Pressure-sensitive adhesive for optical films and pressure-sensitive adhesive layer for optical films

Abstract

To provide means for obtaining an adhesive layer obtained by at least one of heating and optical curing, having a high refractive index, having durability in severe environment (high temperature, highly humid and heat shock, etc.) and excellent even in transparency.SOLUTION: An adhesive for optical films includes a (meth) acrylic ester copolymer (A). The (meth) acrylic ester copolymer (A) includes (a1): a constitutional unit derived from a (meth) acrylic ester monomer having an aromatic hydrocarbon group and (a2); and a constitutional unit derived from a (meth) acrylic monomer having a hydroxy group, where the content of the constitutional unit derived from the (a2) component is 0.1 mass% or more and 25 mass% or less when using the total constitutional units of the (meth) acrylic ester copolymer (A) as 100 mass%, and the refractive index of an adhesive layer cured by subjecting the adhesive for optical films to at least one of heating and optical curing is 1.58 or more and 1.80 or less.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a pressure-sensitive adhesive for an optical film and a pressure-sensitive adhesive layer for an optical film. [Background technology]

[0002] A surface light source device including an organic electroluminescence element (hereinafter also simply referred to as "organic EL element") typically has a surface light emitter including an organic EL element and a light extraction film provided on the light-emitting surface of the surface light emitter. The light extraction film is a film having a concave-convex structure on its surface to increase light extraction efficiency, and may be provided with an adhesive layer for bonding the surface light emitter and the light extraction film together. With such a surface light source device, light generated in the organic EL element passes through the adhesive layer and the light extraction film and is emitted outside the device.

[0003] In such a surface light source device, it is particularly advantageous for the adhesive layer to have a high refractive index in order to improve light extraction efficiency. For example, Patent Document 1 discloses a pressure-sensitive adhesive composition containing, as a main component, an acrylic polymer containing an aromatic ring-containing copolymerizable monomer as a monomer unit, and having a refractive index within a predetermined range after drying and / or curing, as an adhesive agent for obtaining an adhesive layer with a high refractive index.

[0004] Furthermore, Patent Document 2 discloses a pressure-sensitive adhesive characterized by comprising at least an acrylic copolymer containing, as copolymerization components, an acrylic acid alkyl ester that does not contain an aromatic ring and an aromatic ring-containing monomer, and the copolymerization ratio of the aromatic ring-containing monomer component is 40 to 90% by weight of the total monomer components. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2002-173656 [Patent Document 2] Japanese Patent Application Laid-Open No. 2003-13029 Summary of the Invention [Problem to be solved by the invention]

[0006] However, the techniques described in Patent Documents 1 and 2 above have the problem that a high refractive index cannot be ensured, resulting in a decrease in light extraction efficiency. Additionally, the techniques described in the above Patent Documents also have the problem that the resulting pressure-sensitive adhesive layer has insufficient durability and transparency.

[0007] The present invention has been made in consideration of the above circumstances, and aims to provide a means for obtaining an adhesive layer obtained by at least one of a heat treatment and a photocuring treatment, which has a high refractive index, durability under harsh environments (high temperature, high humidity, heat shock, etc.), and excellent transparency. [Means for solving the problem]

[0008] The present inventors have conducted extensive research to solve the above problems, and as a result have found that a pressure-sensitive adhesive having the following configuration can solve the above problems, thereby completing the present invention.

[0009] That is, a pressure-sensitive adhesive for optical films according to one embodiment of the present invention comprises a (meth)acrylic acid ester copolymer (A), which comprises (a1): a structural unit derived from a (meth)acrylic acid ester monomer having an aromatic hydrocarbon group, and (a2): a structural unit derived from a hydroxy group-containing (meth)acrylic monomer, and the content of the structural unit derived from the hydroxy group-containing (meth)acrylic acid ester monomer (a2) is 0.1 mass% or more and 25 mass% or less of all structural units of the (meth)acrylic acid ester copolymer (A), and the refractive index of the pressure-sensitive adhesive layer cured by subjecting the pressure-sensitive adhesive for optical films to at least one of a heat treatment and a photo-curing treatment is 1.58 or more and 1.80 or less. [Effects of the Invention]

[0010] According to the present invention, a means can be provided for obtaining an adhesive layer that has a high refractive index, durability under harsh environments (high temperature, high humidity, heat shock, etc.), and excellent transparency, obtained by performing at least one of a heat treatment and a photocuring treatment. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a schematic cross-sectional view of a polarizing plate with an optical compensation layer. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, embodiments of the present invention will be described, but the technical scope of the present invention should be defined based on the claims and is not limited to the following embodiments. In this specification, unless otherwise specified, operations and measurements of physical properties are performed at room temperature (20°C to 25°C) and a relative humidity of 40% RH to 50% RH. In this specification, "(meth)acrylic" is a general term for acrylic and methacrylic. In addition, in this specification, "(co)polymer" is a general term for a homopolymer formed by polymerization of a single monomer and a copolymer formed by polymerization of multiple types of monomers.

[0013] <Adhesives for optical films> A pressure-sensitive adhesive for optical films (hereinafter also simply referred to as "pressure-sensitive adhesive") according to one embodiment of the present invention comprises a (meth)acrylic acid ester copolymer (A), which comprises (a1): a structural unit derived from a (meth)acrylic acid ester monomer having an aromatic hydrocarbon group, and (a2): a structural unit derived from a hydroxy group-containing (meth)acrylic monomer, and the content of the structural unit derived from the hydroxy group-containing (meth)acrylic acid ester monomer (a2) is 0.1 mass% or more and 25 mass% or less of all structural units of the (meth)acrylic acid ester copolymer (A), and the pressure-sensitive adhesive layer cured by subjecting the pressure-sensitive adhesive for optical films to at least one of a heat treatment and a photo-curing treatment has a refractive index of 1.58 or more and 1.80 or less.

[0014] The pressure-sensitive adhesive for optical films of the present invention having such a configuration can be subjected to at least one of a heat treatment and a photo-curing treatment to form a pressure-sensitive adhesive layer having a high refractive index, durability under harsh environments (high temperature, high humidity, heat shock, etc.), and excellent transparency.

[0015] The present invention will be described in detail below.

[0016] [(Meth)acrylic acid ester copolymer (A)] The pressure-sensitive adhesive for optical films according to the present invention essentially contains a (meth)acrylic acid ester copolymer (a) (hereinafter also simply referred to as "copolymer (A)").

[0017] The weight-average molecular weight (Mw) of the copolymer (A) according to the present invention, as determined by gel permeation chromatography (GPC), is not particularly limited, but is preferably from 500,000 to 2,000,000, and more preferably from 700,000 to 2,000,000. If the weight-average molecular weight (Mw) is less than 500,000, durability may be reduced. On the other hand, if the weight-average molecular weight (Mw) exceeds 2,000,000, the adhesive may become too viscous, failing to ensure coatability, resulting in coating streaks and coating defects, making it difficult to obtain a normal adhesive layer.

[0018] The weight-average molecular weight (Mw) of the copolymer (A) determined by gel permeation chromatography (GPC) is more preferably 900,000 or more and 2,000,000 or less, from the viewpoint of further improving durability under harsh environments (high temperature, high humidity, heat shock, etc.). The weight-average molecular weight (Mw) is particularly preferably more than 1,000,000 and 2,000,000 or less. The weight-average molecular weight (Mw) of the copolymer (A) of the present invention can be easily controlled by those skilled in the art as follows. That is, it can be easily controlled by appropriately adjusting reaction conditions such as the type and / or amount of polymerization initiator used in the polymerization reaction described below, reaction temperature, reaction time, etc.

[0019] The weight average molecular weight (Mw) of the copolymer (A) can be measured in detail by the method shown in the Examples.

[0020] In the present invention, the structural units constituting the copolymer (A) are: (a1) a structural unit derived from a (meth)acrylic acid ester monomer having an aromatic hydrocarbon group (hereinafter also referred to simply as "component (a1)"); (a2) a structural unit derived from a hydroxy group-containing (meth)acrylic monomer (hereinafter also referred to simply as "component (a2)"); In addition, if necessary, (a3) a structural unit derived from a monomer other than the above component (a1) and component (a2) and having one radically polymerizable functional group; Includes.

[0021] In this specification, for example, "copolymer X contains a structural unit derived from monomer Y1 and a structural unit derived from monomer Y2" means that when copolymer X is obtained by copolymerization, monomer Y1 and monomer Y2 are contained as raw material monomers used.

[0022] The structural units derived from each monomer that can constitute the copolymer (A) according to the present invention will be explained below in order. Note that the components (a1) and (a2) are monomers having one (meth)acryloyl group in the molecule. Monomers having two or more (meth)acryloyl groups in the molecule are classified as crosslinking agents (D) described below, and are different from the components (a1) and (a2) and also different from the component (a3) ​​described below.

[0023] Components (a1) to (a3) ​​will be explained below.

[0024] ((Meth)acrylic acid ester monomer (a1) having an aromatic hydrocarbon group) The copolymer (a) contains a structural unit derived from a (meth)acrylic acid ester monomer (a1) (hereinafter also referred to as "component (a1)"). In the pressure-sensitive adhesive of the present invention, the structural unit derived from component (a1) is the basic skeleton of the polymer, and increases the refractive index of the pressure-sensitive adhesive after drying or curing, and improves the durability of the pressure-sensitive adhesive. The component (a1) can be used alone or in combination of two or more. Furthermore, the component (a1) can be a commercially available product or a synthetic product.

[0025] The component (a1) is typically represented by the following formula (1):

[0026] [ka]

[0027] In the above formula (1), R 1 represents a hydrogen atom or a methyl group, and R 2 represents an aromatic hydrocarbon group.

[0028] The aromatic hydrocarbon group is not particularly limited, but preferred examples include aromatic hydrocarbon groups having a carbon number of 6 to 20. Specific examples thereof include a benzene ring group, a biphenyl ring group, a phenoxybenzyl group, a naphthalene ring group, an azulene ring group, an anthracene ring group, a phenanthrene ring group, a pyrene ring group, a chrysene ring group, a naphthacene ring group, a triphenylene ring group, an o-terphenyl ring group, an m-terphenyl ring group, a p-terphenyl ring group, and a fluorene ring group.

[0029] The aromatic hydrocarbon group may further contain a sulfur element. An example of the aromatic hydrocarbon group containing a sulfur element is a dinaphthothiophene group.

[0030] More specific examples of the (meth)acrylic acid ester monomer having an aromatic hydrocarbon group include benzyl (meth)acrylate, phenyl (meth)acrylate, benzylphenyl (meth)acrylate, p-phenylbenzyl acrylate, o-phenylphenol (meth)acrylate, ethoxylated o-phenylphenol (meth)acrylate, phenoxy (meth)acrylate, pt-butylphenyl (meth)acrylate, phenoxyethyl (meth)acrylate, phenoxypropyl (meth)acrylate, phenoxydiethylene glycol (meth)acrylate, ethylene oxide-modified nonylphenol (meth)acrylate, ethylene oxide-modified cresol (meth)acrylate, phenol ethylene oxide-modified (meth)acrylate, 2-hydroxy-3-phenoxypropyl (meth)acrylate, methoxybenzyl (meth)acrylate, Monomers having a benzene ring group, such as acrylate, m-phenoxybenzyl (meth)acrylate, chlorobenzyl (meth)acrylate, cresyl (meth)acrylate, and polystyryl (meth)acrylate; monomers having a naphthalene ring group, such as hydroxyethylated β-naphthol acrylate, 2-naphthoethyl (meth)acrylate, 2-naphthoxyethyl acrylate, 2-(4-methoxy-1-naphthoxy)ethyl (meth)acrylate, 1-naphthylmethyl (meth)acrylate, 2-naphthylmethyl acrylate, and hydroxynaphthyl (meth)acrylate; monomers having a biphenyl ring group, such as biphenyl (meth)acrylate; fluorenyl (meth)acrylate, 9-fluorenylmethyl (meth)acrylate (9-(meth)acryloyloxymethylfluorene), and hydroxyfluorenyl (meth)acrylate.

[0031] Furthermore, more specific examples of the (meth)acrylic acid ester monomer having an aromatic hydrocarbon group containing a sulfur element include monomers having a dinaphthothiophene group, such as 5-dinaphthothiophenylethyl (meth)acrylate, 6-dinaphthothiophenylethyl (meth)acrylate, and 6-dinaphthothiophenylmethyl (meth)acrylate.

[0032] Among these (a1) components, from the viewpoint that the pressure-sensitive adhesive layer cured by at least one of a heat treatment and a photocuring treatment exhibits a higher refractive index and is also excellent in durability, a monomer having at least one group selected from the group consisting of a biphenyl ring group, a phenoxybenzyl group, a naphthalene ring group, and a fluorene ring group is preferred.Furthermore, at least one selected from the group consisting of m-phenoxybenzyl (meth)acrylate, 1-naphthylmethyl (meth)acrylate, hydroxynaphthyl (meth)acrylate, fluorenyl (meth)acrylate, 9-fluorenylmethyl acrylate (9-acryloyloxymethylfluorene), and hydroxyfluorenyl (meth)acrylate is more preferred.

[0033] The content of the structural units derived from the (a1) component in the copolymer (A) is not particularly limited, but is preferably 10% by mass or more and 99.9% by mass or less, with the total structural units in the copolymer (A) being 100% by mass.

[0034] When the content of the structural unit derived from the component (a1) is 10% by mass or more, the refractive index after at least one of a heat treatment and a photocuring treatment becomes higher. On the other hand, when it is 99.9% by mass or less, a high refractive index is easily ensured. The content is more preferably 75% by mass or more and 99% by mass or less, and even more preferably 80% by mass or more and 99% by mass or less.

[0035] ((Meth)acrylic Monomer (a2) Having a Hydroxy Group) The copolymer (a) contains a structural unit derived from a (meth)acrylic monomer (a2) having a hydroxy group (hereinafter also referred to as "component (a2)"). The structural unit derived from the (meth)acrylic monomer (a2) having a hydroxy group is hydrophilic. Therefore, in the pressure-sensitive adhesive layer, the water retention performance of the polymer is improved, and condensation can be prevented. Furthermore, when the pressure-sensitive adhesive layer is left at room temperature after a moist heat test, an increase in haze can be suppressed. The component (a2) can be used alone or in combination of two or more. Furthermore, the component (a2) can be a commercially available product or a synthetic product.

