Stacked optical film and image display device

Abstract

The present application relates to a kind of laminated optical films, which is at least laminated with the 1st optical film and the 2nd optical film via adhesive layer laminated optical film, wherein, the 1st optical film and the 2nd optical film are all resin films with breaking strength of 70 or less, adhesive layer is formed by the cured product layer of adhesive composition containing free radical polymerizable compound, its elongation is 3mm or more and 50mm or less when tensile modulus is measured, the respective HSP value distance between the average HSP value of free radical polymerizable compound and the HSP value of the 1st optical film and the 2nd optical film is 3.5 or less.

Description

Technical Field

[0001] This invention relates to a laminated optical film having at least a first optical film and a second optical film stacked together via an adhesive layer. This laminated optical film can be used to 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 devices, personal computer monitors, and televisions have laminated optical films containing multiple optical films stacked together via adhesive layers and bonding agent layers. Commonly used optical films include transparent resin films such as phase retardation films, polarizers, and transparent protective films.

[0003] In recent years, the demand for thinner image display devices has been increasing. For example, Patent Document 1 describes a liquid crystal display device with a liquid crystal cell that uses an IPS-type liquid crystal cell and has a significantly reduced thickness compared to the past.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Application Publication No. 2015-111236 Summary of the Invention

[0007] The problem that the invention aims to solve

[0008] The technology described in Patent Document 1 has achieved a reduction in oblique light leakage and an improvement in contrast in black displays. However, the optical films used in image display devices include those that, while having low tensile strength and being brittle, are necessary due to environmental limitations and other constraints. The technology described in Patent Document 1 aims to achieve a thinner image display device, but it has not adequately addressed the issue of improving the peel strength from the adhesive layer and enhancing the durability of the product when using specific optical films with low tensile strength and brittleness.

[0009] The present invention was developed in view of the above-mentioned actual situation, and aims to provide a laminated optical film with excellent peel strength between the optical film and the adhesive layer, even in the case of an optical film with low fracture strength and brittleness.

[0010] Problem Solving Methods

[0011] The above-mentioned problems can be solved by the following solution. That is, the present invention relates to a laminated optical film (1), which is a laminated optical film having at least a first optical film and a second optical film laminated together via an adhesive layer, wherein the first optical film and the second optical film are both resin films with a tensile strength of 70 or less, the adhesive layer is formed by a cured layer of an adhesive composition containing a free radical polymerizable compound, and its elongation at tensile modulus measurement is 3 mm or more and 50 mm or less, and the distance between the average HSP value of the free radical polymerizable compound and the HSP values ​​of the first optical film and the second optical film is 3.5 or less.

[0012] In the above-mentioned laminated optical film (1), a laminated optical film (2) is preferred, wherein the glass transition temperature of the adhesive layer is 35°C or less.

[0013] In the above-mentioned laminated optical film (1) or (2), the laminated optical film (3) is preferred, wherein the above-mentioned adhesive composition further contains a polymeric oligomer having polymeric groups.

[0014] In the above-mentioned stacked optical film (3), the stacked optical film (4) is preferred, wherein the above-mentioned polymeric oligomer is urethane (meth) acrylate.

[0015] In the above-mentioned stacked optical film (4), the stacked optical film (5) is preferred, wherein the above-mentioned urethane (meth) acrylate has an ether backbone in its molecule.

[0016] In the above-mentioned stacked optical film (3), the stacked optical film (6) is preferred, wherein the polymeric oligomer does not have an aromatic ring or alicyclic skeleton within its molecule.

[0017] Of any of the above-mentioned stacked optical films (1) to (6), the stacked optical film (7) is preferred, wherein the adhesive composition contains at least one selected from monofunctional free radical polymerizable compounds and polyfunctional free radical polymerizable compounds as a free radical polymerizable compound.

[0018] In the above-mentioned laminated optical film (7), a laminated optical film (8) is preferred, wherein when the total amount of the free radical polymerizable compound in the above-mentioned adhesive composition is set to 100 parts by mass, the content of the above-mentioned multifunctional free radical polymerizable compound is 10 parts by mass or less.

[0019] Of any of the above-mentioned laminated optical films (1) to (8), laminated optical film (9) is preferred, wherein the above-mentioned adhesive composition further contains a monofunctional free radical polymerizable compound represented by the following general formula (1):

[0020] [Chemical Formula 1]

[0021]

[0022] (In the formula, X is a reactive group, Y is an optional alkylene group with 1 to 12 carbon atoms having a branched chain, or an optional phenylene group with a substituent, R...) 1 and R 2 Each of the following groups can be independently represented: hydrogen atom, aliphatic hydrocarbon group, aryl or heterocyclic group (optionally with substituents).

[0023] Of any of the above-mentioned laminated optical films (1) to (9), laminated optical film (10) is preferred, wherein the above-mentioned adhesive composition further contains a monofunctional free radical polymerizable compound having hydroxyl groups.

[0024] Of any of the above-mentioned laminated optical films (1) to (10), laminated optical film (11) is preferred, wherein the adhesive layer preferably has a tensile modulus of 1×10⁻⁶. 3 Pa or higher and 1×10 8 The tensile modulus is below Pa, and the elongation during tensile modulus measurement is above 3 mm and below 50 mm.

[0025] Of any of the above-mentioned stacked optical films (1) to (11), the stacked optical film (12) is preferred, wherein the first optical film is a phase difference film.

[0026] Of any of the above-mentioned stacked optical films (1) to (12), the stacked optical film (13) is preferred, wherein the second optical film is a phase difference film.

[0027] In addition, the present invention relates to an image display device (14) having at least one of the above-mentioned stacked optical films (1) to (13).

[0028] The effects of the invention

[0029] The laminated optical film of 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 with a tensile strength of 70 or less are manufactured, for example, on a substrate such as PET, and laminated with the second optical film or the first optical film via an adhesive layer, and then with other optical films, and then laminated by peeling off the substrate such as PET. However, when peeling off the substrate, there is a risk that the first optical film and / or the second optical film may agglomerate and break, the first optical film and / or the second optical film may fail to perform, or the product may become defective.

[0030] On the other hand, the laminated optical film of the present invention is designed such that the adhesive layer is formed from a cured layer of an adhesive composition containing a free radical polymerizable compound, and the distance between the average HSP value of the free radical polymerizable compound and the HSP values ​​of the first and second optical films is 3.5 or less. As a result, the peel strength between the first optical film and the adhesive layer is excellent, and the peel strength between the second optical film and the adhesive layer is also excellent. The reason for obtaining such an effect is not yet clear, but it can be presumed to be due to the following reasons.

[0031] When the HSP value distance between the average HSP value of the free radical polymerizable compound 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 free radical polymerizable compound 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 easily formed at the interface between the first optical film and the adhesive layer, and a compatible layer is also easily formed 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 that bonds the first and second optical films, the stress relief and toughness of the adhesive layer are improved, and the peel strength between the adhesive layer and the first optical film, as well as the peel strength between the adhesive layer and the second optical film, are increased. As a result, even when peeling a substrate such as PET from the first optical film or from the second optical film, stress concentration is less likely to occur near the interface between the first optical film (which is a fragile layer) and the adhesive layer, or near the interface between the second optical film (which is a fragile layer) and the adhesive layer. As a result, adverse conditions such as coagulation damage of the first optical film and coagulation damage of the second optical film can be prevented.

[0032] Furthermore, when the viscosity of the adhesive composition, which is the raw material for the adhesive layer of the laminated optical film of the present invention, is 10 mPa·s or less before curing, the wettability and permeability of the adhesive composition relative to the first and second optical films are improved. Therefore, a compatible layer is more easily formed at the interface between the first optical film and the adhesive layer, and also more easily at the interface between the second optical film and the adhesive layer. As a result, adverse conditions such as agglomeration damage of the first and second optical films can be more effectively prevented.

[0033] Furthermore, the laminated optical film of the present invention is laminated via an adhesive layer having an elongation of 3 mm or more and 50 mm or less during tensile modulus measurement. Therefore, even with a first optical film and a second optical film exhibiting low tensile strength and brittleness, the peel strength between the adhesive layer and the first optical film, as well as the peel strength between the adhesive layer and the second optical film, is excellent. This prevents adverse conditions such as agglomeration damage of the first and second optical films during the aforementioned peeling of substrates such as PET. The reason for this effect is not yet clear, but in the present invention, when the elongation of the adhesive layer during tensile modulus measurement is adjusted within the aforementioned range, the adhesive layer possesses strong toughness, thereby suppressing agglomeration damage of the first optical film. Therefore, when peeling 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 fragile layer, and the adhesive layer. As a result, adverse conditions such as agglomeration damage of the first optical film (second optical film) can be prevented.

[0034] When the adhesive composition, which is the raw material for the adhesive layer of the laminated optical film of the present invention, further contains a polymeric oligomer having polymeric groups, it is preferable that the adhesive composition further contains urethane (meth)acrylate, and more preferably that the adhesive composition further contains urethane (meth)acrylate having an ether backbone. The peel strength between the adhesive layer and the first optical film, and the peel strength between the adhesive layer and the second optical film are particularly excellent. Even when peeling a substrate such as PET from the first optical film or peeling a substrate such as PET from the second optical film, stress concentration can be more appropriately suppressed near the interface between the first optical film, which is a fragile layer, and the adhesive layer, and near the interface between the second optical film, which is a fragile layer, and the adhesive layer. As a result, the occurrence of adverse conditions such as coagulation damage of the first optical film and coagulation damage of the second optical film can be more effectively prevented. The reasons for this effect are not yet clear, but they can be attributed to the fact that when the adhesive composition, which is the raw material for the adhesive layer, contains the aforementioned polymeric oligomers, the toughness of the adhesive layer is particularly excellent, thereby improving stress relief.

