Laminate and laminate structure

Abstract

Provided is a laminate which can be photocured by visible light and which does not exhibit appearance defects such as discoloration, bubbling, or exfoliation of a polarizing plate even in extreme high-temperature, high-humidity environments, [I] the laminate being obtained by laminating a polarizing plate and a photocurable adhesive sheet in a layered configuration, wherein: [II] the polarizing plate has a layered configuration in which both surfaces of a polarizer are laminated with a protective film; [III] the distance (α) between the photocurable adhesive sheet and the polarizer is no more than 80 μm; [IV-1] the photocurable adhesive sheet is formed from a photocurable adhesive agent composition including a (meth)acrylic acid ester (co)polymer and a photopolymerization initiator (A); [IV-2] the light transmittance at a wavelength of 390 nm is less than 90% and the light transmittance at a wavelength of 410 nm is at least 80%; and [IV-3] the total concentration of an acylphosphine oxide-based photopolymerization initiator and a phenylglyoxylate-based photopolymerization initiator, which are included as the photopolymerization initiator (A) in the photocurable adhesive agent composition, is no more than 0.5 mass%.

Description

[Technical field]

[0001] The present invention relates to a laminate having an adhesive sheet used for bonding resin members having ultraviolet-blocking properties that do not transmit ultraviolet light, the laminate having a photocurable adhesive sheet that has the ability to harden when irradiated with light (hereinafter referred to as "photocurable"). [Background technology]

[0002] In recent years, in order to improve the visibility of image display devices, the gap between an image display panel such as a liquid crystal display (LCD), a plasma display (PDP), or an electroluminescence display (ELD) and a protective panel or a touch panel member disposed on the front side (viewing side) of the image display device has been filled with an adhesive to suppress reflection of incident light or outgoing light from a displayed image at the air layer interface. As a method for filling such gaps between components of an image display device with an adhesive, a method of filling the gaps between the components of an image display device using an adhesive sheet is known.

[0003] In addition, since in-vehicle image display devices are easily exposed to ultraviolet rays, components such as ultraviolet-shielding glass cover members and resin cover members may be used as window members and front panel members to prevent resin members such as conductive members and polarizing plates inside the image display device from yellowing and deteriorating due to exposure to ultraviolet rays. In this case, a photocurable adhesive sheet may be used that can be photocured by light in a wavelength range that can pass through the ultraviolet-shielding component when ultraviolet light is irradiated from outside the ultraviolet-shielding component.

[0004] For example, Patent Document 1 discloses a method for producing a display member, which comprises producing an adhesive sheet from a solventless adhesive composition containing an active energy ray-curable component and a photopolymerization initiator having an absorbance of 0.3 or more at a wavelength of 390 nm and an optical path length of 10 mm in a 0.1% by mass acetonitrile solution, laminating this adhesive sheet with an ultraviolet-shielding member to produce a laminate, and then irradiating the adhesive sheet with active energy rays through the ultraviolet-shielding member to cure the adhesive sheet.

[0005] Patent Document 2 discloses a method for producing a display, in which a laminate is produced by laminating a display component containing an ultraviolet absorber through an ultraviolet-curable adhesive sheet containing a photopolymerization initiator having an absorbance of 0.3 or more at a wavelength of 380 nm in a 0.1% by mass acetonitrile solution, and ultraviolet light is irradiated through the display component containing the ultraviolet absorber to cure the adhesive sheet.

[0006] Patent Document 3 describes a pressure-sensitive adhesive sheet for laminating an ultraviolet-shielding member having ultraviolet-shielding properties, the pressure-sensitive adhesive sheet being made of an active energy ray-curable component and an active energy ray-curable pressure-sensitive adhesive containing a cured product of the active energy ray-curable component (A), and irradiating the pressure-sensitive adhesive sheet with an active energy ray having a substantial emission intensity in a wavelength region of 380 to 450 nm through the ultraviolet-shielding member at 1000 mJ / cm. 2 The present invention discloses an adhesive sheet that has a gel fraction of 70% or more and less than 100% when cured by irradiation with a light amount of 1000 nm.

[0007] Patent Document 4 discloses a method for manufacturing a display body comprising a display body component containing an ultraviolet absorber and a cured adhesive layer for bonding the display body component containing the ultraviolet absorber, in which ultraviolet light is irradiated through the display body component to cure the adhesive layer into a cured adhesive layer, and the gel fraction of the cured adhesive layer is set to 40% or more. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Patent No. 6360605 [Patent Document 2] Patent No. 6420519 [Patent Document 3] Patent No. 6438165 [Patent Document 4] Patent No. 6676720 Summary of the Invention [Problem to be solved by the invention]

[0009] It is known that polarizing plates used as image display device components undergo discoloration in a humid and hot environment, such as discoloration due to polyenation of the polyvinyl alcohol resin constituting the polarizer and discoloration of iodine. In addition, in a laminate in which a polarizing plate and other components are laminated via a photocurable adhesive sheet, the interaction between the polarizing plate and the photocurable adhesive sheet may promote discoloration of the polarizing plate in a humid and hot environment. Therefore, excellent durability in a high-temperature and high-humidity environment is also required for the above-mentioned vehicle-mounted image display device and the like.

[0010] The above Patent Documents 1 to 4 disclose pressure-sensitive adhesive sheets that can be photocured by light in a wavelength range that can transmit a UV-shielding component when irradiated with UV rays from the outside of the UV-shielding component, and that do not exhibit poor appearance such as foaming or peeling even under harsh high-temperature and high-humidity environments, and only acylphosphine oxide-based photopolymerization initiators are exemplified as the photopolymerization initiator used. However, the pressure-sensitive adhesive sheets disclosed in Patent Documents 1 to 4 do not mention the problem of discoloration of polarizing plates under harsh high-temperature and high-humidity environments.

[0011] For this reason, there is no satisfactory photocurable pressure-sensitive adhesive sheet that can be cured by visible light and further suppresses discoloration of a polarizing plate in a humid and hot environment, and there is room for improvement.

[0012] The present invention provides a laminate comprising a polarizing plate and a photocurable adhesive sheet which can be photocured with light in a wavelength range that can transmit through an ultraviolet-shielding component when ultraviolet light is irradiated from outside the ultraviolet-shielding component, and which does not suffer from appearance defects such as discoloration, foaming, or peeling of the polarizing plate even in harsh high-temperature and high-humidity environments. [Means for solving the problem]

[0013] After extensive research, the inventors have found that the above problems can be solved by using a photopolymerization initiator capable of generating radicals when exposed to visible light as a photocurable adhesive sheet, and by using an adhesive layer containing as little acylphosphine oxide-based photopolymerization initiator and phenylglyoxylate-based photopolymerization initiator as possible.

[0014] That is, the gist of the present invention is the following [1] to

[14] . [1] [I] A laminate having a layer structure of a polarizing plate / a photocurable adhesive sheet, [II] The polarizing plate has a layer structure in which a polarizer is laminated with a protective film on both sides thereof, [III] The distance (α) between the photocurable adhesive sheet and the polarizer is 80 μm or less; [IV-1] A photocurable adhesive sheet is formed from a photocurable adhesive composition containing a (meth)acrylic acid ester (co)polymer and a photopolymerization initiator (A), and [IV-2] The light transmittance at a wavelength of 390 nm is less than 90%, and the light transmittance at a wavelength of 410 nm is 80% or more; [IV-3] The total concentration of the acylphosphine oxide-based photopolymerization initiator and the phenyl glyoxylate-based photopolymerization initiator contained in the photocurable pressure-sensitive adhesive composition as the photopolymerization initiator (A) is 0.5 mass% or less. Laminate. [2] [IV-4] The laminate according to [1], wherein the photocurable adhesive sheet is a photocurable adhesive sheet that can be cured even when irradiated with light having a wavelength of 390 to 410 nm. [3] The laminate according to [1] or [2], wherein another component (X) is laminated via the photocurable adhesive sheet, and the other component (X) has a light transmittance of 10% or less at a wavelength of 365 nm and a light transmittance of 60% or more at a wavelength of 405 nm. [4] The laminate according to [3], wherein the other component (X) is an ultraviolet ray-shielding cover material. [5] The laminate according to any one of [1] to [4], wherein the protective film in the polarizing plate is a triacetyl cellulose resin film. [6] The laminate according to any one of [1] to [5], wherein the ratio (α / β) of the distance (α) between the photocurable adhesive sheet and the polarizer to the thickness (β) of the photocurable adhesive sheet is 0.1 to 0.5. [7] The laminate according to any one of [1] to [6], wherein the photocurable pressure-sensitive adhesive sheet has a thickness (β) of 50 to 500 μm. [8] The laminate according to any one of [1] to [7], wherein the photopolymerization initiator (A) contains at least one photopolymerization initiator selected from the group consisting of an α-aminoacetophenone-based photopolymerization initiator and a ketocoumarin-based photopolymerization initiator. [9] The laminate according to any one of [1] to [8], wherein the photocurable pressure-sensitive adhesive sheet has a yellow index value (YI value) of 2.0 or less.

[10] The laminate according to any one of [1] to [9], wherein the photocurable pressure-sensitive adhesive composition contains a tri- or higher functional polyfunctional (meth)acrylate and / or a silane coupling agent.

[11] The laminate according to any one of [1] to

[10] , wherein the (meth)acrylic acid ester (co)polymer is a graft copolymer having a macromonomer as a branch component.

[12] In the photocurable adhesive sheet, the adhesive sheet is exposed to an ultraviolet ray shielding member having an ultraviolet ray shielding property such that an integrated light amount at a wavelength of 405 nm is 3000 (mJ / cm 2 ), a difference between a gel fraction G1 before light irradiation and a gel fraction G2 after light irradiation (gel fraction G2 after light irradiation - gel fraction G1 before light irradiation) is 10% or more.

