Peel-off sheet

Abstract

The present invention pertains to a release sheet having a base material and a release layer formed on the base material. The release layer is formed from a release agent composition containing a silicone-modified acrylic resin (A), a melamine resin (B), an acid catalyst (C), and a filler (D); and the amount of silicon modification in the solid content of the silicone-modified acrylic resin (A) is 0.3 to 0.5 mmol / g.

Description

[Technical Field]

[0001] The present invention relates to a release sheet. [Background technology]

[0002] Generally, a release sheet (sometimes called a "process sheet") has a substrate such as paper, a plastic film, or polyethylene-laminated paper, and a release layer provided on the substrate. The release layer is formed by applying a release agent composition containing a reactive compound onto the substrate and curing it. Release sheets are widely used, for example, as protective sheets for adhesive layers in adhesive sheets, process films for producing resin sheets, process films for forming ceramic green sheets, and process films for producing synthetic leather (see, for example, Patent Documents 1 to 6).

[0003] Also known are transfer sheets (transfer foils) that have a protective layer (hard coat layer) and an adhesive layer in this order on the release layer of a release sheet, transfer sheets that have a functionality-imparting layer such as a decorative layer between the protective layer and the adhesive layer, and transfer sheets that have a protective layer and a functional adhesive layer. By laminating the transfer sheet on an object and peeling off the release sheet, it is possible to impart hard coat properties, decorative properties, or any desired functionality to the surface of the object. In such transfer sheets, the transfer resins of the protective layer, adhesive layer, etc. are curable resin compositions, and the release sheet may be removed after the transfer sheet is laminated to an object and heat-bonded. In this case, while the transfer sheet is laminated to the object, cutting or other processing may be performed before the protective layer and adhesive layer are cured. Therefore, before the protective layer and adhesive layer are cured, they need to have release properties that prevent the protective layer from peeling from the release layer to an extent that unintended peeling does not occur during cutting or other processing. On the other hand, after the protective layer and adhesive layer are cured, they need release properties that allow the protective layer to be easily peeled from the release layer. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2009 / 122984 [Patent Document 2] Japanese Patent Application Publication No. 2017-171617 [Patent Document 3] Japanese Patent Application Laid-Open No. 2018-104661 [Patent Document 4] Japanese Patent Application Publication No. 2019-171617 [Patent Document 5] Japanese Patent Publication No. 2020-146890 [Patent Document 6] Japanese Patent Publication No. 2020-153022 Summary of the Invention [Problem to be solved by the invention]

[0005] However, when the protective layer and adhesive layer change from an uncured state to a cured state, a chemical change occurs in which the intermolecular forces and polarity at the interface between the release layer and the protective layer change. Furthermore, when the protective layer and / or adhesive layer hardens, a physical change occurs in which the difference in elastic modulus between the release layer and these layers becomes significant. These chemical and physical changes make it extremely difficult to control the releasability at the interface between the release layer and the protective layer. Furthermore, since the protective layer and adhesive layer are sometimes cured by a hot press treatment, the effects of the temperature and pressure of the hot press treatment must also be considered in order to control the releasability. Therefore, there has been a strong demand for the development of a release sheet that does not cause the release layer to peel off from the protective layer when processed, such as by cutting, while the protective layer is in an uncured state before the hot press treatment, and that allows the release layer to be easily peeled off from the protective layer after the hot press treatment is in a cured state.

[0006] Therefore, the present invention aims to provide a release sheet in which the release layer does not peel off from the protective layer due to processing such as cutting before the hot press treatment, and the release layer can be easily peeled off from the protective layer after the hot press treatment. [Means for solving the problem]

[0007] The present inventors have discovered that the above-mentioned problems can be solved by a release sheet having a release layer formed from a release agent composition containing a silicone-modified acrylic resin with a controlled amount of silicone modification, a melamine resin, an acid catalyst, and a filler.

[0008] That is, the present invention relates to the following [1] to [6]. [1] A substrate and a release layer formed on the substrate, the release layer is a layer formed from a release agent composition containing a silicone-modified acrylic resin (A), a melamine resin (B), an acid catalyst (C), and a filler (D); The release sheet has a silicone modification amount in the solid content of the silicone-modified acrylic resin (A) of 0.3 to 0.5 mmol / g. [2] The release sheet according to the above [1], wherein the mass ratio (A) / (B) of the silicone-modified acrylic resin (A) to the melamine resin (B) is 50 / 50 to 95 / 5 in terms of solid content. [3] The release sheet according to the above [1] or [2], wherein the content of the acid catalyst (C) is 0.1 to 20 parts by mass, calculated as solid content, per 100 parts by mass of the melamine resin (B). [4] The release sheet according to any one of the above [1] to [3], wherein when the resin component is the total solid content of the release agent composition excluding the filler (D), the content of the filler (D) is 15 to 75 parts by mass per 100 parts by mass of the resin component. [5] The release sheet according to any one of the above [1] to [4], wherein the amount of silicone modification of the silicone-modified acrylic resin (A) is 0.18 to 0.40 mmol / g based on the total solid content of the silicone-modified acrylic resin (A), the melamine resin (B), the acid catalyst (C), and the filler (D). [6] The release sheet according to any one of the above [1] to [5], wherein the filler (D) contains boron nitride particles. [Effects of the Invention]

