Adhesive composition, adhesive sheet, and decorative molded body

Abstract

An adhesive composition according to the present invention contains: an acrylic adhesive polymer having a glass transition temperature of 10°C or less; a modified polymer (B); and a vinyl polymer (other than the modified polymer (B)) that has a structural unit derived from a (meth)acrylic monomer, and has a glass transition temperature of 45°C or higher and a number average molecular weight of at least 500 and less than 50,000.

Description

Pressure-sensitive adhesive composition, pressure-sensitive adhesive sheet, and decorated molded article

[0001] [Cross-reference to related applications] This application claims priority to Japanese Patent Application No. 2023-221664, filed December 27, 2023, the entire contents of which are incorporated herein by reference. The present disclosure relates to a pressure-sensitive adhesive composition, a pressure-sensitive adhesive sheet, and a decorated molded article, and more particularly to a technology for improving the adhesion of an acrylic pressure-sensitive adhesive to a low-polarity material.

[0002] Acrylic pressure-sensitive adhesives are processed into, for example, tapes and labels and are used in a wide range of applications. Acrylic pressure-sensitive adhesives are also applied to a wide range of materials, including plastics, paper, metals, glass, and ceramics. In recent years, decorative films have been applied or transferred to molded products, primarily automotive interior and exterior components and home appliances, for the purpose of improving design and addressing VOC (volatile organic compounds) emissions. Forming methods using decorative films include in-mold molding using injection molding, vacuum forming, and vacuum-pressure forming. Decorative films having a pressure-sensitive adhesive layer are known as decorative films to be applied to molded products.

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

[0004] International Publication No. 2020 / 004355

[0005] Considering that adhesives are used in a wide range of applications, it is desirable for them to exhibit high adhesive properties over a wide temperature range. Furthermore, when adding a design to a molded product using a decorative film, the decorative film is sometimes stretched before being attached to the molded product. A decorative film attached to a molded product in a stretched state is prone to slippage, peeling, or lifting from the molded product at high temperatures, which can result in poor appearance. Therefore, adhesives are required to exhibit excellent adhesive properties not only at room temperature but also at high temperatures.

[0006] When considering the application of decorative films to adhesive layers, not only are substrates with low surface polarity (hereinafter also referred to as "low-polarity substrates") bonded together using an adhesive layer, but also substrates with a surface formed of a polar resin such as acrylonitrile butadiene styrene (ABS) resin or acrylic resin (hereinafter also referred to as "high-polarity substrates") may be bonded to a low-polarity substrate using an adhesive layer. Considering application to a wide range of applications and materials, the adhesive layer is required to have excellent adhesion to both low-polarity substrates and high-polarity substrates. However, modified polyolefins have low polarity and poor adhesion to high-polarity substrates (for example, substrates that have been processed for easy adhesion).

[0007] The present disclosure has been made in view of the above circumstances, and a main object of the present disclosure is to provide a pressure-sensitive adhesive composition that has excellent adhesive properties both at room temperature and at high temperatures and is capable of forming a pressure-sensitive adhesive layer that has excellent adhesive properties to both low-polarity substrates and high-polarity substrates.

[0008] As a result of intensive research to solve the above-mentioned problems, the present inventors have found that the above-mentioned problems can be solved by blending a specific component together with an acrylic adhesive polymer and a low-polarity modified polymer into a pressure-sensitive adhesive composition. Specifically, according to the present disclosure, the following pressure-sensitive adhesive composition, pressure-sensitive adhesive sheet, and decorated molded article are provided.

[0009] [1] A pressure-sensitive adhesive composition comprising an acrylic pressure-sensitive adhesive polymer having a glass transition temperature of 10°C or lower, a modified polymer which is at least one selected from the group consisting of modified polyolefins and modified polydienes, and a vinyl polymer (excluding the modified polymer) which has structural units derived from a (meth)acrylic monomer, has a glass transition temperature of 45°C or higher, and has a number average molecular weight of 500 or higher but less than 50,000. [2] The pressure-sensitive adhesive composition of [1], wherein the concentration of the modified polymer in a surface layer portion of a pressure-sensitive adhesive layer formed using the pressure-sensitive adhesive composition is higher than the concentration of the modified polymer throughout the pressure-sensitive adhesive layer. [3] The pressure-sensitive adhesive composition of [1] or [2], wherein the content of the modified polymer is 0.1 parts by mass or more and 50 parts by mass or less relative to 100 parts by mass of the acrylic adhesive polymer, and when the pressure-sensitive adhesive composition is applied to a separator and dried to obtain a pressure-sensitive adhesive layer, the mass fraction of the modified polymer on the surface of the pressure-sensitive adhesive layer, as determined by X-ray photoelectron spectroscopy, is larger than the mass fraction of the modified polymer in the entire pressure-sensitive adhesive composition. [4] The pressure-sensitive adhesive composition of any of [1] to [3], wherein the weight-average molecular weight of the acrylic adhesive polymer is 100,000 or more. [5] The pressure-sensitive adhesive composition of any of [1] to [4], wherein the modification rate of the modified polymer is 80% or less. [6] The pressure-sensitive adhesive composition of any of [1] to [5], wherein the glass transition temperature of the acrylic adhesive polymer is -50°C or higher. [7] The pressure-sensitive adhesive composition of any of [1] to [6], wherein the vinyl polymer has structural units derived from at least one selected from the group consisting of an aliphatic cyclic vinyl monomer and an aromatic vinyl monomer. [8] The pressure-sensitive adhesive composition of any of [1] to [7], further comprising a crosslinking agent. [9] The pressure-sensitive adhesive composition of any of [1] to [8], wherein the acrylic pressure-sensitive adhesive polymer contains structural units derived from at least one selected from the group consisting of a (meth)acrylic acid alkyl ester having an alkyl group of 1 to 4 carbon atoms in the ester moiety and a (meth)acrylic acid alkoxyalkyl ester having an alkoxyalkyl group of 3 or 4 carbon atoms in an amount of 30 mass% or more based on the total structural units of the acrylic pressure-sensitive adhesive polymer.

[10] The pressure-sensitive adhesive composition of any one of [1] to [9], wherein the modified polymer is at least one selected from the group consisting of acid-modified polyolefin, chlorinated polyolefin, acid-modified chlorinated polyolefin, acrylic-modified polyolefin, and acrylic-modified chlorinated polyolefin.

[11] The pressure-sensitive adhesive composition of any one of [1] to

[10] , wherein the modified polymer is modified with at least one selected from the group consisting of carboxylic acid, carboxylic acid anhydride, (meth)acrylic acid ester, and chlorine.

[12] The pressure-sensitive adhesive composition of any one of [1] to

[11] , wherein the pre-modified polymer has a melting point, and the melting point of the modified polymer is 20°C or higher and 130°C or lower.

[13] The pressure-sensitive adhesive composition of any one of [1] to

[12] , further comprising a solvent, wherein a 50 μm-thick pressure-sensitive adhesive layer formed by applying the pressure-sensitive adhesive composition to a substrate and removing the solvent has a haze value of 3.0% or higher.

[14] A pressure-sensitive adhesive sheet comprising a pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition of any one of [1] to

[13] .

[15] The pressure-sensitive adhesive sheet of

[14] , which is a decorative film.

[16] A decorated molded body, in which the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet of

[15] is attached to a molded body.

[0010] The pressure-sensitive adhesive composition of the present disclosure can provide a pressure-sensitive adhesive layer that exhibits excellent adhesion both at room temperature and at high temperatures, and can also form a pressure-sensitive adhesive layer that exhibits excellent adhesion between low-polarity substrates and between a low-polarity substrate and a high-polarity substrate.

[0011] The present disclosure will be described in detail below. 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 the present disclosure (hereinafter also referred to as "the composition") is used to form a pressure-sensitive adhesive layer, and contains the following components (A), (B), and (C): Component (A): an acrylic adhesive polymer having a glass transition temperature of 10°C or lower Component (B): at least one modified polymer selected from the group consisting of modified polyolefins and modified polydienes Component (C): a vinyl polymer having structural units derived from a (meth)acrylic monomer, having a glass transition temperature of 45°C or higher, and having a number average molecular weight of 500 or higher but lower than 50,000 (excluding component (B)). The components contained in the composition and the optional components that may be contained therein are described below.

[0013] <Component (A): Acrylic Adhesive Polymer>

[0014] 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 adhesiveness at room temperature will be insufficient, and the conformability of the adhesive layer to the adherend will decrease, resulting in insufficient adhesiveness at high temperatures. From the viewpoint of obtaining a pressure-sensitive adhesive layer that has excellent adhesiveness at room temperature and high temperatures, the Tg of the acrylic adhesive polymer is preferably 5°C or lower, more preferably 0°C or lower, even more preferably -5°C or lower, and still more preferably -10°C or lower. The lower limit of the Tg of the acrylic adhesive polymer (A) is preferably -70°C or higher. If the Tg of the acrylic adhesive polymer (A) is -70°C or higher, this is preferred in that the cohesive strength of the pressure-sensitive adhesive layer can be sufficiently increased and sufficient adhesiveness can be ensured. From the viewpoint of achieving better adhesiveness 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 still more preferably −45° C. or higher.

[0015] The preferred range of Tg of the acrylic adhesive polymer (A) can be set by appropriately combining the above-mentioned preferred lower limit and upper limit. From the viewpoint of achieving a good balance between adhesiveness at high temperatures and adhesiveness at room temperature, the range of Tg of the acrylic adhesive polymer (A) is preferably −70° C. or higher and 10° C. or lower, more preferably −60° C. or higher and 5° C. or lower, even more preferably −50° C. or higher and 5° C. or lower, and even more preferably −50° C. or higher and 0° C. or lower.

[0016] In this specification, the Tg of a polymer is a value determined from the intersection of the baseline of a heat flux curve obtained using a differential scanning calorimeter (DSC) and the tangent point at the inflection point. 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, etc.

[0017] The acrylic adhesive polymer (A) has a (meth)acrylic compound as its main structural unit. The acrylic adhesive polymer (A) preferably contains a structural unit (hereinafter also referred to as "structural unit UA") derived from at least one selected from the group consisting of (meth)acrylic acid alkyl esters having an alkyl group of 1 to 12 carbon atoms in the ester moiety and (meth)acrylic acid alkoxyalkyl esters having an alkoxy group of 1 to 4 carbon atoms, in that a polymer having a relatively low Tg and sufficient adhesiveness can be obtained. The monomer constituting the acrylic adhesive polymer (A) may be one type only, or two or more types.

[0018] Specific examples of the (meth)acrylic acid alkyl ester having an alkyl group having 1 to 12 carbon atoms in the ester moiety used in the production of the 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, lauryl (meth)acrylate, etc. In terms of being able to form a pressure-sensitive adhesive layer with excellent adhesion to low-polarity substrates, the (meth)acrylic acid alkyl ester constituting the acrylic adhesive polymer (A) is preferably a compound having an alkyl group having 1 to 8 carbon atoms in the ester moiety. Preferred monomers include methyl (meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, and 2-ethylhexyl (meth)acrylate.

[0019] Specific examples of the alkoxyalkyl (meth)acrylate having an alkoxy group having 1 to 4 carbon atoms, used in the production of the 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 the 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, based on all structural units contained in the acrylic adhesive polymer (A) (i.e., the total amount of monomer units constituting the acrylic adhesive polymer). By making the content of the structural unit UA 50% by mass or more, the adhesive strength, initial adhesive strength (tack), and low-temperature adhesion of the adhesive layer can be sufficiently increased.

[0021] The acrylic adhesive polymer (A) preferably contains a structural unit (hereinafter also referred to as "structural unit UA-1") derived from at least one selected from the group consisting of (meth)acrylic acid alkyl esters having an alkyl group of 1 to 4 carbon atoms in the ester moiety and (meth)acrylic acid alkoxy esters having an alkoxyalkyl group of 3 or 4 carbon atoms, in order to facilitate phase separation between the acrylic adhesive polymer (A) and the modified polymer (component (B)) in the pressure-sensitive adhesive layer, to facilitate a relatively high concentration of the modified polymer in the surface layer portion, and to enhance adhesiveness at high temperatures. Furthermore, the use of such (meth)acrylic acid alkyl esters and / or acrylic acid alkoxy esters in the production of the acrylic adhesive polymer (A) can increase the elastic modulus of the acrylic adhesive polymer (A) and is also effective in improving heat resistance. Among these, the 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. The content of the 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, based on all structural units contained in the acrylic adhesive polymer.

