Film, layered product, film capacitor, and method for providing said film

Abstract

The present invention relates to: a film which contains a copolymer containing a constituent unit (a) derived from 1,1-dicyanoethylene and a constituent unit (b) derived from a specific polymerizable monomer and in which the organic solvent content is 4.0000 mass% or less; a layered product which includes the film and a metal layer that is in contact with a primary surface of the film; a film capacitor that includes the at least one layered product; a method for producing a film that contains a copolymer containing a constituent unit (a) derived from 1,1-dicyanoethylene and a constituent unit (b) derived from a specific polymerizable monomer, the method including a specific first heating step and a specific second heating step; and a method for lowering the content of an organic solvent in a film that contains a copolymer containing a constituent unit (a) derived from 1,1-dicyanoethylene and a constituent unit (b) derived from a specific polymerizable monomer, the method including a specific two heating steps.

Description

Films, laminates, film capacitors, and methods for providing such films

[0001] The present invention relates to a film, a laminate, a film capacitor, and a method for providing the film, and in particular to a film containing a copolymer containing a structural unit derived from 1,1-dicyanoethylene and a structural unit derived from a specific polymerizable monomer, as well as a laminate and a film capacitor containing the film, and a method for providing the film.

[0002] It is known that a copolymer of 1,1-dicyanoethylene (also known as "vinylidene cyanide") and a vinyl compound gives a molded product with a high dielectric constant (Patent Document 1).

[0003] Patent Document 2 discloses a method for producing a polymer electret element, in which a molded product made of a copolymer of vinylidene cyanide and another vinyl compound is heat-treated at a temperature below the glass transition temperature before or simultaneously with poling. According to Patent Document 2, by carrying out such heat treatment, a polymer electret element having a large longitudinal piezoelectric effect (Kt) can be obtained.

[0004] JP-A No. 01-103614 JP-A No. 60-072214

[0005] The present inventors have investigated conventional copolymers of 1,1-dicyanoethylene and vinyl compounds and found that they tend to have high dielectric loss tangents (specifically, the dielectric loss tangent value at 24°C and 1 kHz tends to be greater than 0.070). However, when a copolymer with such a high dielectric loss tangent is used in an element, electrical energy is easily converted into heat and lost, resulting in a problem of poor electrical energy efficiency.

[0006] Therefore, there is a need for a film having a low dielectric loss tangent that contains a copolymer of 1,1-dicyanoethylene and a vinyl compound, or a method for providing such a film. Furthermore, if a film having a low dielectric loss tangent can be provided, it is expected that a laminate or a film capacitor having excellent electrical energy efficiency can be provided.

[0007] A primary object of the present invention is to provide a film having a low dielectric loss tangent and a method for providing the film, as well as a laminate and a film capacitor including the film.

[0008] The present inventors have conducted extensive research into the reason why films of copolymers of 1,1-dicyanoethylene and vinyl compounds have high dielectric loss tangents, and have found that the content of organic solvents in the films affects this.The present inventors have then discovered that, in films containing copolymers of 1,1-dicyanoethylene and specific polymerizable monomers, it is possible to provide films with low dielectric loss tangents by controlling the content of organic solvents in the films to a low level, and have completed the present invention.

[0009] Furthermore, the present inventors have found that simply employing a single heating step is insufficient to reduce the organic solvent content in a film, and based on this finding, the present inventors have been able to provide a method for providing a film with a low dielectric loss tangent, specifically, a method for producing the film and a method for reducing the organic solvent content of the film.

[0010] That is, the present invention provides the following: [1] A film comprising a copolymer containing a structural unit (a) derived from 1,1-dicyanoethylene and a structural unit (b) derived from at least one compound represented by the following general formula (I), wherein the content of an organic solvent is 4.0000% by mass or less relative to 100% by mass of the total amount of the film: CH ２ =CR １ R ２ (I) [In general formula (I), R １ is one selected from the group consisting of a hydrogen atom, an alkyl group, a cycloalkyl group, an aryl group, an alkoxy group, a nitrile group, and a halogen atom; R ２ represents a hydrogen atom, an alkyl group, an alkoxy group, a carboxy group, -COOR ３ (R ３ is an alkyl group having 1 to 12 carbon atoms, a cycloalkyl group having 5 to 12 carbon atoms, or an aryl group having 6 to 12 carbon atoms. ４(R ４ is an alkyl group having 1 to 12 carbon atoms, a cycloalkyl group having 5 to 12 carbon atoms, or an aryl group having 6 to 12 carbon atoms; ５ (R ５ is an alkyl group having 1 to 12 carbon atoms, a cycloalkyl group having 5 to 12 carbon atoms, or an aryl group having 6 to 12 carbon atoms. It is one selected from the group consisting of an acyloxy group represented by the general formula (I) and a cyanoalkyl group.] [2] The film according to the above [1], wherein the compound represented by the general formula (I) is one or more selected from the group consisting of vinyl esters, (meth)acrylic acid esters, styrene, styrene derivatives, isobutylene, and propylene. [3] The film according to the above [1] or [2], wherein the dielectric loss tangent at 24°C and 1 kHz is 0.070 or less. [4] The film according to the above [1] or [2], wherein the stored energy is 2.00 J / cm ３ [5] The film according to any one of [1] to [3] above, having a thickness of less than 30.0 μm. [6] The film according to any one of [1] to [4] above, having a thickness of less than 30.0 μm and a stored energy of 2.00 J / cm ３ or more. [7] The film according to any one of [1] to [6] above, having a tensile modulus of elasticity of 3.2 GPa or more. [8] The film according to any one of [1] to [7] above, having a breakdown voltage of 300 kV / mm or more. [9] The film according to any one of [1] to [8] above, which is a stretched film having an organic solvent content of 3.0000 mass% or less, relative to the total amount (100 mass%) of the film.

[10] A laminate comprising the film according to any one of [1] to [9] above, and a metal layer in contact with a main surface of the film.

[11] The laminate according to

[10] above, which is in the form of a roll.

[12] A film capacitor comprising at least one laminate according to

[10] or

[11] above.

[13] A film capacitor comprising at least one structural unit (a) derived from 1,1-dicyanoethylene and at least one structural unit represented by the following general formula (I): CH ２ =CR １ R ２ (I) [In general formula (I), R １is one selected from the group consisting of a hydrogen atom, an alkyl group, a cycloalkyl group, an aryl group, an alkoxy group, a nitrile group, and a halogen atom; R ２ represents a hydrogen atom, an alkyl group, an alkoxy group, a carboxy group, -COOR ３ (R ３ is an alkyl group having 1 to 12 carbon atoms, a cycloalkyl group having 5 to 12 carbon atoms, or an aryl group having 6 to 12 carbon atoms. ４ (R ４ is an alkyl group having 1 to 12 carbon atoms, a cycloalkyl group having 5 to 12 carbon atoms, or an aryl group having 6 to 12 carbon atoms; ５ (R ５ is an alkyl group having 1 to 12 carbon atoms, a cycloalkyl group having 5 to 12 carbon atoms, or an aryl group having 6 to 12 carbon atoms. (a) is one selected from the group consisting of an acyloxy group and a cyanoalkyl group represented by the following general formula (I): ２ =CR １ R ２ (I) [In general formula (I), R １ is one selected from the group consisting of a hydrogen atom, an alkyl group, a cycloalkyl group, an aryl group, an alkoxy group, a nitrile group, and a halogen atom; R ２ represents a hydrogen atom, an alkyl group, an alkoxy group, a carboxy group, -COOR ３ (R３ is an alkyl group having 1 to 12 carbon atoms, a cycloalkyl group having 5 to 12 carbon atoms, or an aryl group having 6 to 12 carbon atoms. ４ (R ４ is an alkyl group having 1 to 12 carbon atoms, a cycloalkyl group having 5 to 12 carbon atoms, or an aryl group having 6 to 12 carbon atoms; ５ (R ５ is an alkyl group having 1 to 12 carbon atoms, a cycloalkyl group having 5 to 12 carbon atoms, or an aryl group having 6 to 12 carbon atoms. is one selected from the group consisting of an acyloxy group and a cyanoalkyl group represented by the formula (I). A method for reducing the content of an organic solvent in a film containing a copolymer containing a structural unit (b) derived from a compound represented by the formula (I), the method comprising the steps of: heating the film at a temperature in the range of 40 to 130°C; and heating the heated film at a temperature higher than 130°C and not higher than 230°C.

[16] The method according to the above item

[15] , wherein, in the step of heating the film at a temperature in the range of 40 to 130°C, the film is exposed to the temperature in the range of 40 to 130°C for 2 hours or less.

[0011] According to the present invention, it is possible to provide a film having a low dielectric loss tangent, a method for providing the film, and a laminate and a film capacitor including the film.

[0012] The following describes an example of a mode for carrying out the present invention (hereinafter, sometimes referred to as the "present embodiment"). However, the embodiment described below is merely an example for embodying the technical concept of the present invention, and the present invention is not limited to the following description. Furthermore, although preferred embodiments are shown in this specification, a combination of two or more of the individual preferred embodiments is also a preferred embodiment. For matters indicated by numerical ranges, when there are several numerical ranges, the lower limit and upper limit can be selectively combined to form a preferred embodiment. In this specification, when a numerical range is described as "XX to YY," it means "XX or more and YY or less." In addition, in this specification, "(meth)acrylic acid ester" is a general term for "acrylic acid ester" and "methacrylic acid ester."

[0013] [Film] The film according to this embodiment includes a copolymer (hereinafter also referred to as "the copolymer of this embodiment" or simply "the copolymer") containing a structural unit (a) derived from 1,1-dicyanoethylene and a structural unit (b) derived from at least one compound represented by a specific formula (general formula (I) above) (hereinafter also referred to as "specific polymerizable monomer"). The content of an organic solvent is 4.0000% by mass or less, relative to the total mass of the film (100% by mass). In this specification, "a copolymer containing a structural unit (a) derived from 1,1-dicyanoethylene and a structural unit (b) derived from at least one specific polymerizable monomer" means, in other words, that the copolymer contains, as structural units constituting the copolymer, the structural unit (a) derived from 1,1-dicyanoethylene and at least one structural unit (b) derived from the specific polymerizable monomer. In other words, the copolymer may contain only a structural unit represented by one specific structure as the structural unit (b), or may contain structural units represented by multiple structures as the structural unit (b). Since the structural unit (b) contains a plurality of compounds represented by the general formula (I), the number of structural types of the structural unit (b) is equal to the number of types derived from these compounds. In one embodiment of the present invention, the number of types of structural unit (b) contained in the copolymer may be, for example, 1 to 10, 1 to 5, 1 to 3, 1 to 2, or 1. From the viewpoint of ease of copolymer synthesis, the number of types of structural unit (b) contained in the copolymer is preferably 1 to 3, 1 to 2, or 1, more preferably 1 to 2, or 1, and even more preferably 1. That is, in one embodiment of the present invention, the copolymer is more preferably a copolymer containing a structural unit (a) derived from 1,1-dicyanoethylene and a structural unit (b) derived from one compound represented by the general formula (I). The same applies hereinafter to the copolymers contained in the films according to the embodiments described herein.

[0014] <Organic Solvent> The organic solvent is not particularly limited as long as it can dissolve the copolymer of this embodiment. Examples of such organic solvents include ethyl acetate, dimethyl sulfoxide, N,N-dimethylformamide, N,N-dimethylacetamide, tetrahydrofuran, acetone, methanol, cyclohexanone, N-methylpyrrolidone, and propylene carbonate. These organic solvents may be used alone or in combination. In one embodiment of the present invention, from the viewpoint of solubility, at least one selected from N,N-dimethylacetamide and N,N-dimethylformamide is preferred. In one embodiment of the present invention, from the viewpoint of solubility, N,N-dimethylacetamide is preferred. The content of the organic solvent can be determined by gas chromatography measurement, specifically by the method described in the Examples section. This can provide a film with a low dielectric loss tangent, for example, a film with a dielectric loss tangent of 0.070 or less at 24°C and 1 kHz. Specific polymerizable monomers are described below.

[0015] When the content of the organic solvent in the film is 4.0000% by mass or less relative to the total amount (100% by mass) of the film, the dielectric loss tangent of the film is low for the following reasons.

[0016] First, when an organic solvent is present in a film, the dielectric loss tangent of the organic solvent itself is high, and therefore the dielectric loss tangent of the entire film is also high. One possible reason for the presence of an organic solvent in a film is that the organic solvent used in the production of the film remains as a residue. On the other hand, the lower the content of organic solvent in the film, the more effectively the dielectric loss tangent of the entire film can be prevented from increasing. The dielectric loss tangent can be evaluated, for example, by the value of the dielectric loss tangent measured at 24°C and 1 kHz by the method described in the Examples section below.

[0017] From the viewpoint of further reducing the dielectric loss tangent, the content of the organic solvent in the film according to this embodiment is preferably less than 4.0000% by mass, more preferably 3.5000% by mass or less, even more preferably less than 3.2000% by mass, still more preferably 3.0000% by mass or less, still more preferably 2.5000% by mass or less, still more preferably less than 2.5000% by mass, still more preferably 2.0000% by mass or less, and still more preferably less than 1.7000% by mass, based on 100% by mass of the total amount of the film. , and even more preferably 1.5000% by mass or less, even more preferably less than 0.9000% by mass, even more preferably less than 0.5000% by mass, even more preferably less than 0.4000% by mass, even more preferably less than 0.3000% by mass, even more preferably less than 0.2000% by mass, even more preferably less than 0.1000% by mass, even more preferably less than 0.0500% by mass, even more preferably less than 0.0100% by mass, and even more preferably less than 0.0002% by mass. The lower the content of the organic solvent, the more preferable it is, and the lower limit is, for example, 0.0000% by mass or the detection limit, and 0.0001% by mass may be used as a trace amount or the detection limit.

[0018] For example, in one embodiment of the present invention, the content of the organic solvent in the film according to the present embodiment is 0.0000 to 4.0000 mass%, preferably 0.0000 mass% or more and less than 4.0000 mass%, more preferably 0.0000 to 3.5000 mass%, even more preferably 0.0000 mass% or more and less than 3.2000 mass%, still more preferably 0.0000 to 3.0000 mass%, still more preferably 0.0000 to 2.5000 mass%, still more preferably 0.0000 mass% or more and less than 2.5000 mass%, still more preferably 0.0000 to 2.0000 mass%, still more preferably 0.0000 mass% or more and less than 1.7000 mass%, and still more preferably is 0.0000 to 1.5000 mass%, even more preferably 0.0000 mass% or more and less than 0.9000 mass%, even more preferably 0.0000 mass% or more and less than 0.5000 mass%, even more preferably 0.0000 mass% or more and less than 0.4000 mass%, even more preferably 0.0000 mass% or more and less than 0.3000 mass%, even more preferably 0.0000 mass% or more and less than 0.2000 mass%, even more preferably 0.0000 mass% or more and less than 0.1000 mass%, even more preferably 0.0000 mass% or more and less than 0.0500 mass%, even more preferably 0.0000 mass% or more and less than 0.0100 mass%, and even more preferably 0.0000 mass% or more and less than 0.0002 mass%.

[0019] Furthermore, for example, in one embodiment of the present invention, the content of the organic solvent in the film according to the present embodiment is, relative to 100% by mass of the total amount of the film, preferably 0.0001% by mass to 4.0000% by mass, more preferably 0.0001% by mass or more but less than 4.0000% by mass, even more preferably 0.0001% by mass or more but less than 3.5000% by mass, still more preferably 0.0001% by mass or more but less than 3.2000% by mass, still more preferably 0.0001 to 3.0000% by mass, still more preferably 0.0001 to 2.5000% by mass, still more preferably 0.0001% by mass or more but less than 2.5000% by mass, still more preferably 0.0001 to 2.0000% by mass, and still more preferably 0.0001% by mass or more but less than 1.7000% by mass. , even more preferably 0.0001 to 1.5000 mass%, even more preferably 0.0001 mass% or more and less than 0.9000 mass%, even more preferably 0.0001 mass% or more and less than 0.5000 mass%, even more preferably 0.0001 mass% or more and less than 0.4000 mass%, even more preferably 0.0001 mass% or more and less than 0.3000 mass%, even more preferably 0.0001 mass% or more and less than 0.2000 mass%, even more preferably 0.0001 mass% or more and less than 0.1000 mass%, even more preferably 0.0001 mass% or more and less than 0.0500 mass%, even more preferably 0.0001 mass% or more and less than 0.0100 mass%, and even more preferably 0.0001 mass% or more and less than 0.0002 mass%.

[0020] <Copolymer> The copolymer in this embodiment is a copolymer containing a structural unit (a) derived from 1,1-dicyanoethylene and a structural unit (b) derived from at least one specific polymerizable monomer.

[0021] The copolymer of this embodiment contains the structural unit (a) derived from 1,1-dicyanoethylene, and thus can provide a film having a practically high dielectric constant. The dielectric constant can be evaluated, for example, by the value of the relative dielectric constant measured at 24°C and 1 kHz by the method described in the Examples section below.

[0022] By including the structural unit (b) derived from a specific polymerizable monomer in the copolymer of this embodiment, copolymerization (e.g., alternating copolymerization) of 1,1-dicyanoethylene and the specific polymerizable monomer proceeds smoothly, tending to provide a film with excellent mechanical properties. In particular, when the content of organic solvent in the film is high, the organic solvent plasticizes the film, resulting in deterioration of the mechanical properties, particularly the tensile properties. Therefore, for example, when a film may contain a large amount of organic solvent due to its production method, the structural unit (b) that a film-forming copolymer should include is not sufficient if it is derived from an arbitrary vinyl compound, but must be a structural unit derived from the specific polymerizable monomer described above. The tensile properties can be evaluated, for example, by the tensile modulus (GPa) measured by the method described in the Examples section below.

[0023] (Structural Unit (a): 1,1-Dicyanoethylene) 1,1-dicyanoethylene capable of forming the structural unit (a) contained in the copolymer of this embodiment may be produced, for example, according to the production method described in J. Am. Chem. Soc. (USA), 1989, Vol. 111, No. 25, pp. 9078-9081 or the production method described in U.S. Pat. No. 2,476,270. Specifically, 1,1-dicyanoethylene can be produced by the production method described in Production Example 1, which will be described later. The produced 1,1-dicyanoethylene is preferably stored frozen until immediately before use.

[0024] (Purity) The purity of 1,1-dicyanoethylene to be used in the copolymer of this embodiment is preferably 95% or more, more preferably 97% or more, even more preferably 98% or more, and still more preferably 99% or more. The purity of 1,1-dicyanoethylene can be determined, for example, by gas chromatography. Furthermore, for example, in one embodiment of the present invention, the purity of the 1,1-dicyanoethylene is preferably 95 to 100%, more preferably 97 to 100%, even more preferably 98 to 100%, and still more preferably 99 to 100%.

[0025] The content of the structural unit (a) in the copolymer of this embodiment is not limited as long as a film with a low dielectric loss tangent can be provided. From the viewpoint of obtaining a film with a high dielectric constant, the content of the structural unit (a) in the copolymer of this embodiment is preferably 20 to 80 mol %, more preferably 30 to 70 mol %, and even more preferably 40 to 60 mol %, based on 100 mol % of the total amount of structural units of the copolymer. In this specification, the phrase "100 mol % of the total amount of structural units of the copolymer" refers to the total amount of structural units derived from the raw material monomers and does not include structural units derived from the initiator used in polymerization.

[0026] The content of the structural unit (a) in the copolymer is １ This can be determined from the results of H-NMR measurement, specifically by the method described in the Examples section. The contents of the structural unit (b) and other structural units described below can also be determined in the same manner.

