Curable composition, polarizing film, optical film and image display device

Abstract

The present invention provides a curable composition containing a polythiol compound having two or more secondary thiol groups, a curable component, and a radical initiator, and a polarizing film in which an optical film is laminated on at least one surface of a polarizer with an adhesive layer interposed therebetween, the adhesive layer being a cured product layer of the curable composition. The content of the polythiol compound is preferably 0.5-10% by mass when the total amount of the composition is taken as 100% by mass. The content of the radical initiator is preferably 0.5-5 mass% when the total amount of the composition is taken as 100 mass%. If the content of the polythiol compound is a mass% and the content of the radical initiator is b mass%, a / b is preferably 0.5-10.

Description

Technical Field

[0001] The present invention relates to a curable composition and a polarizing film. The curable composition is a raw material for the adhesive layer of a polarizing film in which an optical film is laminated to at least one side of a polarizer via an adhesive layer. The polarizing film can be used alone or as a laminated optical film to form an image display device such as a liquid crystal display (LCD), an organic EL display, a CRT, or a PDP. Background Art

[0002] In recent years, image display devices have become thinner and more flexible, and along with this, the polarizing films used as their components have also become thinner. However, thinner polarizing films tend to experience a decrease in polarization degree in high-temperature and high-humidity environments, leading to deterioration in optical properties.

[0003] Patent Document 1 listed below describes a photocurable adhesive for polarizing plates containing a polythiol compound having two or more thiol groups in one molecule, a polyene compound having two or more carbon-carbon double bonds in one molecule, and a photopolymerization initiator.

[0004] The following patent document 2 describes a photocurable adhesive composition for bonding a polyvinyl alcohol-based polarizing film to a protective film. The photocurable adhesive composition comprises at least: (a) 50 to 99 weight percent of a hydroxyl-containing (meth) alkyl acrylate, (b) 0.5 to 10 weight percent of a photopolymerization initiator, and (c) 0.2 to 5 weight percent of a silane coupling agent selected from an acryloxy- or methacryloyloxy-containing silane coupling agent.

[0005] Prior art literature

[0006] Patent Literature

[0007] Patent Document 1: Japanese Patent Application Laid-Open No. 2005-139401

[0008] Patent Document 2: Japanese Patent Application Laid-Open No. 2010-18721 Summary of the Invention

[0009] Technical problem solved by the invention

[0010] The technology described in Patent Document 1 aims to provide a light-curing adhesive for polarizers that exhibits excellent adhesion and transparency between polarizers and light-transmitting components such as liquid crystal display units. Furthermore, the technology described in Patent Document 2 aims to improve productivity during polarizer manufacturing, reduce equipment and material costs, enhance adhesion, and increase the flexibility of the combination of protective films and the like. In other words, neither document describes or teaches the humidification reliability of the polarization characteristics of polarizing films.

[0011] The present invention has been developed in view of the above-mentioned actual situation, and an object of the present invention is to provide a curable composition serving as a raw material for a polarizing film having excellent humidity reliability of polarization characteristics, and a polarizing film having excellent humidity reliability of polarization characteristics.

[0012] Another object of the present invention is to provide an optical film using the polarizing film, and to provide an image display device using the polarizing film or the optical film.

[0013] Ways to solve the problem

[0014] The above-mentioned problems can be solved by the following constitution: That is, the present invention relates to a curable composition (1) comprising a polythiol compound having two or more secondary thiol groups, a curable component, and a radical initiator.

[0015] Among the curable composition (1), the curable composition (2) in which the radical initiator is a photopolymerization initiator is preferred.

[0016] In the curable composition (1) or (2), preferably, the curable composition (3) has a content of the polythiol compound of 0.5 to 10% by mass, based on 100% by mass of the total amount of the composition.

[0017] Among any of the curable compositions (1) to (3), the curable composition (4) is preferably a curable composition (4) in which the content of the radical initiator is 0.5 to 5% by mass when the total amount of the composition is 100% by mass.

[0018] Among the curable composition (4), preferably, the curable composition (5) is one in which, when the content of the polythiol compound is a% by mass and the content of the radical initiator is b% by mass, a / b is 0.5 to 100.

[0019] Among any of the curable compositions (1) to (5), the curable composition (6) is preferably an active energy ray-curable composition.

[0020] The present invention also relates to a polarizing film (7) comprising an optical film laminated on at least one side of a polarizer via an adhesive layer, wherein the adhesive layer is a cured product layer of any one of the curable compositions (1) to (6).

[0021] In the above-mentioned polarizing film (7), the polarizing film (8) in which the thickness of the above-mentioned polarizer is 7 μm or less is preferred.

[0022] In the above-mentioned polarizing film (7) or (8), it is preferable that the above-mentioned optical film is a polarizing film (9) in which the above-mentioned optical film is a transparent protective film.

[0023] In any one of the polarizing films (7) to (9), it is preferred that the optical film is a polarizing film (10) of a triacetyl cellulose resin film.

[0024] In any one of the polarizing films (7) to (10), it is preferred that the polarizer is a polarizing film (11) that is a polyvinyl alcohol-based film in which a dichroic dye is adsorbed and oriented.

[0025] In any one of the polarizing films (7) to (11), it is preferred that the polarizer is a polarizing film (12) that is a polyvinyl alcohol-based film in which iodine is adsorbed and oriented.

[0026] In addition, the present invention relates to an optical film (13), wherein at least one of the above-mentioned polarizing films (7) to (12) is laminated, and in addition, the present invention relates to an image display device (14), which uses any of the above-mentioned polarizing films (7) to (12) or the above-mentioned optical film (13).

[0027] Effects of the Invention

[0028] As mentioned above, as polarizing films become thinner, their polarization degree decreases in high-temperature, high-humidity environments, leading to a deterioration in optical properties. The curable composition of the present invention contains a polythiol compound having two or more secondary thiol groups, a curable component, and a free radical initiator. When this curable composition is used as a raw material for an adhesive layer used to laminate a polarizer and an optical film, the humidification reliability of the polarization properties of the polarizing film is improved. The reason for this effect is not yet clear, but it can be presumed as follows.

[0029] In order to achieve both excellent polarization characteristics and thinness, it is necessary to suppress the phenomenon of iodine shedding from the polarizer under high temperature and high humidity (hereinafter also referred to as "iodine shedding"). The present inventors have conducted in-depth research and found that when the curable composition is used as a raw material for the adhesive layer for laminating the polarizer and the optical film, the conversion rate (reaction rate) of the double bonds possessed by the curable component increases, thereby improving the curability and promoting the high molecular weight of the polymer constituting the adhesive layer, thereby suppressing the iodine shedding from the polarizer. Here, by making the curable composition of the present invention contain a polythiol compound having two or more secondary thiol groups in addition to the curable component and the free radical initiator, the humidification reliability of the polarization characteristics of the polarizing film is significantly improved. The reason is that the secondary thiol group possessed by the polythiol compound has a good balance of appropriate steric hindrance and acidity, so it does not damage the polarization characteristics of the polarizer. If it is a primary thiol group, the steric hindrance is small and the acidity is high, so it will damage the polarization characteristics of the polarizer under high temperature and high humidity.

[0030] As described above, the polarizing film of the present invention comprises an optical film laminated on at least one side of a polarizer via an adhesive layer. When the adhesive layer is a cured layer of the curable composition, the wetted reliability of the polarization characteristics of the polarizing film is improved. In particular, in the present invention, the wetted reliability of the polarization characteristics of the polarizing film is particularly improved when the polarizer thickness is 7 μm or less. The reason for this effect is not clear, but it can be presumed as follows.

[0031] Polarizers with a thickness of 7 μm or less (hereinafter also referred to as "thin polarizers") necessarily require a high iodine concentration to maintain polarization properties. Consequently, iodine is prone to iodine shedding under high temperature and high humidity conditions due to the influence of moisture intruding into the polarizer. However, when the curable composition serving as the raw material for the adhesive layer contains a polythiol compound having two or more secondary thiol groups in addition to a curable component and a free radical initiator, iodine shedding from the polarizer can be suppressed, allowing the high iodine concentration in the thin polarizer to be maintained. Consequently, the humidification reliability of the polarization properties of the polarizing film is significantly improved. DETAILED DESCRIPTION

[0032] The curable composition of the present invention contains a polythiol compound having two or more secondary thiol groups, a curable component, and a radical initiator.