[0022] In producing the acrylic adhesive polymer (A), a monomer having a crosslinkable functional group (hereinafter also referred to as a "crosslinkable group-containing monomer") is used, thereby making it possible to give the acrylic adhesive polymer (A) a structure having a crosslinkable structural unit. When the acrylic adhesive polymer (A) has a crosslinkable structural unit, it is possible to further improve the adhesiveness of the pressure-sensitive adhesive layer at high temperatures.

[0023] The crosslinkable group-containing monomer used in the production of the acrylic adhesive polymer (A) is not particularly limited. The crosslinkable group-containing monomer is preferably at least one selected from the group consisting of (meth)acrylic acid, a hydroxyalkyl (meth)acrylate compound, an epoxy group-containing (meth)acrylic acid ester compound, and a reactive silyl group-containing (meth)acrylic acid ester compound. Among these, at least one selected from the group consisting of (meth)acrylic acid and a hydroxyalkyl (meth)acrylate compound is preferred, as 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 a hydroxyalkyl (meth)acrylate compound having a hydroxyalkyl group having 2 to 8 carbon atoms is more preferred, and at least one selected from the group consisting of (meth)acrylic acid and a hydroxyalkyl (meth)acrylate compound having a hydroxyalkyl group having 2 to 4 carbon atoms is particularly preferred.

[0024] When the acrylic adhesive polymer (A) has a crosslinkable structural unit, the content of the crosslinkable structural unit 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 making the content of the crosslinkable structural unit in the acrylic adhesive polymer (A) 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. The upper limit of the content of the crosslinkable structural unit is not particularly limited, but from the viewpoint of ensuring the flexibility of the obtained 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). The crosslinkable-containing monomer constituting the acrylic adhesive polymer (A) may be one type or two or more types.

[0025] In addition to the above, the acrylic adhesive polymer (A) may have a structural unit derived from a monomer copolymerizable with the above-mentioned monomer (hereinafter also referred to as "other monomer") within a range that does not impair adhesive performance. Examples of other monomers include 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, etc.

[0026] Specific examples of these include aliphatic cyclic esters of (meth)acrylic acid, such as 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.

[0027] Examples of 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.

[0028] Examples of the polyalkylene glycol mono(meth)acrylate compound 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.

[0029] 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-based compounds such as divinylbenzene; vinylnaphthalene, and the like.

[0030] Examples of the imide group-containing vinyl compound 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-cyclohexylitaconimide; Examples of the imide group-containing vinyl compound include citraconic acid compounds such as cyclohexylcitraconimide 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. Of these, maleimide compounds are preferably used as the imide group-containing vinyl compound.

[0031] Examples of the amino group-containing unsaturated compound 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.

[0032] Examples of the amide group-containing unsaturated compound 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.

[0033] 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.

[0034] Examples of the nitrile group-containing unsaturated compound include (meth)acrylonitrile, ethacrylonitrile, α-ethylacrylonitrile, α-isopropylacrylonitrile, α-chloroacrylonitrile, and α-fluoroacrylonitrile.

[0035] The proportion of the other monomer constituting the acrylic adhesive polymer (A) can be appropriately selected within a range that does not impair the effects of the present disclosure. As the other monomer, one type may be used alone, or two or more types may be used in combination.

[0036] From the viewpoint of improving the adhesiveness of the pressure-sensitive adhesive layer at high temperatures, it is preferable that the acrylic adhesive polymer (A) does not substantially have structural units derived from amino group-containing unsaturated compounds. Specifically, the proportion of structural units derived from amino group-containing unsaturated compounds in the acrylic adhesive polymer (A) is preferably 0.2 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 will be strengthened, which may inhibit phase separation between the acrylic adhesive polymer (A) and the modified polymer, resulting in a decrease in the adhesive performance of the pressure-sensitive adhesive layer. From this viewpoint, the proportion of structural units derived from amino group-containing unsaturated compounds is more preferably 0.1 mass% or less, even more preferably 0.05 mass% or less, and even more preferably 0.01 mass% or less relative to the total structural units of the acrylic adhesive polymer (A).

[0037] - Production of acrylic adhesive polymer (A) The production method of the acrylic adhesive polymer (A) is not particularly limited, and it can be obtained by a known production method. For example, the acrylic adhesive polymer (A) can be obtained by polymerizing the above-mentioned monomers using a known radical polymerization method such as solution polymerization, suspension polymerization, emulsion polymerization, or bulk polymerization.

[0038] For example, a production method using a solution polymerization method includes charging an organic solvent and monomers into a reactor, adding a polymerization initiator, and heating to 50 to 300° C. to polymerize. In this case, the method for charging each raw material including the monomer may be a batch-type initial lump-sum charging in which all raw materials are charged at once, a semi-continuous charging in which at least a portion of the raw materials are continuously fed into the reactor, or a continuous polymerization method in which all raw materials are continuously fed and, at the same time, the produced resin is continuously withdrawn from the reactor.

[0039] Examples of organic solvents used in solution polymerization include cyclic ethers such as tetrahydrofuran, tetrahydropyran, 4-methyltetrahydropyran, and dioxane; aromatic hydrocarbon compounds such as benzene, toluene, and xylene; hydrocarbon compounds such as cyclohexane, methylcyclohexane, and isooctane; esters such as ethyl acetate and butyl acetate; ketones such as acetone, methyl ethyl ketone, and cyclohexanone; alcohols such as methanol, ethanol, and isopropanol; and chain ethers such as methyl orthoformate and methyl orthoacetate. 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 in polymerization is, for example, 1 to 50% by mass relative to the total amount of the organic solvent and the monomers. From the viewpoints of the polymerizability and solubility of the acrylic adhesive polymer (A) and the ease of blending the modified polymer after production, esters, cyclic ethers, aromatic hydrocarbon compounds, hydrocarbon compounds, and ketones are preferred, with toluene, xylene, cyclohexane, ethyl acetate, and butyl acetate being more preferred.

[0040] The polymerization initiator may be any known radical polymerization initiator, such as an azo compound, an organic peroxide, or an inorganic peroxide, and is not particularly limited. Among these, an azo compound is preferred because it is easy to handle safely and is less likely to cause side reactions during radical polymerization. Alternatively, a redox polymerization initiator consisting of a known oxidizing agent and a known reducing agent may be used as the polymerization initiator. Furthermore, a known chain transfer agent may be used in combination with the polymerization initiator.

[0041] Specific examples of the polymerization initiator include azo compounds such as 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), and dimethyl 2,2'-azobis(2-methylpropionate).

[0042] Examples of organic peroxides 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, and 2,5-dimethyl-2,5-di(benzoylperoxy)hexane.

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

[0044] Molecular Weight Characteristics of Acrylic Adhesive Polymer (A) The weight average molecular weight (Mw) of the acrylic adhesive polymer (A) is preferably 100,000 or more from the viewpoint of obtaining a polymer that exhibits sufficient cohesive strength and good adhesiveness. By making the Mw of the acrylic adhesive polymer (A) 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, even more preferably 300,000 or more, still more preferably 400,000 or more, and even more 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 viewpoint of ensuring good coating and handling properties when forming the adhesive layer and ensuring ease of production, it is preferably 3,000,000 or less, more preferably 2,000,000 or less, and even more preferably 1,500,000 or less. The Mw of the acrylic adhesive polymer (A) is preferably in the range of 100,000 or more and 3,000,000 or less, more preferably 200,000 or more and 2,000,000 or less, and even 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] The molecular weight distribution (Mw / Mn) of the acrylic adhesive polymer (A), which is expressed as the ratio of Mw to Mn, is preferably 10.0 or less, more preferably 9.0 or less, from the viewpoint of easily obtaining good adhesiveness and suppressing an increase in viscosity of the adhesive composition. The lower limit of 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 more, and may be 10.00 or more. When the SP value of the acrylic adhesive polymer (A) is within the above range, a pressure-sensitive adhesive layer with higher adhesiveness at both room temperature and high temperatures can be obtained. The SP value according to the Fedors method is specifically calculated by 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 adhesiveness of the pressure-sensitive adhesive layer at room temperature and at high temperatures, the content of the acrylic adhesive polymer (A) in the composition is preferably 50% by mass or more relative to the total amount of solids contained in the composition (i.e., the mass of components other than the solvent in the pressure-sensitive adhesive composition relative to the total mass of the pressure-sensitive 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 the 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 modified by chemical modification, and refers to a polymer containing a structure or functional group different from the unsaturated hydrocarbon unit in the same molecule. Among the modified polymers (B), the modified polyolefin refers to a polyolefin modified by chemical modification, and refers to a polymer containing a structure or functional group different from the olefin unit in the same molecule.

[0050] It is believed that the pressure-sensitive adhesive layer formed from this composition is in a state in which the acrylic adhesive polymer (A) and the modified polymer (B) are phase-separated in the surface layer portion of the pressure-sensitive adhesive layer due to phase separation between the acrylic adhesive polymer (A) and the modified polymer (B) that occurs during the process of forming the pressure-sensitive adhesive layer. Furthermore, it is believed that the phase separation between the acrylic adhesive polymer (A) and the modified polymer (B) in the surface layer portion of the pressure-sensitive adhesive layer allows a good balance between the adhesive performance of the acrylic adhesive polymer (A) and the adhesive performance of the modified polymer (B) to be expressed, resulting in excellent adhesion to low-polarity substrates and high adhesion both at room temperature and at high temperatures.

[0051] Here, in this specification, "phase separation" refers to the separation of the acrylic adhesive polymer (A) and the 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) in accordance with thermodynamic equilibrium conditions in the step of forming a pressure-sensitive adhesive layer. In a state in which the acrylic adhesive polymer (A) and the modified polymer (B) are phase-separated in the surface layer portion of the pressure-sensitive adhesive layer, a sea-island structure is typically formed, but is not limited to this. Note that phase separation is a different concept from segregation (more specifically, surface segregation), which refers to the localization of the second polymer in the outermost layer in the thickness direction of a pressure-sensitive adhesive layer containing different polymers (referred to as a first polymer and a second polymer) relative to the first 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. Specific examples include homopolymers of α-olefins, conjugated dienes, or non-conjugated dienes having 2 to 20 carbon atoms, and copolymers of two or more types 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, 1-dodecene, etc. Specific examples of conjugated or non-conjugated dienes having 2 to 20 carbon atoms include butadiene, 1,5-hexadiene, ethylidenenorbornene, dicyclopentadiene, etc.

[0054] 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, based on the total structural units constituting the modified polyolefin. The α-olefins used in the synthesis of the modified polyolefin may be one type only, or two or more types.

[0055] The polyolefin constituting the modified polyolefin may be copolymerized with other unsaturated monomers in addition to the olefin. Examples of 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 of suitable modified polydiene 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 terminal unsaturated bonds; and conjugated or non-conjugated dienes such as butadiene, 1,5-hexadiene, ethylidene norbornene, and dicyclopentadiene. Similarly, the polydienes constituting the modified polydiene may be copolymerized with other unsaturated monomers in addition to conjugated and non-conjugated dienes. Examples of suitable polyolefins include ethylene / ethyl acrylate copolymers and ethylene / vinyl acetate copolymers. Examples of suitable polydienes include styrene / butadiene copolymers and styrene / isoprene copolymers. When a copolymer is used, a random copolymer, a block copolymer, or a graft copolymer can be appropriately selected.

[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. The polyolefin may also be a blend of these. When a propylene copolymer is used, 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. Of the above, polypropylene or a propylene copolymer is preferred as the polyolefin.

[0057] Commercially available polyolefins may be used, and specific examples thereof include the "L-MODU" series manufactured by Idemitsu Kosan Co., Ltd., the "REXtac" series manufactured by LLC, the "Vestoplast" series manufactured by Evonik, the "Eastoflex" series and the "Aerafin" series manufactured by Eastman, the "Tafmer" series manufactured by Mitsui Chemicals, Inc., the "Prime TPO" series manufactured by Prime Polymer, the "Versify" series manufactured by Dow Chemical Company, the "Vistamaxx" series and the "Linxar" series manufactured by ExxonMobil, the "Licocene" series manufactured by Clariant, and the "Adflex" series manufactured by Basell.

[0058] Examples of the type of modification include acid modification, chlorination, (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 one in which two or more types of modifications have been sequentially performed. Specific examples of polyolefins that have been subjected to two or more types of modifications include acid-modified chlorinated polyolefins, acrylic-modified chlorinated polyolefins, and urethane-modified chlorinated polyolefins. In terms of their high effect of improving adhesiveness at high temperatures and their easy availability, the modified polymer (B) is preferably a modified polyolefin. Furthermore, the modified polyolefin is preferably at least one selected from the group consisting of acid-modified polyolefins, chlorinated polyolefins, acid-modified chlorinated polyolefins, acrylic-modified polyolefins, and acrylic-modified chlorinated polyolefins. Among these, the modified polyolefin is more preferably at least one selected from the group consisting of acid-modified polyolefins, chlorinated polyolefins, acid-modified chlorinated polyolefins, and acrylic-modified polyolefins, and acid-modified polyolefins and acid-modified chlorinated polyolefins are even more preferred, in that the difference in SP value between the acrylic adhesive polymer (A) is larger and phase separation from the acrylic adhesive polymer (A) is more likely to occur, and therefore a pressure-sensitive adhesive layer with further improved high-temperature adhesion can be obtained.

