Resin composition, piezoelectric material, piezoelectric film, and piezoelectric element

Abstract

This resin composition contains: a vinylidene cyanide-vinyl carboxylate copolymer including a structural unit derived from vinylidene cyanide represented by formula (1) and a structural unit derived from a vinyl ester represented by formula (2); and a polymer including a glucose skeleton, or a polymer including a vinyl alcohol skeleton. The polymer including a glucose skeleton is a cellulose ester including a structural unit derived from a cellulose ester represented by formula (3) or a cellulose ether including a structural unit derived from a cellulose ether represented by formula (4), and the polymer including a vinyl alcohol skeleton is a polyvinyl formal having three structural units represented by formula (5).

Description

Resin composition, piezoelectric material, piezoelectric film, and piezoelectric element

[0001] The present invention relates to a resin composition, a piezoelectric material, a piezoelectric film, and a piezoelectric element. This application claims priority to Japanese Patent Application No. 2024-055313, filed on March 29, 2024, the contents of which are incorporated herein by reference.

[0002] Conventionally, the piezoelectric material forming the piezoelectric body of a piezoelectric element has been a ceramic material, PZT (PbZrO ３ -PbTiO ３ PZT (a type solid solution) is widely used. However, PZT contains lead and is a ceramic, so it has the disadvantage of being brittle. For this reason, there is a demand for piezoelectric materials that are environmentally friendly and highly flexible.

[0003] One possible piezoelectric material that can meet these requirements is a polymeric piezoelectric material. Polymeric piezoelectric materials include ferroelectric polymers such as polyvinylidene fluoride (PVDF) and vinylidene fluoride-trifluoroethylene copolymer (P(VDF-TrFE)). However, these ferroelectric polymers have insufficient heat resistance. For this reason, piezoelectric elements made of conventional ferroelectric polymers lose their piezoelectric properties and their physical properties, such as elastic modulus, deteriorate at high temperatures. Therefore, piezoelectric elements having piezoelectric elements made of conventional ferroelectric polymers have a narrow usable temperature range.

[0004] Another piezoelectric material is amorphous polymer piezoelectric material, which acquires piezoelectricity by cooling while polarizing it at a temperature near its glass transition temperature (Tg). Amorphous polymer piezoelectric materials lose their piezoelectric properties when the temperature approaches the glass transition temperature. Therefore, amorphous polymer piezoelectric materials with high glass transition temperatures and good heat resistance are in demand.

[0005] An example of an amorphous polymer piezoelectric material with a high glass transition temperature is vinylidene cyanide-vinyl acetate copolymer (P(VDCN-VAc)) (see, for example, Patent Document 1).

[0006] International Publication No. 1991 / 013922

[0007] However, vinylidene cyanide-vinyl carboxylate copolymer has a polar nitrile group (-CN (cyano group)), and therefore piezoelectric films containing this copolymer have the disadvantage of having a high dielectric constant.

[0008] The present invention has been made in view of the above circumstances, and aims to provide a resin composition that can form a piezoelectric film having excellent heat resistance and a low dielectric constant and that can be suitably used as a piezoelectric material. Another object of the present invention is to provide a piezoelectric material that includes the resin composition of the present invention and that can provide a piezoelectric film having excellent heat resistance and a low dielectric constant. Another object of the present invention is to provide a piezoelectric film that includes the piezoelectric material of the present invention and has excellent heat resistance and a low dielectric constant, and a piezoelectric element that includes the piezoelectric film of the present invention.

[0009] In order to solve the above problems, the following means are provided: A resin composition according to one aspect of the present invention comprises a vinylidene cyanide-vinyl carboxylate copolymer containing a structural unit derived from vinylidene cyanide represented by the following formula (1) and a structural unit derived from a vinyl ester represented by the following formula (2), and a polymer containing a glucose skeleton or a polymer containing a vinyl alcohol skeleton, wherein the polymer containing a glucose skeleton is a cellulose ester containing a structural unit derived from a cellulose ester represented by the following formula (3) or a cellulose ether containing a structural unit derived from a cellulose ether represented by the following formula (4), and the polymer containing a vinyl alcohol skeleton is polyvinyl formal having three structural units represented by the following formula (5).

[0010] (In formula (2), R １ is an organic group having 1 to 15 carbon atoms or a hydrogen atom. ２ are each a hydrogen atom or a carboxylic acid ester group, and three R ２ At least one of the three R is a carboxylic acid ester group. ３ are each a hydrogen atom or an aliphatic ether group, and three R ３ At least one of R is an aliphatic ether group.４ is a carboxylic acid ester group.

[0011] The resin composition of the present invention includes a vinylidene cyanide-vinyl carboxylate copolymer containing a structural unit derived from vinylidene cyanide represented by formula (1) and a structural unit derived from a vinyl ester represented by formula (2), and a polymer containing a glucose skeleton or a polymer containing a vinyl alcohol skeleton. Therefore, the resin composition of the present invention can form a piezoelectric film having excellent heat resistance and a low dielectric constant, and is therefore suitable for use as a piezoelectric material.

[0012] In order to solve the above problems, the present inventors have focused on vinylidene cyanide-vinyl carboxylate copolymer, which is a piezoelectric material having a high glass transition temperature (Tg) and good heat resistance, and have conducted extensive research as described below.

[0013] First, the inventors conceived the idea of ​​forming a piezoelectric film with a low dielectric constant by using a resin composition containing a vinylidene cyanide-vinyl carboxylate copolymer together with another polymer. However, until now, no polymer was known that was even compatible with vinylidene cyanide-vinyl carboxylate copolymer, and no polymer was known that could be used together with vinylidene cyanide-vinyl carboxylate copolymer to form a piezoelectric film with a low dielectric constant.

[0014] Therefore, the present inventors have conducted extensive research into various polymers, focusing on their dielectric constants when formed into a sheet. Generally, a person skilled in the art would not think of using a polymer having a higher dielectric constant when formed into a sheet than a piezoelectric film made of a vinylidene cyanide-vinyl carboxylate copolymer together with a vinylidene cyanide-vinyl carboxylate copolymer in order to form a piezoelectric film having a lower dielectric constant than a piezoelectric film made of a vinylidene cyanide-vinyl carboxylate copolymer.

[0015] However, it has surprisingly been found that a piezoelectric film with a low dielectric constant can be formed by using a specific polymer containing a glucose skeleton or a specific polymer containing a vinyl alcohol skeleton, which has a dielectric constant when formed into a sheet equal to or higher than that of a piezoelectric film made of a specific vinylidene cyanide-vinyl carboxylate copolymer, together with a specific vinylidene cyanide-vinyl carboxylate copolymer. That is, it has been found that a sheet formed using a resin composition containing a specific vinylidene cyanide-vinyl carboxylate copolymer and a polymer containing a specific glucose skeleton or a polymer containing a specific vinyl alcohol skeleton has a lower dielectric constant than a piezoelectric film made of a vinylidene cyanide-vinyl carboxylate copolymer contained in the resin composition, and a sheet made of a polymer containing a glucose skeleton or a polymer containing a vinyl alcohol skeleton contained in the resin composition.

[0016] The reason for this is presumably that hydroxyl groups and / or water molecules contained in the polymer containing a specific glucose skeleton or the polymer containing a specific vinyl alcohol skeleton form hydrogen bonds with the cyano groups of the specific vinylidene cyanide-vinyl carboxylate copolymer, thereby reducing the mobility of the cyano groups of the specific vinylidene cyanide-vinyl carboxylate copolymer.

