Release sheet

Abstract

To provide a release sheet which has small release force at normal temperature, and suppresses increase in release force when being exposed to high temperature.SOLUTION: A release sheet has a base material sheet and a release layer, wherein the release layer is formed of a release agent composition containing a (meth)acrylic block copolymer, a melamine resin and a binder resin, the (meth)acrylic block copolymer has an A block having a structural unit (a-1) represented by formula (1) and a B block having a structural unit (b-1) having a hydroxy group and / or a carboxy group, the binder resin has a hydroxy group and / or a carboxy group, and the release layer has an atomic ratio (N / C) of 0.018 or less, and an atomic ratio (O / C) of 0.058 to 0.24, which are measured on the surface of the release layer by X-ray photoelectron spectroscopy. In the formula (1), R11 is an alkyl group, and R12 represents H or a methyl group.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a release sheet, and more particularly to a release sheet having a small release force at room temperature. [Background technology]

[0002] Electronic components such as semiconductors, various connectors, capacitors, resistors, and printed wiring boards are widely used in a variety of products. During the assembly process of these components, adhesive tapes and sheet adhesives are used to bond or temporarily fasten the components together. It is common for adhesive tapes and sheet adhesives to have a release sheet placed on the adhesive or adhesive surface to protect it during storage.

[0003] Such release sheets are treated with a release agent on the surface that comes into contact with the pressure-sensitive adhesive or adhesive to facilitate release from the pressure-sensitive adhesive or adhesive. For the release agent, a silicone-based, fluorine-based, long-chain alkyl-based, wax-based, polyolefin-based or other release agent is used.

[0004] However, because silicone-based release agents tend to transfer their silicone components to the object being released, when they are used to bond electronic components or temporarily fasten electronic components during the manufacturing process, they can easily cause malfunctions in the electronic components, etc. For this reason, it has been proposed to use non-silicone release agents (release agents that do not contain silicone compounds), such as polyolefin-based release agents and long-chain alkyl-based release agents, for such applications.

[0005] For example, Patent Document 1 describes a release sheet in which a release agent layer is formed from a release agent composition containing an aminoalkyd resin and a (meth)acrylic block copolymer containing a structural unit having an alkyl group having 12 to 28 carbon atoms (see Patent Document 1 (Claim 1)). [Prior art documents] [Patent documents]

[0006] [Patent Document 1] International Publication No. 2022 / 004418 Summary of the Invention [Problem to be solved by the invention]

[0007] Generally, release sheets with various release strengths are desired depending on the application, from a light release type with a low release strength to a heavy release type with a relatively high release strength. Here, the release sheet described in Patent Document 1 has a relatively low release strength, but its release strength is still high compared to release sheets using silicone-based release agents.

[0008] The present invention has been made in consideration of the above circumstances, and aims to provide a release sheet that uses a non-silicone release agent in the release layer, which has a small release force at room temperature and which is inhibited from increasing in release force when exposed to high temperatures. [Means for solving the problem]

[0009] The release sheet of the present invention, which has been able to solve the above-mentioned problems, comprises a base sheet and a release layer formed on at least one surface of the base sheet, wherein the release layer is formed from a release agent composition containing a (meth)acrylic block copolymer, a melamine resin, and a binder resin different from the melamine resin, wherein the (meth)acrylic block copolymer is a (meth)acrylic block copolymer having an A block containing structural units (a-1) represented by formula (1) and a B block containing structural units (b-1) having hydroxy groups and / or carboxy groups, and the binder resin has hydroxy groups and / or carboxy groups. The release layer is characterized in that the atomic ratio of nitrogen atoms to carbon atoms (N / C) is 0.018 or less and the atomic ratio of oxygen atoms to carbon atoms (O / C) is 0.058 to 0.24, as measured on the surface of the release layer by X-ray photoelectron spectroscopy.

[0010] [ka] [In formula (1), R 11 represents an alkyl group having 10 to 28 carbon atoms. 12 represents a hydrogen atom or a methyl group.

[0011] The release layer is formed from a release agent composition containing a specific (meth)acrylic block copolymer, a melamine resin, and a binder resin, and the binder resin is crosslinked by the (meth)acrylic block copolymer and the melamine resin, thereby improving the physical strength of the release layer. Furthermore, by controlling the atomic ratio of nitrogen atoms to carbon atoms (N / C) measured on the surface of the release layer by X-ray photoelectron spectroscopy within a predetermined range, the amount of alkyl groups present near the surface of the release layer and the amount of melamine resin present near the surface of the release layer can be controlled, thereby reducing the peeling force of the release layer and maintaining the mechanical strength of the release layer. Furthermore, by controlling the atomic ratio of oxygen atoms to carbon atoms (O / C) measured on the surface of the release layer by X-ray photoelectron spectroscopy within a predetermined range, the amount of alkyl groups present near the surface of the release layer and the amount of hydroxyl groups and / or carboxyl groups present near the surface of the release layer can be controlled, improving the mechanical strength of the release layer and suppressing an increase in the release force when exposed to high temperatures. Therefore, the release sheet of the present invention, even if it is a release sheet using a non-silicone release agent in the release layer, has a small release force at room temperature and is prevented from increasing in release force when exposed to high temperatures. [Effects of the Invention]

[0012] The release sheet has a low release force at room temperature, and the release force does not increase significantly even when the release layer is subjected to a heating process (for example, heating at 100°C or higher). Furthermore, the release layer of the release sheet is substantially free of silicone compounds. Therefore, by using the release sheet, defects occurring in electronic components and in the manufacturing process of electronic components can be suppressed. DETAILED DESCRIPTION OF THE INVENTION

[0013] (definition) In this specification, "(meth)acrylic" means "at least one of acrylic and methacrylic." "(meth)acrylate" means "at least one of acrylate and methacrylate." "(meth)acrylate" means "an ester compound in which the hydrogen atom of the carboxy group of (meth)acrylic acid is substituted with an organic group." "(meth)acryloyl" means "at least one of acryloyl and methacryloyl." "(meth)acrylic monomer" means "a monomer having a (meth)acryloyl group in the molecule," and includes "(meth)acrylate." "Vinyl monomer" means "a monomer having a radically polymerizable carbon-carbon double bond in the molecule," and includes "(meth)acrylate" and "(meth)acrylic monomer."

[0014] In this specification, "structural unit derived from (meth)acrylate" means "a structural unit in which a radically polymerizable carbon-carbon double bond of a (meth)acrylate is polymerized to form a carbon-carbon single bond." "Structural unit derived from (meth)acrylic monomer" means "a structural unit in which a radically polymerizable carbon-carbon double bond of a (meth)acrylic monomer is polymerized to form a carbon-carbon single bond." "Structural unit derived from vinyl monomer" means "a structural unit in which a radically polymerizable carbon-carbon double bond of a vinyl monomer is polymerized to form a carbon-carbon single bond."

[0015] In this specification, when it is stated that "X to Y" (X and Y are any numbers), it means "X or more, Y or less." Furthermore, when it is stated that "X or more" (X is any number), it also means "X or more than X," and when it is stated that "Y or less" (Y is any number), it also means "Y or less than Y." Furthermore, "X and / or Y (X and Y are optional)" means "at least one of X and Y," and can mean three things: "X only," "Y only," and "X and Y."

[0016] <Release sheet> The release sheet of the present invention comprises a base sheet and a release layer formed on at least one surface of the base sheet. The release sheet is attached to a pressure-sensitive adhesive or adhesive by the release layer to protect the adhesive or bonded surface during storage or during the manufacture of electronic components, and is a sheet with a so-called "peelable function," such as a release sheet or a sheet for processing.

[0017] (Base sheet) The base sheet is not particularly limited, and any base sheet that is used as a base for conventional release sheets can be used. Examples of the base sheet include paper (high-quality paper, dust-free paper, glassine paper, clay-coated paper, resin-coated paper, laminated paper (polyethylene-laminated paper, polypropylene-laminated paper, etc.)), nonwoven fabric, metal foil, polymer sheet, glass sheet, etc.

[0018] Examples of polymeric materials constituting the polymer sheet include polyethylene terephthalate resin, polyethylene naphthalate resin, polycarbonate resin, poly(meth)acrylate resin, polystyrene resin, polyamide resin, polyimide resin, polyacrylonitrile resin, polypropylene resin, polyethylene resin, polycycloolefin resin, cycloolefin copolymer resin, polyphenylene sulfide resin, polyvinyl chloride resin, polyvinylidene chloride resin, polyvinyl alcohol resin, and polyether ether ketone resin. Among these, polyethylene terephthalate resin, polyethylene naphthalate resin, polyimide resin, polycarbonate resin, poly(meth)acrylate resin, polyamide resin, polycycloolefin resin, cycloolefin copolymer resin, and polyether ether ketone resin are preferred in terms of heat resistance, strength, adhesion to release agents, and ease of handling. The polymer sheet may be composed of a single layer containing one or more of the above polymeric materials, or may be composed of two or more layers, such as a layer containing one or more of the above polymeric materials and a layer containing one or more different polymeric materials.

[0019] The thickness of the substrate sheet is not particularly limited, but from the viewpoint of excellent handleability, it is preferably 2 μm to 500 μm, and more preferably 2 μm to 200 μm.

[0020] The substrate sheet may be surface-treated to improve adhesion to the release layer. Examples of surface treatments include corona treatment, plasma treatment, hot air treatment, ozone treatment, and ultraviolet treatment. An easy-adhesion layer may be provided on the surface of the substrate sheet. Furthermore, various functional layers such as a gas barrier property improving layer, an antistatic layer, and an oligomer block layer may be provided on the surface of the substrate sheet.

[0021] (peeling layer) The atomic ratio (N / C) of nitrogen atoms to carbon atoms of the release layer, measured on the surface of the release layer by X-ray photoelectron spectroscopy (hereinafter sometimes referred to as "XPS"), is greater than 0, preferably 0.001 or greater, and is 0.018 or less, preferably 0.015 or less, and more preferably 0.012 or less. If the atomic ratio (N / C) is greater than 0, sufficient crosslinking is formed, improving the mechanical strength of the release layer, and if it is 0.018 or less, the peel force of the release layer is reduced.

[0022] The release layer has an atomic ratio of oxygen atoms to carbon atoms (O / C), measured on the surface of the release layer by XPS, of 0.058 or more, preferably 0.059 or more, and 0.24 or less, preferably 0.20 or less, more preferably 0.11 or less. If the atomic ratio (O / C) is 0.058 or more, sufficient crosslinking is formed, improving the mechanical strength of the release layer. If the atomic ratio (O / C) is 0.24 or less, an increase in the release force after heating caused by hydroxyl groups and / or carboxyl groups remaining on the surface of the release layer can be suppressed.