[0035] The laminated optical film of the present invention has a tensile modulus of 1×10⁻⁶. 3 Pa or higher and 1×10 8When adhesive layers with a tensile modulus of Pa or less are laminated, even with a first optical film and a second optical film that are brittle and have low tensile strength, the peel strength between the adhesive layer and the first optical film, as well as the peel strength between the adhesive layer and the second optical film, is excellent. This prevents adverse conditions such as agglomeration damage of the first and second optical films during the peeling of substrates such as PET. The reason for this effect is not yet clear, but it can be considered that when the adhesive layer is adjusted to a specific tensile modulus in this invention, the adhesive layer has stress-relieving properties and its peel strength relative to the first and second optical films is high. Therefore, even when peeling substrates such as PET from the first (second) optical film, stress concentration is less likely to occur near the interface between the first (second) optical film (which is a weak layer) and the adhesive layer. As a result, adverse conditions such as agglomeration damage of the first (second) optical film can be prevented. Detailed Implementation

[0036] This invention relates to a laminated optical film having at least a first optical film and a second optical film stacked thereon via an adhesive layer. The specific configuration will be described below.

[0037] <First optical film and second optical film>

[0038] In this invention, resin films with a tensile strength of 70 or less are used as the first optical film and the second optical film. The functions of the first and second optical films are not particularly limited. In this invention, even when the first and second optical films are retardation films, the peel strength from the adhesive layer is excellent. When peeling off substrates such as PET, it can effectively prevent adverse conditions such as agglomeration and damage in the retardation films (the first and second optical films), and is therefore preferred.

[0039] When the first and second optical films are phase retardation films, examples can be given of phase retardation films having a frontal phase difference of 10 nm or more and / or a thickness direction phase difference of 60 nm or more. Typically, the frontal phase difference is 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.

[0040] As a phase retardation film, a phase retardation film with reverse wavelength dispersion that satisfies the following equations (1) to (3) can be used:

[0041] 0.70<Re

[450] / Re

[550] <0.99···(1)

[0042] 1.5×10 -3 <Δn<6×10 -3 ···(2)

[0043] 1.13 < NZ < 5.00 ···(3)

[0044] (In the formula, Re

[450] and Re

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

[0045] Examples of resin films constituting the first and second optical films include acrylic resins, styrene resins, maleimide resins, and fumarate resins. The inventors conducted in-depth research and found that, among these, fumarate resins exhibit particularly low tensile strength and are brittle. In this invention, when the first and second optical films are retardation films composed of fumarate resins, the peel strength between the first and second optical films and the adhesive layer is excellent. This effectively prevents agglomeration and damage to the first and second optical films during peeling from substrates such as PET, and is therefore preferred.

[0046] When the adhesive layer of the laminated optical film of the present invention contains at least one free radical polymerizable compound selected from monofunctional and polyfunctional free radical polymerizable compounds, and the HSP value distance between the average HSP value of the free radical polymerizable compound and the HSP value of the first optical film is 3.5 or less, the peel strength between the first and second optical films and the adhesive layer is particularly excellent. In particular, when the resin film constituting the first and second optical films is a fumarate resin, and the adhesive layer contains a free radical polymerizable compound that satisfies the above-mentioned HSP value distance relationship, a compatible layer is more easily and effectively formed at the interface between the fumarate resin and the adhesive layer, further improving the stress relief and toughness of the adhesive layer, thereby more effectively improving the peel strength between the first and second optical films (fumarate resin) and the adhesive layer, which is therefore preferred.

[0047] The thickness of the first optical film and the second optical film is not particularly limited. As a lower limit, 1 μm can be exemplified, more preferably 10 μm, and as an upper limit, 100 μm can be exemplified, more preferably 50 μm.

[0048] <Adhesive layer>

[0049] The following description pertains to the adhesive layer used for laminating the first and second optical films in the laminated optical films of the present invention. The adhesive layer is formed from a cured layer of an adhesive composition containing a free-radical polymerizable compound, wherein the distance between the average HSP value of the free-radical polymerizable compound and the HSP values ​​of the first and second optical films is 3.5 or less. In particular, when the resin film constituting the first and second optical films is a fumarate resin, a compatible layer is more easily and effectively formed at the interface between the fumarate resin and the adhesive layer, further enhancing the stress relief and toughness of the adhesive layer. This more effectively improves the peel strength between the first and second optical films (fumarate resin) and the adhesive layer, which is therefore preferable. It should be noted that in this invention, the "average HSP value of the free radical polymerizable compound" refers to the average HSP value of the monofunctional and polyfunctional free radical polymerizable compounds contained in the adhesive composition. Even when the adhesive composition contains polymeric oligomers, the HSP value of the polymeric oligomers is not taken into account. The methods for determining the average HSP value of the free radical polymerizable compound (excluding polymeric oligomers), the HSP values ​​of the first and second optical films, and the distance between their HSP values ​​will be described later.

[0050] From the viewpoint of ensuring the peel strength between the first and second optical films and the adhesive layer, and effectively preventing adverse conditions such as agglomeration and damage to the first and second optical films when peeling off substrates such as PET, the thickness of the adhesive layer is preferably 0.1 to 5 μm, more preferably 0.3 to 3 μm. Furthermore, the glass transition temperature (Tg) of the adhesive layer is preferably 35°C or less. The method for measuring the glass transition temperature (Tg) of the adhesive layer will be explained later.

[0051] For the adhesive composition used as a raw material for the adhesive layer in the laminated optical film of the present invention, when its liquid viscosity before curing is 10 mPa·s or less, the wettability and permeability of the adhesive composition relative to the first and second optical films are improved. Therefore, a compatible layer is more easily formed at the interface between the first optical film and the adhesive layer, and also more easily at the interface between the second optical film and the adhesive layer. As a result, undesirable conditions such as agglomeration damage of the first and second optical films can be more effectively prevented, which is therefore preferable. The method for measuring the liquid viscosity of the adhesive composition will be described later.

[0052] In the laminated optical films of the present invention, the adhesive composition, which serves as the raw material for the adhesive layer used in laminating the first and second optical films, contains a free radical polymerizable compound. This free radical polymerizable compound exhibits active energy ray curing properties, such as electron beam curing, ultraviolet curing, and visible light curing. In the present invention, active energy rays with wavelengths ranging from 10 nm to less than 380 nm are referred to as ultraviolet light, and active energy rays with wavelengths ranging from 380 nm to 800 nm are referred to as visible light.

[0053] Examples of free radical polymerizable compounds include compounds with functional groups possessing carbon-carbon double bonds, such as (meth)acryloyl or vinyl groups, that exhibit free radical polymerizability. These monomeric components can be any compound selected from monofunctional free radical polymerizable compounds or polyfunctional free radical polymerizable compounds having two or more polymerizable functional groups. Furthermore, these free radical polymerizable compounds can be used alone or in combination of two or more. As such free radical polymerizable compounds, compounds possessing, for example, (meth)acryloyl groups are preferred.

[0054] Examples of monofunctional free radical polymerizable compounds include (meth)acrylic acid derivatives. Examples of (meth)acrylic acid derivatives include: 2-methoxyethyl (meth)acrylic acid, 2-ethoxyethyl (meth)acrylic acid, 2-methoxymethoxyethyl (meth)acrylic acid, 3-methoxybutyl (meth)acrylic acid, ethyl carbitol (meth)acrylic acid, phenoxyethyl (meth)acrylic acid, alkylphenoxy polyethylene glycol (meth)acrylic acid, and other (meth)acrylic acid esters containing alkoxy or phenoxy groups; cyclohexyl (meth)acrylic acid, 4-tert-butylcyclohexyl acrylate, etc. Cycloalkyl methacrylates such as cyclopentyl methacrylate; aralkyl methacrylates such as benzyl methacrylate; polycyclic methacrylates such as 2-isoborneol methacrylate, 2-norborneol methyl methacrylate, 5-norborneol-2-yl methyl methacrylate, 3-methyl-2-norborneol methyl methacrylate, dicyclopentenyl methacrylate, dicyclopentenoxyethyl methacrylate, and dicyclopentyl methacrylate; etc. Among these, when phenoxyethyl methacrylate and 4-tert-butylcyclohexyl acrylate are combined and incorporated into the adhesive composition, especially when the first optical film is a retardation film and the retardation film is a fumarate resin, the adhesion of the adhesive layer is improved, and therefore preferred.

[0055] Other monofunctional free radical polymerizable compounds include various (meth)acrylic acid derivatives having a (meth)acryloyloxy group. Specific examples include: methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, 2-methyl-2-nitropropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, sec-butyl (meth)acrylate, tert-butyl (meth)acrylate, n-pentyl (meth)acrylate, tert-pentyl (meth)acrylate, 3-pentyl (meth)acrylate, 2,2-dimethylbutyl (meth)acrylate, n-hexyl (meth)acrylate, hexadecyl (meth)acrylate, n-octyl (meth)acrylate, lauryl (meth)acrylate, 2-ethylhexyl (meth)acrylate, 4-methyl-2-propylpentyl (meth)acrylate, n-octadecyl (meth)acrylate, and other alkyl esters of (meth)acrylate (1-20 carbon atoms).

