Release film for resin sheet molding

Abstract

To provide a release film for manufacturing a ceramic green sheet which has excellent smoothness, substantially contains no silicone, can peel even a thin layer ceramic green sheet by a low and uniform force, and has no possibility of generating a defect such as a pinhole.SOLUTION: A release film for manufacturing a sheet has a biaxially oriented polyester film as a substrate, where a release layer is laminated on the surface of the substrate directly or via another layer, the release layer is formed by curing a release layer forming composition, the release layer forming composition contains long-chain alkyl group-containing acrylic resin (a), a melamine-based compound (b) and solvent (x) by 5 mass% or more in 100 pts.mass of solvent, the boiling point of the solvent (x) is 110°C or higher, and in the case where an evaporation rate of acetic acid n-butyl at 20°C is 100, the evaporation rate of the solvent (x) at 20°C is 80 or less, the region surface mean roughness (Sa) of the release layer is 3.0nm or less, and the maximum protrusion height (P) is 200nm or less.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a release film for molding resin sheets, and more particularly to a release film used when molding thin resin sheets. [Background technology]

[0002] Conventionally, release films, which use a polyester film as a base material and laminate a release layer on top of it, have been used as process films for molding resin sheets such as adhesive sheets, cover films, polymer films, and optical lenses.

[0003] The aforementioned release film is also used as a process film for molding ceramic green sheets, which require high smoothness for multilayer ceramic capacitors, ceramic substrates, and other applications. In recent years, with the miniaturization and increased capacitance of multilayer ceramic capacitors, there has been a trend towards thinner ceramic green sheets. Ceramic green sheets are molded by coating a slurry containing ceramic components such as barium titanate and a binder resin onto a release film and drying it. After printing electrodes onto the molded ceramic green sheet and peeling it off the release film, the ceramic green sheets are laminated, pressed, fired, and external electrodes are applied to manufacture a multilayer ceramic capacitor.

[0004] When molding a ceramic green sheet onto the surface of a polyester film substrate's release layer, the wettability and smoothness of the release film during ceramic slurry application, as well as the peelability when removing the ceramic green sheet from the release film, are crucial. Poor smoothness can lead to problems such as uneven thickness and sheet defects in the ceramic green sheet obtained after slurry application and drying. Conversely, excessive peeling force can damage the ceramic green sheet during the peeling process, resulting in sheet defects, uneven thickness, pinholes, and sheet cracking.

[0005] In recent years, ceramic green sheets have become thinner, and there is a growing demand for ceramic green sheets with thicknesses of 1.0 μm or less, more specifically between 0.2 μm and 1.0 μm. As a result, the requirements for smoothness and release properties in release films have become even more stringent.

[0006] As a release film with excellent peelability, Patent Document 1 discloses one in which a silicone-based release agent is used in the release layer.

[0007] Furthermore, Patent Documents 2 and 3 disclose a laminated polyester film formed from an acrylic resin containing long-chain alkyl groups in its side chains and a crosslinking agent as a non-silicone release film. [Prior art documents] [Patent Documents]

[0008] [Patent Document 1] Japanese Patent Publication No. 2015-208863 [Patent Document 2] Japanese Patent Publication No. 2018-115224 [Patent Document 3] Japanese Patent Publication No. 2021-14587 [Overview of the Initiative] [Problems that the invention aims to solve]

[0009] However, the technology described in Patent Document 1 raises concerns that using silicone-based release agents in applications related to precision electronic equipment may cause problems in precision electronic equipment due to the migration of low-molecular-weight silicone compounds contained in the release layer. Furthermore, silicone-based release agents have very low surface free energy, resulting in poor coating properties such as repulsion when ceramic slurries are applied.

[0010] Furthermore, the release films described in Patent Documents 2 and 3 contain a large amount of acrylic resin and other resin components containing long-chain alkyl groups. When the resin content is high, the viscosity of the coating solution increases, resulting in poor leveling properties. Therefore, when attempting to make the release layer thicker, groove-like streaks generated during coating remain on the surface of the coating film, leading to a problem of reduced smoothness of the release layer.

[0011] Furthermore, the release films described in Patent Documents 2 and 3 tend to have a high surface roughness of the release layer, which increases the likelihood of defects occurring in the thin ceramic green sheet.

[0012] As a result of diligent research to solve the above problems, the inventors of the present invention found that the above objective can be achieved by a release film having the following configuration, and thus completed the present invention. [Means for solving the problem]

[0013] In other words, the present invention consists of the following configuration. [1] A biaxially oriented polyester film is used as the base material, the base material having a surface layer A, and a release layer is laminated directly or via another layer on the surface of at least one side of the surface layer A, The aforementioned release layer is formed by curing a release layer forming composition. The release layer forming composition contains a long-chain alkyl group-containing acrylic resin (a), a melamine-based compound (b), and the following solvent (X) in an amount of 5% by mass or more per 100 parts by mass of the solvent. The solvent (X) has a boiling point of 110°C or higher, and when the evaporation rate of butyl acetate at 20°C is taken as 100, the evaporation rate of solvent (X) at 20°C is 80 or lower. A release film for sheet manufacturing, having a regional average surface roughness (Sa) of 3.0 nm or less and a maximum protrusion height (P) of 200 nm or less. [2] In one embodiment, the release layer forming composition further comprises a low molecular weight polyol (c), and the total content of the low molecular weight polyol (c) and the melamine compound (b) is 80% by mass or more with respect to 100% by mass of the total solid content of the release layer, a release film for manufacturing resin sheets. [3] In one embodiment, the release film for sheet production, wherein said long-chain alkyl group-containing acrylic resin (a) comprises a resin in which the long-chain alkyl group has 8 to 20 carbon atoms. [4] In one embodiment, the release film, wherein said acrylic resin (a) comprises component a-1 represented by the following chemical formula (1) and component a-2 represented by the following chemical formula (2), and the mass of a-1 is in the range of 40 to 70 parts by mass relative to the total mass of the acrylic resin (a)

[0014]

Chemical Formula

[0015]

Chemical Formula

Effects of the Invention

[0016] The release film for molding a resin sheet according to the present invention has a release layer on one surface of a base film, does not have an excessively low surface free energy of the release layer, and is excellent in surface smoothness, thereby enabling coating of a resin sheet-forming slurry without defects. By achieving both easy release properties, the present invention can provide a release film that can release a thin-film resin sheet, particularly a ceramic green sheet, without defects.

Mode for Carrying Out the Invention

[0017] Hereinafter, the present invention will be described in detail.

[0018] The present invention provides a release film with excellent smoothness, slurry coating properties, and peelability by providing a release layer made of a long-chain alkyl group-containing acrylic resin and a melamine-based compound on one side of a base film with excellent smoothness. Furthermore, by using a solvent with a boiling point of 110°C or higher, and where the evaporation rate of solvent (X) at 20°C is 80 or less compared to the evaporation rate of n-butyl acetate at 20°C (which is set to 100), the occurrence of coating streaks during the release layer processing can be suppressed, and a release layer with excellent surface texture can be obtained. In this specification, "excellent surface texture" means a state in which the release layer has high smoothness and uniform thickness across the entire width of the film, which is preferable as it reduces the likelihood of variations in peeling force due to uneven thickness of the release layer within the surface. In addition, by suppressing the occurrence of coating streaks, it is possible to accommodate thicker release layers of 100 nm or more, and it is possible to fill in substrate protrusions such as oligomers, thereby suppressing the height of protrusions on the surface of the release layer.

