Release film

Abstract

To provide a release film that has excellent heat resistance under high-temperature conditions and release properties equivalent to or better than conventional release films. [Solution] A release film having a resin layer on at least one side of a base film, wherein the resin layer is composed of a resin composition containing an acid-modified polyolefin resin (A), a crosslinking agent (B), and polyvinyl alcohol (C) having an average degree of polymerization of 1500 or more, and is rated at 200°C at 15 kg / cm³. 2 A release film characterized by having a peel strength of 0.40 N / cm or less when pressed with an epoxy prepreg under pressure for 15 minutes.

Description

Technical Field

[0001] The present invention relates to a release film.

Background Art

[0002] Release films are widely used especially in the industrial field. Specific examples thereof include process materials for manufacturing flexible printed wiring boards, multilayer printed wiring boards, ceramic green sheets, polarizing plates, etc., and protective materials for protecting photosensitive resins, adhesive materials, etc.

[0003] In recent years, in electronic substrates and the like, in order to improve manufacturing efficiency, it has been required to thermocompression-bond an adherend in a state where more layers are laminated. Also, in order to achieve high-density mounting, the heat resistance of the adherend used has been improved, and there has been a need to thermocompression-bond the adherend under higher temperature conditions. Along with this, release films used as carrier films are also required to have heat resistance that can withstand use at high temperatures. For example, Patent Document 1 discloses a release film using an acid-modified polyolefin resin layer having good releasability with respect to various adherends.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, when thermocompression-bonding a release film and an adherend under higher temperature conditions than before (for example, about 200°C), the resin layer showing releasability may melt and flow, and there is a risk that the releasability with the adherend may decrease. The release film shown in Patent Document 1 does not disclose anything about the releasability when processed at a higher temperature than before or the heat resistance that can withstand high temperatures.

[0006] In view of the above problems, the present invention provides a release film that has excellent heat resistance under high temperature conditions of about 200°C and release properties equivalent to or better than conventional release films. [Means for solving the problem]

[0007] As a result of diligent research to solve the aforementioned problems, the present inventors have found that a release film that solves the aforementioned problems can be obtained by forming a resin layer on a substrate film surface using an acid-modified polyolefin resin, a crosslinking agent, polyvinyl alcohol having a specific average degree of polymerization, and a liquid resin for forming a resin layer containing a specific compound, and have arrived at the present invention.

[0008] In other words, the gist of the present invention is as follows. (1) A release film having a resin layer on at least one side of a base film, wherein the resin layer is composed of a resin composition comprising an acid-modified polyolefin resin (A), a crosslinking agent (B), and polyvinyl alcohol (C) having an average degree of polymerization of 1500 or more, and is rated at 200°C at 15 kg / cm² 2 A release film characterized by having a peel strength of 0.40 N / cm or less when pressed with an epoxy prepreg under pressure for 15 minutes. (2) The release film according to (1), characterized in that the amount of crosslinking agent (B) in the resin composition is 1 to 20 parts by mass per 100 parts by mass of acid-modified polyolefin resin (A). (3) The release film according to (1), characterized in that the polyvinyl alcohol (C) content in the resin composition is 10 to 1000 parts by mass per 100 parts by mass of acid-modified polyolefin resin (A). (4) The release film according to any one of (1) to (3), characterized in that the change in area of ​​the resin composition before and after heating and compression is less than 1.9, as defined below. (Change in area) For cylindrical samples prepared by curing a resin composition, the ratio of the base area of ​​the cylindrical sample before and after heating and compressing it at 200°C with a load of 1 MPa in the axial direction for 120 seconds (base area after heating and compression / base area before heating and compression). (5) A release film according to any one of (1) to (3), characterized in that the peel force between the resin layer and the adherend when an acrylic adherend is attached to the resin layer and measured is 3.0 N / cm or less. (6) A method for manufacturing the release film described in (1) above, A method for producing a release film, comprising the steps of drying and stretching a substrate film having a coating film formed on at least one side using a liquid resin medium containing a resin composition comprising an acid-modified polyolefin resin (A), a crosslinking agent (B), polyvinyl alcohol (C) having an average degree of polymerization of 1500 or more, and at least one compound (D) selected from the group consisting of amphiphilic oligomers, acetylene glycol, and ethylene oxide adducts of acetylene glycol. [Effects of the Invention]

[0009] The release film of the present invention is a release film that exhibits excellent release properties from various adherends even under high-temperature conditions. Because the resin layer possesses both heat resistance and release properties, the release film of the present invention can be suitably used in applications where high temperatures are expected, such as green sheets for ceramic multilayer capacitors and carrier films for molding in the manufacturing process of insulating resins for multilayer printed circuit boards. [Modes for carrying out the invention]

[0010] The present invention will be described in detail below. The release film of the present invention has a resin layer provided on at least one surface of a base film, and the resin layer is composed of a resin composition containing an acid-modified polyolefin resin, a crosslinking agent, and a specific polyvinyl alcohol.

[0011] <Base film> The base film constituting the release film of the present invention is not particularly limited, but is preferably a polyester film. Examples of polyesters include polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyethylene naphthalate (PEN), poly(1,4-cyclohexylenedimethylene terephthalate), and polylactic acid (PLA), and it is preferable that the film contains a dicarboxylic acid component and a glycol component. Polyesters with rigid aromatic rings within their molecules exhibit excellent mechanical strength and dimensional stability, and their films have superior stiffness, making them suitable for use as protective and carrier materials. From this perspective, polyester films with rigid aromatic rings within their molecules can be suitably used as base films for release films, and polyethylene terephthalate films are preferable in terms of mechanical properties such as elastic modulus, tensile strength, and tensile elongation.

[0012] The polymerization method for the resin constituting the base film is not particularly limited; for example, in the case of polyester polymerization, transesterification and direct polymerization methods can be used. In the present invention, the catalyst used during polymerization is preferably an oxide or acetate of antimony, germanium, phosphorus, platinum, or a sulfonic acid compound, from the viewpoint of reducing fish-eye in the film. In particular, oxides of antimony and germanium, and sulfonic acid compounds are preferred.

