Release sheet

Abstract

To provide a novel release sheet having a base material in which the adhesiveness of the base material is good when used as a release sheet and the base material can be easily separated after use.SOLUTION: There is provided a release sheet which is a laminate having a base material and an intermediate layer and a release agent layer on at least one surface side of the base material in this order, wherein the intermediate layer is a layer formed from a composition for forming an intermediate layer comprising a silane compound (A) which exhibits polycondensation properties by hydrolysis and a melamine compound (B).SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a release sheet having at least a base material, and an intermediate layer and a release agent layer in this order on at least one surface side of the base material.

Background Art

[0002] Generally, a release sheet has a laminated structure in which a release agent layer for functioning is provided on a base material, and as the base material, a paper base material or various plastic base materials are used. In recent years, from the viewpoints of global resource protection and environmental protection, etc., in various fields, movements aiming at the construction of a recycling-based society have been actively carried out through efforts such as suppression of waste generation, reuse, and recycling. The same applies to the field of release sheets. Generally, since release sheets are discarded after use, reduction of the amount of waste is also an urgent matter from the viewpoints of global resource protection and environmental protection, etc. As one of the countermeasures, for example, efforts are being made to separate a base material having a high resin content rate, etc. from a used release sheet, and recover and reuse the resin, etc. However, a release sheet having a release agent layer cannot easily separate the base material as it is, and since the raw material resin of the base material, etc. cannot be recovered and recycled, a mechanism that can easily separate the base material from a used release sheet is required. Against this background, a release sheet that can easily separate the base material after being used as a release sheet is required. For example, Patent Document 1 discloses a release film in which a release layer is formed on at least one side of a base film via an easily soluble resin layer, and after use, the used release film is immersed in a solvent in which the easily soluble resin can be dissolved, and the easily soluble resin is dissolved in the solvent to separate and remove the release layer on the film surface, and only the base film is recovered.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

[0004] On the other hand, simply improving the ability to separate the substrate from the release sheet is insufficient. This can lead to problems during normal use, such as the substrate separating from the release sheet, thus hindering the release sheet's intended use. In other words, when used for its intended purpose, the substrate must not separate from the release sheet. Therefore, there is a need to develop a release sheet that has good adhesion to the substrate during normal use, while also being able to easily separate the substrate after use.

[0005] The present invention has been made in view of the above circumstances, and aims to provide a novel release sheet having a base material, wherein the base material has good adhesion when used as a release sheet, and the base material can be easily separated after use. [Means for solving the problem]

[0006] The present inventors have found that the above problem can be solved by providing a release sheet, which is a laminate having a base material, an intermediate layer, and a release agent layer in that order on at least one surface side of the base material, wherein the intermediate layer is a layer formed from a specific intermediate layer forming composition, and have completed the present invention. In other words, the present invention provides the following [1] to [9]. [1] A release sheet comprising a substrate, an intermediate layer, and a release agent layer in that order on at least one surface side of the substrate, wherein the intermediate layer is formed from an intermediate layer forming composition containing a silane compound (A) and a melamine compound (B) that exhibit polycondensation by hydrolysis. [2] The release sheet according to [1], wherein component (B) is alkylated melamine resin. [3] The release sheet according to [1] or [2], wherein component (A) mainly comprises at least one selected from a tetrafunctional silane compound represented by the following general formula (a) and its oligomers. Si(OR) p (X) 4-p (a) [In general formula (a), R represents an alkyl group and X represents a halogen atom. If there are multiple R and X atoms, they may be the same or different from one another. p represents an integer from 0 to 4.] [4] The release sheet according to [3], wherein the tetrafunctional silane compound is a tetraalkoxysilane represented by the following general formula (a1). Si(OR)4(a1) [In general formula (a1), R represents an alkyl group. If there are multiple Rs, they may be the same or different from one another.] [5] The release sheet according to any one of [1] to [4] above, wherein the total content of component (A) and component (B) in 100% by mass of the solid content of the intermediate layer forming composition is 80% by mass or more. [6] The release sheet according to any one of [1] to [5] above, wherein the content of component (B) in the intermediate layer forming composition is 60% by mass or less of the total content of component (A) and component (B) in 100% by mass. [7] The release sheet according to any one of [1] to [6] above, wherein the base material is a resin film. [8] The release sheet according to any one of [1] to [7], wherein the substrate and the intermediate layer are directly laminated. [9] The release sheet according to any one of [1] to [8], characterized in that the substrate is separated from the release sheet by bringing the intermediate layer into contact with water. [Effects of the Invention]

[0007] According to the present invention, a novel release sheet having a base material is provided, wherein the base material adheres well when used as a release sheet, and the base material can be easily separated after use. [Modes for carrying out the invention]

[0008] The present invention will be described in detail below using embodiments. In this specification, the lower and upper limits described in steps for a preferred numerical range (e.g., a range for content, etc.) can be combined independently. For example, from the description "preferably 10 to 90, more preferably 30 to 60," the "preferred lower limit (10)" and the "more preferred upper limit (60)" can be combined to arrive at "10 to 60." Similarly, from the description "preferably 10 or more, more preferably 30 or more" and the description "preferably 90 or less, more preferably 60 or less" for the same item, the "preferred lower limit (10)" and the "more preferred upper limit (60)" can be combined to arrive at "10 or more and 60 or less." In this specification, "solid content" refers to the components of the composition in question, excluding diluting solvents such as water and organic solvents. Furthermore, in this specification, for example, "energy rays" refers to energy rays such as known gamma rays, electron beams, ultraviolet rays, and visible light. Furthermore, in this specification, "(meth)acrylic" is used as a term meaning either "acrylic" or "methacrylic" or both. Similarly, "(meth)acrylate" is used as a term meaning either "acrylate" or "methacrylate" or both. Similarly, "(meth)acryloyl" is used as a term meaning either "acryloyl" or "methacryloyl" or both.

