Multilayer film and method for producing same

Abstract

Provided is a multilayer film in which a resin layer is provided on at least one surface of a base material film, the multilayer film being characterized in that: the base material film surface on which the resin layer is provided does not substantially contain particles; the resin layer contains an acid-modified polyolefin resin (A) and a crosslinking agent (C); and with respect to the resin layer surface, the developed interfacial area ratio (Sdr) is 0.025 to 0.304% and the maximum height (Sz) is 0.01 to 0.50 μm as determined by a non-contact surface profile measuring machine.

Description

Laminated film and method for producing same

[0001] The present invention relates to a laminated film and a method for producing the same.

[0002] Recently, electronic information devices have become smaller and more highly integrated, and therefore, excellent flatness is required for process films used in the manufacture of electronic information devices. Patent Document 1 discloses a slippery film that has good flatness of a resin layer and good slipperiness during film formation and processing, and is suitable as a release material.

[0003] The substrate film constituting the slippery film disclosed in Patent Document 1 contains particles to impart slipperiness. However, since the resin layer is formed on the substrate film containing particles, the shape of the particles appears on the surface of the resin layer, and there is a risk that this shape will be transferred to the adherend. Therefore, there is room for further improvement in order to satisfy the high flatness required for miniaturization of electronic information devices.

[0004] In a laminate film having a resin layer formed on a substrate film, if the particle content in the substrate film is reduced or the particle diameter of the particles is made smaller in order to improve the smoothness of the resin layer surface, the slipperiness of the substrate film surface tends to decrease. On the other hand, if the particle content in the substrate film is increased to improve the smoothness of the substrate film surface, the smoothness of the resin layer surface tends to decrease. Thus, it has been difficult to obtain a laminate film that achieves both the two contradictory properties of smoothness and smoothness at a high level.

[0005] JP 2012-020429 A

[0006] In view of these problems, the present invention aims to provide a laminated film in which a resin layer provided on a base film exhibits good releasability from an adherend, has excellent flatness that prevents transfer to the adherend, and has excellent lubricity during film formation and processing.

[0007] As a result of intensive research to solve the above-mentioned problems, the inventors discovered that by using a liquid material for forming a resin layer containing a specific compound to form a resin layer on the surface of a substrate film that is substantially free of particles, it is possible to obtain a laminated film that has high levels of both flatness and lubricity and also has good releasability, and thus arrived at the present invention.

[0008] The laminate film of the present invention, which has a resin layer provided on at least one surface of a substrate film, is characterized in that the substrate film surface on which the resin layer is provided is substantially free of particles, the resin layer contains an acid-modified polyolefin resin (A) and a crosslinking agent (C), and the resin layer surface has a developed interface area ratio (Sdr) of 0.025 to 0.304% and a maximum height (Sz) of 0.01 to 0.50 μm, as measured with a non-contact surface profiler. According to the laminate film of the present invention, the olefin component of the acid-modified polyolefin resin (A) preferably contains propylene or 1-octene. According to the laminate film of the present invention, the propylene content in the olefin component is preferably 70% by mass or more. According to the laminate film of the present invention, the 1-octene content in the olefin component is preferably 15% by mass or more. According to the laminate film of the present invention, the peel strength between the resin layer and the epoxy prepreg is preferably 0.5 N / cm or less. The method for producing a laminated film of the present invention is a method for producing the above-mentioned laminated film, and is characterized by comprising the steps of: applying to a substrate film a resin layer-forming liquid material containing an acid-modified polyolefin resin (A), a crosslinking agent (C), and at least one compound (D) selected from the group consisting of an amphiphilic oligomer, acetylene glycol, and an ethylene oxide adduct of acetylene glycol, the liquid material having a liquid temperature of 20 to 40°C; and drying and stretching the substrate film coated with the resin layer-forming liquid material. According to the method for producing a laminated film of the present invention, it is preferable to apply a resin layer-forming liquid material in which the content of compound (D) is 2 to 50 parts by mass per 100 parts by mass of the acid-modified polyolefin resin (A).

[0009] The laminated film of the present invention has an excellent flatness on the surface on the resin layer side, good releasability, and easy slippage suitable for film formation and processing, and therefore can be suitably used as a release film for a variety of applications, such as protective films for double-sided tapes and adhesive materials, protective materials and process materials when manufacturing liquid crystal display components, printed wiring boards, etc., and for forming sheet-like structures such as ion exchange membranes, ceramic green sheets, and heat dissipation sheets.

[0010] The present invention will be described in detail below. The laminate film of the present invention has a resin layer provided on at least one surface of a substrate film that is substantially free of particles. The resin layer contains an acid-modified polyolefin resin (A) and a crosslinking agent (C), and the developed interface area ratio (Sdr) of the resin layer surface measured by a non-contact surface profilometer is 0.025 to 0.304%, and the maximum height (Sz) of the resin layer surface measured by the non-contact surface profilometer is 0.01 to 0.50 μm.

[0011] <Base film> Examples of the substrate film constituting the laminate film of the present invention include polyester films such as polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyethylene naphthalate (PEN), poly(1,4-cyclohexylene dimethylene terephthalate), and polylactic acid (PLA); polyolefin films such as polypropylene; polystyrene films; polyamide 6, poly-p-xylylene adipamide (MXD6 nylon), polyamide 66, polyamide 46, polyamide 4T, polyamide 6T, polyamide 9T, polyamide 10T, polyamide 11T, polyamide 12T, and polyamide 6I; polycarbonate films; polyacrylnitrile films; polyimide films; and composites thereof (e.g., polyamide 6 / MXD6 nylon / polyamide 6, polyamide 6 / ethylene-vinyl alcohol copolymer / polyamide 6, polyamide 6 / 6T, polyamide 6 / 6I, and polyamide 6 / 6T / 6I), and mixtures thereof. Polyester films and polyamide films having mechanical strength and dimensional stability are preferred. Here, T represents terephthalic acid, and I represents isophthalic acid. Among these, the base film is preferably a polyethylene terephthalate film from the viewpoint of adhesion to the resin layer, and is preferably a semi-aromatic polyamide film from the viewpoint of heat resistance and adhesion to the resin layer, and is particularly preferably a polyamide 9T film or a polyamide 10T film.

[0012] (Polyester Resin) The polymerization method of the polyester resin constituting the substrate film is not particularly limited, and examples thereof include transesterification and direct polymerization. Examples of transesterification catalysts include oxides and acetates of Mg, Mn, Zn, Ca, Li, Ti, and other elements. Examples of polycondensation catalysts include oxides and acetates of Sb, Ti, Ge, and other elements. Since the polyester resin after polymerization contains monomers, oligomers, and by-product acetaldehyde, it may be solid-phase polymerized at a temperature of 200°C or higher under reduced pressure or in an inert gas flow.

[0013] The intrinsic viscosity of the polyester resin is preferably 0.55 to 0.80, more preferably 0.60 to 0.75. If the intrinsic viscosity of the polyester resin is below the above range, the resin is prone to breakage during film formation, making stable film formation difficult and resulting films with low strength. On the other hand, if the intrinsic viscosity of the polyester resin exceeds the above range, shear heat generation increases during melt extrusion of the resin in the film production process, increasing the load on the extruder, necessitating a sacrifice in production speed and making film thickness control difficult, thereby reducing film productivity. Furthermore, the resulting film will experience increased thermal decomposition and gelation, resulting in increased surface defects, foreign matter, and surface coarse protrusions. Furthermore, a polyester resin with an intrinsic viscosity that is too high will require a longer polymerization time and process, which can also increase costs.