[0013] There are no particular restrictions on the oxides of antimony or germanium, but examples include antimony trioxide and germanium dioxide. There are no particular restrictions on the sulfonic acid compounds, but examples include methanesulfonic acid, ethanesulfonic acid, methionic acid, cyclopentanesulfonic acid, 1,1-ethanedisulfonic acid, 1,2-ethanedisulfonic acid, 1,2-ethanedisulfonic anhydride, 1,3-propanedisulfonic acid, sulfoacetic acid, β-sulfopropionic acid, isethionic acid, ethionic acid, ethionic anhydride, 3-oxy-1-propanesulfonic acid, propanesartone, butanesartone, 2-aminoethanesulfonic acid, and 2-chloroethanesulfonic acid. 2-Chlorsulfonic acid, fluorosulfonic acid, trifluoromethanesulfonic acid, phenylmethanesulfonic acid, α-phenylethanesulfonic acid, β-phenylethanesulfonic acid, 2-(N-morpholino)ethanesulfonic acid, 3-(N-morpholino)propanesulfonic acid, ammonium chlorosulfonate, triethylammonium ethanesulfonate, benzenesulfonic acid, m-benzenedisulfonic acid, p-benzenedisulfonic acid, 1,3,5-benzenetrisulfonic acid, p-toluenesulfonic acid, o-, m- , or p-sulfobenzoic acid, 5-sulfosalicylic acid, o-hydroxybenzenesulfonic acid, phenol-2,4,6-trisulfonic acid, anisole-o-sulfonic acid, 1,5-naphthalenedisulfonic acid, 1-naphthol-2-sulfonic acid, o-, m-, or p-chlorobenzenesulfonic acid, o-, m-, or p-bromobenzenesulfonic acid, o-, m-, or p-fluorobenzenesulfonic acid, 4-chloro-3-methylbenzenesulfonic acid, chlorobenzene-1,4-disulfonic acid, 1 Examples include -chlornaphthaline-4-sulfonic acid, 2-chlor-4-sulfobenzoic acid, o-, m-, or p-iodobenzenesulfonic acid, 2-sulfobenzoic anhydride, 3,4-dimethyl-2-sulfobenzoic anhydride, 4-methyl-2-sulfobenzoic anhydride, 5-methoxy-2-sulfobenzoic anhydride, 1-sulfonaphthoic acid (2) anhydride, 8-sulfonaphthoic acid (1) anhydride, 3,6-disulfophthalic acid anhydride, 4,6-disulfoisulfalic acid anhydride, and 2,5-disulfoterephthalic acid anhydride. Since the polymerized polyester contains monomers, oligomers, and by-products such as acetaldehyde, solid-phase polymerization may be carried out at a temperature of 200°C or higher under reduced pressure or inert gas flow.

[0014] The base film can contain additives such as lubricants, antioxidants, heat stabilizers, ultraviolet absorbers, antistatic agents, pinning agents, etc., as long as it does not interfere with the effects of the present invention. Examples of lubricants include inorganic particles such as silica, calcium carbonate, magnesium carbonate, barium carbonate, calcium sulfate, calcium phosphate, magnesium phosphate, kaolin, aluminum oxide, titanium oxide, etc., and organic particles such as acrylic resin, styrene resin, urea resin, phenol resin, epoxy resin, benzoguanamine resin, etc. Examples of antioxidants include hindered phenol-based compounds, hindered amine-based compounds, etc. Examples of heat stabilizers include phosphorus-based compounds, etc. Examples of ultraviolet absorbers include benzophenone-based compounds, benzotriazole-based compounds, etc.

[0015] The base film may be subjected to corona treatment, anchor coating treatment, plasma treatment, acid treatment, flame treatment, etc. in order to improve the adhesion to the resin layer.

[0016] The structure of the base film may be a single layer, a multi-layer such as two types in two layers or two types in three layers, or an ultra-multi-layer structure of at least 60 layers or more.

[0017] From the viewpoints of strength and handling properties, the thickness of the base film is preferably 1 to 150 μm, more preferably 10 to 125 μm, and even more preferably 15 to 100 μm.

[0018] <Resin composition> The resin layer constituting the release film of the present invention is composed of a resin composition containing an acid-modified polyolefin resin (A), a crosslinking agent (B), and a polyvinyl alcohol (C) having an average degree of polymerization of 1500 or more.

[0019] (Acid-modified polyolefin resin (A)) The acid-modified polyolefin resin (A) constituting the resin composition is a resin having an olefin component as a main component and modified with an acid-modified component. The olefin component constituting the acid-modified polyolefin resin preferably contains at least one selected from ethylene, propylene, butene, pentene, hexene, heptene, and octene, and more preferably contains ethylene, propylene, or octene from the viewpoint of mold release properties.

[0020] Examples of acid-modified components that make up acid-modified polyolefin resins include unsaturated carboxylic acid components, specifically acrylic acid, methacrylic acid, maleic acid, maleic anhydride, itaconic acid, fumaric acid, crotonic acid, and other examples, as well as half-esters and half-amides of unsaturated dicarboxylic acids. Among these, acrylic acid, methacrylic acid, maleic acid, and maleic anhydride are preferred for stable dispersion of the resin in aqueous dispersion, as described later, and acrylic acid, methacrylic acid, and maleic anhydride are particularly preferred. Two or more of these acid-modified components may be included in the acid-modified polyolefin resin.

[0021] In acid-modified polyolefin resins, the proportion of the acid-modified component is preferably 1 to 10% by mass, and more preferably 2 to 9% by mass, considering release properties, adhesion to the substrate film, and stability of the aqueous dispersion.

[0022] Furthermore, to further improve adhesion to the base film, the acid-modified polyolefin resin may contain an ethylenically unsaturated component with oxygen atoms in its side chains. Examples of ethylenically unsaturated components containing oxygen atoms in the side chain include esters of (meth)acrylic acid with C1-C30 alcohols, among which esters of (meth)acrylic acid with C1-C20 alcohols are preferred due to their availability. Specific examples of such compounds include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, hexyl (meth)acrylate, octyl (meth)acrylate, decyl (meth)acrylate, lauryl (meth)acrylate, dodecyl (meth)acrylate, and stearyl (meth)acrylate. Mixtures of these may also be used. Among these, methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, hexyl acrylate, and octyl acrylate are more preferred from the viewpoint of adhesion to polyester film, ethyl acrylate and butyl acrylate are even more preferred, and ethyl acrylate is particularly preferred. "(meth)acrylic acid~" means "acrylic acid~ or methacrylic acid~". Ethylene-unsaturated components containing oxygen atoms in their side chains, like acid-modified components, have polar groups within their molecules. Therefore, by including ethylenically unsaturated components containing oxygen atoms in their side chains in the acid-modified polyolefin resin, the adhesion of the resin layer to the substrate film is improved. From this viewpoint, the proportion of ethylenically unsaturated components containing oxygen atoms in their side chains in the acid-modified polyolefin resin is preferably 1 to 40% by mass, more preferably 2 to 35% by mass, even more preferably 3 to 30% by mass, and particularly preferably 6 to 18% by mass.

[0023] Acid-modified polyolefin resins may also contain small amounts of other monomers copolymerized into them. Examples of other monomers include dienes, (meth)acrylonitrile, vinyl halides, vinylidene halides, carbon monoxide, and sulfur dioxide.

[0024] The components constituting the acid-modified polyolefin resin only need to be copolymerized within the acid-modified polyolefin resin, and their form is not limited. Examples of copolymerization states include random copolymerization, block copolymerization, and graft copolymerization (graft modification).

[0025] From the viewpoint of resin layer formation, the melting point of the acid-modified polyolefin resin is preferably 70 to 200°C, and more preferably 80 to 150°C.

[0026] (Crosslinking agent (B)) In the present invention, the resin composition constituting the resin layer must contain a crosslinking agent (B). By including a crosslinking agent, the components of the resin layer crosslink, improving release properties, enhancing the cohesive force of the resin layer to make it less likely to migrate to the adherend, and improving water resistance.

