Piezo electric element, liquid discharge head, and printer

Abstract

To provide a piezo electric element capable of reducing leakage current.SOLUTION: A piezo electric element includes: a first electrode and second electrode; and a piezoelectric layer that is provided between the first electrode and the second electrode and has a plurality of layers containing complex oxide of a perovskite-type structure containing kalium, natrium, and niobium. Of the plurality of layers containing complex oxide, a first layer nearest to the first electrode is preferentially oriented in first orientation, which is {100} plane orientation, in a film thickness direction. Of the plurality of layers containing complex oxide, a second layer nearest to the second electrode, in which the first orientation and second orientation, which is {110} plane orientation, are mixed in an in-plane direction intersecting with the film thickness direction, is not preferentially oriented in the first orientation nor the second orientation.SELECTED DRAWING: Figure 6

Description

Technical Field

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

Background Art

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

[0003] For example, Patent Document 1 describes a piezoelectric element including a KNN piezoelectric layer containing potassium, sodium, and niobium as main components.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In the piezoelectric element as described above, it is desired to reduce the leakage current.

Means for Solving the Problems

[0006] One aspect of the piezoelectric element according to the present invention is a first electrode and a second electrode, a piezoelectric layer provided between the first electrode and the second electrode and having a plurality of layers including a complex oxide having a perovskite structure containing potassium, sodium, and niobium, and among the plurality of layers including the complex oxide, a first layer closest to the first electrode is preferentially oriented in a first orientation having a {100} plane orientation in the film thickness direction, Of the layers containing the plurality of composite oxides, the second layer closest to the second electrode has a mixture of the first orientation and a second orientation which is a {110} plane orientation in the in-plane direction intersecting the film thickness direction, and has no preferential orientation to either the first orientation or the second orientation.

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

[0008] One aspect of the printer according to the present invention is the liquid ejection head, a conveyance mechanism for relatively moving a recording medium with respect to the liquid ejection head, a control unit for controlling the liquid ejection head and the conveyance mechanism, and includes.

Brief Description of Drawings

[0009]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Embodiments for Carrying Out the Invention

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

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

[0012] As shown in FIG. 1, the piezoelectric element 100 includes, for example, a first electrode 10, an orientation control layer 20, a piezoelectric layer 30, and a second electrode 40. The piezoelectric element 100 is provided on a substrate 2.

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

[0014] The substrate 2 may have a diaphragm that deforms by the operation of the piezoelectric layer 30. The diaphragm is, for example, a silicon oxide layer, a zirconium oxide layer, or a laminate in which a zirconium oxide layer is provided on a silicon oxide layer.

[0015] The first electrode 10 is provided on the substrate 2. The first electrode 10 is provided between the substrate 2 and the orientation control layer 20. The shape of the first electrode 10 is, for example, layer-like. The thickness of the first electrode 10 is, for example, 5 nm or more and 300 nm or less, preferably 50 nm or more and 200 nm or less.

[0016] The first electrode 10 is, for example, a titanium layer, a platinum layer, an iridium layer, or the like. The first electrode 10 may be laminated in the order of a titanium layer, a platinum layer, and an iridium layer from the substrate 2 side. The titanium layer improves, for example, the adhesion between the substrate 2 and the platinum layer. The first electrode 10 is one of the electrodes for applying a voltage to the piezoelectric layer 30.

[0017] The alignment control layer 20 is provided on the first electrode 10. The alignment control layer 20 is provided between the first electrode 1 and the piezoelectric layer 30. In the illustrated example, the alignment control layer 20 is further provided on the substrate 2. The thickness of the alignment control layer 20 is, for example, 5 nm or more and 100 nm or less, preferably 10 nm or more and 50 nm or less.

[0018] The alignment control layer 20 contains a perovskite-structured composite oxide containing bismuth (Bi), iron (Fe), titanium (Ti), and lead (Pb). The alignment control layer 20 is, for example, a bismuth lead titanate ferrite ((Bi,Pb)(Fe,Ti)O 3 :BFTP) layer. The alignment control layer 20 may be a BFTP layer to which an additive is added. The alignment control layer 20 controls the orientation of the piezoelectric layer 30.

[0019] The piezoelectric layer 30 is provided on the alignment 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 alignment control layer 20 and the second electrode 40. The thickness of the piezoelectric layer 30 is, for example, 100 nm or more and 3 μm or less, preferably 200 nm or more and 2 μm or less. When a voltage is applied between the first electrode 10 and the second electrode 40, the piezoelectric layer 30 deforms.

[0020] The piezoelectric layer 30 includes a plurality of crystal layers 32. The piezoelectric layer 30 is, for example, composed of a plurality of crystal layers 32. The number of the plurality of crystal layers 32 is, for example, 2 or more and 30 or less, preferably 3 or more and 20 or less. In the illustrated example, 5 crystal layers 32 are provided. The thickness of the crystal layer 32 is, for example, 10 nm or more and 200 nm or less, preferably 30 nm or more and 150 nm or less.

