WO2023048103A1

WO2023048103A1 - Release sheet

Info

Publication number: WO2023048103A1
Application number: PCT/JP2022/034850
Authority: WO
Inventors: 知巳深谷
Original assignee: リンテック株式会社
Priority date: 2021-09-24
Filing date: 2022-09-16
Publication date: 2023-03-30
Also published as: KR20240073012A; JPWO2023048103A1

Abstract

The present invention relates to a release sheet having a substrate, and also having an intermediate layer and a release agent layer in the stated order on at least one surface of the substrate, the release sheet being characterized in that the intermediate layer is hydrophilic or is not soluble in water.

Description

release sheet

The present invention provides a release sheet having at least a substrate, an intermediate layer, and a release agent layer in this order, wherein the substrate can be separated from the release sheet after the release sheet is used. Regarding the sheet.

In general, a release sheet has a laminated structure in which a release agent layer is provided on a base material, and as the base material, a paper base material or various plastic base materials are used. there is
In recent years, from the viewpoint of global resource protection, environmental protection, etc., there has been an active movement in various fields to aim at building a recycling-oriented society through initiatives such as waste generation control, reuse, and recycling.
The same applies to the field of release sheets. For example, various methods for separating a base material having a high resin content from a used release sheet and recovering and reusing the resin have been investigated.
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 the release film after use is formed of an easily soluble resin is immersed in a solvent in which the easily soluble resin is dissolved in the solvent, thereby separating and removing the release layer on the surface of the film, and recovering only the base film. is disclosed.
Further, in Patent Document 2, after using a laminated film formed by laminating a readily soluble resin layer and a surface functional layer in this order on at least one side of a base film, the resin constituting the readily soluble resin layer is soluble. By washing with a solvent that does not dissolve the resin constituting the base film, the base film or its pulverized material is separated and recovered from the laminated film, and the separated and recovered material is remelted to form the base film. A method for recycling a laminated film is disclosed, which is characterized by regenerating the resin composition that has been used.
Further, in Patent Document 3, in a method of manufacturing a ceramic green sheet using a carrier sheet, the carrier sheet is formed on at least one side of a base film via a readily soluble resin layer formed of a water-soluble resin. a step of forming a ceramic green sheet layer on the release film by using a release film having a release layer formed thereon and applying a ceramic slurry onto the release layer surface of the release film; A step of peeling the layer from the release film to form a ceramic green sheet, and washing the release film after peeling the ceramic green sheet layer with a solvent that can dissolve the easily soluble resin to remove the adhesion of the base film surface. and separating and removing the components.

JP-A-2002-265665 Japanese Patent Application Laid-Open No. 2004-169005 Japanese Patent No. 4284936

In each of the above-described methods, a method of dissolving a readily soluble resin in a solvent is used to separate the base material. is needed.
However, the solvent used to separate the base material contains a readily soluble resin dissolved therein, and there is a risk that the dissolved resin may re-deposit on the separated base material.
In addition, from the viewpoint of environmental protection, for example, even when water is used as the solvent, it becomes a solution in which the easily soluble resin is dissolved, so it is necessary to reduce the COD (Chemical Oxygen Demand) value. Various types of waste liquid treatment are required. Also, in the waste liquid treatment process, it leads to an increase in the amount of CO ₂ emissions, etc., depending on the degree of the load of the waste liquid treatment.
Therefore, there is a demand for a release sheet that is more effective in reducing the environmental load.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and provides a novel release sheet that allows easy separation of a substrate from a release sheet by using water and that can suppress contamination of the water used to separate the substrate. intended to

The present inventors have found that the release sheet has a base material, a hydrophilic and water-insoluble intermediate layer on at least one surface side of the base material, and a release agent layer in this order. The inventors have found that the problem can be solved and completed the present invention.
That is, the present invention provides the following [1] to [10].
[1] A release sheet having a substrate, an intermediate layer and a release agent layer in this order on at least one surface side of the substrate, wherein the intermediate layer is hydrophilic and water-insoluble. A release sheet characterized by:
[2] The release sheet according to [1], wherein the surface of the intermediate layer on the substrate side has a water contact angle of 55 degrees or less.
[3] The difference between the contact angle of water on the surface of the release agent layer and the contact angle of water on the substrate-side surface of the intermediate layer is 30 degrees or more, according to the above [1] or [2]. release sheet.
[4] The release sheet according to any one of [1] to [3], wherein the substrate and the intermediate layer are directly laminated.
[5] The release sheet of any one of [1] to [4], wherein the intermediate layer is a layer having a siloxane bond.
[6] The release sheet of [5] above, wherein the layer having a siloxane bond is a layer formed from a silane-based compound exhibiting polycondensation properties by hydrolysis.
[7] The release sheet of [6] above, wherein the silane compound contains at least one selected from tetrafunctional silane compounds represented by the following general formula (a) and oligomers thereof as a main component.
Si(OR) _p (X) _4-p (a)
[In general formula (a), R represents an alkyl group, and X represents a halogen atom. When a plurality of R and X are present, the plurality of R and X may be the same or different. p represents an integer of 0 to 4; ]
[8] The release sheet according to [7], 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. When there are multiple R's, the multiple R's may be the same or different. ]
[9] The release sheet according to any one of [1] to [8], wherein the substrate is a resin film.
[10] The release agent layer according to any one of the above [1] to [9], wherein the release agent layer is a layer formed from a release agent composition containing an energy ray-curable or thermosetting resin as a main component. release sheet.

According to the present invention, it is possible to provide a novel release sheet that allows the substrate to be easily separated from the release sheet by using water and that can suppress contamination of the water used to separate the substrate.

Hereinafter, the present invention will be described in detail using embodiments.
As used herein, the term “solid content” refers to components contained in the target composition, excluding diluent solvents such as water and organic solvents.
In this specification, for preferred numerical ranges (for example, ranges of content etc.), the lower and upper limits described stepwise can be independently combined. For example, from the statement "preferably 10 to 90, more preferably 30 to 60", combining "preferred lower limit (10)" and "more preferred upper limit (60)" to "10 to 60" can also Similarly, from the description of "preferably 10 or more, more preferably 30 or more" and "preferably 90 or less, more preferably 60 or less" for the same matter, "preferable lower limit (10)" and "more preferred upper limit Value (60)" can also be combined with "10 or more and 60 or less".
Moreover, in the description in this specification, for example, "energy ray" is a term that means known energy rays such as γ-rays, electron beams, ultraviolet rays, and visible light.

