Adhesive composition for laminated optical films and laminated optical films

Abstract

To provide an adhesive composition for laminated optical films, which serves as a raw material for adhesive layers that have an improved refractive index when used as an adhesive layer, excellent adhesive strength between at least two optical films, and a reduced cure shrinkage rate. The adhesive composition for laminated optical films is for bonding at least two optical films, and comprises a curable component, metal oxide particles, and a compound represented by the following general formula (1): JPEG2026041925000012.jpg37151 (wherein X is a reactive group, Y is an alkylene group having 1 to 12 carbon atoms which may have a branched chain, or a phenylene group which may have a substituent, and R 1 and R 2 each independently represents a hydrogen atom, an aliphatic hydrocarbon group, an aryl group, or a heterocyclic group which may have a substituent.

Description

[Technical Field]

[0001] The present invention relates to an adhesive composition for a laminated optical film for bonding at least two optical films, and to a laminated optical film, which can be used to form image displays such as liquid crystal displays (LCDs), organic electroluminescence displays, CRTs, and PDPs. [Background technology]

[0002] 2. Description of the Related Art Image display devices are known in which a circular polarizer is disposed on the viewing side of a display panel in order to improve poor visibility caused by reflection of external light or glare of the background on the display screen of the image display device.

[0003] For example, Patent Document 1 listed below describes a polarizing plate composite comprising, in this order, a linear polarizing plate, a half-wave layer, a first adhesive layer formed by curing an active energy ray-curable adhesive, and a quarter-wave layer, in which the angle between the fast axis of the half-wave layer and the transmission axis of the linear polarizing plate is 10° or more and 20° or less, and the absolute value of the difference between the refractive index of the first adhesive layer at a wavelength of 589 nm and the refractive index of the half-wave layer in the fast axis direction at a wavelength of 589 nm is less than 0.05.

[0004] Furthermore, Patent Document 2 listed below describes a retardation layer-attached polarizing plate that includes a polarizer, a first retardation layer, and a second retardation layer in this order, the polarizer and the first retardation layer being bonded together via a first adhesive layer, the first retardation layer and the second retardation layer being bonded together via a second adhesive layer, the thicknesses of the first retardation layer and the second retardation layer being 5 μm or less, the average refractive index of the second adhesive layer being 1.55 or more, and the difference between the average refractive index of the second adhesive layer and that of the first retardation layer and that of the second retardation layer being less than 0.08.

[0005] Incidentally, Patent Document 3 listed below describes an active energy ray-curable resin composition characterized by containing metal oxide nanoparticles (A), phenoxybenzyl (meth)acrylates (B), and a bifunctional (meth)acrylate (C) having a (poly)alkylene glycol structure, with the aim of providing an active energy ray-curable resin composition and a cured product thereof that have a balance of various properties required for optical sheets and the like used in optical applications. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2020-52365 [Patent Document 2] Japanese Patent Application Publication No. 2018-17996 [Patent Document 3] Japanese Patent Application Laid-Open No. 2017-128688 Summary of the Invention [Problem to be solved by the invention]

[0007] As a result of intensive research by the present inventors, it has been found that the techniques described in Patent Documents 1 and 2 above leave room for further improvement when it comes to stably improving the refractive index of interlayer adhesives for laminated films. The technique described in Patent Document 3 above relates to an active energy ray-curable resin composition for producing a lens sheet, and is not intended for use in bonding at least two optical films. In addition, adhesive compositions for laminated optical films are applied to optical films at fairly thin thicknesses, and therefore, when metal oxide particles are contained, the adhesive composition must have excellent liquid stability. However, the technique described in Patent Document 3 above does not address this issue, much less describe or suggest a means for solving this issue.

[0008] The present invention was developed in view of the above-described circumstances, and aims to provide an adhesive composition for laminated optical films, which serves as a raw material for adhesive layers that, when formed into an adhesive layer, have an improved refractive index, excellent adhesive strength between at least two optical films, and a reduced cure shrinkage rate.

[0009] A further object of the present invention is to provide a laminated optical film that includes an adhesive layer that is a cured product layer of an adhesive composition for laminated optical films, and that has an adhesive layer with a high refractive index. [Means for solving the problem]

[0010] The above-mentioned problems can be solved by the following configuration: That is, the present invention provides an adhesive composition for laminated optical films for bonding at least two optical films, comprising: A curable component, metal oxide particles, and a composition of the following general formula (1): [ka] (wherein X is a reactive group, Y is an alkylene group having 1 to 12 carbon atoms which may have a branched chain, or a phenylene group which may have a substituent, and R 1 and R 2 each independently represents a hydrogen atom, an optionally substituted aliphatic hydrocarbon group, an aryl group, or a heterocyclic group).

[0011] In the adhesive composition (1) for laminated optical films, when the total amount of the composition is taken as 100 mass %, the content of the metal oxide particles is preferably 10 to 50 mass %.

[0012] In the adhesive composition for laminated optical films (1) or (2), when the total amount of the composition is taken as 100 mass %, the content of the compound represented by the general formula (1) is preferably 0.1 to 10 mass %.

[0013] Of the adhesive compositions for laminated optical films (1) to (3), preferred is an adhesive composition for laminated optical films (4) which further contains a hydroxyl group-containing (meth)acrylate.

[0014] In the adhesive composition (4) for laminated optical films, when the total amount of the composition is taken as 100 mass %, the content of the hydroxyl group-containing (meth)acrylate is preferably 1 to 30 mass %.

[0015] Of the adhesive compositions for laminated optical films (1) to (5), preferred is an adhesive composition for laminated optical films (6) which further contains a (meth)acrylate containing an aromatic ring skeleton.

[0016] In the adhesive composition (6) for laminated optical films, when the total amount of the composition is taken as 100 mass %, the content of the (meth)acrylate containing an aromatic ring skeleton is preferably 30 to 70 mass %.

[0017] In the adhesive composition (6) for laminated optical films, the (meth)acrylate containing an aromatic ring skeleton is preferably at least one selected from the group consisting of (meth)acrylates having a polycyclic aromatic ring skeleton and (meth)acrylates having two or more aromatic rings.

[0018] In the adhesive composition for laminated optical films (6), the (meth)acrylate containing an aromatic ring skeleton is preferably phenoxybenzyl (meth)acrylate, as in the adhesive composition for laminated optical films (9).

[0019] In any of the adhesive compositions (1) to (9) for laminated optical films, preferred is an adhesive composition (10) for laminated optical films further containing a leveling agent containing at least one compound selected from the group consisting of an isocyanurate compound and a polysiloxane compound.

[0020] In the adhesive composition (10) for laminated optical films, when the total amount of the composition is taken as 100 mass %, the content of the isocyanurate compound is preferably 0.05 to 10 mass %.

[0021] In the adhesive composition (10) for laminated optical films, when the total amount of the composition is taken as 100 mass %, the content of the polysiloxane compound is preferably 0.05 to 2.0 mass %.

[0022] Of the adhesive compositions (1) to (12) for laminated optical films, preferred is an adhesive composition (13) for laminated optical films having a viscosity at 25° C. of 100 mPa·s or less.

[0023] The present invention also relates to a laminated optical film (14) in which at least a first optical film and a second optical film are laminated via an adhesive layer, wherein the adhesive layer is a cured product layer of any one of the adhesive compositions (1) to (13) for laminated optical films. [Effects of the Invention]

[0024] The adhesive composition for laminated optical films according to the present invention contains metal oxide particles, and therefore can improve the refractive index of an adhesive layer formed therefrom. Additionally, the adhesive composition for laminated optical films according to the present invention contains a compound represented by general formula (1) in addition to metal oxide particles, thereby achieving both an improved refractive index and improved adhesive strength of the adhesive layer. Furthermore, the adhesive composition for laminated optical films according to the present invention contains a compound represented by general formula (1) in addition to metal oxide particles, and therefore reduces the cure shrinkage of the adhesive layer. Therefore, when a laminated optical film is formed, stress applied to each optical film can be reduced, and improved durability of the laminated optical film can be expected. It is preferable that the adhesive composition for laminated optical films according to the present invention contains a hydroxyl group-containing (meth)acrylate in addition to the metal oxide particles and the compound represented by general formula (1), since this further improves the adhesive strength of the adhesive layer. It is also preferable that the adhesive composition for laminated optical films according to the present invention contains phenoxybenzyl (meth)acrylate in addition to the metal oxide particles and the compound represented by general formula (1), since this further improves the refractive index of the adhesive layer. It is preferable that the adhesive composition for laminated optical films according to the present invention contains, in addition to metal oxide particles and the compound represented by general formula (1), a leveling agent containing at least a modified isocyanurate compound and a modified polydimethylsiloxane compound, since this improves the liquid stability, particularly during storage and when applied to an optical film. [Brief explanation of the drawings]

[0025] [Figure 1] An example of a laminated optical film having a cured product layer of the adhesive composition for laminated optical films according to the present invention as an adhesive layer. DETAILED DESCRIPTION OF THE INVENTION

[0026] The adhesive composition for a laminated optical film according to the present invention comprises a curable component, metal oxide particles, and a compound represented by the following general formula (1): [ka] (wherein X is a reactive group, Y is an alkylene group having 1 to 12 carbon atoms which may have a branched chain, or a phenylene group which may have a substituent, and R 1 and R 2 each independently represents a hydrogen atom, an aliphatic hydrocarbon group, an aryl group, or a heterocyclic group which may have a substituent.

[0027] <Compound represented by general formula (1)> When the adhesive composition for a laminated optical film according to the present invention contains the compound represented by the general formula (1) together with metal oxide particles, the cure shrinkage of the adhesive layer is reduced, and therefore, when the laminated optical film is formed, the stress applied to each optical film can be reduced, and the durability of the laminated optical film can be expected to be improved.

[0028] Examples of the aliphatic hydrocarbon group include a linear or branched alkyl group having 1 to 20 carbon atoms, which may have a substituent; a cyclic alkyl group having 3 to 20 carbon atoms, which may have a substituent; and an alkenyl group having 2 to 20 carbon atoms. Examples of the aryl group include a phenyl group having 6 to 20 carbon atoms, which may have a substituent; and a naphthyl group having 10 to 20 carbon atoms, which may have a substituent. Examples of the heterocyclic group include a 5- or 6-membered ring group containing at least one heteroatom, which may have a substituent. These may be linked together to form a ring. In general formula (1), R 1 and R 2 is preferably a hydrogen atom or a linear or branched alkyl group having 1 to 3 carbon atoms, and most preferably a hydrogen atom.

[0029] X in the compound represented by general formula (1) is a reactive group, which is a functional group that can react with a curable component that constitutes the cured material layer, particularly the adhesive layer, and examples thereof include a hydroxyl group, an amino group, an aldehyde group, a carboxyl group, a vinyl group, a (meth)acrylic group, a styryl group, a (meth)acrylamide group, a vinyl ether group, an epoxy group, an oxetane group, an α,β-unsaturated carbonyl group, a mercapto group, and a halogen group. When the curable resin composition constituting the cured product layer, particularly the adhesive layer, is active energy ray-curable, the reactive group X is preferably at least one reactive group selected from the group consisting of vinyl groups, (meth)acrylic groups, styryl groups, (meth)acrylamide groups, vinyl ether groups, epoxy groups, oxetane groups, and mercapto groups. When the cured product layer, particularly the adhesive layer, is radically polymerizable, the reactive group X is preferably at least one reactive group selected from the group consisting of (meth)acrylic groups, styryl groups, and (meth)acrylamide groups. Compounds represented by general formula (1) containing (meth)acrylamide groups are more preferred because they have high reactivity and increase the copolymerization rate with the curable component in the cured product layer, particularly the adhesive layer. Furthermore, the (meth)acrylamide groups have high polarity and excellent adhesiveness, making it possible to efficiently obtain the effects of the present invention. When the curable resin composition constituting the cured product layer, particularly the adhesive layer, is cationic polymerizable, the reactive group X preferably has at least one functional group selected from a hydroxyl group, an amino group, an aldehyde, a carboxyl group, a vinyl ether group, an epoxy group, an oxetane group, and a mercapto group. In particular, when the reactive group X has an epoxy group, the resulting cured product layer, particularly the adhesive layer, has excellent adhesion to the adherend, and when the reactive group X has a vinyl ether group, the curability of the curable resin composition is excellent.

