CN110268029B

CN110268029B - Active energy ray-curable adhesive composition, adhesive composition for polarizing plate, adhesive, and polarizing plate using same

Info

Publication number: CN110268029B
Application number: CN201880009982.7A
Authority: CN
Inventors: 木田友树; 新嘉津夫; 辻本笃志
Original assignee: Mitsubishi Chemical Corp
Current assignee: Mitsubishi Chemical Corp
Priority date: 2017-02-13
Filing date: 2018-02-06
Publication date: 2021-11-23
Anticipated expiration: 2038-02-06
Also published as: KR20230003629A; TWI821172B; KR102496513B1; WO2018147247A1; CN110268029A; KR20190111973A; JPWO2018147247A1; JP7003910B2; TW201840793A

Abstract

Disclosed is an active energy ray-curable adhesive composition which has excellent adhesive strength, is suitable for bonding a protective film for various polarizing plates and a polarizing plate, and has excellent curability, thermal shock resistance and other durability properties, and which contains an oxetane compound (A), an epoxy compound (B), an ethylenically unsaturated compound (C) and a photopolymerization initiator (D), wherein the epoxy compound (B) contains an aliphatic epoxy compound (B1), and the content of the epoxy compound (B) is 40-80 wt% relative to the total amount of the oxetane compound (A), the epoxy compound (B) and the ethylenically unsaturated compound (C).

Description

Active energy ray-curable adhesive composition, adhesive composition for polarizing plate, adhesive, and polarizing plate using same

Technical Field

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 particularly, to an active energy ray-curable adhesive composition suitable for bonding a polarizing plate and a protective film constituting a polarizing plate used in a liquid crystal display device or the like.

Background

The liquid crystal display device is widely used as an image display device such as a liquid crystal television, a computer monitor, a mobile phone, and a digital camera. The 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 configured by laminating a protective film on at least one surface, preferably both surfaces, of a polarizing plate made of a polyvinyl alcohol film (hereinafter, polyvinyl alcohol is simply referred to as "PVA"). Here, as the polarizing plate, a uniaxially stretched PVA-based film obtained by dispersing and adsorbing a dichroic material such as iodine in a PVA-based film formed using a PVA-based resin having a high saponification degree, and preferably further crosslinking the PVA-based film with a crosslinking agent such as boric acid is widely used. Such a polarizing plate is a uniaxially stretched PVA-based film, and therefore, is easily shrunk under high humidity, and a protective film is attached to the polarizing plate to complement moisture resistance and strength.

As the protective film, a thermoplastic resin such as a cellulose resin, a polycarbonate resin, a cyclic polyolefin resin, (meth) acrylic resin, and a polyester resin is used from the viewpoint of excellent transparency, mechanical strength, thermal stability, moisture barrier property, isotropy, and the like, and a protective film made of triacetyl cellulose (TAC) resin is widely used in particular.

These protective films are bonded to the polarizing plate with an adhesive, and from the viewpoint of adhesion to the polarizing plate having a hydrophilic surface, an aqueous PVA-based resin solution is preferably used as the adhesive, and particularly, an aqueous PVA-based resin solution mainly composed of a PVA-based resin having the same degree of saponification as that of the polarizing plate is preferably used.

However, in recent years, a polarizing plate is required to be thin, and an acrylic film or a Cycloolefin (COP) film is being used instead of the TAC film which has been most frequently used as a protective film. However, these protective films replacing the TAC films have problems that they are difficult to be firmly attached to the polarizing plate and that appearance defects of the obtained polarizing plate occur in the case of a conventional PVA-based adhesive. This is because the acrylic film and the COP film are hydrophobic and have low moisture permeability compared to the TAC film, and water cannot be sufficiently dried. Therefore, as an adhesive that replaces the PVA-based adhesive, various adhesives that are also suitable for bonding protective films such as acrylic films and COP films have been developed.

For example, patent document 1 proposes a cationically polymerizable adhesive containing an aromatic glycidyl ether, a specific amount of an oxetane compound having 2 or more oxetanyl groups and a molecular weight of 100 to 800, a specific amount of a silane coupling agent having an alicyclic epoxy group, and a cationic polymerization initiator, as an adhesive for a polarizing plate having excellent adhesiveness and water resistance.

Patent document 2 proposes a cationically polymerizable adhesive containing a specific oxetane compound having 2 or more oxetanyl groups, an aromatic glycidyl ether and a cationic polymerization initiator, as an adhesive which can maintain excellent normal state adhesive strength for a long time without being affected by heat, light or the like.

Further, patent document 3 proposes a photocurable adhesive composition containing a specific poly (meth) acrylate, a specific polyglycidyl ether, an oxetane compound, a photo cationic polymerization initiator, and the like, for the purpose of curability and durability of the adhesive.

Documents of the prior art

Patent document

Patent document 1: international publication No. 2012/144261

Patent document 2: japanese patent laid-open No. 2010-229392

Patent document 3: japanese patent laid-open publication No. 2015-40283

Disclosure of Invention

Problems to be solved by the invention

However, in the above patent documents 1 and 2, since a large amount of epoxy groups having a ring structure such as alicyclic epoxy groups and aromatic epoxy groups is used, the adhesive itself tends to be too hard, and depending on the kind of protective film to be adhered, sufficient adhesion and durability may not be obtained, and further improvement is required.

In addition, in patent document 3, when diversification of use environments and high durability are required in recent years, sufficient adhesion and durability still become problems, and there is room for improvement.

Under such a background, the present invention provides an active energy ray-curable adhesive composition which can provide an adhesive having excellent adhesive strength, particularly an adhesive suitable for bonding a polarizing plate to a protective film for various polarizing plates, and having excellent durability such as curability, water resistance, and thermal shock resistance; and an adhesive composition for a polarizing plate, an adhesive for a polarizing plate, and a polarizing plate, each using the active energy ray-curable adhesive composition.

Means for solving the problems

That is, the present inventors have conducted intensive studies in view of the above circumstances and as a result, have found that an adhesive agent capable of forming an adhesive layer having excellent durability such as thermal shock resistance and a balance between curability and adhesiveness can be obtained by containing an oxetane compound (a), an epoxy compound (B), an ethylenically unsaturated compound (C) and a photopolymerization initiator (D) and further containing an aliphatic epoxy compound (B1) as the epoxy compound (B) in an active energy ray-curable adhesive composition using a combination of cationic polymerization and radical polymerization.

That is, the 1 st gist of the present invention resides in 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), wherein the epoxy compound (B) contains an aliphatic epoxy compound (B1), and the content 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).

Further, the 2 nd gist of the present invention is an adhesive composition for a polarizing plate, which contains the active energy ray-curable adhesive composition according to the 1 st gist. The 3 rd gist of the present invention is directed to an adhesive for a polarizing plate, which is a cured product of the adhesive composition for a polarizing plate of the 2 nd gist of the present invention. The 4 th gist of the present invention is a polarizing plate, wherein a polarizing plate and a protective film are bonded to each other with the polarizing plate adhesive of the 3 rd gist of the present invention.

The present invention contains a large amount of the epoxy compound (B) when the photo cation polymerization and the photo radical polymerization are used in combination. In general, it is considered that when a combination of photo-radical polymerization is used in order to increase the curing rate and improve the productivity, a sufficient curing rate cannot be obtained if the epoxy compound is contained in a large amount, and the problem of durability arises because the curing of the epoxy compound is insufficient, and therefore, the content ratio of the epoxy compound is not increased.