[0033] The polythiol compound only needs to have two or more secondary thiol groups. Examples of compounds having two secondary thiol groups include 1,4-bis(3-mercaptobutyryloxy)butane, 2,3-butanedithiol, and meso-2,3-dimercaptosuccinic acid. Examples of compounds having three secondary thiol groups include trimethylolpropane tris(3-mercaptobutyrate) and 1,3,5-tris(2-(3-mercaptobutyryloxy)ethyl)-1,3,5-triazine-2,4,6-trione. Examples of compounds having four secondary thiol groups include pentaerythritol tetrakis(3-mercaptobutyrate).

[0034] From the viewpoint of improving the humidification reliability of the polarization characteristics of the polarizing film, the content of the polythiol compound is preferably 0.1 to 20 mass %, more preferably 0.5 to 10 mass %, based on 100 mass % of the total amount of the composition.

[0035] It should be noted that polythiol compounds having two or more secondary thiol groups can be used in combination with a radical initiator, particularly a photopolymerization initiator, to improve the curability of the curable component without impairing the polarization properties of the polarizer, and to increase the molecular weight of the polymer constituting the adhesive layer. In the curable composition of the present invention, particularly the active energy ray-curable composition, when the content of the polythiol compound is a% by mass and the content of the radical initiator, particularly the photopolymerization initiator, is b% by mass, a ratio of a / b of 0.5 to 10 is particularly advantageous, and therefore preferred.

[0036] The curable composition of the present invention contains a free radical initiator. The curable composition of the present invention is preferably an active energy ray-curable composition that is cured by irradiation with active energy rays. The active energy ray-curable composition preferably contains a photopolymerization initiator as the free radical initiator. The amount of the free radical initiator, particularly the photopolymerization initiator, is preferably 0.1 to 10% by mass, and more preferably 0.5 to 5% by mass, based on 100 parts by mass of the total active energy ray-curable composition.

[0037] The photopolymerization initiator is appropriately selected according to the active energy ray. In the case of curing by ultraviolet light or visible light, a photopolymerization initiator that is cleaved by ultraviolet light or visible light can be used. As the above-mentioned photopolymerization initiator, for example, benzophenone compounds such as benzil, benzophenone, benzoylbenzoic acid, 3,3'-dimethyl-4-methoxybenzophenone; aromatic ketone compounds such as 4-(2-hydroxyethoxy)phenyl(2-hydroxy-2-propyl)ketone, α-hydroxy-α, α'-dimethylacetophenone, 2-methyl-2-hydroxypropiophenone, α-hydroxycyclohexylphenylketone; acetophenone compounds such as methoxyacetophenone, 2,2-dimethoxy-2-phenylacetophenone, 2,2-diethoxyacetophenone, 2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropane-1-one; benzoin methyl ether , benzoin ether compounds such as benzoin ethyl ether, benzoin isopropyl ether, benzoin butyl ether, and anisole methyl ether; aromatic ketal compounds such as benzil dimethyl ketal; aromatic sulfonyl chloride compounds such as 2-naphthalenesulfonyl chloride; photoactive oxime compounds such as 1-phenyl-1,1-propanedione-2-(o-ethoxycarbonyl)oxime; thioxanthone compounds such as thioxanthone, 2-chlorothioxanthone, 2-methylthioxanthone, 2,4-dimethylthioxanthone, isopropylthioxanthone, 2,4-dichlorothioxanthone, 2,4-diethylthioxanthone, 2,4-diisopropylthioxanthone, and dodecylthioxanthone; camphorquinone; haloketones; acylphosphine oxides; acylphosphonates, etc.

[0038] When using an active energy ray-curable composition as a visible light-curable composition, it is particularly preferred to use a photopolymerization initiator that is highly sensitive to light of 380 nm or longer.

[0039] As the photopolymerization initiator, it is preferred to use a compound represented by the following general formula (3) alone, or to use the compound represented by the general formula (3) in combination with a photopolymerization initiator having high sensitivity to light of 380 nm or longer, which will be described later.

[0040] [Chemical Formula 1]

[0041]

[0042] (Where R 7 and R 8 Represents -H, -CH2CH3, -iPr or Cl, R 7 and R 8 can be the same or different).

[0043] Compared with the case where a photopolymerization initiator having high sensitivity to light of 380 nm or more is used alone, the case where the compound represented by the general formula (3) is used has excellent adhesiveness. 7 and R 8 The compound represented by the general formula (3) in the active energy ray-curable composition is preferably present in an amount of 0.1 to 4% by mass, more preferably 0.5 to 3% by mass, based on 100% by mass of the total amount of the curable composition.

[0044] In addition, it is preferred to add a polymerization initiation aid as needed. Examples of the polymerization initiation aid include triethylamine, diethylamine, N-methyldiethanolamine, ethanolamine, 4-dimethylaminobenzoic acid, methyl 4-dimethylaminobenzoate, ethyl 4-dimethylaminobenzoate, and isoamyl 4-dimethylaminobenzoate, with ethyl 4-dimethylaminobenzoate being particularly preferred. When a polymerization initiation aid is used, the amount added is preferably 0.1 to 3 parts by mass, more preferably 0.3 to 1 part by mass, based on 100 parts by mass of the total amount of the active energy ray-curable composition.

[0045] In addition, known photopolymerization initiators can be used in combination as needed. The optical functional layer and substrate film with UV absorption ability do not transmit light below 380nm. Therefore, as a photopolymerization initiator, a photopolymerization initiator with high sensitivity to light above 380nm is preferably used. Specifically, 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-morpholinyl)phenyl]-1-butanone, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide, bis(η5-2,4-cyclopentadien-1-yl)bis(2,6-difluoro-3-(1H-pyrrol-1-yl)phenyl)titanium, etc. can be listed.

[0046] The curable composition of the present invention contains a curable component. The curable composition of the present invention is preferably an active energy ray-curable composition. Active energy ray-curable compositions can be divided into free radical polymerization curable compositions and cationic polymerization curable compositions. In the present invention, active energy rays with a wavelength range of 10 nm or more and less than 380 nm can be expressed as ultraviolet rays, and active energy rays with a wavelength range of 380 nm to 800 nm can be expressed as visible light.

[0047] Examples of the curable component constituting the radical polymerization curable composition include compounds represented by the following general formula (2).

[0048] [Chemical Formula 2]

[0049]

[0050] (Where R 4 is a hydrogen atom or a methyl group, R 5 and R 6 are independently a hydrogen atom, an alkyl group, a hydroxyalkyl group, an alkoxyalkyl group or a cyclic ether group, and R 5 and R 6 optionally forming a cyclic heterocycle).

[0051] The number of carbon atoms in the alkyl group, hydroxyalkyl group, and / or alkoxyalkyl group is not particularly limited, and examples thereof include 1 to 4. 5 and R 6 Examples of the cyclic heterocycle that may be formed include N-acryloylmorpholine.

[0052] Specific examples of the compound represented by general formula (2) include: (meth)acrylamide derivatives containing N-alkyl groups such as N-methyl(meth)acrylamide, N,N-dimethyl(meth)acrylamide, N,N-diethyl(meth)acrylamide, N-isopropyl(meth)acrylamide, N-butyl(meth)acrylamide, and N-hexyl(meth)acrylamide; (meth)acrylamide derivatives containing N-hydroxyalkyl groups such as N-hydroxymethyl(meth)acrylamide, N-hydroxyethyl(meth)acrylamide, and N-hydroxymethyl-N-propyl(meth)acrylamide; and (meth)acrylamide derivatives containing N-alkoxy groups such as N-methoxymethylacrylamide and N-ethoxymethylacrylamide. Examples of cyclic ether group-containing (meth)acrylamide derivatives include heterocyclic (meth)acrylamide derivatives in which the nitrogen atom of the (meth)acrylamide group forms a heterocyclic ring, such as N-acryloylmorpholine, N-acryloylpiperidine, N-methacryloylpiperidine, and N-acryloylpyrrolidine. Among these, N-hydroxyethylacrylamide and N-acryloylmorpholine are preferably used due to their excellent reactivity, ability to produce a cured product with a high elastic modulus, and excellent adhesion to polarizers.