[0017] Furthermore, the present inventors formed a piezoelectric film using a resin composition containing a specific vinylidene cyanide-vinyl carboxylate copolymer and a polymer containing a specific glucose skeleton or a polymer containing a specific vinyl alcohol skeleton, and confirmed that a piezoelectric film with a lower dielectric constant could be obtained compared to a piezoelectric film formed in the same manner except that a material not containing the polymer containing the specific glucose skeleton or the polymer containing the specific vinyl alcohol skeleton was used, thereby conceiving the present invention.

[0018] The present invention includes the following aspects.

[0019] [1] A resin composition comprising: a vinylidene cyanide-vinyl carboxylate copolymer containing a structural unit derived from vinylidene cyanide represented by the following formula (1) and a structural unit derived from a vinyl ester represented by the following formula (2); and a polymer containing a glucose skeleton or a polymer containing a vinyl alcohol skeleton, wherein the polymer containing a glucose skeleton is a cellulose ester containing a structural unit derived from a cellulose ester represented by the following formula (3) or a cellulose ether containing a structural unit derived from a cellulose ether represented by the following formula (4), and the polymer containing a vinyl alcohol skeleton is polyvinyl formal having three structural units represented by the following formula (5).

[0020] (In formula (2), R １ is an organic group having 1 to 15 carbon atoms or a hydrogen atom. ２ are each a hydrogen atom or a carboxylic acid ester group, and three R ２ At least one of the three R is a carboxylic acid ester group. ３ are each a hydrogen atom or an aliphatic ether group, and three R ３ At least one of R is an aliphatic ether group. ４ is a carboxylic acid ester group.

[0021] [2] The carboxylic acid ester group of the formula (3) is —C(═O)CH ３ , —C(═O)CH ２ CH ３ , —C(═O)CH ２ CH ２ CH ３ , -C(=O)CH(CH ３ ) ２ and one or more groups selected from groups represented by the following formula (3-1):

[0022]

[0023] [3] The aliphatic ether group in the formula (4) is —O—CH ３ , —O—CH２ CH ２ -OH and -OCH ２ CHOHCH ３ The resin composition according to [1] or [2], wherein the group consisting of one or more groups represented by the formula:

[0024] [4] The R of the formula (5) ４ is -C(=O)CH ３ The resin composition according to any one of [1] to [3],

[0025] [5] The resin composition according to any one of [1] to [4], wherein the content of the polymer containing a glucose skeleton or the polymer containing a vinyl alcohol skeleton relative to the total mass of the vinylidene cyanide-vinyl carboxylate copolymer and the polymer containing a glucose skeleton or the polymer containing a vinyl alcohol skeleton is 0.5 mass% or more and 15 mass% or less.

[0026] [6] A piezoelectric material comprising the resin composition according to any one of [1] to [5]. [7] A piezoelectric film comprising the resin composition according to any one of [1] to [5]. [8] A piezoelectric element having the piezoelectric film according to [7] and electrodes disposed on one surface and the other surface of the piezoelectric film.

[0027] The resin composition, piezoelectric material, piezoelectric film, and piezoelectric element of the present invention will be described in detail below. [Resin Composition, Piezoelectric Material] In this embodiment, the resin composition of the present invention will be described as an example of using it as a piezoelectric material, which is a material for a piezoelectric film. The piezoelectric material (resin composition) of this embodiment contains a vinylidene cyanide-vinyl carboxylate copolymer and a polymer containing a glucose skeleton or a polymer containing a vinyl alcohol skeleton.

[0028] (Vinylidene cyanide-vinyl carboxylate copolymer) The vinylidene cyanide-vinyl carboxylate copolymer contained in the piezoelectric material of the present embodiment contains a structural unit derived from vinylidene cyanide represented by formula (1) (hereinafter, sometimes referred to as a "first structural unit") and a structural unit derived from a vinyl ester represented by formula (2) (hereinafter, sometimes referred to as a "second structural unit") The piezoelectric material of the present embodiment may contain only one type of vinylidene cyanide-vinyl carboxylate copolymer, or two or more types of vinylidene cyanide-vinyl carboxylate copolymers.

[0029] In the vinylidene cyanide-vinyl carboxylate copolymer contained in the piezoelectric material of this embodiment, the arrangement order of the first structural units and the second structural units, which are repeating units, is not particularly limited. Therefore, the vinylidene cyanide-vinyl carboxylate copolymer may be, for example, an alternating copolymer in which the first structural units and the second structural units are arranged alternately, a random copolymer in which the first structural units and the second structural units are arranged in no order, or a block copolymer having a block sequence portion in which the first structural units are arranged consecutively and a block sequence portion in which the second structural units are arranged consecutively.

[0030] In the vinylidene cyanide-vinyl carboxylate copolymer contained in the piezoelectric material of this embodiment, the first structural unit containing the C-CN dipole that contributes to the piezoelectric properties, together with the second structural unit, forms a molecular chain with a large dipole moment. Moreover, the vinylidene cyanide-vinyl carboxylate copolymer has a high glass transition temperature (Tg). For these reasons, the piezoelectric material of this embodiment containing the vinylidene cyanide-vinyl carboxylate copolymer has a piezoelectric constant d ３３ It has a sufficiently high piezoelectric property, and can form a coating film with good heat resistance, making it suitable as a material for piezoelectric films.

[0031] In the second structural unit contained in the vinylidene cyanide-vinyl carboxylate copolymer, R １ is an organic group having 1 to 15 carbon atoms or a hydrogen atom. The vinylidene cyanide-vinyl carboxylate copolymer has, in the molecule, R １ or may contain only one type of second structural unit in which R１ The second structural unit may contain a plurality of second structural units having different structures.

[0032] In the piezoelectric material of this embodiment, the R １ is an organic group having 1 to 15 carbon atoms or a hydrogen atom, so R １ The volume of the first structural unit containing the C—CN dipole is not too large, and the volume ratio of the first structural unit containing the C—CN dipole in the molecule is easily ensured. As a result, when a coating film containing the piezoelectric material of this embodiment is subjected to a polarization treatment, a piezoelectric film with excellent piezoelectric properties is easily obtained.

[0033] R １ is an organic group having 1 to 15 carbon atoms, １ Examples of R include an alkyl group having 1 to 15 carbon atoms which may have a substituent, an aromatic ring group which may have a substituent, a phosphonic acid group which may have a substituent, a heterocyclic group which may have a substituent, and an aliphatic ring group which may have a substituent. １ When is one of these groups, the substituents it may have include halogeno groups such as a fluoro group and a chloro group, a nitrile group, and an alkyl group.

[0034] R １ is an alkyl group having 1 to 15 carbon atoms which may have a substituent, １ Examples of the alkyl group include a linear alkyl group having 1 to 15 carbon atoms, a dichloromethyl group, a trichloromethyl group, a difluoromethyl group, a trifluoromethyl group, a 2-cyanoethyl group, an isobutyl group, a t-butyl group, a 2-ethylhexyl group, a 2-(acetoacetyloxy)ethyl group, etc. Examples of the linear alkyl group having 1 to 15 carbon atoms include a methyl group, an ethyl group, an n-propyl group, an n-butyl group, an n-pentyl group, an n-hexyl group, an n-heptyl group, an n-octyl group, an n-nonyl group, an n-decyl group, an n-undecyl group, an n-dodecyl group, an n-tridecyl group, an n-tetrasil group, and an n-pentadecyl group.

[0035] R １ is an aromatic ring group which may have a substituent, R １Examples of the alkyl group include a phenyl group, a 2-methylphenyl group, a 3-methylphenyl group, a 4-methylphenyl group, a 4-t-butylphenyl group, a 4-nitrophenyl group, a 4-cyanophenyl group, and a naphthyl group.

