Photocurable composition for adhesive sheet, adhesive sheet, optical laminate, and image display device

Abstract

To provide a photocurable composition for an adhesive sheet, which is suitable for forming an adhesive sheet used in an image display device that can be exposed to a high-temperature environment.SOLUTION: The present invention provides a photocurable composition for an adhesive sheet, the photocurable composition containing: a monomer group and / or a partially polymerized product of the monomer group; and a crosslinking agent. The crosslinking agent has an ether chain. A content of a solvent in the photocurable composition is 5 wt.% or less.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a photocurable composition for a pressure-sensitive adhesive sheet, a pressure-sensitive adhesive sheet, an optical laminate, and an image display device. [Background technology]

[0002] Various image display devices, such as liquid crystal display devices and electroluminescence (EL) display devices, generally include an optical laminate including an optical film such as a polarizing film and an adhesive sheet. An adhesive sheet is usually used for bonding between the optical films included in the optical laminate and bonding between the optical laminate and an image display panel. A typical adhesive sheet is a sheet obtained by curing a monomer group including an acrylic monomer, a silicone monomer, etc., by polymerization and crosslinking. Patent Document 1 discloses an optical laminate including an adhesive sheet formed from a photocurable composition (hereinafter, referred to as a photocurable adhesive sheet) and a polarizing film as an optical film. A type of adhesive sheet different from the photocurable type is a thermosetting adhesive sheet formed by curing a layer including an adhesive composition and a solvent by heat. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2015-530942 A Summary of the Invention [Problem to be solved by the invention]

[0004] When a photocurable pressure-sensitive adhesive sheet is used in an optical laminate, problems tend to occur in the quality of images produced in image display devices that may be exposed to high-temperature environments.

[0005] An object of the present invention is to provide a photocurable composition for pressure-sensitive adhesive sheets, which is suitable for forming pressure-sensitive adhesive sheets for use in image display devices that may be exposed to high-temperature environments. [Means for solving the problem]

[0006] The present invention relates to The composition includes a monomer group and / or a partial polymer of the monomer group, and a crosslinking agent, The crosslinking agent has an ether chain, a photocurable composition for pressure-sensitive adhesive sheets, the photocurable composition having a solvent content of 5% by weight or less; to provide.

[0007] Further, the present invention relates to There is provided a pressure-sensitive adhesive sheet formed from the above photocurable composition.

[0008] Further, the present invention relates to There is provided an optical laminate comprising the above pressure-sensitive adhesive sheet and an optical film.

[0009] Further, the present invention relates to There is provided an image display device including the above optical laminate. Effect of the Invention

[0010] According to the present invention, it is possible to provide a photocurable composition suitable for forming a pressure-sensitive adhesive sheet for use in an image display device that may be exposed to a high-temperature environment. [Brief description of the drawings]

[0011] [Figure 1] 1 is a cross-sectional view illustrating a schematic example of a pressure-sensitive adhesive sheet of the present invention. [Diagram 2] FIG. 2 is a schematic diagram illustrating an example of a method for forming the pressure-sensitive adhesive sheet of the present invention from the photocurable composition of the present invention. [Diagram 3] FIG. 1 is a cross-sectional view illustrating an example of an optical laminate of the present invention. [Figure 4] FIG. 1 is a cross-sectional view illustrating an example of an optical laminate of the present invention. [Diagram 5] FIG. 1 is a cross-sectional view illustrating an example of an optical laminate of the present invention. [Figure 6] FIG. 1 is a cross-sectional view illustrating an example of an optical laminate of the present invention. [Figure 7]FIG. 1 is a cross-sectional view illustrating an example of an optical laminate of the present invention. [Figure 8] FIG. 1 is a cross-sectional view that illustrates an example of an image display device of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] The photocurable composition for pressure-sensitive adhesive sheets according to the first aspect of the present invention comprises: The composition includes a monomer group and / or a partial polymer of the monomer group, and a crosslinking agent, The crosslinking agent has an ether chain, The solvent content is 5% by weight or less.

[0013] In the second aspect of the present invention, for example, the photocurable composition according to the first aspect is substantially free of the solvent.

[0014] In a third aspect of the present invention, for example, in the photocurable composition according to the first or second aspect, the ether chain is a polyalkylene glycol chain.

[0015] In a fourth aspect of the present invention, for example, in the photocurable composition according to any one of the first to third aspects, the ether chain is at least one selected from the group consisting of a polyethylene glycol chain and a polypropylene glycol chain.

[0016] In a fifth aspect of the present invention, for example, in the photocurable composition according to any one of the first to fourth aspects, the crosslinking agent has a polymerizable group capable of polymerizing with the monomer group and / or the partial polymer.

[0017] In a sixth aspect of the present invention, for example, in the photocurable composition according to the fifth aspect, the crosslinking agent has a structure in which the polymerizable group is bonded to each of two or more ends of the ether chain.

[0018] In a seventh aspect of the present invention, for example, in the photocurable composition according to the fifth or sixth aspect, the number of the polymerizable groups per molecule of the crosslinking agent is two or less.

[0019] In an eighth aspect of the present invention, for example, in the photocurable composition according to any one of the fifth to seventh aspects, the polymerizable group is a (meth)acryloyl group.

[0020] In a ninth aspect of the present invention, for example, in the photocurable composition according to any one of the first to eighth aspects, the weight average molecular weight of the ether chain is 300 or less.

[0021] In a tenth aspect of the present invention, for example, in the photocurable composition according to any one of the first to ninth aspects, the amount of the crosslinking agent in the photocurable composition is 0.01 parts by weight or more and less than 10 parts by weight per 100 parts by weight in total of the monomer group and the partially polymerized product.

[0022] In an eleventh aspect of the present invention, for example, in the photocurable composition according to any one of the first to tenth aspects, the monomer group includes a (meth)acrylic monomer.

[0023] A pressure-sensitive adhesive sheet according to a twelfth aspect of the present invention is a pressure-sensitive adhesive sheet formed from the photocurable composition according to any one of the first to eleventh aspects.

[0024] In a thirteenth aspect of the present invention, for example, in the pressure-sensitive adhesive sheet according to the twelfth aspect, the amount of the crosslinking agent in the photocurable composition is 0.01 parts by weight or more and less than 10 parts by weight per 100 parts by weight in total of the monomer group and the partially polymerized product.

[0025] In a fourteenth aspect of the present invention, for example, the pressure-sensitive adhesive sheet according to the twelfth or thirteenth aspect has a thickness of 30 μm or less.

[0026] In a fifteenth aspect of the present invention, for example, in the pressure-sensitive adhesive sheets according to the twelfth to fourteenth aspects, the gel fraction is 50% or more and 70% or less.

[0027] An optical laminate according to a sixteenth aspect of the present invention comprises the pressure-sensitive adhesive sheet according to any one of the twelfth to fifteenth aspects, and an optical film.

[0028] In a seventeenth aspect of the present invention, for example, in the optical laminate according to the sixteenth aspect, the optical film is a polarizing film, and the pressure-sensitive adhesive sheet is in contact with the polarizing film.

[0029] An image display device according to an eighteenth aspect of the present invention includes the optical laminate according to the sixteenth or seventeenth aspect.

[0030] The present invention will be described in detail below, but the present invention is not limited to the following embodiments and can be modified in any manner without departing from the gist of the present invention.

[0031] [Photocurable composition] The photocurable composition of this embodiment contains a monomer group and / or a partial polymer of the monomer group, and a crosslinking agent (hereinafter, referred to as crosslinking agent A). The photocurable composition of this embodiment is for use in an adhesive sheet. An adhesive sheet can be formed from the photocurable composition of this embodiment.

[0032] (Crosslinker A) Crosslinking agent A has an ether chain. In this specification, the ether chain means a molecular chain having a structural unit containing an ether structure (-O-). The molecular chain may be composed only of a structural unit containing an ether structure. The ether structure is typically located in the main chain of the ether chain. Crosslinking agent A may have an ether chain in the main chain. In other words, crosslinking agent A may have a skeleton containing an ether chain. The ether chain may be linear or branched.

[0033] According to the study by the present inventors, the deterioration of image quality due to exposure to a high-temperature environment can be caused by the fact that the adhesive sheet in the optical laminate and the adherend (adhesive object) in contact therewith tend to peel off at high temperatures, and the adhesive sheet itself tends to undergo cohesive failure at high temperatures. According to the study, the molecular weight of the polymer after curing tends to be suppressed in the photocurable composition, and a low molecular weight makes it easier to cause cohesive failure. In particular, if the gel fraction is designed to be low in order to suppress the shrinkage (glue slippage) of the adhesive sheet at high temperatures, which is thought to occur due to the low molecular weight, it is easy to cause cohesive failure. The present invention has been made with a focus on the suppression of the above-mentioned peeling and cohesive failure. Compared to other crosslinking agents, the crosslinking agent A having an ether chain may be suitable for imparting stress relaxation properties to the crosslinked product of the polymer contained in the adhesive sheet (hereinafter referred to as a crosslinked polymer). It is presumed that the above-mentioned peeling and cohesive failure are suppressed by improving the stress relaxation properties. The cohesive failure of the adhesive sheet may be observed as a streak-like defect (hereinafter referred to as a streak) in the optical laminate.

[0034] An example of the ether chain is a polyalkylene glycol chain, which is particularly suitable for imparting stress relaxation properties to a crosslinked polymer.