[0009] According to the present invention, it is possible to provide a release sheet in which the release layer does not peel off from the protective layer due to processing such as cutting before the hot press treatment, and the release layer can be easily peeled off from the protective layer after the hot press treatment. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a schematic cross-sectional view of a release sheet according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, embodiments of the present invention will be described in detail. The release sheet (sometimes referred to as a "process film") of the present invention has a substrate and a release layer formed on the substrate, and the release layer is a layer formed from a release agent composition containing a silicone-modified acrylic resin (A) (hereinafter also referred to as "component (A)"), a melamine resin (B) (hereinafter also referred to as "component (B)"), an acid catalyst (C) (hereinafter also referred to as "component (C)"), and a filler (D) (hereinafter also referred to as "component (D)"), and the silicone modification amount in the solid content of the silicone-modified acrylic resin (A) is 0.3 to 0.5 mmol / g. In the present invention, by controlling the amount of silicone modification in the silicone-modified acrylic resin (A) in the release agent composition containing components (A) to (D), the excellent effects are exhibited, in that the release layer does not peel off from the protective layer due to processing such as cutting before the hot press treatment, and the release layer can be easily peeled off from the protective layer after the hot press treatment.

[0012] In this specification, the term "active ingredient" refers to the components contained in the stripping composition excluding the dilution solvent. In this specification, the term "resin component" refers to the total solid content of the release layer (release agent composition) excluding fillers (organic fillers and inorganic fillers). That is, even if the filler (D) contains an organic filler, the resin component does not contain the organic filler. Furthermore, for preferred numerical ranges (e.g., ranges of content, etc.), the lower and upper limits described in stages can be independently combined. For example, the description "preferably 10 to 90, more preferably 30 to 60" can be combined with the "preferable lower limit (10)" and the "more preferable upper limit (60)" to form "10 to 60."

[0013] [Composition of release sheet] The release sheet of the present invention has a substrate and a release layer provided on the substrate. Figure 1 is a schematic cross-sectional view showing an example of a release sheet according to an embodiment of the present invention. Release sheet 1A has a substrate 10 and a release layer 11 provided on the substrate 10. Release layer 11 is a cross-linked product formed from a release agent composition containing a silicone-modified acrylic resin (A), a melamine resin (B), an acid catalyst (C), and a filler (D) (12 in Figure 1). Between the substrate 10 and the release layer 11, other layers such as an easy-adhesion layer and an antistatic layer (not shown) may be provided. The release layer and substrate constituting the release sheet of the present invention will be described below.

[0014] <Release layer> The release layer of the release sheet of the present invention can be formed from a release agent composition containing a silicone-modified acrylic resin (A), a melamine resin (B), an acid catalyst (C), and a filler (D). The release agent composition, which is a material for forming the release layer, will be described below. In the following description, the "content of each component relative to the total amount of active ingredients in the release agent composition" can also be considered as the "content of each component in the release layer formed from the release agent composition."

[0015] <<Removal agent composition>> The present inventors have conducted various studies to find a formulation that will prevent a release layer formed from a release agent composition from peeling off from a protective layer by cutting or other processing before hot press treatment, while allowing the release layer formed from the release agent composition to be easily peeled off from a protective layer after hot press treatment.As a result, they have found that, in a release agent composition in which the release layer contains a silicone-modified acrylic resin (A), a melamine resin (B), an acid catalyst (C), and a filler (D), controlling the amount of silicone modification of the silicone-modified acrylic resin (A) is an effective formulation. Based on these results, the present inventors discovered that a release sheet having a release layer formed from a release agent composition containing a silicone-modified acrylic resin (A) with a controlled amount of silicone modification, a melamine resin (B), an acid catalyst (C), and a filler (D) can solve the above problems, and thus arrived at the present invention.

[0016] In one embodiment of the present invention, the release agent composition may or may not contain additives other than the above-mentioned components (A) to (D), as long as the effects of the present invention are not impaired.

[0017] Each component contained in the stripping agent composition will be described below.

[0018] (Silicone modified acrylic resin (A)) The silicone-modified acrylic resin (A) used in the present invention can function as a base mold release agent. The silicone-modified acrylic resin (A) can be obtained by modifying an acrylic resin with a silicone modifier. A method for modifying an acrylic resin with a silicone modifier includes, for example, reacting an acrylic resin having a functional group with a silicone modifier having a functional group. The acrylic resin having a functional group is an acrylic resin having a functional group that can react with the terminal functional group of the silicone modifier. The silicone modifier having a functional group is a silicone modifier having a terminal functional group that can react with the functional group of the acrylic resin.

[0019] Examples of monomers for acrylic resins include (meth)acrylic acid, methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, cyclohexyl (meth)acrylate, glycidyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, and 2-hydroxypropyl (meth)acrylate. These may be used alone or in combination of two or more. Acrylic resins can be obtained by polymerizing these monomers using known methods. In this specification, the term "(meth)acrylic acid" is a concept that includes both "acrylic acid" and "methacrylic acid."

[0020] Examples of silicone modifiers include organopolysiloxanes having an organic group, such as dimethylpolysiloxane. Examples of the organic group include phenyl, methyl, ethyl, isopropyl, hexyl, cyclohexyl, and vinyl groups. These may be used alone or in combination of two or more.

[0021] Examples of the functional group in the acrylic resin and the silicone modifier include a hydroxyl group, an amino group, a carboxyl group, a thiol group, an isocyanate group, an epoxy group, a hydrosilyl group, an ethynyl group, an ammonium group, an amide group, an imino group, an alkoxysilyl group, an ether group, a sulfonic acid group, and a nitrile group. Specific examples of reactions between functional groups of an acrylic resin and functional groups of a silicone modifier include reactions between active hydrogen groups present in hydroxyl groups, primary amino groups, secondary amino groups, carboxyl groups, thiol groups, etc. and isocyanate groups or epoxy groups; esterification reactions between hydroxyl groups and carboxyl groups; and hydrosilylation reactions between hydrosilyl groups and ethynyl groups.