[0009] [Release sheet] The release sheet of the present invention is a laminate having a base material, an intermediate layer, and a release agent layer in that order on at least one surface side of the base material, wherein the intermediate layer is a layer formed from an intermediate layer forming composition containing a silane compound (A) that exhibits polycondensation by hydrolysis and a melamine compound (B). From the viewpoint of facilitating the recovery and reuse of resins and other materials constituting the substrate from the separated substrate, it is preferable that the substrate and the intermediate layer are directly laminated together. Here, "direct lamination" refers to a configuration in which, for example, there are no other layers between the substrate and the intermediate layer, and each layer is in direct contact with the others. Furthermore, in one embodiment of the release sheet, the base material, the intermediate layer, and the release agent layer may be directly laminated in this order. That is, there may be no other layers between the base material, the intermediate layer, and the release agent layer, and each layer may be in direct contact with one another. The following describes in more detail each layer that makes up the release sheet.

[0010] <Base material> As the aforementioned substrate, for example, a paper substrate or a resin film can be used, and a resin film is preferred from the viewpoint of easier separation. Furthermore, when a resin film is separated, the recovered component is resin. On the other hand, when a paper substrate is separated, the recovered component is pulp fibers. As the resin film, polyester films such as polyethylene terephthalate film, polybutylene terephthalate, and polyethylene naphthalate; polyolefin films such as polyethylene film and polypropylene film; polyimide film; polyamide film; polycarbonate film; polyacetate film; ethylene-vinyl acetate copolymer (EVA) film; ethylene-(meth)acrylic acid copolymer film; ethylene-(meth)acrylic acid ester copolymer film; cycloolefin polymer film; polyurethane film; polyphenylene sulfide film; cellophane; etc. can be used. Among these, polyester film is preferred from the viewpoint of heat resistance and strength. As the polyester film, polyester film mainly composed of polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate is preferred from the viewpoint of ease of resin recovery and recycling. Here, "main component" refers to the component with the highest content among the components constituting the film. As the polyester film, polyethylene terephthalate film, polybutylene terephthalate film, and polyethylene naphthalate film are more preferred, and polyethylene terephthalate film is even more preferred.

[0011] Furthermore, the substrate may be a resin film having only one of the aforementioned resins, or it may have two or more. For example, it may be a single-layer film made of one resin film, or a multi-layer film made by laminating multiple resin films. From the viewpoint of facilitating resin recovery, a single-layer film made of one resin film or a multi-layer film made by laminating one resin film is preferred. Furthermore, the resin film may contain known fillers, colorants, antistatic agents, antioxidants, organic lubricants, catalysts, etc. Also, the resin film may be transparent or colored as desired. In addition, at least one surface of the substrate may be subjected to surface treatment such as sputtering, corona discharge, flame, ultraviolet irradiation, electron beam irradiation, oxidation, or other etching treatments as needed.

[0012] The thickness of the base material is not particularly limited, but from the viewpoints of strength, rigidity, etc., it is preferably 10 to 500 μm, more preferably 15 to 300 μm, and still more preferably 20 to 200 μm. Here, the "thickness of the base material" means the thickness of the entire base material. For example, when using the above-described multi-layer film laminated with two or more layers, the thickness of the base material means the total thickness of all the layers constituting the base material.

[0013] <Intermediate layer> The intermediate layer is a layer formed from a composition for forming an intermediate layer containing a silane compound (A) (hereinafter also referred to as "component (A)") showing polycondensability by hydrolysis and a melamine compound (B) (hereinafter also referred to as "component (B)"). Since the release sheet has the intermediate layer, the above-described excellent effects are exhibited, and the reason is considered as follows. That is, before separating the base material from the release sheet, the intermediate layer is mainly adhered to the base material or other layers on the base material side by hydrogen bonds and an anchor effect. In particular, since the intermediate layer has a siloxane bond (-Si-O-Si-), Si-OH groups are partially formed on the surface of the intermediate layer on the base material side and are hydrogen-bonded to the polar sites present on the surface of the base material. When the release sheet is immersed in water, water easily penetrates into the interface between the base material and the intermediate layer or the interface between the intermediate layer and other layers present on the base material side. Then, the water that has penetrated into the interface inhibits the hydrogen bond, resulting in peeling at the interface, and it is considered that the base material can be easily separated from the release sheet. In addition, since the intermediate layer is formed from a composition for forming an intermediate layer containing a melamine compound (B), it also has a polarity derived from component (B). Therefore, unlike the intermediate layer formed only from component (A), during normal use as a release sheet, intermolecular forces between polar groups act between the base material and the intermediate layer instead of hydrogen bonds, and it is considered that it is possible to prevent the adhesion between the base material and the intermediate layer from being insufficient due to humidity. Therefore, it is possible to obtain a release sheet having good adhesion to the base material during use and capable of easily separating the base material after use. Furthermore, when the intermediate layer comes into contact with the aforementioned water (hereinafter also referred to as "washing water") used to separate the substrate from the release sheet, the elution of the intermediate layer into the washing water can be prevented or suppressed. Therefore, contamination of the washing water can be prevented or reduced.

[0014] (Silane compound (A) exhibiting polycondensation properties due to hydrolysis) The silane compound (A) exhibiting polycondensation properties by hydrolysis is a compound whose hydrolyzed form can undergo polycondensation. For example, component (A) may be an alkoxysilane exhibiting polycondensation properties by hydrolysis.

[0015] Component (A) preferably contains at least one selected from the tetrafunctional silane compounds represented by the following general formula (a) and their oligomers as the main component. Si(OR) p (X) 4-p (a) [In general formula (a), R represents an alkyl group and X represents a halogen atom. If there are multiple R and X atoms, they may be the same or different from one another. p represents an integer from 0 to 4.]

[0016] Examples of alkyl groups that can be selected as R include methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, isobutyl, tert-butyl, n-pentyl, n-hexyl, neopentyl, and methylpentyl groups. Among these, methyl, ethyl, n-propyl, or n-butyl groups are preferred from the viewpoint of further improving the reactivity of silane compounds, and methyl or ethyl groups are more preferred. The alkyl group that can be selected as R may be linear or branched, but linear is preferred. The halogen atoms that can be selected as X are preferably chlorine atoms, bromine atoms, or iodine atoms, with chlorine atoms being more preferred. Furthermore, the silane compound represented by the general formula (a) may be used alone or in combination of two or more types.

[0017] Furthermore, it is preferable that the silane compound represented by the general formula (a) includes a silane compound in which p in the general formula (a) is 4. In other words, the tetrafunctional silane compound is preferably a tetraalkoxysilane represented by the following general formula (a1). Si(OR)4(a1) [In general formula (a1), R represents an alkyl group. If there are multiple Rs, they may be the same or different from one another.]