[0036] A monomer having both a hydroxy group and an aromatic hydrocarbon group is classified as component (a1).

[0037] More specific examples of the (a2) component include 4-hydroxybutyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, hydroxymethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 1,4-cyclohexanedimethanol monoacrylate, N-(2-hydroxyethyl)(meth)acrylamide, N-(2-hydroxypropyl)(meth)acrylamide, and N-(2,2-dimethyl-β-hydroxyethyl)(meth)acrylamide.

[0038] Among these, 4-hydroxybutyl(meth)acrylate and N-(2-hydroxyethyl)(meth)acrylamide are preferred from the viewpoints of good transparency, less gel components in the copolymer, and good appearance.

[0039] The content of the structural units derived from component (a2) in copolymer (a) is 0.1% by mass or more and 25% by mass or less, where the total structural units in copolymer (a) is 100% by mass. If the content derived from component (a2) is less than 0.1% by mass, the haze after a moist heat durability test decreases. On the other hand, if it exceeds 25% by mass, the moist heat durability decreases, and coatability cannot be ensured, resulting in coating streaks and coating defects, making it difficult to obtain a normal pressure-sensitive adhesive layer. The content of the structural units derived from component (a2) is preferably 0.1% by mass or more and 20% by mass or less, more preferably 0.5% by mass or more and 15% by mass or less, and even more preferably 0.7% by mass or more and 12% by mass or less. Furthermore, the content of the structural units derived from component (a2) is even more preferably 0.7% by mass or more and 11% by mass or less, and particularly preferably 1% by mass or more and 10% by mass or less, where the total structural units in copolymer (a) is 100% by mass. Furthermore, the content of structural units derived from component (a2) is preferably at least 0.1% by mass but less than 12% by mass.

[0040] (Monomer (a3) ​​other than component (a1) and component (a2) and having one radically polymerizable functional group) The copolymer (A) according to the present invention preferably further contains a structural unit derived from a monomer (a3) ​​(hereinafter also referred to as "component (a3)") having one radically polymerizable functional group other than the above-mentioned components (a1) and (a2). In the pressure-sensitive adhesive layer, the structural unit derived from component (a3) ​​has the effect of improving adhesiveness and durability. The component (a3) ​​can be used alone or in combination of two or more types. Furthermore, the component (a3) ​​may be a commercially available product or a synthetic product.

[0041] Examples of component (a3) ​​include (meth)acrylic acid alkyl ester monomers, (meth)acrylic acid alkyl ester monomers having an alkoxyalkyl group or an alkoxyalkylene glycol group, (meth)acrylic acid ester monomers having an acyl group or an epoxy group, monomers having a carboxy group, (meth)acrylic monomers having a phosphate group, monomers having a sulfonic acid group, (meth)acrylic monomers having a urethane group, (meth)acrylic monomers having an amino group, (meth)acrylic monomers having an amide group, vinyl monomers having a silane group, styrene, chlorostyrene, α-methylstyrene, vinyltoluene, vinyl chloride, vinyl acetate, vinyl propionate, acrylonitrile, vinylpyridine, and 2-(meth)acryloyloxyethyl phthalate.

[0042] Specific examples of the (meth)acrylic acid alkyl ester monomer include, for example, methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, t-butyl (meth)acrylate, n-pentyl (meth)acrylate, isopentyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-hexyl (meth)acrylate, n n-heptyl (meth)acrylate, n-octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-nonyl (meth)acrylate, n-decyl (meth)acrylate, n-dodecyl (meth)acrylate (n-lauryl (meth)acrylate), cyclopentyl (meth)acrylate, cyclohexyl (meth)acrylate, isobornyl (meth)acrylate, dicyclopentanyl (meth)acrylate, adamantyl (meth)acrylate, and the like.

[0043] Specific examples of (meth)acrylic acid alkyl ester monomers having an alkoxyalkyl group or an alkoxyalkylene glycol group include methoxyethyl (meth)acrylate, ethoxymethyl (meth)acrylate, ethoxyethyl (meth)acrylate, propoxyethyl (meth)acrylate, butoxyethyl (meth)acrylate, methoxypropyl (meth)acrylate, methoxybutyl (meth)acrylate; ethoxy-diethylene glycol (meth)acrylate, ethoxy-triethylene glycol (meth)acrylate, methoxy-triethylene glycol (meth)acrylate, methoxy-diethylene glycol (meth)acrylate, propoxy-diethylene glycol (meth)acrylate, methoxy-triethylene glycol (meth)acrylate, 2-ethylhexyl-diglycol (meth)acrylate (2-ethylhexyloxy-diethylene glycol (meth)acrylate), methoxy-polyethylene glycol (meth)acrylate (n = 4 or more and 10 or less), and methoxydipropylene glycol (meth)acrylate.

[0044] Specific examples of the (meth)acrylic acid ester monomer having an acyl group or an epoxy group include glycidyl (meth)acrylate and 2-acetoacetoxyethyl (meth)acrylate.

[0045] Specific examples of monomers having a carboxy group include (meth)acrylic acid, maleic acid, maleic anhydride, fumaric acid, fumaric anhydride, crotonic acid, itaconic acid, itaconic anhydride, myristoleic acid, palmitoleic acid, and oleic acid.

[0046] Specific examples of the (meth)acrylic monomer having a phosphoric acid group include 2-methacryloyloxyethyl diphenyl phosphate (meth)acrylate, trimethacryloyloxyethyl phosphate (meth)acrylate, and triacryloyloxyethyl phosphate (meth)acrylate.

[0047] Specific examples of the monomer having a sulfonic acid group include sodium sulfopropyl (meth)acrylate, sodium 2-sulfoethyl (meth)acrylate, and sodium 2-acrylamido-2-methylpropanesulfonate.

[0048] A specific example of a (meth)acrylic monomer having a urethane group is urethane(meth)acrylate.

[0049] Specific examples of the (meth)acrylic monomer having an amino group include dimethylaminoethyl (meth)acrylate, diethylaminoethyl (meth)acrylate, Nt-butylaminoethyl (meth)acrylate, and (meth)acryloyloxyethyltrimethylammonium chloride.

[0050] Specific examples of (meth)acrylic monomers having an amide group include N-(meth)acryloylmorpholine, N,N-dimethyl(meth)acrylamide, N,N-diethyl(meth)acrylamide, (meth)acrylamide, N-isopropyl(meth)acrylamide, Nt-butyl(meth)acrylamide, and diacetone(meth)acrylamide.

[0051] Specific examples of vinyl monomers having a silane group include vinyltrimethoxysilane, vinyltriethoxysilane, vinyltris(β-methoxyethyl)silane, vinyltriacetylsilane, and methacryloyloxypropyltrimethoxysilane.

[0052] Among these, n-butyl(meth)acrylate, isobornyl(meth)acrylate, N-(meth)acryloylmorpholine, and 2-ethylhexyl(meth)acrylate are preferred from the viewpoint of more efficiently achieving the effects of the present invention.

[0053] The content of the structural units derived from the (a3) ​​component in copolymer (A) is not particularly limited, but is preferably 3% by mass or more and 80% by mass or less, with the total structural units in copolymer (a) being 100% by mass. Furthermore, the content of the structural units derived from the (a3) ​​component in copolymer (A) is more preferably 5% by mass or more and 50% by mass or less, and even more preferably 10% by mass or more and 30% by mass or less, with the total structural units in copolymer (a) being 100% by mass. When two or more types of (a3) ​​components are used, the above content represents the total content of the (a3) ​​components.

[0054] [Method for producing copolymer (A)] Next, a method for producing the copolymer (A) will be described. In the present invention, the method for producing the copolymer (A) is not particularly limited. Specifically, conventionally known methods such as solution polymerization using a polymerization initiator, bulk polymerization, emulsion polymerization, suspension polymerization, reverse-phase suspension polymerization, thin-film polymerization, and spray polymerization can be used. Examples of polymerization control methods include adiabatic polymerization, temperature-controlled polymerization, and isothermal polymerization. The polymerization initiator may be either a thermal polymerization initiator or a photopolymerization initiator. Furthermore, in addition to or in addition to the method of initiating polymerization using a polymerization initiator, a method of initiating polymerization by irradiation with active energy rays such as radiation, electron beams, and ultraviolet rays can also be used. Among these, solution polymerization using a thermal polymerization initiator or bulk polymerization using a photopolymerization initiator is more preferred because it allows for easy molecular weight control and minimizes impurities.

[0055] In the solution polymerization method using a thermal polymerization initiator, a thermal polymerization initiator is added to a monomer solution that serves as the raw material for copolymer (A), for example, a raw material monomer solution consisting of the above-mentioned monomers, and a polymerization reaction is carried out. More specifically, ethyl acetate, toluene, methyl ethyl ketone, acetone, or the like is used as a solvent, and preferably 0.01 to 1 part by mass of the thermal polymerization initiator is added per 100 parts by mass of the total amount of raw material monomers. Thereafter, the reaction is carried out under a nitrogen atmosphere, for example, at a reaction temperature of 40 to 90°C for a reaction time of 1 to 10 hours.

[0056] Examples of the thermal polymerization initiator include 2,2'-azobisisobutyronitrile (AIBN), 2,2'-azobis(2-methylbutyronitrile), azobiscyanovaleric acid, 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile), 2,2'-azobis(2,4-dimethylvaleronitrile), dimethyl 2,2'-azobis(2-methylpropionate), 2,2'-azobis(2-methylbutyronitrile), tolyl), 1,1'-azobis(cyclohexane-1-carbonitrile), 2,2'-azobis[N-(2-propenyl)-2-methylpropionamide], 2,2'-azobis(N-butyl-2-methylpropionamide), 2,2'-azobis[2-(2-imidazolin-2-yl)propane]dihydrochloride, 2,2'-azobis[2-(2-imidazolin-2-yl)propane]disulfate Dihydrate, 2,2'-azobis(2-methylpropionamidine) dihydrochloride, 2,2'-azobis[N-(2-carboxyethyl)-2-methylpropionamidine]hydrate, 2,2'-azobis[2-(2-imidazolin-2-yl)propane], 2,2'-azobis(1-imino-1-pyrrolidino-2-methylpropane) dihydrochloride, 2,2'-azobis[2-methyl-N-(2-hydro Examples of the thermal polymerization initiator include azo compounds such as t-butyl peroxypivalate, t-butyl peroxybenzoate, t-butylperoxy-2-ethylhexanoate, di-t-butyl peroxide, cumene hydroperoxide, benzoyl peroxide, and t-butyl hydroperoxide; and inorganic peroxides such as hydrogen peroxide, ammonium persulfate, potassium persulfate, and sodium persulfate. These thermal polymerization initiators can be used singly or in combination of two or more.

[0057] An example of a bulk polymerization method using a photopolymerization initiator is a method in which raw material monomers and a photopolymerization initiator are added, and active energy rays are irradiated under a nitrogen atmosphere at a reaction initiation temperature of 20° C. to 35° C. When the temperature in the reaction system rises from the reaction initiation temperature by 5° C. to 20° C., the reaction is stopped by introducing air into the reaction system, for example, to obtain copolymer (A).

[0058] Examples of active energy rays used in bulk polymerization include ultraviolet rays, laser rays, α rays, β rays, γ rays, X-rays, and electron beams. Ultraviolet rays are preferably used from the viewpoints of controllability, ease of handling, cost, and the like. More preferably, ultraviolet rays with a wavelength of 200 nm or more and 400 nm or less are used. Ultraviolet rays can be irradiated using a light source such as a high-pressure mercury lamp, a microwave-excited lamp, a chemical lamp, or a black light.

[0059] Examples of photopolymerization initiators include acetophenones such as acetophenone, 3-methylacetophenone, benzyl dimethyl ketal, 2,2-dimethoxy-1,2-diphenylethan-1-one, 1-(4-isopropylphenyl)-2-hydroxy-2-methylpropan-1-one, 2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropan-1-one, and 2-hydroxy-2-methyl-1-phenylpropan-1-one; benzophenones such as benzophenone, 4-chlorobenzophenone, and 4,4'-diaminobenzophenone; benzoin ethers such as benzoin propyl ether and benzoin ethyl ether; thioxanthones such as 4-isopropylthioxanthone; 1-hydroxycyclohexylphenyl ketone, xanthone, fluorenone, camphorquinone, benzaldehyde, and anthraquinone. These photopolymerization initiators can be used alone or in combination of two or more.

[0060] The amount of the photopolymerization initiator used is preferably 0.0005 to 1 part by mass, more preferably 0.002 to 0.5 parts by mass, relative to 100 parts by mass of the total amount of the raw material monomers.

[0061] A chain transfer agent may also be used to adjust the molecular weight of the copolymer (A). Examples of chain transfer agents include mercaptans such as methyl mercaptan, t-butyl mercaptan, decyl mercaptan, benzyl mercaptan, stearyl mercaptan, n-dodecyl mercaptan, t-dodecyl mercaptan, mercaptoacetic acid, mercaptopropionic acid and its esters, 2-ethylhexyl thioglycol, and octyl thioglycolate; alcohols such as methanol, ethanol, propanol, n-butanol, isopropanol, t-butanol, hexanol, benzyl alcohol, and allyl alcohol; halogenated hydrocarbons such as chloroethane, fluoroethane, and trichloroethylene; carbonyls such as acetone, methyl ethyl ketone, cyclohexanone, acetophenone, acetaldehyde, propionaldehyde, n-butylaldehyde, furfural, and benzaldehyde; and methyl-4-cyclohexene-1,2-dicarboxylic anhydride and α-methylstyrene. These chain transfer agents can be used singly or in combination of two or more.

[0062] The above-mentioned copolymer (A) can be used either alone or in combination of two or more.

[0063] [Inorganic particles (B)] The pressure-sensitive adhesive for optical films of the present invention preferably further contains inorganic particles (B). By containing inorganic particles (B), the refractive index of the pressure-sensitive adhesive layer after at least one of a heat treatment and a photocuring treatment becomes higher. Furthermore, by containing inorganic particles (B), the coatability of the pressure-sensitive adhesive can be improved.

[0064] Specific examples of the inorganic particles include at least one selected from the group consisting of zirconium oxide, zinc oxide, iron oxide, copper oxide, titanium oxide, tin oxide, cerium oxide, tantalum oxide, niobium oxide, tungsten oxide, europium oxide, hafnium oxide, potassium titanate, barium titanate, strontium titanate, potassium niobate, lithium niobate, calcium tungstate, antimony-doped tin oxide (ATO), and indium tin oxide (ITO).