ADVANTAGEOUS EFFECTS OF INVENTION

The active energy ray-curable adhesive composition contains an oxetane compound (A), an epoxy compound (B), an ethylenically unsaturated compound (C), and a photopolymerization initiator (D), wherein the epoxy compound (B) contains an aliphatic epoxy compound (B1), and the content of the epoxy compound (B) is 40 to 80 wt% relative to the total amount of the oxetane compound (A), the epoxy compound (B), and the ethylenically unsaturated compound (C). Therefore, the effect of excellent adhesion is exhibited, and in particular, various protective films for polarizing plates and polarizing plates can be sufficiently adhered, and a polarizing plate having excellent durability such as thermal shock resistance can be obtained.

In the present invention, particularly when the epoxy compound (B) further contains an aromatic epoxy compound (B2), the balance between the adhesiveness and the durability such as thermal shock resistance is more excellent.

In the present invention, particularly, when 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 ratio, the balance between the adhesiveness and the durability such as thermal shock resistance is more excellent.

In the present invention, particularly, when 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 in terms of a weight ratio, the balance between the adhesiveness and the durability such as thermal shock resistance is more excellent.

In the present invention, particularly, 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 durability such as adhesiveness and thermal shock resistance is more excellent.

In the present invention, when the photopolymerization initiator (D) contains a photo cation polymerization initiator (D1) and a photo radical polymerization initiator (D2), the adhesive composition has excellent curability.

In the present invention, particularly, when the content ratio (D1/D2) of the photo cation polymerization initiator (D1) to the photo radical polymerization initiator (D2) is 20/80 to 99/1 in terms of a weight ratio, the adhesive composition is more excellent in curability.

When the adhesive composition of the present invention further contains a silane coupling agent (E), the adhesive composition is more excellent in adhesiveness.

Detailed Description

The present invention will be described in detail below, which shows preferred embodiments.

The active energy ray-curable adhesive composition (hereinafter, may be simply referred to as "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). Hereinafter, each component of the adhesive composition will be described in order.

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

< Oxetane Compound (A) >

The oxetane compound (a) used in the present invention may be any compound having 1 or more oxetanyl groups in the molecule.

Examples of the oxetane compound (A) include oxetane compounds having 1 oxetanyl group in the molecule, such as 3-ethyl-3-hydroxymethyloxetane, 3-ethyl-3- (2-ethylhexyloxymethyl) oxetane, 3-ethyl-3- (phenoxymethyl) oxetane, 3-ethyl-3- (cyclohexyloxymethyl) oxetane, 3-ethyl-3- (oxiranylmethoxy) oxetane, (3-ethyloxetan-3-yl) methyl (meth) acrylate, and the like; and oxetane compounds having 2 or more oxetanyl groups in the molecule, such as 3-ethyl-3 { [ (3-ethyloxetan-3-yl) methoxy ] methyl } oxetane, 1, 4-bis [ (3-ethyl-3-oxetane) methoxymethyl ] benzene, and 4, 4' -bis [ (3-ethyl-3-oxetane) methoxymethyl ] biphenyl. These oxetane compounds (A) can be used alone or in combination of 2 or more.

Among them, from the viewpoints of easy availability, dilutability (low viscosity), excellent compatibility, and the like, 3-ethyl-3-hydroxymethyloxetane, 1, 4-bis [ (3-ethyl-3-oxetanyl) methoxymethyl ] benzene, 3-ethyl-3- (2-ethylhexyloxymethyl) oxetane, 3-ethyl-3- ((oxiranylmethoxy) oxetane, (3-ethyloxetan-3-yl) methyl (meth) acrylate, 3-ethyl-3 { [ (3-ethyloxetan-3-yl) methoxy ] methyl } oxetane, and the like are preferably used.

From the viewpoint of coatability and adhesiveness, the molecular weight is preferably 500 or less, and particularly preferably 100 to 500. Furthermore, an oxetane compound having 2 or more oxetanyl groups in the molecule, an oxetane compound having 1 oxetanyl group and 1 (meth) acryloyl group or 1 epoxy group in the molecule, and particularly 3-ethyl-3 { [ (3-ethyloxetan-3-yl) methoxy ] methyl } oxetane, 3-ethyl-3- (epoxyethylmethoxy) oxetane, and (3-ethyloxetan-3-yl) methyl (meth) acrylate are preferably used, from the viewpoint of being liquid at room temperature (25 ℃) and further excellent in curability and durability.

The oxetane compound containing an epoxy group or a (meth) acryloyl group in the molecule is considered to be contained in the oxetane compound (a), and is not contained in the epoxy compound (B) or the ethylenically unsaturated compound (C) described later.

Specific examples of the OXETANE compound (A) include commercially available "ARON OXETANE OXT-101", "ARON OXETANE OXT-121", "ARON OXETANE OXT-211", "ARON OXETANE OXT-212", "ARON OXETANE OXT-213", "ARON OXETANE OXT-221" (all manufactured by east Asia Co., Ltd.). Particularly preferred are "ARON OXETANE OXT-101" and "ARON OXETANE OXT-221".

< epoxy Compound (B) >

The present invention uses the epoxy compound (B) as the cationic polymerization component. The epoxy compound (B) contains an aliphatic epoxy compound (B1) from the viewpoint of adhesiveness, and an aromatic epoxy compound (B2) is preferably used in combination from the viewpoint of balance between adhesiveness and durability.

Examples of the aliphatic epoxy compound (B1) include aliphatic epoxy compounds having 1 epoxy group in the molecule, such as butyl glycidyl ether, 2-ethylhexyl glycidyl ether, allyl glycidyl ether, glycidyl (glycidyl), alcohol glycidyl ether having 11 to 15 carbon atoms, lauryl alcohol glycidyl ether, 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, glycerol polyglycidyl ether, poly (ethylene glycol) diglycidyl ether, poly (butadiene) diglycidyl ether, poly (ethylene glycol) diglycidyl ether, poly (ethylene glycol) and poly (ethylene glycol) glycidyl ether, And aliphatic epoxy compounds having 2 or more functional groups such as polyglycerol polyglycidyl ether and the like, each having 2 or more epoxy groups in the molecule. These aliphatic epoxy compounds (B1) may be used alone or in combination of 2 or more.

Among them, from the viewpoint of curability, adhesiveness, and durability, an aliphatic epoxy compound having 2 or more functional groups and 2 or more epoxy groups in the molecule is preferable, and 1, 4-butanediol diglycidyl ether, 1, 6-hexanediol diglycidyl ether, and neopentyl glycol diglycidyl ether are more preferable.

Examples of the aromatic epoxy compound (B2) include aromatic epoxy compounds having 1 epoxy group in the molecule, such as phenyl glycidyl ether, p-tert-butylphenyl glycidyl ether, p-sec-butylphenyl glycidyl ether, dibromophenyl glycidyl ether, etc.; aromatic epoxy compounds having 2 or more epoxy groups in the molecule, such as diglycidyl phthalate, diglycidyl terephthalate, resorcinol diglycidyl ether, hydroquinone diglycidyl ether, bromobisphenol a diglycidyl ether, bisphenol a epoxy resins, bisphenol F epoxy resins, bisphenol E epoxy resins, phenol novolac epoxy resins, cresol novolac epoxy resins, biphenyl epoxy resins, and the like. These aromatic epoxy compounds (B2) may be used alone or in combination of 2 or more.

