TWI771452B - Piezoelectric material and composition for piezoelectric material - Google Patents

Abstract

(式中的R係，可被羥基、碳原子數為1或2的烷基及/或碳原子數為1~6的烷氧基取代之具有1至10個碳原子的烷基；具有至少一個碳原子可被氧原子取代之碳原子數為3~6的脂環式烴基之碳原子數為3~12的烴基；亞烷基部份的碳原子數為1~4，且亞烷基部份的一個-CH₂ -可被-O-取代之苯基亞烷基；或者，以-((CH₂ )_m -O-)_n -X表示的基[式中的m及n係各自表示2或3的數字，X係表示氫原子或甲基])。[Problem] The object of the present invention is to provide a piezoelectric material having excellent flexibility and stretchability, and a piezoelectric material composition for obtaining the piezoelectric material. [Solution] A piezoelectric material of the present invention includes: a vinylidene fluoride/trifluoroethylene copolymer; and an acrylic elastomer having a structural unit derived from an acrylic monomer represented by formula (I) , and the weight average molecular weight is more than 1 million;

(R in the formula is an alkyl group with 1 to 10 carbon atoms which can be substituted by a hydroxyl group, an alkyl group with 1 or 2 carbon atoms and/or an alkoxy group with 1 to 6 carbon atoms; An alicyclic hydrocarbon group with 3 to 6 carbon atoms in which one carbon atom can be replaced by an oxygen atom; a hydrocarbon group with 3 to 12 carbon atoms; the alkylene moiety has 1 to 4 carbon atoms, and the alkylene group has 1 to 4 carbon atoms. A part of -CH ₂ - may be substituted by -O- phenylalkylene; or, a group represented by -((CH ₂ ) _m -O-) _n -X [m and n in the formula are each A number representing 2 or 3, and X represents a hydrogen atom or a methyl group]).

Description

Piezoelectric material and composition for piezoelectric material

The present invention relates to piezoelectric materials and compositions for piezoelectric materials.

As a ferroelectric polymer including vinylidene fluoride (VDF) and trifluoroethylene copolymer (TrFE) copolymer, vinylidene fluoride/trifluoroethylene copolymer (P(VDF/TrFE) Piezoelectric materials with characteristics and spontaneous polarization (residual polarization) are widely known. Such piezoelectric materials are used in various piezoelectric elements such as piezoelectric sensors, transducers, and infrared pyroelectric sensors.

Patent Document 1 discloses a piezoelectric film made of a copolymer obtained by copolymerizing vinylidene fluoride and trifluoroethylene at a specific molar ratio.

[Prior Art Document] [Patent Document] [Patent Document 1] International Publication No. 2016/159354

[Summary of the Invention] [Problem to be Solved by the Invention] In recent years, attempts have been made to use piezoelectric materials in fields including wearable devices. For piezoelectric materials used in this field, more excellent flexibility and stretchability than conventional ones are sought. Therefore, the inventors of the present invention have focused on piezoelectric materials comprising copolymers of vinylidene fluoride and trifluoroethylene, and have studied to provide materials with high flexibility and stretchability required in the fields of wearable devices and the like. For example, in the piezoelectric film as described in Patent Document 1, further improvements are sought from the viewpoints of flexibility and stretchability.

Therefore, one of the objects of the present invention is to provide a piezoelectric material having excellent flexibility and stretchability, and a piezoelectric material composition for obtaining the piezoelectric material.

(式中的R係，可被羥基、碳原子數為1或2的烷基及/或碳原子數為1~6的烷氧基取代之具有1至10個碳原子的烷基；具有至少一個碳原子可被氧原子取代之碳原子數為3~6的脂環式烴基之碳原子數為3~12的烴基；亞烷基部份的碳原子數為1~4，且亞烷基部份的一個-CH₂ -可被-O-取代之苯基亞烷基；或者，以-((CH₂ )_m -O-)_n -X表示的基[式中的m及n係各自表示2或3的數字，X係表示氫原子或甲基])。 在本說明書中，亦將偏氟乙烯/三氟乙烯共聚物簡稱為PVT。又，在偏氟乙烯/三氟乙烯的聚合比為80mol%/20mol%時，亦將其簡稱為PVT80/20。[MEANS TO SOLVE THE PROBLEM] [1] The piezoelectric material of the present invention, comprising: a vinylidene fluoride/trifluoroethylene copolymer; and an acrylic elastomer having acrylic acid derived from formula (I) The structural unit of the monomer, and the weight average molecular weight is 1 million or more; Formula (I): [Chemical 1]

(R in the formula is an alkyl group with 1 to 10 carbon atoms which can be substituted by a hydroxyl group, an alkyl group with 1 or 2 carbon atoms and/or an alkoxy group with 1 to 6 carbon atoms; An alicyclic hydrocarbon group with 3 to 6 carbon atoms in which one carbon atom can be replaced by an oxygen atom; a hydrocarbon group with 3 to 12 carbon atoms; the alkylene moiety has 1 to 4 carbon atoms, and the alkylene group has 1 to 4 carbon atoms. A part of -CH ₂ - may be substituted by -O- phenylalkylene; or, a group represented by -((CH ₂ ) _m -O-) _n -X [m and n in the formula are each A number representing 2 or 3, and X represents a hydrogen atom or a methyl group]). In this specification, the vinylidene fluoride/trifluoroethylene copolymer is also abbreviated as PVT. In addition, when the polymerization ratio of vinylidene fluoride/trifluoroethylene is 80 mol %/20 mol %, it is also abbreviated as PVT80/20.

The present invention also includes the following preferred aspects. [2] The piezoelectric material according to [1], wherein the amount of the vinylidene fluoride/trifluoroethylene copolymer is 98 to 70% by mass based on the entire piezoelectric material, and the acrylic elastomer is based on the entire piezoelectric material The amount of 2~30% by mass.

[3] The piezoelectric material according to [1] or [2], wherein the vinylidene fluoride/trifluoroethylene copolymer has a viscosity-average molecular weight of 100,000/mol or more.

[4] The piezoelectric material according to any one of [1] to [3], wherein, in the vinylidene fluoride/trifluoroethylene copolymer, the amount derived from the vinylidene fluoride structural unit is based on the amount of all the structures Department of 55~90mol%.

[5] The piezoelectric material according to any one of [1] to [4], wherein a Young's modulus is 3.1 GPa or less.

(式中的R係，可被羥基、碳原子數為1或2的烷基及/或碳原子數為1~6的烷氧基取代之具有1至10個碳原子的烷基；具有至少一個碳原子可被氧原子取代之碳原子數為3~6的脂環式烴基之碳原子數為3~12的烴基；亞烷基部份的碳原子數為1~4，且亞烷基部份的一個-CH₂ -可被-O-取代之苯基亞烷基；或者，以-((CH₂ )_m -O-)_n -X表示的基[式中的m係表示2或3的數，n係表示1~3的數，X係表示氫原子或甲基])。The composition for piezoelectric materials of the present invention comprises: a vinylidene fluoride/trifluoroethylene copolymer; and an acrylic elastomer having a structural unit derived from the acrylic monomer represented by the formula (I), and The weight average molecular weight is more than 1 million; Formula (I): [Chemical 2]

(R in the formula is an alkyl group with 1 to 10 carbon atoms which can be substituted by a hydroxyl group, an alkyl group with 1 or 2 carbon atoms and/or an alkoxy group with 1 to 6 carbon atoms; An alicyclic hydrocarbon group with 3 to 6 carbon atoms in which one carbon atom can be replaced by an oxygen atom; a hydrocarbon group with 3 to 12 carbon atoms; the alkylene moiety has 1 to 4 carbon atoms, and the alkylene group has 1 to 4 carbon atoms. One part of -CH ₂ - may be substituted by -O- phenylalkylene; or, a group represented by -((CH ₂ ) _m -O-) _n -X [where m represents 2 or A number of 3, n represents a number from 1 to 3, and X represents a hydrogen atom or a methyl group]).

