JP7363631B2 - Active energy ray-curable adhesive composition, adhesive composition for polarizing plates, adhesive for polarizing plates, and polarizing plate using the same - Google Patents

Description

The present invention relates to an active energy ray-curable adhesive composition, an adhesive composition for a polarizing plate, an adhesive for a polarizing plate, and a polarizing plate using the same. The present invention relates to an active energy ray-curable adhesive composition suitable for bonding a polarizer and a protective film constituting a polarizing plate.

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 structure in which polarizing plates are laminated on both sides of a glass substrate in which liquid crystal is sealed, and various optical functional films such as a retardation plate are laminated thereon as necessary.

Conventionally, a polarizing plate has been used as a polarizer made of a polyvinyl alcohol film with a protective film attached to at least one surface, preferably both surfaces.
Here, as a polarizer, dichroism such as iodine is contained in a PVA film formed using a polyvinyl alcohol resin with a high degree of saponification (hereinafter, polyvinyl alcohol is abbreviated as "PVA"). Uniaxially oriented PVA-based films in which materials are dispersed, adsorbed, and preferably further crosslinked with a crosslinking agent such as boric acid are widely used. Since such a polarizer is a uniaxially stretched PVA-based film, it tends to shrink under high humidity, so a protective film is attached to the polarizer to supplement moisture resistance and strength.

As such a protective film, thermoplastic resins such as cellulose resins, polycarbonate resins, cyclic polyolefin resins, (meth)acrylic resins, and polyester resins have properties such as transparency, mechanical strength, thermal stability, moisture barrier properties, isotropy, etc. In particular, protective films made of triacetyl cellulose (TAC) resin have been widely used.

These protective films are bonded to the polarizer using an adhesive, but from the viewpoint of adhesion to the polarizer, which has a hydrophilic surface, an aqueous PVA resin solution, especially one similar to that of the polarizer, is recommended as the adhesive. A PVA resin aqueous solution containing a high saponification degree PVA resin as a main component is preferably used.

By the way, in recent years, there has been a demand for thinner polarizing plates, and acrylic is being used instead of triacetyl cellulose (TAC) film, which has been most commonly used as a protective film, from the viewpoint of durability of polarizing plates. type films, cyclic olefin resin (COP) films, and polyester (PET) films have come into use. However, these protective films that replace triacetyl cellulose (TAC) films are difficult to bond firmly to polarizers using conventional water-based PVA adhesives, and in the first place, these protective films are not permeable to moisture. There was a problem in that the moisture could not be removed in the drying process after bonding due to the extremely low water content, making it unusable. 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 specific proportion of a four-membered cyclic compound having two or more oxygen atoms. The composition exhibits particularly good adhesion between the triacetyl cellulose (TAC) substrate and the polarizer, and also exhibits good durability even in an environment of 60°C and 90% RH. It is described that it is possible to provide a polarizing plate in which protective films are bonded to both sides of a practical polarizer.

Japanese Patent Application Publication No. 2013-043952

However, in recent years, the environments in which polarizing plates are used have diversified, and instead of polarizing plates using TAC films with high moisture permeability, protective films such as COP films, PET films, and acrylic films with low moisture permeability are used, which have higher humidity and heat resistance. Although a durable polarizing plate is desired, the adhesive composition of Patent Document 1 is not fully satisfactory in terms of adhesive strength and durability depending on the type of protective film.

In view of this background, the present invention provides an adhesive that has excellent adhesive strength, is suitable for bonding various protective films for polarizing plates and polarizers, and has high heat and humidity resistance and thermal shock resistance. The present invention provides active energy ray-curable adhesive compositions, adhesive compositions for polarizing plates, adhesives for polarizing plates, and polarizing plates using the same, which have excellent durability.

However, as a result of extensive research in view of the above circumstances, the present inventors have discovered an active compound containing an oxetane compound (A), an epoxy compound having an alicyclic structure (B), and a silane coupling agent (C). By containing a specific amount of an oxetane compound (A) and a larger amount of a silane coupling agent (C) than usual in an energy ray-curable adhesive composition, it is possible to bond various protective films for polarizing plates and polarizers. The present invention was completed based on the discovery that it is possible to obtain an adhesive having good adhesive properties and excellent durability such as heat and humidity resistance and thermal shock resistance.

