Curable resin composition, cured product, and piezoelectric body

Abstract

Provided is a piezoelectric material that can balance softness and piezoelectric properties. A curable resin composition includes piezoelectric particles (A1) having a Curie temperature (Tc) of 0.15 mJ / mg or more, an epoxy resin (B), and a curing agent (C).

Description

Technical Field

[0001] This disclosure relates to curable resin compositions, cured products, and piezoelectrics. Background Technology

[0002] Piezoelectric materials are materials that generate voltage based on the strain produced by applied pressure. Various polymer components and piezoelectric materials obtained by adding piezoelectric particles to polymer components are known as piezoelectric materials. For example, Patent Document 1 discloses a curable composition containing piezoelectric particles and a specific compound.

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: International Publication No. 2023-032866 Summary of the Invention

[0006] In recent years, there has been a demand for piezoelectric materials with flexibility. Piezoelectric materials generate voltage based on the strain produced when pressure is applied to them. However, it is known that when a piezoelectric material is flexible, the pressure applied to it is mitigated due to the material's flexibility, and therefore, compared to applying pressure to a rigid material, the performance of its piezoelectric properties is sometimes reduced. The objective of this disclosure is to provide a piezoelectric material that can balance the flexibility and piezoelectric properties of a piezoelectric material.

[0007] The inventors conducted research to solve the aforementioned problems. As a result, they discovered that the aforementioned problems can be solved according to the following curable resin composition. Therefore, this disclosure includes the following preferred embodiments.

[0008] [1] A curable resin composition comprising:

[0009] Piezoelectric particles (A1) with a Curie temperature (Tc) of 0.15 mJ / mg or higher.

[0010] Epoxy resin (B), and

[0011] Curing agent (C).

[0012] [2] According to the curable resin composition of [1], wherein the tensile modulus of the cured material with a thickness of 200 μm obtained by heating the curable resin composition at 80°C for 3 hours and at 140°C for 3 hours is 100 MPa or less.

[0013] [3] The curable resin composition according to [1] or [2], wherein the epoxy resin (B) comprises an epoxy resin (B1) having a viscosity of less than 500 mPa·s when measured at 25°C.

[0014] [4] The curable resin composition according to [1] to [3], wherein the epoxy resin (B) comprises the epoxy resin (B2) represented by the following formula (1).

[0015]

[0016] In equation (1), A is - [(CH2)] m ] - represents a divalent alkylene group, where m is an independent integer from 1 to 10. R 1 and R 2 Each atom is independently a hydrogen atom or a glycidyl group, at least one of which 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.

[0017] [5] The curable resin composition according to [3] or [4], wherein the ratio of the epoxy resin (B1) to the total amount of epoxy resin (B) contained in the curable resin composition is 60 to 100 by mass.

[0018] [6] The curable resin composition according to any one of [1] to [5], wherein the piezoelectric particles (A1) are barium titanate.

[0019] [7] The curable resin composition according to any one of [1] to [6], wherein the ratio of the above-mentioned piezoelectric particles (A1) to the total amount of piezoelectric particles (A) contained in the curable resin composition is 60 to 100 by mass.

[0020] [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) in the curable resin composition is 65 to 90: 5 to 30: 0.5 to 5.

[0021] [9] The curable resin composition according to any one of [1] to [8], wherein the viscosity is less than 100 Pa·s when measured at 25°C.

[0022]

[10] A cured product of any one of the curable resin compositions described in [1] to [9].

[0023]

[11] A piezoelectric element comprising:

[0024] Piezoelectric particles (A1) with a Curie temperature (Tc) of 0.15 mJ / mg or higher, and

[0025] Epoxy adhesives;

[0026] The tensile modulus of elasticity of the aforementioned piezoelectric materials is below 100 MPa at 25°C.

[0027] piezoelectric constant d 33 It is above 30.

[0028] According to this disclosure, a piezoelectric material that can combine the flexibility and piezoelectric properties of a piezoelectric material can be provided. Detailed Implementation

[0029] The embodiments of this disclosure will now be described in detail. It should be noted that the scope of this invention is not limited to the embodiments described herein, and various modifications can be made without departing from the spirit of the invention. It should also be noted that the range of values ​​indicated by “~” in this specification includes both the upper and lower limits.

