JP7003910B2 - Active energy ray-curable adhesive composition, polarizing plate adhesive composition, polarizing plate adhesive, 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, and 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 and a protective film.

The liquid crystal display device is widely used as an image display device 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, the polarizing plate has 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 (hereinafter, polyvinyl alcohol is abbreviated as “PVA”). ing. Here, as the polarizing element, a dichroic material such as iodine is dispersed and adsorbed in a PVA-based film formed by forming a film using a PVA-based resin having a high degree of saponification, and more preferably crosslinks such as boric acid. A uniaxially stretched PVA-based film crosslinked with an agent is widely used. Since such a splitter is a uniaxially stretched PVA-based film, it easily shrinks under high humidity, and a protective film is attached to the polarizing element 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 has transparency, mechanical strength, thermal stability, moisture barrier property, isotropic property, and the like. In particular, a protective film made of a triacetyl cellulose (TAC) resin has been widely used.

These protective films are bonded to the polarizing element by an adhesive, and the adhesive is similar to a PVA-based resin aqueous solution, particularly a polarizing element, from the viewpoint of adhesiveness to a polarizing element 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 thinner polarizing plates, and acrylic films and cyclic olefin resin (COP) films have been used in place of the TAC films that have been most commonly used as protective films. It has come to be. However, the protective film that replaces these TAC films has a problem that it is difficult to firmly bond the protective film to the polarizing element with the conventional PVA-based adhesive, and the appearance of the obtained polarizing plate is poor. This is because the acrylic film and the COP film are more hydrophobic than the TAC film, and the water permeability is low, so that the water cannot be sufficiently dried. Therefore, as an alternative to PVA-based adhesives, various adhesives suitable for bonding protective films such as acrylic films and COP films have been developed.

For example, Patent Document 1 specifies aromatic glycidyl ether and an oxetane compound having a specific amount of two or more oxetanyl groups and having a molecular weight of 100 to 800 as an adhesive for a polarizing plate having excellent adhesiveness and water resistance. A silane coupling agent having an alicyclic epoxy group in an amount and a cationically polymerizable adhesive containing a cationic polymerization initiator have been proposed.

Further, in Patent Document 2, a specific oxetane compound having two or more oxetanyl groups and an aromatic glycidyl ether are used as an adhesive capable of maintaining excellent normal adhesive strength for a long period of time regardless of the influence of heat or light. , And a cationically polymerizable adhesive containing a cationically polymerizable initiator has been proposed.

Further, in Patent Document 3, for the purpose of curability and durability as an adhesive, a photocurable adhesive containing a specific poly (meth) acrylate, a specific polyglycidyl ether, an oxetane compound, a photocationic polymerization initiator and the like. Agent compositions have been proposed.

International Publication No. 2012/144261 Japanese Unexamined Patent Publication No. 2010-229392 Japanese Unexamined Patent Publication No. 2015-40283

However, in the above Patent Documents 1 and 2, many epoxy groups having a ring structure such as an alicyclic epoxy group and an aromatic epoxy group are used, and the adhesive itself tends to be too hard and is an object of adhesion. Depending on the type of protective film and the like, sufficient adhesive strength and durability may not be obtained, and further improvement has been required.
Further, in Patent Document 3, when the usage environment is diversified and high durability is required in recent years, sufficient adhesive strength and durability are problems, and there is still room for improvement. Met.

Therefore, in the present invention, it is an adhesive having excellent adhesive strength under such a background, and is particularly suitable for bonding various protective films for polarizing plates and a polarizing element, and has curability, water resistance, and heat resistance. An active energy ray-curable adhesive composition capable of obtaining an adhesive having excellent durability such as impact resistance, an adhesive composition for a polarizing plate using the same, an adhesive for a polarizing plate, and a polarizing plate. It is to provide.

That is, as a result of diligent research in view of such circumstances, the present inventors have found that an active energy ray-curable adhesive composition in which cationic polymerization and radical polymerization are used in combination, the oxetane compound (A) and the epoxy compound (B). , The ethylenically unsaturated compound (C) and the photopolymerization initiator (D) are contained, and the aliphatic epoxy compound (B1) is contained as the epoxy compound (B), and the epoxy compound (B) is more than ever. It has been found that an adhesive capable of forming an adhesive layer having an excellent balance between durability such as thermal shock resistance and curability and adhesiveness can be obtained by containing a large amount of the adhesive.

That is, the present invention is an active energy ray-curable adhesive composition containing an oxetane compound (A), an epoxy compound (B), an ethylenically unsaturated compound (C) and a photopolymerization initiator (D). The epoxy compound (B) contains an aliphatic epoxy compound (B1), and the content ratio of the epoxy compound (B) is the oxetane compound (A), the epoxy compound (B), and the ethylenically unsaturated compound (B). The first gist is an active energy ray-curable adhesive composition which is 40 to 80% by weight based on the total amount of C).

Further, the second gist of the present invention is an adhesive composition for a polarizing plate, which comprises the active energy ray-curable adhesive composition of the first gist. Further, the polarizing plate adhesive, which is a cured product of the polarizing plate adhesive composition of the second gist, is the third gist. The fourth gist is a polarizing plate in which a polarizing element and a protective film are bonded to each other by the polarizing plate adhesive of the third gist.

The present invention contains a large amount of the epoxy compound (B) when photocationic polymerization and photoradical polymerization are used in combination. Usually, when photoradical polymerization is used in combination for the purpose of accelerating the curing rate and improving productivity, if a large amount of epoxy compound is contained, a sufficient curing rate cannot be obtained, and the curing of the epoxy compound becomes insufficient. Therefore, since it is considered that a problem of durability occurs, the content ratio of the epoxy compound is not increased, but in the present invention, the problem of curability, adhesiveness, and durability is obtained without causing such a problem. They have found an adhesive composition that can provide an excellent adhesive.

The active energy ray-curable adhesive composition of the present invention contains an oxetane compound (A), an epoxy compound (B), an ethylenically unsaturated compound (C) and a photopolymerization initiator (D), and the above epoxy compound ( B) contains the aliphatic epoxy compound (B1), and the content ratio of the epoxy compound (B) is the total of the oxetane compound (A), the epoxy compound (B) and the ethylenically unsaturated compound (C). It is 40 to 80% by weight based on the amount. Therefore, it has an excellent effect of adhesive strength, and in particular, it is possible to sufficiently bond various protective films for polarizing plates and a polarizing element, and further, a polarizing plate having excellent durability such as thermal shock resistance. Can be obtained.

Further, among the present inventions, in particular, when the epoxy compound (B) further contains an aromatic epoxy compound (B2), the balance between adhesiveness and durability such as thermal shock resistance is excellent. Will be.

Further, among the present inventions, in particular, the content ratio (B1 / B2) of the aliphatic epoxy compound (B1) to the aromatic epoxy compound (B2) is 10/90 to 90/10 by weight. , The balance between adhesiveness and durability such as thermal shock resistance is excellent.

Further, among the present inventions, in particular, the content ratio (AB / C) of the total amount (AB) of the oxetane compound (A) and the epoxy compound (B) to the ethylenically unsaturated compound (C) is the weight ratio. When it is 40/60 to 95/5, the balance between the adhesiveness and the durability such as thermal shock resistance is excellent.

