Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B28—WORKING CEMENT, CLAY, OR STONE
  • B28B—SHAPING CLAY OR OTHER CERAMIC COMPOSITIONS; SHAPING SLAG; SHAPING MIXTURES CONTAINING CEMENTITIOUS MATERIAL, e.g. PLASTER
  • B28B1/00—Producing shaped prefabricated articles from the material
  • B28B1/30—Producing shaped prefabricated articles from the material by applying the material on to a core or other moulding surface to form a layer thereon
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B27/00—Layered products comprising a layer of synthetic resin
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B27/00—Layered products comprising a layer of synthetic resin
  • B32B27/36—Layered products comprising a layer of synthetic resin comprising polyesters
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B3/00—Layered products comprising a layer with external or internal discontinuities or unevennesses, or a layer of non-planar shape; Layered products comprising a layer having particular features of form
  • B32B3/26—Layered products comprising a layer with external or internal discontinuities or unevennesses, or a layer of non-planar shape; Layered products comprising a layer having particular features of form characterised by a particular shape of the outline of the cross-section of a continuous layer; characterised by a layer with cavities or internal voids ; characterised by an apertured layer
  • B32B3/30—Layered products comprising a layer with external or internal discontinuities or unevennesses, or a layer of non-planar shape; Layered products comprising a layer having particular features of form characterised by a particular shape of the outline of the cross-section of a continuous layer; characterised by a layer with cavities or internal voids ; characterised by an apertured layer characterised by a layer formed with recesses or projections, e.g. hollows, grooves, protuberances, ribs
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
  • C08J5/00—Manufacture of articles or shaped materials containing macromolecular substances
  • C08J5/18—Manufacture of films or sheets
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
  • C08J7/00—Chemical treatment or coating of shaped articles made of macromolecular substances
  • C08J7/04—Coating
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE
  • H01G13/00—Apparatus specially adapted for manufacturing capacitors; Processes specially adapted for manufacturing capacitors not provided for in groups H01G4/00 - H01G11/00

Definitions

• the present invention relates to a release film for use in molding resin sheets, and more specifically to a release film used when molding thin resin sheets.
• release films which have a polyester film base and a release layer laminated on top of it, have been used as process films for molding resin sheets such as adhesive sheets, cover films, polymer films, and optical lenses.
• release films are also used as process films for molding ceramic green sheets, which require high smoothness for applications such as multilayer ceramic capacitors and ceramic substrates.
• ceramic green sheets are molded by applying a slurry containing ceramic components such as barium titanate and a binder resin onto a release film and drying it. Electrodes are printed on the molded ceramic green sheets, which are then peeled off from the release film. Multilayer ceramic capacitors are then manufactured by stacking, pressing, firing, and applying external electrodes.
• the wettability and smoothness of the release film when applying 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 pinholes, uneven thickness, and sheet defects in the ceramic green sheet obtained after applying and drying the slurry.
• Patent Document 1 discloses a release film characterized in that a release layer is provided on a film having 1 or less protrusions of 1 ⁇ m or more per square meter.
• Patent Document 2 discloses an oriented polyester film roll that suppresses coating cissing of the sheet formed on the release layer surface, while maintaining a good winding appearance when wound up.
• Reference 3 discloses a method for producing biaxially oriented polyester film, characterized by transverse stretching in a stenter oven where the number of dust particles is below a certain number.
• Patent Document 1 suppresses protrusions of 1 ⁇ m or more, and with recent ceramic green sheets with thicknesses of 0.2 ⁇ m to 1.0 ⁇ m, it is necessary to suppress protrusions that are shorter than conventional ones.
• the film in 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 edges of the substrate, when the relevant mounting positions are coated with a release coating and used to manufacture multilayer ceramic capacitors, the product defect rate is higher than in other mounting positions. Furthermore, powdery material on the edges accumulates in the clean room during the release process, worsening the particle condition, and this accumulation can also cause adhesion during subsequent release processing.
• the biaxially oriented polyester film of Patent Document 3 requires cleaning inside and outside the coating machine and the stenter oven, and films produced before cleaning have a large number of protrusions, and the number of protrusions may vary depending on their position depending on the cleaning conditions.
• the inventors' investigations have revealed that the number of protrusions on the surface of films produced using conventional technology can vary across the width, and that there are previously unnoticed conditions that can be used to suppress this.
• the object of the present invention is to provide a release film that is less likely to produce defects across the entire width, even when molding thin resin sheets, etc.
• the release film described in this specification can suppress variation in the width direction of the number of protrusions on the film surface, and thus completed the present invention.
• the present invention consists of the following:
• a release film having a substrate which is a polyester film having a width of 200 to 900 mm and a release layer 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.