[0059] The acid-modified polyolefin and the acid-modified chlorinated polyolefin are preferably modified with at least one selected from the group consisting of carboxylic acids and carboxylic anhydrides (hereinafter also referred to as "specific acid modifier"). Such modified polyolefins can be obtained, for example, by graft copolymerizing a specific acid modifier with a polyolefin. The modification reaction can be carried out using a conventionally known method, such as a method of adding a specific acid modifier to a polyolefin melted using an extruder to copolymerize it, a method of adding a specific acid modifier to a polyolefin dissolved in a solvent to copolymerize it, or a method of adding a specific acid modifier to a polyolefin suspension in water to copolymerize it. The modified site of the polyolefin chain in the modified polyolefin may be one end of the molecular chain, both ends of the molecular chain, or in the middle of the molecular chain, or multiple of these locations.

[0060] Examples of the specific acid modifier used in the modification 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. Among 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.

[0061] The acid-modified polyolefin and acid-modified chlorinated polyolefin blended in the present composition may be further modified with a (meth)acrylic acid ester in addition to the acid modifier. In other words, in this specification, the term "acid-modified polyolefin" encompasses acid-modified polyolefins that have been acrylic-modified, and the term "acid-modified chlorinated polyolefin" encompasses acid-modified chlorinated polyolefins that have been acrylic-modified. Therefore, for example, acid-modified polyolefins include ethylene-acrylic acid ester-maleic anhydride 3D copolymers, ethylene-methacrylic acid ester-maleic anhydride 3D copolymers, propylene-acrylic acid ester-maleic anhydride 3D copolymers, and propylene-methacrylic acid ester-maleic anhydride 3D copolymers. Specific examples of (meth)acrylic acid esters for acrylic modification are the same as the compounds exemplified in the description of acrylic-modified polyolefins.

[0062] The acrylic-modified polyolefin and the acrylic-modified chlorinated polyolefin are preferably polymers in which a polyolefin is modified with a (meth)acrylic acid ester. The (meth)acrylic acid ester is preferably at least one selected from the group consisting of (meth)acrylic acid alkyl esters and (meth)acrylic acid cycloalkyl esters. Specific examples thereof include (meth)acrylic acid alkyl esters having an alkyl group with 1 to 12 carbon atoms, as exemplified in the description of the acrylic adhesive polymer (A), and the aliphatic cyclic ester compounds of (meth)acrylic acid, as exemplified in the description of the other monomers, as well as (meth)acrylic acid alkyl esters having an alkyl group with 9 or more carbon atoms, such as nonyl (meth)acrylate, tridecyl (meth)acrylate, and stearyl (meth)acrylate.

[0063] Among the above, the modified polyolefin is preferably modified with at least one selected from the group consisting of carboxylic acid, carboxylic acid anhydride, (meth)acrylic acid ester, and chlorine, and more preferably modified with at least one selected from the group consisting of carboxylic acid and carboxylic acid anhydride.

[0064] The acid-modified polyolefin, acid-modified chlorinated polyolefin, acrylic-modified polyolefin, and acrylic-modified chlorinated polyolefin may be modified in combination with other modifiers, such as functional group-containing (meth)acrylic acid alkyl esters, aromatic vinyl compounds, and cyclohexyl vinyl ether.

[0065] Examples of functional group-containing (meth)acrylic acid alkyl esters include hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, glycidyl (meth)acrylate, and isocyanate-containing (meth)acrylic acid esters. Examples of aromatic vinyl compounds include benzyl (meth)acrylate, styrene, o-methylstyrene, p-methylstyrene, and α-methylstyrene. By using other modifiers in combination as a modifier, it is possible to improve the modification rate by the modifier and further improve adhesiveness.

[0066] The modification rate of the modified polymer (B) is preferably 0.1% or more and 80% or less, in order to improve the high-temperature adhesion and room-temperature adhesion of the pressure-sensitive adhesive layer in a well-balanced manner. The modification rate of the modified polymer (B) is more preferably 0.5% or more, even more preferably 1.0% or more, and even more preferably 1.5% or more, in order to enhance the interaction with the acrylic adhesive polymer (A) and increase the cohesive strength of the entire pressure-sensitive adhesive layer. The modification rate of the modified polyolefin may be 75% or less, or even 70% or less. The modification rate of the modified polymer (B) represents the mass proportion of the portion (modified portion) introduced by the modification reaction, 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.

[0067] The weight average molecular weight of the modified polymer (B) measured by GPC is preferably 2,000 to 500,000. When the weight average molecular weight of the modified polymer (B) is 2,000 or more, the heat resistance of the pressure-sensitive adhesive layer is good, and when it is 500,000 or less, the solubility of the modified polymer (B) in solvents is improved, which is preferable in terms of excellent handleability. From the above viewpoints, the weight average molecular weight of the modified polymer (B) is more preferably 3,000 or more, even more preferably 5,000 or more, and even more preferably 10,000 or more. The upper limit of the weight average molecular weight of the modified polymer (B) is more preferably 250,000 or less, even more preferably 200,000 or less, and even more preferably 180,000 or less.

[0068] When the modified polymer (B) has a melting point, 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, from the viewpoint of obtaining a pressure-sensitive adhesive layer with excellent high-temperature adhesion. 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. The melting point of the modified polymer (B) is a value obtained by a differential scanning calorimeter. Details of the measurement conditions are as described in the examples below.

[0069] When the modified polymer (B) has a glass transition point (Tg), the Tg of the modified polymer (B) is preferably higher than 10°C, more preferably 15°C or higher, from the viewpoint of obtaining a pressure-sensitive adhesive layer with excellent high-temperature adhesion. The Tg of the modified polymer (B) is preferably lower than 45°C, 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 tangent point at the inflection point. Details of the measurement conditions are as described in the Examples below.

[0070] The modified polymer (B) may be a commercially available product, and examples thereof include those used in plastic surface modifiers, primers for automotive plastic substrates, primers for electronics substrates, primers for building materials, etc. Specific examples of acid-modified polyolefins include the "Admer" series and "Unistole" series manufactured by Mitsui Chemicals, Inc., the "Hardlen" series manufactured by Toyobo Co., Ltd. (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, and PMA-F7), the "Umex" series manufactured by Sanyo Chemical Industry Co., Ltd., and the "Rexpearl" series manufactured by Japan Polyethylene Corporation.

[0071] Examples of chlorinated polyolefins include Superchlorine 814HA, 814HS, 390S, and 360T manufactured by Nippon Paper Industries Co., Ltd., and Hardlen 13-LP, 13-LLP, 14-LWP, 15-LP, 16-LP, DX-523, DX-523P, DX-526P, and DX-530P manufactured by Toyobo Co., Ltd.

[0072] Examples of acid-modified chlorinated polyolefins include Superchlorine 3228S and 2319S manufactured by Nippon Paper Industries Co., Ltd., and Hardlen HM-21P, M-28P, CY-9124P, CY-1321P, CY-2121P, CY-2129, F-225P, F-2P, F-6P, and F-7P manufactured by Toyobo Co., Ltd.

[0073] Examples of acrylic acid-modified chlorinated polyolefins include Superchlorine 224H and 240H manufactured by Nippon Paper Industries Co., Ltd. Examples of ethylene / acrylic acid / maleic anhydride terpolymers include the Bondine series manufactured by Arkema. 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.

[0074] The content of the modified polymer (B) in the 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, a pressure-sensitive adhesive layer can be obtained that has excellent adhesion to low-polarity substrates and excellent adhesion at both room temperature and high temperatures. From the viewpoint of obtaining a pressure-sensitive adhesive layer that has excellent 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). With regard to the upper limit of the content of the modified polymer (B), from the viewpoint of ensuring adhesion to high-polarity substrates and room-temperature adhesion, it is more preferably 45 parts by mass or less, even more preferably 40 parts by mass or less, and even more preferably 35 parts by mass or less per 100 parts by mass of the acrylic adhesive polymer (A). Note that the modified polymer (B) may be used alone or in combination of two or more types.

[0075] <Component (C): Vinyl Polymer> The vinyl polymer (hereinafter also referred to as "vinyl polymer (C)") which is component (C) is a polymer having structural units derived from a (meth)acrylic monomer, and has a glass transition temperature (Tg) of 45°C or higher and a number average molecular weight (Mn) of 500 or higher but lower than 50,000. By blending such a vinyl polymer (C) together with the acrylic adhesive polymer (A) and the modified polymer (B) to form a pressure-sensitive adhesive layer, it is possible to obtain a pressure-sensitive adhesive layer that has good adhesion to highly polar substrates in addition to adhesion to low-polarity substrates.

[0076] Glass Transition Temperature If the Tg of the vinyl polymer (C) is less than 45°C, when a pressure-sensitive adhesive layer is formed from the composition, the Tg of the surface layer of the pressure-sensitive adhesive layer cannot be sufficiently high, and sufficient adhesive strength and heat resistance under high-temperature conditions cannot be ensured. On the other hand, due to constraints on raw material monomers, the Tg of the vinyl polymer (C) is generally 200°C or less. The Tg of the 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 the Tg is preferably 150°C or lower, more preferably 140°C or lower, and even more preferably 130°C or lower. The Tg range of the vinyl polymer (C) is preferably 45°C or higher and 200°C or lower, more preferably 50°C or higher and 150°C or lower, and even more preferably 60°C or higher and 140°C or lower.

[0077] Monomer The vinyl polymer (C) has structural units derived from a (meth)acrylic monomer. The vinyl polymer (C) may be composed only of structural units derived from a (meth)acrylic monomer, or may have structural units derived from other monomers in addition to the (meth)acrylic monomer. Here, the (meth)acrylic monomer is a monomer having a (meth)acryloyl group, and includes (meth)acrylic acid ester monomers and (meth)acrylamide monomers.

[0078] Various radically polymerizable vinyl monomers can be used as the monomer constituting the vinyl polymer (C). Examples of such vinyl monomers include (meth)acrylic acid alkyl esters, 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, and maleimide compounds. Specific examples of these compounds include the same compounds as those exemplified in the description of the (meth)acrylic adhesive polymer (A). The monomer constituting the vinyl polymer (C) may be a single type or a combination of two or more types.

[0079] 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, based on 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 thought that the vinyl polymer (C) has appropriate compatibility with the acrylic adhesive polymer (A), preventing complete phase separation between the vinyl polymer (C) and the acrylic adhesive polymer (A), making it easier to localize the vinyl polymer (C) toward the surface layer of the pressure-sensitive adhesive layer, and facilitating phase separation of the modified polymer (B) in the surface layer of the pressure-sensitive adhesive layer. This makes it possible to obtain a pressure-sensitive adhesive layer that exhibits good high-temperature adhesion.

[0080] In terms of being able to form a pressure-sensitive adhesive layer with higher adhesive strength at high temperatures, the vinyl polymer (C) preferably has a structural unit (hereinafter also referred to as "structural unit (UC-1)") derived from at least one selected from the group consisting of an aliphatic cyclic vinyl monomer and an aromatic vinyl monomer. Specific examples of the aliphatic cyclic vinyl monomer include vinyl monomers having an aliphatic ring among the above-mentioned monomers, and among these, aliphatic cyclic esters of (meth)acrylic acid are preferred. Specific examples of the aromatic vinyl monomer include vinyl monomers having an aromatic ring among the above-mentioned monomers, and among these, at least one selected from the group consisting of aromatic esters of (meth)acrylic acid and aromatic vinyl compounds is preferred.

[0081] Incidentally, since the vinyl polymer (C) has the structural unit (UC-1), it is possible to make the Tg of the vinyl polymer (C) relatively high, it is possible to make the vinyl polymer (C) more likely to segregate in the surface layer portion of the pressure-sensitive adhesive layer as much as possible when the pressure-sensitive adhesive layer is formed, and it is possible to increase the affinity with the skeleton of the modified polymer (B) (i.e., the polyolefin skeleton and / or the polydiene skeleton). For these reasons, it is believed that the pressure-sensitive adhesive layer obtained from the present composition can exhibit excellent adhesive strength at high temperatures to a variety of materials.

