JP5966310B2 - 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 triacetylcellulose 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. Japanese Patent Application Laid-Open No. 2008-257199 (Patent Document 2) discloses a photocurable adhesive comprising a combination of an alicyclic epoxy compound and an epoxy compound having no alicyclic epoxy group, and further containing a photocationic polymerization initiator. A technique using an agent for bonding a polarizer and a protective film is disclosed.

On the other hand, an adhesive having a vinyl ether compound as a photocationic curable component is also known. For example, International Publication No. 2010/047386 (Patent Document 3) includes an aliphatic epoxy compound, an alicyclic epoxy compound, and an oxetane. A compound selected from a compound and a vinyl ether compound as a main component (photo cation curable component), and a titanate coupling agent and a photo cation polymerization initiator are blended in predetermined amounts to form an adhesive, and this adhesive It is disclosed that a polarizer and a protective film are bonded together to form a polarizing plate. Example 7 of this document includes trimethylolpropane polyglycidyl ether [“Denacol EX-321L” from Nagase ChemteX Corp.], 1,2-epoxy-4-vinylcyclohexane [“Daicel Chemical Industries Ltd.“ Celoxide 2000 "], 3,4-epoxycyclohexylmethyl 3,4-epoxycyclohexanecarboxylate (" Celoxide 2021P "from Daicel Chemical Industries, Ltd.), 2-ethylhexyloxetane [Aron Oxetane OXTane, Toagosei Co., Ltd.
-212 "] and cyclohexyl vinyl ether (" CHVE "from BASF Japan Ltd.) are mixed to form a photocationic curable component, which is combined with a titanate coupling agent and a photocationic polymerization initiator. This document also includes triethylene glycol divinyl ether (“DVE-3” from BASF Japan Ltd.), which is a bifunctional compound, as a specific example of the vinyl ether compound.

JP 2004-245925 A JP 2008-257199 A International Publication No. 2010/047386 Pamphlet

  The adhesive of the composition specifically disclosed in Patent Document 1 and Patent Document 2 described above does not necessarily have a sufficiently low viscosity, and is applied to a polarizer or a protective film bonded thereto, and is uniform in a thin film. It was not always easy to form an adhesive layer. In addition, these adhesives do not necessarily exhibit a sufficient storage elastic modulus after curing, and as a result, when the resulting polarizing plate is subjected to a severe temperature history, for example, at a low temperature and a high temperature. When subjected to a thermal shock test in which the above-mentioned holding was repeated, the polarizer sometimes cracked.

  Furthermore, although these known photocurable adhesives adhere the polarizer and the protective film with an appropriate adhesive force, the adhesive force is not necessarily sufficient. For example, the photocurable adhesive can be polarized using the photocurable adhesive. A polarizing plate obtained by bonding a polarizer and a protective film is applied to a liquid crystal display device. When the edge is polished in a state of being cut into a predetermined size, the protective film is peeled off from the polarizer at the edge. There was something to do.

  On the other hand, the adhesive compounded with the vinyl ether compound specifically disclosed in Patent Document 3 is insufficient in the adhesive strength of the cured product or insufficient in the storage elastic modulus, so that the polarizer and the protective film are peeled off. There was a problem that it was easy to do.

  Thus, the problem of the present invention is that it exhibits a sufficiently low viscosity, can be applied to a polarizer or a protective film at room temperature, gives a sufficient storage elastic modulus after curing, and receives a severe temperature history. Provide a polarizing plate that exhibits an effective protective function even when the polarizer and the protective film are bonded using a photo-curable adhesive that does not easily cause cracking of the polarizer, and has excellent adhesion between the two. There is. 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 polarized light 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 In the plate, the adhesive layer is blended with a predetermined amount of a photocationic polymerization initiator in the photocationic curable component, and the photocationic curable component is mainly composed of an alicyclic diepoxy compound, and an aliphatic group. The present inventors have found that it is effective to form an epoxy compound and a composition (photo-curable adhesive) containing an aliphatic or alicyclic divinyl ether compound. That is, the photocurable adhesive having such a specific composition exhibits a low viscosity at room temperature and gives good coating suitability, and also exhibits a high storage elastic modulus after curing, thereby firmly bonding the polarizer and the protective film. I found out.