[0014] (Semi-aromatic polyamide resin) The semi-aromatic polyamide resin constituting the base film is composed of a dicarboxylic acid component and a diamine component, and has an aromatic component in the dicarboxylic acid component or the diamine component, and is preferably composed of an aromatic dicarboxylic acid component and an aliphatic diamine component.

[0015] (Production of Substrate Film) Next, a method for producing a substrate film will be described. First, a thoroughly dried resin is fed into an extruder, melted at a temperature above the temperature at which it is sufficiently plasticized and exhibits fluidity, and passed through a selected filter as needed. The molten polymer is then extruded into a sheet from a flat die such as a T-die or I-die, and brought into close contact with the cooling surface of a moving cooling body such as a cooling roll or steel belt whose temperature is adjusted to below the glass transition temperature (Tg) to obtain an unstretched film. Methods for cooling and solidifying the extruded molten polymer into a sheet by bringing it into close contact with the moving cooling body include air knife casting, electrostatic application, and vacuum chamber methods. The resulting unstretched film is preferably stretched to improve mechanical properties and heat resistance; that 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 examples that can be used include flat-type sequential biaxial stretching, flat-type simultaneous biaxial stretching, and tubular methods. Among these, the flat type sequential biaxial stretching method is most suitable for stretching polyester films, and the flat type simultaneous biaxial stretching method is most suitable for stretching semi-aromatic polyamide films.

[0016] In the uniaxial stretching method for polyester films, unstretched films are stretched in the longitudinal or width direction at a stretch ratio of approximately 2 to 6 times within a temperature range from the Tg of the resin to 50°C above Tg. In the simultaneous biaxial stretching method, unstretched films are biaxially stretched in the longitudinal and width directions at a stretch ratio of approximately 2 to 4 times within a temperature range from the Tg of the resin to 50°C above Tg. The unstretched film may be subjected to preliminary longitudinal stretching up to approximately 1.2 times before being introduced into the simultaneous biaxial stretching machine. In the sequential biaxial stretching method, the unstretched film is heated with a heated roll or infrared rays, and stretched in the longitudinal direction to obtain a longitudinally stretched film. The longitudinal stretching is preferably performed using the difference in peripheral speed between two or more rolls at a stretch ratio of 2.5 to 4.0 times within a temperature range from the Tg of the polyester to 40°C above Tg. The longitudinally stretched film is then sequentially subjected to transverse stretching in the width direction, heat setting, and heat relaxation to produce a biaxially oriented film. Transverse stretching is initiated at a temperature between Tg and 40°C higher than Tg of the resin, with the maximum temperature preferably being 100 to 40°C lower than the melting point (Tm) of the resin. The transverse stretching ratio is adjusted depending on the required physical properties of the final film, but is preferably 3.5 times or more, further 3.8 times or more, and more preferably 4.0 times or more. After stretching in the longitudinal and width directions, further re-stretching in the longitudinal and / or width directions can also be performed to increase the film's elastic modulus and dimensional stability. Following stretching, it is preferable to heat set the film for several seconds at a temperature 50 to 10°C lower than Tm of the resin, and simultaneously relax the film by 1 to 10% in the width direction. After heat setting, the film is cooled to below Tg to obtain a biaxially stretched film.

[0017] As described above, flat-type simultaneous biaxial stretching is optimal for stretching semi-aromatic polyamide films because it provides high film thickness accuracy and uniform physical properties across the film's width. As stretching devices for flat-type simultaneous biaxial stretching, screw tenters, pantograph tenters, linear motor-driven clip tenters, and the like can be used. The stretching ratio is preferably 1.5 to 10 times in both the longitudinal and width directions, and more preferably 2 to 5 times, in order to ensure excellent heat resistance and mechanical strength of the final semi-aromatic polyamide film. The stretching speed is preferably such that the stretching strain rate in both the longitudinal and width directions exceeds 400% / min, more preferably 800 to 12,000% / min, and even more preferably 1,200 to 6,000% / min. If the strain rate is 400% / min or less, crystal growth during stretching can cause the film to break. Conversely, if the strain rate is too fast, the unstretched sheet may be unable to keep up with the deformation and break. The stretching temperature is preferably equal to or higher than the Tg of the semi-aromatic polyamide resin, and more preferably above Tg and below (Tg + 50)°C. If the stretching temperature is below Tg, the film is prone to breakage and stable production cannot be achieved. Conversely, if the stretching temperature exceeds (Tg + 50)°C, uneven stretching may occur. After the semi-aromatic polyamide film has been stretched as described above, it is preferable to subject it to heat setting as needed while holding the film with the clips used during stretching. The preferred heat setting temperature is 250 to (Tm - 5)°C, and more preferably 280 to (Tm - 10)°C. If the heat setting temperature is less than 250°C, the resin layer containing the acid-modified olefin resin provided on the semi-aromatic polyamide film before stretching will undergo an insufficient curing reaction, resulting in reduced releasability. Furthermore, after heat setting, the film is preferably relaxed by 1 to 10% as needed, and more preferably by 3 to 7%, while still held by the clips. By relaxing the film, sufficient dimensional stability can be achieved. After heat setting or relaxation as desired, the film is cooled and wound onto a take-up roll to obtain a semi-aromatic polyamide resin stretched film roll.The resulting semi-aromatic polyamide resin stretched film roll can be slit to a desired width.

[0018] (Substrate film with multilayer structure) Although the above-mentioned manufacturing method can obtain a substrate film with a single layer structure, the substrate film may also be a film with a multilayer structure formed by laminating two or more layers.The multilayer film can be manufactured by the above-mentioned manufacturing method, in which the resins constituting each layer are melted separately, extruded using a multilayer die, laminated and fused before solidification, and then biaxially stretched and heat-set, or by melting and extruding two or more resins separately to form films, and then laminated and fused in an unstretched state or after stretching.From the viewpoint of process simplicity, it is preferable to use a multilayer die and laminate and fused before solidification.

[0019] In the present invention, the substrate film may have a single layer structure or a multilayer structure (e.g., two-type two-layer, two-type three-layer, three-type three-layer, four-layer or more multilayer, etc.) as described above. However, a multilayer structure is preferred from the viewpoint of being able to control the surface roughness on each side and improving handling properties such as winding. Two-type two-layer and two-type three-layer structures are more preferred, and two-type two-layer is even more preferred. A two-type two-layer structure is a two-layer structure manufactured using two types of layer-forming materials, and these two layers have different compositions (e.g., particle content). A two-type three-layer structure is a three-layer structure manufactured using two types of layer-forming materials, and the two outermost layers and the intermediate layer have different compositions (e.g., particle content). A three-type three-layer structure is a three-layer structure manufactured using three types of layer-forming materials, and these three layers have different compositions (e.g., particle content).

[0020] (Particles) The substrate film may contain particles, primarily for the purpose of imparting easy slippage and preventing scratches in each process. However, the substrate film constituting the laminate film of the present invention must be substantially free of particles on the side on which the resin layer is laminated. Since the surface of the substrate film on which the resin layer is formed is substantially free of particles, the surface on which the resin layer containing the specific acid-modified polyolefin resin (A) and crosslinking agent (C) described below is formed has excellent flatness. On the other hand, each layer of the substrate film other than the surface on which the resin layer is formed may contain particles within a range that does not impair the effects of the present invention. Note that "substantially free of particles" means that the substrate film was produced without adding particles to the surface on which the resin layer is formed. Therefore, it is particularly preferable that the particle content of the substrate film surface on which the resin layer is formed is zero, but it may be 0.001% by mass or less, more preferably 0.0005% by mass or less, within a range that does not impair the effects of the present invention.