[0065] These inorganic particles may be used singly or in combination of two or more kinds. In addition, the inorganic particles may be commercially available products or synthetic products.

[0066] From the viewpoint of having a high refractive index and excellent transparency and durability, the inorganic particles are more preferably at least one type selected from the group consisting of zirconium oxide, titanium oxide, and barium titanate.

[0067] The inorganic particles are preferably coated with one or more coating agents, at least one of which is preferably a coating agent represented by the following formula (I):

[0068] [ka]

[0069] In the above formula (I), R 1 represents a hydrocarbon group having 6 or more carbon atoms.

[0070] A hydrocarbon group having 6 or more carbon atoms has the effect of increasing the dispersibility of inorganic particles, particularly in non-polar solvents.

[0071] Specific examples of coating agents represented by formula (I) include linear carboxylic acids such as hexanoic acid, heptanoic acid, octanoic acid, nonanoic acid, decanoic acid, dodecanoic acid, tetradecanoic acid, and stearic acid; branched carboxylic acids such as 2-ethylhexanoic acid, 2-methylheptanoic acid, 4-methyloctanoic acid, and neodecanoic acid; and cyclic carboxylic acids such as naphthenic acid and cyclohexanedicarboxylic acid. Among these, branched carboxylic acids such as neodecanoic acid and 2-ethylhexanoic acid are preferred. The reason for this is unclear, but it is thought to be because hydrophobic coating agents having branched hydrocarbon chains, rather than linear hydrocarbon chains, can further enhance the particle dispersion effect in hydrophobic organic solvents and the like.

[0072] The coating agent represented by the above formula (I) may be used alone or in combination of two or more kinds.

[0073] It is more preferable that the inorganic particles are coated with other coating agents in addition to the coating agent of formula (I) above. This allows the particles to exhibit excellent dispersibility in various solvents. Examples of other coating agents include coating agents that increase the dispersibility of inorganic particles in polar solvents, coating agents that increase the dispersibility in monomers and polymers, and coating agents that further increase the dispersibility in non-polar solvents.

[0074] Coating agents that enhance the dispersibility of inorganic particles in polar solvents can bond to the surface of inorganic particles and, by having hydrophilic groups, can improve the dispersibility of particles in relatively polar solvents, monomers, etc. Examples include coating agents that have multiple functional groups, including at least one selected from the group consisting of hydroxyl groups, amino groups, thiol groups, carboxyl groups, epoxy groups, and alkoxy groups. Of course, other functional groups may be present in addition to these functional groups.

[0075] Examples of such coating agents include aluminum alkoxides such as aluminum trimethoxide, aluminum triethoxide, aluminum triisopropoxide, aluminum tri-n-butoxide, aluminum tri-sec-butoxide, and aluminum tri-t-butoxide; diisopropoxyaluminum ethyl acetoacetate, diisopropoxyaluminum alkyl acetoacetate, diisopropoxyaluminum monomethacrylate, aluminum stearate oxide trimer, and isopropoxyaluminum. Aluminum coupling agents such as titanium alkyl acetoacetate mono(dioctyl phosphate); titanium alkoxides such as titanium n-butoxide, titanium tetra-t-butoxide, titanium tetra-sec-butoxide, titanium tetraethoxide, titanium tetraisobutoxide, titanium tetramethoxide, titanium tetra(methoxypropoxide), and titanium tetra(methoxyphenoxide); isopropyl triisostearoyl titanate, isopropyl trioctanoyl titanate, Titanium-based coupling agents such as tetraoctylbis(ditridecylphosphite)titanate, tetraisopropylbis(dioctylphosphate)titanate, isopropyltris(dioctylpyrophosphate)titanate, bis(dioctylpyrophosphate)oxyacetate titanate, and bis(dioctylpyrophosphate)ethylene titanate; vinyltrimethoxysilane, vinyltriethoxysilane, 3-methacryloxypropyltriethoxysilane, 3-acryloxypropyltrimethoxysilane, N-(2 silane coupling agents such as N-(2-aminoethyl)-3-aminopropylmethyldimethoxysilane and N-(2-aminoethyl)-3-aminopropyltrimethoxysilane; zirconium alkoxides such as zirconium tetra n-butoxide, zirconium tetra t-butoxide, zirconium tetra(2-ethylhexoxide), zirconium tetraisobutoxide, zirconium tetraethoxide, zirconium tetraisopropoxide, zirconium tetra n-propoxide, and zirconium tetra(2-methyl-2-butoxide);Examples of suitable coating agents include zirconium compounds such as zirconium di-n-butoxide (bis-2,4-pentanedionate), zirconium tri-n-butoxide pentanedionate, and zirconium dimethacrylate dibutoxide; hydroxycarboxylic acids such as hydroxystearic acid and salicylic acid; ether carboxylic acids such as 2-[2-(2-methoxyethoxy)ethoxy]acetic acid; carboxylic acid-based coupling agents such as carboxylated polybutadiene and carboxylated polyisoprene; and carboxylic acid polymers such as maleic acid-modified polypropylene. For example, silane coupling agents form polymers with a siloxane structure that coat inorganic particles and improve the dispersibility of the inorganic particles in polar solvents. Silane coupling agents are particularly useful because they can introduce substituents with high affinity for monomers and the like into the side chains. Among these coating agents, silane coupling agents, hydroxycarboxylic acids, and ether carboxylic acids are preferred.

[0076] The coating agent for enhancing dispersibility in polar solvents may be used alone or in combination of two or more.

[0077] A coating agent that enhances the dispersibility of inorganic particles in monomers or polymers contains a group that exhibits affinity for the inorganic particles as well as a group that exhibits affinity for the monomer, thereby improving the dispersibility of the inorganic particles in the monomer or a polymer composed of the monomer. For example, coating particles with a coating agent having a vinyl group, such as (meth)acrylic acid or a (meth)acrylic acid ester, can improve the dispersibility of the inorganic particles in monomers that also have a vinyl group, such as (meth)acrylic acid or a (meth)acrylic acid ester. Furthermore, coating inorganic particles with a coating agent having an aromatic hydrocarbon group can improve the dispersibility of the particles in monomers or polymers that have a phenyl group, such as the copolymer (A) according to the present invention, or polymers such as styrene resins and phenolic resins.

[0078] Examples of such coating agents include aluminum-based coupling agents such as diisopropoxyaluminum monomethacrylate; and silane coupling agents such as vinyltrimethoxysilane, vinyltriethoxysilane, 3-methacryloxypropyltriethoxysilane, 3-acryloxypropyltrimethoxysilane, p-styryltrimethoxysilane, and phenyltrimethoxysilane.

[0079] When the coating agent represented by formula (I) has a branched hydrocarbon group having 6 or more carbon atoms, examples of coating agents other than the coating agent (I) include coating agents represented by the following formula (II):

[0080] [ka]

[0081] In the above formula (II), R 2 represents a linear hydrocarbon group having 6 or more carbon atoms.

[0082] A coating agent having a branched hydrocarbon group having 6 or more carbon atoms can improve dispersibility in non-polar solvents, etc., and the dispersibility can be further improved by using the coating agent represented by the above formula (II) in combination. Examples of the coating agent of formula (II) include linear carboxylic acids such as hexanoic acid, heptanoic acid, octanoic acid, nonanoic acid, decanoic acid, dodecanoic acid, tetradecanoic acid, and stearic acid.

[0083] The coating agent for coating the inorganic particles may be a total of two types, the coating agent of formula (I) and another coating agent, or a total of three or more types, such as the coating agent of formula (I), a coating agent that improves dispersibility in polar solvents, and a coating agent that improves dispersibility in monomers or polymers, may be used. Also, for example, two or more types of each of the coating agents of formula (I) may be used.

[0084] As described above, inorganic particles are preferably coated with a coating agent other than the coating agent of formula (I) to enhance dispersibility in desired solvents, etc., together with the coating agent of formula (I). The ratio of these coating agents can be adjusted appropriately to enhance dispersibility in the dispersion medium, such as the solvent, monomer, or polymer. Generally, when two types of coating agents are used, the molar ratio of the coating agent other than the coating agent of formula (I) to the coating agent of formula (I) is preferably, for example, 0.1 to 30, more preferably 0.2 to 25, and even more preferably 0.3 to 15. If the molar ratio is within this range, the effect of improving dispersibility in solvents, etc., corresponding to both coating agents is preferably exhibited. The ratio of the coating agent bonded to the surface of the inorganic particles can be determined from the results of analysis using, for example, NMR spectroscopy, a CHN coder, an elemental analyzer, or an X-ray fluorescence analyzer.

[0085] The average particle size of the inorganic particles is not particularly limited, but from the viewpoint of dispersibility, transparency, etc., it is preferably 1 nm or more and 100 nm or less, more preferably 3 nm or more and 30 nm or less, and even more preferably 5 nm or more and 20 nm or less.

[0086] The average particle size can be measured by a conventional method. For example, inorganic particles are magnified and observed using a transmission electron microscope (TEM), a field emission transmission electron microscope (FE-TEM), a field emission scanning electron microscope (FE-SEM), or the like, and 100 inorganic particles are randomly selected and their major axis lengths are measured, and the average value is used as the average particle size. Possible shapes of inorganic particles include spheres, ellipsoids, cubes, rectangular parallelepipeds, pyramidal, needles, columns, rods, cylinders, scales, plates, and flakes. When measuring particle size, the major axis length of each shape is measured. Taking into account dispersibility in solvents, the shape of inorganic particles is preferably spherical, granular, or columnar.

[0087] The ratio of the coating agent to the inorganic particles is preferably 40% by mass or less in terms of the weight loss rate when heated in an air atmosphere to remove the organic components. If the weight loss rate exceeds 40% by mass, the amount of coating agent is too large, and the inherent effects of the inorganic particles may not be fully exhibited. On the other hand, if the weight loss rate is less than 5% by mass, the amount of coating agent is too small, and the dispersibility of the particles may not be sufficiently improved. Therefore, the weight loss rate is preferably 5% by mass or more, and more preferably 10% by mass or more and 30% by mass or less.

[0088] The weight loss rate can be calculated, for example, by using a simultaneous thermogravimetry-differential thermal analyzer (TG-DTA) to heat the particles to 800°C at a rate of 10°C / min in an air atmosphere, and dividing the mass lost by the mass before heating by 100.

[0089] As a method for coating the inorganic particles with the coating agent, a conventionally known method can be appropriately adopted, and for example, the method described in JP-A-2008-44835 can be adopted.

[0090] The content of inorganic particles in the pressure-sensitive adhesive of the present invention is not particularly limited, but is preferably 50 to 2000 parts by mass, more preferably 70 to 1500 parts by mass, and even more preferably 100 to 1000 parts by mass, relative to 100 parts by mass of copolymer (A). By setting the content of inorganic particles in the pressure-sensitive adhesive within the above range, it is possible to obtain a pressure-sensitive adhesive that has a high refractive index after at least one of a heat treatment and a photocuring treatment, and is also excellent in transparency and durability.

[0091] The inorganic particles of this embodiment may be in the form of a powder or a dispersion liquid in which the inorganic particles are dispersed in a dispersion medium. Examples of the dispersion medium include alcohols such as methanol, ethanol, n-propanol, isopropanol, and ethylene glycol; ketones such as methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone; esters such as ethyl acetate, propyl acetate, and propylene glycol monomethyl ether acetate; ethers such as ethylene glycol monomethyl ether and diethylene glycol monobutyl ether; hydrocarbons such as benzene, toluene, xylene, ethylbenzene, and cyclohexane; halogenated hydrocarbons such as dichloromethane and chloroform; amides such as dimethylformamide, N,N-dimethylacetamide, and N-methylpyrrolidone; water; and oils such as mineral oil, vegetable oil, wax oil, and silicone oil. These may be used alone or in combination.

[0092] [Silane coupling agent (C)] The pressure-sensitive adhesive for optical films of the present invention preferably further contains a silane coupling agent (C). In the pressure-sensitive adhesive composition of the present invention, the silane coupling agent (C) can mainly contribute to improving durability and, when the adherend is glass, improving adhesion to glass. In this specification, the term "silane coupling agent" refers to a silane compound that does not have a siloxane bond (Si-O-Si bond) and has two or more reactive groups in the molecule.

[0093] In the present invention, the silane coupling agent (C) is not particularly limited.Specific examples thereof include 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, methyltrimethoxysilane, dimethyldimethoxysilane, trimethylmethoxysilane, n-propyltrimethoxysilane, ethyltrimethoxysilane, diethyldiethoxysilane, n-butyltrimethoxysilane, n-hexyltriethoxysilane, n-octyltrimethoxysilane, phenyltrimethoxysilane, diphenyldimethoxysilane, cyclohexylmethyldimethoxysilane, vinyltrichlorosilane, vinyltrimethoxysilane, vinyltriethoxysilane, vinyltris(β-methoxyethoxy)silane, β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropyltriethoxysilane, γ-methacryloxysilane, Examples of suitable alkylsilanes include propylmethyldimethoxysilane, γ-methacryloxypropyltrimethoxysilane, γ-methacryloxypropylmethyldiethoxysilane, γ-methacryloxypropyltriethoxysilane, γ-acryloxypropyltrimethoxysilane, N-β-(aminoethyl)-γ-aminopropylmethyldimethoxysilane, N-β-(aminoethyl)-γ-aminopropyltrimethoxysilane, N-β-(aminoethyl)-γ-aminopropyltriethoxysilane, γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, N-phenyl-γ-aminopropyltrimethoxysilane, γ-chloropropyltrimethoxysilane, γ-mercaptopropyltrimethoxysilane, γ-mercaptopropylmethyldimethoxysilane, bis-(3-[triethoxysilyl]propyl)tetrasulfide, and γ-isocyanatepropyltriethoxysilane. Further examples include silane coupling agents having functional groups such as epoxy groups (glycidoxy groups), amino groups, mercapto groups, and (meth)acryloyl groups, and silane coupling agents containing functional groups that can react with these functional groups. Compounds having hydrolyzable silyl groups obtained by reacting other coupling agents, polyisocyanates, etc., with each functional group in any ratio can also be used.

[0094] The silane coupling agent (C) may be a commercially available product or a synthetic product. Examples of commercially available silane coupling agents (C) include KBM-303, KBM-403, KBE-402, KBE-403, KBE-502, KBE-503, KBM-5103, KBM-573, KBM-802, KBM-803, KBE-846, and KBE-9007 (all manufactured by Shin-Etsu Chemical Co., Ltd.).