[0019] The release layer is a cured product of a composition containing a long-chain alkyl group-containing acrylic resin (a) and a melamine compound (b). By using a long-chain alkyl group-containing acrylic resin (a) and a melamine compound (b), a release film with excellent wettability and peelability of the slurry can be obtained without the surface free energy being too low.

[0020] (Polyester film) The polyester constituting the polyester film used as the base film (hereinafter sometimes referred to as "base") in the present invention is not particularly limited, and a film-formed polyester commonly used as a base material for release films can be used. Preferably, it is a crystalline linear saturated polyester consisting of an aromatic dibasic acid component and a diol component, and more preferably, polyethylene terephthalate, polyethylene-2,6-naphthalate, polybutylene terephthalate, polytrimethylene terephthalate, or copolymers mainly composed of these resin components. In particular, a polyester film formed from polyethylene terephthalate is especially preferred. The polyethylene terephthalate preferably has 90 mol% or more, more preferably 95 mol% or more of repeating units of ethylene terephthalate, and may also have small amounts of other dicarboxylic acid components and diol components copolymerized. For example, from the viewpoint of cost, it is preferable to have one produced only from terephthalic acid and ethylene glycol. In addition, known additives, such as antioxidants, light stabilizers, ultraviolet absorbers, and crystallizers, may be added within a range that does not hinder the effect of the release film of the present invention. The polyester film is preferably a biaxially oriented polyester film due to reasons such as its high bidirectional modulus of elasticity.

[0021] The intrinsic viscosity of the above polyester film is preferably 0.50 to 0.70 dl / g, and more preferably 0.52 to 0.62 dl / g. An intrinsic viscosity of 0.50 dl / g or higher is preferable because it does not cause many breaks during the stretching process. Conversely, an intrinsic viscosity of 0.70 dl / g or lower is preferable because it allows for good cutting when cutting to a predetermined product width and prevents dimensional defects. Furthermore, it is preferable to thoroughly vacuum dry the raw material pellets. In this specification, when the term "polyester film" is used, it refers to a polyester film having surface layer A and surface layer B (a laminated polyester film).

[0022] The method for manufacturing the polyester film in the present invention is not particularly limited, and conventional methods can be used. For example, the polyester can be melted in an extruder, extruded into a film, cooled in a rotating cooling drum to obtain an unstretched film, and then biaxially stretched to obtain the film. The biaxially oriented film can be obtained by sequentially biaxially stretching a uniaxially oriented film in the longitudinal or transverse direction in the transverse or longitudinal direction, or by simultaneously biaxially stretching an unstretched film in the longitudinal and transverse directions.

[0023] In the present invention, it is preferable that the stretching temperature during stretching of the polyester film be above the secondary transition temperature (Tg) of the polyester. It is also preferable to stretch the film by 1 to 8 times, and particularly 2 to 6 times, in both the longitudinal and transverse directions.

[0024] The polyester film described above preferably has a thickness of 12 to 50 μm, more preferably 15 to 38 μm, and more preferably 19 to 33 μm. A film thickness of 12 μm or more is preferable because it does not risk deformation due to heat during film production, processing, or molding. On the other hand, a film thickness of 50 μm or less is preferable because it does not result in an excessively large amount of film being discarded after use, thus reducing the environmental burden.

[0025] The polyester film substrate described above may be a single layer or a multilayer of two or more layers. For example, the substrate film may be a polyester film having a surface layer A that substantially does not contain particles with a particle size of 1.0 μm or larger, and a surface layer B that contains particles. Preferably, surface layer A substantially does not contain inorganic particles with a particle size of 1.0 μm or larger. In this embodiment, the surface layer A may contain particles with a particle size of less than 1.0 μm and 1 nm or larger. By substantially excluding particles with a particle size of 1.0 μm or larger, such as inorganic particles, the surface of the release layer is smooth when the release layer is formed, and the transfer of the particle shape in the substrate to the resin sheet can be reduced, thereby reducing defects. In one embodiment, by not including particles with a particle size of less than 1.0 μm in the surface layer A, it is possible to more effectively suppress defects caused by the transfer of the particle shape in the substrate to the resin sheet. In one embodiment, the polyester film substrate is preferably a laminated film having a surface layer A on at least one side that is substantially free of inorganic particles. This makes it possible to more effectively suppress defects caused by the transfer of the particle shape in the substrate to the resin sheet. For example, a surface layer A that substantially does not contain particles with a particle size of less than 1.0 μm is preferably also substantially free of particles with a particle size of 1.0 μm or larger.

[0026] In this invention, "substantially free of particles" means, for example, in the case of inorganic particles smaller than 1.0 μm, that the content of inorganic elements is 50 ppm or less, preferably 10 ppm or less, and most preferably below the detection limit when quantified by fluorescence X-ray analysis. This is because even without actively adding particles to the film, contaminants originating from foreign substances, or dirt adhering to the raw material resin or the lines and equipment in the film manufacturing process, may peel off and become mixed into the film. Furthermore, "substantially free of particles with a particle size of 1.0 μm or larger" means that the film actively does not contain particles with a particle size of 1.0 μm or larger. In the case of a laminated polyester film consisting of two or more layers, it is preferable that the surface opposite to surface layer A, which substantially does not contain inorganic particles, has a surface layer B that may contain inorganic particles. In terms of the lamination structure, if the layer on the side to which the release layer is applied is designated as layer A, the layer on the opposite side as layer B, and the remaining core layer as layer C, then the layer configuration in the thickness direction can be a laminated structure such as release layer / A / B or release layer / A / C / B. Naturally, layer C may consist of multiple layers. Furthermore, the surface layer B may not contain inorganic particles. In that case, it is preferable to provide a coating layer containing at least inorganic particles and a binder on the surface layer B in order to provide slipperiness for winding the film into a roll.

[0027] In the polyester film substrate of the present invention, the surface layer B that forms the opposite side of the surface to which the release layer is applied preferably contains inorganic particles from the viewpoint of the film's slipperiness and ease of air release, and it is particularly preferable to use silica particles and / or calcium carbonate particles. The inorganic particle content is preferably 5,000 to 15,000 ppm in total in the surface layer B. In this case, the average surface roughness (Sa) of the surface layer B film is preferably in the range of 1 to 40 nm. More preferably, it is in the range of 5 to 35 nm. When the total amount of silica particles and / or calcium carbonate particles is 5000 ppm or more and Sa is 1 nm or more, when the film is wound into a roll, air can be released uniformly, resulting in a good winding shape and good flatness, making it suitable for the manufacture of ultrathin ceramic green sheets. Furthermore, when the total amount of silica particles and / or calcium carbonate particles is 15000 ppm or less and Sa is 40 nm or less, lubricant aggregation is less likely to occur and no coarse protrusions are formed, resulting in stable quality during the manufacture of ultrathin ceramic green sheets, which is preferable.

[0028] In addition to silica and / or calcium carbonate, other inert inorganic particles and / or heat-resistant organic particles can be used as particles in the above-mentioned B layer, but silica particles and / or calcium carbonate particles are more preferable from the viewpoint of transparency and cost. Other inorganic particles that can be used include alumina-silica composite oxide particles and hydroxyapatite particles. Heat-resistant organic particles include cross-linked polyacrylic particles, cross-linked polystyrene particles and benzoguanamine particles. When silica particles are used, porous colloidal silica is preferred, and when calcium carbonate particles are used, light calcium carbonate surface-treated with a polyacrylic acid-based polymer compound is preferred from the viewpoint of preventing lubricant detachment.

