Adhesive sheet, structure, method for manufacturing structure, and method

Abstract

Provided is an adhesive sheet that can balance low contamination of a bonded object after heating and light peeling after heating. The adhesive sheet has an adhesive layer containing a polymer, a monomer, and a thermal polymerization initiator. The polymer contains an ethylenically unsaturated group. The monomer contains a monomer A. The monomer A has a molecular weight of 250 to 5,000 and has one or two ethylenically unsaturated groups in the molecule.

Description

Technical Field

[0001] This invention relates to adhesive sheets, structures, and methods for manufacturing structures.

[0002] This application claims priority based on Japanese Patent Application No. 2024-056871, filed on March 29, 2024, the entire contents of which are incorporated herein by reference. Background Technology

[0003] Generally, adhesives (also known as pressure-sensitive adhesives, hereinafter the same) have the following properties: they exist as soft solids (viscoelastics) in a temperature range near room temperature and are easily bonded to the substrate by pressure. Considering the excellent workability of applying adhesive to substrates, adhesives are widely used in various fields in the form of adhesive sheets with an adhesive layer on a support, or in the form of adhesive sheets without a support. Among such adhesives, there are those used to bond to substrates and removed from substrates after the bonding purpose is completed. Patent documents 1-4 disclose this prior art. Patent documents 1-4 disclose thermosetting adhesives.

[0004] Existing technical documents Patent documents Patent Document 1: Japanese Patent Application Publication No. 2015-29105 Patent Document 2: Japanese Patent Application Publication No. 2016-204617 Patent Document 3: Japanese Patent Application Publication No. 2019-56101 Patent Document 4: Japanese Patent Application Publication No. Hei 10-209087 Non-patent literature Non-patent literature 1: Simone Napolitano, “Irreversible adsorption of polymer melts and nanoconfinement effects”, SoftMatter, 2020, 16, pp. 5348-5365 Non-Patent Literature 2: Ben O'Shaughnessy and Dimitrios Vavylonis, "Non-Equilibrium in Adsorbed Polymer Layers", J. Phys.: Condens. Matter, 17, 2005, pp. R63-99 Summary of the Invention

[0005] The problem that the invention aims to solve For adhesives intended for removal from adhered materials, it is desirable to have properties that exhibit good adhesion during bonding and allow for easy peeling from the adhered materials after the bonding purpose is completed. For example, for adhesives suitable for heat-treated adhered materials, it is desirable to have easy peelability after heating while still adhered to the adhered materials. However, if adhered materials such as glass, metal, and resin are heated at high temperatures while the adhesive is attached, undesirable conditions may occur, such as the adhesive adsorbing onto the surface of the adhered materials, resulting in increased peel force (re-peeling), decreased peelability, or residue formation. Regarding this, see the cases of various polymers exhibiting adsorption capacity upon heating as described in Non-Patent Documents 1-2. For example, in the case of thermosetting adhesives as described in Patent Documents 1-4, it is difficult to ensure that the curing of the adhesive at high temperatures occurs before the adsorption of the adhesive onto the adhered materials, thus failing to achieve reduced peel force and suppressed increase in peel force based on adhesive curing, and thus failing to maintain stable easy peelability after high-temperature heating.

[0006] Against this backdrop, the inventors of this application focused on the research and development of thermosetting adhesives containing thermal polymerization initiators in the adhesive, and successfully obtained an adhesive that retains easy peelability (heat-resistant peelability) after being applied to the substrate and heated at high temperature. This heat-resistant peelability typically persists even after heat treatment with increased peel force, and can therefore also be referred to as heat-resistant peelability. As described above, this adhesive sheet retains easy peelability after heating and can be peeled from the substrate without leaving adhesive residue. However, it is further desirable that after peeling the adhesive sheet after heat treatment, no adhesive-derived components remain on the surface of the substrate, reducing contamination of the substrate (low contamination of the substrate after heating). Furthermore, the lighter the peel during peeling after heat treatment, the more ideal the peeling workability (light peelability after heating).

[0007] The present invention relates to an improvement of the above-mentioned adhesive sheet with heat-resistant peelability created in view of the above-mentioned circumstances, with the aim of providing an adhesive sheet that can balance low contamination of the adhered material after heating and easy peelability after heating.

[0008] Methods for solving problems According to this specification, an adhesive sheet having an adhesive layer is provided. The adhesive layer comprises a polymer, a monomer, and a thermal polymerization initiator. Furthermore, the polymer comprises an olefinically unsaturated group. Additionally, the monomer comprises monomer A. Monomer A has a molecular weight of 250 to 5000 and contains one or two olefinically unsaturated groups within its molecule. Based on the above configuration, by heat treatment, the polymer and the olefinically unsaturated groups of the monomer (specifically monomer A) in the adhesive layer react, reducing the peel force and enabling easy peeling after heating. Furthermore, since the adhesive layer comprises monomer A with a molecular weight of 250 to 5000 and containing one or two olefinically unsaturated groups within its molecule, it is possible to balance low contamination of the adhered object after heating and easy peeling after heating.

[0009] In some embodiments, the content of the thermal polymerization initiator in the adhesive layer is 0.1 parts by weight or more relative to 100 parts by weight of the polymer. By using a specified amount or more of the thermal polymerization initiator, the collision frequency between the thermal polymerization initiator and the olefinic unsaturated groups is high, and the reaction of the olefinic unsaturated groups is easy to carry out upon heating, thus ideally achieving heat-resistant peelability.

[0010] In some preferred embodiments, the monomer A described above has an ionic site. By using a monomer having an ionic site as monomer A, the effects of the technology disclosed herein can be ideally achieved.

[0011] The adhesive sheet disclosed herein is preferred for use in various methods of removing it from an adhesive surface after it has been applied, due to its reduced contamination of the surface and good peelability. For example, it is preferred for use in methods including: a processing step of processing the adhesive surface to which the adhesive sheet is applied; and a peeling step of peeling the adhesive sheet from the adhesive surface after the processing step.

[0012] Furthermore, according to this specification, a structure comprising any of the adhesive sheets disclosed herein and a substrate to which the adhesive sheet is attached can be provided. The adhesive sheets disclosed herein are used, for example, in a structure comprising an adhesive sheet and a substrate after being attached to a substrate which is the adherend.

[0013] Additionally, according to this specification, a method for manufacturing a structure having any of the adhesive sheets and substrates disclosed herein can be provided. This manufacturing method includes the step of attaching the adhesive sheet to the substrate. The adhesive sheets disclosed herein are used, for example, in the form of a structure obtained as described above.

[0014] Furthermore, the adhesive sheet disclosed herein is preferably used for processing the substrate to which it is applied. Therefore, according to this specification, for example, a method can be provided that includes processing a substrate to which any of the adhesive sheets disclosed herein is attached. This method may further include a peeling step after the aforementioned processing step to remove the adhesive sheet from the substrate. The adhesive sheet disclosed herein is suitable for various methods including such a peeling step because it reduces surface contamination of the substrate and has good easy peelability. Attached Figure Description

[0015] [ Figure 1 This is a cross-sectional view schematically showing one example of an adhesive sheet. Detailed Implementation

[0016] The following describes suitable embodiments of the present invention. Matters necessary for carrying out the present invention, except as specifically mentioned in this specification, can be understood by those skilled in the art based on the teachings on carrying out the invention as set forth in this specification and the technical common sense at the time of filing. The present invention can be carried out based on the disclosures in this specification and the technical common sense in the field.

[0017] It should be noted that in the following figures, the same reference numerals are sometimes used to describe components or parts that perform the same function, and repeated descriptions are sometimes omitted or simplified. Furthermore, the embodiments described in the figures are schematic for the purpose of clearly illustrating the invention and do not necessarily represent the exact dimensions or scaled-down versions of the actual product provided.

[0018] In this specification, the term "base polymer" in the adhesive refers to the main component of the rubber-like polymer contained in the adhesive. The aforementioned rubber-like polymer refers to a polymer that exhibits rubber-like elasticity in a temperature range near room temperature. Furthermore, in this specification, the term "main component," unless otherwise specified, refers to the component contained in a proportion exceeding 50% by weight.

[0019] In this specification, "acrylic polymer" refers to a polymer comprising monomer units derived from a monomer having at least one (meth)acryloyl group in one molecule as monomer units constituting the polymer. In this specification, acrylic polymer is defined as a polymer comprising monomer units derived from acrylic monomers.

[0020] Furthermore, in this specification, the term "acrylic monomer" refers to a monomer having at least one (meth)acryloyl group in one molecule. The term "(meth)acryloyl group" broadly refers to both acryloyl and methacryloyl groups. Therefore, the concept of acrylic monomers as used herein can include both monomers having an acryloyl group (acrylic monomers) and monomers having a methacryloyl group (methacrylic monomers). Similarly, in this specification, the term "(meth)acrylic acid" broadly refers to both acrylic acid and methacrylic acid, and the term "(meth)acrylate" broadly refers to both acrylate and methacrylate. Other similar terms are used in the same way.

[0021] Additionally, in this specification, "weight" can be replaced with "mass". For example, "weight%" can be replaced with "mass%", and "parts by weight" can be replaced with "parts by mass".

[0022] <Adhesive Sheet> The adhesive sheet disclosed herein comprises an adhesive layer. The adhesive sheet can be a substrate-supported adhesive sheet having the aforementioned adhesive layer on one or both sides of a non-peelable substrate (supporting substrate), or a substrate-free adhesive sheet (i.e., an adhesive sheet without a non-peelable substrate; typically, an adhesive sheet formed from an adhesive layer). The concept of adhesive sheet herein may include materials referred to as adhesive tape, adhesive labels, adhesive films, etc. The adhesive sheet disclosed herein can be in roll form or in single sheet form. Alternatively, it can be an adhesive sheet further processed into various shapes.

[0023] The cross-sectional structure of the adhesive sheet is shown in Figure 1 .like Figure 1 As shown, the adhesive sheet 1 has an adhesive surface 1A, and is a single-sided adhesive sheet with an adhesive layer 20 provided on one side 10A of a sheet-like substrate layer (supporting substrate) 10. The adhesive sheet 1 is used to attach the surface 20A of the adhesive layer 20, which is the adhesive surface 1A, to the object to be bonded. The back side 10B of the substrate layer 10 (the side opposite to one side 10A) is also the back side 1B of the adhesive sheet 1, constituting the outer surface of the adhesive sheet 1. Before use (i.e., before being bonded to the object), the adhesive sheet 1 can be in the form of an adhesive sheet 50 with a release liner, where the adhesive surface 1A is protected at least by a release liner 30 on the adhesive layer 20 side. Alternatively, it can be an adhesive sheet in the form where the other side (back side) 10B of the substrate layer 10 becomes the release side, and the adhesive layer 20 is pressed against the back side by the adhesive sheet 1 being rolled into a roll so that the surface (adhesive surface 1A) is protected.

[0024] <Adhesive layer> (polymer) In the technology disclosed herein, the type of adhesive is not particularly limited. The adhesive layer may contain one or more polymers selected from various rubber-like polymers, such as acrylic polymers, rubber polymers (e.g., natural rubber, synthetic rubber, mixtures thereof), polyester polymers, urethane polymers, polyether polymers, silicone polymers, polyamide polymers, and fluoropolymers, which are applicable in the field of adhesives. These polymers serve as the base polymer in the adhesive and function as the structural polymer constituting the adhesive. From the viewpoints of adhesive performance and cost, adhesives containing acrylic polymers or rubber polymers as the base polymer are preferred. Among these, adhesives using acrylic polymers with excellent heat resistance as the base polymer (acrylic adhesives) are preferred.

[0025] The following description focuses primarily on acrylic adhesives and adhesive sheets having an adhesive layer composed of such adhesives, i.e., acrylic adhesive layers, but is not intended to limit the adhesive layers disclosed herein to acrylic adhesive layers.

[0026] (Acrylic polymer) In some methods, an acrylic polymer is used where more than 50% by weight of the monomer components constituting the polymer are acrylic monomers. It is suitable for the acrylic monomers to account for 60% by weight or more of the monomer components, preferably 70% by weight or more, more preferably 80% by weight or more, even more preferably 85% by weight or more, and for example, 90% by weight or more. The upper limit for the proportion of acrylic monomers in the monomer components constituting the acrylic polymer is 100% by weight. From the viewpoint of obtaining the effect of using non-acrylic monomers, the proportion of acrylic monomers can be, for example, 98% by weight or less, 95% by weight or less, or 92% by weight or less. One acrylic monomer can be used alone, or two or more can be used in combination.

[0027] In some preferred embodiments, the monomer component comprises an alkoxy-containing (meth)acrylate. Acrylic polymers comprising an alkoxy-containing (meth)acrylate as a monomer component tend to exhibit good adhesion and, for example, good compatibility with monomers contained in the adhesive layer described later (hereinafter sometimes referred to as "combining monomers" for the purpose of distinguishing them from the monomer components used in the synthesis of the polymer). Alkoxy-containing (meth)acrylates can be used alone or in combination of two or more.

[0028] Examples of alkoxy-containing (meth)acrylates include alkoxyalkyl (meth)acrylates such as methoxyethyl (meth)acrylate, 3-methoxypropyl (meth)acrylate, 2-ethoxyethyl (meth)acrylate, propoxyethyl (meth)acrylate, butoxyethyl (meth)acrylate, and ethoxypropyl (meth)acrylate; alkoxyalkyl (meth)acrylates such as methoxydiethylene glycol (meth)acrylate, methoxydipropylene glycol (meth)acrylate, ethoxydiethylene glycol (meth)acrylate, ethoxydipropylene glycol (meth)acrylate, methoxypolyethylene glycol (meth)acrylate, methoxypolypropylene glycol (meth)acrylate, ethoxypolyethylene glycol (meth)acrylate, and ethoxypolypropylene glycol (meth)acrylate; and so on. Among them, alkoxyalkyl (meth)acrylates are preferred, and more preferably, alkoxyalkyl (meth)acrylates having an alkoxy group having 1 to 4 carbon atoms (e.g., 1, 2 or 3 carbon atoms) are preferred, and methoxyethyl (meth)acrylates are particularly preferred.

[0029] There is no particular limitation on the content of alkoxy-containing (meth)acrylates in the monomer components constituting acrylic polymers. From the viewpoint of effectively obtaining the effects brought about by the use of alkoxy-containing (meth)acrylates, the content of alkoxy-containing (meth)acrylates in the aforementioned monomer components is generally about 1% by weight or more, for example, 10% by weight or more, or 30% by weight or more. In some embodiments, from the viewpoint of adhesive properties such as adhesive strength and compatibility with coordinating monomers, the content of alkoxy-containing (meth)acrylates in the aforementioned monomer components is, for example, more than 30% by weight, preferably 40% by weight or more, more preferably 50% by weight or more (e.g., more than 50% by weight), and even more preferably 55% by weight or more. From the viewpoint of introducing alkoxy-type unsaturated groups into the polymer and obtaining other comonomers such as monomers containing functional groups, in some embodiments, the upper limit of the content of alkoxy-containing (meth)acrylate in the monomer component is about 99% by weight or less, which can be 90% by weight or less, preferably 80% by weight or less, more preferably 70% by weight or less, even more preferably 65% ​​by weight or less, and may also be 60% by weight or less.

[0030] In other embodiments, the monomeric component constituting the acrylic polymer may be a chain alkyl (meth)acrylate containing a straight-chain or branched alkyl group having 1 to 20 carbon atoms at the ester terminus. Hereinafter, chain alkyl (meth)acrylates having an alkyl group having X to Y carbon atoms at the ester terminus will sometimes be designated as "C". X-Y"Alkyl (meth)acrylates". It should be noted that in this specification, the term "chain" is used to include both linear and branched chains. The aforementioned chain alkyl (meth)acrylates can be used alone or in combination of two or more.

[0031] As C 1-20 Non-limiting specific examples of alkyl (meth)acrylates include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, sec-butyl (meth)acrylate, tert-butyl (meth)acrylate, amyl (meth)acrylate, isoamyl (meth)acrylate, hexyl (meth)acrylate, heptyl (meth)acrylate, octyl (meth)acrylate, isooctyl (meth)acrylate, and 2-ethylhexyl (meth)acrylate. Nonyl methacrylate, isononyl methacrylate, decyl methacrylate, isodecyl methacrylate, undecyl methacrylate, dodecyl methacrylate, tridecyl methacrylate, tetradecyl methacrylate, pentadecyl methacrylate, hexadecyl methacrylate, heptadecanyl methacrylate, stearyl methacrylate, isostearyl methacrylate, nonadecanyl methacrylate, eicosyl methacrylate, etc.

[0032] Using C 1-20 In the manner in which alkyl (meth)acrylates are used as monomeric components constituting acrylic polymers, as C 1-20 Alkyl (meth)acrylates, preferably using at least C 4-20 Alkyl (meth)acrylates, more preferably using at least C 4-18 Alkyl (meth)acrylates. In some cases, as C 1-20 Alkyl (meth)acrylates, preferably using C 4-8 Alkyl (meth)acrylates. More preferably, C... 4-8 Alkyl acrylate. C 4-8 Alkyl (meth)acrylates can be used alone or in combination of two or more. (C) 4-8 The use of alkyl (meth)acrylates tends to readily yield good adhesive properties (adhesive strength, etc.). For example, as the monomer components mentioned above, acrylic polymers containing one or both of n-butyl acrylate (BA) and 2-ethylhexyl acrylate (2EHA) are preferred, and acrylic polymers containing at least 2EHA are particularly preferred. Furthermore, when using C... 1-20 In other ways of using alkyl (meth)acrylates, C is preferred. 7-12 Alkyl (meth)acrylates. C 7-12Alkyl (meth)acrylates can be used alone or in combination of two or more. As C 7-12 Alkyl (meth)acrylate, preferably C 7-10 Alkyl acrylate, more preferably C 7-9 Alkyl acrylates, more preferably C8 alkyl acrylates.

[0033] Using C 1-20 In the manner in which alkyl (meth)acrylates are used as monomeric components constituting acrylic polymers, the C in the aforementioned monomeric components... 1-20 There are no particular restrictions on the content of alkyl (meth)acrylates. From effectively obtaining C 1-20 Considering the effects of using alkyl (meth)acrylates, in some methods, the C in the aforementioned monomer components... 1-20 The content of alkyl (meth)acrylates is typically about 1% by weight or more, for example, it can be 10% by weight or more, 30% by weight or more, or 50% by weight or more (e.g., more than 50% by weight). Furthermore, considering the effect of introducing olefinically unsaturated groups into the polymer to obtain other comonomers in some methods, the above C... 1-20 The content of alkyl (meth)acrylates is approximately 99% by weight or less, but can be less than 90% by weight, approximately 70% by weight or less, less than 50% by weight (e.g., less than 50% by weight), less than 30% by weight, less than 10% by weight, less than 1% by weight, or less than 0.1% by weight. The above monomer components can also be substantially free of C. 1-20 The components of alkyl (meth)acrylates.

[0034] In some embodiments, the monomer components constituting the acrylic polymer preferably include monomers other than the aforementioned alkoxyalkyl (meth)acrylates and chain alkyl (meth)acrylates. Such other monomers can be monomers capable of copolymerizing with alkoxyalkyl (meth)acrylates and chain alkyl (meth)acrylates (copolymeric monomers). These other monomers can, for example, be used to introduce olefinically unsaturated groups into the polymer. As these other monomers, monomers having polar groups (e.g., carboxyl groups, hydroxyl groups, nitrogen-containing rings, etc.) can be suitably used. Monomers with polar groups can help introduce crosslinking points into the acrylic polymer and improve the cohesive strength of the adhesive. Other monomers can be used alone or in combination of two or more.

[0035] Other monomers include, for example, monomers containing carboxyl groups, monomers containing acid anhydride groups, monomers containing hydroxyl groups, monomers containing amide groups, monomers containing amino groups, monomers with a ring containing a nitrogen atom, monomers containing sulfonic acid groups or phosphate groups, monomers containing epoxy groups, monomers containing cyano groups, monomers containing isocyanate groups, monomers with a succinimide skeleton, maleimides, itaconimides, aminoalkyl esters of (meth)acrylate, monomers containing alkoxysilyl groups, vinyl esters, vinyl ethers, aromatic vinyl compounds, alkenes, (meth)acrylates with alicyclic hydrocarbon groups, (meth)acrylates with aromatic hydrocarbon groups, and heterocyclic (meth)acrylates such as tetrahydrofurfuryl (meth)acrylate, vinyl chloride, (meth)acrylates containing halogen atoms such as (meth)acrylates containing fluorine atoms, (meth)acrylates containing silicon atoms such as organosilicon (meth)acrylates, and (meth)acrylates obtained from terpene compound derivative alcohols.

