JPWO2016052244A1 - Photocurable adhesive, and polarizing plate, laminated optical member and liquid crystal display device using the same - Google Patents

Abstract

A polymer (B) comprising a photocation curable component (A) including a first photo cation curable component (A1) which is an aromatic epoxy compound, and a predetermined monomer (I) and / or monomer (II). ) And a photocationic polymerization initiator (C), and the content of the polymer (B) is 2 to 10 parts by weight with respect to 100 parts by weight of the total amount of the photocationic curable component (A) and the polymer (B). A photocurable adhesive having a first photocationic curable component (A1) content of 10 to 40 parts by weight and a photocationic polymerization initiator (C) content of 1 to 10 parts by weight; and A polarizing plate, a laminated optical member, and a liquid crystal display device using the same are provided.

Description

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

  The polarizing plate is useful as one of the optical components that constitute the liquid crystal display device. A polarizing plate usually has a structure in which protective films are laminated on both sides of a polarizer, and is incorporated into a liquid crystal display device. It is also known that a protective film is provided only on one side of a polarizer, but in many cases, a film having another optical function is bonded to the other side as a protective film, not just a protective film. The As a method for producing a polarizer, a method in which a uniaxially stretched polyvinyl alcohol-based resin film dyed with a dichroic dye is treated with boric acid, washed with water and dried is widely adopted.

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

  Triacetylcellulose is excellent in transparency, easy to form various surface treatment layers and optical functional layers on its surface, and has a high moisture permeability, after being adhered to a polarizer using an aqueous adhesive as described above. While having excellent advantages as a protective film such that drying can be performed smoothly, due to the high moisture permeability, the polarizing plate using this as a protective film is, for example, 70 ° C. and 90% relative humidity under humid heat. There was a problem that deterioration was likely to occur under the conditions. Therefore, it is also known to use an amorphous polyolefin resin having a lower moisture permeability than that of triacetyl cellulose, for example, a norbornene resin as a representative example as a protective film. Japanese Patent Application Laid-Open No. 06-0511117 (Patent Document 1) describes that a thermoplastic saturated norbornene resin sheet is laminated as a protective film on at least one surface of a polarizer.

  When bonding a protective film made of a resin with low moisture permeability to a polyvinyl alcohol polarizer, an aqueous solution of a polyvinyl alcohol resin conventionally used for bonding a polyvinyl alcohol polarizer and a triacetyl cellulose film is used as an adhesive. There are problems that the adhesive strength is not sufficient or the appearance of the obtained polarizing plate becomes poor. This is because a resin film having low moisture permeability is generally hydrophobic, and water as a solvent cannot be sufficiently dried due to low moisture permeability. On the other hand, it is also known to bond different types of protective films on both sides of the polarizer. For example, in JP-A-2002-174729 (Patent Document 2), a protective film made of a resin having a low moisture permeability such as an amorphous polyolefin resin is bonded to one surface of a polarizer, and the other side of the polarizer is bonded. There is also a proposal for adhering a protective film made of a resin with high moisture permeability such as cellulose resin including triacetyl cellulose on the surface.

  Therefore, a high adhesive force is given between the protective film made of a resin with low moisture permeability and the polyvinyl alcohol polarizer, and it is also high between a resin with high moisture permeability such as a cellulose resin and the polyvinyl alcohol polarizer. There is an attempt to use a photocurable adhesive as an adhesive that gives adhesive strength. For example, Japanese Patent Application Laid-Open No. 2004-245925 (Patent Document 3) discloses an adhesive mainly composed of an epoxy compound that does not contain an aromatic ring, and is based on irradiation with active energy rays, specifically ultraviolet irradiation. It has been proposed to cure the adhesive by cationic polymerization and bond the polarizer and the protective film. JP-A-2008-257199 (Patent Document 4) discloses a photocurable 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 blended. Is disclosed for use in bonding between a polarizer and a protective film.

  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, but is made of a (meth) acrylic resin. When bonding films, it has become clear that the adhesive strength is not always sufficient.

  Japanese Patent Application Laid-Open No. 2012-172026 (Patent Document 5) has an epoxy group or an oxetanyl group in 100% by weight of the active energy ray-curable compound (A) and does not have an active energy ray radically polymerizable functional group. An active energy ray-curable compound (5) containing 5 to 100% by weight of an active energy ray cationic curable compound (a1) having a weight average molecular weight of less than 5000 and an active energy ray radically curable compound (a2) (0 to 95% by weight). A) An adhesive for optical films containing 0.0001 to 2 parts by weight of an acrylic resin (B) having a weight average molecular weight of 5000 to 150,000 having an epoxy group or an oxetanyl group with respect to 100 parts by weight is disclosed. However, when the content of the acrylic resin (B) exceeds 2 parts by weight, the viscosity of the adhesive increases, and on the contrary, the smoothness of the coated surface may be deteriorated (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 a viscosity containing a cationic polymerizable component including a polyfunctional alicyclic epoxy compound (A) and a monofunctional glycidyl compound (B) and a photopolymerization initiator. A method of adhering a polarizer and a protective film using a photocurable adhesive of 10 to 150 mPa · s has been proposed. However, although the epoxy adhesive disclosed in Patent Document 6 is also effective for bonding a protective film made of an amorphous polyolefin resin or a cellulose resin to a polarizer, a (meth) acrylic resin When a protective film made of is adhered, the adhesive force is not always sufficient.

  JP 2013-092762 A (Patent Document 7) discloses a method for producing a polarizing plate in which bubbles are unlikely to be generated between a polarizing film (polarizer) and a transparent film. A step of applying a mold adhesive, a step of laminating a transparent film on one or both sides of a polarizing film with a surface coated with an adhesive, and producing a laminate, and irradiating the laminate with active energy rays And a method for producing a polarizing plate comprising a step of producing a polarizing plate, wherein the diameter of a bonding roll used in the step of producing a laminate is in the range of 50 to 250 mm. Has been.

Japanese Patent Laid-Open No. 06-0511117 JP 2002-174729 A JP 2004-245925 A JP 2008-257199 A JP 2012-172026 A JP 2012-007080 A JP 2013-092762 A

  The present invention provides a polarizing plate having a viscosity sufficiently low to allow coating at room temperature and an improved adhesive force between the polarizer and the protective film when bonding the protective film to the polyvinyl alcohol polarizer. It aims at providing the photocurable adhesive agent which can give. Another object of the present invention is a low viscosity capable of bonding a polyvinyl alcohol polarizer and a protective film without causing bubbles in the adhesive layer even when the thickness of the adhesive layer is reduced. The object is to provide a photocurable adhesive. 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 same.

  The present invention provides the following photocurable adhesive, polarizing plate, laminated optical member, and liquid crystal display device.

[1] A photocurable adhesive for adhering a protective film made of a thermoplastic resin to a polyvinyl alcohol polarizer,
A photocationic curable component (A) comprising a first photocationic curable component (A1) which is an aromatic epoxy compound;
The following formula (I):

(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 the monomer (I) 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. And 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 a structural unit derived from one or more monomers selected from the group consisting of monomers (II) represented by:
A cationic photopolymerization initiator (C);
Containing
The content of the polymer (B) is 2 to 10 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 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),
Photocurability in which the content of the photocationic polymerization initiator (C) is 1 to 10 parts by weight with respect to 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 one or more second photocationic curable components selected from the group consisting of aliphatic diglycidyl compounds, monofunctional aliphatic epoxy compounds, vinyl ether compounds, and oxetane compounds ( The photocurable adhesive according to [1], further comprising 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, -CO-O. It may be substituted with a divalent group selected from —, —O—CO—, —SO ₂ —, —SO— or —CO—.
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 photocationic curable component (A2) is 58 to 88 parts by weight in a total amount of 100 parts by weight of the photocationic curable 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 [6], wherein the polymer (B) has a weight average molecular weight of 6000 to 100,000.

