JP6802708B2 - Photocurable adhesive, polarizing plate using it, laminated optical member and liquid crystal display device - Google Patents

Description

The present invention relates to a photocurable adhesive for adhering a protective film to a polyvinyl alcohol-based 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 constituting the liquid crystal display device. The polarizing plate usually has a structure in which protective films are laminated on both sides of the polarizing element, and is incorporated in a liquid crystal display device. It is also known to provide a protective film on only one side of the polarizer, but in many cases, a film having another optical function, which is not just a protective film, is adhered to the other side as a protective film. To. As a method for producing a polarizer, a method in which a uniaxially stretched polyvinyl alcohol-based resin film dyed with a dichroic dye is treated with boric acid, washed with water, and then dried is widely adopted.

Usually, a protective film is adhered to the polarizer immediately after washing with water and drying as described above. This is because the dried polarizer has a weak physical strength, and once it is wound up, it tends to tear in the processing direction. Therefore, usually, an aqueous adhesive which is an aqueous solution of a polyvinyl alcohol-based resin is immediately applied to the polarizing element after drying, and a protective film is simultaneously adhered to both sides 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.

Triacetyl cellulose has excellent transparency, easily forms various surface treatment layers and optical functional layers on its surface, and has high humidity permeability. After being adhered to a polarizer using the above-mentioned aqueous adhesive, triacetyl cellulose has excellent transparency. Although it has an excellent advantage as a protective film such that it can be dried smoothly, a polarizing plate using this as a protective film has a high humidity permeability, for example, a temperature of 70 ° C. and a relative humidity of 90%. There was a problem that deterioration was likely to occur under the conditions. Therefore, it is also known that an amorphous polyolefin resin having a lower humidity permeation than triacetyl cellulose, for example, a norbornene resin as a typical example, is used as a protective film. Japanese Unexamined Patent Publication No. 06-051117 (Patent Document 1) describes that a thermoplastic saturated norbornene-based resin sheet is laminated on at least one surface of a polarizer as a protective film.

When a protective film made of a resin having low moisture permeability is adhered to a polyvinyl alcohol-based polarizer, an aqueous solution of a polyvinyl alcohol-based resin conventionally used for bonding the polyvinyl alcohol-based polarizer and a triacetyl cellulose film is used as an adhesive. There are problems that the adhesive strength is not sufficient and the appearance of the obtained polarizing plate is poor. This is because a resin film having low moisture permeability is generally hydrophobic, and water, which is a solvent, cannot be sufficiently dried due to low moisture permeability. On the other hand, it is also known to adhere different types of protective films to both sides of the polarizer. For example, in Japanese Patent Application Laid-Open No. 2002-174729 (Patent Document 2), a protective film made of a resin having low moisture permeability such as an amorphous polyolefin resin is adhered to one surface of the polarizer, and the other of the polarizers. There is also a proposal to adhere a protective film made of a highly moisture-permeable resin such as a cellulosic resin such as triacetyl cellulose to the surface of.

Therefore, a high adhesive force is given between the protective film made of a resin having low moisture permeability and the polyvinyl alcohol-based polarizer, and the adhesive strength is also high between the resin having high moisture permeability such as cellulose-based resin and the polyvinyl alcohol-based polarizer. There is an attempt to use a photocurable adhesive as an adhesive that imparts adhesive strength. For example, Japanese Patent Application Laid-Open No. 2004-245925 (Patent Document 3) discloses an adhesive containing an epoxy compound that does not contain an aromatic ring as a main component, and is subjected to irradiation with active energy rays, specifically, irradiation with ultraviolet rays. It has been proposed to cure this adhesive by cationic polymerization to bond the polarizer to the protective film. Further, Japanese Patent Application Laid-Open No. 2008-257199 (Patent Document 4) describes a photocurable adhesive in which an alicyclic epoxy compound and an epoxy compound having no alicyclic epoxy group are combined and further blended with a photocationic polymerization initiator. Is disclosed as a technique for adhering a polarizer to a protective film.

The epoxy adhesive disclosed in Patent Document 3 is effective for adhering a protective film made of an amorphous polyolefin resin, a cellulose resin, or the like to a polarizer, but protects the protective film 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 radical polymerizable functional group. An active energy ray-curable compound containing 5 to 100% by weight of an active energy ray cationically curable compound (a1) having a weight average molecular weight of less than 5000 and 0 to 95% by weight of an active energy ray radical curable compound (a2). A) An adhesive for an optical film containing 0.0001 to 2 parts by weight of an acrylic resin (B) having an epoxy group or an oxetanyl group and having a weight average molecular weight of 5,000 to 150,000 with respect to 100 parts by weight is disclosed. However, if the content of the acrylic resin (B) exceeds 2 parts by weight, the viscosity of the adhesive may increase, and 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.

Japanese Patent Application Laid-Open No. 2012-007080 (Patent Document 6) has a viscosity containing a cationically polymerizable component containing 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 adhering a protective film made of an amorphous polyolefin resin, a cellulose resin, or the like to a polarizer, it is a (meth) acrylic resin. When adhering a protective film made of, the adhesive strength is not always sufficient.

Japanese Patent Application Laid-Open No. 2013-092762 (Patent Document 7) describes active energy ray curing on one side of a transparent film as a method capable of producing a polarizing plate in which bubbles are less likely 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 on the surface coated with the adhesive to prepare a laminate, and irradiating the laminate with active energy rays. Disclosed is a method for producing a polarizing plate including a step of producing a polarizing plate, wherein the diameter of the bonding roll used in the step of producing a laminated body is in the range of 50 to 250 mm. Has been done.

Japanese Unexamined Patent Publication No. 06-051117 JP-A-2002-174729 Japanese Unexamined Patent Publication No. 2004-245925 Japanese Unexamined Patent Publication No. 2008-257199 Japanese Unexamined Patent Publication No. 2012-172026 Japanese Unexamined Patent Publication No. 2012-007080 Japanese Unexamined Patent Publication No. 2013-092762

According to the present invention, when a protective film is adhered to a polyvinyl alcohol-based polarizing element, a polarizing plate having a viscosity sufficiently low enough to be coated at room temperature and having an improved adhesive force between the polarizer and the protective film. It is an object of the present invention to provide a photocurable adhesive capable of giving. Another object of the present invention is a low viscosity that allows the polyvinyl alcohol-based polarizer and the protective film to be adhered to each other without causing bubbles in the adhesive layer even when the thickness of the adhesive layer is reduced. The purpose 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 laminated optical member.

The present invention provides the following photocurable adhesives, polarizing plates, laminated optical members, and liquid crystal display devices.

[1] A photocurable adhesive for adhering a protective film made of a thermoplastic resin to a polyvinyl alcohol-based polarizer.
A photocationic curable component (A) containing 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.
The monomer (I) represented by, and 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. It 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) consisting of a structural unit derived from one or more monomers selected from the group consisting of the monomer (II) represented by
Photocationic polymerization initiator (C) and
Contains,
The content of the polymer (B) is 2 to 10 parts by weight based on 100 parts by weight of the total amount of the photocationic curable component (A) and the polymer (B).
The content of the first photocationic curable component (A1) is 10 to 40 parts by weight out of 100 parts by weight of the total amount of the photocationic curable component (A) and the polymer (B).
The content of the photocationic polymerization initiator (C) is 1 to 10 parts by weight 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 an aliphatic diglycidyl compound, a monofunctional aliphatic epoxy compound, a vinyl ether compound and an oxetane compound. 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. -, - O-CO -, - SO 2 -, - SO- or a divalent group selected from -CO- may be substituted).
The photocurable adhesive according to [2], which is a compound represented by.