[0053] From the viewpoint of improving the adhesion and water resistance between the polarizer and the adhesive layer, and particularly from the viewpoint of improving the adhesion and water resistance when the polarizer is bonded to the transparent protective film via the adhesive layer, the content of the compound represented by the general formula (2) in the curable composition is preferably 10 to 80% by mass, more preferably 20 to 60% by mass.

[0054] The curable composition used in the present invention may contain, in addition to the compound represented by general formula (2), other monofunctional radical polymerizable compounds as curable components. Examples of the monofunctional radical polymerizable compounds include various (meth)acrylic acid derivatives having a (meth)acryloyloxy group. Specific examples include alkyl (meth)acrylates (having 1 to 20 carbon atoms) such as methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, 2-methyl-2-nitropropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, sec-butyl (meth)acrylate, t-butyl (meth)acrylate, n-pentyl (meth)acrylate, t-pentyl (meth)acrylate, 3-pentyl (meth)acrylate, 2,2-dimethylbutyl (meth)acrylate, n-hexyl (meth)acrylate, hexadecyl (meth)acrylate, n-octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, 4-methyl-2-propylpentyl (meth)acrylate, and n-octadecyl (meth)acrylate.

[0055] Examples of the (meth)acrylic acid derivatives include cycloalkyl (meth)acrylates such as cyclohexyl (meth)acrylate and cyclopentyl (meth)acrylate; aralkyl (meth)acrylates such as benzyl (meth)acrylate; polycyclic (meth)acrylates such as 2-isobornyl (meth)acrylate, 2-norbornylmethyl (meth)acrylate, 5-norbornyl-2-ylmethyl (meth)acrylate, 3-methyl-2-norbornylmethyl (meth)acrylate, dicyclopentenyl (meth)acrylate, dicyclopentenyloxyethyl (meth)acrylate, and dicyclopentanyl (meth)acrylate; and alkoxy- or phenoxy-containing (meth)acrylates such as 2-methoxyethyl (meth)acrylate, 2-ethoxyethyl (meth)acrylate, 2-methoxymethoxyethyl (meth)acrylate, 3-methoxybutyl (meth)acrylate, ethyl carbitol (meth)acrylate, phenoxyethyl (meth)acrylate, and alkylphenoxypolyethylene glycol (meth)acrylate. Among them, dicyclopentenyloxyethyl acrylate and phenoxyethyl acrylate are preferred because of their excellent adhesion to various protective films.

[0056] Examples of the (meth)acrylic acid derivatives include hydroxyalkyl (meth)acrylates such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 8-hydroxyoctyl (meth)acrylate, 10-hydroxydecyl (meth)acrylate, and 12-hydroxylauryl (meth)acrylate; hydroxyl-containing (meth)acrylates such as [4-(hydroxymethyl)cyclohexyl]methyl acrylate, cyclohexanedimethanol mono(meth)acrylate, and 2-hydroxy-3-phenoxypropyl (meth)acrylate; epoxy-containing (meth)acrylates such as glycidyl (meth)acrylate and 4-hydroxybutyl (meth)acrylate glycidyl ether; 2,2,2-trifluoroethyl (meth)acrylate, and (meth)acrylate; Halogen-containing (meth)acrylates such as 2,2,2-trifluoroethyl ethyl (meth)acrylate, tetrafluoropropyl (meth)acrylate, hexafluoropropyl (meth)acrylate, octafluoropentyl (meth)acrylate, heptadecafluorodecyl (meth)acrylate, and 3-chloro-2-hydroxypropyl (meth)acrylate; alkylaminoalkyl (meth)acrylates such as dimethylaminoethyl (meth)acrylate; oxetanyl group-containing (meth)acrylates such as 3-oxetanylmethyl (meth)acrylate, 3-methyloxetanylmethyl (meth)acrylate, 3-ethyloxetanylmethyl (meth)acrylate, 3-butyloxetanylmethyl (meth)acrylate, and 3-hexyloxetanylmethyl (meth)acrylate; (meth)acrylates having a heterocyclic ring such as tetrahydrofurfuryl (meth)acrylate and butyrolactone (meth)acrylate, hydroxypivalic acid neopentyl glycol (meth)acrylate adduct, and p-phenylphenol (meth)acrylate. Among them, 2-hydroxy-3-phenoxypropyl acrylate is preferred because of its excellent adhesion to various protective films.

[0057] Examples of the monofunctional radical polymerizable compound include carboxyl group-containing monomers such as (meth)acrylic acid, carboxyethyl acrylate, carboxypentyl acrylate, itaconic acid, maleic acid, fumaric acid, crotonic acid, and isocrotonic acid.

[0058] Examples of monofunctional free radical polymerizable compounds include lactam vinyl monomers such as N-vinylpyrrolidone, N-vinyl-ε-caprolactam, and methylvinylpyrrolidone; vinylpyridine, vinylpiperidone, vinylpyrimidine, vinylpiperazine, vinylpyrazine, vinylpyrrole, vinylimidazole, and vinyl vinyl monomers having nitrogen-containing heterocyclic rings such as oxazole and vinylmorpholine.

[0059] In addition, as a monofunctional free radical polymerizable compound, a free radical polymerizable compound having an active methylene group can be used. A free radical polymerizable compound having an active methylene group is a compound having an active double bond group such as a (meth)acrylic acid group at the end or in the molecule and having an active methylene group. Examples of the active methylene group include acetoacetyl, alkoxymalonyl, or cyanoacetyl. The above-mentioned active methylene group is preferably an acetoacetyl group. Specific examples of radically polymerizable compounds having an active methylene group include acetoacetoxyalkyl (meth)acrylates such as 2-acetoacetoxyethyl (meth)acrylate, 2-acetoacetoxypropyl (meth)acrylate, and 2-acetoacetoxy-1-methylethyl (meth)acrylate; 2-ethoxymalonyloxyethyl (meth)acrylate, 2-cyanoacetoxyethyl (meth)acrylate, N-(2-cyanoacetoxyethyl)acrylamide, N-(2-propionylacetoxybutyl)acrylamide, N-(4-acetoacetoxymethylbenzyl)acrylamide, and N-(2-acetoacetylaminoethyl)acrylamide. The radically polymerizable compound having an active methylene group is preferably an acetoacetoxyalkyl (meth)acrylate.

[0060] As the curable component constituting the radical polymerization curable composition, a polyfunctional radical polymerizable compound having two or more functional groups may be blended. Examples of the polyfunctional radical polymerizable compound include N,N'-methylenebis(meth)acrylamide as a polyfunctional (meth)acrylamide derivative, tripropylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, 1,9-nonanediol di(meth)acrylate, 1,10-decanediol diacrylate, 2-ethyl-2-butylpropylene glycol 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, tricyclodecane dimethanol di(meth)acrylate, cyclic trimethylolpropane formal(meth)acrylate, dimethacrylate. Ester compounds of (meth)acrylic acid and polyols such as alkylene glycol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol penta(meth)acrylate, dipentaerythritol hexa(meth)acrylate, and EO-modified diglycerol tetra(meth)acrylate; and 9,9-bis[4-(2-(meth)acryloyloxyethoxy)phenyl]fluorene. Specific examples include ARONIX M-220 (manufactured by Toagosei Co., Ltd.), LIGHT ACRYLATE 1,9ND-A (manufactured by Kyoeisha Chemical Co., Ltd.), LIGHT ACRYLATE DGE-4A (manufactured by Kyoeisha Chemical Co., Ltd.), LIGHT ACRYLATE DCP-A (manufactured by Kyoeisha Chemical Co., Ltd.), SR-531 (manufactured by Sartomer Co., Ltd.), and CD-536 (manufactured by Sartomer Co., Ltd.). In addition, as needed, examples include various epoxy (meth)acrylates, urethane (meth)acrylates, polyester (meth)acrylates, and various (meth)acrylate monomers. It should be noted that polyfunctional (meth)acrylamide derivatives are preferably included in the curable composition because they not only have a fast polymerization rate and excellent productivity, but also have excellent crosslinking properties when the resin composition is converted into a cured product.

[0061] From the perspective of both adhesion to polarizers and various transparent protective films and optical durability under harsh environments, the radical polymerizable compound is preferably used in combination with a monofunctional radical polymerizable compound and a polyfunctional radical polymerizable compound. The amount of the monofunctional radical polymerizable compound in the curable composition is preferably 20% to 90% by mass, more preferably 30% to 60% by mass. The amount of the polyfunctional radical polymerizable compound in the curable composition is preferably 10% to 80% by mass, more preferably 40% to 70% by mass.