[0036] When using other monomers as described above, there is no particular limitation on their usage amount; setting it to 1% or more of the total monomer component is suitable. From the viewpoint of better utilizing the effects of other monomers, the usage amount can be set to 10% or more, 20% or more, or 30% or more of the total monomer component. Furthermore, from the viewpoint of easily obtaining a balanced adhesive property, the usage amount of other monomers is suitable to be 60% or less of the total monomer component, preferably 50% or less (e.g., less than 50% by weight), and can also be 45% or less.

[0037] In some methods, the monomer components constituting acrylic polymers include monomers containing nitrogen atoms. The use of nitrogen-containing monomers enhances the cohesive force of the adhesive and ideally improves the adhesive strength. Examples of nitrogen-containing monomers include amide-containing monomers, amino-containing monomers, and monomers with nitrogen-containing rings. One nitrogen-containing monomer can be used alone, or two or more can be used in combination.

[0038] The following monomers can be cited as examples of monomers that are not limited to those containing nitrogen atoms.

[0039] Monomers containing amide groups: Examples include (meth)acrylamide; N,N-dimethyl (meth)acrylamide, N,N-diethyl (meth)acrylamide, N,N-dipropyl (meth)acrylamide, N,N-diisopropyl (meth)acrylamide, N,N-di(n-butyl) (meth)acrylamide, N,N-di(tert-butyl) (meth)acrylamide, etc.; N-monoalkyl (meth)acrylamides such as N-ethyl (meth)acrylamide, N-isopropyl (meth)acrylamide, N-butyl (meth)acrylamide, N-n-butyl (meth)acrylamide; N-vinylacetamide and other N-vinylcarboxylic acid amides; monomers with hydroxyl and amide groups, such as N-(2-hydroxyethyl) (meth)acrylamide, N... - (2-hydroxypropyl) (meth)acrylamide, N-(1-hydroxypropyl) (meth)acrylamide, N-(3-hydroxypropyl) (meth)acrylamide, N-(2-hydroxybutyl) (meth)acrylamide, N-(3-hydroxybutyl) (meth)acrylamide, N-(4-hydroxybutyl) (meth)acrylamide and other N-hydroxyalkyl (meth)acrylamides; monomers having alkoxy and amide groups, such as N-methoxymethyl (meth)acrylamide, N-methoxyethyl (meth)acrylamide, N-butoxymethyl (meth)acrylamide and other N-alkoxyalkyl (meth)acrylamides; and N,N-dimethylaminopropyl (meth)acrylamide, alkoxydiacetone (meth)acrylamide, vinylformamide, vinylacetamide and other such monomers.

[0040] Amino-containing monomers: for example, aminoethyl methacrylate, N,N-dimethylaminoethyl methacrylate, and tert-butylaminoethyl methacrylate.

[0041] Monomers having a ring containing a nitrogen atom: for example, N-vinyl-2-pyrrolidone, N-methylvinylpyrrolidone, N-vinylpyridine, N-vinylpiperidone, N-vinylpyrimidine, N-vinylpiperazine, N-vinylpyrrazine, N-vinylpyrrole, N-vinylimidazolium, N-vinyloxazole, N-(meth)acryloyl-2-pyrrolidone, N-(meth)acryloylpiperidine, N-(meth)acryloylpyrrolidine, N-(meth)acryloylmorpholine, N-vinylmorpholine, N-vinyl-3-morpholinone, N-vinyl-2-caprolactam, N-vinyl-1,3-oxazin-2-one, N-vinyl-3,5-morpholinedione, N-vinylpyrazole, N-vinylisooxazole, N-vinylthiazole, N-vinylisothiazole, N-vinylpyridazine, etc. (e.g., N-vinyl-2-caprolactam and other lactams).

[0042] Suitable examples of monomers having nitrogen atoms include monomers having a ring containing nitrogen atoms. Among these, N-vinyl-2-pyrrolidone (NVP) and N-acryloylmorpholine (ACMO) are preferred.

[0043] There is no particular limitation on the amount of nitrogen-containing monomers (preferably monomers with nitrogen-containing rings) used. In some embodiments, the amount of nitrogen-containing monomers in the monomer composition may be 1% by weight or more, or 3% by weight or more. In some preferred embodiments, the amount of nitrogen-containing monomers in the monomer composition may be 5% by weight or more, more preferably 7% by weight or more, even more preferably 9% by weight or more, and may be 10% by weight or more, 12% by weight or more, or 14% by weight or more. The more nitrogen-containing monomers are used, the greater the cohesive force of the adhesive tends to be. In addition, in some embodiments, it is suitable to set the amount of nitrogen-containing monomers to be, for example, 40% by weight or less of the total monomer composition, or 35% by weight or less. In some preferred embodiments, the amount of nitrogen-containing monomers in the monomer composition may be 30% by weight or less, more preferably 25% by weight or less, even more preferably 20% by weight or less, or 18% by weight or less.

[0044] In some methods, the monomer component includes hydroxyl-containing monomers. The use of hydroxyl-containing monomers can adjust the cohesive strength and crosslinking density of the adhesive, and improve its adhesive strength. Furthermore, hydroxyl-containing monomers are also preferably used as a means of introducing olefinic unsaturated groups into the polymer. Examples of hydroxyl-containing monomers include, for example, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 8-hydroxyoctyl (meth)acrylate, 10-hydroxydecyl (meth)acrylate, 12-hydroxylauryl (meth)acrylate, and methyl (4-hydroxymethylcyclohexyl)acrylate, as well as hydroxyalkyl (meth)acrylate esters. For example, 2-hydroxyethyl acrylate (HEA) and 4-hydroxybutyl acrylate (4HBA) are preferred. One hydroxyl-containing monomer can be used alone, or two or more can be used in combination.

[0045] There is no particular limitation on the amount of hydroxyl-containing monomer used. For example, it can be 0.01% or more, 0.1% or more, or 0.5% or more of the total monomer component. In some embodiments, the amount of hydroxyl-containing monomer used is 1% or more of the total monomer component, more preferably 2% or more, or 3% or more. In some preferred embodiments, the amount of hydroxyl-containing monomer used is 5% or more of the total monomer component, more preferably 7% or more, further preferably 10% or more, and particularly preferably 12% or more. Such an amount of hydroxyl-containing monomer is suitable when using the hydroxyl-containing monomer as a means of introducing olefinic unsaturated groups into the polymer. In addition, in some embodiments, it is suitable to set the amount of hydroxyl-containing monomer used to be, for example, 40% or less of the total monomer component, preferably 30% or less, more preferably 20% or less, and further preferably 15% or less.

[0046] In some preferred embodiments, regarding the monomer composition of the acrylic polymer, monomers with polar groups (monomers containing polar groups) are combined with monomers containing nitrogen atoms (e.g., amide-containing monomers such as (meth)acrylamide, and monomers with nitrogen-containing rings such as NVP and ACMO) and monomers containing hydroxyl atoms (e.g., HEA, 4HBA). This achieves a good balance between adhesive and cohesive strength. In the method of combining monomers with nitrogen atoms and monomers containing hydroxyl atoms, the amount A of the monomer with nitrogen atoms... N Amount A of hydroxyl-containing monomers OH weight ratio (A) N / A OH There are no specific limitations; for example, it can be 0.1 or higher, 0.5 or higher, 1.0 or higher, 1.2 or higher, 1.5 or higher, or 1.8 or higher. Additionally, the above weight ratio (A) N / A OH For example, it can be below 10, below 5, below 3, or below 2.5.

[0047] In some methods, the monomer component may include a carboxyl-containing monomer. Non-limiting examples of carboxyl-containing monomers include acrylic acid (AA), methacrylic acid (MAA), carboxyethyl methacrylate, carboxypentyl methacrylate, itaconic acid, maleic acid, fumaric acid, crotonic acid, and isocrotonic acid. Suitable examples include AA and MAA. One carboxyl-containing monomer may be used alone or in combination of two or more. For example, AA and MAA may be used together.

[0048] The amount of carboxyl-containing monomers used can be, for example, 0.01% by weight or more, 0.1% by weight or more, 1% by weight or more, 3% by weight or more, 6% by weight or more, or 8% by weight or more of the total monomer component. The more carboxyl-containing monomers used, the greater the cohesive force of the adhesive tends to be. The aforementioned proportions of carboxyl-containing monomers can be, for example, 20% by weight or less, 10% by weight or less, 3% by weight or less, 1% by weight or less (e.g., less than 1% by weight), or 0.1% by weight or less. The aforementioned monomer component can also be a component that substantially does not contain carboxyl-containing monomers.

[0049] Furthermore, as other monomers, monomers having a functional group (functional group A) that reacts with the functional group (functional group B) of compounds having olefinic unsaturated groups as described later are preferably used. In this manner, the type of other monomer is determined according to the types of compounds described above. As other monomers having functional group A, for example, monomers containing carboxyl groups, monomers containing epoxy groups, monomers containing hydroxyl groups, and monomers containing isocyanate groups are preferred, with monomers containing hydroxyl groups being particularly preferred. By using monomers containing hydroxyl groups as other monomers, acrylic polymers possess hydroxyl groups. In contrast, as compounds having olefinic unsaturated groups, for example, by using monomers containing isocyanate groups, the hydroxyl groups of the acrylic polymer react with the isocyanate groups of the aforementioned compound, and olefinic unsaturated groups derived from the aforementioned compound are introduced into the acrylic polymer.

[0050] Furthermore, when other monomers are used for the purpose of reacting with compounds having olefinic unsaturated groups, from the viewpoint of adhesive properties such as thermosetting properties and cohesive strength, it is suitable to set the amount of the aforementioned other monomers (preferably monomers containing hydroxyl groups) to be about 1% by weight or more of the total monomer composition, preferably about 5% by weight or more, more preferably about 10% by weight or more, and also about 12% by weight or more. Furthermore, from the viewpoint of maintaining adhesive properties such as adhesion strength well, it is suitable to set the amount of the aforementioned other monomers to be about 40% by weight or less of the total monomer composition, preferably about 30% by weight or less, more preferably about 25% by weight or less, and also about 20% by weight or less (e.g., 15% by weight or less).

[0051] In acrylic polymers, polyfunctional monomers having at least two olefinically unsaturated groups such as (meth)acryloyl groups and vinyl groups may be included as other monomer components. By using polyfunctional monomers as monomer components, the cohesive strength of the adhesive can be improved. Polyfunctional monomers can also be used as crosslinking agents. There are no particular limitations on the polyfunctional monomer used; for example, one or more suitable polyfunctional monomers exemplified as coordinating monomers contained in the adhesive layer described later can be used alone or in combination.

[0052] There is no particular limitation on the amount of the multifunctional monomer used, and it can be appropriately set in a way that achieves the intended use of the multifunctional monomer. The amount of the multifunctional monomer used can be set to about 3% by weight or less of the monomer component, preferably about 2% by weight or less, and more preferably about 1% by weight or less (e.g., about 0.5% by weight or less). The lower limit of the amount used when using the multifunctional monomer is greater than 0% by weight, and there is no particular limitation. Generally, by setting the amount of the multifunctional monomer used to about 0.001% by weight or more of the monomer component (e.g., about 0.01% by weight or more), the effect of the multifunctional monomer can be appropriately exerted.

[0053] There are no particular limitations on the method for obtaining acrylic polymers. Various known polymerization methods, such as solution polymerization, emulsion polymerization, bulk polymerization, suspension polymerization, and photopolymerization, can be appropriately employed. For example, solution polymerization is preferred. As for the monomer supply method during solution polymerization, appropriate methods include one-time feeding of all monomer raw materials, continuous feeding (dropwise addition), and batch feeding (dropwise addition). The polymerization temperature can be appropriately selected based on the type of monomer and solvent used, as well as the type of polymerization initiator; for example, it can be set to approximately 20°C to 170°C (typically approximately 40°C to 140°C).

[0054] The solvent used in solution polymerization (polymerization solvent) can be appropriately selected from conventionally known organic solvents. For example, any one solvent or a mixture of two or more solvents can be used, selected from aromatic compounds such as toluene (typically aromatic hydrocarbons); acetates such as ethyl acetate; aliphatic or alicyclic hydrocarbons such as hexane and cyclohexane; haloalkanes such as 1,2-dichloroethane; lower alcohols such as isopropanol (e.g., monohydric alcohols with 1 to 4 carbon atoms); ethers such as tert-butyl methyl ether; ketones such as methyl ethyl ketone; etc.

[0055] The initiator used in the polymerization can be appropriately selected from conventionally known polymerization initiators, depending on the type of polymerization method. For example, without particular limitation, azo polymerization initiators, peroxide polymerization initiators, redox polymerization initiators based on combinations of peroxides and reducing agents, substituted ethane polymerization initiators, etc., can be used. As a polymerization initiator, for example, one or more of the substances exemplified as thermal polymerization initiators added to the binder layer described later can be selected and used.

[0056] The amount of polymerization initiator used can be set to the usual amount corresponding to the polymerization method and polymerization mode, and there is no particular limitation. For example, about 0.001 to 5 parts by weight (typically about 0.01 to 2 parts by weight, for example about 0.01 to 1 part by weight) of polymerization initiator can be used relative to 100 parts by weight of all monomer components of the polymer.

[0057] (Polymers with olefinic unsaturated groups) The adhesive layer disclosed herein comprises a polymer having olefinically unsaturated groups. These olefinically unsaturated groups function as polymerizable functional groups (typically free radical polymerizable functional groups). As a polymer having olefinically unsaturated groups, one or more suitable polymers can be selected from various polymers exemplified as described above (e.g., acrylic polymers) and polymers having olefinically unsaturated groups. The polymer having olefinically unsaturated groups can be used as a base polymer in the adhesive. Examples of olefinically unsaturated groups in the polymer include acryloyl, methacryloyl, vinyl, and allyl groups, but are not limited to these. Suitable examples of olefinically unsaturated groups include acryloyl and methacryloyl. According to the adhesive comprising the polymer having olefinically unsaturated groups, the olefinically unsaturated groups of the polymer react during heat treatment, enabling the adhesive to be thermo-cured with a high degree of curing, resulting in heat-resistant peelability. More specifically, adhesives typically adhere to the surface of the adhered objects when applied, for example, when heated at high temperatures. This increases the adhesive's bond strength, leading to re-peeling. According to the technology disclosed herein, by including a polymer with olefinically unsaturated groups, a coordinating monomer, and a thermal polymerization initiator in the adhesive, the olefinically unsaturated groups in the adhesive react upon heating (free radical polymerization), allowing the adhesive to cure before adsorption to the adhered objects. This reduces the peel force on the adhered objects. Even if heating continues, the peel force does not increase but remains within a specified range, thus providing excellent heat-resistant peelability. It should be noted that the technology disclosed herein is not limited to the above considerations. Furthermore, adhesives containing polymers with olefinically unsaturated groups can achieve sufficient heat-resistant peelability and heat-resistant peelability while limiting the amount of coordinating monomer used.

[0058] In some embodiments, polymers having olefinic unsaturated groups on their side chains can be used as polymers having olefinic unsaturated groups. As monomer components of the polymer having olefinic unsaturated groups, one or more examples of monomer components of the aforementioned polymers can be used within the aforementioned content range.

[0059] The amount of olefinic unsaturated groups in polymers containing olefinic unsaturated groups is not particularly limited. From the viewpoint of thermosetting properties, it is suitable to set it to 0.01 mmol (hereinafter also referred to as mmol / g) or more per 1g of polymer, which can be 0.1 mmol / g or more, or 0.5 mmol / g or more. Furthermore, it is suitable to set the amount of olefinic unsaturated groups in the above-mentioned polymer to be 10.0 mmol / g or less, which can be 5.0 mmol / g or less, 3.0 mmol / g or less, 2.5 mmol / g or less, or 2.0 mmol / g or less.

[0060] The amount of olefinic unsaturated groups in the polymer, for example, in the case where the olefinic unsaturated group is (meth)acryloyl, is determined by the following method.

[0061] First, 0.25 mg of the polymer to be tested was dissolved in 50 mL of THF (tetrahydrofuran), and then 15 mL of methanol was added to obtain a solution. Next, 10 mL of 4N sodium hydroxide aqueous solution was added to the above solution to obtain a mixture. Then, the mixture was stirred at 40°C for 2 hours. Further, 10.2 mL of 4N methanesulfonic acid solution was added to the mixture, and the mixture was stirred. Then, 5 mL of deionized water was added, followed by 2 mL of methanol, to prepare the test solution.

[0062] The content of (meth)acrylic acid in the test solution was determined by HPLC (High Performance Liquid Chromatography) (absolute standard curve method), and the content of olefinic unsaturated groups was calculated.

[0063] (HPLC determination conditions) Column: Phenomenex Synergi 4μ Polar-RP 80A (4.6mm × 250mm) Column temperature: 40℃ Flow rate: 1.0 mL / min Detector wavelength: 210nm Eluent: THF (for HPLC) 55 / Buffer (containing 0.2% phosphate, 0.2% triethylamine) 45 Aqueous solution injection volume: 5 μL As a method for determining the content of olefinic unsaturated groups other than (meth)acryloyl groups, one example is the method for determining the bromine value according to JIS K2605:1996. In this method, the content of olefinic unsaturated groups other than (meth)acryloyl groups can be determined by converting the number of grams of bromine (Br2) added to 100g of the polymer being tested into the number of moles of bromine (Br2) added to 1g of the polymer.

[0064] The method for introducing olefinically unsaturated groups into polymers is not particularly limited, and suitable methods known to those skilled in the art can be selected. From the viewpoint of molecular design, methods that introduce olefinically unsaturated groups into the side chains of polymers are preferred. For example, it is preferable to use a method in which a compound having a functional group (functional group B) that can react with a functional group (functional group A) introduced into an acrylic polymer through copolymerization and an olefinically unsaturated group reacts in a manner that the olefinically unsaturated group does not disappear (typically condensation or addition reactions). Examples of combinations of functional group A and functional group B include combinations of carboxyl and epoxy groups, combinations of carboxyl and aziridinyl groups, and combinations of hydroxyl and isocyanate groups. Among these, combinations of hydroxyl and isocyanate groups are preferred from the viewpoint of reaction traceability. From the viewpoint of polymer design, combinations in which the acrylic polymer has hydroxyl groups and the above-mentioned compounds have isocyanate groups are particularly preferred.

[0065] The compounds having olefinic unsaturated groups described above may, as explained above, have a functional group B that can react with functional group A. Suitable examples of such compounds include, for instance, monomers containing isocyanate groups (compounds containing isocyanate groups), such as 2-(meth)acryloyloxyethyl isocyanate. More preferably, 2-(meth)acryloyloxyethyl isocyanate. By reacting the isocyanate group of the compound having olefinic unsaturated groups with the hydroxyl groups of the acrylic polymer to form a bond (specifically, a urethane bond), an acrylic polymer having olefinic unsaturated groups can be obtained.

[0066] The amount of the compound having an olefinic unsaturated group (e.g., a monomer containing an isocyanate group) added is not particularly limited. From the viewpoint of reactivity with functional group A (e.g., hydroxyl group) in the polymer, the amount of the compound can be determined by the molar ratio (M) of the aforementioned functional group A. A The molar ratio of ) to functional group B (isocyanate group) (M) B molar ratio (M) A / M B The value is set to a range of approximately 0.5 to 2 (e.g., 1 to 1.5).

[0067] It should be noted that the adhesive layer may also contain a polymer that is substantially free of olefinic unsaturated groups (the amount of olefinic unsaturated groups is less than 0.01 mmol / g) without impairing the effects of the technology disclosed herein. It is suitable that the amount of this substantially olefinic unsaturated polymer used is less than 50% by weight of the total polymer (specifically the base polymer) contained in the adhesive layer, and may be less than 30% by weight, less than 10% by weight, less than 3% by weight, or less than 1% by weight. The adhesive layer may also be a component substantially free of the aforementioned substantially olefinic unsaturated polymer.

[0068] The molecular weight of the polymer (e.g., acrylic polymers) is not particularly limited and can be set within a suitable range according to required performance. The weight-average molecular weight (Mw) of the above polymers is approximately 1 × 10⁻⁶. 4 The above is suitable; for example, it could be approximately 10×10. 4 The above. By using polymers with a Mw value greater than or equal to the specified value, a good balance between cohesive and adhesive strength can be achieved. In some cases, from the viewpoint of obtaining heat resistance and good adhesion, the aforementioned Mw can be 20 × 10. 4 The above can be 30×10 4 The above can be approximately 40×10 4 The above can be approximately 50×10 4 The above, for example, could also be approximately 55 × 10. 4 That's all. There is no particular upper limit to the Mw of the aforementioned polymer; for example, it can be approximately 1000 × 10⁻⁶. 4 The following can also be approximately 100×10 4 Below. Here, Mw refers to the value obtained by gel permeation chromatography (GPC) converted to standard polystyrene. For example, a GPC device can be used, such as the model name "HLC-8320GPC" (column: TSKgelGMH-H(S), manufactured by Tosoh Corporation).