[Release sheet]
The release sheet of the present invention is a release sheet having a substrate, an intermediate layer and a release agent layer in this order on at least one surface side of the substrate, wherein the intermediate layer is hydrophilic and non-hydrophilic. It is characterized by being water-soluble.
From the viewpoint of facilitating reuse by recovering the resin constituting the base material from the separated base material, the release sheet preferably has a structure in which the base material and the intermediate layer are directly laminated. preferable. Here, "direct lamination" refers to, for example, a configuration in which each layer is in direct contact with each other without another layer between the substrate and the intermediate layer.
Moreover, as one aspect of the release sheet, the substrate, the intermediate layer, and the functional layer may be directly laminated in this order. That is, the layers may be in direct contact with each other without any other layer between the substrate, the intermediate layer, and the functional layer.
Each layer constituting the release sheet will be described in more detail below.

<Base material>
As the substrate, for example, a paper substrate, a resin film, or the like can be used, and a resin film is preferable from the viewpoint of easier separation. Moreover, when the resin film is separated, the recovered component is the resin. On the other hand, when the paper substrate is separated, the recovered component becomes pulp fibers.
Examples of the resin film include polyester films such as polyethylene terephthalate film, polybutylene terephthalate film and polyethylene naphthalate film; polyolefin films such as polyethylene film and polypropylene film; polyimide film; polyamide film; polycarbonate film; vinyl copolymer (EVA) film; ethylene-(meth)acrylic acid copolymer film; ethylene-(meth)acrylic acid ester copolymer film; cycloolefin polymer film; polyurethane film; can be used. Among these, a polyester film is preferable from the viewpoint of heat resistance and strength. As the polyester film, a polyester film containing polyethylene terephthalate, polybutylene terephthalate, or polyethylene naphthalate as a main component is preferable from the viewpoint of easy recovery and recycling of the resin. Here, the "main component" refers to the component with the highest content among the components constituting the film. As the polyester film, a polyethylene terephthalate film, a polybutylene terephthalate film, and a polyethylene naphthalate film are more preferable, and a polyethylene terephthalate film is even more preferable.

Moreover, the base material may be a resin film containing only one type of the above-mentioned resins, or may contain two or more types thereof. For example, the substrate may be a single-layer film made of one resin film, or a multi-layer film in which a plurality of resin films are laminated. From the viewpoint of facilitating recovery of the resin, the substrate is preferably a single-layer film made of one resin film or a multi-layer film made by laminating one resin film.
Moreover, the resin film may contain known fillers, colorants, antistatic agents, antioxidants, organic lubricants, catalysts, and the like. Moreover, the resin film may be transparent or colored as desired. In addition, at least one surface of the substrate may be previously subjected to surface treatment such as sputtering, corona discharge, flame, ultraviolet irradiation, electron beam irradiation, etching treatment such as oxidation, etc., if necessary.
In addition, from the viewpoint of further reducing the contamination of washing water, the substrate is also preferably water-insoluble, and more preferably both hydrophobic (non-hydrophilic) and water-insoluble.

The thickness of the substrate is not particularly limited, but is preferably 10 to 500 μm, more preferably 15 to 300 μm, still more preferably 20 to 200 μm from the viewpoint of strength, rigidity and the like.
Here, the "thickness of the base material" means the thickness of the entire base material. means the total thickness of all layers

<Middle layer>
The intermediate layer is hydrophilic and water-insoluble. Since the release sheet has a hydrophilic and water-insoluble intermediate layer, the above-described excellent effects are exhibited, and the reason for this is considered as follows.
That is, before the substrate is separated from the release sheet, the intermediate layer is in close contact with the substrate or other layers on the substrate side mainly by hydrogen bonding and anchoring effect. In particular, because the intermediate layer is hydrophilic, when the intermediate layer is brought into contact with water, the interface between the substrate and the intermediate layer or the interface between the intermediate layer and another layer present on the substrate side water can easily enter. It is believed that the water entering the interface inhibits the hydrogen bonding, causing peeling at the interface, and as a result, the substrate can be easily separated from the release sheet.
In addition, since the intermediate layer is both hydrophilic and water-insoluble, the above-mentioned water (hereinafter also referred to as "washing water") used when separating the base material from the release sheet is used. It does not leach into the wash water when it comes into contact with Therefore, contamination of washing water can be prevented.

In this specification, whether or not the intermediate layer is “hydrophilic” is determined to be hydrophilic when the contact angle of water on the substrate-side surface of the intermediate layer is 55 degrees or less. do. In addition, from the viewpoint of promoting separation of the substrate, the contact angle is preferably 50 degrees or less, more preferably 45 degrees or less. The contact angle is measured after the substrate is separated from the release sheet, that is, after the intermediate layer is brought into contact with water and the interface between the intermediate layer and the substrate or the layer on the substrate side is peeled off, the intermediate layer is a value obtained by measuring the water contact angle of the surface (peeling surface) that was in contact with the base material or the layer on the base material side. Specifically, it is a value measured using the method described in Examples described later. Also, the lower limit of the contact angle of water on the substrate-side surface of the intermediate layer is not particularly limited, but is, for example, 0 degree. In other words, in one aspect of the present invention, the contact angle of water on the substrate-side surface of the intermediate layer is preferably 0 to 55 degrees, more preferably 0 to 50 degrees, and even more preferably 0 to 45 degrees. degree.
In this specification, whether or not the intermediate layer is "water-insoluble" is determined by the contact angle of water on the surface of the release agent layer, which is measured using the method described in Examples below, and the If the difference from the contact angle of water on the substrate-side surface is 30 degrees or more, the intermediate layer is determined to be water-insoluble. The contact angle difference is preferably 40 degrees or more, more preferably 50 degrees or more. When the value of this difference is small, it means that the component constituting the intermediate layer is eluted into water and the partly exposed release agent layer is measured. The upper limit of the contact angle difference is not particularly limited, but is preferably 150 degrees, more preferably 140 degrees, and still more preferably 130 degrees. As described above, these stepwise lower and upper limits can be independently combined. For example, in one aspect of the present invention, the contact angle difference is preferably 30 to 150 degrees, more preferably 40 to 140 degrees, and even more preferably 50 to 130 degrees.
The contact angle of water on the release agent layer surface is not particularly limited, but is usually 80 degrees or more, preferably 85 degrees or more, and more preferably 90 degrees or more. The upper limit of the contact angle of water on the release agent layer surface is usually 150 degrees, preferably 140 degrees, and more preferably 130 degrees. As described above, these stepwise lower and upper limits can be independently combined. For example, in one aspect of the present invention, the contact angle of water on the release agent layer surface is preferably 80 to 150 degrees, more preferably 85 to 140 degrees, and even more preferably 90 to 130 degrees. The contact angle of water on the surface of the release agent layer is also a value measured using the method described in Examples below.

