WO2014129261A1

WO2014129261A1 - Cation-polymerizable adhesive

Info

Publication number: WO2014129261A1
Application number: PCT/JP2014/051372
Authority: WO
Inventors: 辰弥山本; 田中　浩二郎; 橋口　恒則
Original assignee: Dic株式会社
Priority date: 2013-02-22
Filing date: 2014-01-23
Publication date: 2014-08-28

Abstract

The present invention addresses the problem of providing a cation-polymerizable adhesive that exhibits superior curability and adhesiveness not only when used with a variety of protective films, but even when used with a protective film that poorly transmits light of 380nm or less. The present invention provides a cation-polymerizable adhesive characterized by containing: an aromatic glycidyl ether (A); an oxetane compound (B) that includes two or more oxetanyl groups inside one molecule; an alicyclic epoxy compound (C); an aliphatic glycidyl ether (D); a cationic-polymerization initiator (E); a thioxanthone compound (F); and a naphthalene compound (G). The cation-polymerizable adhesive according to the present invention exhibits superior curability and adhesiveness not only when used with a variety of protective films, but even when used with a protective film that poorly transmits light of 380nm or less.

Description

Cationic polymerizable adhesive

The present invention relates to a cationic polymerizable adhesive that can be used in various applications including, for example, the production of polarizing plates for use in liquid crystal displays and the like.

As cationic adhesives, cationic polymerizable adhesives that are less likely to cause curing inhibition due to atmospheric oxygen are attracting attention. Therefore, the development of cationically polymerizable adhesives has made remarkable progress in recent years, and various reports have been made.

Examples of the cationic polymerizable adhesive include a glycidyl ether group-containing compound obtained by distilling cyclohexanedimethanol diglycidyl ether, and a glycidyl ether group-containing compound obtained by distilling bisphenol F-type diglycidyl ether. A cationically polymerizable adhesive containing a hydrolyzable silyl group and epoxy group-containing compound and a cationic polymerization initiator and having a chlorine content of 500 ppm is disclosed (for example, see Patent Document 1). .

On the other hand, as the protective film constituting the polarizing plate, a triacetyl cellulose (TAC) film and a cycloolefin polymer (COP) film are conventionally widely used. It has adhesiveness that is practically usable.

However, in recent years, protective films have been diversified in order to further improve performance such as optical characteristics and durability of the polarizing plate. Examples of the protective film include a TAC film in which a phase difference imparting agent and an ultraviolet absorber are blended, an acrylic resin film in which an ultraviolet absorber is blended, and an FPR (Film Patterned Retarder) that is patterned with a polymerizable liquid crystal compound. Although the film etc. are mentioned, the said cationic polymerizable adhesive had the problem that sufficient adhesiveness was not expressed with respect to such a protective film.

This is due to a method for producing a polarizing plate using a cationic polymerizable adhesive, in which an adhesive is applied to one side of two protective films, bonded to a polarizer, and irradiated with ultraviolet rays. .

As cationically polymerizable initiators, sulfonium salts, iodonium salts, and the like are widely used. These cationically polymerizable initiators all have a maximum ultraviolet absorption wavelength in the range of approximately 250 to 400 nm. . In contrast, many of the protective films as described above are difficult to transmit light having a wavelength of 380 nm or less, and there is a problem that cationic polymerization hardly proceeds.

JP 2010-32766 A JP 2012-202111 A

The problem to be solved by the present invention is to provide a cationic polymerizable adhesive that is excellent in curability and adhesiveness even when using various protective films as well as protective films that are difficult to transmit light of 380 nm or less. is there.

The inventors of the present invention conducted intensive studies on the types of cationically polymerizable compounds, cationically polymerizable initiators, photosensitizers and the like while proceeding with studies to solve the above problems.

As a result, it has been found that the subject of the present invention can be solved by further using a specific photosensitizer for a cationic polymerizable adhesive containing a specific cationic polymerizable compound and a cationic polymerizable initiator.

That is, the present invention relates to an aromatic glycidyl ether (A), an oxetane compound (B) having two or more oxetanyl groups in one molecule, an alicyclic epoxy compound (C), an aliphatic glycidyl ether (D), cationic polymerization. The present invention provides a cationic polymerizable adhesive comprising an initiator (E), a thioxanthone compound (F) and a naphthalene compound (G).

The cationically polymerizable adhesive of the present invention is excellent in curability and adhesiveness not only when various protective films are used, but also when a protective film that hardly transmits light of 380 nm or less is used.

Further, since the cationic polymerizable adhesive of the present invention has a low viscosity, even when the adhesive of the present invention is applied to a protective film or a polarizer, unevenness does not occur in the adhesive layer, and the polarizing plate The optical properties are not adversely affected.

