Laminate and laminated structure

Abstract

As a laminate capable of being photocured with visible light and in which discoloration, foaming, peeling, and other appearance defects of the polarizing plate are not observed even in a severe high-temperature high-humidity environment, a laminate is produced as follows: [I] the layer configuration of a polarizing plate / light-curable adhesive sheet is laminated, [II] the polarizing plate has a layer configuration obtained by laminating protective films for both sides of the polarizing sheet, [III] the distance (α) of the light-curable adhesive sheet from the polarizing sheet is 80 μm or less, [IV-1] the light-curable adhesive sheet is formed from a light-curable adhesive composition containing a (meth)acrylate (co)polymer and a photopolymerization initiator (A), and [IV-2] the transmittance of the laminate at a wavelength of 390 nm is less than 90%, the transmittance at a wavelength of 410 nm is 80% or more, [IV-3] as the aforementioned photopolymerization initiator (A), the total concentration of an acyloxyphosphine-based photopolymerization initiator and a phenyl glyoxylate-based photopolymerization initiator contained in the aforementioned light-curable adhesive composition is 0.5% by mass or less.

Description

Technical Field

[0001] The present invention relates to a laminate having an adhesive sheet for bonding a resin component that is UV-resistant and does not allow UV transmission, the laminate having a photocurable adhesive sheet having the property of curing upon exposure to light (hereinafter referred to as "photocurability"). Background Technology

[0002] In recent years, to improve the viewability of image display devices, the following operation has been performed: by filling the gaps between the image display panel (such as a liquid crystal display (LCD), plasma display panel (PDP), and electroluminescent display (ELD) and the protective panel and touch panel components disposed on its front surface side (viewing side) with an adhesive, the reflection of incident light and outgoing light from the displayed image at the air layer interface is suppressed. As a method of filling the gaps between the components of such an image display device with an adhesive, a method of filling the gaps between the components of the image display device using adhesive sheets is known.

[0003] In addition, in automotive image display devices, since they are easily exposed to ultraviolet light, in order to prevent the conductive components, polarizing plates and other resin components inside the image display device from yellowing and deteriorating due to ultraviolet exposure, ultraviolet-shielding glass covering components, resin covering components and other constituent components are sometimes used as window components and windshield panel components.

[0004] In this case, a photocurable adhesive sheet is sometimes used, which can be photocured by using light in the wavelength range that is transmissible to the UV-shielding component when UV light is irradiated from the outside of the UV-shielding component.

[0005] For example, Patent Document 1 discloses a method for manufacturing a display body, wherein an adhesive sheet is manufactured from a solvent-free adhesive composition containing an active energy ray curable component and a photopolymerization initiator with an absorbance of 0.3 or more at a wavelength of 390 nm and an optical path length of 10 mm in an acetonitrile solution at a concentration of 0.1% by mass. The adhesive sheet is then bonded to an ultraviolet shielding member to form a laminate. Subsequently, the adhesive sheet is cured by irradiating it with active energy rays through the ultraviolet shielding member.

[0006] In addition, Patent Document 2 discloses a method for manufacturing a display body, wherein a display body component containing an ultraviolet absorber is bonded together with an ultraviolet curable adhesive sheet containing a photopolymerization initiator with an absorbance of 0.3 or more at a wavelength of 380 nm in a 0.1% by mass acetonitrile solution, thereby creating a laminate, and ultraviolet light is irradiated through the aforementioned display body component containing the ultraviolet absorber to cure the adhesive sheet.

[0007] Patent document 3 discloses an adhesive sheet for bonding a UV-shielding component with UV-shielding properties. The adhesive sheet is formed from an active energy-curing adhesive containing an active energy-curing component and a cured product of the aforementioned active energy-curing component. It is applied across the UV-shielding component at a speed of 1000 mJ / cm². 2 When the adhesive sheet is irradiated with luminescent active energy rays of substantial intensity in the wavelength region of 380-450 nm, the gel fraction of the adhesive sheet is more than 70% and less than 100% when it is cured.

[0008] Patent Document 4 discloses a method for manufacturing a display body, wherein the display body comprises a display body component containing an ultraviolet absorber and a cured adhesive layer for bonding the aforementioned display body component containing the ultraviolet absorber. In the manufacturing method, the adhesive layer is cured by irradiating the aforementioned display body component with ultraviolet light, thereby forming a cured adhesive layer, and the gel fraction of the cured adhesive layer is set to 40% or more.

[0009] Existing technical documents

[0010] Patent documents

[0011] Patent Document 1: Japanese Patent No. 6360605

[0012] Patent Document 2: Japanese Patent No. 6420519

[0013] Patent Document 3: Japanese Patent No. 6438165

[0014] Patent Document 4: Japanese Patent No. 6676720 Summary of the Invention

[0015] The problem the invention aims to solve

[0016] It is known that polarizing plates used as components in image display devices can discolor in humid and hot environments due to polyolefination of the polyvinyl alcohol resin constituting the polarizer and decolorization by iodine. Furthermore, in laminates where polarizing plates are stacked with other components using photocurable adhesive sheets, the interaction between the polarizing plate and the photocurable adhesive sheet can sometimes accelerate discoloration of the polarizing plate in humid and hot environments. Therefore, for the aforementioned image display devices used in vehicles, excellent durability under high temperature and high humidity conditions is also required.

[0017] Patent documents 1-4 disclose adhesive sheets that can be photocured using light in the wavelength range of the UV-shielding component when irradiated with ultraviolet light from the outside of the component, and that show no appearance defects such as foaming or peeling even under harsh high temperature and high humidity environments. Only acylphosphine oxide-based photopolymerization initiators are cited as examples of photopolymerization initiators used. However, the adhesive sheets disclosed in patent documents 1-4 do not address the issue of discoloration of polarizing plates under harsh high temperature and high humidity environments.

[0018] Therefore, as a photocurable adhesive sheet that can be cured using visible light and thus suppress the discoloration of polarizing plates in humid and hot environments, it is not satisfactory and there is still room for improvement.

[0019] The present invention provides a laminate of a photocurable adhesive sheet and a polarizing plate that can be photocured using light in the wavelength range of the UV-transmittable UV-shielding component when UV light is irradiated from the outside of the UV-shielding component, and that no appearance defects such as discoloration, foaming, or peeling of the polarizing plate can be observed even in harsh high temperature and high humidity environments.

[0020] Solution for solving the problem

[0021] Through in-depth research, the inventors discovered that the above-mentioned problems can be solved by using a photopolymerization initiator capable of generating free radicals using visible light as a photocurable adhesive sheet, and by using an adhesive layer that minimizes the amount of acylphosphine oxide-based photopolymerization initiators and phenylacetalate-based photopolymerization initiators contained in the adhesive layer.

[0022] That is, the present invention is based on the following [1] to

[14] .

[0023] [1] A laminate, [I] comprising layers stacked to form a polarizing plate / photocurable adhesive sheet,

[0024] [II] The polarizing plate is composed of layers in which protective films are laminated on both sides of the polarizer.

[0025] [III] The distance (α) between the photocurable adhesive sheet and the polarizer is less than 80 μm.

[0026] [IV-1] The photocurable adhesive sheet is formed from a photocurable adhesive composition comprising a (meth)acrylate (co)polymer and a photopolymerization initiator (A), and

[0027] [IV-2] The aforementioned photocurable adhesive sheet has a transmittance of less than 90% at a wavelength of 390 nm and a transmittance of more than 80% at a wavelength of 410 nm.

[0028] [IV-3] As the aforementioned photopolymerization initiator (A), the total concentration of the acylphosphine oxide-based photopolymerization initiator and the phenylacetalate-based photopolymerization initiator contained in the aforementioned photocurable adhesive composition is less than 0.5% by mass.

[0029] [2] According to the laminate described in [1], wherein [IV-4] the aforementioned photocurable adhesive sheet is a photocurable adhesive sheet that can also be cured under light irradiation with a wavelength of 390 to 410 nm.

[0030] [3] The laminate according to [1] or [2] has other constituent components (X) laminated on it by means of the aforementioned photocurable adhesive sheet, wherein the other constituent components (X) have a transmittance of less than 10% at a wavelength of 365 nm and a transmittance of more than 60% at a wavelength of 405 nm.

[0031] [4] According to the laminate described in [3], wherein the aforementioned other constituent components (X) are ultraviolet-shielding covering materials.

[0032] [5] The laminate according to any one of [1] to [4], wherein the protective film in the aforementioned polarizing plate is a triacetyl cellulose resin film.

[0033] [6] The laminate according to any one of [1] to [5], wherein the ratio (α / β) of the distance (α) between the aforementioned photocurable adhesive sheet and the polarizer to the thickness (β) of the aforementioned photocurable adhesive sheet is 0.1 to 0.5.

[0034] [7] The laminate according to any one of [1] to [6], wherein the thickness (β) of the aforementioned photocurable adhesive sheet is 50 to 500 μm.

[0035] [8] The laminate according to any one of [1] to [7], wherein the aforementioned 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.

[0036] [9] The laminate according to any one of [1] to [8], wherein the yellow index value (YI value) of the aforementioned photocurable adhesive sheet is 2.0 or less.

[0037]

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

[0038]

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

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

[0039]

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

[11] , wherein, in the aforementioned photocurable adhesive sheet, the cumulative light intensity at a wavelength of 405 nm irradiated to the adhesive sheet via an ultraviolet-shielding member having ultraviolet-shielding properties is 3000 (mJ / cm²). 2 When exposed to light, the difference (G2-G1) between the gel fraction G1 before light irradiation and the gel fraction G2 after light irradiation is more than 10%.

