CN107090259B

CN107090259B - Photocurable adhesive, and polarizing plate and laminated optical member using same

Info

Publication number: CN107090259B
Application number: CN201710083973.XA
Authority: CN
Inventors: 久米悦夫; 古川达也; 佐藤和德; 松土和彦; 松本拓也
Original assignee: Adeka Corp; Sumitomo Chemical Co Ltd
Current assignee: Adeka Corp; Sumitomo Chemical Co Ltd
Priority date: 2016-02-17
Filing date: 2017-02-16
Publication date: 2021-06-01
Anticipated expiration: 2037-02-16
Also published as: CN107090259A

Abstract

The invention provides a photocurable adhesive and a polarizing plate using the same, wherein the photocurable adhesive is used for bonding a thermoplastic resin film on a polyvinyl alcohol polarizer, comprises an epoxy compound not containing an aromatic ring as a main component, and further comprises a photocationic curable component (A) and a photocationic polymerization initiator (B), and the photocationic curable component (A) contains a1 st epoxy compound (A1) represented by the formula (I).

Description

Photocurable adhesive, and polarizing plate and laminated optical member using same

Technical Field

The present invention relates to a photocurable adhesive for bonding a thermoplastic resin film to a polyvinyl alcohol-based polarizing plate, and a polarizing plate and a laminated optical member using the same.

Background

The polarizing plate is useful as one of optical members constituting a liquid crystal display device. Polarizing plates generally have a structure in which protective films are laminated on both sides of a polarizer, and are incorporated in a liquid crystal display device. It is known that a protective film is provided only on one side of a polarizing plate, but a single protective film is not bonded to the other side, and a film having another optical function is bonded to the other side as a protective film in many cases. As a method for producing a polarizing plate, a method of subjecting a uniaxially stretched polyvinyl alcohol resin film dyed with a dichroic dye to a boric acid treatment, washing with water, and then drying is widely used.

In general, the protective film is adhered immediately after the polarizing plate is washed with water and dried as described above. This is because the physical strength of the dried polarizing plate is weak, and there is a problem that the polarizing plate is easily broken in the machine direction when it is wound. Therefore, usually, an aqueous adhesive, which is an aqueous solution of a polyvinyl alcohol resin, is applied to the polarizing plate immediately after drying, and protective films are simultaneously bonded to both surfaces of the polarizing plate via the adhesive. Conventionally, a triacetyl cellulose film having a thickness of 30 to 100 μm is used as a protective film.

Triacetylcellulose has an excellent advantage as a protective film in that it has excellent transparency, various surface treatment layers and optical functional layers are easily formed on the surface thereof, and it has high moisture permeability, and drying after bonding to a polarizing plate using the above-mentioned aqueous adhesive can be smoothly performed, but a polarizing plate using triacetylcellulose as a protective film has a problem that deterioration is easily caused under humid heat, for example, at a temperature of 70 ℃ and a relative humidity of 90%, because of its high moisture permeability. Therefore, also known are: in the case where an amorphous polyolefin resin, for example, a norbornene resin, which has a lower moisture permeability than triacetyl cellulose, is used as the protective film, the amorphous polyolefin resin is typically used as the norbornene resin.

When a protective film comprising a resin having low moisture permeability is bonded to a polyvinyl alcohol polarizer, there are problems such as insufficient bonding strength and poor appearance of the resulting polarizing plate when an aqueous solution of a polyvinyl alcohol resin conventionally used for bonding a polyvinyl alcohol polarizer and a triacetyl cellulose film is used as an adhesive. This is because a resin film having low moisture permeability is generally hydrophobic, or because water as a solvent cannot be sufficiently dried due to low moisture permeability. On the other hand, it is also known that different types of protective films are bonded to both surfaces of a polarizing plate. For example, the following solutions are also proposed: a protective film made of a resin having low moisture permeability such as an amorphous polyolefin resin is bonded to one surface of the polarizing plate, and a protective film made of a resin having high moisture permeability such as a cellulose resin typified by triacetyl cellulose is bonded to the other surface of the polarizing plate.

Therefore, as an adhesive for imparting high adhesion between a protective film made of a resin having low moisture permeability and a polyvinyl alcohol-based polarizing plate and also between a resin having high moisture permeability such as a cellulose-based resin and a polyvinyl alcohol-based polarizing plate, use of a photocurable adhesive has been attempted. For example, jp 2008-257199 a discloses a technique in which a photocurable adhesive obtained by combining an alicyclic epoxy compound and an epoxy compound having no alicyclic epoxy group and further blending a photocationic polymerization initiator is used for bonding a polarizing plate and a protective film, but the adhesive strength is insufficient and the polarizing plate and the protective film are peeled off during cutting.

Further, jp 2014-037477 a proposes a photocurable adhesive containing a naphthalene-based epoxy resin, but it is not suitable for optical use because it is colored by light irradiation.

Disclosure of Invention

The present invention has an object to provide a photocurable adhesive for bonding a thermoplastic resin film to a polyvinyl alcohol-based polarizer, which has a high storage modulus of an adhesive layer as a cured product and can bond the polyvinyl alcohol-based polarizer and the thermoplastic resin film with a strong adhesive force, thereby producing a polarizing plate having high durability. Another object of the present invention is to provide a polarizing plate obtained by bonding a polyvinyl alcohol-based polarizer and a thermoplastic resin film to each other using the photocurable adhesive, and a laminated optical member obtained by laminating another optical layer on the polarizing plate and suitable for use in a liquid crystal display device.

The invention provides a photocurable adhesive, a polarizing plate and a laminated optical member shown below.

[1] A photocurable adhesive for bonding a thermoplastic resin film to a vinyl alcohol-based polarizer,

which comprises an epoxy compound containing no aromatic ring as a main component,

the photo-curable adhesive comprises a photo-cation curable component (A) and a photo-cation polymerization initiator (B),

the photo cation curable component (A) contains a1 st epoxy compound (A1) represented by the following formula (I),

wherein n represents an integer of 1 or more, and V represents an n-valent group including a fused ring composed of an alicyclic ring.

[2] The photocurable adhesive according to [1], wherein the photocationic curable component (A) contains 5 to 85 wt% of the 1 st epoxy compound (A1) and 15 to 85 wt% of the 2 nd epoxy compound (A2) represented by the following formula (II) based on the entire amount of the component.

(in the formula, R¹And R²Each independently represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, and may have an alicyclic structure when the number of carbon atoms in the alkyl group is 3 or more;

x represents an oxygen atom, a C1-6 alkanediyl group or a 2-valent group represented by any one of the following formulae (IIa) to (IId),

wherein, Y¹～Y⁴Each represents an alkanediyl group having 1 to 20 carbon atoms, and may have an alicyclic structure when the number of carbon atoms is 3 or more;

a and b each represent an integer of 0 to 20. )

[3] The photocurable adhesive according to [1] or [2], wherein the photocationic-curable component (A) further contains 1 to 70 wt% of a3 rd epoxy compound (A3) represented by the following formula (III) based on the whole amount of the component.

(wherein Z represents a branched alkylene group having 3 to 8 carbon atoms, or formula-C_mH_2m－Z¹－C_nH_2n-a 2-valent radical of formula (I), wherein-Z¹-represents-O-, -CO-O-or-O-CO-, one of m and n represents an integer of 1 or more and the other represents an integer of 2 or more, the total of both being 8 or less, and C_mH_2mAnd C_nH_2nOne of them represents a branched 2-valent saturated hydrocarbon group. )

[4] The photocurable adhesive according to any one of [1] to [3], further comprising 0.1 to 5 parts by weight of at least one compound selected from the group consisting of an anthracene compound represented by the following formula (IVa) and a naphthalene compound represented by the following formula (IVb) per 100 parts by weight of the photocationic curable component (A),

(in the formula, R³And R⁴Each independently represents a hydrogen atom, an alkyl group having 1 to 6 carbon atoms or an alkoxyalkyl group having 2 to 12 carbon atoms, R⁵Represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms. )

(in the formula, R⁶And R⁷Each independently represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms. )

[5] The photocurable adhesive according to any one of [1] to [4], wherein the moisture content is more than 0 part by weight and not more than 4 parts by weight relative to 100 parts by weight of the photocationic curable component (A).

[6] A polarizing plate, comprising:

polyvinyl alcohol-based polarizing plate, and

a thermoplastic resin film laminated on at least one surface of the polyvinyl alcohol-based polarizing plate via a cured product of the photocurable adhesive according to any one of [1] to [5 ].

[7] A laminated optical member comprising the polarizing plate according to [6] and a laminate of 1 or more other optical layers.

[8] The laminated optical member of claim [7], wherein the other optical layer comprises a phase difference plate.

According to the present invention, a photocurable adhesive that is less likely to dissolve a thermoplastic resin film, has a high storage modulus of an adhesive layer as a cured product thereof, and can bond a polyvinyl alcohol-based polarizing plate and a thermoplastic resin film with a strong adhesive force, thereby enabling the production of a polarizing plate having high durability can be provided. The photocurable adhesive of the present invention can provide a polarizing plate having excellent durability and a laminated optical member using the same. Therefore, according to the photocurable adhesive of the present invention, it is possible to provide a polarizing plate in which peeling between the polarizer and the thermoplastic resin film is not easily generated even when cutting is performed, and the polarizer is not easily broken even when a cooling-heating cycle test is performed, for example, and a laminated optical member using the same.

Detailed Description

< Photocurable adhesive >

The photocurable adhesive of the present invention is an adhesive for bonding a thermoplastic resin film to a polyvinyl alcohol-based polarizer, and contains a photocationic-curable component (a) and a photocationic polymerization initiator (B) as main components, and an epoxy compound containing no aromatic ring.