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

[5] The content of the second photocationic curable component (A2) is 58 to 88 parts by weight out of 100 parts by weight of the total amount 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 5000 to 500000.

[7] The photocurable adhesive according to [6], wherein the polymer (B) has a weight average molecular weight of 6000 to 100,000.

[8] Any 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.

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

[10] Polyvinyl alcohol-based polarizer and
A protective film made of a thermoplastic resin, which is 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 one or more resins selected from the group consisting of cellulose-based resins, (meth) acrylic-based resins, amorphous polyolefin-based resins, polyester-based resins, and polycarbonate-based resins. 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 the peel strength between the polyvinyl alcohol-based polarizing element and the protective film measured by the 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 including a liquid crystal cell and the laminated optical member according to [14] or [15] arranged on at least one surface of the liquid crystal cell.

According to the present invention, it is possible to provide a photocurable adhesive having low viscosity, less likely to generate bubbles in the adhesive layer, and capable of adhering a polyvinyl alcohol-based 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 (meth) acrylic resin is adhered, a polarizing plate having 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 have excellent durability.

It is sectional drawing which shows a preferable example of the apparatus which manufactures the polarizing plate which concerns on this invention.

<Photo-curable 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-based polarizer, and comprises a photocationic curable component (A), a polymer (B), and the like. Contains a photocationic polymerization initiator (C).

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

(1-1) First photocationic curable component (A1)
The first photocationic curable component (A1) is composed of an aromatic epoxy compound. The aromatic epoxy compound is an epoxy compound having an aromatic ring. However, in the aromatic epoxy compound referred to here, X and / or Y in the polymer (B) described later has an aromatic ring and an epoxy group, and the polymer (B) belonging to the aromatic epoxy compound is classified. Not included. The first photocationic curable component (A1) may consist of two or more aromatic epoxy compounds. Specific examples of aromatic epoxy compounds include monovalent phenols such as phenol, cresol and butylphenol, bisphenol A, bisphenol derivatives such as bisphenol F, or mono- or polyglycidyl etherified products having alkylene oxide adducts thereof; epoxy novolac resin; resorcinol. Mono or polyglycidyl etherified product of an aromatic compound 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. Glysidyl etherified product; Glysidyl ester of a polybasic acid aromatic compound having two or more carboxyl groups such as phthalic acid, terephthalic acid, and trimellitic acid; Glysidyl ester of benzoic acid, tolulic acid, glycidyl ester of naphthoic acid, etc.; Examples thereof include styrene oxides such as oxides, alkylated styrene oxides and epoxidates of vinylnaphthalene, and diepoxidates of divinylbenzene.

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

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

Commercially available products can be used as the aromatic epoxy compound, for example, "Denacol EX-145", "Denacol EX-146", "Denacol EX-147", "Denacol EX-201", "Denacol EX-711", "Denacol EX-721", "On-coat EX-1020", "On-coat EX-1030", "On-coat EX-1040", "On-coat EX-1050", "On-coat EX-1051", "On-coat" 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 manufactured by Osaka Gas Chemical Co., Ltd.);" HP4032 "," HP4032D "and" HP4700 "(both manufactured by DIC Co., Ltd.);" ESN-475V " "(Nittetsu Sumikin Chemical Co., Ltd.);" 152 "," 154 "," 157S70 "and" YX8800 "(all 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", "Adeka Glycyllol ED-501", "Adeka Glycyllol ED-509E", "Adeka Glycyllol ED-509S" and "Adeka Glycyrrol ED-529" ADEKA Corporation), "TECHMORE VG3101L" (manufactured by Printec Co., Ltd.) and the like.

The content of the first photocationic curable component (A1) is 10 to 40 parts by weight, preferably 12 to 40 parts by weight, based on 100 parts by weight of the total amount of the photocationic curable component (A) and the polymer (B) described later. It is 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, and lower viscosity of the photocurable adhesive can be achieved. It is possible to achieve both the good coatability that accompanies it. On the other hand, if the amount of the first photocationic curable component (A1) exceeds 40 parts by weight, it becomes difficult to achieve both of the above, and the viscosity tends to be particularly high. 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, and two or more of these are curable. It may consist of ingredients. The monofunctional aliphatic epoxy compound referred to here includes the polymer (B) which belongs to the monofunctional aliphatic epoxy compound in terms of classification because X or Y in the polymer (B) described later has an epoxy group. Absent. Further, the oxetane compound referred to here does not include the polymer (B) belonging to the oxetane compound in terms of classification because X or Y in the polymer (B) described later has an oxetane group.

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

It is more preferable to include the compound represented by. In the above formula (III), Z represents a linear or branched alkylene group having 1 to 9 carbon atoms or a divalent alicyclic hydrocarbon group, and the methylene group in the alkylene group is an oxygen atom, −CO. It may be substituted with a divalent group selected from -O-, -O-CO-, -SO _2- , -SO- or -CO-. Typical examples of divalent alicyclic hydrocarbon groups are cyclopentylene groups and cyclohexylene groups.

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

Examples of the monofunctional aliphatic epoxy compound include glycidyl ethers of aliphatic alcohols and glycidyl esters of alkylcarboxylic acids, and specific examples thereof include allyl glycidyl ether, butyl glycidyl ether, sec-butylphenyl glycidyl ether, 2-. It contains ethylhexyl glycidyl ether, alkyl glycidyl ether mixed with 12 and 13 carbon atoms, glycidyl ether of alcohol, monoglycidyl ether of aliphatic higher alcohol, glycidyl ester of higher fatty acid and the like.

Examples of the vinyl ether compound include an aliphatic or alicyclic vinyl ether compound, and specific examples thereof include n-amyl vinyl ether, i-amyl vinyl ether, n-hexyl vinyl ether, n-octyl vinyl ether, 2-ethylhexyl vinyl ether, and n-. Vinyl ethers having 5 to 20 alkyl carbon atoms or alkenyl alcohols such as dodecyl vinyl ethers, stearyl vinyl ethers and oleyl vinyl ethers; hydroxyl group-containing vinyl ethers such as 2-hydroxyethyl vinyl ethers, 3-hydroxypropyl vinyl ethers and 4-hydroxybutyl vinyl ethers; cyclohexyl vinyl ethers, Monoalcoholic vinyl ethers having an aliphatic ring or aromatic ring such as 2-methylcyclohexylvinyl ether, cyclohexylmethylvinyl ether, benzylvinyl ether; glycerol monovinyl ether, 1,4-butanediol divinyl ether, 1,6-hexanediol divinyl ether , Neopentyl glycol divinyl ether, pentaerythritol divinyl ether, pentaerythritol tetravinyl ether, trimethylolpropane divinyl ether, trimethylolpropanetrivinyl ether, 1,4-dihydroxycyclohexanemonovinyl ether, 1,4-dihydroxycyclohexanedivinyl ether, 1,4 -Polyhydric alcohol mono or polyvinyl ethers such as dihydroxymethylcyclohexane monovinyl ether, 1,4-dihydroxymethylcyclohexanedivinyl ether; polyalkylene glycol mono or polyalkylene glycol mono such as diethylene glycol divinyl ether, triethylene glycol divinyl ether, diethylene glycol monobutyl monovinyl ether Divinyl ethers; Including other vinyl ethers such as glycidyl vinyl ether and ethylene glycol vinyl ether methacrylate.

