Film suitable for capacitor applications

Abstract

To provide a film which enables manufacture of a capacitor excellent in security function operability, and has dielectric breakdown strength under high temperature and good element winding suitability.SOLUTION: A film contains a syndiotactic polystyrene-based resin and a polyphenylene ether-based resin, where a percentage content of the syndiotactic polystyrene-based resin in the film is 50 mass% or more, a percentage content of the polyphenylene ether-based resin in the film is 10 mass% or more, and a projection crest height Spk on at least one surface is 0.05 μm or more and 0.30 μm or less.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a film, etc., and particularly to a film suitable for use in a capacitor. [Background technology]

[0002] Capacitors using resin films have conventionally been used in electronic devices, electrical devices, etc., as, for example, high-voltage capacitors, filter capacitors and smoothing capacitors for various switching power supplies, converters, inverters, etc. Resin film capacitors are also used in inverters and converters that control drive motors for electric vehicles, hybrid vehicles, etc., for which demand has been increasing in recent years.

[0003] Capacitors, particularly automotive capacitors, are increasingly being used in high-temperature environments. For example, in devices (inverters, converters, etc.) that control automobile drive motors, the use of highly heat-resistant semiconductors (silicon carbide semiconductors, etc.) has recently increased, and as a result, capacitors used in these devices are also required to have higher heat resistance. For this reason, resin films containing syndiotactic polystyrene are being used as one type of resin film with high heat resistance (Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2011-111592 Summary of the Invention [Problem to be solved by the invention]

[0005] In light of the increasing need for long-term reliability, the present inventors have focused on the importance of the safety function operability of capacitor elements.

[0006] In capacitor elements, a margin where no metal is deposited is typically created by pattern deposition, dividing the element into small electrode groups. By incorporating a fuse, if a breakdown occurs within one of the small electrode groups, current concentrates in the fuse, scattering the metal film. As a result, the broken electrode is cut off, restoring the insulation of the entire element. Therefore, scattering the metal film with the fuse is important for the safety function. As the voltage increases, the small electrode groups break down, but if the safety function is activated, the insulation of the entire element is maintained. On the other hand, if the safety function is not activated, the entire element will short out, resulting in the loss of capacitor performance. While roughening the surface of capacitor film is considered beneficial from the perspective of safety function operability, simply roughening the film surface typically reduces the dielectric breakdown strength.

[0007] Furthermore, there is a growing need for thinner films, particularly for capacitors used in automobiles (e.g., xEVs), due to demands for miniaturization and higher efficiency. However, thin films have problems such as poor suitability for element winding, such as the tendency for winding misalignment to occur during the element winding process when manufacturing capacitors.

[0008] Patent Document 1 discloses a film containing a syndiotactic polystyrene resin and a polyphenylene ether resin, which have excellent heat resistance, and has high breakdown voltage and suitability for winding elements. However, Patent Document 1 does not mention the operation of safety functions.

[0009] Therefore, the main object of the present invention is to provide a film that can provide a capacitor with excellent safety function operability, has high dielectric breakdown strength at high temperatures, and is suitable for winding elements. [Means for solving the problem]

[0010] In the course of their research, the inventors discovered that by adjusting the resin composition and a specific surface roughness parameter (peak height Spk), it is possible to achieve a certain level or higher in safety function operability, dielectric breakdown strength, and element winding suitability. As a result of further intensive research, the inventors discovered that the above-mentioned problems can be solved by a film containing a syndiotactic polystyrene-based resin and a polyphenylene ether-based resin, wherein the content of the syndiotactic polystyrene-based resin in the film is 50% by mass or more, the content of the polyphenylene ether-based resin in the film is 10% by mass or more, and the peak height Spk on at least one surface is 0.05 μm or more and 0.30 μm or less. Based on this finding, the inventors conducted further research and completed the present invention. Specifically, the present invention encompasses the following aspects.

[0011] Item 1. A film, The film contains a syndiotactic polystyrene-based resin and a polyphenylene ether-based resin, the content of the syndiotactic polystyrene resin in the film is 50% by mass or more, The content of the polyphenylene ether resin in the film is 10% by mass or more, and The protruding peak height Spk on at least one surface is 0.05 μm or more and 0.30 μm or less, film.

[0012] Item 2. The film according to Item 1, wherein the content of the syndiotactic polystyrene resin in the film is 50% by mass or more and 85% by mass or less.

[0013] Item 3. The film according to Item 1 or 2, wherein the content of the polyphenylene ether resin in the film is 10% by mass or more and 45% by mass or less.

[0014] Item 4. The film according to any one of Items 1 to 3, which contains a styrene-based thermoplastic elastomer.

[0015] Item 5. The film according to Item 4, wherein the content of the styrene-based thermoplastic elastomer in the film is 1% by mass or more and 20% by mass or less.

[0016] Item 6. The film according to Item 4 or 5, wherein the styrene-based thermoplastic elastomer is a styrene-ethylene-butylene-styrene block copolymer (SEBS).

[0017] Item 7. The film according to any one of Items 1 to 6, which contains inorganic particles.

[0018] Item 8. The film according to Item 7, wherein the content of the inorganic particles in the film is 0.2% by mass or more and 1.0% by mass or less.

[0019] Item 9. The film according to Item 7 or 8, wherein the inorganic particles have an average particle size of 0.1 μm or more and 0.5 μm or less.

[0020] Item 10. The film according to any one of Items 7 to 9, wherein the inorganic particles are metal oxide particles.

[0021] Item 11. The film according to any one of Items 1 to 10, comprising a film-shaped molded layer of a resin composition containing two or more modified polyphenylene ethers having different melt flow rates.

[0022] Item 12. The film according to any one of Items 1 to 11, wherein the heat shrinkage rate of the film in the film-forming direction is 1% or more and 10% or less.

[0023] Item 13. The film according to any one of Items 1 to 12, which is a biaxially stretched film.

[0024] Item 14. The film according to any one of items 1 to 13, which is a single-layer film.

[0025] Item 15. The film according to any one of items 1 to 14, having a thickness of 10 μm or less.

[0026] Item 16. The film according to any one of Items 1 to 15, which is for use in a capacitor.

[0027] Item 17. A metal layer-integrated film comprising the film according to any one of items 1 to 16 and a metal layer laminated on one or both sides of the film.

[0028] Item 18. A capacitor comprising the film according to any one of items 1 to 16 or the metal layer-integrated film according to item 17. [Effects of the Invention]

[0029] According to the present invention, a capacitor having excellent safety function operability can be obtained, and a film having high dielectric breakdown strength at high temperatures and good suitability for winding elements can be provided. In addition, in a preferred embodiment, the film of the present invention has high film formation stability. DETAILED DESCRIPTION OF THE INVENTION

[0030] In this specification, the expressions "contain" and "comprise" include the concepts of "contain," "comprise," "consist essentially of," and "consist only of."

[0031] When the content of each component in each raw material used is known, the content of each component in the film of the present invention is calculated from the content and the blending ratio of the raw materials. When raw materials whose component content is unknown are used, the content of each component in the raw materials is measured by the method described in "(1-3) Measurement and calculation of the content of each component in biaxially stretched film" in the Examples, and the content of each component in the film of the present invention is calculated from the content and the blending ratio of the raw materials. When the content ratio of the raw materials is unknown, the content of each component in the film of the present invention is calculated by the method described in "(1-3) Measurement and calculation of the content of each component in biaxially stretched film" in the Examples.

[0032] 1. Film In one aspect, the present invention relates to a film (sometimes referred to herein as "the film of the present invention") that contains a syndiotactic polystyrene resin and a polyphenylene ether resin, the content of the syndiotactic polystyrene resin in the film being 50% by mass or more, the content of the polyphenylene ether resin in the film being 10% by mass or more, and the height Spk of a protruding peak on at least one surface being 0.05 μm or more and 0.30 μm or less. This will be explained below.

[0033] The syndiotactic polystyrene resin is not particularly limited as long as it is a polystyrene resin having a syndiotactic structure. The syndiotactic structure means that the stereochemical structure is a syndiotactic structure, that is, that the phenyl groups and substituted phenyl groups, which are side chains, are alternately positioned in opposite directions relative to the main chain formed from carbon-carbon bonds. Tacticity is usually measured by nuclear magnetic resonance spectroscopy ( 13 The amount of the hydroxyl group is determined by C-NMR (C-NMR method) and can be expressed as the proportion of multiple consecutive structural units present, for example, a dyad for two, a triad for three, a pentad for five, etc.

[0034] The syndiotactic polystyrene resin has, for example, a racemic diad syndiotacticity of 75% or more, preferably 85% or more, and also has, for example, a racemic pentad syndiotacticity of 30% or more, preferably 50% or more.

[0035] Specific examples of syndiotactic polystyrene resins include polystyrene, poly(alkylstyrene), poly(halogenated styrene), poly(halogenated alkylstyrene), poly(alkoxystyrene), poly(vinyl benzoate ester), hydrogenated polymers thereof, mixtures thereof, and copolymers containing these as main components.

[0036] Examples of poly(alkylstyrenes) include poly(methylstyrene), poly(ethylstyrene), poly(isopropylstyrene), poly(tertiarybutylstyrene), poly(phenylstyrene), poly(vinylstyrene), poly(vinylnaphthalene), etc. Examples of poly(halogenated styrenes) include poly(chlorostyrene), poly(bromostyrene), poly(fluorostyrene), etc. Examples of poly(halogenated alkylstyrenes) include poly(chloromethylstyrene), etc. Examples of poly(alkoxystyrenes) include poly(methoxystyrene), poly(ethoxystyrene), etc.

[0037] Among these, particularly preferred syndiotactic polystyrene resins include polystyrene, poly(p-methylstyrene), poly(m-methylstyrene), poly(p-tertiarybutylstyrene), poly(p-chlorostyrene), poly(m-chlorostyrene), poly(p-fluorostyrene), hydrogenated polystyrene, and styrene-alkylstyrene copolymers such as a copolymer of styrene and p-methylstyrene.

[0038] The molecular weight of the syndiotactic polystyrene resin is not particularly limited. For example, the mass average molecular weight (weight average molecular weight) is, for example, 10,000 to 3,000,000, preferably 50,000 to 1,000,000, and more preferably 100,000 to 500,000. The mass average molecular weight is a value measured by gel permeation chromatography at 135°C using 1,2,4-trichlorobenzene as a solvent.

[0039] The melting point of the syndiotactic polystyrene resin is not particularly limited and is, for example, 200° C. or higher and 320° C. or lower, preferably 220° C. or higher and 280° C. or lower. The melting point is the melting peak temperature measured in accordance with JIS K7121:2012.

[0040] The syndiotactic polystyrene resin can be obtained as a commercially available product or can be produced by a known method. For example, the syndiotactic polystyrene resin can be obtained as "Zalec" (142ZE, 300ZC, 130ZC, 90ZC) manufactured by Idemitsu Kosan Co., Ltd.

[0041] The syndiotactic polystyrene resins can be used alone or in combination of two or more.

