layer.

[0079] Next, a solution of potassium, sodium, niobium, lithium, manganese, and copper 2-ethylhexanoates was used to 0.51 Na 0.49 Li 0.0766 Nb 0.984 Mn 0.01 Cu 0.006 O x The mixture was mixed so that the following was obtained and applied to the BFTP layer by spin coating. After that, it was dried and cured at 180°C and 380°C, and then heated at 700°C for 3 minutes using an RTA. The above series of steps from application to heating using an RTA was repeated five times to form a piezoelectric layer consisting of five layers.

[0080] Next, a platinum layer was formed as a second electrode on the piezoelectric layer by sputtering.

[0081] This completed the formation of the piezoelectric element of Example 1. Fig. 6 shows the compositions of the piezoelectric layers of Example 1, and Example 2 and Comparative Examples 1 to 4, which will be described later.

[0082] Example 2 Cobalt is used instead of copper, 0.51 Na 0.49Li 0.0766 Nb 0.984 Mn 0.01 Co 0.006 O x The piezoelectric element of Example 2 was formed in the same manner as in Example 1, except that the ingredients were mixed so as to obtain the following:

[0083] 5.1.3. Comparative Example 1 Without copper, K 0.51 Na 0.49 Li 0.0766 Nb 0.99 Mn 0.01 O x A piezoelectric element of Comparative Example 1 was formed in the same manner as in Example 1, except that the components were mixed so as to satisfy the following formula.

[0084] 5.1.4. Comparative Example 2 Using chromium instead of copper, K 0.51 Na 0.49 Li 0.0766 Nb 0.984 Mn 0.01 Cr 0.006 O x A piezoelectric element of Comparative Example 2 was formed in the same manner as in Example 1, except that the components were mixed so as to satisfy the following formula.

[0085] 5.1.5. Comparative Example 3 Chromium is used instead of manganese, 0.51 Na 0.49 Li 0.0766 Nb 0.984 Cr 0.01 Cr 0.006 O x A piezoelectric element of Comparative Example 3 was formed in the same manner as in Example 1, except that the components were mixed so as to satisfy the following formula.

[0086] 5.1.6. Comparative Example 4 Cobalt is used instead of manganese, 0.51 Na 0.49 Li 0.0766 Nb 0.984 Co 0.01 Cu 0.006 O x A piezoelectric element of Comparative Example 4 was formed in the same manner as in Example 1, except that the components were mixed so as to satisfy the following formula.

[0087] 5.2. Experimental Method XPS XPS was performed on the piezoelectric layer. The XPS was performed using "ESCALAB250" manufactured by Thermo Fisher Scientific. The X-ray source had a spot diameter of 500 μm. 2 The Al-Kα radiation was used, and the evaluation was performed with the electron gun irradiated to correct for charging. Narrow spectra were measured with a step interval of 0.1 eV, a pass energy of 20 eV, and an accumulation time of 100 ms. To reduce changes in the chemical state due to X-ray damage, measurements were taken at five or more points for each sample, and the average was used as the measurement data.

[0088] For energy axis calibration of the XPS instrument, the binding energy of the peak derived from K2p3 / 2 was normalized to 291.7 eV, and the binding energy of the peak derived from Nb3d5 / 2 was normalized to 207.0 eV.

[0089] From the XPS results obtained, the binding energy of the peak derived from Mn2p3 / 2, which has the maximum intensity, was determined. MAX and Mn observed in the range of 1.0 eV to 1.4 eV subtracted from the binding energy of the maximum Mn peak. 2+ Average peak intensity I AVE and the ratio I AVE / I MAX asked for.

[0090] The intensity of the maximum Mn peak and Mn 2+ The peak intensity is calculated by subtracting the line that linearly approximates the background at binding energies of 634 eV to 637 eV from each value. AVE The binding energy of the maximum Mn peak is in the range of 1.0 eV to 1.4 eV, and the Mn obtained by the peak separation is calculated using the Voigt function. 2+ Calculated from the peak intensity.

[0091] 5.2.2. Leakage current density The leakage current density was measured by evaluating the IV characteristics of the piezoelectric element. The measurement device used was a Keisight "4140B." The voltage was 1 to 40 V in 1 V steps with a 10-second delay per step. The first electrode was used as the drive, and measurements were taken on both the positive and negative sides.

[0092] From the results of the IV characteristics obtained, the leakage current density when 200 kV / cm was applied was calculated.

[0093] 5.3. Experimental Results Fig. 6 is a table showing the experimental results of Examples 1 and 2 and Comparative Examples 1 to 4. Fig. 7 is a graph showing the XPS results of Examples 1 and 2 and Comparative Examples 1 and 2. The numerical values ​​in Fig. 6 are values ​​read from the graph in Fig. 7.

[0094] As shown in Figures 6 and 7, Examples 1 and 2, in which the peak intensity derived from Mn2p3 / 2 was maximized in the binding energy range of 641.18 eV or less, had lower leakage current densities than Comparative Examples 1 and 2, in which the peak intensity derived from Mn2p3 / 2 was maximized in the binding energy range of 641.28 eV or more, and Comparative Examples 3 and 4, in which no peak derived from Mn2p3 / 2 was observed. Because Comparative Examples 3 and 4 did not contain manganese, no peak derived from Mn2p3 / 2 was observed. Therefore, it was found that the leakage current can be reduced by maximizing the intensity of the peak derived from Mn2p3 / 2 in the binding energy range of 641.18 eV or less.