[0021] The crystal layer 32 is a layer containing a complex oxide with a perovskite-type structure containing potassium (K), sodium (Na), and niobium (Nb). The crystal layer 32 is, for example, a potassium sodium niobate ((K,Na)NbO 3 :KNN) layer. The crystal layer 32 may be a KNN layer to which an additive is added. Examples of the additive include lithium (Li), manganese (Mn), and copper (Cu). The content of the additive in the crystal layer 32 is, for example, 10 mol% or less, preferably 5 mol% or less. The additive may be unevenly distributed at the grain boundaries of the crystal layer 32.

[0022] Hereinafter, the structure of the crystal layer 32 is treated as a pseudo-cubic crystal. However, this is an expression for simplifying the explanation and does not deny that the crystal layer 32 has a crystal structure with low symmetry such as tetragonal or orthorhombic. Furthermore, even if the crystal layer 32 has a structure with lower symmetry, it does not cause any particular contradiction.

[0023] The second electrode 40 is provided on the piezoelectric layer 30. Although not shown, if the second electrode 40 is electrically separated from the first electrode 10, it may be further provided on the side surface of the piezoelectric layer 30 and on the substrate 2. The shape of the second electrode 40 is, for example, layered. The thickness of the second electrode 40 is, for example, 15 nm or more and 300 nm or less.

[0024] The second electrode 40 is, for example, a platinum layer, a titanium layer, or an iridium layer. The second electrode 40 may be a laminate of a plurality of the layers exemplified above. The second electrode 40 is the other electrode for applying a voltage to the piezoelectric layer 30.

[0025] 1.2. Orientation, etc. 1.2.1. The first layer Of the plurality of crystal layers 32, the first layer 32a is the layer closest to the first electrode 10 among the plurality of crystal layers 32. In the illustrated example, the first layer 32a is provided on the alignment control layer 20. The first layer 32a is in contact with the alignment control layer 20. The first layer 32a is provided between the alignment control layer 20 and the second layer 32b. The alignment control layer 20 is provided between the first electrode 10 and the first layer 32a. The alignment control layer 20 controls the orientation of the first layer 32a.

[0026] In the film thickness direction, the first layer 32a is preferentially oriented in a first orientation with {100} plane orientation. The film thickness direction is the stacking direction of the plurality of crystal layers 32. In the illustrated example, the film thickness direction is the perpendicular direction to the upper surface of the substrate 2.

[0027] Here, "layer A is preferentially oriented in the first orientation in the film thickness direction" means that the orientation ratio of the first orientation of layer A is 80% or more in the film thickness direction. This is the same even when the "film thickness direction" is replaced with the "in-plane direction".

[0028] The orientation ratio is measured by Electron Back Scattering Diffraction (EBSD). In the film thickness direction, the orientation ratio of the first orientation of the first layer 32a may be 85% or more, 90% or more, 95% or more, or 100%. The first layer 32a may be preferentially oriented in the (001) plane in the film thickness direction.

[0029] In the in-plane direction intersecting the film thickness direction, the first layer 32a may be preferentially oriented in the first orientation. Specifically, the in-plane direction is the direction perpendicular to the film thickness direction. The first layer 32a may be preferentially oriented in the (001) plane in the in-plane direction.

[0030] In the in-plane direction, the first layer 32a may have a mixture of a first orientation with a {100} plane orientation, a second orientation with a {110} plane orientation, and a third orientation with a {111} plane orientation. And in the in-plane direction, the first layer 32a may not be preferentially oriented in any of the first orientation, the second orientation, and the third orientation.

[0031] Hereinafter, when in the in-plane direction, the A layer has a mixture of the first orientation, the second orientation, and the third orientation and is not preferentially oriented in any of the first orientation, the second orientation, and the third orientation, it is also referred to as "random orientation". This also applies when the "in-plane direction" is replaced with the "film thickness direction".

[0032] 1.2.2. The Second Layer The second layer 32b among the plurality of crystal layers 32 is the layer closest to the second electrode 40 among the plurality of crystal layers 32. In the illustrated example, the second layer 32b is in contact with the second electrode 40. The second layer 32b is provided between the first layer 32a and the second electrode 40.

[0033] In the film thickness direction, the second layer 32b may be randomly oriented. In the film thickness direction, the orientation ratio of the first orientation of the second layer 32b may be 85% or more, may be 90% or more, may be 95% or more, or may be 100%. In the film thickness direction, the second layer 32b may be preferentially oriented in the (001) plane.

[0034] In the in-plane direction, the second layer 32b has a mixture of a first orientation with a {100} plane orientation and a second orientation with a {110} plane orientation. Further, in the in-plane direction, the second layer 32b may have a mixture of a third orientation with a {111} plane orientation. And in the in-plane direction, the second layer 32b is not preferentially oriented in any of the first orientation, the second orientation, and the third orientation. In the in-plane direction, the second layer 32b may be randomly oriented.

[0035] The domain diameter in the in-plane direction of the second layer 32b is, for example, 7 μm or less, preferably 5.5 μm or less, more preferably 5.01 μm or less, even more preferably 1 μm or less, and even more preferably 0.22 μm or less. The domain diameter in the in-plane direction of the second layer 32b is measured by EBSD.