Further, among the present inventions, in particular, when the content ratio (A / B) of the oxetane compound (A) to the epoxy compound (B) is 10/90 to 60/40 by weight, the adhesiveness and heat resistance are higher. It has excellent durability such as impact resistance.

Further, among the present inventions, in particular, when the photopolymerization initiator (D) contains a photocationic polymerization initiator (D1) and a photoradical polymerization initiator (D2), the adhesive composition is excellent in curability. It will be a radical.

Further, in the present invention, in particular, the content ratio (D1 / D2) of the photocationic polymerization initiator (D1) and the photoradical polymerization initiator (D2) is 20/80 to 99/1 in weight ratio. The more excellent the curability of the adhesive composition is.

Further, when the adhesive composition of the present invention further contains the silane coupling agent (E), the adhesiveness becomes more excellent.

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 "adhesive composition") is an oxetane compound (A), an epoxy compound (B), or an ethylenically unsaturated compound (C). And the photopolymerization initiator (D). Hereinafter, each component of the adhesive composition will be described in order.

In the present invention, (meth) acrylic means acrylic or methacrylic, (meth) acryloyl means acryloyl or methacrylic, and (meth) acrylate means acrylate or methacrylate.

<Oxetane compound (A)>
The oxetane compound (A) used in the present invention may be any compound having one or more oxetane group 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, and 3-. One oxetane group in a molecule such as ethyl-3- (cyclohexyloxymethyl) oxetane, 3-ethyl-3- (oxylanylmethoxy) oxetane, (meth) acrylic acid (3-ethyloxetane-3-yl) methyl, etc. Oxetane compound, 3-ethyl-3 {[(3-ethyloxetane-3-yl) methoxy] methyl} oxetane, 1,4-bis [(3-ethyl-3-oxetanyl) methoxymethyl] benzene, 4, Examples thereof include oxetane compounds having two or more oxetane groups in a molecule such as 4'-bis [(3-ethyl-3-oxetanyl) methoxymethyl] biphenyl. 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. ) Methyl] benzene, 3-ethyl-3- (2-ethylhexyloxymethyl) oxetane, 3-ethyl-3- (oxylanylmethoxy) oxetane, (meth) acrylic acid (3-ethyloxetane-3-yl) Methyl, 3-ethyl-3 {[(3-ethyloxetane-3-yl) methoxy] methyl} oxetane and the like are preferably used.

Further, from the viewpoint of coatability and adhesiveness, a molecular weight of 500 or less is preferable, and 100 to 500 is particularly preferable. An oxetane compound containing two or more oxetane group in the molecule or one oxetane group in the molecule is preferable because it is liquid at room temperature (25 ° C) and has excellent curability and durability. Oxetane compounds containing one (meth) acryloyl group or one epoxy group are preferred, in particular 3-ethyl-3 {[(3-ethyloxetane-3-yl) methoxy] methyl} oxetane, 3-. Ethyl-3- (oxylanylmethoxy) oxetane and (meth) acrylic acid (3-ethyloxetane-3-yl) methyl are preferably used.

When the oxetane compound contains an epoxy group or a (meth) acryloyl group in the molecule, it is assumed that the oxetane compound is contained in the oxetane compound (A), and the epoxy compound (B) or the ethylenically unsaturated compound (C) described later is used. Does not include.

Specific examples of the oxetane compound (A) include commercially available products such as "Aron Oxetane OXT-101", "Aron Oxetane OXT-121", "Aron Oxetane OXT-111", "Aron Oxetane OXT-212", and "Aron Oxetane OXT-212". "Aron Oxetane OXT-213", "Aron Oxetane OXT-221" (both manufactured by Toagosei Co., Ltd.) and the like can be used. In particular, "Aron Oxetane OXT-101" and "Aron Oxetane OXT-221" are preferable.

<Epoxy compound (B)>
The present invention uses the epoxy compound (B) as a cationic polymerization component. Further, the epoxy compound (B) contains an aliphatic epoxy compound (B1) from the viewpoint of adhesiveness, and further from the viewpoint of the balance between adhesiveness and durability, the aromatic epoxy compound (B2). It is preferable to use in combination.

Examples of the aliphatic epoxy compound (B1) include 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. An aliphatic epoxy compound having one group, 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 Examples thereof include bifunctional or higher aliphatic epoxy compounds having two or more epoxy groups in the molecule such as polyglycidyl ether. These aliphatic epoxy compounds (B1) can be used alone or in combination of two or more.

Among them, a bifunctional or higher aliphatic epoxy compound having two or more epoxy groups in the molecule is preferable from the viewpoint of curability, adhesiveness, and durability, and further, 1,4-butanediol diglycidyl ether, 1, It is preferable to use 6-hexanediol diglycidyl ether and neopentyl glycol diglycidyl ether.

The aromatic epoxy compound (B2) includes, for example, one epoxy group in a molecule such as phenyl glycidyl ether, p-tert-butyl phenyl glycidyl ether, p-sec-butyl phenyl glycidyl ether, and dibromophenyl glycidyl ether. Aromatic epoxy compounds, phthalic acid diglycidyl ester, terephthalic acid diglycidyl ester, resorcin diglycidyl ether, hydroquinone diglycidyl ether, bromobisphenol A diglycidyl ether, bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol Examples thereof include aromatic epoxy compounds having two or more epoxy groups in the molecule such as E-type epoxy resin, phenol novolac type epoxy resin, cresol novolac type epoxy resin, novolak type epoxy resin, and biphenyl type epoxy resin. These aromatic epoxy compounds (B2) can be used alone or in combination of two or more.

Among them, aromatic epoxy compounds having two or more epoxy groups in the molecule are preferable from the viewpoint of adhesiveness and durability, and bisphenol A type epoxy resin and bisphenol F type epoxy resin are particularly excellent from the viewpoint of excellent curability. It is preferable to use it.

In the above epoxy compound (B), when the aliphatic epoxy compound (B1) and the aromatic epoxy compound (B2) are used in combination, the aliphatic epoxy compound (B1) is compared with the aromatic epoxy compound (B2). The content ratio (B1 / B2) is preferably 10/90 to 90/10 in terms of weight ratio, particularly 15/85 to 85/15, further 20/80 to 80/20, and particularly 33 /. It is 67 to 75/25, further 50/50 to 75/25, and particularly 60/40 to 70/30.

If the content ratio is too small (the amount of the aromatic epoxy compound (B2) is too large), the adhesive strength is lowered, the coatability is lowered due to the increase in viscosity, and the compatibility of the adhesive composition is lowered. There is a tendency, and if the content ratio is too large (too much aliphatic epoxy compound (B1)), the durability tends to decrease.

Further, the epoxy compound (B) used in the present invention may contain other epoxy compounds (B3) in addition to the aliphatic epoxy compound (B1) and the aromatic epoxy compound (B2).

Examples of the other epoxy compound (B3) include a triazine skeleton-containing epoxy compound, an alicyclic epoxy compound, and an alicyclic skeleton-containing epoxy compound. These can be used alone or in combination of two or more.

