JP5788841B2 - Adhesive for polarizing plate - Google Patents

Description

  The present invention relates to an adhesive composition for bonding a polarizer and a protective film, which is used when manufacturing a polarizing plate, and a polarizing plate manufactured using the same. More specifically, the present invention relates to an adhesive composition excellent in initial curability and adhesiveness and a polarizing plate using the same.

  In recent years, flat displays such as liquid crystal displays and plasma displays have been widely used as display devices because they are space-saving and have high definition. Among these, liquid crystal displays are attracting attention and are being developed because they are more power-saving and have higher definition.

  In a liquid crystal display panel, a polarizing plate that functions as an optical shutter is used in combination with liquid crystal in order to perform its function. A polarizing plate is an essential component for a liquid crystal display panel including a polarizer. Usually, a polarizer is produced by uniaxially stretching a polyvinyl alcohol resin to a length of 5 to 6 times in a water tank, so that it has a disadvantage that it is easily broken in the stretching direction and is brittle. Therefore, the polarizer is used by forming a polarizing plate by adhering a protective film to the front surface and / or back surface thereof. At that time, the adhesive for adhering the protective film to the polarizer is also required to satisfy a specific requirement when the polarizing plate is used.

  As such an adhesive for polarizing plates, for example, an adhesive that cures a curable component containing an N-substituted amide monomer having a specific structure by irradiation with active energy rays is known (see Patent Document 1). Patent Document 1 describes that a polarizing plate bonded using such an N-substituted amide monomer is excellent in durability under high temperature and high humidity. However, although such N-substituted amide monomers are excellent in initial curability, an adhesive finally obtained by curing is not sufficient in terms of adhesive strength.

  Moreover, the adhesive agent using the epoxy resin which does not contain an aromatic ring is known as an adhesive agent for polarizing plates (refer patent document 2). In Patent Document 2, by using an epoxy resin that does not contain an aromatic ring, when a protective film having low moisture permeability is used, a polarizing plate that has sufficient adhesive strength and does not cause a problem of poor appearance can be obtained. It is described. However, it has been found that an adhesive using an epoxy resin not containing an aromatic ring is inferior in initial curability although it is excellent in adhesive strength.

  Furthermore, a radical polymerizable compound mainly comprising a monofunctional radical polymerizable compound, a main agent comprising a compound having an alicyclic epoxy group and not containing a (meth) acryloyl group, and initiation of radical photopolymerization A photo-curable adhesive containing an agent and a cationic photopolymerization initiator is known (see Patent Document 3). Patent Document 3 describes that the adhesive is excellent not only in the adhesion between the protective film and the polarizer, but also in punching workability and water resistance. However, such an adhesive has good initial curability but does not have sufficient adhesion to a specific film such as a polyethylene terephthalate film.

JP 2008-287207 A JP 2004-245925 A JP 2011-76058 A

  By the way, since a polarizer is drawn and manufactured in a water tank as described above, it usually contains moisture. A polymerizable compound such as an epoxy resin that does not contain an aromatic ring used in the above-described prior art is cured over a period of time after irradiation with active energy rays. In general, there is a problem that initial curability is not good. Such a problem causes peeling of the protective film when the polarizing plate is conveyed while being bent by a roll or a belt in an actual manufacturing process, resulting in a decrease in yield and processability. .

  On the other hand, in order to obtain a polarizing plate having sufficient durability even after long-term use or temperature / humidity changes, the adhesive composition is required to have excellent adhesiveness. Although the N-substituted amide monomer used in Patent Document 1 is excellent in initial curability, it has a disadvantage that it is somewhat inferior in adhesiveness between the polarizer and the protective film.

  Moreover, also in the case of the prior art of the said patent document 3 which used both the alicyclic epoxy resin and the radically polymerizable compound, it turned out that an adhesive composition is still inadequate in terms of adhesiveness.

  This invention is made | formed in view of the said situation, and it aims at providing the adhesive composition for polarizing plates excellent in initial stage curability and adhesiveness. Moreover, the other objective of this invention is to provide the polarizing plate excellent in durability by using such an adhesive composition.

  As a result of diligent research to solve the above problems, the present inventors have used an epoxy resin having a specific structure and an acrylic monomer in combination, so that it has excellent initial curability and adhesiveness. The inventors found that an adhesive could be obtained and completed the present invention.

  That is, the present invention comprises 20 to 70 parts by mass of an epoxy resin and 30 to 80 parts by mass of an acrylic monomer (however, the total is 100 parts by mass), 1 to 7 parts by mass of a photoacid generator, 1 to 7 parts by mass, and the epoxy resin contains at least one selected from the group consisting of resorcin-type epoxy resins, bisphenol S-type epoxy resins and naphthalene-type epoxy resins. It is.

  The adhesive composition for polarizing plates of the present invention has good initial curability and adhesiveness when used for polarizing plates using various protective films by using an epoxy resin having a specific structure and an acrylic monomer in combination. It can be expressed. Therefore, the polarizing plate using the adhesive composition of the present invention can be a highly durable polarizing plate with good adhesion to the protective film.

It is the schematic for demonstrating the manufacturing process of the polarizing plate in an Example. It is the schematic for demonstrating the method of the initial stage sclerosis | hardenability test in an Example. It is the schematic for demonstrating the method of the warm water immersion test in an Example.

  Hereinafter, the present invention will be described in detail for each element.

(1) Adhesive composition for polarizing plate The 1st aspect of this invention is 20-70 mass parts of epoxy resins, 30-80 mass parts (however, a sum total is 100 mass parts), and photo-acid generation | occurrence | production. 1 to 7 parts by mass of an agent and 0.1 to 7 parts by mass of a photopolymerization initiator, and the epoxy resin includes at least one of resorcin type epoxy resin, bisphenol S type epoxy resin and naphthalene type epoxy resin. It is an adhesive composition for polarizing plates.

  As described above, conventional polarizing plate adhesives have not been sufficient in terms of achieving both initial curability and adhesiveness. In the present invention, by combining the epoxy resin having the above specific structure and the acrylic monomer in a specific ratio, both initial curability and adhesiveness are realized. Among these, it is considered that the epoxy resin having a specific structure particularly contributes to the improvement of adhesion, and the acrylic monomer particularly contributes to the initial curability.

