Pressure-sensitive adhesive composition, pressure-sensitive adhesive sheet and production method therefor, decorative film, and decorative molded body

Abstract

This pressure-sensitive adhesive composition comprises an acrylic pressure-sensitive adhesive polymer having a glass transition temperature of 10°C or lower, at least one modified polymer selected from the group consisting of modified polyolefins and modified polydienes, and solvents. The solvents comprise an alicyclic solvent and at least one solvent selected from the group consisting of ester-based solvents and toluene.

Description

Adhesive Composition, Adhesive Sheet and Method for Producing the Same, Decorative Film, and Decorated Molded Body

[0001] [Cross - reference to Related Applications] This application claims priority based on Japanese Patent Application No. 2024 - 225521 filed on December 20, 2024, the entire disclosure of which is incorporated herein by reference. This disclosure relates to an adhesive composition, an adhesive sheet and a method for producing the same, a decorative film, and a decorated molded body.

[0002] Acrylic adhesives are processed into forms such as tapes and labels, for example, and are used in a wide range of applications. Also, the adherents of acrylic adhesives are wide - ranging, and they are applied to various substances such as plastics, papers, metals, glasses, and ceramics, for example. Furthermore, in recent years, for the purpose of improving designability and measures against VOC (Volatile Organic Compounds), etc., decorative films are laminated or transferred onto molded products, mainly in automotive interior and exterior parts and home appliances. As molding methods using decorative films, in - mold molding by injection molding, vacuum molding, vacuum pressure molding, etc. are used. Also, as a decorative film to be laminated on a molded product, a decorative film having an adhesive layer is known.

[0003] In general, adhesives are required to exhibit high adhesiveness to adherents. On the other hand, acrylic adhesives generally have poor adhesiveness to low - polarity materials such as polypropylene. Therefore, conventionally, various techniques for improving the adhesiveness of acrylic adhesives to low - polarity materials have been proposed (for example, see Patent Document 1). Patent Document 1 discloses an adhesive sheet having a layer containing a modified polyolefin on at least one side of an adhesive layer formed from an adhesive composition.

[0004] International Publication No. 2020 / 004355

[0005] Considering the wide range of applications for which adhesives are used, it is desirable that they exhibit high adhesion over a broad temperature range. Furthermore, when decorative films are used to add aesthetic appeal to molded products, the decorative film is sometimes laminated to the molded product while being stretched. When a decorative film is laminated to a molded product in a stretched state, it is prone to shifting, peeling, or lifting at high temperatures, which can result in an undesirable appearance. Therefore, adhesives are required to exhibit excellent adhesion not only at room temperature but also at high temperatures.

[0006] To form an adhesive layer that exhibits excellent adhesion at both room temperature and high temperatures, the inventors attempted to develop a solvent-type adhesive composition by blending an acrylic adhesive polymer with a low-polarity polymer such as a modified polyolefin. However, it is difficult to uniformly dissolve or disperse mutually immiscible compounds, such as the combination of an acrylic adhesive polymer and a modified polyolefin, in a solvent, and gel material sometimes precipitates in the adhesive composition over time, making it impossible to ensure the coating properties of the adhesive composition. The adhesive layer formed by such an adhesive composition cannot ensure surface smoothness, raising concerns that the adhesive performance of the adhesive layer will decrease.

[0007] This disclosure has been made in view of the above circumstances, and its primary purpose is to provide an adhesive composition that can form an adhesive layer that has good coating properties and excellent adhesion at room temperature and high temperature.

[0008] As a result of diligent research to solve the above problems, the present inventors have found that by using a specific solvent in an adhesive composition containing an acrylic adhesive polymer and a low-polarity modified polymer, the acrylic adhesive polymer and the low-polarity modified polymer can be dissolved or dispersed, and an adhesive layer exhibiting excellent adhesion can be formed. Specifically, the present disclosure provides the following adhesive composition, adhesive sheet and method for producing the same, decorative film, and decorative molded article.

[0009] [1] An adhesive composition comprising an acrylic adhesive polymer having a glass transition temperature of 10°C or less, a modified polymer which is at least one selected from the group consisting of modified polyolefins and modified polydienes, and a solvent, wherein the solvent comprises at least one selected from the group consisting of aliphatic cyclic solvents (excluding cyclic esters), ester solvents, and toluene. [2] The adhesive composition according to [1], wherein the content of the aliphatic cyclic solvent is 10 to 60% by mass relative to the total amount of solvent contained in the adhesive composition. [3] The adhesive composition according to [2], wherein the total content of the ester solvent and toluene is 30 to 90% by mass relative to the total amount of solvent contained in the adhesive composition. [4] The adhesive composition according to any one of [1] to [3], wherein the aliphatic cyclic solvent is at least one selected from the group consisting of alicyclic hydrocarbons and cyclic ethers. [5] The adhesive composition according to any one of [1] to [4], wherein the modified polymer is a substituted or unsubstituted polyolefin modified with maleic anhydride. [6] The adhesive composition according to any one of [1] to [5], further containing a vinyl polymer (excluding the modified polymer) having structural units derived from a (meth)acrylic monomer, having a glass transition temperature of 45°C or higher, and a number average molecular weight of 500 or more and less than 50,000. [7] An adhesive sheet comprising an adhesive layer formed by the adhesive composition according to any one of [1] to [6]. [8] A decorative film comprising an adhesive layer formed by the adhesive composition according to any one of [1] to [6] and a decorative layer. [9] A method for producing an adhesive sheet comprising an adhesive layer, wherein the adhesive layer is formed by the adhesive composition according to any one of [1] to [6].

[10] A decorative molded body comprising an adherend, an adhesive layer, and a decorative layer, wherein the adhesive layer and the decorative layer are laminated in this order on the surface of the adherend, and the adhesive layer is formed of an adhesive composition according to any one of [1] to [6].

[0010] According to the adhesive composition of this disclosure, an adhesive layer can be obtained that has good coating properties and excellent adhesion at room temperature and high temperature.

[0011] The following provides a detailed explanation of this disclosure. In this specification, "(meth)acrylic" means acrylic and / or methacrylic. "(meth)acrylo" means acrylo and / or methacrylo. "(meth)acrylate" means acrylate and / or methacrylate.

[0012] ≪Adhesive Composition≫ The adhesive composition of this disclosure (hereinafter also referred to as "this composition") is a polymer composition used for forming an adhesive layer, and contains the following components (A), (B), and a solvent. (A) Component: An acrylic adhesive polymer having a glass transition temperature of 10°C or less. (B) Component: A modified polymer, at least one selected from the group consisting of modified polyolefins and modified polydienes.

[0013] The components included in this composition and optional components are described below. Unless otherwise specified, each component and monomer constituting the polymer in this composition may be used individually or in combination of two or more. In this specification, numerical ranges indicated using "~" include the values ​​indicated before and after "~" as the lower and upper limits, respectively.

[0014] <Component (A): Acrylic Adhesive Polymer> The acrylic adhesive polymer (hereinafter also referred to as "acrylic adhesive polymer (A)"), which is component (A), has a glass transition temperature (Tg) of 10°C or lower. If the Tg of the acrylic adhesive polymer (A) exceeds 10°C, the adhesion at room temperature is insufficient, and the conformability of the adhesive layer to the adherend decreases, resulting in insufficient adhesion at high temperatures. From the viewpoint of obtaining an adhesive layer that exhibits excellent adhesion at room temperature and high temperatures, the Tg of the acrylic adhesive polymer (A) is preferably 5°C or lower, more preferably 0°C or lower, even more preferably -5°C or lower, and even more preferably -10°C or lower. The lower limit of the Tg of the acrylic adhesive polymer (A) is preferably -70°C or higher. A Tg of -70°C or higher for the acrylic adhesive polymer (A) is preferable because it allows for sufficiently high cohesive force of the adhesive layer and ensures sufficient adhesion. From the viewpoint of improving adhesion at high temperatures, the Tg of the acrylic adhesive polymer (A) is more preferably -60°C or higher, even more preferably -50°C or higher, and even more preferably -45°C or higher.

[0015] The preferred range for the Tg of the acrylic adhesive polymer (A) can be set by appropriately combining the preferred lower and upper limits described above. From the viewpoint of achieving a good balance between high-temperature adhesion and room-temperature adhesion, the preferred range for the Tg of the acrylic adhesive polymer (A) is -70°C to 10°C, more preferably -60°C to 5°C, even more preferably -50°C to 5°C, and even more preferably -50°C to 0°C.

[0016] In this specification, the Tg of a polymer is a value determined from the intersection of the baseline and the point of tangency at the inflection point of the heat flux curve obtained using a differential scanning calorimeter (DSC). Details of the measurement conditions are as described in the examples below. The Tg of a polymer can be set to a desired value by changing the type and composition of the constituent monomers.

[0017] Acrylic adhesive polymer (A) has (meth)acrylic compounds as its main structural units. In order to obtain a polymer with a relatively low Tg and sufficient adhesiveness, it is preferable that acrylic adhesive polymer (A) contains structural units (hereinafter also referred to as "structural unit UA") selected from the group consisting of alkyl (meth)acrylate esters having an alkyl group with 1 to 12 carbon atoms in the ester portion and alkoxyalkyl (meth)acrylate esters having an alkoxy group with 1 to 4 carbon atoms.

[0018] Specific examples of alkyl (meth)acrylate esters having an alkyl group with 1 to 12 carbon atoms in the ester portion and used in the production of acrylic adhesive polymer (A) include methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, n-hexyl (meth)acrylate, n-octyl (meth)acrylate, isooctyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-nonyl (meth)acrylate, n-decyl (meth)acrylate, and lauryl (meth)acrylate. In terms of forming an adhesive layer with superior adhesion to substrates with low surface polarity (hereinafter also referred to as "low-polarity substrates"), the alkyl (meth)acrylate ester constituting the acrylic adhesive polymer (A) is preferably a compound having an alkyl group with 1 to 8 carbon atoms in the ester portion. Preferred monomers include methyl (meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, and 2-ethylhexyl (meth)acrylate.

[0019] Specific examples of alkoxyalkyl (meth)acrylates having alkoxy groups with 1 to 4 carbon atoms used in the production of acrylic adhesive polymer (A) include methoxyethyl (meth)acrylate, ethoxymethyl (meth)acrylate, ethoxyethyl (meth)acrylate, butoxyethyl (meth)acrylate, methoxybutyl (meth)acrylate, ethoxybutyl (meth)acrylate, and butoxybutyl (meth)acrylate.

[0020] In the acrylic adhesive polymer (A), the content of structural unit UA is more preferably 50% by mass or more, more preferably 70% by mass or more, even more preferably 80% by mass or more, and even more preferably 90% by mass or more, relative to the total amount of structural units (i.e., the total amount of monomer units constituting the acrylic adhesive polymer) that the acrylic adhesive polymer (A) has. By setting the content of structural unit UA to 50% by mass or more, the adhesive strength, initial adhesion (tack), and low-temperature tackiness of the adhesive layer can be sufficiently increased.

[0021] In the adhesive layer, the acrylic adhesive polymer (A) and the modified polymer (B) component readily undergo phase separation, and the concentration of the modified polymer in the surface layer tends to be relatively high, thereby improving adhesion at high temperatures. Therefore, it is preferable for the acrylic adhesive polymer (A) to contain a structural unit (hereinafter also referred to as "structural unit UA-1") derived from at least one selected from the group consisting of alkyl (meth)acrylate esters having an alkyl group with 1 to 4 carbon atoms in the ester portion and alkoxy (meth)acrylate esters having an alkoxyalkyl group with 3 or 4 carbon atoms. Furthermore, using such alkyl (meth)acrylate esters and / or alkoxy acrylate esters in the production of the acrylic adhesive polymer (A) can increase the elastic modulus of the acrylic adhesive polymer (A), which is also effective in improving heat resistance. Among these, structural unit UA-1 is preferably a structural unit derived from one selected from the group consisting of methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, and methoxyethyl (meth)acrylate.

[0022] The content of structural unit UA-1 in the acrylic adhesive polymer (A) is preferably 30% by mass or more, more preferably 40% by mass or more, even more preferably 50% by mass or more, and even more preferably 60% by mass or more, relative to the total structural units of the acrylic adhesive polymer (A).

[0023] In the production of the acrylic adhesive polymer (A), by using a monomer having a crosslinkable functional group (hereinafter also referred to as "crosslinkable group-containing monomer"), the acrylic adhesive polymer (A) can be made to have a structure with crosslinkable structural units. The presence of crosslinkable structural units in the acrylic adhesive polymer (A) further improves the adhesion of the adhesive layer at high temperatures.