[0030] The curable resin composition disclosed herein is a curable resin composition comprising piezoelectric particles (A1) having a Curie temperature (Tc) of 0.15 mJ / mg or higher, epoxy resin (B), and curing agent (C).

[0031] (Piezoelectric particles)

[0032] The curable resin composition comprises piezoelectric particles (A1) with a Curie temperature (Tc) of 0.15 mJ / mg or higher. Here, piezoelectric particles refer to particles possessing piezoelectric properties, such as piezoelectric ceramics with 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, and lithium tantalate. The curable resin composition disclosed herein may contain one type of piezoelectric particle or two or more types of piezoelectric particles, but is a composition containing at least one type of piezoelectric particle (A1) with a Curie temperature (Tc) of 0.15 mJ / mg or higher.

[0033] From the viewpoint of improving piezoelectric properties, the Curie temperature (Tc) of the piezoelectric particles (Al) is 0.15 mJ / mg or higher, 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 particles can be determined by differential scanning calorimetry (DSC). Furthermore, known methods can be used to adjust the Curie temperature (Tc) to the above range, particularly in the case of piezoelectric ceramics having a perovskite crystal structure represented by the chemical formula ABO3. Examples include changing the metal atoms represented by A or B and adjusting their weight ratio. It should be noted that 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 oxygen located at the center of each facet.

[0034] From the perspective of balancing the flexibility and piezoelectric properties of piezoelectric materials, the average particle size (median particle size, D) of piezoelectric particles is considered. 50 The average particle size (D) is preferably 0.1–20 μm, more preferably 0.2–17.5 μm, and even more preferably 0.5–15 μm. 50 The particle size distribution can be measured using a particle size distribution measuring device. The curable resin composition may contain one piezoelectric material, but from the viewpoint of improving the flowability of the curable resin composition and balancing the flexibility and piezoelectric properties of the piezoelectric material, it is preferable to include an average particle size (D...). 50 Two or more different piezoelectric materials.

[0035] From the viewpoint of balancing the flexibility and piezoelectric properties of piezoelectric materials, the content of piezoelectric particles (Al) in the cured 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, relative to the total amount of the cured resin composition.

[0036] From the viewpoint of balancing the flexibility and piezoelectric properties of piezoelectric materials, the ratio of the above-mentioned 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.

[0037] For piezoelectric particles (A1) contained in a curable resin composition, from the viewpoint of the piezoelectric properties of piezoelectric materials, it is preferable that the crystallites constituting each particle are relatively large in order to obtain a high thermal conductivity (Tc). A crystallite refers to a region in a material having a crystalline structure where individual crystal lattices are perfectly aligned. For example, the average size of the crystallites constituting the piezoelectric particle (A) can be 235 Å or more, and more preferably 240 Å. There is no particular upper limit to the size of the crystallites, but based on the size of the crystallites of piezoelectric particles typically obtained, it is about 400 Å or less. The size of the crystallites of the piezoelectric particles can be determined by X-ray diffraction (XRD).

[0038] (Epoxy resin)

[0039] The curable resin composition disclosed herein further comprises an epoxy resin (B). The epoxy resin (B) is not particularly limited to any resin having an epoxy group. Examples of epoxy resin (B) include polymethylene oxide type epoxy resin, polyol type epoxy resin, bisphenol A type epoxy resin, bisphenol F type epoxy resin, cycloalkyl type epoxy resin, phenolic varnish type epoxy resin, dimer acid modified epoxy resin, and silicone modified epoxy resin. The curable resin composition disclosed herein may comprise one epoxy resin (B) or two or more epoxy resins (B).

[0040] From the perspective of balancing the flexibility and piezoelectric properties of piezoelectric materials, the viscosity of epoxy resin (B), when measured at 25°C, is preferably 10–1000 mPa·s, more preferably 100–900 mPa·s, and even more preferably 200–750 mPa·s. The viscosity of epoxy resin (B) can be measured using an E-type viscometer.

[0041] From the perspective of balancing the flexibility and piezoelectric properties of piezoelectric materials, the epoxy equivalent of epoxy resin (B) is preferably 100 to 1000, more preferably 200 to 800, even more preferably 250 to 700, and even more preferably 300 to 600. The epoxy equivalent of epoxy resin (B) can be calculated from the number of functional groups and the weight-average molecular weight of epoxy resin (B).

