Electromechanical conversion element, method for manufacturing the same, and liquid ejection head

Abstract

The problem addressed by the present invention is to provide: an electromechanical conversion element with which decreases over time in displacement of a piezoelectric body when continuously pulse-driven over a long period in a high-temperature environment are suppressed; a method for manufacturing the electromechanical conversion element; and a liquid discharge head equipped with the electromechanical conversion element.　This electromechanical conversion element comprises a first electrode disposed on a substrate, an electromechanical conversion layer, and a second electrode, wherein: a first high-temperature resistance layer containing a metal oxide is provided between the first electrode and the electromechanical conversion layer, and a second high-temperature resistance layer containing a metal oxide is provided between the electromechanical conversion layer and the second electrode; the electromechanical conversion layer contains perovskite crystals; and the degree of orientation of a (001) face is at least 99.0% in X-ray diffractometry of the electromechanical conversion layer.

Description

Technical Field

[0001] The present invention relates to an electromechanical conversion element, a method for manufacturing the same, and a liquid ejection head. More specifically, the present invention relates to an electromechanical conversion element in which a decrease over time in the displacement amount of a piezoelectric body is suppressed when continuously pulse-driven for a long time in a high-temperature environment, a method for manufacturing the same, and a liquid ejection head.

Background Art

[0002] In recent years, as electromechanical conversion elements for applications such as drive elements and sensors, lead-based piezoelectric bodies such as lead zirconate titanate (Pb(Zr,Ti)O3) and lead-free piezoelectric bodies are used. By forming such a piezoelectric body as a thin film on a substrate such as silicon (Si), it is expected to be applied to MEMS (Micro Electro Mechanical Systems) elements.

[0003] In the manufacture of MEMS elements, since high-precision processing using semiconductor process technologies such as photolithography can be applied, miniaturization and high density of the elements are possible. In particular, by fabricating elements densely in a batch on a relatively large Si wafer such as a 6-inch diameter or an 8-inch diameter, the cost can be significantly reduced compared to single-wafer manufacturing in which the elements are manufactured individually.

[0004] In addition, by thinning the piezoelectric body and MEMSizing the device, the conversion efficiency of mechanical electricity is improved, and new added values such as improved sensitivity and characteristics of the device are generated. For example, in a thermal sensor, the measurement sensitivity can be increased by reducing the thermal conductance by MEMSization, and in an inkjet head for a printer, high-definition patterning is possible due to high density of nozzles. Also, in an electromechanical conversion layer containing a piezoelectric body required for such a device, for example, in an electromechanical conversion layer of a method called the bend mode, a high piezoelectric constant d 31 is required.

[0005] When using an electromechanical conversion layer as a MEMS drive element, depending on the device to be designed, in order to satisfy the required displacement generating force, for example, the electromechanical conversion layer must be formed with a thickness of 1 to 10 μm. To form the electromechanical conversion layer on a substrate such as Si, chemical film formation methods such as CVD (Chemical Vapor Deposition), physical methods such as sputtering and ion plating, and growth methods in the liquid phase such as the sol-gel method are known. It is important to find film formation conditions for obtaining a film with the required performance according to these film formation methods.

[0006] As the above piezoelectric body, lead zirconate titanate (PZT) having a perovskite structure and having ferroelectricity and good piezoelectric characteristics is generally used. Also, it is known that various metals or their oxides can be used for the upper and lower electrodes for applying a voltage in the thickness direction to the above piezoelectric body (see Patent Document 1 and Patent Document 2).

[0007] Also, as described in Patent Documents 1 to 5, thin-film electromechanical conversion elements using a piezoelectric body having a perovskite structure are widely used. For example, when using the above thin-film electromechanical conversion element in an inkjet head, if the displacement amount of the piezoelectric body decreases when it is continuously pulse-driven for a long time, the ejection speed of the ink droplets from the inkjet head will also change over time. From the viewpoint of improving the durability of the thin-film electromechanical conversion element, the piezoelectric body is required to have little change in displacement amount due to long-term use.

[0008] In particular, according to the findings of the present inventors, when a piezoelectric body having a perovskite structure is continuously pulse-driven in a high-temperature environment for a long time, the decrease in the displacement amount is remarkable.

[0009] That is, at room temperature driving, the film properties of PZT can ensure the desired ink ejection amount and ejection speed during ink ejection. However, when the ink is heated to inject high-viscosity ink, the electromechanical conversion layer is also heated. When continuously pulse-driven at a high temperature of 50°C or higher for a long time, it has been found that there is a problem that the piezoelectricity deteriorates and sufficient ejection performance cannot be ensured.

Prior Art Documents

Patent Documents

[0010]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Patent Document 5

Summary of the Invention

Problems to be Solved by the Invention

[0011] The present invention has been made in view of the above problems and situations, and the problem to be solved is to provide an electromechanical conversion element in which a decrease in the displacement amount of a piezoelectric body over time is suppressed when continuously pulse-driven for a long time in a high-temperature environment, a method for manufacturing the same, and a liquid ejection head including the electromechanical conversion element.

Means for Solving the Problems

[0012] In order to solve the above problems, the present inventor has studied the causes of the above problems and the like, and as a result, in an electromechanical conversion element including a first electrode, a first high-temperature durability layer, an electromechanical conversion layer, a second high-temperature durability layer, and a second electrode in this order, it has been found that the problem can be solved when the electromechanical conversion layer contains a perovskite-type crystal and the (001) plane of the crystal is preferentially oriented, leading to the present invention. That is, the above problems according to the present invention are solved by the following means.

[0013] 1. An electromechanical conversion element including a first electrode, an electromechanical conversion layer, and a second electrode provided on a substrate, comprising a first high-temperature durability layer containing a metal oxide between the first electrode and the electromechanical conversion layer, and a second high-temperature durability layer containing a metal oxide between the electromechanical conversion layer and the second electrode, wherein the electromechanical conversion layer contains a perovskite-type crystal, when the diffraction peak intensities of the (001) plane, (101) plane, and (111) plane in the X-ray diffraction measurement of the electromechanical conversion layer are I(001), I(101), and I(111), respectively, the orientation degree of the (001) plane represented by {I(001) / (I(001)+I(101)+I(111))}×100% is 99.0% or more. and When the residual polarization at 50°C is Pr(50°C) [μC / cm 2 and the residual polarization at 20°C is Pr(20°C) [μC / cm 2 , it satisfies the following formula 1 An electromechanical conversion element characterized by the above. (Formula 1): Pr(50°C) / Pr(20°C) ≧ 1.00 2. An electromechanical conversion element including a first electrode, an electromechanical conversion layer, and a second electrode provided on a substrate, comprising a first high-temperature durability layer containing a metal oxide between the first electrode and the electromechanical conversion layer, and a second high-temperature durability layer containing a metal oxide between the electromechanical conversion layer and the second electrode, wherein the electromechanical conversion layer contains perovskite-type crystals, When the diffraction peak intensities of the (001) plane, (101) plane, and (111) plane in the X-ray diffraction measurement of the electromechanical conversion layer are I(001), I(101), and I(111), respectively, the orientation degree of the (001) plane represented by {I(001) / (I(001)+I(101)+I(111))}×100% is 99.0% or more, When the residual polarization at 85°C is Pr(85°C) [μC / cm 2 and the residual polarization at 20°C is Pr(20°C) [μC / cm 2 , an electromechanical conversion element characterized by satisfying the following formula 2. (Formula 2): Pr(85°C) / Pr(20°C) ≧ 0.90