[0030] Preferred specific examples of the compound represented by general formula (1) include the following compounds (1a) to (1d). 3 is a hydrogen atom or a methyl group. [ka]

[0031] In addition to the compounds exemplified above, examples of the compound represented by general formula (1) include esters of (meth)acrylates and boric acid, such as esters of hydroxyethyl acrylamide and boric acid, esters of methylolacrylamide and boric acid, esters of hydroxyethyl acrylate and boric acid, and esters of hydroxybutyl acrylate and boric acid.

[0032] From the viewpoint of improving the adhesive strength of the adhesive layer, the amount of the compound represented by general formula (1) used is preferably 0.1 to 10 mass %, and more preferably 0.3 to 5 mass %, when the total amount of the composition is 100 mass %.

[0033] <Metal oxide particles> The adhesive composition for laminated optical films according to the present invention contains metal oxide particles. Examples of metal oxide particles include silicon oxide, zirconium oxide, titanium oxide, zinc oxide, antimony pentoxide, tin oxide, aluminum oxide, indium oxide, indium tin oxide, ferric oxide, cerium oxide, yttrium oxide, manganese oxide, holmium oxide, copper oxide, bismuth oxide, cobalt oxide, tricobalt tetroxide, triiron tetroxide, magnesium oxide, lanthanum oxide, praseodymium oxide, neodymium oxide, samarium oxide, eurobium oxide, gadolinium oxide, terbium oxide, dysprosium oxide, erbium oxide, thulium oxide, ytterbium oxide, lutetium oxide, scandium oxide, tantalum pentoxide, niobium pentoxide, iridium oxide, rhodium oxide, ruthenium oxide, and composite oxides formed by combining these. Among these, zirconium oxide and titanium oxide are preferred, and zirconium oxide is particularly preferred. The metal oxide particles used in the present invention may be composed solely of the metal oxides listed above, or may contain other components, but it is preferable that the metal oxide accounts for the largest proportion by weight of the components in the particles. The shape of the metal oxide particles may be any shape, such as spherical, ellipsoidal, cubic, rectangular, or pyramidal. In the present invention, the metal oxide particles may be surface-treated by a method known to those skilled in the art.

[0034] From the viewpoint of improving the stability of the metal oxide particles in the adhesive composition and improving the refractive index of the adhesive layer, the average particle size of the metal oxide particles used is preferably 1 to 150 nm, more preferably 1 to 50 nm. In the present invention, the average particle size of the metal oxide particles can be calculated by magnifying and observing the particles 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, randomly selecting, for example, 1,000 particles, measuring their maximum lengths, and calculating the arithmetic mean.

[0035] The average particle size of the metal oxide particles blended in the adhesive composition can also be calculated by dynamic light scattering or laser diffraction. When calculated by dynamic light scattering or laser diffraction, the average particle size means the particle size at 50% of the cumulative value in the particle size distribution determined by laser diffraction / scattering.

[0036] From the standpoint of improving the stability of the metal oxide particles in the adhesive composition and improving the refractive index of the adhesive layer, the amount of metal oxide particles used is preferably 10 to 50 mass %, and more preferably 15 to 40 mass %, when the total amount of the composition is 100 mass %.

[0037] <Curable component> The adhesive composition for laminated optical films according to the present invention contains a curable component. In the present invention, the curable component is preferably an active energy ray-curable component. Active energy ray-curable components can be classified into radical polymerization-curable components and cationic polymerization-curable components. In the present invention, active energy rays in the wavelength range of 10 nm to less than 380 nm are referred to as ultraviolet rays, and active energy rays in the wavelength range of 380 nm to 800 nm are referred to as visible light.

[0038] The adhesive composition for laminated optical films according to the present invention may contain a monofunctional radical polymerizable compound as a curable component. Examples of the monofunctional radical polymerizable compound include various (meth)acrylic acid derivatives having a (meth)acryloyloxy group. Specific examples include (meth)acrylic acid (C1-20) alkyl esters such as methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, 2-methyl-2-nitropropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, s-butyl (meth)acrylate, t-butyl (meth)acrylate, n-pentyl (meth)acrylate, t-pentyl (meth)acrylate, 3-pentyl (meth)acrylate, 2,2-dimethylbutyl (meth)acrylate, n-hexyl (meth)acrylate, cetyl (meth)acrylate, n-octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, 4-methyl-2-propylpentyl (meth)acrylate, and n-octadecyl (meth)acrylate.

[0039] Examples of the (meth)acrylic acid derivatives include cycloalkyl (meth)acrylates such as cyclohexyl (meth)acrylate and cyclopentyl (meth)acrylate; aralkyl (meth)acrylates such as benzyl (meth)acrylate; 2-isobornyl (meth)acrylate, 2-norbornylmethyl (meth)acrylate, 5-norbornen-2-yl-methyl (meth)acrylate, 3-methyl-2-norbornylmethyl (meth)acrylate, dicyclopentenyl (meth)acrylate, and dicyclopentenyloxy (meth)acrylate. Examples of suitable (meth)acrylates include polycyclic (meth)acrylates such as ethyl (meth)acrylate and dicyclopentanyl (meth)acrylate; and alkoxy or phenoxy group-containing (meth)acrylates such as 2-methoxyethyl (meth)acrylate, 2-ethoxyethyl (meth)acrylate, 2-methoxymethoxyethyl (meth)acrylate, 3-methoxybutyl (meth)acrylate, ethyl carbitol (meth)acrylate, phenoxyethyl (meth)acrylate, and alkylphenoxy polyethylene glycol (meth)acrylate. Among these, dicyclopentenyloxyethyl acrylate and phenoxyethyl acrylate are preferred because of their excellent adhesion to various protective films.

[0040] In addition, examples of the (meth)acrylic acid derivatives include hydroxyalkyl (meth)acrylates such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 8-hydroxyoctyl (meth)acrylate, 10-hydroxydecyl (meth)acrylate, and 12-hydroxylauryl (meth)acrylate. hydroxyl group-containing (meth)acrylates such as [4-(hydroxymethyl)cyclohexyl]methyl acrylate, cyclohexanedimethanol mono(meth)acrylate, and 2-hydroxy-3-phenoxypropyl (meth)acrylate; epoxy group-containing (meth)acrylates such as glycidyl (meth)acrylate and 4-hydroxybutyl (meth)acrylate glycidyl ether; 2,2,2-trifluoroethyl (meth)acrylate, 2,2,2-trifluoroethylethyl (meth)acrylate Halogen-containing (meth)acrylates such as acrylates, tetrafluoropropyl (meth)acrylate, hexafluoropropyl (meth)acrylate, octafluoropentyl (meth)acrylate, heptadecafluorodecyl (meth)acrylate, and 3-chloro-2-hydroxypropyl (meth)acrylate; alkylaminoalkyl (meth)acrylates such as dimethylaminoethyl (meth)acrylate; 3-oxetanylmethyl (meth)acrylate, 3-methyl-oxetanylmethyl (meth)acrylate Examples of suitable (meth)acrylates include oxetane group-containing (meth)acrylates such as acrylate, 3-ethyl-oxetanylmethyl (meth)acrylate, 3-butyl-oxetanylmethyl (meth)acrylate, and 3-hexyl-oxetanylmethyl (meth)acrylate; (meth)acrylates having a heterocycle such as tetrahydrofurfuryl (meth)acrylate and butyrolactone (meth)acrylate; hydroxypivalic acid neopentyl glycol (meth)acrylic acid adduct; and p-phenylphenol (meth)acrylate. Among these, 2-hydroxy-3-phenoxypropyl acrylate is preferred because of its excellent adhesion to various protective films.

[0041] The adhesive composition for laminated optical films according to the present invention preferably contains a hydroxyl group-containing (meth)acrylate in addition to the metal oxide particles and the compound represented by general formula (1), since this further improves the adhesive strength of the adhesive layer. From the viewpoint of improving the adhesive strength of the adhesive layer, the blending amount of the hydroxyl group-containing (meth)acrylate is preferably 1 to 30 mass%, and more preferably 3 to 20 mass%, when the total amount of the composition is taken as 100 mass%.

[0042] Furthermore, examples of the monofunctional radically polymerizable compound include carboxyl group-containing monomers such as (meth)acrylic acid, carboxyethyl acrylate, carboxypentyl acrylate, itaconic acid, maleic acid, fumaric acid, crotonic acid, and isocrotonic acid.

[0043] Examples of the monofunctional radically polymerizable compound include lactam vinyl monomers such as N-vinylpyrrolidone, N-vinyl-ε-caprolactam, and methylvinylpyrrolidone; and vinyl monomers having a nitrogen-containing heterocycle such as vinylpyridine, vinylpiperidone, vinylpyrimidine, vinylpiperazine, vinylpyrazine, vinylpyrrole, vinylimidazole, vinyloxazole, and vinylmorpholine.

[0044] Furthermore, as the monofunctional radical polymerizable compound, a radical polymerizable compound having an active methylene group can be used. The radical polymerizable compound having an active methylene group is a compound having an active double bond group such as a (meth)acrylic group at the end or in the molecule, and also having an active methylene group. Examples of the active methylene group include an acetoacetyl group, an alkoxymalonyl group, and a cyanoacetyl group. It is preferable that the active methylene group is an acetoacetyl group. Specific examples of radical polymerizable compounds having an active methylene group include acetoacetoxyalkyl (meth)acrylates such as 2-acetoacetoxyethyl (meth)acrylate, 2-acetoacetoxypropyl (meth)acrylate, and 2-acetoacetoxy-1-methylethyl (meth)acrylate; 2-ethoxymalonyloxyethyl (meth)acrylate, 2-cyanoacetoxyethyl (meth)acrylate, N-(2-cyanoacetoxyethyl)acrylamide, N-(2-propionylacetoxybutyl)acrylamide, N-(4-acetoacetoxymethylbenzyl)acrylamide, and N-(2-acetoacetylaminoethyl)acrylamide. The radical polymerizable compound having an active methylene group is preferably an acetoacetoxyalkyl (meth)acrylate.