[0022] The silicone-modified resin (A) can also be obtained by polymerizing a mixture of an acrylic resin monomer and a silicone modifier having an acrylate functional group.

[0023] Some commercially available silicone-modified acrylic resins (A) are already blended with a melamine resin or the like as a curing agent for curing component (A). When using such a commercially available product, the melamine resin or the like blended as a curing agent in the commercially available product is treated as component (B) melamine resin, which will be described later, and the remaining net amount of silicone-modified acrylic resin is treated as component (A). Examples of commercially available products containing a silicone-modified acrylic resin (A) and a melamine resin (B) include x-62-9088 and x-62-9089 (both of which are product names manufactured by Shin-Etsu Chemical Co., Ltd.), and TA31-291F (both of which are product names manufactured by Showa Denko Materials Co., Ltd.).

[0024] The silicone-modified acrylic resin (A) used in the present invention has a specific silicone modification amount. Here, in this specification, the "silicone modification amount" refers to the amount (mmol) of silyl groups represented by the following formula (X) per gram of solid content of the silicone-modified acrylic resin (A). In formula (X), R and R' are organic groups in the silicone modifier. R and R' may be the same or different.

[0025] [ka]

[0026] The silicone modification amount in the solid content of the silicone-modified acrylic resin (A) is 0.3 to 0.5 mmol / g. If it is less than the lower limit, it may be difficult to peel the release layer from the protective layer after the hot press treatment. If it is more than the upper limit, the release layer may easily peel from the protective layer before the hot press treatment. From the viewpoint of further improving the ease with which the release layer can be peeled from the protective layer after the hot press treatment and the prevention of easy peeling of the release layer from the protective layer before the hot press treatment, the silicone modification amount in the solid content of the silicone-modified acrylic resin (A) is preferably 0.32 to 0.48 mmol / g, more preferably 0.34 to 0.45 mmol / g, and may be 0.35 to 0.43 mmol / g. The silicone modification amount in the solid content of the silicone-modified acrylic resin (A) may be adjusted by using two or more types of silicone-modified acrylic resins (A).

[0027] In one embodiment of the present invention, the silicone modification amount of the silicone-modified acrylic resin (A) relative to the total solids content of the silicone-modified acrylic resin (A), the melamine resin (B), the acid catalyst (C), and the filler (D) is preferably 0.18 to 0.40 mmol / g, more preferably 0.20 to 0.36 mmol / g, even more preferably 0.21 to 0.33 mmol / g, and even more preferably 0.22 to 0.30 mmol / g. When the silicone modification amounts of components (A) to (D) are within the above ranges, the release layer can be easily peeled from the protective layer after hot-pressing, and the release layer can be prevented from easily peeling from the protective layer before hot-pressing.

[0028] In one embodiment of the present invention, the mass ratio (A) / (B) of the silicone-modified acrylic resin (A) to the melamine resin (B) is preferably 50 / 50 to 95 / 5, more preferably 55 / 45 to 90 / 10, and even more preferably 60 / 40 to 85 / 15, calculated on a solids basis. When the mass ratio (A) / (B) is equal to or greater than the lower limit, the release layer is prevented from becoming difficult to peel from the protective layer and from becoming less flexible, which can lead to layer cracking. On the other hand, when the mass ratio (A) / (B) is equal to or less than the upper limit, the release agent composition in the release layer is prevented from being insufficiently cured, which can lead to unstable peeling of the release layer from the protective layer and the migration of components of the release layer to the protective layer.

[0029] The total content of the silicone-modified acrylic resin (A) and the melamine resin (B) in the release agent composition is not particularly limited, but is preferably 40 to 85 parts by mass, more preferably 50 to 80 parts by mass, and even more preferably 55 to 75 parts by mass, based on 100 parts by mass of the total of the silicone-modified acrylic resin (A), the melamine resin (B), the acid catalyst (C), and the filler (D), calculated as solids. When the total content of the silicone-modified acrylic resin (A) and the melamine resin (B) in the release agent composition is equal to or greater than the lower limit above, the release layer can be easily peeled from the protective layer after hot press treatment. When the total content is equal to or less than the upper limit above, the release layer cannot be easily peeled from the protective layer before hot press treatment.

[0030] (Melamine resin (B)) The melamine resin (B) can function as a crosslinking agent for the silicone-modified acrylic resin (A). By including the melamine resin (B) in the release agent composition, the film strength of the release layer formed by the release agent composition can be improved.

[0031] Examples of the melamine resin (B) include methylolated melamine resin, iminomethylolated melamine resin, alkylated melamine resin, etc. These may be used alone or in combination of two or more. For example, an alkylated melamine resin is a methylolated melamine resin in which some or all of the methylol groups have been alkyl-etherified with an alkyl monoalcohol. The type and etherification rate of the alkyl monoalcohol are not particularly limited and can be appropriately selected taking into consideration the compatibility with the silicone-modified acrylic resin (A), solubility in solvents, curability of the resulting release agent composition, adhesion to substrates, etc. Specific examples of alkylated melamine resins include methylated melamine resins, ethylated melamine resins, propylated melamine resins, butylated melamine resins such as normal butylated melamine resins and isobutylated melamine resins, hexylated melamine resins, octylated melamine resins such as normal octylated melamine resins, etc. These may be used alone or in combination of two or more.

