Layered optical film and image display device

Abstract

A layered optical film according to the present invention is formed by layering at least a first optical film and a second optical film with an adhesive layer therebetween, the first optical film being a resin film that has a breaking strength of no more than 70, and the adhesive layer being a layer of a cured product of an adhesive composition that contains an oligomer that has a molecular weight of at least 700. The oligomer is preferably a polymerizable oligomer that has a polymerizable group, the oligomer is preferably a urethane (meth)acrylate, the urethane (meth)acrylate preferably has an ether skeleton in the molecule thereof, and the oligomer preferably does not have an aromatic ring or an alicyclic skeleton in the molecule thereof.

Description

Laminated optical film and image display device

[0001] The present invention relates to a laminated optical film comprising at least a first optical film and a second optical film laminated together via an adhesive layer, which can be used to form image displays such as mobile phones, car navigation devices, personal computer monitors, and televisions.

[0002] Image display devices such as mobile phones, car navigation devices, PC monitors, and televisions are equipped with laminated optical films in which multiple optical films are laminated via adhesive or pressure-sensitive adhesive layers. Transparent resin films such as retardation films, polarizers, and transparent protective films are used as the optical films.

[0003] In recent years, there has been an increasing demand for thinner image display devices. For example, Patent Document 1 listed below describes a liquid crystal display device that is significantly thinner than conventional devices and uses a liquid crystal cell such as an IPS liquid crystal cell.

[0004] JP 2015-111236 A

[0005] The technology described in Patent Document 1 makes it possible to reduce light leakage in oblique directions during black display and increase contrast. Incidentally, some optical films used in image display devices have low breaking strength and are brittle, but they must be used due to environmental regulations and other constraints. While the technology described in Patent Document 1 aims to reduce the thickness of image display devices, it does not fully consider how to increase the peel strength from the adhesive layer and thereby increase product durability when a specific optical film having low breaking strength and being brittle is used.

[0006] The present invention was developed in consideration of the above-mentioned circumstances, and aims to provide a laminated optical film that has excellent peel strength between the optical film and the adhesive layer, even when it has an optical film that has low breaking strength and is brittle.

[0007] The above-mentioned problems can be solved by the following configuration: That is, the present invention relates to a laminated optical film (1) in which at least a first optical film and a second optical film are laminated via an adhesive layer, the first optical film being a resin film having a breaking strength of 70 or less, and the adhesive layer being formed of a cured layer of an adhesive composition containing an oligomer having a molecular weight of 700 or more.

[0008] In the laminated optical film (1), the oligomer is preferably a polymerizable oligomer having a polymerizable group.

[0009] In the laminated optical film (1) or (2), the oligomer is preferably a laminated optical film (3) that is a urethane (meth)acrylate.

[0010] In the laminated optical film (3), the urethane (meth)acrylate preferably has an ether skeleton in the molecule.

[0011] In any one of the laminated optical films (1) to (3), a laminated optical film (5) is preferred in which the oligomer does not have an aromatic ring or an alicyclic skeleton in the molecule.

[0012] In any one of the laminated optical films (1) to (5), the adhesive layer preferably has a glass transition temperature of 35° C. or lower (6).

[0013] In any one of the laminated optical films (1) to (6), a laminated optical film (7) is preferred in which the adhesive composition further contains at least one radically polymerizable compound selected from the group consisting of monofunctional radically polymerizable compounds and polyfunctional radically polymerizable compounds.

[0014] In the laminated optical film (7), a laminated optical film (8) is preferred in which the HSP value distance between the average HSP value of the radical polymerizable compound (excluding the oligomer) contained in the adhesive composition and the HSP value of the first optical film is 3.5 or less.

[0015] In the laminated optical film (7) or (8), a laminated optical film (9) is preferred in which the content of the polyfunctional radical polymerizable compound is 10 parts by mass or less when the total amount of the radical polymerizable compounds in the adhesive composition is 100 parts by mass.

[0016] In any one of the laminated optical films (1) to (9), the adhesive composition further contains a compound represented by the following general formula (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 and each independently represent a hydrogen atom, an aliphatic hydrocarbon group, an aryl group, or a heterocyclic group, which may have a substituent.

[0017] In any one of the laminated optical films (1) to (10), a laminated optical film (11) is preferred in which the adhesive composition further contains a monofunctional radically polymerizable compound having a hydroxyl group.

[0018] In any one of the laminated optical films (1) to (11), a laminated optical film (12) is preferred in which the first optical film is a retardation film.

[0019] In the laminated optical film (12), the second optical film is preferably a retardation film (13).

[0020] The present invention also relates to an image display device (14) comprising at least one of the laminated optical films (1) to (13) above.

[0021] The laminated optical film according to the present invention includes at least a first optical film (resin film) having a breaking strength of not more than 70. Here, the first optical film having a low breaking strength of not more than 70 is manufactured on a substrate such as PET, and is laminated with a second optical film or another optical film via an adhesive layer, and then the substrate such as PET is peeled off to complete the lamination. However, when the substrate is peeled off, the first optical film may suffer cohesive failure, which may prevent the first optical film from exhibiting its performance or may result in a defective product.

[0022] On the other hand, in the laminated optical film according to the present invention, the first optical film and the second optical film are laminated via an adhesive layer formed of a cured layer of an adhesive composition containing an oligomer having a molecular weight of 700 or more. Therefore, even when the laminated optical film according to the present invention includes a first optical film having low breaking strength and being brittle, the peel strength between the first optical film and the adhesive layer is excellent, and the occurrence of defects such as cohesive failure in the first optical film when peeling off a substrate such as PET is prevented. The reason for such effects is not clear, but in the present invention, the adhesive layer is formed of a cured layer of an adhesive composition containing an oligomer having a molecular weight of 700 or more, and therefore has stress relaxation properties and toughness, and exhibits high peel strength with respect to the first optical film and the second optical film. Therefore, even when peeling off a substrate such as PET from the first optical film, stress concentration is unlikely to occur near the interface between the adhesive layer and the first optical film, which is a brittle layer. As a result, it is thought that defects such as cohesive failure in the first optical film can be prevented.

[0023] When the oligomer constituting the adhesive layer of the laminated optical film according to the present invention is a polymerizable oligomer having a polymerizable group, preferably a urethane (meth)acrylate, more preferably a urethane (meth)acrylate having an ether skeleton, the peel strength between the adhesive layer and the first optical film and the second optical film is particularly excellent, and the occurrence of defects such as cohesive failure in the first optical film when a substrate such as PET is peeled from the first optical film as described above can be more effectively prevented. The reason for this effect is not clear, but one possible reason is that when the oligomer constituting the adhesive layer is a polymerizable oligomer having a polymerizable group, preferably a urethane (meth)acrylate, more preferably a urethane (meth)acrylate having an ether skeleton, the toughness of the adhesive layer is particularly excellent and the stress relaxation property is also improved.

[0024] In the laminated optical film according to the present invention, even when the first optical film is a retardation film, the peel strength between the first optical film and the second optical film and the adhesive layer is particularly excellent, and the occurrence of defects such as cohesive failure in the first optical film can be more effectively prevented when a substrate such as PET is peeled from the first optical film. The reason for this effect is unclear, but it is believed that, because the adhesive layer in the present invention has stress relaxation properties and toughness, it can effectively prevent defects such as cohesive failure in the first optical film when a substrate such as PET is peeled from the retardation film (first optical film). In particular, when the oligomer constituting the adhesive layer is a polymerizable oligomer having a polymerizable group, preferably a urethane (meth)acrylate, and more preferably a urethane (meth)acrylate having an ether skeleton, the adhesive layer has particularly excellent toughness and also has improved stress relaxation properties, and it is believed that, therefore, it can more effectively prevent defects such as cohesive failure in the first optical film.