  [8] Any one of [1] to [7], wherein the water content is 4 parts by weight or less with respect to 100 parts by weight of the total amount of the photocationic curable component (A) and the polymer (B). The photocurable adhesive described in 1.

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

[10] A polyvinyl alcohol polarizer,
A protective film made of a thermoplastic resin bonded to at least one surface of the polyvinyl alcohol-based polarizer via a cured product of the photocurable adhesive according to any one of [1] to [9];
A polarizing plate including

  [11] The thermoplastic resin is 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. 10].

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

  [13] The method according to any one of [10] to [12], wherein a peel strength between the polyvinyl alcohol polarizer and the protective film measured by a 180 degree peel test is 0.5 N / 25 mm or more. Polarizing plate.

  [14] A laminated optical member comprising 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] disposed on at least one surface of the liquid crystal cell.

  According to the present invention, it is possible to provide a photocurable adhesive that has a low viscosity, is unlikely to generate bubbles in the adhesive layer, and can bond a polyvinyl alcohol polarizer and a protective film with high adhesive strength. According to the photocurable adhesive of the present invention, even when a protective film made of a (meth) acrylic resin is bonded, a polarizing plate having a high adhesive strength between the polyvinyl alcohol-based polarizer and the protective film is provided. Is possible. The polarizing plate according to the present invention having high adhesive strength, and the laminated optical member and liquid crystal display device using the polarizing plate are excellent in durability.

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 protective film made of a thermoplastic resin to a polyvinyl alcohol polarizer, and is a photocationic curable component (A), a polymer (B), A cationic photopolymerization initiator (C).

(1) Photocationic curable component (A)
The photocationic curable component (A), which is a main component of the photocurable adhesive and provides adhesive force by polymerization curing, includes at least the first photocationic curable component (A1) that is an aromatic epoxy compound. It is preferable that the photocationic curable component (A) further includes a second photocationic curable component (A2) that is a curable component different from the first photocationic curable component (A1).

(1-1) First photocationic curable component (A1)
A 1st photocationic curable component (A1) consists of an aromatic epoxy compound. An aromatic epoxy compound is an epoxy compound having an aromatic ring. However, in the aromatic epoxy compound 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 as follows. Not included. The first photocationic curable component (A1) may be composed of two or more aromatic epoxy compounds. Specific examples of the aromatic epoxy compound include monohydric phenols such as phenol, cresol and butylphenol, bisphenol derivatives such as bisphenol A and bisphenol F, or mono- or polyglycidyl etherified products of their alkylene oxide adducts; epoxy novolac resins; resorcinol Mono- or polyglycidyl etherified products of aromatic compounds having two or more phenolic hydroxyl groups such as hydroquinone and catechol; aromatic compounds having two or more alcoholic hydroxyl groups such as benzenedimethanol, benzenediethanol and benzenedibutanol Glycidyl etherified product; glycidyl ester of polybasic aromatic compound having two or more carboxyl groups such as phthalic acid, terephthalic acid, trimellitic acid; glycidyl benzoic acid Stell and toluic acid, glycidyl ester of naphthoic acid, and the like; styrene oxide or alkylated styrene oxide, etc. diepoxy compound of a styrene oxides or divinylbenzene, such as epoxidized vinyl naphthalene.

  Especially, from a viewpoint of sclerosis | hardenability and adhesiveness, it is preferable that a 1st photocationic curable component (A1) contains a polyfunctional aromatic epoxy compound, and it is more preferable that a trifunctional or more functional aromatic epoxy compound is included.

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

  Commercially available aromatic epoxy compounds can be used, 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 manufactured by Nagase ChemteX Corporation); “Ogsol PG-100”, “Ogsol EG-200”, “Ogsol EG-” "210" and "Ogsol EG-250" (all of which are manufactured by Osaka Gas Chemical Co., Ltd.); "HP "032", "HP4032D" and "HP4700" (all of which are manufactured by DIC Corporation); "ESN-475V" (manufactured by Nippon Steel & Sumikin Chemical Co., Ltd.); "152", "154", "157S70" and " YX8800 "(all of which 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”, “Adekaglycilol ED-501”, “Adekaglycilol ED-” 509E "," Adekaglycilol ED-5 9S "and" Adeka glycinates roll ED-529 "(all being Ltd. ADEKA)," TECHMORE VG3101L "((KK) purine Tech), and the like.

  Content of 1st photocationic curable component (A1) is 10-40 weight part in the total amount of 100 weight part of photocationic curable component (A) and the polymer (B) mentioned later, Preferably 12- 35 parts by weight. By containing 10 parts by weight or more of the first photocationic curable component (A1), excellent adhesive strength between the polyvinyl alcohol-based polarizer and the protective film, lower viscosity of the photocurable adhesive, and It becomes possible to realize coexistence with the accompanying good coatability. On the other hand, when the amount of the first photocationic curable component (A1) exceeds 40 parts by weight, the above-mentioned coexistence becomes difficult, and in particular, the viscosity tends to increase. When the amount of the first photocationic 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. It may consist of ingredients. In addition, in the monofunctional aliphatic epoxy compound here, X or Y in the polymer (B) described later has an epoxy group, and the polymer (B) belonging to the monofunctional aliphatic epoxy compound is included in classification. Absent. Moreover, in the oxetane compound here, X or Y in the polymer (B) described later has an oxetanyl group, and the polymer (B) belonging to the oxetane compound is not included in classification.

  The second photocationic curable component (A2) preferably contains an aliphatic diglycidyl compound. Among them, the viscosity of the photocurable adhesive is reduced, that is, the viscosity at 25 ° C. is adjusted to a range of 2 to 300 mPa · s. From the following formula (III):

It is more preferable that the compound shown by these is included. 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, -CO. It may be substituted with a divalent group selected from —O—, —O—CO—, —SO ₂ —, —SO— or —CO—. 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 diglycidyl ether of alkylene glycol, and specific examples thereof are ethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, 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 (propylene glycol diglycidyl ether, neopentyl glycol diglycidyl ether). Compounds in which Z in III) is a branched alkylene group having 3 to 10 carbon atoms are preferred.

  Examples of monofunctional aliphatic epoxy compounds include glycidyl ethers of aliphatic alcohols, glycidyl esters of alkyl carboxylic acids, and specific examples thereof include allyl glycidyl ether, butyl glycidyl ether, sec-butylphenyl glycidyl ether, 2- Examples include ethyl hexyl glycidyl ether, mixed alkyl glycidyl ether having 12 and 13 carbon atoms, glycidyl ether of alcohol, monoglycidyl ether of higher aliphatic alcohol, glycidyl ester of higher fatty acid, and the like.

  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, n- C5-20 alkyl or alkenyl alcohol vinyl ethers 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, An aliphatic ring such as 2-methylcyclohexyl vinyl ether, cyclohexyl methyl vinyl ether, benzyl vinyl ether, or Vinyl ethers of monoalcohols having an aromatic ring; glycerol monovinyl ether, 1,4-butanediol divinyl ether, 1,6-hexanediol divinyl ether, neopentyl glycol divinyl ether, pentaerythritol divinyl ether, pentaerythritol tetravinyl ether, tri Such as methylolpropane divinyl ether, trimethylolpropane trivinyl ether, 1,4-dihydroxycyclohexane monovinyl ether, 1,4-dihydroxycyclohexane divinyl ether, 1,4-dihydroxymethylcyclohexane monovinyl ether, 1,4-dihydroxymethylcyclohexane divinyl ether, etc. Polyhydric alcohol mono or polyvinyl ethers; diethylene glycol divinyl Including glycidyl vinyl ether, and other vinyl ethers such as ethylene glycol vinyl methacrylate; ether, triethylene glycol divinyl ether, diethylene glycol polyalkylene glycol mono or di ether and monobutyl monovinyl ethers.