[0045] The adhesive composition for laminated optical films according to the present invention may contain a bifunctional or higher polyfunctional radically polymerizable compound as a curable component. Examples of the polyfunctional radically polymerizable compound include polyfunctional (meth)acrylamide derivatives such as N,N'-methylenebis(meth)acrylamide, tripropylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, 1,9-nonanediol di(meth)acrylate, 1,10-decanediol diacrylate, 2-ethyl-2-butylpropanediol di(meth)acrylate, bisphenol A di(meth)acrylate, bisphenol A ethylene oxide adduct di(meth)acrylate, bisphenol A propylene oxide adduct di(meth)acrylate, and bisphenol A diglycidyl ether di(meth)acrylate. esters of (meth)acrylic acid with polyhydric alcohols such as acrylate, neopentyl glycol di(meth)acrylate, tricyclodecane dimethanol di(meth)acrylate, cyclic trimethylolpropane formal (meth)acrylate, dioxane glycol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol penta(meth)acrylate, dipentaerythritol hexa(meth)acrylate, and EO-modified diglycerin tetra(meth)acrylate; and 9,9-bis[4-(2-(meth)acryloyloxyethoxy)phenyl]fluorene. Specific examples include Aronix M-220 (manufactured by Toagosei Co., Ltd.), Light Acrylate 1,9ND-A (manufactured by Kyoeisha Chemical Co., Ltd.), Light Acrylate DGE-4A (manufactured by Kyoeisha Chemical Co., Ltd.), Light Acrylate DCP-A (manufactured by Kyoeisha Chemical Co., Ltd.), SR-531 (manufactured by Sartomer Co., Ltd.), CD-536 (manufactured by Sartomer Co., Ltd.), etc. Furthermore, various epoxy (meth)acrylates, urethane (meth)acrylates, polyester (meth)acrylates, various (meth)acrylate monomers, etc. may also be used as needed.It is preferable to include a polyfunctional (meth)acrylamide derivative in the adhesive composition because it has a high polymerization rate, is excellent in productivity, and has excellent crosslinking properties when the adhesive composition is cured.

[0046] For example, when a polarizer and a transparent protective film are used as the optical film, it is preferable to use a combination of a monofunctional radically polymerizable compound and a polyfunctional radically polymerizable compound as the radically polymerizable compound, from the viewpoint of achieving both adhesion to the polarizer and various transparent protective films and optical durability under harsh environments. The amount of the monofunctional radically polymerizable compound in the adhesive composition is preferably 10 to 95% by mass, and more preferably 30 to 80% by mass, when the total amount of the composition is taken as 100% by mass. The amount of the polyfunctional radically polymerizable compound in the adhesive composition is preferably 0.5 to 60% by mass, and more preferably 1 to 40% by mass, when the total amount of the composition is taken as 100% by mass.

[0047] The adhesive composition for laminated optical films according to the present invention preferably contains a leveling agent containing at least one selected from the group consisting of an isocyanurate compound and a polysiloxane compound, since this allows for more stable dispersion of metal oxide particles. The adhesive composition also preferably contains a leveling agent, since this allows for low viscosity despite the presence of metal oxide particles. From the standpoint of thinning the adhesive layer and laminated optical film by applying a thin coating of the adhesive composition for laminated optical films to an optical film, the viscosity of the composition at 25°C is preferably 100 mPa·s or less, and more preferably 60 mPa·s or less.

[0048] <Leveling agent> The adhesive composition for laminated optical films according to the present invention preferably contains at least one leveling agent selected from the group consisting of an isocyanurate compound and a polysiloxane compound. By including at least one compound selected from the group consisting of an isocyanurate compound and a polysiloxane compound in the composition, metal oxide particles are stably dispersed, resulting in excellent liquid stability of the adhesive composition for laminated optical films. Furthermore, by including metal oxide particles and at least one compound selected from the group consisting of an isocyanurate compound and a polysiloxane compound in the composition, cissing and the generation of bubbles during coating on an optical film can be suppressed. From the viewpoint of further enhancing the above-mentioned effects, the adhesive composition for laminated optical films according to the present invention preferably contains both an isocyanurate compound and a polysiloxane compound. When the adhesive composition for laminated optical films contains both an isocyanurate compound and a polysiloxane compound, the blending amounts thereof are preferably 0.1 to 4 mass %, more preferably 0.1 to 2 mass %, based on the total amount of the composition as 100 mass %. As described below, when an isocyanurate compound is also blended as a crosslinking agent, and when the adhesive composition for laminated optical films contains both an isocyanurate compound and a polysiloxane compound, the blending amount is preferably 0.1 to 14 mass%, and more preferably 0.1 to 7 mass%, when the total amount of the composition is 100 mass%.

[0049] <Isocyanurate compounds> The isocyanurate compound is a compound containing an isocyanurate ring structure formed by the trimerization reaction of isocyanate. In the present invention, it is particularly preferable to use a modified isocyanurate compound having a reactive group. Examples of the reactive group of the modified isocyanurate compound include polymerizable functional groups, specifically, radically polymerizable functional groups having an ethylenic double bond, such as (meth)acryloyl, vinyl, or allyl groups; cationically polymerizable functional groups, such as epoxy groups, such as glycidyl groups; oxetane groups, vinyl ether groups, cyclic ether groups, cyclic thioether groups, and lactone groups. From the viewpoint of reactivity in the adhesive composition for laminated optical films, modified isocyanurate compounds having a double bond as the reactive group are preferred, and modified isocyanurate compounds having a (meth)acryloyl group are more preferred. The amount of the isocyanurate compound in the adhesive composition for laminated optical films is preferably 0.05 to 2% by mass, and more preferably 0.05 to 1% by mass, based on the total amount of the composition as 100% by mass.

[0050] The isocyanurate compound not only contributes to stabilizing the dispersion of metal oxide particles in the composition, but also has the effect of reducing the cure shrinkage rate when, for example, an adhesive layer is formed. Therefore, when an isocyanurate compound is blended as a crosslinking agent in the adhesive composition for a laminated optical film according to the present invention, the blending amount of the isocyanurate compound is preferably as large as possible, specifically, preferably 0.05 to 10 mass %, and more preferably 0.05 to 5 mass %, when the total amount of the composition is taken as 100 mass %.

[0051] <Polysiloxane compounds> The polysiloxane compound is a compound having a polysiloxane skeleton such as polydimethylsiloxane. In the present invention, it is particularly preferable to use a modified polysiloxane compound having a reactive group. Examples of the reactive group possessed by the modified polysiloxane compound include polymerizable functional groups, specifically, radically polymerizable functional groups having an ethylenic double bond such as a (meth)acryloyl group, a vinyl group, or an allyl group; cationically polymerizable functional groups such as an epoxy group such as a glycidyl group; an oxetane group, a vinyl ether group, a cyclic ether group, a cyclic thioether group, or a lactone group. From the viewpoint of reactivity in the adhesive composition for laminated optical films, modified polysiloxane compounds having a double bond as the reactive group are preferred, and modified polysiloxane compounds having a (meth)acryloyl group are more preferred. The amount of the polysiloxane compound in the adhesive composition for laminated optical films is preferably 0.05 to 2% by mass, and more preferably 0.05 to 1% by mass, based on the total amount of the composition as 100% by mass.

[0052] <(Meth)acrylate containing an aromatic ring skeleton> The adhesive composition for laminated optical films according to the present invention preferably contains a (meth)acrylate containing an aromatic ring skeleton together with metal oxide particles, since this improves the refractive index of the adhesive layer. From the viewpoint of more stably increasing the refractive index of the adhesive layer, the (meth)acrylate containing an aromatic ring skeleton preferably contains at least one selected from the group consisting of (meth)acrylates having a polycyclic aromatic ring skeleton and (meth)acrylates having two or more aromatic rings. Examples of (meth)acrylates containing an aromatic ring skeleton include benzyl (meth)acrylate, phenoxyethyl (meth)acrylate, phenoxydiethylene glycol (meth)acrylate, 2-hydroxy-3-phenoxypropyl (meth)acrylate, 1-naphthalenemethyl (meth)acrylate, phenoxybenzyl (meth)acrylate, ethylene oxide-modified orthophenylphenol (meth)acrylate, and a reaction product of 9,9-bis[4-(2-hydroxyethoxy)phenyl]fluorene and (meth)acrylic acid. Among these, it is more preferable to use phenoxybenzyl (meth)acrylate and phenoxyethyl (meth)acrylate, and it is particularly preferable to use phenoxybenzyl (meth)acrylate. Phenoxybenzyl (meth)acrylate is represented by the following formula (A): [ka] In the above formula (A), X is a single bond forming part of an adjacent bonding group, or represents a structure having 1 to 5 repeating ethylene oxide, propylene oxide, butylene oxide or styrene oxide structures. R represents a hydrogen atom or a methyl group. The adhesive composition for laminated optical films according to the present invention is a compound having a structure represented by the following formula (A-1): [ka] It is preferable that the compound contains phenoxybenzyl (meth)acrylate, which is an o- or m-substituted compound represented by the following formula:

[0053] From the viewpoint of improving the refractive index of the adhesive layer, the amount of the (meth)acrylate containing an aromatic ring skeleton used, particularly phenoxybenzyl (meth)acrylate, is preferably 30 to 70% by mass when the total amount in the composition is 100% by mass.

[0054] The adhesive composition for a laminated optical film according to the present invention can be used as an active energy ray-curable adhesive composition when the curable component is an active energy ray-curable component. When an electron beam or the like is used as the active energy ray, the active energy ray-curable adhesive composition does not need to contain a photopolymerization initiator. However, when ultraviolet light or visible light is used as the active energy ray, it is preferable that the adhesive composition contains a photopolymerization initiator.

[0055] The photopolymerization initiator is appropriately selected depending on the active energy ray. When curing with ultraviolet or visible light, a photopolymerization initiator that is cleaved by ultraviolet or visible light is used. Examples of the photopolymerization initiator include benzophenone-based compounds such as benzil, benzophenone, benzoylbenzoic acid, and 3,3'-dimethyl-4-methoxybenzophenone; aromatic ketone compounds such as 4-(2-hydroxyethoxy)phenyl(2-hydroxy-2-propyl)ketone, α-hydroxy-α,α'-dimethylacetophenone, 2-methyl-2-hydroxypropiophenone, and α-hydroxycyclohexylphenyl ketone; acetophenone-based compounds such as methoxyacetophenone, 2,2-dimethoxy-2-phenylacetophenone, 2,2-diethoxyacetophenone, and 2-methyl-1-[4-(methylthio)-phenyl]-2-morpholinopropane-1; benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, and benzoin methyl ether. aromatic sulfonyl chloride compounds such as 2-naphthalenesulfonyl chloride; photoactive oxime compounds such as 1-phenone-1,1-propanedione-2-(o-ethoxycarbonyl)oxime; thioxanthone compounds such as thioxanthone, 2-chlorothioxanthone, 2-methylthioxanthone, 2,4-dimethylthioxanthone, isopropylthioxanthone, 2,4-dichlorothioxanthone, 2,4-diethylthioxanthone, 2,4-diisopropylthioxanthone, and dodecylthioxanthone; camphorquinone; halogenated ketones; acylphosphinoxides; and acylphosphonates.

[0056] The amount of the photopolymerization initiator blended is preferably 0.5 to 5% by mass, and more preferably 1 to 4% by mass, when the total amount in the composition is taken as 100% by mass.

[0057] When the active energy ray-curable adhesive composition is used as a visible light-curable type, it is preferable to use a photopolymerization initiator that is particularly sensitive to light of 380 nm or more. Photopolymerization initiators that are highly sensitive to light of 380 nm or more will be described later.

