Release film for producing ceramic green sheet

Abstract

To provide a release film for producing a ceramic green sheet which has excellent release properties and hardly causes transfer, detachment or poor adhesion of a release layer.SOLUTION: There is provided a release film for producing a ceramic green sheet having a polyester film and a release layer, wherein the release layer is a layer obtained by curing a curable composition comprising a polysiloxane A having two or more alkenyl groups in the molecule, a polysiloxane B having two or more hydrosilyl groups in the molecule and an adhesion-imparting agent C, the adhesion-imparting agent C is a silane coupling agent and the surface free energy γS (mJ / m2) of the surface of the release layer and the hydrogen bond component γSVh (mJ / m2) of γS satisfy the following expressions (a) and (b). 1.0≤γSVh / γS*100≤6.5 (a), γS≤30 (b)SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a release film for producing ceramic green sheets, which has a polyester film and a release layer, and can be suitably used for producing ultra-thin ceramic green sheets and the like. [Background technology]

[0002] Conventionally, release films having a polyester film as a base material and a release layer laminated thereon have been used as various processing films. Among them, release films for producing ceramic green sheets have also been used as processing films for producing ceramic green sheets that require high smoothness, such as for multilayer ceramic capacitors and ceramic substrates.

[0003] In recent years, as multilayer ceramic capacitors have become smaller and have increased capacity, the thickness of ceramic green sheets has also tended to become thinner. Ceramic green sheets are formed by coating a slurry containing ceramic components such as barium titanate and a binder resin onto a release film and drying it. Electrodes are printed on the formed ceramic green sheets, which are then peeled off from the release film. The resulting ceramic green sheets are then laminated, pressed, fired, and coated with external electrodes to produce multilayer ceramic capacitors.

[0004] As ceramic green sheets have become thinner in recent years, the peelability of the ceramic green sheets from release films has become increasingly important. If the peel force is large and uneven, the ceramic green sheets can be damaged during the peeling process, resulting in sheet defects, thickness variations, pinholes, cracks, and other problems. Therefore, there is a demand for ceramic green sheets to be peeled with a lower, more uniform force.

[0005] As a measure to make the release layer easy to release, as in Patent Document 1 and the like, a release film has been proposed in which the release layer is a silicone coating formed by an addition reaction using polydimethylsiloxane having an alkenyl group, polydimethylsiloxane having a hydrosilyl group, and a platinum catalyst, by heat or the like.

[0006] Furthermore, as a measure to improve the curability of the release layer, Patent Document 2 proposes a release film having a release layer formed by curing a radical curing composition containing a polyorganosiloxane having a reactive functional group such as an acryloyl group and a polyfunctional (meth)acrylic acid ester. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Patent No. 6619200 [Patent Document 2] Patent No. 5492352 Summary of the Invention [Problem to be solved by the invention]

[0008] However, in the invention of Patent Document 1, it tends to be difficult to achieve both adhesion of the release layer to the substrate film and releasability of the surface, and there was a concern that the silicone coating would fall off from the release layer during the process of producing the ceramic green sheet, contaminating the process.

[0009] Furthermore, in the invention of Patent Document 2, if the hardening property is increased to the extent that transfer of the release layer can be prevented, there is a problem that sufficient releasability cannot be obtained when peeling off the ceramic.

[0010] Therefore, an object of the present invention is to provide a release film for producing ceramic green sheets that has excellent releasability and is less likely to cause transfer and detachment of the release layer or poor adhesion, and to provide a method for producing ceramic green sheets using the release film. [Means for solving the problem]

[0011] As a result of intensive research to solve the above-mentioned problems, the inventors discovered that the above-mentioned problems can be solved by controlling the ratio of the hydrogen bonding component γSVh in the surface free energy γS within a predetermined range for a release layer that has been hardened by further adding an adhesion promoter, and thus completed the present invention.

[0012] That is, the present invention includes the following:

[0013] [1] A release film for producing a ceramic green sheet having a polyester film and a release layer, the release layer is a layer obtained by curing a curable composition containing polysiloxane A having two or more alkenyl groups in the molecule, polysiloxane B having two or more hydrosilyl groups in the molecule, and adhesion promoter C; The surface free energy γS (mJ / m 2 ) and the hydrogen bond component γSVh (mJ / m 2 ) and satisfy the following formulas (a) and (b): 1.0≦γSVh / γS*100≦6.5 (a) γS≦30 (b)

[0014] [2] The release film for producing a ceramic green sheet according to [1], wherein the adhesion promoter C is a silane coupling agent having one or more functional groups selected from the group consisting of a vinyl group, an epoxy group, an acrylic group, and a methacrylic group.

[0015] [3] The release film for producing a ceramic green sheet according to [1] or [2], wherein the weight average molecular weight of the polysiloxane A is 300,000 or more and 600,000 or less.

[0016] [4] The release film for producing a ceramic green sheet according to any one of [1] to [3], wherein the molar ratio of the amount of hydrosilyl groups in the polysiloxane B to the amount of alkenyl groups in the polysiloxane A in the curable composition satisfies the following formula (c): 1.0≦Si-H / Si-A≦3.8 (c) (In the formula, Si-H represents the molar amount of hydrosilyl groups, and Si-A represents the molar amount of alkenyl groups.)

[0017] [5] The release film for producing a ceramic green sheet according to any one of [1] to [4], wherein the curable composition contains 1% by mass or more and 10% by mass or less of the adhesion promoter C relative to the total amount of the polysiloxane A and the polysiloxane B.

[0018] [6] The polyester film has a surface layer A that is substantially free of inorganic particles, The release layer is laminated on the surface layer A to a thickness of 0.005 μm or more and 0.1 μm or less, The release film for producing a ceramic green sheet according to any one of [1] to [5], wherein the maximum protrusion height (Sp) on the surface of the release layer is 100 nm or less.

[0019] [7] A method for producing a ceramic green sheet, which comprises molding a ceramic green sheet using a release film for producing a ceramic green sheet according to any one of [1] to [6], wherein the molded ceramic green sheet has a thickness of 0.2 μm to 1.0 μm. [Effects of the Invention]

[0020] According to the present invention, it is possible to provide a release film for producing a ceramic green sheet which has excellent releasability and is less likely to cause transfer and detachment of the release layer or poor adhesion. DETAILED DESCRIPTION OF THE INVENTION

[0021] [Release film for ceramic green sheet manufacturing] The release film for producing a ceramic green sheet of the present invention (hereinafter sometimes simply referred to as "release film") has a polyester film and a release layer, and the release layer may be provided on at least one side of the polyester film.

[0022] In addition, an easy-adhesion layer, an antistatic layer, a smoothing layer, etc. may be provided between the release layer and the polyester film, but in the present invention, good adhesion is easily obtained even without the interposition of an easy-adhesion layer, etc. In other words, a preferred embodiment is a release film in which the release layer is provided directly on the polyester film.

[0023] The release layer is a layer formed by curing a curable composition containing polysiloxane A having two or more alkenyl groups in the molecule, polysiloxane B having two or more hydrosilyl groups in the molecule, and adhesion promoter C.

[0024] The release film of the present invention has a surface free energy γS (mJ / m 2 ) and the hydrogen bond component γSVh (mJ / m 2 ) satisfy the following formulas (a) and (b): 1.0≦γSVh / γS*100≦6.5 (a) γS≦30 (b) First, the surface characteristics of the release layer specified by formulas (a) and (b) will be described.

[0025] (Surface characteristics of release layer) The above formulas (a) and (b) include the surface free energy γS and its hydrogen bond component γSVh. We will explain how to calculate these. The surface free energy can be determined by dropping water, methylene iodide, or ethylene glycol onto the release layer and measuring the angle (contact angle) between the droplet and the release layer after a certain period of time. From the contact angle of each solvent, the surface free energy γS of the release layer and its hydrogen bond component γSVh are calculated using the Kitazaki-Hata equation.

[0026] More specifically, a release film is fixed on a flat glass substrate, and 1.9 μL of water is dropped onto the release film. 60 seconds after the droplet has come to rest, the angle formed by the droplet and the release layer is measured and designated as θ1. Similarly, 0.9 μL of methylene iodide is dropped onto the release film. 30 seconds after the droplet has come to rest, the angle formed by the droplet and the release layer is measured and designated as θ2. Furthermore, 0.9 μL of ethylene glycol is dropped onto the release film. 30 seconds after the droplet has come to rest, the angle formed by the droplet and the release layer is measured and designated as θ3.

[0027] From the above θ1, θ2, θ3 and the γLVnd, γLVnp, γLVnh, and γLn (where n = 1, 2, or 3, corresponding to water, methylene iodide, or ethylene glycol) of water, methylene iodide, and ethylene glycol listed in Table 1, the dispersion component γSVd, dipole component γSVp, and hydrogen bond component γSVh of the surface free energy of the release layer were calculated using the Kitazaki-Hata formula below, and the sum of these was taken as the surface free energy γs of the release layer. In other words, γSVd + γSVp + γSVh = γs. The unit of surface free energy and each component is "mJ / m 2 "

[0028] [Table 1]

[0029]

number

[0030] The present inventors have found that when the surface free energy obtained by measuring the release layer under the above conditions satisfies formulas (a) and (b), extremely good releasability can be obtained when peeling off a ceramic green sheet formed by applying and drying a ceramic slurry to the release layer. Furthermore, they have found that satisfying the inequality on the lower limit side of formula (a) improves the hardness of the coating, making the release layer more likely to have sufficient strength and reducing the likelihood of problems such as peeling off of the release layer.

[0031] The excellent releasability of the ceramic green sheet is believed to be due to the low hydrogen bond component of the surface free energy of the release layer. In other words, it is believed that preventing the hydroxyl group component in the binder contained in the ceramic green sheet from forming a hydrogen bond with the unreacted hydrogen component of the release layer contributes to the easy releasability of the ceramic green sheet.