[0040]

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

[12] , wherein the aforementioned photocurable adhesive sheet is composed of two or more layers.

[0041]

[14] A laminated structure, which is obtained by curing the laminated body described in any one of [1] to

[13] using visible light.

[0042] The effects of the invention

[0043] The laminate of the present invention can be cured using visible light, and the polarizing plate will not change color even in harsh high temperature and high humidity environments, thereby suppressing appearance defects such as foaming and peeling. Detailed Implementation

[0044] The following describes in detail the methods used to implement the present invention, but the present invention is not limited thereto.

[0045] In this invention, "(meth)acrylic acid" refers to acrylic acid or methacrylic acid, "(meth)acryloyl" refers to acryloyl or methacryloyl, and "(meth)acrylate" refers to acrylate or methacrylate.

[0046] In addition, "(meth)acrylate (co)polymer" refers to a resin obtained by polymerizing a polymeric component containing at least one (meth)acrylate monomer, and "(co)polymer" has the meaning of including polymers and copolymers.

[0047] In this invention, "sheet" means that "film" and "strip" are not specifically distinguished, but are described in a way that includes them.

[0048] It should be noted that in this invention, when referred to as "X~Y" (where X and Y are arbitrary numbers), unless otherwise specified, it includes the meaning of "X or more and Y or less", as well as the meaning of "preferably greater than X" or "preferably less than Y".

[0049] In addition, when it is indicated as "X or more" (where X is any number) or "Y or less" (where Y is any number), it also includes the meaning of "preferably greater than X" or "preferably less than Y".

[0050] Furthermore, "X and / or Y (X and Y can be any combination)" refers to at least one of X and Y, and specifically to the three possibilities of X only, Y only, and X and Y.

[0051] The laminate of the present invention (hereinafter sometimes referred to as "this laminate") is a laminate composed of layers stacked to form a photocurable adhesive sheet / polarizing plate. Furthermore, the aforementioned laminate may further include other constituent components (X) stacked using the aforementioned photocurable adhesive sheet. This laminate is primarily used in automotive image display devices.

[0052] Typically, photocurable adhesive sheets are bonded to a substrate by curing under ultraviolet light after being applied. However, as mentioned above, in automotive image display devices, polarizers and other components are prone to degradation under ultraviolet light. Therefore, ultraviolet-shielding glass or resin covering components are sometimes used. Thus, the photocurable adhesive sheet constituting this laminate, primarily used in automotive image display devices, possesses visible light curing properties, allowing it to be cured using visible light instead of ultraviolet light.

[0053] The aforementioned photocurable adhesive sheet is characterized in that it is formed from a photocurable adhesive composition comprising a (meth)acrylate (co)polymer and a photopolymerization initiator (A) that generates free radicals using visible light. The photopolymerization initiator (A) in the aforementioned photocurable adhesive composition contains a small amount of acylphosphine oxide-based photopolymerization initiator and phenylglyoxylate-based photopolymerization initiator. The components contained in the photocurable adhesive composition will be described below.

[0054] [(Meth)acrylate (co)polymer]

[0055] As for the (meth)acrylate (co)polymers used in the aforementioned photocurable adhesive compositions, in addition to homopolymers of (meth)acrylate alkyl esters, copolymers obtained by copolymerizing monomer components that can be copolymerized with them can also be listed. Among these, (meth)acrylate copolymers are preferred.

[0056] Examples of the aforementioned (meth)acrylate copolymers include, for instance, alkyl (meth)acrylates with alkyl groups having 1 to 18 carbon atoms and monomer components capable of copolymerizing therewith, or copolymers formed with monomer components comprising one or more monomers selected from (a) carboxyl-containing monomers, (b) hydroxyl-containing monomers, (c) amino-containing monomers, (d) epoxy-containing monomers, (e) amide-containing monomers, (f) vinyl monomers, and (g) macromonomers. Preferably, the copolymer is a (meth)acrylate copolymer obtained from alkyl (meth)acrylates with alkyl groups having 1 to 18 carbon atoms and a copolymer component comprising (e) amide-containing monomers and (g) macromonomers.

[0057] [Alkyl methacrylates with alkyl groups having 1 to 18 carbon atoms]

[0058] Alkyl esters of (meth)acrylate with 1 to 18 carbon atoms as the aforementioned alkyl group include, for example, 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, stearyl (meth)acrylate, and other straight-chain alkyl esters of (meth)acrylate; isopropyl (meth)acrylate, (methyl)... Isobutyl acrylate, sec-butyl acrylate, tert-butyl acrylate, isoamyl acrylate, neopentyl acrylate, 2-ethylhexyl acrylate, isooctyl acrylate, isononyl acrylate, tert-butylcyclohexyl acrylate, isodecanyl acrylate, isostearyl acrylate, isostearyl acrylate, isostearyl acrylate, isostearyl acrylate, isostearyl acrylate, isostearyl acrylate, etc. (meth)acrylate branched alkyl esters; cyclohexyl acrylate, isobornyl acrylate, 3,5,5-trimethylcyclohexane (meth)acrylate, dicyclopentyl acrylate, dicyclopentenyl acrylate, dicyclopentenoxyethyl acrylate, etc. (meth)acrylate cyclocyclic alkyl esters. These can be used alone or in combination of two or more. Preferably, the alkyl group has 6 to 14 carbon atoms and is a straight-chain or branched alkyl ester of (meth)acrylate; more preferably, lauryl acrylate or 2-ethylhexyl acrylate.

[0059] The content of the aforementioned alkyl (meth)acrylate with 1 to 18 carbon atoms is typically 30 to 90% by mass, preferably 35 to 88% by mass, more preferably 40 to 85% by mass, and particularly preferably 55 to 85% by mass in the total monomer components of the copolymer. If the content is too low, the hydrophobicity tends to decrease and water absorption is difficult to suppress; if the content is too high, the polarity tends to decrease and the adhesive strength tends to decrease.

[0060] [(a) Carboxyl-containing monomers]

[0061] Examples of the aforementioned carboxyl-containing monomers (a) include, for example, (meth)acrylic acid, 2-(meth)acryloyloxyethyl hexahydrophthalic acid, 2-(meth)acryloyloxypropyl hexahydrophthalic acid, 2-(meth)acryloyloxyethyl phthalic acid, 2-(meth)acryloyloxypropyl phthalic acid, 2-(meth)acryloyloxyethyl maleic acid, 2-(meth)acryloyloxypropyl maleic acid, 2-(meth)acryloyloxyethyl succinic acid, 2-(meth)acryloyloxypropyl succinic acid, crotonic acid, fumaric acid, maleic acid, itaconic acid, etc. These can be used alone or in combination of two or more.

[0062] The content of the carboxyl-containing monomer in (a) above is generally 10% by mass or less, preferably 8% by mass or less, and particularly preferably 5% by mass or less in the total monomer components of the copolymer.

[0063] [(b) Hydroxyl-containing monomers]

[0064] Examples of hydroxyl-containing monomers as described in (b) above include 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, 3-hydroxypropyl methacrylate, 2-hydroxybutyl methacrylate, and other hydroxyalkyl methacrylates. These can be used alone or in combination of two or more.

[0065] The content of the hydroxyl-containing monomer in (b) above is generally 30% by mass or less, preferably 25% by mass or less, and particularly preferably 20% by mass or less in the total monomer components of the copolymer.

[0066] [(c) Contains amino monomers]

[0067] Examples of amino-containing monomers as described in (c) above include, for instance, aminomethyl methacrylate, aminoethyl methacrylate, aminopropyl methacrylate, aminoisopropyl methacrylate, and other aminoalkyl methacrylates; N-alkylaminoalkyl methacrylate, N,N-dimethylaminoethyl methacrylate, N,N-dimethylaminopropyl methacrylate, and other N,N-dialkylaminoalkyl methacrylates. These can be used alone or in combination of two or more.

[0068] The content of the amino-containing monomer in (c) above is generally less than 20% by mass, preferably less than 10% by mass, in the total monomer components of the copolymer.

[0069] [(d) Epoxy-containing monomers]

[0070] Examples of epoxy-containing monomers as described in (d) above include glycidyl (meth)acrylate, methyl glycidyl (meth)acrylate, 3,4-epoxycyclohexyl methyl (meth)acrylate, and 4-hydroxybutyl (meth)acrylate glycidyl ether. They can be used alone or in combination of two or more.

[0071] The content of the epoxy-containing monomer in (d) mentioned above is generally less than 20% by mass, preferably less than 10% by mass, in the total monomer components of the copolymer.

[0072] [(e) Amide-containing monomers]

[0073] Examples of amide-containing monomers, such as (meth)acrylamide, N,N-dimethyl(meth)acrylamide, N-butyl(meth)acrylamide, N-hydroxymethyl(meth)acrylamide, N-hydroxymethylpropane(meth)acrylamide, N-methoxymethyl(meth)acrylamide, N-butoxymethyl(meth)acrylamide, diacetone(meth)acrylamide, maleamide, and maleimide, can be used alone or in combination of two or more. (meth)acrylamide is preferred.

[0074] The content of the aforementioned amide-containing monomer in (e) is typically 1 to 20% by mass in the total monomer composition of the copolymer, wherein, from the viewpoint of obtaining excellent adhesive properties, it is preferably 1.5 to 15% by mass, and particularly preferably 2 to 10% by mass.

[0075] [(f) Vinyl monomer]

[0076] As the aforementioned vinyl monomer (f), compounds having a vinyl group within the molecule can be listed. 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 styrene; and polyalkylene glycol di(meth)acrylates, etc. They can be one type or a combination of two or more.

