Release film and production method for fuel cell

Abstract

Provided is a release film that comprises a base material layer and a release layer that is layered on at least one surface of the base material layer, the surface free energy of the release layer being no more than 35 mN / m, and the release layer including a resin that has at least one glass transition temperature in the range of 150°C–350°C as measured by viscoelasticity measurement.

Description

Release film and method for producing fuel cell

[0001] The present disclosure relates to a method for producing a release film and a fuel cell.

[0002] In solid polymer fuel cells and hydrogen supply devices, platinum catalysts or platinum-supported carbon are used as catalysts. To obtain a smooth catalyst layer, a method is known in which a catalyst ink is coated on a release film, dried, and then transferred.

[0003] Specifically, a polymer electrolyte fuel cell has a basic structure called a membrane electrode assembly (MEA). An MEA is obtained by laminating electrode membranes (catalyst layers or electrode catalyst membranes) primarily composed of carbon powder carrying a platinum group metal catalyst on both sides of a solid polymer electrolyte membrane, which is an ion exchange membrane, and further sandwiching the resulting laminate between a fuel gas supply layer and an air supply layer, which are conductive porous membranes. In this MEA, both the electrolyte membrane and the electrode membrane contain ion exchange resins, and the electrolyte membrane and the electrode membrane are formed by a casting method and / or a coating method. The electrolyte membrane and the electrode membrane are typically laminated by contacting the two layers, each formed on a support, and then thermocompressing them together at a temperature of approximately 130 to 150°C (approximately 150 to 200°C depending on the material used) at a pressure of approximately 1 to 10 MPa, followed by peeling off the support. Traditionally, a release film has been used as the support.

[0004] A wide variety of properties are required for release films, and extensive development efforts have been made to improve these properties. For example, Patent Document 1 discloses a release film that employs a laminate structure including a release layer formed from a resin composition containing a cyclic olefin resin (A) and a polymethylpentene resin (B) having a specific structure, and a substrate layer, thereby enabling the formation of an ion exchange layer of uniform thickness on the surface of the release layer by coating, and also improving the releasability between the ion exchange layer and the release layer. Patent Document 2 also discloses a release film that employs a laminate structure having a soft polyolefin layer as an intermediate layer and a polymethylpentene layer as at least one outermost layer, and that sets the thermal shrinkage rate in the stretching direction of the laminate within a specific range, thereby preventing fusion with a metal plate used for heating and pressurization, preventing the adhesive from flowing out and adhering to other components, preventing the exposed surface of the electrical circuit from being contaminated by the adhesive that has melted and flowed out, and further preventing wrinkles from occurring in the release film when heated and pressed, thereby enabling the formation of a flexible printed circuit board with a good appearance.

[0005] JP 2016-210129 A JP 2006-212954 A

[0006] As described above, extensive development has been conducted to improve the properties of release films, but further improvements in properties are desired. In particular, in the production of MEAs, where release films are used in high-temperature environments, release performance deteriorates. Development of release films that have excellent releasability even after use in high-temperature environments has not been sufficient, and there is still room for improvement. Therefore, an object of the present disclosure is to provide a release film that has excellent releasability even after exposure to high temperatures.

[0007] As a result of extensive research, the inventors have discovered that the above-mentioned problems can be solved in a release film comprising a base layer and a release layer by controlling the surface free energy of the release layer within a specific range and by incorporating into the release layer a resin having a glass transition temperature within a specific temperature range, and have arrived at the present invention.

[0008] That is, the invention according to the present disclosure has the following features. [1] A release film comprising a base layer and a release layer laminated on at least one surface of the base layer, wherein the surface free energy of the release layer is 35 mN / m or less, and the release layer contains a resin having one or more glass transition temperatures measured by viscoelasticity measurement within a range of 150°C or more and 350°C or less. [2] The release film according to [1], wherein the resin has one or more glass transition temperatures measured by viscoelasticity measurement within a range of 0°C or more and less than 150°C. [3] The release film according to [1] or [2], wherein the resin is a cyclic olefin copolymer containing a structural unit derived from a cyclic olefin monomer and a structural unit derived from an α-olefin monomer having 3 to 20 carbon atoms. [4] The release film according to any one of [1] to [3], wherein the average thickness of the release layer is 0.1 to 10.0 μm. [5] The release film according to any one of [1] to [4], wherein the base layer comprises one or more resins selected from the group consisting of polyethylene terephthalate, polyethylene naphthalate, polyphenylene sulfide, and polyimide. [6] The release film according to any one of [1] to [5], wherein an intermediate layer is provided between the base layer and the release layer. [7] The release film according to any one of [1] to [6], which is used in a manufacturing process of a fuel cell. [8] The release film according to [7], wherein the electrolyte membrane contained in the fuel cell comprises an electrolyte resin having an equivalent weight (EW) of 1000 or less. [9] A manufacturing method of a fuel cell, comprising a step of using the release film according to any one of [1] to [8].

[10] The manufacturing method of a fuel cell according to [9], wherein the electrolyte membrane contained in the fuel cell comprises an electrolyte resin having an equivalent weight (EW) of 1000 or less.

[0009] According to the present disclosure, it is possible to provide a release film that exhibits excellent releasability even after exposure to high temperatures.

[0010] The embodiments of the present disclosure are described in detail below. However, each configuration and combination thereof in each embodiment is merely an example, and additions, omissions, substitutions, and other modifications of configurations are possible as appropriate within the scope of the present disclosure. The present disclosure is not limited by the embodiments, but only by the scope of the claims. In this disclosure, a numerical range expressed using "to" means a range including the numerical values ​​before and after "to" as the lower and upper limits, and "A to B" means A or greater and B or less. In addition, while multiple embodiments are described in this disclosure, various conditions in each embodiment may be applied to each other to the extent applicable. In addition, the expression "A or B" in this disclosure can be interpreted as "at least one selected from the group consisting of A and B." In addition, in this disclosure, "multiple" means "two or more." The dimensions, materials, shapes, relative arrangements, etc. of the components described in this disclosure are merely examples.

[0011] <Release Film> A release film (hereinafter also simply referred to as "release film") according to one embodiment of the present disclosure is a release film comprising a base layer and a release layer laminated on at least one surface of the base layer, wherein the surface free energy of the release layer is 35 mN / m or less, and the release layer contains one or more resins having a glass transition temperature determined by viscoelasticity measurement within a range of 150° C. or more and 350° C. or less. The release film may include components other than the base layer and the release layer, but it is preferable that the release layer be disposed as the outermost layer on one surface of the release film.

[0012] After extensive research, the inventors have discovered that by setting the surface free energy of the release layer to 35 mN / m or less and using a resin contained in the release layer that has a glass transition temperature at a high temperature of 150°C or more and 350°C or less, excellent release properties can be obtained even after exposure to high temperatures.

[0013] The shape of the release film is not particularly limited as long as it is a film shape, and can be appropriately designed depending on the application. The shape of the release film in the planar direction may be, for example, a polygonal shape such as a triangular shape, a rectangular shape, or a pentagonal shape, a circular shape, an elliptical shape, or any other shape that matches the shape of the object to be attached. The conditions for the planar shape can also be applied to components such as the release layer or base layer described below.

[0014] The average thickness of the release film is not particularly limited, and the total value of the average thicknesses of the components such as the release layer and the substrate layer described below can be used.

[0015] [Release Layer] The release film includes a release layer laminated on at least one surface of the base layer. The shape of the release layer is not particularly limited as long as it is a layer shape (including shapes generally referred to as a film shape or a sheet shape), and can be appropriately designed depending on the application.

[0016] The average thickness of the release layer is not particularly limited, but is preferably 0.05 μm or more, more preferably 0.1 μm or more, even more preferably 0.5 μm or more, particularly preferably 0.8 μm or more, and is preferably 15.0 μm or less, more preferably 10.0 μm or less, even more preferably 5.0 μm or less, particularly preferably 1.5 μm or less. When the average thickness is equal to or greater than the lower limit of the above range, stable release properties can be ensured. Stable coating properties can be ensured. Furthermore, when the average thickness is equal to or less than the upper limit of the above range, excellent handling properties are achieved, suitability for roll-to-roll processes, and improved economic efficiency are achieved. The above average thickness can be measured, for example, using a spectral interference film thickness meter. In the case of a coating film, the average thickness may be calculated based on the coating amount (mass of resin composition per unit area) and density of the release layer.

[0017] From the viewpoint of ensuring sufficient releasability, the surface free energy of the release layer may be 35 mN / m or less, preferably 34 mN / m or less, more preferably 33 mN / m or less, and even more preferably 32 mN / m or less. Furthermore, the lower limit is not particularly limited, but from the viewpoint of ensuring coatability, it may be 20 mN / m or more, or even 24 mN / m or more. The means for controlling the surface free energy of the release layer is not particularly limited, but it is preferable to control it from the viewpoint of the resin composition. The method for controlling it from the viewpoint of the resin composition will be described in the explanation of the resin composition. The method for evaluating the surface free energy is as follows. First, the contact angles of water, diiodomethane, and 1-bromonaphthalene, each with a known surface free energy, are measured under conditions of 23°C and 50% RH using a contact angle meter (for example, Kyowa Interface Science Co., Ltd.'s fully automatic contact angle meter DMs-401). The obtained contact angle data is calculated using the "Kitazaki-Hata" theory to determine the dispersion component, polar component, and hydrogen bond component of the surface free energy of the release film, and the sum of these components is taken as the surface free energy γs. This calculation can usually be performed using calculation software within the contact angle meter software (for example, FAMAS).

[0018] (Resin Structure) The resin contained in the release layer is not particularly limited as long as it has at least one glass transition temperature measured by viscoelasticity measurement within the range of 150°C to 350°C. Hereinafter, the expression "having at least one glass transition temperature measured by viscoelasticity measurement within the range of 150°C to 350°C" will also be expressed as "having at least one glass transition temperature within the range of 150°C to 350°C." The type of resin is not particularly limited, and examples thereof include resins having a structure such as polyarylate, polyimide, polyamideimide, polyetherimide, polyethersulfone, or polysulfone. In addition to the above resins, examples thereof include polymers or copolymers of the following polymerizable monomers. In the present disclosure, a polymer (or copolymer) using monomer A as the monomer can be expressed as a polymer (or copolymer) having a structural unit derived from monomer A (also simply referred to as "monomer A unit"). Examples of polymerizable monomers are listed below.

[0019] Examples of polymerizable monomers include olefin monomers, conjugated diene monomers, aromatic vinyl monomers, vinyl carboxylic acid esters, vinyl halides, vinylidene halides, and (meth)acryloyl monomers. Among these, olefin monomers are preferred because they tend to reduce the surface free energy of the release layer. The polymerizable monomers may be used alone or in combination of two or more.

[0020] Examples of the olefin monomer include a chain olefin monomer and a cyclic olefin monomer.