[0029] The average particle size of the inorganic particles added to the surface layer B is preferably 0.1 μm or more and 2.0 μm or less, and particularly preferably 0.5 μm or more and 1.0 μm or less. An average particle size of 0.1 μm or more is preferable because it provides good slipperiness for the release film. Furthermore, an average particle size of 2.0 μm or less is preferable because it does not adversely affect the smoothness of the surface of the release layer, thus preventing the formation of pinholes in the ceramic green sheet.

[0030] In the surface layer A, which is the layer on the side where the release layer is provided, it is preferable not to use recycled materials or the like in order to prevent the inclusion of inorganic particles such as lubricants, from the viewpoint of reducing pinholes.

[0031] The thickness ratio of surface layer A, which is the layer on which the release layer is provided, is preferably 20% to 50% of the total thickness of the base film. If it is 20% or more, the influence of particles contained in surface layer B and the like from inside the film is less likely to occur, and it is easier for the average surface roughness Sa to satisfy the above range, which is preferable. If it is 50% or less of the total thickness of the base film, the proportion of recycled materials used in surface layer B can be increased, which is preferable because it reduces the environmental impact.

[0032] Furthermore, from an economic standpoint, 50 to 90% by mass of recycled film scraps or PET bottles can be used in layers other than the surface layer A (surface layer B or the aforementioned intermediate layer C). Even in this case, it is preferable that the type, amount, particle size, and average surface roughness (Sa) of the lubricant contained in layer B satisfy the above range.

[0033] Furthermore, a coating layer may be applied to the surface of surface layer A and / or surface layer B before stretching or after uniaxial stretching during the film-forming process to improve the adhesion of release layers applied later or to prevent static charge buildup, and corona treatment may also be applied.

[0034] (Release layer) The release layer in the present invention comprises a long-chain alkyl-containing acrylic resin (a) and a melamine-based compound (b). For example, a release layer can be formed by curing a release layer-forming composition comprising a long-chain alkyl-containing acrylic resin (a) and a melamine-based compound (b). In one embodiment, the release layer of the present invention comprises a low-molecular-weight polyol (c).

[0035] (Long-chain alkyl group-containing acrylic resin) The long-chain alkyl-containing acrylic resin (a) may be, for example, an acrylic polymer copolymerized with long-chain alkyl acrylates, a graft polymer with long-chain alkyl grafts, or a block polymer with long-chain alkyl grafts at its ends. Similar embodiments can be adopted for polyester resins and the like that may be included in the matrix. The following describes the details of a long-chain alkyl-containing acrylic resin (a) as an example, but the same applies to polyester resins and other materials that may be included in the matrix. For example, the long-chain alkyl group-containing acrylic resin (a) includes an acrylic resin in which the long-chain alkyl group has 8 or more carbon atoms and 20 or less carbon atoms.

[0036] The long-chain alkyl-containing acrylic resin (a) preferably contains component a-1 represented by the following chemical formula (1) and component a-2 represented by the following chemical formula (2).

[0037] [ka]

[0038] In equation (1), R1 represents (CnH2n+1) (n = an integer between 8 and 20), and R4 represents H or CH3.

[0039] [ka]

[0040] In equation (2), R2 represents (CmH2mOH) (m = an integer between 1 and 10) or H, and R4 represents H or CH3.

[0041] As the long-chain alkyl-containing acrylic resin (a), the constituent units of component a-1 and component a-2 are preferably in the range of a-1: 40-80% by weight and a-2: 20-60% by weight, respectively, relative to the weight of the acrylic resin (a), and more preferably in the range of a-1: 45-70% by weight and a-2: 30-55% by weight. If component a-1 is 40% or more, sufficient release properties can be obtained for thin-film ceramic sheets. If component a-1 is 80% or less, the compatibility with other release layer forming compositions of the acrylic resin is good, and it becomes possible to form a smooth release layer without the raw materials agglomerating.

[0042] In formula (1) representing component a-1, R1 is an alkyl group with 8 to 20 carbon atoms. Having 8 or more carbon atoms allows component a-1 to exhibit good release properties. On the other hand, if the number of carbon atoms n is 20 or less, the flexibility of component a-1 can be maintained, and sufficient wettability of the release layer film surface can be ensured. Furthermore, the cohesive force of the acrylic resin can be suppressed, resulting in no protrusions derived from aggregates and ensuring sufficient smoothness. The number of carbon atoms n is preferably 8 to 18, and more preferably 8 to 16. In one embodiment, the number of carbon atoms n in R1 in formula (1) may be 10 to 15. Furthermore, R1 can be either linear or branched. A linear R1 is preferable because it tends to reduce the peelability of the release layer.

[0043] In formula (1) representing component a-1, R4 is either H or CH3, both of which are preferred. As a raw material for component a-1, the monomer shown in the following chemical formula (3) can be used.

[0044] [ka]

[0045] In equation (3), R1 represents (CnH2n+1) (n = an integer between 8 and 20), and R4 represents H or CH3.

[0046] Specifically, lauryl (meth)acrylate, stearyl (meth)acrylate, ethylhexyl (meth)acrylate, octyl (meth)acrylate, etc. can be used as raw materials for component a-1.

[0047] In formula (2) representing component a-2, the number of carbon atoms m in R2 is between 1 and 10. When the number of carbon atoms m is 10 or less, it is possible to avoid the crosslinking density of the release layer of the present invention becoming sparse, to suppress the weakening of the cohesive force of the release layer itself, and further, to suppress an increase in the peeling force. The number of carbon atoms m is preferably between 2 and 8, and more preferably between 2 and 4.

[0048] In formula (2) representing component a-2, R4 is either H or CH3, both of which are preferred. As a raw material for component a-2, the monomer shown in the following chemical formula (4) can be used.

[0049] [ka]

[0050] In equation (4), R2 represents (CmH2mOH) (m = an integer between 1 and 10) or H, and R4 represents H or CH3.

[0051] Specifically, hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, hydroxybutyl (meth)acrylate, etc., can be used as raw materials for component a-2.

[0052] (Melamine compounds) The melamine-based compound (b) used in the release layer of the present invention can be any common compound and is not particularly limited, but it is preferable that it is obtained by condensing melamine and formaldehyde and has one or more triazine rings and one or more methylol groups and / or alkoxymethyl groups in one molecule. Specifically, a compound obtained by dehydrating and condensing a methylolmelamine derivative obtained by condensing melamine and formaldehyde with a lower alcohol such as methyl alcohol, ethyl alcohol, isopropyl alcohol, or butyl alcohol to obtain an ether compound is preferred. Examples of methylolated melamine derivatives include monomethylolmelamine, dimethylolmelamine, trimethylolmelamine, tetramethylolmelamine, pentamethylolmelamine, and hexamethylolmelamine. One type or two or more types may be used.