[0027] (Structural Unit (b): Specific Polymerizable Monomer) The specific polymerizable monomer capable of forming the structural unit (b) contained in the copolymer of this embodiment is a compound represented by general formula (I) described below. The specific polymerizable monomer is preferably reactive with 1,1-dicyanoethylene. The specific polymerizable monomer may be one type, or may be multiple types. The specific polymerizable monomer may be a radical polymerizable monomer or an anion polymerizable monomer.

[0028] General formula (I) is represented as follows: CH ２ =CR １ R ２ (I) [In general formula (I), R １ is one selected from the group consisting of a hydrogen atom, an alkyl group, a cycloalkyl group, an aryl group, an alkoxy group, a nitrile group, and a halogen atom; R ２ represents a hydrogen atom, an alkyl group, an alkoxy group, a carboxy group, -COOR ３ (R ３ is an alkyl group having 1 to 12 carbon atoms, a cycloalkyl group having 5 to 12 carbon atoms, or an aryl group having 6 to 12 carbon atoms.４ (R ４ is an alkyl group having 1 to 12 carbon atoms, a cycloalkyl group having 5 to 12 carbon atoms, or an aryl group having 6 to 12 carbon atoms; ５ (R ５ is an alkyl group having 1 to 12 carbon atoms, a cycloalkyl group having 5 to 12 carbon atoms, or an aryl group having 6 to 12 carbon atoms. It is one selected from the group consisting of an acyloxy group and a cyanoalkyl group represented by the following formula:

[0029] In general formula (I), R １ The alkyl group in R is preferably an alkyl group having 1 to 12 carbon atoms. １ Examples of the alkyl group of R include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, an n-pentyl group, an isopentyl group, a neopentyl group, an n-hexyl group, a heptyl group, an octyl group, a decyl group, and a dodecyl group. １ The number of carbon atoms in the alkyl group of R is more preferably 1 to 4, even more preferably 1 to 3, even more preferably 1 or 2, and even more preferably 1. In one embodiment of the present invention, １ As the alkyl group, a methyl group is even more preferred.

[0030] R １ The cycloalkyl group in R is preferably a cycloalkyl group having 3 to 12 carbon atoms. １ Examples of the cycloalkyl group include a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, and a cyclohexyl group.

[0031] R １ The aryl group in R is preferably an aryl group having 6 to 20 carbon atoms. １ Examples of the aryl group in R include a phenyl group, a tolyl group, a xylyl group, and a naphthyl group. １ The aryl group is more preferably a phenyl group.

[0032] R １The alkoxy group in R is preferably an alkoxy group having 1 to 12 carbon atoms, and more preferably an alkoxy group having 1 to 10 carbon atoms. １ Examples of the alkoxy group include a methoxy group, an ethoxy group, an n-propoxy group, an isopropoxy group, an n-butoxy group, an isobutoxy group, a sec-butoxy group, and a tert-butoxy group.

[0033] From the viewpoint of achieving both film strength and dielectric properties, R １ is preferably a hydrogen atom, an alkyl group having 1 to 12 carbon atoms, or an aryl group having 6 to 20 carbon atoms, and more preferably a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, or an aryl group having 6 to 20 carbon atoms. In one embodiment of the present invention, R １ is preferably selected from the group consisting of a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, and a phenyl group, and more preferably is one selected from the group consisting of a hydrogen atom, a methyl group, and a phenyl group. １ is more preferably a hydrogen atom. １ may be an aryl group having 6 to 20 carbon atoms. In this case, R １ is preferably, for example, a phenyl group.

[0034] In general formula (I), R ２ The alkyl group in R is preferably an alkyl group having 1 to 12 carbon atoms. ２ Examples of the alkyl group include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, an n-pentyl group, an isopentyl group, a neopentyl group, an n-hexyl group, a heptyl group, an octyl group, a decyl group, and a dodecyl group.

[0035] R ２ The alkoxy group in R is preferably an alkoxy group having 1 to 12 carbon atoms, and more preferably an alkoxy group having 1 to 10 carbon atoms. ２Examples of the alkoxy group include a methoxy group, an ethoxy group, an n-propoxy group, an isopropoxy group, an n-butoxy group, an isobutoxy group, a sec-butoxy group, and a tert-butoxy group.

[0036] R ２ Ha-COOR ３ The ester group may be an ester group represented by the formula: ３ represents an alkyl group having 1 to 12 carbon atoms, a cycloalkyl group having 5 to 12 carbon atoms, or an aryl group having 6 to 12 carbon atoms. ３ Examples of R include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, isopentyl, neopentyl, n-hexyl, heptyl, octyl, decyl, and dodecyl groups; cyclopentyl and cyclohexyl groups; and phenyl, tolyl, xylyl, and naphthyl groups. The alkyl group in the ester group may be substituted with one or more cyano groups, or may be substituted with one or more alkoxy groups. ３ An example of the alkyl group substituted with one or more cyano groups that R may take is a monocyanoalkyl group, and an example of the monocyanoalkyl group is a 2-cyanoethyl group. ３ An example of the alkyl group substituted with one or more alkoxy groups that can be taken by is an alkoxyalkyl group.

[0037] R ２ Examples of the acid anhydride group include acid anhydride groups derived from phthalic anhydride, maleic anhydride, trimellitic anhydride, pyromellitic anhydride, hexahydrophthalic anhydride, tetrahydrophthalic anhydride, methylnadic anhydride, nadic anhydride, glutaric anhydride, dimethylglutaric anhydride, diethylglutaric anhydride, succinic anhydride, methylhexahydrophthalic anhydride, and methyltetrahydrophthalic anhydride.

[0038] R ２ Ha-COR ４ The R in the acyl group may be an acyl group represented by the formula: ４represents an alkyl group having 1 to 12 carbon atoms, a cycloalkyl group having 5 to 12 carbon atoms, or an aryl group having 6 to 12 carbon atoms. ４ Examples of the alkyl group include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, an n-pentyl group, an isopentyl group, a neopentyl group, an n-hexyl group, a heptyl group, an octyl group, a decyl group, a dodecyl group, a cyclopentyl group, a cyclohexyl group, a phenyl group, a tolyl group, a xylyl group, and a naphthyl group.

[0039] R ２ Ha-OCOR ５ The R in the acyloxy group may be an acyloxy group represented by the formula: ５ is an alkyl group having 1 to 12 carbon atoms, a cycloalkyl group having 5 to 12 carbon atoms, or an aryl group having 6 to 12 carbon atoms. ５ Examples of R include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, isopentyl, neopentyl, n-hexyl, heptyl, octyl, decyl, and dodecyl groups, cyclopentyl and cyclohexyl groups, as well as phenyl, tolyl, xylyl, and naphthyl groups. ２ is an acetyloxy group (i.e., R ５ is preferably a methyl group.

[0040] R ２ The cyanoalkyl group R is preferably an alkyl group having a cyano group and having 2 to 12 carbon atoms. ２ The cyanoalkyl group may contain one or more cyano groups. ２ The cyanoalkyl group is more preferably an alkyl group having one cyano group and 2 to 6 carbon atoms, and even more preferably an alkyl group having one cyano group and 2 to 4 carbon atoms.

[0041] From the viewpoint of achieving both film strength and dielectric properties, R ２is preferably a hydrogen atom, an alkyl group having 1 to 12 carbon atoms, or —COOR ３ (R ３ is an alkyl group having 1 to 12 carbon atoms), and ５ (R ５ is an alkyl group having 1 to 12 carbon atoms), more preferably a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, or an acyloxy group represented by -COOR ３ An ester group represented by the formula (in this case, R ３ is an alkyl group having 1 to 6 carbon atoms, and —OCOR ５ An acyloxy group represented by the formula (in this case, R ５ is an alkyl group having 1 to 6 carbon atoms, and more preferably a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, -COOR ３ An ester group represented by the formula (in this case, R ３ is an alkyl group having 1 to 4 carbon atoms, and —OCOR ５ An acyloxy group represented by the formula (in this case, R ５ is an alkyl group having 1 to 4 carbon atoms.

[0042] From the viewpoint of achieving both strength and dielectric properties of the film, it is preferable that R １ is a hydrogen atom, an alkyl group having 1 to 12 carbon atoms, or an aryl group having 6 to 20 carbon atoms, and R ２ represents a hydrogen atom, an alkyl group having 1 to 12 carbon atoms, -COOR ３ (R ３ is an alkyl group having 1 to 12 carbon atoms, a cycloalkyl group having 5 to 12 carbon atoms, or an aryl group having 6 to 12 carbon atoms), and ５ (R ５ is an alkyl group having 1 to 12 carbon atoms, a cycloalkyl group having 5 to 12 carbon atoms, or an aryl group having 6 to 12 carbon atoms), and more preferably, R １ is a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, or an aryl group having 6 to 20 carbon atoms, and R ２represents a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, -COOR ３ An ester group represented by the formula (in this case, R ３ is an alkyl group having 1 to 6 carbon atoms, a cycloalkyl group having 5 to 12 carbon atoms, or an aryl group having 6 to 12 carbon atoms, and —OCOR ５ An acyloxy group represented by the formula (in this case, R ５ is an alkyl group having 1 to 6 carbon atoms, a cycloalkyl group having 5 to 12 carbon atoms, or an aryl group having 6 to 12 carbon atoms; more preferably, it is one selected from the group consisting of a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, and a phenyl group; and R ２ represents a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, -COOR ３ An ester group represented by the formula (in this case, R ３ is an alkyl group having 1 to 4 carbon atoms, and —OCOR ５ An acyloxy group represented by the formula (in this case, R ５ is an alkyl group having 1 to 4 carbon atoms.

[0043] Examples of the compound represented by the general formula (I) include ethylene, propylene, isobutylene, 1-hexene, 1-octene, (meth)acrylic acid esters, vinyl esters (excluding (meth)acrylic acid esters), styrene, styrene derivatives, acrylonitrile, vinyl chloride, vinylidene chloride, vinylidene fluoride, 2-cyanoacrylic acid alkyl esters, 2-cyanopentadienoic acid alkyl esters, and methylidenemalonic acid dialkyl esters.

[0044] Specific examples of (meth)acrylic acid esters include alkyl acrylates such as butyl acrylate; and alkyl methacrylates such as methyl methacrylate and dodecyl methacrylate.

[0045] Specific examples of vinyl esters include vinyl acetate, vinyl propionate, and vinyl butyrate.

[0046] Specific examples of styrene or styrene derivatives include styrene, α-methylstyrene, and p-methylstyrene.

[0047] From the viewpoint of achieving both film strength and dielectric properties, the compound represented by the general formula (I) is preferably at least one selected from the group consisting of vinyl esters, (meth)acrylic esters, styrene, styrene derivatives, isobutylene, and propylene. More preferably, the compound represented by the general formula (I) is at least one selected from the group consisting of vinyl esters, (meth)acrylic esters, styrene, styrene derivatives, and isobutylene. Even more preferably, the compound represented by the general formula (I) is at least one selected from the group consisting of vinyl acetate, vinyl propionate, vinyl butyrate, isopropenyl acetate, vinyl chloroacetate, vinyl isobutyrate, methyl methacrylate, methyl acrylate, ethyl acrylate, butyl acrylate, styrene, α-methylstyrene, and isobutylene. From the viewpoint of being less susceptible to fluctuations in the relative dielectric constant, the compound represented by the general formula (I) is preferably at least one selected from the group consisting of vinyl acetate, vinyl propionate, vinyl butyrate, methyl methacrylate, styrene, and isobutylene.

[0048] In one embodiment of the present invention, the compound represented by the general formula (I) is preferably at least one selected from vinyl esters and (meth)acrylic esters. In this case, the compound represented by the general formula (I) is preferably at least one selected from vinyl acetate, vinyl propionate, vinyl butyrate, and methyl methacrylate, more preferably at least one selected from vinyl acetate, vinyl propionate, and methyl methacrylate. In one embodiment of the present invention, the compound represented by the general formula (I) is preferably vinyl acetate. In one embodiment of the present invention, the compound represented by the general formula (I) is preferably styrene or a styrene derivative, more preferably styrene. In one embodiment of the present invention, the compound represented by the general formula (I) is preferably at least one selected from vinyl acetate, vinyl propionate, methyl methacrylate, and styrene.

[0049] The specific polymerizable monomer may be a commercially available product or may be produced by a known method.

[0050] The content of the structural unit (b) in the copolymer of this embodiment is not limited as long as the desired effects of the present invention are achieved. From the viewpoint of obtaining a film with a high dielectric constant, the content of the structural unit (b) in the copolymer of this embodiment is preferably 20 to 80 mol %, more preferably 30 to 70 mol %, and even more preferably 40 to 60 mol %, based on 100 mol % of the total amount of structural units in the copolymer.

[0051] In the copolymer of the present embodiment, the content of the structural unit (b) is preferably 20 to 80 mol %, more preferably 30 to 70 mol %, and even more preferably 40 to 60 mol %, based on the total content of the structural unit (a) and the structural unit (b) (100 mol %), from the viewpoint of obtaining a film with a high dielectric constant.

[0052] (Other Structural Units (c)) The copolymer of the present embodiment may or may not include a structural unit other than the structural unit (a) and the structural unit (b) as the structural unit (c). In one embodiment of the present embodiment, from the viewpoint of further exerting the effects of the present invention, it is preferable that the copolymer of the present embodiment does not include the structural unit (c). The monomer capable of forming the structural unit (c) is not particularly limited as long as it is a compound other than the above-mentioned 1,1-dicyanoethylene and specific polymerizable monomers. Examples of monomers capable of forming the structural unit (c) include butadiene and isoprene. One type of monomer capable of forming the structural unit (c) may be used, or multiple types may be used. The monomer capable of forming the structural unit (c) may be a radically polymerizable monomer or an anionically polymerizable monomer.

[0053] When the copolymer of this embodiment contains the structural unit (c), the content thereof is preferably 20 mol% or less, more preferably 10 mol% or less, and even more preferably 5 mol% or less, based on 100 mol% of the total structural units of the copolymer. Furthermore, in one embodiment of this embodiment, the lower limit of the content of the structural unit (c) may be, for example, 0.1 mol% based on 100 mol% of the total structural units of the copolymer. In one embodiment of the present embodiment, the content of the structural unit (c) may be, for example, 0.1 to 20 mol%, 0.1 to 10 mol%, or 0.1 to 5 mol%, based on 100 mol% of the total structural units of the copolymer.

[0054] In addition, the content of the structural unit (a) in the copolymer and the content of the structural unit (b) in the copolymer can each independently take the above-mentioned respective contents, but when the selected contents are combined, the total content of the structural unit (a) and the structural unit (b) in the copolymer does not include a range exceeding 100 mol% in 100 mol% of the total amount of the structural units of the copolymer. That is, the total content of the structural unit (a) and the structural unit (b) in the copolymer is 100 mol% or less in 100 mol% of the total amount of the structural units of the copolymer. In addition, when the copolymer contains the structural unit (c), the same applies to the total content of the structural unit (a) in the copolymer, the content of the structural unit (b) in the copolymer, and the content of the structural unit (c) in the copolymer.

[0055] In one embodiment of this embodiment, the total content of the structural units (a) and (b) in the copolymer of this embodiment is, for example, 50 to 100 mol%, more preferably 75 to 100 mol%, even more preferably 80 to 100 mol%, still more preferably 90 to 100 mol%, even more preferably 95 to 100 mol%, and may even be 100 mol%. In one embodiment of this embodiment, the total content of the structural units (a) and (b) in the copolymer of this embodiment may be, for example, 80 to 99.9 mol%, 90 to 99.9 mol%, or 95 to 99.9 mol%, for example, of the total amount of the structural units of the copolymer (100 mol%).

[0056] (Triad Structure) The copolymer in this embodiment may contain at least one selected from the group consisting of the following four triad structures (U-1) to (U-4) composed of the structural unit (a) and the structural unit (b). As described above, the structural unit (b) may be of one type or of two or more types. (a)-(a)-(a) ... (U-1) (a)-(a)-(b) ... (U-2) (b)-(a)-(a) ... (U-3) (b)-(a)-(b) ... (U-4)

[0057] Here, the term "triad structure" refers to a structure in which three structural units selected from the structural unit (a) and the structural unit (b) are linked together, when considering a structure centered around the structural unit (a).

[0058] Specifically, the triad structure (U-1) "(a)-(a)-(a)" means a structure in which three structural units (a) are bonded in succession; the triad structure (U-2) "(a)-(a)-(b)" and the triad structure (U-3) "(b)-(a)-(a)" mean a structure in which, when viewed from the central structural unit (a), structural units (a) and (b) are bonded to both sides of the central structural unit (a); and the triad structure (U-4) "(b)-(a)-(b)" means a structure in which, when viewed from the central structural unit (a), structural units (b) are bonded to both sides of the central structural unit (a).

[0059] In the copolymer of this embodiment, when the total content of the four types of triad structures is taken as 100 mol %, the total content of the triad structures (U-2) and (U-3) is preferably 25.0 mol % or less, relative to the total content of the four types of triad structures (100 mol %).

[0060] Here, the content of each triad structure means the ratio (mol %) of the content of the structural unit (a) that is the center of the triad structure to the content of the structural unit (a) that is the center of all triad structures. Specifically, the content of the triad structure (U-1) means the ratio (mol %) of the content of the structural unit (a) that is between the two structural units (a) in the (a)-(a)-(a) structure that constitutes the triad structure (U-1) to the content of the structural unit (a) that is the center of all triad structures. The contents (ratios) of other triad structures have the same meaning. The contents of the triad structures (U-1) to (U-4) are each １３ It can be measured by C-NMR, specifically by the method described in the Examples section.

[0061] When the total content of the four types of triad structures is taken as 100 mol%, the content of the triad structure (U-1) is preferably 2.2 mol% or less of the total 100 mol% of the content of the four types of triad structures. When the content of the triad structure (U-1) is 2.2 mol% or less, the consecutive arrangement of the structural unit (a) in the copolymer is low, thereby suppressing a decrease in the strength and dielectric properties of the film. From the above viewpoint, when the total content of the four types of triad structures is taken as 100 mol%, the content of the triad structure (U-1) is more preferably 2.0 mol% or less, even more preferably 1.8 mol% or less, even more preferably 1.5 mol% or less, even more preferably 1.4 mol% or less, even more preferably 1.0 mol% or less, and even more preferably 0.5 mol% or less of the total 100 mol% of the content of the four types of triad structures. When the total content of the four types of triad structures is taken as 100 mol %, the content of the triad structure (U-1) may be substantially 0.0 mol % in the total 100 mol % content of the four types of triad structures, or may be, for example, 0.0 mol % or more, more than 0.0 mol %, or 0.01 mol % or more.

[0062] As described above, these stepwise lower and upper limits can be independently combined. For example, in one embodiment of the present invention, the content of the triad structure (U-1) is, relative to the total 100 mol% of the content of the four triad structures, preferably 0.0 to 2.2 mol%, more preferably 0.0 to 2.0 mol%, even more preferably 0.0 to 1.8 mol%, even more preferably 0.0 to 1.5 mol%, even more preferably 0.0 to 1.4 mol%, even more preferably 0.0 to 1.0 mol%, and even more preferably 0.0 to 0.5 mol%. Also, for example, in one embodiment of the present invention, the content of the triad structure (U-1) may be, relative to the total 100 mol% of the content of the four triad structures, more than 0.0 mol% to 2.2 mol%, more than 0.0 mol% to 2.0 mol%, 0.01 to 2.2 mol%, or 0.01 to 2.0 mol%.

