KR20140138634A - Dye-based polarizing element, and polarizing plate - Google Patents

Abstract

식 중, R₁, R₂는 각각 독립적으로, 수소원자, 탄소수 1 내지 4의 알킬기, 탄소수 1 내지 4의 알콕시기, 술포기, 술포기를 갖는 탄소수 1 내지 4의 알콕시기, 또는 할로겐 원자를 나타낸다. ≪ Problem > Development of a polarizing element having good polarization characteristics and having high durability.
[MEANS FOR SOLVING PROBLEMS] A polarizing element comprising a film comprising a polyvinyl alcohol resin or a derivative thereof and a dichroic dye, wherein at least one of the dichroic dyes is an azo compound represented by the formula (1) Polarized light.

Wherein R ₁ and R ₂ each independently represent a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, a sulfo group, an alkoxy group having 1 to 4 carbon atoms having a sulfo group, .

Description

DYE-BASED POLARIZING ELEMENT, AND POLARIZING PLATE

The present invention relates to a dye-based polarizing element and a polarizing plate using the same.

Polarizing elements are generally produced by adsorbing and orienting iodine or a dichroic dye as a dichroic dye on a polyvinyl alcohol-based resin film. A protective film made of triacetyl cellulose or the like is bonded to at least one side of the polarizing element through an adhesive layer to form a polarizing plate and used for a liquid crystal display device or the like. A polarizing plate using iodine as a dichroic dye is called an iodine-based polarizing plate, and a polarizing plate using a dichroic dye as a dichroic dye is called a dye-based polarizing plate. Among these, the dye-based polarizing plate has a problem that the transmittance is low, that is, the contrast is low, compared with an iodine-based polarizing plate having the same degree of polarization. However, a dye having a high heat resistance, high wet heat resistance and high stability, And is characterized by high color selectivity by blending.

In addition, in recent years, the intensity of a light source has increased as an optical use, and there is a problem that the polarizing plate is discolored due to the strong light and the accompanying heat. In addition, there is a demand for polarizers used for liquid crystal displays such as digital signage, which is supposed to be used outdoors, and polarizability and light resistance are required, and there is a high demand for improvement thereof.

Patent Document 1: Japanese Patent No. 3769140 Patent Document 2: JP-A-2003-313451 Patent Document 3: Special Publication 64-5623 Patent Document 4: Japanese Patent Application Laid-Open No. 2004-075719

Non-Patent Document 1: Application of Functional Dyes First Edition Publications, CMC Publishing Co., Ltd. Kang Jung-Ho supervised by P98-100 Non-Patent Document 2: Dye chemistry; Hosoda Yutaka; Gibo Party

Patent Documents 1 and 2 disclose a patent for a polarizing plate requiring light resistance or a dye used for a polarizing plate. In Example 5 of Patent Document 3, a diazo acid in which an amino azo compound is diazotized is disclosed.

However, although the technology as disclosed in Patent Documents 1 and 2 is disclosed, it has not yet reached the market demand, and the dyes disclosed in Patent Document 3 have a relatively high durability but a low polarization characteristic. Therefore, it has been required to develop a polarizing element having good polarization characteristics and high durability.

DISCLOSURE OF THE INVENTION The present inventors have intensively studied to solve the above problems and found that a polarizing element comprising a film containing a polyvinyl alcohol resin or a derivative thereof and a dichroic dye and being stretched, ) Or a salt thereof, has found a polarizing element having good polarization characteristics and high durability.

That is,

(1) A polarizing element comprising a film comprising a polyvinyl alcohol resin or a derivative thereof and a dichroic dye, wherein at least one of the dichroic dyes is an azo dye represented by the formula (1) in the form of a free acid, A compound or a salt thereof,

Wherein R ₁ and R ₂ each independently represent a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, a sulfo group, an alkoxy group having 1 to 4 carbon atoms having a sulfo group, .

(2) A polarizing plate in which a protective layer is provided on one side or both sides of the polarizing element described in (1)

(3) The liquid crystal display device having the polarizing element described in (1) or the polarizing plate described in (2)

(4) A polarizing element described in (1), or a polarizing lens having the polarizing plate described in (2).

The polarizing element or the polarizing plate containing the dichroic dye in the polyvinyl alcohol resin or derivative thereof of the present invention has high durability and good polarization characteristics.