[0025] When the adhesive layer of the laminated optical film according to the present invention contains, in addition to an oligomer, at least one radically polymerizable compound selected from the group consisting of monofunctional radically polymerizable compounds and polyfunctional radically polymerizable compounds, and the HSP value distance between the average HSP value of the radically polymerizable compounds contained other than the oligomer and the HSP value of the first optical film is 3.5 or less, the peel strength between the optical film and the adhesive layer is particularly excellent. Although the reason for this effect is not clear, it is thought that when the HSP value distance between the average HSP value of the radically polymerizable compounds other than the oligomer constituting the adhesive composition and the HSP value of the first optical film is close to 3.5 or less, a compatible layer in which the first optical film and the adhesive layer are compatible with each other is easily formed at the interface between them, thereby further enhancing the aforementioned effects of increasing the stress relaxation property and toughness of the adhesive layer.

[0026] The present invention relates to a laminated optical film in which at least a first optical film and a second optical film are laminated together via an adhesive layer. Hereinafter, each of the components will be described.

[0027] <First Optical Film> In the present invention, a resin film having a breaking strength of not more than 70 is used as the first optical film. The function exhibited by the first optical film is not particularly limited, but in the present invention, even when the first optical film is a retardation film, it is preferable because it has excellent peel strength from the adhesive layer and can effectively prevent defects such as cohesive failure from occurring in the retardation film (first optical film) when a substrate such as PET is peeled off.

[0028] When the first optical film is a retardation film, it may be a retardation film having a front retardation of 10 nm or more and / or a thickness direction retardation of 60 nm or more. The front retardation is usually controlled in the range of 10 to 200 nm, and the thickness direction retardation is usually controlled in the range of 60 to 300 nm.

[0029] The retardation film may be a film satisfying the following formulas (1) to (3): 0.70<Re

[450] / Re

[550] <0.99 (1) 1.5×10 －３ < Δn < 6 × 10 －３... (2) 1.13<NZ<5.00 ... (3) (wherein Re

[450] and Re

[550] 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 in the slow axis direction and the fast axis direction of the retardation film, 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.

[0030] Examples of resin films constituting the first optical film include acrylic resins, styrene resins, maleimide resins, and fumarate ester resins. As a result of extensive research, the present inventors have found that, among these, fumarate ester resins have particularly low breaking strength and are brittle. In the present invention, even when the first optical film is a retardation film made of a fumarate ester resin, the peel strength between the first optical film and the adhesive layer is excellent, and defects such as cohesive failure in the first optical film can be effectively prevented when peeling off a substrate such as PET. As described below, when the oligomer constituting the adhesive layer is a polymerizable oligomer having a polymerizable group, preferably a urethane (meth)acrylate, and more preferably a urethane (meth)acrylate having an ether skeleton, the adhesive layer has particularly excellent toughness and also has improved stress relaxation properties. As a result, even when a fumarate ester-based resin film, which has drawbacks such as low breaking strength and brittleness, is used as the first optical film (retardation film), it is possible to effectively prevent defects such as cohesive failure from occurring in the first optical film when peeling off the substrate such as PET, which is preferable.

[0031] The laminated optical film according to the present invention has an adhesive layer that contains, in addition to an oligomer, at least one radically polymerizable compound selected from the group consisting of monofunctional radically polymerizable compounds and polyfunctional radically polymerizable compounds, and the HSP value distance between the average HSP value of the radically polymerizable compounds contained in addition to the oligomer and the HSP value of the first optical film is 3.5 or less. In particular, when the resin film constituting the first optical film is a fumaric acid ester-based resin and the adhesive layer contains a radically polymerizable compound that satisfies the above-mentioned HSP value distance relationship, a compatible layer is more effectively formed at the interface between the fumaric acid ester-based resin and the adhesive layer, and the aforementioned effect of increasing the stress relaxation property and toughness of the adhesive layer is further exhibited, which is preferable because the peel strength between the first optical film (fumaric acid ester-based resin) and the adhesive layer is more effectively improved.

[0032] The thickness of the first optical film is not particularly limited, but the lower limit can be 1 μm, more preferably 10 μm, and the upper limit can be 100 μm, more preferably 50 μm.

[0033] <Second Optical Film> The function exhibited by the second optical film is not particularly limited. In the present invention, even when the second optical film is a retardation film, it is preferable because it has excellent peel strength from the adhesive layer and can effectively prevent defects such as cohesive failure from occurring in the first optical film when the first optical film is peeled from a substrate such as PET. For example, when the second optical film is a retardation film and the first optical film is also a retardation film, the first optical film (retardation film) satisfies the relationship nz2>nx2>ny2, where nx2 is the refractive index in the in-plane slow axis x direction, ny2 is the refractive index in the fast axis direction, and nz2 is the refractive index in the thickness z direction. The second optical film (retardation film) satisfies the relationship nx1>ny1>nz1, where nx1 is the refractive index in the in-plane slow axis x direction, ny1 is the refractive index in the fast axis direction, and nz1 is the refractive index in the thickness z direction. The slow axes of the first optical film (retardation film) and the second optical film (retardation film) are arranged substantially parallel to each other.

[0034] Examples of the resin film constituting the second optical film include polycarbonate-based resins, polyester-based resins such as polyethylene terephthalate and polyethylene naphthalate, polyarylate-based resins, polyimide-based resins, cyclic polyolefin-based (polynorbornene-based) resins, polyamide resins, and polyolefin-based resins such as polyethylene and polypropylene.

[0035] The thickness of the second optical film is not particularly limited, but the lower limit can be 0.5 μm, more preferably 1 μm, and the upper limit can be 100 μm, more preferably 80 μm.

[0036] <Adhesive Layer> The adhesive layer for laminating the first optical film and the second optical film in the laminated optical film according to the present invention will be described below. This adhesive layer is formed from a cured layer of an adhesive composition containing an oligomer having a molecular weight of 700 or more. From the viewpoint of ensuring the peel strength between the first optical film and the adhesive layer and effectively preventing defects such as cohesive failure in the first optical film when peeling off a substrate such as PET, the thickness of the adhesive layer is preferably 0.1 to 5 μm, more preferably 0.3 to 3 μm. Furthermore, the adhesive layer preferably has a glass transition temperature (Tg) of 35° C. or lower. A method for measuring the glass transition temperature (Tg) of the adhesive layer will be described later.

[0037] The oligomer used in the present invention has a molecular weight of 700 or more, more preferably 1500 or more, and even more preferably 10000 or more. The larger the molecular weight of the oligomer used, the more excellent the toughness of the adhesive layer and the more improved the stress relaxation, which is preferable. In the present invention, it is particularly preferable that the oligomer is a polymerizable oligomer having a polymerizable group. Examples of the polymerizable group include a vinyl group, a (meth)acrylic group, a styryl group, and a (meth)acrylamide group. In the present invention, (meth)acrylic means an acrylic group and / or a methacrylic group.

[0038] In the present invention, it is preferable to use a urethane (meth)acrylate as the polymerizable oligomer, and it is more preferable to use a urethane (meth)acrylate having an ether skeleton. When the adhesive layer is composed of a urethane (meth)acrylate, more preferably a urethane (meth)acrylate having an ether skeleton, as at least a part of the raw materials, the toughness of the adhesive layer is particularly excellent, and further, the stress relaxation property is also improved. As a result, even when a fumarate ester-based resin film, which has drawbacks such as low breaking strength and brittleness, is used as the first optical film (retardation film), it is preferable because the occurrence of defects such as cohesive failure in the first optical film can be effectively prevented when the substrate such as PET is peeled off.