[0077] The content of the aforementioned vinyl monomer in (f) is generally less than 40% by mass, preferably less than 35% by mass, and particularly preferably less than 30% by mass in the total monomer composition of the copolymer.

[0078] [(g) Macromolecular monomers]

[0079] The aforementioned (g) macromonomer refers to a polymer monomer having terminal functional groups and a high molecular weight backbone. Among them, the aforementioned (g) macromonomer is preferably a monomer in which the number of carbon atoms in the side chain is 20 or more when the (meth)acrylate copolymer is formed by copolymerization.

[0080] By using the aforementioned (g) macromonomer, a macromonomer can be introduced as a branch component of the (meth)acrylate copolymer, thus enabling the (meth)acrylate copolymer to be formed into a graft copolymer. Furthermore, the characteristics of the main chain and side chains of the graft copolymer can be modified by selecting (g) macromonomer and other monomers and adjusting their mixing ratios.

[0081] Examples of terminal functional groups in (g) macromonomers include free radical polymerizable groups such as (meth)acryloyl and vinyl groups; and functional groups such as hydroxyl, isocyanate, epoxy, carboxyl, amino, amide, and thiol groups. Preferably, the terminal functional group is capable of copolymerizing with other monomers, and (meth)acryloyl is particularly preferred. One or more of the aforementioned terminal functional groups may be present, but one is particularly preferred.

[0082] In addition, (g) macromolecular monomers may have the aforementioned functional groups in addition to terminal functional groups.

[0083] The backbone of the aforementioned macromonomer (g) is preferably composed of a (meth)acrylate (co)polymer or a vinyl polymer. Examples of its structural units include, for instance, alkyl (meth)acrylates with 1 to 18 carbon atoms in the aforementioned alkyl group, the aforementioned (a) carboxyl-containing monomers, the aforementioned (b) hydroxyl-containing monomers, the aforementioned (d) epoxy-containing monomers, and the aforementioned (e) amide-containing monomers. These can be used alone or in combination of two or more. Preferably, the backbone of the macromonomer (g) contains both hydrophobic and hydrophilic monomers as structural units.

[0084] As the aforementioned hydrophobic monomer, preferably an alkyl ester without a polar group (excluding methyl methacrylate), examples include n-butyl methacrylate, isobutyl methacrylate, sec-butyl methacrylate, tert-butyl methacrylate, amyl methacrylate, isoamyl methacrylate, neopentyl methacrylate, hexyl methacrylate, cyclohexyl methacrylate, heptyl methacrylate, 2-ethylhexyl acrylate, n-octyl acrylate, isooctyl acrylate, and so on. Nonyl methacrylate, isononyl methacrylate, tert-butylcyclohexyl methacrylate, decyl methacrylate, isodecyl methacrylate, undecyl methacrylate, lauryl methacrylate, cetyl methacrylate, stearyl methacrylate, isostearyl methacrylate, behenyl methacrylate, isobornyl methacrylate, cyclohexyl methacrylate, dicyclopentenoxyethyl methacrylate, methyl methacrylate, and other methacrylates. They can be used alone or in combination of two or more.

[0085] In addition to the aforementioned alkyl esters, other hydrophobic monomers include vinyl acetate, styrene, tert-butylstyrene, α-methylstyrene, vinyltoluene, alkyl vinyl monomers, and other vinyl monomers. These can be used alone or in combination of two or more.

[0086] As the aforementioned hydrophilic monomer, methyl methacrylate or esters having polar groups are preferred, such as methyl methacrylate, tetrahydrofurfuryl methacrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate, hydroxybutyl methacrylate, glyceryl methacrylate, and other methyl methacrylates containing hydroxyl groups; methyl acrylic acid, 2-(meth)acryloyloxyethyl hexahydrophthalic acid, 2-(meth)acryloyloxypropyl hexahydrophthalic acid, 2-(meth)acryloyloxyethyl phthalic acid, 2-(meth)acryloyloxypropyl phthalic acid, 2-(meth)acrylic acid... Monomers containing carboxyl groups include acyloxyethyl maleic acid, 2-(meth)acryloyloxypropyl maleic acid, 2-(meth)acryloyloxyethyl succinic acid, 2-(meth)acryloyloxypropyl succinic acid, crotonic acid, fumaric acid, maleic acid, itaconic acid, monomethyl maleate, and monomethyl itaconic acid; monomers containing anhydride groups include maleic anhydride and itaconic anhydride; epoxy-containing monomers include glycidyl acrylate, α-ethyl glycidyl acrylate, and 3,4-epoxybutyl acrylate; alkoxy polyalkylene glycol (meth)acrylates such as methoxy polyethylene glycol (meth)acrylate; and N,N-dimethylacrylamide and hydroxyethylacrylamide. These can be used alone or in combination of two or more.

[0087] In the aforementioned (g) macromonomer, from the viewpoint that the macromonomer from the main chain and side chain of the graft copolymer exhibits a moderate phase separation structure, it is preferable to obtain the macromonomer obtained by reacting isobornyl methacrylate, which is a hydrophobic monomer, and methyl methacrylate, which is a hydrophilic monomer, in a 1:1 ratio.

[0088] Furthermore, the glass transition temperature (Tg) of the aforementioned (g) macromonomer is preferably higher than the glass transition temperature of the copolymer component constituting the aforementioned (meth)acrylate (co)polymer.

[0089] Specifically, the glass transition temperature (Tg) of the (g) macromonomer affects the heating and melting temperature (hot melt temperature) of the photocurable adhesive composition, and is therefore preferably 30–120°C, more preferably 40–110°C, and particularly preferably 50–100°C. If the glass transition temperature (Tg) of the (g) macromonomer is within the aforementioned range, there is a tendency to maintain excellent processability and storage stability by adjusting the molecular weight, and to have hot melt properties around 50–80°C.

[0090] The glass transition temperature of the aforementioned macromonomer (g) refers to the glass transition temperature of the macromonomer itself, which can be determined using a differential scanning calorimeter (DSC).

[0091] If a macromonomer (g) is used as the copolymer component of the (meth)acrylate (co)polymer, the resulting (meth)acrylate (co)polymer can maintain a state where the branch components attract each other and undergo physical cross-linking at room temperature (25°C). Furthermore, by heating to a suitable temperature, the aforementioned physical cross-linking decomposes, resulting in flowability. Therefore, when forming the adhesive sheet described later, the sheet shape can be maintained in an uncured state. To obtain this property, it is preferable to adjust the molecular weight and content of the macromonomer.

[0092] The number average molecular weight of the aforementioned (g) macromonomer is preferably 500 to 20,000, more preferably 600 to 10,000, even more preferably 800 to 8,000, particularly preferably 1,000 to 7,000, and especially preferably 1,500 to 6,000.

[0093] Furthermore, the content of (g) macromonomers in the total monomer components of the copolymer is preferably 5 to 30% by mass, more preferably 6 to 25% by mass, and particularly preferably 8 to 20% by mass. If the content is too low, there is a tendency for the physical cross-linking between the branch components to be too weak, resulting in poor storage stability when placed at room temperature (25°C). If the content is too high, there is a tendency for the physical cross-linking between the branch components to be too strong, resulting in poor flowability when heated.

[0094] The aforementioned (meth)acrylate-based (co)polymers can be obtained by polymerizing (meth)acrylate alkyl esters or (meth)acrylate alkyl esters having 1 to 18 carbon atoms with monomer components capable of copolymerizing with them using existing known methods such as solution free radical polymerization, suspension polymerization, bulk polymerization, and emulsion polymerization.

[0095] The weight-average molecular weight of the (meth)acrylate-based (co)polymers obtained in this way is typically 50,000 to 1,500,000, preferably 70,000 to 1,300,000, particularly preferably 100,000 to 1,200,000, and even more preferably 150,000 to 1,000,000.

[0096] Here, the weight-average molecular weight is determined using the following method.

[0097] The substance obtained by dissolving the (meth)acrylate-based (co)polymer in tetrahydrofuran (THF) was used as the test sample. The molecular weight distribution curve was determined using a gel permeation chromatography (GPC) analyzer (device name: HLC-8320GPC manufactured by Tosoh Corporation) under the following conditions, and the weight-average molecular weight (Mw) was calculated.

[0098] • Protective column: TSKguardcolumnHXL

[0099] • Separation column: TSKgelGMHXL (4 columns)

[0100] Temperature: 40℃

[0101] Injection volume: 100μL

[0102] Polystyrene conversion

[0103] Solvent: THF

[0104] • Flow rate: 1.0 mL / min

[0105] In addition, the aforementioned (meth)acrylate (co)polymer is preferably provided with active energy ray crosslinking structural sites.

[0106] The aforementioned active energy ray crosslinking structure refers to, for example, a structural site that, in the presence of the photopolymerization initiator (A) described later, can react with a portion of the (meth)acrylate (co)polymer or a curing component other than the (meth)acrylate (co)polymer to form a crosslinking structure.

[0107] As cross-linking structural sites for the aforementioned active energy rays, examples include structures with free radical polymerizable functional groups such as (meth)acryloyl groups, vinyl groups, etc., which have unsaturated double bonds.

[0108] By giving the polymer chains of the aforementioned (meth)acrylate (co)polymer free radical polymerizable functional groups, the polymer chains can be directly polymerized to each other even without a crosslinking agent.

[0109] To introduce a structure with free radical polymerizable functional groups into (meth)acrylate (co)polymers, for example, a (meth)acrylate copolymer can be manufactured by using monomers with functional groups such as hydroxyl and carboxyl groups as copolymer components, and then a compound with functional groups capable of reacting with these functional groups and unsaturated double bonds (such as ethyl isocyanate of (meth)acrylate) can be reacted while maintaining the polymerizability of the unsaturated double bonds.