[0018] Examples of alkyl groups that can be selected for R in general formula (a) are the same as those for R in general formula (a) described above, and the preferred embodiments are also the same. More preferred specific examples of the tetraalkoxysilane include tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane, and tetrabutoxysilane. Among these, at least one of tetramethoxysilane and tetraethoxysilane, or a mixture of tetramethoxysilane and tetraethoxysilane, is preferred from the viewpoint of ease of availability and reactivity in hydrolysis reactions.

[0019] Here, the "main component" in component (A) refers to the silane compound that is present in the largest amount in 100% by mass of the total amount of component (A). The content of the silane compound represented by the general formula (a) and its oligomer included as the main component in component (A) is not particularly limited as long as it is greater than the content of other silane compounds. For example, it is preferably 50% by mass or more, more preferably 70% by mass or more, even more preferably 80% by mass or more, and even more preferably 90% by mass or more, and 100% by mass or less, out of 100% by mass of the total amount of component (A).

[0020] Furthermore, the average degree of polymerization of the oligomer of the tetrafunctional silane compound represented by the general formula (a), or the oligomer of the tetraalkoxysilane represented by the general formula (a1), is not particularly limited, but may be independently, for example, 2 to 20 or 2 to 15. That is, the average of each silane compound may be 2 to 20-mers, or the average of each silane compound may be 2 to 15-mers. Furthermore, the "oligomers of tetrafunctional silane compounds represented by general formula (a)" and the "oligomers of tetraalkoxysilanes represented by general formula (a1)" are not limited to those obtained simply from monomers of each of the silane compounds mentioned above as starting materials, but also include compounds whose structure, as a result of synthesis using other compounds as starting materials, is that of a tetrafunctional silane compound represented by general formula (a) or a compound having a structure in which two or more tetraalkoxysilanes represented by general formula (a1) are condensed. The same applies to the "oligomers of 1-3 functional silane compounds" described later.

[0021] As component (A), commercially available products can also be used. Preferred examples of such commercially available products include "Colcoat® N-103X", "Colcoat® PX", "Methyl Silicate 51", which is an average tetramer oligomer of tetramethoxysilane, "Methyl Silicate 53A", which is an average heptomer oligomer of tetramethoxysilane, "Ethyl Silicate 40", which is an average pentamer oligomer of tetraethoxysilane, "Ethyl Silicate 48", which is an average decamer oligomer of tetraethoxysilane, and "EMS-485", which is a mixture of an average decamer oligomer of tetramethoxysilane and an average decamer oligomer of tetraethoxysilane (all manufactured by Colcoat Co., Ltd.).

[0022] Other silane compounds that may be included as component (A) include, for example, 1-3 functional silane compounds as monomers, and oligomers of 1-3 functional silane compounds as oligomers. However, from the viewpoint of further improving the separation of the substrate, as mentioned above, it is preferable to include at least one selected from the tetrafunctional silane compound represented by general formula (a) and its oligomers as the main component. Furthermore, the intermediate layer-forming composition may also use catalysts such as acid catalysts or metal catalysts, from the viewpoint of promoting the hydrolysis or condensation reaction of component (A).

[0023] From the viewpoint of making the effects of the present invention easier to achieve, the content of component (A) in the intermediate layer forming composition is preferably 40% by mass or more, more preferably 45% by mass or more, even more preferably 50% by mass or more, and preferably 95% by mass or less, more preferably 92% by mass or less, and even more preferably 90% by mass or less, out of 100% by mass of the total content of component (A) and component (B).

[0024] (Melamine compound (B)) Examples of the melamine compound (B) include methylolated melamine resin, imino melamine resin, iminomethylolated melamine resin, and alkylated melamine resin. These may be used individually or in combination of two or more. Among these, alkylated melamine resin is preferred from the viewpoint of reactivity.

[0025] Alkylated melamine resin is obtained by alkylating some or all of the methylol groups in methylolated melamine resin with an alkyl monoalcohol. There are no particular restrictions on the type of alkyl monoalcohol or the etherification rate, and they can be appropriately selected considering compatibility with component (A), solubility in solvents, curability of the resulting release agent composition, adhesion to the substrate, etc. However, component (B) preferably has two or more functional groups per molecule, and more preferably has three or more functional groups per molecule. That is, even as an alkylated melamine resin, an alkylated melamine resin having two or more functional groups per molecule is preferred, and an alkylated melamine resin having three or more functional groups per molecule is more preferred.

[0026] Specific examples of the alkylated melamine resin include methylated melamine resin, ethylated melamine resin, propylated melamine resin, butylated melamine resin such as n-butylated melamine resin and isobutylated melamine resin, hexylated melamine resin, octylated melamine resin such as n-octylated melamine resin, and the like. These may be used individually or in combination of two or more. Among these, alkylated melamine resin having an alkyl group with 3 or fewer carbon atoms is preferred from the viewpoint of compatibility with component (A), and methylated melamine resin is more preferred from the viewpoint of reactivity.

[0027] From the viewpoint of making the effects of the present invention easier to achieve, the content of component (B) in the intermediate layer forming composition is preferably 60% by mass or less, more preferably 55% by mass or less, even more preferably 50% by mass or less, and preferably 5% by mass or more, more preferably 8% by mass or more, and even more preferably 10% by mass or more, out of 100% by mass of the total content of component (A) and component (B).

[0028] Furthermore, from the viewpoint of making the effects of the present invention easier to achieve, the total content of component (A) and component (B) in 100% by mass of the solid content of the intermediate layer forming composition is preferably 80% by mass or more, more preferably 85% by mass or more, even more preferably 90% by mass or more, and 100% by mass or less, preferably 99.9% by mass or less, more preferably 99.5% by mass or less, and even more preferably 99% by mass or less.

[0029] (Acid catalyst (C)) Furthermore, the intermediate layer forming composition preferably further contains an acid catalyst (C). By using an acid catalyst (C) (hereinafter also referred to as "component (C)"), the hardening of the melamine compound (B) can be accelerated. Examples of component (C) include inorganic acids such as hydrochloric acid, sulfuric acid, phosphoric acid, and boric acid; carboxylic acids (organic acids) such as acetic acid, monochloroacetic acid, dichloroacetic acid, and butyric acid; organic sulfonic acids (organic acids) such as benzenesulfonic acid, p-toluenesulfonic acid, xylenesulfonic acid, p-phenolsulfonic acid, methanesulfonic acid, and ethanesulfonic acid; and alkyl phosphate esters (organic acids). These may be used individually or in combination of two or more.