The oxetane compound is a compound having an oxetane group, and specific examples thereof include 3,7-bis (3-oxetanyl) -5-oxa-nonane and 1,4-bis [(3-ethyl-3-oxetanylmethoxy). Methyl] benzene, 1,2-bis [(3-ethyl-3-oxetanylmethoxy) methyl] ethane, 1,3-bis [(3-ethyl-3-oxetanylmethoxy) methyl] propane, ethylene glycol bis (3-) Ethyl-3-oxetanylmethyl) ether, triethylene glycol bis (3-ethyl-3-oxetanylmethyl) ether, tetraethylene glycol bis (3-ethyl-3-oxetanylmethyl) ether, 1,4-bis (3-ethyl) -3-oxetanylmethoxy) butane, 1,6-bis (3-ethyl-3-oxetanylmethoxy) hexane, 3-ethyl-3-[(phenoxy) methyl] oxetane, 3-ethyl-3- (hexyloxymethyl) Includes 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 within the above range, but the photocationic curable component (A) and the following will be described. The total amount of the polymer (B) to be used is preferably 58 to 88 parts by weight, more preferably 60 to 85 parts by weight, based on 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 photocationic curable component (A) is a third photocationic curable component (A3) which is a curable component other than the first photocationic curable component (A1) and the second photocationic curable component (A2). Can be further included. The third photocationic curable component (A3) includes an epoxy compound (for example, an alicyclic epoxy compound), a cyclic lactone compound, a cyclic acetal compound, a cyclic thioether compound, and a spiro that do not belong to any of (A1) and (A2). Examples include orthoester compounds. The content of the third photocationic curable component (A3) is not particularly limited as long as the content of the first photocationic curable component (A1) is within the above range, and is preferably the second photocationic curable component. When (A2) is contained, the content of the second photocationic curable component (A2) is within the above range.

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

The monomer (I) represented by, and the following formula (II):

It is a polymer composed of a structural unit derived from one or more kinds of monomers selected from the group consisting of the monomer (II) represented by. Specifically, a homopolymer obtained by polymerizing one type of monomer (I), a copolymer obtained by polymerizing two or more types of monomer (I), and one type of monomer (II) are polymerized. Homopolymer, a copolymer made by polymerizing two or more kinds of monomer (II), a copolymer made by polymerizing one or more kinds of monomer (I) and one or more kinds of monomer (II) , And a mixture of two or more of these.

X in the above formula (I) 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. It represents an alkyl group of 1 to 7, an alkoxy group having 1 to 7 carbon atoms, an aryl group having 6 to 12 carbon atoms, an aryloxy group having 6 to 12 carbon atoms or an alicyclic hydrocarbon group having 6 to 10 carbon atoms.

The alkyl groups 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. Of these, an alkyl group having 1 to 4 carbon atoms is preferable from the viewpoint of durability of the adhesive layer.

Examples of the alkoxy group having 1 to 7 carbon atoms include a methoxy group, an ethoxy group, an n-propyloxy group, an i-propyloxy group, an n-butyloxy group, a sec-butyloxy group, a tert-butyloxy group, an i-butyloxy group and n. -Amiloxy 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. Of these, an alkyl group having 1 to 4 carbon atoms is preferable from the viewpoint of durability of the adhesive layer.

Examples of the 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 to 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 to 10.

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

X in the above formula (I) is an alkyl group having 1 to 7 carbon atoms and carbon partially substituted with one or more functional groups selected from the group consisting of an epoxy group, an oxetanyl group, a hydroxyl group and a carboxyl group. When an alkoxy group having a number of 1 to 7, 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 is used, the functional group undergoes a curing reaction. Since it contributes, it is advantageous in terms of durability of the adhesive layer and suppression of bleeding of low molecular weight components from the adhesive layer. Above all, the functional group is preferably one or more functional groups selected from the group consisting of an epoxy group, an oxetanyl group and a hydroxyl group.

In the above formula (I), the monomer (I) in the case where a part of X is substituted with an epoxy group or an oxetanyl group is represented by, for example, the following formulas (Ia), (Ib) and (Ic). The monomer to be used 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. Alternatively, it represents an alicyclic hydrocarbon group having 6 to 10 carbon atoms.

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 those of X in the formula (I).

Similar to X in formula (I), Y in formula (II) is a carbon partially substituted with one or more functional groups selected from the group consisting of an epoxy group, an oxetanyl group, a hydroxyl group and a carboxyl group. When an alkyl group having a number of 1 to 7, an aryl group having 6 to 12 carbon atoms or an alicyclic hydrocarbon group having 6 to 10 carbon atoms is used, the functional group contributes to the curing reaction, so that the durability of the adhesive layer is durable. It is also advantageous in terms of suppressing bleeding of low molecular weight components from the adhesive layer. Above all, the functional group is preferably one or more functional groups selected from the group consisting of an epoxy group, an oxetanyl group and a hydroxyl group.

In the above formula (II), the monomer (II) in the case where a part of Y is substituted with an epoxy group or an oxetanyl group is represented by, for example, the following formulas (IIa), (IIb) and (IIc). The monomer to be used 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 to standard polystyrene by gel permeation chromatography (GPC) from the viewpoint of achieving both the adhesive strength between the polyvinyl alcohol-based polarizer and the protective film and the low viscosity of the photocurable adhesive. The weight average molecular weight of the above is preferably 5000 to 500,000, more preferably 6000 to 100,000.

The content of the polymer (B) is 2 to 10 parts by weight, preferably 2.5 to 10 parts by weight, out of 100 parts by weight of the total amount of the photocationic 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-based polarizer and the protective film (particularly the protective film made of (meth) acrylic resin) is increased while ensuring low viscosity. The effect can be exhibited. On the other hand, when the content of the polymer (B) exceeds 10 parts by weight, the viscosity of the photocurable adhesive increases. If it is less than 2 parts by weight, the adhesion to the protective film made of (meth) acrylic resin is particularly low. As used herein, the term "(meth) acrylic" means at least one selected from acrylic and methacrylic. The same applies to "(meth) acrylate".

(3) Photocationic polymerization initiator (C)
The photocurable adhesive contains a photocationic polymerization initiator (C). As a result, the photocationic curable component (A) can be cured by cation polymerization by irradiation with active energy rays to form an adhesive layer. The photocationic polymerization initiator (C) generates a cationic species or Lewis acid by 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 with light, it is excellent in storage stability and workability even when mixed with the photocationic curable component (A). As a compound that produces a cationic species or Lewis acid by irradiation with an active energy ray that can be used as a photocationic polymerization initiator (C), for example, an aromatic diazonium salt; an onium salt such as an aromatic iodonium salt or an aromatic sulfonium salt; Examples thereof include an iron-alene complex.

Examples of the aromatic diazonium salt include, for example.
Benzenediazonium hexafluoroantimonate,
Benzenediazonium hexafluorophosphate,
Benzenediazonium hexafluoroborate can be mentioned.

