Curable resin composition, cured product, and piezoelectric material

Abstract

To provide a piezoelectric material that can achieve both flexibility and piezoelectric properties. [Solution] Piezoelectric particles (A1) having a Curie temperature (Tc) of 0.15 mJ / mg or higher, Epoxy resin (B) and, Hardener (C) and Curable resin composition.

Description

[Technical Field]

[0001] This disclosure relates to curable resin compositions, cured products, and piezoelectric materials. [Background technology]

[0002] Piezoelectric materials are materials that generate voltage in response to strain caused by the application of pressure. Known piezoelectric materials include various polymer components and piezoelectric materials in which piezoelectric particles are added to polymer components. For example, Patent Document 1 discloses a curable composition containing piezoelectric particles and a specific compound. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] International Publication No. 2023-032866 [Overview of the Initiative] [Problems that the invention aims to solve]

[0004] In recent years, there has been a demand for piezoelectric materials with flexibility. Piezoelectric materials generate voltage in response to the strain caused by applying pressure to them. However, it has been found that when piezoelectric materials are flexible, the pressure applied to the piezoelectric material is mitigated by the material's flexibility, which can reduce the expression of piezoelectric properties compared to when pressure is applied to a rigid material. This disclosure aims to provide a piezoelectric material that can achieve both flexibility and piezoelectric properties. [Means for solving the problem]

[0005] The inventors conducted studies to solve the above problems. As a result, they found that the above problems can be solved by the following curable resin composition. Therefore, this disclosure includes the following preferred embodiments. [1] Piezoelectric particles (A1) with a Curie temperature (Tc) of 0.15 mJ / mg or higher, Epoxy resin (B) and, Hardener (C) and Curable resin composition. [2] The curable resin composition according to [1], wherein the curable resin composition is heated at 80°C for 3 hours and at 140°C for 3 hours to cure the cured product, and the tensile modulus of a cured product with a thickness of 200 μm is 100 MPa or less. [3] The curable resin composition according to [1] or [2], wherein the epoxy resin (B) comprises an epoxy resin (B1) having a viscosity of 500 mPa·s or less as measured at 25°C. [4] The epoxy resin (B) is a curable resin composition according to [1] to [3], wherein the epoxy resin (B) comprises an epoxy resin (B2) represented by the following formula (1). [ka] [In equation (1), A is -[(CH2) m ]- represents a divalent alkylene group, where m is an independent integer from 1 to 10. 1 and R 2 Each of these is independently either a hydrogen atom or a glycidyl group, and at least one of them is a glycidyl group. X represents a single bond, -O-, or -OA-, n is an integer from 0 to 20, p is 0 or 1, and q is an integer from 0 to 20. [5] The curable resin composition according to [3] or [4], wherein the ratio of epoxy resin (B1) to the total amount of epoxy resin (B) contained in the curable resin composition is 60 to 100% by mass. [6] The curable resin composition according to any one of [1] to [5], wherein the piezoelectric particle (A1) is barium titanate. [7] The curable resin composition according to any one of [1] to [6], wherein the ratio of piezoelectric particles (A1) to the total amount of piezoelectric particles (A) contained in the curable resin composition is 60 to 100% by mass. [8] The curable resin composition according to any one of [1] to [7], wherein the mass ratio of piezoelectric particles (A1): epoxy resin (B): curing agent (C) contained in the curable resin composition is 65-90:5-30:0.5-5. 〔9〕A curable resin composition according to any one of 〔1〕~〔8〕, having a viscosity of 100 Pa·s or less when measured at 25°C. 〔10〕A cured product of the curable resin composition according to any one of 〔1〕~〔9〕. 〔11〕A piezoelectric body comprising piezoelectric particles (A1) having a Curie temperature (Tc) of 0.15 mJ / mg or more, and an epoxy binder, having a tensile elastic modulus of 100 MPa or less at 25°C, and a piezoelectric constant d 33 of 30 or more.

Advantages of the Invention

[0006] According to the present disclosure, it is possible to provide a piezoelectric material capable of achieving both flexibility and piezoelectric properties of the piezoelectric material.

Modes for Carrying Out the Invention

[0007] Hereinafter, embodiments of the present disclosure will be described in detail. Note that the scope of the present invention is not limited to the embodiments described here, and various modifications can be made without departing from the spirit of the present invention. In this specification, the numerical range indicated by "~" includes its upper and lower limits.

[0008] The curable resin composition of the present disclosure is a curable resin composition containing piezoelectric particles (A1) having a Curie temperature (Tc) of 0.15 mJ / mg or more, an epoxy resin (B), and a curing agent (C).