That is, 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. and, the adhesive layer, (a) the light cationically curable component 100 parts by weight, the polymerization initiator as (B) only cationic photopolymerization initiator contains 1 to 10 parts by weight, the light cationically curable Component (A) is based on the total amount of (A1) 50 to 85% by weight of alicyclic diepoxy compound, (A2) 1 to 40% by weight of aliphatic epoxy compound, and (A3) aliphatic or fatty There is provided a polarizing plate formed from a photocurable adhesive containing 1 to 30% by weight of a cyclic divinyl ether compound.

In this polarizing plate, the divinyl ether compound (A3) has the following formula:
_{CH 2 = CH-O-Z} -O-CH = CH 2
In the formula, Z is an alkylene group having 2 to 9 carbon atoms, an alkylene group having 4 to 9 carbon atoms having an ether bond between them, or a carbon number having an alicyclic structure. It is a 6-18 divalent hydrocarbon group. Specific preferred examples of this compound include diethylene glycol divinyl ether.

  The above-mentioned photocurable adhesive used for these polarizing plates can have a viscosity at 25 ° C. before curing of 70 mPa · sec or less.

  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 0.2 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.

  In the adhesive layer constituting the polarizing plate of the present invention, the alicyclic diepoxy compound (A1), the aliphatic epoxy compound (A2), and the aliphatic or alicyclic divinyl ether compound (A3) are blended in a predetermined ratio. It is formed from the photocurable adhesive which mix | blended the photocationic polymerization initiator (B) with the made photocationic curable component (A). This photo-curable adhesive has a low viscosity and exhibits good coating suitability, so that a thin and uniform coating film can be formed on the surface of the polarizer or the protective film. Are better. In addition, the polarizing plate obtained by pasting the polarizer and the protective film through this coating film (adhesive) and curing the adhesive is excellent in the adhesive force between the polarizer and the protective film. Since the adhesive layer, which is a cured product of the adhesive, gives a high storage modulus, even when subjected to a severe temperature history such as a thermal shock test, the polarizer is hardly cracked and has excellent thermal shock resistance. A laminated optical member obtained by laminating another optical layer on this polarizing plate also has excellent thermal shock resistance while fully expressing the function of the polarizing plate.

  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 photocurable adhesive containing a photocationic curable component (A) and a photocationic polymerization initiator (B). 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 contains 1 to 10 parts by weight of the cationic photopolymerization initiator (B) with respect to 100 parts by weight of the cationic photocurable component (A). 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. Therefore, the amount of the cationic photopolymerization initiator (B) is 10 parts by weight or less per 100 parts by weight of the cationic photocurable component (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).

(Photocationic curable component)
The photocationic curable component (A), which is a main component of the photocurable adhesive and gives adhesive strength by polymerization curing, is an alicyclic diepoxy compound (A1), an aliphatic epoxy compound (A2), and an aliphatic or fat. A cyclic divinyl ether compound (A3) is contained.

  The alicyclic diepoxy compound (A1) is a compound having in its molecule two epoxy groups that are directly bonded to the alicyclic ring. Here, as shown in the following formula (I), an epoxy group directly bonded to an alicyclic ring is a bridge formed by bridging two carbon atoms (usually adjacent carbon atoms) constituting the alicyclic ring. It means an oxygen atom -O- to be connected, and m in the following formula (I) represents an integer of 2 to 5.

A group in which one or more hydrogen atoms in (CH ₂ ) _m in formula (I) are removed is bonded to another chemical structure, and an epoxy group directly bonded to such an alicyclic ring Can be an alicyclic diepoxy compound (A1). Further, one or more hydrogen atoms in (CH ₂ ) _m forming the alicyclic ring may be appropriately substituted with a linear alkyl group such as a methyl group or an ethyl group. Among the alicyclic epoxy compounds, an alicyclic diepoxy having an epoxycyclopentane ring [m = 3 in the above formula (I)] or an epoxycyclohexane ring [m = 4 in the above formula (I)]. The compound is preferably used because it provides excellent adhesion. Specific examples of the alicyclic epoxy 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.