[0032] Commercially available methylol melamine resins include Nikalac MS-11 and MW-12LF (both trade names manufactured by Sanwa Chemical Co., Ltd.). Commercially available iminomethylol melamine resins include Nikalac MS-001, Nikalac MX-750, Nikalac MX-706, and Nikalac MX-035 (all trade names manufactured by Sanwa Chemical Co., Ltd.). Commercially available iminated melamine resins include Nikalac MZ-351 and Nikalac MX-730 (both trade names manufactured by Sanwa Chemical Co., Ltd.). Commercially available methylated melamine resins include Cymel 303, Cymel 325, Cymel 327, Cymel 350, and Cymel 370 (all trade names manufactured by Nippon Cytec Industries Co., Ltd.), and Tesfine 200 (trade name manufactured by Hitachi Chemical Polymer Co., Ltd.).

[0033] The silicone-modified acrylic resin (A) and the melamine resin (B) may be prepared separately, or the silicone-modified acrylic resin (A) and the melamine resin (B) may be mixed together in advance to prepare the resin.

[0034] (Acid catalyst (C)) In the release agent composition, the use of an acid catalyst (C) can accelerate the curing of the melamine resin (B) and increase the film strength of the release layer. Examples of the acid catalyst (C) include inorganic acids such as hydrochloric acid, sulfuric acid, phosphoric acid, boric acid, etc.; carboxylic acids (organic acids) such as acetic acid, monochloroacetic acid, dichloroacetic acid, butyric acid, etc.; organic sulfonic acids (organic acids) such as benzenesulfonic acid, p-toluenesulfonic acid, xylenesulfonic acid, p-phenolsulfonic acid, methanesulfonic acid, ethanesulfonic acid, etc.; alkyl phosphate esters (organic acids); etc. These may be used alone or in combination of two or more. The content of the acid catalyst is not particularly limited, but is preferably 0.1 to 20 parts by mass, more preferably 1 to 18 parts by mass, and even more preferably 5 to 15 parts by mass, relative to 100 parts by mass of the melamine resin (B) in terms of solid content.

[0035] (Filler (D)) The release agent composition contains a filler (D), which forms surface irregularities in the release layer, thereby imparting matte properties to the protective layer or other layer in contact with the release layer.

[0036] The average particle size of the filler (D) is not particularly limited, but is preferably 0.1 to 20 μm, more preferably 0.5 to 15 μm, from the viewpoint of imparting matte properties and preventing particle shedding. The average particle size of the filler (D) can be measured by observing the filler on the cross section of the release film with a scanning electron microscope, observing 100 fillers, and taking the average value as the average particle size.

[0037] The shape of the filler (D) is not particularly limited, and may be either spherical or non-spherical and irregular in shape.

[0038] The filler (D) may be either an organic filler or an inorganic filler, and an organic filler and an inorganic filler may be used in combination. Specific examples of organic fillers include crosslinked polymethyl methacrylate particles, crosslinked methyl methacrylate-styrene copolymer particles, crosslinked polystyrene particles, crosslinked methyl methacrylate-methyl acrylate copolymer particles, crosslinked alkyl acrylate-styrene copolymer particles, crosslinked alkyl methacrylate-styrene copolymer particles, melamine-formaldehyde resin particles, benzoguanamine-formaldehyde resin particles, polyacrylonitrile resin particles, and other resin particles. These may be used alone or in combination of two or more. Specific examples of inorganic fillers include boron nitride particles, silica particles, etc. These may be used alone or in combination of two or more.

[0039] The content of the filler (D) is not particularly limited, and is preferably 15 to 75 parts by mass, more preferably 25 to 70 parts by mass, per 100 parts by mass of the resin component, from the viewpoint of imparting matte properties and preventing particle shedding.

[0040] (Total content of silicone-modified acrylic resin (A), melamine resin (B), acid catalyst (C), and filler (D)) The total content of the silicone-modified alkyd resin (A), melamine resin (B), acid catalyst (C), and filler (D) in the release layer (hereinafter sometimes referred to as the "total amount of components (A) to (D)") is not particularly limited. The total amount of components (A) to (D) in the release layer is, in terms of solid content, preferably 60 parts by mass or more, more preferably 70 parts by mass or more, even more preferably 80 parts by mass or more, still more preferably 90 parts by mass or more, particularly preferably 95 parts by mass or more, and may be substantially 100 parts by mass, relative to 100 parts by mass of the release agent composition.

[0041] (Other additives) The release agent composition may contain additives other than the above-mentioned components (A) to (D) as long as the object of the present invention is not impaired. Examples of such additives include various additives such as antioxidants, ultraviolet absorbers, antistatic agents, surfactants, photoinitiators, light stabilizers, matting agents, viscosity modifiers, leveling agents, etc. These may be used alone or in combination of two or more. When the release agent composition contains the other additives, the content of the other additives is preferably 30 parts by mass or less, more preferably 0.1 to 15 parts by mass, and even more preferably 0.1 to 5 parts by mass, per 100 parts by mass of the total amount of the components (A) and (B).

[0042] (Dilution solvent) From the viewpoint of improving the applicability to a substrate, the release agent composition may be in the form of a solution by adding a dilution solvent to the above-mentioned various active ingredients. The dilution solvent is selected from among the organic solvents that have good solubility for the above-mentioned components (A) to (D). Examples of such organic solvents include toluene, xylene, hexane, heptane, octane, methanol, ethanol, isopropyl alcohol, isobutanol, n-butanol, ethyl acetate, acetone, methyl ethyl ketone, cyclohexanone, tetrahydrofuran, etc. These may be used alone or in combination of two or more. The organic solvent used as the dilution solvent may be the same as that used in the synthesis of the component (A) or (B). Alternatively, the organic solvent used in the synthesis of the component (A) or (B) and / or one or more other organic solvents may be added as the dilution solvent so that the release agent composition can be uniformly applied. When a stripping agent composition solution obtained by adding a dilution solvent to the stripping agent composition is used, it is preferable to apply the solution to a substrate to form a coating film, and then heat and dry the coating film.

