Stacked optical films and image display devices

Abstract

To provide a laminated optical film that exhibits excellent peel strength between the optical film and the adhesive layer, even when the optical film has low breaking strength and is brittle. [Solution] A laminated optical film comprising at least a first optical film and a second optical film laminated with an adhesive layer in between, wherein both the first optical film and the second optical film are resin films having a breaking strength of 70 or less, the adhesive layer is formed of a cured layer of an adhesive composition containing a radical polymerizable compound, the elongation when measuring the tensile modulus is 3 mm or more and 50 mm or less, and the respective HSP value distances between the average HSP value of the radical polymerizable compound and the HSP values ​​of the first optical film and the second optical film are both 3.5 or less.

Description

[Technical Field]

[0001] The present invention relates to a laminated optical film in which at least a first optical film and a second optical film are laminated with an adhesive layer in between. This laminated optical film can form image display devices such as mobile phones, car navigation systems, personal computer monitors, and televisions. [Background technology]

[0002] Image display devices such as mobile phones, car navigation systems, computer monitors, and televisions are equipped with laminated optical films in which multiple optical films are laminated with adhesive or tack layers in between. Transparent resin films such as phase difference films, polarizers, and transparent protective films are used as optical films.

[0003] In recent years, there has been a growing demand for thinner image display devices. For example, Patent Document 1 below describes a liquid crystal display device that is significantly thinner than conventional devices and uses liquid crystal cells such as IPS type liquid crystal cells. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2015-111236 [Overview of the Initiative] [Problems that the invention aims to solve]

[0005] The technology described in Patent Document 1 above makes it possible to reduce oblique light leakage in black displays and improve contrast. However, 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. Although the technology described in Patent Document 1 above aims to make image display devices thinner, it has not sufficiently considered how to improve the peel strength from the adhesive layer and enhance product durability when using certain optical films that have low breaking strength and are brittle.

[0006] This invention was developed in view of the above circumstances, and aims to provide a laminated optical film that exhibits excellent peel strength between the optical film and the adhesive layer, even when the optical film has low breaking strength and is brittle. [Means for solving the problem]

[0007] The above 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 with an adhesive layer in between, wherein both the first optical film and the second optical film are resin films having a breaking strength of 70 or less, the adhesive layer is formed of a cured layer of an adhesive composition containing a radical polymerizable compound, the elongation when measuring the tensile modulus is 3 mm or more and 50 mm or less, and the respective HSP value distances between the average HSP value of the radical polymerizable compound and the HSP values ​​of the first optical film and the second optical film are both 3.5 or less.

[0008] In the above-mentioned laminated optical film (1), the adhesive layer is preferably a laminated optical film (2) having a glass transition temperature of 35°C or lower.

[0009] In the above-mentioned laminated optical film (1) or (2), a laminated optical film (3) is preferred in which the adhesive composition further contains a polymerizable oligomer having polymerizable groups.

[0010] In the laminated optical film (3) described above, a laminated optical film (4) in which the polymerizable oligomer is urethane (meth) acrylate is preferable.

[0011] In the laminated optical film (4) described above, a laminated optical film (5) in which the urethane (meth) acrylate has an ether skeleton in the molecule is preferable.

[0012] In the laminated optical film (3) described above, a laminated optical film (6) in which the polymerizable oligomer has no aromatic ring or alicyclic skeleton in the molecule is preferable.

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

[0014] In the laminated optical film (7) described above, a laminated optical film (8) 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 compound in the adhesive composition is 100 parts by mass is preferable.

[0015] In any one of the laminated optical films (1) to (8) described above, the adhesive composition further has the following general formula (1):

Chemical formula

[0016] In any of the above laminated optical films (1) to (9), a laminated optical film (10) is preferred in which the adhesive composition further contains a monofunctional radical polymerizable compound having a hydroxyl group.

[0017] In any of the above laminated optical films (1) to (10), the adhesive layer has a tensile modulus of 1 × 10 3 Pa or more and 1 x 10 8 A laminated optical film (11) is preferred, which has a Pa of less than or equal to 3 mm and an elongation of 3 mm or more and 50 mm or less when measuring the tensile modulus.

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

[0019] In any of the above laminated optical films (1) to (12), a laminated optical film (13) in which the second optical film is a phase difference film is preferred.

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

[0021] The laminated optical film according to the present invention comprises at least a first optical film (resin film) and a second optical film (resin film), both having a tensile strength of 70 or less. Here, the first optical film and the second optical film, which have a low tensile strength of 70 or less, are manufactured on a substrate such as PET, and are laminated with the second optical film or the first optical film, or even other optical films, 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 and / or the second optical film may undergo cohesive failure, which could result in the first optical film and / or the second optical film being unable to perform or in the product being defective.

[0022] On the other hand, the laminated optical film according to the present invention has an adhesive layer formed from a cured product layer of an adhesive composition containing a radical polymerizable compound, and is designed so that the distance between the average HSP value of the radical polymerizable compound and the HSP values ​​of the first optical film and the second optical film is 3.5 or less in both cases. As a result, it exhibits excellent peel strength between the first optical film and the adhesive layer, and also excellent peel strength between the second optical film and the adhesive layer. The reason for obtaining such effects is not clear, but the following reasons can be presumed.

[0023] When the HSP value distance between the average HSP value of the radical polymerizable compounds constituting the adhesive composition and the HSP value of the first optical film is close to 3.5 or less, and the HSP value distance between the average HSP value of the radical polymerizable compounds constituting the adhesive composition and the HSP value of the second optical film is also close to 3.5 or less, a compatible layer is likely to form at the interface between the first optical film and the adhesive layer, and a compatible layer is also likely to form at the interface between the second optical film and the adhesive layer. Here, when a compatible layer is formed on both sides of the adhesive layer interposed between the first optical film and the second optical film to bond them together, the stress relaxation properties and toughness of the adhesive layer are increased, and the peel strength between the adhesive layer and the first optical film, and between the adhesive layer and the second optical film, are increased. As a result, when peeling a substrate such as PET from the first optical film, or when peeling a substrate such as PET from the second optical film, stress concentration is less likely to occur near the interface between the adhesive layer of the first optical film, which is a weak layer, and also near the interface between the adhesive layer of the second optical film, which is a weak layer. Consequently, it is believed that defects such as cohesive failure of the first optical film and cohesive failure of the second optical film can be prevented.

[0024] Furthermore, when the pre-curing viscosity of the adhesive composition, which is the raw material for the adhesive layer in the laminated optical film according to the present invention, is 10 mPa·s or less, the wettability and penetration of the adhesive composition to the first optical film and the second optical film are enhanced. As a result, a compatible layer is more easily formed at the interface between the first optical film and the adhesive layer, and a compatible layer is also more easily formed at the interface between the second optical film and the adhesive layer. Consequently, problems such as cohesive failure of the first optical film and cohesive failure of the second optical film can be prevented more effectively.

[0025] Furthermore, the laminated optical film according to the present invention is laminated via an adhesive layer whose elongation during tensile modulus measurement is 3 mm or more and 50 mm or less. Therefore, even when the first and second optical films have low breaking strength and are brittle, the peel strength between the adhesive layer and the first optical film, and between the adhesive layer and the second optical film, is excellent, and it is possible to prevent problems such as cohesive failure from occurring in the first and second optical films when peeling off a substrate such as PET. The reason why such effects are obtained is not clear, but in the present invention, when the elongation during tensile modulus measurement of the adhesive layer is adjusted to the above range, the adhesive layer becomes tough, which suppresses cohesive failure in the first optical film. Therefore, even when peeling off a substrate such as PET from the first optical film (second optical film), stress concentration is less likely to occur near the interface between the first optical film (second optical film), which is a weak layer, and the adhesive layer, and as a result, it is thought that problems such as cohesive failure of the first optical film (second optical film) can be prevented.