[0039] Examples of urethane (meth)acrylates include those having at least a unit of a polyalkylene glycol such as polyethylene glycol, polypropylene glycol, polybutylene glycol, or polystyrene glycol; a polycarbonate or polyalkylene glycol (poly)carbonate; or a polyester unit in the molecule, a urethane bond, and a polymerizable group. Among these, it is preferable to use a urethane (meth)acrylate having an ether skeleton that has at least a polyalkylene glycol and / or polyalkylene glycol (poly)carbonate, a urethane bond, and a polymerizable group. The urethane bond is formed by the reaction of a hydroxyl group of the polyalkylene glycol or the like that constitutes the urethane (meth)acrylate with an isocyanate such as diphenylmethane diisocyanate, toluene diisocyanate, isophorone diisocyanate, or hexamethylene diisocyanate.

[0040] In the present invention, when a polymerizable oligomer having a molecular weight of 700 or more and not having an aromatic ring or alicyclic skeleton in the molecule is used, the adhesive layer finally formed has appropriate flexibility, and as a result, the stress relaxation property and toughness of the adhesive layer are improved, which is preferable.

[0041] The polymerizable oligomer used in the present invention preferably has at least two polymerizable groups, which has the effect of improving the stress relaxation property and toughness of the adhesive layer that is finally formed.

[0042] In the present invention, polymerizable oligomers other than urethane (meth)acrylates, such as polybutadiene-terminated (meth)acrylates, polyethylene glycol (meth)acrylates, polypropylene glycol (meth)acrylates, and (meth)acrylic (meth)acrylates, can also be used.

[0043] In the present invention, the adhesive composition serving as a raw material for forming the adhesive layer may contain a polymerizable compound other than the polymerizable oligomer. However, from the viewpoint of increasing the peel strength between the first optical film and the adhesive layer and effectively preventing defects such as cohesive failure in the first optical film when a substrate such as PET is peeled off, the content of the polymerizable oligomer is preferably 1 to 30 parts by mass, more preferably 5 to 20 parts by mass, when the total amount of polymerizable components such as the polymerizable oligomer and the polymerizable compound other than the polymerizable oligomer in the adhesive composition is taken as 100 parts by mass.

[0044] Examples of polymerizable compounds other than polymerizable oligomers include active energy ray-curable polymerizable compounds such as electron beam-curable, ultraviolet ray-curable, and visible light-curable compounds. Active energy ray-curable polymerizable compounds can be classified into radically polymerizable compounds and cationically polymerizable compounds. 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.

[0045] Examples of radically polymerizable compounds include compounds having a radically polymerizable functional group of a carbon-carbon double bond, such as a (meth)acrylic group or a vinyl group. These monomer components can be either monofunctional radically polymerizable compounds or polyfunctional radically polymerizable compounds having two or more polymerizable functional groups. These radically polymerizable compounds can be used alone or in combination of two or more. Suitable examples of these radically polymerizable compounds include compounds having a (meth)acrylic group.

[0046] Examples of the monofunctional radical polymerizable compound include (meth)acrylic acid derivatives. Examples of the (meth)acrylic acid derivatives include alkoxy group- 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; cyclohexyl (meth)acrylate, 4-tert-butylcyclohexyl acrylate, and cyclopentyl Examples of suitable adhesives include cycloalkyl (meth)acrylates such as (meth)acrylate; aralkyl (meth)acrylates such as benzyl (meth)acrylate; and polycyclic (meth)acrylates such as 2-isobornyl (meth)acrylate, 2-norbornylmethyl (meth)acrylate, 5-norbornen-2-yl-methyl (meth)acrylate, 3-methyl-2-norbornylmethyl (meth)acrylate, dicyclopentenyl (meth)acrylate, dicyclopentenyloxyethyl (meth)acrylate, and dicyclopentanyl (meth)acrylate. Among these, when phenoxyethyl (meth)acrylate and 4-tert-butylcyclohexyl acrylate are combined and incorporated into the adhesive composition, the adhesive layer has improved adhesion, which is preferable, particularly when the first optical film is a retardation film and the retardation film is a fumaric acid ester-based resin.

[0047] Other examples of the monofunctional radically 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, lauryl (meth)acrylate, 2-ethylhexyl (meth)acrylate, 4-methyl-2-propylpentyl (meth)acrylate, and n-octadecyl (meth)acrylate.

[0048] Other examples of the monofunctional radical polymerizable compound include (meth)acrylamide derivatives having a (meth)acrylamide group. Specific examples of the (meth)acrylamide derivative include N-alkyl group-containing (meth)acrylamide derivatives such as N-methyl(meth)acrylamide, N,N-dimethyl(meth)acrylamide, N,N-diethyl(meth)acrylamide, N-isopropyl(meth)acrylamide, N-butyl(meth)acrylamide, and N-hexyl(meth)acrylamide; N-hydroxyalkyl group-containing (meth)acrylamide derivatives such as N-methylol(meth)acrylamide, N-hydroxyethyl(meth)acrylamide, and N-methylol-N-propane(meth)acrylamide; N-aminoalkyl group-containing (meth)acrylamide derivatives such as aminomethyl(meth)acrylamide and aminoethyl(meth)acrylamide; N-alkoxy group-containing (meth)acrylamide derivatives such as N-methoxymethylacrylamide and N-ethoxymethylacrylamide; and N-mercaptoalkyl group-containing (meth)acrylamide derivatives such as mercaptomethyl(meth)acrylamide and mercaptoethyl(meth)acrylamide. Furthermore, examples of heterocycle-containing (meth)acrylamide derivatives in which the nitrogen atom of the (meth)acrylamide group forms a heterocycle include N-acryloylmorpholine, N-acryloylpiperidine, N-methacryloylpiperidine, and N-acryloylpyrrolidine.

[0049] Other examples of the monofunctional radically polymerizable compound 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; and (meth)acrylates having a hydroxyl group such as [4-(hydroxymethyl)cyclohexyl]methyl acrylate, cyclohexanedimethanol mono(meth)acrylate, and 2-hydroxy-3-phenoxypropyl (meth)acrylate. In the present invention, when a monofunctional radically polymerizable compound having a hydroxyl group, particularly a (meth)acrylate having a hydroxyl group, is blended into the adhesive composition used to laminate the first optical film and the second optical film, this is preferred because it improves adhesion to the adhesive layer of the second optical film, particularly when the second optical film is made of a cyclic polyolefin-based (polynorbornene-based) resin.

[0050] Further, examples of the monofunctional radical polymerizable compound include epoxy group-containing (meth)acrylates such as glycidyl (meth)acrylate and 4-hydroxybutyl (meth)acrylate glycidyl ether; halogen-containing (meth)acrylates such as 2,2,2-trifluoroethyl (meth)acrylate, 2,2,2-trifluoroethylethyl (meth)acrylate, tetrafluoropropyl (meth)acrylate, hexafluoropropyl (meth)acrylate, octafluoropentyl (meth)acrylate, heptadecafluorodecyl (meth)acrylate, and 3-chloro-2-hydroxypropyl (meth)acrylate; and dimethylaminoethyl (meth)acrylate. alkylaminoalkyl(meth)acrylates; oxetane group-containing (meth)acrylates such as 3-oxetanylmethyl(meth)acrylate, 3-methyl-oxetanylmethyl(meth)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, as well as hydroxypivalic acid neopentyl glycol(meth)acrylic acid adduct and p-phenylphenol(meth)acrylate may also be used.