  The oxetane compound is a compound having an oxetanyl group, and specific examples thereof include 3,7-bis (3-oxetanyl) -5-oxa-nonane, 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, tetraethyleneglycol 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.

  The content of the second photocationic curable component (A2) is not particularly limited as long as the content of the first photocationic curable component (A1) is in the above range. The total amount of the polymer (B) to be added is preferably 58 to 88 parts by weight, 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 at 25 ° C. of 2 to 300 mPa · s. On the other hand, if the content of the second photocationic curable component (A2) exceeds 88 parts by weight, the adhesive strength between the polarizer and the protective film tends to be insufficient.

(1-3) Third photocationic curable component (A3)
The photocation curable component (A) is a third photo cation curable component (A3) which is a curable component other than the first photo cation curable component (A1) and the second photo cation curable component (A2). Can further be included. Examples of the third photocationic curable component (A3) include epoxy compounds that do not belong to any of (A1) and (A2) (for example, alicyclic epoxy compounds), cyclic lactone compounds, cyclic acetal compounds, cyclic thioether compounds, spiro Examples include ortho ester 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) is in the above range, and preferably the second photocationic curable component. In the case of containing (A2), the amount of the second photocationic curable component (A2) is such an amount that is in the above range.

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

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

It is a polymer which consists of a structural unit derived from 1 or more types of monomers selected from the group which consists of monomer (II) shown by these. Specifically, a homopolymer obtained by polymerizing one kind of monomer (I), a copolymer obtained by polymerizing two or more kinds of monomer (I), and one kind of monomer (II) are polymerized. A copolymer obtained by polymerizing two or more monomers (II), a copolymer obtained by polymerizing one or more monomers (I) and one or more monomers (II) , And mixtures of two or more thereof.

  X in the above formula (I) is a carbon atom which may be partially substituted with a hydrogen atom or one or more functional groups selected from the group consisting of an epoxy group, an oxetanyl group, a hydroxyl group and a carboxyl group. An alkyl group having 1 to 7 carbon atoms, 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, and n-amyl. 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. Among 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 can be mentioned. Among these, an alkyl 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 a phenyl group, a methylphenyl group, and a naphthyl group. The number of carbon atoms is preferably 6-10.

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

  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, and tricyclodecanyl group. A spirooctyl group, a spirobicyclopentyl group, an adamantyl group, an 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 In the case of 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 functional group is used for the curing reaction. Therefore, it is advantageous in terms of durability of the adhesive layer and suppression of bleeding of low molecular weight components from the adhesive layer. Especially, it is preferable that the said functional group is 1 or more types of functional groups selected from the group which consists of an epoxy group, oxetanyl group, and a hydroxyl group.

  In the above formula (I), the monomer (I) when 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). 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 an alkyl group having 1 to 7 carbon atoms and an aryl group having 6 to 12 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. Or an alicyclic hydrocarbon group having 6 to 10 carbon atoms is represented.

  Examples of the halogen atom include fluorine, chlorine, bromine, iodine and the like. 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).

  Carbon in which Y in 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, as in X in formula (I) Since the said functional group contributes to hardening reaction as it is a C1-C7 alkyl group, a C6-C12 aryl group, or a C6-C10 alicyclic hydrocarbon group, durability of an adhesive bond layer And, it is advantageous in terms of suppressing bleeding of low molecular weight components from the adhesive layer. Especially, it is preferable that the said functional group is 1 or more types of functional groups selected from the group which consists of an epoxy group, oxetanyl group, and a hydroxyl group.

  In the above formula (II), examples of the monomer (II) in the case where a part of Y is substituted with an epoxy group or an oxetanyl group include those represented by the following formulas (IIa), (IIb) and (IIc). 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 converted into standard polystyrene by gel permeation chromatography (GPC) from the viewpoint of coexistence of the adhesive strength between the polyvinyl alcohol polarizer and the protective film and the low viscosity of the photocurable adhesive. Is preferably 5,000 to 500,000, 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 photocation curable component (A) and the polymer (B). By containing 2 parts by weight or more of the polymer (B), the adhesive strength between the polyvinyl alcohol polarizer and the protective film (especially a protective film made of a (meth) acrylic resin) is increased while ensuring low viscosity. An effect can be expressed. On the other hand, when the content of the polymer (B) exceeds 10 parts by weight, the viscosity of the photocurable adhesive increases. If it is less than 2 weight part, adhesiveness with the protective film which consists of (meth) acrylic-type resin especially becomes low. In the present specification, “(meth) acryl” means at least one selected from acryl and methacryl. The same applies to “(meth) acrylate”.

(3) Photocationic polymerization initiator (C)
The photocurable adhesive contains a photocationic polymerization initiator (C). Thereby, a photocationic curable component (A) can be hardened | cured by cationic polymerization by irradiation of an active energy ray, and an adhesive bond layer can be formed. 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 polymerizes the photocationic curable component (A). Is to start. Since the photocationic polymerization initiator (C) acts catalytically by light, it is excellent in storage stability and workability even when mixed with the photocationic curable component (A). Examples of compounds that generate cationic species and Lewis acids upon irradiation with active energy rays 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; Examples thereof include iron-arene complexes.

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

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

As an 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] diphenyl sulfide bishexafluoroantimonate,
4,4′-bis [di (β-hydroxyethoxy) phenylsulfonio] diphenyl sulfide 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-diphenyl sulfide hexafluoroantimonate,
4- (p-tert-butylphenylcarbonyl) -4′-di (p-toluyl) sulfonio-diphenyl sulfide tetrakis (pentafluorophenyl) borate.

As an 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 these, aromatic sulfonium salts are particularly preferably used because they have ultraviolet absorption characteristics even in the wavelength region near 300 nm, and thus can provide an adhesive layer having excellent curability and good mechanical strength and adhesive strength. It is done.

  The content of the photocationic polymerization 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 photocationic curable component (A) and the polymer (B). It is. By containing 1 part by weight or more of the cationic photopolymerization initiator (C), the cationic photocuring component (A) can be sufficiently cured, and high mechanical strength and adhesive strength are imparted to the resulting polarizing plate. On the other hand, when the amount increases, the ionic substance in the cured product increases, so that the hygroscopic property of the cured product increases and the durability performance of the polarizing plate may be lowered. ) Is 10 parts by weight or less with respect to 100 parts by weight of the total amount of the photocationic curable component (A) and the polymer (B).

(4) Photosensitizer The photocurable adhesive may contain a photosensitizer. The above-mentioned photocationic polymerization initiator (C) exhibits maximum absorption in the vicinity of 300 nm or shorter wavelength range, generates a cationic species or a Lewis acid in response to light in the vicinity of the wavelength, and is a photocationic curable component. Although the cationic polymerization of (A) is started, it is preferable that the photosensitizer exhibits maximum absorption in a wavelength region longer than 380 nm so as to be sensitive to light having a longer wavelength than that. As such a photosensitizer, an anthracene compound is preferably used.

