JP6718685B2 - Photocurable adhesive, polarizing plate using the same, laminated optical member and liquid crystal display device - Google Patents

Description

The present invention relates to a photocurable adhesive for adhering a thermoplastic resin film to a polyvinyl alcohol-based polarizer, a polarizing plate using the same, a laminated optical member and a liquid crystal display device.

The polarizing plate is useful as one of the optical components that make up the liquid crystal display device. The 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, a film having another optical function is bonded to the other side as a protective film instead of being simply a protective film. It 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 then dried is widely adopted.

Usually, a protective film is bonded to the polarizer immediately after the above-mentioned washing and drying. This is because the dried polarizer has a weak physical strength, and once it is wound, it has a problem that it tends to tear in the processing direction. Therefore, usually, a water-based adhesive, which is an aqueous solution of a polyvinyl alcohol-based resin, is immediately applied to the dried polarizer, and the protective films are simultaneously adhered to both surfaces of the polarizer through this adhesive. As the protective film, a triacetyl cellulose film having a thickness of 30 to 100 μm is usually used.

Triacetyl cellulose is excellent in transparency, easy to form various surface treatment layers and optical functional layers on the surface thereof, and has high moisture permeability, and after adhering to the polarizer using the water-based adhesive as described above. While it has an excellent advantage as a protective film that it can be dried smoothly, a polarizing plate using this as a protective film due to its high water vapor transmission rate is under humid heat, for example, a temperature of 70° C. and a relative humidity of 90%. There is a problem that deterioration is likely to occur under the conditions. Therefore, it is also known to use, as a protective film, an amorphous polyolefin resin having a lower water vapor transmission rate than triacetyl cellulose, for example, a norbornene resin as a typical example. Japanese Patent Laid-Open No. 06-051117 (Patent Document 1) describes that a thermoplastic saturated norbornene-based resin sheet is laminated as a protective film on at least one surface of a polarizer.

When a protective film made of a resin having a low moisture permeability is bonded to a polyvinyl alcohol-based polarizer, an aqueous solution of a polyvinyl alcohol-based resin that has been conventionally used for bonding a polyvinyl alcohol-based polarizer and a triacetyl cellulose film is used as an adhesive. However, there are problems that the adhesive strength is not sufficient and the resulting polarizing plate has a poor appearance. This is because a resin film having a low moisture permeability is generally hydrophobic, and water having a low moisture permeability cannot sufficiently dry water as a solvent. On the other hand, it is also known to bond different kinds of protective films to both surfaces of the polarizer. For example, in Japanese Unexamined Patent Publication No. 2002-174729 (Patent Document 2), a protective film made of a resin having a low moisture permeability such as an amorphous polyolefin resin is adhered to one surface of a polarizer, and the other side of the polarizer is attached. There is also a proposal to adhere a protective film made of a resin having a high moisture permeability such as a cellulose resin such as triacetyl cellulose to the surface.

Therefore, while providing a high adhesive force between the protective film made of a resin having a low moisture permeability and the polyvinyl alcohol-based polarizer, it is also high between the resin having a high moisture permeability such as a cellulose resin and the polyvinyl alcohol-based polarizer. There is an attempt to use a photocurable adhesive as an adhesive that gives adhesive strength. For example, Japanese Unexamined Patent Application Publication No. 2004-245925 (Patent Document 3) discloses an adhesive containing an epoxy compound that does not contain an aromatic ring as a main component, and is exposed to active energy rays, specifically, ultraviolet rays. It has been proposed to cure this adhesive by cationic polymerization to bond the polarizer and the protective film. Further, JP-A-2008-257199 (Patent Document 4) discloses a photo-curable adhesive in which an alicyclic epoxy compound and an epoxy compound having no alicyclic epoxy group are combined and a photocationic polymerization initiator is further added. There is disclosed a technique of using the above to bond the polarizer and the protective film.

Although the epoxy adhesive disclosed in Patent Document 3 is effective for adhering a protective film made of an amorphous polyolefin resin or a cellulose resin to a polarizer, it is made of a (meth)acrylic resin for protection. It has become clear that when the films are adhered, the adhesive strength is not always sufficient.

JP 2012-172026 A (Patent Document 5) has an epoxy group or an oxetanyl group in 100% by weight of an active energy ray-curable compound (A), and does not have an active energy ray radical-polymerizable functional group. An active energy ray-curable compound (5 to 100% by weight of an active energy ray cation-curable compound (a1) having a weight average molecular weight of less than 5000 and an active energy ray radical-curable compound (a2) of 0 to 95% by weight ( Disclosed is an adhesive for an optical film containing 0.0001 to 2 parts by weight of an acrylic resin (B) having an epoxy group or an oxetanyl group and having a weight average molecular weight of 5,000 to 150,000 per 100 parts by weight of A). However, when the content of the acrylic resin (B) exceeds 2 parts by weight, the viscosity of the adhesive increases, which may rather deteriorate the smoothness of the coated surface (see paragraph [0079]). The content of the acrylic resin (B) is set to 2 parts by weight or less.

JP 2012-007080 A (Patent Document 6) discloses that the viscosity containing a photopolymerization initiator and a cationically polymerizable component containing a polyfunctional alicyclic epoxy compound (A) and a monofunctional glycidyl compound (B). A method of adhering a polarizer and a protective film using a photocurable adhesive of 10 to 150 mPa·s has been proposed. However, the epoxy adhesive disclosed in Patent Document 6 is also effective for adhering a protective film made of an amorphous polyolefin resin or a cellulose resin to a polarizer.

Japanese Patent Application Laid-Open No. 2013-092762 (Patent Document 7) discloses a method for producing a polarizing plate in which bubbles are unlikely to occur between a polarizing film (polarizer) and a transparent film, by curing active energy rays on one side of the transparent film. A step of applying a mold adhesive, a step of producing a laminate by laminating a transparent film on one side or both sides of the polarizing film with the side coated with the adhesive, and irradiating the laminate with active energy rays. And a method for producing a polarizing plate, the method comprising the steps of producing a polarizing plate, wherein the diameter of the laminating roll used in the step of producing the laminate is in the range of 50 to 250 mm. Has been done.

In addition, in JP 2013-205719 A (Patent Document 8), in order to enhance the adhesive force between the polyvinyl alcohol-based polarizer and the protective film, triethylene glycol is blended with the photocurable adhesive. Have been described.

Japanese Patent Laid-Open No. 06-051117 JP, 2002-174729, A JP, 2004-245925, A JP, 2008-257199, A JP2012-172026A JP2012-007080A JP, 2013-092762, A JP, 2013-205719, A

The present invention has a sufficiently low viscosity to allow coating at room temperature in adhering a thermoplastic resin film to a polyvinyl alcohol-based polarizer, and has an adhesive force between the polarizer/thermoplastic resin film. An object is to provide a new photocurable adhesive that can provide an improved polarizing plate. Another object of the present invention is to reduce the thickness of the adhesive layer in producing a polarizing plate in which a thermoplastic resin film is laminated via a cured adhesive layer on a polyvinyl alcohol-based polarizer. Even so, it is an object of the present invention to provide a low-viscosity photocurable adhesive capable of adhering a polyvinyl alcohol-based polarizer and a thermoplastic resin film without causing bubbles in the adhesive layer. Still another object of the present invention is to provide a laminated optical member in which another optical layer is laminated on the polarizing plate, and a liquid crystal display device including the laminated optical member.

The present invention provides a photo-curable adhesive, a polarizing plate, a laminated optical member and a liquid crystal display device shown below.

[1] A photocurable adhesive for adhering a thermoplastic resin film to a polyvinyl alcohol-based polarizer,
A photocationic curable component (A) containing a first photocationic curable component (A1) which is an aromatic epoxy compound;
Formula (I) below:

(In the formula, X is a hydrogen atom, or an alkyl group having 1 to 7 carbon atoms which may be substituted with one or more functional groups selected from the group consisting of an epoxy group, an oxetanyl group, a hydroxyl group and a carboxyl group. Represents an alkoxy group having 1 to 7 carbon atoms, an aryl group having 6 to 12 carbon atoms, an aryloxy group having 6 to 12 carbon atoms, or an alicyclic hydrocarbon group having 6 to 10 carbon atoms).
And a monomer represented by the following formula (II):

(In the formula, R ¹ represents a hydrogen atom, a methyl group or a halogen atom. Y is substituted with one or more functional groups selected from the group consisting of an epoxy group, an oxetanyl group, a hydroxyl group and a carboxyl group. Represents an alkyl group having 1 to 7 carbon atoms, an aryl group having 6 to 12 carbon atoms, or an alicyclic hydrocarbon group having 6 to 10 carbon atoms).
A polymer (B) comprising constitutional units derived from one or more kinds of monomers selected from the group consisting of the monomer (II)
A cationic photopolymerization initiator (C),
A branched alcohol compound (D),
Containing
The content of the polymer (B) is 2 to 10 parts by weight in the total amount of 100 parts by weight of the photocationic curable component (A) and the polymer (B),
The content of the first photocationic curable component (A1) is 10 to 40 parts by weight in 100 parts by weight of the total amount of the photocationic curable component (A) and the polymer (B),
The content of the photocationic polymerization initiator (C) is 1 to 10 parts by weight based on 100 parts by weight of the total amount of the photocationic curable component (A) and the polymer (B),
The content of the branched alcohol compound (D) is 0.1 to 15 parts by weight based on 100 parts by weight of the total amount of the photocationic curable component (A) and the polymer (B). adhesive.

[2] The photocationic curable component (A) is at least one second photocationic curable component (a) selected from the group consisting of an aliphatic diglycidyl compound, a monofunctional aliphatic epoxy compound, a vinyl ether compound and an oxetane compound ( The photocurable adhesive according to [1], further including A2).

[3] The aliphatic diglycidyl compound has the following formula (III):

(In the formula, Z represents a linear or branched alkylene group having 1 to 9 carbon atoms or a divalent alicyclic hydrocarbon group, and the methylene group in the alkylene group is an oxygen atom or -CO-O. -, - O-CO -, - SO 2 -, - SO- or a divalent group selected from -CO- may be substituted).
The photocurable adhesive according to [2], which is a compound represented by:

[4] The photocurable adhesive according to [3], wherein Z in the formula (III) is a branched alkylene group having 3 to 10 carbon atoms.

[5] The content of the second cationic photocurable component (A2) is 58 to 88 parts by weight in 100 parts by weight of the total amount of the cationic photocurable component (A) and the polymer (B). The photocurable adhesive according to any one of [2] to [4].

[6] The photocurable adhesive according to any one of [1] to [5], wherein the polymer (B) has a weight average molecular weight of 5,000 to 500,000.

[7] The photocurable adhesive according to any one of [1] to [6], wherein the branched alcohol compound (D) is a compound having two or more hydroxyl groups in the molecule.

[8] The water content is more than 0 parts by weight and 4 parts by weight or less based on 100 parts by weight of the total amount of the photocationic curable component (A) and the polymer (B), [1] to [7]. ] The photocurable adhesive in any one of these.

[9] The photocurable adhesive according to any one of [1] to [8], which has a viscosity at 25° C. of 2 to 300 mPa·s.

[10] A polyvinyl alcohol-based polarizer,
A thermoplastic resin film laminated on at least one surface of the polyvinyl alcohol-based polarizer via the cured product of the photocurable adhesive according to any one of [1] to [9],
Including a polarizing plate.