[0042] The content of the syndiotactic polystyrene resin in the film of the present invention is 50% by mass or more. The syndiotactic polystyrene resin is preferably the component with the highest content in the film of the present invention. From the viewpoints of safety function operability, dielectric breakdown strength, element winding suitability, film formation stability, etc., the content of the syndiotactic polystyrene resin in the film of the present invention is preferably 50% by mass or more and 85% by mass or less, more preferably 55% by mass or more and 83% by mass or less, even more preferably 58% by mass or more and 75% by mass or less, and still more preferably 60% by mass or more and 70% by mass or less.

[0043] The polyphenylene ether resin is not particularly limited, and is typically a polymer having a structural unit represented by the following general formula (1): The polyphenylene ether resin may be composed of a single type of repeating structural unit, or may contain two or more types of repeating structural units.

[0044] [ka] [In the formula, R 1 , R 2 , R 3 and R 4 are the same or different and represent a hydrogen atom, a halogen atom, an optionally substituted alkyl group, an optionally substituted alkenyl group, an optionally substituted alkynyl group, an optionally substituted aryl group, an optionally substituted aralkyl group, an optionally substituted alkylaralkyl group, or an optionally substituted alkoxy group.

[0045] The halogen atom is not particularly limited, and examples thereof include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom.

[0046] The alkyl group may be linear, branched, or cyclic (preferably linear or branched, more preferably linear). The number of carbon atoms in the alkyl group (in the case of linear or branched chain) is not particularly limited and is, for example, 1 to 8. The number of carbon atoms is preferably 1 to 4, more preferably 1 to 3, even more preferably 1 to 2, and still more preferably 1. The number of carbon atoms in the alkyl group (in the case of cyclic chain) is not particularly limited and is, for example, 3 to 7, preferably 4 to 6. Specific 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 tert-butyl group, a sec-butyl group, an n-pentyl group, a neopentyl group, an n-hexyl group, a 3-methylpentyl group, an n-heptyl group, and an n-octyl group.

[0047] The alkenyl group may be either linear or branched (preferably linear). The number of carbon atoms in the alkenyl group is not particularly limited and is, for example, 2 to 8. The number of carbon atoms is preferably 2 to 4. Specific examples of the alkenyl group include a vinyl group, an allyl group, a 1-propenyl group, an isopropenyl group, a butenyl group, a pentenyl group, and a hexenyl group.

[0048] The alkynyl group may be either linear or branched (preferably linear). The number of carbon atoms in the alkenyl group is not particularly limited and is, for example, 2 to 8. The number of carbon atoms is preferably 2 to 4. Specific examples of the alkynyl group include an ethynyl group, a propynyl group (e.g., a 1-propynyl group, a 2-propynyl group (propargyl group)), a butynyl group, a pentynyl group, and a hexynyl group.

[0049] The aryl group is not particularly limited, but preferably has 6 to 12 carbon atoms, more preferably 6 to 12, and even more preferably 6 to 8. The aryl group may be either monocyclic or polycyclic (e.g., bicyclic, tricyclic, etc.), but is preferably monocyclic. Specific examples of the aryl group include a phenyl group, naphthyl group, biphenyl group, pentalenyl group, indenyl group, anthranyl group, tetracenyl group, pentacenyl group, pyrenyl group, perylenyl group, fluorenyl group, and phenanthryl group, and a preferred example is a phenyl group.

[0050] The aralkyl group is not particularly limited, and examples thereof include aralkyl groups in which the hydrogen atoms (for example, 1 to 3, preferably 1 hydrogen atom) of the alkyl group are substituted with the aryl group. Specific examples of the aralkyl group include a benzyl group and a phenethyl group.

[0051] The alkylaryl group is not particularly limited, and examples thereof include alkylaryl groups in which the hydrogen atoms (for example, 1 to 3, preferably 1 hydrogen atom) of the aryl group are substituted with the alkyl group described above. Specific examples of the alkylaryl group include a tolyl group and a xylyl group.

[0052] The alkylaralkyl group is not particularly limited, and examples thereof include alkylaralkyl groups in which hydrogen atoms (for example, 1 to 3, preferably 1 hydrogen atom) on the aromatic ring of the above-mentioned aralkyl group are substituted with the above-mentioned alkyl group.

[0053] The alkoxy group is not particularly limited, and examples thereof include linear or branched (preferably linear) alkoxy groups having 1 to 8 carbon atoms, preferably 1 to 4, more preferably 1 to 3, even more preferably 1 to 2, and still more preferably 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 t-butoxy group.

[0054] Examples of the substituents of the alkyl group, alkenyl group, alkynyl group, aryl group, aralkyl group, alkylaryl group, alkylaralkyl group, alkoxy group, etc. include a halogen atom, a hydroxy group, etc. The number of substituents is not particularly limited and is, for example, 0 to 3, preferably 0 to 1, and more preferably 0.

[0055] In one preferred embodiment of the present invention, R 1 , R 2 , R 3 and R 4 are the same or different and each represents a hydrogen atom, a halogen atom, or an optionally substituted alkyl group (preferably an unsubstituted alkyl group). 2 and R 3 is preferably a hydrogen atom, and R 1 and R 4 is preferably a group other than a hydrogen atom.

[0056] Specific examples of polyphenylene ether resins include poly(2,3-dimethyl-6-ethyl-1,4-phenylene ether), poly(2-methyl-6-chloromethyl-1,4-phenylene ether), poly(2-methyl-6-hydroxyethyl-1,4-phenylene ether), poly(2-methyl-6-n-butyl-1,4-phenylene ether), poly(2-ethyl-6-isopropyl-1,4-phenylene ether), Poly(2-ethyl-6-n-propyl-1,4-phenylene ether), Poly(2,3,6-trimethyl-1,4-phenylene ether), Poly(2-(4'-methylphenyl)-1,4-phenylene ether), Poly(2-bromo-6-phenyl-1,4-phenylene ether), Poly(2-methyl-6-phenyl-1,4-phenylene ether), Poly(2-phenyl-1,4-phenylene ether) ether), poly(2-chloro-1,4-phenylene ether), poly(2-methyl-1,4-phenylene ether), poly(2-chloro-6-ethyl-1,4-phenylene ether), poly(2-chloro-6-bromo-1,4-phenylene ether), poly(2,6-di-n-propyl-1,4-phenylene ether), poly(2-methyl-6-isopropyl-1,4-phenylene ether), poly(2-chloro-6- Examples of suitable polyphenylene ethers include homopolymers such as poly(2-methyl-6-ethyl-1,4-phenylene ether), poly(2,6-dibromo-1,4-phenylene ether), poly(2,6-dichloro-1,4-phenylene ether), poly(2,6-diethyl-1,4-phenylene ether), and poly(2,6-dimethyl-1,4-phenylene ether), as well as copolymers thereof. Modified versions of these with modifiers such as maleic anhydride and fumaric acid are also suitable. Furthermore, copolymers obtained by graft copolymerizing or block copolymerizing vinyl aromatic compounds such as styrene with the above polyphenylene ethers can also be used. Among these, poly(2,6-dimethyl-1,4-phenylene ether) is particularly preferred.

[0057] The number average molecular weight of the polyphenylene ether resin is not particularly limited, but from the viewpoint of extrusion moldability and continuous stretchability, it is preferably 10,000 to 100,000, and more preferably 15,000 to 50,000. The number average molecular weight is determined by converting the molecular weight value measured by the GPS method into the value of polystyrene.

[0058] The polyphenylene ether resin can be commercially available or produced by a known method. Suitable polyphenylene ether resins include those manufactured by Mitsubishi Engineering-Plastics Corporation under the trade name Iupiace (registered trademark) series (e.g., Iupiace (registered trademark) PX100L, PX100F) and Asahi Kasei Corporation under the trade name Zylon (registered trademark) series (e.g., Zylon (registered trademark) S201A).

[0059] The polyphenylene ether resins can be used singly or in combination of two or more.

[0060] The content of the polyphenylene ether resin in the film of the present invention is 10% by mass or more, and from the viewpoints of safety function operability, dielectric breakdown strength, element winding suitability, film formation stability, etc., this content is preferably from 10% by mass to 45% by mass, more preferably from 12% by mass to 40% by mass, even more preferably from 14% by mass to 35% by mass, still more preferably from 17% by mass to 30% by mass, and particularly preferably from 17% by mass to 25% by mass.

[0061] The film of the present invention preferably contains a styrene-based thermoplastic elastomer, from the viewpoint that this makes it easy to adjust the protruding peak height Spk within the above range, thereby contributing to the safety function operability, dielectric breakdown strength, element winding suitability, etc.

[0062] The styrene-based thermoplastic elastomer is not particularly limited, and known ones can be used. Addition of a styrene-based thermoplastic elastomer can improve dielectric breakdown strength and fold crack resistance at high temperatures. A styrene-based thermoplastic elastomer typically has a styrene monomer polymer block (Hb) as a hard segment and a conjugated diene compound polymer block or its hydrogenated block (Sb) as a soft segment. The structure of this styrene-based thermoplastic elastomer may be a diblock structure represented by Hb-Sb, a triblock structure represented by Hb-Sb-Hb or Sb-Hb-Sb, a tetrablock structure represented by Hb-Sb-Hb-Sb, or a polyblock structure in which a total of five or more Hb and Sb units are linearly bonded.

[0063] The styrene-based monomer used in the styrene monomer polymer block (Hb) is not particularly limited, and examples thereof include styrene and its derivatives. Specific examples include styrenes such as styrene, α-methylstyrene, 2-methylstyrene, 4-methylstyrene, 4-propylstyrene, 4-t-butylstyrene, 4-cyclohexylstyrene, 4-dodecylstyrene, 2-ethyl-4-benzylstyrene, 4-(phenylbutyl)styrene, 2,4,6-trimethylstyrene, monofluorostyrene, difluorostyrene, monochlorostyrene, dichlorostyrene, methoxystyrene, and t-butoxystyrene; vinyl group-containing aromatic compounds such as vinyl naphthalenes such as 1-vinylnaphthalene and 2-vinylnaphthalene; and vinylene group-containing aromatic compounds such as indene and acenaphthylene. Among these, styrene is preferred. The styrene-based monomer may be used alone or in combination.

[0064] The conjugated diene compound used in the conjugated diene compound polymer block (Sb) is not particularly limited. Examples of such conjugated diene compounds include butadiene, isoprene, 2,3-dimethylbutadiene, pentadiene, and hexadiene. Among these, butadiene is preferred. The conjugated diene compound may be one type or two or more types. Furthermore, other comonomers such as ethylene, propylene, butylene, and styrene can also be copolymerized. The conjugated diene compound polymer block (Sb) may be a partially or completely hydrogenated product.

[0065] Specific examples of styrene-based thermoplastic elastomers include styrene-isoprene diblock copolymer (SI), styrene-butadiene diblock copolymer (SB), styrene-isoprene-styrene triblock copolymer (SIS), styrene-butadiene / isoprene-styrene triblock copolymer (SB / IS), and styrene-butadiene-styrene triblock copolymer (SBS), as well as hydrogenated products thereof. Examples of hydrogenated products include styrene-ethylene-butylene-styrene copolymer (SEBS), styrene-ethylene-propylene-styrene copolymer (SEPS), styrene-ethylene-ethylene-propylene-styrene copolymer (SEEPS), and styrene-butylene-butadiene-styrene copolymer (SBBS). Among these, hydrogenated products are preferred, with SEBS being particularly preferred.

