Release film

Abstract

To provide a release film capable of being formed with a reduced production cost and capable of including all of good wettability of a slurry for a sheet or a resin solution and an appropriate sheet peeling force even when the sheet molded on a release layer is further thinned.SOLUTION: A release film has a release layer on at least one surface of a polyester film, in which the release layer is formed by curing a composition containing an acrylic resin having a long-chain alkyl group and a cross-linking agent, an acid value of the acrylic resin having the long-chain alkyl group is 40 mgKOH / g or more and 400 mgKOH / g or less, the cross-linking agent contains at least one selected from an oxazoline-based cross-linking agent or a carbodiimide-based cross-linking agent, and the polyester film is a laminate polyester film composed of a multilayer constitution having two or more layers.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a release film. More specifically, it relates to a release film that can be produced while suppressing manufacturing costs, and that has good wettability with respect to slurries and resin solutions, as well as an appropriate sheet peeling force, even when the sheet formed on the release layer is further thinned. For example, it is particularly preferably used for producing ceramic green sheets, which are intermediate products in the manufacturing process of ceramic multilayer capacitors.

Background Art

[0002] A release film is a member used for uniformly molding and peeling a sheet to be peeled without causing damage. Examples of the sheet include a ceramic green sheet, a sheet containing other particles and resin, or a resin sheet.

[0003] Release films are mainly manufactured by offline coating in which a solvent-based release formulation is applied to a base film obtained in a film-forming process in a separate process (see, for example, Patent Document 1). However, in such a conventional technique, the film-forming process of the film base material and the release layer processing process are separate processes, which has been a factor in cost increase.

[0004] Therefore, a technique for producing a release film by applying an aqueous release formulation by in-line coating during the film-forming process has been disclosed (see, for example, Patent Documents 2 and 3). However, according to such a conventional technique, since the main resin of the aqueous release formulation is a silicone resin, the surface free energy becomes too low, and when the sheet is further thinned, there is a problem that pinholes are generated due to poor wetting of the slurry or resin solution.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

[0006] The present invention has been made against the background of such problems of the prior art. That is, an object of the present invention is to provide a release film that can suppress manufacturing costs and be produced, and that has good wettability of a sheet slurry and a resin solution for a sheet even when the sheet formed on the release layer is further thinned, and also has an appropriate sheet peeling force. [Means for Solving the Problems]

[0007] As a result of intensive studies to achieve such an object, the present inventors have completed the present invention. That is, the present invention has the following configuration. 1. A release film including a polyester film and a release layer, having a release layer directly or via another layer on at least one side of the polyester film, the release layer being a cured composition containing an acrylic resin having a long-chain alkyl group and at least one crosslinking agent selected from an oxazoline-based crosslinking agent or a carbodiimide-based crosslinking agent. 2. The release film according to the first item above, wherein the acrylic resin contains a long-chain alkyl group-containing acrylate monomer, and the copolymerization ratio of the long-chain alkyl group-containing acrylate monomer in the acrylic resin is 5 mol% or more and 60 mol% or less. 3. The release film according to the first or second item above, wherein the crosslinking agent is an oxazoline-based crosslinking agent, and the oxazoline-based crosslinking agent contains 3.0 to 9.0 mmol / g of oxazoline groups. 4. The release film according to any one of the first to third items above, wherein the acid value of the acrylic resin having a long-chain alkyl group is 40 mgKOH / g or more and 400 mgKOH / g or less. 5. The release film according to any one of the above 1 to 4, wherein the thickness of the release layer is 0.001 μm or more and 2 μm or less. 6. The release film according to any one of the above 1 to 5, wherein the release film is a release film for manufacturing a ceramic green sheet. 7. A method for manufacturing a release film including a polyester film and a release layer, the release film has a release layer directly or via another layer on at least one side of the polyester film, the release layer is a release film formed by curing a composition containing an acrylic resin having a long-chain alkyl group and at least one crosslinking agent selected from an oxazoline-based crosslinking agent or a carbodiimide-based crosslinking agent, A method for manufacturing a release film, comprising coating a release coating liquid on an unstretched film or a uniaxially stretched film, stretching in at least one uniaxial direction that has not been stretched, and performing heat treatment. 8. The method for manufacturing a release film according to the above 7, wherein the method for manufacturing the release film is a method for manufacturing a release film for manufacturing a ceramic green sheet. 9. A method for manufacturing a ceramic green sheet, comprising molding a ceramic green sheet using the release film for manufacturing a ceramic green sheet according to the above 6, or the method for manufacturing a release film for manufacturing a ceramic green sheet according to the above 8. 10. The method for manufacturing a ceramic green sheet according to the above 9, wherein the thickness of the ceramic green sheet to be manufactured is 0.2 μm or more and 2.0 μm or less. 11. A method for manufacturing a ceramic capacitor, comprising adopting the method for manufacturing a ceramic green sheet according to the above 9 or 10.

Advantages of the Invention

[0008] According to the present invention, it is possible to suppress the manufacturing cost and produce a release film that can have good wettability of a sheet slurry and a resin solution and an appropriate sheet peeling force even when the molded sheet is further thinned.

Embodiments for Carrying Out the Invention

[0009] Hereinafter, the present invention will be described in detail. The release film of the present invention is preferably a release film having a release layer on at least one side of a polyester film as a base film. The polyester film is preferably a biaxially oriented polyester film.

[0010] In the present invention, as the release layer, a composition containing a resin having a long-chain alkyl group and at least one cross-linking agent selected from an oxazoline-based cross-linking agent or a carbodiimide-based cross-linking agent is cured. For the release layer according to the present invention, since the hardness of the release layer becomes moderately high and the surface free energy of the release layer is within a predetermined range, a good peeling force can be obtained.

[0011] (Polyester film) The polyester constituting the polyester film used as the base material in the present invention is not particularly limited and is a polyester generally commonly used as a base material for release films. Preferably, it is a crystalline linear saturated polyester composed of an aromatic dibasic acid component and a diol component. For example, polyethylene terephthalate, polyethylene-2,6-naphthalate, polybutylene terephthalate, and polytrimethylene terephthalate are more preferable, or a copolymer having the constituent components of these resins as the main components may be used. Among them, polyethylene terephthalate is particularly suitable. In polyethylene terephthalate, the repeating unit of ethylene terephthalate is preferably 90 mol% or more, more preferably 95 mol% or more, and a small amount of other dicarboxylic acid components and diol components may be copolymerized. From the viewpoint of cost, those produced only from terephthalic acid and ethylene glycol are preferred. Also, within a range that does not inhibit the effects of the film of the present invention, known additives such as antioxidants, light stabilizers, ultraviolet absorbers, and crystallization agents may be added. The polyester film is preferably a biaxially oriented polyester film due to reasons such as high biaxial elastic modulus.

[0012] The intrinsic viscosity of the above polyester film is preferably 0.50 to 0.70 dl / g, more preferably 0.52 to 0.62 dl / g. When the intrinsic viscosity is 0.50 dl / g or more, it is preferable because there is little breakage in the stretching process. Conversely, when it is 0.70 dl / g or less, the cuttability is good when cutting to a predetermined product width and no dimensional defects occur, so it is preferable. Also, the raw material pellets are preferably sufficiently vacuum dried.

[0013] As a method for producing the polyester film in the present invention, for example, the above polyester is melted by an extruder, extruded into a film shape, and cooled by a rotary cooling drum to obtain an unstretched film, and the unstretched film can be obtained by uniaxially or biaxially stretching it. The biaxially stretched film can be obtained by a method of sequentially biaxially stretching a uniaxially stretched film in the longitudinal or transverse direction in the transverse or longitudinal direction, or a method of simultaneously biaxially stretching an unstretched film in the longitudinal and transverse directions. In the present invention, a release layer is applied during the manufacturing process of the polyester film. It is preferable to use a so-called in-line coating method.

[0014] In the present invention, the stretching temperature during stretching of the polyester film is preferably equal to or higher than the secondary transition point (Tg) of the polyester. It is preferable to perform stretching 1 to 8 times, particularly 2 to 6 times, in each of the longitudinal and transverse directions.

[0015] The above polyester film preferably has a thickness of 12 to 50 μm, more preferably 15 to 38 μm, and even more preferably 19 μm to 33 μm. If the film thickness is 12 μm or more, there is no risk of deformation due to heat during film production, in the processing step of the release layer, the sheet molding step, etc., which is preferable. On the other hand, if the film thickness is 50 μm or less, the amount of film to be discarded after use does not become extremely large, which is preferable in reducing the environmental load.

[0016] The above polyester film substrate may be a single layer or a multilayer of two or more layers. For example, the polyester film substrate preferably has a surface layer A that substantially does not contain inorganic particles on at least one side. In the case of a laminated polyester film composed of a multilayer structure of two or more layers, it is preferable to have a surface layer B that can contain particles or the like on the opposite side of the surface layer A that substantially does not contain inorganic particles. As for the laminated structure, if the layer on the side where the release layer is applied (the side to be laminated) is the surface layer A, the layer on the opposite side is the surface layer B, and the core layer other than these is the layer C, the layer structure in the thickness direction includes a laminated structure such as a release layer / A / B or a release layer / A / C / B. Naturally, the layer C may have a plurality of layer structures. Also, the surface layer B may not contain particles. In that case, in order to impart slipperiness for winding the film in a roll shape, it is preferable to provide a coat layer containing particles and a binder on the surface layer B.

[0017] In the polyester film substrate of the present invention, the surface area average roughness (Sa) of the surface layer A is preferably 10 nm or less, more preferably 7 nm or less. When Sa is 10 nm or less, it is preferable because generation of pinholes or the like is less likely to occur during molding of the ultra-thin layer sheet to be laminated. When Sa is 7 nm or less, it is more preferable because generation of pinholes or the like is even less likely to occur during molding of the ultra-thin layer sheet to be laminated. The smaller the surface area average roughness (Sa) of the surface layer A, the more preferable. For example, the surface area average roughness (Sa) of the surface layer A is 0.1 nm or more. In one embodiment, the surface area average roughness (Sa) of the surface layer A is 0.1 nm or more and 10 nm or less, for example, 0.1 nm or more and 7 nm or less, 0.1 nm or more and 5 nm or less, or may be 0.5 nm or more and 3 nm or less. Here, when providing an anchor coat layer or the like described later on the surface layer A, it is preferable that the coat layer substantially does not contain inorganic particles, and it is preferable that the surface average roughness (Sa) of the region surface after coat layer lamination falls within the above range. In the present invention, "substantially does not contain inorganic particles" means a content of 50 ppm or less, preferably 10 ppm or less, and most preferably below the detection limit when quantifying inorganic elements by X-ray fluorescence analysis. This is because even if inorganic particles are not actively added to the film, contaminants derived from foreign substances or dirt adhering to the lines and equipment in the raw material resin or film manufacturing process may peel off and mix into the film.