The intermediate layer is preferably a layer having a siloxane bond (--Si--O--Si--) from the viewpoint of facilitating the effects of the present invention.
The layer having a siloxane bond is preferably, for example, a layer formed from a silane-based compound that exhibits polycondensation properties due to hydrolysis. The silane-based compound exhibiting polycondensability by hydrolysis is a compound in which a hydrolyzed compound can undergo polycondensation. For example, the silane-based compound exhibiting polycondensability by hydrolysis may be an alkoxysilane exhibiting polycondensation by hydrolysis.

The silane-based compound exhibiting polycondensability by hydrolysis preferably contains, as a main component, at least one selected from tetrafunctional silane-based compounds represented by the following general formula (a) and oligomers thereof.
Si(OR) _p (X) _4-p (a)
[In general formula (a), R represents an alkyl group, and X represents a halogen atom. When a plurality of R and X are present, the plurality of R and X may be the same or different. p represents an integer of 0 to 4; ]

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 group, neopentyl group, methylpentyl group and the like. Among these, a methyl group, an ethyl group, an n-propyl group, or an n-butyl group is preferable, and a methyl group or an ethyl group is more preferable, from the viewpoint of further improving the reactivity of the silane compound. The alkyl group that can be selected as R may be either straight-chain or branched-chain, preferably straight-chain.
A halogen atom that can be selected as X is preferably a chlorine atom, a bromine atom, or an iodine atom, and more preferably a chlorine atom.
The silane compound represented by the general formula (a) may be used alone or in combination of two or more.

Moreover, it is preferable that the silane-based compound represented by the general formula (a) includes a silane-based compound in which p is 4 in the general formula (a).
That is, 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. When there are multiple R's, the multiple R's may be the same or different. ]

Examples of the alkyl group that can be selected as R in general formula (a1) are the same as those for R in general formula (a) described above, and preferred embodiments thereof are also the same.
More preferred specific examples of the tetraalkoxysilane include tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane, tetrabutoxysilane, and the like. Among these, at least one of tetramethoxysilane and tetraethoxysilane, or a mixture of tetramethoxysilane and tetraethoxysilane is preferable from the viewpoint of availability and reactivity of the hydrolysis reaction.

Here, the "main component" in the silane compound exhibiting polycondensation property by hydrolysis is the silane compound that is the most contained in the total amount of 100% by mass of the silane compound exhibiting polycondensation property by hydrolysis. refers to
In the silane compound exhibiting polycondensation property by hydrolysis, the content of the silane compound represented by the general formula (a) and its oligomer contained as a main component is higher than the content of other silane compounds. Although there is no particular limitation as long as it is large, for example, it is preferably 50% by mass or more, more preferably 70% by mass or more, and still more preferably 80% by mass or more in 100% by mass of the total amount of silane compounds that exhibit polycondensation properties by hydrolysis. , and more preferably 90% by mass or more and 100% by mass or less. In other words, in one aspect of the present invention, the content of the silane-based compound represented by the general formula (a) and its oligomer contained as a main component in the silane-based compound exhibiting polycondensability by hydrolysis is , preferably 50 to 100% by mass, more preferably 70 to 100% by mass, still more preferably 80 to 100% by mass, still more preferably 90% by mass of the total amount of 100% by mass of the silane compound that exhibits polycondensation by hydrolysis. ~100% by mass.

Further, 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 Each independently may be, for example, 2 to 20 or 2 to 15. That is, it may be an average 2- to 20-mer of each silane-based compound, or an average 2- to 15-mer of each of the silane-based compounds.
Further, both the "oligomer of the tetrafunctional silane compound represented by the general formula (a)" and the "oligomer of the tetraalkoxysilane represented by the general formula (a1)" are simply the respective silane-based It is not limited to those obtained using the monomer of the compound as a starting material, and as a result of synthesis using another compound as a starting material, the structure of the compound obtained is a tetrafunctional silane represented by the general formula (a). 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 monofunctional to trifunctional silane compounds" described later.

Commercially available products can also be used as the silane-based compound exhibiting polycondensation properties by hydrolysis, and preferred examples of such commercial products include “Colcoat (registered trademark) N-103X” and “Colcoat (registered trademark) PX”. , "methyl silicate 51" which is an average tetrameric oligomer of tetramethoxysilane, "methyl silicate 53A" which is an average heptamer oligomer of tetramethoxysilane, "ethyl silicate 40" which is an average pentamer oligomer of tetraethoxysilane. "Ethylsilicate 48" which is an average decamer oligomer of tetraethoxysilane, "EMS-485" which is a mixture of an average decamer oligomer of tetramethoxysilane and an average decamer oligomer of tetraethoxysilane ( All of them are manufactured by Colcoat Co., Ltd.) and the like.

Other silane-based compounds that the silane-based compound may contain include mono- to tri-functional silane-based compounds. However, from the viewpoint of improving the hydrophilicity of the intermediate layer, as described above, it is preferable to contain a tetrafunctional silane-based compound as a main component.
In addition, from the viewpoint of promoting the hydrolysis reaction or condensation reaction of the silane-based compound exhibiting polycondensation properties due to hydrolysis, for example, a catalyst such as an acid catalyst or a metal catalyst may be used.

The thickness of the intermediate layer is preferably 0.01 to 1 μm, more preferably 0.03 to 0.5 μm, still more preferably 0, from the viewpoint of facilitating water infiltration when the intermediate layer comes into contact with water. 0.05 to 0.3 μm.

<Release agent layer>
The 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. Examples include silicone compounds; fluorine compounds; long-chain alkyl group-containing compounds; A release agent composition containing a thermoplastic resin material such as a base resin as a main component can be used. Moreover, it is preferable to use a release agent composition containing an energy ray-curable or thermosetting resin as a main component. These release agent compositions may be used singly or in combination of two or more.
Here, the "main component" in the release agent composition refers to the component contained most in the total solid content of 100% by mass of the release agent composition.

In the release agent composition containing a silicone-based compound as a main component, examples of the silicone-based compound include a silicone-based compound having an organopolysiloxane as a basic skeleton. Examples of the silicone-based compound include heat-curable silicone compounds such as addition reaction type and condensation reaction type; energy beam-curable silicone compounds such as ultraviolet-curable and electron beam-curable silicone compounds; and the like.

Specific examples of the above-mentioned addition reaction type silicone compound include alkenyl having 2 to 10 carbon atoms such as vinyl group, allyl group, propenyl group, and hexenyl group in at least one selected from the terminal and side chain of the molecule. Examples include organopolysiloxanes having two or more groups. When using such an addition reaction type silicone compound, it is preferable to use a cross-linking agent and a catalyst together.