The cationic polymerizable adhesive of the present invention includes an aromatic glycidyl ether (A), an oxetane compound (B) having two or more oxetanyl groups in one molecule (hereinafter abbreviated as oxetane compound (B)), and fat. It contains a ring epoxy compound (C), an aliphatic glycidyl ether (D), a cationic polymerization initiator (E), a thioxanthone compound (F) and a naphthalene compound (G).

As the aromatic glycidyl ether (A), one having two or more glycidyl ether groups in one molecule is preferable for imparting good adhesion, and the glycidyl ether in the range of 2 to 6 is used. Those having a group are more preferred. Examples of the aromatic glycidyl ether (A) include bisphenol A glycidyl ether, bisphenol F glycidyl ether, bisphenol S glycidyl ether, and bisphenol AD glycidyl ether. These aromatic glycidyl ethers may be used alone or in combination of two or more. Among these, bisphenol A-type glycidyl ether and bisphenol F-type glycidyl ether are preferably used from the viewpoint of further improving the adhesive strength.

As the bisphenol A glycidyl ether, bisphenol A diglycidyl ether is preferably used from the viewpoint of adhesive strength.

As the bisphenol F-type glycidyl ether, it is preferable to use bisphenol F diglycidyl ether from the viewpoint of adhesive strength.

The oxetane compound (B) has two or more oxetanyl groups that contribute to cationic polymerization, and preferably has 2 to 4 oxetanyl groups from the viewpoint of improving low viscosity.

As the oxetane compound (B), specifically, for example, compounds represented by the following general formulas (1) and (2) can be used.

In the general formulas (1) and (2), each R ¹ is independently a hydrogen atom, a linear, branched or cyclic alkyl group having 1 to 6 carbon atoms, an allyl group, an aryl group, or an aralkyl group. , A furyl group or a thienyl group, each R ² independently represents a divalent organic residue, and each Z independently represents an oxygen atom or a sulfur atom.

Examples of the linear, branched or cyclic alkyl group having 1 to 6 carbon atoms represented by R ¹ include, for example, methyl group, ethyl group, n- or i-propyl group, n-, i- or a t-butyl group, a pentyl group, a hexyl group, a cyclohexyl group, etc., and an aryl group is, for example, phenyl, naphthyl, tolyl, xylyl group, etc., and an aralkyl group is, for example, benzyl, phenethyl Group.

In the general formula (1), examples of the divalent organic residue represented by R ² include a linear, branched or cyclic alkylene group and a poly (4 to 30 carbon atom) There are structures represented by the following general formulas (3) and (4): oxyalkylene) group, phenylene group, xylylene group.

The linear, branched or cyclic alkylene group constituting R ² has 1 carbon atom such as methylene group, ethylene group, 1,2- or 1,3-propylene group, butylene group, cyclohexylene group and the like. An alkylene group of ˜15 is preferred. The poly (oxyalkylene) group having 4 to 30 carbon atoms is preferably one having 4 to 8 carbon atoms, for example, poly (oxyethylene) group, poly (oxypropylene) It is preferably a group.

In the general formula (3), R ³ represents an oxygen atom, a sulfur atom, CH ₂ , NH, SO, SO ₂ , C (CF ₃ ) ₂ or C (CH ₃ ) ₂ .

In the general formula (4), R ⁴ represents an alkylene group having 1 to 6 carbon atoms, an arylene group, and a functional group represented by the following general formula (5).

In the general formula (5), a represents an integer in the range of 1 to 6, and b represents an integer in the range of 1 to 15.

In the general formula (5), b is preferably an integer in the range of 1 to 3.

The oxetane compound having an oxetanyl group in the range of 2 to 4 includes, for example, Aron oxetane OXT-221, Aron oxetane OXT-121, Aron oxetane OXT-223 (above, manufactured by Toagosei Co., Ltd.), etanacol OXBP, etanacol OXTP Etanacol OXIPA (above, manufactured by Ube Industries) is commercially available.

The molecular weight of the oxetane compound (B) is preferably in the range of 100 to 800, more preferably in the range of 100 to 500, from the viewpoint that the low viscosity can be further improved. For example, when the adhesive of the present invention adheres a polarizer and a protective film, the adhesive layer is usually formed as a thin film (several μm thick) in order to sufficiently cure. This is because the adhesive needs to have a low viscosity in order to uniformly apply the adhesive with the above-mentioned film thickness. In addition, the molecular weight of the said oxetane compound (B) shows the molecular weight calculated from structural formula.

Among the oxetane compounds (B), among those described above, those represented by the general formula (2) are preferably used. In particular, bis [1] wherein R ¹ is an ethyl group and Z is an oxygen atom. The use of -ethyl (3-oxetanyl)] methyl ether is particularly preferred because the film thickness of the adhesive after curing can be further reduced and the curability and adhesiveness can be further improved.