[13] The laminate according to any one of [1] to

[12] , wherein the photocurable pressure-sensitive adhesive sheet has a multilayer structure of two or more layers.

[14] A laminate structure obtained by curing the laminate according to any one of [1] to

[13] with visible light. Effect of the Invention

[0015] The laminate of the present invention can be cured by visible light, and the polarizing plate does not discolor even in a severe high-temperature and high-humidity environment, and furthermore, defects in appearance such as foaming and peeling can be suppressed. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] Hereinafter, the embodiments of the present invention will be described in detail, but the present invention is not limited to these. In the present invention, "(meth)acrylic" means acrylic or methacrylic, "(meth)acryloyl" means acryloyl or methacryloyl, and "(meth)acrylate" means acrylate or methacrylate, respectively. In addition, the term "(meth)acrylic acid ester (co)polymer" refers to a resin obtained by polymerizing a polymerization component containing at least one type of (meth)acrylate monomer, and the term "(co)polymer" is intended to encompass polymers and copolymers. In the present invention, the term "sheet" is not particularly differentiated from "film" or "tape" and is used to include these terms. In the present invention, when expressed as "X to Y" (X and Y are any numbers), unless otherwise specified, it includes the meaning of "X or more and Y or less", as well as "preferably larger than X" or "preferably smaller than Y". In addition, when it is expressed as "X or more" (X is any number) or "Y or less" (Y is any number), it also includes the intention that "greater than X is preferable" or "less than Y is preferable." Furthermore, "X and / or Y (X and Y are optional)" means at least one of X and Y, and means the following three cases: X only, Y only, and X and Y.

[0017] The laminate of the present invention (hereinafter, sometimes referred to as "the laminate") is a laminate having a layer structure of a photocurable adhesive sheet / a polarizing plate. The laminate having another component (X) laminated thereon via the photocurable adhesive sheet is mainly used for an image display device mounted on a vehicle. Usually, the photocurable adhesive sheet is applied to the adherend, cured by ultraviolet irradiation, and then laminated to the adherend. However, as described above, in the image display device for vehicle mounting, since the polarizing plate and the like are easily deteriorated by ultraviolet light, a glass cover member or a resin cover member that blocks ultraviolet light may be used. Therefore, the photocurable adhesive sheet constituting the present laminate, which is mainly used in the image display device for vehicle mounting, has visible light curing property that can be cured by visible light instead of ultraviolet light.

[0018] The photocurable adhesive sheet is formed from a photocurable adhesive composition containing a (meth)acrylic acid ester (co)polymer and a photopolymerization initiator (A) that generates radicals by visible light, and is characterized in that the photocurable adhesive composition contains a small amount of an acylphosphine oxide-based photopolymerization initiator and a phenyl glyoxylate-based photopolymerization initiator as the photopolymerization initiator (A). Each component contained in the photocurable adhesive composition will be described below.

[0019] [(Meth)acrylic acid ester (co)polymer] Examples of the (meth)acrylic acid ester (co)polymer used in the photocurable pressure-sensitive adhesive composition include a homopolymer of an alkyl (meth)acrylate and a copolymer obtained by copolymerizing a monomer component copolymerizable therewith. Among these, a (meth)acrylic acid ester copolymer is preferable.

[0020] The (meth)acrylic acid ester copolymer may be, for example, a copolymer of an alkyl(meth)acrylate having an alkyl group with 1 to 18 carbon atoms and a monomer component copolymerizable therewith, for example, a monomer component containing one or more monomers selected from (a) a carboxyl group-containing monomer, (b) a hydroxyl group-containing monomer, (c) an amino group-containing monomer, (d) an epoxy group-containing monomer, (e) an amide group-containing monomer, (f) a vinyl monomer, and (g) a macromonomer. Among these, a (meth)acrylic acid ester copolymer obtained from an alkyl(meth)acrylate having an alkyl group with 1 to 18 carbon atoms and a copolymerization component containing (e) an amide group-containing monomer, and (g) a macromonomer is preferred.

[0021] [Alkyl (meth)acrylate with alkyl group having 1 to 18 carbon atoms] Examples of the alkyl (meth)acrylate having an alkyl group of 1 to 18 carbon atoms include linear alkyl (meth)acrylates such as methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, n-butyl (meth)acrylate, pentyl (meth)acrylate, hexyl (meth)acrylate, heptyl (meth)acrylate, n-octyl (meth)acrylate, nonyl (meth)acrylate, decyl (meth)acrylate, undecyl (meth)acrylate, lauryl (meth)acrylate, tridecyl (meth)acrylate, tetradecyl (meth)acrylate, cetyl (meth)acrylate, and stearyl (meth)acrylate; isopropyl (meth)acrylate, isobutyl (meth)acrylate, and sec-butyl (meth)acrylate. Examples of the methacrylate include branched alkyl (meth)acrylates such as cyclohexyl (meth)acrylate, t-butyl (meth)acrylate, isopentyl (meth)acrylate, neopentyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, isooctyl (meth)acrylate, isononyl (meth)acrylate, t-butylcyclohexyl (meth)acrylate, isodecyl (meth)acrylate, and isostearyl (meth)acrylate; and alicyclic alkyl (meth)acrylates such as cyclohexyl (meth)acrylate, isobornyl (meth)acrylate, 3,5,5-trimethylcyclohexane (meth)acrylate, dicyclopentanyl (meth)acrylate, dicyclopentenyl (meth)acrylate, and dicyclopentenyloxyethyl (meth)acrylate. These may be used alone or in combination of two or more. Among these, linear and branched alkyl (meth)acrylates in which the alkyl group has 6 to 14 carbon atoms are preferred, and lauryl (meth)acrylate and 2-ethylhexyl (meth)acrylate are more preferred.

[0022] The content of the alkyl (meth)acrylate having 1 to 18 carbon atoms in the alkyl group is usually 30 to 90 mass %, preferably 35 to 88 mass %, more preferably 40 to 85 mass %, and particularly preferably 55 to 85 mass % of the total monomer components of the copolymer. If the content is too low, the hydrophobicity tends to decrease and it becomes difficult to suppress water absorption, whereas if the content is too high, the polarity tends to decrease and the adhesive strength tends to decrease.

[0023] [(a) Carboxy group-containing monomer] Examples of the (a) carboxy group-containing monomer include (meth)acrylic acid, 2-(meth)acryloyloxyethylhexahydrophthalic acid, 2-(meth)acryloyloxypropylhexahydrophthalic acid, 2-(meth)acryloyloxyethylphthalic acid, 2-(meth)acryloyloxypropylphthalic acid, 2-(meth)acryloyloxyethylmaleic acid, 2-(meth)acryloyloxypropylmaleic acid, 2-(meth)acryloyloxyethylsuccinic acid, 2-(meth)acryloyloxypropylsuccinic acid, crotonic acid, fumaric acid, maleic acid, itaconic acid, etc. These may be used alone or in combination of two or more.

[0024] The content of the (a) carboxyl group-containing monomer in the total monomer components of the copolymer is usually 10% by mass or less, preferably 8% by mass or less, and particularly preferably 5% by mass or less.

[0025] [(b) Hydroxyl group-containing monomer] Examples of the (b) hydroxyl group-containing monomer include hydroxyalkyl (meth)acrylates such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, and 2-hydroxybutyl (meth)acrylate. These may be used alone or in combination of two or more.

[0026] The content of the (b) hydroxyl group-containing monomer in the total monomer components of the copolymer is usually 30% by mass or less, preferably 25% by mass or less, and particularly preferably 20% by mass or less.

[0027] [(c) Amino group-containing monomer] Examples of the (c) amino group-containing monomer include aminoalkyl (meth)acrylates such as aminomethyl (meth)acrylate, aminoethyl (meth)acrylate, aminopropyl (meth)acrylate, and aminoisopropyl (meth)acrylate, N-alkylaminoalkyl (meth)acrylates, and N,N-dialkylaminoalkyl (meth)acrylates such as N,N-dimethylaminoethyl (meth)acrylate and N,N-dimethylaminopropyl (meth)acrylate, etc. These may be used alone or in combination of two or more kinds.

[0028] The content of the (c) amino group-containing monomer in the total monomer components of the copolymer is usually 20% by mass or less, preferably 10% by mass or less, and particularly preferably 10% by mass or less.

[0029] [(d) Epoxy group-containing monomer] Examples of the (d) epoxy group-containing monomer include glycidyl (meth)acrylate, methyl glycidyl (meth)acrylate, 3,4-epoxycyclohexylmethyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate glycidyl ether, etc. These may be used alone or in combination of two or more.

[0030] The content of the (d) epoxy group-containing monomer in the total monomer components of the copolymer is usually 20% by mass or less, and preferably 10% by mass or less.

[0031] [(e) Amide group-containing monomer] Examples of the (e) amide group-containing monomer include (meth)acrylamide, N,N-dimethyl(meth)acrylamide, N-butyl(meth)acrylamide, N-methylol(meth)acrylamide, N-methylolpropane(meth)acrylamide, N-methoxymethyl(meth)acrylamide, N-butoxymethyl(meth)acrylamide, diacetone(meth)acrylamide, maleic acid amide, and maleimide. These may be used alone or in combination of two or more. Among them, (meth)acrylamide is preferred.

[0032] The content of the (e) amide group-containing monomer in the total monomer components of the copolymer is usually 1 to 20 mass %, preferably 1.5 to 15 mass %, and particularly preferably 2 to 10 mass %, from the viewpoint of obtaining excellent adhesive properties.

[0033] [(f) Vinyl monomer] The vinyl monomer (f) may be a compound having a vinyl group in the molecule. Examples of such compounds include vinyl ester monomers such as vinyl acetate, vinyl propionate, and vinyl laurate, aromatic vinyl monomers such as styrene, chlorostyrene, chloromethylstyrene, α-methylstyrene, and other substituted styrenes, and polyalkylene glycol di(meth)acrylates. These may be used alone or in combination of two or more.

