CN109239831B

CN109239831B - Polarizing plate and laminated optical member

Info

Publication number: CN109239831B
Application number: CN201810801588.9A
Authority: CN
Inventors: 久米悅夫; 竹内智康; 高桥利行; 本间英里
Original assignee: Adeka Corp; Sumitomo Chemical Co Ltd
Current assignee: Adeka Corp; Sumitomo Chemical Co Ltd
Priority date: 2011-03-29
Filing date: 2012-03-23
Publication date: 2021-08-17
Anticipated expiration: 2032-03-23
Also published as: TWI582199B; CN109239831A; CN103430060A; JP2012208246A; JP5945098B2; KR101894120B1; KR20140029415A; WO2012133163A1; TW201245381A

Abstract

The present invention relates to a polarizing plate and a laminated optical member. The present invention relates to a polarizing plate comprising a polyvinyl alcohol-based polarizer and a protective film bonded to the polarizer via an adhesive, wherein the adhesive is formed from a photocurable adhesive composition containing 100 parts by weight of a photocationic curable component (a) and 1 to 10 parts by weight of a photocationic polymerization initiator (B), and a cured product thereof exhibits a storage modulus of 1000MPa or more at 80 ℃, and the photocationic curable component (a) is prepared by containing the following (a1) and (a2) in the following amounts, based on the total amount thereof: 50 to 95% by weight of an alicyclic epoxy compound (A1) having an epoxy group bonded to an alicyclic ring; 5 to 50 wt% of a diglycidyl compound (A2) having a chlorine content of 1 wt% or less and represented by the following formula (I) (Z is an alkylene group or the like).

Description

Polarizing plate and laminated optical member

Technical Field

The present application is a divisional application of a PCT application having application No. 201280015748.8 (international application date of 2012, 3-23), entitled "polarizing plate and laminated optical member", which is at the stage of entering the country.

The present invention relates to a polarizing plate obtained by bonding a protective film to one or both surfaces of a polarizer using a specific photocurable adhesive. The present invention also relates to a laminated optical member in which another optical layer such as a retardation film is laminated on the polarizing plate.

Background

The polarizing plate may be used as one of optical members constituting a liquid crystal display device. In general, a polarizing plate is used by being incorporated into a liquid crystal display device in a state where protective films are laminated on both surfaces of a polarizer. It is also known to provide a protective film only on one side of the polarizer, but in many cases, a layer having another optical function, which is not a protective film but also a protective film, is bonded to the other side. In addition, a method of manufacturing a polarizer is widely known in which a uniaxially stretched polyvinyl alcohol resin film dyed with a dichroic dye is subjected to boric acid treatment, washed with water, and dried.

A protective film is usually attached to the polarizer immediately after the above-mentioned washing with water and drying. This is because the polarizer after drying has a weak physical strength, and when it is curled, a problem such as cracking in the machine direction occurs. Therefore, the polarizer after drying is usually coated with a water-based adhesive immediately, and then protective films are simultaneously bonded to both sides via the adhesive. In general, a triacetyl cellulose film having a thickness of 30 to 100. mu.m is used as the protective film.

Triacetylcellulose has a high moisture permeability, and a polarizing plate obtained by bonding triacetylcellulose as a protective film has a problem of deterioration or the like caused under wet heat, for example, under conditions of a temperature of 70 ℃ and a relative humidity of 90%. Therefore, it is also known that an amorphous polyolefin resin, for example, a norbornene resin, which has a lower moisture permeability than triacetyl cellulose, is used as the protective film.

When a protective film made of a resin having low moisture permeability is bonded to a polyvinyl alcohol polarizer, if an aqueous solution of a polyvinyl alcohol resin, which has been conventionally used as a binder for bonding a polyvinyl alcohol polarizer to triacetyl cellulose, is used, there is a problem that the adhesive strength is insufficient or the appearance of the obtained polarizing plate is poor. This is because a resin film having low moisture permeability is generally hydrophobic, or because of low moisture permeability, water as a solvent cannot be sufficiently dried, and the like. It is also known to attach different types of protective films to both sides of a polarizer. For example, there are also proposals: a protective film made of a resin having a low moisture permeability, such as an amorphous polyolefin resin, is bonded to one surface of the polarizer, and a protective film made of a resin having a high moisture permeability, such as a cellulose resin typified by triacetyl cellulose, is bonded to the other surface of the polarizer.

Therefore, as an adhesive agent for imparting high adhesive force between a protective film made of a resin having low moisture permeability and a polyvinyl alcohol polarizer and also between a resin having high moisture permeability such as a cellulose resin and a polyvinyl alcohol polarizer, an active energy ray-curable adhesive agent has been tried. For example, jp 2004-24925 a (patent document 1) discloses a binder containing an epoxy compound containing no aromatic ring as a main component, and proposes: the adhesive is cured by cationic polymerization by irradiation with active energy rays, and the polarizer and the protective film are bonded. In addition, jp 2008-257199 a (patent document 2) discloses a technique of using a photocurable adhesive in bonding a polarizer and a protective film, the photocurable adhesive being obtained by combining an alicyclic epoxy compound and an epoxy compound having no alicyclic epoxy group, and further blending the resultant with a photo cation polymerization initiator.

On the other hand, japanese patent laid-open No. 2009-: it is described that, because of wettability between the protective film and the adhesive during the production of the polarizing plate and viscosity of the adhesive, appearance defects occur in the polarizing plate after production, and these parameters have a great influence on productivity.

Unlike solvent-based adhesives, epoxy-based photocurable adhesives disclosed in patent documents 1 and 2 are generally prepared substantially without a solvent. Therefore, in many cases, in order to reduce the viscosity, it is necessary to increase the proportion of the low-viscosity component in the composition. The viscosity of the adhesive liquid before curing is reduced by changing the above composition ratio, which often results in insufficient hardness of the adhesive layer after curing, and the polarizing plate after bonding may be difficult to exhibit sufficient durability. Therefore, conventionally, as a measure for avoiding appearance defects in the polarizing plate production process, film surface modification or addition of a leveling agent has been mainly used to improve wettability.

Patent document 1: japanese patent laid-open publication No. 2004-24925

Patent document 2: japanese patent laid-open No. 2008-257199

Patent document 3: japanese laid-open patent publication No. 2009-181046

Patent document 4: japanese patent laid-open publication No. 2002-365432.

Disclosure of Invention

Problems to be solved by the invention

The present inventors have found that when a polarizer and a protective film are bonded to each other using an epoxy-based photocurable adhesive, if the viscosity of the adhesive before curing is lowered, the cured adhesive layer cannot exhibit sufficient hardness, and have conducted extensive studies to improve this problem, and as a result, have completed the present invention. Accordingly, an object of the present invention is to provide a polarizing plate in which a polarizer and a protective film are bonded to each other using an epoxy-based photocurable adhesive, and which can be applied with improved coating applicability by reducing the viscosity of the photocurable adhesive used for the polarizing plate, and can obtain sufficient hardness after curing of the adhesive, thereby improving the adhesion between the polarizer and the protective film. Another object of the present invention is to provide: the polarizer is laminated with other optical layers such as a retardation film, and is suitable for use in a laminated optical member of a liquid crystal display device.

Means for solving the problems

The research result shows that: in a photocurable adhesive containing a combination of an alicyclic epoxy compound and at least 2 kinds of photocationic-curable epoxy compounds of a diglycidyl compound and substantially no solvent, when the amount of chlorine in the diglycidyl compound is reduced, the hardness of the adhesive layer after curing can be kept high, and the viscosity can be reduced by adjusting the composition ratio. The present invention includes the following.