Examples of the above-mentioned cross-linking agent include organopolysiloxanes having at least two silicon-bonded hydrogen atoms in one molecule, specifically dimethylhydrogensiloxy group-blocked dimethylsiloxane-methylhydrogensiloxane covalent Polymers, trimethylsiloxy group end-blocked dimethylsiloxane-methylhydrogensiloxane copolymers, trimethylsiloxy group end-blocked methylhydrogenpolysiloxanes, poly(hydrogensilsesquioxane) and the like.

In addition, the above catalysts include fine particle platinum, fine particle platinum adsorbed on a carbon powder carrier, chloroplatinic acid, alcohol-modified chloroplatinic acid, olefin complexes of chloroplatinic acid, platinum group metals such as palladium and rhodium. system compounds and the like. By using such a catalyst, the curing reaction of the release agent composition can proceed more efficiently.

In the release agent composition containing a fluorine compound as a main component, examples of the fluorine compound include fluorine silicone compounds, fluorine boron compounds, poly(perfluoroalkylene ether) chain-containing compounds, and the like.

In the release agent composition containing a long-chain alkyl group-containing compound as a main component, the long-chain alkyl group-containing compound may be, for example, a polyvinyl alcohol-based polymer having an alkyl group having a carbon number of 12 or more and 40 or less. Polyvinyl carbamate obtained by reacting a chain alkyl isocyanate, an alkyl urea derivative obtained by reacting polyethyleneimine with a long-chain alkyl isocyanate having 12 to 40 carbon atoms in the alkyl group, or an alkyl urea derivative obtained by reacting Examples thereof include long-chain alkyl (meth)acrylate copolymers having 12 to 40 carbon atoms. Furthermore, a long-chain alkyl-modified alkyd resin obtained by a condensation reaction of a polyhydric alcohol and a polybasic acid is obtained by using a long-chain fatty acid having 12 to 40 carbon atoms in the alkyl group as a modifier. may be

Examples of the release agent composition containing an energy ray-curable resin as a main component include, for example, an energy ray-curable compound (A) having a reactive functional group selected from (meth)acryloyl groups, alkenyl groups and maleimide groups, Those containing polyorganosiloxane (B) are preferred. In the release agent layer formed from this release agent composition, since the energy ray-curable compound (A) and the polyorganosiloxane (B) having different molecular structures, polarities, and molecular weights are used, curing after application is possible. Previously, the polyorganosiloxane (B) was pushed up to the vicinity of the outer surface of the release agent layer, and the components derived from the polyorganosiloxane (B) were segregated. This can improve the releasability of the release agent layer.

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

From the viewpoint of curability, the component (A) preferably has three or more of the above reactive functional groups in its molecule. By using an energy ray-curable compound having three or more reactive functional groups in the molecule as component (A), excellent curability, Solvent resistance and releasability can be obtained.

Component (A) includes dipentaerythritol tri(meth)acrylate, dipentaerythritol tetra(meth)acrylate, dipentaerythritol penta(meth)acrylate, dipentaerythritol hexa(meth)acrylate, and pentaerythritol tri(meth)acrylate. , pentaerythritol tetra(meth)acrylate and other polyfunctional (meth)acrylates. Among these, as component (A), dipentaerythritol tri(meth)acrylate, dipentaerythritol tetra(meth)acrylate, dipentaerythritol penta(meth)acrylate, dipentaerythritol hexa(meth)acrylate, pentaerythritol tri It is preferable to use at least one selected from the group consisting of (meth)acrylates and pentaerythritol tetra(meth)acrylates. As a result, even when the release agent composition is applied as a thin film on the surface of the intermediate layer on the substrate, the curability of component (A) is improved.

When the release agent composition contains the component (A), the content of the component (A) is preferably 65% by mass or more and 98.5% by mass or less based on 100% by mass of the solid content of the release agent composition, 70% by mass or more and 95% by mass or less is more preferable.

(Polyorganosiloxane (B))
Polyorganosiloxane (B) is a component that imparts releasability to the release agent layer. Examples of polyorganosiloxane (B) (hereinafter also referred to as "component (B)") include those having linear or branched molecular chains. In addition, as component (B), a reactive functional group selected from (meth)acryloyl groups, alkenyl groups and maleimide groups, directly or via a divalent linking group, is attached to at least one of the terminal of the molecular chain and the side chain. It is preferred to use a modified polyorganosiloxane in which is bonded to the silicon atoms of the molecular chain. Examples of alkenyl groups include vinyl groups, allyl groups, and propenyl groups. Examples of divalent linking groups include an alkylene group, an alkyleneoxy group, an oxy group, an imino group, a carbonyl group, and a combination of these divalent linking groups. The number of carbon atoms in the divalent linking group is preferably 1 or more and 30 or less, more preferably 1 or more and 10 or less. Component (B) may be used alone or in combination of two or more.

According to the modified organopolysiloxane, when the energy ray-curable compound (A) is cured by energy ray irradiation, the modified organopolysiloxane is incorporated into the crosslinked structure of the cured product of the energy ray-curable compound (A). Fixed. This suppresses migration of the polyorganosiloxane contained in the release agent layer to the other party (for example, the adhesive layer, the ceramic green sheet, the back surface of the release sheet itself, etc.) in contact with the outer surface of the release agent layer. can be done.

Examples of organic groups other than the reactive functional groups of component (B) include monovalent hydrocarbon groups having no aliphatic unsaturated bonds. This organic group may have a plurality of the same or different types. The hydrocarbon group preferably has 1 to 12 carbon atoms, more preferably 1 to 10 carbon atoms. Examples of hydrocarbon groups include alkyl groups such as methyl group, ethyl group and propyl group, and aryl groups such as phenyl group and tolyl group.

From the viewpoint of improving the releasability of the release agent layer, the component (B) is preferably one in which 80 mol% or more of the organic groups other than the reactive functional groups in the molecule of the component (B) are methyl groups.

When the release agent composition contains the component (B), the content of the component (B) is preferably 0.5% by mass or more and 5% by mass or less based on 100% by mass of the solid content of the release agent composition, 0.7% by mass or more and 4% by mass or less is more preferable. As a result, for example, when used in the production of a green sheet, the ceramic slurry can be easily applied to the base material without being repelled, and the releasability of the release sheet is improved.

Further, the blending amount of the energy ray-curable compound (A) and the polyorganosiloxane (B) is component (B)/component (A) = 0.7/99.3 or more and 5/95 or less. More preferably, component (B)/component (A) = 1/99 or more and 4.5/95.5 or less. This makes it easier to apply the ceramic slurry onto the release agent layer without repelling the ceramic slurry when it is used, for example, in the production of a green sheet, thereby improving the releasability of the green sheet from the release sheet.