[0058] The photopolymerization initiator may be a compound represented by the following general formula (3): [ka] (In the formula, R 7 and R 8 represents -H, -CH2CH3, -iPr or Cl, and R 7 and R 8 It is preferable to use a compound represented by general formula (3) alone (which may be the same or different), or to use a compound represented by general formula (3) in combination with a photopolymerization initiator highly sensitive to light of 380 nm or longer, which will be described later. When a compound represented by general formula (3) is used, the adhesiveness is superior to when a photopolymerization initiator highly sensitive to light of 380 nm or longer is used alone. Among the compounds represented by general formula (3), R 7 and R 8 Diethylthioxanthone, in which -CH2CH3, is particularly preferred. The amount of the compound represented by general formula (3) in the active energy ray-curable adhesive composition is preferably 0.1 to 5 mass%, and more preferably 0.3 to 3 mass%, when the total amount of the composition is taken as 100 mass%.

[0059] It is also preferable to add a polymerization initiator aid as needed. Examples of the polymerization initiator aid include triethylamine, diethylamine, N-methyldiethanolamine, ethanolamine, 4-dimethylaminobenzoic acid, methyl 4-dimethylaminobenzoate, ethyl 4-dimethylaminobenzoate, and isoamyl 4-dimethylaminobenzoate, with ethyl 4-dimethylaminobenzoate being particularly preferable. When a polymerization initiator aid is used, the amount added is preferably 0.1 to 2% by mass, and more preferably 0.3 to 1% by mass, when the total amount of the composition is taken as 100% by mass.

[0060] If necessary, a known photopolymerization initiator can be used in combination. Since the optical functional layer and the base film having UV absorption ability do not transmit light of 380 nm or less, it is preferable to use a photopolymerization initiator that is highly sensitive to light of 380 nm or more. Specific examples include 2-methyl-1-(4-methylthiophenyl)-2-morpholinopropan-1-one, 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-butanone-1, 2-(dimethylamino)-2-[(4-methylphenyl)methyl]-1-[4-(4-morpholinyl)phenyl]-1-butanone, 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide, bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide, bis(η5-2,4-cyclopentadien-1-yl)-bis(2,6-difluoro-3-(1H-pyrrol-1-yl)-phenyl)titanium, and the like.

[0061] In the present invention, the adhesive composition for laminated optical films preferably contains an acrylic oligomer obtained by polymerizing a (meth)acrylic monomer. By containing an acrylic oligomer in the adhesive composition for laminated optical films, it is possible to reduce cure shrinkage when the composition is irradiated with active energy rays and cured, and to reduce the interfacial stress between the adhesive layer and the optical film. As a result, it is possible to suppress a decrease in adhesion between the adhesive layer and the optical film.

[0062] Considering workability and uniformity during application, adhesive compositions for laminated optical films preferably have low viscosity, and therefore the acrylic oligomer obtained by polymerizing a (meth)acrylic monomer also preferably has low viscosity. Acrylic oligomers that are low in viscosity and can prevent shrinkage of the adhesive layer upon cure preferably have a weight-average molecular weight (Mw) of 15,000 or less, more preferably 10,000 or less, and particularly preferably 5,000 or less. On the other hand, to sufficiently suppress shrinkage of the cured product layer (adhesive layer) upon cure, the weight-average molecular weight (Mw) of the acrylic oligomer is preferably 500 or more, more preferably 1,000 or more, and particularly preferably 1,500 or more. Specific examples of the (meth)acrylic monomer constituting the acrylic oligomer include methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, 2-methyl-2-nitropropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, s-butyl (meth)acrylate, t-butyl (meth)acrylate, n-pentyl (meth)acrylate, t-pentyl (meth)acrylate, 3-pentyl (meth)acrylate, 2,Examples of the methacrylic acid (C1-20) alkyl esters include 2-dimethylbutyl (meth)acrylate, n-hexyl (meth)acrylate, cetyl (meth)acrylate, n-octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, 4-methyl-2-propylpentyl (meth)acrylate, and N-octadecyl (meth)acrylate; and further examples of the methacrylic acid (C1-20) alkyl esters include cycloalkyl (meth)acrylates (e.g., cyclohexyl (meth)acrylate, cyclopentyl (meth)acrylate, etc.), aralkyl (meth)acrylates (e.g., benzyl (meth)acrylate, etc.), polycyclic (meth)acrylates (e.g., 2-isobornyl (meth)acrylate, 2-norbornylmethyl (meth)acrylate, 5-norbornen-2-yl-methyl (meth)acrylate, 3-methyl-2-norbornylmethyl (meth)acrylate, and the like. (meth)acrylate, etc.), hydroxyl group-containing (meth)acrylic acid esters (e.g., hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2,3-dihydroxypropylmethyl-butyl (meth)methacrylate, etc.), alkoxy group- or phenoxy group-containing (meth)acrylic acid esters (2-methoxyethyl (meth)acrylate, 2-ethoxyethyl (meth)acrylate, 2-methoxymethoxyethyl (meth)acrylate, 3-methoxybutyl (meth)acrylate, ethyl carbitol (meth)acrylate, phenoxyethyl (meth)acrylate, etc.), epoxy group-containing (meth)acrylic acid esters (e.g., glycidyl (meth)acrylate, etc.), halogen-containing (meth)acrylic acid esters (e.g., 2,2,2-trifluoroethyl (meth)acrylate, 2,2,Examples of the acrylic oligomer (E) include 2-trifluoroethylethyl (meth)acrylate, tetrafluoropropyl (meth)acrylate, hexafluoropropyl (meth)acrylate, octafluoropentyl (meth)acrylate, heptadecafluorodecyl (meth)acrylate, and alkylaminoalkyl (meth)acrylates (e.g., dimethylaminoethyl (meth)acrylate). These (meth)acrylates can be used alone or in combination of two or more. Specific examples of the acrylic oligomer (E) include "ARUFON" manufactured by Toagosei Co., Ltd., "Actflow" manufactured by Soken Chemical & Engineering Co., Ltd., and "JONCRYL" manufactured by BASF Japan Ltd.

[0063] The blending amount of the acrylic oligomer in the adhesive composition for laminated optical films is preferably 3 to 40 mass %, more preferably 5 to 20 mass %.

[0064] The adhesive composition for laminated optical films according to the present invention may contain a silane coupling agent. Specific examples of the silane coupling agent include active energy ray-curable compounds such as vinyltrichlorosilane, vinyltrimethoxysilane, vinyltriethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3-glycidoxypropyltriethoxysilane, p-styryltrimethoxysilane, 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, 3-methacryloxypropyltriethoxysilane, and 3-acryloxypropyltrimethoxysilane.

[0065] Preferred are 2-(3,4 epoxycyclohexyl)ethyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, and 3-glycidoxypropyltriethoxysilane.

[0066] Specific examples of non-active energy ray-curable silane coupling agents other than those mentioned above include 3-ureidopropyltriethoxysilane, 3-chloropropyltrimethoxysilane, 3-mercaptopropylmethyldimethoxysilane, 3-mercaptopropyltrimethoxysilane, bis(triethoxysilylpropyl)tetrasulfide, 3-isocyanatepropyltriethoxysilane, and imidazole silane.

[0067] The adhesive composition for a laminated optical film according to the present invention may be a cationic polymerization-curable adhesive composition. The curable component (cationically polymerizable compound) used in the cationic polymerization-curable adhesive composition is classified into a monofunctional cationic polymerizable compound having one cationic polymerizable functional group in the molecule and a polyfunctional cationic polymerizable compound having two or more cationic polymerizable functional groups in the molecule. Since monofunctional cationic polymerizable compounds have a relatively low liquid viscosity, their inclusion in the cationic polymerization-curable adhesive composition can reduce the liquid viscosity. Furthermore, monofunctional cationic polymerizable compounds often have functional groups that impart various functions. By including them in the cationic polymerization-curable adhesive composition, various functions can be imparted to the cationic polymerization-curable adhesive composition and / or the cured product of the cationic polymerization-curable adhesive composition. Since polyfunctional cationic polymerizable compounds can three-dimensionally crosslink the cured product of the cationic polymerization-curable resin composition, they are preferably included in the cationic polymerization-curable adhesive composition. The ratio of the monofunctional cationically polymerizable compound to the polyfunctional cationically polymerizable compound is preferably 100% by mass of the monofunctional cationically polymerizable compound to 1000% by mass of the polyfunctional cationically polymerizable compound. Examples of the cationically polymerizable functional group include an epoxy group, an oxetanyl group, and a vinyl ether group. Examples of compounds having an epoxy group include an aliphatic epoxy compound, an alicyclic epoxy compound, and an aromatic epoxy compound. The cationically polymerizable resin composition of the present invention particularly preferably contains an alicyclic epoxy compound because of its excellent curability and adhesive properties.Examples of alicyclic epoxy compounds include 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate, caprolactone-modified products, trimethylcaprolactone-modified products, and valerolactone-modified products of 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate, and specific examples thereof include Celloxide 2021, Celloxide 2021A, Celloxide 2021P, Celloxide 2081, Celloxide 2083, and Celloxide 2085 (all manufactured by Daicel Chemical Industries, Ltd.), and Cyracure UVR-61 Examples of suitable compounds include 05, Cyracure UVR-6107, Cyracure 30, and R-6110 (all manufactured by Dow Chemical Japan Co., Ltd.). Compounds having an oxetanyl group are preferably contained because they have the effect of improving the curing properties of the cationically polymerizable adhesive composition and reducing the liquid viscosity of the composition. Examples of compounds having an oxetanyl group include 3-ethyl-3-hydroxymethyloxetane, 1,4-bis[(3-ethyl-3-oxetanyl)methoxymethyl]benzene, 3-ethyl-3-(phenoxymethyl)oxetane, di[(3-ethyl-3-oxetanyl)methyl]benzoyl]benzoyl]benzoyl]benzoyl]benzoyl]benzoyl]benzoyl]benzoyl]benzoyl]benzoyl] Examples of suitable vinyl ethers include 3-ethyl-3-(2-ethylhexyloxymethyl)oxetane, 3-ethyl-3-(2-ethylhexyloxymethyl)oxetane, and phenol novolac oxetane. Commercially available vinyl ethers include ARON OXT-101, ARON OXT-121, ARON OXT-211, ARON OXT-221, and ARON OXT-212 (all manufactured by Toagosei Co., Ltd.). Compounds having a vinyl ether group are preferably incorporated into the cationically polymerizable adhesive composition because they improve the curing properties of the composition and reduce the liquid viscosity of the composition. Vinyl Examples of compounds having an ether group include 2-hydroxyethyl vinyl ether, diethylene glycol monovinyl ether, 4-hydroxybutyl vinyl ether, diethylene glycol monovinyl ether, triethylene glycol divinyl ether, cyclohexanedimethanol divinyl ether, cyclohexanedimethanol monovinyl ether, tricyclodecane vinyl ether, cyclohexyl vinyl ether, methoxyethyl vinyl ether, ethoxyethyl vinyl ether, and pentaerythritol tetravinyl ether.