  Hereinafter, (A) an epoxy resin, (B) an acrylic monomer, (C) a photoacid generator, (D) a photopolymerization initiator, and (E) a method for producing an adhesive composition will be described.

(A) Epoxy Resin The epoxy resin used in the present invention contains at least one of resorcinol type epoxy resin, bisphenol S type epoxy resin and naphthalene type epoxy resin, and in particular, adhesion between a polarizer and a protective film as a polarizing plate adhesive. It is thought that it contributes to improvement of performance.

  As a resorcinol type epoxy resin, what is represented by following formula (1) can be used.

In the above formula, Y ₁ and Y ₂ each independently represent an alkylene group having 1 to 10 carbon atoms, and any hydrogen atom in the alkylene may be substituted with a halogen atom, preferably 1 carbon atom. -5, more preferably an unsubstituted alkylene group having 1 to 2 carbon atoms. R ₁ each independently represents a hydrogen atom, a halogen atom or an alkyl group having 1 to 5 carbon atoms, preferably a hydrogen atom. X ₁ and X ₂ are epoxy groups represented by the following formula (2).

  Of the above resorcinol-type epoxy resins, most preferred is a diglycidyl etherified product of resorcinol represented by the following formula (3).

  Resorcin-type epoxy resin is an epoxy resin with a relatively small epoxy equivalent, so even when used as an adhesive for polarizing plates, the number of crosslinking points per unit volume of the resulting cured product is increased, resulting in strong adhesion It is thought that it exhibits sex.

  The resorcinol type epoxy resin can be synthesized by, for example, a reaction between resorcinol and epichlorohydrin, but a commercially available product may be used. As a commercial item of the resorcinol type epoxy resin of the said Formula (3), Denacol (trademark) EX-201 (made by Nagase ChemteX Corporation) is mentioned.

  As a naphthalene type epoxy resin, what is represented by following formula (4) can be used.

In the above formula (4), Y ₃ and Y ₄ each independently represent an alkylene group having 1 to 10 carbon atoms, and any hydrogen atom in the alkylene may be substituted with a halogen atom, preferably An unsubstituted alkylene group having 1 to 5 carbon atoms, more preferably 1 to 2 carbon atoms. R ₃ and R ₄ each independently represent a hydrogen atom, a halogen atom or an alkyl group having 1 to 5 carbon atoms, preferably a hydrogen atom. X ₃ and X ₄ are epoxy groups represented by the above formula (2).

  Of the above naphthalene type epoxy resins, most preferred is a diglycidyl etherified product of dihydroxynaphthalene represented by the following formula (5).

  When naphthalene type epoxy resin is used as an adhesive for polarizing plates, the naphthalene ring portion is easy to become familiar with the protective film and the material of the polarizer, so it is thought that it contributes to the adhesion between the polarizing plate and the protective film. Therefore, it is considered that the adhesive property of the polarizing plate has been improved.

  The naphthalene type epoxy resin can be synthesized by, for example, a reaction between dihydroxynaphthalene and epichlorohydrin, but a commercially available product may be used. As a commercial item of the naphthalene type epoxy resin represented by the above formula (5), Epicron (registered trademark) HP-4032 and Epicron (registered trademark) HP-4032D (manufactured by DIC Corporation) may be mentioned.

  As a bisphenol S type epoxy resin, what is represented by following formula (6) can be used.

In the above formula (6), Y ₅ and Y ₆ each independently represent an alkylene group having 1 to 10 carbon atoms, and any hydrogen atom in the alkylene may be substituted with a halogen atom, preferably An unsubstituted alkylene group having 1 to 5 carbon atoms, more preferably 1 to 2 carbon atoms. R ₅ and R ₆ each independently represents a hydrogen atom, a halogen atom or an alkyl group having 1 to 5 carbon atoms, preferably a hydrogen atom. X ₅ and X ₆ are epoxy groups represented by the above formula (2).

  Of the above bisphenol S-type epoxy resins, most preferred is a diglycidyl etherified product of bisphenol S represented by the following formula (7).

Bisphenol S-type epoxy resin, when used as an adhesive for polarizing plates, has a characteristic bonding portion of —SO ₂ — existing between benzene rings in the form of hydrogen bonds between the polarizing plate and the protective film. It is thought that it contributes to adhesiveness, and as a result, it is thought that the adhesive improvement of a polarizing plate is implement | achieved.

  The bisphenol S type epoxy resin can be synthesized by, for example, a reaction of bisphenol S and epichlorohydrin, but a commercially available product may be used. As a commercial product of the bisphenol S-type epoxy resin represented by the above formula (7), Epicron (registered trademark) EXA-1514 (manufactured by DIC Corporation) may be mentioned. Moreover, Denacol (trademark) EX-251 (made by Nagase ChemteX Corporation) is mentioned as a commercial item of the other bisphenol S type epoxy resin which can be used for this invention.

  Among at least one selected from the group consisting of the resorcin type epoxy resin, bisphenol S type epoxy resin and naphthalene type epoxy resin, more preferably at least one type selected from the group consisting of resorcin type epoxy resin and naphthalene type epoxy resin More preferably, it is a resorcinol type epoxy resin. A resorcinol type epoxy resin is most preferable in terms of excellent adhesiveness and reactivity when used as an adhesive for polarizing plates.

  The adhesive composition for polarizing plates of the present invention may further contain other epoxy resins in addition to the epoxy resin having the above specific structure. The other epoxy resin is not particularly limited, and for example, a glycidyl etherified product of an aromatic compound or a chain compound having a hydroxyl group, a glycidyl aminated product of a compound having an amino group, a saturated carbocycle directly or via an alkylene group. Examples include alicyclic epoxy compounds to which a glycidyloxy group or an epoxyethyl group is bonded. These other epoxy resins may be used alone or in combination of two or more.