[0056] In addition, other monofunctional free radical polymerizable compounds include, for example, (meth)acrylamide derivatives having (meth)acrylamide groups. Specific examples of (meth)acrylamide derivatives include: N-methyl (meth)acrylamide, N,N-dimethyl (meth)acrylamide, N,N-diethyl (meth)acrylamide, N-isopropyl (meth)acrylamide, N-butyl (meth)acrylamide, N-hexyl (meth)acrylamide, and other (meth)acrylamide derivatives containing N-alkyl groups; N-hydroxymethyl (meth)acrylamide, N-hydroxyethyl (meth)acrylamide, N-hydroxymethyl-N-propyl (meth)acrylamide, and other (meth)acrylamide derivatives containing N-hydroxyalkyl groups; aminomethyl (meth)acrylamide, aminoethyl (meth)acrylamide, and other (meth)acrylamide derivatives containing N-aminoalkyl groups; N-methoxymethylacrylamide, N-ethoxymethylacrylamide, and other (meth)acrylamide derivatives containing N-alkoxy groups; mercaptomethyl (meth)acrylamide, mercaptoethyl (meth)acrylamide, and other (meth)acrylamide derivatives containing N-mercaptoalkyl groups; and so on. In addition, the nitrogen atom, which is a (meth)acrylamide group, forms heterocyclic (meth)acrylamide derivatives, such as N-acryloylmorpholine, N-acryloylpiperidine, N-methacryloylpiperidine, and N-acryloylpyrrolidine.

[0057] Other examples of monofunctional radical polymerizable compounds include: 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, 3-hydroxypropyl methacrylate, 2-hydroxybutyl methacrylate, 4-hydroxybutyl methacrylate, 6-hydroxyhexyl methacrylate, 8-hydroxyoctyl methacrylate, 10-hydroxydecyl methacrylate, 12-hydroxylaurate methacrylate, and other hydroxyalkyl methacrylates; methyl acrylate [4-(hydroxymethyl)cyclohexyl]acrylate; cyclohexanediol mono(meth)acrylate; and 2-hydroxy-3-phenoxypropyl methacrylate, etc., which are hydroxyl-containing methacrylates. In this invention, when a monofunctional radical polymerizable compound with hydroxyl groups, particularly a hydroxyl-containing methacrylate, is incorporated into the adhesive composition used for laminating the first and second optical films, the adhesion between the first and second optical films and the adhesive layer is improved, which is therefore preferable.

[0058] In addition, as monofunctional free radical polymerizable compounds, the following epoxy-containing (meth)acrylates can also be used: glycidyl methacrylate, 4-hydroxybutyl(meth)acrylate glycidyl ether, etc.; halogen-containing (meth)acrylates such as 2,2,2-trifluoroethyl (meth)acrylate, 2,2,2-trifluoroethyl meth)acrylate, tetrafluoropropyl (meth)acrylate, hexafluoropropyl (meth)acrylate, octafluoropentyl (meth)acrylate, heptadecafluorodecyl (meth)acrylate, 3-chloro-2-hydroxypropyl (meth)acrylate, etc.; and dimethylamino (meth)acrylate. Ethyl methacrylates and other alkyl amino alkyl methacrylates; oxy-heterocyclic butyl methacrylates such as 3-oxetane butyl methacrylate, 3-methyloxetane butyl methacrylate, 3-ethyloxetane butyl methacrylate, 3-butyloxetane butyl methacrylate, and 3-hexyloxetane butyl methacrylate; heterocyclic methacrylates such as tetrahydrofurfuryl methacrylate and butyrolactone methacrylate; neopentyl glycol hydroxypentanoic acid methacrylate adducts; and p-phenylphenol methacrylates.

[0059] In addition, as monofunctional free radical polymerizable compounds, the following carboxyl-containing monomers can also be used: (meth)acrylic acid, carboxyethyl acrylate, carboxypentyl acrylate, itaconic acid, maleic acid, fumaric acid, crotonic acid, isocrotonic acid, etc.

[0060] In addition, as monofunctional free radical polymerizable compounds, lactam vinyl monomers such as N-vinylpyrrolidone, N-vinyl-ε-caprolactam, and methylvinylpyrrolidone can also be used; vinyl monomers with nitrogen-containing heterocycles such as vinylpyridine, vinylpiperidone, vinylpyrimidine, vinylpiperazine, vinylpyrazine, vinylpyrrole, vinylimidazolium, vinyl pyrazole, and vinylmorpholine can also be used.

[0061] Alternatively, radical polymerizable compounds with an active methylene group can also be used as monofunctional free radical polymerizable compounds. A radical polymerizable compound with an active methylene group is a compound having an active double bond group such as a (meth)acryloyl group at the end or in the molecule, and also having an active methylene group. Examples of active methylene groups include acetoacetyl, alkoxymalonyl, or cyanoacetyl. The preferred active methylene group is acetoacetyl. Specific examples of free radical polymerizable compounds containing an active methylene group include: 2-acetylacetoxyethyl methacrylate, 2-acetylacetoxypropyl methacrylate, 2-acetylacetoxy-1-methylethyl methacrylate, and other acetylacetoxyalkyl methacrylates; 2-ethoxymalonyl ethyl methacrylate, 2-cyanoacetoxyethyl methacrylate, N-(2-cyanoacetoxyethyl)acrylamide, N-(2-propionylacetoxybutyl)acrylamide, N-(4-acetylacetoxymethylbenzyl)acrylamide, N-(2-acetylacetylaminoethyl)acrylamide, etc. The preferred free radical polymerizable compound containing an active methylene group is an acetylacetoxyalkyl methacrylate.

[0062] Furthermore, in this invention, the adhesive composition used for laminating the first optical film and the second optical film preferably incorporates a monofunctional free radical polymerizable compound represented by the following general formula (1):

[0063] [Chemical Formula 2]

[0064]

[0065] (In the formula, X is a reactive group, Y is an optional alkylene group with 1 to 12 carbon atoms having a branched chain, or an optional phenylene group with a substituent, R...) 1 and R 2(Each group can be represented independently as a hydrogen atom, an aliphatic hydrocarbon group, an aryl group, or a heterocyclic group with a substituent). When the monofunctional free radical polymeric compound represented by the above formula (1) is incorporated into the adhesive composition, the adhesion between the first optical film and the second optical film and the adhesive layer is improved through the combined use with the polymeric oligomer, which is therefore preferred. From the viewpoint of improving the peel strength between the first optical film and the second optical film and the adhesive layer, and effectively preventing adverse situations such as agglomeration and damage of the first optical film and the second optical film when peeling off substrates such as PET, when the total amount of polymeric components such as polymeric oligomers and polymeric compounds other than polymeric oligomers in the adhesive composition is set to 100 parts by mass, the content of the monofunctional free radical polymeric compound represented by the above formula (1) is preferably 0.5 to 10 parts by mass, more preferably 1 to 5 parts by mass.

[0066] In the monofunctional free radical polymerizable compounds represented by general formula (1), examples of aliphatic hydrocarbon groups include linear or branched alkyl groups with optional substituents having 1 to 20 carbon atoms, cyclic alkyl groups with optional substituents having 3 to 20 carbon atoms, and alkenyl groups with 2 to 20 carbon atoms; examples of aryl groups include phenyl groups with optional substituents having 6 to 20 carbon atoms, and naphthyl groups with optional substituents having 10 to 20 carbon atoms; examples of heterocyclic groups include, for example, groups containing at least one heteroatom and optionally substituents of a 5-membered or 6-membered ring. They can also be linked together to form a ring. In general formula (1), as R 1 and R 2 Preferably, it is a straight-chain or branched alkyl group with 1 to 3 carbon atoms, and most preferably a hydrogen atom.

[0067] The X in the monofunctional free radical polymeric compound represented by general formula (1) is a reactive group, which is a functional group that can react with the curing components that constitute the adhesive layer. Examples include: hydroxyl, amino, aldehyde, carboxyl, vinyl, (meth)acryloyl, styrene, (meth)acrylamide, vinyl ether, epoxy, oxetyl, α,β-unsaturated carbonyl, mercapto, halogen, etc. When the curable adhesive composition constituting the adhesive layer is ray-curable, the reactive group X is preferably selected from at least one reactive group chosen from vinyl, (meth)acryloyl, styrene, (meth)acrylamide, vinyl ether, epoxy, oxetyl, and mercapto. When the curable adhesive composition constituting the adhesive layer is free radical polymerizable, the reactive group X is preferably selected from at least one reactive group chosen from (meth)acryloyl, styrene, and (meth)acrylamide. When the monofunctional free radical polymerizable compound represented by general formula (1) has a (meth)acrylamide group, it has high reactivity and a higher copolymerization rate with the curable component in the adhesive layer, and is therefore more preferred. In addition, the (meth)acrylamide group has high polarity and excellent adhesion, and is therefore preferred from the perspective of effectively obtaining the effects of the present invention. When the curable adhesive composition constituting the adhesive layer is cationicly polymerizable, the reactive group X preferably has at least one functional group selected from hydroxyl, amino, aldehyde, carboxyl, vinyl ether, epoxy, oxetyl, and mercapto. In particular, when epoxy is present, the resulting adhesive layer has excellent adhesion to the adhered object, and is therefore preferred. When vinyl ether is present, the curability of the curable adhesive composition is excellent, and is therefore preferred.

[0068] Preferred examples of monofunctional radical polymerizable compounds represented by general formula (1) include the following compounds (1a) to (1d). It should be noted that R in general formulas (1a) and (1b) 3 It can be a hydrogen atom or a methyl group.

[0069] [Chemical Formula 3]

[0070]

[0071] In addition to the compounds exemplified above, monofunctional free radical polymerizable compounds represented by general formula (1) may also include esters formed by hydroxyethyl acrylamide and boric acid, esters formed by hydroxymethyl acrylamide and boric acid, esters formed by hydroxyethyl acrylate and boric acid, and esters formed by hydroxybutyl acrylate and boric acid, etc. (meth)acrylates formed by boric acid.