[1] A polarizing plate comprising a polarizer made of a polyvinyl alcohol resin film on which a dichroic dye is adsorbed and oriented, and a protective film laminated on at least one surface of the polarizer via an adhesive and made of a transparent resin, the adhesive being formed of a photocurable adhesive composition containing 100 parts by weight of a photocationic curable component (a) and 1 to 10 parts by weight of a photocationic polymerization initiator (B), a cured product of which exhibits a storage modulus of 1000MPa or more at 80 ℃, the photocationic curable component (a) being prepared by containing the following amounts of (a1) and (a2) based on the total amount thereof:

50 to 95% by weight of an alicyclic epoxy compound (A1) having 2 or more epoxy groups in the molecule, at least 1 of which is bonded to an alicyclic ring, and

5 to 50% by weight of a diglycidyl compound (A2) having a chlorine content of 1% by weight or less and represented by the following formula (I):

wherein Z represents an alkylene group having 1 to 9 carbon atoms, an alkylidene group having 3 or 4 carbon atoms, a 2-valent alicyclic hydrocarbon group, or a group represented by the formula-C_mH_2m-Z¹-C_nH_2nA 2-valent radical of formula (I), where-Z¹-represents-SO₂-, -S-O-or-CO-, and m and n are each independently an integer of 1 or more and a total of 9 or less.

[2] [1] the polarizing plate, wherein the protective film attached to at least one surface of the polarizer is made of an acetyl cellulose resin.

[3] [1] the polarizing plate, wherein the protective film attached to at least one surface of the polarizer is made of a transparent resin selected from the group consisting of an amorphous polyolefin resin, a polyester resin, a polycarbonate resin, and a chain polyolefin resin.

[4] [1] A polarizing plate wherein a protective film made of an acetyl cellulose resin is bonded to one surface of a polarizer via the adhesive, and a protective film of a film made of a transparent resin selected from the group consisting of an amorphous polyolefin resin, a polyester resin, a polycarbonate resin, and a chain polyolefin resin is bonded to the other surface of the polarizer via the adhesive.

[5] A laminated optical member comprising a laminate of the polarizing plate of any one of [1] to [4] and another optical layer.

[6] [5] A laminated optical member, wherein the optical layer includes a retardation film.

Effects of the invention

The polarizing plate of the present invention has a low viscosity before curing and improved coating applicability of the photocurable adhesive used for its production, and also has a high storage modulus after curing and a good adhesion between the polarizer and the protective film. The polarizing plate has a small possibility of cracking of the polarizer even when subjected to, for example, a cold-heat impact test (thermal impact test) repeatedly under a high-temperature environment and under a low-temperature environment, and is excellent in reliability. In addition, in a laminated optical member obtained by laminating another optical layer such as a retardation film on the polarizer, similarly, the polarizer is less likely to be broken even under severe conditions, and a liquid crystal display device using the polarizing plate is excellent in reliability.

Detailed Description

The embodiments of the present invention are explained in detail below. In the present invention, a protective film made of a transparent resin is laminated on at least one surface of a polarizer made of a polyvinyl alcohol resin film in which a dichroic dye is adsorbed and oriented via a photocurable adhesive, thereby producing a polarizing plate. The photocurable adhesive is formed from a photocurable adhesive composition which contains 100 parts by weight of a photocationic curable component (A) and 1-10 parts by weight of a photocationic polymerization initiator (B), and a cured product of the composition exhibits a storage modulus of 1000MPa or more at 80 ℃. Further, another optical layer is laminated on the polarizing plate, and a laminated optical member suitable for a liquid crystal display device can be obtained. Therefore, a photocurable adhesive composition used for the production of a polarizing plate, a polarizing plate using the composition, and a laminated optical member using the polarizing plate will be described in order.

[ Photocurable adhesive composition ]

As described above, the photocurable adhesive composition used in the present invention contains 100 parts by weight of the photocationic curable component (a) and 1 to 10 parts by weight of the photocationic polymerization initiator (B), and the photocationic curable component (a) contains the following amounts of (a1) and (a2) based on the total amount thereof:

50 to 95% by weight of an alicyclic epoxy compound (A1) having 2 or more epoxy groups in the molecule, at least 1 of which is bonded to an alicyclic ring: and

5 to 50% by weight of a diglycidyl ether compound (A2) having a chlorine content of 1% or less and represented by the above formula (I).

(Photocationic curable component)

The alicyclic epoxy compound (a1) as the main component of the photocationic curable component (a) may be a generally known epoxy compound, and preferably does not contain an aromatic ring in its molecular structure from the viewpoints of weather resistance, refractive index, and photocurability. Examples of the alicyclic epoxy compound (a1) include compounds represented by the following general formulae (1) to (23).

In each of the above formulae, R¹-R⁴⁶Each independently represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms。R¹-R⁴⁶In the case of an alkyl group, the position bonded to the alicyclic structure is any of the 1-6 positions. The alkyl group having 1 to 6 carbon atoms may be linear or branched, and may have an alicyclic structure. Y is¹Represents an oxygen atom or an alkanediyl group, Y²-Y²¹Each independently represents an alkanediyl group which may be linear or branched and may have an alicyclic structure. Number of carbon atoms as alkanediyl, Y²、Ｙ⁴、Ｙ⁹、Ｙ¹⁰、Ｙ¹¹、Ｙ¹²、Ｙ¹³、Ｙ¹⁴、Ｙ¹⁵、Ｙ¹⁶、Ｙ¹⁹、Ｙ²⁰、Ｙ²¹Is 1-20, Y¹、Ｙ³、Ｙ⁵、Ｙ⁶、Ｙ⁷、Ｙ⁸、Ｙ¹⁷、Ｙ¹⁸Is 2-20. Z¹-Z²Each independently represents an alkanetriyl group which may be linear or branched and may have an alicyclic structure. Number of carbon atoms as alkanetriyl group, Z¹Is 2-20, Z²Is 1-20. T is¹The term "alkyl" refers to an alkyl tetrayl group having 1 to 20 carbon atoms which may be straight-chain, branched-chain or alicyclic. a to r represent an integer of 0 to 20.

The alicyclic epoxy compounds (a1) may be used alone in 1 kind or in a mixture of 2 or more kinds.

The other diglycidyl compound (a2) of the photocationic-curable component (a) is represented by the above formula (I). In the formula (I), Z is an alkylene group having 1 to 9 carbon atoms, an alkylidene group having 3 or 4 carbon atoms, a 2-valent alicyclic hydrocarbon group, or a group represented by the formula-C_mH_2m-Z¹-C_nH_2nA 2-valent radical of formula (I), where-Z¹is-SO₂-, -SO-or-CO-, and m and n are each independently an integer of 1 or more, and the total of both is 9 or less. Typical examples of the alicyclic hydrocarbon group having a valence of 2 are cyclopentylene and cyclohexylene.

In the formula (I), the compound wherein Z is an alkylene group is a diglycidyl ether of an alkylene glycol. Specific examples thereof are ethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, 1, 3-propane diol diglycidyl ether, 1, 4-butane diol diglycidyl ether, 1, 6-hexane diol diglycidyl ether, neopentyl glycol diglycidyl ether, 3-methyl-1, 5-pentane diol diglycidyl ether, 2-methyl-1, 8-octane diol diglycidyl ether, 1, 4-cyclohexanedimethanol, and the like.

In the formula (I), Z is a group of the formula-C_mH_2m-Z¹-C_nH_2n-compounds of the 2-valent radical indicated correspond to: z is an alkylene group having 2 or more carbon atoms, the C-C bond of the alkylene group being-SO₂-, -SO-or-CO-is cleaved.

The diglycidyl compound represented by formula (I) is generally distributed in a state containing a large amount of chlorine for the reason of the production process. That is, in the production of this compound, if a two-step method is employed, that is, a method of producing a chlorohydrin ether by reacting epichlorohydrin with a diol represented by an alkylene glycol and corresponding to the formula HO-Z-OH in the presence of an acidic catalyst such as sulfuric acid, boron trifluoride, and tin tetrachloride, and then ring-closing the chlorohydrin ether intramolecularly with a base, it is inevitable to form an addition product of epichlorohydrin in the addition reaction of epichlorohydrin in the 1 st step, and since the organic chlorine contained in the 2 mol addition product is not decomposed in the intramolecular ring-closing reaction in the 2 nd step, and in addition, the glycidyl ether is usually not distilled and purified, the obtained glycidyl ether contains an organic chlorine compound in an amount of about 1 to 3% by weight as a chlorine component.

