Pressure-sensitive adhesive sheet

Abstract

To provide a pressure-sensitive adhesive sheet which has excellent adhesive strength and has excellent resistance to high temperature or to ultraviolet rays.SOLUTION: A pressure-sensitive adhesive sheet comprises a photocured product of a resin composition comprising a (meth)acrylic polymer (A) and a photoinitiator (B) and a content of an unreacted photoinitiator (B) is 1.0 mass% or less.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a pressure-sensitive adhesive sheet used for bonding optical members. [Background technology]

[0002] In recent years, in order to improve the visibility of image display devices, the gap between an image display panel such as a liquid crystal display (LCD), a plasma display (PDP) or an electroluminescent display (ELD) and an optical component such as a protective panel or a touch panel component placed on the front side (viewing side) of the image display panel has been filled with a resin such as an adhesive or glue to suppress reflection of incident light and outgoing light from the displayed image at the air layer interface.

[0003] For example, Patent Document 1 discloses a method for manufacturing a component laminate for an image display device, which has a configuration in which an image display device component is laminated on at least one side of a transparent double-sided adhesive sheet, in which an adhesive sheet that has been primarily crosslinked by ultraviolet light is attached to the image display device component, and then the adhesive sheet is irradiated with ultraviolet light through the image display device component to cause secondary curing.

[0004] Furthermore, Patent Document 2 discloses a pressure-sensitive adhesive sheet containing a (meth)acrylic copolymer having an ultraviolet-crosslinkable site, as a pressure-sensitive adhesive sheet useful for displays and touch panels. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 4971529 [Patent Document 2] Patent No. 6062740 Summary of the Invention [Problem to be solved by the invention]

[0006] In-vehicle image display devices and the like are required to have excellent durability in harsh temperature environments and ultraviolet light environments, assuming use in tropical or cold regions, etc. Furthermore, in recent years, with the need for diversified designs of in-vehicle image display devices, such as larger screens and curved surfaces, there is a demand for pressure-sensitive adhesive sheets that combine excellent adhesive properties and durability.

[0007] In view of the above circumstances, an object of the present invention is to provide a pressure-sensitive adhesive sheet that has good adhesive strength and good resistance to high temperatures or ultraviolet rays. [Means for solving the problem]

[0008] The present inventors have found that the above problems can be solved by using a pressure-sensitive adhesive sheet with a content of unreacted polymerization initiator below a certain level, and have thus completed the present invention.

[0009] An embodiment of the present invention includes the following: Note that the present invention also includes embodiments that combine features of the following embodiments.

[0010] [1] A first aspect of the present invention is a pressure-sensitive adhesive sheet comprising a photocured resin composition containing a (meth)acrylic polymer (A) and a photopolymerization initiator (B), wherein the content of unreacted photopolymerization initiator (B) is 1.0 mass % or less.

[0011] [2] A second aspect of the present invention is the pressure-sensitive adhesive sheet of the first aspect, wherein the photopolymerization initiator (B) is a hydrogen abstraction photopolymerization initiator. [3] A third aspect of the present invention is the adhesive sheet of the first or second aspect, which is a thermosetting adhesive sheet or a pressure-sensitive adhesive sheet. [4] A fourth aspect of the present invention is the pressure-sensitive adhesive sheet according to any one of the first to third aspects, wherein the gel fraction is 50% or more. [5] A fifth aspect of the present invention is the pressure-sensitive adhesive sheet according to any one of the first to fourth aspects, wherein the content of unreacted photopolymerization initiator (B) is 0.1 mass % or less.

[0012] [6] A sixth aspect of the present invention is the pressure-sensitive adhesive sheet according to any one of the first to fifth aspects, wherein the pressure-sensitive adhesive sheet has an adhesive strength of 4 N / cm or more. [7] The seventh aspect of the present invention is any one of the first to sixth aspects, wherein L * a * b * Chromaticity b in color space * is 1.5 or less. [8] The eighth aspect of the present invention is any one of the first to seventh aspects, wherein L * a * b * Chromaticity b in color space * is 2.0 or less. [Effects of the Invention]

[0013] According to the present invention, it is possible to provide a pressure-sensitive adhesive sheet that has good adhesive strength and good resistance to high temperatures or ultraviolet rays. DETAILED DESCRIPTION OF THE INVENTION

[0014] An example of an embodiment of the present invention will be described in detail below, but the present invention is not limited to the embodiment described below.

[0015] In the present invention, the term "film" conceptually encompasses sheets, films, and tapes. Furthermore, when the term "panel" is used, such as an image display panel or a protective panel, it encompasses a plate, a sheet, and a film.

[0016] In the present invention, when it is written as "x to y" (x and y are any numbers), unless otherwise specified, it means "greater than x and less than y", and also means "preferably greater than x" or "preferably smaller than y". Furthermore, when it is stated that the amount is "x or more" (x is any number), it also means that the amount is "preferably greater than x" unless otherwise specified, and when it is stated that the amount is "y or less" (y is any number), it also means that the amount is "preferably smaller than y" unless otherwise specified. Furthermore, "x and / or y (x and y are optional configurations)" means at least one of x and y, and can mean three possibilities: x only, y only, or x and y.

[0017] In the present invention, "(meth)acrylic" refers to a comprehensive definition of acrylic and methacrylic, "(meth)acrylate" refers to a comprehensive definition of acrylate and methacrylate, and "(meth)acryloyl" refers to a comprehensive definition of acryloyl and methacryloyl. The term "(meth)acrylic polymer" refers to a copolymer having structural units derived from (meth)acrylic monomers. The (meth)acrylic polymer may further have structural units derived from monomers other than (meth)acrylic monomers (e.g., styrene).

[0018] <<Adhesive sheet of the present invention>> A pressure-sensitive adhesive sheet according to one embodiment of the present invention (also referred to as the "pressure-sensitive adhesive sheet of the present invention") is a pressure-sensitive adhesive sheet comprising a photocured product of a resin composition (also referred to as the "resin composition") comprising a (meth)acrylic polymer (A) and a photopolymerization initiator (B).

[0019] (Thermosetting adhesive sheet or pressure-sensitive adhesive sheet) The pressure-sensitive adhesive sheet of the present invention can be used to bond members without further curing treatment by light irradiation. For example, the pressure-sensitive adhesive sheet of the present invention may be a thermosetting pressure-sensitive adhesive sheet or a pressure-sensitive adhesive sheet, and is preferably a pressure-sensitive adhesive sheet.

[0020] Here, the term "thermosetting adhesive sheet" in the present invention means a sheet that has the property of hardening when heated and increasing its adhesive strength, or a sheet that has the property of temporarily softening at a temperature higher than room temperature and hardening and increasing its adhesive strength when maintained at that temperature or when heated to a higher temperature. Furthermore, the term "pressure-sensitive adhesive sheet" refers to an adhesive sheet that does not require a curing treatment, such as light irradiation, after being attached to another member by applying pressure as necessary.

[0021] If the pressure-sensitive adhesive sheet of the present invention is a thermosetting pressure-sensitive adhesive sheet or a pressure-sensitive adhesive sheet, when the pressure-sensitive adhesive sheet of the present invention is to be attached to another member, curing treatment by light irradiation is not required. Depending on the mode of use, when the pressure-sensitive adhesive sheet of the present invention is bonded to another member, pressure is applied to the sheet to remove air bubbles, ensure cohesive force, ensure uniformity, etc. In such a mode of use, if the pressure-sensitive adhesive sheet of the present invention is a thermosetting pressure-sensitive adhesive sheet, it can be bonded to another member simply by applying heat treatment during or after bonding, for example, by applying pressure and heat simultaneously in an autoclave. Furthermore, if the pressure-sensitive adhesive sheet of the present invention is a pressure-sensitive adhesive sheet, it can be bonded to another member simply by applying pressure during or after bonding, which is useful.

[0022] (Content of unreacted polymerization initiator) In the pressure-sensitive adhesive sheet of the present invention, the content of the unreacted photopolymerization initiator (B) is preferably 1.0 mass % or less. When the content of the unreacted photopolymerization initiator is 1.0 mass% or less, even when the composition is exposed to light, particularly ultraviolet light, or placed in a high-temperature environment, bubbles, peeling, or yellowing do not occur, and resistance to heat and ultraviolet light is improved. From this viewpoint, the content of unreacted photopolymerization initiator (B) is preferably 1.0% by mass or less, more preferably 0.5% by mass or less, even more preferably 0.3% by mass or less, even more preferably 0.2% by mass or less, and even more preferably 0.1% by mass or less.

[0023] Methods for reducing the content of unreacted photopolymerization initiator (B) include, for example, selecting the type of photopolymerization initiator (B), adjusting the amount of photopolymerization initiator (B) added, adjusting the amount of light irradiation, etc. However, the methods are not limited to these.

[0024] <The present resin composition> The present resin composition is a resin composition containing a (meth)acrylic polymer (A) and a photopolymerization initiator (B). Each component contained in the resin composition will be described in detail below.

[0025] <(Meth)acrylic polymer (A)> The (meth)acrylic polymer (A) preferably accounts for 70% by mass or more, particularly 80% by mass or more, and even more preferably 90% by mass or more, of 100% by mass of the components of the resin composition excluding the solvent. On the other hand, since it is necessary to contain at least the photopolymerization initiator (B), there is no particular upper limit, and it may be 100% by mass or less, for example, 99.8% by mass or less, particularly 99.5% by mass or less, and even more preferably 99% by mass or less.

[0026] Examples of the (meth)acrylic polymer (A) include a homopolymer of alkyl (meth)acrylate, as well as a copolymer obtained by polymerizing a monomer component copolymerizable therewith. Among these, it is preferable that the (meth)acrylic polymer contains two or more copolymerization components, and at least one of the copolymerization components is an alkyl (meth)acrylate having an alkyl group with 3 to 30 carbon atoms.

[0027] More specifically, examples of the (meth)acrylic polymer (A) include copolymers of monomer components containing an alkyl(meth)acrylate having 3 to 30 carbon atoms in the alkyl group and one or more monomers copolymerizable therewith selected from (a1) a carboxyl group-containing monomer other than the alkyl(meth)acrylate, (a2) a hydroxyl group-containing monomer, (a3) ​​a nitrogen-containing monomer, (a4) an epoxy group-containing monomer, (a5) a vinyl monomer, (a6) an alkyl(meth)acrylate monomer having 1 or 2 carbon atoms in the alkyl group, (a7) an alicyclic monomer, and (a8) other copolymerizable monomers.

[0028] Among the above copolymerizable monomers (a1) to (a8), the following copolymerizable monomers (a1), (a2) and (a3) ​​are particularly preferred. It is particularly preferred that the composition does not contain the copolymerizable monomer (a) but contains either the copolymerizable monomer (a2) or (a3). By containing either the copolymerizable monomer (a2) or (a3), it is possible to achieve corrosion resistance when the adherend contains a corrosive component such as a metal, as well as adhesion and resistance to wet heat whitening. It is particularly preferred that the composition contains both the copolymerizable monomers (a2) and (a3) ​​in order to enhance cohesion. Furthermore, among the copolymerizable monomers (a3), those having a tertiary nitrogen atom are preferred, since they have a sensitizing effect on the hydrogen abstraction reaction described below, and as a result, can efficiently form crosslinks. Among the alkyl (meth)acrylates, alkyl (meth)acrylates containing a tertiary carbon atom in the alkyl group are preferred. By using such alkyl (meth)acrylates, a hydrogen abstraction reaction is likely to occur upon light irradiation, which results in efficient crosslinking.

[0029] The alkyl(meth)acrylate is a linear or branched alkyl(meth)acrylate in which the alkyl group has 3 to 30 carbon atoms, and is represented by the following formula (m1). CH2=C(R 14 )-COO(R 15 )...Equation(m1) (In formula m1, R 14represents a hydrogen atom or a methyl group, and R 15 represents a linear or branched alkyl group having 3 to 30 carbon atoms.

[0030] Examples of the alkyl(meth)acrylate represented by formula (m1) include linear alkyl(meth)acrylates such as n-propyl(meth)acrylate, i-propyl(meth)acrylate, n-butyl(meth)acrylate, n-pentyl(meth)acrylate, n-hexyl(meth)acrylate, n-heptyl(meth)acrylate, n-octyl(meth)acrylate, n-nonyl(meth)acrylate, n-decyl(meth)acrylate, undecyl(meth)acrylate, lauryl(meth)acrylate, n-tridecyl(meth)acrylate, n-tetradecyl(meth)acrylate, cetyl(meth)acrylate, stearyl(meth)acrylate, icosyl(meth)acrylate, heneicosyl(meth)acrylate, and behenyl(meth)acrylate; and sec-butyl Examples of branched alkyl (meth)acrylates include (meth)acrylate, isobutyl (meth)acrylate, t-butyl (meth)acrylate, isopentyl (meth)acrylate, neopentyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, isooctyl (meth)acrylate, isononyl (meth)acrylate, isodecyl (meth)acrylate, isostearyl (meth)acrylate, isoicosyl (meth)acrylate, butyloctyl (meth)acrylate, isomyristyl (meth)acrylate, isocetyl (meth)acrylate, hexyldecyl (meth)acrylate, isostearyl (meth)acrylate, octyldecyl (meth)acrylate, octyldodecyl (meth)acrylate, and isobehenyl (meth)acrylate. These may be used alone or in combination of two or more.

