Release film

Abstract

To provide a release film with suppressed floating or film peeling from the release film on cast film production of a resin film, having good detachability of a resin film from the release film after film production, suppressing detachment electrification on detachment, with easy appearance inspection property, and capable of producing a resin film having resin film thickness uniformity and high smoothness.SOLUTION: A release film includes a substrate film having at least on one side, and in the order of the substrate films side, an antistatic layer and a release layer; in the release film, the antistatic layer includes an electrically conductive polymer, resins constituting the release layer includes 80 mass % or over of a melamine resin, and a surface roughness (Sa) of the release layer is under 10 nm.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a release film, and more particularly to a release film (support film) that is non-silicone and has excellent release properties and is suitable for use in the manufacturing process (cast film production) of interlayer insulating sheets such as epoxy resin films. [Background technology]

[0002] Release films are used as process films (support films) for cast production of resin films, process films for molding green sheets for ceramic capacitors, protective films for pressure-sensitive adhesive sheets, or as support substrates or protective films for photosensitive resin layers (photoresist layers).

[0003] BACKGROUND ART A known process film (release film) for cast production of a resin film is a release film having a release layer made of a silicone resin on a base film (Patent Document 1).

[0004] Also known is a release film having a release layer made of melamine resin on a base film (Patent Document 2). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2010-6079 [Patent Document 2] Japanese Patent Application Laid-Open No. 2014-151448 Summary of the Invention [Problem to be solved by the invention]

[0006] For example, resin films used for optical applications preferably have a uniform thickness and a highly smooth surface. However, even if the release films described in Patent Documents 1 and 2 are used in the cast production of resin films, there are problems such as deterioration of workability due to peeling electrification when peeling the resin film from the release film, and inability to sufficiently improve the uniformity of the thickness of the resin film.

[0007] In addition, in the step of forming a resin film by cast film formation, it is preferable that the release film and the resin film are in moderate adhesion to prevent the resin film from lifting up or peeling off from the release film. On the other hand, in the step of peeling the resin film from the release film after film formation, it is preferable that the release film and the resin film can be peeled off relatively easily.

[0008] Therefore, the object of the present invention is to provide a release film that suppresses lifting and peeling of a resin film from a release film during cast production, provides good peelability of the resin film from the release film after production, suppresses peel electrification during peeling, makes visual inspection easy, and enables the production of a resin film with high uniformity in resin film thickness and smoothness. [Means for solving the problem]

[0009] In order to solve the above problems, the present invention has the following configuration. [1] A release film having an antistatic layer and a release layer, in this order from the substrate film side, on at least one surface of a substrate film, wherein the antistatic layer contains a conductive polymer, the resin constituting the release layer contains 80% by mass or more of a melamine resin, and the surface roughness (Sa) of the release layer is less than 10 nm. [2] A release film according to [1], which has an antistatic layer and a release layer, in that order from the base film side, on only one side of the base film, and the surface roughness (Sa) of the non-release layer surface, which is the side of the release film that does not have the release layer, is 5 to 30 nm. [3] The release film according to [1] or [2], wherein the peel strength between the release layer surface, which is the surface of the release film having the release layer, and the adhesive tape is 1.0 to 5.0 N / 18 mm. [4] The release film according to any one of [1] to [3], wherein the release layer surface, which is the surface of the release film having the release layer, is pressure-bonded to a PET film, and then the release film is peeled off, and immediately thereafter, the charge amount of the release layer surface is −1.5 to 1.5 kV. [5] The release film according to any one of [1] to [4], which is used as a release film for use in the manufacturing process of an interlayer insulating sheet. [Effects of the Invention]

[0010] The release film of the present invention suppresses lifting and peeling of the resin film from the release film during the resin film casting process, provides good releasability from the release film after resin film formation, suppresses peel electrification, makes appearance inspection easy, and allows the production of resin films with high uniformity in resin film thickness and smoothness. DETAILED DESCRIPTION OF THE INVENTION

[0011] The release film of the present invention is suitable as a process film (support film) for cast production of a resin film. Hereinafter, cast production of a resin film will be described as an example. However, the present invention is not limited thereto. As will be described later, the release film of the present invention is suitable for use as a release film for a process for producing an interlayer insulating sheet, and the cast film production method is one of the production methods suitable for use in producing an interlayer insulating sheet.

[0012] The resin film casting method (also called the solvent casting method or solution casting method) is a method for producing a resin film by casting a resin solution onto the release layer of a release film. After the resin film is formed, the release film and the resin film are peeled off.

[0013] The release film of the present invention is a release film having an antistatic layer and a release layer in this order from the substrate film side on at least one surface of the substrate film.

[0014] The substrate film used in the release film of the present invention is not particularly limited, and various plastic films can be used, for example, polyester films such as polyethylene terephthalate film, polybutylene terephthalate film, and polyethylene naphthalate film, polyolefin films such as polypropylene film and polyethylene film, cellulose films such as diacetyl cellulose film and triacetyl cellulose film, polysulfone film, polyether ether ketone film, polyether sulfone film, polyphenylene sulfide film, polyetherimide film, polyimide film, polyamide film, acrylic film, cyclic olefin film, and polycarbonate film.