[0042] From the perspective of balancing the flexibility and piezoelectric properties of piezoelectric materials, the weight-average molecular weight of epoxy resin (B) is preferably 100–5000, more preferably 200–2500, and even more preferably 300–1000. The weight-average molecular weight of epoxy resin (B) can be determined using gel permeation chromatography (GPC).

[0043] In a preferred embodiment, the epoxy resin (B) comprises epoxy resin (B1) having a viscosity of 500 mPa·s or less when measured at 25°C. From the viewpoint of balancing the flexibility and piezoelectric properties of the piezoelectric material, the viscosity of the epoxy resin (B1) is preferably 10–400 mPa·s, more preferably 100–300 mPa·s, when measured at 25°C. The viscosity of the epoxy resin (B1) can be measured using an E-type viscometer.

[0044] From the perspective of balancing the flexibility and piezoelectric properties of piezoelectric materials, the epoxy equivalent of epoxy resin (B1) is preferably 100 to 1000, more preferably 200 to 800, even more preferably 250 to 700, and even more preferably 300 to 600. The epoxy equivalent of epoxy resin (B1) can be calculated from the number of functional groups and the weight-average molecular weight of epoxy resin (B1).

[0045] From the perspective of balancing the flexibility and piezoelectric properties of piezoelectric materials, the weight-average molecular weight of epoxy resin (B1) is preferably 100–5000, more preferably 200–2500, and even more preferably 300–1000. The weight-average molecular weight of epoxy resin (B) can be determined using gel permeation chromatography (GPC).

[0046] The content of epoxy resin (B) in the curable resin composition is preferably 7 to 30% by mass, more preferably 8 to 20% by mass, and even more preferably 9 to 15% by mass, relative to the total amount of the curable resin composition.

[0047] From the viewpoint of balancing the 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 even more preferably 9 to 30% by mass, relative to the total amount of the curable resin composition.

[0048] From the viewpoint of balancing the flexibility and piezoelectric properties of piezoelectric materials, the ratio of the above-mentioned epoxy resin (B1) to the total amount of epoxy resin (B) contained in the curable resin composition is preferably 60 to 100% by mass, more preferably 70 to 100% by mass, and even more preferably 80 to 100% by mass.

[0049] In a preferred embodiment, the epoxy resin (B) comprises epoxy resin (B2) represented by the following formula (1).

[0050]

[0051] In the above formula (1), A is - [(CH2)] m ] - represents a divalent alkylene group, where m is an independent integer from 1 to 10. R 1 and R 2 Each atom is independently a hydrogen atom or a glycidyl group, at least one of which 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.

[0052] From the viewpoint of availability and manufacturability, in the epoxy resin (B2) of the above formula (1), n ​​is preferably 0 to 10, and q is preferably 0 to 10. In addition, the epoxy resin (B2) can be a mixture of multiple epoxy resins (B2) with different structures.

[0053] The epoxy equivalent and weight-average molecular weight of epoxy resin (B2), the content of epoxy resin (B2) in the cured resin composition, and the ratio of epoxy resin (B2) to the total amount of epoxy resin (B) contained in the cured resin composition are the same as those of epoxy resin (B1). Alternatively, epoxy resin (B2) may be epoxy resin (B1).

[0054] The structure of epoxy resin can be determined by nuclear magnetic resonance (NMR) measurement.

[0055] (Curing agent)

[0056] The curable resin composition disclosed herein further comprises a curing agent (C). The curing agent (C) is not particularly limited to any component capable of curing epoxy resin, and 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 disclosed herein 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 composition stability, the content of the curing agent (C) relative to the total amount of the curable resin composition 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. Furthermore, from the viewpoint of curability of the curable resin composition, the content of the curing agent (C) relative to the total amount of epoxy resin (B) contained in the curable resin composition is preferably 1 to 60% by mass, more preferably 2.5 to 45% by mass, and even more preferably 5 to 30% by mass.

[0057] (Other ingredients)

[0058] The curable resin composition disclosed herein may further comprise other components besides those described above. Examples of such other components include, for instance, dispersants, other curable resins besides epoxy resins, curable monomers, and silane coupling agents.