[0009] (Piezoelectric Particles) The curable resin composition contains piezoelectric particles (A1) having a Curie temperature (Tc) of 0.15 mJ / mg or higher. Here, piezoelectric particles are particles that possess piezoelectric properties, and examples include piezoelectric ceramics having a perovskite crystal structure. Examples of piezoelectric particles with a Curie temperature of 0.15 mJ / mg or higher include barium titanate, lead zirconate titanate, potassium sodium niobate, lithium tantalate, and lithium tantalate. The curable resin composition of this disclosure may contain one type of piezoelectric particle or two or more types of piezoelectric particles, but it is a composition that contains at least piezoelectric particles (A1) having a Curie temperature (Tc) of 0.15 mJ / mg or higher.

[0010] The Curie temperature (Tc) of the piezoelectric particle (A1) is 0.15 mJ / mg or higher from the viewpoint of improving piezoelectric properties, preferably 0.15 to 2.00 mJ / mg, more preferably 0.30 to 1.50 mJ / mg, and even more preferably 0.45 to 1.00 mJ / mg. The Curie temperature of the piezoelectric particle can be measured by differential scanning calorimetry (DSC). Furthermore, known methods can be applied to adjust the Curie temperature (Tc) within the above range, and in particular, in the case of piezoelectric ceramics having a perovskite crystal structure represented by the chemical formula ABO3, this includes changing the metal atoms indicated by A or B and adjusting their weight ratio. Hereinafter, A(R) represents the metal atom located at the vertex of the unit crystal structure, B(M) represents the metal atom located at the body center of the unit crystal structure, and O(O) represents the oxygen located at the midpoint of each side.

[0011] The average particle diameter (median diameter, D) of piezoelectric particles. 50 The average particle size (D) is preferably 0.1 to 20 μm, more preferably 0.2 to 17.5 μm, and even more preferably 0.5 to 15 μm, from the viewpoint of achieving both flexibility and piezoelectric properties of the piezoelectric material. 50 The average particle diameter (D) can be measured by a particle size distribution analyzer. The curable resin composition may contain one type of piezoelectric material, but from the viewpoint of improving the fluidity of the curable resin composition and achieving both flexibility and piezoelectric properties of the piezoelectric material, the average particle diameter (D) can be measured by a particle size distribution analyzer. 50 Preferably, the material includes two or more piezoelectric materials that are different from each other.

[0012] The content of piezoelectric particles (A1) in the curable resin composition of this disclosure is preferably 50 to 95% by mass, more preferably 60 to 92% by mass, and even more preferably 65 to 90% by mass or more, relative to the total amount of the curable resin composition, from the viewpoint of achieving both flexibility and piezoelectric properties of the piezoelectric material.

[0013] The ratio of piezoelectric particles (A1) to the total amount of piezoelectric particles (A) contained in the curable resin composition is preferably 60 to 100% by mass, more preferably 70 to 100% by mass, even more preferably 80 to 100% by mass, and even more preferably 90 to 100% by mass, from the viewpoint of achieving both flexibility and piezoelectric properties of the piezoelectric material.

[0014] From the viewpoint of the piezoelectric properties of the piezoelectric material, it is preferable that the crystallites constituting each particle are large in the piezoelectric particles (A1) contained in the curable resin composition in order to obtain a high heat value Tc. A crystallite refers to a region in a material having a crystalline structure in which a single crystal lattice is perfectly arranged. For example, the average size of the crystallites constituting the piezoelectric particle (A) may be 235 Å or more, more preferably 240 Å. There is no particular upper limit to the crystallite size, but generally, based on the crystallite size of piezoelectric particles obtained, it is about 400 Å or less. The crystallite size of piezoelectric particles can be measured by X-ray diffraction (XRD).

[0015] (Epoxy resin) The curable resin composition of this disclosure further comprises an epoxy resin (B). The epoxy resin (B) is not particularly limited as long as it is a resin having epoxy groups. Examples of epoxy resins (B) include polymethylene oxide type epoxy resins, polyol type epoxy resins, bisphenol A type epoxy resins, bisphenol F type epoxy resins, cycloalkyl type epoxy resins, phenol novolac type epoxy resins, dimer acid modified epoxy resins, and silicone modified epoxy resins. The curable resin composition of this disclosure may contain one type of epoxy resin (B) or two or more types of epoxy resins (B).

[0016] The viscosity of epoxy resin (B) is preferably 10 to 1000 mPa·s, more preferably 100 to 900 mPa·s, and even more preferably 200 to 750 mPa·s, measured at 25°C, from the viewpoint of achieving both flexibility and piezoelectric properties of the piezoelectric material. The viscosity of epoxy resin (B) can be measured using an E-type viscometer.