[0036] R １ is an optionally substituted phosphonic acid group, R １ Examples of R include a dimethylphosphonylmethyl group, a diethylphosphonylmethyl group, and a diphenylphosphonylmethyl group. １ is an optionally substituted heterocyclic group, R １ Examples of the alkyl group include a furfuryl group, a tetrahydrofurfuryl group, a 2-oxotetrahydrofuran-3-yl group, and a 4-methyl-2-oxotetrahydro-2H-pyran-4-yl group.

[0037] R １ is an optionally substituted aliphatic cyclic group, R １ Examples of the alkyl group include a 1-adamantyl group, a 2-methyl-2-adamantyl group, a 2-ethyl-2-adamantyl group, a 2-isopropyl-2-adamantyl group, an isobornyl group, and a dicyclopentanyl group.

[0038] R １ Among these, R is preferably a linear alkyl group having 1 to 3 carbon atoms, and particularly preferably a methyl group. １ is a linear alkyl group having 1 to 3 carbon atoms, R １ The volume of the first structural unit containing the C-CN dipole becomes smaller, and it becomes easier to secure a larger volume ratio of the first structural unit containing the C-CN dipole in the molecule. As a result, by performing a polarization treatment on the coating film containing the piezoelectric material containing the vinylidene cyanide-vinyl carboxylate copolymer, it becomes easier to obtain a piezoelectric film with even better piezoelectric properties.

[0039] The vinylidene cyanide-vinyl carboxylate copolymer contained in the piezoelectric material of this embodiment may optionally contain one or more structural units other than the first structural unit and the second structural unit. Examples of the other structural units include structural units derived from known monomers or oligomers having polymerizable unsaturated bonds.

[0040] Of the structural units contained in the vinylidene cyanide-vinyl carboxylate copolymer, the total content of the first structural unit and the second structural unit is preferably 80% by mass or more. This is because the resulting piezoelectric material is capable of forming a coating film with even better piezoelectric properties and heat resistance. The total content of the first structural unit and the second structural unit is more preferably 90% by mass or more, and most preferably consists of only the first structural unit and the second structural unit.

[0041] In the vinylidene cyanide-vinyl carboxylate copolymer contained in the piezoelectric material of this embodiment, the content of the second structural unit relative to 100 moles of the first structural unit, which is a repeating unit, is preferably 95 moles to 105 moles. When the content of the second structural unit relative to 100 moles of the first structural unit is 95 moles or more, it is possible to prevent the molecular polarity from becoming too high due to an excessive number of C-CN dipoles in the molecule. As a result, the relative dielectric constant of a piezoelectric film formed using the piezoelectric material of this embodiment is lowered. Furthermore, when the content of the second structural unit relative to 100 moles of the first structural unit is 105 moles or less, it is easy to ensure the volume ratio of the first structural unit containing a C-CN dipole in the molecule. As a result, when a coating film containing the piezoelectric material of this embodiment is subjected to a polarization treatment, it is easy to obtain a piezoelectric film with excellent piezoelectric properties.

[0042] The weight-average molecular weight (Mw) of the vinylidene cyanide-vinyl carboxylate copolymer contained in the piezoelectric material of this embodiment is preferably 10,000 to 1,000,000. When the weight-average molecular weight (Mw) of the copolymer is 10,000 or more, the film-forming properties are good, and a piezoelectric film containing the piezoelectric material of this embodiment can be easily produced. Furthermore, when the weight-average molecular weight (Mw) of the copolymer is 1,000,000 or less, the compatibility with a polymer containing a glucose skeleton or a polymer containing a vinyl alcohol skeleton is improved, and by mixing with a polymer containing a glucose skeleton or a polymer containing a vinyl alcohol skeleton, a piezoelectric material can be easily and efficiently produced.

[0043] The weight-average molecular weight (Mw) of the vinylidene cyanide-vinyl carboxylate copolymer in this embodiment is a value measured by the following method: The weight-average molecular weight (Mw) of the vinylidene cyanide-vinyl carboxylate copolymer was measured using a liquid chromatograph (LC-2050C; manufactured by Shimadzu Corporation) under the measurement conditions shown below, and the weight-average molecular weight (Mw) was determined by comparison with the following standard substances of known molecular weights.

[0044] <Measurement conditions> Column: TSKGel α-M (Tosoh Corporation), three columns connected Mobile phase solvent: N,N-dimethylformamide (DMF) (10 mM, LiBr added) Flow rate: 1.0 ml / min Column temperature: 40°C Standards: polyethylene glycol, polyethylene oxide (PEG, PEO) (Tosoh Corporation, SCIENTIFIC POLYMER PRODUCTS, INC., Agilent Technologies)

[0045] The vinylidene cyanide-vinyl carboxylate copolymer contained in the piezoelectric material of this embodiment can be produced by a conventionally known method, for example, by radical copolymerizing raw material monomers containing vinylidene cyanide and a vinyl ester having a structure corresponding to the second structural unit using a polymerization initiator such as azobisbutyronitrile.

[0046] (Polymer containing a glucose skeleton or polymer containing a vinyl alcohol skeleton) The piezoelectric material of this embodiment contains a polymer containing a glucose skeleton or a polymer containing a vinyl alcohol skeleton. The polymer containing a glucose skeleton contained in the piezoelectric material of this embodiment is a cellulose ester containing a structural unit derived from a cellulose ester represented by formula (3) (hereinafter sometimes referred to as a "third structural unit"), or a cellulose ether containing a structural unit derived from a cellulose ether represented by formula (4) (hereinafter sometimes referred to as a "fourth structural unit"). The polymer containing a vinyl alcohol skeleton contained in the piezoelectric material of this embodiment is polyvinyl formal having three structural units represented by formula (5). The polymer containing a glucose skeleton or polymer containing a vinyl alcohol skeleton contained in the piezoelectric material of this embodiment may be of only one type, or of two or more types.

[0047] (Cellulose Ester) When the polymer containing a glucose skeleton is a cellulose ester containing a third structural unit, the third structural unit contained in the polymer containing a glucose skeleton may have three R ２ are each a hydrogen atom or a carboxylic acid ester group, and three R ２ At least one of the three R is a carboxylic acid ester group. ２ The number of carboxylic acid ester groups contained in R may be two, or three. ２ may all be carboxylic acid ester groups. ２ When the number of carboxylic acid ester groups contained in the third structural units is two or three, the types of carboxylic acid ester groups contained in each third structural unit may be different from one another, or some or all of them may be the same.

[0048] Furthermore, when the polymer containing a glucose skeleton is a cellulose ester containing a third structural unit, the number of carboxylic acid ester groups possessed by the multiple third structural units contained in the polymer containing a glucose skeleton may be different from one another, or some or all of the third structural units may be the same.

[0049] When the polymer containing a glucose skeleton contained in the piezoelectric material of this embodiment is a cellulose ester containing a third structural unit, the polymer containing a glucose skeleton has an R ２ The ratio of the number of carboxylic acid ester groups to the number of R in the molecule is preferably 20% by mass or more, and more preferably 30% by mass to 95% by mass. ２ When the ratio of the number of carboxylic acid ester groups to the number of vinylidene cyanide-vinyl carboxylate copolymers is 20 mass % or more, the carboxylic acid ester moiety (—O—C(═O)—R in formula (2)) contained in the vinylidene cyanide-vinyl carboxylate copolymer is １ The high affinity between the R ) and the carboxylic acid ester group contained in the polymer containing a glucose skeleton makes the compatibility with the vinylidene cyanide-vinyl carboxylate copolymer even better. ２ When the ratio of the number of carboxylic acid ester groups to the number of groups is 95 mass % or less, the hydroxyl groups contained in the polymer containing a glucose skeleton form hydrogen bonds with the cyano groups of the vinylidene cyanide-vinyl carboxylate copolymer, resulting in a piezoelectric material that can form a coating film with an even lower dielectric constant.