  The aliphatic epoxy compound (A2) is a compound having at least one oxirane ring (3-membered cyclic ether) bonded to an aliphatic carbon atom in the molecule. For example, monofunctional epoxy compounds such as butyl glycidyl ether and 2-ethylhexyl diether, tri- or higher functional epoxy compounds such as trimethylolpropane triglycidyl ether and pentaerythritol tetraglycidyl ether, and 4-vinylcyclohexene dioxide An epoxy compound having one epoxy group directly bonded to an alicyclic ring and an oxirane ring bonded to an aliphatic carbon atom, such as Limonene dioxide and Limonene dioxide, is also a typical example. An aliphatic diepoxy compound having two oxirane rings bonded to a carbon atom in the molecule is preferred. Such a suitable aliphatic diepoxy compound can be represented by the following formula (II), 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 (II) 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 (II) 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. Examples of the alicyclic diol include cyclohexanediol, cyclohexanedimethanol, hydrogenated bisphenol A, and hydrogenated bisphenol F.

Among these aliphatic diepoxy compounds (A2), diglycidyl ethers of alkanediols are preferable, and particularly preferable ones from the viewpoint of easy availability, 1,4-butanediol diglycidyl ether, that is, the above formula ( in II), -Y- is - (CH _{2) 4} - is (1,4-butanediyl), compound.

The aliphatic or alicyclic divinyl ether compound (A3) is a divinyl ether of an aliphatic or alicyclic diol, and can be specifically represented by the following formula (III).
_{CH 2 = CH-O-Z} -O-CH = CH 2 (III)

  In the formula, Z represents an aliphatic or alicyclic divalent group, and an alkylene group having 2 to 9 carbon atoms, an alkylene group having 4 to 9 carbon atoms having an ether bond therebetween, or an alicyclic structure. It is preferably a divalent hydrocarbon group having 6 to 18 carbon atoms.

  In the above formula (III), when Z is an alkylene group having 2 to 9 carbon atoms, it becomes a divinyl ether of alkanediol, and when Z is an alkylene group having 4 to 9 carbon atoms with an ether bond therebetween, It becomes divinyl ether of oligoalkylene glycol having a number of repetitions of up to about 4, and when Z is a bivalent hydrocarbon group having 6 to 18 carbon atoms having an alicyclic structure, it becomes divinyl ether of alicyclic diol.

  Specific examples of the divinyl ether represented by the above formula (III) include ethylene glycol divinyl ether, propylene glycol divinyl ether, 1,3-propanediol divinyl ether, 1,4-butanediol divinyl ether, 1,5-pentane. Examples include diol divinyl ether, diethylene glycol divinyl ether, triethylene glycol divinyl ether, tetraethylene glycol divinyl ether, cyclohexane diol divinyl ether, cyclohexane dimethanol divinyl ether, hydrogenated bisphenol A divinyl ether.

Among these aliphatic or cycloaliphatic divinyl ether compounds (A3), alkanediol or oligoalkylene glycol divinyl ether is preferred, and particularly preferred for reasons such as easy availability, diethylene glycol divinyl ether, that is, In the above formula (III), there is a compound in which —Z— is — (CH ₂ ) ₂ O (CH ₂ ) ₂ —.

  The photocationic curable component (A) constituting the photocurable adhesive includes the alicyclic diepoxy compound (A1), the aliphatic epoxy compound (A2), and the aliphatic or alicyclic divinyl ether compound ( Contains three types of compounds A3). Each amount is 50 to 85% by weight of the alicyclic diepoxy compound (A1), 1 to 40% by weight of the aliphatic epoxy compound (A2) based on the total amount of the photocationically curable component (A), and fat. The aliphatic or alicyclic divinyl ether compound (A3) is 1 to 30% by weight. Of course, the sum of these (A1), (A2) and (A3) does not exceed 100% by weight.

  By making the content of the alicyclic diepoxy compound (A1) in the entire photocationic curable component (A) 50 weight or more, the storage elastic modulus after curing the photocurable adhesive containing the alicyclic diepoxy compound (A1) is For example, the storage elastic modulus at 80 ° C. can be set to 900 MPa or more, and even if the polarizing plate bonded with the polarizer and the protective film through the adhesive is exposed to a severe temperature history, cracking of the polarizer is caused. Can be prevented. On the other hand, when the amount exceeds 85% by weight, the amount of the aliphatic epoxy compound (A2) and the divinyl ether compound (A3) described below becomes relatively small, and the photocurable adhesive contemplated in the present invention. It is difficult to achieve both low viscosity and improved adhesion between the polarizer and the protective film. The alicyclic 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 photocationically curable component (A). If the amount of the alicyclic diepoxy compound (A1) in the photocationic curable component (A) is 60% by weight or more, the storage elastic modulus at 80 ° C. after curing the photocurable adhesive containing the alicyclic diepoxy compound (A1) is Approximately 1,000 MPa or more.