[0035] Examples of the polyalkylene glycol chain are a polyethylene glycol chain, a polypropylene glycol chain, and a neopentyl glycol chain. The polyalkylene glycol chain may be at least one selected from the group consisting of a polyethylene glycol chain and a polypropylene glycol chain. In other words, the ether chain may be at least one selected from the group consisting of a polyethylene glycol chain, a polypropylene glycol chain, and a neopentyl glycol chain, or may be at least one selected from the group consisting of a polyethylene glycol chain and a polypropylene glycol chain. Between the polyethylene glycol chain and the polypropylene glycol chain, the polyethylene glycol chain is more suitable for suppressing peeling and streaks. In addition, the polyethylene glycol chain is particularly suitable for suppressing foaming of the pressure-sensitive adhesive sheet at high temperatures. These tendencies may be influenced by the fact that the polyethylene glycol chain is more hydrophilic than the polypropylene glycol chain. Foaming may also affect the deterioration of image quality.

[0036] The crosslinking agent A usually has a structure capable of bonding to at least one selected from the group consisting of a monomer group, a partial polymer of the monomer group, and a polymer formed by polymerization thereof. The structure capable of bonding may be a polymerizable group capable of polymerizing with the monomer group and / or the partial polymer. In other words, the crosslinking agent A may have a polymerizable group capable of polymerizing with the monomer group and / or the partial polymer. The polymerizable group is preferably bonded to each of two or more ends of the ether chain of the crosslinking agent A. In other words, the crosslinking agent A preferably has a structure in which a polymerizable group is bonded to each of two or more ends of the ether chain.

[0037] The number of polymerizable groups that one molecule of crosslinking agent A can have may be 2 or less, or may be 2. Crosslinking agent A having the above number of 2 or less is particularly suitable for imparting stress relaxation properties to a crosslinked polymer.

[0038] Examples of the polymerizable group are (meth)acryloyl group and vinyl group. The polymerizable group is preferably (meth)acryloyl group, more preferably acryloyl group. The crosslinking agent A may be a diacrylate compound. In this specification, (meth)acryloyl means acryloyl and methacryloyl.

[0039] Specific examples of crosslinking agent A are polyethylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, and neopentyl glycol di(meth)acrylate.

[0040] The weight average molecular weight of the ether chain is, for example, 1000 or less, and may be 800 or less, 500 or less, 400 or less, less than 400, 350 or less, 300 or less, 250 or less, or even 200 or less. A weight average molecular weight of 300 or less is particularly suitable for suppressing peeling and streaks, and is also particularly suitable for suppressing foaming. The lower limit of the weight average molecular weight of the ether chain is not particularly limited, but is, for example, 100 or more. The weight average molecular weight of the ether chain can be calculated, for example, from the molecular structure of the crosslinking agent A and the weight average molecular weight of the crosslinking agent A determined by gel permeation chromatography (GPC).

[0041] The amount of the crosslinking agent A in the photocurable composition is, for example, 0.001 to 20 parts by weight per 100 parts by weight of the total of the monomer group and the partially polymerized product. The lower limit of the amount may be 0.003 parts by weight or more, 0.005 parts by weight or more, 0.007 parts by weight or more, 0.008 parts by weight or more, 0.009 parts by weight or more, 0.01 parts by weight or more, 0.03 parts by weight or more, 0.05 parts by weight or more, 0.07 parts by weight or more, or even 0.08 parts by weight or more. The upper limit of the amount may be 18 parts by weight or less, 15 parts by weight or less, 13 parts by weight or less, 10 parts by weight or less, less than 10 parts by weight, 8 parts by weight or less, 5 parts by weight or less, 3 parts by weight or less, 2 parts by weight or less, 1.5 parts by weight or less, 1 part by weight or less, 0.8 parts by weight or less, 0.5 parts by weight or less, 0.3 parts by weight or less, or even 0.2 parts by weight or less. If the amount of crosslinking agent A is too small, the amount of uncrosslinked components increases, and the cohesive strength of the formed adhesive sheet tends to decrease. On the other hand, if the amount of crosslinking agent A is too large, the stress relaxation property of the formed adhesive sheet tends to decrease. The amount of crosslinking agent A may be 0.01 parts by weight or more and less than 10 parts by weight per 100 parts by weight of the total of the monomer group and the partial polymer. A photocurable composition having an amount of 0.01 parts by weight or more and less than 10 parts by weight is particularly suitable for suppressing peeling from an adherend at high temperatures and suppressing cohesive failure at high temperatures for an adhesive sheet formed from the composition.

[0042] The content of the solvent in the photocurable composition of this embodiment is 5% by weight or less, and may be 4% by weight or less, 3% by weight or less, 2% by weight or less, 1% by weight or less, or even 0.5% by weight or less. The photocurable composition may be substantially free of a solvent. The phrase "substantially free of a solvent" means that the solvent derived from additives and the like is allowed to have a content of, for example, 0.1% by weight or less, preferably 0.05% by weight or less, and more preferably 0.01% by weight or less.

[0043] The monomer group may include a (meth)acrylic monomer. The content of the (meth)acrylic component in the photocurable composition, i.e., the (meth)acrylic monomer and its partial polymer, may be 50% by weight or more, 60% by weight or more, 70% by weight or more, or even 80% by weight or more. In this case, an acrylic adhesive sheet having a (meth)acrylic polymer as a main component can be formed. However, the photocurable composition is not limited to the above example. In this specification, (meth)acrylic means acrylic and methacrylic. (Meth)acrylate means acrylate and methacrylate. In this specification, the main component means the component with the largest content. The content of the main component is, for example, 50% by weight or more, and may be 60% by weight or more, 70% by weight or more, or even 80% by weight or more.

[0044] An example of the (meth)acrylic monomer is a (meth)acrylic acid alkyl ester having an alkyl group having 1 to 20 carbon atoms on the side chain. The number of carbon atoms in the alkyl group may be 7 or less, 6 or less, 5 or less, or even 4 or less. The alkyl group may be linear or branched. Examples of the (meth)acrylic acid alkyl ester are methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, s-butyl (meth)acrylate, t-butyl (meth)acrylate, isobutyl (meth)acrylate, n-pentyl (meth)acrylate, isopentyl (meth)acrylate, n-hexyl (meth)acrylate, isohexyl (meth)acrylate, isoheptyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, and the like. acrylate, n-octyl (meth)acrylate, isooctyl (meth)acrylate, n-nonyl (meth)acrylate, isononyl (meth)acrylate, n-decyl (meth)acrylate, isodecyl (meth)acrylate, n-dodecyl (meth)acrylate (lauryl (meth)acrylate), n-tridecyl (meth)acrylate, n-tetradecyl (meth)acrylate, pentadecyl (meth)acrylate, hexadecyl (meth)acrylate, heptadecyl (meth)acrylate and octadecyl (meth)acrylate. The (meth)acrylic acid alkyl ester may be n-butyl (meth)acrylate.

[0045] The content of the (meth)acrylic acid alkyl ester in the monomer group is, for example, 40% by weight or more, and may be 50% by weight or more, 60% by weight or more, 70% by weight or more, 80% by weight or more, 85% by weight or more, 90% by weight or more, or even 95% by weight or more. In calculating the content, the weight of the partially polymerized product is converted into the weight of each monomer before polymerization.

[0046] The monomer group may contain a carboxyl group-containing monomer. The carboxyl group-containing monomer may be a (meth)acrylic monomer, in other words, the (meth)acrylic monomer may contain a carboxyl group-containing monomer. Examples of the carboxyl group-containing monomer are (meth)acrylic acid, carboxyethyl (meth)acrylate, carboxypentyl (meth)acrylate, itaconic acid, maleic acid, fumaric acid, and crotonic acid. The content of the carboxyl group-containing monomer in the monomer group may be, for example, 10% by weight or less, 9% by weight or less, 8% by weight or less, 7% by weight or less, 6% by weight or less, 5.5% by weight or less, or even 5% by weight or less. The lower limit of the content may be, for example, 0.1% by weight or more, 0.5% by weight or more, 1% by weight or more, 2% by weight or more, or even 3% by weight or more. The monomer group may not contain a carboxyl group-containing monomer.

[0047] The monomer group may include a hydroxyl group-containing monomer. The hydroxyl group-containing monomer may be a (meth)acrylic monomer, in other words, the (meth)acrylic monomer may include a hydroxyl group-containing monomer. Examples of the hydroxyl group-containing monomer are 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 8-hydroxyoctyl (meth)acrylate, 10-hydroxydecyl (meth)acrylate, 12-hydroxylauryl (meth)acrylate, and (4-hydroxymethylcyclohexyl)-methyl acrylate. The hydroxyl group-containing monomer is preferably 2-hydroxyethyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate. The content of the hydroxyl group-containing monomer in the monomer group is, for example, 10% by weight or less, and may be 5% by weight or less, 4% by weight or less, 3% by weight or less, 2% by weight or less, 1% by weight or less, 0.8% by weight or less, 0.5% by weight or less, 0.3% by weight or less, 0.2% by weight or less, or even 0.1% by weight or less. The lower limit of the content may be, for example, 0.01% by weight or more, 0.03% by weight or more, or even 0.05% by weight or more. The monomer group may not contain a hydroxyl group-containing monomer.

[0048] The monomer group may include a nitrogen atom-containing monomer. The nitrogen atom-containing monomer means a monomer having at least one nitrogen atom in the molecule (per molecule). In this specification, a monomer having a hydroxyl group and a nitrogen atom in the molecule is classified as a nitrogen atom-containing monomer. A monomer having a carboxyl group and a nitrogen atom in the molecule is classified as a carboxyl group-containing monomer.

[0049] The nitrogen atom-containing monomer is preferably N-vinyl cyclic amide, (meth)acrylamide, etc. The nitrogen atom-containing monomer may be used alone or in combination of two or more kinds.