Carrying out the invention  Form for

Hereinafter, the present invention will be described in detail.

The present invention relates to a polarizing element comprising a film comprising a polyvinyl alcohol resin or a derivative thereof and a dichroic dye and being stretched, wherein at least one of the dichroic dyes is an azo dye represented by the formula (1) Or a salt thereof, which is characterized by having good polarization characteristics and high durability. The characteristics can be attained by incorporating at least one of the dyes represented by the formula (1) in a polyvinyl alcohol-based film and stretching the film.

Wherein R ₁ and R ₂ each independently represent a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, a sulfo group, an alkoxy group having 1 to 4 carbon atoms having a sulfo group, .

Specific examples of the azo compound represented by the above formula (1) used in the present invention are listed below. The sulfo group, carboxy group and hydroxyl group in the formula are in the form of free acids.

Synthesis method

The azo compound represented by the formula (1) or its salt can be easily produced by coupling according to the production method of a conventional azo dye as described in Non-patent Document 2. [ As specific production methods, for example, an amino compound represented by the formula (10) is diazotized by a known method to obtain N, N-bis (1-hydroxy-3-sulfo-6-naphthyl) amine J acid) at 10 to 20 占 폚 to obtain a disazo compound. The obtained disazo compound is subjected to a copperation reaction at 85 to 95 占 폚, for example, by adding copper sulfate and aqueous ammonia, amine alcohol and hexamethylenetetramine to obtain a solution containing the compound of formula (1).

In the formula, Rx represents the same meaning as R ₁ or R ₂ in the formula (1).

The solution is then evaporated to dryness or salting-out, dried, and triturated to obtain the compound of formula (1) of the present invention. The compound of the formula (1) thus obtained is generally used as a sodium salt, but it can be used as a lithium salt, a potassium salt, an ammonium salt, an alkylamine salt or the like.

The dye of the formula (1) can be used in combination with other organic pigments to improve color hue and polarization performance. The organic dye to be used in this case may be any dye as far as it is a dye having an absorption capacity in a wavelength region in which the dye and an absorption wavelength region are different from those used in the present invention and has a high polarization performance, However, any dyes such as azo dyes, anthraquinone dyes, and quinophthalone dyes may be used as long as they are capable of dyeing hydrophilic polymers, and the dyes described in the color index are also exemplified. For example, Mr. direct. Yellow 12, seed, child. direct. Yellow 28, seed, child. direct. Yellow 44, Mr., child. direct. Orange 26, seed, child. direct. Orange 39, seed, child. direct. Orange 107, seed, child. direct. Red 2, seed, child. direct. Red 31, seed, child. direct. Red 79, seed, child. direct. Red 81, seed, child. direct. Red 247, seed, child. direct. Green 80, seed, child. direct. Green 59, and JP 2001-33627, JP 2002-296417, JP 2003-215338, WO2004 / 092282, JP 2001-056412, JP 2001-027708, JP 11-218611, JP 11-218610, JP 60-156759 Organic dyes described in Non-Patent Document 1, and the like. These organic dyes can be used in addition to free acids as alkali metal salts (for example, Na salts, K salts, Li salts), ammonium salts, or salts of amines. However, the dichroic dye is not limited to these and a known dichroic dye can be used, but an azo dye is preferable. In addition to the dichroic dyes exemplified in these examples, other organic dyes may be used together, if necessary.

The types of organic dyes to be blended differ depending on whether the target polarizing element is a neutral color polarizing element, a liquid crystal projector color polarizing element, or other color polarizing element. The compounding ratio is not particularly limited, and the compounding amount can be arbitrarily set according to requirements such as light source, durability, desired color, and the like.

The dye of the formula (1) is impregnated with a film of a polyvinyl alcohol resin or a derivative thereof. The production method of the polyvinyl alcohol resin constituting the polarizing element is not particularly limited, and for example, polyvinyl acetate resin may be saponified. Examples of the polyvinyl acetate 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 saponification degree of the polyvinyl alcohol resin is usually 85 to 100 mol%, more preferably 95 mol% or more. The polyvinyl alcohol resin may also be modified. For example, polyvinyl formal or polyvinyl acetal modified with aldehydes may be used. The degree of polymerization of the polyvinyl alcohol resin is usually preferably from 1,000 to 10,000, more preferably from 1,500 to 6,000. The derivatives of the polyvinyl alcohol resin that can be used in the present invention include resins subjected to the above-mentioned denaturation treatment.