[0068] The cationic polymerization-curable adhesive composition contains at least one compound selected from the group consisting of the epoxy group-containing compound, the oxetanyl group-containing compound, and the vinyl ether group-containing compound described above as a curable component. Since these compounds all cure via cationic polymerization, a photocationic polymerization initiator is incorporated into the composition. This photocationic polymerization initiator generates cationic species or Lewis acids upon irradiation with active energy rays such as visible light, ultraviolet light, X-rays, and electron beams, thereby initiating the polymerization reaction of the epoxy group or oxetanyl group. The photoacid generators described below are preferably used as the photocationic polymerization initiator. When the cationic polymerization adhesive composition is used as a visible light-curable adhesive, it is preferable to use a photocationic polymerization initiator that is highly sensitive to light of 380 nm or longer. However, since photocationic polymerization initiators generally exhibit a maximum absorption in the wavelength range around 300 nm or shorter, incorporating a photosensitizer that exhibits a maximum absorption in the longer wavelength range, specifically, light of wavelengths longer than 380 nm, can enhance the generation of cationic species or acids from the photocationic polymerization initiator by reacting to light of this wavelength range. Examples of photosensitizers include anthracene compounds, pyrene compounds, carbonyl compounds, organic sulfur compounds, persulfides, redox compounds, azo and diazo compounds, halogen compounds, and photoreducible dyes, and two or more of these may be used in combination. Anthracene compounds are particularly preferred because of their excellent photosensitizing effect, and specific examples include Anthracure UVS-1331 and Anthracure UVS-1221 (manufactured by Kawasaki Chemical Industries, Ltd.). The content of the photosensitizer is preferably 0.1% to 5% by mass, and more preferably 0.5% to 3% by mass.

[0069] In the present invention, the adhesive composition for a laminated optical film may contain a photoacid generator. When the adhesive composition for a laminated optical film contains a photoacid generator, the water resistance and durability of the adhesive layer can be dramatically improved compared to when the adhesive composition does not contain a photoacid generator. The photoacid generator can be represented by the following general formula (4).

[0070] [ka] (However, L + represents any onium cation. - is PF66 - , SbF6 - , AsF6 - , SbCl6 - , BiCl5 - , SnCl6 - , ClO4 - , a dithiocarbamate anion, and a counter anion selected from the group consisting of SCN-.

[0071] Next, the counter anion X in general formula (4) - This article explains:

[0072] Counter anion X in general formula (4) - Although there is no particular limitation in principle, a non-nucleophilic anion is preferred. - When PF6 is a non-nucleophilic anion, nucleophilic reactions are unlikely to occur with the cations coexisting in the molecule or with various materials used in combination, which results in improved stability over time of the photoacid generator represented by general formula (4) itself and compositions using it. The term "non-nucleophilic anion" as used here refers to an anion with a low ability to cause nucleophilic reactions. Examples of such anions include PF6 - , SbF6 - , AsF6 - , SbCl6 - , BiCl5 - , SnCl6 - , ClO4 - , B(C6H5)4 - , dithiocarbamate anion, SCN - Examples include:

[0073] Specifically, these include "Cyracure UVI-6992" and "Cyracure UVI-6974" (both manufactured by Dow Chemical Japan Co., Ltd.), "ADEKA Optomer SP150", "ADEKA Optomer SP152", "ADEKA Optomer SP170", and "ADEKA Optomer SP172" (all manufactured by ADEKA Corporation), "Omnicat250" (manufactured by IGM Resins BV), "CI-5102", and "CI-2855" (all manufactured by Nippon Soda Co., Ltd.), "SAN-AID SI-60L", "SAN-AID SI-80L", "SAN-AID SI-100L", "SAN-AID SI-110L", and "SAN-AID SI-180L" (all manufactured by Sanshin Chemical Co., Ltd.), "IK-1", "CPI-100P", "CPI-101A", "CPI-110P", "CPI-200K", "CPI-210S", and "CPI- Specific preferred examples of the photoacid generator of the present invention include "CPI-310B," "CPI-410B," and "CPI-410S" (all manufactured by San-Apro Ltd.), "WPI-069," "WPI-113," "WPI-116," "WPI-041," "WPI-044," "WPI-054," "WPI-055," "WPAG-281," "WPAG-567," and "WPAG-596" (all manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.).

[0074] The laminated optical film according to the present invention is a laminated optical film in which at least a first optical film and a second optical film are laminated via an adhesive layer, and the adhesive layer is a cured product layer of the adhesive composition for laminated optical films described above.

[0075] FIG. 1 shows an example of a laminated optical film having an adhesive layer formed from a cured product layer of the adhesive composition for laminated optical films according to the present invention. The laminated optical film 10 shown in FIG. 1 includes a first optical film 1 and a second optical film 2 laminated together via an adhesive layer 3, which is a cured product layer of the adhesive composition for laminated optical films according to the present invention. The adhesive composition for laminated optical films according to the present invention has a high refractive index due to the stable dispersion of metal oxide particles. Therefore, when retardation films, preferably liquid crystal retardation films, are used as the first optical film 1 and the second optical film 2, the refractive index difference between the first optical film 1 and the adhesive layer 3 can be reduced. Similarly, the refractive index difference between the second optical film 2 and the adhesive layer 3 can be reduced. This reduces interference unevenness in the laminated optical film and improves visibility.

[0076] The laminated optical film according to the present invention may be a laminated optical film in which at least a first optical film and a second optical film are laminated via an adhesive layer that is a cured product layer of the adhesive composition for a laminated optical film according to the present invention, and may further include any other optical film. The laminated optical film 10 shown in FIG. 1 includes a polarizer 5 on the first optical film 1 (on the viewing side) and a transparent protective film 4. Note that adhesive layers are typically provided between the first optical film 1 and the polarizer 5 and between the polarizer 5 and the transparent protective film 4 (omitted in FIG. 1). These adhesive layers may be the same as adhesive layer 3, which is a cured product layer of the adhesive composition for a laminated optical film according to the present invention, or may be a cured product layer of an adhesive composition for a laminated optical film known to those skilled in the art. The laminated optical film 10 shown in FIG. 1 also includes an organic light-emitting diode layer 7 below the second optical film (on the display device side) via a pressure-sensitive adhesive layer 6.

[0077] The adhesive composition for laminated optical films according to the present invention contains metal oxide particles. When the adhesive composition further contains at least one compound selected from the group consisting of an isocyanurate compound and a polysiloxane compound, the viscosity of the composition can be kept low due to stable dispersion of the metal oxide particles. Therefore, the adhesive composition for laminated optical films can be applied thinly onto the optical film, thereby reducing the thickness of the adhesive layer. The thickness of the adhesive layer provided in the laminated optical film according to the present invention is preferably 0.1 to 5 μm, more preferably 0.3 to 3 μm.

[0078] In the present invention, examples of the first optical film and the second optical film constituting the laminated optical film include a polarizer, a transparent protective film, and a retardation film.

[0079] In the present invention, the polarizer is not particularly limited, and various polarizers can be used. Examples of polarizers include those obtained by uniaxially stretching a hydrophilic polymer film, such as a polyvinyl alcohol film, a partially formalized polyvinyl alcohol film, or a partially saponified ethylene-vinyl acetate copolymer film, after iodine has been adsorbed thereon. The thickness of the polarizer can be, for example, 3 to 20 μm.

[0080] However, in the present invention, from the viewpoint of improving humidification reliability in a harsh environment of high temperature and high humidity, it is preferable to use a thin polarizer having a thickness of 3 μm or more and 15 μm or less as the polarizer. A thickness of 12 μm or less is particularly preferable, and a thickness of 10 μm or less, particularly 8 μm or less, is further preferable. Such a thin polarizer has little thickness unevenness, excellent visibility, and excellent durability against thermal shock due to little dimensional change.

[0081] A polarizer obtained by dyeing a polyvinyl alcohol-based film with iodine and uniaxially stretching it can be produced, for example, by immersing the polyvinyl alcohol in an iodine aqueous solution to dye it and then stretching it to 3 to 7 times its original length. If necessary, the solution may contain boric acid, zinc sulfate, zinc chloride, or the like, or it may be immersed in an aqueous solution of potassium iodide or the like. Furthermore, if necessary, the polyvinyl alcohol-based film may be immersed in water and washed before dyeing. Washing the polyvinyl alcohol-based film with water not only removes dirt and antiblocking agents from the surface of the polyvinyl alcohol-based film, but also swells the polyvinyl alcohol-based film, thereby preventing unevenness such as uneven dyeing. Stretching may be performed after dyeing with iodine, or the film may be stretched while dyeing, or the film may be dyed with iodine after stretching. Stretching may be performed in an aqueous solution of boric acid, potassium iodide, or the like, or in a water bath.

[0082] The polarizer preferably contains boric acid from the viewpoints of stretching stability and humidification reliability. Furthermore, the content of boric acid in the polarizer is preferably 22% by mass or less, and more preferably 20% by mass or less, of the total amount of the polarizer, from the viewpoint of suppressing the occurrence of through cracks. From the viewpoints of stretching stability and humidification reliability, the content of boric acid in the polarizer is preferably 10% by mass or more, and more preferably 12% by mass or more, of the total amount of the polarizer.

[0083] Representative examples of thin polarizers include: Patent No. 4751486 specification, Patent No. 4751481 specification, Patent No. 4815544 specification, Patent No. 5048120 specification, International Publication No. 2014 / 077599, International Publication No. 2014 / 077636, or a thin polarizer obtained by the manufacturing method described therein.

[0084] Among the thin polarizers obtained by manufacturing methods including stretching and dyeing a laminate, those obtained by manufacturing methods including stretching in a boric acid aqueous solution, as described in Japanese Patent Nos. 4751486, 4751481, and 4815544, are preferred because they can be stretched at a high magnification and have improved polarization performance. In particular, those obtained by manufacturing methods including a supplementary in-air stretching step before stretching in a boric acid aqueous solution, as described in Japanese Patent Nos. 4751481 and 4815544, are preferred. These thin polarizers can be obtained by manufacturing methods including stretching a polyvinyl alcohol-based resin (hereinafter also referred to as PVA-based resin) layer and a stretching resin substrate in a laminate state, and dyeing the layer. With this manufacturing method, even if the PVA-based resin layer is thin, it can be stretched without problems such as breakage due to stretching because it is supported by the stretching resin substrate.

[0085] The transparent protective film is made of a thermoplastic resin that exhibits excellent transparency, mechanical strength, thermal stability, moisture barrier properties, and isotropy. Specific examples of such thermoplastic resins include cellulose resins such as triacetyl cellulose-based resin films, polyester resins, polyethersulfone resins, polysulfone resins, polycarbonate resins, polyamide resins, polyimide resins, polyolefin resins, (meth)acrylic resins, cyclic polyolefin resins (norbornene-based resins), polyarylate resins, polystyrene resins, polyvinyl alcohol resins, and mixtures thereof. The transparent protective film may contain one or more suitable additives. Examples of additives include ultraviolet absorbers, antioxidants, lubricants, plasticizers, release agents, color inhibitors, flame retardants, nucleating agents, antistatic agents, pigments, and colorants. The content of the thermoplastic resin in the transparent protective film is preferably 50 to 100% by weight, more preferably 50 to 99% by weight, even more preferably 60 to 98% by weight, and particularly preferably 70 to 97% by weight. If the content of the thermoplastic resin in the transparent protective film is 50% by weight or less, the inherent high transparency of the thermoplastic resin may not be fully exhibited.

[0086] The material for forming the transparent protective film is preferably one that is excellent in transparency, mechanical strength, thermal stability, moisture blocking properties, isotropy, etc., and in particular, a moisture permeability of 150 g / m 2 / 24h or less is more preferable, and 140g / m 2 / 24h or less is particularly preferred, 120g / m 2 / 24h or less is even more preferable.

[0087] The surface of the transparent protective film to which the polarizer is not bonded can be provided with a functional layer such as a hard coat layer, an antireflection layer, an antisticking layer, a diffusion layer, an antiglare layer, etc. The functional layer such as the hard coat layer, the antireflection layer, the antisticking layer, the diffusion layer, or the antiglare layer can be provided on the transparent protective film itself, or can be provided separately from the transparent protective film.