[0072] Examples of multifunctional free radical polymerizable compounds with 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, neopentyl glycol di(meth)acrylate, tricyclodecanediethanol di(meth)acrylate, cyclic trimethylolpropane formal(meth)acrylate, and dimethylolpropane formal(meth)acrylate. Alkanediol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol penta(meth)acrylate, dipentaerythritol hexa(meth)acrylate, EO-modified diglycerol tetra(meth)acrylate, etc., esterifications of (meth)acrylate and polyols, 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 Toa Synthetic Co., Ltd.), LIGHT ACRYLATE 1,9ND-A (manufactured by Kyoeisha Chemical Co., Ltd.), LIGHT ACRYLATE DGE-4A (manufactured by Kyoeisha Chemical Co., Ltd.), LIGHT ACRYLATE DCP-A (manufactured by Kyoeisha Chemical Co., Ltd.), SR-531 (manufactured by Sartomer Co., Ltd.), and CD-536 (manufactured by Sartomer Co., Ltd.). Additionally, various epoxy (meth)acrylates, urethane (meth)acrylates, polyester (meth)acrylates, and various (meth)acrylate monomers can be used as needed. When the total amount of the free radical polymerizable compound in the adhesive composition is set to 100 parts by mass, the content of the multifunctional free radical polymerizable compound is preferably 10 parts by mass or less.

[0073] In the laminated optical film of the present invention, when the adhesive composition, which serves as the raw material for the adhesive layer used in the lamination of the first and second optical films, further contains polymeric oligomers having polymeric groups in addition to free radical polymerizable compounds, it is preferable that the adhesive composition further contains urethane (meth)acrylate, and more preferably, that the adhesive composition further contains urethane (meth)acrylate having an ether backbone. In this case, the peel strength between the adhesive layer and the first optical film, and the peel strength between the adhesive layer and the second optical film are particularly excellent. Even when peeling a substrate such as PET from the first optical film or peeling a substrate such as PET from the second optical film, stress concentration can be more appropriately suppressed near the interface between the first optical film (as a fragile layer) and the adhesive layer, and near the interface between the second optical film (as a fragile layer) and the adhesive layer. As a result, the occurrence of adverse conditions such as coagulation damage of the first optical film and coagulation damage of the second optical film can be more effectively prevented, which is therefore preferred.

[0074] The polymeric oligomers used in this invention have 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 polymeric oligomer used, the better the toughness of the adhesive layer, and consequently, the better the stress relief, which is therefore preferred. Examples of polymeric groups include vinyl, (meth)acryloyl, styrene, or (meth)acrylamido. It should be noted that in this invention, (meth)acryloyl means acryloyl and / or methacryloyl.

[0075] In this invention, urethane (meth)acrylates are preferably used as polymerizable oligomers, and more preferably urethane (meth)acrylates having an ether backbone. When the adhesive layer is composed, at least as a part of the raw material, of urethane (meth)acrylates, more preferably urethane (meth)acrylates having an ether backbone, the adhesive layer exhibits particularly excellent toughness and further improved stress relief. As a result, even when using fumarate resin films, which are particularly prone to low tensile strength and brittleness, as the first and second optical films (phase reversal films), adverse conditions such as coagulation damage in the first optical film can be effectively prevented when peeling off substrates such as PET, and this is therefore preferred.

[0076] Examples of urethane (meth)acrylates include those containing at least polyalkylene glycols such as polyethylene glycol, polypropylene glycol, polybutane glycol, or polystyrene glycol; polycarbonate or polyalkylene glycol (poly)carbonate; polyester units, urethane bonds, and polymerizable groups. Preferably, urethane (meth)acrylates with an ether backbone containing at least polyalkylene glycol and / or polyalkylene glycol (poly)carbonate, urethane bonds, and polymerizable groups are used. The urethane bonds can be formed by reacting the hydroxyl groups of the aforementioned polyalkylene glycols constituting the urethane (meth)acrylate with isocyanates such as diphenylmethane diisocyanate, toluene diisocyanate, isophorone diisocyanate, and hexamethylene diisocyanate.

[0077] In this invention, when a polymeric oligomer with a molecular weight of 700 or more and without an aromatic or alicyclic backbone is used as the polymeric oligomer, the resulting adhesive layer has moderate flexibility. As a result, the stress relief and toughness of the adhesive layer are improved, which is therefore preferred.

[0078] The polymeric oligomers used in this invention preferably have at least two polymeric groups. Polymeric oligomers with at least two polymeric groups have the effect of improving the stress relief and toughness of the final adhesive layer.

[0079] In this invention, polymeric oligomers other than urethane (meth)acrylates can also be used as polymeric oligomers, such as polybutadiene-terminated (meth)acrylates, polyethylene glycol (meth)acrylates, polypropylene glycol (meth)acrylates, (meth)acryloyl (meth)acrylates, etc.

[0080] In this invention, from the viewpoint of improving the peel strength between the first optical film and the second optical film and the adhesive layer, and effectively preventing adverse situations such as coagulation and damage of the first optical film and the second optical film when peeling off substrates such as PET, when the total amount of polymeric components such as polymeric oligomers and polymeric compounds other than polymeric oligomers in the adhesive composition is set to 100 parts by mass, the content of polymeric oligomers is preferably 1 to 30 parts by mass, more preferably 5 to 20 parts by mass.

[0081] In this invention, the adhesive composition, which serves as the raw material for the adhesive layer of the laminated optical film, may contain, in addition to a free radical polymerizable compound, an acrylic oligomer formed by polymerizing (meth)acrylic acid monomers and lacking polymerizable groups. By including this acrylic oligomer in the adhesive composition, curing shrinkage during irradiation with active energy rays and subsequent curing can be reduced, thereby reducing interfacial stress between the adhesive layer and the adhered objects such as polarizers and optical films. As a result, the reduction in adhesion between the adhesive layer and the adhered objects can be suppressed.

[0082] Considering workability and uniformity during application, the active energy radiation-cured adhesive is preferably low in viscosity. Therefore, acrylic oligomers formed by polymerizing (meth)acrylic acid monomers and lacking polymerizable groups are also preferably low in viscosity. As an acrylic oligomer with low viscosity that can prevent curing shrinkage of the adhesive layer, its weight-average molecular weight (Mw) is preferably 15,000 or less, more preferably 10,000 or less, and particularly preferably 5,000 or less. On the other hand, in order to sufficiently suppress curing shrinkage of the cured 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)acrylate monomers constituting acrylic oligomers include: methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, 2-methyl-2-nitropropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, sec-butyl methacrylate, tert-butyl methacrylate, n-pentyl methacrylate, tert-pentyl methacrylate, 3-pentyl methacrylate, 2,2-dimethylbutyl methacrylate, n-hexyl methacrylate, etc. Cetyl methacrylate, n-octyl methacrylate, 2-ethylhexyl methacrylate, 4-methyl-2-propylpentyl methacrylate, n-octadecyl methacrylate, and other alkyl methacrylates (1-20 carbon atoms), as well as cycloalkyl methacrylates (e.g., cyclohexyl methacrylate, cyclopentyl methacrylate), aralkyl methacrylates (e.g., benzyl methacrylate), and polycyclic methacrylates (e.g., 2-isobornyl methacrylate, 2-norberyl methacrylate). Fiber methyl esters, 5-norbornene-2-yl methyl ester (meth)acrylate, 3-methyl-2-norbornene-methyl ester (meth)acrylate, etc.), hydroxyl-containing (meth)acrylates (e.g., hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2,3-dihydroxypropyl methylbutyl (meth)acrylate, etc.), alkoxy or phenoxy (meth)acrylates (2-methoxyethyl (meth)acrylate, 2-ethoxyethyl (meth)acrylate, 2-methoxymethoxyethyl (meth)acrylate, 3-methoxybutyl (meth)acrylate, etc.), These include ethyl carbitol methacrylate, phenoxyethyl methacrylate, etc.; epoxy-containing methacrylates (e.g., glycidyl methacrylate, etc.); halogen-containing methacrylates (e.g., 2,2,2-trifluoroethyl methacrylate, 2,2,2-trifluoroethyl methacrylate, tetrafluoropropyl methacrylate, hexafluoropropyl methacrylate, octafluoropentyl methacrylate, heptadecafluorodecyl methacrylate, etc.); and alkylaminoalkyl methacrylates (e.g., dimethylaminoethyl methacrylate, etc.). These methacrylates can be used alone or in combination of two or more. Specific examples of acrylic oligomers (E) include "ARUFON" manufactured by Toa Synthetic Co., Ltd., "ACTFLOW" manufactured by Soken Chemical Co., Ltd., and "JONCRYL" manufactured by BASF Japan.

[0083] In the case of using free radical polymerizable compounds, the photopolymerization initiator can be appropriately selected based on the active energy of the radiation. When curing by ultraviolet or visible light, a photopolymerization initiator that is pyrolyzed by ultraviolet or visible light can be used. Examples of such photopolymerization initiators include: benzoyl, benzophenone, benzoylbenzoic acid, 3,3′-dimethyl-4-methoxybenzophenone, and other benzophenone compounds; aromatic ketone compounds such as 4-(2-hydroxyethoxy)phenyl(2-hydroxy-2-propyl)one, α-hydroxy-α,α′-dimethylacetophenone, 2-methyl-2-hydroxyphenylacetone, α-hydroxycyclohexylphenyl ketone, etc.; acetophenone compounds such as methoxyacetophenone, 2,2-dimethoxy-2-phenylacetophenone, 2,2-diethoxyacetophenone, 2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropane-1-one, etc.; benzoin methyl ether, Benzoin ethers such as benzoin ethyl ether, benzoin isopropyl ether, benzoin butyl ether, and anisolein methyl ether; aromatic ketals such as benzoin dimethyl ketal; aromatic sulfonyl chlorides such as 2-naphthalenesulfonyl chloride; photoactive oximes such as 1-phenyl-1,1-propanedione-2-(O-ethoxycarbonyl)oxime; thioxanthones such as 2-chlorothioxanthone, 2-methylthioxanthone, 2,4-dimethylthioxanthone, isopropylthioxanthone, 2,4-dichlorothioxanthone, 2,4-diethylthioxanthone, 2,4-diisopropylthioxanthone, and dodecylthioxanthone; camphorquinone; haloketones; acylphosphine oxides; and acylphosphonates.