The chlorine content of the diglycidyl compound (a2) used in the present invention must be 1% or less, and the chlorine content thereof can be reduced, for example, by the following method: (1) a method of reacting 2-membered alcohol and epichlorohydrin while azeotropically removing water in the reaction system with an azeotropic solvent (for example, a hydrocarbon such as n-hexane, cyclohexane, n-heptane, benzene or toluene, an ether such as diethyl ether or isopropyl ether, a halogenated hydrocarbon such as 1, 2-dichloroethane, 1, 2-dichloropropane, trichloroethylene or chloroform, a solvent having an azeotropic temperature of 30 to 90 ℃ such as a sulfoxide compound, etc.) in the presence of an alkali metal hydroxide; (2) a method of adjusting the equivalent of the alkali metal hydroxide to 0.5 to 1.5, reacting it in the presence of epichlorohydrin, treating it by water washing and/or an alkali adsorbent, followed by distilling off the epichlorohydrin; (3) a method of condensing a hydroxyl compound with epichlorohydrin in the presence of an alkali and reacting the resultant product while irradiating the product with ultrasonic waves.

(photo cation polymerization initiator)

The photo-cationic polymerization initiator (B) incorporated in the photocurable adhesive composition is a compound that can release a substance that initiates cationic polymerization by light irradiation, and particularly preferably is a double salt or a derivative thereof that is an onium salt that releases a lewis acid by light irradiation. Representative examples of such compounds are: general formula [ A]^y+[B]^y-Salts of the cations and anions shown.

Here, the cation A^y+Preferably an onium having a structure represented by, for example, [ (R)⁴¹)_xQ]^y+And (4) showing.

And, R⁴⁵Is an organic group having 1 to 60 carbon atoms and may contain atoms other than carbon atoms, and x is an integer of 1 to 5. x number of R⁴⁵Independently of each other, and may be the same or different. It is also preferred that at least one is aromatic. Q is an atom or group of atoms selected from S, N, Se, Te, P, As, Sb, Bi, O, I, Br, Cl, F, N = N. In addition, cation A^y+When the valence of Q in (2) is z, a relationship of y = x-z must be established.

Anion B^y-Preferably a halide complex, which may have a structure of, for example, [ LX_s]^y-And (4) showing.

Here, L is a metal or semimetal (metalloid) of the central atom of the halide complex, and is B, P, As, Sb, Fe, Sn, Bi, Al, Ca, In, Ti, Zn, Sc, V, Cr, Mn, Co, or the like. X is halogen. s is an integer of 3 to 7. In addition, an anion B^y-When the valence of L in (b) is t, a relationship of y = s-t must be established.

Anion of the above formula [ LXs]^y-Specific examples of (d) include: tetrafluoroborate (BF)₄)^-Hexafluorophosphate (PF)₆)^-Hexafluoroantimonate (SbF)₆)^-Hexafluoroarsenate (AsF)₆)^-Antimony hexachloride (SbCl)₆)^-And the like.

In addition, an anion B^y-Can be preferably used [ LXs ]^-1(OH)]^y-The structure shown. L, X, s are the same as described above. Other anions which may be used are also mentioned: perchloric acid ion (ClO)₄)^-Trifluoromethyl sulfite ion (CF)₃SO₃)^-Fluorosulfonic acid ion (FSO)₃)^-Toluene sulfonic acid anion, trinitrobenzene sulfonic acid anion, and the like.

Anion B^y-Tetrakis (pentafluorophenyl) borate may also be preferably used.

In the present invention, among the onium salts, aromatic onium salts are particularly effective. Among them, preferred are aromatic halonium salts described in Japanese patent application laid-open Nos. 50-151997 and 50-158680, group VIA aromatic onium salts described in Japanese patent application laid-open Nos. 50-151997, 52-30899, 56-55420 and 55-125105, group VA aromatic onium salts described in Japanese patent application laid-open No. 50-158698, group oxaoxysulfide (oxo-sulfoxonium) salts described in Japanese patent application laid-open Nos. 56-8428, 56-149402 and 57-192429, aromatic diazonium salts described in Japanese patent application laid-open No. 49-17040, and thiopyrylium salts described in the specification of U.S. Pat. No. 4139655.

Particularly preferred among these aromatic onium salts are as follows.

A compound of a sulfonium oxide cation having the following structure

In the formula, R⁴⁶-R⁵⁹Each of which may be the same or different, a hydrogen atom, a halogen atom, a hydrocarbon group which may contain an oxygen atom or a halogen atom, or an alkoxy group which may have a substituent, and Ar is a phenyl group in which 1 or more hydrogen atoms may be substituted.

A compound having an onium cation as described below:

(tolylcumyl) iodonium, bis (tert-butylphenyl) iodonium, triphenylsulfonium, and the like.

Specific compound names are given, for example, 4- (4-benzoyl-phenylsulfanyl) phenyl-bis- (4-fluorophenyl) sulfonium hexafluorophosphate, 4 '-bis [ bis ((β -hydroxyethoxy) phenyl) sulfonium ] phenylene sulfide-bis-hexafluoroantimonate, 4' -bis (difluorophenylsulfanyl) phenylene sulfide-bis-hexafluorophosphate, 4 '-bis (difluorophenylsulfanyl) phenylene sulfide-bis-hexafluoroantimonate, 4' -bis (phenylsulfanyl) phenylene sulfide-bis-hexafluoroantimonate, 4- (4-benzoylphenylthio) phenyl-bis- (4- (. beta. -hydroxyethoxy) phenyl) sulfonium hexafluorophosphate, 4- (4-benzoylphenylthio) phenyl-bis- (4- (. beta. -hydroxyethoxy) phenyl) sulfonium hexafluoroantimonate, 4- (4-benzoylphenylthio) phenyl-bis- (4-fluorophenyl) sulfonium hexafluoroantimonate, 4- (4-benzoylphenylthio) phenyl-diphenylsulfonium hexafluorophosphate, 4- (4-benzoylphenylthio) phenyl-diphenylsulfonium hexafluoroantimonate, 4- (phenylthio) phenyl-bis- (4- (. beta. -hydroxyethoxy) phenyl) sulfonium hexafluorophosphate 4- (phenylthio) phenyl-bis- (4- (. beta. -hydroxyethoxy) phenyl) sulfonium hexafluoroantimonate, 4- (phenylthio) phenyl-bis- (4-fluorophenyl) sulfonium hexafluoroantimonate, 4- (phenylthio) phenyl-diphenylsulfonium hexafluoroantimonate, 4- (2-chloro-4-benzoylphenylthio) phenyl bis- (4-fluorophenyl) sulfonium hexafluoroantimonate, 4- (2-chloro-4-benzoylphenylthio) phenyl diphenylsulfonium hexafluoroantimonate, sodium hexafluoroantimonate, 4- (2-chloro-4-benzoylphenylthio) phenyldiphenylsulfonium hexafluoroantimonate, 4- (2-chloro-4-benzoylphenylthio) phenylbis (4-hydroxyphenyl) sulfonium hexafluorophosphate, 4- (2-chloro-4-benzoylphenylthio) phenylbis (4-hydroxyphenyl) sulfonium hexafluoroantimonate, triphenylsulfonium hexafluorophosphate, triphenylsulfonium hexafluoroantimonate, (tolylcumyl) iodonium hexafluorophosphate, (tolylcumyl) iodonium hexafluoroantimonate, (tolylcumyl) iodonium tetrakis (pentafluorophenyl) borate, bis (tert-butylphenyl) iodonium hexafluorophosphate, bis (tert-butylphenyl) iodonium hexafluoroantimonate, bis (tert-butylphenyl) iodonium tetrakis (pentafluorophenyl) borate, benzyl-4-hydroxyphenylmethylthioninium hexafluorophosphate, Benzyl-4-hydroxyphenylmethylsulfinylhexafluoroantimonate, benzyldimethylsulfonium hexafluorophosphate, benzyldimethylsulfonium hexafluoroantimonate, p-chlorobenzyl-4-hydroxyphenylmethylsulfinylhexafluorophosphate, p-chlorobenzyl-4-hydroxyphenylmethylsulfinylhexafluoroantimonate, 4-acetoxyphenyldimethylsulfonium hexafluorophosphate, 4-acetoxyphenyldimethylsulfonium hexafluoroantimonate, 4-methoxycarbonyloxyphenyldimethylsulfonium hexafluorophosphate, 4-methoxycarbonyloxyphenyldimethylsulfonium hexafluoroantimonate, 4-ethoxycarbonyloxyphenyldimethylsulfonium hexafluorophosphate, 4-ethoxycarbonyloxyphenyldimethylsulfonium hexafluoroantimonate, α -naphthylmethyldimethylsulfonium hexafluorophosphate, α -naphthylmethyldimethylsulfonium hexafluoroantimonate, p-naphthylmethyldimethylsulfonium, Alpha-naphthylmethylbutylsulfonium hexafluorophosphate, alpha-naphthylmethylbutylsulfonium hexafluoroantimonate, cinnamyl dimethyl sulfonium hexafluorophosphate, cinnamyl dimethyl sulfonium hexafluoroantimonate, cinnamyl butylsulfonium hexafluorophosphate, cinnamyl butylsulfonium hexafluoroantimonate, N- (alpha-phenylbenzyl) cyanopyridinium hexafluorophosphate, N- (alpha-phenylbenzyl) -2-cyanopyridinium hexafluoroantimonate, N-cinnamyl-2-cyanopyridinium hexafluorophosphate, N-cinnamyl-2-cyanopyridinium hexafluoroantimonate, N- (alpha-naphthylmethyl) -2-cyanopyridinium hexafluorophosphate, N- (alpha-naphthylmethyl) -2-cyanopyridinium hexafluoroantimonate, N- (alpha-naphthylmethyl) -2-cyanopyridinium, N-benzyl-2-cyanopyridinium hexafluorophosphate, N-benzyl-2-cyanopyridinium hexafluoroantimonate, and the like.