[0063] The structural unit (a) is reduced in amount of continuous sequence, from the viewpoint of suppressing a decrease in the strength and dielectric properties of the film, the total content of the four types of triad structures (U-2) and (U-3) when the total content is 100 mol%, more preferably 9.0 mol% or less, more preferably 8.5 mol% or less, even more preferably 8.0 mol% or less, even more preferably 7.5 mol% or less, even more preferably 7.0 mol% or less, even more preferably 6.5 mol% or less, even more preferably 6.0 mol% or less. Also, for example, in one embodiment of the present invention, the total content of the four types of triad structures (U-2) and (U-3) when the total content is 100 mol%, is also preferably 5.5 mol% or less, more preferably 5.3 mol% or less, even more preferably 5.0 mol% or less, even more preferably 4.8 mol% or less, even more preferably 4.3 mol% or less. When the total content of the four types of triad structures is taken as 100 mol %, the total content of the triad structures (U-2) and (U-3) may be, for example, 0.1 mol % or more, more than 0 mol %, or 0.001 mol % or more.

[0064] Furthermore, as described above, these stepwise described lower limit values ​​and upper limit values ​​can be independently combined. For example, in one embodiment of the present invention, the total content of the triad structures (U-2) and (U-3) is, relative to the total content of the four triad structures (100 mol%), preferably 0.1 to 25.0 mol%, more preferably 0.1 to 9.0 mol%, even more preferably 0.1 to 8.0 mol%, still more preferably 0.1 to 7.5 mol%, even more preferably 0.1 to 6.5 mol%, and even more preferably 0.1 to 6.0 mol%. Also, for example, in one embodiment of the present invention, the total content of the triad structures (U-2) and (U-3) is, relative to the total content of the four triad structures (100 mol%), preferably 0.1 to 5.5 mol%, more preferably 0.1 to 5.3 mol%, even more preferably 0.1 to 5.0 mol%, even more preferably 0.1 to 4.8 mol%, and even more preferably 0.1 to 4.5 mol%.

[0065] Furthermore, for example, in one embodiment of the present invention, the total content of the triad structures (U-2) and (U-3) is, out of the total 100 mol % of the contents of the four types of triad structures, preferably more than 0 mol % and not more than 25.0 mol %, more preferably more than 0 mol % and not more than 9.0 mol %, even more preferably more than 0 mol % and not more than 8.0 mol %, still more preferably more than 0 mol % and not more than 7.5 mol %, still more preferably more than 0 mol % and not more than 6.5 mol %, and still more preferably more than 0 mol % and not more than 6.0 mol %. Furthermore, for example, in one embodiment of the present invention, the total content of the triad structures (U-2) and (U-3) is preferably more than 0 mol% and not more than 5.5 mol%, more preferably more than 0 mol% and not more than 5.3 mol%, even more preferably more than 0 mol% and not more than 5.0 mol%, still more preferably more than 0 mol% and not more than 4.8 mol%, and still more preferably more than 0 mol% and not more than 4.5 mol%, based on 100 mol% as the total content of the four types of triad structures.

[0066] Furthermore, for example, in one embodiment of the present invention, the total content of the triad structures (U-2) and (U-3) is preferably 0.001 to 25.0 mol%, more preferably 0.001 to 9.0 mol%, even more preferably 0.001 to 8.0 mol%, still more preferably 0.001 to 7.5 mol%, still more preferably 0.001 to 6.5 mol%, and still more preferably 0.001 to 6.0 mol%, relative to 100 mol% of the total content of the four types of triad structures. Furthermore, for example, in one embodiment of the present invention, the total content of the triad structures (U-2) and (U-3) is preferably 0.001 to 5.5 mol %, more preferably 0.001 to 5.3 mol %, even more preferably 0.001 to 5.0 mol %, still more preferably 0.001 to 4.8 mol %, and even more preferably 0.001 to 4.5 mol %, relative to 100 mol % of the total content of the four types of triad structures.

[0067] The total content of the triad structures (U-2) and (U-3) can be adjusted, for example, by carrying out the polymerization at a relatively low temperature of less than 50° C. and controlling the amount of the monomers charged.

[0068] Furthermore, when the total content of the four types of triad structures is taken as 100 mol%, from the viewpoint of enhancing the strength and dielectric properties of the film, the content of the triad structure (U-4) is preferably 90 mol% or more, more preferably 91 mol% or more, even more preferably 92 mol% or more, even more preferably 93 mol% or more, and even more preferably 94 mol% or more, of the total 100 mol% content of the four types of triad structures. The upper limit of the content of the triad structure (U-4) when the total content of the four types of triad structures is taken as 100 mol% is not particularly limited, but for example, the content of the triad structure (U-4) may be 100 mol% or less, or less than 100 mol%, of the total 100 mol% content of the four types of triad structures.

[0069] As described above, these stepwise lower and upper limits can be independently combined. For example, in one embodiment of the present invention, the content of the triad structure (U-4) is preferably 90 to 100 mol%, more preferably 91 to 100 mol%, even more preferably 92 to 100 mol%, still more preferably 93 to 100 mol%, and even more preferably 94 to 100 mol%, based on the total 100 mol% of the content of the four triad structures. Also, for example, in one embodiment of the present invention, the content of the triad structure (U-4) is preferably 90 mol% or more but less than 100 mol%, more preferably 91 mol% or more but less than 100 mol%, even more preferably 92 mol% or more but less than 100 mol%, still more preferably 93 mol% or more but less than 100 mol%, and even more preferably 94 mol% or more but less than 100 mol%, based on the total 100 mol% of the content of the four triad structures.

[0070] Furthermore, the contents of the four types of triad structures in the copolymer can each independently be as described above, but when the selected contents are combined, the total content of the four types of triad structures in the copolymer does not exceed 100 mol % of the total of the four types of triad structures, i.e., the total content of the four types of triad structures in the copolymer is 100 mol % of the total of the four types of triad structures, i.e., 100 mol % of the total of the four types of triad structures.

[0071] (Weight-average molecular weight Mw of copolymer) The weight-average molecular weight Mw of the copolymer in this embodiment is preferably 50,000 or more and 1,500,000 or less, more preferably 50,000 or more and 1,000,000 or less, even more preferably 50,000 or more and 900,000 or less, and even more preferably 50,000 or more and 800,000 or less. When the weight-average molecular weight Mw is within the above range, a film with sufficient strength can be obtained. The weight-average molecular weight Mw can be measured by the method described in the Examples section below.

[0072] (Glass Transition Temperature of Copolymer) The glass transition temperature of the copolymer in this embodiment is not particularly limited, but is preferably set appropriately by changing the content of the structural units depending on the application. The glass transition temperature of the copolymer in this embodiment is preferably 60 to 260°C. The glass transition temperature of the copolymer is more preferably 75 to 260°C, even more preferably 130 to 260°C, still more preferably 150 to 260°C, and even more preferably 170 to 260°C. Furthermore, in one embodiment of the present invention, the glass transition temperature of the copolymer is, for example, 75 to 240°C, 130 to 240°C, 150 to 240°C, 170 to 240°C, 75 to 230°C, 130 to 230°C, 150 to 230°C, 170 to 230°C, 75 to 220°C, 130 to 220°C, 150 to 220°C, 170 to 220°C ...20°C, 150 to 220°C, 170 to 220°C, 75 to 240°C, 130 to 240°C, 15 The temperature may be 210°C, 130 to 210°C, 150 to 210°C, 170 to 210°C, 75 to 200°C, 130 to 200°C, 150 to 200°C, 170 to 200°C, 75 to 190°C, 130 to 190°C, 150 to 190°C, 170 to 190°C, 75 to 180°C, 130 to 180°C, 150 to 180°C, or 170 to 180°C.

[0073] The glass transition temperature of the copolymer can be measured using a differential scanning calorimeter, specifically by the method described in the Examples section below. When the copolymer is in a resin composition or a film, the copolymer can be identified by dissolving the resin composition or film in a solvent, performing a fractionation operation, and then measuring NMR of the fraction.

[0074] (Method for Producing Copolymer) The method for producing the copolymer in this embodiment is not particularly limited. The copolymer is preferably produced at a polymerization temperature of less than 50°C, preferably in the presence of a radical initiator, and more preferably in the presence of a radical initiator at a polymerization temperature of less than 50°C. Furthermore, when producing the copolymer in this embodiment, it is preferable to use a Brønsted acidic compound.

[0075] (Polymerization Temperature) By setting the polymerization temperature to less than 50°C, the total content of the triad structures (U-2) and (U-3) can be easily adjusted to the aforementioned preferred range, for example, preferably 25.0 mol% or less, more preferably 9.0 mol% or less, when the total content of the four triad structures is 100 mol%. From the viewpoint of adjusting the total content of the triad structures (U-2) and (U-3), the polymerization temperature is more preferably 47°C or less, and even more preferably 45°C or less. From the viewpoint of polymerization rate and productivity, the polymerization temperature is preferably 10°C or higher, more preferably 20°C or higher, and even more preferably 30°C or higher. Furthermore, as described above, these stepwise described lower limit and upper limit values ​​can be independently combined. For example, in one embodiment of the present invention, the polymerization temperature is preferably 10°C or higher but less than 50°C, more preferably 20 to 47°C, and even more preferably 30 to 45°C.

[0076] (Radical Polymerization Initiator) In the production of the copolymer of this embodiment, by using a radical polymerization initiator, it becomes easier to adjust the total content of the triad structures (U-2) and (U-3) when the total content of the four types of triad structures is taken as 100 mol %.

[0077] Examples of radical polymerization initiators include azo compounds such as azobisisobutyronitrile, 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile), 2,2'-azobis[2-(2-imidazolin-2-yl)propane], and 2,2'-azobis[N-(2-carboxyethyl)-2-methylpropionamidine]hydrate; inorganic peroxides such as sodium persulfate, potassium persulfate, and hydrogen peroxide; organic peroxides such as t-butyl hydroperoxide, cumene hydroperoxide, and p-menthane hydroperoxide; and redox initiators combining an oxidizing agent and a reducing agent, such as hydrogen peroxide and an iron(II) salt, or a persulfate and sodium hydrogen sulfite. These may be used alone or in combination of two or more.

[0078] By carrying out radical polymerization at low temperatures, specifically below 50° C., it is possible to more easily adjust the total content of the triad structures (U-2) and (U-3) when the total content of the four triad structures is taken as 100 mol %. Therefore, from the viewpoint of ease of use at low temperatures, it is preferable to use, as the radical polymerization initiator, one or more selected from azo compounds and redox initiators, and it is preferable to use one or more selected from azobisisobutyronitrile, 2,2′-azobis(4-methoxy-2,4-dimethylvaleronitrile) and redox initiators.

[0079] The amount of the radical polymerization initiator used is preferably 0.01 to 10 parts by mass, more preferably 0.05 to 5 parts by mass, and even more preferably 0.08 to 3 parts by mass, relative to 100 parts by mass of all the monomers that are raw materials for the copolymer.

[0080] (Ratio of Charge Amounts in Copolymer Production) In the production of the copolymer of this embodiment, the charge amount of the specific polymerizable monomer is preferably 1.5 molar equivalents or more relative to the charge amount of 1,1-dicyanoethylene, more preferably 1.8 molar equivalents or more, and even more preferably 2.2 molar equivalents or more. When the charge amount of the specific polymerizable monomer relative to the charge amount of 1,1-dicyanoethylene is 1.5 molar equivalents or more, it is easy to adjust the total content of the triad structures (U-2) and (U-3) when the total content of the four triad structures is taken as 100 mol %. There is no upper limit to the charge amount of the specific polymerizable monomer relative to the charge amount of 1,1-dicyanoethylene, as long as it does not excessively impair the intended effects of the present invention. However, from the viewpoint of reducing production costs, it is preferably 5.0 molar equivalents or less. Furthermore, as described above, these stepwise lower and upper limits can be independently combined. For example, in one embodiment of the present invention, the amount of the specific polymerizable monomer charged is preferably 1.5 to 5.0 molar equivalents, more preferably 1.8 to 5.0 molar equivalents, and even more preferably 2.2 to 5.0 molar equivalents, relative to the amount of 1,1-dicyanoethylene charged.

[0081] (Water Content) From the viewpoint of suppressing ionic polymerization, it is preferable that the water content of the 1,1-dicyanoethylene used in producing the copolymer of this embodiment is low. The water content of the 1,1-dicyanoethylene is preferably 10,000 ppm by mass or less, more preferably 1,000 ppm by mass or less, even more preferably 500 ppm by mass or less, and even more preferably 300 ppm by mass or less. When the water content of the 1,1-dicyanoethylene is 10,000 ppm by mass or less, it becomes easier to adjust the total content of the triad structures (U-2) and (U-3) when the total content of the four triad structures is taken as 100 mol %. The water content of the 1,1-dicyanoethylene can be measured, for example, by a method in accordance with JIS K0068:2001.

[0082] (Bronsted Acid Compound) When a Bronsted acid compound is used in producing the copolymer of this embodiment, coloration of the film tends to be suppressed.

[0083] There are no particular limitations on the Bronsted acidic compound that can be used when producing the copolymer. Specific examples of the Bronsted acidic compound include mineral acids such as sulfuric acid, hydrochloric acid, nitric acid, phosphoric acid, hydrobromic acid, and partially neutralized salts thereof, as well as organic acids such as formic acid, acetic acid, trifluoroacetic acid, trichloroacetic acid, dichloroacetic acid, phenylphosphonic acid, ethylphosphinic acid, methanesulfonic acid, ethanesulfonic acid, 2-propanesulfonic acid, trifluoromethanesulfonic acid, benzenesulfonic acid, and p-toluenesulfonic acid. These may be used alone or in combination of two or more.

[0084] The Bronsted acidic compound may also include compounds that react with water to exhibit Bronsted acidity, such as sulfur dioxide and diphosphorus pentoxide. These may be used alone or in combination of two or more.

[0085] Among these, from the viewpoint of more significantly achieving the effect of tending to suppress coloration of the film, the Bronsted acidic compound is preferably a compound whose logarithmic acid dissociation constant (pKa) is 4.8 or less, more preferably 3.0 or less, even more preferably 2.5 or less, and even more preferably 2.0 or less.

[0086] The pKa value refers to the logarithmic acid dissociation constant of the conjugate acid in water at 25° C. The pKa value can be calculated from the concentration of the substance in question and the hydrogen ion concentration measured using a pH meter. When a Bronsted acidic compound undergoes multi-stage dissociation, the logarithmic acid dissociation constant of the first stage is usually used as the logarithmic acid dissociation constant pKa.

[0087] The Bronsted acidic compound is preferably a compound having one or more functional groups selected from the group consisting of a phosphate group, a carboxy group, a sulfonic acid group, and a phosphite group. Examples of such Bronsted acidic compounds include phosphoric acid, acetic acid, methanesulfonic acid, and p-toluenesulfonic acid. In one embodiment of the present invention, the Bronsted acidic compound is preferably one or more selected from methanesulfonic acid and p-toluenesulfonic acid. In one embodiment of the present invention, the Bronsted acidic compound is more preferably p-toluenesulfonic acid (pKa=-1.7).

[0088] When a Brønsted acidic compound is used in producing the copolymer of this embodiment, the amount used is preferably 0.01 to 10 parts by mass, more preferably 0.05 to 5 parts by mass, and even more preferably 0.08 to 3 parts by mass, relative to 100 parts by mass of all monomers used as raw materials for the copolymer.

[0089] (Content of the Copolymer) In one embodiment of the present invention, the content of the copolymer in the film is preferably 0.1% by mass or more, more preferably 20% by mass or more, even more preferably 50% by mass or more, even more preferably more than 50% by mass, and even more preferably 60% by mass or more, based on 100% by mass of the total amount of the constituent components of the film excluding the organic solvent, from the viewpoint of easily achieving the effects of the present invention. The upper limit of the content of the copolymer in the film is not particularly limited, and the content of the copolymer in the film may be, for example, 100% by mass or less or 99.999% by mass or less based on 100% by mass of the total amount of the constituent components of the film excluding the organic solvent.

[0090] As described above, these stepwise lower and upper limits can be independently combined. For example, in one embodiment of the present invention, the content of the copolymer in the film is preferably 0.1 to 100% by mass, more preferably 20 to 100% by mass, even more preferably 50 to 100% by mass, still more preferably more than 50% by mass but not more than 100% by mass, and even more preferably 60 to 100% by mass, based on 100% by mass of the total amount of the film's constituent components excluding the organic solvent. Alternatively, it may be, for example, 70 to 100% by mass, 80 to 100% by mass, 70 to 100% by mass, 80 to 100% by mass, 90 to 100% by mass, 95 to 100% by mass, or 97 to 100% by mass. Further, for example, in one embodiment of the present invention, the content of the copolymer in the resin composition is, based on 100% by mass of the total amount of the constituent components of the film excluding the organic solvent, preferably 0.1 to 99.999% by mass, more preferably 20 to 99.999% by mass, even more preferably 50 to 99.999% by mass, still more preferably more than 50% by mass and 99.999% by mass or less, still more preferably 60 to 99.999% by mass, and also, for example, 70 to 99.999% by mass, 80 to 99.999% by mass, 70 to 99.999% by mass, 80 to 99.999% by mass, 90 to 99.999% by mass, 95 to 99.999% by mass, or 97 to 99.999% by mass. Furthermore, in one embodiment of the present invention, the content of the copolymer in the film may be 100% by mass, based on 100% by mass of the total amount of the constituent components of the film excluding the organic solvent.

[0091] <Optional Components> The film according to this embodiment may contain optional components as needed. Examples of optional components include synthetic resins other than the copolymer according to this embodiment, fillers, thickeners, antioxidants, plasticizers, flame retardants, stabilizers, and antioxidants. The film according to this embodiment may also contain at least some of the reagents used in producing the copolymer according to this embodiment. Examples of such reagents include the Bronsted acidic compounds.

[0092] (Synthetic Resins Other Than the Copolymers) Examples of synthetic resins other than the copolymers (also referred to as "other synthetic resins" in this specification) include polyolefin resins such as polyethylene, polypropylene, copolymers of ethylene and one or more α-olefins having 3 to 20 carbon atoms (e.g., propylene, 1-butene, 1-pentene, 1-hexene, etc.), ethylene-propylene-diene copolymers (EPDM), ethylene-vinyl acetate copolymers, and ethylene-acrylic acid copolymers, polyurethane resins, polyamide resins, polyester resins, and polycarbonate resins. These may be used alone or in combination of two or more.

[0093] In one embodiment of the present invention, when the film contains components other than the copolymer and optional components other than the organic solvent (also simply referred to as "optional components" in this specification), the content of the optional components in the film is the same as each preferred content range described below, except that in the total content range of the optional components in the resin composition described in the section on resin composition described below, the description "100% by mass of the total amount of the resin composition" is changed to "100% by mass of the total amount of the constituent components of the film excluding the organic solvent."

[0094] Furthermore, the contents of the copolymer and the various optional components in the film described above can each independently assume the respective contents described above, but when the selected contents are combined, the total content of the copolymer and the various optional components does not exceed 100 mass% based on 100 mass% of the total amount of the film's constituent components excluding the organic solvent. That is, the total content of at least one selected from the group consisting of the copolymer and the various optional components is 100 mass% or less based on 100 mass% of the total amount of the film's constituent components excluding the organic solvent. Furthermore, the contents of the copolymer and the various optional components in the film described above can each independently assume the respective contents described above, but when the selected contents are combined, the total content of the organic solvent and the total amount of the film's constituent components excluding the organic solvent is 100 mass% based on 100 mass% of the total amount of the film.