Among them, an aromatic epoxy compound having 2 or more epoxy groups in the molecule is preferable from the viewpoint of adhesiveness and durability, and a bisphenol a type epoxy resin and a bisphenol F type epoxy resin are particularly preferable from the viewpoint of excellent curability.

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

If the content ratio is too small (if the aromatic epoxy compound (B2) is too large), the adhesive strength tends to decrease, the coating property tends to decrease due to an increase in viscosity, or the compatibility of the adhesive composition tends to decrease, and if the content ratio is too large (if the aliphatic epoxy compound (B1) is too large), the durability tends to decrease.

The epoxy compound (B) used in the present invention may contain another epoxy compound (B3) in addition to the aliphatic epoxy compound (B1) and the aromatic epoxy compound (B2).

Examples of the other epoxy compound (B3) include an epoxy compound having a triazine skeleton, an alicyclic epoxy compound, and an epoxy compound having an alicyclic skeleton. These may be used alone or in combination of 2 or more.

The triazine skeleton-containing epoxy compound is a compound having 1 or more epoxy groups and a triazine skeleton in a molecule, and examples thereof include 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, and tris (7, 8-epoxyoctyl) -isocyanurate. These may be used alone or in combination of 2 or more.

From the viewpoint of further improving the durability (thermal shock resistance), it is also preferable to use an epoxy compound having a triazine skeleton.

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

As the triazine skeleton-containing epoxy compound, there may be used, specifically, commercially available TEPIC series ("TEPIC-G", "TEPIC-S", "TEPIC-SS", "TEPIC-HP", "TEPIC-L", "TEPIC-PAS", "TEPIC-VL", "TEPIC-UC", "TEPIC-FL", and the like) available from Nissan chemical industries. Among these, the liquid epoxy compounds "TEPIC-PAS", "TEPIC-VL", "TEPIC-UC" and "TEPIC-FL" are preferred from the viewpoint of compatibility.

Examples of the alicyclic epoxy compound include dicyclopentadiene oxide, limonene dioxide, 4-vinylcyclohexene dioxide, 3 ', 4' -epoxycyclohexylmethyl-3, 4-epoxycyclohexane carboxylate, epsilon-caprolactone-modified 3 ', 4' -epoxycyclohexylmethyl-3, 4-epoxycyclohexane carboxylate, bis (3, 4-epoxycyclohexylmethyl) adipate, and the like. These may be used alone or in combination of 2 or more.

As the alicyclic epoxy compound, specifically, commercially available compounds such as "celloxide 2021P" and "celloxide 2000" manufactured by Daicel Corporation 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, cyclohexanedimethanol diglycidyl ether, and the like. These may be used alone or in combination of 2 or more.

As the epoxy compound having an alicyclic skeleton, specifically, commercially available epoxy compounds 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 epoxy compound having an alicyclic skeleton is preferably 30% by weight or less, more preferably 20% by weight or less, and particularly preferably 15% by weight or less, based on the total amount of the oxetane compound (a) and the epoxy compound (B). When the content of at least one of the alicyclic epoxy compound and the epoxy compound having an alicyclic skeleton is too large, the adhesive force 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, based on the whole epoxy compound (B). When the content of the other epoxy compound (B3) is too large, the adhesive strength tends to decrease.

< ethylenically unsaturated Compound (C) >

The ethylenically unsaturated compound (C) is a radical polymerizable component and is an unsaturated compound having at least 1 ethylenically unsaturated group in the molecule. By containing the ethylenically unsaturated compound (C), the curing rate and the curability can be improved.

Examples of the ethylenically unsaturated compound (C) include (meth) acrylic compounds having at least 1 (meth) acryloyl group in the molecule.

Examples of the (meth) acrylic compound include a (meth) acrylic compound having 1 (meth) acryloyl group in the molecule (hereinafter, sometimes referred to as "monofunctional (meth) acrylic compound"), and a (meth) acrylic compound having 2 or more (meth) acryloyl groups in the molecule (hereinafter, sometimes referred to as "polyfunctional (meth) acrylic compound").

These (meth) acrylic compounds may be used alone or in combination of 2 or more.

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

Examples of the alkyl (meth) acrylate compound include alkyl (meth) acrylates having an alkyl group having 1 to 20 carbon atoms, particularly 1 to 15 carbon atoms, and further 4 to 10 carbon atoms, and specific examples thereof include methyl (meth) 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, and stearyl (meth) acrylate.

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

Examples of the carboxyl group-containing (meth) acrylic compound include (meth) acrylic acid, crotonic acid, maleic anhydride, itaconic acid, fumaric acid, acrylamide N-glycolic acid, cinnamic acid, michael adducts of (meth) acrylic acid (for example, acrylic acid dimer, methacrylic acid dimer, acrylic acid trimer, methacrylic acid trimer, acrylic acid tetramer, methacrylic acid tetramer, etc.), 2- (meth) acryloyloxyethyl dicarboxylic acid monoesters (for example, 2- (meth) acryloyloxyethyl succinic acid monoester, 2- (meth) acryloyloxyethyl phthalic acid monoester, 2- (meth) acryloyloxyethyl hexahydrophthalic acid monoester, etc.).

Examples of the hydroxyl group-containing (meth) acrylate compound include hydroxyalkyl (meth) acrylate compounds such as 2-hydroxyethyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 5-hydroxypentyl (meth) acrylate, and 6-hydroxyhexyl (meth) acrylate; caprolactone-modified (meth) acrylate compounds such as caprolactone-modified 2-hydroxyethyl (meth) acrylate; glycol mono (meth) acrylate compounds such as ethylene glycol mono (meth) acrylate, propylene glycol mono (meth) acrylate, pentylene glycol mono (meth) acrylate, and hexylene glycol mono (meth) acrylate; polyalkylene glycol mono (meth) acrylate compounds such as diethylene glycol mono (meth) acrylate, triethylene glycol mono (meth) acrylate, tetraethylene glycol mono (meth) acrylate, polyethylene glycol mono (meth) acrylate, dipropylene glycol mono (meth) acrylate, tripropylene glycol mono (meth) acrylate, and polypropylene glycol mono (meth) acrylate; other (meth) acrylate compounds containing a primary hydroxyl group such as 2-acryloyloxyethyl-2-hydroxyethyl phthalate; secondary hydroxyl group-containing (meth) acrylate compounds such as 2-hydroxypropyl (meth) acrylate and 2-hydroxybutyl (meth) acrylate; and (meth) acrylate compounds containing a tertiary hydroxyl group such as 2, 2-dimethyl-2-hydroxyethyl (meth) acrylate.

Among the hydroxyl group-containing (meth) acrylate compounds, a primary hydroxyl group-containing (meth) acrylate compound is preferable, and a hydroxyalkyl (meth) acrylate compound and a mono (meth) acrylate compound of a polyalkylene glycol are particularly preferable, from the viewpoint of easy hydrogen bonding to a substrate or a polarizing plate and excellent reactivity.