[0095] The silane coupling agents (C) can be used singly or in combination of two or more.

[0096] When the pressure-sensitive adhesive for optical films of the present invention contains a silane coupling agent (C), the content of the silane coupling agent (C) is not particularly limited. However, the content is preferably 0.001 to 5 parts by mass relative to 100 parts by mass of the copolymer (A). The content is more preferably 0.001 to 4 parts by mass, and even more preferably 0.01 to 3 parts by mass. A content of 0.001 parts by mass or more is preferred from the viewpoint of being able to exhibit durability effects even under harsh environments. On the other hand, a content of 5 parts by mass or less is preferred from the viewpoint of preventing deterioration of heat foaming due to low molecular weight compounds.

[0097] [Crosslinker (D)] The pressure-sensitive adhesive of the present invention preferably further contains a crosslinking agent (D). The crosslinking agent reacts with the copolymer (A) to form a crosslinked structure. Therefore, in the pressure-sensitive adhesive of the present invention, the crosslinking agent can mainly contribute to adhesiveness (tackiness) and durability.

[0098] In the present invention, the crosslinking agent (D) preferably contains at least one selected from the group consisting of an isocyanate compound, a carbodiimide compound, an oxazoline compound, an epoxy compound, a polyfunctional (meth)acrylic acid ester monomer, and a peroxide. These various crosslinking agents will be described below.

[0099] [Isocyanate Compound] Specific examples of the isocyanate compound used as the crosslinking agent (D) in the present invention include dimer acid diisocyanate, 2,4-tolylene diisocyanate (2,4-TDI), 2,6-tolylene diisocyanate (2,6-TDI), 4,4'-diphenylmethane diisocyanate (4,4'-MDI), 2,4'-diphenylmethane diisocyanate (2,4'-MDI), 1,4-phenylene diisocyanate, xylylene diisocyanate (XDI), tetramethylxylidene diisocyanate (TMXDI), tolidine diisocyanate (TODI), and 1,5-naphthalene diisocyanate (NDI). Examples of suitable diisocyanates include aromatic diisocyanates such as aryl isocyanate, hexamethylene diisocyanate (HDI), trimethylhexamethylene diisocyanate (TMHDI), lysine diisocyanate, and norbornane diisocyanatomethyl (NBDI); alicyclic diisocyanates such as transcyclohexane-1,4-diisocyanate, isophorone diisocyanate (IPDI), H6-XDI (hydrogenated XDI), and H12-MDI (hydrogenated MDI); carbodiimide-modified diisocyanates of the above diisocyanates; and isocyanurate-modified diisocyanates thereof. Adducts of the above isocyanate compounds with polyol compounds such as trimethylolpropane, polytetramethylene ether glycol (PTMG), and polypropylene glycol (PPG), as well as biuret and isocyanurate forms of these isocyanate compounds, can also be used.

[0100] These isocyanate compounds may be commercially available products or synthetic products.

[0101] Commercially available products include, for example, Coronate (registered trademark) L, Coronate (registered trademark) HL, Coronate (registered trademark) HX, Coronate (registered trademark) 2030, Coronate (registered trademark) 2031 (all manufactured by Tosoh Corporation), Takenate (registered trademark) D-102, Takenate (registered trademark) D-110N, Takenate (registered trademark) D-200, Takenate (registered trademark) D-202 (all manufactured by Mitsui Chemicals, Inc.), Duranate (registered trademark) 24A-100, Duranate (registered trademark) TPA-100, Duranate (registered trademark) TKA-100, Duranate (registered trademark) P301-75E, Duranate (registered trademark) E402-90T, Duranate (registered trademark) E405-80T, Duranate (registered trademark) TSE-100, Duranate (registered trademark) D-101, Duranate (registered trademark) Examples of suitable urethane fillers include, but are not limited to, Lanate (registered trademark) D-201 (all manufactured by Asahi Kasei Corporation), Sumidur (registered trademark) N-75, N-3200, and N-3300 (all manufactured by Sumika Covestro Urethane Co., Ltd.), Sanpren (registered trademark) P-6090 (PTMG / MDI based), Sanpren (registered trademark) P-663L (PTMG / TDI based), Sanpren (registered trademark) P-664 (PTMG / TDI based), Sanpren (registered trademark) P-665 (PTMG / TDI based), Sanpren (registered trademark) P-667 (PTMG / TDI based), Sanpren (registered trademark) P-868 (PTMG / HMDI based), Sanpren (registered trademark) P-870 (PTMG / HMDI based), and Sanpren (registered trademark) C-810 (PPG / TDI based) (all manufactured by Sanyo Chemical Industries, Ltd.).

[0102] The isocyanate compound may be used in the form of an unblocked isocyanate compound, or in the form of a blocked isocyanate compound obtained by reacting an isocyanate compound with a blocking agent that protects the isocyanate group. Such blocked isocyanate compounds may be commercially available products or synthetic products. Commercially available blocked isocyanate compounds include, for example, Duranate (registered trademark) MF-B60X (blocked 1,6-hexamethylene diisocyanate) and Duranate (registered trademark) MF-K60X (blocked 1,6-hexamethylene diisocyanate) manufactured by Asahi Kasei Corporation, Coronate (registered trademark) AP-M, 2503, 2507, 2513, 2515, and Millionate (registered trademark) MS-50 manufactured by Tosoh Corporation, and Takenate (registered trademark) B-830 (blocked tolylene diisocyanate), B-815N (blocked 4,4'-methylenebis(cyclohexyl isocyanate)), and B-842N (blocked 1,3-bis(isocyanate)) manufactured by Mitsui Chemicals, Inc. Examples of suitable urethane-modified polyisocyanates include B-846N (blocked 1,3-bis(isocyanatomethyl)cyclohexane), B-874N (blocked isophorone diisocyanate), B-882N (blocked 1,6-hexamethylene diisocyanate), Burnock (registered trademark) D-500 (blocked tolylene diisocyanate) and D-550 (blocked 1,6-hexamethylene diisocyanate) manufactured by DIC Corporation, and Elastron (registered trademark) BN-P17 (blocked 4,4'-diphenylmethane diisocyanate), BN-04, BN-08, BN-44, and BN-45 (all of which are blocked urethane-modified polyisocyanates) manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd. Among these, Duranate (registered trademark) MF-K60X is preferred.

[0103] From the viewpoint of further improving the durability of the pressure-sensitive adhesive, the isocyanate compound is preferably used in the form of an unblocked isocyanate compound.

[0104] [Carbodiimide Compound] In the present invention, the carbodiimide compound used as the crosslinking agent is not particularly limited. For example, a high molecular weight polycarbodiimide produced by subjecting a diisocyanate to a decarboxylation condensation reaction in the presence of a carbodiimidization catalyst is used.

[0105] Examples of diisocyanates used in the decarboxylation condensation reaction include 4,4'-diphenylmethane diisocyanate, 3,3'-dimethoxy-4,4'-diphenylmethane diisocyanate, 3,3'-dimethyl-4,4'-diphenylmethane diisocyanate, 4,4'-diphenylether diisocyanate, 3,3'-dimethyl-4,4'-diphenylether diisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 1-methoxyphenyl-2,4-diisocyanate, isophorone diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, and tetramethylxylylene diisocyanate.

[0106] Examples of the carbodiimidization catalyst used in the decarboxylation condensation reaction include phospholene oxides such as 1-phenyl-2-phospholene-1-oxide, 3-methyl-2-phospholene-1-oxide, 1-ethyl-3-methyl-2-phospholene-1-oxide, 1-ethyl-2-phospholene-1-oxide, and 3-phospholene isomers of these.

[0107] The high-molecular-weight polycarbodiimide may be a commercially available product or a synthetic product. Examples of commercially available products include the Carbodilite (registered trademark) series manufactured by Nisshinbo Chemical Inc. Among them, Carbodilite (registered trademark) V-01, V-03, V-05, V-07, and V-09 are preferred because they have excellent compatibility with organic solvents.

[0108] [Oxazoline compounds] In the present invention, the oxazoline compound used as a crosslinking agent is not particularly limited. However, an oxazoline group-containing acrylic / styrene polymer having a main chain composed of an acrylic skeleton or a styrene skeleton and having an oxazoline group on a side chain of the main chain is preferred. Also preferred are oxazoline group-containing polymers, such as an oxazoline group-containing acrylic polymer having a main chain composed of an acrylic skeleton and having an oxazoline group on a side chain of the main chain.

[0109] Examples of the oxazoline group include a 2-oxazoline group, a 3-oxazoline group, and a 4-oxazoline group, and among these, a 2-oxazoline group is preferred.

[0110] The oxazoline group-containing polymer may also have a polyoxyalkylene group in addition to the oxazoline group.

[0111] Specific examples of the oxazoline group-containing polymer include oxazoline group-containing acrylic polymers such as EPOCROS (registered trademark) WS-300, EPOCROS (registered trademark) WS-500, and EPOCROS (registered trademark) WS-700, all of which are manufactured by Nippon Shokubai Co., Ltd.; and oxazoline group-containing acrylic / styrene polymers such as EPOCROS (registered trademark) K-1000 series and EPOCROS (registered trademark) K-2000 series, all of which are manufactured by Nippon Shokubai Co., Ltd.

[0112] [Epoxy Compound] In the present invention, the epoxy compound used as the crosslinking agent (D) is not particularly limited, and known epoxy-based crosslinking agents can be appropriately used. Commercially available epoxy compounds include liquid epoxy resins such as "TETRAD (registered trademark)-C" and "TETRAD (registered trademark)-X" manufactured by Mitsubishi Gas Chemical Company, Inc., "ADEKA RESIN (registered trademark) EPU series" and "ADEKA RESIN (registered trademark) EPR series" manufactured by ADEKA Corporation, and "CELLOXIDE (registered trademark)" manufactured by Daicel Corporation. These liquid epoxy resins are preferred because they facilitate mixing operations when producing pressure-sensitive adhesives for optical films.

[0113] [Polyfunctional (meth)acrylic acid ester monomer] The polyfunctional (meth)acrylic acid ester monomer used as the crosslinking agent (D) of the present invention is a (meth)acrylic acid ester monomer having multiple (two or more) radically polymerizable functional groups. Examples of such monomers include hydrocarbon-based or hydrocarbon ether-based polyfunctional monomers. The hydrocarbon-based or hydrocarbon ether-based polyfunctional monomers are compounds in which the hydroxyl group of a polyhydric alcohol having a hydrocarbon group or hydrocarbon ether group with a carbon number of 10 to 100 as its main skeleton is (meth)acrylated. Such compounds are preferred from the viewpoint of improving adhesiveness through crosslinking. Examples of the hydrocarbon group of the polyhydric alcohol include linear or branched aliphatic hydrocarbon groups, aromatic hydrocarbon groups, alicyclic hydrocarbon groups, and hydrocarbon groups combining these hydrocarbon groups. Examples of the hydrocarbon ether group include etherified hydrocarbon groups. Examples of polyhydric alcohols having a hydrocarbon ether group as their main skeleton include compounds in which alkylene oxides with a carbon number of 2 to 4 are added to the polyhydric alcohols (addition number: 1 to 30). Further examples include polyalkylene glycols (addition number 1 to 30) obtained from alkylene oxides having 2 to 4 carbon atoms.

[0114] Specific examples of the hydrocarbon-based bifunctional monomer include di(meth)acrylates of alkylene glycols such as ethylene glycol di(meth)acrylate, 1,3-butylene glycol di(meth)acrylate, 1,4-butanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, and neopentyl glycol di(meth)acrylate; di(meth)acrylates of diol compounds having an alicyclic hydrocarbon group such as cyclohexanedimethanol di(meth)acrylate and tricyclodecanedimethanol di(meth)acrylate (dimethylol-tricyclodecane diacrylate); and di(meth)acrylates of diol compounds having an aromatic hydrocarbon group such as bisphenol A di(meth)acrylate.

[0115] Specific examples of hydrocarbon ether-based bifunctional monomers include di(meth)acrylates of compounds obtained by adding alkylene oxide to alkylene glycols or diol compounds described in the above hydrocarbon-based bifunctional monomers, such as alkoxylated hexanediol di(meth)acrylate, alkoxylated cyclohexanedimethanol di(meth)acrylate, alkoxylated di(meth)acrylate, alkoxylated neopentyl glycol di(meth)acrylate, and alkoxylated bisphenol A di(meth)acrylate. More specific examples of hydrocarbon ether-based bifunctional monomers include di(meth)acrylates of polyalkylene glycols, such as diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, tripropylene glycol di(meth)acrylate, and dipropylene glycol di(meth)acrylate, as well as dioxane glycol di(meth)acrylate.

[0116] Examples of hydrocarbon or hydrocarbon ether trifunctional or tetrafunctional monomers include tri(meth)acrylates or tetra(meth)acrylates of tri- or tetraol compounds such as trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, glyceryl tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, and trimethylolpropane tetra(meth)acrylate, as well as tri(meth)acrylates or tetra(meth)acrylates of compounds obtained by adding alkylene oxide to the above-mentioned tri- or tetraol compounds.

[0117] Furthermore, examples of the monomer other than the hydrocarbon or hydrocarbon ether monomers include polyester poly(meth)acrylate and epoxy (meth)acrylate having two or more (meth)acryloyl groups at the terminals.

[0118] [Polyfunctional Allyl Monomer] The polyfunctional allyl monomer used as the crosslinking agent (D) of the present invention is a monomer having at least one allyl group and a plurality (two or more) of radically polymerizable functional groups including the allyl group. Examples of such monomers include allyl (meth)acrylate, diallyl phthalate (DAP), trimethylolpropane diallyl ether, pentaerythritol triallyl ether, and triallyl isocyanurate.

[0119] [Peroxide] In the present invention, the peroxide used as the crosslinking agent (D) is not particularly limited, and known peroxides can be used. Furthermore, taking productivity and stability into consideration, peroxides with a one-minute half-life temperature of 80°C or higher and 160°C or lower are preferred. Peroxides with a one-minute half-life temperature of 80°C or higher and 140°C or lower are more preferred. A one-minute half-life temperature of 80°C or higher and 125°C or lower is even more preferred, and a one-minute half-life temperature of 90°C or higher and 125°C or lower is particularly preferred. The "half-life of a peroxide" is an index representing the decomposition rate of a peroxide, and refers to the time it takes for the remaining amount of peroxide to be reduced to half. The decomposition temperature required to achieve a half-life in a given time and the half-life time at a given temperature are described in manufacturer catalogs, etc., for example, in the Organic Peroxide Catalog, 9th Edition (May 2003), published by NOF Corporation.

