Mold release film for molding of resin sheet

Abstract

To provide a mold release film that comprises a mold release layer having particularly excellent smoothness and release properties, whereby the mold release film enables molding of an ultra-thin resin sheet, particularly an ultra-thin ceramic green sheet without defects.SOLUTION: A mold release film for molding of a resin sheet comprising a polyester film as a base and a mold release layer, wherein the mold release layer is a layer obtained by curing a mold release layer formation composition, the mold release layer formation composition contains a cationic-curable polydimethylsiloxane (a), the content of the cationic-curable polydimethylsiloxane (a) contained in the mold release layer is 90 mg / m2 or less, the regional surface roughness (Sa) of the mold release layer is 2 nm or less, and the number of protrusions having a height of 10 nm or more present on the surface of the mold release layer is 200 / mm2 or less.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a release film for use in molding a resin sheet, and more particularly to a release film used when molding an ultrathin resin sheet. [Background technology]

[0002] Conventionally, release films, which have a polyester film as a base material and a release layer laminated thereon, have been used as process films for molding resin sheets such as pressure-sensitive adhesive sheets, cover films, polymer films, and optical lenses.

[0003] The release film is also used as a process film for molding ceramic green sheets, which require high smoothness for multilayer ceramic capacitors, ceramic substrates, etc. In recent years, as multilayer ceramic capacitors have become smaller and their capacity has increased, the thickness of ceramic green sheets has also tended to become thinner. Ceramic green sheets are molded by coating a slurry containing ceramic components such as barium titanate and a binder resin onto a release film and drying it. Electrodes are printed on the molded 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] When a ceramic green sheet is molded onto the release layer surface of a polyester film substrate, minute protrusions on the release layer surface can affect the molded ceramic green sheet, resulting in defects such as repelling and pinholes. In recent years, ceramic green sheets have become thinner, with a demand for ceramic green sheets with thicknesses of 1.0 μm or less, more specifically, 0.2 μm to 1.0 μm. This has led to increased demand for smoothness of the release layer surface. Furthermore, extremely minute protrusions and foreign matter on the release layer can lead to deformation of the molded ceramic green sheet, resulting in pinholes and sheet cracking during peeling.

[0005] Furthermore, as ceramic green sheets become thinner, the releasability of the ceramic green sheet when peeling it from the release film becomes increasingly important. If the peel force is large and uneven, the ceramic green sheet can be damaged during the peeling process, resulting in sheet defects, thickness variations, pinholes, cracks, and other problems. Therefore, there is a need for ceramic green sheets to be peeled with a lower, more uniform force. In other words, to produce ultrathin resin sheets, especially ceramic green sheets, without defects, a release film with extremely high smoothness and excellent releasability is required.

[0006] Examples of release films with excellent smoothness and releasability include those described in the following patent documents. For example, Patent Document 1 proposes a release film having a release layer mainly composed of a radically curable resin. Patent Document 2 proposes a release film having a laminated structure of a smoothing layer and a release layer. Patent Document 3 proposes a release film having a release layer mainly composed of a cationically curable epoxy resin. Patent Document 4 proposes a release film having a release layer mainly composed of a cationically curable polydimethylsiloxane. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Patent No. 5492352 [Patent Document 2] Japanese Patent Application Laid-Open No. 2015-164762 [Patent Document 3] International Publication No. 2018 / 079337 [Patent Document 4] Japanese Patent Application Laid-Open No. 2016-079349 Summary of the Invention [Problem to be solved by the invention]

[0008] However, the release film of Patent Document 1 has a problem in that the smoothness of the release layer is insufficient because the release layer is provided on a base film with insufficient smoothness. Furthermore, as a result of extensive research, the inventors have found that radical curing resins suffer from poor curing due to oxygen inhibition, which results in poor solvent resistance on the surface of the release layer, and the release layer is corroded by organic solvents used when molding ceramic green sheets or printing internal electrodes, resulting in poor releasability. In the invention of Patent Document 2, a thermosetting melamine resin is used for the smoothing coating layer and the release coating layer, which requires high heat to accelerate the curing reaction. Therefore, there is a risk that the flatness of the release film may be impaired by the heat during processing. In addition, because multiple processes are required for the smoothing coating layer and the release coating layer, there is a risk that foreign matter may be mixed into the release film and that scratches may occur in the release layer. This may result in the transfer of foreign matter or scratches to the ceramic green sheet molded on the release layer, causing defects.

[0009] Patent Documents 3 and 4 each propose a release layer using a cationically curable resin to improve poor curing caused by oxygen inhibition and poor flatness caused by processing heat. However, the release film of Patent Document 3 has a problem in that the smoothness of the release layer surface is poor because the smoothness of the base film is poor. In addition, the release agent components disclosed in Patent Document 3 have poor reactivity and poor solvent resistance, and there are problems with releasability. The release film of Patent Document 4 has a release layer that uses a liquid cationically curable polydimethylsiloxane resin as its main component, which can cause problems with flatness due to the resin agglomerating on the unevenness of the base film and on protrusions such as oligomers present on the surface of the base film.In addition, the crosslink density of the release layer is low, which also causes problems with releasability.

[0010] The present invention has been made in view of the problems of the prior art. That is, an object of the present invention is to provide a release film having a release layer that is particularly excellent in smoothness and releasability, and further to provide a release film that can mold an ultrathin resin sheet, particularly an ultrathin ceramic green sheet, without defects. [Means for solving the problem]

[0011] As a result of extensive research to solve the above problems, the present inventors have found that the above object can be achieved by a release film having the following configuration, and have completed the present invention.

[0012] That is, the present invention comprises the following: [1] A release film for resin sheet molding having a polyester film as a substrate and a release layer, The polyester film has a surface layer A that is substantially free of inorganic particles, The release layer is provided on the surface layer A, the release layer is a layer formed by curing a release layer-forming composition, The release layer-forming composition contains a cationically curable polydimethylsiloxane (a), The surface roughness (Sa) of the release layer is 2 nm or less, The number of protrusions with a height of 10 nm or more present on the surface of the release layer is 200 / mm 2 Below is the Release film for resin sheet molding. [2] In one embodiment, the maximum protrusion height (Sp) of the release layer is 20 nm or less, and the total number of protrusions with a height of 5 nm or more but less than 10 nm present on the surface of the release layer and the number of protrusions with a height of 10 nm or more is 1500 / mm 2 The following is the result. [3] In one embodiment, the cationically curable polydimethylsiloxane (a) has at least one functional group selected from a vinyl ether group, an oxetanyl group, an epoxy group, and an alicyclic epoxy group. [4] In one embodiment, the content of the cationically curable polydimethylsiloxane (a) contained in the release layer is 90 mg / m 2 The following is the result. [5] In one embodiment, the release layer-forming composition further contains a cationically curable compound (b-1) that does not have a silicone skeleton, The cationically curable compound (b-1) has two or more alicyclic epoxy groups in the molecule, and the content of the cationically curable compound (b-1) is 80 mass% or more relative to 100 mass parts in total of the cationically curable polydimethylsiloxane (a) and the cationically curable compound (b-1). [6] In one embodiment, the release layer-forming composition further contains a cyclic siloxane compound (b-2) having an alicyclic epoxy group, The cyclic siloxane compound (b-2) has two or more alicyclic epoxy groups in the molecule, and the content of the cyclic siloxane compound (b-2) is 80 mass% or more relative to 100 mass parts in total of the cationically curable polydimethylsiloxane (a) and the cyclic siloxane compound (b-2). [7] In one embodiment, the release layer-forming composition contains an organic solvent having an SP value (δ) of 14 or more and 17 or less, and the release layer-forming composition contains the organic solvent having an SP value (δ) of 14 or more and 17 or less in an amount of 10% by mass or more relative to 100 parts by mass of the total weight of the release layer-forming composition. [8] In one embodiment, a release film for producing a resin sheet containing an inorganic compound is provided. [9] In one embodiment, the resin sheet containing an inorganic compound is a ceramic green sheet.

[10] In one embodiment, there is provided a release film for molding a resin sheet having a thickness of 0.2 μm or more and 1.0 μm or less. [Effects of the Invention]

[0013] The release film for resin sheet molding of the present invention can improve the smoothness and releasability of the release layer, and further can suppress the occurrence of defects in ultrathin resin sheets, particularly ceramic green sheets. DETAILED DESCRIPTION OF THE INVENTION

[0014] The present invention will be described in detail below. The present invention provides a release film for resin sheet molding having a polyester film as a substrate and a release layer, The polyester film has a surface layer A that is substantially free of inorganic particles, A release layer is provided on the surface layer A, The release layer is a layer formed by curing a release layer-forming composition, The release layer-forming composition contains a cationically curable polydimethylsiloxane (a), The surface roughness (Sa) of the release layer is 2 nm or less, The number of protrusions with a height of 10 nm or more on the release layer surface is 200 / mm 2 The following is a release film for resin sheet molding.

[0015] The present invention having such a configuration has excellent smoothness and releasability of the release layer, so that, for example, a resin sheet having a thickness of 0.2 μm to 1.0 μm or less can be provided with a uniform thickness without defects and defects such as pinholes can be suppressed. The present invention also has the following advantages. In the present invention, a release layer is provided on a substrate film with sufficient smoothness, ensuring the smoothness of the release layer. Furthermore, the present invention can suppress poor curing due to oxygen inhibition in the release layer, thereby achieving high crosslinking of the release layer. The present invention, which has these advantages, can, for example, improve the solvent resistance of the release layer surface. By improving the solvent resistance of the release layer surface, it is possible to prevent the release layer from being eroded by organic solvents used when molding ceramic green sheets and printing internal electrodes, thereby achieving high releasability. Furthermore, the present invention does not require high heat to promote the curing reaction, as compared with, for example, a release layer having a thermosetting melamine resin. Therefore, it is possible to prevent the flatness of the release film from being damaged by heat during processing. Furthermore, the production method of the present invention can prevent the release layer-forming composition from aggregating by undergoing the coating step and drying step of the present invention, and it is possible to obtain a release film having a release layer with extremely high smoothness.