  More specifically, as the glycidyl etherified product, phenyl glycidyl ether, ethylene glycol diglycidyl ether, glycerin diglycidyl ether, trimethylolpropane triglycidyl ether, dicyclopentadiene dimethanol diglycidyl ether, bisphenol A type diglycidyl ether, Bisphenol F type diglycidyl ether, bisphenol AD type diglycidyl ether, glycidyl etherified product of 3,3 ′, 5,5′-tetramethyl-4,4′-biphenol can be used. Of these, bisphenol A type diglycidyl ether and bisphenol F type diglycidyl ether are particularly preferred as other epoxy resins used in the present invention. By containing bisphenol A type diglycidyl ether or bisphenol F type diglycidyl ether, the adhesiveness can be further improved.

  The bisphenol A type epoxy resin may be synthesized by itself or a commercially available product may be used. As commercially available products, Epicoat (registered trademark) 825, 828, 834, 1001, 1002, 1003, 1004, 1007, 1009, 1010 (manufactured by Yuka Shell Epoxy Co., Ltd.), Epototo (registered trademark) YD-128, YD- 011, YD-014, YD-017, YD-019, YD-022 (manufactured by Tohto Kasei Co., Ltd.), Epicron (registered trademark) 840, 850, 1050, 3050, HM-101, EXA850CRP (manufactured by DIC Corporation), etc. Is mentioned.

  Also, polyaromatic glycidyl such as glycidyl etherified product of phenol novolac resin, glycidyl etherified product of cresol novolak resin, glycidyl etherified product of phenol aralkyl resin, glycidyl etherified product of naphthol aralkyl resin, glycidyl etherified product of phenol dicyclopentadiene resin, etc. Etherified products can also be used.

  Further, alkylene glycol type glycidyl etherified products such as ethylene glycol glycidyl etherified products, diethylene glycol glycidyl etherified products, 1,4-butanediol glycidyl etherified products, and 1,6-hexanediol glycidyl etherified products can also be used.

  Also, 1,3-phenylenediamine glycidyl aminated product, 1,4-phenylenediamine glycidyl aminated product, 3-aminophenol glycidyl aminated product and glycidyl etherified product, 4-aminophenol glycidyl aminated product and glycidyl Glycidyl aminated compounds such as sidyl etherified compounds can also be used.

  As the epoxy resin other than the bisphenol A type epoxy resin as described above, a commercially available product may be used. Examples of the commercially available product include Epolite (registered trademark) series (manufactured by Kyoeisha Chemical Co., Ltd.) Epicoat (registered trademark). ) Series (Mitsubishi Chemical Corporation), Epiklon (registered trademark) series (DIC Corporation), Epototo (registered trademark) series (Nippon Steel Chemical Co., Ltd.), Adeka Resin (registered trademark) series (ADEKA Corporation) ), Denacol (registered trademark) series (manufactured by Nagase ChemteX Corporation), Dow epoxy series (manufactured by Dow Chemical Japan Co., Ltd.), Tepic (registered trademark) series (manufactured by Nissan Chemical Industries, Ltd.), DVE-3, CHVE (BASF Japan Ltd.), Celoxide (registered trademark) series (Daicel Corporation) ), And the like.

  When other epoxy resins described above are used in combination, (a) a specific epoxy resin (at least one of resorcin-type epoxy resin, bisphenol S-type epoxy resin and naphthalene-type epoxy resin), (b) other epoxy resin The mass ratio (a) / (b) is preferably 99/1 to 20/80. More preferably, it is 75 / 25-25 / 75, More preferably, it is 60 / 40-40 / 60, Most preferably, it is 50/50. If it is the above-mentioned range, good adhesiveness will be expressed.

(B) Acrylic monomer Any known acrylic monomer can be used without particular limitation as long as it exhibits radical polymerizability. Typical examples include monomers having a (meth) acryloyl group, a (meth) acrylamide group, and the like, such as (meth) acrylic acid and derivatives thereof, (meth) acrylonitrile, (meth) acrylamide and derivatives thereof, and the like. It is done. These monomers may be used alone or in combination of two or more.

More specifically, examples of the acrylic monomer include the following. (Meth) acrylic acid and its salts;
Methyl (meth) acrylate, ethyl (meth) acrylate, methylphenoxyethyl (meth) acrylate, n-propyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, tert-butyl (meth) acrylate, Pentyl (meth) acrylate, cyclohexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, lauryl (meth) acrylate, (meth) acrylate, 2-methoxyethyl (meth) acrylate, (meth) acrylate, 2-hydroxyethyl ( (Meth) acrylate, 2-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, glycerol mono (meth) acrylate, 3 Chloro-2-hydroxypropyl (meth) acrylate, 2-hydroxy-3-phenoxypropyl (meth) acrylate, ethylene glycol di (meth) acrylate, phenoxyethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, phenoxydiethylene glycol (Meth) acrylate, triethylene glycol di (meth) acrylate, phenoxytriethylene glycol di (meth) acrylate, butylene glycol di (meth) acrylate, nonaethylene glycol di (meth) acrylate, polypropylene glycol di (meth) acrylate, di Propylene glycol di (meth) acrylate, neopentyl glycol di (meth) acrylate, 1,3-butanediol di (meth) Acrylate, 1,4-butanediol di (meth) acrylate, 1.6-hexanediol di (meth) acrylate, trimethylolpropane tri (meth) acrylate, neopentyl glycol di (meth) acrylate, pentaerythritol tri (meth) Addition of mono-ε-caprolactone to acrylate, trimethylolmethane tri (meth) acrylate, isobornyl (meth) acrylate, N-vinylpyrrolidone, acryloylmorpholine, urethane (meth) acrylate, tetrahydrofurfuryl (meth) acrylate, tetrahydrofurfuryl alcohol (Meth) acrylate, tetrahydrofurfuryl alcohol di-ε-caprolactone adduct (meth) acrylate, tetrahydrofurfuryl alcohol mono β-methyl- (Meth) acrylate such as (meth) acrylate of δ-valerolactone adduct, (meth) acrylate of diβ-methyl-δ-valerolactone adduct of tetrahydrofurfuryl alcohol, ω-carboxy-polycaprolactone monoacrylate, etc. Compounds;
Nitrile group-containing vinyl compounds such as acrylonitrile and methacrylonitrile; and (meth) acrylamide, N-methyl (meth) acrylamide, N-ethyl (meth) acrylamide, N-propyl (meth) acrylamide, N-isopropyl (meth) acrylamide N-butyl (meth) acrylamide, N, N-dimethyl (meth) acrylamide, N, N-diethyl (meth) acrylamide, N, N-dimethylaminopropyl (meth) acrylamide, N- (hydroxyethyl) acrylamide, N Examples include amide group-containing vinyl compounds such as isopropyl (meth) acrylamide, N-methylol (meth) acrylamide, diacetone (meth) acrylamide, and N, N-methylenebis (meth) acrylamide.