[0027] The crosslinking agent content is not particularly limited, but from the viewpoint of adhesion to the base film, heat resistance of the resin layer, and release properties, it is preferably 1 to 20 parts by mass, more preferably 2 to 15 parts by mass, and even more preferably 2 to 10 parts by mass per 100 parts by mass of acid-modified polyolefin resin.

[0028] As crosslinking agents, compounds having multiple functional groups that react with carboxyl groups in their molecule can be used, including polyfunctional epoxy compounds, polyfunctional isocyanate compounds, polyfunctional aziridine compounds, carbodiimide group-containing compounds, oxazoline group-containing compounds, phenolic resins, and amino resins such as urea compounds, melamine resins, and benzoguanamine resins. One of these may be used, or two or more may be used in combination. Of these, polyfunctional isocyanate compounds, melamine compounds, urea compounds, polyfunctional epoxy compounds, carbodiimide group-containing compounds, and oxazoline group-containing compounds are preferred, carbodiimide group-containing compounds and oxazoline group-containing compounds are more preferred, and oxazoline group-containing compounds are even more preferred. By using oxazoline group-containing compounds, it is possible to obtain a release film with excellent release properties from the adherend and adhesion to the substrate. Furthermore, these crosslinking agents may be used in combination.

[0029] Specifically, polyepoxy compounds, diepoxy compounds, etc., can be used as polyfunctional epoxy compounds. Examples of polyepoxy compounds include sorbitol polyglycidyl ether, polyglycerol polyglycidyl ether, pentaerythritol polyglycidyl ether, diglycerol polyglycidyl ether, triglycidyl tris(2-hydroxyethyl) isocyanate, glycerol polyglycidyl ether, and trimethylolpropane polyglycidyl ether. Examples of diepoxy compounds include neopentyl glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, resorcinol diglycidyl ether, ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, and polytetramethylene glycol diglycidyl ether.

[0030] Examples of polyfunctional isocyanate compounds that can be used include tolylene diisocyanate, diphenylmethane-4,4′-diisocyanate, metaxylylene diisocyanate, hexamethylene-1,6-diisocyanate, 1,6-diisocyanate hexane, adducts of tolylene diisocyanate and hexanetriol, adducts of tolylene diisocyanate and trimethylolpropane, polyol-modified diphenylmethane-4,4′-diisocyanate, carbodiimide-modified diphenylmethane-4,4′-diisocyanate, isophorone diisocyanate, 1,5-naphthalene diisocyanate, 3,3′-vitrylene-4,4′-diisocyanate, 3,3′-dimethyldiphenylmethane-4,4′-diisocyanate, and metaphenylene diisocyanate. Blocked isocyanate compounds may also be used, in which these isocyanate groups are blocked with phenols, alcohols, lactams, oximes, and active methylene compounds containing bisulfites and sulfonic acid groups. Examples of commercially available polyfunctional isocyanate compounds include BASF's "Basonate HW-100".

[0031] Examples of polyfunctional aziridine compounds that can be used include N,N′-hexamethylene-1,6-bis-(1-aziridinecarboxamide) and trimethylolpropane-tri-β-aziridinylpropionate.

[0032] The carbodiimide group-containing compound is not particularly limited as long as it has one or more carbodiimide groups in its molecule. The carbodiimide compound achieves crosslinking by forming an ester with two carboxyl groups in the acid-modified portion of the acid-modified polyolefin resin at one of its carbodiimide moieties. For example, compounds having carbodiimide groups such as p-phenylene-bis(2,6-xylylcarbodiimide), tetramethylene-bis(t-butylcarbodiimide), and cyclohexane-1,4-bis(methylene-t-butylcarbodiimide), as well as polycarbodiimides, which are polymers having carbodiimide groups, can be used. One or more of these can be used. Among these, polycarbodiimides are preferred due to their ease of handling. Commercially available polycarbodiimides include the CarbodiLite series manufactured by Nisshinbo, specifically the water-soluble types "SV-02," "V-02," "V-02-L2," and "V-04"; the emulsion types "E-01" and "E-02"; the organic solution types "V-01," "V-03," "V-07," and "V-09"; and the solvent-free type "V-05."

[0033] The oxazoline group-containing compound is not particularly limited as long as it has two or more oxazoline groups in its molecule. The oxazoline compound achieves crosslinking by forming an amide ester with one carboxyl group in the acid-modified portion of the acid-modified polyolefin resin at each of its two oxazoline moieties. Such polymers can be produced by polymerization of the addition-polymerizable oxazoline group-containing monomer alone or with other monomers. Examples of addition-polymerizable oxazoline group-containing monomers include 2-vinyl-2-oxazoline, 2-vinyl-4-methyl-2-oxazoline, 2-vinyl-5-methyl-2-oxazoline, 2-isopropenyl-2-oxazoline, 2-isopropenyl-4-methyl-2-oxazoline, and 2-isopropenyl-5-ethyl-2-oxazoline. One or a mixture of two or more of these addition-polymerizable oxazoline group-containing monomers can be used. Among these, 2-isopropenyl-2-oxazoline is preferred because it is readily available industrially.Other monomers are not limited as long as they are copolymerizable with addition-polymerizable oxazoline group-containing monomers, for example (meth)acrylic acid esters such as alkyl acrylates and alkyl methacrylates (alkyl groups include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, t-butyl, 2-ethylhexyl, and cyclohexyl groups); unsaturated carboxylic acids such as acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid, crotonic acid, styrene sulfonic acid and their salts (sodium salt, potassium salt, ammonium salt, tertiary amine salt, etc.); unsaturated nitriles such as acrylonitrile and methacrylonitrile; acrylamide, methacrylamide, N-al Examples of unsaturated amides include cytoacrylamide, N-alkylmethacrylamide, N,N-dialkylacrylamide, and N,N-dialkyl methacrylate (alkyl groups include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, t-butyl, 2-ethylhexyl, and cyclohexyl groups); vinyl esters such as vinyl acetate and vinyl propionate; vinyl ethers such as methyl vinyl ether and ethyl vinyl ether; α-olefins such as ethylene and propylene; halogen-containing α,β-unsaturated aliphatic monomers such as vinyl chloride, vinylidene chloride, and vinyl fluoride; and α,β-unsaturated aromatic monomers such as styrene and α-methylstyrene. Other monomers can be one or more of these. Among these, oxazoline group-containing polymers are preferred due to their ease of handling. Examples of commercially available oxazoline group-containing polymers include the Epocross series manufactured by Nippon Shokubai Co., Ltd., specifically the water-soluble types "WS-500" and "WS-700," and the emulsion types "K-1010E," "K-1020E," "K-1030E," "K-2010E," "K-2020E," and "K-2030E."

[0034] As phenolic resins, for example, resol-type phenolic resins and / or novolac-type phenolic resins prepared using phenol, bisphenol A, pt-butylphenol, octylphenol, p-cumylphenol and other alkylphenols, p-phenylphenol, cresol, etc. as raw materials can be used.

[0035] Examples of usable urea compounds include dimethylol urea, dimethylol ethylene urea, dimethylol propylene urea, tetramethylol acetylene urea, and 4-methoxy-5-dimethylpropylene urea dimethylol.