[0015] Among these plastic films, polyester films are preferred because of their relatively high smoothness and good heat resistance. Among polyester films, polyethylene terephthalate films are preferred, with biaxially oriented polyethylene terephthalate films being more preferred.

[0016] The thickness of the substrate film is preferably from 30 to 300 μm, more preferably from 33 to 200 μm, and particularly preferably from 35 to 100 μm.

[0017] The substrate film preferably has a high surface smoothness. Specifically, the surface roughness (Sa) of the surface of the substrate film on which the release layer is laminated is preferably less than 10 nm, more preferably less than 7 nm, and particularly preferably less than 5 nm. The lower limit is about 0.1 nm. Here, the surface roughness (Sa) can be measured by the method described in "(1) Measurement of Surface Roughness (Sa)" in the Examples below.

[0018] The base film may contain particles (fillers). The particles (fillers) are not particularly limited, but examples include silicon dioxide and titanium oxide. In order to achieve a preferred range of surface smoothness of the base film, the content of particles (fillers) in the base film is preferably 0.001 to 5% by mass. When the content of particles (fillers) in the base film is 5% by mass or less, the surface of the release film is less likely to become rough, making it easier to obtain the desired surface roughness of the release film.

[0019] In the present invention, the antistatic layer refers to a layer for suppressing peeling electrification when the resin film is peeled off from the release film.

[0020] In the present invention, the antistatic layer contains a conductive polymer. Here, the conductive polymer is a general term for polymers that exhibit electrical conductivity by adding a small amount of an electron-accepting substance or an electron-donating substance to a main-chain conjugated polymer.

[0021] Examples of conductive polymers include aliphatic conjugated polymers such as polyacetylene, aromatic conjugated polymers such as poly(p-phenylene) and polyfluorene, heterocyclic conjugated polymers such as polypyrrole, polyfuran, polythiophene, and alkylenedioxypolythiophene, mixed conjugated polymers such as polythienylenevinylene and poly(p-phenylenevinylene), and heteroatom-containing conjugated polymers such as polyaniline. The conductive polymer in the present invention is preferably a heterocyclic conjugated polymer because it easily exhibits antistatic properties in the coating film. Among these, polythiophene-based conductive polymers, which have excellent stability, are preferred, and alkylenedioxypolythiophenes are more preferred. Among these, poly(3,4-ethylenedioxythiophene) (PEDOT) doped with polystyrene sulfonic acid (PSS) is particularly preferred.

[0022] The antistatic layer in the present invention is preferably an antistatic layer obtained by coating and drying a composition containing an acrylic resin having a carboxylate anion group, a melamine resin, a polyfunctional aziridine compound, and the above-mentioned conductive polymer, because this makes it easier to obtain an antistatic layer excellent in mechanical strength and solvent resistance.

[0023] An acrylic resin containing a carboxylate anion group (hereinafter sometimes simply referred to as "acrylic resin") is an acrylic resin that contains a carboxylate anion group (-COO - The acrylic resin in the present invention is preferably a copolymer obtained by reacting an α,β-ethylenically unsaturated carboxylic acid monomer with an alkyl (meth)acrylate.

[0024] Specific examples of the α,β-ethylenically unsaturated carboxylic acid include α,β-ethylenically monocarboxylic acids such as acrylic acid, methacrylic acid, crotonic acid, and isocrotonic acid, and α,β-ethylenically dicarboxylic acids such as maleic acid, fumaric acid, and itaconic acid. Monoesters of α,β-ethylenically dicarboxylic acids with various alcohols are also possible. Of these, it is preferable that the α,β-ethylenically unsaturated carboxylic acid be acrylic acid or methacrylic acid, in terms of stable supply of the material.

[0025] The (meth)acrylic acid alkyl ester may be a (meth)acrylic acid alkyl ester having a linear alkyl group, such as methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, or normal butyl (meth)acrylate, or may be one having a branched or cyclic alkyl group.

[0026] In addition to these α,β-ethylenically unsaturated carboxylic acid monomers and alkyl (meth)acrylates, metha(acryl)amides, hydroxyalkyl (meth)acrylates, etc. can also be copolymerized.

[0027] The acrylic resin in the present invention may be one obtained by polymerizing these components by any method such as radical polymerization, anionic polymerization, or cationic polymerization, but one obtained by polymerizing by radical polymerization is preferred. The carboxyl group in the α,β-ethylenically unsaturated carboxylic acid may be in the monomer stage or after polymerization, but by neutralizing it with a neutralizing agent, the carboxylate anion group (-COO - ) and can be easily dissolved in a water-based solvent.

[0028] Examples of the neutralizing agent include ammonia, primary to tertiary amines, alkali metal compounds, alkaline earth metal compounds, etc. Among these, it is preferable to use ammonia or a tertiary amine such as trimethylamine or triethylamine, as this improves the solvent resistance of the antistatic layer.

[0029] The antistatic layer in the present invention preferably further contains a curing agent. By containing a curing agent, adhesion to the substrate film and strength of the coating film are likely to be improved. In particular, it is more preferable to contain a polyfunctional aziridine compound as the curing agent. By containing a polyfunctional aziridine compound, particularly excellent curability is exhibited.