[0021] As the chain olefin monomer, ethylene and α-olefins having 3 to 20 carbon atoms are preferred, α-olefins having 4 to 12 carbon atoms are more preferred, α-olefins having 4 to 10 carbon atoms are even more preferred, α-olefins having 4 to 8 carbon atoms are particularly preferred, and α-olefins having 6 to 8 carbon atoms are most preferred, as they tend to have a small surface free energy. These α-olefins may be linear or branched. More specific examples of the chain olefin monomer include ethylene, propylene, 1-butene, 1-pentene, 1-hexene, 3-methyl-1-butene, 3-methyl-1-pentene, 3-ethyl-1-pentene, 4-methyl-1-pentene, 4-methyl-1-hexene, 4,4-dimethyl-1-hexene, 4,4-dimethyl-1-pentene, 4-ethyl-1-hexene, 3-ethyl-1-hexene, 1-octene, 1-decene, 1-dodecene, and tetrafluoroethylene. Of these, 1-hexene, 1-octene, or 1-decene is preferred, 1-hexene or 1-octene is more preferred, and 1-octene is particularly preferred.

[0022] The chain olefin unit may be a chain olefin unit formed by ring-opening of a cyclic olefin, but is preferably a unit formed by polymerizing a chain olefin, since it is easy to control the ratio of both units.

[0023] The cyclic olefin monomer is a polymerizable cyclic olefin having an ethylenic double bond in the ring, and can be classified into monocyclic olefins, bicyclic olefins, tricyclic or higher polycyclic olefins, and the like.

[0024] Examples of the monocyclic olefin include cycloolefins having 4 to 12 carbon atoms, such as cyclobutene, cyclopentene, cycloheptene, and cyclooctene.

[0025] Examples of bicyclic olefins include 2-norbornene; norbornenes having a methyl group such as 5-methyl-2-norbornene or 5,5-dimethyl-2-norbornene; norbornenes having an alkenyl group such as 5-ethylidene-2-norbornene; norbornenes having an alkoxycarbonyl group such as 5-methoxycarbonyl-2-norbornene or 5-methyl-5-methoxycarbonyl-2-norbornene; norbornenes having a cyano group such as 5-cyano-2-norbornene; norbornenes having an aryl group such as 5-phenyl-2-norbornene or 5-phenyl-5-methyl-2-norbornene; octaline; or octalines having a methyl group such as 6-methyl-octahydronaphthalene.

[0026] Examples of polycyclic olefins include dicyclopentadiene; derivatives such as 2,3-dihydrodicyclopentadiene, methanooctahydrofluorene, tetracyclododecene, dimethanooctahydronaphthalene, dimethanocyclopentadienonaphthalene, and methanooctahydrocyclopentadienonaphthalene; adducts of cyclopentadiene and tetrahydroindene; and trimers and tetramers of cyclopentadiene.

[0027] Among these cyclic olefins, bicyclic olefins are preferred because they provide an excellent balance between the releasability and flexibility of the release film.In the resin, the proportion of bicyclic olefin (particularly norbornenes)-derived structural units relative to the total structural units derived from cyclic olefins is preferably 70 mol% or more, more preferably 80 mol% or more, and even more preferably 90 mol% or more, and the upper limit is not particularly limited, and may be 100 mol% or less.In particular, if the proportion of tricyclic or higher polycyclic olefins is large, it becomes difficult to use in production by a roll-to-roll method.

[0028] Representative examples of bicyclic olefins include norbornene (2-norbornene), which may have a substituent other than an alkyl group having 2 to 10 carbon atoms, and octaline (octahydronaphthalene), which may have a substituent other than an alkyl group having 2 to 10 carbon atoms. Examples of the substituent include a methyl group, an alkenyl group, an aryl group, a hydroxyl group, an alkoxy group, a carboxyl group, an alkoxycarbonyl group, an acyl group, a cyano group, an amide group, or a halogen atom. These substituents may be used alone or in combination of two or more. Of these substituents, non-polar groups such as a methyl group are preferred because they do not impair the releasability of the release film. Of these bicyclic olefins, norbornene or norbornenes (particularly norbornene), such as methylnorbornene, are particularly preferred.

[0029] The cyclic olefin may be a cyclic olefin in which an alkyl group having 2 to 10 carbon atoms is substituted on the cyclic olefin skeleton. A bicyclic olefin (particularly norbornene) is preferred as the cyclic olefin skeleton. Preferred examples of cyclic olefins having an alkyl group having 2 to 10 carbon atoms include alkylnorbornenes having 2 to 10 carbon atoms, such as 5-ethyl-2-norbornene, 5-propyl-2-norbornene, 5-butyl-2-norbornene, 5-pentyl-2-norbornene, 5-hexyl-2-norbornene, 5-octyl-2-norbornene, and 5-decyl-2-norbornene. These cyclic olefins may be used alone or in combination of two or more. Among these cyclic olefins, alkylnorbornenes having a linear alkyl group having 3 to 10 carbon atoms are preferred, and alkylnorbornenes having a linear alkyl group having 4 to 9 carbon atoms (particularly alkylnorbornenes having a linear alkyl group having 4 to 8 carbon atoms, such as 5-hexyl-2-norbornene) are more preferred.

[0030] Examples of the conjugated diene monomer include conjugated dienes having 4 to 16 carbon atoms, such as butadiene, isoprene, chloroprene, 1,3-pentadiene, 2,3-dimethyl-1,3-butadiene, piperylene, 3-butyl-1,3-octadiene, and 1-phenyl-1,3-butadiene.

[0031] Examples of aromatic vinyl monomers include styrene; alkylstyrenes such as o-methylstyrene, m-methylstyrene, p-methylstyrene, 2,4-dimethylstyrene, p-ethylstyrene, p-isopropylstyrene, p-n-butylstyrene, p-tert-butylstyrene, α-methylstyrene, and α-methyl-p-methylstyrene; alkoxystyrenes such as o-methoxystyrene, m-methoxystyrene, p-methoxystyrene, and p-tert-butoxystyrene; halostyrenes such as o-chlorostyrene, m-chlorostyrene, p-chlorostyrene, and p-bromostyrene; and hydroxystyrenes such as o-hydroxystyrene, m-hydroxystyrene, p-hydroxystyrene, and 3,5-dihydroxystyrene.

[0032] Examples of vinyl carboxylates include vinyl carboxylates having 3 to 10 carbon atoms, such as vinyl formate, vinyl acetate, vinyl propionate, and vinyl pivalate.

[0033] Examples of the vinyl halide include vinyl fluoride, vinyl chloride, and vinyl bromide.

[0034] Examples of the vinylidene halide include vinylidene fluoride, vinylidene chloride, and vinylidene bromide.

[0035] Examples of (meth)acryloyl monomers include methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, tert-butyl (meth)acrylate, n-pentyl (meth)acrylate, n-hexyl (meth)acrylate, cyclohexyl (meth)acrylate, n-heptyl (meth)acrylate, n-octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, nonyl (meth)acrylate, decyl (meth)acrylate, dodecyl (meth)acrylate, phenyl (meth)acrylate, toluyl (meth)acrylate, benzyl (meth)acrylate, 2-methoxyethyl (meth)acrylate, and 3-methyl-2 ... -methoxybutyl, stearyl (meth)acrylate, γ-(methacryloyloxypropyl)trimethoxysilane, trifluoromethylmethyl (meth)acrylate, 2-trifluoromethylethyl (meth)acrylate, 2-perfluoroethylethyl (meth)acrylate, 2-perfluoroethyl-2-perfluorobutylethyl (meth)acrylate, perfluoroethyl (meth)acrylate, perfluoromethyl (meth)acrylate, diperfluoromethylmethyl (meth)acrylate, 2-perfluoromethyl-2-perfluoroethylethyl (meth)acrylate, 2-perfluorohexylethyl (meth)acrylate, 2-perfluorodecylethyl (meth)acrylate, and 2-perfluorohexadecylethyl (meth)acrylate.

[0036] There are no particular limitations on the method for reducing the surface free energy of the release layer to 35 mN / m or less while ensuring heat resistance. This can be achieved, for example, by selecting a resin. Specifically, for example, by introducing a low surface free energy region into a resin having one or more glass transition temperatures in the range of 150°C to 350°C by graft polymerization or the like, a resin can be obtained that can reduce the surface free energy while ensuring heat resistance. The low surface free energy region refers to a region with a high density of monomers that can introduce the low surface free energy region (low surface free energy monomer assembly region), or a homopolymer, as described below. Examples of methods for introducing a low surface free energy region include a method of producing a resin having one or more glass transition temperatures in the range of 150°C to 350°C, and then introducing a structure composed of a monomer that can introduce a low surface free energy region, or a method of introducing a structure composed of the monomer when producing a resin having one or more glass transition temperatures in the range of 150°C to 350°C as measured by viscoelasticity measurement. In this case, one or more glass transition temperatures may be obtained in the range of 0° C. or more and less than 150° C. When the resin has one or more glass transition temperatures determined by viscoelasticity measurement in the range of 0° C. or more and less than 150° C., blocking and migration are easily suppressed.

[0037] Examples of monomers capable of introducing a region of low surface free energy include ethylene, α-olefin monomers, vinyl fluoride, vinylidene fluoride, trifluoroethylene, tetrafluoroethylene, chlorotrifluoroethylene, dichlorodifluoroethylene, pentafluoropropylene, hexafluoropropylene, and fluorine-containing compounds such as fluoroalkyl (meth)acrylates. Among these, α-olefin monomers are preferred, and from the viewpoints of environmental impact and productivity, α-olefins having 3 to 20 carbon atoms are more preferred. When introduced after the production of a resin having one or more of the above-mentioned monomers in the range of 150°C to 350°C, the monomer capable of introducing a region of low surface free energy may be polymerized alone, but may also be copolymerized with the above-mentioned chain olefin monomers, etc., as long as the surface free energy is within a range of 35 mN / m or less. A cyclic olefin copolymer containing a structural unit derived from a cyclic olefin monomer and a structural unit derived from an α-olefin monomer having 3 to 20 carbon atoms is preferred.

[0038] When copolymerizing to produce a resin having one or more glass transition temperatures measured by viscoelasticity within the range of 150°C to 350°C, the copolymerization sequence is not particularly limited, but it is preferable to control the surface free energy and glass transition temperature to fall within the desired range. For example, when using a resin containing a copolymer containing a chain olefin monomer unit and a cyclic olefin monomer unit, it is preferable to perform living copolymerization so that a segment of continuous chain olefin monomers capable of reducing surface free energy or a segment of high density of chain olefin monomers (low surface free energy monomer assembly region) is formed in the polymer. The location of the low surface free energy monomer assembly region in a molecule is not particularly limited, and it may be located at one end, both ends, the center, or elsewhere. To obtain such a living copolymer, a method can be used, such as controlling the polymerization temperature to form a low surface free energy monomer assembly region while suppressing chain transfer. For example, a living copolymer can be easily obtained by using a titanocene catalyst as a catalyst, in combination with a borate compound as a co-catalyst, and polymerizing at a low temperature of 20°C or less. When the copolymerization sequence is random, it is difficult to form the low surface free energy monomer assembly domains described above, and therefore the resin is preferably a living copolymer.

