Film, metal-laminated film, and capacitor

Abstract

To provide a film that allows production of a capacitor exhibiting superior operability of safety functions and that maintains withstand voltage at high temperatures, thereby yielding a capacitor with high withstand voltage at high temperatures.SOLUTION: A film has at least an A layer, wherein (1) the A layer contains, based on 100 mass%, 55 mass% or more and 97 mass% or less of a polypropylene resin and 3 mass% or more and 45 mass% or less of a polymer having an alicyclic structure in a side chain, and (2) a reduced peak height Spk of at least one surface is 0.02 μm or more and 0.15 μm or less.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a film, a metal laminated film, and 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] 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.

[0008] Furthermore, capacitors are generally required to have high voltage resistance. In particular, capacitors used in high-temperature environments such as those described above are required to have high voltage resistance at room temperature (23°C) and also to have high voltage resistance in high-temperature environments, such as 135°C, with no decrease in voltage resistance.

[0009] In view of the above circumstances, the present invention aims to provide a film that can provide a capacitor with excellent safety function operation, and that suppresses a decrease in voltage resistance at high temperatures, thereby providing a capacitor with high voltage resistance at high temperatures. [Means for solving the problem]

[0010] As a result of extensive research into achieving the above-mentioned object, the inventors have discovered that the above-mentioned object can be achieved by a film that is composed of a specific resin composition and exhibits a specific surface roughness parameter (protruding peak height Spk), and have thus completed the present invention.

[0011] That is, the present invention relates to the following film, metal layer-integrated film, and capacitor. 1. A film having at least layer A, (1) The layer A contains, in 100% by mass, 55% by mass or more and 97% by mass or less of a polypropylene resin and 3% by mass or more and 45% by mass or less of a polymer having an alicyclic structure in a side chain, and (2) the height Spk of the protruding peaks on at least one surface is 0.02 μm or more and 0.15 μm or less. A film characterized by: 2. The film according to item 1, wherein the polymer has a glass transition temperature of 100°C or higher and 180°C or lower. 3. The film according to item 1 or 2, wherein the alicyclic structure has a cyclohexane structure. 4. The film according to any one of items 1 to 3, wherein the polymer is hydrogenated polystyrene, has atactic stereoregularity, and has a hydrogenation rate of aromatic rings of 95 mol % or more. 5. The film according to any one of items 1 to 4, wherein the sum of the protruding peak height Spk and the protruding valley depth Svk on at least one surface of the film is 0.04 μm or more and 0.23 μm or less. 6. The film according to any one of items 1 to 5, wherein the arithmetic mean height Sa of at least one surface of the film is 0.010 μm or more and 0.050 μm or less. 7. The film according to any one of items 1 to 6, wherein the heat shrinkage rate of the film in the machine direction measured at 140° C. is 1.0% or more and 6.0% or less. 8. The film according to any one of items 1 to 7, wherein the thickness of the film is 10 μm or less. 9. The film according to any one of items 1 to 8, wherein the film is a single-layer film. 10. The film according to any one of items 1 to 9, which is a biaxially stretched film. 11. The film according to any one of items 1 to 10, which is for use in a capacitor. 12. A metal laminated film comprising the film according to any one of items 1 to 11 and a metal layer laminated on one or both sides of the film. 13. A capacitor comprising the film according to any one of items 1 to 11. 14. A capacitor comprising the metal laminated film according to item 12. [Effects of the Invention]

[0012] The film of the present invention can provide a capacitor with excellent safety function operation, and also can suppress the decrease in voltage resistance at high temperatures, thereby providing a capacitor with high voltage resistance at high temperatures. DETAILED DESCRIPTION OF THE INVENTION

[0013] The present invention will be described in detail below.

[0014] In the numerical ranges described in stages in this specification, the upper or lower limit of a certain numerical range can be arbitrarily combined with the upper or lower limit of another numerical range. Furthermore, in the numerical ranges described in this specification, the upper or lower limit of the numerical range may be replaced with a value shown in an example or a value that can be unambiguously derived from an example. Furthermore, in this specification, a numerical value connected with "to" means a numerical range that includes the numbers before and after "to" as the upper and lower limits.

[0015] In this specification, the expressions "contain" and "comprise" include the concepts of "contain," "comprise," "consist essentially of," and "consist only of."

[0016] 1. Film The present invention relates to a film having at least Layer A, in which (1) Layer A contains, based on 100 mass%, 55 mass% to 97 mass% of a polypropylene resin and 3 mass% to 45 mass% of a polymer having an alicyclic structure in its side chain, and (2) the height Spk of a protruding peak on at least one surface is 0.02 μm to 0.15 μm (sometimes referred to simply as "film" or "film of the present invention" in this specification).

[0017] In capacitor elements, a margin where no metal is deposited is typically created by pattern deposition, dividing the element into small electrode segments. By incorporating a fuse, if a breakdown occurs within one of the small electrode segments, current will concentrate in the fuse, causing the metal film to scatter. This will separate the broken electrode segment, restoring the insulation of the entire element. Therefore, scattering the metal film with the fuse is crucial for the safety function. Roughening the surface of the capacitor film can facilitate the scattering of the metal film, creating voids within the capacitor. However, simply roughening the film surface typically results in a decrease in dielectric breakdown strength.

[0018] The film of the present invention having the above-mentioned configuration contains, based on 100% by mass of Layer A, 55% to 97% by mass of a polypropylene resin and 3% to 45% by mass of a polymer having an alicyclic structure in its side chain. Therefore, numerous β-crystals are generated on the film surface during film formation, resulting in the formation of fine protrusions due to the β-crystals. In particular, by heating the film surface at a temperature range near the melting point of the β-crystals, approximately 150°C or less, and stretching it in the machine direction (MD), the β-crystals on the film surface are converted to α-crystals, forming recesses. Then, by stretching it in the transverse direction (TD), fine protrusions are easily formed at the edges of the recesses.

[0019] As described above, the film of the present invention has a configuration in which (1) Layer A contains, based on 100% by mass, 55% to 97% by mass of a polypropylene resin and 3% to 45% by mass of a polymer having an alicyclic structure in its side chain, resulting in the formation of numerous β-crystals on the film surface. Therefore, the film of the present invention can also have a configuration in which (2) the peak height Spk on at least one surface is 0.02 μm to 0.15 μm. A film of this configuration has uniform fine protrusions, resulting in a capacitor with excellent safety function operation. Furthermore, because the film of the present invention is formed from the specific resin component described above in (1) and has the specific surface shape described above in (2), the decrease in voltage resistance at high temperatures of capacitors manufactured using the film of the present invention is suppressed, resulting in a capacitor with high voltage resistance at high temperatures.

[0020] This will be explained below.

[0021] 1-1. Polypropylene resin The layer A of the film of the present invention contains 55% by mass or more and 97% by mass or less of a polypropylene resin, with the mass of the layer A being 100% by mass.

[0022] Examples of the polypropylene-based resin include propylene homopolymers such as isotactic polypropylene and syndiotactic polypropylene; copolymers of propylene with other olefins (e.g., ethylene, 1-butene, etc.) (the copolymer may be a random copolymer or a block copolymer having at least two polymer blocks); long-chain branched polypropylene; and polypropylene-based resins produced from plant-derived raw materials.

[0023] When the polypropylene resin is a copolymer of propylene and another olefin, the propylene content in the copolymer is 50% by mass or more, preferably 80% by mass or more, and more preferably 90% by mass or more, where the mass of the polypropylene resin is 100% by mass. Note that the polypropylene resin does not include a polypropylene resin having an alicyclic structure in a side chain.

[0024] The polypropylene resin contained in the layer A may be one type or two or more types.

[0025] The content of the polypropylene-based resin in Layer A may be 55% by mass or more and 97% by mass or less. In this case, the rigidity, electrical insulation, and stretchability of the film of the present invention are improved. The preferred lower limit of the content is, for example, 60% by mass or more, 62% by mass or more, 65% by mass or more, 68% by mass or more, 69% by mass or more, 70% by mass or more, 75% by mass or more, 78% by mass or more, 80% by mass or more, 82% by mass or more, 83% by mass or more, or 84% by mass or more. The preferred upper limit of the content is, for example, 96% by mass or less, 95% by mass or less, 94% by mass or less, 93% by mass or less, 92% by mass or less, 91% by mass or less, 90% by mass or less, less than 90% by mass, 89% by mass or less, 88% by mass or less, 87% by mass or less, 86% by mass or less, or 85% by mass or less. The effect of improving stretchability includes the case where the film of the present invention is a multilayer film having layers other than Layer A (such as a skin layer, which will be described later), in which the entire multilayer film is stretched (the same applies below).

[0026] The melt mass flow rate (MFR) of the polypropylene resin contained in Layer A, measured at 230°C under a weight of 2.16 kg, is preferably 0.5 g / 10 min to 6 g / 10 min, more preferably 1 g / 10 min to 5 g / 10 min, and even more preferably 1.5 g / 10 min to 4 g / 10 min, inclusive. In this case, appropriate resin fluidity is obtained during stretching of the film, improving stretchability.

[0027] The melting point of the polypropylene resin contained in Layer A is preferably 155°C or higher. In this case, electrical insulation and stretchability at high temperatures are improved. The melting point is more preferably 160°C or higher and 180°C or lower, and even more preferably 161°C or higher and 170°C or lower.

[0028] The polypropylene resin contained in Layer A preferably has a mesopentad fraction of 95 mol% or more and 99.9 mol% or less. When the mesopentad fraction is 95 mol% or more, the rigidity and electrical insulation of the stretched film of the present invention are likely to be improved, and when the mesopentad fraction is 99.9 mol% or less, the stretchability is likely to be improved. The mesopentad fraction of the polypropylene resin is more preferably 96 mol% or more and 99.5 mol% or less, even more preferably 97 mol% or more and 99.2 mol% or less, and particularly preferably 98 mol% or more and 99 mol% or less.

[0029] The heptane insoluble content (HI) of the polypropylene resin contained in Layer A is preferably 94% by mass or more and 99.9% by mass or less. When it is 94% by mass or more, the rigidity and electrical insulation of the stretched film tend to be improved, and when it is 99.9% by mass or less, the stretchability tends to be improved. The heptane insoluble content of the polypropylene resin is more preferably 96% by mass or more and 99.5% by mass or less, even more preferably 97% by mass or more and 99.2% by mass or less, and particularly preferably 98% by mass or more and 99% by mass or less.

[0030] The number average molecular weight (Mn) of the polypropylene resin contained in Layer A is preferably from 30,000 to 70,000, and more preferably from 35,000 to 65,000. When Layer A contains a polypropylene resin with such a number average molecular weight (Mn), the rigidity, electrical insulation, and stretchability of the film of the present invention are likely to be improved.

[0031] The weight-average molecular weight (Mw) of the polypropylene resin contained in Layer A is preferably from 250,000 to 500,000, and more preferably from 300,000 to 450,000. When Layer A contains a polypropylene resin with such a weight-average molecular weight (Mw), the rigidity, electrical insulation, and stretchability of the film of the present invention are likely to be improved.