[0084] When the total amount of the active energy ray curable adhesive composition is set to 100% by weight, the amount of the above-mentioned photopolymerization initiator is 20% by weight or less. The amount of the photopolymerization initiator is preferably 0.01 to 20% by weight, more preferably 0.05 to 10% by weight, and even more preferably 0.1 to 5% by weight.

[0085] Furthermore, when using the curable adhesive for laminated optical films of the present invention in a visible light curable form containing a free radical polymerizable compound as a curing component, it is particularly preferable to use a photopolymerization initiator that is highly sensitive to light above 380 nm. The photopolymerization initiator that is highly sensitive to light above 380 nm will be explained later.

[0086] As the above-mentioned photopolymerization initiator, it is preferred to use the compound represented by the following general formula (2) alone, or to use the compound represented by the general formula (2) in combination with the photopolymerization initiator that is highly sensitive to light above 380 nm as described later.

[0087] [Chemical Formula 4]

[0088]

[0089] (where R is in the formula) 1and R 2 Represents -H, -CH2CH3, -iPr, or Cl, R 1 and R 2 (Can be the same or different). When using compounds represented by general formula (2), the adhesion is superior compared to using photopolymerization initiators that are highly sensitive to light above 380 nm alone. Among the compounds represented by general formula (2), R is particularly preferred. 1 and R 2 The compound is diethylthioxanthone with the formula -CH2CH3. The composition ratio of the compound represented by general formula (2) in the adhesive composition is preferably 0.1 to 5 parts by weight, more preferably 0.5 to 4 parts by weight, and even more preferably 0.9 to 3 parts by weight, relative to 100 parts by weight of the total amount of the curing component.

[0090] Furthermore, a polymerization initiator is preferably added 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 a polymerization initiator, its addition amount relative to 100 parts by weight of the total amount of the curing component is typically 0 to 5 parts by weight, preferably 0 to 4 parts by weight, and most preferably 0 to 3 parts by weight.

[0091] In addition, known photopolymerization initiators can be used in combination as needed. Since transparent protective films with UV absorption capabilities do not transmit light below 380 nm, it is preferable to use photopolymerization initiators that are highly sensitive to light above 380 nm. Specifically, examples include: 2-methyl-1-(4-methylthiophenyl)-2-morpholinopropane-1-one, 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-1-butanone, 2-(dimethylamino)-2-[(4-methylphenyl)methyl]-1-[4-(4-morpholino)phenyl]-1-butanone, 2,4,6-trimethylbenzoyl diphenylphosphine 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, etc.

[0092] In particular, as a photopolymerization initiator, it is preferable to use a compound represented by the following general formula (3) in addition to the photopolymerization initiator of general formula (2).

[0093] [Chemical Formula 5]

[0094]

[0095] (where R is in the formula) 3 R4 and R 5 Represents -H, -CH3, -CH2CH3, -iPr, or Cl, R 3 R 4 and R 5 (These may be the same or different). As compounds represented by general formula (3), 2,4,6-trimethylbenzoyl diphenylphosphine oxide (trade name: Omnirad 819, manufacturer: IGM Resins BV) and 2-methyl-1-(4-methylthiophenyl)-2-morpholinopropane-1-one (trade name: Omnirad 907, manufacturer: IGM Resins BV), which are also commercially available, are preferred due to their high sensitivity. In addition, 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-1-butanone (trade name: Omnirad 369, manufacturer: IGM Resins BV) and 2-(dimethylamino)-2-[(4-methylphenyl)methyl]-1-[4-(4-morpholino)phenyl]-1-butanone (trade name: Omnirad 379, manufacturer: IGM Resins BV) are preferred due to their high sensitivity.

[0096] In this invention, a hydroxyl-containing photopolymerization initiator is preferably used among the aforementioned photopolymerization initiators. When the active energy ray-curable adhesive composition contains a hydroxyl-containing photopolymerization initiator as a polymerization initiator, the solubility of the adhesive layer with a higher concentration of component A on the polarizer side is improved, and the curing properties of the adhesive layer are improved. Examples of photopolymerization initiators containing hydroxyl groups include: 2-methyl-2-hydroxyphenylacetone (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-propane-1-one (trade name "IRGACURE2959", manufactured by BASF), and 2-hydroxy-1-{4-[4-(2-hydroxy-2-methyl-propanoyl)-benzyl]phenyl}-2-methyl-propane-1-one (trade name "IRGACURE127", manufactured by BASF). 1-hydroxycyclohexylphenyl ketone is particularly preferred due to its excellent solubility in adhesive layers with high concentrations of component A.

[0097] In this invention, a cationic polymerizable adhesive composition can be used as the adhesive composition that forms the adhesive layer of a laminated optical film. The cationic polymerizable compound used in the cationic polymerizable adhesive composition can be classified as a monofunctional cationic polymerizable compound having one cationic polymerizable functional group within its molecule, and a polyfunctional cationic polymerizable compound having two or more cationic polymerizable functional groups within its molecule. Monofunctional cationic polymerizable compounds have lower liquid viscosity; therefore, by including a monofunctional cationic polymerizable compound in the resin composition, the liquid viscosity of the resin composition can be reduced. Furthermore, monofunctional cationic polymerizable compounds often have functional groups exhibiting various functions; by including them in the cationic polymerizable adhesive composition, the cationic polymerizable adhesive composition and / or the cured cationic polymerizable adhesive composition can exhibit various functions. Polyfunctional cationic polymerizable compounds are preferably included in the cationic polymerizable adhesive composition because they can cause three-dimensional crosslinking in the cured cationic polymerizable adhesive composition. Regarding the ratio of monofunctional cationic polymeric compounds to polyfunctional cationic polymeric compounds, it is preferable to mix polyfunctional cationic polymeric compounds in the range of 10 to 1000 parts by weight relative to 100 parts by weight of the monofunctional cationic polymeric compound. Examples of cationic polymeric functional groups include epoxy groups, oxetyl groups, and vinyl ether groups. Examples of compounds containing epoxy groups include aliphatic epoxy compounds, alicyclic epoxy compounds, and aromatic epoxy compounds. Due to their excellent curability and adhesive properties, alicyclic epoxy compounds are particularly preferred as the cationic polymeric adhesive composition of the present invention. Examples of alicyclic epoxy compounds include 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexane carboxylate, caprolactone-modified, trimethylcaprolactone-modified, and valproic acid-modified versions of 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexane carboxylate, and more specifically, CELLOXIDE 2021, CELLOXIDE 2021A, CELLOXIDE 2021P, CELLOXIDE 2081, CELLOXIDE 2083, CELLOXIDE 2085 (all manufactured by CELLOXIDE Chemical Industry Co., Ltd.), Cyracure UVR-6105, Cyracure UVR-6107, Cyracure 30, and R-6110 (all manufactured by Dow Chemical Japan Ltd.). Compounds containing oxocyclic butyl groups are preferred because they improve the curability of cationic polymerizable adhesive compositions and reduce the liquid viscosity of the composition.Examples of compounds containing oxetane groups include 3-ethyl-3-hydroxymethyloxetane, 1,4-bis[(3-ethyl-3-oxetane)methoxymethyl]benzene, 3-ethyl-3-(phenoxymethyl)oxetane, di[(3-ethyl-3-oxetane)methyl] ether, 3-ethyl-3-(2-ethylhexyloxymethyl)oxetane, and phenolic varnish oxetane. Commercially available products include ARONOXETANE OXT-101, ARON OXETANE OXT-121, ARON OXETANE OXT-211, ARON OXETANE OXT-221, and ARON OXETANE OXT-212 (all manufactured by Toa Synthetic Co., Ltd.). Compounds containing vinyl ether groups are preferred because they improve the curability of cationic polymerizable adhesive compositions and reduce the liquid viscosity of the composition. Examples of compounds containing a vinyl ether group include: 2-hydroxyethyl vinyl ether, diethylene glycol monovinyl ether, 4-hydroxybutyl vinyl ether, diethylene glycol monovinyl ether, triethylene glycol divinyl ether, cyclohexanediethanol divinyl ether, cyclohexanediethanol monovinyl ether, tricyclodecane vinyl ether, cyclohexyl vinyl ether, methoxyethyl vinyl ether, ethoxyethyl vinyl ether, pentaerythritol-type tetravinyl ether, etc.

[0098] The cationic polymerizable adhesive composition contains at least one compound selected from the above-described compounds having epoxy groups, oxetyl groups, and vinyl ether groups as a curing agent. These are all substances that cure via cationic polymerization, and therefore can be combined with a photocationic polymerization initiator. This photocationic polymerization initiator generates cationic species or Lewis acids upon irradiation with active energy rays such as visible light, ultraviolet light, X-rays, and electron beams, thereby initiating the polymerization reaction of epoxy groups and oxetyl groups. As a photocationic polymerization initiator, a photoacid generator described later can be appropriately used. Furthermore, when using the cationic polymerizable adhesive composition for visible light curability, a photocationic polymerization initiator with high sensitivity to light above 380 nm is particularly preferred. However, photocationic polymerization initiators are compounds that typically exhibit maximum absorption in the wavelength region around 300 nm or shorter than 300 nm. Therefore, by combining a photosensitizer that exhibits maximum absorption in a longer wavelength region, specifically longer than 380 nm, light at nearby wavelengths can be sensed, promoting 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 photoreducing pigments; two or more of these can also be used in combination. Anthracene compounds are particularly preferred due to their excellent photosensitizing effect; 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, more preferably 0.5% to 3% by weight.