[0030] The polyfunctional aziridine compound in the present invention is a compound having at least two aziridinyl groups in the molecule, and from the viewpoint of curability, it is preferable that the polyfunctional aziridine compound has at least three aziridinyl groups.

[0031] The polyfunctional aziridine compound is preferably a polyhydric alcohol ester of an aziridinyl carboxylic acid, such as 3-(1-aziridinyl)propionic acid, 3-(2-methyl-1-aziridinyl)propionic acid, 3-(2-ethyl-1-aziridinyl)propionic acid, 3-(2-propyl-1-aziridinyl)propionic acid, or 3-(2,3-dimethyl-1-aziridinyl)propionic acid. Examples of trifunctional aziridine compounds include glycerol tris[3-(1-aziridinyl)propionic acid] esters of these aziridinyl carboxylic acids, such as tris[3-(1-aziridinyl)propionic acid] trimethylolpropane trimethylolpropane esters, and tetramethylolmethane tris[3-(1-aziridinyl)propionic acid] tetramethylolmethane esters. Examples of tetrafunctional aziridine compounds include pentaerythritol esters of these aziridinyl carboxylic acids, such as tetra[3-(1-aziridinyl)propionic acid] pentaerythritol.

[0032] In the present invention, the relationship between the number of moles X (mol) of the carboxylate anion groups and the number of moles Y (mol) of the aziridinyl groups is preferably X / Y of 0.8 to 2.0 from the viewpoint of the curability of the antistatic layer.

[0033] The solvent used when applying the antistatic layer is preferably water, an alcohol, or a ketone, but it is desirable to use a mixture of these in consideration of coating properties.

[0034] The dried coating thickness of the antistatic layer is preferably 0.02 to 0.3 μm, more preferably 0.03 to 0.2 μm, and even more preferably 0.04 to 0.1 μm. By setting the coating thickness in the range of 0.02 to 0.3 μm, it is possible to easily exhibit antistatic performance economically.

[0035] The release film of the present invention contains 80% by mass or more of melamine resin in the resin constituting the release layer. The content of melamine resin is more preferably 95% by mass or more, particularly preferably 98% by mass or more. By containing 80% by mass or more of melamine resin in the resin constituting the release layer, appropriate adhesion is imparted between the cast-formed resin film and the release layer, thereby suppressing lifting or peeling of the resin film from the release film during film formation, and improving the releasability of the resin film from the release film after film formation. If the content of melamine resin in the resin constituting the release layer is less than 80% by mass, this can cause poor release or reduced adhesion to the resin film.

[0036] The release layer may further contain a resin other than the melamine resin, such as an acrylic resin, a polyurethane resin, a polyester resin, or an epoxy resin.

[0037] The content of resins other than melamine resin in the release layer is 20% by mass or less, more preferably 10% by mass or less, even more preferably 5% by mass or less, and particularly preferably 2% by mass, of the resin constituting the release layer. If the content of resins other than melamine resin exceeds 20% by mass, problems occur such as reduced flowability and adhesion of the resin solution on the release layer during resin film casting.

[0038] The melamine resin is a polycondensation product of a melamine compound. Examples of melamine compounds that can be suitably used in the present invention include methylolated melamine and alkyl-etherified melamine. That is, the melamine resin in the present invention is preferably a methylolated melamine resin or an alkyl-etherified melamine resin. From the viewpoint of improving the film strength of the release layer and improving the adhesion between the release layer and the substrate film, an alkyl-etherified melamine resin is more preferred, and a partially alkyl-etherified melamine resin is even more preferred.

[0039] Methylol melamine can be obtained, for example, by the addition reaction of melamine or a melamine derivative with formaldehyde. Alkyl etherified melamine can be obtained, for example, by partially or completely etherifying the methylol groups of methylol melamine with an alcohol. The alkyl in the alkyl etherified melamine preferably has 1 to 6 carbon atoms, more preferably 1 to 4 carbon atoms.

[0040] Examples of melamine derivatives include guanamine, benzoguanamine, 2,4-diamino-6-methacryloyloxyethyl-S-triazine, 2-vinyl-4,6-diamino-S-triazine, 2-vinyl-4,6-diamino-S-triazine-isocyanuric acid adduct, and 2,4-diamino-6-methacryloyloxyethyl-S-triazine-isocyanuric acid adduct.

[0041] The alcohol used for etherification is preferably an alcohol having 1 to 6 carbon atoms, and examples thereof include methyl alcohol, ethyl alcohol, propyl alcohol, isopropyl alcohol, butyl alcohol, isobutyl alcohol, pentyl alcohol, and hexyl alcohol.

[0042] As the melamine compound, the above-mentioned methylol melamine and alkyl etherified melamine are preferred, and these compounds can be represented by the following general formula (1).

[0043] [ka]

[0044] In the formula, R 1 ~R 6 each independently represents a hydrogen atom, a methylol group, or an alkoxymethyl group, provided that at least one of them is a methylol group or an alkoxymethyl group.