(Photoinitiator)
Moreover, the release agent composition may further contain a photopolymerization initiator.
As the photopolymerization initiator that the release agent composition may contain, from the viewpoint of excellent curability, solvent resistance and release properties, for example, 2-methyl-1[4-(methylthio)phenyl]-2-morpholinopro pan-1-one, 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-butanone-1,2-(dimethylamino)-2-[(4-methylphenyl)methyl]-1- [4-(4-morpholinyl)phenyl]-1-butanone is preferred.
These photopolymerization initiators may be used alone or in combination of two or more.

When the release agent composition contains a photopolymerization initiator, the content of the photopolymerization initiator is preferably 1% by mass or more and 20% by mass or less, and 3% by mass, based on 100% by mass of the solid content of the release agent composition. % or more and 15 mass % or less is more preferable. As a result, even when the thickness of the release agent layer is in a range where it is difficult to obtain curability due to oxygen inhibition, excellent curability, solvent resistance, and releasability can be obtained.
Moreover, as the release agent composition containing an energy ray-curable resin as a main component, a composition containing other components such as a sensitizer and a reactive monomer can be used as long as the effects of the present invention are exhibited.

Further, when the release agent composition containing the energy ray-curable resin as a main component is a release agent composition containing the component (A) and the component (B), the component (A) and the component (B), In addition, the total content of the photopolymerization initiator, which may be contained as necessary, is preferably 70 to 100% by mass, more preferably 80 to 100% by mass.

In addition, since the energy ray-curable resin has a structure in which the chemical bonds that form the main chain are difficult to be decomposed by acids or alkalis, it is difficult to remove foreign substances by chemical treatment. Therefore, in a release sheet having a release agent layer containing an energy ray-curable resin as a main component, the configuration of the present invention makes it possible to easily remove the release agent layer.

Examples of the release agent composition containing a thermosetting resin as a main component include, for example, a release agent composition containing a melamine resin as a main component and a release agent composition containing an epoxy resin as a main component. The release agent composition containing a melamine resin as a main component includes a composition containing a melamine resin as a main component, an acid catalyst for thermally curing the melamine resin, and a polyorganosiloxane that imparts release properties to the release agent layer. . Further, the release agent composition containing epoxy resin as a main component includes the epoxy resin as the main component, an acid or basic thermosetting catalyst for thermally curing the epoxy resin, and a polyorgano Compositions comprising siloxanes are included.

When the release agent composition contains a thermosetting resin as a main component, the content of the thermosetting resin is 65% by mass or more and 98.5% by mass based on 100% by mass of the solid content of the release agent composition. The following is preferable, and 70% by mass or more and 95% by mass or less is more preferable.
Further, when the release agent composition contains a thermosetting resin as a main component, 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, more preferably 2% by mass or more and 6% by mass or less.
Further, when the release agent composition contains a thermosetting resin as a main component, the content of each of the catalysts is independently 10% by mass or more in 100% by mass of the solid content of the release agent composition. % by mass or less is preferable, and 2% by mass or more and 6% by mass or less is more preferable.

Further, when the release agent composition contains a thermosetting resin as a main component, the total content of the thermosetting resin, the polyorganosiloxane that imparts release properties to the release agent layer, and the catalyst is preferably is 70 to 100% by mass, more preferably 80 to 100% by mass.

In addition, the release agent layer may contain other additives in addition to the resin components described above. Other additives include, for example, antioxidants, light stabilizers, flame retardants, conductive agents, antistatic agents, plasticizers, and the like.

In addition, from the viewpoint of further reducing the contamination of washing water, the release agent layer is preferably water-insoluble, and more preferably both hydrophobic (non-hydrophilic) and water-insoluble.
The thickness of the release agent layer can be selected as appropriate and is not particularly limited. 1.5 μm.

Release sheets are generally used for the purpose of protecting the surface of other functional sheets and various parts used for specific purposes during the manufacture, transport, storage, etc. of these sheets and parts. After actually fulfilling the role of protecting these parts, etc., they are often peeled off from the surface and discarded. Therefore, by using the release sheet, the base material can be easily separated from the release sheet, which is a highly contributory application from the viewpoint of resource conservation and environmental protection.

<Manufacturing method of release sheet>
The method for producing the release sheet is not particularly limited as long as the release sheet can be produced, and it can be produced by a known method.
For example, the intermediate layer may be formed by applying an intermediate layer-forming composition or a solution thereof to one surface of the substrate, followed by heating and drying, or curing by energy ray irradiation. An intermediate layer can be formed.
In addition, the method for forming the release agent layer can also be appropriately selected depending on the type of the release agent layer, and is not particularly limited as long as the release sheet can be produced, and is produced by a known method. can do.
For example, a release agent composition or a solution thereof is applied onto an intermediate layer formed on a substrate by the method described above, and then the release agent is cured by heating and drying or by irradiation with energy rays. It can be manufactured by forming layers.

The method for applying the intermediate layer-forming composition, the release agent composition, or the solution thereof is not particularly limited, and known methods can be used. Examples thereof include spin coating, spray coating, bar coating, knife coating, roll coating, blade coating, die coating, and gravure coating.
Moreover, the drying method and drying temperature for drying the intermediate layer or release agent layer are not particularly limited, and can be appropriately selected according to the characteristics of the material forming the intermediate layer or release agent layer. Similarly, when an intermediate layer or a release agent layer is formed by energy beam irradiation, irradiation conditions such as the type of energy beam, illuminance, and light amount can be appropriately selected depending on the characteristics of the material forming the intermediate layer or release agent layer. can do.

As described above, the release sheet can separate the substrate from the release sheet by bringing the intermediate layer into contact with water. Therefore, as one aspect of the present invention, a release sheet having the base material, the hydrophilic and water-insoluble intermediate layer on at least one surface side of the base material, and the release agent layer in this order. 3, the method for separating the base material is characterized in that the base material is separated from the release sheet by bringing the intermediate layer into contact with water.

The method for bringing the intermediate layer into contact with water is not particularly limited, but it is preferable to immerse the release sheet in water.
For example, if the release sheet is wound in a roll form, it may be immersed in the water tank as it is in the roll form. In this case, the release sheet roll may be left still in the water tank, or the water tank may be agitated.
Alternatively, during the process of continuous processing (Roll to Roll processing) until the release sheet is unwound from the delivery roll and wound up by the take-up roll, the release sheet delivered from the delivery roll is placed in the water tank. Alternatively, a treatment such as rubbing water on the sheet with a brush or the like may be performed.
Alternatively, after cutting the release sheet, the cut release sheet may be immersed in a water tank. In this case, the cut release sheet may be left still in a water tank, or the water tank may be agitated. Alternatively, a treatment such as rubbing water with a brush or the like may be performed on the cut release sheet.