[0050] The N-vinyl cyclic amide is preferably represented by the following formula (A). [ka]

[0051] In formula (A), R 1 is a divalent organic group, preferably a divalent saturated or unsaturated hydrocarbon group, and more preferably a divalent saturated hydrocarbon group (e.g., an alkylene group having 3 to 5 carbon atoms). 1 are directly bonded via a single bond to form a ring structure.

[0052] As the N-vinyl cyclic amide represented by formula (A), N-vinyl-2-pyrrolidone (NVP), N-vinyl-2-piperidone, N-vinyl-2-caprolactam, N-vinyl-3-morpholinone, N-vinyl-1,3-oxazin-2-one, N-vinyl-3,5-morpholinedione, etc. are preferred, more preferably N-vinyl-2-pyrrolidone, N-vinyl-2-caprolactam, and even more preferably N-vinyl-2-pyrrolidone.

[0053] Examples of (meth)acrylamides include (meth)acrylamide, N-alkyl(meth)acrylamide, N,N-dialkyl(meth)acrylamide, etc. Examples of N-alkyl(meth)acrylamide include N-ethyl(meth)acrylamide, N-isopropyl(meth)acrylamide, Nn-butyl(meth)acrylamide, N-octylacrylamide, etc. Examples of N-alkyl(meth)acrylamides include (meth)acrylamides having an amino group, such as dimethylaminoethyl(meth)acrylamide, diethylaminoethyl(meth)acrylamide, and dimethylaminopropyl(meth)acrylamide.

[0054] Examples of N,N-dialkyl(meth)acrylamides include N,N-dimethyl(meth)acrylamide, N,N-diethyl(meth)acrylamide, N,N-dipropyl(meth)acrylamide, N,N-diisopropyl(meth)acrylamide, N,N-di(n-butyl)(meth)acrylamide, and N,N-di(t-butyl)(meth)acrylamide.

[0055] (Meth)acrylamides also include, for example, various N-hydroxyalkyl (meth)acrylamides. Examples of N-hydroxyalkyl (meth)acrylamides include N-methylol (meth)acrylamide, N-(2-hydroxyethyl) (meth)acrylamide, N-(2-hydroxypropyl) (meth)acrylamide, N-(1-hydroxypropyl) (meth)acrylamide, N-(3-hydroxypropyl) (meth)acrylamide, N-(2-hydroxybutyl) (meth)acrylamide, N-(3-hydroxybutyl) (meth)acrylamide, N-(4-hydroxybutyl) (meth)acrylamide, and N-methyl-N-2-hydroxyethyl (meth)acrylamide.

[0056] (Meth)acrylamides also include, for example, various N-alkoxyalkyl(meth)acrylamides, such as N-methoxymethyl(meth)acrylamide and N-butoxymethyl(meth)acrylamide.

[0057] Examples of nitrogen atom-containing monomers other than N-vinyl cyclic amides and (meth)acrylamides include amino group-containing monomers such as aminoethyl (meth)acrylate, dimethylaminoethyl (meth)acrylate, dimethylaminopropyl (meth)acrylate, and t-butylaminoethyl (meth)acrylate; cyano group-containing monomers such as acrylonitrile and methacrylonitrile; (meth)acryloylmorpholine, N-vinylpiperazine, N-vinylpyrrole, N-vinylimidazole, N-vinylpyrazine, N-vinylmorpholine, N-vinylpyrazole, vinylpyridine, vinylpyrimidine, vinyloxazole, vinylisoxazole, vinylthiazole, vinylisothiazole, vinylpyridazine, (meth)acryloylpyrrolidone, (meth)acryloylpyrrolidine, (meth)acryloylpiperidine, N-methyl Examples of the monomer include heterocyclic ring-containing monomers such as vinylpyrrolidone; maleimide monomers such as N-cyclohexylmaleimide, N-isopropylmaleimide, N-laurylmaleimide, and N-phenylmaleimide; itaconimide monomers such as N-methylitaconimide, N-ethylitaconimide, N-butylitaconimide, N-octylitaconimide, N-2-ethylhexylitaconimide, N-laurylitaconimide, and N-cyclohexylitaconimide; and succinimide monomers such as N-(meth)acryloyloxymethylenesuccinimide, N-(meth)acryloyl-6-oxyhexamethylenesuccinimide, and N-(meth)acryloyl-8-oxyoctamethylenesuccinimide; and other imide group-containing monomers; and isocyanate group-containing monomers such as 2-(meth)acryloyloxyethylisocyanate.

[0058] The content of the nitrogen atom-containing monomer in the monomer group is, for example, 40% by weight or less, and may be 35% by weight or less, 30% by weight or less, 25% by weight or less, 20% by weight or less, 18% by weight or less, 15% by weight or less, 13% by weight or less, 12% by weight or less, or even 11% by weight or less. The lower limit of the content is, for example, 1% by weight or more, and may be 3% by weight or more, 5% by weight or more, 7% by weight or more, 8% by weight or more, 9% by weight or more, or even 10% by weight or more. The monomer group may not contain a nitrogen atom-containing monomer.

[0059] The monomer group may contain both a nitrogen atom-containing monomer and a carboxyl group-containing monomer.

[0060] In the photocurable composition, each of the above-mentioned monomers may be contained as a partial polymer. The partial polymer may be either a homopolymer or a copolymer. The photocurable composition may not contain a partial polymer.

[0061] The photocurable composition usually contains a photopolymerization initiator. An example of the photopolymerization initiator is a photoradical generator that generates radicals by irradiation with light. The photopolymerization initiator has an absorption coefficient for light of 340 nm, for example, of 0.1 L / (g·cm) or more, and may be 0.5 L / (g·cm) or more, 1.0 L / (g·cm) or more, 3.0 L / (g·cm) or more, or even 5.0 L / (g·cm) or more. The upper limit of this absorption coefficient is not particularly limited, and is, for example, 50 L / (g·cm) or less. The absorption coefficient of the photopolymerization initiator is a calculated value from the absorbance of a 0.01 mg / mL methanol solution measured by a visible-ultraviolet spectrophotometer using a quartz cell with a path length of 1 cm.

[0062] Examples of photopolymerization initiators include benzoin ethers such as benzoin methyl ether, benzoin isopropyl ether, and benzil dimethyl ketal; substituted benzoin ethers such as anisole methyl ether; substituted acetophenones such as 2,2-diethoxyacetophenone and 2,2-dimethoxy-2-phenylacetophenone; α-hydroxyalkylphenones such as 1-hydroxycyclohexyl-phenyl ketone, 2-hydroxy-2-methylpropiophenone, 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylpropiophenone, and 2,2'-dihydroxy-2,2'-dimethyl-1,1'-[methylenebis(4,1-phenylene)]bis(propan-1-one); and substituted alpha alkyl phenones such as 2-methyl-2-hydroxypropiophenone. -ketols; aromatic sulfonyl chlorides such as 2-naphthalenesulfonyl chloride; photoactive oximes such as 1-phenyl-1,1-propanedione-2-(o-ethoxycarbonyl)-oxime; benzophenone compounds such as benzophenone, benzoylbenzoic acid, methyl benzoylbenzoate, 4-phenylbenzophenone, hydroxybenzophenone, acrylated benzophenone, 4-benzoyl-4'-methyldiphenyl sulfide, and 3,3',4,4'-tetra(t-butylperoxycarbonyl)benzophenone; thioxanthone compounds such as thioxanthone, 2-chlorothioxanthone, 2-methylthioxanthone, isopropylthioxanthone, 2,4-diisopropylthioxanthone, and 2,4-diethylthioxanthone;2,4,6-trichloro-s-triazine, 2-phenyl-4,6-bis(trichloromethyl)-s-triazine, 2-(p-methoxyphenyl)-4,6-bis(trichloromethyl)-s-triazine, 2-(p-tolyl)-4,6-bis(trichloromethyl)-s-triazine, 2-piperonyl-4,6-bis(trichloromethyl)-s-triazine, 2,4-bis(trichloromethyl)-6-styryl-s-triazine, 2-(naphth-1-yl)-4,6-bis(trichloromethyl)-s-triazine, 2-(4-methoxy-naphth-1-yl)-4,6-bis(trichloromethyl)-s-triazine, 2,4-trichloromethyl-(piperonyl)-6-triazine, 2,4-trichloromethyl- triazine-based compounds such as (4'-methoxystyryl)-6-triazine; oxime ester-based compounds such as 1,2-octanedione, 1-[4-(phenylthio)-, 2-(O-benzoyloxime)], O-(acetyl)-N-(1-phenyl-2-oxo-2-(4'-methoxy-naphthyl)ethylidene)hydroxylamine; phosphine-based compounds such as bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide and 2,4,6-trimethylbenzoyldiphenylphosphine oxide; quinone-based compounds such as 9,10-phenanthrenequinone, camphorquinone, and ethylanthraquinone; borate-based compounds; carbazole-based compounds; imidazole-based compounds; and titanocene-based compounds. The photocurable composition may contain one or more photopolymerization initiators. In addition, α-hydroxyalkylphenones tend to have high absorption of light with a wavelength of 340±10 nm.