[0018] In the polyester film base material of the present invention, the surface layer B forming the opposite surface of the surface to which the release layer is applied preferably contains particles from the viewpoints of the slipperiness of the film and the ease of air escape, and particularly preferably uses silica particles and / or calcium carbonate particles. The total particle content contained is preferably 5000 to 15000 ppm in total in the surface layer B. When the total of silica particles and / or calcium carbonate particles is 5000 ppm or more, when the film is wound up in a roll shape, air can be uniformly released, the winding shape is good, and the flatness is good, making it suitable for manufacturing an ultra-thin layer sheet. Also, when the total of silica particles and / or calcium carbonate particles is 15000 ppm or less, aggregation of the lubricant is less likely to occur and large protrusions do not form, so the quality is stable during the manufacture of an ultra-thin layer sheet, which is preferable.

[0019] In the polyester film base material of the present invention, the surface layer B forming the surface opposite to the surface to which the release layer is applied preferably contains particles from the viewpoints of the slipperiness of the film and the ease of air escape, and it is particularly preferable to use silica particles and / or calcium carbonate particles. At this time, the average surface roughness (Sa) of the surface layer B of the film is preferably in the range of 1 to 40 nm. More preferably, it is in the range of 5 to 35 nm. When Sa is 1 nm or more, when the film is wound up in a roll shape, air can be uniformly released, the winding shape is good, and the flatness is good, so it is suitable for the production of ultra-thin layer sheets. Further, when Sa is 40 nm or less, aggregation of the lubricant hardly occurs and no coarse protrusions are formed, so the quality is stable during the production of ultra-thin layer sheets, which is preferable.

[0020] As the particles contained in the surface layer B, inactive inorganic particles and / or heat-resistant organic particles other than silica and / or calcium carbonate can be used. From the viewpoints of transparency and cost, it is more preferable to use silica particles and / or calcium carbonate particles. Other inorganic particles that can be used include alumina-silica composite oxide particles and hydroxyapatite particles. Examples of the heat-resistant organic particles include crosslinked polyacrylic particles, crosslinked polystyrene particles, and benzoguanamine particles. When using silica particles, porous colloidal silica is preferable, and when using calcium carbonate particles, light calcium carbonate surface-treated with a polyacrylic acid-based polymer compound is preferable from the viewpoint of preventing the lubricant from falling off.

[0021] The average particle diameter of the 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. If the average particle diameter of the particles is 0.1 μm or more, the slipperiness of the release film is good, which is preferable. Further, if the average particle diameter is 2.0 μm or less, there is no risk of pinholes in the sheet due to coarse particles on the surface of the release layer, which is preferable.

[0022] The above surface layer B may contain two or more types of particles made of different materials. Also, particles of the same type but with different average particle sizes may be contained.

[0023] When the surface layer B does not contain particles, it is preferable to provide a coat layer containing particles on the surface layer B to impart slipperiness. This coat layer is not particularly limited, but it is preferably provided by an in-line coat applied during the film formation of the polyester film. When the surface layer B does not contain particles and has a coat layer containing particles on the surface layer B, for the same reason as the above-mentioned surface area average roughness (Sa) of the surface layer B, the surface area average roughness (Sa) of the coat layer is preferably in the range of 1 to 40 nm. More preferably, it is in the range of 5 to 35 nm.

[0024] From the perspective of pinhole reduction, it is preferable not to use recycled raw materials or the like in the surface layer A, which is the layer on the side where the release layer is provided, in order to prevent the mixing of particles such as lubricants.

[0025] The thickness ratio of the surface layer A, which is the layer on the side where the release layer is provided, is preferably 20% or more and 50% or less of the total layer thickness of the base film. If it is 20% or more, it is difficult to receive the influence of the particles contained in the surface layer B or the like from inside the film, and it is easy and preferable for the surface area average roughness Sa to satisfy the above range. If it is 50% or less of the total layer thickness of the base film, the usage ratio of the recycled raw materials in the surface layer B can be increased, and the environmental load is reduced, which is preferable.

[0026] Also, from the perspective of economy, 50 to 90% by mass of film scraps or recycled raw materials of PET bottles can be used in the layers other than the above surface layer A (the surface layer B or the aforementioned intermediate layer C). Even in this case, it is preferable that the type, amount, particle size, and surface area average roughness (Sa) of the lubricant contained in the surface layer B satisfy the above range.

[0027] In addition, in order to improve the adhesion of a release layer to be applied or prevent charging, a coating layer may be provided on the surface of the surface layer A and / or the surface layer B before stretching in the film forming process or after uniaxial stretching, and corona treatment or the like can also be performed.

[0028] (Release layer) The release film of the present invention preferably has a release layer on one surface of a base film made of polyester as described above. The release layer is a layer formed by curing a composition containing an acrylic resin having a long-chain alkyl group and at least one crosslinking agent selected from an oxazoline-based crosslinking agent and a carbodiimide-based crosslinking agent. The release film of the present invention having such a release layer can be produced at a reduced manufacturing cost. Furthermore, even when the sheet is further thinned, the release film of the present invention can have good wettability with a sheet slurry and a resin solution, and an appropriate sheet peeling force. For example, it is preferable that the release layer contains at least a binder resin, a crosslinking agent, and an additive. The release layer is a layer formed by applying a composition containing the resin and the crosslinking agent according to the present invention, and can also be referred to as a release coating layer.

[0029] (Binder resin in the release layer)

[0030] The binder resin constituting the release layer in the present invention preferably contains an acrylic resin. The acrylic resin is preferably an acrylic resin having at least one selected from the group consisting of a hydroxyl group, a carboxyl group, and a long-chain alkyl group in the molecule. In one embodiment, the acrylic resin is an acrylic resin having a long-chain alkyl group. In the present specification, these acrylic resins may sometimes be simply referred to as acrylic resins. It is more preferable that the constituent unit having a hydroxyl group is contained in an amount of 5 to 90 mol% based on 100 mol% of all the constituent units. When the constituent unit having a hydroxyl group is 5 mol% or more, it is preferable that the water solubility of the acrylic resin can be moderately maintained. On the other hand, when it is 90 mol% or less, it is preferable that the particles contained in the release layer do not extremely interact with the hydroxyl groups of the acrylic resin and the particles are uniformly dispersed. In one embodiment, the constituent unit having a hydroxyl group is 5 to 50 mol%, for example, 5 to 45 mol% based on 100 mol% of all the constituent units.

[0031] To introduce a hydroxyl group into the acrylic resin, monomers having a hydroxyl group such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, or ring-opening adducts of γ-butyrolactone or ε-caprolactone to 2-hydroxyethyl (meth)acrylate may be used as copolymerization components. Among them, 2-hydroxyethyl (meth)acrylate is preferable in that it does not inhibit water solubility. These may be used in combination of two or more.

[0032] The hydroxyl value of the acrylic resin is preferably 2 mgKOH / g or more, more preferably 5 mgKOH / g or more, and still more preferably 10 mgKOH / g or more. If the hydroxyl value of the acrylic resin is 2 mgKOH / g or more, the water solubility of the acrylic resin becomes good, which is preferable.

[0033] The hydroxyl value of the acrylic resin is preferably 250 mgKOH / g or less, more preferably 230 mgKOH / g or less, and still more preferably 200 mgKOH / g or less. If the hydroxyl value of the acrylic resin is 250 mgKOH / g or less, the hydroxyl groups of the acrylic resin do not extremely interact with the particles contained in the release layer and the particles are uniformly dispersed, which is preferable.

[0034] The acrylic resin used in the present invention may contain a resin having a hydroxyl group. Further, it may contain a resin having a carboxyl group. In another aspect, the acrylic resin may contain both a resin having a hydroxyl group and a resin having a carboxyl group. By having a carboxyl group, it becomes possible to form a crosslinked structure with a crosslinking agent and to easily impart water solubility. Examples include monomers containing a carboxyl group such as (meth)acrylic acid, crotonic acid, itaconic acid, maleic acid, fumaric acid, and monomers containing an acid anhydride group such as maleic anhydride and itaconic anhydride.

[0035] The monomer having a carboxyl group is preferably 4 mol% or more, more preferably 10 mol% or more, based on 100 mol% of all the constituent units of the acrylic resin. When it is 4 mol% or more, it is preferable because it becomes easy to form a crosslinked structure in the release layer and to impart water solubility. The monomer having a carboxyl group is preferably 65 mol% or less, more preferably 50 mol% or less. When it is 65 mol% or less, the Tg of the resulting coating film does not become too high with respect to the suitable range described later, and the film-forming property and the stretching appropriateness in in-line coating are good, which is preferable.

[0036] In order to exhibit good water solubility, it is preferable to neutralize the carboxyl groups introduced into the acrylic resin by copolymerization of acrylic acid or methacrylic acid. As basic neutralizing agents, there are amine compounds such as ammonia, trimethylamine, triethylamine, dimethylaminoethanol, and inorganic basic substances such as potassium hydroxide and sodium hydroxide. Among these, in view of the ease of volatilization of the neutralizing agent and the ease of forming a crosslinked structure, it is preferable to use an amine compound as the neutralizing agent. Among them, ammonia is most preferable from the viewpoint that particle aggregation does not occur when particles are contained in the release layer. The neutralization rate is preferably 30 mol% to 95 mol%, more preferably 40 mol% to 90 mol%. When the neutralization rate is 30 mol% or more, the water solubility of the acrylic resin is sufficient, the acrylic resin is easily dissolved when preparing the coating solution, and there is no risk of the coated film surface turning white after drying, which is preferable. On the other hand, when the neutralization rate is 95 mol% or less, the water solubility is not too high, and mixing with alcohol or the like is easy in the preparation of the coating solution, which is preferable.

[0037] The acid value of the acrylic resin is preferably, for example, 40 mgKOH / g or more, more preferably 50 mgKOH / g or more, and still more preferably 60 mgKOH / g or more. If the acid value of the acrylic resin is, for example, 40 mgKOH / g or more, the number of crosslinking points with an oxazoline crosslinking agent or a carbodiimide crosslinking agent increases, so a stronger coating film with a higher crosslink density can be obtained, which is preferable.

[0038] The acid value of the acrylic resin is preferably, for example, 400 mgKOH / g or less, more preferably 350 mgKOH / g or less, and still more preferably 300 mgKOH / g or less. In one embodiment, the acid value of the acrylic resin is 200 mgKOH / g or less, for example, 150 mgKOH / g or less. If the acid value of the acrylic resin is 400 mgKOH / g or less, the crosslink density with an oxazoline crosslinking agent or a carbodiimide crosslinking agent does not become too high, and cracks do not occur when stretched, which is preferable. In addition, even in the mode of using an oxazoline crosslinking agent and a carbodiimide crosslinking agent in combination, such a tendency is considered to be obtained. Also, if the acid value of the acrylic resin is 400 mgKOH / g or less, the carboxyl group of the acrylic resin and the particles contained in the release layer do not cause extreme interaction, and the particles are preferably uniformly dispersed. Good dispersibility of the particles is preferable because no coarse protrusions are generated on the release coating surface and no pinholes are generated in the sheet. In one embodiment, the oxidation of the acrylic resin having a long-chain alkyl group is 40 mgKOH / g or more and 400 mgKOH / g or less, for example, 40 mgKOH / g or more and 300 mgKOH / g or less.