The water to be brought into contact with the intermediate layer may be room temperature, but is preferably warm water. For example, 40° C. or higher is preferable, and 60° C. or higher is more preferable. Also, it is preferably less than 100°C, and more preferably 98°C or less. As described above, these stepwise lower and upper limits can be independently combined. For example, in one aspect of the present invention, the temperature of water to be brought into contact with the intermediate layer is preferably 40° C. or higher and lower than 100° C., more preferably 60° C. or higher and 98° C. or lower.
In the present specification, the water being at "room temperature" means the same temperature as the temperature of the room environment, and refers to the temperature of the water in the state of not being heated by a heat source or the like under the room temperature environment. An example of the room temperature is not particularly limited, but may be, for example, 23°C.

As described above, by using the release sheet, the substrate can be easily separated from the release sheet. In addition, as described above, the intermediate layer in the release sheet that contributes to the separation of the substrate can reduce the contamination of the washing water used when separating the substrate, and furthermore, the contamination of the washing water is suppressed. Also, the resin recovered from the separated substrate is less likely to be contaminated. In addition, suppression of contamination of the wash water leads to reuse of the wash water and simplification of waste treatment.
Therefore, the release sheet can be suitably used when the resin recovered from the base material is reused as it is, or when the monomer, which is the raw material constituting the resin, is decomposed and recycled.
In addition, when the base material is separated using the release sheet, the washing water can be easily separated from the separated base material by simply filtering the washing water, thereby enabling recovery and recycling of the resin. It also simplifies the whole process.
Therefore, as one aspect of the present invention, for example, at least, using a method for separating a substrate using the release sheet, a substrate, and at least one surface side of the substrate, the intermediate layer, the The intermediate layer is brought into contact with water from a release sheet having a release agent layer in this order, and the intermediate layer is peeled off from the surface of the substrate or the surface of the layer on the substrate side, thereby obtaining the release sheet. and a step of recovering the resin from the substrate. The step of recovering the resin from the base material is not particularly limited, and a known recovery method can be appropriately used depending on the type of each resin and the raw material of the resin.

The present invention will be specifically described by the following examples, but the present invention is not limited to the following examples. In addition, the physical property values in the following examples are the values measured by the following methods.

[Thicknesses of substrate, intermediate layer, and release agent layer]
The thickness of the substrate in the release sheet used in each example and each comparative example was measured using a constant pressure thickness measuring instrument manufactured by Teclock Co., Ltd. (model number: "PG-02J", standard specifications: JIS K6783: 1994, JIS Z1702: 1994, JIS Z1709: 1995).
The thicknesses of the intermediate layers of Examples 1 to 4 and Comparative Example 2 were measured using a spectroscopic ellipsometer (manufactured by JA Woollam, product name "M-2000").
The thickness of the release agent layer of each example and each comparative example was measured using a reflective film thickness meter (manufactured by Filmetrics, product name: "F20").

[Evaluation of water insolubility of intermediate layer]
The following method was used to confirm whether the intermediate layer was water-insoluble.
(1) Measurement of contact angle of water on surface of release agent layer The contact angle of water on the surface of the release agent layer of the release sheets obtained in Examples 1 to 4 and Comparative Example 2 was measured. The contact angle was measured according to JIS R3257:1999 by the sessile drop method using a contact angle meter (Kyowa Interface Science Co., Ltd., product name: "DM-701"). For droplets, distilled water was used.
The measurement results are shown in Table 1 below as "contact angle (1)".
(2) Measurement of the contact angle of water on the substrate side surface of the intermediate layer Separate the intermediate layer from the substrate and measure the water contact angle on the substrate side surface of the intermediate layer by the following method. Hydrophilicity was evaluated.
An adhesive tape with a width of 50 mm (manufactured by Nitto Denko Corporation, product name "Polyester Adhesive Tape No. 31B") was attached to the surface of the release agent layer of the release sheets obtained in Examples 1 to 4 and Comparative Example 2. After that, it was cut into a size of 50 mm×50 mm to prepare a test piece.
Then, a glass beaker with a capacity of 500 mL was filled with 300 mL of warm water, and the entire test piece was immersed in warm water of 90° C. and allowed to stand for 3 hours. After that, it was confirmed that the test piece was separated into a laminate in which the release agent layer and the intermediate layer were integrally supported on the adhesive tape and the base material, and the adhesive carrying the release agent layer and the intermediate layer was separated. The tape was taken out of the hot water and dried at room temperature (23° C.) for 24 hours. After that, the contact angle was measured for the surface of the intermediate layer carried on the adhesive tape (the surface of the intermediate layer that was in contact with the substrate surface). The contact angle was measured according to JIS R3257:1999 by the sessile drop method using a contact angle meter (Kyowa Interface Science Co., Ltd., product name: "DM-701"). For droplets, distilled water was used.
The measurement results are shown in Table 1 below as "contact angle (2)".
(3) Method for judging whether or not the intermediate layer is water-insoluble When the difference between the contact angle of water on the substrate-side surface of the layer and the value of the water contact angle was 30 degrees or more, it was judged that the intermediate layer in the release sheet was water-insoluble. The evaluation results are shown in Table 1 below.
If the value of the difference in contact angle is small, the contact angle of the release agent layer that is partially or wholly exposed due to elution of the components constituting the intermediate layer into water in the operation (2) above is measured. means that

[Evaluation of Hydrophilicity of Intermediate Layer]
The hydrophilicity of the release sheets obtained in Examples 1 to 4 and Comparative Example 2 was evaluated based on the results of "(2) Measurement of the contact angle of water on the substrate-side surface of the intermediate layer".
According to the above "(2) Measurement of the water contact angle of the substrate-side surface of the intermediate layer", when the value of the water contact angle of the substrate-side surface of the intermediate layer is 55 degrees or less, the intermediate layer is hydrophilic. I decided there was. The results are shown in Table 1 below.
In Table 1 below, the value of the contact angle (2) of the intermediate layer formed of polyvinyl alcohol in Comparative Example 2 is high. This is because the intermediate layer of Comparative Example 2 was affected by the partially exposed release agent layer eluted in warm water in the measurement of the contact angle of water on the material side surface.
Therefore, in Table 1 below, the evaluation of the hydrophilicity of the intermediate layer is shown only when the intermediate layer is water-insoluble.
As a reference, in Comparative Example 2, a laminate sample was prepared in which only an intermediate layer was formed on a base material without forming a release agent layer, and the surface of the intermediate layer was subjected to the above "(1) Release agent layer surface The contact angle measured according to "Measurement of contact angle of water" was 35.2 degrees. From this point as well, it was confirmed that the intermediate layer of Comparative Example 2 was eluted into the hot water by the treatment in "(2) Measurement of the water contact angle of the substrate-side surface of the intermediate layer".

[Production of release sheet]
A release sheet was produced by the method shown below.

