Active energy ray-curable adhesive composition and adhesive sheet

Abstract

Disclosed is an active energy ray-curable adhesive composition which does not contain a compound having two or more reactive unsaturated bonds in each molecule and which contains an acrylic adhesive polymer (A) that has at least one group or atom that is selected from the group consisting of an ether group, a hydroxyl group, an aliphatic tertiary carbon atom, a secondary amino group and a tertiary amino group in a side chain, wherein: the acrylic adhesive polymer (A) contains a structural unit (U1) that has a hydrogen abstraction type photopolymerization initiator structure; the content ratio of the structural unit (U1) in the acrylic adhesive polymer (A) is 0.1% by mass to 50% by mass with respect to all structural units of the acrylic adhesive polymer (A); and the content of a crosslinking agent is 0 part by mass to 3 parts by mass with respect to 100 parts by mass of the content of the acrylic adhesive polymer (A).

Description

Active energy ray-curable adhesive composition and adhesive sheet

[0001] [Cross-reference to related applications] This application claims priority to Japanese Patent Application No. 2023-108814, filed on June 30, 2023, the entire contents of which are incorporated herein by reference. The present disclosure relates to an active energy ray-curable pressure-sensitive adhesive composition and a pressure-sensitive adhesive sheet.

[0002] Pressure-sensitive adhesives are processed into various forms such as tapes, labels, etc. and are used in a wide range of applications. In recent years, in response to advances in electronics technology, pressure-sensitive adhesive sheets have also been used in the manufacturing process of semiconductor devices for the purposes of improving the handling properties during semiconductor manufacturing and further improving the performance of semiconductor elements (see, for example, Patent Document 1 and Patent Document 2).

[0003] Patent Literature 1 discloses a heat-resistant temporary adhesive tape having an adhesive layer formed thereon, the adhesive layer being made of an adhesive layer-forming material containing an acrylic polymer, an energy ray-polymerizable oligomer, a polymerization initiator, and a crosslinking agent, the material having a weight loss rate of the polymerization initiator measured by thermogravimetry of not more than a predetermined value. Patent Literature 2 also discloses an adhesive tape having an adhesive layer containing a (meth)acrylic polymer and a photopolymerization initiator having a molar absorption coefficient at a wavelength of 385 nm of not less than a predetermined value. These adhesive tapes are used for the purposes of temporarily fixing electronic components or protecting their surfaces, and when the need for fixing electronic components or surface protection is no longer required, the adhesive strength is weakened by irradiation with active energy rays, resulting in easy peelability.

[0004] In recent years, as semiconductor devices have become thinner and more powerful, new semiconductor manufacturing technologies have been proposed, such as Fan Out Wafer Level Package (FOWLP) technology and three-dimensional integrated circuit (3D-IC) technology. FOWLP is a technology that forms a rewiring layer on a semiconductor wafer and extends terminals to the outside of the semiconductor chip, which is said to enable even higher performance and thinner semiconductor devices.

[0005] JP 2012-31316 A JP 2016-89045 A

[0006] In the semiconductor manufacturing process using FOWLP, an adhesive tape is attached to a support substrate such as glass, a semiconductor chip is placed on the adhesive layer of the adhesive tape, and the semiconductor chip is temporarily fixed to the support substrate. Various lamination processes are then performed to form a laminate on the support substrate, and the laminate including the semiconductor chip is then peeled off from the support substrate. This method makes it possible to further reduce the thickness and improve the performance of semiconductor devices while improving the handleability during semiconductor manufacturing. Furthermore, a method of peeling off a laminate including a semiconductor chip from a support substrate using active energy rays, in which the adhesive strength of the adhesive layer is weakened by irradiation with active energy rays, can simplify the peeling process and is also industrially useful.

[0007] The adhesive tape used in the semiconductor manufacturing process is required to exhibit high adhesion to the adherend when a laminate is formed on a support substrate, while at the same time allowing the laminate including the semiconductor chip to be easily peeled from the support substrate when the laminate is peeled from the support substrate. Furthermore, the semiconductor manufacturing process may involve high-temperature heat treatment, for example, at 200°C or higher, and the adhesive tape used in the semiconductor manufacturing process is required to be resistant to lifting or foaming even during high-temperature heat treatment and to have excellent heat resistance.

[0008] The present disclosure has been made in view of the above circumstances, and one object of the present disclosure is to provide an active energy ray-curable pressure-sensitive adhesive composition that exhibits easy peelability upon irradiation with active energy rays and is capable of forming a pressure-sensitive adhesive layer that has excellent heat resistance. Another object of the present disclosure is to provide a pressure-sensitive adhesive sheet that exhibits easy peelability upon irradiation with active energy rays and has excellent heat resistance.

[0009] The present inventors have conducted extensive research to solve the above problems, and have focused on promoting the formation of a crosslinked structure by irradiation with active energy rays, thereby improving the ease of peeling of the pressure-sensitive adhesive layer. Based on this focus, they have found that when a specific structure is introduced into a polymer, the ease of peeling can be improved while ensuring the heat resistance of the pressure-sensitive adhesive layer. Specifically, the present disclosure provides the following active energy ray-curable pressure-sensitive adhesive composition and pressure-sensitive adhesive sheet.

[0010] [1] An active energy ray-curable pressure-sensitive adhesive composition, comprising an acrylic adhesive polymer (A) that does not contain a compound having two or more reactive unsaturated bonds in one molecule and has at least one group selected from the group consisting of an ether group, a hydroxyl group, an aliphatic tertiary carbon, a secondary amino group, and a tertiary amino group in a side chain, wherein the acrylic adhesive polymer (A) contains a structural unit (U1) having a hydrogen abstraction type photopolymerization initiator structure, the content of the structural unit (U1) in the acrylic adhesive polymer (A) being 0.1% by mass or more and 50% by mass or less based on all structural units of the acrylic adhesive polymer (A), and the content of a crosslinking agent being 0 parts by mass or more and 3 parts by mass or less based on 100 parts by mass of the content of the acrylic adhesive polymer (A). [2] The active energy ray-curable pressure-sensitive adhesive composition according to [1], wherein the acrylic adhesive polymer (A) comprises a structural unit (U2) derived from a (meth)acrylic monomer having at least one selected from the group consisting of an ether group, a hydroxyl group, an aliphatic tertiary carbon (excluding the carbon atom constituting the carbon-carbon double bond in a methacryloyl group), a secondary amino group, and a tertiary amino group, and the content of the structural unit (U2) in the acrylic adhesive polymer (A) is 10 mass% or more based on the total structural units of the acrylic adhesive polymer (A). [3] The active energy ray-curable pressure-sensitive adhesive composition according to [1] or [2], wherein the acrylic adhesive polymer (A) comprises a structural unit derived from a monomer represented by the following formula (1): CH ２ =CR １ -C(=O)O-(R ２ O) ｎ -R ３ ...(1) (In formula (1), R １ represents a hydrogen atom or a methyl group, R ２ represents a linear or branched alkylene group having 2 to 6 carbon atoms; R ３represents a hydrogen atom or a monovalent hydrocarbon group having 1 to 20 carbon atoms, and n represents an integer of 2 to 100.) [4] The active energy ray-curable pressure-sensitive adhesive composition according to any one of [1] to [3], wherein the acrylic adhesive polymer (A) has a glass transition temperature of -70°C or higher and 0°C or lower. [5] The active energy ray-curable pressure-sensitive adhesive composition according to any one of [1] to [4], wherein the acrylic adhesive polymer (A) has a weight average molecular weight of 100,000 or higher. [6] The active energy ray-curable pressure-sensitive adhesive composition according to any one of [1] to [5], wherein the acrylic adhesive polymer (A) contains structural units derived from at least one monomer selected from the group consisting of (meth)acrylic monomers having a boiling point of 150°C or lower at atmospheric pressure and (meth)acrylic monomers having a boiling point of 200°C or higher at atmospheric pressure in an amount of 50 mass% or more, based on the total structural units of the acrylic adhesive polymer (A). [7] The active energy ray-curable pressure-sensitive adhesive composition according to any one of [1] to [6], which contains the crosslinking agent. [8] The active energy ray-curable pressure-sensitive adhesive composition according to any one of [1] to [7], which is used in a semiconductor manufacturing process. [9] A pressure-sensitive adhesive sheet comprising a pressure-sensitive adhesive layer formed from the active energy ray-curable pressure-sensitive adhesive composition according to any one of [1] to [8].

[10] The pressure-sensitive adhesive sheet according to [9], in which the pressure-sensitive adhesive layer has a gel fraction based on the acrylic pressure-sensitive adhesive polymer (A) of 90% or less before being attached to an adherend.

[11] The pressure-sensitive adhesive sheet according to [9] or

[10] , in which the pressure-sensitive adhesive layer has a weight loss rate of 5% by weight or less at 200°C, measured by thermogravimetry under conditions of a heating rate of 20°C / min and a heating range of 25 to 350°C.

[12] The pressure-sensitive adhesive sheet according to any one of [9] to

[11] , wherein the ratio (S2 / S1) of the peel strength (S1) before the pressure-sensitive adhesive sheet attached to an adherend is irradiated with active energy rays to the peel strength (S2) after the pressure-sensitive adhesive sheet attached to an adherend is irradiated with active energy rays to increase the gel fraction based on the acrylic adhesive polymer (A) of the pressure-sensitive adhesive layer to more than 90% is 0.7 or less.

[0011] According to the present disclosure, a pressure-sensitive adhesive layer and a pressure-sensitive adhesive sheet can be obtained that can be easily peeled off from an adherend by irradiation with active energy rays and have excellent heat resistance.