[0099] The laminated optical film of the present invention, for example, is disposed on an image display device via an adhesive layer on the side opposite to the side of the first optical film on which the second optical film is laminated.

[0100] <Adhesive layer>

[0101] There are no particular limitations on the adhesive used to form the adhesive layer; adhesives with polymers such as acrylic polymers, silicone polymers, polyesters, polyurethanes, polyamides, polyethers, fluorinated polymers, and rubbers as the base polymer can be appropriately selected. In particular, acrylic adhesives, which exhibit excellent optical transparency and moderate wetting, cohesiveness, and adhesion properties, as well as excellent weather resistance and heat resistance, are preferred.

[0102] For the exposed surface of the adhesive layer, it can be temporarily covered by an adhesive diaphragm to prevent contamination until it is put into actual use. This prevents contact with the adhesive layer under normal handling conditions. As the diaphragm, suitable diaphragms as previously specified can be used, in addition to the thickness conditions mentioned above, by coating suitable thin materials such as plastic films, rubber sheets, paper, cloth, non-woven fabrics, meshes, foam sheets, metal foils, and their laminates with appropriate release agents such as silicone, long-chain alkyl, fluorine, and molybdenum sulfide as needed.

[0103] In addition to the first optical film and the second optical film, the stacked optical film of the present invention may also include the optical film shown below.

[0104] <Polarizing filter>

[0105] In this invention, from the viewpoint of thinness, the thickness of the polarizer is preferably 10 μm or less, more preferably 5 μm or less. Examples of such polarizers include films obtained by uniaxially stretching hydrophilic polymer films such as polyvinyl alcohol films, partially formalized polyvinyl alcohol films, and partially saponified films of ethylene-vinyl acetate copolymers.

[0106] A polarizing mirror made by dyeing a polyvinyl alcohol (PVA) film with iodine and then unidirectionally stretching it can be manufactured as follows: PVA is dyed by immersing it in an aqueous solution of iodine and then stretched to 3-7 times its initial length. If necessary, it can also be immersed in an aqueous solution containing potassium iodide, such as boric acid, zinc sulfate, or zinc chloride. Furthermore, if necessary, the PVA film can be washed with water before dyeing. Washing the PVA film not only removes stains and anti-blocking agents from its surface but also prevents uneven dyeing by causing the film to swell. Stretching can be performed after dyeing with iodine, or during dyeing, or after stretching. Stretching can also be performed in an aqueous solution of boric acid, potassium iodide, etc., or in a water bath.

[0107] Representative examples of thin polarizers include those described in Japanese Patent No. 4751486, Japanese Patent No. 4751481, Japanese Patent No. 4815544, Japanese Patent No. 5048120, International Publication No. 2014 / 077599, and International Publication No. 2014 / 077636, or thin polarizers manufactured using the methods described in these documents.

[0108] As for the aforementioned thin polarizer, from the viewpoint of being able to stretch to high magnification and thus improve polarization performance, a thin polarizer obtained by a method including a stretching step in a boric acid aqueous solution, as described in Japanese Patent Nos. 4751486, 4751481, and 4815544, is preferred. A particularly preferred method is a thin polarizer obtained by a process described in Japanese Patent Nos. 4751481 and 4815544, which includes an auxiliary stretching step in a gas atmosphere before stretching in a boric acid aqueous solution. These thin polarizing films can be obtained by a method including a stretching step of stretching a polyvinyl alcohol resin (hereinafter also referred to as PVA resin) layer and a stretching resin substrate in a laminated state, and a dyeing step. If this method is used, even if the PVA resin layer is thin, it can be stretched by being supported by a stretched resin substrate without causing defects such as breakage due to stretching.

[0109] <Resin Protective Film>

[0110] The laminated optical film of the present invention can also include a transparent protective film as other optical films. As a 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 cellulose triacetate, polyester resins, polyethersulfone resins, polysulfone resins, polycarbonate resins, polyamide resins, polyimide resins, polyolefin resins, (meth)acrylic resins, cyclic polyolefin resins (norbornene resins), polyarylate resins, polystyrene resins, polyvinyl alcohol resins, and mixtures thereof. The transparent protective film may contain one or more suitable additives. Examples of additives include: ultraviolet absorbers, antioxidants, lubricants, plasticizers, release agents, anti-coloring agents, flame retardants, nucleating agents, antistatic agents, pigments, colorants, etc. The content of the aforementioned thermoplastic resin in the transparent protective film is preferably 50-100% by weight, more preferably 50-99% by weight, even more preferably 60-98% by weight, and particularly preferably 70-97% by weight. When the content of the aforementioned thermoplastic resin in the transparent protective film is 50% by weight or less, there is a risk that the high transparency originally possessed by the thermoplastic resin may not be fully manifested.

[0111] Furthermore, as the material for forming the transparent protective film, materials with excellent transparency, mechanical strength, thermal stability, moisture barrier properties, and isotropy are preferred; in particular, materials with a moisture permeability of 150 g / m² are more preferred. 2 Materials with a permeability of less than 24h, preferably with a moisture permeability of 140g / m². 2Materials with a permeability of less than 24h are preferred, with a further optimal permeability of 120g / m³. 2 Materials with a lifespan of less than 24 hours.

[0112] Functional layers such as a hard coating layer, anti-reflective layer, anti-adhesion layer, diffusion layer, or anti-glare layer can be applied to the transparent protective film. It should be noted that these functional layers, such as the hard coating layer, anti-reflective layer, anti-adhesion layer, diffusion layer, and anti-glare layer, can be used not only to protect the transparent protective film itself, but also as separate layers different from the transparent protective film.

[0113] The thickness of the transparent protective film can be appropriately determined. Generally speaking, considering factors such as strength, processability, operability, and thinness, it is about 1~500μm, preferably 1~300μm, more preferably 5~200μm, further preferably 10~200μm, and even more preferably 20~80μm.

[0114] The laminated optical film of the present invention can be manufactured, for example, by the following manufacturing method.

[0115] A method for manufacturing a laminated optical film, wherein the laminated optical film comprises at least a first optical film and a second optical film laminated together via an adhesive layer, wherein the first optical film and the second optical film are resin films with a tensile strength of 70 or less, the adhesive layer is formed by a cured layer of an adhesive composition containing a free radical polymerizable compound, wherein the distance between the average HSP value of the free radical polymerizable compound and the HSP values ​​of the first optical film and the second optical film is 3.5 or less, and the method for manufacturing the laminated optical film includes: a coating step of coating at least one of the first optical film and the second optical film with the adhesive composition; a lamination step of laminating the first optical film and the second optical film; and an adhesive bonding step of curing at least the adhesive composition by irradiating it with active energy rays from the surface side of the first optical film or the surface side of the second optical film to form an adhesive layer, and bonding the first optical film and the second optical film via the adhesive layer.

[0116] The following is a description of each process.

[0117] (Coating process)

[0118] The method for applying the adhesive composition to at least one of the first and second optical films can be appropriately selected based on the viscosity of the composition and the target thickness. Examples include: reverse coaters, gravure coaters (direct, reverse, or offset), bar reverse coaters, roller coaters, die coaters, wire-wound bar coaters, and bar 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. High viscosity results in insufficient surface smoothness after coating, leading to poor appearance, which is undesirable. Therefore, coating can be performed after adjusting the viscosity of each composition to the preferred range by heating or cooling.

[0119] (Lamination process)

[0120] The first optical film and the second optical film are bonded together. When bonding the first optical film and the second optical film using an adhesive composition, a roller laminator or the like is used for bonding.

[0121] (Adhesive bonding process)

[0122] The first optical film and the second optical film are bonded together by an adhesive layer formed by curing the adhesive composition at least from the side of the first optical film or the side of the second optical film by irradiating it with active energy rays. The irradiation direction of the active energy rays (electron beam, ultraviolet light, visible light, etc.) can be any suitable direction.

[0123] The irradiation conditions under electron beam irradiation are only required to cure the adhesive composition; any suitable conditions can be used. For example, the accelerating voltage for electron beam irradiation is preferably 5 kV to 300 kV, more preferably 10 kV to 250 kV. If the accelerating voltage is less than 5 kV, there is a risk that the electron beam may not reach the adhesive, resulting in insufficient curing. If the accelerating voltage is greater than 300 kV, there is a risk that the penetration force through the sample may be too strong, causing damage to the first and second optical films. The irradiation dose is 5 to 100 kGy, more preferably 10 to 75 kGy. If the irradiation dose is less than 5 kGy, the adhesive will not cure sufficiently. If it is greater than 100 kGy, it will damage the first and second optical films, resulting in reduced mechanical strength, yellowing, and failure to obtain the desired optical properties.

[0124] Electron beam irradiation is typically carried out in an inert gas, but it can also be performed in the atmosphere with a small amount of oxygen introduced, depending on the requirements. Although it depends on the materials of the first and second optical films, by appropriately introducing oxygen, the surfaces of the first and second optical films initially irradiated by the electron beam can be made to produce oxygen barriers, thereby preventing damage to the first and second optical films and allowing the electron beam to be effectively irradiated only on the adhesive.