[0045] R 1 ~R 6Among these, preferably three or more are methylol groups or alkoxymethyl groups, more preferably four or more are methylol groups or alkoxymethyl groups, and even more preferably five or more are methylol groups or alkoxymethyl groups. 1 ~R 6 are preferably all methylol groups and / or alkoxymethyl groups, and most preferably a mixture of methylol groups and alkoxymethyl groups. Here, the mixture of methylol groups and alkoxymethyl groups means that the methylolated melamine is partially etherified with an alcohol. Here, the alkoxy group (OR) of the alkoxymethyl group (-CH2OR) is preferably an alkoxy group having 1 to 6 carbon atoms, such as a methoxy group, an ethoxy group, a propoxy group, an n-butoxy group, an isobutoxy group, a pentoxy group, or a hexoxy group. Among these, an alkoxy group having 1 to 4 carbon atoms is more preferred. The alkoxymethyl group (-CH2OR) can be obtained by etherifying a methylol group (-CH2OH) with an alcohol. As the alcohol, an alcohol having 1 to 6 carbon atoms is preferably used, as described above. As the melamine compound included in the above general formula (1), R 1 ~R 6 Methylol melamine, in which 1 to 6 of the groups are methylol groups, R 1 ~R 6 Alkyl etherified melamine in which 1 to 6 of R are alkoxymethyl groups, and R 1 ~R 6 Among the above melamine compounds, R 1 ~R 6 Particularly preferred is a partially alkyl-etherified melamine in which methylol melamine in which all of the above are methylol groups has been partially etherified. Furthermore, the alkyl of the partially alkyl-etherified melamine preferably has 1 to 6 carbon atoms, more preferably 1 to 4 carbon atoms, and particularly preferably a butyl group.

[0046] The degree of etherification of the partially alkyl-etherified melamine is preferably 10 to 95%, more preferably 15 to 90%, and particularly preferably 20 to 80%. Here, the degree of etherification is the ratio of the molar amount of etherified methylol groups to the total molar amount of etherified and unetherified methylol groups. The degree of etherification can be controlled, for example, by adjusting the amount of alcohol added for etherification. A release layer formed using the above-described partially alkyl-etherified melamine is preferred because it tends to improve the flowability of the resin solution on the release layer during cast production of the resin film, and also tends to impart appropriate adhesion between the resin film and the release layer, thereby easily suppressing lifting or peeling of the resin film from the release film during film production, and also tends to further improve the releasability of the resin film from the release film after film production. Furthermore, it tends to increase the hardness of the release layer, which is also preferred in terms of heat resistance and solvent resistance.

[0047] As the above-mentioned melamine compound, for example, "ATOM" manufactured by Mitsuba Research Institute, Ltd. BOND (registered trademark) RP-50, DIC Corporation's "Super Beckamin (registered trademark)" L-105-60, J-820-60, J-821-60, J-1090-65, J-110-60, J-117-60, J-127-60, J-166-60B, J-105-60, G840, and G821, and Mitsui Chemicals' "U-Ban (registered trademark)" 20SB, 20SE60, 21R, 22R, 122, 125, 128, 220, 225, 228, 28-60, 2020, 60R, 62, 62E, 360, 165, and 166- 60, 169, 2061, Sumitomo Chemical Co., Ltd.'s "Sumimal (registered trademark)" M-100, M-40S, M-55, M-66B, Japan Cytec Industries' "Cymel (registered trademark)" 303, 325, 327, 350, 370, 235, 202, 238, 254, 272, 1130, Sanwa Chemical Co., Ltd.'s "Nicalac (registered trademark)" MS17, MX15, MX430, MX600, Harima Chemical Co., Ltd.'s Bansemyn SM-975, SM-960, Hitachi Chemical Co., Ltd.'s "Melan (registered trademark)" 265, 2650L, and the like.

[0048] The coating liquid for forming the release layer preferably contains an acid catalyst. The acid catalyst can promote polycondensation of the melamine compound. Examples of the acid catalyst include sulfuric acid, hydrochloric acid, nitric acid, phosphoric acid, and p-toluenesulfonic acid. When an acid catalyst is contained, the content of the acid catalyst is preferably in the range of 1 to 30 parts by mass, more preferably in the range of 2 to 20 parts by mass, and particularly preferably in the range of 3 to 15 parts by mass, relative to 100 parts by mass of the melamine compound.

[0049] The release layer may contain an ion-conductive antistatic agent, a surfactant, and the like.

[0050] In the release film of the present invention, the surface roughness (Sa) of the release layer is less than 10 nm. The surface roughness (Sa) of the release layer is more preferably less than 7 nm, and particularly preferably less than 5 nm. The lower limit is not particularly limited, but is about 0.1 nm. By making the surface roughness (Sa) of the release layer less than 10 nm, the smoothness of the resin film produced by casting a resin solution onto the release layer of the release film can be within the desired range.

[0051] The surface roughness (Sa) of the release layer is the surface roughness measured in accordance with ISO 25178-3.2 (2010) using a non-contact surface / layer cross-sectional shape measurement system, VertScan R5300GL-Lite-AC, manufactured by Ryoka Systems, with a 50x objective lens set to a measurement area of ​​1 mm square.