[0032] The polypropylene resin contained in Layer A has a molecular weight distribution (Mw / Mn), calculated as the ratio of weight average molecular weight (Mw) to number average molecular weight (Mn), of preferably 3 to 12, more preferably 5 to 10, and even more preferably 6 to 9.5. When Layer A contains a polypropylene resin with such a molecular weight distribution (Mw / Mn), the rigidity, electrical insulation, and stretchability of the film of the present invention are likely to be improved.

[0033] The z-average molecular weight (Mz) of the polypropylene resin contained in Layer A is preferably from 700,000 to 3,000,000, and more preferably from 1,000,000 to 2,500,000. When Layer A contains a polypropylene resin with such a z-average molecular weight (Mz), the rigidity, electrical insulation, and stretchability of the film of the present invention are likely to be improved.

[0034] The molecular weight distribution (Mz / Mw) of the polypropylene resin contained in Layer A, calculated as the ratio of the z-average molecular weight (Mz) to the weight-average molecular weight (Mw), is preferably from 2 to 7, more preferably from 2.5 to 6, and even more preferably from 3 to 5. When Layer A contains a polypropylene resin with such a molecular weight distribution (Mz / Mw), the rigidity, electrical insulation, and stretchability of the film of the present invention are likely to be improved.

[0035] Polypropylene-based resins can be produced using conventionally known methods. Examples of polymerization methods include gas-phase polymerization, bulk polymerization, and slurry polymerization. Polymerization may be single-stage polymerization using one polymerization reactor or multi-stage polymerization using two or more polymerization reactors. Furthermore, polymerization may be carried out by adding hydrogen or a comonomer to the reactor as a molecular weight modifier. Conventional Ziegler-Natta catalysts or metallocene catalysts can be used as polymerization catalysts, and the polymerization catalyst may contain a cocatalyst component or a donor. The mesopentad fraction, melt mass flow rate, molecular weight, and molecular weight distribution of the polypropylene-based resin can be controlled by appropriately adjusting the polymerization catalyst and other polymerization conditions.

[0036] 1-2. Polymers with alicyclic structures in the side chains Layer A of the film of the present invention contains 3% by mass to 45% by mass of a polymer having an alicyclic structure in a side chain, with the mass of Layer A being 100%. The polymer having an alicyclic structure in a side chain contained in Layer A may be one type, or two or more types.

[0037] The content of the polymer having an alicyclic structure in its side chain in Layer A may be 3% by mass or more and 45% by mass or less. In this case, the rigidity, electrical insulation, and stretchability of the film of the present invention are improved. The preferred lower limit of the content is, for example, 4% by mass or more, 5% by mass or more, 6% by mass or more, 7% by mass or more, 8% by mass or more, 9% by mass or more, 10% by mass or more, more than 10% by mass, 11% by mass, 12% by mass or more, 13% by mass or more, 14% by mass or more, or 15% by mass or more. The preferred upper limit of the content is, for example, 40% by mass or less, 38% by mass or less, 35% by mass or less, 32% by mass or less, 31% by mass or less, 30% by mass or less, 25% by mass or less, 22% by mass or less, 20% by mass or less, 18% by mass or less, 17% by mass or less, or 16% by mass or less.

[0038] Here, the alicyclic structure includes one or more saturated and / or unsaturated carbon ring structures that do not have aromaticity. The number of carbon ring structures may be two or more. The carbon ring structure may have a branched aliphatic hydrocarbon structure. The carbon ring structure is bonded directly or via a hydrocarbon chain to the hydrocarbon chain of the polymer main chain.

[0039] Examples of the carbon ring structure include monocyclic structures such as cycloalkane structures such as cyclopropane, cyclobutane, cyclopentane, cyclohexane, cycloheptane, cyclooctane, cyclononane, cyclodecane, cycloundecane, and cyclododecane, and cycloalkene structures such as cyclopropene, cyclobutene, cyclopropene, cyclohexene, cycloheptene, and cyclooctene. Examples of bicyclic structures include bicyclic alkane structures such as bicycloundecane, and bicyclic alkene structures such as norbornene and norbornadiene, which can be suitably used. Of these, a carbon ring structure having 4 to 8 carbon atoms is preferred from the viewpoint of stretchability, a monocyclic carbon ring structure having 4 to 8 carbon atoms is more preferred, a carbon ring structure that is a monocyclic cycloalkane structure having 4 to 8 carbon atoms is even more preferred, and a cyclohexane structure is particularly preferred.

[0040] The polymer main chain is mainly composed of aliphatic hydrocarbons. The polymer main chain may contain cyclic hydrocarbon structures and / or aromatic hydrocarbon structures as structural units, but preferably does not contain these. The aliphatic hydrocarbons in the polymer main chain may have branches of aliphatic hydrocarbon structures and / or aromatic hydrocarbon structures.

[0041] The polymer having an alicyclic structure in the side chain may be a homopolymer having a structure having an alicyclic structure in the side chain as a structural unit. For example, it may be polyvinylcycloolefin obtained by homopolymerizing vinylcycloolefin. Examples of polyvinylcycloolefin include polyvinylcyclopropane, polyvinylcyclobutane, polyvinylcyclopentane, polyvinylcyclohexane, polyvinylcycloheptane, polyvinylcyclooctane, polyvinylcyclononane, polyvinylcyclodecane, polyvinylcycloundecane, and polyvinylcyclododecane. Homopolymers are preferred because they tend to have high rigidity and electrical insulation properties in high-temperature environments. Among these, polyvinylcyclopentane, polyvinylcyclohexane, and polyvinylcycloheptane are preferred, with polyvinylcyclohexane being most preferred.

[0042] (Method of producing polymer having alicyclic structure in the side chain) The method for producing the polymer having an alicyclic structure in the side chain is not particularly limited, and the polymer can be produced using a known method such as a radical polymerization method, an ionic polymerization method (anionic polymerization method, coordination anionic polymerization method, etc.), or a polymerization method such as bulk polymerization, solution polymerization, or suspension polymerization.

[0043] Specifically, a polymer having an alicyclic structure in a side chain can be produced by carrying out a polymerization reaction using a known initiator such as an alkyllithium compound or a dilithium compound to sequentially polymerize a monomer having an alicyclic structure (e.g., vinylcycloolefin, etc.); or a method in which a monomer having an alicyclic structure is sequentially polymerized and then a coupling agent is added to perform coupling.

[0044] Furthermore, a polymer having an alicyclic structure in a side chain can be produced by polymerizing a monomer having an aromatic ring (e.g., styrene) by a known method, followed by a hydrogenation reaction. The hydrogenation reaction can be carried out, for example, by the method described later in the "Method for producing a hydrogenated block copolymer."

[0045] When produced by hydrogenation reaction, the hydrogenation rate of the aromatic ring is preferably 50 mol% or more, more preferably 80 mol% or more, even more preferably 85 mol% or more, particularly preferably 90 mol% or more, and even more particularly preferably 95 mol% or more. The hydrogenation rate may be 100 mol%. By setting the hydrogenation rate within the above range, stretchability tends to be improved, which is preferable.

[0046] The polymer having an alicyclic structure in the side chain may be a copolymer having a structural unit having an alicyclic structure in the side chain and one or more other structural units. The copolymer may be a random copolymer or a block copolymer having at least two polymer blocks. From the viewpoint of stretchability, copolymers are preferred, and block copolymers are more preferred.

[0047] Examples of other structural units include ethylene, propylene, butene, pentene, hexene, heptene, and octene, and may or may not have a side chain. Furthermore, the polymer may contain both structural units with and without a side chain. Examples of structural units with a side chain include propylene, 1-butene, 1-pentene, 1-hexene, and 4-methyl-1-pentene. The other structural units may be unsaturated hydrocarbons, but saturated hydrocarbons are preferred from the viewpoint of electrical insulation.

[0048] Here, when a polymer having an alicyclic structure in a side chain (hereinafter also referred to as simply "polymer" or "the polymer") contains, for example, propylene as another structural unit, the propylene content in the polymer is less than 50% by mass, preferably 20% by mass or less, more preferably 10% by mass or less, even more preferably 5% by mass or less, and particularly preferably 2% by mass or less, based on 100% by mass of the polymer.

[0049] A polymer having an alicyclic structure in a side chain can be obtained, for example, by polymerizing a monomer having the respective structural units by a known method. Alternatively, the polymer can be obtained by hydrogenating a polymer having an aromatic ring in a side chain. Hydrogenating a polymer having an aromatic ring in a side chain is preferred because it is easy to industrially and inexpensively obtain a polymer having an alicyclic structure in a side chain.

[0050] When a polymer having an aromatic ring in a side chain is hydrogenated, the polymer having an aromatic ring in a side chain may be a homopolymer or a copolymer. In the case of a copolymer, a block copolymer having at least a vinyl aromatic polymer block and a conjugated diene polymer block is preferred. By hydrogenating this, a hydrogenated block copolymer having at least a hydrogenated vinyl aromatic polymer block and a hydrogenated conjugated diene polymer block is obtained.

[0051] Hereinafter, a hydrogenated block copolymer having at least a hydrogenated vinyl aromatic polymer block and a hydrogenated conjugated diene polymer block will be described as one preferred embodiment.

[0052] (hydrogenated vinyl aromatic polymer block) The hydrogenated vinyl aromatic polymer block contains structural units derived from a vinyl aromatic compound and hydrogenated therefrom. The hydrogenated vinyl aromatic polymer block contains structural units derived from a vinyl aromatic compound in an amount of 50% by mass or more, preferably 80% by mass or more, more preferably 90% by mass or more, and particularly preferably 100% by mass. By making the structural units derived from a vinyl aromatic compound 50% by mass or more, rigidity and electrical insulation properties in high-temperature environments are likely to be improved.

[0053] Examples of vinyl aromatic compounds include styrene, α-methylstyrene, 2-methylstyrene, 3-methylstyrene, 4-methylstyrene, 4-propylstyrene, 4-cyclohexylstyrene, 4-dodecylstyrene, 2-ethyl-4-benzylstyrene, 4-(phenylbutyl)styrene, vinyltoluene, 1-vinylnaphthalene, 2-vinylnaphthalene, etc. The vinyl aromatic compound is preferably selected from styrene and α-methylstyrene, more preferably styrene.

[0054] The hydrogenated vinyl aromatic polymer block may be composed of only one type of the above vinyl aromatic compound, or may be composed of two or more types.

[0055] The hydrogenated vinyl aromatic polymer block may contain other structural units besides those derived from vinyl aromatic compounds, such as those derived from isoprene, butadiene, 2,3-dimethylbutadiene, 1,3-pentadiene, and 1,3-hexadiene.