[0036] 1.3. Effects In the piezoelectric element 100, the first electrode 10 and the second electrode 40, and a piezoelectric layer 30 including a plurality of crystal layers 32 including a perovskite-type composite oxide containing potassium, sodium, and niobium, provided between the first electrode 10 and the second electrode 40, are included. Among the plurality of crystal layers 32, the first layer 32a closest to the first electrode 10 is preferentially oriented in the first orientation which is {100}-plane orientation in the film thickness direction, and among the plurality of crystal layers 32, the second layer 32b closest to the second electrode 40 has a mixture of the first orientation and the second orientation which is {110}-plane orientation in the in-plane direction intersecting the film thickness direction, and is not preferentially oriented in either the first orientation or the second orientation.

[0037] As described above, in the piezoelectric element 100, since the first layer 32a is preferentially oriented in the first orientation in the film thickness direction, the stress generated at the grain boundary with the misorientation different from the first orientation can be reduced. Therefore, cracks can be suppressed. Cracks are a cause of leakage paths.

[0038] Furthermore, in the piezoelectric element 100, since the second layer 32b is not preferentially oriented in either the first orientation or the second orientation in the in-plane direction, the generation of grain boundaries that can become leakage paths connecting in the film thickness direction from the first electrode to the second electrode can be suppressed. Furthermore, the stress can be dispersed and the crack initiation points due to local stress concentration can be reduced.

[0039] As described above, in the piezoelectric element 100, the leakage current can be reduced.

[0040] In the piezoelectric element 100, in the in-plane direction, the second layer 32b has a mixed orientation of a first orientation, a second orientation, and a third orientation which is a {111} plane orientation, and does not have a preferential orientation in the third orientation. Therefore, in the piezoelectric element 100, generation of grain boundaries that can become leakage paths connecting in the film thickness direction from the first electrode to the second electrode can be suppressed.

[0041] In the piezoelectric element 100, the second layer 32b has a preferential orientation in the film thickness direction in the first orientation. Therefore, in the piezoelectric element 100, the stress generated at the grain boundaries between the first orientation and the misorientation different from the first orientation in the second layer 32b can be reduced.

[0042] The piezoelectric element 100 further includes an orientation control layer 20 provided between the first electrode 10 and the first layer 32a and containing bismuth, iron, titanium, and lead. Therefore, in the piezoelectric element 100, the orientation of the first layer 32a can be controlled.

[0043] In the piezoelectric element 100, the domain diameter in the in-plane direction of the second layer 32b is 5.01 μm or less. Therefore, in the piezoelectric element 100, the second layer 32b can be randomly oriented in the in-plane direction.

[0044] In the piezoelectric element 100, the domain diameter in the in-plane direction of the second layer 32b is 0.22 μm or less. Therefore, in the piezoelectric element 100, the second layer 32b can be randomly oriented in the in-plane direction.

[0045] 2. Method for manufacturing piezoelectric element Next, a method for manufacturing the piezoelectric element 100 according to the present embodiment will be described with reference to the drawings.

[0046] As shown in FIG. 1, a substrate 2 is prepared. Specifically, a silicon oxide layer is formed by thermally oxidizing a silicon substrate. Next, a zirconium layer is formed on the silicon oxide layer by a sputtering method or the like, and a zirconium oxide layer is formed by thermally oxidizing the zirconium layer. Through the above steps, the substrate 2 can be prepared.

[0047] Next, a first electrode 10 is formed on the substrate 2. The first electrode 10 is formed, for example, by a sputtering method, a vacuum evaporation method, or the like. Next, the first electrode 10 is patterned, for example, by photolithography and etching.

[0048] Next, an alignment control layer 20 is formed on the first electrode 10 and the substrate 2. The alignment control layer 20 is formed, for example, by a Chemical Solution Deposition (CSD) method such as a sol-gel method or a Metal Organic Deposition (MOD).

[0049] Specifically, first, a metal complex containing bismuth, a metal complex containing iron, a metal complex containing titanium, and a metal complex containing lead are dissolved or dispersed in an organic solvent to prepare a precursor solution. Next, the precursor solution is applied onto the first electrode 10 by a spin coating method to form a precursor layer. Next, the precursor layer is heated, for example, at 130°C or higher and 250°C or lower for a certain period of time to be dried, and further, the dried precursor layer is heated, for example, at 300°C or higher and 450°C or lower for a certain period of time to be degreased. Next, the degreased precursor layer is crystallized by firing, for example, at 550°C or higher and 800°C or lower. Thus, the alignment control layer 20 made of a BFTP layer can be formed.

[0050] Next, a piezoelectric layer 30 is formed on the alignment control layer 20. The piezoelectric layer 30 is formed, for example, by a CSD method.

[0051] Specifically, first, for example, a metal complex containing potassium, a metal complex containing sodium, a metal complex containing lithium, a metal complex containing niobium, a metal complex containing manganese, and a metal complex containing copper are dissolved or dispersed in an organic solvent to prepare a precursor solution.

[0052] Examples of the metal complex containing potassium include potassium 2-ethylhexanoate, potassium acetate, etc. Examples of the metal complex containing sodium include sodium 2-ethylhexanoate, sodium acetate, etc. Examples of the metal complex containing lithium include lithium 2-ethylhexanoate. Examples of the metal complex containing niobium include niobium 2-ethylhexanoate, niobium ethoxide, pentaethoxynbium, pentabutoxynbium, etc. Examples of the metal complex containing manganese include manganese 2-ethylhexanoate, manganese acetate, etc. Examples of the metal complex containing copper include copper 2-ethylhexanoate. Note that two or more metal complexes may be used in combination. For example, as the metal complex containing potassium, potassium 2-ethylhexanoate and potassium acetate may be used in combination.