[0110] [Photopolymerization initiator (A)]

[0111] The photopolymerization initiator (A) included in the aforementioned photocurable adhesive composition is a visible light initiator that generates free radicals upon irradiation with visible light, light having wavelengths of at least 390 nm, 405 nm, and 410 nm, for example, light in the wavelength region of 380–700 nm, thus becoming the reaction starting point for the (meth)acrylate (co)polymer. By including the aforementioned photopolymerization initiator (A) in the photocurable adhesive composition, the photocurable adhesive composition can be cured using visible light. It should be noted that the aforementioned photopolymerization initiator (A) can generate free radicals solely upon irradiation with visible light, or it can generate free radicals upon irradiation with light in a wavelength region other than the visible light region.

[0112] The aforementioned photopolymerization initiator (A) preferably has an absorption coefficient of 10 mL / (g·cm) or higher at a wavelength of 405 nm, more preferably 15 mL / (g·cm) or higher, and particularly preferably 25 mL / (g·cm) or higher. By ensuring that the absorption coefficient at a wavelength of 405 nm is at or above the aforementioned value, sufficient curing (crosslinking) can be achieved by irradiation with visible light.

[0113] On the other hand, the upper limit of the absorption coefficient at a wavelength of 405 nm is preferably 1×10. 4 mL / (g·cm) or less, more preferably 1×10 3 The absorption coefficient is below mL / (g·cm). It should be noted that in this invention, photopolymerization initiators with an absorption coefficient of less than 10 mL / (g·cm) at a wavelength of 405 nm can be used in combination.

[0114] The aforementioned photopolymerization initiators (A) are broadly classified into two categories based on their free radical initiation mechanisms: cracking photopolymerization initiators, which can generate free radicals by breaking the single bonds of the photopolymerization initiator itself; and hydrogen abstraction photopolymerization initiators, which can transfer hydrogen from the hydrogen donor by forming an excited complex with the hydrogen donor in the system after photoexcitation.

[0115] The aforementioned crack-initiating photopolymerization initiator decomposes into other compounds when free radicals are generated by light irradiation. Once activated, it no longer functions as a reaction initiator. Therefore, it does not remain as an active species in the adhesive after the crosslinking reaction, and there is no possibility of unexpected photodegradation of the adhesive, making it preferred.

[0116] Examples of crack-opening photopolymerization initiators include, for instance, α-aminoacetophenone-based photopolymerization initiators such as 2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropane-1-one, 2-benzyl-2-(dimethylamino)-4'-morpholinopropylbenzophenone, and 2-dimethylamino-2-(4-methylbenzyl)-1-(4-morpholino-4-yl-phenyl)-butane-1-one; and 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. Photoinitiators such as benzoylacetyl ketal initiators, including 2,2-dimethoxy-1,2-diphenylethane-1-one; α-hydroxyacetophenone photoinitiators such as 1-hydroxycyclohexylphenyl ketone, 2-hydroxy-2-methyl-1-phenyl-propane-1-one, 1-(4-(2-hydroxyethoxy)phenyl)-2-hydroxy-2-methyl-1-propane-1-one, 2-hydroxy-1-[4-{4-(2-hydroxy-2-methyl-propanoyl)benzyl}phenyl]-2-methyl-propane-1-one, and oligomeric (2-hydroxy-2-methyl-1-(4-(1-methylvinyl)phenyl)propanone); phenylacetophenone ester photoinitiators such as methyl phenylglyoxylate; and derivatives of these crack-type visible light polymerization initiators.

[0117] As the aforementioned crack-type photopolymerization initiator, an α-aminoacetophenone-based photopolymerization initiator is preferred. α-Aminoacetophenone-based photopolymerization initiators do not produce acid when decomposed by light irradiation; therefore, they tend to suppress color change in polarizing plates.

[0118] It should be noted that in this invention, the center wavelength of the light absorption peak of the α-aminoacetophenone-based photopolymerization initiator deviates from the visible light region, which can lead to poor curing. Therefore, it is desirable to avoid using it. However, even if it is used, there is no such problem, and it can effectively suppress the discoloration of the polarizing plate.

[0119] On the other hand, even with the same crack-type photopolymerization initiator, the center wavelength of the light absorption peak of acylphosphine oxide-based photopolymerization initiators and phenylglyoxylate-based photopolymerization initiators is usually at the visible light absorption peak. From the viewpoint of minimizing concerns about poor curing, when used as photopolymerization initiators, in this invention, by reducing the amount of acylphosphine oxide-based photopolymerization initiators and phenylglyoxylate-based photopolymerization initiators contained in the adhesive sheet, discoloration of the polarizer can be suppressed. That is, among the aforementioned crack-type photopolymerization initiators, acylphosphine oxide-based photopolymerization initiators and phenylglyoxylate-based photopolymerization initiators generate free radicals upon light irradiation and decompose to produce acid. If this acid remains in the adhesive sheet after being bonded to the polarizer, it acts as a catalyst, sometimes causing discoloration due to the polyene formation of the polyvinyl alcohol-based resin constituting the polarizer. Therefore, in this invention, it is preferable not to use acylphosphine oxide-based photopolymerization initiators and phenylglyoxylate-based photopolymerization initiators, and they can be used within a range that does not affect the effect of this invention (0.5% by mass or less of the photocurable adhesive composition).

[0120] Examples of hydrogen-abstracting photopolymerization initiators include, for instance, bis(2-phenyl-2-glyoxylic acid)oxoethylene ester, methyl phenylglyoxylate, a mixture of ethyl 2-[2-oxo-2-phenyl-acetoxy-ethoxy]acetate and ethyl 2-[2-hydroxy-ethoxy]acetate, thioxanthone, 2-chlorothioxanthone, 3-methylthioxanthone, 2,4-dimethylthioxanthone, anthraquinone, 2-methylanthraquinone, 2-ethylanthraquinone, 2-tert-butylanthraquinone, 2-aminoanthraquinone, camphorquinone or its derivatives, ketocumarin or its derivatives, and other ketocumarin-based photopolymerization initiators.

[0121] As the aforementioned hydrogen-abstracting photopolymerization initiator, a ketocumarin-based photopolymerization initiator is preferred. Ketocoumarin-based photopolymerization initiators have sufficient visible light reactivity, and by adjusting the amount added, they tend to adjust yellowing to a practically acceptable level and suppress discoloration of polarizing plates.

[0122] It should be noted that in this invention, the use of ketocumarin-based photopolymerization initiators was avoided due to the anticipated adverse effect of yellowing. However, when used, this adverse effect did not occur, and the discoloration of the polarizing plate was effectively suppressed.

[0123] Among them, as the photopolymerization initiator (A), it is preferred to contain at least one photopolymerization initiator selected from the group consisting of α-aminoacetophenone-based photopolymerization initiators and ketocoumarin-based photopolymerization initiators.

[0124] It should be noted that the photopolymerization initiator (A) is not limited to the substances listed above. Any one of the photopolymerization initiators (A) listed above or its derivatives may be used, or two or more may be used in combination.

[0125] In addition to photopolymerization initiator (A), substances that generate free radicals only through irradiation by other light sources such as ultraviolet light can also be mixed.

[0126] The content of photopolymerization initiator (A) in the photocurable adhesive composition is typically 0.1 to 10 parts by weight relative to 100 parts by weight of (meth)acrylate (co)polymer, preferably 0.2 to 5 parts by weight, and more preferably 0.3 to 3 parts by weight.

[0127] By setting the content of photopolymerization initiator (A) within the aforementioned range, a suitable response sensitivity to visible light can be obtained.

[0128] In addition to the aforementioned (meth)acrylate (co)polymer and photopolymerization initiator (A), the photocurable adhesive composition used in this invention preferably contains a crosslinking agent and / or a silane coupling agent.

[0129] [Cross-linking agent]

[0130] Examples of crosslinking agents include compounds having at least one crosslinking functional group selected from (meth)acryloyl, epoxy, isocyanate, carboxyl, hydroxyl, carbodiimide, oxazoline, aziridinyl, vinyl, amino, imino, and amide groups. These can be used alone or in combination of two or more. Furthermore, the crosslinking functional group can be protected by a deprotecting group, or it can be a crosslinking agent chemically bonded to a (meth)acrylate (co)polymer.

[0131] Preferably, the compounds are photopolymerizable compounds with carbon-carbon double bonds, such as (meth)acryloyl groups and vinyl groups, and particularly preferably are polyfunctional (meth)acrylates. Here, polyfunctional means having two or more (meth)acryloyl groups.

[0132] Examples of the aforementioned multifunctional (meth)acrylates include, for instance, 1,4-butanediol dimethacrylate, glycerol dimethacrylate, neopentyl glycol dimethacrylate, glycerol glycidyl ether dimethacrylate, 1,6-hexanediol dimethacrylate, 1,9-nonanediol dimethacrylate, neopentyl glycol dimethacrylate with hydroxypentanoic acid, dimethacrylate of the ε-caprolactone adduct of neopentyl glycol with hydroxypentanoic acid, tricyclodecane dimethacrylate, tricyclodecanediethanol dimethacrylate, bisphenol A polyethoxydimethacrylate, bisphenol A polypropoxydimethacrylate, bisphenol F polyethoxydimethacrylate, ethylene glycol dimethacrylate, and other difunctional (meth)acrylates; trimethylolpropane trioxyethyl (meth)acrylate, ε-caprolactone-modified tri(2-hydroxyethyl)methacrylate, etc. Trifunctional (meth)acrylates such as tri(meth)acrylate, pentaerythritol tri(meth)acrylate, propoxylated pentaerythritol tri(meth)acrylate, and ethoxylated pentaerythritol tri(meth)acrylate; and tetrafunctional (meth)acrylates such as pentaerythritol tetra(meth)acrylate, propoxylated pentaerythritol tetra(meth)acrylate, ethoxylated pentaerythritol tetra(meth)acrylate, dipentaerythritol hexa(meth)acrylate, polyethylene glycol di(meth)acrylate, tri(acryloyloxyethyl)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 bis(trimethylolpropane tetra(meth)acrylate.

