KR20150008399A - Polarizing plate - Google Patents

Abstract

A transparent resin film is bonded to a polarizer in which a dichroic dye is adsorbed and oriented on a polyvinyl alcohol-based resin through an adhesive. The adhesive is composed of a photo-curable component containing an epoxy compound and a photo- There is provided a polarizing plate formed from a composition. The epoxy compound constituting the photocurable composition preferably has at least two epoxy groups in the molecule, and these epoxy groups are preferably present as a glycidyloxy group. Further, an epoxy compound having no aromatic ring in the molecule is preferable. The photo-base generator constituting the photo-curable composition is preferably a compound having a carbamate structure in the molecule or a quaternary ammonium compound.

Description

POLARIZING PLATE

The present invention relates to a polarizing plate in which a protective film made of a transparent resin is bonded to a polarizer in which a dichroic dye is adsorbed and oriented on a polyvinyl alcohol-based resin.

The polarizing plate is useful as one of the optical components constituting the liquid crystal display device. The polarizing plate is usually inserted into a liquid crystal display device in a state in which a protective film is laminated on both surfaces of the polarizer. It is also known to provide a protective film on only one side of a polarizer. In most cases, a layer having a different optical function is bonded to the other side in combination with the function of a protective film, instead of a simple protective film.

As a method for producing a polarizer, there is widely known a method in which a uniaxially stretched polyvinyl alcohol based resin film dyed with a dichroic dye is subjected to boric acid treatment, washed with water and then dried. The polarizer obtained in this way usually is immediately bonded to the protective film after the above-described washing with water and drying. This is because the polarizer after drying has a weak physical strength and tends to tear in the processing direction. Therefore, the polarizer after drying usually is coated with an aqueous adhesive immediately, and the protective film is simultaneously bonded to both surfaces through the adhesive. Typically, as the protective film, an acetylcellulose resin film having a thickness of 30 to 120 mu m is used.

On the other hand, since the acetylcellulose-based resin film has a high moisture-permeability, the polarizing plate obtained by bonding this film as a protective film is likely to cause deterioration under a humid condition (for example, under conditions such as a temperature of 70 ° C and a relative humidity of 90% There was a problem. Therefore, a method of solving such a problem by using a resin having a lower moisture permeability than an acetylcellulose-based resin as a protective film has been proposed. For example, a cycloolefin-based resin is known to be a protective film. Specifically, it is described in Japanese Patent Application Laid-Open No. 6-51117 (Patent Document 1) that a thermoplastic saturated norbornene resin film is laminated on at least one surface of a polarizer.

When such a resin film having low moisture permeability is bonded to the above-described polarizer by a conventional apparatus, the resin film is bonded using an aqueous adhesive (for example, a polyvinyl alcohol aqueous solution) containing water as a main solvent, In the so-called wet lamination in which drying is carried out, there is a problem that a sufficient adhesive strength can be obtained, or appearance is poor. This is because the resin film having a low moisture permeability is generally hydrophobic as compared with the acetylcellulose resin film, but the water as a solvent can not be sufficiently dried because of low moisture permeability.

Japanese Unexamined Patent Application Publication No. 2000-321432 (Patent Document 2) proposes that the polarizer and the thermoplastic saturated norbornene resin film are adhered by a polyurethane adhesive agent. However, the polyurethane-based adhesive has a problem that not only time is required for curing but also adhesion is not necessarily sufficient.

Further, there is an attempt to use a photo-curing adhesive as an adhesive which gives a high adhesive force between a resin film having a low moisture permeability and a polarizer, and a resin film having a high moisture permeability such as an acetyl cellulose resin and the above- . For example, Japanese Patent Application Laid-Open No. 2004-245925 (Patent Document 3) discloses an adhesive mainly comprising an epoxy compound not containing an aromatic ring, and is disclosed in JP-A-2004-245925 by irradiating an active energy ray (specifically, It has been proposed to cure the adhesive by cationic polymerization and to bond the polarizer and the protective film. In addition, Japanese Patent Application Laid-Open No. 2008-257199 (Patent Document 4) discloses a photocurable adhesive in which an alicyclic epoxy compound and an epoxy compound having no alicyclic epoxy group are combined and a photocationic polymerization initiator is further blended, And a protective film.

The adhesives disclosed in Patent Documents 3 and 4 are intended to be cured by cationic polymerization, so that a photo cationic polymerization initiator, that is, a photoacid generator that generates an acid upon irradiation with light, is blended. On the other hand, a photobase generator that generates a base upon irradiation with light, that is, a photoanion polymerization initiation system, is known.

As photobase generators, carbamate compounds,? -Amino ketone compounds, quaternary ammonium compounds, O-acyloxime compounds, aminocyclopropenone compounds and the like are known. For example, Japanese Patent Application Laid-Open No. 10-77264 (Patent Document 5) discloses a cyclic amine-N-carboxylic acid ester of 2-nitrobenzyl alcohol, which is one type of carbamate compound, 064631 (Patent Document 6) discloses an N-substituted carbamic acid ester of a 1-arylalkanol containing a 1-piperidinecarboxylic acid ester of 1- (2-anthraquinonyl) ethanol as a photo- . Japanese Patent Application Laid-open No. Hei 11-71450 (Patent Document 7) discloses a method for producing an α-amino ketone compound as a kind of α-amino ketone compound, wherein α-aminoacetophenone to which an amino group is bonded at the α- . Japanese Patent Laid-Open Publication No. 2003-212856 (Patent Document 8) discloses that an imidazolium salt, which is one kind of quaternary ammonium compound, is used as a photo-base generator, and JP-A-2005-264156 (Patent Document 9) Discloses that a compound in which a 4-arylthiophenacyl group is bonded to quaternary nitrogen of a specific structure is used as a photo-base generator. Japanese Patent Application Laid-Open No. 2006-36895 (Patent Document 10) discloses that an O-acyloxime compound having a structure in which 3 to 6 acyloxyimino groups are bound in one molecule is used as a photobase generator. Further, Japanese Patent Laid-Open Publication No. 2011-195616 (Patent Document 11) discloses that an aminocyclopropenone compound having an amino group bonded to a cyclopropenone ring is used as a photobase generator.