The amount of the oxetane compound (B) used is in the range of 10 to 1000 parts by mass with respect to 100 parts by mass of the aromatic glycidyl ether (A) from the viewpoint of further improving low viscosity and curability. The range of 50 to 600 parts by mass is more preferable, the range of 100 to 500 parts by mass is more preferable, and the range of 200 to 450 parts by mass is particularly preferable.

In the present invention, an oxetane compound having one oxetanyl group may be used in combination with the oxetane compound (B) as long as the effects of the present invention are not impaired.

As the oxetanyl compound having one oxetanyl group, for example, a compound represented by the following general formula (6) can be used.

(R ¹ in the general formula (6) is a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, an alkoxyalkyl group having 1 to 5 carbon atoms, or 1 to 6 carbon atoms. R ² represents a hydrogen atom, an optionally branched alkyl group having 1 to 10 carbon atoms, an aliphatic cyclic structure, or an aromatic structure.

Examples of the alkyl group having 1 to 8 carbon atoms that can constitute R ¹ in the general formula (6) include a methyl group, an ethyl group, an n-propyl group, an i-propyl group, and a 2-ethylhexyl group. Is mentioned.

Examples of the alkoxyalkyl group having 1 to 5 carbon atoms that can constitute R ¹ in the general formula (6) include a methoxymethyl group, an ethoxymethyl group, a propoxymethyl group, a methoxyethyl group, An ethoxyethyl group, a propoxyethyl group, etc. are mentioned.

Examples of the hydroxyalkyl group having 1 to 6 carbon atoms that can constitute R ¹ in the general formula (6) include a hydroxymethyl group, a hydroxyethyl group, and a hydroxypropyl group. .

In the general formula (6), the alkyl group having 1 to 10 carbon atoms which may be branched and can constitute R ² is a straight chain such as a methyl group, an ethyl group or a propyl group. And branched alkyl groups such as 2-ethylhexyl group.

As the aliphatic cyclic structure may constitute R ² in the general formula (6), such as cyclohexyl group and the like. The cyclohexyl group or the like may have an alkyl group or the like instead of a hydrogen atom.

Further, the aromatic structure may constitute R ² in the general formula (6), for example, a phenyl group and the like. The phenyl group or the like may have an alkyl group or the like instead of a hydrogen atom.

As the alicyclic epoxy compound (C), for example, a compound having 1 to 4 alicyclic epoxy groups can be used. The “alicyclic epoxy group” refers to an alicyclic structure having an epoxy group.

As the alicyclic epoxy compound having one alicyclic epoxy group, an alicyclic epoxy compound represented by the following general formula (7) can be used.

(In formula (7), R ¹ , R ² and R ³ each independently represents a hydrogen atom or a methyl group.)

As the alicyclic epoxy compound represented by the general formula (7), for example, “Celoxide 3000” (manufactured by Daicel Chemical Industries, Ltd.) is commercially available.

Examples of the alicyclic epoxy compound having two alicyclic epoxy groups include 3,4-epoxycyclohexenylmethyl-3,4-epoxycyclohexanecarboxylate represented by the following general formula (8) (general formula (8 ), A compound of which a is 0.), a caprolactone modified product thereof (a compound of which a is 1 in general formula (8)), a trimethylcaprolactone modified product thereof (structural formula (9) and structural formula (10)), And the valerolactone modified substance (Structural formula (11) and Structural formula (12)) and the compound shown by Structural formula (13) can be used.

(A in the general formula (8) represents 0 or 1)

Further, as the alicyclic epoxy compound having two alicyclic epoxy groups, a compound represented by the following general formula (14) can be used.

(In the general formula (14), R ¹ to R ⁶ each independently represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms.)
As the compound represented by the general formula (14), specifically, dicyclohexyl-3,3′-diepoxide can be used.

Further, as the alicyclic epoxy compound having three alicyclic epoxy groups, a compound represented by the following general formula (15) can be used.

(In general formula (15), a and b are each independently 0 or 1, and they may be the same or different.)

As the alicyclic epoxy compound represented by the general formula (15), for example, Epolide GT301, Epolide GT302 (manufactured by Daicel Chemical Industries, Ltd.) and the like are commercially available.

Further, as the alicyclic epoxy compound having four alicyclic epoxy groups, for example, a compound represented by the following general formula (16) can be used.

(In the general formula (16), a to d each independently represent 0 or 1, and they may be the same or different.)

As the alicyclic epoxy compound represented by the general formula (16), for example, Epolide GT401, Epolide GT403 (manufactured by Daicel Chemical Industries, Ltd.) and the like are commercially available.

As the alicyclic epoxy compound (C), an alicyclic epoxy compound having two alicyclic epoxy groups is preferably used from the viewpoint that adhesion to various protective films can be further improved, and 3,4-epoxycyclohexenyl is preferably used. More preferably, methyl-3,4-epoxycyclohexanecarboxylate is used.