The photocurable adhesive contains an epoxy compound containing no aromatic ring as a main component. The epoxy compound containing no aromatic ring is an epoxy compound other than an aromatic epoxy compound, and is hereinafter referred to as an aliphatic epoxy compound. "epoxy compound" means a compound having at least 1 epoxy group in the molecule. The aliphatic epoxy compound as the main component may contain 2 or more epoxy compounds. The "main component" means that the content of the aliphatic epoxy compound is 50% by weight or more based on 100% by weight of the photocurable adhesive. The content of the aliphatic epoxy compound is preferably 60% by weight or more, more preferably 70% by weight or more, further preferably 80% by weight or more, and further preferably 90% by weight or more.

The aliphatic epoxy compound may be an epoxy compound having an alicyclic ring, or an epoxy compound which does not contain an alicyclic ring and is composed of only a linear hydrocarbon structure and/or a branched hydrocarbon structure. The aliphatic epoxy compound may contain an unsaturated bond such as a double bond, or may contain a hetero atom (oxygen atom, nitrogen atom, sulfur atom, halogen atom, etc.) other than the oxygen atom contained in the epoxy group.

(1) Photo cation curable component (A)

The photocationic curable component (a) is a component which imparts adhesion by polymerization curing by irradiation with active energy rays, and contains the 1 st epoxy compound (a1) described in detail below. The photocationic curable component (a) preferably contains the 1 st epoxy compound (a1) and also contains the 2 nd epoxy compound (a2) or the 3 rd epoxy compound (A3) described in detail below, and more preferably contains the 1 st epoxy compound (a1) and also contains at least the 2 nd epoxy compound (a 2). The photocationic curable component (a) preferably further contains a2 nd epoxy compound (a2) and A3 rd epoxy compound (A3) in addition to the 1 st epoxy compound (a 1).

(1-1) epoxy Compound No. 1 (A1)

The 1 st epoxy compound (A1) is a glycidyl compound represented by the following formula (I).

In the formula (I), n represents the number of glycidyloxy groups bonded to V and is an integer of 1 or more. V represents an n-valent group including a condensed ring composed of an alicyclic ring. The "fused ring composed of alicyclic rings" means a fused ring constructed only of alicyclic rings, in other words, a fused ring which is not an aromatic ring or a fused ring which does not include an aromatic ring. The condensed ring may be a 2-or 3-membered ring, or a polycyclic ring having 4 or more rings, but is preferably a 2-or 3-membered ring. The condensed ring may contain an unsaturated bond such as a double bond, a hetero atom (an oxygen atom, a nitrogen atom, a sulfur atom, a halogen atom, etc.), and other substituents (an alkyl group, etc.). The number of carbon atoms of each alicyclic ring constituting the fused ring is usually 4 to 8, preferably 5 or 6, independently.

When the photocationic curable component (a) contains the 1 st epoxy compound (a1), it is advantageous in reducing the ability of the photocurable adhesive to dissolve the thermoplastic resin film bonded to the polyvinyl alcohol-based polarizing plate (hereinafter, this ability is also referred to simply as "dissolving power"), and in improving the storage modulus of a cured product of the photocurable adhesive and the adhesion between the polyvinyl alcohol-based polarizing plate and the thermoplastic resin film. Further, it is also advantageous in improving the coloring resistance of the photocurable adhesive. For example, when the n-valent group V includes an aromatic condensed ring, such a photocurable adhesive containing a large amount of an epoxy compound may be colored due to absorption of the aromatic condensed ring itself in the visible light region. Even when the n-valent group V includes an aromatic condensed ring that is not absorbed in the visible light range, there is a high possibility that the photo-curable adhesive is colored due to a reaction of forming a dimer or an oligomer of the dimer or more by irradiation with active energy rays.

The n-valent group V may be an n-valent group including a condensed ring (for example, a condensed ring of a polycyclic hydrocarbon system, a crosslinked hydrocarbon system, or the like) composed of an alicyclic ring, or an n-valent group composed of the condensed ring and 1 or 2 or more linking groups bonded to the condensed ring. The linking group is a group linking the condensed ring and the glycidyloxy group of the 1 st epoxy compound (a 1). When the n-valent group V is composed of the above condensed ring and 1 or 2 or more linking groups bonded to the condensed ring, each of the condensed ring and the linking group may have a bond to a glycidyloxy group, or only the linking group may have a bond.

n is an integer of usually 6 or less, and is preferably an integer of 1 to 4, more preferably 2 or 3, from the viewpoint of improving the storage modulus and the adhesive strength and from the viewpoint of reducing the viscosity of the photocurable adhesive (photocurable adhesive before curing).

Examples of the linking group linking the condensed ring and the glycidyloxy group of the 1 st epoxy compound (a1) include a 2-valent aliphatic hydrocarbon group. The aliphatic hydrocarbon group having a valence of 2 may contain an alicyclic ring, or may not contain an alicyclic ring and may be composed of only a linear hydrocarbon structure and/or a branched hydrocarbon structure. The aliphatic hydrocarbon group having a valence of 2 is preferably an alkylene group having 1 to 8 carbon atoms, and more preferably an alkylene group having 1 to 4 carbon atoms. The number of carbon atoms is more preferably 1 to 3, and particularly preferably 1 or 2 (i.e., methylene or ethylene). At least 1 CH constituting alkylene₂The radicals may be replaced by oxygen or sulfur atoms. The alkylene group may be linear or branched.

Specific examples of the n-valent group V including a condensed ring composed of an alicyclic ring are shown in the following table. In the following tables, Q is each independently a single bond or the above-mentioned linking group. Denotes a bond to the glycidyloxy group of the 1 st epoxy compound (a 1). Specific examples of the group V shown below are 2-valent groups (n is 2), but the group V is not limited to the 2-valent group as described above.

[ TABLE 1]

Further, as the group V, the following groups can be also mentioned.

(1-2) epoxy Compound 2 (A2)

The 2 nd epoxy compound (a2) is an alicyclic diepoxy compound represented by the following formula (II).

When the photocationic curable component (a) contains the 2 nd epoxy compound (a2) in addition to the 1 st epoxy compound (a1), it is advantageous in improving the storage modulus of a cured product of the photocurable adhesive and the adhesion between the polyvinyl alcohol-based polarizing plate and the thermoplastic resin film. Further, it is also advantageous in improving the coloring resistance of the photocurable adhesive.

In the above formula (II), R¹And R²Each independently represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, and may have an alicyclic structure when the number of carbon atoms in the alkyl group is 3 or more. In the formula (II), when the position of the cyclohexane ring bonded to X is the 1-position (therefore, the positions of the epoxy groups in 2 cyclohexane rings are all 3, 4-positions), the alkyl group may be bonded to any of the 1-position to 6-position. The alkyl group may be linear, or may be branched when the number of carbon atoms is 3 or more. As described above, when the number of carbon atoms is 3 or more, the resin composition may have an alicyclic structure. Typical examples of the alkyl group having an alicyclic structure include a cyclopentyl group and a cyclohexyl group.

In the formula (II), X connecting 23, 4-epoxycyclohexane rings is oxygen atom, C1-6 alkanediyl or 2-valent group represented by any one of the following formulas (IIa) to (IId).

The alkanediyl group is a concept including an alkylene group and an alkylidene group, and the alkylene group may be linear, may be branched when the number of carbon atoms is 3 or more, and may have an alicyclic structure. A in the formula (IIa) and b in the formula (IId) each represent an integer of 0 to 20. a and b are preferably integers of 0 to 12, more preferably 0 to 8, and still more preferably 0 to 4, respectively.

When X is a 2-valent group represented by any one of the formulae (IIa) to (IId), the linking group Y in each formula¹、Y²、Y³And Y⁴Respectively having 1 to c carbon atomsThe alkanediyl group of 20 may have an alicyclic structure when the alkanediyl group has 3 or more carbon atoms. These alkanediyl groups may be linear, or may be branched when the number of carbon atoms is 3 or more. As described above, when the number of carbon atoms is 3 or more, the resin composition may have an alicyclic structure. Typical examples of the alkanediyl group having an alicyclic structure include a cyclopentylene group and a cyclohexylene group.

The 2 nd epoxy compound (A2) represented by the formula (II) will be specifically described below. The compound in which X in the formula (II) is a 2-valent group represented by the formula (IIa) and a in the formula is 0 is an ester of 3, 4-epoxycyclohexylmethanol (to which an alkyl group having 1 to 6 carbon atoms may be bonded to the cyclohexane ring) and 3, 4-epoxycyclohexanecarboxylic acid (to which an alkyl group having 1 to 6 carbon atoms may be bonded to the cyclohexane ring). Specific examples thereof include:

3, 4-epoxycyclohexanecarboxylic acid 3, 4-epoxycyclohexylmethyl ester [ formula (II) (wherein X is a 2-valent group represented by formula (IIa) wherein a is 0 ], wherein R is a hydrogen atom¹＝R²H, a compound of,

3, 4-epoxy-6-methylcyclohexanecarboxylic acid 3, 4-epoxy-6-methylcyclohexylmethyl ester [ in the formula (II) having the same X as above, R¹6-methyl, R²6-methyl compound ],

3, 4-epoxy-1-methylcyclohexanecarboxylic acid 3, 4-epoxy-1-methylcyclohexylmethyl ester [ in the formula (II) having the same X as above, R¹1-methyl, R²1-methyl compound (I),

3, 4-epoxy-3-methylcyclohexanecarboxylic acid 3, 4-epoxy-3-methylcyclohexylmethyl ester [ in the formula (II) having the same X as above, R¹3-methyl, R²3-methyl group, and the like.

The compound of formula (II) wherein X is a 2-valent group represented by formula (IIb) is an ester of an alkylene glycol with 3, 4-epoxycyclohexanecarboxylic acid (to which an alkyl group having 1 to 6 carbon atoms may be bonded to the cyclohexane ring).