[Example 1]
A biaxially oriented polyethylene terephthalate film (thickness: 31 µm) was prepared as a substrate. Next, as a composition for forming an intermediate layer, a silane compound exhibiting polycondensation properties by hydrolysis (manufactured by Colcoat Co., Ltd., product name “Colcoat (registered trademark) N-103X”) was prepared and mixed with isopropyl alcohol. to adjust the solid content concentration to 1.5% by mass.
Next, the resulting composition for forming an intermediate layer was uniformly coated on one side of the substrate with a bar coater so that the thickness of the intermediate layer after drying was 0.1 μm to form a coating layer. The coating layer was cured by heating for 1 minute to form an intermediate layer.
Next, 100 parts by mass of thermosetting addition-reactive silicone (manufactured by Shin-Etsu Chemical Co., Ltd., "KS-847H") is diluted with toluene, and a platinum catalyst (manufactured by Shin-Etsu Chemical Co., Ltd., "CAT-PL- 50T") was added to obtain a solution having a solid content concentration of 2.0% by mass to obtain a coating liquid of the release agent composition. The prepared coating liquid is applied with a bar coater onto the intermediate layer formed on the base material to form a coating layer, and the coating layer is cured by heating at 120 ° C. for 1 minute to obtain a thickness of A release sheet having a configuration in which a release agent layer of 0.1 μm was formed and substrate/intermediate layer/release agent layer laminated in this order was produced.

[Example 2]
An intermediate layer was provided on one side of the substrate in the same manner as in Example 1.
Next, methylated melamine resin (manufactured by Nippon Carbide Industry Co., Ltd., product name "MW-30") 100 parts by mass (solid content conversion value, the same applies hereinafter) and polyorganosiloxane both terminal carbinol-modified polydimethylsiloxane ( Shin-Etsu Chemical Co., Ltd., product name "KF-6000") and 4 parts by mass of a mixed solvent of isopropyl alcohol and methyl ethyl ketone (mixing ratio (mass ratio) is isopropyl alcohol: methyl ethyl ketone: cyclohexanone = 40: 20: 20 ). To the obtained diluted solution, 4.6 parts by mass of an acid catalyst p-toluenesulfonic acid (manufactured by Shin-Etsu Chemical Co., Ltd., product name “PS-80”) is added and uniformly mixed to reduce the solid content. A solution having a concentration of 2.0% by mass was obtained, and a coating liquid of a release agent composition containing a thermosetting resin as a main component was obtained.
The prepared coating liquid is applied with a bar coater onto the intermediate layer formed on the base material to form a coating layer, and the coating layer is cured by heating at 120 ° C. for 1 minute to obtain a thickness of 0. A release sheet having a configuration in which a release agent layer of 1 μm was formed and a substrate/intermediate layer/release agent layer were laminated in this order was produced.

[Example 3]
An intermediate layer was provided on one side of the substrate in the same manner as in Example 1.
Next, a mixture of polyfunctional acrylates dipentaerythritol pentaacrylate and dipentaerythritol hexaacrylate (manufactured by Toagosei Co., Ltd., product name "Aronix (registered trademark) M-400", solid content 100% by mass) 94 parts by mass And, acrylic-modified polydimethylsiloxane (manufactured by Shin-Etsu Chemical Co., Ltd., trade name "X-22-164A", solid content 100% by mass) 1 part by mass, and a photopolymerization initiator (IGM Resins B.V., Trade name “Omnirad (registered trademark) 907” (2-methyl-1[4-(methylthio)phenyl]-2-morifolinopropan-1-one, solid content 100% by mass)) 5 parts by mass, isopropyl alcohol and methyl ethyl ketone (mixing ratio (mass ratio) is isopropyl alcohol: methyl ethyl ketone = 3: 1) to obtain a solution with a solid content concentration of 20% by mass, and energy ray curable resin as the main component. A coating liquid of the agent composition was obtained.
The prepared coating solution was applied onto 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 is irradiated with ultraviolet light (accumulated light amount: 250 mJ/cm ² ) to form a release agent layer (thickness: 1 μm), and a structure in which the base material/intermediate layer/release agent layer are laminated in this order. A release sheet was produced.

[Example 4]
In Example 1, the substrate/intermediate layer/releasing agent layer were laminated in this order in the same manner as in Example 1, except that the composition for forming the intermediate layer was changed as follows to form the intermediate layer. A release sheet having the structure was prepared.
As a composition for forming an intermediate layer, 100 parts by mass of a silane-based compound (manufactured by Colcoat Co., Ltd., product name "Methyl Silicate 53A") exhibiting polycondensation properties by hydrolysis, 35 parts by mass of distilled water, and an acid catalyst. As p-toluenesulfonic acid (manufactured by Shin-Etsu Chemical Co., Ltd., product name "PS-80") was mixed with 2.0 parts by mass in terms of solid content, and adjusted to a solid content concentration of 40% by mass with isopropyl alcohol. After that, it was stirred for 20 minutes. Then, the solid content concentration was adjusted to 1.5% by mass with isopropyl alcohol to obtain an intermediate layer-forming composition.
Next, the resulting composition for forming an intermediate layer was uniformly coated on one side of the substrate with a bar coater so that the thickness of the intermediate layer after drying was 0.1 μm to form a coating layer. The coating layer was cured by heating for 1 minute to form an intermediate layer.

[Comparative Example 1]
A release sheet having a structure in which a base material and a release agent layer were laminated in this order was prepared in the same manner as in Example 1, except that no intermediate layer was provided.

[Comparative Example 2]
A biaxially oriented polyethylene terephthalate film (thickness: 31 μm) was prepared as a substrate.
Next, a 2% by mass aqueous solution of partially saponified polyvinyl alcohol resin (manufactured by Mitsubishi Chemical Corporation, "Gosenol (registered trademark) GL-05") is applied to the substrate so that the thickness after drying is 0.1 μm. An intermediate layer was formed by uniformly coating one side and heating at 120° C. for 1 minute. A release agent layer was formed in the same manner as in Example 1, and a release sheet having a configuration in which substrate/intermediate layer/release agent layer were laminated in this order was produced.