[0036] Melamine resins are compounds having, for example, an imino group, a methylol group, and / or an alkoxymethyl group (e.g., a methoxymethyl group, a butoxymethyl group) as functional groups in one molecule. Suitable melamine resins include imino-type methylated melamine resins, methylol-type melamine resins, methylol-type methylated melamine resins, and fully alkyl-type methylated melamine resins. Among these, methylolated melamine resins are most preferred. Furthermore, to accelerate the thermosetting of the melamine resin, it is preferable to use an acidic catalyst, such as p-toluenesulfonic acid.

[0037] Examples of benzoguanamine resins that can be used include trimethylolbenzoguanamine, hexamethylolbenzoguanamine, trismethoxymethylbenzoguanamine, and hexakismethoxymethylbenzoguanamine.

[0038] (Polyvinyl alcohol (C)) From the viewpoint of improving the heat resistance of the resin layer, the release film of the present invention requires that the resin composition constituting the resin layer contains polyvinyl alcohol (C) with an average degree of polymerization of 1500 or more. The average degree of polymerization of the polyvinyl alcohol is preferably 1500 to 3500, more preferably 1700 to 3400, and even more preferably 2000 to 3300. By providing a resin layer containing polyvinyl alcohol with an average degree of polymerization of 1500 or more, the release film can obtain suitable heat resistance without the surface resin layer undergoing fluid deformation when used as a release film in a high-temperature environment. On the other hand, if the resin does not contain polyvinyl alcohol with an average degree of polymerization of 1500 or more, the dispersion state of the components in the resin layer changes, and the deformation of the resin layer increases when used in a high-temperature environment, which leads to a decrease in the heat resistance and peel strength of the release film.

[0039] Furthermore, in the present invention, the lower limit of the saponification rate of polyvinyl alcohol (C) is not particularly limited, but from the viewpoint of release properties after high-temperature treatment, 80% is preferred, 85% is more preferred, and 90% is even more preferred.

[0040] The polyvinyl alcohol (C) content is preferably 10 to 1000 parts by mass, more preferably 200 to 800 parts by mass, and even more preferably 300 to 600 parts by mass, per 100 parts by mass of acid-modified polyolefin resin, from the viewpoint of improving adhesion between the resin layer and the base film and improving release properties between the resin layer and the adherend. When the polyvinyl alcohol (C) content exceeds 1000 parts by mass, the effects of components other than polyvinyl alcohol (C) in the resin layer become smaller, leading to a decrease in the release properties of the resin layer or making it easier for the resin layer to migrate to the adherend. The resin layer may contain a combination of polyvinyl alcohols with different average degrees of polymerization, or it may contain polyvinyl alcohol with an average degree of polymerization of less than 1500. From the viewpoint of heat resistance, the content of polyvinyl alcohol (C) with an average degree of polymerization of 1500 or more is preferably 50% by mass or more of the total amount of polyvinyl alcohol, and more preferably 60% by mass or more.

[0041] In the present invention, commercially available polyvinyl alcohol (C) with an average degree of polymerization of 1500 or more can be used. For example, "JM-17", "JM-23", "JM-33", "JM-17L", "JC-25", and "JP-24" from Nippon Vitello Vinegar Co., Ltd. can be used.

[0042] The resin composition constituting the resin layer may further contain heat stabilizers, antioxidants, reinforcing agents, degradation inhibitors, weathering agents, flame retardants, plasticizers, preservatives, defoamers, viscosity modifiers, etc., to the extent that it does not impair the effects of the present invention.

[0043] <Resin layer> In the present invention, the thickness of the resin layer composed of the resin composition is preferably 0.01 to 1 μm, more preferably 0.03 to 0.7 μm, and even more preferably 0.05 to 0.5 μm. If the thickness of the resin layer is less than 0.01 μm, sufficient release properties cannot be obtained, and if it exceeds 1 μm, it is undesirable because it is more likely to transfer to the adherend and also increases costs.

[0044] <Manufacturing of release film> A method for producing the release film of the present invention includes a step of applying a liquid for forming a resin layer, which contains a resin composition comprising an acid-modified polyolefin resin (A), a crosslinking agent (B), polyvinyl alcohol (C) having an average degree of polymerization of 1500 or more, and a compound (D) in a liquid medium, to at least one side of an unstretched or uniaxially oriented substrate film, followed by drying and stretching the substrate film on which the coating film has been formed.

[0045] (Compound (D)) The resin layer in the present invention can be formed using a resin layer-forming liquid containing compound (D) along with the components constituting the above-mentioned resin composition. By forming the resin layer with a resin layer-forming liquid containing compound (D), even when polyvinyl alcohol (C) with an average degree of polymerization of 1500 or more is included, the formed resin layer will not have impaired release properties when used in high-temperature environments. Compound (D) is at least one compound selected from the group consisting of amphiphilic oligomers, acetylene glycol, and ethylene oxide adducts of acetylene glycol. An amphiphilic oligomer is an oligomer that has both a hydrophobic structure (also called a hydrophobic segment) and a hydrophilic structure (also called a hydrophilic segment) within its molecule. The hydrophobic segment is not particularly limited, but examples include alkyl groups, alkenyl groups, alkylphenyl groups, perfluoroalkyl groups, and perfluoropolyether groups. These may be present individually or in combination. The hydrophilic segment is not particularly limited, but examples include polyoxyalkylene glycols such as polyethylene glycol and polypropylene glycol; and polyhydric alcohols such as glycerin, sorbitol, sorbitan, polyglycerin, fructose, sucrose, glucose, and maltose. Specific examples of acetylene glycol include 2,5,8,11-tetramethyl-6-dodecine-5,8-diol, 5,8-dimethyl-6-dodecine-5,8-diol, 2,4,7,9-tetramethyl-5-decine-4,7-diol, 4,7-dimethyl-5-decine-4,7-diol, 2,3,6,7-tetramethyl-4-octin-3,6-diol, 3,6-dimethyl-4-octin-3,6-diol, 3,6-diethyl-4-octin-3,6-diol, and 2,5-dimethyl-3-hexyn-2,5-diol. Examples of ethylene oxide adducts of acetylene glycol include the ethylene oxide adducts of the compounds listed as specific examples of acetylene glycol.

[0046] From the viewpoint of dispersibility in the liquid for forming the resin layer, compound (D) is preferably one in which the amount of solubility in 100g of water at 20°C is 0.05g or more, or one in which compound (D) disperses when 0.1g is added to 100g of water at 20°C and stirred.

[0047] From the viewpoint of balance with each component, the content of compound (D) in the liquid for forming the resin layer is preferably 2 to 50 parts by mass, more preferably 3.5 to 45 parts by mass, and even more preferably 5 to 40 parts by mass per 100 parts by mass of acid-modified polyolefin resin (A). If the content of compound (D) exceeds 50 parts by mass, the fluidity of the formed resin layer in a high-temperature environment may increase, which may reduce its heat resistance and release properties. Depending on the type, compound (D) in the liquid for forming the resin layer may volatilize due to heat treatment after application to the base film and may not remain in the formed resin layer.