The compound of formula (II) wherein X is a group having a valence of 2 represented by formula (IIc) is an ester of an aliphatic dicarboxylic acid with 3, 4-epoxycyclohexylmethanol (to which an alkyl group having 1 to 6 carbon atoms may be bonded to the cyclohexane ring).

The compound of formula (II) in which X is a 2-valent group represented by formula (IId) is an ether of 3, 4-epoxycyclohexylmethanol (in which an alkyl group having 1 to 6 carbon atoms may be bonded to the cyclohexane ring) (in the case where b is 0), or an etherate of an alkylene glycol or polyalkylene glycol with 3, 4-epoxycyclohexylmethanol (in which an alkyl group having 1 to 6 carbon atoms may be bonded to the cyclohexane ring) (in the case where b > 0).

Among them, an alicyclic diepoxy compound in which X in the formula (II) is a 2-valent group represented by the formula (IIa) is one of preferable compounds in terms of improvement of the storage modulus of a cured product of the photocurable adhesive and the adhesion between the polyvinyl alcohol-based polarizing plate and the thermoplastic resin film. X in formula (II) is a 2-valent group alicyclic diepoxy compound represented by formula (IIa), and a in formula (IIa) is preferably an integer of 0 to 4, more preferably an integer of 0 to 2, and further preferably 0 or 1.

(1-3) epoxy Compound No. 3 (A3)

The 3 rd epoxy compound (A3) is a diglycidyl compound represented by the following formula (III).

When the photocationic curable component (a) contains the 3 rd epoxy compound (A3) in addition to the 1 st epoxy compound (a1), and particularly contains the 2 nd epoxy compound (a2) and the 3 rd epoxy compound (A3) in addition to the 1 st epoxy compound (a1), it is advantageous in improving the storage modulus of a cured product of the photocurable adhesive and the adhesion between the polyvinyl alcohol-based polarizing plate and the thermoplastic resin film. Further, it is also advantageous in improving the coloring resistance of the photocurable adhesive.

In the formula (III), Z is a branched alkylene group having 3 to 8 carbon atoms or a group represented by the formula-C_mH_2m－Z¹－C_nH_2n-a 2-valent radical as indicated. Wherein，－Z¹-is-O-, -C (═ O) -O-, or-O-C (═ O) -, one of m and n is an integer of 1 or more, the other is an integer of 2 or more, the total of both is 8 or less, and C is_mH_2mAnd C_nH_2nOne of them is a branched 2-valent saturated hydrocarbon group. When the photocationic curable component (a) contains the 3 rd epoxy compound (A3) having a branched structure in Z in addition to the 1 st epoxy compound (a1), it is advantageous in that the above-mentioned dissolving power is reduced, and it is also advantageous in that the viscosity of the photocurable adhesive is reduced.

By reducing the dissolving power of the photocurable adhesive, the occurrence of bubble defects in the cured adhesive layer can be suppressed. The reason is presumed to be: the viscosity increase of the photocurable adhesive due to the melting of the photocurable adhesive into the thermoplastic resin film can be suppressed.

The number of carbon atoms of the branched alkylene group is preferably an integer of 3 to 6 from the viewpoint of improving the storage modulus and the adhesive force and from the viewpoint of reducing the viscosity of the photocurable adhesive.

In the formula (III), the compound wherein Z is a branched alkylene group is a diglycidyl ether of a branched alkanediol. Specific examples thereof include propylene glycol diglycidyl ether, 1, 3-butanediol diglycidyl ether, 1, 2-butanediol diglycidyl ether, neopentyl glycol diglycidyl ether, 3-methyl-1, 5-pentanediol diglycidyl ether, 2-methyl-1, 8-octanediol diglycidyl ether, and 1, 4-cyclohexanedimethanol.

Z in the formula (III) is the above-mentioned formula-C_mH_2m－Z¹－C_nH_2nThe compound having a valence of 2 represented by the formula (I) corresponds to the case where Z is a branched alkylene group and the C-C bond of the alkylene group is interrupted by-O-, -C (═ O) -O-or-O-C (═ O) -.

Among them, from the viewpoint of improving the storage modulus and the adhesive force, and from the viewpoint of reducing the viscosity and the dissolving power of the photocurable adhesive, a diglycidyl compound of a branched alkylene group having 3 to 8 carbon atoms, preferably 3 to 6 carbon atoms is one of the preferable compounds in the formula (III).

(1-4) content of 1 st epoxy compound (A1) to 3 rd epoxy compound (A3)

The photocationic curable component (a) may be composed of only the 1 st epoxy compound (a 1). However, from the viewpoint of improving the storage modulus and the adhesion force, the photocationic curable component (a) preferably contains the 1 st epoxy compound (a1) and the 2 nd epoxy compound (a2) or the 3 rd epoxy compound (A3), more preferably contains the 1 st epoxy compound (a1) and at least the 2 nd epoxy compound (a2), and still more preferably contains the 1 st epoxy compound (a1) and the 2 nd epoxy compound (a2) and the 3 rd epoxy compound (A3).

From the viewpoint of improving the storage modulus and the adhesion force, it is preferable that: the content of the 1 st epoxy compound (a1) in the photocationic curable component (a) is preferably 5 to 85% by weight, more preferably 10 to 50% by weight, still more preferably 12 to 40% by weight, and still more preferably 15 to 30% by weight, based on the total amount of the photocationic curable component (a), that is, 100% by weight of the photocationic curable component (a), and the 2 nd epoxy compound (a2), or the 2 nd epoxy compound (a2) and the 3 rd epoxy compound (A3) are contained in the photocationic curable component (a). If the content of the 1 st epoxy compound (a1) in the photocationic curable component (a) is too small, the dissolving power becomes large, bubble defects are likely to occur, and the storage modulus is also likely to become low. When the content of the 1 st epoxy compound (a1) in the photocationic curable component (a) is too large, the viscosity of the photocurable adhesive tends to increase, and the curing shrinkage upon irradiation with an active energy ray increases, whereby the adhesive force tends to decrease.

When the 2 nd epoxy compound (a2) is contained in the photocationic curable component (a), the content of the 2 nd epoxy compound (a2) in the photocationic curable component (a) is preferably 15 to 85% by weight, more preferably 20 to 85% by weight, even more preferably 25 to 60% by weight, and even more preferably 30 to 50% by weight, based on the total amount of the photocationic curable component (a), from the viewpoint of improving the storage modulus. If the content of the 2 nd epoxy compound (a2) in the photocationic curable component (a) is too small, curing upon irradiation with active energy rays tends to be insufficient, and thus the adhesion force between the polyvinyl alcohol-based polarizing plate and the thermoplastic resin film tends to be low. The content of the 2 nd epoxy compound (a2) in the photocationic curable component (a) may be more than 85% by weight, but is preferably 85% by weight or less in order to contain the 3 rd epoxy compound (A3) in a sufficient amount. From the viewpoint of improving the adhesion force, the content of the 2 nd epoxy compound (a2) in the photocationic curable component (a) is preferably 65 wt% or less, more preferably 60 wt% or less, and still more preferably 55 wt% or less, based on the total amount of the photocationic curable component (a).

When the 3 rd epoxy compound (A3) is contained in the photocationic curable component (a), the content of the 3 rd epoxy compound (A3) in the photocationic curable component (a) is preferably 1 to 70% by weight, more preferably 5 to 60% by weight, even more preferably 5 to 55% by weight, and even more preferably 10 to 50% by weight, based on the total amount of the photocationic curable component (a), from the viewpoint of reducing the viscosity. From the viewpoint of reducing the viscosity of the photocurable adhesive and improving the adhesion force, it is also advantageous to contain 1% by weight or more of the 3 rd epoxy compound (a 3). In order to more effectively achieve a reduction in viscosity of the photocurable adhesive before curing and an improvement in adhesion between the polarizing plate and the thermoplastic resin film due to the cured product thereof, the content of the 3 rd epoxy compound (a3) is preferably 25% by weight or more based on the total amount of the photocationic curable component (a). If the content of the 3 rd epoxy compound (a3) in the photocationic curable component (a) is too large, curing upon irradiation with active energy rays tends to become insufficient, and the adhesive force tends to be low. From the viewpoint of the storage modulus and the dissolving power, the content of the 3 rd epoxy compound (a3) in the photocationic curable component (a) is preferably 60% by weight or less, more preferably 55% by weight or less, and still more preferably 50% by weight or less, based on the total amount of the photocationic curable component (a).

From the viewpoint of improving the storage modulus and the adhesion force, the total content of the 1 st epoxy compound (a1), the 2 nd epoxy compound (a2), and the 3 rd epoxy compound (A3) in the content of the aliphatic epoxy compound is usually 50% by weight or more, preferably 60% by weight or more, more preferably 70% by weight or more, further preferably 80% by weight or more, further preferably 90% by weight or more, particularly preferably 95% by weight or more, and most preferably 100% by weight, of the total content of the aliphatic epoxy compound (A3) in 100% by weight.

(1-5) other Photocationically curable component

The photocationic curable component (a) may contain other photocationic curable compounds than the 1 st epoxy compound (a1), the 2 nd epoxy compound (a2), and the 3 rd epoxy compound (A3). Examples of other photocationic-curable compounds include: an oxetane compound; a vinyl ether compound; epoxy resins other than aliphatic epoxy compounds (aromatic epoxy compounds); aliphatic epoxy compounds other than the 1 st epoxy compound (a1), the 2 nd epoxy compound (a2) and the 3 rd epoxy compound (A3).