[0023] The nitrogen atoms measured by XPS on the surface of the release layer are atoms derived from the melamine resin contained in the release agent composition. The content of nitrogen atoms relative to the total amount of elements on the surface of the release layer is preferably 0.01 atomic % or more, more preferably 0.05 atomic % or more, even more preferably 0.1 atomic % or more, and is preferably 3 atomic % or less, more preferably 2 atomic % or less, and even more preferably 1.2 atomic % or less. If the nitrogen atom content is 0.01 atomic % or more, crosslinking by the melamine resin increases, further improving the mechanical strength of the release layer, while if it is 3 atomic % or less, the increase in release force caused by the nitrogen atoms can be further reduced.

[0024] The oxygen atoms measured by XPS on the surface of the release layer are mainly atoms derived from acryloyl groups, hydroxyl groups, and carboxyl groups contained in the release agent composition. The content of oxygen atoms relative to the total amount of elements on the surface of the release layer is preferably 4 atomic % or more, more preferably 5 atomic % or more, even more preferably 5.5 atomic % or more, and is preferably 12 atomic % or less, more preferably 10 atomic % or less, and even more preferably 9.8 atomic % or less. If the oxygen atom content is 4 atomic % or more, more crosslinks are formed, further improving the mechanical strength of the release layer, and if it is 12 atomic % or less, the increase in release force after heating can be further suppressed.

[0025] The carbon atoms measured by XPS on the surface of the release layer are mainly atoms derived from the alkyl groups of the (meth)acrylic copolymer. The carbon atom content relative to the total amount of elements on the surface of the release layer is preferably 85 atomic % or more, more preferably 90 atomic % or more, even more preferably 91 atomic % or more, and is preferably 95 atomic % or less, more preferably 94.5 atomic % or less, and even more preferably 94 atomic % or less. If the carbon atom content is 85 atomic % or more, the release force of the release layer becomes smaller, and if it is 95 atomic % or less, more crosslinks are formed, and the mechanical strength of the release layer is further improved.

[0026] The release layer preferably contains substantially no silicone compounds in order to reduce adverse effects on electrical components, etc. Note that "substantially no silicone compounds" means that the amount of silicone compounds in the release layer is preferably 500 μg / g or less, more preferably 100 μg / g or less.

[0027] (Removal agent composition) The release layer is formed from a release agent composition containing a (meth)acrylic block copolymer, a melamine resin, and a binder resin different from the melamine resin.

[0028] ((Meth)acrylic block copolymer) The (meth)acrylic block copolymer (hereinafter, sometimes simply referred to as "block copolymer") has an A block having a structural unit (a-1) represented by formula (1) and a B block having a structural unit (b-1) derived from a vinyl monomer having a hydroxy group and / or a carboxy group. The block copolymer bonds with reactive groups in the melamine resin and / or binder resin via the hydroxyl and / or carboxyl groups in the B block, and the alkyl groups with 10 to 28 carbon atoms in the A block are unevenly distributed on the surface of the release layer, thereby improving the release performance of the release layer.

[0029] The block copolymer may be a copolymer containing structural units derived from (meth)acrylic monomers as the main component (50% by mass or more), and may contain structural units derived from vinyl monomers other than (meth)acrylic monomers. The content of structural units derived from (meth)acrylic monomers in the block copolymer is preferably 80% by mass or more, more preferably 90% by mass or more, and even more preferably 95% by mass or more, based on 100% by mass of the entire copolymer. The block copolymer may also be composed solely of structural units derived from (meth)acrylic monomers.

[0030] The content of the structural unit (a-1) in the block copolymer is preferably 40% by mass or more, more preferably 80% by mass or more, and even more preferably 95% by mass or more, and is preferably 99.99% by mass or less, more preferably 99.5% by mass or less, and even more preferably 99.0% by mass or less, based on 100% by mass of the block copolymer. If the content of the structural unit (a-1) is 40% by mass or more, the releasability will be better, and if it is 99.99% by mass or less, the compatibility with the binder resin described below will be better.

[0031] The content of the structural unit (b-1) in the block copolymer is preferably 0.01% by mass or more, more preferably 0.2% by mass or more, even more preferably 1.0% by mass or more, and is preferably 20% by mass or less, more preferably 10% by mass or less, and even more preferably 5% by mass or less, based on 100% by mass of the block copolymer. If the content of the structural unit (b-1) is 0.01% by mass or more, the effect of improving the strength of the release layer by crosslinking becomes greater, and if it is 20% by mass or less, an increase in viscosity of the release agent composition is suppressed, the coatability is improved, and the appearance of the release layer becomes better.

[0032] The total content of the structural unit (a-1) and the structural unit (b-1) in the block copolymer is preferably 40% by mass or more, more preferably 80% by mass or more, and even more preferably 95% by mass or more, based on 100% by mass of the block copolymer. The block copolymer may be composed only of the structural unit (a-1) and the structural unit (b-1).

[0033] The mass ratio ((a-1) / (b-1)) of the structural unit (a-1) to the structural unit (b-1) in the block copolymer is preferably 4 or more, more preferably 10 or more, even more preferably 15 or more, and is preferably 10,000 or less, more preferably 500 or less, even more preferably 60 or less. When the mass ratio ((a-1) / (b-1)) is 4 or more, the appearance of the release layer is improved while maintaining releasability, and when it is 10,000 or less, compatibility with the binder resin is imparted and strength of the release layer can be imparted by crosslinking.

[0034] The total amount of hydroxyl and carboxyl groups per 100 g of the block copolymer is preferably 0.05 mmol / 100 g or more, more preferably 1.2 mmol / 100 g or more, even more preferably 3.0 mmol / 100 g or more, and is preferably 300.0 mmol / 100 g or less, more preferably 150.0 mmol / 100 g or less, even more preferably 70.0 mmol / 100 g or less. If the total amount of hydroxyl and carboxyl groups is 0.05 mmol / 100 g or more, the strength of the release layer can be sufficient, and if it is 300.0 mmol / 100 g or less, good peel strength from the adherend can be obtained.

[0035] The block copolymer preferably does not contain a nitrogen atom.

[0036] The weight-average molecular weight (Mw) of the block copolymer is preferably 5,000 or more, more preferably 7,000 or more, and even more preferably 10,000 or more, and is preferably 400,000 or less, more preferably 200,000 or less, and even more preferably 50,000 or less. If Mw is 5,000 or more, the strength of the release layer can be sufficient, and if it is 400,000 or less, the solubility in solvents can be good. The molecular weight of the block copolymer is measured by gel permeation chromatography (hereinafter referred to as "GPC") method.

[0037] The molecular weight distribution (Mw / Mn) of the block copolymer is preferably 3.0 or less, more preferably 2.0 or less, and even more preferably 1.6 or less. In this specification, the molecular weight distribution (Mw / Mn) is calculated by (weight average molecular weight (Mw) of the copolymer) / (number average molecular weight (Mn) of the copolymer). The smaller the Mw / Mn, the narrower the molecular weight distribution, resulting in a copolymer with a uniform molecular weight. When the Mw / Mn value is 1.0, the molecular weight distribution is narrowest. In other words, the lower limit of Mw / Mn is 1.0.

[0038] The structure of the block copolymer is preferably a linear block copolymer. The linear block copolymer may have any structure (arrangement), but from the viewpoint of the physical properties of the linear block copolymer or the physical properties of the composition, when the A block is represented as A and the B block is represented as B, the structure (AB) m Type, (AB) m - Type A, (BA) m It is preferable that the copolymer has at least one structure selected from the group consisting of -B type (m is an integer of 1 or more, for example, an integer of 1 to 3).

[0039] Among these, AB type diblock copolymers are preferred from the viewpoints of ease of handling during processing and the physical properties of the composition. By forming an AB type diblock copolymer, the structural unit (a-1) in the A block and the structural unit (b-1) in the B block are localized, and the structural unit (a-1) in the A block is efficiently oriented toward the air surface (release surface), thereby improving the release properties. Furthermore, the structural unit (b-1) in the B block is oriented toward the substrate surface, thereby improving crosslinking efficiency and improving the strength of the release layer. The block copolymer may have blocks other than the A block and the B block.

[0040] The content of the A block is preferably 80% by mass or more, more preferably 90% by mass or more, and is preferably 99.9% by mass or less, more preferably 99% by mass or less, and even more preferably 98% by mass or less, based on 100% by mass of the entire block copolymer. The content of the B block is preferably 0.1% by mass or more, more preferably 1% by mass or more, and even more preferably 2% by mass or more, and is preferably 20% by mass or less, more preferably 10% by mass or less, based on 100% by mass of the entire block copolymer. If the content of the B block is 0.1% by mass or more, the strength of the release layer can be sufficient, and if it is 20% by mass or less, the appearance and release force of the release layer will be good.

[0041] The mass ratio of the A block to the B block (A block / B block) in the block copolymer is preferably 80 / 20 or more, more preferably 90 / 10 or more, and is preferably 99.9 / 0.1 or less, more preferably 99 / 1 or less, and even more preferably 98 / 2 or less. When the mass ratio of the A block to the B block is within the above range, the compatibility between the block copolymer and the binder resin is increased, and the releasability and appearance of the release layer are further improved.

[0042] The content of the block copolymer in the release agent composition is preferably 1% by mass or more, more preferably 4% by mass or more, and even more preferably 7% by mass or more, and is preferably 50% by mass or less, more preferably 40% by mass or less, and even more preferably 35% by mass or less, based on 100% by mass of the total of the (meth)acrylic block copolymer, melamine resin, and binder resin. If the content of the block copolymer is 1% by mass or more, the release properties and heat resistance of the release layer are further improved, and if it is 50% by mass or less, whitening of the release layer can be further suppressed.

[0043] (Block A) The A block is a polymer block having a structural unit (a-1) represented by formula (1). The structural unit (a-1) may be of one type or may have two or more types. The A block has an alkyl group having 10 to 28 carbon atoms introduced therein by the structural unit (a-1) represented by formula (1), and thus has excellent release performance.

[0044] [ka] [In formula (1), R 11 represents an alkyl group having 10 to 28 carbon atoms. 12 represents a hydrogen atom or a methyl group.

[0045] R in formula (1) 11 The alkyl group represented by the formula (I) has 10 or more, preferably 12 or more, and 28 or less, preferably 26 or less, carbon atoms. R 11If the alkyl group has 10 or more carbon atoms, the peeling performance of the peeling layer is further improved, and if the alkyl group has 28 or less carbon atoms, the crystallinity of the alkyl group does not become too high, and the peeling force is reduced.

[0046] R 11 Examples of the alkyl group include a linear alkyl group, a branched alkyl group, and a cyclic alkyl group, and the linear alkyl group or the branched alkyl group is preferred.