[11] The thermoplastic resin film contains at least one resin selected from the group consisting of a cellulose resin, a (meth)acrylic resin, an amorphous polyolefin resin, a polyester resin, and a polycarbonate resin, The polarizing plate according to [10].

[12] The polarizing plate according to [10] or [11], wherein the thermoplastic resin film contains an ultraviolet absorber.

[13] Any of [10] to [12], wherein the peel strength between the polyvinyl alcohol-based polarizer and the thermoplastic resin film measured by a 180-degree peel test is 0.5 N/25 mm or more. The polarizing plate described in.

[14] A laminated optical member including a laminate of the polarizing plate according to any one of [10] to [13] and one or more other optical layers.

[15] The laminated optical member according to [14], wherein the other optical layer includes a retardation plate.
[16] A liquid crystal display device comprising a liquid crystal cell and the laminated optical member according to [14] or [15] arranged on at least one surface of the liquid crystal cell.

According to the present invention, it is possible to bond a polyvinyl alcohol-based polarizer and a thermoplastic resin film with high adhesive strength because the viscosity is low and the coating suitability is excellent, bubbles are unlikely to occur in the adhesive layer after curing. A curable adhesive can be provided. The polarizing plate according to the present invention having a high adhesive strength, and the laminated optical member and the liquid crystal display device using the same can have excellent durability and can suppress bubble defects in the adhesive layer.

It is a cross-sectional schematic diagram which shows a preferable example of the apparatus which manufactures the polarizing plate which concerns on this invention.

<Photocurable adhesive>
The photocurable adhesive according to the present invention is an adhesive for adhering a thermoplastic resin film to a polyvinyl alcohol-based polarizer, and comprises a photocationic curable component (A), a polymer (B), and a photocationic polymerization. It contains an initiator (C) and a branched alcohol compound (D).

(1) Photocationic curable component (A)
The photocationic curable component (A), which is the main component of the photocurable adhesive and imparts adhesive force by polymerization curing, contains at least the first photocationic curable component (A1) which is an aromatic epoxy compound. The photocationic curable component (A) preferably further contains, in addition to the first photocationic curable component (A1), a second photocationic curable component (A2) which is a curable component different from this.

(1-1) First photocationic curable component (A1)
The first photo-cationic curable component (A1) is composed of an aromatic epoxy compound. The aromatic epoxy compound is an epoxy compound having an aromatic ring. However, in the aromatic epoxy compound mentioned here, X and/or Y in the polymer (B) described later has an aromatic ring and an epoxy group, and the polymer (B) belonging to the aromatic epoxy compound is classified, Not included. The first photo-cationic curable component (A1) may be composed of two or more kinds of aromatic epoxy compounds. Specific examples of the aromatic epoxy compound include monohydric phenols such as phenol, cresol and butylphenol, or bisphenol derivatives such as bisphenol A and bisphenol F, or mono- or polyglycidyl ether compounds of their alkylene oxide adducts; epoxy novolac resins; resorcinol. Of mono- or polyglycidyl ethers of aromatic compounds having two or more phenolic hydroxyl groups such as quinone, hydroquinone and catechol; aromatic compounds having two or more alcoholic hydroxyl groups such as benzenedimethanol, benzenediethanol and benzenedibutanol Glycidyl ether compound; glycidyl ester of polybasic acid aromatic compound having two or more carboxyl groups such as phthalic acid, terephthalic acid, trimellitic acid; glycidyl ester of benzoic acid, toluic acid, glycidyl ester of naphthoic acid, etc.; styrene Examples thereof include oxides, alkylated styrene oxides, styrene oxides such as vinyl naphthalene epoxides, and divinyl benzene diepoxides.

Among them, from the viewpoint of curability and adhesiveness, the first photocationic curable component (A1) preferably contains a polyfunctional aromatic epoxy compound, more preferably a trifunctional or higher functional aromatic epoxy compound.

From the viewpoint of curability and adhesiveness, the aromatic epoxy compound preferably has an epoxy equivalent of 80 to 500.

As the aromatic epoxy compound, a commercially available product can be used, and for example, “Denacol EX-145”, “Denacol EX-146”, “Denacol EX-147”, “Denacol EX-201”, “Denacol EX-711”, "Denacol EX-721", "Oncoat EX-1020", "Oncoat EX-1030", "Oncoat EX-1040", "Oncoat EX-1050", "Oncoat EX-1051", "Oncoat" EX-1010", "ONCOAT EX-1011" and "ONCOAT 1012" (all of which are manufactured by Nagase Chemtex Co., Ltd.); "OGSOL PG-100", "OGSOL EG-200", "OGSOL EG-" 210" and "OGSOL EG-250" (all of which are manufactured by Osaka Gas Chemicals Co., Ltd.); "HP4032", "HP4032D" and "HP4700" (all of which are manufactured by DIC Corporation); "ESN-475V" "(Nippon Steel & Sumikin Chemical Co., Ltd.); "152", "154", "157S70" and "YX8800" (all are manufactured by Mitsubishi Chemical Corporation); "Adeka Resin EP-4100", "Adeka Resin EP-" 4100G", "Adeka Resin EP-4100E", "Adeka Resin EP-4100L", "Adeka Resin EP-4100TX", "Adeka Resin EP-4000", "Adeka Resin EP-4005", "Adeka Resin EP-4082HT", "Adeka Resin EP-4901". ", "Adeka Resin EP-4901E", "Adeca Glycilol ED-501", "Adeca Glycilol ED-509E", "Adeca Glycilol ED-509S" and "Adeca Glycilol ED-529" (above, all ( Adeka Co., Ltd.), “TECHMORE VG3101L” (Printech Co., Ltd.) and the like.

The content of the first photocationic curable component (A1) is 10 to 40 parts by weight, preferably 12 to 10 parts by weight, based on 100 parts by weight of the total amount of the photocationic curable component (A) and the polymer (B) described later. 35 parts by weight. By containing 10 parts by weight or more of the first photocationic curable component (A1), excellent adhesion strength between the polyvinyl alcohol-based polarizer and the thermoplastic resin film, and reduction in viscosity of the photocurable adhesive and Along with this, it is possible to achieve compatibility with good coatability. On the other hand, if the content of the first photo-cationic curable component (A1) exceeds 40 parts by weight, it becomes difficult to satisfy the above requirements, and the viscosity tends to increase. When the content of the first photo-cationic curable component (A1) is less than 10 parts by weight, excellent adhesive strength cannot be obtained.

(1-2) Second photocationic curable component (A2)
The photocationic curable component (A) preferably further contains a second photocationic curable component (A2) different from the first photocationic curable component (A1). The second photocationic curable component (A2) is a curable component selected from an aliphatic diglycidyl compound, a monofunctional aliphatic epoxy compound, a vinyl ether compound and an oxetane compound, and two or more of these are curable. It may consist of ingredients. The monofunctional aliphatic epoxy compound referred to here includes a polymer (B) which belongs to a monofunctional aliphatic epoxy compound in classification because X or Y in the polymer (B) described later has an epoxy group. Absent. In addition, the oxetane compound mentioned here does not include the polymer (B) belonging to the oxetane compound in classification because X or Y in the polymer (B) described later has an oxetanyl group.

The second photo-cationic curable component (A2) preferably contains an aliphatic diglycidyl compound. Above all, since it becomes easy to lower the viscosity of the photocurable adhesive, that is, to adjust the viscosity at 25° C. to the range of 2 to 300 mPa·s, the following formula (III):

It is more preferable to include a compound represented by In the above formula (III), Z represents a linear or branched alkylene group having 1 to 9 carbon atoms or a divalent alicyclic hydrocarbon group, and the methylene group in the alkylene group is an oxygen atom or -CO. -O - [- C (= O) -O- when], -O-CO - [- O-C (= O) - means a], -SO ₂ - (sulfonyl group), - SO- It may be substituted with a divalent group selected from (sulfinyl group) or —CO— (carbonyl group). Typical examples of the divalent alicyclic hydrocarbon group include a cyclopentylene group and a cyclohexylene group.

The compound in which Z is an alkylene group in the above formula (III) is a diglycidyl ether of alkylene glycol, and specific examples thereof include ethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, and 1,3-propanediol diglycidyl ether. , 1,4-butanediol diglycidyl ether, neopentyl glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether and the like. Among them, from the viewpoint of reducing the viscosity of the photocurable adhesive, the compound in which Z is an alkylene group in the above formula (III) is a compound represented by the above formula (such as propylene glycol diglycidyl ether or neopentyl glycol diglycidyl ether). A compound in which Z in III) is a branched alkylene group having 3 to 10 carbon atoms is preferable.

Examples of the monofunctional aliphatic epoxy compound include a glycidyl ether compound of an aliphatic alcohol and a glycidyl ester of an alkylcarboxylic acid, and specific examples thereof include allyl glycidyl ether, butyl glycidyl ether, sec-butylphenyl glycidyl ether, 2- Examples include ethylhexyl glycidyl ether, C12 and C13 mixed alkyl glycidyl ether, alcohol glycidyl ether, aliphatic higher alcohol monoglycidyl ether, and higher fatty acid glycidyl ester.

Examples of the vinyl ether compound include aliphatic or alicyclic vinyl ether compounds, and specific examples thereof include n-amyl vinyl ether, i-amyl vinyl ether, n-hexyl vinyl ether, n-octyl vinyl ether, 2-ethylhexyl vinyl ether, and n-amyl vinyl ether. Vinyl ethers of C5-20 alkyl or alkenyl alcohols such as dodecyl vinyl ether, stearyl vinyl ether, oleyl vinyl ether; hydroxyl group-containing vinyl ethers such as 2-hydroxyethyl vinyl ether, 3-hydroxypropyl vinyl ether, 4-hydroxybutyl vinyl ether; cyclohexyl vinyl ether, Vinyl ethers of monoalcohols having an aliphatic ring or an aromatic ring such as 2-methylcyclohexyl vinyl ether, cyclohexylmethyl vinyl ether, benzyl vinyl ether; glycerol monovinyl ether, 1,4-butanediol divinyl ether, 1,6-hexanediol divinyl ether. , Neopentyl glycol divinyl ether, pentaerythritol divinyl ether, pentaerythritol tetravinyl ether, trimethylolpropane divinyl ether, trimethylolpropane trivinyl ether, 1,4-dihydroxycyclohexane monovinyl ether, 1,4-dihydroxycyclohexane divinyl ether, 1,4 -Mono- or polyvinyl ethers of polyhydric alcohols such as dihydroxymethyl cyclohexane monovinyl ether and 1,4-dihydroxymethyl cyclohexane divinyl ether; polyalkylene glycol mono or diethylene glycol divinyl ether, triethylene glycol divinyl ether, diethylene glycol monobutyl monovinyl ether, etc. Divinyl ethers; including other vinyl ethers such as glycidyl vinyl ether and ethylene glycol vinyl ether methacrylate.

The oxetane compound is a compound having an oxetanyl group, and specific examples thereof include 3,7-bis(3-oxetanyl)-5-oxa-nonane and 1,4-bis[(3-ethyl-3-oxetanylmethoxy). Methyl]benzene, 1,2-bis[(3-ethyl-3-oxetanylmethoxy)methyl]ethane, 1,3-bis[(3-ethyl-3-oxetanylmethoxy)methyl]propane, ethylene glycol bis(3- Ethyl-3-oxetanylmethyl) ether, triethylene glycol bis(3-ethyl-3-oxetanylmethyl) ether, tetraethylene glycol bis(3-ethyl-3-oxetanylmethyl) ether, 1,4-bis(3-ethyl) -3-Oxetanylmethoxy)butane, 1,6-bis(3-ethyl-3-oxetanylmethoxy)hexane, 3-ethyl-3-[(phenoxy)methyl]oxetane, 3-ethyl-3-(hexyloxymethyl) Oxetane, 3-ethyl-3-(2-ethylhexyloxymethyl)oxetane, 3-ethyl-3-(hydroxymethyl)oxetane, 3-ethyl-3-(chloromethyl)oxetane and the like are included.