(2) Photo cation polymerization initiator (B)

The photocurable adhesive contains a photocationic polymerization initiator (B). The photo cation curable component (a) can be cured by cationic polymerization by irradiation with an active energy ray, thereby forming an adhesive layer. The photo cation polymerization initiator (B) is a polymerization initiator which generates a cationic species or lewis acid by irradiation of active energy rays such as visible rays, ultraviolet rays, X-rays, and electron beams to initiate a polymerization reaction of the photo cation curable component (a). The photo cation polymerization initiator (B) has a photocatalytic action, and therefore, even when it is mixed with the photo cation curable component (a), it is excellent in storage stability and handling properties. Examples of the compound which can be used as the photo cation polymerization initiator (B) and generates a cationic species or a lewis acid by irradiation with an active energy ray include: an aromatic diazonium salt; onium salts such as aromatic iodonium salts and aromatic sulfonium salts; iron-arene complexes, and the like.

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

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

Examples of the aromatic sulfonium salt include: triphenylsulfonium hexafluorophosphate, triphenylsulfonium hexafluoroantimonate, triphenylsulfonium tetrakis (pentafluorophenyl) borate, 4 ' -bis [ diphenylsulfonium ] diphenylsulfide bishexafluorophosphate, 4 ' -bis [ di (. beta. -hydroxyethoxy) phenylsulfonium ] diphenylsulfide bishexafluoroantimonate, 4 ' -bis [ di (. beta. -hydroxyethoxy) phenylsulfonium ] diphenylsulfide bishexafluorophosphate, 7- [ bis (p-toluoyl) sulfonium ] -2-isopropylthioxanthone hexafluoroantimonate, 7- [ bis (p-toluoyl) sulfonium ] -2-isopropylthioxanthone tetrakis (pentafluorophenyl) borate, 4-phenylcarbonyl-4 ' -diphenylsulfonium-diphenylsulfide hexafluorophosphate, 4- (p-tert-butylphenylcarbonyl) -4 ' -diphenylsulfonium-diphenylsulfide hexafluoroantimonate, 4- (p-tert-butylphenylcarbonyl) -4 ' -bis (p-toluoyl) sulfonium-diphenylsulfide tetrakis (pentafluorophenyl) borate.

Examples of the iron-arene complex include: xylene-cyclopentadienyl iron (II) hexafluoroantimonate, cumene-cyclopentadienyl iron (II) hexafluorophosphate, xylene-cyclopentadienyl iron (II) tris (trifluoromethylsulfonyl) methide.

The cationic photopolymerization initiator (B) may be used alone in 1 kind or in combination of 2 or more kinds. Among the above, aromatic sulfonium salts are preferably used because they have ultraviolet absorption characteristics even in the wavelength region of about 300nm and provide an adhesive layer having excellent curability and good mechanical strength and adhesive strength.

The content of the photo cation polymerization initiator (B) is preferably 1 to 10 parts by weight, more preferably 2 to 6 parts by weight, based on 100 parts by weight of the entire photo cation curable component (a). By containing the photo cation polymerization initiator (B) in an amount of 1 part by weight or more, the photo cation curable component (a) can be sufficiently cured, and the polarizing plate obtained can be provided with high mechanical strength and adhesive strength. On the other hand, when the content is increased, the ionic substance in the cured product increases, and thus the hygroscopicity of the cured product increases, and there is a possibility that the durability of the polarizing plate is lowered, and therefore the content of the photo cation polymerization initiator (B) is preferably 10 parts by weight or less with respect to 100 parts by weight of the photo cation curable component (a).

(3) Other components which can be blended in the photocurable adhesive

The photocurable adhesive may contain other components known to be blended in a general photocurable resin or adhesive. Preferable examples of the other components include a photosensitizing agent and a photosensitizing assistant. The photosensitizer is a compound which exhibits a maximum absorption at a wavelength longer than the maximum absorption wavelength exhibited by the photo cation polymerization initiator (B) and promotes the polymerization initiation reaction by the photo cation polymerization initiator (B). In addition, the photosensitizing assistant is a compound that further promotes the action of the photosensitizing agent. It is sometimes preferable to add such a photosensitizing agent or photosensitizing aid depending on the type of thermoplastic resin film.

Examples of the photosensitizing agent and the photosensitizing assistant include anthracene compounds and naphthalene compounds. Examples of the anthracene compound include compounds represented by the following formula (IVa).

In the formula, R³And R⁴Each independently represents a hydrogen atom, an alkyl group having 1 to 6 carbon atoms or an alkoxyalkyl group having 2 to 12 carbon atoms, R⁵Represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms. Specific examples of the anthracene compound represented by the formula (IVa) include the following compounds.

9, 10-dimethoxy anthracene,

9, 10-diethoxyanthracene,

9, 10-dipropoxyanthracene,

9, 10-diisopropoxylanthracene,

9, 10-dibutoxyanthracene,

9, 10-dipentyloxy anthracene,

9, 10-dihexyloxyanthracene,

9, 10-bis (2-methoxyethoxy) anthracene,

9, 10-bis (2-ethoxyethoxy) anthracene,

9, 10-bis (2-butoxyethoxy) anthracene,

9, 10-bis (3-butoxypropoxy) anthracene,

2-methyl-or 2-ethyl-9, 10-dimethoxyanthracene,

2-methyl-or 2-ethyl-9, 10-diethoxyanthracene,

2-methyl-or 2-ethyl-9, 10-dipropoxyanthracene,

2-methyl-or 2-ethyl-9, 10-diisopropoxylanthracene,

2-methyl-or 2-ethyl-9, 10-dibutoxyanthracene,

2-methyl-or 2-ethyl-9, 10-dipentyloxy anthracene,

2-methyl-or 2-ethyl-9, 10-dihexyloxyanthracene, and the like.

Examples of the naphthalene-based compound include compounds represented by the following formula (IVb).

In the formula, R⁶And R⁷Each independently represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms. Specific examples of the anthracene compound represented by the formula (IVb) include the following compounds.

4-methoxy-1-naphthol,

4-ethoxy-1-naphthol,

4-propoxy-1-naphthol,

4-butoxy-1-naphthol,

4-hexyloxy-1-naphthol,

1, 4-dimethoxynaphthalene,

1-ethoxy-4-methoxynaphthalene,

1, 4-diethoxynaphthalene,

1, 4-dipropoxy naphthalene,

1, 4-dibutoxynaphthalene, and the like.

By adding the above-mentioned photosensitizer and photosensitizing auxiliary agent to the photocurable adhesive, the curability of the adhesive can be improved more than when the photosensitizer and photosensitizing auxiliary agent are not added. Such an effect can be obtained by blending the photosensitizing agent and the photosensitizing auxiliary agent in an amount of 0.1 part by weight or more per 100 parts by weight of the photocationic curable component (a).

The content of the anthracene compound is preferably 0.1 to 0.3 parts by weight with respect to 100 parts by weight of the photocationic-curable component (a) from the viewpoint of maintaining a neutral gray color of the polarizing plate and from the viewpoint of suppressing problems such as precipitation during low-temperature storage. From the viewpoint of suppressing the occurrence of problems such as precipitation during low-temperature storage, the content of the naphthalene compound is preferably 5 parts by weight or less, and more preferably 3 parts by weight or less, based on 100 parts by weight of the photocationic-curable component (a).

The photocurable adhesive may contain other additive components than the photosensitizer and the photosensitizing assistant as long as the effects of the present invention are not impaired. As other additive components, there may be mentioned: thermal cationic polymerization initiator, alcohol compound (polyhydric alcohol, etc.), ion scavenger, antioxidant, light stabilizer, chain transfer agent, tackifier, thermoplastic resin, filler, flow control agent, plasticizer, defoaming agent, leveling agent, pigment, organic solvent, etc. When the additive component is contained, the content thereof is preferably 1000 parts by weight or less based on 100 parts by weight of the photocationic-curable component (a).

(4) Moisture content of photo-curable adhesive

The photocurable adhesive may contain moisture. The content of water is usually 4 parts by weight or less, preferably 3 parts by weight or less, and more preferably less than 3 parts by weight, based on 100 parts by weight of the photocationic-curable component (a). When the amount of water is a little more than 0 part by weight, the adhesive strength between the polyvinyl alcohol-based polarizing plate and the thermoplastic resin film is improved. The content of water is usually 0.01 part by weight or more, preferably 0.03 part by weight or more, and more preferably 0.04 part by weight or more, based on 100 parts by weight of the photocationic-curable component (a). However, if the moisture content is too high, separation between the photocurable adhesive and water occurs, and the photocurable adhesive cannot be uniformly applied to the surface of the polarizing plate or the thermoplastic resin film, or the curability of the photocurable adhesive deteriorates. The photocurable adhesive may be intentionally added with water, and in this case, purified water such as distilled water or pure water may be used without particular limitation. The moisture may be moisture derived from raw materials, moisture mixed in a manufacturing process, or the like. The moisture content of the photocurable adhesive was measured by Karl Fischer (Karl Fischer) volumetric method.

(5) Physical Properties of Photocurable adhesive

The photocurable adhesive of the present invention can have low viscosity as described above, and thus can exhibit excellent coating suitability when a thermoplastic resin film is bonded to a polyvinyl alcohol-based polarizing plate using the photocurable adhesive. Specifically, the photocurable adhesive of the present invention can exhibit a viscosity in the range of 2 to 300 mPas at 25 ℃. The viscosity referred to herein is a viscosity in a state substantially not including a solvent. When the viscosity is less than 2mPa · s, the polarizing plate may be peeled from the thermoplastic resin film during conveyance after bonding, and when the viscosity exceeds 300mPa · s, bubbles may be easily mixed between the polarizing plate and the thermoplastic resin film, that is, the adhesive layer, when the polarizing plate and the thermoplastic resin film are bonded via the photocurable adhesive, particularly when the adhesive layer is thin. The viscosity is preferably 5 to 200 mPas, more preferably 10 to 150 mPas, still more preferably 100 mPas or less, and particularly preferably 80 mPas or less. The viscosity of the photocurable adhesive was measured using an E-type viscometer.