That is, the gist of the present invention is an active energy ray-curable adhesive composition comprising an oxetane compound (A), an epoxy compound having an alicyclic structure (B), 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 components (A), (B), and (C). This is an active energy ray-curable adhesive composition characterized in that the amount is 10 parts by weight or more.

The present invention also provides an adhesive composition for a polarizing plate using such an active energy ray-curable adhesive composition, an adhesive for a polarizing plate comprising a cured product of the adhesive composition for a polarizing plate, and an adhesive for a polarizing plate. The present invention also provides a polarizing plate in which a polarizer and a protective film are bonded together 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). An adhesive composition containing 35 to 65 parts by weight of the oxetane compound (A) based on a total of 100 parts by weight of components (A), (B), and (C), and a silane coupling agent ( The active energy ray-curable adhesive composition contains C) in an amount of 10 parts by weight or more. Therefore, various protective films for polarizing plates and polarizers can be sufficiently bonded, and furthermore, polarizing plates with excellent durability can be obtained.

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

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

<Oxetane compound (A)>
The oxetane compound (A) used in the present invention may be any 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, - Oxetanyl group in the molecule of ethyl-3-(cyclohexyloxymethyl)oxetane, 3-ethyl-3-(oxiranylmethoxy)oxetane, (3-ethyloxetan-3-yl)methyl (meth)acrylate, etc. An oxetane compound having one;
3-ethyl-3{[(3-ethyloxetan-3-yl)methoxy]methyl}oxetane, 1,4-bis[(3-ethyl-3-oxetanyl)methoxymethyl]benzene, 4,4'-bis[ Oxetane compounds having two or more oxetanyl groups in the molecule, such as (3-ethyl-3-oxetanyl)methoxymethyl]biphenyl;
etc. can be mentioned. These oxetane compounds (A) can be used alone or in combination of two or more.

Among them, 3-ethyl-3-hydroxymethyloxetane, 1,4-bis[(3-ethyl-3-oxetanyl) ) methoxymethyl]benzene, 3-ethyl-3-[(2-ethylhexyloxymethyl)]oxetane, 3-ethyl-3-(oxiranylmethoxy)oxetane, (meth)acrylic acid (3-ethyloxetane-3- yl)methyl, 3-ethyl-3{[(3-ethyloxetan-3-yl)methoxy]methyl}oxetane, and the like are preferably used.

In addition, from the viewpoint of coating properties, adhesion properties, and curability, it is preferable to have a molecular weight of 500 or less that is liquid at room temperature, and from the viewpoint of excellent curability and durability, it does not contain hydroxyl groups and has two or more in the molecule. Oxetane compounds containing an oxetanyl group are particularly preferred, such as 1,4-bis[(3-ethyl-3-oxetanyl)methoxymethyl]benzene, 3-ethyl-3{[(3-ethyloxetan-3-yl)methoxy] methyl}oxetane is more preferred, and in view of yellowing of the adhesive during durability, 3-ethyl-3{[(3-ethyloxetan-3-yl)methoxy]methyl}oxetane is particularly preferred.

Specifically, the above-mentioned oxetane compound (A) includes commercially available aronoxetane OXT-101, aronoxetane OXT-121, aronoxetane OXT-211, aronoxetane OXT-212, aronoxetane OXT-213, aronoxetane OXT -221 (both manufactured by Toagosei Co., Ltd.) can be used. Aron oxetane OXT-221 is particularly preferred.

The content of the oxetane compound (A) needs to be 35 to 65 parts by weight, preferably 37.5 to 65 parts by weight, based on a total of 100 parts by weight of components (A), (B), and (C). The amount 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 below the lower limit, the curability during low-energy ultraviolet irradiation will be reduced, resulting in poor adhesion, resulting in poor durability, which is undesirable, and if it is above the upper limit, it will be relatively (B). This is not preferable because the amount of component (C) decreases and the number of alicyclic structural sites having temperature resistance in the cured product decreases, resulting in poor cold and heat durability.