[0125] In manufacturing the laminated optical film of the present invention, the active energy ray preferably uses an active energy ray containing visible light in the wavelength range of 380 nm to 450 nm, particularly an active energy ray that provides the highest irradiation of visible light in the wavelength range of 380 nm to 450 nm. When using ultraviolet light or visible light, and using a first or second optical film with ultraviolet absorption capability, such as an ultraviolet-proof transparent protective film, light with wavelengths shorter than about 380 nm is absorbed. Therefore, light with wavelengths shorter than 380 nm does not reach the adhesive composition and does not contribute to its polymerization reaction. Furthermore, the light with wavelengths shorter than 380 nm absorbed by the first or second optical film is converted into heat, causing the first or second optical film to heat up, which becomes a cause of defects such as curling / wrinkling of the laminated optical film. Therefore, in this invention, when using ultraviolet or visible light, it is preferable to use a device that does not emit light with wavelengths shorter than 380 nm as the active energy ray generating device. More specifically, the ratio of cumulative illuminance in the wavelength range of 380-440 nm to cumulative illuminance in the wavelength range of 250-370 nm is preferably 100:0 to 100:50, more preferably 100:0 to 100:40. When manufacturing the laminated optical film of this invention, gallium-encapsulated metal halide lamps, LED light sources emitting light in the wavelength range of 380-440 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 lamps, xenon lamps, halogen lamps, carbon arc lamps, metal halide lamps, fluorescent lamps, tungsten lamps, gallium lamps, excimer lasers, or sunlight, can be used. Ultraviolet light with wavelengths shorter than 380 nm can also be blocked by a bandpass filter before use. To improve the adhesion performance of the adhesive layer between the first optical film and the second optical film and to prevent the stacked optical films from curling, it is preferable to use: active energy rays obtained by using a gallium-encapsulated metal halide lamp and a bandpass filter that can block light with wavelengths shorter than 380 nm, or active energy rays with a wavelength of 405 nm obtained by using an LED light source.

[0126] When manufacturing the laminated optical film of the present invention via a continuous production line, the linear speed varies depending 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 linear speed is too low, productivity is insufficient, or excessive damage is caused to the first or second optical film, making it impossible to produce a laminated optical film capable of withstanding durability tests, etc. If the linear speed is too high, the curing of the adhesive composition may sometimes be insufficient, and the desired adhesion may not be achieved.

[0127] (Layered optical films)

[0128] The laminated optical film of the present invention is preferably used in the formation of various image display devices, such as liquid crystal display devices. The formation of a liquid crystal display device can be performed in a conventional manner. That is, a liquid crystal display device is typically formed by appropriately assembling liquid crystal cells with polarizing films or optical films, and components such as illumination systems used as needed, and incorporating driving circuitry. In the present invention, there are no particular limitations except for the use of the laminated optical film of the present invention, and it can be performed in a conventional manner. Regarding the liquid crystal cells, any type of liquid crystal cell, such as TN type, STN type, or π type, can be used.

[0129] Suitable liquid crystal display devices, such as liquid crystal display devices with optical laminates arranged on one or both sides of the liquid crystal cell, and liquid crystal display devices using backlights or reflectors in the lighting system, can be formed. In this case, the optical laminate of the present invention can be provided on one or both sides of the liquid crystal cell. When optical laminates are provided on both sides, they can be the same or different. Furthermore, when forming the liquid crystal display device, one or more suitable components, such as diffuser plates, anti-glare layers, anti-reflective films, protective plates, prism arrays, lens arrays, light diffuser plates, and backlights, can be arranged at appropriate positions.

[0130] Example

[0131] The following describes embodiments of the present invention, but the implementation of the present invention is not limited to these.

[0132] <First Optical Film>

[0133] (Synthesis of fumarate resins)

[0134] In a 30L autoclave equipped with a stirrer, condenser, nitrogen inlet pipe, and thermometer, 48g of hydroxypropyl methylcellulose (Shin-Etsu Chemical, trade name METOLOSE 60SH-50), 15601g of distilled water, 8161g of diisopropyl fumarate, 240g of 3-ethyl-3-oxetanebutyl methyl acrylate, and 45g of tert-butyl peroxypentanoate as a polymerization initiator were added. After nitrogen bubbling for 1 hour, the mixture was stirred at 200 rpm and maintained at 49°C for 24 hours to carry out free radical suspension polymerization. The mixture was then cooled to room temperature, and the suspension containing the generated 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%).

[0135] The obtained fumarate resin was dissolved in a toluene / methyl ethyl ketone mixed solution (50% by weight / 50% by weight of toluene / methyl ethyl ketone) to prepare a 20% solution. Then, 5 parts by weight of tributyl trimellitate as a plasticizer were added to 100 parts by weight of the fumarate resin. The solution was then cast onto a support substrate (PET film) using a T-die method and dried at 80°C and 130°C for 4 minutes each, yielding a laminated film with a width of 250 mm and a thickness of 93 μm. The laminated film was then subjected to unidirectional stretching (longitudinal stretching process) at a temperature of 150°C and a stretch ratio of 1.04 times in the transport direction using a roller stretching machine, thereby manufacturing a laminated film with a first optical film (phase reversal film) stacked on the support substrate (PET film). The manufactured first optical film has a thickness of 18 μm and is a positive biaxial plate (nz > NX > ny) with a fast axis in the transport direction.

[0136] The fumarate resin film used in the first optical film (phase reversal film) manufactured above exhibits a tensile strength of 59.1 MPa in the MD direction (the direction in which the film is formed) and 55.0 MPa in the TD direction (the direction perpendicular to the MD direction). The tensile strength of the film was measured using samples cut into 10 mm wide sections according to JIS-K-7161.

[0137] The HSP values ​​of the fumarate resin film, calculated using the HSP value calculation method described later, are (δd 17.4, δp 4.5, δh 5.1).

[0138] <Second Optical Film>

[0139] The same film was manufactured using the same manufacturing method as the first optical film described above.

[0140] <Active Energy Rays>

[0141] As an active energy beam, a visible light (gallium-encased metal halide lamp) irradiation device was used: Excelitas Technologies, Corp. Light HAMMER10 Mark III, valve: V valve, peak illuminance: 1600 mW / cm². 2 Cumulative exposure dose 1000 mJ / cm 2 (Wavelength 380~440nm). It should be noted that the illuminance of visible light was measured using the Sola-Check system manufactured by Solatell.

[0142] Examples 1-7 and Comparative Examples 1-2

[0143] On both sides of the laminated film with the first optical film (phase retardation film) laminated on the support substrate (PET film) and the second optical film (phase retardation film) laminated on the support substrate (PET film), the adhesive composition adjusted to the proportions described in Tables 1-2 was applied using an MCD coating machine (manufactured by Fuji Machinery Co., Ltd.) (cell shape: honeycomb, gravure roller line count: 700 lines / inch, speed 140% / pair line speed) to achieve a final adhesive layer thickness of 1 μm, and then laminated using a roller press. The proportions in Tables 1-2 are expressed as mass% when the total amount of the composition excluding the initiator and sensitizer is set to 100% by mass. Then, the adhesive composition is cured by irradiating the support substrate (PET film) of the laminated film having the first optical film with visible light through an active energy irradiation device. The support substrate (PET film) is peeled off from the first optical film (phase difference film) of the laminated film, and then the support substrate (PET film) is peeled off from the second optical film (phase difference film) of the laminated film to obtain the laminated optical film.

[0144] The materials constituting the adhesive composition are described below. The method for calculating the average HSP value of the free radical polymerizable compounds (excluding oligomers) contained in the adhesive composition is explained later.

[0145] (polymeric oligomers)

[0146] • Polymerizable oligomer 1: A urethane (meth)acrylate with an intramolecular ether backbone (molecular weight 50,000, viscosity 200,000 Pa·s (25°C), number of polymerizable groups 2, trade name "PMH-101B", manufactured by Negami Kogyo Co., Ltd.)

[0147] • Polymerizable oligomer 2: urethane (meth)acrylate with an intramolecular ether backbone (molecular weight 19000, viscosity 9000 Pa·s (25°C), number of polymerizable groups 2, trade name "PMH-401B", manufactured by Negami Kogyo Co., Ltd.)

[0148] (polymerizable monomers)

[0149] • Polymerizable monomer 1: Carbamate acrylate (molecular weight 215, viscosity 15~35 Pa·s (25℃), number of polymerizable groups 1, trade name "KRM9276", manufactured by DAICL-ALLNEX)

[0150] (Oligomers that do not have polymerizable groups)

[0151] • Non-polymerizable oligomer 1: Acrylic polymer (molecular weight 1700, viscosity 6000 Pa·s (25°C), number of polymerizable groups 0, trade name "UP1190", manufactured by Toa Synthetic Co., Ltd.)

[0152] (Monofunctional free radical polymeric compounds)

[0153] • Phenoxyethyl methacrylate: (trade name "VISCOAT#192HP", manufactured by Osaka Organic Chemical Industry Co., Ltd.), HSP values ​​(δd 17.8, δp 5.0, δh 6.0)

[0154] • 4-tert-butylcyclohexyl acrylate: (trade name "TBCHA", manufactured by KJ Chemical Co., Ltd.), HSP values ​​(δd 16.2, δp 2.4, δh 3.2)

[0155] • Lauryl acrylate: (trade name "LA", manufactured by Osaka Organic Chemicals Co., Ltd.), HSP values ​​(δd 16.0, δp 2.4, δh 3.2)

[0156] • Phenoxydiethylene glycol acrylate: (trade name "LIGHT ACRYLATE P2H-A", manufactured by Kyoeisha Chemical Co., Ltd.), HSP values ​​(δd 17.5, δp 4.9, δh 6.2)

[0157] • Methyl acrylate (2-methyl-2-ethyl-1,3-dioxolane-4-yl): (trade name "MEDOL-10", manufactured by Osaka Organic Chemicals Co., Ltd.), HSP values ​​(δd 16.7, δp 5.2, δh 5.1)

[0158] • N-(2-Hydroxyethyl)acrylamide: (trade name "HEAA", manufactured by KJ Chemical Co., Ltd.), HSP values ​​(δd 18.3, δp 15.2, δh 15.7)

[0159] Acryloylmorpholine: (trade name "ACMO", manufactured by KJ Chemical Co., Ltd.), HSP values ​​(δd 18.5, δp 11.2, δh 5.8)