Other preferred photocationic polymerization initiators include: xylene-cyclopentadienyl iron (II) hexafluoroantimonate, cumene-cyclopentadienyl iron (II) hexafluorophosphate, iron/aromatic hydrocarbon complexes such as xylene-cyclopentadienyl iron (II) -tris (trifluoromethylsulfonyl) imide, and aluminum complex/photolytic silicon compound-based initiators.

The photo cation polymerization initiators (B) described above may be used alone in 1 kind, or 2 or more kinds may be used in combination, and the amount used is 1 to 10% by weight based on 100 parts by weight of the whole photo cation curable component (A). If the amount of the photo cation polymerization initiator (B) is too small, the curing of the adhesive becomes insufficient, and the adhesive strength is lowered. On the other hand, if the amount is too large, the amount of ionic substances in the cured product increases, and as a result, the hygroscopicity of the cured product increases, and the durability of the polarizing plate decreases.

(other Components that can be blended in the Photocurable adhesive composition)

In order to improve coating applicability, an organic solvent may be blended in a small amount in the photocurable adhesive composition. The organic solvent is not particularly limited as long as it can dissolve the photocurable adhesive composition well without degrading the optical performance of the polarizer. For example, organic solvents such as hydrocarbons typified by toluene and esters typified by ethyl acetate can be used.

The photocurable adhesive composition may further contain a polymerizable monomer other than the alicyclic epoxy compound (a1) and the diglycidyl compound (a 2). Examples of the polymerizable monomer include: cationic polymerizable monomers, radical polymerizable monomers, and the like.

Examples of the cationically polymerizable monomer include oxetanes. Oxetanes are compounds having a 4-membered cyclic ether in the molecule, and examples thereof include: 3-ethyl-3-hydroxymethyloxetane, 1, 4-bis [ (3-ethyl-3-oxetanyl) methoxymethyl ] benzene, 3-ethyl-3- (phenoxymethyl) oxetane, bis [ (3-ethyl-3-oxetanyl) methyl ] ether, 3-ethyl-3- (2-ethylhexyloxymethyl) oxetane, novolak oxetane. These oxetane compounds are readily available commercially, and examples of such trade names include: "アロンオキセタン OXT-101", "アロンオキセタン OXT-121", "アロンオキセタン OXT-211", "アロンオキセタン OXT-221", "アロンオキセタン OXT-212" (manufactured by the above east Asia Kabushiki Kaisha), and the like.

The cationically polymerizable monomer has an effect of improving adhesion after curing of the adhesive, and can be used as needed within a range not affecting weather resistance and photocurability.

Examples of the radical polymerizable monomer include: an acrylate compound, a methacrylate compound (hereinafter, also referred to as (meth) acrylate in the sense of including both acrylate and methacrylate), an allyl urethane compound, an unsaturated polyester compound, and a styrene compound. When used in the photocurable adhesive of the present invention, (meth) acrylate is preferred in view of easy availability and easy application. Examples of (meth) acrylates are: urethane (meth) acrylates, (poly) ester (meth) acrylates, (poly) ether (meth) acrylates, (meth) acrylates of alcohols, and other (meth) acrylates.

The urethane (meth) acrylate exemplified as the (meth) acrylate compound is an ester compound having a urethane bond, and may be a (meth) acrylate obtained by reacting a hydroxyl group-containing (meth) acrylate with 1 or 2 or more kinds of (poly) isocyanate compounds, wherein the hydroxyl group-containing (meth) acrylate is an ester compound of a (meth) acrylic acid and 1 or 2 or more kinds of a polyol such as a (poly) ester polyol, a (poly) ether polyol or a polyol; (meth) acrylate obtained by reacting a hydroxyl group-containing (meth) acrylate with an isocyanate, and the like, with 1 or 2 or more kinds of (poly) ester-type polyol, (poly) ether-type polyol, and the like.

Examples of the polyol from which the (poly) ester polyol is derived include: 1, 3-butane diol, 1, 4-butane diol, 1, 6-hexane diol, diethylene glycol, triethylene glycol, neopentyl glycol, polyethylene glycol, polypropylene glycol, polybutylene glycol, trimethylolpropane, glycerol, pentaerythritol, dipentaerythritol, and the like. Examples of polycarboxylic acids from which the (poly) ester polyols can be derived include: adipic acid, terephthalic acid, phthalic anhydride, trimellitic acid, trimesic acid, and the like.

Examples of the (poly) ether polyol include: the polyol is added with alkylene oxide products such as ethylene oxide, propylene oxide, butylene oxide, etc. The (poly) isocyanate compound includes 1-or 2-or more-membered isocyanate, and preferably 2-or more-membered isocyanate.

Examples of the 2-or more-membered isocyanate include: 2, 4-and/or 2, 6-tolylene diisocyanate, diphenylmethane-4, 4 '-diisocyanate, p-phenylene diisocyanate, xylylene diisocyanate, 1, 5-naphthalene diisocyanate, 3' -dimethyldiphenyl-4, 4 '-diisocyanate, dianisidine diisocyanate, tetramethylxylylene diisocyanate, isophorone diisocyanate, dicyclohexylmethane-4, 4' -diisocyanate, trans-and/or cis-1, 4-cyclohexane diisocyanate, norbornene diisocyanate, 1, 6-hexamethylene diisocyanate, 2, 4-and/or (2,4,4) -trimethylhexamethylene diisocyanate, lysine diisocyanate, triphenylmethane triisocyanate, diphenylmethane diisocyanate, tolylene diisocyanate, and tolylene diisocyanate, 1-methylbenzene-2, 4, 6-triisocyanate, dimethyltriphenylmethane tetraisocyanate.