Examples of aromatic iodonium salts include
Diphenyliodonium tetrakis (pentafluorophenyl) borate,
Diphenyliodonium hexafluorophosphate,
Diphenyliodonium hexafluoroantimonate,
Di (4-nonylphenyl) iodonium hexafluorophosphate can be mentioned.

Examples of the aromatic sulfonium salt include
Triphenylsulfonium hexafluorophosphate,
Triphenylsulfonium hexafluoroantimonate,
Triphenylsulfonium tetrakis (pentafluorophenyl) borate,
4,4'-Bis [diphenylsulfonio] diphenylsulfide bishexafluorophosphate,
4,4'-Bis [di (β-hydroxyethoxy) phenylsulfonio] diphenylsulfide bishexafluoroantimonate,
4,4'-Bis [di (β-hydroxyethoxy) phenylsulfonio] diphenylsulfide bishexafluorophosphate,
7- [di (p-toluyl) sulfonio] -2-isopropylthioxanthone hexafluoroantimonate,
7- [di (p-toluyl) sulfonio] -2-isopropylthioxanthone tetrakis (pentafluorophenyl) borate,
4-Phenylcarbonyl-4'-diphenylsulfonio-diphenylsulfide hexafluorophosphate,
4- (p-tert-Butylphenylcarbonyl) -4'-diphenylsulfonio-diphenylsulfide hexafluoroantimonate,
Examples thereof include 4- (p-tert-butylphenylcarbonyl) -4'-di (p-toluyl) sulfonio-diphenylsulfide tetrakis (pentafluorophenyl) borate.

Examples of the iron-arene complex include, for example.
Xylene-Cyclopentadienyl Iron (II) Hexafluoroantimonate,
Cumene-Cyclopentadienyl Iron (II) Hexafluorophosphate,
Examples thereof include xylene-cyclopentadienyl iron (II) tris (trifluoromethylsulfonyl) metanide.

As the photocationic polymerization initiator (C), only one type may be used alone, or two or more types may be used in combination. Among the above, the aromatic sulfonium salt is preferably used because it has an ultraviolet absorbing property even in a wavelength region near 300 nm and can provide an adhesive layer having excellent curability and good mechanical strength and adhesive strength. Be 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). Is. By containing 1 part by weight or more of the photocationic polymerization initiator (C), the photocationic curable component (A) can be sufficiently cured, and the obtained polarizing plate is provided with high mechanical strength and adhesive strength. On the other hand, if the amount is large, the amount of ionic substances in the cured product increases, which increases the hygroscopicity of the cured product and may reduce the durability performance of the polarizing plate. Therefore, the photocationic polymerization initiator (C) ) 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 photocationic polymerization initiator (C) exhibits maximum absorption in a wavelength region near 300 nm or shorter, generates cation species or Lewis acid in response to light having a wavelength in the vicinity thereof, and is a photocationic curable component. The photosensitizer preferably exhibits maximum absorption in a wavelength region longer than 380 nm so as to initiate the cationic polymerization of (A) but to be sensitive to light having a wavelength longer than that. Anthracene-based compounds are preferably used as such photosensitizers.

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 thereof 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 contained. Such an effect can be exhibited 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 is large, problems such as precipitation during low-temperature storage occur. Therefore, the total amount of the photocationic curable component (A) and the polymer (B) is 100 parts by weight. 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 can be sufficiently obtained. The amount of the photosensitizer is 0.1 to 0.5 parts by weight, and further 0.1 to 0.3 parts by weight with respect to 100 parts by weight of the total amount of the photocationic curable component (A) and the polymer (B). It is preferably in the range of parts by weight.

(5) Photosensitizer The photocurable adhesive may contain a photosensitizer. The photosensitizer is preferably a naphthalene-based photosensitizer.

Specific examples of naphthalene-based photosensitizers 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,
Examples thereof include 1,4-dibutoxynaphthalene.

By including a naphthalene-based photosensitizer in the photocurable adhesive, the curability of the adhesive can be improved as compared with the case where it is not contained. Such an effect is exhibited by setting the content of the naphthalene-based 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). Can be done. On the other hand, if the content of the naphthalene-based photosensitizer increases, problems such as precipitation during low-temperature storage occur. Therefore, the total amount of the photocationic curable component (A) and the polymer (B) is 100. It is preferably 5 parts by weight or less with respect to the weight part. The content of the naphthalene-based photosensitizer is preferably 3 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).

(6) Additive component The photocurable adhesive may contain an additive component as another component which is an optional component as long as the effect of the present invention is not impaired. Additive components include thermal cationic polymerization initiators, polyols, ion trap agents, antioxidants, photostabilizers, chain transfer agents, tackifiers, thermoplastic resins, fillers, flow conditioners, plasticizers, and defoamers. Examples thereof include foaming agents, leveling agents, dyes, organic solvents and the like.

When the additive component is contained, the content thereof 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, the polyvinyl alcohol-based polarizer and the protective film are composed of a combination of the photocationic curable component (A), the polymer (B) and the photocationic polymerization initiator (C), which are essential components. It is possible to satisfactorily exert the effect of achieving both the excellent adhesive strength between the two, the low viscosity of the photocurable adhesive, and the good coatability associated therewith.

(7) Moisture Content of Photocurable Adhesive The photocurable adhesive may contain water. 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 small amount of water, the adhesive strength between the polyvinyl alcohol-based polarizer and the protective film may be improved. However, if the water content is too high, the photocurable adhesive and water will separate, making it impossible to evenly apply the photocurable adhesive to the surface of the polarizer or protective film, or photocuring. The curability of the sex adhesive may deteriorate. Moisture may be intentionally added to the photocurable adhesive, and in this case, purified water such as distilled water and pure water can be used without particular limitation. The water content of the photocurable adhesive is measured by the Karl Fischer titer 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. The viscosity referred to here is a viscosity in a state in which a solvent is substantially not contained. If the viscosity is less than 2 mPa · s, the polarizer and the protective film may peel off during transportation after bonding, and if the viscosity exceeds 300 mPa · s, the polarizer, the protective film and the protective film are bonded via an adhesive. In particular, when the adhesive layer is thin, air bubbles are likely to be mixed between the polarizer and the protective film, that is, in the adhesive layer. The viscosity is more preferably 5 to 200 mPa · s, 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.

<Polarizer>
The polarizing plate according to the present invention includes a polyvinyl alcohol-based polarizing element 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 polarizing element and the protective film is high and the durability is excellent, and air bubbles are mixed into the cured adhesive layer. It is suppressed.

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

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

The uniaxial stretching may be performed before dyeing with the dichroic dye, at the same time as dyeing with the dichroic dye, or after dyeing with the dichroic dye. When the uniaxial stretching is performed after dyeing with a dichroic dye, the uniaxial stretching may be performed before the boric acid treatment or during the boric acid treatment. It is also possible to perform uniaxial stretching in these a plurality of steps. The method of uniaxial stretching is not particularly limited, and may be uniaxially stretched between rolls having different peripheral speeds, or may be uniaxially stretched using a thermal roll. Further, it may be a dry stretching performed in the air, or a wet stretching performed in a state of being swollen with a solvent. The draw ratio is usually about 4 to 8 times.