[0048] Examples of commercially available products that can be used as compound (D) in the present invention include the amphiphilic oligomer "KL-900" from the Polyflow series manufactured by Kyoeisha Chemical Co., Ltd., the acetylene glycol "D-10" from the Orphine series manufactured by Nisshin Kogyo Co., Ltd., and the ethylene oxide adducts of acetylene glycol, such as "E1004", "E1006", and "E1010" from the Orphine series and "420", "440", and "485" from the Surfinol series manufactured by Nisshin Kogyo Co., Ltd.

[0049] (Liquid substance for forming resin layers) In the present invention, the liquid medium constituting the resin layer forming liquid is preferably an aqueous medium. An aqueous medium means a solvent containing water and an amphiphilic organic solvent, wherein the water content is 2% by mass or more, and may consist of water alone. An amphiphilic organic solvent is an organic solvent in which the solubility of water at 20°C is 5% by mass or more (the solubility of water in organic solvents at 20°C is described in literature such as, for example, the "Solvent Handbook" (Kodansha Scientific, 10th edition, 1990)). Specific examples of amphiphilic organic solvents include alcohols such as methanol, ethanol, n-propanol, and isopropanol; ethers such as tetrahydrofuran and 1,4-dioxane; ketones such as acetone and methyl ethyl ketone; esters such as methyl acetate, n-propyl acetate, isopropyl acetate, methyl propionate, ethyl propionate, and dimethyl carbonate; ethylene glycol derivatives such as ethylene glycol-n-butyl ether; and other organic amine compounds including ammonia, such as diethylamine, triethylamine, diethanolamine, triethanolamine, N,N-dimethylethanolamine, and N,N-diethylethanolamine; and lactams such as 2-pyrrolidone and N-methyl-2-pyrrolidone.

[0050] The liquid for forming the resin layer is not limited to this method, but can be prepared, for example, by adding a crosslinking agent (B), polyvinyl alcohol (C), and a compound (D) to a liquid acid-modified polyolefin resin (A).

[0051] As the liquid of the acid-modified polyolefin resin (A), an aqueous dispersion of the acid-modified polyolefin resin can be used. The method for aqueous dispersion of the acid-modified polyolefin resin is not particularly limited, but for example, the method described in International Publication No. 02 / 055598 can be used. The number-average particle size of the acid-modified polyolefin resin dispersed in an aqueous medium is preferably 1 μm or less, and more preferably 0.8 μm or less, from the viewpoint of stability when mixed with other components and storage stability after mixing. Such particle sizes can be achieved by the manufacturing method described in International Publication No. 02 / 055598. The number-average particle size of the acid-modified polyolefin resin is measured by dynamic light scattering. The solid content concentration of the aqueous dispersion of acid-modified polyolefin resin is not particularly limited, but to maintain an appropriate viscosity of the aqueous dispersion, it is preferably 1 to 60% by mass, and more preferably 5 to 30% by mass.

[0052] The solid content concentration of the liquid for forming a resin layer, which contains an acid-modified polyolefin resin (A), a crosslinking agent (B), polyvinyl alcohol (C), and a compound (D), can be appropriately selected depending on the lamination conditions, the desired thickness and performance, etc., and is not particularly limited. However, in order to maintain the viscosity of the liquid and form a uniform resin layer, a concentration of 2 to 30% by mass is preferred, and 3 to 20% by mass is more preferred. The liquid material for forming the resin layer may also contain antioxidants, UV absorbers, lubricants, colorants, etc., to the extent that its performance is not impaired.

[0053] (Manufacturing of base film and formation of resin layer) The release film of the present invention can be manufactured by a method comprising the steps of applying a liquid substance for forming a resin layer to one side of a base film, drying, and stretching. In the manufacturing method of the present invention, it is preferable to apply the liquid substance by an in-line coating method, and it is preferable to further include a step of heat setting treatment after stretching.

[0054] Next, we will explain an example of the manufacturing of a base film and the formation of a resin layer. Thoroughly dried polyester is fed into an extruder, sufficiently plasticized, melted at a temperature above which it exhibits fluidity, passed through a filter as needed, and extruded into a sheet through a T-die. This sheet is then placed in close contact with a cooling drum whose temperature is controlled to be below the glass transition temperature (Tg) of the polyester to obtain an unstretched film. When the base film has a multilayer structure, it can be manufactured by methods such as melting the resins constituting each layer separately in the above process, extruding them using a multilayer die, laminating and fusing them before solidification, followed by biaxial stretching and heat fixing; or by melting and extruding two or more types of resins separately to form films, and then laminating and fusing them in an unstretched state or after stretching. Due to the simplicity of the process, it is preferable to use a multilayer die and laminate and fuse them before solidification.

[0055] The obtained unstretched film is uniaxially oriented by a uniaxial stretching method, or biaxially oriented by a biaxial stretching method. The biaxial stretching method is not particularly limited, but sequential biaxial stretching or simultaneous biaxial stretching can be used. In particular, for reasons of simplicity and operational efficiency, it is preferable to employ sequential biaxial stretching, applying the liquid to a base film stretched in the uniaxial direction, drying the film coated with the liquid, further stretching it in a direction perpendicular to the aforementioned direction, and then heat-treating it.

[0056] The conditions for using the sequential biaxial stretching method will be explained. In the sequential biaxial stretching method, an unstretched film is heated with a heating roll or infrared radiation, and stretched in the longitudinal direction to obtain a longitudinally stretched film. Longitudinal stretching is preferably performed using the difference in peripheral speed of two or more rolls, at a temperature range 40°C higher than the polyester's Tg to Tg, with a stretching ratio of 2.5 to 4.0 times.

[0057] Next, a liquid substance for forming a resin layer is applied to the longitudinally stretched film. Various methods for applying the liquid substance include known methods such as gravure roll coating, die coating, reverse roll coating, wire bar coating, lip coating, air knife coating, curtain flow coating, spray coating, dipping coating, and brush application. From the viewpoint of coating properties, wire bar coating and gravure roll coating are preferred, and gravure roll coating is particularly preferred.

[0058] When a liquid is applied to a film after longitudinal stretching, and then transverse stretching is performed, the coating on the film must be thoroughly dried. For example, depending on the type of liquid applied, if the base film is a polyester film and the liquid is water-based, it is preferable that the drying temperature be 100°C or higher in order to thoroughly dry the coating and then heat the base film to a temperature suitable for stretching. Alternatively, it is possible to set a relatively low stretching temperature by providing a pre-drying zone after applying the liquid substance and before stretching. However, from the viewpoint of simplifying the process, it is preferable to guide the base film to the tenter immediately after applying the liquid substance, and to carry out a series of processes including drying the coating, stretching the film, and heat fixing / curing treatment while gripping only both ends in the film width direction. From the viewpoint of further promoting the crosslinking reaction of the resin layer and obtaining excellent release properties, transverse stretching is preferably performed at 135°C or higher. The ratio of transverse stretching is adjusted depending on the required physical properties of the final film, but it is preferably 3.5 times or higher, more preferably 3.8 times or higher, and even more preferably 4.0 times or higher. After stretching in the longitudinal and width directions, the elastic modulus of the film can be increased or its dimensional stability improved by further stretching in the longitudinal and / or width directions.