[0120] Examples of such peroxides include diisopropyl peroxydicarbonate (one-minute half-life temperature: 88.3°C; hereinafter, the temperature in parentheses indicates the one-minute half-life temperature), di(2-ethylhexyl) peroxydicarbonate (90.6°C), bis(4-t-butylcyclohexyl) peroxydicarbonate (92.1°C), di-sec-butyl peroxydicarbonate (92.4°C), t-butyl peroxyneodecanoate (103.5°C), t-hexyl peroxypivalate (109.1°C), t-butyl peroxypivalate (110°C), and t-butyl peroxypivalate (110°C). Examples of suitable peroxides include dilauroyl peroxide (116.4°C), bis-n-octanoyl peroxide (117.4°C), 1,1,3,3-tetramethylbutylperoxy-2-ethylhexanoate (124.3°C), di(4-methylbenzoyl) peroxide (128.2°C), dibenzoyl peroxide (benzoyl peroxide) (130.0°C), a mixture of dibenzoyl peroxide, benzoyl m-methylbenzoyl peroxide, and m-toluoyl peroxide (131.1°C), and t-butyl peroxybutyrate (136.1°C). Among these, diisopropyl peroxydicarbonate, bis(4-t-butylcyclohexyl) peroxydicarbonate, and t-butyl peroxyneodecanoate are preferred. While these may be used alone, it is also preferred to use two or more of them in combination to control reactivity. As an example of a combination of two or more, a combination of di(4-t-butylcyclohexyl) peroxydicarbonate and dilauroyl peroxide is preferred.

[0121] The peroxide may be a commercially available product or a synthetic product. Examples of commercially available peroxides include those manufactured by NOF Corporation under the trade names "Perloyl (registered trademark, the same applies hereinafter) IB" (85.1°C), "Percumyl (registered trademark, the same applies hereinafter) ND" (94.0°C), "Perloyl NPP" (94.0°C), "Perloyl IPP" (88.3°C), "Perloyl SBP" (92.4°C), "Perocta (registered trademark, the same applies hereinafter) ND" (92.4°C), "Perloyl TCP" (92.1°C), and "Perloyl OPP" (9 0.6°C), "Perhexyl (registered trademark, the same below) ND" (100.9°C), "Perbutyl (registered trademark, the same below) ND" (103.5°C), "Perbutyl NHP" (104.6°C), "Perhexyl PV" (109.1°C), "Perbutyl PV" (110.3°C), "Perloyl 355" (112.6°C), "Perloyl L" (116.4°C), "Perocta O" (124.3°C), "Perloyl SA" (131.8°C), "Perhexa (registered trademark, the same below) 25O" (118.8°C), "Perhexyl O" (132.6°C), "Niper (registered trademark, the same below) PMB" (128.2°C), "Perbutyl O" (134.0°C), "Niper BMT" (131.1°C), "Niper BW" (130.0°C), "Niper BMT-K40" (131.1°C), "Niper BMT-M" (131.1°C), "Perhexa MC" (142.1°C), "Per Examples of such compounds include "Hexa TMH" (147.1°C), "Perhexa HC" (149.2°C), "Perhexa C" (153.8°C), "Pertetra (registered trademark, the same below) A" (153.8°C), "Perhexyl I" (155.0°C), "Perbutyl L" (159.4°C), "Perbutyl I" (158.8°C), "Perhexa 25Z" (158.2°C), "Perbutyl A" (159.9°C), and "Perhexa 22" (159.9°C).

[0122] In the present invention, the crosslinking agent (D) may be used alone or in combination of two or more. When two or more types are combined, two or more crosslinking agents of the same type (for example, two types of isocyanate compounds) may be combined, or one or more crosslinking agents of different types (for example, one type of isocyanate compound and one type of peroxide) may be combined.

[0123] The content of the crosslinking agent (D) in the pressure-sensitive adhesive for optical films of the present invention is not particularly limited, but is preferably 0.01 to 5 parts by mass relative to 100 parts by mass of the (meth)acrylic acid ester copolymer (A). The content is more preferably 0.02 to 4 parts by mass, and even more preferably 0.03 to 3 parts by mass. The content is particularly preferably 0.05 to 2 parts by mass. When the content of the crosslinking agent (D) is within the above range, durability can be ensured.

[0124] [Other added ingredients] The pressure-sensitive adhesive for optical films of the present invention may contain, as necessary, other known additives such as solvents, crosslinking accelerators, antioxidants, fillers, colorants (pigments, dyes, etc.), UV absorbers, antioxidants, plasticizers, softeners, surfactants, and antistatic agents, within the range that does not impair the effects of the present invention.

[0125] <Solvent> The pressure-sensitive adhesive for optical films of the present invention may contain a solvent. By containing a solvent, the productivity during coating can be significantly improved. The solvent is not particularly limited, but examples thereof include organic solvents such as esters such as ethyl acetate and n-butyl acetate; aromatic hydrocarbons such as toluene and benzene; aliphatic hydrocarbons such as n-hexane and n-heptane; alicyclic hydrocarbons such as cyclohexane and methylcyclohexane; and ketones such as methyl ethyl ketone, methyl isobutyl ketone, and acetone. These solvents can be used alone or in combination of two or more.

[0126] <Method for manufacturing (preparing) adhesive> The pressure-sensitive adhesive of the present invention can be prepared by mixing the copolymer (A) and, if necessary, other components such as inorganic particles (B), a silane coupling agent (C), and a crosslinking agent (D). The mixing order and mixing temperature of the components are not particularly limited and can be appropriately adjusted by a person skilled in the art.

[0127] [Application] The pressure-sensitive adhesive for optical films of the present invention described above is suitable for various applications. For example, it is preferably used for optical components such as optical films, and particularly for thin pressure-sensitive adhesive optical films used in large liquid crystal panels. Examples of such optical films include polarizing plates, retardation plates for preventing coloration, optical compensation films such as viewing angle expansion films for improving the viewing angle of liquid crystal displays, brightness improvement films for increasing the contrast of displays, light extraction films for increasing the light extraction efficiency of surface light emitters, and laminates of these films.

[0128] The present invention also provides a pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive for optical films described above, an optical member formed by forming the pressure-sensitive adhesive layer on an optical film or the like, an optical film being a polarizing plate, or an optical member being applied to an image display device such as a liquid crystal display, an organic EL display, a plasma display (PDP), a micro LED display, a curved display, or a flexible display. Each of these embodiments will be described below.

[0129] [Adhesive layer for optical film] According to another aspect of the present invention, there is provided an adhesive layer for an optical film (hereinafter also simply referred to as "adhesive layer") obtained by curing the above-mentioned adhesive for an optical film by at least one of a heat treatment and a photo-curing treatment.

[0130] The thickness of the pressure-sensitive adhesive layer is not particularly limited, but is preferably 5 μm to 500 μm, more preferably 10 μm to 300 μm, and even more preferably 15 μm to 250 μm. When the thickness of the pressure-sensitive adhesive layer is within the above range, coatability and uniformity of the pressure-sensitive adhesive layer thickness can be ensured, and the pressure-sensitive adhesive layer also has excellent transparency and durability.

[0131] [Method for producing pressure-sensitive adhesive layer] According to another aspect of the present invention, there is also provided a method for producing a pressure-sensitive adhesive layer for an optical film, comprising a crosslinking step of applying the above-mentioned pressure-sensitive adhesive for an optical film of the present invention onto a release sheet that has been subjected to a release treatment, and then carrying out at least one of a heat treatment and a photocuring treatment to crosslink the pressure-sensitive adhesive.

[0132] When using a pressure-sensitive adhesive on an optical film, the pressure-sensitive adhesive may be directly coated onto the optical film to form a pressure-sensitive adhesive layer. However, it is preferable to coat the pressure-sensitive adhesive on a film having releasability to form a pressure-sensitive adhesive layer, which is then transferred to various optical films for use. Furthermore, the pressure-sensitive adhesive film with a pressure-sensitive adhesive layer produced in this manner can also be wound up into a roll during the manufacturing process. After cutting or processing as needed, the releasable film can be removed and used when adhering to various optical films, liquid crystal panels, etc. Furthermore, the releasable film can also serve to protect the pressure-sensitive adhesive layer until it is put into practical use. In this specification, such a releasable film is also referred to as a release sheet (separator).

[0133] Examples of materials constituting the release sheet include plastic films such as polyethylene, polypropylene, polyethylene terephthalate, and polyester film, porous materials such as paper, cloth, and nonwoven fabric, nets, foam sheets, metal foils, and appropriate thin sheets such as laminates thereof. Plastic films are preferably used because of their excellent surface smoothness.

[0134] The thickness of the release sheet is usually from 5 μm to 200 μm, and preferably from 5 μm to 100 μm.

[0135] The release sheet can be further subjected to release treatment and antifouling treatment using a silicone-based, fluorine-based, long-chain alkyl-based or fatty acid amide-based release agent, silica powder, etc., as needed, and antistatic treatment such as coating-type, kneading-type or vapor deposition-type etc. In particular, from the viewpoint of further improving releasability from the pressure-sensitive adhesive layer, it is preferable to subject the surface of the release sheet to a release treatment such as silicone treatment, long-chain alkyl treatment or fluorine treatment.

[0136] In the present invention, the coating method for coating the pressure-sensitive adhesive for optical films of the present invention onto a release-treated release sheet is not particularly limited, and various known methods can be used, such as roll coating, kiss roll coating, gravure coating, reverse coating, roll brushing, spray coating, dip roll coating, bar coating, knife coating, air knife coating, curtain coating, lip coating, and extrusion coating using a die coater.

[0137] In the method for producing a pressure-sensitive adhesive layer of the present invention, the above-mentioned pressure-sensitive adhesive for optical films is applied onto a release sheet, and then a crosslinking step is carried out by carrying out at least one of a heat treatment and a photocuring treatment to crosslink the pressure-sensitive adhesive.

[0138] The heat treatment not only dries and removes the solvent in the coating film obtained by coating, but also serves the purpose of causing a crosslinking reaction of the pressure-sensitive adhesive for optical films. The heat treatment temperature is preferably 40°C or higher and 150°C or lower, more preferably 50°C or higher and 130°C or lower, and even more preferably 80°C or higher and 120°C or lower. By setting the heat treatment temperature within the above range, a pressure-sensitive adhesive layer with excellent adhesive properties can be obtained.

[0139] The heat treatment time can be set appropriately, but is preferably from 5 seconds to 20 minutes, more preferably from 5 seconds to 10 minutes, and even more preferably from 10 seconds to 5 minutes.

[0140] The heat treatment method is not particularly limited, and various known methods can be used, such as a parallel drying method in which hot air is blown in the same direction above and below the film in the film transport direction, a counter drying method in which hot air is blown in different directions above and below the film in the film transport direction, and a float drying method in which hot air is blown directly above and below the film.

[0141] In addition, ultraviolet light is generally used as the irradiation light in the photocuring treatment. Examples of ultraviolet irradiation sources include low-pressure mercury lamps, high-pressure mercury lamps, ultra-high-pressure mercury lamps, metal halide lamps, xenon lamps, LEDs, black lights, and chemical lamps. In order to promote the photopolymerization reaction, light irradiation is preferably carried out in an inert gas atmosphere such as nitrogen gas.

[0142] The cumulative irradiation dose during photocuring is 300 mJ / cm 2 More than 3000mJ / cm 2 Less than 500 mJ / cm is preferable. 2 More than 2000mJ / cm 2 The following is more preferred:

[0143] When photocuring treatment is performed, the pressure-sensitive adhesive of the present invention may contain a photopolymerization initiator. Examples of the photopolymerization initiator include photoradical initiators such as hydroxyketones, benzyl dimethyl ketals, aminoketones, acylphosphine oxides, benzophenones, and trichloromethyl group-containing triazine derivatives. The photoradical initiators may be used alone or in combination of two or more.

[0144] When forming the adhesive layer, the adhesive may be subjected to either the heat treatment or the light curing treatment, or both the heat treatment and the light curing treatment.

[0145] <Refractive index> In the pressure-sensitive adhesive for optical films of the present invention, the refractive index of the pressure-sensitive adhesive layer obtained by at least one of the heat treatment and photo-curing treatment described above is 1.58 or more and 1.80 or less. If the refractive index of the pressure-sensitive adhesive layer is less than 1.58, the properties of the optical film or optical component will be degraded. On the other hand, pressure-sensitive adhesives in which the refractive index of the pressure-sensitive adhesive layer obtained by at least one of the heat treatment and photo-curing treatment exceeds 1.80 cannot be substantially produced. The refractive index is preferably 1.59 or more and 1.78 or less, more preferably greater than 1.60 and 1.76 or less, even more preferably greater than 1.60 and 1.75 or less, and even more preferably greater than 1.60 and 1.73 or less.

[0146] The refractive index of the pressure-sensitive adhesive layer can be controlled by appropriately selecting the type and amount of the monomer constituting the copolymer (A), the type and amount of the inorganic particles (B), the type and amount of the crosslinking agent (D), etc. Specifically, the refractive index can be measured by the method described in the Examples.

[0147] <Haze> The pressure-sensitive adhesive layer according to the present invention has excellent transparency, with a haze of 0.05% to 1.0% at a thickness of 20 μm, preferably 0.05% to 0.8%, more preferably 0.05% to 0.6%, and even more preferably 0.05% to 0.4%.

[0148] The haze of the pressure-sensitive adhesive layer can be measured by the method described in the examples.

[0149] [Optical components] According to one embodiment of the present invention, there is provided an optical member having the above-mentioned pressure-sensitive adhesive layer for an optical film and a first optical film provided on one surface of the pressure-sensitive adhesive layer.

[0150] The optical member of the present invention may further include glass or a second optical film on the surface of the pressure-sensitive adhesive layer of the present invention opposite to the surface on which the first optical film is provided. Here, the "first optical film" and the "second optical film" may be films having the same configuration (material, function, etc.) or may be films having different configurations (material, function, etc.). The present invention also provides an embodiment in which the first optical film (or the second optical film) is a polarizing plate.