[0039] The acrylic resin used in the present invention is preferably a resin having at least one selected from the group consisting of a hydroxyl group, a carboxyl group, and a long-chain alkyl group. Having a long-chain alkyl group is preferable because the sheet peeling force can be made lighter. As the acrylic resin having a long-chain alkyl group, those having an alkyl group with 8 to 25 carbon atoms in the side chain of the acrylic resin are preferable, more preferably those having an alkyl group with 12 to 22 carbon atoms in the side chain of the acrylic resin, and even more preferably those having an alkyl group with 16 to 20 carbon atoms in the side chain of the acrylic resin. In addition, a copolymer which is a polymer having (meth)acrylic acid ester as a main repeating unit and containing a long-chain alkyl group with 8 to 20 carbon atoms in the transesterified part can also be preferably used. Examples include lauryl (meth)acrylate, stearyl (meth)acrylate, etc. Among them, stearyl methacrylate is preferably used in terms of easy availability, cost, and good peeling force. For example, the acrylic resin used in the present invention is a resin formed by further using at least one selected from the group consisting of methyl methacrylate (MMA), hydroxyethyl methacrylate (HEMA), and methacrylic acid (MAA) in addition to stearyl methacrylate (SMA). By containing such an acrylic resin, the release film of the present invention can suppress the occurrence of cracks when stretched because the crosslinking density between the acrylic resin and the oxazoline crosslinking agent or carbodiimide crosslinking agent in the release layer does not become too high. Furthermore, by containing such an acrylic resin, it is possible to suppress the manufacturing cost and produce the release film. Further, even when the sheet is further thinned, the release film of the present invention can have good wettability with respect to the slurry for sheet and the resin solution, and an appropriate sheet peeling force.

[0040] The glass transition temperature (Tg) of the acrylic resin is preferably 50°C or higher, more preferably 55°C or higher, and still more preferably 60°C or higher. When the glass transition temperature of the acrylic resin is 50°C or higher, the hardness of the release layer becomes appropriately high, which is preferable.

[0041] The glass transition temperature (Tg) of the acrylic resin is preferably 110°C or lower, more preferably 105°C or lower, and still more preferably 100°C or lower. When the glass transition temperature of the acrylic resin is 110°C or lower, in the stretching step after coating the release layer, the coating film is uniformly stretched without cracks, which is preferable.

[0042] As the monomer for adjusting Tg copolymerized to make Tg within the above range, (meth)acrylic monomers and non-acrylic vinyl monomers can be used. Specific examples of (meth)acrylic monomers include alkyl (meth)acrylates such as methyl (meth)acrylate, ethyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, n-amyl (meth)acrylate, n-hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-octyl (meth)acrylate, decyl (meth)acrylate, dodecyl (meth)acrylate, cyclohexyl (meth)acrylate, isobornyl (meth)acrylate; nitrogen-containing acrylic monomers such as (meth)acrylamide, diacetone acrylamide, n-methylol acrylamide, (meth)acrylonitrile; vinyl methacrylate, etc. These can be used alone or in combination of two or more.

[0043] In addition, as non-acrylic vinyl monomers, there are styrene-based monomers such as styrene, α-methylstyrene, vinyltoluene (a mixture of m-methylstyrene and p-methylstyrene), chlorostyrene; vinyl esters such as vinyl acetate, vinyl propionate, vinyl butyrate, vinyl caproate, vinyl caprylate, vinyl capric acid, vinyl laurate, vinyl myristate, vinyl palmitate, vinyl stearate, vinyl cyclohexanecarboxylate, vinyl pivalate, vinyl octylate, vinyl monochloroacetate, divinyl adipate, vinyl crotonate, vinyl sorbate, vinyl benzoate, vinyl cinnamate; vinyl halide monomers such as vinyl chloride, vinylidene chloride, etc. These can be used alone or in combination of two or more.

[0044] The monomer having a long-chain alkyl group is preferably 60 mol% or less, more preferably 50 mol% or less, based on 100 mol% of all the constituent units of the acrylic resin. When it is 60 mol% or less, the Tg of the resulting coating film does not become too low with respect to the preferred range, and the hardness of the coating film can be maintained high, which is preferable. The monomer having a long-chain alkyl group is preferably 5 mol% or more, more preferably 15 mol% or more, based on 100 mol% of all the constituent units of the acrylic resin. If it is 5 mol% or more, the peel force is reduced due to the decrease in the surface free energy, which is preferable.

[0045] For the monomer for Tg adjustment, it is preferable to determine the appropriate amounts of the hydroxyl group-containing monomer, the carboxyl group-containing monomer, and the long-chain alkyl group-containing monomer, and then use the remainder. The Tg of the copolymer is determined by the following Fox's equation.

[0046] [Number] W n : Mass fraction (mass%) of each monomer Tg n : Tg (K) of the homopolymer of each monomer

[0047] The acrylic resin used in the present invention can be obtained by known radical polymerization. Any of emulsion polymerization, suspension polymerization, solution polymerization, bulk polymerization, etc. can be employed. From the viewpoint of handleability, solution polymerization is preferable. Examples of the water-soluble organic solvent that can be used for solution polymerization include ethylene glycol n-butyl ether, isopropanol, ethanol, n-methylpyrrolidone, tetrahydrofuran, 1,4-dioxane, 1,3-oxolane, methyl cellosolve, ethyl cellosolve, ethyl carbitol, butyl carbitol, propylene glycol monopropyl ether, propylene glycol monobutyl ether, and the like. These may be used by mixing with water.

[0048] The polymerization initiator may be any known compound that generates radicals. For example, water-soluble azo polymerization initiators such as 2,2-azobis-2-methyl-N-2-hydroxyethylpropionamide are preferred. The temperature, time, etc. of the polymerization are appropriately selected.

[0049] The mass average molecular weight (Mw) of the acrylic resin is preferably about 10,000 to 200,000. A more preferred range is 20,000 to 150,000. When Mw is 10,000 or more, there is no risk of thermal decomposition in the tenter, which is preferred. When Mw is 200,000 or less, there is no significant increase in the viscosity of the coating solution, and the coatability is good, which is preferred.

[0050] As the binder of the release layer in the present invention, other binder resins may be used in combination with the acrylic resin. Examples of other binder resins include polyester resins, urethane resins, polyvinyl-based resins (such as polyvinyl alcohol), polyalkylene glycols, polyalkyleneimines, methylcellulose, hydroxycellulose, starches, etc.

[0051] The content of the acrylic resin in the release layer is preferably 20% by mass or more and 95% by mass or less in the total solid content. More preferably, it is 30% by mass or more and 90% by mass or less. When it is 20% by mass or more, the carboxyl group as the cross-linking component does not decrease too much, and the cross-linking density does not decrease, which is preferred. When it is 95% by mass or less, the amount of the cross-linking agent to be cross-linked does not decrease too much, and the cross-linking density does not decrease, which is preferred.

[0052] (Cross-linking agent) In the present invention, in order to form a crosslinked structure in the release layer, it is preferable that the release layer contains at least one crosslinking agent selected from oxazoline-based crosslinking agents or carbodiimide-based crosslinking agents. By containing an oxazoline-based crosslinking agent or a carbodiimide-based crosslinking agent, the adhesion to the PET substrate can be improved, and the crosslinking with the carboxyl group of the acrylic resin can be promoted to improve the coating film strength of the release layer, and as a result, the peeling force can be reduced. Further, other crosslinking agents may be used in combination, and specific crosslinking agents that can be used in combination include urea-based, epoxy-based, melamine-based, isocyanate-based, silanol-based, etc. In addition, in order to promote the crosslinking reaction, a catalyst or the like can be appropriately used as needed.

[0053] Examples of the crosslinking agent having an oxazoline group include polymers having an oxazoline group obtained by copolymerizing a polymerizable unsaturated monomer having an oxazoline group, if necessary, together with other polymerizable unsaturated monomers by a conventionally known method (for example, solution polymerization, emulsion polymerization, etc.).

[0054] Examples of the polymerizable unsaturated monomer having an oxazoline group 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, 2-isopropenyl-5-ethyl-2-oxazoline, etc. These may be used alone or in combination of two or more.

[0055] Examples of other polymerizable unsaturated monomers include alkyl or cycloalkyl esters of (meth)acrylic acid having 1 to 24 carbon atoms, such as methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, cyclohexyl (meth)acrylate, lauryl (meth)acrylate, isobornyl (meth)acrylate; hydroxyalkyl esters of (meth)acrylic acid having 2 to 8 carbon atoms, such as 2-hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate; vinyl aromatic compounds such as styrene, vinyltoluene; adducts of (meth)acrylamide, dimethylaminopropyl (meth)acrylamide, dimethylaminoethyl (meth)acrylate, glycidyl (meth)acrylate and amines; polyethylene glycol (meth)acrylate; N-vinylpyrrolidone, ethylene, butadiene, chloroprene, vinyl propionate, vinyl acetate, (meth)acrylonitrile and the like. These may be used alone or in combination of two or more.

[0056] Other polymerizable unsaturated monomers are preferably hydrophilic monomers from the viewpoint of improving the compatibility with other resins, wettability, crosslinking reaction efficiency, etc. of the obtained crosslinking agent having an oxazoline group as a water-soluble crosslinking agent. Examples of hydrophilic monomers include monomers having a polyethylene glycol chain such as 2-hydroxyethyl (meth)acrylate, methoxypolyethylene glycol (meth)acrylate, monoester compounds of (meth)acrylic acid and polyethylene glycol, 2-aminoethyl (meth)acrylate and its salts, (meth)acrylamide, N-methylol (meth)acrylamide, N-(2-hydroxyethyl)(meth)acrylamide, (meth)acrylonitrile, sodium styrenesulfonate and the like. Among these, monomers having a polyethylene glycol chain such as methoxypolyethylene glycol (meth)acrylate, monoester compounds of (meth)acrylic acid and polyethylene glycol, which have high solubility in water, are preferred.

[0057] The crosslinking agent having an oxazoline group preferably has an oxazoline group content of 3.0 to 9.0 mmol / g. More preferably, it is in the range of 4.0 to 8.0 mmol / g. If it is within the range of 3.0 to 9.0 mmol / g, an appropriate crosslinked structure can be formed, and the peel strength becomes lighter, which is preferable. Further, when the content of the oxazoline crosslinking agent is within the above range, an appropriate crosslinked structure with the acrylic resin can be formed, and no cracks occur when stretched, which is preferable.

[0058] Examples of the carbodiimide-based crosslinking agent include monocarbodiimide compounds and polycarbodiimide compounds. Examples of the monocarbodiimide compounds include dicyclohexylcarbodiimide, diisopropylcarbodiimide, dimethylcarbodiimide, diisobutylcarbodiimide, dioctylcarbodiimide, t-butylisopropylcarbodiimide, diphenylcarbodiimide, di-t-butylcarbodiimide, di-β-naphthylcarbodiimide, and the like. As the polycarbodiimide compound, those produced by a conventionally known method can be used. For example, it can be produced by synthesizing an isocyanate-terminated polycarbodiimide by a condensation reaction accompanied by decarboxylation of diisocyanate.