[0053] Examples of the solvent include propanol, butanol, pentanol, hexanol, octanol, ethylene glycol, propylene glycol, octane, decane, cyclohexane, xylene, toluene, tetrahydrofuran, acetic acid, octylic acid, 2-n-butoxyethanol, n-octane, 2-n-ethylhexane, or a mixed solvent thereof, etc.

[0054] Next, the prepared precursor solution is applied onto the alignment control layer 20 using a spin coating method or the like to form a precursor layer. Next, the precursor layer is heated at, for example, 130°C or higher and 250°C or lower for a certain period of time to be dried, and further, the dried precursor layer is heated at, for example, 300°C or higher and 450°C or lower for a certain period of time to be degreased. Next, the degreased precursor layer is crystallized by firing at, for example, 550°C or higher and 800°C or lower.

[0055] Thus, the crystal layer 32 of the piezoelectric layer 30 can be formed. Then, a series of steps from the application of the precursor solution to the firing of the precursor layer are repeated a plurality of times. Thereby, the piezoelectric layer 30 composed of a plurality of crystal layers 32 can be formed.

[0056] In the step of forming the crystal layer 32, the heating device used for drying and degreasing the precursor layer is, for example, a hot plate. The heating device used for firing the precursor layer is an infrared lamp annealing device (Rapid Thermal Annealing: RTA) device.

[0057] The RTA device used in the firing step has two lamps. In the firing step, the substrate 2 on which the precursor layer is formed is disposed between the two lamps. In other words, the firing step is performed with one lamp disposed above and one lamp disposed below the substrate 2 on which the precursor layer is formed.

[0058] Furthermore, the firing step is performed while performing an oxygen (O 2 ) flow. By the oxygen flow, in particular, the upper part of the substrate 2 on which the precursor layer is formed is cooled. The flow rate of the oxygen flow is, for example, 1 slpm or more and 10 slpm or less, preferably 2 slpm or more and 5 slpm or less.

[0059] Next, a second electrode 40 is formed on the piezoelectric layer 30. The second electrode 40 is formed, for example, by a sputtering method, a vacuum evaporation method, or the like. Next, the second electrode 40 and the piezoelectric layer 30 are patterned, for example, by photolithography and etching. Note that the second electrode 40 and the piezoelectric layer 30 may be patterned in separate steps.

[0060] Through the above steps, the piezoelectric element 100 can be manufactured.

[0061] 3. Liquid ejection head Next, the liquid ejection head according to the present embodiment will be described with reference to the drawings. FIG. 2 is an exploded perspective view schematically showing the liquid ejection head 200 according to the present embodiment. FIG. 3 is a plan view schematically showing the liquid ejection head 200 according to the present embodiment. FIG. 4 is a cross-sectional view taken along line IV-IV of FIG. 3 schematically showing the liquid ejection head 200 according to the present embodiment. In FIGS. 2 to 4, the X-axis, the Y-axis, and the Z-axis are illustrated as three axes orthogonal to each other. In FIGS. 2 and 4, the piezoelectric element 100 is illustrated in a simplified manner.

[0062] As shown in FIGS. 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 diaphragm 230. For convenience, in FIG. 3, the illustration of the circuit board 250 is omitted.

[0063] The flow path forming substrate 210 is, for example, a silicon substrate. A pressure generating chamber 211 is formed in the flow path forming substrate 210. The pressure generating chamber 211 is partitioned by a plurality of partition walls 212. The volume of the pressure generating chamber 211 changes by the piezoelectric element 100.

[0064] A first communication path 213 and a second communication path 214 are formed at the +X-axis direction end of the pressure generating chamber 211 of the flow path forming substrate 210. The first communication path 213 is configured such that its opening area becomes smaller by narrowing the +X-axis direction end of the pressure generating chamber 211 from the Y-axis direction. The size of the second communication path 214 in the Y-axis direction is, for example, the same as the size of the pressure generating chamber 211 in the Y-axis direction. A third communication path 215 communicating with the plurality of second communication paths 214 is formed in the +X-axis direction of the second communication path 214. The third communication path 215 constitutes a part of the manifold 216. The manifold 216 serves as a common liquid chamber for each pressure generating chamber 211. Thus, a supply flow path 217 including the first communication path 213, the second communication path 214, and the third communication path 215 and the pressure generating chamber 211 are formed in the flow path forming substrate 210. The supply flow path 217 communicates with the pressure generating chamber 211 and supplies liquid to the pressure generating chamber 211.

[0065] The nozzle plate 220 is provided on one surface of the flow path forming substrate 210. The material of the nozzle plate 220 is, for example, SUS (Steel Use Stainless). The nozzle plate 220 is joined to the flow path forming substrate 210 by, for example, an adhesive or a heat welding film. A plurality of nozzle holes 222 are formed in the nozzle plate 220 along the Y-axis. The nozzle holes 222 communicate with the pressure generating chamber 211 and discharge the liquid.