[0050] Examples of the carboxylic acid ester group contained in the third structural unit include —C(═O)CH ３ , —C(═O)CH ２ CH ３ , —C(═O)CH ２ CH ２ CH ３ , -C(=O)CH(CH ３ ) ２ , and groups represented by the following formula (3-1). Among these, the carboxylic acid ester group contained in the third structural unit is —C(═O)CH ３ , —C(═O)CH ２ CH ３ , —C(═O)CH ２ CH ２ CH ３ , -C(=O)CH(CH ３ ) ２The reason is that they have a high affinity with the carboxylic acid ester moiety contained in the vinylidene cyanide-vinyl carboxylate copolymer, and thus the compatibility with the vinylidene cyanide-vinyl carboxylate copolymer is improved.

[0051]

[0052] Furthermore, when the polymer containing a glucose skeleton is a cellulose ester containing a third structural unit, the types of carboxylic acid ester groups possessed by the multiple third structural units contained in the polymer containing a glucose skeleton may be different from one another, or some or all of them may be the same.

[0053] When the polymer containing a glucose skeleton contained in the piezoelectric material of this embodiment is a cellulose ester containing a third structural unit, the polymer containing a glucose skeleton may contain one or more structural units other than the third structural unit, as necessary. Examples of the other structural units include, for example, the three R ２ are all hydrogen atoms. When the polymer containing a glucose skeleton is a cellulose ester containing a third structural unit, the content of the third structural unit among the structural units contained in the polymer containing a glucose skeleton is preferably 80% by mass or more. This is because the piezoelectric material can form a coating film with a lower dielectric constant and better piezoelectric properties. The content of the third structural unit is more preferably 90% by mass or more, and most preferably only the third structural unit.

[0054] When the glucose skeleton-containing polymer contained in the piezoelectric material of this embodiment is a cellulose ester containing a third structural unit, the weight-average molecular weight (Mw) of the glucose skeleton-containing polymer is preferably 10,000 to 1,000,000, and more preferably 50,000 to 500,000. When the glucose skeleton-containing polymer has a weight-average molecular weight (Mw) of 10,000 or more, the film-forming properties are improved, and a piezoelectric film containing the piezoelectric material of this embodiment can be easily produced. When the glucose skeleton-containing polymer has a weight-average molecular weight (Mw) of 1,000,000 or less, the compatibility with vinylidene cyanide-vinyl carboxylate copolymer is improved. Therefore, a piezoelectric material containing a glucose skeleton-containing polymer having a weight-average molecular weight (Mw) of 1,000,000 or less can be efficiently produced with good productivity.

[0055] When the polymer containing a glucose skeleton is a cellulose ester containing a third structural unit, the weight-average molecular weight (Mw) of the polymer containing a glucose skeleton in this embodiment is a value measured by the following method. The weight-average molecular weight (Mw) of the polymer containing a glucose skeleton was measured using a liquid chromatograph (LC-2050C; manufactured by Shimadzu Corporation) under the measurement conditions shown below, and the weight-average molecular weight (Mw) was determined by comparison with the following standard substances with known molecular weights:

[0056] <Measurement conditions> Column: TSKgel guard column α + TSKGel α-M (manufactured by Tosoh Corporation) Mobile phase solvent: N-methyl-2-pyrrolidone (NMP) (10 mM, LiBr added) Flow rate: 1.0 ml / min Column temperature: 40°C Standard substance: TSK Standard Polystyrene (manufactured by Tosoh Corporation)

[0057] When the polymer containing a glucose skeleton contained in the piezoelectric material of this embodiment is a cellulose ester containing a third structural unit, the cellulose ester can be produced by a conventionally known method, such as a method of reacting an anhydrous organic acid with cellulose, and may be commercially available. Examples of commercially available cellulose esters include cellulose acetate butyrate (product number 180963; manufactured by Aldrich), cellulose triacetate (product number 22199; manufactured by Aldrich), cellulose triacetate (product number 035-16761; manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.), cellulose acetate propionate (product number 340642; manufactured by Aldrich), and cellulose acetate (product number 419028; manufactured by Aldrich).

[0058] Cellulose acetate butyrate (product number 180963; manufactured by Aldrich) has a weight average molecular weight of 250,000 and a carboxylic acid ester group of -C(=O)CH ３ and -C(=O)CH ２ CH ２ CH ３ and R in formula (3) contained in the molecule ２ Among the number of -C(=O)CH ３ The proportion of -C(=O)CH is 28.0 mass% to 31.0 mass% ２ CH ２ CH ３ The proportion of is 16.5 mass % to 19.0 mass %.

[0059] Cellulose triacetate (product number 22199; manufactured by Aldrich) has a weight average molecular weight of 340,000 and a carboxylic acid ester group of -C(=O)CH ３ and R in formula (3) contained in the molecule ２ The proportion of the number of carboxylic acid ester groups in the total number of cellulose triacetate (product number 035-16761; manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) is 100% by mass. The weight average molecular weight of cellulose triacetate is 310,000, and the carboxylic acid ester groups are —C(═O)CH ３ and R in formula (3) contained in the molecule ２ The proportion of the number of carboxylic acid ester groups in the total number of the carboxylic acid ester groups is 100% by mass.

[0060] Cellulose acetate propionate (product number 340642; manufactured by Aldrich) has a weight average molecular weight of 36,000 and a carboxylic acid ester group of -C(=O)CH ３ and -C(=O)CH ２ CH ３ and R in formula (3) contained in the molecule ２ Among the number of -C(=O)CH ３ The proportion of -C(=O)CH is 0.0 mass% to 1.0 mass% ２ CH ３ The proportion of is 40% by mass to 45% by mass.

[0061] Cellulose acetate (product number 419028; manufactured by Aldrich) has a weight-average molecular weight of 194,000 and a carboxylic acid ester group of -C(=O)CH ３ and R in formula (3) contained in the molecule ２ The proportion of the number of carboxylic acid ester groups in the total number of the polymers is 39.7 mass %.

[0062] (Cellulose Ether) When the polymer containing a glucose skeleton is a cellulose ether containing a fourth structural unit, the fourth structural unit contained in the polymer containing a glucose skeleton may have three R ３ are each a hydrogen atom or an aliphatic ether group, and three R ３ At least one of the three R is an aliphatic ether group. ３ The number of aliphatic ether groups contained in R may be two, or three. ２ may all be aliphatic ether groups. ３ When the number of aliphatic ether groups contained in each fourth structural unit is two or three, the types of the aliphatic ether groups contained in each fourth structural unit may be different from each other, or some or all of the types may be the same.

[0063] Furthermore, when the polymer containing a glucose skeleton is a cellulose ether containing a fourth structural unit, the number of aliphatic ether groups possessed by the multiple fourth structural units contained in the polymer containing a glucose skeleton may be different from one another, or some or all of the fourth structural units may be the same.

[0064] When the polymer containing a glucose skeleton contained in the piezoelectric material of this embodiment is a cellulose ether containing a fourth structural unit, the polymer containing a glucose skeleton has an R ３ The ratio of the number of aliphatic ether groups to the number of R in the molecule is preferably 20% by mass or more, and more preferably 30% by mass to 95% by mass. ３ When the ratio of the number of aliphatic ether groups to the number of aliphatic ether groups is 20 mass % or more, the carboxylic acid ester moiety (—O—C(═O)—R in formula (2)) contained in the vinylidene cyanide-vinyl carboxylate copolymer is １ ) and the aliphatic ether group contained in the polymer containing a glucose skeleton, the compatibility with the vinylidene cyanide-vinyl carboxylate copolymer is further improved. ３ When the ratio of the number of aliphatic ether groups to the number of the polymers is 95 mass % or less, the hydroxyl groups contained in the polymer containing a glucose skeleton form hydrogen bonds with the cyano groups of the vinylidene cyanide-vinyl carboxylate copolymer, resulting in a piezoelectric material that can form a coating film with an even lower dielectric constant.

