JP2021155514A - Active energy ray-curable adhesive composition, adhesive composition for polarizing plate, and adhesive for polarizing plate and polarizing plate using the same - Google Patents

Abstract

To provide: an active energy ray-curable adhesive composition which has excellent adhesivity, is suitable for bonding various protective films for polarizing plates and a polarizer, and has excellent durability such as thermal shock resistance and the like; an adhesive composition for a polarizing plate, an adhesive for a polarizing plate and a polarizing plate formed by using the same.SOLUTION: Provided is an active energy ray-curable adhesive composition, comprising an oxetane compound (A), an epoxy compound (B) having an alicyclic structure, and a silane coupling agent (C), where, relative to a total of 100 pts.wt. of (A), (B), and (C) components, a content of the oxetane compound (A) is 35-65 pts.wt. and a content of the silane coupling agent (C) is 10 pts.wt. or more.SELECTED DRAWING: None

Description

The present invention relates to an active energy ray-curable adhesive composition, a polarizing plate adhesive composition, a polarizing plate adhesive, and a polarizing plate using the same. More specifically, the present invention is used for a liquid crystal display device or the like. The present invention relates to an active energy ray-curable adhesive composition suitable for bonding a polarizing element constituting a polarizing plate to a polarizing plate and a protective film.

Liquid crystal display devices are widely used as image display devices for liquid crystal televisions, computer displays, mobile phones, digital cameras, and the like. Such a liquid crystal display device has a configuration in which polarizing plates are laminated on both sides of a glass substrate in which a liquid crystal is enclosed, and various optical functional films such as a retardation plate are laminated on the polarizing plates as needed.

Conventionally, a polarizing plate has been used as a configuration in which a protective film is bonded to at least one surface, preferably both surfaces of a polarizing element made of a polyvinyl alcohol-based film.
Here, as the polarizing element, a polyvinyl alcohol-based resin having a high degree of saponification (hereinafter, polyvinyl alcohol is abbreviated as "PVA") is used to form a film, and a PVA-based film formed of a bicolor property such as iodine is contained. A uniaxially stretched PVA-based film in which the material is dispersed and adsorbed and preferably further crosslinked with a cross-linking agent such as boric acid is widely used. Since such a polarizer is a uniaxially stretched PVA-based film, it easily shrinks under high humidity, and therefore, a protective film is attached to the polarizer for the purpose of supplementing moisture resistance and strength.

As such a protective film, a thermoplastic resin such as a cellulose resin, a polycarbonate resin, a cyclic polyolefin resin, a (meth) acrylic resin, and a polyester resin is transparent, mechanical strength, thermal stability, moisture blocking property, isotropic property, etc. In particular, a protective film made of a triacetyl cellulose (TAC) resin has been widely used.

These protective films are bonded to the polarizer by an adhesive, and the adhesive is similar to a PVA-based resin aqueous solution, particularly a polarizer, from the viewpoint of adhesiveness to a polarizer having a hydrophilic surface. A PVA-based resin aqueous solution mainly composed of a PVA-based resin having a high degree of saponification is preferably used.

By the way, in recent years, there has been a demand for thinning the polarizing plate, and instead of the triacetyl cellulose (TAC) film, which has been most commonly used as a protective film, acrylic is also used from the viewpoint of the durability of the polarizing plate. Based films, cyclic olefin resin (COP) films, and polyester (PET) films have come to be used. However, it is difficult for the protective film that replaces these triacetyl cellulose (TAC) films to be firmly bonded to the polarizer with the conventional water-based PVA-based adhesive, or in the first place, these protective films are permeable to moisture. Since it is extremely low, there is a problem that it cannot be used because water cannot be removed in the drying process after bonding. Therefore, various adhesives suitable for bonding protective films such as acrylic films, cyclic olefin resin (COP) films, and polyester (PET) films have been developed.

For example, Patent Document 1 proposes a photocurable adhesive composition containing an epoxy compound as a main component and a four-membered cyclic compound having two or more oxygen atoms in a specific ratio. And since the composition shows good adhesiveness particularly in the adhesiveness between a triacetyl cellulose (TAC) base material and a polarizer, and also shows good durability even in an environment of 60 ° C. and 90% RH. It is described that a polarizing plate in which protective films are bonded to both sides of a practical polarizing element can be provided.

Japanese Unexamined Patent Publication No. 2013-043952

However, in recent years, the usage environment of polarizing plates has diversified, and instead of polarizing plates using TAC films with high moisture permeability, higher moist heat using protective films such as COP films, PET films, and acrylic films with low moisture permeability has been used. Although a durable polarizing plate is desired, the adhesive composition of Patent Document 1 is not sufficiently satisfactory in terms of adhesive strength and durability depending on the type of protective film and the like.

Therefore, in the present invention, under such a background, it is an adhesive having excellent adhesive strength, suitable for bonding various protective films for polarizing plates and a polarizer, and also has moisture heat resistance and heat impact resistance. The present invention provides an active energy ray-curable adhesive composition having excellent durability, an adhesive composition for a polarizing plate, an adhesive for a polarizing plate, and a polarizing plate using the same.