In the adhesives cured by the photocationic polymerization as disclosed in the above Patent Documents 3 and 4, the acid generated from the cationic polymerization initiator by irradiation with ultraviolet light remains even after the polymerization curing. Therefore, There is a problem of discoloration due to deterioration of the polarizer.

An object of the present invention is to provide a polarizing plate in which a polarizer and a transparent resin film are bonded to each other using a photo-curable adhesive and has excellent heat resistance.

Thus, the present invention provides a polarizer in which a polarizer having a dichroic dye adsorbed and oriented on a polyvinyl alcohol-based resin is bonded to a transparent resin film through an adhesive, and the adhesive is a photo- curable component containing an epoxy compound and a photo- The present invention provides a polarizing plate characterized in that it is formed of a photo-curing composition containing a curing agent.

In this polarizing plate, it is preferable that the epoxy compound constituting the photo-curable composition to be an adhesive has at least two epoxy groups in the molecule. Particularly, these epoxy groups are preferably present as a glycidyloxy group. These epoxy compounds preferably have no aromatic ring in the molecule.

In these polarizing plates, it is preferable that the photo-base generating agent constituting the photo-curable composition to be an adhesive is a compound having a carbamate structure or a quaternary ammonium compound in the molecule.

In these polarizing plates, it is preferable that the photo-curing composition to be an adhesive contains 0.01 to 400 parts by weight of a photo base generating agent per 100 parts by weight of the photo-curable component containing the epoxy compound.

The polarizer of the present invention exhibits good heat resistance because the adhesive bonding the polarizer and the transparent resin film is formed of a photo-curable composition containing a photo-curable component containing an epoxy compound and a photo base generating agent.

Hereinafter, the present invention will be described in detail. A polarizing plate according to the present invention is obtained by bonding a transparent resin film to one side or both sides of a polarizer in which a dichroic dye is adsorbed and oriented on a polyvinyl alcohol-based resin. First, each member constituting the polarizing plate will be described in order.

[Polarizer]

A polarizer is a film having a function of converting natural light into linearly polarized light, and usually comprises 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 a polyvinyl acetate-based resin. Examples of the polyvinyl acetate-based resin include polyvinyl acetate, which is a homopolymer of vinyl acetate, and copolymers of vinyl acetate and other monomers copolymerizable therewith. Examples of other monomers copolymerizable with vinyl acetate include unsaturated carboxylic acids, olefins, vinyl ethers and unsaturated sulfonic acids. The degree of saponification of the polyvinyl alcohol-based resin is usually 85 to 100 mol%, preferably 98 to 100 mol%. The polyvinyl alcohol-based resin may be further modified. For example, polyvinyl formal or polyvinyl acetal modified with aldehydes may be used. The polymerization degree of the polyvinyl alcohol-based resin is usually in the range of 1,000 to 10,000, preferably 1,500 to 10,000. Such a film of a polyvinyl alcohol-based resin is used as a raw film of a polarizer. The polyvinyl alcohol resin can be formed by a known method.

The polarizing plate can be obtained by a process comprising the steps of uniaxially stretching the polyvinyl alcohol resin film thus formed, dyeing the polyvinyl alcohol resin film with a dichroic dye to adsorb the dichroic dye, A step of treating an alcoholic resin film with an aqueous solution of boric acid, a step of washing with water after treatment with an aqueous solution of boric acid, and a step of bonding a protective film to the polarizer obtained by these steps.

The uniaxial stretching of the polyvinyl alcohol-based resin film may be performed before dyeing with a dichroic dye or simultaneously with dyeing with a dichroic dye or may be performed after dyeing with a dichroic dye. In the case where 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. Of course, it is also possible to perform uniaxial stretching in these plural steps. In order to uniaxially stretch, stretching may be performed by passing between rolls having different peripheral speeds, or may be stretched by a method sandwiching between rolls. In addition, dry stretching may be performed in the atmosphere, or wet stretching may be performed in the state of being swollen by a solvent. The draw ratio is usually about 4 to 8 times.

In order to dye a polyvinyl alcohol-based resin film with a dichroic dye, for example, a polyvinyl alcohol-based resin film may be dipped in an aqueous solution containing a dichroic dye. As the dichroic dye, iodine or a dichroic dye is specifically used.

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

On the other hand, when a dichroic dye is used as the dichroic dye, a method of dying and dyeing the polyvinyl alcohol resin film into an aqueous solution containing a water-soluble dichroic dye is generally adopted. The content of the dichroic dye in the aqueous solution is usually about 1 × 10 ^{-3 to} 1 × 10 ^-2 parts by weight per 100 parts by weight of water. The aqueous solution may contain an inorganic salt such as sodium sulfate. The temperature of the aqueous solution is usually about 20 ° C to 80 ° C, and the immersion time in the aqueous solution is usually about 30 to 300 seconds.