  Moreover, the storage elastic modulus after hardening the photocurable adhesive containing it by making the quantity of an aliphatic epoxy compound (A2) into 1 weight% or more among the whole photocationic curable components (A). While maintaining a high value, the adhesion between the polarizer and the protective film can be increased. On the other hand, when the amount exceeds 40% 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 and the storage elastic modulus after curing of the photocurable adhesive more preferable, the aliphatic epoxy compound (A2) in the photocationic curable component (A) The amount is more preferably 5% by weight or more and 25% by weight or less.

  Furthermore, the viscosity of a photocurable adhesive agent is reduced by making the quantity of a divinyl ether compound (A3) into 1 weight% or more among the whole photocationic curable components (A), and favorable coating property is shown. At the same time, the effect of increasing the adhesive force between the polarizer and the protective film is exhibited. On the other hand, when the amount exceeds 30% by weight, the storage elastic modulus after curing the photocurable adhesive is not sufficiently high, and the polarization is obtained by bonding the polarizer and the protective film through the adhesive. When the plate is exposed to a severe temperature history, the polarizer is prone to cracking. In order to make the adhesive force between the polarizer and the protective film and the storage elastic modulus after curing of the photocurable adhesive more preferable, the amount of the divinyl ether compound (A3) in the photocationic curable component (A) Is more preferably 5 wt% or more and 25 wt% or less.

  In addition to the above alicyclic diepoxy compound (A1), aliphatic epoxy compound (A2), and aliphatic or alicyclic divinyl ether compound (A3), the quantitative ratio of these three components is within the range described above. In addition, other photocationic curable components may be blended within a range not impairing the functions of these three components. Examples of other photocationic curable components include epoxy compounds not corresponding to the above (A1) and (A2), oxetane compounds, and the like. Epoxy compounds not corresponding to (A1) and (A2) include compounds having only one epoxy group directly bonded to the alicyclic ring in the molecule, aromatic epoxy compounds, and the like. An oxetane compound is a compound having an oxetane ring (4-membered ether).

(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.

  Among these photocationic polymerization initiators, especially aromatic sulfonium salts have ultraviolet absorption characteristics even in the wavelength region near 300 nm, and therefore provide 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.

(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) and the photocationic polymerization initiator (B) 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 the main component of the photocurable adhesive. What is necessary is just to select suitably according to the objective.

(Preparation of photocurable adhesive)
A photocurable adhesive agent can be prepared by mixing the photocationic curable component (A) and photocationic polymerization initiator (B) which were demonstrated until now, and another component as needed. 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.

  The photocurable adhesive after preparation can have a low viscosity of 70 mPa · sec or less at 25 ° C. For this reason, when it applies to the polarizer or protective film mentioned later, it becomes what was excellent in workability | operativity and can form a thin and uniform coating film. The viscosity of the photocurable adhesive is more preferably 60 mPa · sec or less.

[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 has a thickness of, for example, about 20 to 100 μm.

  The polarizer described above is a step of uniaxially stretching a polyvinyl alcohol-based resin film, a step of dyeing a polyvinyl alcohol-based resin film with a dichroic dye, and a step of adsorbing the dichroic dye, a polyvinyl on which the dichroic dye is adsorbed It is manufactured through a process of treating an alcohol-based resin film with an aqueous boric acid solution.

  Uniaxial stretching of the polyvinyl alcohol-based resin film may be performed before dyeing with a dichroic dye, may be performed simultaneously with dyeing with a dichroic dye, or may be performed after dyeing with a dichroic dye. Good. When uniaxial stretching is performed after dyeing with a dichroic dye, this 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 an adhesive. 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 storage elastic modulus of the adhesive bond layer which is a hardened | cured material of a photocurable adhesive agent as mentioned above can be raised, and the adhesiveness between a polarizer and a protective film can be improved. Therefore, the adhesive strength by the 180 degree peeling test between the polarizer and the protective film can be made to be 0.2 N / 25 mm or more. Here, the 180 degree peeling test is performed according to JIS K 6854 as shown in the examples described later.
-2: 1999 Performed according to "Adhesive-Peeling adhesion strength test method-Part 2: 180 degree peeling".