[0056] The content of the hydrogenated vinyl aromatic polymer block is preferably 50% by mass or more but less than 100% by mass, based on 100% by mass of the total of the hydrogenated vinyl aromatic polymer block and the hydrogenated conjugated diene polymer block. By making it 50% by mass or more, rigidity and electrical insulation at high temperatures tend to be improved. It is more preferably 60% by mass or more, even more preferably 70% by mass or more, and particularly preferably 80% by mass or more.

[0057] (Hydrogenated conjugated diene polymer block) The hydrogenated conjugated diene polymer block contains structural units derived from a conjugated diene and hydrogenated from the conjugated diene, and the hydrogenated conjugated diene polymer block contains 50% by mass or more, preferably 80% by mass or more, more preferably 90% by mass or more, and particularly preferably 100% by mass of structural units derived from the conjugated diene.

[0058] Examples of conjugated dienes include butadiene, 2-methyl-1,3-butadiene (isoprene), 2,3-dimethyl-butadiene, 1,3-pentadiene, 1,3-hexadiene, etc. The conjugated diene is preferably selected from butadiene and isoprene, and more preferably butadiene.

[0059] The hydrogenated conjugated diene polymer block may contain a structural unit derived from a conjugated diene having no side chain. Examples of the conjugated diene having no side chain include butadiene, 1,3-pentadiene, and 1,3-hexadiene. The preferred conjugated diene having no side chain is butadiene.

[0060] In the hydrogenated conjugated diene polymer block, the bonding form of the conjugated diene, i.e., the microstructure, is not particularly limited. For example, in the case of butadiene, bonding forms of 1,2-bonds and 1,4-bonds can be used. In addition, in the case of isoprene, bonding forms of 1,2-bonds, 3,4-bonds and 1,4-bonds can be used. Only one type of these bonding forms may be present, or two or more types may be present. When two or more types of bonding forms are present, the ratio of the bonding forms is not particularly limited.

[0061] The hydrogenated conjugated diene polymer block may contain other structural units besides those derived from conjugated dienes, such as structural units derived from styrene, α-methylstyrene, 2-methylstyrene, 3-methylstyrene, 4-methylstyrene, 4-propylstyrene, 4-cyclohexylstyrene, 4-dodecylstyrene, 2-ethyl-4-benzylstyrene, 4-(phenylbutyl)styrene, vinyltoluene, 1-vinylnaphthalene, and 2-vinylnaphthalene.

[0062] The content of the hydrogenated conjugated diene polymer block is preferably more than 0% by mass (e.g., 1% by mass or more) and 50% by mass or less, based on 100% by mass of the total of the hydrogenated vinyl aromatic polymer block and the hydrogenated conjugated diene polymer block. By setting it to 50% by mass or less, rigidity and electrical insulation at high temperatures tend to be improved, which is preferable. It is more preferably 40% by mass or less, even more preferably 30% by mass or less, and particularly preferably 20% by mass or less.

[0063] (hydrogenation rate) In the hydrogenated vinyl aromatic polymer block according to this embodiment, the hydrogenation rate of the aromatic rings of the hydrogenated vinyl aromatic polymer block is preferably 50 mol% or more, more preferably 80 mol% or more, even more preferably 85 mol% or more, particularly preferably 90 mol% or more, and even more particularly preferably 95 mol% or more. The hydrogenation rate may be 100 mol%. The hydrogenation rate of the carbon-carbon double bonds derived from the conjugated diene of the hydrogenated conjugated diene polymer block is preferably 90 mol% or more, more preferably 95 mol% or more. The hydrogenation rate may be 100 mol%.

[0064] By setting the hydrogenation rate of the aromatic ring of the hydrogenated vinyl aromatic polymer block and / or the hydrogenation rate of the carbon-carbon double bond derived from the conjugated diene of the hydrogenated conjugated diene polymer block within the above-mentioned ranges, stretchability tends to be improved, which is preferable.

[0065] (Bonding pattern of hydrogenated block copolymer) The bonding mode of the polymer blocks in the hydrogenated block copolymer may be any of linear, branched and radial, or a combination thereof.

[0066] For example, if the hydrogenated vinyl aromatic polymer block is represented by "X" and the hydrogenated conjugated diene polymer block is represented by "Y", examples of the bonding pattern include a diblock copolymer (XY), a triblock copolymer (XYX), a tetrablock copolymer (XYXY), a pentablock copolymer (XYXYX or YXYXY), etc. From the viewpoint of ease of production, the bonding pattern is preferably a diblock copolymer, a triblock copolymer, or a tetrablock copolymer.

[0067] Specific examples of hydrogenated block copolymers include hydrogenated block copolymers of styrene-isoprene diblock copolymer (SI), styrene-butadiene diblock copolymer (SB), styrene-isoprene-styrene triblock copolymer (SIS), styrene-butadiene / isoprene-styrene triblock copolymer (SB / IS), styrene-butadiene-styrene triblock copolymer (SBS), styrene-ethylene-butylene-styrene copolymer (SEBS), styrene-ethylene-propylene-styrene copolymer (SEPS), styrene-ethylene-ethylene-propylene-styrene copolymer (SEEPS), styrene-butylene-butadiene-styrene copolymer (SBBS), etc. Among these, hydrogenated block copolymers of styrene-butadiene diblock copolymer (SB) are particularly preferred.

[0068] (Method of producing hydrogenated block copolymer) The method for producing the hydrogenated block copolymer is not particularly limited, and known methods such as anionic polymerization can be used.

[0069] Specifically, the hydrogenated block copolymer can be produced by carrying out a polymerization reaction using, for example, a method of sequentially polymerizing a vinyl aromatic compound and a conjugated diene using an alkyllithium compound as an initiator; a method of sequentially polymerizing a vinyl aromatic compound and a conjugated diene using an alkyllithium compound as an initiator, followed by coupling by adding a coupling agent; or a method of sequentially polymerizing a conjugated diene and then a vinyl aromatic compound using a dilithium compound as an initiator, followed by carrying out a hydrogenation reaction.

[0070] Examples of the alkyllithium compound include methyllithium, ethyllithium, n-butyllithium, sec-butyllithium, tert-butyllithium, and pentyllithium.

[0071] Examples of coupling agents include divinylbenzene; polyfunctional epoxy compounds such as epoxidized 1,2-polybutadiene, epoxidized soybean oil, and 1,3-bis(N,N-glycidylaminomethyl)cyclohexane; halogen compounds such as dimethyldichlorosilane, dimethyldibromosilane, trichlorosilane, methyltrichlorosilane, tetrachlorosilane, and tetrachlorotin; ester compounds such as methyl benzoate, ethyl benzoate, phenyl benzoate, diethyl oxalate, diethyl malonate, diethyl adipate, dioctyl adipate, dimethyl phthalate, diethyl phthalate, dimethyl isophthalate, and dimethyl terephthalate; carbonate ester compounds such as dimethyl carbonate, diethyl carbonate, and diphenyl carbonate; and alkoxysilane compounds such as dimethyldimethoxysilane, methyltrimethoxysilane, methyltriethoxysilane, tetramethoxysilane, tetraethoxysilane, bis(trimethoxysilyl)hexane, and bis(triethoxysilyl)ethane.

[0072] Examples of dilithium compounds include naphthalenedilithium and dilithiohexylbenzene.

[0073] The polymerization reaction is preferably carried out in the presence of a solvent. The solvent is not particularly limited as long as it is inert to the initiator and does not adversely affect the reaction, and examples thereof include saturated aliphatic hydrocarbons such as hexane, cyclohexane, heptane, octane, and decane; and aromatic hydrocarbons such as toluene, benzene, and xylene. Furthermore, the temperature of the polymerization reaction is preferably 0 to 100°C, more preferably 30 to 90°C, even more preferably 40 to 80°C, and particularly preferably 50 to 80°C, from the viewpoint of controlling the microstructure. The time of the polymerization reaction is preferably 0.5 to 50 hours, from the viewpoint of controlling the microstructure.

[0074] A Lewis base may also be used as a co-catalyst during the polymerization reaction. Examples of Lewis bases include ethers such as dimethyl ether, diethyl ether, and tetrahydrofuran; glycol ethers such as ethylene glycol dimethyl ether and diethylene glycol dimethyl ether; and amines such as triethylamine, N,N,N',N'-tetramethylethylenediamine, and N-methylmorpholine. These Lewis bases may be used alone or in combination of two or more.

[0075] The hydrogenation reaction may be carried out immediately after the polymerization reaction, or may be carried out after the block copolymer has been isolated after the polymerization reaction.

[0076] When the block copolymer is temporarily isolated after the polymerization reaction, the block copolymer can be isolated by pouring the polymerization reaction solution obtained after the polymerization reaction into a poor solvent for the block copolymer, such as methanol, to solidify the block copolymer, or by pouring the polymerization reaction solution together with steam into hot water to remove the solvent by azeotropy (steam stripping), followed by drying.

[0077] The hydrogenation reaction of the block copolymer can be carried out, for example, in the presence of a hydrogenation catalyst at a reaction temperature of 20 to 200° C. and a hydrogen pressure of 0.1 to 20 MPa for 0.1 to 100 hours.

[0078] Examples of hydrogenation catalysts include Raney nickel; heterogeneous catalysts in which a metal such as platinum (Pt), palladium (Pd), ruthenium (Ru), rhodium (Rh), or nickel (Ni) is supported on a carrier such as carbon, alumina, or diatomaceous earth; Ziegler catalysts consisting of a combination of a transition metal compound (nickel octylate, nickel naphthenate, nickel acetylacetonate, cobalt octylate, cobalt naphthenate, or cobalt acetylacetonate) with an organoaluminum compound such as triethylaluminum or triisobutylaluminum, or an organolithium compound; and metallocene catalysts consisting of a combination of a bis(cyclopentadienyl) compound of a transition metal such as titanium, zirconium, or hafnium with an organometallic compound such as lithium, sodium, potassium, aluminum, zinc, or magnesium.

[0079] When the hydrogenation reaction is carried out subsequent to the polymerization reaction, the hydrogenated block copolymer can be isolated by pouring the hydrogenation reaction solution into a poor solvent for the hydrogenated block copolymer, such as methanol, to coagulate it, or by pouring the hydrogenation reaction solution into hot water together with steam to remove the solvent by azeotropy (steam stripping), followed by drying.

[0080] The polymer having an alicyclic structure in the side chain contained in layer A is preferably hydrogenated polystyrene, has atactic stereoregularity, and has a hydrogenation rate of the aromatic ring of 95 mol% or more. The hydrogenation rate is preferably 97 mol% or more, more preferably 98 mol% or more, even more preferably 99 mol% or more, and particularly preferably 99.5 mol% or more. Due to this constitution, the polymer becomes an amorphous resin with a high glass transition temperature, allowing layer A to be formed without relying on crystallization through nucleation, and allowing layer A to exhibit superior heat resistance. In other words, the polymer having an alicyclic structure in the side chain contained in layer A is preferably an amorphous resin.