[0059] Dispersants are components that improve the dispersibility of piezoelectric particles in a curable resin composition. Examples of dispersants include anionic surfactants, cationic surfactants, nonionic surfactants, amphoteric surfactants, polysorbates, polycarboxylic acids, and silane coupling agents. The dispersant is preferably a nonionic surfactant or a polysorbate, more preferably a 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, relative to the total amount of the curable resin composition.

[0060] The curable resin composition disclosed herein may include other curable resins besides epoxy resin. Examples of other curable resins include acrylic resin, polyurethane resin, and silicone resin. From the viewpoint of balancing the flexibility and piezoelectric properties of the piezoelectric material, the content of other curable resins besides 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.

[0061] The curable resin composition disclosed herein may further comprise a curable monomer. Examples of curable monomers include monomers having (meth)acrylate groups, monomers having oxetyl groups, and monomers having maleimide groups. Regarding the content of the curable monomer, from the viewpoint of balancing the flexibility and piezoelectric properties of the piezoelectric material, the content of the curable monomer is preferably low, 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.

[0062] (Curing resin composition)

[0063] The curable resin composition disclosed herein comprises piezoelectric particles (A1) having a specific Curie temperature, epoxy resin (B), and a curing agent (C). From the viewpoint of balancing the flexibility and piezoelectric properties of the piezoelectric material, the total amount of piezoelectric particles (A1), epoxy resin (B), and curing agent (C) in the curable resin composition disclosed herein 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.

[0064] From the viewpoint of balancing the flexibility and piezoelectric properties of piezoelectric materials, the mass ratio of piezoelectric particles (A1): epoxy resin (B): curing agent (C) in the curable resin composition disclosed herein is preferably 65-90:5-30:0.5-5, more preferably 67-87:9-29:1-4.

[0065] From the viewpoint of balancing the flexibility and piezoelectric properties of piezoelectric materials, the average Tc heat of the piezoelectric particles, calculated by weighted 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.

[0066] In the curable resin composition disclosed herein, the cured epoxy resin (B) serving as the curable resin acts as a binder. From the viewpoint of balancing the flexibility and piezoelectric properties of the piezoelectric material, the dielectric constant of the binder alone in the curable resin composition is preferably 3.1 or higher, more preferably 3.5 or higher, and even more preferably 4.0 or higher. There is no particular upper limit to this dielectric constant; for example, it can be 7.0 or lower. The dielectric constant of the binder alone can be measured using an impedance analyzer, taking a cured product obtained by heating the curable resin composition (after removing solid components such as piezoelectric particles) at 80°C for 3 hours and then at 140°C for 3 hours as a test sample.

[0067] For the curable resin composition of this disclosure, the tensile modulus of elasticity 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 is preferably 100 MPa or less, more preferably 75 MPa or less, and even more preferably 50 MPa or less. The lower limit of the tensile modulus of elasticity of the cured product is not particularly limited, and for example, it can be 0.1 MPa or more. The tensile modulus of elasticity of the cured product can be measured by, for example, the method described in the examples.

[0068] The curable resin composition disclosed herein has a viscosity preferably below 100 Pa·s, more preferably 20 to 100 Pa·s, further preferably 25 to 80 Pa·s, and even more preferably 27.5 to 60 Pa·s when measured at 25°C. The viscosity of the curable resin composition can be measured using a rheometer. Specifically, this can be done using a 25 mm parallel plate, at 25°C, and a rotation speed of 5 min. －1 Start the measurement and measure the viscosity 180 seconds after the measurement begins.

[0069] (Preparation method of curable resin composition)

[0070] The curable resin composition disclosed herein can be manufactured by mixing the above-mentioned components using conventionally known methods.

[0071] (Cure of the curable resin composition)

[0072] This disclosure also provides a cured product of a curable resin composition. The cured product of the curable resin composition can be prepared by heating the curable resin composition of this disclosure to cure the curable resin contained therein. As for the curing conditions, there are no particular limitations; it can be prepared by heating at a temperature preferably 50–200°C, more preferably 65–160°C, preferably for 0.5–6 hours, more preferably for 1–4 hours.