[Effect of the Invention] Since the piezoelectric material of the present invention has excellent flexibility and stretchability, it can be applied to fields such as wearable devices.

[Mode for Carrying out the Invention] Hereinafter, an example of an embodiment of the present invention will be described in detail. In addition, the scope of the present invention is not limited to the embodiment described here, and various modifications can be made without departing from the scope of the present invention. In addition, the numerical range shown by "~" includes the upper limit and the lower limit.

The piezoelectric material of the present invention contains a vinylidene fluoride/trifluoroethylene copolymer and a specific acrylic elastomer. The amount of the vinylidene fluoride/trifluoroethylene copolymer contained in the piezoelectric material of the present invention is preferably 98 to 70% by mass based on the amount of the entire piezoelectric material. When the amount of the vinylidene fluoride/trifluoroethylene copolymer is equal to or less than the above upper limit value, flexibility and stretchability are easily improved. In addition, when the amount of the vinylidene fluoride/trifluoroethylene copolymer is equal to or greater than the above lower limit value, the spontaneous polarization of the piezoelectric material is not easily reduced, and the piezoelectric properties are easily improved.

The piezoelectric material of the present invention also includes an aspect containing a vinylidene fluoride/trifluoroethylene copolymer and a material other than a specific acrylic elastomer (hereinafter referred to as other material). For other materials, for example, vinylidene fluoride/trifluoroethylene copolymers and copolymers other than specific acrylic elastomers, additives such as elastomers, oxidation inhibitors, and ultraviolet absorbers; thermally conductive fillers; Conductive fillers, etc., but not limited to this.

The amount of the acrylic elastomer contained in the piezoelectric material of the present invention is preferably 2 to 30% by mass based on the amount of the entire piezoelectric material. When the amount of the acrylic elastomer is at least the above lower limit value, flexibility and stretchability are likely to be improved. In addition, when the amount of the acrylic elastomer is below the above upper limit value, the amount of the vinylidene fluoride/trifluoroethylene copolymer in the piezoelectric material can be relatively increased, and the piezoelectric properties can be easily improved.

The amount of the vinylidene fluoride/trifluoroethylene copolymer contained in the piezoelectric material of the present invention is preferably based on the total weight of the vinylidene fluoride/trifluoroethylene copolymer and the acrylic elastomer contained in the piezoelectric material of the present invention The system is 88~96% by mass. When the amount of the vinylidene fluoride/trifluoroethylene copolymer is equal to or greater than the above lower limit value, the spontaneous polarization of the piezoelectric material is not easily reduced, and the piezoelectric properties are easily improved. Further, when the amount of the vinylidene fluoride/trifluoroethylene copolymer is equal to or less than the above-mentioned upper limit value, the flexibility and stretchability are easily improved.

(式中的R係，可被羥基、碳原子數為1或2的烷基及/或碳原子數為1~6的烷氧基取代之具有1至10個碳原子的烷基；具有至少一個碳原子可被氧原子取代之碳原子數為3~6的脂環式烴基之碳原子數為3~12的烴基；亞烷基部份的碳原子數為1~4，且亞烷基部份的一個-CH₂ -可被-O-取代之苯基亞烷基；或者，以-((CH₂ )_m -O-)_n -X表示的基[式中的m及n係各自表示2或3的數字，X係表示氫原子或甲基])。The composition for piezoelectric materials of the present invention comprises: a vinylidene fluoride/trifluoroethylene copolymer; and an acrylic elastomer having a structural unit derived from the acrylic monomer represented by the formula (I), and The weight-average molecular weight is more than 1 million; Formula (I): [Chem. 3]

(R in the formula is an alkyl group with 1 to 10 carbon atoms which can be substituted by a hydroxyl group, an alkyl group with 1 or 2 carbon atoms and/or an alkoxy group with 1 to 6 carbon atoms; An alicyclic hydrocarbon group with 3 to 6 carbon atoms in which one carbon atom can be replaced by an oxygen atom; a hydrocarbon group with 3 to 12 carbon atoms; the alkylene moiety has 1 to 4 carbon atoms, and the alkylene group has 1 to 4 carbon atoms. A part of -CH ₂ - may be substituted by -O- phenylalkylene; or, a group represented by -((CH ₂ ) _m -O-) _n -X [m and n in the formula are each A number representing 2 or 3, and X represents a hydrogen atom or a methyl group]).

(式中的R係，可被羥基、碳原子數為1或2的烷基及/或碳原子數為1~6的烷氧基取代之具有1至10個碳原子的烷基；具有至少一個碳原子可被氧原子取代之碳原子數為3~6的脂環式烴基之碳原子數為3~12的烴基；亞烷基部份的碳原子數為1~4，且亞烷基部份的一個-CH₂ -可被-O-取代之苯基亞烷基；或者，以-((CH₂ )_m -O-)_n -X表示的基[式中的m及n係各自表示2或3的數字，X係表示氫原子或甲基])。 換言之，本發明壓電材料所包含之丙烯酸系彈性體，係將上述式(I)所示之丙烯酸系單體作為構造單元而含有的聚合物(Polymer)。因為被含於本發明壓電材料之丙烯酸系彈性體的重量平均分子量，係較高之100萬以上，故各分子鏈具有較長的分子鏈。若具有如此之長分子鏈的高分子成為集合體，則具有彈性體的特性。(Acrylic Elastomer) The acrylic elastomer contained in the piezoelectric material of the present invention contains a structural unit derived from the acrylic monomer represented by the formula (I): [Chem. 4]

(R in the formula is an alkyl group with 1 to 10 carbon atoms which can be substituted by a hydroxyl group, an alkyl group with 1 or 2 carbon atoms and/or an alkoxy group with 1 to 6 carbon atoms; An alicyclic hydrocarbon group with 3 to 6 carbon atoms in which one carbon atom can be replaced by an oxygen atom; a hydrocarbon group with 3 to 12 carbon atoms; the alkylene moiety has 1 to 4 carbon atoms, and the alkylene group has 1 to 4 carbon atoms. A part of -CH ₂ - may be substituted by -O- phenylalkylene; or, a group represented by -((CH ₂ ) _m -O-) _n -X [m and n in the formula are each A number representing 2 or 3, and X represents a hydrogen atom or a methyl group]). In other words, the acrylic elastomer contained in the piezoelectric material of the present invention is a polymer (polymer) containing the acrylic monomer represented by the above formula (I) as a structural unit. Since the weight average molecular weight of the acrylic elastomer contained in the piezoelectric material of the present invention is higher than 1 million, each molecular chain has a longer molecular chain. When a polymer having such a long molecular chain is aggregated, it has the properties of an elastomer.

Since the piezoelectric material contains the above-mentioned acrylic elastomer, the flexibility and stretchability of the piezoelectric material can be improved without significantly degrading the electrical properties of the piezoelectric material. Although the reason for this is still unclear, if a highly flexible elastomer is added to improve the flexibility and stretchability of the piezoelectric material, the piezoelectric properties of the piezoelectric material may decrease. In the present invention, by using an acrylic elastomer having a specific structure and a relatively high weight average molecular weight, it is considered that it has both flexibility, stretchability and piezoelectric properties because of good entanglement of polymer chains. , and can minimize the decline in electrical properties, for example, minimize the decline in residual polarization. In addition, although the acrylic elastomer contained in the piezoelectric material of the present invention is considered to have the characteristics of an elastomer because polymer chains having a weight average molecular weight of 1,000,000 or more are intertwined with each other, for example, it may have the properties of an elastomer. Elastomer with a structure in which polymer chains with a weight average molecular weight of 1 million or more are linked.