The above-mentioned triazine skeleton-containing epoxy compound contains one or more epoxy groups and a triazine skeleton in the molecule, and is, for example, tris (2,3-epoxypropyl) -isocyanurate, tris (3,4-epoxybutyl). )-Isocyanurate, Tris (4,5-epoxypentyl) -Isocyanurate, Tris- (5,6-epoxyhexyl) -Isocyanurate, Tris (6,7-epoxyheptyl) -Isocyanurate, Tris (7,8) -Epoxy octyl) -isocyanurate and the like. These can be used alone or in combination of two or more.
From the viewpoint of further improving durability (heat impact resistance), it is also preferable to use a triazine skeleton-containing epoxy compound.

The triazine skeleton-containing epoxy compound preferably has an epoxy equivalent of 120 g / eq or more, particularly preferably 130 to 300 g / eq, and even more preferably 140 to 250 g / eq, from the viewpoint of adhesiveness and durability.

As the above-mentioned triazine skeleton-containing epoxy compound, specifically, a commercially available TEPIC series (“TEPIC-G”, “TEPIC-S”, “TEPIC-SS”, “TEPIC-HP”, manufactured by Nissan Chemical Industry Co., Ltd., "TEPIC-L", "TEPIC-PAS", "TEPIC-VL", "TEPIC-UC", "TEPIC-FL", etc.) and the like can be used. Among them, the liquid epoxy compounds "TEPIC-PAS", "TEPIC-VL", "TEPIC-UC", and "TEPIC-FL" are preferable from the viewpoint of compatibility.

Examples of the alicyclic epoxy compound include dicyclopentadiene oxide, limonendioxide, 4-vinylcyclohexenedioxide, 3', 4'-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate, and ε-caprolactone modification. Examples thereof include 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 "Selokiside 2021P" and "Selokiside 2000" manufactured by Daicel can be used.

Examples of the alicyclic skeleton-containing epoxy compound include an epoxy compound in which an aromatic ring is hydrogenated, such as hydrogenated bisphenol A diglycidyl ether, and 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 Corporation can be used.

The content of at least one of the alicyclic epoxy compound and the alicyclic skeleton-containing epoxy compound is preferably 30% by weight or less based on the total amount of the oxetane compound (A) and the epoxy compound (B), more preferably. It is 20% by weight or less, particularly preferably 15% by weight or less. If the content of at least one of the alicyclic epoxy compound and the alicyclic skeleton-containing epoxy compound is too large, the adhesive strength tends to decrease.

The content of the other epoxy compound (B3) is preferably 30% by weight or less, more preferably 20% by weight or less, and particularly preferably 10% by weight or less with respect to the entire epoxy compound (B). If the content of the other epoxy compound (B3) is too large, the adhesive strength tends to decrease.

<Ethylene unsaturated compound (C)>
The ethylenically unsaturated compound (C) is a radical polymerization component and is an unsaturated compound having at least one ethylenically unsaturated group in the molecule. By containing the ethylenically unsaturated compound (C), the curing rate can be adjusted and the curing property is improved.

Examples of the ethylenically unsaturated compound (C) include (meth) acrylic compounds having at least one (meth) acryloyl group in the molecule.

The (meth) acrylic compound may be described as, for example, a (meth) acrylic compound having one (meth) acryloyl group in the molecule (hereinafter, referred to as “monofunctional (meth) acrylic compound”. ), (Meta) acrylic compounds having two or more (meth) acryloyl groups in the molecule (hereinafter, may be referred to as "polyfunctional (meth) acrylic compounds").
These (meth) acrylic compounds can be used alone or in combination of two or more.

Examples of the monofunctional (meth) acrylic compound include an alkyl (meth) acrylate compound, a polar group-containing (meth) acrylic compound, an alicyclic (meth) acrylate compound, and an aromatic (meth) acrylate compound. Examples thereof include (meth) acrylic compounds having a (meth) acryloyl group and a reactive functional group other than the (meth) acryloyl group in the molecule.

As the alkyl (meth) acrylate-based compound, for example, an alkyl (meth) acrylate having an alkyl group having 1 to 20 carbon atoms, particularly 1 to 15 and 4 to 10 carbon atoms is preferable, and specifically, a methyl (meth) acrylate compound is used. ) Acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, isopropyl (meth) acrylate, butyl (meth) acrylate, isobutyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, octyl (meth) acrylate, isooctyl (meth) ) Acrylate, lauryl (meth) acrylate, stearyl (meth) acrylate and the like can be mentioned.

Examples of the polar group-containing (meth) acrylic compound include a carboxyl group-containing (meth) acrylic compound, a hydroxyl group-containing (meth) acrylate compound, a nitrogen atom-containing (meth) acrylic compound, and an alkoxy group-containing (meth) acrylate. Examples include system compounds.

Examples of the carboxyl group-containing (meth) acrylic compound include (meth) acrylic acid, crotonic acid, maleic acid, maleic anhydride, itaconic acid, fumaric acid, acrylamide N-glycolic acid, silicic acid, and (meth). Michael adducts of acrylic acid (eg, acrylic acid dimer, methacrylic acid dimer, acrylic acid trimmer, methacrylic acid trimmer, tetramer acrylate, tetramer methacrylic acid, etc.), 2- (meth) acryloyloxyethyl dicarboxylic acid monoester (eg, eg) 2- (Meta) acryloyloxyethyl succinic acid monoester, 2- (meth) acryloyloxyethyl phthalic acid monoester, 2- (meth) acryloyloxyethyl hexahydrophthalic acid monoester, etc.) and the like.

Examples of the hydroxyl group-containing (meth) acrylate compound include 2-hydroxyethyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 5-hydroxypentyl (meth) acrylate, and 6-hydroxyhexyl (meth). Hydroxyalkyl (meth) acrylate compounds such as acrylates, caprolactone-modified (meth) acrylate compounds such as caprolactone-modified 2-hydroxyethyl (meth) acrylates, ethylene glycol mono (meth) acrylates, propylene glycol mono (meth) acrylates, and pentane Dihydric alcohol mono (meth) acrylate compounds such as diol mono (meth) acrylate and hexanediol mono (meth) acrylate, diethylene glycol mono (meth) acrylate, triethylene glycol mono (meth) acrylate, tetraethylene glycol. Polyalkylene glycols such as mono (meth) acrylates, mono (meth) acrylates of polyethylene glycol, mono (meth) acrylates of dipropylene glycol, mono (meth) acrylates of tripropylene glycol, and mono (meth) acrylates of polypropylene glycol. Mono (meth) acrylate-based compounds, and other primary hydroxyl group-containing (meth) acrylate-based compounds such as 2-acryloyloxyethyl-2-hydroxyethylphthalic acid; 2-hydroxypropyl (meth) acrylate, 2-hydroxy. Examples thereof include secondary hydroxyl group-containing (meth) acrylate compounds such as butyl (meth) acrylate; and tertiary hydroxyl group (meth) acrylate compounds such as 2,2-dimethyl2-hydroxyethyl (meth) acrylate.
Among such hydroxyl group-containing (meth) acrylate-based compounds, primary hydroxyl group-containing (meth) acrylate-based compounds are preferable, and hydroxyalkyl (meth) acrylate-based compounds are particularly preferable because they are likely to form hydrogen bonds with a substrate or a polarizing element and have excellent reactivity. Meta) acrylate compounds and mono (meth) acrylate compounds of polyalkylene glycol are preferable.