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 (meth) acrylic compound having an amide group include (meth) acrylamide; n, N-dialkyl (meth) acrylamides such as N, N-dimethyl (meth) acrylamide and N, N-diethyl (meth) acrylamide; n-alkoxyalkyl (meth) acrylamides such as N-methoxymethyl (meth) acrylamide, N-ethoxymethyl (meth) acrylamide, N-propoxymethyl (meth) acrylamide, N-isopropoxymethyl (meth) acrylamide, N-N-butoxymethyl (meth) acrylamide, and N-isobutoxymethyl (meth) acrylamide; hydroxyl group-containing acrylamides such as N- (hydroxymethyl) (meth) acrylamide; n- (3-N, N-dimethylaminopropyl) (meth) acrylamide, methylenebis (meth) acrylamide, ethylenebis (meth) acrylamide, and the like.

Examples of the amino group-containing (meth) acrylic compound include a primary amino group-containing (meth) acrylate such as an aminoalkyl (meth) acrylate (e.g., aminomethyl (meth) acrylate and aminoethyl (meth) acrylate), a secondary amino group-containing (meth) acrylate such as t-butylaminoethyl (meth) acrylate, a diethylaminoethyl (meth) acrylate, a dimethylaminoethyl (meth) acrylate, a dialkylaminoalkyl (meth) acrylate such as diethylaminoethyl (meth) acrylate, and a heterocyclic amine monomer such as acryloylmorpholine.

Examples of the alkoxy group-containing (meth) acrylate compound include alkoxyalkyl (meth) acrylate compounds such as 2-methoxyethyl (meth) acrylate, 2-ethoxyethyl (meth) acrylate, 3-methoxybutyl (meth) acrylate, and 2-butoxyethyl (meth) acrylate; polyether chain-containing (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) acrylate, methoxypolyethylene glycol (meth) acrylate, octyloxypolyethylene glycol polypropylene glycol mono (meth) acrylate, lauroxypolyethylene glycol mono (meth) acrylate, and stearoxypolyethylene glycol mono (meth) acrylate.

Examples of the alicyclic (meth) acrylate compound include cyclohexyl (meth) acrylate, isobornyl (meth) acrylate, 1, 4-cyclohexanedimethylol mono (meth) acrylate, dicyclopentenyl (meth) acrylate, dicyclopentenyloxyethyl (meth) acrylate, and 2-adamantyl (meth) acrylate.

Examples of the aromatic (meth) acrylate compound include phenyl (meth) acrylate; benzyl (meth) acrylate; phenoxyalkyl (meth) acrylates such as phenoxyethyl (meth) acrylate and phenoxypropyl (meth) acrylate; phenoxy dialkylene glycol (meth) acrylates such as phenoxy diethylene glycol (meth) acrylate and phenoxy dipropylene glycol (meth) acrylate; phenoxy polyethylene glycol (meth) acrylate; phenoxy polyethylene glycol-polypropylene glycol- (meth) acrylate; p-cumylphenol epoxide adduct (meth) acrylate, (meth) acrylate of o-phenylphenol epoxide adduct, (meth) acrylate of phenol epoxide adduct and (meth) acrylate of nonylphenol epoxide adduct.

Examples of the (meth) acrylic compound having a reactive functional group other than a (meth) acryloyl group and a (meth) acryloyl group in the molecule include epoxy group-containing (meth) acrylate compounds such as glycidyl methacrylate, 4-hydroxybutyl acrylate glycidyl ether and 3, 4-epoxycyclohexylmethyl (meth) acrylate, vinyl group-containing (meth) acrylate compounds such as 2- (2-vinyloxyethoxy) ethyl (meth) acrylate, and isocyanate group-containing (meth) acrylate compounds such as 2- (meth) acryloyloxyethyl isocyanate.

When the ethylenically unsaturated compound is an epoxy group-containing (meth) acrylate compound, it is contained in the ethylenically unsaturated compound (C) and is not contained in the epoxy compound (B).

Other examples of the (meth) acrylate-based compound include (meth) acrylate-based compounds having a cyclic ether structure such as tetrahydrofurfuryl (meth) acrylate and caprolactone-modified tetrahydrofurfuryl (meth) acrylate.

Examples of the polyfunctional (meth) acrylic compound include a 2-functional (meth) acrylic compound and a 3-or more-functional (meth) acrylic compound.

Examples of the 2-functional (meth) acrylic compound include ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, tetraethylene glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate, propylene glycol di (meth) acrylate, dipropylene glycol di (meth) acrylate, polypropylene glycol di (meth) acrylate, 1, 3-butanediol di (meth) acrylate, neopentyl glycol di (meth) acrylate, 1, 4-butanediol di (meth) acrylate, 1, 6-hexanediol di (meth) acrylate, glycerol di (meth) acrylate, pentaerythritol di (meth) acrylate, ethylene glycol diglycidyl ether di (meth) acrylate, diethylene glycol diglycidyl ether di (meth) acrylate, propylene glycol di (meth) acrylate, ethylene glycol di (meth, Di (meth) acrylates having a long chain or branched structure such as hydroxypivalic acid-modified neopentyl glycol di (meth) acrylate; alicyclic-structure-containing di (meth) acrylates such as cyclohexanedimethanol di (meth) acrylate, dimethyloldicyclopentanyl di (meth) acrylate, tricyclodecanedimethanol di (meth) acrylate, and ethylene oxide-modified cyclohexanedimethanol di (meth) acrylate; epoxy-modified bisphenol a type di (meth) acrylates such as ethylene oxide-modified bisphenol a type di (meth) acrylate and propylene oxide-modified bisphenol a type di (meth) acrylate, and di (meth) acrylates having an aromatic ring such as bisphenol a diglycidyl ether di (meth) acrylate and diglycidyl phthalate di (meth) acrylate; and a di (meth) acrylate having a ring structure such as an isocyanuric acid ethylene oxide-modified di (meth) acrylate.

Examples of the (meth) acrylic compound having 3 or more functional groups include trimethylolpropane tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, dipentaerythritol penta (meth) acrylate, dipentaerythritol hexa (meth) acrylate, polyglycerol poly (meth) acrylate; (meth) acrylates having 3 or more functional groups with a long-chain or branched structure, such as (meth) acrylates having 3 or more functional groups with an alkyl-modified structure, e.g., caprolactone-modified dipentaerythritol penta (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 glycerol tri (meth) acrylate, etc.; and a tri (meth) acrylate having a ring structure such as an isocyanuric acid ethylene oxide-modified triacrylate.

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

The ethylenically unsaturated compound (C) is preferably a (meth) acrylic compound having 2 or more functional groups, from the viewpoint of improving curability and durability of the adhesive composition. Particularly preferred are (meth) acrylic compounds having 2 or more functional groups of an alicyclic ring and an aromatic ring, and (meth) acrylic compounds having a linear or branched structure and not having a polyalkylene oxide skeleton, and further preferred are (meth) acrylic compounds having a branched structure and not having a polyalkylene oxide skeleton.

< photopolymerization initiator (D) >

The adhesive composition of the present invention is obtained by irradiating an active energy ray to react the oxetane compound (a), the epoxy compound (B) and the ethylenically unsaturated compound (C) to exhibit adhesiveness, and adding a photopolymerization initiator (D) to the reaction.

The photopolymerization initiator (D) preferably contains a photo cation polymerization initiator (D1), and particularly preferably contains a photo cation polymerization initiator (D1) and a photo radical polymerization initiator (D2) from the viewpoint of obtaining sufficient curability.