[0095] <Resin Composition> The film according to this embodiment may be formed from a resin composition containing at least one of the optional components described above. From the viewpoint of easily achieving the effects of the present invention, the content of the copolymer according to this embodiment in the resin composition is preferably 0.1% by mass or more, more preferably 20% by mass or more, even more preferably 50% by mass or more, even more preferably more than 50% by mass, even more preferably 60% by mass or more, and may also be, for example, 70% by mass or more, 80% by mass or more, 90% by mass or more, 95% by mass or more, or 97% by mass or more, based on the total amount (100% by mass) of the resin composition. The upper limit of the content of the copolymer according to this embodiment in the resin composition is not particularly limited. For example, the content of the copolymer according to this embodiment in the resin composition may be 99.999% by mass or less, or 99% by mass or less, based on the total amount (100% by mass) of the resin composition.

[0096] For example, in one embodiment of the present invention, the content of the copolymer in the resin composition is, based on 100% by mass of the total amount of the resin composition, preferably 0.1 to 99.999% by mass, more preferably 20 to 99.999% by mass, even more preferably 50 to 99.999% by mass, still more preferably more than 50% by mass and 99.999% by mass or less, and even more preferably 60 to 99.999% by mass, and may also be, for example, 70 to 99.999% by mass, 80 to 99.999% by mass, 70 to 99.999% by mass, 80 to 99.999% by mass, 90 to 99.999% by mass, 95 to 99.999% by mass, or 97 to 99.999% by mass. Also, for example, in one embodiment of the present invention, the content of the copolymer in the resin composition is, based on 100% by mass of the total amount of the resin composition, preferably 0.1 to 99% by mass, more preferably 20 to 99% by mass, even more preferably 50 to 99% by mass, even more preferably more than 50% by mass but not more than 99% by mass, and even more preferably 60 to 99% by mass. Also, for example, 70 to 99% by mass, 80 to 99% by mass, 70 to 99% by mass, 80 to 99% by mass, 90 to 99% by mass, 95 to 99% by mass, or 97 to 99% by mass. However, in this specification, when the resin composition contains an "organic solvent" that may be contained in the film after formation, the "total amount of the resin composition (100% by mass)" does not include the content of the organic solvent. The same applies hereinafter.

[0097] When the resin composition contains a synthetic resin other than the copolymer as an optional component, the content of the synthetic resin other than the copolymer in the resin composition is preferably 99.9% by mass or less, more preferably 80% by mass or less, even more preferably 50% by mass or less, even more preferably less than 50% by mass, even more preferably 40% by mass or less, based on the total amount (100% by mass) of the resin composition, from the viewpoint of easily achieving the effects of the present invention. For example, it may be 30% by mass or less, 20% by mass or less, 10% by mass or less, 5% by mass or less, or 3% by mass or less. The lower limit of the content of the synthetic resin other than the copolymer in the resin composition is not particularly limited, but may be, for example, 1% by mass. Furthermore, as described above, these stepwise lower limit and upper limit values ​​can be independently combined. For example, in one embodiment of the present invention, when the resin composition contains a synthetic resin other than the copolymer as an optional component, the content of the synthetic resin other than the copolymer in the resin composition is, relative to the total amount (100 mass%) of the resin composition, preferably 1 to 99.9 mass%, more preferably 1 to 80 mass%, even more preferably 1 to 50 mass%, still more preferably 1 to 50 mass%, even more preferably 1 to 40 mass%, and may also be, for example, 1 to 30 mass%, 1 to 20 mass%, 1 to 10 mass%, 1 to 5 mass%, or 1 to 3 mass%.

[0098] When the resin composition contains optional components other than synthetic resins other than the copolymer as optional components, the total content of the optional components other than the synthetic resins other than the copolymer (for example, at least one component selected from the group consisting of fillers, thickeners, antioxidants, plasticizers, flame retardants, stabilizers, antioxidants, and Bronsted acidic compounds) in the resin composition is not limited, but may be, for example, 10% by mass or less, 3% by mass or less, or 0.001% by mass or more. Furthermore, as described above, these stepwise lower limit values ​​and upper limit values ​​can be independently combined. For example, in one embodiment of the present invention, when the resin composition contains optional components excluding synthetic resins other than the copolymer (for example, at least one component selected from the group consisting of fillers, thickeners, antioxidants, plasticizers, flame retardants, stabilizers, and antioxidants), the total content of the optional components excluding synthetic resins other than the copolymer in the resin composition may be 0.001 to 10% by mass, or 0.001 to 3% by mass, relative to the total amount (100% by mass) of the resin composition.

[0099] When the resin composition contains a Bronsted acidic compound as an optional component, the content of the Bronsted acidic compound in the resin composition is preferably 0.1 to 95,000 ppm by mass, more preferably 0.5 to 90,000 ppm by mass, even more preferably 0.8 to 85,000 ppm by mass, still more preferably 0.8 to 50,000 ppm by mass, still more preferably 1 to 30,000 ppm by mass, still more preferably 5 to 10,000 ppm by mass, still more preferably 5 to 9,000 ppm by mass, still more preferably 10 to 5,000 ppm by mass, and still more preferably 20 to 2,000 ppm by mass. If the content of the Bronsted acidic compound is within the above range, it is preferable because it tends to suppress coloration of the film to be produced.

[0100] In order to adjust the content of the Brønsted acidic compound in the resin composition to fall within the above-mentioned range, for example, the content can be reduced by neutralizing a portion of the Brønsted acidic compound present in the resin composition with an arbitrary compound, or the content can be increased by adding an additional Brønsted acidic compound to the resin composition.

[0101] The content of the Brønsted acid compound in the resin composition can be determined by elemental analysis. For example, when the Brønsted acid is a sulfonic acid, the content can be determined by subjecting a resin composition containing the Brønsted acid to combustion decomposition, converting it into sulfate ions, and quantifying the sulfate ions.

[0102] Furthermore, the contents of the copolymer and the various optional components in the resin composition described above can each independently be the contents described above, but when the selected contents are combined, the total content of the copolymer and the various optional components does not exceed 100% by mass relative to 100% by mass of the total amount of the resin composition. That is, the total content of at least one selected from the group consisting of the copolymer and the various optional components is 100% by mass or less relative to 100% by mass of the total amount of the resin composition.

[0103] (Method for producing resin composition) There is no particular limitation on the method for producing the resin composition, and the resin composition can be produced by a production method including a mixing step of mixing the copolymer of the present embodiment and any optional components used as needed. Note that there is no particular limitation on the method for mixing the components, and they can be mixed by a known method.

[0104] <Film aspects> The film according to this embodiment contains the copolymer according to this embodiment. Therefore, the film according to this embodiment is usually formed using the copolymer according to this embodiment or a resin composition containing the copolymer. The film according to this embodiment may be an unstretched film or a stretched film. Note that the stretched film in this embodiment is a film obtained by subjecting an unstretched film to a stretching treatment described below.

[0105] (Film Thickness) When the film according to the present embodiment is an unstretched film, there are no particular restrictions on its thickness, but from the viewpoint of excellent transparency, it is preferably 5.0 mm or less, more preferably 1.5 mm or less, even more preferably 1.0 mm or less, still more preferably 0.5 mm or less, and even more preferably 0.1 mm or less.

[0106] From the viewpoint of obtaining a film with a low content of organic solvent and a high dielectric breakdown strength, the thickness of the unstretched film is preferably 0.1 mm or less (i.e., 100 μm or less), more preferably 50 μm or less, even more preferably 30 μm or less, and even more preferably less than 30 μm. Furthermore, in one embodiment of this embodiment, the thickness of the unstretched film may be, for example, 29 μm or less, 28 μm or less, 27 μm or less, 26 μm or less, 25 μm or less, 24 μm or less, 23 μm or less, 22 μm or less, 21 μm or less, 20 μm or less, less than 20 μm, or 10 μm or less. The lower limit of the thickness of the unstretched film is naturally determined by the film manufacturing method, but may be, for example, more than 0.001 μm, more than 0.005 μm, or 1.0 μm or more.

[0107] For example, in one embodiment of the present invention, the thickness of the unstretched film may be more than 0.001 μm and not more than 5.0 mm, more than 0.001 μm and not more than 1.5 mm, more than 0.001 μm and not more than 1.0 mm, more than 0.001 μm and not more than 0.5 mm, more than 0.001 μm and not more than 100 μm, more than 0.001 μm and not more than 50 μm, more than 0.001 μm and not more than 30 μm, more than 0.001 μm and not more than 30 μm, more than 0.001 μm and not more than 29 μm, or more than 0.001 μm and not more than 29 μm. It may be more than 0.001 μm and not more than 28 μm, more than 0.001 μm and not more than 27 μm, more than 0.001 μm and not more than 26 μm, more than 0.001 μm and not more than 25 μm, more than 0.001 μm and not more than 24 μm, more than 0.001 μm and not more than 23 μm, more than 0.001 μm and not more than 22 μm, more than 0.001 μm and not more than 21 μm, more than 0.001 μm and not more than 20 μm, more than 0.001 μm and not more than 20 μm, or more than 0.001 μm and not more than 10 μm. Furthermore, for example, in one embodiment of the present invention, the thickness of the unstretched film is more than 0.005 μm and not more than 5.0 mm, more than 0.005 μm and not more than 1.5 mm, more than 0.005 μm and not more than 1.0 mm, more than 0.005 μm and not more than 0.5 mm, more than 0.005 μm and not more than 100 μm, more than 0.005 μm and not more than 50 μm, more than 0.005 μm and not more than 30 μm, more than 0.005 μm and less than 30 μm, or more than 0.005 μm and not more than 29 μm. , more than 0.005 μm and not more than 28 μm, more than 0.005 μm and not more than 27 μm, more than 0.005 μm and not more than 26 μm, more than 0.005 μm and not more than 25 μm, more than 0.005 μm and not more than 24 μm, more than 0.005 μm and not more than 23 μm, more than 0.005 μm and not more than 22 μm, more than 0.005 μm and not more than 21 μm, more than 0.005 μm and not more than 20 μm, more than 0.005 μm and not more than 20 μm, or more than 0.005 μm and not more than 10 μm.Furthermore, for example, in one embodiment of the present invention, the thickness of the unstretched film may be 1.0 μm or more and 5.0 mm or less, 1.0 μm or more and 1.5 mm or less, 1.0 μm or more and 1.0 mm or less, 1.0 μm or more and 0.5 mm or less, 1.0 to 100 μm, 1.0 to 50 μm, 1.0 to 30 μm, 1.0 μm or more and less than 30 μm, 1.0 to 29 μm, 1.0 to 28 μm, 1.0 to 27 μm, 1.0 to 26 μm, 1.0 to 25 μm, 1.0 to 24 μm, 1.0 to 23 μm, 1.0 to 22 μm, 1.0 to 21 μm, 1.0 to 20 μm, 1.0 μm or more and less than 20 μm, or 1.0 to 10 μm.

[0108] When the film according to this embodiment is a stretched film, its thickness is usually smaller than that of the unstretched film from which it is made. The thickness of the stretched film is preferably less than 100 μm, more preferably less than 50 μm, even more preferably less than 30 μm, and even more preferably 29 μm or less. In one embodiment of this embodiment, the thickness of the stretched film may be, for example, less than 29 μm, 28 μm or less, 27 μm or less, 26 μm or less, 25 μm or less, 24 μm or less, 23 μm or less, 22 μm or less, 21 μm or less, 20 μm or less, less than 20 μm, or less than 10 μm. The lower limit of the thickness of the stretched film is naturally determined by the film manufacturing method, but may be, for example, 0.001 μm or more, 0.005 μm or more, or 0.9 μm or more.

[0109] For example, in one embodiment of the present invention, the thickness of the stretched film may be 0.001 μm or more and less than 100 μm, 0.001 μm or more and less than 50 μm, 0.001 μm or more and less than 30 μm, 0.001 to 29 μm, 0.001 μm or more and less than 29 μm, 0.001 to 28 μm, 0.001 to 27 μm, 0.001 to 26 μm, 0.001 to 25 μm, 0.001 to 24 μm, 0.001 to 23 μm, 0.001 to 22 μm, 0.001 to 21 μm, 0.001 to 20 μm, 0.001 μm or more and less than 20 μm, or 0.001 μm or more and less than 10 μm. Furthermore, for example, in one embodiment of the present invention, the thickness of the stretched film may be 0.005 μm or more and less than 100 μm, 0.005 μm or more and less than 50 μm, 0.005 μm or more and less than 30 μm, 0.005 to 29 μm, 0.005 μm or more and less than 29 μm, 0.005 to 28 μm, 0.005 to 27 μm, 0.005 to 26 μm, 0.005 to 25 μm, 0.005 to 24 μm, 0.005 to 23 μm, 0.005 to 22 μm, 0.005 to 21 μm, 0.005 to 20 μm, 0.005 μm or more and less than 20 μm, or 0.005 μm or more and less than 10 μm. Furthermore, for example, in one embodiment of the present invention, the thickness of the stretched film may be 0.9 μm or more and less than 100 μm, 0.9 μm or more and less than 50 μm, 0.9 μm or more and less than 30 μm, 0.9 to 29 μm, 0.9 μm or more and less than 29 μm, 0.9 to 28 μm, 0.9 to 27 μm, 0.9 to 26 μm, 0.9 to 25 μm, 0.9 to 24 μm, 0.9 to 23 μm, 0.9 to 22 μm, 0.9 to 21 μm, 0.9 to 20 μm, 0.9 μm or more and less than 20 μm, or 0.9 μm or more and less than 10 μm.

[0110] (Organic solvent content) As described above, the content of organic solvent in the film according to this embodiment is 4.0000% by mass or less, and the preferred content is also as described above. Furthermore, in one embodiment of the present invention, when the film according to this embodiment is a stretched film, a heating step is performed during the stretching treatment. Therefore, the content of organic solvent in the stretched film is preferably 3.0000% by mass or less, more preferably 2.5000% by mass or less, even more preferably 2.0000% by mass or less, and even more preferably 1.5000% by mass or less. Furthermore, the preferred content of organic solvent in the film according to this embodiment may be even lower. As described above, the lower the content of organic solvent in the stretched film, the more preferable it is. The lower limit is, for example, 0.0000% by mass or the detection limit, and 0.0001% by mass may be used as the trace amount or detection limit.

[0111] For example, in one embodiment of the present invention, the content of the organic solvent in the stretched film is preferably 0.0000 to 3.0000 mass%, more preferably 0.0000 to 2.5000 mass%, even more preferably 0.0000 to 2.0000 mass%, still more preferably 0.0000 to 1.5000 mass%, still more preferably 0.0000 mass% or more but less than 0.9000 mass%, still more preferably 0.0000 mass% or more but less than 0.5000 mass%, based on 100 mass% of the total amount of the film. Preferably, the content is 0.0000% by mass or more and less than 0.4000% by mass, even more preferably 0.0000% by mass or more and less than 0.3000% by mass, even more preferably 0.0000% by mass or more and less than 0.2000% by mass, even more preferably 0.0000% by mass or more and less than 0.1000% by mass, even more preferably 0.0000% by mass or more and less than 0.0500% by mass, even more preferably 0.0000% by mass or more and less than 0.0100% by mass, and even more preferably 0.0000% by mass or more and less than 0.0002% by mass.

[0112] In addition, for example, in one embodiment of the present invention, the content of the organic solvent in the stretched film is preferably 0.0001 to 3.0000 mass%, more preferably 0.0001 to 2.5000 mass%, even more preferably 0.0001 to 2.0000 mass%, still more preferably 0.0001 to 1.5000 mass%, still more preferably 0.0001 mass% or more and less than 0.9000 mass%, still more preferably 0.0001 mass% or more and less than 0.5000 mass%, based on 100 mass% of the total amount of the film. Preferably, it is 0.0001% by mass or more and less than 0.4000% by mass, even more preferably 0.0001% by mass or more and less than 0.3000% by mass, even more preferably 0.0001% by mass or more and less than 0.2000% by mass, even more preferably 0.0001% by mass or more and less than 0.1000% by mass, even more preferably 0.0001% by mass or more and less than 0.0500% by mass, even more preferably 0.0001% by mass or more and less than 0.0100% by mass, and even more preferably 0.0001% by mass or more and less than 0.0002% by mass.

[0113] <Film Properties> (Electrical Properties) (Dielectric Constant) The film according to this embodiment tends to have excellent electrical properties. In particular, the film according to this embodiment contains the structural unit (a) derived from 1,1-dicyanoethylene, and therefore exhibits the property of a high dielectric constant. Because the film according to this embodiment has a high dielectric constant, it is suitable for use in film capacitors.

[0114] The film according to this embodiment has a dielectric constant measured at 24°C and 1 kHz of preferably 3.5 or higher, more preferably 3.6 or higher, even more preferably 3.7 or higher, even more preferably 3.8 or higher, even more preferably 3.9 or higher, even more preferably 4.0 or higher, even more preferably 4.1 or higher, even more preferably 4.2 or higher, even more preferably 4.3 or higher, even more preferably 4.4 or higher, and even more preferably 4.5 or higher. Because of its high dielectric constant, the film according to this embodiment is suitable for use in film capacitors. The upper limit of the dielectric constant is not particularly limited, but in one embodiment of the present invention, it may be, for example, 10.0, 9.0, 8.0, 7.0, or 6.0. As mentioned above, these stepwise lower and upper limits can be independently combined. For example, in one embodiment of the present invention, the relative dielectric constant is 3.5 to 10.0, 3.6 to 10.0, 3.7 to 10.0, 3.8 to 10.0, 3.9 to 10.0, 4.0 to 10.0, 4.1 to 10.0, 4.2 to 10.0, 4.3 to 10.0, 4.4 to 10.0, 4.5 to 10.0, 3.5 to 9.0, 3.6 to 9.0, 3.7 to 9.0, 3.8 to 9.0, 3.9 to 9.0, 4.0 to 9.0, 4.1 to 9.0, 4.2 to 9.0, 4.3 to 9.0, 4.4 to 9.0, 4.5 to 9.0, 3.5 to 8.0, 3.6 to 8.0, 3.7 to 8.0, 3.8 to 8. 0, 3.9 to 8.0, 4.0 to 8.0, 4.1 to 8.0, 4.2 to 8.0, 4.3 to 8.0, 4.4 to 8.0, 4.5 to 8.0, 3.5 to 7.0, 3.6 to 7.0, 3.7 to 7.0, 3.8 to 7.0, 3.9 to 7.0, 4.0 to 7.0, 4.1 to 7.0, 4.2 to 7.0, 4.3 to 7.0, 4.4 to 7.0, 4.5 to 7.0, 3.5 to 6.0, 3.6 to 6.0, 3.7 to 6.0, 3.8 to 6.0, 3.9 to 6.0, 4.0 to 6.0, 4.1 to 6.0, 4.2 to 6.0, 4.3 to 6.0, 4.4 to 6.0, or 4.5 to 6.0. The relative dielectric constant of the film can be measured by forming a metal coating on both sides to form a film capacitor and then using the method described in the Examples section below.

[0115] (Dielectric loss tangent) The film according to this embodiment tends to have an excellent dielectric loss tangent. As described above, the film according to this embodiment has a low content of organic solvent, and therefore exhibits the characteristic of a high dielectric loss tangent. Since the film of the present invention has a low dielectric loss tangent, it can reduce heat loss, making it suitable for use in film capacitors.