A polyvinyl alcohol resin or a derivative thereof (hereinafter collectively referred to as a polyvinyl alcohol-based resin) is used as the original film. The method of forming the polyvinyl alcohol resin is not particularly limited, and a film can be formed by a known method. In this case, the polyvinyl alcohol based resin film may contain glycerin, ethylene glycol, propylene glycol, or a low molecular weight polyethylene glycol as a plasticizer. The amount of the plasticizer is preferably 5 to 20% by weight, more preferably 8 to 15% by weight. The thickness of the original film made of a polyvinyl alcohol-based resin is not particularly limited, but is preferably 5 to 150 탆, more preferably 10 to 100 탆.

In the polyvinyl alcohol-based resin film, a swelling step is first performed. The swelling process is performed by immersing the polyvinyl alcohol resin film in a solution at 20 to 50 캜 for 30 seconds to 10 minutes. The solution is preferably water. In the case of shortening the time for producing the polarizing element, the swelling step can be omitted because the swelling is also caused in the dyeing treatment of the dye.

After the swelling process, a dyeing process is carried out. The dyeing process is a process in which a dye is impregnated by immersing a polyvinyl alcohol resin film in a solution containing a dichroic dye. The solution temperature in this step is preferably 5 to 60 ° C, more preferably 20 to 50 ° C, and particularly preferably 35 to 50 ° C. The time for immersing in the solution can be appropriately adjusted, but it is preferably adjusted from 30 seconds to 20 minutes, more preferably from 1 to 10 minutes. The dyeing method is preferably carried out by immersing in the above solution, but it can be carried out by applying the solution to the polyvinyl alcohol-based resin film.

The solution containing the dichroic dye may contain sodium chloride, sodium sulfate, anhydrous sodium sulfate, sodium tripolyphosphate and the like as a dyeing aid. The content thereof may be adjusted to any concentration depending on the time and temperature depending on the dyeability of the dye. The content thereof is preferably 0 to 5% by weight, and more preferably 0.1 to 2% by weight.

As a method of impregnating the dye, it may be carried out by immersing it in a solution containing a dichroic dye. In the step of molding the disc of the polyvinyl alcohol-based resin film, a dye may be contained.

After the dyeing step, a cleaning step (hereinafter referred to as a cleaning step 1) can be performed before entering the next step. The cleaning step 1 is a step of cleaning the dye solvent adhering to the surface of the polyvinyl alcohol based resin film in the dyeing step. By performing the cleaning step 1, migration of the dye into the next liquid to be treated can be suppressed. In the cleaning step 1, water is generally used.

The cleaning method is preferable to be immersed in the above solution, but the solution can be cleaned by applying it to the polyvinyl alcohol based resin film. The cleaning time is not particularly limited, but is preferably 1 to 300 seconds, and more preferably 1 to 60 seconds. It is necessary that the temperature of the solvent in the cleaning step 1 is a temperature at which the hydrophilic polymer does not dissolve. In general, it is cleaned at 5 to 40 ° C.

After the dyeing step or the washing step 1, a step of containing a crosslinking agent and / or a water-proofing agent can be carried out. Examples of the crosslinking agent include boron compounds such as boric acid, borax or ammonium borate, polyvalent aldehydes such as glyoxal or glutaraldehyde, polyvalent isocyanate compounds such as biuret type, isocyanurate type or block type, Titanium compounds, and the like. In addition, ethylene glycol glycidyl ether, polyamide epichlorohydrin, and the like can be used. Examples of the water-proofing agent include peroxydisuccinic acid, ammonium persulfate, calcium perchlorate, benzoyl ethyl ether, ethylene glycol diglycidyl ether, glycerin diglycidyl ether, ammonium chloride, magnesium chloride and the like. do. A step of containing a crosslinking agent and / or a water-proofing agent is carried out using at least one crosslinking agent and / or a water-repellent agent as described above. As the solvent at this time, water is preferable but not limited. The concentration of the crosslinking agent and / or the water-proofing agent in the solvent in the step of containing the crosslinking agent and / or the water-proofing agent is preferably 0.1 to 6.0% by weight, more preferably 1.0 to 4.0% by weight desirable. The solvent temperature in this step is preferably 5 to 70 캜, more preferably 5 to 50 캜. The method of containing the crosslinking agent and / or the water-proofing agent in the polyvinyl alcohol-based resin film is preferably carried out in the above solution, but the solution may be applied or coated on the polyvinyl alcohol-based resin film. The treatment time in this step is preferably 30 seconds to 6 minutes, more preferably 1 to 5 minutes. However, it is not essential to contain a cross-linking agent and / or a water-repellent agent, and in the case where it is desired to shorten the time, the cross-linking treatment or the water-resistant treatment is not necessary, this treatment step may be omitted.