The amount of the alicyclic epoxy compound (C) used is in the range of 10 to 1000 parts by mass with respect to 100 parts by mass of the aromatic glycidyl ether (A) from the viewpoint that adhesion to various protective films can be further improved. The range of 50 to 500 parts by mass is more preferable, the range of 100 to 450 parts by mass is still more preferable, and the range of 200 to 400 parts by mass is particularly preferable.

Examples of the aliphatic glycidyl ether (D) include trimethylolpropane diglycidyl ether, 1,6-hexanediol diglycidyl ether, 1,4-butanediol diglycidyl ether, cyclohexanedimethanol diglycidyl ether, propylene glycol diester. 3 such as aliphatic glycidyl ether having two glycidyl ether groups such as glycidyl ether, diethylene glycol diglycidyl ether, trimethylolpropane triglycidyl ether, glycerin triglycidyl ether, polyglycerol triglycidyl ether, diglycerol triglycidyl ether An aliphatic glycidyl ether having a glycidyl ether group can be used. These aliphatic glycidyl ethers may be used alone or in combination of two or more. Of these, aliphatic glycidyl ethers having 2 to 3 glycidyl ether groups are preferably used from the viewpoint that adhesion to various protective films can be further improved, and trimethylolpropane diglycidyl ether, cyclohexanedimethanol diglycidyl. It is particularly preferable to use ether.

The amount of the aliphatic glycidyl ether (D) used is in the range of 10 to 1000 parts by mass with respect to 100 parts by mass of the aromatic glycidyl ether (A) because the adhesion to various protective films can be further improved. The range of 50 to 500 parts by mass is more preferable, the range of 100 to 450 parts by mass is still more preferable, and the range of 200 to 400 parts by mass is particularly preferable.

The cationic polymerization initiator (E) refers to a compound that generates an acid capable of initiating cationic polymerization upon irradiation with energy rays such as ultraviolet rays. As the cationic polymerization initiator (E), for example, the cation moiety is aromatic sulfonium, aromatic iodonium, aromatic diazonium, aromatic ammonium, thianthrhenium, thioxanthonium, (2,4-cyclopentadiene-1 -Yl) [(1-methylethyl) benzene] -Fe cation, and the anion moiety is BF ₄ ⁻ , PF ₆ ⁻ , SbF ₆ ⁻ , [BX ₄ ] ⁻ (where X is at least two fluorine atoms) Alternatively, an onium salt composed of a phenyl group substituted with a trifluoromethyl group) may be used alone or in combination of two or more.

Examples of the aromatic sulfonium salt include bis [4- (diphenylsulfonio) phenyl] sulfide bishexafluorophosphate, bis [4- (diphenylsulfonio) phenyl] sulfide bishexafluoroantimonate, bis [4- ( Diphenylsulfonio) phenyl] sulfide bistetrafluoroborate, bis [4- (diphenylsulfonio) phenyl] sulfide tetrakis (pentafluorophenyl) borate, diphenyl-4- (phenylthio) phenylsulfonium hexafluorophosphate, diphenyl-4- ( Phenylthio) phenylsulfonium hexafluoroantimonate, diphenyl-4- (phenylthio) phenylsulfonium tetrafluoroborate, diphenyl-4- ( Enylthio) phenylsulfonium tetrakis (pentafluorophenyl) borate, triphenylsulfonium hexafluorophosphate, triphenylsulfonium hexafluoroantimonate, triphenylsulfonium tetrafluoroborate, triphenylsulfonium tetrakis (pentafluorophenyl) borate, bis [4- ( Di (4- (2-hydroxyethoxy)) phenylsulfonio) phenyl] sulfide bishexafluorophosphate, bis [4- (di (4- (2-hydroxyethoxy)) phenylsulfonio) phenyl] sulfide bishexafluoroantimony Bis [4- (di (4- (2-hydroxyethoxy)) phenylsulfonio) phenyl] sulfide bistetrafluoroborate, The [4- (di (4- (2-hydroxyethoxy)) phenylsulfonio) phenyl] can be used sulfide tetrakis (pentafluorophenyl) borate.

Examples of the aromatic iodonium salt include diphenyliodonium hexafluorophosphate, diphenyliodonium hexafluoroantimonate, diphenyliodonium tetrafluoroborate, diphenyliodonium tetrakis (pentafluorophenyl) borate, bis (dodecylphenyl) iodonium hexafluorophosphate. Bis (dodecylphenyl) iodonium hexafluoroantimonate, bis (dodecylphenyl) iodonium tetrafluoroborate, bis (dodecylphenyl) iodonium tetrakis (pentafluorophenyl) borate, 4-methylphenyl-4- (1-methylethyl) phenyl Iodonium hexafluorophosphate, 4-methylphenyl-4- ( 1-methylethyl) phenyliodonium hexafluoroantimonate, 4-methylphenyl-4- (1-methylethyl) phenyliodonium tetrafluoroborate, 4-methylphenyl-4- (1-methylethyl) phenyliodonium tetrakis (pentafluoro Phenyl) borate and the like can be used.