[0014] 3 . The metal oxide contained in the first high-temperature durability layer and the second high-temperature durability layer independently contains lanthanum lead titanate (PLT), strontium ruthenate (SRO), lanthanum nickelate (LNO), or lead titanate (PT), respectively, according to claim 1. or any one item from item 2 The electromechanical conversion element according to the above.

[0015] 4 . The perovskite crystal according to claim 1, characterized in that it contains lead zirconate titanate (PZT). to Item 3 section any one item The electromechanical conversion element described in the above item.

[0018] 5 . The electromechanical conversion element according to any one of to, characterized in that the relative dielectric constants of the first high-temperature resistant layer and the second high-temperature resistant layer are both smaller than the relative dielectric constant of the electromechanical conversion layer. item 1 From item 4 to any one of the above items.

[0019] 6 . A method for manufacturing an electromechanical conversion element for manufacturing the electromechanical conversion element according to any one of claims 1 to 5 , comprising an electromechanical conversion layer forming step of forming an electromechanical conversion layer on the first high-temperature resistant layer, In the electromechanical conversion layer forming step, the electromechanical conversion layer is heated to 500 °C or higher and then cooled to 300 °C or lower, and this step is repeated two or more times to form the electromechanical conversion layer. A method for manufacturing an electromechanical conversion element, characterized in that.

[0020] 7 5 . A liquid ejection head characterized by comprising the electromechanical conversion element according to any one of claims 1 to section. [Effect of the Invention]

[0021] By the above means of the present invention, it is possible to provide an electromechanical conversion element in which a decrease in the displacement amount of a piezoelectric body over time when continuously pulse-driven for a long time in a high-temperature environment is suppressed, a manufacturing method thereof, and a liquid ejection head including the electromechanical conversion element.

[0022] Although the mechanism or action mechanism for the manifestation of the effect of the present invention is not clear, it is speculated as follows. As a mechanism for exhibiting piezoelectricity, it is generally known that it depends on the magnitude of the polarization of the B site in the perovskite structure. The magnitude of the remanent polarization Pr indicates the degree of polarization, and a higher value indicates the exhibition of higher piezoelectricity.

[0023] Particularly when there is a preferential orientation on the (001) plane in the same direction as the applied voltage direction, the piezoelectric constant d 31 becomes large and functions as an efficient electro-mechanical conversion element. Since the (101) and (111) directions, which are different phases, do not coincide with the applied electric field direction, they do not contribute much to the piezoelectric properties.

[0024] When a large electric field is applied, piezoelectricity is exhibited due to the electrostriction effect caused by the rotation of the polarization, etc. However, the polarization moves repeatedly, leading to polarization fatigue, etc., and piezoelectric loss occurs during continuous driving. Particularly in driving under high-temperature conditions, it is considered that the polarization deterioration progresses easily. Therefore, it is speculated that only the orientation of the (001) plane without polarization rotation, etc., is also advantageous for deterioration during continuous driving.

[0025] In addition, as another factor causing polarization deterioration, the deterioration of the piezoelectric body at the electrode interface is considered. Although the mechanism has not been fully elucidated yet, for example, by exchanging charges during the pulse driving of the element, etc., oxygen defects in the perovskite structure are generated and the polarization deterioration progresses, and a model in which the value of the remanent polarization Pr decreases is considered. Furthermore, under driving conditions at high temperatures, the diffusion of some elements contained in the electrode is also considered as a factor causing piezoelectric body deterioration. Therefore, it is presumed that the introduction of a high-temperature durable layer that relaxes the interaction at the interface between the electro-mechanical conversion layer and the electrode and suppresses the polarization deterioration of the electro-mechanical conversion layer exhibits a remarkable effect under high-temperature driving conditions.

Brief Description of the Drawings

[0026]

Figure 1

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Figure 8

Embodiments for Carrying Out the Invention

[0027] The electromechanical conversion element of the present invention is an electromechanical conversion element including a first electrode, an electromechanical conversion layer, and a second electrode provided on a substrate, including a first high-temperature durable layer containing a metal oxide between the first electrode and the electromechanical conversion layer, and a second high-temperature durable layer containing a metal oxide between the electromechanical conversion layer and the second electrode, wherein the electromechanical conversion layer contains a perovskite-type crystal, and when the diffraction peak intensities of the (001) plane, (101) plane, and (111) plane in the X-ray diffraction measurement of the electromechanical conversion layer are I(001), I(101), and I(111), respectively, the orientation degree of the (001) plane represented by {I(001) / (I(001)+I(101)+I(111))}×100% is 99.0% or more. This feature is a common or corresponding technical feature in each of the following embodiments.

[0028] As an embodiment of the present invention, it is preferable that the metal oxides contained in the first high-temperature durability layer and the second high-temperature durability layer each independently contain lead lanthanum titanate (PLT), strontium ruthenium oxide (SRO), lanthanum nickelate (LNO), or lead titanate (PT). Thereby, good adhesion between the upper and lower electrodes and each high-temperature durability layer can be obtained. In addition, as a buffer layer for the electromechanical conversion layer, deterioration such as oxygen defects in the electromechanical conversion layer can be prevented during continuous driving, so that polarization can be maintained and a decrease in the remnant polarization Pr can be prevented.

[0029] In addition, the first high-temperature durability layer on the lower electrode also has the function of a seed layer that promotes the crystal growth of the electromechanical conversion layer, and has the effect of providing good crystallinity and piezoelectric properties of the electromechanical conversion layer. The second high-temperature durability layer at the interface with the upper electrode, in addition to the above effects, has the effect of making it difficult for a current leakage path to occur from the crystal grain boundaries because the crystallinity becomes discontinuous. As an embodiment of the present invention, it is preferable that the perovskite-type crystal contains lead zirconate titanate (PZT) because high piezoelectric properties can be exhibited, so that a high displacement amount can be obtained and an electromechanical conversion element having high performance can be obtained.