[0069] (monomer) In addition to the polymer described above, the adhesive layer also contains monomers (coordinating monomers). These monomers typically possess olefinically unsaturated groups. The olefinically unsaturated groups of these monomers function as polymerizable functional groups (typically free radical polymerizable functional groups). By including these monomers in the adhesive layer, the monomers are contained in the adhesive layer in a pre-reaction (unreacted) state. Therefore, after the adhesive layer is formed, the monomers contained in the adhesive layer react rapidly with the olefinically unsaturated groups of the polymer during heat treatment, and the adhesive undergoes thermosetting with a high degree of curing, exhibiting excellent heat-resistant peelability. By including these monomers, a thermosetting adhesive that retains heat resistance and peelability after heat treatment can be formed. One of the monomers can be used alone, or two or more can be used in combination.

[0070] Examples of olefinically unsaturated groups in the aforementioned monomers include acryloyl, methacryloyl, vinyl, and allyl groups, but are not limited thereto. Suitable examples of olefinically unsaturated groups include acryloyl and methacryloyl. Acryloyl is preferred. Hereinafter, compounds having acryloyl and / or methacryloyl groups are sometimes referred to as acrylic monomers. Additionally, compounds having vinyl groups are sometimes referred to as vinyl monomers.

[0071] While not specifically limited, monomers with a molecular weight of 100 or higher are suitable as described above. In some preferred embodiments, the molecular weight of the monomer may be, for example, 150 or higher, 250 or higher, 300 or higher, 350 or higher, 400 or higher, 450 or higher, or 500 or higher. Furthermore, the molecular weight of the monomer is generally about 100,000 or less, for example, about 10,000 or less (e.g., less than 10,000) is suitable, preferably 5,000 or less (e.g., less than 5,000), 1,500 or less, 1,000 or less (e.g., less than 1,000), 800 or less, or 600 or less. The use of monomers with molecular weights within the above ranges becomes advantageous from, for example, the ease of preparation and coatability of the adhesive composition. It should be noted that the above molecular weights are based on the manufacturer's nominal value or calculated from the molecular structure. For monomers with molecular weights above the specified range, the weight-average molecular weight (Mw) obtained using GPC and converted to standard polystyrene can also be used.

[0072] In some preferred embodiments, the monomers used are those with a weight reduction rate of 1% or less (specifically 1.0% or less) at 180°C in a TGA (thermogravimetric analysis) under heating conditions of 10°C / min. By using a monomer with heat resistance having a weight reduction rate of 1% or less at 180°C (hereinafter also referred to as "heat-resistant monomer"), the adhesive layer has heat-removable peelability based on the presence of the monomer, and the generation of gas during heating is suppressed. By using the heat-resistant monomer, both heat-removable peelability and gas reduction can be achieved. From the viewpoint of gas reduction, in some preferred embodiments, the weight reduction rate of the heat-resistant monomer at 180°C is 0.9% or less, more preferably 0.8% or less, further preferably 0.7% or less, particularly preferably 0.6% or less, and may also be 0.5% or less. The lower limit of the weight reduction rate of the heat-resistant monomer at 180°C is theoretically 0%, but practically it can be 0.1% or more, 0.2% or more, or 0.3% or more. As heat-resistant monomers, trimethylolpropane triacrylate (TMPTA, with a weight reduction rate of 1% at 180°C) and dipentaerythritol hexaacrylate (DPHA, with a weight reduction rate of 0.5% at 180°C) are preferred. One heat-resistant monomer can be used alone, or two or more monomers can be used in combination.

[0073] Specifically, the weight loss rate of the aforementioned monomers upon heating at 180°C can be measured using a differential thermal analysis apparatus (manufactured by TA Instruments, trade name "Discovery TGA") under the following conditions: heating rate of 10°C / min, air atmosphere, and flow rate of 25 mL / min.

[0074] In some preferred embodiments, multifunctional monomers may be used as the aforementioned monomers. It should be noted that, in this specification, a multifunctional monomer refers to a polymerizable compound having two or more olefinic unsaturated groups in one molecule, and also includes substances referred to as oligomers. Hereinafter, compounds having two or more acryloyl groups and / or methacryloyl groups are sometimes referred to as multifunctional acrylic monomers. Additionally, compounds having two or more vinyl groups are sometimes referred to as multifunctional vinyl monomers.

[0075] In some preferred embodiments, the number of olefinic unsaturated groups in a molecule of the multifunctional monomer can be 3 or more, preferably 4 or more, more preferably 5 or more, and may also be 6 or more. The more olefinic unsaturated groups a multifunctional monomer has, the better its curability during heat treatment and the easier it is to achieve heat-peelability. Furthermore, multifunctional monomers with a higher number of olefinic unsaturated groups (functional groups) can achieve heat-peelability with a relatively small amount of material. This also reduces the amount of gas escape caused by the multifunctional monomer, which is advantageous. The upper limit of the number of olefinic unsaturated groups in a molecule of the multifunctional monomer is not limited to a specific range; for example, it can be 50 or less, 40 or less, 30 or less, 20 or less, or 15 or less. In some embodiments, the number of olefinic unsaturated groups in a molecule of the multifunctional monomer can be, for example, 10 or less, 8 or less, or 6 or less. Based on the number of polyfunctional monomers with the above-mentioned number of olefinic unsaturated groups, there is a tendency to easily achieve both good adhesion and easy peeling upon heating, as well as excellent storage stability.

[0076] As multifunctional monomers, various multifunctional acrylate monomers and multifunctional vinyl monomers with two or more olefinic unsaturated groups can be used. Among them, multifunctional acrylate monomers are preferred. Although not particularly limited, multifunctional acrylate monomers tend to exhibit the desired properties readily and well-compatibly when used in combination with acrylic polymers. One type of multifunctional acrylate monomer and one type of multifunctional vinyl monomer can be used alone, or two or more can be used in combination.

[0077] Examples of multifunctional monomers include 1,6-hexanediol di(meth)acrylate, 1,12-dodecanediol di(meth)acrylate, ethylene glycol di(meth)acrylate, propylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, dipropylene glycol di(meth)acrylate, tripropylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, pentaerythritol di(meth)acrylate, allyl (meth)acrylate, epoxide-modified bisphenol A di(meth)acrylate, epoxide-modified neopentyl glycol di(meth)acrylate, tricyclodecanediethanol di(meth)acrylate, dihydroxymethyldicyclopentane di(meth)acrylate, ethylene (meth)acrylate, and diethylene glycol. Difunctional monomers such as benzoylbenzene; trifunctional monomers such as trimethylolpropane tri(meth)acrylate, trimethylolpropane ethoxytri(meth)acrylate, glycerol propoxytriacrylate, tetramethylolmethane tri(meth)acrylate, and pentaerythritol tri(meth)acrylate; quadrufunctional monomers such as pentaerythritol alkoxytetra(meth)acrylate, di(trimethylolpropane)tetra(meth)acrylate, and pentaerythritol tetra(meth)acrylate; pentafunctional monomers such as sorbitol penta(meth)acrylate and dipentaerythritol penta(meth)acrylate; hexafunctional monomers such as dipentaerythritol hexa(meth)acrylate, sorbitol hexa(meth)acrylate, epoxide-modified hexa(meth)acrylate, and caprolactone-modified dipentaerythritol hexa(meth)acrylate; and epoxy acrylates, polyester acrylates, and urethane acrylates with more than two functionalities. Among preferred examples are 1,6-hexanediol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, and dipentaerythritol hexa(meth)acrylate. Dipentaerythritol hexa(meth)acrylate is particularly preferred.

[0078] In adhesive layers comprising multifunctional monomers, the content of the multifunctional monomers in the adhesive layer is not particularly limited. In some embodiments, the content of the multifunctional monomers may be approximately 1 part by weight or more, or 3 parts by weight or more, relative to 100 parts by weight of the polymer contained in the adhesive layer (specifically, the base polymer, suitably an acrylic polymer). The suitable amount of the multifunctional monomers may vary depending on their molecular weight, number of functional groups, etc. In some preferred embodiments, from the viewpoint of improving heat-resistant peelability, the content of the multifunctional monomers relative to 100 parts by weight of the polymer contained in the adhesive layer may be 5 parts by weight or more, 7 parts by weight or more, 8 parts by weight or more, 9 parts by weight or more, more preferably 10 parts by weight or more (e.g., more than 10 parts by weight), more preferably 12 parts by weight or more, even more preferably 15 parts by weight or more, and even more preferably 18 parts by weight or more. The upper limit of the content of the multifunctional monomers in the adhesive layer is not particularly limited and can be set in a manner that achieves the desired adhesive properties. In some embodiments, from the viewpoint of compatibility with the polymer (specifically, the base polymer, such as an acrylic polymer), it is suitable to set the amount of the multifunctional monomer to about 200 parts by weight or less relative to 100 parts by weight of the polymer, preferably 160 parts by weight or less, more preferably 150 parts by weight or less, even more preferably 140 parts by weight or less, and can be 120 parts by weight or less, or 90 parts by weight or less. In some preferred embodiments, the amount of the multifunctional monomer relative to 100 parts by weight of the polymer can be 70 parts by weight or less, 50 parts by weight or less (e.g., less than 50 parts by weight), 45 parts by weight or less (e.g., less than 45 parts by weight), 40 parts by weight or less, 35 parts by weight or less, 30 parts by weight or less, 25 parts by weight or less, or 20 parts by weight or less. According to the technology disclosed herein, the desired heat-peelability can be ideally achieved by limiting the amount of multifunctional monomer in the adhesive layer as described above. Furthermore, by limiting the amount of multifunctional monomers used, the generation of low-molecular-weight components derived from the multifunctional monomers is suppressed after heat treatment, thus preventing or reducing contamination of the adhered surfaces caused by these low-molecular-weight components. In addition, reducing the amount of multifunctional monomers used tends to easily yield high adhesion.

[0079] In methods using multifunctional monomers as the aforementioned monomers, the amount of the multifunctional monomer in the total monomer is not particularly limited. In some methods, from the viewpoint of effectively utilizing the effects of the multifunctional monomer, it is suitable to set the amount of the multifunctional monomer to approximately 10% by weight or more of the total monomer, preferably 30% by weight or more, and more preferably around 50% by weight or more (e.g., exceeding 50% by weight). In some preferred methods, the amount of the multifunctional monomer in the total monomer is 60% by weight or more, which can be 70% by weight or more, 80% by weight or more, 90% by weight or more, or 95% by weight or more. In other methods, the amount of the multifunctional monomer in the total monomer can be 98% by weight or more, or 99 to 100% by weight. In some methods, the monomer can be substantially formed from the multifunctional monomer. On the other hand, in methods using monofunctional monomers as monomer A (described later), from the viewpoint of effectively utilizing the added effect of monomer A, it is preferable to limit the proportion of the multifunctional monomer. From this perspective, in some approaches, the amount of multifunctional monomers can be less than approximately 99% by weight of the total monomers, less than 90% by weight, or less than 80% by weight.

[0080] Furthermore, as the aforementioned monomers, one or more monofunctional monomers containing one olefinic unsaturated group in one molecule can be used. Known monofunctional acrylate monomers and vinyl monomers can be used as monofunctional monomers. For example, one or more acrylate monomers (alkoxy-containing (meth)acrylates, chain alkyl (meth)acrylates, etc.) exemplified as monomer components of the aforementioned polymers can be used.

[0081] In some methods, surfactants having olefinic unsaturated groups (reactive surfactants) are preferably used as the aforementioned monomers. By using reactive surfactants as coordinating monomers, not only is good heat-resistant peelability obtained, but also improved light peelability after heating and low contamination of adhered objects after heating. Although not particularly limited, the number of olefinic unsaturated groups in one molecule of the reactive surfactant is preferably 1 to 2. Reactive surfactants can be used alone or in combination of two or more.

[0082] As the aforementioned reactive surfactant, surfactants having structures incorporating free radical polymerizable functional groups into anionic, cationic, or nonionic surfactants can be used, for example. Anionic or nonionic reactive surfactants are preferred. Furthermore, the aforementioned free radical polymerizable functional groups include olefinically unsaturated groups. Examples of such free radical polymerizable functional groups include vinyl, propenyl, isopropenyl, vinyl ether (ethoxy), and allyl ether (allyloxy). The concept of propenyl here includes 1-propenyl (CH3-CH=CH-) and 2-propenyl (CH2=CH-CH2-; sometimes also called allyl).

[0083] Examples of anionic reactive surfactants include polyoxyethylene (allyloxymethyl) alkyl ether sulfates (e.g., ammonium salts), polyoxyethylene nonylpropene phenyl ether sulfates (e.g., ammonium salts), alkylallyl sulfosuccinates (e.g., sodium salts), methacryloyloxy polyoxypropylene sulfates (e.g., sodium salts), and polyoxyalkylene ether sulfates (e.g., ammonium salts with an isopropene group at the end of the alkenyl group). When anionic reactive surfactants form salts, these salts can be, for example, metal salts such as sodium salts, or nonmetal salts such as ammonium salts or amine salts.

[0084] Examples of nonionic reactive surfactants include polyoxyethylene nonylpropene phenyl ether and polyoxyalkylene phenyl ether.

[0085] Commercially available reactive surfactants include those manufactured by Daiichi Kogyo Pharmaceutical Co., Ltd. under the trade names "AQUALON HS-05", "AQUALON HS-10", "AQUALON HS-1025", "AQUALON HS-20", "AQUALON KH-10", "AQUALON KH-1025", "AQUALON KH-05", "AQUALON BC-0515", "AQUALON BC-10", "AQUALON BC-1025", "AQUALON BC-20", "AQUALON BC-2020", "AQUALON RN-20", "AQUALON RN-30", "AQUALON RN-50", "AQUALON AR-10", "AQUALON AR-20", "AQUALON AR-1025", "AQUALON AR-2020", and ADEKA. Products manufactured by CORPORATION under the brand names "ADEKA REASOAP SE-10N" and "ADEKA REASOAP SR-1025"; products manufactured by Kao Corporation under the brand names "LATEMUL PD-104", "LATEMUL PD-420", "LATEMUL PD-430", and "LATEMUL PD-450"; products manufactured by Sanyo Chemical Industries, Ltd. under the brand names "ELEMINOL JS-20" and "ELEMINOL RS-3000"; and products manufactured by Nippon Emulsifier Co., Ltd. under the brand name "Antox MS-60".

[0086] In some methods, ionic liquids (reactive ionic liquids) having olefinic unsaturated groups are preferably used as the aforementioned monomers. By using reactive ionic liquids as coordinating monomers, not only is good heat-resistant peeling property obtained, but also improved light peeling property after heating and low contamination of the adhered material after heating. While not particularly limited, the number of olefinic unsaturated groups in one molecule of the reactive ionic liquid is preferably 1 to 2. Furthermore, the term "ionic liquid" (sometimes also referred to as a room-temperature molten salt) in this specification refers to a molten salt that is liquid at any temperature below 100°C. Because the aforementioned ionic liquid is liquid at any temperature below 100°C, it can be easily added to, dispersed, or dissolved in the adhesive compared to solid salts in this temperature range. In addition, ionic liquids do not have vapor pressure (non-volatile) and therefore do not disappear over time.

[0087] The aforementioned reactive ionic liquids possess ionic sites. These ionic sites can be either cationic or anionic. While not particularly limited, reactive ionic liquids possessing both cationic and anionic sites as their ionic sites are preferred. Reactive ionic liquids can be used alone or in combination with two or more types.

[0088] Examples of cations constituting the aforementioned cationic sites include pyridinium cations, piperidinium cations, pyrrolidineium cations, cations having a pyrrolinoline skeleton, cations having a pyrrole skeleton, imidazolium cations, tetrahydropyrimidineium cations, dihydropyridinium cations, pyrazolium cations, pyrazolinolineium cations, tetraalkylammonium cations, trialkylsulfonium cations, and tetraalkylphosphonium cations.

[0089] Examples of anions constituting the aforementioned anionic sites include Cl. - ,Br - AlCl4 - Al2Cl7 - BF4 - PF6 - ClO4 - NO3 - CH3COO - CF3COO - CH3SO3 - CF3SO3 - (CF3SO2)2N - (CF3SO2)3C - AsF6 - SbF6 - NbF6 - TaF6 - F (HF) n - (CN)2N - C4F9SO3 - (C2F5SO2)2N - C3F7COO - (CF3SO2)(CF3CO)N - (FSO2)2N - wait.

[0090] As the aforementioned reactive ionic liquid, an ionic liquid having a radical polymerizable functional group can be used. Specifically, it is preferable to use one or more of nitrogen-containing onium salts, sulfur-containing onium salts, and phosphorus-containing onium salts having a radical polymerizable functional group. The aforementioned radical polymerizable functional group includes an olefinic unsaturated group. Examples of the aforementioned radical polymerizable functional group include vinyl, allyl, and acryloyl groups.

[0091] Examples of such reactive ionic liquids include pyridinium cation-based ionic liquids, imidazolium cation-based ionic liquids, ammonium cation-based ionic liquids, pyridolium cation-based ionic liquids, and indole cation-based ionic liquids. They can be used alone or in combination of two or more.

[0092] Specific examples of pyridinium cation-based ionic liquids include 1-butyl-3-vinylpyridinium tetrafluoroborate, 1-butyl-3-(2-(meth)acryloyloxyethyl)pyridinium tetrafluoroborate, 1-butyl-3-(3-(meth)acryloyloxypropyl)pyridinium tetrafluoroborate, 1-butyl-3-(4-(meth)acryloyloxybutyl)pyridinium tetrafluoroborate, 1-butyl-3-(6-(meth)acryloyloxyhexyl)pyridinium tetrafluoroborate, 1-butyl-3-(8-(meth)acryloyloxyoctyl)pyridinium tetrafluoroborate, 1-butyl-3-vinylpyridinium trifluoromethanesulfonate, and 1-butyl-3-(2-(meth)acryloyloxy) Ethyl)pyridinium trifluoromethanesulfonate, 1-butyl-3-(3-(meth)acryloyloxypropyl)pyridinium trifluoromethanesulfonate, 1-butyl-3-(4-(meth)acryloyloxybutyl)pyridinium trifluoromethanesulfonate, 1-butyl-3-(6-(meth)acryloyloxyhexyl)pyridinium trifluoromethanesulfonate, 1-butyl-3-(8-(meth)acryloyloxyoctyl)pyridinium trifluoromethanesulfonate, 1-butyl-3-vinylpyridinium bis(trifluoromethanesulfonyl)imine, 1-butyl-3-(2-(meth)acryloyloxyethyl)pyridinium bis(trifluoromethanesulfonyl)imine, 1-butyl-3-(3-(meth)acryloyloxypropyl)pyridinium bis(trifluoromethanesulfonyl)imine 1-Butyl-3-(4-(meth)acryloyloxybutyl)pyridinium bis(trifluoromethanesulfonyl)imine, 1-Butyl-3-(6-(meth)acryloyloxyhexyl)pyridinium bis(trifluoromethanesulfonyl)imine, 1-Butyl-3-(8-(meth)acryloyloxyoctyl)pyridinium bis(trifluoromethanesulfonyl)imine, 1-Butyl-3-vinylpyridinium bis(pentafluoroethanesulfonyl)imine, 1-Butyl-3-(2-(meth)acryloyloxyethyl)pyridinium bis(pentafluoroethanesulfonyl)imine, 1-Butyl-3-(3-(meth)acryloyloxypropyl)pyridinium bis(pentafluoroethanesulfonyl)imine, 1-Butyl-3-(4-(meth)acryloyloxy) Butyl)pyridinium bis(pentafluoroethanesulfonyl)imine, 1-butyl-3-(6-(meth)acryloyloxyhexyl)pyridinium bis(pentafluoroethanesulfonyl)imine, 1-butyl-3-(8-(meth)acryloyloxyoctyl)pyridinium bis(pentafluoroethanesulfonyl)imine, 1-butyl-3-vinylpyridinium (trifluoromethanesulfonyl)trifluoroacetamide, 1-butyl-3-(2-(meth)acryloyloxyethyl)pyridinium (trifluoromethanesulfonyl)trifluoroacetamide, 1-butyl-3-(3-(meth)acryloyloxypropyl)pyridinium (trifluoromethanesulfonyl)trifluoroacetamide, 1-butyl-3-(4-(meth)acryloyloxybutyl)pyridinium (trifluoromethanesulfonyl)trifluoroacetamide,1-Butyl-3-(6-(meth)acryloyloxyhexyl)pyridinium (trifluoromethanesulfonyl)trifluoroacetamide, 1-Butyl-3-(8-(meth)acryloyloxyoctyl)pyridinium (trifluoromethanesulfonyl)trifluoroacetamide, etc.