[0053] The melamine used in this invention can also be commercially available. For example, Cymel 300, Cymel 301, Cymel 303LF, Cymel 350, Cymel 370N, Cymel 771, Cymel 325, Cymel 327, Cymel 703, Cymel 712, Cymel 701, Cymel 266, Cymel 267, Cymel 285, Cymel 232, Cymel 235, Cymel 236, Cymel 238, Cymel 272, Cymel 212, Cymel 253, Cymel 254, Cymel 202, Cymel 207 (manufactured by Ornex Japan Co., Ltd.), Nikarac MW-30M, Nikarac MW-30, Nikarac MW-30HM Examples include Nikarac MW-390, Nikarac MW-100LM, Nikarac MX-750LM, Nikarac MW-22, Nikarac MS-21, Nikarac MS-11, Nikarac MW-24X, Nikarac MS-001, Nikarac MX-002, Nikarac MX-730, Nikarac MX-750, Nikarac MX-708, Nikarac MX-706, Nikarac MX-042, Nikarac MX-035, Nikarac MX-45, Nikarac MX-43, Nikarac MX-417, and Nikarac MX-410 (manufactured by Nippon Carbide Co., Ltd.). Among these, full-ether type methylated melamine resins are preferred in terms of their ability to cure at low temperatures and in a short time, and their adhesion to polyester films. Commercially available products include Cymel 303LF and Nikarac MW-30.

[0054] The low molecular weight polyol (c) contained in the release layer in the present invention can be any common polyol and is not particularly limited, but examples include aliphatic diols such as 1,6-hexanediol, 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, 3-methyl-1,5-pentanediol, neopentyl glycol, 2-methyl-1,5-pentanediol, 2,2-diethyl-1,3-propanediol, butylethylpropanediol, and butylethylpentanediol; aliphatic and aromatic cyclic diols such as 1,4-cyclohexanedimethanol and 1,4-benzenedimethanol; trimethylolpropane, pentaerythritol, ditrimethylolpropane, dipentaerythritol, dimer diol, hydrogenated dimer diol, trimertriol, hydrogenated trimertriol, castor oil, castor oil-based modified polyols, alkylene oxide adducts of bisphenol compounds or their derivatives, and one or more of these can be used. By adding these polyols, the crosslinking density of the release layer is increased, resulting in improved solvent resistance and elastic modulus, making it easier to peel off the ceramic green sheet.

[0055] In the present invention, the total content of the melamine compound (b) and the low molecular weight polyol (c) contained in the release layer is preferably 80% by mass or more, and more preferably 85% by mass or more, based on 100% by mass of the total solid content of the release layer. In one embodiment, the total content of the melamine compound (b) and the low molecular weight polyol (c) is 99.9% by mass or less, for example, 98% by mass or less, based on 100% by mass of the total solid content of the release layer. If the total content is 80% by mass or more, sufficient solvent resistance can be obtained, enabling good peeling from the ceramic green sheet. In addition, increasing the content of low molecular weight raw materials can reduce the viscosity of the coating liquid, preventing groove-like streaks caused by the coating from leveling and remaining on the coating surface, thus preventing a decrease in the smoothness of the release layer. In one embodiment, when the release layer forming composition contains a long-chain alkyl group-containing acrylic resin (a) and a melamine-based compound (b), the total amount of these components can be 100% by mass of the total solid content. In another embodiment, the material comprises a long-chain alkyl group-containing acrylic resin (a) and a melamine compound (b), and further comprises a low molecular weight polyol (c), where the low molecular weight polyol (c) is solid at 20°C. In this case, the total solid content of components (a), (b), and (c) may be 100% by mass.

[0056] (curing catalyst) In the present invention, it is preferable to add an acid catalyst to the release layer to promote the crosslinking reaction of the melamine-based compound, and it is preferable to add the acid catalyst to the release layer forming composition, apply it, and cure it. The acid catalyst used is not particularly limited and existing acid catalysts can be used, but it is preferable to use a sulfonic acid-based catalyst.

[0057] As sulfonic acid catalysts, for example, p-toluenesulfonic acid, xylenesulfonic acid, cumenesulfonic acid, dodecylbenzenesulfonic acid, dinonylnaphthalenesulfonic acid, and trifluoromethanesulfonic acid can be suitably used, but from the viewpoint of reactivity, p-toluenesulfonic acid can be particularly suitably used.

[0058] Sulfonic acid-based catalysts have higher acidity and superior reactivity compared to other acid catalysts such as carboxylic acid-based catalysts, allowing for the processing of the release layer at lower temperatures. This is preferable because it suppresses the decrease in film flatness and deterioration of the winding appearance caused by heat during processing.

[0059] The sulfonic acid catalyst used in this invention can also be a commercially available one. Examples of commercially available products include Dryer® 900 (p-toluenesulfonic acid, manufactured by Hitachi Chemical Co., Ltd.), NACURE® DNNDSA series (dinonylnaphthalenedisulfonic acid, manufactured by Kusumoto Chemical Co., Ltd.), NACURE® DNNSA series (dinonylnaphthalene (mono)sulfonic acid, manufactured by Kusumoto Chemical Co., Ltd.), NACURE® DDBSA series (dodecylbenzenesulfonic acid, manufactured by Kusumoto Chemical Co., Ltd.), and NACURE® p-TSA series (p-toluenesulfonic acid, manufactured by Kusumoto Chemical Co., Ltd.).

[0060] In the present invention, release agents such as silicone, wax, or long-chain alkyl pendant polymers without reactive groups may be added to the release layer to adjust the release force, provided that they do not hinder the effects of the present invention. However, silicone is not preferable because its migration may cause problems in precision electronic equipment, and release agents such as wax or long-chain alkyl pendant polymers without reactive groups may reduce solvent resistance.

[0061] In the present invention, the release layer may contain additives such as adhesion enhancers and antistatic agents, as long as they do not hinder the effects of the present invention, but it is preferable that it does not contain particles. By not containing particles in the release layer, deterioration of the smoothness of the release layer surface and contamination of the resin sheet with particles due to particle detachment can be suppressed. In order to improve adhesion to the substrate, the polyester film surface may be pretreated with an anchor coat, corona treatment, plasma treatment, atmospheric pressure plasma treatment, etc., before applying the release coating layer.

[0062] For example, the release layer substantially does not contain particles with a particle size of 1.0 μm or larger. In this embodiment, particles with a particle size of less than 1.0 μm and greater than 1 nm may be present in the release layer. By substantially not containing inorganic particles with a particle size of 1.0 μm or larger in the release layer, the occurrence of pinholes in ultrathin resin sheets requiring high smoothness, such as ceramic green sheets, can be suppressed, and a resin sheet with a uniform film thickness can be formed. In one embodiment, since the release layer preferably has high smoothness, it is preferable to provide the release layer according to the present invention on a substrate film having a surface layer A that is substantially free of inorganic particles, specifically, substantially free of particles with a particle size of less than 1.0 μm, preferably a surface layer A that is substantially free of particles. For example, a release layer that substantially does not contain particles with a particle size of less than 1.0 μm is preferably one that also substantially does not contain particles with a particle size of 1.0 μm or larger. When a release layer is provided on a surface layer A that substantially does not contain inorganic particles, the surface roughness (Sa) of the release layer region is 3 nm or less, and the maximum protrusion height (P) is 200 nm or less. Because the release layer has these characteristics, it is possible to suppress the occurrence of pinholes in ultrathin resin sheets that require high smoothness, such as ceramic green sheets, and to form resin sheets with a uniform film thickness.