[0017] The epoxy equivalent of epoxy resin (B) is preferably 100 to 1,000, more preferably 200 to 800, even more preferably 250 to 700, and even more preferably 300 to 600, from the viewpoint of achieving both flexibility and piezoelectric properties in the piezoelectric material. The epoxy equivalent of epoxy resin (B) can be calculated from the number of functional groups present in epoxy resin (B) and the weight-average molecular weight of epoxy resin (B).

[0018] The weight-average molecular weight of epoxy resin (B) is preferably 100 to 5,000, more preferably 200 to 2,500, and even more preferably 300 to 1,000, from the viewpoint of achieving both flexibility and piezoelectric properties in the piezoelectric material. The weight-average molecular weight of epoxy resin (B) can be measured by gel permeation chromatography (GPC).

[0019] In a preferred embodiment, the epoxy resin (B) includes an epoxy resin (B1) having a viscosity of 500 mPa·s or less when measured at 25°C. From the viewpoint of achieving both flexibility and piezoelectric properties of the piezoelectric material, the viscosity of the epoxy resin (B1) is preferably 10 to 400 mPa·s, more preferably 100 to 300 mPa·s, when measured at 25°C. The viscosity of the epoxy resin (B1) can be measured using an E-type viscometer.

[0020] The epoxy equivalent of epoxy resin (B1) is preferably 100 to 1,000, more preferably 200 to 800, even more preferably 250 to 700, and even more preferably 300 to 600, from the viewpoint of achieving both flexibility and piezoelectric properties in the piezoelectric material. The epoxy equivalent of epoxy resin (B1) can be calculated from the number of functional groups present in epoxy resin (B1) and the weight-average molecular weight of epoxy resin (B1).

[0021] From the viewpoint of achieving both flexibility and piezoelectric properties of the piezoelectric material, the weight-average molecular weight of the epoxy resin (B1) is preferably 100 to 5,000, more preferably 200 to 2,500, and still more preferably 300 to 1,000. The weight-average molecular weight of the epoxy resin (B) can be measured by gel permeation chromatography (GPC).

[0022] The content of the epoxy resin (B) in the curable resin composition is preferably 7 to 30% by mass, more preferably 8 to 20% by mass, and still more preferably 9 to 15% by mass with respect to the total amount of the curable resin composition.

[0023] From the viewpoint of achieving both flexibility and piezoelectric properties of the piezoelectric material, the content of the epoxy resin (B1) in the curable resin composition is preferably 7 to 40% by mass, more preferably 8 to 35% by mass, and still more preferably 9 to 30% by mass with respect to the total amount of the curable resin composition.

[0024] From the viewpoint of achieving both flexibility and piezoelectric properties of the piezoelectric material, the ratio of the epoxy resin (B1) to the total amount of the epoxy resin (B) contained in the curable resin composition is preferably 60 to 100% by mass, more preferably 70 to 100% by mass, and still more preferably 80 to 100% by mass.

[0025] In a preferred embodiment, the epoxy resin (B) includes an epoxy resin (B2) represented by the following formula (1).

Chemical formula

[0026] From the viewpoint of availability and manufacturability, in the epoxy resin (B2) relating to the above formula (1), n ​​is preferably 0 to 10 and q is preferably 0 to 10. Furthermore, the epoxy resin (B2) may be a mixture of multiple epoxy resins (B2) having different structures.

[0027] The epoxy equivalent and weight-average molecular weight of epoxy resin (B2), the content of epoxy resin (B2) in the curable resin composition, and the ratio of epoxy resin (B2) to the total amount of epoxy resin (B) contained in the curable resin composition are the same as those of epoxy resin (B1). Furthermore, epoxy resin (B2) may be epoxy resin (B1).

[0028] The structure of epoxy resins can be determined by nuclear magnetic resonance (NMR) measurements.

[0029] (Hardening agent) The curable resin composition of this disclosure further comprises a curing agent (C). The curing agent (C) is not particularly limited as long as it is a component that can cure epoxy resin, but examples include amine-based curing agents, thiol-based curing agents, imidazole-type curing agents, acid anhydride-based curing agents, polyamide-based curing agents, urea-type curing agents, cationic curing agents, and metal salt curing agents. The curable resin composition of this disclosure may contain one type of curing agent or two or more types of curing agents. The curing agent (C) is preferably an amine-based curing agent, more preferably an imidazole-type curing agent or a thiol-based curing agent. From the viewpoint of the stability of the composition, the content of the curing agent (C) is preferably 0.1 to 10% by mass, more preferably 0.5 to 7.5% by mass, and even more preferably 1.0 to 5% by mass, based on the total amount of the curable resin composition. Furthermore, from the viewpoint of the curability of the curable resin composition, the content of the curing agent (C) is preferably 1 to 60% by mass, more preferably 2.5 to 45% by mass, and even more preferably 5 to 30% by mass, relative to the total amount of epoxy resin (B) contained in the curable resin composition.