[0093] Specific examples of imidazolium cationic ionic liquids include 1-ethyl-3-vinylimidazolium tetrafluoroborate, 1-ethyl-3-(2-(meth)acryloyloxyethyl)imidazolium tetrafluoroborate, 1-ethyl-3-(3-(meth)acryloyloxypropyl)imidazolium tetrafluoroborate, 1-ethyl-3-(4-(meth)acryloyloxybutyl)imidazolium tetrafluoroborate, 1-ethyl-3-(6-(meth)acryloyloxyhexyl)imidazolium tetrafluoroborate, 1-ethyl-3-(8-(meth)acryloyloxyoctyl)imidazolium tetrafluoroborate, 1-ethyl-3-vinylimidazolium trifluoroacetate, and 1-ethyl-3-(2-(meth)acryloyloxyethyl)imidazolium trifluoroacetate. Salts, 1-ethyl-3-(3-(meth)acryloyloxypropyl)imidazolium trifluoroacetate, 1-ethyl-3-(4-(meth)acryloyloxybutyl)imidazolium trifluoroacetate, 1-ethyl-3-(6-(meth)acryloyloxyhexyl)imidazolium trifluoroacetate, 1-ethyl-3-(8-(meth)acryloyloxyoctyl)imidazolium trifluoroacetate, 1-ethyl-3-vinylimidazolium heptafluorobutyrate, 1-ethyl-3-(2-(meth)acryloyloxyethyl)imidazolium heptafluorobutyrate, 1-ethyl-3-(3-(meth)acryloyloxypropyl)imidazolium heptafluorobutyrate, 1-ethyl-3-(4-(meth)acryloyloxybutyl)imidazolium heptafluorobutyrate, 1-ethyl -3-(6-(methyl)acryloyloxyhexyl)imidazolium heptafluorobutyrate, 1-ethyl-3-(8-(methyl)acryloyloxyoctyl)imidazolium heptafluorobutyrate, 1-ethyl-3-vinylimidazolium trifluoromethanesulfonate, 1-ethyl-3-(2-(methyl)acryloyloxyethyl)imidazolium trifluoromethanesulfonate, 1-ethyl-3-(3-(methyl)acryloyloxypropyl)imidazolium trifluoromethanesulfonate, 1-ethyl-3-(4-(methyl)acryloyloxybutyl)imidazolium trifluoromethanesulfonate, 1-ethyl-3-(6-(methyl)acryloyloxyhexyl)imidazolium trifluoromethanesulfonate, 1-ethyl-3-(8-(methyl)acryloyloxyoctyl)imidazolium trifluoromethanesulfonate, 1-ethyl 1-Ethyl-3-vinylimidazolium perfluorobutane sulfonate, 1-ethyl-3-(2-(meth)acryloyloxyethyl)imidazolium perfluorobutane sulfonate, 1-ethyl-3-(3-(meth)acryloyloxypropyl)imidazolium perfluorobutane sulfonate, 1-ethyl-3-(4-(meth)acryloyloxybutyl)imidazolium perfluorobutane sulfonate, 1-ethyl-3-(6-(meth)acryloyloxyhexyl)imidazolium perfluorobutane sulfonate, 1-ethyl-3-(8-(meth)acryloyloxyoctyl)imidazolium perfluorobutane sulfonate, 1-ethyl-3-vinylimidazolium bis(trifluoromethanesulfonyl)imine, 1-ethyl-3-(2-(meth)acryloyloxyethyl)imidazolium bis(trifluoromethanesulfonyl)imine,1-Ethyl-3-(3-(meth)acryloyloxypropyl)imidazolium bis(trifluoromethanesulfonyl)imine, 1-Ethyl-3-(4-(meth)acryloyloxybutyl)imidazolium bis(trifluoromethanesulfonyl)imine, 1-Ethyl-3-(6-(meth)acryloyloxyhexyl)imidazolium bis(trifluoromethanesulfonyl)imine, 1-Ethyl-3-(8-(meth)acryloyloxyoctyl)imidazolium bis(trifluoromethanesulfonyl)imine, 1-Ethyl-3-vinylimidazolium bis(pentafluoroethanesulfonyl)imine, 1-Ethyl-3-(2-(meth)acryloyloxyethyl)imidazolium bis(pentafluoroethanesulfonyl)imine, 1-Ethyl-3-(3-(meth)acryloyloxypropyl)imidazolium bis(pentafluoroethanesulfonyl)imine Acyl)imine, 1-ethyl-3-(4-(methyl)acryloyloxybutyl)imidazolium bis(pentafluoroethanesulfonyl)imine, 1-ethyl-3-(6-(methyl)acryloyloxyhexyl)imidazolium bis(pentafluoroethanesulfonyl)imine, 1-ethyl-3-(8-(methyl)acryloyloxyoctyl)imidazolium bis(pentafluoroethanesulfonyl)imine, 1-ethyl-3-vinylimidazolium tri(trifluoromethanesulfonyl)imine, 1-ethyl-3-(2-(methyl)acryloyloxyethyl)imidazolium tri(trifluoromethanesulfonyl)imine, 1-ethyl-3-(3-(methyl)acryloyloxypropyl)imidazolium tri(trifluoromethanesulfonyl)imine, 1-ethyl-3-(4-(methyl)acryloyloxybutyl)imidazolium tri (Trifluoromethanesulfonyl)imine, 1-ethyl-3-(6-(methyl)acryloyloxyhexyl)imidazolium tri(trifluoromethanesulfonyl)imine, 1-ethyl-3-(8-(methyl)acryloyloxyoctyl)imidazolium tri(trifluoromethanesulfonyl)imine, 1-butyl-3-vinylimidazolium hexafluorophosphate, 1-butyl-3-(2-(methyl)acryloyloxyethyl)imidazolium hexafluorophosphate, 1-butyl-3-(3-(methyl)acryloyloxypropyl)imidazolium hexafluorophosphate, 1-butyl-3-(4-(methyl)acryloyloxybutyl)imidazolium hexafluorophosphate, 1-butyl-3-(6-(methyl)acryloyloxyhexyl)imidazolium hexafluorophosphate, 1-butyl-3-(8-(methyl) Acryloyloxyoctyl)imidazolium hexafluorophosphate, 1-butyl-3-vinylimidazolium trifluoroacetate, 1-butyl-3-(2-(methyl)acryloyloxyethyl)imidazolium trifluoroacetate, 1-butyl-3-(3-(methyl)acryloyloxypropyl)imidazolium trifluoroacetate, 1-butyl-3-(4-(methyl)acryloyloxybutyl)imidazolium trifluoroacetate, 1-butyl-3-(6-(methyl)acryloyloxyhexyl)imidazolium trifluoroacetate, 1-butyl-3-(8-(methyl)acryloyloxyoctyl)imidazolium trifluoroacetate, 1-butyl-3-(2-(methyl)acryloyloxyethyl)imidazolium tetrafluoroborate, 1-butyl-3-(2-(methyl)acryloyloxyethyl)imidazolium tetrafluoroborate,1-Butyl-3-(3-(meth)acryloyloxypropyl)imidazolium tetrafluoroborate, 1-Butyl-3-(4-(meth)acryloyloxybutyl)imidazolium tetrafluoroborate, 1-Butyl-3-(6-(meth)acryloyloxyhexyl)imidazolium tetrafluoroborate, 1-Butyl-3-(8-(meth)acryloyloxyoctyl)imidazolium tetrafluoroborate, 1-Butyl-3-vinylimidazolium heptafluorobutyrate, 1-Butyl-3-(2-(meth)acryloyloxyethyl)imidazolium heptafluorobutyrate, 1-Butyl-3-(3-(meth)acryloyloxypropyl)imidazolium heptafluorobutyrate, 1-Butyl-3-(4-(meth)acryloyloxybutyl)imidazolium heptafluorobutyrate, 1-Butyl-3-(6-(meth)acryloyloxyhexyl)imidazolium heptafluorobutyrate, 1-Butyl-3-(8-(meth)acryloyloxyoctyl)imidazolium heptafluorobutyrate, 1-Butyl-3-vinylimidazolium trifluoromethanesulfonate, 1-Butyl-3-(2-(meth)acryloyloxyethyl)imidazolium trifluoromethanesulfonate, 1-Butyl-3-(3-(meth)acryloyloxypropyl)imidazolium trifluoromethanesulfonate, 1-Butyl-3-(4-(meth)acryloyloxybutyl)imidazolium trifluoromethanesulfonate, 1-Butyl-3-(6-(meth)acryloyloxyhexyl)imidazolium trifluoromethanesulfonate, 1-Butyl-3-(8-(meth)acryloyloxyoctyl)imidazolium trifluoromethanesulfonate Methanesulfonate, 1-Butyl-3-vinylimidazolium perfluorobutane sulfonate, 1-Butyl-3-(2-(meth)acryloyloxyethyl)imidazolium perfluorobutane sulfonate, 1-Butyl-3-(3-(meth)acryloyloxypropyl)imidazolium perfluorobutane sulfonate, 1-Butyl-3-(4-(meth)acryloyloxybutyl)imidazolium perfluorobutane sulfonate, 1-Butyl-3-(6-(meth)acryloyloxyhexyl)imidazolium perfluorobutane sulfonate, 1-Butyl-3-(8-(meth)acryloyloxyoctyl)imidazolium perfluorobutane sulfonate, 1-Butyl-3-vinylimidazolium bis(trifluoromethanesulfonyl)imine, 1-Butyl-3-(2-(meth)acryloyloxyethyl) Imidazolium bis(trifluoromethanesulfonyl)imine, 1-butyl-3-(3-(meth)acryloyloxypropyl)imazolium bis(trifluoromethanesulfonyl)imine, 1-butyl-3-(4-(meth)acryloyloxybutyl)imazolium bis(trifluoromethanesulfonyl)imine, 1-butyl-3-(6-(meth)acryloyloxyhexyl)imazolium bis(trifluoromethanesulfonyl)imine, 1-butyl-3-(8-(meth)acryloyloxyoctyl)imazolium bis(trifluoromethanesulfonyl)imine, 1-hexyl-3-vinylimazolium bromide, 1-hexyl-3-(2-(meth)acryloyloxyethyl)imazolium bromide, 1-hexyl-3-(3-(meth)acryloyloxypropyl)imazolium bromide,1-Hexyl-3-(4-(meth)acryloyloxybutyl)imidazolium bromide, 1-hexyl-3-(6-(meth)acryloyloxyhexyl)imidazolium bromide, 1-hexyl-3-(8-(meth)acryloyloxyoctyl)imidazolium bromide, 1-hexyl-3-vinylimidazolium chloride, 1-hexyl-3-(2-(meth)acryloyloxyethyl)imidazolium chloride, 1-hexyl-3-(3-(meth)acryloyloxypropyl)imidazolium chloride, 1-hexyl-3-(4-(meth)acryloyloxybutyl)imidazolium chloride, 1-hexyl-3-(6-(meth)acryloyloxyhexyl)imidazolium chloride, 1-hexyl-3-(8-(meth)acryloyloxyoctyl)imidazolium chloride, Imidazolium chloride, 1-hexyl-3-vinylimidazolium tetrafluoroborate, 1-hexyl-3-(2-(meth)acryloyloxyethyl)imidazolium tetrafluoroborate, 1-hexyl-3-(3-(meth)acryloyloxypropyl)imidazolium tetrafluoroborate, 1-hexyl-3-(4-(meth)acryloyloxybutyl)imidazolium tetrafluoroborate, 1-hexyl-3-(6-(meth)acryloyloxyhexyl)imidazolium tetrafluoroborate, 1-hexyl-3-(8-(meth)acryloyloxyoctyl)imidazolium tetrafluoroborate, 1-hexyl-3-vinylimidazolium hexafluorophosphate, 1-hexyl-3-(2-(meth)acryloyloxyethyl)imidazolium hexafluorophosphate, 1-hexyl-3-( ... (1-(methyl)acryloyloxypropyl)imidazolium hexafluorophosphate, 1-hexyl-3-(4-(methyl)acryloyloxybutyl)imidazolium hexafluorophosphate, 1-hexyl-3-(6-(methyl)acryloyloxyhexyl)imidazolium hexafluorophosphate, 1-hexyl-3-(8-(methyl)acryloyloxyoctyl)imidazolium hexafluorophosphate, 1-hexyl-3-vinylimidazolium trifluoromethanesulfonate, 1-hexyl-3-(2-(methyl)acryloyloxyethyl)imidazolium trifluoromethanesulfonate, 1-hexyl-3-(3-(methyl)acryloyloxypropyl)imidazolium trifluoromethanesulfonate, 1-hexyl-3-(4-(methyl)acryloyloxybutyl)imidazolium trifluoromethanesulfonate, 1-hexyl-3-(6-(methyl)acryloyloxyethyl)imidazolium trifluoromethanesulfonate, 1-hexyl-3-(6-(methyl)acryloyloxyethyl)imidazolium trifluoromethanesulfonate, 1-hexyl-3-(4-(methyl)acryloyloxybutyl ... Acryloyloxyhexyl)imidazolium trifluoromethanesulfonate, 1-hexyl-3-(8-(methyl)acryloyloxyoctyl)imidazolium trifluoromethanesulfonate, 1-octyl-3-vinylimidazolium tetrafluoroborate, 1-octyl-3-(2-(methyl)acryloyloxyethyl)imidazolium tetrafluoroborate, 1-octyl-3-(3-(methyl)acryloyloxypropyl)imidazolium tetrafluoroborate, 1-octyl-3-(4-(methyl)acryloyloxybutyl)imidazolium tetrafluoroborate, 1-octyl-3-(6-(methyl)acryloyloxyhexyl)imidazolium tetrafluoroborate, 1-octyl-3-(8-(methyl)acryloyloxyoctyl)imidazolium tetrafluoroborate, 1-octyl-3-vinylimidazolium hexafluorophosphate,1-Octyl-3-(2-(meth)acryloyloxyethyl)imidazolium tetrafluoroborate, 1-Octyl-3-(3-(meth)acryloyloxypropyl)imidazolium tetrafluoroborate, 1-Octyl-3-(4-(meth)acryloyloxybutyl)imidazolium tetrafluoroborate, 1-Octyl-3-(6-(meth)acryloyloxyhexyl)imidazolium tetrafluoroborate, 1-Octyl-3-(8-(meth)acryloyloxyoctyl)imidazolium tetrafluoroborate, 1-Hexyl-2,3-Divinylimidazolium tetrafluoroborate, 1,2-Dimethyl-3-vinylimidazolium bis(trifluoromethanesulfonyl)imide, 1,2-Dimethyl-3-(2-(meth)acryloyloxyethyl)imidazolium bis(trifluoromethanesulfonyl)imide, 1,2-Dimethyl-3-(3-(meth)acryloyloxypropyl)imidazolium bis(trifluoromethanesulfonyl)imide, 1,2-Dimethyl-3-(4-(meth)acryloyloxybutyl)imidazolium Bis(trifluoromethanesulfonyl)imine, 1,2-dimethyl-3-(6-(meth)acryloyloxyhexyl)imidazolium bis(trifluoromethanesulfonyl)imine, 1,2-dimethyl-3-(8-(meth)acryloyloxyoctyl)imidazolium bis(trifluoromethanesulfonyl)imine, 1-ethyl-3-vinylimidazolium (trifluoromethanesulfonyl)trifluoroacetamide, 1-ethyl-3-(2-(meth)acryloyloxyethyl)imidazolium (trifluoromethanesulfonyl)trifluoroacetamide, 1-Ethyl-3-(3-(meth)acryloyloxypropyl)imidazolium (trifluoromethanesulfonyl)trifluoroacetamide, 1-Ethyl-3-(4-(meth)acryloyloxybutyl)imidazolium (trifluoromethanesulfonyl)trifluoroacetamide, 1-Ethyl-3-(6-(meth)acryloyloxyhexyl)imidazolium (trifluoromethanesulfonyl)trifluoroacetamide, 1-Ethyl-3-(8-(meth)acryloyloxyoctyl)imidazolium (trifluoromethanesulfonyl)trifluoroacetamide, etc.