The polyester (meth) acrylate is an ester compound of a (poly) ester having 1 or 2 or more hydroxyl groups in the molecule and (meth) acrylic acid. Examples of the (poly) ester having 1 or 2 or more hydroxyl groups in the molecule include: ester compounds of 1 or 2 or more kinds of polyhydric alcohols with 1 or 2 or more kinds of monocarboxylic acids or polycarboxylic acids.

Examples of the polyol from which the (poly) ester having 1 or 2 or more hydroxyl groups in the molecule can be derived include the same compounds as those described above, and examples of the monocarboxylic acid include: formic acid, acetic acid, propionic acid, butyric acid, isobutyric acid, valeric acid, caproic acid, caprylic acid, 2-ethylhexanoic acid, benzoic acid, and the like. Examples of the polycarboxylic acid include the same compounds as those described above.

The (poly) ether (meth) acrylate is an ester compound of a (poly) ether having 1 or 2 or more hydroxyl groups in the molecule and (meth) acrylic acid. Examples of the (poly) ether having 1 or 2 or more hydroxyl groups in the molecule include: a compound obtained by adding 1 or 2 or more kinds of alkylene oxide to 2-methoxyethanol, 2-ethoxyethanol, 2-butoxyethanol, or a polyhydric alcohol. The polyhydric alcohol and the alkylene oxide include the same compounds as those described above. Specifically, the following may be mentioned: diethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate, polypropylene glycol di (meth) acrylate, ethylene oxide-modified trimethylolpropane tri (meth) acrylate, propylene oxide-modified trimethylolpropane tri (meth) acrylate, dipentaerythritol hexa (meth) acrylate, and the like.

The (meth) acrylate of an alcohol is an ester compound of an alcohol (particularly, an aliphatic alcohol or an aromatic alcohol) having 1 or 2 or more hydroxyl groups in the molecule and a (meth) acrylate. Examples thereof include: 2-ethylhexyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, isoamyl (meth) acrylate, lauryl (meth) acrylate, stearyl (meth) acrylate, isooctyl (meth) acrylate, tetrahydrofuryl (meth) acrylate, isobornyl (meth) acrylate, benzyl (meth) acrylate, 1, 3-butanediol (meth) acrylate, 1, 4-butanediol (meth) acrylate, neopentyl glycol (meth) acrylate, 1, 6-hexanediol (meth) acrylate, trimethylolpropane tri (meth) acrylate, pentapentaerythritol tetra (meth) acrylate, and the like.

Other acrylates may be mentioned: and di-pentaerythritol hexa (meth) acrylate modified with epsilon-caprolactone, fluorene derivative di (meth) acrylate, carbazole derivative di (meth) acrylate, and the like.

The radical polymerizable monomer is used for adjusting the curing speed.

When a radical polymerizable monomer is used as the polymerizable monomer, a photo radical polymerization initiator is also blended. Examples of the photo radical polymerization initiator include: ketone compounds such as acetophenone compounds, benzil compounds, benzophenone compounds, and thioxanthone compounds.

Examples of the acetophenone-based compound include: diethoxyacetophenone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, 4' -isopropyl-2-hydroxy-2-methylpropiophenone, 2-hydroxymethyl-2-methylpropiophenone, 2-dimethoxy-1, 2-diphenylethan-1-one, p-dimethylaminoacetophenone, p-tert-butyldichloroacetophenone, p-tert-butyltrichloroacetophenone, p-azidobenzylidene acetophenone, 1-hydroxycyclohexylphenyl ketone, 2-methyl-1- [4- (methylthio) phenyl ] -2-morpholinoacetone-1, 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) -butanone-1, benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzoin-n-butyl ether, benzoin isobutyl ether, and the like, and examples of the benzoin-based compound include: benzil, anisoyl and the like, and examples of the benzophenone-based compound include: benzophenone, methyl o-benzoylbenzoate, meldonium, 4 ' -bisdiethylaminobenzophenone, 4 ' -dichlorobenzophenone, 4-benzoyl-4 ' -methyldiphenyl sulfide and the like, and thioxanthone-based compounds include: thioxanthone, 2-methylthioxanthone, 2-ethylthioxanthone, 2-chlorothioxanthone, 2-isopropylthioxanthone, 2, 4-diethylthioxanthone, and the like.

These photo radical polymerization initiators may be used in combination of 1 or 2 or more depending on the desired performance, and are preferably used in an amount of 0.05 to 10% by mass, more preferably 0.1 to 10% by mass, based on the radical polymerizable monomer. When the amount of the radical photopolymerization initiator added to the radical polymerizable monomer is 0.05% by mass or more, the photocurable adhesive can be cured more favorably, and when the amount is 10% by mass or less, the physical strength of the adhesive layer formed by curing the photocurable adhesive of the present invention is favorable.

The compound used as the polymerizable monomer may be a mixture of 1 or 2 or more. When the photocurable adhesive contains polymerizable monomers other than the alicyclic epoxy compound (a1) and the diglycidyl compound (a2), the amount of the polymerizable monomers used is preferably 100 parts by weight or less based on 100 parts by weight of the alicyclic epoxy compound (a 1). When the amount of the polymerizable monomer used is 100 parts by weight or less, the adhesive strength between the polarizer and the protective film can be kept good when the polarizer is produced using the photocurable adhesive. More preferably, the amount of the polymerizable monomer used is 5 parts by weight or more based on 100 parts by weight of the alicyclic epoxy compound (a1), and in this case, the modification effect by the polymerizable monomer can be obtained favorably. Still more preferably, the amount of the polymerizable monomer used is 50 parts by weight or less.

The photocurable adhesive may contain various additive components within a range not to impair the effects of the present invention. The additive component may contain, in addition to the photo radical polymerization initiator, a photosensitizer, a thermal cation polymerization initiator, a polyol, an ion scavenger, an antioxidant, a light stabilizer, a chain transfer agent, a sensitizer, an adhesion providing agent, a thermoplastic resin, a filler, a flow regulator, a plasticizer, a defoaming agent, a leveling agent, a dye, an organic solvent, and the like.

When the additive component is contained, the amount of the additive component used is preferably 1000 parts by weight or less based on 100 parts by weight of the alicyclic epoxy compound (a 1). When the amount is 1000 parts by weight or less, the effects of ensuring improvement in storage stability, prevention of discoloration, improvement in curing rate, and good adhesion, which are brought about by the combination of at least the alicyclic epoxy compound (a1), the diglycidyl compound (a2), and the photocationic polymerization initiator (B), which are essential components of the photocurable adhesive, can be exhibited well.

[ polarizing plate ]

A polarizer and a protective film were laminated using the photocurable adhesive composition to produce a polarizing plate. The method for applying the photocurable adhesive between the polarizer and the protective film is not particularly limited, and various coating methods such as a doctor blade, a bar coater, a die coater, a comma coater, and a gravure coater can be used. A method in which the photocurable adhesive is dropped between a polarizer and a protective film and then pressed with a roller or the like to be uniformly spread may be used. Here, the material of the roller may be metal, rubber, or the like, and when the material in which the photocurable adhesive is dropped between the polarizer and the protective film is stretched by pressing between the rollers, the rollers may be the same material or different materials. The thickness of the pressure-sensitive adhesive layer is usually 50 μm or less, preferably 20 μm or less, and more preferably 10 μm or less.

In this way, a transparent protective film is bonded to the pressure-sensitive adhesive layer formed of the photocurable pressure-sensitive adhesive. The protective film used here is not particularly limited, and specifically, an acetyl cellulose film such as triacetyl cellulose, which is most widely used as a protective film for a polarizing plate at present, or a film of a transparent resin having a lower moisture permeability than triacetyl cellulose can be used. The moisture permeability of triacetyl cellulose was about 400g/m²And/24 hours or so. When the protective films are bonded to both surfaces of the polarizer, 2 protective films may be bonded to each other step by step, or both surfaces may be bonded to each other in one step.

The acetyl cellulose film used in the present invention includes, in addition to the triacetyl cellulose film described above: diacetyl cellulose membranes, acetyl butyl cellulose membranes, and the like.