[0012] Fig. 1 is a diagram showing an example of a pressure-sensitive adhesive sheet, and Fig. 2 is a diagram showing an example of a method of using the pressure-sensitive adhesive sheet.

[0013] The present disclosure will be described in detail below. In this specification, "(meth)acrylic" means acrylic and / or methacrylic, and "(meth)acrylate" means acrylate and / or methacrylate.

[0014] <<Active Energy Ray-Curable Pressure-Sensitive Adhesive Composition>> The active energy ray-curable pressure-sensitive adhesive composition of the present disclosure (hereinafter also referred to as "the composition") contains an acrylic adhesive polymer (A) having a hydrogen abstraction photopolymerization initiator structure, has a crosslinking agent content within a predetermined range, and does not contain a compound having two or more reactive unsaturated bonds per molecule (hereinafter also referred to as "reactive unsaturated compound"). A pressure-sensitive adhesive layer formed from the composition exhibits high adhesive strength when bonded to an adherend, but the adhesive strength decreases when the pressure-sensitive adhesive layer is irradiated with active energy rays after bonding the pressure-sensitive adhesive layer to the adherend, thereby exhibiting easy peelability. Below, we will first explain the acrylic adhesive polymer (A) contained in the composition and the components that are blended as needed.

[0015] (Acrylic adhesive polymer (A)) The acrylic adhesive polymer (A) is a polymer mainly composed of structural units derived from (meth)acrylic monomers and has adhesive properties. In this specification, the term "the acrylic adhesive polymer (A) is "mainly" composed of (meth)acrylic monomers" means that the proportion of structural units derived from (meth)acrylic monomers is preferably 50% by mass or more relative to all structural units derived from monomers constituting the acrylic adhesive polymer (A) (hereinafter also referred to as "total structural units" or "total monomer units"). From the viewpoint of increasing the adhesive strength of the acrylic adhesive polymer (A), the proportion of structural units derived from (meth)acrylic monomers 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.

[0016] The acrylic adhesive polymer (A) is a polymer having a hydrogen abstraction type photopolymerization initiator structure in a side chain, and includes a structural unit having the hydrogen abstraction type photopolymerization initiator structure (hereinafter also referred to as "structural unit (U1)"). The hydrogen abstraction type photopolymerization initiator structure of the structural unit (U1) is a structure derived from a compound that generates radicals by abstracting hydrogen from other molecules when irradiated with active energy rays (i.e., a hydrogen abstraction type photopolymerization initiator). Examples of active energy rays include ultraviolet rays, visible light, and electron beams, and ultraviolet rays or electron beams are preferred.

[0017] The hydrogen abstraction type photopolymerization initiator structure of the structural unit (U1) can be a structure derived from a known hydrogen abstraction type radical polymerization initiator. Specific examples of hydrogen abstraction type photopolymerization initiators include benzophenone, 2-methylbenzophenone, 3-methylbenzophenone, 4-methylbenzophenone, 2,4,6-trimethylbenzophenone, 4-phenylbenzophenone, 4-(methylphenylthio)phenylphenylmethane, methyl-2-benzophenone, 1-[4-(4-benzoylphenylsulfanyl)phenyl]-2-methyl-2-(4-methylphenylsulfonyl)propan-1-one, 4,4'-bis(dimethylamino)benzophenone, 4,4'-bis(diethylamino)benzophenone, and 4-methoxy-4' benzophenones such as 1-dimethylaminobenzophenone; thioxanthones such as thioxanthone, 2-chlorothioxanthone, 2,4-diethylthioxanthone, isopropylthioxanthone, 1-chloro-4-propylthioxanthone, 3-[3,4-dimethyl-9-oxo-9H-thioxanthone-2-yl-oxy]-2-hydroxypropyl-N,N,N-trimethylammonium chloride, and fluorothioxanthone; as well as benzil ketal, anthraquinone, ethyl anthraquinone, phenanthrenequinone, xanthone, and hydroxyacetophenone. The structural unit (U1) may also have a structure derived from a commercially available hydrogen abstraction photopolymerization initiator, for example, trade names such as OMNIPOL BP, OMNIPOL TX, OMNIRAD ASA, OMNIRAD 4PBZ, OMNIRAD 2702, OMBBB, OMNIRAD BMS, OMNIRAD EMK, OMNIPOL DETX, OMNIRAD ITX, OMNIRAD EDB, OMNIRAD EHA, OMNIRAD BP Flasks, OMNIRAD 4MBZ Flasks, and ESACURE 3644 (all manufactured by IGM Resin).

[0018] Among these, the structural unit (U1) is preferably a structural unit having a benzophenone skeleton, in terms of high efficiency in generating radicals upon irradiation with active energy rays and excellent heat resistance.

[0019] The structural unit (U1) may be a structural unit derived from a (meth)acrylic monomer having a hydrogen abstraction type photopolymerization initiator structure. Such a (meth)acrylic monomer is commercially available. Specific examples thereof include MBP (manufactured by Shinryo Corporation) and the like.

[0020] In the acrylic adhesive polymer (A), the content ratio of the structural unit (U1) is 0.1 mass% or more and 50 mass% or less based on the total structural units of the acrylic adhesive polymer (A).If the content ratio of the structural unit (U1) is less than 0.1 mass%, there is a concern that the crosslinked structure formed by the acrylic adhesive polymer (A) cannot be sufficiently achieved when irradiated with active energy rays.Therefore, the content ratio of the structural unit (U1) is preferably 0.5 mass% or more, more preferably 1 mass% or more based on the total structural units of the acrylic adhesive polymer (A).

[0021] In order to prevent the pressure-sensitive adhesive layer from becoming brittle due to excessive formation of a crosslinked structure upon irradiation with active energy rays, the content of the structural unit (U1) is preferably 40 mass% or less, more preferably 35 mass% or less, even more preferably 30 mass% or less, still more preferably 20 mass% or less, and even more preferably 15 mass% or less, based on the total structural units of the acrylic pressure-sensitive adhesive polymer (A). As the structural unit (U1), one type may be used alone, or two or more types may be used in combination.

[0022] The acrylic adhesive polymer (A) has, together with the structural unit (U1), at least one selected from the group consisting of an ether group, a hydroxyl group, an aliphatic tertiary carbon, a secondary amino group, and a tertiary amino group in a side chain. It is believed that by forming a pressure-sensitive adhesive layer using such an acrylic adhesive polymer (A) and irradiating the pressure-sensitive adhesive layer with active energy rays, hydrogen is abstracted from the side chain portion of the acrylic adhesive polymer (A), and a crosslinked structure is formed via the hydrogen abstraction portion.

[0023] More specifically, when a pressure-sensitive adhesive layer formed from the present composition is irradiated with active energy rays, radicals are generated in the pressure-sensitive adhesive layer due to the hydrogen-abstraction photopolymerization initiator structure in the structural unit (U1). These radicals abstract hydrogen from the side chain portion of the acrylic pressure-sensitive adhesive polymer (A) (more specifically, from the C—H bond adjacent to the ether group, secondary amino group, or tertiary amino group in the side chain, the hydroxyl group, or the aliphatic tertiary carbon), generating carbon radicals and / or oxygen radicals. The radicals thus generated are thought to couple with each other, thereby forming a crosslinked structure. Furthermore, crosslinking between the side chains is thought to form a dense crosslinked structure in the pressure-sensitive adhesive layer, which is thought to reduce the adhesive strength of the pressure-sensitive adhesive sheet. In other words, after being bonded to an adherend, the pressure-sensitive adhesive sheet maintains high adhesive strength before being irradiated with active energy rays, and then, upon irradiation with active energy rays, sufficient crosslinked structures are formed between or within the molecules of the acrylic pressure-sensitive adhesive polymer (A), thereby exhibiting easy peelability.

[0024] Specifically, the acrylic adhesive polymer (A) preferably contains a structural unit (hereinafter also referred to as "structural unit (U2)") derived from a (meth)acrylic monomer having at least one selected from the group consisting of an ether group, a hydroxyl group, an aliphatic tertiary carbon (excluding the carbon atom constituting the carbon-carbon double bond in the methacryloyl group), a secondary amino group, and a tertiary amino group. Polymerization using such a monomer allows for easy introduction of at least one selected from the group consisting of an ether group, a hydroxyl group, an aliphatic tertiary carbon, a secondary amino group, and a tertiary amino group into the side chain of the polymer. As used herein, "aliphatic tertiary carbon" refers to a carbon atom bonded to one hydrogen atom and three carbon atoms, at least one of which constitutes an aliphatic hydrocarbon group. An ether group refers to a group in which one or more hydrogen atoms are directly bonded to at least one of the two carbon atoms bonded to the "-O-" in the "hydrocarbon group -O-hydrocarbon group."

[0025] Specific examples of the monomer that constitutes the structural unit (U2) include (meth)acrylic acid alkoxyalkyl esters, (meth)acrylic acid esters having an aliphatic tertiary carbon, (meth)acrylic acid hydroxyalkyl esters, polyalkylene glycol mono(meth)acrylates, and amino group-containing (meth)acrylic acid esters.

[0026] Specific examples of these include (meth)acrylic acid alkoxyalkyl esters, such as methoxymethyl (meth)acrylate, ethoxymethyl (meth)acrylate, methoxyethyl (meth)acrylate, ethoxyethyl (meth)acrylate, n-propoxyethyl (meth)acrylate, n-butoxyethyl (meth)acrylate, methoxypropyl (meth)acrylate, ethoxypropyl (meth)acrylate, n-propoxypropyl (meth)acrylate, n-butoxypropyl (meth)acrylate, methoxybutyl (meth)acrylate, ethoxybutyl (meth)acrylate, n-propoxybutyl (meth)acrylate, and n-butoxybutyl (meth)acrylate.