[0024] The crosslinkable group-containing monomer used in the production of the acrylic adhesive polymer (A) is not particularly limited. Preferably, the crosslinkable group-containing monomer is at least one selected from the group consisting of (meth)acrylic acid, hydroxyalkyl (meth)acrylate compounds, epoxy group-containing (meth)acrylic acid ester compounds, and reactive silyl group-containing (meth)acrylic acid ester compounds. Among these, at least one selected from the group consisting of (meth)acrylic acid and hydroxyalkyl (meth)acrylate compounds is particularly preferred because it tends to increase the adhesive strength of the acrylic adhesive polymer (A), at least one selected from the group consisting of (meth)acrylic acid and hydroxyalkyl (meth)acrylate compounds having a hydroxyalkyl group with 2 to 8 carbon atoms is more preferred, and at least one selected from the group consisting of (meth)acrylic acid and hydroxyalkyl (meth)acrylate compounds having a hydroxyalkyl group with 2 to 4 carbon atoms is particularly preferred.

[0025] When the acrylic adhesive polymer (A) has crosslinkable structural units, the content of the crosslinkable structural units is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, and even more preferably 1% by mass or more, relative to the total structural units of the acrylic adhesive polymer (A). By setting the content of crosslinkable structural units in the acrylic adhesive polymer (A) to 0.1% by mass or more, a good crosslinked structure can be formed, and an adhesive polymer (A) exhibiting higher heat resistance and durability can be obtained. There is no particular upper limit to the content of crosslinkable structural units, but from the viewpoint of ensuring the flexibility of the resulting adhesive layer, it is preferably 30% by mass or less, more preferably 20% by mass or less, even more preferably 15% by mass or less, and particularly preferably 10% by mass or less, relative to the total structural units of the acrylic adhesive polymer (A).

[0026] In addition to the above, the acrylic adhesive polymer (A) may also have structural units derived from monomers copolymerizable with the above monomer (hereinafter also referred to as "other monomers"), to the extent that it does not impair adhesive performance. Examples of other monomers include alkyl (meth)acrylate esters having alkyl groups with 9 or more carbon atoms, aliphatic cyclic esters of (meth)acrylic acid, aromatic esters of (meth)acrylic acid, polyalkylene glycol mono(meth)acrylate compounds, aromatic vinyl compounds, imide group-containing vinyl compounds, amino group-containing unsaturated compounds, amide group-containing unsaturated compounds, cyano group-containing unsaturated compounds, nitrile group-containing unsaturated compounds, and the like.

[0027] Specific examples of these include alkyl (meth)acrylate esters having an alkyl group with 9 or more carbon atoms, such as nonyl (meth)acrylate, tridecyl (meth)acrylate, and stearyl (meth)acrylate. Aliphatic cyclic esters of (meth)acrylic acid include cyclohexyl (meth)acrylate, methylcyclohexyl (meth)acrylate, tert-butylcyclohexyl (meth)acrylate, cyclododecyl (meth)acrylate, isobornyl (meth)acrylate, 1-adamantyl (meth)acrylate, dicyclopentenyl (meth)acrylate, and dicyclopentanyl (meth)acrylate.

[0028] Aromatic esters of (meth)acrylic acid include phenyl (meth)acrylate, benzyl (meth)acrylate, phenoxymethyl (meth)acrylate, 2-phenoxyethyl (meth)acrylate, and 3-phenoxypropyl (meth)acrylate.

[0029] Examples of polyalkylene glycol mono(meth)acrylate compounds include polyethylene glycol mono(meth)acrylate, polypropylene glycol mono(meth)acrylate, polyethylene glycol-polypropylene glycol mono(meth)acrylate, polyethylene glycol-polybutylene glycol mono(meth)acrylate, methoxypolyethylene glycol mono(meth)acrylate, lauroxypolyethylene glycol mono(meth)acrylate, stearoxypolyethylene glycol mono(meth)acrylate, octoxypolyethylene glycol-polypropylene glycol mono(meth)acrylate, phenoxypolyethylene glycol mono(meth)acrylate, phenoxypolyethylene glycol-polypropylene glycol mono(meth)acrylate, nonylphenoxypolyethylene glycol mono(meth)acrylate, nonylphenoxypolypropylene glycol mono(meth)acrylate, and nonylphenoxypolyethylene glycol-polypropylene glycol mono(meth)acrylate.

[0030] Examples of aromatic vinyl compounds include styrene, α-methylstyrene, β-methylstyrene, vinylxylene, o-methylstyrene, m-methylstyrene, p-methylstyrene, o-ethylstyrene, m-ethylstyrene, p-ethylstyrene, p-n-butylstyrene, p-isobutylstyrene, p-t-butylstyrene, o-methoxystyrene, m-methoxystyrene, p-methoxystyrene, o-chlorostyrene, m-chlorostyrene, p-chlorostyrene, p-hydroxystyrene, m-hydroxystyrene, o-hydroxystyrene, p-isopropenylphenol, m-isopropenylphenol, o-isopropenylphenol, o-vinylbenzoic acid, m-vinylbenzoic acid, p-vinylbenzoic acid, and styrene compounds such as divinylbenzene; vinylnaphthalene, etc.

[0031] Imide group-containing vinyl compounds include maleimide compounds such as maleimide and N-substituted maleimide compounds; itaconimide compounds such as N-methylitaconimide, N-ethylitaconimide, N-butylitaconimide, N-octylitaconimide, N-2-ethylhexylitaconimide, N-cyclohexylitaconimide, and N-laurylitaconimide; N-methylcitraconimide, N-ethylcitraconimide, N-butylcitraconimide, N-octylcitraconimide, N-2-ethylhexylcitraconimide, and N-C Examples include citracomide compounds such as chlorohexylcitraconimide and N-laurylcitraconimide; and (meth)acrylimide compounds such as N-(2-(meth)acryloyloxyethyl)succinimide, N-(2-(meth)acryloyloxyethyl)maleimide, N-(2-(meth)acryloyloxyethyl)phthalimide, N-(4-(meth)acryloyloxybutyl)succinimide, N-(4-(meth)acryloyloxybutyl)maleimide, and N-(4-(meth)acryloyloxybutyl)phthalimide. Among these, maleimide compounds are preferred as imide group-containing vinyl compounds.

[0032] Examples of amino group-containing unsaturated compounds include dimethylaminomethyl (meth)acrylate, diethylaminomethyl (meth)acrylate, 2-dimethylaminoethyl (meth)acrylate, 2-diethylaminoethyl (meth)acrylate, 2-(di-n-propylamino)ethyl (meth)acrylate, 2-dimethylaminopropyl (meth)acrylate, 2-diethylaminopropyl (meth)acrylate, 2-(di-n-propylamino)propyl (meth)acrylate, 3-dimethylaminopropyl (meth)acrylate, 3-diethylaminopropyl (meth)acrylate, and 3-(di-n-propylamino)propyl (meth)acrylate.

[0033] Examples of amide group-containing unsaturated compounds include (meth)acrylamide, (meth)acrylamide derivatives, and N-vinylamide monomers. Specific examples of (meth)acrylamide derivatives include tert-butyl(meth)acrylamide, N,N-dimethyl(meth)acrylamide, N,N-diethyl(meth)acrylamide, N-isopropyl(meth)acrylamide, N,N-dimethylaminopropyl(meth)acrylamide, and (meth)acryloylmorpholine. Specific examples of N-vinylamide monomers include N-vinylacetamide, N-vinylformamide, and N-vinylisobutylamide.

[0034] Examples of cyano group-containing unsaturated compounds include cyanomethyl (meth)acrylate, 1-cyanoethyl (meth)acrylate, 2-cyanoethyl (meth)acrylate, 1-cyanopropyl (meth)acrylate, 2-cyanopropyl (meth)acrylate, 3-cyanopropyl (meth)acrylate, 4-cyanobutyl (meth)acrylate, 6-cyanohexyl (meth)acrylate, 2-ethyl-6-cyanohexyl (meth)acrylate, and 8-cyanooctyl (meth)acrylate.

[0035] Examples of nitrile group-containing unsaturated compounds include (meth)acrylonitrile, ethacrylonitrile, α-ethylacrylonitrile, α-isopropylacrylonitrile, α-chloroacrylonitrile, and α-fluoroacrylonitrile. The proportion of other monomers constituting the acrylic adhesive polymer (A) can be appropriately selected within a range that does not impair the effects of this disclosure.

[0036] From the viewpoint of improving the adhesion of the adhesive layer at high temperatures, it is preferable that the acrylic adhesive polymer (A) substantially does not contain structural units derived from amino group-containing unsaturated compounds. Specifically, it is preferable that the proportion of structural units derived from amino group-containing unsaturated compounds in the acrylic adhesive polymer (A) is 0.2% by mass or less relative to the total structural units of the acrylic adhesive polymer (A). If the acrylic adhesive polymer (A) contains a relatively large amount of structural units derived from amino group-containing unsaturated compounds, the interaction between the acrylic adhesive polymer (A) and the modified polymer becomes stronger, which may suppress phase separation between the acrylic adhesive polymer (A) and the modified polymer, potentially leading to a decrease in the adhesive performance of the adhesive layer. From this viewpoint, it is more preferable that the proportion of structural units derived from amino group-containing unsaturated compounds is 0.1% by mass or less, even more preferable that it is 0.05% by mass or less, and even more preferable that it is 0.01% by mass or less, relative to the total structural units of the acrylic adhesive polymer (A).

[0037] • Manufacturing of acrylic adhesive polymer (A) The acrylic adhesive polymer (A) is not subject to any particular limitations on its manufacturing method and can be obtained by known manufacturing methods. For example, the acrylic adhesive polymer (A) can be obtained by polymerizing the above monomer using known radical polymerization methods such as solution polymerization, suspension polymerization, emulsion polymerization, or bulk polymerization.

[0038] For example, in the case of solution polymerization, a manufacturing method may involve charging an organic solvent and monomers into a reactor, adding a polymerization initiator, and heating to 50 to 300°C to perform polymerization. In this case, the method of charging each raw material, including the monomers, may be a batch-type initial batch charging in which all raw materials are charged at once, a semi-continuous charging in which at least some of the raw materials are continuously supplied into the reactor, or a continuous polymerization method in which all raw materials are continuously supplied and the resulting resin is continuously withdrawn from the reactor at the same time.

[0039] Examples of organic solvents used in solution polymerization include cyclic ethers such as tetrahydrofuran, tetrahydropyran, 4-methyltetrahydropyran, and dioxane; aromatic hydrocarbons such as benzene, toluene, and xylene; aliphatic hydrocarbons such as cyclohexane, methylcyclohexane, and isooctane; esters such as ethyl acetate, butyl acetate, methyl orthoformate, and methyl orthoacetate; ketones such as acetone, methyl ethyl ketone, and cyclohexanone; and alcohols such as methanol, ethanol, and isopropanol. One or more of these organic solvents can be used. The amount of organic solvent used is such that the total amount of monomers used for polymerization is, for example, 1 to 50% by mass of the total amount of organic solvent and monomers. From the viewpoint of the polymerizability and solubility of the acrylic adhesive polymer (A), and the ease of blending component (B) (modified polymer) after production, at least one selected from the group consisting of esters, cyclic ethers, aromatic hydrocarbons, aliphatic hydrocarbons, and ketones is preferred. Among these, at least one selected from the group consisting of toluene, xylene, cyclohexane, ethyl acetate, and butyl acetate is even more preferred.

[0040] As polymerization initiators, known radical polymerization initiators such as azo compounds, organic peroxides, and inorganic peroxides can be used, and are not particularly limited. Of these, azo compounds are preferred because they are easy to handle safely and less likely to cause side reactions during radical polymerization. In addition, redox-type polymerization initiators consisting of known oxidizing agents and reducing agents may be used as polymerization initiators. Furthermore, known chain transfer agents can be used in combination with polymerization initiators.

[0041] Specific examples of the polymerization initiator include, as azo compounds, for example, 2,2'-azobis(isobutyronitrile), 2,2'-azobis(2-methylbutyronitrile), 2,2'-azobis(2,4-dimethylvaleronitrile), 4,4'-azobis(4-cyanovaleric acid), 2-(tert-butylazo)-2-cyanopropane, 2,2'-azobis(2,4,4-trimethylpentane), 2,2'-azobis(2-methylpropane), dimethyl 2,2'-azobis(2-methylpropionate), and the like.

[0042] Examples of the organic peroxide include cyclohexanone peroxide, 3,3,5-trimethylcyclohexanone peroxide, 1,1-bis(tert-butylperoxy)-3,3,5-trimethylcyclohexane, 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane, diisopropylbenzene peroxide, 2,5-dimethyl-2,5-di(benzoylperoxy)hexane, and the like.

[0043] Examples of the inorganic peroxide include potassium persulfate, sodium persulfate, and the like. Examples of the redox-type polymerization initiator include those using, as a reducing agent, sodium sulfite, sodium thiosulfate, sodium formaldehyde sulfoxylate, ascorbic acid, ferrous sulfate, etc., and, as an oxidizing agent, potassium peroxodisulfate, hydrogen peroxide, tert-butyl hydroperoxide, etc. In the production of the acrylic adhesive polymer (A), the amount of the polymerization initiator used is, for example, 0.01 to 20 parts by mass with respect to 100 parts by mass of all the monomers used in the polymerization.