Examples of the nitrogen atom-containing (meth) acrylic compound include an amide group-containing (meth) acrylic compound, an amino group-containing (meth) acrylic compound, and other nitrogen atom-containing (meth) acrylic compounds.
Examples of the amide group-containing (meth) acrylic compound include (meth) acrylamide; N, N-dialkyl (meth) acrylamide such as N, N-dimethyl (meth) acrylamide and N, N-diethyl (meth) acrylamide; N-methoxymethyl (meth) acrylamide, N-ethoxymethyl (meth) acrylamide, N-propoxymethyl (meth) acrylamide, N-isopropoxymethyl (meth) acrylamide, Nn-butoxymethyl (meth) acrylamide, N- N-alkoxyalkyl (meth) acrylamide such as isobutoxymethyl (meth) acrylamide; hydroxylated-containing acrylamide such as N- (hydroxymethyl) (meth) acrylamide; N- (3-N, N-dimethylaminopropyl) (meth) Examples thereof include acrylamide, methylenebis (meth) acrylamide, and ethylenebis (meth) acrylamide.
Examples of the amino group-containing (meth) acrylic compound include, for example, aminomethyl (meth) acrylate, aminoethyl (meth) acrylate and the like, primary amino group-containing (meth) acrylate such as aminoalkyl (meth) acrylate, and tert-butyl. Secondary amino group-containing (meth) acrylate such as aminoethyl (meth) acrylate, ethylaminoethyl (meth) acrylate, dimethylaminoethyl (meth) acrylate, diethylaminoethyl (meth) acrylate, etc., dialkylaminoalkyl (meth) acrylate, etc. Examples thereof include heterocyclic amine monomers such as tertiary amino group-containing (meth) acrylate and acryloylmorpholine.

Examples of the alkoxy group-containing (meth) acrylate compound include 2-methoxyethyl (meth) acrylate, 2-ethoxyethyl (meth) acrylate, 3-methoxybutyl (meth) acrylate, and 2-butoxyethyl (meth) acrylate. Ekoxyalkyl (meth) acrylate compounds such as 2-butoxydiethylene glycol (meth) acrylate, methoxydiethylene glycol (meth) acrylate, methoxytriethylene glycol (meth) acrylate, ethoxydiethylene glycol (meth) acrylate, methoxydipropylene glycol (meth) Contains polyether chains such as acrylate, methoxypolyethylene glycol (meth) acrylate, octoxypolyethylene glycol-polypropylene glycol-mono (meth) acrylate, lauroxypolyethylene glycol mono (meth) acrylate, and stearoxypolyethylene glycol mono (meth) acrylate ( Meta) Examples thereof include acrylate compounds.

Examples of the alicyclic (meth) acrylate compound include cyclohexyl (meth) acrylate, isobornyl (meth) acrylate, 1,4-cyclohexanedimethylolmono (meth) acrylate, dicyclopentanyl (meth) acrylate, and dicyclo. Examples thereof include pentenyl (meth) acrylate, dicyclopentenyloxyethyl (meth) acrylate, and 2-adamantyl (meth) acrylate.

Examples of the aromatic (meth) acrylate compound include phenyl (meth) acrylate; benzyl (meth) acrylate; phenoxyethyl (meth) acrylate, phenoxypropyl (meth) acrylate and the like phenoxyalkyl (meth) acrylate; phenoxydiethylene glycol ( Phenoxydialkylene glycol (meth) acrylates such as meth) acrylates and phenoxydipropylene glycol (meth) acrylates; phenoxypolyethylene glycol (meth) acrylates; phenoxypolyethylene glycol-polypropylene glycol- (meth) acrylates; p-cumylphenolalkylene oxides. Examples thereof include (meth) acrylate of an adduct, (meth) acrylate of an o-phenylphenol alkylene oxide adduct, (meth) acrylate of a phenol alkylene oxide adduct, and (meth) acrylate of a nonylphenol alkylene oxide adduct.

Examples of the (meth) acrylic compound having a (meth) acryloyl group and a reactive functional group other than the (meth) acryloyl group in the molecule include glycidyl methacrylate, 4-hydroxybutyl acrylate glycidyl ether, and 3,4-epoxycyclohexyl. Epoxy group-containing (meth) acrylate compounds such as methyl (meth) acrylate, vinyl group-containing (meth) acrylate compounds such as 2- (2-vinyloxyethoxy) ethyl (meth) acrylate, 2- (meth) acryloyloxy Examples thereof include isocyanate group-containing (meth) acrylate compounds such as ethyl isocyanate.
When the ethylenically unsaturated compound is an epoxy group-containing (meth) acrylate compound, it shall be included in the ethylenically unsaturated compound (C) and not included in the epoxy compound (B).

In addition, (meth) acrylate compounds having a cyclic ether structure such as tetrahydrofurfuryl (meth) acrylate and caprolactone-modified tetrahydrofurfuryl (meth) acrylate can also be mentioned.

Examples of the polyfunctional (meth) acrylic compound include a bifunctional (meth) acrylic compound and a trifunctional or higher functional (meth) acrylic compound.

Examples of the bifunctional (meth) acrylic compound include ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, tetraethylene glycol di (meth) acrylate, and polyethylene glycol di (). Meta) acrylate, propylene glycol di (meth) acrylate, dipropylene glycol di (meth) acrylate, polypropylene glycol di (meth) acrylate, 1,3-butylene glycol di (meth) acrylate, neopentyl glycol di (meth) acrylate, 1,4-Butanediol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, glycerindi (meth) acrylate, pentaerythritol di (meth) acrylate, ethylene glycol diglycidyl ether di (meth) acrylate, Di (meth) acrylate having a long-chain or branched chain structure such as diethylene glycol diglycidyl ether di (meth) acrylate, hydroxypivalic acid-modified neopentyl glycol di (meth) acrylate; cyclohexanedimethanol di (meth) acrylate, dimethylol di. Di (meth) acrylate having an alicyclic structure such as cyclopentane di (meth) acrylate, tricyclodecanedimethanol di (meth) acrylate, ethylene oxide-modified cyclohexanedimethanol di (meth) acrylate; ethylene oxide-modified bisphenol A type di (Meta) acrylate, alkylene oxide modified bisphenol A type di (meth) acrylate such as propylene oxide modified bisphenol A type di (meth) acrylate, bisphenol A diglycidyl ether di (meth) acrylate, phthalic acid diglycidyl ester di (meth) Di (meth) acrylate having an aromatic ring such as acrylate; Di (meth) acrylate having a ring structure such as isocyanuric acid ethylene oxide-modified di (meth) acrylate and the like can be mentioned.

Examples of the trifunctional or higher functional (meth) acrylic compound include trimethylolpropanetri (meth) acrylate, pentaerythritol tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, dipentaerythritol penta (meth) acrylate, and di. Pentaerythritol hexa (meth) acrylate, polyglycerin poly (meth) acrylate; caprolactone-modified dipentaerythritol penta (meth) acrylate, caprolactone-modified dipentaerythritol hexa (meth) acrylate, caprolactone-modified pentaerythritol tri (meth) acrylate, caprolactone-modified Pentaerythritol tetra (meth) acrylate, ethylene oxide-modified dipentaerythritol penta (meth) acrylate, ethylene oxide-modified dipentaerythritol hexa (meth) acrylate, ethylene oxide-modified pentaerythritol tri (meth) acrylate, ethylene oxide-modified pentaerythritol tetra ( Trifunctional or higher (meth) acrylate having a long-chain or branched chain structure such as trifunctional or higher (meth) acrylate having an alkyl-modified structure such as meth) acrylate and ethylene oxide-modified glycerintri (meth) acrylate; isocyanul. Examples thereof include tri (meth) acrylate having a ring structure such as acid ethylene oxide modified triacrylate.