[0059] Examples of the diisocyanate, which is a raw material for synthesizing the polycarbodiimide compound, include isomers of tolylene diisocyanate, aromatic diisocyanates such as 4,4-diphenylmethane diisocyanate, aromatic aliphatic diisocyanates such as xylylene diisocyanate, alicyclic diisocyanates such as isophorone diisocyanate and 4,4-dicyclohexylmethane diisocyanate, 1,3-bis(isocyanatemethyl)cyclohexane, aliphatic diisocyanates such as hexamethylene diisocyanate, and 2,2,4-trimethylhexamethylene diisocyanate. Due to the problem of yellowing, aromatic aliphatic diisocyanates, alicyclic diisocyanates, and aliphatic diisocyanates are preferable.

[0060] Further, the above diisocyanate may be used after controlling the molecule to an appropriate degree of polymerization using a compound that reacts with terminal isocyanate such as monoisocyanate. Examples of the monoisocyanate for terminating the polycarbodiimide and controlling its degree of polymerization include phenyl isocyanate, toluylene isocyanate, dimethylphenyl isocyanate, cyclohexyl isocyanate, butyl isocyanate, naphthyl isocyanate, and the like. In addition, compounds having an OH group, -NH2 group, COOH group, or SO3H group can be used as other terminal blocking agents.

[0061] The condensation reaction of diisocyanate accompanied by the elimination of carbon dioxide proceeds in the presence of a carbodiimidization catalyst. Examples of the catalyst include 1-phenyl-2-phospholene-1-oxide, 3-methyl-2-phospholene-1-oxide, 1-ethyl-2-phospholene-1-oxide, 3-methyl-1-phenyl-2-phospholene-1-oxide, and phospholene oxides such as 3-phospholene isomers thereof. From the viewpoint of reactivity, 3-methyl-1-phenyl-2-phospholene-1-oxide is preferred. The amount of the above catalyst used can be a catalytic amount.

[0062] It is desirable that the above-mentioned mono- or polycarbodiimide compound be maintained in a uniform dispersion state when blended into an aqueous paint. For this purpose, it is preferably used as an emulsion by subjecting it to emulsification treatment using an appropriate emulsifier, or added with a hydrophilic segment in the molecular structure of the polycarbodiimide compound and blended into the paint in the form of a self-emulsifying product or a self-dissolving product.

[0063] The carbodiimide crosslinking agent used in the present invention includes water dispersibility and water solubility. Water solubility is preferred because it has good compatibility with other water-soluble resins and improves the crosslinking reaction efficiency of the release layer. In order to make the carbodiimide compound water-soluble, it can be produced by synthesizing isocyanate-terminated polycarbodiimide through a condensation reaction involving the decarboxylation of isocyanate, and then adding a hydrophilic moiety having a functional group reactive with the isocyanate group.

[0064] Examples of the hydrophilic moiety include (1) quaternary ammonium salts of dialkylaminoalcohols and quaternary ammonium salts of dialkylaminoalkylamines, (2) alkyl sulfonates having at least one reactive hydroxyl group, (3) poly(ethylene oxide) terminated with an alkoxy group, and mixtures of poly(ethylene oxide) and poly(propylene oxide). When the hydrophilic moiety is introduced into the carbodiimide compound, it becomes (1) cationic, (2) anionic, or (3) nonionic. Among them, nonionic, which can be compatible regardless of the ionic nature of other water-soluble resins, is preferred.

[0065] The content of the crosslinking agent in the release layer is preferably 5% by mass or more and 80% by mass or less in the total solid content. More preferably, it is 10% by mass or more and 70% by mass or less. A content of 5% by mass or more is preferred because the crosslinking density of the resin in the coating layer does not decrease. A content of 80% by mass or less is preferred because the amount of carboxyl groups in the acrylic resin to be crosslinked does not decrease too much and the crosslinking density does not become too low.

[0066] (Particles in the release layer) The release layer may contain lubricant particles in order to control the release force at the sheet peeling starting portion and the release force during steady peeling, and to impart slipperiness to the surface. The particles may be inorganic particles or organic particles, and are not particularly limited. Examples include: (1) inorganic particles such as silica, kaolinite, talc, light calcium carbonate, heavy calcium carbonate, zeolite, alumina, barium sulfate, carbon black, zinc oxide, zinc sulfate, zinc carbonate, zirconium oxide, titanium dioxide, satin white, aluminum silicate, diatomaceous earth, calcium silicate, aluminum hydroxide, hydrated halloysite, calcium carbonate, magnesium carbonate, calcium phosphate, magnesium hydroxide, barium sulfate; (2) organic particles such as acrylic or methacrylic, vinyl chloride, vinyl acetate, nylon, styrene / acrylic, styrene / butadiene, polystyrene / acrylic, polystyrene / isoprene, polystyrene / isoprene, methyl methacrylate / butyl methacrylate, melamine, polycarbonate, urea, epoxy, urethane, phenol, diallyl phthalate, polyester.

[0067] The average particle size of the particles is preferably 10 nm or more, more preferably 20 nm or more, and even more preferably 30 nm or more. When the average particle size of the particles is 10 nm or more, it is difficult to aggregate and slipperiness can be ensured, which is preferable.

[0068] The average particle size of the particles is preferably 500 nm or less, more preferably 400 nm or less, and even more preferably 300 nm or less. When the average particle size of the particles is 500 nm or less, pinholes are less likely to occur during sheet processing, and the particles are less likely to fall off, which is preferable.

[0069] The method for measuring the average particle size of the particles was carried out by observing the particles in the cross-section of the processed film with a transmission electron microscope or a scanning electron microscope, observing 100 non-aggregated particles, and taking the average value as the average particle size.

[0070] As long as it meets the object of the present invention, the shape of the particles is not particularly limited, and spherical particles or irregular non-spherical particles can be used. The particle diameter of the irregular particles can be calculated as the equivalent circle diameter. The equivalent circle diameter is a value obtained by dividing the area of the observed particles by π, calculating the square root, and doubling the result.

[0071] The ratio of the particles to the total solid content of the release layer is preferably 50% by mass or less, more preferably 30% by mass or less, and even more preferably 10% by mass or less. If the ratio of the particles to the total solid content of the release layer is 50% by mass or less, pinholes are less likely to occur during sheet processing, and the dropout of particles from the release layer does not occur significantly, which is preferable. Also, it may be 0% by mass.

[0072] As a method for measuring the content rate of the particles contained in the release layer, for example, when the release layer contains a resin of an organic component and inorganic particles, the following method can be used. First, the release layer provided on the processing film is taken out by extracting it from the processing film using a solvent or the like and drying it. Next, heat is applied to the obtained release layer, and the organic component contained in the release layer is burned off by heat to obtain only the inorganic component. By measuring the weight of the obtained inorganic component and the release layer before the combustion and distillation, the mass% of the particles contained in the release layer can be measured. At this time, accurate measurement can be performed by using a commercially available differential thermal and thermogravimetric simultaneous measurement device. Note that the ratio of the above-mentioned particles in the total solid content of the release layer means the ratio of the total amount of the plurality of types when there are a plurality of types of particles.

[0073] (Additive) In the present invention, releasability can be exhibited by using an acrylic resin having a long-chain alkyl group. However, in order to further improve the releasability, an additive may be added. As the additive used for the release layer, silicone-based additives, non-silicone-based additives such as olefin-based, long-chain alkyl-based, and fluorine-based additives can be used. However, from the viewpoint of peelability, it is preferable to use silicone-based additives. The silicone-based additive used in the present invention is effective not only in improving the releasability but also in improving the leveling property during coating and defoaming the coating solution.

[0074] (Silicone-based additives in the release layer) In the present invention, the silicone-based additive used for the release layer is a compound having a silicone structure in the molecule, and is not particularly limited as long as the effects of the present invention can be obtained, but polyorganosiloxane and the like can be preferably used. Among polyorganosiloxanes, polydimethylsiloxane (abbreviation, PDMS) can be preferably used, and those having a functional group in a part of polydimethylsiloxane are also preferable. It is preferable to have a functional group because intermolecular interactions such as hydrogen bonds with the binder resin are likely to occur and migration to the sheet is difficult.

[0075] The functional group introduced into polydimethylsiloxane is not particularly limited, and may be a reactive functional group or a non-reactive functional group. Further, the functional group may be introduced at one end of polydimethylsiloxane, or at both ends or on the side chain. Also, the introduced position may be one or a plurality.

[0076] As the reactive functional group introduced into polydimethylsiloxane, an amino group, an epoxy group, a hydroxyl group, a mercapto group, a carboxyl group, a methacryl group, an acrylic group, etc. can be used. As the non-reactive functional group, a polyether group, an aralkyl group, a fluoroalkyl group, a long-chain alkyl group, an ester group, an amide group, a phenyl group, etc. can be used. Although not particularly bound by theory, among the above, those having an epoxy group, a carboxyl group, a polyether group, a methacryl group, an acrylic group, or an ester group are preferable.

[0077] As the functional group introduced into polydimethylsiloxane, a polyether group and an ester group, which do not react with the binder resin, are likely to be oriented on the surface of the release layer, and have little migration property to the green sheet, are preferable.

[0078] The silicone-based additive used in the present invention preferably has a molecular weight of 40,000 or less. More preferably, it is 30,000 or less. When the molecular weight is 40,000 or less, the silicone-based additive is likely to segregate on the surface of the release layer and has good releasability, which is preferable.

[0079] (Long-chain alkyl-based additive in the release layer) As the long-chain alkyl-based additive, a resin modified with a long-chain alkyl can be used, and those having an alkyl group with about 8 to 20 carbon atoms in the side chain such as polyvinyl alcohol and acrylic resin are preferable. In addition, a polymer having (meth)acrylic acid ester as a main repeating unit and a copolymer containing a long-chain alkyl group with 8 to 20 carbon atoms in the transesterified part can also be preferably used. By using a long-chain alkyl-based additive different from the acrylic resin having a long-chain alkyl group as the main component, the releasability may be improved. Examples of commercially available products include Pyroyl (registered trademark) 406 (above, Lion Specialty Chemicals Co., Ltd.).

[0080] (Other additives in the release layer) In order to impart other functions to the release layer, various additives other than the silicone additive may be contained within a range that does not impair the coating appearance. Examples of the additives include fluorescent dyes, fluorescent brighteners, plasticizers, ultraviolet absorbers, pigment dispersants, antifoaming agents, defoaming agents, preservatives, etc.

[0081] The release layer may also contain additives other than the silicone additive for the purpose of improving the leveling property during coating and defoaming the coating solution. The additive may be any of cationic, anionic, nonionic, etc., but acetylene glycol-based or fluorine-based additives are preferable. These additives are preferably contained in the release layer within a range such that no abnormality in the coating appearance occurs when added excessively.