[0030] When the intermediate layer forming composition contains component (C), there are no particular restrictions on the content of component (C), but it is preferably 1 part by mass or more, more preferably 3 parts by mass or more, even more preferably 5 parts by mass or more, and preferably 45 parts by mass or less, more preferably 40 parts by mass or less, and even more preferably 35 parts by mass or less, per 100 parts by mass of component (B).

[0031] Furthermore, when the intermediate layer forming composition contains component (C), from the viewpoint of making the effects of the present invention easier to achieve, the total content of component (A), component (B), and component (C) in 100% by mass of the solid content of the intermediate layer forming composition is preferably 80 to 100% by mass, more preferably 85 to 100% by mass, even more preferably 90 to 100% by mass, even more preferably 95 to 100% by mass, and even more preferably 98 to 100% by mass.

[0032] From the viewpoint of making the effects of the present invention easier to achieve, the thickness of the intermediate layer is preferably 0.02 to 1 μm, more preferably 0.03 to 0.5 μm, and even more preferably 0.04 to 0.3 μm.

[0033] <Release agent layer> The aforementioned release agent layer is preferably a layer formed from a release agent composition. The release agent composition used to form the release agent layer is not particularly limited as long as it has release properties. For example, release agent compositions mainly composed of silicone compounds, fluorine compounds, long-chain alkyl group-containing compounds, thermoplastic resin materials such as olefin resins and diene resins can be used. It is also preferable to use a release agent composition mainly composed of an energy ray curable or thermosetting resin. These release agent compositions may be used individually or in combination of two or more. Here, the term "main component" in the aforementioned release agent composition refers to the component that is present in the largest quantity in 100% by mass of the solid content of the release agent composition.

[0034] In a release agent composition mainly composed of a silicone compound, the silicone compound may include a silicone compound having an organopolysiloxane as its basic structure. Other examples of the silicone compound include thermosetting silicone compounds such as addition reaction type and condensation reaction type; and energy ray curing silicone compounds such as ultraviolet curing type and electron beam curing type.

[0035] Specific examples of the addition-reaction type silicone compounds mentioned above include organopolysiloxanes having two or more alkenyl groups with 2 to 10 carbon atoms, such as vinyl groups, allyl groups, propenyl groups, and hexenyl groups, at the ends and / or side chains of the molecule. When using such addition-reaction type silicone compounds, it is preferable to use a crosslinking agent and a catalyst in combination.

[0036] Examples of the aforementioned crosslinking agents include organopolysiloxanes having hydrogen atoms bonded to at least two silicon atoms in one molecule, specifically dimethylhydrogensiloxy group-ended dimethylsiloxane-methylhydrogensiloxane copolymers, trimethylsiloxy group-ended dimethylsiloxane-methylhydrogensiloxane copolymers, trimethylsiloxy group-ended methylhydrogenpolysiloxanes, and poly(hydrogensilsesquioxane).

[0037] Furthermore, examples of catalysts mentioned above include particulate platinum, particulate platinum adsorbed on a carbon powder support, chloroplatinic acid, alcohol-modified chloroplatinic acid, olefin complexes of chloroplatinic acid, palladium, and platinum metal compounds such as rhodium. By using such catalysts, the curing reaction of the release agent composition can be made to proceed more efficiently.

[0038] In a release agent composition mainly composed of a fluorine compound, examples of the fluorine compound include fluorosilicone compounds, fluoroboron compounds, and poly(perfluoroalkylene ether) chain-containing compounds.

[0039] In a release agent composition mainly composed of a long-chain alkyl group-containing compound, examples of the long-chain alkyl group-containing compound include polyvinyl carbamate obtained by reacting a polyvinyl alcohol polymer with a long-chain alkyl isocyanate having 12 to 40 carbon atoms in the alkyl group, alkylurea derivatives obtained by reacting polyethyleneimine with a long-chain alkyl isocyanate having 12 to 40 carbon atoms in the alkyl group, or copolymers of long-chain alkyl (meth)acrylates having 12 to 40 carbon atoms in the alkyl group. Furthermore, a long-chain alkyl-modified alkyd resin may be used, in which a long-chain fatty acid having 12 to 40 carbon atoms in the alkyl group is used as a modifier in an alkyd resin obtained by a condensation reaction between a polyhydric alcohol and a polybasic acid.

[0040] A preferred release agent composition mainly composed of an energy ray-curable resin contains, for example, an energy ray-curable compound (D) having a reactive functional group selected from a (meth)acryloyl group, an alkenyl group, and a maleimide group, and a polyorganosiloxane (E). In the release agent layer formed by this release agent composition, since the energy ray-curable compound (D) and the polyorganosiloxane (E), which have different molecular structures, polarities, and molecular weights, are used, the polyorganosiloxane (E) is pushed up to the vicinity of the outer surface of the release agent layer after application and before curing, resulting in a segregated state of components derived from the polyorganosiloxane (E). This improves the release properties of the release agent layer.

[0041] (Energy-ray curable compound (D)) The energy ray-curable compound (D) is a component that imparts curability to the release agent layer. The energy-ray curable compound (D) (hereinafter also referred to as "component (D)") is preferably one having a reactive functional group selected from a (meth)acryloyl group, an alkenyl group, and a maleimide group. Examples of alkenyl groups include vinyl groups, allyl groups, propenyl groups, and hexenyl groups, which have 2 to 10 carbon atoms. Component (D) may be used alone or in combination of two or more types.

[0042] Furthermore, from the viewpoint of curability, component (D) is preferably one that has three or more of the above-mentioned reactive functional groups in its molecule. By using an energy ray curable compound having three or more reactive functional groups in its molecule as component (D), excellent curability, solvent resistance, and peelability can be obtained even for release agent layers of a thickness that is difficult to cure due to oxygen inhibition.