[0052] The method for making the surface roughness (Sa) of the release layer less than 10 nm is not particularly limited, but for example, (i) Use a substrate film with a high surface smoothness. (ii) Coating the release layer so that the coating surface is uniform; (iii) The release layer is substantially free of particles (fillers); (iv) The thickness of the release layer is made relatively large to reduce the influence of the surface properties of the base film. Examples include:

[0053] As an example of the above (i), there is an embodiment in which a substrate film with a low particle (filler) content is used.

[0054] The above (ii) can be achieved by adjusting the solid content concentration and solvent composition of the coating liquid for the release layer. For example, the solid content concentration of the coating liquid for the release layer is preferably 0.5 to 10 mass %, more preferably 2 to 7 mass %. As the solvent composition of the coating liquid for the release layer, for example, it is preferable to use two or more different types of solvents in combination. Examples of the types of solvent include ketones, alcohols, aromatic hydrocarbons, aliphatic hydrocarbons, cyclic hydrocarbons, and halogenated hydrocarbons. A preferred example is the combination of ketones and aromatic hydrocarbons.

[0055] An example of the above (iii) is that the release layer does not substantially contain particles (fillers) with an average particle size of 200 nm or more, where "substantially not containing particles" means that the particle content in the release layer is less than 5% by mass.

[0056] Regarding the above (iv), for example, the thickness (dry thickness) of the release layer is preferably 150 to 500 nm, more preferably 200 to 300 nm.

[0057] In order to make the surface roughness (Sa) of the release layer less than 10 nm, it is preferable to combine two or more of the above (i) to (iv), more preferably to combine three or more, and it is particularly preferable to combine all of the requirements.

[0058] The release film of the present invention preferably has a peel strength between the release layer surface, which is the surface of the release film having the release layer, and the adhesive tape of 1.0 to 5.0 N / 18 mm. The peel strength is particularly preferably 1.5 to 3.0 N / 18 mm. When the peel strength between the release layer surface and the adhesive tape is within the preferred range, the release layer and the cast-formed resin film tend to adhere to each other appropriately in the resin film cast-forming step, which tends to inhibit the resin film from lifting up or peeling off from the release film during cast-forming, and tends to improve the releasability of the resin film from the release film after resin film formation.

[0059] In the present invention, the peel strength between the release layer surface and the adhesive tape refers to the peel strength measured when the adhesive side of an acrylic adhesive tape (No. 31B manufactured by Nitto Denko Corporation) is applied to the surface of the release layer by pressing it with a rubber roller having a weight of 5 kg and moving it back and forth once to bond it, and then the tape is left to stand at room temperature (23±5°C) for 1 hour, and then the adhesive tape side is peeled off at an angle of 180° at a speed of 300 mm / min using a Tensile Tester.

[0060] As a method for adjusting the peel force between the release layer surface of the release film of the present invention and the adhesive tape to fall within a preferred range, for example, the release layer may contain 80% by mass or more of melamine resin relative to the total resin constituting the release layer, and an alkyl-etherified melamine resin may be used as the melamine resin, preferably a partially alkyl-etherified melamine resin, to achieve the above range.

[0061] The thickness of the release layer is preferably 150 to 500 nm, more preferably 200 to 300 nm. When the thickness of the release layer is 150 nm or more, the peeling force from the resin film tends to be sufficiently small, making it easy to obtain a good release film. Furthermore, when the thickness of the release layer is 500 nm or more, the flatness and drying properties are improved, and the appearance of coating unevenness and heat wrinkles during the heating process are less likely to occur.

[0062] In the release film of the present invention, it is more preferable that the release layer contains 80% by mass or more of a melamine resin based on the total mass of the resin, and that the surface roughness (Sa) of the release layer is less than 10 nm. This configuration facilitates the good flowability of the resin solution on the release layer in the resin film casting process, making it easier to form a uniform resin film. This makes it easier to obtain a resin film with the desired smoothness.

[0063] The release film of the present invention has a release layer on at least one surface of the base film. The release layer may be provided on only one surface or on both surfaces of the base film, but is preferably provided on only one surface.

[0064] The release layer of the present invention can be obtained, for example, by applying a coating liquid containing the above-mentioned melamine compound onto a substrate film, followed by drying and heating. A common coating method can be used to apply the coating liquid to form the release layer. Examples of coating methods include gravure coating, gravure reverse coating, lip coating, die coating, microgravure coating, Mayer bar coating, and multi-stage reverse coating. Drying and heating after application of the release layer are usually carried out continuously online. The drying and heating step preferably involves, for example, pre-drying at 50 to 100°C and heating at 100 to 160°C. The pre-drying time is preferably 10 to 100 seconds, and the heating time is preferably 10 to 100 seconds.

[0065] In the release film of the present invention, an antistatic layer and a release layer are provided, in order from the substrate film side, only on one side of the substrate film, and the surface roughness (Sa) of the non-release layer surface, which is the surface of the release film that does not have the release layer, is preferably 5 to 30 nm. When the surface roughness (Sa) of the non-release layer surface is 5 nm or more, conveyance is likely to be improved and defects such as scratches are unlikely to occur. Furthermore, when the surface roughness (Sa) of the non-release layer surface is 30 nm or less, the surface roughness of the film does not become too rough, and problems such as poor conveyance are unlikely to occur in subsequent processes. An example of a method for adjusting the surface roughness of the non-release layer surface within the above range is to incorporate particles (filler) such as silicon dioxide or titanium oxide into the substrate film. The content of particles (filler) in the substrate film is preferably 0.001 to 5 mass%.