However, as a result of intensive studies in view of such circumstances, the present inventors have been active in containing an oxetane compound (A), an epoxy compound having an alicyclic structure (B), and a silane coupling agent (C). In an energy ray-curable adhesive composition, various protective films for polarizing plates and a polarizer are attached by containing a specific amount of the oxetane compound (A) and a larger amount of the silane coupling agent (C) than usual. The present invention has been completed by finding that an adhesive having excellent durability such as moisture and heat resistance and thermal shock resistance can be obtained while having good adhesiveness.

That is, the gist of the present invention is an active energy ray-curable adhesive composition containing an oxetane compound (A), an epoxy compound (B) having an alicyclic structure, and a silane coupling agent (C). The content of the oxetane compound (A) is 35 to 65 parts by weight, and the content of the silane coupling agent (C) is 100 parts by weight in total of the components (A), (B), and (C). It is an active energy ray-curable adhesive composition characterized by having 10 parts by weight or more.

Further, the present invention relates to an adhesive composition for a polarizing plate using such an active energy ray-curable adhesive composition, an adhesive for a polarizing plate made of a cured product of an adhesive composition for a polarizing plate, and an adhesive for a polarizing plate. Also provided is a polarizing plate in which a polarizer and a protective film are bonded to each other via an agent.

The active energy ray-curable adhesive composition of the present invention contains an oxetane compound (A), an epoxy compound having an alicyclic structure (B), and a silane coupling agent (C). In the adhesive composition, the content of the oxetane compound (A) is 35 to 65 parts by weight with respect to a total of 100 parts by weight of the components (A), (B) and (C), and the silane coupling agent ( An active energy ray-curable adhesive composition having a content of C) of 10 parts by weight or more. Therefore, various protective films for polarizing plates and a polarizer can be sufficiently adhered to each other, and a polarizing plate having excellent durability can be obtained.

Hereinafter, the present invention will be described in detail, but these are examples of desirable embodiments.

The active energy ray-curable adhesive composition of the present invention (hereinafter, may be abbreviated as an adhesive composition) includes an oxetane compound (A), an epoxy compound (B) having an alicyclic structure, and a silane coupling. It contains the agent (C). Hereinafter, each component of the adhesive composition will be described in order.

<Oxetane compound (A)>
The oxetane compound (A) used in the present invention may be a compound having one or more oxetanyl groups in the molecule.
Examples of the oxetane compound (A) include 3-ethyl-3-hydroxymethyloxetane, 3-ethyl-3-[(2-ethylhexyloxymethyl)] oxetane, 3-ethyl-3- (phenoxymethyl) oxetane, 3 Oxetane groups in molecules such as -ethyl-3- (cyclohexyloxymethyl) oxetane, 3-ethyl-3- (oxylanylmethoxy) oxetane, and (meth) acrylic acid (3-ethyloxetane-3-yl) methyl. One oxetane compound;
3-Ethyl-3 {[(3-ethyloxetane-3-yl) methoxy] methyl} oxetane, 1,4-bis [(3-ethyl-3-oxetanyl) methoxymethyl] benzene, 4,4'-bis [ (3-Ethyl-3-oxetanyl) Oxetane compound having two or more oxetanyl groups in the molecule such as methoxymethyl] biphenyl;
And so on. These oxetane compounds (A) can be used alone or in combination of two or more.

Among them, 3-ethyl-3-hydroxymethyloxetane and 1,4-bis [(3-ethyl-3-oxetanyl) are easy to obtain, dilute (low viscosity), and have excellent compatibility. ) Ethylmethyl] benzene, 3-ethyl-3-[(2-ethylhexyloxymethyl)] oxetane, 3-ethyl-3- (oxylanylmethoxy) oxetane, (meth) acrylic acid (3-ethyloxetane-3-3) Il) methyl, 3-ethyl-3 {[(3-ethyloxetane-3-yl) methoxy] methyl} oxetane and the like are preferably used.

Further, from the viewpoint of coatability, adhesiveness, and curability, a liquid having a molecular weight of 500 or less at room temperature is preferable, and from the viewpoint of excellent curability and durability, two or more compounds are contained in the molecule without containing a hydroxyl group. Oxetane compounds containing an oxetane group are particularly preferred, with 1,4-bis [(3-ethyl-3-oxetanyl) methoxymethyl] benzene, 3-ethyl-3 {[(3-ethyloxetane-3-yl) methoxy]. Methyl} oxetane is more preferred, and 3-ethyl-3 {[(3-ethyloxetane-3-yl) methoxy] methyl} oxetane is particularly preferred in view of adhesive yellowing during durability.

Specific examples of the oxetane compound (A) include commercially available products Aron Oxetane OXT-101, Aron Oxetane OXT-121, Aron Oxetane OXT-411, Aron Oxetane OXT-212, Aron Oxetane OXT-213, and Aron Oxetane OXT. -221 (both manufactured by Toagosei Co., Ltd.) can be used. In particular, Aron Oxetane OXT-221 is preferable.