The R system (R1) in the above formula (I) may be substituted by a hydroxyl group, an alkyl group having 1 or 2 carbon atoms, and/or an alkoxy group having 1 to 6 carbon atoms, which has 1 to 10 carbon atoms. Alkyl; (R2) a hydrocarbon group with a carbon number of 3 to 12, an alicyclic hydrocarbon group having at least one carbon atom that can be substituted by an oxygen atom; (R3) a carbon atom in an alkylene moiety The number of atoms is 1~4, and one -CH ₂ - of the alkylene part can be substituted by -O- phenylalkylene; or (R4) with -((CH ₂ ) _m -O-) _n - The group represented by X [in the formula, m and n each represent a number of 2 or 3, and X represents a hydrogen atom or a methyl group].

Regarding (R1) an alkyl group having 1 to 10 carbon atoms which may be substituted by a hydroxyl group, an alkyl group having 1 or 2 carbon atoms, and/or an alkoxy group having 1 to 6 carbon atoms From a viewpoint, the number of carbon atoms of the alkyl group is preferably 1-6, more preferably 1-4. In the present specification, the alkyl group may be either linear or branched. Examples of the alkyl group include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, isopentyl, Neopentyl, 1,1-dimethylpropyl, isopentyl, n-hexyl, isohexyl, n-octyl, etc. These alkyl groups having 1 to 10 carbon atoms may be substituted by hydroxyl groups, alkyl groups having 1 or 2 carbon atoms, and/or alkoxy groups having 1 to 6 carbon atoms.

Examples of the alkyl group having 1 to 10 carbon atoms substituted with hydroxy include hydroxymethyl, hydroxyethyl, hydroxy-n-propyl, hydroxyisopropyl, hydroxy-n-butyl, and hydroxyisobutyl. base, hydroxy tert-butyl, etc.

An alkyl group having 1 to 10 carbon atoms substituted by an alkyl group having 1 or 2 carbon atoms is an alkyl group having 1 to 10 carbon atoms as the main chain, and at least one hydrogen atom of the alkyl group is replaced by a carbon atom. A group substituted with an alkyl group (methyl or ethyl) having 1 or 2 atoms. As long as the number of carbon atoms in the alkyl portion of the main chain is 1 to 10, the number of carbon atoms in the entire alkyl group may exceed 10. As an example of such an alkyl group, a 2-ethylhexyl group etc. are mentioned, for example. Moreover, when the carbon number of the whole alkyl group does not exceed 10 groups, this group is a group which is also included in the definition of a C1-C10 branched alkyl group.

The number of carbon atoms of the alkyl group in the alkoxy group having 1 to 6 carbon atoms is preferably 1 to 4, more preferably 1 to 2. The alkyl group in the alkoxy group may be linear or branched.

An alkyl group having 1 to 10 carbon atoms substituted by an alkoxy group having 1 to 6 carbon atoms, preferably an alkyl group having 1 to 6 carbon atoms substituted by an alkoxy group having 1 to 6 carbon atoms alkyl. As an example of a related group, a methoxyethyl group, an ethoxyethyl group, and a methoxybutyl group are mentioned, for example.

For the alkyl group having 1 to 10 carbon atoms substituted by a hydroxyl group and an alkoxy group having 1 to 6 carbon atoms, for example, a hydroxyalkoxy group having 1 to 6 carbon atoms and a carbon number can be used. It is an alkyl group of 1-6, for example, a hydroxymethoxyethyl group, a hydroxyethoxyethyl group, a hydroxypropoxypropyl group etc. are mentioned specifically,.

Among the above-mentioned alkyl groups, from the viewpoint of easy availability, an alkyl group having 1 to 6 carbon atoms which may be substituted by a hydroxyl group and/or an alkoxy group having 1 to 2 carbon atoms is preferable, and more preferable is an alkyl group having 1 to 6 carbon atoms. An alkyl group with 1 to 4 carbon atoms that can be substituted by a hydroxyl group and/or an alkoxy group with 1 to 2 carbon atoms, particularly preferably an alkoxy group that can be substituted by a hydroxyl group and/or an alkoxy group with 1 to 2 carbon atoms A substituted alkyl group having 1 to 2 carbon atoms.

With respect to (R2) a hydrocarbon group having 3 to 12 carbon atoms and a alicyclic hydrocarbon group having 3 to 6 carbon atoms in which at least one carbon atom can be replaced by an oxygen atom, the alicyclic hydrocarbon group having 3 to 6 carbon atoms As a hydrocarbon group, cyclohexane is mentioned, for example.

As for the alicyclic hydrocarbon group having 3 to 6 carbon atoms in which at least one carbon atom is substituted by an oxygen atom, for example, one carbon atom of an alicyclic hydrocarbon group having 3 carbon atoms is substituted by an oxygen atom. Epoxy group, Oxetanyl Ring in which one carbon atom of an alicyclic hydrocarbon group having 4 carbon atoms is substituted by an oxygen atom, and two carbon atoms in an alicyclic hydrocarbon group having 5 carbon atoms Dioxolane rings in which atoms are substituted by oxygen atoms, dioxane rings in which two carbon atoms of an alicyclic hydrocarbon group having 6 carbon atoms are substituted by oxygen atoms, and the like. In addition, the hydrogen atoms on these rings may be substituted with an alkyl group having 1 or 2 carbon atoms. Also, the hydrocarbon group having 3 to 12 carbon atoms and the alicyclic hydrocarbon group containing 3 to 6 carbon atoms preferably has 1 to 4 carbon atoms and one -CH ₂ - may be substituted by -O- The alkylene moiety of and the above-mentioned alicyclic hydrocarbon moiety having 3 to 6 carbon atoms. At this time, although the position of the substituent is not particularly limited, the hydrogen atom at the connecting portion between the alkylene moiety and the ring structure is preferably substituted with a methyl group or an ethyl group. Furthermore, in the structure in which two carbon atoms of an alicyclic hydrocarbon group are substituted with oxygen atoms, among the carbon atoms located between the two oxygen atoms, at least one hydrogen atom is preferably replaced by a carbon atom having one or more carbon atoms. 2 alkyl substitution. Specific examples of such groups include methyl 3-ethyl-3-oxetanyl acrylate, (2-methyl-2-ethyl-1,3-dioxolane) Cyclic-4-yl) methyl acrylate, Cyclic trimethylolpropane formal acrylate, etc.

Regarding (R3) the number of carbon atoms in the alkylene part is 1 to 4, and one -CH ₂ - of the alkylene part can be substituted by -O- phenylalkylene, the relevant group is preferably a A group represented by -(CH ₂ ) _k -C ₆ H ₅ or a group represented by -(CH ₂ ) _k -C ₆ H ₅ [k is 2 or 3].

With respect to the group represented by -((CH ₂ ) _m -O-) _n -X of (R4) [m and n in the formula each represent a number of 2 or 3, and X represents a hydrogen atom or a methyl group] and Preferable examples include methoxyethyl.

From the viewpoint of easily improving the electrical properties, flexibility, stretchability, and deformation resistance of the piezoelectric material, R in the above formula (I) is preferably a system that can be replaced by a hydroxyl group, an alkyl group having 1 or 2 carbon atoms And/or an alkyl group with 1 to 10 carbon atoms substituted by an alkoxy group with 1 to 6 carbon atoms, preferably an alkyl group with 1 to 2 carbon atoms substituted with 2 to 2 carbon atoms 8 alkyl groups.