[0062] The curable composition of the present invention may contain a compound represented by the following general formula (1).

[0063] [Chemical Formula 3]

[0064]

[0065] (wherein, X is a reactive group, Y is an alkylene group having 1 to 12 carbon atoms and optionally having a branch, or a phenylene group having an optionally substituted group, R 1 and R 2(respectively independently represent a hydrogen atom, an aliphatic hydrocarbon group optionally having a substituent, an aryl group or a heterocyclic group). As the above-mentioned aliphatic hydrocarbon group, there can be listed a straight-chain or branched alkyl group having 1 to 20 carbon atoms, an alkyl group having 3 to 20 carbon atoms, an alkenyl group having 2 to 20 carbon atoms, as an aryl group, there can be listed a phenyl group having 6 to 20 carbon atoms, an naphthyl group having 10 to 20 carbon atoms, etc., which can be optionally substituted. As a heterocyclic group, there can be listed, for example, a group of a 5-membered ring or a 6-membered ring containing at least one heteroatom, which can be optionally substituted. They can be linked to each other to form a ring. In the general formula (1), as R 1 and R 2 , preferably a hydrogen atom, a linear or branched alkyl group having 1 to 3 carbon atoms, and most preferably a hydrogen atom.

[0066] X in the compound represented by general formula (1) is a reactive group, which is a functional group capable of reacting with a curable component constituting the cured layer, particularly the adhesive layer, and examples thereof include hydroxyl, amino, aldehyde, carboxyl, vinyl, (meth)acryloyl, styryl, (meth)acrylamide, vinyl ether, epoxy, oxetane, α,β-unsaturated carbonyl, mercapto, and halogen groups. When the curable composition constituting the cured product layer, particularly the adhesive layer, is active energy ray-curable, the reactive group X is preferably at least one reactive group selected from a vinyl group, a (meth)acryloyl group, a styryl group, a (meth)acrylamide group, a vinyl ether group, an epoxy group, an oxetanyl group, and a mercapto group. When the curable composition constituting the cured product layer, particularly the adhesive layer, is free radical polymerizable, the reactive group X is preferably at least one reactive group selected from a (meth)acryloyl group, a styryl group, and a (meth)acrylamide group. When the compound represented by general formula (1) has a (meth)acrylamide group, the reactivity is high, and the copolymerization rate with the curable component in the cured product layer, particularly the adhesive layer, is increased, which is more preferable. In addition, the (meth)acrylamide group has high polarity and excellent adhesion, and therefore is also preferred from the perspective of efficiently achieving the effects of the present invention. When the curable composition constituting the cured product layer, particularly the adhesive layer, is cationically polymerizable, the reactive group X preferably has at least one functional group selected from the group consisting of a hydroxyl group, an amino group, an aldehyde group, a carboxyl group, a vinyl ether group, an epoxy group, an oxetanyl group, and a mercapto group. In particular, when the reactive group X has an epoxy group, the resulting cured product layer, particularly the adhesive layer, exhibits excellent adhesion to the adherend, which is preferred. In particular, when the reactive group X has a vinyl ether group, the curable composition exhibits excellent curability, which is preferred.

[0067] Preferred specific examples of the compound represented by the general formula (1) include the following compounds (1a) to (1d).3 is a hydrogen atom or a methyl group.

[0068] [Chemical Formula 4]

[0069]

[0070] Examples of the compound represented by the general formula (1) include, in addition to the compounds exemplified above, esters of (meth)acrylates and boric acid, such as esters of hydroxyethylacrylamide and boric acid, esters of hydroxymethylacrylamide and boric acid, esters of hydroxyethyl acrylate and boric acid, and esters of hydroxybutyl acrylate and boric acid.

[0071] In the present invention, the curable composition may include an acrylic oligomer obtained by polymerizing a (meth)acrylic monomer. Including an acrylic oligomer in the curable composition can reduce curing shrinkage when the composition is irradiated with active energy rays and cured, thereby reducing the interfacial stress between the adhesive layer and adherends such as the optically functional layer and the substrate film. As a result, it is possible to suppress a reduction in the adhesion between the adhesive layer and the adherend.

[0072] Considering workability and uniformity during coating, the active energy ray-curable composition preferably has a low viscosity. Therefore, the acrylic oligomer obtained by polymerizing (meth)acrylic monomers also preferably has a low viscosity. The low-viscosity acrylic oligomer, which can prevent cure shrinkage of the adhesive layer, preferably has a weight-average molecular weight (Mw) of 15,000 or less, more preferably 10,000 or less, and particularly preferably 5,000 or less. On the other hand, to fully suppress cure shrinkage of the cured product layer (adhesive layer), the weight-average molecular weight (Mw) of the acrylic oligomer is preferably 500 or greater, more preferably 1000 or greater, and particularly preferably 1500 or greater.Specific examples of the (meth)acrylic monomer constituting the acrylic oligomer include methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, 2-methyl-2-nitropropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, sec-butyl (meth)acrylate, t-butyl (meth)acrylate, n-pentyl (meth)acrylate, t-pentyl (meth)acrylate, 3-pentyl (meth)acrylate, 2,2-dimethylbutyl (meth)acrylate, n-hexyl (meth)acrylate, and t-butyl (meth)acrylate. (Meth)acrylate (carbon number 1-20) alkyl esters such as cetyl (meth)acrylate, n-octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, 4-methyl-2-propylpentyl (meth)acrylate, and n-octadecyl (meth)acrylate, and cycloalkyl (meth)acrylates (such as cyclohexyl (meth)acrylate and cyclopentyl (meth)acrylate), aralkyl (meth)acrylates (such as benzyl (meth)acrylate), polycyclic (meth)acrylates (such as 2-isobornyl (meth)acrylate and 2-isobornyl (meth)acrylate), and cyclopentyl (meth)acrylate. Bornyl methyl ester, 5-norbornen-2-ylmethyl (meth)acrylate, 3-methyl-2-norbornylmethyl (meth)acrylate, etc.), hydroxyl-containing (meth)acrylates (e.g., hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2,3-dihydroxypropylmethylbutyl (meth)acrylate, etc.), alkoxy- or phenoxy-containing (meth)acrylates (2-methoxyethyl (meth)acrylate, 2-ethoxyethyl (meth)acrylate, 2-methoxymethoxyethyl (meth)acrylate, 3-methoxybutyl (meth)acrylate, ) ethyl carbitol (meth)acrylate, phenoxyethyl (meth)acrylate, etc.), epoxy-containing (meth)acrylates (such as glycidyl (meth)acrylate, etc.), halogen-containing (meth)acrylates (such as 2,2,2-trifluoroethyl (meth)acrylate, 2,2,2-trifluoroethyl ethyl (meth)acrylate, tetrafluoropropyl (meth)acrylate, hexafluoropropyl (meth)acrylate, octafluoropentyl (meth)acrylate, heptadecafluorodecyl (meth)acrylate, etc.), alkylaminoalkyl (meth)acrylates (such as dimethylaminoethyl (meth)acrylate, etc.). These (meth)acrylates can be used alone or in combination of two or more. Specific examples of the acrylic oligomer (E) include "ARUFON" manufactured by Toagosei Co., Ltd., "ACTFLOW" manufactured by Soken Chemical Co., Ltd., and "JONCRYL" manufactured by BASF Japan Ltd.

[0073] The curable composition used in the present invention may contain a silane coupling agent. Specific examples of the silane coupling agent include active energy ray-curable compounds such as vinyltrichlorosilane, vinyltrimethoxysilane, vinyltriethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3-glycidoxypropyltriethoxysilane, p-phenylyltrimethoxysilane, 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, 3-methacryloxypropyltriethoxysilane, and 3-acryloxypropyltrimethoxysilane.

[0074] Preferred are 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, and 3-glycidoxypropyltriethoxysilane.

[0075] Specific examples of the non-active energy ray-curable silane coupling agents other than those mentioned above include 3-ureidopropyltriethoxysilane, 3-chloropropyltrimethoxysilane, 3-mercaptopropylmethyldimethoxysilane, 3-mercaptopropyltrimethoxysilane, bis(triethoxysilylpropyl)tetrasulfide, 3-isocyanatepropyltriethoxysilane, and imidazole silane.