[0047] Examples of the linear alkyl group include an n-decyl group, an n-undecyl group, an n-dodecyl group (an n-lauryl group), an n-tridecyl group, an n-tetradecyl group, an n-pentadecyl group, an n-hexadecyl group, an n-heptadecyl group, an n-octadecyl group (an n-stearyl group), an n-nonadecyl group, an n-icosyl group, an n-heicosyl group, an n-docosyl group, an n-tricosyl group, an n-tetracosyl group, an n-heptacosyl group, an n-hexacosyl group, an n-heptacosyl group, and an n-octacosyl group. Examples of the branched alkyl group include an isodecyl group, an isoundecyl group, an isododecyl group, an isotridecyl group, an isotetradecyl group, an isopentadecyl group, an isohexadecyl group, an isoheptadecyl group, an isooctadecyl group (an isostearyl group), an isononadecyl group, an isoicosyl group, an isoheicosyl group, an isodocosyl group, an isotricosyl group, an isotetracosyl group, an isoheptacosyl group, an isohexacosyl group, an isoheptacosyl group, an isooctacosyl group, a 2-octyldecyl group, a 2-octyldodecyl group, a 2-octyltetradecyl group, a 2-decyltetradecyl group, a 2-dodecylhexadecyl group, and a 2-tetradecyloctadecyl group. Examples of the cyclic alkyl group include a cyclic alkyl group having a monocyclic structure and a cyclic alkyl group having a bridged ring structure, and the cyclic alkyl group may have a chain portion. Examples of the cyclic alkyl group having a monocyclic structure include an n-undecylcyclohexyl group and an n-dodecylcyclohexyl group. Examples of the cyclic alkyl group having a bridged ring structure include a bornyl group, an isobornyl group, a 1-adamantyl group, a 2-adamantyl group, a 2-methyl-2-adamantyl group, and a 2-ethyl-2-adamantyl group.

[0048] The A block preferably has an aspect 1 in which the structural unit (a-1) represented by formula (1) contains a structural unit (a-11) represented by formula (2); or an aspect 2 in which the structural unit (a-1) represented by formula (1) contains a structural unit (a-12) represented by formula (3) and a structural unit (a-13) represented by formula (4).

[0049] In an embodiment in which the A block contains the structural unit (a-1) represented by formula (1) as the structural unit (a-11) represented by formula (2), the branched alkyl group (-R 13 -CH(R 14 )R 15 The alkyl group has a large number of carbon atoms and low crystallinity, and therefore the peeling performance of the peeling layer is further improved.

[0050] [ka] [In formula (2), R 12 represents a hydrogen atom or a methyl group. 13 represents a linear alkylene group having 1 to 4 carbon atoms. 14 and R 15 Each independently represents a linear alkyl group having 8 to 18 carbon atoms. 13 , R 14 and R 15 The total number of carbon atoms is 18 to 27.

[0051] R in equation (2) 14 The alkyl group represented by the formula (I) preferably has 10 or more carbon atoms and 14 or less carbon atoms. R in equation (2) 15 The alkyl group represented by the formula (I) preferably has 10 or more carbon atoms and 14 or less carbon atoms.

[0052] In an embodiment in which the A block contains the structural unit (a-1) represented by formula (1) as the structural unit (a-12) represented by formula (3) and the structural unit (a-13) represented by formula (4), the release agent composition has good coatability and can obtain a release layer with further improved release performance. Specifically, the structural unit (a-12) represented by formula (3) has low crystallinity of the alkyl group, which can improve the release performance of the obtained release layer, and the introduction of the structural unit (a-13) represented by formula (4) can reduce the viscosity of the release agent composition.

[0053] [ka] [In formula (3), R 16 represents a hydrogen atom or a methyl group. 17 represents a linear alkyl group having 10 to 15 carbon atoms. In equation (4), R 18 represents a hydrogen atom or a methyl group. 19 represents a linear alkyl group having 16 to 28 carbon atoms.]

[0054] The mass ratio ((a-12) / (a-13)) of the structural unit (a-12) represented by formula (3) to the structural unit (a-13) represented by formula (4) in the A block is preferably 0.1 or more, more preferably 0.5 or more, and even more preferably 0.8 or more, and is preferably 3.0 or less, more preferably 2.0 or less, and even more preferably 1.2 or less.

[0055] Specific examples of the (meth)acrylic monomer that forms the structural unit (a-1) represented by the formula (1) include (meth)acrylic monomers having a linear alkyl group with 10 to 28 carbon atoms, (meth)acrylic monomers having a branched alkyl group with 10 to 28 carbon atoms, and (meth)acrylic monomers having a cyclic alkyl group with 10 to 28 carbon atoms.

[0056] Examples of the (meth)acrylic monomer having a linear alkyl group having 10 to 28 carbon atoms include n-decyl (meth)acrylate, n-undecyl (meth)acrylate, n-dodecyl (meth)acrylate (n-lauryl (meth)acrylate), n-tridecyl (meth)acrylate, n-tetradecyl (meth)acrylate, n-pentadecyl (meth)acrylate, n-hexadecyl (meth)acrylate, n-heptadecyl (meth)acrylate, n- Examples of such acrylates include octadecyl (n-stearyl (meth)acrylate), n-nonadecyl (meth)acrylate, n-icosyl (meth)acrylate, n-heicosyl (meth)acrylate, n-docosyl (meth)acrylate, n-tricosyl (meth)acrylate, n-tetracosyl (meth)acrylate, n-heptacosyl (meth)acrylate, n-hexacosyl (meth)acrylate, n-heptacosyl (meth)acrylate, and n-octacosyl (meth)acrylate.

[0057] Examples of the (meth)acrylic monomer having a branched alkyl group having 10 to 28 carbon atoms include isodecyl (meth)acrylate, isoundecyl (meth)acrylate, isododecyl (meth)acrylate, isotridecyl (meth)acrylate, isotetradecyl (meth)acrylate, isopentadecyl (meth)acrylate, isohexadecyl (meth)acrylate, isoheptadecyl (meth)acrylate, isooctadecyl (meth)acrylate (isostearyl (meth)acrylate), isononadecyl (meth)acrylate, isoicosyl (meth)acrylate, and isoheicosyl (meth)acrylate. Examples thereof include acrylate, isodocosyl (meth)acrylate, isotricosyl (meth)acrylate, isotetracosyl (meth)acrylate, isoheptacosyl (meth)acrylate, isohexacosyl (meth)acrylate, isoheptacosyl (meth)acrylate, isooctacosyl (meth)acrylate, 2-octyldecyl (meth)acrylate, 2-octyldodecyl (meth)acrylate, 2-octyltetradecyl (meth)acrylate, 2-decyltetradecyl (meth)acrylate, 2-dodecylhexadecyl (meth)acrylate, and 2-tetradecyloctadecyl (meth)acrylate.

[0058] Examples of the (meth)acrylic monomer having a cyclic alkyl group having 10 to 28 carbon atoms include (meth)acrylates having a cyclic alkyl group with a monocyclic structure and (meth)acrylates having a cyclic alkyl group with a bridged ring structure. The cyclic alkyl group may have a chain portion. Examples of the (meth)acrylate having a cyclic alkyl group having a monocyclic structure and 10 to 28 carbon atoms include cyclic alkyl (meth)acrylates such as n-undecylcyclohexyl (meth)acrylate and n-dodecylcyclohexyl (meth)acrylate. Examples of the cyclic alkyl (meth)acrylate having a bridged ring structure and having 10 to 28 carbon atoms include bornyl (meth)acrylate, isobornyl (meth)acrylate, 1-adamantyl (meth)acrylate, 2-adamantyl (meth)acrylate, 2-methyl-2-adamantyl (meth)acrylate, and 2-ethyl-2-adamantyl (meth)acrylate.

[0059] The A block may contain only the structural unit (a-1), or may contain other structural units. When other structural units are contained, the content of the structural unit (a-1) in the A block is preferably 40% by mass or more, more preferably 80% by mass or more, and even more preferably 95% by mass or more, based on 100% by mass of the A block, in order to maintain excellent releasability.

[0060] Examples of vinyl monomers that can form other structural units of the A block include (meth)acrylic monomers such as (meth)acrylic monomers having a linear alkyl group of 1 to 9 carbon atoms, (meth)acrylic monomers having a branched alkyl group of 3 to 9 carbon atoms, (meth)acrylic monomers having a cyclic alkyl group of 6 to 9 carbon atoms, (meth)acrylic monomers having an aryl group, (meth)acrylic monomers having a polyalkylene glycol structural unit, (meth)acrylic monomers having an alkoxy group, and (meth)acrylic monomers having an oxygen-containing heterocyclic group; and vinyl monomers other than (meth)acrylic monomers such as styrene-based monomers, α-olefins, vinyl monomers containing a sulfur-containing heterocyclic group, vinylamides, vinyl carboxylates, and dienes.

[0061] The (meth)acrylic monomer having a linear alkyl group of 1 to 9 carbon atoms is preferably a (meth)acrylic monomer having a linear alkyl group with a carbon number of 1 to 8, and more preferably a (meth)acrylic monomer having a linear alkyl group with a carbon number of 1 to 5. Examples of the (meth)acrylic monomer having a linear alkyl group of 1 to 9 carbon atoms include methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, n-butyl (meth)acrylate, n-pentyl (meth)acrylate, n-hexyl (meth)acrylate, and n-octyl (meth)acrylate.

[0062] The (meth)acrylic monomer having a branched chain alkyl group of 3 to 9 carbon atoms is preferably a (meth)acrylic monomer having a branched chain alkyl group in which the number of carbon atoms in the branched chain alkyl group is 3 to 8. Examples of the (meth)acrylic monomer having a branched chain alkyl group of 3 to 9 carbon atoms include isopropyl (meth)acrylate, isobutyl (meth)acrylate, sec-butyl (meth)acrylate, tert-butyl (meth)acrylate, isooctyl (meth)acrylate, and 2-ethylhexyl (meth)acrylate.

[0063] Examples of the (meth)acrylic monomer having a cyclic alkyl group having 6 to 9 carbon atoms include cyclohexyl (meth)acrylate and methylcyclohexyl (meth)acrylate.

[0064] Examples of the (meth)acrylic monomer having an aryl group include (meth)acrylates having an aryl group. The aryl group may have a chain moiety such as an alkylaryl group, an aralkyl group, or an aryloxyalkyl group. That is, examples of the (meth)acrylate having an aryl group include a compound in which an aryl group is directly bonded to a (meth)acryloyloxy group, a compound in which an aralkyl group is directly bonded to a (meth)acryloyloxy group, and a compound in which an alkylaryl group is directly bonded to a (meth)acryloyloxy group. Specific examples of the (meth)acrylate having an aryl group include phenyl (meth)acrylate, benzyl (meth)acrylate, and phenoxyethyl (meth)acrylate. The number of carbon atoms in the aryl group is preferably 6 to 9, and more preferably 6 to 8.