[0081] The glass transition temperature (Tg) of the polymer having an alicyclic structure in its side chain contained in Layer A is preferably 100°C or higher and 180°C or lower. A glass transition temperature of 100°C or higher tends to increase rigidity and electrical insulation at high temperatures, while a glass transition temperature of 180°C or lower can improve stretchability. The glass transition temperature is more preferably 120°C or higher and 165°C or lower, more preferably 130°C or higher and 160°C or lower, and particularly preferably 140°C or higher and 155°C or lower.

[0082] The Vicat softening point (1 kg, 50°C / hr) of the polymer having an alicyclic structure in its side chain contained in Layer A is preferably 100°C or higher and 170°C or lower. By setting the Vicat softening point to 100°C or higher, rigidity and electrical insulation at high temperatures tend to be increased, and by setting it to 170°C or lower, stretchability can be improved. The Vicat softening point is more preferably 120°C or higher and 165°C or lower, more preferably 130°C or higher and 160°C or lower, and particularly preferably 140°C or higher and 155°C or lower.

[0083] The glass transition temperature (Tg) and Vicat softening point of the polymer having an alicyclic structure in its side chain contained in Layer A can be adjusted by the type of structural unit having the above-mentioned alicyclic structure in its side chain, or the types and ratios of one or more other structural units.

[0084] The weight-average molecular weight (Mw) of the polymer having an alicyclic structure in its side chain contained in Layer A is not particularly limited, but is preferably from 50,000 to 400,000. When Layer A contains a polymer having an alicyclic structure with such a weight-average molecular weight (Mw), the rigidity, electrical insulation, and stretchability of the film of the present invention are likely to be improved.

[0085] The melt mass flow rate (MFR) of the polymer having an alicyclic structure in its side chain contained in Layer A, measured at 260°C under a load of 2.16 kg, is preferably 1 g / 10 min to 40 g / 10 min, more preferably 2 g / 10 min to 20 g / 10 min, and even more preferably 3 g / 10 min to 15 g / 10 min, inclusive. In this case, appropriate resin fluidity is obtained during stretching of the film, and stretchability is easily improved.

[0086] The polymer having an alicyclic structure in the side chain contained in Layer A may be produced by the method described above, or a commercially available product such as ViviOn (registered trademark) (manufactured by USI Corporation) may be used.

[0087] 1-3.A layer The present invention has Layer A containing 55% by mass to 97% by mass of a polypropylene resin and 3% by mass to 45% by mass of a polymer having an alicyclic structure in its side chain, where the mass of Layer A is 100% by mass.

[0088] Layer A may further contain other resins for the purposes of adjusting the low-temperature impact resistance of the film, adjusting the surface roughness, and adjusting various physical properties such as rigidity, strength, and elongation, as well as adjusting the mixability and stretchability of the polypropylene-based resin and the polymer having an alicyclic structure in the side chain.

[0089] The amount of the other resin added is preferably 20% by mass or less, more preferably 10% by mass or less, and even more preferably 5% by mass or less, based on 100% by mass of Layer A. The other resin is not particularly limited, and conventionally known resins suitable for stretched film applications can be used appropriately in the present invention. Examples include polyolefin resins such as polyethylene, poly(1-butene), polyisobutene, poly(1-pentene), and poly(4-methyl-1-pentene), and copolymer resins thereof, as well as copolymers of α-olefins such as ethylene-propylene copolymer, propylene-butene copolymer, ethylene-butene copolymer, and ethylene-(4-methyl-1-pentene) copolymer. Other examples include polystyrene resins, elastomers, polyvinyl resins, polyester resins, polyurethane resins, nylon resins, and copolymers thereof.

[0090] Here, when the other resin is a copolymer containing propylene, the propylene content is less than 50% by mass (for example, 40% by mass or less), preferably 20% by mass or less, and more preferably 10% by mass or less, based on 100% by mass of the other resin.

[0091] As the other resin, commercially available products may be used, for example, Tafmer (registered trademark) (manufactured by Mitsui Chemicals, Inc.) as a copolymer of α-olefins, which can be suitably used for the above-mentioned purpose.

[0092] Layer A may further contain particles such as inorganic particles and organic particles, either alone or in combination of two or more types. However, in the stretched film of the present invention, Layer A preferably does not contain particles. Therefore, the upper limit of the particle content in Layer A, based on 100% by mass of Layer A, is preferably 1% by mass or less, 0.5% by mass or less, 0.3% by mass or less, 0.1% by mass or less, 0.05% by mass or less, or 0.01% by mass or less. In addition, the lower limit of the particle content in Layer A is not particularly limited and may be 0.005% by mass or more or may be 0% by mass or more.

[0093] Layer A may further contain an antioxidant. Antioxidants are primarily used for the following two purposes. One purpose is to suppress thermal and oxidative degradation of the resin in a film-forming extruder and / or melt kneader, and the other purpose is to suppress the deterioration of physical properties such as strength due to degradation over long-term use of the film. An example of the latter purpose is to contribute to suppressing degradation over long-term use and maintaining the electrical properties of the capacitor when used in a capacitor. An antioxidant that primarily contributes to the former purpose is also called a "primary agent," and an antioxidant that primarily contributes to the latter purpose is also called a "secondary agent." Two or more types of antioxidants may be used for these two purposes, or one type of antioxidant may be used for both purposes.

[0094] An example of a primary antioxidant is 2,6-di-tertiary-butyl-para-cresol (common name: BHT). This antioxidant is mostly oxidized, decomposed, or evaporated in the extruder, and almost none remains after the stretched film is formed. Therefore, if Layer A contains BHT after stretching, the content is usually less than 100 ppm by mass, with the mass of Layer A being 100%.

[0095] Examples of the secondary agent include hindered phenol-based antioxidants having a carbonyl group. Among the hindered phenol-based antioxidants, examples of the hindered phenol-based antioxidants having a carbonyl group include triethylene glycol-bis[3-(3-tert-butyl-5-methyl-4-hydroxyphenyl)propionate] (trade name: Irganox 245), 1,6-hexanediol-bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] (trade name: Irganox 259), pentaerythritol tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] (trade name: Irganox 1010), 2,2-thiazolinone-4-hydroxyphenylpropionate, and the like. Examples include N,N'-hexamethylenebis(3,5-ditertiary-butyl-4-hydroxyphenyl)propionate (trade name: Irganox 1035), octadecyl-3-(3,5-ditertiary-butyl-4-hydroxyphenyl)propionate (trade name: Irganox 1076), and N,N'-hexamethylenebis(3,5-ditertiary-butyl-4-hydroxyhydrocinnamamide) (trade name: Irganox 1098). Pentaerythritol tetrakis(3-(3,5-ditertiary-butyl-4-hydroxyphenyl)propionate) is particularly preferred due to its excellent heat resistance. (Here, all Irganox® trade names are manufactured by BASF Japan Ltd.)

[0096] When Layer A contains one or more hindered phenol-based antioxidants, the total content thereof is preferably from 1,000 to 7,000 ppm by mass, and more preferably from 2,000 to 6,000 ppm by mass, based on 100% by mass of Layer A, from the viewpoint of achieving optimal effects. Note that the hindered phenol-based antioxidant is partially oxidized and decomposed during the extrusion process or the like during stretched film formation, and the remaining amount in the stretched film is generally 60 to 80% by mass of the aforementioned content.

[0097] Layer A may further contain additives. Examples of additives include nucleating agents, chlorine absorbers, lubricants, plasticizers, flame retardants, and colorants. The content of the additives in Layer A is, for example, 0% by mass to 10% by mass, 0% by mass to 5% by mass, 0% by mass to 1% by mass, 0% by mass to 0.5% by mass, or 0% by mass to 0.1% by mass. The substantial lower limit is about 0.01% by mass.

[0098] The thickness of Layer A is not particularly limited. The preferred thickness depends on the application; for example, for packaging applications, separator applications, etc., a thickness of 5 μm to 80 μm, or 10 μm to 50 μm, is preferably used. For capacitor applications, a thinner thickness is preferred from the viewpoint of reducing the volume of the capacitor and increasing the capacitance. From this viewpoint, the thickness is preferably 10 μm or less, more preferably 9 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 viewpoint of stretchability and the metal vapor deposition process, the thickness after stretching 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, and even more preferably 2.2 μm or more.

[0099] 1-4.Film The film of the present invention has at least Layer A, and (1) contains 55% by mass to 97% by mass of a polypropylene resin and 3% by mass to 45% by mass of a polymer having an alicyclic structure in its side chain, where the mass of Layer A is 100% by mass, and (2) has a peak height Spk of 0.02 μm to 0.15 μm on at least one surface. The film of the present invention will be described below.

[0100] The protruding peak height Spk on at least one surface of the film of the present invention is 0.02 μm or more and 0.15 μm or less, and from the viewpoints of safety function operability, dielectric breakdown strength, element winding suitability, etc., the protruding peak height Spk is preferably 0.03 μm or more and 0.147 μm or less, more preferably 0.035 μm or more and 0.142 μm or less, and even more preferably 0.04 μm or more and 0.137 μm or less.

[0101] A method for adjusting the peak height Spk of at least one surface of the film of the present invention to 0.02 μm to 0.15 μm includes: (i) forming a film using a specific resin in which, based on 100 mass%, 55% to 97% by mass of a polypropylene resin and 3% to 45% by mass of a polymer having an alicyclic structure in its side chain are contained in the A layer; thereby, numerous β-crystals are formed on the film surface during film formation, resulting in the formation of fine protrusions due to the β-crystals, thereby adjusting Spk within the above range. A higher content of the polymer having an alicyclic structure in its side chain increases the Spk value, while a lower content of the polymer having an alicyclic structure in its side chain decreases the Spk value. Another method for adjusting Spk within the above range is to (ii) longitudinally stretch the film under the conditions described below to grow recesses based on β-crystals, and then transversely stretch the film under the conditions described below to grow protrusions at the ends of the recesses. As the stretching ratio increases, the Spk value increases, and as the stretching ratio decreases, the Spk value decreases.

[0102] The height Svk of the protruding valley portion on at least one surface of the film of the present invention is preferably 0.02 μm or more and 0.08 μm or less, more preferably 0.025 μm or more and 0.075 μm or less, and even more preferably 0.03 μm or more and 0.07 μm or less, from the viewpoints of safety function operation, dielectric breakdown strength, suitability for element winding, etc.

[0103] The arithmetic mean height Sa of at least one surface of the film of the present invention is preferably 0.010 μm or more and 0.050 μm or less, more preferably 0.014 μm or more and 0.045 μm or less, and even more preferably 0.018 μm or more and 0.040 μm or less, from the viewpoints of safety function operation, dielectric breakdown strength, element winding suitability, etc.