By using the photo cation polymerization initiator (D1), the adhesive composition can be cured at normal temperature (25 ℃ C. + -10 ℃ C.), and the protective film and the polarizing plate can be favorably adhered.

Examples of the compound that generates a cationic species or a lewis acid by irradiation of an active energy ray in the photo-cationic polymerization initiator (D1) include onium salts such as aromatic diazonium salts, aromatic iodonium salts, and aromatic sulfonium salts, iron-arene complexes, and the like.

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

Examples of the aromatic iodonium salts include diphenyliodonium tetrakis (pentafluorophenyl) borate, diphenyliodonium hexafluorophosphate, diphenyliodonium hexafluoroantimonate, and bis (4-nonylphenyl) iodonium hexafluorophosphate.

Examples of the aromatic sulfonium salt include triphenylsulfonium hexafluorophosphate, triphenylsulfonium hexafluoroantimonate, triphenylsulfonium tetrakis (pentafluorophenyl) borate, diphenyl [4- (phenylthio) phenyl ] sulfonium hexafluorophosphate, 4 ' -bis [ diphenylsulfonium ] diphenylsulfide bis-hexafluorophosphate, 4 ' -bis [ di (β -hydroxyethoxy) phenylsulfonium ] diphenylsulfide bis-hexafluoroantimonate, 4 ' -bis [ di (β -hydroxyethoxy) phenylsulfonium ] diphenylsulfide bis-hexafluorophosphate, 7- [ di (p-toluoyl) sulfonium group ] -2-isopropylthioxanthone hexafluoroantimonate, 7- [ di (p-toluoyl) sulfonium group ] -2-isopropylthioxanthone tetrakis (pentafluorophenyl) borate, and mixtures thereof, 4-phenylcarbonyl-4 ' -diphenylsulfonium-diphenylsulfide-hexafluorophosphate, 4- (p-tert-butylphenylcarbonyl) -4 ' -diphenylsulfonium-diphenylsulfide-hexafluoroantimonate, 4- (p-tert-butylphenylcarbonyl) -4 ' -di (p-toluoyl) sulfonium-diphenylsulfide-tetrakis (pentafluorophenyl) borate, and the like.

Examples of the iron-arene complex include xylene-cyclopentadienyl iron (II) -hexafluoroantimonate, cumene-cyclopentadienyl iron (II) -hexafluorophosphate, xylene-cyclopentadienyl iron (II) -tris (trifluoromethylsulfonyl) methanate, and the like.

Among the photo cation polymerization initiators (D1), aromatic iodonium salts and aromatic sulfonium salts are preferably used from the viewpoint of reacting with high sensitivity to light sources having a long wavelength.

The photo cation polymerization initiator (D1) may be used alone or in combination of 2 or more.

The photo radical polymerization initiator (D2) generates radicals by irradiation with active energy rays, and reacts the ethylenically unsaturated compound (C). Examples of the photo radical polymerization initiator (D2) include diethoxyacetophenone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, benzildimethylketal, 4- (2-hydroxyethoxy) phenyl- (2-hydroxy-2-propyl) ketone, 1-hydroxycyclohexylphenylketone, 1- [4- (2-hydroxyethoxy) -phenyl ] -2-hydroxy-2-methyl-1-propan-1-one, 2-methyl-2-morpholino (4-thiomethylphenyl) propan-1-one, 2-benzil-2-dimethylamino-1- (4-morpholinophenyl) butanone, and mixtures thereof, Acetophenones such as 2-hydroxy-2-methyl-1- [4- (1-methylvinyl) phenyl ] propanone oligomer; benzoins such as benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, and benzoin isobutyl ether; benzophenones such as benzophenone, methyl o-benzoylbenzoate, 4-phenylbenzophenone, 4-benzoyl-4 ' -methyl-diphenylsulfide, 3 ', 4,4 ' -tetrakis (t-butylperoxycarbonyl) benzophenone, 2,4, 6-trimethylbenzophenone, 4-benzoyl-N, N-dimethyl-N- [2- (1-oxo-2-propenyloxy) ethyl ] phenylmethanesulfonium bromide, and (4-benzoylbenzil) trimethylammonium chloride; thioxanthones such as 2-isopropylthioxanthone, 4-isopropylthioxanthone, 2, 4-diethylthioxanthone, 2, 4-dichlorothioxanthone, 1-chloro-4-propoxythioxanthone, and 2- (3-dimethylamino-2-hydroxy) -3, 4-dimethyl-9H-thioxanthone-9-one meso-chloride; acylphosphine oxides such as 2,4, 6-trimethylbenzoyl-diphenylphosphine oxide, bis (2, 6-dimethoxybenzoyl) -2,4, 4-trimethyl-pentylphosphine oxide, and bis (2,4, 6-trimethylbenzoyl) -phenylphosphine oxide; oxime esters such as 1, 2-octanedione, 1- [4- (phenylthio) phenyl-, 2- (O-benzoyloxime) ], ethanone, 1- [ 9-ethyl-6- (2-methylbenzoyl) -9H-carbazol-3-yl ] -,1- (O-acetyloxime) and the like.

Among the photo radical polymerization initiators (D2), acylphosphine oxides are preferably used, and 2,4, 6-trimethylbenzoyl-diphenylphosphine oxide, bis (2, 6-dimethoxybenzoyl) -2,4, 4-trimethyl-pentylphosphine oxide, bis (2,4, 6-trimethylbenzoyl) -phenylphosphine oxide, and further 2,4, 6-trimethylbenzoyl-phenylphosphine oxide, bis (2,4, 6-trimethylbenzoyl) -diphenylphosphine oxide are preferably used.

In addition, as the auxiliary agent, triethanolamine, triisopropanolamine, 4 '-dimethylaminobenzophenone (michelson), 4' -diethylaminobenzophenone, 2-dimethylaminoethylbenzoic acid, ethyl 4-dimethylaminobenzoate (n-butoxy), isoamyl 4-dimethylaminobenzoate, 2-ethylhexyl 4-dimethylaminobenzoate, 2, 4-diethylthioxanthone, 2, 4-diisopropylthioxanthone, or the like may be used in combination.

In the present invention, the content of the photopolymerization initiator (D) is preferably 0.5 to 20 parts by weight, particularly preferably 0.5 to 15 parts by weight, and further preferably 1.0 to 10 parts by weight, based on 100 parts by weight of the total amount of the oxetane compound (a), the epoxy compound (B), and the ethylenically unsaturated compound (C), from the viewpoint of obtaining sufficient curability.

When the content is too small, curability tends to be low, and mechanical strength and adhesive strength tend to be low, and when it is too large, solubility of the photopolymerization initiator (D) itself in the composition tends to be low.

When the photo-cationic polymerization initiator (D1) and the photo-radical polymerization initiator (D2) are used in combination, the content ratio (D1/D2) (weight ratio) of the photo-cationic polymerization initiator (D1) and the photo-radical polymerization initiator (D2) is preferably 20/80 to 99/1, particularly preferably 40/60 to 95/5, and further preferably 50/50 to 90/10, from the viewpoint of sufficient curability. When the content ratio is too small, curing of the cationic curing component tends to be insufficiently performed, and when too large, curing of the radical curing component tends to be not performed.