[0031] Among these, linear alkyl(meth)acrylates are preferred from the viewpoint of obtaining flexibility. Furthermore, from the viewpoint of balancing adhesion and flexibility, alkyl(meth)acrylates having 3 to 20 carbon atoms in the alkyl group, particularly 5 or more or 18 or less, particularly 6 or more or 16 or less, and particularly 7 or more or 14 or less, are preferred. For example, n-butyl(meth)acrylate, n-pentyl(meth)acrylate, n-hexyl(meth)acrylate, n-octyl(meth)acrylate, n-nonyl(meth)acrylate, decyl(meth)acrylate, and lauryl(meth)acrylate are preferred. The lower limit and upper limit of the number of carbon atoms in the alkyl group can be arbitrarily combined.

[0032] Among these, it is preferable to use branched alkyl (meth)acrylates because a hydrogen abstraction reaction, which will be described later, is likely to occur upon light irradiation, thereby enabling efficient formation of a crosslinked structure, and among these, branched alkyl (meth)acrylates having an alkyl group with 3 to 20 carbon atoms, of which 5 or more or 18 or less, of which 6 or more or 16 or less, and of which particularly 7 or more or 14 or less are preferred. For example, sec-butyl (meth)acrylate, isobutyl (meth)acrylate, t-butyl (meth)acrylate, isopentyl (meth)acrylate, neopentyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, isooctyl (meth)acrylate, isononyl (meth)acrylate, and isodecyl (meth)acrylate are preferred. The lower limit and upper limit of the number of carbon atoms in the alkyl group can be arbitrarily combined.

[0033] The proportion of the alkyl (meth)acrylate-derived structural units relative to 100% by mass of all structural units constituting the (meth)acrylic polymer (A) is preferably 5% by mass or more and 95% by mass or less, more preferably 10% by mass or more or 90% by mass or less, even more preferably 15% by mass or more or 85% by mass or less, and even more preferably 20% by mass or more or 80% by mass or less. When the proportion of the alkyl (meth)acrylate-derived structural unit is equal to or greater than the lower limit, the flexibility tends to be excellent and the conformability to unevenness tends to be excellent when the adherend has unevenness. When the proportion is equal to or less than the upper limit, the effect of the copolymerizable monomer described below is easily obtained and the adhesive strength and cohesive strength tend to be excellent. The lower limit and upper limit of the content of the structural unit derived from alkyl (meth)acrylate can be combined in any desired manner.

[0034] Examples of the carboxyl group-containing monomer (a1) include (meth)acrylic acid, 2-(meth)acryloyloxyethyl hexahydrophthalic acid, 2-(meth)acryloyloxypropyl hexahydrophthalic acid, 2-(meth)acryloyloxyethyl phthalic acid, 2-(meth)acryloyloxypropyl phthalic acid, 2-(meth)acryloyloxyethyl maleic acid, 2-(meth)acryloyloxypropyl maleic acid, 2-(meth)acryloyloxyethyl succinic acid, 2-(meth)acryloyloxypropyl succinic acid, crotonic acid, fumaric acid, maleic acid, and itaconic acid. These may be used alone or in combination of two or more.

[0035] Examples of the hydroxyl group-containing monomer (a2) include hydroxyalkyl (meth)acrylates such as 2-hydroxyethyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 5-hydroxypentyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, and 8-hydroxyoctyl (meth)acrylate; caprolactone-modified hydroxy (meth)acrylates such as caprolactone-modified 2-hydroxyethyl (meth)acrylate; diethylene glycol (meth)acrylate; polyethylene glycol (meth)acrylate; polypropylene glycol (meth)acrylate; polytetramethylene glycol (meth)acrylate; polyoxyethylene poly(meth)acrylate; Examples of the hydroxyl group-containing (meth)acrylate include (meth)acrylates having an oxyalkylene structure such as propylene glycol (meth)acrylate, primary hydroxyl group-containing (meth)acrylates such as 2-acryloyloxyethyl-2-hydroxyethyl phthalate, secondary hydroxyl group-containing (meth)acrylates such as 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, and 3-chloro-2-hydroxypropyl (meth)acrylate, tertiary hydroxyl group-containing (meth)acrylates such as 2,2-dimethyl 2-hydroxyethyl (meth)acrylate, and vinyl ethers such as 2-hydroxyethyl vinyl ether, diethylene glycol monovinyl ether, and 4-hydroxybutyl vinyl ether. These may be used alone or in combination of two or more. The hydroxyl group-containing monomer (a2) improves the adhesive strength of the pressure-sensitive adhesive sheet and can suppress whitening under heat and humidity. In addition, when the resin composition contains a thermal crosslinking agent described later, the hydroxyl group-containing monomer (a2) serves as a crosslinking reaction site.

[0036] Among the hydroxyl group-containing monomers (a2), preferred are those having a hydroxyalkyl group having 1 or more carbon atoms, preferably 2 or more, more preferably 4 or more, and 10 or less, more preferably 6 or less. For example, 2-hydroxyethyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxyethyl vinyl ether, diethylene glycol monovinyl ether, 4-hydroxybutyl vinyl ether, etc. are preferred, and primary hydroxyl group-containing (meth)acrylates, such as 2-hydroxyethyl (meth)acrylate and 4-hydroxybutyl (meth)acrylate, are particularly preferred. The lower limit and upper limit of the number of carbon atoms in the hydroxyalkyl group can be arbitrarily combined.

[0037] From the viewpoint of imparting adhesive strength and resistance to wet heat whitening, the content of the structural units derived from the hydroxyl group-containing monomer (a2) in the (meth)acrylic polymer (A) is preferably 3 to 30 mass % relative to all structural units of the (meth)acrylic polymer (A), more preferably 5 mass % or more or 25 mass % or less, and even more preferably 7 mass % or more or 20 mass % or less. The lower limit and upper limit of the content of the structural unit derived from the hydroxyl group-containing monomer (a2) in the (meth)acrylic polymer (A) can be combined in any desired manner.

[0038] Examples of the nitrogen-containing monomer (a3) ​​include amino group-containing monomers, amide group-containing monomers, isocyanate group-containing monomers, and (meth)acrylonitrile. The nitrogen-containing monomer (a3) ​​improves the cohesive strength of the PSA sheet and can suppress whitening under heat and humidity. These may be used alone or in combination of two or more. The nitrogen-containing monomer (a3) ​​also has the effect of accelerating the hydrogen abstraction reaction described below.

[0039] Examples of the amino group-containing monomer as the nitrogen-containing monomer include primary amino group-containing (meth)acrylates such as aminomethyl (meth)acrylate and aminoethyl (meth)acrylate; secondary amino group-containing (meth)acrylates such as t-butylaminoethyl (meth)acrylate and t-butylaminopropyl (meth)acrylate; tertiary amino group-containing (meth)acrylates such as ethylaminoethyl (meth)acrylate, dimethylaminoethyl (meth)acrylate, diethylaminoethyl (meth)acrylate, dimethylaminopropyl (meth)acrylate, diethylaminopropyl (meth)acrylate, and dimethylaminopropylacrylamide; and monomers such as N-vinylpyrrolidone, methylvinylpyrrolidone, vinylpyridine, vinylpiperidone, vinylpyrimidine, vinylpiperazine, vinylpyrazine, vinylpyrrole, vinylimidazole, vinyloxazole, vinylmorpholine, (meth)acryloylmorpholine, N-vinylacetamides, and N-vinylcaprolactam.

[0040] Examples of the amide group-containing monomer include (meth)acrylamide; N-alkyl(meth)acrylamides such as N-methyl(meth)acrylamide, N-ethyl(meth)acrylamide, N-propyl(meth)acrylamide, Nn-butyl(meth)acrylamide, diacetone(meth)acrylamide, and N,N'-methylenebis(meth)acrylamide; N,N-dialkyl(meth)acrylamides such as N,N-dimethyl(meth)acrylamide, N,N-diethyl(meth)acrylamide, N,N-dipropyl(meth)acrylamide, N,N-ethylmethylacrylamide, and N,N-diallyl(meth)acrylamide; hydroxyalkyl(meth)acrylamides such as N-hydroxymethyl(meth)acrylamide and N-hydroxyethyl(meth)acrylamide; alkoxyalkyl(meth)acrylamides such as N-methoxymethyl(meth)acrylamide and N-(n-butoxymethyl)(meth)acrylamide; maleimide or a derivative thereof.

[0041] Examples of the isocyanate group-containing monomer include 2-(meth)acryloyloxyethyl isocyanate and alkylene oxide adducts thereof. The isocyanate group may be protected with a blocking agent such as methyl ethyl ketone oxime, 3,5-dimethylpyrazole, 1,2,4-triazole, or diethyl malonate.

[0042] Among these, those having a tertiary nitrogen atom are preferred because they have a sensitizing effect on the hydrogen abstraction reaction described below, and as a result, can efficiently form a crosslinked structure. For example, tertiary amino group-containing (meth)acrylates, N,N-dialkyl(meth)acrylamides, N-vinylpyrrolidone, acryloylmorpholine, and the like are particularly preferred.

[0043] From the viewpoint of imparting cohesive strength and resistance to wet heat whitening, the content of the structural units derived from the nitrogen-containing monomer (a3) ​​in the (meth)acrylic polymer (A) is preferably 0.1 to 15 mass% of all structural units of the (meth)acrylic polymer (A), more preferably 0.5 mass% or more or 13 mass% or less, even more preferably 1 mass% or more or 10 mass% or less, and even more preferably 2 mass% or more or 7 mass% or less. The lower limit and upper limit of the content of the structural unit derived from the nitrogen-containing monomer (a3) ​​in the (meth)acrylic polymer (A) can be combined in any desired manner.

[0044] Examples of the epoxy group-containing monomer (a4) include glycidyl (meth)acrylate, methyl glycidyl (meth)acrylate, 3,4-epoxycyclohexylmethyl (meth)acrylate, and 4-hydroxybutyl (meth)acrylate glycidyl ether. These may be used alone or in combination of two or more.

[0045] Examples of the vinyl monomer (a5) include compounds having a vinyl group in the molecule. Examples of such compounds include vinyl ester monomers such as vinyl acetate, vinyl propionate, vinyl laurate, and vinyl stearate, as well as aromatic vinyl monomers such as styrene, chlorostyrene, chloromethylstyrene, α-methylstyrene, and other substituted styrenes. These may be used alone or in combination of two or more. These may be used alone or in combination of two or more.

[0046] Examples of the alkyl(meth)acrylate monomer (a6) in which the alkyl group has 1 or 2 carbon atoms include methyl(meth)acrylate, ethyl(meth)acrylate, etc. These may be used alone or in combination of two or more. From the viewpoint of imparting cohesive strength to the pressure-sensitive adhesive sheet, the content of the structural units derived from the copolymerizable monomer (a6) in the (meth)acrylic polymer (A) is preferably 0.1 to 15 mass % relative to all structural units of the (meth)acrylic polymer (A), and more preferably 0.5 mass % or more or 13 mass % or less, more preferably 1 mass % or more or 10 mass % or less, and even more preferably 2 mass % or more or 7 mass % or less. The lower limit and upper limit of the content of the structural unit derived from the copolymerizable monomer (a6) in the (meth)acrylic polymer (A) can be combined in any desired manner.

[0047] Examples of the alicyclic monomer (a7) include cyclohexyl (meth)acrylate, 3,3,5-trimethylcyclohexyl (meth)acrylate, isobornyl (meth)acrylate, dicyclopentanyl (meth)acrylate, dicyclopentenyloxyethyl (meth)acrylate, t-butylcyclohexyl (meth)acrylate, adamantyl (meth)acrylate, etc. These may be used alone or in combination of two or more. From the viewpoint of imparting cohesive strength to the pressure-sensitive adhesive sheet, the content of the structural units derived from the copolymerizable monomer (a7) in the (meth)acrylic polymer (A) is preferably 0.1 to 15 mass % relative to all structural units of the (meth)acrylic polymer (A), and more preferably 0.5 mass % or more or 13 mass % or less, more preferably 1 mass % or more or 10 mass % or less, and even more preferably 2 mass % or more or 7 mass % or less. The lower limit and upper limit of the content of the structural unit derived from the copolymerizable monomer (a7) in the (meth)acrylic polymer (A) can be combined in any desired manner.