The content of the oxetane compound (A) needs to be 35 to 65 parts by weight, preferably 37.5 to 5 parts by weight, based on a total of 100 parts by weight of the components (A), (B) and (C). It is 62.5 parts by weight, particularly preferably 40 to 60 parts by weight, and even more preferably 42.5 to 57.5 parts by weight.
If the content is not less than the lower limit value, the curability at the time of irradiation with a low energy amount of ultraviolet rays is lowered and the adhesiveness is deteriorated, and the durability is deteriorated, which is not preferable. , (C) is not preferable because the amount of the component (C) is reduced and the alicyclic structure having temperature resistance in the cured product is reduced, which deteriorates the thermal durability.

<Epoxy compound (B) having an alicyclic structure>
The epoxy compound (B) having an alicyclic structure includes, for example, an epoxy compound having a structure in which an epoxy group is directly introduced into the alicyclic structure, and a structure in which an epoxy group is directly introduced into another alicyclic structure. Examples thereof include epoxy compounds containing no alicyclic structure.

Examples of the epoxy compound having a structure in which an epoxy group is directly introduced into the alicyclic structure include 1,2-epoxy-4-vinylcyclohexanelimone dioxide as having one epoxy group directly introduced into the alicyclic structure. , 4-Vinylcyclohexendioxide, which has two or more epoxy groups directly introduced into the alicyclic structure, is dicyclopentadiene oxide, 3', 4'-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxy Examples include rates, ε-caprolactone-modified 3', 4'-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate, bis (3,4-epoxycyclohexylmethyl) adipate and the like. These can be used alone or in combination of two or more.
As the alicyclic epoxy compound, specifically, commercially available products such as "Celoxide 2021P" and "Celoxiside 2000" manufactured by Daicel Corporation can be used.

Further, examples of the alicyclic structure-containing epoxy compound having no structure in which an epoxy group is directly introduced into the alicyclic structure include an epoxy compound in which an aromatic ring is hydrogenated, such as hydrided bisphenol A diglycidyl ether. Cyclohexanedimethanol diglycidyl ether and the like can be mentioned. These can be used alone or in combination of two or more.
As the alicyclic skeleton-containing epoxy compound, specifically, a commercially available product such as "Denacol EX-216L" manufactured by Nagase ChemteX Corporation can be used.

Among these, an epoxy compound having a structure in which an epoxy group is directly introduced into the alicyclic structure is preferable, and an epoxy compound having two or more epoxy groups directly introduced into the alicyclic structure is particularly preferable. Are 3', 4'-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate, ε-caprolactone-modified 3', 4'-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate.

The content of the epoxy compound (B) having an alicyclic structure is preferably 20 to 50 parts by weight, particularly preferably 20 parts by weight, based on a total of 100 parts by weight of the components (A), (B) and (C). It is 21 to 45 parts by weight, more preferably 22 to 40 parts by weight.
If the content is too large, the content of the component (A) is relatively lowered, the curability at the time of irradiation with a low energy amount of ultraviolet rays is lowered, and the adhesiveness and durability tend to be lowered. If the amount is too small, the alicyclic structure having temperature resistance in the cured product will decrease, and thus the thermal durability tends to decrease.

The silane coupling agent (C) is usually an organosilicon compound containing at least one reactive functional group and one or more silicon atom-bonded alkoxy groups in the structure, and improves the adhesiveness between the adhesive layer and the protective film. Can be made to.

Examples of the reactive functional group of the silane coupling agent include an epoxy group, a (meth) acryloyl group, a mercapto group, a vinyl group, a hydroxyl group, a carboxyl group, an amino group, an amide group, an isocyanate group and the like. It preferably contains a cationically polymerizable functional group such as an epoxy group, a vinyl group and a radical group, and is particularly preferably an epoxy group. The run-coupling agent may have an organic functional group other than the reactive functional group and the alkoxy group, for example, an alkyl group, a phenyl group and the like.

Specific examples of the silane coupling agent include 2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, and 3-glycyl. Epyl group-containing silane coupling agents such as sidoxylpropyltriethoxysilane, 3- (meth) acryloxipropylmethyldimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3- (meth) acryloxipropylmethyldiethoxysilane, (Meta) acryloyl group-containing silane coupling agent such as 3- (meth) acryloxypropyltriethoxysilane, vinyl group-containing silane coupling agent such as vinyltrimethoxysilane and vinyltriethoxysilane, N-2- (aminoethyl) ) -3-Aminopropylmethyldimethoxysilane, N-2- (aminoethyl) -3-aminopropyltrimethoxysilane, N-2- (aminoethyl) -3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxy Amino group-containing silane coupling agent such as silane, 3-aminopropyltriethoxysilane, 3-triethoxysilyl-N- (1,3-dimethyl-butylidene) propylamine, N-phenyl-3-aminopropyltrimethoxysilane , 3-Mercaptopropylmethyldimethoxysilane, 3-mercaptopropyltrimethoxysilane and other mercapto group-containing silane coupling agents, tris- (trimethoxysilylpropyl) isocyanurate and other isocyanurate group-containing silane coupling agents, 3-isocyanate Examples thereof include an isocyanate group-containing silane coupling agent such as propyltriethoxysilane. These can be used alone or in combination of two or more.
Among them, 2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3-glycidoxy from the viewpoint of adhesive strength. It is preferable to use propyltriethoxysilane, vinyltrimethoxysilane, and vinyltriethoxysilane.