[0027] Specific examples of the (meth)acrylic acid ester having an aliphatic tertiary carbon include isobutyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, isooctyl (meth)acrylate, isononyl (meth)acrylate, methylcyclohexyl (meth)acrylate, tert-butylcyclohexyl (meth)acrylate, isobornyl (meth)acrylate, adamantyl (meth)acrylate, dicyclopentenyl (meth)acrylate, dicyclopentanyl (meth)acrylate, and EO-modified 2-ethylhexyl (meth)acrylate.

[0028] Specific examples of the hydroxyalkyl (meth)acrylate include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 3-hydroxybutyl (meth)acrylate, and 4-hydroxybutyl (meth)acrylate.

[0029] A specific example of the polyalkylene glycol mono(meth)acrylate is a monomer represented by the following formula (1): CH ２ =CR １ -C(=O)O-(R ２ O) ｎ -R ３ ...(1) (In formula (1), R １ represents a hydrogen atom or a methyl group, R ２ represents a linear or branched alkylene group having 2 to 6 carbon atoms; R ３ represents a hydrogen atom or a monovalent hydrocarbon group having 1 to 20 carbon atoms, and n represents an integer of 2 to 100.

[0030] R in the above formula (1) ３ is preferably an alkyl group or an aryl group from the viewpoint of availability of raw materials. n is preferably 2 to 50, more preferably 2 to 30, and even more preferably 2 to 10.

[0031] Further specific examples of polyalkylene glycol mono(meth)acrylates include polyethylene glycol mono(meth)acrylate, polypropylene glycol mono(meth)acrylate, polyethylene glycol-polypropylene glycol mono(meth)acrylate, polyethylene glycol-polytetraethylene 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. Commercially available polyalkylene glycol mono(meth)acrylates include, by product name, Aronix M-101A, M-102, M-113, M-120, and M-140 (all manufactured by Toagosei Co., Ltd.); Blenmar PP series, AP series, PME series, and AME series (all manufactured by NOF Corporation).

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

[0033] In terms of having a large number of hydrogen abstraction sites and being easily able to form a crosslinked structure by irradiation with active energy rays, the (meth)acrylic adhesive polymer (A) preferably contains a structural unit derived from at least one selected from the group consisting of an alkoxyalkyl (meth)acrylate ester, a hydroxyalkyl (meth)acrylate ester, and a monomer represented by the above formula (1), and more preferably contains at least a structural unit derived from a monomer represented by the above formula (1).

[0034] In the acrylic adhesive polymer (A), the content of the structural unit (U2) is preferably 10% by mass or more relative to the total structural units of the acrylic adhesive polymer (A), from the viewpoint of facilitating the formation of a crosslinked structure by irradiation with active energy rays. The content of the structural unit (U2) is more preferably 15% by mass or more, even more preferably 20% by mass or more, and even more preferably 25% by mass or more relative to the total structural units of the acrylic adhesive polymer (A). There is no particular upper limit for the content of the structural unit (U2), but from the viewpoint of improving adhesive performance, it is preferably 90% by mass or less, more preferably 85% by mass or less, even more preferably 80% by mass or less, even more preferably 75% by mass or less, and even more preferably 70% by mass or less relative to the total structural units of the acrylic adhesive polymer (A).

[0035] The acrylic adhesive polymer (A) may further contain structural units (hereinafter also referred to as "other structural units") different from the structural units (U1) and (U2). Examples of monomers constituting the other structural units include (meth)acrylic acid alkyl esters, aliphatic cyclic esters of (meth)acrylic acid, aromatic esters of (meth)acrylic acid, epoxy group-containing (meth)acrylic acid esters, silyl group-containing (meth)acrylic acid esters, unsaturated acid anhydrides, (meth)acrylamide or derivatives thereof, nitrile group-containing (meth)acrylic acid esters, aromatic vinyl compounds and imide group-containing vinyl compounds, and unsaturated carboxylic acids.

[0036] Specific examples of these include methyl (meth)acrylate, ethyl (meth)acrylate, isopropyl (meth)acrylate, n-propyl (meth)acrylate, n-butyl (meth)acrylate, tert-butyl (meth)acrylate, n-hexyl (meth)acrylate, n-octyl (meth)acrylate, n-nonyl (meth)acrylate, n-decyl (meth)acrylate, and lauryl (meth)acrylate.

[0037] Specific examples of the aliphatic cyclic esters of (meth)acrylic acid include cyclohexyl (meth)acrylate, cyclododecyl (meth)acrylate, etc. Specific examples of the 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.

[0038] Specific examples of epoxy group-containing (meth)acrylic acid esters include glycidyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate glycidyl ether, 3,4-epoxycyclohexylmethyl (meth)acrylate, etc. Specific examples of silyl group-containing (meth)acrylic acid esters include trimethoxysilylpropyl (meth)acrylate, triethoxysilylpropyl (meth)acrylate, methyldimethoxysilylpropyl (meth)acrylate, and dimethylmethoxysilylpropyl (meth)acrylate, etc. Specific examples of unsaturated acid anhydrides include maleic anhydride, itaconic anhydride, and citraconic anhydride.

[0039] Specific examples of (meth)acrylamide or a derivative thereof include (meth)acrylamide, 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.

[0040] Specific examples of the nitrile group-containing (meth)acrylic acid ester 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.

[0041] Specific 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, as well as vinylnaphthalene.

[0042] Specific 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 Examples of the other structural units include citraconic acid compounds such as N-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. The acrylic adhesive polymer (A) may contain one or more types of other structural units.

[0043] Specific examples of unsaturated carboxylic acids include (meth)acrylic acid, maleic acid, fumaric acid, itaconic acid, crotonic acid, citraconic acid, cinnamic acid, and monoalkyl esters of unsaturated dicarboxylic acids (monoalkyl esters of maleic acid, fumaric acid, itaconic acid, citraconic acid, etc.).

[0044] From the viewpoint of improving adhesive performance, the acrylic adhesive polymer (A) preferably contains a structural unit derived from a (meth)acrylic acid alkyl ester. Furthermore, from the viewpoint of increasing the elastic modulus of the acrylic adhesive polymer (A) and improving heat resistance, the monomer constituting the structural unit derived from a (meth)acrylic acid alkyl ester is preferably a (meth)acrylic acid alkyl ester having an alkyl moiety with 1 to 8 carbon atoms, more preferably a (meth)acrylic acid alkyl ester having an alkyl moiety with 1 to 4 carbon atoms.

[0045] In the acrylic adhesive polymer (A), the proportion of the structural unit derived from (meth)acrylic acid alkyl ester is preferably 3 mass% or more, more preferably 5 mass% or more, and even more preferably 10 mass% or more, based on the total structural units of the acrylic adhesive polymer (A), from the viewpoint of improving the adhesive performance of the acrylic adhesive polymer (A). In the acrylic adhesive polymer (A), the upper limit of the proportion of the structural unit derived from (meth)acrylic acid alkyl ester is not particularly limited, but from the viewpoint of sufficiently performing crosslinking formation by irradiation with active energy rays, it is preferably 95 mass% or less, more preferably 90 mass% or less, and even more preferably 80 mass% or less, based on the total structural units of the acrylic adhesive polymer (A).

[0046] Regarding the monomers constituting the acrylic adhesive polymer (A), from the viewpoint of suppressing foaming and peeling from the adhesive layer when the pressure-sensitive adhesive sheet is subjected to a thermal load, the acrylic adhesive polymer (A) preferably contains a structural unit (hereinafter also referred to as "structural unit (W)") derived from at least one monomer selected from the group consisting of (meth)acrylic monomers having a boiling point of 150°C or less and (meth)acrylic monomers having a boiling point of 200°C or more. Specifically, the proportion of the structural unit (W) relative to the total structural units of 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, even more preferably 60% by mass or more, even more preferably 70% by mass or more, and even more preferably 80% by mass or more. Note that, in this specification, the boiling points of the monomers are predicted values ​​calculated using Fujitsu Limited's Scientific Research Information Management Solution (ACD / Labs). Note that, in this specification, the boiling points are values ​​at atmospheric pressure.

[0047] The acrylic adhesive polymer (A) preferably contains a structural unit (hereinafter also referred to as "structural unit (W1)") derived from a (meth)acrylic monomer having a boiling point of 150°C or less, from the viewpoint of increasing the elastic modulus of the acrylic adhesive polymer (A) and improving its heat resistance, and from the viewpoint of easily volatilizing the polymer during the production of the adhesive sheet and thereby suppressing foaming from the adhesive sheet. Specifically, the proportion of the structural unit (W1) is preferably 10% by mass or more, more preferably 20% by mass or more, and even more preferably 30% by mass or more, based on the total structural units of the acrylic adhesive polymer (A). On the other hand, from the viewpoint of exhibiting excellent peelability upon irradiation with active energy rays, the proportion of the structural unit (W1) is preferably 80% by mass or less, more preferably 70% by mass or less, and even more preferably 65% ​​by mass or less, based on the total structural units of the acrylic adhesive polymer (A).