The boric acid treatment after dyeing with the dichroic dye is carried out by immersing the dyed polyvinyl alcohol resin film in an aqueous solution of boric acid. The content of boric acid in the aqueous solution of boric acid is usually about 2 to 15 parts by weight, preferably 5 to 12 parts by weight, per 100 parts by weight of water. When iodine is used as the dichroic dye, it is preferable that the aqueous solution of boric acid contains potassium iodide. The content of potassium iodide in the aqueous solution of boric acid is usually about 2 to 20 parts by weight, preferably 5 to 15 parts by weight, per 100 parts by weight of water. The immersing time in the aqueous boric acid solution is usually about 100 to 1,200 seconds, preferably 150 to 600 seconds, more preferably 200 to 400 seconds. The temperature of the boric acid aqueous solution is usually 50 占 폚 or higher, and preferably 50 占 폚 to 85 占 폚.

The polyvinyl alcohol-based resin film after treatment with boric acid is usually washed with water. The water washing treatment is carried out, for example, by immersing the boric acid-treated polyvinyl alcohol resin film in water. After washing with water, drying treatment is carried out to obtain a polarizer. The temperature of the water in the water washing treatment is usually about 5 ° C to 40 ° C, and the immersing time is usually about 2 to 120 seconds. The drying process to be performed thereafter is usually carried out using a hot-air dryer or a far-infrared heater. The drying temperature is usually 40 ° C to 100 ° C. The treatment time in the drying treatment is usually about 120 to 600 seconds.

Thus, a polarizer made of a polyvinyl alcohol-based resin film in which iodine or a dichroic dye is adsorbed and oriented can be obtained. The thickness of the polarizer may be about 10 to 40 mu m.

[Transparent resin film]

The polarizing plate of the present invention is obtained by bonding a transparent resin film as a protective film to the polarizer described above. When the resin film is bonded to both surfaces of the polarizer, the two films bonded to both surfaces may be of the same kind or of different kinds. As these resin films, a cycloolefin resin film, a polyester resin film, an acrylic resin film, a polycarbonate resin film, a polysulfone resin film, an alicyclic polyimide resin film, an acetylcellulose resin film and the like can be used .

The above-mentioned transparent resin film may be subjected to adhesion (easy adhesion) treatment such as saponification treatment, corona treatment, primer treatment, and anchor coating treatment to the bonding surface prior to bonding to the polarizer. The transparent resin film may have various treatment layers such as a hard coat layer, an antireflection layer, and an antiglare layer on the surface opposite to the bonding surface to the polarizer. The thickness of the transparent resin film is usually in the range of about 5 to 200 mu m, preferably 10 to 120 mu m, and more preferably 10 to 85 mu m.

[Photocurable composition]

In the above-described bonding of the polarizer and the transparent resin film, a photo-curable composition containing a photo-curable component containing an epoxy compound and a photo base generating agent is used as an adhesive. Here, the epoxy compound refers to a compound or oligomer that has an epoxy group in the molecule and undergoes polymerization reaction by irradiation with ultraviolet rays or the like to cure.

In the present invention, an epoxy compound is used as a photo-curable component contained in the photo-curable composition for forming an adhesive. Examples of the photocurable epoxy compound include alicyclic epoxy compounds, aromatic epoxy compounds, hydrogenated epoxy compounds, aliphatic epoxy compounds, and the like.

First, the alicyclic epoxy compound will be described. This is a compound having at least one epoxy group directly bonded to the alicyclic ring in the molecule. For example, 3,4-epoxycyclohexylmethyl 3,4-epoxycyclohexanecarboxylate, 3,4-epoxy-6-methylcyclohexylmethyl 3,4-epoxy-6-methylcyclohexanecarboxylate, ethylenebis (3,4-epoxycyclohexylmethyl) adipate, bis (3,4-epoxy-cyclohexylmethyl) adipate, diethyleneglycol bis 3,4-epoxycyclohexylmethyl ether), ethylene glycol bis (3,4-epoxycyclohexylmethyl) ether, and the like.

Next, the aromatic epoxy compound will be described. This is a compound having an aromatic ring and an epoxy group in the molecule. Examples thereof include bisphenol-type epoxy compounds such as diglycidyl ether of bisphenol A, diglycidyl ether of bisphenol F and diglycidyl ether of bisphenol S, or oligomers thereof; Novolak type epoxy resins such as phenol novolak epoxy resin, cresol novolac epoxy resin and hydroxybenzaldehyde phenol novolac epoxy resin; A multifunctional epoxy compound such as glycidyl ether of 2,2 ', 4,4'-tetrahydroxydiphenylmethane and glycidyl ether of 2,2', 4,4'-tetrahydroxybenzophenone; Epoxy-modified polyvinylphenol, and the like.

Hydrogenated epoxy compounds will be described. The nuclear hydrogen addition of the above aromatic epoxy compound becomes a hydrogenated epoxy compound. These are polyhydric alcohols, typically hydrogenated bisphenols, obtained by selectively hydrogenating an aromatic polyhydroxy compound, typically a bisphenol, as a raw material of the corresponding aromatic epoxy compound in the presence of a catalyst and under pressure. And then reacting it with epichlorohydrin to obtain chlorohydrin ether, which is then subjected to ring closure in the molecule with an alkali.