[0073] (Piezoelectric element)

[0074] This disclosure also provides a piezoelectric element as a cured product of the above-described curable resin composition. In a preferred embodiment, the piezoelectric element of this disclosure comprises piezoelectric particles (Al) having a Curie temperature (Tc) of 0.15 mJ / mg or higher and an epoxy adhesive, a tensile modulus of elasticity of 100 MPa or lower at 25°C, and a piezoelectric constant d. 33 The piezoelectricity is 30 or higher. The piezoelectric particle (A1) is the piezoelectric particle (A1) described in relation to the curable resin composition. Additionally, the epoxy adhesive is a curable resin of the epoxy resin (B) described in relation to the curable resin composition.

[0075] There is no particular limitation on the manufacturing method of the piezoelectric material. For example, the piezoelectric material of the present disclosure can be manufactured by a process of coating the curable resin composition of the present disclosure onto a substrate, a process of curing epoxy resin (B), and a process of polarization treatment by applying AC voltage and / or DC voltage to generate piezoelectric properties.

[0076] The piezoelectric properties of the piezoelectric material disclosed herein can be derived, for example, from the piezoelectric constant d. 33 This is indicated by the piezoelectric constant d described in the embodiments described later. 33 The piezoelectric constant d is preferably 30 or more, more preferably 60 or more, and even more preferably 100 or more. 33 piezoelectric constant d 33 There is no specific upper limit; for example, it can be below 200.

[0077] The piezoelectric material disclosed herein is a piezoelectric material that combines flexibility and piezoelectric properties, and is therefore suitable for use as components in pressure sensors, thermoelectric sensors, flexible storage elements, etc., and is particularly suitable as components in wearable sensors, actuators, planar loudspeakers, transducers, piezoelectric wires, etc.

[0078] The reasons why the piezoelectric material disclosed herein can combine flexibility and piezoelectric properties are not limited to theory, but are derived from the following: The inventors have discovered that, when the size of the piezoelectric particles is the same, the larger the size of the crystallites constituting each particle, the higher the piezoelectric performance. First, the inventors have discovered that the Curie temperature (Tc) of a piezoelectric particle is related to the size of the crystallites constituting each particle. More specifically, a larger size of the crystallites constituting each piezoelectric particle means that each particle is composed of large crystallites, and the number of crystallites constituting a single particle is small. As a result, the surface area of ​​the crystallites is small, and heat is not easily transferred. Therefore, it can be said that the larger the size of the crystallites constituting each piezoelectric particle, the greater the heat 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 a single particle, so the crystallites are more likely to deform during polarization treatment, the probability of the polarization direction of each crystallites is not necessarily high, and the polarization of the crystallites in a single particle is more likely to cancel each other out. On the other hand, if the crystallites of each particle constituting the piezoelectric particle are large, the probability of random polarization direction of each crystallite is low, and the polarization of each crystallite in a single particle is less likely to cancel each other out. As a result, each piezoelectric particle is considered to have high piezoelectric properties. In addition, piezoelectric particles can easily exhibit high piezoelectric characteristics by being polarized in an environment with a high dielectric constant, such as a resin with a high dielectric constant. The cured epoxy adhesive constituting the curable resin composition of this disclosure exhibits a high dielectric constant, which is considered to help increase the polarization amount of the piezoelectric particles. Furthermore, although the piezoelectric of this disclosure is flexible, it does not exhibit plastic (irreversible) behavior when an external force is applied. The stress during elastic deformation is applied more to the piezoelectric particles (the stress is not easily absorbed by the adhesive), so it is believed that both flexibility and piezoelectric properties can be achieved.

[0079] Example

[0080] The invention will now be described in further detail with reference to examples, but these examples are for illustrative purposes only and do not limit the invention in any way. Furthermore, unless otherwise stated, "%" and "parts" in the examples refer to "mass %" and "parts by mass," respectively. Additionally, the compounds shown below do not necessarily follow IUPAC nomenclature.

[0081] First, the materials used in the embodiments and comparative examples are shown below.

[0082] <Piezoelectric Particle A>

[0083]

[0084] <Epoxy Resin B>

[0085] 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

[0086] 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

[0087] <Curing Agent C>

[0088] C-1: Pentaerythritol tetra(3-mercaptobutyrate), product name Karenz MT PE1 (manufactured by Resonac Co., Ltd.)