[0133] In addition to the above, other examples of multifunctional (meth)acrylates include polyester (meth)acrylates, epoxy (meth)acrylates, urethane (meth)acrylates, and polyether (meth)acrylates. These can be used alone or in combination of two or more.

[0134] Preferably, it is a polyfunctional (meth)acrylate with three or more functions, more preferably a trifunctional (meth)acrylate, and particularly preferably a propoxylated pentaerythritol tri(meth)acrylate.

[0135] The content of the crosslinking agent relative to 100 parts by weight of the aforementioned (meth)acrylate (co)polymer is preferably 0.5 to 50 parts by weight, more preferably 1 to 40 parts by weight, and more preferably 5 to 30 parts by weight. By setting this content within the aforementioned range, the adhesive strength and cohesive strength can be improved, and therefore it is preferred.

[0136] [Silane coupling agent]

[0137] Silane coupling agents can improve adhesion, especially to glass materials, and are therefore preferred.

[0138] Examples of silane coupling agents include compounds having unsaturated groups such as vinyl, acryloyloxy, and methacryloyloxy, as well as amino, epoxy, and hydrolyzable functional groups such as alkoxy.

[0139] Examples of silane coupling agents include N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane, N-(β-aminoethyl)-γ-aminopropylmethyldimethoxysilane, γ-aminopropyltriethoxysilane, γ-epoxypropoxypropyltrimethoxysilane, and γ-methacryloyloxypropyltrimethoxysilane. These can be used alone or in combination of two or more. From the viewpoint of good adhesion and minimal discoloration such as yellowing, γ-epoxypropoxypropyltrimethoxysilane is preferred.

[0140] The content of the aforementioned silane coupling agent is typically 0.05 to 5 parts by weight relative to 100 parts by weight of the (meth)acrylate (co)polymer, preferably 0.1 to 3 parts by weight. By setting this content within the aforementioned range, whitening can be avoided and adhesion can be improved, thus it is preferred.

[0141] It should be noted that, in the aforementioned photocurable adhesive composition, in addition to using silane coupling agents, coupling agents such as organotitanate compounds can also be effectively utilized.

[0142] [Other Materials]

[0143] The aforementioned photocurable adhesive composition may include, as other components, various additives such as light stabilizers, ultraviolet absorbers, metal deactivators, metal corrosion inhibitors, antioxidants, antistatic agents, hygroscopic agents, foaming agents, defoamers, inorganic particles, viscosity modifiers, tackifying resins, photosensitizers, and fluorescent agents; and reaction catalysts (tertiary amine compounds, quaternary ammonium compounds, tin lauryl compounds, etc.). Additionally, other known components commonly formulated into adhesive compositions may be appropriately included. These other components may be used alone or in combination of two or more.

[0144] (Preparation of photocurable adhesive compositions)

[0145] The aforementioned photocurable adhesive composition is obtained by mixing, for example, (meth)acrylate (co)polymer, photopolymerization initiator (A), preferably a crosslinking agent, a silane coupling agent, and other materials as needed, in specified amounts.

[0146] Alternatively, a heat treatment step can be added during the manufacture of the photocurable adhesive composition. In this case, it is desirable to perform heat treatment after the components of the aforementioned photocurable adhesive composition have been mixed in advance.

[0147] Furthermore, in the aforementioned mixing process, a substance that has been masterbatch-concentrated by condensing various mixed components can be used.

[0148] The aforementioned mixing method is not particularly limited, and can be, for example, a universal mixer, planetary mixer, Banbury mixer, kneader, frame mixer, pressure kneader, three-roll mill, two-roll mill, etc. When mixing the components of the photocurable adhesive composition, solvents can be used as needed, or a solvent-free system can be used. By making the photocurable adhesive composition a solvent-free system, the advantages of no solvent residue and improved heat and light resistance can be achieved.

[0149] <Photocurable adhesive sheets>

[0150] The photocurable adhesive sheet is formed from the aforementioned photocurable adhesive composition. For example, the adhesive sheet can be a single layer with only one layer, or a multilayer with two or more layers, preferably a multilayer with two or more layers. In the case of a multilayer composition, it is sufficient that at least the outermost layer is formed from the aforementioned photocurable adhesive composition; all layers can be formed from the aforementioned photocurable adhesive composition.

[0151] To form a photocurable adhesive sheet from the aforementioned photocurable adhesive composition, simply apply the photocurable adhesive composition. As for the method of applying the aforementioned photocurable adhesive composition, any general coating method is not particularly limited, and examples include, for instance, roller coating, die coating, gravure coating, comma coating, and screen printing.

[0152] From a practical standpoint, the thickness (β) of the aforementioned photocurable adhesive sheet is preferably 50–500 μm, more preferably 70–400 μm, and especially preferably 100–300 μm.

[0153] The photocurable adhesive sheet formed by this operation has photocurability and can be cured by irradiation with light. At this time, the photocurable adhesive sheet can be cured into a state with residual photocuring excess (also known as "pre-cured") or into an uncured state that has photocurability (called "uncured").

[0154] If the photocurable adhesive sheet to be formed is a pre-cured or uncured material, then after the photocurable adhesive sheet is pasted onto the substrate, the photocurable adhesive sheet can be photocured (also known as "primary curing"), which results in increased cohesion and improved adhesion.

[0155] In the aforementioned pre-curing process, it is sufficient to irradiate the adhesive sheet to reduce the gel content to 60% or less. However, it is not necessary to irradiate the light-curing adhesive sheet to pre-cur it; it can also be pre-cured by, for example, heat or curing.

[0156] Furthermore, the aforementioned photocurable adhesive sheet can be pre-laminated with a release sheet in an unused state before being applied to the substrate to create an adhesive sheet with a release sheet, which can then be used by peeling off the release sheet. The aforementioned release sheet is typically laminated on both sides of the photocurable adhesive sheet. The aforementioned adhesive sheet with a release sheet can be manufactured, for example, by coating the aforementioned photocurable adhesive composition onto the release sheet to form an adhesive layer, followed by laminating other release sheets.

[0157] As the aforementioned release sheet, known release sheets can be appropriately used. For example, release sheets or release papers can be obtained by coating a sheet formed of polyester resin, polyolefin resin, polycarbonate resin, polystyrene resin, acrylic resin, triacetyl cellulose resin, fluorine resin, etc. with silicone resin and then performing a release treatment. They can exist alone or in layers of two or more.

[0158] The aforementioned release sheet preferably has a light transmittance of 40% or less at wavelengths below 410 nm, more preferably 30% or less, and particularly preferably 20%. If the light transmittance of the release sheet at wavelengths below 410 nm is less than the aforementioned value, it can effectively prevent photopolymerization of the adhesive sheet due to visible light during storage.

[0159] Here, as a release film with a transmittance of 40% or less at wavelengths below 410 nm, that is, a film that partially blocks the transmission of visible light and ultraviolet light, examples such as (1) to (7) can be listed below.

[0160] (1) A laminate with an ultraviolet absorbing layer is formed by coating one side of a cast film or a stretched film made of resins such as polyester resin, polypropylene resin, and polyethylene resin with a micro-adhesive resin that has re-peelability and coating the other side with a coating containing an ultraviolet absorber.

[0161] (2) A laminate obtained by coating one side of a cast film or a stretched film made of resins such as polyester resin, polypropylene resin, or polyethylene resin with a micro-adhesive resin mixed with an ultraviolet absorber and having re-peelability.

[0162] (3) A laminate obtained by coating a micro-adhesive resin with re-peelability onto a cast film or a stretched film formed by mixing a polyester resin, a polypropylene resin, a polyethylene resin or the like with an ultraviolet absorber.

[0163] (4) A layer of resin without ultraviolet absorber is formed on one or both sides of a layer of resin such as polyester resin, polypropylene resin, or polyethylene resin mixed with ultraviolet absorber, and a micro-adhesive resin with re-peelability is coated on one side of the resulting multilayer cast film or stretched film to obtain a laminate.

[0164] (5) A laminate is obtained by coating a coating containing an ultraviolet absorber on one side of a cast film or a stretched film formed of a resin such as a polyester resin, a polypropylene resin, or a polyethylene resin, and then coating the ultraviolet absorber with a micro-adhesive resin having re-peelability.

[0165] (6) A laminate is obtained by coating one side of a cast film or a stretched film formed of a resin such as a polyester resin, a polypropylene resin, or a polyethylene resin with a coating containing an ultraviolet absorber to form an ultraviolet absorbing layer, and coating the other side with a micro-adhesive resin with re-peelability.

[0166] (7) A laminate obtained by laminating one side of a resin film coated with a micro-adhesive resin with re-peelability and formed of a resin such as a polyester resin, a polypropylene resin, or a polyethylene resin with another prepared resin film by means of an adhesive layer and / or an adhesive layer containing an ultraviolet absorber.