[0094] Specific examples of ammonium cation-based ionic liquids include diallyl dimethylammonium tetrafluoroborate, diallyl dimethylammonium trifluoromethanesulfonate, diallyl dimethylammonium bis(trifluoromethanesulfonyl)imine, diallyl dimethylammonium bis(pentafluoroethanesulfonyl)imine, diallyl dimethylammonium (trifluoromethanesulfonyl)trifluoroacetamide, diallyl dimethylammonium (fluorosulfonyl)imine, N,N-dimethyl-N-vinyl-N-propylammonium bis(trifluoromethanesulfonyl)imine, N,N-dimethyl-N-(2-(meth)acryloyloxyethyl)-N-propylammonium bis(trifluoromethanesulfonyl)imine, N,N-dimethyl-N-(3-(meth)acryloyloxypropyl)-N-propylammonium bis(trifluoromethanesulfonyl)imine, N,N- Dimethyl-N-(4-(meth)acryloyloxybutyl)-N-propylammonium bis(trifluoromethanesulfonyl)imine, N,N-dimethyl-N-(6-(meth)acryloyloxyhexyl)-N-propylammonium bis(trifluoromethanesulfonyl)imine, N,N-dimethyl-N-(8-(meth)acryloyloxyoctyl)-N-propylammonium bis(trifluoromethanesulfonyl)imine, N,N-dimethyl-N-vinyl-N-butylammonium bis(trifluoromethanesulfonyl)imine, N,N-dimethyl-N-(2-(meth)acryloyloxyethyl)-N-butylammonium bis(trifluoromethanesulfonyl)imine, N,N-dimethyl-N-(3-(meth)acryloyloxypropyl)-N-butylammonium bis(trifluoromethanesulfonyl)imine, N,N -dimethyl-N-(4-(meth)acryloyloxybutyl)-N-butylammonium bis(trifluoromethanesulfonyl)imine, N,N-dimethyl-N-(6-(meth)acryloyloxyhexyl)-N-butylammonium bis(trifluoromethanesulfonyl)imine, N,N-dimethyl-N-(8-(meth)acryloyloxyoctyl)-N-butylammonium bis(trifluoromethanesulfonyl)imine, N,N-dimethyl-N-vinyl-N-pentylammonium bis(trifluoromethanesulfonyl)imine, N,N-dimethyl-N-(2-(meth)acryloyloxyethyl)-N-pentylammonium bis(trifluoromethanesulfonyl)imine, N,N-dimethyl-N-(3-(meth)acryloyloxypropyl)-N-pentylammonium bis(trifluoromethanesulfonyl)imine, N, N-Dimethyl-N-(4-(meth)acryloyloxybutyl)-N-pentylammonium bis(trifluoromethanesulfonyl)imine, N,N-Dimethyl-N-(6-(meth)acryloyloxyhexyl)-N-pentylammonium bis(trifluoromethanesulfonyl)imine, N,N-Dimethyl-N-(8-(meth)acryloyloxyoctyl)-N-pentylammonium bis(trifluoromethanesulfonyl)imine, N,N-Dimethyl-N-vinyl-N-hexylammonium bis(trifluoromethanesulfonyl)imine, N,N-Dimethyl-N-(2-(meth)acryloyloxyethyl)-N-hexylammonium bis(trifluoromethanesulfonyl)imine, N,N-Dimethyl-N-(3-(meth)acryloyloxypropyl)-N-hexylammonium bis(trifluoromethanesulfonyl)imine, N,N-Dimethyl-N-(4-(meth)acryloyloxybutyl)-N-hexylammonium bis(trifluoromethanesulfonyl)imine, N,N-Dimethyl-N-(6-(meth)acryloyloxyhexyl)-N-hexylammonium bis(trifluoromethanesulfonyl)imine, N,N-Dimethyl-N-(8-(meth)acryloyloxyoctyl)-N-hexylammonium bis(trifluoromethanesulfonyl)imine, N,N-Dimethyl-N-vinyl-N-heptylammonium bis(trifluoromethanesulfonyl)imine, N,N-Dimethyl-N-(2-(meth)acryloyloxyethyl)-N-heptylammonium bis(trifluoromethanesulfonyl)imine, N,N-Dimethyl-N-(3-(meth)acryloyloxypropyl)-N-heptylammonium bis(trifluoromethanesulfonyl)imine Amines, N,N-dimethyl-N-(4-(meth)acryloyloxybutyl)-N-heptylammonium bis(trifluoromethanesulfonyl)imine, N,N-dimethyl-N-(6-(meth)acryloyloxyhexyl)-N-heptylammonium bis(trifluoromethanesulfonyl)imine, N,N-dimethyl-N-(8-(meth)acryloyloxyoctyl)-N-heptylammonium bis(trifluoromethanesulfonyl)imine, N,N-dimethyl-N-vinyl-N-nonylammonium bis(trifluoromethanesulfonyl)imine, N,N-dimethyl-N-(2-(meth)acryloyloxyethyl)-N-nonylammonium bis(trifluoromethanesulfonyl)imine, N,N-dimethyl-N-(3-(meth)acryloyloxypropyl)-N-nonylammonium bis(trifluoromethanesulfonyl)imine Acyl) imine, N,N-dimethyl-N-(4-(meth)acryloyloxybutyl)-N-nonylammonium bis(trifluoromethanesulfonyl)imine, N,N-dimethyl-N-(6-(meth)acryloyloxyhexyl)-N-nonylammonium bis(trifluoromethanesulfonyl)imine, N,N-dimethyl-N-(8-(meth)acryloyloxyoctyl)-N-nonylammonium bis(trifluoromethanesulfonyl)imine, N,N-dimethyl-N,N-dihexylammonium bis(trifluoromethanesulfonyl)imine, N,N-diethyl-N-vinyl-N-propylammonium bis(trifluoromethanesulfonyl)imine, N,N-dimethyl-N-(2-(meth)acryloyloxyethyl)-N-propylammonium bis(trifluoromethanesulfonyl)imine, N,N-dimethyl-N-(4 ... N,N-dimethyl-N-(3-(meth)acryloyloxypropyl)-N-propylammonium bis(trifluoromethanesulfonyl)imine, N,N-dimethyl-N-(4-(meth)acryloyloxybutyl)-N-propylammonium bis(trifluoromethanesulfonyl)imine, N,N-dimethyl-N-(6-(meth)acryloyloxyhexyl)-N-propylammonium bis(trifluoromethanesulfonyl)imine, N,N-dimethyl-N-(8-(meth)acryloyloxyoctyl)-N-propylammonium bis(trifluoromethanesulfonyl)imine, N,N-diethyl-N-vinyl-N-pentylammonium bis(trifluoromethanesulfonyl)imine, N,N-dimethyl-N-(2-(meth)acryloyloxyethyl)-N-pentylammonium bis(trifluoromethanesulfonyl)imine, N,N-Dimethyl-N-(3-(meth)acryloyloxypropyl)-N-pentylammonium bis(trifluoromethanesulfonyl)imine, N,N-dimethyl-N-(4-(meth)acryloyloxybutyl)-N-pentylammonium bis(trifluoromethanesulfonyl)imine, N,N-dimethyl-N-(6-(meth)acryloyloxyhexyl)-N-pentylammonium bis(trifluoromethanesulfonyl)imine, N,N-dimethyl-N-(8-(meth)acryloyloxyoctyl)-N-pentylammonium bis(trifluoromethanesulfonyl)imine, N,N-diethyl-N-vinyl-N-heptylammonium bis(trifluoromethanesulfonyl)imine, N,N-dimethyl-N-(2-(meth)acryloyloxyethyl)-N-heptylammonium bis(trifluoromethanesulfonyl)imine, N,N-dimethyl-N-(2-(meth)acryloyloxyethyl)-N-heptylammonium bis(trifluoromethanesulfonyl)imine, N,N-dimethyl-N-(3 ... (Fluoromethylsulfonyl)imine, N,N-dimethyl-N-(3-(meth)acryloyloxypropyl)-N-heptylammonium bis(trifluoromethanesulfonyl)imine, N,N-dimethyl-N-(4-(meth)acryloyloxybutyl)-N-heptylammonium bis(trifluoromethanesulfonyl)imine, N,N-dimethyl-N-(6-(meth)acryloyloxyhexyl)-N-heptylammonium bis(trifluoromethanesulfonyl)imine, N,N-dimethyl-N-(8-(meth)acryloyloxyoctyl)-N-heptylammonium bis(trifluoromethanesulfonyl)imine, N,N-diethyl-N-propyl-N-vinylammonium bis(trifluoromethanesulfonyl)imine, N,N-diethyl-N-propyl-N-(2-(methylpropene) N,N-diethyl-N-propyl-N-(3-(meth)acryloyloxypropyl)ammonium bis(trifluoromethanesulfonyl)imine, N,N-diethyl-N-propyl-N-(4-(meth)acryloyloxybutyl)ammonium bis(trifluoromethanesulfonyl)imine, N,N-diethyl-N-propyl-N-(6-(meth)acryloyloxyhexyl)ammonium bis(trifluoromethanesulfonyl)imine, N,N-diethyl-N-propyl-N-(8-(meth)acryloyloxyoctyl)ammonium bis(trifluoromethanesulfonyl)imine, N,N-dipropyl-N-vinyl-N-ethylammonium bis(trifluoromethanesulfonyl)imine, N,N-dipropyl-N-(2- (Meth)acryloyloxyethyl)-N-ethylammonium bis(trifluoromethanesulfonyl)imine, N,N-dipropyl-N-(3-(meth)acryloyloxypropyl)-N-ethylammonium bis(trifluoromethanesulfonyl)imine, N,N-dipropyl-N-(4-(meth)acryloyloxybutyl)-N-ethylammonium bis(trifluoromethanesulfonyl)imine, N,N-dipropyl-N-(6-(meth)acryloyloxyhexyl)-N-ethylammonium bis(trifluoromethanesulfonyl)imine, N,N-dipropyl-N-(8-(meth)acryloyloxyoctyl)-N-ethylammonium bis(trifluoromethanesulfonyl)imine, N,N-dipropyl-N-vinyl-N-pentylammonium bis(trifluoromethanesulfonyl)imine, N,N-Dipropyl-N-(2-(meth)acryloyloxyethyl)-N-pentylammonium bis(trifluoromethanesulfonyl)imine, N,N-dipropyl-N-(3-(meth)acryloyloxypropyl)-N-pentylammonium bis(trifluoromethanesulfonyl)imine, N,N-dipropyl-N-(4-(meth)acryloyloxybutyl)-N-pentylammonium bis(trifluoromethanesulfonyl)imine, N,N-dipropyl-N-(6-(meth)acryloyloxyhexyl)-N-pentylammonium bis(trifluoromethanesulfonyl)imine, N,N-dipropyl-N-(8-(meth)acryloyloxyoctyl)-N-pentylammonium bis(trifluoromethanesulfonyl)imine, N,N-dipropyl-N-vinyl- N-Hexylammonium bis(trifluoromethanesulfonyl)imine, N,N-dipropyl-N-(2-(meth)acryloyloxyethyl)-N-hexylammonium bis(trifluoromethanesulfonyl)imine, N,N-dipropyl-N-(3-(meth)acryloyloxypropyl)-N-hexylammonium bis(trifluoromethanesulfonyl)imine, N,N-dipropyl-N-(4-(meth)acryloyloxybutyl)-N-hexylammonium bis(trifluoromethanesulfonyl)imine, N,N-dipropyl-N-(6-(meth)acryloyloxyhexyl)-N-hexylammonium bis(trifluoromethanesulfonyl)imine, N,N-dipropyl-N-(8-(meth)acryloyloxyoctyl)-N-hexylammonium bis(trifluoromethanesulfonyl)imine N,N-dibutyl-N-vinyl-N-pentylammonium bis(trifluoromethanesulfonyl)imine, N,N-dibutyl-N-(2-(meth)acryloyloxyethyl)-N-pentylammonium bis(trifluoromethanesulfonyl)imine, N,N-dibutyl-N-(3-(meth)acryloyloxypropyl)-N-pentylammonium bis(trifluoromethanesulfonyl)imine, N,N-dibutyl-N-(4-(meth)acryloyloxybutyl)-N-pentylammonium bis(trifluoromethanesulfonyl)imine, N,N-dibutyl-N-(6-(meth)acryloyloxyhexyl)-N-pentylammonium bis(trifluoromethanesulfonyl)imine, N,N-dibutyl-N-(8-(meth)acryloyl) N,N-dibutyl-N-vinyl-N-hexylammonium bis(trifluoromethanesulfonyl)imine, N,N-dibutyl-N-vinyl-N-hexylammonium bis(trifluoromethanesulfonyl)imine, N,N-dibutyl-N-(2-(meth)acryloyloxyethyl)-N-hexylammonium bis(trifluoromethanesulfonyl)imine, N,N-dibutyl-N-(3-(meth)acryloyloxypropyl)-N-hexylammonium bis(trifluoromethanesulfonyl)imine, N,N-dibutyl-N-(4-(meth)acryloyloxybutyl)-N-hexylammonium bis(trifluoromethanesulfonyl)imine, N,N-dibutyl-N-(6-(meth)acryloyloxyhexyl)-N-hexylammonium bis(trifluoromethanesulfonyl)imine, N,N-Dibutyl-N-(8-(meth)acryloyloxyoctyl)-N-hexylammonium bis(trifluoromethanesulfonyl)imine, N-methyl-N-ethyl-N-propyl-N-vinylammonium bis(trifluoromethanesulfonyl)imine, N-methyl-N-ethyl-N-propyl-N-(2-(meth)acryloyloxyethyl)ammonium bis(trifluoromethanesulfonyl)imine, N-methyl-N-ethyl-N-propyl-N-(3-(meth)acryloyloxypropyl)ammonium bis(trifluoromethanesulfonyl)imine, N-methyl-N-ethyl-N-propyl Examples of bis(trifluoromethanesulfonyl)imine include: N-methyl-N-ethyl-N-propyl-N-(6-(methyl)acryloyloxyhexyl)ammonium bis(trifluoromethanesulfonyl)imine, N-methyl-N-ethyl-N-propyl-N-(8-(methyl)acryloyloxyoctyl)ammonium bis(trifluoromethanesulfonyl)imine, (2-acryloyloxyethyl)trimethylammonium=bis(trifluoromethanesulfonyl)imine, and (2-acryloyloxyethyl)trimethylammonium(fluorosulfonyl)imine.

[0095] Specific examples of pyrazolium cationic ionic liquids include 1-vinylpyrazolium tetrafluoroborate, 1-(2-(meth)acryloyloxyethyl)pyrazolium tetrafluoroborate, 1-(3-(meth)acryloyloxypropyl)pyrazolium tetrafluoroborate, 1-(4-(meth)acryloyloxybutyl)pyrazolium tetrafluoroborate, 1-(6-(meth)acryloyloxyhexyl)pyrazolium tetrafluoroborate, and 1-(8-(meth)acryloyloxyoctyl)pyrazolium tetrafluoroborate. Pyrazolium tetrafluoroborate, 3-vinylpyrazolium tetrafluoroborate, 3-(2-(meth)acryloyloxyethyl)pyrazolium tetrafluoroborate, 3-(3-(meth)acryloyloxypropyl)pyrazolium tetrafluoroborate, 3-(4-(meth)acryloyloxybutyl)pyrazolium tetrafluoroborate, 3-(6-(meth)acryloyloxyhexyl)pyrazolium tetrafluoroborate, 3-(8-(meth)acryloyloxyoctyl)pyrazolium tetrafluoroborate, etc.

[0096] Specific examples of indole cation-based ionic liquids include 1-ethyl-2-vinylindole tetrafluoroborate, 1-ethyl-2-(2-(methyl)acryloyloxyethyl)indole tetrafluoroborate, 1-ethyl-2-(3-(methyl)acryloyloxypropyl)indole tetrafluoroborate, 1-ethyl-2-(4-(methyl)acryloyloxybutyl)indole tetrafluoroborate, 1-ethyl-2-(6-(methyl)acryloyloxyhexyl)indole tetrafluoroborate, 1-ethyl-2-(8-(methyl)acryloyloxyoctyl)indole tetrafluoroborate, and 1,2-divinylindole tetrafluoroborate.

[0097] The content of the aforementioned monomers in the adhesive layer is not particularly limited. In some embodiments, the content of the aforementioned monomers may be approximately 1 part by weight or more, or 3 parts by weight or more, relative to 100 parts by weight of the polymer (specifically, the base polymer, suitably an acrylic polymer) contained in the adhesive layer. The suitable amount of the aforementioned monomers may vary depending on their molecular weight, number of functional groups, etc. In some preferred embodiments, from the viewpoint of improving heat-resistant peelability, the content of the aforementioned monomers relative to 100 parts by weight of the polymer contained in the adhesive layer may be 5 parts by weight or more, 7 parts by weight or more, 8 parts by weight or more, 9 parts by weight or more, more preferably 10 parts by weight or more (e.g., more than 10 parts by weight), more preferably 12 parts by weight or more, even more preferably 15 parts by weight or more, and even more preferably 18 parts by weight or more. The upper limit of the content of the aforementioned monomers in the adhesive layer is not particularly limited and may be set in a manner that achieves the desired adhesive properties. In some embodiments, from the viewpoint of compatibility with the polymer (specifically, the base polymer, such as an acrylic polymer), it is suitable to set the amount of the monomer relative to 100 parts by weight of the polymer to about 200 parts by weight or less, preferably 160 parts by weight or less, more preferably 150 parts by weight or less, even more preferably 140 parts by weight or less, and can be 120 parts by weight or less, or even 90 parts by weight or less. In some preferred embodiments, the amount of the monomer relative to 100 parts by weight of the polymer can be 70 parts by weight or less, 50 parts by weight or less (e.g., less than 50 parts by weight), 45 parts by weight or less (e.g., less than 45 parts by weight), 40 parts by weight or less, 35 parts by weight or less, 30 parts by weight or less, 25 parts by weight or less, or even 20 parts by weight or less. According to the technology disclosed herein, the desired heat-peelability can be ideally achieved by limiting the amount of monomer in the adhesive layer as described above. Furthermore, by limiting the amount of the aforementioned monomers used, the generation of low molecular weight components derived from these monomers is suppressed after heat treatment, thereby preventing or reducing contamination of the adhered surfaces due to these low molecular weight components. In addition, reducing the amount of the aforementioned monomers tends to easily yield high adhesion.

[0098] (Single A) In the adhesive layer, monomer A, as a coordinating monomer, is included, having a molecular weight in the range of 250 to 5000 and having one or two olefinic unsaturated groups within the molecule. Based on the adhesive layer containing monomer A having the aforementioned molecular weight and chemical structure, both low contamination of the adhered object after heating and easy peeling after heating can be achieved. This is believed to be because monomer A, having one or two olefinic unsaturated groups and a molecular weight of 250 to 5000, easily segregates to the surface of the adhesive layer, contributing to improved easy peeling after heating. Furthermore, during heat treatment, monomer A with olefinic unsaturated groups is incorporated into the adhesive layer through reaction and is less likely to remain on the surface of the adhered object. It should be noted that the technology disclosed herein is not limited to the above explanation. As monomer A, one or more monomers with a molecular weight in the range of 250 to 5000 and having one or two olefinic unsaturated groups within the molecule can be appropriately selected from the monomers described as coordinating monomers above.

[0099] In some preferred embodiments, the monomer A described above has an ionic site. The ionic site in the compound can be an ionic group or an ionic unit. Suitable examples of such a monomer A having an ionic site include reactive surfactants and reactive ionic liquids with a molecular weight in the range of 250 to 5000 and having one or two olefinically unsaturated groups within the molecule.

[0100] The molecular weight of monomer A is in the range of 250 to 5000. Monomer A with a molecular weight within this range can move well within the adhesive layer, for example, it can segregate on the surface of the adhesive layer, thus contributing to and improving easy peelability. Although not particularly limited, in some preferred embodiments, the molecular weight of monomer A can be 3000 or less, or even 2000 or less. It should be noted that the above molecular weight is based on the manufacturer's nominal value or the molecular weight calculated based on the molecular structure.

[0101] Regarding the adhesive layer, the monomer (coordinating monomer) may contain only monomer A, or it may contain one or more monomers, including monomer A and monomers that are not monomer A (hereinafter referred to as "monomer B" for the purpose of distinguishing them from monomer A). The amount of monomer A in the total monomer is not particularly limited; for example, it may be 0.1% by weight or more, or 0.5% by weight or more. In some embodiments, from the viewpoint of effectively utilizing the effect of containing monomer A, the amount of monomer A is preferably set to 1% by weight or more in the total monomer, more preferably 1.2% by weight or more, and even more preferably 1.4% by weight or more. In other embodiments, the amount of monomer A in the total monomer may be 3% by weight or more, 5% by weight or more, 8% by weight or more, or 10% by weight or more. There is a tendency that the more monomer A is used, the better the light peelability after heating. Furthermore, in some embodiments, the amount of monomer A in the total monomer may be, for example, about 90% by weight or less, about 70% by weight or less, or about 50% by weight or less. By limiting the amount of monomer A used, contamination of the adhered surface caused by the presence of the monomer can be ideally suppressed. From this point of view, in some preferred embodiments, the amount of monomer A in the total monomer is less than 50% by weight, more preferably less than 30% by weight, even more preferably less than 15% by weight, even more preferably less than 10% by weight (e.g., less than 10% by weight), particularly preferably less than 7% by weight, and can be less than 5% by weight or less, or less than 3% by weight.

[0102] The content of monomer A in the adhesive layer is not particularly limited. Relative to 100 parts by weight of the polymer (specifically, the base polymer, suitably an acrylic polymer) contained in the adhesive layer, the content of monomer A is, for example, 0.01 parts by weight or more, preferably 0.05 parts by weight or more, more preferably 0.1 parts by weight or more, even more preferably 0.2 parts by weight or more, and can be 0.3 parts by weight or more, 0.5 parts by weight or more, or 0.8 parts by weight or more. In some preferred embodiments, from the viewpoint of improved light peelability after heating, the content of monomer A relative to 100 parts by weight of the polymer contained in the adhesive layer is 1 part by weight or more, more preferably 3 parts by weight or more, even more preferably 5 parts by weight or more, particularly preferably 8 parts by weight or more, and can be 10 parts by weight or more, or 15 parts by weight or more. Furthermore, in some embodiments, it is suitable to set the amount of monomer A relative to 100 parts by weight of the polymer to be approximately 30 parts by weight or less, and can be 25 parts by weight or less, or 20 parts by weight or less. By limiting the amount of monomer A used to a specified amount or less, contamination of the surface of the adhered object after heating can be ideally reduced. From this point of view, in some preferred embodiments, the amount of monomer A relative to 100 parts by weight of the polymer is 15 parts by weight or less, more preferably 12 parts by weight or less, even more preferably 10 parts by weight or less (e.g., less than 10 parts by weight), particularly preferably 5 parts by weight or less, and may be 3 parts by weight or less, or 1.5 parts by weight or less.

[0103] In the method where the adhesive layer comprises monomer A and monomer B as the aforementioned monomers (combining monomers), the content of monomer B in the adhesive layer is not particularly limited. By using monomer B in addition to monomer A, heat-removable properties can be further improved. Furthermore, the use of monomer B can improve the low-contamination properties of the adhered material after heating. This is believed to be due to the reaction of monomer B during heat treatment, which facilitates the incorporation of monomer A into the adhesive layer. It should be noted that the technology disclosed herein is not limited to the above explanation. In some methods, the content of monomer B can be approximately 1 part by weight or more, or 3 parts by weight or more, relative to 100 parts by weight of the polymer contained in the adhesive layer (specifically, the base polymer, suitably an acrylic polymer). The appropriate amount of monomer B can vary depending on its molecular weight, number of functional groups, etc. In some preferred embodiments, from the viewpoint of improving heat-resistant peelability, the content of monomer B is 5 parts by weight or more, 7 parts by weight or more, 8 parts by weight or more, 9 parts by weight or more, more preferably 10 parts by weight or more (e.g., more than 10 parts by weight), more preferably 12 parts by weight or more, even more preferably 15 parts by weight or more, and even more preferably 18 parts by weight or more, relative to 100 parts by weight of polymer contained in the adhesive layer. By using monomer B in a specified amount or more in addition to monomer A, superior low contamination of the adhered material after heating and easy peelability after heating can be achieved. There is no particular upper limit to the content of monomer B in the adhesive layer, and it can be set in a way that achieves the desired adhesive properties. In some embodiments, from the viewpoint of compatibility with the polymer (specifically, the base polymer, such as an acrylic polymer), it is suitable to set the amount of monomer B relative to 100 parts by weight of the polymer to about 200 parts by weight or less, preferably 160 parts by weight or less, more preferably 150 parts by weight or less, even more preferably 140 parts by weight or less, and can be 120 parts by weight or less, or even 90 parts by weight or less. In some preferred embodiments, the amount of monomer B relative to 100 parts by weight of the polymer can be 70 parts by weight or less, 50 parts by weight or less (e.g., less than 50 parts by weight), 45 parts by weight or less (e.g., less than 45 parts by weight), 40 parts by weight or less, 35 parts by weight or less, 30 parts by weight or less, 25 parts by weight or less, or even 20 parts by weight or less. According to the technology disclosed herein, the desired heat-peelability can be ideally achieved by limiting the amount of monomer B in the adhesive layer as described above. Furthermore, by limiting the amount of monomer B used, the generation of low molecular weight components derived from monomer B is suppressed after heat treatment, thus preventing or reducing contamination of the adhered surfaces caused by these low molecular weight components. In addition, reducing the amount of monomer B used tends to easily yield high adhesion.

[0104] (Thermal polymerization initiator) In addition to the aforementioned polymer and monomer, the adhesive layer also contains a thermal polymerization initiator. The thermal polymerization initiator is a polymerization initiator that generates free radicals upon heating. By including a thermal polymerization initiator in the adhesive layer, during heat treatment at a specified temperature or higher, the thermal polymerization initiator reacts with the olefinic unsaturated groups in the adhesive layer, reducing peel strength and achieving heat-resistant peelability. By including a thermal polymerization initiator, a thermosetting adhesive that retains heat resistance and easy peelability after heat treatment can be formed.