Next, the aliphatic epoxy compound will be described. The aliphatic epoxy compounds include polyglycidyl ethers of aliphatic polyhydric alcohols or alkylene oxide adducts thereof. Examples thereof include diglycidyl ether of neopentyl glycol, diglycidyl ether of 1,4-butanediol, diglycidyl ether of 1,6-hexanediol, triglycidyl ether of glycerin, trimethylol propane , Diglycidyl ether of polyethylene glycol, diglycidyl ether of propylene glycol, aliphatic polyhydric alcohols such as ethylene glycol, propylene glycol and glycerin, one or more alkylene oxides (such as ethylene oxide, Propylene oxide), and polyglycidyl ether of polyether polyol.

The epoxy compounds exemplified above may be used alone or in combination of a plurality of epoxy compounds.

In the present invention, from the viewpoint of the reactivity with the amine generated from the photo-base generator, it is preferable that the epoxy compound has at least two epoxy groups in the molecule, and the epoxy group is preferably present as a glycidyloxy group . Among the above-exemplified epoxy compounds, aromatic epoxy compounds, hydrogenated epoxy compounds and aliphatic epoxy compounds correspond to epoxy compounds having at least two glycidyloxy groups in the molecule. From the viewpoints of weatherability and refractive index, it is more preferable to use an epoxy compound having no aromatic ring in the molecule. That is, among the above-exemplified epoxy compounds, hydrogenated epoxy compounds and aliphatic epoxy compounds are more preferable.

The epoxy compound used in the present invention preferably has an epoxy equivalent of 30 to 3,000 g / equivalent and still more preferably 50 to 1,500 g / equivalent. If the epoxy equivalent is too small, there is a possibility that the flexibility of the cured adhesive layer is lowered or the bonding strength between the polarizer and the transparent resin film is lowered. On the other hand, if the epoxy equivalent is too large, there is a possibility that compatibility with other components may be deteriorated. The epoxy equivalent is defined by the molecular weight of the epoxy compound per epoxy group.

In the present invention, in order to solve the problem of deterioration of the polarizer by an acid, the photo-base generator is compounded as a curing agent for the photo-curable component containing the above-mentioned epoxy compound. The photobase generator means a compound that generates an amine by being irradiated with light such as visible light or ultraviolet light. The photo-curing composition containing the photo-curable component containing an epoxy compound and the photo-base generator generates an amine from the photo-base generator upon irradiation with light and reacts with the epoxy compound to proceed the curing reaction. For example, 1- (2-anthraquinone-nonyl) ethyl 1-piperidine-carboxylate used as the photobase generator in an embodiment described later, receives the irradiation of the light (hν), moisture present in the air (H ₂ O) is taken up to decompose as follows to produce the amine piperidine. This amine reacts with the epoxy compound.

By using the photo-base generator as the curing agent of the epoxy compound, an adhesive layer having excellent storage stability is formed as compared with the case where the amine itself known as the curing agent of the epoxy compound is blended.

Hereinafter, the photobase generator will be described. Photocatalytic ion polymerization is put to practical use by virtue of not being inhibited by oxygen as compared with photo radical polymerization, but the acid generated even after curing remains in the adhesive layer. Particularly, in the polarizing plate, if the acid remains in the adhesive layer, it acts as a catalyst, and the polarizing plate may be discolored by the polyenes of the polyvinyl alcohol-based resin constituting the polarizer. On the other hand, when an amine generated from a photobase generator is used as a curing agent, the reaction is not inhibited by oxygen in the air, and no acid remains in the adhesive. In the present invention, by blending a photocurable group-containing component containing an epoxy compound with a photocatalytic group generating agent, the curing can proceed rapidly in air without being inhibited by oxygen, and the discoloration of the polarizing plate due to acid can be prevented even after curing have.

The photobase generator used in the present invention may be any compound that generates an amine upon irradiation with light. The photobase generator may be a carbamate compound having a carbamate structure in the molecule, an? -Amino ketone compound, a quaternary ammonium compound, an O-acyloxime compound, an aminocyclopropenone compound Are known.

Particularly, a compound having a carbamate structure and a quaternary ammonium compound are preferable because they give an excellent curing rate and heat resistance. Here, the carbamate structure means the following structure derived from carbamic acid NH ₂ COOH.

As a carbamate compound which is a photobase generator, for example, the following is known.

1- (2-anthraquinolyl) ethyl 1-piperidinecarboxylate,

1- (2-anthraquinolyl) ethyl 1H-2-ethylimidazole-1-carboxylate,

9-anthrylmethyl 1-piperidinecarboxylate,

9-anthrylmethyl N, N-diethylcarbamate,

9-anthrylmethyl N-propyl carbamate,

9-anthrylmethyl N-cyclohexylcarbamate,

9-anthrylmethyl 1H-imidazole-1-carboxylate,

9-anthrylmethyl N, N-dioctylcarbamate,

9-anthrylmethyl 1- (4-hydroxypiperidine) carboxylate,

1-pyrenylmethyl 1-piperidinecarboxylate,

Bis [1- (2-anthraquinolyl) ethyl] 1,6-hexanediylbiscarbamate,

Bis (9-anthrylmethyl) 1,6-hexanediylbiscarbamate and the like.

Among them, preferred compounds are exemplified below together with their chemical structures.

1- (2-anthraquinolyl) ethyl 1-piperidinecarboxylate

1- (2-anthraquinolyl) ethyl 1H-2-ethylimidazole-1-carboxylate

9-anthrylmethyl N, N-diethylcarbamate

9-anthrylmethyl 1H-imidazole-1-carboxylate

Bis [1- (2-anthraquinolyl) ethyl] 1,6-hexanediylbiscarbamate

Bis (9-anthrylmethyl) 1,6-hexanediylbiscarbamate

As the? -Amino ketone compound which is a photobase generator, for example, the following is known.

