Adhesive agent composition, adhesive sheet, optical layered body, and image display device

Abstract

Provided is a photocurable adhesive agent composition for creating an adhesive sheet suitable for use in a high-temperature environment. The photocurable adhesive agent composition that is provided comprises at least one selected from the group consisting of monomers and partial polymers of these monomers. The monomers include nitrogen atom-containing monomers. The adhesive agent composition contains a radical scavenger.

Description

Pressure-sensitive adhesive composition, pressure-sensitive adhesive sheet, optical laminate, and image display device

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

[0002] Various image display devices, typified by 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 to bond the optical films included in the optical laminate or to bond the optical laminate to an image display panel. Patent Document 1 discloses a photocurable adhesive sheet for bonding polarizing films together. The photocurable adhesive sheet is formed from a photocurable composition.

[0003] Japanese Patent Application Laid-Open No. 2021-56510

[0004] When a photocurable pressure-sensitive adhesive sheet formed from a photocurable composition is used, problems tend to occur in the quality of images displayed on an image display device in a high-temperature environment, for example, at 100° C. or higher.

[0005] An object of the present invention is to provide a photocurable pressure-sensitive adhesive composition for producing a pressure-sensitive adhesive sheet suitable for use in high-temperature environments.

[0006] The present invention provides a photocurable pressure-sensitive adhesive composition comprising at least one member selected from the group consisting of a monomer group and a partial polymer of the monomer group, wherein the monomer group comprises a nitrogen atom-containing monomer, and the pressure-sensitive adhesive composition comprises a radical scavenger.

[0007] The present invention further provides a pressure-sensitive adhesive sheet formed from the above photocurable pressure-sensitive adhesive composition.

[0008] The present invention further provides an optical laminate comprising the pressure-sensitive adhesive sheet and an optical film.

[0009] The present invention further provides an image display device comprising the above optical laminate.

[0010] According to the present invention, it is possible to provide a photocurable pressure-sensitive adhesive composition for producing a pressure-sensitive adhesive sheet suitable for use in high-temperature environments.

[0011] FIG. 1 is a schematic diagram for explaining an example of a method for forming a pressure-sensitive adhesive sheet of the present invention. FIG. 2 is a cross-sectional view schematically showing an example of an optical laminate of the present invention. FIG. 3 is a cross-sectional view schematically showing an example of an optical laminate of the present invention. FIG. 4 is a cross-sectional view schematically showing an example of an optical laminate of the present invention. FIG. 5 is a cross-sectional view schematically showing an example of an optical laminate of the present invention. FIG. 6 is a cross-sectional view schematically showing an example of an image display device of the present invention. FIG. 7 is a cross-sectional view schematically showing a sample of an optical laminate subjected to a high-temperature storage test.

[0012] A photocurable pressure-sensitive adhesive composition according to a first aspect of the present invention is a photocurable pressure-sensitive adhesive composition comprising at least one selected from the group consisting of a monomer group and a partial polymer of the monomer group, wherein the monomer group comprises a nitrogen atom-containing monomer, and the pressure-sensitive adhesive composition comprises a radical scavenger.

[0013] In a second aspect of the present invention, for example, in the photocurable pressure-sensitive adhesive composition according to the first aspect, the radical scavenger has a polymerizable unsaturated double bond and corresponds to a part of the monomers constituting the monomer group.

[0014] In a third aspect of the present invention, for example, in the photocurable pressure-sensitive adhesive composition according to the first aspect, the radical scavenger does not have a polymerizable unsaturated double bond.

[0015] In a fourth aspect of the present invention, for example, in the photocurable pressure-sensitive adhesive composition according to any one of the first to third aspects, the radical scavenger comprises at least one selected from the group consisting of a phenoxy-based radical scavenger, an amine-based radical scavenger, and a phosphite-based radical scavenger.

[0016] In a fifth aspect of the present invention, for example, in the photocurable pressure-sensitive adhesive composition according to the fourth aspect, the radical scavenger includes at least one of a phenoxy-based radical scavenger and a phosphite-based radical scavenger.

[0017] In a sixth aspect of the present invention, for example, in the photocurable pressure-sensitive adhesive composition according to the fifth aspect, the radical scavenger has a phenoxy structure.

[0018] In a seventh aspect of the present invention, for example, in the photocurable pressure-sensitive adhesive composition according to any one of the first to sixth aspects, the content of the solvent in the pressure-sensitive adhesive composition is 5 wt % or less.

[0019] In an eighth aspect of the present invention, for example, in the photocurable pressure-sensitive adhesive composition according to the second aspect, the content of the radical scavenger in the pressure-sensitive adhesive composition is 30 parts by weight or less relative to 100 parts by weight of the monomer group.

[0020] In a ninth aspect of the present invention, for example, in the photocurable pressure-sensitive adhesive composition according to the third aspect, the content of the radical scavenger in the pressure-sensitive adhesive composition is 5 parts by weight or less relative to 100 parts by weight of the monomer group.

[0021] In a tenth aspect of the present invention, for example, in the photocurable pressure-sensitive adhesive composition according to any one of the first to ninth aspects, the group of monomers includes a (meth)acrylic monomer.

[0022] The pressure-sensitive adhesive sheet according to the eleventh aspect of the present invention is formed from the photocurable pressure-sensitive adhesive composition according to any one of the first to tenth aspects.

[0023] In a twelfth aspect of the present invention, for example, in the PSA sheet according to the eleventh aspect, in a test in which the PSA sheet is left to stand for 24 hours in an environment of 105°C, the absolute value |Ga - Gb| of the difference between the gel fraction Ga before the test and the gel fraction Gb after the test is 10% or less.

[0024] An optical laminate according to a thirteenth aspect of the present invention comprises the pressure-sensitive adhesive sheet according to the eleventh or twelfth aspect and an optical film.

[0025] An image display device according to a fourteenth aspect of the present invention includes the optical laminate according to the thirteenth aspect.

[0026] The present invention will be described in detail below, but the present invention is not limited to the following embodiments and can be implemented in any modified form without departing from the gist of the present invention.

[0027] [Adhesive Composition] The adhesive composition of the present embodiment is a photocurable adhesive composition (in other words, a photocurable composition; hereinafter, also simply referred to as "adhesive composition") and contains at least one selected from the group consisting of a monomer group and a partial polymer of the monomer group. The monomer group includes a nitrogen atom-containing monomer. The adhesive composition contains a radical scavenger.

[0028] In image display devices using pressure-sensitive adhesive sheets formed from photocurable pressure-sensitive adhesive compositions, deterioration of image quality due to exposure to high-temperature environments may be due to the tendency of the pressure-sensitive adhesive sheet and the adherend (object to be adhered) in contact with it to peel off at high temperatures in the optical laminate. The deterioration of image quality may also be due to the foaming of monomers remaining in the pressure-sensitive adhesive sheet at high temperatures. According to the inventors' studies, pressure-sensitive adhesive sheets formed from photocurable pressure-sensitive adhesive compositions containing nitrogen-containing monomers tend to suppress the above-mentioned peeling and foaming at high temperatures, for example, at temperatures above 80°C. In pressure-sensitive adhesive sheets formed from pressure-sensitive adhesive compositions, the incorporation of nitrogen-containing monomers has been shown to improve the polymerization rate and increase the molecular weight of the polymer. It is believed that this improved polymerization rate and increased molecular weight of the polymer improve the durability of the pressure-sensitive adhesive sheet at high temperatures.

[0029] Furthermore, according to the studies of the present inventors, in a pressure-sensitive adhesive sheet formed from a photocurable pressure-sensitive adhesive composition containing a radical scavenger in addition to a nitrogen-atom-containing monomer, the above-mentioned peeling and foaming tended to be suppressed even at even higher temperatures, for example, above 100° C. In a pressure-sensitive adhesive sheet formed from a pressure-sensitive adhesive composition, the further incorporation of a radical scavenger in addition to a nitrogen-atom-containing monomer is thought to suppress a decrease in the gel fraction of the crosslinked polymer in the pressure-sensitive adhesive sheet at even higher temperatures, for example, above 100° C. It is presumed that suppressing a decrease in the gel fraction of the pressure-sensitive adhesive sheet in this way improves the durability of the pressure-sensitive adhesive sheet at even higher temperatures.

[0030] <Monomer Group> As described above, the PSA composition includes a monomer group. The monomer group includes, for example, a (meth)acrylic monomer. The content of the (meth)acrylic component, i.e., the (meth)acrylic monomer and its partial polymer, in the PSA composition may be 50 wt% or more, 60 wt% or more, 70 wt% or more, or even 80 wt% or more. In this case, an acrylic PSA sheet containing a (meth)acrylic polymer as the main component can be formed. In other words, the polymer may be a (meth)acrylic polymer. However, as long as the PSA composition contains a nitrogen atom-containing monomer, the PSA composition is not limited to the above examples. In this specification, (meth)acrylic refers to acrylic and methacrylic. (Meth)acrylate refers to acrylate and methacrylate. In this specification, the main component refers to the component with the highest content. The content of the main component may be, for example, 50 wt% or more, 60 wt% or more, 70 wt% or more, or even 80 wt% or more.

[0031] 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 include 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, and 2-ethylhexyl (meth)acrylate. 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.

[0032] 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.

[0033] The monomer group may contain a carboxyl group-containing monomer. In this case, the polymer further contains a structural unit derived from the carboxyl group-containing monomer. The carboxyl group-containing monomer, when present together with the nitrogen atom-containing monomer, contributes to improving the viscosity of the pressure-sensitive adhesive sheet formed from the pressure-sensitive adhesive composition. The carboxyl group-containing monomer may be a (meth)acrylic monomer; in other words, the (meth)acrylic monomer may contain the carboxyl group-containing monomer. Examples of carboxyl group-containing monomers include (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 wt% or less, 9 wt% or less, 8 wt% or less, 7 wt% or less, 6 wt% or less, 5.5 wt% or less, or even 5 wt% or less. The lower limit of the content is, for example, 0.1% by weight or more, and may be 0.5% by weight or more, 1% by weight or more, 1.5% by weight or more, 2% by weight or more, 2.5% by weight or more, 3% by weight or more, 3.5% by weight or more, 4% by weight or more, or even 4.5% by weight or more. The monomer group does not have to contain a carboxyl group-containing monomer.