[0063] (Solvent X) The solvent (X) contained in the release layer forming composition of the present invention has a boiling point of 110°C or higher, and when the evaporation rate of n-butyl acetate at 20°C is set to 100, the evaporation rate of solvent (X) at 20°C is 80 or less. By including a solvent with a boiling point of 110°C or higher and an evaporation rate that satisfies the above requirements, the low viscosity state is extended during the drying of the release layer forming composition, the leveling properties are improved, and the occurrence of groove-like streaks caused by coating bars, etc., can be suppressed. The upper limit of the boiling point of solvent (X) is not particularly limited, but it is preferably 180°C or lower. In one embodiment, the boiling point of solvent (X) is between 115°C and 170°C, for example, between 120°C and 160°C. The boiling point can be measured by methods known in the art.

[0064] The solvent (X) has an evaporation rate of 80 or less at 20°C, with the evaporation rate of n-butyl acetate at 20°C being set to 100. By including a solvent with a boiling point of 110°C or higher and an evaporation rate that satisfies the above requirements, the low viscosity state is extended during the drying of the release layer forming composition of the present invention, the leveling properties are improved, and the occurrence of groove-like streaks caused by coating bars, etc., can be suppressed. Although the specific mechanism has not been analyzed, when the release layer forming composition contains the long-chain alkyl group-containing acrylic resin (a) and the melamine compound (b) according to the present invention, if the boiling point and evaporation rate of the solvent (X) are within the range of the present invention, leveling properties can be improved, groove-like streaks can be suppressed, and the release layer can be effectively crosslinked, resulting in even better release properties. In one embodiment, the evaporation rate at 20°C is 75 or less, for example, 20 to 70.

[0065] Preferably, the solvent (X) in the release layer composition should be 2.0% by mass or more per 100 parts by mass of all solvent components. Including 2.0% by mass or more improves leveling properties and prevents streaks that occur during coating from remaining unleveled. The solvent (X) is present in an amount of 20% by mass or less. By keeping it at 20% by mass or less, a stable coating solution is obtained without degrading compatibility with other release layer compositions. In one embodiment, the content of solvent (X) in the release layer composition is 3.0% by mass or more. It may be 17.0% by mass or less, for example, 4.0% by mass or more and 16.0% by mass or less. This range allows for more effective leveling and prevents problems during coating. This helps to prevent the streaks from remaining unleveled.

[0066] As solvent X, for example, ether-based solvents such as propylene glycol monomethyl ether (PGME) and 2-methoxy-1-methylethyl acetate, ketone-based solvents such as cyclohexanone, alcohol-based solvents such as 1-butanol, and cellosolve-based solvents such as butyl cellosolve can be used. Among these, propylene glycol monomethyl ether, 2-methoxy-1-methylethyl acetate, and cyclohexanone are preferred from the viewpoint of solubility with various raw materials of the release layer forming composition. Furthermore, the release layer composition may contain a combination of multiple types of solvent X, and may also contain other solvents as long as they do not impair the properties of solvent X.

[0067] (Surface roughness of the release layer) In one embodiment, the average surface roughness (Sa) of the release layer region is 3.0 nm or less, and the maximum protrusion height (P) is 200 nm or less. If (Sa) is 3 nm or less and (P) is 200 nm or less, the occurrence of pinholes in the thin film resin sheet, such as a ceramic green sheet, can be suppressed, and a resin sheet with a uniform film thickness can be formed. The average surface roughness (Sa) of the region is preferably small, and may be 3.0 nm or less, for example, 2.0 nm or less, or less than 2.0 nm. The average surface roughness (Sa) of the region is, for example, 0.1 nm or more, and may be 0.3 nm or more. The maximum protrusion height (P) is preferably small, and may be 150 nm or less, or 100 nm or less. The maximum protrusion height (P) may be 10 nm or more, for example, 20 nm or more. Here, with the release layer forming composition of the present invention, the average surface roughness (Sa) and the maximum protrusion height (P) can be kept within a predetermined range. Although it should not be interpreted as being limited to a specific theory, it is thought that the release layer forming composition of the present invention can improve leveling properties and suppress the generation of groove-like streaks caused by coating bars, etc., thereby enabling a balanced approach to bringing the average surface roughness (Sa) and the maximum protrusion height (P) within a predetermined range.

[0068] (Release layer thickness) The thickness of the release layer in this invention is not particularly limited, but is preferably 30 nm or more. More preferably 50 nm or more. A thickness of 30 nm or more provides sufficient release properties, allowing the ceramic green sheet to be peeled off without defects. Furthermore, a thickness of 30 nm or more can fill in protrusions on the polyester film substrate, improving smoothness. The upper limit of the release layer thickness is not particularly limited, but is preferably 600 nm or less. It may also be 450 nm or less, or 300 nm or less. A thickness of 600 nm or less provides sufficient coatability of the release layer forming composition, preventing groove-like streaks from remaining on the coating surface and reducing the smoothness of the release layer. Furthermore, since there is no need to reduce the line speed during release layer processing to suppress streaking, productivity can be increased.

[0069] (Free energy of the release layer surface) The surface free energy (γS) of the release layer in this invention is 25 mJ / m 2 It is preferable that the above is true. The surface free energy is 25 mJ / m 2As a result, ceramic slurry can be applied without any issues such as repulsion. While there is no particular upper limit to the surface free energy, it is 40 mJ / m 2 Preferably, it is 40 mJ / m 2 The following conditions ensure sufficient peelability, allowing the ceramic green sheet to be peeled off without defects.

[0070] (Method of manufacturing release film) In the present invention, the application of the release layer forming composition is preferably carried out in an in-line method during the polyester film manufacturing process or in an off-line method after the polyester film is manufactured. When applying in-line, it is preferable to apply a coating solution containing a dissolved or dispersed release resin to a film stretched in the film flow direction (longitudinal direction) and uniaxially oriented, and then stretch it in the transverse direction (direction perpendicular to the film flow direction) to uniaxially oriented it and simultaneously form a release layer. When applying the coating offline, a coating solution containing a dissolved or dispersed release resin is applied to one side of a biaxially oriented polyester film. After removing the solvent by drying, the film is then heated, heat-cured, or UV-cured.

[0071] When applying the coating solution in an in-line manner, it is preferable to use an aqueous coating solution. The type of aqueous coating solution is not particularly limited, but it is preferable to add a water-soluble organic solvent, such as alcohols. The coating liquid used when applying the coating offline is not particularly limited, but it is preferable to use an organic solvent, and it is preferable to add a solvent with a boiling point of 90°C or higher. Adding a solvent with a boiling point of 90°C or higher prevents bumping during drying, levels the coating film, and improves the smoothness of the coating film surface after drying.

[0072] Any known coating method can be applied to the release layer forming composition. For example, conventional methods such as roll coating methods including gravure coating and reverse coating, bar coating methods such as wire bar coating, die coating, spray coating, and air knife coating can be used.

[0073] In the present invention, the release film is transported roll-to-roll during the processing of the release layer and the hydrophobic layer. Therefore, after processing of the release layer and the hydrophobic layer, the release film is wound into a roll for storage. Furthermore, the molding and peeling of the resin sheet are also performed roll-to-roll.