[0059] Following stretching, it is preferable to perform a heat-setting treatment for several seconds at a temperature (50-10)°C lower than the resin's Tm, and simultaneously allow the film to relax by 1-10% in the film width direction. After the heat-setting treatment, the film is cooled to below Tg to obtain a biaxially oriented film.

[0060] After forming a resin layer on the base film, an aging treatment may be performed in an environment controlled to a constant temperature. From the viewpoint of reducing damage to the base film, a relatively low aging temperature is preferable, but from the viewpoint of ensuring the reaction proceeds sufficiently and quickly, high temperatures are preferable. The aging treatment is preferably performed at 20 to 100°C, more preferably at 30 to 70°C, and even more preferably at 40 to 60°C.

[0061] <Easy layer> The release film of the present invention allows for the lamination of a smooth-slip layer on the surface of the base film opposite to the surface on which the resin layer is laminated. A method for laminating the smooth-slip layer includes applying a liquid for forming a smooth-slip layer, which contains particles for forming the smooth-slip layer and a resin, to the surface of the base film opposite to the surface on which the liquid for forming the resin layer is applied, and then drying, stretching, and heat-treating the film on which the coating has been formed.

[0062] <Characteristics of release film> (heat resistance) The resin composition constituting the resin layer of the release film of the present invention is preferably defined below, and the change in area of ​​the resin composition before and after heating and compression is less than 1.90. (Change in area) For cylindrical samples prepared by curing a resin composition, the ratio of the base area of ​​the cylindrical sample before and after heating and compressing it at 200°C with a load of 1 MPa in the axial direction for 120 seconds (base area after heating and compression / base area before heating and compression). The change in area of ​​this resin composition before and after heating and compression is preferably less than 1.90. When the change in area is within this range, the resin layer is less prone to flow and deformation during the process of using a release film, and good release properties can be maintained even in high-temperature environments. From this viewpoint, the change in area is more preferably 1.60 or less, and even more preferably 1.40 or less.

[0063] (Mold releasability) The release film of the present invention exhibits excellent release properties under high-temperature conditions, for example, 15 kg / cm² at 200°C. 2 The release film exhibits excellent release properties when measured after applying pressure for 15 minutes and pressing an epoxy prepreg, as an epoxy-based adherend, onto a resin layer. The release film of the present invention requires that the peel force between the resin layer and the epoxy prepreg be 0.40 N / cm or less, preferably 0.01 to 0.35 N / cm, and more preferably 0.01 to 0.30 N / cm. Release films with a peel force exceeding 0.40 N / cm may cause thin adherends to peel off while being caught in the film as the adherend becomes thinner, or their handling properties may decrease, potentially leading to a reduction in manufacturing efficiency by slowing down the production line speed.

[0064] Furthermore, by using the release film of the present invention, the peel force between the acrylic adherend (used as an adhesive material) and the resin layer, when measured after attaching the adherend to the resin layer, can be set to 3.0 N / cm or less, preferably 2.5 to 3.0 N / cm, and more preferably 2.5 N / cm or less. If the peel force exceeds 3.0 N / cm, heavy peeling occurs, making it difficult to use the film practically as a release film. [Examples]

[0065] The present invention will be described in detail below with reference to examples, but is not limited thereto. The properties of the resin composition, the liquid for forming the resin layer, and the release film were measured by the following methods.

[0066] (1) Average degree of polymerization and saponification rate of polyvinyl alcohol The average degree of polymerization and saponification rate of polyvinyl alcohol were measured in accordance with JIS K-6726.

[0067] (2) Heat resistance of the resin composition The liquid resin composition prepared for resin layer formation was weighed into a 6 cm diameter circular mold so that the weight of the solid content was 17 g. After drying at 50°C for 20 hours, it was heat-treated at 230°C for 20 seconds to obtain a plate-shaped sample. This plate-shaped sample was punched out using a 1.5 cm diameter circular metal mold to obtain a cylindrical measurement sample. The bottom surfaces of the sample were sandwiched between rubber sheets / sample / rubber sheet, and the cylindrical sample was heated and compressed for 120 seconds under a 1 MPa load in the axial direction and at 200°C. The ratio of the bottom area of ​​the sample before and after heating and compression (bottom area after heating and compression / bottom area before heating and compression) was calculated as the area change. Heat resistance was evaluated as follows: materials with an area change of 1.40 or less were marked "◎", materials with an area change greater than 1.40 and less than or equal to 1.60 were marked "○", materials with an area change greater than 1.60 and less than 1.90 were marked "△", and materials with an area change of 1.90 or more (fail) were marked "×".

[0068] (3) Release properties for epoxy prepregs A 60mm x 100mm epoxy prepreg (EI-6765, manufactured by Sumitomo Bakelite Co., Ltd.) is sandwiched between the resin layers of the resulting release film. It is then heated in a 1.07kPa (8 Torr) vacuum press at a rate of 15°C / min from 30°C to 150°C, held at 150°C for 22 minutes, and then further heated at a rate of 5°C / min to 190°C, with a pressure of 5 kg / cm². 2 After applying a pressure of (490kPa) for 10 minutes, the pressure was 15kg / cm². 2 The samples were obtained by applying a pressure of (1471 kPa) and holding them at 190°C for 70 minutes or at 200°C for 15 minutes. After that, they were cooled to room temperature. The peel strength between the cured epoxy prepreg and the release film of the obtained samples was measured in a constant temperature chamber at 23°C using a tensile testing machine (Shimadzu Autograph AGS-5kNX) under conditions of a peel angle of 180 degrees and a peel speed of 300 mm / min. The release properties were evaluated as follows: those with a peel strength of 0.30 N / cm or less were marked "◎", those greater than 0.30 and 0.35 N / cm or less were marked "○", those greater than 0.35 and 0.40 N / cm or less were marked "△", and those greater than 0.40 N / cm (fail) were marked "×".

[0069] (4) Release properties against acrylic adhesives A 50mm wide, 150mm long acrylic adhesive tape (Nitto Denko No. 31B / acrylic adhesive) was pressed onto the resin layer side of the obtained release film using a rubber roll to prepare the sample. The sample was sandwiched between metal plates / rubber plates / sample / rubber plate / metal plate, and left for 20 hours under a 2kPa load in a 70°C atmosphere. After that, it was cooled for more than 30 minutes to return to room temperature to obtain a sample for peel strength measurement. The peel strength between the acrylic adhesive tape and the release film of the sample used for peel strength measurement was measured in a constant temperature room at 23°C using a tensile testing machine (Shimadzu Autograph AGS-5kNX) under conditions of a peel angle of 180 degrees and a peel speed of 300 mm / min. The release properties were evaluated as follows: those with a peel strength of 2.5 N / cm or less were marked "◎", those with a peel strength greater than 2.5 but 3.0 N / cm or less were marked "○", and those greater than 3.0 N / cm (fail) were marked "×".