[0030] Furthermore, in the present invention, when the remnant polarization at 50 °C is Pr(50 °C) [μC / cm 2 and the remnant polarization at 20 °C is Pr(20 °C) [μC / cm 2 , it is preferable to satisfy the above formula 1 because the polarization is maintained in a large state and high piezoelectric properties are generated.

[0031] As an embodiment of the present invention, when the remnant polarization at 85 °C is Pr(85 °C) [μC / cm 2 and the remnant polarization at 20 °C is Pr(20 °C) [μC / cm 2 , it is preferable to satisfy the above formula 2 because the decrease in polarization is suppressed and the decrease in piezoelectric properties is also small which is preferable.

[0032] Further, it is preferable that the relative dielectric constants of both the first high-temperature durable layer and the second high-temperature durable layer are smaller than the relative dielectric constant of the electromechanical conversion layer. Compared with an electromechanical conversion element formed only of an electromechanical conversion layer, it has the effect of reducing the capacitance, can reduce the load during driving, and has the effect of alleviating the deterioration of the driving life.

[0033] Furthermore, as a method for manufacturing an electromechanical conversion element for manufacturing the electromechanical conversion element of the present invention, it has an electromechanical conversion layer film-forming step of forming an electromechanical conversion layer on the first high temperature. In the electromechanical conversion layer film-forming step, a method of forming the electromechanical conversion layer by repeating a step of heating the electromechanical conversion layer to 500°C or higher and then cooling it to 300°C or lower two or more times is preferable because it can improve the orientation degree of the (001) plane and provide an electromechanical conversion layer with high single-orientation crystallinity.

[0034] The electromechanical conversion element of the present invention can be suitably provided in a liquid ejection head.

[0035] Hereinafter, the present invention, its components, and forms and modes for implementing the present invention will be described in detail. In the present application, "~" is used to mean including the numerical values described before and after it as the lower limit value and the upper limit value.

[0036] 《Electromechanical Conversion Element》 The electromechanical conversion element of the present invention is an electromechanical conversion element including a first electrode, an electromechanical conversion layer, and a second electrode provided on a substrate, including a first high-temperature durable layer containing a metal oxide between the first electrode and the electromechanical conversion layer, and a second high-temperature durable layer containing a metal oxide between the electromechanical conversion layer and the second electrode. The electromechanical conversion layer contains perovskite-type crystals. When the diffraction peak intensities of the (001) plane, (101) plane, and (111) plane in the X-ray diffraction measurement of the electromechanical conversion layer are I(001), I(101), and I(111), respectively, the orientation degree of the (001) plane represented by {I(001) / (I(001)+I(101)+I(111))}×100% is 99.0% or more.

[0037] FIG. 1 is an example of a cross-sectional view of the electromechanical conversion element of the present invention. The electromechanical conversion element 1 includes a first electrode 3, a first high-temperature durable layer 4, an electromechanical conversion layer 5, a second high-temperature durable layer 6, and a second electrode 7 on a substrate 2 in this order. In the present invention, the electromechanical conversion layer contains a perovskite-type crystal and has a plane orientation degree of 99.0% or more with respect to the (001) plane.

[0038] With such a configuration, an electromechanical conversion element can be obtained in which a decrease over time in the displacement amount of the piezoelectric body is suppressed when continuously pulse-driven for a long time in a high-temperature environment.

[0039] [Electromechanical conversion layer] In the present invention, the electromechanical conversion layer contains a perovskite-type crystal and has a plane orientation degree of 99.0% or more with respect to the (001) plane. Further, it is preferable that the perovskite-type crystal contains lead zirconate titanate (PZT). By containing lead zirconate titanate (PZT), the orientation degree of the (001) plane is improved, and an electromechanical conversion layer with high single-orientation crystallinity can be obtained. The content of PZT is preferably 90% by mass or more, and it is more preferable that the perovskite-type crystal is composed of PZT.

[0040] For PZT, a crystal composed of lead (Pb), zirconium (Zr), titanium (Ti), and oxygen (O) is used. Since PZT exhibits a good piezoelectric effect when it has an ABO3-type perovskite structure, it is preferable to make the crystal orientation of the perovskite single-phase. Crystals with a pyrochlore structure or a crystal structure with an amorphous structure do not exhibit piezoelectricity, so they become an inhibitory factor for exhibiting good piezoelectric characteristics, which is not preferable. When forming the PZT film, since Pb evaporation easily occurs, it is required to control the excess lead composition of the target or set optimal film-forming conditions to obtain perovskite crystals.

[0041] The unit cell shape of PZT crystals with an ABO3-type perovskite structure changes depending on the ratio of Ti and Zr, the atoms that enter the B site. That is, when Ti is abundant, the crystal lattice of PZT becomes tetragonal, and when Zr is abundant, the crystal lattice of PZT becomes rhombohedral. When the molar ratio of Zr and Ti is around 52:48, both of these crystal structures exist, and the phase boundary with such a composition ratio is called MPB (Morphotropic Phase Boundary). In this MPB composition, since the maximum values of piezoelectric properties such as piezoelectric constant, polarization value, and dielectric constant can be obtained, piezoelectric materials with MPB composition are actively used.

[0042] Here, when PZT is represented as Pb(Zr x Ti 1-x )O3, it is in the range of x = 0.50 to 0.58, and has an MPB composition or a composition close to it. As a result, higher piezoelectric properties (for example, a high piezoelectric constant d 31 ) can be obtained compared to compositions other than MPB. In particular, the molar ratio of Zr and Ti is preferably around 52:48, which is the MPB composition.

[0043] Also, in the present invention, the electromechanical conversion layer 5 has the (001) plane of the perovskite phase as the main orientation. That is, when the diffraction peak intensities of the (001) plane, (101) plane, and (111) plane in the X-ray diffraction measurement of the electromechanical conversion layer are I(001), I(101), and I(111), respectively, the orientation degree of the (001) plane represented by {I(001) / (I(001)+I(101)+I(111))}×100% is 99.0% or more. In order to improve the orientation degree, as described later, in the film formation process of the electromechanical conversion layer, it is preferable to repeat the process of heating the electromechanical conversion layer to 500 °C or higher and then cooling it to 300 °C or lower two or more times for film formation.