[0063] Another example of the photopolymerization initiator is a compound having a chemical structure shown in the following formula (1) (hereinafter, referred to as chemical structure X) in the molecule. [ka]

[0064] R in the above formula (1) 1 and R 2 are each independently a C1 to C8 alkyl group; -OH, a C1 to C4 alkoxy group, -CN, -COOR51 , -OOCR 52 , or -NR 53 R 54 an alkyl group having 1 to 4 carbon atoms, the hydrogen atom of which is replaced by -CH2-C6H4-R; an alkenyl group having 3 to 6 carbon atoms, the hydrogen atom of which is replaced by -CH2-C6H4-R 55 R 1 and R 2 may be bonded to each other to form a C2 to C9 alkylene group, a C3 to C6 oxyalkylene group, or an azaalkylene group. 51 is an alkyl group having 1 to 8 carbon atoms. 52 is a C1 to C4 alkyl group. 53 and R 54 are each independently a hydrogen atom, a C1-C12 alkyl group; -OH, a C1-C4 alkoxy group, -CN and -COOR 59 R is a C2-C4 alkyl group, the hydrogen atom of which is substituted with at least one group selected from the group consisting of: a C3-C5 alkenyl group; or a cyclohexyl group. 53 and R 54 are bonded to each other to form -O- or -N(R 60 R may be a C3 to C9 alkylene group optionally interrupted by -. 55 is a C1 to C4 alkyl group. 59 is a C1 to C4 alkyl group. 60 is a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an allyl group, a hydroxyalkyl group having 1 to 4 carbon atoms, -CH2CH2-COOR 61 Or -CH2CH2CN. 61 is a C1 to C4 alkyl group.

[0065] X is -OR 56 , or -NR 57 R 58 R 56 is a hydrogen atom, -SiR 62 3. A C1 to C8 alkyl group or a C3 to C6 alkenyl group. R 57 and R 58 represents an alkyl group having 1 to 12 carbon atoms; -OH, an alkoxy group having 1 to 4 carbon atoms, -CN and -COOR63 R is a C2-C4 alkyl group, the hydrogen atom of which is substituted with at least one group selected from the group consisting of: a C3-C5 alkenyl group; or a cyclohexyl group. 57 and R 58 are bonded to each other to form -O- or -N(R 64 R may be a C3 to C9 alkylene group optionally interrupted by -. 62 is a C1 to C6 alkyl group. 63 is a C1 to C4 alkyl group. 64 is a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an allyl group, a hydroxyalkyl group having 1 to 4 carbon atoms, -CH2CH2-COOR 65 Or -CH2CH2CN. 65 is a C1 to C4 alkyl group.

[0066] The chemical structure X can be bonded to a hydrogen atom or a structure substituted with a hydrogen atom via the carbon atom indicated by * in formula (1).

[0067] The alkyl group, alkoxy group, alkenyl group, alkylene group, oxyalkylene group, azaalkylene group, and hydroxyalkyl group described in the explanation of formula (1) may be unbranched or branched. In addition, the description of "Cn1 to Cn2" (n1 and n2 are natural numbers) in this specification, including the explanation of formula (1), means that the number of carbon atoms is in the range of n1 to n2.

[0068] R 1 and R 2 may be, independently of each other, a C1 to C8 alkyl group, a C3 to C6 alkenyl group, or a C1 to C8 alkyl group. 1 and R 2 may be, independently of each other, a C1 to C4 alkyl group, a C1 to C3 alkyl group, or a C1 to C2 alkyl group. 1 and R 2 may be a methyl group.

[0069] R 1and R 2 may be identical.

[0070] X is -OR 56 R 56 may be a hydrogen atom or a C1 to C8 alkyl group, or may be a hydrogen atom In other words, X may be -OH.

[0071] R 1 , R 2 and X may be any combination of the preferred examples above.

[0072] The chemical structure X may be a structure shown in the following formula (2). In the chemical structure X of formula (2), when a hydrogen atom substitution structure is bonded to the carbon atom indicated by *, the substitution structure and -COCR in formula (2) may be bonded to each other. 1 XR 2 The group is in a para-position relationship with respect to the benzene ring of the chemical structure X. [ka]

[0073] The photopolymerization initiator may be a compound having two or more chemical structures X in one molecule.

[0074] The photopolymerization initiator may be a compound represented by the following formula (3). The compound of formula (3) has two chemical structures X in one molecule. The two chemical structures X are located at both ends of the molecule of the photopolymerization initiator, respectively. More specifically, the two chemical structures X are bonded to each other by -A- at the carbon atom of the phenylene group represented by * above. [ka]

[0075] R in Equation (3) 1 ' and R 2 ' are each other and R 1 and R 2 Independently of R 1 and R2 R is a possible group. 1 ' and / or R 2 ' is R 1 and / or R 2 It may be the same as R 1 , R 2 , R 1 ' and R 2 ' may all be the same.

[0076] X' in formula (3) is a possible group for X, independent of X in formula (1). X' and X may be the same.

[0077] A is -O-, -CYR 3 - or -C(CH3)R 4 It is.

[0078] Y is a hydrogen atom, -Cl, -Br, -OR 71 , -NR 72 R 73 , or -SR 74 R 3 is a hydrogen atom, an alkyl group having C1 to C8, an alkenyl group having C3 to C6, a benzyl group, -CH2-C6H4-R 75 or a phenyl group. 4 is a C1 to C6 alkyl or alkylene group, and this alkylene group is bonded to a carbon atom of the phenylene group that the compound of formula (3) has.

[0079] R 71 is a hydrogen atom, -Si(R 76 )3, C1-C12 alkyl groups, C2-C18 acyl groups, -CO-NH-R 77 , C2-C20 hydroxyalkyl group, C2-C20 methoxyalkyl group, 3-R 78 -2-hydroxypropyl group, 3-[1,3,3,3-tetramethyl-1-[(trimethylsilyl)oxy]disiloxanyl]propyl group, 2,3-dihydroxypropyl group, or a C2-C21 hydroxyalkyl group or a C3-C25 alkyl group in which the carbon chain is interrupted by 1 to 9 oxygen atoms. 72and R 73 are each independently a C1 to C12 alkyl group; -OH, a C1 to C4 alkoxy group, -CN, or -COOR 79 a C2-C4 alkyl group, in which a hydrogen atom is substituted with at least one group selected from the group consisting of: a C3-C5 alkenyl group; a cyclohexyl group; or a C7-C9 phenylalkyl group. R 72 and R 73 are bonded to each other to form -O- or -N(R 80 R may be a C3 to C9 alkylene group optionally interrupted by -. 74 is an alkyl group having C1 to C18, a hydroxyethyl group, a 2,3-dihydroxypropyl group, a cyclohexyl group, a benzyl group, a phenyl group, an alkylphenyl group having C1 to C12, -CH2-COOR 81 -CH2CH2-COOR 82 or -CH(CH3)-COOR 83 R 75 is a C1 to C4 alkyl group. 76 is a C1 to C6 alkyl group. 77 is a C1 to C12 alkyl group. 78 is a C1 to C18 alkoxy group. 79 is a C1 to C4 alkyl group. 80 is a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an allyl group, a benzyl group, a hydroxyalkyl group having 1 to 4 carbon atoms, -CH2CH2-COOR 84 , or -CH2CH2CN. 81 , R 82 and R 83 are each independently a C1 to C18 alkyl group. 84 is a C1 to C4 alkyl group.

[0080] The alkyl group, alkenyl group, acyl group, hydroxyalkyl group, methoxyalkyl group, alkoxy group, alkyl moiety in the phenylalkyl group, and alkylene group described in the explanation of formula (3) may be either unbranched or branched.

[0081] R in Equation (3) 1 , R 2 , R 1 ' and R 2 Preferred examples of R 1 and R 2 The preferred examples of X' in formula (3) are the same as the preferred examples of X described above in the explanation of formula (1). A is -CYR 3 Y may be a hydrogen atom. 3 may be a hydrogen atom. 3 - and Y and R 3 and may both be hydrogen atoms. In other words, A may be -CH2-.

[0082] R in Equation (3) 1 , R 2 , R 1 ', R 2 X′, X′, and A may take any combination of the preferred examples above.

[0083] The photopolymerization initiator may be a compound represented by the following formula (4): The compound of formula (4) is a type of compound of formula (3). [ka]

[0084] Specific examples of the photopolymerization initiator are shown in the following formulas (5) to (9). The photopolymerization initiator may be a compound represented by at least one formula selected from the group consisting of formulas (5) to (9), a compound represented by at least one formula selected from the group consisting of formulas (5) to (8), a compound represented by at least one formula selected from the group consisting of formulas (5) to (7), or a compound represented by formula (5). The compound represented by formula (8) is derived from a vinyl compound having a chemical structure X in its side chain. More specifically, it is an oligomer of the vinyl compound.

[0085] [ka]

[0086] [ka]

[0087] [ka]

[0088] [ka]

[0089] [ka]

[0090] The photopolymerization initiators represented by the formulas (5) to (9) are commercially available as Omnirad127, Esacure KIP160, Esacure one, Esacure KIP150, and Omnirad1173 (all manufactured by IGM Resins). The photopolymerization initiator may be at least one selected from these groups.

[0091] Specific examples of photopolymerization initiators include 1-hydroxycyclohexyl-phenyl ketone, bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide, and 2-hydroxy-1-(4-(4-(2-hydroxy-2-methylpropionyl)benzyl)phenyl)2-methylpropan-1-one. Among these, 2-hydroxy-1-(4-(4-(2-hydroxy-2-methylpropionyl)benzyl)phenyl)2-methylpropan-1-one is preferred. Each of the above photopolymerization initiators is commercially available as Omnirad184, Omnirad819, and Omnirad127 (all manufactured by IGM Resin).