[0065] Examples of the (meth)acrylic monomer having an alkoxy group include (meth)acrylates having an alkoxyalkyl group, (meth)acrylates having an alkoxypolyalkylene glycol group, etc. Examples of the (meth)acrylates having an alkoxyalkyl group include 2-methoxyethyl (meth)acrylate, 2-ethoxyethyl (meth)acrylate, etc. Examples of the (meth)acrylate having an alkoxy polyalkylene glycol group include (meth)acrylates having a polyethylene glycol structural unit such as polyethylene glycol (degree of polymerization = 2 to 10) methyl ether (meth)acrylate, polyethylene glycol (degree of polymerization = 2 to 10) ethyl ether (meth)acrylate, and polyethylene glycol (degree of polymerization = 2 to 10) propyl ether (meth)acrylate; and (meth)acrylates having a polypropylene glycol structural unit such as polypropylene glycol (degree of polymerization = 2 to 10) methyl ether (meth)acrylate, polypropylene glycol (degree of polymerization = 2 to 10) ethyl ether (meth)acrylate, and polypropylene glycol (degree of polymerization = 2 to 10) propyl ether (meth)acrylate.

[0066] Examples of the (meth)acrylic monomer having an oxygen-containing heterocyclic group include (meth)acrylates having an oxygen-containing heterocyclic group. Examples of the (meth)acrylates having an oxygen-containing heterocyclic group include tetrahydrofurfuryl (meth)acrylate, (3-ethyloxetan-3-yl)methyl (meth)acrylate, (2-methyl-2-ethyl-1,3-dioxolan-4-yl)methyl (meth)acrylate, (5-ethyl-1,3-dioxan-5-yl)methyl (meth)acrylate, 2-[(2-tetrahydropyranyl)oxy]ethyl (meth)acrylate, and (1,3-dioxan-5-yl)methyl (meth)acrylate. The oxygen-containing heterocyclic group is preferably a 4- to 6-membered ring.

[0067] The styrene-based monomer may be substituted or unsubstituted styrene. Examples of substituents that may be substituted on styrene include alkyl groups, aryl groups, alkoxy groups, and aryloxy groups. The styrene-based monomer also includes fused ring compounds having two or more benzene rings. Examples of the styrene-based monomer include styrene, α-methylstyrene, 2-methylstyrene, 3-methylstyrene, 4-methylstyrene, 2,4-dimethylstyrene, 4-methoxystyrene, 4-phenylstyrene, and 1-vinylnaphthalene, and preferred are styrene and styrenes having an alkyl group. The number of carbon atoms in the alkyl group-containing styrene is preferably 1 to 6.

[0068] Examples of the α-olefin include 1-hexene and 1-octene. Examples of the vinyl monomer containing a sulfur-containing heterocyclic group include 2-vinylthiophene. Examples of the vinylamide include N-vinylformamide, N-vinylacetamide, and N-vinyl-ε-caprolactam. Examples of the vinyl carboxylate include vinyl acetate, vinyl pivalate, and vinyl benzoate. Examples of the dienes include butadiene, isoprene, and 4-methyl-1,4-hexadiene.

[0069] The A block preferably does not substantially contain the structural unit (b-1) described below. That is, the content of the structural unit (b-1) is preferably 5% by mass or less, more preferably 2% by mass or less, and even more preferably 1% by mass or less, based on 100% by mass of the A block. When a release layer is formed using the release agent composition, the block copolymer is thought to segregate on the surface of the release layer. In this case, the B block of the block copolymer is located on the binder resin side, and the A block is located on the surface side of the release layer. Therefore, if the A block does not substantially contain the structural unit (b-1), hydroxy groups and / or carboxy groups will not substantially be present on the surface of the release layer. Therefore, even when the release layer is exposed to high temperatures (e.g., 100°C or higher) while in contact with a pressure-sensitive adhesive or adhesive, an increase in peel strength is further suppressed.

[0070] When two or more types of structural units are contained in the A block, the various structural units contained in the A block may be contained in the A block in any form, such as random copolymerization or block copolymerization, and from the viewpoint of uniformity, they are preferably contained in the A block in the form of random copolymerization. For example, the A block may be formed from a copolymer of structural units consisting of the a1 block and structural units consisting of the a2 block.

[0071] (Block B) The B block is a polymer block having a structural unit (b-1) derived from a (meth)acrylic monomer having a hydroxy group and / or a carboxy group. The structural unit (b-1) may be of one type or may have two or more types. The hydroxy group and / or carboxy group in the B block bonds with a reactive group possessed by the melamine resin and / or binder resin.

[0072] Examples of the vinyl monomer having a reactive functional group that forms the structural unit (b-1) include (meth)acrylic monomers having a hydroxy group and / or a carboxy group, and vinyl monomers other than (meth)acrylic monomers having a hydroxy group and / or a carboxy group. Among these, (meth)acrylic monomers having a hydroxy group and vinyl monomers other than (meth)acrylic monomers having a hydroxy group are preferred.

[0073] Examples of the (meth)acrylic monomer having a hydroxy group include (meth)acrylates having a hydroxyalkyl group, (meth)acrylates having a lactone-modified hydroxy group, (meth)acrylates having a polyalkylene glycol group, etc. The hydroxyalkyl group is an alkyl group in which at least one hydrogen atom is substituted with a hydroxy group.

[0074] Examples of the (meth)acrylate having a hydroxyalkyl group include 2-hydroxyethyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 8-hydroxyoctyl (meth)acrylate, 10-hydroxydecyl (meth)acrylate, 12-hydroxylauryl (meth)acrylate, and 4-hydroxymethylcyclohexyl (meth)acrylate. The hydroxyalkyl group is preferably linear or branched. The number of carbon atoms in the hydroxyalkyl group is preferably 1 to 10, more preferably 1 to 5.

[0075] Examples of the (meth)acrylate having a lactone-modified hydroxy group include those obtained by adding lactone to the (meth)acrylate having a hydroxyalkyl group, and preferred are those obtained by adding caprolactone. The amount of lactone added is preferably 1 mol to 10 mol, more preferably 1 mol to 5 mol. Preferred examples of the (meth)acrylate having a lactone-modified hydroxy group include a 1-mol adduct of 2-hydroxyethyl (meth)acrylate with caprolactone, a 2-mol adduct of 2-hydroxyethyl (meth)acrylate with caprolactone, a 3-mol adduct of 2-hydroxyethyl (meth)acrylate with caprolactone, a 4-mol adduct of 2-hydroxyethyl (meth)acrylate with caprolactone, a 5-mol adduct of 2-hydroxyethyl (meth)acrylate with caprolactone, and a 10-mol adduct of 2-hydroxyethyl (meth)acrylate with caprolactone.

[0076] Examples of the (meth)acrylate having a polyalkylene glycol group include mono(meth)acrylate of polyethylene glycol (degree of polymerization=2 to 10) having a terminal hydroxyl group, and mono(meth)acrylate of polypropylene glycol (degree of polymerization=2 to 10) having a terminal hydroxyl group.

[0077] Examples of the (meth)acrylic monomer having a carboxy group include (meth)acrylic acid; 2-(meth)acryloyloxyethyl hydrogen succinate, 2-((meth)acryloyloxy)ethyl hydrogen hexahydrophthalate, 2-(meth)acryloyloxyethyl hydrogen phthalate, carboxyethyl (meth)acrylate, carboxypentyl (meth)acrylate, 1,4-di(meth)acryloxyethylpyromellitic acid, 4-(meth)acryloxyethyltrimellitic acid, 2-(meth)acryloyloxybenzoic acid, and lactone adducts of (meth)acrylic acid.

[0078] Examples of the vinyl monomer having a hydroxy group other than the (meth)acrylic monomer include allyl alcohol.

[0079] Examples of the vinyl monomer having an acidic group other than the (meth)acrylic monomer include vinyl monomers having a carboxy group such as crotonic acid, maleic acid, itaconic acid, citraconic acid, and cinnamic acid.

[0080] The B block may contain only the structural unit (b-1), or may contain other structural units. When other structural units are contained, the content of the structural unit (b-1) in the B block is preferably 10% by mass or more, more preferably 20% by mass or more, even more preferably 50% by mass or more, and particularly preferably 60% by mass or more, based on 100% by mass of the B block. When the content of the structural unit (b-1) in the B block is within the above range, the releasability of the release layer is reduced.

[0081] Specific examples of vinyl monomers that can form other structural units of the B block include the same monomers as those exemplified as specific examples of vinyl monomers that can form other structural units of the A block.

[0082] The B block preferably contains the structural unit (a-1) as another structural unit. When the B block contains the structural unit (a-1), the content of the structural unit (a-1) is preferably 90% by mass or less, more preferably 80% by mass or less, even more preferably 50% by mass or less, and particularly preferably 40% by mass or less, based on 100% by mass of the B block.

[0083] When two or more types of structural units are contained in the B block, the various structural units contained in the B block may be contained in the B block in any form, such as random copolymerization or block copolymerization, and from the viewpoint of uniformity, they are preferably contained in the B block in the form of random copolymerization. For example, the B block may be formed from a copolymer of structural units consisting of the b1 block and structural units consisting of the b2 block.

[0084] (Method of producing (meth)acrylic block copolymer) Examples of methods for producing the block copolymer include a method in which an A block is first produced by a polymerization reaction of a vinyl monomer, and then a monomer for a B block is polymerized onto the A block; and a method in which a B block is first produced, and then a monomer for an A block is polymerized onto the B block.

[0085] Although the polymerization method is not particularly limited, living polymerization is preferred, that is, the block copolymer is preferably one polymerized by living polymerization. Living polymerization is a chain polymerization process that involves four elementary reactions: initiation, propagation, termination, and chain transfer. In living polymerization, the termination and chain transfer reactions do not occur substantially, and the vinyl monomer reacts and polymer chains grow without deactivating the reactive sites (polymerization growth terminals). This allows the production of copolymers with a narrow molecular weight distribution and uniform composition. Living polymerizations include living radical polymerization, living anionic polymerization, and living cationic polymerization. Among these, living radical polymerization is preferred from the viewpoint of the simplicity of polymerization. Living radical polymerization is also preferred because it maintains the simplicity and versatility of free radical polymerization while enabling precise control of molecular weight distribution and the ease of producing copolymers with uniform composition.

[0086] (living radical polymerization) Living radical polymerizations include those using compounds capable of generating nitroxide radicals (nitroxide method; NMP method), those using metal complexes such as copper or ruthenium to initiate polymerization of halogenated compounds (ATRP), those using dithiocarboxylic acid esters or xanthates (RAFT), those using organotellurium compounds (TERP), those using organic iodine compounds (ITP), and those using iodine compounds as initiators and organic compounds such as phosphorus compounds, nitrogen compounds, oxygen compounds, or hydrocarbons as catalysts (reversible transfer catalyzed polymerization; RTCP, reversible catalyst-mediated polymerization; RCMP). Among these methods, the TERP method is preferred due to its versatile monomer compatibility, molecular weight control in the polymer range, uniform composition, and colorability.