After the dyeing step, the washing step 1, or the step of containing a crosslinking agent and / or a water-proofing agent is carried out, a drawing step is carried out. The stretching step is a step of uniaxially stretching the polyvinyl alcohol-based film. The stretching method may be either a wet stretching method or a dry stretching method.

In the case of the dry stretching method, it is preferable that the stretching heating medium is stretched at room temperature to 180 ° C, and in the case of air medium, the air medium is stretched at room temperature to 180 ° C. The humidity is preferably treated in an atmosphere of 20 to 95% RH. As the heating method, for example, a rolling zone stretching method, a roll heating stretching method, a rolling stretching method, an infrared heating stretching method and the like can be mentioned, but the stretching method thereof is not limited. Although the stretching process can be performed in one stage, it can also be performed in two or more stages in multi-stage stretching.

In the case of the wet stretching method, stretching is performed in water, a water-soluble organic solvent, or a mixed solution thereof. It is preferable to carry out the stretching treatment while immersing it in a solution containing a crosslinking agent and / or a water-proofing agent. Examples of the crosslinking agent include boron compounds such as boric acid, borax or ammonium borate, polyvalent aldehydes such as glyoxal or glutaraldehyde, polyvalent isocyanate compounds such as biuret type, isocyanurate type or block type, Titanium compounds, and the like. In addition, ethylene glycol glycidyl ether, polyamide epichlorohydrin, and the like can be used. Examples of the water-proofing agent include peroxy succinic acid, ammonium persulfate, calcium perchlorate, benzoyl ethyl ether, ethylene glycol diglycidyl ether, glycerin diglycidyl ether, ammonium chloride, magnesium chloride and the like. The stretching is carried out in a solution containing at least one crosslinking agent and / or a water-repellent agent as shown above. The crosslinking agent is preferably boric acid. The concentration of the crosslinking agent and / or the water-proofing agent in the stretching step is preferably 0.5 to 15% by weight, more preferably 2.0 to 8.0% by weight. The draw ratio is preferably 2 to 8 times, more preferably 5 to 7 times. The stretching temperature is preferably 40 to 60 占 폚, more preferably 45 to 58 占 폚. The stretching time is usually 30 seconds to 20 minutes, more preferably 2 to 5 minutes. The wet stretching process can be performed in one stage, but it can also be performed in two or more stages in multi-stage stretching.

After the stretching process, the film surface may be subjected to a cleaning step (hereinafter referred to as a cleaning step 2) for cleaning the surface of the film, due to precipitation of a cross-linking agent and / or a water- The cleaning time is preferably 1 second to 5 minutes. Although it is preferable to immerse the cleaning solution in the cleaning solution, the solution can be cleaned by coating or coating on the polyvinyl alcohol-based resin film. It may be subjected to a washing treatment in one stage or a multi-stage treatment in two or more stages. The solution temperature in the washing step is not particularly limited, but is usually 5 to 50 占 폚, preferably 10 to 40 占 폚.

Examples of the solvent to be used in the above treatment step include water, dimethylsulfoxide, N-methylpyrrolidone, methanol, ethanol, propanol, isopropyl alcohol, glycerin, ethylene glycol, propylene glycol, diethylene glycol, triethylene But are not limited to, alcohols such as glycol, tetraethylene glycol or trimethylolpropane, and amines such as ethylenediamine or diethylenetriamine. Mixtures of one or more of these solvents may also be used. The most preferred solvent is water.