[0066] The content of the styrene monomer polymer block unit (Hb) in the styrene-based thermoplastic elastomer is not particularly limited, but is, for example, 5% by mass or more and 80% by mass or less, preferably 25% by mass or more and 80% by mass or less, more preferably 30% by mass or more and 70% by mass or less, and even more preferably 35% by mass or more and 60% by mass or less.

[0067] The content of the conjugated diene compound polymer block and / or its hydrogenated block (Sb) (preferably ethylene-butylene) in the styrene-based thermoplastic elastomer is not particularly limited, but is, for example, 20% by mass or more and 95% by mass or less, preferably 20% by mass or more and 75% by mass or less, more preferably 30% by mass or more and 70% by mass or less, and even more preferably 40% by mass or more and 65% by mass or less.

[0068] The melt mass flow rate of the styrene-based thermoplastic elastomer is not particularly limited and is, for example, 0.5 to 15 g / 10 min. The melt mass flow rate is preferably 1 to 10 g / 10 min, more preferably 1.5 to 5 g / 10 min, and even more preferably 2 to 4 g / 10 min. The melt mass flow rate is measured in accordance with JIS K 7210:1999 (conditions: 230°C, load 2.16 kg).

[0069] The styrene-based thermoplastic elastomer can be commercially available or can be produced by a known method. Suitable examples of the styrene-based thermoplastic elastomer include the Tuftec (registered trademark) series (e.g., H1517) manufactured by Asahi Kasei Corporation and the Septon (registered trademark) series (e.g., 8000 series) manufactured by Kuraray Co., Ltd.

[0070] The styrene-based thermoplastic elastomers can be used alone or in combination of two or more.

[0071] When the film of the present invention contains a styrene-based thermoplastic elastomer, the content of the styrene-based thermoplastic elastomer is not particularly limited, but it is preferable that the content of the elastomer in the film of the present invention is lower than that of the syndiotactic polystyrene-based resin (preferably lower than that of each of the syndiotactic polystyrene-based resin and the polyphenylene ether-based resin).

[0072] When the film of the present invention contains a styrene-based thermoplastic elastomer, the content of the styrene-based thermoplastic elastomer in the film is, for example, 1% by mass or more and 20% by mass or less, preferably 2% by mass or more and 18% by mass or less, more preferably 3% by mass or more and 15% by mass or less, even more preferably 4% by mass or more and 12% by mass or less, still more preferably 5% by mass or more and 9% by mass or less, and particularly preferably 5% by mass or more and 8% by mass or less.

[0073] It is preferable that the film of the present invention contains inorganic particles, as this makes it easier to adjust the protruding peak height Spk within the above range, and thus contributes to the safety function operability, dielectric breakdown strength, element winding suitability, etc.

[0074] The inorganic particles are not particularly limited, and examples thereof include particles of metal oxides such as titanium oxide, zinc oxide, aluminum oxide, and magnesium oxide; and particles of silicon compounds such as silica and silicone. Other examples of inorganic particles include particles of light calcium carbonate, heavy calcium carbonate, kaolin, calcined kaolin, talc, calcium sulfate, barium sulfate, zinc sulfide, zinc carbonate, satin white, aluminum silicate, diatomaceous earth, calcium silicate, magnesium silicate, alumina, colloidal alumina, boehmite, pseudoboehmite, aluminum hydroxide, magnesium carbonate, magnesium hydroxide, zeolite, and smectite. Examples of inorganic particles include preferably metal oxide particles and silicon compound particles, more preferably metal oxide particles, and even more preferably titanium oxide particles.

[0075] The inorganic particles have an average particle size of, for example, 0.05 μm to 0.7 μm, preferably 0.1 μm to 0.5 μm, more preferably 0.12 μm to 0.4 μm, and even more preferably 0.15 μm to 0.35 μm.

[0076] The average particle size of inorganic particles is a value measured as follows: Powder is scattered on a sample stage so that individual particles do not overlap as much as possible, and at least 100 particles are observed at 10,000 to 30,000 magnifications using an ultra-high resolution field emission scanning electron microscope (FE-SEM, Hitachi High-Technologies S-5200) to obtain images. The longest diameter of each particle is measured from the images using image analysis software, and the measured values ​​are averaged to determine the average particle size.

[0077] When the film of the present invention contains inorganic particles, the content of the inorganic particles in the film is, for example, 0.2% by mass or more and 1.0% by mass or less, preferably 0.25% by mass or more and 0.9% by mass or less, and more preferably 0.3% by mass or more and 0.8% by mass or less.

[0078] The film of the present invention may contain other resins, additives, etc. in addition to the above components.

[0079] The other resin is not particularly limited, but the film of the present invention preferably contains an atactic polystyrene resin as the other resin.

[0080] The atactic polystyrene resin is not particularly limited as long as it is an amorphous resin having a main chain of polystyrene with an atactic structure. As the atactic polystyrene resin, it is preferable that 90% or more, more preferably 95% or more of the structural units constituting the main chain are styrene and / or styrene having a substituent on the aromatic ring.

[0081] The atactic structure means that the phenyl groups or substituted phenyl groups, which are side chains of the main chain formed by carbon-carbon bonds, have a random three-dimensional structure. Tacticity is usually measured by nuclear magnetic resonance spectroscopy using carbon isotopes ( 13The syndiotacticity of atactic polystyrene resins is quantified by C-NMR (C-NMR method) and can be expressed as the proportion of consecutive structural units present, for example, a dyad when two units are present, a triad when three units are present, and a pentad when five units are present. Atactic polystyrene resins are, for example, racemic dyads and have a syndiotacticity of less than 75%, preferably 65% ​​or less. Atactic polystyrene resins are, for example, racemic pentads and have a syndiotacticity of less than 30%, preferably 25% or less.

[0082] Specific examples of atactic polystyrene resins include polystyrene, poly(alkylstyrene), poly(halogenated styrene), poly(halogenated alkylstyrene), poly(alkoxystyrene), and mixtures thereof, as well as copolymers containing these as main components.

[0083] Examples of poly(alkylstyrenes) include poly(methylstyrene), poly(ethylstyrene), poly(isopropylstyrene), poly(tertiarybutylstyrene), poly(phenylstyrene), poly(vinylstyrene), poly(vinylnaphthalene), etc. Examples of poly(halogenated styrenes) include poly(chlorostyrene), poly(bromostyrene), poly(fluorostyrene), etc. Examples of poly(halogenated alkylstyrenes) include poly(chloromethylstyrene), etc. Examples of poly(alkoxystyrenes) include poly(methoxystyrene), poly(ethoxystyrene), etc.

[0084] Among these, particularly preferred atactic polystyrene resins include polystyrene, poly(p-methylstyrene), poly(m-methylstyrene), poly(p-tertiarybutylstyrene), poly(p-chlorostyrene), poly(m-chlorostyrene), poly(p-fluorostyrene), hydrogenated polystyrene, and styrene-alkylstyrene copolymers such as a copolymer of styrene and p-methylstyrene.

[0085] The melt mass flow rate of the atactic polystyrene resin is not particularly limited and is, for example, 0.5 to 20 g / 10 min. The melt mass flow rate is preferably 2 to 15 g / 10 min, more preferably 4 to 12 g / 10 min, and even more preferably 6 to 9 g / 10 min. The melt mass flow rate is measured in accordance with ISO 1133 (conditions: 200°C, load 5 kgf, test piece: pellet).

[0086] Atactic polystyrene resins are commercially available or can be produced by known methods. As commercially available atactic polystyrene resins, resins generally known as general-purpose polystyrene (GPPS) can be suitably used, and are available, for example, as "PSJ-Polystyrene GPPS" (HF77, 679, SGP10, etc.) manufactured by PS Japan Co., Ltd.

[0087] The atactic polystyrene resins can be used alone or in combination of two or more.

[0088] The content of the atactic polystyrene resin is not particularly limited, but it is preferable that the content of the atactic polystyrene resin in the film of the present invention is lower than that of the syndiotactic polystyrene resin (preferably lower than that of each of the syndiotactic polystyrene resin and the polyphenylene ether resin).

[0089] When the film of the present invention contains an atactic polystyrene-based resin, the content of the atactic polystyrene-based resin in the film is, for example, 1% by mass or more and 12% by mass or less, preferably 2% by mass or more and 10% by mass or less, more preferably 3% by mass or more and 8% by mass or less, even more preferably 4% by mass or more and 7% by mass or less, and still more preferably 5% by mass or more and 7% by mass or less.

[0090] When the film of the present invention contains a resin other than the atactic polystyrene-based resin, the content of the resin other than the atactic polystyrene-based resin in the film of the present invention is, for example, 10% by mass or less, 5% by mass or less, 1% by mass or less, 0.5% by mass or less, or 0.1% by mass or less.

[0091] The additives are not particularly limited and include, for example, components that can be incorporated into resin films (particularly resin films for capacitors), specifically, antioxidants, chlorine absorbers, lubricants, plasticizers, flame retardants, colorants, etc. When the film of the present invention contains additives, the content of the additives in the film of the present invention is, for example, 10% by mass or less, 5% by mass or less, 1% by mass or less, 0.5% by mass or less, or 0.1% by mass or less. The film of the present invention can be produced by a method including a step of forming a resin composition (sometimes referred to as the "resin composition of the present invention" in this specification) into a film, the resin composition containing a syndiotactic polystyrene-based resin and a polyphenylene ether-based resin, the content of the syndiotactic polystyrene-based resin in the resin composition being 50% by mass or more, the content of the polyphenylene ether-based resin in the resin composition being 10% by mass or more, and the peak height Spk of at least one surface being 0.05 μm to 0.30 μm. For example, the resin composition of the present invention can be extruded into a film (the film of the present invention obtained in this manner is sometimes referred to as the "unstretched film of the present invention"), and the unstretched film of the present invention can be biaxially stretched (the film of the present invention obtained in this manner is sometimes referred to as the "biaxially stretched film of the present invention") to obtain the film of the present invention.

[0092] The composition of the resin composition of the present invention is the same as that of the film of the present invention.

[0093] The state of the resin composition of the present invention is not particularly limited, and examples of the state of the resin composition of the present invention include a solid state (e.g., an aggregate of resin lumps (the size of which is not particularly limited, and which also includes pellets and powder)) and a liquid state (e.g., a molten mixture of the components).

[0094] The resin composition of the present invention preferably contains a blend resin (including a polymer alloy) obtained by blending some or all of the components in a molten state.

[0095] The resin composition of the present invention preferably contains a modified polyphenylene ether as a blend resin containing a polyphenylene ether-based resin. The modified polyphenylene ether is a resin obtained by melt-kneading (polymer alloying) a polyphenylene ether-based resin with another resin. The modified polyphenylene ether is preferred because of its excellent melt fluidity and extrusion moldability.

[0096] Examples of other resins constituting the modified polyphenylene ether include polystyrene-based resins, styrene-based thermoplastic elastomers, polypropylene-based resins, polyphenylene sulfide-based resins, polyamide-based resins, etc. Among these, polystyrene-based resins (preferably atactic polystyrene-based resins), styrene-based thermoplastic elastomers, etc. are preferred.