[0087] The TERP method is a method of polymerizing a radically polymerizable compound (vinyl monomer) using an organic tellurium compound as a chain transfer agent, and is a method described, for example, in International Publication Nos. 2004 / 14848, 2004 / 14962, 2004 / 072126, 2004 / 096870, and 2020 / 116144.

[0088] Specific polymerization methods of the TERP method include the following (a) to (d). (a) A method of polymerizing a vinyl monomer using an organotellurium compound represented by formula (T1). (b) A method of polymerizing a vinyl monomer using a mixture of an organotellurium compound represented by formula (T1) and an azo-based polymerization initiator. (c) A method of polymerizing a vinyl monomer using a mixture of an organic tellurium compound represented by formula (T1) and an organic ditelluride compound represented by formula (T2). (d) A method of polymerizing a vinyl monomer using a mixture of an organotellurium compound represented by formula (T1), an azo-based polymerization initiator, and an organic ditelluride compound represented by formula (T2).

[0089] [ka] [In formula (T1), R a represents an alkyl group having 1 to 8 carbon atoms, an aryl group, or an aromatic heterocyclic group. b and R c R each independently represents a hydrogen atom or an alkyl group having 1 to 8 carbon atoms. d represents an alkyl group having 1 to 8 carbon atoms, an aryl group, a substituted aryl group, an aromatic heterocyclic group, an alkoxy group, an acyl group, an amido group, an oxycarbonyl group, a cyano group, an allyl group, or a propargyl group. In formula (T2), R a represents an alkyl group having 1 to 8 carbon atoms, an aryl group, or an aromatic heterocyclic group.]

[0090] Specific examples of the organic tellurium compound represented by formula (T1) include ethyl 2-methyl-2-n-butyltellanyl-propionate, ethyl 2-n-butyltellanyl-propionate, (2-hydroxyethyl) 2-methyl-methyltellanyl-propionate, and the organic tellurium compounds described in WO 2004 / 14848, WO 2004 / 14962, WO 2004 / 072126, WO 2004 / 096870, and WO 2020 / 116144. Specific examples of the organic ditelluride compound represented by formula (T2) include dimethyl ditelluride, dibutyl ditelluride, and the like.

[0091] The azo polymerization initiator can be any azo polymerization initiator used in normal radical polymerization without any particular limitation, and examples thereof include 2,2'-azobis(isobutyronitrile) (AIBN), 2,2'-azobis(2,4-dimethylvaleronitrile) (ADVN), 1,1'-azobis(1-cyclohexanecarbonitrile) (ACHN), dimethyl-2,2'-azobisisobutyrate (MAIB), 4,4'-azobis(4-cyanovaleric acid) (ACVA), 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile) (V-70), and 2,2'-azobis(N-butyl-2-methylpropionamide) (VAm-110).

[0092] In the polymerization step, a vinyl monomer and an organotellurium compound of formula (T1) are mixed in a vessel purged with an inert gas, and an azo polymerization initiator and / or an organic ditelluride compound of formula (T2) are further mixed for the purpose of promoting the reaction and controlling the molecular weight and molecular weight distribution depending on the type of vinyl monomer. Examples of the inert gas include nitrogen, argon, and helium. Argon and nitrogen are preferred. The amounts of the vinyl monomer used in steps (a), (b), (c), and (d) can be adjusted appropriately depending on the physical properties of the desired polymer component.

[0093] The polymerization reaction can be carried out without a solvent, but it can also be carried out by stirring the mixture using an aprotic or protic solvent commonly used in radical polymerization. Examples of the aprotic solvent include acetonitrile, methyl ethyl ketone, anisole, benzene, toluene, propylene glycol monomethyl ether acetate, ethyl acetate, tetrahydrofuran (THF), N,N-dimethylformamide (DMF), dimethyl sulfoxide (DMSO), N-methyl-2-pyrrolidone (NMP), acetone, dioxane, chloroform, and carbon tetrachloride. Examples of the protic solvent include water, methanol, ethanol, isopropanol, n-butanol, ethyl cellosolve, butyl cellosolve, 1-methoxy-2-propanol, hexafluoroisopropanol, and diacetone alcohol. The solvents may be used alone or in combination. The amount of solvent used may be adjusted appropriately; for example, 0.01 to 50 ml per 1 g of vinyl monomer is preferred. In addition to the solvent, a surfactant and / or a dispersant may also be used in the polymerization reaction.

[0094] The reaction temperature and reaction time may be adjusted appropriately depending on the molecular weight or molecular weight distribution of the resulting polymer, but typically the reaction is carried out at 0°C to 150°C and for 1 minute to 100 hours with stirring. The pressure during this process is typically atmospheric, but may be increased or decreased. The polymerization reaction may also be carried out under light irradiation. After completion of the polymerization reaction, the solvent used and residual vinyl monomers can be removed from the resulting reaction mixture by conventional separation and purification techniques, thereby isolating the target polymer.

[0095] The growing end of the copolymer obtained by the polymerization reaction is -TeR derived from the tellurium compound. a (In the formula, R ais the same as above), and is deactivated by handling in air after the polymerization reaction is completed, but tellurium atoms may remain. A copolymer with tellurium atoms remaining at the end will be colored and have poor thermal stability, so it is preferable to remove the tellurium atoms. Methods for removing tellurium atoms include radical reduction; adsorption with activated carbon, etc.; and adsorption of metal with ion exchange resin, etc., and these methods can also be used in combination. The other end of the copolymer obtained by the polymerization reaction (the end opposite to the growing end) is formed from -CR derived from the tellurium compound. b R c R d (In the formula, R b , R c and R d is R in formula (T1) b , R c and R d Therefore, the copolymer obtained by the TERP method does not have a substituent containing a sulfur atom at the end.

[0096] (melamine resin) Melamine resin is a general term for compounds in which the amino group of melamine has been modified in various ways, including those in which multiple triazine rings are condensed. As for the type of modification, a methylolated melamine compound in which at least one hydrogen atom of the three amino groups has been methylolated is preferred, and further, an alkyl-etherified melamine compound in which the methylol groups of the methylolated melamine compound have been partially or completely etherified with a lower alcohol having 1 to 4 carbon atoms is preferred.

[0097] The melamine resin has a methylol group and / or an alkoxy group, which bond with the hydroxy group and / or the carboxy group of the binder resin and the (meth)acrylic block copolymer to form a crosslinked structure.

[0098] Commercially available products of the melamine resin include, for example, Nikalac (registered trademark) MW-30M, Nikalac MW-30, Nikalac MW-22, Nikalac MS-11, Nikalac MS-001, Nikalac MX-730, Nikalac MX-750, Nikalac MX-708, Nikalac MX-706, Nikalac MX-035, Nikalac MW-30LF, Nikalac MW-30MLF, Nikalac MW-33LF, and Nikalac MX-035 manufactured by Sanwa Chemical Co., Ltd. Karak MZ-351, Nikalak N-0503, Nikalak N-0504; DIC's Amidair (registered trademark) J-820-60, Amidair L-109-65, Amidair L-117-60, Amidair L-125-60, Amidair L-127-60, Amidair L-150-60, Amidair L-166-608; Changxing Materials Industries' ETERMINO 9211-60-5, ETERMINO 9212-70, ETERMINO 9215-70, ETERMINO 9216-60-1, ETERMINO 9223-60, ETERMINO 9224-60, ETERMINO 9226-60, ETERMINO 9229-60; U-BAN (registered trademark) 10S60, U-BAN 10R, U-BAN 20SB, U-BAN 20SE60, U-BAN 21R, U-BAN 22R, U-BAN 122, U-BAN 125, U-BAN 128, U-BAN 220, U-BAN 225, U-BAN 228, U-BAN 28-60, U-BAN 2020, U-BAN 132, U-BAN 60R, U-BAN 62, U-BAN 62E, U-BAN 360, U-BAN 165, U-BAN 166-60, U-BAN 169, U-BAN 2061, U-BAN 80S, etc. manufactured by Mitsui Chemicals.

[0099] (binder resin) The binder resin is a resin different from the melamine resin, and when used in the release agent composition together with the (meth)acrylic block copolymer, it contributes to the strength of the release layer. The binder resin may be used alone or in combination of two or more.

[0100] The binder resin has a hydroxy group and / or a carboxy group. The hydroxy group and / or the carboxy group of the binder resin reacts with the reactive group of the melamine resin and the (meth)acrylic block copolymer. From the viewpoint of reactivity with the melamine resin, the binder resin preferably has a hydroxy group.

[0101] The binder resin is preferably a polyester resin having a hydroxy group and / or a carboxy group, and / or a (meth)acrylic resin having a hydroxy group and / or a carboxy group.

[0102] (polyester resin) The polyester resin is not particularly limited and can be appropriately selected from known polyester resins for paints. The polyester resin is preferably one obtained by the condensation reaction of a polyhydric alcohol and a polybasic acid, and a linear polyester resin obtained by the condensation reaction of a dibasic acid and a dihydric alcohol is preferred. Examples of the polyester resin include non-convertible polyester resins, which are condensates of dibasic acids and dihydric alcohols or modified with non-drying oil fatty acids, and convertible polyester resins, which are condensates of dibasic acids and trihydric or higher alcohols. The polyester resins may be used alone or in combination of two or more.

[0103] Examples of polyhydric alcohols used as raw materials for the polyester resin include dihydric alcohols such as ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, trimethylene glycol, tetramethylene glycol, and neopentyl glycol; trihydric alcohols such as glycerin, trimethylolethane, and trimethylolpropane; and tetrahydric or higher polyhydric alcohols such as diglycerin, triglycerin, pentaerythritol, dipentaerythritol, mannitol, and sorbitol. The polyhydric alcohols may be used alone or in combination of two or more.

[0104] Examples of polybasic acids used as raw materials for the polyester resin include aromatic polybasic acids such as phthalic anhydride, terephthalic acid, isophthalic acid, and trimellitic anhydride; saturated aliphatic polybasic acids such as succinic acid, adipic acid, and sebacic acid; unsaturated aliphatic polybasic acids such as maleic acid, maleic anhydride, fumaric acid, itaconic acid, and citraconic anhydride; and polybasic acids obtained by the Diels-Alder reaction such as cyclopentadiene-maleic anhydride adduct, terpene-maleic anhydride adduct, and rosin-maleic anhydride adduct. The polybasic acids may be used alone or in combination of two or more.