[0066] In the release film of the present invention, after the release layer surface, which is the surface of the release film having the release layer, is pressure-bonded to a PET film, the charge amount of the release layer surface immediately after peeling off the release film (hereinafter, sometimes simply referred to as the charge amount after peeling) is preferably −1.5 to 1.5 kV. If the charge amount after peeling is less than −1.5 kV or more than 1.5 kV, peeling charge is likely to occur, which may lead to defects in the resin film or reduced work efficiency. An example of a method for adjusting the charge amount after peeling to fall within the above range is to adjust the coating thickness of the antistatic layer after drying. The coating thickness of the antistatic layer is preferably 0.02 to 0.3 μm, more preferably 0.03 to 0.2 μm, and even more preferably 0.04 to 0.1 μm. By setting the coating thickness within the above range, antistatic performance can be easily and economically achieved.

[0067] In the present invention, the charge amount after peeling refers to the potential measured by pressing the release layer surface and a biaxially oriented polyethylene terephthalate film (manufactured by Toray Industries, Inc., type name: #188 U48) together with a rubber roller having a weight of 5 kg and moving it back and forth three times to press them together, and then peeling off the release film. The charge amount on the release layer surface immediately after peeling off the release film is measured using an electrometer (manufactured by Simco Japan Co., Ltd., FMX-003) under conditions of 23±2°C and 60±10% RH.

[0068] The release film of the present invention can be used as a process film (support film) for cast production of resin films, a process film for molding green sheets of ceramic capacitors, a protective film for pressure-sensitive adhesive sheets, or a support substrate or protective film for photosensitive resin layers (photoresist layers), and is particularly suitable as a process film (support film) for cast production of resin films.As a process film (support film) for cast production of resin films, it is suitable for cast production of optical resin films that require high smoothness, such as those used in the production of interlayer insulating sheets.In other words, the release film of the present invention is preferably used as a release film for the production of interlayer insulating sheets.

[0069] Examples of resin films that can be cast using the release film of the present invention include polyimide resin films, polycarbonate resin films, cellulose acylate resin films, cyclic polyolefin resin films, acrylic resin films, methacrylic resin films, and polyurethane resin films. Among these, the release film of the present invention is suitable for cast production of polyimide resin films, cellulose acylate resin films, cyclic polyolefin resin films, and polycarbonate resin films. These resin films may be composed of a single film or may have a multi-layer laminate structure of two or more layers. [Example]

[0070] EXAMPLES The present invention will be described in more detail with reference to examples, but the present invention is not limited to the following examples. Evaluation methods and measurement methods used in the examples and comparative examples are shown below.

[0071] [Measurement and evaluation methods] (1) Measurement of surface roughness (Sa) The release layer surface and non-release layer surface were measured in accordance with ISO 25178-3.2 (2010) using a non-contact surface / layer cross-sectional shape measurement system VertScan R5300GL-Lite-AC manufactured by Ryoka Systems, with a 50x objective lens and a measurement area of ​​1 mm square.

[0072] (2) Peel force measurement The adhesive side of an acrylic adhesive tape (No. 31B manufactured by Nitto Denko Corporation) was applied to the surface of the release layer of the release film by pressing it down with a rubber roller weighing 5 kg and rolling it back and forth once to bond it together, and after leaving it at room temperature (23±5°C) for 1 hour, the adhesive tape side was peeled off at an angle of 180° at a speed of 300 mm / min using an A&D tensile tester (RTG-1210) to measure the peel force.

[0073] (3) Measurement of charge amount after peeling The release layer surface and PET (Toray Industries, Inc. #188U48) were pressed together with a 5 kg rubber roller, which was rolled back and forth three times to bond them together, and then the release film was peeled off. The amount of charge on the release layer surface immediately after peeling off the release film was measured using a Simco Japan FMX-003 under the conditions of 23±2°C and 60±10% RH.

[0074] (4) Measurement of substrate adhesion An adhesive tape (405 tape manufactured by Nichiban Co., Ltd.) was attached to the surface of the release layer of the release film, and the adhesive tape side was peeled off at an angle of 180°. The peeling of the release layer was visually confirmed, and if the release layer did not peel off, it was marked as ◯, and if it did peel off, it was marked as ×.

[0075] (5) Measurement method for antistatic layer and release layer thickness The release layer surface was measured using an Optical NanoGauge film thickness meter (C13027-11) manufactured by Hamamatsu Photonics.

[0076] (6) Test method for film-forming properties of resin films <Preparation of Resin Composition A> Ten parts of a bisphenol A epoxy resin (828US manufactured by Mitsubishi Chemical Corporation), 20 parts of a biphenyl epoxy resin (YX4000H manufactured by Mitsubishi Chemical Corporation), 10 parts of a bisphenol AF epoxy resin (YL7760 manufactured by Mitsubishi Chemical Corporation), 3 parts of a phosphazene resin (SPH-100 manufactured by Otsuka Chemical Co., Ltd.), and 10 parts of a phenoxy resin (YL7553BH30 manufactured by Mitsubishi Chemical Corporation) were heated and dissolved in 60 parts of MEK. After cooling to room temperature, 30 parts of an active ester curing agent (HPC-8000-65T manufactured by DIC Corporation), 16 parts of a phenolic curing agent (LA-3018-50P manufactured by DIC Corporation), 3 parts of a benzoxazine compound (ODA-BOZ manufactured by JFE Chemical Corporation), 4 parts of 4-dimethylaminopyridine (DMAP) as a curing accelerator, and 110 parts of finely pulverized silica were mixed to prepare Resin Composition A (hereinafter referred to as Resin Composition A).