Specific examples of anthracene compounds 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,
Examples include 2-methyl or 2-ethyl-9,10-dihexyloxyanthracene.

  By including a photosensitizer in the photocurable adhesive, the curability of the adhesive can be improved as compared with the case where it is not included. Such an effect can be expressed by setting the content of the photosensitizer to 0.1 parts by weight or more with respect to 100 parts by weight of the total amount of the photocationic curable component (A) and the polymer (B). On the other hand, if the content of the photosensitizer increases, problems such as precipitation during low-temperature storage occur, so the amount is 100 parts by weight in total 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 protective film is sufficiently obtained. The amount of the photosensitizer is 0.1 to 0.5 parts by weight, more preferably 0.1 to 0.3 parts by weight based on 100 parts by weight of the total amount of the photocation curable component (A) and the polymer (B). A range of parts by weight is preferred.

(5) Photosensitizing aid The photocurable adhesive may contain a photosensitizing aid. The photosensitizer is preferably a naphthalene photosensitizer.

Specific examples of naphthalene photosensitizing aids 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 is mentioned.

  By including a 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 included. By making the content of the naphthalene-based photosensitization aid to 0.1 parts by weight or more with respect to 100 parts by weight of the total amount of the photocationic curable component (A) and the polymer (B), such an effect is exhibited. Can do. On the other hand, if the content of the naphthalene-based photosensitization aid is increased, problems such as precipitation during low-temperature storage occur. Therefore, the amount is 100 in total of the photocation curable component (A) and the polymer (B). The amount is preferably 5 parts by weight or less with respect to parts by weight. The content of the naphthalene-based photosensitization aid is preferably 3 parts by weight or less with respect to 100 parts by weight of the total amount of the photocation curable component (A) and the polymer (B).

(6) Additive component As long as the effects of the present invention are not impaired, the photocurable adhesive may contain an additive component as an optional component. Additive components include thermal cationic polymerization initiators, polyols, ion trapping agents, antioxidants, light stabilizers, chain transfer agents, tackifiers, thermoplastic resins, fillers, flow regulators, plasticizers, quenchers. Examples include foaming agents, leveling agents, pigments, organic solvents, and the like.

  When the additive component is contained, the content is preferably 1000 parts by weight or less with respect to 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, a polyvinyl alcohol-based polarizer and a protective film by a combination of the essential photocationic curable component (A), the polymer (B), and the photocationic polymerization initiator (C) It is possible to satisfactorily exhibit the effect of achieving both the excellent adhesive strength between the two, the low viscosity of the photocurable adhesive and the good coating properties associated therewith.

(7) Water content of photocurable adhesive The photocurable adhesive may contain moisture. The water content is usually 4 parts by weight or less, preferably less than 3 parts by weight, based on 100 parts by weight of the total amount of the photocationic curable component (A) and the polymer (B). By containing a slight amount of moisture, the adhesive strength between the polyvinyl alcohol polarizer and the protective film may be improved. However, if the water content is too high, separation of the photocurable adhesive and water occurs, making it impossible to apply the photocurable adhesive uniformly to the surface of the polarizer or protective film, or photocuring The curability of the adhesive may deteriorate. Water may be intentionally added to the photocurable adhesive. In this case, although not particularly limited, purified water such as distilled water and pure water can be used. The water content of the photocurable adhesive is measured by the Karl Fischer capacity method.

(8) 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. Viscosity here is a viscosity in the state which does not contain a solvent substantially. When the viscosity is less than 2 mPa · s, the polarizer and the protective film may be peeled off during conveyance after bonding, and when the viscosity exceeds 300 mPa · s, the polarizer, the protective film and the adhesive are bonded together. At this time, particularly when the adhesive layer is thin, air bubbles are easily mixed between the polarizer and the protective film, that is, in the adhesive layer. The viscosity is more preferably 5 to 200 mPa · s, and still more 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 polarizer and a protective film made of a thermoplastic resin bonded to at least one surface of the polarizing plate via a cured product of the photocurable adhesive. Since the polarizing plate uses the photocurable adhesive according to the present invention, the adhesive strength between the polarizer and the protective film is high and excellent in durability, and bubbles are mixed into the cured adhesive layer. It is suppressed.

(1) Polyvinyl alcohol-type polarizer A polyvinyl alcohol-type polarizer is comprised with the polyvinyl-alcohol-type resin film by which the dichroic pigment | dye was adsorption-oriented. The polyvinyl alcohol resin constituting the polarizer can be obtained by saponifying a polyvinyl acetate resin. Examples of the polyvinyl acetate resin include polyvinyl acetate, which is a homopolymer of vinyl acetate, as well as copolymers of vinyl acetate and other monomers copolymerizable therewith. Examples of other monomers copolymerized with vinyl acetate include unsaturated carboxylic acids, olefins, vinyl ethers, and unsaturated sulfonic acids. The degree of saponification of the polyvinyl alcohol resin is usually 85 to 100 mol%, preferably 98 to 100 mol%. The polyvinyl alcohol-based resin may be further modified, and for example, polyvinyl formal and polyvinyl acetal modified with aldehydes may be used. The degree of polymerization of the polyvinyl alcohol-based resin is usually 1000 to 10,000, 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, a polyvinyl on which the dichroic dye is adsorbed It is manufactured through a process of treating an alcohol-based resin film with an aqueous boric acid solution.

  Uniaxial stretching may be performed before dyeing with a dichroic dye, may be performed simultaneously with dyeing with a dichroic dye, or may be performed after dyeing with a dichroic dye. When uniaxial stretching is performed after dyeing with a dichroic dye, this uniaxial stretching may be performed before boric acid treatment or during boric acid treatment. It is also possible to perform uniaxial stretching in these plural stages. The method of uniaxial stretching is not particularly limited, and uniaxial stretching may be performed between rolls having different peripheral speeds, or uniaxial stretching may be performed using a hot roll. Moreover, the dry-type extending | stretching which extends | stretches in air | atmosphere may be sufficient, and the wet extending | stretching which extends | stretches in the state swollen with the solvent may be sufficient. 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. As the dichroic dye, iodine or a dichroic organic dye is used.

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

On the other hand, when a dichroic organic dye is used as the dichroic dye, a method of immersing and dyeing a polyvinyl alcohol-based resin film in an aqueous solution containing a water-soluble dichroic organic dye is usually employed. The content of the dichroic organic dye in this aqueous solution is usually about 1 × 10 ⁻³ to 1 × 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-based resin film in an aqueous boric acid solution. The boric acid content in the boric acid aqueous solution is usually about 2 to 15 parts by weight, preferably about 5 to 12 parts by weight per 100 parts by weight of water. When iodine is used as the dichroic dye, the boric acid aqueous solution preferably contains potassium iodide. The content of potassium iodide in the boric acid aqueous solution is usually about 2 to 20 parts by weight, preferably 5 to 15 parts by weight per 100 parts by weight of water. The immersion time in the boric acid aqueous solution is usually about 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 resin film after the boric acid treatment is usually washed with water. The water washing treatment can be performed, for example, by immersing a boric acid-treated polyvinyl alcohol resin film in water. After washing with water, a drying process is performed to obtain a polarizer. The temperature of water in the water washing treatment is usually about 5 to 40 ° C., and the immersion time is usually about 2 to 120 seconds. The drying process performed after that can be normally performed using a hot air dryer or a far-infrared heater. The drying temperature is usually 40 to 100 ° C. Moreover, the time of a drying process is about 120 to 600 seconds normally. The thickness of the polyvinyl alcohol-based polarizer can be about 5 to 50 μm.