[0043] The amount of dilution solvent may be appropriately selected so that the stripping composition has an appropriate viscosity when applied. The solid content concentration of the stripping composition solution is not particularly limited, but is preferably 0.1 to 60 mass %, more preferably 0.2 to 50 mass %, and particularly preferably 0.5 to 40 mass %.

[0044] <Thickness of release layer> The thickness of the release layer is not particularly limited, but is usually 25 to 5000 nm, preferably 100 to 4000 nm. If the thickness of the release layer is 25 nm or more, variations in release force due to variations in the coating amount can be suppressed. Furthermore, if the thickness of the release layer is 5000 nm or less, the curability of the coating film of the release agent composition can be improved. The thickness of the release layer is measured, for example, by the method described in the Examples below.

[0045] <Surface of the peeling layer> Arithmetic mean roughness Ra (surface roughness) The release layer has a surface irregularity, and the arithmetic mean roughness Ra of the release layer measured in accordance with JIS B 0601-2013 is preferably 500 to 650 nm, more preferably 500 to 600 nm, from the viewpoints of matte properties and release properties. The arithmetic mean roughness Ra can be adjusted by selecting the resin component, the particle size and content of the filler (D), and the like. More specifically, the arithmetic mean roughness Ra of the release layer is measured by the method described in the examples below.

[0046] <Base material> The substrate used in the release sheet of the present invention is not particularly limited as long as it can support the release layer, and examples thereof include paper substrates and resin films. Examples of paper substrates include fine paper, medium-quality paper, glassine paper, art paper, coated paper, clay-coated paper, cast-coated paper, and kraft paper; laminated paper obtained by laminating these papers with a thermoplastic resin such as polyethylene resin; and synthetic paper. These may be used alone or in combination of two or more. Examples of resin films include films made of synthetic resins such as polyolefin resins such as polyethylene resin, polypropylene resin, and polymethylpentene resin; polyester resins such as polybutylene terephthalate resin, polyethylene terephthalate resin, and polyethylene naphthalate resin; polyetherimide resin; acetate resin; polystyrene resin; and vinyl chloride resin. These may be used alone or in combination of two or more. The substrate may be a single layer, or may be a multi-layer consisting of two or more layers of the same or different types. The thickness of the substrate is not particularly limited, but is usually 5 to 300 μm, preferably 10 to 200 μm. If the thickness of the substrate is 5 to 300 μm, it can provide, for example, a pressure-sensitive adhesive sheet using a release sheet with stiffness and strength suitable for processing such as printing, cutting, and application.

[0047] Furthermore, when a synthetic resin is used as the substrate, the surface of the substrate on which the release layer is to be provided may be subjected to a surface treatment by a method such as an oxidation method or a roughening method, if desired, in order to improve the adhesion between the substrate and the release layer. Examples of oxidation methods include corona discharge surface treatment, chromic acid surface treatment (wet), flame surface treatment, hot air surface treatment, ozone and ultraviolet irradiation surface treatment, etc. Examples of roughening methods include sandblasting and solvent treatment. These surface treatment methods are appropriately selected depending on the type of substrate, but corona discharge surface treatment is generally preferred from the viewpoints of effectiveness and operability. Primer treatment can also be performed.

[0048] The release sheet of the present invention may be embossed on the surface of the release layer to form projections and recesses on the surface of the release sheet. The release sheet of the present invention may consist of only a substrate and a release layer, or may have other layers such as an easy-adhesion layer, an antistatic layer, etc. The provision of an easy-adhesion layer on the release sheet can effectively prevent the release layer from falling off from the release sheet.

[0049] The easy-adhesion layer is usually formed by applying an easy-adhesion coating agent to the surface of the substrate on the release layer side. Examples of easy-adhesion coating agents include polyester resins, urethane resins, acrylic resins, melamine resins, oxazoline group-containing resins, carbodiimide group-containing resins, epoxy group-containing resins, isocyanate-containing resins, and copolymers thereof, as well as coating agents containing natural rubber or synthetic rubber as the main component. These may be used alone or in combination of two or more. In order to improve the applicability of the easy-adhesion coating agent to the surface of the substrate and the adhesion between the substrate and the easy-adhesion layer, the surface of the substrate to which the easy-adhesion coating agent is to be applied may be subjected to a surface treatment such as a chemical treatment or a discharge treatment.

[0050] The thickness of the easy-adhesion layer is not particularly limited, but is preferably 50 nm to 5 μm, more preferably 100 nm to 1 μm. When the thickness of the easy-adhesion layer is equal to or greater than the lower limit, the effect of the easy-adhesion layer can be obtained satisfactorily, and when the thickness is equal to or less than the upper limit, the slipperiness of the surface of the easy-adhesion layer opposite to the substrate is improved, and the workability of applying the release agent composition onto the easy-adhesion layer is improved.