[0065] Examples of the aliphatic ether group contained in the fourth structural unit include —O—CH ３ , —O—CH ２ CH ２ -OH and -OCH ２ CHOHCH ３ Among these, the aliphatic ether group contained in the fourth structural unit is a group represented by —O—CH ３ , -OCH ２ CHOHCH ３ The reason is that they have a high affinity with the carboxylic acid ester moiety contained in the vinylidene cyanide-vinyl carboxylate copolymer, and thus the compatibility with the vinylidene cyanide-vinyl carboxylate copolymer is improved.

[0066] Furthermore, when the polymer containing a glucose skeleton is a cellulose ether containing a fourth structural unit, the types of aliphatic ether groups possessed by the multiple fourth structural units contained in the polymer containing a glucose skeleton may be different from one another, or some or all of the fourth structural units may be the same.

[0067] When the polymer containing a glucose skeleton contained in the piezoelectric material of this embodiment is a cellulose ether containing a fourth structural unit, the polymer containing a glucose skeleton may contain one or more structural units other than the fourth structural unit, as necessary. Examples of the other structural units include, for example, the three R in the structural unit represented by formula (4): ３ are all hydrogen atoms. When the polymer containing a glucose skeleton is a cellulose ether containing a fourth structural unit, the content of the fourth structural unit among the structural units contained in the polymer containing a glucose skeleton is preferably 80 mass% or more. This is because the piezoelectric material can form a coating film with an even lower dielectric constant and excellent piezoelectric properties. The content of the fourth structural unit is more preferably 90 mass% or more, and most preferably the fourth structural unit is the only structural unit.

[0068] When the polymer containing a glucose skeleton contained in the piezoelectric material of this embodiment is a cellulose ether containing a fourth structural unit, the weight-average molecular weight (Mw) of the polymer containing a glucose skeleton is preferably 10,000 to 1,000,000, and more preferably 50,000 to 500,000. When the weight-average molecular weight (Mw) of the polymer containing a glucose skeleton is 10,000 or more, the film-forming properties are improved, and a piezoelectric film containing the piezoelectric material of this embodiment can be easily produced. When the weight-average molecular weight (Mw) of the polymer containing a glucose skeleton is 1,000,000 or less, the compatibility with vinylidene cyanide-vinyl carboxylate copolymer is improved. Therefore, a piezoelectric material containing a polymer containing a glucose skeleton having a weight-average molecular weight (Mw) of 1,000,000 or less can be efficiently produced with good productivity.

[0069] When the polymer containing a glucose skeleton is a cellulose ether containing a fourth structural unit, the weight-average molecular weight (Mw) of the polymer containing a glucose skeleton in this embodiment is a value measured by the following method. The weight-average molecular weight (Mw) of the polymer containing a glucose skeleton was measured using a liquid chromatograph (LC-2050C; manufactured by Shimadzu Corporation) under the measurement conditions shown below, and the weight-average molecular weight (Mw) was determined by comparison with the following standard substances with known molecular weights:

[0070] <Measurement conditions> Column: TSKgel guard column α + TSKGel α-M (manufactured by Tosoh Corporation) Mobile phase solvent: N-methyl-2-pyrrolidone (NMP) (10 mM, LiBr added) Flow rate: 1.0 ml / min Column temperature: 40°C Standard substance: TSK Standard Polystyrene (manufactured by Tosoh Corporation)

[0071] When the polymer containing a glucose skeleton contained in the piezoelectric material of this embodiment is a cellulose ether containing a fourth structural unit, the cellulose ether can be produced by a conventionally known method, such as a method of contacting cellulose with an alkaline solution to prepare alkali cellulose, followed by an etherification reaction using an etherifying agent, or may be a commercially available cellulose ether. Examples of commercially available cellulose ethers include methyl cellulose (Model No. SM-15; manufactured by Shin-Etsu Chemical Co., Ltd.) and hydroxypropyl methyl cellulose (Model No. 60SH-50; manufactured by Shin-Etsu Chemical Co., Ltd.).

[0072] (Polyvinyl formal) When the polymer containing a vinyl alcohol skeleton is polyvinyl formal having three structural units represented by formula (5), R ４ is a carboxylic acid ester group.

[0073] When the polymer containing a vinyl alcohol skeleton contained in the piezoelectric material of this embodiment is polyvinyl formal having three structural units represented by formula (5), １The high affinity between the vinyl alcohol skeleton-containing polymer and the carboxylic acid ester group contained in the vinyl alcohol skeleton-containing polymer leads to further improved compatibility with the vinylidene cyanide-vinyl carboxylate copolymer. In addition, when the vinyl alcohol skeleton-containing polymer is a polyvinyl formal having three structural units represented by formula (5), and when the R ４ is a carboxylic acid ester group, the hydroxyl group contained in the polymer containing a vinyl alcohol skeleton forms a hydrogen bond with the cyano group of the vinylidene cyanide-vinyl carboxylate copolymer, resulting in a piezoelectric material that can form a coating film with an even lower dielectric constant.

[0074] Examples of the carboxylic acid ester group contained in polyvinyl formal include —C(═O)CH ３ The reason is that they have a high affinity with the carboxylic acid ester moiety contained in the vinylidene cyanide-vinyl carboxylate copolymer, and thus have better compatibility with the vinylidene cyanide-vinyl carboxylate copolymer.

[0075] When the polymer containing a vinyl alcohol skeleton contained in the piezoelectric material of this embodiment is polyvinyl formal having three structural units represented by formula (5), the weight-average molecular weight (Mw) of the polymer containing a vinyl alcohol skeleton is preferably 10,000 to 1,000,000, and more preferably 50,000 to 500,000. When the weight-average molecular weight (Mw) of the polymer containing a vinyl alcohol skeleton is 10,000 or more, the film-forming properties are improved, and a piezoelectric film containing the piezoelectric material of this embodiment can be easily produced. When the weight-average molecular weight (Mw) of the polymer containing a vinyl alcohol skeleton is 1,000,000 or less, the compatibility with vinylidene cyanide-vinyl carboxylate copolymer is improved. Therefore, a piezoelectric material containing a polymer containing a vinyl alcohol skeleton having a weight-average molecular weight (Mw) of 1,000,000 or less can be efficiently produced with good productivity.

[0076] When the polymer containing a vinyl alcohol skeleton is polyvinyl formal having three structural units represented by formula (5), the weight-average molecular weight (Mw) of the polymer containing a vinyl alcohol skeleton in this embodiment is a value measured by the following method. The weight-average molecular weight (Mw) of the polymer containing a vinyl alcohol skeleton was measured using a liquid chromatograph (LC-2050C; manufactured by Shimadzu Corporation) under the measurement conditions shown below, and the weight-average molecular weight (Mw) was determined by comparison with the following standard substances of known molecular weight:

[0077] <Measurement conditions> Column: TSKgel guard column α + TSKGel α-M (manufactured by Tosoh Corporation) Mobile phase solvent: N-methyl-2-pyrrolidone (NMP) (10 mM, LiBr added) Flow rate: 1.0 ml / min Column temperature: 40°C Standard substance: TSK Standard Polystyrene (manufactured by Tosoh Corporation)

[0078] When the polymer containing a vinyl alcohol skeleton contained in the piezoelectric material of this embodiment is polyvinyl formal having the three structural units represented by formula (5), the polyvinyl formal can be produced by a conventionally known method, such as a method in which polyvinyl alcohol obtained by hydrolysis of polyvinyl acetate is formalized using formaldehyde, and may be commercially available. Examples of commercially available polyvinyl formal include polyvinyl formal (model number Vinyleck-K; manufactured by JNC Corporation).