[0097] The composition ratio of each resin constituting the modified polyphenylene ether is not particularly limited and can be appropriately adjusted depending on the type of resin. The content of polyphenylene ether-based resin in the modified polyphenylene ether is, for example, 40% by mass or more and 95% by mass or less, preferably 50% by mass or more and 90% by mass or less, more preferably 60% by mass or more and 85% by mass or less, even more preferably 65% ​​by mass or more and 80% by mass or less, and still more preferably 65% ​​by mass or more and 75% by mass or less, and the content of other resins in the modified polyphenylene ether is, for example, 5% by mass or more and 60% by mass or less, preferably 10% by mass or more and 50% by mass or less, more preferably 15% by mass or more and 40% by mass or less, even more preferably 20% by mass or more and 35% by mass or less, and still more preferably 25% by mass or more and 35% by mass or less.

[0098] The melt flow rate of the modified polyphenylene ether is not particularly limited, but from the viewpoint of extrusion moldability and continuous stretchability, it is preferably 1 to 20 g / 10 min, more preferably 1 to 10 g / 10 min, and even more preferably 1 to 8 g / 10 min. The melt flow rate (MFR) is measured in accordance with JIS K 7210, Condition M, using a melt indexer manufactured by Toyo Seiki Co., Ltd. Specifically, a 4 g sample is first inserted into a cylinder heated to a test temperature of 300°C and preheated for 3.5 minutes under a load of 2.16 kg. The weight of the sample extruded through the bottom hole over 30 seconds is then measured, and the MFR (g / 10 min) is calculated. The above measurement is repeated three times, and the average value is used as the measured MFR.

[0099] The modified polyphenylene ether can be obtained as a commercially available product or can be produced by a known method. Suitable commercially available products include, for example, the Iupiace (registered trademark) series (e.g., Iupiace (registered trademark) AH91) manufactured by Mitsubishi Engineering Plastics Corporation, the Zylon (registered trademark) series (e.g., Zylon (registered trademark) 1000H) manufactured by Asahi Kasei Corporation, and the Noryl (registered trademark) series manufactured by SHPP Japan LLC.

[0100] The modified polyphenylene ethers may be used singly or in combination of two or more.

[0101] The content of the modified polyphenylene ether is not particularly limited as long as the final content of each component in the resin composition of the present invention is a predetermined amount. The content of the modified polyphenylene ether in the resin composition of the present invention is, for example, 5% by mass or more and 50% by mass or less, preferably 10% by mass or more and 45% by mass or less, more preferably 15% by mass or more and 40% by mass or less, and even more preferably 20% by mass or more and 40% by mass or less.

[0102] The resin composition of the present invention is preferably a resin composition containing two or more (preferably two) modified polyphenylene ethers (e.g., modified polyphenylene ether A and modified polyphenylene ether B) having different melt flow rates, from the viewpoint that it can easily adjust the protruding peak height Spk within the above range and thereby contribute to the safety function operability, dielectric breakdown strength, element winding suitability, etc. For this reason, the film of the present invention preferably includes a film-shaped molded layer of a resin composition containing two or more modified polyphenylene ethers having different melt flow rates. The film-shaped molded layer preferably constitutes at least one surface of the film of the present invention, i.e., is arranged as the outermost layer.

[0103] The modified polyphenylene ether A preferably contains a polyphenylene ether resin and a polystyrene resin (preferably an atactic polystyrene resin).

[0104] The content of polyphenylene ether resin in the modified polyphenylene ether A is, for example, 40% by mass or more and 95% by mass or less, preferably 50% by mass or more and 90% by mass or less, more preferably 60% by mass or more and 85% by mass or less, even more preferably 65% ​​by mass or more and 80% by mass or less, and still more preferably 65% ​​by mass or more and 75% by mass or less. The content of polystyrene resin (preferably atactic polystyrene resin) in the modified polyphenylene ether A is, for example, 5% by mass or more and 60% by mass or less, preferably 10% by mass or more and 50% by mass or less, more preferably 15% by mass or more and 40% by mass or less, even more preferably 20% by mass or more and 35% by mass or less, and still more preferably 25% by mass or more and 35% by mass or less.

[0105] The melt flow rate of the modified polyphenylene ether A is preferably from 4.5 to 10 g / 10 min, more preferably from 4.8 to 8 g / 10 min, and even more preferably from 5 to 7 g / 10 min.

[0106] The content of the modified polyphenylene ether A is not particularly limited as long as the final content of each component in the resin composition of the present invention is a predetermined amount. The content of the modified polyphenylene ether A in the resin composition of the present invention is, for example, 3% by mass or more and 40% by mass or less, preferably 10% by mass or more and 35% by mass or less, more preferably 10% by mass or more and 30% by mass or less, and even more preferably 15% by mass or more and 25% by mass or less.

[0107] The modified polyphenylene ether B preferably contains a polyphenylene ether resin and a styrene-based thermoplastic elastomer.

[0108] The content of the polyphenylene ether resin in the modified polyphenylene ether B is, for example, 40% by mass or more and 95% by mass or less, preferably 50% by mass or more and 90% by mass or less, more preferably 60% by mass or more and 85% by mass or less, even more preferably 65% ​​by mass or more and 80% by mass or less, and still more preferably 65% ​​by mass or more and 75% by mass or less. The content of the styrene thermoplastic elastomer in the modified polyphenylene ether B is, for example, 5% by mass or more and 60% by mass or less, preferably 10% by mass or more and 50% by mass or less, more preferably 15% by mass or more and 40% by mass or less, even more preferably 20% by mass or more and 35% by mass or less, and still more preferably 25% by mass or more and 35% by mass or less.

[0109] The melt flow rate of the modified polyphenylene ether B is preferably from 1 to 4 g / 10 min, more preferably from 1.2 to 3.5 g / 10 min, even more preferably from 1.2 to 3 g / 10 min, and even more preferably from 1.3 to 2.5 g / 10 min.

[0110] The content of the modified polyphenylene ether B is not particularly limited as long as the final content of each component in the resin composition of the present invention is a predetermined amount. The content of the modified polyphenylene ether B in the resin composition of the present invention is, for example, 2% by mass or more and 40% by mass or less, preferably 5% by mass or more and 30% by mass or less, more preferably 7% by mass or more and 20% by mass or less, and even more preferably 7% by mass or more and 15% by mass or less.

[0111] The resin composition of the present invention may contain a styrene-based thermoplastic elastomer alone, but preferably contains a blend resin (blend resin X) containing a styrene-based thermoplastic elastomer and a syndiotactic polystyrene-based resin as a blend resin containing a styrene-based thermoplastic elastomer (preferably further containing inorganic particles). More specifically, the resin composition of the present invention preferably contains a styrene-based thermoplastic elastomer melted together with a syndiotactic polystyrene-based resin.

[0112] The composition ratio of each resin constituting the blend resin X is not particularly limited and can be adjusted appropriately depending on the type of resin. The content of the syndiotactic polystyrene resin in the blend resin X is preferably 60% by mass or more and 95% by mass or less, and more preferably 70% by mass or more and 90% by mass or less. From the same viewpoint, the content of the styrene thermoplastic elastomer in the blend resin X is preferably 5% by mass or more and 40% by mass or less, and more preferably 10% by mass or more and 30% by mass or less.

[0113] The blend resin X may be used singly or in combination of two or more kinds.

[0114] The content of the blend resin X in the resin composition of the present invention is not particularly limited as long as the final content of each component in the resin composition of the present invention is a predetermined amount. The content of the blend resin X in the resin composition of the present invention is, for example, 1% by mass or more and 30% by mass or less, preferably 5% by mass or more and 25% by mass or less, and more preferably 10% by mass or more and 20% by mass or less.

[0115] The blend resin can be obtained by melt-kneading each component. Melt-kneading can be performed using a single-screw, twin-screw, or multi-screw melt-kneader, among others. Twin-screw melt-kneaders are particularly effective in reducing the breakability of films and are therefore preferred. In the case of twin-screw types, either co-rotating or counter-rotating kneading types can be used, but co-rotating is preferred from the viewpoint of suppressing resin degradation. The screw diameter-to-length ratio (L / D) is preferably 20 or more, more preferably 25 or more, and even more preferably 28 or more. There is no upper limit to L / D, but from the viewpoint of suppressing resin degradation, it is 100 or less, preferably 80 or less.

[0116] The temperature during melt-kneading is preferably 250° C. to 350° C., more preferably 290° C. to 330° C., in order to balance the prevention of resin deterioration and dispersibility. During melt-kneading, it is preferable to purge the kneader with an inert gas such as nitrogen in order to prevent the resin from deteriorating.

[0117] The method for extrusion molding the resin composition of the present invention is not particularly limited, and known extrusion molding methods can be used. For example, a method can be used in which the solid resin composition of the present invention is supplied to an extruder, heated to a molten state, filtered through a filter, extruded into a film using a T-die, and solidified by contact with a cooling roll set at a predetermined surface temperature. After being molded into a film, the unstretched film of the present invention can be made into a roll by winding it around a core.

[0118] The resin composition of the present invention is preferably mixed before being melted. The mixing method is not particularly limited, but examples thereof include a method in which a plurality of resin blocks (pellets, etc.) are dry-blended using a mixer or the like.

[0119] The resin composition of the present invention is preferably dried before being melted. The drying conditions are not particularly limited. The drying temperature is not particularly limited, but is, for example, 70 to 150°C, preferably 80 to 130°C. The drying time can be adjusted appropriately depending on the drying temperature, and is, for example, 2 to 50 hours, preferably 3 to 20 hours.

[0120] The resin composition of the present invention is usually melted using an extruder. Examples of extruders include single-screw types, twin-screw types, and multi-screw types with three or more screws. In the case of twin or more screws, the screw rotation type may be, for example, co-rotating or counter-rotating. The melt temperature is preferably 280 to 300°C, preferably 280 to 299°C, more preferably 280 to 297°C, even more preferably 285 to 297°C, still more preferably 290 to 297°C, and particularly preferably 293 to 297°C. To suppress deterioration during kneading and mixing of the resin, it is preferable to purge the kneader with an inert gas such as nitrogen.

[0121] The filtration accuracy of the filter used to filter the resin composition of the present invention in a molten state is not particularly limited, but is, for example, 2 to 20 μm, preferably 3 to 10 μm, and more preferably 3 to 7 μm.

[0122] The temperature during extrusion through a T-die is not particularly limited, but is preferably 280 to 300° C., preferably 280 to 299° C., more preferably 280 to 297° C., even more preferably 285 to 297° C., still more preferably 290 to 297° C., and particularly preferably 293 to 297° C. This allows the resin to be appropriately dispersed, making it easier to adjust the protruding peak height Spk within the above range, which in turn contributes to the safety function operability, dielectric breakdown strength, element winding suitability, etc.

[0123] The method of contacting the film-like material extruded from the T-die with a cooling roll to solidify it is not particularly limited, and examples thereof include air knife, electrostatic pinning, elastic roll nip, metal roll nip, elastic metal roll nip, etc. The surface temperature of the cooling roll is not particularly limited, and is, for example, 70 to 110°C, and preferably 80 to 100°C.

[0124] The thickness of the unstretched film of the present invention is not particularly limited, but is, for example, 10 to 100 μm, and preferably 20 to 60 μm.