[0044] - Molecular weight characteristics of acrylic adhesive polymer (A) From the perspective of obtaining a polymer that exhibits sufficient cohesive force and good adhesiveness, the weight average molecular weight (Mw) of the acrylic adhesive polymer (A) is preferably 100,000 or more. By setting the Mw of the acrylic adhesive polymer (A) to 100,000 or more, sufficient adhesiveness and solvent resistance can be ensured. The Mw of the acrylic adhesive polymer (A) is more preferably 200,000 or more, still more preferably 300,000 or more, even more preferably 400,000 or more, and particularly preferably 450,000 or more.

[0045] The upper limit of the Mw of the acrylic adhesive polymer (A) is not particularly limited, but from the perspective of ensuring good coating properties and handling properties during the formation of the adhesive layer and further ensuring ease of manufacture, it is preferably 3,000,000 or less, more preferably 2,000,000 or less, and still more preferably 1,500,000 or less. The preferred range of the Mw of the acrylic adhesive polymer (A) is 100,000 or more and 3,000,000 or less, more preferably 200,000 or more and 2,000,000 or less, and still more preferably 400,000 or more and 1,500,000 or less. In this specification, the molecular weight of the polymer is a polystyrene equivalent value measured by gel permeation chromatography (GPC).

[0046] Regarding the acrylic adhesive polymer (A), the molecular weight distribution (Mw / Mn) represented by the ratio of Mw to Mn is preferably 10.0 or less, and more preferably 9.0 or less, from the viewpoints of easily obtaining good adhesiveness and suppressing the increase in viscosity of the adhesive composition. The lower limit of the Mw / Mn of the acrylic adhesive polymer (A) is not particularly limited and can be 1.0 or more.

[0047] The solubility parameter value (SP value) of the acrylic adhesive polymer (A) calculated by the Fedors method is, for example, 9.95 or higher, and may also be 10.00 or higher. When the SP value of the acrylic adhesive polymer (A) is within the above range, an adhesive layer with higher adhesion at both room temperature and high temperature can be obtained. Specifically, the SP value calculated by the Fedors method is calculated using the method shown in the following formula (1). δ: SP value ((cal / cm ３ ) １／２ ) ΔEvap: Molar heat of vaporization of each atomic group (cal / mol) V: Molar volume of each atomic group (cm ３ / mol)

[0048] From the viewpoint of ensuring sufficient adhesion in the adhesive layer at room temperature and high temperatures, the content of the acrylic adhesive polymer (A) in this composition is preferably 50% by mass or more, relative to the total amount of solids contained in this composition (i.e., the mass of components other than the solvent in the adhesive composition relative to the total mass of the adhesive composition). From the above viewpoint, the content of the acrylic adhesive polymer (A) is more preferably 60% by mass or more, even more preferably 70% by mass or more, and even more preferably 80% by mass or more, relative to the total amount of solids contained in this composition.

[0049] <Component (B): Modified Polymer> The modified polymer (hereinafter also referred to as "modified polymer (B)"), which is component (B), is a polyolefin and / or polydiene that has been chemically modified, and contains structures or functional groups different from unsaturated hydrocarbon units within the same molecule. The modified polyolefin and / or polydiene may be unsubstituted or may have substituents. Furthermore, if the modified polymer (B) has substituents, substituents may be introduced into the modified polymer (B) by modification of the polyolefin and / or polydiene. In this specification, unless otherwise specified, the terms "polyolefin" and "polydiene" are used to include cases where substituents are present.

[0050] The adhesive layer formed by this composition is thought to be in a state where the acrylic adhesive polymer (A) and the modified polymer (B) are in phase separation at the surface of the adhesive layer due to the phase separation of the acrylic adhesive polymer (A) and the modified polymer (B) that occurs during the process of forming the adhesive layer. Furthermore, it is thought that the adhesive performance of the acrylic adhesive polymer (A) and the modified polymer (B) are well balanced due to the phase separation of the acrylic adhesive polymer (A) and the modified polymer (B) at the surface of the adhesive layer. As a result, the adhesive layer formed by this composition is thought to exhibit excellent adhesion to low-polarity substrates and high adhesion at both room temperature and high temperature.

[0051] Herein, in this specification, "phase separation" refers to the separation of an acrylic adhesive polymer (A) and a modified polymer (B) in a single phase into a phase mainly composed of the acrylic adhesive polymer (A) and a phase mainly composed of the modified polymer (B) according to thermodynamic equilibrium conditions during the process of forming an adhesive layer. In the state where the acrylic adhesive polymer (A) and the modified polymer (B) have undergone phase separation in the surface layer of the adhesive layer, a sea-island structure is typically formed, but is not limited to this. It should be noted that phase separation is a different concept from segregation (more specifically, surface segregation), which refers to the localization of the second polymer relative to the first polymer in the outermost layer in the thickness direction of the adhesive layer within an adhesive layer containing different polymers (referred to as the first polymer and the second polymer).

[0052] Examples of polyolefins and polydienes include polymers containing structural units derived from at least one monomer selected from the group consisting of α-olefins, conjugated dienes, and non-conjugated dienes having 2 to 20 carbon atoms. Specifically, examples include homopolymers of α-olefins, conjugated dienes, or non-conjugated dienes having 2 to 20 carbon atoms, and copolymers of two or more molecules selected from the group consisting of α-olefins, conjugated dienes, and non-conjugated dienes having 2 to 20 carbon atoms.

[0053] Specific examples of α-olefins having 2 to 20 carbon atoms include ethylene, propylene, 1-butene, 1-pentene, 3-methyl-1-butene, 1-hexene, 3-methyl-1-pentene, 4-methyl-1-pentene, 1-heptene, 4-methyl-1-hexene, 1-octene, 4,4-dimethyl-1-hexene, 1-nonene, 1-decene, 1-undecene, and 1-dodecene. Specific examples of conjugated or unconjugated dienes having 2 to 20 carbon atoms include butadiene, 1,5-hexadiene, ethylidenenorbornene, and dicyclopentadiene.

[0054] Furthermore, polyolefins and polydienes may be copolymerized with other unsaturated monomers in addition to olefins and / or conjugated or unconjugated dienes. Such unsaturated monomers include unsaturated monocarboxylic acids such as (meth)acrylic acid, crotonic acid, isocrotonic acid, and cinnamic acid; unsaturated dicarboxylic acids such as fumaric acid, maleic acid, citraconic acid, chloromaleic acid, glutaconic acid, and itaconic acid; half-esters or half-amides of unsaturated dicarboxylic acids; unsaturated tricarboxylic acids such as trans-anicotic acid; maleic anhydride, citraconic anhydride, chloromaleic anhydride, itaconic anhydride, 3, 4, 5, Examples include carboxylic acid anhydrides such as 6-tetrahydrophthalic anhydride; (meth)acrylic acid esters such as methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, n-butyl (meth)acrylate, and tert-butyl (meth)acrylate; oligomers of these unsaturated compounds having an unsaturated bond at the terminal; and conjugated or unconjugated dienes such as butadiene, 1,5-hexadiene, ethylidene norbornene, and dicyclopentadiene. Examples of polyolefins include ethylene / ethyl acrylate copolymers and ethylene / vinyl acetate copolymers. Examples of polydienes include styrene / butadiene copolymers and styrene / isoprene copolymers. When copolymers are used, random copolymers, block copolymers, and graft copolymers can be appropriately selected.

[0055] In terms of its high effectiveness in improving adhesion at high temperatures and its availability, the modified polymer (B) is preferably a modified polyolefin obtained by modifying a polyolefin. The modified polyolefin is preferably a polymer containing structural units derived from α-olefins having 2 to 20 carbon atoms. In the modified polyolefin, the proportion of structural units derived from α-olefins having 2 to 20 carbon atoms is preferably 10% by mass or more, more preferably 20% by mass or more, even more preferably 30% by mass or more, and even more preferably 50% by mass or more, relative to the total structural units constituting the polyolefin.

[0056] Preferred examples of polyolefins include polypropylene, propylene / ethylene copolymer, propylene / 1-butene copolymer, propylene / ethylene / 1-butene copolymer, and propylene / ethylene / 1-octene copolymer. Polyolefins may also be blends thereof. When using a propylene copolymer, the propylene content is preferably 50% by mass or more, more preferably 60% by mass or more, and even more preferably 75% by mass or more. Among the above, polypropylene or propylene copolymer is preferred.

[0057] Commercially available polyolefins may be used. Specific examples include the "L-MODU" series from Idemitsu Kosan, the "REXTAC" series from LLC, the "Vestoplast" series from Evonik, the "Eastoflex" and "Aerafin" series from Eastman, the "Tafmer" series from Mitsui Chemicals, the "Prime TPO" series from Prime Polymer, the "Versify" series from Dow Chemical, the "Vistamax" and "Linxar" series from ExxonMobil, the "Licocene" series from Clariant, and the "Adflex" series from Basel.

[0058] Examples of modification methods include acid modification, halogenation, (meth)acrylic acid ester modification (hereinafter also referred to as "acrylic modification"), carbodiimide modification, urea modification, and imine modification. Furthermore, the modified polymer (B) may be subjected to two or more modifications in sequence. For example, specific examples of modified polyolefins subjected to two or more modifications include acid-modified halogenated polyolefins, acrylic-modified halogenated polyolefins, and urethane-modified halogenated polyolefins. Halogenation of polyolefins and / or polydienes is preferably chlorination.

[0059] The modified polymer (B) is preferably modified with at least one selected from the group consisting of carboxylic acids, carboxylic acid anhydrides, (meth)acrylic acid esters, and chlorine, and more preferably modified with at least one selected from the group consisting of carboxylic acids and carboxylic acid anhydrides.

[0060] Acid-modified polyolefins and polydienes are preferably modified with at least one selected from the group consisting of carboxylic acids and carboxylic acid anhydrides (hereinafter also referred to as "specific acid modifier"). For example, such modified polyolefins can be obtained by graft copolymerization of a specific acid modifier with a polyolefin. Conventionally known methods can be used for the modification reaction. For example, a method of copolymerizing a molten polyolefin using an extruder by adding a specific acid modifier; a method of copolymerizing a polyolefin dissolved in a solvent by adding a specific acid modifier; a method of copolymerizing a polyolefin in an aqueous suspension by adding a specific acid modifier; and so on. The modification sites of the polyolefin chain in the modified polyolefin may be at one end of the molecular chain, both ends of the molecular chain, in the middle of the molecular chain, or multiple of these sites. Furthermore, polyolefins and polydienes modified by the specific acid modifier may undergo modifications other than acid modification, and further modifications other than acid modification may be performed after modification with the specific acid modifier.

[0061] Examples of specific acid modifiers used in the denaturation reaction include unsaturated monocarboxylic acids such as (meth)acrylic acid, crotonic acid, isocrotonic acid, and cinnamic acid; unsaturated dicarboxylic acids such as fumaric acid, maleic acid, citraconic acid, chloromaleic acid, glutaconic acid, and itaconic acid; half-esters or half-amides of unsaturated dicarboxylic acids; unsaturated tricarboxylic acids such as trans-anicotic acid; and carboxylic acid anhydrides such as maleic anhydride, citraconic anhydride, chloromaleic anhydride, itaconic anhydride, and 3,4,5,6-tetrahydrophthalic anhydride. Of these, at least one selected from the group consisting of unsaturated monocarboxylic acids and carboxylic acid anhydrides is preferred, at least one selected from the group consisting of (meth)acrylic acid, maleic acid, and maleic anhydride is more preferred, and maleic anhydride is even more preferred.

[0062] Modified polymer (B) is preferably a modified polyolefin due to its high effectiveness in improving adhesion at high temperatures and its availability. In particular, modified polymer (B) is preferably an acid-modified substituted or unsubstituted polyolefin, more preferably a maleic anhydride-modified substituted or unsubstituted polyolefin, and even more preferably a maleic anhydride-modified halogen-substituted or unsubstituted polyolefin, due to the larger difference in SP value between it and the acrylic adhesive polymer (A), which facilitates phase separation between the acrylic adhesive polymer (A) and the modified polymer (B), and consequently allows for the acquisition of an adhesive layer with further improved high-temperature adhesion. Among these, modified polymer (B) is even more preferably at least one selected from the group consisting of maleic anhydride-modified polyolefin and maleic anhydride-modified chlorinated polyolefin, and maleic anhydride-modified polyolefin is even more preferred due to its higher solubility and adhesion in a mixed solvent of the first and second solvents. Note that maleic anhydride-modified polyolefin differs from maleic anhydride-modified chlorinated polyolefin in that it is not chlorinated.