[0048] In addition, the acrylic adhesive polymer (A) preferably contains a structural unit derived from a (meth)acrylic monomer having a boiling point of 200°C or higher (hereinafter also referred to as "structural unit (W2)"), from the viewpoint of exhibiting excellent peelability upon irradiation with active energy rays and being able to suppress volatilization of a monomer (i.e., unreacted monomer) contained in the pressure-sensitive adhesive layer when subjected to a thermal load. Specifically, the proportion of the structural unit (W2) is preferably 10% by mass or more, more preferably 20% by mass or more, and even more preferably 30% by mass or more, based on the total structural units of the acrylic adhesive polymer (A). In addition, from the viewpoint of improving adhesive performance, the proportion of the structural unit (W2) is preferably 80% by mass or less, more preferably 70% by mass or less, and even more preferably 65% ​​by mass or less, based on the total structural units of the acrylic adhesive polymer (A).

[0049] In producing the acrylic adhesive polymer (A), a monomer having a crosslinkable functional group (hereinafter also referred to as a "crosslinkable group-containing monomer") may be used so that the acrylic adhesive polymer (A) contains a structural unit having a crosslinkable functional group. By introducing a structural unit having a crosslinkable functional group into the acrylic adhesive polymer (A), it is possible to easily adjust the gel fraction of the pressure-sensitive adhesive layer.

[0050] 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 this tends to increase the adhesive strength of the acrylic adhesive polymer (A), 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 8 carbon atoms is more preferred.

[0051] When a structural unit having a crosslinkable functional group is introduced into the acrylic adhesive polymer (A), the content of the structural unit having a crosslinkable functional group 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, based on the total structural units of the acrylic adhesive polymer (A). By making the content of the structural unit having a crosslinkable functional group in the acrylic adhesive polymer (A) 0.1% by mass or more, a crosslinked structure can be appropriately formed, thereby suppressing the flow of the pressure-sensitive adhesive layer. In the acrylic adhesive polymer (A), the upper limit of the content of the structural unit having a crosslinkable functional group is not particularly limited, but from the viewpoint of ensuring the adhesive performance of the obtained pressure-sensitive 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, based on the total structural units of the acrylic adhesive polymer (A).

[0052] - 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.

[0053] In the case of the solution polymerization method, 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 polymerize.

[0054] The method of feeding each raw material including the monomer may be a batch-type initial lump-sum feeding in which all raw materials are fed at once, a semi-continuous feeding in which at least some 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.

[0055] Examples of organic solvents used in solution polymerization include cyclic ethers such as tetrahydrofuran and dioxane, aromatic hydrocarbon compounds such as benzene, toluene, and xylene, esters such as ethyl acetate and butyl acetate, ketones such as acetone, methyl ethyl ketone, and cyclohexanone, and alcohols such as methyl orthoformate, methyl orthoacetate, methanol, ethanol, and isopropanol. One or more of these organic solvents can be used. The amount of organic solvent used is, for example, 1 to 50% by mass of the total amount of monomers used in polymerization relative to the total amount of the organic solvent and the monomers.

[0056] 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. An azo compound is preferred. 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.

[0057] 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).

[0058] 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.

[0059] 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.

[0060] Glass Transition Temperature The glass transition temperature (Tg) of the acrylic adhesive polymer (A) is preferably in the range of -80°C or higher and 10°C or lower. If the Tg of the acrylic adhesive polymer (A) is -80°C or higher, this is preferable 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 increasing the adhesiveness of the pressure-sensitive adhesive layer, the Tg of the acrylic adhesive polymer (A) is more preferably -70°C or higher, even more preferably -60°C or higher, and even more preferably -55°C or higher.

[0061] On the other hand, if the Tg of the acrylic adhesive polymer (A) is 10°C or less, it is preferable in that a pressure-sensitive adhesive sheet with good conformability to the adherend can be obtained. The upper limit of the Tg of the acrylic adhesive polymer (A) is more preferably 5°C or less, even more preferably 0°C or less, still more preferably -5°C or less, and particularly preferably -10°C or less. The preferred range of the Tg of the acrylic adhesive polymer (A) is more preferably -80°C or more and 5°C or less, even more preferably -70°C or more and 0°C or less.

[0062] 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 selected arbitrarily by changing the type and composition of the constituent monomers, etc.

[0063] Molecular Weight Characteristics The weight average molecular weight (Mw) of the acrylic adhesive polymer (A) is preferably 100,000 or more from the viewpoint of exhibiting sufficient cohesive strength and good adhesiveness. When the Mw of the acrylic adhesive polymer (A) is 100,000 or more, sufficient adhesiveness and solvent resistance can be ensured. The Mw of the acrylic adhesive polymer (A) is more preferably 120,000 or more, even more preferably 150,000 or more, and even more preferably 200,000 or more.

[0064] The upper limit of the Mw of the acrylic adhesive polymer (A) is not particularly limited, but from the viewpoint of ensuring good coating properties and handling when forming a pressure-sensitive adhesive sheet and further 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 range of the acrylic adhesive polymer (A) is preferably 100,000 or more and 3,000,000 or less, more preferably 150,000 or more and 2,000,000 or less, and even more preferably 200,000 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).

[0065] The molecular weight distribution (Mw / Mn) of the acrylic adhesive polymer (A), expressed as the ratio of Mw to the number average molecular weight (Mn), is preferably 10.0 or less, more preferably 9.0 or less, from the viewpoint of easily obtaining good adhesive properties and suppressing the 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. In this specification, the Mw and Mn of the polymer are values ​​calculated in terms of standard polystyrene obtained using gel permeation chromatography (GPC).

[0066] (Reactive Unsaturated Compound) The present composition is substantially free of compounds having two or more reactive unsaturated bonds in one molecule (reactive unsaturated compounds). Reactive unsaturated compounds have two or more unsaturated bonds (specifically, carbon-carbon unsaturated bonds) in one molecule that react upon irradiation with active energy rays, and upon irradiation with active energy rays, the reactive unsaturated compounds react with each other to form a crosslinked structure in the pressure-sensitive adhesive layer. Examples of reactive unsaturated compounds include compounds having two or more carbon-carbon unsaturated bonds in one molecule, and specific examples thereof include polyfunctional (meth)acrylic compounds and polyfunctional vinyl compounds. When a reactive unsaturated compound is further blended into the present composition, a pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer formed from this composition may undergo a reaction of the reactive unsaturated compound in the pressure-sensitive adhesive layer upon application of a heat load (e.g., about 200°C), resulting in the formation of a crosslinked structure, resulting in an unintended decrease in strength of the pressure-sensitive adhesive layer, or the reactive unsaturated compound itself may volatilize, resulting in a decrease in heat resistance. However, in this specification, the term "free of reactive unsaturated compounds" does not exclude the presence of trace amounts of reactive unsaturated compounds in the composition to the extent that the effects of the present disclosure are not impaired. Specifically, the content of reactive unsaturated compounds in the composition is preferably 0.2% by mass or less, more preferably 0.1% by mass or less, and even more preferably 0.05% by mass or less, based on the total amount of the composition.

[0067]

[0013] The present composition differs from so-called syrup-type active energy ray-curable pressure-sensitive adhesive compositions in that it does not contain a reactive unsaturated compound. Here, the syrup-type active energy ray-curable pressure-sensitive adhesive composition contains a polymer component that will constitute a part of the acrylic adhesive polymer in the pressure-sensitive adhesive layer and a monomer component that will constitute the remainder. The acrylic adhesive polymer, which is the main component of the pressure-sensitive adhesive layer, is produced by irradiating the active energy ray-curable pressure-sensitive adhesive composition with active energy rays. At least one of the monomer components contained in such a syrup-type active energy ray-curable pressure-sensitive adhesive composition corresponds to the "reactive unsaturated compound" in the present disclosure.

[0068] (Other Components) The present composition may further contain components other than the acrylic adhesive polymer (A) (hereinafter also referred to as "other components"), as long as the effects of the present disclosure are not impaired. Examples of other components include a hydrogen abstraction photopolymerization initiator, a solvent, a crosslinking agent, a tackifier, and a plasticizer.

[0069] Hydrogen Abstraction Photopolymerization Initiator In order to further increase the crosslinking efficiency in the pressure-sensitive adhesive layer, a hydrogen abstraction photopolymerization initiator may be blended into the composition in addition to the acrylic adhesive polymer (A). As the hydrogen abstraction photopolymerization initiator, a known hydrogen abstraction radical polymerization initiator can be used. Specific examples of the hydrogen abstraction photopolymerization initiator include the specific examples of the hydrogen abstraction photopolymerization initiators exemplified in the description of the structural unit (U1) and commercially available products.

[0070] In the present composition, the content of the hydrogen abstraction photopolymerization initiator is preferably 30 parts by mass or less relative to 100 parts by mass of the acrylic adhesive polymer (A). From the viewpoint of suppressing embrittlement of the pressure-sensitive adhesive layer due to excessive formation of crosslinked structures upon irradiation with active energy rays, the amount of the hydrogen abstraction photopolymerization initiator is more preferably 20 parts by mass or less, and even more preferably 15 parts by mass or less, relative to 100 parts by mass of the acrylic adhesive polymer (A). As the hydrogen abstraction photopolymerization initiator, one type may be used alone, or two or more types may be used in combination.

[0071] Solvent: The present composition is preferably a solvent-based pressure-sensitive adhesive composition further containing a solvent. The solvent contained in the present composition is preferably an organic solvent capable of dissolving the acrylic pressure-sensitive adhesive polymer (A). Specific examples of the organic solvent include aprotic polar solvents, phenolic solvents, alcoholic solvents, ester solvents, ketone solvents, ether solvents, and hydrocarbon solvents. The organic solvent may be one of these solvents or a mixed solvent of two or more of these solvents. The solvent contained in the present composition is preferably at least one selected from the group consisting of ethyl acetate, butyl acetate, ethyl methyl ketone, and toluene.