[0026] When the adhesive composition that serves as the raw material for the adhesive layer of the laminated optical film according to the present invention further contains a polymerizable oligomer having polymerizable groups, preferably when the adhesive composition further contains a urethane (meth)acrylate, and more preferably when the adhesive composition further contains a urethane (meth)acrylate having an ether skeleton, the peel strength between the adhesive layer and the first optical film, and between the adhesive layer and the second optical film are particularly excellent. As a result, when peeling a substrate such as PET from the first optical film, or when peeling a substrate such as PET from the second optical film, the occurrence of stress concentration near the interface between the first optical film, which is a fragile layer, and the adhesive layer of the second optical film, which is a fragile layer, can be more effectively suppressed. As a result, the occurrence of defects such as cohesive failure of the first optical film and cohesive failure of the second optical film can be more effectively prevented. The reason why such effects are obtained is not clear, but it is thought that when the adhesive composition that serves as the raw material for the adhesive layer contains the polymerizable oligomer mentioned above, the toughness of the adhesive layer is particularly excellent, and the stress relaxation properties are also improved.

[0027] The laminated optical film according to the present invention has a tensile modulus of 1 × 10⁻⁶ 3 Pa or more and 1 x 10 8When laminated via an adhesive layer with a tensile modulus of Pa or less, even if the first and second optical films have low breaking strength and are brittle, the peel strength between the adhesive layer and the first optical film, and between the adhesive layer and the second optical film, is excellent, and it is possible to prevent problems such as cohesive failure from occurring in the first and second optical films when peeling off a substrate such as PET, as described above. The reason why such an effect is obtained is not clear, but in the present invention, when the adhesive layer is adjusted to a specific tensile modulus, the adhesive layer has stress-relaxing properties and the peel strength to the first and second optical films is high. Therefore, when peeling off a substrate such as PET from the first optical film (second optical film), stress concentration is less likely to occur near the interface between the brittle first optical film (second optical film) and the adhesive layer, and as a result, it is thought that problems such as cohesive failure of the first optical film (second optical film) can be prevented. [Modes for carrying out the invention]

[0028] The present invention relates to a laminated optical film in which at least a first optical film and a second optical film are laminated with an adhesive layer in between. The configurations are described below.

[0029] <First optical film and second optical film> In this invention, resin films with a breaking strength of 70 or less are used as the first optical film and the second optical film. The functions exhibited by the first optical film and the second optical film are not particularly limited, but in this invention, even when the first optical film and the second optical film are phase difference films, they exhibit excellent peel strength from the adhesive layer, and it is preferable that problems such as cohesive failure occur in the phase difference films (first optical film and second optical film) when peeling off a substrate such as PET.

[0030] When the first and second optical films are phase difference films, examples of phase difference films can be provided that have a front-facing phase difference of 10 nm or more and / or a thickness-direction phase difference of 60 nm or more. The front-facing phase difference is typically controlled in the range of 10 to 200 nm, and the thickness-direction phase difference is typically controlled in the range of 60 to 300 nm.

[0031] As for the phase difference film, the following formulas (1) to (3): 0.70 <Re

[0450] / Re

[0550] <0.99···(1) 1.5 × 10 -3 <Δn<6×10 -3 ...(2) 1.13 <NZ<5.00···(3) A reverse wavelength-dispersive phase difference film that satisfies the following equation may also be used: (In the formula, Re

[0450] and Re

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

[0032] Examples of resin films constituting the first optical film and the second optical film include acrylic resins, styrene resins, maleimide resins, and fumarate ester resins. As a result of diligent research by the inventors, it was found that among these, fumarate ester resins have particularly low tensile strength and are brittle. In the present invention, even when the first optical film and the second optical film are phase difference films composed of fumarate ester resins, the peel strength between the first optical film and the second optical film and the adhesive layer is excellent, and it is preferable because it can effectively prevent problems such as cohesive failure from occurring in the first optical film and the second optical film when peeling off a substrate such as PET.

[0033] The adhesive layer of the laminated optical film according to the present invention contains at least one radical polymerizable compound selected from the group consisting of monofunctional radical polymerizable compounds and polyfunctional radical polymerizable compounds, and when the HSP value distance between the average HSP value of the radical polymerizable compound and the HSP value of the first optical film is 3.5 or less, the peel strength between the first optical film and the second optical film and the adhesive layer is particularly excellent. In particular, when the resin films constituting the first optical film and the second optical film are fumarate ester resins, and the adhesive layer contains a radical polymerizable compound that satisfies the above-mentioned relationship of HSP value distance, it is preferable because a compatible layer, in which mutually compatible materials are more effectively formed at the interface between the fumarate ester resin and the adhesive layer, and the aforementioned effect of enhancing the stress relaxation and toughness of the adhesive layer is further exhibited, thereby more effectively improving the peel strength between the first optical film and the second optical film (fumarate ester resin) and the adhesive layer.

[0034] The thickness of the first optical film and the second optical film is not particularly limited, but a lower limit of 1 μm, more preferably 10 μm, can be exemplified, and an upper limit of 100 μm, more preferably 50 μm, can be exemplified.

[0035] <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 is described below. The adhesive layer is formed of a cured layer of an adhesive composition containing a radical polymerizable compound, and is characterized in that the distance between the average HSP value of the radical polymerizable compound and the HSP values ​​of the first optical film and the second optical film is 3.5 or less in both cases. In particular, when the resin films constituting the first optical film and the second optical film are fumarate ester resins, a compatible layer is more effectively formed at the interface between the fumarate ester resin and the adhesive layer, and the aforementioned effect of enhancing the stress relaxation and toughness of the adhesive layer is further exhibited, which is preferable because it more effectively improves the peel strength between the first optical film and the second optical film (fumarate ester resin) and the adhesive layer. In this invention, "average HSP value of radical polymerizable compounds" refers to the average HSP value of monofunctional radical polymerizable compounds and polyfunctional radical polymerizable compounds contained in the adhesive composition. Even if the adhesive composition contains polymerizable oligomers, the HSP value of the polymerizable oligomers is not taken into consideration. The methods for measuring the average HSP value of radical polymerizable compounds (excluding polymerizable oligomers), the HSP values ​​of the first optical film and the second optical film, and the HSP value distance between them will be described later.

[0036] To ensure peel strength between the first and second optical films and the adhesive layer, and to effectively prevent defects such as cohesive failure in the first and second optical films when peeling off a substrate such as PET, the thickness of the adhesive layer is preferably 0.1 to 5 μm, and more preferably 0.3 to 3 μm. Furthermore, the glass transition temperature (Tg) of the adhesive layer is preferably 35°C or lower. The method for measuring the glass transition temperature (Tg) of the adhesive layer will be described later.

[0037] In the laminated optical film according to the present invention, if the adhesive composition used as the raw material for the adhesive layer for laminating the first optical film and the second optical film has a liquid viscosity of 10 mPa·s or less before curing, the wettability and penetration of the adhesive composition to the first optical film and the second optical film are enhanced. As a result, a compatible layer is more easily formed at the interface between the first optical film and the adhesive layer, and a compatible layer is also more easily formed at the interface between the second optical film and the adhesive layer. This is preferable because it can more effectively prevent problems such as cohesive failure of the first optical film and cohesive failure of the second optical film. The method for measuring the liquid viscosity of the adhesive composition will be described later.

[0038] In the laminated optical film according to the present invention, the adhesive composition that serves as the raw material for the adhesive layer used to laminate the first optical film and the second optical film contains a radical polymerizable compound. The radical polymerizable compound exhibits active energy ray curability, such as electron beam curability, ultraviolet curability, and visible light curability. In the present invention, active energy rays with a wavelength range of 10 nm to less than 380 nm are referred to as ultraviolet rays, and active energy rays with a wavelength range of 380 nm to 800 nm are referred to as visible light.

[0039] Radical 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 radical polymerizable compounds or polyfunctional radical polymerizable compounds having two or more polymerizable functional groups. Furthermore, these radical polymerizable compounds can be used individually or in combination of two or more. Among these radical polymerizable compounds, compounds having a (meth)acrylic group are preferred, for example.