Further, as the silane coupling agent, the above-mentioned monomer type silane compound may be used, or an oligomer type silane compound which is partially hydrolyzed and polycondensed may be used.

The content of the silane coupling agent (C) needs to be 10% by weight or more, preferably 15 to 30% by weight, based on 100 parts by weight of the total of the components (A), (B) and (C). Parts, particularly preferably 18-25 parts by weight.
If the content is not more than the lower limit value, the interfacial adhesive force with respect to the poorly adhesive substrate deteriorates, which is not preferable. Further, if the content is too large, the curability is weakened, so that the durability tends to decrease.

Here, in the present invention, the content ratio ((A) :( C), weight ratio) of the oxetane compound (A) and the silane coupling agent (C) is (A) :( C) = 80: 20 to. It is preferably 50:50, particularly preferably (A) :( C) = 77: 23 to 57:43, and even more preferably (A) :( C) = 75: 25 to 65:35.
If the amount of the silane coupling agent (C) with respect to the oxetane compound (A) is too large, the curability tends to be weakened and the durability tends to be lowered. It tends to be difficult to obtain the effect of.

In the present invention, in addition to the oxetane compound (A), the epoxy compound (B) having an alicyclic structure, and the silane coupling agent (C), an epoxy having an alicyclic structure is used for the purpose of further improving the adhesiveness. Epoxy compounds (D) other than compound (B) (hereinafter, abbreviated as other epoxy compounds (D)) can be used.

Examples of the other epoxy compound (D) include a triazine skeleton-containing epoxy compound, an aliphatic epoxy compound, and an epoxy compound having at least one aromatic ring in the molecule (aromatic epoxy compound). These can be used alone or in combination of two or more.

Examples of the triazine skeleton-containing epoxy compound include tris (2,3-epoxypropyl) -isocyanurate, tris (3,4-epoxybutyl) -isocyanurate, tris (4,5-epoxypentyl) -isocyanurate, and the like. Examples thereof include tris- (5,6-epoxyhexyl) -isocyanurate, tris (6,7-epoxyheptyl) -isocyanurate, tris (7,8-epoxyoctyl) -isocyanurate and the like.

Examples of the aliphatic epoxy compound include one epoxy group in the molecule such as butyl glycidyl ether, 2-ethylhexyl glycidyl ether, allyl glycidyl ether, glycidol, alcohol glycidyl ether having 11 to 15 carbon atoms, and lauryl alcohol glycidyl ether. Poliable aliphatic epoxy compounds, neopentyl glycol diglycidyl ether, 1,4-butanediol diglycidyl ether, 1,6-hexanediol diglycidyl ether, trimethylpropan polyglycidyl ether, pentaerythritol polyglycidyl ether, ethylene Glycol diglycidyl ether, polyethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, polytetramethylene glycol diglycidyl ether, polybutadiene diglycidyl ether, sorbitol polyglycidyl ether, glycerin polyglycidyl ether, polyglycerin polyglycidyl Examples thereof include bifunctional or higher aliphatic epoxy compounds having two or more epoxy groups in a molecule such as ether.

Examples of the aromatic epoxy compound include an epoxy group in the molecule of phenyl glycidyl ether, p-tert-butyl phenyl glycidyl ether, p-sec-butyl phenyl glycidyl ether, dibromophenyl glycidyl ether, resorcin diglycidyl ether and the like. One aromatic epoxy compound, phthalic acid diglycidyl ester, terephthalic acid diglycidyl ester, hydroquinone diglycidyl ether, bisphenol A diglycidyl ether, bisphenol F diglycidyl ether, bromobisphenol A diglycidyl ether, phenol novolac type epoxy resin , Cresol novolak type epoxy resin, novolak type epoxy resin, biphenyl type epoxy resin and other aromatic epoxy compounds having two or more epoxy groups in the molecule.

<Photocationic polymerization initiator (E)>
In the present invention, it is preferable that the adhesive composition further contains the photocationic polymerization initiator (E). By using the photocationic polymerization initiator (E), the adhesive composition can be cured at room temperature, and the protective film can be adhered well. The photocationic polymerization initiator (E) is a compound that produces a cationic species or Lewis acid by irradiation with active energy rays, and is, for example, an onium salt such as an aromatic diazonium salt, an aromatic iodonium salt, or an aromatic sulfonium salt. , Iron-allene complex and the like.