[0160] ·4-Vinylphenylboronic acid (compound represented by general formula (1): (manufactured by Pure Chemical Co., Ltd.), HSP value (δd 19.6, δp 6.9, δh 22.7)

[0161] • 4-Hydroxybutyl acrylate (a polymeric compound containing hydroxyl groups): (trade name "4HBA", manufactured by Mitsubishi Chemical Corporation), HSP values ​​(δd 16.7, δp 6.6, δh 10.8)

[0162] • m-Phenoxyphenyl acrylate: (trade name "LIGHT ACRYLATE POB-A", manufactured by Kyoeisha Chemical Co., Ltd.), HSP values ​​(δd 18.7, δp 3.8, δh 4.6)

[0163] (Multifunctional free radical polymeric compounds)

[0164] • 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 Kyoei Chemical Co., Ltd.), HSP values ​​(δd 16.6, δp 5.2, δh 6.8)

[0165] • Dimethyloltricyclodecane diacrylate: (trade name "LIGHT ACRYLATE DCP-A", manufactured by Kyoei Chemical Co., Ltd.), HSP values ​​(δd 17.1, δp 4.0, δh 4.1)

[0166] • Tripropylene glycol diacrylate: (trade name "ARONIX M-220", manufactured by Toa Synthetic Co., Ltd.), HSP values ​​(δd 16.3, δp 3.6, δh 5.3)

[0167] • 1,9-Nonanediol diacrylate: (trade name "LIGHT ACRYLATE 1,9ND-A", manufactured by Kyoeisha Chemical Co., Ltd.), HSP values ​​(δd 16.2, δp 3.3, δh 4.2)

[0168] (Initiator, sensitizer)

[0169] ·2-Methyl-4'-methylthio-2-morpholinophenylacetone: Trade name "Omnirad 907", manufactured by IGM Resins BV

[0170] ·2,4-Diethylthioxanone: Trade name "DETX-S", manufactured by Nippon Kayaku Co., Ltd.

[0171] <Method for calculating the average HSP value of free radical polymerizable compounds (excluding polymeric oligomers) contained in the adhesive composition>

[0172] The average HSP value of the free-radical polymerizable compounds (excluding polymerizable oligomers) contained in the adhesive composition is obtained by calculating the Hansen solubility parameter (HSP) for each free-radical polymerizable compound using the Y-MB method of Hansen Solubility Parameter in Practice (HSPiP), and taking the average corresponding to the molar ratio of each free-radical polymerizable compound in the composition.

[0173] <Calculation method of HSP value of optical film>

[0174] The above optical film was immersed in a mixed solvent of 9 solvents with different solubilities, acetone, ethyl acetate, trichlorobenzene, propylene carbonate, γ-butyrolactone, methyl ethyl ketone, diacetone alcohol, hexane, and methanol for 24 hours. The conditions of the optical film after 24 hours of immersion were classified into three grades: (1) dissolved, (2) swollen, and (3) insoluble. Based on the solubility information in each solvent obtained in this way, the Hansen solubility parameter (HSP value) was calculated using Hansen Solubility Parameter in Practice (HSPiP) ver.5.4.04 (http: / / www. hansen-solubility.com / index.php).

[0175] <Calculation method of HSP distance>

[0176] When the dispersion term of the Hansen solubility parameter of the above optical film is set as σd, the polar term is set as σp, the hydrogen bond term is set as σh, and the dispersion term of the Hansen solubility parameter of the free-radical polymerizable compound (excluding oligomers) contained in the adhesive composition is set as σAd, the polar term is set as σAp, and the hydrogen bond term is set as σAh, the following mathematical 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). The calculation was performed using the Hansen solubility parameters of the optical film and the adhesive composition calculated by the above method.

[0177] <Measurement method of liquid viscosity of adhesive composition>

[0178] The liquid viscosity was measured using a viscometer (manufactured by Toki Sangyo Co., Ltd., trade name "E-type viscometer: TV-22 type"). 1.1 mL of the adhesive was placed and set in the holder of the device, and the rotational speed was changed so that the TQ (torque) fell within the range of 20 to 80%. ​

[0179] <Method for determining the glass transition temperature of adhesive layers>

[0180] The glass transition temperature (Tg) was determined by measuring the cured film of the adhesive monomer using a dynamic viscoelasticity measuring device (TA Instruments, trade name "RSA-G2") under the following conditions, and the glass transition temperature (Tg) was obtained from the peak temperature of tanδ obtained from the measured dynamic viscoelasticity measurement results.

[0181] (Load Mode): Tension

[0182] (Heating rate): 5℃ / min

[0183] (Frequency): 1Hz

[0184] (Initial strain): 0.1%

[0185] <Method for determining the storage modulus of adhesive layers>

[0186] For the storage modulus, the storage modulus (E') at 25°C was measured using a dynamic viscoelasticity measuring device (TA Instruments, trade name "RSA-G2") under the following conditions.

[0187] (Load Mode): Tension

[0188] (Heating rate): 5℃ / min

[0189] (Frequency): 1Hz

[0190] (Initial strain): 0.1%

[0191] <Methods for determining the tensile modulus, elongation, and fracture stress of the adhesive layer>

[0192] The strain-stress curves were obtained by setting a cured film of the adhesive monomer in a tensile testing machine (Shimadzu Corporation's product name "Autograph AG-IS") and performing tensile testing under the following conditions.

[0193] (Test type): Tension

[0194] (Test speed): 30 mm / min

[0195] (Sample width): 10mm

[0196] (Distance between clamps): 10mm

[0197] <Method for determining the tensile strength of adhesive layers>

[0198] A cured film of the adhesive monomer was placed in a tensile testing machine (Shimadzu Corporation product name "Autograph AG-IS"), and the strain-stress curves obtained by stretching under the following conditions were measured based on JIS-K-7161.

[0199] (Test type): Tension

[0200] (Test speed): 30 mm / min

[0201] (Sample width): 10mm

[0202] (Distance between clamps): 10mm

[0203] (Methods for determining peel strength)

[0204] The obtained laminated optical film was cut to a size of 200mm × 15mm and then attached to a glass plate. A cut was then made between the first and second optical films using a cutting tool. Using an angle-free adhesive / film peeling analysis device "VPA-2" (manufactured by Kyowa Interface Chemical Co., Ltd.), the first and second optical films were peeled off at a 90-degree angle at a peeling speed of 5000mm / min, and their peel strength (N / 15mm) was measured.

[0205] (Evaluation methods for peeling morphology)

[0206] The peel morphology during the above peel strength determination was evaluated using the following method.

[0207] The infrared absorption spectrum of the peeled surface after peeling was measured using the ATR method. If both sides of the peeled surface are adhesive layers (including the compatibility layer between the first optical film and the adhesive layer), then it is considered "agglomeration failure of the adhesive layer (including the compatibility layer between the first optical film and the adhesive layer)". Since agglomeration failure of the first optical film is prevented, this is considered good. In Tables 1 to 5, the case of "agglomeration failure of the adhesive layer (including the compatibility layer between the first optical film and the adhesive layer)" is indicated by ○. On the other hand, if both sides of the peeled surface are the first optical film, then "agglomeration failure of the first optical film" occurs, which is considered undesirable. In Tables 1 to 5, "agglomeration failure of the first optical film" is indicated by ×.

[0208]

[0209]

Claims

1. A laminated optical film, wherein a first optical film and a second optical film are at least laminated together via an adhesive layer, wherein, Both the first optical film and the second optical film are resin films with a tensile strength of 70 or less. The adhesive layer is formed from a cured layer of an adhesive composition containing a free radical polymerizable compound, and its elongation during tensile modulus measurement is 3 mm or more and 50 mm or less. The distance between the average HSP value of the free radical polymerizable compound and the HSP values ​​of the first and second optical films is less than 3.

5.

2. The stacked optical film according to claim 1, wherein, The glass transition temperature of the adhesive layer is below 35°C.

3. The stacked optical film according to claim 1, wherein, The viscosity of the adhesive composition before curing is below 10 mPa·s.

4. The stacked optical film according to claim 1, wherein, The adhesive composition further contains polymeric oligomers having polymeric groups.

5. The stacked optical film according to claim 4, wherein, The polymeric oligomer is a urethane (meth) acrylate.

6. The stacked optical film according to claim 5, wherein, The urethane (meth)acrylate has an intramolecular ether backbone.

7. The stacked optical film according to claim 4, wherein, The polymeric oligomer does not have an aromatic or alicyclic backbone within its molecule.

8. The stacked optical film according to claim 1, wherein, The adhesive composition contains at least one free radical polymerizable compound selected from monofunctional free radical polymerizable compounds and polyfunctional free radical polymerizable compounds.

9. The stacked optical film according to claim 7, wherein, When the total amount of the free radical polymerizable compound in the adhesive composition is set to 100 parts by mass, the content of the multifunctional free radical polymerizable compound is less than 10 parts by mass.

10. The stacked optical film according to claim 1, wherein, The adhesive composition further comprises a monofunctional radical polymerizable compound represented by the following general formula (1): ， In the formula, X is a reactive group, Y is an alkylene group with 1 to 12 carbon atoms that is optionally branched, or a phenylene group that is optionally substituent, and R... 1 and R 2 Each can independently represent a hydrogen atom, an aliphatic hydrocarbon group with optional substituents, an aryl group, or a heterocyclic group.

11. The stacked optical film according to claim 1, wherein, The adhesive composition further contains a monofunctional free radical polymerizable compound having hydroxyl groups.

12. The stacked optical film according to claim 1, wherein, The tensile modulus of the adhesive layer is 1×10⁻⁶. 3 Pa or higher and 1×10 8 Below Pa.

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

14. The stacked 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 any one of claims 1 to 14.

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