[0089] C-2: 1-Benzyl-2-phenylimidazole, product name CUREZOL (manufactured by Shikoku Kasei Corporation).

[0090] C-3: m-Phenylenediamine, product name MXDA (manufactured by Mitsubishi Gas Chemical Co., Ltd.)

[0091] <Polymer compound D>

[0092] D-1: Acryloyl-terminated polyacrylate, product name KANEKA XMAP RC100C (manufactured by Kaneka Corporation).

[0093] D-2: Hydrogenated polybutadiene diacrylate (SPBDA), synthesized based on Synthesis Example 1 described later.

[0094] D-3: Isodecyl acrylate, product name IDAA (manufactured by Osaka Organic Chemical Industry Co., Ltd.)

[0095] D-4: 4-Hydroxybutyl acrylate, product name 4-HBA (manufactured by Osaka Organic Chemical Industry Co., Ltd.)

[0096] D-5: Acryloylmorpholine, product name ACMO (manufactured by KJ Chemical Co., Ltd.)

[0097] D-6: 2-Acryloyloxyethyl succinate, product name HOA-MS (manufactured by Kyoei Chemical Co., Ltd.)

[0098] <Polymerization Initiator E>

[0099] E-1: 2-Ethylperoxyhexanoate tert-butyl ester, product name PERBUTYL O (manufactured by Nippon Oil Co., Ltd.)

[0100] <Dispersant F (surfactant)>

[0101] F-1: Sorbitan trioleate, product name RHEODOL SP-O30V (manufactured by Kao Corporation).

[0102] The physical properties of piezoelectric particles, epoxy resins, resin compositions, or cured resin compositions are determined by the following methods.

[0103] <Curie Temperature>

[0104] The Curie temperature of each piezoelectric particle A described above was determined by differential scanning calorimetry (DSC). Specifically, 10 mg of each piezoelectric particle was weighed, placed in an aluminum dish, and heated from 30 °C to 200 °C at a rate of 10 °C / min, and the Curie temperature was measured. The calorific value was obtained by integrating the DSC curve of the Curie temperature and dividing by the weight.

[0105] <Tc heat (average Tc) of piezoelectric particles>

[0106] For the average heat of piezoelectric particles A contained in each resin composition, when the resin composition contains one type of piezoelectric particle, the Curie temperature of that piezoelectric particle is used as the average heat of piezoelectric particles and is recorded in Table 1. Furthermore, when the resin composition contains two or more types of piezoelectric particles, the value obtained by weighting the Curie temperatures (Tc) of the piezoelectric particles contained in the examples and comparative examples as measured above according to their blending ratios is used as the "Heat of Piezoelectric Particles" and is recorded in Tables 1 and 2.

[0107] <Weight-average molecular weight>

[0108] Weight-average molecular weight was determined using gel permeation chromatography (GPC). Specifically, a 0.5% by mass solution of the resin dissolved in tetrahydrofuran was used as the test sample. The determination conditions are as follows.

[0109] Equipment: Manufactured by Tosoh Corporation, Product No.: HLC-8320GPC

[0110] Pillar: Manufactured by Tosoh Corporation, Product Number: TSKgel SuperH2500

[0111] Eluent: Tetrahydrofuran

[0112] Flow rate: 0.6 mL / min

[0113] Temperature: 40℃

[0114] Detector: RI

[0115] Molecular weight standard: Standard polystyrene

[0116] <Viscosity of epoxy resin B>

[0117] 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°C, and a rotation speed of 20 min. －1 Begin the measurement; the viscosity of epoxy resin B will be determined 180 seconds after the measurement begins.

[0118] <Synthesis example 1>

[0119] (Synthesis of hydrogenated diacrylated polybutadiene (SPBDA))

[0120] In a 300 mL four-necked flask equipped with a Dean-Stark splitter and a stirrer, 100.0 g of terminally hydroxyl-modified polybutadiene (hydrogenation rate ≥97%: CRAY VALLEY "HLBH-P2000"), 23.6 g of methyl acrylate, 50.0 g of n-hexane, and 0.2 g of di-n-octyltin oxide were added. Methanol generated was removed, and the mixture was reacted at reflux for 8 hours. After the reaction was complete, the mixture was concentrated to obtain 100.5 g of diacrylated hydrogenated polybutadiene as a pale yellow viscous liquid. The weight-average molecular weight (Mw) of the obtained diacrylated hydrogenated polybutadiene, determined by GPC, was 4400.