[0032] The ratio of hydrogen bonding components in the surface free energy of the release layer (γSVh / γS*100) is preferably 6.5% or less, more preferably 6.0% or less, and even more preferably 5.0% or less. When this ratio is 6.5% or less, the peeling force is good and the ceramic green sheet is less likely to deform or break during peeling.

[0033] On the other hand, the lower limit of the ratio (γSVh / γS*100) is preferably 1.0% or more, more preferably 1.2% or more. When this ratio is 1.0% or more, the amount of unreacted vinyl groups is small, the coating film tends to have sufficient strength, and problems such as peeling of the release layer are less likely to occur.

[0034] It is also desirable that the surface free energy γs of the release layer is low. This is because if the surface free energy of the release layer is close to that of the ceramic green sheet, the energy required to peel the ceramic green sheet from the release layer increases, resulting in poor peelability. The surface free energy γs is 30 mJ / m 2 It is desirable that the concentration is less than 25 mJ / m 2 or less, and more preferably 20 mJ / m 2 The following is the result.

[0035] The lower limit of the surface free energy γs is not particularly limited, but from the viewpoint of the coating property of the ceramic slurry, the surface free energy γs is preferably 12 mJ / m 2 It is preferable that the concentration is 14 mJ / m or more. 2 More preferably, it is equal to or greater than this.

[0036] [Release layer] The material constituting the release layer of the release film is preferably a curable composition shown below, in order to form a release layer that satisfies the above-mentioned physical properties. In other words, the release layer is preferably formed from a layer obtained by curing the curable composition shown below.

[0037] The curable composition contains polysiloxane A having two or more alkenyl groups in the molecule, polysiloxane B having two or more hydrosilyl groups in the molecule, and adhesion promoter C.

[0038] (Polysiloxane A) Polysiloxane A may have two or more alkenyl groups in the side chain and / or at the terminal, and is preferably a polyorganosiloxane having alkenyl groups at least in the side chain, and more preferably a polyorganosiloxane having alkenyl groups only in the side chain. Furthermore, a copolymer containing a siloxane unit having an alkenyl group and a dialkylsiloxane unit or an alkylphenylsiloxane unit is preferred because it exhibits releasability while making it easy to adjust the amount of alkenyl groups in one molecule. The terminal silicon atom is preferably a trialkylsilane structure such as trimethylsilane.

[0039] Examples of the alkenyl group include alkenyl groups having 2 to 10 carbon atoms. The presence of such an alkenyl group results in an excellent strength of the release layer. The alkenyl group is preferably an alkenyl group having 2 to 8 carbon atoms, more preferably an alkenyl group having 2 to 6 carbon atoms, and particularly preferably a vinyl group or a hexenyl group. The silicon atom to which the alkenyl group is bonded may have multiple alkenyl groups bonded, but it is preferable that the alkenyl group is bonded to an alkyl group. In this case, the alkyl group is preferably a methyl group or the like.

[0040] In addition to the siloxane units having an alkenyl group, preferred examples of the dialkylsiloxane units contained in polysiloxane A include dimethylsiloxane units and phenylmethylsiloxane units.

[0041] An example of the polysiloxane is the polysiloxane represented by the following structural formula (1).

[0042] [ka]

[0043] In the above formula (1), l, m, and n are integers of 0 or greater (provided that m+n is 2 or greater), but it is preferable for l to be in the range of 1,000 to 10,000 and m+n to be in the range of 2 to 100, because this allows the crosslinking reaction to proceed smoothly while exhibiting sufficient releasability, thereby improving the strength of the release layer. From the same viewpoint, (m+n) / (l+m+n+2) is preferably in the range of 0.006 to 0.03, and more preferably in the range of 0.01 to 0.024.

[0044] Note that the above formula does not mean that it is a block copolymer, but merely indicates that the total number of units is 1, m, or n. Therefore, the polysiloxane in the above formula may be either a random copolymer or a block copolymer.

[0045] In the present invention, as the polysiloxane A, one of the above polysiloxanes may be used alone, or a polysiloxane having two or more different types of alkenyl groups in one molecule may be used, or two or more polysiloxanes having different structures, such as having different alkenyl groups, may be used in combination.

[0046] The weight-average molecular weight of polysiloxane A is preferably 300,000 or more and 600,000 or less, and particularly preferably 400,000 or more and 550,000 or less. In this specification, the weight-average molecular weight is a value measured by gel permeation chromatography (GPC) in terms of standard polystyrene.

[0047] When the weight-average molecular weight of polysiloxane A is 300,000 or more, the release layer after crosslinking has an appropriate coating strength, and the coating can be more effectively prevented from falling off. Also, when the weight-average molecular weight is 600,000 or less, the coating has good flatness after drying.

[0048] (Polysiloxane B) Polysiloxane B may have two or more hydrosilyl groups (groups in which hydrogen atoms are directly bonded to silicon atoms) on the side chain and / or terminal. Hydrogenpolysiloxanes having hydrosilyl groups at least on the side chain are preferred, and hydrogenpolysiloxanes having hydrosilyl groups only on the side chain are more preferred. Furthermore, copolymers containing siloxane units having hydrosilyl groups and dialkylsiloxane units or alkylphenylsiloxane units are preferred because they facilitate adjustment of the amount of hydrosilyl groups per molecule while exhibiting releasability. A silicon atom directly bonded to a hydrogen atom may have multiple hydrogen atoms directly bonded thereto, but it is preferred that the hydrogen atom be bonded to an alkyl group. In this case, the alkyl group is preferably a methyl group or the like. The terminal silicon atom preferably has a trialkylsilane structure such as trimethylsilane.

[0049] In addition to the siloxane unit having a hydrosilyl group, preferred examples of the dialkylsiloxane unit contained in polysiloxane B include a dimethylsiloxane unit and a phenylmethylsiloxane unit.

[0050] An example of such hydrogen polysiloxane is polysiloxane represented by the following structural formula (2).

[0051] [ka]

[0052] In the above formula (2), o is an integer of 0 or more and p is an integer of 2 or more, and it is preferable that o is in the range of 0 to 120, p is in the range of 2 to 120, and o+p is in the range of 2 to 240, because the crosslinking reaction proceeds smoothly and the strength of the release layer is improved. From the same viewpoint, it is also preferable that (p) / (o+p+2) is in the range of 0.3 to 1.

[0053] The above formula does not imply that it is a block copolymer, but merely indicates that the total number of units is o or p. Therefore, the hydrogenpolysiloxane in the above formula may be either a random copolymer or a block copolymer.

[0054] As the polysiloxane B, one of the above hydrogen polysiloxanes may be used alone, or two or more hydrogen polysiloxanes having different structures, such as different numbers of hydrosilyl groups in one molecule, may be used in combination.

[0055] The weight-average molecular weight of polysiloxane B is preferably 5,000 or more and 100,000 or less, and particularly preferably 7,000 or more and 20,000 or less. When the weight-average molecular weight of polysiloxane B is 5,000 or more, the release layer after crosslinking has an appropriate coating strength, making it possible to prevent the coating from falling off. Furthermore, when the weight-average molecular weight is 100,000 or less, the flatness of the coating after drying is good.

[0056] In the present invention, the release layer is primarily formed by addition polymerization of the polysiloxane A and polysiloxane B, preferably in the presence of a platinum-based catalyst, as described below. The term "addition polymerization" refers to a reaction in which a functional group at the molecular end or in the molecular side chain of polysiloxane A, represented by ~Si-CH=CH2 or ~Si-R-CH=CH2, and a functional group at the molecular end or in the molecular side chain of polysiloxane B, represented by H-Si~, form ~Si-CH2CH2-Si~ or ~Si-R-CH2CH2-Si~. The "~" in the functional group indicates that a further molecule is connected. This reaction can be expressed as the following reaction formula: Here, R represents an alkylene group having 1 to 8 carbon atoms.

[0057] [ka]

[0058] (Polysiloxane content) It is preferable that the molar ratio of the amount of hydrosilyl groups in the polysiloxane B to the amount of alkenyl groups in the polysiloxane A satisfies the following formula (c) in the curable composition. 1.0≦Si-H / Si-A≦3.8 (c) (In the formula, Si-H represents the molar amount of hydrosilyl groups, and Si-A represents the molar amount of alkenyl groups.)

[0059] In other words, the release layer satisfies formula (a), and to satisfy this formula, it is preferable to adjust the amount of hydrosilyl groups in polysiloxane B in the curable composition. It is desirable that the amount of hydrosilyl groups in polysiloxane B is a molar amount that is equal to or greater than the amount of alkenyl groups in polysiloxane A, up to 3.8 times. When the amount of hydrosilyl groups in polysiloxane B is equal to or greater than the amount of alkenyl groups in polysiloxane A, the coating film tends to have sufficient strength, and problems such as peeling of the release layer are less likely to occur. From this perspective, the molar ratio is more preferably 1.5 or greater, and even more preferably greater than 2.0.

[0060] On the other hand, when the amount of hydrosilyl groups in polysiloxane B is 3.8 times or less than the amount of alkenyl groups in polysiloxane A, the amount of hydrogen bond components contained in the surface free energy of the release layer becomes appropriate, resulting in good releasability. From this perspective, the above molar ratio is more preferably 3.5 or less, and even more preferably 3.0 or less.

[0061] In the present invention, it is preferable to satisfy formula (c) by adjusting the mixing mass ratio (B / A) of polysiloxane A to polysiloxane B in the curable composition to preferably 0.5 or more and 5 or less, more preferably 0.9 or more and 3 or less. By adjusting the mixing mass ratio (B / A) in this manner, polysiloxane A and polysiloxane B react appropriately, and it is possible to prevent either component from precipitating on the surface of the release layer.