[0066] The diaphragm 230 is provided on the other surface of the flow path forming substrate 210. The diaphragm 230 is composed of, for example, a silicon oxide layer 232 provided on the flow path forming substrate 210 and a zirconium oxide layer 234 provided on the silicon oxide layer 232.

[0067] The piezoelectric element 100 is provided, for example, on the diaphragm 230. A plurality of piezoelectric elements 100 are provided. The number of piezoelectric elements 100 is not particularly limited. For convenience, in FIG. 4, the illustration of the orientation control layer 20 is omitted.

[0068] In the liquid discharge head 200, the diaphragm 230 and the first electrode 10 are displaced by the deformation of the piezoelectric layer 30 having electro-mechanical conversion characteristics. That is, in the liquid discharge head 200, the diaphragm 230 and the first electrode 10 substantially function as a diaphragm. Note that the diaphragm 230 may be omitted and only the first electrode 10 may function as a diaphragm. When the first electrode 10 is directly provided on the flow path forming substrate 210, it is preferable to protect the first electrode 10 with an insulating protective film or the like so that the liquid does not come into contact with the first electrode 10.

[0069] The first electrode 10 is configured as an individual electrode independent for each pressure generation chamber 211. The size of the first electrode 10 in the Y-axis direction is smaller than the size of the pressure generation chamber 211 in the Y-axis direction. The size of the first electrode 10 in the X-axis direction is larger than the size of the pressure generation chamber 211 in the X-axis direction. In the X-axis direction, both ends of the first electrode 10 are located outside both ends of the pressure generation chamber 211. A lead electrode 202 is connected to the -X-axis direction end of the first electrode 10.

[0070] The size of the piezoelectric layer 30 in the Y-axis direction is, for example, larger than the size of the first electrode 10 in the Y-axis direction. The size of the piezoelectric layer 30 in the X-axis direction is, for example, larger than the size of the pressure generation chamber 211 in the X-axis direction. The +X-axis direction end of the piezoelectric layer 30 is, for example, located outside the +X-axis direction end of the first electrode 10. The +X-axis direction end of the first electrode 10 is covered by the piezoelectric layer 30. On the other hand, the -X-axis direction end of the piezoelectric layer 30 is, for example, located inside the -X-axis direction side end of the first electrode 10. The -X-axis direction side end of the first electrode 10 is not covered by the piezoelectric layer 30.

[0071] The second electrode 40 is, for example, continuously provided on the piezoelectric layer 30 and the diaphragm 230. The second electrode 40 is configured as a common electrode common to a plurality of piezoelectric elements 100.

[0072] The protective substrate 240 is joined to the flow path forming substrate 210 by an adhesive 203. A through hole 242 is formed in the protective substrate 240. In the illustrated example, the through hole 242 penetrates the protective substrate 240 in the Z-axis direction and communicates with the third communication path 215. The through hole 242 and the third communication path 215 constitute a manifold 216 that is a common liquid chamber for each pressure generation chamber 211. Further, a through hole 244 that penetrates the protective substrate 240 in the Z-axis direction is formed in the protective substrate 240. The end of the lead electrode 202 is located in the through hole 244.

[0073] The protective substrate 240 is formed with an opening 246. The opening 246 is a space for not inhibiting the driving of the piezoelectric element 100. The opening 246 may or may not be sealed.

[0074] The circuit board 250 is provided on the protective substrate 240. The circuit board 250 includes a semiconductor integrated circuit (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.

[0075] The compliance substrate 260 is provided on the protective substrate 240. The compliance substrate 260 has a sealing layer 262 provided on the protective substrate 240 and a fixing plate 264 provided on the sealing layer 262. The sealing layer 262 is a layer for sealing the manifold 216. The sealing layer 262 has, for example, flexibility. The fixing plate 264 is formed with a through hole 266. The through hole 266 penetrates the fixing plate 264 in the Z-axis direction. The through hole 266 is provided at a position overlapping the manifold 216 when viewed from the Z-axis direction.

[0076] 4. Printer Next, the printer according to the present embodiment will be described with reference to the drawings. FIG. 5 is a perspective view schematically showing a printer 300 according to the present embodiment.

[0077] 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, a liquid ejection head 200. The number of the liquid ejection heads 200 is not particularly limited. The head unit 310 is detachably provided with cartridges 312 and 314 constituting supply means. A carriage 316 on which the head unit 310 is mounted is provided to be axially movable on a carriage shaft 322 attached to the apparatus main body 320, and ejects the liquid supplied from the liquid supply means.

[0078] Here, the liquid may be any material in the liquid phase state, and liquid-state materials such as sols and gels are also included in the liquid. Further, not only the liquid as a state of matter, but also those in which particles of functional materials composed of solids such as pigments and metal particles are dissolved, dispersed, or mixed in a solvent are included in the liquid. Representative examples of the liquid include ink and liquid crystal emulsifiers. The ink shall include general aqueous inks, oil-based inks, and various liquid compositions such as gel inks and hot melt inks.