[0044] (Orientation degree of the (001) plane in XRD measurement) The X-ray diffraction measurement of the electromechanical conversion layer is performed under the following conditions. In the electromechanical conversion layer 5, when the diffraction peak intensities of the (001), (101), and (111) planes of the perovskite phase obtained by 2θ / θ measurement of X-ray diffraction (XRD) are denoted as I(001), I(101), and I(111), respectively, the orientation degree of the (001) plane represented by {I(001) / (I(001)+I(101)+I(111))}×100% is 99.0% or more.

[0045] As a measuring device, an X-ray diffractometer RINT-TTR III manufactured by Rigaku Corporation can be used for measurement under the following conditions. Out-of-plane measurement: Measurement angle range 10 - 110° (001)-(004)

[0046] (Remnant polarization) The electromechanical conversion element having an electromechanical conversion layer with an improved orientation degree of the above-mentioned (001) plane and a high single-orientation crystallinity can reduce the decrease in remnant polarization even at high temperatures, and can suppress the decrease over time in the displacement amount of the piezoelectric body when continuously pulse-driven for a long time in a high-temperature environment.

[0047] The electromechanical conversion element of the present invention preferably satisfies the following formula 1 when the remnant polarization at 50°C is Pr(50°C) [μC / cm 2 , and the remnant polarization at 20°C is Pr(20°C) [μC / cm 2 . (Formula 1): Pr(50°C) / Pr(20°C) ≧ 1.00

[0048] Furthermore, it preferably satisfies the following formula 2 when the remnant polarization at 85°C is Pr(85°C) [μC / cm 2 , and the remnant polarization at 20°C is Pr(20°C) [μC / cm 2 . (Formula 2): Pr(85°C) / Pr(20°C) ≧ 0.90

[0049] Figure 2 shows an example of the polarization - electric field hysteresis of the electromechanical conversion element of the present invention. Generally, in an electromechanical element, the polarization - electric field hysteresis (hereinafter also referred to as P - E hysteresis) showing the relationship between polarization (P) and electric field (E) has a shape such that the polarization (absolute value) is almost symmetric on the positive electric field side and the negative electric field side with respect to the vertical axis (E = 0V). However, it is known that when a donor is added to the electromechanical conversion layer, the P - E hysteresis shifts to the + or - side. Also, in a memory element, it is known that hysteresis shift occurs even when used for a long time while repeatedly reversing the polarization. In that case, as is known that the shift amount is alleviated when the electrodes are changed, the change in hysteresis also occurs depending on the state of the interface with the electrodes. The point where the vertical axis (E = 0V) of the P - E hysteresis intersects is called the remanent polarization Pr, and the point where it intersects the horizontal axis (P = 0 μC / cm 2 ) is called the coercive electric field.

[0050] Here, Pr is related to the magnitude of the piezoelectric property, and it can be said that the larger Pr is, the larger the piezoelectric property is. Therefore, even in an asymmetric hysteresis, it is important for the performance as an electromechanical conversion element that Pr is large. When an electromechanical conversion element is configured by sandwiching the electromechanical conversion layer of the present invention between a first electrode and a second electrode, when the first electrode is used as a common electrode and the second electrode is used as an individual electrode, and a + electric field is applied to the second electrode for driving, an electromechanical conversion element having an asymmetric P - E hysteresis as shown in Figure 2 is obtained. When Pr on the + electric field side (+Pr) is defined as Pr, it can be seen that Pr changes depending on the temperature used.

[0051] In the present invention, due to the effect of the high - temperature durability layer, no deterioration of Pr is observed at 55°C, and almost the same Pr is maintained even in the high - temperature region of 85°C. Therefore, as defined by Equation 1 and Equation 2, it is considered that having the characteristic of little decrease in the remanent polarization even at high temperatures suggests that sufficient durability is maintained even in use in the high - temperature region. Figure 3 shows an example of the temperature dependence of the remanent polarization in the electromechanical conversion elements of the present invention and the comparative example. As will be described later in the examples, even in the high - temperature region, a remanent polarization Pr almost equivalent to that at room temperature (20°C) is maintained.

[0052] The remnant polarization Pr can be obtained by measuring the P-E hysteresis using a ferroelectric tester Precision LCII manufactured by Radiant Technologies, applying a triangular wave at -120 to +120 kV / cm, a frequency of 1 kHz.

[0053] [First High-Temperature Durability Layer and Second High-Temperature Durability Layer] The metal oxides contained in the first high-temperature durability layer and the second high-temperature durability layer are each preferably independently lead lanthanum titanate (PLT), strontium ruthenium oxide (SRO), lanthanum nickelate (LNO), or lead titanate (PT). Thereby, good adhesion between the first electrode and the second electrode and each high-temperature durability layer can be obtained. Further, as a buffer layer with the electromechanical conversion layer, deterioration such as oxygen defects in the electromechanical conversion layer during continuous driving can be prevented, so that polarization can be maintained and a decrease in the remnant polarization Pr can be prevented.

[0054] It is preferable to select and use the metal oxide as a material for the seed layer of PZT or the buffer layer of the orientation control layer of the electromechanical conversion layer. Since it has a high affinity with the PZT layer, the bonding state at the interface is good and high adhesion can be obtained. Therefore, there is no mechanical loss during vibration, and there is no electrical loss due to charge exchange, so it functions without impairing durability and element performance. Although not clearly understood, it is considered that the first high-temperature durability layer and the second high-temperature durability layer can relax oxygen defects and the like generated by the interaction between the interface between the first and second electrodes during PZT driving, and suppress deterioration during driving.

[0055] Furthermore, it is preferable that the metal oxide has a lower relative permittivity than PZT. Thereby, compared with the case of only the electromechanical conversion layer, it is possible to reduce the capacitance of all the layers sandwiched between the electrodes of the electromechanical conversion element, and since the displacement current generated during pulse driving becomes smaller, the generation of heat and the like is reduced and the load becomes smaller. Also, since the charge exchange is reduced, an effect of suppressing deterioration of the interface and the like is expected. For this reason, the load during driving is reduced, which is advantageous for long-time driving and can suppress deterioration. That is, it is preferable that the relative permittivities of both the first high-temperature durability layer and the second high-temperature durability layer are smaller than the relative permittivity of the electromechanical conversion layer.

[0056] The relative permittivity can be measured at 20°C using an impedance analyzer 4194A manufactured by Yokogawa and Hewlett Packard as the measuring instrument. The capacitance measurement is performed under the conditions of 1 kHz and 1 V, and can be obtained by conversion from the area and thickness of the element. Note that it is not essential for the first and second high-temperature durability layers to be insulators, and it is also possible to select a conductive metal oxide.