[0016] More specifically, a release layer having extremely high smoothness can be obtained by applying a release layer-forming composition containing a predetermined amount of cationically curable polydimethylsiloxane (a) to the surface layer A of the substrate film, which does not substantially contain inorganic particles, and then curing the composition. Furthermore, by controlling the content of the cationically cured polydimethylsiloxane (a) in the release layer to a predetermined amount or less, it is possible to prevent the cationically cured polydimethylsiloxane (a) from aggregating on minute protrusions derived from oligomers, which are extremely small foreign matter present on the substrate film during processing of the release layer. Although interpretation should not be limited to a specific theory, it is possible to prevent the aggregation of component (a) on minute protrusions derived from the raw film by increasing the first drying temperature (by intensifying the drying). Furthermore, by preventing poor curing due to oxygen inhibition, improving the solvent resistance of the release layer surface, suppressing the inclusion of foreign matter in the release layer, and suppressing scratches on the release layer, it is possible to prevent damage to the release target, such as a ceramic green sheet, during peeling, and sheet deformation due to the transfer of scratches and foreign matter, etc. As a result, it is possible to obtain a release layer that is excellent in smoothness, hardness, releasability, and contamination prevention for the release target layer. Furthermore, the cationically curable polydimethylsiloxane (a) is less likely to aggregate during drying of the organic solvent contained in the release layer-forming composition, making it possible to form a release layer with excellent smoothness, as will be described in detail later.

[0017] In another aspect, the present invention provides a method for producing a release film for resin sheet molding, comprising the following steps: A coating step of coating a release layer-forming composition onto the surface layer A of a polyester film having a surface layer A, The surface layer A is a layer that does not substantially contain inorganic particles, The release layer-forming composition contains a cationically curable polydimethylsiloxane (a), Application process; A drying step of heating and drying the polyester film coated with the release layer-forming composition, The heat drying includes a first drying step and a second drying step, a drying step, wherein a drying temperature T1 in the first drying step is higher than a drying temperature T2 in the second drying step; After the drying step, a photocuring step of irradiating the release layer-forming composition with active energy rays to cure the composition.

[0018] In the production method according to the present invention, a release layer with high smoothness can be formed by, in particular, setting the production conditions when processing the release layer in a predetermined manner. For example, the amount of the release layer-forming composition to be applied, the organic solvent composition, the drying time, the drying temperature, etc. can be controlled. By producing a release film under the conditions of the present invention, aggregation of the cationically cured polydimethylsiloxane (a) contained in the release layer-forming composition can be suppressed, and a release layer with excellent smoothness can be obtained. Details will be described later.

[0019] (polyester film) The polyester constituting the polyester film used as the substrate of the present invention is not particularly limited, and a film of 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. For example, polyethylene terephthalate, polyethylene-2,6-naphthalate, polybutylene terephthalate, polytrimethylene terephthalate, or a copolymer primarily composed of these resin components is more preferred, with polyester films formed from polyethylene terephthalate being particularly preferred. The polyethylene terephthalate preferably contains 90 mol% or more, more preferably 95 mol% or more, of ethylene terephthalate repeating units. While small amounts of other dicarboxylic acid components and diol components may be copolymerized, from a cost perspective, polyethylene terephthalate produced solely from terephthalic acid and ethylene glycol is preferred. Furthermore, known additives, such as antioxidants, light stabilizers, UV absorbers, and crystallization agents, may be added within limits that do not impair the effects of the film of the present invention. The polyester film is preferably a biaxially oriented polyester film due to its high bidirectional elastic modulus.

[0020] The intrinsic viscosity of the polyester film is preferably 0.50 to 0.70 dL / g, more preferably 0.52 to 0.62 dL / g. When the intrinsic viscosity is 0.50 dL / g or more, 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. In addition, it is preferable to thoroughly vacuum dry the raw material pellets. In this specification, the term "polyester film" simply refers to a polyester film having (laminated with) a surface layer A. In the present invention, the polyester film has a surface layer A that is substantially free of inorganic particles, and has the release layer on the surface layer A. When specified in the specification, the polyester film further having (laminated with) the surface layer B may be simply referred to as a "polyester film."

[0021] The method for producing the polyester film of the present invention is not particularly limited, and any conventionally commonly 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 stretched. Biaxial stretching is preferred in terms of mechanical properties, etc. A biaxially stretched film can be obtained by sequentially biaxially stretching a uniaxially stretched film in the longitudinal or transverse direction in the transverse or longitudinal direction, or by simultaneously biaxially stretching an unstretched film in the longitudinal and transverse directions.

[0022] In the present invention, the stretching temperature during stretching of the polyester film is preferably equal to or higher than the second-order transition point (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.

[0023] The polyester film preferably has a thickness of 12 to 50 μm, more preferably 15 to 38 μm, and even more preferably 19 to 33 μm. A film thickness of 12 μm or more is preferred because there is no risk of deformation due to heat during film production, during the processing of the release layer, or during molding of ceramic green sheets, etc. On the other hand, a film thickness of 50 μm or less is preferred in terms of reducing the environmental impact because the amount of film discarded after use is not excessively large.

[0024] The polyester film may be a single layer or a multilayer structure having two or more layers. The polyester film has a surface layer A that is substantially free of inorganic particles. For example, the polyester film may have a single layer of surface layer A or a multilayer structure having surface layer A and another layer, such as surface layer B described below. In the case of a laminated polyester film having a multilayer structure of two or more layers, it is preferable to have a surface layer B, which can contain particles, on the side opposite to the surface layer A, which is substantially free of inorganic particles. As for the layer structure, if the layer on the side to which the release layer is applied is surface layer A, the layer on the opposite side is surface 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, surface layer B may not contain particles. In this case, it is preferable to provide a coating layer containing particles and a binder on surface layer B to impart slip properties for winding the film into a roll.

[0025] In the polyester film of the present invention, the surface layer A located on the surface to which the release layer is applied does not substantially contain inorganic particles. In the present invention, since the surface layer A does not substantially contain inorganic particles, it can exhibit the following regional surface average roughness. In the present invention, the regional surface average roughness (Sa) of the surface layer A refers to the regional surface average roughness (Sa) of the surface on which the release layer is disposed, and the regional surface average roughness (Sa) of the surface on which the release layer is disposed is 7 nm or less. When Sa is 7 nm or less, the release layer laminated on the surface layer A can also exhibit high smoothness, and pinholes and the like are less likely to occur when molding the ultrathin ceramic green sheet laminated on the release layer. Furthermore, when forming the release layer, aggregation of the release layer components on the protrusions on the surface layer A can be suppressed, and deterioration of the smoothness of the release layer surface can be prevented.

[0026] The smaller the regional average surface roughness (Sa) of the surface layer A, the better, and it may be 0.1 nm or more. In one embodiment, the regional average surface roughness (Sa) of the surface layer A is 0.1 nm or more and 7 nm or less, for example, 0.5 nm or more and 5 nm or less, or 0.5 nm or more and 4 nm or less. By keeping it within such a range, the smoothness of the release layer can be improved, and the occurrence of pinholes and the like can be suppressed during molding of the laminated ultrathin ceramic green sheets. Furthermore, when forming the release layer, aggregation of the release layer components on the protrusions on the surface layer A can be suppressed, and deterioration of the smoothness of the release layer surface can be prevented.

[0027] In the present invention, "substantially free of inorganic particles" means that the content of inorganic elements, when quantified by X-ray fluorescence analysis, is 50 ppm or less, preferably 10 ppm or less, and most preferably below the detection limit. This is because even if inorganic particles are not actively added to the film, contaminants derived from foreign substances and dirt adhering to the raw material resin or the lines and equipment used in the film manufacturing process may be mixed into the film.

[0028] The polyester film substrate of the present invention may have a surface layer B on the side opposite to the side on which the release layer is disposed. The surface layer B preferably contains particles. By containing particles, the film has excellent slip properties and easy air escape, and can have excellent transportability and windability. In particular, it is preferable that the surface layer B contains silica particles and / or calcium carbonate particles. The total amount of particles contained in the surface layer B is 1,000 to 15,000 ppm. In this case, the area surface average roughness (Sa) of the film of the surface layer B is, for example, 1 nm or more and 40 nm or less, more preferably 5 nm or more and 35 nm or less. When the total amount of silica particles and / or calcium carbonate particles is 1,000 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 appearance and good flatness. Due to these characteristics, when an ultrathin resin sheet having a thickness of 0.2 μm to 1.0 μm, for example, a ceramic green sheet, is produced, wrinkles and misalignment of the wound ceramic green sheet can be prevented, and a release film with excellent transportability, winding, and storage properties can be provided. 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 particles that also function as a lubricant are less likely to aggregate and large protrusions (e.g., protrusions with a height of 1 μm or more) are not formed. Therefore, when an ultrathin resin sheet, such as a ceramic green sheet, is produced, pinholes caused by winding can be suppressed, and a resin sheet with stable quality can be provided.

[0029] In addition to silica and / or calcium carbonate, inactive inorganic particles and / or heat-resistant organic particles can be used as particles contained in the surface layer B. 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. Furthermore, heat-resistant organic particles include cross-linked polyacrylic particles, cross-linked polystyrene particles, and benzoguanamine particles. Furthermore, 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 particle shedding.