Examples of the aromatic diazonium salt include benzenediazonium / hexafluoroantimonate, benzenediazonium / hexafluorophosphate, benzenediazonium / hexafluoroborate and the like. These can be used alone or in combination of two or more.

Examples of the aromatic iodonium salt include diphenyliodonium / tetrakis (pentafluorophenyl) borate, diphenyliodonium / hexafluorophosphate, diphenyliodonium / hexafluoroantimonate, di (4-nonylphenyl) iodonium / hexafluorophosphate and the like. can give. These can be used alone or in combination of two or more.

Examples of the aromatic sulfonium salt include triphenylsulfonium / hexafluorophosphate, triphenylsulfonium / hexafluoroantimonate, triphenylsulfonium / tetrakis (pentafluorophenyl) borate, and diphenyl [4- (phenylthio) phenyl] sulfonium. Hexafluorophosphate, 4,4'-bis [diphenylsulfonio] diphenylsulfide bishexafluorophosphate, 4,4'-bis [di (β-hydroxyethoxy) phenylsulfonio] diphenylsulfide bishexafluoroantimonate, 4,4'-Bis [di (β-hydroxyethoxy) phenylsulfonium] diphenylsulfide bishexafluorophosphate, 7- [di (p-toluyl) sulfonio] -2-isopropylthioxanthone hexafluoroantimonate, 7- [Di (p-toluyl) Sulfonio] -2-Isopropylthioxanthone tetrakis (pentafluorophenyl) borate, 4-phenylcarbonyl-4'-diphenylsulfonio-diphenylsulfide hexafluorophosphate, 4- (p-tert-butyl) Phenylcarbonyl) -4'-diphenylsulfonio-diphenylsulfide hexafluoroantimonate, 4- (p-tert-butylphenylcarbonyl) -4'-di (p-toluyl) sulfonio-diphenylsulfide tetrakis (pentafluorophenyl) ) Volate etc. can be mentioned. These can be used alone or in combination of two or more.

Examples of the iron-allene complex include xylene-cyclopentadienyl iron (II) -hexafluoroantimonate, cumene-cyclopentadienyl iron (II) -hexafluorophosphate, and xylene-cyclopentadienyl iron (II). ) -Tris (trifluoromethylsulfonyl) metanide and the like. These can be used alone or in combination of two or more.

Among them, it is preferable to use an aromatic iodonium salt or an aromatic sulfonium salt from the viewpoint of reacting with a long wavelength light source with high sensitivity.

The content of the photocationic polymerization initiator (E) is 0. 0. It is preferably 5 to 20 parts by weight, particularly 1.0 to 10 parts by weight, and more preferably 1.5 to 5 parts by weight. If the content of the photocationic polymerization initiator (E) is too large, the solubility tends to decrease, and it becomes difficult to cure to a deep part, so that the durability tends to decrease. On the other hand, if the content of the photocationic polymerization initiator (E) is too small, the curing tends to be insufficient, and the adhesive strength and the heat resistance to moisture tend to decrease.

In the present invention, in addition to the above components, an unsaturated compound having at least one ethylenically unsaturated group in the molecule as a radical polymerization component (hereinafter, ethylenically unsaturated) as long as the effect of the present invention is not impaired. (Sometimes abbreviated as compound.), Photoradical polymerization initiator, photosensitizer, polyols, antistatic agent, other adhesives, acrylic resin, urethane resin, rosin, rosin ester, hydrogenated rosin ester, phenol Adhesive-imparting agents such as resins, aromatic-modified terpene resins, aliphatic petroleum resins, alicyclic petroleum resins, styrene resins, xylene resins, plasticizers, colorants, fillers, antioxidants, UV absorbers , Other additives such as functional dyes, and compounds that cause coloration or discoloration by irradiation with ultraviolet rays or irradiation can be blended. The blending amount of these additives is appropriately set for each additive, but for example, it is preferably 30% by weight or less, and particularly preferably 20% by weight or less of the entire adhesive composition.
Further, in addition to the above additives, impurities and the like contained in the raw materials for producing the constituent components of the adhesive composition may be contained in a small amount.

Examples of the ethylenically unsaturated compound include (meth) acrylic compounds having at least one (meth) acryloyl group in the molecule, and examples thereof include (meth) acrylates and (meth) acrylamides. Examples thereof include (meth) acrylic acid, (meth) acryloyl morpholine, and (meth) acrylic aldehyde. Oligomers such as urethane (meth) acrylate, polyester (meth) acrylate and epoxy (meth) acrylate can also be used as the (meth) acrylic compound. Furthermore, compounds having an ethylenically unsaturated bond other than the (meth) acryloyl group can also be used as the (meth) acrylic compound, and specific examples thereof include allyl (meth) acrylate and N, N-diallyl (meth). Examples include acrylamide.