[0034] The monomer group may include a hydroxy group-containing monomer. In this case, the polymer further has a structural unit derived from the hydroxy group-containing monomer. The hydroxy group-containing monomer may be a (meth)acrylic monomer; in other words, the (meth)acrylic monomer may include a hydroxy group-containing monomer. Examples of hydroxy group-containing monomers 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 hydroxy group-containing monomer is preferably 2-hydroxyethyl (meth)acrylate or 4-hydroxybutyl (meth)acrylate. The content of the hydroxy 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 hydroxy group-containing monomer.

[0035] The monomer group may contain a benzyl group-containing monomer. In this case, the polymer further contains a structural unit derived from the benzyl group-containing monomer. The benzyl group-containing monomer may be a (meth)acrylic monomer, in other words, the (meth)acrylic monomer may contain the benzyl group-containing monomer. Examples of the benzyl group-containing monomer include benzyl (meth)acrylate and methoxybenzyl (meth)acrylate. The content of the benzyl group-containing monomer in the monomer group may be, for example, 30% by weight or less, 25% by weight or less, 20% by weight or less, 15% by weight or less, 10% by weight or less, or even 5% by weight or less. The lower limit of the content may be, for example, 1% by weight or more, 2% by weight or more, or even 3% by weight or more. The monomer group may not contain the benzyl group-containing monomer.

[0036] As described above, the monomer group includes a nitrogen atom-containing monomer. The nitrogen atom-containing monomer means a monomer having at least one nitrogen atom in the molecule (per molecule).

[0037] Preferred nitrogen atom-containing monomers are N-vinyl cyclic amides, (meth)acrylamides, etc. The nitrogen atom-containing monomers may be used alone or in combination of two or more.

[0038] The N-vinyl cyclic amide is preferably one represented by the following formula (A):

[0039] 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.

[0040] The N-vinyl cyclic amide represented by formula (A) is preferably 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, or the like, more preferably N-vinyl-2-pyrrolidone or N-vinyl-2-caprolactam, and even more preferably N-vinyl-2-pyrrolidone.

[0041] Examples of (meth)acrylamides include (meth)acrylamide, N-alkyl(meth)acrylamide, and N,N-dialkyl(meth)acrylamide. Examples of N-alkyl(meth)acrylamides include N-ethyl(meth)acrylamide, N-isopropyl(meth)acrylamide, N-n-butyl(meth)acrylamide, and N-octylacrylamide. N-Alkyl(meth)acrylamides also include (meth)acrylamides having an amino group, such as dimethylaminoethyl(meth)acrylamide, diethylaminoethyl(meth)acrylamide, and dimethylaminopropyl(meth)acrylamide.

[0042] 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.

[0043] (Meth)acrylamides also include, for example, various N-hydroxyalkyl(meth)acrylamides, such as 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.

[0044] (Meth)acrylamides also include, for example, various N-alkoxyalkyl(meth)acrylamides, such as N-methoxymethyl(meth)acrylamide and N-butoxymethyl(meth)acrylamide.

[0045] 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 heterocycle-containing monomers such as ethylvinylpyrrolidone; maleimide-based monomers such as N-cyclohexylmaleimide, N-isopropylmaleimide, N-laurylmaleimide, and N-phenylmaleimide; itaconimide-based monomers such as N-methylitaconimide, N-ethylitaconimide, N-butylitaconimide, N-octylitaconimide, N-2-ethylhexylitaconimide, N-laurylitaconimide, and N-cyclohexylitaconimide; imide group-containing monomers of succinimide-based monomers such as N-(meth)acryloyloxymethylenesuccinimide, N-(meth)acryloyl-6-oxyhexamethylenesuccinimide, and N-(meth)acryloyl-8-oxyoctamethylenesuccinimide; and isocyanate group-containing monomers such as 2-(meth)acryloyloxyethylisocyanate.

[0046] The content of the nitrogen atom-containing monomer in the monomer group is, for example, 30% by weight or less, and may be 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, 11% by weight or less, or even 10% by weight or less. The lower limit of the content is, for example, 0.1% by weight or more, and may be 0.5% by weight or more, 1% by weight or more, 2% by weight or more, or even 3% by weight or more.

[0047] In the pressure-sensitive adhesive composition, each of the above-mentioned monomer groups may be contained as a partial polymer. The partial polymer may be either a homopolymer or a copolymer. The pressure-sensitive adhesive composition may not contain a partial polymer.

[0048] <Photopolymerization Initiator> As described above, the pressure-sensitive adhesive composition is a photocurable composition, and therefore typically contains a photopolymerization initiator. An example of the photopolymerization initiator is a photoradical generator that generates radicals upon irradiation with light. The photopolymerization initiator has an absorption coefficient with respect to light having a wavelength of 340 nm of, for example, 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 value calculated from the absorbance of a 0.01 mg / mL methanol solution measured with a visible-ultraviolet spectrophotometer using a quartz cell with an optical path length of 1 cm.

[0049] Examples of the photopolymerization initiator 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. aromatic sulfonyl chlorides such as 2-naphthalenesulfonyl chloride; photoactive oximes such as 1-phenyl-1,1-propanedione-2-(o-ethoxycarbonyl)-oxime; benzophenone-based 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-based 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- Examples of suitable adhesive compositions include triazine-based compounds such as (4'-methoxystyryl)-6-triazine; oxime ester-based compounds such as 1,2-octanedione, 1-[4-(phenylthio)-, 2-(O-benzoyloxime)], and 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 adhesive composition may contain one or more photopolymerization initiators. Alpha-hydroxyalkylphenones tend to have high absorption of light with a wavelength of 340±10 nm.

[0050] 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.

[0051] R in the formula (1) 1 and R 2 are each independently a C1 to C8 alkyl group; —OH, a C1 to C4 alkoxy group, —CN, —COOR 51 , -OOCR 52 , or -NR 53 R 54a C1-C4 alkyl group in which a hydrogen atom is substituted by -; a C3-C6 alkenyl group; or -CH2-C6H4-R 55 It is. 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 a C1 to C8 alkyl group. 52 is a C1 to C4 alkyl group. 53 and R 54 are each independently a hydrogen atom, a C1 to C12 alkyl group; —OH, a C1 to C4 alkoxy group, —CN, or —COOR 59 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; or a cyclohexyl group. 53 and R 54 are bonded to each other to form —O— or —N(R 60 )-Optionally, it may be a C3 to C9 alkylene group. 55 is a C1 to C4 alkyl group. 59 is a C1 to C4 alkyl group. 60 represents a hydrogen atom, a C1-C4 alkyl group, an allyl group, a C1-C4 hydroxyalkyl group, -CH2CH2-COOR 61 Or -CH2CH2CN. 61 is a C1 to C4 alkyl group.

[0052] X is -OR 56 , or -NR 57 R 58 It is. 56 is a hydrogen atom, -SiR 62 3. A C1 to C8 alkyl group or a C3 to C6 alkenyl group. 57 and R 58 represents a C1 to C12 alkyl group; —OH, a C1 to C4 alkoxy group, —CN, and —COOR 63a 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; or a cyclohexyl group. 57 and R 58 are bonded to each other to form —O— or —N(R 64 )-Optionally, it may be a C3 to C9 alkylene group. 62 is a C1 to C6 alkyl group. 63 is a C1 to C4 alkyl group. 64 represents a hydrogen atom, a C1-C4 alkyl group, an allyl group, a C1-C4 hydroxyalkyl group, -CH2CH2-COOR 65 Or -CH2CH2CN. 65 is a C1 to C4 alkyl group.

[0053] The chemical structure X can be bonded to a hydrogen atom or a structure substituted with a hydrogen atom in formula (1) via the carbon atom indicated by *.

[0054] 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. Furthermore, in this specification, including the explanation of formula (1), the expression "Cn1 to Cn2" (n1 and n2 are natural numbers) means that the number of carbon atoms is in the range of n1 to n2.

[0055] In formula (1), R 1 and R 2 may be the same.

[0056] R1, R2 and X may take any combination of the above preferred examples.

[0057] The chemical structure X may be a structure shown in the following formula (2): In the chemical structure X of formula (2), when a substitution structure of a hydrogen atom 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.

[0058] The photopolymerization initiator may be a compound having two or more chemical structures X in one molecule.

[0059] 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 photopolymerization initiator molecule. More specifically, the two chemical structures X are bonded to each other via -A- at the carbon atom of the phenylene group represented by * above.

[0060] R in formula (3) 1 ' and R 2 ' are mutually exclusive and R 1 and R 2 Independently of 1 and R 2 R 1 ' and / or R 2 ' is R 1 and / or R 2 may be the same as R 1 , R 2 , R 1 ' and R 2 ' may all be the same.

[0061] X' in formula (3) is a possible group for X, independently of X in formula (1). X' and X may be the same.

[0062] A is -O-, -CYR 3 - or -C(CH3)R 4 is.

[0063] Y is a hydrogen atom, —Cl, —Br, or —O—R 71 , -NR 72 R 73 , or -S-R 74 It is. 3 represents a hydrogen atom, a C1-C8 alkyl group, a C3-C6 alkenyl group, a benzyl group, -CH2-C6H4-R 75 or a phenyl group. 4 is a C1-C6 alkyl or alkylene group, and this alkylene group is bonded to a carbon atom of the phenylene group of the compound of formula (3).