[0105] As a thermal polymerization initiator, for example, one or more suitable thermal polymerization initiators can be selected and used from various thermal polymerization initiators such as peroxide-based polymerization initiators, azo-based polymerization initiators, redox-based polymerization initiators based on the combination of peroxide and reducing agent, and substituted ethane-based polymerization initiators.

[0106] In some methods, peroxide-based polymerization initiators are preferred as the aforementioned thermal polymerization initiators. By including a peroxide-based polymerization initiator in the adhesive layer as the thermal polymerization initiator, the curing reaction of the adhesive layer during heat treatment proceeds rapidly, easily yielding excellent heat-peelability and heat-resistant peelability. One reason for this is the high initiation efficiency of peroxide-based polymerization initiators (especially organic peroxide-based polymerization initiators). Furthermore, peroxide-based polymerization initiators generate free radicals (-O·) through the cleavage of the -OO- group in the compound. However, this cleavage reaction is reversible, therefore, it is believed that -OO- can recombine even if the free radical does not collide with the olefinic unsaturated groups of the polymer, etc. This recombinated initiator undergoes another cleavage reaction during the prescribed heat treatment, colliding with the polymer, etc., to carry out the reaction. Therefore, according to the peroxide-based polymerization initiator, the thermal curing of the adhesive layer proceeds rapidly at a faster reaction rate compared to other initiators (e.g., azo initiators). Furthermore, it is believed that its thermosetting speed is faster than the speed at which the heat-based adhesive layer firmly bonds to the substrate, thus effectively reducing the peel force after heating and easily achieving excellent heat-resistant and heat-resistant peelability. It should be noted that the technology disclosed herein is not limited to the above-described considerations.

[0107] As peroxide-based polymerization initiators, organic peroxides such as acyl peroxides, peroxide esters, peroxide dicarbonates, monoperoxide carbonates, peroxide ketals, dialkyl peroxides, hydroperoxides, and ketone peroxides are preferred. Suitable examples of peroxide-based polymerization initiators include benzoyl peroxide compounds having substituted benzoyl groups (typically dibenzoyl peroxide (BPO)). One peroxide-based polymerization initiator can be used alone or in combination of two or more.

[0108] Specific examples of peroxide-based polymerization initiators include BPO, 1,1-di(tert-hexylperoxy)cyclohexane, cyclohexanone peroxide, 3,3,5-trimethylcyclohexanone peroxide, methylcyclohexanone peroxide, 1,1-bis(tert-butylperoxy)-3,3,5-trimethylcyclohexane, 1,1-bis(tert-butylperoxy)cyclohexane, 4,4-bis(tert-butylperoxy)valerate, cumene hydroperoxide, 2,5-dimethyl-2,5-dihydrohexane peroxide, and 1,3-bis(tert-butylperoxy) m-Propane, 2,5-Dimethyl-2,5-di(tert-butylperoxy)hexane, 2,5-Dimethyl-2,5-di(tert-butylperoxy)-3-hexyne, diisopropylbenzene hydroperoxide, tert-butylcumyl peroxide, didecanoyl peroxide, dilauroyl peroxide, 2,4-dichlorobenzoyl peroxide, di(4-tert-butylcyclohexyl) percarbonate, tert-butyl peroxide, 2,5-Dimethyl-2,5-di(benzoylperoxy)hexane, tert-butyl hydrogen peroxide, ditert-butyl peroxide, etc.

[0109] When the adhesive layer contains a peroxide-based polymerization initiator, the content of the peroxide-based polymerization initiator in the adhesive layer is not particularly limited. For example, it can be 0.01 parts by weight or more, or 0.05 parts by weight or more, relative to 100 parts by weight of the polymer contained in the adhesive layer (specifically, the base polymer, such as an acrylic polymer). In some embodiments, it is suitable to set the content of the peroxide-based polymerization initiator to 0.1 parts by weight or more relative to 100 parts by weight of the polymer contained in the adhesive layer, preferably 0.2 parts by weight or more, more preferably 0.3 parts by weight or more, even more preferably 0.4 parts by weight or more, even more preferably 0.5 parts by weight or more, even more preferably 0.6 parts by weight or more, particularly preferably 0.7 parts by weight or more, and may also be 0.8 parts by weight or more. The higher the content of the peroxide-based polymerization initiator, the higher the collision frequency between the peroxide-based polymerization initiator and the olefinic unsaturated groups in the adhesive layer, and the easier the curing reaction is to proceed. In some embodiments, the amount of peroxide-based polymerization initiator relative to 100 parts by weight of the polymer is, for example, about 10 parts by weight or less, or about 5 parts by weight or less. In some preferred embodiments, the amount of peroxide-based polymerization initiator relative to 100 parts by weight of the polymer is suitable to be 3 parts by weight or less (less than 3 parts by weight), preferably 2.5 parts by weight or less, more preferably 2.0 parts by weight or less, further preferably 1.5 parts by weight or less, particularly preferably less than 1.2 parts by weight (e.g., less than 1.1 parts by weight), and may also be 1.0 parts by weight or less (e.g., less than 1.0 parts by weight). By keeping the content of the peroxide-based polymerization initiator within a specified range, it is possible to ideally achieve an adhesive with highly efficient thermosetting properties and heat-resistant peelability while obtaining adhesive properties such as adhesive strength and storage stability.

[0110] In adhesive layers comprising a coordinating monomer and a peroxide-based polymerization initiator, the content of the peroxide-based polymerization initiator in the adhesive layer can be determined by its relative relationship with the coordinating monomer in the adhesive layer. In some embodiments, from the viewpoint of rapidly thermosetting by increasing the collision frequency with the olefinic unsaturated groups of the monomer, and from the viewpoint of thermosetting the adhesive layer with a high degree of curing, it is suitable to set the amount of the peroxide-based polymerization initiator relative to 100 parts by weight of the monomer to be 0.1 parts by weight or more, preferably 0.5 parts by weight or more, more preferably 1.0 parts by weight or more, even more preferably 2.0 parts by weight or more, further preferably 2.5 parts by weight or more, particularly preferably 3.0 parts by weight or more, and may also be 3.5 parts by weight or more. In compositions where, for example, the monomer content is limited, the amount of the peroxide-based polymerization initiator used is preferably adopted. Furthermore, in some embodiments, the amount of the peroxide-based polymerization initiator relative to 100 parts by weight of the monomer may, for example, be about 20 parts by weight or less, 15 parts by weight or less, 12 parts by weight or less, or 10 parts by weight or less. In some methods, the amount of peroxide-based polymerization initiator relative to 100 parts by weight of the monomer can be 7 parts by weight or less, or 5 parts by weight or less.

[0111] Other examples of usable thermal polymerization initiators include, specifically, persulfates such as potassium persulfate and ammonium persulfate; azo compounds such as 2,2'-azobisisobutyronitrile (AIBN), 2,2'-azobis(N-butyl-2-methylpropionamide), and 2,2'-azobis(2,4,4-trimethylpentane); substituted ethane initiators such as phenyl-substituted ethane; redox initiators based on combinations of peroxides and reducing agents, such as combinations of persulfates and sodium bisulfite, or combinations of peroxides and sodium ascorbate; and so on. They can be used alone or in combination of two or more.

[0112] While not particularly limited, from the viewpoint of effectively utilizing the peroxide-based polymerization initiator, in some embodiments, the proportion of the peroxide-based polymerization initiator contained in the adhesive layer to the total thermal polymerization initiator can be about 10% by weight or more, preferably about 30% by weight or more, more preferably 50% by weight or more, more preferably 70% by weight or more, further preferably 90% by weight or more, and particularly preferably 95% to 100% by weight. The thermal polymerization initiator contained in the adhesive layer can be formed from the peroxide-based polymerization initiator.

[0113] In some methods, a thermal polymerization initiator is preferably used that satisfies the following formula: Self-Accelerating Decomposition Temperature (SADT) [°C]: SADT + 10 ≥ 60. The SADT of a thermal polymerization initiator is defined as the lowest temperature at which it causes heating above 6°C or self-accelerated decomposition within 7 days when contained in a container of a certain quantity. SADT represents the ambient temperature at which the thermal polymerization initiator causes decomposition. Based on the fact that the maximum temperature exposed to the adhesive during storage is 60°C, the inventors of this application experimentally confirmed that if the thermal polymerization initiator has an SADT that is -10°C or higher than the aforementioned maximum storage temperature, the self-decomposition of the thermal polymerization initiator in the adhesive is suppressed, resulting in good heat-resistant peelability after storage. This is believed to be because heat conduction is more difficult in the adhesive (solid) compared to the case of a thermal polymerization initiator alone. Based on this discovery, adhesives designed using thermal polymerization initiators with SADT satisfying the above formula (hereinafter also referred to as high SADT initiators) exhibit suppressed decomposition of the thermal polymerization initiator even when the adhesive is exposed to a temperature of approximately 60°C before use, thus maintaining the desired heat-peelability. Adhesives containing thermal polymerization initiators with high SADT initiators demonstrate good storage stability even under long-term storage conditions and temperature variations during storage, and maintain good heat-peelability after storage. It should be noted that in this specification, the SADT used as the thermal polymerization initiator is the nominal value listed in manufacturer catalogs, etc.

[0114] The amount of thermal polymerization initiator contained in the adhesive layer is not particularly limited. For example, relative to 100 parts by weight of the polymer (specifically, the base polymer, such as an acrylic polymer) contained in the adhesive layer, the content of the thermal polymerization initiator in the adhesive layer can be 0.01 parts by weight or more, or 0.05 parts by weight or more. In some embodiments, it is suitable to set the content of the thermal polymerization initiator in the adhesive layer to 0.1 parts by weight or more relative to 100 parts by weight of the polymer contained in the adhesive layer, preferably 0.2 parts by weight or more, more preferably 0.3 parts by weight or more, even more preferably 0.4 parts by weight or more, even more preferably 0.5 parts by weight or more, even more preferably 0.6 parts by weight or more, particularly preferably 0.7 parts by weight or more, and may also be 0.8 parts by weight or more. The higher the content of the thermal polymerization initiator, the higher the collision frequency between the thermal polymerization initiator and the olefinic unsaturated groups in the adhesive layer, and the easier the curing reaction is to proceed. In some embodiments, the amount of the thermal polymerization initiator relative to 100 parts by weight of the polymer is, for example, about 10 parts by weight or less, or about 5 parts by weight or less. In some preferred embodiments, the amount of the thermal polymerization initiator relative to 100 parts by weight of the polymer is suitable to be 3 parts by weight or less (less than 3 parts by weight), preferably 2.5 parts by weight or less, more preferably 2.0 parts by weight or less, even more preferably 1.5 parts by weight or less, particularly preferably less than 1.2 parts by weight (e.g., less than 1.1 parts by weight), and may also be 1.0 parts by weight or less (e.g., less than 1.0 parts by weight). By keeping the total amount of the thermal polymerization initiator within a specified range, it is possible to ideally achieve an adhesive with highly efficient thermosetting properties and heat-resistant peelability while obtaining adhesive properties such as adhesive strength and maintaining stability.

[0115] Although not particularly limited, in some preferred embodiments, from the viewpoint of effectively demonstrating the reduction of peel force during heating, it is suitable for the total proportion of the above-mentioned polymer (specifically the base polymer, such as an acrylic polymer), the above-mentioned monomer (such as monomer A), and the thermal polymerization initiator (such as a peroxide polymerization initiator, etc.) in the total adhesive layer to be 50% by weight or more (e.g., more than 50% by weight and less than 100% by weight), preferably 70% by weight or more, more preferably 80% by weight or more, further preferably 90% by weight or more, and may be 95% by weight or more, 98% by weight or more, or 99% by weight or more (e.g., 99 to 100% by weight).

[0116] (Cross-linking agent) In adhesive compositions used to form adhesive layers, crosslinking agents may be included as needed, primarily for crosslinking within the adhesive layer or between the adhesive layer and its adjacent surfaces. Typically, the crosslinking agent is contained within the adhesive layer in the form of the crosslinked reaction. By using a crosslinking agent, the cohesive strength of the adhesive layer can be appropriately adjusted.

[0117] There are no particular limitations on the type of crosslinking agent; it can be selected from known crosslinking agents, for example, based on the composition of the adhesive, in a manner that allows the crosslinking agent to perform a suitable crosslinking function within the adhesive layer. Examples of usable crosslinking agents include isocyanate-based crosslinking agents, epoxy-based crosslinking agents, oxazoline-based crosslinking agents, aziridine-based crosslinking agents, carbodiimide-based crosslinking agents, melamine-based crosslinking agents, urea-based crosslinking agents, metal alkoxide-based crosslinking agents, metal chelate-based crosslinking agents, metal salt-based crosslinking agents, hydrazine-based crosslinking agents, and amine-based crosslinking agents. They can be used alone or in combination of two or more. From the viewpoint of achieving a good balance between adhesion and cohesion, isocyanate-based crosslinking agents, epoxy-based crosslinking agents, oxazoline-based crosslinking agents, aziridine-based crosslinking agents, and carbodiimide-based crosslinking agents are preferred, with isocyanate-based crosslinking agents being particularly preferred.

[0118] As isocyanate-based crosslinking agents, multifunctional isocyanate compounds with two or more functions can be used. Examples include aromatic isocyanates such as toluene diisocyanate, xylene diisocyanate, polymethylene polyphenyl diisocyanate, tris(p-isocyanatophenyl)thiophosphate, and diphenylmethane diisocyanate; alicyclic isocyanates such as isophorone diisocyanate; aliphatic isocyanates such as hexamethylene diisocyanate; and so on. Examples of commercially available products include trimethylolpropane / toluene diisocyanate trimer adduct (manufactured by Tosoh Corporation, trade name "Coronate L"), trimethylolpropane / hexamethylene diisocyanate trimer adduct (manufactured by Tosoh Corporation, trade name "Coronate HL"), isocyanurate form of hexamethylene diisocyanate (manufactured by Tosoh Corporation, trade name "Coronate HX"), trimethylolpropane / phenylenediamine diisocyanate adduct (manufactured by Mitsui Chemicals, trade name "Takenate D-110N"), and other isocyanate adducts.

[0119] As epoxy crosslinking agents, substances having two or more epoxy groups per molecule can be used without particular limitation. Epoxy crosslinking agents having three to five epoxy groups per molecule are preferred. Specific examples of epoxy crosslinking agents include N,N,N',N'-tetraglycidyl-m-phenylenediamine, 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane, 1,6-hexanediol diglycidyl ether, polyethylene glycol diglycidyl ether, and polyglycerol polyglycidyl ether. Commercially available epoxy crosslinking agents include those manufactured by Mitsubishi Gas Chemical Company, Inc. under the trade names "TETRAD-X" and "TETRAD-C", manufactured by DIC CORPORATION under the trade name "EPICLON CR-5L", manufactured by Nagase ChemteX Corporation under the trade name "Denacol EX-512", and manufactured by Nissan Chemical Industries, Inc. under the trade name "TEPIC-G".

[0120] As an oxazoline crosslinking agent, oxazoline crosslinking agents having more than one oxazoline group in one molecule can be used without particular restrictions.

[0121] Examples of aziridine-based crosslinking agents include trimethylolpropane tris[3-(1-acrididinyl)propionate] and trimethylolpropane tris[3-(1-(2-methyl)acrididinylpropionate)].

[0122] As a carbodiimide-based crosslinking agent, it is possible to use low-molecular-weight or high-molecular-weight compounds having two or more carbodiimide groups.

[0123] In some methods, isocyanate-based crosslinking agents can be used as crosslinking agents. According to isocyanate-based crosslinking agents, adhesives with well-balanced adhesive strength, cohesive strength, and other bonding properties, as well as good heat-removable properties, can be easily formed. One isocyanate-based crosslinking agent can be used alone, or two or more can be used in combination. Although not particularly limited, the amount of isocyanate-based crosslinking agent used is preferably less than 3 parts by weight relative to 100 parts by weight of the polymer (specifically, the base polymer, such as an acrylic polymer) contained in the adhesive layer. By limiting the amount of isocyanate-based crosslinking agent used, the crosslinking density can be moderately suppressed. At this crosslinking density, during heat treatment, the olefinic unsaturated groups in the adhesive layer frequently collide with the thermal polymerization initiator, resulting in thermosetting, which tends to easily obtain the desired heat-removable and heat-resistant peelable properties. From this perspective, in some preferred embodiments, the amount of isocyanate-based crosslinking agent used relative to 100 parts by weight of the polymer is 2 parts by weight or less, more preferably 1.5 parts by weight or less, even more preferably 1.0 parts by weight or less, even more preferably 0.8 parts by weight or less, and particularly preferably 0.6 parts by weight or less. By limiting the amount of isocyanate-based crosslinking agent used, it is easier to obtain sufficient adhesive strength. In addition, relative to 100 parts by weight of the polymer, the amount of isocyanate-based crosslinking agent used can be, for example, 0.01 parts by weight or more, and in some preferred embodiments, it can be 0.05 parts by weight or more, 0.1 parts by weight or more, 0.3 parts by weight or more, or 0.5 parts by weight or more. By appropriately setting the amount of isocyanate-based crosslinking agent used within the above range, the effects brought about by the technology disclosed herein can be ideally achieved, and an adhesive that exhibits well-balanced adhesive strength, cohesive strength, and other adhesive properties can be ideally obtained.

[0124] Regarding the amount of crosslinking agent used, from the viewpoint of achieving a well-balanced adhesive with good adhesion, cohesion, and other bonding properties, it is acceptable to use an amount more than 0 parts by weight relative to 100 parts by weight of the polymer (specifically, the base polymer, such as an acrylic polymer) contained in the adhesive layer. For example, it can be set to 0.001 parts by weight or more, or 0.01 parts by weight or more. In some preferred embodiments, the amount of crosslinking agent used relative to 100 parts by weight of the aforementioned polymer can be 0.05 parts by weight or more, 0.1 parts by weight or more, 0.3 parts by weight or more, or 0.5 parts by weight or more. Furthermore, the upper limit of the amount of crosslinking agent used may vary depending on the type of crosslinking agent used, and is therefore not limited to a specific range, but is preferably limited to a specified amount or less. By limiting the amount of crosslinking agent used, the crosslinking density can be moderately suppressed. At this crosslinking density, during heat treatment, the olefinic unsaturated groups in the adhesive layer frequently collide with the thermal polymerization initiator and undergo thermosetting, tending to easily obtain the desired heat-resistant and heat-resistant peelability. From this perspective, it is suitable, for example, to use less than 10 parts by weight of crosslinking agent relative to 100 parts by weight of the polymer mentioned above; in some cases, less than 5 parts by weight is preferred, and less than 3 parts by weight is also acceptable. In some cases, it is suitable to use less than 1 part by weight of crosslinking agent relative to 100 parts by weight of the polymer mentioned above; preferably less than 0.9 parts by weight, less than 0.8 parts by weight, less than 0.7 parts by weight, less than 0.6 parts by weight, or less than 0.5 parts by weight. By limiting the amount of crosslinking agent used, there is a tendency to easily obtain sufficient adhesive strength.

[0125] To facilitate a more efficient crosslinking reaction, a crosslinking catalyst may be used. Examples of crosslinking catalysts include tetrabutyl titanate, tetraisopropyl titanate, tri(acetylacetone)ferric, butyltin oxide, and dioctyltin dilaurate, among other metal-based crosslinking catalysts. There is no particular limitation on the amount of crosslinking catalyst used. Relative to 100 parts by weight of the polymer contained in the binder layer (specifically, the base polymer, such as an acrylic polymer), the amount of crosslinking catalyst used can be, for example, approximately 0.0001 parts by weight or more, approximately 0.001 parts by weight or more, or approximately 0.005 parts by weight or more, and can also be approximately 1 part by weight or less, approximately 0.1 parts by weight or less, or approximately 0.05 parts by weight or less.

[0126] In adhesive compositions used for forming adhesive layers, it is desirable to include compounds that generate keto-enol tautomers as crosslinking inhibitors. For example, compounds that generate keto-enol tautomers are preferably used in adhesive compositions containing isocyanate-based crosslinking agents or adhesive compositions that can be used in conjunction with isocyanate-based crosslinking agents. This can extend the pot life of the adhesive composition.

[0127] Various β-dicarbonyl compounds can be used as compounds that generate keto-enol tautomerism. Specific examples include β-diketones such as acetylacetone and 2,4-hexanedione; acetoacetate esters such as methyl acetoacetate and ethyl acetoacetate; propionylacetate esters such as ethyl propionyl; isobutyrylacetate esters such as ethyl isobutyryl; malonates such as methyl malonate and ethyl malonate; and so on. Among these, acetylacetone and acetoacetate esters are suitable compounds. One or more compounds can be used alone or in combination to generate keto-enol tautomerism.