[0092] The amount of the photopolymerization initiator in the photocurable composition is, for example, 20 parts by weight or less, and may be 10 parts by weight or less, 5.0 parts by weight or less, 3.0 parts by weight or less, 1.0 parts by weight or less, 0.5 parts by weight or less, 0.3 parts by weight or less, 0.25 parts by weight or less, or even 0.2 parts by weight or less, relative to 100 parts by weight of the total of the monomer group and its partial polymer. The lower limit of the amount of the photopolymerization initiator is, for example, 0.01 parts by weight or more, and may be 0.03 parts by weight or more, 0.05 parts by weight or more, or even 0.06 parts by weight or more, relative to 100 parts by weight of the total of the monomer group and its partial polymer.

[0093] The photocurable composition may contain a crosslinking agent B other than the crosslinking agent A. An example of the crosslinking agent B is a polyfunctional monomer having two or more polymerizable functional groups in one molecule. The polyfunctional monomer may be a (meth)acrylic monomer. An example of the polyfunctional monomer is a monomer having two or more C=C bonds in one molecule, and a monomer having one or more C=C bonds and one or more polymerizable functional groups such as epoxy groups, aziridine groups, oxazoline groups, hydrazine groups, and methylol groups in one molecule. The polyfunctional monomer is preferably a monomer having two or more C=C bonds in one molecule.

[0094] Examples of polyfunctional monomers that can be crosslinking agent B include polyfunctional acrylates (such as ester compounds of polyhydric alcohols and (meth)acrylic acid) such as pentaerythritol di(meth)acrylate, pentaerythritol tri(meth)acrylate, 1,2-ethylene glycol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, 1,9-nonanediol diacrylate (NDDA), 1,12-dodecanediol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, and tetramethylolmethane tri(meth)acrylate; allyl (meth)acrylate, vinyl (meth)acrylate, divinylbenzene, epoxy acrylate, polyester acrylate, urethane acrylate, butyl di(meth)acrylate, and hexyl di(meth)acrylate. The polyfunctional monomer is preferably a polyfunctional acrylate, and more preferably 1,9-nonanediol diacrylate, trimethylolpropane tri(meth)acrylate, hexanediol di(meth)acrylate, or dipentaerythritol hexa(meth)acrylate.

[0095] The amount of the crosslinking agent B varies depending on the molecular weight, the number of functional groups, etc., but may be, for example, 5 parts by weight or less, 3 parts by weight or less, 2 parts by weight or less, 1 part by weight or less, 0.5 parts by weight or less, 0.3 parts by weight or less, 0.2 parts by weight or less, or even 0.15 parts by weight or less, relative to 100 parts by weight of the total of the monomer group and its partial polymer. The lower limit of the amount may be, for example, 0.01 parts by weight or more, 0.03 parts by weight or more, 0.05 parts by weight or more, 0.06 parts by weight or more, 0.08 parts by weight or more, or even 0.1 parts by weight or more. The photocurable composition may not contain the crosslinking agent B.

[0096] The photocurable composition may contain additives other than those described above. Examples of additives include chain transfer agents, silane coupling agents, viscosity modifiers, tackifiers, plasticizers, softeners, antioxidants, fillers, colorants, antioxidants, surfactants, antistatic agents, and ultraviolet absorbing agents. The photocurable composition may not contain additives.

[0097] Examples of the silane coupling agent are γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropyltriethoxysilane, γ-aminopropyltrimethoxysilane, and N-phenyl-aminopropyltrimethoxysilane. The silane coupling agent is preferably γ-glycidoxypropyltrimethoxysilane. However, the silane coupling agent is not limited to the above examples. The photocurable composition may contain one or more kinds of silane coupling agents.

[0098] The amount of the silane coupling agent in the photocurable composition is, for example, 0.01 to 1 part by weight, and may be 0.03 to 0.5 parts by weight, based on 100 parts by weight in total of the monomer group and its partial polymer.

[0099] The viscosity of the photocurable composition is preferably 5 to 150 poise, and may be 5 to 100 poise. A photocurable composition having a viscosity in the above range is particularly suitable for application to the method for producing a pressure-sensitive adhesive sheet described below.

[0100] The content of the solvent in the photocurable composition is as described above. The solvent is typically an organic solvent capable of dissolving the monomer group and its partial polymer, as well as the crosslinking agent.

[0101] [Adhesive sheet] An example of the adhesive sheet of this embodiment is shown in FIG. 1. The adhesive sheet 1 of FIG. 1 is a sheet formed from the photocurable composition of this embodiment. The adhesive sheet 1 contains a crosslinked polymer formed from the photocurable composition of this embodiment. In other words, the adhesive sheet 1 typically contains a crosslinked polymer C having a polymer chain having a constituent unit derived from a monomer contained in the photocurable composition of this embodiment and a crosslinking portion that crosslinks the polymer chains. The crosslinking portion of the crosslinked polymer C contains a molecular chain derived from the crosslinking agent A, in other words, a molecular chain having a constituent unit containing an ether structure. The fact that the crosslinking portion has a molecular chain derived from the crosslinking agent A can contribute to imparting stress relaxation properties to the crosslinked polymer C. The content of the solvent in the adhesive sheet 1 may be within the range of the content of the solvent described in the description of the photocurable composition of this embodiment. The adhesive sheet 1 may be substantially free of a solvent.

[0102] The weight average molecular weight (Mw) of the polymer (a portion excluding the crosslinked portion in the crosslinked polymer C) contained in the pressure-sensitive adhesive sheet 1 may be, for example, 500,000 or more, 600,000 or more, 650,000 or more, 700,000 or more, 750,000 or more, 800,000 or more, 850,000 or more, or even 900,000 or more. The upper limit of Mw is not particularly limited, and is, for example, 3,000,000 or less. The number average molecular weight (Mn) of the polymer may be, for example, 150,000 or more, 170,000 or more, 180,000 or more, 190,000 or more, or even 200,000 or more. The upper limit of Mn is not particularly limited, and is, for example, 600,000 or less. Mw / Mn, which means the molecular weight distribution, may be, for example, 1.8 to 10, 1.8 to 7, or even 1.8 to 5. Mw and Mn are determined from values ​​measured by GPC (gel permeation chromatography) and calculated in terms of polystyrene.

[0103] The gel fraction of the pressure-sensitive adhesive sheet 1 is, for example, 50% or more, and may be 51% or more, 52% or more, 53% or more, 54% or more, 55% or more, 56% or more, 57% or more, 58% or more, 59% or more, or even 60% or more. The upper limit of the gel fraction may be 75% or less, 70% or less, less than 70%, 69% or less, 68% or less, 67% or less, 66% or less, or even 65% or less. The gel fraction may be 50% or more and 70% or less, 55% or more and 67% or less, or 60% or more and 65% or less.

[0104] The gel fraction of the adhesive sheet 1 can be evaluated as follows. A test piece of about 0.1 g is taken from the adhesive sheet 1, wrapped in a polytetrafluoroethylene porous sheet (average pore size 0.2 μm, product name "NTF1122", manufactured by Nitto Denko Corporation), and then tied with a kite string to obtain a measurement sample. Next, the weight of the obtained measurement sample (weight before immersion c) is measured. The weight before immersion c is the total weight of the test piece, the polytetrafluoroethylene porous sheet, and the kite string. Separately from this, the bag weight b, which is the total weight of the polytetrafluoroethylene porous sheet and the kite string, is measured. Next, the measurement sample is placed in a container with a volume of 50 mL filled with ethyl acetate and left to stand at 23° C. for 7 days. After standing, the measurement sample is removed from the container and transferred to an aluminum cup, and the ethyl acetate is removed by drying at 130° C. for 2 hours using a dryer. The weight of the measurement sample after drying (weight after immersion a) is measured. The value calculated from the following formula is specified as the gel fraction of the adhesive sheet 1. Gel fraction (%) = (ab) / (cb) × 100

[0105] The thickness of the pressure-sensitive adhesive sheet 1 is, for example, 2 to 500 μm, and may be 2 to 300 μm, 2 to 200 μm, or even 2 to 150 μm. The upper limit of the thickness may be 100 μm or less, 70 μm or less, 60 μm or less, 50 μm or less, 40 μm or less, 30 μm or less, 25 μm or less, or even 20 μm or less. The lower limit of the thickness may be 5 μm or more, 10 μm or more, or even 15 μm or more.

[0106] The pressure-sensitive adhesive sheet 1 can be used, for example, in an optical laminate or an image display device. However, the uses of the pressure-sensitive adhesive sheet 1 are not limited to the above examples.

[0107] (Manufacturing method of adhesive sheets) The pressure-sensitive adhesive sheet 1 can be formed, for example, by irradiating light 14 to a first laminate 10 including a base sheet 11, a coating layer 12 containing the photocurable composition of the present embodiment, and a release liner 13 in this order (see FIG. 2). The coating layer 12 is irradiated with light 14 and hardened to become the pressure-sensitive adhesive sheet 1. Irradiation with light 14 is typically performed from the side of the base sheet 11. At this time, the light 14 penetrates the base sheet 11 and reaches the coating layer 12, hardening the coating layer 12. However, irradiation with light 14 may be performed from the side of the release liner 13, or may be performed from both the side of the release liner 13 and the side of the base sheet 11.

[0108] The formed pressure-sensitive adhesive sheet 1 is sandwiched between the base sheet 11 and the release liner 13 until the release liner 13 is peeled off, and constitutes a part of the second laminate 17. By peeling the release liner 13 from the second laminate 17, a third laminate 15 including the base sheet 11 and the pressure-sensitive adhesive sheet 1 is obtained. In the third laminate 15, the surface of the pressure-sensitive adhesive sheet 1 is exposed to the outside. An optical film can be laminated onto the exposed surface of the pressure-sensitive adhesive sheet 1 directly or via another layer.