[0051] Furthermore, as the monofunctional radical polymerizable compound, a carboxyl group-containing monomer such as (meth)acrylic acid, carboxyethyl acrylate, carboxypentyl acrylate, itaconic acid, maleic acid, fumaric acid, crotonic acid, or isocrotonic acid may be used.

[0052] Furthermore, examples of the monofunctional radically polymerizable compound that may be used 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.

[0053] Furthermore, as the monofunctional radical polymerizable compound, a radical polymerizable compound having an active methylene group may 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 radically 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 radically polymerizable compound having an active methylene group is preferably an acetoacetoxyalkyl (meth)acrylate.

[0054] In the present invention, the adhesive composition used to laminate the first optical film and the second optical film contains a compound represented by the following general formula (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 ２each independently represent a hydrogen atom, an optionally substituted aliphatic hydrocarbon group, an aryl group, or a heterocyclic group). When the monofunctional radically polymerizable compound represented by formula (1) is incorporated into the adhesive composition, the combined effect of the compound with the polymerizable oligomer improves adhesion to the first optical film, increasing the peel strength between the first optical film and the adhesive layer, and also improving adhesion to the second optical film, particularly when the second optical film is a cyclic polyolefin-based (polynorbornene-based) resin. From the viewpoint of increasing the peel strength between the first optical film and the adhesive layer and effectively preventing defects such as cohesive failure in the first optical film when peeling it from a substrate such as PET, the content of the monofunctional radically polymerizable compound represented by formula (1) is preferably 0.5 to 10 parts by mass, and more preferably 1 to 5 parts by mass, when the total amount of polymerizable components in the adhesive composition, such as the polymerizable oligomer and polymerizable compounds other than the polymerizable oligomer, is taken as 100 parts by mass.

[0055] In the monofunctional radical polymerizable compound represented by general formula (1), 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; and examples of the heterocyclic group include a 5- or 6-membered ring group which contains at least one hetero atom and may have a substituent. These may be linked to each other 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.

[0056] X in the monofunctional radically polymerizable 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 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 adhesive composition constituting 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 curable adhesive composition constituting 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. When the monofunctional radically polymerizable compound represented by general formula (1) has a (meth)acrylamide group, this is more preferred because it has high reactivity and increases the copolymerization rate with the curable component in the adhesive layer. Furthermore, this is also preferred because the (meth)acrylamide group has high polarity and excellent adhesion, allowing the effects of the present invention to be obtained efficiently. When the curable adhesive composition constituting the adhesive layer is cationically 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, this is preferred because the resulting adhesive layer has excellent adhesion to the adherend, and when the reactive group X has a vinyl ether group, this is preferred because the curability of the curable adhesive composition is excellent.

[0057] Preferred specific examples of the monofunctional radical polymerizable compound represented by the general formula (1) include the following compounds (1a) to (1d). ３ is a hydrogen atom or a methyl group.

[0058] In addition to the compounds exemplified above, examples of the monofunctional radically polymerizable compound represented by general formula (1) include esters of (meth)acrylate 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.

[0059] Examples of polyfunctional radically polymerizable compounds having two or more polymerizable functional groups include tripropylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, polyethylene glycol diacrylate, 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, bisphenol A diglycidyl ether di(meth)acrylate, Examples of the ester include esters of (meth)acrylic acid and polyhydric alcohols such as pentyl 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 Light Acrylate 9EG-A (manufactured by Kyoeisha Chemical Co., Ltd.), 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.), and CD-536 (manufactured by Sartomer Co., Ltd.). Furthermore, various epoxy (meth)acrylates, urethane (meth)acrylates, polyester (meth)acrylates, and various (meth)acrylate monomers may also be used as needed. When the total amount of radically polymerizable compounds in the adhesive composition is taken as 100 parts by mass, the content of the polyfunctional radically polymerizable compound is preferably 10 parts by mass or less.

[0060] The adhesive layer of the laminated optical film according to the present invention contains, in addition to the oligomer, at least one radically polymerizable compound selected from the group consisting of monofunctional radically polymerizable compounds and polyfunctional radically polymerizable compounds. When the HSP value distance between the average HSP value of the radically polymerizable compounds contained other than the oligomer and the HSP value of the first optical film is 3.5 or less, the peel strength between the optical film and the adhesive layer is particularly excellent. In particular, when the resin film constituting the first optical film is a fumaric acid ester-based resin, a mutually compatible layer is more effectively formed at the interface between the fumaric acid ester-based resin and the adhesive layer. This further enhances the stress relaxation and toughness of the adhesive layer, which is preferable, thereby more effectively improving the peel strength between the first optical film (fumaric acid ester-based resin) and the adhesive layer. Methods for measuring the average HSP value of the radically polymerizable compounds contained other than the oligomer, the HSP value of the first optical film, and the HSP value distance between them will be described later.

[0061] In the present invention, the adhesive composition serving as the raw material for the adhesive layer of the laminated optical film may contain, in addition to a radically polymerizable compound, an acrylic oligomer obtained by polymerizing a (meth)acrylic monomer and having no polymerizable group. By including the acrylic oligomer in the adhesive composition, cure shrinkage upon irradiation and curing of the composition with active energy rays can be reduced, and interfacial stress between the adhesive layer and an adherend such as a polarizer or an optical film can be reduced. As a result, a decrease in adhesion between the adhesive layer and the adherend can be suppressed.

[0062] Considering workability and uniformity during application, active energy ray-curable adhesives preferably have low viscosity, and therefore, it is preferable that the acrylic oligomer obtained by polymerizing a (meth)acrylic monomer and having no polymerizable group also has low viscosity. As an acrylic oligomer having low viscosity and capable of preventing cure shrinkage of the adhesive layer, one having a weight average molecular weight (Mw) of preferably 15,000 or less, more preferably 10,000 or less, and particularly preferably 5,000 or less is preferred. On the other hand, in order to sufficiently suppress cure shrinkage of the cured product layer (adhesive layer), 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,(Meth)acrylic acid (C1-20) alkyl esters such as 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; further, for example, cycloalkyl (meth)acrylates (for example, cyclohexyl (meth)acrylate, cyclopentyl (meth)acrylate, etc.), aralkyl (meth)acrylates (for example, benzyl (meth)acrylate, etc.), polycyclic (meth)acrylates (for example, 2-isobornyl (meth)acrylate, 2-norbornylmethyl (meth)acrylate, 5-norbornen-2-yl-methyl (meth)acrylate, 3-methyl-2-norbornylmethyl (meth)acrylate, 4-methyl-2-propylpentyl (meth)acrylate, and 4-methyl-2-propylpentyl (meth)acrylate; (meth)acrylate, etc.), hydroxyl group-containing (meth)acrylic acid esters (for example, 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 (for example, glycidyl (meth)acrylate, etc.), halogen-containing (meth)acrylic acid esters (for example, 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, etc., and alkylaminoalkyl (meth)acrylates (for example, dimethylaminoethyl (meth)acrylate, etc.). 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] When a radical polymerizable compound is used, the photopolymerization initiator is appropriately selected depending on the active energy ray. When curing with ultraviolet light or visible light, a photopolymerization initiator that is cleaved by ultraviolet light 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.

[0064] The amount of the photopolymerization initiator is 20% by weight or less, preferably 0.01 to 20% by weight, more preferably 0.05 to 10% by weight, and even more preferably 0.1 to 5% by weight, based on the total amount of the active energy ray-curable adhesive composition being 100% by weight.

[0065] Furthermore, when the curable adhesive for laminated optical films of the present invention is used as a visible light curable type containing a radically polymerizable compound as a curable component, 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.