Further, as the aromatic diazonium salt, for example, phenyldiazonium hexafluorophosphate, phenyldiazonium hexafluoroantimonate, phenyldiazonium tetrafluoroborate, phenyldiazonium tetrakis (pentafluorophenyl) borate and the like can be used.

Examples of the aromatic ammonium salt include 1-benzyl-2-cyanopyridinium hexafluorophosphate, 1-benzyl-2-cyanopyridinium hexafluoroantimonate, 1-benzyl-2-cyanopyridinium tetrafluoroborate, 1-benzyl -2-cyanopyridinium tetrakis (pentafluorophenyl) borate, 1- (naphthylmethyl) -2-cyanopyridinium hexafluorophosphate, 1- (naphthylmethyl) -2-cyanopyridinium hexafluoroantimonate, 1- (naphthylmethyl) -2-Cyanopyridinium tetrafluoroborate, 1- (naphthylmethyl) -2-cyanopyridinium tetrakis (pentafluorophenyl) borate, and the like can be used.

Further, as the thioxanthonium salt, S-biphenyl 2-isopropyl thioxanthonium hexafluorophosphate or the like can be used.

The (2,4-cyclopentadien-1-yl) [(1-methylethyl) benzene] -Fe salt includes (2,4-cyclopentadien-1-yl) [(1-methylethyl) benzene. ] -Fe (II) hexafluorophosphate, (2,4-cyclopentadien-1-yl) [(1-methylethyl) benzene] -Fe (II) hexafluoroantimonate, 2,4-cyclopentadiene-1- Yl) [(1-methylethyl) benzene] -Fe (II) tetrafluoroborate, 2,4-cyclopentadien-1-yl) [(1-methylethyl) benzene] -Fe (II) tetrakis (pentafluorophenyl) ) Borate or the like can be used.

Examples of the cationic polymerization initiator (E), from viewpoint of further improving the curability, a cationic moiety is aromatic sulfonium, anionic moiety, PF 6 _^- it is preferable to use a.

Examples of the cationic polymerization initiator (E) include CPI-100P, CPI-101A, CPI-110P, CPI-200K, CPI-210S (manufactured by San Apro Co., Ltd.), a syracure photocuring initiator UVI-6990, SyraCure photocuring initiator UVI-6922, Syracure photocuring initiator UVI-6976 (above, manufactured by Dow Chemical Japan Co., Ltd.), Adekaoptomer SP-150, Adekaoptomer SP-152, Adekaoptomer SP-170, Adekaoptomer SP-172, Adekaoptomer SP-300 (manufactured by ADEKA Co., Ltd.), Esacure 1064, Esacure 1187 (manufactured by Lamberti), Omnicat 550 (manufactured by IG Resin), Irgacure 250 (BASF Japan Made by formula companies), such as Rodoshiru photo initiator 2074 (RHODORSIL PHOTOINITIATOR 2074 (manufactured by Rhodia Japan Co., Ltd.) are commercially available.

The amount of the cationic polymerization initiator (E) used is in the range of 5 to 100 parts by mass as an active ingredient with respect to 100 parts by mass of the aromatic glycidyl ether (A) from the viewpoint that the curability can be further improved. The range of 10 to 70 parts by mass is more preferable, the range of 20 to 60 parts by mass is still more preferable, and the range of 30 to 50 parts by mass is particularly preferable.

The thioxanthone compound (F) acts as a photosensitizer, and cures the cationic polymerizable adhesive of the present invention even when light irradiation is performed on a protective film that hardly transmits light of 380 nm or less. Is an essential ingredient.

Examples of the thioxanthone compound (F) include thioxanthone; thioxanthone compounds having an alkyl group such as 2-isopropylthioxanthone, 2-dodecylthioxanthone, 2-cyclohexylthioxanthone, 2,4-diethylthioxanthone, 2,4-dimethylthioxanthone; 1-methoxycarbonylthioxanthone, 2-ethoxycarbonylthioxanthone, 3- (2-methoxyethoxycarbonyl) -thioxanthone, 4-butoxycarbonylthioxanthone, 3-butoxycarbonyl-7-methylthioxanthone, 1-ethoxycarbonyl-3-ethoxythioxanthone, etc. A thioxanthone compound having an alkoxy group: 2-chlorothioxanthone, 1-cyano-3-chlorothioxanthone, 1-chloro-4-iso Ropi Lucio xanthone, 1-chloro-4-propoxy thioxanthone, or the like can be used thioxanthone compounds having a 1-ethoxycarbonyl-3-chloro chlorine atom, such as thioxanthone. These thioxanthone compounds may be used alone or in combination of two or more. Among these, it is preferable to use a thioxanthone compound having an alkyl group, and more preferable to use 2-isopropylthioxanthone and 2,4-diethylthioxanthone from the viewpoint that the curability and adhesiveness can be further improved.