[0039] When the resin contains a chain olefin monomer unit, the mass ratio of the chain olefin monomer unit to the mass of the entire resin (100% by mass) is preferably 15% by mass or more, more preferably 20% by mass or more, even more preferably 25% by mass or more, particularly preferably 30% by mass or more, and preferably 50% by mass or less, more preferably 45% by mass or less, even more preferably 40% by mass or less, particularly preferably 35% by mass or less. If this ratio is equal to or greater than the lower limit of the above range, the surface free energy of the release layer is easily reduced. Furthermore, if this ratio is equal to or less than the upper limit of the above range, heat resistance is easily ensured.

[0040] When the resin contains a cyclic olefin monomer unit, the mass ratio of the cyclic olefin monomer unit to the mass of the entire resin (100% by mass) is preferably 50% by mass or more, more preferably 55% by mass or more, even more preferably 60% by mass or more, particularly preferably 65% ​​by mass or more, and preferably 85% by mass or less, more preferably 80% by mass or less, even more preferably 75% by mass or less, particularly preferably 70% by mass or less. If this ratio is equal to or greater than the lower limit of the above range, heat resistance is easily ensured. Furthermore, if this ratio is equal to or less than the upper limit of the above range, the surface free energy of the release layer is easily reduced.

[0041] When the resin contains a chain olefin monomer unit and a cyclic olefin monomer unit, the content ratio of the cyclic olefin monomer unit to the chain olefin monomer unit is not particularly limited, but is preferably 1 or more, more preferably 1.5 or more, even more preferably 2 or more, in molar ratio, and is preferably 5.5 or less, more preferably 5 or less, even more preferably 4.5 or less. If the ratio is equal to or higher than the lower limit of the above range, heat resistance is easily ensured. Furthermore, if the ratio is equal to or higher than the lower limit of the above range, the surface free energy of the release layer is easily reduced.

[0042] When the resin contains a chain olefin monomer unit and a cyclic olefin monomer unit, the ratio of the mass of monomer units other than the chain olefin monomer unit and the cyclic olefin monomer unit to the mass of the entire resin (100% by mass) may be 0% by mass, more than 0% by mass, or 1% by mass or more, or, from the viewpoint of easily achieving the effects of the present disclosure, may be 5% by mass or less, 4% by mass or less, or 3% by mass or less.

[0043] With regard to the glass transition temperature determined by viscoelasticity measurement, from the viewpoint of ensuring excellent heat resistance, there are no particular limitations as long as the resin has at least one glass transition temperature of 150°C or higher. However, this glass transition temperature is preferably 170°C or higher, more preferably 190°C or higher, and even more preferably 210°C or higher. From the viewpoint of ease of production, the glass transition temperature is preferably 350°C or lower, more preferably 330°C or lower, and even more preferably 300°C or lower.

[0044] The content of the above-mentioned resin in the release layer is not particularly limited, but from the viewpoint of easily obtaining the effects of the present disclosure, it is preferably 90% by mass or more, more preferably 95% by mass or more, and even more preferably 97% by mass or more. Furthermore, the upper limit is not particularly limited, and it may be 100% by mass, 100% by mass or less, or less than 100% by mass.

[0045] From the viewpoint of suppressing blocking and migration, the glass transition temperature within the range of 0° C. or higher and lower than 150° C. is preferably 40° C. or higher and 130° C. or lower, more preferably 50° C. or higher and 120° C. or lower, and even more preferably 60° C. or higher and 110° C. or lower. Furthermore, from the viewpoint of heat resistance, the glass transition temperature within the range of 150° C. or higher and 350° C. or lower is preferably 160° C. or higher and 320° C. or lower, more preferably 180° C. or higher and 300° C. or lower, and even more preferably 200° C. or higher and 280° C. or lower.

[0046] The glass transition temperature measured by viscoelasticity measurement can be measured by observing viscoelastic behavior using a solid-state rheometer. In the present application, the glass transition temperature is the peak-top temperature in a tan δ chart obtained by measurement in the temperature range of 150°C or higher and 350°C or lower. In the temperature range of 0°C or higher and lower than 150°C, the point at which the value in a chart obtained by differentiating the loss modulus value with temperature changes from positive to negative with increasing temperature, i.e., the maximum point of the loss modulus, is considered to be the peak, and the temperature at which the peak occurs is considered to be the glass transition temperature. In the present application, if the chart obtained by differentiating the loss modulus value with temperature in the temperature range of 0°C or higher and lower than 150°C does not have a point at which the value changes from positive to negative with increasing temperature, i.e., if the loss modulus chart does not substantially have a maximum point, it is considered that there is no glass transition temperature in that temperature range.

[0047] The number average molecular weight of the resin, as measured by gel permeation chromatography (GPC) in terms of polystyrene, may be, for example, 10,000 to 500,000, preferably 20,000 to 450,000, more preferably 30,000 to 430,000, and even more preferably 50,000 to 400,000. If the number average molecular weight is too small, film-forming properties tend to decrease, while if it is too large, viscosity increases, making it difficult to handle.

[0048] The method for analyzing the resin structure is not particularly limited. １ This can be done by a known method using H-NMR or the like.

[0049] (Method for Producing Resin) The method for producing the resin is not particularly limited and can be carried out by a known method or a combination of known methods. For example, when the resin is a cyclic olefin copolymer, addition polymerization can be used, specifically addition polymerization using a Ziegler catalyst, addition polymerization using a metallocene catalyst, or the like. Specific polymerization methods include those described in, for example, JP 2004-107442 A, JP 2007-119660 A, JP 2008-255341 A, Macromolecules, 43, 4527 (2010), Polyhedron, 24, 1269 (2005), J. Appl. Polym. Sci, 128 (1), 216 (2013), and Polymer Journal, 43, 331 (2011). Furthermore, catalysts synthesized by the methods described in these documents can also be used as catalysts for polymerization. The conditions when the resin is a cyclic olefin copolymer will be explained in more detail below.

[0050] The proportion of the catalyst may be, for example, 0.0001 to 0.05 parts by mass, preferably 0.0005 to 0.01 parts by mass, and more preferably 0.001 to 0.01 parts by mass, relative to 100 parts by mass of all the monomers constituting the resin.

[0051] Furthermore, conventional catalysts and co-catalysts may be used in the polymerization of the resin. Examples of the catalyst include titanocene catalysts, and examples of the co-catalyst include aluminoxane compounds, which are partial hydrolysates of alkylaluminum (raw material) such as trimethylaluminum, and borate compounds.

[0052] Specific examples of titanocene catalysts include (isopropylamido)dimethyl-9-fluorenylsilanetitanium dimethyl, (isobutylamido)dimethyl-9-fluorenylsilanetitanium dimethyl, (t-butylamido)dimethyl-9-fluorenylsilanetitanium dimethyl, (isopropylamido)dimethyl-9-fluorenylsilanetitanium dichloride, (isobutylamido)dimethyl-9-(3,6-dimethylfluorenyl)silanetitanium dichloride, (t-butylamido)dimethyl-9-fluorenylsilanetitanium dichloride, (isopropylamido)dimethyl-9-fluorenylsilanetitanium dichloride, (isobutylamido)dimethyl-9-(3,6-dimethylfluorenyl)silanetitanium dichloride, (t-butylamido)dimethyl-9-(3,6-dimethylfluorenyl)silanetitanium dimethyl, (isopropylamido)dimethyl-9-[3,6-di(i-propyl)fluorenyl]silanetitanium dichloride, (isobutylamido)dimethyl-9-[3,6-di(i-propyl)fluorenyl]silanetitanium dichloride, (t-butylamido)dimethyl-9- [3,6-di(i-propyl)fluorenyl]silanetitanium dimethyl, (isopropylamido)dimethyl-9-[3,6-di(t-butyl)fluorenyl]silanetitanium dichloride, (isobutylamido)dimethyl-9-[3,6-di(t-butyl)fluorenyl]silanetitanium dichloride, (t-butylamido)dimethyl-9-[3,6-di(t-butyl)fluorenyl]silanetitanium dimethyl, (isopropylamido)dimethyl-9-[2,7-di(t-butyl)fluorenyl]silanetitanium dichloride, (isobutylamido)dimethyl- Examples thereof include 9-[2,7-di(t-butyl)fluorenyl]silanetitanium dichloride, (t-butylamido)dimethyl-9-[2,7-di(t-butyl)fluorenyl]silanetitanium dimethyl, (isopropylamido)dimethyl-9-(2,3,6,7-tetramethylfluorenyl)silanetitanium dichloride, (isobutylamido)dimethyl-9-(2,3,6,7-tetramethylfluorenyl)silanetitanium dichloride, and (t-butylamido)dimethyl-9-(2,3,6,7-tetramethylfluorenyl)silanetitanium dimethyl.

[0053] Examples of the aluminoxane compound include aluminoxanes having an alkyl group having 1 to 8 carbon atoms, such as methylisobutylaluminoxane or methylaluminoxane, and polymers of aluminoxanes having an alkyl group having 1 to 8 carbon atoms, such as polymethylaluminoxane. These aluminoxane compounds may be used alone or in combination of two or more.

[0054] The proportion of the co-catalyst is not particularly limited as long as it is a proportion that can exhibit sufficient catalytic activity, and can be selected depending on the catalytic activity. When an aluminoxane compound is used, the proportion of aluminum atoms per catalyst molecule may usually be from 1 to 10,000 times, preferably 10 to 5,000 times, and more preferably about 50 to 2,000 times.

[0055] When a titanocene catalyst is used as the catalyst, it is preferable to use a borate compound as a co-catalyst from the viewpoint of forming a low surface free energy monomer assembly region and imparting living polymerization properties. As the borate compound, any borate compound that has conventionally been used as a co-catalyst in the homopolymerization or copolymerization of cyclic olefin monomers can be used without particular limitation. Preferred examples of the borate compound include triphenylmethylium tetrakis(pentafluorophenyl)borate, dimethylphenylammonium tetrakis(pentafluorophenyl)borate, N,N-dimethylanilinium tetrakis(pentafluorophenyl)borate, and N-methyldin-normal-decylammonium tetrakis(pentafluorophenyl)borate.

[0056] As raw materials for the resin, monomers that can constitute the resin described in the section on resin composition can be used, and from these, an appropriate monomer can be selected so as to achieve both surface free energy and heat resistance properties.

[0057] As mentioned above, the resin may be a graft copolymer. In this case, the resin can be obtained by, for example, obtaining a resin having one or more glass transition temperatures in the range of 150° C. to 350° C., and then grafting a monomer capable of introducing a region with low surface free energy onto the resin. Specific polymerization conditions, etc. can be set with reference to known methods.