[0128] The amount of the compound that generates keto-enol tautomerism may be, for example, 0.1 to 20 parts by weight or 0.5 to 15 parts by weight or 1 part by weight or 1 part by weight or 5 parts by weight relative to 100 parts by weight of the polymer (specifically, the base polymer, such as an acrylic polymer) contained in the adhesive layer.

[0129] (Other ingredients) The adhesive layer may contain, as needed, various additives commonly found in the adhesive field, such as tackifiers, silane coupling agents, peel strength modifiers, viscosity modifiers (e.g., thickeners), leveling agents, plasticizers, fillers, colorants such as pigments and dyes, stabilizers, preservatives, and anti-aging agents. Given these various additives, conventionally known additives can be used by conventional methods; therefore, detailed descriptions are omitted as they do not specifically characterize the present invention.

[0130] It should be noted that the technology disclosed herein can achieve the desired adhesive properties, such as adhesive strength, without the use of an adhesive agent. In some embodiments, the content of the adhesive agent in the adhesive layer can be set to less than 10 parts by weight, and further to less than 5 parts by weight, relative to 100 parts by weight of the polymer (specifically, the base polymer, such as an acrylic polymer) contained in the adhesive layer. The aforementioned content of the adhesive agent can be less than 1 part by weight (e.g., less than 0.5 parts by weight) or less than 0.1 parts by weight (more than 0 parts by weight and less than 0.1 parts by weight). The adhesive layer can be a substance without an adhesive agent.

[0131] (The morphology of the adhesive composition) Although not specifically limited, the adhesive layer disclosed herein is preferably formed using a solvent-based adhesive composition. The aforementioned solvent-based adhesive composition is an adhesive composition in which adhesive-forming components are contained in an organic solvent. Typically, the solvent-based adhesive composition contains a solution polymer of monomeric components, a complexing monomer, a thermal polymerization initiator (specifically a peroxide-based polymerization initiator), and optionally other additives. The effects of the technology disclosed herein can be effectively achieved when the solvent-based adhesive (layer) is present. The solvent contained in the solvent-based adhesive composition can be appropriately selected from conventionally known organic solvents. For example, any one solvent, or a mixture of two or more solvents, can be used from aromatic compounds such as toluene (typically aromatic hydrocarbons); esters such as ethyl acetate and butyl acetate; aliphatic or alicyclic hydrocarbons such as hexane and cyclohexane; haloalkanes such as 1,2-dichloroethane; lower alcohols such as isopropanol (e.g., monohydric alcohols with 1 to 4 carbon atoms); ethers such as tert-butyl methyl ether; ketones such as methyl ethyl ketone; etc.

[0132] As described above, according to this specification, an adhesive composition containing the components that may be included in the adhesive layer disclosed herein can be provided. Specifically, an adhesive composition comprising a polymer, a monomer, and a thermal polymerization initiator is provided. The polymer contains olefinically unsaturated groups. Additionally, the monomer contains monomer A. Monomer A has a molecular weight of 250 to 5000 and has one or two olefinically unsaturated groups within its molecule. According to this adhesive composition, an adhesive that balances low contamination of the adhered material after heating and easy peeling after heating can be formed. Furthermore, the adhesive composition may contain the components that may be included in the adhesive layer (e.g., crosslinking agents). The content (by weight) of each component that may be included in the adhesive layer can be converted into the content (by weight) of solid component (also called non-volatile component) in the adhesive composition. Details regarding other adhesive compositions are as described in the adhesive layer description, and therefore, repeated descriptions are omitted.

[0133] (Formation of the adhesive layer) The adhesive layer disclosed herein can be formed using methods known in the art. After the adhesive composition is applied (e.g., coated) to a suitable surface, the adhesive can be formed in a layered (adhesive layer) form by appropriate curing treatment. One curing method (e.g., drying, crosslinking, polymerization, cooling, etc.) of the adhesive composition can be used, or two or more can be used simultaneously or in multiple stages. In the case of solvent-based adhesive compositions, typically, the composition can be dried (preferably further crosslinked) to form the adhesive.

[0134] For example, in the case of a substrate-free double-sided adhesive sheet, the following method can be used: after applying an adhesive composition to a peelable surface (peel surface), an adhesive layer can be formed on the surface by curing the adhesive composition. In the case of an adhesive sheet with a substrate, a method can be used to form an adhesive layer by directly applying (typically coating) an adhesive composition to the substrate and curing it (direct method). Alternatively, a method can be used to form an adhesive layer on a peelable surface (peel surface) by applying an adhesive composition to it and curing it, and then transferring the adhesive layer to the substrate (transfer method). The peel surface can be the surface of a release liner, the back side of a substrate that has been peeled, etc. It should be noted that the adhesive layer disclosed herein is typically formed continuously, but is not limited to this form; for example, it can also be an adhesive layer formed in a regular or irregular pattern such as dots or stripes.

[0135] The coating of the adhesive composition can be performed using known or conventional coating machines such as gravure roller coaters, reverse roller coaters, kiss roller coaters, dip roller coaters, die coaters, bar coaters, doctor blade coaters, and spray coaters. Alternatively, the adhesive composition can be coated by impregnation, curtain coating, or other methods.

[0136] From the viewpoint of promoting crosslinking reactions and improving manufacturing efficiency, drying the adhesive composition is preferably carried out under heating. The drying temperature is not particularly limited, but can be set to around 40–100°C, and is generally preferred to be around 60–80°C. For example, drying at the above temperatures (e.g., drying for about 1–10 minutes, more specifically about 3–7 minutes) involves low heating temperatures, and solvent evaporation sometimes occurs. In adhesive compositions containing monomers and thermal polymerization initiators, the reaction of monomers and the deactivation of thermal polymerization initiators are negligible. Furthermore, after drying the adhesive composition, aging can be performed to adjust component transfer within the adhesive layer, promote crosslinking reactions, and relax strain present in the substrate and adhesive layer.

[0137] (thickness) The thickness of the adhesive layer is not particularly limited. The thickness of the adhesive layer is typically 1 μm or more, but can be 2 μm or more, or 3 μm or more. There is a tendency that a greater adhesive layer thickness results in increased adhesion to the adhered objects. In some preferred embodiments, the adhesive layer thickness is 5 μm or more, but can also be 10 μm or more, 15 μm or more, 20 μm or more, or 25 μm or more. An upper limit for the adhesive layer thickness is suitable, for example, around 200 μm or less, but can be 100 μm or less (e.g., less than 100 μm), or even 50 μm or less. By limiting the thickness of the adhesive layer within a specified range, residual adhesive caused by cohesive failure is prevented, and easy peelability is easily achieved. Furthermore, a thin adhesive layer is advantageous in terms of the thinness of the adhesive sheet, and also tends to have excellent conformability to the adhered objects. In some preferred embodiments, the adhesive layer thickness is 40 μm or less, or even 30 μm or less.

[0138] <Substrate Layer> The adhesive sheet disclosed herein may include a substrate layer. Various sheet-like substrates can be used as the substrate (layer) supporting (lining) the adhesive layer. As such substrates, resin films, paper, cloth (woven fabric, non-woven fabric, etc.), rubber sheets, foam sheets, metal foils, and composites thereof can be used. Examples of resin films include polyolefin films; polyester films; vinyl chloride resin films; vinyl acetate resin films; polyamide resin films; fluoropolymer films; celluloid; and so on. Non-limiting examples of polyester films include polyethylene terephthalate (PET), polyethylene naphthalate (PEN), etc. Other examples of resin films include resin films formed from one or more engineering plastics (which may be super engineering plastics) selected from polyphenylene sulfide resins, polysulfone resins, polyethersulfone resins, polyetheretherketone resins, polyetherketone resins, polyphthalamide resins, polyarylate resins, polyamide-imide resins, polyimide resins, and polyetherimide resins. The use of engineering plastics is preferred from the viewpoint of heat resistance.

[0139] In some preferred embodiments, a resin film with specified rigidity (strength) and excellent processability and operability is used as the substrate (layer). From the viewpoint of heat resistance, polyester films, polyamide resin films, and engineering plastic films (e.g., polyimide-based resin films) are preferred as the resin film substrate. It should be noted that, in this specification, the term "resin film" typically refers to a non-porous film, specifically a resin film that is substantially free of air bubbles (pore-free). Therefore, the above-mentioned resin film is a concept distinct from foamed films and nonwoven fabrics. The density of the resin film that can be used as a substrate is, for example, approximately 0.85 to 1.80 g / cm³. 3 Around 1.00 g / cm³ 3The above can also be 1.10 g / cm³. 3 Above (e.g., 1.20 g / cm³) 3 (above), and also, it can be 1.60 g / cm³. 3 The following can also be 1.50 g / cm³. 3 The resin film described above can be a single-layer structure or a multi-layer structure with two or more layers (e.g., a three-layer structure).

[0140] In the substrate layer (e.g., resin film), known additives such as light stabilizers, antioxidants, antistatic agents, colorants (dyes, pigments, etc.), fillers, slip agents, and anti-blocking agents can be added as needed. The amount of additives is not particularly limited and can be appropriately set according to the application.

[0141] There are no particular limitations on the manufacturing method of the resin film. For example, conventional resin film forming methods known in the past, such as extrusion molding, blow molding, T-die casting, and calendering roll forming, can be appropriately used.

[0142] The aforementioned substrate layer may be substantially composed of a resin film. Alternatively, in addition to the aforementioned resin film, the aforementioned substrate layer may also include auxiliary layers. Examples of such auxiliary layers include optical property adjustment layers (e.g., coloring layers, anti-reflective layers), printing layers for imparting a desired appearance, laminated layers, antistatic layers, primer layers, release layers, and other surface treatment layers.

[0143] The thickness of the substrate layer is not particularly limited and can be appropriately selected according to the purpose, typically ranging from 1 to 500 μm. From the viewpoints of processability, operability, and workability, a substrate layer thickness of 2 μm or more (e.g., 3 μm or more) is suitable, preferably 5 μm or more, and can be approximately 7 μm or more, or 10 μm or more. In some embodiments, the substrate layer thickness can be 20 μm or more, 30 μm or more, or 40 μm or more. Furthermore, a substrate layer thickness of approximately 200 μm or less is suitable, and from the viewpoints of lightweighting and thinness, approximately 100 μm or less is preferred, more preferably approximately 80 μm or less, and can also be 60 μm or less. When the substrate layer thickness is reduced, there is a tendency for improved flexibility of the adhesive sheet and increased conformability to the surface shape of the adhered object.

[0144] As needed, conventional surface treatments such as corona treatment, plasma treatment, ultraviolet irradiation treatment, acid treatment, alkali treatment, and application of a primer can be applied to the adhesive layer side surface of the substrate layer. Such surface treatments can be used to improve the adhesion between the substrate layer and the adhesive layer (in other words, the anchoring of the adhesive layer to the substrate layer). The composition of the primer is not particularly limited and can be appropriately selected from known substances. The thickness of the primer layer is not particularly limited; for example, approximately 0.01 μm to 1 μm is suitable, and preferably approximately 0.1 μm to 1 μm. Furthermore, the various surface treatments described above, antistatic treatments, and other surface treatments can be applied to the back side of the substrate layer.

[0145] <Total Thickness> The total thickness of the adhesive sheet disclosed herein (which may include an adhesive layer and a substrate layer, but excluding a release liner) is not particularly limited, and a range of approximately 5 to 1000 μm is suitable. From the viewpoint of adhesive properties and operability, the total thickness of the adhesive sheet can be 10 μm or more, 30 μm or more, or 50 μm or more. Furthermore, from the viewpoint of lightweighting and thinning, in some embodiments, the total thickness of the adhesive sheet is 500 μm or less, or 300 μm or less. In some preferred embodiments, the total thickness of the adhesive sheet is 150 μm or less, 120 μm or less, or 100 μm or less (e.g., less than 100 μm). Reducing the thickness of the adhesive sheet is also advantageous in terms of thinning, miniaturization, lightweighting, and resource conservation.

[0146] <Removing Liner> The release liner used for the adhesive sheet disclosed herein is not particularly limited, and can include, for example, release liners whose surfaces have been peeled off from a resin film, paper, or other liner substrate, or release liners formed from low-adhesion materials such as fluoropolymers (polytetrafluoroethylene, etc.) or polyolefin resins (polyethylene, polypropylene, etc.). In the aforementioned peeling treatment, for example, silicone-based or long-chain alkyl-based release agents can be used. In some embodiments, a peeled resin film is preferably used as the release liner.

[0147] <Properties of Adhesive Sheets> (Reduction rate of peel force after heating) In some methods, the preferred adhesive sheet exhibits a peel strength reduction rate exceeding 50% after heating, calculated using the following formula: Peel force reduction rate after heating [%] = (1 - F1 / F0) × 100 (In the above formula, F1 is the peel force after heating [N / 20mm] after being attached to the substrate and heated at 180℃ for 30 minutes, and measured at 23℃; F0 is the peel force before heating [N / 20mm]).

[0148] Adhesive sheets that meet the above characteristics can adhere well to the substrate and exhibit good heat-peelability and heat-resistant peelability upon peeling after heat treatment. In some preferred embodiments, the reduction rate of peel force after heating can be 60% or more, 70% or more, 80% or more, 85% or more, 90% or more, or 95% or more. The greater the reduction rate of peel force after heating, the better the heat-peelability and heat-resistant peelability. Furthermore, it is preferable that the reduction rate of peel force after heating is less than 99.9%. Adhesive sheets with a reduction rate of peel force after heating less than 99.9% exhibit heat-peelability and maintain adhesion to the substrate before peeling after heating. This prevents the adhesive sheet from naturally peeling off from the substrate due to heating and the resulting adverse conditions. From this perspective, the reduction rate of peel force after heating can be 99.0% or less, for example, 98.0% or less, or less than 95.0%.

[0149] (Peeling force F0 before heating) While not particularly limited, in some methods, it is suitable for the pre-heating peel force F0 of the adhesive sheet to be 1.0 N / 20 mm or more, preferably 3.0 N / 20 mm or more, more preferably 5.0 N / 20 mm or more, further preferably 7.0 N / 20 mm or more, particularly preferably 9.0 N / 20 mm or more, and may also be 10 N / 20 mm or more. Adhesive sheets exhibiting the above-mentioned pre-heating peel force F0 can provide good adhesion to substrates such as silicon wafers. The upper limit of the above-mentioned pre-heating peel force F0 is appropriately set according to the required adhesion and is therefore not limited to a specific range; for example, it may be about 30 N / 20 mm or less, or about 20 N / 20 mm or less. Specifically, the above-mentioned pre-heating peel force F0 refers to the peel force on a silicon wafer measured at 23°C with a peel angle of 180 degrees and a speed of 300 mm / min. The above-mentioned pre-heating peel force F0 is also called the initial peel force. The peeling force F0 before heating was measured more specifically by the method described in the embodiments described later.

[0150] (Peeling force F1 after heating) While not particularly limited, in some embodiments, it is preferred that the peel force (post-heat peel force) F1 of the adhesive sheet to the adhered object after heat treatment at 180°C for 30 minutes is 5 N / 20 mm or less. An adhesive sheet exhibiting the above-mentioned post-heat peel force F1 can be considered an adhesive sheet with heat-resistant peelability, and further, heat-resistant peelability after heat treatment. From the viewpoint of peelability, in some preferred embodiments, the above-mentioned post-heat peel force F1 is 3 N / 20 mm or less, more preferably 2 N / 20 mm or less, even more preferably 1.5 N / 20 mm or less, even more preferably 1.0 N / 20 mm or less, particularly preferably 0.6 N / 20 mm or less, and may also be 0.3 N / 20 mm or less. The lower limit of the above-mentioned post-heat peel force F1 may be 0.0 N / 20 mm or more (e.g., 0.1 N / 20 mm or more). The adhesive sheet with a post-heating peel strength F1 of the aforementioned value is characterized by easy peeling after heating and maintaining adhesion to the substrate before peeling after heating. This prevents the adhesive sheet from naturally peeling off from the substrate due to heating, and avoids any resulting defects. Specifically, the post-heating peel strength F1 refers to the peel strength measured at 23°C with a peel angle of 180 degrees and a peel speed of 300 mm / min after being heated to 180°C for 30 minutes while attached to the substrate. A silicon wafer can be used as the substrate. More specifically, the post-heating peel strength F1 is measured using the method described in the embodiments described later.

[0151] (Peeling force at the end after heating) In some embodiments, the peel strength of the heated end of the adhesive sheet, measured by the method described in the examples below, is preferably 15 N / 10 mm or less. Adhesive sheets with the aforementioned peel strength after heating experience light peeling after heat treatment at a specified temperature or higher, exhibiting excellent peeling workability. In some preferred embodiments, the aforementioned peel strength after heating can be 12 N / 10 mm or less, or 10 N / 10 mm or less (e.g., less than 10 N / 10 mm). The lower limit of the aforementioned peel strength after heating is not particularly limited; for example, it can be 1 N / 10 mm or more, or 3 N / 10 mm or more.

[0152] <Peeling Method> According to this specification, a method for peeling an adhesive sheet attached to an adhesive substrate is provided. The peeling method includes: heat-treating the substrate with the adhesive sheet attached at a temperature above a predetermined temperature, and then peeling the adhesive sheet from the substrate. The adhesive sheet disclosed herein has heat-resistant peelability (heat-resistant peelability), and therefore can be easily peeled from the substrate even after exposure to heat under predetermined conditions.

[0153] In some methods, the heat treatment temperature for the adhered object with the adhesive sheet is above 100°C, for example, approximately 110°C or above, approximately 120°C or above, approximately 130°C or above, or approximately 150°C or above. In some preferred methods, the heat treatment temperature for the adhered object with the adhesive sheet is above 150°C, for example, approximately 160°C or above, or above 170°C. The upper limit of the heat treatment temperature can vary depending on the purpose of the heat treatment, the heat resistance of the adhered object, etc., and is generally below 260°C, approximately 250°C, below 230°C, below 200°C, or below 180°C. The heat treatment time is not particularly limited and can be within 10 hours, within 5 hours, or within 3 hours. From the viewpoint of heating process efficiency, in some preferred methods, the heat treatment time can be within 1 hour, within 30 minutes, within 15 minutes, within 10 minutes, or within 5 minutes. The adhesive sheet disclosed herein exhibits heat-curing properties through a short heat treatment, resulting in heat-resistant peelability. Furthermore, the heat treatment time can be 1 minute or more, 3 minutes or more, 5 minutes or more, 7 minutes or more, or 9 minutes or more. In some embodiments, the heat treatment time can be 10 minutes or more, 30 minutes or more, 60 minutes or more, exceeding 1 hour, exceeding 3 hours, exceeding 4 hours, or exceeding 5 hours. The adhesive sheet disclosed herein exhibits heat-curing properties through heat treatment based on the aforementioned heating temperature, resulting in reduced peel strength. Even with prolonged heating, an increase in peel strength (re-peeling) is not observed or is suppressed. Therefore, heat-resistant peelability is maintained even after prolonged heat treatment.

[0154] <Applications> The adhesive sheet disclosed herein has heat-peelability, and therefore can be used as an adhesive sheet for various applications requiring heat-peelability, such as applications where it can be peeled off from the adhered object by heating. For example, it can be used in a state attached to the adhered object for applications where it will be exposed to heat exceeding 100°C (e.g., approximately 120°C to 260°C). Furthermore, it can ideally be used in a state attached to the adhered object for applications where it will be exposed to heat exceeding 150°C (e.g., approximately 160°C to 260°C).

[0155] For example, applications of the adhesive sheet disclosed herein include masking, temporary fixing, and protective applications where heat resistance is required. It is also preferably used as a process material for fixing and peeling off objects in the manufacturing processes of electronic devices and electronic components. Furthermore, suitable applications of the adhesive sheet disclosed herein include semiconductor device manufacturing. For example, in semiconductor wafer processing (typically silicon wafer processing), it is preferably used as a wafer holding sheet to fix the wafer to a mounting plate. Ideally, it can be used as a process material for processing semiconductor wafers while they are held in place by an adhesive layer and then peeled off from the semiconductor after processing. Additionally, the adhesive sheet disclosed herein is also preferably used as a protective sheet to protect the wafer during the aforementioned wafer processing. Especially in the manufacturing of semiconductor devices, where heating may occur during processing steps, an adhesive sheet with heat resistance and easy peeling is preferred. Furthermore, the adhesive sheet disclosed herein is also suitable for optical applications requiring heat resistance. More specifically, the adhesive sheet disclosed herein can be used, for example, in applications such as bonding optical components (for bonding optical components) and manufacturing articles using the aforementioned optical components (optical articles). It should be noted that the aforementioned optical components refer to components possessing optical properties (e.g., polarization, refraction, scattering, reflection, transmission, absorption, diffraction, optical rotation, visual recognition, etc.).