[0057] Since both the first high-temperature durability layer and the second high-temperature durability layer have low piezoelectric performance, if they are formed thick, the displacement amount will decrease. Therefore, the thickness of the layer is preferably in the range of 0.05 to 0.5 μm, and more preferably in the range of 0.1 to 0.3 μm.

[0058] The first high-temperature durability layer and the second high-temperature durability layer are also called seed layers or buffer layers. They are provided between the electromechanical conversion layer and the first and second electrodes, and also play a role in improving the adhesiveness between the electromechanical conversion layer and the electrodes. Both the so-called seed layer and buffer layer here basically play a role in improving adhesion and promoting crystal growth of the piezoelectric body. Generally, the seed layer is thin and mainly plays a role in improving adhesion. The orientation is such that metal oxides precipitate in an island shape on the film surface, which serves as nuclei for oriented growth. The buffer layer has an oriented structure in order to more accurately control the oriented growth of the piezoelectric body as an orientation control layer.

[0059] In particular, the first high-temperature durability layer plays a very important role in controlling the orientation of the electromechanical conversion layer. By using an optimal first high-temperature durability layer, the orientations such as the (101) plane and the (111) plane can be reduced. The high-temperature durable layer may not be a single layer but may have a laminated structure. Since LNO and SRO are conductive metal oxides, a structure in which LNO is formed on the first electrode and PLT is laminated thereon also functions as a high-temperature durable layer. In this case, since PLT can more effectively function as a buffer layer, it contributes to good crystal orientation of the piezoelectric thin film. Similarly, the second high-temperature durable layer may also have a laminated structure in which the layer in contact with the second electrode is a conductive metal oxide layer. Also, it is possible to adopt a laminated structure of an insulator and a conductive metal oxide.

[0060] [First Electrode and Second Electrode] The first electrode 3 is provided so as to sandwich the electromechanical conversion layer 5 in the thickness direction between the second electrode 7. The first electrode 3 and the second electrode 7 are made of a known conductive material, and for example, it is preferably a layer made of platinum (Pt), platinum (Pt), and titanium (Ti). The thickness of the Ti layer is, for example, about 0.02 μm, and the thickness of the Pt layer is, for example, about 0.1 to 0.2 μm. Instead of the Pt layer, a layer made of iridium (Ir) may be formed.

[0061] [Substrate] The substrate can be composed of a semiconductor substrate made of a single crystal Si (silicon) alone with a thickness of, for example, about 250 to 750 μm or an SOI (Silicon on Insulator) substrate. The substrate may be composed of other materials, but it is desirable to be composed of an Si substrate or an SOI (Silicon on Insulator) substrate.

[0062] [Other Layers] In addition to the above layers, other layers such as an intermediate layer can be provided as needed, for example, to improve adhesion.

[0063] 《Manufacturing Method of Electromechanical Conversion Element》 The manufacturing method of the electromechanical conversion element of the present invention has an electromechanical conversion layer film-forming step of forming an electromechanical conversion layer on a first high-temperature resistant layer. In the electromechanical conversion layer film-forming step, the step of heating the electromechanical conversion layer to 500°C or higher and then cooling it to 300°C or lower is repeated two or more times to form the electromechanical conversion layer.

[0064] [Electromechanical conversion layer] In the present invention, in order to form an electromechanical conversion layer with a predetermined thickness, it is characterized by forming the film in a divided manner. It is not necessary to evenly distribute the thickness of each layer, but attention is required because if the ratio of the thickness of each layer changes extremely, there may be a difference in crystal growth in the thickness direction. Generally, in a film-forming method in which crystal growth is performed while heating the substrate, when the thickness is thick and the deposition is continuous, the crystal growth is disturbed by fluctuations in the inner surface of the apparatus, particularly the influence of temperature changes, and the orientation of a different phase such as the (101) plane is likely to occur. When the thickness is thick, the film-forming time becomes long, so this tendency is likely to appear. Also, when the film is formed and taken out at once while heating the substrate, in order to release the film stress that has entered during film formation all at once, cracks are generated and a film with a large internal stress is formed.

[0065] On the other hand, by performing divided film formation, the crystal growth of each layer is less affected by fluctuations in the apparatus, so there is no growth of different phases, and a single-phase and good crystal growth state can be formed. Also, by heating to 500°C or higher, the growth of the (001) plane can be formed. Furthermore, a cooling step is performed to release the stress accumulated inside the film.

[0066] As a method of performing without impairing the piezoelectric characteristics, a step of heating the electromechanical conversion layer to 500°C or higher and then cooling it to 300°C or lower is necessary. It is considered that this is because polarization appears during film formation due to film formation at a high temperature, and in the case of PZT, by cooling to a temperature below the Curie point by cooling to 300°C or lower, the polarization can be fixed.

[0067] Also, from the perspective of improving the reliability when made into a device, it is more preferable to have a cleaning process when performing divided film formation. In the cleaning process, it is preferable to clean for each film formation. When using a solution for cleaning, an alkaline cleaning agent, for example, Clean Ace manufactured by Shibata Scientific Technology Co., Ltd., is used, and foreign substances mixed during film formation are removed by a cleaning method mainly using physical cleaning such as brush cleaning, so that defects in the portion removed in the next film formation can be filled. When a predetermined film formation is performed at once, if foreign substances mixed during film formation fall off after film formation, voids will occur and the effective thickness of that portion will become thinner. In that case, a leakage current will flow when a voltage is applied, and device breakdown will occur. By performing divided film formation, it is possible to ensure at least the minimum effective thickness, so that the reliability of the device can be ensured at a high level.

[0068] Specifically, for example, while heating the first high-temperature durable layer provided on the substrate to 580°C, high-frequency power of 2000 W is applied to form an electromechanical conversion layer to a predetermined thickness. Assuming that the desired thickness is, for example, 3.0 μm, in the case of one-time divided film formation (when dividing the electromechanical conversion layer into two layers), first, a film of 1.5 μm is formed, and after cooling to at least 300°C or lower, it is taken out of the chamber. After that, in order to remove foreign substances during film formation, it is preferable to perform wet rubbing cleaning using a brush or a wipe, and after rinsing, the substrate is dried sufficiently. The substrate is put into the chamber again, and film formation is carried out under the same film formation conditions as the first time. The thickness is similarly increased by 1.5 μm to reach 3.0 μm, and the electromechanical conversion layer can be completed. In the case of two or more divided film formations, the substrate is taken out after forming a film of a predetermined thickness in the same manner, cleaned, and the same cycle is repeated to complete a total 3.0 μm electromechanical conversion layer. The divided thickness can be changed as appropriate.