The photocurable adhesive of the present invention can be used for manufacturing a polarizing plate by bonding a thermoplastic resin film to a polyvinyl alcohol-based polarizing plate. In this case, when the adhesive dissolves the thermoplastic resin film, bubble defects may be generated in the adhesive layer of the polarizing plate due to the dissolution as described above. The photocurable adhesive of the present invention can be an adhesive having a small ability to dissolve a thermoplastic resin film (dissolving power) as described above. When the 3 rd epoxy compound (a3) containing a branched alkylene group, preferably a branched alkylene group, Z in the formula (III) is contained, it is advantageous in suppressing the increase in the dissolving power. The photocurable adhesive of the present invention may be used in which the weight reduction of the thermoplastic resin film bonded to the polyvinyl alcohol-based polarizing plate is 0 to 30 wt%, more preferably 25 wt% or less, when the thermoplastic resin film is immersed at 23 ℃ for 2 days. The photocurable adhesive of the present invention can have a small dissolving power for, for example, an acetyl cellulose-based resin film after stretching. Examples of the stretched acetyl cellulose resin film include those having an in-plane retardation value of 10nm or more, and further 50nm or more at a wavelength of 590 nm.

The weight reduction when the thermoplastic resin film was immersed in the photocurable adhesive was determined as follows. That is, first, the thermoplastic resin film is cut into an appropriate size, and the weight thereof is determined. Next, the cut thermoplastic resin film was immersed in a photocurable adhesive prepared in a liquid state and kept at 23 ℃, and left to stand for 2 days, and then taken out, and the adhesive attached to the surface was wiped off, and the weight thereof was determined. Then, the weight loss after immersion was determined by the following equation.

Weight reduction (%) { (weight of film before immersion-weight of film after immersion)/weight of film before immersion } × 100

< polarizing plate >

The polarizing plate of the present invention comprises a polyvinyl alcohol-based polarizer and a thermoplastic resin film bonded to at least one surface of the polyvinyl alcohol-based polarizer via an adhesive layer which is a cured product of the photocurable adhesive.

In the polarizing plate of the present invention, the cured adhesive layer may be an adhesive layer having a high storage modulus and excellent adhesion between the polarizer and the thermoplastic resin film. In the polarizing plate of the present invention, the storage modulus of the adhesive layer may be, for example, 1000MPa or more, and further 1500MPa or more at 80 ℃. In the polarizing plate of the present invention, the peel strength between the polarizer and the thermoplastic resin film may be 0.5N/25mm or more, 0.6N/25mm or more, further 0.7N/25mm or more, particularly 1.0N/25mm or more. The storage modulus at 80 ℃ of the adhesive layer and the peel strength between the polarizing plate and the thermoplastic resin film were measured as described in the examples below.

(1) Polyvinyl alcohol polarizing plate

The polyvinyl alcohol-based polarizing plate is composed of a polyvinyl alcohol-based resin film in which a dichroic dye is adsorbed and oriented. The polyvinyl alcohol resin constituting the polarizing plate is obtained by saponifying a polyvinyl acetate resin. Examples of the polyvinyl acetate resin include polyvinyl acetate which is a homopolymer of vinyl acetate, and a copolymer of vinyl acetate and another monomer copolymerizable therewith. Examples of the other monomer copolymerizable with vinyl acetate include unsaturated carboxylic acids, olefins, vinyl ethers, and unsaturated sulfonic acids. The saponification degree of the polyvinyl alcohol resin is usually 85 to 100 mol%, preferably 98 to 100 mol%. The polyvinyl alcohol resin may be further modified, and for example, polyvinyl formal, polyvinyl acetal, or the like modified with aldehydes may be used. The polymerization degree of the polyvinyl alcohol resin is usually 1000 to 10000, preferably 1500 to 5000.

The polarizing plate can be produced by subjecting a polyvinyl alcohol resin film to uniaxial stretching, a step of dyeing the polyvinyl alcohol resin film with a dichroic dye to adsorb the dichroic dye, and a step of treating the polyvinyl alcohol resin film adsorbed with the dichroic dye with an aqueous boric acid solution.

The uniaxial stretching 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. When uniaxial stretching is performed after dyeing with a dichroic dye, the uniaxial stretching may be performed before boric acid treatment or in boric acid treatment. The uniaxial stretching may be performed in the above-mentioned plural stages. The method of uniaxial stretching is not particularly limited, and uniaxial stretching may be performed between rolls having different peripheral speeds, or uniaxial stretching may be performed using a hot roll. The stretching may be performed in a dry manner by stretching in the air, or may be performed in a wet manner by stretching in a state of being swollen by a solvent. The draw ratio is usually about 4 to 8 times.

The polyvinyl alcohol resin film is immersed in an aqueous solution containing a dichroic dye, whereby the dichroic dye can be adsorbed. As the dichroic dye, iodine or a dichroic organic dye may be used.

When iodine is used as the dichroic dye, a method of immersing a polyvinyl alcohol resin film in an aqueous solution containing iodine and potassium iodide to dye the film is generally used. The content of iodine in the aqueous solution is usually about 0.01 to 0.5 parts by weight relative to 100 parts by weight of water, and the content of potassium iodide is usually about 0.5 to 10 parts by weight relative to 100 parts by weight of water. The temperature of the aqueous solution is usually about 20 to 40 ℃, and the immersion time (dyeing time) in the 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 a polyvinyl alcohol-based resin film in an aqueous solution containing a water-soluble dichroic organic dye to perform dyeing is generally employed. The content of the dichroic organic dye in the aqueous solution is usually 1X 10 relative to 100 parts by weight of water^－3～1×10^－2About the weight portion. The aqueous solution may also contain inorganic salts such as sodium sulfate. The temperature of the aqueous solution is usually about 20 to 80 ℃, and the immersion time (dyeing time) in the aqueous solution is usually about 30 to 300 seconds.

The boric acid treatment after dyeing is performed by dipping the dyed polyvinyl alcohol resin film in an aqueous boric acid solution. The boric acid content in the aqueous boric acid solution is usually about 2 to 15 parts by weight, preferably about 5 to 12 parts by weight, based on 100 parts by weight of water. In the case of using iodine as the dichroic dye, the aqueous boric acid solution preferably contains potassium iodide. The content of potassium iodide in the aqueous boric acid solution is usually about 2 to 20 parts by weight, preferably 5 to 15 parts by weight, based on 100 parts by weight of water. The immersion time in the aqueous boric acid solution is usually about 100 to 1200 seconds, preferably about 150 to 600 seconds, and more preferably about 200 to 400 seconds. The temperature of the aqueous boric acid solution is usually 50 ℃ or higher, preferably 50 to 85 ℃.

The polyvinyl alcohol resin film after the boric acid treatment is usually subjected to a water washing treatment. The water washing treatment can be performed by, for example, immersing the boric acid-treated polyvinyl alcohol resin film in water. After washing with water, the resultant was dried to obtain a polarizing plate. The temperature of the water for washing treatment is usually about 5 to 40 ℃, and the immersion time is usually about 2 to 120 seconds. The subsequent drying treatment can be performed by using a hot air dryer or a far infrared heater. The drying temperature is usually 40 to 100 ℃. The drying time is usually about 120 to 600 seconds. The thickness of the polyvinyl alcohol-based polarizing plate may be about 2 to 50 μm (e.g., 5 to 20 μm).

(2) Thermoplastic resin film

The thermoplastic resin film may be an acetyl cellulose resin film represented by triacetyl cellulose, which has been most widely used as a protective film for a polarizing plate, or a transparent resin film having a lower moisture permeability than triacetyl cellulose. The moisture permeability of triacetyl cellulose is about 400g/m²And/24 hr or so. The moisture permeability of the thermoplastic resin film was measured by the cup method specified in JIS Z0208 at a temperature of 40 ℃ and a relative humidity of 90%.

The thermoplastic resin film may be an unstretched film or a uniaxially or biaxially stretched film. The thermoplastic resin film may be, for example, a protective film for a polarizing plate, or an optical compensation film such as a retardation film.

In one preferred embodiment, the thermoplastic resin film bonded to at least one surface of the polarizing plate is made of an acetyl cellulose resin. The acetyl cellulose resin film may contain an ultraviolet absorber. In another preferred embodiment, the thermoplastic resin film to be bonded to at least one surface of the polarizing plate is a thermoplastic resin film having a lower moisture permeability than triacetylcellulose, for example, a thermoplastic resin film having a moisture permeability of 300g/m²A thermoplastic resin film of 24hr or less. Examples of the resin constituting such a thermoplastic resin film having low moisture permeability include amorphous polyolefin resins, polyester resins, (meth) acrylic resins, polycarbonate resins, and chain polyolefin resins. Among them, amorphous polyolefin resins, polyester resins, and chain polyolefin resins are preferably used. In another preferred embodiment, a1 st thermoplastic resin film containing an acetyl cellulose resin is bonded to one surface of a polarizing plate via an adhesive layer which is a cured product of the photocurable adhesive of the present invention, and a2 nd thermoplastic resin film containing a transparent resin having a lower moisture permeability as described above is bonded to the other surface of the polarizing plate via an adhesive layer which is a cured product of the photocurable adhesive of the present invention.

The acetyl cellulose resin is a resin in which at least a part of hydroxyl groups in cellulose is esterified with acetic acid, and may be a mixed ester in which a part is esterified with acetic acid and a part is esterified with another acid. Specific examples of the acetyl cellulose resin include triacetyl cellulose, diacetyl cellulose, cellulose acetate propionate, and cellulose acetate butyrate.