<Epoxy compound (B) having an alicyclic structure>
Examples of the epoxy compound (B) having an alicyclic structure include epoxy compounds having a structure in which an epoxy group is directly introduced into an alicyclic structure, and structures in which an epoxy group is directly introduced into other alicyclic structures. Examples include epoxy compounds containing an alicyclic structure.

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

In addition, examples of epoxy compounds containing an alicyclic structure that do not have a structure in which an epoxy group is directly introduced into the alicyclic structure include epoxy compounds in which an aromatic ring is hydrogenated, such as hydrogenated bisphenol A diglycidyl ether; Examples include cyclohexanedimethanol diglycidyl ether. These can be used alone or in combination of two or more.
Specifically, as the alicyclic skeleton-containing epoxy compound, a commercially available product such as "Denacol EX-216L" manufactured by Nagase ChemteX can be used.

Among these, preferred are epoxy compounds having a structure in which an epoxy group is directly introduced into an alicyclic structure, particularly preferred are epoxy compounds having two or more epoxy groups directly introduced into an alicyclic structure, and even more preferred are epoxy compounds having a structure in which an epoxy group is directly introduced into an alicyclic structure. are 3',4'-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate and 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 100 parts by weight in total of components (A), (B), and (C). The amount is 21 to 45 parts by weight, more preferably 22 to 40 parts by weight.
If this content is too large, the content of component (A) will be relatively reduced, resulting in a decrease in curability when irradiated with low-energy ultraviolet rays, and a tendency for adhesiveness and durability to decrease. If the amount is too small, the number of alicyclic structural sites having temperature resistance in the cured product will decrease, which will tend to reduce the cold and heat durability.

The silane coupling agent (C) is usually an organosilicon compound containing one or more reactive functional groups and one or more silicon-bonded alkoxy groups in its structure, and improves the adhesion between the adhesive layer and the protective film. can be done.

Examples of the reactive functional group of the silane coupling agent include an epoxy group, (meth)acryloyl group, mercapto group, vinyl group, hydroxyl group, carboxyl group, amino group, amide group, isocyanate group, etc. Among these, It is preferable to include a cationically polymerizable functional group such as an epoxy group, a vinyl group, or a radical group, and an epoxy group is particularly preferable. Note that the run coupling agent may have a reactive functional group and an organic functional group other than an alkoxy group, such as an alkyl group or a phenyl group.

Examples of the silane coupling agent include 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, and 3-glycidoxypropylmethyldiethoxysilane. Epoxy group-containing silane coupling agents such as sidoxypropyltriethoxysilane, 3-(meth)acryloxypropylmethyldimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-(meth)acryloxypropylmethyldiethoxysilane, (meth)acryloyl group-containing silane coupling agents such as 3-(meth)acryloxypropyltriethoxysilane, vinyl group-containing silane coupling agents such as vinyltrimethoxysilane and vinyltriethoxysilane, N-2-(aminoethyl )-3-aminopropylmethyldimethoxysilane, N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, N-2-(aminoethyl)-3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxy Silane coupling agents containing amino groups such as silane, 3-aminopropyltriethoxysilane, 3-triethoxysilyl-N-(1,3-dimethyl-butylidene)propylamine, and N-phenyl-3-aminopropyltrimethoxysilane , 3-mercaptopropylmethyldimethoxysilane, mercapto group-containing silane coupling agents such as 3-mercaptopropyltrimethoxysilane, isocyanurate group-containing silane coupling agents such as tris-(trimethoxysilylpropyl)isocyanurate, 3-isocyanate Examples include isocyanate group-containing silane coupling agents such as propyltriethoxysilane. These can be used alone or in combination of two or more.
Among them, from the viewpoint of adhesive strength, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3-glycidoxy It is preferable to use propyltriethoxysilane, vinyltrimethoxysilane, and vinyltriethoxysilane.

Further, as the silane coupling agent, a monomer-type silane compound such as that described above may be used, or an oligomer-type silane compound partially hydrolyzed and polycondensed may be used.