[0034] The content of the (f) vinyl monomer in the total monomer components of the copolymer is usually 40% by mass or less, preferably 35% by mass or less, and particularly preferably 30% by mass or less.

[0035] [(g) Macromonomer] The (g) macromonomer is a polymer monomer having a terminal functional group and a high molecular weight skeleton component. In particular, the (g) macromonomer is preferably a monomer having a side chain with 20 or more carbon atoms when copolymerized into a (meth)acrylic acid ester copolymer.

[0036] By using the (g) macromonomer, the macromonomer is introduced as a branch component of the (meth)acrylic acid ester copolymer, and the (meth)acrylic acid ester copolymer can be made into a graft copolymer. In addition, the properties of the main chain and side chain of the graft copolymer can be changed by selecting and mixing the (g) macromonomer and other monomers.

[0037] (g) Examples of the terminal functional group of the macromonomer include radically polymerizable groups such as (meth)acryloyl group and vinyl group, and functional groups such as hydroxyl group, isocyanate group, epoxy group, carboxyl group, amino group, amide group, and thiol group. Among these, those having a radically polymerizable group copolymerizable with other monomers are preferred, and (meth)acryloyl group is particularly preferred. The terminal functional group may be one or two or more, and those having one are particularly preferred. The (g) macromonomer may have the above-mentioned functional groups in addition to the terminal functional groups.

[0038] The backbone component of the (g) macromonomer is preferably composed of a (meth)acrylic acid ester (co)polymer or a vinyl polymer, and examples thereof include the alkyl (meth)acrylate having 1 to 18 carbon atoms in the alkyl group, the (a) carboxyl group-containing monomer, the (b) hydroxyl group-containing monomer, the (d) epoxy group-containing monomer, and the (e) amide group-containing monomer. These may be used alone or in combination of two or more. In particular, the backbone component of the (g) macromonomer preferably contains a hydrophobic monomer and a hydrophilic monomer as constituent units.

[0039] The hydrophobic monomer is preferably an alkyl ester having no polar group (excluding methyl (meth)acrylate), such as n-butyl (meth)acrylate, isobutyl (meth)acrylate, sec-butyl (meth)acrylate, t-butyl (meth)acrylate, pentyl (meth)acrylate, isopentyl (meth)acrylate, neopentyl (meth)acrylate, hexyl (meth)acrylate, cyclohexyl (meth)acrylate, heptyl (meth)acrylate, 2-ethylhexyl acrylate, n-octyl acrylate, isooctyl acrylate, Examples of (meth)acrylates include nonyl (meth)acrylate, isononyl (meth)acrylate, t-butylcyclohexyl (meth)acrylate, decyl (meth)acrylate, isodecyl (meth)acrylate, undecyl (meth)acrylate, lauryl (meth)acrylate, cetyl (meth)acrylate, stearyl (meth)acrylate, isostearyl (meth)acrylate, behenyl (meth)acrylate, isobornyl (meth)acrylate, cyclohexyl (meth)acrylate, dicyclopentenyloxyethyl (meth)acrylate, and methyl methacrylate. These may be used alone or in combination of two or more.

[0040] Examples of hydrophobic monomers other than the alkyl esters include vinyl monomers such as vinyl acetate, styrene, t-butylstyrene, α-methylstyrene, vinyl toluene, and alkyl vinyl monomers. These may be used alone or in combination of two or more.

[0041] The hydrophilic monomer is preferably methyl (meth)acrylate or an ester having a polar group, for example, methyl (meth)acrylate, tetrahydrofurfuryl (meth)acrylate, hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, hydroxybutyl (meth)acrylate, glycerol (meth)acrylate or other hydroxyl group-containing (meth)acrylates, (meth)acrylic acid, 2-(meth)acryloyloxyethyl hexahydrophthalic acid, 2-(meth)acryloyloxypropyl hexahydrophthalic acid, 2-(meth)acryloyloxyethyl phthalic acid, 2-(meth)acryloyloxypropyl phthalic acid, 2-(meth)acryloyloxyethyl maleic acid, 2-(meth)acryloyloxyethyl phthal ... Examples of the monomers include carboxyl group-containing monomers such as -(meth)acryloyloxypropyl maleic acid, 2-(meth)acryloyloxyethyl succinic acid, 2-(meth)acryloyloxypropyl succinic acid, crotonic acid, fumaric acid, maleic acid, itaconic acid, monomethyl maleate, monomethyl itaconate, etc., acid anhydride group-containing monomers such as maleic anhydride, itaconic anhydride, etc., epoxy group-containing monomers such as glycidyl (meth)acrylate, α-ethyl glycidyl acrylate, 3,4-epoxybutyl (meth)acrylate, etc., alkoxy polyalkylene glycol (meth)acrylate such as methoxy polyethylene glycol (meth)acrylate, N,N-dimethylacrylamide, hydroxyethylacrylamide, etc. These may be used alone or in combination of two or more.

[0042] Among the (g) macromonomers, from the viewpoint of forming an appropriate phase-separated structure between the main chain and side chain macromonomers of the graft copolymer, a macromonomer obtained by reacting isobornyl (meth)acrylate as a hydrophobic monomer and methyl (meth)acrylate as a hydrophilic monomer in a 1:1 ratio is preferred.

[0043] The glass transition temperature (Tg) of the (g) macromonomer is preferably higher than the glass transition temperature of the copolymerization component constituting the (meth)acrylic acid ester (co)polymer. Specifically, the glass transition temperature (Tg) of the (g) macromonomer affects the heat melting temperature (hot melt temperature) of the photocurable pressure-sensitive adhesive composition, and is therefore preferably 30 to 120° C., more preferably 40 to 110° C., and particularly preferably 50 to 100° C. If the glass transition temperature (Tg) of the (g) macromonomer is within the above range, there is a tendency that excellent processability and storage stability can be maintained and hot melt properties can be obtained at around 50 to 80° C. by adjusting the molecular weight. The glass transition temperature of the (g) macromonomer means the glass transition temperature of the macromonomer itself, and can be measured by a differential scanning calorimeter (DSC).

[0044] When the (g) macromonomer is used as a copolymerization component of the (meth)acrylic acid ester (co)polymer, the resulting (meth)acrylic acid ester (co)polymer can maintain a state in which the branch components are attracted to each other and physically crosslinked at room temperature (25°C). Moreover, the physical crosslinks can be broken by heating to an appropriate temperature to obtain fluidity. Therefore, when forming a pressure-sensitive adhesive sheet as described below, the sheet shape can be maintained in an uncured state. In order to obtain such physical properties, it is also preferable to adjust the molecular weight and content of the macromonomer.

[0045] The number average molecular weight of the (g) macromonomer is preferably 500 to 20,000, more preferably 600 to 10,000, further preferably 800 to 8,000, particularly preferably 1,000 to 7,000, and especially preferably 1,500 to 6,000.

[0046] The content of the (g) macromonomer is preferably 5 to 30 mass % of the total monomer components of the copolymer, more preferably 6 to 25 mass %, and particularly preferably 8 to 20 mass %. If the content is too low, the physical crosslinks between the branch components are too weak, and the storage stability at room temperature (25°C) tends to be poor, whereas if the content is too high, the physical crosslinks between the branch components are too strong, and the fluidity when heated tends to be poor.

[0047] The (meth)acrylic acid ester (co)polymer can be obtained by polymerizing an alkyl (meth)acrylate or an alkyl (meth)acrylate having 1 to 18 carbon atoms in the alkyl group and a monomer component copolymerizable therewith, according to a conventionally known method such as solution radical polymerization, suspension polymerization, bulk polymerization, emulsion polymerization, or the like.

[0048] The weight average molecular weight of the (meth)acrylic acid ester (co)polymer thus obtained is usually 50,000 to 1.5 million, preferably 70,000 to 1.3 million, particularly preferably 100,000 to 1.2 million, and further preferably 150,000 to 1 million.

[0049] Here, the weight average molecular weight is measured by the following method. A (meth)acrylic acid ester (co)polymer dissolved in tetrahydrofuran (THF) is used as a measurement sample, and a molecular weight distribution curve is measured under the following conditions using a gel permeation chromatography (GPC) analyzer (device name: Tosoh Corporation HLC-8320GPC) to determine the weight average molecular weight (Mw). Guard column: TSKguardcolumnHXL Separation column: TSKgelGMHXL (4 columns) ·Temperature: 40℃ ·Injection volume: 100μL Polystyrene equivalent Solvent: THF ·Flow rate: 1.0mL / min

[0050] The (meth)acrylic acid ester (co)polymer also preferably has an active energy ray crosslinkable structural site. The active energy ray crosslinkable structure is, for example, a structural portion that can react with a part of the (meth)acrylic acid ester (co)polymer or a curing component other than the (meth)acrylic acid ester (co)polymer in the presence of a photopolymerization initiator (A) described later to form a crosslinked structure.

[0051] Examples of the active energy ray crosslinkable structural moiety include structures having a radical polymerizable functional group having a carbon-carbon double bond, such as a functional group having an unsaturated double bond, such as a (meth)acryloyl group or a vinyl group. Since the polymer chains of the (meth)acrylic acid ester (co)polymer have a radically polymerizable functional group, the polymer chains can be directly polymerized with each other even in the absence of a crosslinking agent.

[0052] To introduce a structure having a radically polymerizable functional group into a (meth)acrylic acid ester (co)polymer, for example, a (meth)acrylic acid ester copolymer may be produced using a monomer having a functional group such as a hydroxyl group or a carboxyl group as a copolymerization component, and then a compound having a functional group and an unsaturated double bond that can react with the functional group (e.g., 2-isocyanatoethyl (meth)acrylate, etc.) may be reacted with the copolymer while maintaining the polymerizability of the unsaturated double bond.