[0043] Examples of component (D) include polyfunctional (meth)acrylates such as dipentaerythritol tri(meth)acrylate, dipentaerythritol tetra(meth)acrylate, dipentaerythritol penta(meth)acrylate, dipentaerythritol hexa(meth)acrylate, pentaerythritol tri(meth)acrylate, and pentaerythritol tetra(meth)acrylate. Among these, it is preferable to use at least one selected from the group consisting of dipentaerythritol tri(meth)acrylate, dipentaerythritol tetra(meth)acrylate, dipentaerythritol penta(meth)acrylate, dipentaerythritol hexa(meth)acrylate, pentaerythritol tri(meth)acrylate, and pentaerythritol tetra(meth)acrylate as component (D). This ensures good curability of component (D) even when the release agent composition is applied as a thin film to the intermediate layer surface of the substrate.

[0044] If the release agent composition contains component (D), the content of component (D) is preferably 65% ​​by mass or more and 98.5% by mass or less, and more preferably 70% by mass or more and 95% by mass or less, based on 100% by mass of the solid content of the release agent composition.

[0045] (Polyorganosiloxane (E)) Polyorganosiloxane (E) is a component that imparts peelability to the release agent layer. Examples of polyorganosiloxane (E) (hereinafter also referred to as "component (E)") include those having linear or branched molecular chains. Furthermore, it is preferable to use a modified polyorganosiloxane in which a reactive functional group selected from (meth)acryloyl groups, alkenyl groups, and maleimide groups is bonded to the silicon atoms of the molecular chain, either directly or via a divalent linking group, at least one of the terminal and side chains of the molecular chain as component (E). Examples of alkenyl groups include vinyl groups, allyl groups, and propenyl groups. Examples of divalent linking groups include alkylene groups, alkylene oxy groups, oxy groups, imino groups, carbonyl groups, and divalent linking groups combining these. The number of carbon atoms in the divalent linking group is preferably 1 to 30, and more preferably 1 to 10. Component (E) may be used alone or in combination of two or more types.

[0046] With the modified organopolysiloxane, when the energy-curable compound (D) hardens due to energy ray irradiation, the modified organopolysiloxane is incorporated into and fixed in the cross-linked structure of the hardened product of the energy-curable compound (D). This makes it possible to suppress the migration of the polyorganosiloxane contained in the release agent layer to the surface that comes into contact with the outer surface of the release agent layer (for example, the adhesive layer, the ceramic green sheet, or the back surface of the release sheet itself).

[0047] Organic groups other than the reactive functional group of component (E) include monovalent hydrocarbon groups that do not have aliphatic unsaturated bonds. Multiple identical or different organic groups may be present. Hydrocarbon groups with 1 to 12 carbon atoms are preferred, and those with 1 to 10 carbon atoms are more preferred. Examples of hydrocarbon groups include alkyl groups such as methyl, ethyl, and propyl groups, and aryl groups such as phenyl and tolyl groups.

[0048] As for component (E), from the viewpoint of improving the peelability of the release agent layer, it is preferable that 80 mol% or more of the organic groups other than the reactive functional groups in the molecule of component (E) are methyl groups.

[0049] If the release agent composition contains component (E), the content of component (E) is preferably 0.5% to 5% by mass, and more preferably 0.7% to 4% by mass, based on 100% by mass of the solid content of the release agent composition. This makes it easier to apply the ceramic slurry to the substrate without repelling it, for example, when used in the manufacture of green sheets, and improves the release properties of the release sheet.

[0050] Furthermore, the preferred ratio of the energy ray-curable compound (D) to the polyorganosiloxane (E) is 0.7 / 99.3 to 5 / 95, and more preferably 1 / 99 to 4.5 / 95. This makes it easier to apply the ceramic slurry onto the release agent layer without repelling it, for example, when used in the manufacture of green sheets, and improves the release properties of the green sheet from the release sheet.

[0051] (Photopolymerization initiator) Furthermore, the release agent composition may also contain a photopolymerization initiator. A photopolymerization initiator is a component that improves the curability of a release agent composition when curing the release agent composition using energy rays such as ultraviolet light. As photopolymerization initiators that may be included in the release agent composition, from the viewpoint of excellent curability, solvent resistance and release properties, for example, 2-methyl-1[4-(methylthio)phenyl]-2-morpholinopropan-1-one, 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-butanone-1, and 2-(dimethylamino)-2-[(4-methylphenyl)methyl]-1-[4-(4-morpholinyl)phenyl]-1-butanone are preferred. These photopolymerization initiators may be used individually or in combination of two or more.

[0052] When the release agent composition contains a photopolymerization initiator, the content of the photopolymerization initiator is preferably 1% to 20% by mass, and more preferably 3% to 15% by mass, based on 100% by mass of the solid content of the release agent composition. This makes it possible to obtain excellent curability, solvent resistance, and release properties even when the thickness of the release agent layer is in a range where curability is difficult to obtain due to oxygen inhibition. Furthermore, as a release agent composition mainly composed of energy-ray curable resin, other components such as sensitizers and reactive monomers can also be used, within the range that achieves the effects of the present invention.

[0053] Furthermore, if the release agent composition mainly comprising the energy ray curable resin is a release agent composition containing component (D) and component (E), the total content of component (D) and component (E), as well as the photopolymerization initiator which may be included as needed, is preferably 70 to 100% by mass, more preferably 80 to 100% by mass.

[0054] Furthermore, energy-ray curable resins have a structure in which the chemical bonds forming the main chain are resistant to decomposition by acids and alkalis, making them less susceptible to chemical treatment for removing foreign substances. For this reason, in release sheets having a release agent layer mainly composed of energy-ray curable resin, the configuration of the present invention allows for easy removal of the release agent layer.

[0055] Examples of release agent compositions mainly composed of thermosetting resins include release agent compositions mainly composed of melamine resin and release agent compositions mainly composed of epoxy resin. Examples of release agent compositions mainly composed of melamine resin include compositions containing melamine resin as the main component, an acid catalyst for thermosetting the melamine resin, and a polyorganosiloxane for imparting release properties to the release agent layer. Examples of release agent compositions mainly composed of epoxy resin include compositions containing epoxy resin as the main component, an acid or basic thermosetting catalyst for thermosetting the epoxy resin, and a polyorganosiloxane for imparting release properties to the release agent layer.