[0062] (Adhesion promoter C) The release layer of the present invention contains an adhesion promoter C as an essential component. The adhesion promoter tends to migrate between the polyester film and the release layer during the formation of the release layer, improving the adhesion between the polyester film and the release layer. This prevents the release layer from falling off the polyester film during the process of processing a ceramic green sheet using the release film, resulting in a reduction in the defective rate in the production of ceramic green sheets.

[0063] In order to provide adhesion to the silicone resin of the release layer, the adhesion promoter desirably has a functional group that reacts with at least one of polysiloxane A and polysiloxane B. Specifically, it preferably has one or more functional groups that react with a hydrosilyl group and are selected from the group consisting of a vinyl group, an epoxy group, an acrylic group, and a methacrylic group.

[0064] The adhesion promoter is preferably a silane coupling agent to impart adhesion to the polyester film, which is compatible with the polysiloxane and can impart good adhesion to the polyester film (e.g., due to hydrogen bonding).

[0065] The silane coupling agent is preferably one represented by the following general formula:

[0066] [ka]

[0067] In the above general formula, X 1 represents the above functional group, and a represents an integer of 1 or more and 3 or less. In particular, a is preferably 1.

[0068] R 1 represents a hydrolyzable group selected from an alkoxy group, an acyloxy group, and a halogen, or an alkyl group. Among these, an alkoxy group and an acyloxy group are preferred. As the alkoxy group, an alkoxy group having 1 to 10 carbon atoms is preferred, an alkoxy group having 1 to 6 carbon atoms is more preferred, and a methoxy group and an ethoxy group are particularly preferred. As the acyloxy group, an acyloxy group having 2 to 11 carbon atoms is preferred, an acyloxy group having 2 to 7 carbon atoms is more preferred, and an acetoxy group is particularly preferred. As the halogen, a chloro group is preferred. As the alkyl group, an alkyl group having 1 to 6 carbon atoms is preferred.

[0069] R 1 By adopting the above-mentioned embodiment, the adhesiveness between the base film and the release layer is excellent.

[0070] In the above general formula, (4-a) R 1 represents that the bond is to Si, but these R 1 In the present invention, (4-a) R 1At least one of the R is preferably an alkoxy group or an acyloxy group, and all of the R 1 is more preferably an alkoxy group or an acyloxy group.

[0071] Silane coupling agents such as those of the general formula may be used alone or in combination of two or more, and it is also possible to use a reaction product obtained by reacting two or more silane coupling agents.

[0072] In order to improve the adhesion between the silane coupling agent and the polyester film, acetic acid, paratoluenesulfonic acid, or the like may be added to the silane coupling agent.

[0073] The amount of adhesion promoter added to the curable composition is preferably 1% by mass or more and 10% by mass or less, and more preferably 2.0% by mass or more and 8.0% by mass or less, relative to the total amount of polysiloxane A and polysiloxane B. When the amount is 1% by mass or more, the adhesion between the release layer and the substrate is improved, and when the amount is 10% by mass or less, excess adhesion promoter is less likely to adversely affect the release layer, resulting in improved flatness and releasability.

[0074] (Catalyst D) The curable composition for forming the release layer preferably further contains a catalyst D. The catalyst is not particularly limited as long as it can accelerate the curing reaction of the curable composition, but among these, platinum group metal compounds are preferred.

[0075] Examples of platinum group metal compounds include fine particle platinum, fine particle platinum adsorbed on a carbon powder carrier, chloroplatinic acid, alcohol-modified chloroplatinic acid, olefin complexes of chloroplatinic acid, palladium, rhodium, etc. When the curable composition contains such a catalyst, the curing reaction of the curable composition can proceed more efficiently.

[0076] The content of catalyst D in the curable composition according to this embodiment is preferably about 1 ppm or more and 1000 ppm or less relative to the total amount of solids other than catalyst D, from the viewpoint of adjusting the curing reaction rate within a suitable range.

[0077] (optional ingredient) In addition to the above components, the curable composition may contain a reaction inhibitor, a solvent, a silicone resin having no reactive functional groups, an antistatic agent, and the like.

[0078] (Release layer properties) The thickness of the release layer is preferably 0.005 μm or more and 0.1 μm or less, and particularly preferably 0.01 μm or more and 0.05 μm or less. When the thickness of the release layer is 0.005 μm or more, it is thick enough to function as a release layer. On the other hand, when the thickness of the release layer is 0.1 μm or less, peeling of the coating film from the release layer is less likely to occur.

[0079] The surface of the release layer is desirably flat to prevent defects from occurring in the ceramic green sheet that is coated and molded thereon, and preferably has an area surface average roughness (Sa) of 7 nm or less and a maximum protrusion height (Sp) of 100 nm or less. It is even more preferable that the area surface average roughness is 5 nm or less and a maximum protrusion height is 80 nm or less. For example, the maximum protrusion height (Sp) may be 45 nm or less.

[0080] If the average regional surface roughness is 7 nm or less and the maximum protrusion height is 100 nm or less, defects such as pinholes do not occur during ceramic green sheet formation, and the yield is good, which is preferable. The smaller the average regional surface roughness (Sa), the better, but it can be 0.1 nm or more, or 0.3 nm or more. The smaller the maximum protrusion height (Sp), the better, but it can be 1 nm or more, or 3 nm or more.

[0081] [Polyester film] The polyester film used as the substrate film (hereinafter sometimes referred to as substrate) in the present invention is a film containing polyester as a resin component, and preferably a film in which polyester is the largest component in the resin component (for example, 90 mass % or more).

[0082] The polyester constituting the polyester film is not particularly limited, and a film formed from a polyester commonly used as a substrate for release films can be used. Preferably, it is a crystalline linear saturated polyester composed of an aromatic dibasic acid component and a diol component, and more preferably, for example, polyethylene terephthalate, polyethylene-2,6-naphthalate, polybutylene terephthalate, polytrimethylene terephthalate, or a copolymer mainly composed of these resin components.

[0083] In particular, polyester films formed from polyethylene terephthalate are particularly suitable. The polyethylene terephthalate preferably contains 90 mol % or more, more preferably 95 mol % or more, of repeating ethylene terephthalate units, and may be copolymerized with small amounts of other dicarboxylic acid components or diol components. For example, from the viewpoint of cost, polyethylene terephthalate produced from only terephthalic acid and ethylene glycol is preferred. Furthermore, known additives such as antioxidants, light stabilizers, ultraviolet absorbers, and crystallization agents may be added within a range that does not impair the effects of the release film of the present invention. The polyester film is preferably a biaxially oriented polyester film due to its high bidirectional elastic modulus.

[0084] The intrinsic viscosity of the polyethylene terephthalate film is preferably 0.50 dL / g or more and 0.70 dL / g or less, more preferably 0.52 dL / g or more and 0.62 dL / g or less. When the intrinsic viscosity is 0.50 dL / g or more, breakage does not occur frequently during the stretching process, which is preferable. Conversely, when the intrinsic viscosity is 0.70 dL / g or less, cuttability is good when cutting to a predetermined product width, and dimensional defects do not occur, which is preferable. It is also preferable to thoroughly vacuum dry the raw material pellets.

[0085] In this specification, when simply referring to a "polyester film", it may refer to a polyester film having (laminated with) a surface layer A and a surface layer B.

[0086] The method for producing the polyester film of the present invention is not particularly limited, and any conventionally used method can be used. For example, the polyester can be melted in an extruder, extruded into a film, and cooled on a rotating cooling drum to obtain an unstretched film, which can then be biaxially stretched. A biaxially stretched film can be obtained by sequentially biaxially stretching a uniaxially stretched film in the longitudinal or transverse direction, or by simultaneously biaxially stretching an unstretched film in the longitudinal and transverse directions.

[0087] In the present invention, the stretching temperature during stretching of the polyester film is preferably equal to or higher than the second-order transition temperature (Tg) of the polyester, and the stretching is preferably 1 to 8 times, particularly 2 to 6 times, in both the longitudinal and transverse directions.

[0088] The polyester film preferably has a thickness of 12 μm or more and 50 μm or less, more preferably 15 μm or more and 38 μm or less, and even more preferably 19 μm or more and 33 μm or less. A film thickness of 12 μm or more is preferable because there is no risk of deformation due to heat during film production, processing, or molding. On the other hand, a film thickness of 50 μm or less is preferable because the amount of film discarded after use is not excessively large, thereby reducing the environmental impact.

[0089] The polyester film substrate may be a single layer or a multilayer structure of two or more layers. For example, the substrate film may be a polyester film having a surface layer A that is substantially free of particles having a particle size of 1.0 μm or more and a surface layer B that contains particles. Preferably, the surface layer A is substantially free of inorganic particles having a particle size of 1.0 μm or more.

[0090] In this embodiment, particles having a particle size of less than 1.0 μm and 1 nm or more may be present in the surface layer A. By making the surface layer A substantially free of particles having a particle size of 1.0 μm or more, such as inorganic particles, it is possible to reduce defects caused by the shape of particles in the substrate being transferred to the resin sheet.

[0091] In one embodiment, the surface layer A does not contain particles with a particle size of less than 1.0 μm, so that problems caused by the shape of particles in the substrate being transferred to the resin sheet can be more effectively prevented.

[0092] In one embodiment, the polyester film substrate is preferably a laminate film having a surface layer A substantially free of inorganic particles on at least one side, which more effectively prevents defects caused by the transfer of particle shapes in the substrate to the resin sheet.

[0093] For example, a preferred embodiment is that the surface layer A that does not substantially contain particles with a particle size of less than 1.0 μm also does not substantially contain particles with a particle size of 1.0 μm or more.