[0030] The average particle size of the particles added to the surface layer B is preferably 0.1 μm or more and 2.0 μm or less, and particularly preferably 0.5 μm or more and 1.0 μm or less. An average particle size of 0.1 μm or more is preferable because the release film has good slip properties. Furthermore, an average particle size of 2.0 μm or less suppresses deformation of the surface layer A, thereby suppressing thickness variations and pinholes in the ceramic green sheet.

[0031] The surface layer B may contain two or more types of particles made of different materials. Alternatively, the same type of particles may be contained, but with different average particle sizes. The two or more different types of particles may have different average particle sizes within the above range. By containing two different types of particles, the unevenness formed on the surface layer B can be precisely controlled, and both lubricity and smoothness can be achieved, which is preferable.

[0032] It is preferable that recycled raw materials are not used for the surface layer A, which is the layer on the side where the release layer is to be provided, in order to prevent particles or impurities from being mixed in, from the viewpoint of reducing pinholes.

[0033] The thickness ratio of the surface layer A, which is the layer on which the release layer is to be provided, is preferably 20% to 50% of the total thickness of the base film. If it is 20% or more, the film is less susceptible to the influence of particles contained in the surface layer B, etc. from the inside, and the regional surface average roughness Sa can 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 co-extruded surface layer B and the above-mentioned intermediate layer C can be increased, which is preferable because it reduces the environmental impact.

[0034] From an economical standpoint, 50 to 90% by mass of recycled raw materials such as film scraps or PET bottles can be used 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 the lubricant contained in the surface layer B, its particle size, and the area surface average roughness (Sa) satisfy the above ranges.

[0035] Furthermore, in order to improve the adhesion of a release layer or the like to be applied later, to prevent static electricity, or the like, a coating layer may be provided on the surface of surface layer A and / or surface layer B before stretching or after uniaxial stretching in the film-forming process, and corona treatment or the like may also be performed. When a coating layer is provided on surface layer A, it is preferable that the coating layer does not substantially contain particles.

[0036] (Release layer) In the present invention, the release layer is laminated on the surface layer A. In the present invention, the release layer is a layer obtained by curing a release layer-forming composition, and the release layer and the release layer-forming composition contain at least a cationically curable polydimethylsiloxane (a), and the surface roughness (Sa) of the region of the release layer is 2 nm or less, The number of protrusions with a height of 10 nm or more on the release layer surface is 200 / mm 2 The following is the result. The release layer having such characteristics can suppress the occurrence of pinholes in an ultra-thin resin sheet that requires high smoothness, such as a ceramic green sheet, and can form a resin sheet with a uniform thickness. More specifically, the present invention can suppress poor curing due to oxygen inhibition in the release layer, and achieve high crosslinking of the release layer. The present invention, which achieves these effects, can, for example, improve the solvent resistance of the surface of the release layer. By improving the solvent resistance of the surface of the release layer, it is possible to suppress erosion of the release layer by organic solvents used when molding ceramic green sheets and printing internal electrodes, and to achieve high releasability. Furthermore, with the present invention, high heat of 130°C or higher is not required to promote the curing reaction. Therefore, it is possible to prevent the flatness of the release film from being damaged by heat during processing. Furthermore, it is possible to prevent the incorporation of foreign matter into the release film for resin sheet molding and the occurrence of scratches on the release layer, and it is possible to prevent sheet damage caused by the transfer of foreign matter and scratches to the object to be released, such as a ceramic green sheet.

[0037] The average surface roughness (Sa) of the release layer is 2 nm or less. The number of protrusions with a height of 10 nm or more present on the surface of the release layer is 200 / mm 2The release layer surface of the release film has a predetermined surface average roughness (Sa) and number of protrusions of 10 nm or more in the above region so as to prevent defects from occurring in the ceramic sheet that is coated and molded on it. Area surface roughness (Sa) is 2 nm or less, and the number of protrusions with a height of 10 nm or more is 200 / mm 2 If the thickness is less than this, defects such as pinholes do not occur in the ceramic sheet during molding, and the yield is favorable. More preferably, the area surface roughness (Sa) is 1.7 nm or less, for example, 1.6 nm or less, and may be 1.5 nm or less. In one embodiment, the area surface roughness (Sa) is 1.3 nm or less. Alternatively, the area surface roughness (Sa) may be 0.1 nm or more, or may be 0.2 nm or more. On the other hand, in one embodiment, the number of protrusions having a height of 10 nm or more is 180 / mm 2 For example, 170 pieces / mm 2 less than 160 pieces / mm 2 In one embodiment, the number of protrusions having a height of 10 nm or more is 120 / mm 2 It may be less than 100 pieces / mm 2 The number of protrusions with a height of 10 nm or more may be 1 / mm 2 For example, 10 pieces / mm 2 It may be more than that. By keeping the number of protrusions having a height of 10 nm or more within the above range, defects such as pinholes do not occur in the ceramic sheet, and excellent releasability can also be achieved in a well-balanced manner. More preferably, the surface roughness (Sa) of the region is 1.0 nm or less, and the number of protrusions with a height of 10 nm or more is 100 / mm 2 The following is the result. The release layer according to the present invention, which has a region surface average roughness (Sa) and a number of protrusions, can exhibit extremely excellent smoothness.

[0038] In one embodiment, the maximum protrusion height (Sp) of the release layer is 20 nm or less. By having the maximum protrusion height in this range, defects in the ceramic sheet can be further suppressed. More preferably, the maximum protrusion height (Sp) is 15 nm or less, and even more preferably 10 nm or less. In one embodiment, the total number of protrusions with a height of 5 nm or more and less than 10 nm present on the surface of the release layer and the total number of protrusions with a height of 10 nm or more is 1500 / mm 2 The total number of protrusions with a height of 5 nm or more but less than 10 nm present on the release layer and the number of protrusions with a height of 10 nm or more is 1500 / mm 2 By satisfying the condition of 0.1 to 1.0, defects in the ceramic sheet can be further suppressed, and a release layer having high smoothness can be obtained, which is preferable. More preferably, the total number of protrusions having a height of 5 nm or more but less than 10 nm and the number of protrusions having a height of 10 nm or more is 1000 / mm 2 For example, 500 pieces / mm 2 It is even more preferable that:

[0039] The release layer of the release film for resin sheet molding of the present invention is a layer formed by curing a release layer-forming composition, and the release layer-forming composition contains at least a cationically curable polydimethylsiloxane (a). The cationically curable polydimethylsiloxane (a) undergoes a crosslinking reaction via a cationic curing reaction, so that poor curing due to oxygen inhibition does not occur, resulting in a release layer with excellent solvent resistance. Therefore, there is no risk of the release layer being corroded by organic solvents used during molding of ceramic green sheets, printing of internal electrodes, etc., and a release layer with excellent releasability can be obtained.

[0040] Furthermore, the present inventors have found that in a release layer containing cationically curable polydimethylsiloxane (a), the amount of cationically curable polydimethylsiloxane (a) is important for realizing a release layer having high smoothness. The cationically curable polydimethylsiloxane (a) is contained in the release layer at a concentration of 90 mg / m 2 Below, for example, 60 mg / m 2 Below 50mg / m 2It is preferable that it is contained in an amount of 40 mg / m or less. 2 More preferably, it is 30 mg / m or less. 2 It is more preferable that the concentration of the cationically curable polydimethylsiloxane (a) is 20 mg / m or less. 2 It may be the following: The content of cation-curable polydimethylsiloxane (a) in the release layer is 50 mg / m 2 If the above ratio is less than 1, aggregation of polydimethylsiloxane (a) during the process of forming the release layer, for example, during the drying process, can be suppressed, and there is no risk of a large number of protrusions that fall outside the scope of the present invention occurring, thereby achieving the effects of the present invention. In one embodiment, the release layer or the release layer-forming composition may contain components other than the cationically curable polydimethylsiloxane (a). In this case, too, the determination should not be based on a particular theory, but in the present invention, it is possible for the polydimethylsiloxane (a) to segregate on the surface of the release layer during processing of the release layer, and the content is 50 mg / m 2 If the content is less than this, aggregation is unlikely to occur, and a release layer having high smoothness can be formed. The lower the content of polydimethylsiloxane (a) according to the present invention, the less likely it is to aggregate. 2 If the amount is 0.1 mg / m or more, the leveling property of the release layer is maintained, the coating appearance is excellent, and a release layer with high smoothness can be obtained. 2 For example, the content of polydimethylsiloxane (a) is 0.5 mg / m or more, since this provides excellent releasability. 2 It may be more than that. In the present invention, the release layer-forming composition contains a cationically curable polydimethylsiloxane (a). Furthermore, in the release layer obtained by curing the release layer-forming composition, a compound (cured product) derived from the cationically curable polydimethylsiloxane (a) is present. In this specification, the compound derived from (a) present in the release layer may also be simply referred to as the cationically curable polydimethylsiloxane (a).

[0041] In the present invention, the cationically curable polydimethylsiloxane (a) refers to a polydimethylsiloxane having a cationically curable functional group. The cationically curable functional group is a reactive functional group exhibiting cation curability, and specific examples thereof include a vinyl ether group, an oxetanyl group, an epoxy group, and an alicyclic epoxy group. Among these, from the viewpoint of reactivity, it is preferable to have at least one functional group selected from an oxetanyl group, an epoxy group, and an alicyclic epoxy group, and an alicyclic epoxy group is most preferable. The presence of such a functional group is preferable because a crosslinked structure is formed by the cationic curing reaction, resulting in a release layer with excellent solvent resistance and excellent releasability.

