JP6047905B2 - Polarizing plate and laminated optical member using the same - Google Patents

Description

  The present invention relates to a polarizing plate in which a protective film made of a transparent resin is bonded to at least one surface of a polarizer made of a polyvinyl alcohol-based resin film on which a dichroic dye is adsorbed and oriented via an adhesive layer. It is about. 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.

  The polarizing plate is useful as one of the optical components constituting the liquid crystal display device. A polarizing plate usually has a structure in which protective films are laminated on both sides of a polarizer, and is incorporated in a liquid crystal display device. It is also known to provide a protective film only on one side of the polarizer, but in many cases, the other side is not just a protective film, but a layer having another optical function also serves as the protective film. Pasted together.

  As a method for producing a polarizer, a method in which a uniaxially stretched polyvinyl alcohol-based resin film dyed with a dichroic dye is treated with boric acid, washed with water, and dried is widely adopted. The polarizer thus obtained has problems such as weak physical strength and easy tearing in the processing direction. Therefore, as described above, a protective film is bonded to at least one side, usually both sides, via an adhesive layer. Is done. As an adhesive for this purpose, a water-based adhesive made of an aqueous solution of a polyvinyl alcohol resin has been traditionally used. Traditionally, a triacetyl cellulose film having a thickness of 30 to 100 μm has been used as a protective film.

  Triacetyl cellulose is excellent in transparency, easy to form various surface treatment layers and optical functional layers, has high moisture permeability, and can be dried after being bonded to a polarizer using an aqueous adhesive as described above. Since it has an excellent advantage as a protective film that it can be smoothly performed, it is still widely used today. On the other hand, due to the large moisture permeability, a polarizing plate bonded with a triacetyl cellulose film as a protective film tends to cause deterioration under wet heat, for example, at a temperature of 70 ° C. and a relative humidity of 90%. There was a problem. Therefore, it is also known that the protective film is an amorphous polyolefin resin having a moisture permeability smaller than that of triacetyl cellulose, for example, a norbornene resin as a representative example, for applications in which such a problem is likely to manifest.

  When a protective film made of a resin with low moisture permeability is bonded to a polyvinyl alcohol polarizer, an aqueous solution of a polyvinyl alcohol resin generally used for bonding a polyvinyl alcohol polarizer and a triacetyl cellulose film is conventionally used. When the adhesive is used, there are problems that the adhesive strength is not sufficient or the appearance of the obtained polarizing plate becomes poor. This is because a resin film having a low moisture permeability is generally hydrophobic, and water as a solvent cannot be sufficiently dried due to a low moisture permeability. On the other hand, it is also known to bond different types of protective films on both sides of the polarizer. For example, a protective film made of a resin with low moisture permeability such as an amorphous polyolefin resin is bonded to one surface of the polarizer, and a cellulose resin such as triacetyl cellulose is bonded to the other surface of the polarizer. There is also a proposal to bond a protective film made of a resin with high moisture permeability such as.

  Therefore, a high adhesion force is provided between the protective film made of a resin having a low moisture permeability and the polyvinyl alcohol polarizer, and a high adhesion between a resin having a high moisture permeability such as a cellulose resin and the polyvinyl alcohol polarizer. There is an attempt to use a photo-curable adhesive as an adhesive that gives force. For example, JP-A-2004-245925 (Patent Document 1) discloses an adhesive mainly composed of an epoxy compound not containing an aromatic ring, and irradiation with active energy rays, specifically irradiation with ultraviolet rays. It has been proposed that this adhesive is cured by cationic polymerization by, thereby bonding the polarizer and the protective film. JP-A-2008-257199 (Patent Document 2) discloses a photo-curing property in which an alicyclic epoxy compound and an epoxy compound having no alicyclic epoxy group are combined and a photocationic polymerization initiator is further blended. A technique of using an adhesive for bonding a polarizer and a protective film is disclosed.

  On the other hand, it is also known to increase the adhesive force by blending a polyol compound with a curable component. For example, JP 2007-224235 A (Patent Document 3) discloses an epoxy compound having an alicyclic structure and an epoxy group in a molecule, a polyol having a number average molecular weight of 400 or more, and an active energy ray-sensitive catalyst (polymerization initiation). It is proposed that an active energy ray-curable adhesive is blended. This adhesive is said to be able to improve adhesion and heat resistance while maintaining transparency.

JP 2004-245925 A JP 2008-257199 A JP 2007-224235 A

  However, the adhesive having the composition specifically disclosed in Patent Document 1 and Patent Document 2 does not necessarily have a sufficient adhesive force depending on the type of the protective film. Also, just by adding a polyol to an epoxy compound having an alicyclic structure and an epoxy group as disclosed in Patent Document 3, the adhesive force is still weak, especially for applications that require high durability such as a polarizing plate. May be insufficient.

  Therefore, the problem of the present invention is that a protective film made of a transparent resin is bonded to a polarizer made of a polyvinyl alcohol-based resin film via a photocurable adhesive, and the polarizer and the protective film are firmly bonded. It is to provide a polarizing plate. Another object of the present invention is to provide a laminated optical member suitably used for a liquid crystal display device by laminating another optical layer such as a retardation film on the polarizing plate.

  As a result of intensive studies to solve such problems, the present inventors have completed the present invention. Specifically, a polarizing plate in which a protective film made of a transparent resin is bonded to at least one surface of a polarizer made of a polyvinyl alcohol resin film on which a dichroic dye is adsorbed and oriented via an adhesive layer In which a specific two kinds of compounds are combined as a photocationic curable component for forming the adhesive layer, and then a predetermined amount of a photocationic polymerization initiator and a diol compound are blended therein (photocurable) It has been found that it is effective to use an adhesive. That is, it has been found that such a photocurable adhesive having a specific composition strongly bonds the polarizer and the protective film.

According to the present invention, a protective film made of a transparent resin is bonded to at least one surface of a polarizer made of a polyvinyl alcohol-based resin film on which a dichroic dye is adsorbed and oriented via an adhesive layer. The adhesive layer consists of (A) (A1) 50 to 90% by weight of a diepoxy compound having an alicyclic ring in the molecule and two epoxy groups, and (A2) a fat having no aromatic ring in the molecule. 1 to 100 parts by weight of a photocationic curable component containing 10 to 50% by weight of a reactive aliphatic compound selected from the group consisting of an aliphatic epoxy compound and an aliphatic vinyl ether compound. 10 parts by weight, and (C) a polarizing plate photocurable adhesives containing 0.5 to 19 parts by weight of a diol compound having two hydroxyl groups in the molecule is a layer formed by hardening are provided.

In this polarizing plate, the diol compound (C) has the following formula (I)
HO-X-OH (I)
In indicated, X in the formula Ri compound der an alkylene group having a total carbon number of 2-8 may be interrupted by an oxygen atom, especially, the formula (Ia)
_{HO- (C m H2 m -O)} n -H (Ia)
In the formula, m is 2 or 3, and n is an integer of 2 or more, but m × n is preferably an oligoalkylene glycol of 8 or less. Among the oligoalkylene glycols represented by the formula (Ia), triethylene glycol is preferable.

  In these polarizing plates, the protective film bonded to one surface of the polarizer can be composed of an acetylcellulose-based resin film in which an ultraviolet absorber is blended. What is necessary is just to bond to a polarizer through said photocurable adhesive agent. For example, a protective film made of an acetylcellulose-based resin film containing an ultraviolet absorber is bonded to one surface of a polarizer, and an acetylcellulose-based material not containing an ultraviolet absorber is bonded to the other surface of the polarizer. A form in which a resin film is bonded is also effective. In this case, the acetylcellulose-based resin film not containing an ultraviolet absorber can be a retardation film.