[0076] The curable composition used in the present invention may be a cationic polymerization curable composition. Cationic polymerizable compounds used in cationic polymerization curable compositions can be classified into monofunctional cationic polymerizable compounds having one cationic polymerizable functional group in the molecule and polyfunctional cationic polymerizable compounds having two or more cationic polymerizable functional groups in the molecule. Monofunctional cationic polymerizable compounds have a low liquid viscosity, so by including them in a cationic polymerization curable composition, the liquid viscosity can be reduced. In addition, monofunctional cationic polymerizable compounds often have functional groups that exhibit various functions. By including them in a cationic polymerization curable composition, the cationic polymerization curable composition and / or the cured product of the cationic polymerization curable composition can exhibit various functions. Polyfunctional cationic polymerizable compounds can cause the cured product of the cationic polymerization curable composition to undergo three-dimensional crosslinking, so they are preferably included in a cationic polymerization curable composition. With respect to the ratio of monofunctional cationic polymerizable compounds to polyfunctional cationic polymerizable compounds, it is preferred that the polyfunctional cationic polymerizable compounds be mixed in an amount ranging from 10 parts by mass to 1000 parts by mass relative to 100 parts by mass of the monofunctional cationic polymerizable compounds. Examples of the cationically polymerizable functional group include epoxy groups, oxetanyl groups, and vinyl ether groups. Examples of compounds having an epoxy group include aliphatic epoxy compounds, alicyclic epoxy compounds, and aromatic epoxy compounds. The cationically polymerizable resin composition of the present invention preferably contains an alicyclic epoxy compound from the perspective of excellent curability and adhesion. Examples of the alicyclic epoxy compound include 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate, caprolactone-modified products of 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate, trimethylcaprolactone-modified products, and valerolactone-modified products. Specific examples include CELLOXIDE 2021, CELLOXIDE 2021A, CELLOXIDE 2021P, CELLOXIDE 2081, CELLOXIDE 2083, and CELLOXIDE 2085 (all manufactured by Daicel Chemical Industries, Ltd.), Cyracure UVR-6105, Cyracure UVR-6107, Cyracure 30, and R-6110 (all manufactured by Dow Chemical Japan Ltd.). A compound having an oxetane group is preferably contained because it has the effect of improving the curability of the cationically polymerizable resin composition and reducing the liquid viscosity of the composition.Examples of the compound having an oxetane group 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 novolac oxetane. Commercially available compounds include ARON OXETANE OXT-101, ARON OXETANE OXT-121, ARON OXETANE OXT-211, ARON OXETANE OXT-221, and ARON OXETANE OXT-212 (all manufactured by Toagosei Co., Ltd.). Compounds having a vinyl ether group are preferably present because they have the effects of improving the curability of the cationically polymerizable resin composition and reducing the liquid viscosity of the composition. Examples of the compound having a vinyl ether group include 2-hydroxyethyl vinyl ether, diethylene glycol monovinyl ether, 4-hydroxybutyl vinyl ether, diethylene glycol monovinyl ether, triethylene glycol divinyl ether, cyclohexanedimethanol divinyl ether, cyclohexanedimethanol monovinyl ether, tricyclodecane vinyl ether, cyclohexyl vinyl ether, methoxyethyl vinyl ether, ethoxyethyl vinyl ether, and pentaerythritol tetravinyl ether.

[0077] The cationic polymerization curable composition contains at least one compound selected from the compounds having epoxy groups, compounds having oxetane groups, and compounds having vinyl ether groups as curable components. They are all substances that are cured by cationic polymerization, so they can be combined with a photocationic polymerization initiator. The photocationic polymerization initiator generates cationic species or Lewis acids by irradiation with active energy rays such as visible light, ultraviolet rays, X-rays, and electron beams, thereby initiating the polymerization reaction of epoxy groups and oxetane groups. As the photocationic polymerization initiator, it is preferred to use a photoacid generator described later. In addition, when using a cationic polymerizable resin composition with visible light curability, it is particularly preferred to use a photocationic polymerization initiator with high sensitivity to light above 380nm. However, the photocationic polymerization initiator is a compound that generally shows maximum absorption in a wavelength region near 300nm or shorter than 300nm. Therefore, by combining a photosensitizer that shows maximum absorption in a wavelength region longer than it, specifically, light with a wavelength longer than 380nm, it can sense light of a wavelength near it and promote the generation of cationic species or acid from the photocationic polymerization initiator. As photosensitizer, for example: anthracene compounds, pyrene compounds, carbonyl compounds, organic sulfur compounds, persulfides, redox compounds, azo and diazo compounds, halogen compounds, photoreduction pigments etc. can be enumerated, and they can also be mixed with two or more kinds of use. In particular, anthracene compounds have excellent photosensitizing effects, and thus preferably, Anthracure UVS-1331 and Anthracure UVS-1221 (Kawasaki Chemicals Co., Ltd.) can be specifically enumerated. The content of photosensitizer is preferably 0.1% by mass to 5% by mass, more preferably 0.5% by mass to 3% by mass.

[0078] In the present invention, the active energy ray-curable composition may contain a photoacid generator. When the active energy ray-curable composition contains a photoacid generator, the water resistance and durability of the adhesive layer can be significantly improved. The photoacid generator can be represented by the following general formula (4).

[0079] General formula (4)

[0080] [Chemical Formula 5]

[0081]

[0082] (Where, L + Indicates any In addition, X - Indicates selection from PF66 - 、SbF6 - 、AsF6 - 、SbCl6 - 、BiCl5 - 、SnCl6 -、ClO4 - , dithiocarbamate anion, and counter anion in SCN-.)

[0083] Next, the counter anion X in the general formula (4) - Provide explanation.

[0084] In principle, the counter anion X in the general formula (4) - There are no particular limitations, but non-nucleophilic anions are preferred. When the counter anion X is a non-nucleophilic anion, it is not easy to cause nucleophilic reactions of coexisting cations in the molecule or various materials used in combination, thereby improving the temporal stability of the photoacid generator represented by the general formula (4) itself and the composition using the same. The non-nucleophilic anion referred to here refers to an anion with a low ability to cause nucleophilic reactions. Examples of such anions include PF6 - 、SbF6 - 、AsF6 - 、SbCl6 - 、BiCl5 - 、SnCl6 - 、ClO4 - 、B(C6H5)4 - , dithiocarbamate anion, SCN - wait.

[0085] Specifically, preferred examples of the photoacid generator of the present invention include: "CYRACURE UVI-6992", "CYRACURE UVI-6974" (all manufactured by DOW CHEMICAL JAPAN), "Adeka Optomer SP150", "Adeka Optomer SP152", "Adeka Optomer SP170", "Adeka Optomer SP172" (all manufactured by ADEKA), "Omnicat 250" (manufactured by IGM Resins BV), "CI-5102", "CI-2855" (all manufactured by Nippon Soda Co., Ltd.), "San-Aid SI-60L", "San-Aid SI-80L", "San-Aid SI-100L", "San-Aid SI-110L", "San-Aid SI-180L" (all manufactured by Sanshin Chemical Co., Ltd.), "IK-1", "CPI-100P", "CPI-101A", "CPI-110P", "CPI-200K", "CPI-210S", "CPI-310B", "CPI-410B", "CPI-410S" (all manufactured by SAN-APRO), "WPI-069", "WPI-113", "WPI-116", "WPI-041", "WPI-044", "WPI-054", "WPI-055", "WPAG-281", "WPAG-567", "WPAG-596" (all manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.).

[0086] The polarizing film of the present invention is a polarizing film in which an optical film is laminated on at least one surface of a polarizer via an adhesive layer, and the adhesive layer is a cured product layer of the curable composition.

[0087] From the viewpoint of improving the humidification reliability of the polarization characteristics of the polarizing film, the thickness of the cured product layer (adhesive layer) is preferably 0.5 μm or more and 5.0 μm or less.