In addition, oligomers such as urethane (meth) acrylate, polyester (meth) acrylate and epoxy (meth) acrylate can also be used as the (meth) acrylic compound.

As the ethylenically unsaturated compound (C), it is preferable to use a bifunctional or higher functional (meth) acrylic compound from the viewpoint of improving the curability of the adhesive composition and enhancing the durability. In particular, a bifunctional or higher functional (meth) acrylic compound having an alicyclic ring or an aromatic ring, or a (meth) acrylic compound having a linear or branched chain structure without a polyalkylene oxide skeleton is preferable, and further. , A (meth) acrylic compound having a branched chain structure without a polyalkylene oxide skeleton is preferable.

<Photopolymerization initiator (D)>
The adhesive composition of the present invention exhibits adhesiveness by reacting the above-mentioned oxetane compound (A), epoxy compound (B), and ethylenically unsaturated compound (C) by irradiating with active energy rays. In such a reaction, the photopolymerization initiator (D) is contained.
As the photopolymerization initiator (D), it is preferable to contain a photocationic polymerization initiator (D1), and in particular, it is sufficient to contain a photocationic polymerization initiator (D1) and a photoradical polymerization initiator (D2). It is preferable in terms of obtaining a good curability.

By using the photocationic polymerization initiator (D1), the adhesive composition can be cured at room temperature (25 ° C. ± 10 ° C.), and the protective film and the polarizing element can be adhered well.
The photocationic polymerization initiator (D1) is a compound that produces a cationic species or Lewis acid by irradiation with active energy rays, and is, for example, an aromatic diazonium salt, an onium salt such as an aromatic iodonium salt or an aromatic sulfonium salt, and the like. Examples thereof include an iron-allene complex.

Examples of the aromatic diazonium salt include benzenediazonium / hexafluoroantimonate, benzenediazonium / hexafluorophosphate, benzenediazonium / hexafluoroborate and the like.

Examples of the aromatic iodine salt include diphenyliodonium / tetrakis (pentafluorophenyl) borate, diphenyliodonium / hexafluorophosphate, diphenyliodonium / hexafluoroantimonate, di (4-nonylphenyl) iodinenium / hexafluorophosphate and the like. can give.

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) phenylsulfonate] diphenylsulfide / bishexafluoroantimonate, 4,4'-Bis [di (β-hydroxyethoxy) phenylsulfonate] diphenylsulfide bishexafluorophosphate, 7- [di (p-toluyl) sulfonate] -2-isopropylthioxanthone hexafluoroantimonate, 7- [Di (p-Truyl) 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) sulfonate-diphenylsulfide tetrakis (pentafluorophenyl) ) Volate etc. can be mentioned.

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.

Among such photocationic polymerization initiators (D1), it is preferable to use an aromatic iodonium salt or an aromatic sulfonium salt from the viewpoint of reacting with a light source having a long wavelength with high sensitivity.
The photocationic polymerization initiator (D1) can be used alone or in combination of two or more.

Further, the photoradical polymerization initiator (D2) generates radicals by irradiation with active energy rays to react the ethylenically unsaturated compound (C). Examples of the photoradical polymerization initiator (D2) include diethoxyacetophenone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, benzyldimethylketal, and 4- (2-hydroxyethoxy) phenyl-( 2-Hydroxy-2-propyl) ketone, 1-hydroxycyclohexylphenylketone, 1- [4- (2-hydroxyethoxy) -phenyl] -2-hydroxy-2-methyl-1-propane-1-one, 2- Methyl-2-morpholino (4-thiomethylphenyl) propan-1-one, 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) butanone, 2-hydroxy-2-methyl-1- [4- (1-Methylvinyl) phenyl] Acetphenones such as propanone oligomers; benzoins such as benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzoin isobutyl ether; benzophenone, o-methyl benzoyl benzoate, 4-phenyl Benzoyl, 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, benzophenones such as (4-benzoylbenzyl) trimethylammonium 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-on Thioxanthons such as mesochloride; 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, bis (2,6-dimethoxybenzoyl) -2,4,4-trimethyl-pentylphosphinoxide, bis (2,4) 6-trimethylbenzoyl) -acylphosphinoxides such as phenylphosphinoxide; 1,2-octanedione, 1- [4- (phenylthio) phenyl-, 2- (O-benzoyloxime)], etanone, 1- [9-Ethyl-6- (2-Methylbenzoyl) -9H-Carbazole-3-yl]-, 1- (O-Acetylo) Examples thereof include oxime esters such as xim).

Among the above-mentioned photoradical polymerization initiators (D2), it is preferable to use acylphosphine oxides, and in particular, 2,4,6-trimethylbenzoyl-diphenylphosphinoxide and bis (2,6-dimethoxybenzoyl). ) -2,4,4-trimethyl-pentylphosphine oxide, bis (2,4,6-trimethylbenzoyl) -phenylphosphinoxide are preferable, and further 2,4,6-trimethylbenzoyl-phenylphosphin oxide. , Bis (2,4,6-trimethylbenzoyl) -phenylphosphine oxide is preferably used.

In addition, as these auxiliaries, triethanolamine, triisopropanolamine, 4,4'-dimethylaminobenzophenone (Michler ketone), 4,4'-diethylaminobenzophenone, 2-dimethylaminoethyl benzoic acid, 4-dimethylaminobenzoic acid Ethyl, 4-dimethylaminobenzoic acid (n-butoxy) ethyl, 4-dimethylaminobenzoate isoamyl, 4-dimethylaminobenzoate 2-ethylhexyl, 2,4-diethylthioxanthone, 2,4-diisopropylthioxanson Etc. can be used together.

In the present invention, the content of the photopolymerization initiator (D) is the sum of the oxetane compound (A), the epoxy compound (B), and the ethylenically unsaturated compound (C) in terms of obtaining sufficient curability. The amount is preferably 0.5 to 20 parts by weight, particularly preferably 0.5 to 15 parts by weight, and more preferably 1.0 to 10 parts by weight with respect to 100 parts by weight.
If the content is too small, the curability tends to decrease, the mechanical strength and the adhesive strength tend to decrease, and if the content is too large, the solubility of the photopolymerization initiator (D) itself in the composition tends to decrease.

Further, when the photocationic polymerization initiator (D1) and the photoradical polymerization initiator (D2) are used in combination, the content ratio (D1 /) of the photocationic polymerization initiator (D1) and the photoradical polymerization initiator (D2). The D2) (weight ratio) is preferably 20/80 to 99/1, particularly 40/60 to 95/5, and more preferably 50/50 to 90/10 in terms of obtaining sufficient curability. If the content ratio is too small, the curing of the cationic curing component tends not to proceed sufficiently, and if it is too large, the curing of the radical curing component tends not to proceed.