[0094] In the present invention, "substantially free of particles" means, for example, in the case of inorganic particles less than 1.0 μm in size, that the content of inorganic elements quantified by fluorescent X-ray analysis is 50 ppm or less, preferably 10 ppm or less, and most preferably below the detection limit. This is because even if particles are not actively added to the film, contaminants from foreign substances or dirt adhering to the raw resin or the production line or equipment during the film manufacturing process may peel off and be mixed into the film. Furthermore, "substantially free of particles with a particle size of 1.0 μm or more" means that particles with a particle size of 1.0 μm or more are not actively included.

[0095] In the case of a laminated polyester film having a multi-layer structure of two or more layers, it is preferable that a surface layer B that can contain inorganic particles or the like is provided on the surface opposite to a surface layer A that does not substantially contain inorganic particles.

[0096] In terms of the laminate structure, if the layer on the side to which the release layer is applied is Layer A, the layer on the opposite side is Layer B, and the other core layer is Layer C, the layer structure in the thickness direction can be a laminate structure such as release layer / A / B or release layer / A / C / B. Naturally, Layer C may be a multi-layer structure. Furthermore, the surface layer B may not contain inorganic particles. In this case, it is preferable to provide a coating layer D containing at least inorganic particles and a binder on the surface layer B to provide slip properties for winding the film into a roll.

[0097] In the polyester film substrate of the present invention, the surface layer B, which forms the surface opposite to the surface to which the release layer is applied, preferably contains inorganic particles, particularly silica particles and / or calcium carbonate particles, from the viewpoint of the slipperiness of the film and ease of air escape. The content of the inorganic particles contained in the surface layer B is preferably 5,000 ppm or more and 15,000 ppm or less in total.

[0098] In this case, the area surface average roughness (Sa) of the film of surface layer B is preferably in the range of 1 nm to 40 nm, more preferably in the range of 5 nm to 35 nm. When the total amount of silica particles and / or calcium carbonate particles is 5,000 ppm or more and Sa is 1 nm or more, air can be uniformly released when the film is wound into a roll, resulting in a good wound shape and good flatness, making it suitable for producing ultrathin ceramic green sheets. Furthermore, when the total amount of silica particles and / or calcium carbonate particles is 15,000 ppm or less and Sa is 40 nm or less, the lubricant is less likely to aggregate and large protrusions are not formed, which is preferable because it ensures stable quality when producing ultrathin ceramic green sheets.

[0099] In addition to silica and / or calcium carbonate, inactive inorganic particles and / or heat-resistant organic particles can also be used as particles contained in Layer B. However, 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. Heat-resistant organic particles include crosslinked polyacrylic particles, crosslinked polystyrene particles, and benzoguanamine particles. When silica particles are used, porous colloidal silica is preferred. When calcium carbonate particles are used, light calcium carbonate that has been surface-treated with a polyacrylic acid-based polymer compound is preferred from the viewpoint of preventing the lubricant from falling off.

[0100] The average particle diameter of the inorganic particles added to the surface layer B is preferably 0.1 μm or more and 2.0 μm or less, and particularly preferably 0.5 μm or more and 1.0 μm or less. An average particle diameter of 0.1 μm or more is preferable because the slipperiness of the release film is good. Furthermore, an average particle diameter of 2.0 μm or less is preferable because it does not adversely affect the smoothness of the release layer surface and therefore does not cause pinholes in the ceramic green sheet. The average particle diameter of the particles can be measured by observing the particles on the cross section of the processed film using a scanning electron microscope, observing 100 particles, and calculating the average value as the average particle diameter. The shape of the particles is not particularly limited as long as it satisfies the objectives of the present invention, and spherical particles and irregular, non-spherical particles can be used. The particle diameter of irregular particles can be calculated as the circle-equivalent diameter. The circle-equivalent diameter is calculated by dividing the area of ​​the observed particles by pi (π), calculating the square root, and then multiplying it by two.

[0101] From the viewpoint of reducing pinholes, it is preferable that recycled raw materials are not used for the surface layer A, which is the layer on which the release layer is to be formed, in order to prevent the inclusion of inorganic particles such as lubricants.

[0102] The thickness ratio of the surface layer A, which is the layer on which the release layer is provided, is preferably 20% to 50% of the total thickness of the base film. If it is 20% or more, the film is less likely to be affected from the inside by particles contained in the surface layer B, etc., and it is easy for the regional surface average roughness Sa to satisfy the above range, which is preferable. If it is 50% or less of the total thickness of the base film, the proportion of recycled materials used in the surface layer B can be increased, which is preferable as it reduces the environmental impact.

[0103] From an economical standpoint, recycled raw materials such as film scraps and PET bottles may be used in an amount of 50% by mass to 90% by mass for the layers (surface layer B or the aforementioned intermediate layer C) other than the surface layer A. Even in this case, it is preferable that the type and amount of lubricant contained in layer B, its particle size, and the area surface average roughness (Sa) satisfy the above ranges.

[0104] Furthermore, in order to improve the adhesion of a release layer or the like to be applied later, or to prevent static electricity, a coating layer D may be provided on the surface of the surface layer A and / or the surface layer B before stretching or after uniaxial stretching in the film-forming process, and corona treatment or the like may also be performed.

[0105] When surface layer B does not contain particles, it is also preferable to provide easy slippage by coating layer D containing particles on surface layer B. The means for providing this coating layer D is not particularly limited, but it is preferable to provide it by a so-called in-line coating method in which coating is performed during the film formation of the polyester film. Furthermore, when coating layer D that provides easy slippage is provided on the surface of the polyester film on the side on which the release layer is not laminated, the polyester film does not need to have surface layers A and B, and may be made of a single-layer polyester film that does not substantially contain inorganic particles.

[0106] The regional surface average roughness (Sa) of the surface layer B is preferably 40 nm or less, more preferably 35 nm or less, and even more preferably 30 nm or less. When the surface of the surface layer B or the monolayer polyester film on the side on which the release layer is not laminated is made slippery by the coating layer D, the Sa of that surface is measured on the surface on which the coating layer D is laminated, and is preferably in the same range as the regional surface average roughness (Sa) of the surface layer B.

[0107] It is preferable that the coating layer D on the surface of the polyester film on which the release layer is not laminated contains at least a binder resin and particles.

[0108] (Binder resin of coating layer D) The binder resin constituting the easy coating layer is not particularly limited, and specific examples of polymers include polyester resin, acrylic resin, urethane resin, polyvinyl resin (such as polyvinyl alcohol), polyalkylene glycol, polyalkyleneimine, methyl cellulose, hydroxycellulose, and starches. Among these, polyester resin, acrylic resin, and urethane resin are preferably used from the viewpoint of particle retention and adhesion. Furthermore, polyester resin is particularly preferred when compatibility with polyester film is taken into consideration. In order to achieve solubility and dispersibility in solvents and adhesion to the substrate film and other layers, the binder polyester is preferably a copolymer polyester. The polyester resin may be polyurethane-modified. Another preferred binder resin constituting the easy coating layer on the polyester substrate film is urethane resin. Examples of urethane resins include polycarbonate polyurethane resin. Furthermore, polyester resins and polyurethane resins may be used in combination, and the above-mentioned other binder resins may also be used in combination.

[0109] (Crosslinking agent for coating layer D) In the present invention, the easy-to-apply coating layer may be formed by containing a crosslinking agent in order to form a crosslinked structure in the easy-to-apply coating layer. By containing a crosslinking agent, it is possible to further improve adhesion under high temperature and high humidity conditions. Specific crosslinking agents include urea-based, epoxy-based, melamine-based, isocyanate-based, oxazoline-based, carbodiimide-based, and aziridine-based crosslinkers. In addition, in order to promote the crosslinking reaction, a catalyst or the like can be appropriately used as needed.

[0110] (Particles in coating layer D) The easy coating layer preferably contains lubricant particles to impart slipperiness to the surface. The particles may be inorganic or organic, and are not particularly limited. Examples of suitable particles 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, and magnesium hydroxide; and (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, and polyester. Silica is particularly preferred because it provides the coating layer with adequate slip properties.

[0111] 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, the particles are less likely to aggregate and lubricity can be ensured, which is preferable.

[0112] The average particle size of the particles is preferably 1000 nm or less, more preferably 800 nm or less, and even more preferably 600 nm or less. When the average particle size of the particles is 1000 nm or less, transparency is maintained and the particles do not fall off, which is preferable.

[0113] In addition, for example, it is also preferable to mix small particles having an average particle size of about 10 nm to 270 nm with large particles having an average particle size of about 300 nm to 1000 nm, in order to achieve both slipperiness and smoothness by reducing the average length of the roughness curve element (RSm) while maintaining the regional surface average roughness (Sa) and maximum protrusion height (Sp) described below small, and it is particularly preferable to combine small particles having an average particle size of 30 nm to 250 nm with large particles having an average particle size of 350 nm to 600 nm. When small particles and large particles are mixed, it is preferable to make the mass content of the small particles higher than the mass content of the large particles relative to the total solid content of the coating layer.

[0114] [Formation of release layer] In the present invention, the method for forming the release layer is not particularly limited, and a method is used in which a coating liquid in which a release compound is dissolved or dispersed is spread by coating or the like on one side of the polyester film substrate, the solvent and the like are removed by drying, and then the layer is cured.

[0115] When the release layer of the present invention is applied to a substrate film by solution coating, the drying temperature for drying the solvent is preferably 50°C or higher and 120°C or lower, more preferably 60°C or higher and 100°C or lower. The drying time is preferably 30 seconds or shorter, more preferably 20 seconds or shorter. After the solvent is dried, it is preferable to irradiate the film with active energy rays to promote the curing reaction. The active energy rays used in this case can be ultraviolet rays, electron beams, X-rays, etc., but ultraviolet rays are preferred because they are easy to use. The amount of ultraviolet rays to be irradiated is 30 mJ / cm. 2 More than 300mJ / cm 2 Preferably, it is equal to or less than 30 mJ / cm 2 , more preferably 30 mJ / cm 2 2 More than 200mJ / cm 2 Less than 30mJ / cm2 By setting the curing rate at 300 mJ / cm or more, the curing of the composition will proceed sufficiently, and the curing rate will be 300 mJ / cm 2 By setting the amount to the following, the processing speed can be improved, and therefore the release film can be produced economically, which is preferable.