  Among the above, at least one of a hydroxy group-containing acrylic monomer and a phenoxy group-containing acrylic monomer is more preferable because it is excellent in initial curability as an adhesive composition for polarizing plates and increases the adhesion to a film. 2-hydroxyethyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, methylphenoxyethyl (meth) acrylate, phenoxydiethylene glycol (meth) acrylate, and 2-hydroxy-3-phenoxypropyl acrylate are more preferable.

  Commercially available products may be used as the above acrylic monomers. For example, the KAYARAD series (manufactured by Nippon Kayaku Co., Ltd.), the NK ester series (manufactured by Shin-Nakamura Chemical Co., Ltd.), the Koei hard series (Guangei Chemical Industry Co., Ltd.) Company), Seika Beam (registered trademark) series (Daicel Seika Kogyo Co., Ltd.), KRM series (Daicel Cytec Co., Ltd.), EB series, UVECRYL (registered trademark) series (Daicel UCB Co., Ltd.), ACRICID series (made by DIC Corporation), Aurex (registered trademark) series (made by China Paint Co., Ltd.), Sunrad (registered trademark) series (made by Sanyo Chemical Industries, Ltd.), RCC series (made by Grace Japan Co., Ltd.) , Aronix (registered trademark) series (manufactured by Toagosei Co., Ltd.), LA The door acrylate series (manufactured by Kyoeisha Chemical Co., Ltd.) and the like can be used.

  Moreover, 20-80 mass parts of epoxy resins and 30-80 mass parts of acrylic monomers are contained in the composition for polarizing plates of this invention (however, a total is 100 mass parts). When the amount of epoxy resin is larger than the above range, the initial curing property of the adhesive is not sufficient, and the adhesive becomes opaque, so that the use of the polarizing plate may be limited. On the other hand, if the amount of the acrylic monomer is larger than the above range, the adhesive property of the polarizing plate may not be sufficient. The epoxy resin is preferably 25 to 70 parts by mass, more preferably 40 to 60 parts by mass, most preferably 50 parts by mass, and the acrylic monomer is preferably 75 to 30 parts by mass, more preferably 60 to 40 parts by mass. , Most preferably 50 parts by weight.

  The adhesive composition for polarizing plates of the present invention may further contain a rotaxane polymer. The rotaxane polymer is also referred to as a slide ring material, and has a structure in which a linear polymer in which a molecule serving as a stopper is bonded to a terminal passes through a ring of a plurality of cyclic molecules. In the present invention, among the rotaxane polymers having such a structure, those in which a substituent having a vinyl group as a functional group is bonded to the cyclic molecular portion can be used. Rotaxane polymer with such a vinyl group modification forms a supramolecular network because the cyclic molecular part moves freely during radical polymerization with acrylic monomers, contributing to improved adhesion of polarizing plate adhesives. Therefore, it is preferable.

  As the rotaxane polymer that can be used in the present invention, cyclodextrin, crown ether, cyclophane, calixarene, cucurbituril, cyclic amide, etc. are used as a cyclic molecule, and polyethylene glycol, alkyl chain, amide, ammonium are used as axial molecules. And those using adamantaneamine or the like as the stopper molecule. Among these, a rotaxane polymer using cyclodextrin as a cyclic molecule, polyethylene glycol as an axial molecule, and adamantaneamine as a stopper molecule is more preferable because it easily forms a network with an acrylic monomer.

  As the rotaxane polymer, a commercially available product can be preferably used. As a commercially available product that can be used in the present invention, a cyclodextrin as a cyclic molecule, polyethylene glycol as an axial molecule, and adamantaneamine as a stopper molecule are used. Trademarks) Elastomers S1000 and M1000, and Celum (registered trademark) Superpolymer A1000 (manufactured by Advanced Soft Materials Co., Ltd.).

  When a rotaxane polymer is used, the acrylic monomer / rotaxane polymer mass ratio is preferably 99/1 to 70/30, more preferably 95/5 to 75/25. If it is said range, it is enough in order to acquire the effect of the further adhesive improvement. Moreover, if the mixing ratio of the rotaxane polymer is not more than the above upper limit value, the flexibility of the adhesive is not increased too much, and the shrinkage of the polarizer during heat resistance can be suppressed, and problems such as cracking of the polarizer are more reliably ensured. Can be prevented.

(C) Photoacid generator As the photoacid generator, a conventionally known photoacid generator can be used without particular limitation. Specific examples include aromatic diazonium salts, onium salts such as aromatic iodonium salts and aromatic sulfonium salts, and iron-allene complexes. These may be used alone or in combination of two or more.

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

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

  Examples of the aromatic sulfonium salt include triphenylsulfonium hexafluorophosphate, triphenylsulfonium hexafluoroantimonate, triphenylsulfonium tetrakis (pentafluorophenyl) borate, diphenyl [4- (phenylthio) phenyl] sulfonium hexafluoroantimonate, 4,4′-bis [diphenylsulfonio] diphenyl sulfide bishexafluorophosphate, 4,4′-bis [di (β-hydroxyethoxy) phenylsulfonio] diphenyl sulfide bishexafluoroantimonate, 4,4′-bis [Di (β-hydroxyethoxy) phenylsulfonio] diphenylsulfide bishexafluorophosphate, 7- [di (p-toluyl) sulfonio 2-Isopropylthioxanthone hexafluoroantimonate, 7- [di (p-toluyl) sulfonio] -2-isopropylthioxanthone tetrakis (pentafluorophenyl) borate, 4-phenylcarbonyl-4'-diphenylsulfonio-diphenyl sulfide hexafluoro Phosphate, 4- (p-tert-butylphenylcarbonyl) -4′-diphenylsulfonio-diphenylsulfide hexafluoroantimonate, 4- (p-tert-butylphenylcarbonyl) -4′-di (p-toluyl) sulfonio -Diphenyl sulfide Tetrakis (pentafluorophenyl) borate, diphenyl [4- (phenylthio) phenyl] sulfonium phosphate, and the like.