[0063] Acid-modified substituted or unsubstituted polyolefins (including maleic anhydride-modified polyolefins and maleic anhydride-modified chlorinated polyolefins) may be further modified with (meth)acrylic acid esters in addition to being modified with an acid modifier. That is, in this specification, "acid-modified substituted or unsubstituted polyolefins" is a concept that includes substituted or unsubstituted polyolefins that have been acrylic-modified with (meth)acrylic acid esters and acid-modified with an acid modifier. Therefore, for example, maleic anhydride-modified polyolefins include ethylene-acrylic acid ester-maleic anhydride three-dimensional copolymers, ethylene-methacrylic acid ester-maleic anhydride three-dimensional copolymers, propylene-acrylic acid ester-maleic anhydride three-dimensional copolymers, and propylene-methacrylic acid ester-maleic anhydride three-dimensional copolymers. Specific examples of (meth)acrylic acid esters for acrylic modification include alkyl (meth)acrylates and aliphatic cyclic ester compounds of (meth)acrylic acid, as exemplified in the description of acrylic adhesive polymer (A). Furthermore, during the denaturation reaction, denaturing agents such as functional group-containing alkyl (meth)acrylates, aromatic vinyl compounds, and cyclohexyl vinyl ethers may be used in combination. Examples of functional group-containing alkyl (meth)acrylates include hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, glycidyl (meth)acrylate, and isocyanate-containing (meth)acrylates.

[0064] From the viewpoint of availability, acrylic-modified polyolefins and polydienes are preferably acrylic-modified polyolefins or acrylic-modified chlorinated polyolefins, and it is particularly preferable that the polyolefin is a polymer modified with a (meth)acrylic acid ester. As the (meth)acrylic acid ester, at least one selected from the group consisting of alkyl (meth)acrylates and cycloalkyl (meth)acrylates can be preferably used. Specific examples include alkyl (meth)acrylates having C1 to C12 alkyl groups as exemplified in the description of acrylic adhesive polymer (A), aliphatic cyclic ester compounds of (meth)acrylic acid as exemplified in the description of other monomers, and alkyl (meth)acrylates having C9 or more alkyl groups such as nonyl (meth)acrylate, tridecyl (meth)acrylate, and stearyl (meth)acrylate.

[0065] The modification rate of the modified polymer (B) is preferably 0.1% to 80% in order to balance and improve the high-temperature adhesion and room-temperature adhesion of the adhesive layer. More preferably, the modification rate of the modified polymer (B) is 0.5% or more, even more preferably 1.0% or more, and even more preferably 1.5% or more, from the viewpoint of increasing the interaction with the acrylic adhesive polymer (A) and increasing the cohesive force of the entire adhesive layer. The modification rate of the modified polymer (B) may also be 75% or less, or 70% or less. The modification rate of the modified polymer (B) represents the mass ratio of the portion introduced by the modification reaction (modified portion) when the total mass of the modified polymer (B) is taken as 100% by mass. The mass of the modified portion can be determined by Fourier transform infrared spectroscopy or nuclear magnetic resonance spectroscopy.

[0066] The weight-average molecular weight of the modified polymer (B), as measured by GPC, is preferably 2,000 to 500,000. A weight-average molecular weight of 2,000 or more of the modified polymer (B) is preferable because it provides good heat resistance to the adhesive layer, and a weight-average molecular weight of 500,000 or less is preferable because it improves the solubility of the modified polymer (B) in solvents and makes it easy to handle. From the above viewpoint, a weight-average molecular weight of 3,000 or more of the modified polymer (B) is more preferable, 5,000 or more is even more preferable, and 10,000 or more is even more preferable. The upper limit of the weight-average molecular weight of the modified polymer (B) is more preferable to be 250,000 or less, 200,000 or less is even more preferable, and 180,000 or less is even more preferable.

[0067] If the modified polymer (B) has a melting point, from the viewpoint of obtaining an adhesive layer with excellent high-temperature adhesion, the melting point of the modified polymer (B) is preferably 20°C or higher, more preferably 30°C or higher, even more preferably 40°C or higher, and even more preferably 50°C or higher. Furthermore, if the melting point of the modified polymer (B) is too high, the wettability to the adherend decreases. From this viewpoint, the melting point of the modified polymer (B) is preferably 130°C or lower, more preferably 120°C or lower, even more preferably 110°C or lower, and even more preferably 100°C or lower. Note that the melting point of the modified polymer (B) is a value obtained using a differential scanning calorimeter.

[0068] If the modified polymer (B) has a glass transition temperature (Tg), the Tg of the modified polymer (B) is preferably higher than 10°C, and more preferably 15°C or higher, from the viewpoint of obtaining an adhesive layer with excellent high-temperature adhesion. Furthermore, the Tg of the modified polymer (B) is preferably less than 45°C, and more preferably 40°C or lower. The Tg of the modified polymer (B) is a value determined from the intersection of the baseline of the heat flux curve obtained using DSC and the point of junction at the inflection point.

[0069] Commercially available products may be used as the modified polymer (B), for example, those used as plastic surface modifiers, primers for automotive plastic substrates, primers for electronics substrates, primers for building materials, etc. Specifically, examples of acid-modified polyolefins include the "Admer" series and "Unistol" series from Mitsui Chemicals, the "Hardren" series from Toyobo MC (e.g., PMA-LE, PMA-L, PMA-LH, PMA-KE, PMA-K, PMA-KH, PMA-TE, PMA-T, PMA-TH, PMA-TZ, PMA-F6, PMA-F2, PMA-F7), the "Yumex" series from Sanyo Chemical Industries, and the "Rexpearl" series from Nippon Polyethylene Co., Ltd. Examples of ethylene / acrylic acid / maleic anhydride ternary copolymers include the "Bondyne" series from Arkema.

[0070] Examples of chlorinated polyolefins include Superclon 814HA, 814HS, 390S, and 360T from Nippon Paper Industries, and Hardlen 13-LP, 13-LLP, 14-LWP, 15-LP, 16-LP, DX-523, DX-523P, DX-526P, and DX-530P from Toyobo Co., Ltd.

[0071] Examples of acid-modified chlorinated polyolefins include Superclon 3228S and 2319S from Nippon Paper Industries, and Hardlen HM-21P, M-28P, CY-9124P, CY-1321P, CY-2121P, CY-2129, F-225P, F-2P, F-6P, and F-7P from Toyobo MC Co., Ltd.

[0072] Examples of acrylic acid-modified chlorinated polyolefins include Superclon 224H and 240H manufactured by Nippon Paper Industries Co., Ltd. Examples of acrylic-modified polyolefins include S-7083S and S-7098S manufactured by Nippon Paper Industries Co., Ltd., and Hardlen NP-3000, NP-3003, and NP-3002 manufactured by Toyobo Co., Ltd.

[0073] The content of the modified polymer (B) in this composition is preferably 0.5 parts by mass or more and 50 parts by mass or less per 100 parts by mass of the acrylic adhesive polymer (A). By setting the content of the modified polymer (B) within the above range, an adhesive layer can be obtained that exhibits excellent adhesion to low-polarity substrates and excellent adhesion at both room temperature and high temperature. From the viewpoint of obtaining an adhesive layer with superior adhesion to low-polarity substrates and high-temperature adhesion, the content of the modified polymer (B) is more preferably 1 part by mass or more, even more preferably 2 parts by mass or more, and even more preferably 5 parts by mass or more, per 100 parts by mass of the acrylic adhesive polymer (A). Regarding the upper limit of the modified polymer (B) content, from the viewpoint of ensuring adhesion to substrates whose surfaces are formed of polar resins such as acrylonitrile butadiene styrene (ABS) resin or acrylic resin (hereinafter also referred to as "high-polarity substrates") and room-temperature adhesion, it is more preferable to have 45 parts by mass or less, even more preferable to have 40 parts by mass or less, and even more preferable to have 35 parts by mass or less, per 100 parts by mass of the acrylic adhesive polymer (A) content.

[0074] <Solvent> This composition contains, as a solvent, an aliphatic cyclic solvent (excluding cyclic esters) and at least one selected from the group consisting of ester solvents and toluene. For convenience, hereinafter, aliphatic cyclic solvents excluding cyclic esters will be referred to as the first solvent, and at least one selected from the group consisting of ester solvents and toluene will be referred to as the second solvent. In this specification, cyclic esters will be classified as the second solvent.

[0075] Here, by forming an adhesive layer with an adhesive composition containing an acrylic adhesive polymer (A), a modified polymer (B), and a solvent, phase separation between the acrylic adhesive polymer (A) and the modified polymer (B) can be induced during the process of forming the adhesive layer. The adhesive layer thus formed (i.e., an adhesive layer having a phase-separated structure of acrylic adhesive polymer (A) and modified polymer (B)) can exhibit good adhesive performance at both room temperature and high temperatures. In particular, by using a mixed solvent of a first solvent and a second solvent as the solvent, the coatability of the adhesive composition can be improved even when different polymers such as acrylic adhesive polymer (A) and modified polymer (B) are included in the adhesive composition. This ensures surface smoothness of the adhesive layer formed by the adhesive composition containing acrylic adhesive polymer (A) and modified polymer (B), and as a result, it is believed that the adhesive performance of the adhesive layer can be improved.

[0076] (First Solvent) The aliphatic cyclic solvent as the first solvent can be any non-aromatic organic solvent other than cyclic esters. Examples of such organic solvents include alicyclic hydrocarbons, cyclic ketones, and cyclic ethers. Specific examples of these include cyclohexane and methylcyclohexane as alicyclic hydrocarbons; cyclohexanone as a cyclic ketone; and tetrahydrofuran, tetrahydropyran, 4-methyltetrahydropyran, and 1,4-dioxane as cyclic ethers.

[0077] The first solvent is preferably at least one selected from the group consisting of alicyclic hydrocarbons and cyclic ethers, in order to maintain a stable state in which the acrylic adhesive polymer (A) and the modified polymer (B) are dissolved or dispersed in the solvent, in addition to having high solubility for the modified polymer (B). Among these, the first solvent is more preferably an alicyclic hydrocarbon, and is particularly preferably at least one of cyclohexane and methylcyclohexane.

[0078] (Second Solvent) The ester solvent used as the second solvent may be a chain ester or a cyclic ester. Specific examples of ester solvents include, as chain esters, methyl acetate, ethyl acetate, butyl acetate, methyl propionate, ethyl propionate, propyl propionate, vinyl acetate, n-butyrate-n-butyl, methyl orthoformate, and orthomethyl acetate; and as cyclic esters, γ-butyrolactone, etc. Of these, chain esters are preferred in terms of their excellent solubility in the acrylic adhesive polymer (A), and at least one selected from the group consisting of methyl acetate, ethyl acetate, and butyl acetate is particularly preferred.

[0079] As the second solvent, either an ester-based solvent or toluene may be used, or a mixed solvent of an ester-based solvent and toluene may be used. Here, while toluene, an aromatic hydrocarbon solvent, has high solubility in both the acrylic adhesive polymer (A) and the modified polymer (B), in recent years there has been a movement to restrict the use of aromatic hydrocarbon solvents based on regulations in various countries. From this perspective, an ester-based solvent is preferred as the second solvent.

[0080] The solvent component of this composition may be a mixed solvent consisting of two solvents, one of which is a first solvent and one of which is a second solvent, or it may be a mixed solvent of three or more solvents, in which at least one of the first and second solvents is a mixture of multiple types. Furthermore, the solvent component of this composition may also contain a third solvent different from the first and second solvents. Examples of such a third solvent include benzene, xylene, methanol, ethanol, isopropanol, methyl ethyl ketone, and methyl isobutyl ketone. However, from the viewpoint of maintaining good coating properties of this composition and obtaining an adhesive layer with excellent adhesion performance, it is preferable to use as little of the third solvent as possible. Specifically, the content of the third solvent is preferably 30% by mass or less, more preferably 20% by mass or less, even more preferably 10% by mass or less, and particularly preferably 5% by mass or less, based on the total amount of solvent contained in this composition. Furthermore, from the viewpoint of restricting the use of aromatic hydrocarbon solvents, the content of aromatic hydrocarbon solvents including toluene is preferably 70% by mass or less, more preferably 50% by mass or less, even more preferably 30% by mass or less, and particularly preferably 10% by mass or less, based on the total amount of solvent contained in this composition.

[0081] In this composition, the content of the first solvent (i.e., aliphatic cyclic solvent) is preferably 10 to 60% by mass relative to the total amount of solvent contained in the adhesive composition. By keeping the content of the first solvent within the above range, aggregation and sedimentation of the acrylic adhesive polymer (A) and the modified polymer (B) in the adhesive composition can be effectively suppressed, and the coatability of the adhesive composition can be sufficiently ensured. From the above viewpoint, the content of the first solvent is more preferably 15% by mass or more, and even more preferably 20% by mass or more, relative to the total amount of solvent contained in the adhesive composition. Furthermore, the content of the first solvent is more preferably 55% by mass or less, even more preferably 50% by mass or less, and even more preferably 45% by mass or less, relative to the total amount of solvent contained in the adhesive composition. The range of the content of the first solvent is more preferably 15 to 55% by mass, even more preferably 15 to 50% by mass, even more preferably 15 to 45% by mass, and particularly preferably 20 to 45% by mass.