[0151] In the present invention, the above-mentioned pressure-sensitive adhesive may be used by directly applying it to one or both sides of the optical film to form a pressure-sensitive adhesive layer. However, for the reasons mentioned above, it is desirable to form a pressure-sensitive adhesive layer in advance on a separator or the like and then transfer it to one or both sides of the optical film. Furthermore, before transfer, the surface of the optical film may be subjected to a surface treatment such as the formation of an easy-adhesion treatment layer or the formation of an antistatic layer, depending on the material of the optical film. Furthermore, the surface of the pressure-sensitive adhesive layer may also be subjected to an easy-adhesion treatment. From the viewpoint of firmly adhering the optical film and the pressure-sensitive adhesive layer, it is preferable to have an easy-adhesion treatment layer between the optical film and the pressure-sensitive adhesive layer for the optical film of the present invention.

[0152] <Easy-adhesion treated layer (easy-adhesion layer)> The optical member of the present invention preferably further comprises at least one easy-adhesion treated layer between the first optical film and the pressure-sensitive adhesive layer for an optical film.

[0153] In a more preferred embodiment, the easy-adhesion treatment layer has a first easy-adhesion treatment layer and a second easy-adhesion treatment layer. The optical member has a first optical film, a first easy-adhesion treatment layer, a second easy-adhesion treatment layer, and a pressure-sensitive adhesive layer for an optical film laminated in this order. In this way, a configuration in which the optical member has both the first and second easy-adhesion treatment layers is preferred from the viewpoint of more firmly adhering the optical film and the pressure-sensitive adhesive layer.

[0154] The adhesion-facilitating treatment layer may be a layer obtained by treating the surface of a member that comes into contact with the pressure-sensitive adhesive layer with corona treatment, plasma treatment, etc. Alternatively, a separate member such as a primer layer may be provided on the surface of a member that comes into contact with the pressure-sensitive adhesive layer.

[0155] The material constituting the primer layer is preferably one that has good adhesion to members that come into contact with the primer layer and forms a film with excellent cohesion. For example, various polymers, metal oxide sols, silica sols, etc. are used, and polymers are particularly preferred. The primer layer may have an antistatic function.

[0156] Examples of polymers constituting the primer layer include oxazoline group-containing polymers, polyurethane resins, polyester resins, and polymers containing amino groups in the molecule. Among these, polyurethane resins and oxazoline group-containing polymers are more preferably used.

[0157] Commercially available oxazoline group-containing polymers can be used. Examples include, but are not limited to, the EPOCROS (registered trademark) series (e.g., EPOCROS (registered trademark) WS700) manufactured by Nippon Shokubai Co., Ltd. In addition, polyurethane resins, polyester resins, and polymers containing amino groups in the molecule can be appropriately selected from those disclosed in paragraphs "0107" to "0113" of JP 2011-105918 A.

[0158] The thickness of the primer layer is preferably 10 nm to 5000 nm, more preferably 50 nm to 500 nm, in which case the primer layer can exhibit sufficient strength and adhesion while maintaining optical properties.

[0159] The method for forming the primer layer is not particularly limited, and examples thereof include a method in which the raw material for the primer layer (undercoat agent) is applied by a coating method such as coating, dipping, or spraying, followed by drying.

[0160] <Optical film> In the present invention, examples of the optical film (first optical film or second optical film) include polarizing plates, retardation plates for preventing coloration, optical compensation films such as viewing angle widening films for improving the viewing angle of liquid crystal displays, brightness enhancement films for increasing the contrast of displays, light extraction films for increasing the light extraction efficiency of surface light emitters, and laminates of these. However, the optical film (first optical film or second optical film) is preferably a polarizing plate with an optical compensation layer. Hereinafter, polarizing plates with an optical compensation layer will be described.

[0161] [Polarizing plate with optical compensation layer] FIG. 1 is a schematic cross-sectional view of a polarizing plate with an optical compensation layer according to one embodiment of the present invention. Note that the thickness ratios of the layers and optical films constituting the polarizing plate with an optical compensation layer in FIG. 1 differ from the actual thickness ratios. The polarizing plate with an optical compensation layer 100 of this embodiment includes a polarizer 10, a first protective layer 21 disposed on one side of the polarizer 10, a second protective layer 22 disposed on the other side of the polarizer 10, a first optical compensation layer 30 disposed on the side of the second protective layer 22 opposite the polarizer 10, and a second optical compensation layer 40, in this order. That is, the polarizing plate with an optical compensation layer 100 includes the polarizer 10, the first retardation layer 30, and the second retardation layer 40, in this order. Depending on the purpose and the configuration of the image display device to which the polarizing plate with an optical compensation layer is applied, at least one of the first protective layer 21 and the second protective layer 22 may be omitted.

[0162] (polarizer) Any appropriate polarizer can be adopted as the polarizer 10. For example, the resin film forming the polarizer may be a single-layer resin film or a laminate of two or more layers.

[0163] Specific examples of polarizers made of a single-layer resin film include hydrophilic polymer films such as polyvinyl alcohol (PVA) films, partially formalized PVA films, and partially saponified ethylene-vinyl acetate copolymer films that have been dyed with iodine or a dichroic substance such as a dichroic dye and stretched, as well as polyene-based oriented films such as dehydrated PVA films and dehydrochlorinated polyvinyl chloride films. Polarizers obtained by dyeing a PVA film with iodine and uniaxially stretching it are preferred because of their excellent optical properties.

[0164] The dyeing with iodine is carried out, for example, by immersing the PVA film in an aqueous iodine solution. The stretching ratio of the uniaxial stretching is preferably 3 to 7 times. The stretching may be carried out after the dyeing treatment or while dyeing. Alternatively, the stretching may be carried out before dyeing. If necessary, the PVA film may be subjected to a swelling treatment, a crosslinking treatment, a washing treatment, a drying treatment, or the like. For example, by immersing the PVA film in water and washing it before dyeing, it is possible to wash away dirt and antiblocking agents on the surface of the PVA film, and also to swell the PVA film, thereby preventing uneven dyeing.

[0165] Specific examples of polarizers obtained using laminates include a laminate of a resin substrate and a PVA-based resin layer (PVA-based resin film) laminated on the resin substrate, or a polarizer obtained using a laminate of a resin substrate and a PVA-based resin layer coated on the resin substrate. A polarizer obtained using a laminate of a resin substrate and a PVA-based resin layer coated on the resin substrate can be produced, for example, by applying a PVA-based resin solution to the resin substrate and drying the resin substrate to form a PVA-based resin layer on the resin substrate, thereby obtaining a laminate of the resin substrate and the PVA-based resin layer, and then stretching and dyeing the laminate to convert the PVA-based resin layer into a polarizer. In this embodiment, stretching typically involves immersing the laminate in an aqueous boric acid solution and stretching it. Furthermore, stretching can optionally further include in-air stretching the laminate at an elevated temperature (e.g., 95°C or higher) before stretching in the aqueous boric acid solution. The obtained resin substrate / polarizer laminate may be used as it is (i.e., the resin substrate may be used as a protective layer for the polarizer), or the resin substrate may be peeled off from the resin substrate / polarizer laminate and any appropriate protective layer depending on the purpose may be laminated on the peeled surface. Details of the method for producing such a polarizer are described in, for example, JP 2012-73580 A.

[0166] The thickness of the polarizer is preferably 25 μm or less, more preferably 1 μm or more and 12 μm or less. When the thickness of the polarizer is in this range, curling during heating can be well suppressed and good durability of appearance during heating can be obtained.

[0167] The polarizer preferably exhibits absorption dichroism at a wavelength of 380 nm or more and 780 nm or less.

[0168] (First protective layer) The first protective layer 21 is formed of any appropriate film that can be used as a protective layer for a polarizer. Specific examples of materials that can be the main component of the film include cellulose-based resins such as triacetyl cellulose (TAC), and transparent resins such as polyesters, polyvinyl alcohols, polycarbonates, polyamides, polyimides, polyethersulfones, polysulfones, polystyrenes, polynorbornenes, polyolefins, (meth)acrylics, and acetates. Other examples include thermosetting or ultraviolet-curing resins such as (meth)acrylics, urethanes, (meth)acrylic urethanes, epoxy resins, and silicone resins. Other examples include glassy polymers such as siloxane polymers. The polymer films described in JP 2001-343529 A (WO 01 / 37007 A) can also be used. The material for this film can be, for example, a resin composition containing a thermoplastic resin having substituted or unsubstituted imide groups in the side chains and a thermoplastic resin having substituted or unsubstituted phenyl groups and nitrile groups in the side chains. For example, a resin composition containing an alternating copolymer of isobutene and N-methylmaleimide and an acrylonitrile-styrene copolymer can be used.

[0169] As described below, the polarizing plate with an optical compensation layer of this embodiment is typically placed on the viewing side of an image display device, and the first protective layer 21 is typically placed on the viewing side. Therefore, the first protective layer 21 may be subjected to surface treatments such as hard coating, anti-reflection, anti-sticking, and anti-glare treatment, as needed. Furthermore, the first protective layer 21 may be subjected to treatments (typically, by imparting an (elliptically) circular polarization function or an ultra-high phase difference) to improve visibility when viewed through polarized sunglasses, as needed.

[0170] Any appropriate thickness can be adopted for the first protective layer 21. The thickness of the first protective layer 21 is, for example, 10 μm or more and 50 μm or less, and preferably 15 μm or more and 40 μm or less. Note that if a surface treatment is applied, the thickness of the first protective layer includes the thickness of the surface treatment layer.

[0171] (Second protective layer) The second protective layer 22 is also formed of any appropriate film that can be used as a protective layer for a polarizer. The main component material of this film is as described in the section on the first protective layer. The second protective layer 22 is preferably optically isotropic. In this specification, "optically isotropic" means that the in-plane retardation Re(550) is 0 nm or more and 10 nm or less, and the retardation in the thickness direction Rth(550) is -10 nm or more and +10 nm or less.

[0172] The thickness of the second protective layer 22 is, for example, 15 μm or more and 35 μm or less, and preferably 20 μm or more and 30 μm or less. The difference in thickness between the first protective layer 21 and the second protective layer 22 is preferably 15 μm or less, and more preferably 10 μm or less. If the difference in thickness is within this range, curling during lamination can be effectively suppressed. The thicknesses of the first protective layer 21 and the second protective layer 22 may be the same, or the first protective layer 21 may be thicker, or the second protective layer 22 may be thicker. Typically, the first protective layer 21 is thicker than the second protective layer 22.

[0173] (First Optical Compensation Layer) The first optical compensation layer 30 can function as a λ / 2 plate. The in-plane retardation Re(550) of the first optical compensation layer 30 is usually 220 nm or more and 320 nm or less, and preferably 240 nm or more and 300 nm or less.

[0174] The first optical compensation layer 30 is a liquid crystal alignment solidification layer, more specifically, a layer in which a discotic liquid crystal compound is fixed in a vertically aligned state. Discotic liquid crystal compounds generally refer to liquid crystal compounds having a discotic molecular structure in which a cyclic core such as benzene, 1,3,5-triazine, or calixarene is located at the center of the molecule and linear alkyl groups, alkoxy groups, substituted benzoyloxy groups, or the like are radially substituted as side chains. Conventionally known compounds can be used as discotic liquid crystals.

[0175] The first optical compensation layer 30 can be formed, for example, by the following procedure. Here, we will explain the formation of a long-sized first optical compensation layer on a long-sized polarizer. First, while transporting a long-sized substrate, a coating liquid for forming an alignment film is applied to the substrate and dried to form a coating film. The coating film is rubbed in a predetermined direction to form an alignment film on the substrate. The predetermined direction corresponds to the slow axis direction of the resulting first optical compensation layer, and is, for example, at an angle of approximately 15° relative to the longitudinal direction of the substrate. Next, a coating liquid for forming a first optical compensation layer (a solution containing a discotic liquid crystal compound and, if necessary, a crosslinkable monomer) is applied to the formed alignment film and heated. Heating removes the solvent from the coating liquid and promotes the alignment of the discotic liquid crystal compound. Heating may be performed in a single step or in multiple steps at different temperatures. Next, ultraviolet light is irradiated to crosslink (or polymerize) the crosslinkable (or polymerizable) monomer, thereby fixing the alignment of the discotic liquid crystal compound. In this way, a first optical compensation layer is formed on the substrate. Finally, the first optical compensation layer is attached to the polarizer via the adhesive layer, and the substrate is peeled off (i.e., the first optical compensation layer is transferred from the substrate to the polarizer). In this manner, the first optical compensation layer can be laminated on the polarizer. Note that a method for vertically aligning a discotic liquid crystal compound is described, for example, in

[0153] of JP-A-2006-133652.

[0176] The thickness of the first optical compensation layer 30 is usually 1.5 μm or more, and preferably 1.6 μm or more and 2.0 μm or less.

[0177] (Second Optical Compensation Layer) The second optical compensation layer 40 can function as a λ / 4 plate. The in-plane retardation Re(550) of the second optical compensation layer 40 is typically 100 nm or more and 200 nm or less, and preferably 110 nm or more and 180 nm or less.

[0178] In the second optical compensation layer 40, rod-shaped liquid crystal compounds are typically aligned in the slow axis direction of the second optical compensation layer (homogeneous alignment). Examples of liquid crystal compounds include liquid crystal compounds whose liquid crystal phase is a nematic phase (nematic liquid crystals). Examples of such liquid crystal compounds that can be used include liquid crystal polymers and liquid crystal monomers. The liquid crystal compound may exhibit liquid crystallinity via either a lyotropic or thermotropic mechanism. The liquid crystal polymer and liquid crystal monomer may be used alone or in combination.

[0179] When the liquid crystal compound is a liquid crystal monomer, the liquid crystal monomer is preferably a polymerizable monomer and a crosslinkable monomer. This is because the orientation state of the liquid crystal monomer can be fixed by polymerizing or crosslinking the liquid crystal monomer. After the liquid crystal monomer is aligned, for example, the alignment state can be fixed by polymerizing or crosslinking the liquid crystal monomers with each other. Here, a polymer is formed by polymerization, and a three-dimensional network structure is formed by crosslinking, but these are non-liquid crystals. Therefore, the formed second optical compensation layer does not undergo, for example, a transition to a liquid crystal phase, glass phase, or crystalline phase due to temperature changes, which is unique to liquid crystal compounds. As a result, the second optical compensation layer 40 becomes a retardation layer that is not affected by temperature changes and has excellent stability.