[0082] The additive used in the present invention is preferably 20% by mass or less. If it is 20% by mass or less, excessive migration of the additive to the sheet does not occur, which is preferable. Also, the additive may be 0% by mass.

[0083] As the coating method, either a so-called in-line coating method in which coating is performed simultaneously during the formation of the polyester base film, or a so-called off-line coating method in which the polyester base film is formed and then coated separately with a coater can be applied. However, the in-line coating method is more efficient and preferable.

[0084] As a method for applying a coating liquid to a polyethylene terephthalate (hereinafter sometimes abbreviated as PET) film as the coating method, any known method can be used. For example, a reverse roll coating method, a gravure coating method, a kiss coating method, a die coater method, a roll brush coating method, a spray coating method, an air knife coating method, a wire bar coating method, a pipe doctor method, an impregnation coating method, a curtain coating method, etc. can be mentioned. These methods are applied alone or in combination.

[0085] In the present invention, as a method for providing a release layer on a polyester film, a method of applying and drying a coating liquid containing a solvent, particles, and a resin to the polyester film can be mentioned. Examples of the solvent include organic solvents such as toluene, water, or a mixed system of water and a water-soluble organic solvent. Preferably, from the viewpoint of environmental problems, water alone or a so-called aqueous solvent in which a water-soluble organic solvent is mixed with water is preferable.

[0086] The solid content concentration of the release coating liquid depends on the type of binder resin, the type of solvent, etc., but is preferably 0.5% by mass or more, and more preferably 1% by mass or more. The solid content concentration of the coating liquid is preferably 35% by mass or less, and more preferably 20% by mass or less. Note that the release coating liquid may be described as a release coating liquid.

[0087] Regarding the drying temperature after coating, it also depends on the type of binder resin, the type of solvent, the presence or absence of a crosslinking agent, the solid content concentration, etc., but is preferably 70°C or higher and preferably 250°C or lower.

[0088] In the case of in-line coating, it may be applied to the unstretched film before longitudinal stretching or to the uniaxially stretched film after longitudinal stretching and before transverse stretching. When applying before longitudinal stretching, it is preferable to provide a drying step before roll stretching. When applying to the uniaxially stretched film before transverse stretching, since the drying step can be combined with the film heating step in the tenter, it is not always necessary to provide a separate drying step. The same applies to the case of simultaneous biaxial stretching.

[0089] The film thickness of the release layer is preferably 0.001 μm or more, more preferably 0.01 μm or more, still more preferably 0.02 μm or more, and particularly preferably 0.03 μm or more. When the film thickness of the release layer is 0.001 μm or more, the film-forming property of the coating film is maintained and a uniform coating film can be obtained, which is preferable.

[0090] The film thickness of the release layer is preferably 2 μm or less, more preferably 1 μm or less, still more preferably 0.8 μm or less, and particularly preferably 0.5 μm or less. When the film thickness of the coating layer is 2 μm or less, there is no risk of blocking, which is preferable.

[0091] When the surface roughness of both sides of the base polyester film is different, the release layer can be laminated on either side, but since the surface roughness of the obtained release surface becomes smoother, it is preferable to laminate the release layer on the smooth surface of the base material.

[0092] The outer surface of the film with the release layer formed thereon (the surface of the release layer of the entire coating film not in contact with the polyester film) is preferably flat so as not to cause defects in the sheet coated and molded thereon. It is preferable that the average surface roughness (Sa) of the region is 5 nm or less and the maximum protrusion height (P) is 50 nm or less. More preferably, the average surface roughness of the region is 5 nm or less and the maximum protrusion height is 40 nm or less. If the surface roughness of the region is 5 nm or less and the maximum protrusion height is 50 nm or less, there will be no defects such as pinholes during sheet formation, and the yield is preferably good. It can be said that the smaller the average surface roughness (Sa) of the region, the better, but it may be 0.1 nm or more, or 0.3 nm or more. It can also be said that the smaller the maximum protrusion height (P), the better, but it may be 1 nm or more, or 3 nm or more. In one embodiment, the average surface roughness of the region is less than 4.4 nm and the maximum protrusion height is 40 nm or less, for example, 4 nm or less and the maximum protrusion height is 40 nm or less.

[0093] The surface free energy of the release layer is preferably 45 mJ / m 2 or less, and more preferably 35 mJ / m 2 or less. When the surface free energy of the release layer is 45 mJ / m 2 or less, the peeling force of the sheet becomes lighter, which is preferable. The surface free energy of the release layer is preferably 20 mJ / m 2 or more, and more preferably 25 mJ / m 2 or more. When the surface free energy of the release layer is 20 mJ / m 2 or more, the peeling force of the sheet does not become too light, and it is preferable that repelling of the slurry or resin solution does not easily occur.

[0094] (Ceramic Green Sheet and Ceramic Capacitor) Generally, a multilayer ceramic capacitor has a rectangular parallelepiped ceramic body. Inside the ceramic body, a first internal electrode and a second internal electrode are alternately provided along the thickness direction. The first internal electrode is exposed on a first end face of the ceramic body. A first external electrode is provided on the first end face. The first internal electrode is electrically connected to the first external electrode at the first end face. The second internal electrode is exposed on a second end face of the ceramic body. A second external electrode is provided on the second end face. The second internal electrode is electrically connected to the second external electrode at the second end face.

[0095] The release film of the present invention is particularly preferably used for manufacturing such a multilayer ceramic capacitor. For example, it is manufactured as follows. First, the release film of the present invention is used as a carrier film, and a ceramic slurry for forming a ceramic body is applied and dried. A conductive layer for forming a first or second internal electrode is printed on the applied and dried ceramic green sheet. A ceramic green sheet, a ceramic green sheet on which a conductive layer for forming a first internal electrode is printed, and a ceramic green sheet on which a conductive layer for forming a second internal electrode is printed are appropriately laminated and pressed to obtain a mother laminate. The mother laminate is divided into a plurality to produce a raw ceramic body. The raw ceramic body is fired to obtain a ceramic body. Thereafter, a multilayer ceramic capacitor can be completed by forming first and second external electrodes.

Examples

[0096] Next, the present invention will be described in detail using examples and comparative examples, but the present invention is of course not limited to the following examples. Further, the evaluation methods used in the present invention are as follows.

[0097] (NMR measurement) The ratio of the copolymerized component introduced into an acrylic resin (for example, acrylic polyol) is determined by nuclear magnetic resonance spectroscopy ( 1 1H-NMR, 1313C-NMR: Confirmed using a Varian Unity 400 (manufactured by Agilent). The measurement was carried out after removing the solvent in the synthesized acrylic resin (acrylic polyol) with a vacuum dryer, and then dissolving the dried solid in deuterated chloroform. From the obtained NMR spectrum, the peaks of the chemical shift δ (ppm) attributed to the sites of each group were identified. The integrated intensity of each obtained peak was determined, and from the number of hydrogens and the integrated intensity of the sites of each group, the composition ratio (mol%) of the copolymerized components introduced into the acrylic resin (acrylic polyol) was confirmed.

[0098] (Confirmation of Tg) The Tg of each acrylic resin (acrylic polyol) was determined from the composition ratio of the copolymerized components obtained by the above NMR measurement and the Fox's equation described above.

[0099] (Drawability) To evaluate the drawability of the acrylic resin (acrylic polyol) itself, the synthesized acrylic resins (acrylic polyols) (1) to (5) were put into a mixed solvent (at 25 °C) of 30% by mass of isopropanol and 70% by mass of water so that the solid content concentration became 12% by mass to prepare a solution of the acrylic resin (acrylic polyol) alone. Then, the solution was applied onto the surface of a polyester film that had been drawn only longitudinally with a Mayer bar #5. Next, the film sample with the applied layer (thickness: 6.5 μm) was left standing in a hot air circulation oven set at 60 °C for 30 seconds, and then the film sample was taken out of the oven and pre-dried. Then, the sample was set in a hand-rewinding drawing apparatus (manufactured by Toyobo Engineering Co., Ltd.) and placed in a hot air circulation oven at 100 °C, and a slow drawing operation was performed. The drawing operation was carried out until the length became 4 times the length before drawing, and the drawing apparatus was taken out of the hot air circulation oven. Thereafter, the drawn coating film was observed with an optical microscope (magnification: 200 times), and the presence or absence of cracking due to drawing was judged according to the following criteria. ○: No cracks are visible at all. △: Slight cracks are visible (1 to 4 cracks). ×: 5 or more cracks, or cracks are visible over the entire surface.

[0100] (Measurement of Acid Value) Weigh accurately about 0.2 g of the sample into a conical flask with a stopper (A (g)), add 10 ml of benzyl alcohol, and heat it at 230 °C for 15 minutes with a heater under a nitrogen atmosphere to dissolve the resin. After allowing it to cool to room temperature, add 10 ml of benzyl alcohol, 20 ml of chloroform, and a few drops of phenolphthalein solution, and titrate it with 0.02 N KOH solution (titration volume = B (ml), normality of KOH solution = p). Perform a blank measurement in the same manner (titration volume = C (ml)), and calculate according to the following formula. Acid value (mgKOH / g) = (B - C) × 0.02 × 56.11 × p ÷ A

[0101] (Quantification of Oxazoline Groups in Resin with Oxazoline Groups) Freeze-dry the resin having oxazoline groups, and from 1H-NMR analysis using a nuclear magnetic resonance spectrometer (NMR) (Varian Gemini-200), determine the absorption peak intensity derived from oxazoline groups and the absorption peak intensity derived from other monomers, and calculate the oxazoline group amount (mmol / g) from the peak intensities.

[0102] (Surface Characteristics of Coated Film and Uncoated Substrate Film) The values measured under the following conditions using a non-contact surface profilometry system (VertScan R550H-M100). The average surface roughness of the area (Sa) was the average value of 5 measurements, and the maximum protrusion height (P) was the maximum value of 5 measurements. (Measurement Conditions) · Measurement mode: WAVE mode · Objective lens: 50× · 0.5× Tube lens · Measurement area 187 × 139 μm (for Sa, P measurement)

[0103] (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), diiodomethane (droplet volume 0.9 μL), and ethylene glycol (droplet volume 0.9 μL) were produced on the release surface of the release film, and their contact angles were measured. The contact angle adopted was the contact angle 10 seconds after each liquid was dropped onto the release film. The contact angle data of water, diiodomethane, and ethylene glycol obtained by the above method were calculated from the "Kitazaki-Hata" theory to obtain the dispersion component γsd, polar component γsp, and hydrogen bond component γsh of the surface free energy of the release film, and the sum of each component was taken as the surface free energy γs. This calculation was performed using the calculation software within this contact angle meter software (FAMAS).