The content of the second photo-cationic curable component (A2) is not particularly limited as long as the content of the first photo-cationic curable component (A1) falls within the above range, but the content of the photo-cationic curable component (A) and the later-described The total amount of the polymer (B) to be added is preferably 58 to 88 parts by weight, and more preferably 60 to 85 parts by weight, in 100 parts by weight. When the content of the second photocationic curable component (A2) is within the above range, it becomes easy to prepare a photocurable adhesive having a viscosity of 2 to 300 mPa·s at 25°C. On the other hand, when the content of the second photo-cationic curable component (A2) exceeds 88 parts by weight, the adhesive strength between the polarizer and the thermoplastic resin film tends to be insufficient.

(1-3) Third photo-cationic curable component (A3)
The photocationic curable component (A) is a third photocationic curable component (A3) which is a curable component other than the first photocationic curable component (A1) and the second photocationic curable component (A2). Can be further included. As the third photo-cationic curable component (A3), an epoxy compound (for example, an alicyclic epoxy compound) that does not belong to either (A1) or (A2), a cyclic lactone compound, a cyclic acetal compound, a cyclic thioether compound, or spiro Examples thereof include orthoester compounds. The content of the third photocationic curable component (A3) is not particularly limited as long as the content of the first photocationic curable component (A1) falls within the above range, and preferably the second photocationic curable component. When it contains (A2), the content of the second photocationic curable component (A2) is within the above range.

(2) Polymer (B)
The polymer (B) has the following formula (I):

And a monomer represented by the following formula (II):

Is a polymer composed of constitutional units derived from one or more kinds of monomers selected from the group consisting of the monomer (II). Specifically, a homopolymer prepared by polymerizing one kind of the monomer (I), a copolymer prepared by polymerizing two or more kinds of the monomer (I), and one kind of the monomer (II) are prepared. Homopolymer obtained by the polymerization, a copolymer obtained by polymerizing two or more kinds of the monomer (II), a copolymer obtained by polymerizing one or more kinds of the monomer (I) and one or more kinds of the monomer (II). , And mixtures of two or more thereof.

X in the above formula (I) is a hydrogen atom or the number of carbon atoms which may be partially substituted with one or more functional groups selected from the group consisting of an epoxy group, an oxetanyl group, a hydroxyl group and a carboxyl group. It represents an alkyl group having 1 to 7, an alkoxy group having 1 to 7 carbon atoms, an aryl group having 6 to 12 carbon atoms, an aryloxy group having 6 to 12 carbon atoms, or an alicyclic hydrocarbon group having 6 to 10 carbon atoms.

Examples of the alkyl group having 1 to 7 carbon atoms include methyl group, ethyl group, n-propyl group, i-propyl group, n-butyl group, sec-butyl group, tert-butyl group, i-butyl group, n-amyl group. Group, i-amyl group, tert-amyl group, n-hexyl group, 2-hexyl group, 3-hexyl group, cyclohexyl group, 4-methylcyclohexyl group, n-heptyl group, 2-heptyl group, 3-heptyl group , I-heptyl group, tert-heptyl group and the like. Of these, an alkyl group having 1 to 4 carbon atoms is preferable from the viewpoint of durability of the adhesive layer.

Examples of the alkoxy group having 1 to 7 carbon atoms include methoxy group, ethoxy group, n-propyloxy group, i-propyloxy group, n-butyloxy group, sec-butyloxy group, tert-butyloxy group, i-butyloxy group, n. -Amyloxy group, i-amyloxy group, tert-amyloxy group, n-hexyloxy group, 2-hexyloxy group, 3-hexyloxy group, cyclohexyloxy group, 4-methylcyclohexyloxy group, n-heptyloxy group, 2 -Heptyloxy group, 3-heptyloxy group, i-heptyloxy group, tert-heptyloxy group and the like. Of these, an alkoxy group having 1 to 4 carbon atoms is preferable from the viewpoint of durability of the adhesive layer.

Examples of the aryl group having 6 to 12 carbon atoms include phenyl group, methylphenyl group and naphthyl group. The carbon number is preferably 6 to 10.

Examples of the aryloxy group having 6 to 12 carbon atoms include phenyloxy group, methylphenyloxy group and naphthyloxy group. The carbon number is preferably 6 to 10.

Examples of the alicyclic hydrocarbon group having 6 to 10 carbon atoms include cyclohexyl group, methylcyclohexyl group, norbornyl group, bicyclopentyl group, bicyclooctyl group, trimethylbicycloheptyl group, tricyclooctyl group, tricyclodecanyl group. , Spirooctyl group, spirobicyclopentyl group, adamantyl group, isobornyl group and the like.

X in the above formula (I) is an alkyl group having 1 to 7 carbon atoms partially substituted with one or more functional groups selected from the group consisting of epoxy group, oxetanyl group, hydroxyl group and carboxyl group, carbon When it is an alkoxy group having 1 to 7 carbon atoms, an aryl group having 6 to 12 carbon atoms, an aryloxy group having 6 to 12 carbon atoms, or an alicyclic hydrocarbon group having 6 to 10 carbon atoms, the above functional group is involved in the curing reaction. Since it contributes, it is advantageous in terms of durability of the adhesive layer and suppression of bleeding of low molecular weight components from the adhesive layer. Among them, the functional group is preferably one or more functional groups selected from the group consisting of an epoxy group, an oxetanyl group and a hydroxyl group.

In the above formula (I), the monomer (I) in the case where a part of X is substituted with an epoxy group or an oxetanyl group is, for example, represented by the following formulas (Ia), (Ib) and (Ic). The monomer to be mentioned can be mentioned.

(In the formula, R ⁴ represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, and m represents an integer of 1 to 6.)

(In the formula, R ⁵ represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, and n represents an integer of 1 to 6.)

(In the formula, R ⁶ represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, and s represents an integer of 1 to 6).

R ¹ in the above formula (II) represents a hydrogen atom, a methyl group or a halogen atom. Y is a C1-7 alkyl group which may be substituted with one or more functional groups selected from the group consisting of an epoxy group, an oxetanyl group, a hydroxyl group and a carboxyl group, and an aryl group having 6-12 carbon atoms. Alternatively, it represents an alicyclic hydrocarbon group having 6 to 10 carbon atoms.

Examples of the halogen atom include fluorine, chlorine, bromine and iodine. Specific examples of the alkyl group having 1 to 7 carbon atoms, the aryl group having 6 to 12 carbon atoms, and the alicyclic hydrocarbon group having 6 to 10 carbon atoms are the same as X in the formula (I).

Like X in the formula (I), carbon in which Y in the formula (II) is partially substituted with one or more functional groups selected from the group consisting of an epoxy group, an oxetanyl group, a hydroxyl group and a carboxyl group. When it is an alkyl group having 1 to 7 carbon atoms, an aryl group having 6 to 12 carbon atoms, or an alicyclic hydrocarbon group having 6 to 10 carbon atoms, the functional group contributes to the curing reaction, and thus the durability of the adhesive layer And, it is advantageous in suppressing the bleeding of low molecular weight components from the adhesive layer. Among them, the functional group is preferably one or more functional groups selected from the group consisting of an epoxy group, an oxetanyl group and a hydroxyl group.

In the above formula (II), the monomer (II) in the case where a part of Y is substituted with an epoxy group or an oxetanyl group is, for example, represented by the following formulas (IIa), (IIb) and (IIc). The monomer to be mentioned can be mentioned.

(In the formula, R ¹ is the same as the above formula (II), R ⁷ represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, and t represents an integer of 1 to 6.)

(In the formula, R ¹ is the same as the above formula (II), R ⁸ represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, and p represents an integer of 1 to 6.)

(In the formula, R ¹ is the same as the above formula (II), R ⁹ represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, and q represents an integer of 1 to 6).

The polymer (B) is a standard by gel permeation chromatography (GPC) from the viewpoint of both the adhesive strength between the polyvinyl alcohol-based polarizer and the thermoplastic resin film and the low viscosity of the photocurable adhesive. The polystyrene-equivalent weight average molecular weight is preferably 5,000 to 500,000, and more preferably 6,000 to 100,000.

The content of the polymer (B) is 2 to 10 parts by weight, preferably 2.5 to 10 parts by weight, in 100 parts by weight of the total amount of the photocationic curable component (A) and the polymer (B). By containing the polymer (B) in an amount of 2 parts by weight or more, the polyvinyl alcohol-based polarizer and the thermoplastic resin film (particularly, the thermoplastic resin film made of a (meth)acrylic resin) are secured while maintaining a low viscosity. The effect of increasing the adhesive strength can be exhibited. On the other hand, when the content of the polymer (B) exceeds 10 parts by weight, the viscosity of the photocurable adhesive increases. If the amount is less than 2 parts by weight, the adhesion with the protective film made of a (meth)acrylic resin is particularly low. In the present specification, “(meth)acrylic” means at least one selected from acrylic and methacrylic. The same applies to "(meth)acrylate".

(3) Photocationic polymerization initiator (C)
The photocurable adhesive contains a photocationic polymerization initiator (C). Thereby, the photocationic curable component (A) can be cured by cationic polymerization by irradiation with an active energy ray to form an adhesive layer. The cationic photopolymerization initiator (C) generates a cationic species or a Lewis acid upon irradiation with active energy rays such as visible light, ultraviolet rays, X-rays, and electron beams, and undergoes a polymerization reaction of the cationic photocurable component (A). Is to start. Since the cationic photopolymerization initiator (C) acts catalytically with light, it is excellent in storage stability and workability even when mixed with the cationic photocurable component (A). Examples of the compound that produces a cationic species or a Lewis acid upon irradiation with an active energy ray that can be used as the photocationic polymerization initiator (C) include aromatic diazonium salts; onium salts such as aromatic iodonium salts and aromatic sulfonium salts; An iron-arene complex etc. can be mentioned.

As the aromatic diazonium salt, for example,
Benzenediazonium hexafluoroantimonate,
Benzenediazonium hexafluorophosphate,
Examples thereof include benzenediazonium hexafluoroborate.

As the aromatic iodonium salt, for example,
Diphenyliodonium tetrakis(pentafluorophenyl)borate,
Diphenyliodonium hexafluorophosphate,
Diphenyliodonium hexafluoroantimonate,
Di(4-nonylphenyl)iodonium hexafluorophosphate may be mentioned.

As the aromatic sulfonium salt, for example,
Triphenylsulfonium hexafluorophosphate,
Triphenylsulfonium hexafluoroantimonate,
Triphenylsulfonium tetrakis(pentafluorophenyl)borate,
4,4′-bis[diphenylsulfonio]diphenyl sulfide bishexafluorophosphate,
4,4′-bis[di(β-hydroxyethoxy)phenylsulfonio]diphenylsulfide bishexafluoroantimonate,
4,4′-bis[di(β-hydroxyethoxy)phenylsulfonio]diphenylsulfide bishexafluorophosphate,
7-[di(p-toluyl)sulfonio]-2-isopropylthioxanthone hexafluoroantimonate,
7-[di(p-toluyl)sulfonio]-2-isopropylthioxanthone tetrakis(pentafluorophenyl)borate,
4-phenylcarbonyl-4'-diphenylsulfonio-diphenyl sulfide hexafluorophosphate,
4-(p-tert-butylphenylcarbonyl)-4′-diphenylsulfonio-diphenylsulfide hexafluoroantimonate,
4-(p-tert-butylphenylcarbonyl)-4′-di(p-toluyl)sulfonio-diphenylsulfide tetrakis(pentafluorophenyl)borate.