[0040] Examples of monofunctional radical polymerizable compounds include (meth)acrylic acid derivatives. Examples of (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, alkylphenoxy polyethylene glycol (meth)acrylate; cyclohexyl (meth)acrylate, 4-tert-butylcyclohexyl acrylate, and cyclopentyl Examples include cycloalkyl(meth)acrylates such as (meth)acrylate; aralkyl(meth)acrylates such as benzyl(meth)acrylate; polycyclic(meth)acrylates such as 2-isobornyl(meth)acrylate, 2-norbornylmethyl(meth)acrylate, 5-norbornen-2-ylmethyl(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-butylcyclohexylacrylate are combined and incorporated into the adhesive composition, it is particularly preferable when the first optical film is a phase difference film and the phase difference film is a fumarate ester resin, as this improves the adhesion of the adhesive layer.

[0041] Other examples of monofunctional radical polymerizable compounds include various (meth)acrylic acid derivatives having a (meth)acryloyloxy group. Specifically, examples include alkyl esters of (meth)acrylic acid (with 1-20 carbon atoms), 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.

[0042] Other examples of monofunctional radical polymerizable compounds include (meth)acrylamide derivatives having a (meth)acrylamide group. Specific examples of (meth)acrylamide derivatives include, for example, 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 heterocyclic (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.

[0043] Other monofunctional radical polymerizable compounds 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, as well as (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, it is preferable to incorporate a monofunctional radical polymerizable compound having a hydroxyl group, particularly a (meth)acrylate having a hydroxyl group, into the adhesive composition used to laminate the first optical film and the second optical film, because this improves the adhesion between the first optical film and the second optical film and the adhesive layer.

[0044] Furthermore, monofunctional radical polymerizable compounds 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-trifluoroethyl ethyl (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, etc. 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; heterocyclic (meth)acrylates such as tetrahydrofurfuryl (meth)acrylate and butyrolactone (meth)acrylate; or hydroxypivalate neopentyl glycol (meth)acrylic acid adducts and p-phenylphenol (meth)acrylate may be used.

[0045] Furthermore, as monofunctional radical polymerizable compounds, carboxyl group-containing monomers such as (meth)acrylic acid, carboxyethyl acrylate, carboxypentyl acrylate, itaconic acid, maleic acid, fumaric acid, crotonic acid, and isocrotonic acid may be used.

[0046] Furthermore, as monofunctional radical polymerizable compounds, for example, lactam-based vinyl monomers such as N-vinylpyrrolidone, N-vinyl-ε-caprolactam, and methylvinylpyrrolidone; and vinyl monomers having nitrogen-containing heterocyclic rings such as vinylpyridine, vinylpiperidone, vinylpyrimidine, vinylpiperazine, vinylpyrazine, vinylpyrrole, vinylimidazole, vinyloxazole, and vinylmorpholine may be used.

[0047] In addition, as the monofunctional radically polymerizable compound, a radically polymerizable compound having an active methylene group may be used. The radically polymerizable compound having an active methylene group is a compound having an active double bond group such as a (meth)acrylic group at the terminal or in the molecule and also having an active methylene group. Examples of the active methylene group include an acetoacetyl group, an alkoxymalonyl group, or a cyanoacetyl group. It is preferable that the active methylene group is an acetoacetyl group. Specific examples of the radically polymerizable compound 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-ethoxymalonyl oxyethyl (meth)acrylate, 2-cyanoacetoxyethyl (meth)acrylate, N-(2-cyanoacetoxyethyl)acrylamide, N-(2-propionylacetoxybutyl)acrylamide, N-(4-acetoacetoxymethylbenzyl)acrylamide, N-(2-acetoacetylaminoethyl)acrylamide, and the like. The radically polymerizable compound having an active methylene group is preferably an acetoacetoxyalkyl (meth)acrylate.

[0048] In the present invention, in the adhesive composition used for laminating the first optical film and the second optical film, the following general formula (1):

Chemical formula

[0049] In the monofunctional radical polymerizable compound represented by general formula (1), the aliphatic hydrocarbon group may be a linear or branched alkyl group having 1 to 20 substituents, a cyclic alkyl group having 3 to 20 substituents, or an alkenyl group having 2 to 20 substituents. The aryl group may be a phenyl group having 6 to 20 substituents, a naphthyl group having 10 to 20 substituents, etc. The heterocyclic group may be a 5-membered or 6-membered ring containing at least one heteroatom and having substituents. These may be linked together to form a ring. In general formula (1), R 1 and R 2 Preferably, the member is a hydrogen atom, a linear or branched alkyl group having 1 to 3 carbon atoms, and most preferably a hydrogen atom.

[0050] In the monofunctional radical polymerizable compound represented by general formula (1), X is a reactive group that can react with the curable components constituting the adhesive layer. Examples include hydroxyl groups, amino groups, aldehyde groups, carboxyl groups, vinyl groups, (meth)acrylic groups, styryl groups, (meth)acrylamide groups, vinyl ether groups, epoxy groups, oxetane groups, α,β-unsaturated carbonyl groups, mercapto groups, halogen groups, and the like. When the curable adhesive composition constituting the adhesive layer is curable by active energy rays, the reactive group X is preferably at least one reactive group selected from the group consisting of vinyl group, (meth)acrylic group, styryl group, (meth)acrylamide group, vinyl ether group, epoxy group, oxetane group, and mercapto group. When the curable adhesive composition constituting the adhesive layer is radical polymerizable, the reactive group X is preferably at least one reactive group selected from the group consisting of (meth)acrylic group, styryl group, and (meth)acrylamide group. When the monofunctional radical polymerizable compound represented by general formula (1) has a (meth)acrylamide group, it is more preferable because it is highly reactive and increases the copolymerization rate with the curable component in the adhesive layer. Furthermore, it is also preferable because the (meth)acrylamide group has high polarity and excellent adhesive properties, which allows the effects of the present invention to be obtained efficiently. When the curable adhesive composition constituting the adhesive layer is cationic polymerizable, the reactive group X preferably has at least one functional group selected from hydroxyl group, amino group, aldehyde, carboxyl group, vinyl ether group, epoxy group, oxetane group, and mercapto group. In particular, the presence of an epoxy group is preferred because it provides excellent adhesion between the resulting adhesive layer and the adherend, and the presence of a vinyl ether group is preferred because it provides excellent curability of the curable adhesive composition.

[0051] Preferred specific examples of monofunctional radical polymerizable compounds represented by general formula (1) include the following compounds (1a) to (1d). Note that R in general formulas (1a) and (1b) 3 This is either a hydrogen atom or a methyl group. [ka]

[0052] Examples of monofunctional radical polymerizable compounds represented by general formula (1) include, in addition to the examples given above, esters of (meth)acrylates and boric acid, such as esters of hydroxyethyl acrylamide and boric acid, methylol acrylamide and boric acid, esters of hydroxyethyl acrylate and boric acid, and esters of hydroxybutyl acrylate and boric acid.

[0053] Examples of polyfunctional radical 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, and Examples include esters of (meth)acrylic acid with polyhydric alcohols such as opentyl 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, as well as 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), CD-536 (manufactured by Sartomer), etc. Additionally, various epoxy (meth)acrylates, urethane (meth)acrylates, polyester (meth)acrylates, and various (meth)acrylate monomers may be used as needed. When the total amount of radical polymerizable compounds in the adhesive composition is 100 parts by mass, it is preferable that the content of the polyfunctional radical polymerizable compound is 10 parts by mass or less.

[0054] In the laminated optical film according to the present invention, if the adhesive composition that serves as the raw material for the adhesive layer for laminating the first optical film and the second optical film contains a polymerizable oligomer having polymerizable groups in addition to a radical polymerizable compound, preferably if the adhesive composition further contains a urethane (meth)acrylate, and more preferably if the adhesive composition further contains a urethane (meth)acrylate having an ether skeleton, then the peel strength between the adhesive layer and the first optical film, and between the adhesive layer and the second optical film are particularly excellent, and when peeling a substrate such as PET from the first optical film, or peeling a substrate such as PET from the second optical film, the occurrence of stress concentration near the interface between the first optical film, which is a fragile layer, and the adhesive layer, and further near the interface between the second optical film, which is a fragile layer, can be more effectively suppressed, and as a result, the occurrence of defects such as cohesive failure of the first optical film and cohesive failure of the second optical film can be more effectively prevented, which is preferable.