[0088] In the present invention, the polarizer is not particularly limited, and various polarizers can be used. Examples of polarizers include those obtained by adsorbing and aligning a dichroic dye, particularly iodine, on a hydrophilic polymer film such as a polyvinyl alcohol film, a partially formalized polyvinyl alcohol film, or a partially saponified ethylene-vinyl acetate copolymer film. Of these, a polyvinyl alcohol film on which a dichroic dye is adsorbed and oriented is preferred, and a polyvinyl alcohol film on which iodine is adsorbed and oriented is more preferred. The thickness of the polarizer is, for example, 3 to 20 μm.

[0089] In the present invention, a thin polarizer with a thickness of 3 μm to 15 μm is preferably used to improve humidification reliability in harsh environments of high temperature and high humidity. A thickness of 12 μm or less is particularly preferred, 10 μm or less is even more preferred, and 7 μm or less is particularly preferred. Such a thin polarizer has minimal thickness variation, excellent visual recognition, and minimal dimensional change, resulting in excellent durability against thermal shock.

[0090] In the present invention, an adhesive layer in contact with a thin polarizer having a thickness of 7 μm or less, a high iodine density, and a high risk of iodine shedding is formed using a cured layer of a curable composition containing, in addition to a curable component and a photopolymerization initiator, a polythiol compound having two or more secondary thiol groups. This prevents iodine shedding from the polarizer, maintaining a high iodine concentration within the thin polarizer. Consequently, the humidification reliability of the polarization characteristics of the polarizing film is significantly improved.

[0091] Polarizers made by dyeing a polyvinyl alcohol film with iodine and then uniaxially stretching it can be made, for example, by immersing the polyvinyl alcohol in an aqueous solution of iodine for dyeing and stretching it to 3 to 7 times its original length. Alternatively, the film can be immersed in an aqueous solution of boric acid, zinc sulfate, zinc chloride, or potassium iodide, as needed. Furthermore, the film can be rinsed by immersing it in water before dyeing, as needed. Rinsing the film not only cleans stains and anti-blocking agents from the film's surface but also prevents uneven dyeing by causing the film to swell. Stretching can be performed after dyeing with iodine, while dyeing, or after dyeing with iodine. Stretching can also be performed in an aqueous solution of boric acid, potassium iodide, or a water bath.

[0092] From the perspectives of tensile stability and humidification reliability, the polarizer preferably contains boric acid. Furthermore, from the perspective of suppressing the occurrence of through-cracks, the boric acid content in the polarizer is preferably 22% by mass or less, more preferably 20% by mass or less, relative to the total amount of the polarizer. From the perspectives of tensile stability and humidification reliability, the boric acid content is preferably 10% by mass or more, more preferably 12% by mass or more, relative to the total amount of the polarizer.

[0093] Representative 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, International Publication No. 2014 / 077636, and the like, or thin polarizers obtained by the production methods described in these documents.

[0094] As the thin polarizer, in a production method comprising a step of stretching a laminate and a step of dyeing, a thin polarizer obtained by a production method comprising a step of stretching in a boric acid aqueous solution as described in Japanese Patent Nos. 4751486, 4751481, and 4815544 is preferred from the viewpoint of being able to stretch to a high ratio and thus improving polarization performance. Particularly preferred is a thin polarizer obtained by a production method comprising a step of supplementary stretching in an air atmosphere before stretching in a boric acid aqueous solution as described in Japanese Patent Nos. 4751481 and 4815544. These thin polarizing films can be obtained by a production method comprising a step of stretching a polyvinyl alcohol-based resin (hereinafter also referred to as PVA-based resin) layer and a stretching resin substrate in a laminate and a step of dyeing. According to this production method, even if the PVA-based resin layer is thin, it can be stretched without causing problems such as breakage due to stretching because it is supported by the stretchable resin substrate.

[0095] As an optical film constituting the polarizing film, for example, a transparent protective film can be cited. As a material constituting the transparent protective film, for example, a thermoplastic resin having excellent transparency, mechanical strength, thermal stability, moisture barrier properties, isotropy, etc. can be used. Specific examples of such thermoplastic resins include cellulose resins such as cellulose triacetate resin films, 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. Regarding the polarizing film of the present invention, a cellulose triacetate resin film is preferably used. In the case of a polarizing film in which a cellulose triacetate resin film is laminated on at least one side of the polarizer via an adhesive layer, the cellulose triacetate resin film has high moisture permeability and poor wet heat durability, so there is a tendency for the humidification reliability of the polarization characteristics of the polarizing film to deteriorate. However, in the polarizing film of the present invention, an adhesive layer is formed by a cured layer of a curable composition containing a polythiol compound having two or more secondary thiol groups, a curable component, and a free radical initiator. Therefore, even when the polarizing film has a cellulose triacetate resin film, the humidification reliability of the polarization characteristics of the polarizing film is improved, and thus it is preferred. The transparent protective film may contain one or more appropriate additives. As additives, for example, there can be listed: ultraviolet absorbers, antioxidants, lubricants, plasticizers, release agents, anti-coloring agents, flame retardants, nucleating agents, antistatic agents, pigments, colorants, etc. The content of the above-mentioned thermoplastic resin in the transparent protective film is preferably 50 to 100% by weight, more preferably 50 to 99% by weight, further preferably 60 to 98% by weight, and particularly preferably 70 to 97% by weight. When the content of the above-mentioned thermoplastic resin in the transparent protective film is less than 50% by weight, there is a hidden danger that the high transparency originally possessed by the thermoplastic resin cannot be fully exhibited.

[0096] In addition, as a material for forming the transparent protective film, a material having excellent transparency, mechanical strength, thermal stability, moisture barrier properties, isotropy, etc. is preferred, and a moisture permeability of 150 g / m 2 / 24h or less, particularly preferably 140g / m 2 / 24h or less, more preferably 120g / m 2 / Less than 24 hours

[0097] A functional layer such as a hard coating layer, an anti-reflection layer, an anti-blocking layer, a diffusion layer, or an anti-glare layer may be provided on the side of the transparent protective film that is not bonded to the polarizer. It should be noted that the functional layers such as the hard coating layer, the anti-reflection layer, the anti-blocking layer, the diffusion layer, and the anti-glare layer may be provided as a layer other than the transparent protective film itself or as a separate layer from the transparent protective film.

[0098] The thickness of the transparent protective film can be appropriately determined. Generally, from the perspectives of strength, workability such as handling, and thinness, it is about 1 to 500 μm, preferably 1 to 300 μm, more preferably 5 to 200 μm, further preferably 10 to 200 μm, and even more preferably 20 to 80 μm.

[0099] As the transparent protective film, a retardation film having a front retardation of 40 nm or more and / or a thickness direction retardation of 80 nm or more can be used. The front retardation is usually controlled to be in the range of 40 to 200 nm, and the thickness direction retardation is usually controlled to be in the range of 80 to 300 nm. When a retardation film is used as a transparent protective film, it also functions as a transparent protective film, thereby enabling thinning.

[0100] Examples of retardation films include birefringent films made by uniaxially or biaxially stretching a polymer material, oriented films of liquid crystal polymers, and films supporting an oriented layer of liquid crystal polymers. The thickness of the retardation film is also not particularly limited, but is typically around 20 to 150 μm.

[0101] As the retardation film, a reverse wavelength dispersion type retardation film satisfying the following formulas (1) to (3) can be used.

[0102] 0.70 <Re

[450] / Re

[550] <0.97···(1)

[0103] 1.5×10 -3 <Δn<6×10 -3 ···(2)

[0104] 1.13<NZ<1.50···(3)

[0105] (Wherein, Re

[450] and Re

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

[0106] The polarizing film of the present invention may be provided with a retardation layer. The retardation layer may be a single layer or a multilayer, and the retardation layer may also serve as a protective layer for the polarizer.

[0107] In the formation of the phase difference layer, a liquid crystal compound is preferably used, and a solution containing the liquid crystal compound can be applied using, for example, a wire rod, a slit coater, a comma coater, a gravure coater, a slit die, etc. At this time, the liquid crystal solution after coating can be dried naturally or heated and dried. It should be noted that the liquid crystal solution is preferably applied at a concentration lower than the isotropic phase-liquid crystal phase transition concentration, i.e., in the isotropic phase state. In this case, it can be stably oriented by methods such as friction treatment and photo-orientation.

[0108] The polarizing film of the present invention can be produced, for example, by the following production method.