The amorphous polyolefin resin may be a polymer having a polymerized unit of a cyclic olefin, such as norbornene, tetracyclododecene (also referred to as "dimethanonaphthalene"), or a compound having a substituent bonded thereto, or may be a copolymer obtained by copolymerizing a cyclic olefin with a linear olefin and/or an aromatic vinyl compound. In the case of a homopolymer of a cyclic olefin or a copolymer of 2 or more cyclic olefins, double bonds remain due to ring-opening polymerization, and therefore, a hydrogenated resin thereof is generally used as the amorphous polyolefin resin. Among them, the thermoplastic norbornene-based resin is a representative resin.

The polyester resin is a polymer obtained by polycondensation of a dibasic acid and a glycol, and is typically polyethylene terephthalate. The (meth) acrylic resin is a polymer containing methyl methacrylate as a main monomer, and may be a copolymer of methyl methacrylate and a monomer other than methyl methacrylate (e.g., a (meth) acrylic monomer such as an acrylic ester like methyl acrylate, an aromatic vinyl compound, etc.) in addition to a homopolymer of methyl methacrylate. In the present specification, "(meth) acrylic" means at least one selected from acrylic acid and methacrylic acid.

The polycarbonate-based resin is a polymer having a carbonate bond-O-CO-O-) in the main chain, and is typically a polymer obtained by polycondensation of bisphenol A and phosgene. The chain polyolefin resin is a polymer mainly composed of a chain olefin such as ethylene or propylene, and may be a homopolymer or a copolymer. Of these, a homopolymer of propylene and a copolymer obtained by copolymerizing propylene with a small amount of ethylene are typical.

The thermoplastic resin film may contain a known additive を as needed. Examples of the known additives include lubricants, antiblocking agents, heat stabilizers, ultraviolet absorbers, antioxidants, antistatic agents, light stabilizers, impact modifiers, and surfactants. The ultraviolet absorber includes salicylate-based compounds, benzophenone-based compounds, benzotriazole-based compounds, cyanoacrylate-based compounds, nickel complex salt-based compounds, and the like. However, since the thermoplastic resin film laminated on the polarizing plate must have transparency, the amount of these additives is preferably limited to a minimum.

As the thermoplastic resin film, a film provided with an optical compensation function may be used. Further, an acetyl cellulose resin film may be used. Examples of such optical compensation films include: a retardation film in which an acetyl cellulose resin contains a compound having a function of adjusting a retardation, a retardation film in which a compound having a function of adjusting a retardation is coated on a surface of an acetyl cellulose resin, a retardation film obtained by uniaxially or biaxially stretching an acetyl cellulose resin, or the like. As the optical compensation film, a film containing another thermoplastic resin may also be used.

The thickness of the thermoplastic resin film is usually about 5 to 200 μm, preferably 10 to 120 μm, and more preferably 10 to 100 μm. The thermoplastic resin film may have various surface treatment layers (coating layers) such as a hard coat layer, an antireflection layer, an antiglare layer, an antistatic layer, and a light diffusion layer on the surface opposite to the surface to be bonded to the polarizing plate.

(3) Manufacture of polarizing plates

A thermoplastic resin film was bonded to at least one surface of the polarizer using the above-mentioned photocurable adhesive, thereby obtaining a polarizing plate. Specifically, the coating layer of the photocurable adhesive is formed on the bonding surface of the polarizing plate and/or the thermoplastic resin film, and after the polarizing plate and the thermoplastic resin film are bonded via the coating layer, the coating layer of the uncured photocurable adhesive is cured by irradiation with an active energy ray, thereby fixing the thermoplastic resin film to the polarizing plate. In forming the coating layer of the photocurable adhesive, various coating methods such as a doctor blade, a wire bar, die coating, comma coating, and gravure coating can be used. Further, a method of casting an adhesive between the polarizing plate and the thermoplastic resin film while continuously supplying the polarizing plate and the thermoplastic resin film so that the bonding surface therebetween is on the inside may be employed.

The viscosity of the photocurable adhesive can be adjusted by using a solvent according to the application method of the photocurable adhesive. The solvent is not particularly limited as long as it can dissolve the photocurable adhesive well without degrading the optical performance of the polarizing plate. For example, organic solvents such as hydrocarbons typified by toluene and esters typified by ethyl acetate can be used. However, when the solvent is contained, a drying step for removing the solvent is required before the irradiation with the active energy ray, and therefore it is preferable to use no solvent as much as possible.

The thickness of the cured adhesive layer may be arbitrarily set according to the characteristic design of the polarizing plate, but a small thickness is preferable from the viewpoint of reducing the cost of the adhesive material. Generally, the thickness is 0.01 to 20 μm, preferably 0.1 to 10 μm, and more preferably 0.5 to 5 μm. When the thickness of the adhesive layer is reduced, bubble incorporation into the adhesive layer and reduction in adhesion and durability are likely to occur, but the photocurable adhesive of the present invention can effectively suppress such contamination. When the adhesive layer is too thick, the reaction rate of the adhesive decreases, and the moist heat resistance of the polarizing plate tends to be poor.

When the thermoplastic resin film is bonded to only one surface of the polarizing plate, for example, a pressure-sensitive adhesive layer for bonding to another optical member such as a liquid crystal cell may be directly provided on the other surface of the polarizing plate. On the other hand, when thermoplastic resin films are bonded to both surfaces of the polarizing plate, the thermoplastic resin films may be composed of the same type of resin or different types of resins. The thermoplastic resin film bonded to one surface of the polarizing plate is bonded using the photocurable adhesive of the present invention described above, but the thermoplastic resin film bonded to the other surface of the polarizing plate may be bonded using the photocurable adhesive of the present invention, or may be bonded using another adhesive.

Before the thermoplastic resin film is bonded to the polarizing plate, the bonding surface of the thermoplastic resin film and/or the polarizing plate may be subjected to an easy-bonding treatment such as saponification treatment, corona treatment, plasma treatment, undercoating treatment, anchor coating treatment, flame treatment, or the like.

The light source for irradiating the coating layer of the photocurable adhesive with active energy rays may be any light source that can generate ultraviolet rays, electron rays, X-rays, or the like. Particularly, for example, a low-pressure mercury lamp, a medium-pressure mercury lamp, a high-pressure mercury lamp, an ultra-high-pressure mercury lamp, a chemical lamp, a black light lamp, a microwave-excited mercury lamp, a metal halide lamp, or the like having an emission distribution at a wavelength of 400nm or less is preferably used.

The irradiation intensity of the active energy ray of the photocurable adhesive is not particularly limited, and the irradiation intensity in the wavelength region effective for activation of the photocationic polymerization initiator (B) is preferably 0.1 to 3000mW/cm². If it is less than 0.1mW/cm²The reaction time is too long, and if the reaction time exceeds 3000mW/cm²There is a possibility that the photocurable adhesive is yellowed and the polarizing plate is deteriorated due to heat radiated from the lamp and heat generated during polymerization of the photocurable adhesive.

The light irradiation time of the photocurable adhesive is not particularly limited, and it is preferable that the cumulative light amount represented by the product of the irradiation intensity and the irradiation time is 10 to 5000mJ/cm²The mode of (2) is set. If notFoot 10mJ/cm²If the cumulative light amount exceeds 5000mJ/cm, the generation of active species from the photo cation polymerization initiator (B) may be insufficient, and the curing of the resulting adhesive layer may be insufficient²The irradiation time is very long, which is disadvantageous in improving productivity.

When the thermoplastic resin films are bonded to both sides of the polarizing plate, the irradiation with the active energy ray may be performed from any thermoplastic resin film side, but for example, when one thermoplastic resin film contains an ultraviolet absorber and the other thermoplastic resin film does not contain an ultraviolet absorber, it is preferable to irradiate the active energy ray from the thermoplastic resin film side not containing an ultraviolet absorber in terms of effectively utilizing the irradiated active energy ray and increasing the curing speed.

The polarizing plate obtained by curing the photocurable adhesive has a peel strength between the polarizer and the thermoplastic resin film, measured as described in the section of examples, which will be described later, of preferably 0.5N/25mm or more, more preferably 0.6N/25mm or more, and still more preferably 0.7N/25mm or more. When the peel strength is less than 0.5N/25mm, peeling may occur between the polarizer and the adhesive layer when the polarizing plate is cut.

< stacked optical Member and liquid Crystal display device >

The polarizing plate of the present invention can be manufactured as a laminated optical member by laminating optical layers having optical functions other than the polarizing plate. Typically, a laminated optical member is produced by laminating and bonding an optical layer on a thermoplastic resin film of a polarizing plate via an adhesive or a pressure-sensitive adhesive, and for example, the thermoplastic resin film may be bonded to one surface of a polarizing plate via a photocurable pressure-sensitive adhesive of the present invention, and the optical layer may be laminated and bonded to the other surface of the polarizing plate via an adhesive or a pressure-sensitive adhesive. In the latter case, when the photocurable adhesive of the present invention is used as an adhesive for bonding a polarizing plate and an optical layer, the optical layer may be a thermoplastic resin film. More than 2 optical layers may be stacked on the polarizing plate.

As the optical layer laminated on the polarizing plate, a polarizing plate disposed on the back side of the liquid crystal cell includes a reflective layer, a semi-transmissive reflective layer, a light diffusion layer, a light collecting plate, a brightness enhancement film, and the like laminated on the opposite side of the polarizing plate from the liquid crystal cell. The polarizing plate disposed on the front side of the liquid crystal cell and/or the polarizing plate disposed on the back side of the liquid crystal cell include a retardation plate (retardation film) laminated on the liquid crystal cell side of the polarizing plate.