• the numbers of coarse protrusions with a height 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 number of coarse protrusions represented by A1, A2 and A3 is in the range of 10 to 1000 pieces/ m2
• a release film having a ratio X of the number of coarse protrusions calculated by X ((A1 + A3)/2)/A2 of 0.2 to 5.0.
• the resin layer-forming composition for evaluation is applied to the surface of the release layer and dried so that the thickness after drying is 500 nm.
• the positions of the 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 obtained protrusion height is then added to the thickness of the resin layer (500 nm) to determine the protrusion height, and the number of coarse protrusions with a protrusion height of 500 nm or more is counted.
• 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.
• the present invention provides a release film that allows for the resin sheet-forming slurry to be applied without defects, without compromising the rollability of the release film, and that is particularly capable of forming ceramic green sheets without defects.
• FIG. 2 is a cross-sectional view schematically showing the height of the coarse projections in the present invention.
• the present invention makes it possible to obtain a release film with excellent smoothness, slurry coatability, and releasability.
• 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 a release layer, a release film with excellent releasability can be obtained.
• the substrate film in the present invention is a polyester film having a width of 200 to 900 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.
• a release layer may be applied to a polyester film having a width of more than 900 mm, the film may be cut to within the range of the present invention, and the cut release film may be wound up.
• the base film is wound up when its width is significantly greater than 900 mm, for example, it is difficult for the air to escape near the center during winding, and the film becomes more susceptible to movement due to expansion and contraction caused by temperature changes, which can lead to particle shedding on the base film or protrusions caused by scratches.
• the number of protrusions on the release layer surface and the distribution of the protrusions in the width direction may deviate from the original design conditions.
• the present invention makes it possible to obtain a release film and 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, making it possible to apply the resin sheet-forming slurry without any defects and without deteriorating the rollability of the release film.
• the polyester constituting the polyester film used as the base film (hereinafter sometimes referred to as the base material) in the present invention is not particularly limited, and a film of a polyester commonly used as a base material for release films can be used.
• a film of a polyester commonly used as a base material for release films can be used.
• Preferred are crystalline linear saturated polyesters composed of an aromatic dibasic acid component and a diol component.
• 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.
• polyethylene terephthalate produced solely from terephthalic acid and ethylene glycol is preferred.
• 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 due to its high bidirectional elastic modulus.
• the intrinsic viscosity of the polyester film is preferably 0.50 to 0.70 dl/g, and more preferably 0.52 to 0.62 dl/g.
• An intrinsic viscosity of 0.50 dl/g or higher is preferable because it prevents frequent breakage during the stretching process.
• an intrinsic viscosity of 0.70 dl/g or lower is preferable because it allows for good cuttability when cutting to the specified product width and prevents dimensional defects. It is also preferable to thoroughly vacuum dry the raw material pellets.
• polyester film when simply referring to a “polyester film,” it means a polyester film having (laminated) surface layer A and surface layer B.
• the method for producing the polyester film of the present invention is not particularly limited, and conventional methods can be used.
• 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 in the transverse or longitudinal direction, or by simultaneously biaxially stretching an unstretched film in the longitudinal and transverse directions.
• the stretching temperature during stretching of polyester film is preferably set to the second-order transition point (Tg) of the polyester or higher. Stretching of 1 to 8 times, and especially 2 to 6 times, in both the longitudinal and transverse directions is preferred.
• the polyester film preferably has a thickness of 12 to 50 ⁇ m, more preferably 15 to 38 ⁇ m, and even more preferably 19 to 33 ⁇ m.
• a film thickness of 12 ⁇ m or more is preferable because there is no risk of deformation due to heat during film production, processing, or molding.
• a film thickness of 50 ⁇ m or less is preferable in terms of reducing the environmental impact because the amount of film discarded after use is not excessively large.
• the polyester film substrate may be a single layer or a multi-layer structure of two or more layers.
• the substrate film may be a polyester film having a surface layer A that is substantially free of particles with a particle size of 1.0 ⁇ m or more, and a surface layer B that contains particles.
• surface layer A is substantially free of inorganic particles with a particle size of 1.0 ⁇ m or more.
• surface layer A may contain particles with a particle size of less than 1.0 ⁇ m and equal to or greater than 1 nm.
• surface layer A substantially free of particles with a particle size of 1.0 ⁇ m or greater, such as inorganic particles, the surface of the release layer formed is smooth, reducing the risk of defects caused by the particle shape in the substrate being transferred to the resin sheet.
• surface layer A does not contain particles with a particle size of less than 1.0 ⁇ m, thereby more effectively preventing defects caused by the particle shape in the substrate being transferred to the resin sheet.
• the polyester film substrate is preferably a laminated film having a surface layer A on at least one side that is substantially free of inorganic particles. This more effectively prevents defects caused by the transfer of particle shapes in the substrate to the resin sheet.
• a preferred embodiment is one in which the surface layer A is substantially free of particles with a particle size of less than 1.0 ⁇ m, and is also substantially free of particles with a particle size of 1.0 ⁇ m or more.