[0104] (Pinhole evaluation of ceramic slurry) The following composition consisting of materials was stirred and mixed, and dispersed with zirconia beads with a diameter of 0.5 mm for 60 minutes using a bead mill to obtain a ceramic slurry. 38.3 parts by mass of toluene 38.3 parts by mass of ethanol Barium titanate (HPBT-1 manufactured by Fuji Titanium Co., Ltd.) 64.8 parts by mass Polyvinyl butyral (Esrec BM-S manufactured by Sekisui Chemical Co., Ltd.) 6.5 parts by mass DOP (dioctyl phthalate) 3.3 parts by mass Next, the obtained release film sample was coated on the release surface using an applicator so that the dried slurry became 1 μm, and dried at 90°C for 1 minute to form a ceramic green sheet. Then, the release film was peeled off from the release film with the formed ceramic green sheet to obtain a ceramic green sheet. In the central region in the film width direction of the obtained ceramic green sheet, light was applied from the opposite side of the coating surface of the ceramic slurry within a range of 25 cm 2 to observe the occurrence status of pinholes through which light could be seen transmitted, and visually judged according to the following criteria. ○: No pinholes generated △: Almost no pinholes generated ×: Numerous pinholes occurred

[0105] (Evaluation of the peelability of ceramic green sheets) In the same manner as the evaluation of the coatability of the ceramic slurry, it was applied so that the dried ceramic sheet had a thickness of 0.8 μm, dried at 60 °C for 1 minute, and the ceramic green sheet was formed on the release film. After the release film with the obtained ceramic green sheet was neutralized using a neutralizer (manufactured by Keyence Corporation, SJ-F020), it was peeled using a peeling tester (manufactured by Kyowa Interface Science Co., Ltd., VPA-3) at a peeling angle of 90 degrees, a peeling temperature of 25 °C, and a peeling speed of 10 m / min. As the peeling direction, a double-sided adhesive tape (manufactured by Nitto Denko Corporation, No. 535A) was attached to the SUS plate attached to the peeling tester, and the release film was fixed in such a way that the ceramic green sheet side was adhered to the double-sided tape, and peeled by pulling the release film side. Among the obtained measured values, the average value of the peeling force at a peeling distance of 20 mm to 70 mm was calculated, and that value was taken as the peeling force. The measurement was carried out 5 times in total, the average value of the peeling force was adopted, and the evaluation was performed. It was judged according to the following criteria from the obtained numerical values of the peeling force. ○: 3.5 mN / mm or less △: Greater than 3.5 mN / mm and 6.0 mN / mm or less ×: Greater than 6.0 mN / mm

[0106] (Pinhole evaluation of resin sheets) Using the following method, three types of resin solutions for resin sheet molding were prepared. (Resin sheet (1)) 0.5 part by mass of cyclic olefin resin (ARTON (registered trademark) G7810 / manufactured by JSR Corporation, solid content 100% by mass) was dissolved in 80 parts by mass of toluene and 20 parts by mass of tetrahydrofuran to prepare a resin solution (1). The release surface of the release film sample was coated using an applicator so that the dried sheet had a thickness of 0.5 μm and dried at 100 °C for 1 minute to form a cyclic olefin resin sheet. Next, the release film was peeled from the release film with the formed cyclic olefin resin sheet to obtain a cyclic olefin resin sheet (1). (Resin Sheet (2)) 10 parts by mass of an ion exchange resin (20% Nafion (registered trademark) 20 Dispersion Solution DE2021 CS type, manufactured by Wako Pure Chemical Industries, Ltd., solid content 20% by mass), 10 parts by mass of water, and 20 parts by mass of isopropyl alcohol were mixed to prepare a resin solution (2). Using an applicator, the release surface of the release film sample was coated so that the dried sheet would be 0.5 μm thick, and then dried at 100 °C for 1 minute to form an ion exchange resin sheet. Next, the release film was peeled off from the release film with the formed ion exchange resin sheet to obtain an ion exchange resin sheet (2). (Resin Sheet (3)) 20 parts by mass of an ultraviolet curable resin (urethane acrylate, product name: 8UX-015A, manufactured by Dainippon Fine Chemical Co., Ltd., solid content 100% by mass), 40 parts by mass of methyl ethyl ketone, 39 parts by mass of isopropyl alcohol, and 1 part by mass of a photo radical initiator (Irgacure (registered trademark) 907, manufactured by BASF) were mixed to prepare a resin solution (3). Using an applicator, the release surface of the release film sample was coated so that the dried sheet would be 1.0 μm thick, dried at 90 °C for 15 seconds, and then irradiated with ultraviolet light using a high-pressure mercury lamp so that it would be 300 mJ / cm 2 to form an ultraviolet curable resin sheet. Next, the release film was peeled off from the release film with the formed ultraviolet curable resin sheet to obtain an ultraviolet curable resin sheet (3). All three types of the obtained resin sheets were evaluated by the following method. In the central region in the film width direction of the obtained resin sheet, light was applied from the opposite side of the coating surface of the resin slurry in the range of 25 cm 2 and the occurrence of pinholes through which light could be seen passing through was observed, and visual judgment was made according to the following criteria. ○: No occurrence of pinholes △: Almost no occurrence of pinholes ×: Many pinholes occurred

[0107] (Preparation of Polyethylene Terephthalate Pellets (PET (I))) As an esterification reactor, a continuous esterification reactor consisting of a three-stage completely mixed tank having a stirring device, a partial condenser, a raw material charging port, and a product discharging port was used. TPA (terephthalic acid) was set at 2 tons / hour, EG (ethylene glycol) was set at 2 moles per 1 mole of TPA, antimony trioxide was set at an amount such that the Sb atoms were 160 ppm with respect to the produced PET, and these slurries were continuously supplied to the first esterification reaction tank of the esterification reactor and reacted at 255 °C with an average residence time of 4 hours under normal pressure. Next, the reaction product in the first esterification reaction tank was continuously taken out of the system and supplied to the second esterification reaction tank. 8% by mass of EG distilled off from the first esterification reaction tank with respect to the produced PET was supplied to the second esterification reaction tank. Further, an EG solution containing magnesium acetate tetrahydrate in an amount such that the Mg atoms were 65 ppm with respect to the produced PET and an EG solution containing TMPA (trimethyl phosphate) in an amount such that the P atoms were 40 ppm with respect to the produced PET were added, and the reaction was carried out at 260 °C with an average residence time of 1 hour under normal pressure. Next, the reaction product of the second esterification reaction tank was continuously taken out of the system and supplied to the third esterification reaction tank, and while adding 0.2% by mass of porous colloidal silica having an average particle size of 0.9 μm and 0.4% by mass of synthetic calcium carbonate having an average particle size of 0.6 μm to which 1% by mass of an ammonium salt of polyacrylic acid was attached per calcium carbonate as 10% EG slurries respectively, the reaction was carried out at 260 °C with an average residence time of 0.5 hour under normal pressure. The esterification reaction product produced in the third esterification reaction tank was continuously supplied to a three-stage continuous polycondensation reactor for polycondensation, filtered with a filter obtained by sintering stainless steel fibers having a 95% cut diameter of 20 μm, then ultrafiltration was carried out and extruded into water, and after cooling, it was cut into chips to obtain PET chips having 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. 2 ) of pressure and subjected to dispersion treatment with an average number of treatment passes of 5 passes to obtain a porous colloidal silica having an average particle size of 0.9 μm and 0.4% by mass of synthetic calcium carbonate having an average particle size of 0.6 μm to which 1% by mass of an ammonium salt of polyacrylic acid was attached per calcium carbonate were added as 10% EG slurries respectively, and the reaction was carried out at 260 °C with an average residence time of 0.5 hour under normal pressure. The esterification reaction product produced in the third esterification reaction tank was continuously supplied to a three-stage continuous polycondensation reactor for polycondensation, filtered with a filter obtained by sintering stainless steel fibers having a 95% cut diameter of 20 μm, then ultrafiltration was carried out and extruded into water, and after cooling, it was cut into chips to obtain PET chips having 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.

[0108] (Preparation of polyethylene terephthalate pellets (PET(II))) On the other hand, in the production of the above PET(I) chips, PET chips having an intrinsic viscosity of 0.62 dl / g and containing no particles such as calcium carbonate and silica were obtained (hereinafter abbreviated as PET(II)).

[0109] (Preparation of polyethylene terephthalate pellets (PET(III))) On the other hand, in the production of the above PET(I) chips, PET chips having an intrinsic viscosity of 0.62 dl / g were obtained in the same manner except that the particles such as calcium carbonate and silica were changed to porous colloidal silica having an average particle size of 0.2 μm and synthetic calcium carbonate having an average particle size of 0.1 μm (hereinafter abbreviated as PET(III)).

[0110] (Production of acrylic resin (acrylic polyol) A-1) Into a four-necked flask equipped with a stirrer, a reflux condenser, a thermometer, and a nitrogen blowing tube, 103 parts by mass of methyl methacrylate (MMA), 173 parts by mass of stearyl methacrylate (SMA), 100 parts by mass of hydroxyethyl methacrylate (HEMA), 22 parts by mass of methacrylic acid (MAA), and 929 parts by mass of isopropyl alcohol (IPA) were charged, and the temperature inside the flask was raised to 80 °C while stirring. While maintaining the temperature inside the flask at 80 °C, stirring was carried out for 3 hours, and then 0.5 part by mass of 2,2-azobis-2-methyl-N-2-hydroxyethylpropionamide was added to the flask. After performing nitrogen substitution while raising the temperature inside the flask to 120 °C, the mixture was stirred at 120 °C for 2 hours. Next, a depressurization operation at 1.5 kPa was performed at 120 °C to remove unreacted raw materials and the solvent, and an acrylic resin (acrylic polyol) was obtained. The pressure inside the flask was returned to atmospheric pressure and cooled to room temperature, and 1592 parts by mass of an IPA aqueous solution (water content 50% by mass) was added and mixed. Then, while stirring, ammonia was added using a dropping funnel, and the acrylic resin (acrylic polyol) was neutralized until the pH of the solution was in the range of 5.5 to 7.5, and an acrylic resin (acrylic polyol) (A-1) having a solid content concentration of 20% by mass was obtained. The composition ratio, Tg, drawability, and acid value of the acrylic resin (acrylic polyol) (A-1) determined by NMR measurement are shown in Table 1.

[0111] (Production of Acrylic Resins (Acrylic Polyols) (A-2) to (A-6)) As shown in Table 1, except for changing the amounts of MMA, SMA, HEMA, MAA, IPA at the time of charging, and IPA aqueous solution at the time of dilution, acrylic polyols ((A-2) to (A-6)) with a solid content concentration of 20% by mass were obtained in the same manner as the production of acrylic resin (acrylic polyol) 1. The composition ratios, Tg, drawability, and acid value of the acrylic resins (acrylic polyols) (A-2) to (A-6) by NMR measurement are also shown in Table 1. The composition ratios are represented as n1 (units) of MMA, n2 (units) of SMA, n3 (units) of HEMA, and n4 (units) of MAA, respectively.