[0051] [Peeling force to peel the release sheet from the object] Generally, the peel force required to peel a release sheet from an object varies depending on the application and the type of protective layer or adhesive layer to be laminated. In addition, a low peel force may be preferable to ensure a smooth peeling operation, while a high peel force may be preferable to improve the retention of the object until the peeling operation. The peel force required to peel the release sheet from the object varies depending on the thickness and hardness of the substrate in the release sheet, the rigidity of the object, the components and physical properties of the protective layer and adhesive layer, etc. Therefore, in this specification, the peel force is evaluated by the method described in the examples below.

[0052] [Release sheet manufacturing method] The release sheet of the present invention can be produced, for example, by applying a release agent composition to at least one surface of a substrate, followed by heat treatment to cure the release agent composition and form a release layer. The coating film formed on the substrate may be cured by heating. Furthermore, when component (A) and component (B) have functional groups that react with active energy rays, the coating film may be cured by irradiating with active energy rays. Furthermore, the coating film may be cured by a combination of heating and irradiating with active energy rays. Examples of active energy rays include ultraviolet rays and electron beams. The stripping composition may be in the form of a solution diluted with a diluting solvent, as described above.

[0053] The heat treatment temperature is not particularly limited, but is preferably 80 to 250°C, more preferably 100 to 230°C, even more preferably 100 to 170°C, and particularly preferably 130 to 160°C. The heat treatment time is not particularly limited, but is preferably 15 seconds to 5 minutes, more preferably 20 seconds to 5 minutes, and particularly preferably 30 seconds to 3 minutes.

[0054] Examples of methods for applying the release agent composition include gravure coating, bar coating, spray coating, spin coating, knife coating, air knife coating, roll coating, roll knife coating, blade coating, gate roll coating, die coating, etc. These may be used alone or in combination of two or more.

[0055] The coating thickness of the release agent composition is adjusted so that the thickness of the resulting release layer falls within the above-mentioned range.

[0056] [Uses of release sheet] The release sheet of the present invention can be used as a protective sheet for various adhesive bodies such as adhesive sheets, and is used, for example, by attaching it to the adhesive layer side of an adhesive sheet comprising a substrate and an adhesive layer provided on one side of the substrate. It can also be used as a processing film when producing various resin sheets, ceramic green sheets, synthetic leather, various composite materials, etc. Furthermore, it can also be used as a transfer sheet when producing electromagnetic wave shielding films, etc. When the release sheet of the present invention is used as a processing film or transfer sheet, it is used in the process of peeling various sheet materials formed by applying a resin or the like to the release layer side of the release sheet from the release sheet.

[0057] [How to use the release sheet] The release sheet of the present invention can be used in a variety of applications as follows. For example, the case where the release sheet of the present invention is used as a transfer sheet will be described. First, coating liquids (protective layer coating liquid, adhesive layer coating liquid) for forming the protective layer and adhesive layer constituting the transfer layer of the transfer sheet on the release layer of the release sheet are prepared. The protective layer coating liquid and adhesive layer coating liquid are sequentially applied to the release layer of the release sheet, and if necessary, heated and dried to form a transfer sheet. If the adhesive layer, which is the outermost layer applied, remains adhesive even after drying, another release sheet may be laminated to protect the adhesive surface of the adhesive layer. Here, suitable components of the protective layer that directly contacts the release sheet include, for example, thermosetting acrylic resin, epoxy resin, melamine resin, etc. The transfer layer (protective layer) of the transfer sheet obtained in this manner is then transferred to the object to be transferred. To perform the transfer, various steps are performed: a cutting process for cutting the transfer sheet to the required size, a peeling process for peeling off a separate release sheet, a lamination process for laminating the transfer sheet onto the object, a heat pressing process for heat-pressing the laminated transfer layer (protective layer) to adhere and fix it to the object, and a peeling process for peeling off the release sheet, resulting in the manufacture of an article having a structure of "object-adhesive layer-protective layer." Here, the adhesive layer and the protective layer are in direct contact with each other, but an optional functional layer may be provided between the adhesive layer and the protective layer. The transfer operation includes an operation in which peeling must not occur, such as the cutting step, and an operation that can change the peelability between the release sheet and the transfer layer (protective layer), such as the hot-pressing step. The temperature of the hot-pressing step is preferably 100 to 240°C, more preferably 130 to 210°C, and even more preferably 160 to 180°C. The pressure of the hot-pressing step is preferably 0.1 to 10 MPa, more preferably 0.5 to 5 MPa, and even more preferably 1 to 3 MPa. The time of the hot-pressing step is preferably 1 second to 30 minutes, more preferably 1 to 10 minutes, and even more preferably 2 to 8 minutes. [Example]

[0058] The present invention will be specifically described with reference to the following examples, but the present invention is not limited to these examples.

[0059] [Examples and Comparative Examples] The release sheets of Examples 1 to 6 and Comparative Examples 1 to 6 were prepared by the following procedure. The components used in each of the examples and comparative examples are as follows: <(A)+(B) component-1> Silicone-modified acrylic resin containing melamine resin (Solid content concentration: 35% by mass, mass ratio of silicone-modified acrylic resin to melamine resin [silicone-modified acrylic resin / melamine resin] = 70 / 30, product name: X-62-9088, manufactured by Shin-Etsu Chemical Co., Ltd., silicone modification amount of silicone-modified acrylic resin: 0.57 mmol / g) <(A)+(B) component-2> Silicone-modified acrylic resin containing melamine resin (Solid content concentration: 35% by mass, mass ratio of silicone-modified acrylic resin to melamine resin [silicone-modified acrylic resin / melamine resin] = 70 / 30, product name: X-62-9089, manufactured by Shin-Etsu Chemical Co., Ltd., silicone modification amount of silicone-modified acrylic resin: 0.11 mmol / g) <Acrylic resin> acrylic resin (Solid content concentration: 48% by mass; mass ratio of stearyl-modified alkyd resin, stearyl-modified acrylic resin, and melamine resin [stearyl-modified alkyd resin / stearyl-modified acrylic resin / melamine resin] = 40 / 40 / 20; product name: TF303, manufactured by Showa Denko Materials Co., Ltd.)