The reflective layer, the semi-transmissive reflective layer, and the light diffusion layer are provided to form a laminated optical member as a reflective polarizing plate, a semi-transmissive reflective polarizing plate, and a diffusion polarizing plate, respectively. The reflective polarizing plate is used for a liquid crystal display device of a type that reflects incident light from a viewing side to perform display, and can easily make the liquid crystal display device thin because a light source such as a backlight can be omitted. The transflective polarizing plate is used in a liquid crystal display device of a type that reflects light in a bright place and displays light from a backlight in a dark place. The reflective polarizing plate can be produced by forming a reflective layer by attaching a foil made of a metal such as aluminum or a vapor deposited film to a thermoplastic resin film on a polarizing plate, for example. The semi-transmissive polarizing plate can be produced by using the reflective layer as a semi-reflective mirror, or by bonding a reflective plate containing pearl pigment and exhibiting light transmittance to a polarizing plate. On the other hand, the diffusion type polarizing plate can be produced by forming a fine uneven structure on the surface by various methods such as a method of matting a thermoplastic resin film on a polarizing plate, a method of coating a resin containing fine particles, and a method of bonding a film containing fine particles.

The laminated optical member may be a polarizing plate for both reflection and diffusion. The polarizing plate for both reflection and diffusion can be produced by, for example, providing a reflection layer reflecting (japanese: reflection) the uneven structure on the fine uneven structure surface of the diffusion-type polarizing plate. The reflective layer having a fine uneven structure diffuses incident light by diffuse reflection, thereby preventing directivity and glare and suppressing unevenness of brightness. Further, the resin layer or film containing fine particles has an advantage that unevenness in brightness can be suppressed because incident light and reflected light thereof are diffused. The reflective layer reflecting the surface fine uneven structure can be formed by directly attaching a metal to the surface of the fine uneven structure by, for example, vapor deposition such as vacuum vapor deposition, ion plating, or sputtering, or plating. The fine particles blended to form the fine uneven surface structure may be inorganic fine particles such as silicon oxide, aluminum oxide, titanium oxide, zirconium oxide, tin oxide, indium oxide, cadmium oxide, and antimony oxide having an average particle diameter of 0.1 to 30 μm, or organic fine particles such as crosslinked or uncrosslinked polymers.

The light-collecting plate is a member used for optical path control and the like, and may be formed as a prism array sheet, a lens array sheet, or a sheet with dots (ドット) attached thereto.

The brightness enhancement film is a member used for the purpose of enhancing the brightness of a liquid crystal display device, and specific examples thereof include: a reflective polarization separator in which a plurality of films having different refractive index anisotropy are laminated to generate anisotropy in reflectance, a circular polarization separator in which an alignment film of cholesteric liquid crystal polymer or an alignment liquid crystal layer thereof is supported on a film substrate, and the like.

A retardation plate (retardation film) is used for the purpose of compensating for a phase difference due to a liquid crystal cell, and the like. The concrete examples include: birefringent films formed of stretched films of various plastics and the like, films in which a discotic liquid crystal or a nematic liquid crystal is fixed in orientation, films in which the above-mentioned liquid crystal layer is formed on a film substrate, and the like. When a liquid crystal layer is formed on a film substrate, an acetyl cellulose resin film such as triacetyl cellulose is preferably used as the film substrate.

Examples of the plastic forming the birefringent film include: non-crystalline polyolefin resins, polycarbonate resins, (meth) acrylic resins, chain polyolefin resins such as polypropylene, polyvinyl alcohol, polystyrene, polyarylate, polyamide, and the like. The stretched film may be a film treated by an appropriate means such as uniaxial or biaxial. For the purpose of controlling optical characteristics such as a wide frequency band, 2 or more retardation plates may be used in combination.

From the viewpoint of effective optical compensation when applied to a liquid crystal display device, it is preferable to use a laminated optical member including a retardation plate (retardation film) as an optical layer other than the polarizing plate. The retardation value (in-plane and thickness direction) of the retardation plate is adjusted according to the liquid crystal cell to be used.

The laminated optical member may be a 2-layer or 3-layer or more laminated body formed by combining a polarizing plate and 1 or 2 or more layers selected from the above various optical layers depending on the purpose of use. In this case, the various optical layers forming the laminated optical member are integrated with the polarizing plate using an adhesive or a pressure-sensitive adhesive (also referred to as a pressure-sensitive adhesive), and the adhesive or the pressure-sensitive adhesive used therefor is not particularly limited as long as the adhesive layer or the pressure-sensitive adhesive layer can be formed satisfactorily. From the viewpoints of simplicity of the bonding operation, prevention of occurrence of optical strain, and the like, a binder is preferably used. As the binder, a binder containing a (meth) acrylic polymer, a silicone polymer, a polyester, a polyurethane, a polyether, or the like as a matrix polymer can be used. Among them, it is preferable to select and use an adhesive which is excellent in optical transparency, retains appropriate wettability and cohesive force, is excellent in adhesion to a substrate, has weather resistance, heat resistance and the like, and does not cause problems such as lifting or peeling under heating and humidifying conditions, like a (meth) acrylic adhesive. Among the (meth) acrylic adhesives, a (meth) acrylic copolymer having a weight average molecular weight of 10 ten thousand or more is useful as a matrix polymer, and the (meth) acrylic copolymer having a weight average molecular weight of 10 ten thousand or more is obtained as follows: an alkyl (meth) acrylate having an alkyl group having 20 or less carbon atoms such as a methyl group, an ethyl group, or a butyl group is blended with a functional group-containing (meth) acrylic monomer such as (meth) acrylic acid or hydroxyethyl (meth) acrylate so that the glass transition temperature is preferably 25 ℃ or less, more preferably 0 ℃ or less.

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

The pressure-sensitive adhesive layer may contain, as necessary, fillers, pigments, colorants, antioxidants, ultraviolet absorbers, and the like, which are composed of glass fibers, glass beads, resin particles, metal powder, other inorganic powder, and the like. The ultraviolet absorber includes salicylate-based compounds, benzophenone-based compounds, benzotriazole-based compounds, cyanoacrylate-based compounds, nickel complex salt-based compounds, and the like.

The liquid crystal display device includes a liquid crystal cell and the polarizing plate or the laminated optical member disposed on at least one surface thereof. The polarizing plate and the laminated optical member may be laminated on one side or both sides of the liquid crystal cell via an adhesive layer. The polarizing plate and the laminated optical member may be respectively a polarizing plate and a laminated optical member in which an adhesive layer with adhesive for bonding to an adhesive layer of a liquid crystal cell is laminated on the outer surface layer thereof. The liquid crystal cell to be used is arbitrary, and various liquid crystal cells such as an active matrix drive type liquid crystal cell typified by a thin film transistor type and a simple matrix drive type liquid crystal cell typified by a super twisted nematic type can be used to form a liquid crystal display device.

Examples

The present invention will be described more specifically below with reference to examples and comparative examples, but the present invention is not limited to these examples. Hereinafter, "parts" and "%" indicating the amount or content of the compound are based on weight unless otherwise specified. The photocationic-curable component (a), the photocationic polymerization initiator (B), and the photosensitizer/photosensitizing auxiliary agent (C) used in the following examples are shown below and represented by the following symbols. In table 2, the photocationic-curable component (a), the photocationic polymerization initiator (B), and the photosensitizer/photosensitization assistant (C) are abbreviated as (a), (B), and (C), respectively.

[ Photocationically curable component (A) ]

(a1)3, 4-Epoxycyclohexanecarboxylic acid 3, 4-epoxycyclohexylmethyl ester [ in the above formula (II), R¹＝R²＝H、X＝－C(＝O)－O－CH₂-the compound of (a),

(a2) Neopentyl glycol diglycidyl ether [ in the above formula (III), Z ═ CH₂C(CH₃)₂CH₂-the compound of (a),

(a3) "Adeka Resin EP-4088S" manufactured by ADEKA K.K. (wherein V is a 2-valent group obtained by removing 2 OH groups from tricyclodecanedimethanol and n is 2),

(a4) Oxetane Compound manufactured by Toyo Synthesis Ltd., trade name "OXT-221"),

(a5) Naphthalene type epoxy resins available from DIC corporation under the trade name "HP-4032D"),

(a6) Isosorbide diglycidyl ether.

[ Photocationic polymerization initiator (B) ]

(b1) A 50% solution of propylene carbonate in a mixture of a compound represented by the following formula (V) and a compound represented by the following formula (VI).

[ photosensitizing agent-photosensitizing auxiliary (C) ]

(c1)1, 4-diethoxynaphthalene,

(c2)9, 10-dibutoxyanthracene.

< examples 1 to 15, comparative examples 1 to 3 >

(1) Preparation of photo-curable adhesive

The components shown in tables 2 and 3 were mixed in the mixing ratios shown in tables 2 and 3, and then defoamed to prepare a photocurable adhesive (liquid). The unit of the blending amount of each component in tables 2 and 3 is "part". The photo cation polymerization initiator (B) was a 50% propylene carbonate solution, and the amount of the photo cation polymerization initiator added based on the amount of the solid component is shown in tables 2 and 3.

[ TABLE 2]

[ TABLE 3]

(2) Measurement of viscosity at 25 ℃ of Photocurable adhesive

The viscosity (mPa · s) at 25 ℃ was measured for each photocurable adhesive (adhesive liquid) prepared in (1) using an E-type viscometer "TVE-25L" manufactured by eastern industries, ltd. The results are shown in tables 4 and 5.

(3) Measurement of moisture content of photocurable adhesive at 25 deg.C

For each of the photocurable adhesives (adhesive liquids) prepared in (1), moisture (parts by weight per 100 parts by weight of the photocationic curable component (a)) at a temperature of 25 ℃ was measured using a moisture meter "AQV-2100 ST" manufactured by the shinkansu corporation. The results are shown in tables 4 and 5.