[0104] In the film of the present invention, the Svk and Sa can be adjusted by (i) forming a film using a specific resin in which, based on 100% by mass, the A layer contains 55% to 97% by mass of a polypropylene resin and 3% to 45% by mass of a polymer having an alicyclic structure in its side chain. This results in the formation of numerous β-crystals on the film surface during film formation, resulting in the formation of fine protrusions due to the β-crystals, thereby adjusting Spk within the above range. A higher content of the polymer having an alicyclic structure in its side chain increases the Svk and Sa values, while a lower content of the polymer having an alicyclic structure in its side chain decreases the Svk and Sa values. Another adjustment method is (ii) longitudinally stretching the film under the conditions described below to grow recesses based on β-crystals, and then transversely stretching the film under the conditions described below to grow protrusions at the edges of the recesses, thereby adjusting Svk and Sa within the above range. A higher stretch ratio increases the Svk and Sa values, while a lower stretch ratio decreases the Svk and Sa values.

[0105] The sum of the protruding peak height Spk and the protruding valley depth Svk on at least one surface of the film of the present invention is preferably 0.04 μm or more and 0.23 μm or less, more preferably 0.05 μm or more and 0.22 μm or less, and even more preferably 0.06 μm or more and 0.20 μm or less, from the viewpoints of safety function operability, dielectric breakdown strength, element winding suitability, etc.

[0106] The above Sa, Spk, and Svk values ​​are specified in ISO 25278-2 and are measured as follows. Specifically, a "VertScan 2.0 (Model: R5500GML)" manufactured by Ryoka Systems Co., Ltd. was used as the optical interference non-contact surface profilometer. The film was cut into a measurement sample of approximately 20 cm square. 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 one field of view (470.92 μm × 353.16 μm). This procedure was performed at five locations, spaced 1 cm apart in the machine direction, on the chill roll side of the sample, starting from the center in both the machine and cross directions. Next, the obtained data is subjected to noise removal processing using a median filter (3x3), followed by Gaussian filtering with a cutoff value of 30μm to remove waviness components. This makes it possible to properly measure the condition of the roughened surface. Next, analysis is performed using the "ISO parameters" in the "Bearing" plug-in function of the "VS-Viewer" analysis software for "VertScan2.0," to determine Sa, Spk, and Svk (μm), and the average of each value obtained at the above 10 locations is calculated. Measurements are taken on both the front and back sides, and the value of the larger surface is used for each parameter.

[0107] The film of the present invention may be an unstretched film (hereinafter also referred to as an "unstretched film" or "unstretched film of the present invention"), but is preferably a stretched film (hereinafter also referred to as a "stretched film" or "stretched film of the present invention"), and is also preferably a biaxially stretched film (hereinafter also referred to as a "biaxially stretched film" or "biaxially stretched film of the present invention"). The stretched film of the present invention is preferably stretched in at least one direction from the viewpoint of facilitating adjustment of the Spk value to the range specified in the present invention.

[0108] The film of the present invention may be a single-layer film consisting of Layer A, or may be a multilayer film obtained by laminating multiple layers and / or films using a conventionally known lamination method, such as coextrusion, lamination, heat sealing, coating, etc., either alone or in combination. Lamination may be performed before or after stretching Layer A.

[0109] The multilayer film can have, for example, a three-layer structure (layer b / layer a / layer b) consisting of a surface layer (skin layer: layer b) and a core layer (layer a); a three-layer structure (layer b / layer a / layer c) in which one surface layer is further added with another layer (layer c); a four-layer structure (layer b / layer a / layer a / layer c) in which there are two core layers; a four-layer structure (layer b / layer a / layer a' / layer c) in which one core layer is replaced with the other core layer (layer a'); a so-called super multilayer film including a two-layer or more structure in which two or more layers of layer a are laminated, or a laminate structure in which ten or more layers of layer a are laminated. Each layer may be made of a different resin or the same resin.

[0110] The Layer A of the present invention can be used as any of Layer a, Layer a', Layer b, Layer c, Layer d, etc. For example, when used as a surface layer, it tends to have excellent stretchability, and when used as a core layer, it tends to have excellent rigidity and insulation properties at high temperatures.

[0111] In order to facilitate the realization of the effects of the present invention, the thickness ratio of layer A to the stretched film of the present invention is preferably 50% or more, more preferably 60% or more, even more preferably 70% or more, and particularly preferably 80% or more, relative to 100% of the stretched film thickness.

[0112] When the layer A of the present invention is used as a core layer, a preferred surface layer to be laminated is a layer containing a polypropylene resin as a main component and a pigment. The polypropylene resin and pigment may be the same as those for the layer A.

[0113] The preferred layer configuration depends on the application, but for example, in applications such as packaging and separators, two or more layers are preferred from the viewpoint of functional separation between the core layer and the skin layer. In applications such as capacitors, a single layer is preferred from the viewpoint of reducing the thickness, and two or more layers are preferred from the viewpoint of electrical insulation.

[0114] Specific examples of coextrusion methods include pre-die lamination, in which molten resins are brought into contact in a feed block before the die, in-die lamination, in which they are brought into contact along a path inside the die, and out-of-die lamination, in which they are discharged from multiple concentric lips and brought into contact, etc. For example, in-die lamination can be performed using a multi-layer die such as a three-layer multi-manifold die.

[0115] The thickness of the stretched film of the present invention is not particularly limited. The preferred thickness depends on the application; for example, for packaging applications, separator applications, etc., a thickness of 5 μm to 80 μm, or 10 μm to 50 μm, is preferred. For capacitor applications, a thinner thickness is preferred from the viewpoint of reducing the volume of the capacitor and increasing the capacitance. From this viewpoint, the thickness is preferably 10 μm or less, more preferably 9 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 viewpoint of stretchability and the metal vapor deposition process, the thickness after stretching 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, and even more preferably 2.2 μm or more.

[0116] 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.

[0117] The film of the present invention has high dielectric breakdown strength at room temperature and at high temperatures, as measured at 23°C and 135°C according to the method described in the Examples below.

[0118] The dielectric breakdown strength of the film of the present invention in an environment of 23°C is preferably 450V DC / μm or more, preferably 470V DC / μm or more, more preferably 490V DC / μm or more, particularly preferably 500V DC / μm or more, more particularly preferably 510V DC The upper limit of the dielectric breakdown strength at the above temperature is not particularly limited, and is, for example, 700V DC / μm or less, 650V DC / μm or less, 620 DC / μm or less.

[0119] The dielectric breakdown strength of the film of the present invention in an environment of 135°C is preferably 420V DC / μm or more, preferably 440V DC / μm or more, more preferably 450V DC The upper limit of the dielectric breakdown strength at the above temperature is not particularly limited, and is, for example, 650V DC / μm or less, 600V DC / μm or less, 550V DC / μm or less, 500V DC / μm or less.

[0120] The film of the present invention is preferred because it exhibits little change in dielectric breakdown strength with temperature rise. The dielectric strength retention rate (%), which is the ratio of the dielectric breakdown strength in a 135°C environment to the dielectric breakdown strength in a 23°C environment (dielectric breakdown strength in a 135°C environment / dielectric breakdown strength in a 23°C environment), is preferably 70% or more, more preferably 75% or more, and even more preferably 80% or more. The upper limit is not particularly limited, and may be, for example, 100%, 99%, or 98%. Note that the load related to dielectric breakdown strength differs significantly between a 23°C environment and a 135°C environment. Therefore, a typical polypropylene film is not preferred because it reduces the dielectric strength retention rate and reduces the temperature stability of the electrical properties of a capacitor using the film. The film of the present invention is preferred because it suppresses change in dielectric breakdown strength from a 23°C environment to a 135°C environment, improving the temperature stability of the electrical properties of a capacitor using the film.

[0121] 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 packaging film or separator with excellent heat resistance by taking advantage of its heat resistance. The film of the present invention can also be suitably used as a film for capacitors. In particular, it can be very suitably used in capacitors that are used in high-temperature environments of 135°C or higher, and that are small in size and have a high capacity (for example, 5 μF or more, preferably 10 μF or more, and more preferably 20 μF or more).

[0122] 1-5.Film manufacturing method If the raw materials for the film of the present invention (including at least the polypropylene resin and the polymer having an alicyclic structure in the side chain) contain a large amount of water, they are dried before use. The drying conditions are not particularly limited, but are, 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 30 hours, preferably 3 to 20 hours. If the water content is low, the drying step can be omitted.

[0123] The raw materials may be individually fed into the film-forming extruder and mixed inside the film-forming extruder, or may be mixed before being fed into the film-forming extruder and then fed into the film-forming extruder as a raw material mixture.

[0124] The mixing method for preparing the raw material mixture is not particularly limited, but examples include a method in which a plurality of types of resin blocks (pellets, etc.) are dry-blended using a mixer or the like.

[0125] As a mixing method, melt kneading (melt blending) may be used. Melt kneading is preferred because if the resins can be kneaded uniformly, the rigidity, electrical insulation properties, stretchability, etc. of the stretched film are likely to be improved.

[0126] As a method of melt kneading, a single-screw type, twin-screw type, or multi-screw type melt kneader having more than one screw can be used. Twin-screw melt kneaders are particularly suitable because they are highly effective in improving the rigidity, electrical insulation, stretchability, etc. of the stretched film. In the case of twin-screw types, either co-rotating or counter-rotating kneading types can be used, but co-rotating types are preferred from the viewpoint of suppressing resin degradation. The screw diameter-to-length ratio (L / D) of the melt kneader is preferably 20 or more, more preferably 25 or more, and even more preferably 28 or more. By setting the L / D to 20 or more, the resins are thoroughly mixed, improving the rigidity, electrical insulation, and stretchability of the stretched film. There is no upper limit to L / D, but from the viewpoint of suppressing resin degradation, it is 80 or less, preferably 50 or less.

[0127] The temperature during melt kneading is preferably 200° C. to 300° C., more preferably 220° C. to 280° C., in order to balance suppression of resin deterioration and kneadability. During melt kneading, it is preferable to purge the kneader with an inert gas such as nitrogen in order to suppress resin deterioration.

[0128] The raw materials and / or raw material mixture for producing the film of the present invention are supplied to a film-forming extruder and extruded. The extrusion method is not particularly limited, and any known extrusion method can be used. For example, the solid raw materials or resin composition of the present invention supplied to the film-forming extruder are mixed in a heated, molten state by a screw, filtered, extruded into a film form through a die such as a single-layer T-die, and solidified by contact with a cooling roll set at a predetermined surface temperature to form the unstretched film of the present invention.

[0129] Examples of film-forming 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 200 to 300°C, preferably 230 to 280°C, and more preferably 240 to 275°C. This allows the resin to be appropriately kneaded, which tends to improve the rigidity, electrical insulation, stretchability, etc. of the film. To suppress deterioration of the resin during melt extrusion, it is preferable to purge the extruder with an inert gas such as nitrogen.

[0130] The filtration accuracy of the filter used to filter the molten resin is not particularly limited, but is, for example, 2 to 30 μm, preferably 5 to 25 μm, and more preferably 10 to 25 μm.

[0131] The temperature of the die is not particularly limited, but is preferably 200 to 300°C, more preferably 210 to 280°C, more preferably 215 to 270°C, and even more preferably 220 to 260°C.