[0058] (Other Components) The release layer may contain resins other than the above-described resins (other resins) and conventional additives as long as the effects of the present disclosure are obtained. Examples of other resins include linear olefin resins (polyethylene, polypropylene, etc.). Examples of conventional additives include fillers, lubricants (waxes, fatty acid esters, fatty acid amides, etc.), antistatic agents, stabilizers (antioxidants, heat stabilizers, light stabilizers, etc.), flame retardants, viscosity modifiers, thickeners, and antifoaming agents. Furthermore, the release layer may contain organic or inorganic particles (particularly antiblocking agents such as zeolites) as long as the surface smoothness is not impaired.

[0059] The arithmetic mean roughness (Ra) of the surface of the release layer in accordance with JIS B0601 is not particularly limited, but is preferably 1 μm or less (for example, 1 nm to 1 μm), more preferably 1 to 800 nm, even more preferably 1 to 500 nm, and particularly preferably 1 to 300 nm (particularly 1 to 200 nm). If Ra is too large, there is a risk that the appropriate adhesion to the ion exchange layer and the adhesion to the substrate layer will be reduced.

[0060] [Substrate Layer] The release film includes a substrate layer having a release layer laminated on at least one surface. The substrate layer is preferably formed of a material with high heat resistance and dimensional stability, from the viewpoint of improving the dimensional stability of the release film, for example, during the fuel cell manufacturing process, suppressing elongation even when tension is applied in a roll-to-roll process, maintaining high dimensional stability even when exposed to high temperatures during drying processes and thermocompression bonding processes, and suppressing peeling from the ion exchange layer of the electrolyte membrane, electrode membrane, etc. Specifically, the substrate layer may be formed of a resin with an elastic modulus of 100 to 1000 MPa at 150°C. The elastic modulus may be, for example, 120 to 1000 MPa, preferably 150 to 1000 MPa, and more preferably about 200 to 1000 MPa. If the elastic modulus is too small, the dimensional stability of the release film may be reduced, causing peeling between the release layer and the ion exchange layer during roll-to-roll manufacturing, which may reduce the productivity of the fuel cell.

[0061] As such a resin, for example, various thermoplastic resins and thermosetting resins can be used, but thermoplastic resins are preferred because of their flexibility, which allows them to be manufactured using a roll-to-roll process. Examples of thermoplastic resins include polyolefins (such as polypropylene-based resins or cyclic polyolefins), polyvinyl alcohol-based polymers, polyesters, polyamides, polyimides, polycarbonates, polyphenylene ethers, polyphenylene sulfide, and cellulose derivatives (such as cellulose esters such as cellulose acetate). These thermoplastic resins may be used alone or in combination of two or more. In the present disclosure, since the release layer has excellent adhesion to the substrate layer, it is preferable that these thermoplastic resins substantially do not have reactive groups or polar groups (such as side chains formed by reactive groups) for improving adhesion. Among these thermoplastic resins, from the viewpoint of heat resistance, one or more resins selected from the group consisting of polyesters such as polyethylene terephthalate or polyethylene naphthalate, polyphenylene sulfide, and polyimides are preferred. Polyesters are particularly preferred because of their excellent balance between heat resistance and flexibility.

[0062] The base layer may be formed of a stretched film from the viewpoint of improving the film strength of the release film. The stretching may be uniaxial stretching, but biaxial stretching is preferred from the viewpoint of improving the film strength. The stretching ratio may be, for example, 1.5 times or more (e.g., 1.5 to 6 times) in each of the longitudinal and transverse directions, preferably 2 to 5 times, and more preferably about 3 to 4 times. If the stretching ratio is too low, the film strength is likely to be insufficient.

[0063] The base layer may also contain the conventional additives exemplified in the section on the release layer above. The content of the resin in the base layer is, for example, preferably 80% by mass or more, more preferably 90% by mass or more, and even more preferably 95% by mass or more (for example, 95 to 100% by mass) relative to the entire base layer.

[0064] The surface smoothness of the substrate layer is not particularly limited as long as a release layer can be formed by a treatment such as coating, but the arithmetic mean roughness Ra in accordance with JIS B0601 may be 1 μm or less, and preferably 100 nm or less (for example, 10 to 100 nm).

[0065] The surface of the substrate layer may be subjected to a surface treatment to improve adhesion to the release layer. Examples of the surface treatment include conventional surface treatments such as corona discharge treatment, flame treatment, plasma treatment, ozone treatment, or ultraviolet irradiation treatment. Of these, corona discharge treatment is preferred.

[0066] The substrate layer may have an easy-adhesion layer formed of a conventional adhesive resin (for example, when the substrate layer is a polyester resin, the easy-adhesion layer may be formed of an adhesive resin such as a low-molecular-weight polyester resin, an aliphatic polyester resin, or an amorphous polyester resin). The average thickness of the easy-adhesion layer is not particularly limited and may be, for example, 30 to 200 nm, preferably 40 to 180 nm, and more preferably 50 to 150 nm.

[0067] The average thickness of the substrate layer is not particularly limited, but may be, for example, 1 to 300 μm, preferably 5 to 200 μm, and more preferably 10 to 100 μm (particularly 20 to 80 μm). If the substrate layer is too thick, production using a roll-to-roll system becomes difficult, while if it is too thin, dimensional stability and transportability using a roll-to-roll system decrease, and wrinkles and the like may be introduced.

[0068] [Intermediate layer] An intermediate layer may be further provided between the above-mentioned substrate layer and release layer to improve the adhesion between the two layers. By interposing the intermediate layer, the release layer can be firmly fixed to the substrate layer even if the substrate layer does not have an easy-adhesion layer or is not surface-treated. The intermediate layer may be a conventional adhesive layer, but when the release layer contains a cyclic olefin resin, it is preferable that the intermediate layer contains a chlorine-containing resin in order to improve the adhesion of the release layer to the substrate layer.

[0069] The chlorine-containing resin may be a chlorinated resin such as chlorinated polyethylene or chlorinated polypropylene, but is usually a polymer containing a chlorine-containing monomer as a polymerization component. Examples of the chlorine-containing monomer include vinyl chloride monomer and vinylidene chloride monomer. These chlorine-containing monomers can be used alone or in combination. Among these, vinylidene chloride monomer is preferred in terms of adhesion to the substrate layer and the release layer (particularly the release layer).

[0070] The chlorine-containing resin may contain copolymerizable units other than the chlorine-containing monomer units. Examples of polymerization components for forming the other copolymerizable units include the monomers exemplified in the resin section above (olefin-based monomers, vinyl ester-based monomers, diene-based monomers, (meth)acrylic monomers, etc.). The monomers may be used alone or in combination of two or more. Among the above-mentioned monomers, vinyl acetate, (meth)acrylic acid, (meth)acrylic acid alkyl esters, (meth)acrylic acid hydroxyalkyl esters, glycidyl (meth)acrylate, (meth)acrylonitrile, etc. are commonly used.

[0071] The proportion of the other copolymerizable units (copolymerizable monomers) may be such that the properties of the chlorine-containing resin are not impaired, and is usually 0.1 to 50 mass% (e.g., 0.3 to 25 mass%), preferably 0.5 to 20 mass%, and more preferably 1 to 15 mass% (particularly 3 to 10 mass%), based on the total mass of the chlorine-containing resin.

[0072] Examples of chlorine-containing resins include vinyl chloride polymers [homopolymers of vinyl chloride monomers (polyvinyl chloride), or vinyl chloride copolymers (vinyl chloride-vinyl acetate copolymers, vinyl chloride-(meth)acrylic acid ester copolymers, etc.)], or vinylidene chloride polymers [homopolymers of vinylidene chloride (polyvinylidene chloride), or vinylidene chloride copolymers (vinylidene chloride-vinyl chloride copolymers, vinylidene chloride-vinyl acetate copolymers, vinylidene chloride-(meth)acrylic acid copolymers, vinylidene chloride-(meth)acrylic acid ester copolymers, vinylidene chloride-(meth)acrylonitrile copolymers, etc.)]. These chlorine-containing resins may be used alone or in combination of two or more.

[0073] Among these chlorine-containing resins, vinylidene chloride polymers (particularly vinylidene chloride copolymers such as vinylidene chloride-vinyl chloride copolymers) are preferred because they can improve the adhesion between the release layer and the substrate layer. In vinylidene chloride-vinyl chloride copolymers, the ratio (molar ratio) of vinylidene chloride units to vinyl chloride units is, for example, about 99 / 1 to 5 / 95, preferably 97 / 3 to 10 / 90, and more preferably 95 / 5 to 50 / 50. The vinylidene chloride polymer may not contain emulsifiers, surfactants, etc., which are contained in aqueous emulsions.

[0074] The number average molecular weight of the chlorine-containing resin may be, for example, 10,000 to 500,000, preferably 20,000 to 250,000, and more preferably 25,000 to 100,000, in terms of polystyrene, as determined by gel permeation chromatography (GPC).

[0075] The intermediate layer may further contain an adhesive component, if necessary, to enhance adhesion between the release layer and the substrate layer. Examples of the adhesive component include polyolefin resins (e.g., modified polyethylenes such as polyethylene graft copolymers), acrylic resins, polyamide resins, polyester resins (e.g., thermoplastic copolymer polyesters), and reactive adhesive components (e.g., isocyanate compounds or imino group-containing polymers (e.g., polyethyleneimine)). These adhesive components can be used alone or in combination. Among these adhesive components, reactive adhesive components are preferred, and isocyanate compounds are particularly preferred.

[0076] The isocyanate compound may be a prepolymer or oligomer having a terminal isocyanate group, or may generally be a polyisocyanate such as an aliphatic isocyanate, an alicyclic isocyanate, or an aromatic isocyanate, or a derivative thereof.

[0077] Examples of aliphatic isocyanates include trimethylene diisocyanate, tetramethylene diisocyanate, and hexamethylene diisocyanate (HDI). Examples of alicyclic isocyanates include 1,3-cyclopentane diisocyanate, 1,3-cyclopentene diisocyanate, 1,4-cyclohexane diisocyanate, 1,3-cyclohexane diisocyanate, isophorone diisocyanate (IPDI), hydrogenated tolylene diisocyanate (hydrogenated TDI), hydrogenated xylylene diisocyanate (hydrogenated XDI), and hydrogenated diphenylmethane-4,4'-diisocyanate (hydrogenated MDI). Examples of the aromatic isocyanate include tolylene diisocyanate (TDI), xylylene diisocyanate (XDI), tetramethylxylylene diisocyanate (TMXDI), and diphenylmethane-4,4'-diisocyanate (MDI).