[0074] The tension applied when winding the release film into a roll is preferably between 10 N / m and 300 N / m. A winding tension of 10 N / m or more is preferable as it prevents winding misalignment. It is also preferable that there is no unwinding during storage in a roll, and there is no risk of scratches being introduced into the release layer or an increase in static charge during unwinding. A winding tension of 300 N / m or less is preferable as it prevents deformation of the release film due to winding tightness or the occurrence of blocking.

[0075] When winding the release film into a roll, it is preferable to use a touch roll. The touch pressure of the touch roll is preferably 100 to 3000 N / m. A touch pressure of 100 N / m or more is preferable because it can reduce the amount of accompanying air mixed in during winding, thereby suppressing the occurrence of winding misalignment. A touch pressure of 3000 N / m or less is preferable because it suppresses deformation of the release film due to the touch roll pressure, resulting in a release film with excellent flatness.

[0076] (Resin sheet) In one embodiment, the release film of the present invention is not particularly limited as long as it is a resin sheet, and may be applied to the manufacture of adhesives and optical films. In one embodiment, it is a release film for resin sheet molding that contains an inorganic compound. Examples of inorganic compounds include metal particles, metal oxides, minerals, etc., such as calcium carbonate, silica particles, aluminum particles, barium titanate particles, etc. Examples of resins include polyvinyl acetal resin and poly(meth)acrylic acid ester resin. Because the present invention has a highly smooth release layer and a back layer with excellent smoothness, handling properties, and antistatic properties, even when these inorganic compounds are included in the resin sheet, it is possible to suppress drawbacks that may be caused by the inorganic compounds, such as damage to the resin sheet and difficulty in peeling the resin sheet from the release layer. The resin components used to form the resin sheet can be selected as appropriate depending on the application. In one embodiment, the resin sheet containing the inorganic compound is a ceramic green sheet. For example, the ceramic green sheet may contain barium titanate as the inorganic compound. In one embodiment, the resin sheet has a thickness of 0.2 μm or more and 1.0 μm or less.

[0077] (Ceramic green sheet and ceramic capacitor) Generally, a multilayer ceramic capacitor has a rectangular parallelepiped ceramic body. Inside the ceramic body, first internal electrodes and second internal electrodes are alternately arranged along the thickness direction. The first internal electrodes are exposed on the first end face of the ceramic body. A first external electrode is provided on the first end face. The first internal electrodes are electrically connected to the first external electrode at the first end face. The second internal electrodes are exposed on the second end face of the ceramic body. A second external electrode is provided on the second end face. The second internal electrodes are electrically connected to the second external electrode at the second end face.

[0078] In one embodiment, the release film of the present invention is a release film for manufacturing ceramic green sheets and is used to manufacture such multilayer ceramic capacitors. For example, a method for manufacturing ceramic green sheets using the release film for manufacturing ceramic green sheets of the present invention can produce ceramic green sheets having a thickness of 0.2 μm to 1.0 μm. More specifically, the ceramic green sheet is manufactured as follows: First, the release film of the present invention is used as a carrier film, and a ceramic slurry for forming the ceramic body is applied and dried. There is a growing demand for extremely thin ceramic green sheets with a thickness of 0.2 to 1.0 μm. A conductive layer for forming the first or second internal electrode is printed on the applied and dried ceramic green sheet. A mother laminate is obtained by appropriately laminating the ceramic green sheet, the ceramic green sheet with the conductive layer for forming the first internal electrode printed on it, and the ceramic green sheet with the conductive layer for forming the second internal electrode printed on it, and pressing them. The mother laminate is divided into multiple parts to produce raw ceramic bodies. Ceramic bodies are obtained by firing the raw ceramic bodies. After that, a multilayer ceramic capacitor can be completed by forming the first and second external electrodes. [Examples]

[0079] The present invention will be described in more detail below using examples, but the present invention is not limited in any way by these examples. The characteristic values ​​used in the present invention were evaluated using the following method.

[0080] (Thickness measurement) The cut-out release film was embedded in resin and then ultrathin sectioned using an ultramicrotome. Cross-sectional observation was then performed using a JEOL JEM2100 transmission electron microscope, and the thickness of the release layer was measured from the observed TEM images. If the thickness was too thin to be accurately evaluated by cross-sectional observation, a reflectance spectrophotometer (Otsuka Electronics FE-3000) was used for measurement.

[0081] (Average surface roughness Sa, maximum protrusion height P) Measurements were taken using a non-contact surface shape measurement system (VertScan R550H-M100) under the following conditions. The average surface roughness (Sa) and maximum protrusion height (P) were measured 36 times, and the average value of the 25 measurement results was adopted, excluding the 7 points with the largest values ​​(including the maximum value) and the 4 points with the smallest values ​​(including the minimum value). (Measurement conditions) • Measurement mode: WAVE mode • Objective lens: 50x 0.5x Tube Lens ·Measurement area 187μm×139μm (Analysis conditions) • Surface correction: 4th order correction • Interpolation process: Full interpolation

[0082] (Evaluation of coating properties of ceramic slurry) A composition consisting of the following materials was stirred and mixed, and then dispersed using a bead mill with 0.5 mm diameter zirconia beads at a rotation speed of 2500 rpm for 15 minutes to obtain a ceramic slurry. Toluene 30.1 parts by mass Ethanol 26.2 parts by mass Barium titanate (HPBT-1, manufactured by Fuji Titanium Co., Ltd.) 38.5 parts by mass Polyvinyl butyral (Sekisui Chemical Co., Ltd., Esrec BM-S) 3.2 parts by mass DOP (Dioctyl phthalate) 0.6 parts by mass Next, the release surface of the obtained release film sample was coated using an applicator so that the dried slurry had a thickness of 3 μm, dried at 90°C for 1 minute, and a ceramic green sheet was formed on the release film. The coating properties were then evaluated according to the following criteria. ○: The coating was applied evenly across the entire surface without any defects such as streaks, and no coating marks were observed visually. △: There is some slight repulsion at the edges of the coating, but the coating is applied to almost the entire surface. Also, the edges of the coating Some paint streaks were observed. ×: There are many areas that are repelled, and the coating has not been applied properly.

[0083] (Pinhole evaluation of ceramic green sheets) The release film was peeled off from the molded ceramic green sheet with release film as described above to obtain the ceramic green sheet. In the central region of the obtained ceramic green sheet in the film width direction, 25 cm 2Within this range, light is irradiated from the surface opposite to the coated surface of the ceramic slurry, the occurrence status of pinholes visible through transmitted light is observed, and visual judgment is performed according to the following criteria. ○: No pinholes generated △: Almost no pinholes generated ×: Many pinholes generated

[0084] (Evaluation of Peelability of Ceramic Green Sheets) The release film with ceramic green sheet obtained above was subjected to static elimination using a static eliminator (manufactured by Keyence Corporation, model SJ-F020), and then peeled at a width of 30 mm, a peeling angle of 90 degrees, and a peeling speed of 10 m / min. The stress applied during peeling was measured and defined as the peeling force. Judgment was made according to the following criteria based on the obtained numerical value of peeling force. ○: 1.5 mN / mm 2 or less △: 1.5 mN / mm 2 greater than and 2.0 mN / mm 2 or less ×: 2.0 mN / mm 2 greater than

[0085] (Surface Free Energy) Under the conditions of 25°C and 50% RH, using a contact angle meter (manufactured by Kyowa Interface Science Co., Ltd.: fully automatic contact angle meter DM-701), droplets of water (droplet volume: 1.8 μL) and diiodomethane (droplet volume: 0.9 μL) were formed on the release surface of the release film, and their contact angles were measured. The contact angle at 30 seconds after dropping was adopted. The contact angle data obtained by the above method was calculated by the Owens-Wendt method to obtain the surface free energy γs of the release film. This calculation was performed using the calculation software in the contact angle meter software (FAMAS).