[0048] Examples of the other copolymerizable monomers (a8) include (meth)acrylates having an alkoxyalkylene glycol skeleton, such as methoxydiethylene glycol (meth)acrylate, methoxypolyethylene glycol (meth)acrylate, butoxypolyethylene glycol (meth)acrylate, methoxypolypropylene glycol (meth)acrylate, butoxypolypropylene glycol (meth)acrylate, methoxypolytetramethylene glycol (meth)acrylate, butoxypolytetramethylene glycol (meth)acrylate, methoxypolyoxyethylene polyoxypropylene glycol (meth)acrylate, and butoxypolyoxyethylene polyoxypropylene glycol (meth)acrylate; phenyl (meth)acrylate, benzyl (meth)acrylate, phenoxyethyl (meth)acrylate, phenyldiethylene glycol (meth)acrylate, phenoxypolyethylene glycol (meth)acrylate, and phenoxypolyethylene glycol-polypropylene glycol-(meth)acrylate; Aromatic (meth)acrylates such as acrylates and nonylphenol ethylene oxide adduct (meth)acrylates, 4-acryloyloxybenzophenone, 4-acryloyloxyethoxybenzophenone, 4-acryloyloxy-4'-methoxybenzophenone, 4-acryloyloxyethoxy-4'-methoxybenzophenone, 4-acryloyloxy-4'-bromobenzophenone, 4-acryloyloxyethoxy-4'-bromobenzophenone, 4-methacryloyloxybenzophenone, 4- Examples include (meth)acrylates having a benzophenone structure such as methacryloyloxyethoxybenzophenone, 4-methacryloyloxy-4'-methoxybenzophenone, 4-methacryloyloxyethoxy-4'-methoxybenzophenone, 4-methacryloyloxy-4'-bromobenzophenone, 4-methacryloyloxyethoxy-4'-bromobenzophenone, and mixtures thereof, heterocycle-containing (meth)acrylates such as tetrahydrofurfuryl (meth)acrylate, and macromonomers, etc. These can be used alone or in combination of two or more.

[0049] The content of the structural units derived from the copolymerizable monomer (a8) in the (meth)acrylic polymer (A) is preferably 1% by mass or more and 30% by mass or less, more preferably 3% by mass or more or 20% by mass or less, and even more preferably 5% by mass or more or 15% by mass or less, based on all structural units constituting the (meth)acrylic polymer (A). The lower and upper limits of the content can be combined in any manner. The lower limit and upper limit of the content of the structural unit derived from the copolymerizable monomer (a8) in the (meth)acrylic polymer (A) can be combined in any desired manner.

[0050] The (meth)acrylic polymer (A) may have a photoactive moiety, such as a polymerizable carbon-carbon double bond group, introduced into its side chain, which can enhance the crosslinking efficiency of the resin composition and crosslink the resin composition in a shorter time, thereby increasing productivity.

[0051] Examples of a method for introducing a polymerizable carbon-carbon double bond group into the side chain of the (meth)acrylic polymer (A) include a method in which a copolymer containing the above-mentioned hydroxyl group-containing monomer (a2) or a functional group-containing ethylenically unsaturated monomer is prepared, and then a compound having a polymerizable carbon-carbon double bond group and a functional group reactive with the functional group is subjected to a condensation or addition reaction while maintaining the activity of the polymerizable carbon-carbon double bond group.

[0052] Examples of combinations of these functional groups include an epoxy group (glycidyl group) and a carboxy group, an amino group and a carboxy group, an amino group and an isocyanate group, an epoxy group (glycidyl group) and an amino group, a hydroxyl group and an epoxy group, and a hydroxyl group and an isocyanate group. Among these combinations of functional groups, a combination of a hydroxyl group and an isocyanate group is preferred because of the ease of reaction control. Among these, a combination in which the copolymer has a hydroxyl group and the compound has an isocyanate group is preferred.

[0053] Examples of the isocyanate compound having a polymerizable carbon-carbon double bond group include the above-mentioned 2-(meth)acryloyloxyethyl isocyanate and alkylene oxide adducts thereof.

[0054] From the viewpoint of improving adhesiveness and stress relaxation properties, the content of the compound having a functional group reactive with the functional group and a polymerizable carbon-carbon double bond group is preferably 10 parts by mass or less, more preferably 5 parts by mass or less, even more preferably 1 part by mass or less, and particularly preferably 0.1 parts by mass or less, relative to 100 parts by mass of the (meth)acrylic polymer (A). The lower limit is usually 0 part by mass.

[0055] The mass average molecular weight (Mw) of the (meth)acrylic polymer (A) is preferably 200,000 or more, more preferably 300,000 or more, and even more preferably 400,000 or more, from the viewpoint of obtaining a resin composition having high cohesive strength. In addition, the upper limit of the mass average molecular weight (Mw) of the (meth)acrylic polymer (A) is preferably 1.5 million or less, more preferably 1.2 million or less, even more preferably 1.1 million or less, and particularly preferably 1 million or less, from the viewpoints of handleability and uniform stirring. The lower limit and upper limit of the mass average molecular weight of the (meth)acrylic polymer (A) can be combined arbitrarily. The mass average molecular weight of the (meth)acrylic polymer (A) is a value calculated as a standard polystyrene as measured by gel permeation chromatography (GPC).

[0056] The method for producing the (meth)acrylic polymer (A) is not particularly limited, but for example, a method of polymerizing a monomer mixture containing an alkyl (meth)acrylate having an alkyl group with 3 to 30 carbon atoms and one or more copolymerizable monomers selected from the copolymerizable monomers (a1) to (a8) used as needed can be used.

[0057] <Photopolymerization initiator (B)> The photopolymerization initiator is a compound that generates radicals when exposed to active energy rays. Photopolymerization initiators are broadly classified into two types based on the radical generation mechanism: cleavage-type photopolymerization initiators, which can generate radicals by cleaving the single bond of the initiator itself, and hydrogen abstraction-type photopolymerization initiators, which can generate radicals by the excited initiator abstracting hydrogen from a hydrogen donor in the system.

[0058] In the present resin composition, the photopolymerization initiator (B) is preferably a photopolymerization initiator having a molar absorption coefficient at a wavelength of 405 nm of 10 (L / mol cm) or more, more preferably a photopolymerization initiator having a molar absorption coefficient at a wavelength of 405 nm of 20 (L / mol cm) or more, and even more preferably a photopolymerization initiator having a molar absorption coefficient at a wavelength of 405 nm of 30 (L / mol cm) or more.

[0059] The use of the cleavage-type photopolymerization initiator is preferred in that it exhibits high photosensitivity to light. The type of cleavage-type photopolymerization initiator is not particularly limited as long as the effects of the present invention can be obtained, but for example, α-aminoacetophenone-based or acylphosphine oxide-based photopolymerization initiators can be used.

[0060] On the other hand, in view of the fact that some types of cleavage-type photopolymerization initiators may generate outgassing such as benzaldehyde, hydrogen abstraction-type photopolymerization initiators are preferred from the viewpoint of suppressing outgassing derived from the polymerization initiator. When a hydrogen abstraction polymerization initiator is used, the type thereof is not particularly limited as long as the effects of the present invention can be obtained. For example, a photopolymerization initiator containing oxanthone, anthraquinone, glyoxylate, or a structure similar thereto in the molecule is preferred in that it does not produce photodecomposition products and can therefore suppress the generation of outgassing, etc.

[0061] Among hydrogen abstraction polymerization initiators, a hydrogen abstraction photopolymerization initiator (b1) having a glyoxylate structure in the molecule (hereinafter, may be referred to as a "glyoxylate-type photopolymerization initiator" or "photopolymerization initiator (b1)") is preferred from the viewpoint of being able to reduce the content of unreacted polymerization initiator, since it has a relatively high molar absorption coefficient for light with a wavelength of 405 nm and is unlikely to leave unreacted polymerization initiator after curing.

[0062] (Glyoxylate-type photopolymerization initiator (b1)) Next, the use of the glyoxylate-type photopolymerization initiator (b1) will be described in detail, but the present invention is not limited to the following embodiment.

[0063] The glyoxylate-type photopolymerization initiator (b1) has a good molar absorption coefficient for 405 nm light and is therefore highly sensitive to long-wavelength active energy rays, and therefore, the photopolymerization initiator (b1) can be used to obtain the present resin composition that can be cured with relatively long-wavelength active energy rays (for example, active energy rays with a wavelength of 405 nm, which is longer than 380 nm). From this viewpoint, the molar absorption coefficient is usually 30 (L / mol cm) or more, preferably 40 (L / mol cm) or more, more preferably 50 (L / mol cm) or more, even more preferably 60 (L / mol cm) or more, and particularly preferably 70 (L / mol cm) or more. The upper limit of the molar absorption coefficient is 1.0 × 10 in terms of internal (or deep) curability. 6 (L / mol cm) or less is preferable, and 5.0 × 10 5 (L / mol cm) or less, and more preferably 1.0 × 10 5 (L / mol cm) or less, and particularly preferably 5.0 × 10 4 (L / mol·cm) or less. The lower and upper limits of the molar extinction coefficient can be combined arbitrarily.

[0064] The molar absorption coefficient of the photopolymerization initiator (b1) for light with a wavelength of 405 nm is calculated from the absorbance obtained by dissolving a predetermined concentration of the photopolymerization initiator (b1) in chloroform or the like, measuring the absorbance at 405 nm using an ultraviolet-visible spectrophotometer, and using the following formula: A=εLc (A is absorbance, ε is molar absorption coefficient (L / mol cm), c is molar concentration of photopolymerization initiator (b1) (mol / L), and L is optical path length (cm).

[0065] The photopolymerization initiator (b1) has a glyoxylate structure represented by the following formula 1.

[0066] TIFF2025134267000001.tif45170

[0067] In the formula 1, R 1 is a substituted or unsubstituted C1-C 20 Alkyl, substituted or unsubstituted C3-C 20 Cycloalkyl or substituted or unsubstituted C2-C 20 It is heterocycloalkyl. * indicates a bond. In addition, "C1~C 20 "Alkyl" means an alkyl group having 1 to 20 carbon atoms (C3 to C 20 Cycloalkyl, C2-C 20 The same applies to heterocycloalkyl, etc.).

[0068] In the formula 1, R 1 C1~C 20 When the alkyl is C1 to C 20 Alkyl is one or more of the same or different O, S, N(R 3 ), C(O), C(O)O and OC(O), and may be interrupted by one or more identical or different groups R 1a may have Here, the R 1a are each independently F, Cl, Br, I, CN, NO2, SR 5 , OR 6 , N.R.7 R 8 , C(O)R 9 , C(O)OR 10 , C(O)NR 11 R 12 , C3-C optionally interrupted by one or more C(O) groups 20 Cycloalkyl, C6-C 10 It is selected from the group consisting of aryl and (meth)acryloyloxy groups. R 1a C3 to C in 20 Cycloalkyl and C6-C 10 Aryl can be one or more identical or different groups R 1aa may have

[0069] The R 1aa are each independently C1 to C 12 Alkyl, C2-C 12 Alkenyl, F, Cl, Br, I, NO2, SR 5 , OR 6 and NR 7 R 8 is selected from the group consisting of: R 1aa C1 to C in 12 Alkyl is O, S, N(R 3 ), C(O), C(O)O, and OC(O), and may be interrupted by one or more groups selected from the group consisting of F, Cl, Br, I, NO, SR 5 , OR 6 , N.R. 7 R 8 , C(O)R 9 , C(O)OR 10 and C(O)NR 11 R 12 may have one or more identical or different groups selected from the group consisting of:

[0070] In the formula 1, R 1 C3~C 20 Cycloalkyl or C2-C 20 When the heterocycloalkyl is a C3 to C 20Cycloalkyl or C2-C 20 Heterocycloalkyl may be interrupted by one or more C(O) groups and may contain one or more identical or different groups R 1b may have Here, the R 1b are each independently C1 to C 12 Alkyl, C2-C 12 Alkenyl, F, Cl, Br, I, CN, NO2, SR 5 , OR 6 and NR 7 R 8 is selected from the group consisting of: R 1b C1 to C in 12 Alkyl is F, Cl, Br, I, NO2, SR 5 , OR 6 , N.R. 7 R 8 , C(O)R 9 , C(O)OR 10 , and C(O)NR 11 R 12 may have one or more identical or different groups selected from the group consisting of:

[0071] The N(R 3 )R 3 are hydrogen atoms, C1 to C 18 Alkyl, C2-C 18 Alkanoyl, C6-C 10 Aryl and C7-C 11 aroyl. R 3 C1 to C in 18 Alkyl is O, S, N(C1-C 12 alkyl), C(O), C(O)O, and OC(O), and may be interrupted by one or more groups selected from the group consisting of F, Cl, Br, I, C3-C 10 Cycloalkyl, C2-C 10 Heterocycloalkyl, C6-C 10It may have one or more identical or different groups selected from the group consisting of aryl, OH, and SH. R 3 C2~C in 20 The alkanoyl may be interrupted by one or more groups selected from the group consisting of O, S, CO, C(O)O, and OC(O), and may be any of F, Cl, Br, I, C3-C 10 Cycloalkyl, C2-C 10 Heterocycloalkyl and C6-C 10 It may have one or more identical or different groups selected from the group consisting of aryl. R 3 C6~C in 10 Aryl is F, Cl, Br, I, C1-C 10 Alkyl, C1-C 10 Alkoxy and C2-C 11 It may have one or more identical or different groups selected from the group consisting of acyloxy. R 3 C7~C 11 Aroyl is F, Cl, Br, I, C1-C 10 Alkyl, C1-C 10 Alkoxy and C2-C 11 It may have one or more identical or different groups selected from the group consisting of acyloxy.