[0082] The content of the second solvent (i.e., the total content of the ester solvent and toluene in this composition) is preferably 30 to 90% by mass relative to the total amount of solvent contained in the adhesive composition. From the viewpoint of effectively suppressing aggregation and sedimentation of the acrylic adhesive polymer (A) and the modified polymer (B) and ensuring sufficient coating properties of the adhesive composition, the content of the second solvent is more preferably 40% by mass or more, even more preferably 50% by mass or more, and even more preferably 55% by mass or more, relative to the total amount of solvent contained in the adhesive composition. Furthermore, the content of the second solvent is more preferably 85% by mass or less, and even more preferably 80% by mass or less, relative to the total amount of solvent contained in the adhesive composition.

[0083] Furthermore, the content of the ester solvent is preferably 25 to 90% by mass relative to the total amount of solvent contained in the adhesive composition. In order to effectively suppress aggregation and sedimentation of the acrylic adhesive polymer (A) and the modified polymer (B) and to ensure sufficient coating properties of the adhesive composition, the content of the ester solvent is more preferably 35% by mass or more, even more preferably 45% by mass or more, and even more preferably 50% by mass or more, relative to the total amount of solvent contained in the adhesive composition. Furthermore, the content of the ester solvent is more preferably 85% by mass or less, and even more preferably 80% by mass or less, relative to the total amount of solvent contained in the adhesive composition.

[0084] <Other Components> This composition may further contain various components other than those described above (A), (B), and the solvent (hereinafter also referred to as "other components"), as necessary. The other components are described below.

[0085] <Component (C): Vinyl Polymer> Component (C), the vinyl polymer (hereinafter also referred to as "vinyl polymer (C)"), is a polymer having structural units derived from (meth)acrylic monomers, with a glass transition temperature (Tg) of 45°C or higher and a number-average molecular weight (Mn) of 500 or more and less than 50,000. Note that vinyl polymer (C) is a component that is blended separately from the modified polymer (B).

[0086] When considering the application of adhesive layers to decorative films, the adhesive layer can be used not only to bond low-polarity substrates together, but also to bond high-polarity substrates to low-polarity substrates. Considering a wide range of applications and materials, the adhesive layer must exhibit excellent adhesion to both low-polarity and high-polarity substrates. In this regard, by further compounding a vinyl polymer (C) with an acrylic adhesive polymer (A) and a modified polymer (B) to form the adhesive layer, an adhesive layer can be obtained that exhibits better adhesion to high-polarity substrates in addition to good adhesion to low-polarity substrates.

[0087] When the Tg of vinyl polymer (C) is 45°C or higher, the Tg of the surface portion of the adhesive layer can be sufficiently high when an adhesive layer is formed with this composition, and sufficient adhesive strength and heat resistance can be ensured under high-temperature conditions. Also, due to constraints on the raw material monomer, the Tg of vinyl polymer (C) is generally 200°C or lower. The Tg of vinyl polymer (C) is preferably 50°C or higher, more preferably 55°C or higher, even more preferably 60°C or higher, even more preferably 70°C or higher, and particularly preferably 80°C or higher. The upper limit of Tg is preferably 150°C or lower, more preferably 140°C or lower, and even more preferably 130°C or lower. The range of Tg for vinyl polymer (C) is preferably 45°C to 200°C, more preferably 50°C to 150°C, and even more preferably 60°C to 140°C.

[0088] The vinyl polymer (C) has structural units derived from (meth)acrylic monomers. The vinyl polymer (C) may consist solely of structural units derived from (meth)acrylic monomers, or it may have structural units derived from other monomers along with (meth)acrylic monomers. Here, (meth)acrylic monomers are monomers having a (meth)acryloyl group, and include (meth)acrylic acid ester monomers and (meth)acrylamide monomers.

[0089] Various vinyl monomers with radical polymerizability can be used as monomers constituting the vinyl polymer (C). Examples of such vinyl monomers include alkyl (meth)acrylates, aliphatic cyclic esters of (meth)acrylic acid, aromatic esters of (meth)acrylic acid, aromatic vinyl compounds, unsaturated carboxylic acids, unsaturated acid anhydrides, hydroxyl group-containing unsaturated compounds, amino group-containing unsaturated compounds, amide group-containing unsaturated compounds, alkoxy group-containing unsaturated compounds, cyano group-containing unsaturated compounds, nitrile group-containing unsaturated compounds, maleimide compounds, and the like. Specific examples of these compounds include those similar to those exemplified in the description of the (meth)acrylic adhesive polymer (A).

[0090] In the vinyl polymer (C), the content of structural units derived from (meth)acrylic monomers is preferably 20% by mass or more, more preferably 30% by mass or more, even more preferably 40% by mass or more, and even more preferably 50% by mass or more, relative to the total structural units of the vinyl polymer (C). By setting the content of structural units derived from (meth)acrylic monomers in the vinyl polymer (C) within the above range, it is considered that the vinyl polymer (C) can be made to have appropriate compatibility with the acrylic adhesive polymer (A), thereby preventing complete phase separation between the vinyl polymer (C) and the acrylic adhesive polymer (A), while making it easier to unevenly distribute the vinyl polymer (C) toward the surface layer of the adhesive layer, and also making it easier to induce phase separation of the modified polymer (B) in the surface layer of the adhesive layer. As a result, an adhesive layer exhibiting good high-temperature adhesion can be obtained.

[0091] In terms of forming an adhesive layer with higher adhesive strength at high temperatures, it is preferable that the vinyl polymer (C) has structural units (hereinafter also referred to as "structural units (UC-1)") derived from at least one selected from the group consisting of aliphatic cyclic vinyl monomers and aromatic vinyl monomers. Specific examples of aliphatic cyclic vinyl monomers include vinyl monomers having an aliphatic ring among the monomers mentioned above, with aliphatic cyclic esters of (meth)acrylic acid being preferred. Specific examples of aromatic vinyl monomers include vinyl monomers having an aromatic ring among the monomers mentioned above, with at least one selected from the group consisting of aromatic esters of (meth)acrylic acid and aromatic vinyl compounds being preferred.

[0092] Because the vinyl polymer (C) has a structural unit (UC-1), the Tg of the vinyl polymer (C) can be made relatively high; when forming an adhesive layer, the vinyl polymer (C) can be easily segregated to the surface layer of the adhesive layer; and the affinity with the backbone of the modified polymer (B) (i.e., the polyolefin backbone and / or polydiene backbone) can be increased. For these reasons, the adhesive layer obtained from this composition is expected to exhibit excellent adhesive strength at high temperatures for various materials.

[0093] In the vinyl polymer (C), the content of structural units (UC-1) is preferably 5% by mass or more, more preferably 10% by mass or more, even more preferably 15% by mass or more, even more preferably 20% by mass or more, even more preferably 30% by mass or more, and even more preferably 50% by mass or more, relative to the total structural units of the vinyl polymer (C). Regarding the upper limit of the content of structural units (UC-1), from the viewpoint of ensuring appropriate compatibility with the (meth)acrylic adhesive polymer (A), it is preferably 99% by mass or less, more preferably 95% by mass or less, and even more preferably 90% by mass or less, relative to the total structural units of the vinyl polymer (C).

[0094] As monomers constituting the structural unit (UC-1), among the above, at least one selected from the group consisting of isobornyl (meth)acrylate, dicyclopentanyl (meth)acrylate, cyclohexyl (meth)acrylate, adamantyl (meth)acrylate, and styrene is preferably used because it allows for a high Tg, facilitates segregation of the vinyl polymer (C) to the surface layer of the phase mainly composed of (meth)acrylic adhesive polymer (A) when the adhesive layer is formed, and tends to yield good heat resistance.

[0095] Furthermore, in order to increase the Tg of the surface portion of the adhesive layer and obtain an adhesive layer exhibiting good heat resistance, it is preferable that the vinyl polymer (C) contains structural units derived from at least one selected from the group consisting of methyl methacrylate, ethyl methacrylate, butyl methacrylate, isobornyl (meth)acrylate, dicyclopentanyl (meth)acrylate, cyclohexyl (meth)acrylate, adamantyl (meth)acrylate, and styrene. The content of said structural units is preferably 50% by mass or more, more preferably 60% by mass or more, even more preferably 75% by mass or more, even more preferably 80% by mass or more, and even more preferably 90% by mass or more, relative to the total structural units of the vinyl polymer (C).

[0096] Furthermore, it is preferable that the vinyl polymer (C) has a lower total content of structural units derived from monomers selected from the group consisting of α-olefins, conjugated dienes, and non-conjugated dienes than the modified polymer (B). Specifically, in vinyl polymer (C), the total content of structural units derived from monomers selected from the group consisting of α-olefins, conjugated dienes, and non-conjugated dienes is preferably less than 10% by mass, more preferably 5% by mass or less, even more preferably 1% by mass or less, and even more preferably 0.5% by mass or less, relative to the total structural units of vinyl polymer (C).

[0097] The number-average molecular weight (Mn) of the vinyl polymer (C) is 500 or more and less than 50,000. When Mn is less than 50,000, sufficient segregation of the vinyl polymer (C) can be produced in the phase mainly composed of the (meth)acrylic adhesive polymer (A), ensuring adhesion and heat resistance under high-temperature conditions, and suppressing a decrease in compatibility with the acrylic adhesive polymer (A). When Mn is 500 or more, the amount of polymerization initiator and chain transfer agent used when producing the polymer can be set to an appropriate amount, ensuring the productivity of the polymer. The Mn of the vinyl polymer (C) is preferably 1,000 or more, more preferably 1,500 or more, even more preferably 1,700 or more, and even more preferably 2,000 or more. The upper limit of Mn for the vinyl polymer (C) is preferably 40,000 or less, more preferably 30,000 or less, even more preferably 25,000 or less, and even more preferably 15,000 or less. Furthermore, the range of Mn in the vinyl polymer (C) is preferably 1,000 to 40,000, more preferably 1,000 to 30,000, even more preferably 1,500 to 25,000, and even more preferably 1,700 to 20,000.

[0098] In vinyl polymer (C), the molecular weight distribution (Mw / Mn), expressed as the ratio of Mw to Mn, is preferably 3.0 or less, as this facilitates obtaining good adhesive strength. More preferably, Mw / Mn is 2.5 or less, and even more preferably 2.0 or less. The lower limit of Mw / Mn for vinyl polymer (C) is not particularly limited, but is 1.0 or more.

[0099] The vinyl polymer (C) may have the property of phase-separating from the (meth)acrylic adhesive polymer (A). Having such a property makes it possible to form an adhesive layer with high heat resistance and durability against temperature changes. Furthermore, by adjusting the difference ΔSP (absolute value) when comparing the SP value of the vinyl polymer (C), which is calculated using a known method for calculating the SP value (e.g., the Fedors method), with the SP value of the (meth)acrylic adhesive polymer (A), a vinyl polymer (C) that phase-separates from the (meth)acrylic adhesive polymer (A) can be designed.

[0100] The vinyl polymer (C) can be obtained by polymerizing the above monomer using known radical polymerization methods such as solution polymerization, suspension polymerization, emulsion polymerization, or bulk polymerization. In the case of solution polymerization, for example, the target vinyl polymer (C) can be obtained by charging an organic solvent and monomer into a reactor, adding a polymerization initiator, and copolymerizing by heating to 50 to 300°C. The details of the polymerization method are the same as for the (meth)acrylic adhesive polymer (A), so they are omitted here.

[0101] This composition preferably contains vinyl polymer (C) in an amount of 0.5 parts by mass or more and 50 parts by mass or less per 100 parts by mass of (meth)acrylic adhesive polymer (A), on a solid content basis. By setting the content of vinyl polymer (C) to 0.5 parts by mass or more, the effects of incorporating vinyl polymer (C), particularly the improvement of adhesion to highly polar substrates, can be sufficiently obtained. Furthermore, by setting the content of vinyl polymer (C) to 50 parts by mass or less, the improvement of adhesion to highly polar substrates, as well as the improvement of adhesion at room temperature and high temperature, can be sufficiently obtained while ensuring the flexibility and transparency of the adhesive layer. From this viewpoint, the lower limit of the content of vinyl polymer (C) is preferably 1 part by mass or more, more preferably 1.5 parts by mass or more, and even more preferably 2 parts by mass or more, per 100 parts by mass of (meth)acrylic adhesive polymer (A). The upper limit of the content of vinyl polymer (C) is preferably 40 parts by mass or less, more preferably 30 parts by mass or less, even more preferably 25 parts by mass or less, and even more preferably 15 parts by mass or less, per 100 parts by mass of (meth)acrylic adhesive polymer (A).