Examples of the photoradical polymerization initiator include diethoxyacetophenone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, benzyl dimethyl ketal, and 4- (2-hydroxyethoxy) phenyl- (2-hydroxy). -2-propyl) ketone, 1-hydroxycyclohexylphenyl ketone, 2-methyl-2-morpholino (4-thiomethylphenyl) propan-1-one, 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) ) Butanone, acetophenones such as 2-hydroxy-2-methyl-1- [4- (1-methylvinyl) phenyl] propanone oligomer; benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzoin isobutyl ether, etc. Benzoyls; benzophenone, methyl o-benzoyl benzoate, 4-phenylbenzophenone, 4-benzoyl-4'-methyl-diphenylsulfide, 3,3', 4,4'-tetra (t-butylperoxycarbonyl) benzophenone , 2,4,6-trimethylbenzophenone, 4-benzoyl-N, N-dimethyl-N- [2- (1-oxo-2-propenyloxy) ethyl] benzenemethanamineium bromide, (4-benzoylbenzyl) trimethyl Benzoyls such as ammonium chloride; 2-isopropylthioxanthone, 4-isopropylthioxanthone, 2,4-diethylthioxanthone, 2,4-dichlorothioxanthone, 1-chloro-4-propoxythioxanthone, 2- (3-dimethylamino-2-) Hydroxy) -3,4-dimethyl-9H-thioxanthone-9-onemethochloride and other thioxanthones; 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide, bis (2,6-dimethoxybenzoyl) -2, Acylphosphon oxides such as 4,4-trimethyl-pentylphosphine oxide, bis (2,4,6-trimethylbenzoyl) -phenylphosphine oxide; and the like.

By using this photosensitizer, the reactivity can be improved, and the mechanical strength and adhesive strength of the cured product can be improved. Examples of the photosensitizer include anthracene derivatives such as 9,10-diethoxyanthracene and 9,10-dibutoxyanthracene; benzoins such as benzoin methyl ether, benzoin isopropyl ether and α, α-dimethoxy-α-phenylacetophenone. Derivatives; benzophenone derivatives such as benzophenone, 2,4-dichlorobenzophenone, methyl o-benzoylbenzoate, 4,4'-bis (dimethylamino) benzophenone, 4,4'-bis (diethylamino) benzophenone; 2-chloroanthracene, Carbonyl compounds such as anthracene derivatives such as 2-methylanthraquinone; organic sulfur compounds such as thioxanthone derivatives such as 2-chlorothioxanthone, 2-isopropylthioxanthone, 2,4-diethylthioxanthene-9-one; persulfides, redox Examples thereof include system compounds, azo and diazo compounds, halogen compounds, and photoreducing dyes. These can be used alone or in combination of two or more. Of these, it is preferable to use an anthracene derivative and a thioxanthone derivative.

The photosensitizer is preferably contained in the range of 0.01 to 20 parts by weight when the total amount of the photocationic polymerization initiator (E) is 100 parts by weight. If the content of the photosensitizer is too large, the composition and the obtained adhesive layer tend to be colored, and if it is too small, the reactivity tends to decrease and the sensitizing effect tends not to be obtained.

The adhesive composition of the present invention can be obtained by blending and mixing each of the above components in a predetermined ratio.

In this way, the active energy ray-curable adhesive composition of the present invention is obtained. The adhesive composition of the present invention functions as an adhesive by being cured by irradiation with active energy rays, and can be suitably used as an adhesive for a polarizing plate for adhering a polarizer and a protective film. It is a thing.

<Polarizer>
The polarizing plate of the present invention is obtained by bonding a polarizing element and a protective film via a polarizing plate adhesive, and more specifically, for the polarizing plate of the present invention, on at least one surface, preferably both sides of the polarizing element. Protective films are bonded together using an adhesive, and usually, a liquid polarizing plate adhesive composition is uniformly applied to the polarizer surface, the protective film surface, or both surfaces, and then both are bonded. A polarizing plate is formed by combining, crimping, and irradiating with active energy rays.

The above-mentioned polarizer is usually an aqueous solution of iodine-potassium iodide using a film made of a polyvinyl alcohol-based resin having an average degree of polymerization of 1,500 to 10,000 and a saponification degree of 85 to 100 mol% as a raw film. Alternatively, a uniaxially stretched film dyed with a dichroic dye (usually a stretch ratio of about 2 to 10 times, preferably about 3 to 7 times) is used.

The polyvinyl alcohol-based resin is usually produced by saponifying polyvinyl acetate obtained by polymerizing vinyl acetate, but a small amount of unsaturated carboxylic acid (including salts, esters, amides, nitriles, etc.), olefins, vinyl ethers, etc. , Unsaturated sulfonate, and other components that can be copolymerized with vinyl acetate may be contained. Further, examples thereof include so-called polyvinyl acetal resins such as polyvinyl butyral resin and polyvinyl formal resin and polyvinyl alcohol derivatives obtained by reacting polyvinyl alcohol with aldehydes in the presence of acid.

As the protective film for the polarizing plate, an acrylic film (PMMA), a polyester film (PET), a cycloolefin film (COP), or the like can be used in addition to the conventional TAC film, and the adhesive composition of the present invention can be used. Is preferably used for any protective film selected from TAC-based films, acrylic-based films, cycloolefin-based films (COP), polyester-based films (PET) -based films, and the like.