[0105] Examples of non-drying oil fatty acids that are modifiers for the polyester resin include octylic acid, lauric acid, palmitic acid, stearic acid, oleic acid, linoleic acid, linolenic acid, eleostearic acid, ricinoleic acid, dehydrated ricinoleic acid, as well as coconut oil, linseed oil, tung oil, castor oil, dehydrated castor oil, soybean oil, safflower oil, and their fatty acids. The modifiers may be used alone or in combination of two or more.

[0106] The polyester resin preferably has an acid value of 2 mgKOH / g to 30 mgKOH / g, more preferably 4 mgKOH / g to 25 mgKOH / g, and even more preferably 6 mgKOH / g to 12 mgKOH / g. The polyester resin also preferably has a hydroxyl value of 50 mgKOH / g to 300 mgKOH / g, more preferably 80 mgKOH / g to 270 mgKOH / g, and even more preferably 100 mgKOH / g to 250 mgKOH / g. By setting the acid value and hydroxyl value within these ranges, a cured product with excellent heat resistance and strength can be obtained.

[0107] ((Meth)acrylic resin) The (meth)acrylic resin is not particularly limited as long as it is different from the (meth)acrylic block copolymer, and can be appropriately selected from those used as (meth)acrylic resins for paints. The (meth)acrylic resin is a random copolymer containing 50 mass % or more of structural units derived from (meth)acrylic monomers.

[0108] The (meth)acrylic resin has a structural unit derived from a (meth)acrylic monomer having a hydroxy group and / or a structural unit derived from a (meth)acrylic monomer having a carboxy group.

[0109] The (meth)acrylic monomer having a hydroxy group is not particularly limited, and examples thereof include hydroxyalkyl (meth)acrylates such as 2-hydroxyethyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 8-hydroxyoctyl (meth)acrylate, 10-hydroxydecyl (meth)acrylate, and 12-hydroxylauryl (meth)acrylate; caprolactone adducts of hydroxyalkyl (meth)acrylate, etc. The (meth)acrylic monomer having a hydroxy group may be used alone or in combination of two or more.

[0110] Examples of the (meth)acrylic monomer having a carboxy group include (meth)acrylic acid, 2-(meth)acryloyloxyethyl hydrogen succinate, 2-((meth)acryloyloxy)ethyl hydrogen hexahydrophthalate, 2-(meth)acryloyloxyethyl hydrogen phthalate, carboxyethyl (meth)acrylate, carboxypentyl (meth)acrylate, 1,4-di(meth)acryloxyethyl pyromellitic acid, 4-(meth)acryloxyethyl trimellitic acid, 2-(meth)acryloyloxybenzoic acid, and lactone adducts of (meth)acrylic acid. One type of the (meth)acrylic monomer having a carboxy group may be used alone, or two or more types may be used in combination.

[0111] The (meth)acrylic resin may have a structural unit derived from a vinyl monomer other than the (meth)acrylic monomer having a hydroxy group and the (meth)acrylic monomer having a carboxy group. Examples of the other vinyl monomers include (meth)acrylic acid ester compounds such as methyl (meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, lauryl (meth)acrylate, stearyl (meth)acrylate, cyclohexyl (meth)acrylate, benzyl (meth)acrylate, isobornyl (meth)acrylate, trifluoropropyl (meth)acrylate, perfluorobutylethyl (meth)acrylate, and perfluorooctylethyl (meth)acrylate; epoxy group-containing vinyl monomers such as glycidyl (meth)acrylate, β-methylglycidyl (meth)acrylate, and 3,4-epoxycyclohexylmethyl (meth)acrylate; γ-methacryloxypropyltrimethoxysilane, ...ethoxysilane, γ-methacryloxypropyltriethoxysilane, γ-methacryloxypropyltriethoxysilane, γ-methacryloxypropyltriethoxysilane, γ-methacryloxypropyltriethoxysilane, γ-methacryloxypropyltriethoxysilane, γ-methacryloxypropyltriethoxysilane, γ-methacryloxypropyltriethoxysilane, γ-methacryloxypropyltriethoxysilane, γ-methacryloxypropyltrieth Examples of the radical polymerizable silane compounds include acryloxypropylmethyldimethoxysilane, γ-methacryloxypropyldimethylmethoxysilane, γ-methacryloxypropyltriethoxysilane, γ-methacryloxypropylmethyldiethoxysilane, γ-methacryloxypropyltributoxysilane, γ-methacryloxypropyltriisopropenoxysilane, γ-acryloxypropyltrimethoxysilane, acryloxymethyltrimethoxysilane, γ-acryloxypropyltriethoxysilane, γ-acryloxypropylmethyldiethoxysilane, styryltrimethoxysilane, styryltriethoxysilane, and α-methylstyryltrimethoxysilane; polyoxyalkylene group-containing radical polymerizable monomers; and glycerol (meth)acrylate.

[0112] The binder resin preferably has a long-chain alkyl group from the viewpoint of further improving the releasability of the release layer. From the viewpoint of releasability from the adherend, the carbon number of the long-chain alkyl group is preferably 12 or more, more preferably 14 or more, and even more preferably 16 or more. Furthermore, from the viewpoint of availability and handling of raw materials, the carbon number of the long-chain alkyl group is preferably 28 or less, more preferably 26 or less, and even more preferably 22 or less.

[0113] The melamine resin and binder resin may be a commercially available mixture thereof. Commercially available mixtures of melamine resin and polyester resin include, for example, Tesfine (registered trademark) 303, 305, and 314 manufactured by Resonac Co., Ltd. Commercially available mixtures of melamine resin and (meth)acrylic resin include, for example, Tesfine (registered trademark) 322 manufactured by Resonac Co., Ltd.

[0114] The blending amounts of the melamine resin and the binder resin may be adjusted depending on the atomic ratio (N / C) and the atomic ratio (O / C).

[0115] (acidic catalyst) The stripping agent composition may contain an acidic catalyst, if necessary. Examples of the acidic catalyst include organic acids such as acetic acid and oxalic acid; mineral acids such as hydrochloric acid, sulfuric acid, and phosphoric acid; organic sulfonic acids such as diethylsulfuric acid, paratoluenesulfonic acid, paraphenolsulfonic acid, benzenesulfonic acid, and methanesulfonic acid; and organic phosphonic acids such as 1-hydroxyethylidene-1,1'-diphosphonic acid and 2-phosphonobutane-1,2,4-tricarboxylic acid. Among these, paratoluenesulfonic acid is preferred. The acidic catalysts may be used alone or in combination of two or more.

[0116] When the acidic catalyst is added, the content of the acidic catalyst is preferably 0.1 parts by mass or more, more preferably 0.5 parts by mass or more, and even more preferably 1 part by mass or more, and is preferably 15 parts by mass or less, more preferably 10 parts by mass or less, and even more preferably 5 parts by mass or less, relative to 100 parts by mass of the total of the (meth)acrylic block copolymer, melamine resin, and binder resin in the release agent composition. If the content of the acidic catalyst is within the above range, the strength of the release layer is further improved.

[0117] (Other additives) The release agent composition may contain other additives, if necessary, in addition to the above components. Examples of other additives include antioxidants, chlorine absorbers, ultraviolet absorbers, plasticizers, flame retardants, antistatic agents, colorants, and antiblocking agents. These are appropriately selected and blended depending on the application and purpose of the release sheet. The other additives may be used alone or in combination of two or more.

[0118] Examples of the antioxidant include phenol-based antioxidants, hindered amine-based antioxidants, phosphite-based antioxidants, lactone-based antioxidants, tocopherol-based antioxidants, etc. Specific examples include 2,6-di-t-butyl-p-cresol, pentaerythritol tetrakis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate], 1,3,5-trimethyl-2,4,6-tris(3,5-di-t-butyl-4-hydroxy)benzene, tris(2,4-di-t-butylphenyl)phosphite, etc.

[0119] Examples of the chlorine absorbent include metal soaps such as calcium stearate. Examples of the ultraviolet absorber include benzotriazole, benzophenone, and hydroxybenzoate. Examples of the plasticizer include citrate esters, dibutyl phthalate, polyethylene glycols, propylene glycols, and glycerin. Examples of the flame retardant include phosphazene-based compounds, phosphate esters, condensed phosphate esters, inorganic phosphorus-based, halogen-based, and silicone-based flame retardants, metal oxide-based flame retardants, metal hydroxide-based flame retardants, organic metal salt-based flame retardants, nitrogen-based flame retardants, and boron compound-based flame retardants. Examples of antistatic agents include glycerin monoesters (such as glycerin monostearate), ethoxylated secondary amines, and the like. Examples of the colorant include various colored dyes, colored pigments, and fluorescent dyes.

[0120] The antiblocking agent is added to prevent blocking and is not particularly limited as long as it functions as a nucleating agent. Examples of antiblocking agents include inorganic particles and organic solid particles. Examples of inorganic particles include silica, alumina, (synthetic) zeolite, calcium carbonate, kaolin, talc, mica, zinc oxide, magnesium oxide, quartz, magnesium carbonate, barium sulfate, and titanium dioxide. Examples of organic solid particles include particles of polystyrene resin, polyacrylic resin, polymethyl methacrylate (PMMA) resin, cross-linked polyethylene resin, polyester resin, polyamide resin, polycarbonate resin, polyether resin, polyethersulfone resin, polyetherimide resin, polyphenylene sulfide resin, polyetheretherketone resin, polyamideimide resin, benzoguanamine resin, furan resin, epoxy resin, phenolic resin, unsaturated polyester resin, vinyl ester resin, diallyl phthalate resin, polyimide resin, fatty acid amide resin, and fatty acid glycerin ester compound. Among these, PMMA resin particles and silica particles are more preferred because they are excellent in blocking resistance and imparting slip properties.The anti-blocking agent preferably has a particle size of 0.1 μm to 10 μm.

[0121] The release agent composition is preferably substantially free of silicone compounds, which means that the content of silicone compounds in the solid content (components other than the solvent) of the release agent composition is 10% by mass or less, more preferably 5% by mass or less, and most preferably 0% by mass.

[0122] (Preparation of Stripping Composition) The release agent composition can be prepared by mixing a (meth)acrylic block copolymer, a melamine resin, a binder resin, and an acidic catalyst and other additives, which are used as needed. The release agent composition may be a solution containing a solvent derived from the production of the (meth)acrylic block copolymer, or may be a solution diluted with an appropriate solvent to have a viscosity suitable for forming a release layer.

[0123] Examples of solvents used in the release agent composition include organic solvents such as alcohol-based solvents such as ethanol, isopropyl alcohol (IPA), n-butyl alcohol (NBA), ethylene glycol monomethyl ether (EGM), ethylene glycol monoisopropyl ether (IPG), propylene glycol monomethyl ether (PGM), and diethylene glycol monobutyl ether; ketone-based solvents such as methyl ethyl ketone (MEK), methyl isobutyl ketone (MIBK), cyclohexanone, and acetone; aromatic hydrocarbon-based solvents such as toluene and xylene; ester-based solvents such as ethyl acetate (EtAc), propyl acetate, isopropyl acetate, and butyl acetate (BuAc); and amide-based solvents such as N-methylpyrrolidone, acetamide, and dimethylformamide. These solvents may be used alone or in combination of two or more.