[0077] <Preparation of sample for film-forming test> The resin composition A prepared above was uniformly applied to the surface of the release layer of the release film using an applicator so that the thickness of the resin composition A layer after drying would be 30 μm, and the resulting film was dried at 100°C for 3 minutes to prepare an epoxy resin film.

[0078] <Judgment method> 1) Resin film forming properties The film formability of the resin film was judged based on the uniformity and smoothness of the resin film. The film-forming test sample was visually observed under reflected fluorescent light, and a sample with no coating unevenness or cissing was rated as a uniform and highly smooth resin film, and a sample with coating unevenness or cissing was rated as an x.

[0079] 2) Peelability of resin film from release film The peel strength of the resin film from the release film was measured using an A&D tensile tester (RTG-1210) at a speed of 300 mm / min, with the release film side peeled at an angle of 180°. Peel strengths of 0.01 to 0.6 N / 18 mm were deemed good and rated as ◯, peel strengths of 0.6 to 1.5 N / 18 mm as △, and peel strengths of over 1.5 N / 18 mm as poor and ×. Note that if the peel strength is less than 0.01 N / 18 mm, the resin film is more likely to lift off the release film or peel off.

[0080] 3) Surface condition of the resin film after removing the release film After peeling the resin film from the release film, the surface of the resin film on the side peeled from the release film was measured using a Ryoka Systems non-contact surface and layer cross-sectional shape measurement system, VertScan R5300GL-Lite-AC, with a 50x objective lens, set to a 1mm square measurement area, in accordance with ISO 25178-3.2 (2010). If the measured value was 100nm or less, the surface condition was rated as good, and if the measured value was over 100nm, the resin surface condition was deemed poor and rated as bad. If the surface condition of the resin film after peeling is good (good), it becomes easier to perform an appearance inspection.

[0081] [Example 1] Antistatic layer coating solution 1 was prepared by mixing 0.7 parts by mass of an aqueous solution containing 70% by mass of melamine resin as a binder (P795 manufactured by Chukyo Yushi Co., Ltd.) and 2 parts by mass of an aqueous solution containing 0.5% by mass of poly(3,4-ethylenedioxythiophene) (PEDOT) doped with polystyrene sulfonic acid (PSS), a polythiophene-based conductive polymer (S948 manufactured by Chukyo Yushi Co., Ltd.), as a conductive polymer, into a mixed solution of ion-exchanged water and isopropyl alcohol (IPA) (7 / 7 parts by mass).

[0082] A solution of 1 part by mass of a melamine compound (RP-50 manufactured by Mitsuba Research Institute, Inc., solids content 50% by mass) which is a thermosetting resin, and 9 parts by mass of a mixture of toluene, anion, and methanol (4.5 / 3.6 / 0.9) was mixed with 0.1 part by mass of DEP Clear (manufactured by Washin Chemical Industry Co., Ltd.) which is a curing agent to prepare release layer coating liquid 1. In each example and comparative example, the melamine resin content by mass (solids content %) was calculated using the solids mass of the melamine compound in the release layer coating liquid as the numerator and the total solids mass of the melamine compound and other components (total solids mass of the melamine compound, ion-conductive Colcoat N103X, and curing agent) as the denominator.

[0083] Antistatic layer coating solution 1 was applied to a 100 μm thick polyethylene terephthalate film ("Lumirror" (registered trademark) R41, manufactured by Toray Industries, Inc.) using wire bar No. 3 so that the coating thickness after drying would be 50 nm, and this was dried and cured at 135°C for 20 seconds. Subsequently, release layer coating solution 1 was applied using wire bar No. 5 so that the coating thickness would be 300 nm, and this was dried and cured at 140°C for 30 seconds to obtain a release film.

[0084] [Example 2] A release film was obtained in the same manner as in Example 1, except that instead of release layer coating liquid 1 in Example 1, release layer coating liquid 2 was used, which was prepared by mixing a solution of 1 part by mass of a melamine compound (RP-50 manufactured by Miwa Research Institute Co., Ltd., solid content 50% by mass), which is a thermosetting resin, and 9 parts by mass of a mixed liquid of toluene, anion, and methanol (4.5 / 3.6 / 0.9), with 1 part by mass of ion-conductive Colcoat N103X (Colcoat Co., Ltd., solid content 2% by mass), and 0.1 part by mass of DEP Clear (manufactured by Washin Chemical Co., Ltd.), which is a curing agent.

[0085] [Example 3] A release film was produced in the same manner as in Example 1, except that a 38 μm thick polyethylene terephthalate film ("Lumirror" (registered trademark) R80, manufactured by Toray Industries, Inc.) was used instead of a 100 μm thick polyethylene terephthalate film ("Lumirror" (registered trademark) R41, manufactured by Toray Industries, Inc.).