[0030] (Other ingredients) The curable resin composition of this disclosure may further contain other components in addition to the components described above. Examples of other components include dispersants, curable resins other than epoxy resins, curable monomers, and silane coupling agents.

[0031] Dispersants are components that can improve the dispersibility of piezoelectric particles in a curable resin composition. Examples of dispersants include surfactants such as anionic surfactants, cationic surfactants, nonionic surfactants, and amphoteric surfactants, as well as polysorbates, polycarboxylic acids, and silane coupling agents. The dispersant is preferably a nonionic surfactant or polysorbate, and more preferably polysorbate. The content of the dispersant in the curable resin composition is preferably 0.01 to 10% by mass, more preferably 0.05 to 5% by mass, and even more preferably 0.1 to 2.5% by mass, based on the total amount of the curable resin composition.

[0032] The curable resin composition of this disclosure may contain curable resins other than epoxy resins. Examples of other curable resins include acrylic resins, polyurethane resins, and silicone resins. From the viewpoint of achieving both flexibility and piezoelectric properties of the piezoelectric material, the content of the curable resin other than epoxy resin is preferably 0 to 5% by mass, more preferably 0 to 2.5% by mass, and even more preferably 0 to 1% by mass, relative to the total amount of the curable resin composition.

[0033] The curable resin composition of this disclosure may further contain a curable monomer. Examples of curable monomers include monomers having a (meth)acrylate group, monomers having an oxetane group, and monomers having a maleimide group. From the viewpoint of achieving both flexibility and piezoelectric properties of the piezoelectric material, it is preferable to have a low content of curable monomers, preferably 0 to 5% by mass, more preferably 0 to 2.5% by mass, and even more preferably 0 to 1% by mass, relative to the total amount of the curable resin composition.

[0034] (Curable resin composition) The curable resin composition of this disclosure is a composition comprising piezoelectric particles (A1) having a specific Curie temperature, an epoxy resin (B), and a curing agent (C). The total amount of piezoelectric particles (A1), epoxy resin (B), and curing agent (C) contained in the curable resin composition of this disclosure is preferably 90 to 100% by mass, more preferably 95 to 100% by mass, and even more preferably 99 to 100% by mass, relative to the total amount of the curable resin composition, from the viewpoint of achieving both flexibility and piezoelectric properties of the piezoelectric material.

[0035] The mass ratio of piezoelectric particles (A1): epoxy resin (B): curing agent (C) contained in the curable resin composition of this disclosure is preferably 65-90:5-30:0.5-5, and more preferably 67-87:9-29:1-4, from the viewpoint of achieving both flexibility and piezoelectric properties of the piezoelectric material.

[0036] The average Tc heat quantity of piezoelectric particles, calculated by weight-averaging the Curie temperatures of the piezoelectric particles contained in the curable resin composition of this disclosure, is preferably 0.15 to 2.00 mJ / mg, more preferably 0.30 to 1.50 mJ / mg, and even more preferably 0.45 to 1.00 mJ / mg, from the viewpoint of achieving both flexibility and piezoelectric properties of the piezoelectric material.

[0037] In the curable resin composition of this disclosure, the cured product of the epoxy resin (B), which is the curable resin, is a resin that acts as a binder. The dielectric constant of the binder alone of the curable resin composition is preferably 3.1 or higher, more preferably 3.5 or higher, and even more preferably 4.0 or higher, from the viewpoint of achieving both flexibility and piezoelectric properties of the piezoelectric material. The upper limit of the dielectric constant is not particularly limited and may be, for example, 7.0 or lower. The dielectric constant of the binder alone can be measured using an impedance analyzer with a measurement sample, using a cured product obtained by curing the curable resin composition, from which solid components such as piezoelectric particles have been removed, by heating at 80°C for 3 hours and at 140°C for 3 hours.

[0038] The curable resin composition of this disclosure has a tensile modulus of 100 MPa or less, more preferably 75 MPa or less, and even more preferably 50 MPa or less, measured using a cured product with a thickness of 200 μm obtained by heating the resin composition at 80°C for 3 hours and then at 140°C for 3 hours. The lower limit of the tensile modulus of the cured product is not particularly limited, but may be, for example, 0.1 MPa or more. The tensile modulus of the cured product can be measured, for example, by the method described in the examples.