[0069] [First High-Temperature Durable Layer and Second High-Temperature Durable Layer] The first high-temperature resistant layer is formed on the first electrode, and it is preferably made of lead lanthanum titanate (PLT), strontium ruthenium oxide (SRO), lanthanum nickelate (LNO), lead titanate (PT), or the like. It functions as a seed layer for the crystal orientation of the electromechanical conversion layer formed thereon, or has the function of an orientation control film as a buffer layer for controlling the orientation. The film formation conditions and the like are adjusted so that the (001) plane of the electromechanical conversion layer is preferentially oriented. The thickness is 0.05 - 0.3 μm, preferably 0.1 - 0.2 μm so as to have orientation.

[0070] The second high-temperature resistant layer is formed on the electromechanical conversion layer, and it is preferably made of lead lanthanum titanate (PLT), strontium ruthenium oxide (SRO), lanthanum nickelate (LNO), lead titanate (PT), or the like independently of the first high-temperature resistant layer. An oriented film is preferred, but different from the first high-temperature resistant layer, it is selected considering the interaction such as the adhesion between the electromechanical conversion layer and the second electrode and the diffusion at the film interface rather than the orientation. The first high-temperature resistant layer and the second high-temperature resistant layer can be formed by known methods, for example, methods such as vapor deposition method and sputtering method.

[0071] [First Electrode and Second Electrode] For the first electrode, a conductive material is used. For example, using a platinum (Pt) target, high-frequency power of 200 W can be applied for 12 minutes while heating the substrate to 400 °C in argon gas with a vacuum degree of 1 Pa to form a film.

[0072] The second electrode can also be formed on the second high-temperature resistant layer in the same manner as the first electrode.

[0073] 《Liquid Discharge Head》 Next, a liquid discharge head provided with the electromechanical conversion element of the present invention will be described. FIG. 4 is an example of a cross-sectional view of the liquid discharge head of the present invention. It shows a liquid discharge head in which a plurality of nozzles are arranged in parallel.

[0074] The liquid ejection head of the present invention is a liquid ejection head including a nozzle 52 that ejects ink droplets as a liquid, a pressure chamber 51 that communicates with the nozzle 52, and ejection driving means for boosting the pressure of the liquid in the pressure chamber. The ejection driving means is an electromechanical conversion element 62 including a diaphragm 55 that forms a part of a substrate (wall substrate) 54 of the pressure chamber 51. The pressure chamber 51 is formed by removing a part of the substrate 54 by etching from the back surface and bonding a nozzle plate 53 provided with the nozzle 52 to the substrate 54.

[0075] The electromechanical conversion element 62 is formed by sequentially laminating a diaphragm 55, an adhesion layer 56, a first electrode 57, a first high-temperature durability layer 58, an electromechanical conversion layer 59, a second high-temperature durability layer 60, and a second electrode 61 on a substrate (wall substrate) 54 and then patterning them by photolithography.

[0076] The liquid ejection head manufactured in this way can be manufactured by a simple manufacturing process. Further, since it is provided with the electromechanical conversion element of the present invention having performance equivalent to that of bulk ceramics, good ejection characteristics can be obtained. The liquid ejection head can be suitably used as an inkjet head that ejects inkjet ink.

[0077] In the figure, descriptions of liquid supply means, flow paths, and fluid resistance set in the flow paths for supplying a liquid such as ink to the pressure chamber are omitted.

[0078] 《Image Recording Apparatus》 Next, an example of an image recording apparatus equipped with the liquid ejection head of the present invention will be described with reference to FIGS. 5 and 6. FIG. 5 shows a perspective view of the image recording apparatus. FIG. 6 shows a side view of the mechanism portion of the image recording apparatus.

[0079] The image recording device 81 houses a printing mechanism unit 82 and the like, which is composed of a carriage movable in the main scanning direction inside the main body, a liquid ejection head 94 implementing the present invention mounted on the carriage, an ink cartridge 95 for supplying ink to the liquid ejection head 94, etc. A paper feed cassette (or a paper feed tray may also be used) 84 capable of loading a large number of sheets of paper 83 from the front side can be detachably attached to the lower part of the main body 81. Also, a manual feed tray 85 for manually feeding the paper 83 can be opened and laid down. The paper 83 fed from the paper feed cassette 84 or the manual feed tray 85 is taken in, a required image is recorded by the printing mechanism unit 82, and then it is discharged to a paper discharge tray 86 mounted on the rear side.

[0080] The printing mechanism unit 82 holds a carriage 93 slidably in the main scanning direction by a main guide rod 91 and a sub-guide rod 92, which are guide members horizontally mounted on left and right side plates (not shown). On this carriage 93, a liquid ejection head 94 of the present invention that ejects ink droplets of each color of yellow (Y), cyan (C), magenta (M), and black (Bk) is mounted with a plurality of nozzles arranged in a direction intersecting the main scanning direction and the ink droplet ejection direction being downward. Also, each ink cartridge 95 for supplying each color of ink to the liquid ejection head 94 is detachably mounted on the carriage 93.

Example

[0081] Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto. In the examples, the display of "parts" or "%" is used, which represents "parts by mass" or "% by mass" unless otherwise specified.

[0082] 〔Example 1〕 《Fabrication of Electromechanical Conversion Element》 The electromechanical conversion element was fabricated by sequentially depositing a first electrode, a first high-temperature durable layer, an electromechanical conversion layer, a second high-temperature durable layer, and a second electrode on a substrate by sputtering.

[0083] 〈Fabrication of Electromechanical Conversion Element 1-1〉 (Formation of the First Electrode) The first electrode was formed by applying a DC power of 800 W while heating a substrate (silicon wafer) to 350 °C in a mixed gas of argon and oxygen with a vacuum degree of 1 Pa using an Ir target. The first electrode was formed to a thickness of 100 nm.

[0084] (Formation of the first high-temperature durable layer) The first high-temperature durable layer was formed by applying an RF power of 2000 W while heating a substrate to 550 °C in a mixed gas of argon and oxygen with a vacuum degree of 1 Pa using a PLT target having a perovskite structure of a metal oxide containing at least lead (Pb), lanthanum (La), and titanium (Ti) (consisting of (Pb·La)TiO3 in which 10% of Pb at the A site was replaced by La). It was formed to a thickness of 100 nm. PLT has an excessive lead composition in which Pb is 5% more than the stoichiometric composition, and the relative permittivity when formed under the above conditions was 180.