• substantially free of particles means, for example, in the case of inorganic particles less than 1.0 ⁇ m in size, that when the inorganic elements are quantified by fluorescent X-ray analysis, the content 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 matter, or dirt adhering to the raw resin or the lines and equipment used in 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 ⁇ m or more” means that particles with a particle size of 1.0 ⁇ m or more are not actively included.
• a surface layer B that can contain inorganic particles on the side opposite to the surface layer A that contains substantially no inorganic particles.
• the layer structure in the thickness direction can be a laminate structure such as release layer/A/B or release layer/A/C/B.
• Layer C can also be a multi-layer structure.
• surface layer B can be free of 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 when winding the film into a roll.
• surface layer B which forms the surface opposite to the surface to which the release layer is applied, preferably contains inorganic particles, in terms of the film's slipperiness and ease of air escape, and it is particularly preferable to use silica particles and/or calcium carbonate particles.
• the inorganic particle content in surface layer B is preferably 5,000 to 15,000 ppm in total.
• the regional surface average roughness (Sa) of the film of 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.
• the total 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 ultra-thin ceramic green sheets.
• the lubricant is less likely to agglomerate and large protrusions are not formed, which is preferable as it ensures stable quality when producing ultra-thin ceramic green sheets.
• the particles contained in Layer B can also include inert inorganic particles and/or heat-resistant organic particles.
• silica particles and/or calcium carbonate particles include alumina-silica composite oxide particles and hydroxyapatite particles.
• Heat-resistant organic particles include cross-linked polyacrylic particles, cross-linked polystyrene particles, and benzoguanamine particles.
• silica particles porous colloidal silica is preferred.
• calcium carbonate particles light calcium carbonate that has been surface-treated with a polyacrylic acid-based polymer compound is preferred from the standpoint of preventing the lubricant from falling off.
• the average particle size of the inorganic particles added to the surface layer B is preferably 0.1 ⁇ m or more and 2.0 ⁇ m or less, and particularly preferably 0.5 ⁇ m or more and 1.0 ⁇ m or less. If the average particle size of the inorganic particles is 0.1 ⁇ m or more, the slipperiness of the release film is good, which is preferable. Furthermore, if the average particle size is 2.0 ⁇ m 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.
• 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.
• the thickness ratio of surface layer A which is the layer on which the release layer is provided, is preferably 20% or more and 50% or less of the total layer thickness of the base film. If it is 20% or more, the film is less likely to be affected from the inside by particles contained in surface layer B, etc., and it is easier 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 materials used in surface layer B can be increased, which is preferable as it reduces the environmental impact.
• layers other than the surface layer A can be made from 50 to 90% by mass of recycled raw materials such as film scraps or PET bottles. Even in this case, it is preferable that the type and amount of lubricant contained in layer B, its particle size, and the area surface average roughness (Sa) satisfy the above ranges.
• a coating layer may be provided on the surface of surface layer A and/or surface layer B before stretching or after uniaxial stretching during the film-forming process, and corona treatment or the like may also be applied.
• 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.
• the range 100 mm from one width direction end toward the center is defined as R1
• the range 50 mm on both sides of the center in the width direction is defined as R2
• the range 100 mm from the other width direction end toward the center is defined as R3.
• the resin layer-forming composition for evaluation is applied to the surface of the release layer and dried so that the thickness after drying is 500 nm.
• the positions of the 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 obtained protrusion height is then added to the thickness of the resin layer (500 nm) to determine the protrusion height, and the number of coarse protrusions with a protrusion height of 500 nm or more is counted.
• a release layer meeting these conditions is preferably formed by curing a composition containing, for example, a silicone-based or long-chain alkyl-containing resin.
• a composition containing for example, a silicone-based or long-chain alkyl-containing resin.
• other components such as binder components, crosslinking agents, adhesion promoters, and antistatic agents can also be added, provided that the effects of the present invention are not impaired.
• 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 crosslink 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, the present invention does not exclude an embodiment in which the binder component consists solely of a resin having a reactive functional group or a crosslinking agent.
• the resin having a reactive functional group is not particularly limited, but polyester resins, poly(meth)acrylic resins, polyurethane resins, polyolefin resins, epoxy resins, melamine resins, etc. can be suitably used. 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.
• the resin having a reactive functional group 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 to aggregate during drying and improving smoothness.
• alkyd resins with long-chain alkyl groups on the side chains they can be obtained by mixing an acid with the aforementioned long-chain alkyl groups (such as octylic acid or stearyl acid) with a polybasic acid such as phthalic acid, then mixing it with a polyhydric alcohol component (such as pentaerythritol or diethylene glycol), and allowing it to undergo a dehydration condensation reaction.