The acrylic elastomer contained in the piezoelectric material of the present invention may have only one structural unit represented by the above formula (I), or may have two or more structural units represented by the above formula (I). In addition, the acrylic elastomer contained in the piezoelectric material of the present invention may contain at least one structural unit derived from another monomer within a range that does not impair the properties of the piezoelectric material of the present invention. In other words, the acrylic elastomer contained in the piezoelectric material of the present invention may be a monomer of one acrylic monomer having a structural unit represented by the above formula (I), or may be a monomer represented by the above formula (I). The copolymer of two or more acrylic monomers of the structural unit represented may be a copolymer of one acrylic monomer and at least one other monomer of the structural unit represented by the above formula (I).

Other monomers which can be copolymerized with one kind of acrylic monomer of the structural unit represented by the above formula (I) include, for example, a carboxyl group-containing monomer and a monomer having a structural unit represented by the formula (I). Carboxylic acid alkyl ester-based monomers other than acrylic monomers, amide group-containing monomers, aryl group-containing monomers, styrene-based monomers, nitrogen atom-containing monomers, fatty acid vinyl ester-based monomers , betaine monomer, etc.

As a carboxyl group-containing monomer, (meth)acrylic acid, maleic acid, fumaric acid, citraconic acid, mesaconic acid, itaconic acid, crotonic acid, etc. are mentioned, for example.

Examples of alkyl carboxylate monomers other than acrylic monomers having a structural unit represented by formula (I) include dodecyl (meth)acrylate, stearyl (methyl) ) Alkyl acrylates with alkyl groups such as acrylates having 11 to 20 carbon atoms; alkyl itaconate with 1 to 4 carbon atoms in the alkyl groups such as methyl itaconic acid, ethyl itaconic acid, etc. Wait.

Examples of the amide group-containing monomer include N-methyl(meth)acrylamide, N-ethyl(meth)acrylamide, and N-propyl(meth)acrylamide. Amine, N-isopropyl(meth)acrylamide, N-tert-butyl(meth)acrylamide, N,N-dimethyl(meth)acrylamide, N,N-diethyl (Meth) acrylamide etc. C1-C8 alkyl (meth) acrylamide etc. of the alkyl group.

Examples of the aryl group-containing monomer include aryl (meth)acrylates having 6 to 12 carbon atoms in the aryl group, such as benzyl (meth)acrylate.

As a styrene-type monomer, styrene, (alpha)-methylstyrene etc. are mentioned, for example.

As a nitrogen atom-containing monomer, N-vinylpyrrolidone, N-vinylcaprolactam, etc. are mentioned, for example.

As a fatty acid vinyl ester type monomer, vinyl acetate, vinyl propionate, etc. are mentioned, for example.

As a betaine monomer, for example, N-acryloyloxymethyl-N,N-dimethylammonium methyl-α-sulfobetaine, N-methacryloyloxymethyl- N,N-Dimethylammoniummethyl-α-sulfobetaine, N-acryloyloxymethyl-N,N-dimethylammoniumethyl-α-sulfobetaine, N-methylpropene Ethyloxymethyl-N,N-dimethylammoniumethyl-α-sulfobetaine, N-propenyloxymethyl-N,N-dimethylammoniumpropyl-α-sulfobetaine , N-methacryloyloxymethyl-N,N-dimethylammoniopropyl-α-sulfobetaine, N-acryloyloxymethyl-N,N-dimethylammoniobutyl- α-Sulfobetaine, N-methacryloyloxymethyl-N,N-dimethylammoniumbutyl-α-sulfobetaine, N-acryloyloxyethyl-N,N-di Methylammonium methyl-α-sulfobetaine, N-methacryloyloxyethyl-N,N-dimethylammonium methyl-α-sulfobetaine, N-acryloyloxyethyl -N,N-dimethylammoniumethyl-α-sulfobetaine, N-methacryloyloxyethyl-N,N-dimethylammoniumethyl-α-sulfobetaine, N- Acryloyloxyethyl-N,N-dimethylammoniopropyl-α-sulfobetaine, N-methacryloyloxyethyl-N,N-dimethylammoniopropyl-α-sulfonic acid Betaine, N-acryloyloxyethyl-N,N-dimethylammoniumbutyl-α-sulfobetaine, N-methacryloyloxyethyl-N,N-dimethylammonium Butyl-α-sulfobetaine, N-acryloyloxypropyl-N,N-dimethylammonium methyl-α-sulfobetaine, N-methacryloyloxypropyl-N, N-dimethylammonium methyl-α-sulfobetaine, N-acryloyloxypropyl-N,N-dimethylammoniumethyl-α-sulfobetaine, N-acryloyloxypropyl -N,N-dimethylammoniumethyl-α-sulfobetaine, N-acryloyloxypropyl-N,N-dimethylammoniumpropyl-α-sulfobetaine, N-methyl Acryloyloxypropyl-N,N-dimethylammoniumpropyl-α-sulfobetaine, N-acryloyloxypropyl-N,N-dimethylammoniumbutyl-α-sulfobetaine Base, N-methacryloyloxypropyl-N,N-dimethylammoniumbutyl-α-sulfobetaine, N-acryloyloxybutyl-N,N-dimethylammoniummethyl -α-sulfobetaine, N-methacryloyloxybutyl-N,N-dimethylammonium methyl-α-sulfobetaine, N-acryloyloxybutyl-N,N- Dimethylammoniumethyl-α-sulfobetaine, N-methacryloyloxybutyl-N,N-dimethylammoniumethyl-α-sulfobetaine, N-acryloyloxybutyl Base-N,N-dimethylammoniumpropyl-α-sulfobetaine, N-methacryloyloxybutyl-N,N-dimethylammoniumpropyl-α-sulfobetaine, N - Acryloyloxybutyl-N,N-dimethylammoniobutyl-α-sulfobetaine, N-methacryloyloxybutyl-N,N-dimethylammoniobutyl-α- N-(meth)acryloyloxyalkyl-N,N-dimethylammonium alkyl-α-sulfonic acid such as sulfobetaine Sultaines such as sulfobetaine monomers, etc.

From the viewpoint of easily obtaining an acrylic elastomer having sufficient piezoelectric properties, the content of the acrylic monomer represented by the formula (I) in the monomer components for producing the acrylic elastomer is preferably 90 mass % or more, more preferably 93 mass % or more, particularly preferably 95 mass % or more; and the content rate of the monomer copolymerizable with the acrylic monomer represented by formula (I) in the monomer component, preferably 10 mass % or less, more preferably 7 mass % or less, and particularly preferably 5 mass % or less. Furthermore, from the viewpoint of sufficiently discovering the effects obtained by using the acrylic monomer represented by the formula (I), among the monomer components in the production of the acrylic elastomer, the acrylic monomer represented by the formula (I) The content of the monomer is preferably 99% by mass or less, more preferably 98% by mass or less, and particularly preferably 97% by mass or less; and a monomer that can be copolymerized with the acrylic monomer represented by the formula (I) in the monomer component The content rate of MgO is preferably 1 mass % or more, more preferably 2 mass % or more, and particularly preferably 3 mass % or more.