[0086] (Preparation of Polyethylene Terephthalate Pellets (PET (I))) A continuous esterification reactor consisting of a three-stage complete mixing tank equipped with a stirrer, a partial condenser, a raw material inlet, and a product outlet was used as the esterification reactor. Terephthalic acid (TPA) was supplied at a rate of 2 tons / hour, ethylene glycol (EG) at a ratio of 2 moles per mole of TPA, and antimony trioxide was added in an amount that resulted in 160 ppm of Sb atoms relative to the produced PET. This slurry was continuously supplied to the first esterification reactor of the esterification reactor and reacted at atmospheric pressure at 255°C for an average residence time of 4 hours. Next, the reaction products in the first esterification reactor were continuously removed from the system and supplied to the second esterification reactor. EG distilled off from the first esterification reactor was supplied to the second esterification reactor at 8% by mass relative to the generated PET. Furthermore, an EG solution containing magnesium acetate tetrahydrate in an amount that resulted in 65 ppm of Mg atoms relative to the generated PET, and an EG solution containing TMPA (trimethyl phosphate) in an amount that resulted in 40 ppm of P atoms relative to the generated PET were added, and the reaction was carried out at atmospheric pressure at 260°C for an average residence time of 1 hour. Next, the reaction products from the second esterification reactor were continuously removed from the system and supplied to the third esterification reactor. There, 0.2% by mass of porous colloidal silica with an average particle size of 0.9 μm, which had been dispersed using a high-pressure disperser (manufactured by Nippon Seiki Co., Ltd.) at a pressure of 39 MPa (400 kg / cm2) for an average of 5 passes, and 0.4% by mass of synthetic calcium carbonate with an average particle size of 0.6 μm, which had 1% by mass of polyacrylic acid ammonium salt attached to calcium carbonate, were added as 10% EG slurry each, and the mixture was reacted at atmospheric pressure at 260°C for an average residence time of 0.5 hours. The esterification reaction product generated in the third esterification reaction vessel was continuously supplied to a three-stage continuous polycondensation reactor for polycondensation. The product was filtered through a filter made of sintered stainless steel fibers with a 95% cut diameter of 20 μm, then ultrafiltration was performed, and the product was extruded into water. After cooling, it was cut into chips to obtain PET chips with an intrinsic viscosity of 0.60 dl / g (hereinafter abbreviated as PET(I)). The lubricant content in the PET chips was 0.6% by mass.

[0087] (Preparation of polyethylene terephthalate pellets (PET(II))) On the other hand, in the production of the above-mentioned PET(I) chip, a PET chip with an intrinsic viscosity of 0.62 dl / g that does not contain any particles such as calcium carbonate or silica was obtained (hereinafter abbreviated as PET(II)).

[0088] (Manufacturing of laminated film F1) After drying, these PET chips were melted at 285°C and then melted again at 290°C in a separate extruder. A two-stage filtration process was performed using a filter made of sintered stainless steel fibers with a 95% cut diameter of 15 μm and a filter made of sintered stainless steel particles with a 95% cut diameter of 15 μm. The mixture was then combined in a feed block, and PET(I) was laminated as surface layer B (release side layer) and PET(II) as surface layer A (release side layer). The sheet was extruded (cast) at a speed of 45 m / min and electrostatically adhered and cooled on a casting drum at 30°C using the electrostatic adhesion method to obtain an unstretched polyethylene terephthalate sheet with an intrinsic viscosity of 0.59 dl / g. The layer ratio was adjusted so that PET(I) / (II) = 60 mass% / 40 mass% based on the discharge rate calculation of each extruder. Next, this unstretched sheet was heated with an infrared heater and then stretched 3.5 times in the longitudinal direction by the speed difference between the rolls at a roll temperature of 80°C. Subsequently, the material was guided to a tenter and stretched 4.2 times laterally at 140°C. Next, it was heat-treated at 210°C in a heat-setting zone. After that, a 2.3% relaxation treatment was performed laterally at 170°C to obtain a biaxially oriented polyethylene terephthalate film F1 with a thickness of 31 μm. The Sa of surface layer A of the obtained film F1 was 2 nm, and the Sa of surface layer B was 28 nm. In the table, the laminated film is referred to as the substrate.

[0089] (Laminated film F2) As the laminated film F2, we used E5101 (Toyobo Ester® Film, manufactured by Toyobo Co., Ltd.) with a thickness of 25 μm. E5101 has a structure in which silica particles with an average particle size of 2.4 μm are contained in surface layer A and surface layer B. The Sa of surface layer A of laminated film X2 was 24 nm, and the Sa of surface layer B was also 24 nm.

[0090] (Example 1) (Preparation of acrylic resin (a1) and release layer coating liquid) 2-Ethylhexyl acrylate (CH2=C(H)COOC8H 17 ), hydroxyethyl acrylate (CH2=C(H)COOC2H4OH) was mixed in a weight ratio of 50:50, toluene was added to bring the solid content concentration to 50% by mass, and under a nitrogen atmosphere, 0.5 mol% of azobisisobutyronitrile (AIBN) was added to copolymerize and obtain acrylic resin (a1). Acrylic resin (a1), melamine resin (Nikarac MW-30M, manufactured by Nippon Carbide Co., Ltd.) as a crosslinking agent (b), cyclohexanedimethanol (CHDM, manufactured by Tokyo Chemical Industry Co., Ltd.) as a polyol (c), and p-toluenesulfonic acid (Dryer #900, manufactured by Hitachi Chemical Polymer Co., Ltd.) as a curing catalyst were added in the amounts listed in Table 1. A solvent (MEK / toluene / propylene glycol monomethyl ether (PGME) = 50 / 40 / 10: mass ratio) was then added to obtain a release layer coating solution with a solid content concentration of 3.3% by mass.

[0091] (Formation of release layer) The obtained coating solution was applied to the laminated film F1 using a gravure coater, and then dried at 150°C for 30 seconds to form a release layer with a thickness of 150 nm. The resulting release film was evaluated for contact angle, smoothness, and ceramic release force.

[0092] (Example 2) A release layer was formed using the same procedure as in Example 1, except that the acrylic resin was changed to an acrylic resin (a2) obtained by copolymerizing acrylic resin (a2) by mixing lauryl acrylate (CH2=C(H)COOC12H25) and hydroxyethyl acrylate (CH2=C(H)COOC2H4OH) in a weight ratio of 50:50, adding toluene to achieve a solid content concentration of 50% by mass, and adding 0.5 mol% azobisisobutyronitrile (AIBN) under a nitrogen atmosphere.

[0093] (Example 3) A release layer was formed using the same procedure as in Example 1, except that the acrylic resin was changed to an acrylic resin (a3) ​​obtained by copolymerizing an acrylic resin with lauryl acrylate (CH2=C(H)COOC12H25) and hydroxyethyl acrylate (CH2=C(H)COOC2H4OH) in a weight ratio of 70:30, adding toluene to achieve a solid content concentration of 50% by mass, and adding 0.5 mol% azobisisobutyronitrile (AIBN) under a nitrogen atmosphere.