(2) Protective film The protective film made of a thermoplastic resin may be either an unstretched film or a uniaxially or biaxially stretched film.

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

  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 repeating units are composed of ethylene terephthalate, and may contain structural units derived from other copolymerization components.

  Examples of other copolymer components 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 and the like can be mentioned. Examples of the diol component include propylene glycol, butanediol, neopentyl glycol, diethylene glycol, cyclohexanediol, ethylene oxide adduct of bisphenol A, polyethylene glycol, polypropylene glycol, and polytetramethylene glycol. These dicarboxylic acid components and diol components can also be used in combination of two or more as required. It is also possible to use a hydroxycarboxylic acid such as p-hydroxybenzoic acid or p-β-hydroxyethoxybenzoic acid together with the dicarboxylic acid component or diol component. As 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.

  After making a film of polyethylene terephthalate-based resin and using a stretched film as a protective film, a polarizing plate with excellent mechanical properties, solvent resistance, scratch resistance, cost, etc. and reduced thickness Can be obtained.

  The polycarbonate resin is a polyester formed from carbonic acid and glycol or bisphenol. Among them, an aromatic polycarbonate having diphenylalkane in the molecular chain is preferably used because it is excellent in heat resistance, weather resistance and acid resistance. Such polycarbonates include 2,2-bis (4-hydroxyphenyl) propane (also known as bisphenol A), 2,2-bis (4-hydroxyphenyl) butane, 1,1-bis (4-hydroxyphenyl) cyclohexane, Examples are 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 other comonomer components are copolymerized. . This copolymer can usually be 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, a third monofunctional monomer can be copolymerized with the (meth) acrylic resin.

  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 acrylic acids such as (hydroxymethyl) methyl acrylate, 2- (1-hydroxyethyl) methyl acrylate, 2- (hydroxymethyl) ethyl acrylate, and 2- (hydroxymethyl) butyl acrylate Stealth; Unsaturated acids such as methacrylic acid and acrylic acid; Halogenated styrenes such as chlorostyrene and bromostyrene; Substituted styrenes such as vinyltoluene and α-methylstyrene; Unsaturated nitriles such as acrylonitrile and methacrylonitrile And unsaturated acid anhydrides such as maleic anhydride and citraconic anhydride; unsaturated imides such as phenylmaleimide and cyclohexylmaleimide. The third monofunctional monomer may be used alone or in combination with a plurality of 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, and nonaethylene glycol di (meth). Ester and ethylene glycol such as tetradecaethylene glycol di (meth) acrylate, or both oligomeric hydroxyl groups esterified with acrylic acid or methacrylic acid; propylene glycol or oligomeric both terminal hydroxyl groups of acrylic acid or methacrylic acid Esterified with dihydric alcohol such as neopentyl glycol di (meth) acrylate, hexanediol di (meth) acrylate, and butanediol di (meth) acrylate Esterified with acrylic acid or methacrylic acid; bisphenol A, an alkylene oxide adduct of bisphenol A, or esterified with acrylic acid or methacrylic acid at both terminal hydroxyl groups thereof; trimethylolpropane and penta Those obtained by esterifying polyhydric alcohols such as erythritol with acrylic acid or methacrylic acid, and those obtained by ring-opening addition of an epoxy group of glycidyl acrylate or glycidyl methacrylate to the terminal hydroxyl groups; succinic acid, adipic acid, terephthalic acid, phthalic acid , A dibasic acid such as a halogen-substituted product thereof, and an alkylene oxide adduct thereof or the like obtained by ring-opening addition of an epoxy group of glycidyl acrylate or glycidyl methacrylate; aryl (meth) acrylate; Aromatic divinyl compounds such as divinylbenzene and the like. Among these, ethylene glycol dimethacrylate, tetraethylene glycol dimethacrylate, and neopentyl glycol dimethacrylate are preferably used.

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

  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 to the above range, the polymerization ratio of the methacrylic ester monomer and the acrylate ester monomer, the carbon chain length of each ester group, or it has A method of appropriately selecting the type of functional group or the polymerization ratio of the polyfunctional monomer with respect to the whole monomer is employed.

  The (meth) acrylic resin may contain a known additive as necessary. Known additives include, for example, lubricants, antiblocking agents, heat stabilizers, antioxidants, antistatic agents, light resistance agents, impact resistance improvers, surfactants and the like. However, since transparency is required as a protective 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 that are impact modifiers from the viewpoints of film-formability on the film and impact resistance of the film. The acrylic rubber particles here are particles having an elastic polymer mainly composed of an acrylate ester as an essential component, and those having a single layer structure consisting essentially of this elastic polymer, or this elastic polymer. Can be a multi-layer structure having a single layer. An example of such an elastic polymer is a cross-linked elastic copolymer obtained by copolymerizing an alkyl acrylate as a main component with another vinyl monomer and a cross-linkable monomer copolymerizable therewith. Examples of the alkyl acrylate as the main component of the elastic polymer include those having about 1 to 8 carbon atoms in the alkyl group, such as methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, etc. An acrylate having an alkyl group of several 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 include esters, aromatic vinyl compounds such as styrene, vinylcyan compounds such as acrylonitrile, and the like. Examples of the crosslinkable monomer include a crosslinkable compound having at least two polymerizable carbon-carbon double bonds in the molecule, and more specifically, ethylene glycol di (meth) acrylate and butanediol. Examples include (meth) acrylates of polyhydric alcohols such as di (meth) acrylate, alkenyl esters of (meth) acrylic acid such as allyl (meth) acrylate, and divinylbenzene.

  Further, a laminate of a film made of (meth) acrylic resin not containing rubber particles and a film made of (meth) acrylic resin containing rubber particles can be used as a protective film. Commercially available (meth) acrylic resins can be easily obtained. For example, “Sumipex” (manufactured by Sumitomo Chemical Co., Ltd.), “Acrypet” (manufactured by Mitsubishi Rayon Co., Ltd.) under the trade name, respectively. , “Delpet” (manufactured by Asahi Kasei Corporation), “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 from cyclopentadiene and olefins using norbornene or its derivative obtained by Diels-Alder reaction as a monomer, followed by hydrogenation; dicyclopentadiene and olefin A resin obtained by performing ring-opening metathesis polymerization using tetracyclododecene or a derivative thereof obtained by Diels-Alder reaction with a monomer or methacrylic acid ester, followed by hydrogenation; norbornene, tetracyclododecene and their Resins obtained by conducting ring-opening metathesis copolymerization in the same manner using two or more selected from derivatives and other cyclic polyolefin monomers, followed by hydrogenation; norbornene, tetracyclododecene or the like Luo derivatives, resins obtained by addition copolymerization of aromatic compounds and the like having a vinyl group. Examples of commercially available amorphous polyolefin resins include “Arton” from JSR Corporation, “ZEONEX” and “ZEONOR” from Nippon Zeon Corporation, “APO” and “APO” from Mitsui Chemicals, Inc. Appel "etc.

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

  A cellulose resin film provided with an optical compensation function can also be used. As such an optical compensation film, for example, a film in which a compound having a retardation adjusting function is contained in a cellulose resin, a film in which a compound having a retardation adjusting function is applied to the surface of the cellulose resin, a cellulose resin is uniaxially or biaxially formed. Examples thereof include a film obtained by stretching on a shaft. Examples of commercially available optical compensation films for cellulose resins include “Wide View Film WV BZ 438” and “Wide View Film WV EA” manufactured by Fuji Film Co., Ltd., manufactured by Konica Minolta Opto Corporation. There are “KC4FR-1” and “KC4HR-1”.