[0056] When the release agent composition contains a thermosetting resin as its main component, the content of the thermosetting resin is preferably 65% ​​by mass or more and 98.5% by mass or less, and more preferably 70% by mass or more and 95% by mass or less, based on 100% by mass of the solid content of the release agent composition. Furthermore, when the release agent composition mainly contains a thermosetting resin, the content of polyorganosiloxane that imparts release properties to the release agent layer is preferably 1% by mass or more and 8% by mass or less, and more preferably 2% by mass or more and 6% by mass or less, based on 100% by mass of the solid content of the release agent composition. Furthermore, when the release agent composition mainly contains a thermosetting resin, the content of each catalyst is preferably 1% by mass or more and 10% by mass or less, and more preferably 2% by mass or more and 6% by mass or less, based on 100% by mass of the solid content of the release agent composition.

[0057] Furthermore, when the release agent composition mainly contains a thermosetting resin, the total content of the thermosetting resin, the polyorganosiloxane that imparts release properties to the release agent layer, and the catalyst is preferably 70 to 100% by mass, more preferably 80 to 100% by mass.

[0058] Furthermore, the release agent layer may contain other additives in addition to the resin components mentioned above. Examples of other additives include anti-aging agents, light stabilizers, flame retardants, conductive agents, antistatic agents, and plasticizers.

[0059] The thickness of the release agent layer can be selected as appropriate and is not particularly limited, but for example, it is preferably 0.02 to 5 μm, more preferably 0.03 to 2 μm, and even more preferably 0.05 to 1.5 μm.

[0060] Release sheets are generally used to protect the surfaces of other functional sheets and various components used for specific applications during manufacturing, transportation, and storage. After fulfilling their protective role, they are often peeled off the surface and discarded. Therefore, using release sheets allows for easy separation of the substrate from the release sheet, making it a highly beneficial application from the perspective of resource conservation and environmental protection.

[0061] <Method for manufacturing release sheets> The method for manufacturing the release sheet is not particularly limited, as long as it can produce the release sheet, and can be manufactured by known methods. For example, the intermediate layer can be formed by a method for forming an intermediate layer, which includes the steps of: applying the intermediate layer forming composition or a solution thereof to one surface of a substrate; then heating and drying the intermediate layer forming composition or a solution thereof, and thermally curing components (A) and (B) in the intermediate layer forming composition to form an intermediate layer; in this order.

[0062] Furthermore, the method for forming the release agent layer can be appropriately selected depending on the type of release agent layer, and there are no particular restrictions as long as the release sheet can be manufactured; it can be manufactured by known methods. For example, the release agent layer can be formed and manufactured by a forming method that includes, in this order: applying the release agent composition or a solution thereof onto an intermediate layer formed on a substrate by the method described above, then heating and drying the release agent composition or solution thereof to form a coating layer; and then curing the coating layer by energy ray irradiation to form a release agent layer.

[0063] As described above, the release sheet can separate the substrate from the release sheet by bringing the intermediate layer into contact with water. Therefore, one aspect of the present invention is a method for separating a substrate, characterized in that the substrate is separated from the release sheet by bringing the intermediate layer into contact with water, in a release sheet having the substrate, the intermediate layer and the release agent layer in that order on at least one surface side of the substrate.

[0064] There are no particular limitations on the method of bringing the intermediate layer into contact with water, but it is preferable to do so by immersing the release sheet in water. For example, if the release sheet is in the form of a roll, it may be immersed in the water tank while still in its roll form. In this case, the roll of release sheet may be left undisturbed in the water tank, or the water tank may be agitated. Alternatively, during the process of continuously processing the release sheet from the dispensing roll to the winding roll (roll-to-roll processing), the release sheet dispensed from the dispensing roll may be passed through a water tank, or water may be rubbed onto the sheet with a brush or the like. Alternatively, after cutting the release sheet, the cut release sheet may be immersed in a tank of water. In this case, the cut release sheet may be left undisturbed in the tank, or the tank may be agitated. Alternatively, the cut release sheet may be treated by rubbing water onto it with a brush or the like.

[0065] The water brought into contact with the intermediate layer may be at room temperature, but heated water is preferred. For example, 40°C or higher is preferred, and 60°C or higher is more preferred. Also, less than 100°C is preferred, and 98°C or lower is more preferred.

[0066] As described above, by using the release sheet, the substrate can be easily separated from the release sheet by bringing the intermediate layer into contact with water. Therefore, the release sheet is preferable from the viewpoint of reducing environmental impact, as it eliminates the need to use acidic or alkaline solutions or organic solvents to separate the substrate from the release sheet. On the other hand, the release sheet exhibits good adhesion to the substrate during normal use. Therefore, the release sheet can avoid problems caused by the separation of the base material when used for its intended purpose as a release sheet, and after use as a release sheet, the base material can be easily separated, making it suitable for reuse of the resin recovered from the separated base material, or for recycling by decomposing it into monomers and other raw materials that make up the resin.

[0067] Furthermore, when separating the substrate using the release sheet, the washing water can be easily separated from the separated substrate simply by filtering the washing water, which also leads to a simplification of the entire process of resin recovery and recycling. Furthermore, as mentioned above, the intermediate layer in the release sheet that contributes to the separation of the substrate can also reduce contamination of the washing water used when separating the substrate. Therefore, since contamination of the washing water is suppressed, it is less likely that the resin recovered from the separated substrate will be re-contaminated by the washing water. In addition, suppressing contamination of the washing water leads to the reuse of washing water and simplification of disposal. Accordingly, one aspect of the present invention is, for example, a resin recycling method that includes the steps of: separating the substrate from the release sheet by using a substrate separation method using the release sheet, by bringing the intermediate layer and the release agent layer in that order into contact with water, thereby peeling the intermediate layer from the surface of the substrate or the surface of the layer on the substrate side; and recovering the resin from the substrate. The step of recovering the resin from the substrate is not particularly limited, and a known recovery method can be used as appropriate depending on the type of resin and the raw material of the resin. [Examples]

[0068] The present invention will be specifically described by the following examples, but the present invention is not limited to these examples. The physical properties in the following examples were measured by the following methods.

[0069] [Thickness of base material, intermediate layer, and release agent layer] The thickness of the substrate in the release sheets used in each example and comparative example was measured using a constant-pressure thickness gauge manufactured by Teclock Co., Ltd. (model number: "PG-02J", compliant with standards: JIS K6783:1994, JIS Z1702:1994, JIS Z1709:1995). The thickness of the intermediate layer in each example and comparative example was measured using a spectroscopic ellipsometer (JAWoollam, product name "M-2000"). The thickness of the release agent layer in each example and comparative example was measured using a reflective film thickness gauge (Filmetrics Co., Ltd., product name "F20").