  Moreover, the protective film bonded to one surface of the polarizer may be composed of a resin film having a low moisture permeability, such as an amorphous polyolefin resin, a polyester resin, and a chain polyolefin resin. it can. In this case as well, such a protective film made of a resin film having a low moisture permeability may be bonded to the polarizer via the above-mentioned photocurable adhesive. These resin films with low moisture permeability can be bonded to both sides of the polarizer as desired. When the protective film on the liquid crystal cell side when applied to a liquid crystal display device is composed of such a resin film with low moisture permeability, the resin film with low moisture permeability on the liquid crystal cell side is a retardation film. You can also. A protective film made of an acetylcellulose-based resin film in which the above ultraviolet absorber is blended is bonded to one surface of the polarizer, and the other surface of the polarizer has a low moisture permeability. A form of laminating a film is also effective.

  By using the above-mentioned photo-curable adhesive, the polarizing plate of the present invention is such that the adhesive strength according to the 180 degree peeling test between the polarizer and the protective film is 0.6 N / 25 mm or more. it can.

  Moreover, according to this invention, the laminated optical member which consists of a laminated body of one of the said polarizing plates and another optical layer is also provided. The other optical layer constituting the laminated optical member advantageously includes a retardation film.

  The adhesive layer constituting the polarizing plate of the present invention comprises a diepoxy compound (A1) having two epoxy groups together with an alicyclic ring in the molecule, an aliphatic epoxy compound and an aliphatic vinyl ether having no aromatic ring in the molecule. A photocationic curable component (A) in which a reactive aliphatic compound (A2) selected from the group consisting of compounds is blended at a predetermined ratio, a photocationic polymerization initiator (B), and two hydroxyl groups in the molecule It is formed from a photo-curable adhesive in which a predetermined amount of each diol compound (C) having A polarizing plate obtained by laminating a polarizer and a protective film via this photo-curable adhesive and curing the adhesive is excellent in adhesive force between the polarizer and the protective film. . If another optical layer is laminated on this polarizing plate, a laminated optical member having a polarizing plate excellent in adhesion between the polarizer and the protective film is obtained.

  Hereinafter, embodiments of the present invention will be described in detail. In the present invention, a protective film made of a transparent resin is bonded to at least one surface of a polarizer made of a polyvinyl alcohol-based resin film on which a dichroic dye is adsorbed and oriented with an adhesive layer, To do. This adhesive layer is formed from a photo-curable adhesive containing a photo-cation curable component (A), a photo-cation polymerization initiator (B), and a diol compound (C) having two hydroxyl groups in the molecule. . Specifically, this photo-curable adhesive is cured by ultraviolet irradiation to form an adhesive layer. The obtained polarizing plate can be laminated with another optical layer to form a laminated optical member. For the photocurable adhesive, the polarizer, and the protective film used for the production of the polarizing plate, and the laminated optical member produced by laminating another optical layer on the polarizing plate, the explanation will be advanced step by step. I will do it.

[Photocurable adhesive]
The photocurable adhesive is a diol compound (C) having 1 to 10 parts by weight of the cationic photopolymerization initiator (B) and two hydroxyl groups in the molecule with respect to 100 parts by weight of the cationic photocurable component (A). Is contained in an amount of 0.5 to 19 parts by weight. In addition, the photocationic curable component (A) includes 50 to 90% by weight of a diepoxy compound (A1) having an alicyclic ring and two epoxy groups in the molecule, and an aliphatic group having no aromatic ring in the molecule. 10 to 50% by weight of a reactive aliphatic compound (A2) selected from the group consisting of an epoxy compound and an aliphatic vinyl ether compound. Of course, the sum of these (A1) and (A2) does not exceed 100% by weight.

  When the content of the diepoxy compound (A1) exceeds 90% by weight in the entire photocationic curable component (A), the amount of the reactive aliphatic compound (A2) described below becomes relatively small, and the present invention. It is difficult to improve the adhesive strength between the polarizer and the protective film of the photo-curable adhesive intended in the above. The diepoxy compound (A1) is more preferably contained in an amount of 60% by weight or more, particularly 70% by weight or more based on the total amount of the photocationic curable component (A).

  Moreover, the adhesive force between a polarizer and a protective film can be improved by making content of a reactive aliphatic compound (A2) into 10 weight% or more among photocationic curable components (A) whole. it can. On the other hand, when the amount exceeds 50% by weight, the adhesive force between the polarizer and the protective film is not sufficient, and the storage elastic modulus after curing the photocurable adhesive tends to be low. . In order to make the adhesive force between the polarizer and the protective film more preferable, the amount of the reactive aliphatic compound (A2) in the photocationic curable component (A) is more preferably 25% by weight or less. .

  By blending 1 part by weight or more of the cationic photopolymerization initiator (B) per 100 parts by weight of the cationic photocurable component (A), the cationic photocurable component (A) can be sufficiently cured and obtained. Gives high mechanical strength and adhesive strength to the polarizing plate. On the other hand, when the amount increases, the ionic compound increases in the adhesive layer, which is a cured product, so that the hygroscopicity of the adhesive layer increases and the durability of the polarizing plate may be lowered. Then, the compounding quantity of a photocationic polymerization initiator (B) shall be 10 weight part or less per 100 weight part of photocationic curable components (A). The compounding amount of the photocationic polymerization initiator (B) is preferably 2 parts by weight or more and preferably 6 parts by weight or less per 100 parts by weight of the photocationic curable component (A).

  Moreover, the adhesive force of a polarizer and a protective film can be improved by mix | blending 0.5 weight part or more of diol compounds (C) with respect to 100 weight part of photocationic curable components (A). On the other hand, since the diol compound (C) is hydrophilic, when the amount of the diol compound (C) increases, the epoxy compound constituting the photocationic curable component (A) is cured by phase separation from other components or by the hydroxyl group. Is likely to be disturbed. Moreover, since the quantity of a photocationic curable component (A) and a photocationic polymerization initiator (B) will become relatively small when the quantity of a diol compound (C) increases, the storage elasticity of the adhesive layer which is hardened | cured material A rate may become low and it may become easy to break a polarizer. Then, the compounding quantity of a diol compound (C) shall be 19 weight part or less per 100 weight part of photocationic curable components (A). The blending amount of the diol compound (C) is preferably 10 parts by weight or less per 100 parts by weight of the photocation curable component (A).

(Photocationic curable component)
The photocationic curable component (A), which is the main component of the photocurable adhesive and gives adhesive strength by polymerization and curing, has a diepoxy compound (A1) having an alicyclic ring in the molecule and two epoxy groups. And a reactive aliphatic compound (A2) selected from the group consisting of an aliphatic epoxy compound having no aromatic ring in the molecule and an aliphatic vinyl ether compound.

  In the diepoxy compound (A1) having an alicyclic ring in the molecule and two epoxy groups, the epoxy group may be directly bonded to the alicyclic ring, or a site different from the alicyclic ring. May be present.

  A compound having two epoxy groups directly bonded to an alicyclic ring in the molecule is also called an alicyclic diepoxy compound. Here, the epoxy group directly bonded to the alicyclic ring means that two carbon atoms constituting the alicyclic ring (usually adjacent carbon atoms) are bridged as shown in the following formula (II). It means an oxygen atom -O- to be connected, and p in the following formula (II) represents an integer of 2 to 5.