• an acid with the aforementioned long-chain alkyl groups (such as octylic acid or stearyl acid) with a polybasic acid such as phthalic acid, then mixing it with a polyhydric alcohol component (such as pentaerythritol or diethylene glycol), and allowing it to undergo a dehydration condensation reaction.
• a polyhydric alcohol component such as pentaerythritol or diethylene glycol
• a (meth)acrylic resin having a long-chain alkyl group can be included as a binder component, and it may be, for example, a (meth)acrylic resin having a long-chain alkyl group on the side chain.
• (Meth)acrylic resins having long-chain alkyl groups in their side chains are preferably obtained by copolymerizing two or more types of (meth)acrylic monomers.
• the copolymerized monomers preferably include monomers having long-chain alkyl groups (e.g., lauryl (meth)acrylate, stearyl (meth)acrylate, isodecyl (meth)acrylate, etc.), and preferably include monomers having hydroxy groups as reactive functional group sites (e.g., hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, hydroxybutyl (meth)acrylate, etc.).
• monomers having long-chain alkyl groups e.g., lauryl (meth)acrylate, stearyl (meth)acrylate, isodecyl (meth)acrylate, etc.
• monomers having hydroxy groups as reactive functional group sites e.g., hydroxyethyl (meth)
• the content of monomers having long-chain alkyl groups that make up the resulting acrylic resin is preferably between 1 mol% and 50 mol% of the total monomers that make up 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 proportion of monomers having reactive functional groups is relatively high, resulting in a high crosslink density of the resin.
• reactive functional group-containing resins that have a silicone skeleton within the resin skeleton include alkyd resins or acrylic resins that have a polydimethylsiloxane skeleton in the side chain.
• reactive functional group-containing resins that have a silicone skeleton within the resin skeleton include alkyd resins or acrylic resins that have a polydimethylsiloxane skeleton in the side chain.
• 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).
• the release layer may contain a melamine resin as a binder component.
• the resin may be selected from a full-ether type methylated melamine resin, a methylol type methylated melamine resin, and a polymer thereof.
• 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 their low-temperature, short-time curing properties and adhesion to polyester films.
• Commercially available products include Cymel 303LF and Nikalac MW-30.
• the release layer may contain an alicyclic epoxy resin as a binder component.
• alicyclic epoxy resins include those manufactured by Daicel Corporation under the trade names EHPE-3150, CEL2021P, and CEL2000.
• 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.
• 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.
• a melamine-based compound is preferred from the viewpoint of reactivity.
• a melamine-based compound even a thin release layer with a coating amount of 0.2 g/ m2 or less after curing can be cured quickly, and the crosslinking density is high, which is preferable.
• the melamine-based compound used in the present invention can be any common compound and is not particularly limited. However, it is preferable that the compound be obtained by condensing melamine with formaldehyde and have 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.
• a lower alcohol such as methyl alcohol, ethyl alcohol, isopropyl alcohol, or butyl alcohol
• methylol melamine derivatives include monomethylol melamine, dimethylol melamine, trimethylol melamine, tetramethylol melamine, pentamethylol melamine, and hexamethylol melamine. One type or two or more types may be used.
• hexamethylolmelamine or hexamethoxymethylolmelamine which have many crosslinking points per molecule, as this can increase the crosslink density of the binder component.
• hexamethoxymethylmethylolmelamine obtained by dehydration condensation with methyl alcohol is particularly preferred from the standpoint of reactivity.
• the melamine used in the present invention can also be commercially available.
• full-ether type methylated melamine resins are preferred due to their low-temperature, short-time curing properties and adhesion to polyester film.
• Commercially available products include Cymel 303LF and Nikalac MW-30.
• 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 is capable of forming a resin film by self-condensation, the binder component may consist solely of the crosslinking agent. Including 15% by mass or more of crosslinking agent is preferred because it increases the crosslink density of the release layer and improves solvent resistance and elastic modulus.
• 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 that forms the release layer.
• the release layer-forming composition of the present invention may contain a catalyst to cure the crosslinking agent.
• a catalyst to cure the crosslinking agent.
• an acid catalyst it is preferable to use an acid catalyst.
• carboxylic acid-based, metal salt-based, phosphate ester-based, and sulfonic acid-based catalysts are suitable.
• Block-type catalysts in which the acid moiety is blocked can also be used.
• Paratoluenesulfonic acid is particularly suitable from the standpoint of reactivity.
• an isocyanate-based compound common catalysts can be used, and organotin, amine compounds, trialkylphosphine compounds, and the like are suitable.
• a platinum catalyst can be used.
• Sulfonic acid catalysts that can be used preferably include, for example, p-toluenesulfonic acid, xylenesulfonic acid, cumenesulfonic acid, dodecylbenzenesulfonic acid, dinonylnaphthalenesulfonic acid, and trifluoromethanesulfonic acid, but from the perspective of reactivity, p-toluenesulfonic acid is particularly preferred.