1-phenyl-2- (4-morpholinobenzoyl) -2-dimethylaminobutane,

2- (4-methylthiobenzoyl) -2-morpholinopropane and the like.

As quaternary ammonium compounds which are photo-base generators, for example, the following are known.

1- (4-phenylthiophenacyl) -1-azonia-4-azabicyclo [2,2,2] octanetetraphenylborate,

5- (4-phenylthiophenacyl) -1-aza-5-azoniabicyclo [4,3,0] -5-nonene tetraphenylborate,

8- (4-phenylthiophenacyl) -1-aza-8-azoniabicyclo [5,4,0] -7-undecene tetraphenylborate and the like.

As the aminocyclopropenone compound which is a photobase generator, for example, the following is known.

2-diethylamino-3-phenylcyclopropene,

2-diethylamino-3- (1-naphthyl) cyclopropenone,

2-pyrrolidinyl-3-phenylcyclopropene,

2-imidazolyl-3-phenylcyclopropene,

2-isopropylamino-3-phenylcyclopropene and the like.

The blending amount of the photobase generator is usually 0.01 to 400 parts by weight, preferably 0.5 to 200 parts by weight, more preferably 1 to 150 parts by weight, per 100 parts by weight of the photocurable component. If the blending amount is too small, the curing of the adhesive layer becomes insufficient, and the mechanical strength of the adhesive layer and the adhesive strength between the polarizer and the transparent resin film are lowered. On the other hand, if the amount is too large, the light resistance may be lowered or the possibility of coloring may occur.

The amine generated from the photo-base generator reacts with the epoxy group in the epoxy compound to advance the curing of the photo-curable composition. In order to accelerate the curing reaction, if necessary, heating curing may be performed after light irradiation. When the resulting amine is a primary amine or a secondary amine, it is preferable that the active hydrogen of the epoxy group and the amino group be almost equal in consideration of the progress of the reaction. In the case where a quaternary ammonium compound is used as the photo-base generator, a tertiary amine is generated from the photo-base generating agent. In this case, the reaction may proceed sufficiently in the catalytic amount of the produced amine, There is a case where curing at a high temperature is required in comparison with the case of generating a secondary amine.

In addition to the photo-curable component and the photo-base generator containing the above-described epoxy compound, the photo-curable composition may also contain a thermal base generator as a curing accelerator. As used herein, a heat nucleating agent means a compound that generates an amine by heating or a compound that increases basicity. Examples of the heat nucleating agent include phenol salts of diazabicyclo-undecene, octylates of diazabicyclo-undecene, tetraphenyl borate salts of diazabicyclo-undecene, and the like. In some cases, curing at the time of heating curing may be accelerated by blending them.

The photo-curing composition may further contain other additives such as an ion trap agent, an antioxidant, a chain transfer agent, a sensitizer, a tackifier, a thermoplastic resin, a filler, a flow regulator, a plasticizer , Defoaming agents, leveling agents, and the like. Examples of the ion trap agent include inorganic compounds such as powdery bismuth, antimony, magnesium, aluminum, calcium, titanium, and mixtures thereof. Examples of the antioxidant include hindered phenol oxide And the like.

[Polarizing plate and manufacturing method thereof]

The polarizing plate of the present invention can be produced by bonding a polarizer and a transparent resin film through the above-described photo-curable composition and irradiating light thereon to cure the uncured photo-curable composition and fixing the transparent resin film on the polarizer . The photo-curing composition may be applied to at least one of the bonding surfaces of the polarizer and the transparent resin film. When a transparent resin film is bonded to both sides of a polarizer, two transparent resin films may be bonded stepwise or side by side in a stepwise manner.

There is no particular limitation on the coating method of the photocurable composition, and various coating methods such as a doctor blade, a wire bar, a die coater, a comma coater, and a gravure coater can be used. Further, since each coating method has an optimum viscosity range, it is also a useful technique to adjust the viscosity of the photocurable composition using a solvent. As the solvent for this purpose, it may be used that the photo-curable component containing an epoxy compound is dissolved well without deteriorating the optical performance of the polarizer. For example, organic solvents such as hydrocarbons typified by toluene and esters typified by ethyl acetate can be used. The thickness of the adhesive layer after curing is usually 50 占 퐉 or less, preferably 20 占 퐉 or less, more preferably 10 占 퐉 or less.

The light source used for the light irradiation is not particularly limited, but a light source having a light emission wavelength of 400 nm or less may be used. For example, a low pressure mercury lamp, a medium pressure mercury lamp, a high pressure mercury lamp, a super high pressure mercury lamp, a chemical lamp, Etc. are suitably used. The light irradiation intensity to the photo-curing composition is determined for each desired composition and is not particularly limited, but it is preferable that the irradiation intensity in the wavelength range effective for activating the photo-base generator is 0.1 to 1,000 mW / cm 2 . If the light irradiation intensity to the photo-curing composition is too small, the reaction time becomes long, and if the intensity becomes too large, heat radiated from the lamp and heat generated during polymerization of the photo- There is a possibility of causing deterioration. The light irradiation time to the photo-curing composition is controlled for each composition to be cured, and is not particularly limited, but is preferably set so that the integrated light amount expressed by the product of irradiation intensity and irradiation time is 10 to 5000 mJ / cm 2 . If the amount of accumulated light is too small, the generation of amine derived from the photo-base generator is not sufficient and the curing of the obtained adhesive layer may be insufficient. On the other hand, if the accumulated light amount is made too large, Which is disadvantageous for improvement of productivity.