[0064] R 71 is a hydrogen atom, -Si(R 76 ) 3, C1 to C12 alkyl group, C2 to C18 acyl group, —CO—NH—R 77 , a C2 to C20 hydroxyalkyl group, a C2 to 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 to C21 hydroxyalkyl group or a C3 to C25 alkyl group in which the carbon chain is interrupted by 1 to 9 oxygen atoms. 72 and R 73 are each independently a C1 to C12 alkyl group; —OH, a C1 to C4 alkoxy group, —CN, and —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. 72 and R 73 are bonded to each other to form —O— or —N(R 80 )-Optionally, it may be a C3 to C9 alkylene group. 74 represents a C1 to C18 alkyl group, a hydroxyethyl group, a 2,3-dihydroxypropyl group, a cyclohexyl group, a benzyl group, a phenyl group, a C1 to C12 alkylphenyl group, -CH2-COOR 81 -CH2CH2-COOR 82 , or —CH(CH3)—COOR 83 It is. 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. 80represents a hydrogen atom, a C1-C4 alkyl group, an allyl group, a benzyl group, a C1-C4 hydroxyalkyl group, -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.

[0065] In the alkyl group, alkenyl group, acyl group, hydroxyalkyl group, methoxyalkyl group, alkoxy group, and phenylalkyl group described in the explanation of formula (3), the alkyl group portion and the alkylene group may be either unbranched or branched.

[0066] R in formula (3) 1 , R 2 , R 1 ' and R 2 Preferred examples of R ′ are those described above in the explanation of formula (1). 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. R 3 may be a hydrogen atom. 3 - and Y and R 3 and may both be hydrogen atoms. In other words, A may be —CH—.

[0067] R in formula (3) 1 , R 2 , R 1 ', R 2 ', X, X', and A may take any combination of the preferred examples above.

[0068] 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).

[0069] Specific examples of photopolymerization initiators 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 of formula (8) is derived from a vinyl compound having chemical structure X in its side chain. More specifically, it is an oligomer of the vinyl compound.

[0070]

[0071]

[0072]

[0073]

[0074]

[0075] The photopolymerization initiators represented by formulas (5) to (9) are commercially available as Omnirad 127D, Esacure KIP160, Esacure one, Esacure KIP150, and Omnirad 1173 (all manufactured by IGM Resins). The photopolymerization initiator may be at least one selected from these groups.

[0076] Specific examples of the photopolymerization initiator 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. Of 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 Omnirad 184, Omnirad 819, and Omnirad 127, respectively (all manufactured by IGM Resin).

[0077] The amount of the photopolymerization initiator in the pressure-sensitive adhesive 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 monomers (total of 100 parts by weight of the monomers and their partial polymers). 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 monomers.

[0078] <Crosslinking Agent> The pressure-sensitive adhesive composition may contain a crosslinking agent. An example of the crosslinking agent is a polyfunctional monomer having two or more polymerizable functional groups in one molecule. The polyfunctional monomer may be a (meth)acrylic monomer. Examples of the polyfunctional monomer are 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, methylol groups, etc. in one molecule. The polyfunctional monomer is preferably a monomer having two or more C=C bonds in one molecule.

[0079] Examples of the polyfunctional monomer include (poly)ethylene glycol di(meth)acrylate, (poly)propylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, pentaerythritol di(meth)acrylate, pentaerythritol tri(meth)acrylate, dipentaerythritol hexa(meth)acrylate, 1,2-ethylene glycol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, 1,9-nonanediol diacrylate (N Polyfunctional acrylates (e.g., ester compounds of polyhydric alcohols and (meth)acrylic acid) such as 1,12-dodecanediol di(meth)acrylate, 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.

[0080] The amount of crosslinking agent to be added 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 monomer group. The lower limit of the amount to be added 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 pressure-sensitive adhesive composition may not contain a crosslinking agent.

[0081] <Radical Scavenger> As described above, the pressure-sensitive adhesive composition further contains a radical scavenger. The radical scavenger can limit the amount of radicals generated at high temperatures in a pressure-sensitive adhesive sheet formed from the pressure-sensitive adhesive composition. A pressure-sensitive adhesive composition that, when made into a pressure-sensitive adhesive sheet, limits the amount of radicals generated at high temperatures is suitable for use in optical laminates in environments where high temperatures are a consideration.

[0082] A pressure-sensitive adhesive sheet formed from a pressure-sensitive adhesive composition containing an appropriate amount of radical scavenger in addition to a nitrogen atom-containing monomer may be less susceptible to a decrease in durability in a heat shock test. Specifically, when an optical laminate using the pressure-sensitive adhesive sheet is subjected to a heat shock test, the above-mentioned peeling and foaming may be less likely to occur. This is thought to be because a pressure-sensitive adhesive sheet formed from a pressure-sensitive adhesive composition containing an appropriate amount of radical scavenger is less susceptible to a decrease in the molecular weight of the polymer in the heat shock test, and as a result, the cohesive strength of the pressure-sensitive adhesive sheet is less likely to decrease. It is presumed that by suppressing the decrease in cohesive strength of the pressure-sensitive adhesive sheet in this way, the durability in the heat shock test is less likely to decrease.

[0083] The radical scavenger has a polymerizable unsaturated double bond and may correspond to a part of the monomer constituting the above-mentioned monomer group. In this case, the content of the radical scavenger in the PSA composition is, for example, 30 parts by weight or less, 29 parts by weight or less, 28 parts by weight or less, 27 parts by weight or less, 26 parts by weight or less, 25 parts by weight or less, 24 parts by weight or less, 23 parts by weight or less, 22 parts by weight or less, 21 parts by weight or less, or even 20 parts by weight or less, based on 100 parts by weight of the monomer group. In this case, the content of the radical scavenger is, for example, 1 part by weight or more, 2 parts by weight or more, 3 parts by weight or more, 4 parts by weight or more, 5 parts by weight or more, 6 parts by weight or more, 7 parts by weight or more, 8 parts by weight or more, 9 parts by weight or more, 10 parts by weight or more, 11 parts by weight or more, 12 parts by weight or more, 13 parts by weight or more, 14 parts by weight or more, or even 15 parts by weight or more, based on 100 parts by weight of the monomer group. When the radical scavenger content is within the above range, the adhesive sheet formed from the adhesive composition has improved durability at high temperatures of 100°C or higher, and is less likely to exhibit reduced durability in heat shock tests.

[0084] The radical scavenger does not need to have a polymerizable unsaturated double bond. In this case, the content of the radical scavenger in the pressure-sensitive adhesive composition is, for example, 5 parts by weight or less, 4 parts by weight or less, 3 parts by weight or less, 2 parts by weight or less, 1 part by weight or less, 0.9 parts by weight or less, 0.8 parts by weight or less, 0.7 parts by weight or less, 0.6 parts by weight or less, or even 0.5 parts by weight or less, relative to 100 parts by weight of the monomer group. In addition, in this case, the content of the radical scavenger is, for example, 0.01 parts by weight or more, 0.02 parts by weight or more, 0.03 parts by weight or more, 0.04 parts by weight or more, 0.05 parts by weight or more, 0.06 parts by weight or more, 0.07 parts by weight or more, 0.08 parts by weight or more, 0.09 parts by weight or more, or even 0.1 parts by weight or more. When the content of the radical scavenger is within the above range, the pressure-sensitive adhesive sheet formed from the pressure-sensitive adhesive composition has improved durability at high temperatures of 100°C or more and is less likely to deteriorate in durability in a heat shock test.

[0085] The radical scavenger preferably comprises at least one selected from the group consisting of a phenoxy-based radical scavenger, an amine-based radical scavenger, and a phosphite-based radical scavenger, and more preferably comprises at least one of a phenoxy-based radical scavenger and a phosphite-based radical scavenger. According to this configuration, the PSA sheet formed from the PSA composition has improved durability at high temperatures of 100°C or higher.

[0086] When the phenoxy radical scavenger has a polymerizable unsaturated double bond, it is preferably a phenoxy (meth)acrylate compound. In this specification, the term "phenoxy" encompasses phenolic compounds. When the phenoxy radical scavenger does not have a polymerizable unsaturated double bond, it is preferably at least one selected from the group consisting of phenolic antioxidants and hindered phenolic antioxidants, and more preferably a hindered phenolic antioxidant.

[0087] Examples of the phenoxy(meth)acrylate compound include phenoxy(meth)acrylate, phenoxyethyl(meth)acrylate, and phenoxyethoxyethyl(meth)acrylate.

[0088] Examples of the phenolic antioxidants include monophenolic antioxidants, bisphenolic antioxidants, and polymeric phenolic antioxidants. Examples of the monophenolic antioxidants include 2,6-di-t-butyl-p-cresol, butylated hydroxyanisole, 2,6-di-t-butyl-4-ethylphenol, and stearin-β-(3,5-di-t-butyl-4-hydroxyphenyl)propionate. Examples of the bisphenol antioxidant are 2,2'-methylenebis(4-methyl-6-t-butylphenol), 2,2'-methylenebis(4-ethyl-6-t-butylphenol), 4,4'-thiobis(3-methyl-6-t-butylphenol), 4,4'-butylidenebis(3-methyl-6-t-butylphenol), and 3,9-bis[1,1-dimethyl-2-[β-(3-t-butyl-4-hydroxy-5-methylphenyl)propionyloxy]ethyl]2,4,8,10-tetraoxaspiro[5,5]undecane. Examples of the polymeric phenolic antioxidant are 1,1,3-tris(2-methyl-4-hydroxy-5-t-butylphenyl)butane, 1,3,5-trimethyl-2,4,6-tris(3,5-di-t-butyl-4-hydroxybenzyl)benzene, tetrakis-[methylene-3-(3',5'-di-t-butyl-4'-hydroxyphenyl)propionate]methane, bis[3,3'-bis-(4'-hydroxy-3'-t-butylphenyl)butyric acid]glycol ester, 1,3,5-tris(3',5'-di-t-butyl-4'-hydroxybenzyl)-S-triazine-2,4,6-(1H,3H,5H)trione, and tocopherol.