[0021] The type of particles contained in the substrate film is not particularly limited as long as they are particles that can impart slipperiness, and specific examples include inorganic particles such as silica, calcium carbonate, magnesium carbonate, barium carbonate, calcium sulfate, calcium phosphate, magnesium phosphate, kaolin, aluminum oxide, and titanium oxide, and organic particles such as acrylic resin, styrene resin, urea resin, phenolic resin, epoxy resin, and benzoguanamine resin. Furthermore, precipitated particles obtained by precipitating and finely dispersing a part of a metal compound such as a catalyst during the manufacturing process of the resin that constitutes the substrate can also be used.

[0022] The shape of the particles is not particularly limited, and may be any of spherical, blocky, rod-like, flat, etc. The hardness, specific gravity, color, etc. of the particles are also not particularly limited. Two or more types of particles may be used in combination as needed. The average particle size of the particles is preferably 5 μm or less, more preferably in the range of 0.01 to 3 μm. If the average particle size exceeds 5 μm, the surface roughness of the base film becomes too high, which may affect the surface shape of the molding surface to be transferred, for example, when used for transfer.

[0023] The particle content in the base film is usually 5% by mass or less, preferably in the range of 0.0003 to 3% by mass. If the particle content exceeds 5% by mass, the film may be prone to breakage during the stretching step in the production of the laminated film of the present invention.

[0024] The method for adding the particles is not particularly limited, and any conventionally known method can be used. For example, the particles can be added at any stage in the production of the resin constituting each layer. In the case of the polyester production process, the particles are preferably added after the completion of the esterification or transesterification reaction.

[0025] (Additives) The base film may contain, as necessary, additives such as antioxidants, heat stabilizers, ultraviolet absorbers, antistatic agents, pinning agents, etc. Examples of antioxidants include hindered phenol compounds and hindered amine compounds, examples of heat stabilizers include phosphorus compounds, etc. Examples of ultraviolet absorbers include benzophenone compounds and benzotriazole compounds, etc.

[0026] (Thickness) The thickness of the substrate film is not particularly limited as long as it is within a range that allows film formation, but from the viewpoints of mechanical strength, handling properties, productivity, etc., it is usually 5 to 300 μm, and preferably 10 to 150 μm.

[0027] <Resin Layer> The laminate film of the present invention has a resin layer provided on at least one side of the layer of the above-mentioned base film that is substantially free of particles. The resin component constituting the resin layer is an acid-modified polyolefin resin (A) from the viewpoint of imparting good releasability to the resin layer, and it is necessary that the resin layer further contains a crosslinking agent (C). The resin layer can be formed by applying a liquid material for forming a resin layer, which contains the acid-modified polyolefin resin (A), the crosslinking agent (C), and at least one compound (D) selected from the group consisting of an amphiphilic oligomer, acetylene glycol, and an ethylene oxide adduct of acetylene glycol.

[0028] (Acid-modified polyolefin resin (A)) The acid-modified polyolefin resin is a resin containing an olefin component as a main component and modified with an acid-modifying component. The resin layer may contain two or more types of acid-modified polyolefin resin (A). The olefin component constituting the acid-modified polyolefin resin can be at least one selected from ethylene, propylene, 1-butene, 1-pentene, 1-hexene, 1-octene, and 1-nonene.

[0029] From the viewpoint of releasability from the acrylic pressure-sensitive adhesive, the olefin component more preferably contains ethylene. From the viewpoint of further improving releasability from the acrylic pressure-sensitive adhesive, the ethylene content in the olefin component is preferably 50% by mass or more, more preferably 80% by mass or more, and even more preferably 90% by mass or more.

[0030] From the viewpoint of releasability from the epoxy resin, the olefin component more preferably contains propylene. From the viewpoint of further improving releasability from the epoxy resin, the propylene content in the olefin component is preferably 50% by mass or more, more preferably 60% by mass or more, even more preferably 70% by mass or more, still more preferably 80% by mass or more, still more preferably 90% by mass or more, and most preferably 95% by mass or more.

[0031] From the viewpoint of improving lubricity, the olefin component preferably contains an olefin component having 6 or more carbon atoms, such as 1-hexene, 1-octene, or 1-nonene, and particularly preferably contains 1-octene. From the viewpoint of further improving lubricity, the content of 1-octene in the olefin component is preferably 15% by mass or more, and more preferably 25% by mass or more.

[0032] From the viewpoint of improving flatness, which is an object of the present invention, the olefin component constituting the acid-modified polyolefin resin preferably has a 1-butene or 1-pentene content of 20% by mass or less, more preferably 15% by mass or less, and even more preferably 10% by mass or less, of the polyolefin component, and it is particularly preferable that the resin does not contain 1-butene or 1-pentene.

[0033] Examples of the acid-modified component constituting the acid-modified polyolefin resin include unsaturated carboxylic acid components, specifically acrylic acid, methacrylic acid, maleic acid, maleic anhydride, itaconic acid, itaconic anhydride, fumaric acid, crotonic acid, etc., as well as half esters and half amides of unsaturated dicarboxylic acids. Among these, in order to stably disperse the resin in the aqueous dispersion of the resin described below, acrylic acid, methacrylic acid, maleic acid, and maleic anhydride are preferred, and acrylic acid, methacrylic acid, and maleic anhydride are particularly preferred. Two or more of these acid-modified components may be contained in the acid-modified polyolefin resin.

[0034] The proportion of the acid-modified component in the acid-modified polyolefin resin is preferably 1 to 10% by mass, more preferably 2 to 9% by mass. If the proportion of the acid-modified component is less than 1% by mass, the proportion of polar groups in the acid-modified polyolefin resin contained in the resin layer will be reduced, and the resin layer will tend to be unable to achieve sufficient adhesion to the substrate film, which may contaminate the adherend released from the resin layer. Furthermore, it tends to be difficult to stably disperse the resin in the aqueous dispersion of the resin described below. On the other hand, if the proportion of the acid-modified component exceeds 10% by mass, the proportion of polar groups will be increased, resulting in sufficient adhesion between the resin layer and the substrate film, but at the same time, the adhesion between the resin layer and the adherend will also be increased, which tends to reduce releasability from the adherend.

[0035] Furthermore, in order to further improve adhesion to the substrate film, the acid-modified polyolefin resin may contain an ethylenically unsaturated component containing an oxygen atom in the side chain. Examples of ethylenically unsaturated components containing an oxygen atom in the side chain include esters of (meth)acrylic acid with alcohols having 1 to 30 carbon atoms, and among these, esters of (meth)acrylic acid with alcohols having 1 to 20 carbon atoms are preferred in terms of 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 compounds may also be used. Among these, from the viewpoint of adhesion to polyester films, methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, hexyl acrylate, and octyl acrylate are more preferred, with ethyl acrylate and butyl acrylate being even more preferred, and ethyl acrylate being particularly preferred. "(Meth)acrylic acid or more" means "acrylic acid or methacrylic acid or more." Ethylenically unsaturated components containing oxygen atoms in the side chain, like acid-modified components, have polar groups in their molecules. Therefore, by including an ethylenically unsaturated component containing an oxygen atom in the side chain in an acid-modified polyolefin resin, the resin layer exhibits enhanced adhesion to the substrate film. However, if the amount of ethylenically unsaturated components containing oxygen atoms in the side chain is too high, the properties of the olefin-derived resin may be lost, and the resin layer may have reduced releasability from the adherend. The proportion of ethylenically unsaturated components containing oxygen atoms in the side chain 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. Even if an acid-modified polyolefin resin containing an ethylenically unsaturated component containing an oxygen atom in the side chain is used, the releasability of the resin layer is not impaired in addition to the adhesiveness to the substrate film.