[0060] <(C) component> p-Toluenesulfonic acid (solid content concentration 50% by mass) <(D) component> Boron nitride particles (average particle size 0.7 μm, product name UHP-S2, manufactured by Showa Denko K.K.)

[0061] Example 1 To a 1:1 mixed solvent of toluene and methyl ethyl ketone, 8.17 g (solids equivalent) of (A) + (B) component-1 and 3.50 g (solids equivalent) of (A) + (B) component-2 were added, followed by 3.75 g of boron nitride particles as component (D), and the mixture was dispersed at 2,000 rpm for 20 minutes using a disperser. The amount of the mixed solvent was adjusted so that the solids concentration of the mixed solution immediately after the addition of component (D) was 20% by mass. Next, 0.33 g (solids equivalent) of a methanol solution of p-toluenesulfonic acid as component (C) was added to the mixed solution, and the mixture was stirred at 1,500 rpm for 5 minutes using a disperser to prepare a coating solution of the release agent composition. The obtained coating solution of the release agent composition was applied to one side of a polyethylene terephthalate film (product name: PET50A4160, manufactured by Toyobo Co., Ltd., thickness 50 μm) using a Mayer bar, and dried and cured at 150°C for 1 minute to produce a release sheet having a release layer with a thickness of 2.0 μm after curing.

[0062] <Example 2> A release sheet was prepared in the same manner as in Example 1, except that in Example 1, (A) + (B) component-1 was changed to 5.83 g (solid content equivalent) and (A) + (B) component-2 was changed to 5.83 g (solid content equivalent).

[0063] Example 3 A release sheet was prepared in the same manner as in Example 1, except that the amount of component (D) was changed to 7.50 g.

[0064] Example 4 A release sheet was prepared in the same manner as in Example 1, except that in Example 1, (A) + (B) component-1 was changed to 7.58 g (solid content equivalent), (A) + (B) component-2 was changed to 4.08 g (solid content equivalent), and (D) component was changed to 7.50 g.

[0065] <Example 5> A release sheet was prepared in the same manner as in Example 1, except that in Example 1, (A) + (B) component-1 was changed to 7.00 g (solid content equivalent), (A) + (B) component-2 was changed to 4.67 g (solid content equivalent), and (D) component was changed to 7.50 g.

[0066] Example 6 A release sheet was prepared in the same manner as in Example 2, except that the amount of component (D) was changed to 7.50 g.

[0067] <Comparative Example 1> A release sheet was prepared in the same manner as in Example 1, except that in Example 1, (A) + (B) component-1 was changed to 11.67 g (solid content equivalent) and (A) + (B) component-2 was changed to 0 parts by mass (not added).

[0068] <Comparative Example 2> A release sheet was prepared in the same manner as in Example 1, except that in Example 1, (A) + (B) component-1 was changed to 0 parts by mass (not added) and (A) + (B) component-2 was changed to 11.67 parts by mass.

[0069] <Comparative Example 3> A release sheet was prepared in the same manner as in Example 1, except that in Example 1, (A) + (B) component-1 was changed to 3.50 g (solid content equivalent), (A) + (B) component-2 was changed to 8.17 g (solid content equivalent), and (D) component was changed to 7.50 g.

[0070] <Comparative Example 4> A release sheet was prepared in the same manner as in Example 1, except that in Example 1, (A) + (B) component-1 was changed to 1.17 g (solid content equivalent), (A) + (B) component-2 was changed to 10.50 g (solid content equivalent), and (D) component was changed to 7.50 g.

[0071] <Comparative Example 5> A release sheet was prepared in the same manner as in Example 1, except that 11.67 g (solid content equivalent) of acrylic resin was added instead of (A) + (B) component-1 and (A) + (B) component-2 in Example 1.

[0072] <Comparative Example 6> A release sheet was prepared in the same manner as in Example 1, except that in Example 1, 11.67 g (solid content equivalent) of acrylic resin was added instead of (A) + (B) component-1 and (A) + (B) component-2, and the (D) component was changed to 7.50 g.

[0073] [evaluation] The release sheets of Examples 1 to 6 and Comparative Examples 1 to 6 were subjected to the following measurements and evaluations.

[0074] <Thickness of release layer> The thickness of the release layer was measured using a spectroscopic ellipsometer (manufactured by J.A. Woollam Japan, trade name: Spectroscopic Ellipsometry 2000U).

[0075] <Surface roughness Ra> The arithmetic mean roughness Ra of the release layers of the release sheets obtained in Examples 1 to 6 and Comparative Examples 1 to 6 was measured in accordance with JIS B 0601-2013 using a surface roughness measuring device (product name: SV3000S4, stylus type, manufactured by Mitutoyo Corporation). The results are shown in Table 1. The measurement conditions are as follows: (Measurement conditions) Reference length = 2.5 mm, λc = 0.25 mm, λs = 0.008 mm, Evaluation length = 10 mm, Scanning speed = 1.0 mm / s, Range = 800 μm.