The amount of the thioxanthone compound (F) used is in the range of 5 to 70 parts by mass with respect to 100 parts by mass of the aromatic glycidyl ether (A) from the viewpoint that the curability and adhesiveness can be further improved. The range of 10 to 60 parts by mass is more preferable, and the range of 20 to 55 parts by mass is still more preferable.

The naphthalene compound (G) acts as a photosensitizer and is used to cure the cationically polymerizable adhesive of the present invention even when light irradiation is performed on a protective film that hardly transmits light of 380 nm or less. Is an essential ingredient.

Examples of the naphthalene compound (G) include 1-methoxynaphthalene, 1-ethoxynaphthalene, 1-propoxynaphthalene, 1-butoxynaphthalene, 1,4-dimethoxynaphthalene, 1-ethoxy-4-methoxynaphthalene, 1,4. -Naphthalene compounds having an alkoxy group such as diethoxynaphthalene, 1,4-dipropoxynaphthalene, 1,4-dibutoxynaphthalene, 1-naphthol, 2-naphthol, 1- (2-hydroxyethoxy) naphthalene, 2- A naphthalene compound having a hydroxyl group such as (2-hydroxyethoxy) naphthalene can be used. These naphthalene compounds may be used alone or in combination of two or more. Among these, a naphthalene compound having an alkoxy group is preferably used, and 1,4-dimethoxynaphthalene and 1,4-diethoxynaphthalene are more preferably used from the viewpoint that the curability and adhesiveness can be further improved.

The amount of the naphthalene compound (G) used is in the range of 0.5 to 50 parts by mass with respect to 100 parts by mass of the aromatic glycidyl ether (A) because the curability and adhesiveness can be further improved. Preferably, the range is 1 to 30 parts by mass, more preferably 5 to 20 parts by mass.

The mass ratio [(F) / (G)] between the thioxanthone compound (F) and the naphthalene compound (G) is 30/70 to 90/10 because the curability and adhesiveness can be further improved. Preferably, the range is 50/50 to 85/15, more preferably 60/40 to 85/15.

The cationic polymerizable adhesive of the present invention contains the components (A) to (G) as essential components, but may contain other additives as necessary.

As the other additives, for example, thixotropic agents, leveling agents, antioxidants, heat stabilizer organic solvents, antistatic agents, foam stabilizers, antifoaming agents and the like can be used.

In addition to the above, for the purpose of further reducing the rigidity of the cationic polymerizable adhesive of the present invention, a polyol such as a polyether polyol may be contained.

In addition to the polyol, the cationic polymerizable adhesive of the present invention is intended to further improve the curability and viscosity, and to further improve the cationic polymerizable compound such as vinyl ether and oxolane, and the adhesiveness. A silane coupling agent may be contained.

The cationically polymerizable adhesive of the present invention has low viscosity and has a viscosity at room temperature in the range of 10 to 100 mPa · s. The viscosity of the cationic polymerizable adhesive is a value measured with a B-type viscometer at 25 ° C.

Next, a method for producing the cationic polymerizable adhesive of the present invention will be described. The cationically polymerizable adhesive of the present invention can be produced, for example, by the following method.

The cationic polymerizable adhesive of the present invention can be prepared by using, for example, a container equipped with a stirrer, the aromatic glycidyl ether (A), the oxetane compound (B), the alicyclic epoxy compound (C), the aliphatic. It can be produced by mixing and stirring glycidyl ether (D), the cationic polymerization initiator (E), the thioxanthone compound (F), the naphthalene compound (G) and the other additives as required. .

The cationic polymerizable adhesive of the present invention can be cured by irradiation with energy rays such as ultraviolet rays. The cationically polymerizable adhesive of the present invention exhibits adhesiveness only after irradiation with energy rays such as ultraviolet rays.

The irradiation of energy rays such as ultraviolet rays is preferably in the range of 0.001 to 5 J / cm ² , more preferably in the range of 0.002 to 2.5 J / cm ² , and particularly preferably 0.003 to 1.5 J / cm ^2. it is in the range of cm ^2.

As the ultraviolet ray generation source, for example, a known lamp such as a xenon lamp, a xenon-mercury lamp, a metal halide lamp, a high pressure mercury lamp, or a low pressure mercury lamp can be used. The amount of ultraviolet irradiation is based on a value measured in a wavelength range of 300 to 390 nm using a UV checker; UV Power PucK (II) (manufactured by Electronic Instrumentation and Technology).