[0070] <Materials for manufacturing liquid substances for resin layer formation> The materials for manufacturing the liquid substance for forming the resin layer are as follows:

[0071] <Production of aqueous dispersion of acid-modified polyolefin resin (A-1)> 280 g of propylene-ethylene copolymer (propylene / ethylene = 99 / 1 (mass ratio)) was heated and melted in a four-necked flask under a nitrogen atmosphere. The system temperature was then maintained at 170°C and stirred. 32.0 g of maleic anhydride as an unsaturated carboxylic acid and 6.0 g of dicumyl peroxide as a radical generator were added over 1 hour each, and the reaction was continued for another hour. After the reaction was complete, the resulting reaction product was placed in a large amount of acetone to precipitate the resin. This resin was further washed several times with acetone to remove unreacted maleic anhydride, and then dried under reduced pressure in a vacuum dryer to obtain acid-modified polyolefin resin (A-1) (acid modification amount 2.3%, melting point 145°C). Using a stirrer equipped with a sealed, pressure-resistant 1-liter glass container with a heater, 60.0 g of acid-modified polyolefin resin (A-1) produced by the above method, 45.0 g of ethylene glycol-n-butyl ether (boiling point 171°C), 4.2 g of N,N-dimethylethanolamine (boiling point 134°C, 1.0 equivalent to the carboxyl groups of the maleic anhydride units in the resin), and 190.8 g of distilled water were placed in the glass container, and the mixture was stirred at a rotation speed of 300 rpm. No resin sedimentation was observed at the bottom of the container, and it was confirmed that the resin was suspended. Maintaining this state, the heater was turned on after 10 minutes to heat the mixture. The system temperature was then maintained at 140°C and stirred for another 60 minutes. After that, the mixture was cooled to room temperature (approximately 25°C) by air cooling while stirring at a rotation speed of 300 rpm. After cooling, a uniform aqueous dispersion of acid-modified polyolefin resin (A-1) (solid content concentration 25% by mass, volume average particle size (Mv) 30 nm) was obtained by pressure filtration (air pressure 0.2 MPa) using a 300-mesh stainless steel filter (wire diameter 0.035 mm, plain weave). Almost no residual resin remained on the filter.

[0072] <Production of aqueous dispersion of acid-modified polyolefin resin (A-2)> 80 g of ethylene-octene copolymer (mass ratio: ethylene / octene = 71 / 29, weight-average molecular weight = 68,000) was heated and dissolved in 350 g of xylene in a four-necked flask under a nitrogen atmosphere. Then, while stirring and maintaining the system temperature at 140°C, 30 g of maleic anhydride as an unsaturated carboxylic acid and 5 g of dicumyl peroxide as a radical generator were added over 2 hours each, and the reaction was continued for 6 hours. After the reaction was complete, the resulting reaction product was placed in a large amount of acetone to precipitate the resin. This resin was further washed several times with acetone to remove unreacted maleic anhydride, and then dried under reduced pressure to obtain acid-modified polyolefin resin (A-2). Next, using a stirrer equipped with a heater-equipped, airtight, pressure-resistant 1L glass container, 30g of acid-modified polyolefin resin (A-2), 100g of tetrahydrofuran, 18g of triethylamine, and 252g of distilled water were placed in the glass container, and the mixture was stirred at a rotation speed of 300 rpm. While maintaining this state, the heater was turned on to heat the mixture, and the system temperature was maintained at 120°C while stirring for 60 minutes. After that, the mixture was cooled to room temperature (approximately 25°C) while being stirred in a water bath, and 64.5g of distilled water was added. The resulting dispersion was placed in a 1L round-bottom flask, and 176g of aqueous medium was removed by distillation under reduced pressure using an evaporator while the flask was placed in a water bath heated to 60°C. After cooling, the liquid components in the flask were pressure filtered (air pressure 0.2 MPa) through a 300-mesh stainless steel filter (wire diameter 0.035 mm, plain weave) to obtain a milky white, uniform aqueous dispersion of acid-modified polyolefin resin (A-2) (solid content concentration 12.5% ​​by mass, volume-average particle size (Mv) 12 nm).

[0073] <Production of aqueous dispersion of acid-modified polyolefin resin (A-3)> In the production of the above-mentioned acid-modified polyolefin resin (A-1), an aqueous dispersion of acid-modified polyolefin resin (A-3) (solid content concentration 20% by mass, volume average particle size (Mv) 150 nm) was obtained in the same manner, except that the propylene-ethylene copolymer (propylene / ethylene = 99 / 1 (mass ratio)) was replaced with an ethylene-ethyl acrylate copolymer (acid modification amount 2.5%, ethyl acrylate amount 6.5%, melting point 104°C).

[0074] To prepare the liquid for forming the resin layer, the following was used as the crosslinking agent (B). • WS-700: Epocross WS-700 manufactured by Nippon Shokubai Co., Ltd., aqueous solution of an oxazoline group-containing compound, solid content concentration 25% by mass. • V-02-L2: Carbodilite V-02-L2 manufactured by Nisshinbo Co., Ltd., aqueous solution of a carbodiimide group-containing compound, solid content concentration 25% by mass • HW-100: BASF's Basonate HW-100, an aqueous solution of a polyfunctional isocyanate compound, solid content concentration 25% by mass.

[0075] The following aqueous solutions were used as polyvinyl alcohol (C). • JT-05: JT-05 manufactured by Nippon Vivaceae Co., Ltd., saponification rate 94.2%, average degree of polymerization 500, solids content concentration 8% by mass • JM-17: JM-17 manufactured by Nippon Vivaceae Co., Ltd., saponification rate 97.0%, average degree of polymerization 1700, solid content concentration 8% by mass • JM-23: JM-23 manufactured by Nippon Vivaceae Co., Ltd., saponification rate 97.2%, average degree of polymerization 2300, solid content concentration 8% by mass • JM-33: JM-33 manufactured by Nippon Vivoval Vinegar Co., Ltd., saponification rate 94.9%, average degree of polymerization 3300, solid content concentration 5% by mass • JC-25: JC-25 manufactured by Nippon Vivaceae Co., Ltd., saponification rate 99.0%, average degree of polymerization 2500, solid content concentration 8% by mass • JP-24: JP-24 manufactured by Nippon Vivaceuil Co., Ltd., saponification rate 88.0%, average degree of polymerization 2400, solids content concentration 8% by mass

[0076] The following compound (D) was used: • KL-900: Polyflow KL-900 manufactured by Kyoeisha Chemical Co., Ltd., amphiphilic oligomeric surfactant • D-10: Orphine D-10 manufactured by Nisshin Chemical Industry Co., Ltd., an acetylene glycol-based surfactant. • E1010: Orphine E1010 manufactured by Nisshin Chemical Industry Co., Ltd., an acetylene glycol-based ethylene oxide adduct. • KL-401: Polyflow KL-401 manufactured by Kyoeisha Chemical Co., Ltd., modified silicone

[0077] <Manufacturing of liquid materials for forming slippery surfaces> A urethane resin emulsion (Hydran RCP-A-220, manufactured by DIC Corporation, with a solid content of 40%), a crosslinking agent (Epocross WS-700, manufactured by Nippon Shokubai Co., Ltd., an aqueous solution of an oxazoline group-containing compound, with a solid content of 25% by mass), and slippery particles (PL-7, manufactured by Fuso Chemical Industry Co., Ltd., colloidal silica, with an average particle size of 0.075 μm) was mixed with water to obtain a liquid substance S-1 for forming a slippery layer. The mixture consisted of 69 parts by mass of urethane resin solids, 21 parts by mass of crosslinking agent solids, 10 parts by mass of colloidal silica solids, and a solid content concentration of 6.6% by mass after mixing.