[0072] Crosslinking Agent When the acrylic adhesive polymer (A) has a crosslinkable functional group, a crosslinking agent (curing agent) capable of reacting with the crosslinkable functional group may be blended into the composition to facilitate adjustment of the gel fraction of the adhesive layer formed using the composition. Examples of the crosslinkable functional group include a hydroxyl group and a carboxyl group, preferably a hydroxyl group. Examples of the crosslinking agent include a compound that does not have a reactive unsaturated bond, such as 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, and a butylated melamine compound. Among these, an isocyanate compound is preferred because it can form an adhesive layer with higher cohesive strength.

[0073] 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.

[0074] Examples of isocyanate compounds include 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; 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.

[0075] 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).

[0076] From the viewpoint of improving the adhesive performance and conformability of the pressure-sensitive adhesive layer formed using the composition in a well-balanced manner, the content of the crosslinking agent in the composition is preferably 0 to 5 parts by mass, more preferably 0 to 3 parts by mass, even more preferably 0 to 2 parts by mass, still more preferably 0 to 1 part by mass, and still more preferably 0 to 0.8 parts by mass, relative to 100 parts by mass of the content of the acrylic adhesive polymer (A).

[0077] Tackifier The present composition may further 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 0 to 20 parts by mass, more preferably 0 to 10 parts by mass, and even more preferably 0 to 5 parts by mass, per 100 parts by mass of the acrylic adhesive polymer (A).

[0078] 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.

[0079] The content of the plasticizer is preferably 0 to 20 parts by mass, more preferably 0 to 10 parts by mass, and even more preferably 0 to 5 parts by mass, based on 100 parts by mass of the acrylic adhesive polymer (A).

[0080] Other additives that may be blended into the composition include, for example, an intramolecular cleavage-type photopolymerization initiator, an antioxidant, an ultraviolet absorber, an antiaging agent, a flame retardant, an antifungal agent, a silane coupling agent, a filler, a colorant, etc. The content of the additive can be appropriately set depending on the various compounds within a range that does not impair the effects of the present disclosure.

[0081] When the present composition is a solvent-based composition, the solids concentration in the PSA 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 present composition is more preferably 5 to 50 mass%, and even more preferably 10 to 45 mass%.

[0082] The viscosity of the present composition is preferably 500 to 10,000 mPa·s. A viscosity of 10,000 mPa·s or less ensures good coatability. Furthermore, the present composition can be used as is without diluting it to a viscosity suitable for coating, resulting in good handleability. From these perspectives, the viscosity of the present composition is more preferably 8,000 mPa·s or less, and even more preferably 6,000 mPa·s or less. Furthermore, from the viewpoint of preventing the film thickness from becoming too thin, the lower limit of the viscosity of the present composition is more preferably 1,000 mPa·s or more, and even more preferably 1,500 mPa·s or more. The viscosity of the pressure-sensitive adhesive composition is a value measured at 25°C using a Brookfield viscometer on a pressure-sensitive adhesive composition with a solids concentration of 25%.

[0083] <<Adhesive Sheet>> The adhesive sheet of the present disclosure (hereinafter also referred to as the “present adhesive sheet”) includes an adhesive layer formed from an active energy ray-curable adhesive composition containing the above-described acrylic adhesive polymer (A).

[0084] The pressure-sensitive adhesive layer in the pressure-sensitive adhesive sheet can be formed by applying the composition described above to a separator or the like, and optionally drying the composition. Resin films made of various resin materials can be used as the separator. Examples of resin materials constituting the resin film include polyester resins such as polyethylene terephthalate, polyethersulfone resins, acetate resins, polycarbonate resins, and polyolefin resins.

[0085] When forming a pressure-sensitive adhesive layer using a solvent-based pressure-sensitive adhesive composition, the composition is first applied to a separator by a known coating method, and the solvent is preferably removed by a drying treatment such as heating. The heating temperature and heating time when forming the pressure-sensitive adhesive layer are not limited as long as they are sufficient to remove the solvent, and can be appropriately set depending on the type of solvent contained in the composition, the solids concentration, etc. The thickness of the pressure-sensitive adhesive layer is, for example, 2 to 150 μm, preferably 2 to 100 μm, and more preferably 2 to 75 μm. Furthermore, to achieve the desired thickness of the pressure-sensitive adhesive layer, the pressure-sensitive adhesive layer may be formed by laminating multiple thin films.

[0086] In the production process for obtaining the present pressure-sensitive adhesive sheet, the present composition may be applied to a separator or the like, and the solvent may be removed as necessary, followed by irradiating the pressure-sensitive adhesive layer with active energy rays to perform pre-crosslinking. However, in the treatment of irradiating with active energy rays in the production process for the present pressure-sensitive adhesive sheet, it is preferable to appropriately set the irradiation dose of the active energy rays so that the gel fraction based on the acrylic pressure-sensitive adhesive polymer (A) in the pressure-sensitive adhesive layer is 90% or less, preferably 80% or less, and more preferably 70% or less.

[0087] One embodiment of the pressure-sensitive adhesive sheet thus obtained is a so-called substrateless embodiment in which a pressure-sensitive adhesive layer is sandwiched between two separators having the same or different peel strengths, as shown in Figure 1. The pressure-sensitive adhesive sheet 10 in Figure 1 is a laminate in which a first separator 11, a pressure-sensitive adhesive layer 12, and a second separator 13 are laminated in this order. It is preferable that the first separator 11 and the second separator 13 have different release properties. For example, the first separator 11 may be a heavy release film, and the second separator 13 may be a light release film.

[0088] The pressure-sensitive adhesive sheet may also have a configuration in which a substrate is disposed on one side of the pressure-sensitive adhesive layer and a separator is disposed on the other side. There are no particular limitations on the shape of the pressure-sensitive adhesive sheet, and it may be appropriately set depending on the mode of use. The pressure-sensitive adhesive sheet may be, for example, in the form of a sheet, a roll, or cut into strips. It may also have any shape depending on the adhesive location. One embodiment of the pressure-sensitive adhesive sheet is a pressure-sensitive adhesive tape.

[0089] <Physical properties of the pressure-sensitive adhesive layer> Gel fraction Before being attached to an adherend (i.e., before using the pressure-sensitive adhesive sheet), the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet preferably has a gel fraction based on the acrylic adhesive polymer (A) in the range of 90% or less. By ensuring that the gel fraction of the pressure-sensitive adhesive layer is 90% or less in the pressure-sensitive adhesive sheet before being attached to an adherend, the adhesive strength of the pressure-sensitive adhesive layer can be sufficiently ensured. Furthermore, when the pressure-sensitive adhesive layer is irradiated with active energy rays after being attached to the adherend, the difference in peel strength before and after irradiation with active energy rays can be ensured, and the easy peelability of the pressure-sensitive adhesive layer can be improved.

[0090] From the viewpoint of obtaining a pressure-sensitive adhesive sheet having excellent heat resistance while ensuring adhesiveness before irradiation with active energy rays and easy peelability after being irradiated with active energy rays after being attached to an adherend, the gel fraction of the pressure-sensitive adhesive layer in the pressure-sensitive adhesive sheet before being attached to an adherend is more preferably 85% or less, even more preferably 80% or less, and even more preferably 75% or less.

[0091] The lower limit of the gel fraction of the pressure-sensitive adhesive layer in the pressure-sensitive adhesive sheet before being bonded to an adherend is not particularly limited. From the viewpoint of obtaining a pressure-sensitive adhesive sheet with excellent heat resistance while ensuring adhesion before irradiation with active energy rays and easy peelability after being bonded to an adherend and being irradiated with active energy rays, the gel fraction of the pressure-sensitive adhesive layer in the pressure-sensitive adhesive sheet before being bonded to an adherend is preferably 1% or more, more preferably 3% or more, and even more preferably 4% or more. A preferred range of the gel fraction of the pressure-sensitive adhesive layer in the pressure-sensitive adhesive sheet before being bonded to an adherend can be determined by appropriately combining the above-mentioned upper and lower limits. Specifically, 1 to 90% is more preferred, 2 to 85% is more preferred, and 4 to 80% is even more preferred. Details of the measurement method follow the method described in the Examples below.

[0092] Weight Loss Rate The weight loss rate at 200°C of the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet, measured by thermogravimetry under conditions of a heating rate of 20°C / min and a temperature range of 25 to 350°C, is preferably 5% by weight or less. If the weight loss rate is 5% by weight or less, when the pressure-sensitive adhesive sheet is subjected to a thermal load, volatilization of components from the pressure-sensitive adhesive layer is unlikely, and a highly heat-resistant pressure-sensitive adhesive sheet in which foaming or lifting due to thermal load is suppressed can be obtained. From the viewpoint of improving the heat resistance of the pressure-sensitive adhesive sheet, the weight loss rate measured under the above conditions is more preferably 4% by weight or less, and even more preferably 3% by weight or less. In this specification, the method for measuring the weight loss rate of the pressure-sensitive adhesive layer by thermogravimetry follows the method described in the Examples below.