[0079] In the piezoelectric material of this embodiment, the content of the polymer containing a glucose skeleton or the polymer containing a vinyl alcohol skeleton relative to the total mass of the vinylidene cyanide-vinyl carboxylate copolymer and the polymer containing a glucose skeleton or the polymer containing a vinyl alcohol skeleton is preferably 0.5% by mass or more and 15% by mass or less, and more preferably 1% by mass or more and 5% by mass or less. When the content of the polymer containing a glucose skeleton or the polymer containing a vinyl alcohol skeleton is 1% by mass or more, the effect of reducing the relative dielectric constant of the piezoelectric film containing the piezoelectric material due to the inclusion of the polymer containing a glucose skeleton or the polymer containing a vinyl alcohol skeleton is significant. When the content of the polymer containing a glucose skeleton or the polymer containing a vinyl alcohol skeleton is 15% by mass or less, it is possible to suppress the deterioration of the piezoelectric properties of the piezoelectric film containing the piezoelectric material due to an excessive content of the polymer containing a glucose skeleton or the polymer containing a vinyl alcohol skeleton, and the voltage output g ３３ It is possible to form a piezoelectric film with high electrical conductivity.

[0080] The content of vinylidene cyanide-vinyl carboxylate copolymer and the content of the polymer containing a glucose skeleton or the polymer containing a vinyl alcohol skeleton contained in the piezoelectric material of this embodiment can be calculated using the results of analyzing the piezoelectric material using a known analytical method. １ H-NMR (nuclear magnetic resonance) analysis, １３ One or more of the following methods can be used: C-NMR analysis, gas chromatography mass spectrometry (GC-MS), etc. The content of vinylidene cyanide-vinyl carboxylate copolymer and the content of the polymer containing a glucose skeleton or the polymer containing a vinyl alcohol skeleton contained in the piezoelectric material may be calculated using the results of analyzing components extracted from the piezoelectric material by a known extraction method, using known analytical methods. For example, an organic solvent in which vinylidene cyanide-vinyl carboxylate copolymer is not dissolved, such as chloroform or dichloroethane, can be used to extract the polymer containing a glucose skeleton or the polymer containing a vinyl alcohol skeleton from the piezoelectric material.

[0081] The piezoelectric material of this embodiment may contain one or more polymers and / or copolymers other than the vinylidene cyanide-vinyl carboxylate copolymer, the polymer containing a glucose skeleton, and the polymer containing a vinyl alcohol skeleton, depending on the properties required of the piezoelectric material, such as the heat resistance and strength of a piezoelectric film containing the piezoelectric material, the properties of a coating liquid when a piezoelectric film containing the piezoelectric material is formed by a coating method, etc. Preferably, the other polymers and / or copolymers are compatible with the vinylidene cyanide-vinyl carboxylate copolymer, the polymer containing a glucose skeleton, and the polymer containing a vinyl alcohol skeleton.

[0082] Of the polymers and copolymers contained in the piezoelectric material of this embodiment, the total content of the vinylidene cyanide-vinyl carboxylate copolymer and the polymer containing a glucose skeleton or the polymer containing a vinyl alcohol skeleton is preferably 80 mass % or more, more preferably 90 mass % or more, and most preferably consists of only the vinylidene cyanide-vinyl carboxylate copolymer and the polymer containing a glucose skeleton or the polymer containing a vinyl alcohol skeleton.

[0083] The piezoelectric material of this embodiment preferably contains a solvent to prepare a coating solution that is easy to apply when manufacturing a piezoelectric film using a coating method. Examples of solvents that can be used include known solvents such as acetonitrile, dimethylformamide, dimethylacetamide, dimethyl sulfoxide, N-methylpyrrolidone, 1,3-dimethyl-2-imidazolidinone, 3-methoxy-N,N-dimethylpropanamide, 3-butoxy-N,N-dimethylpropanamide, dihydrolevoglucosenone, γ-butyrolactone, γ-valerolactone, ethylene carbonate, propylene carbonate, and hexamethylphosphoric triamide. These solvents may be used alone or in combination.

[0084] The piezoelectric material of this embodiment may contain known additives, if necessary, in addition to the vinylidene cyanide-vinyl carboxylate copolymer, the polymer containing a glucose skeleton, and the polymer containing a vinyl alcohol skeleton, such as various antioxidants, hydrolysis inhibitors, fillers, surface conditioners, and thixotropic agents.

[0085] "Method for Producing Piezoelectric Material (Resin Composition)" The piezoelectric material (resin composition) of this embodiment can be produced by mixing raw materials consisting of the vinylidene cyanide-vinyl carboxylate copolymer, the polymer containing a glucose skeleton or the polymer containing a vinyl alcohol skeleton, and optionally other polymers and / or copolymers other than the vinylidene cyanide-vinyl carboxylate copolymer and the polymer containing a glucose skeleton or the polymer containing a vinyl alcohol skeleton, additives, and a solvent. When producing the piezoelectric material of this embodiment, known methods can be used to mix the raw materials, such as stirring using a magnetic stirrer, a mechanical stirrer, or a planetary mixer.

[0086] "Piezoelectric Film" The piezoelectric film of this embodiment includes the piezoelectric material (resin composition) of this embodiment. The piezoelectric film of this embodiment can be manufactured, for example, by the method described below. The piezoelectric material (resin composition) of this embodiment is applied to a peelable substrate to a predetermined thickness to form a coating film. A known substrate such as a resin film can be used. The method for applying the piezoelectric material can be a known method depending on the application thickness, the viscosity of the piezoelectric material, and the like. The coating film is then dried to remove the solvent in the coating film, resulting in a piezoelectric material sheet. The piezoelectric material sheet may be stretched as needed.

[0087] The piezoelectric material sheet is then peeled off from the substrate, and electrodes made of a known conductive material such as aluminum are placed on one side and the other side of the piezoelectric material sheet. A voltage is then applied to the piezoelectric material sheet at a predetermined electric field strength via the electrodes placed on both sides at a predetermined polarization temperature near the glass transition temperature (Tg) of the piezoelectric material forming the piezoelectric material sheet. The piezoelectric material sheet is then cooled with the voltage still applied. This allows the piezoelectric material sheet to acquire piezoelectricity. Through these steps, a sheet-like piezoelectric film is obtained. The electrodes used to acquire piezoelectricity may be used as components for forming a piezoelectric element, or may be removed.

[0088] "Piezoelectric Element" The piezoelectric element of this embodiment has the piezoelectric film of this embodiment and electrodes arranged on one side and the other side of the piezoelectric film. Specifically, it can have a sheet-like piezoelectric film and electrodes arranged on one side and the other side of the piezoelectric film. Known conductive materials such as aluminum can be used as the material for the electrodes. The piezoelectric element of this embodiment can be manufactured, for example, by providing electrodes on one side and the other side of the piezoelectric film by a known method such as vapor deposition.

[0089] The piezoelectric material (resin composition) of this embodiment includes a vinylidene cyanide-vinyl carboxylate copolymer containing a structural unit derived from vinylidene cyanide represented by formula (1) and a structural unit derived from a vinyl ester represented by formula (2), and a polymer containing a glucose skeleton, i.e., a cellulose ester containing a structural unit derived from a cellulose ester represented by formula (3) or a cellulose ether containing a structural unit derived from a cellulose ether represented by formula (4), or a polymer containing a vinyl alcohol skeleton, i.e., polyvinyl formal having three structural units represented by formula (5). Therefore, a piezoelectric film having excellent heat resistance and a low dielectric constant can be formed, and the film can be suitably used as a piezoelectric material. Furthermore, the piezoelectric film of this embodiment includes the piezoelectric material of this embodiment. Therefore, the piezoelectric film of this embodiment and the piezoelectric element of this embodiment have excellent heat resistance and excellent piezoelectric properties.