[0121] <Preparation of Curable Resin Compositions>

[0122] Curable resin compositions of various examples and comparative examples were prepared by mixing the components at room temperature according to the formulations shown in Tables 1 and 2 below, and the viscosity was measured under the conditions described below. The amounts of each component shown in the tables refer to the mass percentage relative to the total curable resin composition (excluding solvent). In addition, the Tc heat of the piezoelectric particles contained in each example and comparative example is a theoretical value (average Tc heat) calculated by weighted averaging of the Curie temperature (Tc) of each piezoelectric particle contained in each example and comparative example and their formulation ratio.

[0123] <Viscosity>

[0124] The viscosity of each cured resin composition obtained above was determined using a rheometer (Anton Paar, MCR 302). The test was conducted using a 25 mm parallel plate, at 25°C, and a rotation speed of 5 min. －1 Begin the measurement, and use the viscosity 180 seconds after the start of the measurement as the viscosity of each curable resin composition. The results are shown in Tables 1 and 2.

[0125] <Determination of the properties of cured products>

[0126] Using the curable resin compositions obtained above, the following tests were conducted to determine the properties of the cured products. Details of each test are recorded below, and the results are shown in Tables 1 and 2.

[0127] (piezoelectric constant d) 33 )

[0128] Production of test pieces

[0129] Using a coating applicator with a gap size set to 400 μm, the aforementioned curable resin compositions were coated onto a stainless steel panel (MiSUMi Corporation, material: SUS304, 100 mm × 200 mm flat plate). After standing for 3 hours in a warm air dryer set to 80°C (ESPEC CORP., trade name: LC-113), the temperature was increased to 140°C and left to stand for another 3 hours. Then, the panels were slowly cooled to room temperature, thereby forming test pieces (cured products) for each example and comparative example. The thickness of the test pieces was measured using a coolant-resistant micrometer (Mitutoyo Corporation, trade name: MDC-25MX), and the results were all approximately 200 μm.

[0130] polarization treatment

[0131] Each of the test pieces obtained above was attached to a grounding electrode, and a voltage of -12kV was applied for 120 minutes using an electret processing device (manufactured by Wedge Corporation) to perform polarization treatment.

[0132] piezoelectric constant d 33 Measurement

[0133] After each polarized test piece was peeled from the stainless steel panel, nine points were selected at intervals of at least 15 mm within a 50 mm long and 50 mm wide area of ​​the test piece. The piezoelectric constant d was measured using a piezoelectric constant measuring device (Lead Techno, trade name: LPF-02). 33 Specifically, the determination is carried out according to the following steps.

[0134] (1) Clamp the membrane using the measuring head.

[0135] (2) Set the load applied to the membrane by the measuring head to 1N and let it stand.

[0136] (3) Measure the amount of charge A generated when a force of 1N is applied.

[0137] (4) Increase the load applied to the membrane by the measuring head by 3N, and set the load applied to the membrane by the measuring head to 4N.

[0138] (5) Measure the amount of charge B generated when a force of 4N is applied.

[0139] (6) Reduce the load applied to the membrane by the measuring head by 3N to 1N.

[0140] (7) Perform steps (3) to (6) above four times. Take the average value of the difference (A-B) between the measured values ​​of charge A and B in the second to fourth times as the charge of the membrane in each example and comparative example. Divide this average charge by the measurement load (3N) to calculate the piezoelectric constant d of each test piece. 33 The results are shown in Tables 1 and 2.

[0141] (Tensive modulus of elasticity)

[0142] Production of test pieces

[0143] By performing the above piezoelectric constant d 33 After the measurement, each test piece was punched into a dumbbell shape No. 7 as specified in JIS K6251 (2017) 6.1 to obtain each test piece for the determination of tensile modulus of elasticity.