[0109] The light 14 is, for example, visible light or ultraviolet light having a wavelength shorter than 450 nm. The light may contain light having a wavelength in the same region as the absorption wavelength of the photopolymerization initiator contained in the photocurable composition. Light with a short wavelength of 300 nm or less may be cut by a filter or the like, and cutting short wavelength light is suitable for suppressing deterioration of the base sheet 11 and / or the release liner 13 caused by the light 14. The light source is, for example, a light irradiation device equipped with an ultraviolet irradiation lamp. Examples of the ultraviolet irradiation lamp are an ultraviolet LED, a low pressure mercury lamp, a medium pressure mercury lamp, a high pressure mercury lamp, an ultra-high pressure mercury lamp, a metal halide lamp, a xenon lamp, a microwave excited mercury lamp, a black light lamp, a chemical lamp, a germicidal lamp, a low pressure discharge mercury lamp, and an excimer laser. Two or more ultraviolet irradiation lamps may be combined. With an ultraviolet LED, the band of the ultraviolet light to be irradiated can be narrowed compared to the case of using other light sources.

[0110] When an ultraviolet LED is used as the light source, an LED having a peak wavelength at 340±10 nm (hereinafter referred to as LED340) may be selected. According to the study by the present inventors, the use of LED340 may contribute to improving the polymerization rate of the monomer group in the adhesive sheet 1 and / or reducing the amount of remaining photopolymerization initiator, compared to the use of a black light source, for example. In addition, LED340 tends to suppress heat generation compared to the use of an LED having a peak wavelength around 365 nm. The suppression of heat generation can contribute to the control of the temperature of the coating layer 12. The peak wavelength means the wavelength at which the intensity is at a maximum value in a spectrum showing the relationship between the wavelength and intensity of light.

[0111] The illuminance of the light 14 irradiated onto the first laminate 10 (specifically, the coating layer 12) is, for example, 2.0 to 30 mW / cm 2 The illuminance is 2.5mW / cm 2 More than 3.0mW / cm 2 More than 3.5mW / cm 2 More than 4.0mW / cm 2 More than 5.0mW / cm 2 More than 6.0mW / cm 2 More than 7.0mW / cm 2More than 8.0mW / cm 2 More than 9.0mW / cm 2 or even 10mW / cm 2 The upper limit of the illuminance is, for example, 25 mW / cm 2 Less than 20mW / cm 2 Below 15mW / cm 2 It may be the following.

[0112] The time for irradiating the first laminate 10 (specifically, the coating layer 12) with the light 14 is, for example, 10 to 1000 seconds, and may be 60 seconds or more, 100 seconds or more, 150 seconds or more, or even 200 seconds or more. The upper limit of the time is, for example, 800 seconds or less, and may be 600 seconds or less, 500 seconds or less, 400 seconds or less, 300 seconds or less, or even 250 seconds or less. The irradiation with the light 14 may be continuous or intermittent.

[0113] The integrated amount of light 14 applied to the first laminate 10 (specifically, the coating layer 12) is, for example, 25 mJ / cm 2 More than 100 mJ / cm 2 More than 250mJ / cm 2 More than 500mJ / cm 2 More than 750mJ / cm 2 More than 850mJ / cm 2 More than 1000mJ / cm 2 More than 1250mJ / cm 2 or even 1500mJ / cm 2 The upper limit of the integrated light amount is not particularly limited, and may be, for example, 3000 mJ / cm 2 Less than 2500 mJ / cm 2 Below, 2000mJ / cm 2 Below, 1750mJ / cm 2 Below, 1500mJ / cm 2 Below, 1250mJ / cm 2 Below that, even 1000mJ / cm 2 It may be the following.

[0114] An example of the substrate of the release liner 13 (hereinafter, "liner substrate") is a resin film. Examples of resins that can be contained in the liner substrate are polyesters such as polyethylene terephthalate and polyethylene naphthalate, acetate resins, polyethersulfone, polycarbonate, polyamide, polyimide, polyolefin, (meth)acrylic resins, polyvinyl chloride, polyvinylidene chloride, polystyrene, polyvinyl alcohol, polyarylate, and polyphenylene sulfide. The resin is preferably a polyester such as polyethylene terephthalate.

[0115] The release liner 13 may have a layer other than the liner substrate. The release liner 13 may have a release layer. The release liner 13 has, for example, a liner substrate and a release layer formed on one surface of the liner substrate. This release liner 13 can be used such that the release layer is on the coating layer 12 side. The release layer is typically a cured layer of a release agent composition containing a release agent. As the release agent, various release agents such as silicone-based release agents, fluorine-based release agents, long-chain alkyl-based release agents, fatty acid amide-based release agents, and silica powder can be used.

[0116] The release liner 13 may be in the form of a sheet or a continuous piece.

[0117] An example of the base sheet 11 is a resin film. Examples of the resin contained in the base sheet 11 are the same as the examples of the resin that can be contained in the liner base material.

[0118] The thickness of the base sheet 11 is, for example, 10 to 200 μm, and may be 25 to 150 μm.

[0119] The base sheet 11 may have a release layer on the surface on the side of the coating layer 12. Examples of the release layer that may be provided on the base sheet 11 are the same as the examples of the release layer that may be provided on the release liner 13. Both the release liner 13 and the base sheet 11 may have a release layer.

[0120] For the base sheet 11, a sheet having a greater peeling strength from the adhesive sheet 1 than the release liner 13 can usually be selected.

[0121] The base sheet 11 may be in the form of a sheet or a continuous length.

[0122] The first laminate 10 can be formed, for example, by forming a coating layer 12 on a base sheet 11 (or a release liner 13) and then disposing a release liner 13 (or base sheet 11) on the formed coating layer 12. Alternatively, the first laminate 10 may be formed by applying a photocurable composition in a poured manner into the space between the base sheet 11 and the release liner 13 that are held at a predetermined distance such that their main surfaces face each other.

[0123] The coating layer 12 can be formed by various coating methods such as roll coating, kiss roll coating, gravure coating, reverse coating, roll brush, spray coating, dip roll coating, bar coating, knife coating, air knife coating, curtain coating, lip coating, and die coating.

[0124] The thickness of the coating layer 12 can be adjusted according to the desired thickness of the pressure-sensitive adhesive sheet 1, and may be, for example, 2 to 500 μm, 2 to 300 μm, 2 to 200 μm, or even 2 to 150 μm. The upper limit of the thickness may be 100 μm or less, 70 μm or less, 60 μm or less, 50 μm or less, 40 μm or less, 30 μm or less, 25 μm or less, or even 20 μm or less. The lower limit of the thickness may be 5 μm or more, 10 μm or more, or even 15 μm or more.

[0125] The first laminate 10 may include a long base sheet 11, a long coating layer 12, and a long release liner 13, in other words, may be long. The long first laminate 10 can be obtained, for example, by forming the coating layer 12 between the base sheet 11 and the release liner 13 while conveying them, the base sheet 11 and the release liner 13 being unwound from a roll.

[0126] As described above, the present invention further provides a method for producing a pressure-sensitive adhesive sheet, comprising irradiating a coating layer of a photocurable composition containing a monomer group and / or a partial polymer of the monomer group, and a photopolymerization initiator having chemical structure X in its molecule with light 14 to photocure the coating layer.

[0127] [Optical laminate] An example of the optical laminate of this embodiment is shown in Fig. 3. The optical laminate 20A in Fig. 3 includes an adhesive sheet 1 and an optical film 2. The adhesive sheet 1 and the optical film 2 are laminated to each other. The adhesive sheet 1 is in contact with the optical film 2. The optical laminate 20A can be used as an optical film with an adhesive sheet.

[0128] Examples of the optical film 2 include a polarizing film, a retardation film, and a laminated film including a polarizing film and / or a retardation film. However, the optical film 2 is not limited to the above examples. The optical film 2 may include a glass film.

[0129] The optical film 2 may be a polarizing film, and the pressure-sensitive adhesive sheet 1 may be in contact with the optical film 2. The optical laminate 20A in which the optical film 2 is a polarizing film can be used as a polarizing film with a pressure-sensitive adhesive sheet.

[0130] FIG. 4 shows an example of an optical laminate in which the optical film 2 is a polarizing film 2A. The optical laminate 20B in FIG. 4 includes the polarizing film 2A as the optical film 2. The polarizing film 2A includes a polarizer 51. The polarizing film 2A in FIG. 4 includes a polarizer 51 and a pair of protective films (transparent protective films) 52 (52A, 52B). The protective films 52A and 52B are disposed in contact with the respective main surfaces (surfaces having the widest areas) of the polarizer 51. The polarizer 51 is disposed between the two protective films 52A and 52B. The protective film may be disposed only on one of the main surfaces of the polarizer 51. The polarizing film 2A in FIG. 4 is a double-protected film in which both main surfaces are protected. The polarizing film 2A may be a single-protected film in which only one of the main surfaces is protected.

[0131] The polarizer 51 is not particularly limited, and examples thereof include hydrophilic polymer films such as polyvinyl alcohol films, partially formalized polyvinyl alcohol films, and partially saponified ethylene-vinyl acetate copolymer films, which are uniaxially stretched after adsorbing a dichroic substance such as iodine or a dichroic dye; polyene-based oriented films such as dehydrated polyvinyl alcohol and dehydrochlorinated polyvinyl chloride; etc. The polarizer 51 is typically made of a polyvinyl alcohol film (polyvinyl alcohol films include partially saponified ethylene-vinyl acetate copolymer films) and a dichroic substance such as iodine.