Moreover, in the range which does not inhibit the objective of this invention, a crosslinkable monomer may be contained suitably in a monomer component. As described above, the acrylic elastic system contained in the piezoelectric material of the present invention includes a polymer derived from a structural unit having an acrylic monomer represented by the above formula (I). A crosslinkable monomer system: (1) It is contained as a structural unit in the main chain of a polymer having a structural unit derived from the acrylic monomer represented by the above formula (I), and it is contained in the above formula ( 1) The polymers having the acrylic monomer represented by the above formula (I) as the structural unit are bonded (crosslinked); and/or (2) they are not included in the polymers having the acrylic monomer represented by the above formula (I) as the structural unit unit and the main chain of the polymer containing the acrylic monomer represented by the above formula (I) is bonded to the side chain of the polymer containing the acrylic monomer represented by the above formula (I) as a structural unit, and the above formula (I) The polymers contained in the acrylic monomer as structural units are bonded (crosslinked). In the aspect of any one of (1) and (2), since the acrylic elastic system includes a structural unit derived from a crosslinkable monomer, the acrylic monomer represented by the above formula (I) is contained as a structural unit. Plural polymer bonds can form a polymer with a larger molecular weight.

As for the crosslinkable monomers, the polyfunctional monomers of the following compounds can be mentioned, for example, carbon atoms of alkylene groups such as methylenebisacrylamide and methylenebismethacrylamide. A (meth)acrylamide compound having two or more (meth)acrylamide groups, preferably having two (meth)propylene groups, of 1 to 4 alkylene bis(meth)acrylamides Acryloyl (meth)acrylamido compounds; ethylene di(meth)acrylate, ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, propylene glycol di(meth)acrylate Acrylates, triethylene glycol di(meth)acrylate, 1,4-butanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, 1,9-nonanediol Alcohol di(meth)acrylate, 2-n-butyl-2-ethyl-1,3-propanediol di(meth)acrylate, triethylene glycol di(meth)acrylate, tripropylene glycol di(meth)acrylate ) acrylate, tetraethylene glycol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, etc. having two or more (meth)acryloyl groups (meth)acrylate compound, preferably a (meth)acrylate compound with 2 or 3 (meth)acryloyl groups; diallylamine, triallylamine, etc. have 2 or more carbon-carbon Amine compounds with double bonds, preferably amine compounds with 2 or 3 carbon-carbon double bonds; aromatic compounds with more than 2 carbon-carbon double bonds such as divinylbenzene, diallylbenzene, etc., Preferred are aromatic compounds having 2 or 3 carbon-carbon double bonds; however, the present invention is not limited to the compounds listed in the relevant examples. These crosslinkable mono-systems may be used alone or in combination of two or more.

The weight average molecular weight of the acrylic elastomer contained in the piezoelectric material of the present invention is 1 million or more, preferably 1.1 million or more, more preferably 1.2 million or more, particularly preferably 1.3 million or more, and most preferably 1.4 million or more. If the weight-average molecular weight of the acrylic elastomer is less than 1 million, since the entanglement of polymer chains is sparse, the deformation of the piezoelectric material obtained at the end becomes large, and the flexibility and stretchability of the piezoelectric material are impaired. When the weight average molecular weight of an acrylic elastomer is more than the said lower limit, it will expand and contract easily. In addition, from the viewpoint of ease of manufacture, the weight average molecular weight of the acrylic elastomer is preferably 4 million or less, more preferably 3 million or less, and particularly preferably 2 million or less.

The weight average molecular weight of the acrylic elastomer can be measured using gel permeation chromatography (Gel permeation chromatography). Details such as measurement conditions are as described in Examples.

(Production method of acrylic elastomer) The acrylic elastomer contained in the piezoelectric material of the present invention can be obtained by polymerizing monomer components.

The method for polymerizing the monomer components includes a block polymerization method, a solution polymerization method, an emulsion polymerization method, a suspension polymerization method, and the like, but the present invention is not limited to the exemplified methods. Among these polymerization methods, the bulk polymerization method and the solution polymerization method are preferable from the viewpoint of easily obtaining an acrylic elastomer having a large amount of displacement at a low applied voltage. Also, from the viewpoint of easily obtaining an acrylic elastomer having a weight average molecular weight of 1,000,000 or more, a block polymerization method is preferred. The acrylic elastomer contained in the piezoelectric material of the present invention is not only a conventional acrylic rubber, but also by polymerizing the monomer components of the raw material by a suspension polymerization method, and preferably by a bulk polymerization method. obtained by polymerization. When the bulk polymerization method is used, it is possible to easily prepare an acrylic elastomer which is excellent in elongation, exhibits a large amount of displacement when a low voltage is applied, and has a weight average molecular weight of 1 million or more.

When polymerizing the monomer components by the solution polymerization method, a solvent can be used. As a solvent, a non-aqueous organic solvent is preferable. Examples of non-aqueous organic solvents include hydrocarbon-based organic solvents such as hexane, heptane, octane, isooctane, decane, and liquid paraffin; ether-based organic solvents such as dimethyl ether, diethyl ether, and tetrahydrofuran. ; ketone-based organic solvents such as acetone and methyl ethyl ketone; ester-based organic solvents such as methyl acetate, ethyl acetate, and butyl acetate; chloride-based organic solvents such as dichloromethane, chloroform, and carbon tetrachloride; dimethyl acetate diethylformamide; dimethylsulfoxide; dioxane, etc., but the present invention is not limited to the exemplified solvents. These organic solvents may be used independently, respectively, or may use 2 or more types together. Although the amount of the solvent cannot be generally limited depending on the type of the solvent, in general, it is preferable to use about 100 to 1,000 parts by mass of the solvent per 100 parts by mass of the monomer.

When polymerizing the monomer components, a polymerization initiator can be used. As a polymerization initiator, a photopolymerization initiator, a thermal polymerization initiator, etc. are mentioned, for example. Among these polymerization initiators, a photopolymerization initiator is preferable from the viewpoint of not leaving the thermal history of the (meth)acrylic-based elastomer.

As the photopolymerization initiator, for example, 2,4,6-trimethylbenzyldiphenylphosphine oxide, 2,2'-bis(o-chlorophenyl)-4,4 ',5,5'-tetraphenyl-1,1'-biimidazole, 2,4,6-tris(trichloromethyl)-1,3,5-triazine, 2,4-bis(trichloromethyl) Methyl)-6-(p-methoxyphenylvinyl)-1,3,5-triazine, diphenyliodonium tetrafluoroborate, diphenyliodonium hexafluorophosphate, 4,4' -Di-tert-butyldiphenyliodonium tetrafluoroborate, 4-diethylaminophenyldiazonium hexafluorophosphate, benzoin, 2-hydroxy-2-methyl-1-phenylpropane-2 - Ketone, benzophenone, thioxanthone, 2,4,6-trimethylbenzyldiphenylphosphine oxide, tetraethylammonium triphenylbutylborate, diphenyl-4-phenylsulfide Phenyl perylene hexafluorophosphate, 2,2-dimethoxy-1,2-diphenylethan-1-one, methyl phenylglyoxylate, 2-methyl-1-[4-( Methylthio)phenyl]-2-morpholinopropan-1-one, bis(2,4,6-trimethylbenzyl)phenylphosphine oxide, 1,2-octanedione, 1- [4-(phenylthio)-2-(o-benzoyl oxime)], bis(η5-2,4-cyclopentadien-1-yl)bis[2,6-difluoro-3-( 1H-pyrrol-1-yl) phenyl titanium] and other photo-radical polymerization initiators; 2,4,6-tris(trichloromethyl)-1,3,5-triazine, 2,4-bis( Trichloromethyl)-6-(p-methoxyphenylvinyl)-1,3,5-triazine, diphenyliodonium tetrafluoroborate, 4,4'-di-tert-butyldiphenyl Photocationic ring-opening polymerization initiators such as iodonium tetrafluoroborate, 4-diethylaminobenzenediazonium hexafluorophosphate, diphenyl-4-phenylthiophenyl hexafluorophosphate, etc., but the present invention It is not limited to the compounds listed in the relevant examples. These photopolymerization initiators may be used alone or in combination of two or more.