[0078] Examples of the isocyanate derivatives include polymers of the above isocyanates [dimers (uretdione group-containing isocyanates), trimers (isocyanurate ring-containing isocyanates), pentamers, heptamers, etc.], modified products of the above isocyanates (allophanate-modified isocyanates, biuret-modified isocyanates, urea-modified isocyanates, carbodiimide-modified isocyanates, etc.), and adducts of polyhydric alcohols and the above isocyanates.

[0079] Among these isocyanate compounds, aromatic isocyanates such as TDI, MDI, XDI, or TMXDI, or derivatives thereof are preferred.

[0080] The proportion of the adhesive component may be 0.1 to 30 parts by mass, preferably 0.5 to 20 parts by mass, and more preferably 1 to 10 parts by mass, relative to 100 parts by mass of the chlorine-containing resin.

[0081] The intermediate layer may also contain the conventional additives exemplified in the section on the release layer above. The total proportion of the chlorine-containing resin and adhesive component in the intermediate layer may be, for example, 80% by mass or more, preferably 90% by mass or more, and more preferably 95% by mass or more (e.g., 95 to 100% by mass), based on the entire intermediate layer.

[0082] The average thickness of the intermediate layer is not particularly limited, but may be, for example, 0.01 to 80 μm, preferably 0.05 to 50 μm, and more preferably 0.1 to 20 μm (particularly 0.2 to 10 μm).

[0083] [Characteristics of Release Film] The total light transmittance of the release film is not particularly limited, but may be 70% or more, preferably 80 to 99%, more preferably 82 to 95%, and even more preferably 84 to 92% (particularly 85 to 90%). The total light transmittance can be measured in accordance with JIS K7361-1.

[0084] The haze of the release film is not particularly limited, but may be 30% or less (for example, 0.1 to 30%), preferably 0.2 to 20%, more preferably 0.3 to 15%, and even more preferably 0.5 to 10% (particularly 1 to 5%). Haze can be measured in accordance with JIS K7136.

[0085] <Method for Producing Release Film> The method for producing the release film described above is not particularly limited, but from the viewpoint of facilitating the formation of a thin film with a smooth surface, a method of coating a release layer coating agent (for example, a solution-like coating agent) containing a resin composition and a solvent onto a base layer (or the intermediate layer, if an intermediate layer is formed), specifically, a method of coating (or casting) a coating agent containing a resin and a solvent onto a base layer and then drying may be used.

[0086] Examples of the coating method include conventional methods such as a roll coater, air knife coater, blade coater, rod coater, reverse coater, bar coater, comma coater, die coater, gravure coater, screen coater method, spray method, spinner method, etc. Among these methods, the blade coater method, bar coater method, and gravure coater method are commonly used.

[0087] For example, when the resin is a cyclic olefin copolymer, the solvent preferably contains at least a hydrocarbon (a hydrocarbon that may contain a halogen atom) in view of excellent solubility for the resin. Examples of hydrocarbons include aliphatic hydrocarbons (aliphatic hydrocarbons having 5 to 12 carbon atoms, such as pentane, hexane, or heptane), alicyclic hydrocarbons (cycloalkanes having 3 to 8 carbon atoms, which may have an alkyl group, such as cyclopentane, methylcyclopentane, cyclohexane, or methylcyclohexane), and aromatic hydrocarbons (benzene, toluene, or xylene). Examples of hydrocarbons containing halogen atoms include chlorinated hydrocarbons (halogenated aliphatic hydrocarbons having 1 to 6 carbon atoms, such as chloroform, chloromethanes such as carbon tetrachloride, or chloroethanes such as trichloroethane), hydrocarbons containing chlorine atoms or fluorine atoms (dichlorodifluoroethane, trichlorodifluoroethane, trichlorotrifluoroethane, etc.), brominated hydrocarbons (tetrabromoethane, etc.), and iodinated hydrocarbons (carbon tetraiodide, etc.). These solvents may be used alone or in combination of two or more.

[0088] Among these solvents, preferred are cycloalkanes having 4 to 8 carbon atoms which may have a methyl group, such as cyclopentane or cyclohexane, and from the viewpoint of solubility, particularly preferred are cycloalkanes having 5 to 7 carbon atoms which have a methyl group, such as methylcyclohexane.

[0089] The solvent is not limited to those described above and may be changed appropriately depending on the resin used. For example, when polyarylate is used as the resin, examples of the solvent include chlorine-based solvents such as methylene chloride, 1,2-dichloroethane, chloroform, carbon tetrachloride, chlorobenzene, 1,1,2,2-tetrachloroethane, and 1,1,1-trichloroethane; aromatic hydrocarbons such as toluene, benzene, and xylene; and tetrahydrofuran. When polyimide is used as the resin, examples of the solvent include N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, N-butyl-2-pyrrolidone, γ-butyrolactone, γ-valerolactone, 1,3-dimethylimidazolidinone, N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, methyl ethyl ketone, cyclohexanone, and cyclopentanone. When polyamideimide is used as the resin, examples of the solvent include amide-based solvents.

[0090] The resin composition concentration (active ingredient concentration) in the coating agent for the release layer may be, for example, 0.1 to 50 mass %, preferably 0.3 to 30 mass %, and more preferably 0.5 to 20 mass % (particularly 0.8 to 15 mass %).

[0091] The drying may be natural drying, or may be performed by heating to volatilize the solvent. The drying temperature may be 50°C or higher, or may be 50 to 200°C, preferably 60 to 150°C, and more preferably 80 to 120°C.

[0092] When forming an intermediate layer, the method for forming the intermediate layer is not particularly limited, but a method of coating a coating agent for the intermediate layer (for example, a solution-like coating agent) containing a chlorine-containing resin and a solvent onto the base layer is preferred because it is easy to form a uniform and thin intermediate layer, and specifically, a method of coating (or casting) a coating agent containing a chlorine-containing resin and a solvent onto the base layer and then drying it may be used. As the coating method, a coating method for forming a release layer can be used.

[0093] The solvent is not particularly limited as long as it can dissolve the chlorine-containing resin. For example, polar solvents can be used in addition to the nonpolar solvents exemplified for coating the release layer. Examples of polar solvents include dialkyl ketones such as acetone or methyl ethyl ketone, and ethers such as tetrahydrofuran or dioxane. These solvents can be used alone or in combination of two or more. Among these, a combination of a nonpolar solvent and a polar solvent is preferred, and the mass ratio of the two may be approximately 1 / 99 to 50 / 50 (particularly 10 / 90 to 40 / 60). In particular, the nonpolar solvent may be an aromatic hydrocarbon (e.g., toluene). Alternatively, the polar solvent may be a combination of a dialkyl ketone (e.g., methyl ethyl ketone) and a cyclic ether (e.g., tetrahydrofuran), and the mass ratio of the two may be approximately 1 / 99 to 50 / 50 (particularly 10 / 90 to 30 / 70).

[0094] The resin composition concentration (active ingredient concentration) in the coating agent for the intermediate layer may be, for example, 0.1 to 50 mass %, preferably 0.3 to 20 mass %, and more preferably 0.5 to 10 mass % (particularly 0.8 to 5 mass %).

[0095] The drying may be natural drying, or may be performed by heating to evaporate the solvent. The drying temperature may be 50°C or higher, or may be 50 to 200°C, preferably 80 to 180°C, and more preferably 100 to 150°C.

[0096] By selecting a substrate layer with excellent flexibility, the release film can be produced by a roll-to-roll method, thereby improving productivity.

[0097] <Fuel Cells> The release film described above has excellent releasability and can be used as an industrial release film, etc., and has excellent coatability for an ion exchange layer and appropriate adhesion and releasability to the ion exchange layer, so it can be used in the manufacturing process of a fuel cell. For example, it can be used in the manufacturing process of a membrane electrode assembly (MEA) included in a fuel cell. More specifically, it can be used as a release film for manufacturing a membrane electrode assembly (MEA) of a polymer electrolyte fuel cell or a hydrogen supply device, and is preferably used as a film to be peeled from an MEA after laminating an electrolyte membrane and / or an electrode membrane containing an ion exchange resin thereon to manufacture the MEA.

[0098] When the release film is used in the manufacturing process of a fuel cell, from the viewpoint of proton conductivity, the electrolyte membrane included in the fuel cell preferably contains an electrolyte resin having an equivalent weight (EW; number of grams of polymer per equivalent of ion exchange groups) of 1000 or less. From the same viewpoint, the EW of the electrolyte resin is preferably 1200 or less, more preferably 1000 or less, and even more preferably 900 or less, and from the viewpoint of ease of synthesis, it is preferably 500 or more, more preferably 600 or more, and even more preferably 700 or more. The type of electrolyte resin is not particularly limited, and for example, the types of ion exchange resins described in the section on laminates below can be similarly applied.

[0099] A method for manufacturing a fuel cell according to another embodiment of the present disclosure is a method for manufacturing a fuel cell that includes a step of using the above-described release film. For example, the release film can be used in manufacturing a fuel cell membrane electrode assembly (MEA) as described above. A specific method for manufacturing a fuel cell membrane electrode assembly (MEA) will be described later. Known processes can be adopted for the steps in manufacturing a fuel cell other than the step of manufacturing the fuel cell membrane electrode assembly (MEA). Furthermore, the configuration and manufacturing conditions of the fuel cell membrane electrode assembly (MEA) included in the fuel cell can be appropriately adopted from the configuration and manufacturing conditions described in the present disclosure.

[0100] Another embodiment of the present disclosure is the use of the above-described release film in a fuel cell. The manner of use is not particularly limited, but for example, as described above, it can be used in the production of a fuel cell membrane electrode assembly (MEA).

[0101] A laminate according to another embodiment of the present disclosure will now be described. The laminate is preferably used for producing a membrane electrode assembly (MEA) for a fuel cell or the like.

[0102] <Laminate> A laminate according to another embodiment of the present disclosure includes the release film described above and an ion exchange layer laminated on the release layer of the release film and containing an ion exchange resin. When the release film is a release film for producing a polymer electrolyte fuel cell, the laminate has an ion exchange layer (electrolyte membrane, electrode membrane, or membrane electrode assembly) containing an ion exchange resin adhered to the release layer of the release film. Therefore, the laminate may be a laminate in which the ion exchange layer is laminated on the release layer of the release film (a laminate of a release film and an ion exchange layer).

[0103] As the ion exchange resin, a conventional ion exchange resin used in fuel cells can be used. Among them, a cation exchange resin such as a strong acid cation exchange resin or a weak acid cation exchange resin is preferred. Examples include ion exchange resins having a sulfonic acid group, a carboxyl group, a phosphoric acid group, a phosphonic acid group, or the like (more specifically, ion exchange resins into which a sulfonic acid group, a carboxyl group, a phosphoric acid group, a phosphonic acid group, or the like has been introduced as an electrolyte group having an electrolyte function), and an ion exchange resin having a sulfonic acid group (an ion exchange resin into which a sulfonic acid group has been introduced as an electrolyte group) is particularly preferred.