An epoxy group in which one or a plurality of hydrogen atoms in (CH ₂ ) _p in the above formula (II) are bonded to another chemical structure and directly bonded to such an alicyclic ring Can be an alicyclic diepoxy compound. One or more hydrogen atoms in (CH ₂ ) _p forming the alicyclic ring may be appropriately substituted with a linear alkyl group such as a methyl group or an ethyl group. Among them, an alicyclic diepoxy compound having an epoxycyclopentane ring (p = 3 in the above formula (II)) or an epoxycyclohexane ring (p = 4 in the above formula (II)) has excellent adhesion. It is preferably used because it imparts sex. Specific examples of the alicyclic diepoxy compound are listed below. Here, the compound name is given first, and then the chemical formula corresponding to each is shown, and the same symbol is attached to the chemical name and the corresponding chemical formula.

A: 3,4-epoxycyclohexylmethyl 3,4-epoxycyclohexanecarboxylate,
B: 3,4-epoxy-6-methylcyclohexylmethyl 3,4-epoxy-6-methylcyclohexanecarboxylate,
C: ethylene bis (3,4-epoxycyclohexanecarboxylate),
D: Bis (3,4-epoxycyclohexylmethyl) adipate,
E: bis (3,4-epoxy-6-methylcyclohexylmethyl) adipate,
F: Diethylene glycol bis (3,4-epoxycyclohexyl methyl ether),
G: ethylene glycol bis (3,4-epoxycyclohexyl methyl ether),
H: 2,3,14,15-diepoxy-7,11,18,21-tetraoxatrispiro [5.2.2.5.2.2] henicosane,
I: 3- (3,4-epoxycyclohexyl) -8,9-epoxy-1,5-dioxaspiro [5.5] undecane,
J: bis (2,3-epoxycyclopentyl) ether,
K: Dicyclopentadiene dioxide and the like.

  A compound having an alicyclic ring in the molecule and having two epoxy groups at a site different from the alicyclic ring is typically a diglycidyl ether of an alicyclic diol. For example, it can be a diglycidyl ether of cycloalkanediol, typically cyclohexanediol, but can also be a compound in which an aromatic ring of an aromatic diepoxy compound is hydrogenated. The latter uses a dihydric alcohol obtained by selectively subjecting an aromatic dihydroxy compound, which is a raw material of an aromatic diepoxy compound, to a hydrogenation reaction in the presence of a catalyst and under pressure. In the presence of an acidic catalyst such as boron or tin tetrachloride, epichlorohydrin is reacted to produce chlorohydrin ether, and the resulting chlorohydrin ether is produced by a two-stage method in which intramolecular ring closure is performed with alkali. be able to. Examples of the aromatic diepoxy compound include bisphenol type epoxy compounds such as diglycidyl ether of bisphenol A, diglycidyl ether of bisphenol F, and diglycidyl ether of bisphenol S. The nuclear hydrogenated product of these aromatic diepoxy compounds is a diepoxy compound (A1) having an alicyclic ring in the molecule and two epoxy groups. Among them, hydrogenated bisphenol A glycidyl ether Is preferred.

  Next, the reactive aliphatic compound (A2) will be described. The reactive aliphatic compound (A2) is an aliphatic epoxy compound or an aliphatic vinyl ether compound having no aromatic ring in the molecule. Among these, an aliphatic epoxy compound having no aromatic ring in the molecule is a compound having at least one oxirane ring (3-membered cyclic ether) bonded to an aliphatic carbon atom in the molecule. For example, methyl glycidyl ether, ethyl glycidyl ether, n-butyl glycidyl ether, allyl glycidyl ether, 2-ethylhexyl glycidyl ether, 1,2-epoxyhexane, 1,2-epoxyoctane, 1,2-epoxydecane, 1,2 -Monofunctional epoxy compounds such as epoxide dodecane, 1,2-epoxytetradecane, 1,2-epoxyhexadecane, 1,2-epoxyoctadecane, glycidyl methacrylate, trimethylolpropane triglycidyl ether and pentaerythritol tetraglycidyl ether Such trifunctional or higher functional epoxy compounds also correspond to this, and in particular, an aliphatic diepoxy compound having two oxirane rings bonded to an aliphatic carbon atom in the molecule and having no aromatic ring is preferable. Such a suitable aliphatic diepoxy compound can be represented by the following formula (III), for example.

  Y in the formula is an alkylene group having 2 to 9 carbon atoms, an alkylene group having 4 to 9 carbon atoms having an ether bond therebetween, or a divalent hydrocarbon group having 6 to 18 carbon atoms having an alicyclic structure. is there.

  Specifically, the aliphatic diepoxy compound represented by the above formula (III) is diglycidyl ether of alkanediol, diglycidyl ether of oligoalkylene glycol having up to about 4 repetitions, or diglycidyl ether of alicyclic diol. is there.

  Specific examples of the diol (glycol) that can be an aliphatic diepoxy compound represented by the formula (III) are listed below. Examples of alkanediol include ethylene glycol, propylene glycol, 1,3-propanediol, 2-methyl-1,3-propanediol, 2-butyl-2-ethyl-1,3-propanediol, and 1,4-butanediol. Neopentyl glycol, 3-methyl-2,4-pentanediol, 2,4-pentanediol, 1,5-pentanediol, 3-methyl-1,5-pentanediol, 2-methyl-2,4-pentane Diol, 2,4-diethyl-1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 3,5-heptanediol, 1,8-octanediol, 2-methyl-1,8 -Octanediol, 1,9-nonanediol and the like. Examples of the oligoalkylene glycol include diethylene glycol, triethylene glycol, tetraethylene glycol, and dipropylene glycol.

Among these aliphatic diepoxy compounds, diglycidyl ethers of alkanediols are preferable, and 1,4-butanediol diglycidyl ether is particularly preferable because of easy availability. This compound is a compound of the above formula (III) in which —Y— is — (CH ₂ ) ₄ —, that is, 1,4-butanediyl.

  Of the reactive aliphatic compounds (A2), an aliphatic vinyl ether compound having no aromatic ring in the molecule is a compound in which an aliphatic hydrocarbon and a vinyl group are linked by an ether bond. Specific examples thereof include ethylene glycol divinyl ether, propylene glycol divinyl ether, 1,3-propanediol divinyl ether, 1,4-butanediol divinyl ether, 1,5-pentanediol divinyl ether, diethylene glycol divinyl ether, and triethylene glycol divinyl ether. Vinyl ether, tetraethylene glycol divinyl ether, ethyl vinyl ether, n-propyl vinyl ether, isopropyl vinyl ether, n-butyl vinyl ether, isobutyl vinyl ether, 2-ethylhexyl vinyl ether, dodecyl vinyl ether, octadecyl vinyl ether, allyl vinyl ether, hydroxyethyl vinyl ether, hydroxybutyl vinyl ether, diethylene glycol Monobini Ethers, such as ethyl oxetane methyl vinyl ether.

  Among these aliphatic divinyl ethers, alkanediols or oligoalkylene glycol divinyl ethers are preferable. Among them, diethylene glycol divinyl ether is particularly preferable because it is easily available.