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

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

On the other hand, when a dichroic organic dye is used as the dichroic dye, a method of immersing a polyvinyl alcohol-based resin film in an aqueous solution containing a water-soluble dichroic organic dye and dyeing is usually adopted. 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 (staining 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 content of boric acid in the boric acid aqueous solution is usually about 2 to 15 parts by weight, preferably about 5 to 12 parts by weight per 100 parts by weight of water. When iodine is used as the dichroic dye, this boric acid aqueous solution preferably contains potassium iodide. The content of potassium iodide in an aqueous boric acid solution is usually about 2 to 20 parts by weight, preferably 5 to 15 parts by weight, per 100 parts by weight of water. The immersion time in the 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-based resin film after the boric acid treatment is usually washed with water. The water washing treatment can be performed, for example, by immersing the boric acid-treated polyvinyl alcohol-based resin film in water. After washing with water, a drying treatment is performed to obtain a polarizer. The temperature of water in the washing treatment is usually about 5 to 40 ° C., and the immersion time is usually about 2 to 120 seconds. Subsequent drying treatments can usually be performed using a hot air dryer or a far infrared heater. The drying temperature is usually 40 to 100 ° C. The drying treatment time is usually about 120 to 600 seconds. 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 a non-stretched 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-based resins, (meth) acrylic-based resins, amorphous polyolefin-based resins, polyester-based resins, and polycarbonate-based resins. Is.

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

Examples of other copolymerization components include a dicarboxylic acid component and a diol component. The dicarboxylic acid components include isophthalic acid, 4,4'-dicarboxydiphenyl, 4,4'-dicarboxybenzophenone, bis (4-carboxyphenyl) ethane, adipic acid, sebacic acid, 5-sodium sulfoisophthalic acid, and Examples thereof include 1,4-dicarboxycyclohexane. Examples of the diol component include propylene glycol, butanediol, neopentyl glycol, diethylene glycol, cyclohexanediol, ethylene oxide adduct of bisphenol A, polyethylene glycol, polypropylene glycol, polytetramethylene glycol and the like. Two or more of these dicarboxylic acid components and diol components can be used in combination, if necessary. Further, it is also possible to use a hydroxycarboxylic acid such as p-hydroxybenzoic acid and p-β-hydroxyethoxybenzoic acid in combination with the above dicarboxylic acid component and diol component. As the other copolymerization component, a small amount of a dicarboxylic acid component and / or a diol component having an amide bond, a urethane bond, an ether bond, a carbonate bond and the like may be used.

By forming a polyethylene terephthalate resin into a film and then stretching it to use it as a protective film, a polarizing plate with excellent mechanical properties, solvent resistance, scratch resistance, cost, etc., and a reduced thickness can be obtained. Obtainable.

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

The (meth) acrylic resin is not particularly limited, but is generally a polymer containing a methacrylic acid ester as a main monomer, and a copolymer in which a small amount of other comonomer components are copolymerized with the polymer is preferable. .. 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- Hydroxyalkylacrylic acid esters such as methyl (hydroxymethyl) acrylate, methyl 2- (1-hydroxyethyl) acrylate, ethyl 2- (hydroxymethyl) acrylate, and butyl 2- (hydroxymethyl) acrylate; methacrylic. Unsaturated acids such as acids and acrylic acids; halogenated styrenes such as chlorostyrene and bromostyrene; substituted styrenes such as vinyltoluene and α-methylstyrene; unsaturated nitriles such as acrylonitrile and methacrylic acid; maleic anhydride And unsaturated acid anhydrides such as citraconic anhydride; unsaturated imides such as phenylmaleimide and cyclohexylmaleimide can be mentioned. As the third monofunctional monomer, only one type may be used alone, or a plurality of different types may be used in combination.

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). Acrylate and tetradecaethylene glycol di (meth) acrylate and other ethylene glycols or oligomers thereof are esterified with acrylic acid or methacrylic acid; propylene glycol or oligomers thereof are esterified with acrylic acid or methacrylic acid. Esterated with acrylic acid or methacrylic acid; the hydroxyl group of a dihydric alcohol such as neopentyl glycol di (meth) acrylate, hexanediol di (meth) acrylate, and butanediol di (meth) acrylate; Bisphenol A, an alkylene oxide adduct of bisphenol A, or acrylates of both terminal hydroxyl groups of these halogen substituents with acrylic acid or methacrylic acid; polyhydric alcohols such as trimethylolpropane and pentaerythritol are acrylic acid or methacrylate. The one esterified with, and the one in which an epoxy group of glycidyl acrylate or glycidyl methacrylate is ring-added to these terminal hydroxyl groups; Examples thereof include those obtained by ring-opening addition of an epoxy group of glycidyl acrylate or glycidyl methacrylate to these alkylene oxide adducts and the like; aryl (meth) acrylates; aromatic divinyl compounds such as divinylbenzene. Of these, ethylene glycol dimethacrylate, tetraethylene glycol dimethacrylate, and neopentyl glycol dimethacrylate are preferably used.

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

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

The (meth) acrylic resin may contain a known additive, if necessary. Known additives include, for example, lubricants, antiblocking agents, heat stabilizers, antioxidants, antistatic agents, lightfasteners, 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 which are impact improving agents from the viewpoint of film forming property on the film, impact resistance of the film, and the like. The acrylic rubber particles referred to here are particles containing an elastic polymer mainly composed of an acrylic acid ester as an essential component, and have a single-layer structure substantially consisting of only this elastic polymer, or this elastic polymer. There is a multi-layered structure having one layer. Examples of such an elastic polymer include a crosslinked elastic copolymer containing an alkyl acrylate as a main component and copolymerizing another copolymerizable vinyl monomer and a crosslinkable monomer. Examples of the alkyl acrylate that is the main component of the elastic polymer include those having an alkyl group having about 1 to 8 carbon atoms, such as methyl acrylate, ethyl acrylate, butyl acrylate, and 2-ethylhexyl acrylate, and in particular, carbon. An acrylate having an alkyl group of several 4 or more is preferably used. Examples of other vinyl monomers copolymerizable with this alkyl acrylate include compounds having one polymerizable carbon-carbon double bond in the molecule, and more specifically, methacrylic acid such as methyl methacrylate. Examples thereof include esters, aromatic vinyl compounds such as styrene, and vinyl cyan compounds such as acrylonitrile. 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 thereof include (meth) acrylates of polyhydric alcohols such as di (meth) acrylates, alkenyl esters of (meth) acrylic acids such as allyl (meth) acrylates, and divinylbenzene.

Further, a laminate of a film made of a (meth) acrylic resin containing no rubber particles and a film made of a (meth) acrylic resin containing rubber particles can be used as a protective film. Commercially available products of (meth) acrylic resin are easily available. For example, "Sumipex" (manufactured by Sumitomo Chemical Co., Ltd.) and "Acrypet" (manufactured by Mitsubishi Rayon Co., Ltd.) under their respective product names. , "Delpet" (manufactured by Asahi Kasei Corporation), "Parapet" (manufactured by Kuraray Co., Ltd.), "Acrylic" (manufactured by Nippon Shokubai Co., Ltd.) and the like.