[0125] The method for biaxially stretching the unstretched film of the present invention is not particularly limited, and any known biaxial stretching method can be used. For example, there is a method in which the unstretched film of the present invention is heated with a heating roll and stretched in the machine direction (MD), then stretched in the width direction (TD) at a predetermined temperature, subsequently heat-set at a predetermined temperature, relaxed in the width direction, and cooled.

[0126] The temperature of the heating rolls before stretching in the machine direction is not particularly limited, but is, for example, 100 to 160° C., and preferably 115 to 145° C. The stretching ratio in the machine direction is not particularly limited, but is, for example, 1.5 to 4.5 times, and preferably 2.5 to 4 times.

[0127] The temperature during stretching in the width direction is not particularly limited, but is, for example, 120 to 180° C., and preferably 135 to 170° C. The stretching ratio in the width direction is not particularly limited, but is, for example, 2 to 5 times, and preferably 3 to 4.5 times.

[0128] The heat setting temperature is not particularly limited, but is, for example, 200 to 280° C., and preferably 230 to 260° C. The heat setting time is not particularly limited, but is, for example, 5 to 20 seconds.

[0129] The temperature for relaxation (relaxation) in the width direction is not particularly limited, but is, for example, 100 to 160° C., preferably 120 to 140° C. The relaxation (relaxation) rate in the width direction is not particularly limited, but is, for example, 3 to 7%, preferably 4 to 6%.

[0130] The thickness of the film of the present invention is not particularly limited, but is, for example, 30 μm or less, or 20 μm or less. The thinner the thickness, the more preferable it is to reduce the volume of the capacitor and increase the capacitance. From this perspective, the thickness is preferably 10 μm or less, more preferably 9.5 μm or less, even more preferably 8 μm or less, even more preferably 6 μm or less, particularly preferably 5 μm or less, especially more preferably 4 μm or less, and particularly preferably 3 μm or less. Furthermore, from the perspective of further improving the dielectric breakdown strength and slitting processability, and further improving continuous film formation, the thickness is, for example, 1 μm or more, preferably 1.5 μm or more, more preferably 1.8 μm or more, even more preferably 2 μm or more, even more preferably 2.3 μm or more, and particularly preferably 2.5 μm or more. The thickness range of the film of the present invention can be set by arbitrarily combining the above upper and lower limits.

[0131] The thickness of the film of the present invention, such as the unstretched film of the present invention or the biaxially stretched film of the present invention, is measured using an outside micrometer (high-precision digimatic micrometer MDH-25MB manufactured by Mitutoyo Corporation) in accordance with JIS K 7130:1999 Method A.

[0132] The layer structure of the film of the present invention is not particularly limited. The film of the present invention may be a single layer consisting of one layer, or may be a multi-layer structure having the same or different compositions. The film of the present invention is preferably a film consisting of one or more film-shaped layers of the resin composition of the present invention, and more preferably a single-layer film (a film consisting of one film-shaped layer of the resin composition of the present invention).

[0133] The protruding peak height Spk on at least one surface of the film of the present invention is 0.05 μm or more and 0.30 μm or less. From the viewpoints of safety function operability, dielectric breakdown strength, element winding suitability, etc., the protruding peak height Spk is preferably 0.06 μm or more and 0.30 μm or less, more preferably 0.07 μm or more and 0.25 μm or less, even more preferably 0.10 μm or more and 0.23 μm or less, still more preferably 0.11 μm or more and 0.21 μm or less, particularly preferably 0.12 μm or more and 0.20 μm or less, and especially more preferably 0.12 μm or more and 0.18 μm or less.

[0134] The peak height (Spk) is specified in ISO 25278-2 and is measured as follows. A non-contact optical interferometric surface profiler, the VertScan 2.0 (Model: R5500GML) manufactured by Ryoka Systems Co., Ltd., was used. The film was cut into a desired size (approximately 20 cm square) for measurement. After smoothing out any wrinkles, it was placed on the measurement stage using an electrostatic contact plate or similar. Measurements were first performed in WAVE mode using a 530 white filter, a 1x BODY lens barrel, and a 10x objective lens, measuring a field of view (470.92 μm x 353.16 μm). This procedure was repeated for five locations, spaced 1 cm apart in the flow direction, from the center of the chill roll surface in both the flow and cross directions. The resulting data was then subjected to a median filter (3x3) to remove noise, followed by a Gaussian filter with a cutoff value of 30 μm to remove waviness. This allows the condition of the roughened surface to be measured appropriately. Next, an analysis is performed using the "ISO parameters" in the "Bearing" plug-in function of the "VS-Viewer" analysis software for "VertScan2.0," to determine Spk (μm), and calculate the average value of each value obtained at the above 10 locations.

[0135] From the viewpoint of the operability of the safety function, the film of the present invention preferably has a heat shrinkage of 10% or less, measured by the method described in the examples, even when measured in the film-forming direction (machine direction). Setting the heat shrinkage within this range is preferable because when the film is wound into a capacitor and used in a high-temperature environment, deterioration of the safety function operability due to tightening is unlikely to occur. The heat shrinkage is preferably 8% or less, more preferably 7% or less, even more preferably less than 6.5%, and particularly preferably 6% or less. From the viewpoint of suppressing sagging of the film due to heat during vapor deposition, the lower limit is preferably 1% or more, more preferably 2% or more, and even more preferably 3% or more. The heat shrinkage in the direction perpendicular to the film-forming direction (width direction) of the film is preferably 0% or more and 6% or less, and preferably 1% or more and 5% or less.

[0136] The above-mentioned heat shrinkage rate can be achieved by controlling the combination of resins of the present invention and film-forming conditions, particularly the stretching ratio, stretching speed, heating temperature (heat setting, etc.) after stretching, and width relaxation rate.

[0137] The film of the present invention can provide a capacitor with excellent safety function operation. The safety function operation is measured according to the method in the examples described below.

[0138] The number of elements that maintained their element performance up to a capacitance change rate of -90% is preferably 4 or more, more preferably 5 or more, and even more preferably 6 out of 6 elements.

[0139] The potential gradient when the capacitance change rate reaches -20% is preferably 280 V / μm or more, more preferably 290 V / μm or more, even more preferably 300 V / μm or more, still more preferably 310 V / μm or more, particularly preferably 320 V / μm or more, even more preferably 330 V / μm or more, and particularly preferably 340 V / μm or more. The upper limit of the potential frequency is not particularly limited, and is, for example, 400 V / μm, 390 V / μm, 380 V / μm, 370 V / μm, or 360 V / μm.

[0140] The film of the present invention has high dielectric breakdown strength at high temperatures, which is measured according to the method described in the Examples below.

[0141] The dielectric breakdown strength of the film of the present invention in a 120°C environment is preferably 480V DC / μm or more, preferably 490V DC / μm or more, more preferably 500V DC / μm or more, even more preferably 510V DC / μm or more, particularly preferably 520V DC / μm or more.

[0142] The dielectric breakdown strength of the film of the present invention in a 150°C environment is preferably 470V DC / μm or more, preferably 480V DC / μm or more, more preferably 490V DC / μm or more, and even more preferably 500V DC / μm or more, particularly preferably 510V DC / μm or more, and especially preferably 520V DC / μm or more.

[0143] The upper limit of the dielectric breakdown strength at each of the above temperatures is not particularly limited, and may be, for example, 650V. DC / μm, 620V DC / μm, 600V DC / μm, 580V DC / μm, or 560V DC / μm.

[0144] The films of the present invention have a smaller rate of change in dielectric breakdown strength with increasing temperature.

[0145] The ratio of the dielectric breakdown strength in a 150°C environment to the dielectric breakdown strength in a 120°C environment (dielectric breakdown strength in a 150°C environment / dielectric breakdown strength in a 120°C environment) is preferably 0.92 or more, more preferably 0.94 or more, even more preferably 0.95 or more, still more preferably 0.96 or more, particularly preferably 0.97 or more, and particularly preferably 0.98 or more.

[0146] Although both environments are "high temperature" at 120°C and 150°C, the loads related to dielectric breakdown strength are generally significantly different. According to the present invention, even in a high load environment such as 150°C, higher dielectric breakdown strength can be exhibited and / or maintained.

[0147] The upper limit of each of the above ratios is not particularly limited, and is, for example, 1.1, 1.05, or 1.0.

[0148] The film of the present invention has good suitability for winding elements. The suitability for winding elements is measured according to the method described in the Examples below. The ratio of the number of rejected films to the total number of films produced is preferably 80% or more, more preferably 90% or more.

[0149] The use of the film of the present invention is not particularly limited. For example, the film of the present invention can be used as a heat-resistant film by taking advantage of its heat resistance. Furthermore, the film of the present invention (particularly the biaxially stretched film of the present invention) can be suitably used as a film for capacitors, where its properties can be fully utilized. In particular, the film of the present invention (particularly the biaxially stretched film of the present invention) can be extremely suitably used in capacitors that are used in high-temperature environments, are small, and have a high capacity (for example, 5 μF or more, preferably 10 μF or more, and more preferably 20 μF or more).

[0150] 2. Metal layer integrated film In one aspect, the present invention relates to a metal layer-integrated film (sometimes referred to herein as the "metal layer-integrated film of the present invention") having the film of the present invention and a metal layer laminated on one or both sides of the film. This will be described below.

[0151] The film of the present invention can be processed into a capacitor by attaching a metal layer (e.g., an electrode) to one or both sides. The metal layer is not particularly limited as long as the capacitor intended by the present invention can be obtained. However, since capacitors are required to be small and lightweight, it is preferable to form (laminated) a metal layer directly on one or both sides of the film of the present invention to form a metal layer-integrated film.

[0152] Examples of methods for laminating a metal layer on the surface of the film of the present invention include vacuum plating such as metal vapor deposition and sputtering, coating and drying of a metal-containing paste, and pressure bonding of metal foil or metal powder. Among these, vacuum vapor deposition and sputtering are preferred to meet the growing demand for smaller and lighter capacitors, and vacuum vapor deposition is preferred from the standpoints of productivity and economy. Examples of vacuum vapor deposition methods include the crucible method and the wire method, but are not particularly limited as long as the capacitor intended by the present invention can be obtained, and an optimal method can be selected as appropriate.

[0153] The metal used in the metal layer may be, for example, a single metal such as zinc, lead, silver, chromium, aluminum, copper, or nickel, a mixture of two or more of these, or an alloy of these. However, taking into consideration the environment, economy, and capacitor performance, zinc and aluminum are preferred.

[0154] From the viewpoint of the electrical characteristics of the capacitor, the film resistance of the metal layer is preferably about 1 to 100 Ω / □. A higher value within this range is desirable from the viewpoint of self-healing characteristics, and the film resistance is more preferably 5 Ω / □ or more, and even more preferably 10 Ω / □ or more. Furthermore, from the viewpoint of safety as a capacitor, the film resistance is more preferably 50 Ω / □ or less, and even more preferably 30 Ω / □ or less.

[0155] When forming an electrode (metal vapor deposition film) by vacuum deposition, the film resistance can be measured during deposition, for example, by a four-terminal method known to those skilled in the art. The film resistance of the metal vapor deposition film can be adjusted, for example, by adjusting the output of the evaporation source to adjust the evaporation amount.