Although the thermal polymerization initiators include, for example, dimethyl-2,2'-azobis(2-methylpropionic acid), 2,2'-azobisisobutyronitrile (AIBN), Azo-based polymerization initiators such as dimethyl 2,2'-azobisisobutyrate, azodimethylvaleronitrile, etc.; peroxides such as benzyl peroxide, potassium persulfate, ammonium persulfate, etc. A polymerization initiator, but the present invention is not limited to the compounds listed in the relevant examples. These polymerization initiators may be used independently, respectively, or may use 2 or more types together.

Although the amount of the polymerization initiator is different depending on the type of the polymerization initiator, it cannot be generally limited, but in general, it is preferable to use about 0.01 to 20 mass parts of the polymerization initiator per 100 mass parts of the monomers. .

When polymerizing the monomer component, a chain transfer agent for adjusting the molecular weight of the obtained acrylic elastomer can be used. The chain transfer agent includes, for example, compounds having a thiol group such as lauryl mercaptan, dodecyl mercaptan, and thioglycerol; and inorganic salts such as sodium hypophosphite and sodium hydrogen sulfite. The present invention is not limited to the compounds exemplified in the relevant examples. These chain transfer agents may be used alone or in combination of two or more. Although the amount of the chain transfer agent cannot be generally limited depending on the type of the chain transfer agent, it is generally preferable to use about 0.01 to 10 parts by mass of the chain transfer agent per 100 parts by mass of the monomer.

The atmosphere at the time of polymerizing the monomer components is not particularly limited, and it may be in the air or in an inert gas atmosphere such as nitrogen and argon.

Although it does not specifically limit about the temperature at the time of superposing|polymerizing a monomer component, Usually, the temperature of about 5-100 degreeC is preferable. The time required to polymerize the monomer components is not generally limited due to differences in the polymerization conditions, and may be arbitrary, but is usually about 1 to 20 hours.

When the amount of the remaining monomer components becomes 20 mass % or less, the polymerization reaction can be stopped arbitrarily. In addition, the amount of the remaining monomer component can be measured using, for example, gel permeation chromatography (Gel permeation chromatography).

By polymerizing the monomer components as described above, the acrylic elastomer contained in the piezoelectric material of the present invention can be obtained.

(Vinylidene fluoride/trifluoroethylene copolymer) The vinylidene fluoride/trifluoroethylene copolymer contained in the piezoelectric material of the present invention includes a copolymer derived from a vinylidene fluoride structuring unit and a trifluoroethylene structuring unit. From the viewpoint of easily obtaining a piezoelectric material having excellent heat resistance and deformation resistance, the amount of the structural units derived from vinylidene fluoride in the vinylidene fluoride/trifluoroethylene copolymer is preferably based on the amount of all the structural units More than 55mol%, more preferably more than 70mol%, still more preferably more than 75mol%, especially preferably more than 80mol%, and most preferably more than 85mol%. Also, from the viewpoint of obtaining a piezoelectric material having good piezoelectric properties, the amount of the structural units derived from vinylidene fluoride is preferably 90 mol % or less, more preferably 86 mol % or less, based on the total structural unit amount.

From the viewpoint of obtaining a piezoelectric material with good piezoelectric properties, the amount of the structural units derived from trifluoroethylene in the vinylidene fluoride/trifluoroethylene copolymer is preferably 10 mol % or more based on the amount of all the structural units, and more The best system is more than 14mol%. In addition, from the viewpoint of obtaining a piezoelectric material having good heat resistance, the amount of the above-mentioned structural units derived from trifluoroethylene is preferably 45 mol % or less, more preferably 30 mol % or less, and still more preferably based on the amount of all structural units. Department of 25mol% or less, especially preferably 20mol% or less.

The piezoelectric material of the present invention may contain one type of vinylidene fluoride/trifluoroethylene copolymer, or may contain two or more types of vinylidene fluoride/trifluoroethylene copolymer.

Although the viscosity-average molecular weight of the vinylidene fluoride/trifluoroethylene copolymer contained in the piezoelectric material of the present invention is not particularly limited, from the viewpoint of easily obtaining a piezoelectric material that is hardly damaged by severe fracture deformation, the viscosity-average molecular weight is not particularly limited. The molecular weight is preferably more than 100,000/mol, more preferably more than 300,000/mol, still more preferably more than 500,000/mol, particularly preferably more than 5.5 million/mol, and most preferably more than 600,000/mol. The upper limit of the viscosity-average molecular weight is not particularly limited, and is, for example, about 2 million/mol or less. The viscosity-average molecular weight can be measured using a known method. In a preferred aspect of the present invention, the piezoelectric material includes a vinylidene fluoride/trifluoroethylene copolymer having a viscosity average molecular weight of not less than the lower limit (preferably not less than 300,000/mol), which is considered to be capable of With the acrylic elastomer having a relatively high weight average molecular weight, better polymer chain entanglement occurs, and as a result, a piezoelectric material having excellent flexibility, stretchability, and excellent deformation resistance can be obtained. Such piezoelectric materials can be particularly suitable for fields such as wearable devices.

The vinylidene fluoride/trifluoroethylene copolymer contained in the piezoelectric material of the present invention includes a structural unit derived from vinylidene fluoride and a structural unit derived from trifluoroethylene within the range that does not impair the effects of the present invention. , and may also contain structural units derived from other monomers that can be copolymerized with vinylidene fluoride/trifluoroethylene. As an example of another monomer, the other monomer which can be copolymerized with an acrylic monomer about the above-mentioned acrylic elastomer can be mentioned. From the viewpoint of easily obtaining a piezoelectric material excellent in heat resistance and piezoelectric properties, in the vinylidene fluoride/trifluoroethylene copolymer, the content ratios of structural units derived from vinylidene fluoride and structural units derived from trifluoroethylene are relatively high. Preferably it is 90 mass% or more, more preferably 93 mass% or more, and particularly preferably 95 mass% or more; and the content of structural units derived from other monomers that can be copolymerized with vinylidene fluoride/trifluoroethylene is preferably 10 mass % or less, more preferably 7 mass % or less, and particularly preferably 5 mass % or less. In addition, in the vinylidene fluoride/trifluoroethylene copolymer, the content ratio of structural units derived from vinylidene fluoride and structural units derived from trifluoroethylene is preferably 99% by mass, from the viewpoint of easily exerting the effects of other monomers. Hereinafter, it is more preferably 98 mass % or less, particularly preferably 97 mass % or less; and the content of structural units derived from other monomers that can be copolymerized with vinylidene fluoride/trifluoroethylene is preferably 1 mass % or more, more preferably 2 mass % or more of the best system, and 3 mass % or more of the extra-best system.

As the vinylidene fluoride/trifluoroethylene copolymer contained in the piezoelectric material of the present invention, for example, those having the composition and molecular weight shown in Patent Document 1 can be used, or commercially available ones can also be used. Examples of commercially available vinylidene fluoride/trifluoroethylene copolymers include "FC20", "FC25", and "FC30" manufactured by PIEZOTECH, for example.