[0090] Although the embodiments of the present invention have been described above in detail, the configurations and combinations thereof in each embodiment are merely examples, and additions, omissions, substitutions, and other modifications of the configurations are possible within the scope of the present invention. For example, in the above-described embodiments, the resin composition is used as a piezoelectric material, but the use of the resin composition of the present invention is not limited to piezoelectric materials.

[0091] (Production of Piezoelectric Materials) "Examples 1 to 57, Comparative Examples 1 to 17" The vinylidene cyanide-vinyl carboxylate copolymers shown in Tables 1 to 4, the additive resins shown in Table 1, and dimethylformamide as a solvent were mixed in the proportions shown in Table 1 by stirring using a magnetic stirrer, to produce the piezoelectric materials of Examples 1 to 57 and Comparative Examples 1 to 17.

[0092] The vinylidene cyanide-vinyl carboxylate copolymers and additive resin species shown in Tables 1 to 4 were polymers listed below. The contents of the additive resin species shown in Tables 1 to 4 are the contents relative to the total mass of the polymers contained in the piezoelectric materials of Examples 1 to 57 and Comparative Examples 1 to 17. In Tables 1 to 4, the polymers contained in the piezoelectric materials are vinylidene cyanide-vinyl carboxylate copolymers, polymers used in place of vinylidene cyanide-vinyl carboxylate copolymers, cellulose esters containing structural units derived from cellulose esters represented by formula (3), cellulose ethers containing structural units derived from cellulose ethers represented by formula (4), polyvinyl formals having three structural units represented by formula (5), polycarbonates, polyamideimides, and polyimides.

[0093] (Vinylidene cyanide-vinyl carboxylate copolymer) The copolymers <11> to <15> shown below were used as vinylidene cyanide-vinyl carboxylate copolymers. <11> R in formula (2) contained in molecule １ are all methyl groups, the polymer is composed only of first structural units and second structural units, the molar ratio of the first structural units to the second structural units is the same, and the weight average molecular weight (Mw) is 580,000. １are all ethyl groups, the polymer is composed only of first structural units and second structural units, the molar ratio of the first structural units to the second structural units is the same, and the weight average molecular weight (Mw) is 297,000. １ are all propyl groups, the polymer is composed only of first structural units and second structural units, the molar ratio of the first structural units to the second structural units is the same, and the weight average molecular weight (Mw) is 480,000. １ are methyl groups and propyl groups, the molar ratio of the methyl groups to the propyl groups is 1:1, the polymer is composed only of first structural units and second structural units, the molar ratio of the first structural units to the second structural units is the same, and the weight average molecular weight (Mw) is 341,000. １ are all tert-butyl groups, the copolymer is composed of only first structural units and second structural units, the molar ratio of the first structural units to the second structural units is the same, and the weight average molecular weight (Mw) is 304,000.

[0094] <16> In Comparative Example 7, instead of vinylidene cyanide-vinyl carboxylate copolymer, a polymer of formula (1): a polymer consisting of structural units derived from vinylidene cyanide represented by formula (1) was used in an amount of 99 mass% as the polymer. <17> In Comparative Example 8, instead of vinylidene cyanide-vinyl carboxylate copolymer, a polymer of formula (2): a vinyl ester represented by formula (2) (R １ A polymer (polyvinyl acetate; 189480, manufactured by Sigma-Aldrich) consisting of structural units derived from (wherein all of the groups are methyl groups) was used in an amount of 99% by mass as the polymer.

[0095] (Type of added resin) Cellulose ester containing a structural unit derived from a cellulose ester represented by formula (3): As the cellulose ester containing a structural unit derived from a cellulose ester represented by formula (3), the following polymers shown in Tables 1 to 4 were used. Cellulose acetate butyrate (product number 180963; manufactured by Aldrich) (weight average molecular weight (Mw): 250,000) Cellulose triacetate (product number 22199; manufactured by Aldrich) (weight average molecular weight (Mw): 340,000) Cellulose acetate (product number 419028; manufactured by Aldrich) (weight average molecular weight (Mw): 194,000)

[0096] Cellulose ethers containing structural units derived from cellulose ethers represented by the following formula (4): As cellulose ethers containing structural units derived from cellulose ethers represented by formula (4), the following polymers shown in Tables 1 to 4 were used. Methylcellulose (Model No. SM-15; manufactured by Shin-Etsu Chemical Co., Ltd.) (weight average molecular weight (Mw): 56,400) Hydroxypropyl methylcellulose (1) (Model No. 60SH-50; manufactured by Shin-Etsu Chemical Co., Ltd.) (weight average molecular weight (Mw): 94,700) Hydroxypropyl methylcellulose (2) (Model No. 65SH-50; manufactured by Shin-Etsu Chemical Co., Ltd.) (weight average molecular weight (Mw): 103,000) Hydroxypropyl methylcellulose (3) (Model No. 90SH-100; manufactured by Shin-Etsu Chemical Co., Ltd.) (weight average molecular weight (Mw): 133,000)

[0097] Polyvinyl formal represented by formula (5): As the polyvinyl formal represented by formula (5), the following polymers shown in Tables 1 to 4 were used: Polyvinyl formal (model number Vinyleck-K; manufactured by JNC Corporation) (weight average molecular weight (Mw): 19,900)

[0098] Other polymers: The following polymers shown in Table 1 were used as polymers other than the cellulose ester containing a structural unit derived from the cellulose ester represented by formula (3), the cellulose ether containing a structural unit derived from the cellulose ether represented by formula (4), and the polyvinyl formal having three structural units represented by formula (5): Polycarbonate: Model No. PCZ-200, manufactured by Mitsubishi Gas Chemical Company, Inc. Polyamideimide: Model No. HR11NN, manufactured by Toyobo Co., Ltd. Polyimide: KPI-MX300F, manufactured by Kawamura Sangyo Co., Ltd.

[0099]

[0100]

[0101]

[0102]

[0103] (Manufacturing of Piezoelectric Films) "Examples 1 to 57, Comparative Examples 1 to 17" Piezoelectric films were manufactured using the piezoelectric materials of Examples 1 to 57 and Comparative Examples 1 to 17, respectively, by the method described below.

[0104] The piezoelectric material was applied to a PET film (trade name: Lumirror (registered trademark), manufactured by Toray Industries, Inc.) as a substrate so that the thickness after drying would be 50 μm to form a coating film. Thereafter, the coating film formed on the PET film was dried on a hot plate at 120° C. for 6 hours to remove the solvent in the coating film, and a piezoelectric material sheet was obtained.

[0105] The obtained piezoelectric material sheet was peeled from the PET film, and aluminum electrodes were provided on one side and the other side of the piezoelectric material sheet by vapor deposition. The electrodes of the piezoelectric material sheet were then electrically connected to a high-voltage power supply HARB-20R60 (manufactured by Matsusada Precision Co., Ltd.), and the sheet was maintained at a polarization temperature of 165°C for 15 minutes while an electric field with a field strength of 80 MV / m was applied. The sheet was then slowly cooled to room temperature with the voltage still applied, and subjected to a poling treatment to obtain a sheet-like piezoelectric film.

[0106] The appearance of the piezoelectric films thus obtained in Examples 1 to 57 and Comparative Examples 1 to 17 was visually observed, and the compatibility was evaluated according to the following criteria. The results are shown in Tables 1 to 4. [Evaluation criteria] A (compatible): The piezoelectric film is transparent. B (not compatible): The piezoelectric film is cloudy.