[0082] In the vinyl polymer (C), the content of the structural unit (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, based on all structural units contained in the vinyl polymer (C). From the viewpoint of ensuring appropriate compatibility with the (meth)acrylic adhesive polymer (A), the upper limit of the content of the structural unit (UC-1) is preferably 99% by mass or less, more preferably 95% by mass or less, and even more preferably 90% by mass or less, based on all structural units contained in the vinyl polymer (C).

[0083] 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 as the monomer constituting the structural unit (UC-1), since it can set a high Tg, can easily segregate the vinyl polymer (C) to a more outer layer portion of the phase mainly composed of the (meth)acrylic adhesive polymer (A) when a pressure-sensitive adhesive layer is formed, and tends to provide good heat resistance.

[0084] Furthermore, in terms of being able to increase the Tg of the surface layer portion of the pressure-sensitive adhesive layer and obtain a pressure-sensitive adhesive layer that exhibits good heat resistance, it is preferable that the vinyl polymer (C) contains a structural unit 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 this structural unit 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, based on the total structural units contained in the vinyl polymer (C).

[0085] The vinyl polymer (C) preferably 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, the total content of structural units derived from monomers selected from the group consisting of α-olefins, conjugated dienes, and non-conjugated dienes in the vinyl polymer (C) 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, based on the total structural units contained in the vinyl polymer (C).

[0086] The number average molecular weight (Mn) of the vinyl polymer (C) is 500 or more and less than 50,000. If Mn is 50,000 or more, segregation of the vinyl polymer (C) is insufficient in the phase mainly composed of the (meth)acrylic adhesive polymer (A), resulting in reduced adhesion and heat resistance under high temperature conditions and reduced compatibility with the acrylic adhesive polymer (A). Furthermore, producing a polymer with an Mn of less than 500 requires the use of large amounts of polymerization initiator and chain transfer agent, which may result in reduced productivity. 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 of 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. The Mn of the vinyl polymer (C) is preferably in the range of 1,000 or more and 40,000 or less, more preferably 1,000 or more and 30,000 or less, even more preferably 1,500 or more and 25,000 or less, and still more preferably 1,700 or more and 20,000 or less.

[0087] In the vinyl polymer (C), the molecular weight distribution (Mw / Mn), which is the ratio of Mw to Mn, is preferably 3.0 or less, since good adhesive strength is easily obtained. Mw / Mn is more preferably 2.5 or less, and even more preferably 2.0 or less. The lower limit of Mw / Mn of the vinyl polymer (C) is not particularly limited, but is 1.0 or more.

[0088] The vinyl polymer (C) may have the property of phase separation from the (meth)acrylic adhesive polymer (A). Such a property makes it possible to form a pressure-sensitive adhesive layer with high heat resistance and durability against temperature changes. The difference ΔSP (absolute value) between the SP value of the vinyl polymer (C) calculated by a known method for calculating the SP value (e.g., the Fedors method), which is a solubility parameter, and the SP value of the (meth)acrylic adhesive polymer (A) can be adjusted to design a vinyl polymer (C) that phase separates from the (meth)acrylic adhesive polymer (A).

[0089] The vinyl polymer (C) can be obtained by polymerizing the above-mentioned monomers using a known radical polymerization method such as solution polymerization, suspension polymerization, emulsion polymerization, or bulk polymerization. In the case of solution polymerization, for example, an organic solvent and monomers are charged into a reactor, a polymerization initiator is added, and the mixture is heated to 50 to 300°C to copolymerize, thereby obtaining the desired vinyl polymer (C). Details of the polymerization method are the same as those for the (meth)acrylic adhesive polymer (A), and therefore will not be described here.

[0090] The composition preferably contains the vinyl polymer (C) in an amount of 0.5 parts by mass or more and 50 parts by mass or less, based on 100 parts by mass of the (meth)acrylic adhesive polymer (A) in terms of solid content. By setting the content of the vinyl polymer (C) to 0.5 parts by mass or more, the effects of incorporating the vinyl polymer (C), particularly the effect of improving adhesion to highly polar substrates, can be fully obtained. Furthermore, by setting the content of the vinyl polymer (C) to 50 parts by mass or less, the flexibility and transparency of the pressure-sensitive adhesive layer can be ensured, while the effect of improving adhesion to highly polar substrates and the effect of improving adhesion at room temperature and at high temperatures can be fully obtained. From this perspective, the lower limit of the content of the 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, based on 100 parts by mass of the (meth)acrylic adhesive polymer (A). The upper limit of the content of the 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 still more preferably 15 parts by mass or less, relative to 100 parts by mass of the (meth)acrylic adhesive polymer (A).

[0091] The content of the vinyl polymer (C) is preferably from 0.5 to 40 parts by mass, more preferably from 0.5 to 30 parts by mass, even more preferably from 0.5 to 25 parts by mass, and still more preferably from 1 to 15 parts by mass, relative to 100 parts by mass of the (meth)acrylic adhesive polymer (A).

[0092] <Other Components> The present composition may further contain various components (hereinafter also referred to as "other components") other than the above-described components (A), (B), and (C), as necessary. The other components are described below.

[0093] [Crosslinking Agent] When the acrylic adhesive polymer (A) has a crosslinkable functional group, it is preferable to incorporate a crosslinking agent capable of reacting with the crosslinkable functional group into the pressure-sensitive adhesive composition, since this can further improve the adhesiveness at high temperatures, heat resistance, and durability against temperature changes. Also, it is preferable because the formation of a crosslinked structure in the acrylic adhesive polymer (A) facilitates phase separation from the modified polymer (B) in the process of forming the pressure-sensitive adhesive layer.

[0094] Examples of the crosslinking agent (curing agent) include a glycidyl compound having two or more glycidyl groups, an isocyanate compound having two or more isocyanate groups, an aziridine compound having two or more aziridinyl groups, an oxazoline compound having an oxazoline group, a metal chelate compound, a butylated melamine compound, etc. Among these, an isocyanate compound is preferred because of its excellent adhesive properties under high temperature conditions.

[0095] Specific examples of the crosslinking agent include glycidyl 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.

[0096] As the isocyanate compound, various polyfunctional isocyanate compounds of 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 (LDI); 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 compounds, dimers, trimers, carbodiimide-modified compounds, urea-modified compounds, isocyanurate-modified compounds, oxazolidone-modified compounds, and isocyanate-terminated prepolymers.

[0097] Examples of the aziridine compound include 1,6-bis(1-aziridinylcarbonylamino)hexane, 1,1'-(methylene-di-p-phenylene)bis-3,3-aziridyl urea, ethylene bis-(2-aziridinyl propionate), 2,4,6-triaziridinyl-1,3,5-triazine, and trimethylolpropane-tris(2-aziridinyl propionate).

[0098] When a crosslinking agent is blended into the composition, the content of the crosslinking agent in the composition is not particularly limited and 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, per 100 parts by mass of the acrylic adhesive polymer (A).

[0099] [Tackifier] The composition may contain a tackifier. Examples of tackifiers include rosin derivatives such as rosin ester, gum rosin, tall oil rosin, hydrogenated rosin ester, maleated rosin, and disproportionated rosin ester; terpene-based resins mainly composed of terpene phenol resins, α-pinene, β-pinene, or limonene; coumarone-indene resins, hydrogenated aromatic copolymers, and phenolic resins. One type of tackifier may be used alone, or two or more types may be used in combination. 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.

[0100] [Plasticizer] The composition may contain a plasticizer. Examples of the plasticizer include phthalates such as di-n-butyl phthalate, di-n-octyl phthalate, bis(2-ethylhexyl) phthalate, and di-n-decyl phthalate; adipates such as bis(2-ethylhexyl) adipate and di-n-octyl adipate; sebacates; azelaates; paraffins such as chlorinated paraffin; glycols such as polypropylene glycol; epoxy-modified vegetable oils such as epoxidized soybean oil and epoxidized linseed oil; phosphates such as trioctyl phosphate and triphenyl phosphate; phosphites such as triphenyl phosphite; ester oligomers such as esters of 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 content of the plasticizer 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 content of the acrylic adhesive polymer (A).

[0101] Examples of additives that may be blended into the composition include the above-mentioned crosslinking agents, tackifiers, and plasticizers, as well as antioxidants, ultraviolet absorbers, antiaging agents, flame retardants, mildew inhibitors, silane coupling agents, fillers, colorants, antistatic agents, etc. The content of the additives can be appropriately set depending on the various compounds within a range that does not impair the effects of the present disclosure.

[0102] [Solvent] The present composition preferably contains a solvent from the viewpoint of inducing phase separation between the acrylic adhesive polymer (A) and the modified polymer (B) in the surface layer portion of the adhesive layer when forming a pressure-sensitive adhesive layer from the present composition. An organic solvent capable of dissolving the acrylic adhesive polymer (A), the modified polymer (B), and the vinyl polymer (C) is preferably used as the solvent. In this case, a solvent-based pressure-sensitive adhesive composition can be obtained as the present composition. From the viewpoint of inducing phase separation between the acrylic adhesive polymer (A) and the modified polymer (B), phase-separating the modified polymer (B) at the surface of the pressure-sensitive adhesive layer, and segregating the modified polymer (B) at the surface of the pressure-sensitive adhesive layer, the present composition preferably dissolves the acrylic adhesive polymer (A), the modified polymer (B), and the vinyl polymer (C) in a solvent, thereby forming a liquid composition in which the acrylic adhesive polymer (A), the modified polymer (B), and the vinyl polymer (C) are in a single phase.

[0103] Specific examples of the organic solvent include aprotic polar solvents, phenolic solvents, alcoholic solvents, ester solvents, ketone solvents, ether solvents, aromatic hydrocarbon solvents, aliphatic hydrocarbon solvents, etc. The organic solvent may be one of these, or a mixed solvent of two or more of these.

[0104] Among these, the solvent is preferably at least one selected from the group consisting of ester solvents, ketone solvents, aromatic hydrocarbon solvents, and aliphatic hydrocarbon solvents. For example, from the viewpoint of forming a pressure-sensitive adhesive layer having a phase-separated structure of the acrylic adhesive polymer (A) and the modified polymer (B) using the present composition, it is preferable to dissolve the acrylic adhesive polymer (A), the modified polymer (B), and the vinyl polymer (C) in an organic solvent containing one or more of ethyl acetate, butyl acetate, ethyl methyl ketone, cyclohexane, methylcyclohexane, cyclohexanone, 4-methyltetrahydropyran, tetrahydropyran, tetrahydrofuran, and toluene.

[0105] The solids concentration in the composition (i.e., the ratio of the mass of components other than the solvent in the PSA composition to the total mass of the PSA composition) is not particularly limited, but is preferably 1 to 70 mass%. When the solids concentration is 1 mass% or more, a PSA layer with sufficient thickness can be formed. When the solids concentration is 70 mass% or less, good coatability can be ensured and a PSA layer with uniform thickness can be easily formed. The solids concentration in the composition is more preferably 5 to 50 mass%, and even more preferably 10 to 45 mass%.

[0106] <<Adhesive Layer>> The adhesive layer can be formed by applying the composition to a substrate and, if necessary, removing the solvent from the composition on the substrate. Resin films made of various resin materials can be used as the substrate to which the composition is applied. Both low-polarity and high-polarity resins can be used as the resin material, and examples of the resin material 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) resins.

[0107] The substrate preferably has a surface onto which the composition is applied that has releasability that allows the PSA layer to be peeled off. Such a substrate is called a separator or release film. The releasability of the coating surface may be imparted by a known release treatment, or may be due to the material of the substrate.

[0108] The composition can be applied by a known coating method, specifically, for example, a method using various coating machines such as a bar coater, an applicator, a gravure coater, a knife coater, a slot die coater, a doctor blade, or a dip coater, or a method using various printing machines such as gravure printing, offset printing, screen printing, or inkjet printing.

[0109] In order to induce phase separation between the acrylic adhesive polymer (A) and the modified polymer (B) in the pressure-sensitive adhesive layer formed from the composition, the composition coated on the substrate preferably contains a solvent, and the composition on the substrate is subjected to a heat treatment when forming the pressure-sensitive adhesive layer on the substrate. The heating temperature and heating time during the heat treatment can be appropriately set depending on the type of solvent in the composition, the solids concentration of the composition, etc. The composition may be heated under normal pressure or under reduced pressure. The composition coated on the substrate is preferably subjected to a heat treatment to remove the solvent, thereby forming a pressure-sensitive adhesive layer, thereby causing phase separation between the acrylic adhesive polymer (A) and the modified polymer (B) during the pressure-sensitive adhesive layer formation process. The thickness of the pressure-sensitive adhesive layer formed in this manner is, for example, 2 to 200 μm.