Further, the content of the photo cation polymerization initiator (D1) is preferably 0.5 to 20 parts by weight, particularly preferably 1 to 15 parts by weight, and further preferably 1.5 to 10 parts by weight, based on 100 parts by weight of the total amount of the oxetane compound (a) and the epoxy compound (B). When the content of the photo cation polymerization initiator (D1) is too large, the solubility tends to be low or the durability tends to be low, and when it is too small, the curability tends to be low, and the mechanical strength and the adhesive strength tend to be low.

The content of the photo radical polymerization initiator (D2) is preferably 15 parts by weight or less, particularly preferably 10 parts by weight or less, and further preferably 5 parts by weight or less, based on 100 parts by weight of the ethylenically unsaturated compound (C). When the content of the photo radical polymerization initiator (D2) is too large, the solubility of the photo radical polymerization initiator (D2) tends to be lowered, or the durability of the adhesive layer tends to be lowered. The lower limit is usually 0.1 part by weight, and when too small, curability tends to decrease, and adhesive strength and mechanical strength of the adhesive layer tend to decrease.

In particular, from the viewpoint of curing efficiency (curing can be efficiently performed with a small irradiation dose of active energy rays), a preferable combination of the photo-cationic polymerization initiator (D1) and the photo-radical polymerization initiator (D2) is a combination of an aromatic sulfonium salt and an aromatic iodonium salt as the photo-cationic polymerization initiator (D1) and an acylphosphine oxide as the photo-radical 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 is characterized in that the content of the epoxy compound (B) is 40 to 80% by weight, preferably 42 to 70% by weight, and more preferably 45 to 65% by weight, based on the total amount of the oxetane compound (a), epoxy compound (B) and ethylenically unsaturated compound (C). When the content ratio of the epoxy compound (B) is too small, the adhesive strength is lowered, and when it is too large, the curing rate is lowered, the mechanical strength is lowered, or the durability is lowered.

Further, from the viewpoint of balance between adhesion and durability, 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 preferably 40/60 to 95/5, particularly preferably 50/50 to 90/10, and further preferably 60/40 to 85/15 in terms of a weight ratio. If the content ratio is too small ((AB) is too small), curing shrinkage tends to increase and adhesive strength tends to decrease, and if it is too large ((AB) is too large), curing speed tends to decrease.

From the viewpoint of adhesion and durability, the content ratio (a/B) of the oxetane compound (a) to the epoxy compound (B) is preferably 10/90 to 60/40, particularly preferably 12/88 to 50/50, and further preferably 15/85 to 40/60 in terms of a weight ratio. If the content ratio is too small ((a) too small), the curing of the epoxy compound (B) tends to be insufficient, and the durability tends to be low, and if it is too large ((a) too large), the adhesive strength tends to be low.

< 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 generally an organosilicon compound having a structure containing 1 or more each of a reactive functional group and a silicon-bonded alkoxy group, and can improve the adhesion between the adhesive layer and the protective film.

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, an isocyanate group-containing 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 may be used alone or in combination of 2 or more.

Examples of the epoxy group-containing silane coupling agent include a monomeric epoxy group-containing silane coupling agent such as a glycidoxy (aliphatic epoxy group) -containing silane coupling agent such as 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3-glycidoxypropylmethyldimethoxysilane and the like, and an alicyclic epoxy group-containing silane coupling agent such as 2- (3, 4-epoxycyclohexyl) ethyltrimethoxysilane, and oligomer-type silane coupling agents obtained by hydrolytic polycondensation of a part of the silane compound, or copolycondensation of the silane compound with an alkyl-containing silane compound such as methyltriethoxysilane, ethyltriethoxysilane, methyltrimethoxysilane, or ethyltrimethoxysilane. These may be used alone or in combination of 2 or more.

When the silane coupling agent contains an epoxy group, the silane coupling agent (E) is contained in the silane coupling agent (E), and is not contained in the epoxy compound (B).

Examples of the mercapto group-containing silane coupling agent include monomeric mercapto group-containing silane coupling agents such as 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, γ -mercaptopropyldimethoxymethylsilane, and 3-mercaptopropylmethyldimethoxysilane, oligomer-type silane coupling agents in which a part of the silane compound is subjected to hydrolytic polycondensation, or the silane compound is subjected to copolycondensation with an alkyl group-containing silane compound such as methyltriethoxysilane, ethyltriethoxysilane, methyltrimethoxysilane, and ethyltrimethoxysilane. These may be used alone or in combination of 2 or more.

Examples of the (meth) acryloyl group-containing silane coupling agent include 3-acryloyloxypropyltrimethoxysilane, 3-methacryloyloxypropyltrimethoxysilane, 3-methacryloyloxypropylmethyldiethoxysilane, 3-methacryloyloxypropyltriethoxysilane, and 3-acryloyloxypropyltrimethoxysilane. These may be used alone or in combination of 2 or more.

When the silane coupling agent contains a (meth) acryloyl group, it is included in the silane coupling agent (E) and is 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, 3-aminopropyltriethoxysilane, 3-triethoxysilyl-N- (1, 3-dimethyl-butenyl) propylamine, N-phenyl-3-aminopropyltrimethoxysilane, and the like. These may be used alone or in combination of 2 or more.

Examples of the isocyanate group-containing silane coupling agent include 3-isocyanatopropyltriethoxysilane, and the like. These may be used alone or in combination of 2 or more.

Examples of the vinyl group-containing silane coupling agent include vinyltrimethoxysilane and vinyltriethoxysilane. These may be used alone or in combination of 2 or more.

When the silane coupling agent contains a vinyl group, it is contained in the silane coupling agent (E) and is not contained in the ethylenically unsaturated compound (C).

Among the silane coupling agents (E), from the viewpoint of excellent reactivity with the cationic polymerization component (oxetane compound (a) and epoxy compound (B)) and the radical polymerization component (C), an epoxy group-containing silane coupling agent, a vinyl group-containing silane coupling agent, and a (meth) acryloyl group-containing silane coupling agent are preferably used, and an epoxy group-containing silane coupling agent and a (meth) acryloyl group-containing silane coupling agent are particularly preferred. The silane coupling agent (E) may be a monomeric silane coupling agent or an oligomeric silane coupling agent partially hydrolyzed and condensed, and from the viewpoint of compatibility and adhesiveness, a monomeric silane coupling agent is preferably used.

The content of the silane coupling agent (E) is preferably 2 to 50 parts by weight, particularly preferably 3 to 40 parts by weight, and further preferably 5 to 30 parts by weight, based on 100 parts by weight of the total amount of the oxetane compound (a), the epoxy compound (B), and the ethylenically unsaturated compound (C). When the content of the silane coupling agent (E) is too large, the liquid stability tends to be lowered or the durability (thermal shock resistance) after curing tends to be lowered, and when it is too small, a further effect of improving the adhesiveness tends to be not sufficiently obtained.

The adhesive composition of the present invention may contain, in addition to the above components, other additives such as a photosensitizer, a polyol, an antistatic agent, other adhesives, an acrylic resin, a polyurethane resin, rosin, a rosin ester, a hydrogenated rosin ester, a phenol resin, an aromatic modified terpene resin, a tackifier such as an aliphatic petroleum resin, an alicyclic petroleum resin, a styrene resin, and a xylene resin, a plasticizer, a colorant, a filler, an antioxidant, an ultraviolet absorber, and a functional pigment, and a compound that develops color or changes color when irradiated with ultraviolet light or radiation, within a range in which the effects of the present invention are not impaired. The amount of these additives is appropriately set for each additive, and is, for example, preferably 30% by weight or less, particularly preferably 20% by weight or less, of the entire adhesive composition.