[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 plates include birefringent films made 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 substrate film, etc. 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. Moreover, the photocationic curable component and the photocationic polymerization initiator 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) Alicyclic diepoxy compound (a1) 3,4-epoxycyclohexylmethyl 3,4-epoxycyclohexanecarboxylate: obtained from Daicel Chemical Industries, Ltd., trade name “Celoxide 2021P” .

(A2) Aliphatic epoxy compound (a2) 1,4-butanediol diglycidyl ether: obtained from Nagase Chemkex Corporation, trade name “Denacol EX-121”.

(A3) Divinyl ether compound (a3) Diethylene glycol divinyl ether: obtained from Nippon Carbide Industries Co., Ltd.

(AX) Other photocationic curable compounds (ax) 2-hydroxyethyl vinyl ether: also known as ethylene glycol monovinyl ether, obtained from Nippon Carbide Industries, 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) Triarylsulfonium salt photocationic polymerization initiator: Obtained from Sun Apro Co., Ltd. in the form of a 50% propylene carbonate solution, trade name “CPI-100P”.

[Examples 1 and 2 and Comparative Examples 1 to 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. After mixing 25 parts, defoaming was performed to prepare a photocurable adhesive liquid.

(2) Viscosity measurement of adhesive liquid at 25 ° C. For each adhesive liquid prepared in (1) above, using a rotary viscoelasticity measuring device “Physica MCR 301” manufactured by Anton Paar, at a temperature of 25 ° C. The viscosity was measured. The results are shown in Table 1.

(3) Measurement of storage elastic modulus of cured adhesive at 80 ° C A coating machine [Daiichi Rika Co., Ltd.] on one side of a polyethylene terephthalate film (trade name “Toyobo Ester Film E7002”) obtained from Toyobo ) Manufactured bar coater], each adhesive solution prepared in the above (1) was applied so that the film thickness after curing was about 30 μm. Next, the adhesive was cured by irradiating ultraviolet rays with a “D bulb” manufactured by Fusion UV Systems Co., Ltd. so that the integrated light amount was 3,000 mJ / cm ² . This was cut into a size of 5 mm × 30 mm, and the polyethylene terephthalate film was peeled off to obtain a cured film of adhesive. The cured film is gripped at a distance of 2 cm between the grips using the dynamic viscoelasticity measuring device “DVA-220” manufactured by IT Measurement Control Co., Ltd. The storage elastic modulus at a temperature of 80 ° C. was determined by setting the frequency of 1 Hz and the rate of temperature increase to 3 ° C./min. The results are shown in Table 1.

(4) 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. The adhesive solution prepared above was applied to the treated surface using a bar coater so that the film thickness after curing was about 2 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 Further, the same adhesive solution as above was applied using a bar coater so that the film thickness after curing was about 2 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, using an ultraviolet irradiation device with a belt conveyor (the lamp uses a “D bulb” manufactured by Fusion UV Systems), the ultraviolet light is adjusted so that the integrated light quantity becomes 250 mJ / cm ^2. To cure the adhesive. Thus, a polarizing plate in which protective films were bonded to both sides of the polarizer was produced.

(5) 180 degree peeling test The polarizing plate produced in the above (4) 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 shown 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.

  From the results in Table 1, in Comparative Example 1 in which the photocationic curable component (A) was a binary system of an alicyclic diepoxy compound (A1) and an aliphatic epoxy compound (A2), the storage elastic modulus of the cured adhesive was In addition, although the adhesive force (peeling strength) between the polarizer and the protective film is good, the viscosity of the adhesive liquid exceeds 100 mPa · sec, and the coatability is not sufficient.

  In Comparative Examples 2 and 3, the divinyl ether compound (a3) was blended with the alicyclic diepoxy compound (A1) for the purpose of reducing the viscosity of the adhesive liquid, and the viscosity reducing effect of the adhesive liquid was observed. The adhesive force (peeling strength) between the polarizer and the protective film was not sufficient. In Comparative Examples 4 and 5, ethylene glycol monovinyl ether (ax) was blended with the alicyclic diepoxy compound (A1) for the purpose of lowering the viscosity of the adhesive liquid, and the viscosity reducing effect of the adhesive liquid was recognized. However, the adhesive force (peeling strength) between the polarizer and the protective film was even smaller than in Comparative Examples 2 and 3. In Comparative Example 5 in which the proportion of ethylene glycol monovinyl ether (ax) in the photocationically curable component (A) is increased to 30%, the storage elastic modulus when the adhesive is cured is extremely low. This is presumably because the molecular weight of the cured product (polymer) did not increase due to the hydroxyl group of ethylene glycol monovinyl ether (ax). Thus, since the storage elastic modulus of the adhesive layer after curing is low, the protective function of the polarizer is insufficient when the polarizing plate receives, for example, a severe temperature history.