[0066] The photopolymerization initiator may be a compound represented by the following general formula (2):

[0067] (In the formula, R １ and R ２ -H, -CH ２ CH ３ , -iPr or Cl, R １ and R ２ may be the same or different) is used alone, or it is preferred to use the compound represented by general formula (2) in combination with a photopolymerization initiator highly sensitive to light of 380 nm or longer, which will be described later. When the compound represented by general formula (2) 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 (2), R １ and R ２ Ga-CH ２ CH ３ The composition ratio of the compound represented by general formula (2) in the adhesive composition is preferably 0.1 to 5 parts by weight, more preferably 0.5 to 4 parts by weight, and even more preferably 0.9 to 3 parts by weight, relative to 100 parts by weight of the total amount of the curable components.

[0068] It is also preferable to add a polymerization initiation aid as needed. Examples of the polymerization initiation 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 preferred. When a polymerization initiation aid is used, the amount added is usually 0 to 5 parts by weight, preferably 0 to 4 parts by weight, and most preferably 0 to 3 parts by weight, relative to 100 parts by weight of the total amount of the curable components.

[0069] Furthermore, a known photopolymerization initiator can be used in combination as needed. Because a transparent protective film having UV absorption ability does not transmit light of 380 nm or shorter, it is preferable to use a photopolymerization initiator that is highly sensitive to light of 380 nm or longer. 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.

[0070] In particular, as the photopolymerization initiator, in addition to the photopolymerization initiator of general formula (2), a compound represented by the following general formula (3):

[0071] (In the formula, R ３ , R ４ and R ５ -H, -CH ３ , -CH ２ CH ３ , -iPr or Cl, R ３ , R ４ and R ５As the compound represented by general formula (3), commercially available products such as 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide (trade name: Omnirad 819, manufacturer: IGM Resins B.V.) and 2-methyl-1-(4-methylthiophenyl)-2-morpholinopropan-1-one (trade name: Omnirad 907, manufacturer: IGM Resins B.V.) can be suitably used. In addition, 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-butanone-1 (trade name: Omnirad369, manufacturer: IGM Resins B.V.) and 2-(dimethylamino)-2-[(4-methylphenyl)methyl]-1-[4-(4-morpholinyl)phenyl]-1-butanone (trade name: Omnirad379, manufacturer: IGM Resins B.V.) are preferred due to their high sensitivity.

[0072] In the present invention, among the above photopolymerization initiators, it is preferable to use a hydroxyl group-containing photopolymerization initiator. When the active energy ray-curable adhesive composition contains a hydroxyl group-containing photopolymerization initiator as a polymerization initiator, the solubility in the adhesive layer on the polarizer side where the concentration of component A is high is increased, and the curability of the adhesive layer is improved. Examples of photopolymerization initiators having a hydroxyl group include 2-methyl-2-hydroxypropiophenone (trade name "DAROCUR1173", manufactured by BASF), 1-hydroxycyclohexyl phenyl ketone (trade name "IRGACURE184", manufactured by BASF), 1-[4-(2-hydroxyethoxy)-phenyl]-2-hydroxy-2-methyl-1-propan-1-one (trade name "IRGACURE2959", manufactured by BASF), and 2-hydroxy-1-{4-[4-(2-hydroxy-2-methyl-propionyl)-benzyl]phenyl}-2-methyl-propan-1-one (trade name "IRGACURE127", manufactured by BASF). 1-Hydroxycyclohexyl phenyl ketone is particularly preferred because of its excellent solubility in adhesive layers having a high concentration of component A.

[0073] In the present invention, a cationically polymerizable adhesive composition may be used as the adhesive composition serving as the raw material for the adhesive layer of the laminated optical film. The cationically polymerizable compounds used in the cationically polymerizable adhesive composition are classified into monofunctional cationically polymerizable compounds having one cationically polymerizable functional group in the molecule and polyfunctional cationically polymerizable compounds having two or more cationically polymerizable functional groups in the molecule. Monofunctional cationically polymerizable compounds have relatively low liquid viscosity, and their inclusion in a resin composition can reduce the liquid viscosity of the resin composition. Furthermore, monofunctional cationically polymerizable compounds often have functional groups that impart various functions. Their inclusion in a cationically polymerizable adhesive composition can impart various functions to the cationically polymerizable adhesive composition and / or the cured product of the cationically polymerizable adhesive composition. Polyfunctional cationically polymerizable compounds are preferably included in the cationically polymerizable adhesive composition because they can three-dimensionally crosslink the cured product of the cationically polymerizable adhesive composition. The ratio of the monofunctional cationically polymerizable compound to the polyfunctional cationically polymerizable compound is preferably in the range of 10 to 1,000 parts by weight per 100 parts by weight of the monofunctional 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 adhesive composition of the present invention particularly preferably contains an alicyclic epoxy compound because of its excellent curability and adhesive properties. Examples of the alicyclic epoxy compound 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-6105, Cyracure UVR-6107, Cyracure 30, and R-6110 (all manufactured by Dow Chemical Japan 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]ether, 3-ethyl-3-(2-ethylhexyloxymethyl)oxetane, and phenol novolac oxetane. Commercially available compounds include Aronoxetane OXT-101, Aronoxetane OXT-121, Aronoxetane OXT-211, Aronoxetane OXT-221, and Aronoxetane OXT-212 (all manufactured by Toagosei Co., Ltd.). Compounds having a vinyl ether 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 a vinyl 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.

[0074] The cationically polymerizable 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 by cationic polymerization, a photocationic polymerization initiator is incorporated into the composition. This photocationic polymerization initiator generates cationic species or a Lewis acid upon irradiation with active energy rays such as visible light, ultraviolet light, X-rays, or electron beams, thereby initiating the polymerization reaction of the epoxy group or the oxetanyl group. The photoacid generator described below is preferably used as the photocationic polymerization initiator. Furthermore, when the cationically polymerizable adhesive composition is used as a visible light-curable composition, 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 be used to stimulate the generation of cationic species or acid from the photocationic polymerization initiator. 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% by weight to 5% by weight, and more preferably 0.5% by weight to 3% by weight.

[0075] The laminated optical film according to the present invention is placed on an image display device, for example, via a pressure-sensitive adhesive layer on the surface of the first optical film opposite to the surface on which the second optical film is laminated.

[0076] <Adhesive Layer> The adhesive for forming the adhesive layer is not particularly limited, and can be appropriately selected and used, for example, those having a base polymer such as an acrylic polymer, a silicone polymer, a polyester, a polyurethane, a polyamide, a polyether, a fluorine-based polymer, a rubber-based polymer, etc. In particular, those having excellent optical transparency, exhibiting adhesive properties such as appropriate wettability, cohesion, and adhesiveness, and having excellent weather resistance, heat resistance, etc., such as acrylic adhesives, can be preferably used.

[0077] The exposed surface of the pressure-sensitive adhesive layer is covered with a temporary separator to prevent contamination until the product is put into practical use. This prevents contact with the pressure-sensitive adhesive layer during normal handling. As the separator, apart from the thickness requirements mentioned 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.

[0078] The laminated optical film according to the present invention may include the following optical films in addition to the first optical film and the second optical film.

[0079] In the present invention, from the viewpoint of thinning, the thickness of the polarizer is preferably 10 μm or less, and more preferably 5 μm or less. Examples of such polarizers include those obtained by adsorbing iodine onto 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, followed by uniaxial stretching.

[0080] 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 polyvinyl alcohol-based film may contain boric acid, zinc sulfate, zinc chloride, or the like, or 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 polyvinyl alcohol-based film surface, 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 also be performed in an aqueous solution of boric acid, potassium iodide, or the like, or in a water bath.