[0116] The film according to this embodiment has a dielectric loss tangent measured at 24°C and 1 kHz of preferably 0.070 or less, more preferably 0.060 or less, even more preferably 0.050 or less, even more preferably 0.040 or less, even more preferably 0.030 or less, even more preferably 0.025 or less, even more preferably 0.020 or less, and even more preferably 0.015 or less. The lower the dielectric loss tangent value, the better. There is no particular restriction on the lower limit, but in one embodiment of the present invention, for example, 0.001 or 0.002 may be adopted. As mentioned above, these stepwise lower and upper limits can be independently combined. For example, in one embodiment of the present invention, the dielectric loss tangent is preferably 0.001 to 0.070, more preferably 0.001 to 0.060, even more preferably 0.001 to 0.050, still more preferably 0.001 to 0.040, still more preferably 0.001 to 0.030, still more preferably 0.001 to 0.025, still more preferably 0.001 to 0.020, and still more preferably 0.001 to 0.015. In one embodiment of the present invention, the dielectric loss tangent is preferably 0.002 to 0.070, more preferably 0.002 to 0.060, even more preferably 0.002 to 0.050, still more preferably 0.002 to 0.040, still more preferably 0.002 to 0.030, still more preferably 0.002 to 0.025, still more preferably 0.002 to 0.020, and still more preferably 0.002 to 0.015. The dielectric loss tangent of the film can be measured by forming a metal coating on both sides of the film to form a film capacitor and then measuring it by the method described in the Examples section below.

[0117] (Insulating Properties) The film according to this embodiment tends to have excellent insulating properties. In particular, the film according to this embodiment has a low organic solvent content, specifically 4.0000% by mass or less, as described above, and therefore exhibits the property of a high breakdown voltage. The reason why a film with an organic solvent content of 4.0000% by mass or less has excellent insulating performance is as follows: Generally, organic solvents themselves are easily conductive. Therefore, if a large amount of organic solvent is present in the film, the film as a whole becomes more easily conductive, resulting in a decrease in insulating performance. On the other hand, the lower the content of organic solvent present in the film, the better the insulating performance of the film as a whole. The film according to this embodiment has a high breakdown voltage, which allows for expected operating voltage and long-term use, making it suitable for use in film capacitors.

[0118] The film according to this embodiment preferably has a breakdown voltage of 300 kV / mm or more, more preferably 350 kV / mm or more, even more preferably 400 kV / mm or more, even more preferably 450 kV / mm or more, even more preferably 500 kV / mm or more, even more preferably 520 kV / mm or more, even more preferably 530 kV / mm or more, even more preferably 540 kV / mm or more, even more preferably 550 kV / mm or more, and even more preferably 560 kV / mm or more. The upper limit of the breakdown voltage is not particularly limited, but in one embodiment of the present invention, it may be, for example, 800 kV / mm. As mentioned above, these stepwise lower and upper limits can be independently combined. For example, in one embodiment of the present invention, the breakdown voltage is preferably 300 to 800 kV / mm, more preferably 350 to 800 kV / mm, even more preferably 400 to 800 kV / mm, still more preferably 450 to 800 kV / mm, still more preferably 500 to 800 kV / mm, still more preferably 520 to 800 kV / mm, still more preferably 530 to 800 kV / mm, still more preferably 540 to 800 kV / mm, still more preferably 550 to 800 kV / mm, and still more preferably 560 to 800 kV / mm. The breakdown voltage of the film can be measured by the method described in the Examples section below.

[0119] Furthermore, the film according to this embodiment has a high breakdown voltage and exhibits the characteristic of high stored energy relative to the thickness of the film, and therefore, the film according to this embodiment can be made thin (for example, less than 30 μm), making it suitable for use in film capacitors.

[0120] The film according to this embodiment preferably has a storage energy of 2.00 J / cm ３ More preferably, 2.20 J / cm ３ More preferably, 2.40 J / cm ３ More preferably, 2.50 J / cm ３ More preferably, 3.00 J / cm ３ More preferably, 3.20 J / cm３ More preferably, 4.00 J / cm ３ More preferably, 4.40 J / cm ３ More preferably, 4.80 J / cm ３ More preferably, 5.00 J / cm ３ More preferably, 5.20 J / cm ３ More preferably, 5.40 J / cm ３ More preferably, 5.60 J / cm ３ More preferably, 5.80 J / cm ３ More preferably, 6.00 J / cm ３ There is no particular upper limit to the value of the stored energy, but in one embodiment of the present invention, it is, for example, 12.75 J / cm ３ , 12.00J / cm ３ , 11.00J / cm ３ , or 10.00 J / cm ３ may be.

[0121] As mentioned above, the lower and upper limits described in stages can be independently combined. For example, in one embodiment of the present invention, the stored energy is preferably 2.00 to 12.75 J / cm ３ , more preferably 2.20 to 12.75 J / cm ３ , more preferably 2.40 to 12.75 J / cm ３ , and even more preferably 2.50 to 12.75 J / cm ３ , and even more preferably 3.00 to 12.75 J / cm ３ , and even more preferably 3.20 to 12.75 J / cm ３ , and even more preferably 4.00 to 12.75 J / cm ３ , and even more preferably 4.40 to 12.75 J / cm ３ , and even more preferably 4.80 to 12.75 J / cm ３ , and even more preferably 5.00 to 12.75 J / cm ３ , and even more preferably 5.20 to 12.75 J / cm ３ , and even more preferably 5.40 to 12.75 J / cm３ , and even more preferably 5.60 to 12.75 J / cm ３ , and even more preferably 5.80 to 12.75 J / cm ３ , and even more preferably 6.00 to 12.75 J / cm ３ In one embodiment of the present invention, the stored energy is, for example, 2.00 to 12.00 J / cm ３ , 2.20~12.00J / cm ３ , 2.40~12.00J / cm ３ , 2.50~12.00J / cm ３ , 3.00~12.00J / cm ３ , 3.20~12.00J / cm ３ , 4.00~12.00J / cm ３ , 4.40~12.00J / cm ３ , 4.80-12.00J / cm ３ , 5.00~12.00J / cm ３ , 5.20~12.00J / cm ３ , 5.40~12.00J / cm ３ , 5.60~12.00J / cm ３ , 5.80~12.00J / cm ３ , or 6.00 to 12.00 J / cm ３ In one embodiment of the present invention, the stored energy may be, for example, 2.00 to 11.00 J / cm ３ , 2.20~11.00J / cm ３ , 2.40~11.00J / cm ３ , 2.50~11.00J / cm ３ , 3.00~11.00J / cm ３ , 3.20~11.00J / cm ３ , 4.00~11.00J / cm ３ , 4.40~11.00J / cm ３ , 4.80~11.00J / cm ３ , 5.00~11.00J / cm ３ , 5.20~11.00J / cm ３ , 5.40~11.00J / cm ３ , 5.60~11.00J / cm ３ , 5.80~11.00J / cm３ , or 6.00 to 11.00 J / cm ３ In one embodiment of the present invention, the stored energy may be, for example, 2.00 to 10.00 J / cm ３ , 2.20~10.00J / cm ３ , 2.40~10.00J / cm ３ , 2.50~10.00J / cm ３ , 3.00~10.00J / cm ３ , 3.20~10.00J / cm ３ , 4.00~10.00J / cm ３ , 4.40~10.00J / cm ３ , 4.80~10.00J / cm ３ , 5.00~10.00J / cm ３ , 5.20~10.00J / cm ３ , 5.40~10.00J / cm ３ , 5.60~10.00J / cm ３ , 5.80~10.00J / cm ３ , or 6.00 to 10.00 J / cm ３ The stored energy of the film can be measured by the method described in the Examples section below.

[0122] (Mechanical Properties) The film according to this embodiment tends to have excellent mechanical properties. In particular, the film according to this embodiment exhibits excellent tensile properties because plasticization by organic solvents is suppressed. The film according to this embodiment has excellent tensile properties, so the strength of the film is high. Furthermore, the film according to this embodiment has excellent tensile properties, so it is advantageous in that breakage is less likely to occur when producing a laminate.

[0123] The tensile modulus of the film according to this embodiment is not particularly limited, but is preferably 3.2 GPa or more, more preferably 3.4 GPa or more, even more preferably 3.6 GPa or more, even more preferably 3.8 GPa or more, even more preferably 4.0 GPa or more, and even more preferably 4.2 GPa or more. The upper limit of the tensile modulus is not particularly limited, but in one embodiment of the present invention, it may be, for example, 5.0 GPa. As described above, these stepwise lower and upper limits can be independently combined. For example, in one embodiment of the present invention, the tensile modulus is preferably 3.2 to 5.0 GPa, more preferably 3.4 to 5.0 GPa, even more preferably 3.6 to 5.0 GPa, even more preferably 3.8 to 5.0 GPa, even more preferably 4.0 to 5.0 GPa, and even more preferably 4.2 to 5.0 GPa or more. The tensile modulus of the film can be measured by the method described in the Examples section below.

[0124] [Method for Providing a Film with a Low Dielectric Loss Tangent] A method for providing a film with a low dielectric loss tangent according to this embodiment will be described. A preferred embodiment of the film obtained by the method for providing a film with a low dielectric loss tangent according to this embodiment is the film according to the embodiment described above, and since the film and its preferred embodiments are the same as those described above, their description will be omitted. Similarly, in this embodiment, the structural unit (a), the structural unit (b), the structural unit (c), and the copolymer are as described in the film according to the embodiment described above, and their preferred embodiments are also the same, so their description will be omitted.

[0125] The first method for providing a film with a low dielectric loss tangent is the method for producing the film. The second method for providing a film with a low dielectric loss tangent is to reduce the organic solvent content of the film.

[0126] <First Method: Film Manufacturing Method> The film manufacturing method according to this embodiment is a method for manufacturing a film by using a structural unit (a) derived from 1,1-dicyanoethylene and at least one structural unit represented by the following general formula (I): CH ２ =CR １R ２ (I) [In general formula (I), R １ is one selected from the group consisting of a hydrogen atom, an alkyl group, a cycloalkyl group, an aryl group, an alkoxy group, a nitrile group, and a halogen atom; R ２ represents a hydrogen atom, an alkyl group, an alkoxy group, a carboxy group, -COOR ３ (R ３ is an alkyl group having 1 to 12 carbon atoms, a cycloalkyl group having 5 to 12 carbon atoms, or an aryl group having 6 to 12 carbon atoms. ４ (R ４ is an alkyl group having 1 to 12 carbon atoms, a cycloalkyl group having 5 to 12 carbon atoms, or an aryl group having 6 to 12 carbon atoms; ５ (R ５ is an alkyl group having 1 to 12 carbon atoms, a cycloalkyl group having 5 to 12 carbon atoms, or an aryl group having 6 to 12 carbon atoms. (b) is one selected from the group consisting of an acyloxy group and a cyanoalkyl group represented by the formula (I). A method for producing a film comprising a copolymer containing a structural unit (b) derived from a compound represented by the formula (I), the method comprising: a first heating step of heating a first film formed from a coating liquid containing the copolymer and an organic solvent at a first temperature that satisfies the conditions of being lower than the boiling point of the organic solvent and lower than a temperature 30°C lower than the glass transition temperature of the copolymer to obtain a second film; and a second heating step of heating the second film at a second temperature that satisfies the conditions of being at least 30°C lower than the glass transition temperature of the copolymer to obtain a third film. This method makes it possible to provide a film with a low dielectric loss tangent.

[0127] (Organic Solvent) The organic solvent used to form the first film is not particularly limited as long as it can dissolve the copolymer according to this embodiment. Examples of such organic solvents include ethyl acetate, dimethyl sulfoxide, N,N-dimethylformamide, N,N-dimethylacetamide, tetrahydrofuran, acetone, methanol, cyclohexanone, N-methylpyrrolidone, and propylene carbonate. These organic solvents may be used alone or in combination of two or more. In one embodiment of the present invention, from the viewpoint of solubility, at least one selected from N,N-dimethylacetamide and N,N-dimethylformamide is preferred. In one embodiment of the present invention, from the viewpoint of solubility, N,N-dimethylacetamide is preferred.

[0128] (Coating Liquid) The coating liquid (solution) used in this embodiment contains the copolymer and the organic solvent. The coating liquid may or may not contain components other than the copolymer and the organic solvent. The method for preparing the coating liquid is not limited as long as the copolymer can be dissolved in the organic solvent. When preparing the coating liquid, stirring is preferably performed, and stirring and heating are more preferably performed.

[0129] The content of the copolymer in the coating liquid is not particularly limited as long as it is soluble in an organic solvent. While the content of the copolymer in the coating liquid is not particularly limited, the content of the copolymer is preferably 3% by mass or more, more preferably 6% by mass or more, even more preferably 10% by mass or more, even more preferably 12% by mass or more, even more preferably 14% by mass or more, even more preferably 15% by mass or more, even more preferably 18% by mass or more, and even more preferably 20% by mass or more, based on 100% by mass of the total amount of the coating liquid. The upper limit of the copolymer content in the coating liquid may be, for example, 75% by mass, 50% by mass, or 30% by mass. Furthermore, as described above, these stepwise lower and upper limits can be independently combined. For example, in one embodiment of the present invention, the content of the copolymer in the coating liquid is preferably 3 to 75% by mass, more preferably 6 to 75% by mass, even more preferably 10 to 75% by mass, and even more preferably 12 to 75% by mass, based on 100% by mass of the total amount of the coating liquid. In one embodiment of the present invention, the content of the copolymer in the coating liquid is preferably 3 to 50 mass%, more preferably 6 to 50 mass%, even more preferably 10 to 50 mass%, and still more preferably 12 to 50 mass%, based on 100 mass% of the total amount of the coating liquid. In one embodiment of the present invention, the content of the copolymer in the coating liquid is preferably 3 to 30 mass%, more preferably 6 to 30 mass%, even more preferably 10 to 30 mass%, and still more preferably 12 to 30 mass%, based on 100 mass% of the total amount of the coating liquid.

[0130] (First Film) In this embodiment, the first film is a film formed from a coating liquid containing the copolymer and the organic solvent. There are no particular limitations on the method for producing the first film, and it can be formed by a conventionally known method using an organic solvent. Examples of the forming method include a solution casting method.

[0131] The content of the organic solvent in the first film is likely to be, for example, 25.0000% by mass or more, based on 100% by mass of the total amount of the first film, due to the film being formed from a coating liquid. However, according to this embodiment, the content of the organic solvent can be reduced, so the content of the organic solvent in the first film may be, for example, less than 97.0000% by mass, based on 100% by mass of the total amount of the first film. Furthermore, for example, in one embodiment of the present invention, the content of the organic solvent in the first film may be 25.0000% by mass or more and less than 97.0000% by mass, based on 100% by mass of the total amount of the first film. The content of such organic solvent can be determined by gas chromatography measurement, specifically, by the method described in the Examples section.

[0132] The solution casting method for forming the first film is preferred because it makes it easier to obtain the effects of the present invention than other film-forming methods. Furthermore, the solution casting method is advantageous over other film-forming methods when handling a copolymer whose moldable temperature and thermal decomposition temperature are close to each other, such as the copolymer of the present embodiment.

[0133] (Solution Casting Method) The method for applying the solution in the solution casting method is not particularly limited, and examples thereof include application methods using an applicator, a wire bar, a die coater, a comma coater, a gravure coater, and a dip nip.

[0134] When forming a film by a solution casting method, the coating liquid may be applied to a substrate. The type of substrate is not particularly limited, and examples thereof include polypropylene, polyethylene terephthalate, polyimide, glass, and metal plate. In addition, from the viewpoint of improving adhesion between the substrate surface and the coating film formed from the coating liquid, the substrate may be a substrate whose surface has been subjected to a surface treatment such as corona treatment, ozone treatment, flame treatment, plasma treatment, or ultraviolet treatment. From the viewpoint of adhesion between the substrate and the coating liquid and film releasability, the substrate is preferably one selected from corona-treated polypropylene and non-corona-treated polyethylene terephthalate.

[0135] (First Heating Step) In the first heating step of the method according to this embodiment, the first film is heated at a first temperature. When the first film is formed on a substrate, a laminate consisting of the substrate and the first film formed on the substrate may be heated, or only the first film peeled from the laminate may be heated. From the viewpoint of workability, it is preferable to heat a laminate consisting of the substrate and the first film formed on the substrate.

[0136] By performing the first heating step, the content of organic solvent in the first film is reduced to a certain extent, thereby making it possible to obtain a second film with a reduced content of organic solvent. Furthermore, when the first film is formed on a substrate, heating the first film in this first heating step makes it possible to easily peel the obtained second film from the substrate. One reason why the second film is easily peeled from the substrate is that the strength of the film is increased by heating.

[0137] (First Temperature) As described above, the first temperature is a temperature that satisfies the conditions of being lower than the boiling point of the organic solvent and lower than a temperature 30°C lower than the glass transition temperature of the copolymer. When the first temperature satisfies this condition, it is possible to prevent the appearance of the second film from being impaired. One factor that can impair the appearance of the film is significant evaporation of the organic solvent in the film during heating. Therefore, when multiple types of organic solvents are used, the boiling point of the organic solvent with the lowest boiling point among the multiple types of organic solvents is used as the boiling point of the organic solvent specified in the first temperature condition.

[0138] In one embodiment of the present invention, the first temperature may be, for example, below the boiling point of the organic solvent and below a temperature 40° C. lower than the glass transition temperature of the copolymer, below the boiling point of the organic solvent and below a temperature 50° C. lower than the glass transition temperature of the copolymer, below the boiling point of the organic solvent and below a temperature 60° C. lower than the glass transition temperature of the copolymer, below the boiling point of the organic solvent and below a temperature 70° C. lower than the glass transition temperature of the copolymer, below the boiling point of the organic solvent and below a temperature 80° C. lower than the glass transition temperature of the copolymer, or below the boiling point of the organic solvent and below a temperature 90° C. lower than the glass transition temperature of the copolymer. In one embodiment of the present invention, the first temperature may be, for example, 40° C. or higher, 50° C. or higher, or 55° C. or higher.

[0139] As mentioned above, the lower limit and upper limit values ​​described in stages can be independently combined. For example, in one embodiment of the present invention, the first temperature may be 40°C or higher and lower than the boiling point of the organic solvent and lower than a temperature 30°C lower than the glass transition temperature of the copolymer; 40°C or higher and lower than the boiling point of the organic solvent and lower than a temperature 40°C lower than the glass transition temperature of the copolymer; 40°C or higher and lower than the boiling point of the organic solvent and lower than a temperature 50°C lower than the glass transition temperature of the copolymer; 40°C or higher and lower than the boiling point of the organic solvent and lower than a temperature 60°C lower than the glass transition temperature of the copolymer; 40°C or higher and lower than the boiling point of the organic solvent and lower than a temperature 70°C lower than the glass transition temperature of the copolymer; 40°C or higher and lower than the boiling point of the organic solvent and lower than a temperature 80°C lower than the glass transition temperature of the copolymer; or 40°C or higher and lower than the boiling point of the organic solvent and lower than a temperature 90°C lower than the glass transition temperature of the copolymer. Furthermore, for example, in one embodiment of the present invention, the first temperature may be 50°C or higher and lower than the boiling point of the organic solvent and lower than a temperature 30°C lower than the glass transition temperature of the copolymer; 50°C or higher and lower than the boiling point of the organic solvent and lower than a temperature 40°C lower than the glass transition temperature of the copolymer; 50°C or higher and lower than the boiling point of the organic solvent and lower than a temperature 50°C lower than the glass transition temperature of the copolymer; 50°C or higher and lower than the boiling point of the organic solvent and lower than a temperature 60°C lower than the glass transition temperature of the copolymer; 50°C or higher and lower than the boiling point of the organic solvent and lower than a temperature 70°C lower than the glass transition temperature of the copolymer; 50°C or higher and lower than the boiling point of the organic solvent and lower than a temperature 80°C lower than the glass transition temperature of the copolymer; or 50°C or higher and lower than the boiling point of the organic solvent and lower than a temperature 90°C lower than the glass transition temperature of the copolymer.Furthermore, for example, in one embodiment of the present invention, the first temperature may be 55°C or higher and lower than the boiling point of the organic solvent and lower than a temperature 30°C lower than the glass transition temperature of the copolymer; 55°C or higher and lower than the boiling point of the organic solvent and lower than a temperature 40°C lower than the glass transition temperature of the copolymer; 55°C or higher and lower than the boiling point of the organic solvent and lower than a temperature 50°C lower than the glass transition temperature of the copolymer; 55°C or higher and lower than the boiling point of the organic solvent and lower than a temperature 60°C lower than the glass transition temperature of the copolymer; 55°C or higher and lower than the boiling point of the organic solvent and lower than a temperature 70°C lower than the glass transition temperature of the copolymer; 55°C or higher and lower than the boiling point of the organic solvent and lower than a temperature 80°C lower than the glass transition temperature of the copolymer; or 55°C or higher and lower than the boiling point of the organic solvent and lower than a temperature 90°C lower than the glass transition temperature of the copolymer.