Examples of the transparent resin film having low moisture permeability used in the present invention include: amorphous polyolefin resin films, polyester resin films, acrylic resin films, polycarbonate resin films, polysulfone resin films, alicyclic polyimide resin films, and the like. Among them, a film made of an amorphous polyolefin resin is particularly preferably used. The amorphous polyolefin resin usually has a polymerized unit of a cyclic olefin such as norbornene or polycyclic norbornene monomer, and may be a copolymer of a cyclic olefin and a linear olefin. Among them, thermoplastic saturated norbornene-based resins are representative. In addition, a resin having polar groups introduced thereto is also effective. Commercially available amorphous polyolefin resins include: ジェイエスアール ("アートン" manufactured by nippon corporation), "ZEONEX" and "ZEONOR" manufactured by japanese ゼオン ("ZEONEX"), and "APO" and "アペル" manufactured by mitsui chemical corporation. The amorphous polyolefin resin is formed into a film by a known method such as a solvent casting method or a melt extrusion method.

In the present invention, it is preferable that the protective film is made of an amorphous polyolefin resin and has a thickness of 300g/m²Moisture permeability of less than 24 hours.

When the protective films are attached to both surfaces of the polarizer, the protective films may be of the same type or different types. When different types of protective films are bonded to both surfaces of the polarizer, a resin film having low moisture permeability such as the above-described amorphous polyolefin resin film, polyester resin film, acrylic resin film, polycarbonate resin film, polysulfone resin film, or alicyclic polyimide resin film may be used as one of the protective films, and a cellulose acetate film such as the above-described triacetyl cellulose film, diacetyl cellulose film, or acetylbutyl cellulose film may be used as the other protective film. In the case where a protective film made of a resin film having a relatively high moisture permeability such as a cellulose acetate film is provided on one surface of the polarizer as described above, an adhesive other than an epoxy adhesive such as a polyvinyl alcohol adhesive can be used for the bonding surface of the resin film having a high moisture permeability.

The surface to be bonded of the protective film may be subjected to an easy-adhesion treatment such as saponification treatment, corona treatment, plasma treatment, anchor coating treatment, or the like, before being bonded to the polarizer. The surface of the protective film opposite to the surface thereof to be bonded to the polarizer may have various treatment layers such as a hard coat layer, an antireflection layer, and an antiglare layer. The thickness of the protective film is usually in the range of about 5 to 200. mu.m, preferably 10 to 120. mu.m, and more preferably 10 to 85 μm.

The polarizer obtained by attaching the protective film to the polarizer via the uncured adhesive layer as described above was irradiated with active energy rays, whereby the adhesive layer made of the epoxy resin composition was cured and the protective film was fixed to the polarizer.

The light source of the active energy ray is not particularly limited, and for example, a low-pressure mercury lamp, a medium-pressure mercury lamp, a high-pressure mercury lamp, an ultra-high-pressure mercury lamp, a chemical lamp, a black light lamp, a microwave-excited mercury lamp, a metal halide lamp, or the like having a light emission distribution at a wavelength of 400nm or less can be used. The irradiation intensity of the epoxy resin composition is determined for each target composition, and is not particularly limited, and it is preferable that the irradiation intensity of the wavelength region effective for activation of the initiator is 0.1 to 100mW/cm². If the intensity of light irradiation to the resin composition is less than 0.1mW/cm²The reaction time is too long, and if it exceeds 100mW/cm²The yellowing of the epoxy resin composition or the deterioration of the polarizer may be caused by heat radiated from the lamp and heat generation of the composition at the time of polymerization. The light irradiation time for the composition is controlled by each composition to be cured, and is not particularly limited, and is preferably set to: the cumulative light amount expressed by the product of the irradiation intensity and the irradiation time is 10-5,000mJ/cm². If the cumulative amount of light for the above epoxy resin composition is less than 10mJ/cm²Then, the occurrence of the activated species from the initiator is insufficient, the curing of the resulting protective film may be insufficient, and the cumulative light amount exceeds 5,000mJ/cm²The irradiation time is very long, and the productivity is disadvantageously improved.

When the photocurable adhesive is cured by irradiation with an active energy ray, it is preferable to cure the adhesive within a range in which the functions of the polarizing plate, such as the polarization degree, transmittance, and hue of the polarizer, and the transparency of the protective film, do not decrease.

[ laminated optical Member ]

When the polarizing plate is used, an optical member provided with an optical layer exhibiting an optical function other than a polarizing function may be formed through the protective film of the present invention. Examples of the optical layer for forming the optical member laminated on the target polarizing plate include a reflective layer, a semi-transmissive reflective layer, a light diffusion layer, a retardation plate, a light collecting plate, and a luminance improving film, which are used for forming a liquid crystal display device. The reflective layer, the semi-transmissive reflective layer, and the light diffusion layer are used to form an optical member made of a reflective polarizer, a semi-transmissive polarizer, a diffusive polarizer, or a dual-purpose polarizer.

The reflective polarizing plate is used for a liquid crystal display device of a type that performs display by reflecting incident light from a viewer side, and can easily make the liquid crystal display device thin because a light source such as a backlight can be omitted. The transflective polarizing plate is used for a liquid crystal display device of a type that displays light in a bright place as a reflection type or in a dark place via a light source such as a backlight. The optical member of the reflective polarizer may be, for example, a reflective layer formed by attaching a foil or a vapor-deposited film made of a metal such as aluminum to a protective film of a polarizer. The optical member of the semi-transmissive polarizing plate is formed by making the reflecting layer into a semi-transparent mirror, or by bonding a reflecting plate containing a pearl pigment and exhibiting semi-transmissive properties to the polarizing plate. On the other hand, as an optical member of a diffusion type polarizing plate, for example, a method of performing a light extinction treatment on a protective film on a polarizing plate is used; a method of coating a resin containing microparticles; a fine uneven structure is formed on the surface by various methods such as a method of bonding a film containing fine particles.

The optical member in the form of a reflection-diffusion dual-purpose polarizing plate can be formed, for example, by providing a reflection layer reflecting the uneven structure on the fine uneven structure surface of the diffusion-type polarizing plate. The reflective layer having a fine uneven structure has advantages of diffusing incident light by scattering, preventing directivity or glare, suppressing unevenness of brightness, and the like. Further, the resin layer or film containing fine particles has an advantage that unevenness in brightness and darkness can be suppressed by diffusing incident light and reflected light thereof when they pass through the fine particle-containing layer. The reflective layer reflecting the surface fine uneven structure can be formed by directly applying a metal to the surface of the fine uneven structure by a method such as vapor deposition such as vacuum vapor deposition, ion plating, or sputtering, or a plating layer. The fine particles to be blended for forming the fine uneven structure on the surface may be, for example, inorganic fine particles including silica, alumina, titania, zirconia, tin oxide, indium oxide, cadmium oxide, antimony oxide, etc. having an average particle diameter of 0.1 to 30 μm, organic fine particles made of crosslinked or non-crosslinked polymer, etc.

On the other hand, the retardation plate in the form of the optical layer is intended to be used for retardation compensation of a liquid crystal element and the like. Examples thereof include: birefringent films made of stretched films of various plastics and the like, films in which discotic liquid crystals or nematic liquid crystals are oriented and fixed, and materials in which the above-described liquid crystal layer is formed on a film substrate. In this case, a cellulose resin film such as triacetyl cellulose is preferably used as a film substrate for supporting the alignment liquid crystal layer.

Examples of the plastic forming the birefringent film include: polycarbonates, polyvinyl alcohols, polystyrenes, polymethacrylates, polyolefins such as polypropylene, polyarylates, polyamides, and the like. The stretched film can be obtained by a suitable treatment such as uniaxial or biaxial treatment. By applying a shrinking force and/or a stretching force to the heat-shrinkable film while it is bonded thereto, a birefringent film in which the refractive index in the thickness direction of the film is controlled can be obtained. The retardation plate is intended to control optical characteristics such as a wider bandwidth, and 2 or more retardation plates may be used in combination.