[0079] In the printer 300, the driving force of the driving motor 330 is transmitted to the carriage 316 via a plurality of gears (not shown) and a timing belt 332, whereby the carriage 316 on which the head unit 310 is mounted is moved along the carriage shaft 322. On the other hand, the apparatus main body 320 is provided with a conveyance roller 340 as a conveyance mechanism for relatively moving a sheet S, which is a recording medium such as paper, with respect to the liquid ejection head 200. The conveyance mechanism for conveying the sheet S is not limited to the conveyance roller and may be a belt, a drum, or the like.

[0080] The printer 300 includes a printer controller 350 as a control unit for controlling the liquid ejection head 200 and the conveyance roller 340. The printer controller 350 is electrically connected to the circuit board 250 of the liquid ejection head 200. The printer controller 350 includes, for example, a RAM (Random Access Memory) for temporarily storing various data, a ROM (Read Only Memory) storing a control program and the like, a CPU (Central Processing Unit), and a drive signal generation circuit for generating a drive signal for supplying to the liquid ejection head 200.

[0081] Note that the piezoelectric element 100 can be used in a wide range of applications, not limited to liquid ejection heads and printers. The piezoelectric element 100 is suitably used, for example, as a piezoelectric actuator such as an ultrasonic motor, a vibration type dust removing device, a piezoelectric transformer, a piezoelectric speaker, a piezoelectric pump, and a pressure-electric conversion device. Further, the piezoelectric element 100 is suitably used, for example, as a piezoelectric sensor element such as an ultrasonic detector, an angular velocity sensor, an acceleration sensor, a vibration sensor, an inclination sensor, a pressure sensor, a collision sensor, a human sensor, an infrared sensor, a terahertz sensor, a heat detection sensor, a pyroelectric sensor, and a piezoelectric sensor. Further, the piezoelectric element 100 is suitably used as a ferroelectric element such as a ferroelectric memory (FeRAM), a ferroelectric transistor (FeFET), a ferroelectric arithmetic circuit (FeLogic), and a ferroelectric capacitor. Further, the piezoelectric element 100 is suitably used as a voltage control type optical element such as a wavelength converter, an optical waveguide, an optical path modulator, a refractive index control element, and an electronic shutter mechanism.

[0082] 5. Examples and Comparative Examples 5.1. Preparation of Samples 5.1.1. Example 1 By thermally oxidizing the surface of a single crystal silicon substrate, an SiO layer with a thickness of 1460 nm was formed. Next, a Zr film with a thickness of 400 nm was formed by DC (Direct Current) sputtering method, and a ZrO layer was formed by heat treatment at 850 °C. 2 Next, on the ZrO layer, as the first electrode, a Ti layer, a Pt layer, and an Ir layer with thicknesses of 20 nm, 80 nm, and 5 nm, respectively, were formed by DC sputtering method. 2

[0083] Next, on the ZrO 2 layer, as the first electrode, a Ti layer, a Pt layer, and an Ir layer with thicknesses of 20 nm, 80 nm, and 5 nm, respectively, were formed by DC sputtering method.

[0084] Next, a precursor solution was prepared so as to have a molar ratio of Bi:Pb:Fe:Ti = 110:10:50:50. Then, the prepared precursor solution was spin-coated on the Ir layer and the ZrO 2It was applied onto the layer, dried at 180 °C for 3 minutes, degreased at 380 °C for 3 minutes, and fired at 650 °C for 3 minutes. The firing was performed using lamp annealing. Thus, a BFTP layer with a thickness of 20 nm was formed.

[0085] Next, a precursor solution composed of potassium 2-ethylhexanoate, sodium 2-ethylhexanoate, lithium 2-ethylhexanoate, niobium 2-ethylhexanoate, manganese 2-ethylhexanoate, and copper 2-ethylhexanoate was used to prepare K 0.5136 Na 0.4934 Li 0.053 Nb 0.99 Mn 0.005 Cu 0.005 O x (where x is any number greater than 0). Then, the prepared precursor solution was applied onto the BFTP layer by the spin coating method, dried at 180 °C for 3 minutes, degreased at 380 °C for 3 minutes, and fired at 700 °C for 3 minutes. The firing was carried out with a heating rate of 10 °C / second using lamp annealing in which lamps were arranged above and below the sample. During firing, an oxygen flow with a flow rate of 3 slpm was performed on the upper part of the sample. Thus, a crystal layer with a thickness of 80 nm was formed. Then, a series of steps from the application of the above precursor solution to the firing of the precursor layer were repeated 5 times to form a piezoelectric layer composed of 5 crystal layers.

[0086] Next, a Pt layer with a thickness of 50 nm was formed on the piezoelectric layer by the DC sputtering method. Then, the Pt layer was patterned by photolithography and etching to form the second electrode.

[0087] Thus, the piezoelectric element of Example 1 was formed. Fig. 6 is a table showing the manufacturing conditions of Example 1 and Examples 2 and Comparative Examples 1 to 4 described later. In Fig. 6, "additive" refers to lithium, manganese, and copper.

[0088] 5.1.2. Example 2 The composition of the crystal layer was K 0.50 Na 0.50 Nb 1.00 O xA piezoelectric element of Example 2 was formed in the same manner as in Example 1, except for the above.