[0140] The first temperature is preferably, for example, 40 to 130° C. From the viewpoint of further reducing the content of organic solvent in the first film, the first temperature is more preferably 50 to 130° C., even more preferably 55 to 130° C., still more preferably 60 to 130° C., and still more preferably 70 to 130° C. Furthermore, in one embodiment of the present invention, the first temperature may be, for example, 40 to 120°C, 50 to 120°C, 55 to 120°C, 60 to 120°C, 70 to 120°C, 40 to 110°C, 50 to 110°C, 55 to 110°C, 60 to 110°C, 70 to 110°C, 40 to 100°C, 50 to 100°C, 55 to 100°C, 60 to 100°C, 70 to 100°C, 40 to 90°C, 50 to 90°C, 55 to 90°C, 60 to 90°C, or 70 to 90°C.

[0141] (First Time) In the first heating step, the time for which the first film is exposed to the first temperature (hereinafter also referred to as the "first time") is not limited as long as the aforementioned effect is not excessively impaired. For example, it can be 2 hours or less, less than 2 hours, 1 hour or less, or 45 minutes or less. The first time may be 1 minute or more, 5 minutes or more, or 10 minutes or more, as long as the aforementioned effect is achieved. That is, the first time is, for example, in the range of 1 minute to 2 hours. From the viewpoint of further reducing the content of the organic solvent, the first time is preferably 20 minutes or more, and may be 24 minutes or more, or 25 minutes or more. Furthermore, as described above, these stepwise lower and upper limits can be independently combined. For example, in one embodiment of the present invention, the first time may be 1 minute to 2 hours, 5 minutes to 2 hours, 10 minutes to 2 hours, 20 minutes to 2 hours, 24 minutes to 2 hours, or 25 minutes to 2 hours. Furthermore, for example, in one embodiment of the present invention, the first time period may be 1 minute or more and less than 2 hours, 5 minutes or more and less than 2 hours, 10 minutes or more and less than 2 hours, 20 minutes or more and less than 2 hours, 24 minutes or more and less than 2 hours, or 25 minutes or more and less than 2 hours. Furthermore, for example, in one embodiment of the present invention, the first time period may be 1 minute or more and less than 1 hour, 5 minutes or more and less than 1 hour, 10 minutes or more and less than 1 hour, 20 minutes or more and less than 1 hour, 24 minutes or more and less than 1 hour, or 25 minutes or more and less than 1 hour. Furthermore, for example, in one embodiment of the present invention, the first time period may be 1 to 45 minutes, 5 to 45 minutes, 10 to 45 minutes, 20 to 45 minutes, 24 to 45 minutes, or 25 to 45 minutes. The first film may also be exposed to heat treatment at a temperature that does not reach the first temperature, but this time period is not included in the first time period.

[0142] In one embodiment of the present invention, the heat treatment in the first heating step is preferably a method in which at least one surface (exposed surface) of the first film is brought into contact with an atmosphere satisfying a first temperature, preferably air satisfying the first temperature, thereby volatilizing the organic solvent from the surface of the first film.

[0143] The heating device for performing the first heating step is not limited. An example of such a heating device is an oven. The oven may be a commercially available product. The oven is preferably equipped with a pressure reducing device or an exhaust device, which allows the volatilized organic solvent to be discharged. The oven is also preferably equipped with a blower. This allows the high-temperature atmosphere generated in the oven to be circulated evenly. The oven is also preferably equipped with a temperature control device. In this case, the first temperature may be the temperature set in the temperature control device, or may be a value measured as the temperature inside the oven near the first film. However, if the temperature inside the oven is expected to be uneven, it is preferable to use the temperature inside the oven near the first film as the first temperature. The oven does not need to be a sealed system as long as temperature control is possible, and may be an open system. For example, when the first film is heat-treated in an apparatus for continuously producing the first film, such as a roll-to-roll system, the film may be heat-treated while passing through an oven with an open inlet and outlet.

[0144] (Second Heating Step) In the second heating step of the method according to this embodiment, the second film is heated at a second temperature. Here, when the second film is formed on a substrate, it is preferable to first peel the second film from the substrate and then attach the second film to a predetermined jig so that both the first and second main surfaces of the second film are directly exposed to the second temperature. Examples of the predetermined jig include a metal rectangular frame and a plurality of metal clips. In one embodiment of the present invention, a metal rectangular frame is preferably used, and in this case, the second film is attached to the metal rectangular frame. In this specification, the "first main surface" refers to the surface with the largest area among the surfaces of the film, and the "second main surface" refers to the surface with the same area as the first main surface or the surface with the second largest area after the first main surface. The areas of the "first main surface" and the "second main surface" may be the same. The second main surface is preferably a surface of the film located on the opposite side to the first main surface.

[0145] By performing the second heating step, the content of the organic solvent in the second film is further reduced, thereby making it possible to obtain a third film having a further reduced content of the organic solvent. The third film thus obtained has an organic solvent content of 4.0000 mass% or less, similar to the film according to the above embodiment, and the preferred range of the organic solvent content is also as described above. In this way, a film having a low dielectric loss tangent similar to the film according to the above embodiment can be obtained.

[0146] (Second Temperature) As described above, the second temperature is a temperature that satisfies the condition of being at least 30°C lower than the glass transition temperature of the copolymer. In one embodiment of the present invention, the second temperature may be, for example, at least 20°C lower than the glass transition temperature of the copolymer, at least 10°C lower than the glass transition temperature of the copolymer, more than 5°C lower than the glass transition temperature of the copolymer, at least the glass transition temperature of the copolymer, higher than the glass transition temperature of the copolymer, or at least 2°C higher than the glass transition temperature of the copolymer. In one embodiment of the present invention, the second temperature may be, for example, at most 60°C higher than the glass transition temperature of the copolymer, at most 50°C higher than the glass transition temperature of the copolymer, or at most 40°C higher than the glass transition temperature of the copolymer.

[0147] For example, in one embodiment of the present invention, the second temperature may be a temperature that is 30° C. lower than the glass transition temperature of the copolymer and 60° C. higher than the glass transition temperature of the copolymer, a temperature that is 30° C. lower than the glass transition temperature of the copolymer and 50° C. higher than the glass transition temperature of the copolymer, a temperature that is 30° C. lower than the glass transition temperature of the copolymer and 40° C. higher than the glass transition temperature of the copolymer, a temperature that is 20° C. lower than the glass transition temperature of the copolymer and 60° C. higher than the glass transition temperature of the copolymer, a temperature that is 20° C. lower than the glass transition temperature of the copolymer and 50° C. higher than the glass transition temperature of the copolymer, a temperature that is 20° C. lower than the glass transition temperature of the copolymer and 40° C. higher than the glass transition temperature of the copolymer, a temperature that is 10° C. lower than the glass transition temperature of the copolymer and 60° C. higher than the glass transition temperature of the copolymer, a temperature that is 10° C. lower than the glass transition temperature of the copolymer and 50° C. higher than the glass transition temperature of the copolymer, a temperature that is 10° C. lower than the glass transition temperature of the copolymer and 4 ... the temperature may be more than 5°C lower than the glass transition temperature of the copolymer but not exceeding 60°C higher, more than 5°C lower than the glass transition temperature of the copolymer but not exceeding 50°C higher, more than 5°C lower than the glass transition temperature of the copolymer but not exceeding 40°C higher, more than 60°C higher than the glass transition temperature of the copolymer but not exceeding 60°C higher, more than 50°C higher than the glass transition temperature of the copolymer but not exceeding 40°C higher, more than 60°C higher than the glass transition temperature of the copolymer but not exceeding 50°C higher, more than 40°C higher than the glass transition temperature of the copolymer but not exceeding 60°C higher, more than 50°C higher than the glass transition temperature of the copolymer but not exceeding 40°C higher, more than 2°C higher than the glass transition temperature of the copolymer but not exceeding 60°C higher, more than 2°C higher than the glass transition temperature of the copolymer but not exceeding 50°C higher, or more than 2°C higher than the glass transition temperature of the copolymer but not exceeding 40°C higher.

[0148] In one embodiment of the present invention, the second temperature is preferably within the above-mentioned temperature range or each of the preferred temperature ranges and is equal to or higher than the boiling point of the organic solvent. When multiple organic solvents are used, the boiling point of the organic solvent with the highest boiling point among the multiple organic solvents is used as the boiling point of the organic solvent specified in the second temperature condition.

[0149] The second temperature varies depending on the glass transition temperature of the film, but is preferably, for example, higher than 130° C. and equal to or lower than 230° C. From the viewpoint of further reducing the content of organic solvent in the second film, the second temperature is more preferably 140 to 230° C., even more preferably 150 to 230° C., still more preferably 160 to 230° C., still more preferably 165 to 230° C., still more preferably 170 to 230° C., still more preferably 175 to 230° C., and still more preferably 180 to 230° C. Moreover, in one embodiment of the present invention, the second temperature may be, for example, greater than 130°C and less than 220°C, 140 to 220°C, 150 to 220°C, 160 to 220°C, 165 to 220°C, 170 to 220°C, 175 to 220°C, 180 to 220°C, greater than 130°C and less than 210°C, 140 to 210°C, 150 to 210°C, 160 to 210°C, 165 to 210°C, 170 to 210°C, 175 to 210°C, 180 to 210°C, greater than 130°C and less than 200°C, 140 to 200°C, 150 to 200°C, 160 to 200°C, 165 to 200°C, 170 to 200°C, 175 to 200°C, or 180 to 200°C.

[0150] (Second Time) In the second heating step, the time for which the second film is exposed to the second temperature (hereinafter also referred to as the "second time") is not limited as long as the aforementioned effect is not excessively impaired, and can be, for example, 2 hours or less, less than 2 hours, 90 minutes or less, or 80 minutes or less. The second time may be 1 minute or more, 2 minutes or more, 3 minutes or more, 4 minutes or more, 5 minutes or more, or 10 minutes or more, as long as the aforementioned effect is achieved. That is, the second time is, for example, in the range of 1 minute to 2 hours. From the viewpoint of achieving a further reduction in the content of the organic solvent, the second time is preferably 30 minutes or more, and may be 45 minutes or more, 50 minutes or more, 55 minutes or more, or 60 minutes or more. Furthermore, as described above, these stepwise lower and upper limits can be independently combined. For example, in one embodiment of the present invention, the second time period may be 1 minute to 2 hours, 2 minutes to 2 hours, 3 minutes to 2 hours, 4 minutes to 2 hours, 5 minutes to 2 hours, 10 minutes to 2 hours, 30 minutes to 2 hours, 45 minutes to 2 hours, 50 minutes to 2 hours, 55 minutes to 2 hours, or 1 to 2 hours. Also, for example, in one embodiment of the present invention, the second time period may be 1 minute to less than 2 hours, 2 minutes to less than 2 hours, 3 minutes to less than 2 hours, 4 minutes to less than 2 hours, 5 minutes to less than 2 hours, 10 minutes to less than 2 hours, 30 minutes to less than 2 hours, 45 minutes to less than 2 hours, 50 minutes to less than 2 hours, 55 minutes to less than 2 hours, or 60 minutes to less than 2 hours. Furthermore, for example, in one embodiment of the present invention, the second time period may be 1 to 90 minutes, 2 to 90 minutes, 3 to 90 minutes, 4 to 90 minutes, 5 to 90 minutes, 10 to 90 minutes, 30 to 90 minutes, 45 to 90 minutes, 50 to 90 minutes, 55 to 90 minutes, or 60 to 90 minutes. Furthermore, for example, in one embodiment of the present invention, the second time period may be 1 to 80 minutes, 2 to 80 minutes, 3 to 80 minutes, 4 to 80 minutes, 5 to 80 minutes, 10 to 80 minutes, 30 to 80 minutes, 45 to 80 minutes, 50 to 80 minutes, 55 to 80 minutes, or 60 to 80 minutes. The second film may also be exposed to heat treatment at a temperature below the second temperature, but this time period is not included in the second time period.

[0151] In one embodiment of the present invention, the heat treatment in the second heating step is preferably a method in which at least one surface (exposed surface) of the second film is brought into contact with an atmosphere satisfying the second temperature, preferably air satisfying the second temperature, thereby volatilizing the organic solvent from the surface of the second film. The heating device used in the second heating step is not limited. Such a heating device may be the same as or different from the heating device used in the first heating step. As mentioned above, an example of a heating device is an oven, and a description thereof will be omitted.

[0152] The method according to this embodiment includes the first and second heating steps, which significantly reduces the organic solvent content in the film. Furthermore, by performing the first heating step prior to the second heating step, it is possible to prevent the appearance of the film from being damaged.

[0153] (Optional Step) The method according to the present embodiment may include an optional step. The optional step is typically a step other than the first heating step and the second heating step. However, the optional step may be a heating step similar to the second heating step. That is, in the method according to the present embodiment, the second heating step may be performed multiple times, thereby increasing the possibility of achieving further reduction in the organic solvent content. However, in this specification, the second heating step or subsequent times is an optional step. From the viewpoint of maintaining the appearance of the film, the upper limit of the number of times the second heating step can be performed, including the second heating step or subsequent times, which is an optional step, is preferably 5 times, more preferably 4 times, and even more preferably 3 times. In other words, in the method according to the present embodiment, the number of times the second heating step can be performed is at least once, preferably 1 to 5 times, more preferably 1 to 4 times, and even more preferably 1 to 3 times. Furthermore, for example, in one embodiment of the present invention, the number of times the second heating step can be performed in the method according to the present embodiment may be 1 or 2 times.

[0154] (Cooling Step) Another example of an optional step is a cooling step. The cooling step is a step of lowering the temperature of the film by cooling the heat-treated film. The cooling may be performed by leaving the film to cool or by exposing it to cold air. When the method according to this embodiment includes the cooling step, storage of the film (for example, primary storage of the second film before subjecting it to the second heating step) becomes possible.

[0155] The cooling step may be carried out between the first heating step and the second heating step. In this case, the first heating step and the second heating step do not need to be consecutive. In the first step, the content of the organic solvent is reduced to a certain extent while preventing significant evaporation of the organic solvent. Therefore, in the second heating step, the possibility of significant evaporation of the organic solvent in the second film after cooling is also reduced.

[0156] (Stretching Process) Yet another example of an optional process is a stretching process. The stretching process is a process of stretching the film. Known stretching processes can be used as the stretching process. The stretching may be uniaxial stretching or biaxial stretching. By including the stretching process in the method according to the present embodiment, the strength of the film can be increased. The stretching process may also include a heating process. If the temperature in such a heating process satisfies the second temperature condition of the second heating process, the stretching process may also be considered to serve as the second heating process. However, if the second heating process is carried out prior to the stretching process, the stretching process does not need to be considered to serve as the second heating process.

[0157] The stretching step may be carried out between the first heating step and the second heating step, or may be carried out after the second heating step. In one embodiment of the present invention, the stretching treatment after the second heating step is preferred because it is expected to improve yield reductions (e.g., occurrence of breakage, occurrence of wrinkles or voids, or decrease in transparency) caused by the organic solvent in the film.

[0158] Furthermore, in one embodiment of the present invention, it is preferable that the type of organic solvent reduced in the first heating step and the second heating step is the same, and therefore it is preferable that the optional step does not include a step of washing the second film with an organic solvent different from the organic solvent contained in the second film.

[0159] <Second Method: Method for Reducing the Content of Organic Solvent in Film> The method for reducing the content of organic solvent in a film according to this embodiment is a method for reducing the content of organic solvent in a film by combining a structural unit (a) derived from 1,1-dicyanoethylene and at least one type of structural unit represented by the following general formula (I): CH ２ =CR １ R ２ (I) [In general formula (I), R １ is one selected from the group consisting of a hydrogen atom, an alkyl group, a cycloalkyl group, an aryl group, an alkoxy group, a nitrile group, and a halogen atom; R ２ represents a hydrogen atom, an alkyl group, an alkoxy group, a carboxy group, -COOR ３ (R ３ is an alkyl group having 1 to 12 carbon atoms, a cycloalkyl group having 5 to 12 carbon atoms, or an aryl group having 6 to 12 carbon atoms. ４ (R ４ is an alkyl group having 1 to 12 carbon atoms, a cycloalkyl group having 5 to 12 carbon atoms, or an aryl group having 6 to 12 carbon atoms; ５ (R ５ is an alkyl group having 1 to 12 carbon atoms, a cycloalkyl group having 5 to 12 carbon atoms, or an aryl group having 6 to 12 carbon atoms. It is one selected from the group consisting of an acyloxy group and a cyanoalkyl group represented by the formula (I). A method for reducing the content of organic solvent in a film containing a copolymer containing a structural unit (b) derived from a compound represented by the formula (I), the method comprising the steps of: heating the film at a temperature in the range of 40 to 130°C; and heating the heated film at a temperature higher than 130°C and not higher than 230°C. This makes it possible to reduce the content of organic solvent in the film, and by using this method, it is also possible to provide a film with a low dielectric loss tangent.

[0160] The temperature ranges in the step of heating at a temperature range of 40 to 130°C (hereinafter also referred to as the "first step") and the temperature range in the step of heating at a temperature greater than 130°C and equal to or less than 230°C (hereinafter also referred to as the "second step") in the method according to this embodiment are the same as those described above for the preferred ranges of the first temperature and the second temperature in the film manufacturing method according to the embodiment, and further preferred aspects thereof are also the same, so descriptions thereof will be omitted. Similarly, the time for which the film is exposed to the temperature range in the first step and the time for which the film that has undergone at least the first step is exposed to the temperature range in the second step are the same as those described above for the preferred ranges of the first time and the preferred ranges of the second time in the film manufacturing method according to the embodiment, and further preferred aspects thereof are also the same, so descriptions thereof will be omitted.

[0161] In the method according to this embodiment, the film to be subjected to reduction of the organic solvent content (hereinafter also referred to as the “target film”) is the same as the first film in the film manufacturing method according to the above-described embodiment. However, the target film in this embodiment differs from the first film in that the boiling point of the organic solvent that may be contained and the glass transition temperature of the copolymer that is contained may both be known, or at least one of the boiling point of the organic solvent and the glass transition temperature of the copolymer that is contained may be unknown.

[0162] From the viewpoint of confirming the reduction of the organic solvent content by the method according to this embodiment, the content of the organic solvent in the target film may be, for example, 25.0000 mass% or more relative to 100% by mass of the total amount of the target film. Furthermore, in one embodiment of the present invention, the content of the organic solvent in the target film may be less than 97.0000 mass% relative to 100% by mass of the total amount of the target film. Furthermore, in one embodiment of the present invention, the content of the organic solvent in the target film may be 25.0000 mass% or more but less than 97.0000 mass% relative to 100% by mass of the total amount of the target film. Furthermore, in one embodiment of the present invention, the preferred range of the glass transition temperature of the copolymer contained in the target film is the same as the preferred range of the glass transition temperature of the copolymer contained in the first film described above.