[0089] The hindered phenolic antioxidant may have a structure in which a tertiary butyl group is bonded to at least one carbon atom adjacent to the carbon atom on the aromatic ring to which the phenolic OH group is bonded. Examples of the hindered phenolic antioxidant include dibutylhydroxytoluene (BHT); Irganox 1010, Irganox 1010FF, Irganox 1035, Irganox 1035FF, Irganox 1076, Irganox 1076FD, Irganox 1076DWJ, Irganox 1098, Irganox 109 ... Irganox 1135, Irganox 1330, Irganox 1726, Irganox 1425WL, Irganox 1520L, Irganox 245, Irganox 245FF, Irganox 259, Irganox 3114, Irganox 565 and Irganox 295 (all of which are trade names manufactured by BASF).

[0090] The amine radical scavenger is preferably an amine antioxidant, more preferably a hindered amine antioxidant. The hindered amine antioxidant may have at least one hindered piperazine group in one molecule. Examples of hindered amine antioxidants include Adeka STAB LA-63, Adeka STAB LA-63P, Adeka STAB LA-52, and Adeka STAB LA-57 (all of which are trade names, manufactured by ADEKA Corporation).

[0091] The phosphite-based radical scavenger is preferably a phosphite-based antioxidant. Examples of the phosphite-based antioxidant include triphenyl phosphite, diphenyl isodecyl phosphite, and phenyl diisodecyl phosphite; and Adeka STAB 2112, Adeka STAB 2112RG, Adeka STAB 1178, and Adeka STAB 3010 (all of which are trade names, manufactured by ADEKA Corporation).

[0092] The radical scavenger (e.g., antioxidant) preferably has a phenoxy structure. According to studies by the present inventors, radical scavengers having a phenoxy structure are particularly suitable for improving the durability of PSA sheets formed from the PSA composition at high temperatures of 100°C or higher.

[0093] The molecular weight of the radical scavenger (e.g., antioxidant) may be 1,000 or less, 900 or less, 850 or less, 800 or less, 700 or less, 600 or less, 500 or less, 450 or less, or even 400 or less. The lower limit of the molecular weight is, for example, 100 or more. According to studies by the present inventors, radical scavengers having a molecular weight within the above range are particularly suitable for suppressing the amount of radicals generated in a PSA sheet formed from the PSA composition.

[0094] The radical scavenger (for example, an antioxidant) may be liquid at room temperature (25°C).

[0095] The PSA composition may contain additives other than those described above. Examples of the additives include chain transfer agents, silane coupling agents, viscosity modifiers, tackifiers, plasticizers, softeners, antioxidants, fillers, colorants, antioxidants, surfactants, antistatic agents, and UV absorbers. The PSA composition may not contain any additives.

[0096] The viscosity of the adhesive composition is preferably 5 to 100 poise. An adhesive composition having a viscosity in the above range is particularly suitable for forming the adhesive sheet 1.

[0097] The solvent content in the pressure-sensitive adhesive composition is, for example, 5 wt% or less, and may be 4 wt% or less, 3 wt% or less, 2 wt% or less, 1 wt% or less, or even 0.5 wt% or less. The pressure-sensitive adhesive composition may be substantially free of solvent. "Substantially free of solvent" means that solvents derived from additives and the like are allowed at a content of, for example, 0.1 wt% or less, preferably 0.05 wt% or less, and more preferably 0.01 wt% or less. The solvent content in the pressure-sensitive adhesive sheet 1 may be within the above range. The pressure-sensitive adhesive sheet 1 may be substantially free of solvent.

[0098] [Adhesive Sheet] The adhesive sheet of this embodiment is formed from an adhesive composition. Specifically, the adhesive composition is irradiated with light to produce a polymer from at least one selected from the group consisting of a monomer group and a partial polymer of the monomer group, thereby forming the adhesive sheet (see "Adhesive Sheet 1" in Figure 1).

[0099] <Method of Producing Pressure-Sensitive Adhesive Sheet> An example of a method of producing a pressure-sensitive adhesive sheet of the present embodiment is shown in Figure 1. The pressure-sensitive adhesive sheet 1 is formed, for example, by irradiating light 24 onto a first laminate 20 comprising, in this order, a base sheet 21, a coating layer 22 containing a pressure-sensitive adhesive composition, and a release liner 23. The coating layer 22 is cured by irradiation with light 24 to form the pressure-sensitive adhesive sheet 1. The light 24 is typically irradiated from the side of the base sheet 21 using a light source 28. At this time, the light 24 passes through the base sheet 21 and reaches the coating layer 22, curing the coating layer 22. However, the light 24 may be irradiated from the side of the release liner 23, or from the side of both the release liner 23 and the base sheet 21.

[0100] The formed pressure-sensitive adhesive sheet 1 is sandwiched between the base sheet 21 and the release liner 23 until the release liner 23 is peeled off, and constitutes part of the second laminate 27. By peeling the release liner 23 from the second laminate 27, a third laminate 25 including the base sheet 21 and the pressure-sensitive adhesive sheet 1 is obtained. In the third laminate 25, 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.

[0101] The light 24 is, for example, visible light or ultraviolet light having a wavelength shorter than 450 nm. The light may include light having a wavelength in the same range as the absorption wavelength of the photopolymerization initiator contained in the pressure-sensitive adhesive composition. Light in which short-wavelength light of 300 nm or less has been filtered out using a filter or the like may be irradiated. Filtering out short-wavelength light is suitable for suppressing deterioration of the base sheet 21 and / or the release liner 23 due to the light 24. The light source is, for example, a light irradiation device equipped with an ultraviolet irradiation lamp. Examples of ultraviolet irradiation lamps include ultraviolet LEDs, low-pressure mercury lamps, medium-pressure mercury lamps, high-pressure mercury lamps, ultra-high-pressure mercury lamps, metal halide lamps, xenon lamps, microwave-excited mercury lamps, black light lamps, chemical lamps, germicidal lamps, low-pressure discharge mercury lamps, and excimer lasers. Two or more ultraviolet irradiation lamps may be combined. The ultraviolet LED allows the irradiated ultraviolet light band to be narrower than when other light sources are used.

[0102] When using an ultraviolet LED as the light source, an LED having a peak wavelength of 340±10 nm (hereinafter referred to as "LED 340") may be selected. According to the inventors' studies, the use of LED 340 may contribute to at least one of improving the polymerization rate of the monomer group in the pressure-sensitive adhesive sheet 1, improving the molecular weight of the polymer, and reducing the amount of residual photopolymerization initiator, compared to using a black light source, for example. Furthermore, LED 340 tends to suppress heat generation compared to using an LED having a peak wavelength around 365 nm. The suppression of heat generation can contribute to controlling the temperature of the coating layer 22. The peak wavelength refers to the wavelength at which the intensity reaches a maximum value in a spectrum showing the relationship between light wavelength and intensity.

[0103] The illuminance of the light 24 irradiated onto the first laminate 20 (specifically, the coating layer 22) is, for example, 2.0 to 30 mW / cm 2 The illuminance is 2.5 mW / cm 2 Above, 3.0mW / cm 2 Above, 3.5mW / cm 2 Above, 4.0mW / cm 2 Above, 5.0mW / cm 2 Above, 6.0mW / cm 2 Above, 7.0mW / cm 2 Above, 8.0mW / cm 2 Above, 9.0mW / cm 2 or more, and even 10 mW / cm 2 The upper limit of the illuminance may be, for example, 25 mW / cm 2 less than 20 mW / cm 2 Below 15mW / cm 2 It may be the following:

[0104] The time for irradiating the first laminate 20 (specifically, the coating layer 22) with the light 24 is, for example, 10 to 1,000 seconds, and may be 60 seconds or more, 100 seconds or more, 150 seconds or more, 200 seconds or more, 250 seconds or more, or even 300 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, 350 seconds or less, 300 seconds or less, or even 250 seconds or less. The irradiation with the light 24 may be continuous or intermittent.

[0105] The integrated light amount of the light 24 on the first laminate 20 (specifically, the coating layer 22) is, for example, 25 mJ / cm 2 or more, and 100 mJ / cm 2 Above, 250mJ / cm 2 Above, 500mJ / cm 2 Above, 750mJ / cm 2 Above, 850mJ / cm 2 Above, 1000mJ / cm 2 Above, 1250mJ / cm 2 or more, and even 1500 mJ / cm 2 The upper limit of the integrated light amount is not particularly limited, and may be, for example, 3000 mJ / cm 2 or less, and 2 Below, 2000mJ / cm 2 Below, 1750mJ / cm 2 Below, 1500mJ / cm 2 Below, 1250mJ / cm 2 Below 1000 mJ / cm 2 The pressure-sensitive adhesive sheet 1 is suitable for formation with a low integrated light amount, and therefore the pressure-sensitive adhesive sheet 1 has excellent productivity.

[0106] An example of the substrate of the release liner 23 (hereinafter referred to as the "liner substrate") is a resin film. Examples of resins that can be contained in the liner substrate include 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.

[0107] The release liner 23 may include a layer other than the liner substrate. The release liner 23 may include a release layer. The release liner 23 includes, for example, a liner substrate and a release layer formed on one surface of the liner substrate. This release liner 23 can be used such that the release layer faces the coating layer 22. The release layer is typically a cured layer of a release agent composition containing a release agent. Various release agents can be used as the release agent, 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.

[0108] The release liner 23 may be in the form of a sheet or a continuous piece.

[0109] An example of the base sheet 21 is a resin film. Examples of the resin contained in the base sheet 21 are the same as the examples of the resin that can be contained in the liner base material.

[0110] The thickness of the base sheet 21 is, for example, 10 to 200 μm, and may be 25 to 150 μm.

[0111] The base sheet 21 may have a release layer on the surface facing the coating layer 22. Examples of the release layer that may be provided on the base sheet 21 are the same as the examples of the release layer that may be provided on the release liner 23. Both the release liner 23 and the base sheet 21 may have a release layer.

[0112] For the base sheet 21 , a sheet having a greater peel strength from the pressure-sensitive adhesive sheet 1 than the release liner 23 can usually be selected.

[0113] The base sheet 21 may be in the form of a sheet or a continuous sheet.