[0070] [Manufacturing of release sheets] The release sheet was manufactured by the method described below.

[0071] [Example 1] A biaxially oriented polyethylene terephthalate film [thickness: 31 μm] was prepared as the base material. Next, a silane compound "A1" (manufactured by Colcoat Co., Ltd., product name "Colcoat® N-103X") which exhibits polycondensation by hydrolysis, and a methylated melamine resin "B1" (manufactured by Nippon Carbide Industries Co., Ltd., product name "MW-30") which is a melamine compound, were mixed in a solid content ratio (mass ratio) of 90:10. Then, p-toluenesulfonic acid monohydrate (manufactured by Tokyo Chemical Industry Co., Ltd.), diluted to approximately 10% by mass with isopropyl alcohol, was added as an acid catalyst at a ratio of 30 parts by mass (solid content ratio) per 100 parts by mass of the melamine compound. Furthermore, the mixture was adjusted with isopropyl alcohol to a solid content of 1.0% by mass to prepare a coating solution for the intermediate layer forming composition. Next, the coating solution of the obtained intermediate layer-forming composition was uniformly applied to one side of the substrate using a bar coater and dried at 130°C for 1 minute to obtain an intermediate layer (thickness: 0.04 μm). Next, 94 parts by mass of a mixture of the polyfunctional acrylates dipentaerythritol pentaacrylate and dipentaerythritol hexaacrylate (manufactured by Toagosei Co., Ltd., product name "Aronics® M-400", solids content 100% by mass), 1 part by mass of acrylic-modified polydimethylsiloxane (manufactured by Shin-Etsu Chemical Co., Ltd., product name "X-22-164A", solids content 100% by mass), and 5 parts by mass of a photopolymerization initiator (manufactured by IGM Resins BV, trade name "Omnirad® 907" (2-methyl-1[4-(methylthio)phenyl]-2-molifolinopropan-1-one, solids content 100% by mass)) were diluted with a mixed solvent of isopropyl alcohol and methyl ethyl ketone (mixing ratio (by mass) isopropyl alcohol:methyl ethyl ketone = 3:1) to obtain a coating solution of a release agent composition with a solids content of 20% by mass. The coating solution of the obtained release agent composition was applied to the intermediate layer formed on the substrate using a bar coater, and dried at 80°C for 1 minute to obtain a coating layer. Next, the coating layer was irradiated with ultraviolet light (cumulative light intensity: 250 mJ / cm²). 2 A release agent layer (thickness: 1 μm) was formed by ) and a release sheet was obtained in which the substrate / intermediate layer / release agent layer was laminated in this order.

[0072] [Example 2] A release sheet was prepared in the same manner as in Example 1, except that a silane compound "A1" (manufactured by Colcoat Co., Ltd., product name "Colcoat® N-103X") which exhibits polycondensation properties by hydrolysis of the intermediate layer forming composition, and a methylated melamine resin "B1" (manufactured by Nippon Carbide Industries, Ltd., product name "MW-30") were mixed in a solid content ratio (mass ratio) of 80:20.

[0073] [Example 3] In Example 1, a release sheet was prepared in the same manner as in Example 1, except that a silane compound "A1" (manufactured by Colcoat Co., Ltd., product name "Colcoat® N-103X") which exhibits polycondensation properties by hydrolysis of the intermediate layer forming composition, and a methylated melamine resin "B1" (manufactured by Nippon Carbide Industries, Ltd., product name "MW-30") were mixed in a solid content ratio (mass ratio) of 50:50, and the amount of acid catalyst added was changed to 10 parts by mass (solid content ratio) per 100 parts by mass of melamine compound.

[0074] [Comparative Example 1] In Example 1, a release sheet was prepared in the same manner as in Example 1, except that an intermediate layer was not provided, with the substrate / release agent layer laminated in that order.

[0075] [Comparative Example 2] In Example 1, a release sheet was prepared in the same manner as in Example 1, except that the methylated melamine resin "B1" and the acid catalyst, which are components (B) of the intermediate layer forming composition, were not mixed.

[0076] [Comparative Example 3] A biaxially oriented polyethylene terephthalate film [thickness: 31 μm] was prepared as the base material. Next, amorphous polyester resin "P" (manufactured by Toyobo Co., Ltd., product name "Byron® GK-640") was diluted with methyl ethyl ketone (MEK) to prepare a diluted solution with a solid content of 1% by mass. Next, the resulting diluted solution was uniformly applied to one side of the substrate so that its thickness after drying was 0.04 μm, and an intermediate layer was formed by heating at 130°C for 1 minute. The release agent layer was formed in the same manner as in Example 1, and a release sheet was prepared in which the substrate / intermediate layer / release agent layer was laminated in this order.

[0077] [Separability of the substrate] The release sheets obtained by the methods described in the Examples and Comparative Examples were cut into 50 mm x 50 mm pieces to obtain test specimens. Next, 300 mL of 90°C hot water was filled into a 500 mL glass beaker, and one test specimen was placed in the hot water so that it was completely submerged, and left to stand for 2 hours while maintaining a temperature of 90°C. After that, the test specimens were removed from the hot water, washed by immersion in distilled water at room temperature, and prepared as samples for separation performance evaluation. For the sample in question, the thickness of the thin film layer was measured on the substrate surface on the side where the release agent layer was provided, using a spectroscopic ellipsometer (JAWoollam, product name "M-2000") and a reflective film thickness gauge (Firmetrics, Inc., product name "F20"). Subsequently, the separation of the substrate was evaluated based on the amount of silicon (Si), a specific element derived from the chemical composition of the release agent layer and intermediate layer, measured on the same surface by X-ray photoelectron spectroscopy (XPS). If the thickness of the measured thin film layer was below the measurement accuracy (10 nm or less), and the ratio of each element calculated using the following formula showed that the specific element derived from the chemical composition of the release agent layer and intermediate layer was less than 0.05 Atom%, then it was determined that there was no thin film layer on the substrate surface. In this case, it was determined that the release agent layer and intermediate layer corresponding to the thin film layer were not on the substrate surface, i.e., the substrate could be separated from the release sheet. The results are shown in Table 1 below. In Table 1, values ​​less than 0.05 Atom% are denoted as "A," and values ​​of 0.05 Atom% or greater are denoted as "F." In the following formulas, N represents the amount of nitrogen, Si represents the amount of silicon, C represents the amount of carbon, and O represents the amount of oxygen. • Silicon (Si) element ratio (Atom%) = [Si / (C+O+N+Si)] × 100