[0039] The curable resin composition of this disclosure has a viscosity, measured at 25°C, preferably 100 Pa·s or less, more preferably 20 to 100 Pa·s, even more preferably 25 to 80 Pa·s, and even more preferably 27.5 to 60 Pa·s. The viscosity of the curable resin composition can be measured using a rheometer. Specifically, a 25 mm parallel plate, 25°C, and a rotation speed of 5 min⁻¹ are used. -1 The measurement is started at [time], and the viscosity measured 180 seconds after the start of the measurement may be used.

[0040] (Method for preparing a curable resin composition) The curable resin composition of this disclosure can be produced by mixing the above components in a conventionally known manner.

[0041] (Cured product of a curable resin composition) This disclosure also provides cured products of curable resin compositions. Cured products of curable resin compositions can be prepared by heating the curable resin composition of this disclosure to cure the curable resin contained in the curable resin composition. The curing conditions are not particularly limited, but can be prepared by heating preferably at 50 to 200°C, more preferably at 65 to 160°C, for preferably 0.5 to 6 hours, more preferably 1 to 4 hours.

[0042] (Piezoelectric material) This disclosure also provides a piezoelectric material which is a cured product of the above-mentioned curable resin composition. In a preferred embodiment, the piezoelectric material of this disclosure comprises piezoelectric particles (A1) having a Curie temperature (Tc) of 0.15 mJ / mg or higher and an epoxy binder, having a tensile modulus of 100 MPa or less at 25°C, and a piezoelectric constant d 33 The piezoelectric material has a value of 30 or more. The piezoelectric particle (A1) is the piezoelectric particle (A1) described for the curable resin composition. The epoxy binder is the curable resin of epoxy resin (B) described for the curable resin composition.

[0043] The method for manufacturing a piezoelectric material is not particularly limited, but for example, a piezoelectric material can be manufactured by generating piezoelectric properties through the steps of applying the curable resin composition of the present disclosure onto a substrate, curing the epoxy resin (B), and applying an AC voltage and / or DC voltage to perform polarization treatment.

[0044] The piezoelectric properties of the piezoelectric material disclosed herein are, for example, the piezoelectric constant d 33 It can be expressed by the piezoelectric constant d described in the embodiments below. 33 The piezoelectric constant d is measured by the measurement method and preferably 30 or more, more preferably 60 or more, and even more preferably 100 or more. 33 It is preferable to have a piezoelectric constant d. 33 The upper limit is not particularly limited and may be, for example, 200 or less.

[0045] The piezoelectric material of this disclosure is a piezoelectric material that combines flexibility and piezoelectric properties, and is therefore suitable as a component for, for example, pressure sensors, pyroelectric sensors, and flexible memory elements, and is particularly suitable as a component for wearable sensors, actuators, planar speakers, transducers, and piezoelectric wires.

[0046] The reason why the piezoelectric material disclosed herein can achieve both flexibility and piezoelectric properties is not limited by theory, but stems from the inventors' discovery that, when the size of piezoelectric particles is the same, larger crystallites constituting each particle result in higher piezoelectric performance. First, the inventors found that the Curie temperature (Tc) of a piezoelectric particle is related to the size of the crystallites constituting each particle. More specifically, a larger crystallite size in each piezoelectric particle indicates that each particle is composed of large crystallites, and the number of crystallites constituting one particle is small. As a result, the surface area of ​​the crystallites of the particle is small, and heat is not easily transferred, so the larger the crystallites constituting each piezoelectric particle, the greater the heat energy of the Curie temperature (Tc) of the piezoelectric particle. In other words, piezoelectric particles with a low Curie temperature (Tc) have a large number of crystallites constituting one particle, making them more susceptible to strain during polarization treatment, increasing the probability that the polarization direction of each crystallite will not be constant, and making it easier for the polarization of each crystallite within a single particle to cancel each other out. On the other hand, if the size of the crystallites constituting each piezoelectric particle is large, the probability of the polarization direction of each crystallite being random is low, and cancellation of the polarization of each crystallite within a single particle is less likely to occur, and as a result, each piezoelectric particle is thought to have high piezoelectric performance. Furthermore, piezoelectric particles tend to exhibit high piezoelectric properties when polarized in an environment with a high dielectric constant, for example, in a resin with a high dielectric constant. The cured product of the epoxy binder constituting the curable resin composition of this disclosure exhibits a relatively high dielectric constant, which is thought to contribute to improving the polarization amount of the piezoelectric particles. Moreover, the piezoelectric material of this disclosure is flexible but does not exhibit plastic (irreversible) behavior when an external force is applied, and the stress during elastic deformation is greater on the piezoelectric particles (because the stress is not easily absorbed by the binder), so it is thought that flexibility and piezoelectric properties can be achieved at the same time. [Examples]

[0047] Next, the present invention will be described in more detail with reference to examples, but these examples are for illustrative purposes only and do not limit the present invention in any way. Also, unless otherwise specified, "%" and "parts" in the examples mean "mass%" and "parts by mass," respectively. Furthermore, the compounds shown below do not necessarily follow IUPAC nomenclature.