[0085] (Formation of the electromechanical conversion layer) The electromechanical conversion layer was formed on the first high-temperature durable layer using a sputtering apparatus. As the target, a sintered body target of PZT (the composition ratio of zirconium (Zr) and titanium (Ti) entering the B site is Zr / Ti = 52 / 48, and Pb entering the A site is 20 mol% excessive) with a larger Pb amount than the stoichiometric composition was used. In a mixed atmosphere of argon and oxygen with a vacuum degree of 0.5 Pa, a high-frequency power of 2000 W was applied while heating the substrate to a temperature of 580 °C to form a 3.0-μm-thick electromechanical conversion layer. PZT has an excessive lead composition in which Pb is 5% more than the stoichiometric composition, and the composition ratio of Zr and Ti was the same as that of the target, 52 / 48. The relative permittivity when formed under the above conditions was 950.

[0086] (Formation of the second high-temperature durable layer) The second high-temperature durability layer was formed up to the electro-mechanical conversion layer in a mixed gas of argon and oxygen with a vacuum degree of 1 Pa using a PLT target having a perovskite structure of a metal oxide containing at least lead (Pb), lanthanum (La), and titanium (Ti) (consisting of (Pb·La)TiO3 in which 10% of Pb at the A site was replaced by La). Similar to the first high-temperature durability layer, a substrate was heated to 550 °C while applying an RF power supply power of 2000 W for film formation, and formed to a thickness of 200 nm.

[0087] (Formation of the second electrode) For the second electrode, a Cu target was used, and a film was formed on the second high-temperature durability layer by applying a DC power supply power of 1000 W in argon gas with a vacuum degree of 0.5 Pa. The thickness of the second electrode was formed to a thickness of 1000 nm.

[0088] In the film formation of the electro-mechanical conversion layer, the film was continuously formed under the above film formation conditions to a target thickness of 3.0 μm in one pass and completed. In this way, the electro-mechanical conversion element 1-1 was fabricated.

[0089] 〈Fabrication of electro-mechanical conversion elements 2-1 to 4-1〉 In the fabrication of the electro-mechanical conversion layer in the electro-mechanical conversion element 1-1, after forming the film to a desired thickness without forming the film to the target thickness at one time, the substrate temperature was once lowered to room temperature (20 °C), then the above cleaning and drying were performed, and then the film was formed in a cycle of heating film formation → cooling → cleaning and drying to form an electro-mechanical conversion layer with the same total thickness. The electro-mechanical conversion elements 2-1 to 4-1 were fabricated in the same manner as the electro-mechanical conversion element 1-1.

[0090] In the electromechanical conversion element 2-1, the total thickness of 3.0 μm was equally divided into two layers for film formation (single split film formation). Specifically, in the case of a single split film formation, first, a film of 1.5 μm was formed, cooled to 20 °C, and then taken out of the chamber. After that, in order to remove foreign substances during film formation, wet rubbing cleaning using a brush was performed. A 5% dilution of Clean Ace (manufactured by AS ONE Corporation), an alkaline cleaning solution, was used as the cleaning solution. After cleaning, the substrate was rinsed with pure water and then sufficiently dried. Then, the substrate was put into the chamber again, and film formation was carried out under the same conditions as the first film formation. The thickness was similarly increased by 1.5 μm to form a 3.0 μm electromechanical conversion layer.

[0091] In the electromechanical conversion element 3-1, the total thickness of 3.0 μm was equally divided into three layers for film formation (double split film formation).

[0092] In the electromechanical conversion element 4-1, the total thickness of 3.0 μm was equally divided into four layers for film formation (triple split film formation).

[0093] [Fabrication of Electromechanical Conversion Element 5-1] In the fabrication of the electromechanical conversion element 1-1, only the electromechanical conversion layer was formed between the first electrode and the second electrode without forming the first and second high-temperature durability layers, and the electromechanical conversion element 5-1 was fabricated in the same manner as the fabrication of the electromechanical conversion element 1-1.

[0094] For each of the electromechanical conversion elements 1-1 to 5-1, two more of each electromechanical conversion element were created under the same conditions as the fabrication of each electromechanical conversion element, for a total of three. That is, a total of 15 electromechanical conversion elements of 1-1 to 1-3, 2-1 to 2-3, 3-1 to 3-3, 4-1 to 4-3, and 5-1 to 5-3 were fabricated.

[0095] [Evaluation of Orientation Degree] XRD measurements were performed on the obtained 15 electromechanical conversion elements. Specifically, using a Rigaku X-ray diffractometer RINT-TTR III, out-of-plane measurement: the orientation degree was evaluated from the diffraction of (001)-(004) with a measurement angle range of 10-110°. When the diffraction peak intensities of the (001) plane, (101) plane, and (111) plane were denoted as I(001), I(101), and I(111), respectively, the orientation degree of the (001) plane represented by {I(001) / (I(001)+I(101)+I(111))}×100% was evaluated. The results are shown in Table I.

[0096] In addition, Fig. 7 shows the number of heating and cooling cycles (split film formation) of the electromechanical conversion layer and the orientation degree (%) of the (001) plane in the XRD measurement. In the figure, ● represents the orientation degree of the electromechanical conversion element *-1, □ represents the electromechanical conversion element *-2, and △ represents the electromechanical conversion element *-3, and * represents 1 to 4. Regarding the electromechanical conversion elements 1-1, 2-1, 3-1, 4-1, and 5-1, the details of the peak intensities of the (001) plane, (101 plane), and (111) plane are shown in Table II below.

[0097] [Table 1]

[0098] [Table 2]

[0099] As can be seen from the electromechanical conversion elements 1-1 to 4-3 in Table 1, by performing split film formation, an orientation degree of 99.0% or more can be obtained, indicating that it is possible to fabricate an electromechanical conversion layer with a high orientation degree. Also, it can be seen that for the electromechanical conversion elements 5-1 to 5-3 without the first and second high-temperature durable layers, both the components and diffraction intensities of different phases increase, and the orientation degree of the (001) plane decreases.

[0100] [Example 2] (Temperature Dependence of Residual Polarization) Figure 3 shows the temperature dependence of the remanent polarization in the electromechanical conversion elements of the electromechanical conversion element 2-1 (the present invention) and the electromechanical conversion element 5-1 (comparative example), which was measured by the method described above. In the electromechanical conversion element of the present invention, even at a high temperature of 50 °C, the remanent polarization is larger than that at room temperature. Also, the remanent polarization at 85 °C also shows a high value with respect to room temperature and satisfies the above-described formula 2. Since the decrease in the remanent polarization during high-temperature driving is small in this way, it can be understood that the deterioration of the piezoelectric characteristics is suppressed even under high-temperature driving conditions, and the decrease in the displacement amount of the piezoelectric body over time is suppressed.