[0078] [Adhesion of the substrate] The release sheets obtained by the methods described in the Examples and Comparative Examples were attached to the release agent layer side of a 20 mm wide acrylic adhesive tape (manufactured by Nitto Denko Corporation, product name "31B Tape") using a hand roller under conditions of a temperature of 23°C and a relative humidity of 50% RH, and left for 30 minutes to obtain test specimens. Next, the release sheet side of the test specimen was fixed to a SUS plate using a tensile testing machine, and the 31B tape side was peeled off at a 180° peel angle and peel speed of 300 mm / min using a tensile testing machine (Shimadzu Corporation, product name "AG-IS500N"). After this process, the thickness of the thin film layer was measured on the surface of the release sheet to which the 31B tape had been attached, using a spectroscopic ellipsometer (JAWoollam, product name "M-2000") and a reflective film thickness gauge (Firmetrics, Inc., product name "F20"). Subsequently, X-ray photoelectron spectroscopy (XPS) was performed on the surface in the same manner as the separation performance evaluation of the substrate. The adhesion of the substrate was evaluated based on the amount of silicon (Si), a specific element derived from the chemical composition measured by XPS. When the release agent layer and intermediate layer of the release sheet are removed by the peeling process of the 31B tape, and the substrate surface is exposed, the thickness of the thin film layer to be measured will be below the measurement accuracy (10 nm or less), and the silicon (Si) element ratio (Atom%) on the measurement surface will be less than the minimum detectable value of 0.05 Atom% (no silicon element is detected). Case A was defined as the case where the release agent layer was not removed, and case F was defined as the case where the release agent layer was removed and the substrate was exposed. The results are shown in Table 1 below.

[0079] [Table 1]

[0080] The details of the materials represented by the abbreviations in the column for the resin component ratio in the intermediate layer forming composition (intermediate layer resin component ratio) in Table 1 are as follows: <Silane compound (A) exhibiting polycondensation synthesis properties by hydrolysis> • "A1": A silane compound exhibiting polycondensation properties through hydrolysis; product name "Corcoat (registered trademark) N-103X" (manufactured by Corcoat Co., Ltd.)

[0081] <Melamine compound (B)> • "B1": Methylated melamine resin "B1", product name "MW-30" (manufactured by Nippon Carbide Industries Co., Ltd.)

[0082] <Other compounds> • "P": Amorphous polyester resin, product name "Byron (registered trademark) GK-640" (manufactured by Toyobo Co., Ltd.) In Table 1, "Intermediate layer resin component ratio" refers to the content (mass%) of each component based on a 100% mass total content of component (A) and component (B).

[0083] As shown in Table 1, the results of the separation performance evaluation of the substrates using the release sheets of Examples 1 to 3 confirmed that in a release sheet which is a laminate having a substrate, an intermediate layer formed on the substrate from an intermediate layer forming composition containing component (A) and component (B), and a release agent layer in this order, it is possible to separate the substrate from the release sheet by bringing the intermediate layer into contact with water and peeling the intermediate layer from the substrate surface. Furthermore, it was confirmed that the release sheets of Examples 1 to 3 exhibited good separation of the substrate using the method described above, while also maintaining good adhesion to the substrate during normal use.

[0084] On the other hand, when the release sheet of Comparative Example 1 was used, since it did not have the aforementioned intermediate layer, Si elements were detected on the release agent layer side of the substrate even after the substrate separation performance evaluation was performed. This confirmed that the release agent layer was not removed from the substrate and the substrate could not be separated. Furthermore, when the release sheet of Comparative Example 2, which does not contain component (B), was used as the component forming the intermediate layer, the base material layer was separated by contact between the intermediate layer and water. However, it was confirmed that the adhesion of the base material during normal use was inferior. Furthermore, when the release sheet of Comparative Example 3, which does not contain both component (A) and component (B) as the component forming the intermediate layer, was used, it was confirmed that the substrate could not be separated, similar to Comparative Example 1, and it was also confirmed that the adhesion of the substrate during normal use was inferior.

Claims

1. A laminate comprising a substrate, an intermediate layer, and a release agent layer in that order on at least one surface side of the substrate, wherein the intermediate layer is formed from an intermediate layer forming composition containing a silane compound (A) and a melamine compound (B) that exhibit polycondensation properties by hydrolysis. The content of component (A) in the aforementioned intermediate layer forming composition is 40 to 95% by mass of the total content of component (A) and component (B) in 100% by mass. The content of component (B) in the aforementioned intermediate layer forming composition is 5 to 60% by mass of the total content of component (A) and component (B) in 100% by mass. A release sheet wherein the total content of component (A) and component (B) is 80% by mass or more of the solid content of 100% by mass of the intermediate layer forming composition.

2. The release sheet according to claim 1, wherein component (B) is alkylated melamine resin.

3. The release sheet according to claim 1 or 2, wherein component (A) mainly comprises at least one selected from a tetrafunctional silane compound represented by the following general formula (a) and its oligomers. Si(OR) ｐ (X) ４－ｐ (a) [In general formula (a), R represents an alkyl group and X represents a halogen atom. If there are multiple R and X atoms, they may be the same or different from one another. p represents an integer from 0 to 4.]

4. The release sheet according to claim 3, wherein the tetrafunctional silane compound is a tetraalkoxysilane represented by the following general formula (a1). Si(OR) ４ (a1) [In general formula (a1), R represents an alkyl group. If there are multiple Rs, they may be the same or different from one another.]

5. The release sheet according to any one of claims 1 to 4, wherein the base material is a resin film.

6. The release sheet according to any one of claims 1 to 5, wherein the base material and the intermediate layer are directly laminated together.

7. The release sheet according to any one of claims 1 to 6, characterized in that the substrate is separated from the release sheet by bringing the intermediate layer into contact with water.

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