[0081] Representative examples of the thin polarizer include the thin polarizers described in Japanese Patent No. 4751486, Japanese Patent No. 4751481, Japanese Patent No. 4815544, Japanese Patent No. 5048120, WO 2014 / 077599, and WO 2014 / 077636, and the like, as well as thin polarizers obtained by the manufacturing methods described therein.

[0082] Among the thin polarizers obtained by manufacturing methods including a stretching step and a dyeing step in a laminated state, those obtained by a manufacturing method including a stretching step 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 a manufacturing method 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 a manufacturing method including a stretching step and a dyeing step of a polyvinyl alcohol-based resin (hereinafter also referred to as PVA-based resin) layer and a stretching resin substrate in a laminated state. 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.

[0083] <Resin Protective Film> The laminated optical film according to the present invention may include a transparent protective film as another optical film. Examples of materials used for the transparent protective film include thermoplastic resins that are excellent in transparency, mechanical strength, thermal stability, moisture barrier properties, and isotropy. Specific examples of such thermoplastic resins include cellulose resins such as triacetyl cellulose, polyester resins, polyethersulfone resins, polysulfone resins, polycarbonate resins, polyamide resins, polyimide resins, polyolefin resins, (meth)acrylic resins, cyclic polyolefin resins (norbornene-based resins), polyarylate resins, polystyrene resins, polyvinyl alcohol resins, and mixtures thereof. The transparent protective film may contain one or more suitable additives. Examples of additives include ultraviolet absorbers, antioxidants, lubricants, plasticizers, release agents, coloring 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 and other properties of the thermoplastic resin may not be fully exhibited.

[0084] The material for forming the transparent protective film is preferably one that is excellent in transparency, mechanical strength, thermal stability, moisture blocking property, 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, and 120g / m ２ / 24 hours or less is even more preferable.

[0085] The transparent protective film may be provided with a functional layer such as a hard coat layer, an anti-reflection layer, an anti-sticking layer, a diffusion layer, an anti-glare layer, etc. The functional layer such as the hard coat layer, the anti-reflection layer, the anti-sticking layer, the diffusion layer, or the anti-glare layer may be provided on the transparent protective film itself, or may be provided separately from the transparent protective film.

[0086] 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 workability such as strength and handleability, thinness, etc.

[0087] 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, wherein the first optical film is a resin film having a breaking strength of 70 or less, and the adhesive layer is formed of a cured layer of an adhesive composition containing an oligomer having a molecular weight of 700 or more, the method comprising: a coating step of applying the adhesive composition to at least one of the first optical film and the second optical film; a laminating step of laminating the first optical film and the second optical film; 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 side or the second optical film side with active energy rays to cure at least the adhesive composition. Each step will be described below.

[0088] (Coating Step) The method for applying the adhesive composition to at least one of the first optical film and the second optical film is appropriately selected depending on the viscosity of the composition and the desired thickness, and examples thereof 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. The viscosity of the adhesive composition is preferably 0.1 to 200 mPa·s, more preferably 1 to 100 mPa·s, and most preferably 5 to 50 mPa·s. A high viscosity of the composition is undesirable because it results in poor surface smoothness after application and poor appearance. For this reason, each composition can be heated or cooled to adjust the viscosity to a preferred range before application.

[0089] (Laminating Step) The first optical film and the second optical film are laminated together. When laminating the first optical film and the second optical film via the adhesive composition, they are laminated together using a roll laminator or the like.

[0090] (Bonding Step) The first optical film and the second optical film are bonded together via an adhesive layer formed by curing at least the adhesive composition by irradiating the first optical film surface side or the second optical film surface side with active energy rays. The irradiation direction of the active energy rays (electron beams, ultraviolet rays, visible light, etc.) can be any appropriate direction.

[0091] When irradiating with electron beams, any suitable irradiation conditions can be adopted as long as they are sufficient to at least cure the adhesive composition. 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 beam may not reach the adhesive, resulting in insufficient curing. If the acceleration voltage is greater than 300 kV, the penetration force through the sample may be too strong, potentially damaging the first optical film and the second optical film. The irradiation dose is 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 greater than 100 kGy, the first optical film and the second optical film may be damaged, resulting in a decrease in mechanical strength and yellowing, making it impossible to obtain the desired optical properties.

[0092] Electron beam irradiation is usually performed in an inert gas atmosphere, but may be performed in the atmosphere or with a small amount of oxygen introduced, if necessary. Depending on the materials of the first and second optical films, by appropriately introducing oxygen, oxygen inhibition is intentionally caused on the first and second optical film surfaces that are first hit by the electron beam, thereby preventing damage to the first and second optical films and allowing the electron beam to be efficiently irradiated only on the adhesive.

[0093] When producing the laminated optical film according to 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 using ultraviolet light or visible light, if a first optical film or a second optical film that has been given ultraviolet absorption ability, such as an ultraviolet-opaque transparent protective film, is used, light with a wavelength shorter than approximately 380 nm is absorbed, and therefore light with a wavelength shorter than 380 nm does not reach the adhesive composition and does not contribute to the polymerization reaction. Furthermore, light with a wavelength shorter than 380 nm absorbed by the first optical film or the second optical film is converted into heat, causing the first optical film or the second optical film itself to generate heat, which can cause defects such as curling and wrinkling in the laminated optical film. Therefore, when ultraviolet rays and visible light are 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 according to the present invention, the active energy ray is preferably a gallium-encapsulated metal halide lamp or an LED light source that emits light in the wavelength range of 380 to 440 nm. Alternatively, light sources containing 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 rays 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.

[0094] 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, 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 or 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 will not cure sufficiently, and the desired adhesiveness may not be obtained.

[0095] (Laminated Optical Film) The laminated optical film according to the present invention can be preferably used for forming various image display 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 an optical film, and components such as an optional lighting system, and incorporating a drive circuit, but in the present invention, there are no particular limitations except for the use of the laminated optical film according to the present invention, and the method can be carried out in a conventional manner. Regarding the liquid crystal cell, any type, such as a TN type, an STN type, or a π type, can be used.

[0096] 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 according to 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.

[0097] Examples of the present invention will be described below, but the embodiments of the present invention are not limited to these.

[0098] <First Optical Film> (Synthesis of Fumarate Ester-Based Resin) 48 g of hydroxypropyl methylcellulose (manufactured by Shin-Etsu Chemical Co., Ltd., trade name: Metrose 60SH-50), 15,601 g of distilled water, 8,161 g of diisopropyl fumarate, 240 g of 3-ethyl-3-oxetanylmethyl acrylate, and 45 g of polymerization initiator t-butyl peroxypivalate were placed in a 30 L autoclave equipped with a stirrer, a cooling tube, a nitrogen inlet tube, and a thermometer. Nitrogen bubbling was performed for 1 hour, and then the mixture was stirred at 200 rpm while maintaining the temperature at 49°C for 24 hours to carry out radical suspension polymerization. The mixture was then cooled to room temperature, and the suspension containing the produced polymer particles was centrifuged. The resulting polymer particles were washed twice with distilled water and twice with methanol, and then dried under reduced pressure at 80°C (yield: 80%).

[0099] The resulting fumarate ester resin was dissolved in a toluene-methyl ethyl ketone mixed solution (toluene / methyl ethyl ketone 50% by weight / 50% by weight) to prepare a 20% solution. 5 parts by weight of tributyl trimellitate was added as a plasticizer to 100 parts by weight of the fumarate ester resin. The solution was then cast onto a support substrate (PET film) in a solution casting apparatus using a T-die method and dried at 80°C and 130°C for 4 minutes each to obtain a laminate film with a width of 250 mm and a thickness of 93 μm. The resulting laminate film was uniaxially stretched in the conveying direction at a temperature of 150°C and a stretch ratio of 1.04x (longitudinal stretching process) using a roll stretcher to produce a laminate film in which a first optical film (retardation film) was laminated on a support substrate (PET film). The resulting first optical film had a thickness of 18 μm and was a positive biaxial plate (nz>nx>ny) with a fast axis in the conveying direction.