[0112]

Table 1

[0113] (Production of Oxazoline Crosslinking Agent C-1) 460.6 parts of isopropyl alcohol was charged into a flask equipped with a stirrer, reflux condenser, nitrogen inlet tube, and thermometer, and heated to 80°C while gently flowing nitrogen gas. A monomer mixture consisting of 126 parts of methyl methacrylate, 210 parts of 2-isopropenyl-2-oxazoline, and 84 parts of methoxypolyethylene glycol acrylate, which had been prepared in advance, and an initiator solution consisting of 21 parts of 2,2'-azobis(2-methylbutyronitrile) ("ABN-E" manufactured by Nippon Hydrazine Industry Co., Ltd.) and 189 parts of isopropyl alcohol were each added dropwise from a dropping funnel over 2 hours to cause a reaction, and the reaction was continued for 5 hours after the addition was completed. Nitrogen gas was continuously flowed during the reaction, and the temperature inside the flask was maintained at 80 ± 1°C. Thereafter, the reaction solution was cooled to obtain a resin (C-1) having an oxazoline group with a solid content concentration of 10%. The amount of oxazoline groups in the obtained resin (C-1) having an oxazoline group was 7.7 mmol / g, and the number average molecular weight measured by GPC (gel permeation chromatography) was 40000.

[0114] (Production of Oxazoline Crosslinking Agent C-2) In the same manner as the synthesis of the resin (C-1) having the above oxazoline group, a resin (C-2) having an oxazoline group with a solid content concentration of 25% and different compositions (amount of oxazoline group and molecular weight) was obtained. The amount of oxazoline group of the obtained resin (C-2) having an oxazoline group was 4.3 mmol / g, and the number average molecular weight measured by GPC was 20,000.

[0115] (Production of carbodiimide crosslinking agent D-1) 168 parts by mass of hexamethylene diisocyanate and 220 parts by mass of polyethylene glycol monomethyl ether (M400, average molecular weight 400) were charged into a flask equipped with a stirrer, a thermometer, and a reflux condenser, and stirred at 120 °C for 1 hour. Further, 26 parts by mass of 4,4'-dicyclohexylmethane diisocyanate and 3.8 parts by mass of 3-methyl-1-phenyl-2-phospholene-1-oxide (2% by mass based on all isocyanates) as a carbodiimidization catalyst were added, and the mixture was further stirred at 185 °C for 5 hours under a nitrogen stream. The infrared spectrum of the reaction solution was measured, and it was confirmed that the absorption at a wavelength of 2200 to 2300 cm -1 disappeared. The reaction solution was allowed to cool to 60 °C, and 567 parts by mass of ion-exchanged water was added to obtain a carbodiimide water-soluble resin (D-1) having a solid content of 40% by mass.

[0116] (Production of isocyanate crosslinking agent E-1) 100 parts by mass of a polyisocyanate compound having an isocyanurate structure using hexamethylene diisocyanate as a raw material (Duranate TPA, manufactured by Asahi Kasei Chemicals), 55 parts by mass of propylene glycol monomethyl ether acetate, and 30 parts by mass of polyethylene glycol monomethyl ether (average molecular weight 750) were charged into a flask equipped with a stirrer, a thermometer, and a reflux condenser, and held at 70 °C for 4 hours under a nitrogen atmosphere. Then, the temperature of the reaction solution was lowered to 50 °C, and 47 parts by mass of methyl ethyl ketoxime was added dropwise. The infrared spectrum of the reaction solution was measured, and it was confirmed that the absorption of the isocyanate group disappeared, and a blocked polyisocyanate aqueous dispersion (E-1) having a solid content of 75% by mass was obtained.

[0117] (Silica particles F-1) Colloidal silica (manufactured by Nissan Chemical Industries, Ltd., trade name Snowtex XL, average particle size 40 nm, solid content concentration 40 mass%)

[0118] (Example 1) (Preparation of Release Coating Liquid 1) Release coating liquid 1 having the following composition was prepared. (Release coating liquid 1) Water 48.01 parts by mass Isopropyl alcohol 25.95 parts by mass Acrylic resin (acrylic polyol resin) A-1 (solid content concentration 20 mass%) 14.00 parts by mass Oxazoline-based crosslinking agent C-1 (solid content concentration 10 mass%) 12.00 parts by mass Additive G-1 0.04 parts by mass (Polyether-modified polydimethylsiloxane, 67Additive, solid content concentration 100 mass%, manufactured by Toray Dow Corning Co., Ltd.)

[0119] (Manufacture of polyester film) After drying PET chips, they were melted at 285°C and then melted at 290°C by a separate melt extruder. Two-stage filtration was performed using a filter obtained by sintering stainless steel fibers with a 95% cut-off diameter of 15 μm and a filter obtained by sintering stainless steel particles with a 95% cut-off diameter of 15 μm. They were combined in the feed block and laminated so that PET (I) became the surface layer B (anti-release surface side layer) and PET (II) became the surface layer A (release surface side layer), and then extruded (cast) in a sheet form at a speed of 45 m / min and electrostatically adhered and cooled on a casting drum at 30°C to obtain an unstretched polyethylene terephthalate sheet. The layer ratio was adjusted so that PET (I) / (II) = 60 mass% / 40 mass% by calculating the discharge amounts 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.

[0120] Next, after applying the above release coating liquid to the surface layer A of the PET film with a bar coater, it was dried at 80°C for 15 seconds. In addition, it was adjusted so that the coating amount after the final stretching and drying would be 0.07 μm. Subsequently, with a tenter, it was stretched 4.0 times in the width direction at 150°C, and while fixing the length in the width direction of the film, it was heated at 230°C for 4 seconds, and further relaxation treatment in the width direction of 3% was performed at 170°C to obtain an in-line release coating polyester film with a thickness of 31 μm. The Sa of the surface layer B (anti-release surface side) of the obtained film was 28 nm, and the P was 754 nm. Here, let the PET base material not containing the release layer be Z. The intrinsic viscosity of the obtained PET base material was 0.59 dl / g. Also, the Sa of the surface layer A of the PET base material not containing the release layer was 1 nm, and the P was 16 nm.

[0121] (Example 2) A release polyester film was obtained in the same manner as in Example 1, except that the release coating liquid 1 was changed to the following release coating liquid 2. (Release Coating Liquid 2) Water 54.03 parts by mass Isopropyl alcohol 23.93 parts by mass Acrylic resin (acrylic polyol resin) A-1 (solid content concentration 20% by mass) 18.00 parts by mass Oxazoline-based crosslinking agent C-1 (solid content concentration 10% by mass) 4.00 parts by mass Additive G-1 0.04 parts by mass (Polyether-modified polydimethylsiloxane, 67Additive, solid content concentration 100% by mass, manufactured by Toray Dow Corning Co., Ltd.)

[0122] (Example 3) A release polyester film was obtained in the same manner as in Example 1, except that the release coating liquid 1 was changed to the following release coating liquid 3. (Release Coating Liquid 3) Water 51.01 parts by mass Isopropyl alcohol 24.95 parts by mass Acrylic resin (acrylic polyol resin) A-1 (solid content concentration: 20% by mass) 16.00 parts by mass Oxazoline-based crosslinking agent C-1 (solid content concentration: 10% by mass) 8.00 parts by mass Additive G-1 0.04 parts by mass (Polyether-modified polydimethylsiloxane, 67Additive, solid content concentration: 100% by mass, manufactured by Toray Dow Corning Co., Ltd.)

[0123] (Example 4) A release polyester film was obtained in the same manner as in Example 1, except that Release coating liquid 1 was changed to the following Release coating liquid 4. (Release coating liquid 4) Water 41.99 parts by mass Isopropyl alcohol 27.97 parts by mass Acrylic resin (acrylic polyol resin) A-1 (solid content concentration: 20% by mass) 10.00 parts by mass Oxazoline-based crosslinking agent C-1 (solid content concentration: 10% by mass) 20.00 parts by mass Additive G-1 0.04 parts by mass (Polyether-modified polydimethylsiloxane, 67Additive, solid content concentration: 100% by mass, manufactured by Toray Dow Corning Co., Ltd.)

[0124] (Example 5) A release polyester film was obtained in the same manner as in Example 1, except that the acrylic resin (acrylic polyol resin) A-1 (solid content concentration: 20% by mass) in the release coating liquid 1 used in Example 1 was changed to acrylic resin (acrylic polyol resin) A-2 (solid content concentration: 20% by mass).

[0125] (Example 6) A release polyester film was obtained in the same manner as in Example 1, except that Release coating liquid 6 in which the crosslinking agent in the release coating liquid 1 used in Example 1 was changed to oxazoline-based crosslinking agent C-2 (solid content concentration: 25% by mass) was used. (Release Coating Liquid 6) Water 55.23 parts by mass Isopropyl alcohol 25.93 parts by mass Acrylic resin (acrylic polyol resin) A-1 (solid content concentration: 20% by mass) 14.00 parts by mass Oxazoline-based crosslinking agent C-2 (solid content concentration: 25% by mass) 4.80 parts by mass Additive G-1 0.04 parts by mass (Polyether-modified polydimethylsiloxane, 67 Additive, solid content concentration: 100% by mass, manufactured by Toray Dow Corning Co., Ltd.)

[0126] (Example 7) A release polyester film was obtained in the same manner as in Example 1, except that the acrylic resin (acrylic polyol resin) A-1 (solid content concentration: 20% by mass) in the release coating liquid 1 used in Example 1 was changed to acrylic resin (acrylic polyol resin) A-2 (solid content concentration: 20% by mass), and the crosslinking agent was changed to oxazoline-based crosslinking agent C-2 (solid content concentration: 25% by mass). (Release Coating Liquid 7) Water 55.23 parts by mass Isopropyl alcohol 25.93 parts by mass Acrylic resin (acrylic polyol resin) A-2 (solid content concentration: 20% by mass) 14.00 parts by mass Oxazoline-based crosslinking agent C-2 (solid content concentration: 25% by mass) 4.80 parts by mass Additive G-1 0.04 parts by mass (Polyether-modified polydimethylsiloxane, 67 Additive, solid content concentration: 100% by mass, manufactured by Toray Dow Corning Co., Ltd.)

[0127] (Example 8) A release polyester film was obtained in the same manner as in Example 1, except that the crosslinking agent in the release coating liquid 1 used in Example 1 was changed to a carbodiimide-based crosslinking agent D-1 (solid content concentration: 40% by mass), to obtain a release coating liquid 8. (Release coating liquid 8) Water 56.63 parts by mass Isopropyl alcohol 26.97 parts by mass Acrylic resin (acrylic polyol resin) A-1 (solid content concentration: 20% by mass) 12.00 parts by mass Carbodiimide-based crosslinking agent D-1 (solid content concentration: 40% by mass) 4.00 parts by mass Additive G-1 0.04 parts by mass (Polyether-modified polydimethylsiloxane, 67Additive, solid content concentration: 100% by mass, manufactured by Toray Dow Corning Co., Ltd.)