[0104] The ion exchange resin having a sulfonic acid group can be any of various resins having a sulfonic acid group, such as polyolefins such as polyethylene and polypropylene, (meth)acrylic resins, styrene resins, polyacetal, polyester, polycarbonate, polyamide, polyamideimide, polyimide, polyether, polyetherimide, polyether ketone, polyether ether ketone, polysulfone, polyethersulfone, polyphenylene sulfide, and fluororesins.

[0105] Among ion exchange resins having sulfonic acid groups, fluororesins having sulfonic acid groups or sulfonated crosslinked polystyrene are preferred, and polystyrene-graft-polyethylene tetrafluoroethylene copolymers or polystyrene-graft-polytetrafluoroethylene copolymers having sulfonic acid groups may also be used. Among these, fluororesins having sulfonic acid groups (fluorohydrocarbon resins in which at least some hydrogen atoms are substituted with fluorine atoms, etc.) are particularly preferred from the standpoint of mold releasability, etc. In particular, in solid polymer fuel cells, fluororesins having sulfonic acid groups (or -CF ２ CF ２ SO ３ H group), for example, a copolymer (block copolymer, etc.) of [2-(2-sulfotetrafluoroethoxy)hexafluoropropoxy]trifluoroethylene and tetrafluoroethylene, etc., is preferably used.

[0106] The ion exchange capacity of the ion exchange resin may be 0.1 meq / g or more, for example, 0.1 to 2.0 meq / g, preferably 0.2 to 1.8 meq / g, and more preferably 0.3 to 1.5 meq / g (particularly 0.5 to 1.5 meq / g).

[0107] As such an ion exchange resin, a commercially available product such as "Nafion" (registered trademark) manufactured by DuPont can be used. Note that the ion exchange resin described in JP 2010-234570 A may also be used.

[0108] The ion exchange layer may be an electrolyte membrane formed of an ion exchange resin, or an electrode membrane containing an ion exchange resin and catalyst particles.

[0109] In the electrode membrane (catalyst layer or electrode catalyst membrane), the catalyst particles contain a metal component having catalytic activity (particularly, a noble metal such as platinum (Pt) or an alloy containing a noble metal), and typically, the electrode membrane for the cathode electrode contains platinum, while the electrode membrane for the anode electrode contains a platinum-ruthenium alloy. Furthermore, the catalyst particles are typically used as composite particles in which the metal component is supported on a conductive material (e.g., a carbon material such as carbon black). In the electrode membrane, the proportion of the ion exchange resin may be, for example, 5 to 300 parts by mass, preferably 10 to 250 parts by mass, and more preferably 20 to 200 parts by mass, relative to 100 parts by mass of the catalyst particles.

[0110] The ion exchange layer may also contain the conventional additives exemplified in the release layer section, and may also contain, for example, inorganic materials such as inorganic particles and inorganic fibers (carbonaceous materials, glass, ceramics, etc.).

[0111] The ion exchange layer may be formed on at least one surface of the release layer, and may be formed on both surfaces of the release layer, or may be formed on only one surface of the release layer.

[0112] The average thickness of the ion exchange layer may be, for example, 1 to 500 μm, preferably 1.5 to 300 μm, and more preferably 2 to 200 μm.

[0113] The average thickness of the electrolyte membrane may be, for example, 1 to 500 μm, preferably 5 to 300 μm, and more preferably 10 to 200 μm.

[0114] The average thickness of the electrode film may be, for example, 1 to 100 μm, preferably 2 to 80 μm, and more preferably 2 to 50 μm.

[0115] <Method for manufacturing laminate and membrane electrode assembly> A laminate according to another embodiment of the present disclosure is obtained by a manufacturing method including a lamination step of laminating an ion exchange layer (an electrolyte membrane containing an ion exchange resin and / or an electrode membrane containing an ion exchange resin) on the release layer of the release film described above. The ion exchange layer is usually laminated by a coating method. The laminate may be manufactured, for example, by laminating an electrolyte membrane on the release layer of a first film (release film) by coating to manufacture a laminate in which the electrolyte membrane is laminated on the first release film, and by laminating an electrode membrane on the release layer of a second film by coating to manufacture a laminate in which the electrode membrane is laminated on the second release film.

[0116] In order to form the electrolyte membrane and the electrode membrane by coating (or casting), the electrolyte membrane and the electrode membrane are subjected to coating in the form of a solution or dispersion in which the ion exchange resin (and catalyst particles) are dissolved or dispersed in a solvent.

[0117] Examples of the solvent include water, alcohols (e.g., alkanols having 1 to 4 carbon atoms, such as methanol, ethanol, isopropanol, or 1-butanol), ketones (e.g., acetone or methyl ethyl ketone), ethers (e.g., dioxane or tetrahydrofuran), and sulfoxides (e.g., dimethyl sulfoxide). These solvents may be used alone or in combination of two or more. Of these solvents, water or a mixed solvent of water and an alkanol having 1 to 4 carbon atoms is commonly used from the viewpoint of ease of handling. The concentration of the solute or solid content (ion exchange resin or catalyst particles) in the solution or dispersion may be, for example, 1 to 80% by mass, preferably 2 to 60% by mass, and more preferably 3 to 50% by mass.

[0118] Examples of the coating method include the conventional methods exemplified in the method for producing a release film, and among these methods, the blade coater method, the bar coater method, etc. are commonly used.

[0119] After coating the solution containing the ion exchange resin (and catalyst particles), the solvent may be evaporated by heating and drying. The drying temperature may be 50°C or higher, for example, 80 to 200°C (particularly 100 to 150°C) for an electrolyte membrane, and 50 to 150°C (particularly 60 to 120°C) for an electrode membrane.

[0120] The laminate obtained in the lamination step is usually subjected to the bonding step, but in the case of continuous production, the laminate is transported to a location in the lamination step where the bonding step is carried out before the bonding step.

[0121] Because the release film has excellent flexibility, the lamination process involving such transportation can be carried out using a roll-to-roll method, thereby improving productivity. Furthermore, the combination of the release layer and the substrate layer provides excellent dimensional stability of the release film, so that elongation due to tension in the release film is suppressed even in the roll-to-roll method. Therefore, the ion-exchange layer can be wound into a roll without peeling, thereby improving productivity.

[0122] The obtained laminate may be subjected to a bonding step in which the electrolyte membrane and the electrode membrane, which are respectively laminated on the release layers of the first and second release films, are bonded to each other to prepare a membrane-electrode assembly.

[0123] The electrolyte membrane and the electrode membrane are usually bonded together by thermocompression. The heating temperature may be, for example, 80 to 250° C., preferably 90 to 230° C., and more preferably 100 to 200° C. The pressure may be, for example, 0.1 to 20 MPa, preferably 0.2 to 15 MPa, and more preferably 0.3 to 10 MPa.

[0124] The composite bonded in the bonding step (a laminate in which the electrolyte layer and the electrode membrane are bonded) is subjected to a peeling step in which the release film is peeled from the ion exchange layer (electrolyte membrane and / or electrode membrane), thereby obtaining a membrane electrode assembly for a polymer electrolyte fuel cell. Since the laminate has an appropriate peel strength even after the drying step and the heat-pressing treatment described above, the release film does not peel from the ion exchange layer in the lamination step or the bonding step, and the release film can be easily peeled in the peeling step, thereby improving workability.

[0125] The release layer of the release film needs to have a predetermined releasability with respect to the ion exchange layer, and the peel strength between the release layer and the ion exchange layer (particularly, the peel strength of the laminate in the peeling step) may be, for example, 0.1 to 20 mN / mm, and preferably 0.1 to 15 mN / mm. If the peel strength is too high, the peeling operation becomes difficult, and if it is too low, the workability in the lamination step and the adhesion step decreases.

[0126] The peel strength can be measured by leaving the film at rest for at least 1 hour at 20° C. and 50% RH, and then peeling it off at 180° at a rate of 300 mm / min.

[0127] Furthermore, in the same manner as in the above-described adhesion step and peeling step, an electrode film of a laminate in which an electrode film (an electrode film for a cathode electrode, when the second release film is an electrode film for an anode electrode) is laminated on the release layer of a third release film is adhered to the electrolyte membrane from which the first release film has been peeled off, and the release film is peeled off, and a fuel gas supply layer and an air supply layer are respectively laminated on each electrode film by a conventional method, thereby obtaining a membrane electrode assembly (MEA).

[0128] The present disclosure will be described in more detail below with reference to examples, but the present disclosure should not be construed as being limited to the following examples.

[0129] <Characteristics Evaluation> [Water Contact Angle] The water contact angle on the surface of the release layer was measured using a contact angle meter (manufactured by Kyowa Interface Science Co., Ltd.: fully automatic contact angle meter DMs-401).

[0130] [Surface Free Energy] Using a contact angle meter (Kyowa Interface Science Co., Ltd.: Fully Automatic Contact Angle Meter DMs-401), the contact angles of water, diiodomethane, and 1-bromonaphthalene, which have known surface free energies, on the surface of the release layer were measured under conditions of 23°C and 50% RH. The contact angles used in the calculations were the contact angles measured 1 second after each liquid was dropped. The obtained contact angle data was calculated using the Kitazaki-Hata theory to determine the dispersion component, polar component, and hydrogen bond component of the surface free energy of the release film, and the sum of these components was taken as the surface free energy γs. The calculations were performed using calculation software within the contact angle meter software (FAMAS).

[0131] [Glass Transition Temperature] A 50 μm thick vacuum press film was formed from the resin used for each release layer described below, and the glass transition temperature of the resin was measured by observing the viscoelastic behavior of this film at 0 to 350°C using a solid rheometer (TA Instruments: RSA 3 viscoelasticity measuring device). The conditions were as follows: Heating rate: 4°C / min Frequency: 10 Hz Strain: 0.02% A 50 μm thick film sample was prepared under the following conditions: 1. A mold with a depth of 50 μm was prepared using "Kapton (registered trademark) film" (manufactured by DuPont-Toray Co., Ltd.) (size: 10 cm x 10 cm x 50 μm). 2. The mold was filled with resin and vacuum pressed under conditions of a pressure of 15 MPa, a temperature of 320 to 340°C, and a time of 15 minutes. 3. The film obtained by vacuum pressing was sandwiched between metal plates at room temperature and rapidly cooled to obtain a 50 μm thick film as a sample. However, for the films used in Comparative Examples 5 and 6, measurements were performed on the obtained film. The method for measuring the glass transition temperature from the viscoelastic behavior observation results is as follows. In the temperature range of 150°C or higher and 350°C or lower, the peak top temperature of the peak in the tan δ chart obtained by measurement was taken as the glass transition temperature. In the temperature range of 0°C or higher and lower than 150°C, the point where the value in the chart obtained by differentiating the loss modulus value with temperature changes from positive to negative with increasing temperature, i.e., the maximum point of the loss modulus, was considered to be the peak, and the temperature at which the peak occurred was taken as the glass transition temperature. In this example, if a chart of values ​​obtained by differentiating loss modulus values ​​with respect to temperature in the temperature range of 0°C or higher and lower than 150°C does not have a point where the value changes from positive to negative with increasing temperature, i.e., if the loss modulus chart does not have a substantial maximum point, it was determined that there is no glass transition temperature in that temperature range. However, measurements were carried out in the range of -100 to 350°C, and Table 1 lists the glass transition temperatures obtained in the range of 0 to 350°C.