[0094] (Example 4) A release layer was formed using the same procedure as in Example 1, except that the acrylic resin was changed to an acrylic resin (a4) obtained by copolymerizing acrylic resin (a4) by mixing stearyl acrylate (CH2=C(H)COOC18H37) and hydroxyethyl acrylate (CH2=C(H)COOC2H4OH) in a weight ratio of 50:50, adding toluene to achieve a solid content concentration of 50% by mass, and adding 0.5 mol% azobisisobutyronitrile (AIBN) under a nitrogen atmosphere.

[0095] (Example 5) The release layer was formed using the same procedure as in Example 1, except that the acrylic resin was changed to a COOH group-containing long-chain alkyl acrylic resin (ARUFON UC-5080 manufactured by Toagosei Co., Ltd.).

[0096] (Examples 6, 7) The release layer was formed using the same procedure as in Example 1, except that the polyol (C) was changed to one of those listed in the table.

[0097] (Examples 8, 9) The release layer was formed using the same procedure as in Example 1, except that the acrylic resin listed in the table was used and no polyol component was added.

[0098] (Examples 10, 11, 12) The release layer was formed using the same procedure as in Example 1, except that the acrylic resin content was changed to that listed in the table.

[0099] (Example 13) A release layer was formed using the same procedure as in Example 1, except that the release layer coating solution from Example 1 was used to form a release layer with a thickness of 300 nm.

[0100] (Examples 14, 15, 16) The release layer was formed using the same procedure as in Example 1, except that the solvent (X) was changed from PGME to one of the solvents listed in the table.

[0101] (Reference example 1) The release layer was formed using the same procedure as in Example 1, except that the polyester substrate was changed to F2, and the average surface roughness and maximum protrusion height of the release layer were set to be outside the range of the present invention. Due to the high surface roughness, pinholes occurred in the ceramic green sheet.

[0102] (Comparative Example 2) A release layer was formed using the same procedure as in Example 1, except that the release layer forming composition was changed to a solution diluted in toluene with 100 parts by weight of addition-reaction type silicone resin (LTC761, manufactured by Toray Dow Corning) and 0.6 parts by weight of catalyst (SRX212, manufactured by Toray Dow Corning). Because the release layer forming composition was different from that of the present invention, the surface free energy was too low, resulting in a decrease in the coating properties of the ceramic slurry.

[0103] (Comparative Example 3) The release layer was formed using the same procedure as in Example 1, except that the long-chain alkyl group-containing acrylic resin (a) was removed and the release layer composition was modified to match the content shown in Table 1. Because it does not contain long-chain alkyl group-containing acrylic resin (a), the peeling force was heavy, and the ceramic green sheet could not be peeled off properly.

[0104] (Comparative Example 4) A release layer was formed using the same procedure as in Example 1, except that the long-chain alkyl group-containing acrylic resin (a) was replaced with a non-acrylic long-chain alkyl pendant polymer (P-Royl 1050, manufactured by Lion Specialty Chemicals Co., Ltd.) that does not contain reactive groups. Due to the high cohesiveness of the raw materials and poor compatibility with low molecular weight polyols and solvent X, aggregates were formed. As a result, the (Sa) and (P) properties of the release layer were poor, and pinholes occurred in the ceramic green sheet.

[0105] (Comparative Examples 5, 6, 7) The release layer was formed using the same procedure as in Example 1, except that the solvent composition was changed to that listed in the table. The solvent drying speed was fast, resulting in reduced leveling properties and leaving groove-like streaks on the coating surface.

[0106] (Comparative Example 8) A release layer was formed in the same manner as in Example 1, except that silicone oil (X-22-176GX-A, manufactured by Shin-Etsu Chemical Co., Ltd.) was added to the release layer forming composition described in Example 1 in the amount shown in the table. The surface free energy was reduced, and the coating properties of the ceramic green sheet were slightly decreased.

[0107] [Table 1A]

[0108] [Table 1B]

[0109] [Table 2A]

[0110] [Table 2C]

[0111] The release film for resin sheet molding of the present invention has a release layer on one side of the base film, and the surface free energy of the release layer is not too low, and the surface smoothness is excellent, so that the resin sheet forming slurry can be coated without defects, and by achieving both easy peelability and a release film that can peel off thin resin sheets, especially ceramic green sheets, without defects. On the other hand, in Comparative Example 2, because the release layer forming composition was different from that of the present invention, the surface free energy was too low, resulting in a decrease in the coating properties of the ceramic slurry. Comparative Example 3, lacking the long-chain alkyl group-containing acrylic resin (a), had a heavy peeling force and could not properly peel off the ceramic green sheet. Comparative Example 4, lacking the long-chain alkyl group-containing acrylic resin (a), exhibited high cohesiveness of the raw materials and poor compatibility with low-molecular-weight polyols and solvent X, resulting in the formation of aggregates. Consequently, the release layer (Sa) and (P) were poor, and pinholes occurred in the ceramic green sheet. Comparative Examples 5, 6, and 7 did not have the solvent composition according to the present invention, resulting in a faster solvent drying speed, reduced leveling properties, and groove-like streaks remaining on the coating surface. In Comparative Example 8, because the release layer forming composition contained silicone oil, the surface free energy was lower, resulting in a slight decrease in the coating properties of the ceramic green sheet. [Industrial applicability]

[0112] According to the present invention, a release film is provided that has a release layer on one side of the base film and exhibits excellent peelability and smoothness, enabling the manufacture of thin resin sheets without the risk of defects.

Claims

1. A biaxially oriented polyester film is used as the base material, the base material has a surface layer A, and a release layer is laminated directly or via another layer on the surface of at least one side of the surface layer A. A method for manufacturing release film for resin sheets, The manufacturing method includes curing a release layer forming composition to form the release layer, The aforementioned release layer forming composition contains an acrylic resin (a) having an alkyl group having 8 to 20 carbon atoms, a melamine compound (b), a polyol (c), and a solvent (X) in an amount of 5% to 16.0% by mass in the solvent. The total content of the melamine compound (b) and the polyol (c) is 80% by mass or more and 98% by mass or less based on 100% by mass of the total solid content of the release layer, provided that the total solid content of components (a), (b), and (c) is 100% by mass. The solvent (X) has a boiling point of 110°C or higher. The solvent (X) is propylene glycol monomethyl ether, 2-methoxy-1-methylethyl acetate, or cyclohexanone. If the evaporation rate of n-butyl acetate at 20°C is set to 100, then the evaporation rate of solvent (X) at 20°C is 80 or less. The average surface roughness (Sa) of the formed release layer region is 3.0 nm or less and the maximum protrusion height (P) is 200 nm or less. The surface free energy of the release layer is 25 mJ / m 2 That's all. A method for manufacturing release film for resin sheets.

2. The polyol (c) is an aliphatic diol selected from 1,6-hexanediol, 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, 3-methyl-1,5-pentanediol, neopentyl glycol, 2-methyl-1,5-pentanediol, 2,2-diethyl-1,3-propanediol, butylethylpropanediol, and butylethylpentanediol; A diol selected from 1,4-cyclohexanedimethanol or 1,4-benzenedimethanol; A method for manufacturing a release film for resin sheets according to claim 1, wherein the method is at least one selected from the following.

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