[0156] When forming a metal vapor deposition film on one side of the film, a certain width from one end of the film is left undeposited to form an insulating margin so that the film will become a capacitor when wound. Furthermore, to strengthen the bond between the metal layer-integrated film and the metallikon electrode, it is preferable to form a heavy edge structure on the end opposite the insulating margin. The film resistance of the heavy edge is usually about 1 to 8 Ω / □, preferably about 1 to 5 Ω / □. The thickness of the metal film of the heavy edge is not particularly limited, but is preferably 1 to 200 nm.

[0157] There are no particular restrictions on the deposition pattern (margin pattern) of the metal deposition film to be formed, but from the viewpoint of improving the characteristics of the capacitor, such as safety, it is preferable to form the fuse as a pattern including a so-called special margin, such as a fishnet pattern or a T-margin pattern. Forming a metal deposition film on at least one side of the film of the present invention in a deposition pattern including a special margin improves the safety of the resulting capacitor and is effective in preventing breakdown and short circuits of the capacitor, and is therefore preferable.

[0158] The margin can be formed by any known method without any limitation, such as a tape method in which masking is performed with tape during vapor deposition, or an oil method in which masking is performed by applying oil.

[0159] A protective layer may be provided on the metal layer-integrated film of the present invention for the purposes of physical protection of the metal vapor deposition film, prevention of moisture absorption, prevention of oxidation, etc. Silicone oil, fluorine oil, etc. can be preferably used as the protective layer.

[0160] The metal layer-integrated film of the present invention can be processed into the capacitor of the present invention described below. The metal layer-integrated film of the present invention can also be used as a barrier film against oxygen and other gases, for example.

[0161] 3. Capacitor In one aspect, the present invention relates to a capacitor (sometimes referred to herein as the "capacitor of the present invention") comprising the film of the present invention or the metal layer-integrated film of the present invention. This will be described below.

[0162] In such capacitors, the film of the present invention can be used as a dielectric film for a capacitor by, for example, (i) using the above-mentioned metal layer-integrated film, or (ii) laminating the film of the present invention having no electrodes with another conductor (for example, metal foil, the film of the present invention having one or both sides metallized, paper having one or both sides metallized, other plastic film, etc.).

[0163] In the process of producing a capacitor, a film is wound. For example, two pairs of metal layer-integrated films of the present invention are overlapped and wound so that the metal films in the metal layer-integrated film of the present invention and the film of the present invention are alternately stacked, and further so that the insulating margins are on opposite sides. In this case, it is preferable to stack the two pairs of metal layer-integrated films of the present invention with a 1 to 2 mm offset. The winding machine used is not particularly limited, and for example, an automatic winding machine 3KAW-N2 manufactured by Kaito Seisakusho Co., Ltd. can be used.

[0164] The film wrapping process is not limited to the above method, and other methods may be used, for example, by alternately laminating and winding a double-sided vapor-deposited film of the present invention (in which case the heavy edges are positioned at the opposite ends of the front and back surfaces) and a non-vapor-deposited film of the present invention (2 to 3 mm narrower than the double-sided vapor-deposited film of the present invention).

[0165] When producing a flat capacitor, after winding, the resulting wound product is usually pressed. Pressing promotes tightening of the capacitor and element formation. From the viewpoint of controlling and stabilizing the interlayer gap, the optimum pressure to be applied varies depending on the thickness of the film of the present invention, but is generally 2 to 20 kg / cm. 2 is.

[0166] Next, metal is sprayed onto both end surfaces of the wound body to provide metallikon electrodes, thereby producing a capacitor.

[0167] The capacitor is further subjected to a predetermined heat treatment. That is, the present invention includes a step of subjecting the capacitor to heat treatment (hereinafter, sometimes referred to as "thermal aging"). The heat treatment temperature is not particularly limited, but is, for example, 80 to 190°C. The method for subjecting the capacitor to heat treatment may be appropriately selected from known methods, including, for example, a method using a thermostatic bath in a vacuum atmosphere or a method using high-frequency induction heating. The heat treatment time is preferably 1 hour or more, more preferably 10 hours or more, from the viewpoint of obtaining mechanical and thermal stability, but more preferably 20 hours or less, from the viewpoint of preventing molding defects such as heat wrinkles and molding.

[0168] The heat treatment provides the effect of thermal aging. Specifically, the gaps between the films constituting the capacitor based on the metal layer integrated film of the present invention are reduced, corona discharge is suppressed, and the internal structure of the metal layer integrated film of the present invention changes, promoting crystallization. As a result, it is believed that the voltage resistance is improved. If the heat treatment temperature is lower than the specified temperature, the above-mentioned effect of thermal aging cannot be fully obtained. On the other hand, if the heat treatment temperature is higher than the specified temperature, the film of the present invention may undergo thermal decomposition, oxidative degradation, etc.

[0169] Lead wires are usually welded to the metallikon electrodes of the heat-aged capacitor. To impart weather resistance, particularly to prevent humidity degradation, the capacitor is preferably encapsulated in a case and potted with epoxy resin.

[0170] The capacitor of the present invention, which uses the film of the present invention, can be suitably used in high-temperature environments, and can be made into a small-sized capacitor with a high capacity (for example, 5 μF or more, preferably 10 μF or more, and more preferably 20 μF or more). Therefore, the capacitor of the present invention can be used as a high-voltage capacitor, a filter capacitor and a smoothing capacitor for various switching power supplies, converters, inverters, etc., which are used in electronic devices and electrical equipment. The capacitor of the present invention can also be suitably used as an inverter capacitor, a converter capacitor, etc., which control the drive motors of electric vehicles and hybrid vehicles, which have seen increasing demand in recent years. [Example]

[0171] The present invention will be described in detail below based on examples, but the present invention is not limited to these examples.

[0172] (1)Measurement method The various measurement methods are as follows.

[0173] (1-1) Measurement of average particle size The average particle size of inorganic particles was measured as follows. The powder was scattered on a sample stage with minimal overlap between individual particles, and at least 100 particles were observed at 10,000 to 30,000 magnifications using an ultra-high resolution field emission scanning electron microscope (FE-SEM, Hitachi High-Technologies S-5200) to obtain images. The longest diameter of each particle was measured using image analysis software, and the measured values ​​were averaged to determine the average particle size.

[0174] (1-2) Melt flow rate measurement The melt flow rate (MFR) of each resin in the form of raw resin pellets was measured using a melt indexer manufactured by Toyo Seiki Co., Ltd. in accordance with JIS K 7210, Condition M. Specifically, a 4-g sample was first inserted into a cylinder heated to a test temperature of 300°C and preheated for 3.5 minutes under a load of 2.16 kg. The sample was then extruded through the bottom hole in 30 seconds, weighed, and the MFR (g / 10 min) was calculated. The above measurement was repeated three times, and the average value was used as the measured MFR.

[0175] (1-3) Measurement and calculation of the content of each component in biaxially stretched film In the examples and comparative examples, the content of each component in the biaxially stretched films was calculated from the content and the blending ratio of the raw materials when the content of the component in each raw material used was known. When a blend resin and / or modified polyphenylene ether with an unknown component content was used as a raw material, the content of each component in the raw material was measured by the following method, and the content was calculated from the content and the blending ratio of the raw materials. When the content of the raw materials was unknown, the content of each component in the biaxially stretched film was measured by the following method.

[0176] The raw material or biaxially stretched film was dissolved in 1,1,2,2-tetrachloroethane-d2 as the measurement sample. 1 H-NMR measurement and 13 C-NMR measurements were performed. 1 H-NMR measurement, and 13 The conditions for C-NMR measurement are shown below.

[0177] 13 In the C-NMR measurement, the components were identified from the measured signals. 1 The integrated intensity ratio (molar ratio) per H atom of each component was determined from the signals measured by H-NMR measurement, and converted into a weight ratio using the formula weight of each component to determine the contents of the polyphenylene ether component, styrene component, and ethylene-butylene component.

[0178] Here, the content of the polyphenylene ether resin in the biaxially stretched film is equal to the content of the polyphenylene ether component determined above.

[0179] [ 1 H-NMR measurement] Measurement equipment: Bruker Biospin AVANCE III-600 with Cryo Probe Measurement frequency: 600MHz Measurement solvent: 1,1,2,2-tetrachloroethane-d2 Measurement temperature: 300K Chemical shift standard: 1,1,2,2-tetrachloroethane-d2( 1 H;6.00ppm) [ 13 C-NMR measurement] Measurement device: Bruker Biospin AVANCE III-600 with Cryo Probe Measurement frequency: 150MHz Measurement solvent: 1,1,2,2-tetrachloroethane-d2 Measurement temperature: 300K Chemical shift standard: 1,1,2,2-tetrachloroethane-d2( 13 C;73.78 ppm).

[0180] (1-4) Measurement of ethylene-butylene content in SEBS The ethylene-butylene content in the SEBS-type hydrogenated styrene-based thermoplastic elastomer, which was the resin used in the examples and comparative examples, was measured as follows. SEBS was dissolved in deuterated chloroform (CDCl3) and used as a measurement sample under the following conditions: 1 H-NMR measurement was performed. The components were identified from the measured signals, and the integrated intensity ratio (molar ratio) per H atom of each component was calculated. This was converted to a weight ratio using the formula weight of each component to determine the ethylene-butylene content.

[0181] [ 1 H-NMR measurement] Measurement device: Bruker Biospin AVANCE III-600 with Cryo Probe Measurement frequency: 600MHz Measurement solvent: CDCl3 Measurement temperature: 300K Chemical shift standard: CDCL3( 1 H;7.25 ppm).

[0182] (2) Preparation of resin composition and film (2-1)Resin used (A) Syndiotactic polystyrene resin (sPS) A1: Xarec (registered trademark) 90ZC manufactured by Idemitsu Kosan Co., Ltd.

[0183] (B) Polyphenylene ether resin (PPE) B1: Iupiace (registered trademark) PX100F manufactured by Mitsubishi Engineering Plastics Corporation B2: Iupiace (registered trademark) PX100L manufactured by Mitsubishi Engineering Plastics Corporation

[0184] (C) SEBS type hydrogenated styrene thermoplastic elastomer C1: Tuftec (registered trademark) H1517 (ethylene-butylene content = 57%) manufactured by Asahi Kasei Corporation

[0185] (D) Atactic polystyrene (aPS) D1: HF77 manufactured by PS Japan Co., Ltd.

[0186] (E) Titanium oxide E1: Ishihara Sangyo Kaisha PT-501R E2: Ishihara Sangyo Kaisha PT-401L E3: Sakai Chemical Industry Co., Ltd. R-38L

[0187] (F) Silica F1: SeaHostar (registered trademark) KE P50 manufactured by Nippon Shokubai Co., Ltd. F2: SeaHostar (registered trademark) KE P30 manufactured by Nippon Shokubai Co., Ltd. F3: Seahoster (registered trademark) KE P100 manufactured by Nippon Shokubai Co., Ltd.