Further, the content of the photocationic polymerization initiator (D1) is preferably 0.5 to 20 parts by weight based on 100 parts by weight of the total amount of the oxetane compound (A) and the epoxy compound (B). Is preferably 1 to 15 parts by weight, more preferably 1.5 to 10 parts by weight. If the content of the photocationic polymerization initiator (D1) is too high, the solubility tends to decrease or the durability tends to decrease, and if it is too small, the curability tends to decrease, and the mechanical strength and the adhesive strength tend to decrease. be.

The content of the photoradical polymerization initiator (D2) is preferably 15 parts by weight or less, particularly 10 parts by weight or less, and further 5 parts by weight with respect to 100 parts by weight of the ethylenically unsaturated compound (C). The following is preferred. If the content of the photoradical polymerization initiator (D2) is too large, the solubility of the photoradical polymerization initiator (D2) tends to decrease, and the durability of the adhesive layer tends to decrease. The lower limit is usually 0.1 parts by weight, and if it is too small, the curability tends to decrease, and the adhesive strength and mechanical strength of the adhesive layer tend to decrease.

Further, in particular, in terms of curing efficiency (which can be efficiently cured with a small irradiation amount of active energy rays), a preferable combination of the photocationic polymerization initiator (D1) and the photoradical polymerization initiator (D2) is a photocation. This is a combination in which an aromatic sulfonium salt and an aromatic iodonium salt are used as the polymerization initiator (D1), and acylphosphine oxides are used as the photoradical polymerization initiator (D2).

The adhesive composition of the present invention contains the above-mentioned oxetane compound (A), epoxy compound (B), ethylenically unsaturated compound (C) and photopolymerization initiator (D), and further the present invention. The most characteristic feature of the above is that the content ratio of the epoxy compound (B) is 40 to 80% by weight based on the total amount of the oxetane compound (A), the epoxy compound (B) and the ethylenically unsaturated compound (C). It is preferably 42 to 70% by weight, more preferably 45 to 65% by weight. If the content of the epoxy compound (B) is too small, the adhesive strength will decrease, and if it is too large, the curing speed will decrease, the mechanical strength will decrease, and the durability will decrease.

Further, the content ratio (AB / C) of the total amount (AB) of the oxetane compound (A) and the epoxy compound (B) to the ethylenically unsaturated compound (C) is 40/60 to 95/5 by weight. This is preferable in terms of the balance between adhesive strength and durability, and particularly preferably 50/50 to 90/10, more preferably 60/40 to 85/15. If the content ratio is too small ((AB) is too small), the curing shrinkage tends to be large and the adhesive strength tends to decrease, and if it is too large ((AB) is too large), the curing rate tends to decrease. ..

The content ratio (A / B) of the oxetane compound (A) to the epoxy compound (B) is preferably 10/90 to 60/40 by weight, and is particularly preferable in terms of adhesive strength and durability. It is preferably / 88 to 50/50, more preferably 15/85 to 40/60. If the content ratio is too small (if (A) is too small), the epoxy compound (B) does not cure sufficiently, the durability tends to decrease, and the adhesive strength is too large ((A) is too large). Tends to decrease.

<Silane coupling agent (E)>
The adhesive composition of the present invention preferably further contains a silane coupling agent (E) from the viewpoint of improving adhesiveness.

The silane coupling agent (E) 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 silane coupling agent (E) include an epoxy group-containing silane coupling agent, a mercapto group-containing silane coupling agent, a (meth) acryloyl group-containing silane coupling agent, an amino group-containing silane coupling agent, and an isocyanate group. Examples thereof include a contained silane coupling agent, a vinyl group-containing silane coupling agent, a hydroxyl group-containing silane coupling agent, a carboxyl group-containing silane coupling agent, and an amide group-containing silane coupling agent. These can be used alone or in combination of two or more.

Examples of the epoxy group-containing silane coupling agent include 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, and 3-glycidoxypropyl. A monomer type silane coupling agent containing a glycidyloxy group (aliphatic epoxy group) such as methyldimethoxysilane, and an alicyclic epoxy group-containing silane coupling agent such as 2- (3,4 epoxycyclohexyl) ethyltrimethoxysilane. An epoxy group-containing silane coupling agent or a part of the above silane compound is hydrolyzed and polymerized, or the above silane compound and an alkyl group such as methyltriethoxysilane, ethyltriethoxysilane, methyltrimethoxysilane, or ethyltrimethoxysilane. Examples thereof include an oligomer-type silane coupling agent in which the contained silane compound is co-condensed. These can be used alone or in combination of two or more.
When the silane coupling agent contains an epoxy group, it shall be included in the silane coupling agent (E) and not included in the epoxy compound (B).

Examples of the mercapto group-containing silane coupling agent include monomer-type mercaptos such as 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, γ-mercaptopropyldimethoxymethylsilane, and 3-mercaptopropylmethyldimethoxysilane. A group-containing silane coupling agent or a part of the above silane compound is hydrolyzed and polymerized, or the above silane compound contains an alkyl group such as methyltriethoxysilane, ethyltriethoxysilane, methyltrimethoxysilane, or ethyltrimethoxysilane. Examples thereof include an oligomer-type silane coupling agent in which a silane compound is co-condensed. These can be used alone or in combination of two or more.

Examples of the (meth) acryloyl group-containing silane coupling agent include 3-acryloxypropyltrimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, and 3-methacryloxypropyltri. Examples thereof include ethoxysilane and 3-acryloxypropyltrimethoxysilane. These can be used alone or in combination of two or more.
When the silane coupling agent contains a (meth) acryloyl group, it shall be included in the silane coupling agent (E) and not included in the ethylenically unsaturated compound (C).

Examples of the amino group-containing silane coupling agent include N-2- (aminoethyl) -3-aminopropylmethyldimethoxysilane, N-2- (aminoethyl) -3-aminopropyltrimethoxysilane, and 3-amino. Examples thereof include propyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-triethoxysilyl-N- (1,3-dimethyl-butylidene) propylamine, N-phenyl-3-aminopropyltrimethoxysilane. These can be used alone or in combination of two or more.

Examples of the isocyanate group-containing silane coupling agent include 3-isocyanatepropyltriethoxysilane. These can be used alone or in combination of two or more.

Examples of the vinyl group-containing silane coupling agent include vinyltrimethoxysilane and vinyltriethoxysilane. These can be used alone or in combination of two or more.
When the silane coupling agent contains a vinyl group, it shall be included in the silane coupling agent (E) and not included in the ethylenically unsaturated compound (C).

Among the silane coupling agents (E), the epoxy group-containing silane coupling is excellent in reactivity with the cationic polymerization component (oxetane compound (A) and epoxy compound (B)) and the radical polymerization component (C). It is preferable to use an agent, a vinyl group-containing silane coupling agent, and a (meth) acryloyl group-containing silane coupling agent, and particularly preferably an epoxy group-containing silane coupling agent and a (meth) acryloyl group-containing silane coupling agent. The silane coupling agent (E) may be a monomer-type silane coupling agent or an oligomer-type silane coupling agent that is partially hydrolyzed and polycondensed, but from the viewpoint of compatibility and adhesiveness, it may be used. It is preferable to use a monomer-type silane coupling agent.