  Examples of iron-allene complexes include xylene-cyclopentadienyl iron (II) hexafluoroantimonate, cumene-cyclopentadienyl iron (II) hexafluorophosphate, xylene-cyclopentadienyl iron (II) -tris. And (trifluoromethylsulfonyl) methanide.

  Commercially available photoacid generators may be used, for example, CPI-100P, 101A, 200K, 210S (manufactured by Sun Apro Co., Ltd.), Kayarad (registered trademark) PCI-220, PCI-620 (manufactured by Nippon Kayaku Co., Ltd.). ), UVI-6990 (manufactured by Union Carbide), Adeka optomer SP-150, SP-170 (manufactured by ADEKA), CI-5102, CIT-1370, 1682, CIP-1866S, 2048S, 2064S, Co., Ltd.), DPI-101, 102, 103, 105, MPI-103, 105, BBI-101, 102, 103, 105, TPS-101, 102, 103, 105, MDS-103, 105, DTS-102 103 (Midori Chemical Co., Ltd.), PI-2074 (Rhodia Japan Co., Ltd.) Company, Ltd.) and the like.

  As for the usage-amount of a photo-acid generator, 1-7 mass parts is preferable with respect to a total of 100 mass parts of (A) epoxy resin and (B) acrylic monomer, More preferably, it is 1-4 mass parts. If the amount of the photoacid generator used is less than 1 part by mass, the curability of the stored-goods composition after ultraviolet irradiation is poor, and if it exceeds 7 parts by mass, the durability may be insufficient.

  In addition, the adhesive composition of the present invention is used in combination with a photosensitizer such as a thioxanthone compound, a naphthalene compound, and an anthracene compound in addition to the photopolymerization initiator in order to improve the reactivity of the polymerization reaction. May be.

(D) Photopolymerization initiator The adhesive composition of the present invention further contains a photopolymerization initiator. There is no restriction | limiting in particular as a photoinitiator, A conventionally well-known photoinitiator can be used preferably. A photoinitiator may be used individually or may be used in combination of 2 or more type.

  Specifically, photopolymerization initiators include hydrogen peroxide, inorganic peroxides such as potassium persulfate and ammonium persulfate, t-butyl hydroperoxide, t-dibutyl peroxide, cumene hydroperoxide, acetyl peroxide. Organic peroxides such as benzoyl peroxide and lauroyl peroxide, azobisisobutyronitrile, azobis-2,4-dimethylvaleronitrile, azobiscyclohexanecarbonitrile, methyl azobisisobutyrate, azobisisobutylamidine hydrochloride and azobiscyano Azo compounds such as valeric acid, acetophenones, benzoins, benzophenones, phosphine oxides, ketals, anthraquinones, thioxanthones, 2,3-dialkyldione compounds, disulfide compounds, fluoroamine compounds, aromatic sulfoni Arm, lophine dimers, onium salts, borate salts, active esters, active halogens, inorganic complexes and coumarins.

  More specifically, acetophenone, 3-methylacetophenone, benzyldimethyl ketal, 1- (4-isopropylphenyl) -2-hydroxy-2-methylpropan-1-one, 2-methyl-1- [4- (methylthio ) Phenyl] -2-morpholinopropan-1-one, acetophenones such as 2-hydroxy-2-methyl-1-phenylpropan-1-one; benzophenone, 4-chlorobenzophenone, 4,4′-diaminobenzophenone And benzoin ethers such as benzoin propyl ether and benzoin ethyl ether; thioxanthones such as 4-isopropylthioxanthone; xanthone, fluorenone, camphorquinone, benzaldehyde, anthraquinone, and the like.

  Commercially available photopolymerization initiators may be used, such as IRGACURE (registered trademark) -184, 819, 907, 651, 1700, 1800, 819, 369, 261, DAROCUR-TPO (manufactured by BASF Japan Ltd.), Darocur (Registered trademark) -1173 (manufactured by Merck), Ezacure-KIP150, TZT (manufactured by DKSH Japan), Kayacure (registered trademark) BMS, DMBI (manufactured by Nippon Kayaku Co., Ltd.) and the like.

  For inorganic peroxides and organic peroxides, amines such as ethylamine, triethanolamine and dimethylaniline, polyamines, divalent iron salt compounds, organometallic compounds such as ammonia, triethylaluminum, triethylboron and diethylzinc An appropriate reducing agent such as sodium sulfite, sodium hydrogen sulfite, cobalt naphthenate, sulfinic acid or mercaptan may be used in combination.

  The usage-amount of a photoinitiator is 0.1-7 mass parts with respect to a total of 100 mass parts of (A) epoxy resin and (B) acrylic monomer, Preferably it is 0.5-2.5 mass parts. It is. When the amount of the photopolymerization initiator used is less than 0.1 parts by mass, it is difficult to cure even by ultraviolet irradiation, and when it exceeds 7 parts by mass, the durability may be insufficient.

  In addition, in order to improve the reactivity of the polymerization reaction, the adhesive composition of the present invention includes, for example, carbonyl compounds, organic sulfur compounds, persulfides, redox compounds, azo and diazo compounds in addition to the photopolymerization initiator. Further, a photosensitizer such as a halogen compound and a photoreductive dye may be used in combination.

(E) Method for Producing Adhesive Composition There are no particular limitations on the production of the adhesive composition of the present invention, and usually the specific epoxy resin, acrylic monomer, photoacid generator, and photopolymerization described above. An initiator composition is mixed to obtain an adhesive composition. An organic solvent may be appropriately used for adjusting the viscosity. The mixing method is not particularly limited, and may be sufficiently stirred and mixed at room temperature (25 ° C.) until the inside of the liquid becomes uniform.