• Sulfonic acid catalysts have higher acidity and superior reactivity than other acid catalysts such as carboxylic acid catalysts, making it possible to process the release layer at lower temperatures. This makes them preferable because they can prevent the film from losing flatness and the winding appearance from being affected by heat during processing.
• the sulfonic acid catalyst used in the present invention can also be commercially available.
• 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 DNNDSA series (dinonylnaphthalene (mono)sulfonic acid, manufactured by Kusumoto Chemicals Co., Ltd.), NACURE DDBSA series (dodecylbenzenesulfonic acid, manufactured by Kusumoto Chemicals Co., Ltd.), and NACURE p-TSA series (p-toluenesulfonic acid, manufactured by Kusumoto Chemicals Co., Ltd.).
• 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.
• 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 the effects of the present invention can be obtained, but polyorganosiloxanes and the like can be suitably used.
• polyorganosiloxanes polydimethylsiloxane (abbreviated as PDMS) can be suitably 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 bonding with the binder resin to occur, making it less likely to transfer to the ceramic green sheet.
• the functional group to be introduced into the polydimethylsiloxane is not particularly limited, and may be either a reactive or non-reactive functional group. Furthermore, the functional group may be introduced into one end of the polydimethylsiloxane, both ends, or a side chain. Furthermore, the functional group may be introduced into one or more positions.
• Reactive functional groups that can 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.
• 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, of the above, those containing epoxy groups, carboxyl groups, polyether groups, methacryl groups, acrylic groups, and ester groups are preferred.
• 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 solids content of the composition that forms the release layer. It is more preferably present in an amount of 0.2 to 15% by mass. It is even more preferably present in an amount of 0.5 to 15% by mass.
• the silicone-based release agent in such an amount, it is possible to form a release film in which the number of coarse protrusions represented by A1, A2, and A3 is each in the range of 10 to 1000/ m2 , and the coarse protrusion number ratio X [((A1+A3)/2)/A2] is 0.2 to 5.0.
• additives such as adhesion improvers and antistatic agents may be added to the release layer as long as they do not impair the effects of the present invention, 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.
• 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.
• One example of how to evaluate the resistance to charging is to bring the release layer into contact with surface layer B, apply a load, and then evaluate the amount of charge on the release layer after maintaining this for a certain period of time.
• This evaluation method makes it possible to model the amount of charge that increases over time when the film is stored in roll form. Details of the evaluation method will be described later.
• the charge amount of the release layer measured by the evaluation method described below is preferably ⁇ 5 kV or less, for example ⁇ 3.4 kV or less, and more preferably ⁇ 3 kV or less, with the smaller the absolute value, the better.
• the charge amount of the release layer is preferably ⁇ 5 kV or less, for example ⁇ 3.4 kV or less, and more preferably ⁇ 3 kV or less, with the smaller the absolute value, the better.
• the release film of the present invention can have a functional layer between the substrate and the release layer.
• functional layers include, but are not limited to, an antistatic layer or a readily soluble resin layer.
• an antistatic layer is preferable because it prevents the adhesion of foreign matter due to static electricity and suppresses static electricity when peeling off ceramic green sheets, etc., thereby achieving stable peelability.
• the release layer formed on the surface of the release film can be easily separated and removed, and it is possible to recover only the base film with no or very little release layer residue, which is preferable.
• the release layer is substantially free of particles with a particle size of 1.0 ⁇ m or more.
• the release layer may contain particles with a particle size of less than 1.0 ⁇ m and 1 nm or more.
• the release layer be substantially free of inorganic particles with a particle size of 1.0 ⁇ m or more, it is possible to suppress the occurrence of pinholes in ultra-thin resin sheets that require high smoothness, such as ceramic green sheets, and to form resin sheets with a uniform film thickness.
• the release layer since it is preferable for the release layer to have high smoothness, it is preferable to provide the release layer of the present invention on a substrate film having a surface layer A that is substantially free of inorganic particles, specifically substantially free of particles with a particle size of less than 1.0 ⁇ m, preferably a surface layer A that is substantially free of particles.
• a release layer that contains substantially no particles with a particle size of less than 1.0 ⁇ m is preferably also substantially free of particles with a particle size of 1.0 ⁇ m or more.
• the surface roughness (Sa) of the release layer is 3.0 nm or less
• the maximum protrusion height (P) is 200 nm or less.
• (Sa) may be 0.1 nm or more and 3.0 nm or less
• the maximum protrusion height (P) may be 1 nm or more and 200 nm or less
• (Sa) may be 0.2 nm or more and 3 nm or less
• the maximum protrusion height (P) may be 1 nm or more and 100 nm or less.
• 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 the maximum protrusion height (P) may be 1 nm or more and 35 nm or less.
• the release layer meets these conditions, it is possible to prevent pinholes from occurring in thin resin sheets, such as ceramic green sheets, and to form resin sheets with a uniform thickness.