  The thickness of the protective film is usually in the range of about 5 to 200 μm, preferably 10 to 120 μm, and more preferably 10 to 85 μm. Various surfaces of the surface treatment layer (coating layer) such as a hard coat layer, an antireflection layer, an antiglare layer and a light diffusion layer may be provided on the surface of the protective film opposite to the adhesive surface to the polarizer.

  The protective film adhered to at least one surface of the polarizer may contain an ultraviolet absorber. By disposing a protective film containing an 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 ultraviolet absorbers include salicylic acid ester compounds, benzophenone compounds, benzotriazole compounds, cyanoacrylate compounds, nickel complex compounds, and the like.

(3) Manufacture of a polarizing plate A polarizing plate is obtained by adhere | attaching a protective film on the at least one surface of a polarizer using the above-mentioned photocurable adhesive agent. Specifically, the above-mentioned photocurable adhesive coating layer is formed on the adhesive surface of the polarizer and / or protective film, the polarizer and the protective film are bonded through the coating layer, and then uncured. The coating layer of the photocurable adhesive is cured by irradiation with active energy rays, and the protective film is fixed 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 for forming the photocurable adhesive coating layer. It is also possible to adopt a method in which the polarizer and the protective film are continuously supplied so that the adhesive surfaces of both are inside, and the adhesive is cast between them.

  Depending on the coating method of the photocurable adhesive, the viscosity of the photocurable adhesive may be adjusted using a solvent. As the solvent, a solvent that dissolves the photocurable adhesive satisfactorily without degrading the optical performance of the polarizer is used, but there is no particular limitation on the type thereof. For example, organic solvents such as hydrocarbons typified by toluene and esters typified by ethyl acetate can be used. However, when a solvent is contained, it is necessary to provide a drying step for removing the solvent before irradiation with 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 depending on the characteristic design of the polarizing plate, but is preferably smaller from the viewpoint of reducing the cost of the adhesive material. Generally, it is 0.01-20 micrometers, Preferably, it is 0.1-10 micrometers, More preferably, it is 0.5-5 micrometers. If the thickness of the adhesive layer is reduced, bubbles are likely to be mixed into the adhesive layer, and adhesion and durability are likely to deteriorate. However, according to the photocurable adhesive of the present invention, this can be effectively suppressed. Can do.

  When adhering the protective film only to one surface of the polarizer, for example, it is possible to take a form such as directly providing an adhesive layer for adhering to another optical member such as a liquid crystal cell on the other surface of the polarizer. . On the other hand, when a protective film is bonded to both surfaces of the polarizer, these protective films may be made of the same kind of resin or different kinds of resins. The protective film bonded to one surface of the polarizer is bonded using the above-described photocurable adhesive according to the present invention, but the protective film bonded to the other surface of the polarizer is bonded to the present invention. You may adhere | attach using the photocurable adhesive which concerns, and you may adhere | attach using another adhesive agent.

  Prior to adhesion of the protective film to the polarizer, the adhesive surface of the protective film and / or polarizer is subjected to easy adhesion treatment such as saponification treatment, corona treatment, plasma treatment, primer treatment, anchor coating treatment, and flame treatment. May be.

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

The irradiation intensity of active energy rays to the photocurable adhesive is not particularly limited, but the irradiation intensity in the wavelength region effective for the activation of 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 photocurable adhesive is caused by heat radiated from the lamp and heat generated during polymerization of the photocurable adhesive. May cause yellowing and deterioration of the polarizer.

The light irradiation time to the photocurable adhesive is not particularly limited, but is preferably set so that the integrated light amount expressed as 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 the 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. If it exceeds 5000 mJ / cm ² , the irradiation time becomes very long, which is disadvantageous for improving productivity.

  When bonding protective films to both sides of the polarizer, active energy rays may be irradiated from either protective film side. For example, one protective film contains an ultraviolet absorber and the other protective film is ultraviolet. When the absorbent is not contained, it is preferable to irradiate the active energy rays from the protective film side not containing the ultraviolet absorber in order to effectively utilize the irradiated active energy rays and increase the curing rate.

  The polarizing plate obtained by curing the photocurable adhesive preferably has a peel strength between the polarizer and the protective film measured by a 180 degree peel test of 0.5 N / 25 mm or more. More preferably, it is 25 mm or more. When 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 polarizing plate manufacture will be described with reference to FIG. FIG. 1 is a schematic cross-sectional view showing a preferred example of an apparatus for producing a polarizing plate. A photo-curable adhesive is applied to one side of each of the protective films 2 and 3 that is continuously drawn out from the state of being wound in a roll shape by the adhesive application devices 11 and 12. Then, the protective films 2 and 3 are respectively overlapped on both surfaces of the polarizer 1 which is continuously drawn out in the same manner as the protective films 2 and 3 through the adhesive rolls by the bonding rolls 5a and 5b. 4 is produced. The diameter of the bonding rolls 5a and 5b is, for example, 50 to 250 mm.

  Next, a polarizing plate can be produced by irradiating the laminate 4 with active energy rays and curing the adhesive coating layer. In the example shown in FIG. 1, the produced laminate 4 is conveyed while being in 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 are located downstream of the roll direction. A beam irradiation device 17 and a fourth active energy beam irradiation device 18 are sequentially provided along the transport direction. Thereby, the application layer of the adhesive agent which the laminated body 4 has is the process in which the laminated body 4 is conveyed while adhering to the outer peripheral surface of the roll 13, and the active energy rays from the first active energy ray irradiating devices 14 and 15. Is further polymerized and cured by 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 disposed 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 laminate 4 passes through the conveyance nip roll 19 and is taken up by the take-up roll 20 as a polarizing plate.

  The roll 13 is a convex curved surface whose outer peripheral surface is mirror-finished. The roll 13 is transported while the laminate 4 is in close contact with the surface, and the application layer of the adhesive is polymerized and cured by the active energy ray irradiation devices 14 and 15 in the process. . The diameter of the roll 13 is not particularly limited when the adhesive is polymerized and cured, and the films constituting the laminate 4 are sufficiently adhered. The roll 13 may be driven or rotated in accordance with 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 dissipating heat generated in the laminate 4 at the time of polymerization and curing by irradiation with active energy rays. In that case, it is preferable that the surface temperature of the roll 13 acting as a cooling roll is set to 4 to 30 ° C.

<Laminated 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 optical functions other than the polarizing plate. Typically, a laminated optical member is obtained by laminating and sticking an optical layer on a protective film of a polarizing plate via an adhesive or a pressure-sensitive adhesive. In addition, for example, the present invention is applied to one surface of a polarizer. The protective film can be adhered via the photo-curable adhesive according to the above, and the optical layer can be laminated and adhered to the other surface of the polarizer via the adhesive or the 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 protective film. Two or more optical layers may be laminated on the polarizing plate.

  As an optical layer laminated on the polarizing plate, a reflective layer, a transflective layer, a light laminated on the side opposite to the liquid crystal cell in the polarizing plate with respect to the polarizing plate arranged on the back side of the liquid crystal cell. Examples include a diffusion layer, a light collector, and a brightness enhancement film. Moreover, the retardation plate etc. which are laminated | stacked on the liquid crystal cell side in the polarizing plate with respect to the polarizing plate arrange | positioned at the front side of a liquid crystal cell and / or the polarizing plate arrange | positioned at the back side of a liquid crystal cell are mentioned.