[0053] [Photopolymerization initiator (A)] The photopolymerization initiator (A) contained in the photocurable pressure-sensitive adhesive composition is a visible light initiator that generates radicals by irradiation with visible light, light having wavelengths of at least 390 nm, 405 nm, and 410 nm, for example, light in a wavelength range of 380 to 700 nm, and serves as the starting point for the reaction of the (meth)acrylic acid ester (co)polymer. By containing the photopolymerization initiator (A) in the photocurable pressure-sensitive adhesive composition, the photocurable pressure-sensitive adhesive composition can be cured by visible light. The photopolymerization initiator (A) may generate radicals only by irradiation with visible light, or may generate radicals also by irradiation with light in a wavelength range other than the visible light range.

[0054] The photopolymerization initiator (A) preferably has an absorption coefficient at a wavelength of 405 nm of 10 mL / (g cm) or more, more preferably 15 mL / (g cm) or more, and particularly preferably 25 mL / (g cm) or more. By having an absorption coefficient at a wavelength of 405 nm that is equal to or greater than the above value, curing (crosslinking) can proceed sufficiently by irradiation with visible light. On the other hand, the upper limit of the absorption coefficient at a wavelength of 405 nm is 1 × 10 4 mL / (g cm) or less is preferable, and 1×10 3 mL / (g cm) or less is more preferable. In the present invention, a photopolymerization initiator having an absorption coefficient of less than 10 mL / (g cm) at a wavelength of 405 nm may be used in combination.

[0055] The photopolymerization initiator (A) is roughly classified into two types according to the radical generation mechanism; that is, a cleavage-type photopolymerization initiator capable of generating radicals by cleaving and decomposing a single bond of the photopolymerization initiator itself, and a hydrogen abstraction-type photopolymerization initiator capable of transferring hydrogen from the hydrogen donor by forming an exciplex with a photoexcited initiator and a hydrogen donor in the system. The cleavage-type photopolymerization initiator is decomposed into another compound when generating radicals by light irradiation, and once excited, it no longer functions as a reaction initiator. Therefore, it is preferable because it does not remain as an active species in the adhesive after the crosslinking reaction is completed, and there is no possibility of causing unexpected photodegradation of the adhesive.

[0056] Examples of the cleavage-type photopolymerization initiator include α-aminoacetophenone-based photopolymerization initiators such as 2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropan-1-one, 2-benzyl-2-(dimethylamino)-4'-morpholinobutyrophenone, and 2-dimethylamino-2-(4-methylbenzyl)-1-(4-morpholin-4-yl-phenyl)-butan-1-one; acylphosphine oxide-based photopolymerization initiators such as bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide, 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, (2,4,6-trimethylbenzoyl)ethoxyphenylphosphine oxide, and bis(2,6-dimethoxybenzoyl)2,4,4-trimethylpentylphosphine oxide; Examples of the photopolymerization initiator include benzyl ketal-based photopolymerization initiators such as 2-dimethoxy-1,2-diphenylethan-1-one; α-hydroxyacetophenone-based photopolymerization initiators such as 1-hydroxycyclohexyl phenyl ketone, 2-hydroxy-2-methyl-1-phenyl-propan-1-one, 1-(4-(2-hydroxyethoxy)phenyl)-2-hydroxy-2-methyl-1-propan-1-one, 2-hydroxy-1-[4-{4-(2-hydroxy-2-methyl-propionyl)benzyl}phenyl]-2-methyl-propan-1-one, and oligo(2-hydroxy-2-methyl-1-(4-(1-methylvinyl)phenyl)propanone); and phenyl glyoxylate-based photopolymerization initiators such as methyl phenyl glyoxylate, as well as derivatives of these cleavage-type visible light polymerization initiators.

[0057] The cleavage-type photopolymerization initiator is preferably an α-aminophenone-based photopolymerization initiator, which tends to suppress discoloration of the polarizing plate since it does not generate acid when decomposed by irradiation with light. In the present invention, it would be desirable to avoid the use of α-aminophenone-based photopolymerization initiators because the central wavelength of their light absorption peak is outside the visible light region and it is anticipated that this may result in poor curing. However, when they were used, no such problems occurred and discoloration of the polarizing plate was effectively suppressed.

[0058] On the other hand, even if they are the same cleavage type photoinitiators, acylphosphine oxide-based photopolymerization initiators and phenylglyoxylate-based photopolymerization initiators are usually used as photopolymerization initiators because the central wavelength of the light absorption peak is the visible light absorption peak and there is little concern about poor curing. In the present invention, the discoloration of the polarizing plate can be suppressed by reducing the amount of acylphosphine oxide-based photopolymerization initiators and phenylglyoxylate-based photopolymerization initiators contained in the adhesive sheet. That is, among the cleavage type photopolymerization initiators, acylphosphine oxide-based photopolymerization initiators and phenylglyoxylate-based photopolymerization initiators decompose when generating radicals by light irradiation to generate acid. If this acid remains in the adhesive sheet after laminating with the polarizing plate, it may act as a catalyst and cause discoloration due to polyenation of the polyvinyl alcohol-based resin constituting the polarizer. Therefore, in the present invention, it is preferable not to use acylphosphine oxide-based photopolymerization initiators and phenylglyoxylate-based photopolymerization initiators, but they may be used within a range that does not affect the effects of the present invention (0.5 mass% or less of the photocurable adhesive composition).

[0059] Examples of the hydrogen abstraction type photopolymerization initiator include bis(2-phenyl-2-oxoacetic acid)oxybisethylene, phenylglyoxylic acid methyl ester, a mixture of oxy-phenyl-acetic acid 2-[2-oxo-2-phenyl-acetoxy-ethoxy]ethyl ester and oxy-phenyl-acetic acid 2-[2-hydroxy-ethoxy]ethyl ester, thioxanthone, 2-chlorothioxanthone, 3-methylthioxanthone, 2,4-dimethylthioxanthone, anthraquinone, 2-methylanthraquinone, 2-ethylanthraquinone, 2-tert-butylanthraquinone, 2-aminoanthraquinone, camphorquinone and derivatives thereof, and ketocoumarin-based photopolymerization initiators such as ketocoumarin and derivatives thereof.

[0060] The hydrogen abstraction type photopolymerization initiator is preferably a ketocoumarin-based photopolymerization initiator. The ketocoumarin-based photopolymerization initiator has sufficient visible light reactivity, and yellowing can be adjusted to a practically acceptable level by adjusting the amount added, which tends to suppress discoloration of the polarizing plate. In the present invention, it would be desirable to avoid using a ketocoumarin-based photopolymerization initiator because of the suspected drawback of yellowing. However, when it was used, no such drawback occurred and discoloration of the polarizing plate could be effectively suppressed.

[0061] Among these, it is preferable that the photopolymerization initiator (A) contains at least one photopolymerization initiator selected from the group consisting of α-aminoacetophenone-based photopolymerization initiators and ketocoumarin-based photopolymerization initiators. The photopolymerization initiator (A) is not limited to the above-listed substances. Any one of the above-listed photopolymerization initiators (A) or its derivative may be used, or two or more of them may be used in combination. In addition to the photopolymerization initiator (A), a substance that generates radicals only when irradiated with other light such as ultraviolet light may be mixed.

[0062] The content of the photopolymerization initiator (A) in the photocurable pressure-sensitive adhesive composition is usually 0.1 to 10 parts by mass, preferably 0.2 to 5 parts by mass, and more preferably 0.3 to 3 parts by mass, based on 100 parts by mass of the (meth)acrylic acid ester (co)polymer. By setting the content of the photopolymerization initiator (A) within the above range, appropriate reaction sensitivity to visible light can be obtained.

[0063] The photocurable pressure-sensitive adhesive composition used in the present invention preferably contains a crosslinking agent and / or a silane coupling agent in addition to the (meth)acrylic acid ester (co)polymer and the photopolymerization initiator (A).

[0064] [Crosslinking agent] Examples of the crosslinking agent include compounds having at least one crosslinkable functional group selected from (meth)acryloyl group, epoxy group, isocyanate group, carboxyl group, hydroxyl group, carbodiimide group, oxazoline group, aziridine group, vinyl group, amino group, imino group, and amide group. These may be used alone or in combination of two or more. In addition, the crosslinking agent may be one in which the crosslinkable functional group is protected with a deprotectable protecting group, or the crosslinking agent may be chemically bonded to a (meth)acrylic acid ester (co)polymer.

[0065] Among these, photopolymerizable compounds having a carbon-carbon double bond such as a (meth)acryloyl group or a vinyl group, particularly polyfunctional (meth)acrylates, are preferred, where polyfunctional refers to having two or more (meth)acryloyl groups.