[0036] The acid-modified polyolefin resin may be copolymerized with a small amount of other monomers, such as dienes, (meth)acrylonitrile, vinyl halides, vinylidene halides, carbon monoxide, and sulfur dioxide.

[0037] The components constituting the acid-modified polyolefin resin may be copolymerized in the acid-modified polyolefin resin in any form, including, for example, random copolymerization, block copolymerization, and graft copolymerization (graft modification).

[0038] The melting point of the acid-modified polyolefin resin is preferably 80 to 200° C., more preferably 90 to 150° C. If the melting point of the acid-modified polyolefin resin exceeds 200° C., high-temperature treatment may be required when forming a resin layer on the surface of the substrate film. On the other hand, if the melting point of the acid-modified polyolefin resin is less than 80° C., the releasability of the resin layer may decrease.

[0039] Examples of acid-modified polyolefin resins that can be used in the present invention include the Bondine series manufactured by Arkema, the Nucrel series manufactured by DuPont-Mitsui Polychemicals, the Rexpearl series manufactured by Japan Polyethylene Corporation, the Umex series manufactured by Sanyo Chemical Industries, Ltd., the Bestplast series manufactured by Evonik, the Primacol series and Affinity series manufactured by Dow Chemical Company, Ltd., the Admer series manufactured by Mitsui Chemicals, Inc., and the Toyotack series manufactured by Toyobo Co., Ltd.

[0040] (Polyvinyl alcohol (B)) In the present invention, the resin layer preferably contains polyvinyl alcohol from the viewpoint of improving releasability. The polyvinyl alcohol is not particularly limited, but examples thereof include a completely or partially saponified vinyl ester polymer. When polyvinyl alcohol is contained in the resin layer, it has the effect of improving the adhesion between the resin layer and the substrate film and improving the releasability between the resin layer and the adherend. The polyvinyl alcohol in the present invention is preferably water-soluble in order to be used as a liquid material as described below.

[0041] From the viewpoint of the surface flatness of the resin layer and the releasability in a high temperature range, the polyvinyl alcohol preferably has a saponification degree of 90% or more, more preferably 93% or more.

[0042] From the viewpoint of improving the releasability between the resin layer and the adherend and suppressing transfer to the adherend after peeling, the content of polyvinyl alcohol is preferably 10 to 1,000 parts by mass, more preferably 100 to 1,000 parts by mass, even more preferably 210 to 800 parts by mass, and particularly preferably 300 to 600 parts by mass, relative to 100 parts by mass of the resin.

[0043] Examples of polyvinyl alcohol that can be used in the present invention include "JP-15," "JT-05," "JL-05E," "JM-33," "JM-17," "JF-05," and "VC-10" manufactured by Japan Vinyl Acetate & Poval Co., Ltd., and "Kuraray Poval" products such as "PVA-CST," "PVA-624," "PVA-203," "PVA-220," and "PVA-405" manufactured by Kuraray Co., Ltd.

[0044] (Crosslinking Agent (C)) In the present invention, the resin layer needs to contain a crosslinking agent together with the acid-modified polyolefin resin in order to impart good releasability. By containing the crosslinking agent, the components of the resin layer are crosslinked, improving releasability, improving the cohesive force of the resin layer, making it less likely to transfer to an adherend, and improving water resistance.

[0045] The content of the crosslinking agent 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 the acid-modified polyolefin resin. If the content of the crosslinking agent is less than 1 part by mass, the resin layer will have weak cohesive strength, poor adhesion to the substrate film, and will tend to be easily transferred to the adherend. On the other hand, if the content exceeds 20 parts by mass, the resin layer may react with the adherend, resulting in poor releasability, or the liquid used to form the resin layer may thicken and become less stable.

[0046] Examples of crosslinking agents include compounds having multiple functional groups reactive with carboxyl groups within the molecule, such as 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. These crosslinking agents may be used alone or in combination. Among these, polyfunctional isocyanate compounds, melamine resins, urea compounds, polyfunctional epoxy compounds, carbodiimide group-containing compounds, and oxazoline group-containing compounds are preferred, with carbodiimide group-containing compounds and oxazoline group-containing compounds being more preferred, and oxazoline group-containing compounds being even more preferred. The use of oxazoline group-containing compounds makes it possible to obtain a laminated film with excellent releasability from the adherend and adhesion to the substrate film. These crosslinking agents may also be used in combination.

[0047] Specific examples of polyfunctional epoxy compounds that can be used include polyepoxy compounds and diepoxy compounds. Examples of polyepoxy compounds that can be used 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 that can be used 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.

[0048] Examples of polyfunctional isocyanate compounds that can be used include tolylene diisocyanate, diphenylmethane-4,4'-diisocyanate, meta-xylylene diisocyanate, hexamethylene-1,6-diisocyanate, 1,6-diisocyanatehexane, an adduct of tolylene diisocyanate and hexanetriol, an adduct 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'-bitrylene-4,4'-diisocyanate, 3,3'-dimethyldiphenylmethane-4,4'-diisocyanate, and meta-phenylene diisocyanate. It is also possible to use blocked isocyanate compounds in which these isocyanate groups are blocked with bisulfites and sulfonic acid group-containing phenols, alcohols, lactams, oximes, active methylene compounds, etc. Commercially available polyfunctional isocyanate compounds include, for example, "Basonate HW-100" manufactured by BASF.

[0049] Examples of usable polyfunctional aziridine compounds include N,N'-hexamethylene-1,6-bis-(1-aziridinecarboxamide) and trimethylolpropane-tri-β-aziridinylpropionate.

[0050] The carbodiimide group-containing compound is not particularly limited as long as it has one or more carbodiimide groups in the molecule. The carbodiimide compound forms an ester with two carboxyl groups in the acid-modified portion of the acid-modified polyolefin resin at one carbodiimide moiety, thereby achieving crosslinking. 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 polycarbodiimide, which is a polymer having a carbodiimide group, can be used. One or more of these can be used. Among these, polycarbodiimide is preferred due to its ease of handling. Commercially available polycarbodiimides include the Carbodilite series manufactured by Nisshinbo Chemical Inc., and specific examples include water-soluble types "SV-02," "V-02," "V-02-L2," and "V-04," emulsion types "E-01" and "E-02," organic solution types "V-01," "V-03," "V-07," and "V-09," and solvent-free type "V-05."

[0051] The oxazoline group-containing compound is not particularly limited as long as it has two or more oxazoline groups in its molecule. In the oxazoline compound, each of the two oxazoline moieties forms an amide ester with one carboxyl group in the acid-modified portion of the acid-modified polyolefin resin, thereby achieving crosslinking. Such a polymer can be prepared by polymerizing an 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. The addition-polymerizable oxazoline group-containing monomer can be one of these or a mixture of two or more of these. Among these, 2-isopropenyl-2-oxazoline is preferred due to its industrial availability.The other monomer is not limited as long as it is copolymerizable with the addition-polymerizable oxazoline group-containing monomer, and examples thereof include (meth)acrylic acid esters such as alkyl acrylate and alkyl methacrylate (the alkyl group can be methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, t-butyl, 2-ethylhexyl, or cyclohexyl); unsaturated carboxylic acids such as acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid, crotonic acid, styrenesulfonic acid, and salts thereof (sodium salt, potassium salt, ammonium salt, tertiary amine salt, etc.); unsaturated nitriles such as acrylonitrile and methacrylonitrile; acrylamide, methacrylamide, N-alkenyl acrylate, methacrylic acid, ... Examples of the other monomer include unsaturated amides such as alkyl acrylamide, N-alkyl methacrylamide, N,N-dialkyl acrylamide, and N,N-dialkyl methacrylate (the alkyl group can be, for example, a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a t-butyl group, a 2-ethylhexyl group, or a cyclohexyl group); 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. One or more of these monomers can be used as the other monomer. Among these, oxazoline group-containing polymers are preferred for ease of handling. Commercially available oxazoline group-containing polymers include the Epocross series manufactured by Nippon Shokubai Co., Ltd., and specific examples thereof include water-soluble types "WS-500" and "WS-700"; emulsion types "K-1010E", "K-1020E", "K-1030E", "K-2010E", "K-2020E", and "K-2030E".