[0114] The first laminate 20 is formed, for example, by forming a coating layer 22 on a base sheet 21 (or a release liner 23), and then placing the release liner 23 (or base sheet 21) on the formed coating layer 22. Alternatively, the first laminate 20 may be formed by applying the PSA composition in a pouring manner into the space between the base sheet 21 and the release liner 23, which are held at a predetermined distance so that their main surfaces face each other.

[0115] The coating layer 22 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.

[0116] The thickness of the coating layer 22 can be adjusted depending on the desired thickness of the pressure-sensitive adhesive sheet 1, and may be, for example, 5 to 100 μm, 5 to 50 μm, 5 to 25 μm, or even 5 to 20 μm.

[0117] The first laminate 20 may include a long base sheet 21, a long coating layer 22, and a long release liner 23, in other words, may be long. The long first laminate 20 can be obtained, for example, by forming the coating layer 22 between the base sheet 21 and the release liner 23 while conveying them after they have been unwound from a roll.

[0118] <Weight-average molecular weight of polymer contained in pressure-sensitive adhesive sheet> The weight-average molecular weight (Mw) of the polymer contained in the pressure-sensitive adhesive sheet 1 is, for example, 600,000 or more, 650,000 or more, 700,000 or more, 750,000 or more, 800,000 or more, 850,000 or more, 900,000 or more, 950,000 or more, 1,000,000 or more, 1,100,000 or more, 1,200,000 or more, 1,300,000 or more, or even 1,400,000 or more. Note that Mw is the weight-average molecular weight without a crosslinking agent. The upper limit of Mw is not particularly limited, and is, for example, 3,000,000 or less. The Mw of the polymer is measured by GPC (gel permeation chromatography) and determined from the value calculated in polystyrene equivalent.

[0119] The polymerization rate of the monomer group in the pressure-sensitive adhesive sheet 1 may be 97.5% or more, 98% or more, or even 98.5% or more. The upper limit of the polymerization rate is, for example, 99.99% or less. A high polymerization rate contributes to, for example, suppression of odor from the pressure-sensitive adhesive sheet 1.

[0120] Both the molecular weight of the polymer and the polymerization rate of the monomer group can be increased in the pressure-sensitive adhesive sheet 1. The weight-average molecular weight (Mw) of the polymer contained in the pressure-sensitive adhesive sheet 1 may be 600,000 or more, and the polymerization rate of the monomer group in the pressure-sensitive adhesive sheet 1 may be 98% or more. The Mw and polymerization rate may each be within the above-mentioned numerical ranges.

[0121] <Gel Fraction of Pressure-Sensitive Adhesive Sheet> The gel fraction of the pressure-sensitive adhesive sheet 1 can be evaluated as follows. A test piece of approximately 0.1 g is collected from the pressure-sensitive adhesive sheet 1, wrapped in a polytetrafluoroethylene porous sheet (average pore size 0.2 μm, product name "NTF1122", manufactured by Nitto Denko Corporation), and tied with kite string to obtain a measurement sample. Next, the weight of the obtained measurement sample (weight C before immersion) is measured. The weight C before immersion is the total weight of the test piece, the polytetrafluoroethylene porous sheet, and the kite string. Separately, 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 50 mL container filled with ethyl acetate and allowed 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 in a dryer at 130°C for 2 hours. The weight of the measurement sample after drying (weight A after immersion) is measured. The value calculated from the following formula is determined as the gel fraction of the pressure-sensitive adhesive sheet 1: Gel fraction G (%)=(A−B) / (C−B)×100

[0122] The gel fraction of the pressure-sensitive adhesive sheet 1 (gel fraction Ga described below) is, for example, 55% or more, and may be 60% or more, 65% or more, 70% or more, 75% or more, 78% or more, 80% or more, more than 80%, 81% or more, 82% or more, 83% or more, 84% or more, or even 85% or more. The upper limit of the gel fraction may be 95% or less, 94% or less, 93% or less, 92% or less, 91% or less, 90% or less, or even 89% or less.

[0123] When left in a 105°C environment for 24 hours (hereinafter referred to as "high-temperature storage"), the gel fraction of the PSA sheet 1 after high-temperature storage (gel fraction Gb, described below) is, for example, 55% or more, and may be 60% or more, 65% or more, 70% or more, 75% or more, 78% or more, 80% or more, more than 80%, 81% or more, 82% or more, 83% or more, 84% or more, or even 85% or more. The upper limit of the gel fraction may be 95% or less, 94% or less, 93% or less, 92% or less, 91% or less, 90% or less, or even 89% or less.

[0124] The absolute value |Ga - Gb| of the difference between the gel fraction Ga of the pressure-sensitive adhesive sheet 1 before being left at high temperature and the gel fraction Gb of the pressure-sensitive adhesive sheet 1 after being left at high temperature is, for example, 10% or less, and may be 9% or less, 8% or less, 7% or less, 6% or less, 5% or less, 4% or less, 3% or less, 2% or less, or even 1% or less. With this configuration, the gel fraction does not change much before and after being left at high temperature, which makes it easier to improve the durability of the pressure-sensitive adhesive sheet 1 at high temperatures of 100°C or more.

[0125] The thickness of the pressure-sensitive adhesive sheet 1 is, for example, 2 to 70 μm. The thickness may be 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. A thin pressure-sensitive adhesive sheet 1, for example, a pressure-sensitive adhesive sheet 1 having a thickness of 30 μm or less, is susceptible to polymerization inhibition by oxygen in the environment during photocuring formation. On the other hand, the pressure-sensitive adhesive sheet 1 is suitable for formation with a low integrated light dose, in other words, for formation by photocuring in a short period of time. Therefore, even when the pressure-sensitive adhesive sheet 1 is thin, the effects of polymerization inhibition can be suppressed. Furthermore, even when the pressure-sensitive adhesive sheet 1 has a thickness of, for example, 30 μm or less, it is suitable for suppressing foaming and peeling from the adherend in a high-temperature environment. The adherend is, for example, a glass substrate.

[0126] [Optical Laminate] An example of an optical laminate of this embodiment is shown in Figure 2. The optical laminate 30 of Figure 2 comprises a pressure-sensitive adhesive sheet 1 and an optical film 2. The pressure-sensitive adhesive sheet 1 and the optical film 2 are in contact with each other. The pressure-sensitive adhesive sheet 1 is a photocurable pressure-sensitive adhesive sheet formed from the pressure-sensitive adhesive composition described above. As described above, the pressure-sensitive adhesive sheet 1 contains a polymer having a structural unit derived from a nitrogen atom-containing monomer.

[0127] <Optical Film> Examples of the optical film 2 include a polarizing film, a retardation film, and a laminate 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 also include a glass film.

[0128] The optical film 2 may be a polarizing film, and the pressure-sensitive adhesive sheet 1 may be in contact with the polarizing film. Among optical films, polarizing films tend to undergo large dimensional changes due to heat. Dimensional changes in the polarizing film can cause peeling from the pressure-sensitive adhesive film. For this reason, the present invention is particularly advantageous when the optical laminate further includes a polarizing film.

[0129] The polarizing film may include a polarizer. The polarizing film may include, for example, a polarizer and a transparent protective film. The transparent protective film may be disposed in contact with, for example, a main surface (the surface having the largest area) of the polarizer. The polarizer may be disposed between two transparent protective films. The transparent protective film may be disposed on at least one surface of the polarizer.

[0130] The polarizer is not particularly limited, and examples thereof include a hydrophilic polymer film such as a polyvinyl alcohol film, a partially formalized polyvinyl alcohol film, or a partially saponified ethylene-vinyl acetate copolymer film, which has been uniaxially stretched after adsorbing a dichroic substance such as iodine or a dichroic dye; and a polyene-based oriented film such as a dehydrated polyvinyl alcohol film or a dehydrochlorinated polyvinyl chloride film. The polarizer 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.

[0131] The thickness of the polarizer 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 polarizer thickness 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) is suppressed in dimensional change and can contribute to improving the durability of the optical laminate, particularly durability at high temperatures.

[0132] The transparent protective film may be made of a thermoplastic resin having excellent transparency, mechanical strength, thermal stability, moisture-blocking properties, and isotropy. 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 transparent protective film may be made of a thermosetting resin or a UV-curable resin, such as a (meth)acrylic, urethane, acrylic urethane, epoxy, or silicone-based resin. When the polarizing film has two transparent protective films, the materials of the two transparent protective films may be the same or different. For example, a transparent protective film made of a thermoplastic resin is bonded to one main surface of a polarizer via an adhesive, and a transparent protective film made of a thermosetting resin or a UV-curable resin is bonded to the other main surface of the polarizer. The transparent protective film may contain one or more optional additives, such as ultraviolet absorbers, antioxidants, lubricants, plasticizers, release agents, color inhibitors, flame retardants, nucleating agents, antistatic agents, pigments, and colorants.

[0133] The thickness of the transparent protective film can be determined as appropriate, but is generally about 5 to 200 μm in view of strength, workability such as handling, thinness, and the like.

[0134] The polarizer and the transparent protective film are usually adhered to each other via an aqueous adhesive or the like. Examples of aqueous adhesives include isocyanate-based adhesives, polyvinyl alcohol-based adhesives, gelatin-based adhesives, vinyl latex, aqueous polyurethane, and aqueous polyester. 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 adhesive properties for various transparent protective films. The adhesive may contain a metal compound filler.

[0135] In the polarizing film, a retardation film or the like can be formed on the polarizer instead of the transparent protective film. Another transparent protective film or a retardation film or the like can be further provided on the transparent protective film.

[0136] The transparent protective film may have a hard coat layer on the surface opposite to the surface bonded to the polarizer, and may also be subjected to treatments for purposes such as anti-reflection, anti-sticking, diffusion, and anti-glare.

[0137] The polarizing film may be a circular polarizing film.

[0138] The thickness of the polarizing film 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 may be, for example, 10 μm or more, 25 μm or more, or even 40 μm or more.

[0139] 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.