[0124] (Formation of peeling layer) The release layer is formed on at least one surface of the substrate sheet. The release layer can be formed by applying the release agent composition and, if necessary, drying, curing, or the like. When the release agent composition is cured, the (meth)acrylic block copolymer, melamine resin, and binder resin are crosslinked by the N-methylol groups and / or N-alkoxymethylol groups contained in the composition, thereby forming an interpenetrating polymer network. Therefore, the release layer formed from the release agent composition has excellent strength.

[0125] The method for applying the release agent composition is not particularly limited, and a coating method (reverse gravure coating, direct gravure coating, die coating, bar coating, wire bar coating, roll coating, spin coating, dip coating, spray coating, knife coating, kiss coating, etc.), an inkjet method, or a printing method (offset printing, screen printing, flexographic printing, etc.) can be used.

[0126] From the viewpoint of the curability of the coating film, the release agent composition is dried and cured preferably at 100 to 170°C for 10 to 60 seconds, more preferably at 140 to 160°C for 20 to 40 seconds.

[0127] The thickness of the release layer is preferably 0.03 μm or more, more preferably 0.05 μm or more, and even more preferably 0.07 μm or more, from the viewpoint of release performance, processability, etc. The thickness of the release layer is preferably 0.5 μm or less, more preferably 0.3 μm or less, and even more preferably 0.2 μm or less, from the viewpoint of curability.

[0128] The release layer may have a matte surface (the surface that comes into contact with the pressure-sensitive adhesive or adhesive). When an adhesive is applied to a release sheet having a matte surface of the release layer, the adhesive surface becomes matte. Therefore, for example, when the release sheet is used as an adhesive sheet for an interphase insulating film of a printed wiring board, the adhesive surface of the adhesive sheet becomes matte, thereby improving processability in the manufacturing process of the printed wiring board.

[0129] When the surface of the release layer is matted, the arithmetic mean roughness Ra (JIS B0601:2013) of the surface of the release layer is preferably 0.05 μm to 1.0 μm, more preferably 0.1 μm to 0.5 μm. Furthermore, the maximum height Rz (JIS B0601:2013) of the surface of the release layer is preferably 1 μm to 11 μm, more preferably 3 μm to 7 μm. When the arithmetic mean roughness and maximum height of the surface of the release layer are within the above ranges, the surface of the adhesive or pressure-sensitive adhesive to be applied can be made sufficiently rough, improving the ease of positioning when bonding printed wiring boards together and facilitating the removal of air bubbles between the adhesive or pressure-sensitive adhesive and the printed wiring board.

[0130] An example of a method for matting the surface of the release layer is a method of subjecting a substrate sheet on which a release layer is formed to a matte treatment. By subjecting the substrate sheet to a matte treatment, the surface of the release layer formed on the substrate sheet is also matte. Examples of matte treatment methods include a method of sandblasting the substrate sheet surface, a method of forming a matte layer on the substrate sheet by coating, a method of forming a resin kneaded with inorganic or organic particles, and a method of forming a resin using a matte roll while molding. Among these, the method of forming a matte layer by coating is preferred from the viewpoint of ease of controlling surface roughness.

[0131] The method for forming the matte layer by coating can be the same as the method used for forming the release layer, and examples thereof include a method in which a coating composition containing a coating film-forming resin and particles is applied to a substrate sheet and cured to form the matte layer, and a method in which a matte layer is formed by phase separation of two or more materials.

[0132] (Application) The release sheet can be used to protect the adhesive or bonding surface of a pressure-sensitive adhesive tape or sheet-like adhesive. Furthermore, even when the release sheet is exposed to high temperatures while attached to a pressure-sensitive adhesive or adhesive, an increase in peel strength is suppressed. Therefore, the release sheet is suitable for use in applications where it is exposed to temperatures of 100°C or higher (particularly 150°C or higher) while attached to a pressure-sensitive adhesive or adhesive. Specific examples include release sheets used in the process of forming a sheet-like adhesive or sheet-like pressure-sensitive adhesive, which are exposed to temperatures of 100°C or higher when forming an adhesive or pressure-sensitive adhesive layer; release sheets used when hot-press transferring a sheet-like adhesive to an adherend, which are exposed to temperatures of 100°C or higher (particularly 150°C or higher) during hot-pressing; and the like. The pressure-sensitive adhesive or adhesive to which the release sheet can be attached is not limited, but examples include pressure-sensitive adhesives or adhesives having a hydroxy group, a carboxy group, or an epoxy group. [Example]

[0133] The present invention will be described in more detail below based on specific examples. The present invention is not limited to the following examples and can be practiced with appropriate modifications within the scope of the present invention. The polymerization rate, weight average molecular weight (Mw), molecular weight distribution (Mw / Mn) of the copolymer, as well as the thickness, XPS analysis, peel force, and strength of the release layer were evaluated according to the following methods.

[0134] The meanings of the abbreviations are as follows: BTEE: Ethyl 2-methyl-2-n-butyltellanyl propionate AIBN: 2,2'-azobis(isobutyronitrile) DTDA: 2-decyltetradecyl acrylate SA: n-Stearyl acrylate LA: n-lauryl acrylate 4-HBA: 4-hydroxybutyl acrylate AcOEt: ethyl acetate MeOH: Methanol MEK: Methyl ethyl ketone

[0135] [Evaluation method] (Polymerization rate) Using a nuclear magnetic resonance (NMR) measurement device (Bruker Biospin, model: AVANCE500 (frequency 500 MHz)), 1 H-NMR was measured (solvent: CDCl3, internal standard: trimethylsilane). The integral ratio of the peaks of the vinyl group derived from the monomer and the ester side chain derived from the polymer was calculated for the obtained NMR spectrum, and the polymerization rate of the monomer was calculated.

[0136] (Weight average molecular weight (Mw), molecular weight distribution (Mw / Mn)) The molecular weights were determined by gel permeation chromatography (GPC) using a high-performance liquid chromatograph (Tosoh Corporation, Model HLC-8320GPC). Two TSKgel Super Multipore HZ-H (Tosoh Corporation) columns were used, the mobile phase was tetrahydrofuran solution, and the detector was a differential refractometer. The measurement conditions were a column temperature of 40°C, a sample concentration of 10 mg / mL, a sample injection volume of 10 μm, and a flow rate of 0.2 mL / min. A calibration curve was prepared using polystyrene standards (molecular weights: 2,110,000, 1,090,000, 706,000, 427,000, 190,000, 96,400, 37,900, 10,200, 2,630, and 416), and the weight-average molecular weight (Mw) and number-average molecular weight (Mn) were measured. The molecular weight distribution (Mw / Mn) was calculated from these measurements.

[0137] (thickness of release layer) The thickness of the release layer was measured by spectral interferometry using a film thickness measurement system (Filmetrics, Inc., "Filmetrics F20").

[0138] (X-ray electron spectroscopy (XPS) analysis) The surface of the release layer of the release sheet was subjected to photoelectron spectroscopy using an X-ray photoelectron spectrometer (JEOL, "JPS-9200") to measure the content (atomic %) of carbon atoms, nitrogen atoms, and oxygen atoms present at that position relative to the total element content. Furthermore, the atomic ratio of nitrogen atoms to carbon atoms (N / C) and the atomic ratio of oxygen atoms to carbon atoms (O / C) were calculated from the obtained carbon, nitrogen, and oxygen atom contents. The measurement conditions were as follows: Excited X-ray: monochromatic MgKα X-ray diameter: φ2.6mm

[0139] (Normal peel strength) The release surface (release layer) of the release sheet was attached to the adhesive layer of polyester-based adhesive tape "NO. 31B" (manufactured by Nitto Denko Corporation, tape width 25 mm, adhesive layer thickness 8 μm, total thickness 50 μm), and the bonded assembly was placed on a glass plate and pressed with a 5 kg roller by rolling it back and forth once. After that, it was aged at room temperature (23°C) for 20 hours to prepare a sample for measuring normal peel strength. The normal peel force measurement sample was measured for peel force using a precision universal testing machine (Shimadzu Corporation, "Autograph (registered trademark) AGS-1kNX" (50N load cell)) in an environment of 23°C and 50% humidity at a peel speed of 0.3 m / min and a peel angle of 180° (T-peel).

[0140] (Peeling force after heating) The release surface (release layer) of the release sheet was attached to the adhesive layer of polyester-based adhesive tape "NO. 31B" (manufactured by Nitto Denko, tape width 25 mm, adhesive layer thickness 8 μm, total thickness 50 μm), and the bonded body was placed on a glass plate and pressed back and forth with a 5 kg roller. The bonded body was then sandwiched between two glass plates, a 760 g load was applied, and the body was heated in a thermostatic oven at 100°C for 20 hours to prepare a sample for post-heating peel force measurement. After heating, the peel force of the sample for peel force measurement was measured using a precision universal testing machine (Shimadzu Corporation, "Autograph (registered trademark) AGS-1kNX" (50N load cell)) in an environment of 23°C and 50% humidity at a peel speed of 0.3 m / min and a peel angle of 180° (T-peel).

[0141] (strength) The release surface (release layer) of the release sheet was rubbed strongly with a finger five times, and the rubbed area was visually observed. The evaluation criteria were as follows: ◯: No smear (the rubbed area becomes cloudy) or rub-off (the rubbed area falls off) occurs. ×: Smear or rub-off occurs.

[0142] <Synthesis of block copolymer> (Block copolymer No. 1) A flask equipped with an argon gas inlet tube and a stirrer was charged with DTDA (441.0 g), AIBN (0.985 g), and AcOEt (294.0 g). After replacing the atmosphere with argon, BTEE (9.0 g) was added and the reaction was carried out at 60°C for 24 hours to polymerize the A block. The polymerization rate was 92%.

[0143] A mixture of 4-HBA (9.0 g), AIBN (0.246 g), and AcOEt (6.0 g), which had been previously purged with argon, was added to the reaction solution, and the mixture was reacted at 60°C for 24 hours to polymerize the B block. The polymerization rate was 94%.

[0144] After the reaction was completed, the mixture was poured into stirred MeOH to form a precipitate. The supernatant was then removed and the precipitate was dried to obtain block copolymer No. 1. The resulting block copolymer No. 1 had an Mw of 13,000 and an Mw / Mn ratio of 1.37. Toluene was added to the resulting block copolymer No. 1 to adjust the solids concentration to 39.4% by mass.