[0167] The thickness of the aforementioned release sheet is not particularly limited, but from the viewpoint of processability and operability, it is preferably 25 to 500 μm, more preferably 38 to 250 μm, and particularly preferably 50 to 200 μm.

[0168] In the case of release sheets stacked on both sides of the adhesive layer of the aforementioned photocurable adhesive sheet, these release sheets can have the same stacking configuration, material, and thickness, or they can have different stacking configurations, materials, and thicknesses. Furthermore, these release sheets can use release sheets with different peel forces.

[0169] In addition, the aforementioned release sheet may have other layers as needed, such as an antistatic layer, a hard coating layer, and an anchoring layer.

[0170] By layering other release sheets on the formed adhesive layer, it is possible to obtain an adhesive sheet with release sheets.

[0171] In addition, when the photocurable adhesive sheet is composed of multiple layers, it can be manufactured by the following methods: applying the aforementioned photocurable adhesive composition onto a substrate sheet or release sheet to form a first adhesive sheet, further applying the photocurable adhesive composition onto the first adhesive sheet to form a second adhesive sheet, and repeating the above operations; forming the first adhesive sheet and the second adhesive sheet separately, and then bonding their respective coated surfaces together; or forming the first adhesive sheet and the second adhesive sheet simultaneously from the aforementioned photocurable adhesive composition by multilayer coating and co-extrusion molding.

[0172] It should be noted that the aforementioned photocurable adhesive sheet can be formed without a release sheet, for example, by directly coating the photocurable adhesive composition onto the polarizing plate and the adherend (other constituent components (X)) and forming a sheet. Alternatively, the photocurable adhesive composition can be directly extruded to form the photocurable adhesive sheet. Furthermore, the photocurable adhesive sheet can be formed by injecting the photocurable adhesive composition into a mold, or by directly filling the space between the polarizing plate and the other constituent components (X) that are the adherend to form the photocurable adhesive sheet.

[0173] Regarding the photocurable adhesive sheet obtained through such operation, when the photocurable adhesive composition includes an acylphosphine oxide-based photopolymerization initiator and a phenylglyoxylate-based photopolymerization initiator as photopolymerization initiators (A), its 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. It should be noted that the lower limit is of course 0% by mass. That is, the aforementioned photocurable adhesive sheet can suppress the discoloration of the polarizer caused by acid by reducing the content of the acylphosphine oxide-based photopolymerization initiator and the phenylglyoxylate-based photopolymerization initiator, which decompose and generate acid due to light irradiation.

[0174] In addition, when the photocurable adhesive sheet is composed of two or more layers, the concentrations of the acylphosphine oxide-based photopolymerization initiator and the phenylacetaldehyde ester-based photopolymerization initiator contained in the photocurable adhesive composition forming the layer in contact with the polarizing plate are within the aforementioned range.

[0175] (Light transmittance)

[0176] The aforementioned photocurable adhesive sheet has a transmittance of less than 90% at a wavelength of 390 nm and a transmittance of more than 80% at a wavelength of 410 nm.

[0177] Regarding photocurable adhesive compositions obtained by mixing photopolymerization initiators that have absorption in the ultraviolet-visible light region at a wavelength of around 400nm, the greater the light absorption of the photopolymerization initiator, the lower the light transmittance at the wavelength of 390nm from which the absorption originates, the better the photosensitivity and the easier it is to cure.

[0178] On the other hand, if the transmittance at a wavelength of 410nm is not high enough, the color of the photocurable adhesive sheet will be yellow when it is made, making it difficult to use in image display devices.

[0179] If the transmittance at a wavelength of 390 nm is less than 90%, sufficient visible light curability can be ensured. Therefore, it is preferable that if the transmittance at a wavelength of 410 nm is greater than 80%, a sufficiently low yellow index (YI) value can be achieved for the bonding of optical components that require transparency.

[0180] The aforementioned photocurable adhesive sheet has a transmittance of less than 90% at a wavelength of 390 nm, preferably less than 88%.

[0181] In addition, the aforementioned photocurable adhesive sheet has a light transmittance of 80% or more at a wavelength of 410 nm, preferably 85% or more, and particularly preferably 90% or more.

[0182] To set the transmittance of the photocurable adhesive sheet as described above, any photopolymerization initiator (A) that absorbs visible light can be used, provided that the absorption peak edge sufficiently reaches 390 nm and the absorption peak at 410 nm is relatively smaller. In particular, at least one selected from the group consisting of α-aminoacetophenone-based photopolymerization initiators and ketocoumarin-based photopolymerization initiators can be used. However, this method is not limited to this method.

[0183] Furthermore, the aforementioned photocurable adhesive sheet can also be cured under light irradiation with a wavelength of 390–410 nm.

[0184] (Yellow Index Value)

[0185] Regarding the aforementioned photocurable adhesive sheet, from the viewpoint of transparency, the cumulative light intensity is 3000 (mJ / cm²). 2 After being irradiated with UV light from a high-pressure mercury lamp in a manner that allows for illumination, the yellow index value measured according to JIS K7103 is preferably 2.0 or less, and more preferably 1.9 or less.

[0186] (Gel fraction)

[0187] The gel fraction G1 of the aforementioned photocurable adhesive sheet before light irradiation is typically 50% or less, preferably 40% or less, and particularly preferably 20% or less. It should be noted that the lower limit is 0%. If the gel fraction is below the aforementioned value, there is a tendency for a sufficient amount of excess uncrosslinked components that can be cured by light irradiation (in a pre-cured or uncured state), resulting in increased flexibility.

[0188] The aforementioned gel fraction was determined using the following method.

[0189] The mass of the aforementioned photocurable adhesive sheet (mass before impregnation) was determined by wrapping it in a bag using an SUS sieve (#200), impregnating it with ethyl acetate, and storing it in the dark at 23°C for 24 hours. Subsequently, the bag was 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 impregnation) was then determined, and the gel fraction was calculated using the following formula.

[0190] Gel fraction (%) = [(mass after impregnation) / (mass before impregnation)] × 100

[0191] To adjust the gel fraction G1 before light irradiation to the aforementioned range, it is sufficient to thoroughly remove residual catalyst during the polymerization of the (meth)acrylate (co)polymer and the processing of the photocurable adhesive sheet, or to use polymerization inhibitors, antioxidants, etc., to prevent unexpected curing (crosslinking) reactions due to heat, light, etc., before the main curing. Furthermore, in the case of pre-curing by light irradiation, it is sufficient to sufficiently reduce the cumulative amount of light irradiated for pre-curing to increase the amount of uncrosslinked components. However, this method is not limited to this approach.

[0192] Furthermore, the cumulative light intensity at a wavelength of 405 nm when the photocurable adhesive sheet is irradiated through a UV-shielding component is 3000 mJ / cm². 2 When exposed to light, the gel fraction G2 after light irradiation is typically 40–100%, preferably 50–100%, and particularly preferably 60–100%. If the gel fraction G2 of the photocurable adhesive sheet after light irradiation is within the aforementioned range, there is a tendency that no appearance defects such as foaming or peeling can be observed even under harsh high temperature and high humidity environments.

[0193] Furthermore, the difference (G2-G1) between the gel fraction G1 before light irradiation and the gel fraction G2 after light irradiation is preferably 10% or more, more preferably 30% or more, and particularly preferably 60% or more. If the difference in gel fraction between the photocurable adhesive sheet before and after light curing is greater than or equal to the aforementioned values, it tends to exhibit high cohesiveness and increased foaming resistance even under harsh high-temperature and high-humidity environments. It should be noted that the upper limit is typically 100%.

[0194] To achieve a gel fraction difference of more than the aforementioned value in the photocurable adhesive sheet before and after light irradiation, a photopolymerization initiator (A) with absorption at a wavelength of 405 nm can be used, for example. However, this method is not limited to this approach.

[0195] It should be noted that the aforementioned "ultraviolet shielding property" refers to a transmittance of less than 10% at a wavelength of 365nm and a transmittance of more than 60% at a wavelength of 405nm. For this ultraviolet shielding component, a material such as "Iupilon sheet MR58, 1.0mm thick" manufactured by Mitsubishi Gas Chemical Co., Ltd. is sufficient.

[0196] Furthermore, "cumulative light intensity at a wavelength of 405 nm" refers to the total amount of irradiation energy received per unit area. Specifically, it refers to the total amount of light irradiation energy measured using an ultraviolet cumulative light intensity meter "UIT-250" (manufactured by USIO Electric Corporation) and a light receiver "UVD-C405" (manufactured by USIO Electric Corporation) within a wavelength range that corresponds to the photosensitivity characteristics of the light receiver (having a photosensitivity with a peak at 405 nm extending to a wavelength range of 320–470 nm). More specifically, it refers to the cumulative light intensity obtained according to the method described in the embodiments.

[0197] As described above, the aforementioned photocurable adhesive sheets are stacked to form a polarizing plate / photocurable adhesive sheet layer, and an object having this stacked structure becomes the stack.

[0198] (Polarizing plate)

[0199] The aforementioned polarizing plate is not particularly limited, and examples include polarizing plates obtained by laminating a protective film such as a triacetyl cellulose resin film, an acrylic resin film, a polyester resin film, or a cyclic olefin polymer resin film onto both sides of a polyvinyl alcohol resin layer (polarizer) obtained by adsorbing and oriented iodine compound molecules onto a polyvinyl alcohol resin film. Among these, from the viewpoint that it has excellent optical isotropy due to not being stretched, a polarizing plate obtained by laminating a triacetyl cellulose resin film onto both sides of the polarizer is preferred.