[0132] The thickness of the polarizer 51 is not particularly limited, and may be, for example, 80 μm or less, 50 μm or less, 30 μm or less, 25 μm or less, or even 20 μm or less. The lower limit of the thickness of the polarizer 51 is not particularly limited, and may be, for example, 1 μm or more, 5 μm or more, 10 μm or more, or even 15 μm or more. A thin polarizer (for example, a thickness of 20 μm or less) 51 is suppressed in dimensional change, and can contribute to improving the durability of the optical laminate, particularly the durability at high temperatures.

[0133] The material of the protective film 52 is, for example, a thermoplastic resin having excellent transparency, mechanical strength, thermal stability, moisture blocking properties, isotropy, etc. Specific examples of such thermoplastic resins include cellulose resins such as triacetyl cellulose, polyester resins, polyethersulfone resins, polysulfone resins, polycarbonate resins, polyamide resins, polyimide resins, polyolefin resins, (meth)acrylic resins, cyclic polyolefin resins (norbornene-based resins), polyarylate resins, polystyrene resins, polyvinyl alcohol resins, and mixtures thereof. The material of the protective film 52 may be a thermosetting resin or an ultraviolet-curing resin such as a (meth)acrylic, urethane, acrylic urethane, epoxy, or silicone-based resin. When the polarizing film 2A has two protective films 52A and 52B, the materials of the two protective films may be the same or different from each other. For example, a protective film 52A (or 52B) made of a thermoplastic resin may be attached to one main surface of the polarizer 51 via an adhesive, and a protective film 52B (or 52A) made of a thermosetting resin or an ultraviolet-curable resin may be attached to the other main surface of the polarizer. The protective film 52 may contain one or more types of additives. Examples of additives include ultraviolet absorbers, antioxidants, lubricants, plasticizers, release agents, coloring inhibitors, flame retardants, nucleating agents, antistatic agents, pigments, and colorants.

[0134] The thickness of the protective film 52 can be appropriately determined, but is generally about 10 to 200 μm in terms of strength, workability such as handleability, thinness, and the like.

[0135] The polarizer 51 and the protective film 52 are usually adhered to each other via a water-based adhesive or the like. Examples of water-based adhesives include isocyanate-based adhesives, polyvinyl alcohol-based adhesives, gelatin-based adhesives, vinyl latex, water-based polyurethane, water-based polyester, and the like. Examples of adhesives other than the above-mentioned adhesives include ultraviolet-curable adhesives and electron beam-curable adhesives. Electron beam-curable polarizing film adhesives exhibit suitable adhesion to various protective films. The adhesive may contain a metal compound filler.

[0136] In the polarizing film 2A, a retardation film or the like can be formed on the polarizer instead of the protective film 52. On the protective film 52, another protective film or a retardation film or the like can also be provided.

[0137] The protective film 52 may have a hard coat layer on the surface opposite to the surface adhered to the polarizer 51, and may also be subjected to treatments for the purposes of anti-reflection, anti-sticking, diffusion, anti-glare, etc.

[0138] The polarizing film 2A may be a circular polarizing film.

[0139] The thickness of the polarizing film 2A is, for example, 500 μm or less, and may be 300 μm or less, 200 μm or less, 100 μm or less, or even 60 μm or less. The lower limit of the thickness is, for example, 10 μm or more, 25 μm or more, or even 40 μm or more.

[0140] The retardation film is a film having birefringence in the in-plane direction and / or the thickness direction, and is, for example, a stretched resin film or a film in which a liquid crystal material is oriented and fixed.

[0141] The retardation film may be a λ / 4 plate, a λ / 2 plate, an anti-reflection retardation film (see, for example, paragraphs 0221, 0222, and 0228 of JP 2012-133303 A), a retardation film for compensating for viewing angles (see, for example, paragraphs 0225 and 0226 of JP 2012-133303 A), or a tilted orientation retardation film for compensating for viewing angles (see, for example, paragraph 0227 of JP 2012-13303 A). The retardation film is not limited to the above examples as long as it has birefringence in the in-plane direction and / or the thickness direction. There are also no limitations on the retardation value, arrangement angle, three-dimensional birefringence, whether it is a single layer or a multilayer, and the like, of the retardation film. A known film can be used for the retardation film.

[0142] The optical film 2 has a thickness of, for example, 1 to 200 μm.

[0143] The optical film 2 may be a single layer or a laminated film composed of two or more layers. When the optical film 2 is a laminated film, the pressure-sensitive adhesive sheet 1 may be used to bond the layers together.

[0144] The optical laminates 20A and 20B can be used, for example, by attaching the pressure-sensitive adhesive sheet 1 to the image-forming layer. In other words, the pressure-sensitive adhesive sheet 1 may be located on the panel side (opposite the viewing side) of the image display device with respect to the optical film 2 (e.g., the polarizing film 2A).

[0145] Another example of the optical laminate of the present embodiment is shown in Fig. 5. The optical laminate 20C in Fig. 5 has a laminated structure in which a separator 3, an adhesive sheet 1, and an optical film 2 are laminated in this order. By peeling off the separator 3, the optical laminate 20C can be used as an optical film with an adhesive sheet.

[0146] The separator 3 is typically a resin film. Examples of resins constituting the separator 3 include polyesters such as polyethylene terephthalate (PET), polyolefins such as polyethylene and polypropylene, polycarbonate, acrylic, polystyrene, polyamide, and polyimide. The surface of the separator 3 that contacts the adhesive sheet 1 may be subjected to a release treatment. The release treatment is, for example, a treatment using a silicone compound. However, the separator 3 is not limited to the above example. The separator 3 is peeled off when the optical laminate 20C is used, for example, when it is attached to the image forming layer.

[0147] Another example of the optical laminate of the present embodiment is shown in Fig. 6. The optical laminate 20D in Fig. 6 has a laminated structure in which a separator 3, an adhesive sheet 1, and a polarizing film 2A are laminated in this order. The polarizing film 2A has a laminated structure including a protective film 52A, a polarizer 51, and a protective film 52B. By peeling off the separator 3, the optical laminate 20D can be used as a polarizing film with an adhesive sheet.

[0148] Another example of the optical laminate of the present embodiment is shown in Fig. 7. The optical laminate 20E in Fig. 7 has a laminated structure in which a separator 3, a pressure-sensitive adhesive sheet 1, a polarizing film 2A, and a protective film 5 are laminated in this order. After peeling off the separator 3, the optical laminate 20E can be used by being attached to, for example, an image forming layer.

[0149] The protective film 5 has a function of protecting the optical film 2 (polarizing film 2A) which is the outermost layer during distribution and storage of the optical laminate 20E and in a state where the optical laminate 20E is incorporated into an image display device. The protective film 5 may also function as a window to the external space in a state where it is incorporated into an image display device. The protective film 5 is typically a resin film. The resin constituting the protective film 5 is, for example, polyester such as PET, polyolefin such as polyethylene and polypropylene, acrylic, cycloolefin, polyimide, and polyamide, and polyester is preferable. However, the protective film 5 is not limited to the above examples. The protective film 5 may be a glass film or a laminated film including a glass film. The protective film 5 may be subjected to surface treatment such as anti-glare, anti-reflection, and anti-static.

[0150] The protective film 5 may be bonded to the polarizing film 2A by any adhesive. Bonding by an adhesive sheet 1 is also possible.

[0151] The optical laminate may have any configuration as long as it includes the pressure-sensitive adhesive sheet 1 and the optical film 2.

[0152] The optical laminate of this embodiment can be distributed and stored, for example, as a rolled body obtained by rolling up a strip-shaped optical laminate, or as a sheet-shaped optical laminate.

[0153] The optical laminate of the present embodiment is typically used in an image display device, such as a liquid crystal display, an organic EL display, or an inorganic EL display.

[0154] [Image display device] An example of the image display device of this embodiment is shown in Fig. 8. The image display device 21 in Fig. 8 has a laminated structure in which a substrate 7, an image forming layer (e.g., an organic EL layer or a liquid crystal layer) 6, an adhesive sheet 1, and a polarizing film 2A are laminated in this order. The image display device 21 has the optical laminates 20A, 20B, 20C, and 20D of Figs. 3 to 6 (excluding the separator 3). The substrate 7 and the image forming layer 6 may have the same configurations as the substrate and the image forming layer, respectively, of a known image display device.

[0155] The image display device 21 in Fig. 8 may be an organic EL display or a liquid crystal display. However, the image display device 21 is not limited to this example. The image display device 21 may be an electroluminescence (EL) display, a plasma display (PD), a field emission display (FED), or the like. The image display device 21 may be used for home appliances, in-vehicle applications, public information displays (PID), and the like.

[0156] The image display device 21 may have any configuration as long as it includes the pressure-sensitive adhesive sheet 1 and / or the optical laminate 20. EXAMPLES

[0157] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the examples shown below.

[0158] [Preparation of photocurable composition] (Monomer Syrup A1) 95.1 parts by weight of n-butyl acrylate (BA), 0.1 parts by weight of 4-hydroxybutyl acrylate (HBA), 4.8 parts by weight of acrylic acid (AA), 0.16 parts by weight of Omnirad184 (manufactured by IGM Resin) and 0.04 parts by weight of Omnirad819 (manufactured by IGM Resin) as photopolymerization initiators were placed in a four-neck flask. Next, the liquid in the flask was irradiated with ultraviolet light under a nitrogen atmosphere to obtain Monomer Syrup A1 in which the monomers were partially photopolymerized. The UV irradiation was continued until the viscosity of the liquid in the flask (measurement conditions: BH viscometer No. 5 rotor, 10 rpm, measurement temperature 30°C) reached 20 Pa·s. The composition of Monomer Syrup A1 is shown in Table 1 below.