[0055] The polymerizable oligomer used in the present invention preferably has a molecular weight of 700 or more, more preferably 1500 or more, and even more preferably 10000 or more. The higher the molecular weight of the polymerizable oligomer used, the better the toughness of the adhesive layer and the better the stress relaxation properties, which is therefore preferable. Examples of polymerizable groups include vinyl groups, (meth)acrylic groups, styryl groups, or (meth)acrylamide groups. In the present invention, (meth)acrylic means acrylic groups and / or methacrylic groups.

[0056] In the present invention, it is preferable to use urethane (meth)acrylate as the polymerizable oligomer, and more preferably to use urethane (meth)acrylate having an ether skeleton. When the adhesive layer is composed of urethane (meth)acrylate, more preferably urethane (meth)acrylate having an ether skeleton, as at least part of the raw materials, the toughness of the adhesive layer is particularly excellent, and stress relaxation is also improved. As a result, even when using fumarate ester resin films, which have the disadvantage of being particularly low in breaking strength and brittle, as the first optical film and the second optical film (phase difference film), it is preferable because it is possible to effectively prevent problems such as cohesive failure from occurring in the first optical film when peeling off a substrate such as PET.

[0057] Examples of urethane (meth)acrylates include those having at least units of polyalkylene glycols such as polyethylene glycol, polypropylene glycol, polybutylene glycol, or polystyrene glycol; polycarbonate or polyalkylene glycol (poly)carbonate; or polyester, along with 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 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 such as the polyalkylene glycol constituting the urethane (meth)acrylate with isocyanates such as diphenylmethane diisocyanate, toluene diisocyanate, isophorone diisocyanate, or hexamethylene diisocyanate.

[0058] In the present invention, when a polymerizable oligomer with a molecular weight of 700 or more and without an aromatic ring or alicyclic skeleton in its molecule is used, it is preferable because the adhesive layer that is ultimately formed has moderate flexibility, resulting in improved stress relaxation and toughness of the adhesive layer.

[0059] In the present invention, it is preferable that the polymerizable oligomer has at least two polymerizable groups. A polymerizable oligomer having at least two polymerizable groups has the effect of improving the stress relaxation and toughness of the final adhesive layer.

[0060] In the present invention, polymerizable oligomers other than urethane (meth)acrylate can also be used, such as polybutadiene-terminated (meth)acrylate, polyethylene glycol (meth)acrylate, polypropylene glycol (meth)acrylate, and (meth)acrylic (meth)acrylate.

[0061] In the present invention, with the aim of increasing the peel strength between the first optical film and the second optical film and the adhesive layer, and effectively preventing problems such as cohesive failure from occurring in the first optical film and the second optical film when peeling off a substrate such as PET, the content of polymerizable oligomers is preferably 1 to 30 parts by mass, and more preferably 5 to 20 parts by mass, when the total amount of polymerizable components such as polymerizable oligomers and polymerizable compounds other than polymerizable oligomers in the adhesive composition is 100 parts by mass.

[0062] In the present invention, the adhesive composition that serves as the raw material for the adhesive layer of the laminated optical film may contain, in addition to radical polymerizable compounds, an acrylic oligomer obtained by polymerizing (meth)acrylic monomers and which does not have polymerizable groups. By including the acrylic oligomer in the adhesive composition, curing shrinkage when the composition is irradiated and cured with active energy rays can be reduced, and interfacial stress between the adhesive layer and adherends such as polarizers and optical films can be reduced. As a result, a decrease in the adhesion between the adhesive layer and adherends can be suppressed.

[0063] For active energy ray curing adhesives, low viscosity is preferable when considering workability and uniformity during coating. Therefore, acrylic oligomers formed by polymerizing (meth)acrylic monomers and not having polymerizable groups are also preferably low viscosity. As acrylic oligomers that are low viscosity and can prevent curing shrinkage of the adhesive layer, those with a weight-average molecular weight (Mw) of 15,000 or less are preferable, those with a weight-average molecular weight (Mw) of 10,000 or less are preferable, and those with a weight-average molecular weight (Mw) of 5,000 or less are particularly preferable. On the other hand, in order to sufficiently suppress curing 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. Examples of (meth)acrylic monomers that constitute acrylic oligomers include, specifically, 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,Alkyl esters of (meth)acrylic acid (C1-C20) 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, N-octadecyl (meth)acrylate, and also, for example, 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)acrylates, 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, 2,2Examples include 2-trifluoroethylethyl (meth)acrylate, tetrafluoropropyl (meth)acrylate, hexafluoropropyl (meth)acrylate, octafluoropentyl (meth)acrylate, heptadecafluorodecyl (meth)acrylate, etc., and alkylaminoalkyl (meth)acrylates (e.g., dimethylaminoethyl (meth)acrylate). These (meth)acrylates can be used alone or in combination of two or more types. Specific examples of acrylic oligomers (E) include "ARUFON" from Toagosei Co., Ltd., "Actflow" from Soken Chemical Co., Ltd., and "JONCRYL" from BASF Japan.

[0064] When using radical polymerizable compounds, the photopolymerization initiator is appropriately selected based on the active energy ray. When curing is performed with ultraviolet or visible light, a photopolymerization initiator that cleaves with ultraviolet or visible light is used. Examples of such photopolymerization initiators include benzophenone compounds such as benzyl, 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 compounds such as methoxyacetophenone, 2,2-dimethoxy-2-phenylacetophenone, 2,2-diethoxyacetophenone, and 2-methyl-1-[4-(methylthio)-phenyl]-2-morpholinopropane-1; benzioin methyl ether, benzioin ethyl ether, benzoin isopropyl ether, and Examples include benzoin ether compounds such as benzoin butyl ether and anisoin methyl ether; aromatic ketal compounds such as benzyldimethyl ketal; 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.

[0065] The amount of the photopolymerization initiator is 20% by weight or less, when the total amount of the active energy ray curable adhesive composition is considered to be 100% by weight. Preferably, the amount of the photopolymerization initiator is 0.01 to 20% by weight, more preferably 0.05 to 10% by weight, and more preferably 0.1 to 5% by weight.

[0066] Furthermore, when the curable adhesive for laminated optical films of the present invention is used as a visible light curable type containing a radical polymerizable compound as a curable component, it is particularly preferable to use a photopolymerization initiator that is highly sensitive to light of 380 nm or higher. Photopolymerization initiators highly sensitive to light of 380 nm or higher will be described later.

[0067] The aforementioned photopolymerization initiator is a compound represented by the following general formula (2);

[0068] [ka] (In the formula, R 1 and R 2 R represents -H, -CH2CH3, -iPr, or Cl. 1 and R 2 It is preferable to use the compound represented by general formula (2) alone (which may be the same or different) or to use it in combination with a photopolymerization initiator that is highly sensitive to light of 380 nm or higher, as described later. When the compound represented by general formula (2) is used, the adhesion is superior to when the photopolymerization initiator that is highly sensitive to light of 380 nm or higher is used alone. Among the compounds represented by general formula (2), R 1 and R 2 Diethylthioxanthone, in which is -CH2CH3, is particularly preferred. 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, based on 100 parts by weight of the total amount of curable components.

[0069] Furthermore, it is preferable to add polymerization initiators as needed. Examples of polymerization initiators 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 using polymerization initiators, 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, per 100 parts by weight of the total amount of curable components.

[0070] Furthermore, known photopolymerization initiators can be used in combination as needed. Since transparent protective films with UV absorption ability do not transmit light below 380 nm, it is preferable to use a photopolymerization initiator that is highly sensitive to light above 380 nm. Specifically, 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, and bis(η5-2,4-cyclopentadien-1-yl)-bis(2,6-difluoro-3-(1H-pyrrole-1-yl)-phenyl)titanium.