[0048] First, the materials used in the examples and comparative examples are shown below.

[0049] <Piezoelectric particle A> TIFF2026093686000003.tif103164

[0050] <Epoxy resin B> B-1: Liquid epoxy resin, product name jER YX7400N (manufactured by Mitsubishi Chemical Corporation), viscosity (25℃) 0.2 Pa·s, weight-average molecular weight 880 g / mol, epoxy equivalent 440 g / eq B-2: Bisphenol A diglycidyl ether, product name jER828EL (manufactured by Mitsubishi Chemical Corporation), viscosity 13 Pa·s, weight-average molecular weight 380 g / mol, epoxy equivalent 190 g / eq

[0051] <Hardening agent C> C-1: Pentaerythritol tetrakis(3-mercaptobutyrate), product name Karenz MT PE1 (manufactured by Resonac Co., Ltd.) C-2: 1-Benzyl-2-phenylimidazole, product name: Curesol (manufactured by Shikoku Chemicals Co., Ltd.) C-3: Metaxylenediamine, product name MXDA (manufactured by Mitsubishi Gas Chemical Company, Inc.)

[0052] <Polymerizable compound D> D-1: Acryloyl-terminated polyacrylate, product name KANEKA XMAP RC100C (manufactured by Kaneka Corporation) D-2: Hydrogenated polybutadiene diacrylate (SPBDA), synthesized based on Synthesis Example 1 described later. D-3: Isodecyl acrylate, product name IDAA (manufactured by Osaka Organic Chemical Industry Co., Ltd.) D-4: 4-Hydroxybutyl acrylate, product name 4-HBA (manufactured by Osaka Organic Chemical Industry Co., Ltd.) D-5: Acryloylmorpholine, product name ACMO (manufactured by KJ Chemicals Co., Ltd.) D-6: 2-Acryloyloxyethyl succinic acid, product name HOA-MS (manufactured by Kyoeisha Chemical Co., Ltd.)

[0053] <Polymerization initiator E> E-1: t-butyl=2-ethylperoxyhexanoate, product name Perbutyl O (manufactured by NOF Corporation) <Dispersant F (surfactant)> F-1: Sorbitan trioleate, product name: Leodor SP-O30V (manufactured by Kao Corporation)

[0054] The physical properties of piezoelectric particles, epoxy resin, resin composition, or cured resin composition were measured using the following method.

[0055] <Curie temperature> The Curie temperature of each piezoelectric particle A described above was measured by differential scanning calorimetry (DSC). Specifically, 10 mg of each piezoelectric particle was weighed, placed in an aluminum pan, and heated from 30°C to 200°C at a rate of 10°C / min to measure the Curie temperature. The heat quantity was obtained by integrating the DSC curve of the Curie temperature and dividing it by the weight. <Tc calorific value (average Tc) of piezoelectric particles> The average Tc heat quantity of piezoelectric particles A contained in each resin composition is shown in Table 1, where the Curie temperature of the piezoelectric particle is used as the average Tc heat quantity if the resin composition contains only one type of piezoelectric particle. If the resin composition contains two or more types of piezoelectric particles, the Curie temperature (Tc) of the piezoelectric particles contained in the examples and comparative examples, measured as described above, is weighted averaged based on their blending ratios and is shown in Tables 1 and 2 as the "Tc heat quantity of piezoelectric particles."

[0056] <Weight average molecular weight> The weight-average molecular weight was measured by gel permeation chromatography (GPC). Specifically, a 0.5% by mass solution obtained by dissolving the resin in tetrahydrofuran was used as the sample. The measurement conditions were as follows: Equipment: Manufactured by Tosoh Corporation, Part Number: HLC-8320GPC Column: Manufactured by Tosoh Corporation, Part Number: TSKgel SuperH2500 Eluent: Tetrahydrofuran Flow rate: 0.6mL / min Temperature: 40℃ Detector: RI Molecular weight standard: Standard polystyrene

[0057] <Viscosity of epoxy resin B> The viscosity of epoxy resin B was measured using an E-type viscometer (TOKI Sangyo Co., Ltd., TVE-100EH). Measurements were taken at 1°34'×R24, 25℃, and a rotation speed of 20 min. -1 Measurement was started, and the viscosity 180 seconds after the start of measurement was defined as the viscosity of epoxy resin B.