[0116] In the present invention, the surface tension of the coating liquid when applying the release layer is not particularly limited, but is preferably 30 mN / m or less. By adjusting the surface tension to the above range, the wettability after application can be improved and the unevenness of the coating film surface after drying can be reduced.

[0117] As a method for applying the coating liquid, any known coating method can be applied, and conventionally known methods such as roll coating methods such as gravure coating and reverse coating, bar coating methods such as wire bar coating, die coating, spray coating, and air knife coating can be used.

[0118] [Ceramic green sheet] The release film for producing a ceramic green sheet of the present invention is suitably used for producing a ceramic green sheet. The method for producing a ceramic green sheet of the present invention is a method for producing a ceramic green sheet by molding a ceramic green sheet using the release film described above, and is characterized in that the molded ceramic green sheet has a thickness of 0.2 μm to 1.0 μm.

[0119] The ceramic green sheet is not particularly limited as long as it contains ceramic. In one embodiment, the release film of the present invention is a release film for molding a ceramic green sheet containing an inorganic compound. Examples of inorganic compounds include metal particles, metal oxides, and minerals, such as calcium carbonate, silica particles, aluminum particles, and barium titanate particles. Because the present invention has a highly smooth release layer, even in an embodiment in which the ceramic green sheet contains such an inorganic compound, defects that can be attributed to inorganic compounds, such as breakage of the ceramic green sheet and difficulty in peeling the ceramic green sheet from the release layer, can be suppressed.

[0120] The resin component forming the ceramic green sheet can be appropriately selected depending on the application. In one embodiment, the ceramic green sheet is a ceramic green sheet containing an inorganic compound. For example, the ceramic green sheet can contain barium titanate as the inorganic compound. Furthermore, the resin component can contain, for example, a polyvinyl butyral resin.

[0121] In one embodiment, the ceramic green sheet has a thickness of 0.2 μm or more and 1.0 μm or less.

[0122] For example, the present invention can provide a method for producing a release film for producing a ceramic green sheet containing such an inorganic compound. The method for producing a release film in the present invention may include a step of molding a ceramic green sheet having a thickness of 0.2 μm or more and 1.0 μm or less.

[0123] [Ceramic green sheets and ceramic capacitors] Generally, a multilayer ceramic capacitor has a rectangular parallelepiped ceramic body. First internal electrodes and second internal electrodes are alternately arranged inside the ceramic body along the thickness direction. The first internal electrodes are exposed at 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 at 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.

[0124] In one embodiment, the release film of the present invention is a release film and is used to produce such a multilayer ceramic capacitor.

[0125] For example, the method for producing a ceramic green sheet in which a ceramic green sheet is formed using the release film of the present invention can form a ceramic green sheet having a thickness of 0.2 μm or more and 1.0 μm or less.

[0126] More specifically, for example, ceramic green sheets are manufactured as follows. First, a ceramic slurry for forming a ceramic element is applied to the release film of the present invention as a carrier film and then dried. Ultra-thin ceramic green sheets with a thickness of 0.2 μm or more and 1.0 μm or less are in demand. A conductive layer for forming a first or second internal electrode is printed on the applied and dried ceramic green sheet. A mother laminate is obtained by appropriately stacking and pressing 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. The mother laminate is then divided into multiple pieces to produce green ceramic elements. The green ceramic elements are then fired to obtain ceramic elements. Then, first and second external electrodes are formed to complete a multilayer ceramic capacitor. [Example]

[0127] The present invention will be described in more detail below with reference to examples and comparative examples. In the present invention, physical properties were measured or evaluated by the following methods. Unless otherwise specified, "parts" means "parts by mass" and "%" means "% by mass."

[0128] (Amount of functional groups in polysiloxane mixture) Deuterated chloroform was added to a silicone mixture having the same mixing ratio as the polysiloxanes A and B used, to make a solid content of 10% by mass, and the resulting mixture was placed in an NMR tube. NMR measurement was performed on the sample placed in the NMR tube using a nuclear magnetic resonance apparatus (BRUKER, NMR AVANCE NEO 600), and the amount (mmol) of each functional group of alkenyl groups and hydrosilyl groups was quantified.

[0129] From the above measurement results, the molar ratio of alkenyl groups to hydrosilyl groups was calculated using the following formula. Molar ratio = Si-H / Si-A (In the formula, Si-H represents the molar amount of hydrosilyl groups, and Si-A represents the molar amount of alkenyl groups.)

[0130] (Weight average molecular weight) The sample solution, with the sample concentration adjusted to 0.2%, was filtered through a 0.2 μm membrane filter and analyzed by gel permeation chromatography (GPC) under the following conditions to determine the weight-average molecular weight. The molecular weight was calculated in terms of standard polystyrene. Equipment: TOSOH HLC-8320GPC Column: TSKgel SuperHM-H × 2 + TSKgel SuperH2000 (TOSOH) Solvent: 100% chloroform Flow rate: 0.6ml / min Concentration: 0.2% Injection volume: 20μl Temperature: 40℃ Detector: RI

[0131] (Release layer thickness) The release film was embedded in resin and cut into ultrathin sections using an ultramicrotome. Cross-sectional observation was then performed using a JEOL JEM2100 transmission electron microscope, and the film thickness of the release layer was measured from the TEM images. When the thickness was too thin to be accurately evaluated by cross-sectional observation, the Si intensity was measured using a fluorescent X-ray analyzer (Rigaku ZSX PRIMUS II), and the coating amount was calculated using the calibration curve method.

[0132] (Release layer area surface average roughness Sa, maximum protrusion height Sp) Measurements were taken under the following conditions using a non-contact surface shape measurement system (VertScan R550H-M100): The area surface average roughness (Sa) was calculated by averaging five measurements, and the maximum protrusion height (Sp) was calculated by measuring seven times and excluding the maximum and minimum values, and the maximum value of the five measurement results was used.

[0133] (Measurement conditions) Measurement mode: WAVE mode Objective lens: 50x 0.5x Tube Lens ·Measurement area 187μm×139μm (Analysis conditions) Surface correction: 4th order correction Interpolation: Full interpolation

[0134] (Surface free energy of release layer) A release film was fixed on a flat glass substrate, and 1.9 μL of water was dropped onto the release film using a contact angle meter (Kyowa Interface Science DM-501). 60 seconds after the droplet had come to rest, the angle between the droplet and the release layer was measured, and the average of five measurements was defined as θ1. Similarly, 0.9 μL of methylene iodide was dropped onto the release film, and 30 seconds after the droplet had come to rest, the angle between the droplet and the release layer was measured, and the average of five measurements was defined as θ2. Furthermore, 0.9 μL of ethylene glycol was dropped onto the release film, and 30 seconds after the droplet had come to rest, the angle between the droplet and the release layer was measured, and the average of five measurements was defined as θ3.

[0135] From the above θ1, θ2, θ3 and γLVnd, γLVnp, γLVnh, and γLn (where n = 1, 2, or 3, corresponding to water, methylene iodide, or ethylene glycol) of water, methylene iodide, and ethylene glycol listed in Table 2, the dispersion component γSVd, dipole component γSVp, and hydrogen bond component γSVh of the surface free energy of the release layer were calculated by the following formulas, and the sum of these was taken as the surface free energy γS of the release layer. The unit of surface free energy and each component is "mJ / m 2 "

[0136] [Table 2]

[0137]

number

[0138] γSVd+γSVp+γSVh=γS (Peeling force of ceramic green sheet) Slurry composition I, consisting of the materials listed below, was stirred and mixed for 10 minutes, and then dispersed for 10 minutes using a bead mill with zirconia beads of 0.5 mm diameter to obtain a primary dispersion. Slurry composition II, consisting of the materials listed below, was then added to the primary dispersion in a ratio of (slurry composition I):(slurry composition II) = 3.4:1.0, and secondary dispersion was performed for 10 minutes using a bead mill with zirconia beads of 0.5 mm diameter to obtain a ceramic slurry. (Slurry Composition I) Toluene 22.3 parts by mass Ethanol 18.3 parts by mass Barium titanate (average particle size 100 nm) 57.5 parts by mass Homogenol L-18 (Kao Corporation) 1.9 parts by mass (Slurry Composition II) Toluene 39.6 parts by mass Ethanol 39.6 parts by mass Dioctyl phthalate 3.3 parts by mass Polyvinyl butyral (S-LEC BM-S, manufactured by Sekisui Chemical Co., Ltd.) 16.3 parts by mass 1-Ethyl-3-methylimidazolium ethyl sulfate 0.5 parts by mass The release surface of the resulting release film sample was then coated with an applicator to a thickness of 1.0 μm after drying and dried at 60°C for 1 minute to obtain a release film with a ceramic green sheet. The resulting release film with a ceramic green sheet was then destaticized using a static eliminator (Keyence Corporation, SJ-F020) and then peeled using a peel tester (Kyowa Interface Science Co., Ltd., VPA-3, load cell load 0.1 N) at a peel angle of 90°, a peel temperature of 25°C, and a peel speed of 10 m / min. For the peel direction, double-sided adhesive tape (Nitto Denko Corporation, No. 535A) was attached to the SUS plate attached to the peel tester, and the release film was fixed on the double-sided tape by adhering the ceramic green sheet side to the tape. The release film was then peeled by pulling the release film side. The average peel force was calculated from the measured values ​​over a peel distance of 20 mm to 70 mm. A total of five measurements were performed, and the average peel force was used.