[0071] In particular, as a photopolymerization initiator, in addition to the photopolymerization initiator of general formula (2), a compound represented by the following general formula (3);

[0072] [ka] (In the formula, R 3 , R 4 and R 5 R represents -H, -CH3, -CH2CH3, -iPr, or Cl. 3 , R 4 and R5 It is preferable to use compounds that are the same or different. As compounds represented by general formula (3), commercially available products such as 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide (trade name: Omnirad819, manufacturer: IGM Resins BV) and 2-methyl-1-(4-methylthiophenyl)-2-morpholinopropan-1-one (trade name: Omnirad907, manufacturer: IGM Resins BV) can be suitably used. In addition, 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-butanone-1 (trade name: Omnirad369, manufacturer: IGM Resins BV) and 2-(dimethylamino)-2-[(4-methylphenyl)methyl]-1-[4-(4-morpholinyl)phenyl]-1-butanone (trade name: Omnirad379, manufacturer: IGM Resins BV) are preferred due to their high sensitivity.

[0073] In the present invention, it is preferable to use a hydroxyl group-containing photopolymerization initiator among the above-mentioned photopolymerization initiators. 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 with a high concentration of component A on the polarizer side increases, and the curability of the adhesive layer increases. Examples of photopolymerization initiators having a hydroxyl group include 2-methyl-2-hydroxypropiophenone (trade name "DAROCUR1173", manufactured by BASF), 1-hydroxycyclohexylphenyl 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-methylpropionyl)-benzyl]phenyl}-2-methyl-propan-1-one (trade name "IRGACURE127", manufactured by BASF). 1-hydroxycyclohexylphenyl ketone is particularly preferred because of its excellent solubility in adhesive layers with a high concentration of component A.

[0074] In the present invention, a cationic polymerizable adhesive composition may be used as the adhesive composition that serves as the raw material for the adhesive layer of the laminated optical film. Cationic polymerizable compounds used in cationic polymerizable adhesive compositions are classified into monofunctional cationic polymerizable compounds having one cationic polymerizable functional group in the molecule, and polyfunctional cationic polymerizable compounds having two or more cationic polymerizable functional groups in the molecule. Monofunctional cationic polymerizable compounds have relatively low liquid viscosity, so including them in a resin composition can reduce the liquid viscosity of the resin composition. Furthermore, monofunctional cationic polymerizable compounds often have functional groups that exhibit various functions, and including them in a cationic polymerizable adhesive composition can exhibit various functions in the cationic polymerizable adhesive composition and / or the cured product of the cationic polymerizable adhesive composition. Polyfunctional cationic polymerizable compounds are preferable to include in a cationic polymerizable adhesive composition because they can cause three-dimensional crosslinking of the cured product of the cationic polymerizable adhesive composition. The ratio of monofunctional cationic polymerizable compounds to polyfunctional cationic polymerizable compounds is preferably in the range of 10 to 1000 parts by weight of polyfunctional cationic polymerizable compounds per 100 parts by weight of monofunctional cationic polymerizable compounds. Examples of cationic polymerizable functional groups include epoxy groups, oxetanyl groups, and vinyl ether groups. Examples of compounds having epoxy groups include aliphatic epoxy compounds, alicyclic epoxy compounds, and aromatic epoxy compounds. The cationic polymerizable adhesive composition of the present invention is particularly preferably composed of an alicyclic epoxy compound because it exhibits excellent curability and adhesion. Examples of alicyclic epoxy compounds include 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate, caprolactone-modified, trimethylcaprolactone-modified, and valerolactone-modified 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate, and specifically, Celoxide 2021, Celoxide 2021A, Celoxide 2021P, Celoxide 2081, Celoxide 2083, Celoxide 2085 (all manufactured by Daicel Chemical Industries, Ltd.), and Cyracure UVR-6105, Cyracure UVR-6107, Cyracure 30, R-6110 (all manufactured by Dow Chemical Japan Ltd.).Compounds containing an oxetanyl group are preferable to include in cationic polymerizable adhesive compositions because they improve the curability of the composition and reduce its liquid viscosity. Examples of compounds containing 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. Aronoxetane OXT-101, Aronoxetane OXT-121, Aronoxetane OXT-211, Aronoxetane OXT-221, and Aronoxetane OXT-212 (all manufactured by Toagosei Co., Ltd.) are commercially available. Compounds having vinyl ether groups are preferable to include because they have the effect of improving the curability of cationic polymerizable adhesive compositions and reducing the liquid viscosity of the compositions. Examples of compounds having vinyl ether groups 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-type tetravinyl ether.

[0075] Cationic polymerizable adhesive compositions contain at least one compound selected from the epoxy group-containing compounds, oxetanyl group-containing compounds, and vinyl ether group-containing compounds described above as curable components, all of which cure by cationic polymerization; therefore, a photocationic polymerization initiator is included. 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, and initiates the polymerization reaction of epoxy groups and oxetanyl groups. As the photocationic polymerization initiator, the photoacid generator described later is preferably used. Furthermore, when using a cationic polymerizable adhesive composition that is curable with visible light, it is preferable to use a photocationic polymerization initiator that is particularly sensitive to light of 380 nm or higher. However, since photocationic polymerization initiators are generally compounds that show maximum absorption around 300 nm or shorter wavelengths, by incorporating a photosensitizer that shows maximum absorption in a longer wavelength range, specifically light with wavelengths longer than 380 nm, it is possible to stimulate light of this wavelength range and promote the generation of cationic species or acids from the photocationic polymerization initiator. Examples of photosensitizers include anthracene compounds, pyrene compounds, carbonyl compounds, organosulfur compounds, persulfides, redox compounds, azo and diazo compounds, halogen compounds, and photoreducible dyes. Two or more of these may be used in combination. Anthracene compounds are particularly preferred due to their excellent photosensitizing effect, and specific examples include Anthracure UVS-1331 and Anthracure UVS-1221 (manufactured by Kawasaki Chemical Co., Ltd.). The photosensitizer content is preferably 0.1% to 5% by weight, and more preferably 0.5% to 3% by weight.

[0076] The laminated optical film according to the present invention is, for example, placed on an image display device via an adhesive layer on the side of the first optical film opposite to the side on which the second optical film is laminated.

[0077] <Adhesive layer> The adhesive forming the adhesive layer is not particularly limited, but for example, adhesives based on polymers such as acrylic polymers, silicone polymers, polyesters, polyurethanes, polyamides, polyethers, fluorine-based or rubber-based polymers can be appropriately selected and used. In particular, adhesives that have excellent optical transparency, exhibit appropriate wettability, cohesiveness and adhesion properties, and have excellent weather resistance and heat resistance, such as acrylic adhesives, are preferably used.

[0078] For the exposed surface of the adhesive layer, a separator is temporarily attached and covered to prevent contamination until it is put into practical use. This prevents contact with the adhesive layer under normal handling conditions. As for the separator, except for the thickness conditions mentioned above, suitable thin materials such as plastic film, rubber sheet, paper, cloth, nonwoven fabric, net, foam sheet, metal foil, or laminates thereof can be used, and may be coated with a suitable release agent such as silicone-based, long-chain alkyl-based, fluorine-based, or molybdenum sulfide as needed, in accordance with conventional methods.

[0079] The laminated optical film according to the present invention may also include the optical films shown below, in addition to the first optical film and the second optical film.

[0080] <Polarizer> In the present invention, from the viewpoint of miniaturization, the thickness of the polarizer is preferably 10 μm or less, and more preferably 5 μm or less. Examples of such polarizers include those made by adsorbing iodine onto a hydrophilic polymer film such as a polyvinyl alcohol-based film, a partially formalized polyvinyl alcohol-based film, or a partially saponified ethylene-vinyl acetate copolymer film and then uniaxially stretching it.

[0081] A polarizer made by dyeing a polyvinyl alcohol-based film with iodine and then uniaxially stretching it can be produced, for example, by dyeing the polyvinyl alcohol by immersing it in an aqueous solution of iodine and then stretching it to 3 to 7 times its original length. Boric acid, zinc sulfate, zinc chloride, etc., may be included as needed, or the film may be immersed in an aqueous solution of potassium iodide, etc. 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 removes dirt and anti-blocking agents from the film surface, and also prevents uneven dyeing by swelling the film. Stretching may be performed after dyeing with iodine, while dyeing, or after stretching. Stretching can also be performed in aqueous solutions of boric acid or potassium iodide, or even in a water bath.

[0082] Typical 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 pamphlet, International Publication No. 2014 / 077636 pamphlet, Examples include thin polarizers described in the text or thin polarizers obtained from the manufacturing methods described therein.