[0072] The SR 5 R 5 , and OR 6 R 6 are each independently a hydrogen atom, C1 to C 20 Alkyl, C2-C 20 Alkanoyl, C6-C 10 Aryl and C7-C 11 aroyl. R 5 and R 6 C1 to C in 20 Alkyl is O, S, N(C1-C 12alkyl), C(O), C(O)O, and OC(O), and may be interrupted by one or more groups selected from the group consisting of F, Cl, Br, I, C3-C 10 Cycloalkyl, C2-C 10 Heterocycloalkyl, C6-C 10 It may have one or more identical or different groups selected from the group consisting of aryl, OH, and SH. R 5 and R 6 C2~C in 20 The alkanoyl may be interrupted by one or more groups selected from the group consisting of O, S, C(O), C(O)O, and OC(O), and may be any of F, Cl, Br, I, C3-C 10 Cycloalkyl, C2-C 10 Heterocycloalkyl and C6-C 10 It may have one or more identical or different groups selected from the group consisting of aryl. R 5 and R 6 C6~C in 10 Aryl is F, Cl, Br, I, C1-C6 alkyl, C1-C 10 Alkoxy and C2-C 11 It may have one or more identical or different groups selected from the group consisting of acyloxy. R 5 and R 6 C7~C 11 Aroyl is F, Cl, Br, I, C1-C 10 Alkyl, C1-C 10 Alkoxy and C2-C 11 It may have one or more identical or different groups selected from the group consisting of acyloxy.

[0073] The NR 7 R 8 R 7 and R 8 are each independently a hydrogen atom, C1 to C 20 Alkyl, C2-C 20Alkanoyl, C7-C 11 Aroyl, C6~C 10 aryl. R 7 and R 8 C1 to C in 20 Alkyl is O, S, N(C1-C 12 alkyl), C(O), C(O)O, and OC(O), and may be interrupted by one or more groups selected from the group consisting of F, Cl, Br, I, NO, C-C 10 It may have one or more identical or different groups selected from the group consisting of cycloalkyl, heterocycloalkyl, phenyl, OH, SH and CN. R 7 and R 8 C2~C in 20 The alkanoyl may be interrupted by one or more groups selected from the group consisting of O and S, and may have one or more identical or different groups selected from the group consisting of F, Cl, Br, I, OH and C1-C6 alkoxy. R 7 and R 8 C7~C 11 The aroyl may have one or more identical or different groups selected from the group consisting of F, Cl, Br, I, C1-C6 alkyl, —OH and C1-C6 alkoxy. R 7 and R 8 C6~C in 10 The aryl may have one or more identical or different groups selected from the group consisting of F, Cl, Br, I, C1-C6 alkyl, —OH and C1-C6 alkoxy. R 7 and R 8 may be taken together with the nitrogen atom to which they are attached to form a saturated 5-, 6- or 7-membered nitrogen heterocycle, said ring containing O, S, N(C1-C 12The ring may have a group selected from the group consisting of C(alkyl), C(O), and C(O)O as a ring member, and the ring may have one or more C1-C4 alkyls.

[0074] The C(O)R 9 R 9 are each independently a hydrogen atom, C1 to C 20 Alkyl and C6-C 20 aryl. R 9 C1 to C in 20 The alkyl may be interrupted by one or more groups selected from the group consisting of O, S and C(O), and may be interrupted by one or more of the same or different R 9a may have R 9a are each independently F, Cl, Br, I, C3 to C 10 It is selected from the group consisting of cycloalkyl, heterocycloalkyl, phenyl, OH, and SH. R 9 C6~C in 20 Aryl is F, Cl, Br, I, SR 5 , OR 6 , N.R. 7 R 8 , C1~C 12 Alkyl and C2-C 12 It may have one or more identical or different groups selected from the group consisting of acyloxy.

[0075] Said C(O)OR 10 R 10 is R 6 and the C(O)NR 11 R 12 R 11 and R 12 is R 7 , R 8 is synonymous with.

[0076] By having a glyoxylate structure, the photopolymerization initiator (b1) functions as a hydrogen abstraction type photopolymerization initiator. The hydrogen abstraction photopolymerization initiator is preferred because it does not generate photodecomposition products like the cleavage photopolymerization initiator. The hydrogen abstraction photopolymerization initiator is also preferred because it easily forms a crosslinked structure with many crosslinking points by causing a hydrogen abstraction reaction from the (meth)acrylic polymer (A) and incorporating the (meth)acrylic polymer (A) into the crosslinked structure.

[0077] Hydrogen abstraction photopolymerization initiators are broadly classified into intermolecular hydrogen abstraction photopolymerization initiators that abstract hydrogen from other molecules, and intramolecular hydrogen abstraction photopolymerization initiators that also undergo a hydrogen abstraction reaction within the same molecule. By having the glyoxylate structure, the photopolymerization initiator (b1) functions as an intramolecular hydrogen abstraction photopolymerization initiator. The intramolecular hydrogen abstraction type photopolymerization initiator is preferred in that it not only functions as a hydrogen donor in the system but also can itself be a starting point for radical generation.

[0078] In terms of solubility, R in Eq. 1 is preferably a linear or branched alkyl group or a cycloalkyl group, more preferably a linear or branched alkyl group. In terms of light curing, R 1 The alkyl group preferably has 1 to 20 carbon atoms, more preferably 1 to 12 carbon atoms, even more preferably 1 to 8 carbon atoms, and particularly preferably 1 or 2 carbon atoms. In terms of light curing, R 1 The cycloalkyl group preferably has 3 to 20 carbon atoms, and more preferably 3 to 10 carbon atoms.

[0079] The photopolymerization initiator (b1) is preferably a compound having two or more radical generating groups in the molecule (provided that at least one of the radical generating groups has a glyoxylate structure). Here, the term "radical generating group" refers to a group that generates a radical that initiates a polymerization reaction when excited by active energy rays. The "radical generating group" is preferably a group having a structure that is excited by irradiation with active energy rays and generates a radical by causing a hydrogen abstraction reaction. When the photopolymerization initiator (b1) has two or more radical generating groups, the resin composition can form crosslinks with high efficiency.

[0080] Examples of radical generating groups other than the glyoxylate structure include a benzophenone structure, a benzyl structure, a thioxanthone structure, a 3-ketocoumarin structure, an anthraquinone structure, and a camphorquinone structure.

[0081] Examples of the photopolymerization initiator (b1) include compounds represented by the following formula 2.

[0082] TIFF2025134267000002.tif49170

[0083] In the formula 2, A is O, S, NR 4 or a straight or branched alkylene or cycloalkylene having 1 to 6 carbon atoms. where R 4 is R 3 It is synonymous with R. 1 is the same as Equation 1 above. R 2 is a hydrogen atom, a substituted or unsubstituted C1-C 20 Alkyl, substituted or unsubstituted C3-C 20 Cycloalkyl, substituted or unsubstituted C2-C 20 Heterocycloalkyl, substituted or unsubstituted C6-C 20 Aryl, substituted or unsubstituted C1-C 20 Heteroaryl, SR 5 , OR 6 , N.R. 7 R 8 , C(O)R 9 , or C(O)OR 13 where R 13 is R 1 is synonymous with.

[0084] In the formula 2, R 2 C1~C 20 When the alkyl is C1 to C 20Alkyl is one or more of the same or different O, S, N(R 3 ), C(O), C(O)O, and OC(O), and may be interrupted by one or more identical or different groups R 2a may have where R 2a is R 1a is synonymous with.

[0085] In the formula 2, R 2 C3~C 20 Cycloalkyl or C2-C 20 When the heterocycloalkyl is a C3 to C 20 Cycloalkyl or C2-C 20 Heterocycloalkyl may be interrupted by one or more C(O) groups and may contain one or more identical or different groups R 2b where R 2b is R 1b is synonymous with.

[0086] In the formula 2, R 2 C6~C 20 Aryl or C1-C 20 When the heteroaryl is a C6 to C 20 Aryl or C1-C 20 Heteroaryl can be one or more identical or different groups R 2c may have R 2c are each independently C1 to C 12 Alkyl, C2-C 12 Alkenyl, F, Cl, Br, I, CN, NO2, SR 5 , OR 6 , N.R. 7 R 8 , C(O)R 9 , C(O)OR 10 , C(O)NR 11 R 12 , C6~C 10 Aryl, C1-C 20 Heteroaryl, C3-C 10 Cycloalkyl and C2-C10 heterocycloalkyl. R 2c C1 to C in 12 Alkyl is F, Cl, Br, I, NO2, SR 5 , OR 6 , N.R. 7 R 8 , C(O)R 9 , C(O)OR 10 , and C(O)NR 11 R 12 may have one or more identical or different groups selected from: R 2c C1 to C in 12 Alkyl, C3-C 10 Cycloalkyl and C2-C 10 The heterocycloalkyl may be interrupted by one or more C(O) groups. R 2c C6~C in 10 Aryl, C1-C 20 Heteroaryl, C3-C 10 Cycloalkyl and C2-C 10 Heterocycloalkyl may be one or more of the same or different groups R 1ca where R 1ca is the R 1aa is synonymous with.

[0087] Among the compounds represented by formula 2, diphenyl sulfide derivatives in which A in the formula is a sulfur atom are preferred from the viewpoint of photoreactivity. Among these, R 2 is a substituted or unsubstituted aromatic group having 6 to 20 carbon atoms or (O)OR 13 Preferably, R 13 is R 1 is synonymous with.

[0088] The photopolymerization initiator (b1) is more preferably one or more compounds selected from the compounds represented by the following formulas 3 to 5.

[0089] TIFF2025134267000003.tif48170

[0090] TIFF2025134267000004.tif49170

[0091] In formula 4, n is an integer of 0 to 5.

[0092] TIFF2025134267000005.tif58170

[0093] In formula 5, o is an integer of 0 to 3, and p is an integer of 0 to 4.

[0094] Among these, from the viewpoint of photoreactivity, the photopolymerization initiator (b1) is a compound represented by the formulas 3 to 5, wherein R 1 and R 13 is a linear or branched alkyl having 1 to 8 carbon atoms, and n, o, and p are 0. Compounds including either or both of a compound represented by the following formula 3-1 and a compound represented by the following formula 4-1 are particularly preferred.

[0095] TIFF2025134267000006.tif76170

[0096] The photopolymerization initiator (b1) can be used alone or in combination of two or more. The content of the photopolymerization initiator (b1) in the resin composition is preferably 0.1 parts by mass or more, more preferably 0.5 parts by mass or more, and even more preferably 1 part by mass or more, relative to 100 parts by mass of the (meth)acrylic polymer (A). The upper limit is preferably 10 parts by mass or less, more preferably 8 parts by mass or less, even more preferably 5 parts by mass or less, and particularly preferably 3 parts by mass or less. When the content of the photopolymerization initiator (b1) is equal to or greater than the lower limit, poor curing tends to be prevented, and when it is equal to or less than the upper limit, bleeding out of the photopolymerization initiator (b1) is suppressed and problems such as embrittlement and coloration tend to be easily suppressed. The lower limit and upper limit of the content of the photopolymerization initiator (b1) can be arbitrarily combined.

[0097] The terms used in the photopolymerization initiator (b1) are defined as follows:

[0098] The term "alkyl" in the photopolymerization initiator (b1) generally refers to a saturated, linear or branched hydrocarbon group having 1 to 20, preferably 1 to 12, and more preferably 1 to 10 carbon atoms. Examples of the alkyl group include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, s-butyl, t-butyl, n-pentyl, neo-pentyl, n-hexyl, n-heptyl, n-octyl, 2-ethylhexyl, n-nonyl, n-decyl, n-undecyl, n-dodecyl, n-tridecyl, n-tetradecyl, n-hexadecyl, n-octadecyl, and n-eicosyl. Alkyl is one or more of the same or different O, S, N(R 3 ), C(O), C(O)O, and OC(O). Multiple O, S, N(R 3 When present, C(O), C(O)O, and OC(O) are usually separated from each other by at least one methylene group. 3 is as defined above. Examples of alkyl interrupted by one or more O atoms are -CH2-O-CH3, -CH2CH2-O-CH2CH3, -[CH2CH2O] y -CH3 (y is 1 to 9), -(CH2CH2O) y CH2CH3 (y is 1 to 9), -CH2-CH(CH3)-O-CH2-CH2CH3, -CH2-CH2CH(CH3)-O-CH2-CH2CH3, -CH2-CH2CH(CH3)-O-CH2CH3, -CH2-CH2CH(CH3)-O-CH2CH3, -CH2-CH2CH(CH3)-O-CH3 and -CH2CH(CH3)-O-CH2CH3.