[0139] (Evaluation of pinholes in ceramic green sheets) In the same manner as in the evaluation of the peel strength of the ceramic green sheet, a ceramic green sheet having a thickness of 1 μm was molded on the release surface of the release film. Next, the release film was peeled off from the molded ceramic green sheet-attached release film to obtain a ceramic green sheet. 2 Light was applied to the surface opposite to the ceramic slurry coating within the range of 100 mm, and the occurrence of pinholes through which light was transmitted was observed, and the occurrence was visually evaluated according to the following criteria. ○: No pinholes ×: One or more pinholes

[0140] (Amount of Si transferred to PVB sheet) Polyvinyl butyral (S-LEC BM-S, manufactured by Sekisui Chemical Co., Ltd.) was applied to the release surface of the release film sample using an applicator so that the resin thickness after drying would be 1.0 μm, and then dried at 60°C for 1 minute to obtain a release film with a PVB sheet. After leaving the release film with the PVB sheet to stand in an environment of 23°C and 65 RH for 24 hours, the PVB sheet was peeled off from the release film, and the Si intensity (Kcps) of the surface of the PVB sheet that had come into contact with the release film was measured using a fluorescent X-ray analyzer (ZSX PRIMUS II, manufactured by Rigaku).

[0141] (Set-off of release layer onto polyester substrate) Six release film samples were cut into 5cm x 5cm pieces, and the six pieces were stacked so that the release surface and the opposite surface of the release surface were in contact, and pressure treatment was performed for 10 minutes with a load of 30MPa applied. After that, the six release films were peeled off, and the opposite surface of each of the six pieces was painted red with a red magic marker (MGD-T2 made by Teranishi Chemical Industry Co., Ltd.) to check whether the magic marker ink was repelled. 〇: No repelling spots on any of the 6 sheets ×: One or more repelling spots on any of the six sheets

[0142] (Adhesion of release layer over time) After storing the release film sample in an environment of 60°C and 90% RH for 3 days, the release layer was subjected to a Gakushin friction tester (Yamaguchi Scientific Industry Co., Ltd.) with a load of 200 gf / 25 mm on the head using pearl paper (Toyobo Ester Film P4255-35, Toyobo Co., Ltd.) with gauze (Hakujuji Gauze, Hakujuji Co., Ltd.) at the contact point between the load head and the film. 2 (5mm x 5mm) [0.0785MPa], and the film was rubbed against the load head by going back and forth 10 times. Then, the release surface was painted red with a red magic marker (MGD-T2 manufactured by Teranishi Chemical Industry Co., Ltd.) to check whether the magic marker ink was repelled. 〇: Magic ink repels △: There are some areas where the magic marker does not repel. ×: Magic ink is not repelled

[0143] (Preparation of polyethylene terephthalate pellets (PET(I))) The esterification reactor used was a continuous esterification reactor consisting of a three-stage complete mixing vessel equipped with a stirrer, a partial condenser, a raw material inlet, and a product outlet. The TPA (terephthalic acid) was fed at 2 tons / h, EG (ethylene glycol) at 2 moles per mole of TPA, and antimony trioxide at a concentration that would result in 160 ppm Sb atoms in the PET produced. The resulting slurry was continuously fed into the first esterification reactor and reacted at 255°C for an average residence time of 4 hours at atmospheric pressure. Next, the reaction product in the first esterification reactor was continuously removed from the system and fed to a second esterification reactor, and EG distilled off from the first esterification reactor was fed into the second esterification reactor in an amount of 8 mass% based on the produced PET. Further, an EG solution containing magnesium acetate tetrahydrate in an amount such that the Mg atoms would be 65 ppm based on the produced PET, and an EG solution containing TMPA (trimethyl phosphate) in an amount such that the P atoms would be 40 ppm based on the produced PET were added, and the reaction was carried out at atmospheric pressure for an average residence time of 1 hour at 260°C. Next, the reaction product in the second esterification reactor was continuously removed from the system and fed to a third esterification reactor, and the reaction was carried out at 39 MPa (400 kg / cm) using a high-pressure disperser (manufactured by Nippon Seiki Co., Ltd.). 2 0.2% by mass of porous colloidal silica (average particle size: 0.9 μm), which had been dispersed at a pressure of 1000 kJ / cm² for an average number of passes (5 times), and 0.4% by mass of synthetic calcium carbonate (average particle size: 0.6 μm), each containing 1% by mass of ammonium salt of polyacrylic acid per calcium carbonate, were added as 10% EG slurry and reacted at atmospheric pressure for an average residence time of 0.5 hours at 260°C. The esterification reaction product produced in the third esterification reactor was continuously fed to a three-stage continuous polycondensation reactor for polycondensation. The product was filtered through a filter made of sintered stainless steel fibers with a 95% cutoff diameter of 20 μm, then ultrafiltered and extruded into water. After cooling, the product was cut into chips to yield PET chips with an intrinsic viscosity of 0.60 dL / g (hereinafter abbreviated as PET(I)). The lubricant content in the PET chips was 0.6% by mass.

[0144] (Preparation of polyethylene terephthalate pellets (PET(II))) On the other hand, in the production of the PET(I) chips, PET chips containing absolutely no particles such as calcium carbonate or silica and having an intrinsic viscosity of 0.62 dl / g were obtained (hereinafter abbreviated as PET(II)).

[0145] (Manufacturing of laminated film X1) These PET chips were dried and then melted at 285°C. Then, the melts were melted at 290°C in separate melt extruders. The resulting mixture was filtered through two filters: one containing sintered stainless steel fibers with a 95% cutoff diameter of 15 μm, and the other containing sintered stainless steel particles with a 95% cutoff diameter of 15 μm. The resulting mixture was then combined in a feedblock. The resulting mixture was laminated with PET (I) as surface layer B (the layer opposite the release surface) and PET (II) as surface layer A (the release surface). The resulting sheet was extruded (cast) at a speed of 45 m / min and electrostatically bonded and cooled on a casting drum at 30°C to obtain an unstretched polyethylene terephthalate sheet with an intrinsic viscosity of 0.59 dl / g. The layer ratio was adjusted to PET (I) / (II) = 60% by mass / 40% by calculation of the extrusion rate. The unstretched sheet was then heated with an infrared heater and stretched 3.5 times in the machine direction at a roll temperature of 80°C using a roll speed differential. The film was then introduced into a tenter and stretched 4.2 times in the transverse direction at 140°C. It was then heat-treated at 210°C in a heat-setting zone. It was then relaxed 2.3% in the transverse direction at 170°C to obtain a biaxially stretched polyethylene terephthalate film X1 having a thickness of 31 μm. The surface layer A of the obtained film X1 had an Sa of 1 nm, and the surface layer B had an Sa of 28 nm.

[0146] (Manufacturing of laminated film X2) Laminate film X2 was prepared in the same manner as laminate film X1, using PET (II) on both the surface layer A and surface layer B. The laminate was extruded (cast) into a sheet at a speed of 45 m / min, electrostatically bonded to a casting drum at 30°C, and cooled to obtain an unstretched polyethylene terephthalate sheet with an intrinsic viscosity of 0.59 dl / g. This unstretched PET sheet was heated to 100°C using a group of heated rolls and an infrared heater, and then stretched 3.5 times in the longitudinal direction using a group of rolls with different peripheral speeds to obtain a uniaxially stretched PET film. The following lubrication coating solution was then applied to one side of the PET film using a bar coater and dried at 80°C for 15 seconds. The coating thickness was adjusted to 0.1 μm after final stretching and drying. The film was then stretched 4.0 times in the width direction at 150°C in a tenter, and while the length of the film in the width direction was fixed, it was heated at 230°C for 0.5 seconds and further subjected to a 3% width direction relaxation treatment at 230°C for 10 seconds to obtain an in-line coated polyester film with a thickness of 31 μm. The surface layer A of the obtained film X2 had an Sa of 1 nm, and the surface layer B had an Sa of 14 nm.

[0147] (Smooth coating liquid) Water 45.82 parts by mass Isopropyl alcohol 35.00 parts by mass Acrylic polyol resin 10.36 parts by mass (DSM Coating Resins NeoCryl A-614, Tg 74°C, acid value 55%, solid content 32% by mass) Oxazoline crosslinking agent D-1 5.68 parts by mass (Solid content concentration 25% by mass) Acrylic particle water dispersion 2.37 parts by mass (Nippon Shokubai, product name MX200W, average particle size 350nm, solid concentration 10% by mass) Acrylic particle water dispersion 0.47 parts by mass (Nippon Shokubai, product name MX300W, average particle size 450 nm, solid content concentration 10% by mass) Surfactant H-1 (fluorine-based, solids concentration 10% by mass) 0.30 parts by mass

[0148] Example 1 A vinyl-modified silicone resin represented by structural formula (1) (weight average molecular weight: 466,000, in structural formula (1), l=3,120, m=46, n=0) was used as polysiloxane A, and a polymethylhydrogensiloxane represented by structural formula (2) (weight average molecular weight: 8,400, in structural formula (2), o=3, p=65) was used as polysiloxane B. A silicone mixture R1 was prepared by adjusting the molar ratio (amount of hydrosilyl groups / amount of alkenyl groups) to 2.0, and the following coating liquid M1 for forming a release layer was prepared, containing the silicone mixture R1, an adhesion promoter S1, and a catalyst P1. (Release layer forming coating liquid M1) Methyl ethyl ketone 64.3 parts Toluene 34.0 parts 1.5 parts silicone mixture R1 Adhesion promoter S1 0.083 parts (SD7200 manufactured by Dow Toray Industries, Inc. (reaction product of vinyltriacetoxysilane and glycidoxypropyltrimethoxysilane, solid concentration 90%) Catalyst P1 0.1 parts (SRX212 (1,1,3,3-tetramethyl-1,3-divinyldisiloxane platinum complex, solids concentration 5%) manufactured by Dow Toray Industries, Inc. The release layer-forming coating solution M1 having the above composition was applied onto the surface layer A of the laminated film X1 using reverse gravure so that the coating thickness after drying would be 0.020 μm. Then, the processing speed was adjusted so that the film entered the first drying oven 0.5 seconds later, and the film was heated and dried continuously at a first drying oven temperature of 120°C and a second drying oven temperature of 90°C. After the drying process, the film was irradiated on a cooling roll with an ultraviolet irradiator (Heraeus, H bulb) at an integrated light dose of 100 mJ / cm. 2 The release layer was cured by irradiating it with ultraviolet light, and a release film for producing ceramic green sheets was obtained. The release layer-forming coating solution and laminated film used in this process are outlined in Table 3. The physical properties of the obtained release film were evaluated, and the results are shown in Table 4.