The content of the silane coupling agent (C) needs to be 10 parts by weight or more, preferably 15 to 30 parts by weight, based on a total of 100 parts by weight of components (A), (B), and (C). parts, particularly preferably 18 to 25 parts by weight.
If the content is below the lower limit, the interfacial adhesion force to the substrate, which is difficult to adhere to, will deteriorate, which is not preferable. Furthermore, if the content is too high, the curability becomes weak and 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 from (A):(C)=80:20 to The ratio 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) relative to the oxetane compound (A) is too large, the curability becomes weak and durability tends to decrease; if the amount is too small, the interfacial adhesion to the base material is difficult to adhere to. It tends to be difficult to obtain the desired effect.

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

Examples of the other epoxy compounds (D) include triazine skeleton-containing epoxy compounds, aliphatic epoxy compounds, and epoxy compounds having at least one aromatic ring in the molecule (aromatic epoxy compounds). 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, Examples include tris-(5,6-epoxyhexyl)-isocyanurate, tris(6,7-epoxyheptyl)-isocyanurate, tris(7,8-epoxyoctyl)-isocyanurate, and the like.

Examples of the aliphatic epoxy compounds include butyl glycidyl ether, 2-ethylhexyl glycidyl ether, allyl glycidyl ether, glycidol, alcohol glycidyl ether having 11 to 15 carbon atoms, lauryl alcohol glycidyl ether, etc. aliphatic epoxy compounds, neopentyl glycol diglycidyl ether, 1,4-butanediol diglycidyl ether, 1,6-hexanediol diglycidyl ether, trimethylolpropane 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 include bifunctional or higher-functional aliphatic epoxy compounds having two or more epoxy groups in the molecule, such as ether.

Examples of the aromatic epoxy compounds include phenylglycidyl ether, p-tert-butylphenylglycidyl ether, p-sec-butylphenylglycidyl ether, dibromophenylglycidyl ether, resorcin diglycidyl ether, etc. Aromatic epoxy compound having one 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 , aromatic epoxy compounds having two or more epoxy groups in the molecule, such as cresol novolac type epoxy resin, novolac type epoxy resin, biphenyl type epoxy resin, and the like.

<Photocationic polymerization initiator (E)>
In the present invention, it is preferable that the adhesive composition further contains a 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 bonded well. The above-mentioned photocationic polymerization initiator (E) is a compound that generates a cationic species or a Lewis acid upon irradiation with active energy rays, such as an onium salt such as an aromatic diazonium salt, an aromatic iodonium salt, or an aromatic sulfonium salt. , iron-alene complexes, etc.

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 salts 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 salts include triphenylsulfonium hexafluorophosphate, triphenylsulfonium hexafluoroantimonate, triphenylsulfonium tetrakis(pentafluorophenyl)borate, 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)phenylsulfonio]diphenylsulfide bishexafluorophosphate, 7-[di(p-tolyl)sulfonio]-2-isopropylthioxanthone hexafluoroantimonate, 7- [di(p-tolyl)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-tolyl)sulfonio-diphenylsulfide tetrakis(pentafluorophenyl) ) borate etc. These can be used alone or in combination of two or more.

Examples of the iron-alene complexes include xylene-cyclopentadienyl iron (II)-hexafluoroantimonate, cumene-cyclopentadienyl iron (II)-hexafluorophosphate, xylene-cyclopentadienyl iron (II) )-tris(trifluoromethylsulfonyl)methanide and the like. These can be used alone or in combination of two or more.

Among these, it is preferable to use aromatic iodonium salts and aromatic sulfonium salts because they react with high sensitivity to long wavelength light sources.

The content of the photocationic polymerization initiator (E) is 0.00 parts by weight based on 100 parts by weight of the oxetane compound (A), the epoxy compound having an alicyclic structure (B), and the silane coupling agent (C). It is preferably 5 to 20 parts by weight, particularly 1.0 to 10 parts by weight, and even 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 harden to a deep part, so that durability tends to decrease. Moreover, if the content of the photocationic polymerization initiator (E) is too small, curing will be insufficient, and adhesive strength and heat-and-moisture resistance will tend to decrease.