[0058] <Synthesis Example 1> (Synthesis of bisacrylated hydrogenated polybutadiene (SPBDA)) In a 300 mL four-necked flask equipped with a Dean-Stark splitter and stirrer, 100.0 g of terminally hydroxyl-modified polybutadiene (hydrogenation rate 97% or higher: CRAY VALLEY "HLBH-P2000"), 23.6 g of methyl acrylate, 50.0 g of n-hexane, and 0.2 g of di-n-octyl tin oxide were added. The reaction was carried out at reflux temperature for 8 hours, while removing the methanol produced. After the reaction was complete, the mixture was concentrated to obtain 100.5 g of bisacrylated hydrogenated polybutadiene as a pale yellow viscous liquid. The weight-average molecular weight (Mw) of the obtained bisacrylated hydrogenated polybutadiene, determined by GPC, was 4,400.

[0059] <Preparation of curable resin composition> The curable resin compositions for each example and comparative example were prepared by mixing each component at room temperature according to the formulations shown in Tables 1 and 2 below, and the viscosity was measured under the conditions described later. The amounts of each component shown in the tables represent mass % of the total curable resin composition (excluding the solvent). Furthermore, the Tc heat quantity of the piezoelectric particles contained in each example and comparative example is a theoretical value (average Tc heat quantity) calculated by weighting the Curie temperature (Tc) of each piezoelectric particle contained in each example and comparative example and their mixing ratio.

[0060] <Viscosity> The viscosity of each curable resin composition obtained above was measured using a rheometer (Anton Paar, MCR 302). Measurement was started using a 25 mm parallel plate at 25°C and a rotation speed of 5 min-1, and the viscosity at 180 seconds from the start of measurement was taken as the viscosity of each curable resin composition. The results are shown in Tables 1 and 2.

[0061] <Measurement of properties of cured material> The following tests were performed using each of the curable resin compositions obtained above, and the properties of the cured products were measured. Details of each test are described below, and the results are shown in Tables 1 and 2.

[0062] (Piezoelectric constant d) 33 ) Preparation of test specimens Each curable resin composition obtained above was applied to a stainless steel panel (MiSUMi Co., Ltd., material: SUS304, 100 mm x 200 mm flat plate) using an applicator with a gap size of 400 μm. The panels were then left to stand for 3 hours in a hot air dryer (ESPEC Corporation, product name: LC-113) set to 80°C, and then the temperature was raised to 140°C and left to stand for another 3 hours. After that, the panels were slowly cooled to room temperature to form test pieces (cured products) corresponding to each example and comparative example. The thickness of the test pieces was measured using a coolant-proof micrometer (Mitutoyo Corporation, product name: MDC-25MX), and all were found to be approximately 200 μm.

[0063] Polarization treatment Each of the test specimens obtained above was attached to an earth electrode, and polarization treatment was performed by applying a voltage of -12kV for 120 minutes using an electret processing device (manufactured by Wedge).

[0064] Piezoelectric constant d 33 Measurement After removing each polarized test specimen from the stainless steel panel, nine points were selected within a 50mm x 50mm area of ​​the specimen, such that each point was at least 15mm apart, and the piezoelectric constant d was measured. 33 The piezoelectric constant was measured using a piezoelectric constant measuring device (manufactured by Lead Techno, product name: LPF-02). Specifically, the measurement was performed according to the following procedure. (1) The membrane was held between the measuring probes. (2) The load applied to the membrane from the measuring probe was set to 1N and left undisturbed. (3) The amount of charge A generated when a force of 1 N was applied was measured. (4) The load applied to the membrane from the measuring probe was increased by 3N, and the load applied to the membrane from the measuring probe was set to 4N. (5) The amount of charge B generated when a force of 4N was applied was measured. (6) The load applied to the membrane from the measuring probe was reduced by 3N to 1N. (7) Repeat steps (3) to (6) above four times. The average of the difference (AB) between the measured charge amounts A and B measured in the 2nd to 4th steps is taken as the charge amount of the film in each example and comparative example. Divide this average charge amount by the measurement load (3N) to obtain the piezoelectric constant d of each test piece. 33 The following was calculated. The results are shown in Tables 1 and 2.

[0065] (Tensile modulus of elasticity) Preparation of test specimens The above piezoelectric constant d 33 After the measurement was performed on each test piece, each piece was punched out into a dumbbell shape (Type 7) as specified in JIS K6251 (2017) 6.1 to obtain test pieces for measuring the tensile modulus.

[0066] Measurement of Tensile Modulus Each test specimen obtained as described above was mounted on a tensile testing machine (A&D Co., Ltd., model number: Tensilon RTG-1310) at 25°C with a chuck distance of 19 mm. A tensile load was applied at a tensile speed of 50 mm / min until the specimen fractured, and the tensile modulus was calculated from the slope of the tensile strength between 3% and 5% elongation. The results are shown in Tables 1 and 2.