[0145] (Block copolymers No. 2 to 4) Block copolymers Nos. 2 to 4 were prepared in the same manner as block copolymer No. 1. Table 1 shows the monomers, organotellurium compounds, azo-based polymerization initiators, solvents, reaction conditions, and polymerization rates used. Table 2 shows the composition, Mw, and Mw / Mn of each block copolymer. The content of each structural unit in the block copolymer was calculated from the charge ratio of the monomers used in the polymerization reaction and the polymerization rate.

[0146] [Table 1]

[0147] [Table 2]

[0148] <Preparation of Stripping Composition> The block copolymer, melamine resin, binder resin, and acid catalyst were mixed to obtain the formulation (solid content equivalent) shown in Table 3, and then diluted with a solvent (toluene, n-heptane, methyl ethyl ketone) to obtain the solid content concentration shown in Table 3, to prepare a release agent composition.

[0149] [Table 3] Mixture of melamine resin and binder resin No. 1: "Tesfine (registered trademark) 322" manufactured by Resonac Corporation (solid content concentration: 40% by mass (solvent: toluene, methanol, xylene, isobutanol)), a mixture of melamine resin and (meth)acrylic resin having a hydroxy group Melamine resin and binder resin mixture No. 2: "Tesfine (registered trademark) 305" manufactured by Resonac Corporation (solid content: 50% by mass (solvent: toluene, methanol, xylene, isobutanol)), a mixture of melamine resin and alkyd resin having a hydroxyl group Acidic catalyst: "Dryer 900" manufactured by Resonac Corporation (acidic catalyst (toluene solution of paratoluenesulfonic acid, solid content concentration 50% by mass)

[0150] <Preparation of release sheet> The release agent composition was applied to a PET (polyethylene terephthalate) film "E5100" (manufactured by Toyobo Co., Ltd., thickness 50 μm) using a wire bar so that the thickness after drying would be as shown in Table 3, and the composition was dried and cured at 150°C for 30 seconds to prepare a release sheet. The evaluation results of the obtained release sheet are shown in Table 3.

[0151] Release sheets Nos. 1 to 6 have a release layer formed on one side of a base sheet, which is formed from a specific release agent composition, and the atomic ratio of nitrogen atoms to carbon atoms (N / C) measured on the surface of the release layer by X-ray photoelectron spectroscopy is greater than 0 and 0.018 or less, and the atomic ratio of oxygen atoms to carbon atoms (O / C) is 0.058 or more and 0.24 or less. These release sheets Nos. 1 to 6 have excellent release layer strength, small normal release force, and even when exposed to high temperatures while in contact with a pressure-sensitive adhesive, an increase in release force is suppressed.

[0152] Release sheets Nos. 7 and 10 have an atomic ratio of nitrogen atoms to carbon atoms (N / C) of greater than 0.018, as measured on the release layer surface by X-ray photoelectron spectroscopy. Release sheets Nos. 7 and 10 have high normal release strength, and the release strength increased when exposed to high temperatures while in contact with an adhesive.

[0153] Release sheet No. 8 was formed from a release agent composition that did not contain a (meth)acrylic block copolymer, and had an atomic ratio of nitrogen atoms to carbon atoms (N / C) of greater than 0.018 and an atomic ratio of oxygen atoms to carbon atoms (O / C) of less than 0.058. This release sheet No. 8 had particularly high normal peel strength, and when exposed to high temperatures while in contact with a pressure-sensitive adhesive, the peel strength increased significantly.

[0154] Release sheet No. 9 was formed from a release agent composition that did not contain a (meth)acrylic block copolymer, and had an atomic ratio of nitrogen atoms to carbon atoms (N / C) of greater than 0.018 as measured on the release layer surface by X-ray photoelectron spectroscopy. This release sheet No. 9 had particularly high normal peel strength, and when exposed to high temperatures while in contact with a pressure-sensitive adhesive, the peel strength increased significantly.

[0155] The present invention includes the following aspects.

[0156] (Aspect 1) A substrate sheet and a release layer formed on at least one surface of the substrate sheet, the release layer is formed from a release agent composition containing a (meth)acrylic block copolymer, a melamine resin, and a binder resin different from the melamine resin; the (meth)acrylic block copolymer is a (meth)acrylic block copolymer having an A block having a structural unit (a-1) represented by formula (1) and a B block having a structural unit (b-1) containing a hydroxy group and / or a carboxy group, the binder resin has a hydroxy group and / or a carboxy group, The release layer is characterized in that the atomic ratio of nitrogen atoms to carbon atoms (N / C) is 0.018 or less, and the atomic ratio of oxygen atoms to carbon atoms (O / C) is 0.058 to 0.24, as measured on the surface of the release layer by X-ray photoelectron spectroscopy.

[0157] [ka] [In formula (1), R 11 represents an alkyl group having 10 to 28 carbon atoms. 12 represents a hydrogen atom or a methyl group.

[0158] (Aspect 2) 2. The release sheet according to embodiment 1, wherein the binder resin is a polyester resin having a hydroxy group and / or a carboxy group, or a (meth)acrylic resin having a hydroxy group and / or a carboxy group.

[0159] (Aspect 3) The release sheet according to aspect 1 or 2, wherein the release agent composition contains the (meth)acrylic block copolymer in an amount of 1 to 50% by mass based on 100% by mass of the total of the (meth)acrylic block copolymer, the melamine resin, and the binder resin.

[0160] (Aspect 4) A release sheet according to any one of Aspects 1 to 3, wherein the release layer has a carbon atom content of 85 atomic % to 95 atomic % relative to the total amount of elements as measured on the surface of the release layer by X-ray photoelectron spectroscopy.

[0161] (Aspect 5) the (meth)acrylic block copolymer has a mass ratio of the A block to the B block (A block / B block) of 80 / 20 to 99.9 / 0.1; the content of the structural unit (a-1) in the A block is 40% by mass or more in 100% by mass of the A block, A release sheet according to any one of aspects 1 to 4, wherein the content of the structural unit (b-1) in the B block is 10% by mass or more relative to 100% by mass of the B block.

[0162] (Aspect 6) The release sheet according to any one of aspects 1 to 5, wherein the A block contains, as the structural unit (a-1) represented by formula (1), a structural unit (a-11) represented by formula (2), or contains, as the structural unit (a-1) represented by formula (1), a structural unit (a-12) represented by formula (3) and a structural unit (a-13) represented by formula (4).

[0163] [ka] [In formula (2), R 13 represents a hydrogen atom or a methyl group. 14 represents a linear alkylene group having 1 to 4 carbon atoms. 15 and R 16 Each independently represents a linear alkyl group having 8 to 18 carbon atoms. 14 , R 15 and R 16 The total number of carbon atoms is 18 to 27.

[0164] [ka] [In formula (3), R 16 represents a hydrogen atom or a methyl group.17 represents an alkyl group having 10 to 15 carbon atoms. In equation (4), R 18 represents a hydrogen atom or a methyl group. 19 represents an alkyl group having 16 to 28 carbon atoms.]

[0165] (Aspect 7) A release agent composition for forming a release layer of the release sheet according to any one of Aspects 1 to 6, comprising a (meth)acrylic block copolymer, a melamine resin, and a binder resin different from the melamine resin, wherein the (meth)acrylic block copolymer is a (meth)acrylic block copolymer having an A block having a structural unit (a-1) represented by formula (1), and a B block having a structural unit (b-1) containing a hydroxy group and / or a carboxy group.

Claims

1. A substrate sheet and a release layer formed on at least one surface of the substrate sheet, the release layer is formed from a release agent composition containing a (meth)acrylic block copolymer, a melamine resin, and a binder resin different from the melamine resin; the (meth)acrylic block copolymer is a (meth)acrylic block copolymer having an A block having a structural unit (a-1) represented by formula (1) and a B block having a structural unit (b-1) containing a hydroxy group and / or a carboxy group, the binder resin has a hydroxy group and / or a carboxy group, The release layer is characterized in that the atomic ratio of nitrogen atoms to carbon atoms (N / C) is 0.018 or less, and the atomic ratio of oxygen atoms to carbon atoms (O / C) is 0.058 to 0.24, as measured on the surface of the release layer by X-ray photoelectron spectroscopy. 【Chemical 1】 [In formula (1), R 11 represents an alkyl group having 10 to 28 carbon atoms. 12 represents a hydrogen atom or a methyl group.

2. 2. The release sheet according to claim 1, wherein the binder resin is a polyester resin having a hydroxy group and / or a carboxy group, and / or a (meth)acrylic resin having a hydroxy group and / or a carboxy group.

3. 2. The release sheet according to claim 1, wherein the release agent composition contains the (meth)acrylic block copolymer in an amount of 1 to 50% by mass based on a total of 100% by mass of the (meth)acrylic block copolymer, the melamine resin, and the binder resin.

4. 2. The release sheet according to claim 1, wherein the release layer has a carbon atom content of 85 atomic % to 95 atomic % relative to the total amount of elements as measured on the surface of the release layer by X-ray photoelectron spectroscopy.

5. the (meth)acrylic block copolymer has a mass ratio of the A block to the B block (A block / B block) of 80 / 20 to 99.9 / 0.1; the content of the structural unit (a-1) in the A block is 40% by mass or more based on 100% by mass of the A block; 2. The release sheet according to claim 1, wherein the content of the structural unit (b-1) in the B block is 10% by mass or more relative to 100% by mass of the B block.

6. The release sheet according to claim 1, wherein the A block contains a structural unit (a-11) represented by formula (2) as the structural unit (a-1) represented by formula (1), or contains a structural unit (a-12) represented by formula (3) and a structural unit (a-13) represented by formula (4) as the structural unit (a-1) represented by formula (1). 【Chemistry 2】 [In formula (2), R 13 represents a hydrogen atom or a methyl group. 14 represents a linear alkylene group having 1 to 4 carbon atoms. 15 and R 16 Each independently represents a linear alkyl group having 8 to 18 carbon atoms. 14 , R 15 and R 16 The total number of carbon atoms is 18 to 27.] 【Chemistry 3】 [In formula (3), R 16 represents a hydrogen atom or a methyl group. 17 represents a linear alkyl group having 10 to 15 carbon atoms. In formula (4), R 18 represents a hydrogen atom or a methyl group. 19 represents a linear alkyl group having 16 to 28 carbon atoms.

7. A release agent composition for forming a release layer of the release sheet according to any one of claims 1 to 6, comprising: The composition contains a (meth)acrylic block copolymer, a melamine resin, and a binder resin different from the melamine resin, A release agent composition, characterized in that the (meth)acrylic block copolymer is a (meth)acrylic block copolymer having an A block having a structural unit (a-1) represented by formula (1) and a B block having a structural unit (b-1) containing a hydroxy group and / or a carboxy group: 【Chemistry 4】 [In formula (1), R 11 represents an alkyl group having 10 to 28 carbon atoms. 12 represents a hydrogen atom or a methyl group.

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