[0132] The method of contacting the molten resin extruded from the die with a chill roll to solidify it is not particularly limited, and examples include air knife, electrostatic pinning, elastic roll nip, metal roll nip, elastic metal roll nip, etc. The surface temperature of the chill roll is, for example, 30 to 130°C, preferably 35 to 120°C, and more preferably 40 to 110°C.

[0133] The draft ratio when the molten resin extruded from the die is brought into contact with the cooling roll is preferably 1 to 20, more preferably 1.1 to 16, more preferably 1.2 to 10, and even more preferably 1.3 to 8. By setting the draft ratio within this range, the longitudinal orientation of the film can be set to an appropriate range, and the stretchability can be improved. The draft ratio is determined based on the density d (g / cm) of the molten resin. 3), width W (cm) of the die lip outlet, average slit gap t (cm) of the die lip outlet, resin discharge rate Q (g / min), and peripheral speed V (cm / min) of the cooling and forming roll, are used to calculate the cooling and forming rate using the following formula. Draft ratio = dVWt / Q

[0134] The thickness of the unstretched film of the present invention is not particularly limited, but is, for example, 20 to 300 μm.

[0135] The film of the present invention is preferably a stretched film stretched in at least one direction.

[0136] The method for stretching the unstretched film of the present invention is not particularly limited, and known stretching methods can be used. For example, there are mentioned a method in which the unstretched film of the present invention is heated with a heated roll and stretched in the longitudinal direction (machine direction, MD) (longitudinal uniaxial roll stretching method), a method in which the unstretched film of the present invention is stretched in the transverse direction (width direction, TD) in an oven (commonly called a tenter) at a predetermined temperature (transverse uniaxial stretching method), a method in which longitudinal uniaxial roll stretching is followed by transverse uniaxial stretching (sequential biaxial stretching method), a method in which longitudinal uniaxial roll stretching is followed by transverse uniaxial stretching and then longitudinal uniaxial (roll or tenter method) stretching (multistage sequential biaxial stretching method), a method in which the unstretched film of the present invention is longitudinally stretched and transversely stretched sequentially in a tenter at a predetermined temperature (tenter method sequential biaxial stretching method), a method in which the unstretched film of the present invention is longitudinally stretched and transversely stretched simultaneously in a tenter (simultaneous biaxial stretching method), etc. As a method for stretching the unstretched film of the present invention, a method of longitudinal uniaxial roll stretching followed by transverse uniaxial stretching (sequential biaxial stretching method) is preferred, as it provides excellent rigidity, electrical insulation, stretchability, etc. of the stretched film.

[0137] In the longitudinal uniaxial roll stretching method, a plurality of heating rolls may be used. The stretching point may be one or two or more. When there is one stretching point, the temperature of the roll immediately before the stretching point (roll before stretching) (T MD-延伸前 ), and if there are two or more stretching points, the surface temperature of the roll before stretching at the point where the stretching ratio is maximum (T MD-延伸前) is preferably 125°C or higher and 175°C or lower, more preferably 130°C or higher and 170°C or lower, even more preferably 135°C or higher and 168°C or lower, and particularly preferably 140°C or higher and 166°C or lower. In addition, when there is one stretching point, the temperature of the roll (post-stretching roll) immediately after the stretching point (T MD-延伸後 ), and if there are two or more stretching points, the surface temperature of the roll after stretching at the point where the stretching ratio is maximum (T MD-延伸後 ) is preferably 80°C or higher and 140°C or lower, more preferably 90°C or higher and 130°C or lower, even more preferably 100°C or higher and 120°C or lower, and particularly preferably 105°C or higher and 115°C or lower.

[0138] The stretching ratio in the machine direction (the product of the stretching ratios when there are two or more stretching points) is preferably 1.5 to 5.0, more preferably 2.0 to 4.6, and even more preferably 2.2 to 4.2. By setting the temperature and stretching ratio within these ranges, orientation in the machine direction is suppressed within an appropriate range, and a stretched film excellent in rigidity, electrical insulation, stretchability, etc. can be easily obtained.

[0139] The tenter to be used preferably has three or more temperature zones, and more preferably five or more temperature zones, so that heating, stretching, and the later-described heating treatment, relaxation treatment, cooling treatment, etc. can be performed at different temperatures.

[0140] When longitudinal stretching is performed in a tenter, the oven temperature during stretching (T MD ) is preferably 125° C. or higher and 175° C. or lower, more preferably 130° C. or higher and 170° C. or lower, even more preferably 135° C. or higher and 168° C. or lower, and particularly preferably 140° C. or higher and 166° C. or lower. The draw ratio in the machine direction is preferably 1.5 times or higher and 5.0 times or lower, more preferably 2.0 times or higher and 4.6 times or lower, and even more preferably 2.2 times or higher and 4.2 times or lower.

[0141] When transverse stretching is performed in a tenter, the oven temperature during stretching (T TD) is preferably 140°C or higher and 175°C or lower, more preferably 145°C or higher and 170°C or lower, even more preferably 150°C or higher and 168°C or lower, and particularly preferably 155°C or higher and 166°C or lower. The stretching ratio in the transverse direction is preferably 5.0 times or higher and 11.0 times or lower, more preferably 6.0 times or higher and 10.0 times or lower, and even more preferably 7.0 times or higher and 9.5 times or lower. By setting the temperature and stretching ratio within these ranges, orientation in the transverse direction is suppressed within an appropriate range, making it easy to obtain a stretched film that is excellent in rigidity, electrical insulation, stretchability, etc.

[0142] The above-mentioned stretching temperature (T MD , T MD-延伸前 , and T TD ) is more preferably adjusted depending on the glass transition temperature (Tg) of the polymer having an alicyclic structure in the side chain contained in Layer A of the present invention. MD , and T MD-延伸前 is preferably Tg-10°C or more and Tg+25°C or less, more preferably Tg-5°C or more and Tg+20°C or less, and even more preferably Tg or more and Tg+16°C or less. TD is preferably Tg or higher and Tg+30° C. or lower, more preferably Tg+5° C. or higher and Tg+28° C. or lower, and even more preferably Tg+10° C. or higher and Tg+25° C. or lower. By setting the temperature within this range, the orientation of the stretched film is suppressed within an appropriate range, and a stretched film excellent in rigidity, electrical insulation, stretchability, etc. can be easily obtained.

[0143] In addition, the aforementioned stretching temperature (T MD , T MD-延伸前 , and T TD If the temperature is below the aforementioned range, if the kneading properties during resin blending or extrusion are poor, or if the draft ratio during extrusion molding is inappropriate, pores may form in Layer A during stretching. If many pores form, the rigidity, electrical insulation, and stretchability of the stretched film tend to decrease.

[0144] Since the total light transmittance of the stretched film is likely to decrease when many pores are formed, the total light transmittance of the film of the present invention is preferably 80% or more, more preferably 85% or more, even more preferably 88% or more, and particularly preferably 90% or more. From the viewpoint of the electrical characteristics (safety) of the capacitor, the total light transmittance is preferably 99% or less, more preferably 98% or less, even more preferably 97% or less, and particularly preferably 96% or less.

[0145] The product of the longitudinal stretching ratio and the transverse stretching ratio of the stretched film (when a relaxation treatment described below is performed, the product is calculated using the longitudinal stretching ratio and the transverse stretching ratio before relaxation) is preferably 15 to 48, more preferably 17 to 42, even more preferably 19 to 38, particularly preferably 21 to less than 35, and more particularly preferably 22 to 34. By setting the temperature and stretching ratio within these ranges, a stretched film excellent in rigidity, electrical insulation, stretchability, etc. can be easily obtained.

[0146] Stretched films with an area ratio of 12% or less and unstretched films (with an area ratio of 1%) tend to have reduced rigidity and electrical insulation. Furthermore, if the area ratio at which a film can be stretched without breaking is 12% or less, the film's stretchability is not very good.

[0147] The stretched film of the present invention may be subjected to a relaxation treatment (a treatment of reducing the stretch ratio after stretching, for example, by up to 20% of the original stretch ratio), a heating treatment, or a cooling treatment, as needed. These treatments may be performed independently or in combination, for example, by performing the relaxation treatment and the heating treatment simultaneously, or by performing the relaxation treatment and the cooling treatment simultaneously. Appropriate performance of the relaxation treatment, the heating treatment, and the cooling treatment can improve the flatness of the stretched film, its dimensional stability against temperature changes, its passability through the vapor deposition process, and the like.

[0148] The relaxation in the transverse direction is preferably 3% to 20% of the maximum stretching ratio in the transverse direction, more preferably 5% to 16%, and even more preferably 6.5% to 14%.

[0149] The heat treatment temperature is preferably 150° C. to 180° C., more preferably 155° C. to 175° C., and even more preferably 160° C. to 172° C. The heat treatment time is preferably 1 second to 20 seconds, and more preferably 2 seconds to 15 seconds.

[0150] The stretched film of the present invention may be subjected to corona treatment, static electricity removal treatment, heating treatment, etc. Appropriately performing corona treatment, static electricity removal treatment, heating treatment, etc. can improve the passability through the deposition process. The heating treatment temperature is preferably 20°C or higher and 80°C or lower, more preferably 25°C or higher and 60°C or lower, and even more preferably 30°C or higher and 55°C or lower. The heating treatment time is preferably 3 hours or higher and 50 hours or lower, and more preferably 6 hours or higher and 30 hours or lower.

[0151] 2. Metal laminated film In one aspect, the present invention relates to a metal laminated film (sometimes referred to herein as the "metal laminated 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.

[0152] The film of the present invention may be provided with a metal layer on one or both sides, for example, to adjust the permeability of gases such as oxygen and water vapor when used as a packaging film, or as an electrode when used as a capacitor.

[0153] 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, from the viewpoints of productivity and economy, vacuum vapor deposition and sputtering are more preferred, and vacuum vapor deposition is even more preferred. Examples of vacuum vapor deposition methods include the crucible method and the wire method, but are not particularly limited, and the most suitable method can be selected as appropriate.

[0154] 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 metals, or an alloy of these metals. However, taking into consideration the environment, economy, and performance, one or more of zinc and aluminum are preferred.

[0155] The film resistance of the metal layer is preferably about 0.5 to 10 Ω / □ from the viewpoint of permeability to gases such as oxygen and water vapor, and about 1 to 60 Ω / □ from the viewpoint of the electrical properties of the capacitor. From the viewpoint of the electrical properties of the capacitor, in order to exhibit self-healing properties, the film resistance is more preferably 5 Ω / □ or more, and even more preferably 10 Ω / □ or more, and 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.

[0156] In this specification, "Ω / □" is a unit that is also expressed as "Ω / square."

[0157] When forming an electrode (metal vapor deposition film) by vacuum deposition, the film resistance can be measured during deposition, for example, by a non-contact eddy current method or light transmittance 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.

[0158] When the film is used in capacitors, when a metal vapor deposition film is formed on one side of the film, an insulating margin (vertical margin) of a certain width where no metal is laminated is formed so that it will become an insulating part when the film is rolled up to make a capacitor.