[0180] The temperature range in which the liquid crystal monomer exhibits liquid crystallinity varies depending on the type of the liquid crystal monomer, but specifically, the temperature range is preferably 40°C or higher and 120°C or lower, and more preferably 50°C or higher and 100°C or lower.

[0181] As the liquid crystal monomer, any suitable liquid crystal monomer known in the art can be used.

[0182] The second optical compensation layer 40 can be formed by performing an alignment treatment on the surface of a predetermined substrate, applying a coating liquid containing a liquid crystal compound to the surface to align the liquid crystal compound in a direction corresponding to the alignment treatment, and fixing the aligned state. In one embodiment, the substrate is any appropriate resin film, and the second optical compensation layer 40 formed on the substrate can be transferred to the surface of the first optical compensation layer 30 via an adhesive layer.

[0183] Any appropriate alignment treatment can be employed as the alignment treatment. Specific examples include mechanical alignment treatment, physical alignment treatment, and chemical alignment treatment. Specific examples of mechanical alignment treatment include rubbing treatment and stretching treatment. Specific examples of physical alignment treatment include magnetic field alignment treatment and electric field alignment treatment. Specific examples of chemical alignment treatment include oblique deposition and photo-alignment treatment. Any appropriate treatment conditions can be employed for the various alignment treatments depending on the purpose. In embodiments of the present invention, photo-alignment treatment is preferred because photo-alignment treatment does not generate foreign matter such as rubbing debris. By forming a thin λ / 4 plate using photo-alignment treatment, display defects caused by foreign matter can be suppressed.

[0184] The alignment of liquid crystal compounds is achieved by treating them at a temperature at which they exhibit a liquid crystal phase depending on the type of liquid crystal compound. By performing such temperature treatment, the liquid crystal compounds assume a liquid crystal state and are aligned in accordance with the alignment treatment direction on the substrate surface.

[0185] In one embodiment, the alignment state is fixed by cooling the liquid crystal compound aligned as described above. When the liquid crystal compound is a polymerizable monomer or a crosslinkable monomer, the alignment state is fixed by subjecting the liquid crystal compound aligned as described above to a polymerization treatment or a crosslinking treatment.

[0186] The thickness of the second optical compensation layer 40 is preferably 0.5 μm or more and 1.2 μm or less. With such a thickness, the second optical compensation layer 40 can function appropriately as a λ / 4 plate.

[0187] (Conductive layer or conductive layer with substrate) The conductive layer can be formed by depositing a metal oxide film on a suitable substrate by any suitable film-forming method (e.g., vacuum deposition, sputtering, CVD, ion plating, spraying, etc.). After deposition, a heat treatment (e.g., 100°C or higher and 200°C or lower) may be performed as needed. Heat treatment can crystallize an amorphous film. Examples of metal oxides include indium oxide, tin oxide, zinc oxide, indium-tin composite oxide, tin-antimony composite oxide, zinc-aluminum composite oxide, and indium-zinc composite oxide. Indium oxide may be doped with divalent metal ions or tetravalent metal ions. Indium-based composite oxides are preferred, and indium-tin composite oxide (ITO) is more preferred. Indium-based composite oxides are characterized by high transmittance (e.g., 80% or higher) in the visible light region (wavelength 380 nm or higher and 780 nm or lower) and low surface resistance per unit area.

[0188] When the conductive layer contains a metal oxide, the thickness of the conductive layer is preferably 50 nm or less, more preferably 35 nm or less. The lower limit of the thickness of the conductive layer is preferably 10 nm or more.

[0189] The surface resistance value of the conductive layer is preferably 300 Ω / □ or less, more preferably 150 Ω / □ or less, and even more preferably 100 Ω / □ or less.

[0190] The conductive layer can be formed as an electrode by patterning the metal oxide film by etching or the like. The electrode can function as a touch sensor electrode that senses touch on the touch panel.

[0191] The conductive layer may be transferred from the substrate to the second optical compensation layer and used alone as a constituent layer of the polarizing plate with an optical compensation layer, or may be laminated on the second optical compensation layer as a laminate with the substrate (a substrate-attached conductive layer, i.e., a conductive film or a sensor film).Typically, as described above, the conductive layer and the substrate can be introduced into the polarizing plate with an optical compensation layer as a substrate-attached conductive layer.

[0192] The material constituting the substrate may be any appropriate resin, preferably a resin with excellent transparency, such as a cyclic olefin resin, a polycarbonate resin, a cellulose resin, a polyester resin, or an acrylic resin.

[0193] Preferably, the substrate is optically isotropic, and therefore the conductive layer can be used as an isotropic substrate-attached conductive layer in a polarizing plate with an optical compensation layer. Examples of materials constituting an optically isotropic substrate (isotropic substrate) include materials having a non-conjugated resin as the main skeleton, such as norbornene resins and olefin resins, and materials having a cyclic structure, such as a lactone ring or glutarimide ring, in the main chain of an acrylic resin. Using such materials can minimize the occurrence of retardation due to molecular chain orientation when an isotropic substrate is formed.

[0194] The thickness of the substrate is preferably 10 μm or more and 200 μm or less, and more preferably 20 μm or more and 60 μm or less.

[0195] (others) Any appropriate adhesive (adhesive layer) is used for laminating each layer constituting the polarizing plate with optical compensation layers according to the present invention. A water-based adhesive (e.g., a PVA-based adhesive) can be typically used for laminating the polarizer and the protective layer. An active energy ray (e.g., ultraviolet) curable adhesive is typically used for laminating the optical compensation layer. The thickness of the adhesive layer is preferably 0.01 μm or more and 7 μm or less, more preferably 0.01 μm or more and 5 μm or less.

[0196] Although not shown, a pressure-sensitive adhesive layer of the present invention is provided on the second optical compensation layer 40 side of the polarizing plate with optical compensation layers 100 (on the substrate side if a conductive layer and a substrate are provided), resulting in the pressure-sensitive adhesive layer and polarizing plate with optical compensation layers according to this embodiment. The pre-providing of the pressure-sensitive adhesive layer of the present invention allows for easy attachment to other optical components (e.g., image display cells). For practical purposes, a separator is temporarily and releasably attached to the pressure-sensitive adhesive layer to protect the pressure-sensitive adhesive layer until actual use and to enable roll formation.

[0197] [Image display device] The present invention also provides an image display device using at least one of the optical members described above.

[0198] The image display device is not particularly limited, and examples thereof include a liquid crystal display device, an organic EL display device, a plasma display (PDP), a micro LED display, etc. Furthermore, from the viewpoint of more significantly exhibiting the effects of the pressure-sensitive adhesive for optical films of the present invention, a particularly thin image display device is preferably used. [Example]

[0199] The present invention will be described in more detail below with reference to examples, but these examples are not intended to limit the present invention in any way. In the following description, all "parts" mean "parts by mass." Unless otherwise specified, operations and measurements of physical properties were carried out at room temperature of 23°C and a relative humidity of 55% RH.

[0200] <Measurement of weight average molecular weight (Mw)> The weight average molecular weight (Mw) of the (meth)acrylic acid ester copolymer (A) was measured by GPC (gel permeation chromatography) under the following conditions: Analytical equipment: Tosoh Corporation, HLC-8120GPC Column: Tosoh Corporation, G7000H XL +GMH XL +GMH XL Column size: 7.8mmφ x 30cm each, total 90cm Column temperature: 40℃ Flow rate: 0.8ml / min Injection volume: 100μl Eluent: tetrahydrofuran Detector: Differential refractometer (RI) Standard sample: polystyrene.

[0201] <Preparation of (Meth)acrylic Acid Ester Copolymer (A1)> [Manufacturing Example 1] A four-neck flask equipped with a stirring blade, thermometer, nitrogen gas inlet tube, and condenser was charged with 99 parts by weight of m-phenoxybenzyl acrylate (Light Acrylate POB-A, manufactured by Kyoeisha Chemical Co., Ltd.), 1% by weight of 4-hydroxybutyl acrylate (manufactured by Osaka Organic Chemical Industry Co., Ltd.), and 0.1 parts by weight of 2,2'-azobisisobutyronitrile (AIBN, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) as a polymerization initiator, along with 100 parts by weight of ethyl acetate. Nitrogen gas was then introduced while gently stirring. After nitrogen gas replacement, the liquid temperature in the flask was controlled at around 55°C, and polymerization reaction was carried out for 5 hours to prepare a solution of (meth)acrylic acid ester copolymer (A1) with a weight-average molecular weight (Mw) of 1,020,000 and Mw / Mn = 2.5.

[0202] [Manufacturing Examples 2 to 28] (Meth)acrylic acid ester copolymers (A-2) to (A-28) were obtained in the same manner as in Production Example 1, except that the types and ratios of monomers and the amount of photopolymerization initiator were changed as shown in Table 1 below. The compositions and weight average molecular weights (Mw) of (meth)acrylic acid ester copolymers (A-1) to (A-28) are shown in Table 1 below.

[0203] The monomers in Table 1 are as follows: Note that blank spaces in Table 1 indicate that the monomer was not used.

[0204] POB-A: Phenoxybenzyl acrylate (Light Acrylate POB-A, manufactured by Kyoeisha Chemical Co., Ltd.) A-LEN-10: Ethoxylated o-phenylphenol acrylate (A-LEN-10, manufactured by Shin-Nakamura Chemical Co., Ltd.) NMT-A: 1-naphthylmethyl acrylate (Kyoeisha Chemical Co., Ltd.) A-BPML: p-phenylbenzyl acrylate (manufactured by Shin-Nakamura Chemical Co., Ltd.) PhEA: Phenoxyethyl acrylate (Kyoeisha Chemical Co., Ltd.) BzA: benzyl acrylate (Osaka Organic Chemical Industry Ltd.) FLM-A: 9-fluorenylmethyl acrylate (synthesized based on JP 2013-181097 A) 4HBA: 4-hydroxybutyl acrylate (Osaka Organic Chemical Industry Ltd.) HEAA (registered trademark): N-hydroxyethyl acrylamide (KJ Chemicals Co., Ltd.) IBXA: Isobornyl acrylate (Osaka Organic Chemical Industry Ltd.) ACMO (registered trademark): N-acryloylmorpholine (manufactured by KJ Chemicals Co., Ltd.) BA: n-butyl acrylate (manufactured by Nippon Shokubai Co., Ltd.) MEA: Methoxyethyl acrylate (manufactured by Nippon Shokubai Co., Ltd.).

[0205] [Table 1]

[0206] <Preparation of Pressure-Sensitive Adhesive, Pressure-Sensitive Adhesive Layer, and Optical Component> [Example 1] (Preparation of adhesive for optical film) To 100% by mass of the solids content of the (meth)acrylic acid ester copolymer (A1) solution obtained in Production Example 1 (i.e., 100 parts by mass of the (meth)acrylic acid ester copolymer (A1)), 0.1 parts by mass (active ingredient equivalent) of Takenate (registered trademark) D-110N (75% ethyl acetate solution of an adduct of xylylene diisocyanate (XDI) and trimethylolpropane, number of isocyanate groups per molecule: 3, manufactured by Mitsui Chemicals, Inc., number average molecular weight Mn = 700) as a crosslinking agent and 0.1 parts by mass of a silane coupling agent (trade name: KBM-403, manufactured by Shin-Etsu Chemical Co., Ltd., 3-glycidoxypropyltrimethoxysilane) were added and mixed to prepare an adhesive for optical films (solids content 25% by mass, solvent 75% by mass).

[0207] (Formation of pressure-sensitive adhesive layer for optical film) The pressure-sensitive adhesive obtained above was applied to one side of a release-treated (silicone-treated) 38 μm-thick polyethylene terephthalate (PET) film (Mitsubishi Chemical Corporation, MRF38, without oligomer blocking layer) so that the thickness of the pressure-sensitive adhesive layer after drying would be 20 μm. The film was then heated at 120°C for 2 minutes to form a pressure-sensitive adhesive layer for optical films.

[0208] The heat treatment was carried out by a float drying method in which hot air was blown directly from above and below the film.

[0209] (Preparation of Optical Members (Polarizing Plates with Pressure-Sensitive Adhesive Layers and Optical Compensation Layers)) 1-1. Preparation of polarizing plates A-PET (amorphous polyethylene terephthalate) film (manufactured by Mitsubishi Chemical Corporation, product name: Novaclear® SH046, thickness 200 μm) was prepared as a substrate, and the surface was corona-treated (corona discharge rate 58 W·min / m 2) was applied. Separately, polyvinyl alcohol (PVA, polymerization degree 4200, saponification degree 99.2%) to which 1% by mass of acetoacetyl-modified polyvinyl alcohol (manufactured by Mitsubishi Chemical Corporation, trade name: Gohsefimer (trade name) Z200, polymerization degree 1200, saponification degree 99.0% or more, acetoacetyl-modification degree 4.6%) was added was prepared. This polyvinyl alcohol was applied to the corona-treated surface of the A-PET film so that the film thickness after drying would be 12 μm, and the film was dried by hot air drying in an atmosphere of 60°C for 10 minutes. In this way, a laminate having a polyvinyl alcohol (PVA)-based resin layer provided on the substrate was produced.

[0210] Next, this laminate was first stretched 2.0 times in air at 130°C to obtain a stretched laminate. Next, the stretched laminate was immersed in a boric acid insolubilizing aqueous solution at a liquid temperature of 30°C for 30 seconds to insolubilize the PVA-based resin layer in which polyvinyl alcohol molecules contained in the stretched laminate were oriented. This boric acid insolubilizing aqueous solution had a boric acid content of 3% by mass relative to 100% by mass of water. A colored laminate was produced by dyeing this stretched laminate. The colored laminate was produced by immersing the stretched laminate in a dyeing solution containing iodine and potassium iodide at a liquid temperature of 30°C, thereby adsorbing iodine to the PVA-based resin layer contained in the stretched laminate. The iodine concentration and immersion time were adjusted so that the resulting polarizer had a single transmittance of 44.5%. Specifically, the dye solution contained water as a solvent, had an iodine concentration of 0.08% by mass to 0.25% by mass, and a potassium iodide concentration of 0.56% by mass to 1.75% by mass, with the ratio of the iodine and potassium iodide concentrations being 1:7.