• the numbers of coarse projections indicated by A1, A2, and A3 are each in the range of 10 to 1000/ m2 , which can contribute to the formation of a release film in which the coarse projection number ratio X [((A1+A3)/2)/A2] is 0.2 to 5.0.
• release layer makes it possible to suppress the occurrence of pinholes in ultra-thin resin sheets that require high smoothness, such as ceramic green sheets, and to form resin sheets with a uniform thickness.
• the numbers of coarse protrusions having a height of 500 nm or more present on the surface of the release layer confirmed in a range R1 of 100 mm from one widthwise end toward the center and in a range R3 of 100 mm from the other widthwise end toward the center are defined as A1 and A3.
• the number of coarse protrusions confirmed in a range R2 of 50 mm left and right from the center point in the film width direction is defined as A2 (center).
• the numbers of coarse projections represented by A1, A2 and A3 are each in the range of 10 to 1000 projections/ m2 , for example, in the range of 10 to 900 projections/ m2 .
• the numbers of coarse projections are each in the range of 10 to 850 projections/ m2 , for example, in the range of 10 to 700 projections/ m2 , and may be in the range of 20 to 700 projections/ m2 .
• the coarse protrusion number ratio X [((A1+A3)/2)/A2] of the release layer is 0.2 to 5.0.
• the ratio X of the number of coarse protrusions is, for example, in the range of 0.4 to 2.5, or alternatively, in the range of 0.4 to 2.10, or alternatively, in the range of 0.7 to 1.5.
• the coarse protrusion count ratio X is less than 0.2
• the number of coarse protrusions A2 (center) found within a range R2 of 50 mm on either side of the center point in the film width direction tends to be excessively greater than the numbers A1 and A3 of coarse protrusions near the film edges.
• air escape is poor, winding becomes difficult, and the film becomes more susceptible to static electricity and foreign matter becomes more likely to be caught in it.
• 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 add the thickness of the resin layer (500 nm) to the obtained protrusion height to calculate the protrusion height.
• the resin layer-forming composition for evaluation include those used in the examples.
• Figure 1 is a schematic diagram showing the height of coarse protrusions in the present invention.
• the diagram shows an embodiment in which coarse protrusions 40 protrude from the surface of the substrate 10 toward the release layer 20.
• 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 Figure 1.
• the protrusion height can then be calculated by adding the thickness of the resin layer, 500 nm, to the obtained protrusion height, and the actual protrusion height 42 in Figure 1 can be calculated.
• the number of coarse protrusions with a height of 500 nm or more present on the surface of the release layer can be calculated in this manner.
• the resin layer used to evaluate the number of coarse protrusions can be formed using the same components and conditions as the resin sheet in the present invention.
• the thickness of the release layer in the present invention is not particularly limited, but is preferably 30 nm or more. It is more preferably 50 nm or more, and even more preferably 100 nm or more. A thickness of 30 nm or more provides sufficient releasability, allowing the ceramic green sheet to be peeled off without defects. Furthermore, a thickness of 30 nm or more can fill in protrusions on the polyester film substrate, improving smoothness.
• the upper limit of the release layer thickness is not particularly limited, but is preferably 1000 nm or less. It may be 800 nm or less, or even 500 nm or less.
• a 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 surface and reducing the smoothness of the release layer. Furthermore, since there is no need to reduce the line speed during release layer processing to prevent streaks from occurring, productivity can be increased, which is preferable.
• the application of the release layer-forming composition to form the release layer is preferably carried out 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.
• a coating liquid in which a release resin is dissolved or dispersed is applied to one side of the biaxially oriented polyester film, and after the solvent is removed by drying, the film is heated, dried, or cured by heat or ultraviolet light.
• an aqueous coating liquid When applying using the in-line method, it is preferable to use an aqueous coating liquid. There are no particular restrictions on the type of aqueous coating liquid, but it is preferable to add a water-soluble organic solvent, such as an alcohol.
• 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, a continuous step is preferable.
• the temperature for the heat curing process 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.
• 180°C or lower the flatness of the film is maintained and there is little risk of uneven thickness in the ceramic green sheet, which is preferable.
• 140°C or lower the film can be processed without impairing the flatness, and there is even less risk of uneven thickness in the ceramic green sheet, which is particularly preferable.
• 80°C or higher in the case of thermosetting resins, curing proceeds sufficiently, which is preferable.
• the time required for the heat curing process is preferably between 2 and 30 seconds, and more preferably between 2 and 20 seconds.
• a time of 2 seconds or more is preferred as this allows the thermosetting resin to cure more rapidly.
• a time of 30 seconds or less is also preferred as this prevents the flatness of the film from being reduced by heat.
• the number of coarse protrusions and the coarse protrusion number ratio X according to the present invention can be brought within a predetermined range.