The light collecting plate is used for the purpose of optical path control and the like, and therefore can be made into a prism array plate, a lens array plate, a plate with dots, or the like.

The purpose of the brightness enhancement film is to enhance the brightness of a liquid crystal display device or the like, and examples thereof include: a reflection-type polarization separation sheet designed to laminate a plurality of films having different refractive index anisotropies to produce a reflectance anisotropy; and a circularly polarized light separator formed of an oriented film in which a cholesteric liquid crystal polymer is supported on a film base or the oriented liquid crystal layer.

The optical member may be a laminate of 2 or 3 or more layers, which is obtained by combining a polarizing plate and 1 or 2 or more optical layers selected from the above-mentioned reflective layer, transflective layer, light diffusion layer, retardation plate, light collecting plate, brightness enhancement film, and the like according to the purpose of use. In this case, 2 or more optical layers such as a light diffusion layer, a phase difference plate, a light collector, and a brightness enhancement film may be provided. The arrangement of each optical layer is not particularly limited.

The various optical layers forming the laminated optical member are integrated with an adhesive, and the adhesive used for this purpose is not particularly limited as long as it can form a good adhesive layer. From the viewpoint of easiness of the bonding operation, prevention of occurrence of optical deviation, and the like, an adhesive (also referred to as a pressure-sensitive adhesive) is preferably used. As the adhesive, a material using an acrylic polymer, a silicone polymer, polyester, polyurethane, polyether, or the like as a base polymer can be used. Among these, acrylic adhesives are preferably selected from those which have excellent optical transparency, maintain appropriate wettability and aggregating force, have excellent adhesion to substrates, have weather resistance and heat resistance, and are used without causing peeling problems such as lifting and peeling under heating or humidifying conditions. In the acrylic adhesive, an acrylic copolymer, which is obtained by blending an alkyl ester of (meth) acrylic acid having an alkyl group having 20 or less carbon atoms such as a methyl group, an ethyl group, or a butyl group, and a functional group-containing acrylic monomer such as (meth) acrylic acid or hydroxyethyl (meth) acrylate, and which has a glass transition temperature of preferably 25 ℃ or less, more preferably 0 ℃ or less, and a weight average molecular weight of 10 ten thousand or more, is used as a base polymer.

The formation of the adhesive layer on the polarizing plate can be performed, for example, by: dissolving or dispersing the adhesive composition in organic solvent such as toluene or ethyl acetate to prepare 10-40 wt% solution, and directly coating the solution on a polarizer to form an adhesive layer; or a method in which an adhesive layer is formed on a protective film in advance and then transferred to and bonded to a polarizing plate to form an adhesive layer. The thickness of the adhesive layer is determined by the adhesive strength thereof, and the like, and is preferably in the range of about 1 to 50 μm.

If necessary, a filler made of glass fibers or glass beads, resin beads, metal powder or other inorganic powder, a pigment or colorant, an antioxidant, an ultraviolet absorber, or the like may be blended in the adhesive layer. The ultraviolet absorbent comprises: salicylic acid ester compounds, benzophenone compounds, benzotriazole compounds, cyanoacrylate compounds, nickel complex salt compounds, and the like.

The optical member may be disposed on one side or both sides of the liquid crystal element. The liquid crystal element to be used is arbitrary, and for example, an active matrix drive type typified by a thin film transistor type, a simple matrix drive type typified by a super twisted nematic type, or the like is used. The optical members disposed on both sides of the liquid crystal element may be the same or different.

Examples

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples. In the examples, unless otherwise specified,% and parts indicating the contents and amounts used are by weight. First, a reference example of producing a polyethylene terephthalate film with an antiglare layer used as a protective film on the polarizer side is given.

Reference example (production of polyethylene terephthalate film with anti-glare layer)

The following components were dissolved in ethyl acetate at a solid content of 60%, and cured to obtain an ultraviolet-curable resin composition having a refractive index of 1.53.

60 parts of pentaerythritol triacrylate

40 parts of multifunctional urethane acrylate.

Multifunctional urethanized acrylates: reaction product of hexamethylene diisocyanate and pentaerythritol triacrylate.

Subsequently, 2 parts of porous silica particles (trade name: サイリシア, manufactured by fuji シリシア chemical corporation) and 5 parts of 2,4, 6-trimethylbenzoyldiphenylphosphine oxide (trade name: ルシリン TPO, manufactured by BASF) as a photopolymerization initiator were added to 100 parts of the solid content of the ultraviolet-curable resin composition to prepare a coating liquid for an antiglare layer.

The coating liquid was applied to a surface of a biaxially stretched polyethylene terephthalate film having a thickness of 38 μm on which an easy adhesion layer was not provided (surface made of polyethylene terephthalate itself) to form an ultraviolet-curable resin composition layer, and the layer was dried in a dryer set at 80 ℃ for 3 minutes. At UVA (315-400nm) wavelength and illumination intensity of 250mW/cm²And a cumulative light amount of 300mJ/cm²The ultraviolet-curable resin composition layer was cured by irradiating the ultraviolet-curable resin composition layer side of the dried film with light from a high-pressure mercury lamp to obtain an antiglare film comprising a laminate of an antiglare layer (cured resin) having an uneven surface and a thickness of 5 μm and a biaxially stretched polyethylene terephthalate film. Using haze transmittance Instrument "HM-150" [ (Ltd.) village color technical research]The haze value of the antiglare film was measured to obtain a haze value of 10%.

Next, a photocurable adhesive composition was prepared, and examples and comparative examples suitable for the production of a polarizing plate were given. The photocationic curable components and the photocationic polymerization initiators used in the following examples are shown below and are represented by the following symbols, respectively.

(A) Photo cation curable component

(A1) Alicyclic epoxy compound

a 1: 3, 4-Epoxycyclohexanecarboxylic acid 3, 4-epoxycyclohexylmethyl ester

(A2) Diglycidyl compounds

a 21: 1, 4-Butanediol diglycidyl ether [ chlorine content 0.5% ]

a21 c: 1, 4-Butanediol diglycidyl ether [ chlorine content 8.0% ]

a 22: neopentyl glycol diglycidyl ether [ chlorine content 0.5% ]

a22 c: neopentyl glycol diglycidyl ether [ chlorine content 8.1% ]

a 23: cyclohexanedimethanol diglycidyl ether [ chlorine content 0.4% ]

a23 c: cyclohexanedimethanol diglycidyl ether [ chlorine content 7.7% ].

(B) Photo cation polymerization initiator (abbreviated as "initiator" in the tables)

(b1) Triarylsulfonium hexafluorophosphate salts

Examples 1 and 2 and comparative examples 1 to 9

(1) Preparation of Photocurable adhesive composition

A photo-cation curable component and a photo-cation polymerization initiator were mixed in the proportions shown in table 1, and then defoamed to prepare a photo-curable adhesive liquid. The photo-cationic polymerization initiator (b1) was added as a 50% propylene carbonate solution, and the amount of the solid matter thereof is shown in table 1.

(2) Determination of the chlorine concentration of the Binder before curing

The chlorine concentration contained in each of the binder liquids prepared above was measured as follows. That is, each binder liquid was first decomposed in a combustion apparatus "TOX-100" [ (manufactured by Ltd.) ダイアインスツルメンツ, and the gas was trapped in the absorbing liquid, and then the chlorine amount was determined by an ion chromatography apparatus "ICS-2000" (ダイオネクス), and the chlorine concentration was calculated from this amount and the amount of the binder liquid used in the first decomposition. The results of chlorine concentration measurement are shown in Table 1.