[0110] To obtain a pressure-sensitive adhesive layer in which the acrylic adhesive polymer (A) and the modified polymer (B) are phase-separated, for example, the degree of modification of the modified polymer (B) contained in the pressure-sensitive adhesive composition can be adjusted, the molecular weight of the modified polymer (B) can be adjusted, a crosslinking agent can be added, or a combination of these can be used. 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 closer the molecular weight of the modified polymer (B) is to 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).

[0111] Alternatively, a pressure-sensitive adhesive layer in which the acrylic adhesive polymer (A) and the modified polymer (B) are phase-separated at the surface layer may be obtained by adjusting the difference in SP value (Fedors method) between the acrylic adhesive polymer (A) and the modified polymer (B) contained in the pressure-sensitive adhesive composition to a predetermined value or more. Furthermore, the phase separation between the acrylic adhesive polymer (A) and the modified polymer (B) can be easily observed by observing the structure of a pressure-sensitive adhesive layer obtained using a pressure-sensitive adhesive composition in which a polymer blend of the intended acrylic adhesive polymer (A) and the modified polymer (B) is dissolved in a solvent using an electron microscope, a scanning probe microscope (such as an atomic force microscope), small-angle X-ray scattering, or the like.

[0112] In a pressure-sensitive adhesive layer formed using the present composition, the concentration of the modified polymer (B) in the surface layer portion of the pressure-sensitive adhesive layer is preferably higher than the concentration of the modified polymer (B) throughout the pressure-sensitive adhesive layer. A pressure-sensitive adhesive layer having a relatively high concentration of the modified polymer (B) in the surface layer portion is advantageous in that it exhibits higher adhesiveness both at room temperature and at high temperatures.

[0113] Herein, the "concentration of modified polymer (B) in the entire pressure-sensitive adhesive layer" is a value calculated as the ratio of the mass of modified polymer (B) to the total mass of the acrylic adhesive polymer (A) and modified polymer (B) in the pressure-sensitive adhesive composition used to form the pressure-sensitive adhesive layer. The "concentration of modified polymer (B) in the surface layer portion of the pressure-sensitive adhesive layer" is the composition ratio of modified polymer (B) in the surface layer portion of the pressure-sensitive adhesive layer obtained by X-ray photoelectron spectroscopy. Details of the calculation method follow the method described in the Examples below.

[0114] The concentration of the modified polymer (B) in the entire pressure-sensitive adhesive layer is preferably 0.5% or more, more preferably 1% or more, even more preferably 1.5% or more, and even more preferably 2% or more. The concentration of the modified polymer (B) in the entire pressure-sensitive adhesive layer is preferably 40% or less, more preferably 30% or less, even more preferably 25% or less, and even more preferably 15% or less.

[0115] When a pressure-sensitive adhesive layer is formed using a pressure-sensitive adhesive composition containing an acrylic pressure-sensitive adhesive polymer and a modified polymer (B), the content of the modified polymer (B) in the surface layer portion of the pressure-sensitive adhesive layer (mass fraction W Ｂ The mass fraction W of the modified polymer (B) in the surface layer of the pressure-sensitive adhesive layer can be determined by composition analysis using X-ray photoelectron spectroscopy. Ｂ ) is specifically expressed by the following formulas (2) and (3): Ｂ W = (mass of modified polymer (B)) / (total mass of modified polymer (B) and acrylic adhesive polymer (A)) (2) B = 1 - W A ...(3) (In the formulas (2) and (3), W Ａ is the mass fraction of the acrylic adhesive polymer (A) relative to the total mass of the modified polymer (B) and the acrylic adhesive polymer (A) in the surface layer portion of the adhesive layer, and W Ｂ is the mass fraction of the modified polymer (B) relative to the total mass of the modified polymer (B) and the acrylic adhesive polymer (A) in the surface layer portion of the pressure-sensitive adhesive layer.

[0116] Mass fraction W of the modified polymer (B) in the surface layer portion of the pressure-sensitive adhesive layer Ｂis preferably a value of 10% or more when expressed as a percentage. Within this range, phase separation between the acrylic adhesive polymer (A) and the modified polymer (B) occurs in the pressure-sensitive adhesive layer, and the concentration of the modified polymer (B) in the surface layer portion becomes relatively high, thereby making it possible to obtain a pressure-sensitive adhesive layer that exhibits high adhesiveness at room temperature and at high temperatures. The mass fraction W when expressed as a percentage is Ｂ is more preferably 15% or more, even more preferably 20% or more, still more preferably 25% or more, and even more preferably 30% or more. Ｂ is a value measured at room temperature (25°C) and atmospheric pressure.

[0117] The relatively high concentration of the modified polymer (B) in the surface layer of the pressure-sensitive adhesive layer is believed to be mainly due to the difference in polarity and molecular weight between the modified polymer (B) and the acrylic pressure-sensitive adhesive polymer (A). Specifically, this is believed to be because the modified polymer (B) with lower polarity or smaller molecular weight tends to be present in greater amounts on the low-surface-energy interface side in the thickness direction of the pressure-sensitive adhesive layer.

[0118] Furthermore, when only one of the two outermost surfaces in the thickness direction of the pressure-sensitive adhesive layer is on the low surface energy interface side, it is possible to obtain a pressure-sensitive adhesive layer in which only the interface side contains a higher concentration of the modified polymer (B). Furthermore, when both of the two outermost surfaces in the thickness direction of the pressure-sensitive adhesive layer are on the low surface energy interface side, it is possible to obtain a pressure-sensitive adhesive layer in which each of the two outermost surfaces contains a higher concentration of the modified polymer (B). In the latter case, the phrase "the concentration of the modified polymer (B) in the surface layer portion of the pressure-sensitive adhesive layer obtained by X-ray photoelectron spectroscopy analysis" is "higher than the concentration of the modified polymer (B) in the entire pressure-sensitive adhesive layer" means that the concentration of the modified polymer (B) on each of the two outermost surfaces in the thickness direction is higher than the concentration of the modified polymer (B) in the entire pressure-sensitive adhesive layer.

[0119] Specifically, when the content of the modified polymer (B) in the present composition is set to 0.1 parts by mass or more and 50 parts by mass or less relative to 100 parts by mass of the acrylic adhesive polymer (A), the present composition is applied to a separator and dried to obtain a pressure-sensitive adhesive layer, and the mass fraction of the modified polymer (B) on the surface of the pressure-sensitive adhesive layer obtained by X-ray photoelectron spectroscopy analysis (i.e., the concentration [%] of the modified polymer (B) in the entire pressure-sensitive adhesive layer) is 0.1 parts by mass or more and 50 parts by mass or less relative to 100 parts by mass of the acrylic adhesive polymer (A). Ｂ It is preferable that the ratio is larger than 1 / 2 [%].

[0120] For example, the mass fraction W of the modified polymer (B) in the surface layer portion of the pressure-sensitive adhesive layer Ｂ is the mass fraction of the modified polymer (B) in the entire pressure-sensitive adhesive layer (this is called Q Ｂ The ratio (= W Ｂ / Q Ｂ , which is also referred to as "surface ratio"), the surface ratio is preferably 1.2 or more. From the viewpoint of obtaining a pressure-sensitive adhesive layer that has excellent adhesion to low-polarity substrates and exhibits higher adhesion both at room temperature and at high temperatures, the surface ratio is more preferably 1.5 or more, even more preferably 2.5 or more, and even more preferably 5.0 or more. There are no particular restrictions on the upper limit of the surface ratio, but from the viewpoint of ensuring adhesiveness, it may be, for example, 50 or less, or may be 30 or less.

[0121] Haze Value: The pressure-sensitive adhesive layer formed from the present composition has a phase-separated structure between the acrylic pressure-sensitive adhesive polymer (A) and the modified polymer (B), and therefore exhibits a relatively high haze value, which is an index of the degree of cloudiness. Specifically, the haze value of the pressure-sensitive adhesive layer is preferably 3.0% or more as measured by a haze meter after a 50 μm-thick pressure-sensitive adhesive layer is attached to a glass substrate and left to stand for one day under conditions of 23°C and 50% RH. From the viewpoint of exhibiting high adhesive strength at room temperature and high temperatures due to the formation of a phase-separated structure between the acrylic pressure-sensitive adhesive polymer (A) and the modified polymer (B), the haze value of the pressure-sensitive adhesive layer under the above conditions is more preferably 3.5% or more, and even more preferably 4.0% or more. Furthermore, when applied to applications where transparency of the pressure-sensitive adhesive layer is not required, the haze value of the pressure-sensitive adhesive layer measured under the above conditions may be 15% or more, or even 20% or more, since this allows for a pressure-sensitive adhesive layer with higher adhesive strength to be obtained. There is no particular upper limit to the haze value of the pressure-sensitive adhesive layer measured under the above conditions. When the pressure-sensitive adhesive layer is used in applications requiring transparency, the haze value of the pressure-sensitive adhesive layer measured under the above conditions is preferably 30% or less, and more preferably 25% or less. Details of the method for measuring the haze value follow the method described in the Examples below.

[0122] In the pressure-sensitive adhesive composition used to form the pressure-sensitive adhesive layer of the present disclosure, the acrylic adhesive polymer (A) and the modified polymer (B) are homogeneous and have a single phase. In the process of forming a pressure-sensitive adhesive layer using such a homogeneous pressure-sensitive adhesive composition, phase separation between the acrylic adhesive polymer (A) and the modified polymer (B) occurs, resulting in a pressure-sensitive adhesive layer obtained using this composition exhibiting a relatively high haze value. Therefore, in a pressure-sensitive adhesive layer that contains the acrylic adhesive polymer (A) and the modified polymer (B) but has a sufficiently low haze value (e.g., 1.5% or less, e.g., less than 1.0%), it can be said that the acrylic adhesive polymer (A) and the modified polymer (B) are not phase-separated.

[0123] Gel Fraction When the composition contains a crosslinking agent, the gel fraction of the pressure-sensitive adhesive layer made of the composition is preferably 50% or more. A gel fraction of 50% or more can sufficiently enhance the heat resistance and durability against temperature changes of the pressure-sensitive adhesive layer, and can also provide a pressure-sensitive adhesive layer that exhibits high adhesiveness at high temperatures. The gel fraction of the pressure-sensitive adhesive layer is more preferably 55% or more, even more preferably 60% or more, and even more preferably 65% ​​or more. The upper limit of the gel fraction is preferably 95% or less, more preferably 90% or less, and even more preferably 85% or less. In this specification, the gel fraction of the pressure-sensitive adhesive layer is the ratio of the mass W2 of the pressure-sensitive adhesive layer remaining after solvent immersion to the initial mass W1 of the pressure-sensitive adhesive layer. Details are given in accordance with the measurement method described in the Examples below.

[0124] Glass Transition Temperature The pressure-sensitive adhesive layer preferably has a glass transition temperature (Tg). Specifically, the Tg of the entire pressure-sensitive adhesive layer is preferably 20°C or lower. When the Tg of the entire adhesive layer is 20°C or lower, a pressure-sensitive adhesive layer with better adhesion at room temperature can be obtained. From the viewpoint of obtaining a pressure-sensitive adhesive layer with higher adhesion at room temperature, the Tg of the entire pressure-sensitive adhesive layer is more preferably 10°C or lower, even more preferably 0°C or lower, and even more preferably -5°C or lower. The Tg of the entire pressure-sensitive adhesive layer is preferably -80°C or higher, more preferably -70°C or higher, and even more preferably -60°C or higher. The Tg of the entire adhesive layer is a value obtained using a differential scanning calorimeter (DSC) at a heating rate of 10°C / min in a nitrogen atmosphere. Details of the measurement conditions are as described in the examples below.

[0125] <<Adhesive Sheet>> The adhesive sheet of the present disclosure (hereinafter also referred to as "the sheet") comprises a pressure-sensitive adhesive layer formed using the composition of the present disclosure. The pressure-sensitive adhesive layer of the sheet and the pressure-sensitive adhesive composition for forming the layer are as described above. Therefore, after the pressure-sensitive adhesive layer of the sheet is attached to a molded body, the pressure-sensitive adhesive layer is unlikely to peel off from the molded body under both room temperature and high temperature environments, and the sheet has excellent room-temperature adhesion and high-temperature adhesion. Furthermore, the sheet also has excellent adhesion to not only low-polarity substrates but also high-polarity substrates.