[0093] Peel strength: The adhesive strength of the present pressure-sensitive adhesive sheet is reduced by irradiating the pressure-sensitive adhesive layer and the adherend with active energy rays to crosslink or further crosslink the acrylic adhesive polymer (A) after bonding the pressure-sensitive adhesive layer to the adherend, thereby exhibiting easy peelability. When comparing the adhesive strength of the present pressure-sensitive adhesive sheet (preferably a pressure-sensitive adhesive sheet having a gel fraction of the pressure-sensitive adhesive layer of 90% or less) bonded to the adherend before irradiating with active energy rays with the adhesive strength of the present pressure-sensitive adhesive sheet bonded to the adherend after irradiating with active energy rays, it is preferable that the adhesive strength before active energy ray irradiation is high, thereby suppressing peeling from the adherend. On the other hand, from the viewpoint of achieving easy peelability by irradiating with active energy rays, it is preferable that the adhesive strength after irradiating with active energy rays is lower than that before irradiating with active energy rays.

[0094] Specifically, when the ratio (S2 / S1) of the peel strength (referred to as "S1") before irradiating the present pressure-sensitive adhesive sheet (preferably a pressure-sensitive adhesive sheet having a gel fraction of the pressure-sensitive adhesive layer of 90% or less) with active energy rays to the peel strength (referred to as "S2") after irradiating the present pressure-sensitive adhesive sheet with active energy rays so that the gel fraction based on the acrylic pressure-sensitive adhesive polymer (A) of the pressure-sensitive adhesive layer exceeds 90% and is used as an index, the ratio (S2 / S1) is preferably 0.7 or less. In terms of further increasing the adhesiveness before irradiation with active energy rays and the ease of releasability after irradiation with active energy rays, the ratio (S2 / S1) is more preferably 0.65 or less, even more preferably 0.6 or less, and even more preferably 0.5 or less. The peel strength is a value measured in accordance with JIS Z-0237. Details of the measurement method follow the method described in the Examples below.

[0095] <Use of the Pressure-Sensitive Adhesive Sheet> The pressure-sensitive adhesive sheet is resistant to foaming and lifting from the adherend even when heated to high temperatures (e.g., 200°C or higher), demonstrating excellent heat resistance. Therefore, the pressure-sensitive adhesive sheet is suitable as a pressure-sensitive adhesive sheet used in semiconductor manufacturing processes (i.e., a pressure-sensitive adhesive sheet for semiconductor manufacturing processes). Furthermore, the pressure-sensitive adhesive sheet exhibits easy peelability when irradiated with active energy rays after being attached to an adherend. The pressure-sensitive adhesive sheet is used in semiconductor manufacturing processes for the purpose of temporarily fixing an adherend or protecting the surface of an adherend, and is suitable for applications where the pressure-sensitive adhesive layer can be peeled off by irradiating the pressure-sensitive adhesive layer with active energy rays when temporary fixation and surface protection by the pressure-sensitive adhesive layer are no longer required.

[0096] For example, in a semiconductor manufacturing process using FOWLP technology or three-dimensional integrated semiconductor (3D-IC) technology, an adhesive tape is attached to a support substrate (e.g., a glass substrate), a semiconductor chip is placed on the adhesive layer of the adhesive tape attached to the support substrate, and the semiconductor chip is temporarily fixed to the support substrate. After that, various lamination steps are performed to form a laminate on the support substrate, and then the support substrate and the adhesive layer are peeled off. The present adhesive sheet can be preferably used as the adhesive tape in such manufacturing processes.

[0097] Examples of active energy rays irradiated to the pressure-sensitive adhesive sheet when peeling it off include ultraviolet light, visible light, and electron beams. Of these, ultraviolet light or electron beams are preferred. The irradiation energy of the active energy rays can be appropriately set depending on the type of active energy rays, the formulation composition of the pressure-sensitive adhesive layer, etc.

[0098] For example, when ultraviolet rays are used as the active energy rays, the wavelength is, for example, 250 to 400 nm. Examples of ultraviolet irradiation devices include high-pressure mercury lamps, metal halide lamps, ultraviolet electrodeless lamps, and ultraviolet light-emitting diodes (UV-LEDs). The cumulative light amount of ultraviolet rays with a wavelength of 365 nm is 500 mJ / cm. ２ More than 1,000 mJ / cm is preferred. ２ More preferably, 1,500 mJ / cm or more ２The upper limit of the cumulative light amount is preferably 100,000 mJ / cm from the viewpoint of minimizing the influence on each component in the pressure-sensitive adhesive layer and from the viewpoint of reducing energy. ２ Preferably, 50,000 mJ / cm or less ２ The following is more preferred:

[0099] The illuminance and irradiation time of the ultraviolet light can be appropriately set so that the integrated light amount is a desired amount. For example, the illuminance of ultraviolet light with a wavelength of 365 nm is 1.0 mW / cm ２ More than 2.0 mW / cm is preferable. ２ More preferably, 3.0 mW / cm or more ２ The upper limit of the illuminance is more preferably 3,000 mW / cm. ２ Preferably, 2,000 mW / cm or less ２ More preferably, 1,000 mW / cm or less ２ The following is even more preferred:

[0100] When electron beams are used as the active energy rays, the electron beam irradiation device is not particularly limited, but examples include Cockcroft-Walton type, Van de Graaff type, and resonant transformer type devices. The absorbed dose of the electron beam is preferably 1 to 200 kGy, more preferably 10 to 100 kGy. The acceleration voltage of the electron beam may be appropriately set within a range of 80 to 300 kV depending on the film thickness of the substrate. The oxygen concentration of the electron beam irradiation atmosphere is preferably 500 ppm or less, more preferably 300 ppm or less.

[0101] An example of the case where a laminate is produced using the pressure-sensitive adhesive sheet in a semiconductor manufacturing process is shown in Figure 2. Here, the case where an encapsulated semiconductor body including a semiconductor chip and an encapsulating layer is produced as the laminate will be described.

[0102] First, the first separator 11 is peeled off from the adhesive sheet 10 shown in FIG. 1 , and the adhesive sheet 10 is attached to the glass substrate 21 so that the surface of the adhesive layer 12 of the adhesive sheet 10 is in contact with the surface of the glass substrate 21. Thereafter, the second separator 13 is peeled off to expose the surface of the adhesive layer 12 (see FIG. 2( a)). Next, the semiconductor chip 22 is placed on the adhesive layer 12, and the semiconductor chip 22 is temporarily fixed to the glass substrate 21 (see FIG. 2( b)). Furthermore, a sealing layer 23 is formed so as to cover the surface of the glass substrate 21 and the semiconductor chip 22. This results in a sealed semiconductor 24 in which the semiconductor chip 22 is sealed by the sealing layer 23 on the glass substrate 21 (see FIG. 2( c)). The material for forming the sealing layer 23 is not particularly limited, and an epoxy resin or the like may be used, for example.

[0103] Thereafter, the laminate of the glass substrate 21 and the encapsulated semiconductor body 24 is irradiated with active energy rays, which reduces the adhesive strength of the pressure-sensitive adhesive layer 12, allowing the encapsulated semiconductor body 24 to be peeled off from the glass substrate 21 at the interface 25 between the encapsulated semiconductor body 24 and the pressure-sensitive adhesive layer 12 (see FIGS. 2(c) and 2(d)).

[0104] 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 the examples and comparative examples were analyzed using the following methods.

[0105] <Molecular weight measurement> Using a gel permeation chromatograph (model "HLC-8320", manufactured by Tosoh Corporation), the number average molecular weight (Mn) and weight average molecular weight (Mw) in terms of polystyrene were obtained under the following conditions. The molecular weight distribution (Mw / Mn) was calculated from the obtained values. 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

[0106] <Measurement of Glass Transition Temperature (Tg)> The glass transition temperature (Tg) of the polymer was determined from the intersection of the baseline of a heat flux curve obtained using a differential scanning calorimeter and the tangent at the inflection point. The heat flux curve was obtained by heating approximately 10 mg of a sample from room temperature (25°C) to 150°C at 10°C / min, subsequently cooling to -100°C, holding for 5 minutes, and then heating to 150°C at 10°C / min. Measurement equipment: DSC6220 manufactured by SII Nanotechnology Inc. Measurement atmosphere: nitrogen atmosphere

[0107] <Calculation of Monomer Composition of Polymer> The monomer composition of the polymer was calculated from the charged amounts and the consumed amounts of monomers measured by gas chromatography (GC).

[0108] 1. Synthesis of Acrylic Self-Adhesive Polymer [Synthesis Example 1] Polymer A-1 used in Examples 1 to 3 and Comparative Examples 1 and 2 A four-neck flask having an internal volume of 1 liter was charged with 4-benzoylphenyl methacrylate (hereinafter also referred to as "BPMA") (11 parts by mass), methyl acrylate (hereinafter also referred to as "MA") (99 parts by mass), 2-ethylhexyl EO-modified (n≒2) acrylate (trade name "Aronix M-120", manufactured by Toagosei Co., Ltd., hereinafter also referred to as "M-120") (99 parts by mass), 4-hydroxybutyl acrylate (hereinafter also referred to as "4HBA") (11 parts by mass), and ethyl acetate (320 parts by mass). This mixture was thoroughly degassed by bubbling nitrogen gas, the internal temperature of the mixture was raised to 75°C, and 2,2'-azobis(2,4-dimethylvaleronitrile) (manufactured by Wako Pure Chemical Industries, Ltd., hereinafter also referred to as "V-65") (0.20 parts by mass) was charged to initiate polymerization. After 5 hours, ethyl acetate was added so that the solids content was 30% by mass, thereby obtaining an ethyl acetate solution of polymer A-1. The obtained polymer A-1 consisted of 5% by mass of BPMA, 45% by mass of MA, 45% by mass of M-120, and 5% by mass of 4HBA, and had a Mw of 590,000, a Mw / Mn of 4.7, and a Tg of -30°C.