[0102] Furthermore, the content range of the vinyl polymer (C) is preferably 0.5 parts by mass or more and 40 parts by mass or less, more preferably 0.5 parts by mass or more and 30 parts by mass or less, even more preferably 0.5 parts by mass or more and 25 parts by mass or less, and even more preferably 1 part by mass or more and 15 parts by mass or less, per 100 parts by mass of the (meth)acrylic adhesive polymer (A).

[0103] [Crosslinking agent] When the acrylic adhesive polymer (A) has crosslinkable functional groups, it is preferable to incorporate a crosslinking agent that can react with these crosslinkable functional groups into the adhesive composition, as this can further improve adhesion at high temperatures, heat resistance, and durability against temperature changes. It is also preferable that, in the process of forming the adhesive layer, the formation of a crosslinked structure in the acrylic adhesive polymer (A) facilitates phase separation with the modified polymer (B).

[0104] Examples of crosslinking agents (curing agents) include epoxy compounds having two or more epoxy groups, isocyanate compounds having two or more isocyanate groups, aziridine compounds having two or more aziridinyl groups, oxazoline compounds having oxazoline groups, metal chelate compounds, and butylated melamine compounds. Among these, isocyanate compounds are preferred because they exhibit excellent tackiness under high-temperature conditions.

[0105] Specific examples of crosslinking agents include polyfunctional epoxy compounds such as ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, tetraglycidylxylenediamine, 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane, and trimethylolpropane polyglycidyl ether.

[0106] As isocyanate compounds, various polyfunctional isocyanate compounds of the aromatic, aliphatic, and alicyclic types, as well as modified products (prepolymers, etc.) of these polyfunctional isocyanate compounds can be used. Specifically, aromatic isocyanate compounds such as diphenylmethane diisocyanate (MDI), tolylene diisocyanate (TDI), naphthalene diisocyanate (NDI), p-phenylene diisocyanate (PPDI), xylene diisocyanate (XDI), tetramethylxylylene diisocyanate (TMXDI), and tolidine diisocyanate (TODI); hexamethylene diisocyanate (HDI), and lysine diisocyanate (L Examples include aliphatic isocyanate compounds such as DI; alicyclic isocyanate compounds such as isophorone diisocyanate (IPDI), cyclohexyl diisocyanate (CHDI), hydrogenated XDI (H6XDI), and hydrogenated MDI (H12MDI); and modified isocyanate compounds such as urethane modified, dimer, trimer, carbodiimide modified, urea modified, isocyanurate modified, oxazolidone modified, and isocyanate group-terminated prepolymers.

[0107] Examples of aziridine compounds include 1,6-bis(1-aziridinylcarbonylamino)hexane, 1,1'-(methylene-di-p-phenylene)bis-3,3-aziridylurea, ethylenebis-(2-aziridinylpropionate), 2,4,6-triaziridinyl-1,3,5-triazine, and trimethylolpropane-tris(2-aziridinylpropionate).

[0108] When a crosslinking agent is incorporated into this composition, the content of the crosslinking agent in this composition is not particularly limited. The content of the crosslinking agent is usually 0.01 to 10 parts by mass, preferably 0.03 to 5 parts by mass, and more preferably 0.05 to 2 parts by mass, based on 100 parts by mass of the acrylic adhesive polymer (A).

[0109] [Tackifier] This composition may contain a tackifier. Examples of tackifiers include rosin derivatives such as rosin esters, gum rosin, tall oil rosin, hydrogenated rosin esters, maleated rosin, and disproportionated rosin esters; terpene phenol resins, terpene resins mainly composed of α-pinene, β-pinene, or limonene; coumarone-indene resins, hydrogenated aromatic copolymers, and phenolic resins. The tackifier may be used alone or in combination of two or more. The content of the tackifier is preferably 10 parts by mass or less, more preferably 5 parts by mass or less, and even more preferably 1 part by mass or less, per 100 parts by mass of the acrylic adhesive polymer.

[0110] [Plasticizers] This composition may contain plasticizers. Examples of plasticizers include phthalate esters such as di-n-butyl phthalate, di-n-octyl phthalate, bis(2-ethylhexyl) phthalate, and di-n-decyl phthalate; adipic acid esters such as bis(2-ethylhexyl) adipate and di-n-octyl adipate; sebacate acid esters; azelaic acid esters; paraffins such as chlorinated paraffin; glycols such as polypropylene glycol; epoxy-modified vegetable oils such as epoxidized soybean oil and epoxidized linseed oil; phosphate esters such as trioctyl phosphate and triphenyl phosphate; phosphite esters such as triphenyl phosphite; ester oligomers such as esterified adipic acid and 1,3-butylene glycol; low molecular weight polymers such as low molecular weight polybutene, low molecular weight polyisobutylene, and low molecular weight polyisoprene; and oils such as process oil and naphthenic oil. The plasticizer content is preferably 20 parts by mass or less, more preferably 10 parts by mass or less, and even more preferably 5 parts by mass or less, based on 100 parts by mass of the acrylic adhesive polymer (A).

[0111] Additives that may be incorporated into this composition include, in addition to the crosslinking agents, tackifiers, and plasticizers mentioned above, antioxidants, UV absorbers, anti-aging agents, flame retardants, fungicides, silane coupling agents, fillers, colorants, antistatic agents, and the like. The content of the additives can be appropriately set according to the various compounds, as long as it does not impair the effects of this disclosure.

[0112] The solid content concentration in this composition (i.e., the ratio of the mass of components other than the solvent in the adhesive composition to the total mass of the adhesive composition) is not particularly limited, but is preferably 1 to 70% by mass. When the solid content concentration is 1% by mass or more, an adhesive layer with sufficient thickness can be formed. When the solid content concentration is 70% by mass or less, good coating properties can be ensured, and an adhesive layer of uniform thickness can be easily formed. The solid content concentration in this composition is more preferably 5 to 50% by mass, and even more preferably 10 to 45% by mass.

[0113] <<Adhesive Layer>> An adhesive layer can be formed by applying this composition onto a substrate and, if necessary, removing the solvent from the composition on the substrate. A resin film made of various resin materials can be used as the substrate to which this composition is applied. Both low-polarity and high-polarity substrates can be used as resin materials, and examples include polyester resins such as polyethylene terephthalate (PET), polyethersulfone resins, acetate resins, polycarbonate resins, polyolefin resins, acrylic resins, polyamide resins, and acrylonitrile butadiene styrene (ABS) resin.

[0114] The substrate is preferably such that the coated surface to which the composition is applied has release properties that allow the adhesive layer to be peeled off. Such a substrate is referred to as a separator or release film. The release properties of the coated surface may be imparted by known release treatments or by the material of the substrate.

[0115] The composition can be applied by known coating methods. Specifically, these methods include using various coating machines such as bar coaters, applicators, gravure coaters, knife coaters, slot die coaters, doctor blades, and dip coaters, as well as using various printing machines such as gravure printing, offset printing, screen printing, and inkjet printing.

[0116] In order to ensure sufficient phase separation between the acrylic adhesive polymer (A) and the modified polymer (B) in the adhesive layer formed by this composition, it is preferable to heat-treat the composition on the substrate when forming the adhesive layer on the substrate. The heating temperature and heating time during the heat treatment can be appropriately set according to the type of solvent in the composition, the solid content concentration of the composition, etc. The heating of the composition may be carried out under normal pressure or under reduced pressure. By preferably heat-treating the composition applied to the substrate to remove the solvent and thereby forming an adhesive layer, phase separation between the acrylic adhesive polymer (A) and the modified polymer (B) can be caused during the formation process of the adhesive layer. The thickness of the adhesive layer thus formed is, for example, 2 to 200 μm.

[0117] To obtain an adhesive layer in which an acrylic adhesive polymer (A) and a modified polymer (B) are phase-separated, this can be done, for example, by adjusting the degree of modification of the modified polymer (B) contained in the adhesive composition, adjusting the molecular weight of the modified polymer (B), adding a crosslinking agent, or combining these methods. The lower the degree of modification of the modified polymer (B), the more likely the modified polymer (B) is to phase-separate from the acrylic adhesive polymer (A). Furthermore, the higher the molecular weight of the modified polymer (B) is made to approach the molecular weight of the acrylic adhesive polymer (A), the more likely the modified polymer (B) is to phase-separate from the acrylic adhesive polymer (A).

[0118] In addition, the difference in SP values ​​(Fedors method) between the acrylic adhesive polymer (A) and the modified polymer (B) contained in the adhesive composition may be set to a predetermined value or greater to obtain an adhesive layer in which the acrylic adhesive polymer (A) and the modified polymer (B) are phase-separated in the surface layer. Furthermore, the phase separation between the acrylic adhesive polymer (A) and the modified polymer (B) can be easily observed by observing the structure of the adhesive layer obtained using an adhesive composition in which the intended polymer blend of the acrylic adhesive polymer (A) and the modified polymer (B) is dissolved in a solvent using an electron microscope, scanning probe microscope (atomic force microscope, etc.), or small-angle X-ray scattering.

[0119] The adhesive composition used to form the adhesive layer in this disclosure has a uniform acrylic adhesive polymer (A) and a modified polymer (B), and has a single phase. During the process of forming the adhesive layer with such a uniform adhesive composition, phase separation occurs between the acrylic adhesive polymer (A) and the modified polymer (B), resulting in an adhesive layer obtained using this composition exhibiting a relatively high haze value. Specifically, the haze value of the adhesive layer is preferably 3.0% or higher, as measured by a haze meter after attaching a 50 μm thick adhesive layer to a glass substrate and leaving it standing for one day under 23°C and 50% RH conditions. Therefore, in an adhesive layer containing an acrylic adhesive polymer (A) and a modified polymer (B), but with a sufficiently low haze value (e.g., 1.5% or less, or less than 1.0%), it can be said that the acrylic adhesive polymer (A) and the modified polymer (B) have not undergone phase separation.

[0120] ≪Adhesive Sheet≫ The adhesive sheet of this disclosure (hereinafter also referred to as "this sheet") comprises an adhesive layer formed using this composition. The adhesive layer of this sheet and the adhesive composition for forming it are as described above. Therefore, after the adhesive layer of this sheet is attached to a molded body, the adhesive layer is difficult to peel off from the molded body in both room temperature and high temperature environments, and it exhibits excellent adhesion at both room temperature and high temperature.

[0121] The adhesive sheet may be a so-called substrate-less configuration in which the adhesive layer is sandwiched between two separators, or one of the objects to be joined may be a substrate. In the substrate-less configuration, the peel strengths of the two separators may be the same or different. There are no particular restrictions on the shape of the adhesive sheet, and it can be set as appropriate according to the usage situation. The adhesive sheet may be, for example, in the form of a single sheet, in the form of a roll, or cut into strips. The thickness of the adhesive layer can be set as appropriate depending on the type of objects to be joined, the area and shape of the joining area, etc. In addition, to achieve the desired thickness of the adhesive layer of the adhesive sheet, the adhesive layer of the adhesive sheet may be formed by laminating multiple adhesive layers.

[0122] The adhesive sheets obtained in this manner can be used as adhesives in a wide range of applications. Specifically, they can be used as adhesives in various applications such as clothing (including fashion accessories), sporting goods (e.g., sportswear, sports shoes, sports gloves, bat and racket grips, etc.), medical supplies (e.g., supporters and corsets, etc.), automotive interior or exterior parts, outdoor goods, handicraft supplies, toys, household goods, furniture, and housing equipment.

[0123] ≪Decorative Film≫ One preferred embodiment of the adhesive sheet of the present disclosure is a decorative film comprising an adhesive layer formed by the present composition and a decorative layer. In this case, the present composition is used for the decorative film, and the adhesive layer formed by the present composition is used for attaching the decorative layer. Examples of decorative films include a single-layer film in which the decorative layer is formed by coloring the base layer, and a laminated film in which the decorative layer and the base layer are laminated in this order. A decorative film having such a configuration is preferably used as a decorative film for a lamination method to obtain a decorative molded body by laminating it to an adherend.

[0124] In a decorative film, the base layer is located on the outermost layer of the decorated adherend (i.e., the decorated molded body) after the adherend has been decorated by the decorative film, and functions as a protective layer for the decorated molded body. The material constituting the base layer is preferably a flexible material, and a resin material is preferred. More preferably, it is a thermoplastic resin. The thermoplastic resin is not particularly limited, but examples include vinyl chloride (PVC) resin, polyester resin, acrylic resin, acrylonitrile butadiene styrene (ABS) resin, polycarbonate resin, polyamide resin, polypropylene resin, and polyethylene resin.

[0125] The thickness of the base layer is preferably 25 μm to 500 μm, more preferably 50 μm to 400 μm, and even more preferably 100 to 300 μm. Having the base layer thickness within this range results in good processability, shape conformability, and handling when manufacturing the decorated molded body by injection molding (also known as insert molding), vacuum forming, or vacuum pressure forming.