[0107] As shown in Tables 1 to 3, in Examples 1 to 48, which included a vinylidene cyanide-vinyl carboxylate copolymer and a polymer containing a glucose skeleton or a polymer containing a vinyl alcohol skeleton of the present invention, the compatibility was evaluated as A, and a piezoelectric material in which two types of polymers were mixed was obtained. Also, as shown in Table 1, in Comparative Example 8, which included a polymer of formula (2) and cellulose acetate butyrate, the compatibility was also evaluated as A, and a piezoelectric material in which two types of polymers were mixed was obtained. Also, as shown in Table 4, in Examples 49 to 57, which included a vinylidene cyanide-vinyl carboxylate copolymer and a polymer containing a glucose skeleton or a polymer containing a vinyl alcohol skeleton of the present invention, the compatibility was also evaluated as A, and a piezoelectric material in which two types of polymers were mixed was obtained.

[0108] However, the compatibility evaluations of Comparative Example 4, which included a vinylidene cyanide-vinyl carboxylate copolymer and polycarbonate, Comparative Example 5, which included a vinylidene cyanide-vinyl carboxylate copolymer and polyamideimide, and Comparative Example 6, which included a vinylidene cyanide-vinyl carboxylate copolymer and polyimide, were all B, and no piezoelectric material was obtained in which two types of polymers were mixed. Furthermore, as shown in Table 1, the compatibility evaluation of Comparative Example 7, which included the polymer of formula (1) and cellulose acetate butyrate, was also B, and no piezoelectric material was obtained in which two types of polymers were mixed.

[0109] The piezoelectric materials of Comparative Examples 1, 14, 15, 16, and 17 contained only vinylidene cyanide-vinyl carboxylate copolymer as a polymer, without any added resin species mixed in, and therefore were not evaluated for compatibility. The piezoelectric materials of Comparative Examples 2 to 3 and 9 to 13 contained only additive resin species as a polymer, without any added resin species mixed in, and therefore were not evaluated for compatibility.

[0110] Furthermore, the relative dielectric constant and piezoelectric constant d ３３ Measure the voltage output g ３３ The results are shown in Tables 5 to 8. In Comparative Examples 4 to 7, where the compatibility was evaluated as B and no piezoelectric material containing two polymers was obtained, sheet-shaped piezoelectric films were not obtained, and therefore the relative permittivity and piezoelectric constant d ３３ , voltage output g ３３ No evaluation has been conducted on this matter.

[0111] (Method for measuring relative permittivity) The capacitance of the piezoelectric film was measured at room temperature with an LCR meter (ZM2372; manufactured by NF Corporation) under conditions of an applied voltage of 1.00 V and a frequency of 1 kHz. The thickness of the piezoelectric film was also measured at room temperature with a micrometer (ID-C112XB; manufactured by Mitutoyo Corporation). The measured capacitance and thickness of the piezoelectric film were then used to calculate the dielectric constant, and the relative permittivity was determined.

[0112] (piezoelectric constant d ３３ Measurement method for the piezoelectric constant d) The piezoelectric film was attached to the measurement device using a pin with a tip diameter of 1.5 mm as a sample fixing jig. ３３ The measuring device used was a piezometer system PM200 manufactured by PIEZOTEST. ３３ The measured value of the piezoelectric constant d is a positive or negative value depending on the front and back of the piezoelectric film being measured. ３３ The absolute value of the actual measurement is recorded as the value.

[0113] (Voltage output g ３３ Calculation method of voltage output g using the following formula ３３ The voltage output g was calculated. ３３ (mVm / N) = piezoelectric constant d ３３ (pC / N) / relative dielectric constant

[0114]

[0115]

[0116]

[0117]

[0118] As shown in Tables 5 to 8, the piezoelectric films of Examples 1 to 57 manufactured using the piezoelectric materials of Examples 1 to 57 had lower dielectric constants than the piezoelectric films of Comparative Example 1 and Comparative Examples 14 to 17 manufactured using the piezoelectric materials of Comparative Examples 14 to 17 containing only a single polymer or copolymer. Furthermore, the piezoelectric films of Examples 1 to 10 and 13 to 48 manufactured using the piezoelectric materials of Examples 1 to 10 and 13 to 48, in which the content of the polymer containing a glucose skeleton or the polymer containing a vinyl alcohol skeleton of the present invention is 15% by mass or less, had lower voltage output g compared to the piezoelectric films of Examples 11 to 12 and 49 to 57, in which the content of the polymer containing a glucose skeleton or the polymer containing a vinyl alcohol skeleton of the present invention is greater than 15% by mass. ３３ It was a very high-quality product.

[0119] Furthermore, as shown in Table 5, the piezoelectric film of Comparative Example 8, which was manufactured using the piezoelectric material of Comparative Example 8 that did not contain vinylidene cyanide-vinyl carboxylate copolymer, was non-polarizable and had a piezoelectric constant d ３３ cannot be measured, and the voltage output g ３３ could not be calculated.

[0120] The materials of Comparative Examples 2 to 3 and 9 to 13 do not contain vinylidene cyanide-vinyl carboxylate copolymer, and the films of Comparative Examples 2 to 3 and 9 to 13 produced using these materials do not provide piezoelectric properties, and therefore, a piezoelectric body cannot be obtained. Therefore, the piezoelectric constant d ３３is not measured, and the voltage output g ３３ has not been calculated.

Claims

1. A resin composition comprising: a vinylidene cyanide-vinyl carboxylate copolymer containing a structural unit derived from vinylidene cyanide represented by the following formula (1) and a structural unit derived from a vinyl ester represented by the following formula (2); and a polymer containing a glucose skeleton or a polymer containing a vinyl alcohol skeleton, wherein the polymer containing a glucose skeleton is a cellulose ester containing a structural unit derived from a cellulose ester represented by the following formula (3) or a cellulose ether containing a structural unit derived from a cellulose ether represented by the following formula (4), and the polymer containing a vinyl alcohol skeleton is polyvinyl formal having three structural units represented by the following formula (5). (In formula (2), R １ is an organic group having 1 to 15 carbon atoms or a hydrogen atom. ２ are each a hydrogen atom or a carboxylic acid ester group, and three R ２ At least one of the three R is a carboxylic acid ester group. ３ are each a hydrogen atom or an aliphatic ether group, and three R ３ At least one of R is an aliphatic ether group. ４ is a carboxylic acid ester group.

2. The carboxylic acid ester group in formula (3) is —C(═O)CH ３ , —C(═O)CH ２ CH ３ , —C(═O)CH ２ CH ２ CH ３ , -C(=O)CH(CH ３ ) ２ and any one or more selected from the group consisting of groups represented by the following formula (3-1):

3. The aliphatic ether group in formula (4) is —O—CH ３ , —O—CH ２ CH ２ -OH and -OCH ２ CHOHCH ３ The resin composition according to claim 1, wherein the aryl group is one or more groups selected from the group consisting of groups represented by the formula:

4. The R in the formula (5) ４ is -C(=O)CH ３ The resin composition according to claim 1, 5. The resin composition according to claim 1, wherein the content of the polymer containing a glucose skeleton or the polymer containing a vinyl alcohol skeleton relative to the total mass of the vinylidene cyanide-vinyl carboxylate copolymer and the polymer containing a glucose skeleton or the polymer containing a vinyl alcohol skeleton is 0.5 mass % or more and 15 mass % or less.

6. A piezoelectric material comprising the resin composition according to any one of claims 1 to 5.

7. A piezoelectric film comprising the resin composition according to any one of claims 1 to 5.

8. A piezoelectric element comprising the piezoelectric film according to claim 7 and electrodes disposed on one surface and the other surface of said piezoelectric film.

Images