[0140] The retardation film can be selected from any film adjusted to an appropriate refractive index (nx, ny, nz). Note that "nx" is the refractive index in the direction in which the in-plane refractive index is maximized (i.e., the slow axis direction), "ny" is the refractive index in the direction perpendicular to the slow axis in the plane (i.e., the fast axis direction), and "nz" is the refractive index in the thickness direction. 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-A-2012-133303), a viewing angle compensation retardation film (see, for example, paragraphs 0225 and 0226 of JP-A-2012-133303), or an inclined orientation retardation film for viewing angle compensation (see, for example, paragraph 0227 of JP-A-2012-13303). The retardation film is not limited to the above examples, as long as it has birefringence in the in-plane direction and / or thickness direction. There are no limitations on the retardation value, arrangement angle, three-dimensional birefringence, whether the retardation film is a single layer or a multilayer, etc. Any known film can be used as the retardation film.

[0141] The thickness of the optical film 2 is, for example, 1 to 200 μm.

[0142] 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.

[0143] The optical laminate 30 may include layers other than the pressure-sensitive adhesive sheet 1 and the optical film 2. Other layers may be disposed between the pressure-sensitive adhesive sheet 1 and the optical film 2, but it is preferable that the pressure-sensitive adhesive sheet 1 and the optical film 2 are in contact with each other.

[0144] The optical laminate 30 is used in, for example, an image display device, but the use of the optical laminate 30 is not limited to the above example.

[0145] Another example of the optical laminate of the present embodiment is shown in Figure 3. The optical laminate 30A in Figure 3 includes the above-mentioned pressure-sensitive adhesive sheet 1. The optical laminate 30A has a layered structure in which a release liner 3, a pressure-sensitive adhesive sheet 1, and an optical film 2 are layered in this order. By peeling off the release liner 3, the optical laminate 30A can be used as an optical film with a pressure-sensitive adhesive sheet.

[0146] <Release Liner> The release liner 3 is typically a resin film. Examples of resins that make up the release liner 3 include polyesters such as polyethylene terephthalate (PET), polyolefins such as polyethylene and polypropylene, polycarbonate, acrylic, polystyrene, polyamide, and polyimide. The surface of the release liner 3 that comes into contact with the pressure-sensitive adhesive sheet 1 may be subjected to a release treatment. The release treatment is, for example, a treatment with a silicone compound. However, the release liner 3 is not limited to the above examples. The release liner 3 is peeled off when the optical laminate 30A 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. 4. The optical laminate 30B in Fig. 4 includes the above-mentioned pressure-sensitive adhesive sheet 1. The optical laminate 30B has a layered structure in which a release liner 3, a pressure-sensitive adhesive sheet 4, a retardation film 2B, a pressure-sensitive adhesive sheet 1, and a polarizing film 2A are layered in this order. After the release liner 3 is peeled off, the optical laminate 30B is used by being attached to, for example, an image forming layer of an image display device.

[0148] A known adhesive sheet can be used as the adhesive sheet 4. The adhesive sheet 1 may also be used as the adhesive sheet 4.

[0149] Another example of the optical laminate of the present embodiment is shown in Figure 5. Optical laminate 30C in Figure 5 includes the above-mentioned pressure-sensitive adhesive sheet 1. Optical laminate 30C has a layered structure in which a release liner 3, a pressure-sensitive adhesive sheet 4, an optical film (retardation film) 2B, a pressure-sensitive adhesive sheet 1, an optical film (polarizing film) 2A, and a transparent protective film 5 are layered in this order. After peeling off the release liner 3, optical laminate 30C is used by being attached to, for example, an image forming layer of an image display device.

[0150] A known adhesive sheet can be used as the adhesive sheet 4. The adhesive sheet 1 may also be used as the adhesive sheet 4.

[0151] The transparent protective film 5 has the function of protecting the optical film 2 (polarizing film 2A), which is the outermost layer, during distribution and storage of the optical laminate 30C and when the optical laminate 30C is incorporated into an image display device. The transparent protective film 5 may also function as a window to the external space when incorporated into an image display device. The transparent protective film 5 is typically a resin film. Examples of resins constituting the transparent protective film 5 include polyesters such as PET, polyolefins such as polyethylene and polypropylene, acrylics, cycloolefins, polyimides, and polyamides, with polyesters being preferred. However, the transparent protective film 5 is not limited to the above examples. The transparent protective film 5 may also be a glass film or a laminate film including a glass film. The transparent protective film 5 may be subjected to surface treatments such as anti-glare, anti-reflection, and anti-static.

[0152] The transparent protective film 5 may be bonded to the optical film 2 by any adhesive. Bonding by an adhesive sheet 1 is also possible.

[0153] Another example of the optical laminate of this embodiment is shown in Figure 6. The optical laminate 30D in Figure 6 includes the above-mentioned pressure-sensitive adhesive sheet 1. The optical laminate 30D has a laminated structure in which a first retardation film 21D, a second retardation film 22D, a polarizer 23D, and a transparent protective film 24D are laminated in this order. The first retardation film 21D and the second retardation film 22D can each be selected from the examples of the retardation films described above. The optical laminate 30D is used, for example, by being attached to an image forming layer of an image display device.

[0154] The optical laminate of this embodiment may include any layer other than the above-mentioned layers. The optical laminate of this embodiment may have any configuration as long as it includes the pressure-sensitive adhesive sheet 1 and the optical film 2. The optical laminate of this embodiment may include other films such as an anti-reflection film, a light diffusion film, a brightness enhancement film, and an electromagnetic wave shielding film.

[0155] 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.

[0156] The optical laminate of this embodiment is typically used in image display devices, such as liquid crystal displays, organic EL displays, and inorganic EL displays.

[0157] [Image Display Device] An example of an image display device according to an embodiment of the present invention is shown in FIG. 7. The image display device 50 of FIG. 7 has the optical laminate 30C of FIG. 5 (excluding the release liner 3). Specifically, the image display device 50 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, a pressure-sensitive adhesive sheet 4, an optical film (retardation film) 2B, a pressure-sensitive adhesive sheet 1, an optical film (polarizing film) 2A, and a protective film 5 are laminated in this order. The optical laminate (in FIG. 7, the pressure-sensitive adhesive sheet 4, the optical film (retardation film) 2B, the pressure-sensitive adhesive sheet 1, the optical film (polarizing film) 2A, and the protective film 5) may be another optical laminate including the pressure-sensitive adhesive sheet 1. The substrate 7 and the image forming layer 6 may have the same configurations as the substrate and the image forming layer, respectively, of known image display devices.

[0158] 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.

[0159] [Preparation of Pressure-Sensitive Adhesive Composition] (Monomer Syrup A1) 97.1 parts by weight of n-butyl acrylate (BA), 2.9 parts by weight of acrylic acid (AA), and 0.2 parts by weight of Omnirad 127D (manufactured by IGM Resin) as a photopolymerization initiator 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. 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.

[0160] (Monomer Syrup A2) Monomer Syrup A2 was prepared in the same manner as Monomer Syrup A1, except that the blending amounts of the monomers were changed as shown in Table 1.

[0161]

[0162] The abbreviations in Table 1 are as follows: BA: n-butyl acrylate AA: acrylic acid HBA: 4-hydroxybutyl acrylate Omnirad127D: 2-hydroxy-1-(4-(4-(2-hydroxy-2-methylpropionyl)benzyl)phenyl)-2-methylpropan-1-one (Omnirad127D, manufactured by IGM Resin).

[0163] (Adhesive compositions C1 to C9) Next, photocurable adhesive compositions C1 to C9 were obtained by mixing monomer syrup, monomer, crosslinking agent, and radical scavenger so as to obtain the compositions shown in the following Table 2. The crosslinking agent and radical scavenger were blended in the amounts shown in Table 3 (final compositions of the adhesive compositions) described below.

[0164]

[0165] The abbreviations in Table 2 are as follows: AA: Acrylic acid, NVP: N-vinyl-2-pyrrolidone, PEA: Phenoxyethyl acrylate, HBA: 4-hydroxybutyl acrylate, BzA: Benzyl acrylate, NDDA: 1,9-nonanediol diacrylate, Adekastab LA-52: Tetrakis(1,2,2,6,6-pentamethyl-4-piperidyl)butane-1,2,3,4-tetracarboxylate (Adekastab LA-52 (hindered amine antioxidant), manufactured by ADEKA Corporation), Adekastab 2112: 3,9-bis(octadecyloxy)-2,4,8,10-tetraoxa-3,9-diphosphaspiro[5,5]undecane (Adekastab 2112 (phosphite antioxidant), manufactured by ADEKA Corporation), Irganox 1010: Pentaerythritol Tetrakis(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate) (Irganox 1010 (hindered phenol-based antioxidant), manufactured by BASF) Irganox 1135: C7-C9 side chain alkyl ester of 3,5-bis(1,1-dimethylethyl)-4-hydroxybenzenepropanoate (Irganox 1135 (hindered phenol-based antioxidant), manufactured by BASF)

[0166] The final composition of the monomers contained in each PSA composition is shown in Table 3 below. Abbreviations in Table 3 are the same as those in Tables 1 and 2. In Table 3, the monomer (PEA) indicated with an asterisk (*) also functions as a radical scavenger. As will be described later, when a PSA sheet is obtained from the PSA composition, the monomer (PEA) is copolymerized with the monomers constituting the monomer group and incorporated into the polymer. The amount of the radical scavenger incorporated into the polymer in the PSA sheet is shown in Table 3 in the "Monomer" column as the amount incorporated per 100 parts by weight of the monomer group. In contrast, as will be described later, when a PSA sheet is obtained from the PSA composition, the radical scavenger (PEA) is not incorporated into the polymer, but is included in the PSA sheet as an additive separate from the polymer. The amount of the radical scavenger included in the PSA sheet as an additive separate from the polymer is shown in Table 3 in the "Radical Scavenger" column as the amount incorporated per 100 parts by weight of the monomer group.