[0099] The term "cycloalkyl" in the photopolymerization initiator (b1) refers to a monocyclic or polycyclic aliphatic group having usually 3 to 20, preferably 3 to 16, more preferably 3 to 12 carbon atoms. Examples of the monocyclic aliphatic group include cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, and cyclooctyl, with cyclopentyl and cyclohexyl being particularly preferred. Examples of polycyclic rings include perhydroanthracyl, perhydronaphthyl, perhydrofluorenyl, perhydrochrysenyl, perhydropicenyl, adamantyl, bicyclo[1.1.1]pentyl, bicyclo[2.2.1]heptyl, bicyclo[4.2.2]decyl, bicyclo[2.2.2]octyl, bicyclo[3.3.0]octyl, bicyclo[3.3.2]decyl, bicyclo[4.4.0]decyl, bicyclo[4.3.2]undecyl, bicyclo[4.3.3]dodecyl, bicyclo[3.3.3]undecyl, bicyclo[4.3.1]decyl, bicyclo[4.2.1]nonyl, bicyclo[3.3.1]nonyl, and bicyclo[3.2.1]octyl. Cycloalkyl may be interrupted by one or more C(O) groups. An example of a cycloalkyl interrupted by one C(O) is 3-oxobicyclo[2.2.1]heptyl.

[0100] The term "heterocycloalkyl" in the photopolymerization initiator (b1) generally refers to a 3- to 8-membered, particularly a 5-, 6-, 7-, or 8-membered, monocyclic heterocyclic non-aromatic group and a bicyclic heterocyclic non-aromatic group. The monocyclic and bicyclic non-aromatic groups may be saturated or unsaturated. The monocyclic and bicyclic non-aromatic groups typically contain 1, 2, 3, or 4 heteroatoms selected from N, O, and S, particularly 1 or 2 heteroatoms, as ring members, where the S atom as a ring member may be present as S, SO, or SO. The heterocycloalkyl may be interrupted by one or more C(O) groups, typically 1 or 2 groups. Examples of saturated or unsaturated 3- to 8-membered non-aromatic heterocyclic groups include oxiranyl, oxetanyl, thietanyl, thietanyl-S-oxide (S-oxothietanyl), thietanyl-S-dioxide (S-dioxothietanyl), pyrrolidinyl, pyrazolinyl, imidazolinyl, pyrrolinyl, pyrazolinyl, imidazolinyl, tetrahydrofuranyl, dihydrofuranyl, 1,3-dioxolanyl, dioxolenyl, thiolanyl, S-oxothiolanyl, S-dioxothiolanyl, dihydrothienyl, S-oxodihydrothienyl, S-dioxodihydrothienyl, oxazolidinyl, isoxazolidinyl, oxazolinyl, and isoxazolinyl. Examples of the alkyl group include thiazolinyl, isothiazolinyl, thiazolidinyl, isothiazolidinyl, oxathiolanyl, piperidinyl, piperazinyl, pyranyl, dihydropyranyl, tetrahydropyranyl, 1,3- and 1,4-dioxanyl, thiopyranyl, S-oxothiopyranyl, S-dioxothiopyranyl, dihydrothiopyranyl, S-oxodihydrothiopyranyl, S-dioxodihydrothiopyranyl, tetrahydrothiopyranyl, S-oxotetrahydrothiopyranyl, S-dioxotetrahydrothiopyranyl, morpholinyl, thiomorpholinyl, S-oxothiomorpholinyl, S-dioxothiomorpholinyl, and thiazinyl. Examples of heterocyclic rings containing one or two carbonyl groups as ring members include pyrrolidin-2-onyl, pyrrolidine-2,5-dioneyl, imidazolidin-2-onyl, oxazolidin-2-onyl, and thiazolidin-2-onyl.

[0101] The term "aryl" in the photopolymerization initiator (b1) refers to monovalent monocyclic aromatic groups and polycyclic aromatic groups having ring carbon atoms. Monocyclic aromatic groups include, for example, phenyl. Polycyclic aromatic groups include, for example, bicyclic, tricyclic, or tetracyclic aromatic groups, such as naphthyl, phenanthrenyl, anthracenyl, or pyrenyl. Preferred examples of aryl are phenyl and naphthyl. Substituted phenyl is substituted with 1, 2, 3, 4 or 5 substituents. Naphthyl is usually substituted with 1, 2, 3, 4, 5, 6 or 7 substituents, preferably 1, 2, 3 or 4 substituents. Substituted phenyl is, for example, pentafluorophenyl, 2-methylphenyl, 3-methylphenyl, 4-methylphenyl, 2-ethylphenyl, 3-ethylphenyl, 4-ethylphenyl, 2-methoxyphenyl, 3-methoxyphenyl, 4-methoxyphenyl, 2-ethoxyphenyl, 3-ethoxyphenyl, 4-ethoxyphenyl, 3-nitrophenyl, 4-nitrophenyl, 2-chlorophenyl, 3-chlorophenyl, 4-chlorophenyl, 3-vinylphenyl, 4-vinylphenyl, 4-trifluoromethylphenyl, 3,5-diethoxycarbonylphenyl.

[0102] The term "heteroaryl" in the photoinitiator (b1) generally refers to unsaturated monocyclic heterocyclic groups as well as polycyclic heterocyclic groups that are aromatic. Heteroaryl typically contains, in addition to one or more carbon atoms as ring members, 1, 2, 3 or 4 heteroatoms selected from N, O and S as ring members. Examples of monocyclic heteroaromatic groups include 2-furyl, 3-furyl, 2-thienyl, 3-thienyl, 1-pyrrolyl, 2-pyrrolyl, 3-pyrrolyl, 1-pyrazolyl, 3-pyrazolyl, 4-pyrazolyl, 5-pyrazolyl, 2-oxazolyl, 4-oxazolyl, 5-oxazolyl, 2-thiazolyl, 4-thiazolyl, 5-thiazolyl, 3-isoxazolyl, 4-isoxazolyl or 5-isoxazolyl, 3-isothiazolyl, 4-isothiazolyl or 5-isothiazolyl, 1-imidazolyl, 2-imidazolyl, 4-imidazolyl, 2- or 5-[1,3,4]oxadiazolyl, 4- or 5-(1,2,3-oxadiazol)yl, 3- or 5-(1,2,4-oxadiazol)yl, thiadiazolyl, 2- or 5-(1,3,4-thiadiazol)yl, 2- or 5-(1,3,4-thiadiazol)yl, 4- or 5-(1,2,3-thiadiazol)yl, 3- or 5-(1,2,4-thiadiazol)yl, 1H-, 2H- or 3H-1,2,3-triazol-4-yl, 1,3,4-triazol-2-yl, 2H-triazol-3-yl, 1H-, 2- or 4H-1,2,4-triazolyl, 1H- or 2H-tetrazolyl, 2-pyridinyl, 3-pyridinyl, 4-pyridinyl, 3-pyridazinyl, 4-pyridazinyl, 2-pyrimidinyl, 4-pyrimidinyl, 5-pyrimidinyl and 2-pyrazinyl. Examples of polycyclic heterocyclic groups include benzofuranyl, benzothienyl, indolyl, indazolyl, benzimidazolyl, benzoxathiazolyl, benzoxadiazolyl, benzothiadiazolyl, benzoxazinyl, quinolinyl, isoquinolinyl, purinyl, 1,8-naphthyridyl, pteridyl, pyrido[3,2-d]pyrimidyl, pyridoimidazolyl, carbazoyl, and acridinyl.

[0103] The term "alkanoyl" in the photopolymerization initiator (b1) is alkyl-C(O), which refers to a saturated, linear or branched alkyl group as defined above, typically having 3 to 20 carbon atoms, bonded at any position in the alkyl group through the carbon atom of a carbonyl group, such as acetyl, propanoyl, 2-methyl-propanoyl, butanoyl, pentanoyl, or hexanoyl.

[0104] The term "aroyl" in the photoinitiator (b1) is aryl-C(O) and refers to a group bonded at any position in the aryl group defined above through the carbon atom of a carbonyl group, such as benzoyl and naphthoyl.

[0105] The term "heteroaroyl" in the photopolymerization initiator (b1) is heteroaryl-C(O), and refers to a group bonded at any position in the heteroaryl group defined above through the carbon atom of a carbonyl group.

[0106] The term "alkylene" in the photopolymerization initiator (b1) refers in each case to an alkyl group having carbon atoms as defined above, in which one hydrogen atom at any position of the alkyl group is replaced by an additional bonding site to form a divalent group. Thus, C1-C6 alkylene can include divalent branched or unbranched saturated aliphatic chains having 1 to 6 carbon atoms, such as -CH2-, -CH2CH2-, -CH(CH3)-, -CH2CH2CH2-, -CH(CH3)CH2-, -C(CH3)2-, -CH2CH2CH2CH2-, -CH2CH(CH3)CH2-, -CH(CH3)CH(CH3)-, -CH2CH2CH2CH2CH2-, -CH2CH2CH2CH2-, -CH2CH2CH2CH(CH3)-, -CH2C(CH3)2CH2-, and -CH2CH2CH2CH2CH2-.

[0107] The term "cycloalkylene" in photoinitiator (b1) refers to a cycloalkyl group, as defined above, in which one hydrogen atom at any position of the cycloalkyl is replaced by an additional bonding site to form a divalent group. In the case of polycyclic cycloalkylenes, the bonding points are located either in the same ring or in different rings. Monocyclic rings include, for example, cyclopropylene, cyclobutylene, cyclopentylene, cyclohexylene or cycloheptylene, in particular cyclohexylene. Examples of polycyclic rings include perhydroanthracylene, perhydronaphthylene, perhydrofluorenylene, perhydrochrysenylene, perhydropicenylene, adamantylene, bicyclo[1.1.1]pentylene, bicyclo[2.2.1]heptylene, bicyclo[4.2.2]decylene, bicyclo[2.2.2]octylene, bicyclo[3.3.2]decylene, bicyclo[4.3.2]undecylene, bicyclo[4.3.3]dodecylene, bicyclo[3.3.3]undecylene, bicyclo[4.3.1]decylene, bicyclo[4.2.1]nonylene, bicyclo[3.3.1]nonylene, and bicyclo[3.2.1]octylene.

[0108] (Photopolymerization initiator (b2)) The resin composition may contain, as the photopolymerization initiator (B), a photopolymerization initiator (b2) other than the glyoxylate-type photopolymerization initiator (b1) as long as the effects of the present invention are not impaired. The photopolymerization initiator (b2) may be either a hydrogen abstraction type photopolymerization initiator or a cleavage type photopolymerization initiator, and each may be used alone or in combination of the two.

[0109] Examples of the hydrogen abstraction type photopolymerization initiator as the photopolymerization initiator (b2) include benzophenone, 4-methylbenzophenone, 2,4,6-trimethylbenzophenone, 4-phenylbenzophenone, 3,3'-dimethyl-4-methoxybenzophenone, methyl 2-benzoylbenzoate, 4-[(4-methylphenyl)thio]benzophenone, 4-acryloyloxybenzophenone, 4-acryloyloxyethoxybenzophenone, 4-acryloyloxy-4'-methoxybenzophenone, 4-acryloyloxyethoxy-4'-methoxybenzophenone, 4-acryloyloxy-4'-bromobenzophenone, and 4-acryloyloxyethoxy-4'-bromobenzophenone. intermolecular hydrogen abstraction photopolymerization initiators such as benzophenone, 4-methacryloyloxybenzophenone, 4-methacryloyloxyethoxybenzophenone, 4-methacryloyloxy-4'-methoxybenzophenone, 4-methacryloyloxyethoxy-4'-methoxybenzophenone, 4-methacryloyloxy-4'-bromobenzophenone, and 4-methacryloyloxyethoxy-4'-bromobenzophenone; and intramolecular hydrogen abstraction photopolymerization initiators such as methyl benzoylformate, oxyphenylacetic acid-2-(2-oxo-2-phenyl-acetoxy-ethoxy)ethyl ester, and oxyphenylacetic acid-2-(2-hydroxy-ethoxy)ethyl ester. Among these, 4-acryloyloxybenzophenone, 4-acryloyloxyethoxybenzophenone, 4-acryloyloxy-4'-methoxybenzophenone, 4-acryloyloxyethoxy-4'-methoxybenzophenone, etc., which have a radically polymerizable functional group with a carbon-carbon double bond in the molecule, are preferred in that they are incorporated into the polymerization structure after the photoreaction, thereby suppressing bleed-out of the photopolymerization initiator and improving the cohesive strength of the adhesive sheet. Furthermore, an intramolecular hydrogen abstraction type photopolymerization initiator is preferred in that it not only functions as a hydrogen donor in the system but also can itself serve as a starting point for radical generation.