[0163] In the method according to this embodiment, the second step, which is a step of heating at a temperature higher than 130° C. and not higher than 230° C., is carried out subsequent to the first step, which is a step of heating at a temperature in the range of 40° C. to 130° C. In addition, in this embodiment, it is preferable that the first step and the second step are continuous steps.

[0164] In this embodiment, when the first and second steps are continuous, it is possible to subject the film, which has flexibility due to heating in the first step, to the second step, which is preferred. This is preferred because it allows the content of organic solvent in the film to be efficiently reduced. It is also preferred because it allows the total time required for the first and second steps to be reduced. For example, this total time is preferably 2 hours or less, more preferably less than 2 hours, even more preferably 110 minutes or less, even more preferably 100 minutes or less, and even more preferably 90 minutes or less. Furthermore, the total time may be, for example, 2 minutes or more, 5 minutes or more, 10 minutes or more, 20 minutes or more, 30 minutes or more, 50 minutes or more, or 60 minutes or more, as long as the above-described effects are achieved. Furthermore, as described above, these stepwise lower and upper limits can be independently combined. For example, in one embodiment of the present invention, the total time may be 2 minutes to 2 hours, 5 minutes to 2 hours, 10 minutes to 2 hours, 20 minutes to 2 hours, 30 minutes to 2 hours, 50 minutes to 2 hours, or 60 minutes to 2 hours. Furthermore, for example, in one embodiment of the present invention, the total time may be 2 minutes to less than 2 hours, 5 minutes to less than 2 hours, 10 minutes to less than 2 hours, 20 minutes to less than 2 hours, 30 minutes to less than 2 hours, 50 minutes to less than 2 hours, or 60 minutes to less than 2 hours. Furthermore, for example, in one embodiment of the present invention, the total time may be 2 to 110 minutes, 5 to 110 minutes, 10 to 110 minutes, 20 to 110 minutes, 30 to 110 minutes, 50 to 110 minutes, or 60 to 110 minutes. Furthermore, for example, in one embodiment of the present invention, the total time may be 2 to 100 minutes, 5 to 100 minutes, 10 to 100 minutes, 20 to 100 minutes, 30 to 100 minutes, 50 to 100 minutes, or 60 to 100 minutes. Furthermore, for example, in one embodiment of the present invention, the total time may be 2 to 90 minutes, 5 to 90 minutes, 10 to 90 minutes, 20 to 90 minutes, 30 to 90 minutes, 50 to 90 minutes, or 60 to 90 minutes.

[0165] Furthermore, other steps (optional steps) that may be included in the method according to this embodiment are the same as the optional steps described in the first method (film manufacturing method) according to the above-described embodiment, and therefore their description will be omitted. Other effects achieved by the method according to this embodiment are the same as the effects described in the film manufacturing method according to the above-described embodiment, and therefore their description will be omitted.

[0166] [Applications of Film] The film according to the above-described embodiment or the film obtained by the method according to the above-described embodiment can be used in various applications. A preferred application of such a film is a film capacitor.

[0167] Applications other than film capacitors include insulating layers for EL elements, electrostatic induction conversion elements, sensors (e.g., touch sensors, vibration sensors, biosensors, tire sensors (especially sensors installed on the inside surface of tires)), actuators, touch panels, haptic devices, vibration power generation devices (e.g., vibration power generation floors, vibration power generation tires), speakers, microphones, vibration-damping sheets, hollow fiber membranes for water purification, and resist films. An example of a haptic device is a device that has the function of providing tactile feedback to the user.

[0168] [Laminate] The laminate according to this embodiment is a laminate including the film according to the above-described embodiment and a metal layer in contact with the main surface of the film. The laminate according to this embodiment preferably includes the film and a metal layer laminated on the film. Since the laminate according to this embodiment includes a film with an excellent dielectric constant, it exhibits excellent performance, for example, as a film capacitor.

[0169] There are no particular limitations on the metal layer included in the laminate according to this embodiment. Such a metal layer is, for example, a layer made of a conductive metal such as aluminum, zinc, gold, platinum, or copper. The metal layer is preferably a metal foil or a metal coating. The metal layer may include both a metal foil and a metal coating.

[0170] An example of the metal coating is a vapor-deposited metal coating, which is advantageous in that it can reduce the thickness of the metal layer, increase the capacitance relative to the volume of the metal layer, improve the adhesion between the metal layer and the dielectric, and reduce the variation in thickness of the metal layer.

[0171] There is no particular limitation on the thickness of the metal layer. From the viewpoint of achieving both the capacitance and strength of the film capacitor, the thickness of the metal layer is preferably 10 to 200 nm, and more preferably 20 to 100 nm.

[0172] When the metal layer is a vapor-deposited metal coating, the method for forming the coating is not particularly limited, and may be, for example, one selected from vacuum deposition, sputtering, and ion plating. In one embodiment of the present invention, vacuum deposition is preferably used as the method for forming the coating. The vapor-deposited metal coating may be formed on one or both main surfaces of the film.

[0173] Examples of methods for forming the metal layer include a batch method applied to molded products, a semi-continuous method applied to long products, and a continuous (air to air) method, with the mainstream semi-continuous method being preferred. The semi-continuous method can also be used in metal vapor deposition. This method involves depositing metal on a film in a vacuum system, winding up the metal-deposited film, and then returning the vacuum system to an atmospheric system, thereby obtaining the metal-deposited film in a roll. Therefore, a preferred embodiment of the laminate of this embodiment is a roll.

[0174] [Film Capacitor] The film capacitor according to this embodiment is a film capacitor including at least one laminate according to the above-described embodiment.

[0175] In one aspect of the film capacitor according to the present embodiment, the film capacitor includes a plurality of the laminates in order to increase the capacitance. In another aspect of the film capacitor according to the present embodiment, the film capacitor includes at least one laminate in a roll form in order to increase the capacitance.

[0176] The film capacitor according to the present embodiment can be suitably used as an inverter capacitor for controlling a motor included in an electric vehicle, etc. The film capacitor according to the present embodiment can also be suitably used for railway vehicles, wind power generation, solar power generation, industrial use, general home appliances, etc.

[0177] The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples. [Components] The components used in the examples and comparative examples are as follows.

[0178] (Compounds capable of forming structural unit (a)) 1,1-dicyanoethylene: 1,1-dicyanoethylene (purity 99%) produced according to Production Example 1 below.

[0179] (Production Example 1: Production of 1,1-dicyanoethylene) 1,1-dicyanoethylene was produced as follows. 1,1,3,3-tetracyanopropane was synthesized from malononitrile in a yield of 73% by the production method described in J. Am. Chem. Soc. (USA), 1989, Vol. 111, No. 25, pp. 9078-9081. The resulting crystalline 1,1,3,3-tetracyanopropane was mixed with diphosphorus pentoxide and subjected to thermal decomposition at 180°C, yielding a crude product of 1,1-dicyanoethylene (yield: 60%). The crude product was purified by distillation under reduced pressure (480 Pa) to obtain 1,1-dicyanoethylene with a purity of 99%.

[0180] (Compounds capable of forming structural unit (b)) Vinyl acetate: vinyl acetate manufactured by Fujifilm Wako Pure Chemical Industries, Ltd. Vinyl propionate: vinyl propionate manufactured by Fujifilm Wako Pure Chemical Industries, Ltd. Methyl methacrylate: methyl methacrylate manufactured by Fujifilm Wako Pure Chemical Industries, Ltd. Styrene: styrene manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.

[0181] Example 1 1-1. Production of Copolymer A 100 mL four-neck flask equipped with a stirrer, a Dimroth reaction vessel, and a thermometer was charged with 2.0 g (0.026 mol) of 1,1-dicyanoethylene obtained in Production Example 1, 5.5 g (0.064 mol) of vinyl acetate, 25 mL of ethyl acetate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.), 18 mg of 2,2′-azobis(4-methoxy-2,4-dimethylvaleronitrile), and 68 mg of p-toluenesulfonic acid monohydrate (manufactured by Tokyo Chemical Industry Co., Ltd.), and radical polymerization was carried out by heating and stirring under a nitrogen gas stream at 40° C. for 6 hours.

[0182] After the polymerization was completed, the precipitated copolymer was filtered. The precipitate was then washed with ethyl acetate and n-hexane (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) in that order, and then dried under reduced pressure at 40°C for 24 hours. This yielded a copolymer containing structural units derived from 1,1-dicyanoethylene and structural units derived from vinyl acetate (hereinafter also referred to as "copolymer A"). Copolymer A was in powder form.

[0183] As a result of measurements of the obtained copolymer A described below, it was found that the content of the structural unit derived from 1,1-dicyanoethylene (structural unit (a)) to the content of the structural unit derived from vinyl acetate (structural unit (b)) was in a molar ratio of 1:1, the glass transition temperature was 177°C, the weight average molecular weight was 400,000, and the content of the triad structure (U-1): the total content of the triad structures (U-2) and (U-3): the triad structure (U-4) was in a molar ratio of 0:6:94.

[0184] (Content of Structural Units) The content (mol %) of structural units contained in Copolymer A was calculated as follows: １ The value was determined from the results of H-NMR (nuclear magnetic resonance spectroscopy). The nuclear magnetic resonance spectroscopy used was a JNM-ECX400 manufactured by JEOL Ltd.

[0185] １ The following conditions were used for the H-NMR measurement: Measurement solvent: Dimethyl sulfoxide-d6 Sample concentration: 25 mg / mL Measurement temperature: 65° C. Chemical shift value reference: Tetramethylsilane Number of accumulations: 32

[0186] ​From the measurement results (integral values), the content (molar ratio) of each structural unit was calculated as follows. First, the integral value b (peak value: near 5.6 ppm) of the chemical shift of the methine group contained in the structural unit derived from vinyl acetate was set to 1. Next, the ratio of the integral value a (peak value: near 2.6 ppm) of the chemical shift of the methylene group contained in the structural unit derived from 1,1-dicyanoethylene to the integral value b was calculated. In this way, the content of each structural unit was obtained as a molar ratio.

[0187] (Glass Transition Temperature) The glass transition temperature of Copolymer A was determined from the results of DSC (differential scanning calorimetry) measurement as follows: A "DSC25" manufactured by TA Instruments was used as the differential scanning calorimeter.

[0188] The following conditions were used for DSC measurement (heat flow rate DSC): Measurement weight: 5 mg ± 0.5 mg Measurement environment: under nitrogen atmosphere Measurement temperatures: First heating step: -50°C to 210°C (heating rate 20°C / min) First isothermal step: 210°C, 5 minutes First cooling step: 210°C to -50°C (cooling rate 10°C / min) Second isothermal step: -50°C, 1 minute Second heating step: -50°C to 250°C (heating rate 20°C / min)

[0189] From the DSC measurement results, the midpoint of the heat absorption curve obtained in the second heating step (i.e., the midpoint glass transition temperature) was adopted as the glass transition temperature in accordance with JIS K 7121:2012.

[0190] (Weight-Average Molecular Weight Mw) The weight-average molecular weight Mw of copolymer A was calculated in terms of polystyrene from the measurement results of GPC (gel permeation chromatography) as follows: The gel permeation chromatography measurement device used was "HLC (registered trademark)-8320GPC EcoSEC (registered trademark)" manufactured by Tosoh Corporation.

[0191] The following conditions were used for the GPC measurement: Column: Tosoh "TSKgel (registered trademark) GMHXL" (average particle size = 9 μm, column inner diameter = 7.8 mm, column length = 30 cm) Eluent: 0.01 mol / L LiBr in DMF (0.8 mL / min) Column temperature: 40°C Detection method: differential refractive index (RI) Injection volume: 10 μL Collection time: 0.0-20.0 min (collection for 20 minutes from the start of measurement) Sample concentration: 0.5 mg / 1 mL (sample amount / volume of 0.01 mol / L LiBr in DMF)

[0192] (Content of Triad Structure) The contents of the following four types of triad structures in Copolymer A are determined as follows: １３ The content was determined from the results of C-NMR (nuclear magnetic resonance spectroscopy). The nuclear magnetic resonance spectroscopy used was a "JNM-ECX400" manufactured by JEOL Ltd. (Triad structure) Triad structure (U-1): (a)-(a)-(a) Triad structure (U-2): (a)-(a)-(b) Triad structure (U-3): (b)-(a)-(a) Triad structure (U-4): (b)-(a)-(b) The (a) refers to the structural unit (a), and the (b) refers to the structural unit (b).

[0193] １３ The following conditions were used for the C-NMR measurement: Measurement solvent: Dimethyl sulfoxide-d6 Sample concentration: 25 mg / mL Measurement temperature: 65°C Measurement method: Proton decoupling method Pulse width: 45°C Pulse repetition time: 10 seconds Chemical shift value reference: Tetramethylsilane Number of accumulations: 14,000

[0194] From the measurement results (integral values), Riichiro Chujo et al. 13 The content (molar ratio) of each triad structure was calculated according to the analytical method described in "C NMR Analysis of Microstructure in the Highly Piezoelectric Copolymer Vinylidene Cyanide-Vinyl Acetate," Macromolecules, (USA), October 1, 1985, Vol. 18, No. 10, pp. 1850-1855.​

[0195] <1-2. Provision of a film having a low dielectric loss tangent> (1-2-1. First film) A first film formed from a coating liquid containing the copolymer A and an organic solvent was obtained as follows: A solution casting method was employed to obtain the first film.

[0196] First, 4.0 g of copolymer A was dissolved in 29 g of N,N-dimethylacetamide (Tokyo Chemical Industry Co., Ltd., first-class reagent, boiling point 165°C), which is an organic solvent, to prepare a coating liquid (concentration: 12% by mass). It was confirmed that copolymer A was completely dissolved in the organic solvent.

[0197] Next, using a film applicator (manufactured by Tester Sangyo Co., Ltd.), the coating liquid was applied to a 500 μm thick corona-treated PP sheet (manufactured by Sanvic, product name: PP Gloss / CP) as a substrate so that the coating film formed would be 24 cm square and 225 μm thick. The formed coating film was air-dried at 24°C for 3 minutes. This yielded a laminate B consisting of the substrate and the coating film formed on the substrate. The coating film was in the form of a film (this coating film will also be referred to as the "first film").

[0198] The content of the organic solvent in the first film was measured as follows and found to be 70.0000% by mass. Note that, because the first film could not be peeled from the substrate, it was not possible to evaluate the electrical properties, mechanical properties, and insulating properties described below.

[0199] (Analysis of Organic Solvent Content) (Preparation of Film to be Measured) The film to be measured was stored for 1 hour under conditions of a temperature of 24° C. and a humidity of 40%.

[0200] (Preparation of Measurement Sample Solution) First, mesitylene (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was dissolved as an internal standard substance in N-methylpyrrolidone (manufactured by Tokyo Chemical Industry Co., Ltd.) to obtain a standard solvent.

[0201] Next, the film to be measured was dissolved in the reference solvent at room temperature (20° C.±15° C.), thereby obtaining a measurement sample solution.

[0202] (Measurement) Then, the measurement sample solution was subjected to gas chromatography (GC measurement). The gas chromatography device used was a Shimadzu GC-2014.

[0203] The following GC measurement conditions were used: Column: InertCap (registered trademark) for Amines 2 m Temperature conditions: First temperature rise: 60 to 120°C (heating rate: 20°C / min) Second temperature rise: 120 to 200°C (heating rate: 10°C / min) Third temperature rise: 200 to 260°C (heating rate: 50°C / min) Calibration curves for mesitylene and various organic solvents such as N,N-dimethylacetamide were prepared in advance. The content of organic solvent in the film to be measured was calculated from the peak area of ​​the organic solvent obtained for the measurement sample solution / the peak area of ​​mesitylene. The organic solvent was identified in advance by GC measurement of only that organic solvent and the retention time at which the strongest peak was detected. The water peak was excluded from the measurement results. In this example, it was clear that only N,N-dimethylacetamide was used as the organic solvent, so the content of the organic solvent in the film to be measured was calculated from the peak area of ​​N,N-dimethylacetamide / peak area of ​​mesitylene obtained for the measurement sample solution. However, in Example 15, only N,N-dimethylformamide was used as the organic solvent instead of N,N-dimethylacetamide, so the content of the organic solvent in the film to be measured was calculated from the peak area of ​​N,N-dimethylformamide / peak area of ​​mesitylene obtained for the measurement sample solution.

[0204] (1-2-2. First Heat Treatment) Next, the laminate B including the first film was placed in an oven. A "Clean Oven DE-41" (manufactured by Yamato Scientific Co., Ltd.) was used as the oven. The first heat treatment was carried out by heating the laminate B in the oven at a first temperature of 80°C and -100 kPa (gauge pressure) for a first time of 25 minutes. This resulted in a laminate C including a second film. Subsequently, the laminate C was removed from the oven. Thereafter, the second film was peeled off from the laminate C. The thickness of the second film was measured and found to be 16 μm.

[0205] (1-2-3. Second Heat Treatment) A metal frame (with an inner periphery of 23 cm square and an outer periphery of 25 cm square) was prepared by punching out a 25 cm square metal plate. The second film was then attached to the metal frame using polyimide tape so that the four sides of the second film were located between the inner and outer peripheries of the metal frame.

[0206] Next, the second film was subjected to a second heat treatment by heating it in an oven at a second temperature of 180°C and a pressure of -100 kPa (gauge pressure) for a second time of 60 minutes, thereby obtaining a third film attached to a metal frame.

[0207] Next, the third film attached to the metal frame was removed from the oven. The third film was then removed from the metal frame by cutting it out along the inner periphery of the metal frame with a cutter. In this way, a 23 cm square third film was obtained. The thickness of the third film was measured and found to be 16 μm.

[0208] (1-2-4. Evaluation) The content of organic solvent in the third film was measured, and the electrical properties, mechanical properties, and insulating properties were evaluated as follows. From the evaluation results, it was confirmed that a film with a low dielectric loss tangent can be provided, that is, the content of organic solvent in the first film can be reduced, and that a film with a low dielectric loss tangent can be produced.

[0209] [Evaluation Method] <Measurement of Organic Solvent Content> The organic solvent content of the third film was measured in the same manner as for the first film. The results are shown in Table 1.

[0210] <Evaluation of Electrical Properties: Measurement of Relative Dielectric Constant and Dielectric Loss Tangent> First, the film to be evaluated was conditioned at 26°C and 60% RH (vapor deposition pretreatment conditions). Then, a metal layer made of an Au—Pd alloy and having a diameter of 30 mm was vapor-deposited on one main surface of the film to be evaluated to a thickness that ensured surface conductivity (vapor deposition conditions). Next, similar vapor deposition was performed on the other main surface of the film to be evaluated (vapor deposition conditions). This produced a film capacitor sample including the film to be evaluated and metal layers (conductive layers) formed on both main surfaces of the film to be evaluated.

[0211] The electrical properties of the sample were evaluated. Specifically, the relative permittivity and dielectric loss tangent of the sample were measured at 24°C and 1 kHz using a measuring device. The measuring device used was an LCR meter "E4980A" manufactured by Keysight Corporation. The measurement results are shown in Table 1.