[0149] Example 2 A vinyl-modified silicone resin represented by structural formula (1) (weight average molecular weight: 495,000, in structural formula (1), l = 2,820, m = 60, n = 0) was used as polysiloxane A, and a polymethylhydrogensiloxane represented by structural formula (2) (weight average molecular weight: 8,400, in structural formula (2), o = 3, p = 65) was used as polysiloxane B, and the molar ratio (amount of hydrosilyl groups / amount of alkenyl groups) of these was adjusted to 1.0 to prepare a silicone mixture R2. A release film for producing a ceramic green sheet was obtained in the same manner as in Example 1, except that a coating liquid M2 for forming a release layer described below containing the silicone mixture R2, an adhesion promoter S1, and a catalyst P1 was prepared. (Coating liquid M2 for mold release layer formation) Methyl ethyl ketone 64.3 parts Toluene 34.0 parts Silicone mixture R2 1.5 parts Adhesion promoter S1 0.083 parts Catalyst P1 0.1 parts The release layer-forming coating liquid and laminated film used are outlined in Table 3. Table 4 also shows the results of evaluation of various physical properties of the resulting release film.

[0150] Example 3 A vinyl-modified silicone resin represented by structural formula (1) (weight average molecular weight: 520,000, in structural formula (1), l=3,700, m=40, n=0) was used as polysiloxane A, and a polymethylhydrogensiloxane represented by structural formula (2) (weight average molecular weight: 8,400, in structural formula (2), o=3, p=65) was used as polysiloxane B, and the molar ratio (amount of hydrosilyl groups / amount of alkenyl groups) of these was adjusted to 3.0 to prepare a silicone mixture R3. A release film for producing a ceramic green sheet was obtained in the same manner as in Example 1, except that a coating liquid M3 for forming a release layer described below containing the silicone mixture R3, an adhesion promoter S1, and a catalyst P1 was prepared. (Release layer forming coating liquid M3) Methyl ethyl ketone 64.3 parts Toluene 34.0 parts 1.5 parts silicone mixture R3 Adhesion promoter S1 0.083 parts Catalyst P1 0.1 parts The release layer-forming coating liquid and laminated film used are outlined in Table 3. Table 4 also shows the results of evaluation of various physical properties of the resulting release film.

[0151] Example 4 A release film for producing a ceramic green sheet was obtained in the same manner as in Example 1, except that the coating liquid M1 for forming a release layer was applied so that the coating thickness after drying would be 0.050 μm. An overview of the coating liquid for forming a release layer and the laminated film used at that time is shown in Table 3. In addition, the results of evaluation of various physical properties of the obtained release film are shown in Table 4.

[0152] Example 5 A release film for producing a ceramic green sheet was obtained in the same manner as in Example 1, except that the coating liquid M1 for forming a release layer was applied so that the coating thickness after drying would be 0.080 μm. An overview of the coating liquid for forming a release layer and the laminated film used at that time is shown in Table 3. In addition, the results of evaluation of various physical properties of the obtained release film are shown in Table 4.

[0153] Example 6 A release film for producing a ceramic green sheet was obtained in the same manner as in Example 1, except that the following coating liquid M4 for forming a release layer, which contains a silicone mixture R1, an adhesion promoter S2, and a catalyst P1, was applied so that the coating thickness after drying was 0.020 μm. (Coating liquid M4 for mold release layer formation) Methyl ethyl ketone 64.3 parts Toluene 34.0 parts 1.5 parts silicone mixture R1 Adhesion promoter S2 0.075 parts (Shinetetsu Chemical Co., Ltd., KBM503 (3-methacryloxypropyltrimethoxysilane, solid concentration 100%)) p-Toluenesulfonic acid 0.008 parts Catalyst P1 0.1 parts The release layer-forming coating liquid and laminated film used are outlined in Table 3. Table 4 also shows the results of evaluation of various physical properties of the resulting release film.

[0154] Example 7 A release film for producing a ceramic green sheet was obtained in the same manner as in Example 1, except that the following coating liquid M5 for forming a release layer, which contained a silicone mixture R1, an adhesion promoter S3, and a catalyst P1, was applied so that the coating thickness after drying was 0.020 μm. (Release layer forming coating liquid M5) Methyl ethyl ketone 64.3 parts Toluene 34.0 parts 1.5 parts silicone mixture R1 Adhesion promoter S3 0.075 parts (Shinetetsu Chemical Co., Ltd., KBM403 (3-glycidoxypropyltrimethoxysilane, solid concentration 100%)) p-Toluenesulfonic acid 0.008 parts Catalyst P1 0.1 parts The release layer-forming coating liquid and laminated film used are outlined in Table 3. Table 4 also shows the results of evaluation of various physical properties of the resulting release film.

[0155] Example 8 A release film for producing a ceramic green sheet was obtained in the same manner as in Example 1, except that the following coating liquid M6 for forming a release layer, which contained a silicone mixture R1, an adhesion promoter S4, and a catalyst P1, was applied so that the coating thickness after drying was 0.020 μm. (Release layer forming coating liquid M6) Methyl ethyl ketone 64.3 parts Toluene 34.0 parts 1.5 parts silicone mixture R1 Adhesion promoter S4 0.075 parts (Shinetetsu Chemical Co., Ltd., KBM1003 (vinyltrimethoxysilane, solid concentration 100%)) p-Toluenesulfonic acid 0.008 parts Catalyst P1 0.1 parts The release layer-forming coating liquid and laminated film used are outlined in Table 3. Table 4 also shows the results of evaluation of various physical properties of the resulting release film.

[0156] Example 9 A release film for producing a ceramic green sheet was obtained in the same manner as in Example 1, except that the following coating solution M7 for forming a release layer, which had a different content ratio of the adhesion promoter S1, was applied so that the coating amount after drying was 0.020 μm. (Release layer forming coating liquid M7) Methyl ethyl ketone 64.4 parts Toluene 34.0 parts 1.5 parts silicone mixture R1 Adhesion promoter S1 0.042 parts Catalyst P1 0.1 parts The release layer-forming coating liquid and laminated film used are outlined in Table 3. Table 4 also shows the results of evaluation of various physical properties of the resulting release film.

[0157] Example 10 A release film for producing a ceramic green sheet was obtained in the same manner as in Example 1, except that the following coating solution M8 for forming a release layer, which had a different content ratio of the adhesion promoter S1, was applied so that the coating thickness after drying was 0.020 μm. (Release layer forming coating liquid M8) Methyl ethyl ketone 64.3 parts Toluene 34.0 parts 1.5 parts silicone mixture R1 Adhesion promoter S1 0.125 parts Catalyst P1 0.1 parts The release layer-forming coating liquid and laminated film used are outlined in Table 3. Table 4 also shows the results of evaluation of various physical properties of the resulting release film.

[0158] Example 11 A release film for producing a ceramic green sheet was obtained in the same manner as in Example 1, except that the following coating solution M9 for forming a release layer, which had a different content ratio of the adhesion promoter S1, was applied so that the coating amount after drying was 0.020 μm. (Release layer forming coating liquid M9) Methyl ethyl ketone 64.3 parts Toluene 34.0 parts 1.5 parts silicone mixture R1 Adhesion promoter S1 0.008 parts Catalyst P1 0.1 parts The release layer-forming coating liquid and laminated film used are outlined in Table 3. Table 4 also shows the results of evaluation of various physical properties of the resulting release film.

[0159] Example 12 A release film for producing a ceramic green sheet was obtained in the same manner as in Example 1, except that the following coating solution M10 for forming a release layer, which had a different content ratio of the adhesion promoter S1, was applied so that the coating amount after drying would be 0.020 μm. (Release layer forming coating liquid M10) Methyl ethyl ketone 64.1 parts Toluene 34.0 parts 1.5 parts silicone mixture R1 Adhesion promoter S1 0.250 parts Catalyst P1 0.1 parts The release layer-forming coating liquid and laminated film used are outlined in Table 3. Table 4 also shows the results of evaluation of various physical properties of the resulting release film.

[0160] Example 13 A release film for producing a ceramic green sheet was obtained in the same manner as in Example 1, except that the coating liquid for forming a release layer M1 was applied to the laminate film X2. An overview of the coating liquid for forming a release layer and the laminate film used at that time is shown in Table 3. In addition, the results of evaluation of various physical properties of the obtained release film are shown in Table 4.

[0161] Example 14 A vinyl-modified silicone resin represented by structural formula (1) (weight average molecular weight: 18,000, in structural formula (1), l = 110, m = 3, n = 1) was used as polysiloxane A, and a polymethylhydrogensiloxane represented by structural formula (2) (weight average molecular weight: 8,400, in structural formula (2), o = 3, p = 65) was used as polysiloxane B, and the molar ratio (amount of hydrosilyl groups / amount of alkenyl groups) of these was adjusted to 1.6 to prepare a silicone mixture R4. A release film for producing a ceramic green sheet was obtained in the same manner as in Example 1, except that a coating liquid M11 for forming a release layer described below containing silicone mixture R4, adhesion promoter S1, and catalyst P1 was prepared. (Release layer forming coating liquid M11) Methyl ethyl ketone 64.3 parts Toluene 34.0 parts 1.5 parts silicone mixture R4 Adhesion promoter S1 0.083 parts Catalyst P1 0.1 parts The release layer-forming coating liquid and laminated film used are outlined in Table 3. Table 4 also shows the results of evaluation of various physical properties of the resulting release film.