In curing the photo-curing composition by light irradiation, it is necessary to set the various conditions described above within a range in which various functions of the polarizing plate such as the polarizing degree, transmittance and hue of the polarizer, and transparency of the transparent resin film are not deteriorated desirable.

[Other optical layers that can be laminated on the polarizing plate]

The polarizing plate of the present invention may be a laminated optical member combined with an optical layer having an optical function other than the polarization function. For example, a reflective layer, a semi-transmissive reflective layer, a light diffusion layer, a retardation plate, a light-collecting plate, a brightness enhancement film, and the like used for forming a liquid crystal display device and the like are used for the optical layer laminated on the polarizing plate for the purpose of forming an optical member. The reflection layer, the semi-transmission type reflection layer, and the light diffusion layer may be formed by using a reflective polarizing plate (optical member), a transflective polarizing plate (optical member) and a diffusing polarizing plate (optical member), or both of these types of polarizing plates Is formed.

The reflection type polarizing plate is used in a liquid crystal display device of the type in which incident light from the viewer side is reflected and displayed, and since a light source such as a backlight can be omitted, the liquid crystal display device can be easily made thin. Further, the transflective type polarizing plate is used in a liquid crystal display device of a type in which light is reflected through a light source such as a backlight in a dark place while being reflective in a bright place. The optical member as the reflection type polarizing plate may be, for example, a structure in which a reflective layer is formed by laying a foil or a vapor deposition film made of a metal such as aluminum on a transparent resin film on a polarizer. The optical member as the transflective type polarizing plate may be one having a structure in which the above-mentioned reflective layer is formed as a half mirror, or a reflective plate exhibiting light transmittance is attached to a polarizing plate by containing a pearl pigment or the like. On the other hand, the optical member as a diffusion type polarizing plate can be obtained by various methods such as a method of performing a mat treatment on a transparent resin film on a polarizing plate, a method of applying a resin containing a fine particle, a method of adhering a fine particle- And may have a fine uneven structure on its surface.

The formation of the optical member as the polarizing plate for both of the reflection diffusion and the reflection can be performed by, for example, forming a reflective layer reflecting the concavo-convex structure on the fine uneven structure surface of the polarizing plate. The reflective layer of the micro concavo-convex structure has the advantage of preventing directivity and glittering by diffusing incident light by diffuse reflection, and suppressing unevenness of light and shade. Further, the resin layer or film containing fine particles has an advantage that the incident light and the reflected light thereof are diffused when they penetrate the fine particle-containing layer, whereby the non-uniformity of light and shade can be further suppressed. The reflecting layer reflecting the surface micro concavo-convex structure can be formed by laying the metal directly on the surface of the fine concave-convex structure by vapor deposition such as vacuum deposition, ion plating, sputtering, plating, or the like. Examples of the fine particles to be blended in order to form the surface fine uneven structure include inorganic fine particles made of silica, , Crosslinked or uncrosslinked polymer, and the like can be used.

On the other hand, the above-mentioned retardation plate as the optical layer is used for the purpose of compensating the retardation by the liquid crystal cell or the like. 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 aligned and fixed, and those having the liquid crystal layer formed on a film substrate. In this case, an acetylcellulose-based resin film such as triacetylcellulose is preferably used as the film substrate for supporting the aligned liquid crystal layer.

Examples of the plastic forming the birefringent film include polyolefins such as polycarbonate, polyvinyl alcohol, polystyrene, polymethyl methacrylate and polypropylene, polyarylate, polyamide and the like. The stretched film may be processed by an appropriate method such as uniaxial stretching or biaxial stretching. Further, a birefringent film in which the refractive index in the thickness direction of the film is controlled by applying a shrinking force and / or a stretching force under adhesion with the heat-shrinkable film may be used. Further, two or more retardation plates may be used in combination for the purpose of controlling optical characteristics such as broadening.

The light-collecting plate is used for the purpose of optical path control or the like, and can be formed as a prism array sheet, a lens array sheet, or a dot-laid sheet.

The brightness enhancement film is used for the purpose of improving brightness in a liquid crystal display device or the like. Examples of the brightness enhancement film include a reflective polarized light separation sheet designed to have a plurality of thin film films having different refractive index anisotropies, , An orientation film of cholesteric liquid crystal polymer, and a circularly polarized light separation sheet on which the alignment liquid crystal layer is supported on a film base.

The optical member includes a polarizing plate and a single layer or two or more layers selected from optical layers such as the above-mentioned reflective layer, transflective reflective layer, light diffusing layer, retardation plate, A laminate of three or more layers can be formed. Two or more kinds of optical layers may be combined as desired. The arrangement of each optical layer is not particularly limited.

The various optical layers forming the optical member are integrated using an adhesive. Therefore, the adhesive to be used is not particularly limited as long as the adhesive layer is formed satisfactorily. It is preferable to use a pressure-sensitive adhesive (also referred to as a pressure-sensitive adhesive) from the viewpoints of simplicity of the bonding operation and prevention of occurrence of optical distortion. When a transparent resin film as a protective film is bonded to one surface of a polarizer and an optical layer such as a retarder is directly bonded to the other surface of the polarizer, a polarizer, a transparent resin film as a protective film, and an optical layer ) Can also be bonded by using a photo-curable composition containing a photo-curable component and a photo-base generator specified in the present invention.