In the present invention, in addition to the above-mentioned components, an unsaturated compound having at least one ethylenically unsaturated group in the molecule (hereinafter referred to as ethylenically unsaturated ), radical photopolymerization initiators, photosensitizers, polyols, antistatic agents, other adhesives, acrylic resins, urethane resins, rosin, rosin esters, hydrogenated rosin esters, phenol Tackifiers such as resins, aromatic modified terpene resins, aliphatic petroleum resins, alicyclic petroleum resins, styrene resins, xylene resins, plasticizers, colorants, fillers, anti-aging agents, ultraviolet absorbers , other additives such as functional dyes, and compounds that cause coloration or discoloration when irradiated with ultraviolet rays or radiation can be added. The blending amount of these additives is appropriately set for each additive, but, for example, it is preferably 30% by weight or less, particularly preferably 20% by weight or less of the entire adhesive composition.
In addition to the above-mentioned additives, a small amount of impurities etc. contained in the manufacturing raw materials of the constituent components of the adhesive composition may be contained.

Examples of the ethylenically unsaturated compounds include (meth)acrylic compounds having at least one (meth)acryloyl group in the molecule, such as (meth)acrylates, (meth)acrylamides, Examples include (meth)acrylic acid, (meth)acryloylmorpholine, (meth)acrylaldehyde, and the like. Moreover, 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 other ethylenically unsaturated bonds in addition to a (meth)acryloyl group can also be used as (meth)acrylic compounds, and specific examples thereof include allyl (meth)acrylate, 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, 4-(2-hydroxyethoxy)phenyl-(2-hydroxy -2-propyl)ketone, 1-hydroxycyclohexylphenylketone, 2-methyl-2-morpholino(4-thiomethylphenyl)propan-1-one, 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl) ) Acetophenones such as butanone, 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. Benzoins; benzophenone, methyl o-benzoylbenzoate, 4-phenylbenzophenone, 4-benzoyl-4'-methyl-diphenyl sulfide, 3,3',4,4'-tetra(t-butylperoxycarbonyl)benzophenone , 2,4,6-trimethylbenzophenone, 4-benzoyl-N,N-dimethyl-N-[2-(1-oxo-2-propenyloxy)ethyl]benzenemethanaminium bromide, (4-benzoylbenzyl)trimethyl Benzophenones 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-thioxanthon-9-one Thioxanthone such as mesochloride; 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide, bis(2,6-dimethoxybenzoyl)-2, Acylphosphophone oxides such as 4,4-trimethyl-pentylphosphine oxide and bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide; and the like.

By using the above-mentioned photosensitizer, the reactivity can be improved and the mechanical strength and adhesive strength of the cured product can be improved. Examples of photosensitizers include anthracene derivatives such as 9,10-diethoxyanthracene and 9,10-dibutoxyanthracene; benzoin 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-chloroanthraquinone, Carbonyl compounds such as anthraquinone 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 include azo-based compounds, azo and diazo compounds, halogen compounds, photoreducible dyes, and the like. These can be used alone or in combination of two or more. Among them, it is preferable to use anthracene derivatives and thioxanthone derivatives.

The photosensitizer is preferably contained in an amount 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 adhesive layer obtained will tend to be colored, and if it is too small, the reactivity will decrease and there will be a tendency for no sensitizing effect to be obtained.

The adhesive composition of the present invention is obtained by blending and mixing the above-mentioned 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 active energy ray irradiation, and can be suitably used as a polarizing plate adhesive for bonding a polarizer and a protective film. It is something.

<Polarizing plate>
The polarizing plate of the present invention has a polarizer and a protective film bonded together via an adhesive for polarizing plates. Specifically, the polarizing plate of the present invention is attached to at least one surface, preferably both surfaces, of the polarizer. A protective film is pasted together using an adhesive. Usually, a liquid polarizing plate adhesive composition is uniformly applied to the polarizer surface, the protective film surface, or both surfaces, and then the two are pasted together. A polarizing plate is formed by combining, pressing, and irradiating active energy rays.