[0110] Furthermore, as the photopolymerization initiator (b2), a cleavage-type photopolymerization initiator may also be used to the extent that photodecomposition products do not affect the quality. The cleavage-type photopolymerization initiator is preferred because it has high photosensitivity. Examples of the cleavage-type photopolymerization initiator include 2,2-dimethoxy-1,2-diphenylethan-1-one, 1-hydroxycyclohexyl phenyl ketone, 2-hydroxy-2-methyl-1-phenyl-propan-1-one, 1-[4-(2-hydroxyethoxy)phenyl]-2-hydroxy-2-methyl-1-propan-1-one, 2-hydroxy-1-{4-[4-(2-hydroxy-2-methyl-propionyl)benzyl]phenyl}-2-methyl-propan-1-one, oligo(2-hydroxy-2-methyl-1-(4-(1-methylvinyl)phenyl)propanone), 2-benzyl-2-dimethylamino-1-( 4-morpholinophenyl)butan-1-one, 2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropan-1-one, 2-(dimethylamino)-2-[(4-methylphenyl)methyl]-1-[4-(4-morpholinyl)phenyl]-1-butanone, bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, (2,4,6-trimethylbenzoyl)ethoxyphenylphosphine oxide, bis(2,6-dimethoxybenzoyl)2,4,4-trimethylpentylphosphine oxide, and their derivatives The following can be mentioned:

[0111] The content of the photopolymerization initiator (b2) in the resin composition is preferably 5 parts by mass or less, more preferably 4 parts by mass or less, still more preferably 3 parts by mass or less, and particularly preferably 2 parts by mass or less, relative to 100 parts by mass of the (meth)acrylic polymer (A). The lower limit is usually 0 parts by mass.

[0112] <Polyfunctional (meth)acrylate (C)> In one embodiment, the resin composition preferably contains a multifunctional (meth)acrylate (C) as a photocrosslinking agent from the viewpoint of promoting the crosslinking reaction. This allows the resin composition to quickly form a crosslinked structure even with the same amount of light irradiation, for example. Furthermore, when a crosslinked structure is formed in a pressure-sensitive adhesive sheet using the resin composition, it is possible to prevent adhesive extrusion during storage or when wound into a roll, and it is also possible to obtain good adhesiveness and cohesive strength. However, when the acrylic polymer (A) undergoes a hydrogen abstraction reaction due to the action of the photopolymerization initiator (B) or the like, and a sufficient crosslinked structure can be formed within the acrylic polymer (A) and / or between the acrylic polymers (A), it is not necessarily necessary to contain the polyfunctional (meth)acrylate (C).

[0113] Examples of the polyfunctional (meth)acrylate (C) include (meth)acrylic monomers and (meth)acrylic oligomers having two or more functional groups, which can be used alone or in combination of two or more.

[0114] Examples of the (meth)acrylic monomer having two or more functional groups include pentanediol di(meth)acrylate, hexadiol di(meth)acrylate, heptanediol di(meth)acrylate, octanediol di(meth)acrylate, nonanediol di(meth)acrylate, decanediol di(meth)acrylate, undecanediol di(meth)acrylate, dodecanediol di(meth)acrylate, 1,4-Butanediol di(meth)acrylate, glycerin di(meth)acrylate, neopentyl glycol di(meth)acrylate, glycerin glycidyl ether di(meth)acrylate, tricyclodecane dimethacrylate, tricyclodecane dimethanol di(meth)acrylate, bisphenol A polyethoxy di(meth)acrylate, bisphenol A polypropoxy di(meth)acrylate, bisphenol F polyethoxy di(meth)acrylate, ethylene glycol di(meth)acrylate Tris(2-hydroxyethyl)isocyanurate tri(meth)acrylate, pentaerythritol tri(meth)acrylate, propoxylated pentaerythritol tri(meth)acrylate, ethoxylated pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, prop ... Pentaerythritol tetra(meth)acrylate, ethoxylated pentaerythritol tetra(meth)acrylate, dipentaerythritol hexa(meth)acrylate, polyethylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, polytetramethylene glycol di(meth)acrylate, tris(acryloxyethyl) isocyanurate, dipentaerythritol hexa(meth)acrylate, dipentaerythritol penta(meth)acrylate Examples of the hydroxypivalic acid di(meth)acrylate include tripentaerythritol hexa(meth)acrylate, tripentaerythritol penta(meth)acrylate, hydroxypivalic acid neopentyl glycol di(meth)acrylate, di(meth)acrylate of hydroxypivalic acid neopentyl glycol ε-caprolactone adduct, trimethylolpropane tri(meth)acrylate, trimethylolpropane polyethoxytri(meth)acrylate, and ditrimethylolpropane tetra(meth)acrylate.

[0115] Examples of polyfunctional (meth)acrylic oligomers include polyester (meth)acrylate oligomers, epoxy (meth)acrylate oligomers, urethane (meth)acrylate oligomers, and polyether (meth)acrylate oligomers. Among these, (meth)acrylate monomers and oligomers having a glycol structure are preferred from the viewpoint of imparting appropriate flexibility to the cured product.

[0116] The content of the polyfunctional (meth)acrylate (C) in the resin composition is preferably 0.1 parts by mass or more, more preferably 0.5 parts by mass or more, and even more preferably 1 part by mass or more, per 100 parts by mass of the (meth)acrylic polymer (A), from the viewpoint of imparting shape stability to the pressure-sensitive adhesive sheet and durability when made into a laminate for an image display device. The upper limit is preferably 20 parts by mass or less, more preferably 15 parts by mass or less, even more preferably 12 parts by mass or less, and particularly preferably 10 parts by mass or less, from the viewpoint of maintaining the flexibility of the pressure-sensitive adhesive sheet. The lower limit and the upper limit of the content of the polyfunctional (meth)acrylate (C) can be combined arbitrarily.

[0117] <Thermal crosslinking agent> The resin composition may also contain a thermal crosslinking agent in order to impart thermosetting properties to the pressure-sensitive adhesive sheet of the present invention or to further increase the crosslink density and improve long-term reliability. Examples of such thermal crosslinking agents include isocyanate-based crosslinking agents, epoxy-based crosslinking agents, aziridine-based crosslinking agents, melamine-based crosslinking agents, aldehyde-based crosslinking agents, amine-based crosslinking agents, and metal chelate-based crosslinking agents. Among these, it is preferable to use an isocyanate-based crosslinking agent because of its excellent reactivity with the (meth)acrylic polymer (A).

[0118] <Other ingredients> The resin composition may contain, as needed, various additives such as silane coupling agents, plasticizers, tackifying resins, antioxidants, light stabilizers, metal deactivators, antioxidants, moisture absorbents, rust inhibitors, and inorganic particles as "other components" within the scope of the present invention, as long as the effects of the present invention are not impaired. If necessary, a reaction catalyst such as a tertiary amine compound, a quaternary ammonium compound, or a tin laurate compound may be appropriately contained. These may be used alone or in combination of two or more.

[0119] <Configuration of the Pressure-Sensitive Adhesive Sheet of the Present Invention> The adhesive sheet of the present invention may be a single-layer sheet consisting only of an adhesive layer formed from the present resin composition (hereinafter also referred to as the "present adhesive layer"), or a multi-layer sheet in which multiple present adhesive layers are laminated.

[0120] <Physical Properties of the Pressure-Sensitive Adhesive Sheet of the Present Invention> The pressure-sensitive adhesive sheet of the present invention can have the following physical properties.

[0121] (gel fraction) Since the pressure-sensitive adhesive sheet of the present invention is a pressure-sensitive adhesive sheet containing a photocured product of the present resin composition, the gel fraction thereof is preferably 50% or more. When the pressure-sensitive adhesive sheet of the present invention has a gel fraction of 50% or more, the sheet has excellent durability. From this viewpoint, the gel fraction of the pressure-sensitive adhesive sheet of the present invention is preferably 50% or more, more preferably 55% or more, even more preferably 60% or more, and particularly preferably 65% ​​or more. On the other hand, from the viewpoint of obtaining flexibility, the gel fraction of the pressure-sensitive adhesive sheet of the present invention is preferably 95% or less, more preferably 90% or less, even more preferably 85% or less, and particularly preferably 80% or less. Furthermore, when the adhesive sheet of the present invention is thermosetting, it is preferable to leave room for three-dimensional crosslinking by heat, so the gel fraction of the adhesive sheet of the present invention is preferably 90% or less, more preferably 85% or less, even more preferably 80% or less, and particularly preferably 75% or less. The lower limit and upper limit of the gel fraction can be arbitrarily combined. The gel fraction is a measure of the degree of crosslinking (degree of hardening) and can be measured under the measurement conditions described in the examples below.

[0122] Methods for adjusting the gel fraction of the pressure-sensitive adhesive sheet of the present invention include, but are not limited to, adjusting the amount of photopolymerization initiator (B), blending and adjusting the amount of polyfunctional (meth)acrylate (C), and adjusting the light irradiation dose. The gel fraction can be measured by the method described in the Examples below.

[0123] (Adhesive strength) The adhesive strength of the pressure-sensitive adhesive sheet of the present invention to soda-lime glass at a peel angle of 180° and a peel rate of 60 mm / min is preferably 4 N / cm or more, more preferably 5 N / cm or more, more preferably 6 N / cm or more, and even more preferably 7 N / cm or more. When the adhesive strength of the pressure-sensitive adhesive sheet of the present invention is 4 N / cm or more, a laminate for an image display device using the pressure-sensitive adhesive sheet of the present invention will have excellent durability.

[0124] (chromaticity b * ) The pressure-sensitive adhesive sheet of the present invention is * a * b * Chromaticity in color space (b * 0) is preferably 1.5 or less, more preferably 1.2 or less, and even more preferably 1.0 or less. In this specification, "L * a * b * "Color space" is the CIE L color space defined by the CIE (International Commission on Illumination) in 1976.* a * b * (CIELAB) color space. The chromaticity (b * 0) is 1.5 or less, a pressure-sensitive adhesive sheet with reduced yellowing can be obtained.

[0125] The pressure-sensitive adhesive sheet of the present invention has a L * a * b * Chromaticity in color space (b * 1) is preferably 1.5 or less, more preferably 1.2 or less, and even more preferably 1.0 or less. The chromaticity (b * When 1) is equal to or less than the upper limit, the pressure-sensitive adhesive sheet can be evaluated as having excellent resistance to high temperatures. In addition, the pressure-sensitive adhesive sheet of the present invention has a color value (b * 1) and the color before heating (b * 0) (b * 1-b * 0) is preferably 1.5 or less, more preferably 1.0 or less, even more preferably 0.5 or less, and particularly preferably 0 or less. The above (b * 1) and (b * 1-b * 0) satisfies the above range, a pressure-sensitive adhesive sheet that is inhibited from yellowing due to heating can be obtained.

[0126] The pressure-sensitive adhesive sheet of the present invention is irradiated with active energy rays having a wavelength of 405 nm in an integrated amount of light of 2000 to 4000 mJ / cm 2 The chromaticity (b * 2) is preferably 2.5 or less, more preferably 2.0 or less, even more preferably 1.5 or less, and particularly preferably 1.0 or less. Furthermore, the pressure-sensitive adhesive sheet of the present invention has a color value (b * 2) and the chromaticity (b * 0) (b * 2-b* 0) is preferably 2.5 or less, more preferably 2.0 or less, even more preferably 1.5 or less, even more preferably 1.2 or less, particularly preferably 1.0 or less, and especially preferably 0.5 or less. The above (b * 2) and (b * 2-b * 0) satisfies the above range, a pressure-sensitive adhesive sheet that is inhibited from yellowing due to irradiation with active energy rays can be obtained.

[0127] The chromaticity (b * 0), chromaticity (b * 1) and chromaticity (b * 2) can be measured by the method described in the Examples below.

[0128] Photopolymerization initiators that are highly sensitive to light in the long wavelength region generally have the problem of being prone to coloration, but acylphosphine oxide-based photopolymerization initiators have a photobleaching effect and have been widely used in applications where coloration is a concern. However, this effect is due to the decomposition of cleavage-type photopolymerization initiators after photoreaction, and it was thought that hydrogen abstraction-type photopolymerization initiators, which do not photodecompose, did not have a photobleaching effect. However, it has been surprisingly found that by using the above-mentioned photopolymerization initiator (b1), even though it is a hydrogen abstraction type photopolymerization initiator, not only does it not turn yellow after heating or exposure to light, but also it has a photobleaching effect. The pressure-sensitive adhesive sheet of the present invention has excellent coloring resistance when exposed to high temperatures and ultraviolet radiation. Therefore, it can be suitably used for applications such as image display devices.

[0129] [Total light transmittance, haze] The total light transmittance of the pressure-sensitive adhesive sheet of the present invention is preferably 80% or more, more preferably 85% or more, and even more preferably 90% or more. The total light transmittance can be measured by the method described in the examples below.

[0130] The haze of the pressure-sensitive adhesive sheet of the present invention is preferably 1.0% or less, more preferably 0.8% or less, and even more preferably 0.5% or less. When the pressure-sensitive adhesive sheet of the present invention has a haze of 1.0% or less, it can be used as a pressure-sensitive adhesive sheet for image display devices that require transparency. The haze can be measured with a haze meter. In order to set the haze of the pressure-sensitive adhesive sheet of the present invention within the above range, it is preferable that the pressure-sensitive adhesive sheet of the present invention does not contain particles such as organic particles.