[0100] The fumarate ester-based resin film used as the first optical film (retardation film) produced above had a breaking strength of 59.1 MPa in the MD direction (the direction in which the film was formed) and 55.0 MPa in the TD direction (the direction perpendicular to the MD direction). The breaking strength of the film was measured in accordance with JIS-K-7161 using a sample cut to a width of 10 mm.

[0101] The HSP values ​​of the fumarate ester-based resin film calculated by the method for calculating the HSP value of an optical film described below were (δd 17.4, δp 4.5, δh 5.1).

[0102] <Second Optical Film> A cyclic olefin resin (ZEONOR 1420R manufactured by ZEON Corporation) was melt-mixed in a twin-screw melt extruder to form a composition, which was then extruded into a film using a single-screw extruder equipped with a T-die to obtain a cyclic olefin resin film having a thickness of 30 μm.

[0103] The obtained film was uniaxially stretched in the width direction with fixed ends using a tenter stretching machine at 145°C so that the film width became 4.3 times the original film width (transverse stretching step), thereby producing a second optical film (retardation film). The produced second optical film had a thickness of 7 µm and was a negative biaxial plate (nx>ny>nz) having a fast axis in the transport direction.

[0104] The cyclic olefin resin film used as the second optical film (retardation film) produced above had a breaking strength of 157.8 MPa in the MD direction (film forming direction) and 342.4 MPa in the TD direction (direction perpendicular to the MD direction).

[0105] <Active energy rays> Visible light (gallium-filled metal halide lamp) was used as the active energy rays. Irradiation device: Light HAMMER10 Mark III manufactured by Excelitas Technologies Corp. Bulb: V bulb Peak irradiance: 1600 mW / cm ２ , cumulative irradiation dose 1000 mJ / cm ２ The illuminance of visible light was measured using a Sola-Check system manufactured by Solatell.

[0106] Examples 1 to 27 and Comparative Examples 1 to 6: A laminate film in which a first optical film (retardation film) was laminated on a support substrate (PET film) was coated with an adhesive composition prepared in the amounts listed in Tables 1 to 5 on both sides of the first optical film and the second optical film using an MCD coater (manufactured by Fuji Machine Co., Ltd.) (cell shape: honeycomb, gravure roll line count: 700 rolls / inch, rotation speed: 140% vs. line speed) so that the final adhesive layer thickness was 1 μm. The adhesive compositions were then bonded using a rolling mill. The amounts listed in Tables 1 to 5 are expressed in mass % relative to the total amount of the composition excluding the initiator and sensitizer, taken as 100 mass %. The adhesive composition was then cured by irradiating the laminate film with visible light from the support substrate (PET film) side using an active energy ray irradiation device. The support substrate (PET film) was then peeled off from the first optical film (retardation film) of the laminate film to obtain a laminate optical film.

[0107] The materials constituting the adhesive composition are as follows. The method for calculating the average HSP value of the radically polymerizable compounds (excluding oligomers) contained in the adhesive composition will be described later. (Polymerizable Oligomers) Polymerizable Oligomer 1: urethane (meth)acrylate having an ether skeleton in the molecule (molecular weight 19,000, viscosity 9,000 Pa·s (25°C), number of polymerizable groups 2, trade name "PMH-401B", manufactured by Negami Chemical Industrial Co., Ltd.) Polymerizable Oligomer 2: urethane (meth)acrylate having an ether skeleton in the molecule (molecular weight 7,000, number of polymerizable groups 2, trade name "EBECRYL4491", manufactured by Daicel-Allnex Corporation) Polymerizable Oligomer 3: urethane (meth)acrylate having an ether skeleton in the molecule (molecular weight 12,000, number of polymerizable groups 2, trade name "EBECRYL8411", manufactured by Daicel-Allnex Corporation) Polymerizable oligomer 4: urethane (meth)acrylate having an ether skeleton in the molecule (molecular weight 50,000, viscosity 200,000 Pa·s (25°C), number of polymerizable groups 2, trade name "PMH-101B", manufactured by Negami Chemical Industrial Co., Ltd.) Polymerizable oligomer 5: urethane (meth)acrylate having an ether skeleton in the molecule (molecular weight 27,000, viscosity 70,000 Pa·s (25°C), number of polymerizable groups 2, trade name "UN6207", manufactured by Negami Chemical Industrial Co., Ltd.) Polymerizable oligomer 6: urethane (meth)acrylate having an ether skeleton in the molecule (molecular weight 10,000, viscosity 15,000 Pa·s (25°C), number of polymerizable groups 2, trade name "UF-C052", manufactured by Kyoeisha Chemical Co., Ltd.) Polymerizable oligomer 7: urethane (meth)acrylate having an ether skeleton in the molecule (molecular weight 22,000, viscosity 100,000 Pa·s (25°C), number of polymerizable groups 2, trade name "UF-A01P", manufactured by Kyoeisha Chemical Co., Ltd.) Polymerizable oligomer 8: polybutadiene-terminated diacrylate (molecular weight 10,000, viscosity 4,000-8,000 Pa·s (25°C), number of polymerizable groups 2, trade name "BAC-45", manufactured by Osaka Organic Chemical Industry Ltd.) Polymerizable oligomer 9: polyethylene glycol dimethacrylate (molecular weight 771, number of polymerizable groups 2, trade name "PDE-600", manufactured by NOF Corporation) Polymerizable oligomer 10: dimethacrylate having methacryloyl groups at both ends of polyethylene glycol having a molecular weight of 6,000 to 9,000, number of polymerizable groups 2, trade name "PDE-6000", manufactured by NOF Corporation)Polymerizable oligomer 11: acrylic acrylate (molecular weight 80,000, viscosity 2,000,000 Pa·s (20°C), 50,000 Pa·s (80°C), number of polymerizable groups 2 or more, trade name "RA-341", manufactured by Negami Chemical Industrial Co., Ltd.) Polymerizable oligomer 12: methoxypolyethylene glycol methacrylate (molecular weight 4,000, number of polymerizable groups 1, trade name "PME-4000", manufactured by NOF Corporation)

[0108] (Oligomers not having polymerizable groups) Non-polymerizable oligomer 1: acrylic polymer (molecular weight 1700, viscosity 6000 Pa·s (25°C), number of polymerizable groups 0, product name "UP1190", manufactured by Toagosei Co., Ltd.)

[0109] (Polymerizable Monomer) Polymerizable Monomer 1: Urethane acrylate (molecular weight 215, viscosity 15 to 35 Pa·s (25°C), number of polymerizable groups 1, trade name "KRM9276", manufactured by Daicel Allnex Co., Ltd.)