[0126] The decorative layer is an ink layer to which patterns and designs such as text, figures, and trademarks are applied by printing or other means. This decorative layer imparts design appeal to the decorative film. The patterns and designs of the decorative layer can be formed by known printing methods such as gravure printing, offset printing, silkscreen printing, transfer printing from a transfer sheet, sublimation transfer printing, and inkjet printing using printing inks. The thickness of the decorative layer is preferably 1 to 40 μm, more preferably 1 to 30 μm. When the thickness of the decorative layer is within the above range, sufficient thickness can be ensured to express complex designs such as gradients. The surface layer of the decorative film may be given an uneven pattern. The uneven pattern can be formed, for example, by transferring the uneven pattern using an embossing roller. Furthermore, decorative functions can also be imparted to the base layer and adhesive layer by incorporating pigments, dyes, brightening agents, etc., into the base layer and adhesive layer.

[0127] Before being bonded to the substrate, the decorative film may further include a release layer on the outermost layer on the adhesive side, along with the adhesive layer. The release layer prevents unintended adhesion and is peeled off when the decorative film is bonded to the substrate. The material constituting the release layer is not particularly limited and can be, for example, resin materials such as polyester such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate, polyolefins such as polypropylene and polyethylene; or paper materials such as glassine paper, kraft paper, or clay-coated paper. The thickness of the release layer can be about 10 to 400 μm.

[0128] In addition, the decorative film may be a film that, before being bonded to the substrate, comprises a hard coat layer (protective layer) and a decorative layer on the release layer of a release film, and is bonded to the substrate via an adhesive layer provided on the decorative layer side. A decorative film with such a configuration is suitably used as a transfer film. With a decorative film with this configuration, a decorated molded article can be obtained by a transfer method that transfers from the hard coat layer to the adhesive layer to the substrate.

[0129] The hard coat layer is preferably made of a material that can be cured and / or crosslinked by irradiation with active energy rays after being transferred to the adherend. Examples of materials constituting the hard coat layer include polymers or oligomers having (meth)acryloyl groups, a semi-cured active energy ray curable composition obtained by irradiating it with an appropriate amount of active energy rays, or an active energy ray curable resin composition blended with isocyanate compounds and polyol resins and appropriately crosslinked. The thickness of the hard coat layer is not particularly limited, and is, for example, about 1 to 50 μm.

[0130] ≪Decorated Molded Article≫ According to this disclosure, a decorated molded article is provided comprising an adherend, an adhesive layer, and a decorative layer, wherein the adhesive layer and the decorative layer are laminated in this order on the surface of the adherend, and the adhesive layer is formed by the composition. The decorated molded article of this disclosure is decorated by bonding the decorative layer with the adhesive layer obtained using the composition. For this reason, the decorative film is less likely to lift or peel off at both room temperature and high temperature, and has excellent heat resistance and durability.

[0131] When bonding a decorative layer to the surface of an object via an adhesive layer, an adhesive sheet comprising an adhesive layer and a decorative layer (i.e., an adhesive-backed decorative film) may be used, and the adhesive layer side of this adhesive sheet may be bonded to the surface of the object. Alternatively, an adhesive sheet without a decorative layer and a decorative film without an adhesive layer may be prepared separately, the adhesive sheet may be bonded to the surface of the object first, and then the decorative film may be bonded to the adhesive sheet.

[0132] The molded body to which the decorative film is bonded is not particularly limited, and any article to which a decorative film can be bonded is acceptable, such as resin products, metal products, ceramic products, glass products, etc. Specifically, examples include various home appliances such as household appliances, kitchen appliances, health appliances, and seasonal appliances; interior and exterior components of residential equipment such as toilets, bathrooms, doors, and walls; interior and exterior automotive parts such as bumpers, dashboards, doors, roofs, and hoods; various miscellaneous goods such as household goods and daily necessities; electronic components; nursing care and medical supplies; and interior and exterior parts of ships and aircraft. The adhesive layer formed by this composition softens upon heating and can conform to the surface shape of the adherend, and moreover, maintains high adhesive performance while conforming to the surface shape of the adherend after bonding, making it particularly suitable for bonding the adhesive layer to molded bodies having a three-dimensional shape.

[0133] For the manufacture of the decorated molded body, vacuum forming, vacuum pressure forming, and injection molding methods can be used. In the vacuum forming method, the decorative film is heated and softened while being stretched, and the space on the molded body side of the decorative film is depressurized, thereby forming and bonding the decorative film to the surface shape (e.g., three-dimensional shape) of the molded body. In the vacuum pressure forming method, after the molding process of the vacuum forming method, the space on the opposite side is further pressurized, thereby forming and bonding the decorative film to the surface shape of the molded body. Examples of vacuum pressure forming machines include the TFH series of hot plate type vacuum coating molding machines manufactured by Asano Research Institute, the NGF series of TOM molding machines manufactured by Fuse Vacuum, and the NATS air transfer machine manufactured by Navitas. In the injection molding method, the decorative film is set in the mold cavity of the injection molding machine, and injection molding is performed to bond the decorative film to the surface shape of the molded body. By these methods, a decorated molded body can be obtained that is decorated via an adhesive layer formed by this composition.

[0134] The present invention will be specifically described below with reference to examples. However, the present invention is not limited to these examples. In the following, "parts" and "%" mean "parts by mass" and "mass%", respectively, unless otherwise specified. The analytical methods for the polymers used in each example are as follows.

[0135] <Molecular Weight Measurement> Using a gel permeation chromatograph (model "HLC-8320", manufactured by Tosoh Corporation), the weight-average molecular weight (Mw) and number-average molecular weight (Mn) in polystyrene equivalent were obtained under the following conditions: ○Measurement conditions Column: 4 x TSKgel SuperMultiporeHZ-M (manufactured by Tosoh Corporation) Column temperature: 40°C Eluent: Tetrahydrofuran Detector: RI Flow rate: 600 μL / min

[0136] <Measurement of Glass Transition Temperature (Tg)> The glass transition temperature (Tg) of the polymer was determined from the intersection of the baseline of the heat flux curve obtained using a differential scanning calorimeter (DSC) and the tangent line at the inflection point. The heat flux curve was obtained by cooling approximately 10 mg of the sample to -100°C, holding for 5 minutes, then raising the temperature to 300°C at a rate of 10°C / min, continuing to cool to -100°C, holding for 5 minutes, and then raising the temperature to 350°C at a rate of 10°C / min. Measurement instrument: DSC6220, manufactured by SII Nanotechnology Inc. Measurement atmosphere: Nitrogen atmosphere

[0137] <Measurement of Melting Point (Tm)> The melting point (Tm) of the modified polyolefin was defined as the melting peak of the heat flux curve obtained using a differential scanning calorimeter (DSC). The heat flux curve was obtained by cooling approximately 5 mg of the sample to -70°C, holding for 5 minutes, then raising the temperature to 150°C at a rate of 10°C / min, continuing to cool to -70°C, holding for 5 minutes, and then raising the temperature to 150°C at a rate of 10°C / min. Measurement instrument: DSC6220, manufactured by SII Nanotechnology Inc. Measurement atmosphere: Nitrogen atmosphere

[0138] <SP Value> The SP value of the polymer was calculated using the Fedors method. The unit is [cal / cm]. ３ ] １／２ That is the case.

[0139] 1. Synthesis of Acrylic Adhesive Polymers [Synthesis Example 1] (Synthesis of Polymer A-1) Butyl acrylate (hereinafter also referred to as "BA") (17 parts by mass), 2-methoxyethyl acrylate (hereinafter also referred to as "MEA") (78 parts by mass), 2-hydroxyethyl acrylate (hereinafter also referred to as "HEA") (5 parts by mass), and ethyl acetate (150 parts) were charged into a four-necked flask. The mixture was thoroughly degassed by bubbling with nitrogen gas, and the internal temperature of the mixture was raised to 75°C. 2,2'-azobis(2,4-dimethylbutyronitrile) (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., trade name "V-65") (0.0191 parts by mass) was added as an initiator, and polymerization was carried out for 5 hours. Ethyl acetate was added to obtain an ethyl acetate solution of polymer A-1 by adjusting the solid content concentration to 22%. The obtained polymer consisted of 17% by mass of BA, 78% by mass of MEA, and 5% by mass of HEA, with Mn = 92,000, Mw = 800,000, and Mw / Mn = 8.7. The Tg was -35°C, and the SP value was 10.27. Table 1 shows the composition (charging ratio), reaction conditions, and analysis results of polymer A-1. The monomer composition ratio of polymer A-1 was calculated from the amount of monomer charged and the amount of monomer consumed by gas chromatography (GC) measurement, and it was found to be equivalent to the monomer charging ratio.

[0140] [Synthesis Examples 2-7] (Synthesis of Polymers A-2 to A-7) The same procedure as in Synthesis Example 1 was performed, except that the type and amount of raw materials charged into the flask and the reaction conditions were changed as shown in Table 1, to obtain solutions containing polymers A-2 to A-7, respectively. The results of the analysis of the obtained polymers are shown in Table 1. For polymers A-2 to A-7, the monomer composition ratio was calculated in the same way as for polymer A-1, and the monomer composition ratio of each polymer was equivalent to the monomer charging ratio.

[0141]

[0142] The abbreviations for monomers in Table 1 are as follows: MA: Methyl acrylate BA: Butyl acrylate MEA: 2-methoxyethyl acrylate HEA: 2-hydroxyethyl acrylate AA: Acrylic acid

[0143] 2. Synthesis of Vinyl Polymers [Synthesis Example 8] (Synthesis of Polymer C-1) A mixture of butyl acetate (200 parts by mass) and dimethyl-2,2'-azobis(2-methylpropionate) (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., trade name "V-601", hereinafter also referred to as "V-601") (0.9 parts by mass) was charged into a 1-liter four-necked flask. This mixture was thoroughly degassed by bubbling with nitrogen gas, and the internal temperature of the mixture was raised to 90°C. Separately, a mixture of methyl methacrylate (hereinafter also referred to as "MMA") (165 parts by mass), isobornyl methacrylate (hereinafter also referred to as "IBXMA") (44 parts by mass), V-601 (17 parts by mass), and butyl acetate (90 parts by mass) was added dropwise to the flask from a dropping funnel over a period of 5 hours to carry out polymerization. After the dropwise addition was complete, the polymerization solution was added dropwise to a mixed solution consisting of methanol (4800 parts by mass) and distilled water (1200 parts by mass) to isolate the vinyl polymer in the polymerization solution and obtain polymer C-1. The composition ratio of the monomers constituting the obtained polymer C-1 was １ Based on calculations from 1H-NMR measurements, the composition was 80% MMA and 20% IBXMA (Table 2). The molecular weight characteristics of polymer C-1 were Mn = 4,370, Mw = 6,700, and Mw / Mn = 1.53. The Tg of polymer C-1 was 108°C.

[0144] [Synthesis Example 9] (Synthesis of Polymer C-2) The same procedure as in Synthesis Example 8 was performed, except that the initial charge was changed to butyl acetate (280 parts by mass) and V-601 (0.3 parts by mass), and the dropwise added mixture was changed to MMA (233 parts by mass), IBXMA (26 parts by mass), V-601 (5.1 parts by mass), and butyl acetate (90 parts by mass), to obtain vinyl polymer C-2.

[0145] [Synthesis Example 10] (Synthesis of Polymer C-3) A mixture of butyl acetate (200 parts by mass), styrene (15 parts by mass), and methyl methacrylate (22 parts by mass) was placed in a 1-liter four-necked flask, and the mixture was thoroughly degassed by bubbling with nitrogen gas to raise the internal temperature of the mixture to 90°C. A mixture of V-601 (11.4 parts by mass) and butyl acetate (15 parts by mass) was added to start polymerization. Polymerization was then carried out by adding a mixture of styrene (123 parts by mass), methyl methacrylate (90 parts by mass), V-601 (65 parts by mass), and butyl acetate (90 parts by mass) dropwise into the flask from a dropping funnel over a period of 5 hours. After the addition was complete, the polymerization solution was isolated from the polymerization solution by adding it dropwise to a mixed solvent of methanol (4800 parts by mass) and water (1200 parts by mass) to obtain polymer C-3.

[0146] [Synthesis Example 11] (Synthesis of Polymer C-4) The same procedure as in Synthesis Example 8 was performed, except that the initial charge was changed to butyl acetate (205 parts by mass) and V-601 (3.9 parts by mass), and the dropwise added mixture was changed to MMA (12 parts by mass), IBXMA (240 parts by mass), V-601 (60 parts by mass) and butyl acetate (90 parts by mass), to obtain vinyl polymer C-4.