  In addition to the above-mentioned diepoxy compound (A1) and reactive aliphatic compound (A2), other photocationic curings are possible as long as their quantitative ratio is in the range described above and does not inhibit the functions of these two components. Sexual components may be blended. Examples of the other photocationic curable component include epoxy compounds that do not correspond to the above diepoxy compound (A1) and reactive aliphatic compound (A2), and oxetane compounds. Epoxy compounds not corresponding to the diepoxy compound (A1) and the reactive aliphatic compound (A2) include compounds having only one epoxy group directly bonded to the alicyclic ring in the molecule, aromatic epoxy compounds, etc. Is done.

  The oxetane compound is a compound having a 4-membered ring ether (oxetanyl group) in the molecule. Specific examples thereof include 3-ethyl-3-hydroxymethyloxetane, 1,4-bis [{(3-ethyloxetane-3-yl) methoxy} methyl] benzene (also referred to as xylylenebisoxetane), 3- Ethyl-3- (phenoxymethyl) oxetane, bis (3-ethyloxetane-3-ylmethyl) ether, 2-ethylhexylsyloxetane, 3-ethyl-3- (2-ethylhexyloxymethyl) oxetane, 3-ethyl -3-[{(3-triethoxysilyl) propoxy} methyl] oxetane, oxetanylsilsesquioxane, phenol novolac oxetane, and the like. Here, the oxetanyl silsesquioxane is obtained by hydrolytic condensation of a silane compound having an oxetanyl group, for example, the above 3-ethyl-3-[{(3-triethoxysilyl) propoxy} methyl] oxetane. And a network-like polysiloxane compound having a plurality of oxetanyl groups. These oxetane compounds can be used alone or in combination of two or more.

(Photocationic polymerization initiator)
In the present invention, the photocationic curable component (A) described above is cured by cationic polymerization by irradiation of active energy rays to form an adhesive layer. (B) is blended. The cationic photopolymerization initiator generates a cationic species or a Lewis acid by irradiation with an active energy ray such as visible light, ultraviolet ray, X-ray, or electron beam, and initiates a polymerization reaction of the photocationic curable component (A). Is. Since the cationic photopolymerization initiator acts catalytically by light, it is excellent in storage stability and workability even when mixed with the cationic photocurable component (A). Examples of the compound that generates a cationic species or a Lewis acid upon irradiation with active energy rays include onium salts such as aromatic iodonium salts and aromatic sulfonium salts, aromatic diazonium salts, and iron-arene complexes.

  An aromatic iodonium salt is a compound having a diaryl iodonium cation, and typical examples of the diaryl iodonium cation include a diphenyl iodonium cation. An aromatic sulfonium salt is a compound having a triarylsulfonium cation, and typical examples of the triarylsulfonium cation include triphenylsulfonium cation and 4,4′-bis (diphenylsulfonio) diphenylsulfide cation. Can do. The aromatic diazonium salt is a compound having a diazonium cation, and typical examples of the diazonium cation include a benzenediazonium cation. The iron-arene complex is typically a cyclopentadienyl iron (II) arene cation complex salt.

The cation shown above forms a photocationic polymerization initiator in combination with an anion (anion). Examples of anions constituting the photocationic polymerization initiator include hexafluorophosphate anion PF ₆ ⁻ , hexafluoroantimonate anion SbF ₆ ⁻ , pentafluorohydroxyantimonate anion SbF ₅ (OH) ⁻ , hexafluoroarsenate anion. AsF ₆ ⁻ , tetrafluoroborate anion BF ₄ ⁻ , tetrakis (pentafluorophenyl) borate anion B (C ₆ F ₅ ) ₄ ^{— and the} like are available.

  Among these cationic photopolymerization initiators, especially aromatic sulfonium salts have ultraviolet absorption characteristics even in the wavelength region near 300 nm, and thus give a cured product having excellent curability and good mechanical strength and adhesive strength. Therefore, it is preferably used.

  Various photocationic polymerization initiators are commercially available. Examples of commercially available products include the “CPI” series sold by Sun Apro Co., Ltd., the “CYRACURE UVI” series sold by Union Carbide, Inc., and the “Adekaoptomer” sold by ADEKA Corporation. "SP" series, "IRGACURE" series sold by BASF Germany (but classified as a cationic photopolymerization initiator), "Sun Aid SI" series sold by Sanshin Chemical Industry Co., Ltd., There is “UVACURE 1590” sold by Daicel-Cytec.

(Diol compound)
In the present invention, in addition to the above-mentioned photocationic curable component (A) and photocationic polymerization initiator (B), the diol compound (C) is blended to obtain a photocurable adhesive. The diol compound (C) is a compound having two hydroxyl groups in the molecule, and can typically be a compound represented by the above formula (I), but particularly an oligo group represented by the above formula (Ia). Alkylene glycol is preferably used.

  Specific examples of the diol compound (C) include ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, There are 1,8-octanediol, diethylene glycol, triethylene glycol and the like. Of these diol compounds (C), triethylene glycol is preferred because it is easily available and has high solubility in polyvinyl alcohol resins.

  In the present invention, in addition to the photocationic curable component (A) and the photocationic polymerization initiator (B), by adding the diol compound (C), the adhesive force, particularly the adhesive force between the polarizer and the protective film can be improved. It is improving. Since the diol compound (C) has the property of dissolving the polyvinyl alcohol resin, the diol compound (C) dissolves the polyvinyl alcohol resin on the polarizer surface, and as a result, the adhesion interface on the polarizer surface is modified. It is considered that the adhesive strength is improved.

(Other components that can be blended in the photo-curable adhesive)
The photocurable adhesive may contain other components in addition to the photocationic curable component (A), the photocationic polymerization initiator (B), and the diol compound (C) described above. Examples of other components that can be incorporated include photosensitizers, photosensitizers, thermal cationic polymerization initiators, chain transfer agents, thermoplastic resins, flow regulators, antifoaming agents, leveling agents, organic solvents. and so on. Depending on the type of protective film to be bonded to the polarizer, it may be preferable to blend a photosensitizer and further a photosensitization aid.

  The photosensitizer is a compound that exhibits maximum absorption at a wavelength longer than the maximum absorption wavelength indicated by the photocationic polymerization initiator (B) and promotes the polymerization initiation reaction by the photocationic polymerization initiator (B). As such a photosensitizer, an anthracene compound is preferably used. As anthracene compounds that can be used as photosensitizers, 9,10-dimethoxyanthracene, 9,10-diethoxyanthracene, 9,10-dipropoxyanthracene, 9,10-diisopropoxyanthracene, 9,10-dibutoxyanthracene 9,10-dipentyloxyanthracene, 9,10-dihexyloxyanthracene and the like.

  The photosensitizing assistant is a compound that further promotes the action of the photosensitizer. As such a photosensitizing assistant, naphthalene compounds are preferably used. 1,4-dimethoxynaphthalene, 1-ethoxy-4-methoxynaphthalene, 1,4-diethoxynaphthalene, 1,4-dipropoxynaphthalene, 1,4-dibutoxy as naphthalene compounds that can serve as photosensitizers And naphthalene.

  When these other components are blended, the amount is blended from, for example, a range of 10 parts by weight or less with respect to 100 parts by weight of the photocationic curable component (A) which is a main component of the photocurable adhesive What is necessary is just to select suitably according to the objective.

(Preparation of photocurable adhesive)
The photocurable adhesive is obtained by mixing the photocationic curable component (A), the photocationic polymerization initiator (B), the diol compound (C), and other components as necessary. Can be prepared. At the time of mixing, it heats at about 30-50 degreeC as needed, and stirs until it becomes uniform with a stirrer. The stirring time is not particularly limited, but is usually about 5 to 20 minutes.