[0066] Examples of the polyfunctional (meth)acrylate include 1,4-butanediol di(meth)acrylate, glycerin di(meth)acrylate, neopentyl glycol di(meth)acrylate, glycerin glycidyl ether di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, 1,9-nonanediol di(meth)acrylate hydroxypivalic acid neopentyl glycol di(meth)acrylate, and di(meth)acrylate of hydroxypivalic acid neopentyl glycol adduct of ε-caprolactone adduct of hydroxypivalic acid neopentyl glycol. acrylate, tricyclodecane dimethacrylate, tricyclodecane dimethanol di(meth)acrylate, bisphenol A polyethoxy di(meth)acrylate, bisphenol A polypropoxy di(meth)acrylate, bisphenol F polyethoxy di(meth)acrylate, ethylene glycol di(meth)acrylate and other bifunctional (meth)acrylates; trimethylolpropane trioxyethyl (meth)acrylate, ε-caprolactone modified tris(2-hydroxyethyl)isocyanurate tri(meth)acrylate, ) acrylate, pentaerythritol tri(meth)acrylate, propoxylated pentaerythritol tri(meth)acrylate, ethoxylated pentaerythritol tri(meth)acrylate and other trifunctional (meth)acrylates; pentaerythritol tetra(meth)acrylate, propoxylated pentaerythritol tetra(meth)acrylate, ethoxylated pentaerythritol tetra(meth)acrylate, dipentaerythritol hexa(meth)acrylate, polyethylene glycol di(meth)acrylate and tetrafunctional or higher (meth)acrylates such as tris(acryloxyethyl)isocyanurate, dipentaerythritol hexa(meth)acrylate, dipentaerythritol penta(meth)acrylate, tripentaerythritol hexa(meth)acrylate, tripentaerythritol penta(meth)acrylate, trimethylolpropane tri(meth)acrylate, trimethylolpropane polyethoxytri(meth)acrylate, and ditrimethylolpropane tetra(meth)acrylate. In addition to the above, examples of the polyfunctional (meth)acrylate include polyfunctional (meth)acrylic oligomers such as polyester (meth)acrylate, epoxy (meth)acrylate, urethane (meth)acrylate, polyether (meth)acrylate, etc. These may be used alone or in combination of two or more kinds. Among these, tri- or higher functional (meth)acrylates are preferred, trifunctional (meth)acrylates are more preferred, and propoxylated pentaerythritol tri(meth)acrylate is particularly preferred.

[0067] The content of the crosslinking agent is preferably 0.5 to 50 parts by mass, more preferably 1 to 40 parts by mass, and even more preferably 5 to 30 parts by mass, relative to 100 parts by mass of the (meth)acrylic acid ester (co)polymer. By setting the content within the above range, the adhesive strength and cohesive strength can be increased, which is preferable.

[0068] [Silane coupling agents] A silane coupling agent is preferred because it can improve adhesion, particularly adhesion to glass materials.

[0069] Examples of the silane coupling agent include compounds having an unsaturated group such as a vinyl group, an acryloxy group, or a methacryloxy group, an amino group, an epoxy group, or the like, as well as a hydrolyzable functional group such as an alkoxy group.

[0070] Examples of silane coupling agents include N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane, N-(β-aminoethyl)-γ-aminopropylmethyldimethoxysilane, γ-aminopropyltriethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-methacryloxypropyltrimethoxysilane, etc. These may be used alone or in combination of two or more. Among them, γ-glycidoxypropyltrimethoxysilane is preferred from the viewpoints of good adhesion and little discoloration such as yellowing.

[0071] The content of the silane coupling agent is usually 0.05 to 5 parts by mass, and preferably 0.1 to 3 parts by mass, based on 100 parts by mass of the (meth)acrylic acid ester (co)polymer. By setting the content within the above range, it is possible to avoid the problem of whitening and to increase the adhesive strength, which is preferable.

[0072] In addition to the silane coupling agent, a coupling agent such as an organic titanate compound can also be effectively used in the photocurable pressure-sensitive adhesive composition.

[0073] [Other materials] The photocurable adhesive composition may contain, as other components, various additives such as light stabilizers, ultraviolet absorbers, metal deactivators, metal corrosion inhibitors, antiaging agents, antistatic agents, moisture absorbers, foaming agents, defoamers, inorganic particles, viscosity modifiers, tackifier resins, photosensitizers, fluorescent agents, and reaction catalysts (tertiary amine compounds, quaternary ammonium compounds, tin laurate compounds, etc.). In addition, other known components that are blended in normal adhesive compositions may be appropriately contained. These other components may be used alone or in combination of two or more.

[0074] (Preparation of Photocurable Adhesive Composition) The photocurable pressure-sensitive adhesive composition can be obtained by mixing, for example, a (meth)acrylic acid ester (co)polymer, a photopolymerization initiator (A) (preferably a crosslinking agent), a silane coupling agent, and, if necessary, other materials in predetermined amounts. A heat treatment step may be added during the production of the photocurable pressure-sensitive adhesive composition. In this case, it is preferable to previously mix the components of the photocurable pressure-sensitive adhesive composition and then perform the heat treatment. Furthermore, in the above-mentioned mixing, various mixed components may be concentrated and used in the form of a master batch.

[0075] The mixing method is not particularly limited, and for example, a universal kneader, a planetary mixer, a Banbury mixer, a kneader, a gate mixer, a pressure kneader, a three-roll mill, a two-roll mill, etc. can be used. When mixing the components of the photocurable adhesive composition, a solvent may be used as necessary, or the components may be mixed as a solventless system that does not contain a solvent. By making the photocurable adhesive composition a solventless system, the solvent does not remain, and the heat resistance and light resistance can be improved.

[0076] <Photocurable adhesive sheet> The photocurable adhesive sheet is formed from the photocurable adhesive composition, and may be, for example, a single-layer structure of the adhesive sheet, or a multi-layer structure of two or more layers, but a multi-layer structure of two or more layers is preferable. In the case of a multi-layer structure, it is sufficient that at least the outermost layer is formed from the photocurable adhesive composition, but all layers may be formed from the photocurable adhesive composition.

[0077] To form a photocurable adhesive sheet from the photocurable adhesive composition, the photocurable adhesive composition may be applied. The method for applying the photocurable adhesive composition is not particularly limited as long as it is a general application method, and examples thereof include roll coating, die coating, gravure coating, comma coating, and screen printing.

[0078] The thickness (β) of the photocurable pressure-sensitive adhesive sheet is preferably from 50 to 500 μm from the viewpoint of practicality, more preferably from 70 to 400 μm, and even more preferably from 100 to 300 μm.

[0079] The photocurable adhesive sheet thus formed has photocurability, that is, it is cured by irradiation with light. In this case, the photocurable adhesive sheet may be cured to a state where there is still room for photocuring (also referred to as "temporarily cured"), or may be uncured (referred to as "uncured"), that is, it has not yet been cured and has photocurability. If the photocurable adhesive sheet that is formed is provisionally cured or uncured, the photocurable adhesive sheet can be photocured (also referred to as "full curing") after being attached to an adherend, thereby increasing the cohesive strength and improving the adhesion.

[0080] In the case of the provisional curing, light may be irradiated to set the gel fraction of the present adhesive sheet to 60% or less. However, the photocurable adhesive sheet does not necessarily have to be provisionally cured by light irradiation, and the present adhesive sheet may be provisionally cured, for example, by heat or curing.

[0081] In addition, the photocurable adhesive sheet may be laminated with a release sheet in an unused state before being attached to an adherend, and the release sheet may be peeled off when used. The release sheet is usually laminated on both sides of the photocurable adhesive sheet. The release sheet-attached adhesive sheet may be produced, for example, by applying the photocurable adhesive composition onto a release sheet to form an adhesive layer, and then laminating another release sheet thereon.

[0082] As the release sheet, a known release sheet can be appropriately used, for example, a sheet made of a polyester resin, a polyolefin resin, a polycarbonate resin, a polystyrene resin, an acrylic resin, a triacetyl cellulose resin, a fluorine resin, etc., which is subjected to a release treatment by coating with a silicone resin, a release paper, etc. These may be used alone or in a laminate of two or more kinds.

[0083] The release sheet preferably has a light transmittance of 40% or less at a wavelength of 410 nm or less, more preferably 30% or less, and particularly preferably 20%. When the release sheet has a light transmittance of 410 nm or less at a wavelength of 410 nm or less, the pressure-sensitive adhesive sheet can be effectively prevented from undergoing photopolymerization due to visible light during storage, etc.

[0084] Here, examples of release sheets having a light transmittance of 40% or less at wavelengths of 410 nm or less, that is, sheets having the effect of partially blocking the transmission of visible light and ultraviolet light, include the following (1) to (7). (1) A laminated sheet having an ultraviolet absorbing layer formed by applying a removable, slightly adhesive resin to one side of a cast film or stretched film made of a resin such as polyester-based resin, polypropylene-based resin, or polyethylene-based resin, and applying a paint containing an ultraviolet absorbing agent to the other side. (2) A laminated sheet in which one side of a cast film or stretched film made of a resin such as polyester resin, polypropylene resin, or polyethylene resin is coated with a removable, slightly adhesive resin containing an ultraviolet absorber. (3) A laminated sheet in which a removable, slightly adhesive resin is applied to a cast film or stretched film made of resin such as polyester resin, polypropylene resin, or polyethylene resin containing an ultraviolet absorber. (4) A laminated sheet in which a layer of a resin that does not contain an ultraviolet absorber is molded on one or both sides of a layer of a resin such as a polyester resin, a polypropylene resin, or a polyethylene resin containing an ultraviolet absorber, and one side of the multilayer cast film or stretched film is coated with a slightly adhesive resin that can be peeled off. (5) A laminated sheet in which a coating material containing an ultraviolet absorber is applied to one side of a cast film or stretched film made of a resin such as polyester resin, polypropylene resin, or polyethylene resin to form an ultraviolet absorbing layer, and then a removable, slightly adhesive resin is applied on top of the ultraviolet absorbing layer. (6) A laminated sheet in which a coating material containing an ultraviolet absorber is applied to one side of a cast film or stretched film made of a resin such as polyester resin, polypropylene resin, or polyethylene resin to provide an ultraviolet absorbing layer, and a removable, slightly adhesive resin is applied to the other side. (7) A laminated sheet in which one side of a resin film made of a resin such as a polyester resin, a polypropylene resin, a polyethylene resin, etc., having a releasable slightly adhesive resin applied thereto, is laminated with a separately prepared resin film via an adhesive or pressure-sensitive adhesive layer containing an ultraviolet absorber.

[0085] The thickness of the release sheet is not particularly limited, but from the viewpoints of processability and handleability, the thickness is preferably from 25 to 500 μm, more preferably from 38 to 250 μm, and particularly preferably from 50 to 200 μm.

[0086] When release sheets are laminated on both sides of the pressure-sensitive adhesive layer of the photocurable pressure-sensitive adhesive sheet, one release sheet may have the same layer structure, material, and thickness as the other release sheet, or may have a different layer structure, material, and thickness. In addition, one release sheet and the other release sheet may have different peel strengths.