• An initial drying oven (first drying oven) may also 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.
• 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 inside the drying oven leaking into the coating section. Furthermore, it is less likely that contaminants caused by the volatilization of the coating material inside the drying oven will leak into the coating section, thereby suppressing the deterioration of particles.
• a final drying oven can be provided following the initial drying oven (first drying oven) and used to perform the heat curing process.
• 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.
• 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.
• 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 or later.
• the internal pressure difference (drying oven internal pressure - clean tunnel pressure) of the drying ovens in the second drying process or later 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.
• 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.
• the internal air pressure in the initial drying step is desirably within the internal air pressure of the final drying oven + 10 Pa. This condition makes it possible to more effectively bring the coarse protrusion count ratio X within the range specified by the present invention, thereby reducing variation in the number of protrusions on the film surface in the width direction.
• active energy ray irradiation step Known techniques such as ultraviolet rays and electron beams can be used as the active energy rays used in the present invention.
• the cumulative dose of active energy rays can be expressed as the product of illuminance and irradiation time. For example, in the case of ultraviolet rays, 20 to 500 mJ/ cm2 is preferred, and in the case of electron beams, approximately 0.1 to 40 kGy is preferred. Setting the dose at or above the lower limit is preferred because the release layer can be sufficiently cured, while setting the dose at or below the upper limit is preferred because thermal damage to the film due to heat during irradiation can be suppressed and flatness can be maintained.
• a backup roll When irradiating a film with active energy rays, it is preferable to hold the back side 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 for uniform irradiation. It is also preferable to cool the surface of the backup roll and irradiate the film with active energy rays while cooling the film. This is preferable because cooling makes the film less susceptible to heat damage even when irradiated with active energy rays, allowing it to maintain its flatness.
• the release film obtained by the present invention is preferably wound into a roll after passing through the heat curing step and/or the active energy ray curing step.
• the time until winding into a roll after passing through the heat curing step or the active energy ray curing step is preferably 2 seconds or more, and more preferably 3 seconds or more. If it is 2 seconds or more, the release film, whose temperature has risen in the heat curing step or the active energy ray irradiation step, is cooled before being wound into a roll, which is preferable because it does not deteriorate the flatness.
• 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.
• 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, the winding section, or both.
• the particles of 0.5 ⁇ m or larger are preferably 300 particles/CF or less, more preferably 250 particles/CF or less, and even more preferably 200 particles/CF or less.
• the number may be 5 particles/CF or more, or even 10 particles/CF or more.
• Methods for reducing particles include cleaning the clean room where the processing machine stand is located and cleaning the rolls on the processing machine stand. Performing processing in an environment with an extremely low and stable particle count is preferable because it reduces the number of protrusions on the release layer surface caused by foreign particles being drawn into the release layer and by adhesion or entrapment on the release layer surface.
• the release film of the present invention is not particularly limited as long as it is a resin sheet, and may be used in the production of pressure-sensitive adhesives and optical films.
• the release film for resin sheet molding contains an inorganic compound.
• inorganic compounds include metal particles, metal oxides, and minerals, such as calcium carbonate, silica particles, aluminum particles, and barium titanate particles.
• the resin examples include polyvinyl acetal resin and poly(meth)acrylic acid ester resin.
• the present invention has a release layer with high smoothness and a back layer with excellent smoothness, handling properties, and antistatic properties, and therefore, even in an embodiment in which these inorganic compounds are contained in the resin sheet, 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 selected appropriately depending on the application.
• the resin sheet containing an inorganic compound is a ceramic green sheet.
• the ceramic green sheet may contain barium titanate as the inorganic compound.
• the resin sheet has a thickness of 0.2 ⁇ m or more and 1.0 ⁇ m or less.
• 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 surface of the ceramic body.
• a first external electrode is provided on the first end surface.
• the first internal electrode is electrically connected to the first external electrode at the first end surface.
• the second internal electrode is exposed at a second end surface of the ceramic body.
• a second external electrode is provided on the second end surface.
• the second internal electrode is electrically connected to the second external electrode at the second end surface.
• the release film of the present invention is a release film for producing ceramic green sheets and is used to produce such multilayer ceramic capacitors.
• 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 ⁇ m to 1.0 ⁇ m.
• 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 ⁇ m 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.
• first and second external electrodes are formed to complete a multilayer ceramic capacitor.
• the cut-out release film was embedded in resin and cut into ultrathin sections using an ultramicrotome.
• the cross sections were then observed using a JEOL JEM2100 transmission electron microscope, and the film thickness of the release layer was measured from the observed TEM image.
• the range of 100 mm from one end of the width direction of the roll-shaped release film toward the center was designated R1, the range of 50 mm on both sides of the center in the width direction was designated R2, and the range of 100 mm from the other end of the width direction toward the center was designated R3.
• the number of coarse protrusions was evaluated for each of the ranges R1, R2, and R3.