[Separability of substrate]
A test piece was obtained by cutting the release sheet obtained by the method described in Examples and Comparative Examples into a size of 50 mm×50 mm. Next, a glass beaker with a capacity of 500 mL was filled with 300 mL of hot water at 90°C, and the test piece was entirely immersed in the warm water and allowed to stand at 90°C for 1 hour. After that, the test piece taken out from the warm water was immersed in distilled water at room temperature (23° C.) and washed to obtain a sample for evaluation of separability.
Regarding the sample, nitrogen (N), which is a specific element derived from the chemical composition of the release agent layer measured by X-ray photoelectron spectroscopy (XPS), was applied to the substrate surface on the side where the release agent layer was provided. , the separability of the substrate was evaluated based on the amount of silicon (Si) detected. The ratio of each element was calculated by the following formula, and it was determined that the release agent layer was separated and removed from the substrate surface when the specific element derived from the chemical composition of the release agent layer was less than 0.05 atom %. The results are shown in Table 2 below. In addition, in Table 2, the case of less than 0.05 Atom % was described as not detected (N.D.).
In each formula below, N represents the amount of nitrogen element, Si represents the amount of silicon element, C represents the amount of carbon element, and O represents the amount of oxygen element.
・ Nitrogen (N) element ratio (Atom%) = [N / (C + O + N + Si)] × 100
・ Silicon (Si) element ratio (Atom%) = [Si / (C + O + N + Si)] × 100

[Contamination evaluation of washing water]
(i) Measurement of COD Value The release sheets obtained by the methods described in Examples 1 to 4 and Comparative Example 2 were cut into 50 mm×50 mm size test pieces to obtain test pieces. Next, a glass beaker with a capacity of 200 mL is filled with 100 mL of distilled water as washing water and heated to 90 ° C., immersed so that the entire ten test pieces are immersed in the cleaning water, and kept at 90 ° C. Let it stand for a while. After that, all the test pieces were taken out from the beaker, heat retention was stopped, and the washing water was cooled to room temperature (23°C) in an environment of room temperature (23°C). After cooling, the wash water was filtered through a polyethylene mesh (#380), the water temperature was adjusted to 25°C, and a water quality tester (manufactured by Kyoritsu Rikagaku Kenkyusho Co., Ltd., product name “Packtest (registered trademark) COD”) was used. , model: WAK-COD-2) was used to measure the COD value of the wash water, and evaluated according to the following criteria. The results are shown in Table 2 below.
・A (no contamination of wash water): COD value is less than 10 mg/L ・F (contaminated wash water): COD value is 10 mg/L or more

(ii) Measurement of dry weight of eluted portion In addition to the above method (i), the dry weight of the eluted portion into the wash water was measured by the following method to evaluate the contamination of the wash water.
The release sheets obtained in Example 1 and Comparative Example 2 were cut into a size of 100 mm×100 mm to prepare test pieces. Next, a glass beaker with a capacity of 2,000 mL was filled with 1,500 mL of distilled water, and 10 test pieces were immersed in water so that the entirety was immersed in the water and allowed to stand at 90° C. for 3 hours. After that, the base material separated from the test piece was taken out from the water, and the release agent layer with the intermediate layer floating on the surface of the water was filtered to obtain the eluted water. Heat drying and vacuum drying were repeated to obtain components eluted in water from the release sheet, and the weight thereof was measured. The results are shown in Table 2 below as elution amounts.
Since the substrate and the release agent layer constituting the release sheets obtained in Example 1 and Comparative Example 2 are water-insoluble, the components eluted by this method are the components of the intermediate layer. Therefore, this method can also be used as an evaluation method for determining whether or not the intermediate layer in the release sheet is water-insoluble. In addition, the value of the eluted amount in Table 2 below indicates the value (unit: μg/m ² ) of (dry weight of eluted portion)/(area of immersed release sheet).

As shown in Table 2, from the evaluation results of the separability of the substrate using the release sheets of Examples 1 to 4, it was formed from a substrate and a silane-based compound exhibiting polycondensation by hydrolysis on the substrate. In a release sheet having an intermediate layer and a release agent layer provided in this order, the intermediate layer is brought into contact with water to separate the intermediate layer from the surface of the substrate, thereby removing the substrate from the release sheet. It was confirmed that it is possible to separate Furthermore, when the release sheets of Examples 1 to 4 are used and the substrate is separated from the release sheet, the intermediate layer is water-insoluble, so the COD value in the washing water used for separating the substrate is It was confirmed that the release sheet is excellent as a release sheet for use in a method of separating substrates with low environmental load.
On the other hand, when the release sheet of Comparative Example 1 was used, the Si element was detected on the release agent layer side of the substrate even after the separability evaluation of the substrate, and the release agent layer was removed from the substrate. It was confirmed that the substrate was not separated.
When the release sheet of Comparative Example 2 was used, the base layer was separated by bringing the intermediate layer into contact with water. However, since the intermediate layer is water-soluble, it was confirmed that the COD value in the washing water used for separating the substrate was increased.

As described above, when the release sheet of the present invention is used to separate the substrate by bringing the intermediate layer into contact with water, the intermediate layer is insoluble in the washing water used, so the amount of washing water is less than that of the conventional product. Contamination can be suppressed. Therefore, for example, in the process of separating the substrate, it is possible to treat the used wash water by a simple method such as filtration, thereby reducing the burden of waste liquid treatment. In addition, there is also the advantage of facilitating reuse of the washing water.
Therefore, when the release sheet of the present invention is used, it is more effective in reducing the environmental load than before, from the viewpoint of simplifying or omitting the waste liquid treatment process of washing water, and from the viewpoint of being able to reuse washing water. is. Furthermore, the simplification of the waste liquid treatment process, etc., is also very effective industrially from the viewpoint of leading to cost reduction in the separation of the substrate.

Claims

A release sheet comprising a substrate, an intermediate layer and a release agent layer in this order on at least one surface side of the substrate, wherein the intermediate layer is hydrophilic and water-insoluble. and release sheet.
The release sheet according to claim 1, wherein the surface of the intermediate layer on the substrate side has a water contact angle of 55 degrees or less.
The release sheet according to claim 1 or 2, wherein the difference between the contact angle of water on the surface of the release agent layer and the contact angle of water on the substrate-side surface of the intermediate layer is 30 degrees or more.
The release sheet according to any one of claims 1 to 3, wherein the base material and the intermediate layer are directly laminated.
The release sheet according to any one of claims 1 to 4, wherein the intermediate layer is a layer having a siloxane bond.
The release sheet according to claim 5, wherein the layer having a siloxane bond is a layer formed from a silane-based compound exhibiting polycondensation by hydrolysis.
7. The release sheet according to claim 6, wherein the silane-based compound contains, as a main component, at least one selected from tetrafunctional silane-based compounds represented by the following general formula (a) and oligomers thereof.
Si(OR) p (X) 4-p (a)
[In general formula (a), R represents an alkyl group, and X represents a halogen atom. When a plurality of R and X are present, the plurality of R and X may be the same or different. p represents an integer of 0 to 4; ]
The release sheet according to claim 7, 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. When there are multiple R's, the multiple R's may be the same or different. ]
The release sheet according to any one of claims 1 to 8, wherein the substrate is a resin film.
The release sheet according to any one of claims 1 to 9, wherein the release agent layer is a layer formed from a release agent composition containing an energy ray-curable or thermosetting resin as a main component.