  Moreover, the adhesive composition for polarizing plates of the present invention includes an ultraviolet absorber, an antioxidant, a heat stabilizer, a silane coupling agent, an inorganic filler, a softener, an antioxidant, and an anti-aging agent as necessary. Agent, stabilizer, tackifying resin, modifying resin (polyol resin, phenol resin, acrylic resin, polyester resin, polyolefin resin, epoxy resin, epoxidized polybutadiene resin, etc.), leveling agent, antifoaming agent, plasticizer, dye, Pigments (colored pigments, extender pigments, etc.), treatment agents, ultraviolet blocking agents, fluorescent brighteners, dispersants, light stabilizers, antistatic agents, lubricants, and the like may be added.

(2) Polarizing plate According to the 2nd aspect of this invention, the polarizing plate provided with the protective film and polarizer which were adhere | attached using the adhesive composition of this invention is provided. The polarizing plate of this invention is excellent in the process property at the time of manufacture, and shows sufficient adhesiveness. Hereinafter, the configuration of the polarizing plate of the present invention will be described.

(A) Polarizer There is no restriction | limiting in particular as a polarizer, A conventionally well-known thing can be used. For example, dichroic materials such as iodine and dichroic dyes are adsorbed on hydrophilic polymer films such as polyvinyl alcohol films, partially formalized polyvinyl alcohol films, and ethylene / vinyl acetate copolymer partially saponified films. And polyene-based oriented films such as a uniaxially stretched product, a polyvinyl alcohol dehydrated product and a polyvinyl chloride dehydrochlorinated product.

  Among these, a polarizer produced by dyeing a polyvinyl alcohol film having an average polymerization degree of 2000 to 2800 and a saponification degree of 90 to 100 mol% with iodine and uniaxially stretching it 5 to 6 times is particularly preferable. More specifically, such a polarizer is obtained by, for example, immersing and stretching a polyvinyl alcohol film by immersing it in an aqueous solution of iodine. As an aqueous solution of iodine, for example, it is preferable to immerse in an aqueous solution of 0.1 to 1.0% by mass of iodine / potassium iodide. If necessary, it may be immersed in an aqueous solution such as boric acid or potassium iodide at 50 to 70 ° C., or may be immersed in water at 25 to 35 ° C. in order to prevent washing or uneven dyeing. Stretching may be performed after dyeing with iodine, may be stretched while dyeing, or may be dyed with iodine after stretching. After dyeing and stretching, it may be washed with water and dried at 35 to 55 ° C. for about 1 to 10 minutes.

(B) Protective film As the protective film, a material excellent in transparency, mechanical strength, thermal stability, moisture barrier property, isotropy and the like is preferable. For example, cellulose resins such as cellulose diacetate and cellulose triacetate, polyester resins such as polyethylene terephthalate and polyethylene naphthalate, acrylic resins such as polymethyl methacrylate, styrene such as polystyrene and acrylonitrile / styrene copolymer (AS resin) Resin, polycarbonate resin, polyethylene, polypropylene, polyolefin having cyclo or norbornene structure, polyolefin resin such as ethylene / propylene copolymer, vinyl chloride resin, amide resin such as nylon and aromatic polyamide, imide resin Resin, sulfone resin, polyether sulfone resin, polyether ether ketone resin, polyphenylene sulfide resin, vinyl alcohol resin, vinylidene chloride Resins, vinyl butyral resins, arylate resins, polyoxymethylene resins, such as blends of epoxy resin or the resin, and the like.

  Among the above, for the polarizing plate protective film, a cellulose-based resin that is an ester of cellulose and a fatty acid, a cycloolefin polymer (COP film), or polyethylene terephthalate (PET film) is preferable. Examples of the cellulose resin include cellulose triacetate (TAC film), cellulose diacetate, cellulose tripropionate, and cellulose dipropionate. Among these, cellulose triacetate, polyethylene terephthalate and cycloolefin polymer are particularly preferable from the viewpoint of availability and cost. Cellulose triacetate may be saponified, but is preferably unsaponified. Examples of the cycloolefin polymer include polymers having as a constituent a polymer obtained by hydrogenating a ring-opening polymer of tetracyclododecene described in JP-B-2-9619.

  Examples of commercially available TAC films include UV-50, UV-80, SH-80, TD-80U, TD-TAC, UZ-TAC, and Kika series manufactured by Konica Minolta Opto, Inc. . Examples of commercially available COP films include Arton (registered trademark) manufactured by JSR Corporation, ZEONEX (registered trademark) series, and ZEONOR (registered trademark) series manufactured by ZEON Corporation. Examples of commercially available PET films include Cosmo Shine (registered trademark) series manufactured by Toyobo Co., Ltd.

  The surface of the protective film is preferably modified by corona discharge treatment. There is no restriction | limiting in particular as a method of a corona discharge treatment, It can process using a common corona discharge treatment apparatus (for example, Kasuga Electric Co., Ltd. product). By performing the corona discharge treatment, an active group such as a hydroxyl group is formed on the surface of the protective film, which is considered to contribute to an improvement in adhesion. When saponified cellulose triacetate is used as the protective film, the effect of improving adhesion similar to that of the corona discharge treatment can be expected, and therefore the corona discharge treatment is not necessarily required. However, since the saponification process is complicated and expensive, it is preferable in the production process to use unsaponified cellulose triacetate after corona discharge treatment.

Although there is no restriction | limiting in particular as a discharge amount in the case of a corona treatment, 30-300 W * min / m < ² > is preferable, More preferably, it is 50-250 W * min / m < ² >. Within such a range, the adhesion between the protective film and the adhesive can be improved without deteriorating the protective film itself, which is preferable. Here, the discharge amount is a work amount to an object by corona discharge obtained by the following calculation, and corona discharge power is determined based on this.
(Discharge amount) = (discharge power) ÷ {(target object processing speed) × (electrode length)}
(C) Manufacturing method of polarizing plate There is no restriction | limiting in particular as a manufacturing method of a polarizing plate, It manufactures by bonding together a protective film and a polarizer using the adhesive composition of this invention by a conventionally well-known method. obtain. The applied adhesive composition expresses adhesiveness by ultraviolet irradiation and constitutes an adhesive layer.