[0126] The pressure-sensitive adhesive sheet may be in a so-called substrate-less form in which the pressure-sensitive adhesive layer is sandwiched between two separators, or may be one in which one of the objects to be joined serves as the substrate. In a substrate-less form, the peel strengths of the two separators may be the same or different. The shape of the pressure-sensitive adhesive sheet is also not particularly limited and is appropriately set depending on the usage situation. The pressure-sensitive adhesive sheet may be, for example, in the form of a sheet, a roll, or cut into strips. The thickness of the pressure-sensitive adhesive layer may be appropriately set depending on the type of objects to be joined, the area and shape of the joining location, etc. Furthermore, in order to achieve a desired thickness for the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet, the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet may be formed by laminating multiple pressure-sensitive adhesive layers.

[0127] The PSA sheet of the present disclosure thus obtained can be used as a PSA in a wide range of applications, specifically, for example, clothing (including clothing accessories), sports goods (e.g., sportswear, sports shoes, sports gloves, bat and racket grips, etc.), medical supplies (e.g., supports and corsets, etc.), automotive interior and exterior parts, outdoor goods, handicraft supplies, toys, lifestyle goods, household goods, furniture, etc.

[0128] Decorative Film One preferred embodiment of the pressure-sensitive adhesive sheet of the present disclosure is a decorative film. Examples of the decorative film include a single-layer film in which a decorative layer is formed by coloring a substrate layer, and a laminate film in which a decorative layer and a substrate layer are laminated in this order. A decorative film of this configuration is preferably used as a decorative film for a lamination method in which the film is attached to an adherend to obtain a decorated molded body.

[0129] In the decorative film, after the adherend is decorated with the decorative film, the substrate layer is located as the outermost layer of the decorated adherend (i.e., the decorated molded body) and functions as a protective layer for the decorated molded body. The material constituting the substrate layer is preferably a flexible material, and preferably a resin material. More preferably, it is a thermoplastic resin. The thermoplastic resin is not particularly limited, but examples include polyvinyl chloride (PVC) resin, polyester resin, acrylic resin, acrylonitrile butadiene styrene (ABS) resin, polycarbonate resin, polyamide resin, polypropylene resin, and polyethylene resin. In particular, the adhesive layer provided in this sheet is useful in that it has excellent adhesion not only to low-polarity substrates but also to high-polarity substrates.

[0130] The thickness of the substrate layer is preferably 25 μm to 500 μm, more preferably 50 μm to 400 μm, and even more preferably 100 to 300 μm. When the thickness of the substrate layer is within the above range, the processability, shape conformability, and handleability are improved when the decorative molded body is produced by injection molding (also known as insert molding), vacuum molding, vacuum pressure molding, or the like.

[0131] The decorative layer is an ink layer onto which designs and patterns such as text, figures, and trademarks are printed or otherwise applied. This decorative layer imparts design properties to the decorative film. The designs and patterns of the decorative layer can be formed by known printing methods such as gravure printing using printing ink, offset printing, silk screen printing, transfer printing from a transfer sheet, sublimation transfer printing, and inkjet printing. 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, a sufficient thickness can be ensured to express complex designs such as gradations. A textured pattern may be applied to the surface layer of the decorative film. The textured pattern can be formed, for example, by transferring the textured pattern using an embossing roller. Furthermore, the base layer or adhesive layer can be imparted with decorative functionality by incorporating pigments, dyes, brighteners, etc. into the base layer or adhesive layer.

[0132] Before being attached to an adherend, the decorative film may further include a release layer on the outermost layer on the adhesive layer side, in addition to the adhesive layer. The release layer prevents unintended adhesion and is peeled off when the decorative film is attached to the adherend. The material constituting the release layer is not particularly limited, and examples that can be used include resin materials such as polyesters such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate, polyolefins such as polypropylene and polyethylene, and paper materials such as glassine paper, kraft paper, and clay-coated paper. The thickness of the release layer can be approximately 10 to 400 μm.

[0133] Alternatively, the decorative film may be a film having a hard coat layer (protective layer) and a decorative layer on a release layer of a release film having a release layer before being attached to an adherend, and the film may be attached to an adherend via an adhesive layer provided on the decorative layer side. A decorative film of this configuration is suitable for use as a transfer film. With this decorative film, a decorated molded article can be obtained by a transfer method in which the hard coat layer and the adhesive layer are transferred to the adherend.

[0134] The hard coat layer is preferably composed of a material that can be cured and / or crosslinked by irradiation with active energy rays or the like after being transferred to an adherend. Examples of materials that can be used for the hard coat layer include polymers or oligomers having a (meth)acryloyl group, active energy ray-curable compositions that have been semi-cured by irradiating them with an appropriate amount of active energy rays, and active energy ray-curable resin compositions that have been blended with an isocyanate compound, a polyol resin, or the like and appropriately crosslinked. The thickness of the hard coat layer is not particularly limited and is, for example, about 1 to 50 μm.

[0135]

[0013] The present disclosure provides a decorative molded body in which the adhesive layer of the decorative film described above is attached to a molded body. The decorative molded body is decorated with a decorative film having an adhesive layer obtained using the present composition, and therefore the decorative film is less likely to lift or peel at both room temperature and high temperatures, and has excellent heat resistance and durability.

[0136] The molded article to which the decorative film is adhered is not particularly limited, and may be any article to which the decorative film can be adhered, such as a resin product, a metal product, a ceramic product, a glass product, etc. Specific examples include various household appliances such as home appliances, kitchen appliances, health appliances, and seasonal appliances; interior and exterior components of housing facilities such as toilets, bathrooms, doors, and walls; automobile interior and exterior components such as bumpers, dashboards, doors, roofs, and hoods; various miscellaneous goods such as household goods and daily necessities; electronic components; nursing and medical supplies; and interior and exterior components of ships and aircraft. When the adhesion surface of the molded article to which the decorative film is adhered is made of a low-polarity material, the properties of the pressure-sensitive adhesive layer of the present disclosure, i.e., the effect of exhibiting high adhesion at both room temperature and high temperatures, can be more suitably exhibited. In particular, the pressure-sensitive adhesive layer formed from the present composition is useful in that it can exhibit excellent adhesion whether the adhesion surface is a low-polarity substrate such as polypropylene or a high-polarity substrate such as polycarbonate or acrylic resin.

[0137] The decorative molded body can be manufactured using methods such as vacuum forming, vacuum pressure forming, and injection molding. 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 adhering the decorative film to the surface shape of the molded body. In the vacuum pressure forming method, after the forming process of the vacuum forming method, the space on the opposite side is further pressurized, thereby forming and adhering the decorative film to the surface shape of the molded body. Examples of vacuum pressure forming machines include the TFH series hot plate type vacuum coating molding machine manufactured by Asano Laboratory, the NGF series TOM molding machine manufactured by Fuse Vacuum, and the NATS air transfer machine manufactured by Navitas. In the injection molding method, the decorative film is placed in the mold cavity of the injection molding machine and injection molded, thereby adhering the decorative film to the surface shape of the molded body. These methods can be used to obtain the decorative molded body.

[0138] Here, the reason why the pressure-sensitive adhesive layer formed from the present composition exhibits a good balance between adhesion performance to low-polarity substrates and adhesion performance to high-polarity substrates is unclear, but the following may be considered, for example. It is believed that the pressure-sensitive adhesive layer formed from the present composition is in a state in which the acrylic pressure-sensitive adhesive polymer (A) and the modified polymer (B) are phase-separated in the surface layer portion of the pressure-sensitive adhesive layer due to phase separation between the acrylic pressure-sensitive adhesive polymer (A) and the modified polymer (B) occurring during the process of forming the pressure-sensitive adhesive layer. It is also believed that the vinyl polymer (C) segregates in the surface layer of the phase mainly composed of the acrylic pressure-sensitive adhesive polymer (A). When such a pressure-sensitive adhesive layer is bonded to a low-polarity substrate, the modified polymer (B), which has better affinity with low-polarity substrates, is likely to appear in the surface layer portion of the pressure-sensitive adhesive layer, while the vinyl polymer (C) is unlikely to appear on the surface of the pressure-sensitive adhesive layer. As a result, it is believed that the pressure-sensitive adhesive layer formed from the present composition exhibits good adhesion to low-polarity substrates due to the adhesive performance of the modified polymer (B).

[0139] In contrast, when a pressure-sensitive adhesive layer formed from the present composition is bonded to a high-polarity substrate, the vinyl polymer (C), which has a better affinity with high-polarity substrates, is more likely to appear in the surface layer of the pressure-sensitive adhesive layer. As a result, the pressure-sensitive adhesive layer formed from the present composition exhibits good adhesion to high-polarity substrates due to the adhesive properties of the vinyl polymer (C). In other words, the composition of the surface layer of the pressure-sensitive adhesive layer formed from the present composition may change slightly depending on the polarity of the substrate to which the pressure-sensitive adhesive layer is bonded. This suggests that the present composition can form a pressure-sensitive adhesive layer that exhibits good adhesion not only to low-polarity substrates but also to high-polarity substrates. In particular, when bonding a decorative film to a molded body, heat treatment activates molecular movement, making it easier for the vinyl polymer (C) to migrate toward the high-polarity substrate, resulting in excellent adhesive performance. Note that the above is merely speculation and does not limit the present disclosure.

[0140] The present disclosure will be specifically described below using examples. However, the present disclosure is not limited to these examples. In the following, "parts" and "%" mean "parts by mass" and "% by mass", respectively, unless otherwise specified. The polymers used in each example were analyzed using the following methods.

[0141] <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 terms of polystyrene were obtained under the following conditions: Measurement conditions Column: 4 columns of TSKgel SuperMultiporeHZ-M manufactured by Tosoh Corporation Column temperature: 40°C Eluent: tetrahydrofuran Detector: RI Flow rate: 600 μL / min

[0142] <Measurement of Glass Transition Temperature (Tg)> The glass transition temperature (Tg) of a polymer was determined from the intersection of the baseline of a heat flux curve obtained using a differential scanning calorimeter (DSC) and the tangent at the inflection point. The heat flux curve was obtained by cooling approximately 10 mg of a sample to -100°C, holding it for 5 minutes, then heating it at 10°C / min to 300°C, subsequently cooling it to -100°C, holding it for 5 minutes, and then heating it at 10°C / min to 350°C. Measuring instrument: DSC6220 manufactured by SII Nanotechnology Inc. Measurement atmosphere: nitrogen atmosphere

[0143] <Measurement of Melting Point (Tm)> The melting point (Tm) of the modified polyolefin was determined as the melting peak top of the heat flux curve obtained using a differential scanning calorimeter (DSC). The heat flux curve was obtained by cooling approximately 5 mg of a sample to -70°C, holding it for 5 minutes, then heating it at 10°C / min to 150°C, subsequently cooling it to -70°C, holding it for 5 minutes, and then heating it at 10°C / min to 150°C. Measuring instrument: DSC6220 manufactured by SII Nanotechnology Inc. Measurement atmosphere: nitrogen atmosphere

[0144] <SP Value> The SP value of the polymer was calculated by the Fedors method. The unit is [cal / cm ３ ] １／２ is.

[0145] 1. Synthesis of Acrylic Adhesive Polymer [Synthesis Example 1] (Synthesis of Polymer A-1) A four-neck flask was charged with 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). 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 Wako Pure Chemical Industries, Ltd., trade name "V-65") (0.0191 parts by mass) was charged as an initiator, and polymerization was carried out for 5 hours. Ethyl acetate was added so that the solids concentration was 22%, to obtain an ethyl acetate solution of Polymer A-1. The obtained polymer consisted of 17% by mass of BA, 78% by mass of MEA, and 5% by mass of HEA, and had Mn=92,000, Mw=800,000, and Mw / Mn=8.7. The Tg was −35° C., and the SP value was 10.27. The composition (feed ratio), reaction conditions, and analysis results of Polymer A-1 are shown in Table 1. The monomer composition ratio of Polymer A-1 was calculated from the amount of monomers charged and the amount of monomer consumed measured by gas chromatography (GC), and was found to be equivalent to the monomer feed ratio.

[0146] Synthesis Examples 2 to 7 (Synthesis of Polymers A-2 to A-7) Solutions containing Polymers A-2 to A-7 were obtained by the same procedure as in Synthesis Example 1, except that the types and amounts of raw materials charged to the flask and the reaction conditions were changed as shown in Table 1. In Synthesis Example 7, where the reaction conditions are described as "65°C 3 h → 75°C 5 h," the mixed solution was polymerized at 65°C for 3 hours, and then the temperature was raised to 75°C and the reaction was continued for 5 hours. The analysis results of the obtained polymers are shown in Table 1. The monomer composition ratios of Polymers A-2 to A-7 were calculated in the same manner as for Polymer A-1, and the monomer composition ratios of each polymer were equivalent to the monomer charge ratios.