  The reflective layer, the semi-transmissive reflective layer, and the light diffusing layer are provided to form laminated optical members that are a reflective polarizing plate, a semi-transmissive reflective polarizing plate, and a diffusing polarizing plate, respectively. The reflective polarizing plate is used in a liquid crystal display device of a type that reflects and displays incident light from the viewing side, and a light source such as a backlight can be omitted, so that the liquid crystal display device can be easily thinned. Further, the transflective polarizing plate is used in a liquid crystal display device of a type that displays in a bright place as a reflection type and in a dark place with light from a backlight. The reflective polarizing plate can be produced, for example, by forming a reflective layer by attaching a foil or vapor deposition film made of a metal such as aluminum to a protective film on a polarizer. The transflective polarizing plate can be produced by using the above reflective layer as a half mirror, or by adhering a reflective plate exhibiting optical transparency by containing a pearl pigment or the like to the polarizing plate. On the other hand, the diffusion type polarizing plate is applied to the surface using various methods such as a method of performing a mat treatment on the protective film on the polarizing plate, a method of applying a resin containing fine particles, and a method of adhering a film containing fine particles. It can be produced by forming a fine relief structure.

  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 reflective layer reflecting the concavo-convex structure on the fine concavo-convex structure surface of the diffusing polarizing plate. The reflective layer having a fine concavo-convex structure has advantages such that incident light is diffused by irregular reflection, directivity and glare can be prevented, and unevenness in brightness and darkness can be suppressed. In addition, since the resin layer or film containing fine particles diffuses incident light and its reflected light, it also has an advantage that unevenness in brightness and darkness can be suppressed. The reflective layer reflecting the surface fine concavo-convex structure can be formed by directly attaching a metal to the surface of the fine concavo-convex structure by a method such as vapor deposition such as vacuum deposition, ion plating, sputtering, or plating. The fine particles to be blended to form the surface fine concavo-convex structure are, for example, silica, aluminum oxide, titanium oxide, zirconia, tin oxide, indium oxide, cadmium oxide, and antimony oxide having an average particle diameter of 0.1 to 30 μm. Inorganic fine particles, organic fine particles such as a crosslinked or non-crosslinked polymer, and the like.

  The condensing plate is used for the purpose of optical path control 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 a specific example thereof is that a plurality of thin film films having different refractive index anisotropies are laminated to produce anisotropy in reflectance. Reflection-type polarized light separation sheet designed in such a manner, a cholesteric liquid crystal polymer alignment film and a circularly polarized light separation sheet in which the alignment liquid crystal layer is supported on a film substrate.

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

  Examples of the plastic forming the birefringent film include amorphous polyolefin resin, polycarbonate resin, (meth) acrylic resin, chain polyolefin resin such as polypropylene, polyvinyl alcohol, polystyrene, polyarylate, polyamide. Etc. The stretched film can 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 broadening the bandwidth.

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

  A laminated optical member can be made into a laminated body of two layers or three or more layers by combining a polarizing plate and one layer or two or more layers selected according to the purpose of use from the various optical layers described above. In that case, the various optical layers forming the laminated optical member are integrated with the polarizing plate using an adhesive or a pressure-sensitive adhesive (also called a pressure-sensitive adhesive). If an agent layer and an adhesive layer are formed favorably, there will be no limitation in particular. It is preferable to use a pressure-sensitive adhesive from the viewpoint of simplicity of bonding work and prevention of optical distortion. As the pressure-sensitive adhesive, those having (meth) acrylic polymer, silicone polymer, polyester, polyurethane, polyether or the like as a base polymer can be used. Above all, like (meth) acrylic pressure-sensitive adhesive, it has excellent optical transparency, retains moderate wettability and cohesion, and has excellent adhesion to the substrate, and also has weather resistance, heat resistance, etc. It is preferable to select and use one that does not cause problems such as floating or peeling under the conditions of heating or humidification. In (meth) acrylic pressure-sensitive adhesives, alkyl esters of (meth) acrylic acid having an alkyl group having 20 or less carbon atoms such as methyl group, ethyl group, butyl group, (meth) acrylic acid and (meth) acrylic A functional group-containing (meth) acrylic monomer such as hydroxyethyl acid is blended so that the glass transition temperature is preferably 25 ° C. or lower, more preferably 0 ° C. or lower. ) Acrylic copolymers are useful as the base polymer.

  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% by weight solution, which is directly on the polarizing plate. It can be carried out by a coating method, a method in which a pressure-sensitive adhesive layer is previously formed on a release film, and transferred onto a polarizing plate. Although the thickness of an adhesive layer is determined according to the adhesive force etc., the range of about 1-50 micrometers is suitable.

  If necessary, the pressure-sensitive adhesive layer contains fillers made of glass fibers, glass beads, resin beads, metal powder and other inorganic powders, pigments and colorants, antioxidants, UV absorbers, etc. Also good. Examples of ultraviolet absorbers include salicylic acid ester compounds, benzophenone compounds, benzotriazole compounds, cyanoacrylate compounds, nickel complex compounds, and the like.

  The 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 instead of the laminated optical member. It 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 with an adhesive layer in which an adhesive layer for bonding to a liquid crystal cell is laminated on the outer surface thereof. 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 driving type typified by a thin film transistor type and a simple matrix driving type typified by a super twisted nematic type. Can be formed.

  EXAMPLES Hereinafter, although an Example and a comparative example are shown and this invention is demonstrated further more concretely, this invention is not limited by these examples. Hereinafter, the part and% showing usage-amount thru | or content are a basis of weight unless there is particular notice. Moreover, the photocationic curable component (A), polymer (B), and photocationic polymerization initiator (C) used in the following examples are as follows.

[Photocationic curable component (A)]
First photocationic curable component (A1):
a1-I: Bisphenol A type epoxy resin “Adeka Resin EP-4100L” manufactured by ADEKA Corporation,
a1-II: Bisphenol A type polyfunctional epoxy resin “ADEKA RESIN EP-5100R” manufactured by ADEKA Corporation,
a1-III: aromatic trifunctional epoxy resin “TECHMORE VG3101” manufactured by Printec Co., Ltd.
a1-IV: A phenol novolac type epoxy resin “EPPN-201” manufactured by Nippon Kayaku Co., Ltd.
a1-V: Special novolac type epoxy resin “157S20” manufactured by Mitsubishi Chemical Corporation,
a1-VI: Phenyl glycidyl ether.

Second photocationic curable component (A2):
a2-I: neopentyl glycol diglycidyl ether [compound of the above formula (III), Z = —CH ₂ C (CH ₃ ) ₂ CH ₂ —],
a2-II: 1,4-butanediol diglycidyl ether [compound of the above formula (III), Z = —CH ₂ CH ₂ CH ₂ CH ₂ —],
a2-III: 3-ethyl-3 {[(3-ethyloxetane-3-yl) methoxy] methyl} oxetane,
a2-IV: 2-ethylhexyl glycidyl ether,
a2-V: 4-hydroxybutyl vinyl ether,
a2-VI: Triethylene glycol divinyl ether.

Third photocationic curable component (A3):
a3-I: Daicel Co., Ltd. alicyclic epoxy resin “Celoxide 2021P”,
a3-II: Limonene dioxide.

[Polymer (B)]
b-I: 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),
b-II: a polymer having a weight average molecular weight of 8000 (GMA monopolymer) obtained by radical polymerization of glycidyl methacrylate,
b-III: a polymer having a weight average molecular weight of 60000 (GMA-MMA copolymer) obtained by radical polymerization of a monomer composition comprising 25 parts of glycidyl methacrylate and 75 parts of methyl methacrylate,
b-IV: A polymer having a weight average molecular weight of 200,000 (GMA-MMA copolymer) obtained by radical polymerization of a monomer composition comprising 50 parts of glycidyl methacrylate and 50 parts of methyl methacrylate.