[0109] A method for producing a polarizing film, comprising laminating an optical film onto at least one side of a polarizer via an adhesive layer, wherein the adhesive layer is a cured layer of a curable composition comprising a polythiol compound having two or more secondary thiol groups, a curable component, and a photopolymerization initiator. The method comprises: a coating step of coating the curable composition onto one or both of the laminating surfaces of the polarizer and the laminating surface of a transparent protective film; a laminating step of laminating the polarizer and the optical film; and a bonding step of irradiating the polarizer surface or the optical film surface with active energy rays to cure the curable composition to form an adhesive layer, and bonding the polarizer and the optical film via the adhesive layer. Each step is described below.

[0110] As the method for applying curable composition, can suitably select according to the viscosity of composition, target thickness, for example, can enumerate: reverse coater, gravure coater (directly, reversely or offset plate), rod reverse coater, roller coater, die coater, wire rod coater and rod coater etc.The viscosity of curable composition is preferably 3~100mPa·s, more preferably 5~50mPa·s, most preferably 10~30mPa·s.When the viscosity of composition is high, the surface smoothness after coating is not enough, and outward appearance is bad, thus not preferred.Therefore, each composition can be heated or cooled and the viscosity adjusted to preferred range is coated.

[0111] It should be noted that the polarizer and / or optical film may be subjected to a surface modification treatment before the coating process. It is particularly preferred to perform a surface modification treatment on the polarizer. Examples of surface modification treatments include corona treatment, plasma treatment, and ITRO treatment, with corona treatment being particularly preferred. Corona treatment generates reactive functional groups such as carbonyl and amino groups on the polarizer surface, improving adhesion to the adhesive layer. Furthermore, ashing can be used to remove foreign matter from the surface or reduce surface irregularities, thereby producing a polarizing film with excellent appearance characteristics.

[0112] The polarizer and the optical film are bonded together using a roll laminator or the like via the curable composition applied as described above (bonding step).

[0113] After laminating the polarizer and the optical film, the curable composition is cured by irradiation with active energy rays (electron beam, ultraviolet light, visible light, etc.) to form an adhesive layer. The irradiation direction of the active energy rays (electron beam, ultraviolet light, visible light, etc.) can be any appropriate direction.

[0114] The irradiation conditions under the electron beam irradiation condition can be any appropriate conditions as long as they are conditions that can cure the above-mentioned curable composition. For example, the acceleration voltage of the electron beam irradiation is preferably 5kV~300kV, more preferably 10kV~250kV. When the acceleration voltage is less than 5kV, there is a hidden danger that the electron beam cannot reach the adhesive and causes insufficient curing. If the acceleration voltage exceeds 300kV, there is a hidden danger that the penetration force through the sample is too strong and damages the polarizer and the transparent protective film. As the irradiation dose, it is 5~100kGy, more preferably 10~75kGy. When the irradiation dose is less than 5kGy, the adhesive is not cured enough. If it is greater than 100kGy, the optical functional layer and the base film will be damaged, resulting in a reduction in mechanical strength and yellowing, and it is impossible to obtain the given optical properties.

[0115] Electron beam irradiation is typically performed in an inert gas atmosphere, but can be performed in the atmosphere with a small amount of oxygen introduced, if necessary. While this depends on the materials of the polarizer and transparent protective film, the appropriate introduction of oxygen actively creates an oxygen barrier on the optically functional layer and substrate film surface, where the electron beam is initially irradiated. This prevents damage to the polarizer and transparent protective film, allowing efficient electron beam irradiation to target only the adhesive.

[0116] In the case of manufacturing the polarizing film of the present invention, as the active energy ray, it is preferred to use active energy rays containing visible light in the wavelength range of 380nm~450nm, especially active energy rays with the largest irradiation amount of visible light in the wavelength range of 380nm~450nm. When ultraviolet rays, visible light, and a transparent protective film endowed with ultraviolet absorption ability (ultraviolet non-transmissive transparent protective film) are used, light with a wavelength shorter than about 380nm is absorbed. Therefore, light with a wavelength shorter than 380nm does not reach the curable composition and does not contribute to its polymerization reaction. In addition, light with a wavelength shorter than 380nm absorbed by the polarizer or the transparent protective film is converted into heat, and the polarizer or the transparent protective film itself generates heat, which causes adverse conditions such as curling / wrinkling of the polarizing film. Therefore, in the present invention, when ultraviolet rays or visible light are used, it is preferred to use a device that does not emit light with a wavelength shorter than 380 nm as the active energy ray generating device. More specifically, the ratio of the cumulative illuminance in the wavelength range of 380 to 440 nm to the cumulative illuminance in the wavelength range of 250 to 370 nm is preferably 100:0 to 100:50, more preferably 100:0 to 100:40. When manufacturing the polarizing film of the present invention, as active energy rays, metal halide lamps enclosed with gallium or LED light sources emitting light in the wavelength range of 380 to 440 nm are preferred. Alternatively, a light source containing ultraviolet rays and visible light, such as a low-pressure mercury lamp, a medium-pressure mercury lamp, a high-pressure mercury lamp, an ultra-high-pressure mercury lamp, an incandescent lamp, a xenon lamp, a halogen lamp, a carbon arc lamp, a metal halide lamp, a fluorescent lamp, a tungsten lamp, a gallium lamp, an excimer laser, or sunlight, can be used. Ultraviolet rays with wavelengths shorter than 380 nm can also be blocked using a bandpass filter. In order to improve the bonding performance of the adhesive layer between the polarizer and the transparent protective film and prevent curling of the polarizing film, it is preferred to use a metal halide lamp encapsulated with gallium, and use active energy rays obtained by a bandpass filter that can block light with a wavelength shorter than 380 nm, or active energy rays with a wavelength of 405 nm obtained using an LED light source.

[0117] When producing the polarizing film of the present invention on a continuous production line, the line speed varies depending on the curing time of the curable composition, but is preferably 1 to 500 m / min, more preferably 5 to 300 m / min, and even more preferably 10 to 100 m / min. If the line speed is too low, productivity may be insufficient, or damage to the polarizer or transparent protective film may be excessive, making it impossible to produce a polarizing film that can withstand durability tests, etc. If the line speed is too high, the curable composition may not cure sufficiently, and the desired adhesion may not be achieved.

[0118] An adhesive layer for bonding to other components such as a liquid crystal cell may be provided on the polarizing film or a laminated optical film having at least one polarizing film layered thereon. The adhesive forming the adhesive layer is not particularly limited; for example, an adhesive having a base polymer such as an acrylic polymer, silicone polymer, polyester, polyurethane, polyamide, polyether, fluorine-based polymer, or rubber-based polymer can be appropriately selected. Acrylic adhesives are particularly preferred, as they offer excellent optical transparency, exhibit appropriate adhesive properties such as wettability, cohesiveness, and adhesion, and possess excellent weather resistance and heat resistance.

[0119] The adhesive layer can be provided on one or both sides of the polarizing film or optical film as a laminate of layers having different compositions or types. Furthermore, when provided on both sides, adhesive layers having different compositions, types, thicknesses, etc. can be formed on the front and back sides of the polarizing film or optical film. The thickness of the adhesive layer can be appropriately determined depending on the intended use, adhesive strength, etc., and is generally 1 to 500 μm, preferably 1 to 200 μm, and particularly preferably 1 to 100 μm.

[0120] For the exposed surface of the adhesive layer, a diaphragm is temporarily bonded to cover it until it is actually used in order to prevent contamination. This prevents contact with the adhesive layer under normal handling conditions. As a diaphragm, in addition to the above-mentioned thickness conditions, a diaphragm can be used, which is obtained by coating a suitable thin layer such as a plastic film, a rubber sheet, paper, a cloth, a non-woven fabric, a net, a foam sheet, a metal foil, or a laminate thereof with a suitable release agent such as silicone, long-chain alkyl, fluorine, or molybdenum sulfide as needed, and other suitable diaphragms previously specified.

[0121] The polarizing film and optical film of the present invention can be preferably used to form various devices such as liquid crystal displays. Liquid crystal displays can be formed using conventional methods. Specifically, a liquid crystal display is typically formed by appropriately assembling a liquid crystal cell with a polarizing film or optical film, and optionally, components such as a lighting system, and incorporating a drive circuit. In the present invention, there are no particular limitations other than using the polarizing film or optical film of the present invention, and conventional methods can be used. Liquid crystal cells of any type, such as TN, STN, or π, can be used.