[0087] The release sheet may further include other layers, such as an antistatic layer, a hard coat layer, and an anchor layer, if necessary.

[0088] A separate release sheet is laminated on the formed pressure-sensitive adhesive layer to obtain a pressure-sensitive adhesive sheet with a release sheet.

[0089] Furthermore, when the photocurable adhesive sheet has a multilayer structure, it can be produced by a method in which the photocurable adhesive composition is applied onto a base sheet or a release sheet to form a first adhesive sheet, and then the photocurable adhesive composition is applied onto the first adhesive sheet thus formed to form a second adhesive sheet, and this process is repeated; a method in which the first adhesive sheet and the second adhesive sheet are formed separately and then the coated surfaces of each sheet are bonded together; or a method in which the photocurable adhesive composition is applied by multi-layer coating or co-extrusion molding to simultaneously form the first adhesive sheet and the second adhesive sheet.

[0090] The photocurable adhesive sheet may be formed into a sheet shape by, for example, directly applying the photocurable adhesive composition to a polarizing plate or an adherend (another component (X)) without using a release sheet as described above, or the photocurable adhesive composition may be directly extruded to form a photocurable adhesive sheet. Furthermore, the photocurable adhesive sheet may be formed by injecting the photocurable adhesive composition into a mold to form the adhesive sheet, or by directly filling the space between the polarizing plate and the adherend, which is the other component (X), with the photocurable adhesive composition.

[0091] In the photocurable adhesive sheet thus obtained, when the photocurable adhesive composition contains an acylphosphine oxide-based photopolymerization initiator and a phenylglyoxylate-based photopolymerization initiator as the photopolymerization initiator (A), the total concentration is 0.5% by mass or less, preferably 0.2% by mass or less, more preferably 0.1% by mass or less, and particularly preferably 0.05% by mass or less. The lower limit is, of course, 0% by mass. That is, the photocurable adhesive sheet can suppress discoloration of the polarizing plate caused by acid by reducing the content of the acylphosphine oxide-based photopolymerization initiator and the phenylglyoxylate-based photopolymerization initiator that are decomposed by light irradiation and generate acid. In addition, when the photocurable adhesive sheet has a multilayer structure of two or more layers, the concentrations of the acylphosphine oxide-based photopolymerization initiator and the phenylglyoxylate-based photopolymerization initiator contained in the photocurable adhesive composition that forms the layer in contact with the polarizing plate may be within the above-mentioned ranges.

[0092] (Light transmittance) The photocurable pressure-sensitive adhesive sheet has a light transmittance of less than 90% at a wavelength of 390 nm and a light transmittance of 80% or more at a wavelength of 410 nm. For photocurable pressure-sensitive adhesive compositions containing a photopolymerization initiator that absorbs in the ultraviolet to visible light region with a wavelength of around 400 nm, the greater the light absorption of the photopolymerization initiator and the lower the light transmittance at a wavelength of 390 nm resulting from that absorption, the better the photosensitivity and the easier the curing will proceed. On the other hand, if the light transmittance at a wavelength of 410 nm is not high enough, the photocurable adhesive sheet will be colored yellow and will be difficult to use in an image display device. A light transmittance of less than 90% at a wavelength of 390 nm is preferable because sufficient visible light curing properties can be ensured, and a light transmittance of 80% or more at a wavelength of 410 nm can achieve a sufficiently low yellow index value (YI value) necessary for lamination of optical components that require transparency.

[0093] The light transmittance of the photocurable pressure-sensitive adhesive sheet at a wavelength of 390 nm is less than 90%, and preferably 88% or less. The light transmittance of the photocurable pressure-sensitive adhesive sheet at a wavelength of 410 nm is 80% or more, preferably 85% or more, and particularly preferably 90% or more. In order to achieve the above-mentioned light transmittance of the photocurable adhesive sheet, among the photopolymerization initiators (A) that absorb visible light, those that have an absorption peak characteristic in which the base of the absorption peak reaches sufficiently up to 390 nm, but the absorption peak becomes small at 410 nm, particularly at least one selected from the group consisting of α-aminoacetophenone-based photopolymerization initiators and ketocoumarin-based photopolymerization initiators, may be used. However, the present invention is not limited to such a method.

[0094] The photocurable adhesive sheet can also be cured by irradiation with light having a wavelength of 390 to 410 nm.

[0095] (Yellow Index Value) The photocurable adhesive sheet is preferably applied with an integrated light amount of 3000 (mJ / cm 2 ) in terms of transparency. 2 After irradiation with UV light from a high pressure mercury lamp so as to obtain a yellow index value of 2.0 or less, preferably 1.9 or less, as measured in accordance with JIS K7103.

[0096] (Gel fraction) The gel fraction G1 of the photocurable adhesive sheet before light irradiation is usually 50% or less, preferably 40% or less, and particularly preferably 20% or less. The lower limit is 0%. If the gel fraction is less than the above value, there is a sufficient amount of uncrosslinked components that can be cured by light irradiation (in a provisionally cured or uncured state), and flexibility tends to be high.

[0097] The gel fraction is determined by the following method. The mass of the photocurable adhesive sheet (mass before immersion) is measured, this is wrapped in a bag using SUS mesh (#200), immersed in ethyl acetate, and stored in a dark place for 24 hours at 23° C. The wrapper is then removed and heated at 70° C. for 4.5 hours to evaporate the adhering ethyl acetate, the mass of the remaining photocurable adhesive sheet (mass after immersion) is measured, and the gel fraction is calculated using the following formula. Gel fraction (%) = [(mass after immersion) / (mass before immersion)] × 100

[0098] In order to adjust the gel fraction G1 before the light irradiation to the above range, the remaining catalyst may be sufficiently removed during polymerization of the (meth)acrylic acid ester (co)polymer and during processing of the photocurable adhesive sheet, or a polymerization inhibitor or antioxidant may be used to prevent unintended curing (crosslinking) reactions caused by heat, light, etc. from proceeding before the main curing. In addition, when provisional curing is performed by light irradiation, the integrated light amount of light irradiated for provisional curing may be sufficiently small so that the amount of uncrosslinked components is sufficiently large. However, the present invention is not limited to such a method.

[0099] In addition, the photocurable adhesive sheet is exposed to an ultraviolet ray shielding member having an ultraviolet ray shielding property, and the integrated light amount at a wavelength of 405 nm is 3000 (mJ / cm 2 ), the gel fraction G2 after light irradiation is usually 40 to 100%, preferably 50 to 100%, and particularly preferably 60 to 100%. When the gel fraction G2 after light irradiation of the photocurable pressure-sensitive adhesive sheet is within the above range, defects in appearance such as foaming and peeling tend not to be observed even in a harsh high-temperature and high-humidity environment.

[0100] In addition, the difference between the gel fraction G1 before light irradiation and the gel fraction G2 after light irradiation (gel fraction G2 after light irradiation - gel fraction G1 before light irradiation) is preferably 10% or more, more preferably 30% or more, and particularly preferably 60% or more. If the difference in gel fraction of the photocurable adhesive sheet before and after photocuring is equal to or greater than the above-mentioned numerical value, the sheet tends to have high cohesive strength even in harsh high-temperature and high-humidity environments, and to have high foaming resistance. The upper limit is usually 100%. In order to make the difference in gel fraction of the photocurable adhesive sheet before and after the light irradiation equal to or greater than the above-mentioned numerical value, for example, a photopolymerization initiator (A) having absorption at a wavelength of 405 nm may be used, although the method is not limited to this.

[0101] The term "having ultraviolet shielding properties" means that the light transmittance at a wavelength of 365 nm is 10% or less and the light transmittance at a wavelength of 405 nm is 60% or more. As such an ultraviolet shielding member, for example, "Iupilon Sheet MR58, thickness 1.0 mm" manufactured by Mitsubishi Gas Chemical Company, Inc. may be used.

[0102] The term "integrated light amount at a wavelength of 405 nm" refers to the total amount of irradiation energy received per unit area, and refers to the total amount of light irradiation energy measured using an ultraviolet integrating light meter "UIT-250" (manufactured by Ushio Inc.) and a receiver "UVD-C405" (manufactured by Ushio Inc.) among the light irradiated by a high-pressure mercury lamp or the like, and refers to the integrated light amount in the wavelength region according to the photosensitive characteristics of the receiver (having a photosensitivity that has a peak at 405 nm and a broad base in the wavelength range of 320 to 470 nm). More specifically, it refers to the integrated light amount obtained in accordance with the method described in the Examples.

[0103] As described above, the photocurable pressure-sensitive adhesive sheet is laminated in a layer structure of polarizing plate / photocurable pressure-sensitive adhesive sheet, and the laminate having this layer structure becomes the present laminate.

[0104] (Polarizing plate) The polarizing plate is not particularly limited, and examples thereof include a polarizing plate in which both sides of a polyvinyl alcohol-based resin layer (polarizer) in which iodine compound molecules are adsorbed and oriented in a polyvinyl alcohol-based resin film are laminated with protective films such as a triacetyl cellulose-based resin film, an acrylic resin film, a polyester resin film, a cycloolefin polymer resin film, etc. Among these, a polarizing plate in which both sides of a polarizer are laminated with a triacetyl cellulose-based resin film is preferred because it is non-stretched and therefore has excellent optical isotropy. The protective film has a moisture permeability of 1 to 1000 (g / m) in order to prevent discoloration of the polarizer due to the infiltration of moisture. 2 / day), and particularly 5 to 800 (g / m 2 / day), and even 10~600(g / m 2 / day) is preferred.