  When apply | coating an adhesive composition, you may apply | coat to any of a protective film and a polarizer, and may apply | coat to both. The adhesive composition is preferably applied so that the thickness of the adhesive layer after drying is 10 nm to 5 μm. The thickness of the adhesive layer is more preferably 500 nm to 3 μm from the viewpoint of obtaining a uniform in-plane thickness and sufficient adhesive strength. The thickness of the adhesive layer can be adjusted by the solid content concentration in the solution of the adhesive composition or the application device for the adhesive composition. The thickness of the adhesive layer can be confirmed by observing the cross section with a scanning electron microscope (SEM). There is no restriction | limiting in particular also in the method of apply | coating an adhesive composition, Various means, such as the method of dripping an adhesive composition directly, the roll coat method, the spraying method, the immersion method, are employable.

  After apply | coating an adhesive composition, a polarizer and a protective film are bonded together by a roll laminator etc.

After bonding, the polarizing plate is irradiated with ultraviolet rays for curing the adhesive composition. Although the ultraviolet light source is not particularly limited, a low-pressure mercury lamp, medium-pressure mercury lamp, high-pressure mercury lamp, ultrahigh-pressure mercury lamp, chemical lamp, black light lamp, microwave-excited mercury lamp, metal halide lamp, or the like having a light emission distribution at a wavelength of 400 nm or less should be used. Can do. Although the ultraviolet irradiation intensity | strength is not specifically limited, It is preferable that the ultraviolet irradiation amount of the wavelength range effective for activation of a polymerization initiator is 100-2000 mJ / cm < ² >. Within this range, the reaction time is appropriate, and there is no possibility of causing deterioration of the adhesive itself or the polarizing film due to heat radiated from the lamp and heat generated during polymerization.

  After the ultraviolet irradiation, since a dark reaction proceeds for the epoxy resin, the polarizing plate is stored at room temperature (23 ° C.) for about 16 to 30 hours immediately after the ultraviolet irradiation. A polarizing plate is completed upon completion of curing.

  Hereinafter, the present invention will be described using examples and comparative examples. However, the technical scope of the present invention is not limited only to the following examples.

<Example 1>
<Preparation of adhesive composition>
As an epoxy resin, 65 parts by mass of a resorcinol type epoxy resin (Nagase Chemtex Co., Ltd. Denacol (registered trademark) EX-201), as an acrylic monomer, 25 parts by mass of 2-hydroxyethyl acrylate (manufactured by Osaka Organic Chemical Co., Ltd.) 10 parts by mass of phenoxydiethylene glycol acrylate (NK ester AMP-20GY manufactured by Shin-Nakamura Kogyo Co., Ltd.), 3 parts by mass of photoacid generator (CPI210S manufactured by San Apro Co., Ltd.), photopolymerization initiator (Irgacure (registered trademark) manufactured by BASF Japan Ltd.) 907) 1 part by mass was stirred and mixed in a temperature-controlled room at 23 ° C. and 50% RH until it became uniform visually to obtain an adhesive composition. The materials used and their blending ratios are as shown in Table 1 below.

<Manufacture of polarizing plate>
The polarizer was produced by the following method. A polyvinyl alcohol film having a mean polymerization degree of 2400 and a saponification degree of 99.9% and a thickness of 75 μm is immersed in warm water at 28 ° C. for 90 seconds to swell, then iodine / potassium iodide (weight ratio 2/3) concentration 0 A polyvinyl alcohol film was dyed while being immersed in a 6% by weight aqueous solution and stretched 2.1 times. Then, it extended | stretched so that a total draw ratio might be set to 5.8 times in 60 degreeC boric-acid-ester aqueous solution, and it washed with water and dried for 3 minutes at 45 degreeC, and produced the polarizer (25 micrometers in thickness).

FIG. 1 is a schematic view showing a method for producing a polarizing plate in this example. As shown in FIG. 1, the polarizer 1 is sandwiched between the protective film 3 and the protective film 4, and the adhesive composition 2 obtained as described above is used as the protective film 3, the polarizer 1, the protective film 4, and A suitable amount of each was dropped between the polarizers 1 with a dropper, and bonded by a roll press equipped with rolls 6 and 7. In this example, a COP film (Nippon Zeon Corporation, thickness 30 μm) was used as the protective film 3, and a cellulose triacetate film (TAC film, Fuji Film Corporation, thickness 80 μm) was used as the protective film 4. The thus-bonded polarizing plate 5 before ultraviolet irradiation was irradiated with ultraviolet rays having an irradiation amount of 1000 mJ / cm ² (365 nm metal halide lamp) from the protective film 3 side. In addition, from the process of bonding the polarizer and the protective film using the adhesive composition to the ultraviolet irradiation, the temperature was 23 ° C. and the humidity was 50% RH.

  After the ultraviolet irradiation, the polarizing plate was stored in a thermostatic chamber (23 ° C., humidity 50% RH) for 24 hours to cure the adhesive composition and complete the polarizing plate. The thickness of the adhesive layer in the completed polarizing plate was 2.0 μm.

  The polarizing plate was evaluated as follows by performing an initial curability test immediately after irradiation with ultraviolet rays, further storing it at room temperature for 24 hours after irradiation with ultraviolet rays, and performing a cutting test and a hot water immersion test. The evaluation results are shown in Table 1 below.

<Examples 2 to 12 >
In Examples 2 to 12 , adhesive compositions were prepared in the same manner as in Example 1 except that the materials and blending amounts shown in Tables 1 to 3 below were used. Furthermore, using each obtained adhesive composition, except having used the protective film shown in Tables 1-3, each was bonded to a polarizer with a protective film, and ultraviolet irradiation was performed similarly to Example 1. The polarizing plate was completed. In addition, Examples 2 to 12 were also evaluated by the same test as in Example 1.