Examples of the substrate or protective film to which the cationic polymerizable adhesive of the present invention is applied include, for example, cycloolefin resin films such as norbornene, (meth) acrylic resin films, silicon resin films, epoxy resin films, fluororesin films, polystyrene resins. Film, polyester resin film, polysulfone resin film, polyarylate resin film, polyvinyl chloride resin film, polyvinylidene chloride film, amorphous polyolefin resin film, polyimide resin film, alicyclic polyimide resin film, cellulose resin film, TAC ( Triacetylcellulose) film, COP (cycloolefin polymer) film, PC (polycarbonate) film, PBT (polybutylene terephthalate) film, modified P E (polyphenylene ether) film, PEN (polyethylene naphthalate) film, and PET (polyethylene terephthalate) film, a biodegradable film such as polylactic acid polymers.

Examples of the protective film include those in which a known ultraviolet absorber or retardation control agent is blended in the base material or the protective film, and those obtained by pattern retardering with a known polymerizable liquid crystal compound. A protective film that hardly transmits light can also be used. The protective film that hardly transmits light of 380 nm or less refers to a protective film having a light transmittance of approximately 10% or less at a wavelength of 380 nm. The light transmittance is a value measured with a V-570 spectrophotometer manufactured by JASCO Corporation.

As the ultraviolet absorber that can be blended in the protective film, known ultraviolet absorbers can be used in various applications, such as phenyl salicylate, pt-butylphenyl salicylate, p-octylphenyl salicylate. Tyrate, 2-hydroxy-4-benzyloxybenzophenone, 2,4-dihydroxybenzophenone, 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-octoxybenzophenone, 2-hydroxy-4-dodecyloxybenzophenone, 2, 2'-dihydroxy-4-methoxybenzophenone, 2-2'-dihydroxy-4,4'-dimethoxybenzophenone, 2- (2'-hydroxy-5'-t-octylphenyl) -benzotriazole, 2- (2 ' -Hydroxy-5'-t-octylphenyl) -benzo Triazole, 2- (2′-hydroxy-5′-methylphenyl) benzotriazole, 2- (2′-hydroxy-3′5′-di-t-butylphenyl) benzotriazole, 2- (2′-hydroxy- 3′-t-butyl-5′-methylphenyl) -5-chlorobenzotriazole, 2- (2′-hydroxy-3′5′-di-t-butylphenyl) 5-chlorobenzotriazole, etc. may be used. it can. These may be used alone or in combination of two or more.

Examples of the method for applying the cationic polymerizable adhesive of the present invention to the base material and the protective film include a slit coater method such as a curtain flow coater method and a die coater method, a knife coater method, a roll coater method, a gravure coater method, A method of applying by spraying or the like can be used.

Hereinafter, the present invention will be described in detail by way of examples.

[Production method of polarizer]
An aqueous polyvinyl alcohol solution (non-volatile content: 8% by mass) obtained by dissolving Kuraray Poval PVA-117H (polyvinyl alcohol manufactured by Kuraray Co., Ltd., degree of polymerization 1,700, completely saponified product, powder) into water, Was applied onto a release film, and then dried in an environment at 80 ° C. for 5 minutes, and then the release film was removed to prepare a polyvinyl alcohol film having a thickness of 75 μm.
Next, the obtained polyvinyl alcohol film was fixed to a stretching machine, and the film was stretched in hot water at 40 ° C. until it became three times larger in a uniaxial direction.
After removing water adhering to the surface of the stretched film obtained above, the stretched film was adjusted to 30 ° C. containing 0.02 parts by mass of iodine, 2 parts by mass of potassium iodide and 100 parts by mass of water. It was immersed in the aqueous solution.
Next, the stretched film was immersed in an aqueous solution adjusted to 56.5 ° C. containing 12 parts by mass of potassium iodide, 5 parts by mass of boric acid, and 100 parts by mass of water.
After the immersed stretched film is washed in pure water adjusted to 8 ° C. and dried in an environment of 65 ° C., a polarizer in which iodine is adsorbed and oriented on the surface of the stretched film made of polyvinyl alcohol (polarized light) Film).

[Example 1]
In a reaction vessel equipped with a stirrer, reflux condenser, thermometer, dropping funnel and nitrogen gas inlet, bisphenol F type glycidyl ether (“EPICLON EXA-830CRP” manufactured by DIC Corporation) is used as the aromatic glycidyl ether (A). 100 parts by mass, 350 parts by mass of bis [1-ethyl (3-oxetanyl)] methyl ether as the oxetane compound (B), and 3,4-epoxycyclohexenylmethyl-3,4 as the alicyclic epoxy compound (C) -250 parts by mass of epoxycyclohexanecarboxylate, 300 parts by mass of trimethylolpropane diglycidyl ether as aliphatic glycidyl ether (D), diphenyl-4- (phenylthio) phenylsulfonium hexa as photocationic polymerization initiator (E) Fluorophosphate 80 parts by mass of a 50% by mass solution of propylene carbonate, 40 parts by mass of 2,4-diethylthioxanthone as a thioxanthone compound (F), and 10 parts by mass of 1,4-diethoxynaphthalene as a naphthalene compound (G) were mixed and mixed. The cationic polymerizable adhesive (Y-1) was obtained by stirring.