[0088] The thickness of the transparent protective film can be determined as appropriate, but is generally about 1 to 500 μm, preferably 1 to 300 μm, more preferably 5 to 200 μm, further preferably 10 to 200 μm, and more preferably 20 to 80 μm, from the viewpoints of strength, workability such as handleability, thinness, etc.

[0089] The transparent protective film can be a retardation film having a front retardation of 40 nm or more and / or a thickness retardation of 80 nm or more. The front retardation is usually controlled to be in the range of 40 to 200 nm, and the thickness retardation is usually controlled to be in the range of 80 to 300 nm. When a retardation film is used as the transparent protective film, the retardation film also functions as the transparent protective film, allowing for a thinner film.

[0090] Examples of the retardation film include a birefringent film obtained by uniaxially or biaxially stretching a polymer material, an oriented film of a liquid crystal polymer, an oriented layer of a liquid crystal polymer supported by a film, etc. The thickness of the retardation film is not particularly limited, but is generally about 1 to 150 μm.

[0091] The retardation film may be a film represented by the following formulas (1) to (3): 0.70 <Re

[0450] / Re

[0550] <0.97···(1) 1.5×10 -3 <Δn<6×10 -3 ···(2) 1.13 <NZ<1.50···(3) (wherein Re

[0450] and Re

[0550] are in-plane retardation values ​​of the retardation film measured at 23°C with light of wavelengths of 450 nm and 550 nm, respectively; Δn is in-plane birefringence, which is nx-ny, where nx and ny are the refractive indices of the retardation film in the slow axis direction and the fast axis direction, respectively; and NZ is the ratio of nx-nz, which is the birefringence in the thickness direction, to nx-ny, which is the in-plane birefringence, where nz is the refractive index in the thickness direction of the retardation film) may be used.

[0092] The laminated optical film according to the present invention may be provided with a retardation layer. The retardation layer may be a single layer or multiple layers, and the retardation layer may also serve as a protective layer for the polarizer.

[0093] A liquid crystalline compound is preferably used to form the retardation layer, and a solvent containing the liquid crystalline compound can be applied using, for example, a wire bar, a gap coater, a comma coater, a gravure coater, a slot die, or the like. In this case, the applied liquid crystalline solution may be naturally dried or dried by heating. It is preferable that the liquid crystalline solution be applied at a concentration lower than the isotropic phase-liquid crystal phase transition concentration, i.e., in an isotropic phase state. In this case, stable alignment can be achieved by methods such as rubbing treatment or photoalignment.

[0094] The laminated optical film according to the present invention can be produced, for example, by the following production method. A method for producing a laminated optical film in which at least a first optical film and a second optical film are laminated via an adhesive layer, the method comprising the steps of: applying an adhesive composition for laminated optical films to one or both of a bonding surface of the first optical film and a bonding surface of the second optical film; a bonding step of bonding the first optical film and the second optical film together; and a bonding step of bonding the first optical film and the second optical film via the adhesive layer formed by irradiating the first optical film surface side or the second optical film surface side with active energy rays to cure at least the adhesive composition for laminated optical films, the adhesive composition for laminated optical films being an adhesive composition for bonding at least two optical films, the adhesive composition comprising a curable component, metal oxide particles, and a compound represented by the following general formula (1): [ka] (wherein X is a reactive group, Y is an alkylene group having 1 to 12 carbon atoms which may have a branched chain, or a phenylene group which may have a substituent, and R 1 and R 2 and each independently represent a hydrogen atom, an aliphatic hydrocarbon group, an aryl group, or a heterocyclic group, which may have a substituent.

[0095] In the above coating step, the method for applying the adhesive composition for laminated optical films to one or both of the bonding surface of the first optical film and the bonding surface of the second optical film is appropriately selected depending on the viscosity of the composition and the desired thickness, and examples include a reverse coater, a gravure coater (direct, reverse, or offset), a bar reverse coater, a roll coater, a die coater, a bar coater, and a rod coater.

[0096] The first optical film and / or the second optical film may be subjected to a surface modification treatment before the coating process. In particular, when a polarizer is used as the optical film, it is preferable to perform a surface modification treatment on the polarizer. Examples of surface modification treatments include corona treatment, plasma treatment, and Itro treatment, with corona treatment being particularly preferable. Corona treatment generates reactive functional groups such as carbonyl groups and amino groups on the polarizer surface, improving adhesion to the adhesive layer. Furthermore, the ashing effect removes foreign matter from the surface and reduces surface irregularities, allowing the production of a laminated optical film with excellent appearance characteristics.

[0097] The first optical film and the second optical film are bonded together via the adhesive composition for laminated optical films coated as described above using a roll laminator or the like (bonding step).

[0098] After the first optical film and the second optical film are bonded together, the adhesive composition for laminated optical films is cured by irradiating with active energy rays (electron beams, ultraviolet rays, visible light, etc.) to form an adhesive layer. The active energy rays (electron beams, ultraviolet rays, visible light, etc.) can be irradiated from any appropriate direction.

[0099] When irradiating with electron beams, any suitable irradiation conditions can be used as long as they are sufficient to cure the adhesive composition for laminated optical films. For example, the acceleration voltage for electron beam irradiation is preferably 5 kV to 300 kV, more preferably 10 kV to 250 kV. If the acceleration voltage is less than 5 kV, the electron beams may not reach the adhesive, resulting in insufficient curing. If the acceleration voltage is more than 300 kV, the electron beams may have too strong a penetration force through the sample, potentially damaging the first optical film and the second optical film. The irradiation dose is preferably 5 to 100 kGy, more preferably 10 to 75 kGy. If the irradiation dose is less than 5 kGy, the adhesive may not be cured sufficiently. If the irradiation dose is more than 100 kGy, the first optical film and the second optical film may be damaged, resulting in reduced mechanical strength and yellowing, and the desired optical properties may not be achieved.

[0100] Electron beam irradiation is usually performed in an inert gas atmosphere, but if necessary, it can be performed in the atmosphere or with a small amount of oxygen introduced. Depending on the materials of the first and second optical films, introducing oxygen appropriately can intentionally cause oxygen inhibition on the surfaces of the first and second optical films that are first hit by the electron beam, preventing damage to the first and second optical films and allowing the electron beam to be efficiently irradiated only on the adhesive.

[0101] When producing the laminated optical film of the present invention, it is preferable to use active energy rays that include visible light in the wavelength range of 380 nm to 450 nm, and particularly active energy rays that have the highest exposure dose of visible light in the wavelength range of 380 nm to 450 nm. When ultraviolet light and visible light are used, if a transparent protective film with ultraviolet absorption ability (an ultraviolet-opaque transparent protective film) is used as the optical film, light with wavelengths shorter than approximately 380 nm is absorbed, and therefore light with wavelengths shorter than 380 nm does not reach the curable resin composition and does not contribute to its polymerization reaction. Furthermore, light with wavelengths shorter than 380 nm absorbed by the first optical film and the second optical film is converted into heat, causing the first optical film or the second optical film to generate heat, resulting in defects such as curling and wrinkling of the laminated optical film. Therefore, when ultraviolet light or visible light is used in the present invention, it is preferable to use an active energy ray generator that does not emit light with a wavelength shorter than 380 nm. More specifically, the ratio of the integrated illuminance in the wavelength range of 380 to 440 nm to the integrated illuminance in the wavelength range of 250 to 370 nm is preferably 100:0 to 100:50, more preferably 100:0 to 100:40. When producing the laminated optical film of the present invention, the active energy ray is preferably a gallium-encapsulated metal halide lamp or an LED light source emitting light in the wavelength range of 380 to 440 nm. Alternatively, light sources that emit ultraviolet and visible light, such as low-pressure mercury lamps, medium-pressure mercury lamps, high-pressure mercury lamps, ultra-high-pressure mercury lamps, incandescent lamps, xenon lamps, halogen lamps, carbon arc lamps, metal halide lamps, fluorescent lamps, tungsten lamps, gallium lamps, excimer lasers, or sunlight, can be used. A bandpass filter can also be used to block ultraviolet light with a wavelength shorter than 380 nm. In order to prevent curling of the laminated optical film while improving the adhesive performance of the adhesive layer between the first optical film and the second optical film, it is preferable to use active energy rays obtained by using a gallium-encapsulated metal halide lamp and passing through a bandpass filter capable of blocking light with wavelengths shorter than 380 nm, or active energy rays with a wavelength of 405 nm obtained by using an LED light source.

[0102] When the laminated optical film according to the present invention is produced on a continuous line, the line speed depends on the curing time of the adhesive composition for laminated optical films, but is preferably 1 to 500 m / min, more preferably 5 to 300 m / min, and even more preferably 10 to 100 m / min. If the line speed is too slow, productivity will be poor or the damage to the first optical film and the second optical film will be too great, making it impossible to produce a laminated optical film that can withstand durability tests and the like. If the line speed is too high, the adhesive composition for laminated optical films will not cure sufficiently, and the desired adhesiveness may not be obtained.

[0103] The laminated optical film according to the present invention may also be provided with an adhesive layer for bonding to other components such as a liquid crystal cell. The adhesive for forming the adhesive layer is not particularly limited, and may be appropriately selected and used, for example, from an acrylic polymer, a silicone polymer, a polyester, a polyurethane, a polyamide, a polyether, a fluorine-based polymer, a rubber-based polymer, or the like. In particular, an acrylic adhesive, which has excellent optical transparency, exhibits adhesive properties such as moderate wettability, cohesion, and adhesiveness, and is excellent in weather resistance, heat resistance, and the like, can be preferably used.

[0104] The adhesive layer can be provided on one or both sides of the laminated optical film according to the present invention as a superposed layer of layers with different compositions or types. When provided on both sides, the adhesive layers on the front and back of the laminated optical film according to the present invention can have different compositions, types, thicknesses, etc. The thickness of the adhesive layer can be appropriately determined depending on the intended use, adhesive strength, etc., and is generally 1 to 500 μm, preferably 1 to 200 μm, and particularly preferably 1 to 100 μm.

[0105] The exposed surface of the adhesive layer is covered with a temporary separator to prevent contamination until the adhesive layer is put into practical use. This prevents contact with the adhesive layer during normal handling. As the separator, apart from the thickness requirements described above, any suitable conventional separator can be used, such as a suitable thin sheet such as a plastic film, rubber sheet, paper, cloth, nonwoven fabric, net, foam sheet, metal foil, or a laminate thereof, optionally coated with a suitable release agent such as a silicone-based, long-chain alkyl-based, fluorine-based, or molybdenum sulfide-based release agent.

[0106] The laminated optical film according to the present invention can be preferably used to form various devices such as liquid crystal display devices. The formation of a liquid crystal display device can be carried out in a conventional manner. That is, a liquid crystal display device is generally formed by appropriately assembling a liquid crystal cell, a polarizing film or a laminated optical film, and, if necessary, components such as an illumination system, and incorporating a driving circuit. However, in the present invention, there are no particular limitations except for the use of the polarizing film or laminated optical film according to the present invention, and the method can be carried out in a conventional manner. Any type of liquid crystal cell, such as a TN type, STN type, or π type, can be used.

[0107] Appropriate liquid crystal display devices can be formed, such as those in which an optical laminate is disposed on one or both sides of a liquid crystal cell, or those in which a backlight or reflector is used in the illumination system. In such cases, the optical laminate of the present invention can be disposed on one or both sides of the liquid crystal cell. When optical laminates are disposed on both sides, they may be the same or different. Furthermore, when forming a liquid crystal display device, appropriate components such as a diffuser, anti-glare layer, anti-reflection film, protective plate, prism array, lens array sheet, light diffuser, backlight, etc. can be disposed in one or more layers at appropriate positions. [Example]

[0108] Examples of the present invention will be described below, but the embodiments of the present invention are not limited to these.