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

The above polyvinyl alcohol resin is usually produced by saponifying polyvinyl acetate obtained by polymerizing vinyl acetate, but it contains a small amount of unsaturated carboxylic acids (including salts, esters, amides, nitriles, etc.), olefins, and vinyl ethers. , unsaturated sulfonate, etc., which can be copolymerized with vinyl acetate. Also included are so-called polyvinyl acetal resins and polyvinyl alcohol derivatives, such as polybutyral resins and polyvinyl formal resins, which are obtained by reacting polyvinyl alcohol with aldehydes in the presence of an acid.

As the protective film for the polarizing plate, in addition to conventional TAC films, acrylic films (PMMA), polyester films (PET), cycloolefin films (COP), etc. can also be used, and the adhesive composition of the present invention is suitably used for any protective film selected from TAC films, acrylic films, cycloolefin films (COP), polyester films (PET), and the like.

When coating the adhesive composition of the present invention on 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, Coating can be performed using a rod coater or the like or by a dipping method.

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

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

As a light source for the above-mentioned ultraviolet irradiation, a high-pressure mercury lamp, an electrodeless lamp, an ultra-high-pressure mercury lamp, a carbon arc lamp, a xenon lamp, a metal halide lamp, a chemical lamp, a black light, an LED lamp, etc. are used.
The above-mentioned ultraviolet irradiation is carried out under conditions of usually 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 active energy rays (ultraviolet rays, electron beams, etc.) can be irradiated from any suitable direction, but from the viewpoint of productivity, it is preferable to irradiate from one side of the transparent protective film.

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, particularly preferably 1 to 5 μm. If the thickness is too thin, there is a tendency that the cohesive force of the adhesive itself cannot be obtained, and adhesive strength cannot be obtained, and if it is too thick, the workability of the polarizing plate tends to decrease due to cracks during punching, etc.

The adhesive composition of the present invention is an adhesive that has excellent adhesive strength both initially and over time, and can be used for various purposes, but is particularly suitable for bonding various protective films for polarizing plates and polarizers. This shows good adhesion. Furthermore, the adhesive layer has excellent durability.

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 unless it exceeds the gist thereof. In addition, in the examples, "parts" and "%" mean weight basis.

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-ethyloxetan-3-yl)methoxy]methyl}oxetane (oxetane compound having two oxetanyl groups in the molecule: Toagosei Co., Ltd., Aronoxetane OXT- 221)

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

[Silane coupling agent (C)]
(C-1): 3-glycidoxypropyltrimethoxysilane (KBM-403 manufactured by Shin-Etsu Chemical)

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

[Examples 1-2, Comparative Examples 1-4]
<Preparation of adhesive composition>
An adhesive composition was prepared by blending and mixing the above ingredients in the proportions shown in Table 1 below.

<Preparation of polarizer>
First, a 60 μm PVA film was stretched 1.5 times while being immersed in a water bath with a water temperature of 30°C. Next, it was stretched 1.3 times while being immersed for 240 seconds in a dyeing tank (30° C.) containing 0.2 g/L of iodine and 15 g/L of potassium iodide. Furthermore, it was immersed in a boric acid treatment tank (50° C.) containing 50 g/L of boric acid and 30 g/L of potassium iodide, and at the same time was subjected to boric acid treatment for 5 minutes while being uniaxially stretched to 3.08 times. Thereafter, it was dried at 90° C. to produce a polarizer with a total stretching ratio of 6 times. Note that the moisture content of the polarizer was 1%.

<Preparation of polarizing plate test piece>
A PET film with a size of 200 mm x 150 mm and a thickness of 80 μm (manufactured by Toyobo Co., Ltd., product name “Cosmoshine SRF”) and a cyclic olefin resin (COP) film (manufactured by Nippon Zeon Co., Ltd., product name: “Cosmoshine SRF”) with a size of 200 mm × 150 mm and a thickness of 50 μm. Corona treatment (manufactured by KASUGA DENKI, TEC-4AX 67W 2.0m/min 2pass) was applied to each film (name: "ZEONOR"), and the adhesive composition obtained above was coated with a bar coater to a film thickness of 4 μm. A film with an adhesive composition was obtained. Then, each film with an adhesive composition layer was laminated on both sides of the above polarizer having a size of 180 mm x 120 mm, and rolled at 2.5 kg/cm ² using a roll machine (manufactured by MUROMACHI KAGAKU, "MDL601"). They were laminated at a rate of 3.0 m/min to obtain a laminated film.