[Examples 2 to 8, Comparative Examples 1 to 3]
A cationically polymerizable adhesive was obtained in the same manner as in Example 1, except that the amounts of the oxetane compound (B), alicyclic epoxy compound (C) and thioxanthone compound (F) used were changed as shown in Table 1. It was.

[Examples 9 to 21, Comparative Examples 4 to 6]
[Evaluation method of curability]
On each surface of the two protective films shown in Tables 2 to 3, the cationic polymerizable adhesive shown in Tables 2 to 3 was applied to a thickness of about 2 μm using a wire bar, The coated substrate was bonded to both sides of the polarizer (polarizing film). Next, after pressurizing with a rubber roller, using a conveyor type UV irradiation device (Fusion LH-6 output 60%, conveyor speed 7.0 m / min), integration of 300 to 390 nm from the protective film side of the upper layer is performed. By irradiating ultraviolet rays having a light amount of 1.0 J / cm ² , a laminate having a structure of protective film / cationic polymerizable adhesive layer / polarizer / cationic polymerizable adhesive layer / protective film is formed from above. Obtained. The obtained laminate was cut into a length of 3 cm in length and 5 cm in width to obtain a test piece.
The curability was evaluated based on the degree of color loss of iodine adsorbed on the polarizer. Specifically, the test piece was immersed in warm water at 60 ° C. for 24 hours, and evaluated as follows based on the difference in transmittance (%) between the test pieces before and after the immersion. The transmittance of the test piece was measured by “RETS-100” (manufactured by Otsuka Electronics Co., Ltd.).
“◯”: Difference in transmittance (%) is 3 or less.
“Δ”: The difference in transmittance (%) is in the range of more than 3 and less than 10.
“×”: The difference in transmittance (%) is 10 or more.

[Adhesion evaluation method]
A laminate was obtained in the same manner as in the above [Method for evaluating curability], and then the laminate was cut into a length of 3 cm in length and 5 cm in width to obtain a test piece.
Using a tensile tester (“SV-55C” manufactured by Imada Seisakusho Co., Ltd.), the test piece was peeled T-shaped under the condition of a tensile speed of 50 mm / min. The adhesiveness was evaluated as follows according to the peeled state of the test piece.
“◯”: The base material is broken.
“×”: Peeled due to insufficient adhesive force.

Abbreviations in Tables 2 to 3 will be described.
“UV-TAC”: a triacetyl cellulose film containing a UV absorber (light transmittance at a wavelength of 380 nm is 10% or less)
"UV-PMMA"; acrylic resin film with UV absorber (light transmittance at a wavelength of 380 nm is 10% or less)
“COP”; cycloolefin polymer film “FPR-UVTAC”; film patterned retardered by a polymerizable liquid crystal compound on one side of the above “UV-TAC” (light transmittance at a wavelength of 380 nm is 10% or less)

It was found that the cationic polymerizable adhesive of the present invention is excellent in curability and adhesiveness even when a protective film that hardly transmits light of 380 nm or less is used.

On the other hand, Comparative Example 1 is an embodiment in which 9,10-dibutoxyanthracene is used in place of the thioxanthone compound (F). However, when a protective film that hardly transmits light of 380 nm or less is used, the curability and adhesion Was found to be poor.

Comparative Example 2 is an embodiment that does not contain a thioxanthone compound (F), but it was found that when a protective film that hardly transmits light of 380 nm or less is used, curability and adhesiveness are poor.

Comparative Example 3 is an embodiment that does not contain a naphthalene compound (G), but it was found that when a protective film that hardly transmits light of 380 nm or less is used, curability and adhesiveness are poor.

Claims

Aromatic glycidyl ether (A), oxetane compound (B) having two or more oxetanyl groups in one molecule, alicyclic epoxy compound (C), aliphatic glycidyl ether (D), cationic polymerization initiator (E), A cationically polymerizable adhesive comprising a thioxanthone compound (F) and a naphthalene compound (G).
The cationically polymerizable adhesive according to claim 1, wherein the thioxanthone compound (F) is used in an amount of 5 to 70 parts by mass with respect to 100 parts by mass of the aromatic glycidyl ether (A).
The cationically polymerizable adhesive according to claim 1, wherein the mass ratio [(F) / (G)] of the thioxanthone compound (F) and the naphthalene compound (G) is in the range of 30/70 to 90/10.
The cationically polymerizable adhesive according to claim 1, wherein the thioxanthone compound (F) has an alkyl group.
The cationically polymerizable adhesive according to claim 1, wherein the naphthalene compound (G) has an alkoxy group.