[0131] <Thickness> The thickness of the pressure-sensitive adhesive sheet of the present invention is not particularly limited, but a thickness of 10 μm or more provides good handleability, and a thickness of 1000 μm or less can contribute to making the pressure-sensitive adhesive sheet of the present invention thinner. From this perspective, the thickness of the pressure-sensitive adhesive sheet of the present invention is preferably 10 μm or more, more preferably 15 μm or more, even more preferably 20 μm or more, and particularly preferably 25 μm or more. On the other hand, the upper limit is preferably 1000 μm or less, more preferably 500 μm or less, even more preferably 400 μm or less, particularly preferably 300 μm or less, and especially preferably 250 μm or less. The lower limit and upper limit of the thickness of the pressure-sensitive adhesive sheet of the present invention can be combined arbitrarily.

[0132] <Method of manufacturing the pressure-sensitive adhesive sheet of the present invention> Next, a method for producing the pressure-sensitive adhesive sheet of the present invention will be described. However, the following description is an example of a method for producing the pressure-sensitive adhesive sheet of the present invention, and the pressure-sensitive adhesive sheet of the present invention is not limited to sheets produced by this production method.

[0133] The pressure-sensitive adhesive sheet of the present invention can be produced, for example, by preparing the present resin composition, molding the present resin composition into a sheet, curing it by crosslinking, i.e., polymerization reaction, and then processing it appropriately as necessary. Alternatively, the pressure-sensitive adhesive sheet of the present invention may be formed by preparing the present resin composition, coating it onto a component for an image display device, and curing the resin composition.

[0134] (Preparation of the Resin Composition) When preparing the present resin composition, the raw materials may be mixed using a propeller stirrer or kneader (for example, a single-screw extruder, a twin-screw extruder, a planetary mixer, a twin-screw mixer, a pressure kneader, etc.). When mixing various raw materials, various additives such as silane coupling agents and antioxidants may be blended together with the resin in advance and then supplied to a mixer or kneader, or all materials may be melt-mixed in advance and then supplied, or a master batch may be prepared in advance by concentrating only the additives in the resin and then supplied.

[0135] (Formed into sheets) The resin composition can be formed into a sheet by any known method, such as wet lamination, dry lamination, extrusion casting using a T-die, extrusion lamination, calendaring, inflation, injection molding, and liquid injection curing. Of these, wet lamination, extrusion casting, and extrusion lamination are preferred for producing a sheet.

[0136] (hardening) The resin composition can be cured by irradiation with active energy rays, and the pressure-sensitive adhesive sheet of the present invention can be produced by irradiating a molded product of the resin composition, for example, a sheet, with active energy rays. In addition to irradiation with active energy rays, further curing can be achieved by heating.

[0137] The irradiation energy, irradiation time, irradiation method, etc. of the active energy ray are not particularly limited as long as they can activate the photopolymerization initiator and polymerize the monomer component.

[0138] Examples of the active energy rays used in the active energy ray irradiation include light rays such as far ultraviolet rays, ultraviolet rays, near ultraviolet rays, infrared rays, and visible light rays, as well as ionizing radiation such as X-rays, α-rays, β-rays, γ-rays, electron beams, proton beams, and neutron beams. Among these, ultraviolet rays or visible light rays are preferred from the viewpoints of suppressing damage to components of the image display device and facilitating reaction control. Furthermore, curing by irradiation with ultraviolet rays or visible light rays is advantageous from the viewpoints of curing speed, ease of availability of irradiation equipment, cost, and the like. Among these, curing by visible light rays, for example, active energy rays of 405 nm, is preferred from the viewpoint of preventing curing inhibition by ultraviolet absorbers.

[0139] Examples of light sources for active energy ray irradiation include high-pressure mercury lamps, ultra-high-pressure mercury lamps, low-pressure mercury lamps, carbon arc lamps, metal halide lamps, xenon lamps, chemical lamps, electrodeless discharge lamps, and LEDs, all of which emit light in the wavelength range of 150 to 450 nm.

[0140] The amount of active energy ray irradiation (cumulative light amount) is 50 to 10,000 mJ / cm from the viewpoint of curing. 2 is preferred, and 100 mJ / cm 2 or above 5500mJ / cm 2 It is more preferable that the dose is 150 mJ / cm or less, and particularly 150 mJ / cm 2 or more than 5000mJ / cm 2 It is more preferable that the intensity is 200 mJ / cm or less, and more preferably 200 mJ / cm or less. 2 or more than 4000mJ / cm 2 It is particularly preferable that the dose is 300 mJ / cm or less. 2 or more than 3000mJ / cm 2 It is particularly preferred that: The amount of active energy ray irradiation is the sum of the integrated energy on one side and the integrated energy on the other side when active energy ray is irradiated from both sides. The lower limit and the upper limit of the active energy ray irradiation amount (accumulated light amount) can be combined arbitrarily.

[0141] (Another embodiment of the manufacturing method) Another embodiment of the method for producing the pressure-sensitive adhesive sheet of the present invention is a method in which the resin composition is dissolved in an appropriate solvent, formed into a film using various coating techniques, and then cured as described above and appropriately processed as necessary. When a coating method is used, the pressure-sensitive adhesive sheet of the present invention can be obtained by heat curing in addition to the above-mentioned curing by irradiation with active energy rays. In the case of coating, the thickness of the pressure-sensitive adhesive sheet can be adjusted by the coating thickness and the solids concentration of the coating liquid.

[0142] For example, the present resin composition can be dissolved in a solvent, coated on a release film, dried, and cured by active energy ray irradiation to form the pressure-sensitive adhesive sheet of the present invention. Furthermore, a release film may be laminated, if necessary. In this case, the resin composition may be coated on a release film, dried, cured by active energy ray irradiation, and a release film may be laminated thereon. Alternatively, the resin composition may be coated on a release film, dried, and a release film may be laminated thereon, and then cured by active energy ray irradiation to form the pressure-sensitive adhesive sheet of the present invention.

[0143] The solvent is not particularly limited as long as it dissolves the resin composition, and examples thereof include ester solvents such as methyl acetate, ethyl acetate, butyl acetate, methyl acetoacetate, and ethyl acetoacetate; ketone solvents such as acetone, methyl ethyl ketone, and methyl isobutyl ketone; aromatic solvents such as toluene and xylene; and alcohol solvents such as methanol, ethanol, and propyl alcohol. These can be used alone or in combination of two or more. Among these, ethyl acetate, acetone, methyl ethyl ketone, and toluene are preferred in terms of solubility, drying properties, cost, and the like, and ethyl acetate is particularly preferred.

[0144] The amount of the solvent used is preferably 600 parts by mass or less, more preferably 500 parts by mass or less, even more preferably 400 parts by mass or less, and particularly preferably 300 parts by mass or less, relative to 100 parts by mass of the (meth)acrylic polymer (A) in terms of drying properties, while preferably 1 part by mass or more, more preferably 50 parts by mass or more, even more preferably 100 parts by mass or more, and particularly preferably 150 parts by mass or more. The coating method can be a conventional method such as roll coating, die coating, gravure coating, comma coating, screen printing, bar coating, etc. The lower and upper limits of the amount of the solvent used can be combined arbitrarily.

[0145] The solvent content in the resin composition after drying is preferably 1% by mass or less, more preferably 0.5% by mass or less, particularly preferably 0.1% by mass or less, and most preferably 0% by mass.

[0146] The drying temperature is preferably 50 to 130° C., particularly preferably 55 to 120° C. Within this temperature range, the solvent can be removed efficiently and relatively stably while suppressing thermal deformation of the release film.

[0147] The drying time is usually 1 to 30 minutes, more preferably 3 to 25 minutes, and even more preferably 5 to 20 minutes. Within this time range, the solvent can be removed efficiently and sufficiently. The above lower and upper limits can be combined in any desired manner.

[0148] Examples of drying methods include drying with a dryer, drying with a heated roll, and drying by blowing hot air onto the film. Among these, using a dryer is preferred because it allows for uniform and easy drying. These methods can be used alone or in combination of two or more.

[0149] <<Adhesive sheet with release film>> The pressure-sensitive adhesive sheet of the present invention can also be provided as a pressure-sensitive adhesive sheet with a release film (pressure-sensitive adhesive sheet laminate) by laminating a release film on one or both sides of the pressure-sensitive adhesive layer (pressure-sensitive adhesive sheet of the present invention) made of the resin composition. When release films are provided on both sides of the pressure-sensitive adhesive sheet of the present invention, a laminate configuration is preferably formed in which a light-release film with a relatively low release strength and a heavy-release film with a relatively high release strength are laminated together. When using a pressure-sensitive adhesive sheet with release films provided on both sides, first, one release film (light-release film) is peeled off to expose one side of the pressure-sensitive adhesive sheet, which is then bonded to a component of an image display device (referred to as the first component), and the other release film (heavy-release film) is peeled off to expose the other side of the pressure-sensitive adhesive sheet, to which another component of an image display device (referred to as the second component) is then bonded.

[0150] As such a release film, any known release film can be used appropriately. The material for the release film can be appropriately selected and used, for example, a polyester film, a polyolefin film, a polycarbonate film, a polystyrene film, an acrylic film, a triacetyl cellulose film, a fluororesin film, or the like, which has been subjected to a release treatment by coating with a release agent such as a silicone resin, or release paper, etc. Among these, polyester film, and even more so polyethylene terephthalate (PET) film, particularly biaxially oriented PET film, is preferred because of its excellent transparency, mechanical strength, heat resistance, flexibility, etc. A release film can be used in which a release layer formed by curing a curable silicone-based release agent containing a silicone resin as the main component is provided on the above-mentioned substrate.

[0151] The thickness of the release film is not particularly limited. Among them, from the viewpoint of processability and handleability, for example, it is preferably 10 to 250 μm, more preferably 25 μm or more or 200 μm or less, and even more preferably 35 μm or more or 190 μm or less. The lower limit and upper limit of the thickness of the release film can be combined arbitrarily.

[0152] <Preferred uses of the pressure-sensitive adhesive sheet of the present invention> The pressure-sensitive adhesive sheet of the present invention is suitable for use in bonding optical components, and is particularly useful as a pressure-sensitive adhesive sheet for, for example, an organic EL display device. Specifically, it is suitable for use in bonding components constituting a display, particularly components used in manufacturing a display, and is used as a pressure-sensitive adhesive sheet for bonding an image display panel and image display device components such as a protective panel or touch panel disposed on the front side (viewing side) of the image display panel, or components constituting the image display device components. The image display device components can be the same as those described below.

[0153] <<Laminate for image display device>> A laminate for an image display device according to one embodiment of the present invention (hereinafter sometimes referred to as "the laminate for the image display device") is a laminate for an image display device having a configuration in which two components of the image display device are laminated via the pressure-sensitive adhesive sheet of the present invention. The laminate for the image display device is preferably a laminate for an image display device having a configuration in which two components of the image display device are laminated via the pressure-sensitive adhesive sheet of the present invention.

[0154] Of the components of the laminate for an image display device, the pressure-sensitive adhesive sheet of the present invention is as described above, and the components other than the pressure-sensitive adhesive sheet will be described below.

[0155] <Image display device components> Examples of image display device components constituting the present laminate for image display devices include flat panel image display device components and flexible image display device components. Examples of such image display device components include flexible displays such as liquid crystal displays and organic electroluminescence (EL) displays, cover lenses (cover films), polarizing plates, polarizers, retardation films, barrier films, viewing angle compensation films, brightness enhancement films, contrast enhancement films, diffusion films, semi-transparent reflective films, electrode films, transparent conductive films, metal mesh films, and touch sensor films. Any one of these may be used alone or in combination. Examples include a combination of a flexible display with another image display device component, or a combination of a cover lens with another image display device component.

[0156] The term "flexible image display device component" refers to a bendable component, such as a component used in an image display device having a curved surface or a component that can be repeatedly bent. In particular, it is preferable that the component be a component that can be fixed to a curved shape with a curvature radius of 25 mm or less, particularly a component that can withstand bending at a curvature radius of less than 25 mm, or a component that can withstand bending at a curvature radius of less than 3 mm.

[0157] In the above-described configuration, examples of the components constituting the image display device include a resin sheet and glass. Examples of materials for such resin sheets include polyester resins, cycloolefin resins, triacetyl cellulose resins, polymethyl methacrylate resins, polyurethanes, epoxy resins, polyimide resins, and aramid resins, which may be one type of resin or two or more types of resins. Among these, resin sheets containing at least one type of resin selected from the group consisting of polyester resins, cycloolefin resins, triacetyl cellulose resins, polymethyl methacrylate resins, epoxy resins, polyimide resins, aramid resins, and polyurethane resins as a main component are preferred. Here, "main component" refers to a component that occupies the largest mass ratio among the components that constitute the components of the image display device, and specifically, it is a component that occupies 50 mass% or more of the resin composition (resin sheet) that forms the components of the image display device, and it is preferable that it occupies 55 mass% or more, and particularly 60 mass% or more.