[0167]

[0168] [Preparation of Pressure-Sensitive Adhesive Sheet] Example 1 (Preparation of Release Liner) A silicone-based release agent composition was obtained by mixing 30 parts by weight of an addition reaction curable silicone (LTC761 containing a hexenyl group-containing polyorganosiloxane, a 30 wt % toluene solution, manufactured by Dow Corning Toray), 0.9 parts by weight of a release control agent (BY24-850 containing an unreactive silicone resin, manufactured by Dow Corning Toray), and 2 parts by weight of a curing catalyst (SRX212 containing a platinum catalyst, manufactured by Dow Corning Toray), and a toluene / hexane mixed solvent (volume ratio 1:1) as a dilution solvent. The concentration of silicone solids in the release agent composition was 1.0 wt %. Next, the release agent composition was applied with a wire bar to one side of a liner substrate (Lumirror XD500P, a polyester film, 75 μm thick), and heated at 130° C. for 1 minute to prepare a release liner having a release layer (thickness 60 nm) on one side.

[0169] (Preparation of Pressure-Sensitive Adhesive Sheet) The pressure-sensitive adhesive composition was applied to one side of a substrate sheet (PET release liner, manufactured by Mitsubishi Plastics, MRF38) using an applicator to form a coating layer (thickness: 15 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, an illuminance of 9 mW / cm was applied from the substrate sheet side of the first laminate. 2 and irradiation time was 56 seconds (integrated light dose 500 mJ / cm 2 An LED was used as the light source, and the peak wavelength of the irradiated light was 340 nm. Furthermore, an illuminance of 9 mW / cm was applied from the side of the base sheet of the first laminate. 2 and irradiation time was 22 seconds (integrated light dose 200 mJ / cm 2 ). A metal halide lamp was used as the light source. This photocured the coating layer, and the PSA sheet of Example 1 (thickness 15 μm) sandwiched between the base sheet and release liner was obtained. The illuminance of the light was measured using an illuminance meter (UD-T3040T2, manufactured by Topcon Technohouse Co., Ltd.) at a position on the base sheet near the surface where the ultraviolet light was incident.

[0170] Examples 2 to 8, Comparative Example PSA sheets of Examples 2 to 8 and the Comparative Example were obtained by the same method as Example 1, except that PSA compositions C2 to C8 were used in Examples 2 to 8, respectively, and PSA composition C9 was used in the Comparative Example. The PSA sheet of Example 7, which was formed from PSA composition C7, was dried by heating after the PSA sheet was formed.

[0171] In the PSA sheets of Examples 6 and 7 formed from PSA compositions C6 and C7, respectively, most of the radical scavenger (PEA) in PSA compositions C6 and C7 was incorporated into the polymer (see the "Monomer" column for PSA compositions "C6" and "C7" in Table 3). In the PSA sheets of Examples 6 and 7, the radical scavenger (PEA) incorporated into the polymer was 20 parts by weight per 100 parts by weight of the monomer group. In the PSA sheet of Example 6, a portion of the radical scavenger (PEA) in PSA composition C6 was not incorporated into the polymer, but was included in the PSA sheet as an additive separate from the polymer (see the "Radical Scavenger" column for PSA composition "C6" in Table 3). In the PSA sheet of Example 6, the radical scavenger (PEA) included as an additive in the PSA sheet was 0.09 parts by weight per 100 parts by weight of the monomer group. On the other hand, in the PSA sheet of Example 7, the part of the radical scavenger that was not incorporated into the polymer was removed from the PSA sheet by volatilizing it through the above-mentioned heat drying so that it would not be included in the PSA sheet as an additive separate from the polymer. Therefore, in the PSA sheet of Example 7, the radical scavenger (PEA) was not included as an additive in the PSA sheet (see the "Radical Scavenger" column for PSA composition "C7" in Table 3).

[0172] [Gel Fraction] The gel fraction of each PSA sheet in the Examples and Comparative Examples was measured using the method described above. For each PSA sheet, the gel fraction was measured twice: (1) immediately after the PSA sheet was produced, and (2) after the PSA sheet was left in an environment at 105°C for 24 hours. The measurement results of the gel fraction for each PSA sheet are shown in Table 4.

[0173] [Reliability Test] The following high temperature storage test (hereinafter referred to as "105°C test") and heat shock test (hereinafter referred to as "HS test") were carried out on each of the pressure-sensitive adhesive sheets of the Examples and Comparative Examples.

[0174] <Preparation of Samples for Reliability Test (105°C Test)> (Preparation of Optical Film 2E) A polyvinyl alcohol film was stretched 3 times between rolls with different speed ratios while dyeing for 1 minute in a 0.3 wt% iodine solution at 30°C. Next, the film was stretched to a total stretch ratio of 6 times while immersing for 0.5 minutes in an aqueous solution containing 4 wt% boric acid and 10 wt% potassium iodide at 60°C. The film was then immersed for 10 seconds in an aqueous solution containing 1.5 wt% potassium iodide at 30°C for cleaning, followed by drying at 50°C for 4 minutes to obtain a polarizer (reference numeral 22E in FIG. 8 ) with a thickness of 18 μm. A 30 μm-thick transparent protective film (reference numeral 21E in FIG. 8 ) made of a modified acrylic polymer having a lactone ring structure was attached to one side of the polarizer using a polyvinyl alcohol adhesive. Furthermore, a 47 μm-thick transparent protective film (reference numeral 23E in FIG. 8 ) made of a triacetyl cellulose film (manufactured by Konica Minolta, product name "KC4UY") with a hard coat layer (HC) formed thereon was bonded to the other surface of the polarizer using a polyvinyl alcohol-based adhesive. This was then heated and dried for 5 minutes in an oven set at 70° C., thereby producing an optical film 2E composed of a transparent protective film 21E, a polarizer 22E, and a transparent protective film 23E, as shown in FIG. 8 . Furthermore, a discharge amount of 63 W / m was applied to the surface of the optical film 2E on the side of the transparent protective film 21E made of a modified acrylic polymer. 2 Corona treatment was carried out for 1 min.

[0175] (Preparation of optical laminate 30E) The optical laminate 30E was prepared by disposing the above-mentioned optical film 2E on the exposed surface of each pressure-sensitive adhesive sheet 1 prepared in the examples and comparative examples. The optical film 2E was arranged so that the surface on the side of the transparent protective film 21E made of a modified acrylic polymer was in contact with the pressure-sensitive adhesive sheet 1.

[0176] <Reliability Test (105°C Test)> The reliability of the prepared optical laminate 30E was evaluated by the following 105°C test. First, the optical laminate 30E was cut into a strip measuring 300 mm long x 220 mm wide to prepare a test specimen. Next, the test specimen was attached to the surface of 0.7 mm thick alkali-free glass (manufactured by Corning Incorporated, product name "EG-XG") using an adhesive sheet 1. The test specimen was attached to the alkali-free glass using a laminator. After attaching the test specimen, the specimen was placed in an autoclave at 50°C and 0.5 MPa for 15 minutes to homogenize the bond between the alkali-free glass and the adhesive sheet 1, thereby adhering the adhesive sheet 1 to the alkali-free glass. Next, the test specimen was subjected to a heat treatment at 105°C for 500 hours under atmospheric pressure. The vicinity of the edge of the test specimen was observed with an optical microscope to confirm the presence or absence of peeling from the edge of the test specimen and foaming near the edge. A: No peeling or foaming that would affect image display was observed. B: There was slight foaming at the edge, but not to the extent that it would affect image display. C: There were multiple bubbles at the edge, but not to the extent that it would affect image display. D: There was peeling and / or foaming that would affect image display. The reliability evaluation results for each PSA sheet in the 105°C test are shown in Table 4.

[0177] <Preparation of Sample for Reliability Test (HS Test)> (Optical Film 2D) First, an optical film 2D shown in FIG. 6 was prepared as a sample for the HS test.

[0178] (Polarizer 23D) The polarizer 23D constituting the optical film 2D was produced as follows. First, a long, amorphous isophthalic copolymerized polyethylene terephthalate film (thickness: 100 μm) having a Tg of approximately 75°C was used as a thermoplastic resin substrate, and one side of the resin substrate was subjected to a corona treatment. A PVA-based resin prepared by mixing polyvinyl alcohol (degree of polymerization: 4200, degree of saponification: 99.2 mol%) and acetoacetyl-modified PVA (manufactured by Nippon Synthetic Chemical Industry Co., Ltd., trade name "GOHSEFIRMER") at a ratio of 9:1 was prepared by adding 13 parts by weight of potassium iodide to 100 parts by weight of the resulting PVA-based resin, and the resulting solution was dissolved in water to prepare an aqueous PVA solution (coating solution). The PVA-based resin layer was coated on the corona-treated surface of the resin substrate and dried at 60°C to form a 13 μm-thick PVA-based resin layer, thereby producing a laminate.

[0179] The obtained laminate was uniaxially stretched 2.4 times in the longitudinal direction (machine direction) in an oven at 130°C (in-air auxiliary stretching treatment). Next, the laminate after the in-air auxiliary stretching treatment was immersed in an insolubilizing bath at a liquid temperature of 40°C for 30 seconds (insolubilizing treatment). The insolubilizing bath was a boric acid aqueous solution obtained by blending 4 parts by weight of boric acid with 100 parts by weight of water. Next, the laminate was immersed in a dye bath at a liquid temperature of 30°C for 60 seconds while adjusting the concentration so that the single transmittance (Ts) of the finally obtained polarizer would be a desired value (dyeing treatment). The dye bath was an iodine aqueous solution obtained by blending iodine and potassium iodide with 100 parts by weight of water in a weight ratio of 1:7.

[0180] Next, the laminate was immersed in a crosslinking bath at a liquid temperature of 40°C for 30 seconds (crosslinking treatment). The crosslinking bath was a boric acid aqueous solution obtained by blending 3 parts by weight of potassium iodide and 5 parts by weight of boric acid with 100 parts by weight of water. Thereafter, while immersed in the boric acid aqueous solution at a liquid temperature of 70°C, the laminate was uniaxially stretched in the longitudinal direction (longitudinal direction) between rolls with different peripheral speeds to a total stretch ratio of 5.5 times (underwater stretching treatment). The boric acid aqueous solution was an aqueous solution containing a boric acid concentration of 4 wt% and a potassium iodide concentration of 5 wt%.