[Polarizer]
The polarizer is a film having a function of converting natural light into linearly polarized light, and is composed of a polyvinyl alcohol resin film adsorbed and oriented with a dichroic dye. The polyvinyl alcohol resin can be obtained by saponifying a polyvinyl acetate resin. The polyvinyl acetate resin may be a copolymer of vinyl acetate which is a homopolymer of vinyl acetate, or a copolymer of vinyl acetate and other monomers copolymerizable therewith. Examples of other monomers copolymerized with vinyl acetate include unsaturated carboxylic acids, olefins, vinyl ethers, and unsaturated sulfonic acids. The degree of saponification of the polyvinyl alcohol resin is usually 85 to 100 mol%, preferably 98 to 100 mol%. The polyvinyl alcohol-based resin may be modified, and for example, polyvinyl formal or polyvinyl acetal modified with aldehydes may be used. The degree of polymerization of the polyvinyl alcohol resin is usually 1,000 to 10,000, preferably 1,500 to 5,000.

  What formed such a polyvinyl alcohol-type resin into a film is used as a raw film of a polarizer. The film formation of the polyvinyl alcohol resin can be performed by a known method. The original film of polyvinyl alcohol resin can have a thickness of, for example, about 20 to 100 μm.

  A polarizer is a step of uniaxially stretching a polyvinyl alcohol resin film, a step of dyeing a polyvinyl alcohol resin film with a dichroic dye, and adsorbing the dichroic dye, a polyvinyl alcohol system on which the dichroic dye is adsorbed The resin film is manufactured through a step of treating with a boric acid aqueous solution.

  Uniaxial stretching of the polyvinyl alcohol-based resin film may be performed before dyeing with the dichroic dye, may be performed simultaneously with dyeing with the dichroic dye, or may be performed after dyeing with the dichroic dye. Also good. When uniaxial stretching is performed after dyeing with a dichroic dye, the uniaxial stretching may be performed before boric acid treatment or during boric acid treatment. Moreover, uniaxial stretching can also be performed in these several steps. For uniaxial stretching, rolls having different peripheral speeds may be uniaxially stretched or may be stretched uniaxially using a hot roll. Furthermore, it may be dry stretching in which stretching is performed in the air, or may be wet stretching in which stretching is performed in a state where a polyvinyl alcohol-based resin is swollen using a solvent such as water. The draw ratio is usually about 3 to 8 times.

  The polyvinyl alcohol resin film can be dyed with a dichroic dye by, for example, a method of immersing the polyvinyl alcohol resin film in an aqueous solution containing the dichroic dye. Specifically, iodine or a dichroic organic dye is used as the dichroic dye.

  When iodine is used as the dichroic dye, a method of dyeing a polyvinyl alcohol resin film by dipping in an aqueous solution containing iodine and potassium iodide is usually employed. The content of iodine in this aqueous solution is usually about 0.01 to 0.5 parts by weight per 100 parts by weight of water, and the content of potassium iodide is usually about 0.5 to 10 parts by weight per 100 parts by weight of water. It is. The temperature of this aqueous solution is usually about 20 to 40 ° C., and the immersion time (dyeing time) in this aqueous solution is usually about 30 to 300 seconds.

On the other hand, when a dichroic organic dye is used as the dichroic dye, a method of immersing and dyeing a polyvinyl alcohol-based resin film in an aqueous solution containing a water-soluble dichroic organic dye is usually employed. The content of the dichroic organic dye in this aqueous solution is usually about 1 × 10 ⁻³ to 1 part by weight per 100 parts by weight of water. This aqueous solution may contain an inorganic salt such as sodium sulfate as a dyeing assistant. The temperature of this aqueous solution is usually about 20 to 80 ° C. Moreover, the immersion time (dyeing time) in this aqueous solution is usually about 30 to 300 seconds.

  The boric acid treatment after dyeing with a dichroic dye is performed by immersing the dyed polyvinyl alcohol resin film in an aqueous boric acid solution. The boric acid content in the boric acid aqueous solution is usually about 2 to 15 parts by weight, preferably about 5 to 12 parts by weight, per 100 parts by weight of water. When iodine is used as the dichroic dye, the aqueous boric acid solution preferably contains potassium iodide. The content of potassium iodide in the boric acid aqueous solution is usually about 2 to 20 parts by weight, preferably about 5 to 15 parts by weight per 100 parts by weight of water. The immersion time in the boric acid aqueous solution is usually about 60 to 1,200 seconds, preferably about 150 to 600 seconds, and more preferably about 200 to 400 seconds. The temperature of the boric acid aqueous solution is usually 50 ° C. or higher, preferably 50 to 85 ° C.

  The polyvinyl alcohol resin film after the boric acid treatment is usually washed with water. The water washing treatment is performed, for example, by immersing a boric acid-treated polyvinyl alcohol resin film in water. After washing with water, a drying process is performed to obtain a polarizer. The temperature of water in the water washing treatment is usually about 5 to 40 ° C., and the immersion time is usually about 2 to 120 seconds. The drying process performed after washing with water is performed using a hot air dryer or a far infrared heater. A drying temperature is about 40-100 degreeC normally, Preferably it is about 50-80 degreeC. The time for the drying treatment is usually about 120 to 600 seconds.

  Thus, the thickness of the polarizer which consists of a polyvinyl alcohol-type resin film can be about 10-40 micrometers.

[Protective film]
The protective film is provided on the surface of the polarizer for the purpose of compensating for the polarizer composed of the polyvinyl alcohol-based resin film described above, since the physical strength is poor as described above. A protective film is bonded to the polarizer via the photocurable adhesive described above, and the photocurable adhesive is cured to obtain a polarizing plate. The protective film can be composed of an acetylcellulose-based resin film such as triacetylcellulose, which has been most widely used as a protective film for polarizing plates, or a resin film having a lower moisture permeability than triacetylcellulose. The moisture permeability of triacetyl cellulose is approximately 400g / m ² / 24hr approximately.

  In one preferable form of the present invention, the protective film bonded to at least one surface of the polarizer is composed of an acetylcellulose-based resin film. An acetyl cellulose resin is a resin in which at least a part of hydroxyl groups in cellulose is esterified, and a mixed ester in which part is acetated and partly esterified with another acid. Good. Examples of the acetyl cellulose resin include triacetyl cellulose, diacetyl cellulose, cellulose acetate propionate, and cellulose acetate butyrate.

The acetyl cellulose resin may contain an ultraviolet absorber. One surface of the polarizer, specifically, the surface that is far from the liquid crystal cell of the polarizing plate that is bonded to the liquid crystal cell, that is, the surface that becomes the viewing side or the backlight side, is blended with an ultraviolet absorber. Often, the resin film is bonded as a protective film. As ultraviolet absorbers, salicylic acid ester compounds, benzophenone compounds, benzotriazole compounds, cyanoacrylate compounds, nickel complex compounds, and the like are known.

  A protective film made of an acetyl cellulose resin containing an ultraviolet absorber is bonded to one surface of the polarizer, and an acetyl cellulose resin not containing an ultraviolet absorber is bonded to the other surface of the polarizer. It is also effective to form a retardation film having a phase difference.

In another preferred embodiment of the present invention, the protective film bonded to at least one surface of the polarizer is composed of a resin film having a moisture permeability lower than that of triacetyl cellulose. As such a resin film, for example, moisture permeability can be cited the following resin film 300g / m ² / 24hr. Specifically, amorphous polyolefin resin, polyester resin, acrylic resin, polycarbonate resin, chain polyolefin resin, and the like correspond to this.