[Photocationic polymerization initiator (C)]
Diphenyl (phenylthio) phenylsulfonium hexafluorophosphate.

[Photosensitizer and photosensitizer]
d-I: 1,4-diethoxynaphthalene,
d-II: 9,10-dibutoxyanthracene.

<Examples 1-27 and Comparative Examples 1-9>
(1) Preparation of photocurable adhesive After mixing each component shown by Table 1, it defoamed and prepared the photocurable adhesive (liquid) of Examples 1-27 and Comparative Examples 1-9. . The unit of the amount of each component in Table 1 is “parts”. The photocationic polymerization initiator (C) was actually blended as a 50% propylene carbonate solution, but 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 solution) prepared above, an E-type viscometer “TVE-25L” manufactured by Toki Sangyo Co., Ltd. was used. The viscosity at a temperature of 25 ° C. was measured. The results are shown in Table 2.

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

(4) Production of polarizing plate Containing a protective film made of (meth) acrylic resin (PMMA) [trade name “Technoloy S001”, manufactured by Sumitomo Chemical Co., Ltd.] having a thickness of 80 μm containing an ultraviolet absorber, and a norbornene resin. One side of a 50 μm-thick retardation film [trade name “ZEONOR”, manufactured by Nippon Zeon Co., Ltd.] is subjected to corona treatment, and each of the adhesive liquids prepared in (1) above is applied to these corona-treated surfaces. Each was coated using a coating apparatus. Under the present circumstances, the line speed of the film in an adhesive agent coating apparatus was 25 m / min, and the gravure roll was rotated in the reverse direction to the conveyance direction of a film. The thickness of the adhesive layer was set to 2.8 μm after curing.

  Next, the protective film made of the (meth) acrylic resin is applied to one surface of a polyvinyl alcohol-iodine polarizer having a thickness of 25 μm, and the retardation film made of the norbornene resin is bonded to the other surface. It bonded through the agent layer. For the bonding, a pair of nip rolls having a diameter of 250 mm [bonding roll (chromium-plated metal roll / rubber roll)] was used, and the pressing pressure was 1.5 MPa.

The obtained laminate is 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 280 to 320 nm) is about 200 mJ /. The adhesive layer was cured by irradiating with ultraviolet rays (UVB) so as to be cm ² (measurement device: measurement value by UV Power Pack II manufactured by FusionUV) to obtain a polarizing plate.

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

<Evaluation criteria>
A: Bubbles were not confirmed,
B: Air bubbles were confirmed.

(6) 180 degree peeling test of polarizing plate After the polarizing plate prepared in the above (4) is cut into a size of 200 mm length × 25 mm width, an acrylic pressure-sensitive adhesive is provided on the protective film side made of (meth) acrylic resin. A layer was provided as a test piece for measuring the peel strength between the protective film and the polarizer. Separately from this, an acrylic pressure-sensitive adhesive layer was provided on the retardation film side to obtain a test piece for measuring the peel strength between the retardation film and the polarizer.

  Each test piece is attached to a glass plate using the pressure-sensitive adhesive layer, and the cutter is placed between the polarizer and the protective film (protective film made of (meth) acrylic resin or norbornene-based retardation film) on the pressure-sensitive adhesive layer side. The blade was inserted, and 30 mm was peeled off from the end in the length direction, and the peeled portion was grasped by the grasping portion of the testing machine. With respect to the test piece in this state, in accordance with JIS K 6854-2: 1999 “Adhesive—Peeling adhesive strength test method—Part 2: 180 degree peeling” in an atmosphere having a temperature of 23 ° C. and a relative humidity of 55%. Then, a 180 degree peel test was performed at a grip moving speed of 300 mm / min, and an average peel force over a length of 170 mm excluding 30 mm of the grip part was obtained. The measurement is performed 24 hours after the polarizing plate is produced. The results are shown in Table 2. In Table 2, “PMMA / PVA peel strength” represents the peel strength between the protective film made of the (meth) acrylic resin and the polarizer, and “COP / PVA peel strength” Represents the peel strength between the norbornene-based retardation film and the polarizer. In Table 2, “base material breakage” means that the peel strength is large, and at least one of the polarizer and the protective film (or retardation film) was torn during the peel test.

(7) Measurement of Tg and Tensile Elastic Modulus of Cured Adhesive Layer Each photocurable adhesive prepared in (1) above was applied to an untreated PET (“Soft Shine” manufactured by Toyobo Co., Ltd.) with a bar coater # 20. After the application, ultraviolet rays were irradiated using an ultraviolet irradiation device with a belt conveyor (the lamp was a “D bulb” manufactured by Fusion UV Systems) so that the integrated light amount was 3000 mJ / cm ² (UVB). After 24 hours, the cured adhesive layer was taken out of the film, and the glass transition temperature Tg and the tensile modulus (80 ° C.) were measured using a viscoelasticity measuring device “DMA7100” manufactured by Hitachi High-Tech Science Co., Ltd. The results are shown in Table 2. The adhesive of Comparative Example 9 did not cure under the above conditions.

  DESCRIPTION OF SYMBOLS 1 Polarizer, 2, 3 Protective film, 4 Laminated body, 5a, 5b Bonding roll, 11, 12 Adhesive coating apparatus, 13 roll, 14, 15 1st active energy ray irradiation apparatus, 16 2nd active energy ray Irradiation device, 17 3rd active energy ray irradiation device, 18 4th active energy ray irradiation device, 19 nip roll for conveyance, 20 winding roll.

Claims (16)

A photo-curable adhesive for bonding a protective film made of a thermoplastic resin to a polyvinyl alcohol polarizer,
A photocationic curable component (A) comprising a first photocationic curable component (A1) which is an aromatic epoxy compound;
The following formula (I):

(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 the monomer (I) 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. And 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 a structural unit derived from one or more monomers selected from the group consisting of monomers (II) represented by:
A cationic photopolymerization initiator (C);
Containing
The content of the polymer (B) is 2 to 10 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 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),
Photocurability in which the content of the photocationic polymerization initiator (C) is 1 to 10 parts by weight with respect to 100 parts by weight of the total amount of the photocationic curable component (A) and the polymer (B). adhesive.   The photocationic curable component (A) includes 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, -CO-O. It may be substituted with a divalent group selected from —, —O—CO—, —SO ₂ —, —SO— or —CO—.
The photocurable adhesive agent of Claim 2 which is a compound shown by these.   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). The photocurable adhesive agent of any one of -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 claim 6, wherein the polymer (B) has a weight average molecular weight of 6,000 to 100,000.   The moisture content according to any one of claims 1 to 7, wherein the water content is 4 parts by weight or less with respect to 100 parts by weight of the total amount of the photocationic curable component (A) and the polymer (B). Photo-curable adhesive.   The photocurable adhesive according to any one of claims 1 to 8, wherein the viscosity at 25 ° C is 2 to 300 mPa · s. A polyvinyl alcohol polarizer,
A protective film made of a thermoplastic resin that is bonded to 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,
A polarizing plate including   The thermoplastic resin is 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 as described.   The polarizing plate of Claim 10 or 11 in which the said protective film contains a ultraviolet absorber.   The polarizing plate according to any one of claims 10 to 12, wherein a peel strength between the polyvinyl alcohol polarizer and the protective film measured by a 180 degree peel test is 0.5 N / 25 mm or more. .   The laminated optical member which consists of a laminated body of the polarizing plate of any one of Claims 10-13, 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.

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