[0132] [Release Properties] A coating liquid was obtained by mixing 4 parts by mass of an ion exchange resin solution ("Aquivion (registered trademark) D72-25BS", Sigma-Aldrich) and 1 part by mass of 2-propanol. The equivalent mass of this ion exchange resin solution was 720±20 g / mol (SO ３ H), and the solid content was 20% by mass ±1% by mass. The coating liquid was applied onto the release layer provided on the release film using a Mayer bar to obtain a coating film. This coating film was held at a temperature of 100°C for 3 minutes and dried. This coating film was further subjected to a heat treatment by holding at a temperature of 180°C for 30 minutes to obtain an ion exchange layer. The ion exchange layer was peeled from the release film using an autograph ("AGS-X", manufactured by Shimadzu Corporation), and the peel force was measured and the average value of three measurements was used. The conditions were as follows: - Width of test piece: 25 mm - Angle: 180° - Speed: 600 mm / min

[0133] <Preparation of Release Film> [Synthesis of Polyolefin Resin] The synthesis of polyolefin resin will be described below. In this description, CC1 and CC2 refer to the following components. CC1: 6.5% by mass (as Al atom content) MMAO-3A toluene solution ([(CH ３ ) ０．７ (iso-C ４ H ９ ) ０．３ AlO] ｎ (t-BuNSiMe) is a methylisobutylaluminoxane solution represented by the formula (1), manufactured by Tosoh Finechem Co., Ltd., containing 6 mol % trimethylaluminum based on the total Al.) CC2: 9.0 mass % (as the content of Al atoms) TMAO-211 toluene solution (a methylaluminoxane solution, manufactured by Tosoh Finechem Co., Ltd., containing 26 mol % trimethylaluminum based on the total Al). In addition, as the titanocene catalyst, a titanium complex represented by the formula (t-BuNSiMe) is used. ２ Flu)TiMe ２ " was used.

[0134]

[0135] (Synthesis of Polyolefin Resin 1) 95.0 mmol of 2-norbornene, 23.8 mmol of 1-octene, 0.97 mmol of CC1 (calculated as Al atoms contained in CC1), and 0.68 mmol of CC2 (calculated as Al atoms contained in CC2) were added to a 500 mL eggplant-shaped flask purged with nitrogen. The contents of the flask were then diluted with toluene to a volume of 258 mL. The contents of the flask were then heated to 40°C. After heating, a toluene solution containing a titanocene catalyst at a concentration of 0.04 mmol / L was added to the reaction solution so that the amount of titanocene catalyst was 0.22 mmol. After addition polymerization was initiated by adding the titanocene catalyst, the reaction solution was stirred with a magnetic stirrer at 40°C for 4 hours. After the 4-hour reaction, a small amount of 2-propanol was added to the reaction solution to terminate the addition polymerization. Hydrochloric acid was added to the reaction solution and stirred for 10 minutes, and the organic layer was then washed with ion-exchanged water. The mixture was repeatedly washed with ion-exchanged water until the aqueous layer became neutral, and then the washed organic layer was recovered. The recovered organic layer was added dropwise to a large amount of acetone to precipitate the resulting cyclic olefin copolymer (random copolymer). The precipitated copolymer was recovered by filtration, and then washed twice or more with methanol and acetone. The washed copolymer was dried under reduced pressure at 110°C for 16 hours or more, and a dried product (polyolefin resin 1; number average molecular weight 73,000) that did not have low surface free energy monomer assembly regions was recovered.

[0136] (Synthesis of Polyolefin Resin 2) 29.7 mmol of 2-norbornene, 89.1 mmol of 1-octene, 0.97 mmol of CC1 (calculated as Al atoms contained in CC1), and 0.68 mmol of CC2 (calculated as Al atoms contained in CC2) were added to a 500 mL eggplant-shaped flask purged with nitrogen. The contents of the flask were then diluted with toluene to a volume of 258 mL. The contents of the flask were then heated to 40°C. After heating, a toluene solution containing a titanocene catalyst at a concentration of 0.04 mmol / L was added to the reaction solution so that the amount of titanocene catalyst was 0.22 mmol. After initiating addition polymerization by adding the titanocene catalyst, the reaction solution was stirred with a magnetic stirrer at 40°C for 4 hours. After the 4-hour reaction, a small amount of 2-propanol was added to the reaction solution to terminate the addition polymerization. Hydrochloric acid was added to the reaction solution and stirred for 10 minutes, and the organic layer was then washed with ion-exchanged water. The mixture was repeatedly washed with ion-exchanged water until the aqueous layer became neutral, and then the washed organic layer was recovered. The recovered organic layer was added dropwise to a large amount of acetone to precipitate the resulting cyclic olefin copolymer (random copolymer). The precipitated copolymer was recovered by filtration, and then washed twice or more with methanol and acetone. The washed copolymer was dried under reduced pressure at 110°C for 16 hours or more, and a dried product (polyolefin resin 2; number average molecular weight 75,100) that did not have low surface free energy monomer assembly regions was recovered.

[0137] (Synthesis of Polyolefin Resin 3) 14.59 mmol of 2-norbornene, 2.69 mmol of 1-octene, 0.0032 mmol of triisobutylaluminum, and 0.0064 mmol of 2,6-di-tert-butyl-4-hydroxytoluene were added to a 50 mL Schlenk flask purged with nitrogen. The resulting mixture was diluted with decalin to a volume of 18.6 mL. The contents of the flask were then cooled to 0°C. After cooling, a toluene solution containing a titanocene catalyst at a concentration of 0.032 mmol / mL was added to the reaction solution to adjust the amount of titanocene catalyst to 0.0032 mmol. Next, a toluene solution containing a borate compound at a concentration of 0.008 mmol / L was added to the reaction solution to adjust the amount of borate compound to 0.0032 mmol. Triphenylmethylium tetrakis(pentafluorophenyl)borate was used as the borate compound. After initiating addition polymerization by adding a titanocene catalyst and a borate compound, the reaction mixture was stirred with a magnetic stirrer and the addition polymerization reaction was continued for 30 minutes at 0°C. After 30 minutes of reaction, a small amount of 2-propanol was added to the reaction mixture to terminate the addition polymerization reaction. Hydrochloric acid was added to the reaction mixture and stirred for 10 minutes, after which the organic layer was washed with ion-exchanged water. The aqueous layer was repeatedly washed with ion-exchanged water until it became neutral, and the washed organic layer was recovered. The recovered organic layer was added dropwise to a large amount of acetone to precipitate the resulting cyclic olefin copolymer (living copolymer). The precipitated copolymer was recovered by filtration and then washed twice or more with methanol and acetone. The washed copolymer was dried under reduced pressure at 110°C for 16 hours or more, and a dried product (polyolefin resin 3; number average molecular weight 298,000) having low surface free energy monomer assembly regions was recovered.

[0138] (Synthesis of Polyolefin Resin 4) 47.52 mmol of 2-norbornene, 11.88 mmol of 1-octene, 0.198 mmol of tri-n-octylaluminum, and 0.396 mmol of 2,6-di-tert-butyl-4-hydroxytoluene were added to a 500 mL eggplant-shaped flask purged with nitrogen. The resulting mixture was diluted with decalin to a volume of 258 mL. The contents of the flask were then cooled to 0°C. After cooling, a toluene solution containing a titanocene catalyst at a concentration of 0.04 mmol / L was added to the reaction solution to adjust the amount of titanocene catalyst to 0.22 mmol. Next, a toluene solution containing a borate compound at a concentration of 0.008 mmol / L was added to the reaction solution to adjust the amount of borate compound to 0.22 mmol. Triphenylmethylium tetrakis(pentafluorophenyl)borate was used as the borate compound. After initiating addition polymerization by adding a titanocene catalyst and a borate compound, the reaction mixture was stirred with a magnetic stirrer and allowed to continue for 10 minutes at 0°C. After 10 minutes of reaction, 47.52 mmol of 2-norbornene, 11.88 mmol of 1-octene, 0.022 mmol of tri-n-octylaluminum, and 0.044 mmol of 2,6-di-tert-butyl-4-hydroxytoluene were added to the eggplant-shaped flask. The addition polymerization reaction was then allowed to continue for 15 minutes. After a total of 25 minutes of reaction, a small amount of 2-propanol was added to the reaction mixture to terminate the addition polymerization reaction. Hydrochloric acid was added to the reaction mixture and stirred for 10 minutes, after which the organic layer was washed with ion-exchanged water. The aqueous layer was repeatedly washed with ion-exchanged water until it became neutral, and the washed organic layer was then recovered. The recovered organic layer was added dropwise to a large amount of acetone to precipitate the resulting cyclic olefin copolymer (living copolymer). The precipitated copolymer was collected by filtration, washed twice or more with methanol and acetone, and then dried under reduced pressure at 110°C for 16 hours or more to collect a dried product (polyolefin resin 4; number average molecular weight 61,000) having low surface free energy monomer assembly domains.

[0139] (Synthesis of Polyolefin Resin 5) 8.64 mmol of 2-norbornene, 8.64 mmol of 1-octene, 0.0032 mmol of triisobutylaluminum, and 0.0064 mmol of 2,6-di-tert-butyl-4-hydroxytoluene were added to a 50 mL Schlenk flask purged with nitrogen. The resulting mixture was diluted with decalin to a volume of 18.6 mL. The contents of the flask were then cooled to 0°C. After cooling, a toluene solution containing a titanocene catalyst at a concentration of 0.032 mmol / mL was added to the reaction solution to adjust the amount of titanocene catalyst to 0.0032 mmol. Next, a toluene solution containing a borate compound at a concentration of 0.008 mmol / L was added to the reaction solution to adjust the amount of borate compound to 0.0032 mmol. Triphenylmethylium tetrakis(pentafluorophenyl)borate was used as the borate compound. After initiating addition polymerization by adding a titanocene catalyst and a borate compound, the reaction mixture was stirred with a magnetic stirrer and the addition polymerization reaction was continued for 30 minutes at 0°C. After 30 minutes of reaction, a small amount of 2-propanol was added to the reaction mixture to terminate the addition polymerization reaction. Hydrochloric acid was added to the reaction mixture and stirred for 10 minutes, after which the organic layer was washed with ion-exchanged water. After repeated washing with ion-exchanged water until the aqueous layer became neutral, the washed organic layer was recovered. The recovered organic layer was added dropwise to a large amount of acetone to precipitate the resulting cyclic olefin copolymer (living copolymer). The precipitated copolymer was recovered by filtration and then washed twice or more with methanol and acetone. The washed copolymer was dried under reduced pressure at 110°C for 16 hours or more to recover a dried product (polyolefin resin 5; number average molecular weight 218,000) having low surface free energy monomer assembly regions.