After the stretching process or the cleaning process 2, the drying process of the film is performed. The drying treatment can be carried out by natural drying. However, in order to further improve the drying efficiency, moisture can be removed from the surface and / or air drying can be carried out by a roll compression, an air knife or an absorbing roll. The drying treatment temperature is preferably a drying treatment at 20 to 100 占 폚, more preferably a drying treatment at 60 to 100 占 폚. The drying treatment time is 30 seconds to 20 minutes, preferably 5 to 10 minutes.

In this way, the polyvinyl alcohol-based resin film polarizing element of the present invention having improved durability can be obtained. Even if the film that adsorbs the dichroic dye in the polarizing element is not a polyvinyl alcohol-based resin, even if a film can be obtained from an amylose resin, a starch-based resin, a cellulose resin, or a polyacrylate-based resin, And orientation of the hydrophilic resin by stretching, shear alignment, or the like, thereby making it possible to produce the same polarizing element, but a polarizing element film made of a polyvinyl alcohol based resin film is most suitable.

The obtained polarizing element is provided with a transparent protective layer on one side or on both sides thereof to form a polarizing plate. The transparent protective layer can be provided as a coating layer of a polymer or as a laminate layer of a film. As the transparent polymer or film forming the transparent protective layer, a transparent polymer or film having high mechanical strength and good thermal stability is preferable. As the material used as the transparent protective layer, for example, a cellulose acetate resin or a film thereof such as triacetylcellulose or diacetylcellulose, an acrylic resin or a film thereof, a polyvinyl chloride resin or a film thereof, a nylon resin or a film thereof, Or a film thereof, a polyallylate resin or a film thereof, a cyclic olefin resin or a film thereof using a cyclic olefin such as norbornene as a monomer, a polyethylene, a polypropylene, a polyolefin having a cyclo- or norbornene skeleton or a copolymer thereof, An imide and / or an amide resin or a polymer or a film thereof, and the like. Further, as the transparent protective layer, a resin having liquid crystallinity or a film thereof can be provided. The thickness of the protective film is, for example, about 0.5 to 200 mu m. A polarizing plate is produced by providing one or more layers of a homogeneous or heterogeneous resin or film on one side or both sides thereof.

In order to bond the transparent protective layer to the polarizing element, an adhesive is necessary. The adhesive is not particularly limited, but a polyvinyl alcohol-based adhesive is preferable. As the polyvinyl alcohol-based adhesive, for example, Goseonol NH-26 (manufactured by Nippon Synthetic Chemical Industry Co., Ltd.) and Ekseval RS-2117 (manufactured by Kuraray Co., Ltd.) can be cited. To the adhesive, a cross-linking agent and / or a water-proofing agent may be added. As the polyvinyl alcohol-based adhesive, a maleic anhydride-isobutylene copolymer is used, but if necessary, an adhesive mixed with a crosslinking agent can be used. Examples of the maleic anhydride-isobutylene copolymer include isobarane # 18 (manufactured by Kuraray Co., Ltd.), isoban # 04 (manufactured by Kuraray Co., Ltd.), ammonia modified isoban # 104 (Manufactured by Kuraray Co., Ltd.), imidized isoban # 304 (manufactured by Kuraray Co., Ltd.) and imidized isoban # 310 (manufactured by Kuraray Co., Ltd.). A water-soluble polyfunctional epoxy compound may be used as the crosslinking agent. Examples of the water-soluble polyvalent epoxy compound include Denacol EX-521 (manufactured by Nagase ChemteX Corporation) and Tetralat-C (manufactured by Mitsui Gas Chemical). As the adhesive other than the polyvinyl alcohol-based resin, a known adhesive such as urethane-based, acrylic-based, or epoxy-based adhesive may be used. Further, additives such as zinc compounds, chlorides, iodides and the like can be contained at a concentration of about 0.1 to 10% by weight at the same time for the purpose of improving the adhesion of the adhesive or improving the water resistance. The additives are not limited either. The transparent protective layer is bonded with an adhesive, and then dried or heat-treated at a suitable temperature to obtain a polarizing plate.