[0128] (Example 9) A release polyester film was obtained in the same manner as in Example 1, except that the release coating liquid 1 was changed to the following release coating liquid 9. (Release coating liquid 9) Water 47.51 parts by mass Isopropyl alcohol 25.95 parts by mass Acrylic resin (acrylic polyol resin) A-1 (solid content concentration: 20% by mass) 14.00 parts by mass Oxazoline-based crosslinking agent C-1 (solid content concentration: 10% by mass) 12.00 parts by mass Silica particles F-1 0.50 parts by mass (Average particle size: 40 nm, solid content concentration: 40% by mass) Additive G-1 0.04 parts by mass (Polyether-modified polydimethylsiloxane, 67Additive, solid content concentration: 100% by mass, manufactured by Toray Dow Corning Co., Ltd.)

[0129] (Example 10) A release polyester film was obtained in the same manner as in Example 1, except that the release coating liquid 1 was changed to the following release coating liquid 10. (Release coating liquid 10) Water 47.01 parts by mass Isopropyl alcohol 25.95 parts by mass Acrylic resin (acrylic polyol resin) A-1 (solid content concentration: 20% by mass) 14.00 parts by mass Oxazoline-based crosslinking agent C-1 (solid content concentration: 10% by mass) 12.00 parts by mass Silica particles F-1 1.00 part by mass (Average particle diameter: 40 nm, solid content concentration: 40% by mass) Additive G-1 0.04 part by mass (Polyether-modified polydimethylsiloxane, 67Additive, solid content concentration: 100% by mass, manufactured by Toray Dow Corning Co., Ltd.)

[0130] (Example 11) A release polyester film was obtained in the same manner as in Example 1, except that the release coating liquid 11, in which the additive in the release coating liquid 1 used in Example 1 was changed to polyester-modified polydimethylsiloxane G-2 (solid content concentration: 25% by mass), was used. (Release coating liquid 11) Water 47.90 parts by mass Isopropyl alcohol 25.93 parts by mass Acrylic resin (acrylic polyol resin) A-1 (solid content concentration: 20% by mass) 14.00 parts by mass Oxazoline-based crosslinking agent C-1 (solid content concentration: 10% by mass) 12.00 parts by mass Additive G-2 0.17 part by mass (Polyester-modified polydimethylsiloxane, BYK-315N, solid content concentration: 25% by mass, manufactured by Big Chemie Japan Co., Ltd.)

[0131] (Example 12) A release polyester film was obtained in the same manner as in Example 1, except that release coating liquid 12, in which the additive in release coating liquid 1 used in Example 1 was changed to long-chain alkyl-based additive G-1 (solid content concentration: 15% by mass), was used. (Release Coating Liquid 12) Water 47.80 parts by mass Isopropyl alcohol 25.93 parts by mass Acrylic resin (acrylic polyol resin) A-1 (solid content concentration: 20% by mass) 14.00 parts by mass Oxazoline-based crosslinking agent C-1 (solid content concentration: 10% by mass) 12.00 parts by mass Additive H-1 0.27 parts by mass (Pyroil (registered trademark) 406, solid content concentration: 15% by mass, manufactured by Lion Specialty Chemical Co., Ltd.)

[0132] (Example 13) A release polyester film was obtained in the same manner as in Example 1, except that the following release coating liquid 13, which does not contain the additive in release coating liquid 1 used in Example 1, was used. (Release Coating Liquid 13) Water 48.05 parts by mass Isopropyl alcohol 25.95 parts by mass Acrylic resin (acrylic polyol resin) A-1 (solid content concentration: 20% by mass) 14.00 parts by mass Oxazoline-based crosslinking agent C-1 (solid content concentration: 10% by mass) 12.00 parts by mass

[0133] (Example 14) A release polyester film was obtained in the same manner as in Example 1, except that the release layer thickness was changed to 0.035 μm.

[0134] (Example 15) A release polyester film was obtained in the same manner as in Example 1, except that the thickness of the release layer was changed to 0.100 μm.

[0135] (Example 16) A release polyester film was obtained in the same manner as in Example 1, except that the thickness of the release layer was changed to 0.140 μm.

[0136] (Example 17) A release polyester film was obtained in the same manner as in Example 1, except that the acrylic resin (acrylic polyol resin) A-1 (solid content concentration: 20% by mass) in the release coating liquid 1 used in Example 1 was changed to acrylic resin (acrylic polyol resin) A-4 (solid content concentration: 20% by mass).

[0137] (Example 18) A release polyester film was obtained in the same manner as in Example 1, except that the acrylic resin (acrylic polyol resin) A-1 (solid content concentration: 20% by mass) in the release coating liquid 1 used in Example 1 was changed to acrylic resin (acrylic polyol resin) A-5 (solid content concentration: 20% by mass).

[0138] (Example 19) A release polyester film was obtained in the same manner as in Example 1, except that the PET (II) in the surface layer A of the PET substrate was changed to PET (III). Here, let the PET substrate without the release layer be Y. The intrinsic viscosity of the obtained PET substrate was 0.59 dl / g. Also, the Sa of the surface layer A of the PET substrate Y before laminating the release layer was 10 nm, and the P was 130 nm.

[0139] (Example 20) A release polyester film was obtained in the same manner as in Example 1, except that the release coating liquid 1 was changed to the following release coating liquid 16. (Release Coating Liquid 16) Water 47.85 parts by mass Isopropyl Alcohol 25.95 parts by mass Acrylic resin (acrylic polyol resin) A-1 (solid content concentration: 20% by mass) 14.00 parts by mass Oxazoline-based crosslinking agent C-1 (solid content concentration: 10% by mass) 12.00 parts by mass Additive G-1 0.20 parts by mass (Polyether-modified polydimethylsiloxane, 67Additive, solid content concentration: 100% by mass, manufactured by Toray Dow Corning)

[0140] (Example 21) A release polyester film was obtained in the same manner as in Example 1, except that the acrylic resin (acrylic polyol resin) A-1 (solid content concentration: 20% by mass) in the release coating liquid 1 used in Example 1 was changed to acrylic resin (acrylic polyol resin) A-6 (solid content concentration: 20% by mass) (release coating liquid 17).

[0141] (Comparative Example 1) A release polyester film was obtained in the same manner as in Example 1, except that the release coating liquid 1 was changed to the following release coating liquid 18. (Release coating liquid 18) Water 76.76 parts by mass Isopropyl alcohol 19.19 parts by mass Hardening type silicone aqueous emulsion B-1 4.01 parts by mass (Manufactured by Shin-Etsu Silicone Co., Ltd., solid content concentration: 40%, KM3951) Platinum-based catalyst B-2 0.04 parts by mass (Manufactured by Shin-Etsu Silicone Co., Ltd., CAT-PM-10A)

[0142] (Comparative Example 2) A release polyester film was obtained in the same manner as in Example 1, except that the acrylic resin (acrylic polyol resin) A-1 (solid content concentration: 20% by mass) in the release coating liquid 1 used in Example 1 was changed to acrylic resin (acrylic polyol resin) A-3 (solid content concentration: 20% by mass) and release coating liquid 19 was used.

[0143] (Comparative Example 3) A polyester film was obtained in the same manner as in Example 1, except that Release Coating Liquid 1 was changed to the following Release Coating Liquid 20. (Release Coating Liquid 20) Water 58.30 parts by mass Isopropyl alcohol 25.95 parts by mass Acrylic resin (acrylic polyol resin) A-1 (solid content concentration: 20% by mass) 14.00 parts by mass Isocyanate crosslinking agent E-1 (solid content concentration: 75% by mass) 1.72 parts by mass Surfactant G-1 0.04 parts by mass (Polyether-modified polydimethylsiloxane, 67Additive, solid content concentration: 100% by mass, manufactured by Toray Dow Corning Co., Ltd.)

[0144] (Comparative Example 4) A polyester film was obtained in the same manner as in Example 1, except that Release Coating Liquid 1 was changed to the following Release Coating Liquid 21. (Release Coating Liquid 21) Water 57.04 parts by mass Isopropyl alcohol 22.93 parts by mass Acrylic resin (acrylic polyol resin) A-1 (solid content concentration: 20% by mass) 20.00 parts by mass Surfactant G-1 0.04 parts by mass (Polyether-modified polydimethylsiloxane, 67Additive, solid content concentration: 100% by mass, manufactured by Toray Dow Corning Co., Ltd.)

[0145] The evaluation results of each example and comparative example are shown in Table 2.

[0146]

Table 2

[0147] In Table 2 above, the compositions of the resin, crosslinking agent, particles, and additive in the release coating liquid are described as parts by mass of the solid content. The sum of the parts by mass of the solid content of the resin, crosslinking agent, particles, and additive present in the release coating liquid is the part by mass of the total solid content of the release layer. For the resin, crosslinking agent, particles, and additive, by dividing the part by mass of each solid content by the part by mass of the total solid content of the release layer, the mass percentage in the total solid content in the release layer of the resin, crosslinking agent, particles, and additive can be obtained.

[0148] In Examples 1 to 21, it was possible to suppress the manufacturing cost by in-line coating, and even when the molded sheet was further thinned, good wettability of the slurry for sheet and resin solution, and an appropriate sheet peeling force were exhibited. On the other hand, in Comparative Example 1, when the sheet was further thinned, the wettability of the slurry for sheet and resin solution was poor and pinholes occurred. In Comparative Example 2, since the acrylic resin did not contain a long-chain alkyl component, the surface free energy increased and the sheet peeling force increased. Due to the heavy sheet peeling force, pinholes occurred in the sheet during peeling. In Comparative Examples 3 and 4, since an oxazoline-based crosslinking agent or a carbodiimide-based crosslinking agent was not used, the curing of the coating film was insufficient and the sheet peeling force increased. Due to the heavy sheet peeling force, pinholes occurred in the sheet during peeling.

Industrial Applicability

[0149] According to the present invention, it is possible to manufacture a release film that can suppress the manufacturing cost and has good wettability of the slurry for sheet and resin solution, and an appropriate sheet peeling force even when the sheet is further thinned.

Claims

1. A release film comprising a polyester film and a release layer, having a release layer directly or via another layer on at least one side of the polyester film, wherein the release layer is formed by curing a composition containing an acrylic resin having a long-chain alkyl group and a crosslinking agent, the acid value of the acrylic resin having the long-chain alkyl group is 40 mgKOH / g or more and 400 mgKOH / g or less, the crosslinking agent includes at least one selected from oxazoline-based crosslinking agents or carbodiimide-based crosslinking agents, and the polyester film is a laminated polyester film having a multi-layer structure of two or more layers. A release film.

2. The laminated polyester film has a surface layer B on the side opposite to the release layer, and the surface layer B contains a recycled raw material. The release film according to claim 1.

3. The laminated polyester film has a surface layer B on the side opposite to the release layer, and further has a layer C as a core layer, wherein the layer C contains a recycled raw material. The release film according to claim 1.

4. The recycled raw material is at least one of a film recycled raw material or a PET bottle recycled raw material. The release film according to claim 2.

5. The recycled raw material is at least one of a film recycled raw material or a PET bottle recycled raw material. The release film according to claim 3.

6. The acrylic resin contains a long-chain alkyl group-containing acrylate monomer, and the copolymerization ratio of the long-chain alkyl group-containing acrylate monomer in the acrylic resin is 5 mol% or more and 60 mol% or less. The release film according to claim 1.

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