As the iron-arene complex, for example,
Xylene-cyclopentadienyl iron(II) hexafluoroantimonate,
Cumene-cyclopentadienyl iron(II) hexafluorophosphate,
Xylene-cyclopentadienyl iron(II) tris(trifluoromethylsulfonyl)methanide.

The photocationic polymerization initiator (C) may be used alone or in combination of two or more. Among the above, the aromatic sulfonium salt is particularly preferably used because it has an ultraviolet absorbing property even in a wavelength region of around 300 nm, and thus it is excellent in curability and can give an adhesive layer having good mechanical strength and adhesive strength. To be

The content of the cationic photopolymerization initiator (C) is 1 to 10 parts by weight, preferably 2 to 6 parts by weight, based on 100 parts by weight of the total amount of the cationic photocurable component (A) and the polymer (B). Is. By containing 1 part by weight or more of the cationic photopolymerization initiator (C), the cationic photocurable component (A) can be sufficiently cured, and the resulting polarizing plate has high mechanical strength and adhesive strength. On the other hand, when the amount is large, the ionic substance in the cured product increases, and the hygroscopicity of the cured product increases, which may reduce the durability performance of the polarizing plate. The amount of) is 10 parts by weight or less based on 100 parts by weight of the total amount of the cationic photocurable component (A) and the polymer (B).

(4) Branched alcohol compound (D)
The photocurable adhesive contains a branched alcohol compound (D) in addition to the photocationic curable component (A), the polymer (B) and the photocationic polymerization initiator (C). According to the photocurable adhesive containing these components, it has a low viscosity, bubble defects are less likely to occur in the adhesive layer after curing, the adhesive force between the polyvinyl alcohol-based polarizer and the thermoplastic resin film Can be improved.

The branched alcohol compound (D) has the following formula (IV):

The compound represented by R ³ represents an n-valent hydrocarbon group having a branched structure. n is an integer of 1 or more, represents the number of hydroxyl groups per molecule of the branched alcohol compound (D), and is the same as the valence number of the hydrocarbon group. "The hydrocarbon group has a branched structure" means that the main chain of the branched alcohol compound (D) is so composed as to contain at least one hydroxyl group represented by the above formula (IV) and to have the largest number of carbon atoms. When set, it means that the hydrocarbon group represented by R ³ has one or more side chains containing a carbon atom branched from the main chain.

The hydrocarbon group having a branched structure represented by R ³ can be, for example, a saturated hydrocarbon group having 3 or more carbon atoms or an unsaturated hydrocarbon group, preferably a saturated hydrocarbon group, and more preferably An aliphatic saturated hydrocarbon group, more preferably an alkylene group. The hydrocarbon group may contain atoms (hetero atoms) other than C and H atoms such as O atom, S atom, P atom, and halogen atom. For example, when the hydrocarbon group contains one or more methylene groups (—CH ₂ —) as in the case of an alkylene group, one or more of the methylene groups is a divalent linking group, for example, It may be substituted with -O-, -C(=O)-O-, or -OC(=O)-. The divalent linking group substituting the methylene group is preferably -O-.

Among the branched alcohol compounds (D), polyhydric alcohols having one or more hydroxyl groups bonded to secondary or tertiary carbons in the molecule, or polyhydric alcohols having secondary or tertiary carbons in the molecule are preferable.

Specific examples of the branched alcohol compound (D) include isopropyl alcohol, isobutyl alcohol, 2-butyl alcohol, 2-methyl-1-pentanol, 2-ethylhexyl alcohol, 2-nonyltridecanol, 2-undecylpenta. Decanol, 2-heptylundecanol, 2-ethylhexanol, 2-pentyl alcohol, isopentyl alcohol, isohexyl alcohol, isoheptyl alcohol, isooctyl alcohol, isononyl alcohol, isodecyl alcohol, isoundecyl alcohol, iso Monofunctional alcohols such as dodecyl alcohol, isotridecyl alcohol, isomyristyl alcohol, isopentadecyl alcohol, isopalmityl alcohol, isostearyl alcohol, isoicosyl alcohol; 1,2-propanediol, 1,2-butanediol, 1,5-hexanediol, dipropylene glycol, tripropylene glycol, 2-methyl-1,3-propanediol, 2,2-dimethyl-1,3-propanediol (neopentyl glycol), 1,1′-[ 1-methyl-1,2-ethanediylbis(oxy)]bis(2-propanol) (tripropylene glycol), 2,2-diethyl-1,3-propanediol, 3-methyl-1,5-pentanediol, 2 -Ethyl-1,3-hexanediol, 2,2,4-trimethyl-1,3-pentanediol, glycerin, trimethylolpropane, trimethylolethane, pentaerythritol, ditrimethylolpropane, tritrimethylolpropane, dipentaerythritol, Examples thereof include polyfunctional alcohols such as tripentaerythritol (compounds having two or more hydroxyl groups in the molecule). A commercial item can also be used as a branched alcohol compound (D).

From the viewpoint of lowering the viscosity, accelerating curing, and adhesive strength, the molecular weight of the branched alcohol compound (D) is preferably 400 or less, more preferably 300 or less, and further preferably 200 or less. Therefore, the number of carbon atoms in the hydrocarbon group is preferably 20 or less. The molecular weight of the branched alcohol compound (D) is usually 60 or more, preferably 80 or more, more preferably 100 or more.

The branched alcohol compound (D) may be a monofunctional alcohol, but is preferably a polyfunctional alcohol (compound having two or more hydroxyl groups in the molecule) from the viewpoint of lowering viscosity, promoting curing and adhesive strength, That is, n in the above formula (IV) is preferably 2 or more. n is usually 12 or less, preferably 10 or less, and more preferably 8 or less. n is more preferably an integer of 2 to 6.

The branched alcohol compound (D) is preferably a polyfunctional alcohol having a molecular weight of 60 to 400, more preferably a polyfunctional alcohol having a molecular weight of 80 to 300, and further preferably a polyfunctional alcohol having a molecular weight of 100 to 200. Suitable examples of the branched alcohol compound (D) are glycols such as dipropylene glycol and tripropylene glycol from the viewpoints of availability and safety, and reduction of viscosity, acceleration of curing and adhesive strength. The dipropylene glycol and tripropylene glycol mentioned here are compounds represented by the following formulas (a) and (b), respectively.

The inclusion of the branched alcohol compound (D) in the photocurable adhesive is also advantageous in that the ability to dissolve the thermoplastic resin film adhered to the polyvinyl alcohol-based polarizer (dissolving power) is not increased. In the photocurable adhesive to which the linear alcohol is added, it has been revealed by the study by the present inventors that when the solubility of the photocurable adhesive is high, bubble defects are likely to occur in the adhesive layer after curing. There is. It is speculated that this is because the film was dissolved in the photo-curable adhesive to increase the viscosity. According to the photocurable adhesive of the present invention containing the branched alcohol compound (D), since the contribution of the photocurable adhesive to the dissolving power is very small, the frequency of bubble generation before and after addition is not changed. On the other hand, when a linear alcohol compound is used instead of the branched alcohol compound (D), many bubble defects occur.

(5) Photosensitizer The photocurable adhesive may contain a photosensitizer. The above-mentioned photocationic polymerization initiator (C) exhibits maximum absorption in a wavelength range of around 300 nm or shorter, generates a cationic species or a Lewis acid in response to light having a wavelength in the vicinity thereof, and is a photocationic curable component. Although the cationic polymerization of (A) is initiated, the photosensitizer preferably has a maximum absorption in a wavelength region longer than 380 nm so as to be sensitive to light having a longer wavelength. Anthracene compounds are preferably used as the photosensitizer.

Specific examples of the anthracene-based compound include, for example,
9,10-dimethoxyanthracene,
9,10-diethoxyanthracene,
9,10-dipropoxyanthracene,
9,10-diisopropoxyanthracene,
9,10-dibutoxyanthracene,
9,10-dipentyloxyanthracene,
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-diisopropoxyanthracene,
2-methyl or 2-ethyl-9,10-dibutoxyanthracene,
2-methyl or 2-ethyl-9,10-dipentyloxyanthracene,
2-methyl or 2-ethyl-9,10-dihexyloxyanthracene may be mentioned.

By containing the photosensitizer in the photocurable adhesive, the curability of the adhesive can be improved as compared with the case where the photosensitizer is not contained. By setting the content of the photosensitizer to 0.1 parts by weight or more based on 100 parts by weight of the total amount of the cationic photocurable component (A) and the polymer (B), such an effect can be exhibited. On the other hand, when the content of the photosensitizer increases, problems such as precipitation during low temperature storage occur. Therefore, the content is 100 parts by weight of the total amount of the photocationic curable component (A) and the polymer (B). On the other hand, it is preferably 2 parts by weight or less. Further, from the viewpoint of maintaining the neutral gray of the polarizing plate, it is advantageous to reduce the content of the photosensitizer within a range in which the effect of improving the adhesive strength between the polarizer and the thermoplastic resin film can be sufficiently obtained. For example, the content of the photosensitizer is 0.1 to 0.5 parts by weight, more preferably 0.1 to 100 parts by weight with respect to the total amount of the cationic photocurable component (A) and the polymer (B). It is preferably in the range of 0.3 to 0.3 parts by weight.

(6) Photosensitization auxiliary agent The photocurable adhesive may contain a photosensitization auxiliary agent. The photosensitizer is preferably a naphthalene photosensitizer.

Specific examples of the naphthalene photosensitizer include, for example,
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-dipropoxynaphthalene,
1,4-dibutoxynaphthalene may be mentioned.

By containing the naphthalene-based photosensitization aid in the photocurable adhesive, the curability of the adhesive can be improved as compared with the case where it is not contained. The content of the naphthalene-based photosensitization aid is 0.1 part by weight or more based on 100 parts by weight of the total amount of the photo-cationic curable component (A) and the polymer (B), so that such effects can be exhibited. You can On the other hand, when the content of the naphthalene-based photosensitization aid increases, problems such as precipitation during low-temperature storage occur, so the content is the total amount of the photocationic curable component (A) and the polymer (B). It is preferably 5 parts by weight or less with respect to 100 parts by weight. The content of the naphthalene photosensitizer is preferably 3 parts by weight or less based on 100 parts by weight of the total amount of the photocationic curable component (A) and the polymer (B).

(7) Additive component The photocurable adhesive may contain an additive component as another optional component as long as the effect of the present invention is not impaired. As the additive component, a thermal cationic polymerization initiator, an alcohol compound other than the branched alcohol compound (polyols other than the branched alcohol compound), an ion trap agent, an antioxidant, a light stabilizer, a chain transfer agent, a tackifier, Examples include thermoplastic resins, fillers, flow regulators, plasticizers, defoamers, leveling agents, dyes, organic solvents and the like.