[0083] As for the thin polarizers, among manufacturing methods that include a step of stretching in a laminated state and a step of dyeing, those obtained by a manufacturing method that includes a step of stretching in a boric acid aqueous solution, as described in Japanese Patent No. 4751486, Japanese Patent No. 4751481, and Japanese Patent No. 4815544, are preferred because they can be stretched to a high magnification and their polarization performance can be improved. In particular, those obtained by a manufacturing method that includes a step of auxiliary air stretching before stretching in a boric acid aqueous solution, as described in Japanese Patent No. 4751481 and Japanese Patent No. 4815544, are preferred. These thin polarizers can be obtained by a manufacturing method that includes a step of stretching a polyvinyl alcohol-based resin (hereinafter also referred to as PVA-based resin) layer and a stretching resin substrate in a laminated state and a step of dyeing. With this manufacturing method, even if the PVA-based resin layer is thin, it is possible to stretch it without problems such as breakage due to stretching because it is supported by the stretching resin substrate.

[0084] <Resin protective film> The laminated optical film according to the present invention may also include a transparent protective film as another optical film. As the material constituting the transparent protective film, for example, a thermoplastic resin with excellent transparency, mechanical strength, thermal stability, moisture barrier properties, and isotropy can be used. Specific examples of such thermoplastic resins include cellulose resins such as triacetylcellulose, 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, mold 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 high transparency and other properties inherent to the thermoplastic resin may not be fully realized.

[0085] Furthermore, the material used to form the transparent protective film is preferably one that is excellent in terms of transparency, mechanical strength, thermal stability, moisture barrier properties, and isotropy, and is particularly good if it has a moisture permeability of 150 g / m². 2 It is more preferable that the amount is 24 hours or less, and 140 g / m² 2 Products with a shelf life of 24 hours or less are particularly preferred, and 120 g / m² 2 Even better are those with a shelf life of 24 hours or less.

[0086] The transparent protective film may be provided with functional layers such as a hard coat layer, an anti-reflective layer, an anti-sticking layer, a diffusion layer, or an anti-glare layer. These functional layers, such as the hard coat layer, anti-reflective layer, anti-sticking layer, diffusion layer, and anti-glare layer, can be provided on the transparent protective film itself, or they can be provided separately from the transparent protective film.

[0087] The thickness of the transparent protective film can be determined as appropriate, but generally it is about 1 to 500 μm, preferably 1 to 300 μm, and more preferably 5 to 200 μm, considering factors such as strength, workability, and thinness. Furthermore, 10 to 200 μm is preferred, and 20 to 80 μm is preferred.

[0088] The laminated optical film according to the present invention can be manufactured, for example, by the following manufacturing method. A method for manufacturing a laminated optical film in which at least a first optical film and a second optical film are laminated with an adhesive layer in between, The first optical film and the second optical film are resin films with a breaking strength of 70 or less. The adhesive layer is formed of a cured layer of an adhesive composition containing a radical polymerizable compound. The HSP value distance between the average HSP value of the radical polymerizable compound and the HSP values ​​of the first optical film and the second optical film is 3.5 or less in both cases. A coating step of applying the adhesive composition to at least one of the first optical film and the second optical film, A lamination step of bonding the first optical film and the second optical film together, A method for manufacturing a laminated optical film, comprising an bonding step of bonding the first optical film and the second optical film via an adhesive layer formed by irradiating at least the adhesive composition with active energy rays from the first optical film surface side or the second optical film surface side. Each step will be described below.

[0089] (Coating process) A method for coating at least one of the first optical film and the second optical film with the adhesive composition is appropriately selected depending on the viscosity of the composition and the desired thickness. Examples include reverse coaters, gravure coaters (direct, reverse, and offset), bar reverse coaters, roll coaters, die coaters, bar coaters, and rod coaters. 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. If the viscosity of the composition is high, the surface smoothness after coating will be poor, resulting in an undesirable appearance. For this reason, each composition can be heated or cooled to adjust the viscosity to a preferred range before application.

[0090] (Lamination process) The first optical film and the second optical film are laminated together. When laminating the first optical film and the second optical film via an adhesive composition, a roll laminator or the like is used.

[0091] (Adhesion process) The first optical film and the second optical film are bonded together via an adhesive layer formed by irradiating them with active energy rays from either the first optical film surface or the second optical film surface to cure at least the adhesive composition. The irradiation direction of the active energy rays (electron beam, ultraviolet light, visible light, etc.) can be any suitable direction.

[0092] When irradiating with an electron beam, any suitable irradiation conditions can be adopted, as long as they are conditions that can at least cure the adhesive composition. For example, the acceleration voltage for electron beam irradiation is preferably 5kV to 300kV, and more preferably 10kV to 250kV. If the acceleration voltage is less than 5kV, the electron beam may not reach the adhesive, resulting in insufficient curing. If the acceleration voltage exceeds 300kV, the penetrating force through the sample may be too strong, potentially damaging the first and second optical films. The irradiation dose is 5 to 100kGy, more preferably 10 to 75kGy. If the irradiation dose is less than 5kGy, the adhesive will not cure sufficiently. If it exceeds 100kGy, the first and second optical films will be damaged, resulting in a decrease in mechanical strength and yellowing, making it impossible to obtain the desired optical properties.

[0093] Electron beam irradiation is usually performed in an inert gas environment, but if necessary, it can also be performed in air or under conditions with a small amount of oxygen introduced. Depending on the materials of the first and second optical films, by appropriately introducing oxygen, oxygen inhibition can be intentionally caused on the first and second optical film surfaces that are initially hit by the electron beam, thereby preventing damage to the first and second optical films and allowing the electron beam to be efficiently directed only at the adhesive.

[0094] When manufacturing the laminated optical film according to the present invention, it is preferable to use an active energy ray that includes visible light in the wavelength range of 380 nm to 450 nm, and more preferably an active energy ray that has the highest irradiation amount of visible light in the wavelength range of 380 nm to 450 nm. When ultraviolet light and visible light are used, and a first optical film or second optical film with ultraviolet absorption capability, such as an ultraviolet-opaque transparent protective film, is used, light with wavelengths shorter than approximately 380 nm is absorbed, so light with wavelengths shorter than 380 nm does not reach the adhesive composition and does not contribute to its polymerization reaction. Furthermore, light with wavelengths shorter than 380 nm absorbed by the first optical film or second optical film is converted into heat, causing the first optical film or second optical film itself to generate heat, which can cause defects such as curling and wrinkling of the laminated optical film. Therefore, when ultraviolet and visible light are used in the present invention, it is preferable to use a device that does not emit light with a wavelength shorter than 380 nm as the active energy ray generator. More specifically, it is preferable that 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 100:0 to 100:50, and more preferably 100:0 to 100:40. When manufacturing the laminated optical film according to the present invention, gallium-filled metal halide lamps and LED light sources that emit light in the wavelength range of 380 to 440 nm are preferred as active energy rays. 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 bulbs, xenon lamps, halogen lamps, carbon arc lamps, metal halide lamps, fluorescent lamps, tungsten lamps, gallium lamps, excimer lasers, or sunlight can be used, and ultraviolet light with a wavelength shorter than 380 nm can also be blocked using a bandpass filter. To improve the adhesion performance of the adhesive layer between the first optical film and the second optical film while preventing curling of the laminated optical film, it is preferable to use an active energy ray obtained by using a gallium-filled metal halide lamp and passing it through a bandpass filter capable of blocking light with wavelengths shorter than 380 nm, or to use an active energy ray with a wavelength of 405 nm obtained using an LED light source.

[0095] When manufacturing the laminated optical film according to the present invention in 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 low, productivity will be poor, or the damage to the first or second optical film will be too great, making it impossible to produce a laminated optical film that can withstand durability tests. If the line speed is too high, the curing of the adhesive composition will be insufficient, and the desired adhesion may not be obtained.

[0096] (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 displays. The formation of liquid crystal displays can be carried out in accordance with conventional methods. That is, liquid crystal displays are generally formed by assembling components such as liquid crystal cells, polarizing films or optical films, and, if necessary, lighting systems, and incorporating drive circuits. However, the present invention is not particularly limited except for the use of the laminated optical film according to the present invention, and can be carried out in accordance with conventional methods. Any type of liquid crystal cell can be used, such as TN type, STN type, or π type.