[0200] Furthermore, from the viewpoint of preventing discoloration of the polarizer due to moisture infiltration, the moisture permeability of the aforementioned protective film is preferably 1 to 1000 g / m³. 2 / day), preferably 5-800 (g / m³) 2 / day), further preferably 10-600 (g / m 2 / sky).

[0201] In addition, in this laminate, it is important that the distance (α) between the photocurable adhesive sheet and the polarizer is 80 μm or less, preferably 10 to 80 μm, and more preferably 10 to 50 μm.

[0202] It should be noted that the aforementioned distance (α) between the photocurable adhesive sheet and the polarizer refers to the distance from the surface of the polarizer (polyvinyl alcohol resin film layer) on the side of the polarizer to be bonded to the photocurable adhesive sheet to the surface where the photocurable adhesive sheet contacts the polarizer.

[0203] Furthermore, from the viewpoint of suppressing color change of the polarizing plate, the ratio (α / β) of the distance (α) between the adhesive sheet and the polarizing sheet to the thickness (β) of the aforementioned 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.

[0204] In recent years, there has been a trend towards thinner displays in order to reduce weight, and there has also been a trend towards thinner polarizing plates. However, when the polarizing plate is made thinner, from the viewpoint that even if the distance (α) between the photocurable adhesive sheet and the polarizer is similar, the polarizing plate color change can be suppressed, the above range is preferred.

[0205] This laminate is preferably further laminated with other constituent components (X) using the aforementioned photocurable adhesive sheet.

[0206] (Other constituent components (X))

[0207] As other constituent components (X), it is preferable to have a transmittance of less than 10% at a wavelength of 365nm and a transmittance of more than 60% at a wavelength of 405nm, that is, a component with ultraviolet light blocking properties (ultraviolet light blocking covering material).

[0208] If the transmittance of other constituent components (X) is less than 10% at a wavelength of 365nm and more than 60% at a wavelength of 405nm, it can effectively block (isolate) the transmission of ultraviolet rays, suppress the light degradation of other constituent components (X) themselves and the polarizing plate that exists in the presence of the photocurable adhesive sheet, and reduce the yellow index value (YI value) to the level required for the laminate.

[0209] As other constituent components (X), examples include constituent components that use resin material as the main component and are adjusted to have the aforementioned transmittance by using ultraviolet absorbers.

[0210] Examples of resin materials mentioned above include those containing polycarbonate or acrylic resins as the main component resin. Here, "main component resin" refers to the resin that constitutes the other constituent component (X) and contains the largest amount by mass of it.

[0211] There is no particular limitation on the method of using a photocurable adhesive sheet to laminate other constituent components (X). After laminating one of the polarizing plate or other constituent components (X) with the photocurable adhesive sheet, the other can be laminated with the photocurable adhesive sheet. Alternatively, the polarizing plate and other constituent components (X) can be laminated with the photocurable adhesive sheet simultaneously.

[0212] The resulting laminate is then cured by irradiating it with visible light to form a laminated structure. This laminated structure is primarily used as a component of automotive image display devices.

[0213] Example

[0214] Hereinafter, embodiments and comparative examples of the present invention will be described in further detail. However, the present invention is not limited to the embodiments described below.

[0215] [Example 1]

[0216] (Manufacturing of UV-curable adhesive sheets)

[0217] For an acrylic graft copolymer (weight-average molecular weight: 160,000) formed by random copolymerization of 13.5 parts by mass of a macromonomer with methacryloyl group at the end (number average molecular weight: 3000) formed by random copolymerization of isobornyl methacrylate and methyl methacrylate in a 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, 1 kg of which is formed by random copolymerization of these components, 15 g of α-aminoacetophenone-based 2-benzyl-2-(dimethylamino)-4'-morpholinopropyl benzophenone (manufactured by IGM Corporation: Omnirad 369) as a photopolymerization initiator, 50 g of propoxylated pentaerythritol triacrylate (manufactured by Shin-Nakamura Chemical Co., Ltd., NK ESTER ATM-4PL) as a crosslinking agent, and 1.5 g of 3-glycidoxypropyltrimethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd.: KBM403) as a silane coupling agent, a photocurable adhesive composition is obtained by uniformly mixing.

[0218] Next, the aforementioned photocurable adhesive composition is molded into a sheet with a thickness of 150 μm on a surface-peeled polyethylene terephthalate film (manufactured by Mitsubishi Chemical Corporation, DIAFOIL MRV, thickness 100 μm), and then covered with a surface-peeled polyethylene terephthalate film (manufactured by Mitsubishi Chemical Corporation, DIAFOIL MRQ, thickness 75 μm) to produce a photocurable adhesive sheet with a release sheet.

[0219] (Polarizing plate)

[0220] As a polarizing plate, the following polarizing plate is used: an adhesive layer, a triacetyl cellulose resin film, and a coating are sequentially stacked on both sides of a polyvinyl alcohol resin film (12 μm) with iodine adsorption orientation, wherein the surface of the aforementioned polyvinyl alcohol resin film layer is located at a depth of 35 μm from the outermost surface of the polarizing plate to be bonded.

[0221] (Other constituent components (X))

[0222] As other constituent components (X), a polycarbonate resin sheet with UV shielding properties (1.0 mm thick, 0% transmittance at 365 nm, 83% transmittance at 405 nm, manufactured by Mitsubishi Gas Chemical Co., Ltd., Iupilonsheet MR58) is used.

[0223] (Manufacturing of laminates)

[0224] After peeling off one side of the photocurable adhesive sheet with a release sheet, roll-bonding it on one side of the aforementioned polarizing plate, peeling off the other side of the release sheet with the photocurable adhesive sheet, and roll-bonding a polycarbonate resin plate with UV shielding properties as the aforementioned other constituent components (X), a laminate having a polarizing plate / photocurable adhesive sheet / UV shielding polycarbonate resin plate is obtained.

[0225] The distance between the photocurable adhesive sheet and the polarizer in the resulting laminate (the distance from the surface of the polyvinyl alcohol-based resin film layer on the side of the polarizer to which the photocurable adhesive sheet is to be bonded to the surface where the photocurable adhesive sheet contacts the polarizer) is 35 μm. Furthermore, the ratio of the distance between the photocurable adhesive sheet and the polarizer to the thickness of the photocurable adhesive sheet is 0.2.

[0226] [Example 2]

[0227] As a photopolymerization initiator, 15 g of α-aminoacetophenone-based 2-dimethylamino-2-(4-methylbenzyl)-1-(4-morpholinylphenyl)-butane-1-one (IGM Corporation: Omnirad 379) was used. Otherwise, the same procedure as in Example 1 was followed to obtain a photocurable adhesive sheet with a release liner and a laminate of a polarizing plate / photocurable adhesive sheet / polycarbonate resin plate with UV shielding properties.

[0228] [Example 3]

[0229] As a photopolymerization initiator, 15 g of 2-methyl-1-[4-(methylthio)phenyl]-2-morpholinylpropane-1-one (IGM Corporation: Omnirad 907) was used. Otherwise, the same procedure as in Example 1 was followed to obtain a photocurable adhesive sheet with a release liner and a laminate of a polarizing plate / photocurable adhesive sheet / polycarbonate resin plate with UV shielding properties.

[0230] [Example 4]

[0231] As a photopolymerization initiator, 5g of a ketocoumarin derivative (manufactured by IGM: Esacure 3644) was used. Otherwise, the same procedure as in Example 1 was followed to obtain 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.

[0232] [Example 5]

[0233] As a photopolymerization initiator, 3g of ethyl phenyl (2,4,6-trimethylbenzoyl)phosphinate (IGM Corporation: Omnirad TPO-L) was used, and 50g of pentaerythritol triacrylate (Ninakamura Chemical Co., Ltd.: NK ESTER ATMM-3L) was used as a crosslinking agent. Otherwise, the same procedure as in Example 1 was followed, and the resulting photocurable adhesive composition was used as an adhesive sheet (1) for the intermediate layer (thickness: 200μm).

[0234] As a photopolymerization initiator, 3g of ethyl phenyl (2,4,6-trimethylbenzoyl)phosphinate (manufactured by IGM Corporation: Omnirad TPO-L) was used; as a crosslinking agent, 80g of propoxylated pentaerythritol triacrylate (manufactured by Shin-Nakamura Chemical Co., Ltd.: NK ESTER ATM-4PL) was used. Otherwise, the procedure was the same as in Example 1 to obtain a photocurable adhesive composition. Furthermore, the procedure was the same as in Example 1 to manufacture photocurable adhesive sheets with release sheets from the obtained photocurable adhesive composition, producing adhesive sheets (2) (thickness: 25 μm) for both the inner and outer layers, and ('2') (thickness: 25 μm).

[0235] The PET films on both sides of the middle layer adhesive sheet are peeled off in sequence, and the adhesive surfaces of the inner and outer layers adhesive sheets (2) and ('2') are sequentially bonded to the two surfaces to make a photocurable adhesive sheet with a thickness of 250μm consisting of (2) / (1) / ('2').

[0236] Subsequently, the same procedure as in Example 1 was followed to obtain a photocurable adhesive sheet with a release liner, and a laminate of a polarizing plate / photocurable adhesive sheet / polycarbonate resin plate with UV shielding properties.

[0237] [Comparative Example 1]

[0238] As a photopolymerization initiator, 15g of diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide (manufactured by IGM Corporation: Omnirad TPO) was used. Otherwise, the same procedure as in Example 1 was followed to obtain 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.