The amorphous polyolefin resin is a resin obtained by ring-opening metathesis polymerization using norbornene or a derivative thereof obtained by a deal alder reaction from cyclopentadiene and olefins as a monomer, and then hydrogenated; dicyclopentadiene and olefin. A resin obtained by ring-opening metathesis polymerization using tetracyclododecene or a derivative thereof obtained by a deal alder reaction with a class or a methacrylic acid ester as a monomer, followed by water addition; norbornene, tetracyclododecene and their derivatives. A resin obtained by similarly performing ring-opening metathesis copolymerization using two or more kinds selected from derivatives and other cyclic polyolefin monomers and subsequent hydrogenation; to norbornene, tetracyclododecene or derivatives thereof. , A resin obtained by addition-copolymerizing an aromatic compound having a vinyl group or the like. Examples of commercially available amorphous polyolefin resins include "Arton" from JSR Corporation, "ZEONEX" and "ZEONOR" from Zeon Corporation, and "APO" and "APO" from Mitsui Chemicals, Inc. There is "Apel" etc.

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

A cellulosic resin film to which an optical compensation function is provided can also be used. As such an optical compensation film, for example, a film in which a cellulosic resin contains a compound having a phase difference adjusting function, a film in which a compound having a phase difference adjusting function is coated on the surface of the cellulosic resin, or a cellulosic resin uniaxially or biaxially. Examples thereof include a film obtained by stretching on a shaft. Examples of commercially available cellulosic resin optical compensation films include "Wide View Film WV BZ 438" and "Wide View Film WV EA" manufactured by Fujifilm Corporation, and Konica Minolta Opto Co., Ltd. There are "KC4FR-1", "KC4HR-1" and the like.

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 surface treatment layers (coating layers) 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 surface to be adhered to the polarizer.

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

(3) Production of Polarizing Plate A polarizing plate can be obtained by adhering a protective film to at least one surface of a polarizer using the above-mentioned photocurable adhesive. Specifically, the above-mentioned coating layer of the photocurable adhesive is formed on the adhesive surface of the polarizer and / or the protective film, and the polarizer and the protective film are bonded to each other 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. For the formation of the coating layer of the photocurable adhesive, various coating methods such as a doctor blade, a wire bar, a die coater, a comma coater, and a gravure coater can be used. 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 on the inner side, and the adhesive is spread 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 well without deteriorating the optical performance of the polarizer is used, but the type is not particularly limited. For example, organic solvents such as hydrocarbons typified by toluene and esters typified by ethyl acetate can be used. However, when a solvent is contained, it is necessary to provide a drying step for removing the solvent before irradiation with the active energy ray, so it is preferable not to use the solvent as much as possible.

The thickness of the adhesive layer after curing can be arbitrarily set by designing the characteristics of the polarizing plate, but it is preferably smaller from the viewpoint of reducing the cost of the adhesive material. Generally, it is 0.01 to 20 μm, preferably 0.1 to 10 μm, and more preferably 0.5 to 5 μm. When the thickness of the adhesive layer is reduced, air bubbles are likely to be mixed into the adhesive layer and the adhesion and durability are likely to be deteriorated. However, according to the photocurable adhesive of the present invention, this can be effectively suppressed. Can be done.

When the protective film is adhered to only one side of the polarizer, for example, an adhesive layer for adhering to another optical member such as a liquid crystal cell may be directly provided on the other surface of the polarizer. .. On the other hand, when the protective films are adhered to both sides of the polarizer, these protective films may be made of the same kind of resin or different kinds of resins. The protective film adhered to one surface of the polarizer is adhered using the photocurable adhesive according to the present invention described above, whereas the protective film adhered to the other surface of the polarizer is according to the present invention. It may be bonded using such a photocurable adhesive, or may be bonded using another adhesive.

Prior to adhering the protective film to the polarizer, the protective film and / or the adhering surface of the 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 done.

The light source used to irradiate the coating layer of the photocurable adhesive with active energy rays may be any light source capable of generating ultraviolet rays, electron beams, X-rays and the like. In particular, low-pressure mercury lamps, medium-pressure mercury lamps, high-pressure mercury lamps, ultra-high-pressure mercury lamps, chemical lamps, black light lamps, microwave-excited mercury lamps, metal halide lamps, and the like having an emission distribution having a wavelength of 400 nm or less are preferably used.

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

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

When the protective films are adhered to both sides of the polarizer, the active energy rays may be irradiated from either side of the protective film. For example, one protective film contains an ultraviolet absorber and the other protective film contains ultraviolet rays. When the absorbent is not contained, it is preferable to irradiate the active energy rays from the protective film side that does not contain 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 of 0.5 N / 25 mm or more between the polarizing element and the protective film measured by a 180-degree peel test, and is 1 N /. It is more preferably 25 mm or more. If the peeling 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.

An embodiment of polarizing plate production will be described with reference to FIG. FIG. 1 is a schematic cross-sectional view showing a preferable example of an apparatus for manufacturing a polarizing plate. The protective films 2 and 3 that are continuously unwound from the rolled state are coated with a photocurable adhesive on one side by the adhesive coating devices 11 and 12, respectively. Then, the protective films 2 and 3 are laminated on both sides of the polarizing element 1 which is continuously fed out in the same manner as the protective films 2 and 3 by the bonding rolls 5a and 5b via the adhesive coating layer, and the laminated body is formed. 4 is produced. The diameters of the laminating rolls 5a and 5b are, for example, 50 to 250 mm.

Next, a polarizing plate can be manufactured by irradiating the laminated body 4 with active energy rays and curing the coating layer of the adhesive. In the example shown in FIG. 1, the produced laminated body 4 is conveyed while being in close contact with the outer peripheral surface of the roll 13. The first active energy ray irradiating devices 14 and 15 are installed at positions facing the outer peripheral surface of the roll 13, and the second active energy ray irradiating device 16 and the third active energy are on the downstream side in the transport direction. The ray irradiation device 17 and the fourth active energy ray irradiation device 18 are provided in order along the transport direction. As a result, the coating layer of the adhesive contained in the laminated body 4 is conveyed while the laminated body 4 is in close contact with the outer peripheral surface of the roll 13, and the active energy rays from the first active energy ray irradiating devices 14 and 15 are transmitted. It is polymerized and cured by the active energy rays from the second active energy ray irradiation device 16, the third active energy ray irradiation device 17, and the fourth active energy ray irradiation device 18 on the downstream side. The second and subsequent active energy ray irradiation devices 16, 17, and 18 arranged on the downstream side in the transport direction are devices for completely polymerizing and curing the adhesive, and can be added or omitted as necessary. Finally, the cured laminate 4 passes through the transport nip roll 19 and is wound on the winding roll 20 as a polarizing plate.

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

<Laminate optical member and liquid crystal display device>
The polarizing plate of the present invention can be made into a laminated optical member by laminating optical layers having an optical function other than the polarizing plate. Typically, an optical layer is laminated and adhered on a protective film of a polarizing plate via an adhesive or an adhesive to form a laminated optical member. In addition, for example, the present invention is applied to one surface of a polarizing element. It is also possible to adhere the protective film via the photocurable adhesive according to the above, and to laminate and attach the optical layer to the other surface of the polarizing element via an adhesive or an adhesive. In the latter case, if the photocurable adhesive according to the present invention is used as the adhesive for adhering the polarizer and the optical layer, the optical layer can also serve as a protective film at the same time. Two or more optical layers may be laminated on the polarizing plate.

The optical layer laminated on the polarizing plate includes a reflective layer, a transflective reflective layer, and light that are laminated on the opposite side of the polarizing plate to the liquid crystal cell with respect to the polarizing plate arranged on the back side of the liquid crystal cell. Examples thereof include a diffusion layer, a condenser plate, and a brightness improving film. Further, with respect to the polarizing plate arranged on the front side of the liquid crystal cell and / or the polarizing plate arranged on the back side of the liquid crystal cell, a retardation plate laminated on the liquid crystal cell side of the polarizing plate can be mentioned.