As the pressure-sensitive adhesive, an acrylic polymer, a silicone-based polymer, a polyester, a polyurethane, a polyether, or the like may be used as the base polymer. Among them, as in the case of an acrylic pressure-sensitive adhesive, it has excellent optical transparency, maintains adequate wettability and cohesive force, has excellent adhesiveness to a substrate, has weathering resistance and heat resistance, and peels off, It is preferable to select and use those that do not cause a problem. In the 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 or a butyl group and an acrylic monomer containing a functional group such as (meth) acrylic acid or (meth) An acrylic copolymer having a weight-average molecular weight of 100,000 or more and having a transition temperature of preferably 0 占 폚 or less is useful as a base polymer.

The pressure-sensitive adhesive layer on the polarizing plate can be formed, for example, by dissolving or dispersing the pressure-sensitive adhesive composition in an organic solvent such as toluene or ethyl acetate to prepare a solution of 10 to 40% by weight and directly coating the solution on the polarizing plate to form a pressure- Or a method in which a pressure-sensitive adhesive layer is formed by previously forming a pressure-sensitive adhesive layer on a protective film in a sheet form and then transferring the pressure-sensitive adhesive layer onto a polarizing plate. The thickness of the pressure-sensitive adhesive layer is determined depending on the adhesive strength and the like, but is preferably in the range of about 1 to 50 mu m.

The pressure-sensitive adhesive layer may contain a filler, pigment, colorant, antioxidant, ultraviolet absorber, antistatic agent, etc., made of glass fiber, glass bead, resin bead, metal powder or other inorganic powder, if necessary. Examples of the ultraviolet absorber include a salicylate ester compound, a benzophenone compound, a benzotriazole compound, a cyanoacrylate compound, and a nickel complex salt compound.

The optical member can be disposed on one side or both sides of the liquid crystal cell. The above-described pressure-sensitive adhesive layer can also be used to adhere the optical member to the liquid crystal cell. The liquid crystal cell may be any liquid crystal cell, for example, a liquid crystal cell of an active matrix drive type typified by a thin film transistor type, a simple matrix driven liquid crystal cell typified by a super twisted nematic type, Device can be formed. The optical members provided on both surfaces of the liquid crystal cell may be the same or different.

Example

Hereinafter, the present invention is described in more detail with reference to examples and comparative examples, but the present invention is not limited to these examples. In the following examples, the following compounds were used as epoxy compounds, photo-base generators, and photoacid generators for comparison. At the beginning of each, the name with "" attached is the product name.

<Epoxy Compound>

"Denacol EX-211 ": neopentyl glycol diglycidyl ether obtained from Nagase Chemtex Co., Ltd. Since the oligomer is a mixture product, its epoxy equivalent is about 138 g / equivalent. If neopentyl glycol diglycidyl ether is a pure product, its epoxy equivalent is about 108 g / equivalent.

&Lt; Photobase generators &gt;

"WPBG056": 1- (2-anthraquinolyl) ethyl 1-piperidinecarboxylate obtained from Wako Pure Chemical Industries, Ltd.

&Lt;

"CPI-100P ": 50 wt% propylene carbonate solution of diphenyl (4-phenylthiophenyl) sulfonium hexafluorophosphate obtained from San A Pro Co., Ltd.

[Example 1]

(a) Preparation of photocurable composition

2.0 g of the epoxy compound "Denacol EX-211" and 150 mg of the photoacid generator "WPBG056" were measured in a 20 ml screw tube, taken, mixed and defoamed to prepare a liquid photo-curable composition.

(b) Production of polarizing plate

Two triacetyl cellulose films (trade name: "N-TAC KC4FR-1") having a thickness of 40 μm and not containing an ultraviolet absorber obtained from Konica Minolta Opt Co., Ltd. were prepared and subjected to corona discharge treatment on each side thereof Each of the corona discharge treated surfaces was coated with the photocurable composition prepared in the above (a) using a bar coater so that the film thickness after curing was 2.5 占 퐉. Separately, a polyvinyl alcohol-iodine polarizer having a thickness of 30 占 퐉 was prepared, and triacetylcellulose films on which the coating film of the photo-curing composition was formed were superposed on both sides thereof. The resulting laminate was loaded on a belt conveyor of an ultraviolet irradiator equipped with a belt conveyor, and an ultraviolet lamp "D bulb" manufactured by Fusion UV System Co., Ltd. installed on the ultraviolet irradiator was used to measure the total amount of light from the triacetyl cellulose film side to 500 mJ / , And the coating film on both sides of the polarizer was cured. Thus, a polarizing plate having a triacetyl cellulose film bonded to both sides of the polarizer was produced.

(c) Evaluation of Durability of Polarizer

On the outside of the triacetylcellulose film of the polarizing plate produced above, an ionic compound was compounded to form a layer of an acrylic pressure-sensitive adhesive having an antistatic function. The polarizing plate having the pressure-sensitive adhesive layer thus formed was cut to a size of 30 mm x 30 mm, and the pressure-sensitive adhesive layer was bonded to a non-alkali glass (trade name "EAGLE XG " The resulting polarizer / glass laminate was subjected to a durability test in which it was kept at a high temperature of 90 DEG C for 48 hours.