[0105] In addition, in the present laminate, it is important that the distance (α) between the photocurable pressure-sensitive adhesive sheet and the polarizer is 80 μm or less, preferably 10 to 80 μm, and more preferably 10 to 50 μm. The distance (α) between the photocurable adhesive sheet and the polarizer is the distance from the surface of the polarizer (polyvinyl alcohol-based resin film layer) on which the photocurable adhesive sheet of the polarizing plate is bonded to the surface where the photocurable adhesive sheet contacts the polarizing plate.

[0106] Furthermore, the ratio (α / β) of the distance (α) between the adhesive sheet and the polarizer to the thickness (β) of the photocurable adhesive sheet is preferably 0.1 to 0.5, more preferably 0.1 to 0.4, and particularly preferably 0.1 to 0.3, in order to suppress discoloration of the polarizing plate.

[0107] In recent years, there has been a trend toward thinner displays to reduce weight, and thus thinner polarizing plates as well. When the polarizing plate is made thinner, it is preferable for the present laminate to have the above-mentioned range since discoloration of the polarizing plate can be suppressed even in a configuration in which the distance (α) between the photocurable adhesive sheet and the polarizer is closer.

[0108] It is preferable that the present laminate further includes another component (X) laminated thereon via the photocurable pressure-sensitive adhesive sheet.

[0109] (Other components (X)) The other component (X) is preferably a component having a light transmittance of 10% or less at a wavelength of 365 nm and 60% or more at a wavelength of 405 nm, i.e., a component having ultraviolet ray blocking properties (ultraviolet ray blocking cover material). If the other component (X) has a light transmittance of 10% or less at a wavelength of 365 nm and 60% or more at a wavelength of 405 nm, it can sufficiently block (cut) the transmission of ultraviolet light, suppress photodegradation of the other component (X) itself and the polarizing plate located via the photocurable adhesive sheet, and reduce the yellow index value (YI value) to the level required for the laminate.

[0110] Such other constituent member (X) may be, for example, a material that contains a resin material as a main component and is adjusted to have the above-mentioned light transmittance by using an ultraviolet absorbing agent.

[0111] The resin material may be, for example, a material containing a polycarbonate resin or an acrylic resin as a main component resin. Here, the term "main component resin" refers to the resin that is contained in the largest amount by mass among the resins that constitute the other component (X).

[0112] The method for laminating the other component (X) via the photocurable adhesive sheet is not particularly limited, and either the polarizing plate or the other component (X) may be laminated with the photocurable adhesive sheet and then the other may be laminated with the photocurable adhesive sheet, or the polarizing plate and the other component (X) may be simultaneously laminated with the photocurable adhesive sheet.

[0113] The laminate thus obtained is then irradiated with visible light to form a laminate structure in which the photocurable adhesive sheet is cured. This laminate structure can be used as a component of an image display device, mainly for in-vehicle use. EXAMPLES

[0114] Examples of the present invention will be described in more detail below together with comparative examples. However, the present invention is not limited to the examples described below.

[0115] [Example 1] (Manufacture of photocurable adhesive sheets) A photocurable adhesive composition was obtained by randomly copolymerizing 13.5 parts by mass of a macromonomer (number average molecular weight: 3000) having a terminal functional group of methacryloyl group, consisting of isobornyl methacrylate: methyl methacrylate = 1:1 (mass ratio), 43.7 parts by mass of lauryl acrylate, 40 parts by mass of 2-ethylhexyl acrylate, and 2.8 parts by mass of acrylamide, to 1 kg of an acrylic graft copolymer (mass average molecular weight: 160,000). 15 g of α-aminoacetophenone-based 2-benzyl-2-(dimethylamino)-4'-morpholinobutyrophenone (IGM: Omnirad369) as a photopolymerization initiator, 50 g of propoxylated pentaerythritol triacrylate (Shin-Nakamura Chemical Co., Ltd., NK Ester ATM-4PL) as a crosslinking agent, and 1.5 g of 3-glycidyloxypropyltrimethoxysilane (Shin-Etsu Chemical Co., Ltd.: KBM403) as a silane coupling agent were added to the mixture and mixed uniformly to obtain a photocurable adhesive composition. Next, the photocurable adhesive composition was formed into a sheet having a thickness of 150 μm on a polyethylene terephthalate film having a release-treated surface (Diafoil MRV, manufactured by Mitsubishi Chemical Corporation, thickness 100 μm), and then covered with a polyethylene terephthalate film having a release-treated surface (Diafoil MRQ, manufactured by Mitsubishi Chemical Corporation, thickness 75 μm) to produce a photocurable adhesive sheet with a release sheet.

[0116] (Polarizing plate) The polarizing plate used was a polyvinyl alcohol-based resin film (12 μm) that had been oriented by adsorption of iodine, with an adhesive layer, a triacetyl cellulose-based resin film, and a coating layer laminated in that order on both sides, with the surface of the polyvinyl alcohol-based resin film layer located 35 μm deep from the outermost surface of the polarizing plate to which the adhesive sheet was attached.

[0117] (Other components (X)) As another component (X), a polycarbonate resin plate having ultraviolet light shielding properties (thickness 1.0 mm, light transmittance 0% at 365 nm, light transmittance 83% at 405 nm, manufactured by Mitsubishi Gas Chemical Company, Inc., Iupilon Sheet MR58) was used.

[0118] (Manufacture of laminates) The release sheet was peeled off from one side of the photocurable adhesive sheet with release sheet and the sheet was roll-laminated to one side of the polarizing plate. Then, the release sheet was peeled off from the other side of the photocurable adhesive sheet and a polycarbonate-based resin plate having ultraviolet ray blocking properties was roll-laminated as the other component (X) to obtain a laminate of polarizing plate / photocurable adhesive sheet / polycarbonate-based resin plate having ultraviolet ray blocking properties. The distance between the photocurable adhesive sheet and the polarizer of the obtained laminate (the distance from the surface of the polyvinyl alcohol-based resin film layer on the surface of the polarizing plate on which the photocurable adhesive sheet is attached to the surface where the photocurable adhesive sheet contacts the polarizing plate) was 35 μm. The ratio of the distance between the photocurable adhesive sheet and the polarizer to the thickness of the photocurable adhesive sheet was 0.2.

[0119] [Example 2] A photocurable adhesive sheet with a release sheet and a laminate of a polarizing plate / photocurable adhesive sheet / polycarbonate resin plate with UV-shielding properties were obtained in the same manner as in Example 1, except that 15 g of an α-aminoacetophenone-based 2-dimethylamino-2-(4-methylbenzyl)-1-(4-morpholinophenyl)-butan-1-one (Omnirad379, manufactured by IGM) was used as the photopolymerization initiator.

[0120] [Example 3] A photocurable adhesive sheet with a release sheet and a laminate of a polarizing plate / photocurable adhesive sheet / polycarbonate resin plate with UV-shielding properties were obtained in the same manner as in Example 1, except that 15 g of α-aminoacetophenone-based 2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropan-1-one (IGM: Omnirad907) was used as the photopolymerization initiator.

[0121] [Example 4] A photocurable adhesive sheet with a release sheet and a laminate of a polarizing plate / photocurable adhesive sheet / polycarbonate resin plate having UV-shielding properties were obtained in the same manner as in Example 1, except that 5 g of a ketocoumarin derivative (Esacure 3644, manufactured by IGM) was used as the photopolymerization initiator.

[0122] [Example 5] A photocurable adhesive composition was obtained in the same manner as in Example 1, except that 3 g of ethyl phenyl(2,4,6-trimethylbenzoyl)phosphinate (Omnirad TPO-L, manufactured by IGM) of the acylphosphine oxide type was used as the photopolymerization initiator, and 50 g of pentaerythritol triacrylate (NK Ester ATMM-3L, manufactured by Shin-Nakamura Chemical Co., Ltd.) was used as the crosslinking agent, to prepare an intermediate layer adhesive sheet (1) (thickness: 200 μm). The photocurable adhesive composition was obtained in the same manner as in Example 1, except that 3 g of ethyl phenyl(2,4,6-trimethylbenzoyl)phosphinate (Omnirad TPO-L, manufactured by IGM) of the acylphosphine oxide type was used as the photopolymerization initiator, and 80 g of propoxylated pentaerythritol triacrylate (NK Ester ATM-4PL, manufactured by Shin-Nakamura Chemical Co., Ltd.) was used as the crosslinking agent, to prepare adhesive sheets (2) (thickness: 25 μm) and ('2') (thickness: 25 μm) for the front and back layers. The PET films on both sides of the intermediate layer adhesive sheet were peeled off in turn, and the adhesive surfaces of the surface layer adhesive sheets (2) and ('2') were sequentially bonded to both surfaces to produce a 250 μm thick photocurable adhesive sheet with a release sheet consisting of (2) / (1) / ('2'). Thereafter, in the same manner as in Example 1, a photocurable adhesive sheet with a release sheet, and a laminate of polarizing plate / photocurable adhesive sheet / polycarbonate resin plate having ultraviolet light shielding properties were obtained.

[0123] [Comparative Example 1] A photocurable adhesive sheet with a release sheet, and a laminate of a polarizing plate / photocurable adhesive sheet / polycarbonate resin plate having UV-shielding properties were obtained in the same manner as in Example 1, except that 15 g of an acylphosphine oxide-based diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide (Omnirad TPO manufactured by IGM) was used as the photopolymerization initiator.

[0124] [Comparative Example 2] A photocurable adhesive sheet with a release sheet and a laminate of a polarizing plate / photocurable adhesive sheet / polycarbonate resin plate having UV-shielding properties were obtained in the same manner as in Example 1, except that 15 g of ethyl phenyl(2,4,6-trimethylbenzoyl)phosphinate (manufactured by IGM: Omnirad TPO-L) of an acylphosphine oxide type was used as the photopolymerization initiator.