Next, from the COP film side of the laminated film, peak illuminance: 400 mW/cm ² (confirmation required), cumulative exposure amount: 200 mJ/cm ² ( The adhesive composition was cured by irradiation with ultraviolet light (UVA region) to prepare a polarizing plate test piece.
Performance evaluation was performed as follows using the polarizing plate test piece obtained above.

<Performance evaluation>
[Adhesive strength]
A polarizing plate test piece was cut into 120 mm x 25 mm, and the adhesion (adhesion strength) between the COP film and the polarizer, and the PET film and the polarizer was measured using a measuring device: Autograph when stress was applied in a 90° direction. It was measured using Based on the above measured values, evaluation was made according to the following criteria.
(Evaluation criteria)
○...All were firmly adhered.
△...Both were weakly adhered.
×...None of them were adhered.

[Moist heat durability]
A test piece was cut into a size of 40 mm x 40 mm and left in an environment of 85° C. and 85% RH for 100 hours to perform a heat and humidity durability test. After the test, evaluation was made according to the following criteria.
(Evaluation criteria)
○...The amount of change in transmittance is less than 1% △...The amount of change in transmittance is 1% or more and less than 5% ×...The amount of change in transmittance is 5% or more

[Cold heat durability]
A thermal shock test was conducted in which a test piece was cut into a size of 100 mm x 100 mm, and a cycle of standing at -40°C for 30 minutes and then standing at 85°C for 30 minutes was repeated 100 times. After the test, evaluation was made according to the following criteria.
(Evaluation criteria)
○...No appearance defects were observed.
×...Poor appearance (cracks occurred in the polarizer layer) was observed.

From the above results, the adhesive compositions of Examples 1 and 2 containing the oxetane compound (A), the epoxy compound having an alicyclic structure (B), and the silane coupling agent (C) exhibited good curability. With this technology, the polarizer and protective film could be bonded together with high adhesive strength, and excellent results were obtained in terms of water resistance and durability. From this, it was found to be suitable for practical use as a well-balanced adhesive composition for polarizing plates.

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

The adhesive composition of the present invention and the adhesive composition for polarizing plates made of the adhesive composition described above have excellent adhesive properties between polarizers and protective films, and can be used with various protective films for polarizing plates and polarizers. Suitable for bonding with. Furthermore, the polarizing plate has excellent durability, especially thermal shock resistance. In addition to the above adhesive applications for polarizing plates, the adhesive composition of the present invention can be used, for example, for laminating various optical films or sheets, and for laminating electronic parts, precision instruments, packaging materials, display materials, etc. 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 comprising (A), (B), and (C).
For a total of 100 parts by weight of ingredients,
The content of the oxetane compound (A) is 35 to 65 parts by weight, and the silane coupling agent (C
) is 15 to 30 parts by weight . 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 epoxy compound (B) having an alicyclic structure has 2 epoxy groups introduced directly into the alicyclic structure.
The active energy ray-curable adhesive composition according to claim 1 or 2, characterized in that it contains at least one epoxy compound. 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. Content ratio of oxetane compound (A) and silane coupling agent (C) ((A):(C),
Claim 1, wherein the weight ratio (A):(C) is from 80:20 to 50:50.
The active energy ray-curable adhesive composition according to any one of 4 to 4. An adhesive composition for a polarizing plate, comprising the active energy ray-curable adhesive composition according to any one of claims 1 to 5. An adhesive for polarizing plates, comprising a cured product of the adhesive composition for polarizing plates according to claim 6. A polarizing plate comprising a polarizer and a protective film bonded together via the polarizing plate adhesive according to claim 7.