When the additive component is contained, its content is preferably 1000 parts by weight or less based on 100 parts by weight of the total amount of the photocationic curable component (A) and the polymer (B). When the content is 1000 parts by weight or less, polyvinyl alcohol is obtained by combining the photocationic curable component (A), the polymer (B), the photocationic polymerization initiator (C) and the branched alcohol compound (D) which are essential components. Of excellent adhesive strength between a resin-based polarizer and a thermoplastic resin film, a low viscosity of a photocurable adhesive and good coatability associated therewith, and an effect of suppressing bubble defects in an adhesive layer after curing Can be exhibited satisfactorily.

(8) Water Content of Photocurable Adhesive The photocurable adhesive may contain water. The content of water is usually 4 parts by weight or less, preferably 3 parts by weight or less, and more preferably 3 parts by weight, based on 100 parts by weight of the total amount of the photocationic curable component (A) and the polymer (B). Is less than. By containing a slight amount of water exceeding 0 part by weight, the adhesive strength between the polyvinyl alcohol-based polarizer and the thermoplastic resin film may be improved. The water content is usually 0.01 parts by weight or more, preferably 0.03 parts by weight or more, based on 100 parts by weight of the total amount of the photocationic curable component (A) and the polymer (B). More preferably, it is 0.04 part by weight or more. However, if the water content is too high, the photocurable adhesive and the water are separated from each other, and the photocurable adhesive cannot be evenly applied to the surface of the polarizer or the thermoplastic resin film, or The curability of the photocurable adhesive may deteriorate. Water may be intentionally added to the photocurable adhesive, and in this case, purified water such as distilled water and pure water can be used, although not particularly limited thereto. The water content may be water content derived from raw materials, water content mixed in the manufacturing process, or the like. The water content of the photocurable adhesive is measured by the Karl Fischer capacitance method.

(9) Physical Properties of Photocurable Adhesive The photocurable adhesive according to the present invention can have low viscosity, and specifically, the viscosity at 25° C. is in the range of 2 to 300 mPa·s. it can. The viscosity referred to here is the viscosity in a state that the solvent is not substantially contained. If the viscosity is less than 2 mPa·s, the polarizer and the thermoplastic resin film may be peeled off during transportation after bonding, and if the viscosity exceeds 300 mPa·s, the polarizer, the thermoplastic resin film, and the adhesive may intervene. When they are laminated together, particularly when the adhesive layer is thin, air bubbles are easily mixed between the polarizer and the thermoplastic resin film, that is, the adhesive layer. The viscosity is more preferably 5 to 200 mPa·s, further preferably 10 to 150 mPa·s. When the viscosity is 150 mPa·s or less, even when the thickness of the adhesive layer is as thin as 2.8 μm or less, it is possible to more effectively suppress the generation of bubbles in the adhesive layer. The viscosity of the photocurable adhesive is measured using an E-type viscometer.

<Polarizing plate>
The polarizing plate according to the present invention includes a polyvinyl alcohol-based polarizer and a thermoplastic resin film that is bonded to at least one surface of the polyvinyl alcohol-based polarizer via the cured product of the photocurable adhesive. Since the polarizing plate uses the photo-curable adhesive according to the present invention, the adhesive strength between the polarizer and the thermoplastic resin film is high and the durability is excellent, and at the same time, bubbles of the cured adhesive layer are not formed. Contamination (bubble defect) is suppressed.

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

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

Uniaxial stretching may be performed before dyeing with a dichroic dye, simultaneously with dyeing with a dichroic dye, or after dyeing with a dichroic dye. When the uniaxial stretching is performed after dyeing with the dichroic dye, the uniaxial stretching may be performed before the boric acid treatment or during the boric acid treatment. It is also possible to carry out uniaxial stretching in these plural stages. The method of uniaxial stretching is not particularly limited, and may be uniaxially stretched between rolls having different peripheral speeds, or may be uniaxially stretched using a hot roll. Further, it may be dry stretching in which stretching is performed in the atmosphere, or wet stretching in which stretching is performed in a state of being swollen by a solvent. The draw ratio is usually about 4 to 8 times.

The dichroic dye can be adsorbed by immersing the polyvinyl alcohol-based resin film in an aqueous solution containing the dichroic dye. Iodine or a dichroic organic dye is used as the dichroic pigment.

When iodine is used as the dichroic dye, a method of immersing the polyvinyl alcohol-based resin film in an aqueous solution containing iodine and potassium iodide and dyeing is usually adopted. 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. 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 a polyvinyl alcohol resin film in an aqueous solution containing a water-soluble dichroic organic dye and dyeing is usually employed. The content of the dichroic organic dye in this aqueous solution is usually about 1×10 ⁻³ to 1×10 ⁻² parts by weight per 100 parts by weight of water. This aqueous solution may contain an inorganic salt such as sodium sulfate. The temperature of this aqueous solution is usually about 20 to 80° C., and the immersion time (dyeing time) in this aqueous solution is usually about 30 to 300 seconds.

The boric acid treatment after dyeing is performed by immersing the dyed polyvinyl alcohol resin film in an aqueous boric acid solution. The content of boric acid 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, this 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, per 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 boric acid aqueous solution is usually 50°C or higher, preferably 50 to 85°C.

The polyvinyl alcohol-based resin film after the boric acid treatment is usually washed with water. The water washing treatment can be carried out by, for example, immersing the boric acid-treated polyvinyl alcohol-based 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 subsequent drying treatment can be usually performed using a hot air dryer or a far infrared heater. The drying temperature is usually 40 to 100°C. The time for the drying process is usually about 120 to 600 seconds. The polyvinyl alcohol-based polarizer may have a thickness of about 5 to 50 μm.

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

The thermoplastic resin forming the thermoplastic resin film is preferably one or more selected from the group consisting of cellulose resins, (meth)acrylic resins, amorphous polyolefin resins, polyester resins and polycarbonate resins. Resin.

The polyester resin is not particularly limited, but a polyethylene terephthalate resin is preferable in terms of mechanical properties, solvent resistance, scratch resistance, cost and the like. The polyethylene terephthalate-based resin means a resin in which 80 mol% or more of the repeating unit is composed of ethylene terephthalate, and may contain a constituent unit derived from another copolymerization component.

Examples of the other copolymerization component include a dicarboxylic acid component and a diol component. Examples of the dicarboxylic acid component include isophthalic acid, 4,4′-dicarboxydiphenyl, 4,4′-dicarboxybenzophenone, bis(4-carboxyphenyl)ethane, adipic acid, sebacic acid, 5-sodium sulfoisophthalic acid, and 1,4-dicarboxycyclohexane etc. are mentioned. Examples of the diol component include propylene glycol, butane diol, neopentyl glycol, diethylene glycol, cyclohexane diol, ethylene oxide adduct of bisphenol A, polyethylene glycol, polypropylene glycol, and polytetramethylene glycol. These dicarboxylic acid components and diol components may be used in combination of two or more kinds, if necessary. It is also possible to use a hydroxycarboxylic acid such as p-hydroxybenzoic acid or p-β-hydroxyethoxybenzoic acid together with the above-mentioned dicarboxylic acid component and diol component. As the other copolymerization component, a small amount of a dicarboxylic acid component and/or a diol component having an amide bond, a urethane bond, an ether bond, a carbonate bond or the like may be used.

By using polyethylene terephthalate resin as a film and then stretching it as a thermoplastic resin film, it has excellent mechanical properties, solvent resistance, scratch resistance, cost, etc. The board can be obtained.

Polycarbonate resin is a polyester formed from carbonic acid and glycol or bisphenol. Among them, aromatic polycarbonate having diphenylalkane in the molecular chain is preferably used because it has excellent heat resistance, weather resistance and acid resistance. Examples of such polycarbonate include 2,2-bis(4-hydroxyphenyl)propane (also called bisphenol A), 2,2-bis(4-hydroxyphenyl)butane, 1,1-bis(4-hydroxyphenyl)cyclohexane, Examples include polycarbonates derived from bisphenols such as 1,1-bis(4-hydroxyphenyl)isobutane and 1,1-bis(4-hydroxyphenyl)ethane.

The (meth)acrylic resin is not particularly limited, but is generally a polymer having a methacrylic acid ester as a main monomer, and is preferably a copolymer in which a small amount of another comonomer component is copolymerized. .. This copolymer can be usually obtained by polymerizing a monofunctional monomer composition containing methyl methacrylate and methyl acrylate in the presence of a radical polymerization initiator and a chain transfer agent. Further, the (meth)acrylic resin may be copolymerized with a third monofunctional monomer.

Examples of the third monofunctional monomer include methacrylic acid such as ethyl methacrylate, butyl methacrylate, cyclohexyl methacrylate, phenyl methacrylate, benzyl methacrylate, 2-ethylhexyl methacrylate, and 2-hydroxyethyl methacrylate. Methacrylic acid esters other than methyl; acrylic acid esters such as ethyl acrylate, butyl acrylate, cyclohexyl acrylate, phenyl acrylate, benzyl acrylate, 2-ethylhexyl acrylate, and 2-hydroxyethyl acrylate; 2- Hydroxyalkyl acrylates such as methyl (hydroxymethyl)acrylate, methyl 2-(1-hydroxyethyl)acrylate, ethyl 2-(hydroxymethyl)acrylate, and butyl 2-(hydroxymethyl)acrylate; methacryl Unsaturated acids such as acids and acrylic acids; halogenated styrenes such as chlorostyrene and bromostyrene; substituted styrenes such as vinyltoluene and α-methylstyrene; unsaturated nitriles such as acrylonitrile and methacrylonitrile; maleic anhydride And unsaturated acid anhydrides such as citraconic anhydride; and unsaturated imides such as phenylmaleimide and cyclohexylmaleimide. The third monofunctional monomer may be used alone or in combination of two or more different types.

A polyfunctional monomer may be copolymerized with the (meth)acrylic resin. Examples of the polyfunctional monomer include ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, nonaethylene glycol di(meth). Acrylate and ethylene glycol such as tetradecaethylene glycol di(meth)acrylate or the oligomer thereof whose both end hydroxyl groups are esterified with (meth)acrylic acid; propylene glycol or its oligomer both end hydroxyl groups of (meth)acrylic acid Esterified with; a hydroxyl group of a dihydric alcohol such as neopentyl glycol di(meth)acrylate, hexanediol di(meth)acrylate, and butanediol di(meth)acrylate esterified with (meth)acrylic acid; Bisphenol A, an alkylene oxide adduct of bisphenol A, or a halogen-substituted product thereof having both hydroxyl groups at both ends esterified with (meth)acrylic acid; polyhydric alcohols such as trimethylolpropane and pentaerythritol (meth)acrylic acid Esterified with, and those obtained by ring-opening addition of epoxy group of glycidyl (meth)acrylate to these terminal hydroxyl groups; dibasic acids such as succinic acid, adipic acid, terephthalic acid, phthalic acid, halogen substitution products thereof, And those obtained by ring-opening addition of an epoxy group of (meth)glycidyl acrylate to these alkylene oxide adducts; aryl (meth)acrylate; aromatic divinyl compounds such as divinylbenzene. Among them, ethylene glycol dimethacrylate, tetraethylene glycol dimethacrylate, and neopentyl glycol dimethacrylate are preferably used.

The (meth)acrylic resin may be modified by further reacting the functional groups of the copolymer. As the reaction, for example, a polymer chain demethanol condensation reaction between a methyl ester group of methyl acrylate and a hydroxyl group of 2-(hydroxymethyl)methyl acrylate, a carboxyl group of acrylic acid and 2-(hydroxymethyl)acryl Examples include dehydration condensation reaction in the polymer chain with the hydroxyl group of methyl acidate.