[0147]

[0148] The abbreviations of the monomers in Table 1 are as follows: MA: methyl acrylate BA: butyl acrylate MEA: 2-methoxyethyl acrylate HEA: 2-hydroxyethyl acrylate LA: lauryl acrylate AA: acrylic acid

[0149] 2. Synthesis of Vinyl Polymers [Synthesis Example 8] (Synthesis of Polymer C-1) A 1-liter four-neck flask was charged with a mixed solution consisting of butyl acetate (200 parts by mass) and dimethyl-2,2'-azobis(2-methylpropionate) (manufactured by Wako Pure Chemical Industries, Ltd., trade name "V-601", hereinafter also referred to as "V-601") (0.9 parts by mass). This mixed solution was thoroughly degassed by bubbling nitrogen gas, and the internal temperature of the mixed solution was raised to 90°C. Separately, a mixed solution consisting 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 from a dropping funnel into the flask over 5 hours to carry out polymerization. After the dropwise addition, the polymerization solution was added dropwise to a mixed solution of methanol (4,800 parts by mass) and distilled water (1,200 parts by mass), thereby isolating the vinyl polymer in the polymerization solution and obtaining polymer C-1. The composition ratio of the monomers constituting the obtained polymer C-1 was １ As a result of calculation from H-NMR measurement, the content of MMA was 80% by mass and that of IBXMA was 20% by mass (Table 2). The molecular weight characteristics of polymer C-1 were Mn = 6,700, Mw = 6,700, and Mw / Mn = 1.53. The Tg of polymer C-1 was 108°C.

[0150] Synthesis Example 9 Synthesis of Polymer C-2 The same operation as in Synthesis Example 8 was carried out, except that the initial charge was changed to butyl acetate (280 parts by mass) and V-601 (0.3 parts by mass), and the mixed liquid to be added dropwise 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.

[0151] Synthesis Example 10 Synthesis of Polymer C-3 A 1-liter four-neck flask was charged with a mixed solution consisting of butyl acetate (200 parts by mass), styrene (15 parts by mass), and methyl methacrylate (22 parts by mass), and the mixture was thoroughly degassed by bubbling nitrogen gas through it. The internal temperature of the mixed solution was raised to 90°C. To this was added a mixed solution consisting of V-601 (11.4 parts by mass) and butyl acetate (15 parts by mass), and polymerization was initiated. Furthermore, a mixed solution consisting 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) was added dropwise from the dropping funnel into the flask over 5 hours to carry out polymerization. After completion of the dropwise addition, the polymerization solution was added dropwise to a mixed solvent consisting of methanol (4800 parts by mass) and water (1200 parts by mass), and the vinyl polymer in the polymerization solution was isolated to obtain Polymer C-3.

[0152] Synthesis Example 11 Synthesis of Polymer C-4 The same operation as in Synthesis Example 8 was carried out, except that the initial charges were changed to butyl acetate (205 parts by mass) and V-601 (3.9 parts by mass), and the mixed liquid to be added dropwise 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.

[0153] Synthesis Example 12 Synthesis of Polymer C-5 A 1-liter four-neck flask was charged with a mixed solution consisting of butyl acetate (255 parts by mass), styrene (37 parts by mass), and 2-hydroxyethyl methacrylate (hereinafter also referred to as "HEMA") (4 parts by mass), and the mixture was thoroughly degassed by bubbling nitrogen gas through it, and the internal temperature of the mixed solution was raised to 90°C. To this was added a mixed solution consisting of V-601 (5.0 parts by mass) and butyl acetate (15 parts by mass) to initiate polymerization. Furthermore, a mixed solution consisting of styrene (146 parts by mass), HEMA (72 parts by mass), V-601 (60 parts by mass), and butyl acetate (90 parts by mass) was added dropwise from the dropping funnel into the flask over 5 hours to carry out polymerization. After completion of the dropwise addition, the polymerization solution was added dropwise to a mixed solvent consisting of methanol (4800 parts by mass) and water (1200 parts by mass), and the vinyl polymer in the polymerization solution was isolated to obtain Polymer C-5.

[0154] Synthesis Example 13 Synthesis of Polymer C-6 Vinyl polymer C-6 was obtained by the same operation as in Synthesis Example 8, except that the initial charge was changed to butyl acetate (90 parts by mass) and V-601 (1.7 parts by mass) and the mixed liquid to be added dropwise was changed to MMA (80 parts by mass), dicyclopentanyl methacrylate (hereinafter also referred to as "FA513M") (63 parts by mass), V-601 (33 parts by mass), and butyl acetate (90 parts by mass).

[0155] Synthesis Example 14 Synthesis of Polymer C-7 The same operation as in Synthesis Example 8 was carried out, except that the initial charge was changed to butyl acetate (216 parts by mass) and V-601 (3.3 parts by mass), and the mixed liquid to be added dropwise was changed to MMA (115 parts by mass), cyclohexyl methacrylate (hereinafter also referred to as "CHMA") (141 parts by mass), V-601 (62 parts by mass), and butyl acetate (90 parts by mass), to obtain vinyl polymer C-7.

[0156] The analytical results of the obtained polymers C-1 to C-7 are shown in Table 2. The monomer composition ratio of each polymer was １ Calculated from H-NMR measurements.

[0157]

[0158] The abbreviations of the monomers in Table 2 are as follows: MMA: methyl methacrylate IBXMA: isobornyl methacrylate St: styrene HEMA: 2-hydroxyethyl methacrylate CHMA: cyclohexyl methacrylate FA513M: dicyclopentanyl methacrylate

[0159] 3. Production of Pressure-Sensitive Adhesive Composition and Pressure-Sensitive Adhesive Sheet [Example 1] The ethyl acetate solution of polymer A-1 obtained in Synthesis Example 1 was desolvated and redissolved in a mixed solvent of toluene and cyclohexane (toluene:cyclohexane = 75:25 (mass ratio)) to obtain a polymer A-1 solution. Polymer B-1 (Hardlen PMA-TE, manufactured by Toyobo Co., Ltd., maleic anhydride-modified polyolefin, modification rate 1.8%, melting point 90°C, Mw 60,000) was dissolved in toluene to obtain a polymer B-1 solution with a solids concentration of 7 mass%, which was mixed with the polymer A-1 solution, and polymer C-1 was further added to prepare a polymer solution with a solids content of 25 mass% containing polymer A-1 (100 parts by mass), polymer B-1 (7 parts by mass), and polymer C-1 (4 parts by mass). To this was added 0.20 parts by mass of a crosslinking agent, a trimethylolpropane adduct of metaxylylene diisocyanate (Takenate D-110N, manufactured by Mitsui Chemicals, Inc., solids concentration 75% by mass, isocyanate group content 11.5%), to obtain a pressure-sensitive adhesive composition. The obtained pressure-sensitive adhesive composition was applied to a 50 μm thick polyethylene terephthalate (hereinafter referred to as "PET") separator so that the thickness after drying would be 50 μm. The pressure-sensitive adhesive composition was dried at 120°C for 4 minutes to remove the solvent. A 38 μm thick PET separator with a different peel strength from the above separator was attached, and the resulting sheet was left to stand at 40°C for 5 days for aging, to obtain a pressure-sensitive adhesive sheet with a double-sided separator.

[0160] Examples 2 to 17, Comparative Examples 1 to 19: Pressure-sensitive adhesive compositions were produced using the compositions and solids concentrations shown in Tables 3 to 6, in the same manner as in Example 1. For examples in which the solvent did not contain ethyl acetate (AcOEt) (Examples 2 to 13, 15 to 17, Comparative Examples 1 to 13, 15, and 17), the ethyl acetate solution of the acrylic pressure-sensitive adhesive polymer obtained in each Synthesis Example was desolvated, and the acrylic pressure-sensitive adhesive polymer was redissolved in the solvent shown in Tables 3 to 6. The polymer solution was used to prepare a pressure-sensitive adhesive composition. For examples in which the solvent contained ethyl acetate (AcOEt) (Example 14, Comparative Examples 14, 16, 18, and 19), the ethyl acetate solution of the acrylic pressure-sensitive adhesive polymer obtained in each Synthesis Example was used directly to prepare a pressure-sensitive adhesive composition. Furthermore, a pressure-sensitive adhesive sheet with a double-sided separator was obtained using the obtained pressure-sensitive adhesive composition in the same manner as in Example 1. In Tables 3 to 6, the numerical values ​​of the compositions of the pressure-sensitive adhesive compositions represent the amount (parts by mass) of the solid content of each component used in preparing the pressure-sensitive adhesive composition for the acrylic pressure-sensitive adhesive polymer (BP), modified polyolefin (PO), and vinyl polymer, and represent the amount (parts by mass) including the solvent for the crosslinking agent.

[0161] 4. Evaluation The resulting double-sided separator-attached PSA sheets (hereinafter referred to as "evaluation sheets") were subjected to various measurements and evaluations using the methods described below. The results are shown in Tables 3 to 6.

[0162] <Gel fraction> 0.2 g of adhesive was collected from the adhesive layer of the evaluation sheet, and the initial mass of the adhesive was weighed. The adhesive was immersed in 50 g of ethyl acetate and allowed to stand at room temperature for 16 hours. Thereafter, it was filtered through a 200-mesh wire netting, and the residue remaining on the mesh was dried at 80°C for 3 hours and weighed. The gel fraction was calculated from the initial mass and the mass of the residue.

[0163] <Haze Value> The release film was peeled off from the evaluation sheet (adhesive layer thickness: 50 μm), transferred to a glass plate (thickness: 1 mm), and the other release film was peeled off. After leaving the sheet to stand for 1 day under conditions of 23°C and 50% RH, the haze value was measured using a haze meter "COH7700" (model name) manufactured by Nippon Denshoku Industries Co., Ltd.

[0164] <Tg of entire pressure-sensitive adhesive layer> The Tg of the entire pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition (referred to as "Tg of pressure-sensitive adhesive layer" in Tables 3 to 6) was measured by DSC in accordance with JIS K7121 under the following conditions: Measuring device: TA Instrument (Q-100) Heating temperature: 10°C / min Measurement atmosphere: Nitrogen atmosphere

[0165] <Composition of the surface portion of the pressure-sensitive adhesive layer> From the peak area ratio of O1s and C1s measured by an X-ray photoelectron spectrometer (XPS) of a pressure-sensitive adhesive film sample, the mass fraction (W Ａ and W Ｂ The XPS measurement was carried out under the following conditions: Apparatus: PHI5000 VersaProbe manufactured by ULVAC-PHI, Inc. X-ray: Al-Kα (1486.6 eV) X-ray incident angle to sample: 0° (angle with respect to the normal to the sample measurement surface) Photoelectron detection angle: 45° (angle with respect to the normal to the sample measurement surface)

[0166] A specific method for calculating the mass fraction is described below. The ratio of oxygen atoms to the total number of oxygen atoms and carbon atoms calculated from the peak area ratio of O1s and C1s by XPS measurement represents the ratio of oxygen atoms to the total number of oxygen atoms and carbon atoms present per unit area of ​​the surface layer of the pressure-sensitive adhesive layer formed from a pressure-sensitive adhesive composition comprising an acrylic pressure-sensitive adhesive polymer and a modified polyolefin, as shown in the following formula (4):

[0167] Here, O Ａ＋Ｂ : the ratio of the number of oxygen atoms to the total number of carbon atoms and oxygen atoms, calculated from the peak area ratio of O1s and C1s determined by XPS measurement of the pressure-sensitive adhesive layer obtained by drying the pressure-sensitive adhesive composition; x: the volume fraction of the acrylic adhesive polymer in the surface layer of the pressure-sensitive adhesive layer; N ＯＡ N: The ratio of the number of oxygen atoms derived from the acrylic adhesive polymer to the total number of carbon atoms and oxygen atoms in a unit area of ​​the surface layer of the adhesive layer ＯＢN: The ratio of the number of oxygen atoms derived from modified polyolefin to the total number of carbon atoms and oxygen atoms in the surface layer of the adhesive layer ｃ N: Number of carbon atoms per unit area of ​​the surface of the adhesive layer ｏ : Number of oxygen atoms per unit area of ​​the adhesive layer surface

[0168] Furthermore, the ratio of oxygen atoms to the total number of carbon atoms and oxygen atoms calculated from the peak area ratio of O1s and C1s determined by XPS measurement of films obtained by drying each of the acrylic adhesive polymer and modified polyolefin alone is expressed by the following formula (5) and formula (6), respectively. Here, O Ａ N: The ratio of the number of oxygen atoms to the total number of carbon atoms and oxygen atoms, calculated from the peak area ratio of O1s and C1s obtained by XPS measurement of a film obtained by drying an acrylic adhesive polymer ＯＡ N: O1s peak area obtained by XPS measurement of a film obtained by drying an acrylic adhesive polymer ＣＡ : C1s peak area determined by XPS measurement of a film obtained by drying an acrylic adhesive polymer Here, O Ｂ N: The ratio of the number of oxygen atoms to the total number of carbon atoms and oxygen atoms, calculated from the peak area ratio of O1s and C1s determined by XPS measurement of a film obtained by drying the modified polyolefin ＯＢ N: O1s peak area determined by XPS measurement of a film obtained by drying the modified polyolefin ＣＢ : C1s peak area determined by XPS measurement of a film obtained by drying the modified polyolefin

[0169] The density of the acrylic adhesive polymer and modified polyolefin is close, Ｃ +N Ｏ = N ＣＡ +N ＯＡ = N ＣＢ +N ＯＢ x = W Ａ Based on this approximation, the following formula (7) is derived from the above formulas (4) to (6), and the mass fraction W of the acrylic adhesive polymer is calculated from this formula. Ais calculated. Furthermore, the W calculated above Ａ From the value of and the following formula (8), the mass fraction of the modified polyolefin (W Ｂ ) is calculated. Ｂ = 1 - W Ａ ...(8) where W Ａ W: Mass fraction of acrylic adhesive polymer Ｂ : mass fraction of modified polyolefin

[0170] For Example 1, the elements in the above formula (7) are as follows: Ａ＋Ｂ : 0.073 (measured value) O Ａ : 0.318 (measured value) O Ｂ : 0.016 (measured value) By substituting these values ​​into the above formula (4), W Ａ = 0.189, W Ｂ = 0.811 was obtained.