[0181] The laminate was then immersed in a cleaning bath at a liquid temperature of 20°C (cleaning treatment). The cleaning bath was an aqueous solution obtained by mixing 4 parts by weight of potassium iodide with 100 parts by weight of water. Thereafter, the laminate was brought into contact with a SUS heated roll whose surface temperature was maintained at about 75°C while being dried in an oven maintained at about 90°C (drying shrinkage treatment).

[0182] In this manner, a polarizer 23D having a thickness of about 5 μm was formed on the resin substrate.

[0183] (First Retardation Film 21D) The first retardation film 21D constituting the optical film 2D was produced as follows. 48 parts by weight of hydroxypropyl methylcellulose (manufactured by Shin-Etsu Chemical Co., Ltd., trade name: Metolose 60SH-50), 15,601 parts by weight of distilled water, 8,161 parts by weight of diisopropyl fumarate, 240 parts by weight of 3-ethyl-3-oxetanylmethyl acrylate, and 45 parts by weight of t-butyl peroxypivalate as a polymerization initiator were placed in an autoclave equipped with a stirrer, a cooling tube, a nitrogen inlet tube, and a thermometer. Nitrogen bubbling was performed for 1 hour, and then the mixture was stirred at 49 ° C. for 24 hours to carry out radical suspension polymerization. The mixture was then cooled to room temperature, and the suspension containing the produced polymer particles was centrifuged. The obtained polymer was washed twice with distilled water and twice with methanol, and then dried under reduced pressure to obtain a white fumarate ester-based resin.

[0184] The obtained fumaric acid ester-based resin was dissolved in methyl ethyl ketone to prepare a solution with a solid content of 20% by weight. Further, 5 parts by weight of tributyl trimellitate as a plasticizer was added to 100 parts by weight of the fumaric acid ester-based resin to prepare a dope.

[0185] A 75 μm thick polyester film (biaxially stretched film of polyethylene-terephthalate / isophthalate copolymer) was used as the support film. The dope was applied to a film thickness of approximately 6 μm after drying and dried to obtain a laminate A in which a coating film of a fumaric acid ester resin was tightly laminated on the support. The laminate A was subjected to free-end uniaxial stretching to obtain a first retardation film 21D (positive B plate) on the support, which had a refractive index anisotropy of nz > nx > ny.

[0186] (Second Retardation Film 22D) As the second retardation film 22D constituting the optical film 2D, a cyclic olefin-based film (positive C plate; manufactured by Zeon Corporation, product name "ZEONORFILM ZT12-50135") having a refractive index anisotropy of nz>nx=ny was used.

[0187] Thereafter, a second retardation film 22D was bonded onto the first retardation film 21D via an ultraviolet-curable adhesive to obtain a laminate B. Thereafter, the support was peeled off from the laminate B to obtain a laminate C of the first retardation film 21D and the second retardation film 22D.

[0188] (Transparent Protective Film 24D) An acrylic resin film having a glutarimide structure (manufactured by Kaneka Corporation, product name "HTX") was used as the transparent protective film 24D constituting the optical film 2D. The thickness of the transparent protective film 24D was 40 μm.

[0189] These films 21D to 24D were laminated in this order on a laminate C (first retardation film 21D and second retardation film 22D), a polarizer 23D, and a transparent protective film 24D to produce an optical film 2D. The laminate C and the polarizer 23D were bonded together via an ultraviolet-curable adhesive so that the second retardation film 22D and the polarizer 23D faced each other. Similarly, the polarizer 23D and the transparent protective film 24D were bonded together via an ultraviolet-curable adhesive.

[0190] <Preparation of Optical Laminated Film> Furthermore, a transparent protective film and an anti-reflection film were prepared. An acrylic resin film (transparent protective film) having a glutarimide structure (manufactured by Kaneka Corporation, product name "HTX") was used as the transparent protective film. The thickness of the transparent protective film was 40 μm. An anti-reflection film manufactured by Dexerials Corporation (total thickness of anti-reflection layer and hard coat layer: 4 μm, substrate thickness: 80 μm) was used as the anti-reflection film. The transparent protective film and the anti-reflection film were then laminated in this order on the transparent protective film 24D side (see FIG. 6 ) of the optical film 2D to prepare an optical laminated film. The optical film 2D and the transparent protective film were bonded together using a photo-curable adhesive sheet corresponding to each Example and Comparative Example. The thickness of this adhesive sheet was 12 μm. The transparent protective film and the anti-reflection film were bonded together using a photo-curable adhesive sheet corresponding to each Example and Comparative Example. The thickness of this adhesive sheet was 12 μm.

[0191] <Preparation of Optical Laminate> An optical laminate was prepared by disposing the above-described optical laminate film on the exposed surface of each pressure-sensitive adhesive sheet 1 (see FIG. 6) prepared in the Examples and Comparative Examples. The optical laminate film was arranged so that the surface on the optical film 2D side (the first retardation film 21D side) was in contact with the pressure-sensitive adhesive sheet 1 (see FIG. 6).

[0192] <Reliability Test (HS Test)> The reliability of the prepared optical laminate was evaluated by the following HS test. First, the optical laminate was cut into a strip measuring 300 mm long x 220 mm wide to prepare a test specimen. Next, the test specimen was attached to the surface of 0.7 mm thick alkali-free glass (manufactured by Corning Incorporated, product name "EG-XG") using an adhesive sheet 1 (see FIG. 6). The test specimen was attached to the alkali-free glass using a laminator. After attaching the test specimen, the specimen was placed in an autoclave at 50°C and 0.5 MPa for 15 minutes to homogenize the bond between the alkali-free glass and the adhesive sheet 1, and the adhesive sheet 1 was tightly attached to the alkali-free glass. Next, the test specimen was subjected to 200 cycles of a cycle consisting of holding at a low temperature (-40°C) and a high temperature (85°C). Specifically, in one cycle, the test piece was first held at -40°C for 30 minutes, then heated to 85°C in 2 to 5 minutes, then held at 85°C for 30 minutes, and then cooled to -40°C in 2 to 5 minutes. After 200 cycles, the vicinity of the edge of the test piece was observed with an optical microscope, and the presence or absence of peeling from the edge of the test piece and foaming near the edge was confirmed, as in the above-mentioned 105°C test. A: No peeling or foaming that affects image display was observed. B: Slight foaming at the edge, but not to a level that affects image display. C: Multiple bubbles were present at the edge, but not to a level that affects image display. D: Peeling and / or foaming that affects image display. The reliability evaluation results of each PSA sheet in the HS test are shown in Table 4.

[0193]

[0194] As shown in Table 4, the absolute value of the difference in gel fraction before and after 24 hours of standing in a 105°C environment for the pressure-sensitive adhesive sheets of the Examples is smaller than that for the pressure-sensitive adhesive sheets of the Comparative Examples. Furthermore, each of the pressure-sensitive adhesive sheets of the Examples was rated A in the 105°C test, indicating that the condition after the 105°C test was better than that of the pressure-sensitive adhesive sheets of the Comparative Examples. Furthermore, each of the pressure-sensitive adhesive sheets of the Examples was rated C or higher in the HS test, indicating that no peeling or foaming occurred to a level that would affect image display. These results confirm that each of the pressure-sensitive adhesive sheets of the Examples has improved durability at even higher temperatures, such as 100°C or higher, and is less likely to decrease in durability in a heat shock test.

[0195] The pressure-sensitive adhesive composition of the present invention can be used in pressure-sensitive adhesive sheets, optical laminates, and image display devices.

Claims

1. A photocurable pressure-sensitive adhesive composition comprising at least one selected from the group consisting of a monomer group and a partial polymer of the monomer group, wherein the monomer group contains a nitrogen atom-containing monomer, and the pressure-sensitive adhesive composition contains a radical scavenger.

2. The photocurable pressure-sensitive adhesive composition according to claim 1, wherein the radical scavenger has a polymerizable unsaturated double bond and corresponds to a part of the monomers constituting the monomer group.

3. The photocurable pressure-sensitive adhesive composition according to claim 1, wherein the radical scavenger does not have a polymerizable unsaturated double bond.

4. The photocurable pressure-sensitive adhesive composition according to claim 1, wherein the radical scavenger contains at least one selected from the group consisting of a phenoxy-based radical scavenger, an amine-based radical scavenger, and a phosphite-based radical scavenger.

5. The photocurable pressure-sensitive adhesive composition according to claim 4, wherein the radical scavenger contains at least one of a phenoxy-based radical scavenger and a phosphite-based radical scavenger.

6. The photocurable pressure-sensitive adhesive composition according to claim 5, wherein the radical scavenger has a phenoxy structure.

7. The photocurable pressure-sensitive adhesive composition according to claim 1, wherein the content of the solvent in the pressure-sensitive adhesive composition is 5% by weight or less.

8. The photocurable pressure-sensitive adhesive composition according to claim 2, wherein the content of the radical scavenger in the pressure-sensitive adhesive composition is 30 parts by weight or less per 100 parts by weight of the monomer group.

9. The photocurable pressure-sensitive adhesive composition according to claim 3, wherein the content of the radical scavenger in the pressure-sensitive adhesive composition is 5 parts by weight or less with respect to 100 parts by weight of the monomer group.

10. The photocurable pressure-sensitive adhesive composition according to claim 1, wherein the monomer group contains a (meth)acrylic monomer.

11. A pressure-sensitive adhesive sheet formed from the photocurable pressure-sensitive adhesive composition according to any one of claims 1 to 10.

12. The pressure-sensitive adhesive sheet according to claim 11, wherein in a test of leaving it standing for 24 hours in an environment of 105°C, the absolute value |Ga - Gb| of the difference between the gel fraction Ga before the test and the gel fraction Gb after the test is 10% or less.

13. An optical laminate comprising the pressure-sensitive adhesive sheet according to claim 11 and an optical film.

14. An image display device comprising the optical laminate according to claim 13.

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