The glass transition temperature Tg of the (meth)acrylic resin is preferably in the range of 80 to 120°C. In order to adjust the Tg of the (meth)acrylic resin within the above range, the polymerization ratio of the methacrylic acid ester monomer and the acrylic acid ester monomer, the carbon chain length of each ester group, or the ratio A method of appropriately selecting the type of functional group or the polymerization ratio of the polyfunctional monomer to the entire monomer is adopted.

The (meth)acrylic resin may contain known additives as necessary. Examples of known additives include a lubricant, an antiblocking agent, a heat stabilizer, an antioxidant, an antistatic agent, a light resistance agent, an impact resistance improving agent, and a surfactant. However, since transparency is required as the thermoplastic resin film laminated on the polarizer, it is preferable to keep the amount of these additives to a minimum.

The (meth)acrylic resin may contain acrylic rubber particles, which are impact modifiers, from the viewpoint of film-forming property on the film, impact resistance of the film, and the like. The acrylic rubber particles as referred to herein are particles having an elastic polymer mainly composed of an acrylic ester as an essential component, and having a single-layer structure consisting essentially of this elastic polymer, or this elastic polymer. There is a multi-layer structure in which is one layer. Examples of such an elastic polymer include a crosslinked elastic copolymer in which an alkyl acrylate as a main component is copolymerized with another copolymerizable vinyl monomer and a crosslinkable monomer. Examples of the alkyl acrylate as the main component of the elastic polymer include those having an alkyl group having about 1 to 8 carbon atoms such as methyl acrylate, ethyl acrylate, butyl acrylate, and 2-ethylhexyl acrylate, and particularly carbon. An acrylate having an alkyl group of 4 or more is preferably used. Examples of other vinyl monomers copolymerizable with the alkyl acrylate include compounds having one polymerizable carbon-carbon double bond in the molecule, and more specifically, methacrylic acid such as methyl methacrylate. Examples thereof include esters, aromatic vinyl compounds such as styrene, and vinyl cyan compounds such as acrylonitrile. Further, examples of the crosslinkable monomer include crosslinkable compounds having at least two polymerizable carbon-carbon double bonds in the molecule, and more specifically, ethylene glycol di(meth)acrylate and butanediol. Examples thereof include (meth)acrylates of polyhydric alcohols such as di(meth)acrylate, alkenyl esters of (meth)acrylic acid such as allyl (meth)acrylate, and divinylbenzene.

Also, a laminate of a film made of a (meth)acrylic resin containing no rubber particles and a film made of a (meth)acrylic resin containing rubber particles can be used as the thermoplastic resin film. Commercially available (meth)acrylic resins can be easily obtained. For example, "SUMIPEX" (manufactured by Sumitomo Chemical Co., Ltd.) and "ACRYPET" (manufactured by Mitsubishi Rayon Co., Ltd.) are trade names. , "Delpet" (manufactured by Asahi Kasei Co., Ltd.), "Parapet" (manufactured by Kuraray Co., Ltd.), "Acryviewer" (manufactured by Nippon Shokubai Co., Ltd.) and the like.

Amorphous polyolefin resin is a resin obtained by performing ring-opening metathesis polymerization using norbornene or its derivative obtained by Diels-Alder reaction from cyclopentadiene and olefins as a monomer and then hydrogenating it; dicyclopentadiene and olefin. Of tetracyclododecene or its derivative obtained by Diels-Alder reaction with bisphenol or methacrylic acid ester as a monomer, and subjected to ring-opening metathesis polymerization, followed by hydrogenation; norbornene, tetracyclododecene and their resins. A resin obtained by similarly performing ring-opening metathesis copolymerization using two or more kinds selected from derivatives and other cyclic polyolefin monomers, and then obtained by hydrogenation; norbornene, tetracyclododecene or their derivatives. And resins obtained by addition-copolymerizing aromatic compounds having a vinyl group. Examples of commercially available amorphous polyolefin resins include "Arton" from JSR Corporation, "ZEONEX" and "ZEONOR" from Nippon Zeon Co., Ltd., "APO" and "ZEPO" from Mitsui Chemicals, Inc. "Apel" etc.

The cellulosic resin is a resin in which at least a part of hydroxyl groups in cellulose is acetic acid esterified, and a part thereof is acetic acid esterified and a part thereof is esterified with another acid, and may be a mixed ester. .. The cellulose resin is preferably a cellulose ester resin, and more preferably an acetyl cellulose resin. Specific examples of the acetyl cellulose-based resin include triacetyl cellulose, diacetyl cellulose, cellulose acetate propionate, and cellulose acetate butyrate. Examples of commercially available films of such acetyl cellulose-based resins include "Fujitac TD80", "Fujitac TD80UF" and "Fujitac TD80UZ" manufactured by Fuji Film Co., Ltd., and "KC8UX2M" manufactured by Konica Minolta Opto Co., Ltd. And “KC8UY” and the like.

As the thermoplastic resin film, a cellulose resin film having an optical compensation function may be used. As such an optical compensation film, for example, a film containing a compound having a retardation adjusting function in a cellulose resin, a film in which a compound having a retardation adjusting function is coated on the surface of the cellulose resin, a uniaxial or biaxial cellulose resin. Examples thereof include a film obtained by stretching in the axis. Examples of commercially available cellulose-based resin optical compensation films include "Wide View Film WV BZ 438" and "Wide View Film WV EA" manufactured by Fuji Film Co., Ltd., manufactured by Konica Minolta Opto Co., Ltd. There are "KC4FR-1" and "KC4HR-1".

The thickness of the thermoplastic resin film is usually in the range of about 5 to 200 μm, preferably 10 to 120 μm, more preferably 10 to 85 μm. Even if the surface of the thermoplastic resin film opposite to the adhesive surface to the polarizer is provided with various surface treatment layers (coating layers) such as a hard coat layer, an antireflection layer, an antiglare layer, and a light diffusion layer. Good.

The thermoplastic resin film adhered to at least one surface of the polarizer may contain an ultraviolet absorber. By disposing the thermoplastic resin film containing the ultraviolet absorber on the viewing side of the liquid crystal cell, the liquid crystal cell can be protected from deterioration due to ultraviolet rays. Examples of the ultraviolet absorber include salicylic acid ester compounds, benzophenone compounds, benzotriazole compounds, cyanoacrylate compounds, nickel complex salt compounds, and the like.

(3) Production of Polarizing Plate A polarizing plate can be obtained by bonding a thermoplastic resin film to at least one surface of a polarizer using the above-mentioned photocurable adhesive. Specifically, after the coating layer of the above-mentioned photocurable adhesive is formed on the adhesive surface of the polarizer and/or the thermoplastic resin film, the polarizer and the thermoplastic resin film are bonded via the coating layer. The coating layer of the uncured photocurable adhesive is cured by irradiation with active energy rays to fix the thermoplastic resin film on the polarizer. Various coating methods such as a doctor blade, a wire bar, a die coater, a comma coater, and a gravure coater can be used to form the coating layer of the photocurable adhesive. Further, it is possible to adopt a method in which the polarizer and the thermoplastic resin film are continuously supplied so that the bonding surfaces of the polarizer and the thermoplastic resin film are on the inside, and the adhesive is cast between them.

Depending on the coating method of the photocurable adhesive, a solvent may be used to adjust the viscosity of the photocurable adhesive. As the solvent, a solvent that can dissolve the photocurable adhesive well without deteriorating the optical performance of the polarizer is used, but the kind thereof is not particularly limited. For example, organic solvents such as hydrocarbons typified by toluene and esters typified by ethyl acetate can be used. However, when a solvent is contained, it is necessary to provide a drying step for removing the solvent before the irradiation with the active energy rays. Therefore, it is preferable not to use the solvent as much as possible.

The thickness of the adhesive layer after curing can be arbitrarily set by designing the characteristics of the polarizing plate, but it is preferably smaller from the viewpoint of reducing the adhesive material cost. Generally, it 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, air bubbles are likely to be mixed into the adhesive layer, and the adhesion and durability are likely to decrease, but the photocurable adhesive of the present invention effectively suppresses this. You can

When the thermoplastic resin film is adhered only on one side of the polarizer, for example, a form such as directly providing an adhesive layer for adhering to another optical member such as a liquid crystal cell on the other side of the polarizer is adopted. Can also On the other hand, when the thermoplastic resin films are adhered to both surfaces of the polarizer, these thermoplastic resin films may be made of the same kind of resin or different kinds of resins. The thermoplastic resin film adhered to one surface of the polarizer is adhered using the above-described photo-curable adhesive according to the present invention, but the thermoplastic resin film adhered to the other surface of the polarizer is The photo-curable adhesive according to the present invention may be used for adhesion, or another adhesive may be used for adhesion.

Prior to adhering the thermoplastic resin film to the polarizer, the adhesive surface of the thermoplastic resin film and/or the polarizer can be easily subjected to saponification treatment, corona treatment, plasma treatment, primer treatment, anchor coating treatment, flame treatment, etc. Adhesion treatment may be performed.

The light source used for irradiating the coating layer of the photocurable adhesive with the active energy ray may be any one that can generate ultraviolet rays, electron beams, X-rays and 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, and a metal halide lamp, which have a light emission distribution at a wavelength of 400 nm or less, are preferably used.

The irradiation intensity of the active energy ray to the photocurable adhesive is not particularly limited, but the irradiation intensity in the wavelength region effective for activating the photocationic polymerization initiator (C) is 0.1 to 3000 mW/cm ^2. preferable. If it is less than 0.1 mW/cm ² , the reaction time becomes too long, and if it exceeds 3000 mW/cm ² , the heat radiated from the lamp and the heat generated during the polymerization of the photocurable adhesive cause a photocurable adhesive. Yellowing and deterioration of the polarizer may occur.

The light irradiation time to the photocurable adhesive is not particularly limited, but it is preferable to set it so that the integrated light amount represented by the product of the irradiation intensity and the irradiation time is 10 to 5000 mJ/cm ² . If it is less than 10 mJ/cm ² , the generation of active species derived from the photocationic polymerization initiator (C) may not be sufficient, and the resulting adhesive layer may be insufficiently cured, while the accumulated light amount thereof is insufficient. When it exceeds 5000 mJ/cm ² , the irradiation time becomes very long, which is disadvantageous for improving productivity.

When adhering the thermoplastic resin film on both sides of the polarizer, irradiation of active energy rays may be performed from either thermoplastic resin film side, for example, one thermoplastic resin film contains an ultraviolet absorber, If the other thermoplastic resin film does not contain an ultraviolet absorber, irradiating the active energy ray from the thermoplastic resin film side that does not contain the ultraviolet absorber, effectively utilize the active energy ray irradiated, It is preferable for increasing the curing rate.

The polarizing plate obtained by curing the photo-curable adhesive preferably has a peel strength of 0.5 N/25 mm or more between the polarizer and the thermoplastic resin film, which is measured by a 180-degree peel test. It is more preferably 1 N/25 mm or more. If the peel strength is less than 0.5 N/25 mm, peeling may occur between the polarizer and the adhesive layer when the polarizing plate is cut.