[0086] [Example 4] A release film was produced in the same manner as in Example 1, except that instead of antistatic coating solution 1 in Example 1, an antistatic layer coating solution 2 was used, which was prepared by mixing 0.036 parts by mass of an aqueous solution containing 70% by mass of melamine resin as a binder (P795, manufactured by Chukyo Yushi Co., Ltd.) and 3.5 parts by mass of an aqueous solution containing 0.5% by mass of poly(3,4-ethylenedioxythiophene) (PEDOT) doped with polystyrene sulfonic acid (PSS), a polythiophene-based conductive polymer (U690, manufactured by Chukyo Yushi Co., Ltd.), in a mixed solution of ion-exchanged water and isopropyl alcohol (IPA) (9.8 / 9.8 parts by mass).

[0087] [Example 5] A release film was produced in the same manner as in Example 1, except that instead of antistatic coating solution 1 in Example 1, antistatic layer coating solution 3 was used, which was prepared by mixing 0.018 parts by mass of an aqueous solution containing 70% by mass of melamine resin as a binder (P795, manufactured by Chukyo Yushi Co., Ltd.) and 2.1 parts by mass of an aqueous solution containing 0.5% by mass of poly(3,4-ethylenedioxythiophene) (PEDOT) doped with polystyrene sulfonic acid (PSS), a polythiophene-based conductive polymer (W787, manufactured by Chukyo Yushi Co., Ltd.), in a mixed solution of ion-exchanged water and isopropyl alcohol (IPA) (9.8 / 9.8 parts by mass).

[0088] [Comparative Example 1] A release film was obtained in the same manner as in Example 1, except that the application and drying of the antistatic coating liquid 1 in Example 1 were not carried out.

[0089] Comparative Example 2 A release film was obtained in the same manner as in Example 1, except that instead of release layer coating liquid 1 in Example 1, release layer coating liquid 3 was used, which was prepared by mixing a solution of 1 part by mass of a melamine compound (RP-50 manufactured by Miwa Research Institute Co., Ltd., solid content 50% by mass), which is a thermosetting resin, and 9 parts by mass of a mixed liquid of toluene, anon, and methanol (4.5 / 3.6 / 0.9), with 10 parts by mass of ion-conductive Colcoat N103X (Colcoat Co., Ltd., solid content 2% by mass), and 0.1 part by mass of DEP Clear (manufactured by Washin Chemical Industry Co., Ltd.), which is a curing agent.

[0090] Comparative Example 3 A release film was produced in the same manner as in Example 1, except that a 75 μm thick polyethylene terephthalate film ("Lumirror" (registered trademark) S28, manufactured by Toray Industries, Inc.) was used instead of a 100 μm thick polyethylene terephthalate film ("Lumirror" (registered trademark) R41, manufactured by Toray Industries, Inc.) in Example 1, and the application and drying of antistatic coating liquid 1 were not carried out.

[0091] Comparative Example 4 A release film was produced in the same manner as in Example 1, except that an antistatic layer coating solution 4 was used, which was a mixture of 40 parts by mass of ion-conductive Colcoat N103X (Colcoat Co., Ltd., solid content 2% by mass) and 60 parts by mass of a MEK / IPA (30 / 30) mixed solution.

[0092] [evaluation] The release films of the examples and comparative examples prepared above were evaluated according to the measurement and evaluation methods described above. The results are shown in Table 1.

[0093] [Table 1]

Claims

1. A release film having an antistatic layer and a release layer on at least one surface of a base film, in that order from the base film side, wherein the antistatic layer contains a conductive polymer, the resin constituting the release layer contains 80% by mass or more of a melamine resin, and the surface roughness (Sa) of the release layer is less than 10 nm.

2. 2. The release film according to claim 1, wherein an antistatic layer and a release layer are provided on only one surface of the base film in this order from the base film side, and the surface roughness (Sa) of the non-release layer surface, which is the surface of the release film that does not have the release layer, is 5 to 30 nm.

3. 3. The release film according to claim 1, wherein the peel strength between the release layer surface, which is the surface of the release film having the release layer, and the adhesive tape is 1.0 to 5.0 N / 18 mm.

4. 4. The release film according to claim 1, wherein the release layer surface, which is the surface of the release film having the release layer, is pressure-bonded to a PET film, and then the release film is peeled off. Immediately after this, the amount of charge on the release layer surface is −1.5 to 1.5 kV.

5. The release film according to any one of claims 1 to 4, which is used as a release film for use in a manufacturing process of an interlayer insulating sheet.

6. A release film according to any one of claims 1 to 4, which is used as a process film for cast production of resin films.

7. A release film according to any one of claims 1 to 4, used for casting epoxy resin films.

8. A release film described in any one of claims 1 to 7, wherein the antistatic layer further contains a melamine resin.

9. A release film described in any one of claims 1 to 8, wherein the antistatic layer contains a polythiophene-based conductive polymer and a melamine resin.

10. A release film as described in claim 9, wherein the mass ratio of the polythiophene-based conductive polymer to the melamine resin is 1:1.2 to 1:49.

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