[0239] [Comparative Example 2]

[0240] As a photopolymerization initiator, 15g of ethyl phenyl (2,4,6-trimethylbenzoyl)phosphinate (manufactured by IGM Corporation: Omnirad TPO-L) was used. Otherwise, the same procedure as in Example 1 was followed to obtain a photocurable adhesive sheet with a release liner and a laminate of a polarizing plate / photocurable adhesive sheet / polycarbonate resin plate with UV shielding properties.

[0241] [Comparative Example 3]

[0242] As a photopolymerization initiator, 15 g of a mixture of acylphosphine oxides [2,4,6-trimethylbenzoyl-diphenylphosphine oxide (concentration ratio: about 46%), oligomer (2-hydroxy-2-methyl-1-(4-(1-methylvinyl)phenyl)acetone (concentration ratio: about 50%), 2,4,6-trimethylbenzophenone (concentration ratio: about 3.2%), 4-methylbenzophenone (concentration ratio: about 0.8%)] (manufactured by IGM: Esacure KTO46) was used. Otherwise, the procedure was the same as in Example 1 to obtain a photocurable adhesive sheet with a release sheet and a laminate of a polarizing plate / photocurable adhesive sheet / polycarbonate resin sheet with UV shielding properties.

[0243] [Comparative Example 4]

[0244] As a photopolymerization initiator, 15g of methyl benzoylformate (manufactured by IGM Corporation: Omnirad MBF) was used. Otherwise, the same procedure as in Example 1 was followed to obtain 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.

[0245] [Reference Example]

[0246] As a polarizing plate, a polarizing plate with the surface of a polyvinyl alcohol-based resin film layer positioned at a depth of 90 μm from the outermost surface of the polarizing plate to be bonded to the adhesive sheet is used. Otherwise, the same procedure as in Comparative Example 1 is followed to obtain a laminate of polarizing plate / photocurable adhesive sheet / polycarbonate-based resin plate with UV shielding properties.

[0247] The photocurable adhesive sheets and laminates with release sheets obtained in Examples 1-5, Comparative Examples 1-4, and Reference Examples were evaluated as follows. The results are shown in Table 1 below.

[0248] (1) Light transmittance

[0249] Peel off the release sheet from the photocurable adhesive sheet with the release sheet attached, and use a spectrophotometer (Shimadzu UV2000) to measure the spectral transmittance (%T) of the photocurable adhesive sheet at wavelengths of 300–800 nm.

[0250] (2) Yellow Index (YI value)

[0251] Peel off the release film from the photocurable adhesive sheet with the release film to accumulate a light intensity of 3000 (mJ / cm). 2 After irradiating the high-pressure mercury lamp with UV light, the yellow index (YI value) was measured using a spectrophotometer (Suga Test Instruments) "SC-T" according to JIS K7103.

[0252] (3) Gel fraction

[0253] Peel the release sheet off the light-curing adhesive sheet with the release sheet attached. Wrap the package in a bag using a SUS sieve (#200) with a pre-measured mass (M). Fold and seal the opening of the bag. Measure the mass (M1) of the package. Immerse the package in 100 mL of ethyl acetate and store it in the dark at 23°C for 24 hours. Remove the package and heat it at 70°C for 4.5 hours to evaporate the attached ethyl acetate. Measure the mass (M2) of the dried package. Substitute the calculated mass into the following formula to determine the gel fraction G1 before light irradiation.

[0254] Gel fraction G1 (%) = [(M2-M) / (M1-M)] × 100

[0255] In addition, for the laminate of polarizing plate / photocurable adhesive sheet / polycarbonate resin board with UV shielding, a high-pressure mercury lamp was used, and the cumulative light intensity at 405nm was 3000 (mJ / cm). 2 After irradiating the side of the polycarbonate resin plate with UV shielding, the cured photocurable adhesive sheet was scraped off with a scraper, and the gel fraction G2 after irradiation was determined using the same method.

[0256] (4) High temperature and high humidity resistance reliability

[0257] For a laminate of polarizing plate / photocurable adhesive sheet / polycarbonate resin board with UV shielding properties, the cumulative light intensity at 405 nm using a high-pressure mercury lamp is 3000 (mJ / cm). 2 A high-temperature and high-humidity reliability evaluation sample was prepared by irradiating light from the side of a polycarbonate resin plate with ultraviolet shielding properties.

[0258] After exposing the aforementioned evaluation samples to an environment of 85°C and 85%RH for 1000 hours, the following evaluation was performed.

[0259] [Appearance Evaluation]

[0260] No defects such as foaming or peeling are observed and are marked as "○ (good)", while defects such as foaming or peeling are observed and are marked as "× (poor)".

[0261] [Evaluation of color fading on polarizing plates]

[0262] Based on visual observation, cases where no discoloration of the polarizing plate is observed are judged as "○ (good)", and cases where a significant lightening of the color is observed are judged as "× (poor)".

[0263] [Table 1]

[0264]

[0265] In the laminates of Examples 1-5, the photocurable adhesive composition forming the layer in contact with the polarizing plate does not use acylphosphine oxide-based photopolymerization initiators or phenylacetaldehyde ester-based photopolymerization initiators as photopolymerization initiators. The photocurable adhesive sheet is fully cured by irradiating the laminate side of the polycarbonate resin board with UV shielding properties. Furthermore, the aforementioned laminates do not experience polarizing plate discoloration after exposure to 85°C and 85% RH for 1000 hours after irradiation. In addition, good moisture and heat resistance reliability is achieved without foaming, peeling, or other appearance defects.

[0266] In the laminates of polarizing plates / photocurable adhesive sheets / polycarbonate resin sheets with UV shielding properties in Comparative Examples 1 to 4, the adhesive layer contains a specific amount or more of acylphosphine oxide-based photopolymerization initiator or phenylacetalate-based photopolymerization initiator. Therefore, after exposure to light at 85°C and 85%RH for 1000 hours, the laminates did not exhibit any appearance defects such as foaming or peeling, but the polarizing plates showed significant discoloration.

[0267] In addition, in the reference example where the surface of the polyvinyl alcohol-based resin film layer is located at a depth of 90 μm from the outermost surface of the polarizing plate of the adhesive sheet, even when using the photocurable adhesive sheet of Comparative Example 1, which contains a specific amount or more of an acylphosphine oxide-based photopolymerization initiator in the photocurable adhesive composition, the polarizing plate did not change color, showing good results.

[0268] This demonstrates that the present invention is particularly suitable for use in configurations where the distance between the photocurable adhesive sheet and the polarizer is close.

[0269] The above embodiments illustrate specific forms of the present invention, but these embodiments are merely illustrative and not intended to be limiting. Various modifications that are obvious to those skilled in the art should be considered to fall within the scope of the present invention.

[0270] Industrial availability

[0271] The laminate of the present invention can be cured by visible light, and can suppress appearance defects such as discoloration, foaming, and peeling of polarizing plates even under high temperature and high humidity. Therefore, it can be suitable for use as a component of an image display device for vehicle use.

Claims

1. A laminate which is layered into a layer configuration of a polarizing plate / photocurable adhesive sheet, the polarizing plate has a layer configuration obtained by laminating protective films for both sides of a polarizing sheet, a distance (a) of the photocurable adhesive sheet from the polarizing sheet is 10 to 80 μm, and a thickness (β) of the photocurable adhesive sheet is 50 to 500 μm, a ratio (a / β) of the distance (a) of the photocurable adhesive sheet from the polarizing sheet to the thickness (β) of the photocurable adhesive sheet is 0.1 to 0.5, the photocurable adhesive sheet is formed from a photocurable adhesive composition containing a (meth)acrylate polymer and a photopolymerization initiator (A), and a light transmittance at a wavelength of 390 nm of the laminate is less than 90%, and a light transmittance at a wavelength of 410 nm is 80% or more, a total concentration of an acyloxyphosphine-based photopolymerization initiator and a phenyl glyoxylate-based photopolymerization initiator contained in the photocurable adhesive composition as the photopolymerization initiator (A) is 0.5% by mass or less.

2. The laminate according to claim 1, wherein The photocurable adhesive sheet is a photocurable adhesive sheet which is capable of undergoing curing also under irradiation of light having a wavelength of 390 to 410 nm.

3. The laminate according to claim 1 or 2, which is layered with other constituent members (X) by means of the photocurable adhesive sheet, the other constituent members (X) having a light transmittance at a wavelength of 365 nm of 10% or less and a light transmittance at a wavelength of 405 nm of 60% or more.

4. The laminate according to claim 3, wherein The other constituent members (X) are ultraviolet light-shielding cover materials.

5. The laminate according to claim 1 or 2, wherein The protective film in the polarizing plate is a triacetyl cellulose-based resin film.

6. The laminate according to claim 1 or 2, wherein The photopolymerization initiator (A) contains at least one photopolymerization initiator selected from the group consisting of an a-aminoacetophenone-based photopolymerization initiator and a ketocoumarin-based photopolymerization initiator.

7. The laminate according to claim 1 or 2, wherein The photocurable adhesive sheet has a yellow index value (YI value) of 2.0 or less.

8. The laminate according to claim 1 or 2, wherein The photocurable adhesive composition contains a multifunctional (meth)acrylate having a functionality of three or more and / or a silane coupling agent.

9. The laminate according to claim 1 or 2, wherein The (meth)acrylate polymer is a (meth)acrylate copolymer.

10. The laminate according to claim 1 or 2, wherein The (meth)acrylate polymer is a graft copolymer having a macromonomer as a branch component.

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

12. The laminate according to claim 1 or 2, wherein The photocurable adhesive sheet is a multilayer configuration of two or more layers.

13. A laminated structure which is obtained by curing the laminate according to any one of claims 1 to 12 using visible light.

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