[0109] (Preparation of adhesive composition for laminated optical film) The components shown below were mixed according to the recipe in Table 1 and stirred at 50°C for 1 hour to obtain adhesive compositions for laminated optical films used in Examples 1 to 6 and Comparative Examples 1 and 2. The values ​​in the table indicate % by weight when the total amount of the composition is taken as 100% by mass.

[0110] The materials constituting the adhesive composition for laminated optical films are shown below. (i) Metal oxide particles Zirconia Dispersion 1: Phenoxybenzyl acrylate dispersion of zirconium oxide with an average particle size of 100 nm (particle concentration 50% by weight) Zirconia dispersion 2: Phenoxybenzyl acrylate dispersion of zirconium oxide with an average particle size of 20 nm (particle concentration 50% by weight) Zirconia Dispersion 3: Phenoxybenzyl acrylate dispersion of zirconium oxide with an average particle size of 8 nm (particle concentration 50% by weight) Zirconia Dispersion 4: Phenoxydiethylene glycol acrylate dispersion of zirconium oxide with an average particle size of 8 nm (particle concentration 50% by weight) Zirconia Dispersion 5: Phenoxyethyl acrylate dispersion of zirconium oxide with an average particle size of 8 nm (particle concentration 50% by weight) Titania Dispersion 1: Phenoxybenzyl acrylate dispersion of titanium oxide with an average particle size of 20 nm (particle concentration 30% by weight) (ii) (Meth)acrylate containing an aromatic ring skeleton Phenoxybenzyl acrylate: Product name "Light Acrylate POB-A", manufactured by Kyoeisha Chemical Co., Ltd. Phenoxyethyl acrylate: Product name "Light Acrylate PO-A", manufactured by Kyoeisha Chemical Co., Ltd. (iii) Curable component Compound represented by general formula (1) (3-methacrylamidophenylboronic acid): trade name "MAPBA", manufactured by Junsei Chemical Co., Ltd. Hydroxyl group-containing (meth)acrylate (4-hydroxybutyl acrylate): Product name "4HBA", manufactured by Mitsubishi Chemical Corporation Acryloylmorpholine: Trade name "ACMO", manufactured by KJ Chemicals Multifunctional radical polymerizable compound (tripropylene glycol diacrylate): Trade name "Aronix M-220", manufactured by Toagosei Co., Ltd. (iv) Leveling agent (a leveling agent containing a modified isocyanurate compound having a (meth)acryloyl group and a modified polysiloxane compound having a (meth)acryloyl group): trade name "BYK UV-3505", manufactured by BYK (v) Acrylic oligomer obtained by polymerizing (meth)acrylic monomer: trade name "ARUFON UP-1190", manufactured by Toagosei Co., Ltd. (vi) Photopolymerization initiator Photopolymerization initiator 1 (bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide): trade name "Omnirad 819", manufactured by IGM Resins BV Photopolymerization initiator 2 (1-hydroxycyclohexyl phenyl ketone): Trade name "Omnirad 184", manufactured by IGM Resins BV Photopolymerization initiator 3 (diethylthioxanthone): trade name "KAYACURE DETX-S", manufactured by Nippon Kayaku Co., Ltd. The above Zirconia Dispersions 1 to 5 and Titania Dispersion 1 were produced by the following methods.

[0111] (Synthesis of Dispersant A) 415 g (1 mole) of tristyrenated phenol and 1 g (0.018 mole) of potassium hydroxide were charged into an autoclave and mixed uniformly. 352 g (8 moles) of ethylene oxide (EO) was added dropwise to the reaction system at 130°C. After the dropwise addition of ethylene oxide was completed, the pressure was maintained at 0.1 MPa and the reaction system was aged for 1 hour at 130°C, yielding an adduct of 8 moles of EO with tristyrenated phenol.

[0112] 767 g (1 mol) of the above tristyrenated phenol EO 8 mole adduct and 152 g (1.3 mol) of sodium monochloroacetate were placed in a reactor and stirred until homogeneous. Next, 52 g of sodium hydroxide was added under conditions of 60 ° C. of reaction system, and then the temperature was raised to 80 ° C. and aged for 3 hours. After aging, the mixture was cooled to 50 ° C., and 117 g (1.2 mol) of 98% sulfuric acid was added dropwise at the same temperature to obtain a white suspension. This white suspension was washed with distilled water, and the solvent was distilled off under reduced pressure to obtain Dispersant A.

[0113] (Preparation of Zirconia Dispersion 1) An aqueous dispersion of zirconium oxide (Sigma-Aldrich, average particle size 100 nm, zirconium oxide solids concentration: 10%) was concentrated using an ultrafiltration membrane. An equal volume of methanol to the filtrate was added to the resulting concentrated dispersion. The dispersion was continuously and simultaneously concentrated and diluted with methanol. This resulted in a 10 wt% zirconium oxide particle concentration in the dispersion. The dispersion medium was replaced from water to methanol, maintaining the zirconium oxide particle concentration in the dispersion at 10 wt%. To 100 parts of the resulting methanol dispersion of zirconium oxide, 0.5 parts of Dispersant A and 9.5 parts of m-phenoxybenzyl acrylate (Kyoeisha Chemical, trade name "Light Acrylate POB-A"; hereinafter referred to as "POB-A") were added and mixed. The solvent was then removed under reduced pressure using a rotary evaporator to obtain Zirconia Dispersion 1, a zirconium oxide monomer dispersion. This zirconia dispersion A contained zirconium oxide / dispersant A / POB-A in a weight ratio of 50 / 2.5 / 47.5.

[0114] (Preparation of Zirconia Dispersion 2) 1.5 parts of Dispersant A and 28.5 parts of m-phenoxybenzyl acrylate (Kyoeisha Chemical Industry, trade name "Light Acrylate POB-A"; hereinafter referred to as "POB-A") were mixed with 100 parts of a methyl ethyl ketone dispersion of zirconium oxide (Nissan Chemical Industries, Ltd., grade "OZ-S40K-AC," average particle size (D50) measured by dynamic light scattering: 20 nm, zirconium oxide solids concentration: 30%). The solvent was then removed under reduced pressure using a rotary evaporator to obtain Zirconia Dispersion 2, a monomer dispersion of zirconium oxide. Zirconia Dispersion A contained zirconium oxide / Dispersant A / POB-A in a weight ratio of 50 / 2.5 / 47.5.

[0115] (Preparation of Zirconia Dispersion 3) To 100 parts of a methanol dispersion of zirconium oxide (manufactured by Sakai Chemical Industry Co., Ltd., grade "SZR-CM," average particle size (D50) measured by dynamic light scattering: 8 nm, zirconium oxide solids concentration: 30%), 1.5 parts of Dispersant A and 28.5 parts of m-phenoxybenzyl acrylate (manufactured by Kyoeisha Chemical Co., Ltd., trade name "Light Acrylate POB-A"; hereinafter referred to as "POB-A") were added and mixed. The solvent was then removed under reduced pressure using a rotary evaporator to obtain Zirconia Dispersion A, a monomer dispersion of zirconium oxide. This Zirconia Dispersion 3 contained zirconium oxide / Dispersant A / POB-A in a weight ratio of 50 / 2.5 / 47.5.

[0116] (Preparation of Zirconia Dispersion 4) 1.5 parts of Dispersant A and 28.5 parts of phenoxydiethylene glycol acrylate (Kyoeisha Chemical Industry Co., Ltd., trade name "Light Acrylate P2H-A"; hereinafter referred to as "P2H-A") were mixed with 100 parts of a methanol dispersion of zirconium oxide (manufactured by Sakai Chemical Industry Co., Ltd., grade "SZR-CM," average particle size (D50) measured by dynamic light scattering: 8 nm, zirconium oxide solids concentration: 30%). The solvent was then removed under reduced pressure using a rotary evaporator to obtain Zirconia Dispersion 4, a monomer dispersion of zirconium oxide. This Zirconia Dispersion A contained zirconium oxide / Dispersant A / P2H-A in a weight ratio of 50 / 2.5 / 47.5.

[0117] (Preparation of Zirconia Dispersion 5) 1.5 parts of Dispersant A and 28.5 parts of phenoxyethyl acrylate (Kyoeisha Chemical Industry Co., Ltd., trade name "Light Acrylate PO-A"; hereinafter referred to as "PO-A") were mixed with 100 parts of a methanol dispersion of zirconium oxide (manufactured by Sakai Chemical Industry Co., Ltd., grade "SZR-CM," average particle size (D50) measured by dynamic light scattering: 8 nm, zirconium oxide solids concentration: 30%). The solvent was then removed under reduced pressure using a rotary evaporator to obtain Zirconia Dispersion 5, a monomer dispersion of zirconium oxide. Zirconia Dispersion A contained zirconium oxide / Dispersant A / PO-A in a weight ratio of 50 / 2.5 / 47.5.

[0118] (Preparation of Titania Dispersion 1) To 100 parts of a methanol dispersion of titanium oxide (manufactured by Nissan Chemical Industries, Ltd., grade "OT-RA305M7-20," mean particle size (D50) measured by dynamic light scattering: 20 nm, titanium oxide solids concentration: 30%), 1.5 parts of Dispersant A and 68.5 parts of m-phenoxybenzyl acrylate (manufactured by Kyoeisha Chemical Industry, trade name "Light Acrylate POB-A"; hereinafter referred to as "POB-A") were added and mixed. The solvent was then removed under reduced pressure using a rotary evaporator to obtain Zirconia Dispersion A, a monomer dispersion of zirconium oxide. This Zirconia Dispersion A contained zirconium oxide / Dispersant A / POB-A in a weight ratio of 30 / 1.5 / 68.5.

[0119] The materials constituting the laminated optical film are listed below.

[0120] <Manufacture of polarizer> A laminate having a 9 μm-thick PVA layer formed on an amorphous PET substrate was subjected to in-air auxiliary stretching at a stretching temperature of 130°C to produce a stretched laminate, which was then dyed to produce a dyed laminate, and the dyed laminate was further stretched in boric acid water at a stretching temperature of 65°C to produce an optical film laminate including a 5 μm-thick PVA layer, stretched together with the amorphous PET substrate to a total stretch ratio of 5.94. This two-stage stretching process resulted in highly oriented PVA molecules in the PVA layer formed on the amorphous PET substrate, and an optical film laminate including a 5 μm-thick PVA layer was obtained, which constitutes a thin polarizer in which iodine adsorbed by dyeing was highly oriented in one direction as a polyiodine ion complex.

[0121] <Transparent protective film> "TAC": Triacetyl cellulose (TAC) film (product name "TJ25UL", thickness 25 μm, manufactured by Fujifilm Corporation)

[0122] <Photopolymerizable liquid crystal composition> A photopolymerizable liquid crystal compound exhibiting a nematic liquid crystal phase (BASF's "Paliocolor LC242") was dissolved in cyclopentanone to prepare a solution with a solids concentration of 30% by weight. A surfactant (BYK-Chemie's "BYK-360") and a photopolymerization initiator (IGM Resins' "Omnirad907") were added to this solution to prepare a liquid crystal composition solution. The amounts of the leveling agent and polymerization initiator added were 0.01 parts by weight and 3 parts by weight, respectively, per 100 parts by weight of the photopolymerizable liquid crystal compound.