The reflective layer, the transflective reflective layer, and the light diffusing layer are provided to form a laminated optical member which is a reflective polarizing plate, a transflective polarizing plate, and a diffused 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 since a light source such as a backlight can be omitted, the liquid crystal display device can be easily made thinner. Further, the transflective polarizing plate is used in a liquid crystal display device of a type that displays light from a backlight in a dark place as a reflective type in a bright place. The reflective polarizing plate can be produced, for example, by attaching a foil made of a metal such as aluminum or a vapor-deposited film to a protective film on a polarizer to form a reflective layer. The transflective polarizing plate can be produced by using the above-mentioned reflective layer as a half mirror, or by adhering a reflector containing a pearl pigment or the like to exhibit light transmittance to the polarizing plate. On the other hand, the diffusion type polarizing plate is used on the surface by various methods such as a method of applying a matte treatment to 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 concavo-convex structure.

Further, the laminated optical member can be a polarizing plate for both reflection and diffusion. A polarizing plate for both reflection and diffusion can be produced, for example, by providing a reflective layer reflecting the uneven structure on the fine uneven structure surface of the diffusion type polarizing plate. The reflective layer having a fine concavo-convex structure has advantages such as diffusing incident light by diffuse reflection, preventing directivity and glare, and suppressing unevenness of light and dark. Further, since the resin layer or film containing fine particles diffuses the incident light and the reflected light thereof, it has an advantage that uneven brightness can be suppressed. The reflective layer reflecting the surface fine uneven structure can be formed by directly attaching the metal to the surface of the fine uneven structure by, for example, a method such as vacuum deposition, ion plating, vapor deposition such as sputtering, or plating. The fine particles blended to form the surface fine uneven structure include, for example, silica, aluminum oxide, titanium oxide, zirconia, tin oxide, indium oxide, cadmium oxide, and antimony oxide having an average particle size of 0.1 to 30 μm. It can be inorganic fine particles, organic fine particles such as crosslinked or non-crosslinked polymers, and the like.

The condensing plate is used for the purpose of controlling the optical path, and can be formed as a prism array sheet, a lens array sheet, a sheet with dots, or the like.

The brightness improving 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 films having different refractive index anisotropies are laminated to cause anisotropy in reflectance. Includes a reflective polarizing separation sheet designed as described above, an alignment film of a cholesteric liquid crystal polymer, and a circular polarization separation sheet in which the oriented liquid crystal layer is supported on a film substrate.

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

Examples of the plastic forming the birefractive film include an amorphous polyolefin resin, a polycarbonate resin, a (meth) acrylic resin, a chain polyolefin resin such as polypropylene, polyvinyl alcohol, polystyrene, polyarylate, and polyamide. And so on. 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 widening the bandwidth.

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

The laminated optical member can be a laminated body having two layers or three or more layers by combining a polarizing plate and one layer or two or more layers selected from the various optical layers described above according to the purpose of use. In that case, the various optical layers forming the laminated optical member are integrated with the polarizing plate by using an adhesive or an adhesive (also called a pressure-sensitive adhesive), but the adhesive or the adhesive used for that purpose is adhered. There is no particular limitation as long as the agent layer and the pressure-sensitive adhesive layer are well formed. It is preferable to use an adhesive from the viewpoint of ease of bonding work and prevention of occurrence of optical distortion. As the pressure-sensitive adhesive, a (meth) acrylic polymer, a silicone-based polymer, a polyester, a polyurethane, a polyether, or the like as a base polymer can be used. Among them, like (meth) acrylic adhesive, it has excellent optical transparency, retains appropriate wettability and cohesive force, has excellent adhesion to the base material, and has weather resistance and heat resistance. It is preferable to select and use an adhesive that does not cause problems such as floating and peeling under the conditions of heating and humidification. In the (meth) acrylic pressure-sensitive adhesive, an alkyl ester of (meth) acrylic acid having an alkyl group having 20 or less carbon atoms such as a methyl group, an ethyl group, and a butyl group, and (meth) acrylic acid and (meth) acrylic. A functional group-containing (meth) acrylic monomer such as hydroxyethyl acid acid is blended so that the glass transition temperature is preferably 25 ° C. or lower, more preferably 0 ° C. or lower, and the weight average molecular weight is 100,000 or more (meth). ) Acrylic copolymers are useful as base polymers.

To form the pressure-sensitive adhesive layer on the polarizing plate, for example, a pressure-sensitive adhesive composition is dissolved or dispersed in an organic solvent such as toluene or ethyl acetate to prepare a 10 to 40% by weight solution, which is directly placed on the polarizing plate. It can be carried out by a coating method, a method in which an adhesive layer is formed on a release film in advance, and the adhesive layer is transferred onto a polarizing plate. The thickness of the pressure-sensitive adhesive layer is determined according to the adhesive strength and the like, but a range of about 1 to 50 μm is appropriate.

The pressure-sensitive adhesive layer contains, if necessary, a filler composed of glass fibers, glass beads, resin beads, metal powder, other inorganic powders, pigments and colorants, antioxidants, ultraviolet absorbers, and the like. May be good. Examples of the ultraviolet absorber include salicylic acid ester compounds, benzophenone compounds, benzotriazole compounds, cyanoacrylate compounds, and nickel complex salt compounds.

The liquid crystal display device according to the present invention includes a liquid crystal cell and a laminated optical member of the present invention arranged on at least one surface thereof, and includes a 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 the 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 their outer surfaces, respectively. The liquid crystal cell used is arbitrary, and a liquid crystal display device using various liquid crystal cells such as an active matrix drive type represented by a thin film transistor type and a simple matrix drive type represented by a super twisted nematic type. Can be formed.

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to these examples. Hereinafter, the portion and% indicating the amount used or the content are based on weight unless otherwise specified. 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 REGIN EP-4100L" manufactured by ADEKA Corporation,
a1-II: Bisphenol A type polyfunctional epoxy resin "ADEKA REGIN EP-5100R" manufactured by ADEKA Corporation,
a1-III: Aromatic trifunctional epoxy resin "TECHMORE VG3101" manufactured by Printec Co., Ltd.,
a1-IV: Phenolic 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: Phenylglycidyl ether.

Second photocationic curable component (A2):
a2-I: Neopentyl glycol diglycidyl ether [compound of Z = -CH ₂ C (CH ₃ ) ₂ CH _{2- in the} above formula (III)],
a2-II: 1,4-butanediol diglycidyl ether [compound of Z = -CH ₂ CH ₂ CH ₂ CH _2- in the above formula (III)],
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: Alicyclic epoxy resin "Selokiside 2021P" manufactured by Daicel Corporation,
a3-II: Limonene dioxide.

[Polymer (B)]
b-I: A polymer (GMA-MMA copolymer) having a weight average molecular weight of 8000 obtained by radical polymerization of a monomer composition consisting of 25 parts of glycidyl methacrylate (GMA) and 75 parts of methyl methacrylate (MMA).
b-II: A polymer (GMA homopolymer) having a weight average molecular weight of 8000 obtained by radical polymerization of glycidyl methacrylate,
b-III: A polymer (GMA-MMA copolymer) having a weight average molecular weight of 60,000 obtained by radical polymerization of a monomer composition consisting of 25 parts of glycidyl methacrylate and 75 parts of methyl methacrylate.
b-IV: A polymer (GMA-MMA copolymer) having a weight average molecular weight of 200,000 obtained by radical polymerization of a monomer composition consisting of 50 parts of glycidyl methacrylate and 50 parts of methyl methacrylate.