[0109] [Synthesis Example 2] Polymer A-2 used in Example 4 A 1-liter four-neck flask was charged with BPMA (22 parts by mass), MA (121 parts by mass), M-120 (66 parts by mass), 4HBA (11 parts by mass), and ethyl acetate (320 parts by mass). This mixture was thoroughly degassed by bubbling nitrogen gas, the internal temperature of the mixture was raised to 75°C, and V-65 (0.20 parts by mass) was charged to initiate polymerization. After 5 hours, ethyl acetate was added so that the solids content was 30% by mass, yielding an ethyl acetate solution of polymer A-2. The resulting polymer A-2 consisted of 10% by mass of BPMA, 55% by mass of MA, 30% by mass of M-120, and 5% by mass of 4HBA, and had a Mw of 560,000, a Mw / Mn of 4.1, and a Tg of -14°C.

[0110] [Synthesis Example 3] Polymer A-3 used in Example 5 A 1-liter four-neck flask was charged with BPMA (22 parts by mass), n-butyl acrylate (hereinafter also referred to as "BA") (121 parts by mass), M-120 (66 parts by mass), 4HBA (11 parts by mass), and ethyl acetate (320 parts by mass). This mixture was thoroughly degassed by bubbling nitrogen gas, the internal temperature of the mixture was raised to 75°C, and V-65 (0.20 parts by mass) was charged to initiate polymerization. After 5 hours, ethyl acetate was added so that the solids content was 30% by mass, yielding an ethyl acetate solution of polymer A-3. The obtained polymer A-3 consisted of 5% by mass of BPMA, 45% by mass of BA, 45% by mass of M-120, and 5% by mass of 4HBA, and had a Mw of 550,000, a Mw / Mn of 4.2, and a Tg of -54°C.

[0111] [Synthesis Example 4] Polymer A-4 used in Comparative Example 3 Into a 3-liter four-neck flask, n-butyl acrylate (hereinafter also referred to as "BA") (90 parts by mass), 2-methoxyethyl acrylate (hereinafter also referred to as "C1") (413 parts by mass), 2-hydroxyethyl acrylate (hereinafter also referred to as "HEA") (27 parts by mass), and ethyl acetate (980 parts by mass) were charged. This mixture was thoroughly degassed by bubbling nitrogen gas, the internal temperature of the mixture was raised to 75°C, and V-65 (0.25 parts by mass) was charged to initiate polymerization. After 5 hours, ethyl acetate was added so that the solids content was 30% by mass, and an ethyl acetate solution of polymer A-4 was obtained. The obtained polymer A-4 consisted of 17% by mass of BA, 78% by mass of C1, and 5% by mass of HEA, and had a Mw of 570,000, a Mw / Mn of 3.6, and a Tg of -35°C.

[0112] 2. Preparation of Pressure-Sensitive Adhesive Composition and Fabrication of Pressure-Sensitive Adhesive Sheet [Example 1] A pressure-sensitive adhesive composition was prepared by adding 0.2 parts by mass (solid content) of the isocyanate curing agent "Takenate D-110N" (manufactured by Mitsui Chemicals, Inc.) as a crosslinking agent to an ethyl acetate solution of Polymer A-1 obtained in Synthesis Example 1 (based on 100 parts by mass of solid content). This pressure-sensitive adhesive composition was applied to a 38 μm thick polyethylene terephthalate (hereinafter also referred to as "PET") separator so that the dried thickness would be 40 μm. The pressure-sensitive adhesive composition was dried at 100°C for 4 minutes to remove the ethyl acetate. Thereafter, a 38 μm thick PET separator with a different peel strength from the separator was attached, and the resulting sheet was left to stand at 40°C for 5 days for aging (aging), thereby obtaining a pressure-sensitive adhesive sheet sample with a crosslinked double-sided separator. The resulting pressure-sensitive adhesive sheet sample was then subjected to various evaluations using the methods described below.

[0113] <Evaluation Method> Gel Fraction Measurement 0.2 g of adhesive was sampled from the adhesive layer of a pressure-sensitive adhesive sheet sample (i.e., a pressure-sensitive adhesive sheet before being attached to an adherend), 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, the sample was filtered through a 200-mesh wire gauze, and the residue remaining on the mesh was dried at 80°C for 3 hours and weighed. From the initial mass and the mass of the residue, the gel fraction based on the acrylic adhesive polymer was calculated using the following formula: Gel fraction (%) = (mass of residue) / [(initial mass) × (solid content of acrylic adhesive polymer) / (solid content of entire pressure-sensitive adhesive composition)] × 100

[0114] Evaluation of easy peelability A pressure-sensitive adhesive sheet sample was transferred to a polyimide film (Apical (registered trademark), 25 μm thick, manufactured by Kaneka Corporation) to obtain a first pressure-sensitive adhesive sheet for evaluation. A glass plate (Fabritec FL11A, 1 mm thick, manufactured by AGC) was used as the adherend, and the first pressure-sensitive adhesive sheet for evaluation was bonded to the glass plate to obtain a glass plate / pressure-sensitive adhesive layer / polyimide film laminate. After manual bonding with a hand roller, the 180-degree peel strength of the first pressure-sensitive adhesive sheet for evaluation was measured at 23 ° C. using a tensile tester (Autograph AGS, manufactured by Shimadzu Corporation) in accordance with JIS Z-0237 "Test methods for pressure-sensitive adhesive tapes and pressure-sensitive adhesive sheets." The peel speed was 300 mm / min. This measured value was defined as the peel strength S1 before UV irradiation. Separately, a pressure-sensitive adhesive sheet sample was transferred to a polyimide film (Apical (registered trademark), 25 μm thick, manufactured by Kaneka Corporation) to obtain a second pressure-sensitive adhesive sheet for evaluation. A glass plate (Fabritec FL11A, 1 mm thick, manufactured by AGC) was used as the adherend, and the second pressure-sensitive adhesive sheet for evaluation was attached to the glass plate to form a glass plate / pressure-sensitive adhesive layer / polyimide film laminate. After manual attachment with a hand roller, ultraviolet light with a wavelength of 365 nm was applied from the glass plate side at room temperature (25°C) at 3,000 mJ / cm using a UV irradiator (Mini Grandage ECS-1511U, equipped with a metal halide lamp, manufactured by iGraphics). ２The second evaluation pressure-sensitive adhesive sheet was then irradiated with an exposure dose of 180°. Thereafter, the 180-degree peel strength of the second evaluation pressure-sensitive adhesive sheet was measured in the same manner as above, and this was designated as the peel strength S2 after UV irradiation. The gel fraction of the second evaluation pressure-sensitive adhesive sheet after UV irradiation was measured using the method described above, and was found to be greater than 90%. The ratio (S2 / S1) of the peel strength S2 after UV irradiation to the peel strength S1 before UV irradiation was determined, and the ease of releasability was evaluated according to the following criteria: ○: S2 / S1 is 0.7 or less ×: S2 / S1 is greater than 0.7

[0115] - Evaluation of heat resistance (heating test) Two glass plates (size 30 mm x 50 mm, 0.15 mm thick) were used as adherends, and the separator was peeled off from the pressure-sensitive adhesive sheet sample and manually attached to the glass plates with a hand roller to obtain a laminate of glass plate / pressure-sensitive adhesive layer / glass plate. After manually attaching with the hand roller, the laminate was heated on a hot plate at 200°C for 10 minutes. The appearance of the laminate after heating was visually observed, and the heat resistance was evaluated according to the following criteria. Note that the smaller the size of the bubbles and the fewer the number of bubbles, the less foaming and peeling from the pressure-sensitive adhesive layer due to heating, and the better the heat resistance. ○: No bubbles of 1 mm or more in diameter ×: Bubbles of 1 mm or more in diameter

[0116] Evaluation of Heat Resistance (Thermogravimetry) The separator was peeled off from the pressure-sensitive adhesive sheet sample, and the pressure-sensitive adhesive layer alone was weighed into an aluminum pan. The aluminum pan was then set in a thermogravimetry device (TG / DTA, STA2500Regulus model, manufactured by NETZSCH). Under a nitrogen atmosphere, the measurement sample was heated from 25°C to 350°C at a heating rate of 20°C / min using the thermogravimetry device, and the weight loss rate at 200°C was measured. The heat resistance of the pressure-sensitive adhesive layer was evaluated based on the measured weight loss rate according to the following criteria. Note that the smaller the weight loss rate, the less foaming occurred when the pressure-sensitive adhesive layer was subjected to a thermal load, and the better the heat resistance. ○: Weight loss rate was 5 wt% or less ×: Weight loss rate was more than 5 wt%

[0117] [Example 2] A pressure-sensitive adhesive composition was produced by the same procedure as in Example 1, except that the amount of the crosslinking agent "Takenate D-110N" added was 0.4 parts by mass relative to 100 parts by mass of the acrylic pressure-sensitive adhesive polymer, and various evaluations were carried out in the same manner as in Example 1.

[0118] Example 3 An ethyl acetate solution of polymer A-1 obtained in Synthesis Example 1 was used as a pressure-sensitive adhesive composition, and this pressure-sensitive adhesive composition was applied to a 38 μm-thick PET separator so that the thickness after drying would be 40 μm. The pressure-sensitive adhesive composition was dried at 120°C for 4 minutes to remove the ethyl acetate. Thereafter, a 38 μm-thick PET separator with a different peel strength from the separator was laminated, and UV with a wavelength of 365 nm was applied at 500 mJ / cm using a UV irradiator (Mini Grandage ECS-1511U, equipped with a metal halide lamp, manufactured by iGraphics Co., Ltd.). ２ The polymer was partially crosslinked (pre-crosslinked) by contact with the adhesive sheet. This resulted in a pressure-sensitive adhesive film sample with a double-sided separator. Furthermore, various evaluations were performed in the same manner as in Example 1 using the resulting pressure-sensitive adhesive sheet sample.