[0147] [Synthesis Example 12] (Synthesis of Polymer C-5) Butyl acetate (203 parts by mass) was placed in a 1-liter four-necked flask, and the flask was thoroughly degassed by bubbling nitrogen gas, raising the internal temperature to 90°C. Polymerization was carried out by adding a mixture of MMA (100 parts by mass), IBXMA (109 parts by mass), V-601 (20 parts by mass), and butyl acetate (90 parts by mass) dropwise into the flask from a dropping funnel over a period of 5 hours. After the addition was complete, the polymerization solution was isolated from the polymerization solution by adding hexane (6000 parts by mass) to obtain vinyl polymer C-5.

[0148] [Synthesis Example 13] (Synthesis of Polymer C-6) A mixture consisting of MMA (63 parts by mass), butyl acetate (250 parts by mass), and V-601 (4.2 parts by mass) was placed in a 1-liter four-necked flask. The mixture was thoroughly degassed by bubbling with nitrogen gas, and the internal temperature of the mixture was raised to 90°C. Separately, a mixture consisting of MMA (18.8 parts by mass), V-601 (46 parts by mass), and butyl acetate (90 parts by mass) was added dropwise to the flask from a dropping funnel over a period of 5 hours to carry out polymerization. After the addition was complete, the polymerization solution was isolated from the polymerization solution by adding hexane (6000 parts by mass) to obtain vinyl polymer C-6.

[0149] The analysis results for the obtained polymers C-1 to C-6 are shown in Table 2. The monomer composition ratio of each polymer is as follows: １ Calculated from H-NMR measurements.

[0150]

[0151] The abbreviations for monomers in Table 2 are as follows: MMA: Methyl methacrylate IBXMA: Isobornyl methacrylate St: Styrene

[0152] 3. Manufacture of adhesive composition and adhesive sheet [Example 1] The ethyl acetate solution of polymer A-1 obtained in Synthesis Example 1 was desoluble and redissolved in butyl acetate to obtain polymer A-1 solution. Polymer B-1 (Hardren PMA-TE manufactured by Toyobo MC Co., Ltd., maleic anhydride modified polyolefin, modification rate 1.8%, melting point 95°C, Mw 60,000) was dissolved in cyclohexane to obtain a polymer B-1 solution with a solid content of 5% by mass, which was mixed with polymer A-1 solution. Polymer C-1 and a mixed solvent of butyl acetate and cyclohexane were then added so that the overall solvent mixing ratio was butyl acetate:cyclohexane = 65 / 35 (by mass ratio), and a polymer solution with a solid content of 25% by mass containing polymer A-1 (100 parts by mass), polymer B-1 (2 parts by mass), and polymer C-1 (4 parts by mass) was prepared. Here, 0.14 parts by mass of trimethylolpropane modified tolylene diisocyanate (Takenate D-101E, manufactured by Mitsui Chemicals, 75% solids content, 13.3% isocyanate group content) was mixed as a crosslinking agent to obtain an adhesive composition. The obtained adhesive composition was applied to a polyethylene terephthalate (hereinafter, "PET") separator with a thickness of 50 μm so that the thickness after drying was 50 μm. The solvent was removed by drying the adhesive composition at 120°C for 4 minutes. A PET separator with a thickness of 38 μm and a different peeling strength from the above separator was bonded to it, and the sheet was left to mature (age) at 40°C for 5 days to obtain an adhesive sheet with separators on both sides.

[0153] [Examples 2-20, Comparative Examples 1-3] Based on the compositions and solid content concentrations shown in Tables 3-5, adhesive compositions were prepared in the same manner as in Example 1. For examples where the solvent did not contain ethyl acetate (AE) (Examples 2, 12, 14, 15, 17, 18, 19, 20, Comparative Example 3), the ethyl acetate solution of the acrylic adhesive polymer obtained in each synthesis example was desoluble, and the polymer solution obtained by redissolving the acrylic adhesive polymer in the solvents listed in Tables 3-5 was used to prepare the adhesive composition. For examples where the solvent contained ethyl acetate (AE) (Examples 3-11, 13, 16, Comparative Examples 1, 2), the ethyl acetate solution of the acrylic adhesive polymer obtained in each synthesis example was used as is to prepare the adhesive composition. Furthermore, using the obtained adhesive compositions, adhesive sheets with double-sided separators were obtained in the same manner as in Example 1. In addition, for the composition values ​​of the adhesive compositions in Tables 3 to 5, the values ​​for acrylic adhesive polymers (indicated as BP in the tables), modified polymers (indicated as PO in the tables), and vinyl polymers (C) (indicated as PC in the tables) represent the amount of solids (parts by mass) of each component used in the preparation of the adhesive composition, while the values ​​for crosslinking agents represent the amount including solvent (parts by mass).

[0154] 4. Evaluation The coating properties of the adhesive compositions prepared in each example were evaluated using the method described below. In addition, peel tests were performed on the double-sided separator adhesive sheets obtained in each example (hereinafter referred to as "evaluation sheets") using the method described below. The results are shown in Tables 3 to 5.

[0155] <Coating Properties> Each adhesive composition was applied to a PET separator with a thickness of 50 μm so that the thickness after drying was 50 μm. The state of the adhesive layer after drying the adhesive composition at 120°C for 4 minutes was evaluated according to the following three-stage criteria. Coating properties were evaluated for the adhesive composition immediately after mixing each component, and for the adhesive composition after mixing each component (excluding the crosslinking agent) and leaving it at room temperature (25°C) for one month. ○: Good coating properties, and a coating film with good surface smoothness is obtained. △: Coating is possible, but streaks and defects due to precipitates occur in the coating film. The defects in the coating film after drying are small. ×: Gel material precipitates in the adhesive composition, making coating impossible.

[0156] <Peel Test> An evaluation sheet (adhesive layer thickness: 50 μm) was transferred to an easily bonded PET film (125 μm) to obtain a peel test sheet. This peel test sheet was laminated to a polypropylene (PP) plate (manufactured by Resonaq, product name PP-N-BN, 2 mm thick), and a peel test specimen was obtained by pressing it for 20 seconds under conditions of 120°C and 0.8 MPa using a precision heating and pressing device (manufactured by Shinto Kogyo Co., Ltd.). The peel strength of the adhesive sheet at 180 degrees was measured using a Stroggraph R-type tensile testing machine with a constant temperature bath (manufactured by Toyo Seiki Co., Ltd.) under conditions of temperatures of 23°C and 85°C and a peel speed of 300 mm / min., in accordance with JIS Z-0237 "Test Method for Adhesive Tapes and Adhesive Sheets", and the peel strength at each temperature (unit: N / 25 mm) was expressed.

[0157]

[0158]

[0159]

[0160] The abbreviations for the modified polymer (PO), additives, and solvents in Tables 3 to 5 are as follows: "BP" refers to the acrylic adhesive polymers A-1 to A-7 obtained in Synthesis Examples 1 to 7, and "PC" refers to the vinyl polymers C-1 to C-6 obtained in Synthesis Examples 8 to 13. B-1: Hardlen PMA-TE manufactured by Toyobo MC Co., Ltd., maleic anhydride-modified polyolefin, modification rate 1.8%, melting point 95°C, Mw 60,000) B-2: Hardlen PMA-T manufactured by Toyobo MC Co., Ltd., maleic anhydride-modified polyolefin, modification rate 1.5%, melting point 95°C, Mw 75,000) B-3: Hardlen PMA-TZ manufactured by Toyobo MC Co., Ltd., maleic anhydride-modified polyolefin, modification rate 1.4%, melting point 95°C, Mw 115,000) B-4: Hardlen PMA-KE manufactured by Toyobo MC Co., Ltd., maleic anhydride-modified polyolefin, modification rate 2.0%, melting point 80°C, Mw 60,000) B-5: Hardlen PMA-LE manufactured by Toyobo MC Co., Ltd., maleic anhydride-modified polyolefin, modification rate 2.0%, melting point 70°C, Mw 60,000) B-6: Hardlen HM-21P manufactured by Toyobo MC Co., Ltd., maleic anhydride-modified chlorinated polyolefin, modification rate: chlorination modification rate 21%, maleic anhydride modification rate 1.6%, melting point 87°C, Mw 45,000) B-7: Hardlen M-28P manufactured by Toyobo MC Co., Ltd., maleic anhydride-modified chlorinated polyolefin, modification rate: chlorination modification rate 20%, maleic anhydride modification rate 1.7%, melting point 75°C, Mw 68,000) Crosslinking agent D-110N: Takenate D-110N manufactured by Mitsui Chemicals, Ltd., trimethylolpropane modified metaxylylene diisocyanate, solid content concentration 75% by mass, isocyanate group content 11.5% Crosslinking agent D-101E: Takenate D-101E manufactured by Mitsui Chemicals, a trimethylolpropane modified form of tolylene diisocyanate, solid content 75%, isocyanate group content 13.3% AB: Butyl acetate AE: Ethyl acetate CH: Cyclohexane MCH: Methylcyclohexane THF: Tetrahydrofuran MTHP: 4-methyltetrahydrofuran diox: 1,4-dioxane In Example 20, the solvent mixing ratio (AB / Tol / CH) was set to butyl acetate:toluene:cyclohexane = 15 / 62 / 23 (mass ratio). In Table 5, the "-" notation in the PP peel strength column indicates that the coating properties evaluation result was poor and evaluation was not possible.

[0161] From the results in Tables 3 to 5, Examples 1 to 20, which used a first solvent (aliphatic cyclic solvent) and a second solvent (ester-based solvent, toluene) as solvents, showed good coating properties for the adhesive composition, high peel strength of the adhesive layer at 23°C and 85°C, and good adhesion at both room temperature and high temperatures. Furthermore, Examples 1 to 20 maintained good coating properties even after being left for one month after preparation, showing little change over time. In addition, when comparing examples using alicyclic hydrocarbons as the aliphatic cyclic solvent with examples using cyclic ethers (comparison between Example 7 and Examples 13 and 14), the examples using alicyclic hydrocarbons showed higher peel strength.

[0162] In contrast, Comparative Example 1, which contained ethyl acetate as the first solvent and did not contain the second solvent, showed lower peel strength of the adhesive layer at 23°C and 85°C than Examples 1 to 20, and exhibited poor adhesion at both room temperature and high temperatures. Furthermore, Comparative Example 2, which contained butyl acetate as the first solvent and did not contain the second solvent, and Comparative Example 3, which contained cyclohexane as the second solvent and did not contain the first solvent, showed gel deposition in the adhesive composition, resulting in poor coating properties.

[0163] From the above results, it was revealed that an adhesive composition containing an acrylic adhesive polymer (A), a modified polymer, a first solvent, and a second solvent can form an adhesive layer with good coating properties and excellent adhesion at room temperature and high temperatures.

[0164] The present invention is not limited to the embodiments described above, and encompasses various modifications and variations within the scope of equivalents, without departing from the spirit of the invention. Therefore, various combinations and forms, as well as other combinations and forms that include only one, more, or fewer of these elements, should be understood to fall within the scope and conceptual range of the present invention in light of the above teachings.

Claims

1. An adhesive composition comprising: an acrylic adhesive polymer having a glass transition temperature of 10°C or less; a modified polymer which is at least one selected from the group consisting of modified polyolefins and modified polydienes; and a solvent, wherein the solvent comprises at least one selected from the group consisting of aliphatic cyclic solvents (excluding cyclic esters), ester solvents, and toluene.

2. The adhesive composition according to claim 1, wherein the content of the aliphatic cyclic solvent is 10 to 60% by mass relative to the total amount of solvent contained in the adhesive composition.

3. The adhesive composition according to claim 2, wherein the total content of the ester solvent and toluene is 30 to 90% by mass relative to the total amount of solvent contained in the adhesive composition.

4. The adhesive composition according to claim 1, wherein the aliphatic cyclic solvent is at least one selected from the group consisting of alicyclic hydrocarbons and cyclic ethers.

5. The adhesive composition according to claim 1, wherein the modified polymer is a maleic anhydride-modified substituted or unsubstituted polyolefin.

6. The adhesive composition according to claim 1, further comprising a vinyl polymer (excluding the modified polymer) having structural units derived from a (meth)acrylic monomer, having a glass transition temperature of 45°C or higher, and a number average molecular weight of 500 or more and less than 50,000.

7. An adhesive sheet comprising an adhesive layer formed by the adhesive composition according to any one of claims 1 to 6.

8. A decorative film comprising an adhesive layer formed by the adhesive composition according to any one of claims 1 to 6, and a decorative layer.

9. A method for manufacturing an adhesive sheet comprising an adhesive layer, wherein the adhesive layer is formed using an adhesive composition according to any one of claims 1 to 6.

10. A decorative molded body comprising an adherend, an adhesive layer, and a decorative layer, wherein the adhesive layer and the decorative layer are laminated in this order on the surface of the adherend, and the adhesive layer is formed of the adhesive composition described in any one of claims 1 to 6.

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