[0188] (G) Spherical silicone G1: Tospearl 120FL (registered trademark) manufactured by Momentive Performance Materials Japan, LLC

[0189] (2-2) Blended resin Modified polyphenylene ether resin 1 (m-PPE1) B1 and D1 were mixed and charged into a twin-screw melt kneader (2D30W2, L / D=30, manufactured by Toyo Seiki Seisakusho Co., Ltd.) together with nitrogen gas. The mixture was melt-kneaded at a cylinder temperature of 320°C and a rotation speed of 100 rpm, and extruded through a strand die. The strand was water-cooled and cut into pellets to obtain m-PPE1. The MFR at 300°C and a load of 2.16 kg was 5.7 g / 10 min.

[0190] Modified polyphenylene ether resin 2 (m-PPE2) B2 and C1 were mixed and charged into a twin-screw melt kneader (2D30W2, L / D=30, manufactured by Toyo Seiki Seisakusho Co., Ltd.) together with nitrogen gas. The mixture was melt-kneaded at a cylinder temperature of 320°C and a rotation speed of 100 rpm, and extruded through a strand die. The strand was water-cooled and cut into pellets to obtain m-PPE2. The MFR at 300°C and a load of 2.16 kg was 1.8 g / 10 min.

[0191] Modified polyphenylene ether resin 3 (m-PPE3) B2 and D1 were mixed and charged into a twin-screw melt kneader (Toyo Seiki Seisakusho, Ltd., 2D30W2, L / D=30) together with nitrogen gas. The mixture was melt-kneaded at a cylinder temperature of 320°C and a rotation speed of 100 rpm, and extruded through a strand die. The strand was water-cooled and cut into pellets to obtain m-PPE3. The MFR at 300°C and a load of 2.16 kg was 3.1 g / 10 min.

[0192] Particle-containing blend resin 1 (X1) A1, C1, and E1 were mixed at appropriately varied ratios to obtain multiple mixtures with different component ratios. Each mixture was fed into a twin-screw melt mixer (Toyo Seiki Seisakusho Co., Ltd., 2D30W2, L / D=30) together with nitrogen gas. The mixture was melt-mixed at a cylinder temperature of 300°C and a rotation speed of 100 rpm, and extruded through a strand die. The strand was water-cooled and then cut into pellets to obtain X1.

[0193] Particle-containing blend resin 2 (X2) A1, C1, and E2 were mixed and charged into a twin-screw melt kneader (2D30W2, L / D=30, manufactured by Toyo Seiki Seisakusho Co., Ltd.) together with nitrogen gas. The mixture was melt-kneaded at a cylinder temperature of 300°C and a rotation speed of 100 rpm, and extruded through a strand die. The strand was water-cooled and then cut into pellets to obtain X2.

[0194] Particle-containing blend resin 3 (X3) A1, C1, and E3 were mixed and charged into a twin-screw melt kneader (2D30W2, L / D=30, manufactured by Toyo Seiki Seisakusho Co., Ltd.) together with nitrogen gas. The mixture was melt-kneaded at a cylinder temperature of 300°C and a rotation speed of 100 rpm, and then extruded through a strand die. The strand was water-cooled and then cut into pellets to obtain X3.

[0195] Particle-containing blend resin 4 (X4) A1, C1, and F1 were mixed and charged into a twin-screw melt kneader (2D30W2, L / D=30, manufactured by Toyo Seiki Seisakusho Co., Ltd.) together with nitrogen gas. The mixture was melt-kneaded at a cylinder temperature of 300°C and a rotation speed of 100 rpm, and then extruded through a strand die. The strand was water-cooled and then cut into pellets to obtain X4.

[0196] Particle-containing blend resin 5 (X5) A1, C1, and F3 were mixed and charged into a twin-screw melt kneader (Toyo Seiki Seisakusho Co., Ltd., 2D30W2, L / D=30) together with nitrogen gas. The mixture was melt-kneaded at a cylinder temperature of 300°C and a rotation speed of 100 rpm, and extruded through a strand die. The strand was water-cooled and then cut into pellets to obtain X5.

[0197] Particle-containing blend resin 6 (X6) A1, B2, and G1 were mixed and charged into a twin-screw melt mixer (Toyo Seiki Seisakusho Co., Ltd., 2D30W2, L / D=30) together with nitrogen gas. The mixture was melt mixed at a cylinder temperature of 300°C and a rotation speed of 100 rpm, and extruded through a strand die. The strand was water-cooled and then cut into pellets to obtain X6.

[0198] Particle-containing blend resin 7 (X7) A1 and F2 were mixed and charged into a twin-screw melt kneader (Toyo Seiki Seisakusho Co., Ltd., 2D30W2, L / D=30) together with nitrogen gas. The mixture was melt-kneaded at a cylinder temperature of 300°C and a rotation speed of 100 rpm, and extruded through a strand die. The strand was water-cooled and then cut into pellets to obtain X7.

[0199] (2-3) Resin composition and film production method [Example 1] [Preparation of unstretched sheet] A1, m-PPE1, m-PPE2, and X1 were mixed to the content ratios shown in Table 2 to obtain a resin composition, which was then placed in a pellet dryer and dried at 120°C for 5 hours. The dried raw materials were then placed in a single-screw film-forming machine (GM-50, manufactured by GM Engineering Co., Ltd.) along with nitrogen gas. After melting at a cylinder temperature of 290°C, the mixture was filtered through a filter with a filtration accuracy of 5 μm, adjusted to 290°C, and extruded through a T-die at 290°C. The molten resin was solidified by contact with a mirror-finished metal roll (cooling roll) with a surface temperature of 90°C using an electrostatic adhesion method, and then molded into a film to obtain an unstretched film. The thickness of the unstretched film was approximately 35 μm, but the extrusion rate and take-up speed were adjusted to achieve the target thickness after stretching.

[0200] [Preparation of stretched film] The unstretched film was introduced into a roll-type longitudinal stretching machine, heated with rolls at 130°C, and stretched 3.2 times in the machine direction (MD). It was then introduced into a tenter and stretched 3.6 times in the transverse direction (TD) in an oven with a stretching zone temperature of 150°C. It was then heat-set in an oven at 240°C and relaxed 5% in the transverse direction in an oven at 130°C. The end of the film emerging from the tenter was slit and wound up to obtain a biaxially stretched film roll. The extrusion rate and take-up speed were finely adjusted to achieve a film thickness of 2.9 μm.

[0201] [Example 2] An unstretched film and a biaxially stretched film having a thickness of 2.9 μm were obtained in the same manner as in Example 1, except that a resin composition obtained by mixing A1, m-PPE1, m-PPE2, and X1 so that each component had a content as shown in Table 2 was used, and the film-forming conditions were set to those shown in Table 1.

[0202] [Example 3] An unstretched film and a biaxially stretched film having a thickness of 2.9 μm were obtained in the same manner as in Example 1, except that a resin composition obtained by mixing A1, m-PPE1, m-PPE2, and X1 so that each component had a content as shown in Table 2 was used, and the film-forming conditions were set to those shown in Table 1.

[0203] [Example 4] An unstretched film and a biaxially stretched film having a thickness of 2.9 μm were obtained in the same manner as in Example 1, except that a resin composition obtained by mixing A1, m-PPE1, m-PPE2, and X1 so that each component had a content as shown in Table 2 was used, and the film-forming conditions were set to those shown in Table 1.

[0204] [Example 5] An unstretched film and a biaxially stretched film having a thickness of 2.9 μm were obtained in the same manner as in Example 1, except that a resin composition obtained by mixing A1, m-PPE1, m-PPE2, and X1 so that each component had a content as shown in Table 2 was used, and the film-forming conditions were set to those shown in Table 1.

[0205] [Example 6] An unstretched film and a biaxially stretched film having a thickness of 2.9 μm were obtained in the same manner as in Example 1, except that a resin composition obtained by mixing A1, m-PPE1, m-PPE2, and X1 so that each component had a content as shown in Table 2 was used, and the film-forming conditions were set to those shown in Table 1.

[0206] [Example 7] An unstretched film and a biaxially stretched film having a thickness of 2.9 μm were obtained in the same manner as in Example 1, except that a resin composition obtained by mixing A1, m-PPE1, m-PPE2, and X2 so that each component had a content as shown in Table 2 was used, and the film-forming conditions were set to those shown in Table 1.

[0207] [Example 8] An unstretched film and a biaxially stretched film having a thickness of 2.9 μm were obtained in the same manner as in Example 1, except that a resin composition obtained by mixing A1, m-PPE1, m-PPE2, and X3 so that each component had a content as shown in Table 2 was used, and the film-forming conditions were set to those shown in Table 1.

[0208] [Example 9] An unstretched film and a biaxially stretched film having a thickness of 2.9 μm were obtained in the same manner as in Example 1, except that a resin composition obtained by mixing A1, m-PPE1, m-PPE2, and X4 so that each component had a content as shown in Table 2 was used, and the film-forming conditions were set to those shown in Table 1.

[0209] [Example 10] An unstretched film and a biaxially stretched film having a thickness of 2.9 μm were obtained in the same manner as in Example 1, except that a resin composition obtained by mixing A1, m-PPE1, m-PPE2, and X1 so that each component had a content as shown in Table 2 was used, and the film-forming conditions were set to those shown in Table 1.

[0210] [Example 11] An unstretched film and a biaxially stretched film having a thickness of 2.9 μm were obtained in the same manner as in Example 1, except that a resin composition obtained by mixing A1, m-PPE1, m-PPE2, and X1 so that each component had a content as shown in Table 2 was used, and the film-forming conditions were set to those shown in Table 1.

[0211] [Example 12] An unstretched film and a biaxially stretched film having a thickness of 2.9 μm were obtained in the same manner as in Example 1, except that a resin composition obtained by mixing A1, m-PPE2, and X1 so that each component had a content shown in Table 2 was used, and the film-forming conditions were set to those shown in Table 1.

[0212] [Example 13] An unstretched film and a biaxially stretched film having a thickness of 2.9 μm were obtained in the same manner as in Example 1, except that a resin composition obtained by mixing A1, m-PPE1, m-PPE3, and X1 so that each component had a content as shown in Table 2 was used, and the film-forming conditions were set to those shown in Table 1.

[0213] [Example 14] An unstretched film and a biaxially stretched film having a thickness of 2.9 μm were obtained in the same manner as in Example 1, except that a resin composition obtained by mixing A1, m-PPE1, m-PPE3, and X1 so that each component had a content as shown in Table 2 was used, and the film-forming conditions were set to those shown in Table 1.

[0214] [Comparative Example 1] A biaxially stretched film having a thickness of 2.9 μm was obtained in the same manner as in Example 1, except that X6 was used as the resin composition and the film-forming conditions were as shown in Table 1.

[0215] Comparative Example 2 An unstretched film and a biaxially stretched film having a thickness of 2.9 μm were obtained in the same manner as in Example 1, except that X7 was used as the resin composition and the film-forming conditions were as shown in Table 1.

[0216] Comparative Example 3 An unstretched film and a biaxially stretched film having a thickness of 2.9 μm were obtained in the same manner as in Example 1, except that a resin composition obtained by mixing A1, m-PPE1, and C1 so that each component had a content as shown in Table 2 was used, and the film-forming conditions were the conditions in Table 1.

[0217] Comparative Example 4 An unstretched film and a biaxially stretched film having a thickness of 2.9 μm were obtained in the same manner as in Example 1, except that a resin composition obtained by mixing A1, m-PPE1, and X1 so that each component had a content shown in Table 2 was used, and the film-forming conditions were set to those shown in Table 1.