[0052] As the phenolic resin, for example, resol-type phenolic resins and / or novolac-type phenolic resins prepared using phenol, bisphenol A, alkylphenols such as p-t-butylphenol, octylphenol, and p-cumylphenol, p-phenylphenol, cresol, etc. as raw materials can be used.

[0053] Usable urea resins include, for example, dimethylol urea, dimethylol ethylene urea, dimethylol propylene urea, tetramethylol acetylene urea, and 4-methoxy 5-dimethyl propylene urea dimethylol.

[0054] Melamine resins are compounds having, for example, imino groups, methylol groups, and / or alkoxymethyl groups (e.g., methoxymethyl groups, butoxymethyl groups) as functional groups in one molecule. Examples of melamine resins that can be used include imino group-type methylated melamine resins, methylol group-type methylated melamine resins, and fully alkylated methylated melamine resins. To promote the thermal curing of melamine resins, it is preferable to use an acidic catalyst such as p-toluenesulfonic acid.

[0055] As the benzoguanamine resin, for example, trimethylolbenzoguanamine, hexamethylolbenzoguanamine, trismethoxymethylbenzoguanamine, hexakismethoxymethylbenzoguanamine, etc. can be used.

[0056] (Compound (D)) The resin layer of the present invention can be formed using a liquid material for forming a resin layer containing a resin component and a compound (D). By incorporating the compound (D) into the liquid material for forming the resin layer and forming the resin layer using a specific method, it is possible to achieve both flatness and slipperiness in the resin layer. The compound (D) is at least one compound selected from the group consisting of an amphiphilic oligomer, acetylene glycol, and an ethylene oxide adduct of acetylene glycol. The amphiphilic oligomer refers to an oligomer having both a hydrophobic structure (also referred to as a hydrophobic segment) and a hydrophilic structure (also referred to as a hydrophilic segment) in the molecule. Examples of hydrophobic segments include, but are not limited to, alkyl groups, alkenyl groups, alkylphenyl groups, perfluoroalkyl groups, and perfluoropolyether groups. These may be contained alone or in a structure in which a plurality of them are combined. The hydrophilic segment is not particularly limited, but examples thereof 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 glycols include 2,5,8,11-tetramethyl-6-dodecyne-5,8-diol, 5,8-dimethyl-6-dodecyne-5,8-diol, 2,4,7,9-tetramethyl-5-decyne-4,7-diol, 4,7-dimethyl-5-decyne-4,7-diol, 2,3,6,7-tetramethyl-4-octyne-3,6-diol, 3,6-dimethyl-4-octyne-3,6-diol, 3,6-diethyl-4-octyne-3,6-diol, and 2,5-dimethyl-3-hexyne-2,5-diol. Examples of the ethylene oxide adduct of acetylene glycol include ethylene oxide adducts of the compounds listed as specific examples of acetylene glycol.

[0057] The compound (D) preferably has a solubility of 0.05 g or more in 100 g of water at 20° C., or disperses when 0.1 g of the compound (D) is added to 100 g of water at 20° C. and stirred. If the solubility of the compound (D) is less than 0.05 g or if the compound (D) is not dispersible in water, it will not mix with the liquid material for forming a resin layer and will separate over time, which may not only result in poor stability of the liquid material for forming a resin layer, but also tend to impair the appearance of the formed resin layer.

[0058] The content of compound (D) in the resin layer-forming liquid is preferably 2 to 50 parts by mass, more preferably 3.5 to 30 parts by mass, and even more preferably 5 to 25 parts by mass, per 100 parts by mass of the acid-modified polyolefin resin (A). If the content of compound (D) in the resin layer-forming liquid is less than 2 parts by mass, it may be difficult to obtain a resin layer surface having a developed interface area ratio (Sdr) of 0.025 to 0.304% as determined by a non-contact surface profiler. On the other hand, if the content of compound (D) exceeds 50 parts by mass, the resin layer may exhibit reduced releasability, exhibit interference fringes, or exhibit reduced flatness, resulting in a maximum height (Sz) that does not satisfy the requirement of 0.01 to 0.50 μm. Depending on the type, compound (D) in the resin layer-forming liquid may volatilize during heat treatment after application to the substrate film, and may not remain in the formed resin layer.

[0059] Examples of commercially available products that can be used as compound (D) in the present invention include, as an amphiphilic oligomer, Polyflow series "KL-900" manufactured by Kyoeisha Chemical Co., Ltd., as an acetylene glycol, Olfine series "D-10" manufactured by Nissin Kogyo Co., Ltd., as an acetylene glycol, and Olfine series "E1004," "E1006," and "E1010," and Surfynol series "420," "440," and "485," etc., manufactured by Nissin Kogyo Co., Ltd. as an ethylene oxide adduct of acetylene glycol.

[0060] In the present invention, the resin layer may contain a lubricant within a range that does not impair the effects of the present invention. Examples of the lubricant include inorganic particles such as calcium carbonate, magnesium carbonate, calcium oxide, zinc oxide, magnesium oxide, silicon oxide, sodium silicate, aluminum hydroxide, iron oxide, zirconium oxide, barium sulfate, titanium oxide, tin oxide, antimony trioxide, carbon black, and molybdenum disulfide; organic particles such as acrylic crosslinked polymers, styrene crosslinked polymers, silicone resins, fluororesins, benzoguanamine resins, phenolic resins, nylon resins, and polyethylene wax; and surfactants.

[0061] <Liquid Material for Forming Resin Layer> In the present invention, the liquid medium constituting the liquid material for forming the resin layer containing the acid-modified polyolefin resin (A), the crosslinking agent (C), and the compound (D) is preferably an aqueous medium. The aqueous medium refers to a solvent containing water and an amphipathic organic solvent, with a water content of 2% by mass or more, or may be water alone. The amphipathic organic solvent refers to an organic solvent in which the solubility of water in the organic solvent 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 "Solvent Handbook" (Kodansha Scientific, 10th edition, 1990)). Specific examples of amphipathic 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; organic amine compounds containing 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.

[0062] The solids concentration of the liquid material for forming a resin layer is not particularly limited and can be appropriately selected depending on the lamination conditions, the desired thickness, performance, etc. However, in order to maintain an appropriate viscosity of the liquid material and form a uniform resin layer, the solids concentration is preferably 2 to 30 mass %, more preferably 3 to 20 mass %. The liquid material for forming a resin layer can also contain antioxidants, ultraviolet absorbers, lubricants, colorants, etc., within the range that does not impair its performance.