[0162] Example 15 A vinyl-modified silicone resin represented by structural formula (1) (weight average molecular weight: 500,000, in structural formula (1), l=3460, m=25, n=4) was used as polysiloxane A, and a polymethylhydrogensiloxane represented by structural formula (2) (weight average molecular weight: 8,400, in structural formula (2), o=3, p=65) was used as polysiloxane B, and the molar ratio (amount of hydrosilyl groups / amount of alkenyl groups) of these was adjusted to 3.5 to prepare a silicone mixture R5. A release film for producing a ceramic green sheet was obtained in the same manner as in Example 1, except that a coating liquid M12 for forming a release layer described below containing silicone mixture R5, adhesion promoter S1, and catalyst P1 was prepared. (Release layer forming coating liquid M12) Methyl ethyl ketone 64.3 parts Toluene 34.0 parts 1.5 parts silicone mixture R5 Adhesion promoter S1 0.083 parts Catalyst P1 0.1 parts The release layer-forming coating liquid and laminated film used are outlined in Table 3. Table 4 also shows the results of evaluation of various physical properties of the resulting release film.

[0163] (Comparative Example 1) A vinyl-modified silicone resin represented by structural formula (1) (weight average molecular weight: 480,000; in structural formula (1), l = 3,220, m = 13, n = 7) was used as polysiloxane A, and a polymethylhydrogensiloxane represented by structural formula (2) (weight average molecular weight: 8,400; in structural formula (2), o = 3, p = 65) was used as polysiloxane B, and the molar ratio (amount of hydrosilyl groups / amount of alkenyl groups) of these was adjusted to 4.0 to prepare a silicone mixture R6. A release film for producing a ceramic green sheet was obtained in the same manner as in Example 1, except that a coating liquid M13 for forming a release layer described below containing silicone mixture R6, adhesion promoter S1, and catalyst P1 was prepared. (Release layer forming coating liquid M13) Methyl ethyl ketone 64.3 parts Toluene 34.0 parts 1.5 parts silicone mixture R6 Adhesion promoter S1 0.083 parts Catalyst P1 0.1 parts The release layer-forming coating liquid and laminated film used are outlined in Table 3. Table 4 also shows the results of evaluation of various physical properties of the resulting release film.

[0164] (Comparative Example 2) A vinyl-modified silicone resin represented by structural formula (1) (weight average molecular weight: 462,000, in structural formula (1), l = 2,820, m = 60, n = 0) was used as polysiloxane A, and a polymethylhydrogensiloxane represented by structural formula (2) (weight average molecular weight: 8,400, in structural formula (2), o = 3, p = 65) was used as polysiloxane B, and the molar ratio (amount of hydrosilyl groups / amount of alkenyl groups) of these was adjusted to 0.8 to prepare a silicone mixture R7. A release film for producing a ceramic green sheet was obtained in the same manner as in Example 1, except that a coating liquid M14 for forming a release layer described below containing silicone mixture R7, adhesion promoter S1, and catalyst P1 was prepared. (Release layer forming coating liquid M14) Methyl ethyl ketone 64.3 parts Toluene 34.0 parts 1.5 parts silicone mixture R7 Adhesion promoter S1 0.083 parts Catalyst P1 0.1 parts The release layer-forming coating liquid and laminated film used are outlined in Table 3. Table 4 also shows the results of evaluation of various physical properties of the resulting release film.

[0165] (Comparative Example 3) A release film for producing a ceramic green sheet was obtained in the same manner as in Example 1, except that the following coating liquid M15 for forming a release layer, which contains a silicone mixture R1, an adhesion promoter S5, and a catalyst P1, was applied so that the coating thickness after drying was 0.020 μm. (Release layer forming coating liquid M15) Methyl ethyl ketone 64.3 parts Toluene 34.0 parts 1.5 parts silicone mixture R1 Adhesion promoter S5 0.075 parts (Shinetetsu Chemical Co., Ltd., KBM503 (N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, solid concentration 100%)) p-Toluenesulfonic acid 0.008 parts Catalyst P1 0.1 parts The release layer-forming coating liquid and laminated film used are outlined in Table 3. Table 4 also shows the results of evaluation of various physical properties of the resulting release film.

[0166] Comparative Example 4 A release film for producing a ceramic green sheet was obtained in the same manner as in Example 1, except that the following coating liquid M16 for forming a release layer, which contains a silicone mixture R1 and a catalyst P1 but does not contain an adhesion promoter, was applied so that the coating thickness after drying was 0.020 μm. (Release layer forming coating liquid M16) Methyl ethyl ketone 64.4 parts Toluene 34.0 parts 1.5 parts silicone mixture R1 Catalyst P1 0.1 parts The release layer-forming coating liquid and laminated film used are outlined in Table 3. Table 4 also shows the results of evaluation of various physical properties of the resulting release film.

[0167] [Table 3]

[0168] [Table 4]

[0169] As the results in Table 4 show, in Examples 1 to 15, the release layer was a layer formed by curing a curable composition containing polysiloxane A, polysiloxane B, and adhesion promoter C, and satisfied formulas (a) and (b). Therefore, release films were obtained that had excellent release properties and were less susceptible to transfer and detachment of the release layer or poor adhesion.

[0170] In Example 11, the adhesion promoter content was too low, resulting in a small improvement in adhesion over time, indicating that there is a preferred lower limit for the adhesion promoter content. In Example 12, the adhesion promoter content was too high, resulting in a slightly high release force, indicating that there is a preferred upper limit for the adhesion promoter content. In Example 14, the weight-average molecular weight of polysiloxane A was too low, resulting in a slightly high amount of silicone transferred to the PVB, indicating that there is a preferred lower limit for the weight-average molecular weight of polysiloxane A. In Example 15, the molar ratio (amount of hydrosilyl groups / amount of alkenyl groups) was slightly high, resulting in a slightly high ceramic release force, indicating that there is a preferred upper limit for the molar ratio.

[0171] In contrast, in Comparative Example 1, where the molar ratio (amount of hydrosilyl groups / amount of alkenyl groups) was large and exceeded the upper limit of formula (a), the peel force increased. In Comparative Example 2, where the molar ratio (amount of hydrosilyl groups / amount of alkenyl groups) was small and therefore below the lower limit of formula (a), the offset was poor, and the release layer was transferred to the surface of the substrate opposite the release layer, raising concerns about significant contamination of the ceramic green sheet processing process, and the amount of Si transferred to the PVB sheet was also large. In Comparative Example 3, where an undesirable adhesion promoter was used and the upper limit of formula (a) was exceeded, the adhesion promoter inhibited curing, resulting in poor offset and a significant concern about contamination of the ceramic green sheet processing process. In Comparative Example 4, where no adhesion promoter was used, the peel force increased, adhesion over time decreased, and the amount of Si transferred to the PVB sheet was also slightly increased. [Industrial Applicability]

[0172] According to the present invention, by improving the smoothness and releasability of the release layer, a release film is provided that can mold ceramic green sheets with few defects even in ultra-thin products with a thickness of 1 μm or less, thereby making it possible to produce ceramic green sheets without the risk of defects.

Claims

1. A release film for producing a ceramic green sheet, comprising a polyester film and a release layer, the release layer is a layer obtained by curing a curable composition containing: polysiloxane A having two or more alkenyl groups in the molecule; polysiloxane B having two or more hydrosilyl groups in the molecule; and adhesion promoter C; The adhesion promoter C is a reaction product obtained by reacting one or more silane coupling agents represented by the following general formula: 【Chemical 1】 (where X １ has one or more functional groups selected from the group consisting of a vinyl group, an epoxy group, an acrylic group, and a methacrylic group, a represents an integer of 1 or more and 3 or less, R １ represents a hydrolyzable group selected from an alkoxy group, an acyloxy group, and a halogen, or an alkyl group. The surface free energy γS (mJ / m ２ ) and the hydrogen bond component γSVh (mJ / m ２ ) and satisfy the following formula (a) and formula (b): 1.0≦γSVh / γS*100≦6.5 (a) γS≦30 (b)

2. 2. The release film for producing a ceramic green sheet according to claim 1, wherein the weight average molecular weight of the polysiloxane A is 300,000 or more and 600,000 or less.

3. 2. The release film for producing a ceramic green sheet according to claim 1, wherein the molar ratio of the amount of hydrosilyl groups in the polysiloxane B to the amount of alkenyl groups in the polysiloxane A in the curable composition satisfies the following formula (c): 1.0≦Si-H / Si-A≦3.8 (c) (In the formula, Si-H represents the molar amount of hydrosilyl groups, and Si-A represents the molar amount of alkenyl groups.)

4. 5. The release film for producing a ceramic green sheet according to claim 1, wherein the curable composition contains 1% by mass or more and 10% by mass or less of the adhesion promoter C relative to the total amount of the polysiloxane A and the polysiloxane B.

5. the polyester film has a surface layer A that is substantially free of inorganic particles, the release layer is laminated on the surface layer A to a thickness of 0.005 μm or more and 0.1 μm or less; 2. The release film for producing a ceramic green sheet according to claim 1, wherein the release layer has a maximum protrusion height (Sp) on the surface of the release layer of 100 nm or less.

6. A method for producing a ceramic green sheet, comprising molding a ceramic green sheet using the release film for producing a ceramic green sheet according to any one of claims 1 to 5, wherein the molded ceramic green sheet has a thickness of 0.2 μm to 1.0 μm.

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