[0212] (Measurement Method) Specifically, the relative dielectric constant and dielectric loss tangent of the sample were measured under the following conditions. [Measurement conditions for relative dielectric constant and dielectric loss tangent] Measurement method: electrostatic capacitance method Measurement environment: 24°C and 1 kHz Method of calculating relative dielectric constant: The relative dielectric constant ε (24°C and 1 kHz) was calculated using the following formula: C = ε × ε ０ × S / d(ε ０ is the dielectric constant of a vacuum), C: capacitance of the sample ε ０ : Dielectric constant of vacuum (= 8.85 × 10 －１４ (F / cm)) S: electrode area d: thickness of film to be evaluated Dielectric loss tangent: The value displayed on an LCR meter was read.

[0213] <Mechanical Property Evaluation: Tensile Modulus Measurement> First, a rectangular test piece measuring 80 mm in length and 10 mm in width was cut out from the film to be evaluated. Next, a 50 μm thick polyimide tape was attached to both ends of the test piece in the longitudinal direction, folded in half. This provided gripping portions of the polyimide tape at both ends of the test piece. Thereafter, the tensile properties of the film to be evaluated were evaluated by pulling the polyimide tape portion using a tensile tester manufactured by Shimadzu Corporation (Shimadzu Precision Universal Testing Machine "Autograph (registered trademark) AG-X").

[0214] Specifically, a tensile test was performed on a test piece of the film to be evaluated under the following measurement conditions: test temperature 23° C., chuck distance 50 mm, and tensile speed 100 mm / min, to measure the tensile modulus. The measurement results are shown in Table 1.

[0215] <Evaluation of Insulation Properties: Measurement of Dielectric Breakdown and Calculation of Stored Energy> The insulation properties of the films to be evaluated were evaluated as follows. Specifically, a dielectric breakdown test was conducted under the following measurement conditions to measure the breakdown voltage (kV / mm) and calculate the stored energy. For the dielectric breakdown test, a direct current dielectric breakdown tester "YST-243-D30MP" manufactured by Yamayo Test Instruments Co., Ltd. was used. The measurement results are shown in Table 1.

[0216] The following conditions were used as measurement conditions for the dielectric breakdown test. Test method standard: JIS C 2151:2019 Measurement environment: 24°C, in air, 30% RH Upper electrode: 25 mm diameter cylindrical electrode Lower electrode: 75 mm diameter cylindrical electrode Voltage rise rate: 0.5 kV / sec Breakdown detection current: 2 mA

[0217] In addition, the breakdown voltage (kV / mm) obtained as a result of the above measurement was used to calculate the stored energy E (J / cm) based on the following formula: ３ The calculation results are shown in Table 1. E = ε × ε ０ × (V × 10000) ２ / 2 E: Storage energy (J / cm ３ ) ε: relative permittivity ε ０ : Dielectric constant of vacuum (= 8.85 × 10 －１４ (F / cm)) V: Breakdown voltage (kV / mm)

[0218] [Examples 2 to 7] Second and third films were produced under the same conditions as in Example 1, except that the conditions for the first heat treatment and the second heat treatment (first temperature, first time, second temperature, second time) for the first film obtained in Example 1 were changed as shown in Table 1. The produced third films were subjected to the same evaluations as in Example 1. The evaluation results are shown in Table 1.

[0219] [Example 8] A stretched film was produced as follows using the third film obtained in Example 1. The produced stretched film was subjected to the same evaluations as in Example 1. The evaluation results are shown in Table 1.

[0220] (Preparation of Stretched Film) In preparing a stretched film, first, the third film obtained in Example 1 was cut into a 21 cm square. This gave a film before stretching (unstretched film). The unstretched film was then stretched using a batch-type stretching device "SDR-563K" (manufactured by Ever Sokki Co., Ltd.) at a stretching temperature of 185°C, a stretching speed of 450% / min, and a stretch ratio of 1.4 times longitudinally and 1.4 times transversely. This gave a stretched film. The obtained stretched film had a size of 29 cm square and a thickness of 8 μm.

[0221] [Example 9] A second film and a third film were produced under the same conditions as in Example 1, except that the thickness of the first film was changed to 500 μm so that the thickness of the third film was 36 μm. The produced third film was subjected to the same evaluation as in Example 1. The evaluation results are shown in Table 2.

[0222] [Example 10] A second film and a third film were produced under the same conditions as in Example 1, except that the conditions of the first heat treatment (first temperature, first time) for the first film obtained in Example 1 were changed as shown in Table 2. The produced third film was subjected to the same evaluation as in Example 1. The evaluation results are shown in Table 2.

[0223] [Example 11] A second film and a third film were produced using the first film obtained in Example 1 under the same conditions as in Example 1, except that the conditions for the first heat treatment (first temperature, first time) were changed as shown in Table 1. The surface of the third film in Example 11 was slightly rough when the second film was removed from the oven, and voids occurred within the film. However, since it was determined to be in a state that could be evaluated, it was subjected to the same evaluation as in Example 1. The reason for the slightly rough surface of the second film in Example 11 and the occurrence of voids within the film was thought to be that the first temperature conditions in the first heat treatment were somewhat harsh, which allowed the organic solvent in the first film to evaporate easily. The evaluation results are shown in Table 2.

[0224] Example 12 A 100 mL four-neck flask equipped with a stirrer, a Dimroth reaction vessel, and a thermometer was charged with 2.0 g (0.026 mol) of 1,1-dicyanoethylene obtained in Production Example 1, 6.4 g (0.064 mol) of vinyl propionate, 25 mL of ethyl acetate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.), 18 mg of 2,2′-azobis(4-methoxy-2,4-dimethylvaleronitrile), and 34 mg of p-toluenesulfonic acid monohydrate (manufactured by Tokyo Chemical Industry Co., Ltd.), and the mixture was heated and stirred at 40° C. for 6 hours under a nitrogen gas stream to carry out radical polymerization.

[0225] After the polymerization was completed, the precipitated copolymer was filtered. The precipitate was then washed with ethyl acetate and n-hexane (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) in that order, and then dried overnight at 40°C under reduced pressure. This yielded a copolymer containing structural units derived from 1,1-dicyanoethylene and structural units derived from vinyl propionate (hereinafter also referred to as "copolymer B"). Copolymer B was in powder form.

[0226] As a result of measurements of the obtained copolymer B in the same manner as in Example 1, it was found that the content of the structural unit derived from 1,1-dicyanoethylene (structural unit (a)) to the content of the structural unit derived from vinyl propionate (structural unit (b)) was in a molar ratio of 1:1, the glass transition temperature was 173°C, the weight average molecular weight was 660,000, and the content of triad structure (U-1):the total content of triad structures (U-2) and (U-3):the triad structure (U-4) was in a molar ratio of 0:4:96.

[0227] Using the copolymer B, a second film and a third film were produced under the same conditions as in Example 1. The produced third film was subjected to the same evaluation as in Example 1. The produced third film was subjected to the same evaluation as in Example 1. The evaluation results are shown in Table 2.

[0228] [Example 13] A second film and a third film were produced using the copolymer B under the same conditions as in Example 12, except that the conditions of the first heat treatment (first temperature, first time) were changed as shown in Table 2. The produced third film was subjected to the same evaluation as in Example 1. The evaluation results are shown in Table 2.

[0229] Example 14 Into a 100 mL four-neck flask equipped with a stirrer, a Dimroth tube, and a thermometer, 2.0 g (0.026 mol) of 1,1-dicyanoethylene obtained in Production Example 1, 6.4 g (0.064 mol) of methyl methacrylate, 25 mL of toluene (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.), 18 mg of 2,2′-azobis(4-methoxy-2,4-dimethylvaleronitrile), and 34 mg of p-toluenesulfonic acid monohydrate (manufactured by Tokyo Chemical Industry Co., Ltd.) were placed, and radical polymerization was carried out by heating and stirring under a nitrogen gas stream at 40° C. for 6 hours.

[0230] After the polymerization was completed, the precipitated copolymer was filtered. The precipitate was then washed with toluene and n-hexane (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) in that order, and then dried overnight at 80°C under reduced pressure. This yielded a copolymer containing structural units derived from 1,1-dicyanoethylene and structural units derived from methyl methacrylate (hereinafter also referred to as "copolymer C"). Copolymer C was in powder form.

[0231] The copolymer C thus obtained was measured in the same manner as in Example 1, and the glass transition temperature was found to be 148° C. and the weight average molecular weight was 390,000.

[0232] A second film and a third film were produced under the same conditions as in Example 1, except that Copolymer C was used. The produced third film was subjected to the same evaluations as in Example 1. The evaluation results are shown in Table 2.

[0233] Example 15 A 100 mL four-neck flask equipped with a stirrer, a Dimroth reaction vessel, and a thermometer was charged with 2.0 g (0.026 mol) of 1,1-dicyanoethylene obtained in Production Example 1, 2.7 g (0.026 mol) of styrene, 17 mL of toluene (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.), 18 mg of 2,2′-azobis(4-methoxy-2,4-dimethylvaleronitrile), and 34 mg of p-toluenesulfonic acid monohydrate (manufactured by Tokyo Chemical Industry Co., Ltd.), and the mixture was heated and stirred at 40° C. for 4 hours under a nitrogen gas stream to carry out radical polymerization.

[0234] After the polymerization was completed, the precipitated copolymer was filtered. The precipitate was then washed with toluene and n-hexane (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) in that order, and then dried overnight at 80°C under reduced pressure. This yielded a copolymer containing structural units derived from 1,1-dicyanoethylene and structural units derived from styrene (hereinafter also referred to as "copolymer D"). Copolymer D was in powder form.

[0235] As a result of measurements on the obtained copolymer D in the same manner as in Example 1, it was found that the content of the structural unit derived from 1,1-dicyanoethylene (structural unit (a)) to the content of the structural unit derived from styrene (structural unit (b)) was in a molar ratio of 1:1, the glass transition temperature was 171°C, the weight average molecular weight was 320,000, and the content of the triad structure (U-1):the total content of the triad structures (U-2) and (U-3):the triad structure (U-4) was in a molar ratio of 2:4:94.

[0236] A second film and a third film were produced under the same conditions as in Example 1, except that copolymer D was used and N,N-dimethylformamide (manufactured by Tokyo Chemical Industry Co., Ltd., purity >99.5% (GC), boiling point 153°C) was used as the solvent. The produced third film was subjected to the same evaluations as in Example 1. The evaluation results are shown in Table 2.

[0237] (Preparation of Roll Body) Using the stretched film prepared in Example 8, a roll-shaped laminate (film capacitor) was produced as follows.

[0238] First, a metal layer made of aluminum was vapor-deposited on one main surface of the prepared stretched film to a size of 29 cm square and a thickness of 30 nm. Similarly, a metal layer made of aluminum was vapor-deposited on the other main surface of the stretched film. This resulted in a laminate including the stretched film and metal layers (conductive layers) formed on both main surfaces of the stretched film. The resulting laminate was wound up to obtain a rolled laminate. It was thus confirmed that a film capacitor could be produced using the rolled laminate.

[0239] [Comparative Example 1] The second film obtained in Example 1 was subjected to the same evaluation as in Example 1. That is, in Comparative Example 1, the second heat treatment of Example 1 was not carried out. The evaluation results are shown in Table 3.

[0240] Comparative Example 2 A second film was produced under the same conditions as in Example 1, except that the conditions for the first heat treatment (first temperature, first time) for the first film obtained in Example 1 were changed as shown in Table 2 and the second heat treatment was not performed. The produced second film was subjected to the same evaluations as in Example 1. The evaluation results are shown in Table 3.

[0241] Comparative Example 3 Laminate B was obtained under the same conditions as in Example 1, except that the substrate was changed from a 500 μm thick corona-treated PP sheet to a 100 μm thick non-corona-treated polyethylene terephthalate film ("Lumirror (registered trademark)" manufactured by Toray Industries, Inc.) and the thickness of the coating film was changed to 28 μm.

[0242] Then, for laminate B, the conditions of the first heat treatment (first temperature, first time) were changed as shown in Table 2, and a second film was produced under the same conditions as in Example 1, except that the second heat treatment was not performed.

[0243] The prepared second film was subjected to the same evaluation as in Example 1. However, the surface of the second film according to Comparative Example 3 was so rough that it was not possible to evaluate the dielectric properties, mechanical properties, and insulating properties. The reason for the surface of the second film according to Comparative Example 3 being so rough is thought to be that the first temperature conditions in the first heat treatment were so severe that the organic solvent in the first film evaporated significantly. The evaluation results are shown in Table 3.

[0244] Comparative Example 4 A second film and a third film were produced under the same conditions as in Example 1, except that the conditions for the first heat treatment and the second heat treatment (first temperature, first time, second temperature, second time) for the first film obtained in Example 1 were changed as shown in Table 2. The produced third film was subjected to the same evaluation as in Example 1. The evaluation results are shown in Table 3.

[0245]

[0246]

[0247]

[0248] From Tables 1, 2, and 3, it was found that the films according to the examples had an organic solvent content of 4.0000% by mass or less, which was lower than the films according to the comparative examples, and therefore it was possible to provide a film with a low dielectric dissipation factor, specifically, a film with a dielectric dissipation factor of 0.070 or less at 24°C and 1 kHz. Furthermore, it was also found that the ability to provide a film with a low dielectric dissipation factor makes it possible to provide a laminate and a film capacitor including the film. Furthermore, it was found that in order to provide a film with a low dielectric dissipation factor, it is necessary to manufacture the film so that the organic solvent content is 4.0000% by mass or less, or to reduce the organic solvent content to 4.0000% by mass or less by performing a heat treatment.

[0249] Furthermore, since the films according to the examples had sufficiently high relative dielectric constant values, it was presumed that the properties of the structural unit (a) derived from 1,1-dicyanoethylene were maintained without being impaired.

[0250] Furthermore, since the tensile modulus values ​​of the films according to the Examples were higher than those of the films according to Comparative Examples 1, 2, and 4, it was presumed that the properties, particularly the mechanical properties, of the copolymer containing the structural unit (a) derived from 1,1-dicyanoethylene and the structural unit (b) derived from a specific polymerizable monomer were maintained without being impaired.

[0251] Furthermore, since the breakdown voltage and stored energy values ​​of the films according to the examples were higher than those of the films according to the comparative examples 1, 2, and 4, it was estimated that the insulating properties were not impaired by reducing the content of organic solvent.

[0252] Furthermore, it was found that the film according to Comparative Example 3 could not provide a good film because the first temperature in the first heat treatment was too high, or because the second temperature (higher than the first temperature) in the second heat treatment was adopted without performing the first heat treatment. Therefore, it was found that in order to provide a good film, it is necessary to adopt a relatively low first temperature in the first heat treatment and a relatively high second temperature in the second heat treatment.

Claims

1. A film comprising a copolymer containing a structural unit (a) derived from 1,1-dicyanoethylene and a structural unit (b) derived from at least one compound represented by the following general formula (I), wherein the content of an organic solvent is 4.0000% by mass or less relative to 100% by mass of the total amount of the film: CH ２ =CR １ R ２ (I) [In general formula (I), R １ is one selected from the group consisting of a hydrogen atom, an alkyl group, a cycloalkyl group, an aryl group, an alkoxy group, a nitrile group, and a halogen atom; R ２ represents a hydrogen atom, an alkyl group, an alkoxy group, a carboxy group, -COOR ３ (R ３ is an alkyl group having 1 to 12 carbon atoms, a cycloalkyl group having 5 to 12 carbon atoms, or an aryl group having 6 to 12 carbon atoms. ４ (R ４ is an alkyl group having 1 to 12 carbon atoms, a cycloalkyl group having 5 to 12 carbon atoms, or an aryl group having 6 to 12 carbon atoms; ５ (R ５ is an alkyl group having 1 to 12 carbon atoms, a cycloalkyl group having 5 to 12 carbon atoms, or an aryl group having 6 to 12 carbon atoms. It is one selected from the group consisting of an acyloxy group and a cyanoalkyl group represented by the following formula:

2. The film according to claim 1, wherein the compound represented by general formula (I) is at least one selected from the group consisting of vinyl esters, (meth)acrylic acid esters, styrene, styrene derivatives, isobutylene, and propylene.

3. The film according to claim 1, having a dielectric loss tangent of 0.070 or less at 24°C and 1 kHz.

4. The stored energy is 2.00 J / cm ３ The film according to claim 1 .

5. The film of claim 1, having a thickness of 50.0 μm or less.

6. The thickness is 50.0 μm or less and the stored energy is 2.00 J / cm ３ The film according to claim 1 .

7. The film of claim 1, having a tensile modulus of 3.2 GPa or greater.

8. The film according to claim 1, having a breakdown voltage of 300 kV / mm or more.

9. The film according to claim 1, which is a stretched film having an organic solvent content of 3.0000% by mass or less based on 100% by mass of the total amount of the film.

10. A laminate comprising the film of claim 1 and a metal layer in contact with a major surface of the film.

11. The laminate of claim 10 in the form of a roll.

12. A film capacitor comprising at least one laminate according to claim 10.

13. A compound having a structural unit (a) derived from 1,1-dicyanoethylene and at least one structural unit represented by the following general formula (I): CH ２ =CR １ R ２ (I) [In general formula (I), R １ is one selected from the group consisting of a hydrogen atom, an alkyl group, a cycloalkyl group, an aryl group, an alkoxy group, a nitrile group, and a halogen atom; R ２ represents a hydrogen atom, an alkyl group, an alkoxy group, a carboxy group, -COOR ３ (R ３ is an alkyl group having 1 to 12 carbon atoms, a cycloalkyl group having 5 to 12 carbon atoms, or an aryl group having 6 to 12 carbon atoms. ４ (R ４ is an alkyl group having 1 to 12 carbon atoms, a cycloalkyl group having 5 to 12 carbon atoms, or an aryl group having 6 to 12 carbon atoms; ５ (R ５ is an alkyl group having 1 to 12 carbon atoms, a cycloalkyl group having 5 to 12 carbon atoms, or an aryl group having 6 to 12 carbon atoms. is one selected from the group consisting of an acyloxy group and a cyanoalkyl group represented by the formula (I). A method for producing a film comprising a copolymer containing a structural unit (b) derived from a compound represented by the formula (I), the method comprising: a first heating step of heating a first film formed from a coating liquid containing the copolymer and an organic solvent at a first temperature that satisfies the conditions of being lower than the boiling point of the organic solvent and lower than a temperature 30°C lower than the glass transition temperature of the copolymer to obtain a second film; and a second heating step of heating the second film at a second temperature that satisfies the conditions of being at least 30°C lower than the glass transition temperature of the copolymer to obtain a third film.

14. A compound having a structural unit (a) derived from 1,1-dicyanoethylene and at least one structural unit represented by the following general formula (I): CH ２ =CR １ R ２ (I) [In general formula (I), R １ is one selected from the group consisting of a hydrogen atom, an alkyl group, a cycloalkyl group, an aryl group, an alkoxy group, a nitrile group, and a halogen atom; R ２ represents a hydrogen atom, an alkyl group, an alkoxy group, a carboxy group, -COOR ３ (R ３ is an alkyl group having 1 to 12 carbon atoms, a cycloalkyl group having 5 to 12 carbon atoms, or an aryl group having 6 to 12 carbon atoms. ４ (R ４ is an alkyl group having 1 to 12 carbon atoms, a cycloalkyl group having 5 to 12 carbon atoms, or an aryl group having 6 to 12 carbon atoms; ５ (R ５ is one selected from the group consisting of an alkyl group having 1 to 12 carbon atoms, a cycloalkyl group having 5 to 12 carbon atoms, or an aryl group having 6 to 12 carbon atoms. ) and a cyanoalkyl group.] A method for reducing the content of an organic solvent in a film containing a copolymer containing a structural unit (b) derived from a compound represented by the following formula:

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