[0156] Furthermore, the adhesive sheet disclosed herein exhibits excellent heat-resistant peelability to organic material surfaces, making it ideal for use in applications where it is attached to the surface of a substrate (the adherend) made of an organic material and then peeled off. Examples of such substrate materials include circuit boards (e.g., printed circuit boards (PCBs) and flexible printed circuit boards (FPCs)). The adhesive sheet can ideally be used as a temporary fixing piece for the circuit board.

[0157] There is no particular limitation on the type of material (adhesive material) to which the adhesive sheet disclosed herein is attached. The adhesive sheet disclosed herein can be used for fixing, protecting, etc., various components and materials. As the adhesive material, materials composed of any of the following can be used: organic materials, inorganic materials, and composites thereof. Examples of adhesive materials include: alkaline glass, alkali-free glass, and other glass; stainless steel (SUS), aluminum, and other metal materials; alumina, silicon dioxide, and other ceramic materials; polyester resins such as PET, acrylic resins, ABS resins, polycarbonate resins, polystyrene resins, transparent polyimide resins, epoxy resins, phenolic resins, and other resin materials; and so on. Suitable examples of adhesive materials include circuit boards with surfaces made of epoxy resin (e.g., glass cloth substrate epoxy resin copper-clad laminates). Other suitable examples of adhesive materials include glass materials such as alkaline glass, semiconductor wafers, etc. The aforementioned glass material can be, for example, a glass plate with a transparent conductive film (e.g., ITO (indium tin oxide) film) and a partially FPC (flexible printed circuit board) surface, as used in tablet computers, mobile phones, organic LEDs (light-emitting diodes), etc.

[0158] <Structures, their manufacturing methods and techniques> As described above, according to this specification, a structure having the adhesive sheet disclosed herein and an adherend to which the adhesive sheet is attached, as well as a method for manufacturing the structure including the step of attaching the adhesive sheet to the adherend, can be provided. In this structure and its manufacturing method, various adherends exemplified above, workpieces made of various adherend materials, components, etc., can be used as adherends. Suitable examples of adherends include various substrates such as semiconductor wafers, optical components, and circuit boards. The manufacturing method may include steps for preparing the adherend and the adhesive sheet.

[0159] Furthermore, the adhesive sheet disclosed herein is preferably used for processing the adhered object using the adhesive sheet. Therefore, according to this specification, for example, a method including processing steps of processing an adhered object to which the adhesive sheet disclosed herein is attached can be provided. This method can be called a method for processing the adhered object, or a method for using the adhesive sheet in the processing of the adhered object. Examples of adhered objects used include various adhered objects exemplified above, workpieces made of various adhered object materials, components, etc. They are also referred to as workpieces before the processing steps and as workpieces after the processing steps. Suitable examples of adhered objects include various substrates such as semiconductor wafers, optical components, and circuit boards. Additionally, for example, when the adhered object is a semiconductor wafer, the above method can be a method for manufacturing semiconductor elements. The processing steps are not particularly limited and can be various processing steps performed on various adhered objects. For example, in cases where the adhered material is a semiconductor wafer, PCB, FPC, or other circuit substrate, the processing steps performed on the adhered material may include laser cutting, back-side grinding, etching, photolithography, ion implantation, chip bonding, wire bonding, molding, and packaging. These processing steps may also involve heating, i.e., heat treatment.

[0160] In one embodiment, the above-described method (e.g., a method for processing an adhered object, a method for using an adhesive sheet in the processing of the adhered object, etc.) may further include a peeling step after the above-described processing step to remove the adhesive sheet from the adhered object. The adhesive sheet disclosed herein is suitable for various methods including such a peeling step because it reduces contamination on the surface of the adhered object and has good easy peelability. It should be noted that the above-described method may include a step of preparing the adhesive sheet and the adhered object, and a step of attaching the adhesive sheet to the adhered object, before the above-described processing step.

[0161] In one embodiment, the substrate to which the adhesive sheet is attached is subjected to heat treatment before, during, or after a processing step. Such heat treatment can also be a processing step accompanied by heating. For example, laser cutting, as described above, is a heat-generating process. Furthermore, molding processes, such as sealing chips on a PCB with resins like epoxy resin, may include processes involving heating to around 175°C. Additionally, the processing of circuit boards such as FPCs typically includes chip bonding processes based on reflow soldering at 250°C or higher. It should be noted that the heating temperatures and other conditions for the heat treatment are as described above and will not be repeated here. By undergoing the aforementioned heat treatment, the adhesive sheet can be easily peeled off from the substrate due to its heat-removable properties.

[0162] As described above, the adhesive sheet disclosed herein is preferred for use in various methods of removing it from an adhesive surface after it has been applied, due to reduced contamination of the surface of the adhered object and good peelability. For example, it is preferred for use in methods including: a processing step of processing the adhered object, which is the object to which the adhesive sheet is applied; and a peeling step of peeling the adhesive sheet from the adhered object after the processing step.

[0163] The matters disclosed in this specification include the following.

[0164] [1] An adhesive sheet, which is an adhesive sheet having an adhesive layer. The aforementioned adhesive layer comprises a polymer, monomers, and a thermal polymerization initiator. The aforementioned polymer contains olefinic unsaturated groups. The aforementioned monomer includes monomer A, wherein monomer A has a molecular weight of 250 to 5000 and has one or two olefinic unsaturated groups within the molecule.

[0165] [2] The adhesive sheet as described in [1] above, wherein the content of the aforementioned thermal polymerization initiator in the aforementioned adhesive layer is 0.1 parts by weight or more relative to 100 parts by weight of the aforementioned polymer.

[0166] [3] The adhesive sheet as described in [1] or [2] above, wherein the aforementioned monomer A has an ionic site.

[0167] [4] The adhesive sheet as described in any one of [1] to [3] above, used in a method comprising the following steps: a processing step, processing an object to be bonded, which is to which the aforementioned adhesive sheet is attached; and The peeling process involves peeling the adhesive sheet from the adhered object after the aforementioned processing steps.

[0168] [5] A structure comprising an adhesive sheet as described in any one of [1] to [3] above, and a substrate to which the adhesive sheet is attached.

[0169] [6] A method for manufacturing a structure, which is a method for manufacturing a structure having a substrate and an adhesive sheet as described in any one of [1] to [3] above. The aforementioned method includes the process of attaching the aforementioned adhesive sheet to the aforementioned substrate.

[0170] [7] A method comprising: The processing step involves processing the substrate to which the adhesive sheet described in any one of [1] to [3] is attached.

[0171] [8] The method described in [7] above further includes: a peeling step, wherein the adhesive sheet is peeled off from the substrate after the aforementioned processing step.

[0172] [9] An adhesive composition comprising a polymer, a monomer, and a thermal polymerization initiator, The aforementioned polymer contains olefinic unsaturated groups. The aforementioned monomer includes monomer A, wherein monomer A has a molecular weight of 250 to 5000 and has one or two olefinic unsaturated groups within the molecule.

[0173]

[10] The adhesive composition as described in [9] above, wherein the content of the aforementioned thermal polymerization initiator is 0.1 parts by weight or more relative to 100 parts by weight of the aforementioned polymer.

[0174]

[11] An adhesive composition as described in [9] or

[10] above, wherein the aforementioned monomer A has an ionic site.

[0175] Example The following describes some embodiments of the present invention, but it is not intended to limit the invention to the contents shown in these embodiments. It should be noted that, unless otherwise stated, in the following description, "parts" and "%" are based on weight.

[0176] <Evaluation Methods> (Peeling force F0 before heating) The adhesive sheet was cut to a size of 20 mm wide and 100 mm long. At 23°C and 50% RH, the adhesive surfaces of the sheet were pressed together and adhered to the substrate using a hand roller. The substrate with the adhesive sheet attached was left to stand for 2 hours under these conditions and then used as an evaluation sample. The evaluation sample was placed in a tensile testing machine at 23°C and 50% RH, and the peel strength (peel force before heating) F0 [N / 20 mm width] was measured when the adhesive sheet was peeled from the substrate at a peel angle of 180 degrees and a speed of 300 mm / min. As the substrate, a silicon wafer (manufactured by Shin-Etsu Chemical Co., Ltd., 6-inch N) was used. <100> The tensile tester (-100) is attached to the mirror surface of the silicon wafer with the adhesive side of the adhesive sheet attached. The tensile tester can be the "EZ-S 500N" or equivalent manufactured by Shimadzu Corporation. Alternatively, if the object being tested is a double-sided adhesive sheet, the non-test side can be backed with a PET film for measurement.

[0177] (Peeling force F1 after heating) Using the adhesive sheet, an evaluation sample was prepared according to the method described in the above-described determination of peel strength F0 before heating. The obtained evaluation sample was heated in an oven at 180°C for 30 minutes, removed from the oven, and allowed to stand for 30 minutes at 23°C and 50%RH. Then, the evaluation sample was placed in a tensile testing machine under this environment, and the peel strength (peel strength after heating) F1 [N / 20mm width] was measured when the adhesive sheet was peeled from the adherend at a peel angle of 180 degrees and a speed of 300mm / min. The adherend, tensile testing machine, and other matters are the same as those for the determination of peel strength F0 before heating.

[0178] (Reduction rate of peel force after heating) The reduction rate of peel force after heating can be calculated using the following formula based on the peel force F0 before heating and the peel force F1 after heating.

[0179] Peel force reduction rate after heating [%] = (1 - F1 / F0) × 100 (Peeling force at the end after heating) The adhesive sheet was cut to a width of 10 mm and a length of 100 mm. Under conditions of 23°C and 50% RH, the adhesive surfaces of the adhesive sheet were pressed together with a hand roller and bonded to an alkaline glass plate (Matsunami Glass Ind., Ltd., 1.35 mm thick, with a blue-edged edge) serving as the substrate. The alkaline glass plate with the adhesive sheet attached was left to stand for 2 hours under the same conditions, then heated in an oven at 180°C for 30 minutes. After being removed from the oven, it was left to stand for 30 minutes under conditions of 23°C and 50% RH before being used as an evaluation sample. The evaluation sample was placed in a tensile testing machine at 23°C and 50% RH, along a peel angle of 20 degrees, at a speed of 1.6 × 10⁻⁶. 3 The adhesive sheet is peeled from the adhered object at a speed of mm / min, and the peel strength at the end of the adhesive sheet (end peel force after heating) [N / 10mm width] is measured. If the end peel force after heating is less than 15N / 10mm, it is considered to be light peel. The tensile testing machine can be the "EZ-S 500N" or equivalent manufactured by Shimadzu Corporation. Alternatively, if the object being evaluated is a double-sided adhesive sheet, the non-test side can be backed with a PET film for measurement.

[0180] (Residue of component C after heat peeling) At 23°C and 50%RH, adhesive sheets cut to 50mm x 50mm size are pressed and bonded to a silicon wafer (manufactured by Shin-Etsu Chemical Co., Ltd., 6-inch N) using a hand roller. <100> A mirror surface with an adhesive film (-100) was obtained. The silicon wafer with the adhesive film attached was left to stand for 2 hours under the same conditions, then heated in an oven at 180°C for 30 minutes. After being removed from the oven, it was left to stand for 30 minutes at 23°C and 50%RH before being used as an evaluation sample. The evaluation sample was placed in a tensile testing machine at 23°C and 50%RH, and the adhesive film was peeled off from the silicon wafer at a peel angle of 180 degrees and a speed of 300 mm / min. The amount of carbon (C) on the surface of the silicon wafer after the adhesive film was peeled off, relative to the total elemental mass [atomic%], was determined using X-ray photoelectron spectroscopy (XPS) and recorded as the C component residue after heat peeling.

[0181] Specifically, XPS involves performing elemental analysis (qualitative analysis) on the wafer surface using a wide scan, followed by narrow scan analysis of the elements detected by the wide scan to calculate the carbon (C) content relative to the total element content. The XPS measurement conditions are shown below.

[0182] (Measurement conditions) XPS: Manufactured by ULVAC-PHI, Quantum SXM X-ray source: Monochromatic Al Kα X-ray setting: 100μm [15kV, 25W] Photoelectron extraction angle: 45° relative to the sample surface Neutralization conditions: Use a neutralization gun with an Ar ion gun (neutralization mode). Application speed: 3mm / second As a tensile testing machine, the product name "EZ-S 500N" or its equivalent manufactured by Shimadzu Corporation can be used. Furthermore, when the object being evaluated is a double-sided adhesive sheet, the non-test side can be lined with a PET film for measurement.

[0183] <Example 1> (Preparation of adhesive composition) 100 parts of monomer components comprising methoxyethyl acrylate (MEA), acryloylmorpholine (ACMO), and hydroxyethyl acrylate (HEA) in a molar ratio of 80:20:20, and 65 parts of toluene as a polymerization solvent were added to a reaction vessel equipped with a condenser, a nitrogen inlet, a thermometer, and a stirrer. The reaction was carried out at 61°C for 6 hours under a nitrogen atmosphere (solution polymerization) to obtain a solution containing acrylic polymer a. Methacryloxyethyl isocyanate (MOI) was added to this acrylic polymer a solution in an amount equivalent to 16 moles of 20 moles of HEA used as a raw material for acrylic polymer a. The reaction was then carried out in an air stream at 50°C for 48 hours as an addition reaction to obtain a solution of acrylic polymer A with methacryloyl groups at the end of its side chains.

[0184] To a solution of the acrylic polymer A described above, 0.3 parts of a reactive surfactant (manufactured by Daiichi Kogyo Pharmaceutical Co., Ltd., trade name "AQUALON AR-20", an ether sulfate salt having a 1-propenyl group, molecular weight 1200-1300, and 1 olefinic unsaturated group) as monomer A, 20 parts of dipentaerythritol hexaacrylate (DPHA, molecular weight 520, 6 olefinic unsaturated groups) as monomer B, 0.5 parts of an isocyanate crosslinking agent (manufactured by Mitsui Chemicals Co., Ltd., trade name "Takenate D-101E"), and 0.8 parts of benzoyl peroxide (manufactured by NOF CORPORATION, trade name "NYPER BW", SADT: 75°C) as a thermal polymerization initiator were added and mixed uniformly to prepare the adhesive composition described in this example.

[0185] (Making of adhesive sheets) The adhesive composition obtained as described above was applied to the release surface of a commercially available PET release liner and dried at 80°C for 5 minutes to form an adhesive layer with a thickness of 30 μm. A 50 μm thick polyimide (PI) film (product name "Kapton200H", manufactured by Du Pont-Toray Co., Ltd.) was then bonded to this adhesive layer and aged at 50°C for 3 days. This produced the adhesive sheet (a single-sided adhesive sheet with a substrate) described in this example. The adhesive surface of the adhesive sheet is protected by the release liner.

[0186] <Examples 2-4> As shown in Table 1, the amount of monomer A was changed. Otherwise, the adhesive compositions involved in each example were prepared by the same method as in Example 1. The resulting adhesive compositions were used to produce the substrate-coated single-sided adhesive sheets involved in each example by operating in the same manner as in Example 1.

[0187] <Example 5> Without using monomer B, the adhesive composition involved in this example was prepared by the same method as in Example 3. Using the obtained adhesive composition, the substrate-coated single-sided adhesive sheet involved in this example was produced by operating in the same manner as in Example 1.

[0188] <Comparative Examples 1-3> Using the additives shown in Table 1 instead of monomer A, the adhesive compositions of Comparative Examples 1 and 2 were prepared by the same method as in Example 3. Alternatively, without using monomer A, the adhesive composition of Comparative Example 3 was prepared by the same method as in Example 1. Using the obtained adhesive compositions, the substrate-coated single-sided adhesive sheets of each example were manufactured by operating in the same manner as in Example 1. It should be noted that in Table 1, the non-reactive surfactant shown as the additive is sodium 1-dodecanesulfonate (molecular weight 272, number of olefinic unsaturated groups 0), and the acrylic oligomer is urethane acrylate manufactured by Nekami Kogyo Co., Ltd. (trade name "UN-6200", molecular weight 6200, number of olefinic unsaturated groups 2).

[0189] <Comparative Example 4> Without using monomer A, the adhesive composition involved in this example was prepared by the same method as in Example 5. Using the obtained adhesive composition, the substrate-coated single-sided adhesive sheet involved in this example was produced by operating in the same manner as in Example 1.

[0190] Table 1 summarizes the results of each case and provides an evaluation.

[0191] [Table 1] As shown in Table 1, in Examples 1-5, which used a reactive surfactant as monomer A containing a polymer and a thermal polymerization initiator, with a molecular weight of 250-5000 and 1-2 olefinic unsaturated groups, compared to Comparative Examples 3-4, which did not use monomer A, the peeling after heating was lighter, and the C component residue on the surface of the adhered after heating was also at the same level or lower than that of Comparative Examples 3-4. More specifically, comparing Examples 1-4, which had the same composition except for monomer A, with Comparative Example 3, Examples 1-3 showed excellent peeling properties after heating and reduced C component residue on the surface of the adhered after heating compared to Comparative Example 3. In addition, in Example 4, where the amount of monomer A was increased, the C component residue on the surface of the adhered after heating was 24 atomic%, maintaining low contamination of the adhered after heating, and exhibiting particularly excellent peeling properties after heating. Furthermore, comparing Example 5 and Comparative Example 4, which have the same composition except for monomer A, it was also confirmed that the use of monomer A resulted in improved easy peelability after heating and reduced C component residue on the surface of the adhered object after heating. This is believed to be because monomer A, based on its molecular weight and chemical structure, segregates to the surface of the adhesive layer, contributing to improved easy peelability. Furthermore, during heat treatment, monomer A, having 1-2 olefinically unsaturated groups, is incorporated into the adhesive layer through a reaction, thus reducing the amount of C component residue on the surface of the adhered object. Thus, Examples 1-5 achieve a balance between low contamination of the adhered object after heating and easy peelability after heating. It should be noted that while a comparison between Examples 3 and 5 confirms that monomer B also has a certain effect on reducing end-peel force after heating, a comparison between Examples 1-2 and Example 5 shows that the use of monomer A yields an excellent effect on reducing end-peel force after heating.

[0192] On the other hand, in Comparative Examples 3-4, which did not use monomer A, the residual C component on the surface of the adhered objects after heat peeling was relatively low, but the end-peel force after heating was greater than 15 N / 10 mm, indicating poor light peel performance. Furthermore, in Comparative Example 1, which used a non-reactive surfactant instead of monomer A, the end-peel force after heating was reduced, but a large amount of C component was detected on the surface of the adhered objects after peeling. It is believed that the non-reactive surfactant used in Comparative Example 1 segregated onto the adhesive layer surface, which helped reduce the end-peel force after heating, but because it is non-reactive, it did not incorporate into the adhesive layer during heat treatment and remained on the surface of the adhered objects. In Comparative Example 2, which used a high molecular weight acrylic oligomer instead of monomer A, the end-peel force after heating was greater than 15 N / 10 mm, and there was also a large amount of C component residue on the surface of the adhered objects. In Comparative Example 2, it is believed that residual adhesive was generated during peeling after heat treatment. In Comparative Examples 1-4, neither low contamination of the adhered objects after heating nor light peel performance after heating was achieved.

[0193] The specific examples of the present invention have been described in detail above, but these are merely examples and do not limit the scope of the claims. The technology described in the claims includes examples obtained by various modifications and alterations to the specific examples described above.

[0194] Explanation of reference numerals in the attached figures 1. Adhesive sheet 1A Adhesive Surface 1B Back 10 Substrate layer 10A One side 10B Another side 20 Adhesive layers Surface of 20A adhesive layer 30 Peeling gasket 50 Adhesive sheets with release liner

Claims

1. An adhesive sheet, which is an adhesive sheet with an adhesive layer. The adhesive layer comprises a polymer, a monomer, and a thermal polymerization initiator. The polymer contains olefinically unsaturated groups. The monomer comprises monomer A, wherein monomer A has a molecular weight of 250 to 5000 and has one or two olefinic unsaturated groups within the molecule.

2. The adhesive sheet as claimed in claim 1, wherein, The content of the thermal polymerization initiator in the adhesive layer is 0.1 parts by weight or more relative to 100 parts by weight of the polymer.

3. The adhesive sheet as described in claim 1, wherein, The monomer A has an ionic site.

4. The adhesive sheet as described in any one of claims 1 to 3, used in a method comprising the following steps: The processing steps include processing the object to which the adhesive sheet is attached; and The peeling process involves peeling the adhesive sheet from the adhered object after the processing step.

5. A structure comprising an adhesive sheet according to any one of claims 1 to 3, and a substrate to which the adhesive sheet is attached.

6. A method for manufacturing a structure, comprising a method for manufacturing a structure having a substrate and an adhesive sheet as described in any one of claims 1 to 3. The method includes the step of attaching the adhesive sheet to the substrate.

7. A method, comprising: The processing step involves processing the substrate to which the adhesive sheet according to any one of claims 1 to 3 is attached.

8. The method of claim 7, further comprising: The peeling process involves peeling the adhesive sheet from the substrate after the processing step.

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