[0089] 5.1.3. Comparative Example 1 Oxygen flow during firing was not performed. However, before firing, the chamber of the RTA apparatus was subjected to oxygen replacement at 0.1 slpm for 10 seconds. Further, the firing was performed by lamp heating from above the sample without performing lamp heating from below the sample.

[0090] A piezoelectric element of Comparative Example 1 was formed in the same manner as in Example 1, except for the above.

[0091] 5.1.4. Comparative Example 2 The composition of the crystal layer was changed to K 0.50 Na 0.50 Nb 1.00 O x A piezoelectric element of Comparative Example 2 was formed in the same manner as in Comparative Example 1, except for the above.

[0092] 5.1.5. Comparative Example 3 A piezoelectric element of Comparative Example 3 was formed in the same manner as in Comparative Example 1, except that the BFTP layer was not formed.

[0093] 5.1.6. Comparative Example 4 The composition of the crystal layer was changed to K 0.50 Na 0.50 Nb 1.00 O x A piezoelectric element of Comparative Example 4 was formed in the same manner as in Comparative Example 1, except that the BFTP layer was not formed.

[0094] 5.2. Experimental Method 5.2.1. Orientation Ratio The orientation ratios of the lowermost layer and the uppermost layer (hereinafter, also simply referred to as the "lowermost layer" and the "uppermost layer") among a plurality of crystal layers were measured. The measurement of the orientation ratio of the lowermost layer was performed after forming the first crystal layer and before forming the second crystal layer. The measurement of the orientation ratio of the uppermost layer was performed after forming the fifth crystal layer and before forming the Pt layer.

[0095] As the measuring device, EBSD manufactured by Oxford Instruments Co., Ltd. was used. As the analysis software, "AZtec Crystal" was used. The measurement area was set to 50 μm × 50 μm. For the EBSD in the measurement area, each orientation region was specified in the "Texture Components" mode. Each orientation composition was defined by the "fiber axis".

[0096] The orientation ratio in the film thickness direction was specified and measured as follows. 100 orientation: <100> || Z0 110 orientation: <110> || Z0 111 orientation: <111> || Z0

[0097] The orientation ratio in the in-plane direction was specified and measured as follows. 100 orientation: <100> || X0 110 orientation: <110> || X0 111 orientation: <111> || X0

[0098] The deviation angle, that is, the allowable range of deviation from the specified direction, was set to 15°.

[0099] In Fig. 6, those with {100} preferred orientation were designated as "{100}", and those with random orientation were designated as "random". In Fig. 6, "{100}" refers to those with an orientation ratio of the {100} plane of 95% or more.

[0100] 5.2.2. Domain diameter Using the measuring device and analysis software for measuring the orientation ratio, the domain diameter in the in-plane direction of the top layer was measured. The size of the measurement area was the same as that in the measurement of the orientation ratio. For the EBSD data in the in-plane direction of the top layer, the domain diameter was measured in the "particle size analysis mode". The "threshold value" for distinguishing orientations was set to 8°, and boundary particles were excluded.

[0101] The average size of all domains targeted with the above settings was defined as the domain diameter.

[0102] 5.2.3. Crack The presence or absence of cracks in the top layer was evaluated by dark-field observation of a metal microscope. In Figure 6, those in which no cracks occurred in the top layer were designated as "A", and those in which cracks occurred in the top layer were designated as "C".

[0103] 5.2.4. Leakage current The leakage current was measured by evaluating the IV characteristics. As the device, "4140B" manufactured by Keysight was used. It was set to 1 to 40 V / 1 V step and 10 s delay / step. The first electrode was used as the drive. In Figure 6, the leakage current was -6 A / cm 2 equal to or less than 1×10 -6 A / cm 2 was designated as "A", greater than 1×10 -5 A / cm 2 and equal to or less than 1×10 -5 A / cm 2 was designated as "B", and greater than 1×10

[0104] 5.3. Experimental results Figure 6 shows the results of the orientation ratio measurement, domain diameter measurement, crack evaluation, and leakage current evaluation. Figure 7 is the pole figure of Examples 1 and 2 and Comparative Example 1 by EBSD. Figure 8 is the domain observation map of Examples 1 and 2 and Comparative Example 1 by EBSD. The orientation and domain diameter shown in Figure 6 were calculated based on Figures 7 and 8. Figure 9 is the metal microscope image of Example 1 and Comparative Example 3. In Figure 9, cracks were confirmed as white streak-like regions.

[0105] As shown in Figure 6, in Examples 1 and 2 and Comparative Examples 1 and 2 in which the BFTP layer was formed, the bottom layer was preferentially oriented in the {100} plane in the film thickness direction. In Examples 1 and 2 and Comparative Examples 1 and 2 in which the bottom layer was preferentially oriented in the {100} plane in the film thickness direction, no cracks were confirmed. Therefore, it was found that the generation of cracks can be suppressed by preferentially orienting the bottom layer in the {100} plane in the film thickness direction.

[0106] Furthermore, in Examples 1 and 2 where the top layer was randomly oriented in the in-plane direction, the leakage current was small. In Comparative Examples 3 and 4, although the top layer was randomly oriented in the in-plane direction, cracks occurred, and these cracks served as leakage paths, resulting in a large leakage current. In Example 1 to which an additive was added, the leakage current could be reduced compared to Example 2 to which no oxidizing agent was added. It was found that the additive contributed to the reduction of the leakage current.