[0123] <λ / 2 phase difference film> A biaxially stretched norbornene film (Zeon Corporation's "Zeonor Film", thickness: 33 μm, front retardation: 135 nm) was used as a substrate. The liquid crystal composition was applied to the substrate with a bar coater so that the phase difference was λ / 2, and the liquid crystal was aligned by heating at 100°C for 3 minutes. After cooling to room temperature, the liquid crystal was aligned by irradiating the film with an integrated light dose of 400 mJ / cm under a nitrogen atmosphere. 2 The laminate was then photocured by irradiating it with ultraviolet light of 1000 kJ / cm 2 , to obtain a laminate provided with a homogeneously aligned liquid crystal layer.

[0124] <λ / 4 phase difference film> A biaxially stretched norbornene film (Zeon Corporation's "Zeonor Film", thickness: 33 μm, front retardation: 135 nm) was used as a substrate. The liquid crystal composition was applied to the substrate with a bar coater so that the phase difference was λ / 4, and the liquid crystal was aligned by heating at 100°C for 3 minutes. After cooling to room temperature, the liquid crystal was aligned by irradiating the film with an integrated light dose of 400 mJ / cm under a nitrogen atmosphere. 2 The laminate was then photocured by irradiating it with ultraviolet light of 1000 kJ / cm 2 , to obtain a laminate provided with a homogeneously aligned liquid crystal layer.

[0125] <Polarizing film (1)> An MCD coater (manufactured by Fuji Machinery Co., Ltd.) (cell shape: honeycomb, gravure roll line count: 700 / inch, rotation speed: 140% / line speed) was used, and a corona treatment machine was used to treat the coating at a density of 50 W·min / m 2The adhesive composition for laminated optical films according to Comparative Example 2 was applied to the corona-treated surface of the PVA layer of the polarizer, and the corona treatment density was 50 W·min / m 2 The corona-treated surface of the TAC film was then laminated with a roll machine (the lamination line speed was 15 m / min). After that, a visible light irradiation device (Heraeus Light HAMMER 10 Mark III, bulb: V bulb, peak irradiance: 1600 mW / cm) was used from the TAC film side. 2 , cumulative irradiation dose 1000 / mJ / cm 2 The illuminance and cumulative exposure dose of the active energy rays were measured using a Power Puck 2 (manufactured by EIT, UVV measurement values) to irradiate the adhesive composition for laminated optical films with active energy rays, thereby producing a polarized film (1) in which an amorphous PET substrate, a polarizer, and a TAC film were laminated via a cured layer of the adhesive composition for laminated optical films. The thickness of the cured layer of the adhesive composition for laminated optical films was 1 μm.

[0126] <Polarizing film (2)> Next, the amorphous PET substrate of the polarizing film (1) was peeled off, and the polarizer surface of the peeled surface was treated with a corona treatment machine at a treatment density of 50 W·min / m 2 The adhesive composition for a laminated optical film according to Comparative Example 2 was applied to the polarizer that had been subjected to the corona treatment using an MCD coater (manufactured by Fuji Machinery Co., Ltd.) (cell shape: honeycomb, gravure roll line count: 700 / inch, rotation speed: 140% / line speed), and the adhesive composition was then applied to the polarizer using the same corona treatment machine at a treatment density of 50 W·min / m 2 The homogeneously aligned liquid crystal layer surface of the corona-treated λ / 2 retardation film was laminated to the polarizer using a roller so that the slow axis of the λ / 2 retardation film was at a 15° angle with the transmission axis of the polarizer (lamination line speed: 15 m / min). After that, a visible light irradiation device (Heraeus Light HAMMER 10 Mark III, bulb: V bulb, peak irradiance: 1600 mW / cm) was used from the λ / 2 retardation film side. 2 , cumulative irradiation dose 1000 / mJ / cm 2The illuminance and cumulative exposure dose of the active energy rays were measured using a Power Puck 2 (manufactured by EIT, UVV measurement values) to irradiate the adhesive composition for laminated optical films with active energy rays, thereby producing a polarized film (2) in which a λ / 2 retardation film, a polarizer, and a TAC film were laminated via a cured layer of the adhesive composition for laminated optical films. The thickness of the cured layer of the adhesive composition for laminated optical films was 1 μm.

[0127] (Example of laminated optical film manufacturing) The biaxially stretched norbornene film of the polarizing film (2) was peeled off, and the λ / 2 retardation film surface on the peeled surface was treated with a corona treatment machine at a treatment density of 50 W·min / m 2 Using an MCD coater (manufactured by Fuji Machinery Co., Ltd.) (cell shape: honeycomb, gravure roll line count: 700 rolls / inch, rotation speed: 140% / line speed), the adhesive compositions for laminated optical films according to Examples 1 to 6 and Comparative Examples 1 and 2, which had the formulations shown in Table 1, were applied to the corona-treated λ / 2 retardation film surface, and the same corona treatment machine was used to apply the adhesive compositions at a treatment density of 50 W·min / m 2 The homogeneously aligned liquid crystal layer surface of the corona-treated λ / 4 retardation film was laminated to the λ / 2 retardation film surface using a roller so that the slow axis of the λ / 4 retardation film was at a 75° angle with the transmission axis of the polarizer (lamination line speed: 15 m / min). Then, from the λ / 4 retardation film side, a visible light irradiation device (Heraeus Light HAMMER10 Mark III, bulb: V bulb, peak irradiance: 1600 mW / cm) was used. 2 , cumulative irradiation dose 1000 / mJ / cm 2 The illuminance and cumulative exposure dose of the active energy rays were determined using a Power Puck 2 (manufactured by EIT, UVV measurement values) to irradiate the adhesive compositions for laminated optical films according to Examples 1 to 6 and Comparative Examples 1 and 2 with active energy rays to cure them, thereby producing laminated optical films in which a λ / 4 retardation film surface, a λ / 2 retardation film, a polarizer, and a TAC film were laminated via a cured layer of the adhesive composition for laminated optical films. The thickness of the cured layer of the adhesive composition for laminated optical films was 1 μm.

[0128] Details of each evaluation method are as follows.

[0129] <Viscosity of adhesive composition for laminated optical film> The viscosity of the adhesive compositions for laminated optical films according to Examples 1 to 6 and Comparative Examples 1 and 2 was measured using an E-type viscometer TVE22LT manufactured by Toki Sangyo Co., Ltd.

[0130] <Measurement of refractive index of adhesive layer> The adhesive compositions for laminated optical films according to Examples 1 to 6 and Comparative Examples 1 to 2 were coated (100 μm thick) onto a cycloolefin polymer film (COP film), and the same COP film was attached to the coated surface. The coated surface was then irradiated with visible light using an active energy ray irradiation device to obtain cured layers (single films) of the adhesive compositions for laminated optical films according to Examples 1 to 6 and Comparative Examples 1 to 2. The in-plane and thickness-direction refractive indices of the obtained cured layers were measured using a prism coupler SPA-4000 (manufactured by Cylon Technology), and the average value was taken as the average refractive index of the adhesive layer. The measurement temperature was 23°C and the measurement wavelength was 594 nm.

[0131] <Cure shrinkage rate of adhesive composition for laminated optical film> The cure shrinkage rate was measured with a resin cure shrinkage measuring device CUSTRON EU201C (manufactured by Acroedge Co., Ltd.) using a laser displacement meter, and the cure shrinkage rate was calculated by the method described in JP-A 2013-104869.

[0132] <Peel force between laminated optical films> The biaxially stretched norbornene film of the laminated optical film was peeled off, and double-sided tape (No. 500, manufactured by Nitto Denko Corporation) was attached to the λ / 4 retardation film surface. A 200mm x 15mm sample was then cut, and a slit was made between the λ / 4 retardation film and the λ / 2 retardation film with a utility knife. The release film was then peeled off from the double-sided tape, and the adhesive side was attached to a glass plate. The λ / 4 retardation film and the λ / 2 retardation film were peeled off at a 90° angle at a peel speed of 20,000mm / min using a flexible angle adhesive and film peel analyzer (VPA-2, manufactured by Kyowa Interface Science Co., Ltd.), and the peel strength (N / 15mm) was measured.

[0133] [Table 1]

[0134] Compared to the cured product layers (adhesive layers) of the adhesive compositions for laminated optical films according to Comparative Examples 1 and 2, which do not contain metal oxide particles, the cured product layers of the adhesive compositions for laminated optical films according to Examples 1 to 6, which contain metal oxide particles, are able to achieve both an improved refractive index and an improved adhesive strength of the adhesive layer, and further, are able to reduce the cure shrinkage rate of the adhesive layer.

Claims

1. An adhesive composition for laminated optical films for bonding at least two optical films, comprising: A curable component, metal oxide particles, and a composition of the following general formula (1): 【Chemistry 1】 (wherein X is a reactive group, Y is an alkylene group having 1 to 12 carbon atoms which may have a branched chain, or a phenylene group which may have a substituent, and R １ and R ２ each independently represents a hydrogen atom, an optionally substituted aliphatic hydrocarbon group, an aryl group, or a heterocyclic group.

2. 2. The adhesive composition for laminated optical films according to claim 1, wherein the content of the metal oxide particles is 10 to 50% by mass when the total amount of the composition is taken as 100% by mass.

3. 2. The adhesive composition for laminated optical films according to claim 1, wherein the content of the compound represented by general formula (1) is 0.1 to 10% by mass when the total amount of the composition is 100% by mass.

4. The adhesive composition for laminated optical films according to claim 1 , further comprising a hydroxyl group-containing (meth)acrylate.

5. 5. The adhesive composition for laminated optical films according to claim 4, wherein the content of the hydroxyl group-containing (meth)acrylate is 1 to 30% by mass when the total amount of the composition is taken as 100% by mass.

6. The adhesive composition for laminated optical films according to claim 1 , further comprising a (meth)acrylate containing an aromatic ring skeleton.

7. 7. The adhesive composition for laminated optical films according to claim 6, wherein the content of the (meth)acrylate containing an aromatic ring skeleton is 30 to 70 mass % when the total amount of the composition is 100 mass %.

8. 7. The adhesive composition for laminated optical films according to claim 6, wherein the (meth)acrylate containing an aromatic ring skeleton contains at least one selected from the group consisting of (meth)acrylates having a polycyclic aromatic ring skeleton and (meth)acrylates having two or more aromatic rings.

9. 7. The adhesive composition for laminated optical films according to claim 6, wherein the (meth)acrylate containing an aromatic ring skeleton is phenoxybenzyl (meth)acrylate.

10. 2. The adhesive composition for laminated optical films according to claim 1, further comprising a leveling agent containing at least one compound selected from the group consisting of an isocyanurate compound and a polysiloxane compound.

11. 11. The adhesive composition for laminated optical films according to claim 10, wherein the content of the isocyanurate compound is 0.05 to 10% by mass when the total amount of the composition is taken as 100% by mass.

12. 11. The adhesive composition for laminated optical films according to claim 10, wherein the content of the polysiloxane compound is 0.05 to 2.0% by mass when the total amount of the composition is taken as 100% by mass.

13. 2. The adhesive composition for laminated optical films according to claim 1, which has a viscosity at 25°C of 100 mPa·s or less.

14. A laminated optical film in which at least a first optical film and a second optical film are laminated via an adhesive layer, A laminated optical film, wherein the adhesive layer is a cured product layer of the adhesive composition for laminated optical films according to claim 1 .

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