<Comparative Examples 1-4>
In Comparative Examples 1 to 4, adhesive compositions were prepared in the same manner as in Example 1 except that the materials and blending amounts shown in Table 4 below were used. Further, using the obtained adhesive composition, except that the protective film shown in Table 4 was used, in the same manner as in Example 1, the polarizer and the protective film were bonded to each other, and ultraviolet irradiation was performed. A polarizing plate was completed. Further, Comparative Examples 1 to 4 were also evaluated by the same test as in Example 1.

<Initial curability test>
As shown in FIG. 2, the polarizing plates immediately after the ultraviolet irradiation produced in Examples 1 to 12 and Comparative Examples 1 to 4 were folded so that the interval between the folded polarizing plates 8 was 10 mm (R10 mm), and the protective film It was visually determined whether there was any peeling. When peeling was not observed, it was set as (circle), and when observed, it was set as x. The evaluation results are shown in Tables 1 to 4 below.

<Cutting test>
The polarizing plates produced in Examples 1 to 12 and Comparative Examples 1 to 4 were cut into 50 mm × 50 mm with a Thomson blade, and the state of peeling off at the end of the cutting was visually observed. As evaluation criteria, 0.5 mm or less was set as the pass. The evaluation results are shown in Tables 1 to 4.

<Hot water immersion test>
The polarizing plates produced in Examples 1 to 12 and Comparative Examples 1 to 4 were cut into 50 mm × 50 mm with a Thomson blade, immersed in a water bath at 60 ° C., and held for 2 hours. Then, each sample was taken out from the water tank and the magnitude | size of the shrinkage | contraction of a polarizer was measured. As shown in FIG. 3A, from the end of the polarizing plate 8 before the test to the end of the polarizing plate 8 contracted in the stretching direction as shown in FIG. 9 was set. The higher the adhesiveness of the adhesive, the smaller the shrinkage. If the adhesiveness is not sufficient, the shrinkage of the polarizing plate becomes a larger value. As an evaluation standard, the size of shrinkage was set to 2.0 mm or less. The evaluation results are shown in Tables 1 to 4.

As shown in Tables 1 to 4, in Examples 1 to 12 , good results were shown in all of the cutting test, the hot water immersion test, and the initial curing test. In contrast, Comparative Example 3 not containing a specific epoxy resin resulted in inferior initial curability, and in Comparative Example 4 containing no epoxy resin, the results of the hot water immersion test and the cutting test did not satisfy the evaluation criteria. The result was inferior in adhesiveness. In Comparative Example 1 where the acrylic monomer content is low, the initial curability is inferior. In Comparative Example 2 where the specific epoxy resin content is low, the initial curability is good, but the hot water immersion test and the cutting test are performed. It was inferior to the adhesiveness shown in.

  Further, when Example 8 using a bisphenol S type epoxy resin as an epoxy resin having a specific structure is compared with Example 4 using a resorcin type epoxy resin, Example 4 is shown in a cutting test and a hot water immersion test. It turns out that it is excellent by adhesiveness. Furthermore, when Example 10 using a naphthalene type epoxy resin is compared with Example 9 using a resorcinol type epoxy resin, Example 9 is superior to the adhesiveness shown in the cutting test and the hot water immersion test. I understand.

  In addition, Example 2 in which the mass ratio of epoxy resin / acrylic monomer is 50/50 is slightly superior in adhesiveness shown in the cutting test and the hot water immersion test as compared with Example 1 in which 65/35 is used. I understand that. Moreover, it turns out that Example 11 and 12 containing a rotaxane polymer is excellent by the adhesiveness shown by a cutting test and a warm water immersion test compared with Example 4 which does not contain a rotaxane polymer.

  As described above, from the comparison between Examples and Comparative Examples, the adhesive composition of the present invention using an epoxy resin having a specific structure and an acrylic monomer at a specific ratio was excellent when used for a polarizing plate. It was shown that both initial curability and adhesiveness are compatible.

DESCRIPTION OF SYMBOLS 1 Polarizer 2 Adhesive composition solution 3, 4 Protective film 5 Pre-UV irradiation polarizing plate 6, 7 Roll 8 Polarizing plate 9 Shrinkage magnitude

Claims (5)

20 to 70 parts by mass of epoxy resin and 30 to 80 parts by mass of acrylic monomer (the total is 100 parts by mass);
1 to 7 parts by mass of a photoacid generator,
0.1 to 7 parts by mass of a photopolymerization initiator,
The epoxy resin includes at least one selected from the group consisting of a resorcinol type epoxy resin, a bisphenol S type epoxy resin and a naphthalene type epoxy resin,
And further comprising at least one epoxy resin other than at least one selected from the group consisting of the resorcin type epoxy resin, bisphenol S type epoxy resin and naphthalene type epoxy resin, and (a) resorcin type epoxy resin, bisphenol S type epoxy resin and naphthalene The mass ratio (a) / (b) between at least one selected from the group consisting of type epoxy resins and (b) other epoxy resins is 99/1 to 20/80,
The other epoxy resin (b) is a glycidyl etherified product of an aromatic compound or a chain compound having a hydroxyl group, or a fatty acid in which a glycidyloxy group or an epoxyethyl group is bonded to a saturated carbocycle directly or via an alkylene group. An adhesive composition for a polarizing plate, which is a cyclic epoxy compound, and the acrylic monomer is at least one of a hydroxy group-containing acrylic monomer and a phenoxy group-containing acrylic monomer.   The adhesive composition for polarizing plates according to claim 1, wherein the epoxy resin contains a resorcin type epoxy resin.   The adhesive composition for polarizing plates according to claim 1 or 2, wherein the (b) other epoxy resin is bisphenol A type diglycidyl ether or bisphenol F type diglycidyl ether.   The polarizing plate according to any one of claims 1 to 3, wherein the polarizing plate adhesive composition further comprises a rotaxane polymer, and a mass ratio of the rotaxane polymer / the acrylic monomer is from 1/99 to 30/70. Adhesive composition. A polarizing plate provided with the protective film and the polarizer which were adhere | attached using the adhesive composition for polarizing plates as described in any one of Claims 1-4 .