One embodiment of manufacturing a polarizing plate will be described with reference to FIG. FIG. 1 is a schematic sectional view showing a preferred example of an apparatus for producing a polarizing plate. A photo-curable adhesive is applied to one surface of each of the thermoplastic resin films 2 and 3 that are continuously unrolled from the rolled state by the adhesive application devices 11 and 12. Then, the thermoplastic resin films 2 and 3 are superposed on both surfaces of the polarizer 1 that is continuously drawn out in the same manner as the thermoplastic resin films 2 and 3 by the bonding rolls 5a and 5b with the adhesive coating layer interposed therebetween. Then, the laminated body 4 is manufactured. The diameter of the bonding rolls 5a and 5b is, for example, 50 to 250 mm.

Then, the laminate 4 is irradiated with an active energy ray to cure the coating layer of the adhesive, whereby a polarizing plate can be manufactured. In the example shown in FIG. 1, the manufactured laminated body 4 is conveyed while being brought into close contact with the outer peripheral surface of the roll 13. The first active energy ray irradiation devices 14 and 15 are installed at positions facing the outer peripheral surface of the roll 13, and the second active energy ray irradiation device 16 and the third active energy irradiation devices are disposed downstream from the first active energy ray irradiation devices 14 and 15. The ray irradiation device 17 and the fourth active energy ray irradiation device 18 are sequentially provided along the transport direction. As a result, the adhesive coating layer of the laminated body 4 receives the active energy rays from the first active energy ray irradiation devices 14 and 15 in the process in which the laminated body 4 is conveyed while being in close contact with the outer peripheral surface of the roll 13. Is further polymerized and cured, and further cured by the active energy rays from the second active energy ray irradiation device 16, the third active energy ray irradiation device 17 and the fourth active energy ray irradiation device 18 on the downstream side. The second and subsequent active energy ray irradiation devices 16, 17 and 18 arranged on the downstream side in the transport direction are devices for completely polymerizing and curing the adhesive, and can be added or omitted as necessary. Finally, the cured laminated body 4 passes through the transport nip roll 19 and is wound around the winding roll 20 as a polarizing plate.

The roll 13 is composed of a convex curved surface having a mirror-finished outer peripheral surface, and conveys the laminated body 4 while closely adhering to the surface thereof, and in the process, the active energy ray irradiation devices 14 and 15 polymerize and cure the adhesive coating layer. .. The diameter of the roll 13 is not particularly limited in order to polymerize and cure the adhesive and sufficiently bring the films constituting the laminate 4 into close contact with each other. The roll 13 may be driven or rotationally driven by the movement of the line of the laminate 4, or may be fixed so that the laminate 4 slides on the surface. Further, the roll 13 may act as a cooling roll for radiating the heat generated in the laminated body 4 at the time of polymerization and curing by irradiation with active energy rays. In that case, the surface temperature of the roll 13 which acts as a cooling roll is preferably set to 4 to 30° C.

<Laminate optical member and liquid crystal display device>
The polarizing plate of the present invention can be made into a laminated optical member by laminating optical layers having an optical function other than the polarizing plate. Typically, it is a laminated optical member by laminating and adhering an optical layer on a thermoplastic resin film of a polarizing plate via an adhesive or a pressure-sensitive adhesive, but in addition, for example, on one surface of a polarizer. The thermoplastic resin film may be adhered via the photo-curable adhesive according to the present invention, and the optical layer may be laminated and adhered to the other surface of the polarizer via an adhesive or a pressure-sensitive adhesive. In the latter case, if the photocurable adhesive according to the present invention is used as an adhesive for adhering the polarizer and the optical layer, the optical layer can simultaneously serve as a thermoplastic resin film. Two or more optical layers may be laminated on the polarizing plate.

The optical layer laminated on the polarizing plate is a reflective layer, a semi-transmissive reflective layer, or a light-transmitting layer, which is laminated on the opposite side of the polarizing plate to the liquid crystal cell with respect to the polarizing plate arranged on the back side of the liquid crystal cell. Examples thereof include a diffusion layer, a light collector, and a brightness enhancement film. Further, with respect to the polarizing plate arranged on the front side of the liquid crystal cell and/or the polarizing plate arranged on the back side of the liquid crystal cell, a retardation plate laminated on the liquid crystal cell side of the polarizing plate and the like can be mentioned.

The reflective layer, the semi-transmissive reflective layer, and the light diffusion layer are provided to form a laminated optical member that is a reflective polarizing plate, a semi-transmissive reflective polarizing plate, and a diffusive polarizing plate, respectively. The reflective polarizing plate is used in a liquid crystal display device of a type that reflects incident light from the viewing side and displays the light. Since a light source such as a backlight can be omitted, the liquid crystal display device can be easily thinned. Further, the semi-transmissive polarizing plate is used in a liquid crystal display device of a type that is reflective in a bright place and is displayed in a dark place by light from a backlight. The reflective polarizing plate can be produced, for example, by forming a reflective layer by attaching a foil or a vapor deposition film made of a metal such as aluminum to a thermoplastic resin film on the polarizer. A semi-transmissive polarizing plate can be produced by using the above-mentioned reflective layer as a half mirror or by adhering a light-reflecting reflecting plate containing a pearl pigment or the like to the polarizing plate. On the other hand, the diffusion type polarizing plate may be prepared by various methods such as a method of matting a thermoplastic resin film on the polarizing plate, a method of applying a resin containing fine particles, a method of adhering a film containing fine particles, etc. It can be manufactured by forming a fine concavo-convex structure on the surface.

Further, the laminated optical member can be a polarizing plate for both reflection and diffusion. The polarizing plate for both reflection and diffusion can be produced, for example, by providing a reflecting layer reflecting the uneven structure on the surface of the fine uneven structure of the diffusion type polarizing plate. The reflection layer having a fine concavo-convex structure has advantages such as diffused incident light by diffuse reflection, prevention of directivity and glare, and suppression of uneven brightness. Further, the resin layer or film containing fine particles diffuses incident light and reflected light thereof, and therefore has an advantage that uneven brightness can be suppressed. 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 a method such as vacuum deposition, ion plating, vapor deposition such as sputtering, or plating. The fine particles to be added to form the surface fine uneven structure are, for example, silica having an average particle diameter of 0.1 to 30 μm, aluminum oxide, titanium oxide, zirconia, tin oxide, indium oxide, cadmium oxide, antimony oxide. Inorganic fine particles, organic fine particles such as crosslinked or non-crosslinked polymers, and the like.

The light collector is used for the purpose of controlling the optical path, and can be formed as a prism array sheet, a lens array sheet, a dot-attached sheet, or the like.

The brightness enhancement film is used for the purpose of improving the brightness in a liquid crystal display device, and its specific example is a laminate of a plurality of thin films having different anisotropies in refractive index, resulting in anisotropy in reflectance. The reflective polarization separation sheet designed as described above, the oriented film of the cholesteric liquid crystal polymer, and the circular polarization separation sheet in which the oriented liquid crystal layer is supported on the film substrate.

The retardation plate is used for the purpose of compensating the retardation of the liquid crystal cell. Specific examples thereof include a birefringent film made of a stretched film of various plastics, a film in which discotic liquid crystal or nematic liquid crystal is fixed in alignment, and a film in which the above liquid crystal layer is formed on a film substrate. When the liquid crystal layer is formed on the film substrate, a cellulose resin film such as triacetyl cellulose is preferably used as the film substrate.

As the plastic forming the birefringent film, for example, amorphous polyolefin resin, polycarbonate resin, (meth)acrylic resin, chain polyolefin resin such as polypropylene, polyvinyl alcohol, polystyrene, polyarylate, polyamide Etc. The stretched film may be processed by an appropriate method such as uniaxial or biaxial. Two or more retardation plates may be used in combination for the purpose of controlling optical characteristics such as widening the band.

As the laminated optical member, a laminated optical member including a retardation plate as an optical layer other than the polarizing plate is preferably used because it can effectively perform optical compensation when applied to a liquid crystal display device. The retardation value (in-plane and thickness direction) of the retardation plate is adjusted according to the applied liquid crystal cell.

The laminated optical member can be made into a laminated body of 2 layers or 3 layers by combining a polarizing plate and 1 layer or 2 layers or more selected from the above various optical layers according to the purpose of use. In that case, various optical layers forming the laminated optical member are integrated with the polarizing plate by using an adhesive or a pressure-sensitive adhesive (also referred to as a pressure-sensitive adhesive). There is no particular limitation as long as the agent layer and the pressure-sensitive adhesive layer are well formed. It is preferable to use a pressure-sensitive adhesive from the viewpoints of easiness of adhesion work and prevention of optical distortion. As the pressure-sensitive adhesive, one having a (meth)acrylic polymer, a silicone polymer, polyester, polyurethane, polyether or the like as a base polymer can be used. Among them, like (meth)acrylic pressure-sensitive adhesives, they have excellent optical transparency, maintain appropriate wettability and cohesive force, and also have excellent adhesiveness to base materials, and further have weather resistance, heat resistance, etc. It is preferable to select and use a material that has no problem such as floating or peeling under the conditions of heating and humidification. In the (meth)acrylic pressure-sensitive adhesive, an alkyl ester of (meth)acrylic acid having an alkyl group having 20 or less carbon atoms such as a methyl group, an ethyl group, and a butyl group, and (meth)acrylic acid or (meth)acrylic A functional group-containing (meth)acrylic monomer such as hydroxyethyl acid is mixed so that the glass transition temperature is preferably 25° C. or lower, more preferably 0° C. or lower, and the weight average molecular weight is 100,000 or more (meth ) Acrylic copolymers are useful as base polymers.

The pressure-sensitive adhesive layer is formed on the polarizing plate by, for example, dissolving or dispersing the pressure-sensitive adhesive composition in an organic solvent such as toluene or ethyl acetate to prepare a 10 to 40 wt% solution, which is directly applied to the polarizing plate. It can be performed by a coating method, a method of previously forming an adhesive layer on a release film, and then transferring the adhesive layer onto a polarizing plate. The thickness of the pressure-sensitive adhesive layer is determined according to its adhesive strength and the like, but a range of about 1 to 50 μm is suitable.

If necessary, the adhesive layer contains glass fibers, glass beads, resin beads, fillers made of metal powder or other inorganic powder, pigments or colorants, antioxidants, ultraviolet absorbers and the like. Good. Examples of the ultraviolet absorber include salicylic acid ester compounds, benzophenone compounds, benzotriazole compounds, cyanoacrylate compounds, nickel complex salt compounds, and the like.

A liquid crystal display device according to the present invention includes a liquid crystal cell and the laminated optical member of the present invention disposed on at least one surface thereof, and includes the polarizing plate of the present invention in place of the laminated optical member. May be The polarizing plate and the laminated optical member can 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 according to the present invention may be a polarizing plate and a laminated optical member each having an adhesive layer on the outer surface of which an adhesive layer for laminating to a liquid crystal cell is laminated. 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 represented by a thin film transistor type and a simple matrix drive type represented by a super twisted nematic type. Can be formed.

Hereinafter, the present invention will be described more specifically by showing Examples and Comparative Examples, but the present invention is not limited to these Examples. In the following, parts and% representing the used amount or the content are based on weight unless otherwise specified. The photocationic curable component (A), polymer (B), photocationic polymerization initiator (C) and branched alcohol compound (D) used in the following examples are as follows.

[Cationic photo-curable component (A)]
First photo-cationic curable component (A1):
a1-I: bisphenol A type epoxy resin "ADEKA RESIN EP-4100L" manufactured by ADEKA Corporation,
a1-II: Bisphenol A type multifunctional epoxy resin "ADEKA RESIN EP-5100R" manufactured by ADEKA CORPORATION,
a1-III: aromatic trifunctional epoxy resin “TECHMORE VG3101” manufactured by Printec Co., Ltd.