[0218] Comparative Example 5 An unstretched film and a biaxially stretched film having a thickness of 2.9 μm were obtained in the same manner as in Example 1, except that a resin composition obtained by mixing A1, m-PPE1, m-PPE2, and X1 so that each component had a content as shown in Table 2 was used, and the film-forming conditions were set to those shown in Table 1.

[0219] Comparative Example 6 An unstretched film and a biaxially stretched film having a thickness of 2.9 μm were obtained in the same manner as in Example 1, except that a resin composition obtained by mixing A1, m-PPE1, m-PPE2, and X5 so that each component had a content as shown in Table 2 was used, and the film-forming conditions were set to those shown in Table 1.

[0220] Comparative Example 7 An unstretched film and a biaxially stretched film having a thickness of 2.9 μm were obtained in the same manner as in Example 1, except that a resin composition obtained by mixing A1, m-PPE1, m-PPE2, and X1 so that each component had a content as shown in Table 2 was used, and the film-forming conditions were set to those shown in Table 1.

[0221] [Table 1]

[0222] (3) Measurement and evaluation of film formation characteristics and film properties (3-1) Evaluation of film formation stability The film formation stability was evaluated according to the following criteria based on the film length that could be formed without breakage when a biaxially stretched film was formed under the conditions described in each Example or Comparative Example. ◎: The film length is 2000m or more. ◯: The film length is 1000m or more but less than 2000m. △: The film length is 500 m or more and less than 1000 m. ×: The film length is less than 500 m.

[0223] (3-2) Measurement of dielectric breakdown strength at high temperatures The dielectric breakdown strength of the biaxially stretched films of the Examples and Comparative Examples at high temperatures was evaluated as follows. A measuring device conforming to 17.2.2 (Plate Electrode Method) of JIS C2151:2006 was prepared. However, instead of the elastic material described in 17.2.2 of JIS C2151:2006, a conductive rubber (E12S10 manufactured by Seiwa Electric Co., Ltd.) was used as the lower electrode, and aluminum foil was not wrapped around it. The measurement environment was a forced circulation oven set at a temperature of 120°C or 150°C, and the electrodes and films were used after 30 minutes of temperature adjustment in the oven. The voltage was increased from 0 V at a rate of 100 V / sec, and breakdown was considered to have occurred when the current value exceeded 5 mA. The dielectric breakdown voltage measurement was performed 20 times, and the dielectric breakdown voltage value V DC Divide by the film thickness (μm), and the top two and bottom two points are excluded from the 20 calculation results to obtain the average of 16 points, which is the dielectric breakdown strength (V DC / μm).

[0224] (3-3) Measurement of protruding peak height Spk The protruding peak heights Spk of the biaxially stretched films of the Examples and Comparative Examples were measured as follows.

[0225] The optical interference non-contact surface shape measuring instrument used was the "VertScan2.0 (Model: R5500GML)" manufactured by Ryoka Systems Co., Ltd. As a measurement sample, the film was cut into an arbitrary size of about 20 cm square, and after fully smoothing out any wrinkles, it was set on the measurement stage using an electrostatic contact plate or the like.

[0226] First, measurements were taken in WAVE mode using a 530 white filter, a 1x BODY lens barrel, and a 10x objective lens, measuring one field of view (470.92µm x 353.16µm). This procedure was performed at five locations, 1cm apart in the flow direction, from the center in both the flow and width directions on the chill roll side of the sample surface.

[0227] Next, the obtained data was subjected to noise removal processing using a median filter (3 × 3), and then subjected to Gaussian filtering processing with a cutoff value of 30 μm to remove waviness components, thereby enabling the state of the roughened surface to be properly measured.

[0228] Next, analysis was performed using the "ISO parameters" in the "Bearing" plug-in function of the "VS-Viewer" analysis software for "VertScan2.0," to determine Spk (μm), and the average value of each value obtained at the above 10 locations was calculated.

[0229] (3-4) Measurement of heat shrinkage rate A 10 cm long gauge line was marked on a strip of film (2 cm x 15 cm with the long side in the measurement direction). The strip of film was hung in a hot air oven at 200°C for 10 minutes, then removed from the oven and allowed to cool to room temperature (23°C). The gauge line length after treatment was measured, and the thermal shrinkage rate (longitudinal and transverse directions) of the film was determined. Three sheets were measured per measurement, and the shrinkage rates calculated using the following formula were averaged to calculate the shrinkage rate: (Gauge line length after treatment - Gauge line length before treatment) / Gauge line length before treatment (unit: %).

[0230] (4) Measurement and evaluation of capacitor characteristics (4-1) Making a capacitor Capacitors were fabricated using the biaxially stretched films of the examples and comparative examples as follows. A special vapor deposition pattern margin and an insulating margin were formed on the biaxially stretched film to provide film capacitor safety. Aluminum vapor deposition was then applied to the biaxially stretched film to achieve a surface resistivity of 20 Ω / □, resulting in a metal layer-integrated film. The metal layer-integrated film was then slit into a 30 mm width. Two sheets of the metal layer-integrated film were combined and wound using a Kaito Seisakusho automatic winding machine, Model 3KAW-N2-60 / 83, with the number of turns set to achieve a capacitance of 10 μF. The wound element was then flattened by pressing. While the pressing load was applied, zinc metal was sprayed onto the element end surfaces to form electrode leads, and the element was then heat-cured at 120°C for 15 hours. After heat curing, leads were soldered to the element end surfaces and sealed with epoxy resin to obtain a flat film capacitor.

[0231] (4-2) Evaluation of end face misalignment of capacitor elements The biaxially stretched films of the Examples and Comparative Examples were used to produce metal layer-integrated films in the same manner as in (4-1) above. The resulting metal layer-integrated films were then slit into 30 mm widths. Two sheets of the metal layer-integrated film were then combined and wound using a 3KAW-N2-60 / 83 automatic winding machine manufactured by Kaito Seisakusho. The entire winding process was visually inspected, and any film with edge misalignment was deemed a failure. The percentage of the number of failed films relative to the total number of films produced (30-50) was used as an index of edge misalignment. Evaluation was performed using a "◎" for 90% or more, a "○" for 80% to less than 90%, a "△" for 70% to less than 80%, and an "×" for less than 70%.

[0232] (4-3) Step-up test The capacitor obtained in (4-1) above was preheated at 120°C for 1 hour, and then the capacitance was measured (initial capacitance) using an LCR HiTester 3522-50 manufactured by Hioki E.E. Corporation. Next, a DC voltage of 290 V was applied to the capacitor for 1 hour in a thermostatic chamber at 120°C. The capacitance of the capacitor after voltage application was measured in the same manner, and the rate of change in capacitance before and after the test was calculated using the following formula. (Capacitance change rate) = [(Capacitance after voltage application) - (Initial capacitance)] / (Initial capacitance) x 100 (%)

[0233] The capacitors were then returned to the thermostatic chamber, and the voltage was increased by 50V each time, and the capacitance change rate was measured repeatedly. The test was conducted using six capacitors, and the number of capacitors whose capacitance change rate reached -90% or less was counted. Capacitors that short-circuited before the capacitance change rate reached -90% or less and lost insulation were deemed defective and were not subjected to further testing. A short circuit failure is determined when the capacitor's resistance value falls below 10 kΩ. The measurement device used was a Hioki E.E. Corporation Super Megohmmeter DSM-8104. The upper limit of the current measurement range of this device is 10 mA, and when the current value at an applied voltage of 100 V exceeds the upper limit of the measurement range, the capacitor's resistance value is considered to be 10 kΩ or less.

[0234] (4-4) Measurement of the potential gradient when the capacitance change rate reaches 20% In the step voltage increase test, the voltage at which the capacitance change rate first reaches -20% or less was divided by the film thickness (μm), and the average value of six capacitors was taken as the potential gradient when the capacitance change rate reached -20%. Note that capacitors that short-circuited before the capacitance change rate reached -20% and lost insulation were excluded from the average value.

[0235] (5) Measurement and evaluation results The measurement results of the content of each component and the peak height Spk of the biaxially stretched films of the Examples and Comparative Examples, as well as the measurement results of the average particle size of the blended inorganic particles, are shown in Table 2. Table 3 also shows the evaluation results of the film formation characteristics and film properties of the biaxially stretched films of the Examples and Comparative Examples, as well as the evaluation and measurement results of the capacitor properties of the capacitors obtained using the films.

[0236] [Table 2]

[0237] [Table 3]

[0238] From the above, it was found that a film (Examples 1 to 14) containing a syndiotactic polystyrene resin and a polyphenylene ether resin, in which the content of the syndiotactic polystyrene resin in the film is 50% by mass or more and the content of the polyphenylene ether resin in the film is 10% by mass or more, and in which the height Spk of the protruding peaks on at least one surface is 0.05 μm or more and 0.30 μm or less, can produce a capacitor with excellent safety function operation, and the film has high dielectric breakdown strength at high temperatures and good suitability for element winding.

Claims

1. A film, The film contains a syndiotactic polystyrene-based resin and a polyphenylene ether-based resin, the content of the syndiotactic polystyrene resin in the film is 50% by mass or more, The content of the polyphenylene ether resin in the film is 10% by mass or more, and The height Spk of the protruding peak on at least one surface is 0.05 μm or more and 0.30 μm or less. film.

2. The film according to claim 1 , wherein the content of the syndiotactic polystyrene resin in the film is 50% by mass or more and 85% by mass or less.

3. The film according to claim 1 or 2, wherein the content of the polyphenylene ether resin in the film is 10% by mass or more and 45% by mass or less.

4. The film according to any one of claims 1 to 3, which contains a styrene-based thermoplastic elastomer.

5. The film according to claim 4 , wherein the content of the styrene-based thermoplastic elastomer in the film is 1% by mass or more and 20% by mass or less.

6. 6. The film according to claim 4, wherein the styrene-based thermoplastic elastomer is a styrene-ethylene-butylene-styrene block copolymer (SEBS).

7. The film according to any one of claims 1 to 6, which contains inorganic particles.

8. The film according to claim 7 , wherein the content of the inorganic particles in the film is 0.2% by mass or more and 1.0% by mass or less.

9. 9. The film according to claim 7, wherein the inorganic particles have an average particle size of 0.1 μm or more and 0.5 μm or less.

10. The film according to any one of claims 7 to 9, wherein the inorganic particles are metal oxide particles.

11. The film according to any one of claims 1 to 10, comprising a film-shaped molded layer of a resin composition containing two or more modified polyphenylene ethers having different melt flow rates.

12. The film according to any one of claims 1 to 11, wherein the heat shrinkage rate of the film in the film-forming direction is 1% or more and 10% or less.

13. The film according to any one of claims 1 to 12, which is a biaxially stretched film.

14. The film according to any one of claims 1 to 13, which is a monolayer film.

15. The film according to any one of claims 1 to 14, having a thickness of 10 µm or less.

16. The film according to any one of claims 1 to 15, which is for use in a capacitor.

17. A metal layer-integrated film comprising the film according to any one of claims 1 to 16 and a metal layer laminated on one or both sides of the film.

18. A capacitor comprising the film according to any one of claims 1 to 16 or the metal layer-integrated film according to claim 17.

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