For the polarizer / glass laminate before and after the durability test, the a value and the b value of the transmission color were measured. For the measurement, an ultraviolet visible spectrophotometer "UV-2450" manufactured by Shimadzu Seisakusho Co., Ltd. and an optional accessory "film holder with polarizer" First, the parallel transmission spectrum (transmission spectrum when linearly polarized light having a vibration plane parallel to the transmission axis of the polarizing plate is incident) and the orthogonal transmission spectrum of the laminate in the wavelength region of 380 to 780 nm (Transmission spectrum when linearly polarized light having an orthogonal vibration plane is incident), and from these, a single transmittance spectrum of the laminate (when natural light is incident) by the software "UV-Probe" attached to "UV-2450" , And the a value and the b value of the transmission color were calculated. Based on the a value and the b value of the transmission color obtained from the software "UV-Probe ", ab value was calculated by the following equation (1).

ab = (a ² + b ² ) ^1/2 (1)

Ab [= ab (after the test)] -ab (before the test) a value obtained by subtracting the ab value [ab (before the test)] of the transmission color before the durability test from the ab value of the transmission color after the durability test [ab ] Was calculated and used as an index of the color change by the high temperature endurance test. In the polarizing plate produced in this example,? Ab was 2.04. The polarizing plate after the durability test was visually observed, and it was examined whether or not the appearance of the polarizing plate was changed before the test. In this example, the appearance of the polarizing plate was not changed before and after the test.

Here, a description will be made of the a value and the b value and the ab value of the transmission color used for evaluating the hue change of the polarizing plate. The transmission color means the color of light transmitted through the other side when natural light is irradiated from one side to one polarizing plate. This color can be expressed by a value and b value in the hunter's Lab colorimetric system and is measured using standard light. The Lab colorimetric system is represented by Hunter's brightness index (L) and color coordinates a and b as described in "5.5 Accelerated Weatherability Test" of JIS K 5981: 2006 "Synthetic Resin Powder Coating Film". The values of the brightness index L and the color coordinates a and b are calculated from the tristimulus values X, Y and Z defined by JIS Z 8722: 2009 "Method of measuring color - reflection and transmitted object color" by the following equation.

L = 10Y ^1/2

a = 17.5 (10.2 X Y) / Y ^1/2

b = 7.0 (Y-0.847Z) / Y1 / ² .

In the Lab colorimetric system, the color space in which the lightness is represented by the L axis and the axis of the chromaticity is represented by the a value and the b value, and these three axes are three-dimensionally orthogonal is considered. The chromaticity diagram is an orthogonal graph in which the a axis is the abscissa axis and the b axis is the ordinate axis, so that the L axis is an orthogonal point between the a axis and the b axis. the plus side of the a axis becomes the red region and the minus side becomes the green region and the positive side of the b axis becomes the yellow region and the minus side becomes the blue region and the orthogonal point (a = 0, a point of b = 0) becomes an achromatic point .

Here, the ab value calculated in the above formula (1), which means the state of separation from the orthogonal point, is used as an index of the hue of the polarizing plate. The change amount ab of the ab value before and after the durability test was regarded as an index of color change by the high temperature endurance test. Of course, if? Ab is 0, it means that there is no color change, and the larger the change, the larger the color change. Experience has shown that when Δab exceeds 3, the color change to the naked eye becomes slightly noticeable, and if it is less, the color change to the naked eye is hardly felt. It is more preferable that? Ab is 2.5 or less.

[Comparative Example 1]

(a) Preparation of photocurable composition

A photocurable composition was prepared in the same manner as in Example 1 (a) except that the photoacid generator "WPBG056" was changed to 90 mg of the above photo acid generator "CPI-100P ". The photoacid generator "CPI-100P" used here was obtained as a 50 wt% propylene carbonate solution as described above. The 90 mg compounded in this example was a solution containing propylene carbonate as a solvent This is the value taken.

(b) Polarizing plate production and durability evaluation

A polarizer in which triacetyl cellulose films were bonded to both sides of a polarizer was prepared in the same manner as in Example 1 (b) except that the photo-curable composition prepared above, that is, the photo-curable composition containing the photoacid generator "CPI-100P & Respectively. The polarizing plate was subjected to a durability test in the same manner as in Example 1 (c). As a result,? Ab was 4.57, and discoloration and discoloration were confirmed on the polarizing plate by the durability test even with visual observation.

As can be seen from the above Examples and Comparative Examples, in Comparative Example 1 in which a photo-curing composition containing a photo-acid generator (light-ion polymerization initiator) is blended as an adhesive, the polarizing plate tends to be discolored by heat, In Example 1 using the photo-curing composition in which the photo-curable polymerization initiator (photo anion polymerization initiator) is blended as an adhesive, discoloration due to such heat can be effectively suppressed.

The polarizer of the present invention exhibits good heat resistance because the adhesive bonding the polarizer and the transparent resin film is formed of a photo-curable composition containing a photo-curable component containing an epoxy compound and a photo base generating agent.

Claims (6)

A transparent resin film is bonded to a polarizer in which a dichroic dye is adsorbed and oriented on a polyvinyl alcohol-based resin through an adhesive,
Wherein the adhesive is formed of a photo-curing composition containing a photo-curable component containing an epoxy compound and a photo-base generator. The polarizing plate according to claim 1, wherein the epoxy compound has at least two epoxy groups in the molecule. The polarizing plate according to claim 2, wherein the epoxy group exists as a glycidyloxy group. The polarizing plate according to any one of claims 1 to 3, wherein the epoxy compound has no aromatic ring in the molecule. The polarizing plate according to any one of claims 1 to 4, wherein the photobase generator is a compound having a carbamate structure in a molecule or a quaternary ammonium compound. The polarizing plate according to any one of claims 1 to 5, wherein the photo-curable composition contains 0.01 to 400 parts by weight of the photo-base generator per 100 parts by weight of the photo-curable component containing an epoxy compound.