[0078] Example 1 <Preparation of liquid for resin layer formation> An aqueous dispersion of acid-modified polyolefin resin (A-1), an aqueous solution of an oxazoline group-containing compound as a crosslinking agent "WS-700," and an aqueous solution of polyvinyl alcohol "JM-23" were mixed so that the solid content was 100 parts by mass, 7 parts by mass, and 300 parts by mass, respectively. The final solid content concentration was then adjusted with water to 6.0% by mass. To this solution, 13 parts by mass of compound (D) "KL-900" was added and mixed to obtain a liquid for resin layer formation. <Manufacturing of release film> Polyethylene terephthalate (PET, polymerization catalyst: antimony trioxide, intrinsic viscosity: 0.62, glass transition temperature: 78°C, melting point: 255°C) containing 0.08% by mass of amorphous silica particles with an average particle size of 2.3 μm was melt-extruded at 280°C, and rapidly cooled in close contact with a casting drum using a T-die method-electrostatic pinning to form an unstretched film with a thickness of 600 μm. Subsequently, this unstretched film was stretched 3.5 times using a longitudinal stretching roll heated to 90°C. On one side of this longitudinally stretched film, the above liquid is applied using a reverse gravure coater at a rate of 6 g / m². 2 The material was applied to the specified amount (wet equivalent), stretched 4.5 times at 120°C in a transverse stretching tenter, heat-treated at 230°C for 10 seconds, then cooled and wound up. The resulting release film had a thickness of 38 μm, and the resin layer had a thickness of approximately 0.08 μm.

[0079] Examples 2-18, 20-22, Comparative Examples 1-7 A release film was obtained in the same manner as in Example 1, except that a liquid for forming the resin layer was prepared to have the composition and resin layer thickness described in Table 1, and this liquid was used.

[0080] Example 19 Polyethylene terephthalate (PET: polymerization catalyst: antimony trioxide, intrinsic viscosity: 0.62, glass transition temperature: 78.0°C, melting point: 255.0°C) was fed into an extruder (screw diameter: 65 mm) and melted at 280°C. The molten material was then adjusted to a thickness of 600 μm and extruded from the T-die outlet, where it was rapidly cooled and solidified to obtain an unstretched film. This unstretched film was stretched 3.5 times in a roll-type longitudinal stretcher at 85°C. Next, the resin layer-forming liquid prepared by the method described in Example 1 is applied to the surface of the longitudinally stretched film layer at a rate of 6 g / m² using a gravure roll. 2 After applying the coating in this manner, apply the smooth-slip layer-forming liquid S-1 to the surface opposite to the surface to which the resin layer-forming liquid was applied, using a gravure roll at a rate of 10 g / m². 2The film was then coated in the manner described above. The ends of the film were then continuously gripped by the clips of a flat stretcher and stretched to 4.5 times its original length at 135°C. After that, with a lateral relaxation rate of 3%, it was heat-treated at 243°C for 3 seconds, and then the film was wound onto a roll to obtain a 38 μm thick laminated film in which a resin layer with a thickness of 0.08 μm was provided on one side of the base film and a smooth layer with a thickness of 0.15 μm was provided on the other side.

[0081] Table 1 shows the results of various evaluations conducted on the release films obtained in the examples and comparative examples.

[0082] [Table 1]

[0083] The release films obtained in Examples 1 to 22 exhibited good release properties, heat resistance, and release properties after high-temperature treatment. In particular, the resin layers in Examples 1 to 6, 8 to 10, 12 to 15, 17, and 19 to 21 contained polyvinyl alcohol (C) within a preferred range for average degree of polymerization, saponification rate, and content, and the content of compound (D) and crosslinking agent (B) was within a preferred range. As a result, the fluidity of the resin layer at high temperatures was suppressed, and it exhibited excellent heat resistance and release properties after high-temperature treatment.

[0084] The resin layer-forming liquids of Comparative Examples 1 to 3 did not contain at least one compound (D) selected from the group consisting of amphiphilic oligomers, acetylene glycol, and ethylene oxide adducts of acetylene glycol as defined in the present invention. As a result, the resin layers had poor heat resistance and insufficient release properties after high-temperature treatment. The resin layer of Comparative Example 4 contained only polyvinyl alcohol with a degree of polymerization lower than the average degree of polymerization defined in the present invention. As a result, it became highly fluid at high temperatures, had poor heat resistance, and exhibited insufficient mold release properties after high-temperature treatment. The liquid material for forming the resin layer in Comparative Example 5 did not contain polyvinyl alcohol (C), resulting in poor coating properties. Furthermore, the resin layer flowed at high temperatures and could not maintain its release properties. The resin layer of Comparative Example 6 did not contain the crosslinking agent (B), resulting in low strength and poor heat resistance and mold release properties. The resin layer of Comparative Example 7 did not contain acid-modified polyolefin resin (A), and therefore had high peel strength from acrylic adhesives and epoxy prepregs, but poor mold release properties.

Claims

1. A release film having a resin layer on at least one side of a base film, wherein the resin layer is composed of a resin composition containing an acid-modified polyolefin resin (A), a crosslinking agent (B), and polyvinyl alcohol (C) having an average degree of polymerization of 1500 or more, and with a yield of 15 kg / cm² at 200°C. ２ A release film characterized by having a peel strength of 0.40 N / cm or less when pressed with an epoxy prepreg under pressure for 15 minutes.

2. The release film according to claim 1, characterized in that the amount of crosslinking agent (B) in the resin composition is 1 to 20 parts by mass per 100 parts by mass of acid-modified polyolefin resin (A).

3. The release film according to claim 1, characterized in that the polyvinyl alcohol (C) content in the resin composition is 10 to 1000 parts by mass per 100 parts by mass of acid-modified polyolefin resin (A).

4. The release film according to any one of claims 1 to 3, characterized in that the change in area of ​​the resin composition before and after heating and compression, as defined below, is less than 1.

9. (Change in area) For cylindrical samples prepared by curing a resin composition, the ratio of the base area of ​​the cylindrical sample before and after heating and compressing it at 200°C with a load of 1 MPa in the axial direction for 120 seconds (base area after heating and compression / base area before heating and compression).

5. The release film according to any one of claims 1 to 3, characterized in that the peel force between the resin layer and the adherend when an acrylic adherend is attached to the resin layer and measured is 3.0 N / cm or less.

6. A method for manufacturing the release film described in claim 1, A method for producing a release film, comprising the steps of drying and stretching a substrate film having a coating film formed on at least one surface using a liquid resin medium containing a resin composition comprising an acid-modified polyolefin resin (A), a crosslinking agent (B), polyvinyl alcohol (C) having an average degree of polymerization of 1500 or more, and at least one compound (D) selected from the group consisting of amphiphilic oligomers, acetylene glycol, and ethylene oxide adducts of acetylene glycol.

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