[0063] <Production of Laminated Film> The method for producing a laminated film of the present invention includes the steps of applying a resin layer-forming liquid to a substrate film, drying, and stretching the applied substrate film. To obtain a resin layer surface having the developed interface area ratio (Sdr) specified in the present invention, the liquid temperature during application of the resin layer-forming liquid must be 20 to 40°C, preferably 25 to 35°C. If the liquid temperature during application is less than 20°C, the resin layer-forming liquid may thicken, making it difficult to apply uniformly, and the maximum height (Sz) of the resin layer surface may increase. On the other hand, if the liquid temperature during application exceeds 40°C, bumping may occur during drying of the resin layer, and the developed interface area ratio (Sdr) of the resin layer surface may increase. Methods for applying the liquid material for forming a resin layer to the substrate film include known methods such as gravure roll coating, reverse roll coating, wire bar coating, lip coating, air knife coating, curtain flow coating, spray coating, dip coating, and brush coating. The liquid material for forming a resin layer is particularly effective when gravure roll coating is used, as it can suppress the occurrence of coating streaks.

[0064] The laminate film manufacturing method of the present invention includes a step of applying a resin layer-forming liquid material during the manufacturing process of a substrate film, and a step of drying and stretching the applied material together with the substrate film. It is preferable that the method further includes a step of orientation stretching and heat setting treatment. By applying the resin layer-forming liquid material during the manufacturing process of the substrate film, a resin layer can be formed with a low degree of orientation crystallization on the substrate film surface, thereby improving the adhesion between the substrate film and the resin layer. Furthermore, since the resin layer can be heat-treated at a higher temperature while the substrate film is under tension, it is possible to improve the releasability and residual adhesive strength without degrading the quality of the substrate film. For reasons of simplicity and operational efficiency, it is preferable to employ a sequential biaxial stretching method, in which the liquid material is applied to a uniaxially stretched substrate film, the coated substrate film is dried, and then the substrate film is further stretched in a direction perpendicular to the uniaxial stretching direction and heat-treated.

[0065] <Resin Layer Characteristics> In order to provide easy slippage and suppress transfer to the adherend, the laminate film of the present invention must have a developed interface area ratio (Sdr) of the resin layer surface measured using a non-contact surface profilometer of 0.025 to 0.304%, preferably 0.03 to 0.30%, and more preferably 0.04 to 0.25%. If the developed interface area ratio (Sdr) of the resin layer surface is less than 0.025%, the air layer contained on the resin layer surface is very small, resulting in insufficient easy slippage, which can cause problems during winding, rewinding, slitting, etc. during the film production process, leading to scratches on the surface and a deterioration in the appearance of the wound roll. Furthermore, if the developed interface area ratio (Sdr) of the resin layer surface exceeds 0.304%, the resin layer surface becomes increasingly uneven, impairing flatness, making it difficult to meet the flatness required for small electronic devices, etc. On the other hand, the developed interface area ratio (Sdr) of the surface of the substrate film not provided with the resin layer, as determined by a non-contact surface profilometer, is preferably 0.20% or more. If the developed interface area ratio (Sdr) of the surface of the substrate film not provided with the resin layer is less than 0.20%, the slipperiness decreases, and processing of the film may become difficult when used in various processes.

[0066] In the present invention, the surface of the resin layer constituting the laminate film must have a surface roughness parameter maximum height (Sz) of 0.01 to 0.50 μm, preferably 0.01 to 0.40 μm, and more preferably 0.01 to 0.20 μm, from the viewpoint of suppressing transfer of surface texture to the adherend. By having the surface roughness of the resin layer within the above range, the resin layer is flattened and the transfer of coarse protrusions of the resin layer to the adherend is suppressed.

[0067] In the laminated film of the present invention, the peel strength between the resin layer and the epoxy prepreg, when measured by attaching the epoxy prepreg to the resin layer, is preferably 0.01 to 0.5 N / cm, more preferably 0.01 to 0.35 N / cm, and even more preferably 0.01 to 0.15 N / cm. If the peel strength exceeds 0.5 N / cm, peeling becomes too strong, making it difficult to practically use the film as a release film.

[0068] In the laminated film of the present invention, when an acrylic adherend as a pressure-sensitive adhesive material is attached to the resin layer and measured, the peel strength between the resin layer and the adherend is preferably 3.0 N / cm or less, more preferably 2.8 N / cm or less, and even more preferably 2.6 N / cm or less. If the peel strength exceeds 3.0 N / cm, peeling becomes too strong, making it difficult to practically use the film as a release film.

[0069] In the present invention, the thickness of the resin layer 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 releasability cannot be obtained, and if it exceeds 1 μm, the resin layer is likely to transfer to the adherend and costs increase, which is not preferable.

[0070] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. The properties of the laminated film were measured by the following methods.

[0071] (1) Flatness (Developed Interface Area Ratio (Sdr), Maximum Height (Sz)) Using a non-contact surface profiler (VS1800 manufactured by Hitachi High-Tech Corporation), the developed interface area ratio (Sdr) and maximum height (Sz) were measured for the resin layer surface in accordance with ISO 25178, and the developed interface area ratio (Sdr) was measured for the surface of the base film on which the resin layer was not provided. Measurements were conducted at 10 locations on each layer surface, and the average value was used as the measurement result. (Measurement conditions) Objective lens: 50x Measurement area: 112 μm × 112 μm Measurement mode: WAVE (Analysis conditions) Surface correction: 4th order

[0072] (2) Slipperiness (dynamic friction coefficient (μd)) Using a tensile tester (EZ-LX manufactured by Shimadzu Corporation), the dynamic friction coefficient (μd) between the resin layer surface and the surface of the base film on which the resin layer was not provided was determined in accordance with JIS K7125, and evaluated according to the following criteria. Measurements were made at five locations, and the average value was used as the measurement result. Excellent: Less than 0.25 Good: 0.25 or more, less than 0.30 Passable: 0.30 or more, less than 0.40 Fail: 0.40 or more

[0073] (3) Demoldability (peel strength) from epoxy prepreg Both sides of an epoxy prepreg (EI-6765 manufactured by Sumitomo Bakelite Co., Ltd.) measuring 60 mm × 100 mm were sandwiched between the resin layer sides of the obtained laminated film, and the temperature was raised from 30°C to 150°C at a rate of 15°C / min in a vacuum press at 1.07 kPa (8 Torr), held at 150°C for 22 minutes, and then further raised to 190°C at a rate of 5°C / min, and the pressure was 5 kg / cm. ２ After applying a pressure of 15 kg / cm for 10 minutes, ２ The sample was held at 190°C for 70 minutes while applying a pressure of 100 psi. The sample was then cooled to room temperature to obtain a sample. The peel strength between the cured epoxy prepreg and the laminated film of the obtained sample was measured using a tensile tester (Shimadzu Autograph AGX-V) in a thermostatic chamber at 23°C under conditions of a peel angle of 180° and a peel speed of 300 mm / min. Measurements were conducted at five locations, and the average value was used as the measurement result.

[0074] (4) Releasability (peel strength) from acrylic adhesive: A 50 mm wide, 150 mm long acrylic adhesive tape (Nitto Denko Corporation No. 31B / acrylic adhesive) was pressed onto the resin layer side of the resulting laminate film using a rubber roll to prepare a sample. The sample was sandwiched between metal plate / rubber plate / sample / rubber plate / metal plate and left under a load of 2 kPa in an atmosphere at 70°C for 20 hours. It was then cooled for at least 30 minutes and returned to room temperature to obtain a sample for peel strength measurement. The peel strength between the acrylic adhesive tape and the laminate film for the peel strength measurement sample was measured using a tensile tester (Shimadzu Corporation Autograph AGX-V) in a thermostatic chamber at 23°C, at a peel angle of 180° and a peel speed of 300 mm / min. Measurements were performed at five locations, and the average value was used as the measurement result.