  Amorphous polyolefin resin is a polymer having a polymer unit of cyclic olefin, such as norbornene, tetracyclododecene (also known as dimethanooctahydronaphthalene), or a compound having a substituent bonded thereto. It may be a copolymer obtained by copolymerizing a chain polyolefin and / or an aromatic vinyl compound. In the case of a homopolymer of a cyclic olefin or a copolymer of two or more types of cyclic olefins, a double bond remains by ring-opening polymerization, and hydrogenated ones are generally used as amorphous polyolefin resins. Used for. Of these, thermoplastic norbornene resins are typical.

  The polyester resin is a polymer obtained by condensation polymerization of a dibasic acid and a dihydric alcohol, and polyethylene terephthalate is representative. Acrylic resin is a polymer with methyl methacrylate as the main monomer. In addition to methyl methacrylate homopolymer, methyl methacrylate and acrylic esters and aromatic vinyl compounds such as methyl acrylate It may be a copolymer. The polycarbonate-based resin is a polymer having a carbonate bond (—O—CO—O—) in the main chain, and is typically obtained by condensation polymerization of bisphenol A and phosgene. The chain polyolefin-based resin is a polymer having a chain polyolefin such as ethylene or propylene as a main monomer, and can be a homopolymer or a copolymer. Among them, a propylene homopolymer and a copolymer in which a small amount of ethylene is copolymerized with propylene are representative.

  In still another preferred embodiment, a protective film made of an acetylcellulose-based resin is bonded to one surface of the polarizer via the adhesive layer, and the other surface of the polarizer is also interposed via the adhesive layer. Then, a protective film made of a transparent resin having a low moisture permeability as described above is bonded.

  These protective films are subjected to various surface treatments such as hard coat treatment, antireflection treatment, antiglare treatment, antistatic treatment, or antifouling treatment on the surface opposite to the surface to be bonded to the polarizer. Can be applied.

[Production method of polarizing plate]
The polarizer and the protective film are bonded via the adhesive described above. In bonding the polarizer and the protective film, the photocurable adhesive coating layer described above is formed on one or both of the bonded surfaces of the polarizer and the protective film, and the polarizer and the protective film are interposed through the coating layer. A protective film is pasted. Easy adhesion treatment such as corona discharge treatment, plasma treatment, flame treatment, primer treatment, anchor coating treatment on one or both of the bonded surfaces of the polarizer and protective film before forming the adhesive coating layer May be applied. And an active energy ray is irradiated and hardened to the application layer of an uncured photocurable adhesive agent, and a protective film is fixed on a polarizer.

  For forming the coating layer, various coating methods such as a doctor blade, a wire bar, a die coater, a comma coater, and a gravure coater can be used. Moreover, it is also possible to employ a method in which an adhesive is cast while a polarizer and a protective film are continuously supplied so that the bonding surfaces of both are inside. Since each coating method has an optimum viscosity range, it is also a useful technique to adjust the viscosity of the photocurable adhesive using a solvent. As the solvent for this purpose, a solvent that dissolves the photocurable adhesive satisfactorily without reducing the optical performance of the polarizer is used, but there is no particular limitation on the type thereof. For example, organic solvents such as hydrocarbons typified by toluene and esters typified by ethyl acetate can be used. The thickness of the adhesive layer is usually 20 μm or less, preferably 10 μm or less, more preferably 5 μm or less. When the adhesive layer is thick, the reaction rate of the adhesive is lowered, and the wet heat resistance of the polarizing plate tends to deteriorate.

  The active energy ray light source used for curing the coating layer of the photocurable adhesive may be any one that generates ultraviolet rays, electron beams, X-rays, and the like. In particular, a light source having a light emission distribution at a wavelength of 400 nm or less is preferable, and examples thereof include a low pressure mercury lamp, a medium pressure mercury lamp, a high pressure mercury lamp, an ultrahigh pressure mercury lamp, a chemical lamp, a black light lamp, a microwave excitation mercury lamp, and a metal halide lamp.

The active energy ray irradiation intensity to the photocurable adhesive is determined for each target composition and is not particularly limited, but the light irradiation intensity in the wavelength region effective for the activation of the photocationic polymerization initiator. Is preferably 0.1 to 100 mW / cm ² . If the light irradiation intensity is too small, the reaction time becomes too long. On the other hand, if the light irradiation intensity is too large, the photocurable adhesive is caused by heat radiated from the lamp and heat generated during polymerization of the photocurable adhesive. May cause yellowing and deterioration of the polarizer. The light irradiation time to the photocurable adhesive is also controlled for each composition to be cured and is not particularly limited, but the integrated light amount expressed as the product of the light irradiation intensity and the light irradiation time is 10 to 10. It is preferably set to be 5,000 mJ / cm ² . If the integrated light amount is too small, the generation of active species derived from the initiator may not be sufficient, and the resulting adhesive layer may be insufficiently cured. On the other hand, if the integrated light amount is too large, the light irradiation time Tends to be very long and disadvantageous for productivity improvement.

  When bonding a protective film on both surfaces of a polarizer, irradiation of an active energy ray may be performed from which protective film side. For example, when one protective film contains an ultraviolet absorber and the other protective film does not contain an ultraviolet absorber, it is preferable to irradiate active energy rays from the protective film side that does not contain the ultraviolet absorber. By irradiating in this way, it is possible to effectively use the irradiated active energy rays and increase the curing rate.

  In this invention, the adhesiveness between a polarizer and a protective film can be improved by using the photocurable adhesive mentioned above. Therefore, the adhesive strength by the 180 degree peeling test between the polarizer and the protective film can be 0.6 N / 25 mm or more. Here, the 180 degree peeling test is performed according to JIS K 6854-2: 1999 “Adhesive—Peeling adhesive strength test method—Part 2: 180 degree peeling” as shown in the examples described later.

[Laminated optical member]
The polarizing plate of the present invention can be made into a laminated optical member by laminating optical layers having optical functions other than the polarizing plate. Typically, a laminated optical member is obtained by laminating and attaching an optical layer to a protective film of a polarizing plate via an adhesive or a pressure-sensitive adhesive. According to the invention, a protective film may be bonded via a photocurable adhesive, and an optical layer may be laminated and bonded to the other surface of the polarizer via an adhesive or an adhesive. In the latter case, if the photocurable adhesive defined in the present invention is used as an adhesive for adhering the polarizer and the optical layer, the optical layer can simultaneously be a protective film defined in the present invention.

  As an example of an optical layer laminated on a polarizing plate, a polarizing plate arranged on the back side of the liquid crystal cell is laminated on the side opposite to the side facing the liquid crystal cell of the polarizing plate. Examples include a light plate, a brightness enhancement film, a reflective layer, a transflective layer, and a light diffusion layer. In addition, for both the polarizing plate disposed on the front side of the liquid crystal cell and the polarizing plate disposed on the back side of the liquid crystal cell, a retardation film laminated on the side of the polarizing plate facing the liquid crystal cell, etc. There is.

  The light collector is used for the purpose of optical path control, and may be a prism array sheet, a lens array sheet, or a dot-attached sheet.