[0097] Appropriate liquid crystal display devices can be formed, such as liquid crystal display devices in which optical laminates are arranged on one or both sides of a liquid crystal cell, or in which a backlight or reflector is used in the illumination system. In this case, the optical laminate according to the present invention can be installed on one or both sides of the liquid crystal cell. When optical laminates are provided on both sides, they may be the same or different. Furthermore, when forming a liquid crystal display device, appropriate components such as diffusers, anti-glare layers, anti-reflective films, protective plates, prism arrays, lens array sheets, light diffusers, and backlights can be arranged in appropriate positions in one or more layers. [Examples]

[0098] The following describes some embodiments of the present invention, but the embodiments of the present invention are not limited to these.

[0099] <First Optical Film> (Synthesis of fumarate ester resins) In a 30 L autoclave equipped with a stirrer, condenser, nitrogen inlet tube, and thermometer, 48 g of hydroxypropyl methylcellulose (Shin-Etsu Chemical Co., Ltd., trade name Metroze 60SH-50), 1560 g of distilled water, 8161 g of diisopropyl fumarate, 240 g of 3-ethyl-3-oxetanylmethyl acrylate, and 45 g of t-butyl peroxypivalate as a polymerization initiator were placed. After 1 hour of nitrogen bubbling, radical suspension polymerization was carried out by holding the mixture at 49°C for 24 hours while stirring at 200 rpm. The mixture was then cooled to room temperature, and the suspension containing the resulting polymer particles was centrifuged. The obtained polymer particles were washed twice with distilled water and twice with methanol, and then dried under reduced pressure at 80°C (yield 80%).

[0100] The obtained fumarate ester resin was dissolved in a toluene-methyl ethyl ketone mixed solution (toluene / methyl ethyl ketone 50% by weight / 50% by weight) to make a 20% solution. Further, 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) of a solution casting apparatus using the T-die method, and dried at 80°C and 130°C for 4 minutes each to obtain a laminated film with a width of 250 mm and a thickness of 93 μm. The obtained laminated film was then uniaxially stretched at the free end in the transport direction using a roll stretcher at a temperature of 150°C and a stretching ratio of 1.04 times (longitudinal stretching process) to produce a laminated film in which a first optical film (phase difference film) was laminated onto the support substrate (PET film). The thickness of the produced first optical film was 18 μm, and it was a positive biaxial plate (nz>nx>ny) with a leading axis in the transport direction.

[0101] The breaking strength of the fumarate ester resin film used as the first optical film (phase difference film) manufactured as described above was 59.1 MPa in the MD direction (film molding direction) and 55.0 MPa in the TD direction (perpendicular to the MD direction). The breaking strength of the film was measured using a sample cut to a width of 10 mm, in accordance with JIS-K-7161.

[0102] The HSP values ​​of the fumarate ester resin film, calculated using the method for calculating the HSP values ​​of optical films described later, were (δd 17.4, δp 4.5, δh 5.1).

[0103] <Second Optical Film> The same film, manufactured using the same manufacturing method as the first optical film described above, was used.

[0104] <Activated energy rays> The active energy source is visible light (gallium-filled metal halide lamp). Irradiation device: Light HAMMER10 Mark III manufactured by Excelitas Technologies, Corp. Bulb: V-bulb Peak illuminance: 1600 mW / cm 2 Total irradiation dose: 1000 mJ / cm² 2 (Wavelengths of 380-440 nm were used.) Illuminance of visible light was measured using a Solatell Sola-Check system.

[0105] Examples 1-7 and Comparative Examples 1-2 An adhesive composition, adjusted to the formulations listed in Tables 1-2, was applied to both the first optical film side of a laminated film in which a first optical film (phase difference film) was laminated on a support substrate (PET film), and the second optical film side of a laminated film in which a second optical film (phase difference film) was laminated on a support substrate (PET film), using an MCD coater (manufactured by Fuji Machinery Co., Ltd.) (cell shape: honeycomb, gravure roll line count: 700 lines / inch, rotation speed 140% / line speed) so that the final thickness of the adhesive layer was 1 μm, and the two laminated films were bonded together using a roll machine. The formulations in Tables 1-2 are shown as mass% when the total amount of the composition excluding the initiator and sensitizer is taken as 100% by mass. Subsequently, the adhesive composition was cured by irradiating the laminated film, which includes the first optical film, with visible light from the support substrate (PET film) side using an active energy ray irradiation device, peeling the support substrate (PET film) from the first optical film (phase difference film) of the laminated film, and then peeling the support substrate (PET film) from the second optical film (phase difference film) of the laminated film to obtain a laminated optical film.

[0106] The materials constituting the adhesive composition are as follows. The method for calculating the average HSP value of the radical polymerizable compounds (excluding oligomers) contained in the adhesive composition will be described later. (Polymerizable oligomer) • Polymerizable oligomer 1: Urethane (meth)acrylate with an ether skeleton in the molecule (molecular weight 50,000, viscosity 200,000 Pa·s (25℃), number of polymerizable groups 2, product name "PMH-101B", manufactured by Negami Kogyo Co., Ltd.) • Polymerizable oligomer 2: Urethane (meth)acrylate with an ether skeleton in the molecule (molecular weight 19000, viscosity 9000 Pa·s (25℃), number of polymerizable groups 2, product name "PMH-401B", manufactured by Negami Kogyo Co., Ltd.)

[0107] (polymerizable monomer) • Polymerizable monomer 1: Urethane acrylate (molecular weight 215, viscosity 15-35 Pa·s (25℃), number of polymerizable groups 1, trade name "KRM9276", manufactured by Daicel Ornex Co., Ltd.)

[0108] (Oligomers without polymerizable groups) • Non-polymerizable oligomer 1: Acrylic polymer (molecular weight 1700, viscosity 6000 Pa·s (25℃), number of polymerizable groups 0, trade name "UP1190", manufactured by Toagosei Co., Ltd.)

[0109] (Monofunctional radical polymerizable compound) • Phenoxyethyl (meth)acrylate: (Product name "Viscoat #192HP", manufactured by Osaka Organic Chemical Industry Co., Ltd.), HSP value (δd 17.8, δp 5.0, δh 6.0) • 4-tert-butylcyclohexyl acrylate: (Trade name "TBCHA", manufactured by KJ Chemicals), HSP values ​​(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: (Product name "Light Acrylate P2H-A", manufactured by Kyoeisha Chemical Co., Ltd.), HSP value (δd 17.5, δp 4.9, δh 6.2) • (2-methyl-2-ethyl-1,3-dioxolan-4-yl)methyl acrylate: (Trade name "MEDOL-10", manufactured by Osaka Organic Chemical Industry Co., Ltd.), HSP value (δd 16.7, δp 5.2, δh 5.1) • N-(2-hydroxyethyl)acrylamide: (Trade name "HEAA", manufactured by KJ Chemicals), HSP values ​​(δd 18.3, δp 15.2, δh 15.7) • Acryloylmorpholine: (Trade name "ACMO", manufactured by KJ Chemicals), HSP values ​​(δd 18.5, δp 11.2, δh 5.8) • 4-Vinylphenylboronic acid (compound represented by general formula (1)): (manufactured by Junsei Chemical Co., Ltd.), HSP values ​​(δd 19.6, δp 6.9, δh 22.7) • 4-Hydroxybutyl acrylate (polymerizable compound containing a hydroxyl group): (Trade name "4HBA", manufactured by Mitsubishi Chemical Corporation), HSP value (δd 16.7, δp 6.6, δh 10.8) • m-Phenoxyphenyl methyl acrylate: (Product name "Light Acrylate POB-A", manufactured by Kyoeisha Chemical Co., Ltd.), HSP value (δd 18.7, δp 3.8, δh 4.6)

[0110] (Polyfunctional radical polymerizable compound) • Polyethylene glycol diacrylate: (Diacrylate with acryloyl groups at both ends of polyethylene glycol with 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-tricyclodecanediaacrylate (product 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 "Aronics M-220", manufactured by Toagosei Co., Ltd.), HSP values ​​(δd 16.3, δp 3.6, δh 5.3) • 1,9-nonanediol diacrylate: (Product name "Light Acrylate 1,9ND-A", manufactured by Kyoeisha Chemical Co., Ltd.), HSP value (δd 16.2, δp 3.3, δh 4.2)

[0111] (Initiator, sensitizer) • 2-Methyl-4'-(methylthio)-2-morpholinopropiophenone: (Product label: "Omnirad 907", manufactured by IGM Resins BV) • 2,4-Diethylthioxanthone: Trade name "DETX-S", manufactured by Nippon Kayaku Co., Ltd.