[0158] <Method of manufacturing the laminate for the image display device> The method for manufacturing the present laminate for an image display device is not particularly limited, and as described above, for example, the resin composition may be applied to a component of the image display device to form an adhesive sheet, or an adhesive sheet with a release film may be formed in advance and then laminated to the component of the image display device.

[0159] <<Image display devices>> An image display device according to one embodiment of the present invention (hereinafter sometimes referred to as "the present image display device") is an image display device incorporating a laminate for an image display device having a configuration in which two components of the image display device are bonded together via the pressure-sensitive adhesive sheet of the present invention. For example, the present image display device including the laminate can be formed by laminating a laminate for an image display device having a configuration in which two components of the image display device are bonded together via the pressure-sensitive adhesive sheet of the present invention onto another component of the image display device. [Example]

[0160] An example of an embodiment of the present invention will be described in detail below, but the present invention is not limited to the embodiment described below.

[0161] First, the raw materials of the resin compositions prepared in the examples will be described in detail.

[0162] <(Meth)acrylic polymer (A)> (Meth)acrylic polymer (A-1): an acrylic copolymer (mass average molecular weight: approximately 460,000) obtained by random copolymerization of 64.0 parts by mass of 2-ethylhexyl acrylate, 19.0 parts by mass of methyl acrylate, and 17.0 parts by mass of hydroxyethyl acrylate.

[0163] <Photopolymerization initiator (B)> Photopolymerization initiator (B-1): A hydrogen abstraction type photopolymerization initiator having a glyoxylate structure represented by the following formula 3-1 (molar absorption coefficient (405 nm) 3.3 × 10 2 L (L / mol cm)

[0164] TIFF2025134267000007.tif43170

[0165] Photopolymerization initiator (B-2): A hydrogen abstraction type photopolymerization initiator consisting of a mixture of 2,4,6-trimethylbenzophenone and 4-methylbenzophenone (IGM "Esacure TZT")

[0166] [Example 1] A resin composition was prepared by uniformly mixing 100 parts by mass of the (meth)acrylic polymer (A-1) and 1.5 parts by mass of the photopolymerization initiator (B-1). The resin composition was spread in a sheet shape to a thickness of 100 μm on a silicone release-treated release film (PET film manufactured by Mitsubishi Chemical Corporation) having a thickness of 100 μm.

[0167] Next, a 75 μm thick release film (PET film manufactured by Mitsubishi Chemical Corporation) treated with silicone release agent was laminated on top of the sheet-like resin composition to form a laminate, thereby obtaining an adhesive sheet with release film consisting of release film / adhesive sheet 1 / release film. Next, a high-pressure mercury lamp "H12.8KL / 63" was used from one side of the adhesive sheet with release film, and the cumulative light intensity measured using an ultraviolet integrating light meter "UIT-250" (manufactured by Ushio Inc.) and a photodetector "UVD-C365" (manufactured by Ushio Inc.) was 3000 mJ / cm. 2 The adhesive sheet was photocured by irradiating it with light so that the adhesive sheet was cured.

[0168] [Examples 2 to 4, Comparative Examples 1 and 2] Pressure-sensitive adhesive sheets 2 to 6 with release films were prepared in the same manner as in Example 1, except that the formulation was changed as shown in Table 1.

[0169] [Physical property measurement and evaluation] The pressure-sensitive adhesive sheets produced in the above Examples and Comparative Examples were subjected to the following various measurements and evaluations. The evaluation results are summarized in Table 1.

[0170] <Content of unreacted photopolymerization initiator> The release film was peeled off from the adhesive sheets with release film prepared in the Examples and Comparative Examples, and 60 mg of the adhesive sheet alone was weighed and placed in a vial, to which 5 ml of acetonitrile was added. After stirring for 4 hours with a rolling mixer, the mixture was allowed to stand for at least one day, and the supernatant was filtered through a 0.24 μm syringe filter to obtain the measurement solution. The content (wt %) of unreacted photopolymerization initiator in the pressure-sensitive adhesive sheet was quantified using the measurement solution by liquid chromatography mass spectrometry (LC / MS) under the measurement conditions below.

[0171] [Analysis conditions for photopolymerization initiator (B-1)] Apparatus (LC): Waters Acquity UPLC Equipment (MS): Waters SQ Detector 2 Column ACQUITY UPLC CSH C18 2.1μm x 100mm 1.7μm Mobile phase A: 10mM ammonium acetate aq. B: acetonitrile A / B:=80 / 20(0 min)→10 / 90(12 min)→10 / 90(3 min)→80 / 20(3 min) Flow 0.40mL / min PDA 190~700nm Analysis wavelength 220nm Ionization method: ESI Measurement range: Full Scan m / z=100~1500 Degassing temperature: 400℃

[0172] [Analysis conditions for photopolymerization initiator (B-2)] Equipment Shimadzu GC / MS-QP2020 Column UltraALLOY-1 0.25 mm IDx 30m df = 0.1μm Col.Temp.70 ℃(1 min hold)→25 ℃ / min→320 ℃(5 min hold) Injection Temp. 320℃ Detection Scan (m / z 35-800) Ionization mode EI(70eV) Interface temperature 320℃ Ion source temperature: 250℃

[0173] <Gel fraction> For the adhesive sheets with release film prepared in the Examples and Comparative Examples, approximately 0.1 g of adhesive sheet pieces were collected from the adhesive sheets after peeling off the release film. The collected adhesive sheet pieces were wrapped in a SUS mesh (#150) bag with a mass (X) and the bag was closed to prepare a sample, and the mass (Y) of the sample was measured. The sample was immersed in ethyl acetate and stored in a dark place at 23°C for 24 hours, then removed and heated at 70°C for 4.5 hours to evaporate the ethyl acetate, and the mass (Z) of the dried sample was measured. The gel fraction (%) of each measured mass was calculated using the following formula: Gel fraction (%) = [(ZX) / (YX)] × 100

[0174] <Chromaticity> The release films were removed from the pressure-sensitive adhesive sheets with release films prepared in the Examples and Comparative Examples, and the exposed adhesive surfaces on both sides were sandwiched between two pieces of soda lime glass (thickness 0.55 mm) to prepare a bonded sample. The chromaticity (b * 0) was measured. Chromaticity (b * 0) was 1 or less, it was determined that there was no practical problem.

[0175] <Adhesive strength> One of the release films was peeled off from the adhesive sheets with release films prepared in the examples and comparative examples, and a 100 μm thick polyethylene terephthalate film (Cosmoshine A4300 manufactured by Toyobo Co., Ltd.) was attached as a backing film to prepare a laminate. The laminate was cut to a length of 150 mm and a width of 10 mm, and the remaining release film was peeled off to expose the adhesive surface, which was then roll-pressurized onto a soda lime glass sheet (pressure of approximately 0.02 MPa / cm). The laminate was then cured at 60°C for 30 minutes and then finished to form a sample for measuring adhesive strength. The adhesive strength (P) was calculated by measuring the peel force (N / cm) to glass when this adhesive strength measurement sample was peeled at a peel angle of 180° and a peel speed of 60 mm / min in an environment of 23°C and 40% RH.

[0176] <Evaluation sample for 95°C heat resistance test and xenon irradiation test> The release films were removed from the pressure-sensitive adhesive sheets with release films produced in the Examples and Comparative Examples, and the exposed adhesive surfaces on both sides were sandwiched between two sheets of soda-lime glass (size: 155 mm x 68 mm x 0.55 mm thick) and laminated with a hand roller to produce a soda-lime glass / pressure-sensitive adhesive sheet / soda-lime glass laminated sample. The resulting laminated sample was degassed using an autoclave at a temperature of 60°C, a pressure of 0.2 MPa, and for 30 minutes to prepare an evaluation sample for the 95°C heat resistance test and xenon irradiation test described below.

[0177] <95℃ heat resistance test> The evaluation sample for the 95°C heat resistance test was left standing in a dryer set at 95°C for 1000 hours, and the appearance and yellowing degree were evaluated.

[0178] The appearance was evaluated (bubble evaluation) by visual observation, and the pass / fail was judged according to the following evaluation criteria. ○ (good): No defects in appearance such as foaming or peeling were observed × (poor): Foaming or peeling was observed

[0179] To evaluate the degree of yellowing, a spectrophotometer (Suga Test Instruments Co., Ltd.) "SC-T" was used to measure the chromaticity (b * 1) was measured.

[0180] <Xenon irradiation test> The evaluation sample for the xenon irradiation test was exposed to an illuminance of 0.60 (W / m ) using a xenon accelerated exposure device, Suntest XLS+ (manufactured by Atlas Co., Ltd.). 2 , 340 nm) at a black panel temperature of 100°C for 240 hours, and the appearance and yellowing were evaluated.

[0181] The appearance was evaluated (bubble evaluation) by visual observation, and the pass / fail was judged according to the following evaluation criteria. ○ (good): No defects in appearance such as foaming or peeling were observed × (poor): Foaming or peeling was observed

[0182] To evaluate the degree of yellowing, a spectrophotometer (Suga Test Instruments Co., Ltd.) "SC-T" was used to measure the chromaticity (b * 2) was measured.

[0183] [Table 1]

[0184] As shown in Table 1, it can be seen that all of the pressure-sensitive adhesive sheets of Examples 1 to 4 have sufficient adhesive strength of 4.0 N / cm or more. In addition, with regard to chromaticity, all of the pressure-sensitive adhesive sheets of Examples 1 to 4 had a value of b * 0≦1.5 or less, which is good. Furthermore, the pressure-sensitive adhesive sheets of Examples 1 to 4 all had a * 1 is 1.5 or less, b * Since 2 is 2.5 or less, it is clear that yellowing when exposed to high temperatures or ultraviolet rays can be suppressed. Furthermore, the pressure-sensitive adhesive sheets of Comparative Examples 1 and 2 each generated bubbles when exposed to high temperatures and ultraviolet light, but no bubbles were generated in either the heat resistance test or the xenon lamp irradiation test for the pressure-sensitive adhesive sheets of Examples 1 to 4. This demonstrates that in addition to the aforementioned adhesive strength and suppression of yellowing, Examples 1 to 4 can also suppress the generation of bubbles when exposed to severe high temperatures or ultraviolet light.

[0185] As described above, it has been found that, in an adhesive sheet containing a photocured product of a resin composition containing a (meth)acrylic polymer (A) and a photopolymerization initiator (B), if the content of unreacted photopolymerization initiator (B) is 1.0 mass% or less, the adhesive sheet can have good adhesive strength and good resistance to high temperatures or ultraviolet rays.

[0186] The following are possible reasons why the present invention can achieve such effects. That is, if a large amount of unreacted photopolymerization initiator remains in the pressure-sensitive adhesive sheet, the photopolymerization initiator will turn yellow when exposed to high temperatures, causing the pressure-sensitive adhesive sheet to turn yellow. Furthermore, if a large amount of unreacted photopolymerization initiator, particularly hydrogen abstraction photopolymerization initiator, remains in the adhesive sheet, when the sheet is exposed to light, particularly ultraviolet light, the unreacted photopolymerization initiator will be activated to generate radicals, which are thought to cause deterioration of the adhesive sheet, resulting in yellowing and foaming. Because of this assumed mechanism of action, it is believed that when the content of unreacted photopolymerization initiator (B) is 1.0 mass% or less, bubbles, peeling, and / or yellowing can be suppressed even when exposed to high temperatures or ultraviolet rays, and an adhesive sheet with good resistance to high temperatures or ultraviolet rays can be provided. Therefore, even if the content of the (meth)acrylic polymer (A) in the pressure-sensitive adhesive sheet increases or decreases, or the type or amount of the photopolymerization initiator changes, it is expected that a pressure-sensitive adhesive sheet with good adhesive strength and good resistance to high temperatures or ultraviolet rays can be provided as long as the content of the unreacted photopolymerization initiator (B) is 1.0 mass% or less.

Claims

1. A pressure-sensitive adhesive sheet comprising a photocured product of a resin composition containing a (meth)acrylic polymer (A) and a photopolymerization initiator (B), wherein the content of unreacted photopolymerization initiator (B) is 1.0 mass% or less.

2. The pressure-sensitive adhesive sheet according to claim 1 , wherein the photopolymerization initiator (B) is a hydrogen abstraction photopolymerization initiator.

3. The adhesive sheet according to claim 1 , which is a thermosetting adhesive sheet or a pressure-sensitive adhesive sheet.

4. The pressure-sensitive adhesive sheet according to claim 1 , which has a gel fraction of 50% or more.

5. The pressure-sensitive adhesive sheet according to claim 1 , wherein the content of unreacted photopolymerization initiator (B) is 0.1% by mass or less.

6. The pressure-sensitive adhesive sheet according to claim 1, having an adhesive strength of 4 N / cm or more.

7. L ＊ a ＊ b ＊ Chromaticity b in color space ＊ The pressure-sensitive adhesive sheet according to claim 1, wherein the σ is 1.5 or less.

8. When heated in air at 95°C for 1000 hours, L ＊ a ＊ b ＊ Chromaticity b in color space ＊ The pressure-sensitive adhesive sheet according to claim 1 , wherein the σ is 2.0 or less.

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