The content of the silane coupling agent (E) shall be 2 to 50 parts by weight with respect to 100 parts by weight of the total amount of the oxetane compound (A), the epoxy compound (B) and the ethylenically unsaturated compound (C). Is preferable, and particularly preferably 3 to 40 parts by weight, still more preferably 5 to 30 parts by weight. If the content of the silane coupling agent (E) is too large, the liquid stability tends to decrease, and the durability (heat impact resistance) after curing tends to decrease. If the content is too small, the adhesiveness is further improved. Tends not be obtained sufficiently.

In addition to the above components, the adhesive composition of the present invention includes photosensitizers, polyols, antistatic agents, other adhesives, acrylic resins, urethane resins, as long as the effects of the present invention are not impaired. Adhesives, plasticizers, colorants such as rosin, rosin ester, hydrogenated rosin ester, phenol resin, aromatic modified terpene resin, aliphatic petroleum resin, alicyclic petroleum resin, styrene resin, xylene resin, etc. , Other additives such as fillers, antioxidants, UV absorbers, functional dyes, and compounds that cause color development or discoloration by UV 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.

By using the photosensitizer, the reactivity can be improved, and the mechanical strength and the adhesive strength of the cured product can be improved. Examples of the photosensitizer include anthracene derivatives such as 9,10-dibutoxyanthrasene and 9,10-diethoxyanthracene; 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-diethylthioxanthen-9-one; persulfides, redox-based Examples thereof include compounds, azo and diazo compounds, halogen compounds, photoreducing dyes and the like. These can be used alone or in combination of two or more. Among them, 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 photopolymerization initiator (D) 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.

<Adhesive composition>
The adhesive composition of the present invention is 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 active energy ray-curable adhesive composition of the present invention becomes an adhesive by being cured by irradiation with active energy rays, and in particular, an adhesive for a polarizing plate for adhering a polarizing element and a protective film. Can be suitably used as.

<Polarizer>
The polarizing plate of the present invention is obtained by bonding a polarizing element and a protective film via a polarizing plate adhesive. Specifically, a protective film is bonded to at least one surface, preferably both sides of the polarizing element, using the polarizing plate adhesive of the present invention, and usually, a liquid polarizing plate adhesive composition is used. A polarizing plate can be obtained by uniformly applying the polarizing element surface, the protective film surface, or both surfaces, then bonding the two together, crimping them, and irradiating them with active energy rays.

As the substituent, a film made of a PVA-based resin having an average degree of polymerization of 1,500 to 10,000 and a degree of saponification of 85 to 100 mol%, preferably 95 to 100 mol% is usually used as a raw film. A uniaxially stretched film (usually 2 to 10 times, preferably about 3 to 7 times) dyed with an aqueous solution of iodine-potassium iodide or a dichroic dye is used.

The PVA-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. It may contain a component that can be copolymerized with vinyl acetate, such as unsaturated sulfonate. Further, the PVA-based resin also includes so-called polyvinyl acetal resins such as polyvinyl butyral resin and polyvinyl formal resin and PVA derivatives obtained by reacting PVA with aldehydes in the presence of an acid.

As the protective film for the polarizing plate, an acrylic film, a polyethylene film, a polypropylene film, a cycloolefin film or the like can be used in addition to the conventional TAC film, and the adhesive composition of the present invention is a TAC film. It is suitably used for any protective film selected from films, acrylic films, cycloolefin films, polyethylene terephthalates (PET) films and the like.

When the adhesive composition of the present invention is applied onto a stator 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, far ultraviolet rays, ultraviolet rays, near ultraviolet rays, rays such as infrared rays, electromagnetic waves such as X-rays and γ-rays, as well as electron beams, proton rays, neutron rays and the like can be used. Ultraviolet rays are preferable because of their 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, a 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 3000 mJ / cm ² , preferably 10 to 2000 mJ / cm ² , and more preferably 20 to 1000 mJ / cm ² .

In particular, in the case of the high-pressure mercury lamp, for example, it is usually carried out under the condition of usually 5 to 3000 mJ / cm ² , preferably 50 to 2000 mJ / cm ² .
Further, in the case of the above-mentioned electrodeless lamp, for example, it is usually carried out under the condition of 2 to 2000 mJ / cm ² , preferably 10 to 1000 mJ / cm ² .

The irradiation time varies depending on the type of light source, the distance between the light source and the coated surface, the coating thickness, and other conditions, but is usually several seconds to several tens of seconds, and in some cases, a fraction of a second.

On the other hand, in the case of the above-mentioned electron beam irradiation, for example, it is preferable to use an electron beam having an energy in the range of 50 to 1000 keV and set the irradiation amount to 2 to 50 Mrad.

The irradiation direction of the active energy rays (ultraviolet rays, electron beams, etc.) can be any suitable direction, but it is preferable to irradiate the active energy rays from the transparent protective film side in order to prevent deterioration of the substituent.

The thickness of the adhesive layer in the polarizing plate of the present invention obtained as described above is usually 0.1 to 10 μm, preferably 0.2 to 5 μm, particularly preferably 0.3 to 3 μm, and further preferably 0.5 to 2 μm. be. 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 active energy ray-curable adhesive composition of the present invention can be used for various adhesive applications, and is particularly suitable for bonding various protective films for polarizing plates and a polarizing element, and is very suitable. It shows excellent adhesiveness.

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 thereof is not exceeded. In the example, the term "part" means a 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-221" manufactured by Toagosei Co., Ltd. ")

[Epoxy compound (B)]
[Aliphatic epoxy compound (B1)]
(B1-1) Neopentyl Glycol Diglycidyl Ether (“EX-211” manufactured by Nagase ChemteX Corporation)

[Aromatic epoxy compound (B2)]
(B2-1) Bisphenol F type epoxy resin ("jER806" manufactured by Mitsubishi Chemical Corporation)

[Ethylene unsaturated compound (C)]
(C-1) Neopentyl Glycol Diacrylate ("Light Acrylate NP-A" manufactured by Kyoeisha Chemical Co., Ltd.)

[Photocationic polymerization initiator (D1)]
(D1-1) Diphenyl [4- (Phenylthio) Phenyl] Sulfonium / Hexafluorophosphate (Aromatic Sulfonium Salt: "CPI-100P" manufactured by San-Apro)

[Photoradical Polymerization Initiator (D2)]
(D2-1) 2,4,6-trimethylbenzoyl-phenylphosphine oxide ("Irgacure TPO" manufactured by BASF)

[Silane coupling agent (E)]
(E-1) Epoxy group-containing silane coupling agent (“KBM-403 (3-glycidoxypropyltrimethoxysilane)” manufactured by Shin-Etsu Chemical Co., Ltd.)
(E-2) Acrylo group-containing silane coupling agent ("KBM-5103 (3-acryloxypropyltrimethoxysilane)" manufactured by Shin-Etsu Chemical Co., Ltd.)

[Examples 1 to 10, Comparative Examples 1 to 7]
<Preparation of active energy ray-curable adhesive composition>
Each of the above-mentioned compounding components was blended in the ratio shown in Table 1 below and mixed to prepare an active energy ray-curable adhesive composition.
The obtained active energy ray-curable adhesive composition was used as an adhesive composition for a polarizing plate and evaluated as follows.

<Making a polarizing element>
First, a PVA film having a thickness of 60 μm 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.) consisting of 0.2 g / L of iodine and 15 g / L of potassium iodide for 240 seconds. Further, the boric acid 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 performed for 5 minutes while uniaxially stretching 3.08 times. Then, it was dried at 90 ° C. to produce a substituent having a total draw ratio of 6 times.