[0075] (5) Transfer to Adherend (Maximum Height (Sz) of Adherend Surface After Peeling) An epoxy resin composition obtained by mixing 100 parts by weight of a bisphenol-type epoxy resin (jER828 manufactured by Mitsubishi Chemical Corporation), 50 parts by weight of an acid anhydride whose main component is 4-methylhexahydrophthalic anhydride (MH-700 manufactured by New Japan Chemical Co., Ltd.), and 2 parts by weight of a curing accelerator (U-CAT18X manufactured by Acid Apro Co., Ltd.) was applied to the resin layer side of the obtained laminate film using a Meyer bar to a thickness of 20 μm after drying. The film was then dried at 160°C for 30 minutes to obtain a laminate laminated with the epoxy resin composition. The epoxy resin composition / laminated film was then peeled off, and the maximum height (Sz) of the resin layer side of the epoxy resin composition was measured using the method described above in "(1) Flatness," and the average value was calculated. The maximum height (Sz) of the surface of the epoxy resin composition after peeling is preferably 0.40 μm or less, more preferably 0.30 μm or less, and even more preferably 0.10 μm or less.

[0076] To prepare a liquid material for forming a resin layer, an acid-modified polyolefin resin and an aqueous dispersion were produced by the following methods.

[0077] <Production 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-neck flask under a nitrogen atmosphere, and then, while maintaining the temperature in the system at 170°C and stirring, 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, and then the reaction was allowed to proceed for 1 hour. After completion of the reaction, the resulting reaction product was poured into a large amount of acetone to precipitate a 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).

[0078] <Production of Acid-Modified Polyolefin Resin A-2> Acid-modified polyolefin resin A-2 (acid modification amount 2.0%, melting point 105°C) was obtained in the same manner as in the production of acid-modified polyolefin resin A-1, except that in the production of acid-modified polyolefin resin A-1, the propylene-ethylene copolymer (propylene / ethylene = 99 / 1 (mass ratio)) was changed to an ethylene-ethyl acrylate copolymer (ethylene / ethyl acrylate = 93 / 7 (mass ratio)).

[0079] <Production of Acid-Modified Polyolefin Resin A-3> 70 g of ethylene-1-octene copolymer (ethylene / 1-octene = 61.9 / 38.1 (mass ratio)) and 14 g of maleic anhydride as an unsaturated carboxylic acid were heated and dissolved in 320.4 g of xylene under a nitrogen atmosphere in a four-neck flask, and stirring was continued while the temperature in the system was maintained at 140°C. In a separate flask, 4.2 g of dicumyl peroxide as a radical generator and 15.6 g of xylene were added to obtain a homogeneous solution, and then the system was purged with nitrogen. A xylene solution of dicumyl peroxide was added over 30 minutes to the xylene solution in which the ethylene-octene copolymer and maleic anhydride had been dissolved. Stirring was continued for 5 hours under a nitrogen atmosphere while the temperature in the system was maintained at 140°C. The solution in the four-neck flask was then cooled to 50°C, and the entire solution was poured into a large amount of methanol to precipitate a 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 an acid-modified polyolefin resin A-3 (acid modification amount 2.2%).

[0080] <Production of Acid-Modified Polyolefin Resin A-4> Acid-modified polyolefin resin A-4 (acid modification amount 6.3%, melting point 135°C) was obtained in the same manner as in the production of acid-modified polyolefin resin A-1, except that in the production of acid-modified polyolefin resin A-1, the propylene-ethylene copolymer (propylene / ethylene = 99 / 1 (mass ratio)) was changed to a propylene-1-butene-ethylene terpolymer (propylene / 1-butene / ethylene = 64.8 / 23.9 / 11.3 (mass ratio)).

[0081] Table 1 shows the structures of the obtained acid-modified polyolefin resins A-1 to A-4.

[0082]

[0083] <Production of Aqueous Dispersion of Acid-Modified Polyolefin Resin A-1> Using a stirrer equipped with a sealable, pressure-resistant 1-liter glass container with a heater, 60.0 g of the acid-modified polyolefin resin A-1 produced by the above method, 45.0 g of ethylene glycol-n-butyl ether (boiling point 171 ° C), 6.9 g of N,N-dimethylethanolamine (boiling point 134 ° C, 1.0 equivalent relative to the carboxyl groups of the maleic anhydride units in the resin), and 188.1 g of distilled water were charged into the glass container, and the stirring blade rotation speed was set to 300 rpm. As a result, no resin precipitation was observed at the bottom of the container, and it was confirmed that the resin was in a floating state. Therefore, while maintaining this state, the heater was turned on after 10 minutes and heating was performed. The temperature in the system was then maintained at 140 ° C and stirring was continued for another 60 minutes. The mixture was then cooled to room temperature (approximately 25 ° C) by air cooling while stirring at a rotation speed of 300 rpm. Further, pressure filtration (air pressure 0.2 MPa) was performed using a 300-mesh stainless steel filter (wire diameter 0.035 mm, plain weave) to obtain a uniform aqueous dispersion of acid-modified polyolefin resin A-1 (solid content concentration 25% by mass). Note that almost no resin remained on the filter.

[0084] <Production of aqueous dispersion of acid-modified polyolefin resin A-2> An aqueous dispersion of acid-modified polyolefin resin A-2 (solid content concentration 25% by mass) was obtained in the same manner as for aqueous dispersion of A-1, except that the acid-modified polyolefin resin used was changed to A-2.

[0085] <Production of Aqueous Dispersion of Acid-Modified Polyolefin Resin A-3> Using a stirrer equipped with a sealable, pressure-resistant 1-liter glass container with a heater, 30.0 g of the acid-modified polyolefin resin A-3 produced by the above method, 90.0 g of tetrahydrofuran, 15.0 g of triethylamine, 2.4 g of 2-dimethylaminoethanol, and 165.0 g of distilled water were charged into the glass container, and the stirring blade rotation speed was set to 300 rpm. While maintaining this state, the heater was turned on after 10 minutes to start heating. The temperature in the system was then maintained at 120°C, and stirring was continued for an additional 60 minutes. The mixture was then cooled to room temperature (approximately 25°C) by air-cooling while stirring, and the entire amount of the resulting dispersion was transferred to a 1-liter recovery flask. While immersed in a water bath heated to 60°C, the solvent was removed under reduced pressure using an evaporator, and 74 g of the aqueous medium was distilled off. Subsequently, 93.6 g of distilled water was added to the dispersion in the recovery flask, and then the solvent was removed under reduced pressure using an evaporator while the flask was immersed in a water bath heated to 60° C., and 82 g of the aqueous medium was distilled off. After cooling, the dispersion in the recovery flask was pressure filtered (air pressure 0.2 MPa) using a 300-mesh stainless steel filter (wire diameter 0.035 mm, plain weave) to obtain a uniform aqueous dispersion of acid-modified polyolefin resin A-3 (solid content concentration 12.5% ​​by mass).

[0086] <Production of aqueous dispersion of acid-modified polyolefin resin A-4> An aqueous dispersion of acid-modified polyolefin resin A-4 (solid content concentration 25% by mass) was obtained in the same manner as for aqueous dispersion of A-1, except that the acid-modified polyolefin resin used was changed to A-4.