[Photocationic polymerization initiator (C)]
Diphenyl (Phenylthio) Phenyl Sulfonium Hexafluorophosphate.

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

<Examples 1-27, Comparative Examples 1-9>
(1) Preparation of Photocurable Adhesive After mixing each component shown in Table 1, the photocurable adhesives (liquid) of Examples 1 to 27 and Comparative Examples 1 to 9 were prepared by defoaming. .. The unit of the blending amount of each component in Table 1 is "part". 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 liquid) prepared above, use an E-type viscometer "TVE-25L" manufactured by Toki Sangyo Co., Ltd. The viscosity was measured at a temperature of 25 ° C. The results are shown in Table 2.

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

(4) Preparation of polarizing plate Consists of a protective film made of (meth) acrylic resin (PMMA) [trade name "Technoloy S001", manufactured by Sumitomo Chemical Co., Ltd.] containing an ultraviolet absorber and having a thickness of 80 μm, 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 the respective adhesive liquids prepared in (1) above are applied to these corona-treated surfaces. Each was coated using a coating device. At this time, the line speed of the film in the adhesive coating apparatus was set to 25 m / min, and the gravure roll was rotated in the direction opposite to the film conveying direction. The thickness of the adhesive layer was 2.8 μm after curing.

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

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

(5) Confirmation of air bubbles in the adhesive layer The obtained polarizing plate is cut into a size of 300 mm in length × 200 mm in width, and the surface thereof is viewed 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: No bubbles were found,
B: Bubbles were confirmed.

(6) 180-degree peeling test of polarizing plate After cutting the polarizing plate produced in (4) above into a size of 200 mm in length × 25 mm in width, an acrylic pressure-sensitive adhesive is applied to the protective film side made of (meth) acrylic resin. A layer was provided and used as a test piece for measuring the peeling 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 prepare 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 adhesive layer, and a cutter is placed between the polarizer and the protective film on the adhesive layer side (protective film made of (meth) acrylic resin or norbornen-based retardation film). The blade was inserted and peeled 30 mm from the end in the length direction, and the peeled part was grasped by the grip part of the testing machine. For the test piece in this state, in an atmosphere of a temperature of 23 ° C. and a relative humidity of 55%, according to JIS K 6854-2: 1999 "Adhesive-Peeling Adhesive Strength Test Method-Part 2: 180 ° Peeling". A 180-degree peeling test was performed at a gripping movement speed of 300 mm / min, and an average peeling force over a length of 170 mm excluding 30 mm of the gripped portion was determined. The measurement is performed 24 hours after the polarizing plate is produced. The results are shown in Table 2. In Table 2, "PMMA / PVA peeling strength" represents the peeling strength between the protective film made of the (meth) acrylic resin and the polarizer, and "COP / PVA peeling strength" is , Represents the peel strength between the Norbornen-based retardation film and the polarizer. Further, in Table 2, "base material fracture" means that the peeling strength is large and at least one of the polarizer and the protective film (or the retardation film) is torn during the peeling test.

(7) Measurement of Tg and tensile elastic modulus of the cured adhesive layer Each photocurable adhesive prepared in (1) above was applied to an untreated PET (“Soft Shine” film manufactured by Toyo Spinning Co., Ltd.) with a bar coater # 20. After the coating, an ultraviolet irradiation device with a belt conveyor (the lamp is a "D valve" manufactured by Fusion UV Systems) was used to irradiate ultraviolet rays so that the integrated light amount was 3000 mJ / cm ² (UVB). After 24 hours, the cured adhesive layer was taken out from the film, and the glass transition temperature Tg and the tensile elastic 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.

1 Polarizer, 2, 3 Protective film, 4 Laminate, 5a, 5b Laminating roll, 11, 12 Adhesive coating device, 13 roll, 14, 15 First active energy ray irradiation device, 16 Second active energy ray Irradiation device, 17th active energy ray irradiation device, 18th active energy ray irradiation device, 19 transport nip roll, 20 take-up roll.

Claims (16)

A photocurable adhesive for adhering a protective film made of a thermoplastic resin to a polyvinyl alcohol-based polarizer.
A photocationic curable component (A) containing a first photocationic curable component (A1), which is an aromatic epoxy compound,
Monomers represented by the following formulas (Ia), (Ib) and (Ic):

(In the formula, R ⁴ represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, 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), and.
Monomers represented by the following formulas (IIa), (IIb) and (IIc):

(In the formula, R ¹ represents a hydrogen atom, a methyl group or a halogen atom, 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 represents a hydrogen atom, a methyl group or a halogen atom, 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 represents a hydrogen atom, a methyl group or a halogen atom, 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).
A polymer (B) consisting of a structural unit derived from one or more monomers selected from the group consisting of
Photocationic polymerization initiator (C) and
Contains,
The content of the polymer (B) is 2.5 to 10 parts by weight based on 100 parts by weight of the total amount of the photocationic curable component (A) and the polymer (B).
The content of the first photocationic curable component (A1) is 10 to 40 parts by weight out of 100 parts by weight of the total amount of the photocationic curable component (A) and the polymer (B).
The content of the photocationic polymerization initiator (C) is 1 to 10 parts by weight 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) is one or more second photocationic curable components (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. -, - O-CO -, - SO 2 -, - SO- or a divalent group selected from -CO- may be substituted).
The photocurable adhesive according to claim 2, which is a compound represented by. The photocurable adhesive according to claim 3, wherein Z in the formula (III) is a branched alkylene group having 3 to 10 carbon atoms. 2. The content of the second photocationic curable component (A2) is 58 to 88 parts by weight out of 100 parts by weight of the total amount of the photocationic curable component (A) and the polymer (B). The photocurable adhesive according to any one of No. 4 to 4. The photocurable adhesive according to any one of claims 1 to 5, wherein the polymer (B) has a weight average molecular weight of 5000 to 500000. The photocurable adhesive according to claim 6, wherein the polymer (B) has a weight average molecular weight of 6000 to 100,000. The method 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). Photocurable adhesive. The photocurable adhesive according to any one of claims 1 to 8, which has a viscosity at 25 ° C. of 2 to 300 mPa · s. With a polyvinyl alcohol-based polarizer,
A protective film made of a thermoplastic resin, which is 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 claims 1 to 9.
A polarizing plate including. 10. The thermoplastic resin is one or more resins selected from the group consisting of cellulose-based resins, (meth) acrylic-based resins, amorphous polyolefin-based resins, polyester-based resins, and polycarbonate-based resins. The polarizing plate according to the description. The polarizing plate according to claim 10 or 11, wherein the protective film contains an ultraviolet absorber. The polarizing plate according to any one of claims 10 to 12, wherein the peel strength between the polyvinyl alcohol-based polarizing element and the protective film measured by a 180-degree peel test is 0.5 N / 25 mm or more. .. A laminated optical member comprising a laminate of the polarizing plate according to any one of claims 10 to 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 a laminated optical member according to claim 14 or 15, which is arranged on at least one surface of the liquid crystal cell.

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