(3) Measurement of storage modulus of cured product at 80 ℃

Using a coater [ bar coater, first physical chemical plant)]Polyethylene terephthalate film having no easy adhesion layer on the surface thereof (trade name "Toyo Boseki エステルフィルム E7002", manufactured by Toyo Boseki Co., Ltd.)]On one side of the substrate was coated with each of the binder solutions prepared in (1) above so that the cured film thickness was about 25 μm. Next, the resultant was irradiated with ultraviolet light at a cumulative light amount of 3,000mJ/cm by "D バルブ" manufactured by フュージョン UV システムズ Co²And curing the adhesive. Cutting into 5mm × 30mm size, and peeling off polyethylene terephthalate film to obtain cured film of adhesive. The obtained cured film was held at a clamp interval of 2cm by using a dynamic viscoelasticity measuring apparatus "DVA-220" manufactured by アイティー measurement control Co., Ltd. with the long side being the stretching direction, the frequency of stretching and shrinking being 1Hz, and the temperature rise rate being set to 3 ℃/min, and the storage modulus at a temperature of 80 ℃ was determined. The results are shown in Table 1.

(4) Production of polarizing plate

A triacetyl cellulose film having a thickness of 80 μm and containing an ultraviolet absorber (trade name: フジタック, Fuji フイルム Co., Ltd.)]The surface of (2) was subjected to corona discharge treatment, and each of the binder solutions prepared in (1) was applied to the corona discharge treated surface with a bar coater, and the cured film thickness was about 3 μm. A polyvinyl alcohol-iodine polarizer was attached to the adhesive layer. The biaxially stretched polyethylene terephthalate film having an antiglare layer and a thickness of 43 μm produced in the reference example was subjected to corona discharge treatment on the surface (easy-adhesion layer surface) on the side opposite to the antiglare layer, and the same adhesive liquid as described above was applied to the corona discharge treated surface using a bar coater, and the cured film had a thickness of about 3 μm. A polarizer side of the polarizer on one surface of which the triacetyl cellulose film prepared above was bonded to the pressure-sensitive adhesive layer to prepare a laminate. Using an ultraviolet irradiation apparatus with a conveyor belt, ultraviolet rays were irradiated from the biaxially stretched polyethylene terephthalate film side having an antiglare layer of the laminate by "D バルブ" manufactured by フュージョン UV システムズ, and the cumulative light amount was 750mJ/cm²And curing the adhesive. In this way, a polarizing plate in which protective films were attached to both surfaces of the polarizer was produced.

(5) Evaluation of durability of polarizing plate by Cold thermal shock test

The polarizing plate produced in (4) above was cut into a size of 170mm × 110mm, an acrylic adhesive layer having a thickness of 25 μm was provided on the triacetyl cellulose film side, and the adhesive layer was attached to a glass plate to perform a cold and hot impact test (thermal shock test). In the cold thermal shock test, a polarizing plate sample bonded to the glass plate was held at-35 ℃ for 1 hour, then heated to 70 ℃ for 1 hour, and this operation was repeated for a total of 30 cycles as 1 cycle. This test was performed on each of 6 polarizing plate samples, and the ratio of the number of cracks observed in the polarizer after the test to the total number of samples (6) was evaluated. The results are shown in Table 1.

[ Table 1]

As shown in table 1, in the photocurable adhesive composition in which the alicyclic epoxy compound (a1) and the diglycidyl compound (a2) in the photocationic curable component (a) were 50 to 60% and 50 to 40% respectively, in comparative examples 2 to 5 using 1, 4-butanediol diglycidyl ether (a21c), neopentyl glycol diglycidyl ether (a22c), or cyclohexanedimethanol diglycidyl ether (a23c) each having a large chlorine content as the diglycidyl compound (a2), the cured product of the adhesive showed only a low storage modulus, and when the polarizing plate was produced, the state thereof was that the polarizer was easily broken by a cold and heat shock test.

On the other hand, in examples 1 to 6 using 1, 4-butanediol diglycidyl ether (a21), neopentyl glycol diglycidyl ether (a22), or cyclohexanedimethanol diglycidyl ether (a23), all of which have a small chlorine content, the cured product of the adhesive combined with the alicyclic epoxy compound (a1) exhibited a high storage modulus, and it was confirmed that cracking of the polarizer could be effectively prevented when the polarizer was produced.

When 1, 4-butanediol diglycidyl ether (a21) having a small chlorine content was used, the adhesive of comparative example 1, in which the blending amount was 50% of that of the photocationic-curable component (a), exhibited a low storage modulus of the cured product, and the state when the adhesive was used as a polarizing plate was as follows: the cold and heat shock test results in easy breakage of the polarizer. Thus, even if the chlorine content is reduced because of the difference in the kind of the diglycidyl compound (a2), if the blending amount of the diglycidyl compound (a2) in the photocationic curable component (a) is in the vicinity of 50%, the cured product will not have a sufficient storage modulus, but it can be understood that: as defined in the present invention, the alicyclic epoxy compound (A1) and the diglycidyl compound (A2) may be combined in order to make the cured product exhibit a storage modulus of 1000MPa or more at 80 ℃.

In examples 1 to 6, if the amount of the alicyclic epoxy compound (a1= a1) in the photocationic curable component (a) was increased to 70% or 80%, and the remainder was changed to a diglycidyl compound (a21, a22, or a23) having a small chlorine content, the viscosity of the adhesive liquid was controlled to a degree that the adhesive liquid could be applied at room temperature, and the cured product had a high storage modulus, and cracking of the polarizer could be effectively prevented when the cured product was formed into a polarizing plate.

Claims

1. A polarizing plate composed of a polarizer made of a polyvinyl alcohol-based resin film to which a dichroic dye is adsorbed and oriented, and a protective film, the protective film is made of a transparent resin bonded to at least one surface of the polarizer via an adhesive, the adhesive being formed of a photocurable adhesive composition, the photo-curable adhesive composition contains 100 parts by weight of a photo-cation curable component (A) and 1 to 10 parts by weight of a photo-cation polymerization initiator (B), the above-mentioned photocationic-curable component (A) contains 50 to 95 wt% of an alicyclic epoxy compound (A1) having 2 or more epoxy groups in the molecule and at least 1 of which is bonded to an alicyclic ring, based on the total amount of the component (A), and 5 to 50% by weight of a diglycidyl compound (A2) having a chlorine content of 1% by weight or less and represented by the following formula (I):

wherein Z represents an alkylene group having 1 to 9 carbon atoms, an alkylidene group having 3 or 4 carbon atoms, a 2-valent alicyclic hydrocarbon group, or a group represented by the formula-C_mH_2m-Z¹-C_nH_2nA 2-valent radical of formula (I), where-Z¹-represents-SO₂-, -SO-or-CO-, and m and n are each independently an integer of 1 or more and a total of 9 or less;

the cured product thereof exhibits a storage modulus of 1000MPa or more at 80 ℃.

2. The polarizing plate according to claim 1, wherein the protective film attached to at least one side of the polarizer is made of an acetyl cellulose-based resin.

3. The polarizing plate according to claim 1, wherein the protective film attached to at least one surface of the polarizer is made of at least one transparent resin selected from the group consisting of an amorphous polyolefin-based resin, a polyester-based resin, and a chain polyolefin-based resin.

4. The polarizing plate according to claim 1, wherein the protective film attached to at least one surface of the polarizer is made of a transparent resin of a polycarbonate-based resin.

5. The polarizing plate according to claim 1, wherein a protective film made of an acetyl cellulose-based resin is bonded to one surface of the polarizer via the adhesive, and a protective film as a film made of at least one transparent resin selected from the group consisting of an amorphous polyolefin-based resin, a polyester-based resin, and a chain polyolefin-based resin is bonded to the other surface of the polarizer via the adhesive.

6. The polarizing plate according to claim 1, wherein a protective film made of an acetyl cellulose resin is bonded to one surface of the polarizer via the adhesive, and a protective film as a film made of a transparent resin of a polycarbonate resin is bonded to the other surface of the polarizer via the adhesive.

7. A laminated optical member comprising a laminate of the polarizing plate of claim 1 and other optical layers.

8. The laminated optical member according to claim 7, wherein the optical layer contains a retardation film.