[0076] <Peeling force before heat press treatment> Acrylic resin and melamine resin were used as thermosetting resins for the protective layer, and each was coated onto the release layer of the release sheets obtained in Examples 1 to 6 and Comparative Examples 1 to 6, and dried at 160°C for 30 seconds to form a film of acrylic resin or melamine resin approximately 3 μm thick, forming a protective layer on the release layer to prepare a sample. The obtained sample was fixed to a universal tensile tester (product name: Autograph AGS-20NX, manufactured by Shimadzu Corporation), and the release sheet was peeled from the sample at a pulling rate of 0.3 m / min in the 180° direction in accordance with JIS K6854:1999. The stress required for peeling at this time was recorded as the peel strength (mN / 50 mm) of the release sheet before the hot press treatment. The results are shown in Table 1. The acrylic resin and melamine resin used as the thermosetting resin are as follows: <Acrylic resin> A composition consisting of acrylic resin (product name: UC-3000, manufactured by Toa Gosei Co., Ltd.) / melamine resin (product name: TF-200, manufactured by Showa Denko Materials Co., Ltd.) / p-toluenesulfonic acid (solid content concentration 50% by mass) in a blending ratio (mass ratio) of 0.7 / 0.3 / 0.1. <Melamine resin> A composition consisting of melamine resin (product name: TF-200, manufactured by Showa Denko Materials Co., Ltd.) / p-toluenesulfonic acid (solid content concentration 50% by mass) in a blending ratio (mass ratio) of 1 / 0.1.

[0077] <Peeling force after heat press treatment> Acrylic resin and melamine resin were used as thermosetting resins for the protective layer, and each was coated onto the release layer of the release sheets obtained in Examples 1 to 6 and Comparative Examples 1 to 6, and dried at 160°C for 30 seconds to form a film of acrylic resin or melamine resin approximately 3 μm thick, forming a sample in which a protective layer was formed on the release layer. The obtained sample was subjected to a hot-press treatment at 170°C, 2 MPa, and 5 minutes using a press (product name: Manual Hydraulic Hot Press 180C, manufactured by Imoto Machinery Co., Ltd.). The sample was then mounted on a universal tensile tester (product name: Autograph AGS-20NX, manufactured by Shimadzu Corporation), and the release sheet was peeled from the sample at a 180° direction at a pulling rate of 0.3 m / min in accordance with JIS K6854:1999. The stress required for peeling was recorded as the release force (mN / 50 mm) of the release sheet after the hot-press treatment. The results are shown in Table 1. The acrylic resin and melamine resin used as the thermosetting resin are the same as those used in the above [Peeling force before hot press treatment].

[0078] [Table 1]

[0079] The notations in Table 1 are as follows: (A) + (B) component - 1: The total solid content (g) of component (A) and component (B), and the solid content mass ratio (A) / (B) = 70 / 30. (A) + (B) component - 2: The total solid content (g) of component (A) and component (B), and the solid content mass ratio (A) / (B) was 70 / 30. ·Si modification amount (mmol / g): The silicone modification amount (mmol / g) in the solid content of component (A). Component (C): Solid content (g). Total solids (g): The total amount of solids (g) in the stripping composition. ·Si modification amount in composition (mmol / g): The silicone modification amount (mmol / g) of component (A) in the total solid content of the release composition. *1: The content (parts by mass) of component (C) per 100 parts by mass of component (B), converted to solid content. *2: The content (parts by mass) of component (D) relative to 100 parts by mass of the resin component.

[0080] From Table 1, it was found that Examples 1 to 6 exhibited the excellent effect of adjusting the peel strength of an acrylic resin protective layer before hot pressing to 80 mN / 50 mm or more and adjusting the peel strength of an acrylic resin protective layer after hot pressing to 400 mN / 50 mm or less. Also, it was found that Examples 1 to 6 exhibited the excellent effect of adjusting the peel strength of a melamine resin protective layer before hot pressing to 150 mN / 50 mm or more and adjusting the peel strength of an acrylic resin protective layer after hot pressing to 450 mN / 50 mm or less. On the other hand, in Comparative Examples 1 to 6, in which the amount of silicone modification in the solid content of the silicone-modified acrylic resin (A) did not satisfy the specified range, it was found that it was difficult to adjust the peel strength both before and after the hot press treatment to the desired range for both the acrylic resin and melamine resin protective layers. [Explanation of symbols]

[0081] 1A Peel-off sheet 10 Base material 11 Peeling layer 12 Filler

Claims

1. A substrate and a release layer formed on the substrate, the release layer is a layer formed from a release agent composition containing a silicone-modified acrylic resin (A), a melamine resin (B), an acid catalyst (C), and a filler (D); The release sheet has a silicone modification amount in the solid content of the silicone-modified acrylic resin (A) of 0.3 to 0.5 mmol / g.

2. 2. The release sheet according to claim 1, wherein the mass ratio (A) / (B) of the silicone-modified acrylic resin (A) to the melamine resin (B) is 50 / 50 to 95 / 5 in terms of solid content.

3. 3. The release sheet according to claim 1, wherein the content of the acid catalyst (C) is 0.1 to 20 parts by mass, calculated as solid content, per 100 parts by mass of the melamine resin (B).

4. 4. The release sheet according to claim 1, wherein, when the resin component is a total solid content of the release agent composition excluding the filler (D), the content of the filler (D) is 15 to 75 parts by mass per 100 parts by mass of the resin component.

5. 5. The release sheet according to claim 1, wherein the amount of silicone modification of the silicone-modified acrylic resin (A) is 0.18 to 0.40 mmol / g based on the total solid content of the silicone-modified acrylic resin (A), the melamine resin (B), the acid catalyst (C), and the filler (D).

6. The release sheet according to claim 1 , wherein the filler (D) comprises boron nitride particles.

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