[0042] The number of cationically curable functional groups possessed by the cationically curable polydimethylsiloxane (a) may be one or more. For example, having two or more cationically curable functional groups is preferable because it facilitates the progress of the cationic curing reaction and results in a release layer with a high crosslink density. The position at which the cationically curable functional group is introduced is not particularly limited, and it is generally located on the side chain or terminal of the polydimethylsiloxane. The structure of the polydimethylsiloxane may be a linear structure or a branched structure, and it can be used without any problems even if it has functional groups other than the cationically curable functional group.

[0043] The cationically curable polydimethylsiloxane (a) may be commercially available. Examples include SILICORISE® UV POLY200, UV POLY201, UV POLY215, UV RCA200, and UV RCA251 manufactured by Arakawa Chemical Industries, Ltd., X-62-7622, ​​X-62-7629, X-62-7660, KF-101, KF-105, X-22-343, X-22-169AS, X-22-169B, X-22-163, X-22-173BX, X-22-173DX, and X-22-9002 manufactured by Shin-Etsu Chemical Co., Ltd., and UV9440E and UV9430 manufactured by Momentive Performance Materials, Inc.

[0044] The weight-average molecular weight of the cationically curable polydimethylsiloxane (a) is preferably 1,000 to 500,000, and more preferably 5,000 to 100,000. A weight-average molecular weight of 1,000 or more is preferred because the cationic curing reaction proceeds easily and the release layer has excellent release properties. A weight-average molecular weight of 500,000 or less is preferred because the viscosity does not become too high, the release layer has excellent coatability, and the release layer has high flatness.

[0045] The release layer-forming composition of the present invention can contain other resins in addition to the cationically curable polydimethylsiloxane (a). In this case, the thickness of the release layer can be reduced. In the present invention, the release layer is provided on the surface layer A of the substrate film that does not substantially contain inorganic particles, so even if the release layer is thin, it can have extremely high smoothness. Furthermore, because the release layer is thin, the curing reaction proceeds easily, allowing for faster processing, and the release layer can be obtained economically.

[0046] Furthermore, when the film thickness is thin, there is no risk of extremely small foreign matter present in the base film, the release processing step, etc. being taken into the release layer. Therefore, there is no risk of protrusions due to foreign matter being generated on the surface of the release layer, and it is possible to obtain a release layer having the above-mentioned smooth surface.

[0047] In the case of a release layer formed by curing a composition containing cationically curable polydimethylsiloxane (a) as a main component, the thickness of the release layer is preferably 0.001 μm or more and less than 0.050 μm. A thickness of 0.001 μm or more is preferred because it provides excellent release properties. A thickness of less than 0.050 μm is preferred because it prevents aggregation of the release layer-forming composition and results in a smooth release layer. In the present invention, when the cationically curable polydimethylsiloxane (a) is the main component, the composition contains 50 parts by mass or more, for example, more than 50 parts by mass, preferably 70 parts by mass or more, for example, 80 parts by mass or more, and in one embodiment, 90 parts by mass or more of the cationically curable polydimethylsiloxane (a) relative to 100 parts by mass of the resin solid content of the release layer. In another embodiment, the cationically curable polydimethylsiloxane (a) is contained in substantially the entire resin solid content of the release layer.

[0048] The release layer-forming composition of the present invention can also contain a cationically curable resin (b) in addition to the cationically curable polydimethylsiloxane (a). In this case, (b) is a resin different from (a), and the resin (b) does not have a polydimethylsiloxane structure. Specifically, they are broadly classified into two types: cationically curable compounds (b-1) that do not have a silicone skeleton, and cyclic siloxane compounds (b-2) that have an alicyclic epoxy group.

[0049] In one embodiment, the release layer-forming composition contains, in addition to the cationically curable polydimethylsiloxane (a), a cationically curable compound (b-1) that does not have a silicone skeleton. Examples of the cationically curable compound (b-1) that does not have a silicone skeleton include polymers and monomers that have two or more cationically curable functional groups in the molecule but do not have a silicone skeleton. Among these, resins having two or more epoxy groups or alicyclic epoxy groups are preferred, and resins having two or more alicyclic epoxy groups are more preferred. For example, the number of alicyclic epoxy groups may be six or less. By having two or more alicyclic epoxy groups, a crosslinking reaction proceeds through a cationic curing reaction, resulting in a release layer with excellent solvent resistance. At the same time, a crosslinking reaction proceeds with the polydimethylsiloxane (a) contained in the release layer, resulting in excellent releasability and suppressing the migration of the polydimethylsiloxane (a) to the ceramic green sheet, which is preferable.

[0050] In one embodiment, the release layer-forming composition contains both a silicone-free cationic curable resin (b-1) and a polydimethylsiloxane (a), thereby achieving a release layer with high smoothness. By forming a release layer containing the compound (b-1), minute irregularities, minute foreign matter, and oligomer-derived protrusions present on the substrate film can be filled, resulting in an ultra-smooth release layer. Furthermore, the curing reaction proceeds with ultraviolet light, resulting in a release layer with high smoothness. While not limited to a specific theory, it is assumed that during the drying process of the release layer-forming composition during release layer processing, (b-1) and (a) uniformly level, improving flatness before curing, resulting in a release layer with high smoothness. Furthermore, in the present invention, the polydimethylsiloxane (a) simultaneously contained in the composition segregates on the surface of the release layer during the drying process, resulting in a release layer with excellent releasability.

[0051] The cationically curable compound (b-1) without a silicone skeleton is preferably a low-molecular-weight monomer. Specifically, the number-average molecular weight is preferably 200 or more and less than 5,000, more preferably 200 or more and less than 2,500, and even more preferably 200 or more and less than 1,000. A number-average molecular weight of 200 or more is preferable because the boiling point is not low and there is no risk of the cationically curable compound (b-1) volatilizing during the drying process of the release layer-forming composition during release layer processing. A number-average molecular weight of less than 5,000 is preferable because the crosslink density of the release layer is increased and the solvent resistance is excellent. In addition, since the compound can exist in a fluid liquid state during the drying process, it is preferable because it provides an ultra-smooth release layer with excellent leveling properties.

[0052] As the cationically curable compound (b-1) without a silicone skeleton, commercially available products can be suitably used. Examples of compounds having an alicyclic epoxy group include CELLOXIDE 2021P, CELLOXIDE 2081, EPOLEAD GT401, and EHPE3150 manufactured by Daicel Corporation, HiREM-1 manufactured by Shikoku Chemicals Corporation, and THI-DE, DE-102, and DE-103 manufactured by ENEOS Corporation. Examples of resins having an epoxy group include EPICLON (registered trademark) 830, 840, 850, 1051-75M, N-665, N-670, N-690, N-673-80M, and N-690-75M manufactured by DIC Corporation, and DENACOL (registered trademark) EX-611, EX-313, and EX-321 manufactured by Nagase Chemtec Corporation.

[0053] The content of the cationically curable compound (b-1) not having a silicone skeleton is preferably 80 mass% or more, more preferably 85 mass% or more, and even more preferably 90 mass% or more, relative to a total of 100 mass parts of the cationically curable polydimethylsiloxane (a) and the cationically curable compound (b-1) in the release layer. By making the content of the cationically curable compound (b-1) 80% by mass or more and making it the main component of the release layer, a release layer with high crosslink density and excellent releasability is obtained, which is preferable. Furthermore, the content of the cationically curable polydimethylsiloxane (a) contained in the release layer can be reduced, which prevents the polydimethylsiloxane (a)-derived composition from aggregating on the release layer surface during the drying process, and is therefore preferable as it prevents deterioration of flatness. The higher the content of the cationically curable compound (b-1), the more excellent the smoothness of the release layer. However, to ensure releasability by containing the cationically curable polydimethylsiloxane (a), the content of the cationically curable compound (b-1) is preferably 99.9% by mass or less. In the present invention, in the release layer obtained by curing the release layer-forming composition, a compound (cured product) derived from the cationically curable compound (b-1) that does not have a silicone skeleton is present. In this specification, the compound derived from (b-1) present in the release layer may also be simply referred to as the cationically curable compound (b-1) that does not have a silicone skeleton.

[0054] When the release layer-forming composition contains a cationically curable polydimethylsiloxane (a) and a cationically curable compound (b-1), the release layer has a high crosslink density, excellent solvent resistance, and excellent peel strength, which is preferable. Furthermore, when the release layer-forming composition contains a cationically curable compound (b-1), the release layer can be thickened while maintaining the content of the cationically curable polydimethylsiloxane (a) within a predetermined range, which is preferable. By thickening the release layer, scratches and minute irregularities present on the substrate film can be filled, which is preferable because a smooth release layer can be obtained as described above.

[0055] When the release layer-forming composition contains a cationically curable polydimethylsiloxane (a) and a cationically curable compound (b-1), the thickness of the release layer is preferably 0.05 μm or more and 1.0 μm or less, and more preferably 0.1 μm or more and 0.5 μm or less. A thickness of 0.05 μm or more is preferable because a smooth release layer is obtained. A thickness of 1.0 μm or less is preferable because a release film with excellent flatness is obtained without curling.

[0056] In one embodiment, the release layer-forming composition may further contain a cyclic siloxane compound (b-2) having an alicyclic epoxy group. Examples of the cyclic siloxane compound (b-2) having an alicyclic epoxy group include those represented by the following structural formula (Chemical Formula 1) (in Chemical Formula 1, R 2 is an alkyl group having 1 to 4 carbon atoms). In addition, the cationically curable compound (b-2) having a cyclic siloxane skeleton preferably has at least two alicyclic epoxy groups. When there are two or more alicyclic epoxy groups, the cationic curing reaction proceeds, and a release layer with a high crosslink density is obtained, which is preferable.

[0057] [ka]

[0058] The use of a cyclic siloxane compound (b-2) having an alicyclic epoxy group is preferred because it results in an ultra-smooth release layer for the same reasons as when the cationically curable compound (b-1) is used. That is, it can fill in minute irregularities, minute foreign matter, and oligomer-derived protrusions present on the substrate film. Furthermore, because the curing reaction proceeds under ultraviolet light, compound (b-2) and polydimethylsiloxane (a) are uniformly leveled during the drying process of the release layer-forming composition during release layer processing, and curing proceeds after the flatness is enhanced, resulting in an ultra-smooth release layer. Furthermore, in the present invention, the polydimethylsiloxane (a) simultaneously contained in the composition segregates on the surface of the release layer during the drying process, resulting in a release layer with excellent releasability.

[0059] The cyclic siloxane compound (b-2) having an alicyclic epoxy group has good compatibility with the cationically cured polydimethylsiloxane (a), allowing them to mix appropriately in the release layer and undergo a crosslinking reaction with each other. This is preferable because it results in a release layer with excellent solvent resistance and excellent releasability. Furthermore, the cyclic siloxane compound (b-2) has a cyclic siloxane structure, which gives it a rigid molecular skeleton and increases film hardness upon curing, making it preferable. Increased film hardness reduces deformation of the release layer when peeling off a resin sheet, such as a ceramic green sheet, and allows for good releasability. Furthermore, scratches are less likely to occur in the release layer, which is preferable because scratches on the release layer are less likely to be transferred to the resin sheet, such as a ceramic green sheet, causing problems.

[0060] The release layer-forming composition preferably contains a cyclic siloxane compound (b-2) because the adhesion of the release layer to the substrate film is improved. Improved adhesion of the release layer is preferable because it can prevent scratches during the transport process and also because there is no risk of the release layer being transferred when the resin sheet is peeled off.

[0061] In one embodiment, the cyclic siloxane compound (b-2) has two or more alicyclic epoxy groups in the molecule. By having two or more alicyclic epoxy groups in the molecule, a crosslinking reaction proceeds through a cationic curing reaction, resulting in a release layer with excellent solvent resistance. Furthermore, since a crosslinking reaction also proceeds with the polydimethylsiloxane (a) contained in the release layer, the release layer has excellent releasability and is prevented from migrating to the ceramic green sheet, which is preferable. For example, the cyclic siloxane compound (b-2) has six or less alicyclic epoxy groups in the molecule.

[0062] The cyclosiloxane compound (b-2) having an alicyclic epoxy group can be a commercially available product, such as X-40-2670 or X-40-2678 manufactured by Shin-Etsu Chemical Co., Ltd.

[0063] The content of the cyclic siloxane compound (b-2) is preferably 80% by mass or more, more preferably 85% by mass or more, and even more preferably 90% by mass or more, relative to a total of 100 parts by mass of the cationically cured polydimethylsiloxane (a) and the cyclic siloxane compound (b-2) in the release layer. By making the content of the cyclic siloxane compound (b-2) 80% by mass or more and making it the main component of the release layer, a release layer with high crosslink density and excellent releasability is obtained, which is preferable. Furthermore, the content of the cationically cured polydimethylsiloxane (a) contained in the release layer can be reduced, and in the present invention, aggregation of the cationically cured polydimethylsiloxane (a) on the surface of the release layer during the drying process can be suppressed, which is preferable because there is no risk of deterioration in flatness. The higher the content of the cyclic siloxane compound (b-2), the more excellent the smoothness of the release layer will be. For example, in order to contain the cationically cured polydimethylsiloxane (a) and ensure releasability, the cyclic siloxane compound (b-2) is preferably 99.9 mass% or less. In the present invention, a compound (cured product) derived from the cyclic siloxane compound (b-2) is present in the release layer obtained by curing the release layer-forming composition. In this specification, the compound derived from the cyclic siloxane compound (b-2) present in the release layer may also be simply referred to as the cyclic siloxane compound (b-2).

[0064] When the release layer-forming composition contains a cationically curable polydimethylsiloxane (a) and a cyclic siloxane compound (b-2), the thickness of the release layer is preferably 0.05 μm or more and 1.0 μm or less, and more preferably 0.1 μm or more and 0.5 μm or less. A thickness of 0.05 μm or more is preferable because a smooth release layer is obtained. A thickness of 1.0 μm or less is preferable because a release film with excellent flatness is obtained without curling.

[0065] In one embodiment, the release layer may contain both the cationically curable resin (b-1) and the cyclic siloxane compound (b-2), and the total amount of the cationically curable resin (b-1) and the cyclic siloxane compound (b-2) can be 80% by mass or more and 99.9% by mass or less, relative to 100 parts by mass of the total of the cationically curable polydimethylsiloxane (a), the cationically curable compound (b-1), and the cyclic siloxane compound (b-2) in the release layer.

[0066] In the present invention, a cationic curing reaction must be allowed to proceed in order to form a release layer. Therefore, the release layer-forming composition preferably contains an acid generator (c). Furthermore, a compound derived from the acid generator (c) may be present in the release layer. Here, the compound derived from the acid generator (c) present in the release layer may also be simply referred to as the acid generator (c). The acid generator is not particularly limited and any commonly used one can be used, but using a photoacid generator that generates acid under ultraviolet irradiation is preferred because it reduces the amount of heat generated during processing and results in a release layer with excellent flatness.

[0067] As the photoacid generator, a salt consisting of an onium ion and a non-nucleophilic anion is preferably used from the viewpoint of reactivity. Alternatively, an organometallic complex such as an iron arene complex, a carbocation salt such as tropylium, an anthracene derivative, or a phenol substituted with an electron-withdrawing group, such as pentafluorophenol, may also be used.

[0068] When a salt composed of the onium ion and a non-nucleophilic anion is used as a photoacid generator, the onium ion can be, for example, iodonium, sulfonium, or ammonium. The organic group of the onium ion can be triaryl, diaryl(monoalkyl), monoaryl(dialkyl), or trialkyl. Benzophenone or 9-fluorene can be incorporated, or other organic groups can be used. Hexafluorophosphate, hexafluoroantimonate, hexafluoroborate, or tetra(pentafluorophenyl)borate is preferred as the non-nucleophilic anion. Furthermore, tetra(pentafluorophenyl)gallium ions or anions in which some of the fluorine anions are replaced with perfluoroalkyl groups or organic groups can also be used, as well as other anion components.

[0069] The amount of photoacid generator added is 0.1 to 10 mass% relative to 100 parts by mass of the total of the cationically curable polydimethylsiloxane (a) and the cationically curable compound (b-1) and / or cyclic siloxane compound (b-2) in the release layer, and more preferably 0.5 to 8 mass%. It is even more preferably 1 to 5 mass%. A content of 0.1 mass% or more is preferred because it prevents the risk of insufficient acid being generated and insufficient curing. Furthermore, a content of 10 mass% or less is preferred because it generates an appropriate amount of acid and prevents the migration of acid to the ceramic green sheet being molded.

[0070] In this specification, the total of 100 parts by mass of the cationically curable polydimethylsiloxane (a) and the cationically curable compound (b-1) and / or cyclic siloxane compound (b-2) in the release layer means the total value of the solid content of the cationically curable polydimethylsiloxane (a) and the solid content of the cationically curable resin (b). In an embodiment in which the release layer does not contain the cationically curable resin (b), the weight of the cationically curable polydimethylsiloxane (a) corresponds to 100 parts by mass of the resin solid content in the release layer.

[0071] In one embodiment, the release layer-forming composition contains an organic solvent having an SP value (δ) of 14 or more and 17 or less, and the release layer-forming composition contains the organic solvent having an SP value (δ) of 14 or more and 17 or less in an amount of 10% by mass or more per 100 parts by mass of the total weight of the release layer-forming composition. An organic solvent having an SP value (δ) of 14 to 17 exhibits excellent solubility for the cationically curable polydimethylsiloxane (a). Therefore, even if the organic solvent is dried in the drying step after the coating step and the concentration of (a) in the release layer-forming composition increases, the (a) can remain uniformly dissolved, and a smooth release layer can be obtained by leveling cleanly without aggregation. Furthermore, if the content is 10% by mass or more, the cationically curable polydimethylsiloxane (a) can remain dissolved for a long period of time during drying, which is preferable since there is no risk of aggregation during drying and deterioration of smoothness. The organic solvent having an SP value (δ) of 14 or more and 17 or less will be described in detail later.

[0072] In the present invention, additives such as an adhesion improver and an antistatic agent may be added to the release layer as long as the effects of the present invention are not impaired. In order to improve adhesion to the substrate, it is also preferable to subject the surface of the polyester film to pretreatment such as anchor coating, corona treatment, plasma treatment, or atmospheric pressure plasma treatment before providing the release coating layer.

[0073] The release film obtained by the present invention preferably has a peeling force when peeling off a ceramic green sheet of 0.01 mN / mm or more and 2.0 mN / mm or less. More preferably, it is 0.05 mN / mm or more and 1.0 mN / mm or less. A peeling force of 0.01 mN / mm or more is preferable because there is no risk of the ceramic green sheet lifting up during transportation. A peeling force of 2.0 mN / mm or less is preferable because there is no risk of the ceramic green sheet being damaged during peeling.

[0074] The release film obtained by the present invention uses a highly planarized substrate film, so the surface of the release layer can be made smooth even when the thickness of the release layer is 1.0 μm or less, further 0.5 μm or less, or even 0.3 μm or less. Therefore, the amount of solvent and resin used can be reduced, making it environmentally friendly and inexpensive to produce a release film for molding ultrathin ceramic green sheets.

[0075] (Release film manufacturing method) In another embodiment, the present invention provides a method for producing a release film for resin sheet molding, comprising the following steps: A coating step of coating a release layer-forming composition onto the surface layer A of a polyester film having a surface layer A, the surface layer A is a layer that does not substantially contain inorganic particles, The release layer-forming composition contains a cationically curable polydimethylsiloxane (a), Application process; A drying step of heating and drying the polyester film coated with the release layer-forming composition, The heat drying includes a first drying step and a second drying step, a drying step, wherein a drying temperature T1 in the first drying step is higher than a drying temperature T2 in the second drying step; After the drying step, a photocuring step of irradiating the release layer-forming composition with active energy rays to cure the composition.

[0076] In the manufacturing method of the present invention, by strengthening the first drying conditions (by increasing the drying), aggregation of the resin that constitutes the release layer can be prevented, and a release layer with high smoothness can be obtained. Furthermore, by adjusting the SP value of the solvent in the release layer-forming composition to a predetermined value, it is possible to prevent aggregation of the resin constituting the release layer, and to obtain a release layer having high smoothness. As described above, in the present invention, the first drying step has predetermined conditions, and in one embodiment, a release layer having high smoothness can be obtained by using a specific solvent.

[0077] The method for producing a release film of the present invention includes, in order, a coating step of coating a release layer-forming composition containing at least a cationically curable polydimethylsiloxane (a) onto a surface layer A of a polyester film that is substantially free of inorganic particles, a drying step of heating and drying the film after coating, for example, using a drying oven, and a photocuring step of curing the film using active energy rays after heating and drying. In particular, it is preferable to adopt a method in which the coating step, drying step, and photocuring step are performed in this order.

[0078] It has been discovered that the manufacturing method of the present invention can realize a release layer with high smoothness by optimizing the manufacturing conditions in the coating step. Specifically, by including an organic solvent with an SP value (δ) of 14 to 17 in the release layer-forming composition, aggregation of the cationically curable polydimethylsiloxane (a) can be suppressed, resulting in an excellent release layer. The SP value (δ) can be used to predict the solubility of a substance, and organic solvents with an SP value (δ) of 14 to 17 exhibit excellent solubility for the cationically curable polydimethylsiloxane (a). Therefore, even if the organic solvent is dried in the drying step after the coating step and the concentration of (a) in the release layer-forming composition increases, it can remain uniformly dissolved, resulting in clean leveling without aggregation, resulting in a smooth release layer.

[0079] The content of the organic solvent having an SP value (δ) of 14 to 17 contained in the release layer-forming composition is preferably 10% by mass or more, and more preferably 15% by mass or more, relative to 100 parts by mass of the release layer-forming composition. A content of 10% by mass or more allows the cationically curable polydimethylsiloxane (a) to remain dissolved for a long period of time during drying, which is preferable because there is no risk of aggregation during drying and deterioration of smoothness. For example, the content of the organic solvent having an SP value (δ) of 14 to 17 may be 80% by mass or less, for example 65% by mass or less, or even less than 50% by mass, relative to 100 parts by mass of the release layer-forming composition.

[0080] The SP value (δ) used in this specification is the Hildebrand solubility parameter, which can be experimentally calculated from the Hansen solubility parameters (HSP values) using Equation 1. SP value (δ) = ((δ d ) 2 +(δ p ) 2 +(δ h ) 2 ) 1 / 2 ...(Formula 1) where (δ D ) is the dispersion force term, (δ P ) is the polar term, (δ H ) is the hydrogen bonding force term, and the Hansen solubility parameter is the concept of decomposing the Hildebrand solubility parameter into three components. It can also be calculated using computer software such as HSPiP (Hansen Solubility Parameters in Practice), and the values ​​described in this specification are calculated according to Equation 1 using the HSP values ​​listed in the database within HSPiP ver. 4.0.

[0081] Examples of organic solvents with an SP value (δ) of 14 to 17 include normal hexane (δ: 14.9), normal heptane (δ: 15.3), normal octane (δ: 15.5), isopropyl ether (δ: 15.8), 1,1-diethoxyethane (δ: 15.9), methylcyclohexane (δ: 16.0), cyclopentane (δ: 16.5), and cyclohexane (δ: 16.8).

[0082] The coating amount of the release layer-forming composition was 10 g / m 2 Preferably, it is 8 g / m or less. 2 It is more preferable that the coating amount is 10 g / m or less. 2 If the thickness is less than this, when coating is performed by gravure coating, for example, liquid turbulence is less likely to occur at the kiss portion between the film and the gravure roll, and a release layer with excellent smoothness is obtained, which is preferable.

[0083] In the present invention, the release layer-forming composition preferably contains two or more types of solvents, at least one of which has an SP value (δ) of 14 to 17 as described above, and at least one of which preferably has a boiling point of 100° C. or higher. Adding a solvent with a boiling point of 100° C. or higher can prevent bumping during drying, level the coating film, and improve the smoothness of the coating film surface after drying. The amount of the solvent added is preferably about 10 to 70% by mass based on the total amount of the release layer-forming composition. Examples of solvents having a boiling point of 100°C or higher include toluene, xylene, normal octane, cyclohexanone, methyl isobutyl ketone, propylene glycol monomethyl ether, propylene glycol monopropyl ether, isobutyl acetate, and normal butanol.

[0084] In the present invention, it is preferable to filter the coating liquid of the release layer-forming composition before coating. The filtration method is not particularly limited and any known method can be used, but it is preferable to use a surface-type, depth-type, or adsorption-type cartridge filter. The use of a cartridge-type filter allows the coating liquid to be continuously delivered from a tank to a coating unit, which is preferable because it allows for efficient filtration with good productivity. The filtration accuracy of the filter is preferably such that it can remove 99% or more of particles with a size of 1 μm, and more preferably such that it can filter 99% or more of particles with a size of 0.5 μm. Using a filter with the above filtration accuracy is preferable because it can remove foreign matter mixed in the coating liquid that forms the release layer, reduce foreign matter adhering to the release film of the present invention, and obtain a release layer with excellent smoothness.

[0085] 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.

[0086] Methods for applying the release layer-forming composition to the substrate film and drying it include known methods such as hot air drying and infrared heaters, but hot air drying is preferred because it has a fast drying rate. Drying is preferably carried out in a drying oven, and any known drying oven can be used without any particular limitation. The drying oven method may be either a roll support method or a floating method, but the roll support method is preferred because it has a wider range of adjustable air volume during drying and therefore allows the air volume to be adjusted according to the type of release layer.

[0087] The drying process can be divided into two steps: a constant-rate drying step in the initial stage of drying (hereinafter referred to as the first drying step), and a falling-rate drying step (hereinafter referred to as the second drying step). The two steps are preferably performed consecutively in the order of the first drying step and the second drying step, and can be distinguished by dividing the drying oven into zones; the first (initial) drying step can be performed using the first drying oven, and the second (later) drying step can be performed using the second drying oven.

[0088] The present inventors have found that in order to improve the smoothness of the release layer, it is important that the drying temperature T1 in the first drying step is higher than the drying temperature T2 in the second drying step. The first drying oven temperature and the second drying oven temperature are preferably set within the ranges described below. By producing under these conditions, the constant rate drying time in the first drying step can be shortened and the falling rate drying time in the second drying step can be lengthened, which is preferable because a release layer with excellent flatness can be obtained.

[0089] Furthermore, the present inventors have found that it is important to increase the temperature inside the first drying oven and shorten the constant rate drying time. More specifically, the drying temperature T1 is preferably 90°C or higher and 180°C or lower, and more preferably 100°C or higher and 150°C or lower. Increasing the temperature in the first drying oven and shortening the constant-rate drying time is preferable because it is possible to prevent aggregation of the cationically cured polydimethylsiloxane (a) contained in the release layer-forming composition. The higher the temperature of the first drying oven, the shorter the constant-rate drying time, which is preferable. However, if the temperature is too high, the flatness of the film will deteriorate due to heat, so a temperature of 180°C or lower is preferable. A temperature of 90°C or higher is preferable because it provides sufficient drying capacity.

[0090] The temperature inside the second drying oven is preferably 60° C. or higher and 140° C. or lower, and more preferably 80° C. or higher and 120° C. or lower. In the second drying step, by slowing down the drying time, the release layer surface before photocuring can be dried without being roughened, which is preferable because the smoothness of the release layer is improved.

[0091] For example, the constant rate drying time in the first drying step is preferably shorter than the falling rate drying time in the second drying step, which prevents the film from becoming flat and allows the release layer to be dried without roughening the surface before photocuring, thereby improving the smoothness of the release layer.

[0092] After application, the time required for entry into the first drying oven is preferably 0.1 to 2.5 seconds, and more preferably 0.1 to 2.0 seconds, with shorter times being preferable. By shortening the time required for entry into the first drying oven, the drying time in the first drying step can be shortened, which is preferable because it suppresses aggregation of the cationically cured polydimethylsiloxane (a) and results in a release layer with excellent smoothness. The time required for entry into the drying oven can be calculated from the processing speed and the structure of the processing machine base.

[0093] The production method of the present invention includes, after the drying step, a photocuring step of irradiating the release layer-forming composition with active energy rays to cure the composition. In the photocuring step, irradiation with active energy rays promotes a cationic curing reaction of the release layer-forming composition after drying. Known techniques such as ultraviolet rays and electron beams can be used as the active energy rays used, and ultraviolet rays are preferred. The cumulative light amount when using ultraviolet rays can be expressed as the product of illuminance and irradiation time. For example, it can be 10 to 500 mJ / cm. 2 It is preferable that the content is equal to or greater than the lower limit, because the release layer can be sufficiently cured. It is preferable that the content is equal to or less than the upper limit, because thermal damage to the film due to heat during irradiation can be suppressed and the smoothness of the surface of the release layer can be maintained.

[0094] When irradiating with active energy rays, it is preferable to hold the back surface of the film with a backup roll. By providing a backup roll, it is possible to maintain a constant distance from the active energy ray source, which is preferable, allowing for uniform irradiation. It is also preferable to irradiate with active energy rays while cooling the surface of the backup roll and cooling the film. By cooling, the film is less likely to be damaged by heat even when irradiated with active energy rays, and the smoothness of the release layer surface can be maintained, which is preferable.

[0095] In one embodiment, the manufacturing method of the present invention provides a method for manufacturing a release film for manufacturing a resin sheet containing an inorganic compound.

[0096] (resin sheet) The resin sheet in the present invention is not particularly limited as long as it is a sheet containing a resin. In one embodiment, the release film of the present invention is a release film for molding a resin sheet containing an inorganic compound. Examples of inorganic compounds include metal particles, metal oxides, minerals, and the like, 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 resin sheet contains such an inorganic compound, defects that can be attributed to inorganic compounds, such as damage to the resin sheet and difficulty in peeling the resin sheet from the release layer, can be suppressed. The resin component forming the resin sheet can be appropriately selected depending on the application. In one embodiment, the resin sheet containing an inorganic compound is a ceramic green sheet. 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. In one embodiment, the resin sheet has a thickness of 0.2 μm or more and 1.0 μm or less. For example, the present invention can provide a method for producing a release film for producing a resin sheet containing such an inorganic compound. The method for producing a release film for resin sheet molding in the present invention may include a step of molding a resin sheet having a thickness of 0.2 μm or more and 1.0 μm or less.

[0097] (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.

[0098] In one embodiment, the release film of the present invention is a release film for producing a ceramic green sheet, and is used to produce such a multilayer ceramic capacitor. For example, the method for producing a ceramic green sheet in which a ceramic green sheet is formed using the release film for producing a ceramic green sheet 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. More specifically, for example, ceramic green sheets are manufactured as follows. First, using the release film of the present invention as a carrier film, a ceramic slurry for forming a ceramic element is applied and dried. Ultra-thin ceramic green sheets with a thickness of 0.2 to 1.0 μm 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 divided into multiple pieces to produce green ceramic elements. The green ceramic elements are fired to obtain ceramic elements. Subsequently, first and second external electrodes are formed to complete a multilayer ceramic capacitor. [Example]

[0099] The present invention will be described in more detail below using examples, but the present invention is not limited to these examples. The property values ​​used in the present invention were evaluated using the following methods.

[0100] (Release layer thickness) The cut-out release film was embedded in resin and cut into ultrathin sections using an ultramicrotome. Then, cross-sections were observed using a JEOL JEM2100 transmission electron microscope, and the film thickness of the release layer was measured from the observed TEM images. When the thickness was too thin to be accurately evaluated by cross-sectional observation, it was measured using a reflection spectroscopic film thickness meter (Otsuka Electronics Co., Ltd., FE-3000).

[0101] (Weight of release layer) In this specification, the weight per 1 μm of release layer thickness is 1 g / m 2 For example, when the thickness of the release layer measured by the above method is 0.2 μm, the total weight of the release layer is 0.2 g / m 2The weight of the cationically curable polydimethylsiloxane (a), the weight of the cationically curable resin (b), and the weight of the acid generator (c) contained in the release layer were calculated from the blending ratio of each component contained in the release layer-forming composition and the total weight of the release layer. For example, when the thickness of the release layer is 0.2 μm and the weight ratio of the cationically curable polydimethylsiloxane (a) to the release layer is 5 parts by mass, the weight of (a) contained in the release layer is 0.01 g / m 2 The weight ratio (mass %) of the release layer was calculated assuming that the total of the components (a) and (b) was 100 parts by mass.

[0102] (Amount of Release Layer-Forming Composition Applied) The value calculated from the liquid consumption weight of the release layer-forming composition used in the coating step and the processed area was used.

[0103] (Time from application to first drying oven) The value calculated from the film travel distance from the coating section to the first drying oven and the processing speed was used.

[0104] (area surface 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. (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

[0105] (Number of protrusions with a height of 10 nm or more, Number of protrusions with a height of 5 nm or more) Particle analysis was performed using the measurement data that showed the median value of the seven measurements of the maximum protrusion height. Particle analysis was performed using the analysis software of the Vertscan R550H-M100 under the following conditions. Particle analysis was performed on the same measurement area as the above-mentioned area surface roughness and maximum protrusion height measurements, and the number of protrusions with a maximum size of 10 nm or more, or the number of protrusions with a maximum size of 5 nm or more, was calculated. The number of protrusions was calculated based on the number of protrusions per 1 mm 2 The converted values ​​were used. (Particle analysis conditions) Surface correction: 4th order correction Storage processing: Fully interpolated ·Surprise analysis Reference height: Zero plane

[0106] (Ceramic sheet peeling force) 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 peeling direction, double-sided adhesive tape (Nitto Denko Corporation, No. 535A) was attached to a 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 obtained measurements over peel distances of 20 mm to 70 mm, and this value was used as the peel force. Measurements were performed five times, and the average peel force was used for evaluation. The peel strength was evaluated based on the following criteria. 〇: 0.1mN / mm or more, less than 1.0mN / mm ×: 1.0 mN / mm or more

[0107] (Evaluation of pinholes in ceramic green sheets) In the same manner as in the evaluation of the releasability of the ceramic slurry, 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

[0108] (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.

[0109] (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)).

[0110] (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.

[0111] (Manufacturing of laminated film X2) As the laminate film X2, E5101 (Toyobo Ester (registered trademark) film, manufactured by Toyobo Co., Ltd.) having a thickness of 25 μm was used. E5101 is configured to contain particles in surface layer A and surface layer B. The Sa of surface layer A of laminate film X2 was 24 nm, and the Sa of surface layer B was 24 nm.

[0112] (cationic curing polydimethylsiloxane (a)) (a)-1: UV POLY215 (Arakawa Chemical Industries, Ltd., solids content 100%)

[0113] (cationic curing resin (b)) (b)-1: Celloxide 2021P (manufactured by Daicel Corporation, solid content 100%) (b)-2: X-40-2670 (Shin-Etsu Chemical Co., Ltd., solid content 100%)

[0114] (Acid generator (c)) (c)-1: CPI-101A (manufactured by San-Apro Co., Ltd., solid content 50%)

[0115] Example 1 A release layer-forming composition 1 having the following composition was applied to the surface layer A of the laminated film X1 through a filter capable of removing 99% or more of foreign matter of 0.5 μm or more, and then coated in an amount of 5.0 g / m using a reverse gravure machine. 2 The processing speed was then 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 placed on a cooling roll and irradiated with an ultraviolet ray 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 resin sheet molding was obtained. The smoothness, releasability, and pinhole evaluation of the obtained release film were also performed, and the results were good, as shown in Table 1. The thus obtained release film for resin sheet molding was a release film that could be used to produce a resin sheet having a thickness of, for example, 0.2 μm or more and 1.0 μm or less. The weight (mg / m) of each component (a), (b), and (c) in the table is 2 ) indicates the content ratio per solid content (weight of each component relative to the total weight of the release layer). (Release layer-forming composition 1) Methyl ethyl ketone 24,000 parts by mass (SP value (δ): 19.1, (δ D ):16.0, (δ P ):9.0, (δ H ):5.1) Toluene 24,000 parts by mass (SP value (δ): 18.2, (δ D ):18.0, (δ P ):1.4, (δ H ):2.0) Normal heptane 48,000 parts by mass (SP value (δ): 15.3, (δ D ):15.3, (δ P ):0.0, (δ H ):0.0) (a)-1 0.039 parts by mass (b)-1 3.883 parts by mass (c)-1 0.078 parts by mass

[0116] Examples 2 to 4 A release film for resin sheet molding was obtained in the same manner as in Example 1, except that the composition and production method of the release layer were changed as shown in Table 1.

[0117] Example 5 A release film for resin sheet molding was obtained in the same manner as in Example 1, except that a release layer-forming composition 2 having the following composition was used. (Release layer-forming composition 2) Methyl ethyl ketone 38,400 parts by mass (SP value (δ): 19.1, (δ D ):16.0, (δ P ):9.0, (δ H ):5.1) Toluene 38,400 parts by mass (SP value (δ): 18.2, (δ D ):18.0, (δ P ):1.4, (δ H ):2.0) Normal heptane 19,200 parts by mass (SP value (δ): 15.3, (δ D ):15.3, (δ P ):0.0, (δ H ):0.0) (a)-1 0.196 parts by mass (b)-1 3.726 parts by mass (c)-1 0.078 parts by mass

[0118] Example 6 The normal heptane in the release layer-forming composition was replaced with cyclohexane (SP value (δ): 16.8, (δ D ):16.8, (δ P ):0.0, (δ H A release film for resin sheet molding was obtained in the same manner as in Example 2, except that the viscosity was changed to 0.2).

[0119] (Examples 7 and 8) A release film for resin sheet molding was obtained in the same manner as in Example 2, except that the coating amount and solid content ratio were changed to those shown in Table 1. At this time, the organic solvent ratio was adjusted to be the same as in the release layer-forming composition 1.

[0120] Example 9 A release film for resin sheet molding was obtained in the same manner as in Example 1, except that the composition for forming a release layer 3 was changed to the following composition. (Release layer forming composition 3) Methyl ethyl ketone 24,000 parts by mass (SP value (δ): 19.1, (δ D ):16.0, (δ P ):9.0, (δ H ):5.1) Toluene 24,000 parts by mass (SP value (δ): 18.2, (δ D ):18.0, (δ P ):1.4, (δ H ):2.0) Normal heptane 48,000 parts by mass (SP value (δ): 15.3, (δ D ):15.3, (δ P ):0.0, (δ H ):0.0) (a)-1 0.039 parts by mass (b)-2 3.883 parts by mass (c)-1 0.078 parts by mass

[0121] Examples 10 to 12 A release film for resin sheet molding was obtained in the same manner as in Example 1, except that the composition and production method of the release layer were changed as shown in Table 1.

[0122] Example 13 A release film for resin sheet molding was obtained in the same manner as in Example 1, except that a release layer-forming composition 4 having the following composition was used. (Release layer-forming composition 4) Methyl ethyl ketone 38,400 parts by mass (SP value (δ): 19.1, (δ D ):16.0, (δ P ):9.0, (δ H ):5.1) Toluene 38,400 parts by mass (SP value (δ): 18.2, (δ D ):18.0, (δ P ):1.4, (δ H ):2.0) Normal heptane 19,200 parts by mass (SP value (δ): 15.3, (δ D ):15.3, (δ P ):0.0, (δ H ):0.0) (a)-1 0.196 parts by mass (b)-2 3.726 parts by mass (c)-1 0.078 parts by mass

[0123] Example 14 The normal heptane in the release layer-forming composition was replaced with cyclohexane (SP value (δ): 16.8, (δ D ):16.8, (δ P ):0.0, (δ H A release film for resin sheet molding was obtained in the same manner as in Example 2, except that the viscosity was changed to 0.2).

[0124] (Examples 15 and 16) A release film for resin sheet molding was obtained in the same manner as in Example 2, except that the coating amount and solid content ratio were changed to those shown in Table 1. At this time, the organic solvent ratio was adjusted to be the same as in the release layer-forming composition 3.

[0125] Example 17 A release film for molding an ultrathin resin sheet was obtained in the same manner as in Example 1, except that a release layer-forming composition 5 having the following composition was used. (Release layer forming composition 5) Methyl ethyl ketone 24.950 parts by mass (SP value (δ): 19.1, (δ D ):16.0, (δ P ):9.0, (δ H ):5.1) Toluene 24.950 parts by mass (SP value (δ): 18.2, (δ D ):18.0, (δ P ):1.4, (δ H ):2.0) Normal heptane 49,900 parts by mass (SP value (δ): 15.3, (δ D ):15.3, (δ P ):0.0, (δ H ):0.0) (a)-1 0.196 parts by mass (c)-1 0.004 parts by mass

[0126] Example 18 A release film for resin sheet molding was obtained in the same manner as in Example 1, except that the solid content concentration was changed to that shown in Table 1 and the organic solvent ratio was adjusted to be the same as in release layer-forming composition 5.

[0127] Example 19 A release film for resin sheet molding was obtained in the same manner as in Example 17, except that the production method was changed to that shown in Table 1.

[0128] Example 20 A release film for molding an ultrathin resin sheet was obtained in the same manner as in Example 1, except that the release layer-forming composition was changed to 6. (Release layer forming composition 6) Methyl ethyl ketone 39.920 parts by mass (SP value (δ): 19.1, (δ D):16.0, (δ P ):9.0, (δ H ):5.1) Toluene 39.920 parts by mass (SP value (δ): 19.1, (δ D ):16.0, (δ P ):9.0, (δ H ):5.1) Normal heptane 19.960 parts by mass (SP value (δ): 15.3, (δ D ):15.3, (δ P ):0.0, (δ H ):0.0) (a)-1 0.196 parts by mass (c)-1 0.004 parts by mass

[0129] Example 21 The normal heptane in the release layer-forming composition 5 was replaced with cyclohexane (SP value (δ): 16.8, (δ D ):16.8, (δ P ):0.0, (δ H A release film for resin sheet molding was obtained in the same manner as in Example 1, except that the viscosity was changed to 0.2).

[0130] (Examples 22 and 23) A release film for resin sheet molding was obtained in the same manner as in Example 17, except that the coating amount and solid content concentration were changed to those shown in Table 1. At this time, the organic solvent ratio was adjusted to be the same as in release layer-forming composition 5.

[0131] (Comparative Example 1) A release film for molding an ultrathin resin sheet was obtained in the same manner as in Example 1, except that the release layer-forming composition 7 was changed to the following composition. (Release layer-forming composition 7) Methyl ethyl ketone 24,000 parts by mass (SP value (δ): 19.1, (δ D ):16.0, (δ P ):9.0, (δ H ):5.1) Toluene 24,000 parts by mass (SP value (δ): 18.2, (δ D ):18.0, (δ P ):1.4, (δ H ):2.0) Normal heptane 48,000 parts by mass (SP value (δ): 15.3, (δ D ):15.3, (δ P ):0.0, (δ H ):0.0) (b)-1 3.922 parts by mass (c)-1 0.078 parts by mass

[0132] (Comparative Example 2) A release film for molding an ultrathin resin sheet was obtained in the same manner as in Example 1, except that the release layer-forming composition 8 was changed to the following composition. (Release layer-forming composition 8) Methyl ethyl ketone 24,000 parts by mass (SP value (δ): 19.1, (δ D ):16.0, (δ P ):9.0, (δ H ):5.1) Toluene 24,000 parts by mass (SP value (δ): 18.2, (δ D ):18.0, (δ P ):1.4, (δ H ):2.0) Normal heptane 48,000 parts by mass (SP value (δ): 15.3, (δ D ):15.3, (δ P ):0.0, (δ H ):0.0) (a)-1 2.941 parts by mass (b)-2 0.981 parts by mass (c)-1 0.078 parts by mass

[0133] (Comparative Example 3) A release film for molding an ultrathin resin sheet was obtained in the same manner as in Example 1, except that the release layer-forming composition 9 was changed to the following composition. (Release layer-forming composition 9) Methyl ethyl ketone 24,000 parts by mass (SP value (δ): 19.1, (δ D ):16.0, (δ P ):9.0, (δ H ):5.1) Toluene 24,000 parts by mass (SP value (δ): 18.2, (δ D ):18.0, (δ P ):1.4, (δ H ):2.0) Normal heptane 48,000 parts by mass (SP value (δ): 15.3, (δ D ):15.3, (δ P ):0.0, (δ H ):0.0) (a)-1 3.922 parts by mass (c)-1 0.078 parts by mass

[0134] Comparative Example 4 A release film for molding an ultrathin resin sheet was obtained in the same manner as in Example 10, except that it was applied to laminate film X2.

[0135] [Table 1A]

[0136] [Table 1B]

[0137] [Table 1C]

[0138] [Table 2A]

[0139] [Table 2B]

[0140] [Table 2C]

[0141] In Comparative Example 1, the ceramic sheet did not contain the cationically curable polydimethylsiloxane (a), and therefore the peeling force was too strong and it was impossible to peel it off. In Comparative Examples 2 to 4, the number of protrusions with a height of 10 nm or more was 200 / mm 2 In Comparative Example 4, inorganic particles were present throughout the substrate, and the smoothness of the release film was extremely poor, resulting in breakage of the green sheet and pinholes. [Industrial Applicability]

[0142] According to the present invention, by improving the smoothness and releasability of the release layer, a release film is provided that can mold resin sheets with few defects even in ultra-thin products with a thickness of 1 μm or less, thereby making it possible to manufacture resin sheets without the risk of defects.

Claims

1. A release film for resin sheet molding having a polyester film as a substrate and a release layer, The polyester film has a surface layer A that is substantially free of inorganic particles, The release layer is provided on the surface layer A, the release layer is a layer formed by curing a release layer-forming composition, The release layer-forming composition contains a cationically curable polydimethylsiloxane (a), the content of the cationically curable polydimethylsiloxane (a) contained in the release layer is 90 mg / m 2 or less; The release layer has an average surface roughness (Sa) of 2 nm or less, The number of protrusions having a height of 10 nm or more present on the surface of the release layer is 200 / mm 2 Below is the Release film for resin sheet molding.

2. the cationically curable polydimethylsiloxane (a) has at least one functional group selected from an oxetanyl group, an epoxy group, and an alicyclic epoxy group; The release film for resin sheet molding according to claim 1 .

3. the release layer-forming composition further contains a cationically curable compound (b-1) that does not have a silicone skeleton, The cationically curable compound (b-1) has two or more alicyclic epoxy groups in the molecule, 2. The release film for resin sheet molding according to claim 1, wherein the content of the cationic curable compound (b-1) is 80% by mass or more relative to a total of 100 parts by mass of the cationic curable polydimethylsiloxane (a) and the cationic curable compound (b-1).

4. The release layer-forming composition further contains a cyclic siloxane compound (b-2) having an alicyclic epoxy group, The cyclic siloxane compound (b-2) has two or more alicyclic epoxy groups in the molecule, 2. The release film for resin sheet molding according to claim 1, wherein the content of the cyclic siloxane compound (b-2) is 80% by mass or more relative to a total of 100 parts by mass of the cationically curable polydimethylsiloxane (a) and the cyclic siloxane compound (b-2).

5. the release layer-forming composition contains an organic solvent having an SP value (δ) of 14 or more and 17 or less, The release layer-forming composition contains the organic solvent having an SP value (δ) of 14 or more and 17 or less in an amount of 10% by mass or more relative to 100 parts by mass of the total weight of the release layer-forming composition. The release film for resin sheet molding according to claim 1 .

6. 2. The release film for resin sheet molding according to claim 1, wherein the resin sheet is a resin sheet containing an inorganic compound or a ceramic green sheet.

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