<Preparation of polarizing plate test piece>
TAC film with a size of 200 mm x 150 mm and a thickness of 60 μm (manufactured by Fuji Film Co., Ltd., trade name "Fujitac") and cyclic olefin resin (COP) film with a size of 200 mm x 150 mm and a thickness of 50 μm (manufactured by Zeon Corporation, trade name). Each film of "ZEONOR") was coated with the adhesive composition obtained above with a bar coater so as to have a film thickness of 3 μm to obtain a film with an adhesive composition. Then, each film with an adhesive composition layer was laminated on both sides of the above-mentioned polarizing element having a size of 180 mm × 120 mm, and bonded at a nip pressure of 2 MPa using a roll machine to obtain a laminated film (layer of laminated film). Composition: TAC film / modulator / COP film).

Then, from the COP film side of the laminated film, ultraviolet irradiation was performed with an ultraviolet irradiation device equipped with an electrodeless lamp at a peak illuminance of 400 mW / cm ² and an integrated exposure amount of 150 mJ / cm ² (wavelength 365 nm). The composition was cured to prepare a polarizing plate test piece.
Using the polarizing plate test piece obtained above, the performance was evaluated as follows.

<Performance evaluation>
[Curability]
The interface between the splitter and the TAC film was peeled off with a cutter knife, and the tackiness of the peeled portion was confirmed (touched by a finger).
(Evaluation criteria)
○… Tackiness did not remain.
△… Tackiness did not remain, but there were slight finger marks.
×… Tackiness remained.

[Adhesive strength]
The polarizing plate test piece was cut into 120 mm × 25 mm, and the adhesion between the TAC film and the polarizing element and the COP film and the polarizing element when stressed in the 90 ° direction was evaluated according to the following criteria.
(Evaluation criteria)
◎… It was particularly firmly adhered.
○… It was firmly adhered.
△… Weakly adhered.
× ... It was not glued.

[Durability (heat impact resistance)]
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 methods)
○… No appearance defects were confirmed.
Δ: Slightly poor appearance (short cracks were generated in the polarizing layer to the extent that the display was not affected) was confirmed.
×: Poor appearance (penetration cracks occurred in the polarizing layer) was confirmed.

From the above results, Examples 1 to 1 to Example 1 to which contain an oxetane compound (A), an aliphatic epoxy compound (B1), preferably an aromatic epoxy compound (B2), and also an ethylenically unsaturated compound (C). It can be seen that the adhesive composition of No. 10 has good curability, is excellent in adhesiveness between the substituent and the protective film, and is also excellent in durability. From this, it can be seen that it is practically suitable as an adhesive composition for a polarizing plate having an excellent balance in various performances.

On the other hand, Comparative Example 1 containing no aliphatic epoxy compound (B1) is inferior in adhesiveness, and Comparative Example 2 not containing the oxetane compound (A) has both curability and adhesiveness. Comparative Example 3 which was inferior and did not contain the ethylenically unsaturated compound (C) was inferior in curability, and none of them was practically used. Further, in Comparative Example 4, Comparative Example 5 and Comparative Example 6 in which the oxetane compound (A), the epoxy compound (B) and the ethylenically unsaturated compound (C) are contained, but the content ratio of the epoxy compound (B) is too low. , Sufficient adhesiveness could not be obtained. Further, in Comparative Example 7 in which the content ratio of the epoxy compound (B) was too high, the curability and durability were inferior. From these facts, it can be said that the adhesive composition of the comparative example cannot satisfy all of various performances and cannot be put into practical use as an adhesive composition for a polarizing plate.
From the above, it can be seen that the adhesive composition of the present invention is extremely excellent especially in the use of an adhesive for polarizing plates.

Although the specific embodiments of the present invention have been shown in the above examples, the above examples are merely examples and are not to be construed in a limited manner. Various variations apparent to those skilled in the art are intended to be within the scope of the present invention.

The adhesive composition of the present invention and the adhesive composition for a polarizing plate comprising the above-mentioned adhesive composition are excellent in the adhesiveness between the polarizing element and the protective film, and various protective films for polarizing plates and the polarizing element are excellent. Suitable for bonding with. Further, in addition to adhesiveness, it is excellent in all of curability, water resistance of the polarizing plate, durability, and particularly thermal impact resistance in a well-balanced manner. 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 equipment, packaging materials, display materials, and the like. It can also be used for.

Claims (8)

An active energy ray-curable adhesive composition containing an oxetane compound (A), an epoxy compound (B), an ethylenically unsaturated compound (C) and a photopolymerization initiator (D).
As the oxetane compound (A), an oxetane compound containing two or more oxetanel groups in the molecule, or one oxetaneyl group and one (meth) acryloyl group or one epoxy group in the molecule is contained. Contains oxetane compounds,
The epoxy compound (B) contains an aliphatic epoxy compound (B1), and the aliphatic epoxy compound (B1) has two or more epoxy groups in the molecule and has a bifunctional or higher functional aliphatic epoxy. It is a compound
As the ethylenically unsaturated compound (C), a bifunctional or higher functional (meth) acrylic compound is contained, and the compound is contained.
As the photopolymerization initiator (D), a photocationic polymerization initiator (D1) and a photoradical polymerization initiator (D2) are contained, and the photocationic polymerization initiator (D1) and the photoradical polymerization initiator (D2) are combined. Content ratio (D1 / D2) (weight ratio) is 20/80 to 99/1.
The content ratio of the epoxy compound (B) is 40 to 80% by weight based on the total amount of the oxetane compound (A), the epoxy compound (B) and the ethylenically unsaturated compound (C) .
The content of the photocationic polymerization initiator (D1) is 0.5 to 20 parts by weight with respect to 100 parts by weight in total of the oxetane compound (A) and the epoxy compound (B).
The content of the photoradical polymerization initiator (D2) is 0.1 parts by weight or more with respect to 100 parts by weight of the ethylenically unsaturated compound (C), which is an active energy ray-curable adhesive composition. A characteristic adhesive composition for a polarizing plate. The adhesive composition for a polarizing plate according to claim 1, wherein the epoxy compound (B) further contains an aromatic epoxy compound (B2). The polarization according to claim 2, wherein the content ratio (B1 / B2) of the aliphatic epoxy compound (B1) to the aromatic epoxy compound (B2) is 10/90 to 90/10 by weight. Epoxy composition for plates. The content ratio (AB / C) of the total amount (AB) of the oxetane compound (A) and the epoxy compound (B) to the ethylenically unsaturated compound (C) is 40/60 to 95/5 by weight. The adhesive composition for a polarizing plate according to any one of claims 1 to 3. The invention according to any one of claims 1 to 4, wherein the content ratio (A / B) of the oxetane compound (A) to the epoxy compound (B) is 10/90 to 60/40 by weight. Adhesive composition for polarizing plates. The adhesive composition for a polarizing plate according to any one of claims 1 to 5 , further comprising a silane coupling agent (E). An adhesive for a polarizing plate, which is a cured product of the adhesive composition for a polarizing plate according to any one of claims 1 to 6 . The polarizing plate having the polarizing plate adhesive, the polarizing element, and the protective film according to claim 7 , wherein the polarizing element and the protective film are bonded to each other by the polarizing plate adhesive. Polarizer.