  The brightness enhancement film is used for the purpose of improving brightness in a liquid crystal display device. Specifically, a reflective polarized light separation sheet, an alignment film of a cholesteric liquid crystal polymer, and an alignment film that are designed so that anisotropy occurs in the reflectance by laminating a plurality of thin film films having different refractive index anisotropies Examples thereof include a circularly polarized light separating sheet having a liquid crystal layer supported on a film substrate.

  The reflective layer, the transflective layer, or the light diffusing layer is provided to make the polarizing plate into a reflective optical member, a transflective optical member, or a diffusing optical member, respectively. A reflective optical member including a polarizing plate is used in a liquid crystal display device of a type that reflects incident light from the viewing side and displays a light source such as a backlight. Therefore, the liquid crystal display device can be easily thinned. A transflective optical member including a polarizing plate is used as a reflective liquid crystal display device in a bright place and a liquid crystal display device that displays light from a backlight in a dark place. In addition, a diffusing optical member including a polarizing plate is used in a liquid crystal display device that imparts light diffusibility and suppresses display defects such as moire.

  A method for forming these reflective layer, transflective layer, and light diffusion layer will be described. The reflective layer constituting the reflective optical member can be formed, for example, by attaching a foil or vapor deposition film made of a metal such as aluminum on the protective film on the polarizer. The semi-transmissive reflective layer constituting the semi-transmissive optical member is formed by using the reflective layer as a half mirror, or by adhering a reflective plate containing a pearl pigment or the like and exhibiting light transmittance to the polarizing plate. it can. The light diffusing layer constituting the diffusing optical member is formed by, for example, a method of performing a mat treatment on a protective film on a polarizing plate, a method of applying a resin containing fine particles, a method of bonding a film containing fine particles, and the like. It can be formed as a surface layer having a fine relief structure. The resin layer or film containing fine particles has an advantage that incident light and its reflected light are diffused when passing through the fine particle-containing layer, and light and dark unevenness can be suppressed. The fine particles to be blended for forming the surface fine concavo-convex structure are, for example, silica, aluminum oxide, titanium oxide, zirconia, tin oxide, indium oxide, cadmium oxide, antimony oxide having an average particle diameter of 0.1 to 30 μm. It can be inorganic fine particles, organic fine particles such as a crosslinked or non-crosslinked polymer, and the like.

  The laminated optical member may be a reflection / diffusion polarizing plate. The reflection / diffusion polarizing plate can be produced by, for example, a method of providing a reflective layer reflecting the uneven structure on the fine uneven structure surface of the diffusion optical member including the polarizing plate. The reflective layer having a fine concavo-convex structure has advantages such that incident light is diffused by irregular reflection, directivity and glare can be prevented, and unevenness in brightness and darkness can be suppressed. The reflective layer reflecting the surface fine concavo-convex structure can be formed by directly attaching a metal to the surface of the fine concavo-convex structure by a method such as vapor deposition or plating such as vacuum deposition, ion plating, or sputtering.

  The retardation film acting as an optical layer is used for the purpose of compensation of retardation by a liquid crystal cell. Examples of retardation films include birefringent films composed of stretched films of various plastics, films in which discotic liquid crystals and nematic liquid crystals are oriented and fixed, and those in which the above liquid crystal layer is formed on a base film. Can be mentioned. When the liquid crystal layer is formed on the base film, a cellulose acetate resin film such as triacetyl cellulose is preferably used as the base film.

  Examples of the plastic forming the birefringent film include amorphous polyolefin resins, polycarbonate resins, acrylic resins, chain polyolefin resins such as polypropylene, polyvinyl alcohol, polystyrene, polyarylate, polyamide, and the like. It is done. The stretched film can be processed by an appropriate method such as uniaxial or biaxial. Two or more retardation films may be used in combination for the purpose of controlling optical characteristics such as broadening the bandwidth.

  The laminated optical member is preferable because optical compensation can be effectively performed when a retardation film is applied to the liquid crystal display device as an optical layer other than the polarizing plate. The optimum retardation value (in-plane and thickness direction) of the retardation film may be selected according to the applied liquid crystal cell.

  A laminated optical member can be made into a laminated body of two layers or three or more layers by combining a polarizing plate and one layer or two or more layers selected according to the purpose of use from the various optical layers described above. In that case, the various optical layers forming the laminated optical member are integrated with the polarizing plate using an adhesive or pressure-sensitive adhesive, but the adhesive or pressure-sensitive adhesive layer used for this purpose is good. As long as it is formed, there is no particular limitation. It is preferable to use a pressure-sensitive adhesive (also referred to as a pressure-sensitive adhesive) from the viewpoint of easy bonding work and prevention of optical distortion. Usually, an adhesive layer is also provided on the surface of the laminated optical member to be bonded to the liquid crystal cell.

  As the pressure-sensitive adhesive for integrating the various optical layers and the polarizing plate, those having a base polymer such as an acrylic polymer, a silicone polymer, polyester, polyurethane, or polyether can be used. Above all, like acrylic adhesives, it has excellent transparency, retains appropriate wettability and cohesion, has excellent adhesion to the substrate, and has weather resistance, heat resistance, etc. It is preferable to select and use a material that does not cause separation problems such as floating and peeling under humidification conditions. In acrylic adhesives, alkyl esters of (meth) acrylic acid having an alkyl group having 20 or less carbon atoms such as methyl, ethyl and butyl groups, and (meth) acrylic acid and hydroxyethyl (meth) acrylate An acrylic copolymer having a weight average molecular weight of 100,000 or more, in which a glass transition temperature is preferably 25 ° C. or less, more preferably 0 ° C. or less, and a functional group-containing acrylic monomer comprising Useful as a base polymer.

  The pressure-sensitive adhesive layer is formed on the polarizing plate or the laminated optical member by, for example, preparing a 10 to 40% by weight solution by dissolving or dispersing the pressure-sensitive adhesive composition in an organic solvent such as toluene or ethyl acetate. Direct coating on the target surface of the film (polarizing plate or laminated optical member), or by previously forming an adhesive layer on the protective film and applying it to the target film (polarizing plate or laminated optical member) This can be done by transferring to the surface. The thickness of the pressure-sensitive adhesive layer is determined according to the adhesive force and the like, but a range of about 1 to 50 μm is appropriate.

  In addition, the pressure-sensitive adhesive layer is blended with fillers made of glass fibers, glass beads, resin beads, metal powders and other inorganic powders, pigments, colorants, antioxidants, UV absorbers, etc. as necessary. It may be. Examples of ultraviolet absorbers include salicylic acid ester compounds, benzophenone compounds, benzotriazole compounds, cyanoacrylate compounds, and nickel complex compounds.

  The laminated optical member can be disposed on one side or both sides of the liquid crystal cell via the above-mentioned pressure-sensitive adhesive layer. The liquid crystal cell to be used is arbitrary. For example, a liquid crystal display device using various liquid crystal cells such as an active matrix drive type typified by a thin film transistor type and a simple matrix drive type typified by a super twisted nematic type. Can be formed.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to these examples. In the examples, “%” and “part” representing the content or amount used are based on weight unless otherwise specified. In addition, the photocationic curable component, the photocationic polymerization initiator, and the diol compound used in the following examples are as follows, respectively, and may be indicated by symbols at the beginning of each.

(A) Photocationic curable component (A1) Diepoxy compound having an alicyclic ring in the molecule (a11) 3,4-epoxycyclohexylmethyl 3,4-epoxycyclohexanecarboxylate: obtained from Daicel Chemical Industries, Ltd. Product name "Celoxide Side 2021P".
(A12) Hydrogenated bisphenol A diglycidyl ether: trade name “jER YX8000” obtained from Mitsubishi Chemical Corporation.