[0095] Furthermore, the ratio I AVE / I MAX In Examples 1 and 2, where the ratio I is 0.54 or more, the leakage current density was lower than in Comparative Examples 1 to 4. AVE / I MAX It was found that the leakage current can be reduced when the value of is 0.54 or more.

[0096] The manganese-free Comparative Examples 3 and 4 had high leakage current densities. In Comparative Example 2, chromium was present in a state close to metal, which is presumably why the leakage current density was high.

[0097] FIG. 8 is a graph showing the results of XPS depth profile analysis of Example 1 and Comparative Example 1. XPS analysis was performed while sputtering the piezoelectric layer with argon. The horizontal axis represents the distance from the surface of the piezoelectric layer, with "0" corresponding to the surface position of the piezoelectric layer. The vertical axis represents the manganese composition ratio. In FIG. 8, Example 1 is shown by a solid line, and Comparative Example 1 is shown by a dashed line.

[0098] As shown in Fig. 8, in Comparative Example 1, the manganese content was greatest at the surface of the piezoelectric layer. On the other hand, in Example 1, the manganese content at the surface of the piezoelectric layer was smaller than the maximum manganese content in the depth direction of the piezoelectric layer. This indicates that manganese was not precipitated at the surface of the piezoelectric layer in Example 1. From the above, it was found that leakage current can be reduced if manganese is not precipitated at the surface of the piezoelectric layer.

[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 and a second electrode; a piezoelectric layer provided between the first electrode and the second electrode and including a complex oxide with a perovskite structure containing potassium, sodium, and niobium; Including, the piezoelectric layer contains lithium, manganese, and an additive element; the additional element is copper or cobalt, In X-ray photoelectron spectroscopy of the piezoelectric layer, when the binding energy of the peak derived from K2p3 / 2 is normalized to 291.7 eV and the binding energy of the peak derived from Nb3d5 / 2 is normalized to 207.0 eV, the intensity of the peak derived from Mn2p3 / 2 becomes maximum in the binding energy range of 641.18 eV or less.

[0103] Such a piezoelectric element can reduce leakage current.

[0104] In one aspect of the piezoelectric element, Maximum intensity I of the largest peak observed in the binding energy range of 638 eV to 650 eV MAX and the average intensity of the peaks observed in a given range of binding energies, I AVE and the ratio I AVE / I MAX is greater than or equal to 0.54, The predetermined range may be a range from a value obtained by subtracting 1.4 eV from the binding energy of the maximum peak to a value obtained by subtracting 1.0 eV from the binding energy of the maximum peak.

[0105] In such a piezoelectric element, the proportion of divalent manganese is high.

[0106] In one aspect of the piezoelectric element, The ratio I AVE / I MAX may be 0.71 or greater.

[0107] In such a piezoelectric element, the proportion of divalent manganese is high.

[0108] In one aspect of the piezoelectric element, When the amount of all metal elements contained in the piezoelectric layer is 100 at %, The lithium content is 5.0 at% or less, The manganese content is 1.5 at% or less, The content of the additional element may be 0.5 at % or less.

[0109] Such a piezoelectric element can prevent lithium, manganese, and the additive elements from being deposited in excessive amounts.

[0110] In one aspect of the piezoelectric element, The piezoelectric layer is made up of a plurality of layers, When a depth direction analysis is performed on the piezoelectric layer, the manganese content at the surface of the layer among the plurality of layers that is closest to the second electrode may be smaller than the maximum value of the manganese content in the depth direction of the piezoelectric layer.

[0111] Such a piezoelectric element can prevent manganese from being deposited on the surface of the piezoelectric layer.

[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...seed layer, 30...piezoelectric layer, 32, 32a...layer, 34...surface, 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...oxidized silicon Silicon 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 and a second electrode; a piezoelectric layer provided between the first electrode and the second electrode and including a complex oxide with a perovskite structure containing potassium, sodium, and niobium; Including, the piezoelectric layer contains lithium, manganese, and an additive element; the additional element is copper or cobalt, A piezoelectric element in which, in X-ray photoelectron spectroscopy of the piezoelectric layer, when the binding energy of the peak derived from K2p3 / 2 is normalized to 291.7 eV and the binding energy of the peak derived from Nb3d5 / 2 is normalized to 207.0 eV, the intensity of the peak derived from Mn2p3 / 2 becomes maximum when the binding energy is in the range of 641.18 eV or less.

2. In claim 1, The maximum intensity I of the largest peak observed in the binding energy range of 638 eV to 650 eV ＭＡＸ and the average value I of the intensities of peaks observed in a given range of binding energies. ＡＶＥ The ratio of I ＡＶＥ / I ＭＡＸ is equal to or greater than 0.54, A piezoelectric element, wherein the predetermined range is a range from a value obtained by subtracting 1.4 eV from the binding energy of the maximum peak to a value obtained by subtracting 1.0 eV from the binding energy of the maximum peak.

3. In claim 2, The ratio I ＡＶＥ / I ＭＡＸ is 0.71 or more.

4. In claim 1, When the amount of all metal elements contained in the piezoelectric layer is 100 at %, The lithium content is 5.0 at% or less, The manganese content is 1.5 at% or less, A piezoelectric element, wherein the content of the additional element is 0.5 at % or less.

5. In claim 1, The piezoelectric layer is made up of a plurality of layers, A piezoelectric element, wherein, when a depth direction analysis is performed on the piezoelectric layer, the manganese content at the surface of the layer among the plurality of layers that is closest to the second electrode is smaller than the maximum value of the manganese content in the depth direction of the piezoelectric layer.

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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