[0112] <Method for calculating the average HSP value of radical polymerizable compounds (excluding polymerizable oligomers) contained in adhesive compositions> The average HSP value of the radically polymerizable compound (excluding the polymerizable oligomer) 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 taking the average value according to the molar ratio of each radically polymerizable compound in the composition.

[0113] <Calculation Method for HSP Value of Optical Film> The above optical film was immersed in 9 solvents with different solubilities, acetone, ethyl acetate, trichlorobenzene, propylene carbonate, γ-butyrolactone, methyl ethyl ketone, diacetone alcohol, hexane, methanol, and their mixed solvents for 24 hours. The state of the optical film after 24 hours of immersion was classified into three stages: (1) dissolved, (2) swollen, and (3) insoluble. Based on the solubility information obtained for each solvent, the Hansen solubility parameter (HSP) was calculated using Hansen Solubility Parameter in Practice (HSPiP) ver.5.4.04 (http: / / www.hansen-solubility.com / index.php).

[0114] <Calculation Method for HSP Distance> When the dispersion term of the Hansen solubility parameter of the above optical film is σd, the polar term is σp, the hydrogen bond term is σh, and the dispersion term of the Hansen solubility parameter of the radically polymerizable compound (excluding the oligomer) contained in the adhesive composition is σAd, the polar term is σAp, and the hydrogen bond term is σAh, 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). It was calculated using the Hansen solubility parameters of the optical film and the adhesive composition calculated by the above method.

[0115] ​<Method for measuring the liquid viscosity of adhesive compositions> The viscosity of the liquid was measured using a viscometer (manufactured by Toki Sangyo Co., Ltd., product name "Type E Viscometer: TV-22") by placing 1.1 mL of adhesive into the device's holder and setting it in place, then varying the rotation speed so that the TQ (torque) remained within the range of 20-80%.

[0116] <Method for measuring the glass transition temperature of adhesive layers> The glass transition temperature (Tg) was determined from the peak top temperature of tanδ obtained from dynamic viscoelasticity measurements of the cured film of the adhesive alone, using a dynamic viscoelasticity analyzer (TA Instruments, product name "RSA-G2") under the following conditions. (Load mode): Pulling (Heating rate): 5℃ / min (Frequency): 1Hz (Initial distortion): 0.1%

[0117] <Method for measuring the storage modulus of adhesive layers> The storage modulus was measured using a dynamic viscoelasticity measuring device (TA Instruments, product name "RSA-G2") under the following conditions, and the value of the storage modulus (E') at 25°C was used as the measurement value. (Load mode): Pulling (Heating rate): 5℃ / min (Frequency): 1Hz (Initial distortion): 0.1%

[0118] <Method for measuring the tensile modulus of adhesive layers, elongation during tensile modulus measurement, and fracture stress> The cured film of the adhesive alone was placed on a tensile testing machine (Shimadzu Corporation, product name "Autograph AG-IS") and the strain-stress curve obtained when it was pulled under the following conditions was used to determine the results. (Test type): Tensile (Test speed): 30 mm / min (Sample width): 10mm (Distance between gripping parts): 10mm

[0119] <Method for measuring the rupture strength of adhesive layers> The cured film of the adhesive alone was placed on a tensile testing machine (Shimadzu Corporation, product name "Autograph AG-IS"), and the strain-stress curve obtained when it was pulled under the following conditions was measured in accordance with JIS-K-7161. (Test type): Tensile (Test speed): 30 mm / min (Sample width): 10mm (Distance between gripping parts): 10mm

[0120] (Method for measuring peel strength) The obtained laminated optical film was cut to a size of 200 mm x 15 mm, and the laminated optical film was bonded to a glass plate. Then, an incision was made between the first optical film and the second optical film with a utility knife, and the first optical film and the second optical film were peeled off at a 90-degree angle at a peeling speed of 5000 mm / min using the angle-adjustable adhesive / film peeling analyzer "VPA-2" (manufactured by Kyowa Interface Chemical Co., Ltd.), and the peeling strength (N / 15 mm) was measured.

[0121] (Method for evaluating peeling morphology) The peeling morphology during the measurement of the peel strength described above was evaluated using the following method. The infrared absorption spectrum of the peeled surface after delamination is measured by the ATR method. If both sides of the peeled surface are adhesive layers (including the compatible layer between the first optical film and the adhesive layer), this indicates "cohesive failure of the adhesive layer (including the compatible layer between the first optical film and the adhesive layer)," meaning that cohesive failure of the first optical film has been prevented, which is considered good. In Tables 1 to 5, cases where "cohesive failure of the adhesive layer (including the compatible layer between the first optical film and the adhesive layer)" occurs are indicated by ○. On the other hand, if both sides of the peeled surface are the first optical film, this indicates that "cohesive failure of the first optical film" has occurred, which is undesirable. In Tables 1 to 5, "cohesive failure of the first optical film" is indicated by ×.

[0122] [Table 1]

[0123] Table 2

Claims

1. A laminated optical film in which at least a first optical film and a second optical film are laminated with an adhesive layer in between, The first optical film and the second optical film are both resin films with a breaking strength of 70 or less. The adhesive layer is formed of a cured layer of an adhesive composition containing a radical polymerizable compound, and its elongation during tensile modulus measurement is 3 mm or more and 50 mm or less. A laminated optical film characterized in that the HSP value distance between the average HSP value of the radical polymerizable compound and the HSP values ​​of the first optical film and the second optical film is 3.5 or less in both cases.

2. The laminated optical film according to claim 1, wherein the adhesive layer has a glass transition temperature of 35°C or less.

3. The laminated optical film according to claim 1, wherein the adhesive composition has a liquid viscosity of 10 mPa·s or less before curing.

4. The laminated optical film according to claim 1, wherein the adhesive composition further contains a polymerizable oligomer having a polymerizable group.

5. The laminated optical film according to claim 34, wherein the polymerizable oligomer is urethane (meth)acrylate.

6. The laminated optical film according to claim 5, wherein the urethane (meth)acrylate has an ether skeleton within the molecule. Hmm.

7. The laminated optical film according to claim 4, wherein the polymerizable oligomer does not have an aromatic ring or alicyclic skeleton within the molecule.

8. The laminated optical film according to claim 1, wherein the adhesive composition contains at least one selected from the group consisting of monofunctional radical polymerizable compounds and polyfunctional radical polymerizable compounds as a radical polymerizable compound.

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

10. The adhesive composition further comprises the following general formula (1): 【Chemistry 1】 A monofunctional radical polymerizable compound represented by (where X is a reactive group, Y is a C1-C12 alkylene group which may have a branched chain, or a phenylene group which may have a substituent, R １ and R ２ The laminated optical film according to claim 1, wherein each of the following independently contains a hydrogen atom, an aliphatic hydrocarbon group which may have a substituent, an aryl group, or a heterocyclic group.

11. The laminated optical film according to claim 1, wherein the adhesive composition further contains a monofunctional radical polymerizable compound having a hydroxyl group.

12. The aforementioned adhesive layer has a tensile modulus of 1 × 10⁻⁶. ３ Pa or greater and 1 × 10 ８ The laminated optical film according to claim 1, wherein the hardness is Pa or less.

13. The laminated optical film according to claim 1, wherein the first optical film is a phase difference film.

14. The laminated optical film according to claim 1, wherein the second optical film is a phase difference film.

15. An image display device comprising at least one laminated optical film as described in claim 1.

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