  In Comparative Example 6, as the cationic curable component (A), in addition to the alicyclic diepoxy compound (A1) and the aliphatic epoxy compound (A2), ethylene glycol monovinyl ether (ax) was blended. In this case, the adhesive force (peeling strength) between the polarizer and the protective film was not sufficient, although the viscosity was reduced and the viscosity reduction effect of the adhesive liquid was observed.

  On the other hand, in addition to the alicyclic diepoxy compound (A1) and the aliphatic epoxy compound (A2), Examples 1 and 2 in which a predetermined amount of the divinyl ether compound (A3) was blended had a low viscosity of the adhesive solution. While excellent in coatability, the cured adhesive gives a high storage modulus, so even when the polarizing plate is subjected to a severe temperature history, it is excellent in the protective function of the polarizer, the polarizer is difficult to break, and the polarizer The adhesive strength (peeling strength) between the protective film and the protective film also gives a high value.

Claims (11)

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) For 100 parts by weight of the photocation curable component,
As a polymerization initiator, it contains only 1 to 10 parts by weight of (B) a cationic photopolymerization initiator,
The photocationic curable component (A) is based on the total amount thereof.
(A1) 50 to 85% by weight of an alicyclic diepoxy compound,
(A2) 1-40% by weight of an aliphatic epoxy compound and (A3) 1-30% by weight of an aliphatic or alicyclic divinyl ether compound
A polarizing plate characterized by being formed from a photocurable adhesive containing. The divinyl ether compound (A3) has the following formula (III)
_{CH 2 = CH-O-Z} -O-CH = CH 2 (III)
Z 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 bivalent divalent having 6 to 18 carbon atoms having an alicyclic structure. The polarizing plate according to claim 1, which is a hydrocarbon group. The polarizing plate according to claim 2, wherein the divinyl ether compound (A3) is diethylene glycol divinyl ether. On one surface of the polarizer, via said adhesive layer, according to any one of claims 1 to 3, protective film ultraviolet absorber consisting of acetyl cellulose resin film are blended is stuck Polarizing plate. A protective film made of a resin film selected from the group consisting of an amorphous polyolefin resin, a polyester resin, and a chain polyolefin resin is bonded to one surface of the polarizer via the adhesive layer. The polarizing plate according to any one of claims 1 to 4 . The polarizing plate according to any one of claims 1 to 5 , wherein an adhesive strength by a 180 degree peeling test between the polarizer and the protective film is 0.2 N / 25 mm or more. A laminated optical member comprising a laminate of the polarizing plate according to any one of claims 1 to 6 and another optical layer. The laminated optical member according to claim 7 , wherein the other optical layer includes a retardation film. Method for producing 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 And
On one or both of the bonding surfaces of the polarizer and the protective film,
(A) For 100 parts by weight of the photocation curable component,
As a polymerization initiator, it contains only 1 to 10 parts by weight of (B) a cationic photopolymerization initiator,
The photocationic curable component (A) is based on the total amount thereof.
(A1) 50 to 85% by weight of an alicyclic diepoxy compound,
(A2) 1 to 40% by weight of an aliphatic epoxy compound, and
(A3) 1-30% by weight of an aliphatic or alicyclic divinyl ether compound
Form a coating layer of the photocurable adhesive containing,
Bonding the polarizer and the protective film through the coating layer,
The coating layer is cured by irradiating active energy rays.
The manufacturing method of the said polarizing plate characterized by the above-mentioned. The manufacturing method according to claim 9, wherein the photocurable adhesive has a viscosity at 25 ° C. before curing of 70 mPa · sec or less. An adhesive used for a polarizing plate,
(A) For 100 parts by weight of the photocation curable component,
As a polymerization initiator, it contains only 1 to 10 parts by weight of (B) a cationic photopolymerization initiator,
The photocationic curable component (A) is based on the total amount thereof.
(A1) 50 to 85% by weight of an alicyclic diepoxy compound,
(A2) 1-40% by weight of an aliphatic epoxy compound and (A3) 1-30% by weight of an aliphatic or alicyclic divinyl ether compound
Contains photocurable adhesive.