When the adhesive composition of the present invention is applied onto a polarizer or a protective film, for example, a reverse coater, a gravure coater (direct, reverse or offset), a bar reverse coater, a roll coater, a die coater, a bar coater, etc. A rod coater or the like can be used, or coating can be performed by a dipping method.

At the time of the above bonding and crimping, for example, a roll laminator or the like can be used, and the pressure is usually selected from the range of 0.1 to 10 MPa.

As the active energy rays, in addition to far-ultraviolet rays, ultraviolet rays, near-ultraviolet rays, rays such as infrared rays, electromagnetic waves such as X-rays and γ-rays, electron beams, proton rays, neutron rays and the like can be used. Curing by ultraviolet irradiation is advantageous because of its availability and price.

As the light source for irradiating the ultraviolet rays, a high-pressure mercury lamp, an electrodeless lamp, an ultra-high pressure mercury lamp carbon arc lamp, a xenon lamp, a metal halide lamp, a chemical lamp, a black light, an LED lamp and the like are used.
The above-mentioned ultraviolet irradiation is usually carried out under the conditions of ^{2 to 1000 mJ / cm 2} , preferably 10 to 500 mJ / cm ² , and 15 to 300 mJ / cm 2 from the viewpoint of excellent productivity.

The irradiation direction of the active energy rays (ultraviolet rays, electron beams, etc.) can be any suitable direction, but from the viewpoint of productivity, it is preferable to irradiate from one transparent protective film side.

The thickness of the adhesive layer in the polarizing plate of the present invention obtained as described above is usually 0.01 to 10 μm, preferably 0.5 to 8 μm, and particularly preferably 1 to 5 μm. If the thickness is too thin, the cohesive force of the adhesive force itself cannot be obtained, and the adhesive strength tends not to be obtained. If the thickness is too thick, the processability of the polarizing plate tends to decrease due to cracking during punching.

The adhesive composition of the present invention becomes an adhesive having excellent adhesive strength at the initial stage and over time, and can be used for various purposes, but is particularly suitable for bonding various protective films for polarizing plates and a polarizer. It shows good adhesiveness. In addition, the durability of the adhesive layer is also excellent.

Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to the following examples as long as the gist of the present invention is not exceeded. In the example, "part" and "%" mean the weight standard.

Prior to Examples and Comparative Examples, each component of the adhesive composition shown below was prepared.

[Oxetane compound (A)]
(A-1): 3-Ethyl-3 {[(3-ethyloxetane-3-yl) methoxy] methyl} oxetane (oxetane compound having two oxetane group in the molecule: Aron oxetane OXT- manufactured by Toagosei Co., Ltd. 221)

[Epoxy compound (B) having an alicyclic structure]
(B-1): 3', 4'-epoxycyclohexylmethyl 3,4-epoxycyclohexanecarboxylate; seroxide 2021P (manufactured by Daicel)

[Silane Coupling Agent (C)]
(C-1): 3-glycidoxypropyltrimethoxysilane (KBM-403 manufactured by Shin-Etsu Chemical Co., Ltd.)

[Photocationic polymerization initiator (E)]
(E-1): (1: 1) mixture of diphenyl [4- (phenylthio) phenyl] sulfonium hexafluorophosphate and propylene carbonate (aromatic sulfonium salt: manufactured by San-Apro, CPI-100P)

[Examples 1 and 2, Comparative Examples 1 and 4]
<Preparation of adhesive composition>
An adhesive composition was prepared by blending each of the above-mentioned compounding components in the ratio shown in Table 1 below and mixing them.

<Making a polarizer>
First, a 60 μm PVA film was stretched 1.5 times while being immersed in a water tank having a water temperature of 30 ° C. Next, it was stretched 1.3 times while being immersed in a dyeing tank (30 ° C.) composed of 0.2 g / L of iodine and 15 g / L of potassium iodide for 240 seconds. Further, it was immersed in a boric acid treatment tank (50 ° C.) having a composition of 50 g / L of boric acid and 30 g / L of potassium iodide, and at the same time, boric acid treatment was carried out for 5 minutes while uniaxially stretching 3.08 times. Then, it was dried at 90 ° C. to produce a polarizer having a total draw ratio of 6 times. The water content of the polarizer was 1%.

<Preparation of polarizing plate test piece>
PET film with a size of 200 mm x 150 mm and a thickness of 80 μm (manufactured by Toyobo Corporation, trade name "Cosmo Shine SRF") and cyclic olefin resin (COP) film with a size of 200 mm x 150 mm and a thickness of 50 μm (manufactured by Nippon Zeon) Each film of the name "ZEONOR") is subjected to corona treatment (manufactured by KASUGA DENKI, TEC-4AX 67W 2.0 m / min 2 pass), and the adhesive composition obtained above is coated with a bar coater to a thickness of 4 μm. To obtain a film with an adhesive composition. Then, each film with an adhesive composition layer was superposed on both sides of the above-mentioned polarizer having a size of 180 mm × 120 mm, and 2.5 kg / cm ² using a roll machine (“MDL601” manufactured by MUROMACHI KAGAKU). It was bonded at 3.0 m / min to obtain a laminated film.