(Composition for Piezoelectric Material and Piezoelectric Material) Although the method for producing the piezoelectric material of the present invention is not particularly limited, for example, the above-mentioned specific acrylic elastomer containing vinylidene fluoride/trifluoroethylene copolymer can be coated A piezoelectric material is produced by heat-treating and crystallizing a vinylidene fluoride/trifluoroethylene copolymer to develop piezoelectric properties after drying a solution of a solvent and a solvent. In addition, drying and heat treatment may be performed simultaneously. Another example includes a method for producing a piezoelectric material including a mixing step in which a vinylidene fluoride/trifluoroethylene copolymer, a monomer constituting the above-mentioned specific acrylic elastomer, and a solvent as necessary are mixed together. mixing; an acrylic elastomer obtaining step, polymerizing the aforementioned monomers to obtain the aforementioned specific acrylic elastomer; a piezoelectric characteristic generating step, generating piezoelectric characteristics by crystallizing a vinylidene fluoride/trifluoroethylene copolymer. Another example includes a method for producing a piezoelectric material including a mixing step in which the above-mentioned specific acrylic elastomer, a monomer constituting a vinylidene fluoride/trifluoroethylene copolymer, and a solvent as necessary are mixed together. mixing; a vinylidene fluoride/trifluoroethylene copolymer obtaining step of polymerizing the aforementioned monomers to obtain the aforementioned vinylidene fluoride/trifluoroethylene copolymer; a piezoelectric characteristic generating step, by making the vinylidene fluoride/trifluoroethylene copolymer Crystallization produces piezoelectric properties. The solution containing the vinylidene fluoride/trifluoroethylene copolymer, the above-mentioned specific acrylic elastomer, and a solvent required for the production of a piezoelectric material is also referred to as a "piezoelectric material composition" hereinafter. The composition for piezoelectric materials may contain any one of the vinylidene fluoride/trifluoroethylene copolymer and the specific acrylic elastomer described above, and a composition containing the other in the state of constituting each of the monomers. The present invention also provides a composition for a piezoelectric material. In addition, in this specification, the description about the acrylic elastomer and the vinylidene fluoride/trifluoroethylene copolymer contained in the piezoelectric material of the present invention can be similarly applied to the piezoelectric material contained in the present invention. Description of the composition of acrylic elastomer and vinylidene fluoride/trifluoroethylene copolymer.

The solvent that can be included in the composition for piezoelectric materials is not particularly limited as long as it can dissolve the vinylidene fluoride/trifluoroethylene copolymer and the acrylic elastomer. For example, N , N-dimethylformamide, N,N-dimethylacetamide, 1-methyl-2-pyrrolidone, etc.

Although not particularly limited, the vinylidene fluoride/trifluoroethylene copolymer can be prepared by heating and mixing the vinylidene fluoride/trifluoroethylene copolymer, the acrylic elastomer, and the necessary solvent as necessary. and the acrylic elastomer are dissolved in a solvent to produce the piezoelectric material composition of the present invention. In addition, the composition for piezoelectric materials can be produced by heating and mixing the vinylidene fluoride/trifluoroethylene copolymer, the monomer and solvent constituting the above-mentioned specific acrylic elastomer, if necessary, at the same time. In this case, the composition containing the acrylic elastomer obtained after being polymerized with the monomer constituting the above-mentioned specific acrylic elastomer contained in the composition for piezoelectric material is also the composition for piezoelectric material of the present invention. The composition for piezoelectric materials containing the monomer which comprises a vinylidene fluoride/trifluoroethylene copolymer and the said specific acrylic elastomer can also be manufactured similarly.

Next, the composition for piezoelectric material of the present invention is applied on a substrate, and as necessary, the monomer constituting the acrylic elastomer or the monomer constituting the vinylidene fluoride/trifluoroethylene copolymer is polymerized, and dried by drying The piezoelectric material of the present invention can be produced by crystallization and heat treatment to develop piezoelectric properties. For example, in the case of the piezoelectric material-based piezoelectric film of the present invention, the composition for a piezoelectric material of the present invention may be coated on the surface of the substrate. For example, in the case of the piezoelectric material-based piezoelectric wire of the present invention, the composition for piezoelectric material of the present invention can be coated on a conductive wire such as a copper wire using a conventional method, such as Coated on a single wire made of conductive material.

The method for drying the piezoelectric material composition of the present invention after coating is not particularly limited, and it can be heated and dried under atmospheric pressure or reduced pressure at a temperature at which the solvent is evaporated. For example, drying is preferably carried out at a temperature of 15 to 80°C.

The temperature of the heat treatment in the production of the piezoelectric material of the present invention is preferably a temperature equal to or higher than the Curie point of the vinylidene fluoride/trifluoroethylene copolymer and equal to or lower than the melting point. The heating time is preferably 30 minutes or more, more preferably 2 hours or more. By performing such a heat treatment, the vinylidene fluoride/trifluoroethylene copolymer can be crystallized, and piezoelectric properties can be found.

The piezoelectric material of the present invention can be a piezoelectric film, a piezoelectric wire, or a piezoelectric block. The piezoelectric material is preferably a piezoelectric film from the viewpoint of easily utilizing the features of the piezoelectric material of the present invention having excellent flexibility and stretchability.

From the viewpoint of easily obtaining sufficient piezoelectric properties, the electromechanical coupling coefficients k ₃₁ and k _t of the piezoelectric material of the present invention are preferably k ₃₁ of 0.03 or more and k _t of 0.1 or more, more preferably k ₃₁ It is 0.045 or more and k _t is 0.15 or more, and it is especially preferable that k ₃₁ is 0.06 or more and k _t is 0.2 or more. The method for measuring the electromechanical coupling coefficient is as described in the Examples.

From the viewpoint of easily obtaining the excellent flexibility and stretchability required in the fields of wearable devices and the like, the Young's ratio of the piezoelectric material of the present invention is preferably 3.1 GPa or less, more preferably 2.9 GPa or less, and particularly preferably Department of 2.5GPa or less. The Young's ratio was measured as described in the Examples. The lower limit value of the Young's ratio is not particularly limited, but from the viewpoint of easily improving the dimensional stability of the piezoelectric material, it can be, for example, 0.1 GPa or more.

[Examples] Hereinafter, the present invention will be described in more detail by way of examples, but these examples are intended to illustrate the present invention, and the present invention is not limited to the following examples. In addition, unless otherwise noted, "%" and "part" in the examples represent "mass %" and "quality part", respectively.

In Examples and Comparative Examples to be described later, the following polymers were used. ‧Vinylidene fluoride/trifluoroethylene copolymer A1 VDF: TrFE = 85:15 (mol ratio) viscosity average molecular weight 650,000/mol ‧Vinylidene fluoride/trifluoroethylene copolymer A2 VDF: TrFE = 75:25 (mol ratio) Ear ratio) Viscosity average molecular weight 350,000/mol ‧Acrylic Elastomer B1 "Suave-00" manufactured by Osaka Organic Chemical Industry Co., Ltd., homopolymer of ethyl acrylate, weight average molecular weight 1.5-1.6 million

(Weight Average Molecular Weight of Acrylic Elastomer) The weight average molecular weight of the acrylic elastomer was measured by gel permeation chromatography (GPC). Specifically, a 0.05 to 0.1 mass % solution obtained by dissolving an acrylic elastomer in tetrahydrofuran is used as a measurement sample. The measurement conditions are as follows. Machine: Tosoh Corporation, Model: HLC-8320GPC Column: Tosoh Corporation, Model: TSKgel GMHHR Eluent: THF Flow Rate: 0.6mL/min Temperature: 40°C Detector: Refractive Index Detection Refractive index (RI, refractive index) Molecular weight standard: standard polystyrene

Example 1: Production of piezoelectric material composition 1 and piezoelectric material 1 5.5617 g of vinylidene fluoride/trifluoroethylene copolymer (P(VDF/TrFE) A1, 0.2825 g of acrylic elastomer B1, and 53.9796g of N,N-dimethylformamide was mixed in a flask with a stopper, and the production of vinylidene fluoride/trifluoroethylene copolymer A1 and acrylic elastomer B1 having the mass ratio shown in Table 1 Composition 1 for piezoelectric materials.