[0067] (Tensile modulus and piezoelectric constant d) 33 (Evaluation based on relationship with) Tensile modulus and piezoelectric constant d 33 In light of the relationship, the test specimens for each example and comparative example were evaluated according to the following criteria. Note that the tensile modulus and piezoelectric constant d 33 The relationship between the piezoelectric particles and the resin composition varies depending on the content of the piezoelectric particles and the application in which the piezoelectric material is used. Therefore, the relationship described below is not necessarily desirable. However, in this application, in order to compare the effects of resin compositions containing piezoelectric particles at similar concentrations, the following criteria were used for evaluation. (1) When the tensile modulus is less than 5 A: Piezoelectric constant d 33 15 or more B: Piezoelectric constant d 33 less than 15 (2) When the tensile modulus is 5 or more but less than 25 S: piezoelectric constant d 33 80 or more A: Piezoelectric constant d 33 30 or more B: Piezoelectric constant d 33 less than 30 (3) When the modulus of elasticity is 25 or more but less than 50 S: piezoelectric constant d 33 80 or more A: Piezoelectric constant d 33 50 or more B: Piezoelectric constant d 33 less than 50 (4) When the modulus of elasticity is 50 or more A: Piezoelectric constant d 33 60 or more B: Piezoelectric constant d 33 less than 60

[0068] (cracked) Each test specimen was prepared in the same manner as the test specimens used for measuring the tensile modulus of elasticity described above. The specimen was then held at both ends and bent until the plate sections at both ends were parallel. The state of the specimen was evaluated according to the following criteria. ○: No cracks were observed visually. ×: Cracks were observed visually. No cracks were observed in the specimens obtained in Examples 1-7 and 9-15, confirming high toughness. However, cracks were observed in the specimen from Example 8. No cracks were observed in the specimens obtained in Comparative Examples 1-5.

[0069] <Dielectric constant of binder resin> After preparing a resin composition that does not contain piezoelectric particles A, a cured product was prepared as described above and measured with an impedance analyzer (AMETEK, part number 1260A) to obtain a dielectric constant of 1 kHz.

[0070] [Table 1]

[0071] [Table 2]

Claims

1. Piezoelectric particles (A1) with a Curie temperature (Tc) of 0.15 mJ / mg or higher, Epoxy resin (B) and Hardener (C) and Curable resin composition.

2. The curable resin composition according to claim 1, wherein the curable resin composition is heated at 80°C for 3 hours and at 140°C for 3 hours to cure the curable resin composition, and the tensile modulus of a cured product with a thickness of 200 μm is 100 MPa or less.

3. The curable resin composition according to claim 1, wherein the epoxy resin (B) comprises an epoxy resin (B1) having a viscosity of 500 mPa·s or less as measured at 25°C.

4. The curable resin composition according to claim 1, wherein the epoxy resin (B) comprises an epoxy resin (B2) represented by the following formula (1). 【Chemistry 1】 [In equation (1), A is -[(CH ２ ) ｍ ] is a divalent alkylene group, where m is an integer from 1 to 10, independently. １ and R ２ Each of these is independently either a hydrogen atom or a glycidyl group, and at least one of them is a glycidyl group. X represents a single bond, -O-, or -O-A-, n is an integer from 0 to 20, p is 0 or 1, and q is an integer from 0 to 20.

5. The curable resin composition according to claim 3, wherein the ratio of epoxy resin (B1) to the total amount of epoxy resin (B) contained in the curable resin composition is 60 to 100% by mass.

6. The curable resin composition according to claim 1 or 2, wherein the piezoelectric particle (A1) is barium titanate.

7. The curable resin composition according to claim 1 or 2, wherein the ratio of piezoelectric particles (A1) to the total amount of piezoelectric particles (A) contained in the curable resin composition is 60 to 100% by mass.

8. The curable resin composition according to claim 1 or 2, wherein the mass ratio of piezoelectric particles (A1): epoxy resin (B): curing agent (C) contained in the curable resin composition is 65 to 90: 5 to 30: 0.5 to 5.

9. A curable resin composition according to claim 1 or 2, having a viscosity of 100 Pa·s or less as measured at 25°C.

10. A cured product of the curable resin composition according to claim 1 or 2.

11. Piezoelectric particles (A1) with a Curie temperature (Tc) of 0.15 mJ / mg or higher, Contains an epoxy binder, The tensile modulus is 100 MPa or less at 25°C. Piezoelectric constant d ３３ A piezoelectric material in which the value is 30 or more.

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