[0107] In Examples 1 and 2 where the top layer was randomly oriented in the in-plane direction, the domain diameter was smaller than that in Comparative Examples 1 and 2. It was found that when the domain diameter was small, it was easier to randomly orient the top layer in the in-plane direction.

[0108] The above-described embodiments and modifications are merely examples and are not intended to be limiting. For example, it is also possible to appropriately combine each embodiment and each modification.

[0109] The present invention includes configurations that are substantially the same as the configurations described in the embodiments, for example, configurations having the same functions, methods, and results, or configurations having the same objectives and effects. The present invention also includes configurations in which non-essential parts of the configurations described in the embodiments are replaced. The present invention also includes configurations that exhibit the same operational effects as the configurations described in the embodiments or configurations that can achieve the same objectives. The present invention also includes configurations in which known techniques are added to the configurations described in the embodiments.

[0110] The following content is derived from the above-described embodiments and modifications.

[0111] One aspect of the piezoelectric element is a first electrode and a second electrode, a piezoelectric layer provided between the first electrode and the second electrode and including a plurality of layers containing a perovskite-type composite oxide containing potassium, sodium, and niobium, and among the plurality of layers containing the composite oxide, the first layer closest to the first electrode is preferentially oriented in a first orientation with a {100} plane orientation in the film thickness direction. Of the layers containing the plurality of composite oxides, the second layer closest to the second electrode has a mixture of the first orientation and a second orientation which is a {110} plane orientation in the in-plane direction intersecting the film thickness direction, and does not preferentially orient to either the first orientation or the second orientation.

[0112] According to this piezoelectric element, leakage current can be reduced.

[0113] In one aspect of the piezoelectric element, In the in-plane direction, the second layer has a mixture of the first orientation, the second orientation, and a third orientation which is a {111} plane orientation, and may not preferentially orient to the third orientation.

[0114] According to this piezoelectric element, generation of grain boundaries that can become leakage paths connecting in the film thickness direction from the first electrode to the second electrode can be suppressed.

[0115] In one aspect of the piezoelectric element, In the film thickness direction, the second layer may preferentially orient to the first orientation.

[0116] According to this piezoelectric element, stress generated at grain boundaries between different orientations different from the first orientation in the second layer can be reduced.

[0117] In one aspect of the piezoelectric element, An orientation control layer provided between the first electrode and the first layer and containing bismuth, iron, titanium, and lead may be further included.

[0118] According to this piezoelectric element, the orientation of the first layer can be controlled.

[0119] In one aspect of the piezoelectric element, The domain diameter in the in-plane direction of the second layer may be 5.01 μm or less.

[0120] According to this piezoelectric element, the second layer can be randomly oriented in the in-plane direction.

[0121] In one aspect of the piezoelectric element, the domain diameter in the in-plane direction of the second layer may be 0.22 μm or less.

[0122] According to this piezoelectric element, the second layer can be randomly oriented in the in-plane direction.

[0123] 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 by the piezoelectric element is formed, a nozzle plate in which nozzle holes communicating with the pressure generating chamber are formed, and includes.

[0124] One aspect of the printer is one aspect of the liquid ejection head, a transport mechanism that relatively moves a recording medium with respect to the liquid ejection head, a control unit that controls the liquid ejection head and the transport mechanism, and includes.

Explanation of reference numerals

[0125] 2…Substrate, 10…First electrode, 20…Alignment control layer, 30…Piezoelectric layer, 32…Crystal layer, 32a…First layer, 32b…Second layer, 40…Second electrode, 100…Piezoelectric element, 200…Liquid ejection head, 202…Lead electrode, 203…Adhesive, 204…Connection wiring, 210…Flow path forming substrate, 211…Pressure generating chamber, 212…Partition wall, 213…First communication path, 214…Second communication path, 215…Third communication path, 216…Manifold, 217…Supply flow path, 220…Nozzle plate, 222…Nozzle hole, 230…Diaphragm, 232…Silicon oxide layer, 234…Zirconium oxide layer, 240…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…Apparatus 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 having a plurality of layers containing a composite oxide having a perovskite-type structure containing potassium, sodium, and niobium, comprising: Among the plurality of layers containing the composite oxide, the first layer closest to the first electrode is preferentially oriented in a first orientation with a {100} plane orientation in the film thickness direction, Among the plurality of layers containing the composite oxide, the second layer closest to the second electrode has a mixture of the first orientation and a second orientation with a {110} plane orientation in the in-plane direction intersecting the film thickness direction, and is not preferentially oriented in either the first orientation or the second orientation, a piezoelectric element.

2. In Claim 1, the second layer has a mixture of the first orientation, the second orientation, and a third orientation with a {111} plane orientation in the in-plane direction, and is not preferentially oriented in the third orientation, a piezoelectric element.

3. In Claim 1, the second layer is preferentially oriented in the first orientation in the film thickness direction, a piezoelectric element.

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

5. In Claim 1, the domain diameter of the second layer in the in-plane direction is 5.01 μm or less, a piezoelectric element.

6. In Claim 5, the domain diameter of the second layer in the in-plane direction is 0.22 μm or less, a piezoelectric element.

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

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

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