[0144] Determination of tensile modulus of elasticity

[0145] The test pieces obtained above were mounted on a tensile testing machine (manufactured by A&D Corporation, product number: Tensilon RTG-1310) at 25°C with a clamp spacing of 19 mm. Tensile loads were applied at a tensile speed of 50 mm / min until the test piece broke. The tensile modulus of elasticity was calculated from the slope of the tensile strength with an elongation of 3-5%. The results are shown in Tables 1 and 2.

[0146] (Based on tensile modulus of elasticity and piezoelectric constant d) 33 (Relational evaluation)

[0147] Given the tensile modulus of elasticity and the piezoelectric constant d 33 The relationship between the tensile modulus of elasticity and the piezoelectric constant d is evaluated according to the following criteria. It should be noted that the tensile modulus of elasticity is related to the piezoelectric constant d. 33 The relationship varies depending on the content of piezoelectric particles and the application of the piezoelectric material. Therefore, the following relationship may not be ideal. However, in this application, in order to compare the effects of resin compositions containing piezoelectric particles at the same level, the following criteria are used for evaluation.

[0148] (1) When the tensile modulus of elasticity is less than 5

[0149] A: Piezoelectric constant d 33 15 or above

[0150] B: Piezoelectric constant d 33 Less than 15

[0151] (2) Cases where the tensile modulus of elasticity is 5 or higher but less than 25

[0152] S: piezoelectric constant d33 80 and above

[0153] A: Piezoelectric constant d 33 30 and above

[0154] B: Piezoelectric constant d 33 Less than 30

[0155] (3) The case where the elastic modulus is above 25 and less than 50

[0156] S: piezoelectric constant d 33 80 and above

[0157] A: Piezoelectric constant d 33 50 or above

[0158] B: Piezoelectric constant d 33 Less than 50

[0159] (4) Cases with an elastic modulus of 50 or higher

[0160] A: Piezoelectric constant d 33 For 60 and above

[0161] B: Piezoelectric constant d 33 Less than 60

[0162] (crack)

[0163] Each test piece is prepared in the same manner as the test pieces used for the tensile modulus determination described above, and the condition of the test piece when held at both ends and bent until the plate portions at both ends are parallel is evaluated according to the following criteria.

[0164] 〇: No cracks were observed visually.

[0165] ×: Cracks were observed visually.

[0166] No cracks were observed in the test pieces obtained in Examples 1-7 and 9-15, confirming high toughness, but cracks were observed in the test piece of Example 8. No cracks were also observed in the test pieces obtained in Comparative Examples 1-5.

[0167] <Dielectric constant of adhesive resin>

[0168] After preparing a resin composition that does not contain piezoelectric particles A, a cured product was made as described above, and the dielectric constant was measured using an impedance analyzer (AMETEK, model 1260A) to obtain a dielectric constant of 1 kHz.

[0169] [Table 1]

[0170]

[0171] [Table 2]

[0172]

Claims

1. A curable resin composition comprising: Piezoelectric particles A1 with a Curie temperature Tc of 0.15 mJ / mg or higher, Epoxy resin B, and Curing agent C.

2. The curable resin composition according to claim 1, wherein, The tensile modulus of a cured material with a thickness of 200 μm obtained by heating the curable resin composition at 80°C for 3 hours and at 140°C for 3 hours is less than 100 MPa.

3. The curable resin composition according to claim 1, wherein, The epoxy resin B comprises epoxy resin B1 having a viscosity of less than 500 mPa·s when measured at 25°C.

4. The curable resin composition according to claim 1, wherein, The epoxy resin B comprises epoxy resin B2 represented by the following formula (1). In equation (1), A is - [(CH2)] m ] - represents a divalent alkylene group, where m is an independent integer from 1 to 10, and R 1 and R 2 Each is independently a hydrogen atom or a glycidyl group, at least one of which 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 the 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, and curing agent C in the curing resin composition is 65-90: 5-30: 0.5-5.

9. The curable resin composition according to claim 1 or 2, wherein, It has a viscosity of less than 100 Pa·s when measured at 25°C.

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

11. A piezoelectric element comprising: Piezoelectric particles A1 with a Curie temperature Tc of 0.15 mJ / mg or higher, and Epoxy adhesives; The tensile elastic modulus of the piezoelectric material is below 100 MPa at 25°C. piezoelectric constant d 33 It is above 30.

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