When the polarizing plate is bonded to a display device such as liquid crystal or organic electroluminescence according to circumstances, the obtained polarizing plate may have various functional layers for improving the viewing angle, contrast, and brightness A layer or a film having a property can be provided. In order to bond the polarizing plate to these films or display devices, it is preferable to use an adhesive.

The polarizing plate may have various known functional layers such as an antireflection layer, an antiglare layer (hardening layer), and a hard coat layer on the other surface, that is, the exposed surface of the protective layer or film. In order to produce the layer having various functions, a coating method is preferable, but a film having the function can be bonded through an adhesive or a pressure-sensitive adhesive. Further, the various functional layers may be layers or films for controlling the retardation.

In this way, the polarizing element and the polarizing plate of the present invention can be obtained. The display using the polarizing element or the polarizing plate of the present invention has high reliability, high contrast in the long term, and high color reproducibility.

The thus obtained polarizing element of the present invention can be used as a polarizing plate by attaching a protective film and providing a protective layer, a functional layer, a support or the like as necessary to provide a liquid crystal projector, an electronic tabletop calculator, a clock, a notebook personal computer, Polarized lenses, polarized glasses, car navigation systems, and indoor and outdoor meters and displays.

Example

Hereinafter, the present invention will be described in more detail by way of examples, but the present invention is not limited thereto. The transmittance and the degree of polarization shown in the examples were evaluated as follows. In the following, " part " means " part by weight ".

Each transmittance was measured using a spectrophotometer (manufactured by Hitachi, Ltd., "U-4100").

The transmittance was measured using a spectrophotometer ("U-4100" manufactured by Hitachi, Ltd.) with a transmittance of 43% after the visual sensitivity correction based on JIS-Z8701 (C light source 2 ° field of view) An iodine-based polarizing plate (SKN-18043P manufactured by Polar Techno Co., Ltd.) having a purity of 99.99% was provided so that the polarized light could be incident on the measurement sample. The protective layer of the iodine-based polarizer at this time is triacetylcellulose having no ultraviolet absorption ability.

Absolute polarized light is incident on the polarizing plate of the present invention and the measurement is performed such that the oscillation direction of the absolute polarized light and the absorption axis direction of the polarizing plate of the present invention are orthogonal (the absorption axis of the polarizing plate of the present invention is parallel to the polarizer of the present invention) The obtained absolute parallel transmittance is Ky, the absolute orthogonal transmittance obtained by measuring the absolute parallel light transmittance in such a manner that the oscillation direction of the absolute polarized light is parallel to the absorption axis direction of the polarizing plate of the present invention (the absolute polarizer and the polarizing plate of the present invention are orthogonal to the absorption axis) Respectively.

The unitary transmittance Ts was obtained from the following equation (i) from the absolute parallel transmittance Ky and the absolute orthogonal transmittance Kz.

Ts = (Ky + Kz) / 2 Expression (i)

The degree of polarization? Was calculated from the absolute parallel transmittance Ky and the absolute orthogonal transmittance Kz by the following calculation formula (ii).

ρ = (Ky-Kz) / (Ky + Kz) (ii)

Example  A-1

≪ Preparation of dye &

17.9 parts of 3-amino-4-methoxybenzoic acid was dissolved in 145 parts of water, and the mixture was added to 140 parts of water containing 26 parts of 35% hydrochloric acid, and 6.9 parts of sodium nitrite was added thereto at 15 to 20 DEG C and diazotization was carried out for 1 hour. Subsequently, this was added to an aqueous solution composed of 31.5 parts of N, N-bis (1-hydroxy-3-sulfo-6-naphthyl) amine (common name: DIC), 125 parts of water and 11 parts of soda ash, The solution was kept at pH 8.5 to 9.5 while being poured, and the coupling was carried out until the disazo compound was not confirmed by the spot test at 20 占 폚 over 3 hours to obtain a disazo compound. Subsequently, copper complex salt prepared by adding 30.5 parts of monoethanolamine to 25 parts of copper sulfate was added, and the copperation reaction was carried out at 95 ° C for 10 hours until no unreacted material could be identified on the thin layer chromatography. 25% by weight, followed by salting out with water, and evaporating to dryness at 60 ° C to prepare a dye represented by the formula (4).

≪ Production of polarizing element &

A polyvinyl alcohol-based resin film (VF series, manufactured by Kuraray Co., