Mold release film for resin sheet molding

Abstract

The present invention provides a mold release film which can be peeled with a low, uniform force even with a thin ceramic green sheet, in which there is no risk of occurrence of defects such as pinholes, and which has excellent smoothness. The present invention is a mold release film comprising a base material, which is a polyester film having a width of more than 900 mm but not more than 2,500 mm, and a mold release layer, said mold release film being characterized in that, when R1 is defined as a range of 100 mm from one end in the width direction and toward the center when the mold release film is wound in a roll, R2 is defined as a range of 50 mm from the center and toward both sides in the width direction, R3 is defined as a range of 100 mm from the other end in the width direction and toward the center, and A1, A2, and A3 are defined as the number of coarse protrusions which have a height of 500 nm or more and which exist on the surface of the mold release layer in the respective ranges R1, R2, R3 as evaluated by a described method, the number of coarse protrusions represented by each of A1, A2, and A3 is in the range of 10-1,000 protrusions / m2, and a ratio X of the number of coarse protrusions calculated as X=((A1+A3) / 2) / A2 is 0.2-5.0.

Description

Release film for resin sheet molding

[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 a thin resin sheet.

[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 larger in capacity, the thickness of ceramic green sheets has tended to decrease. Ceramic green sheets are molded by coating a release film with a slurry containing ceramic components such as barium titanate and a binder resin, and then drying the coating. After printing electrodes on the molded ceramic green sheets and peeling them from the release film, the ceramic green sheets are stacked, pressed, fired, and external electrodes are applied to produce a multilayer ceramic capacitor.

[0004] When molding a ceramic green sheet onto the surface of the release layer of a polyester film substrate, the wettability and smoothness of the release film when coating the ceramic slurry, as well as the releasability when peeling the ceramic green sheet from the release film, are important. Poor smoothness can lead to problems such as pinholes, thickness variations, and sheet defects in the ceramic green sheet obtained by coating and drying the slurry.

[0005] When a polyester film roll is wide, the central region in the width direction is prone to static buildup, which can lead to the adhesion of a large amount of film debris and other disturbances. Furthermore, air is difficult to remove from the central region during winding, which can lead to film movement due to expansion and contraction caused by temperature changes, which can cause particles to fall off the base film or protrusions caused by scratches.

[0006] In the present invention, a wide polyester film roll refers to a film having a width exceeding 900 mm. Although problems such as charging at the center portion can occur even with a film having a width of 900 mm or less, such a tendency is more pronounced with a film having a width exceeding 900 mm.

[0007] In recent years, ceramic green sheets have become thinner, and there is a growing demand for ceramic green sheets with a thickness of 1.0 μm or less, more specifically, 0.2 μm to 1.0 μm. As a result, the demand for smoothness required of release films is increasing.

[0008] Patent Document 1 describes a release film with excellent smoothness, which has a number of protrusions of 1 μm or more at 1 / m ２ The following release film is disclosed, characterized in that a release layer is provided on the film.

[0009] Furthermore, Patent Document 2 discloses an oriented polyester film roll that suppresses coating cissing of a sheet formed on the surface of a release layer, while maintaining a good winding appearance when wound up.

[0010] Furthermore, Reference 3 discloses a method for producing a biaxially stretched polyester film, characterized in that the film is transversely stretched in a stenter oven in which the number of dust particles is not more than a certain number.

[0011] JP 2007-237497 A JP 2022-159254 A JP 2009-012242 A

[0012] However, the technology of Patent Document 1 is a technology that suppresses protrusions of 1 μm or more, and with recent ceramic green sheets with thicknesses of 0.2 μm to 1.0 μm, it is necessary to suppress protrusions that are shorter than conventional ones.

[0013] Similarly, the film of Patent Document 2 has large protrusions that make it difficult to accommodate the thickness of recent ceramic green sheets, and because there are many protrusions on the substrate edge, when the corresponding mounting positions are coated with a release coating and used to manufacture multilayer ceramic capacitors, the product defect rate is higher than that of other mounting positions. Furthermore, powdery material on the edges accumulates in the clean room during the release process, causing problems such as worsening particle problems and adhesion during the subsequent release process.

[0014] Furthermore, the biaxially oriented polyester film of Patent Document 3 requires cleaning inside and outside the coating machine and inside the stenter oven, and the film produced before cleaning has a large number of protrusions, and the number of protrusions may vary depending on the cleaning conditions.

[0015] Thus, there is a demand for technology to further reduce the occurrence of pinholes in ceramic green sheets with thicknesses of approximately 0.2 μm to 1.0 μm that have been produced in recent years. Furthermore, in preparation for the further thinning of resin sheets such as ceramic green sheets in the future, there is a demand for reducing the risk of pinhole occurrence. There is also a demand for reducing the defective rate of resin sheets and reducing waste.

[0016] As a result of extensive research into solving the above problems, the present inventors have newly discovered the existence of a condition that has not been noticed in the past.

[0017] According to the investigations of the present inventors, the number of protrusions on the surface of a film produced using conventional technology can vary in the width direction, and it has been found that there are conditions that have not been given attention in the past that can be used to suppress this.

[0018] Therefore, an object of the present invention is to provide a release film that is less likely to have defects across the entire width, even when forming a thin resin sheet or the like.

[0019] As a result of intensive research to solve the above problems, the inventors have found that the release film described in this specification can suppress the variation in the width direction of the number of protrusions on the film surface, and have completed the present invention.

[0020] That is, the present invention comprises the following:

[0021] [1] A release film having a base material that is a polyester film having a width of more than 900 mm and not more than 2500 mm and a release layer, wherein when wound into a roll, a range of 100 mm from one end in the width direction toward the center is defined as R1, a range of 50 mm on both sides in the width direction from the center is defined as R2, and a range of 100 mm from the other end in the width direction toward the center is defined as R3, and the numbers of coarse protrusions with a height of 500 nm or more present on the surface of each range R1, R2, R3 of the release layer evaluated by the following method are defined as A1, A2, and A3, respectively: the numbers of coarse protrusions represented by A1, A2, and A3 are each 10 to 1000 protrusions / m ２ and the ratio X of the number of coarse protrusions calculated by X = ((A1 + A3) / 2) / A2 is 0.2 to 5.0. (Method for evaluating the number of coarse protrusions) A resin layer-forming composition for evaluation is applied to the surface of the release layer so that the thickness after drying is 500 nm, and then dried. The positions of pinholes in the resulting resin layer are marked, and the height of the protrusions is measured using the surface of the resin layer as a reference. The resulting protrusion height is then added to the thickness of the resin layer (500 nm), and the number of coarse protrusions having a protrusion height of 500 nm or more is counted.

[0022] [2] The release film according to [1], wherein the surface of the release layer has an area average surface roughness (Sa) of 3.0 nm or less and a maximum protrusion height (Rp) of 200 nm or less.

[0023] [3] The release film according to [1] or [2], wherein the thickness of the release layer is 800 nm or less.

[0024] [4] The release film according to any one of [1] to [3], wherein the release film is a release film for producing a ceramic green sheet or for molding a resin sheet.

[0025] The release film for resin sheet molding of the present invention has a release layer on one side of a base film, and is a release film in which the number of protrusions on the surface of the release layer and the distribution of the protrusions in the width direction are controlled.

[0026] The present invention can provide a release film that can coat a resin sheet-forming slurry without defects without deteriorating the winding properties of the release film, and in particular can form a ceramic green sheet without defects.

[0027] FIG. 2 is a cross-sectional view schematically illustrating the height of the coarse projections in the present invention.

[0028] The present invention will be described in detail below.

[0029] In the present invention, by providing a release layer on one side of a substrate film having excellent smoothness, it is possible to obtain a release film having excellent smoothness, slurry coatability, and releasability.

[0030] The release layer is not particularly limited, and silicone or a resin containing a long-chain alkyl group can be used as a release agent. By using these compositions to form the release layer, a release film with excellent releasability can be obtained.

[0031] (Polyester film) The substrate film in the present invention is a polyester film having a width of more than 900 mm and not more than 2500 mm. By using a polyester film having a width of more than 900 mm and not more than 2500 mm, a release film is provided in which the number of protrusions on the release layer surface and the distribution of the protrusions in the width direction are more effectively controlled. Although the specific mechanism has not been analyzed, it has been found that with a release film having a polyester film having a width of more than 900 mm and not more than 2500 mm, when the release film is wound into a roll (sometimes simply referred to as a release film roll), warping of the release film does not substantially occur, the film thickness from one end of the release film to the other end is maintained uniform, and the distribution of the protrusions in the width direction can be uniformly controlled.

[0032] In one embodiment, a release layer may be formed on a polyester film having a width of more than 2500 mm, the film may be cut to within the range of the present invention, and the cut release film may be wound up.

[0033] On the other hand, if the base film is wound up with a width significantly exceeding 2500 mm, for example, the central region in the width direction is likely to become charged, which may result in the adhesion of a large amount of disturbances such as film debris. Furthermore, air is difficult to remove near the center during winding, which makes the film prone to movement due to expansion and contraction caused by temperature changes, and this may result in particle shedding on the base film or protrusions caused by scratches.

[0034] As a result, when manufacturing the green sheet or resin sheet, the number of protrusions on the surface of the release layer and the distribution of the protrusions in the width direction may deviate from the initial design conditions.

[0035] Thus, in the present invention, by setting the width of the base film to more than 900 mm and not more than 2500 mm, it is possible to obtain a release film and a release film roll in which the number of protrusions on the release layer surface and the distribution of the protrusions in the width direction are more effectively controlled. Furthermore, even during storage until the green sheet is produced, the number of protrusions on the release layer surface and the distribution of the protrusions in the width direction can be well maintained, and the resin sheet-forming slurry can be applied without defects without deteriorating the winding property of the release film.

[0036] The polyester constituting the polyester film used as the base film (hereinafter sometimes referred to as the base film) in the present invention is not particularly limited, and a film of a polyester commonly used as a base film for release films can be used. Preferred are crystalline linear saturated polyesters composed of an aromatic dibasic acid component and a diol component. For example, polyethylene terephthalate, polyethylene-2,6-naphthalate, polybutylene terephthalate, polytrimethylene terephthalate, or copolymers primarily composed of these resin components are even more preferred. Polyester films formed from polyethylene terephthalate are particularly preferred. The polyethylene terephthalate preferably contains 90 mol% or more, more preferably 95 mol% or more, of ethylene terephthalate repeating units, and may be copolymerized with small amounts of other dicarboxylic acid components or diol components. For example, from the standpoint of cost, 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 release film of the present invention. The polyester film is preferably a biaxially oriented polyester film because of its high modulus of elasticity in both directions.

[0037] 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. An intrinsic viscosity of 0.50 dl / g or higher is preferred because it prevents frequent breakage during the stretching process. Conversely, an intrinsic viscosity of 0.70 dl / g or lower is preferred because it allows for good cuttability when cut to a predetermined product width and prevents dimensional defects. It is also preferred that the raw material pellets are thoroughly vacuum dried.

[0038] In this specification, when simply referring to a "polyester film," it means a polyester film having (laminated with) a surface layer A and a surface layer B.

[0039] The method for producing the polyester film of the present invention is not particularly limited, and any conventionally used method can be used. For example, the polyester can be melted in an extruder, extruded into a film, and cooled on a rotating cooling drum to obtain an unstretched film, which can then be biaxially stretched. A biaxially stretched film can be obtained by sequentially biaxially stretching a uniaxially stretched film in the longitudinal or transverse direction, or by simultaneously biaxially stretching an unstretched film in the longitudinal and transverse directions.

[0040] In the present invention, the stretching temperature during stretching of the polyester film is preferably equal to or higher than the second-order transition temperature (Tg) of the polyester, and the stretching is preferably 1 to 8 times, particularly 2 to 6 times, in both the longitudinal and transverse directions.

[0041] 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, processing, or molding. On the other hand, a film thickness of 50 μm or less is preferred in terms of reducing the environmental impact by preventing excessively large amounts of film from being discarded after use.

[0042] The polyester film substrate may be a single layer or a multilayer structure of two or more layers. For example, the substrate film may be a polyester film having a surface layer A that is substantially free of particles having a particle size of 1.0 μm or more and a surface layer B that contains particles. Preferably, the surface layer A is substantially free of inorganic particles having a particle size of 1.0 μm or more.

[0043] In this embodiment, particles having a particle size of less than 1.0 μm and 1 nm or more may be present in the surface layer A. When the surface layer A is substantially free of particles having a particle size of 1.0 μm or more, such as inorganic particles, the surface of the release layer formed is smooth, and defects caused by the particle shape in the substrate being transferred to the resin sheet can be reduced.

[0044] In one embodiment, the surface layer A does not contain particles having a particle size of less than 1.0 μm, so that defects caused by the transfer of particle shapes in the substrate to the resin sheet can be more effectively prevented.

[0045] In one embodiment, the polyester film substrate is preferably a laminate film having a surface layer A substantially free of inorganic particles on at least one side. This more effectively prevents defects caused by the transfer of particle shapes in the substrate to the resin sheet. For example, a preferred embodiment is that the surface layer A substantially free of particles having a particle size of less than 1.0 μm also substantially free of particles having a particle size of 1.0 μm or more.

[0046] In the present invention, "substantially free of particles" means, for example, in the case of inorganic particles less than 1.0 μm in size, that the content of inorganic elements quantified by fluorescent X-ray analysis is 50 ppm or less, preferably 10 ppm or less, and most preferably below the detection limit. This is because even if particles are not actively added to the film, contaminants from foreign substances or dirt adhering to the raw resin or the production line or equipment during the film manufacturing process may peel off and be mixed into the film. Furthermore, "substantially free of particles with a particle size of 1.0 μm or more" means that particles with a particle size of 1.0 μm or more are not actively included.

[0047] In the case of a laminated polyester film having a multi-layer structure of two or more layers, it is preferable that a surface layer B that can contain inorganic particles or the like is provided on the surface opposite to a surface layer A that does not substantially contain inorganic particles.

[0048] As for the laminate structure, if the layer on the side to which the release layer is applied is layer A, the layer on the opposite side is layer B, and the other core layer is layer C, the layer structure in the thickness direction can be a laminate structure such as release layer / A / B or release layer / A / C / B. Naturally, layer C may have a multi-layer structure. Furthermore, surface layer B may not contain inorganic particles. In that case, it is preferable to provide a coating layer containing at least inorganic particles and a binder on surface layer B to impart slip properties for winding the film into a roll.

[0049] In the polyester film substrate of the present invention, the surface layer B, which forms the surface opposite to the surface to which the release layer is applied, preferably contains inorganic particles, particularly silica particles and / or calcium carbonate particles, from the viewpoint of the slipperiness of the film and ease of air escape. The content of the inorganic particles contained in the surface layer B is preferably 5,000 to 15,000 ppm in total.

[0050] In this case, the area surface average roughness (Sa) of the film of the surface layer B is preferably in the range of 1 to 40 nm. More preferably, it is in the range of 5 to 35 nm. When the total content of silica particles and / or calcium carbonate particles is 5,000 ppm or more and Sa is 1 nm or more, air can be uniformly released when the film is wound into a roll, resulting in a good wound shape and good flatness, making it suitable for producing ultrathin ceramic green sheets. Furthermore, when the total content of silica particles and / or calcium carbonate particles is 15,000 ppm or less and Sa is 40 nm or less, the lubricant is less likely to aggregate and large protrusions are not formed, which is preferable because it ensures stable quality when producing ultrathin ceramic green sheets.

[0051] In addition to silica and / or calcium carbonate, inactive inorganic particles and / or heat-resistant organic particles can also be used as particles contained in Layer B. However, from the viewpoints of transparency and cost, it is more preferable to use silica particles and / or calcium carbonate particles. Other inorganic particles that can be used include alumina-silica composite oxide particles and hydroxyapatite particles. Heat-resistant organic particles include crosslinked polyacrylic particles, crosslinked polystyrene particles, and benzoguanamine particles. When silica particles are used, porous colloidal silica is preferred, and when calcium carbonate particles are used, light calcium carbonate that has been surface-treated with a polyacrylic acid-based polymer compound is preferred from the viewpoint of preventing the lubricant from falling off.

[0052] The average particle size of the inorganic particles added to the surface layer B is preferably 0.1 μm or more and 2.0 μm or less, particularly preferably 0.5 μm or more and 1.0 μm or less. If the average particle size of the inorganic particles is 0.1 μm or more, the slipperiness of the release film is good, which is preferable. Furthermore, if the average particle size is 2.0 μm or less, there is no risk of adversely affecting the smoothness of the release layer surface, and there is no risk of pinholes occurring in the ceramic green sheet, which is preferable.

[0053] From the viewpoint of reducing pinholes, it is preferable that recycled raw materials or the like are not used for the surface layer A, which is the layer on which the release layer is to be formed, in order to prevent the inclusion of inorganic particles such as lubricants.

[0054] The thickness ratio of the surface layer A, which is the layer on which the release layer is provided, is preferably 20% to 50% of the total layer thickness of the base film. If it is 20% or more, the film is less likely to be affected from the inside by particles contained in the surface layer B, etc., and it is easy for the regional surface average roughness Sa to satisfy the above range, which is preferable. If it is 50% or less of the total layer thickness of the base film, the proportion of recycled raw materials used in the surface layer B can be increased, which is preferable as it reduces the environmental load.

[0055] From an economical standpoint, recycled raw materials such as film scraps and PET bottles may be used in an amount of 50 to 90% by mass for any layer (surface layer B or the aforementioned intermediate layer C) other than the surface layer A. Even in this case, it is preferable that the type and amount of lubricant contained in layer B, its particle size, and the area surface average roughness (Sa) satisfy the above-mentioned ranges.

[0056] Furthermore, in order to improve the adhesion of a release layer or the like to be applied later, or to prevent charging, a coating layer may be provided on the surface of the surface layer A and / or the surface layer B before stretching or after uniaxial stretching in the film-forming process, and corona treatment or the like may also be performed.

[0057] (Release Layer) The release film of the present invention has the substrate and release layer as described above, and the number of coarse protrusions on the surface of the release layer is adjusted within each of the ranges R1, R2, and R3.

[0058] That is, when wound into a roll, the range of 100 mm from one end in the width direction toward the center is defined as R1, the range of 50 mm on both sides in the width direction from the center is defined as R2, and the range of 100 mm from the other end in the width direction toward the center is defined as R3. When the numbers of coarse protrusions of 500 nm or more present on the surface of each of the ranges R1, R2, and R3 of the release layer evaluated by the following method are defined as A1, A2, and A3, respectively, the numbers of coarse protrusions indicated by A1, A2, and A3 are each 10 to 1000 pieces / m ２ and the ratio X of the number of coarse protrusions calculated by X = ((A1 + A3) / 2) / A2 is 0.2 to 5.0. (Method for evaluating the number of coarse protrusions) A resin layer-forming composition for evaluation is applied to the surface of the release layer so that the thickness after drying is 500 nm, and then dried. The positions of pinholes in the resulting resin layer are marked, and the height of the protrusions is measured using the surface of the resin layer as a reference. The resulting protrusion height is then added to the thickness of the resin layer (500 nm), and this value is defined as the protrusion height, and the number of coarse protrusions having a protrusion height of 500 nm or more is counted.

[0059] A release layer satisfying these conditions is preferably formed by curing a composition containing, for example, a silicone-based or long-chain alkyl-containing resin. In addition to the resin or compound, other components such as a binder component, a crosslinking agent, an adhesion promoter, and an antistatic agent can be added within a range that does not impair the effects of the present invention.

[0060] (Binder Component) The binder component contained in the release layer-forming composition of the present invention is not particularly limited, but it is preferable that a component capable of crosslinking is crosslinked in order to increase the crosslinking density of the release layer and improve the durability and solvent resistance of the release layer. Therefore, it is preferable that the binder component is formed by reacting a resin having a reactive functional group with a crosslinking agent. It is also preferable that either the reactive functional group or the crosslinking agent is self-crosslinked alone. However, in the present invention, an embodiment in which the binder component is formed only from a resin having a reactive functional group or a crosslinking agent is not excluded.

[0061] The resin having a reactive functional group is not particularly limited, but suitable examples include polyester resins, poly(meth)acrylic resins, polyurethane resins, polyolefin resins, epoxy resins, melamine resins, etc. These resins preferably have at least one reactive functional group selected from the group consisting of carboxyl groups, hydroxyl groups, epoxy groups, amino groups, etc.

[0062] The resin having a reactive functional group preferably has a long-chain alkyl group and / or a silicone skeleton as part of the resin skeleton. Having a low surface free energy moiety such as a long-chain alkyl group and / or a silicone skeleton as part of the resin skeleton is preferable because it increases the compatibility between the silicone-based release agent described below and the binder component, making it less likely for aggregation to occur during drying and improving smoothness.

[0063] In the case of an alkyd resin having a long-chain alkyl group in the side chain, the resin can be obtained by mixing an acid having the aforementioned long-chain alkyl group (e.g., octylic acid or stearyl acid) with a polybasic acid such as phthalic acid, mixing it with a polyhydric alcohol component (e.g., pentaerythritol or diethylene glycol), and subjecting it to a dehydration condensation reaction.

[0064] For example, a (meth)acrylic resin having a long-chain alkyl group can be included as a binder component, and may be, for example, a (meth)acrylic resin having a long-chain alkyl group on the side chain.

[0065] The (meth)acrylic resin having a long-chain alkyl group in the side chain is preferably obtained by copolymerizing two or more (meth)acrylic monomers. The copolymerized monomer preferably contains a monomer having a long-chain alkyl group (e.g., lauryl (meth)acrylate, stearyl (meth)acrylate, isodecyl (meth)acrylate, etc.), and preferably contains a monomer having a hydroxy group as a reactive functional group site (e.g., hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, hydroxybutyl (meth)acrylate, etc.). In addition to the above, other known monomers such as methyl methacrylate, ethyl methacrylate, butyl methacrylate, hexanediol dimethacrylate, and butanediol diacrylate may also be included to adjust the Tg of the resulting polymer and to impart crosslinkability and reactivity.

[0066] The content of the monomer having a long-chain alkyl group constituting the obtained acrylic resin is preferably 1 mol% or more and 50 mol% or less relative to the total monomers constituting the acrylic resin. A content of 1 mol% or more is preferred because it has the effect of lowering the surface free energy. A content of 50 mol% or less is preferred because the content of the monomer having a reactive functional group is relatively high, thereby increasing the crosslink density of the resin.

[0067] Specific examples of reactive functional group-containing resins having a silicone skeleton in the resin skeleton include alkyd resins or acrylic resins having a polydimethylsiloxane skeleton in the side chain. Specific examples of commercially available products include SIMAC (registered trademark) US350 and US352 (manufactured by Toagosei Co., Ltd., reactive functional group: carboxyl group), and SIMAC (registered trademark) US270 (manufactured by Toagosei Co., Ltd., reactive functional group: hydroxyl group).

[0068] In the present invention, the release layer may contain a melamine resin as a binder component, for example, a resin selected from a full-ether type methylated melamine resin, a methylol type methylated melamine resin, and a polymer thereof.

[0069] Preferably, the release layer contains a full-ether type methylated melamine resin as a binder component. Full-ether type methylated melamine resins are preferred in terms of low-temperature, short-time curing properties and adhesion to polyester films. Commercially available products include Cymel 303LF and Nikalac MW-30.

[0070] In one embodiment, the release layer may contain an alicyclic epoxy resin as a binder component. Examples of alicyclic epoxy resins include those manufactured by Daicel Corporation under the trade names EHPE-3150, CEL2021P, and CEL2000.

[0071] In the present invention, the binder component is contained in an amount of 55% by mass or more and 95% by mass or less, and preferably 60% by mass or more and 90% by mass or less, relative to 100% by mass of the composition that forms the release layer.

[0072] (Crosslinking Agent) It is also preferable that the binder component contains a crosslinking agent. The crosslinking agent is not particularly limited, but melamine-based, isocyanate-based, carbodiimide-based, oxazoline-based, epoxy-based crosslinking agents, etc. can be used, and one type or two or more types can be used in combination. Particularly preferred is a crosslinking agent that reacts with the reactive functional group introduced into the binder component.

[0073] As the crosslinking agent used in the present invention, a melamine-based compound is preferred from the viewpoint of reactivity. By using a melamine-based compound, the coating amount of the release layer after curing can be reduced to 0.2 g / m ２ This is preferable because it can quickly harden even thin films such as those shown below, and the crosslink density is high.

[0074] The melamine-based compound used in the present invention can be any common compound, but is not particularly limited thereto. It is preferably a compound obtained by condensing melamine with formaldehyde and having one or more triazine rings and one or more methylol groups and / or alkoxymethyl groups per molecule. Specifically, a compound obtained by etherifying a methylol melamine derivative obtained by condensing melamine with formaldehyde through a dehydration condensation reaction with a lower alcohol such as methyl alcohol, ethyl alcohol, isopropyl alcohol, or butyl alcohol is preferred. Examples of methylol melamine derivatives include monomethylol melamine, dimethylol melamine, trimethylol melamine, tetramethylol melamine, pentamethylol melamine, and hexamethylol melamine. One or more compounds may be used.

[0075] As the melamine compound, it is preferable to use hexamethylolmelamine, hexamethoxymethylolmelamine, etc., which have many crosslinking points in one molecule, because this can increase the crosslink density of the binder component. When using an ether compound obtained by dehydration condensation reaction of a methylolmelamine derivative with an alcohol, hexamethoxymethylmethylolmelamine obtained by dehydration condensation with methyl alcohol is particularly preferable from the viewpoint of reactivity.

[0076] The melamine used in the present invention may be commercially available, for example, Cymel 300, Cymel 301, Cymel 303LF, Cymel 350, Cymel 370N, Cymel 771, Cymel 325, Cymel 327, Cymel 703, Cymel 712, Cymel 701, Cymel 266, Cymel 267, Cymel 285, Cymel 232, Cymel 235, Cymel 236, Cymel 238, Cymel 272, Cymel 212, Cymel 253, Cymel 254, Cymel 202, Cymel 207 (manufactured by Allnex Japan Co., Ltd.), Nikalac MW-30M, Nikalac MW-30, and Nikalac MW-30HM. , Nikalac MW-390, Nikalac MW-100LM, Nikalac MX-750LM, Nikalac MW-22, Nikalac MS-21, Nikalac MS-11, Nikalac MW-24X, Nikalac MS-001, Nikalac MX-002, Nikalac MX-730, Nikalac MX-750, Nikalac MX-708, Nikalac MX-706, Nikalac MX-042, Nikalac MX-035, Nikalac, MX-45, Nikalac MX-43, Nikalac MX-417, Nikalac MX-410 (manufactured by Nippon Carbide Corporation), and the like.

[0077] Among these, full-ether type methylated melamine resins are preferred in terms of low-temperature, short-time curing properties and adhesion to polyester films. Commercially available products include Cymel 303LF and Nikalac MW-30.

[0078] The amount of crosslinking agent contained in the binder component in the present invention is preferably 15% by mass or more, more preferably 30% by mass or more, and even more preferably 50% by mass, relative to the resin having a reactive functional group. Furthermore, if the crosslinking agent can form a resin film by self-condensation, the binder component may be composed solely of the crosslinking agent. By including 15% by mass or more of the crosslinking agent, the crosslinking density of the release layer can be increased, and the solvent resistance and elastic modulus can be improved, which is preferable.

[0079] For example, in the present invention, the crosslinking agent is contained in an amount of 5% by mass or more and 40% by mass or less, and preferably 10% by mass or more and 40% by mass or less, relative to 100% by mass of the composition forming the release layer.

[0080] (Catalyst) The release layer-forming composition of the present invention may contain a catalyst to cure the crosslinking agent. When a melamine-based compound is used, it is preferable to use an acid catalyst. Although not particularly limited, carboxylic acid-based, metal salt-based, phosphate ester-based, and sulfonic acid-based catalysts can be suitably used. Block-type catalysts in which the acid moiety is blocked can also be used. Paratoluenesulfonic acid is particularly suitable from the viewpoint of reactivity. When an isocyanate-based compound is used, common catalysts can be used, and organotin, amine compounds, trialkylphosphine compounds, and the like can be suitably used. Furthermore, when a release layer is formed by a hydrosilylation reaction using a polysiloxane having an alkenyl group and a polysiloxane having a hydrosilyl group, a platinum catalyst can be used.

[0081] As the sulfonic acid catalyst, for example, p-toluenesulfonic acid, xylenesulfonic acid, cumenesulfonic acid, dodecylbenzenesulfonic acid, dinonylnaphthalenesulfonic acid, trifluoromethanesulfonic acid, etc. can be suitably used, and p-toluenesulfonic acid is particularly suitable from the viewpoint of reactivity.

[0082] Sulfonic acid catalysts have higher acidity and better reactivity than other acid catalysts such as carboxylic acid catalysts, and therefore can process the release layer at lower temperatures, which is preferable because it can prevent the film from losing flatness and the rolled appearance from being deteriorated due to heat during processing.

[0083] The sulfonic acid catalyst used in the present invention may be commercially available. Examples of commercially available products include Dryer (registered trademark) 900 (p-toluenesulfonic acid, manufactured by Hitachi Chemical Co., Ltd.), NACURE (registered trademark) DNNDSA series (dinonylnaphthalene disulfonic acid, manufactured by Kusumoto Chemicals Co., Ltd.), NACURE (registered trademark) DNNDSA series (dinonylnaphthalene (mono)sulfonic acid, manufactured by Kusumoto Chemicals Co., Ltd.), NACURE (registered trademark) DDBSA series (dodecylbenzenesulfonic acid, manufactured by Kusumoto Chemicals Co., Ltd.), and NACURE (registered trademark) p-TSA series (p-toluenesulfonic acid, manufactured by Kusumoto Chemicals Co., Ltd.).

[0084] The catalyst content is preferably 0.1 to 40% by mass relative to 100% by mass of the solids content of the composition forming the release layer. It is more preferably 0.5 to 30% by mass. It is even more preferably 0.5 to 20% by mass. A content of 0.1% by mass or more is preferred because it facilitates the curing reaction. On the other hand, a content of 40% by mass or less is preferred because there is no risk of the acid catalyst migrating to the ceramic green sheet to be molded and there is no risk of adverse effects. For example, the catalyst content may be 0.5 to 10% by mass.

[0085] (Silicone-based release agent) The silicone-based release agent used in the release layer in the present invention is a compound having a silicone structure in the molecule, and is not particularly limited as long as it can obtain the effects of the present invention, but polyorganosiloxane and the like can be preferably used. Among polyorganosiloxanes, polydimethylsiloxane (abbreviated as PDMS) can be preferably used, and polydimethylsiloxanes having functional groups in part are also preferred. Having a functional group is preferred because it makes it easier for intermolecular interactions such as hydrogen bonds with the binder resin to occur, making it less likely to transfer to the ceramic green sheet.

[0086] The functional group to be introduced into the polydimethylsiloxane is not particularly limited, and may be either a reactive functional group or a non-reactive functional group. The functional group may be introduced into one end of the polydimethylsiloxane, or into both ends or a side chain. The functional group may be introduced into one or more positions.

[0087] Examples of reactive functional groups to be introduced into polydimethylsiloxane include amino groups, epoxy groups, alicyclic epoxy groups, oxetane groups, hydroxyl groups, mercapto groups, carboxyl groups, methacryl groups, and acrylic groups. Examples of non-reactive functional groups that can be used include polyether groups, aralkyl groups, fluoroalkyl groups, long-chain alkyl groups, ester groups, amide groups, and phenyl groups. While not being bound by any particular theory, among the above, those having epoxy groups, carboxyl groups, polyether groups, methacryl groups, acrylic groups, and ester groups are preferred.

[0088] The silicone-based release agent is preferably present in an amount of 0.1 to 20% by mass relative to 100% by mass of the solid content of the composition forming the release layer. More preferably, it is present in an amount of 0.2 to 15% by mass. Even more preferably, it is present in an amount of 0.5 to 15% by mass. By including the silicone-based release agent in such amounts, the number of coarse protrusions represented by A1, A2, and A3 can be increased to 10 to 1000 protrusions / m, respectively. ２ and a release film having a ratio of the number of coarse protrusions X [((A1+A3) / 2) / A2] of 0.2 to 5.0 can be formed.

[0089] (Initiator) When the binder component and the silicone-based release agent have functional groups such as epoxy groups, alicyclic epoxy groups, and oxetane groups, cationic curing by UV is possible, and an initiator can be used to carry out this curing.

[0090] It is preferable to use an acid generator as the initiator. The acid generator used is not particularly limited and a common one can be used, but using a photoacid generator that generates an acid under irradiation with active energy rays is preferred because it can reduce the amount of heat generated during processing. Using common acids such as sulfonic acids or carboxylic acids can also produce a release layer with a high crosslinking density that can suppress erosion by organic solvents, but the high processing temperature required can cause the release layer surface to become rough due to thermal shrinkage of the raw sheet or a decrease in smoothness. Other acid generators that can be used include metal salts, phosphate esters, and block-type acid generators in which the acid moiety is blocked. However, for the reasons mentioned above, it is most preferable to use a photoacid generator in terms of the amount of heat generated during processing.

[0091] 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.

[0092] 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 introduced, or other organic groups can be used. Hexafluorophosphate, hexafluoroantimonate, hexafluoroborate, or tetra(pentafluorophenyl)borate is preferably used 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, or other anion components can be used.

[0093] When using the photoacid generator, the addition of a sensitizer can increase the reactivity of the polymerization reaction and further suppress erosion of the release layer by the organic solvent. There are no particular restrictions on the sensitizer, and a common one can be used, but anthracene derivatives and naphthalene derivatives are preferred. One or more types of sensitizers may be used.

[0094] The amount of photoacid generator added to the coating liquid is preferably 0.1 to 10 parts by mass relative to the total mass of the binder a and release agent b, which are composed of a cationically curable substance contained in the release layer. It is more preferably 0.5 to 8 parts by mass. It is even more preferably 1 to 5 parts by mass. By adding an amount of 0.1 parts by mass or more, the amount of acid generated is preferably not insufficient, which can lead to insufficient curing. Furthermore, by adding an amount of 10 parts by mass or less, the amount of acid generated becomes appropriate, which is preferable because it is possible to suppress the amount of acid migrating to the ceramic green sheet being molded.

[0095] The amount of sensitizer added is preferably 0.1 to 5 times by mass relative to the photoacid generator, and more preferably 0.1 to 2 times. If it is more than 0.1 times, there is a risk that a sufficient sensitizing effect will not be obtained, which is preferable. If it is less than 5 times, there is a risk that the absorption of active energy rays by the photoacid generator will be inhibited, resulting in insufficient acid generation, which is preferable.

[0096] In the present invention, the release layer may contain additives such as adhesion improvers and antistatic agents as long as the effects of the present invention are not impaired, but it is preferable that the release layer does not contain particles. The absence of particles in the release layer can prevent the smoothness of the release layer surface from deteriorating and particles from falling off and becoming mixed into the resin sheet. In order to improve adhesion to the substrate, the polyester film surface can also be pretreated with anchor coating, corona treatment, plasma treatment, atmospheric pressure plasma treatment, etc. before providing the release coating layer.

[0097] The release film of the present invention preferably has a release layer that is difficult to charge. More specifically, charging can become a problem when the film is wound up after the release layer processing in the release film production process and stored in roll form. For example, if the amount of charge on the rolled film is large, extremely small environmental foreign matter during the slitting process or the ceramic green sheet molding process and film debris generated during slitting are likely to adhere to the film. Since these foreign matter adhering to the film may get mixed into the ceramic green sheet and lead to defects, a release film having a release layer that is difficult to charge is preferred.

[0098] As an example of evaluating the resistance to charging, the release layer can be brought into contact with the surface layer B, and the amount of charge on the release layer after applying a load and maintaining the contact for a certain period of time can be evaluated. This evaluation method can be used to model the amount of charge that increases over time when the film is stored in a roll. The detailed evaluation method will be described later.

[0099] The charge amount of the release layer measured by the evaluation method described below is preferably ±20 kV or less, for example ±15 kV or less, more preferably ±10 kV or less, and the smaller the absolute value, the better. By setting the charge amount of the release layer to ±20 kV or less, adhesion of foreign matter to the film due to charging during unwinding and winding can be prevented, which is preferable. The smaller the charge amount of the release layer, the better, but it may be 0.1 kV or more, or may be 0.3 kV or more.

[0100] The present invention is a release film having a polyester film with a width of more than 900 mm and not more than 2500 mm, and the ratio of the number of coarse protrusions X [((A1+A3) / 2) / A2] falls within the range of the present invention.

[0101] For example, in the release film roll according to the present invention, it is presumed that the ratio X of the number of coarse protrusions contributes to bringing the charge amount of the release layer to ±20 kV or less. Although the detailed mechanism has not been analyzed, it is thought that the protrusions on the surface of the release film also affect the control of chargeability because the release film roll is wound up and unwound.

[0102] Preferably, in one embodiment, by having the release layer described in this specification and the ratio X of the number of coarse protrusions satisfying a predetermined condition, the charge amount E2 in the central region in the width direction can be more effectively brought to ±20 kV or less, for example, ±15 kV or less, or ±10 kV or less.

[0103] As a result, even with a wide release film, charging in the central region in the width direction can be suppressed, and adhesion of disturbances such as film debris that may be caused by charging can be reduced.

[0104] In one embodiment, the charge amount in a range E1 extending 100 mm from one widthwise end toward the center, a range E3 extending 100 mm from the other widthwise end toward the center, and a widthwise center position E2 is preferably ±20 kV or less in any of these ranges, for example, ±15 kV or less, and more preferably ±10 kV or less, with the smaller the absolute value, the better.

[0105] The charge amount at the widthwise central position E2 is preferably ±20 kV or less, for example ±15 kV or less, and more preferably ±10 kV or less, with the smaller the absolute value the better.

[0106] Even with a wide release film, charging can be suppressed in the central region in the width direction, and adhesion of disturbances such as film debris that may be caused by charging can be reduced.

[0107] The release film of the present invention may have a functional layer between the substrate and the release layer. Examples of the functional layer include, but are not limited to, an antistatic layer and an easily soluble resin layer.

[0108] By providing an antistatic layer, adhesion of foreign matter due to static charge can be prevented, and static charge can be suppressed when peeling off a ceramic green sheet or the like, so that stable peeling properties can be achieved, which is preferable.

[0109] By providing an easily soluble resin layer, the release layer formed on the surface of the release film can be easily separated and removed, and only the base film with no or very little residue of the release layer can be recovered, which is preferable.

[0110] For example, the release layer is substantially free of particles having a particle size of 1.0 μm or more. In this embodiment, particles having a particle size of less than 1.0 μm and 1 nm or more may be present in the release layer. By having the release layer be substantially free of inorganic particles having a particle size of 1.0 μm or more, it is possible to suppress the occurrence of pinholes in an ultra-thin resin sheet that requires high smoothness, such as a ceramic green sheet, and to form a resin sheet with a uniform film thickness.

[0111] In one embodiment, since it is preferable that the release layer has high smoothness, it is preferable to provide the release layer of the present invention on a substrate film having a surface layer A that does not substantially contain inorganic particles, specifically does not substantially contain particles with a particle size of less than 1.0 μm, preferably a surface layer A that does not substantially contain particles.

[0112] For example, a release layer that does not substantially contain particles with a particle size of less than 1.0 μm preferably also does not substantially contain particles with a particle size of 1.0 μm or more.

[0113] When a release layer is provided on the surface layer A that does not substantially contain inorganic particles, the surface roughness (Sa) of the release layer is 3 nm or less, and the maximum protrusion height (P) is 200 nm or less. For example, (Sa) may be 0.1 nm or more and 3 nm or less, and the maximum protrusion height (P) may be 1 nm or more and 200 nm or less, or (Sa) may be 0.2 nm or more and 3 nm or less, and the maximum protrusion height (P) may be 1 nm or more and 100 nm or less.

[0114] Preferably, the maximum protrusion height (P) is 1 nm or more and 50 nm or less, and may be 1 nm or more and 40 nm or less, or may be 1 nm or more and 35 nm or less.

[0115] When the release layer satisfies these conditions, it is possible to suppress the occurrence of pinholes in a thin resin sheet, such as a ceramic green sheet, and to form a resin sheet with a uniform thickness.

[0116] When the surface roughness (Sa) and the maximum protrusion height (P) of the release layer are within such ranges, the numbers of the coarse protrusions indicated by A1, A2, and A3 are 10 to 1000 pieces / m ２ This can contribute to the formation of a release film in which the ratio of the number of coarse protrusions X [((A1+A3) / 2) / A2] is 0.2 to 5.0.

[0117] In the present invention, even if the area surface roughness (Sa) and maximum projection height (P) of the release layer are simply within the above ranges, it is not easy to derive the numbers of coarse projections indicated by A1, A2, and A3 and the coarse projection number ratio X. However, by satisfying the various conditions described in this specification in a composite manner, conditions such as the coarse projection number ratio X can be derived.

[0118] 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.

[0119] (Number of coarse protrusions) In a release film roll obtained by winding a release film into a roll, the numbers of coarse protrusions with a height of 500 nm or more present on the surface of the release layer confirmed in a range R1 extending 100 mm from one widthwise end toward the center and in a range R3 extending 100 mm from the other widthwise end toward the center are defined as A1 and A3. In addition, the number of coarse protrusions confirmed in a range R2 extending 50 mm to the left and right from the center point in the film width direction is defined as A2 (center).

[0120] In the present invention, the numbers of coarse protrusions indicated by A1, A2 and A3 are each 10 to 1000 pieces / m ２ and for example, 10 to 900 pieces / m ２ Preferably, the number of coarse projections is in the range of 10 to 850 projections / m. ２ For example, the range is 10 to 700 pieces / m ２ The range is 20 to 700 pieces / m ２ may be in the range of

[0121] By keeping the number of coarse protrusions within the above range, defects such as pinholes and sheet deformation can be suppressed when a ceramic green sheet or a resin sheet is formed on the surface of the release layer. ２ The inclusion of the above protrusions is preferable because it is possible to prevent deterioration of the wound shape of the film roll.

[0122] Furthermore, in polyester films with widths exceeding 900 mm and not exceeding 2,500 mm, when the numbers A1, A2, and A3 of coarse protrusions satisfy the above conditions, excessive charging in the central region in the width direction can be suppressed, and disturbances such as film debris that may be caused by charging can be suppressed. Furthermore, air can be effectively removed from the central region during winding. Furthermore, the film can be prevented from becoming easily mobile due to expansion and contraction caused by temperature changes, and particle shedding from the base film and the occurrence of protrusions due to scratches can also be suppressed.

[0123] For example, in a polyester film having a width of more than 900 mm and not more than 2500 mm, if the relationship in the number of coarse protrusions, expressed as [((A1+A3) / 2) / A2], satisfies the conditions of the present invention, excessive charging in the central region in the width direction can be suppressed, and air near the center can be efficiently released during winding.

[0124] Although not intended to be limited to a particular theory, it is believed that the presence of the predetermined coarse protrusions defined in the present invention allows the film (film roll) of the present invention to reduce the contact area between the wound polyester films, and particularly to suppress charging in the central region in the width direction, compared to, for example, films (film rolls) whose coarse protrusions are outside the scope of the present invention. Similarly, compared to films (film rolls) whose coarse protrusions are outside the scope of the present invention, the present invention allows air present near the center to escape more effectively.

[0125] In the present invention, the coarse protrusion number ratio X [((A1+A3) / 2) / A2] of the release layer is 0.2 to 5.0. When the coarse protrusion number ratio X is within the above range, it is possible to achieve a state in which there is no or very little variation in the number of coarse protrusions in the film width direction.

[0126] For example, when used as a process film, the number of coarse protrusions can be maintained at zero or extremely low levels across the width of the release film, resulting in no variation in the number of coarse protrusions across the entire release film, further reducing the occurrence of pinholes in ceramic green sheets with thicknesses of approximately 0.2 μm to 1.0 μm. This also reduces the risk of pinholes occurring in ceramic green sheets and other materials. Furthermore, it also reduces the defective rate of resin sheets such as ceramic green sheets, enabling waste reduction.

[0127] The ratio X of the number of coarse protrusions represented by [((A1+A3) / 2) / A2] is, for example, in the range of 0.4 to 2.5, or alternatively, in the range of 0.4 to 2.10, or in the range of 0.5 to 1.5, or alternatively, in the range of 0.55 to 1.2.

[0128] Here, when the ratio X of the number of coarse protrusions is less than 0.2, the number A2 (center) of coarse protrusions observed in a range R2 of 50 mm on either side of the center point in the film width direction tends to be excessively larger than the numbers A1 and A3 of coarse protrusions near the film edges, resulting in poor air release, poor winding properties, and the film becoming more prone to static electricity and entraining foreign matter.

[0129] For example, in order to set the ratio X of the number of coarse protrusions within the range described in this specification, the width of the polyester film may preferably be more than 900 mm and not more than 2000 mm, or more than 900 mm and not more than 1700 mm.

[0130] (Method for evaluating the number of coarse protrusions) The method for evaluating the number of coarse protrusions is, for example, to apply a resin layer-forming composition for evaluation to the surface of the release layer so that the thickness after drying is 500 nm, dry the composition, measure and mark the number of pinholes in the resulting resin layer, measure the height of the protrusions at 50 times magnification using a VertScan (registered trademark), and calculate the value obtained by adding the thickness of the resin layer (500 nm) to the obtained protrusion height. Examples of the resin layer-forming composition for evaluation include those used in the examples.

[0131] FIG. 1 is a schematic diagram showing the coarse protrusion height in the present invention. For example, in a release film having a film substrate 10 and a release layer 20 in this order, the figure shows an embodiment in which coarse protrusions 40 protrude from the surface of the substrate 10 toward the release layer 20. In the above-described method for evaluating coarse protrusions, a resin layer 30 is formed, the number of pinholes in the resulting resin layer is measured and marked, and the protrusion height is measured at 50x magnification using a VertScan (registered trademark). The protrusion height measured at this time corresponds to the measured protrusion height 41 in FIG. 1. Next, the value obtained by adding the thickness of the resin layer, 0.5 μm, to the obtained protrusion height can be calculated as the protrusion height, and the actual protrusion height 42 in FIG. 1 can be calculated.

[0132] In the present invention, the number of coarse protrusions having a height of 500 nm or more present on the surface of the release layer can be calculated in this manner. Note that in the present invention, the resin layer used for evaluating the number of coarse protrusions can be formed using the same components and conditions as the resin sheet in the present invention.

[0133] (Release Layer Film Thickness) The film thickness of the release layer in the present invention is not particularly limited, but is preferably 30 nm or more. More preferably, it is 50 nm or more, and even more preferably, it is 100 nm or more. A film thickness of 30 nm or more provides sufficient releasability, allowing the ceramic green sheet to be peeled off without defects. Furthermore, a film thickness of 30 nm or more can fill in protrusions on the polyester film substrate, improving smoothness. The upper limit of the release layer film thickness is not particularly limited, but is preferably 1000 nm or less. It may be 800 nm or less, or 500 nm or less. In particular, a film thickness of 800 nm or less provides sufficient coatability of the release layer-forming composition, preventing groove-like streaks caused by coating from remaining on the coating film surface, which would reduce the smoothness of the release layer. Furthermore, since there is no need to reduce the line speed during release layer processing to prevent streaks from occurring, productivity can be increased, which is preferable.

[0134] (Method for Producing Release Film) In the present invention, the release layer-forming composition for forming the release layer is preferably applied by an in-line method carried out during the production process of the polyester film or an off-line method carried out after the production of the polyester film.

[0135] When applying using the in-line method, a preferred method is to apply a coating liquid in which a release resin is dissolved or dispersed to a film that has been stretched and uniaxially oriented in the film flow direction (longitudinal direction), and then stretch the film in the transverse direction (direction perpendicular to the film flow direction) to form a release layer while simultaneously biaxially orienting the film.

[0136] When coating is performed by the offline method, a coating liquid in which a release resin is dissolved or dispersed is applied to one side of a biaxially oriented polyester film, the solvent and the like are removed by drying, and then the coating is dried by heating, heat-cured, or ultraviolet-cured.

[0137] When coating by the in-line method, it is preferable to use an aqueous coating liquid. The type of aqueous coating liquid is not particularly limited, but it is preferable to add a water-soluble organic solvent, such as an alcohol.

[0138] The coating liquid used in offline coating is not particularly limited, but is preferably one that uses an organic solvent, and it is preferable to add a solvent with a boiling point of 90° C. or higher. Adding a solvent with a boiling point of 90° C. or higher can prevent bumping during drying, level the coating film, and improve the smoothness of the coating film surface after drying.

[0139] Any known coating method can be used as the coating method for the release layer-forming composition, and conventionally known methods such as roll coating methods such as gravure coating and reverse coating, bar coating methods such as wire bars, die coating, spray coating, and air knife coating can be used.

[0140] In the release film of the present invention, the substrate film is transported in a roll-to-roll manner during the processing of the release layer and the hydrophobic layer. Therefore, after the processing of the release layer and the hydrophobic layer, the release film is wound up in a roll and stored. In addition, the molding of the resin sheet and the peeling of the resin sheet are also performed in a roll-to-roll manner.

[0141] The tension when winding the release film into a roll is preferably 10 N / m to 300 N / m. If the winding tension is 10 N / m or more, there is no shearing of the winding, which is preferable. In addition, there is no unwinding during storage in a roll, which is preferable, and there is no risk of scratches being mixed into the release layer or an increase in the amount of charge when unwound. If the winding tension is 300 N / m or less, there is no risk of deformation of the release film due to tight winding, or of blocking occurring, which is preferable.

[0142] When the release film is wound into a roll, it is preferable to wind it using a touch roll. The touch pressure of the touch roll is preferably 100 to 3000 N / m. If it is 100 N / m or more, the amount of air entrained during winding can be reduced, and the occurrence of winding slippage can be suppressed, which is preferable. If it is 3000 N / m or less, deformation of the release film due to the touch roll pressure can be suppressed, and a release film with excellent flatness can be obtained, which is preferable.

[0143] (Heat Curing Step) The heat curing step is not particularly limited, and a known drying oven can be used. The drying oven may be either a roll support type or a floating type. The heat curing step may be a step continuous with the initial drying step or a step discontinuous therewith, but from the viewpoint of productivity, it is preferable that the heat curing step be a continuous step.

[0144] The temperature in the heat curing step is preferably 80°C or higher and 180°C or lower, more preferably 90°C or higher and 160°C or lower, and most preferably 90°C or higher and 140°C or lower. At 180°C or lower, the flatness of the film is maintained and there is little risk of uneven thickness of the ceramic green sheet, which is preferable. At 140°C or lower, the film can be processed without impairing the flatness, and there is a further reduction in the risk of uneven thickness of the ceramic green sheet, which is particularly preferable. At 80°C or higher, in the case of a thermosetting resin, curing proceeds sufficiently, which is preferable.

[0145] The time for passing through the heat curing step is preferably 2 to 30 seconds, more preferably 2 to 20 seconds. A passing time of 2 seconds or more is preferred because the curing of the thermosetting resin progresses. A passing time of 30 seconds or less is also preferred because the flatness of the film is not reduced by heat.

[0146] In the heat curing step according to the present invention, for example, by using a plurality of drying ovens, the number of coarse projections and the coarse projection number ratio X according to the present invention can be brought into a predetermined range.

[0147] An example of the drying process will be shown below, but the present invention should not be construed as being limited to this method.

[0148] (Initial drying process) An initial drying oven (first drying oven) may be used. The internal pressure difference of the initial drying oven (first drying oven) (first drying oven chamber pressure - clean tunnel pressure) is preferably positive. The internal pressure difference is preferably 10 to 40 Pa. More preferably, it is 15 to 30 Pa. A pressure difference of 10 Pa or more is preferable because it can suppress the inflow of air from the coating section into the drying oven and maintain good cleanliness inside the drying oven. Furthermore, by setting the pressure to 40 Pa or less, it is possible to prevent the evaporation of the solvent due to the high-temperature air in the drying oven leaking into the coating section. Furthermore, it is less likely that contaminants caused by the volatilization of the coating material in the drying oven will leak into the coating section, thereby suppressing the deterioration of particles.

[0149] (Final Drying Oven) A final drying oven can be provided following the initial drying oven (first drying oven) to carry out the heat curing process. For example, the internal pressure difference of the final drying oven (final drying oven internal pressure - clean tunnel pressure) is preferably positive. The internal pressure difference is preferably 10 to 40 Pa. More preferably, it is 15 to 30 Pa. A pressure difference of 10 Pa or more is preferable because it can suppress the inflow of air from the drying oven outlet (winding chamber) into the drying oven and maintain good cleanliness inside the drying oven. Furthermore, a pressure of 40 Pa or less is preferable because it can prevent the air from the final drying oven from flowing out into the winding chamber, creating an air flow that stirs up dust and causes particles to rise.

[0150] (Second Drying Process and After) For example, one or more drying ovens may be provided between the initial drying oven (first drying oven) and the final drying oven. Such drying ovens are referred to as, for example, the second drying process and after. For example, the internal pressure difference (drying oven internal pressure - clean tunnel pressure) of the drying oven in the second drying process and after is preferably a positive pressure. The internal pressure difference is preferably 10 to 40 Pa. More preferably, it is preferably 15 to 30 Pa. A pressure difference of 10 Pa or more is preferable because it can suppress the inflow of air from the drying oven outlet (winding chamber) into the drying oven and maintain good cleanliness inside the drying oven. Furthermore, a pressure of 40 Pa or less is preferable because it can prevent the air from the final drying oven from flowing out into the winding chamber, creating an air flow that stirs up dust and causes particles to rise.

[0151] In one embodiment, the internal air pressure in the initial drying step is desirably the internal air pressure of the final drying oven + 10 Pa or less. Under such conditions, the ratio X of the number of coarse protrusions can be more effectively brought into the range of the present invention, and variation in the number of protrusions on the film surface in the width direction can be reduced.

[0152] (Active energy ray irradiation step) As the active energy ray used in the present invention, known techniques such as ultraviolet rays and electron beams can be used. The cumulative irradiation amount of the active energy ray can be expressed as the product of the illuminance and the irradiation time. For example, in the case of ultraviolet rays, it is 20 to 500 mJ / cm ２ In the case of electron beams, the dose is preferably about 0.1 to 40 kGy. By setting the dose to be equal to or greater than the lower limit, the release layer can be sufficiently cured, which is preferable, and by setting the dose to be equal to or less than the upper limit, thermal damage to the film due to heat during irradiation can be suppressed, and flatness can be maintained, which is preferable.

[0153] When irradiating a film 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 the film with active energy rays while cooling the surface of the backup roll. By cooling, the film is less susceptible to heat damage even when irradiated with active energy rays, and flatness can be maintained, which is preferable.

[0154] The release film obtained by the present invention is preferably wound up into a roll after passing through the heat curing step and / or the active energy ray curing step. The time until winding up into a roll after passing through the heat curing step or the active energy ray curing step is preferably 2 seconds or more, more preferably 3 seconds or more. If it is 2 seconds or more, the release film whose temperature has increased in the heat curing step or the active energy ray irradiation step is cooled before being wound up into a roll, which is preferable because the flatness is not deteriorated.

[0155] The release film obtained by the present invention may be subjected to various treatments after the heat curing step and before being wound into a roll, such as static elimination treatment, corona treatment, plasma treatment, ultraviolet irradiation treatment, and electron beam irradiation treatment.

[0156] (Particles) In the production process of the release film, a particle meter can be used to manage the cleanliness of the processing plant. The particle meter can be used to measure at the unwinding section or the winding section, or both. The particles are preferably 300 particles / CF or less, more preferably 250 particles / CF or less, and even more preferably 200 particles / CF or less, for dust particles of 0.5 μm or more. By keeping the number of particles at 300 particles / CF or less, it is possible to reduce the amount of dust that is taken into the release layer and the amount of dust that adheres to the release layer, and it is possible to reduce the number of protrusions on the surface of the release layer of the obtained release film.

[0157] It is desirable that the number of particles be as small as possible, such as dust particles of 0.5 μm or larger, but the number may be, for example, 5 particles / CF or more, or 10 particles / CF or more.

[0158] Methods for reducing particles include cleaning the clean room where the processing machine stand is located, cleaning the rolls on the processing machine stand, etc. By performing processing in an environment with an extremely low and stable particle count, it is possible to reduce the number of protrusions on the surface of the release layer due to the incorporation of disturbing foreign matter into the release layer and the adhesion or entrapment of the particles on the surface of the release layer, which is preferable.

[0159] (Resin Sheet) In one embodiment, the release film of the present invention is not particularly limited as long as it is a resin sheet, and may be applied to the production of pressure-sensitive adhesives and optical films. In one embodiment, it is a release film for resin sheet molding containing an inorganic compound. Examples of inorganic compounds include metal particles, metal oxides, minerals, etc., such as calcium carbonate, silica particles, aluminum particles, and barium titanate particles.

[0160] Examples of the resin include polyvinyl acetal resin and poly(meth)acrylic acid ester resin.

[0161] The present invention has a release layer with high smoothness and a back layer with excellent smoothness, handleability, and antistatic properties, and therefore, even in an embodiment in which the resin sheet contains these inorganic compounds, defects that can be caused by 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 components that form the resin sheet can be appropriately selected depending on the application.

[0162] In one embodiment, the resin sheet containing an inorganic compound is a ceramic green sheet. For example, the ceramic green sheet may contain barium titanate as the inorganic compound. In one embodiment, the resin sheet has a thickness of 0.2 μm or more and 1.0 μm or less.

[0163] (Ceramic Green Sheet and Ceramic Capacitor) Generally, a multilayer ceramic capacitor has a rectangular parallelepiped ceramic body. First internal electrodes and second internal electrodes are alternately provided 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.

[0164] 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.

[0165] For example, the method for producing a ceramic green sheet in which a release film for producing a ceramic green sheet of the present invention is used to form a ceramic green sheet can form a ceramic green sheet having a thickness of 0.2 μm to 1.0 μm.

[0166] 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 then divided into multiple pieces to produce green ceramic elements. The green ceramic elements are then fired to obtain ceramic elements. Subsequently, first and second external electrodes are formed to complete a multilayer ceramic capacitor.

[0167] 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.

[0168] (Measurement of Film Width) Using a tape measure, the length from one end to the other end in the film width direction (TD direction) was measured, and the obtained value was taken as the film width.

[0169] (Thickness Measurement) The cut-out release film was embedded in resin and cut into ultrathin slices using an ultramicrotome. Then, the cross section was observed using a JEOL JEM2100 transmission electron microscope, and the film thickness of the release layer was measured from the observed TEM image.

[0170] (Evaluation of the number of coarse protrusions) The range of 100 mm from one end in the width direction of the roll-shaped release film toward the center was designated R1, the range of 50 mm from the center on both sides in the width direction was designated R2, and the range of 100 mm from the other end in the width direction toward the center was designated R3, and the number of coarse protrusions was evaluated for each of the ranges R1, R2, and R3.

[0171] That is, polyvinyl acetal resin (Sekisui Chemical Co., Ltd. S-LEC BM-S) was added to the release layer surface of the release film in a solvent (ethanol / toluene = 50 / 50: mass ratio), and the solids concentration was 10.0 mass% and the thickness after drying was 0.5 μm. The resin sheet was then coated using an applicator, dried at 90 ° C. for 1 minute, and the resin sheet was molded onto the release film. The positions of pinholes visually confirmed within a 10 cm x 10 cm area on the resin sheet surface were marked, and the height of the protrusion was measured at VertScan (registered trademark) × 50 times. The value obtained by adding 0.5 μm to the thickness of the resin sheet to the measured protrusion was taken as the actual protrusion height, and protrusions of 500 nm or more were measured. 10 measurements were also taken at different locations, and the average value was calculated as 1 m ２ The value converted to this was used as the number of protrusions. (Measurement conditions) Measurement mode: WAVE mode Objective lens: 50x, 0.5x Tube lens Measurement area: 187 μm x 139 μm (Analysis conditions) Surface correction: 4th order correction Interpolation processing: Full interpolation

[0172] (Area surface average roughness Sa, maximum protrusion height P) Measurements were made using a VertScan (registered trademark) R550H-M100 under the following conditions. The area surface average roughness (Sa) and maximum protrusion height (P) were measured 36 times, and the average values ​​of 25 measurement results were used, excluding 7 points with large values ​​including the maximum value and 4 points with small values ​​including the minimum value. (Measurement conditions) Measurement mode: WAVE mode Objective lens: 50x, 0.5x Tube lens Measurement area: 187 μm x 139 μm (Analysis conditions) Surface correction: 4th order correction Interpolation processing: Full interpolation

[0173] (Evaluation of Removability of Ceramic Green Sheet) A composition consisting of the following materials was stirred and mixed, and dispersed with zirconia beads having a diameter of 0.5 mm using a bead mill at a rotation speed of 2500 rpm for 15 minutes to obtain a ceramic slurry.

[0174] Toluene 30.1 parts by weight Ethanol 26.2 parts by weight Barium titanate (manufactured by Fuji Titanium Co., Ltd., HPBT-1) 38.5 parts by weight Polyvinyl butyral (manufactured by Sekisui Chemical Co., Ltd., S-LEC BM-S) 3.2 parts by weight DOP (dioctyl phthalate) 0.6 parts by weight Then, using an applicator, the release surface of the obtained release film sample was coated with a slurry so that the dried thickness was 3 μm, dried at 90 ° C. for 1 minute, and a ceramic green sheet was molded on the release film. The obtained release film with the ceramic green sheet was de-ionized using a static eliminator (manufactured by Keyence Corporation, SJ-F020), and then peeled at a width of 30 mm, a peel angle of 90 degrees, and a peel speed of 10 m / min. The stress applied during peeling was measured and taken as the peel force.

[0175] (Unwinding Charge Amount) The antistatic release film obtained in each Example and Comparative Example was wound into a roll having a length of 5,000 m to obtain a film roll. This film roll was stored for 30 days in an environment of 40°C and humidity of 50% or less, and then the charge amount when rewinding at 300 m / min was measured using a Kasuga Electric Co., Ltd. "KSD-0103." Measurement positions were an area E1 extending 100 mm from one widthwise end toward the center, an area E3 extending 100 mm from the other widthwise end toward the center, and a widthwise center position E2. The charge amount was measured at a location 100 mm away from unwinding every 500 m of the unwinding length, and the average value was calculated. ⊚: Absolute value of charge amount less than 5 kV. ◯: Absolute value of charge amount 5 kV or more but less than 10 kV. △: Absolute value of charge amount 10 kV or more but less than 20 kV. ×: Absolute value of charge amount greater than 20 kV.

[0176] (Preparation of polyethylene terephthalate pellets (PET(I))) 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 was used. TPA (terephthalic acid) was supplied at 2 ton / h, EG (ethylene glycol) was supplied at 2 moles per mole of TPA, and antimony trioxide was supplied in an amount such that the Sb atom concentration in the produced PET was 160 ppm. The resulting slurry was continuously supplied to a first esterification reactor of the esterification reactor and reacted at normal pressure for an average residence time of 4 hours at 255°C. 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 product was dispersed 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 having an average particle size of 0.9 μm, which had been subjected to dispersion treatment at a pressure of 1000 kJ / cm² and an average number of treatments of 5, and 0.4% by mass of synthetic calcium carbonate having an average particle size of 0.6 μm and having an ammonium salt of polyacrylic acid attached thereto at 1% by mass per calcium carbonate, were added as 10% EG slurry, and the reaction was carried out 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, filtered through a filter made of sintered stainless steel fibers with a 95% cut diameter of 20 μm, then ultrafiltered, extruded into water, cooled, and cut into chips to obtain PET chips with an intrinsic viscosity of 0.60 dl / g (hereinafter abbreviated as PET(I)). The lubricant content in the PET chips was 0.6% by mass.

[0177] (Preparation of polyethylene terephthalate pellets (PET(II))) Meanwhile, in the production of the above-mentioned PET(I) chips, PET chips with an intrinsic viscosity of 0.62 dl / g containing no particles such as calcium carbonate or silica were obtained (hereinafter abbreviated as PET(II)).

[0178] (Production of Laminated Film F1) After drying, these PET chips were melted at 285 ° C. and melted at 290 ° C. in separate melt extruders. The mixture was filtered through two stages: a filter made of sintered stainless steel fibers with a 95% cut diameter of 15 μm, and a filter made of sintered stainless steel particles with a 95% cut diameter of 15 μm. The resulting mixture was merged in a feed block, and PET (I) was laminated as surface layer B (non-release surface layer) and PET (II) as surface layer A (release surface layer). The resulting mixture was extruded (cast) into a sheet at a speed of 45 m / min, electrostatically bonded to a casting drum at 30 ° C., and cooled to obtain an unstretched polyethylene terephthalate sheet with an intrinsic viscosity of 0.59 dl / g. The layer ratio was adjusted to PET (I) / (II) = 60% by mass / 40% by mass based on the output of each extruder. Next, this unstretched sheet was heated with an infrared heater and then stretched 3.5 times in the machine direction at a roll temperature of 80°C using the speed difference between the rolls. It 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 F1 with a thickness of 31 μm. The surface layer A of the resulting film F1 had an Sa of 2 nm, and the surface layer B had an Sa of 28 nm.

[0179] (Laminate film F2) A 25 μm thick A4100 (Cosmoshine (registered trademark), manufactured by Toyobo Co., Ltd.) was used as laminate film F2. A4100 does not substantially contain particles in the film, and a coating layer containing particles is provided by in-line coating on the surface layer B side. The surface layer A of laminate film F2 had an Sa of 1 nm, and the surface layer B had an Sa of 2 nm.

[0180] (Laminated film F3) As the laminated film F3, E5101 (Toyobo Ester (registered trademark) film, manufactured by Toyobo Co., Ltd.) having a thickness of 25 μm was used. E5101 has a configuration in which particles are contained in surface layer A and surface layer B. The Sa of surface layer A of laminated film F3 was 24 nm, and the Sa of surface layer B was 24 nm.

[0181] (Resin solution a) 20 mol% of long-chain alkyl group-containing acrylic resin stearyl (meth)acrylate, 40 mol% of hydroxyethyl (meth)acrylate, and 40 mol% of methyl (meth)acrylate were mixed, diluted with toluene to a solids concentration of 40% by mass, and 0.5 mol% of azobisisobutyronitrile was added under a nitrogen stream to copolymerize, yielding Resin solution A. The weight-average molecular weight of the resulting polymer was 30,000.

[0182] (Example 1) (Preparation of Release Layer Coating Liquid) Acrylic resin (a), melamine resin (Nikarak MW-30M, manufactured by Nippon Carbide Corporation) as crosslinking agent (b), silicone-based release agent (polyether-modified polydimethylsiloxane, TSF4446, manufactured by Momentive Corporation, solids content 100%), and paratoluenesulfonic acid (Dryer #900, manufactured by Hitachi Chemical Polymer Co., Ltd.) as curing catalyst were added in the blending amounts shown in Table 1, and a solvent (MEK / toluene / n-heptane=50 / 30 / 20: mass ratio) was further added to adjust the solids concentration to 5.0 mass%, thereby obtaining a release layer coating liquid.

[0183] (Formation of Release Layer) The obtained coating liquid was passed through a filter capable of removing 99% or more of foreign matter of 0.5 μm or more, and then coated onto laminated film F1 (1,400 mm wide) using reverse gravure so that the thickness of the release layer after drying would be 200 nm. The fan rotation speed of the drying oven and the internal pressure of the drying oven were set to the contents shown in Table 2, and the film was dried at 140° C. for 15 seconds to obtain a release film. The number of particles in the unwinding section and the winding section is as shown in Table 2.

[0184] Examples 2, 3, 4, and 5 Release layers were formed in the same manner as in Example 1, except that the solid content of the coating liquid was adjusted and the thickness of the release layer after drying was changed to the values ​​shown in Table 2.

[0185] (Example 6) A release layer was formed in the same manner as in Example 1, except that the silicone-based release agent was changed to (single-terminal carboxyl-modified polydimethylsiloxane, X22-3710, solids content 100%, manufactured by Shin-Etsu Chemical Co., Ltd., an alkyl group is interposed between the dimethylsiloxane and the carboxyl group).

[0186] Examples 7 and 8 A release layer was formed in the same manner as in Example 1, except that the rotation speed of the circulation fan in the first drying furnace and the internal pressure of the furnace were changed to those shown in Table 2.

[0187] Example 9 A release layer was formed in the same manner as in Example 1 except that a release layer coating liquid was prepared using the blending amounts shown in Table 1 of a melamine compound (full-ether type methylated melamine, solids content 100%, manufactured by Sanwa Chemical Co., Ltd., product name MW-30M, weight average degree of polymerization 1.3), a silicone release agent (one-terminal carboxyl-modified polydimethylsiloxane, X22-3710, solids content 100%, manufactured by Shin-Etsu Chemical Co., Ltd., an alkyl group being interposed between the dimethylsiloxane and the carboxyl group), an acid catalyst (p-toluenesulfonic acid, manufactured by Hitachi Chemical Co., Ltd., product name Dryer (registered trademark) 900, solids content 50%), and a solvent (MEK / toluene = 50 / 50: mass ratio) with a solids concentration of 12.5 mass%.

[0188] (Example 10) In the amounts shown in Table 1, 3',4'-epoxycyclohexylmethyl 3,4-epoxycyclohexanecarboxylate (product name: CELLOXIDE (registered trademark) 2021P, manufactured by Daicel Corporation, solid content 100% by mass, bifunctional), release agent b: alicyclic epoxy group-containing polydimethylsiloxane (product name: UV Poly215, manufactured by Arakawa Chemical Industries, Ltd., solid content 100%), acid generator: 0.26 parts by mass of boron-based cationic curing UV catalyst (product name: UV A release layer coating solution was prepared using a solvent (MEK / toluene = 50 / 50: mass ratio) with a solid content of 5.0 mass%, CATA211, active ingredient 19 mass%, manufactured by Arakawa Chemical Industries, Ltd., and the solvent (MEK / toluene = 50 / 50: mass ratio) with a solid content of 5.0 mass%, and the obtained coating solution was passed through a filter and coated on laminate film F1 using reverse gravure so that the release layer film thickness after drying would be 200 nm. After drying at 90°C for 15 seconds, the coating was applied to a laminate film F2 with an integrated light intensity of 100 mJ / cm. ２A release layer was formed in the same manner as in Example 1, except that the release layer was cured by irradiating it with ultraviolet light using a UV lamp (H bulb, manufactured by Heraeus).

[0189] Example 11 A release layer was formed in the same manner as in Example 1, except that the width of the substrate of the laminated film F1 was changed to 1000 mm.

[0190] Example 12 A release layer was formed in the same manner as in Example 1, except that the width of the substrate of the laminated film F1 was changed to 1800 mm.

[0191] Example 13 A release layer was formed in the same manner as in Example 1, except that the width of the substrate of the laminated film F1 was changed to 2500 mm.

[0192] Example 14 A release layer was formed in the same manner as in Example 1, except that the laminated film was changed to F2.

[0193] (Example 15) A release layer was formed in the same manner as in Example 1, except that polyester powder was removed from the film-coated surface using a microfiber film cleaning cloth before release processing. Example 15 shows that removing polyester powder that may be present on the substrate before release processing tends to reduce the number of coarse protrusions per unit area. Furthermore, the coarse protrusion number ratio X can also be maintained within the range of the present invention. Furthermore, there is a tendency for the amount of charge to be further reduced.

[0194] (Comparative Example 1) A release layer was formed in the same manner as in Example 1, except that the laminated film was changed to F3 and coating was performed on the surface layer A side. Since the surface roughness of the coated surface was large, the number of protrusions on the surface of the release layer was large.

[0195] (Comparative Example 2) A release layer was formed in the same manner as in Example 1, except that the rotation speed of the circulation fan was changed to the value shown in Table 2. The change in the rotation speed of the circulation fan changed the internal pressure balance, significantly worsening the number of particles and resulting in a large number of protrusions on the surface of the release layer.

[0196] (Comparative Example 3) A release layer was formed in the same manner as in Example 9, except that the coating liquid used in Example 9 was the coating liquid shown in Table 1, in which no silicone release agent was added. The result was that there were many protrusions on the surface of the release layer. It is believed that the obtained release film roll was prone to static electricity, making it easy for dust to be trapped.

[0197] Comparative Example 4 A release layer was formed in the same manner as in Example 1, except that polyester powder was collected from the film surface using a microfiber film cleaning cloth and then sprinkled on the edge of another polyester film to form a release coating.

[0198] (Reference Example 1) The solids concentration of the coating liquid described in Example 9 was adjusted, and the thickness of the release layer after drying was changed to the contents shown in Table 2. The coating liquid had a high solids content, resulting in a high viscosity coating liquid, and streaks occurred on the surface of the resulting release layer under the coating conditions described in Example 1. Therefore, to gain more time for leveling, the line speed was slowed to two-thirds, and a release layer was formed using the same procedure as in Example 9. Because the release layer was thick, protrusions and dust on the coated surface of the substrate could be firmly embedded in the release layer, resulting in a significantly smaller number of protrusions on the surface of the release layer. On the other hand, the line speed had to be slowed down, which reduced productivity.

[0199] (Reference Example 2) In order to confirm the stability of the processing conditions, continuous processing was performed under the conditions of Example 1, and the performance of the processed sample was evaluated two days after the start of processing. Although the processing conditions were not changed, the processing was performed in an environment with a slightly high particle concentration at the processing site. On the other hand, it was confirmed that the number of protrusions on the surface of the release layer was stable.

[0200] (Reference Example 3) An antistatic layer described below was provided on surface layer B (layer opposite the release surface), and then the release layer was processed, except that a release layer was formed in the same manner as in Example 1. (Formation of Antistatic Layer) The following antistatic layer-forming composition 1 was applied to the surface layer B of film F1 using a reverse gravure coater so that the thickness after drying would be 0.05 μm, and then the coating was dried and cured with hot air at 140° C. for 30 seconds, to obtain an antistatic release film. (Antistatic layer forming composition 1) Water 42.24 parts by weight Isopropyl alcohol 42.24 parts by weight Antistatic agent E-1 (polythiophene-based conductive polymer, solid content 1.20% by weight) 11.67 parts by weight Thermosetting binder resin F-1 (manufactured by Nippon Carbide Corporation, melamine resin, full ether type, solid content 70% by weight) 0.80 parts by weight Conductive assistant G-1 (NMP) 3.00 parts by weight Surfactant H-1 (manufactured by Nissin Chemical Co., Ltd., Dynol 604, solid content 100% by weight) 0.06 parts by weight The antistatic layer can suppress static electricity during unwinding and winding during release processing, and can prevent disturbance adhesion such as film debris. On the other hand, providing an antistatic layer requires production costs and coating costs.

[0201]

[0202]

[0203]

[0204] As shown in Table 3, the release film of the present invention is a release film in which the number of protrusions on the release layer surface and the distribution of the protrusions in the width direction are controlled. Furthermore, the present invention can provide a release film that allows the resin sheet-forming slurry to be applied without defects without deteriorating the winding properties of the release film, and in particular, allows the formation of ceramic green sheets without defects.

[0205] On the other hand, in Comparative Examples 1 to 4, the number of coarse protrusions was 1000 / m２ This exceeds the range of the present invention, which may result in pinholes being generated during the production of ceramic green sheets, etc. Furthermore, in Comparative Example 4, the ratio X of the number of coarse protrusions is outside the range of the present invention, and the number of protrusions near the edges of the film is large, resulting in an uneven distribution of the coarse protrusions. For this reason, it is necessary to use the area near the center of the release film, which results in a larger amount of film being discarded than in the present invention.

[0206] According to the present invention, a release film having a release layer on one side of a base film and excellent releasability and smoothness is provided, and a thin-layer resin sheet can be produced without the risk of defects.

[0207] 10 Film substrate 20 Release layer 30 Resin layer 40 Coarse protrusion 41 Measured protrusion height 42 Actual protrusion height

Claims

1. A release film having a polyester film substrate with a width of more than 900 mm and not more than 2500 mm and a release layer, wherein when wound into a roll, the range from one end in the width direction to the center in 100 mm direction is defined as R1, the range from the center in 50 mm direction on both sides in the width direction is defined as R2, and the range from the other end in the width direction to the center in 100 mm direction is defined as R3, and the numbers of coarse protrusions of 500 nm or more in height present on the surface of each range R1, R2, R3 of the release layer evaluated by the method below are defined as A1, A2, and A3, respectively: the numbers of coarse protrusions represented by A1, A2, and A3 are each 10 to 1000 / m ２ and the ratio X of the number of coarse protrusions calculated by X = ((A1 + A3) / 2) / A2 is 0.2 to 5.

0. (Method for evaluating the number of coarse protrusions) A resin layer-forming composition for evaluation is applied to the surface of the release layer so that the thickness after drying is 500 nm, and then dried. The positions of pinholes in the resulting resin layer are marked, and the height of the protrusions is measured using the surface of the resin layer as a reference. The resulting protrusion height is then added to the thickness of the resin layer (500 nm), and the number of coarse protrusions having a protrusion height of 500 nm or more is counted.

2. The release film according to claim 1, wherein the area surface average roughness (Sa) of the release layer surface is 3.0 nm or less and the maximum protrusion height (Rp) is 200 nm or less.

3. The release film according to claim 1, wherein the thickness of the release layer is 800 nm or less.

4. The release film according to claim 1, which is a release film for use in producing ceramic green sheets or molding resin sheets.

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