[0159] Furthermore, it is preferable to form a heavy edge portion to strengthen the bond between the metal layer of the metal layer-integrated film and the metallikon electrode. The film resistance of the heavy edge portion is usually about 1 to 8 Ω / □, preferably about 1 to 5 Ω / □. The thickness of the metal film in the heavy edge portion is not particularly limited, but is preferably 1 to 200 nm.

[0160] In capacitor applications, there are no particular limitations on the deposition pattern (fuse pattern) of the metal deposition film to be formed, but from the viewpoint of improving the safety and other properties of the capacitor, it is preferable to form fuses by pattern deposition such as a fishnet pattern, a T-margin pattern, etc. Forming a metal deposition film with a deposition pattern including a fuse on at least one surface of the stretched film of the present invention is preferable because it improves the safety of the resulting capacitor and is effective in preventing breakdown and short circuits of the capacitor.

[0161] As a method for forming the fuse and the insulating margin, any known method can be used without any restrictions, 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.

[0162] A protective agent may be applied to the metal laminated film of the present invention for the purposes of physical protection of the metal layer, prevention of moisture absorption, prevention of oxidation, etc. As the protective agent, silicone oil, fluorine oil, etc. can be preferably used. The protective agent may be provided as a layer on the metal layer, or may be impregnated into the metal layer.

[0163] The metal laminated film of the present invention can be processed into the capacitor of the present invention described below. The metal laminated film of the present invention can also be used for packaging purposes, for example, as a barrier film against oxygen and other gases.

[0164] 3. Capacitor In one aspect, the present invention relates to a capacitor (film capacitor) (sometimes referred to as "the capacitor of the present invention" in this specification) comprising the film of the present invention or the metal laminated film of the present invention. This will be described below.

[0165] 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 laminated film, (ii) laminating the stretched film of the present invention having no electrodes with a dielectric having metallized surfaces (such as the stretched film of the present invention or other plastic films), or (iii) laminating the film of the present invention having no electrodes with another conductor (such as a metal foil).

[0166] In the process of producing a capacitor, a film is wound. For example, a pair of metal laminated films of the present invention are overlapped and wound so that the metal layers of the metal laminated 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 pair of metal laminated 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.

[0167] The film winding process is not limited to the above method, and other methods may be used, for example, a double-sided vapor-deposited stretched film of the present invention (in which case the heavy edges are positioned at the opposite ends of the front and back surfaces) and an undeposited film of the present invention (2 to 3 mm narrower than the double-sided vapor-deposited film of the present invention) may be alternately laminated and wound.

[0168] When producing a flat capacitor, the resulting roll is usually pressed after winding. 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 stretched film of the present invention, but is generally 2 to 20 kg / cm. 2 is.

[0169] Next, metal is sprayed onto both end surfaces of the wound body to provide metallikon electrodes, thereby fabricating a capacitor.

[0170] 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, and more preferably 5 hours or more, from the viewpoint of obtaining mechanical and thermal stability, but is more preferably 20 hours or less, from the viewpoint of preventing molding defects such as heat wrinkles and molding.

[0171] The heat treatment provides the effect of thermal aging. Specifically, the gaps between the films constituting the capacitor based on the film of the present invention are reduced, corona discharge is suppressed, and the internal structure of the film of the present invention changes, promoting crystallization. As a result, it is believed that the electrical insulation properties are improved. If the heat treatment temperature is lower than the specified temperature, the above-mentioned effect of thermal aging cannot be fully achieved. 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.

[0172] Lead wires or bus bars 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.

[0173] The capacitor of the present invention using 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 used in electronic devices, electrical devices, etc.; various switching power supplies; filter capacitors, smoothing capacitors for converters, inverters, etc. Furthermore, the capacitor of the present invention can also be suitably used as an inverter capacitor, converter capacitor, etc. for controlling the drive motor of electric vehicles, hybrid vehicles, etc., for which demand has been increasing in recent years. [Example]

[0174] The present invention will be described in detail below based on examples, but the present invention is not limited to these examples.

[0175] (1)Measurement method The various measurement methods are as follows.

[0176] (1-1) Number average molecular weight (Mn), weight average molecular weight (Mw), z-average molecular weight (Mz), molecular weight distribution (Mw / Mn), and molecular weight distribution (Mz / Mw) of polypropylene resin The number average molecular weight (Mn), weight average molecular weight (Mw), z-average molecular weight (Mz), molecular weight distribution (Mw / Mn), and molecular weight distribution (Mz / Mw) of each resin were measured using GPC (gel permeation chromatography) under the following conditions.

[0177] Specifically, a Tosoh Corporation HLC-8121GPC-HT model high-temperature GPC system with a built-in differential refractometer (RI) was used. Three Tosoh Corporation TSKgel GMHHR-H(20)HT columns were connected together. Measurements were performed at a column temperature of 140°C using trichlorobenzene as the eluent at a flow rate of 1.0 ml / min. A calibration curve for the molecular weight M was created using standard polystyrene manufactured by Tosoh Corporation, and the measured values ​​were converted to polypropylene molecular weights using the Q-factor to obtain the number-average molecular weight (Mn), weight-average molecular weight (Mw), and z-average molecular weight (Mz). The molecular weight distribution (Mw / Mn) was obtained using the Mw and Mn values. The molecular weight distribution (Mz / Mw) was also obtained using the Mz and Mw values.

[0178] (1-2) Mesopentad fraction of polypropylene resin The polypropylene resin was dissolved in a solvent, and the measurement was carried out using a high-temperature Fourier transform nuclear magnetic resonance spectrometer (high-temperature FT-NMR) under the following conditions. High-temperature nuclear magnetic resonance (NMR) spectrometer: JEOL Ltd., high-temperature Fourier transform nuclear magnetic resonance spectrometer (high-temperature FT-NMR), JNM-ECP500 Observed nucleus: 13C (125MHz) Measurement temperature: 135℃ Solvent: ortho-dichlorobenzene (ODCB: a mixed solvent of ODCB and deuterated ODCB (mixing ratio = 4 / 1)) Measurement mode: Single pulse proton broadband decoupling Pulse width: 9.1 μsec (45° pulse) Pulse interval: 5.5 seconds Accumulation count: 4,500 times Shift standard: CH3 (mmmm) = 21.7 ppm The pentad fraction, which indicates the degree of stereoregularity, was calculated as a percentage (%) from the integrated intensity of each signal derived from a combination of five pentads (pentads) consisting of meso (m) pentads arranged in the same direction and racemo (r) pentads arranged in the opposite direction (e.g., mmmm and mrrm). The assignment of each signal derived from mmmm, mrrm, etc. was based on the spectral descriptions in, for example, T. Hayashi et al., Polymer, Vol. 29, p. 138 (1988).

[0179] (1-3) Heptane insolubles (HI) of polypropylene resins Polypropylene resin was press-molded to a size of 10 mm x 35 mm x 0.3 mm to prepare a measurement sample weighing approximately 3 g. Next, approximately 150 mL of heptane was added and Soxhlet extraction was performed for 8 hours. The heptane-insoluble content was calculated from the sample mass before and after extraction.

[0180] (1-4) Melt mass flow rate of resin The melt flow rate (MFR) of each resin in the form of raw resin pellets was measured using a Toyo Seiki melt indexer in accordance with JIS K 7210-1:2014. Specifically, 4 g of raw material was placed in a cylinder heated to the test temperature (230°C for polypropylene resins, 260°C for polymers with alicyclic structures in the side chain and polymers with alicyclic structures in the main chain) and preheated for 3.5 minutes under a load of 2.16 kg. The weight of the raw resin extruded through the bottom hole over 30 seconds was then measured, 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.

[0181] (1-5) Melting point and glass transition temperature of resin The calculations were performed using a Perkin-Elmer Diamond DSC (power compensation type). Five mg of each resin was weighed, placed in an aluminum sample holder, and placed in the DSC instrument. Under a nitrogen flow, the resin was heated from 30°C to 230°C at a rate of 20°C / min, held at 230°C for 5 minutes, cooled to 30°C at 20°C / min, and held at 30°C for 5 minutes. The melting point and glass transition temperature were then determined from the DSC curve obtained while the temperature was again raised to 230°C at 20°C / min. Specifically, the melting peak (the largest melting peak in the case of multiple melting peaks) as defined in JIS-K7121, 9.1(1), was used as the melting point, and the midpoint glass transition temperature as defined in JIS-K7121, 9.3(1), was used as the glass transition temperature.

[0182] (2) Preparation of resin composition and stretched film (2-1)Resin used etc. [Polypropylene resin] Raw material A: Polypropylene resin A1: Isotactic polypropylene resin manufactured by Prime Polymer Co., Ltd. Prime Polypro (registered trademark) MFR: 3.5g / 10min (measurement temperature 230℃) Melting point: 164℃ Mesopentad fraction: 98.6mol% Heptane insolubles: 98.1% by mass Number average molecular weight (Mn): 49000 Weight average molecular weight (Mw): 390000 z average molecular weight (Mz): 1520000 Molecular weight distribution (Mw / Mn): 8.0 Molecular weight distribution (Mz / Mw): 3.9

[0183] A2: Isotactic polypropylene resin manufactured by Prime Polymer Co., Ltd. Prime Polypro (registered trademark) MFR: 2.3g / 10min (measurement temperature 230℃) Melting point: 164℃ Mesopentad fraction: 98.8mol% Heptane insolubles: 98.0% by mass Number average molecular weight (Mn): 46000 Weight average molecular weight (Mw): 380000 z average molecular weight (Mz): 1600000 Molecular weight distribution (Mw / Mn): 8.3 Molecular weight distribution (Mz / Mw): 4.1

[0184] Raw material B: Polymer with an alicyclic structure in the side chain B1: Made by USI Corporation ViviOn® 0645 Glass transition temperature: 146℃ MFR: 5.5g / 10min (measurement temperature 260℃) Hydrogenated polystyrene with cyclohexane structures in the side chains Stereoregularity: Atactic Aromatic ring hydrogenation rate: 99.9%

[0185] B2: Made by USI Corporation ViviOn® 1325 Glass transition temperature: 128℃ MFR: 13g / 10min (measurement temperature 260℃) A hydrogenated block copolymer of styrene-butadiene diblock copolymer with cyclohexane structures in the side chains, but not hydrogenated polystyrene.

[0186] Raw material C: Polymer with an alicyclic structure in the main chain C1: Polyplastics Co., Ltd. TOPAS (registered trademark) COC6013S-04 Glass transition temperature: 138℃ MFR: 14g / 10min (measurement temperature 260℃) Contains a norbornene structure in the main chain

[0187] (2-2) Resin composition and method for producing stretched film [Preparation of unstretched film] Raw materials A, B, and C were weighed so that each raw material was mixed in the amounts shown in Table 1, and the raw material mixture for layer A obtained by dry blending using a tumbler was fed into a single-screw film extruder (GM-50, manufactured by GM Engineering Co., Ltd., L / D=32). The raw materials were melted in the extruder set to the melting temperature shown in Table 1, then filtered through a filter with a filtration accuracy of 20 μm and extruded through a T-die set to 260°C.