Then, from the COP film side of the laminated film, with an ultraviolet irradiation device (manufactured by Heleus) equipped with an electrodeless lamp (D valve), peak illuminance: confirmation required 400 mW / cm ² , cumulative exposure: 200 mJ / cm ² ( The adhesive composition was cured by irradiating with ultraviolet rays in the UVA region) to prepare a polarizing plate test piece.
Using the polarizing plate test piece obtained above, the performance was evaluated as follows.

<Performance evaluation>
[Adhesive strength]
The degree of adhesion (adhesive strength) between the COP film and the polarizing element and the PET film and the polarizing element when the polarizing plate test piece is cut into 120 mm × 25 mm and stressed in the 90 ° direction is measured by the measuring device: Autograph. Was measured. Then, based on the above measured values, evaluation was performed according to the following criteria.
(Evaluation criteria)
○… All were firmly adhered.
△… All were weakly adhered.
×… None of them were glued.

[Moist heat durability]
The test piece was cut into 40 mm × 40 mm and left in an environment of 85 ° C. and 85% RH for 100 hours to carry out a wet heat durability test. After the test, it was evaluated according to the following criteria.
(Evaluation criteria)
○… Transmittance change amount is less than 1% Δ… Transmittance change amount is 1% or more and less than 5% ×… Transmittance change amount is 5% or more

[Cold heat durability]
A thermal shock test was carried out in which the test piece was cut into 100 mm × 100 mm, left at −40 ° C. for 30 minutes, and then left at 85 ° C. for 30 minutes, repeating a cycle of 100 times. After the test, it was evaluated according to the following criteria.
(Evaluation criteria)
○… No appearance defects were confirmed.
×: Poor appearance (cracks occurred in the polarizer layer) was confirmed.

From the above results, the adhesive compositions of Examples 1 and 2 containing the oxetane compound (A), the epoxy compound (B) having an alicyclic structure, and the silane coupling agent (C) have good curability. In addition to being able to bond the polarizer and the protective film with high adhesive strength, excellent results were also obtained in terms of water resistance and durability. From this, it was suitable for practical use as an adhesive composition for a polarizing plate having an excellent balance.

On the other hand, in the adhesive compositions of Comparative Examples 1 to 4, good results were obtained in terms of curability and water resistance, but inferior results were obtained in adhesive strength or durability. From this, it can be said that it cannot be put into practical use as an adhesive composition for a polarizing plate. Therefore, it was found that the adhesive composition of the present invention is very excellent particularly in the use of an adhesive for polarizing plates.

The adhesive composition of the present invention and the adhesive composition for a polarizing plate composed of the above-mentioned adhesive composition are excellent in adhesiveness between a polarizing element and a protective film, and various protective films for a polarizing plate and a polarizing element. Suitable for bonding with. Further, the durability of the polarizing plate, particularly the heat impact resistance, is also excellent. In addition to the above-mentioned adhesive applications for polarizing plates, the adhesive composition of the present invention can be used for, for example, bonding various optical films or sheets, or bonding electronic parts, precision instruments, packaging materials, display materials, and the like. It can also be used for.

Claims (8)

Oxetane compound (A),
Epoxy compound (B) having an alicyclic structure and silane coupling agent (C)
An active energy ray-curable adhesive composition containing the above, with respect to a total of 100 parts by weight of the components (A), (B) and (C).
An active energy ray-curable adhesive composition characterized in that the content of the oxetane compound (A) is 35 to 65 parts by weight and the content of the silane coupling agent (C) is 10 parts by weight or more. The active energy ray-curable adhesive composition according to claim 1, wherein the oxetane compound (A) is an oxetane compound that does not contain a hydroxyl group and has two or more oxetanyl groups. The active energy ray-curable adhesive according to claim 1 or 2, wherein the epoxy compound (B) having an alicyclic structure is an epoxy compound containing two or more epoxy groups directly introduced into the alicyclic structure. Agent composition. The active energy ray-curable adhesive composition according to any one of claims 1 to 3, wherein the silane coupling agent (C) is a silane coupling agent containing an epoxy group. The content ratio ((A): (C), weight ratio) of the oxetane compound (A) and the silane coupling agent (C) is (A): (C) = 80:20 to 50:50. The active energy ray-curable adhesive composition according to any one of claims 1 to 4. An adhesive composition for a polarizing plate, which comprises using the active energy ray-curable adhesive composition according to any one of claims 1 to 5. An adhesive for a polarizing plate, which comprises a cured product of the adhesive composition for a polarizing plate according to claim 6. A polarizing plate characterized in that a polarizing element and a protective film are bonded to each other via the polarizing plate adhesive according to claim 7.