• the coating was carried out using an applicator so that the thickness after drying was 500 nm, and the resin sheet was dried at 90 ° C for 1 minute.
• the positions of pinholes visually confirmed within 10 cm x 10 cm on the resin sheet surface were marked, and the height of the protrusions was measured at VertScan (registered trademark) ⁇ 50 times.
• the reaction product in the first esterification reactor was continuously removed from the system and fed to a second esterification reactor.
• 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.
• 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.
• reaction product from the second esterification reactor was continuously removed from the system and supplied to a third esterification reactor, and a reaction was carried out at normal pressure for an average residence time of 0.5 hours at 260°C while adding, as 10% EG slurries, 0.2% by mass of porous colloidal silica having an average particle size of 0.9 ⁇ m that had been dispersed using a high-pressure disperser (manufactured by Nippon Seiki Co., Ltd.) at a pressure of 39 MPa (400 kg/ cm2 ) for an average number of treatment passes of 5, and 0.4% by mass of synthetic calcium carbonate having an average particle size of 0.6 ⁇ m and having an ammonium salt of polyacrylic acid attached thereto at 1% by mass per calcium carbonate.
• a high-pressure disperser manufactured by Nippon Seiki Co., Ltd.
• 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 ⁇ m, and then ultrafiltered and extruded into water. After cooling, the extruded product was cut into chips to obtain PET chips with an intrinsic viscosity of 0.60 dl/g (hereinafter referred to as PET(I)). The lubricant content in the PET chips was 0.6% by mass.
• PET (II) Preparation of polyethylene terephthalate pellets (PET (II))
• PET(II) PET chips containing absolutely no particles such as calcium carbonate or silica and having an intrinsic viscosity of 0.62 dl/g were obtained (hereinafter abbreviated as PET(II)).
• PET (Production of laminated film F1) These PET chips were dried, melted at 285°C, and then melted at 290°C in separate melt extruders. The resulting mixture was filtered through two stages: a filter made of sintered stainless steel fibers with a 95% cut diameter of 15 ⁇ m, and a filter made of sintered stainless steel particles with a 95% cut diameter of 15 ⁇ m. The resulting mixture was joined in a feed block, and PET (I) was laminated as surface layer B (the layer opposite the release surface) and PET (II) as surface layer A (the release surface).
• 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.
• 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.
• laminate film F2 A 25 ⁇ m thick A4100 (Cosmoshine (registered trademark), manufactured by Toyobo Co., Ltd.) was used as the laminate film F2. A4100 does not substantially contain particles in the film, but has a particle-containing coating layer provided by in-line coating on the surface layer B side.
• the surface layer A of the laminate film F2 had an Sa of 1 nm, and the surface layer B had an Sa of 2 nm.
• E5101 Toyobo Ester (registered trademark) film, manufactured by Toyobo Co., Ltd.) having a thickness of 25 ⁇ m 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 laminate film F3 was 24 nm, and the Sa of surface layer B was 24 nm.
• the obtained coating liquid was passed through a filter capable of removing 99% or more of foreign matter of 0.5 ⁇ m or larger, and then coated onto laminated film F1 (350 mm wide) using reverse gravure so that the release layer thickness 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 1, and the film was dried at 140° C. for 15 seconds to obtain a release film.
• the number of particles in the unwinding and winding sections is as shown in Table 1.
• Example 2 A release layer was formed in the same manner as in Example 1, except that the solid content concentration of the coating liquid was adjusted and the thickness of the release layer after drying was changed to the contents shown in Table 1.
• 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 being interposed between the dimethylsiloxane and the carboxyl group).
• Example 7 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 1.
• a melamine compound full-
• 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 250 mm.
• 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 450 mm.
• 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 800 mm.
• Example 14 The substrate width of the laminated film F1 was changed to 1400 mm, and a release layer was formed in the same manner as in Example 1. After producing the release film, the film was cut into three pieces of 450 mm each using a slit and evaluated.
• Example 15 A release layer was formed in the same manner as in Example 1, except that the laminated film was changed to F2.
• Example 16 A release layer was formed in the same manner as in Example 1, except that polyester powder was removed from the surface of the film coating with a microfiber film cleaning cloth before release processing.
• 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. Because the surface roughness of the coated surface was high, the number of protrusions on the surface of the release layer was large.
• 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 values shown in Table 1. 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.
• 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.
• Example 17 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.
• Tables 1 to 3 show the various compositions, film-forming conditions, and physical properties of the examples and comparative examples.
• 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 for the resin sheet-forming slurry to be applied without defects without deteriorating the rollability of the release film, and in particular, allows for the formation of ceramic green sheets without defects.
• the present invention provides a release film with excellent releasability and smoothness, which has a release layer on one side of the base film, and can be produced without the risk of defects in the thin-layer resin sheet.

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