[0188] The molten resin was brought into contact with a mirror-finished metal roll (cooling roll) having a surface temperature of 90°C using an air knife, solidified, and formed into a film to obtain a single-layer unstretched film.

[0189] [Preparation of stretched film] The unstretched film was introduced into a roll-type longitudinal stretching machine, heated sequentially by five preheating rolls, and then heated to the temperature (T MD-延伸前 ), and stretched uniaxially in the machine direction (MD) at the ratio shown in Table 1. MD-延伸後 The film was then introduced into a tenter, heated in a preheating zone whose furnace temperature was adjusted to the preheating temperature shown in the table, and then cooled at the temperature (T TD The film was stretched in the transverse direction (TD) at the ratios listed in Table 1 in a stretching zone where the furnace temperature was adjusted to 100°C. The film was then relaxed in the width (transverse direction) by 10% in a heating zone set at 170°C. The end of the stretched film emerging from the tenter was slit to a width of 620 mm, and the side where the air knife had been used was subjected to corona treatment before being wound up to obtain a roll of stretched film. The extrusion rate and take-up speed were finely adjusted so that the film thickness was 2.8 μm. The film stretchability was good in all of Examples 1 to 9 and Comparative Examples 1, 3, and 4. On the other hand, although the films of Comparative Examples 2 and 5 could be stretched, breakage occurred when film rolls with a wound length of 2000 m or more were produced, and the stretchability was not considered to be good.

[0190] [Table 1]

[0191] (3) Fabrication of metal layer integrated film and capacitor Using the biaxially stretched films of the Examples and Comparative Examples, metal layer-integrated films and capacitors were fabricated by the following method. Specifically, a special vapor deposition pattern margin and an insulating margin were formed on the biaxially stretched film to provide film capacitor safety, and aluminum was vapor-deposited to achieve a surface resistivity of 20 Ω / □ to obtain the metal layer-integrated film. In Examples 1 to 9 and Comparative Examples 1, 3, and 4, no breaks occurred during vapor deposition, and the required metal layer-integrated film was obtained. On the other hand, the films of Comparative Examples 2 and 5 broke during vapor deposition, and the required metal layer-integrated film could not be obtained. The metal layer-integrated film was then slit into a 30 mm width, and 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 device capacitance of 20 μF. The wound element was flattened by pressing, and then zinc metal was sprayed onto the element end faces while the press load was still applied 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 faces and sealed with epoxy resin to obtain a flat film capacitor.

[0192] (4) Measurement and evaluation of the physical properties and characteristics of stretched films (4-1) Measurement of total light transmittance The total light transmittance of the stretched films obtained in the examples and comparative examples was measured using a haze meter NDH-5000 manufactured by Nippon Denshoku Industries Co., Ltd. in accordance with JIS-K7361.

[0193] (4-2) Haze measurement The haze of the stretched films obtained in the examples and comparative examples was measured using a haze meter NDH-5000 manufactured by Nippon Denshoku Industries Co., Ltd. in accordance with JIS K 7136:2000.

[0194] (4-3) Evaluation of surface roughness (measurement of arithmetic mean height Sa, protruding peak height Spk, protruding valley depth Svk) The arithmetic mean height Sa, protruding peak height Spk, and protruding valley depth Svk of the stretched films obtained in the examples and comparative examples were measured as follows.

[0195] 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.

[0196] 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.

[0197] 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.

[0198] Next, an analysis was performed using the "ISO parameters" in the "Bearing" plug-in function of the "VS-Viewer" analysis software for "VertScan2.0," to determine Sa, Spk, and Svk (μm), and calculate the average of each value obtained at the above 10 locations. Measurements were taken on both the front and back, and the value of the larger surface was used for each parameter.

[0199] (4-4) Evaluation of heat shrinkage rate [MD direction] The stretched films obtained in the Examples and Comparative Examples were cut into rectangular shapes with a width of 20 mm and a length of 130 mm to prepare measurement samples. The samples were cut so that the length direction of the sample coincided with the MD direction. Three measurement samples were prepared. Next, a point 100 mm in length was measured with a ruler, and a benchmark was marked at that point. The three measurement samples were hung without load in a hot air circulating thermostatic chamber at 140°C and held there for 15 minutes. Thereafter, the samples were cooled to room temperature (23°C), and the spacing between the benchmark lines was measured with a ruler. The thermal shrinkage (%) in the MD direction was calculated using the following formula: Heat shrinkage rate (%) = [(gauge line spacing before heating - gauge line spacing after heating) / (gauge line spacing before heating)] x 100 The average of the three measurements was taken as the thermal shrinkage rate (%) in the MD direction. Note that measurement conditions other than those described here were in accordance with "25. Dimensional change" of JIS C 2151:2019.

[0200] [TD direction] The stretched films obtained in the examples and comparative examples were cut into rectangular pieces 20 mm wide and 130 mm long to prepare measurement samples. The heat shrinkage in the TD direction (%) was calculated in the same manner as in the measurement of the heat shrinkage in the MD direction, except that the samples were cut out so that the length direction of the samples coincided with the TD direction.

[0201] (4-5) Evaluation of dielectric breakdown strength The dielectric breakdown strength at high temperatures of the stretched films obtained in the Examples and Comparative Examples 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 the electrode.

[0202] The measurement environment was a forced circulation oven set at a temperature of 23°C or 135°C, and the electrodes and films were used after 30 minutes of temperature adjustment in the oven. The voltage was increased at a rate of 100V / sec starting from 0V, and the voltage when the current value exceeded 5mA was taken as the breakdown voltage. The breakdown voltage was measured 20 times, and each breakdown voltage value VDC was divided by the thickness (μm) of the stretched film. The top two and bottom two points were excluded from the 20 calculation results, and the average of 16 points was taken as the breakdown strength (V DC / μm).

[0203] (5) Measurement and evaluation of the physical properties and characteristics of capacitors (5-1) Evaluation of voltage resistance [Voltage resistance at 23°C] The capacitance of the capacitor obtained above was measured (initial capacitance) using a Hioki E.E. Corporation LCR HiTester 3522-50. Next, a DC voltage of 700 V was applied to the capacitor for 10 seconds in a thermostatic chamber at room temperature. The capacitance of the capacitor after the 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 (%)

[0204] The capacitors were then returned to the thermostatic chamber, and the voltage was increased by 50 V each time, and the capacitance change rate was measured repeatedly. The test was performed using five capacitors, and measurements were continued until the capacitance change rate reached -2% or less.

[0205] Here, the applied voltage just before it reaches -2% is V before_-2% , the rate of change of capacitance is ΔC before_-2% / C, the applied voltage immediately after reaching -2% is V after_-2% , the rate of change of capacitance is ΔC after_-2% The voltage resistance was calculated using the following formula, where the film thickness is t and the film thickness is t. (Voltage resistance) = [(V after_-2% -V before_-2% ) / (|ΔC after_-2% / C|―|ΔC before_-2% / C|)×(2-|ΔC before_-2% / C|)+V before_-2%] / t(V / μm)

[0206] [Voltage resistance at 135℃] The capacitors obtained above were preheated at 135°C for 1 hour, and then the capacitance was measured (initial capacitance) using a Hioki E.E. Corporation LCR HiTester 3522-50. Next, a DC voltage of 700 V was applied to the capacitors for 10 seconds in a thermostatic chamber at 135°C. The capacitance of the capacitors after the 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 (%)

[0207] The capacitors were then returned to the thermostatic chamber at 135°C, and the voltage was increased by 50 V each time, and the capacitance change rate was measured repeatedly. The test was conducted using five capacitors, and measurements were continued until the capacitance change rate reached -2% or less.

[0208] Here, the applied voltage just before it reaches -2% is V before_-2% , the rate of change of capacitance is ΔC before_-2% / C, the applied voltage immediately after reaching -2% is V after_-2% , the rate of change of capacitance is ΔC after_-2% The voltage resistance was calculated using the following formula, where the film thickness is t and the film thickness is t. (Voltage resistance) = [(V after_-2% -V before_-2% ) / (|ΔC after_-2% / C|―|ΔC before_-2% / C|)×(2-|ΔC before_-2% / C|)+V before_-2% ] / t(V / μm)

[0209] (5-2) Safety evaluation The capacitor obtained above was preheated at 135°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 280 V was applied to the capacitor for 1 hour in a thermostatic chamber at 135°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 (%)

[0210] The capacitors were then returned to the thermostatic chamber, and the voltage was increased by 50 V each time, and the capacitance change rate was measured repeatedly. The test was conducted using five capacitors, and measurements were continued until the capacitance change rate reached -95% or less. Capacitors that short-circuited and lost insulation before the capacitance change rate reached -95% or less were deemed defective and were not subjected to further testing.

[0211] 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.

[0212] The safety was evaluated according to the following evaluation criteria. Good: Of the five capacitors, all have a capacitance change rate of -95% or less and a resistance value greater than 10 kΩ. ×: The resistance value of one or more of the five capacitors becomes 10 kΩ or less before the capacitance change rate reaches -95% or less.

[0213] The results are shown in Table 2.

[0214] [Table 2]

[0215] In Table 2, * indicates that the film broke during deposition and an element could not be fabricated.

Claims

1. A film having at least Layer A, (1) The layer A contains, in 100% by mass, 55% by mass or more and 97% by mass or less of a polypropylene-based resin and 3% by mass or more and 45% by mass or less of a polymer having an alicyclic structure in a side chain, (2) The height Spk of the protruding peaks on at least one surface is 0.02 μm or more and 0.15 μm or less; A film characterized by:

2. The film according to claim 1 , wherein the polymer has a glass transition temperature of 100° C. or higher and 180° C. or lower.

3. The film according to claim 1 , wherein the alicyclic structure has a cyclohexane structure.

4. The film according to claim 1 , wherein the polymer is hydrogenated polystyrene, has atactic stereoregularity, and has a hydrogenation rate of aromatic rings of 95 mol % or more.

5. 2. The film according to claim 1, wherein the sum of the protruding peak height Spk and the protruding valley depth Svk on at least one surface of the film is 0.04 μm or more and 0.23 μm or less.

6. 2. The film according to claim 1, wherein the arithmetic mean height Sa of at least one surface of the film is 0.010 μm or more and 0.050 μm or less.

7. 2. The film according to claim 1, wherein the film has a heat shrinkage in the machine direction measured at 140°C of 1.0% or more and 6.0% or less.

8. 10. The film of claim 1, wherein the film has a thickness of 10 μm or less.

9. 10. The film of claim 1 which is a monolayer film.

10. 10. The film of claim 1 which is a biaxially stretched film.

11. The film of claim 1 for use in a capacitor.

12. A metal laminated film comprising the film according to any one of claims 1 to 11 and a metal layer laminated on one or both sides of the film.

13. A capacitor comprising the film of claim 1.

14. A capacitor comprising the metal laminate film of claim 12.

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