[0087] To prepare the liquid material for forming the resin layer, the following aqueous solutions were used as polyvinyl alcohol (B): B-1: JT-05 manufactured by Nippon Vinyl Acetate & Poval Co., Ltd., saponification rate 94.5%, polymerization degree 500, solid content 8.0% B-2: VC-10 manufactured by Nippon Vinyl Acetate & Poval Co., Ltd., saponification rate 99.3%, polymerization degree 1000, solid content 8.0%

[0088] The following crosslinking agents (C) were used: C-1: oxazoline group-containing compound (Epocross WS-700 manufactured by Nippon Shokubai Co., Ltd., solid content concentration 25% by mass) C-2: carbodiimide group-containing compound (Carbodilite V-02-L2 manufactured by Nisshinbo Chemical Inc., solid content concentration 40% by mass)

[0089] The following compounds were used as compound (D): D-1: amphiphilic oligomer (Polyflow KL-900 manufactured by Kyoeisha Chemical Co., Ltd.) D-2: acetylene glycol (Olfine D-10 manufactured by Nissin Chemical Industry Co., Ltd.) D-3: acetylene glycol-based ethylene oxide adduct (Olfine E1010 manufactured by Nissin Chemical Industry Co., Ltd.) D-4: modified silicone (Polyflow KL-401 manufactured by Kyoeisha Chemical Co., Ltd.)

[0090] The polyethylene terephthalate constituting the substrate film was produced by the following method. <Polyethylene terephthalate P-1> Polyethylene terephthalate P-1, which was substantially free of particles, was obtained by polymerization of terephthalic acid and ethylene glycol using antimony oxide as a catalyst in a conventional manner. <Polyethylene terephthalate P-2> During the polymerization of P-1, silica particles having an average particle size of 2.3 μm were added in an amount of 0.08% by mass relative to the polyethylene terephthalate, to obtain melt-polymerized polyethylene terephthalate P-2.

[0091] Example 1 <Preparation of liquid for forming resin layer> An aqueous dispersion of acid-modified polyolefin resin A-1, an aqueous polyvinyl alcohol solution B-1, an aqueous solution C-1 of an oxazoline group-containing compound as a crosslinking agent, and a compound D-1 were mixed so that the solid contents were 100 parts by mass, 300 parts by mass, 5 parts by mass, and 20 parts by mass, respectively, and the final solid content was adjusted with water to 7% by mass, to obtain a liquid for forming a resin layer. <Production of laminated film> Polyethylene terephthalate P-1 was added to an extruder 1 (screw diameter: 50 mm), and polyethylene terephthalate P-2 was added to an extruder 2 (screw diameter: 65 mm), respectively, and melted at 280 ° C., and then each melt was mixed at the outlet of the T-die, and the layer thickness ratio (P layer consisting of P-1 / S layer consisting of P-2) was 33 / 5, and the two layers were laminated together so that the total thickness was 600 μm. The laminated molten material was extruded from the T-die outlet of the multilayer die and rapidly cooled in close contact with a casting drum using the T-die method-electrostatic pinning system to form an unstretched film with a thickness of 600 μm. This unstretched film was then stretched 3.5 times using a longitudinal stretching roll heated to 90°C. A resin layer-forming liquid having a liquid temperature of 30°C was applied to one side of this longitudinally stretched film (the side of the P layer made of polyethylene terephthalate P-1) at a rate of 10 g / m using a reverse gravure coater. ２ The longitudinally stretched film coated with the resin layer-forming liquid was dried at 120°C and stretched 4.5 times in a transverse stretching tenter, then heat-treated at 230°C for 10 seconds, cooled, and wound up. The thickness of the resulting laminated film was 38 μm, and the thickness of the resin layer was approximately 0.10 μm. The developed interface area ratio (Sdr) of the substrate film surface not provided with the resin layer was 0.33.

[0092] Examples 2 to 19, Comparative Examples 2 to 4, 6 to 8, 10, 12 Laminated films were obtained in the same manner as in Example 1, except that the layer structure of the base film, the structure of the resin layer-forming liquid material, and the liquid temperature during application were changed as shown in Table 2.

[0093] Comparative Example 1 Polyethylene terephthalate P-1 was introduced into extruder 1 (screw diameter: 50 mm), and polyethylene terephthalate P-2 was introduced into extruder 2 (screw diameter: 65 mm), and melted at 280 ° C., respectively. Before reaching the outlet of the T-die of the multilayer die, the layer thickness ratio (S layer consisting of P-2 / P layer consisting of P-1 / S layer consisting of P-2) was 5 / 28 / 5, and the three layers were joined and laminated to a total thickness of 600 μm. The laminated melt was extruded from the T-die outlet of the multilayer die, and quenched in close contact with a casting drum using the T-die method-electrostatic pinning method, forming an unstretched film with a thickness of 600 μm. Subsequently, this unstretched film was stretched 3.5 times with a longitudinal stretching roll heated to 90 ° C. Then, a laminated film was obtained in the same manner as in Example 1, except that a liquid material for forming a resin layer was applied to one side of this longitudinally stretched film.

[0094] Comparative Examples 5, 9, and 11 Laminated films were obtained in the same manner as in Comparative Example 1, except that the composition of the resin layer-forming liquid material was changed as shown in Tables 2 to 4.

[0095] The laminated films obtained in the examples and comparative examples were subjected to various evaluations, and the results are shown in Tables 2 to 4.

[0096]

[0097]

[0098]

[0099] The resin layers of the laminate films of Examples 1 to 19 had developed interface area ratios (Sdr) and maximum heights (Sz) within the ranges specified in the present invention, and were excellent in lubricity, allowing the formation of good winding rolls, and also affording a flat surface shape and good releasability.

[0100] The resin layers of the laminate films of Comparative Examples 1, 5, 9, and 11 were formed in the particle-containing S layer of a multilayer substrate film, so the maximum height (Sz) was outside the range specified by the present invention, resulting in poor flatness and a high maximum height (Sz) of the adherend surface after peeling. The resin layers of the laminate films of Comparative Examples 2, 3, and 10 were formed in the particle-free P layer of a multilayer substrate film, so the maximum height (Sz) was within the range specified by the present invention and they had excellent flatness, but because they were formed by applying a resin layer-forming liquid that did not contain or had a low content of compound (D), the developed interface area ratio (Sdr) was outside the range specified by the present invention and they had poor slipperiness. The resin layers of the laminate films of the other comparative examples also had Sdr and Sz outside the range specified by the present invention, resulting in poor slipperiness and flatness.

Claims

1. A laminated film comprising a base film and a resin layer on at least one side thereof, the base film surface on which the resin layer is provided is substantially free of particles, the resin layer contains an acid-modified polyolefin resin (A) and a crosslinking agent (C), and the resin layer surface has a developed interface area ratio (Sdr) of 0.025-0.304% and a maximum height (Sz) of 0.01-0.50 μm, as determined by a non-contact surface profiler.

2. The laminated film according to claim 1, wherein the olefin component of the acid-modified polyolefin resin (A) contains propylene or 1-octene.

3. The laminate film according to claim 2, characterized in that the propylene content in the olefin component is 70 mass % or more.

4. The laminate film according to claim 2, wherein the 1-octene content in the olefin component is 15% by mass or more.

5. A laminate film according to any one of claims 1 to 4, characterized in that the peel strength between the resin layer and the epoxy prepreg is 0.5 N / cm or less.

6. A method for producing the laminated film according to any one of claims 1 to 5, comprising the steps of: applying to a substrate film a liquid material for forming a resin layer, the liquid material containing an acid-modified polyolefin resin (A), a crosslinking agent (C), and at least one compound (D) selected from the group consisting of an amphiphilic oligomer, acetylene glycol, and an ethylene oxide adduct of acetylene glycol, and the liquid material having a temperature of 20 to 40°C; and drying and stretching the substrate film to which the liquid material for forming a resin layer has been applied.

7. A method for producing a laminated film according to claim 6, characterized in that a liquid for forming a resin layer, the liquid containing the compound (D) being 2 to 50 parts by mass per 100 parts by mass of the acid-modified polyolefin resin (A), is applied.

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