[0101] [Example 3] [Fabrication of Actuator and Inkjet Head] Using each of the fabricated electromechanical conversion elements 1-1 (comparative example), 3-1 (the present invention), and 5-1 (comparative example), a diaphragm and a pressure chamber were formed to fabricate an actuator, and further, a flow path substrate and a nozzle plate were bonded together to fabricate the liquid ejection head shown in FIG. 4 as an inkjet head.

[0102] (Evaluation of Capacitance of One Element of Actuator) The capacitance of one element of the actuator corresponding to each nozzle was measured. The capacitances of one element of the actuators corresponding to the electromechanical conversion elements 1-1, 3-1, and 5-1 were 200 pF, 195 pF, and 285 pF, respectively.

[0103] (Continuous Drive Pulse Drive Durability Test) The inkjet heads having the above electromechanical conversion elements 1-1 (comparative), 3-1 (the present invention), and 5-1 (comparative) were mounted on the image forming apparatus shown in FIGS. 5 and 6, and a pulse drive durability test at 60 kHz was performed by adjusting the waveform so that the initial speed became 7 m / sec in a high-temperature environment of 50 °C. FIG. 8 is a graph showing the relationship between the number of applied pulses and the ejection speed (relative value with respect to the initial speed) when a drive voltage of 10 billion pulses was applied to each inkjet head.

[0104] As is clear from FIG. 8, it can be seen that when the electromechanical conversion element 3-1 is used in an inkjet head and continuously ejected under a high-temperature environment, a decrease in ejection speed over time is suppressed.

Industrial Applicability

[0105] Since the displacement amount of the piezoelectric body over time is suppressed when the electromechanical conversion element of the present invention is continuously pulse-driven for a long time under a high-temperature environment, it can be suitably used for a liquid ejection head that ejects inkjet ink.

Explanation of Signs

[0106] 1 Electromechanical conversion element 2 Substrate 3 First electrode 4 First high-temperature durable layer 5 Electromechanical conversion layer 6 Second high-temperature durable layer 7 Second electrode 51 Pressure chamber 52 Nozzle 53 Nozzle plate 54 Substrate (wall substrate) 55 Diaphragm 56 Adhesion layer 57 First electrode 58 First high-temperature durable layer 59 Electromechanical conversion layer 60 Second high-temperature durable layer 61 Second electrode 62 Electromechanical conversion element 81 Image recording device 82 Printing mechanism unit 83 Paper 84 Paper feed cassette 85 Manual feed tray 86 Paper discharge tray 91 Main guide rod 92 Subordinate guide rod 93 Carriage 94 Liquid ejection head 95 Ink cartridge 97 Main scanning motor 98 Driving pulley 99 Driven pulley 100 Timing belt 101 Paper feed roller 102 Friction pad 103 Guide member 104 Conveyor roller 105 Conveyor roller 106 Tip roller 107 Sub-scanning motor 109 Printing and receiving member 111 Conveyor roller 112 Impulse 113 Paper discharge roller 114 Impulse 115, 116 Guide member 117 Recovery device

Claims

1. An electromechanical conversion element including a first electrode, an electromechanical conversion layer, and a second electrode provided on a substrate, comprising a first high-temperature durability layer containing a metal oxide between the first electrode and the electromechanical conversion layer, and a second high-temperature durability layer containing a metal oxide between the electromechanical conversion layer and the second electrode, wherein the electromechanical conversion layer contains perovskite-type crystals, when the diffraction peak intensities of the (001) plane, (101) plane, and (111) plane in the X-ray diffraction measurement of the electromechanical conversion layer are I(001), I(101), and I(111), respectively, the degree of orientation of the (001) plane represented by {I(001) / (I(001)+I(101)+I(111))}×100% is 99.0% or more, and the electromechanical conversion element is characterized by satisfying the following formula 1 when the remanent polarization at 50°C is Pr(50°C) [μC / cm 2 ] and the remanent polarization at 20°C is Pr(20°C) [μC / cm 2 ]. (Formula 1): Pr(50°C) / Pr(20°C)≥1.00

2. An electromechanical conversion element including a first electrode, an electromechanical conversion layer, and a second electrode provided on a substrate, comprising a first high-temperature durability layer containing a metal oxide between the first electrode and the electromechanical conversion layer, and a second high-temperature durability layer containing a metal oxide between the electromechanical conversion layer and the second electrode, wherein the electromechanical conversion layer contains perovskite-type crystals, when the diffraction peak intensities of the (001) plane, (101) plane, and (111) plane in the X-ray diffraction measurement of the electromechanical conversion layer are I(001), I(101), and I(111), respectively, the degree of orientation of the (001) plane represented by {I(001) / (I(001)+I(101)+I(111))}×100% is 99.0% or more, and the electromechanical conversion element is characterized by satisfying the following formula 2 when the remanent polarization at 85°C is Pr(85°C) [μC / cm 2 ] and the remanent polarization at 20°C is Pr(20°C) [μC / cm 2 ]. (Formula 2): Pr(85°C) / Pr(20°C)≥0.90

3. The electromechanical conversion element according to claim 1 or claim 2, wherein the metal oxides contained in the first high-temperature durability layer and the second high-temperature durability layer each independently contain lead lanthanum titanate (PLT), strontium ruthenium oxide (SRO), lanthanum nickelate (LNO), or lead titanate (PT).

4. The electromechanical conversion element according to any one of claims 1 to 3, wherein the perovskite-type crystal contains lead zirconate titanate (PZT).

5. The electromechanical conversion element according to any one of claims 1 to 4, wherein the relative permittivities of the first high-temperature durable layer and the second high-temperature durable layer are both smaller than the relative permittivity of the electromechanical conversion layer.

6. A method for manufacturing an electromechanical conversion element, which manufactures the electromechanical conversion element according to any one of claims 1 to 5, having an electromechanical conversion layer film-forming step of forming an electromechanical conversion layer on the first high-temperature durable layer, The method for manufacturing an electromechanical conversion element is characterized in that, in the electromechanical conversion layer film-forming step, the step of heating the electromechanical conversion layer to 500 °C or higher and then cooling it to 300 °C or lower is repeated two or more times to form the electromechanical conversion layer.

7. A liquid ejection head comprising the electromechanical conversion element according to any one of claims 1 to 5.

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