[0140] [Preparation of Coating Liquid] (Coating Liquid 1) Coating Liquid 1 was prepared by dissolving 5 parts by mass of TOPAS (registered trademark) 6013S-04 (manufactured by Polyplastics Co., Ltd.; number average molecular weight 40900) in 95 parts by mass of toluene.

[0141] (Coating Liquid 2) Coating liquid 2 was prepared by dissolving 5 parts by mass of TOPAS (registered trademark) 6017S-04 (manufactured by Polyplastics Co., Ltd.; number average molecular weight 40,500) in 95 parts by mass of toluene.

[0142] (Coating Solution 3) Coating Solution 3 was prepared by dissolving 5 parts by mass of Polyolefin Resin 1 in 95 parts by mass of toluene.

[0143] (Coating Solution 4) Coating Solution 4 was prepared by dissolving 5 parts by mass of Polyolefin Resin 2 in 95 parts by mass of toluene.

[0144] (Coating Solution 5) Coating Solution 5 was prepared by dissolving 5 parts by mass of Polyolefin Resin 3 in 95 parts by mass of toluene.

[0145] (Coating Solution 6) Coating Solution 6 was prepared by dissolving 5 parts by mass of Polyolefin Resin 4 in 95 parts by mass of toluene.

[0146] (Coating Solution 7) Coating Solution 7 was prepared by dissolving 5 parts by mass of Polyolefin Resin 5 in 95 parts by mass of toluene.

[0147] (Coating Solution 8) 5 parts by mass of Polyolefin Resin 4 was dissolved in 95 parts by mass of toluene, and then a fluorochemical surfactant Megafac F-52 (manufactured by DIC Corporation) was added and dissolved in an amount of 1 part by mass per 10 parts by mass of Polyolefin Resin 4 to prepare Coating Solution 8.

[0148] [Preparation of Release Film] (Comparative Example 1) A polyester film with an easy-adhesion layer (Cosmoshine (registered trademark) A4160, manufactured by Toyobo Co., Ltd.) was prepared as a substrate layer. The thickness of this polyester film was 50 μm. Coating Liquid 1 was applied to the surface of the easy-adhesion layer of this polyester film using a wire bar #10 to obtain a coating film. This coating film was held at a temperature of 100° C. for 1 minute and dried to obtain a release film of Comparative Example 1 (average thickness of the release layer: 0.5 μm).

[0149] Comparative Example 2 A release film of Comparative Example 2 (average thickness of release layer: 0.5 μm) was obtained in the same manner as in Comparative Example 1, except that Coating Liquid 1 was changed to Coating Liquid 2.

[0150] Comparative Example 3 A release film of Comparative Example 3 (average thickness of release layer: 0.5 μm) was obtained in the same manner as in Comparative Example 1, except that Coating Liquid 1 was changed to Coating Liquid 3.

[0151] Comparative Example 4 A release film of Comparative Example 4 (average thickness of release layer: 0.5 μm) was obtained in the same manner as in Comparative Example 1, except that Coating Liquid 1 was changed to Coating Liquid 4.

[0152] Comparative Example 5 A polymethylpentene film (Opulent (registered trademark) X-88, manufactured by Mitsui Chemicals, Inc.) was prepared and used as the release film of Comparative Example 5 (average thickness of release layer: 50 μm).

[0153] (Comparative Example 6) A polyester film with an easy-adhesion layer (Cosmoshine (registered trademark) A4160, manufactured by Toyobo Co., Ltd.) was used as the base layer, and a biaxially oriented polypropylene film (FOR, manufactured by Futamura Chemical Co., Ltd., thickness 12 μm, one-sided corona treatment) was dry laminated onto this base layer as a release layer to obtain a release film of Comparative Example 7. That is, 18 parts by mass of dry lamination adhesive TM-570V (manufactured by Toyo-Morton Co., Ltd.) and 1 part by mass of its curing agent TOMOFLEX (registered trademark) CAT-RT37 (manufactured by Toyo-Morton Co., Ltd.) were dissolved in ethyl acetate, and the solid content was adjusted to 35% by mass to obtain a coating liquid (adhesive). This coating liquid was applied to a polyester film (base layer) so that the mass after drying was 2.0 g / m ２ The coating was applied with a Mayer bar so that the thickness would be 1 / 4 μm, and then dried for 30 seconds at 80° C. The biaxially oriented polypropylene film was placed on the adhesive layer (intermediate layer) side having an average thickness of 2 μm obtained after drying, with the corona-treated surface facing the film, and the two films were bonded together by dry lamination to obtain a release film of Comparative Example 6 (average thickness of release layer: 12 μm).

[0154] Example 1 A release film of Example 1 (average thickness of release layer: 0.5 μm) was obtained in the same manner as in Comparative Example 1, except that Coating Liquid 1 was changed to Coating Liquid 5.

[0155] Example 2 A release film of Example 2 (average thickness of release layer: 0.5 μm) was obtained in the same manner as in Comparative Example 1, except that Coating Liquid 1 was changed to Coating Liquid 6.

[0156] Example 3 A release film of Example 3 (average thickness of release layer: 0.5 μm) was obtained in the same manner as in Comparative Example 1, except that Coating Liquid 1 was changed to Coating Liquid 7.

[0157] Example 4 A biaxially stretched polyester film (Lumirror (registered trademark) T60, manufactured by Toray Industries, Inc.) was used as the substrate layer, and a modified polyolefin resin (Arrowbase (registered trademark) SE-1200, manufactured by Unitika Ltd.) was applied on the substrate layer in a dry coating amount of 0.1 g / m ２ An intermediate layer was formed by coating the intermediate layer with Coating Solution 6 using a Mayer bar #10 and drying at 100°C for 1 minute to obtain a release film of Example 4 (average thickness of release layer: 0.5 µm).

[0158] (Example 5) A release film of Example 5 (average thickness of release layer: 0.5 μm) was obtained in the same manner as in Example 2, except that an antistatic treated polyester film (Diafoil (registered trademark) T600J75, manufactured by Mitsubishi Chemical Corporation) was used as the base layer.

[0159] Example 6 A release film of Example 6 (average thickness of release layer: 0.5 μm) was obtained in the same manner as in Example 2, except that a low-oligomer precipitated polyester film (Lumirror (registered trademark) AP-8, thickness 50 μm, manufactured by Toray Industries, Inc.) was used as the base layer.

[0160] (Example 7) A release film of Example 7 (average thickness of release layer: 0.5 μm) was obtained in the same manner as in Example 2, except that a matte polyester film (Toyobo Ester (registered trademark) U4, manufactured by Toyobo Co., Ltd.) was used as the base layer.

[0161] (Example 8) A release film of Example 8 (average thickness of release layer: 0.5 μm) was obtained in the same manner as in Example 2, except that a polyethylene naphthalate film (Teonex (registered trademark) Q53, thickness 50 μm, manufactured by Toyobo Co., Ltd.) was used as the base layer.

[0162] Example 9 A release film of Example 9 (average thickness of release layer: 0.5 μm) was obtained in the same manner as in Example 2, except that a polyphenylene sulfide film (TORELINA 75-3030, thickness 75 μm, manufactured by Toray Industries, Inc.) was used as the base layer.

[0163] (Example 10) A release film of Example 10 (average thickness of release layer: 0.5 μm) was obtained in the same manner as in Example 2, except that a polyimide film (Kapton (registered trademark) 300H thickness 75 μm, manufactured by DuPont-Toray Co., Ltd.) was used as the base layer.

[0164] Example 11 A release film of Example 11 (average thickness of release layer: 0.5 μm) was obtained in the same manner as in Example 2, except that Coating Liquid 6 was changed to Coating Liquid 8.

[0165] The evaluation results of the above-mentioned properties are shown in Table 1. Note that, for the release layers used in Comparative Examples 1 to 6, only one glass transition temperature was confirmed in the range of 0 to 350°C.

[0166]

[0167] From Table 1, it can be seen that the release films according to Examples 1 to 11 exhibit low peel strength even after heat treatment in which they were held at a temperature of 180°C for 30 minutes. This means that they retain an excellent release layer even after exposure to a high temperature of 180°C. Furthermore, it can be seen that the release films according to Examples 1 to 11 also have glass transition temperatures in a temperature range below 150°C. It can be seen that the release film according to Comparative Example 1 has a low glass transition temperature and high surface free energy, and the release films according to Comparative Examples 2 and 3 have high surface free energy, resulting in poor releasability. Furthermore, it can be seen that the release films according to Comparative Examples 4 to 6 have a surface free energy of 35 mN / m or less, but do not have a glass transition temperature within the range of 150 to 350°C, resulting in poor releasability after exposure to high temperatures.

[0168] From the above, it has been found that by setting the surface free energy of the release layer to 35 mN / m or less and by having the release layer contain one or more resins whose glass transition temperature, as determined by viscoelasticity measurement, is in the range of 150°C or more and 350°C or less, it is possible to provide a release film that exhibits excellent releasability even after exposure to high temperatures.

Claims

1. A release film comprising a base layer and a release layer laminated on at least one surface of the base layer, wherein the surface free energy of the release layer is 35 mN / m or less, and the release layer contains one or more resins having a glass transition temperature, as determined by viscoelasticity measurement, in the range of 150°C or higher and 350°C or lower.

2. The release film according to claim 1, wherein the resin has one or more glass transition temperatures determined by viscoelasticity measurement within the range of 0°C or higher and lower than 150°C.

3. The release film according to claim 1 or 2, wherein the resin is a cyclic olefin copolymer containing a structural unit derived from a cyclic olefin monomer and a structural unit derived from an α-olefin monomer having 3 to 20 carbon atoms.

4. The release film according to any one of claims 1 to 3, wherein the release layer has an average thickness of 0.1 to 10.0 µm.

5. The release film according to any one of claims 1 to 4, wherein the base layer comprises one or more resins selected from the group consisting of polyethylene terephthalate, polyethylene naphthalate, polyphenylene sulfide, and polyimide.

6. The release film according to any one of claims 1 to 5, wherein an intermediate layer is provided between the base layer and the release layer.

7. The release film according to any one of claims 1 to 6, which is used in the manufacturing process of a fuel cell.

8. The release film according to claim 7, wherein the electrolyte membrane contained in the fuel cell contains an electrolyte resin having an equivalent weight (EW) of 1,000 or less.

9. A method for producing a fuel cell, comprising a step of using the release film according to any one of claims 1 to 8.

10. The method for producing a fuel cell according to claim 9, wherein the electrolyte membrane contained in the fuel cell comprises an electrolyte resin having an equivalent weight (EW) of 1,000 or less.