Second photo-cationic curable component (A2):
a2-I: neopentyl glycol diglycidyl ether [In the formula _{(III), Z = -CH 2} C (CH 3) 2 CH 2 - compound]
a2-II: 3-ethyl-3{[(3-ethyloxetane-3-yl)methoxy]methyl}oxetane.

Third photo-cationic curable component (A3):
a3: An alicyclic epoxy resin “Ceroxide 2021P” manufactured by Daicel Corporation.

[Polymer (B)]
b: a polymer having a weight average molecular weight of 8000 (GMA-MMA copolymer) obtained by radical polymerization of a monomer composition comprising 25 parts of glycidyl methacrylate (GMA) and 75 parts of methyl methacrylate (MMA).

[Cationic photopolymerization initiator (C)]
Diphenyl(phenylthio)phenylsulfonium hexafluorophosphate.

[Branched alcohol compound (D)]
d-I: dipropylene glycol (a compound represented by the above formula (a)),
d-II: Tripropylene glycol (a compound represented by the above formula (b)).

<Examples 1 to 7, Comparative Examples 1 to 4>
(1) Preparation of Photocurable Adhesive The components shown in Table 1 were mixed and then defoamed to prepare photocurable adhesives (liquid) of Examples 1-7 and Comparative Examples 1-4. .. The unit of the blending amount of each component in Table 1 is "part". The cationic photopolymerization initiator (C) was actually blended as a 50% propylene carbonate solution, and Table 1 shows the blending amount based on the solid content.

(2) Viscosity measurement of photocurable adhesive at 25° C. For each photocurable adhesive (adhesive liquid) prepared above, E-type viscometer “TVE-25L” manufactured by Toki Sangyo Co., Ltd. was used. Was used to measure the viscosity at a temperature of 25°C. The results are shown in Table 2.

(3) Moisture Measurement of Photocurable Adhesive at 25° C. For each photocurable adhesive (adhesive liquid) prepared above, a moisture meter “AQV-2100ST” manufactured by Hiranuma Sangyo Co., Ltd. was used. The water content at a temperature of 25° C. was measured. The results are shown in Table 2.

(4) Production of Polarizing Plate Protective film made of triacetyl cellulose containing an ultraviolet absorber and having a thickness of 80 μm [trade name “FT TD80ULM” manufactured by FUJIFILM Corporation], and thickness of 50 μm made of norbornene-based resin One side of the retardation film [trade name "ZEONOR" manufactured by Nippon Zeon Co., Ltd.] is subjected to corona treatment, and the adhesive solution prepared in the above (1) is applied to the corona treated surface with an adhesive coating device. Used for coating. At this time, the line speed of the film in the adhesive coating device was set to 25 m/min, and the gravure roll was rotated in the direction opposite to the film transport direction. The thickness of the adhesive layer after curing was 2.8 μm.

Next, a protective film made of the above triacetyl cellulose is provided on one surface of the polyvinyl alcohol-iodine polarizer having a thickness of 25 μm, and a retardation film made of the norbornene resin is provided on the other surface thereof, and an adhesive layer thereof is provided. Pasted through. For the bonding, a pair of nip rolls having a diameter of 250 mm [bonding roll (chrome-plated metal roll/rubber roll)] were used and the pressing pressure was 1.5 MPa.

The obtained laminate was conveyed at a line speed of 25 m/min while applying a tension of 600 N/m in the longitudinal direction, and the total integrated light amount (the integrated amount of light irradiation intensity in the wavelength region of wavelength 280 to 320 nm) was about 200 mJ/. The adhesive layer was cured by irradiating with ultraviolet rays (UVB) so as to have a cm ² (measurement device: a value measured by UV Power Puck II manufactured by Fusion UV) to obtain a polarizing plate.

(5) Confirmation of bubbles in the adhesive layer The obtained polarizing plate was cut into a size of length 300 mm×width 200 mm, and from the surface thereof, with a microscope (measuring instrument: Digital Microscope VHX-500 manufactured by Keyence Corporation), It was observed at a magnification of 100 times to confirm the presence or absence of bubbles of 50 μm or more in the cured adhesive layer.

<Evaluation criteria>
A: No bubbles were confirmed,
B: Bubbles were confirmed.

(6) 180° Peeling Test of Polarizing Plate After cutting the polarizing plate prepared in (4) above into a size of length 200 mm×width 25 mm, an acrylic pressure-sensitive adhesive layer was provided on the protective film side made of triacetyl cellulose. A test piece for measuring the peel strength between the protective film and the polarizer was prepared. Stick the test piece on a glass plate using the adhesive layer, put a blade of a cutter between the polarizer and the protective film (protective film consisting of triacetyl cellulose) on the adhesive layer side, and from the end in the length direction. It was peeled off by 30 mm, and the peeled portion was gripped by the grip portion of the tester. With respect to the test piece in this state, in an atmosphere of a temperature of 23° C. and a relative humidity of 55%, according to JIS K 6854-2:1999 “Adhesive-Peeling Adhesive Strength Test Method-Part 2: 180 Degree Peeling”. Then, a 180 degree peeling test was performed at a grip moving speed of 300 mm/min, and an average peeling force over a length of 170 mm excluding 30 mm of the grip portion was obtained, and this was peeled between the protective film made of triacetyl cellulose and the polarizer. Strength (“TAC/PVA peel strength”). The measurement was made 24 hours after the polarizing plate was produced. The results are shown in Table 2. In the column of "TAC/PVA peel strength" in Table 2, "-" indicates that the measurement was not performed.

1 Polarizer, 2,3 Protective film, 4 Laminated body, 5a, 5b Laminating roll, 11,12 Adhesive coating device, 13 roll, 14,15 1st active energy ray irradiation device, 16 2nd active energy ray Irradiation device, 17 Third active energy ray irradiation device, 18 Fourth active energy ray irradiation device, 19 Conveying nip roll, 20 Winding roll.

Claims (16)

A polyvinyl alcohol-based polarizer, a photocurable adhesive for adhering a thermoplastic resin film,
A photocationic curable component (A) containing a first photocationic curable component (A1) which is an aromatic epoxy compound;
Formula (I) below:

(In the formula, X is a hydrogen atom, or an alkyl group having 1 to 7 carbon atoms which may be substituted with one or more functional groups selected from the group consisting of an epoxy group, an oxetanyl group, a hydroxyl group and a carboxyl group. Represents an alkoxy group having 1 to 7 carbon atoms, an aryl group having 6 to 12 carbon atoms, an aryloxy group having 6 to 12 carbon atoms, or an alicyclic hydrocarbon group having 6 to 10 carbon atoms).
And a monomer represented by the following formula (II):

(In the formula, R ¹ represents a hydrogen atom, a methyl group or a halogen atom. Y is substituted with one or more functional groups selected from the group consisting of an epoxy group, an oxetanyl group, a hydroxyl group and a carboxyl group. Represents an alkyl group having 1 to 7 carbon atoms, an aryl group having 6 to 12 carbon atoms, or an alicyclic hydrocarbon group having 6 to 10 carbon atoms).
A polymer (B) comprising constitutional units derived from one or more kinds of monomers selected from the group consisting of the monomer (II)
A cationic photopolymerization initiator (C),
A branched alcohol compound (D),
Containing
The content of the polymer (B) is 2 to 10 parts by weight in the total amount of 100 parts by weight of the photocationic curable component (A) and the polymer (B),
The content of the first photocationic curable component (A1) is 10 to 40 parts by weight in 100 parts by weight of the total amount of the photocationic curable component (A) and the polymer (B),
The content of the photocationic polymerization initiator (C) is 1 to 10 parts by weight based on 100 parts by weight of the total amount of the photocationic curable component (A) and the polymer (B),
The content of the branched alcohol compound (D) is 100 parts by weight of the total amount of the photo cationic curing component (A) and the polymer (B), Ri 0.1-15 parts by der,
The monomer (I) has the following formulas (Ia), (Ib) and (Ic):

(In the formula, R ⁴ represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, m represents an integer of 1 to 6, R ⁵ represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, and n represents Represents an integer of 1 to ^6. R ⁶ represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, and s represents an integer of 1 to ^6. )
Including one or more selected from the group consisting of,
The monomer (II) has the following formulas (IIa), (IIb) and (IIc):

(In the formula, R ¹ represents the same meaning as described above. R ⁷ represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, t represents an integer of ¹ to 6. R ⁸ represents a hydrogen atom or 1 carbon atom. Represents an alkyl group of 6 and p represents an integer of 1 to 6. R ⁹ represents a hydrogen atom or an alkyl group having 1 to 6 carbons, and q represents an integer of 1 to 6.)
A photo-curable adhesive containing at least one selected from the group consisting of: The photocationic curable component (A) comprises at least one second photocationic curable component (A2) selected from the group consisting of an aliphatic diglycidyl compound, a monofunctional aliphatic epoxy compound, a vinyl ether compound and an oxetane compound. The photocurable adhesive according to claim 1, further comprising: The aliphatic diglycidyl compound has the following formula (III):

(In the formula, Z represents a linear or branched alkylene group having 1 to 9 carbon atoms or a divalent alicyclic hydrocarbon group, and the methylene group in the alkylene group is an oxygen atom or -CO-O. -, - O-CO -, - SO 2 -, - SO- or a divalent group selected from -CO- may be substituted).
The photocurable adhesive according to claim 2, which is a compound represented by: The photocurable adhesive according to claim 3, wherein Z in the formula (III) is a branched alkylene group having 3 to 10 carbon atoms. The content of the second photocationic curable component (A2) is 58 to 88 parts by weight in 100 parts by weight of the total amount of the photocationic curable component (A) and the polymer (B). 5. The photocurable adhesive according to any one of 4 to 4. The photocurable adhesive according to any one of claims 1 to 5, wherein the polymer (B) has a weight average molecular weight of 5,000 to 500,000. The photocurable adhesive according to any one of claims 1 to 6, wherein the branched alcohol compound (D) is a compound having two or more hydroxyl groups in the molecule. The water content is more than 0 parts by weight and 4 parts by weight or less based on 100 parts by weight of the total amount of the photocationic curable component (A) and the polymer (B). The photocurable adhesive according to item. The photocurable adhesive according to any one of claims 1 to 8, which has a viscosity at 25°C of 2 to 300 mPa·s. A polyvinyl alcohol-based polarizer,
A thermoplastic resin film laminated on at least one surface of the polyvinyl alcohol-based polarizer via the cured product of the photocurable adhesive according to any one of claims 1 to 9,
Including a polarizing plate. The thermoplastic resin film contains at least one resin selected from the group consisting of a cellulose resin, a (meth)acrylic resin, an amorphous polyolefin resin, a polyester resin, and a polycarbonate resin. The polarizing plate described in. The polarizing plate according to claim 10 or 11, wherein the thermoplastic resin film contains an ultraviolet absorber. The peeling strength between the polyvinyl alcohol-based polarizer and the thermoplastic resin film measured by a 180-degree peeling test is 0.5 N/25 mm or more, according to any one of claims 10 to 12. Polarizer. A laminated optical member comprising a laminated body of the polarizing plate according to claim 10 and one or more other optical layers. The laminated optical member according to claim 14, wherein the other optical layer includes a retardation plate. A liquid crystal display device comprising a liquid crystal cell, and the laminated optical member according to claim 14 disposed on at least one surface of the liquid crystal cell.