[0159] [Table 1]

[0160] The abbreviations in Table 1 are as follows. BA: n-butyl acrylate HBA: 4-hydroxybutyl acrylate AA: Acrylic acid Omnirad184: 1-Hydroxycyclohexyl-phenyl ketone (Omnirad184, IGM Resin) Omnirad819: Bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide (Omnirad819, IGM Resins)

[0161] (Photocurable compositions C1 to C6) Next, photocurable compositions C1 to C6 were obtained by mixing the monomer syrup and the crosslinking agent so as to obtain the compositions shown in the following Table 2. The photocurable compositions C1 to C6 were substantially free of a solvent.

[0162] [Table 2]

[0163] The abbreviations in Table 2 are as follows. A200: Polyethylene glycol (#200) diacrylate APG200: Polypropylene glycol (#200) diacrylate NDDA: 1,9-nonanediol diacrylate A200 has a polyethylene glycol chain (average degree of polymerization: 200). APG200 has a polypropylene glycol chain (average degree of polymerization: 200).

[0164] [Preparation of adhesive sheet] <Example 1> (Preparation of release liner) Addition reaction curing type silicone (LTC761 containing hexenyl group-containing polyorganosiloxane, 30 wt% toluene solution, manufactured by Dow Corning Toray) 30 parts by weight, release control agent (BY24-850 containing unreactive silicone resin, manufactured by Dow Corning Toray) 0.9 parts by weight, curing catalyst (SRX212 containing platinum catalyst, manufactured by Dow Corning Toray) 2 parts by weight, and toluene / hexane mixed solvent (volume ratio 1: 1) as a dilution solvent were mixed to obtain a silicone-based release agent composition. The concentration of silicone solids in the release agent composition was 1.0 wt%. Next, the release agent composition was applied to one side of a liner substrate (Lumirror XD500P, a polyester film, thickness 75 μm) with a wire bar and heated at 130 ° C for 1 minute to prepare a release liner having a release layer (thickness 60 nm) on one side.

[0165] (Preparation of adhesive sheet) Monomer syrup C1 was applied to one side of a base sheet (PET separator, manufactured by Mitsubishi Plastics, MRF38) with an applicator to form a coating layer (thickness 20 μm). Next, a release liner was placed on the formed coating layer to obtain a first laminate. The release liner was placed so that the release layer was in contact with the coating layer. Next, light was irradiated from the side of the base sheet in the first laminate. As a result, the coating layer was photocured, and a pressure-sensitive adhesive sheet (thickness 20 μm) of Example 1 sandwiched between the base sheet and the release liner was obtained. A combination of a black light source (BL) and an LED was used as the light source. The peak wavelength of the LED was 340 nm. The irradiation conditions for each light source were as follows. The illuminance of the light was measured using an illuminometer (manufactured by Topcon Technohouse, UD-T3040T2) as the illuminance at a position near the ultraviolet ray incident surface of the base sheet. BL: Illuminance 6.2mW / cm 2 and irradiation time 95 seconds (accumulated light intensity 589 mJ / cm 2 ) LED: Illuminance 3.1mW / cm 2 and irradiation time 90 seconds (accumulated light intensity 279 mJ / cm 2 )

[0166] <Examples 2 to 5, Comparative Example 1> Pressure-sensitive adhesive sheets of Examples 2 to 5 and Comparative Example 1 were obtained in the same manner as in Example 1, except that the photocurable composition used was changed as shown in Table 3.

[0167] [Evaluation method] <Gel fraction> The gel fraction of each of the pressure-sensitive adhesive sheets of the Examples and Comparative Examples was measured by the method described above.

[0168] <Reliability test> (Preparation of polarizing film) A polyvinyl alcohol film having a thickness of 80 μm was stretched to 3 times while being dyed for 1 minute in an iodine solution having a concentration of 0.3% at a temperature of 30° C. between rolls having different speed ratios. Next, the film was stretched to a total stretching ratio of 6 times while being immersed for 0.5 minutes in an aqueous solution having a temperature of 60° C. and containing boric acid at a concentration of 4% and potassium iodide at a concentration of 10%. Next, the film was immersed for 10 seconds in an aqueous solution having a temperature of 30° C. and containing potassium iodide at a concentration of 1.5%, and then dried at 50° C. for 4 minutes to obtain a polarizer having a thickness of 28 μm. A transparent protective film having a thickness of 30 μm and made of a modified acrylic polymer having a lactone ring structure was attached to one side of the polarizer with a polyvinyl alcohol adhesive. Furthermore, a 47 μm-thick transparent protective film made of a triacetyl cellulose film (Konica Minolta, product name "KC4UY") with a hard coat layer (HC) was attached to the other surface of the polarizer using a polyvinyl alcohol adhesive. The polarizing film was produced by heating and drying for 5 minutes in an oven set at 70°C. Furthermore, a discharge amount of 63 W / m was applied to the surface of the polarizing film on the transparent protective film side made of modified acrylic polymer. 2 Corona treatment was performed for 1 min.

[0169] (Preparation of polarizing film with adhesive sheet) The above-mentioned polarizing film was placed on the exposed surface of each of the pressure-sensitive adhesive sheets prepared in the Examples and Comparative Examples to prepare a polarizing film with a pressure-sensitive adhesive sheet. The polarizing film was placed so that the surface of the transparent protective film made of a modified acrylic polymer was in contact with the pressure-sensitive adhesive sheet.

[0170] <Reliability test (95℃)> The prepared polarizing film with adhesive sheet was evaluated for reliability (95°C reliability) by the following method. First, the polarizing film with adhesive sheet was cut into a strip of 228mm length x 215mm width to prepare a test piece. Next, the test piece was attached to the surface of 0.7mm thick alkali-free glass (manufactured by Corning, product name "EG-XG") with an adhesive sheet. The test piece was attached to the alkali-free glass using a laminator. After the test piece was attached, it was placed in an autoclave at 50°C and 0.5MPa for 15 minutes to homogenize the bonding between the alkali-free glass and the adhesive sheet, and the adhesive sheet was adhered to the alkali-free glass. Next, the test piece was subjected to a heat treatment at 95°C for 500 hours under atmospheric pressure. The vicinity of the end of the test piece was observed with an optical microscope to confirm the presence or absence of peeling from the end of the test piece and foaming near the end. A: No peeling, streaks or bubbles that would affect image display were observed. B: Slight bubbling is observed at the edge, but not to the extent that it affects the image display. C: Multiple streaks or peeling are observed within 2 mm from the edge, but the level is not enough to affect the image display. D: Multiple streaks or peeling are observed in an area more than 2 mm from the edge, affecting image display.

[0171] The evaluation results are shown in Table 3 below.

[0172] [Table 3]

[0173] As shown in Table 3, the photocurable compositions of the Examples were able to improve the reliability of the polarized film with an adhesive sheet in a high temperature environment, compared to the photocurable compositions of the Comparative Examples. [Industrial Applicability]

[0174] The photocurable composition of the present invention can be used to form a pressure-sensitive adhesive sheet and an optical laminate. [Explanation of symbols]

[0175] 1 Adhesive sheet 2. Optical Film 2A Polarizing Film 20A, 20B, 20C, 20D, 20E Optical laminate 21 Image display device

Claims

1. The composition includes a monomer group and / or a partial polymer of the monomer group, and a crosslinking agent, The crosslinking agent has an ether chain, A photocurable composition for pressure-sensitive adhesive sheets, the photocurable composition having a solvent content of 5% by weight or less.

2. The photocurable composition of claim 1 which is substantially free of said solvent.

3. The photocurable composition according to claim 1 , wherein the ether chain is a polyalkylene glycol chain.

4. The photocurable composition according to claim 1 , wherein the ether chain is at least one selected from the group consisting of a polyethylene glycol chain and a polypropylene glycol chain.

5. The photocurable composition according to claim 1 , wherein the crosslinking agent has a polymerizable group capable of polymerizing with the monomer group and / or the partially polymerized product.

6. The photocurable composition according to claim 5 , wherein the crosslinking agent has a structure in which the polymerizable group is bonded to each of two or more ends of the ether chain.

7. The photocurable composition according to claim 5 , wherein the number of the polymerizable groups per molecule of the crosslinking agent is 2 or less.

8. The photocurable composition according to claim 5 , wherein the polymerizable group is a (meth)acryloyl group.

9. The photocurable composition according to claim 1 , wherein the ether chain has a weight average molecular weight of 300 or less.

10. 2. The photocurable composition according to claim 1, wherein the amount of the crosslinking agent in the photocurable composition is 0.01 parts by weight or more and less than 10 parts by weight per 100 parts by weight of the total of the monomer group and the partially polymerized product.

11. The photocurable composition of claim 1 , wherein the monomer group includes a (meth)acrylic monomer.

12. A pressure-sensitive adhesive sheet formed from the photocurable composition according to claim 1 .

13. The pressure-sensitive adhesive sheet according to claim 12 , wherein the amount of the crosslinking agent in the photocurable composition is 0.01 parts by weight or more and less than 10 parts by weight per 100 parts by weight of the total of the monomer group and the partially polymerized product.

14. The pressure-sensitive adhesive sheet according to claim 12, wherein the pressure-sensitive adhesive sheet has a thickness of 30 μm or less.

15. The pressure-sensitive adhesive sheet according to claim 12 , having a gel fraction of 50% or more and 70% or less.

16. An optical laminate comprising the pressure-sensitive adhesive sheet according to any one of claims 12 to 15 and an optical film.

17. The optical film is a polarizing film, The optical laminate according to claim 16 , wherein the pressure-sensitive adhesive sheet is in contact with the polarizing film.

18. An image display device comprising the optical laminate according to claim 16.

Images