[0211] Next, the colored laminate was immersed in a boric acid crosslinking aqueous solution at 30° C. for 60 seconds to remove iodide. A process was then carried out to crosslink PVA molecules in the PVA-based resin layer to which the dye had been adsorbed. The boric acid crosslinking aqueous solution used in this process had a boric acid content of 3% by mass relative to 100% by mass of water and a potassium iodide content of 3% by mass relative to 100% by mass of water. The resulting colored laminate was then stretched 2.7 times in the same direction as the air stretching process described above at a stretching temperature of 70°C in the boric acid aqueous solution, resulting in a final stretching ratio of 5.4 times, thereby obtaining a substrate / polarizer laminate. The polarizer had a thickness of 5 μm. The boric acid crosslinking aqueous solution used in this process had a boric acid content of 6.5% by mass relative to 100% by mass of water and a potassium iodide content of 5% by mass relative to 100% by mass of water. The resulting laminate was removed from the boric acid aqueous solution, and the boric acid adhering to the polarizer surface was washed with an aqueous solution containing 2% by mass of potassium iodide relative to 100% by mass of water. The washed laminate was dried with hot air at 60°C.

[0212] A 40 μm thick acrylic film was attached to the polarizer surface of the substrate / polarizer laminate via a PVA adhesive, and a polarizing plate having a protective layer / polarizer / resin substrate structure was obtained.

[0213] 1-2. Preparation of liquid crystal alignment solidified layer constituting the first optical compensation layer A liquid crystal alignment solidified layer (first optical compensation layer) was formed on a substrate (TAC film) according to the procedure described in paragraphs

[0151] to

[0156] of JP 2006-133652 A. The rubbing direction was set at 15° counterclockwise relative to the absorption axis of the polarizer when viewed from the viewing side when the film was attached to the polarizer. The thickness of the first optical compensation layer was 1.7 μm, and the in-plane retardation Re(550) was 270 nm. The first optical compensation layer was a negative A plate exhibiting refractive index characteristics of nx = nz > ny. No protrusions with a height of 0.4 μm or more were observed on the surface of the first optical compensation layer (negative A plate).

[0214] 1-3. Preparation of liquid crystal alignment solidified layer constituting the second optical compensation layer A liquid crystal composition (coating liquid) was prepared by dissolving 10 g of a polymerizable liquid crystal compound exhibiting a nematic liquid crystal phase (manufactured by BASF under the trade name "Paliocolor (registered trademark) LC242", a compound represented by the following formula) and 3 g of a photopolymerization initiator for the polymerizable liquid crystal compound (Omnirad (registered trademark) 907, manufactured by IGM Resins BV) in 40 g of toluene.

[0215] [ka]

[0216] A photo-alignment film was coated on the surface of a polyethylene terephthalate (PET) film (thickness: 38 μm), and then photo-alignment treatment was performed. The direction of the photo-alignment treatment was set to a 75° counterclockwise direction, as viewed from the viewing side, with respect to the direction of the absorption axis of the polarizer when it was attached to the polarizer. The liquid crystal composition described above was coated on this photo-alignment-treated surface using a bar coater, and the liquid crystal compound was aligned by heating and drying at 90°C for 2 minutes. The liquid crystal layer thus formed was then irradiated with 1 mJ / cm using a metal halide lamp. 2 The liquid crystal layer was cured by irradiating it with light, forming a liquid crystal alignment solidified layer (second optical compensation layer) on the substrate (PET film). The second optical compensation layer had a thickness of 1.2 μm and an in-plane retardation Re(550) of 140 nm. Furthermore, the second optical compensation layer was a positive A plate exhibiting refractive index characteristics of nx>ny=nz.

[0217] 1-4. Preparation of polarizing plate with optical compensation layer The A-PET film substrate was peeled from the polarizing plate obtained above, and the first optical compensation layer was transferred from the substrate / first optical compensation layer laminate to the peeled surface via a UV-curable adhesive. Furthermore, the second optical compensation layer was transferred from the substrate / second optical compensation layer laminate to the surface of the first optical compensation layer via a UV-curable adhesive. In this way, a polarizing plate with optical compensation layers was obtained, having a configuration of protective layer / polarizer / first optical compensation layer (negative A plate: λ / 2 plate) / second optical compensation layer (positive A plate: λ / 4 plate).

[0218] 1-5. Preparation of a polarizing plate with an adhesive layer and an optical compensation layer The polarizing plate side (opposite to the protective film side) on which the pressure-sensitive adhesive layer of the polarizing plate with optical compensation layer obtained above is to be formed was subjected to a corona discharge of 80 W·min / m 2 The PET film having the pressure-sensitive adhesive layer formed thereon was then bonded to the film so that the formed adhesion-facilitating treatment layer and the pressure-sensitive adhesive layer were in contact with each other, thereby producing an optical member, i.e., a polarizing plate with a pressure-sensitive adhesive layer and an optical compensation layer.

[0219] (Fabrication of organic EL display devices) The obtained pressure-sensitive adhesive layer and polarizing plate with an optical compensation layer was cut into a size of 100 mm x 50 mm.

[0220] An organic EL display device was taken out by disassembling a smartphone (Galaxy-S10) manufactured by Samsung Electronics Co., Ltd. The polarizing film attached to this organic EL display device was peeled off, and the polarizing plate with an optical compensation layer cut out above was attached instead to obtain an organic EL display device.

[0221] [Examples 2 to 30, Comparative Examples 1 to 5] In the <Preparation of adhesive composition> of Example 1, an adhesive, an adhesive layer, and a polarizing plate with an optical compensation layer were obtained in the same manner as in Example 1, except that the type of (meth)acrylic acid ester copolymer (A) and the type and amount of additive were changed as shown in Table 2 below.

[0222] Two types of particles (compatibility improved product 1 and compatibility improved product 2) in which zirconium oxide was coated with a coating agent were used as the inorganic particles in Table 2. The amount added shown in Table 2 is the amount of zirconium oxide particles (amount of active ingredient) per 100 parts by mass of copolymer (A).

[0223] Furthermore, KBE-403, which is the silane coupling agent (C) in Table 2, is 3-glycidoxypropyltriethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd.).

[0224] <Evaluation> (Refractive index of adhesive layer) The refractive index of the adhesive layer at sodium D line was measured at 25°C using an Abbe refractometer.

[0225] (Hayes) A pressure-sensitive adhesive layer was formed in the same manner as in (Formation of pressure-sensitive adhesive layer for optical film) above, and then a release film was attached to the exposed surface of the pressure-sensitive adhesive layer to prepare a pressure-sensitive adhesive sheet.

[0226] The release film on one side of the obtained pressure-sensitive adhesive sheet was peeled off, and the exposed adhesive surface was roll-pressed onto alkali-free glass (82 mm × 53 mm × 0.5 mm thick). Next, the other PET film was peeled off, and alkali-free glass (82 mm × 53 mm × 0.5 mm thick) was laminated using a roll. After that, the sheet was autoclaved (50 ° C, gauge pressure 0.4 MPa, 20 minutes) to perform finish lamination, and an evaluation sample was prepared.

[0227] The haze of the obtained evaluation sample was measured in an environment of 25° C. and a relative humidity of 55% RH using a haze meter (NDH5000, manufactured by Nippon Denshoku Industries Co., Ltd.) in accordance with JIS K7136 (2000).

[0228] (durability) The organic EL display device to which the polarizing plate with an optical compensation layer having the pressure-sensitive adhesive layer prepared above was attached was used as a sample for durability evaluation. The obtained sample was subjected to the following tests, and its appearance was evaluated visually: (1) Treated at 85°C for 500 hours (heating test) (2) Treated for 500 hours in an atmosphere of 60°C and 95% relative humidity (humidification test) (3) Heat shock (HS) testing was performed for 300 cycles (300 hours), with one cycle consisting of 30 minutes at 85°C and then 30 minutes at -40°C. -Visual evaluation- ◎: No bubbles at the edge ○: There are a few bubbles at the edge, but this does not pose a problem in practical use. △: There are bubbles at the edge, but unless it is for a special purpose, there is no problem in practical use. ×: A significant number of bubbles were found at the edge, which was problematic for practical use.

[0229] (Haze value after 500 hours of humidification test and 1 hour of standing at room temperature (23°C 55% RH) The sample subjected to the durability humidification test was taken out and left to stand in a room temperature (23°C, 55% RH) environment for 3 hours, and then the haze was measured using the method described in the above (Haze) section. The measured haze value was evaluated on the following 5-point scale. 5 is the best, and 3 or more is usable: 5: Less than 1.0% 4: 1.0% or more and less than 2.0% 3: 2.0% or more but less than 3.0% 2: 3.0% or more and less than 5.0% 1: 5.0% or more.

[0230] (Coatability) The surface condition of the pressure-sensitive adhesive layer formed in the above (Formation of pressure-sensitive adhesive layer for optical film) immediately after formation was visually observed and evaluated according to the following criteria. 5-point scale is the best, and 3 or more is practical: 5: No coating streaks or uneven coating 4: Weak coating streaks or uneven coating in some areas 3: Weak coating streaks or uneven coating all over the surface 2: Strong coating streaks or uneven coating all over the surface 1: A uniform coating surface cannot be formed.

[0231] The composition and evaluation results of each adhesive are shown in Table 2. Note that "-" in the inorganic particles column indicates that no inorganic particles were used.

[0232] [Table 2]

[0233] From the results in Table 2 above, it was found that the adhesive of the present invention in the examples can obtain an adhesive layer that has a high refractive index, is durable in harsh environments (high temperature, high humidity, heat shock), and has excellent transparency after at least one of a heat treatment and a photocuring treatment.

[0234] Furthermore, in Examples 13 to 30 in which inorganic particles were used, there was a tendency for the coating properties to be improved. [Explanation of symbols]

[0235] 10 polarizers, 21 first protective layer, 22 second protective layer, 30 first optical compensation layer (first retardation layer), 40 second optical compensation layer (second retardation layer), 100 Polarizing plate with optical compensation layer.

Claims

1. A pressure-sensitive adhesive for optical films, comprising a (meth)acrylic acid ester copolymer (A) and inorganic particles (B), The (meth)acrylic acid ester copolymer (A) is (a1): a structural unit derived from a (meth)acrylic acid ester monomer having an aromatic hydrocarbon group, and (a2): Contains a structural unit derived from a (meth)acrylic monomer having a hydroxy group, the content of the structural units derived from the component (a1) is 65% by mass or more and 99% by mass or less, with the total amount of all structural units of the (meth)acrylic acid ester copolymer (A) being 100% by mass; the content of the structural units derived from the component (a2) is 0.1% by mass or more and 25% by mass or less, with the total amount of all structural units of the (meth)acrylic acid ester copolymer (A) being 100% by mass; the weight average molecular weight of the (meth)acrylic acid ester copolymer (A) is 500,000 or more and 2,000,000 or less, The average particle diameter of the inorganic particles (B) is 1 nm or more and 100 nm or less, the content of the inorganic particles (B) is more than 100 parts by mass and not more than 2,000 parts by mass relative to 100 parts by mass of the (meth)acrylic acid ester copolymer (A); The pressure-sensitive adhesive for optical films, wherein the pressure-sensitive adhesive layer obtained by curing the pressure-sensitive adhesive for optical films through at least one of a heat treatment and a photo-curing treatment has a refractive index of 1.58 or more and 1.80 or less.

2. The pressure-sensitive adhesive for optical films according to claim 1 , wherein the (meth)acrylic acid ester copolymer (A) has a weight average molecular weight of 700,000 or more and 2,000,000 or less.

3. The pressure-sensitive adhesive for optical films according to claim 1 or 2, wherein the (meth)acrylic acid ester copolymer (A) has a weight average molecular weight of 900,000 or more and 2,000,000 or less.

4. The pressure-sensitive adhesive for optical films according to any one of claims 1 to 3, wherein the content of the structural units derived from the component (a2) is 0.1 mass% or more and less than 12 mass%, with the total structural units of the (meth)acrylic acid ester copolymer (A) being 100 mass%.

5. The (meth)acrylic acid ester copolymer (A) further has a structural unit derived from a monomer (a3) ​​having one radically polymerizable functional group other than the component (a1) and the component (a2). The pressure-sensitive adhesive for optical films according to any one of claims 1 to 4.

6. The pressure-sensitive adhesive for optical films according to claim 5, wherein the content of the structural units derived from the component (a3) ​​is 3% by mass or more and 80% by mass or less, with the total structural units of the (meth)acrylic acid ester copolymer (A) being 100% by mass.

7. The pressure-sensitive adhesive for optical films according to any one of claims 1 to 6, wherein the (a1) (meth)acrylic acid ester monomer having an aromatic hydrocarbon group has at least one group selected from the group consisting of a biphenyl ring group, a phenoxybenzyl group, a naphthalene ring group, and a fluorene ring group.

8. The pressure-sensitive adhesive for optical films according to any one of claims 1 to 7, wherein the (a1) (meth)acrylic acid ester monomer having an aromatic hydrocarbon group comprises at least one selected from the group consisting of phenoxybenzyl (meth)acrylate, naphthyl (meth)acrylate, hydroxynaphthyl (meth)acrylate, fluorenyl (meth)acrylate, and hydroxyfluorenyl (meth)acrylate.

9. The content of the inorganic particles (B) is 300 parts by mass or more and 1000 parts by mass or less per 100 parts by mass of the (meth)acrylic acid ester copolymer (A).

10. The pressure-sensitive adhesive for optical films according to any one of claims 1 to 9, wherein the inorganic particles (B) are at least one selected from the group consisting of zirconium oxide, zinc oxide, iron oxide, copper oxide, titanium oxide, tin oxide, cerium oxide, tantalum oxide, niobium oxide, tungsten oxide, europium oxide, hafnium oxide, potassium titanate, barium titanate, strontium titanate, potassium niobate, lithium niobate, calcium tungstate, antimony-doped tin oxide (ATO), and indium tin oxide (ITO).

11. The pressure-sensitive adhesive for optical films according to any one of claims 1 to 10, wherein the inorganic particles (B) are at least one selected from the group consisting of zirconium oxide, titanium oxide, and barium titanate.

12. The pressure-sensitive adhesive for optical films according to any one of claims 1 to 11, wherein the inorganic particles (B) are coated with one or more coating agents.

13. A pressure-sensitive adhesive layer for an optical film, obtained by curing the pressure-sensitive adhesive for an optical film according to any one of claims 1 to 12 by at least one of a heat treatment and a photo-curing treatment, A pressure-sensitive adhesive layer for optical films, having a haze value of 0.05% or more and 1.0% or less when the layer has a thickness of 20 μm.

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