The piezoelectric material composition 1 produced as described above was applied on a glass substrate to a thickness of 0.9 mm, heated at 3 hPa and 65° C. for one hour or more, and the solvent in the piezoelectric material composition was dried. The obtained coating film was heated at 142° C. for two hours in the atmosphere, and heat-treated to crystallize the vinylidene fluoride/trifluoroethylene copolymer, thereby finding piezoelectric properties. Next, the coating film after the heat treatment was peeled off from the glass substrate to obtain a film. Next, using a resistance heating type vacuum vapor deposition machine, the aluminum was heated and evaporated in a pressure range of 5x10 ^-3 to 5x10 ^-4 Pa, and electrode coatings were formed on both sides of the film. Between the electrodes on both sides of the film thus obtained, a triangular-wave alternating current with a voltage amplitude of 120 MV/m and a frequency of 100 mHz or less was directly applied for 6 cycles (Our company: (stock) Ire Alstar System, Using a polling processing system), polarization processing was performed, and piezoelectric material 1 was obtained. Hereinafter, the measurement method, calculation method, and evaluation method of physical properties will be described.

(Residual polarization/Anti-electric field) Residual polarization and anti-electric field were read from a hysteresis curve of D (electrical displacement)-E (electric field). Here, the hysteresis curve of D-E is the value of the last 6 cycles of the polarization treatment performed by the above-mentioned division method, and the voltage applied to the sample and the capacitor voltage on the side of the Sawyer-tower circuit are two types. The voltage measurement data is converted into the values of D (electrical displacement) and E (electric field) and plotted.

[式中，C₀ =(ε_r ×S×ε₀ )/t [式中，ε_r ：相對介電常數，ε₀ ：真空介電常數「F/m」，S：電極面積「m² 」，t：膜厚「m」] K_t ：機電耦合係數，ψ：機械損失，φ：介電損失，v：音速[m/s] ，ω：角速度[rad/s](=2πf，f：頻率[Hz])]。(Electromechanical Coupling Coefficient) The piezoelectric material 1 after polarization treatment was used as a test material for the electromechanical coupling coefficient in the extension direction ( _{k 31} ), and cut out into 30 x 5 mm; A sample of the test material for the electromechanical coupling coefficient, and cut out to 5 x 5mm. For each measurement sample, admission-phase data (Admittance-phase data) was measured in the range of 1 k to 110 MHz with an impedance analyzer (manufactured by Agilent Technologies (current keysite technology), 4294A). The obtained measurement results were applied to the admittance formula of free resonance to obtain the electromechanical coupling coefficient. Specifically, taking the case in the thickness direction as an example, the absolute value and phase result of the admission data measured by the impedance analyzer are substituted into the values of the respective constants so as to agree with the calculated values of the following equations , and calculate the electromechanical coupling coefficient in the thickness direction. [Number 1]

[where, C ₀ =(ε _r ×S ×ε ₀ )/t [where, ε _r : relative permittivity, ε ₀ : vacuum permittivity "F/m", S: electrode area "m ² ”, t: film thickness “m”] K _t : electromechanical coupling coefficient, ψ: mechanical loss, φ: dielectric loss, v: sound velocity [m/s], ω: angular velocity [rad/s] (=2πf, f : Frequency [Hz])].

(Fracture Deformation/Young's Ratio) Piezoelectric material 1 was cut into test pieces having a size of 15 mm in width and 100 mm in length. The tensile test was performed using Autograph AGS-1kNX manufactured by Shimadzu Corporation under the conditions of distance between chucks: 50 mm and tensile speed: 50 mm/min. From the obtained load-displacement amount, fracture deformation and Young's ratio were obtained. Here, the distance between the punctuation points is used as the distance between the chucks, and it is calculated by the least squares method using the data of the Young's ratio in the stress range of 5 to 15 MPa. In addition, a low Young's ratio means that the piezoelectric material is excellent in flexibility and stretchability. In addition, the large fracture deformation means that the piezoelectric material is hardly damaged by stress and is excellent in deformation resistance.

The results obtained for Piezoelectric Material 1 of Example 1 are shown in Table 2.

Examples 2 to 4 and Comparative Examples 1 to 2 The piezoelectric materials were prepared in the same manner as in Example 1, except that the compositions shown in Table 1 were changed. The same measurement was performed for the obtained piezoelectric material, and the results are shown in Table 2.

[Table 1]

[Table 2]

none

Claims (10)

A piezoelectric material comprising: a vinylidene fluoride/trifluoroethylene copolymer; and an acrylic elastomer having a structural unit derived from an acrylic monomer represented by formula (I) and having a weight average molecular weight of 100 more than ten thousand; formula (I):

(R in the formula is an alkyl group with 1 to 10 carbon atoms which can be substituted by a hydroxyl group, an alkyl group with 1 or 2 carbon atoms and/or an alkoxy group with 1 to 6 carbon atoms; An alicyclic hydrocarbon group with 3 to 6 carbon atoms in which one carbon atom can be replaced by an oxygen atom; a hydrocarbon group with 3 to 12 carbon atoms; the alkylene moiety has 1 to 4 carbon atoms, and the alkylene group has 1 to 4 carbon atoms. A part of -CH ₂ - may be substituted by -O- phenylalkylene; or, a group represented by -((CH ₂ ) _m -O-) _n -X [m and n in the formula are each A number representing 2 or 3, and X represents a hydrogen atom or a methyl group]). The piezoelectric material according to claim 1, wherein the amount of the vinylidene fluoride/trifluoroethylene copolymer is 98 to 70% by mass based on the entire piezoelectric material, and the amount of the acrylic elastomer is based on the entire piezoelectric material 2 to 30% by mass. The piezoelectric material according to claim 1 or 2, wherein the viscosity-average molecular weight of the vinylidene fluoride/trifluoroethylene copolymer is 100,000/mol or more. The piezoelectric material according to claim 1 or 2, wherein, in the vinylidene fluoride/trifluoroethylene copolymer, the amount derived from the vinylidene fluoride structural unit is 55 to 90 mol % based on the amount of the entire structure. The piezoelectric material according to claim 3, wherein, in the vinylidene fluoride/trifluoroethylene copolymer, the amount derived from the vinylidene fluoride structural unit is 55 to 90 mol % based on the amount of the entire structure. The piezoelectric material according to claim 1 or 2, wherein the Young's ratio is 3.1 GPa or less. The piezoelectric material according to claim 3, wherein the Young's ratio is 3.1 GPa or less. The piezoelectric material according to claim 4, wherein the Young's ratio is 3.1 GPa or less. The piezoelectric material according to claim 5, wherein the Young's ratio is 3.1 GPa or less. A composition for a piezoelectric material, comprising: a vinylidene fluoride/trifluoroethylene copolymer; and an acrylic elastomer having a structural unit derived from an acrylic monomer represented by formula (I) and having a weight average of Molecular weight is more than 1 million; formula (I):

(R in the formula is an alkyl group with 1 to 10 carbon atoms which can be substituted by a hydroxyl group, an alkyl group with 1 or 2 carbon atoms and/or an alkoxy group with 1 to 6 carbon atoms; An alicyclic hydrocarbon group with 3 to 6 carbon atoms in which one carbon atom can be replaced by an oxygen atom; a hydrocarbon group with 3 to 12 carbon atoms; the alkylene moiety has 1 to 4 carbon atoms, and the alkylene group has 1 to 4 carbon atoms. One part of -CH ₂ - may be substituted by -O- phenylalkylene; or, a group represented by -((CH ₂ ) _m -O-) _n -X [where m represents 2 or A number of 3, n represents a number from 1 to 3, and X represents a hydrogen atom or a methyl group]).