[0171] <Modified polyolefin concentration in the entire pressure-sensitive adhesive layer and the modified polyolefin concentration in the surface layer portion of the pressure-sensitive adhesive layer> The ratio (unit: %) of the mass of the modified polyolefin to the total mass of the acrylic adhesive polymer and modified polyolefin used in preparing the pressure-sensitive adhesive composition was calculated, and this was taken as the modified polyolefin concentration in the entire pressure-sensitive adhesive layer (referred to as "PO concentration in the pressure-sensitive adhesive layer"). In addition, the W calculated from the XPS measurement results of the pressure-sensitive adhesive film sample was used as the modified polyolefin concentration in the surface layer portion of the pressure-sensitive adhesive layer. Ｂ The value expressed as a percentage was taken as the concentration of modified polyolefin in the surface layer portion of the pressure-sensitive adhesive layer (referred to as "PO surface concentration").

[0172] <Peel test> The evaluation sheet (adhesive layer thickness: 50 μm) was transferred to an easily adhesive treated PET film (125 μm) to obtain a peel test sheet. This peel test sheet was attached to a polypropylene (PP) plate (manufactured by Resonac, trade name PP-N-BN, 2 mm thick) and pressed 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.) to obtain a peel test specimen. The peel test specimen was measured for 180° peel strength of the adhesive sheet using a thermostatic oven equipped tensile tester Strograph R type (manufactured by Toyo Seiki Co., Ltd.) at 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 was recorded. In addition, instead of the polypropylene plate, an acrylonitrile butadiene styrene (ABS) plate (manufactured by TP Giken Co., Ltd., ABS resin plate, 2.0 mm thick), a polycarbonate (PC) plate (manufactured by Mitsubishi Engineering Plastics Corporation, trade name Iupilon NF-2000, 1.5 mm thick), a polymethyl methacrylate (PMMA) plate (manufactured by Mitsubishi Chemical Corporation, trade name Acrylite L, 2.0 mm thick), and a nylon sheet (manufactured by TP Giken Co., Ltd., trade name Polyamide PA66, 1.0 mm thick) were used, and the 180-degree peel strength of the pressure-sensitive adhesive sheet was measured in the same manner as above, and the peel strength at each temperature (unit: N / 25 mm) was recorded.

[0173]

[0174]

[0175]

[0176]

[0177] The abbreviations for the modified polyolefin (PO), additives, and solvents in Tables 3 to 6 are as follows: "BP" refers to acrylic adhesive polymers A-1 to A-7 obtained in Synthesis Examples 1 to 7, and "vinyl polymer" refers to vinyl polymers C-1 to C-7 obtained in Synthesis Examples 8 to 14. B-1: Toyobo Co., Ltd., Hardlen PMA-TE, maleic anhydride modified polyolefin, modification rate 1.8%, melting point 90°C, Mw 60,000) B-2: Toyobo Co., Ltd., Hardlen PMA-TZ, maleic anhydride modified polyolefin, modification rate 1.4%, melting point 90°C, Mw 115,000) B-3: Toyobo Co., Ltd., Hardlen 13-LP, chlorinated polyolefin, modification rate 26%, melting point 79°C, Mw 200,000) B-4: Toyobo Co., Ltd., Hardlen DX-523, chlorinated polyolefin, modification rate 23%, melting point 84°C, Mw 100,000) B-5: Nippon Paper Industries Co., Ltd., Superchlorine 814HA, chlorinated polypropylene, modification rate 41%, melting point 60°C, Mw 10,000-30,000) B-6: Nippon Paper Industries Co., Ltd. Superchlorine 360T, chlorinated polyolefin, modification rate 31%, melting point 60°C, Mw 0.5-20,000) B-7: Toyobo Co., Ltd. Hardlen HM-21P, 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-8: Toyobo Co., Ltd. Hardlen M28-P, maleic anhydride modified chlorinated polyolefin, modification rate: chlorination modification rate 20%, maleic anhydride modification rate 1.7%, melting point 75°C, Mw 68,000) B-9: Toyobo Co., Ltd. Hardlen F-2P, maleic anhydride modified chlorinated polyolefin, modification rate: chlorination modification rate 20%, maleic anhydride modification rate 1.7%, melting point 70°C, Mw 68,000) B-10: Toyobo Co., Ltd. Hardlen F-7P, maleic anhydride modified chlorinated polyolefin, modification rate: chlorination modification rate 20%, maleic anhydride modification rate 1.2%, melting point 70°C, Mw 110,000) B-11: Nippon Paper Industries Co., Ltd. S-7083S, acrylic modified polyolefin, modification rate 20%, melting point 72°C, glass transition point 20°C, Mw 30,000) B-12: Nippon Paper Industries Co., Ltd. S-7098S, acrylic modified polyolefin, modification rate 70%, melting point 62°C, glass transition point 25°C, Mw 60,000)Crosslinking agent D-110N: Takenate D-110N manufactured by Mitsui Chemicals, Inc., a trimethylolpropane-modified meta-xylylene diisocyanate, solids concentration 75% by mass, NCO content 11.5% Crosslinking agent D-101E: Takenate D-101E manufactured by Mitsui Chemicals, Inc., a trimethylolpropane-modified tolylene diisocyanate, solids concentration 75% by mass, NCO content 13.3% Tol: toluene CH: cyclohexane AcOBu: butyl acetate AcOEt: ethyl acetate Tol / CH: mixed solvent of toluene and cyclohexane (mass ratio Tol / CH = 75 / 25 to 80 / 20) AcOBu / CH: mixed solvent of butyl acetate and cyclohexane (mass ratio AcOBu / CH = 75 / 25 to 80 / 20) AcOEt / CH: mixed solvent of ethyl acetate and cyclohexane (mass ratio AcOEt / CH = 75 / 25) Tol / CH / AcOBu: a mixed solvent of toluene, cyclohexane, and butyl acetate (mass ratio Tol / CH / AcOBu = 60 / 25 / 15)

[0178] From the results of Tables 3 to 6, the pressure-sensitive adhesive compositions of Examples 1 to 17 had high peel strengths at 23°C and 80°C against PP board, ABS board, PC board, PMMA board and nylon film, and had good adhesion at room temperature and at high temperatures against both low-polarity and high-polarity substrates.

[0179] In contrast, the PSA compositions of Comparative Examples 1 to 17, which contained a modified polyolefin together with an acrylic adhesive polymer but no vinyl polymer, tended to have inferior adhesion to highly polar substrates (ABS plate, PC plate, PMMA plate, and nylon film) at high temperatures compared to Examples 1 to 17. Furthermore, the PSA compositions of Comparative Example 18, which contained an acrylic adhesive polymer but no modified polyolefin or vinyl polymer, and Comparative Example 19, which contained a vinyl polymer together with an acrylic adhesive polymer but no modified polyolefin, exhibited inferior adhesion to both low-polarity and high-polarity substrates at high temperatures.

[0180] From the above results, it has become clear that a pressure-sensitive adhesive composition containing an acrylic pressure-sensitive adhesive polymer (A), a modified polyolefin, and a vinyl polymer (C) can form a pressure-sensitive adhesive layer that has excellent adhesion both at room temperature and at high temperatures, and that has excellent adhesion to both low-polarity substrates and high-polarity substrates.

[0181] The present invention is not limited to the above-described embodiments, and encompasses various modifications and equivalent modifications within the scope of the spirit of the present invention. Therefore, in light of the above teachings, various combinations and forms, as well as other combinations and forms including only one element, more than one element, or less than one element, are to be understood as falling within the scope and spirit of the present invention.

Claims

1. An adhesive composition containing: 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 a modified polyolefin and a modified polydiene; and a vinyl polymer (excluding the above-mentioned modified polymer) having a structural unit derived from a (meth)acrylic monomer, a glass transition temperature of 45°C or higher, and a number average molecular weight of 500 or more and less than 50,000.

2. The adhesive composition according to claim 1, wherein the concentration of the modified polymer in the surface layer portion of the adhesive layer formed using the adhesive composition is higher than the concentration of the modified polymer in the entire adhesive layer.

3. The content of the modified polymer is 0.1 part by mass or more and 50 parts by mass or less with respect to 100 parts by mass of the acrylic pressure-sensitive adhesive polymer. When the adhesive composition is applied to a separator and dried to obtain an adhesive layer, the mass fraction of the modified polymer on the surface of the adhesive layer obtained by X-ray photoelectron spectroscopy is larger than the mass fraction of the modified polymer in the entire adhesive composition. The adhesive composition according to claim 1.

4. The adhesive composition according to claim 1, wherein the weight average molecular weight of the acrylic pressure-sensitive adhesive polymer is 100,000 or more.

5. The adhesive composition according to claim 1, wherein the modification rate of the modified polymer is 80% or less.

6. The adhesive composition according to claim 1, wherein the glass transition temperature of the acrylic pressure-sensitive adhesive polymer is -50°C or higher.

7. The adhesive composition according to claim 1, wherein the vinyl polymer has a structural unit derived from at least one selected from the group consisting of an aliphatic cyclic vinyl monomer and an aromatic vinyl monomer.

8. The adhesive composition according to claim 1, further containing a crosslinking agent.

9. The acrylic pressure-sensitive adhesive polymer contains, based on all the structural units of the acrylic pressure-sensitive adhesive polymer, 30% by mass or more of a structural unit derived from at least one selected from the group consisting of an alkyl (meth)acrylate having an alkyl group having 1 to 4 carbon atoms in the ester moiety and an alkoxyalkyl (meth)acrylate having an alkoxyalkyl group having 3 or 4 carbon atoms. The adhesive composition according to claim 1.

10. The pressure-sensitive adhesive composition according to claim 1, wherein the modified polymer is at least one selected from the group consisting of an acid-modified polyolefin, a chlorinated polyolefin, an acid-modified chlorinated polyolefin, an acrylic-modified polyolefin, and an acrylic-modified chlorinated polyolefin.

11. The pressure-sensitive adhesive composition according to claim 1, wherein the modified polymer is modified with at least one selected from the group consisting of a carboxylic acid, a carboxylic anhydride, a (meth)acrylate ester, and chlorine.

12. The pressure-sensitive adhesive composition according to claim 1, wherein the pre-modified polymer has a melting point, and the melting point of the modified polymer is 20°C or higher and 130°C or lower.

13. The pressure-sensitive adhesive composition according to claim 1, further containing a solvent, wherein a haze value of an adhesive layer having a thickness of 50 μm formed by applying the pressure-sensitive adhesive composition onto a substrate and removing the solvent is 3.0% or higher.

14. A pressure-sensitive adhesive sheet comprising an adhesive layer formed from the pressure-sensitive adhesive composition according to any one of claims 1 to 13.

15. The pressure-sensitive adhesive sheet according to claim 14, which is a decorative film.

16. A decorated molded article, wherein the adhesive layer provided in the pressure-sensitive adhesive sheet according to claim 15 is adhered to a molded article.

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