(A2) Reactive aliphatic compound (a21) 1,4-butanediol diglycidyl ether: trade name “Denacol EX-121” obtained from Nagase Chemkex Co., Ltd.
(A22) Diethylene glycol divinyl ether: Obtained from Nippon Carbide Industries Co., Ltd.

  The four types of photocationic curable components shown here are compounds each having a structure of the following formula.

(B) Photocationic polymerization initiator (b1) 50% propylene carbonate solution of triarylsulfonium salt-based photocationic polymerization initiator: trade name “CPI-100P” obtained from San Apro Co., Ltd.

(C) Diol compound (c1) Triethylene glycol: Obtained from Tokyo Chemical Industry Co., Ltd.

[Examples 1-6 and Comparative Examples 1-6]
(1) Preparation of Photocurable Adhesive Solution The photocationic curable component was blended in the proportions shown in Table 1 (100 parts in total), and the photocationic polymerization initiator (b1) shown above was used as a solid content. 25 parts and the diol compound (c1) were blended in the proportions shown in Table 1, and then defoamed to prepare a photocurable adhesive solution.

(2) Preparation of polarizing plate Corona discharge treatment was applied to the surface of an 80 μm thick triacetylcellulose film (trade name “Konicatak KC8UX2MW”) containing an ultraviolet absorber obtained from Konica Minolta Opto Co., Ltd. Each adhesive solution prepared above was applied to the treated surface using a bar coater so that the film thickness after curing was about 3 μm. A 28 μm-thick polyvinyl alcohol-iodine polarizer was bonded to the adhesive layer. In addition, the surface of a 40 μm thick retardation film [trade name “N-TAC KC4FR-1”] made of acetylcellulose resin obtained from Konica Minolta Opto Co., Ltd. was subjected to corona discharge treatment, and its corona discharge treatment surface The same adhesive solution as above was applied using a bar coater so that the film thickness after curing was about 3 μm. The adhesive layer was bonded to the polarizer side of the polarizer having the triacetylcellulose film prepared above bonded on one side, to prepare a laminate. From the acetylcellulose-based phase difference film side of this laminate, ultraviolet rays are applied so that the integrated light quantity becomes 250 mJ / cm ² using an ultraviolet irradiation device with a belt conveyor (the lamp uses “D bulb” manufactured by Fusion UV Systems). Irradiated to cure the adhesive. Thus, a polarizing plate in which protective films were bonded to both sides of the polarizer was produced.

(3) 180 degree peeling test The polarizing plate produced in the above (2) was cut into a size of 200 mm × 25 mm, and a polyvinyl alcohol-iodine polarizer and an acetylcellulose retardation film “N-TAC KC4FR-1” And the peel strength between the 80 μm thick triacetyl cellulose film “Konikatak KC8UX2MW”. When measuring the peel strength between the acetylcellulose retardation film and the polarizer, an acrylic pressure-sensitive adhesive layer is provided on the exposed surface of the acetylcellulose retardation film, and the triacetylcellulose film having a thickness of 80 μm is polarized. When the peel strength between the children was measured, an acrylic pressure-sensitive adhesive layer was provided on the exposed surface of the 80 μm-thick triacetyl cellulose film, and each pressure-sensitive adhesive layer was attached to a glass plate. Then, insert a cutter blade between the polarizer and the protective film on the adhesive side (acetylcellulose-based retardation film “N-TAC KC4FR-1” or 80 μm thick triacetylcellulose film “Konicatak KC8UX2MW”), 30 mm was peeled from the end in the length direction, and the peeled portion was grasped by the grip portion of the testing machine. The test piece in this state was subjected to JIS K 6854 in an atmosphere at a temperature of 23 ° C. and a relative humidity of 55%.
-2: 1999 According to "Adhesive-Peeling adhesion strength test method-Part 2: 180 degree peeling", a 180 degree peeling test was conducted at a gripping movement speed of 300 mm / min, and the length of 170 mm excluding 30 mm of the gripping part The average peeling force over all was obtained. The results are summarized in Table 1.

  In the section of 180 degree peel strength in Table 1, the column of “N-TAC / PVA” is the column between the acetylcellulose retardation film “N-TAC KC4FR-1” and the polyvinyl alcohol-iodine polarizer. The column “TAC / PVA” means the peel strength between the 80 μm thick triacetyl cellulose film “Konicatak KC8UX2MW” and the polyvinyl alcohol-iodine polarizer. In addition, in the section of 180 degree peel strength, “−” means that the film is peeled off almost without applying force even after the protective film on the opposite side of the adhesive and the polarizer are grasped and peeled off 30 mm from the end. Therefore, it means that no significant peeling force was obtained.

(4) Curability test The surface of the polarizer after peeling off from the protective film by the 180 degree peeling test of (3) above is confirmed with the finger, and the case where there is no stickiness is considered to have good curability (○). The results are summarized in Table 1, assuming that there are some cases with poor curability (x).

  From the results of Table 1, the photocationic curable component (A) is a binary system of a diepoxy compound (A1) having an alicyclic ring and a reactive aliphatic compound (A2), and a photocationic polymerization initiator is added thereto. In Comparative Examples 1, 3 and 5 which were simply blended, the curability of the cured adhesive was good, but the adhesive force (peeling strength) between the polarizer and the protective film was not sufficient. On the other hand, Comparative Examples 2, 4 and 6 were mixed with 20 parts by weight of triethylene glycol per 100 parts by weight of the photocationic curable component (A) in the adhesives of Comparative Examples 1, 3 and 5, respectively. However, these adhesives had insufficient curability.

  On the other hand, the photocationic curable component (A) itself is a binary system of a diepoxy compound (A1) having an alicyclic ring and a reactive aliphatic compound (A2). In addition, in Examples 1 to 6, in which a predetermined amount of triethylene glycol, which is a diol compound, is mixed to form an adhesive, the adhesive force (peeling strength) between the polarizer and the protective film is high, and the curability is sufficient. Met.

Claims (5)

A protective film made of a transparent resin is bonded to at least one surface of a polarizer made of a polyvinyl alcohol-based resin film on which a dichroic dye is adsorbed and oriented through an adhesive layer,
The adhesive layer is
(A) (A1) 50 to 90% by weight of a diepoxy compound having an alicyclic ring and two epoxy groups in the molecule;
(A2) For 100 parts by weight of the photocationic curable component containing 10 to 50% by weight of a reactive aliphatic compound selected from the group consisting of an aliphatic epoxy compound having no aromatic ring in the molecule and an aliphatic vinyl ether compound ,
(B) 1-10 parts by weight of a cationic photopolymerization initiator, and (C) the following formula (I)
HO-X-OH (I)
A photocurable adhesive containing 0.5 to 10 parts by weight of a diol compound which is an alkylene group having 2 to 8 carbon atoms which may be interrupted by an oxygen atom is cured. A polarizing plate characterized by being a layer formed by The diol compound (C) has the following formula (Ia)
_{HO- (C m H 2m -O)} n -H (Ia)
The polarizing plate according to claim 1 , wherein m is 2 or 3, n is an integer of 2 or more, and m × n is 8 or less. The polarizing plate according to claim 2 , wherein the diol compound (C) is triethylene glycol. A laminated optical member comprising a laminate of the polarizing plate according to any one of claims 1 to 3 and another optical layer. The laminated optical member according to claim 4 , wherein the other optical layer includes a retardation film.