(4) Measurement of ability (dissolving power) of photo-curable adhesive to dissolve thermoplastic resin film

A retardation film (trade name "N-TAC KC4 FR-1" manufactured by Konica Minolta Opto) having a thickness of 40 μm and formed from Triacetylcellulose (TAC) was prepared. The retardation film is a member used for producing a polarizing plate, which is bonded to a polyvinyl alcohol polarizing plate as a thermoplastic resin film having an optical compensation function. The retardation film was cut into a size of 10mm × 40mm, and then immersed in 20g of each of the photocurable adhesives (adhesive solutions) prepared above at a temperature of 23 ℃ for 2 days. After 2 days, the retardation film was taken out, and the adhesive liquid attached to the retardation film was wiped with BEMCOT (ベンコットン) to measure the weight. The weight reduction of the film was determined from the weight of the film before immersion in the adhesive solution and the weight of the film after immersion according to the following formula, and this was taken as the dissolving power. The results are shown in tables 4 and 5. The greater the weight loss, the higher the solvency.

(5) Determination of storage modulus of adhesive layer at 80 deg.C

Each of the photocurable adhesives (adhesive liquids) prepared in (1) above was applied to an untreated polyethylene terephthalate film (trade name "SOFT SHINE" manufactured by Toyo Boseki) with a bar coater #20, and an ultraviolet irradiation device (metal halide lamp) with a belt conveyor was used so that the cumulative light amount became 3000mJ/cm²The ultraviolet ray is irradiated in the form of (UVA). After 24 hours, the adhesive cured product (cured adhesive layer) was peeled from the polyethylene terephthalate film to obtain a cured film. The obtained cured film was held at a jig interval of 2cm so that the long side thereof was oriented in the stretching direction by a viscoelasticity measuring apparatus "DMA 7100" manufactured by Hitachi High-Tech Science, and the storage modulus (MPa) at 80 ℃ was measured with the frequency of stretching and shrinking set to 10Hz and the temperature increase rate set to 3 ℃/min. The results are shown in tables 4 and 5.

Production of [6] polarizing plate

One surface of a phase difference film having a thickness of 40 μm formed from Triacetylcellulose (TAC) (trade name "N-TAC KC4 FR-1" manufactured by Konica Minolta Opto (ltd.) (abbreviated as "phase difference TAC") in tables 4 and 5) and a phase difference film having a thickness of 50 μm formed from Triacetylcellulose (TAC) having a thickness of 80 μm and containing an ultraviolet absorber (trade name "ZEONOR" manufactured by japan ZEON (ltd.) (abbreviated as "TAC") in tables 4 and 5) or a norbornene resin (cyclic polyolefin resin) (trade name "ZEONOR" manufactured by japan ZEON (ltd.) (abbreviated as "COP" in tables 4 and 5) was subjected to corona treatment, and the photocurable adhesive (adhesive solution) prepared in (1) was applied to these corona-treated surfaces by an adhesive application apparatus. A polyvinyl alcohol-iodine polarizing plate having a thickness of 25 μm was laminated on the coating layer of the adhesive, and the laminate was bonded using a nip roll (extrusion pressure: 1.5 MPa). Then, the total cumulative quantity of light (cumulative quantity of light irradiation intensity in the wavelength region of 320-400 nm) is about 350mJ/cm²(measurement value obtained by UV Power PuckII manufactured by FusionUV Co., Ltd.) was used as an ultraviolet ray (UVA) to make a pasteThe adhesive layer is cured to obtain a polarizing plate in which a thermoplastic resin film is laminated on one surface of the polarizer. The thickness of the adhesive layer was 2.8 μm in terms of the thickness after curing.

(7) 180 degree peel test of polarizing plate

The polarizing plate produced in (6) above was cut into a size of 200mm in length × 25mm in width, and then an acrylic pressure-sensitive adhesive layer was provided on the thermoplastic resin film side to prepare a test piece for measuring the peel strength between the thermoplastic resin film and the polarizing plate. The test piece was adhered to a glass plate using the adhesive layer, a blade of a cutter was placed between the polarizing plate and the thermoplastic resin film, the test piece was peeled off 30mm from the end in the longitudinal direction, and the peeled portion was held by a holding portion of a testing machine. The test piece in this state was subjected to a temperature of 23 ℃ and a relative humidity of 55% in an atmosphere in accordance with JIS K6854-2: 1999 "adhesive-peel adhesion Strength test method-part 2: 180 degree peeling ", in the nip portion moving speed 300 mm/min under 180 degree peeling test, except the nip portion 30mm length of 170mm average peeling force, it is set as the thermoplastic resin film and the polarizer peeling strength. The peel strength was measured for each of the 3 resins described above as the thermoplastic resin film. The time measured was 24 hours after the polarizing plate was produced. The results are shown in tables 4 and 5. Tables 4 and 5. The term "not peelable" means that the polarizing plate and the thermoplastic resin film cannot be peeled off under the above conditions.

[ TABLE 4]

[ TABLE 5]

Claims

1. A polarizing plate comprising a polyvinyl alcohol-based polarizer and a thermoplastic resin film laminated on at least one surface of the polyvinyl alcohol-based polarizer via a cured product of a photocurable adhesive,

the photocurable adhesive contains an epoxy compound containing no aromatic ring as a main component,

the photo cation curable component (A) contains a1 st epoxy compound (A1) represented by the following formula (I) and a2 nd epoxy compound (A2) represented by the following formula (II),

wherein n represents an integer of 1 or more, V represents an n-valent group including a condensed ring composed of an alicyclic ring, but the condensed ring does not include a condensed ring containing a hetero atom,

in the formula, R¹And R²Each independently represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, and may have an alicyclic structure when the number of carbon atoms in the alkyl group is 3 or more;

x represents an oxygen atom, an alkanediyl group having 1 to 6 carbon atoms or a 2-valent group represented by any one of the following formulae (IIa) to (IId),

a and b each represent an integer of 0 to 20.

2. A polarizing plate comprising a polyvinyl alcohol-based polarizer and a thermoplastic resin film laminated on at least one surface of the polyvinyl alcohol-based polarizer via a cured product of a photocurable adhesive,

wherein n represents an integer of 1 or more, V represents an n-valent group including a fused ring composed of an alicyclic ring, the fused ring being a 3-ring fused ring,

a and b each represent an integer of 0 to 20.

3. A polarizing plate comprising a polyvinyl alcohol-based polarizer and a thermoplastic resin film laminated on at least one surface of the polyvinyl alcohol-based polarizer via a cured product of a photocurable adhesive,

wherein n represents an integer of 1 or more, V represents an n-valent group including a condensed ring composed of an alicyclic ring and a linking group linking the condensed ring and the glycidyloxy group in formula (I),

a and b each represent an integer of 0 to 20.

4. The polarizing plate according to any one of claims 1 to 3, wherein the photocationic-curable component (A) further comprises 1 to 70% by weight, based on the whole amount thereof, of a3 rd epoxy compound (A3) represented by the following formula (III),

wherein Z represents a branched alkylene group having 3 to 8 carbon atoms or formula-C_mH_2m-Z¹-C_nH_2n-a 2-valent radical of formula (I), wherein-Z¹-represents-O-, -CO-O-or-O-CO-, one of m and n represents an integer of 1 or more and the other represents an integer of 2 or more, the total of both being 8 or less, and C_mH_2mAnd C_nH_2nOne of them represents a branched 2-valent saturated hydrocarbon group.

5. The polarizing plate according to any one of claims 1 to 3, further comprising 0.1 to 5 parts by weight of at least one compound selected from the group consisting of an anthracene compound represented by the following formula (IVa) and a naphthalene compound represented by the following formula (IVb) per 100 parts by weight of the photocationic-curable component (A),

in the formula (IVa), R³And R⁴Each independently represents a hydrogen atom, an alkyl group having 1 to 6 carbon atoms or an alkoxyalkyl group having 2 to 12 carbon atoms, R⁵Represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms,

in the formula (IVb), R⁶And R⁷Each independently represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms.

6. The polarizing plate according to any one of claims 1 to 3, wherein a moisture content is more than 0 part by weight and 4 parts by weight or less with respect to 100 parts by weight of the photocationic-curable component (A).

7. A photocurable adhesive for bonding a thermoplastic resin film to a polyvinyl alcohol-based polarizer,

wherein n represents an integer of 1 or more, V represents an n-valent group containing a condensed ring composed of an alicyclic ring,

wherein, Y¹～Y⁴Each represents an alkanediyl group having 1 to 20 carbon atoms in which the number of carbon atoms is3 or more may have an alicyclic structure; a and b each represent an integer of 0 to 20,

the content of the 2 nd epoxy compound (A2) is 30 to 65 wt% based on the total amount of the photocationic curable component (A).

8. The photocurable adhesive according to claim 7, wherein the photocationic-curable component (A) further comprises 1 to 70% by weight, based on the entire amount thereof, of a3 rd epoxy compound (A3) represented by the following formula (III),

9. The photocurable adhesive according to claim 7, further comprising 0.1 to 5 parts by weight, relative to 100 parts by weight of the photocationic-curable component (A), of at least 1 compound selected from the group consisting of an anthracene-based compound represented by the following formula (IVa) and a naphthalene-based compound represented by the following formula (IVb),

10. The photocurable adhesive according to claim 7, wherein the moisture content is more than 0 part by weight and 4 parts by weight or less with respect to 100 parts by weight of the photocationic-curable component (A).

11. A polarizing plate, comprising:

polyvinyl alcohol-based polarizing plate, and

a thermoplastic resin film laminated on at least one surface of the polyvinyl alcohol-based polarizing plate via a cured product of the photocurable adhesive according to any one of claims 7 to 10.

12. A laminated optical member comprising a laminate of the polarizing plate according to any one of claims 1 to 3 or 11 and 1 or more other optical layers.

13. The laminated optical member of claim 12, wherein the other optical layers comprise phase difference plates.