In addition to the above additives, impurities and the like contained in production raw materials and the like of the constituent components of the adhesive composition may be contained in a small amount.

By using the above photosensitizer, reactivity can be improved, and mechanical strength and adhesive strength of a cured product can be improved. Examples of the photosensitizer include anthracene derivatives such as 9, 10-dibutoxyanthracene and 9, 10-diethoxyanthracene; benzil derivatives such as benzil methyl ether, benzil isopropyl ether, and α, α -dimethoxy- α -phenylacetophenone; benzophenone derivatives such as benzophenone, 2, 4-dichlorobenzophenone, methyl benzoylbenzoate, 4 '-bis (dimethylamino) benzophenone, and 4, 4' -bis (diethylamino) benzophenone; carbonyl compounds such as anthraquinone derivatives such as 2-chloroanthraquinone and 2-methylanthraquinone; organic sulfur compounds such as thioxanthone derivatives such as 2-chlorothioxanthone, 2-isopropylthioxanthone and 2, 4-diethylthioxanthone-9-one; persulfides, redox compounds, azo and diazo compounds, halogen compounds, photoreducing pigments, and the like. These may be used alone or in combination of 2 or more. Among them, anthracene derivatives and thioxanthone derivatives are preferably used.

The photosensitizer is preferably contained in an amount of 0.01 to 20 parts by weight based on 100 parts by weight of the photopolymerization initiator (D). When the content of the photosensitizer is too large, the composition and the obtained adhesive layer tend to be colored, and when 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 mixing and blending the above components at a predetermined ratio.

The active energy ray-curable adhesive composition of the present invention can be obtained by such an operation.

The active energy ray-curable adhesive composition of the present invention is cured by irradiation with active energy rays to form an adhesive, and is particularly suitable as an adhesive for polarizing plates for bonding a polarizing plate and a protective film.

< polarizing plate >

The polarizing plate of the present invention is formed by bonding a polarizer and a protective film to each other with an adhesive for a polarizing plate. Specifically, a protective film is bonded to at least one surface, preferably both surfaces, of a polarizing plate using the adhesive for polarizing plates of the present invention, and usually, a liquid adhesive composition for polarizing plates is uniformly applied to the surface of the polarizing plate or the surface of the protective film, or both surfaces thereof, and then the both are bonded and pressure-bonded, followed by irradiation with active energy rays, thereby obtaining a polarizing plate.

The polarizing plate is generally a uniaxially stretched film (generally, a stretch ratio of about 2 to 10 times, preferably about 3 to 7 times) obtained by dyeing a film made of a PVA-based resin having an average polymerization degree of 1500 to 10000 and a saponification degree of 85 to 100 mol%, preferably 95 to 100 mol%, as a base film with an aqueous solution of iodine-potassium iodide or a dichroic dye.

The PVA-based resin is usually produced by saponifying polyvinyl acetate obtained by polymerizing vinyl acetate, and may contain a small amount of a component copolymerizable with vinyl acetate, such as an unsaturated carboxylic acid (including salts, esters, amides, nitriles, etc.), olefins, vinyl ethers, and unsaturated sulfonates. The PVA-based resin may contain a so-called polyvinyl acetal resin such as a polybutyral resin and a polyvinyl formal resin, which is obtained by reacting PVA with an aldehyde in the presence of an acid, and a PVA derivative.

As the protective film for the polarizing plate, an acrylic film, a polyethylene film, a polypropylene film, a cycloolefin film, or the like is preferably used in addition to the conventional TAC-based film, and the adhesive composition of the present invention is suitable for any one of the protective films selected from the TAC-based film, the acrylic film, the cycloolefin film, and the polyethylene terephthalate (PET) -based film.

When the adhesive composition of the present invention is applied to a polarizer or a protective film, it can be applied by, 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, or the like, or by a dipping method.

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

The active energy ray may be light such as far ultraviolet ray, near ultraviolet ray, infrared ray, electromagnetic wave such as X-ray, gamma ray, etc., or electron beam, proton beam, neutron beam, etc., and is preferably ultraviolet ray in view of curing speed, availability of irradiation apparatus, price, etc.

As a light source for performing the ultraviolet irradiation, a high-pressure mercury lamp, an electrodeless lamp, an ultrahigh-pressure mercury lamp, a carbon arc lamp, a xenon lamp, a metal halide lamp, a chemical lamp, a black light lamp, an LED lamp, or the like can be used.

The ultraviolet irradiation is usually 2 to 3000mJ/cm²Preferably 10 to 2000mJ/cm²And more preferably 20 to 1000mJ/cm²Under the conditions of (1).

Particularly, in the case of the above-mentioned high-pressure mercury lamp, it is usually 5 to 3000mJ/cm, for example²Preferably 50 to 2000mJ/cm²Under the conditions of (1).

In addition, in the case of the electrodeless lamp, for example, the thickness is usually 2 to 2000mJ/cm²Preferably 10 to 1000mJ/cm²Under the conditions of (1).

The irradiation time varies depending on the type of the light source, the distance between the light source and the coated surface, the coating thickness, and other conditions, and may be usually several seconds to several tens of seconds, or 1 second which may be several minutes in some cases.

On the other hand, in the case of the electron beam irradiation, for example, an electron beam having an energy in the range of 50 to 1000keV is used, and the irradiation dose is set to 2 to 50 Mrad.

The irradiation direction of the active energy ray (ultraviolet ray, electron beam, or the like) may be any appropriate direction, and from the viewpoint of preventing deterioration of the polarizing plate, irradiation from the transparent protective film side is preferable.

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. When the thickness is too small, the adhesive strength tends to be unable to be obtained due to the cohesive force itself, and when the thickness is too large, the workability of the polarizing plate tends to be deteriorated due to cracks or the like at the time of press working.

The active energy ray-curable adhesive composition of the present invention can be used for various adhesive applications, and is particularly suitable for bonding a protective film for various polarizing plates and a polarizing plate, and exhibits very excellent adhesion.

Examples

The present invention will be described more specifically with reference to the following examples, but the present invention is not limited to the following examples as long as the gist thereof is not exceeded. In the examples, "part" means a weight basis.

Prior to the examples and comparative examples, the following components of the adhesive composition were prepared.

[ Oxetane compound (A) ]

(A-1) 3-Ethyl-3 { [ (3-ethyloxetan-3-yl) methoxy ] methyl } OXETANE (OXETANE compound having 2 oxetanyl groups in the molecule: ARON OXETANE OXT-221, manufactured by Toyo Seisaku 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 ("jER 806" manufactured by Mitsubishi chemical corporation)

[ ethylenically unsaturated Compound (C) ]

(C-1) neopentyl glycol diacrylate (product of Kyoeisha chemical Co., Ltd. "LIGHT ACRYLATE NP-A")

[ Photocationic polymerization initiator (D1) ]

(D1-1) Diphenyl [4- (phenylthio) phenyl ] sulfonium hexafluorophosphate (aromatic sulfonium salt: San-Apro Ltd. "CPI-100P")

[ photo radical polymerization initiator (D2) ]

(D2-1)2,4, 6-trimethylbenzoyl-diphenylphosphine oxide ("Irgacure TPO" manufactured by BASF Co.)

[ 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) acrylic group-containing silane coupling agent ("KBM-5103 (3-acryloyloxypropyltrimethoxysilane)" manufactured by shin-Etsu chemical Co., Ltd.)

[ examples 1 to 10, comparative examples 1 to 7 ]

< preparation of active energy ray-curable adhesive composition >

The respective components were mixed at the ratios shown in table 1 below 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.

< preparation of polarizing plate >

First, a PVA film having a thickness of 60 μm was stretched 1.5 times while being immersed in a water bath at a temperature of 30 ℃. Then, the sheet was immersed in a dyeing bath (30 ℃ C.) containing 0.2g/L of iodine and 15g/L of potassium iodide for 240 seconds and stretched 1.3 times. Further, the resulting film was immersed in a boric acid treatment bath (50 ℃ C.) having a composition of boric acid of 50g/L and potassium iodide of 30g/L, and boric acid treatment was carried out for 5 minutes while uniaxially stretching the film to 3.08 times. Then, the film was dried at 90 ℃ to produce a polarizing plate having a total draw ratio of 6 times.

< preparation of polarizing plate test piece >

The adhesive compositions obtained above were applied to films of a TAC film (trade name "fujitac" manufactured by Fuji film Co., Ltd.) having a size of 200mm × 150mm and a thickness of 60 μm and a cycloolefin resin (COP) film (trade name "ZEONOR" manufactured by Japan Zeon Corporation) having a size of 200mm × 150mm and a thickness of 50 μm, respectively, by a bar coater to form a film having a thickness of 3 μm, thereby obtaining a film with an adhesive composition. Then, films having adhesive composition layers were superposed on both sides of the polarizing plate having a size of 180mm × 120mm, and the superposed films were bonded to each other with a nip pressure of 2MPa by a roll machine to obtain a laminated film (laminated film layer constitution: TAC film/polarizing plate/COP film).

Next, from the COP film side of the laminated film, an ultraviolet irradiation apparatus equipped with an electrodeless lamp was used to obtain a peak illuminance: 400mW/cm²And accumulated exposure: 150mJ/cm²(wavelength: 365nm) was irradiated with ultraviolet rays to cure the adhesive composition, thereby producing a polarizing plate test piece.

Using the polarizing plate test piece obtained above, performance evaluation was performed as follows.

< evaluation of Properties >

[ curing Property ]

The interface between the polarizing plate and the TAC film was peeled off with a utility knife, and the tackiness of the peeled portion was confirmed (touched) with a finger.

(evaluation criteria)

O … shows no residual tackiness.

Δ … although no tack remained, some finger mark remained.

X … residual tackiness.

[ adhesive force ]

The polarizing plate test piece was cut to 120mm × 25mm, and adhesion of the TAC film and the polarizer and adhesion of the COP film and the polarizer when stress was applied in the 90 ° direction were evaluated according to the following criteria.

(evaluation criteria)

C … is particularly strongly bonded.

O … was firmly adhered.

Δ … was weakly adhered.

X … not bonded.

[ durability (thermal shock resistance) ]

The test piece was cut into 100mm × 100mm, and a thermal shock test was performed by repeating a cycle of leaving at-40 ℃ for 30 minutes and then leaving at 85 ℃ for 30 minutes 100 times. After the test, evaluation was performed according to the following criteria.

(evaluation method)

No poor appearance was observed at all in o ….

A few appearance defects (short cracks were observed in the polarizer layer to such an extent that they did not affect the display) were observed in Δ ….

X … confirmed poor appearance (through cracks in the polarizer layer).

[ Table 1]

From the above results, it is understood that the adhesive compositions of examples 1 to 10 containing the oxetane compound (a) and the aliphatic epoxy compound (B1), further preferably containing the aromatic epoxy compound (B2) and also containing the ethylenically unsaturated compound (C) have good curability, excellent adhesion between the polarizing plate and the protective film, and excellent durability. From these results, it is found that the adhesive composition for polarizing plates is suitable for practical use as an adhesive composition for polarizing plates having a well-balanced and excellent balance of various performances.

On the other hand, comparative example 1 containing no aliphatic epoxy compound (B1) was poor in adhesion, comparative example 2 containing no oxetane compound (A) was poor in both curability and adhesion, and comparative example 3 containing no ethylenically unsaturated compound (C) was poor in curability, and thus was not practically used. Further, in comparative examples 4,5 and 6, which contain the oxetane compound (a), the epoxy compound (B) and the ethylenically unsaturated compound (C) but have too low a content ratio of the epoxy compound (B), sufficient adhesiveness could not be obtained. In comparative example 7 in which the content ratio of the epoxy compound (B) was too high, curability and durability were poor. From these, it is considered that the adhesive compositions of the comparative examples could not satisfy all of the various performances, and could not be practically used as an adhesive composition for a polarizing plate.

As described above, the adhesive composition of the present invention is excellent particularly in the application to adhesives for polarizing plates.

The above embodiments are merely examples and are not to be construed as limiting. Variations that are obvious to those skilled in the art are included within the scope of the invention.

Industrial applicability

The adhesive composition of the present invention and the adhesive composition for polarizing plates comprising the adhesive composition are excellent in adhesion between a polarizer and a protective film, and are suitable for bonding various protective films for polarizing plates and polarizers. In addition to the adhesiveness, the curability and the water resistance and durability of the polarizing plate, particularly the thermal shock resistance, are well-balanced and excellent. The adhesive composition of the present invention can be used for bonding various optical films or sheets, electronic components, precision instruments, packaging materials, display materials, and the like, in addition to the above-mentioned uses of the adhesive for polarizing plates.

Claims

1. An active energy ray-curable adhesive composition characterized by 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 an aromatic epoxy compound B2,

the content ratio of the epoxy compound B is 45 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 ratio B1/B2 of the aliphatic epoxy compound B1 to the aromatic epoxy compound B2 is 10/90 to 90/10 by weight.

2. The active energy ray-curable adhesive composition according to claim 1, wherein a 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 in terms of a weight ratio.

3. The active energy ray-curable adhesive composition according to claim 1 or 2, wherein the content ratio A/B of the oxetane compound A to the epoxy compound B is 10/90 to 60/40 in terms of a weight ratio.

4. The active energy ray-curable adhesive composition according to claim 1 or 2, wherein the photopolymerization initiator D contains a photo cation polymerization initiator D1 and a photo radical polymerization initiator D2.

5. The active energy ray-curable adhesive composition according to claim 4, wherein the content ratio D1/D2 of the photo cation polymerization initiator D1 to the photo radical polymerization initiator D2 is 20/80 to 99/1 in terms of a weight ratio.

6. The active energy ray-curable adhesive composition according to claim 1 or 2, further comprising a silane coupling agent E.

7. An adhesive composition for a polarizing plate, comprising the active energy ray-curable adhesive composition according to any one of claims 1 to 6.

8. An adhesive for polarizing plates, which is a cured product of the adhesive composition for polarizing plates according to claim 7.

9. A polarizing plate comprising the adhesive for polarizing plate according to claim 8, a polarizing plate, and a protective film, wherein the polarizing plate and the protective film are bonded to each other by the adhesive for polarizing plate.