[0125] [Comparative Example 3] A photocurable adhesive sheet with a release sheet and a laminate of a polarizing plate / photocurable adhesive sheet / UV-shielding polycarbonate resin plate were obtained in the same manner as in Example 1, except that 15 g of an acylphosphine oxide-based mixture [2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide (concentration ratio: about 46%), oligo(2-hydroxy-2-methyl-1-(4-(1-methylvinyl)phenyl)propanone) (concentration ratio: about 50%), 2,4,6-trimethylbenzophenone (concentration ratio: about 3.2%), 4-methylbenzophenone (concentration ratio: about 0.8%)] (IGM: Esacure KTO46) was used as the photopolymerization initiator.

[0126] [Comparative Example 4] A photocurable adhesive sheet with a release sheet and a laminate of a polarizing plate / photocurable adhesive sheet / polycarbonate resin plate having UV-shielding properties were obtained in the same manner as in Example 1, except that 15 g of phenylglyoxylate-based methyl benzoylformate (Omnirad MBF, manufactured by IGM) was used as the photopolymerization initiator.

[0127] [Reference example] A laminate of polarizing plate / photocurable adhesive sheet / polycarbonate-based resin plate with ultraviolet shielding properties was obtained in the same manner as in Comparative Example 1, except that a polarizing plate in which the surface of the polyvinyl alcohol-based resin film layer was located at a depth of 90 μm from the outermost surface of the polarizing plate to which the adhesive sheet was attached was used.

[0128] The following evaluations were carried out using the obtained photocurable pressure-sensitive adhesive sheets with release sheets and laminates of Examples 1 to 5, Comparative Examples 1 to 4, and Reference Example. The results are shown in Table 1 below.

[0129] (1) Light transmittance The release sheet was peeled off from the photocurable adhesive sheet with the release sheet attached, and the spectral transmittance (% T) of the photocurable adhesive sheet at wavelengths of 300 to 800 nm was measured using a spectrophotometer (Shimadzu Corporation, UV2000).

[0130] (2) Yellow Index Value (YI Value) The release sheet was peeled off from the photocurable adhesive sheet with release sheet, and the accumulated light intensity was 3000 (mJ / cm 2 ), the yellow index value (YI value) was measured based on JIS K7103 using a spectrophotometer (manufactured by Suga Test Instruments Co., Ltd.) "SC-T."

[0131] (3) Gel fraction The release sheet is peeled off from the photocurable adhesive sheet with the release sheet attached, and the sheet is wrapped in a bag with a SUS mesh (#200) whose mass (M) has been measured in advance. The opening of the bag is folded and closed, and the mass (M 1), then immersed in 100 mL of ethyl acetate and stored in the dark at 23°C for 24 hours, after which the package was removed and heated at 70°C for 4.5 hours to evaporate the ethyl acetate adhering to the package, and the mass of the dried package (M 2 ) was measured, and the gel fraction G1 before light irradiation was calculated by substituting the calculated mass into the following formula: Gel fraction G1 (%) = [(M 2 -M) / (M 1 -M)] x 100

[0132] In addition, for a laminate of a polarizing plate / photocurable adhesive sheet / polycarbonate-based resin plate having ultraviolet shielding properties, a high-pressure mercury lamp was used to irradiate the laminate from the polycarbonate-based resin plate having ultraviolet shielding properties with an integrated light amount of 3000 (mJ / cm2) at 405 nm. 2 ), the cured photocurable adhesive sheet portion was scraped off with a spatula, and the gel fraction G2 after light irradiation was determined in the same manner.

[0133] (4) High temperature and humidity resistance reliability A high-pressure mercury lamp was used to irradiate the polarizing plate / photocurable adhesive sheet / UV-shielding polycarbonate-based resin plate laminate from the UV-shielding polycarbonate-based resin plate side with an integrated light intensity of 3000 (mJ / cm2) at 405 nm. 2 ) to prepare a sample for evaluating the reliability of resistance to high temperature and high humidity. The evaluation sample was exposed to an environment of 85° C. and 85% RH for 1000 hours, and then the following evaluations were carried out. [Appearance evaluation] Those in which no defects in appearance such as bubbling or peeling were observed were rated as "◯ (good)", and those in which bubbling or peeling was observed were rated as "× (poor)". [Evaluation of polarizing plate decolorization] By visual observation, the polarizing plate where no discoloration was observed was rated as "◯ (good)", and the polarizing plate where the color was clearly faded was rated as "× (poor)".

[0134] [Table 1]

[0135] The laminates of Examples 1 to 5 did not use an acylphosphine oxide-based photopolymerization initiator or a phenyl glyoxylate-based photopolymerization initiator as a photopolymerization initiator in the photocurable adhesive composition forming the layer in contact with the polarizing plate, and the photocurable adhesive sheet was sufficiently cured by light irradiation from the laminate side of the polycarbonate-based resin plate having ultraviolet shielding properties. Furthermore, the laminate after the light irradiation did not cause discoloration of the polarizing plate even after exposure at 85°C, 85% RH, and 1000 hours, and good humidity and heat resistance reliability was obtained without appearance defects such as foaming or peeling.

[0136] The laminates of polarizing plate / photocurable adhesive sheet / UV-shielding polycarbonate-based resin plate in Comparative Examples 1 to 4 contain a specific amount or more of an acylphosphine oxide-based photopolymerization initiator or a phenyl glyoxylate-based photopolymerization initiator in the adhesive layer, and therefore the laminate after light irradiation did not show any appearance defects such as foaming or peeling after being exposed to 85°C, 85% RH, and 1,000 hours, but the polarizing plate suffered significant discoloration.

[0137] Furthermore, in a reference example in which the surface of the polyvinyl alcohol-based resin film layer was located at a depth of 90 μm from the outermost surface of the polarizing plate to which the adhesive sheet was attached, even when the photocurable adhesive sheet of Comparative Example 1 in which the photocurable adhesive composition contained a specific amount or more of an acylphosphine oxide-based photopolymerization initiator was used, no discoloration occurred in the polarizing plate, and good results were obtained. This shows that the present invention can be suitably used particularly in a configuration in which the photocurable pressure-sensitive adhesive sheet and the polarizer are close to each other.

[0138] In the above embodiment, specific embodiments of the present invention are shown, but the above embodiment is merely illustrative and should not be interpreted as being limiting. Various modifications that are obvious to those skilled in the art are intended to be within the scope of the present invention. [Industrial Applicability]

[0139] The laminate of the present invention is cured by visible light and can suppress appearance defects such as discoloration, foaming, and peeling of a polarizing plate even under high temperature and high humidity conditions, and therefore can be suitably used as a component of an in-vehicle image display device.

Claims

1. [I] A laminate having a layer structure of a polarizing plate / a photocurable adhesive sheet, [II] The polarizing plate has a layer structure in which a polarizer is laminated with a protective film on both sides thereof, [III] The distance (α) between the photocurable adhesive sheet and the polarizer is 80 μm or less, and the ratio (α / β) of the distance (α) between the photocurable adhesive sheet and the polarizer to the thickness (β) of the photocurable adhesive sheet is 0.1 to 0.5; [IV-1] A photocurable adhesive sheet is formed from a photocurable adhesive composition containing a (meth)acrylic acid ester (co)polymer and a photopolymerization initiator (A), and [IV-2] The light transmittance at a wavelength of 390 nm is less than 90%, and the light transmittance at a wavelength of 410 nm is 80% or more; [IV-3] A laminate, in which the total concentration of an acylphosphine oxide-based photopolymerization initiator and a phenyl glyoxylate-based photopolymerization initiator contained in the photocurable pressure-sensitive adhesive composition as the photopolymerization initiator (A) is 0.5 mass% or less.

2. [IV-4] The laminate according to claim 1, wherein the photocurable adhesive sheet is a photocurable adhesive sheet that can be cured even when irradiated with light having a wavelength of 390 to 410 nm.

3. 3. The laminate according to claim 1 or 2, wherein another component (X) is laminated via the photocurable adhesive sheet, and the other component (X) has a light transmittance of 10% or less at a wavelength of 365 nm and a light transmittance of 60% or more at a wavelength of 405 nm.

4. 4. The laminate according to claim 3, wherein the other component (X) is an ultraviolet ray shielding cover material.

5. The laminate according to any one of claims 1 to 4, wherein the protective film in the polarizing plate is a triacetyl cellulose-based resin film.

6. The laminate according to any one of claims 1 to 5, wherein the photocurable adhesive sheet has a thickness (β) of 50 to 500 μm.

7. The laminate according to any one of claims 1 to 6, wherein the photopolymerization initiator (A) contains at least one photopolymerization initiator selected from the group consisting of an α-aminoacetophenone-based photopolymerization initiator and a ketocoumarin-based photopolymerization initiator.

8. The laminate according to any one of claims 1 to 7, wherein the photocurable adhesive sheet has a yellow index value (YI value) of 2.0 or less.

9. The laminate according to any one of claims 1 to 8, wherein the photocurable pressure-sensitive adhesive composition contains a trifunctional or higher polyfunctional (meth)acrylate and / or a silane coupling agent.

10. The laminate according to any one of claims 1 to 9, wherein the (meth)acrylic acid ester (co)polymer is a graft copolymer having a macromonomer as a branch component.

11. In the photocurable adhesive sheet, an integrated light amount at a wavelength of 405 nm is 3000 (mJ / cm) through an ultraviolet ray shielding member having an ultraviolet ray shielding property. 2 11. The laminate according to claim 1, wherein, when the laminate is irradiated with light having a gel fraction of G1 before light irradiation and a gel fraction of G2 after light irradiation, a difference between the gel fraction G1 before light irradiation and the gel fraction G2 after light irradiation (gel fraction G2 after light irradiation - gel fraction G1 before light irradiation) is 10% or more.

12. The laminate according to any one of claims 1 to 11, wherein the photocurable pressure-sensitive adhesive sheet has a multilayer structure of two or more layers.

13. A laminate structure obtained by curing the laminate according to any one of claims 1 to 12 with visible light.

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