[0110] (Monofunctional radical polymerizable compounds) 4-vinylphenylboronic acid (compound represented by general formula (1)): (manufactured by Junsei Chemical Co., Ltd.), HSP value (δd 19.6, δp 6.9, δh 22.7) 4-hydroxybutyl acrylate (polymerizable compound having a hydroxyl group): (trade name "4HBA", manufactured by Mitsubishi Chemical Corporation), HSP value (δd 16.7, δp 6.6, δh 10.8) Phenoxyethyl (meth)acrylate: (trade name "Viscoat #192HP", manufactured by Osaka Organic Chemical Industry Ltd.), HSP value (δd 17.8, δp 5.0, δh 6.0) 4-tert-butylcyclohexyl acrylate: (trade name "TBCHA", manufactured by KJ Chemicals), HSP value (δd 16.2, δp 2.4, δh 3.2) Lauryl acrylate: (trade name "LA", manufactured by Osaka Organic Chemical Industry Co., Ltd.), HSP value (δd 16.0, δp 2.4, δh 3.2) Phenoxydiethylene glycol acrylate: (trade name "Light Acrylate P2H-A", manufactured by Kyoeisha Chemical Co., Ltd.), HSP value (δd 17.5, δp 4.9, δh 6.2)

[0111] (Polyfunctional radical polymerizable compounds) Polyethylene glycol diacrylate: (a diacrylate having acryloyl groups at both ends of polyethylene glycol having a molecular weight of 400, trade name "Light Acrylate 9EG-A", manufactured by Kyoeisha Chemical Co., Ltd.), HSP value (δd 16.6, δp 5.2, δh 6.8) Dimethylol-tricyclodecane diacrylate: (trade name "Light Acrylate DCP-A", manufactured by Kyoeisha Chemical Co., Ltd.), HSP value (δd 17.1, δp 4.0, δh 4.1) Tripropylene glycol diacrylate: (trade name "Aronix M-220", manufactured by Toagosei Co., Ltd.), HSP value (δd 16.3, δp 3.6, δh 5.3) 1,9-nonanediol diacrylate: (trade name "Light Acrylate 1,9ND-A", manufactured by Kyoeisha Chemical Co., Ltd.), HSP value (δd 16.2, δp 3.3, δh 4.2)

[0112] (Initiator, Sensitizer) 2-methyl-4'-(methylthio)-2-morpholinopropiophenone: (trade name "Omnirad 907", manufactured by IGM Resins B.V.) 2,4-diethylthioxanthone: (trade name "DETX-S", manufactured by Nippon Kayaku Co., Ltd.)

[0113] <Method for Calculating Average HSP Value of Radically Polymerizable Compounds (excluding Oligomers) Contained in Adhesive Composition> The average HSP value of the radically polymerizable compounds (excluding oligomers) contained in the adhesive composition was determined by calculating the Hansen solubility parameter (HSP) for each radically polymerizable compound using the Y-MB method of Hansen Solubility Parameter in Practice (HSPiP), and then averaging the values ​​according to the molar ratio of each radically polymerizable compound in the composition.

[0114] <Method for Calculating the HSP Value of an Optical Film> The optical film was immersed for 24 hours in nine solvents with different solubilities: acetone, ethyl acetate, trichlorobenzene, propylene carbonate, γ-butyrolactone, methyl ethyl ketone, diacetone alcohol, hexane, methanol, and a mixture thereof. The state of the optical film after immersion for 24 hours was classified into three stages: (1) dissolved, (2) swollen, and (3) insoluble. Based on the solubility information in each solvent obtained in this way, the Hansen Solubility Parameter (HSP) was calculated using Hansen Solubility Parameter in Practice (HSPiP) version 5.4.04 (http: / / www.hansen-solubility.com / index.php).

[0115] <Method of Calculating HSP Distance> When the dispersion term of the Hansen solubility parameter of the optical film is σd, the polar term is σp, and the hydrogen bond term is σh, and the dispersion term of the Hansen solubility parameter of the radical polymerizable compound (excluding oligomers) contained in the adhesive composition is σAd, the polar term is σAp, and the hydrogen bond term is σAh, the HSP distance can be calculated by the following formula: Ra-1=[4×(σd-σAd)] ２ +2×(σp−σAp) ２ +2×(σh−σAh) ２ ] １／２ was defined as the "HSP distance between the HSP of the optical film and the HSP of the adhesive composition" (= Ra-1). Calculation was performed using the Hansen solubility parameters of the optical film and adhesive composition calculated by the above-mentioned method.

[0116] <Method for measuring glass transition temperature of adhesive layer> The glass transition temperature (Tg) was determined from the peak top temperature of tan δ obtained from the dynamic viscoelasticity measurement results obtained under the following conditions using a dynamic viscoelasticity measuring device (manufactured by TA Instruments, trade name "RSA-G2"): (load mode): tension (heating rate): 5°C / min (frequency): 1 Hz (initial strain): 0.1%

[0117] (Method for measuring peel strength (peel force)) The obtained laminated optical film was cut into a size of 200 mm × 15 mm, and the laminated optical film was attached to a glass plate. Then, an incision was made between the first optical film and the second optical film with a cutter knife, and the first optical film and the second optical film were peeled in a 90-degree direction at a peel speed of 5000 mm / min using an angle-free type adhesive / film peeling analyzer "VPA-2" (manufactured by Kyowa Interface Science Co., Ltd.), and the peel strength (N / 15 mm) was measured.

[0118] (Method for Evaluating Peeling Morphology) The peeling morphology during the measurement of the peel strength was evaluated by the following method. The infrared absorption spectrum of the peeled surface after peeling was measured by the ATR method. If both peeled surfaces were adhesive layers (including a compatible layer between the first optical film and the adhesive layer), this indicated "cohesive failure of the adhesive layer (including a compatible layer between the first optical film and the adhesive layer)," which means that cohesive failure of the first optical film was prevented and therefore was good. In Tables 1 to 5, cases of "cohesive failure of the adhesive layer (including a compatible layer between the first optical film and the adhesive layer)" are indicated by "O." On the other hand, cases where both peeled surfaces were first optical films indicate that "cohesive failure of the first optical film" has occurred and therefore is not preferable. In Tables 1 to 5, "cohesive failure of the first optical film" is indicated by "X."

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Claims

1. A laminated optical film in which at least a first optical film and a second optical film are laminated via an adhesive layer, wherein the first optical film is a resin film having a breaking strength of 70 or less, and the adhesive layer is formed from a cured layer of an adhesive composition containing an oligomer having a molecular weight of 700 or more.

2. The laminated optical film according to claim 1 or 2, wherein the oligomer is a polymerizable oligomer having a polymerizable group.

3. The laminated optical film according to any one of claims 1 to 3, wherein the oligomer is a urethane (meth)acrylate.

4. The laminated optical film according to claim 3, wherein the urethane (meth)acrylate has an ether skeleton in the molecule.

5. The laminated optical film according to any one of claims 1 to 4, wherein the oligomer does not have an aromatic ring or an alicyclic skeleton in the molecule.

6. The laminated optical film according to any one of claims 1 to 5, wherein the adhesive layer has a glass transition temperature of 35°C or lower.

7. The laminated optical film according to any one of claims 1 to 6, wherein the adhesive composition further contains at least one radically polymerizable compound selected from the group consisting of monofunctional radically polymerizable compounds and polyfunctional radically polymerizable compounds.

8. The laminated optical film according to claim 7, wherein the HSP value distance between the average HSP value of the radical polymerizable compounds (excluding the oligomer) contained in the adhesive composition and the HSP value of the first optical film is 3.5 or less.

9. A laminated optical film according to claim 7 or 8, wherein the content of the polyfunctional radical polymerizable compound is 10 parts by mass or less when the total amount of the radical polymerizable compounds in the adhesive composition is 100 parts by mass.

10. The adhesive composition further comprises a compound represented by the following general formula (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 aliphatic hydrocarbon group, an aryl group, or a heterocyclic group which may have a substituent.

11. The laminated optical film according to any one of claims 1 to 10, wherein the adhesive composition further contains a monofunctional radically polymerizable compound having a hydroxyl group.

12. The laminated optical film according to any one of claims 1 to 11, wherein the first optical film is a retardation film.

13. The laminated optical film according to any one of claims 1 to 12, wherein the second optical film is a retardation film.

14. An image display device comprising at least one laminated optical film according to any one of claims 1 to 13.

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