[0122] A suitable liquid crystal display device such as a liquid crystal display device in which an optical laminate is arranged on one side or both sides of a liquid crystal cell, a liquid crystal display device in which a backlight or a reflector is used in a lighting system, etc. can be formed. In this case, the optical laminate of the present invention can be arranged on one side or both sides of the liquid crystal cell. When optical laminates are arranged on both sides, they can be the same or different. Furthermore, when forming the liquid crystal display device, suitable components such as a diffusion plate, an anti-glare layer, an anti-reflection film, a protective plate, a prism array, a lens array sheet, a light diffusion plate, a backlight, etc., can be arranged at an appropriate position.

[0123] Example

[0124] Examples of the present invention will be described below, but the embodiments of the present invention are not limited thereto.

[0125] Polarizer

[0126] A laminate comprising a 9 μm thick PVA layer formed on an amorphous PET substrate was subjected to auxiliary stretching in an atmosphere at a stretching temperature of 130°C to produce a stretched laminate. The stretched laminate was then dyed to produce a colored laminate. The colored laminate was further stretched in a boric acid aqueous solution at a stretching temperature of 65°C to a total stretch ratio of 5.94 times, integrally with the amorphous PET substrate, to produce an optical film laminate comprising a 5 μm thick PVA layer. This produced an optical film laminate comprising a 5.5 μm thick PVA layer constituting a thin polarizer. The thin polarizer was characterized by high-order orientation of the PVA molecules in the PVA layer formed on the amorphous PET substrate through the two-stage stretching described above, and high-order orientation of the iodine adsorbed by the dyeing in the form of a polyiodide ion complex in one direction.

[0127] <Optical Film (Transparent Protective Film)>

[0128] Optical film 1: Cellulose triacetate resin film (trade name "KC2UA", manufactured by Konica Minolta Co., Ltd.)

[0129] <Active Energy Rays>

[0130] Visible light (gallium-encapsulated metal halide lamp) was used as the active energy ray. Irradiation device: Light HAMMER 10 manufactured by Fusion UV Systems, Inc. Bulb: V bulb Peak illuminance: 1600 mW / cm 2 , cumulative exposure 1000 / mJ / cm 2 (Wavelength: 380 to 440 nm) The illuminance of visible light was measured using a Sola-Check system manufactured by Solatell.

[0131] (Preparation of Curable Composition)

[0132] Curable compositions of Examples 1 to 7 and Comparative Examples 1 and 2 were prepared according to the formulations shown in Table 1. The numerical values in the table represent weight % when the total amount of each composition is taken as 100 mass %.

[0133] The materials constituting the curable composition are shown below.

[0134] (Polythiol compound)

[0135] Pentaerythritol tetrakis(3-mercaptobutyrate): Trade name "Karenz MT-PE1", manufactured by Showa Denko K.K.

[0136] 1,4-Bis(3-mercaptobutyryloxy)butane: Trade name "Karenz MT-BD1", manufactured by Showa Denko K.K.

[0137] (Curing component)

[0138] N-Acryloylmorpholine (compound represented by general formula (2)): trade name "ACMO", manufactured by KOHJIN Corporation

[0139] Tripropylene glycol diacrylate: Trade name "TPGDA", manufactured by Toagosei Co., Ltd.

[0140] (Initiator)

[0141] Bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide: Trade name "Omnirad 819", manufactured by IGM Resins B.V.

[0142] (Manufacturing of Polarizing Film)

[0143] Examples 1-7 and Comparative Examples 1-2

[0144] Using an MCD coater (manufactured by Fuji Machine Co., Ltd.) (cell shape: honeycomb, gravure roll line count: 1000 lines / inch, rotation speed 140% relative to line speed), the effective resin composition listed in Table 1 was applied to the bonding surface of the transparent protective film 1 (coating step). Subsequently, the transparent optical film 1 and the optical film laminate with a thin polarizer were bonded together from the coated side using a roller machine (bonding step). The bonded transparent protective film was then irradiated with visible light using an active energy ray irradiation device to cure the curable composition, thereby forming an adhesive layer. The thin polarizer and the transparent protective film were then bonded together via this adhesive layer. The amorphous PET substrate of the optical film laminate was then peeled off.

[0145] <Humidification Reliability Evaluation of Polarization Characteristics of Polarizing Film>

[0146] Polarizing films prepared in Examples 1-7 and Comparative Examples 1-2 were bonded to one side of a 0.7 mm thick alkali-free glass sheet via an adhesive layer (20 μm thick) (samples for humidity durability testing). Using these samples, a humidity reliability test of polarization characteristics was conducted in an environment of 85°C and 85% humidity. Details of the humidity reliability test are shown below.

[0147] The resulting polarizing film was exposed to an environment at 85°C and 85% humidity for 120 hours. The polarization degree before and after exposure was measured using a spectrophotometer with an integrating sphere (JASCO Corporation V7100). The change in polarization degree, ΔPz(%), was calculated as |(polarization degree before exposure(%)) - (polarization degree after exposure(%))|. A smaller change in polarization degree, ΔPz(%), indicates greater humidification reliability of the polarization characteristics in a harsh humidification environment.

[0148] <Evaluation of Curability of Adhesive Layer>

[0149] Double-sided tape (No. 500, manufactured by Nitto Denko Corporation) was applied to the PVA surface of the polarizing film obtained by the above-described manufacturing method. Furthermore, a 200 mm section parallel to the stretching direction of the polarizing film and a 15 mm section perpendicular to the stretching direction of the polarizing film was cut. A slit was made between the polarizing film and the transparent protective film using a cutter. The release film of the double-sided tape was then peeled off, and the adhesive surface was attached to a glass plate. The polarizing film and transparent protective film were peeled off, and the transparent protective film side after peeling was measured using FT-IR (ATR method). If only a peak from the TAC film was detected, a value of ○ was assigned; if a peak from the adhesive component was detected, cohesive failure of the adhesive occurred, and this value was assigned as ×.

[0150]

[0151] The results in Table 1 indicate that the polarizing films of Examples 1 to 7 exhibit excellent humidification reliability of their polarization characteristics. Furthermore, the adhesive layer exhibits excellent curability, indicating excellent durability and reliability as polarizing films. On the other hand, the polarizing film of Comparative Example 1 fails to suppress iodine shedding under high temperature and humidity conditions, indicating poor humidification reliability. It should be noted that the polarizing film of Comparative Example 2 exhibits insufficient curability, resulting in poor peel strength of the adhesive layer, indicating poor durability and reliability.

Claims

1. A curable composition comprising: a polythiol compound having two or more secondary thiol groups, a curable component, and a radical initiator.

2. The curable composition according to claim 1, wherein The free radical initiator is a photopolymerization initiator.

3. The curable composition according to claim 1 or 2, wherein When the total amount of the composition is 100% by mass, the content of the polythiol compound is 0.5 to 10% by mass.

4. The curable composition according to any one of claims 1 to 3, wherein When the total amount of the composition is 100% by mass, the content of the radical initiator is 0.5 to 5% by mass.

5. The curable composition according to claim 4, wherein When the content of the polythiol compound is a% by mass and the content of the radical initiator is b% by mass, a / b is 0.5 to 10.

6. The curable composition according to any one of claims 1 to 5, wherein The curable composition is an active energy ray-curable composition.

7. A polarizing film comprising an optical film laminated on at least one side of a polarizer via an adhesive layer, The adhesive layer is a cured product layer of the curable composition according to any one of claims 1 to 6.

8. The polarizing film according to claim 7, wherein The thickness of the polarizer is less than 7 μm.

9. The polarizing film according to claim 7 or 8, wherein The optical film is a transparent protective film.

10. The polarizing film according to any one of claims 7 to 9, wherein The optical film is a cellulose triacetate resin film.

11. The polarizing film according to any one of claims 7 to 10, wherein The polarizer is a polyvinyl alcohol-based film on which a dichroic dye is adsorbed and oriented.

12. The polarizing film according to any one of claims 7 to 11, wherein The polarizer is a polyvinyl alcohol film on which iodine is adsorbed and oriented. 13 . An optical film comprising at least one laminated polarizing film according to claim 7 . 14 . An image display device using the polarizing film according to claim 7 or the optical film according to claim 13 .

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