[0119] [Example 4] A pressure-sensitive adhesive composition was produced by the same operation as in Example 1, except that the polymer A-2 obtained in Synthesis Example 2 was used instead of the polymer A-1, and the amount of the crosslinking agent "Takenate D-110N" added was 0.4 parts by mass relative to 100 parts by mass of the acrylic pressure-sensitive adhesive polymer, and various evaluations were carried out in the same manner as in Example 1.

[0120] [Example 5] A pressure-sensitive adhesive composition was produced by the same operation as in Example 1, except that polymer A-3 obtained in Synthesis Example 3 was used instead of polymer A-1, and the amount of crosslinking agent "Takenate D-110N" added was 0.4 parts by mass relative to 100 parts by mass of the acrylic pressure-sensitive adhesive polymer, and various evaluations were carried out in the same manner as in Example 1.

[0121] [Example 6] A pressure-sensitive adhesive composition was produced by the same operation as in Example 1, except that the amount of the crosslinking agent "Takenate D-110N" added was 0.04 parts by mass relative to 100 parts by mass of the acrylic pressure-sensitive adhesive polymer, and various evaluations were carried out in the same manner as in Example 1.

[0122] Comparative Example 1 A pressure-sensitive adhesive composition was produced by the same procedure as in Example 1, except that the amount of the crosslinking agent "Takenate D-110N" added was 4 parts by mass relative to 100 parts by mass of the acrylic pressure-sensitive adhesive polymer, and various evaluations were carried out in the same manner as in Example 1.

[0123] Comparative Example 2 A pressure-sensitive adhesive composition was produced by the same operation as in Example 1, except that the amount of crosslinking agent "Takenate D-110N" added was 0.4 parts by mass relative to 100 parts by mass of the acrylic adhesive polymer, 30 parts by mass of a polyfunctional acrylate with a trade name of "Aronix M-402" (manufactured by Toagosei Co., Ltd.) was added relative to 100 parts by mass of the acrylic adhesive polymer, and 3 parts by mass of a photoinitiator "OMNIRAD 184" was added relative to 100 parts by mass of the acrylic adhesive polymer, and various evaluations were carried out in the same manner as in Example 1.

[0124] Comparative Example 3 A pressure-sensitive adhesive composition was produced by the same operation as in Example 1, except that polymer A-4 obtained in Synthesis Example 4 was used instead of polymer A-1, and the amount of crosslinking agent "Takenate D-110N" added was 0.4 parts by mass relative to 100 parts by mass of the acrylic pressure-sensitive adhesive polymer, and various evaluations were carried out in the same manner as in Example 1.

[0125] The compositions and evaluation results of the pressure-sensitive adhesive compositions of Examples 1 to 6 and Comparative Examples 1 to 3 are shown in Table 1.

[0126]

[0127] The abbreviations in Table 1 represent the following names: BPMA: 4-benzoylphenyl methacrylate (boiling point 418°C) MA: methyl acrylate (boiling point 80°C) M-120: 2-ethylhexyl EO-modified (n≈2) acrylate, trade name "Aronix M-120", manufactured by Toagosei Co., Ltd. (boiling point 340°C) BA: n-butyl acrylate (boiling point 145°C) C1: 2-methoxyethyl acrylate (boiling point 151°C) 4HBA: 4-hydroxybutyl acrylate (boiling point 298°C) HEA: 2-hydroxyethyl acrylate (boiling point 196°C) D-110N: isocyanate-based curing agent, trade name "Takenate D-110N", manufactured by Mitsui Chemicals, Inc. M-402: multifunctional acrylate, trade name "Aronix M-402", manufactured by Toagosei Co., Ltd. OMNIRAD: Intramolecular cleavage type photopolymerization initiator, product name "OMNIRAD 184", manufactured by IGM RESINS. The amounts of crosslinker, multifunctional acrylate, and photopolymerization initiator are based on 100 parts by mass of the acrylic adhesive polymer. The boiling points of the monomers are predicted values ​​under atmospheric pressure calculated using Fujitsu Limited's Scientific Research Information Management Solution (ACD / Labs). The boiling points (predicted values) of each monomer are also shown in Table 1.

[0128] As shown in Table 1, all of the PSA sheets produced using PSA compositions containing polymers A-1 to A-3 as acrylic PSA polymers, having a sufficiently low content of crosslinking agent, and not containing a polyfunctional acrylate had good peelability and heat resistance (Examples 1 to 6).

[0129] In contrast, a pressure-sensitive adhesive sheet formed using a pressure-sensitive adhesive composition in which the content of crosslinking agent was 4 parts by mass per 100 parts by mass of the acrylic adhesive polymer was rated as "x" for ease of peeling (Comparative Example 1). A pressure-sensitive adhesive sheet in which a pressure-sensitive adhesive layer was formed using a pressure-sensitive adhesive composition containing a polyfunctional acrylate was rated as "x" for heat resistance (Comparative Example 2). Furthermore, a pressure-sensitive adhesive sheet formed using a pressure-sensitive adhesive composition containing Polymer A-4 as the acrylic adhesive polymer was rated as "x" for both ease of peeling and heat resistance (Comparative Example 3).

[0130] 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.

[0131] REFERENCE SIGNS LIST 10...adhesive sheet, 11...first separator, 12...adhesive layer, 13...second separator, 21...glass substrate, 22...semiconductor chip, 23...sealing layer, 24...semiconductor sealed body, 25...interface

Claims

1. An active energy ray-curable pressure-sensitive adhesive composition, comprising: an acrylic adhesive polymer (A) that does not contain a compound having two or more reactive unsaturated bonds in one molecule; and has at least one group selected from the group consisting of an ether group, a hydroxyl group, an aliphatic tertiary carbon, a secondary amino group, and a tertiary amino group in a side chain; the acrylic adhesive polymer (A) contains a structural unit (U1) having a hydrogen abstraction type photopolymerization initiator structure; the content of the structural unit (U1) in the acrylic adhesive polymer (A) is 0.1 mass% or more and 50 mass% or less with respect to all structural units of the acrylic adhesive polymer (A); and the content of a crosslinking agent is 0 mass% or more and 3 mass% or less with respect to 100 mass parts of the content of the acrylic adhesive polymer (A).

2. The active energy ray-curable pressure-sensitive adhesive composition according to claim 1, wherein the acrylic adhesive polymer (A) contains a structural unit (U2) derived from a (meth)acrylic monomer having at least one selected from the group consisting of an ether group, a hydroxyl group, an aliphatic tertiary carbon (excluding the carbon atom constituting the carbon-carbon double bond in a methacryloyl group), a secondary amino group, and a tertiary amino group, and the content of the structural unit (U2) in the acrylic adhesive polymer (A) is 10 mass% or more based on the total structural units of the acrylic adhesive polymer (A).

3. The active energy ray-curable pressure-sensitive adhesive composition according to claim 1, wherein the acrylic pressure-sensitive adhesive polymer (A) contains a structural unit derived from a monomer represented by the following formula (1): CH ２ =CR １ -C(=O)O-(R ２ O) ｎ -R ３ ...(1) (In formula (1), R １ represents a hydrogen atom or a methyl group, R ２ represents a linear or branched alkylene group having 2 to 6 carbon atoms; R ３ represents a hydrogen atom or a monovalent hydrocarbon group having 1 to 20 carbon atoms, and n represents an integer of 2 to 100.

4. The active energy ray-curable pressure-sensitive adhesive composition according to claim 1, wherein the glass transition temperature of the acrylic pressure-sensitive adhesive polymer (A) is from -70°C to 0°C.

5. The active energy ray-curable pressure-sensitive adhesive composition according to claim 1, wherein the acrylic pressure-sensitive adhesive polymer (A) has a weight-average molecular weight of 100,000 or more.

6. The active energy ray-curable pressure-sensitive adhesive composition according to claim 1, wherein the acrylic adhesive polymer (A) contains structural units derived from at least one monomer selected from the group consisting of (meth)acrylic monomers having a boiling point of 150°C or less at atmospheric pressure and (meth)acrylic monomers having a boiling point of 200°C or more at atmospheric pressure in an amount of 50 mass% or more relative to all structural units of the acrylic adhesive polymer (A).

7. The active energy ray-curable pressure-sensitive adhesive composition according to claim 1, which contains the crosslinking agent.

8. The active energy ray-curable pressure-sensitive adhesive composition according to claim 1, which is used in the semiconductor manufacturing process.

9. An adhesive sheet comprising an adhesive layer formed from the active energy ray-curable adhesive composition according to any one of claims 1 to 8.

10. The adhesive sheet according to claim 9, wherein the gel fraction based on the acrylic adhesive polymer (A) of the adhesive layer before bonding to an adherend is 90% or less.

11. The adhesive sheet according to claim 9, wherein the adhesive layer has a weight loss rate of 5% by weight or less at 200°C, as measured by thermogravimetry under conditions of a heating rate of 20°C / min and a heating range of 25 to 350°C.

12. The adhesive sheet according to claim 9, wherein the ratio (S2 / S1) of the peel strength (S1) before the adhesive sheet attached to the adherend is irradiated with active energy rays to the peel strength (S2) after the gel fraction based on the acrylic adhesive polymer (A) of the adhesive layer is increased to more than 90% by irradiating the adhesive sheet attached to the adherend with active energy rays is 0.7 or less.

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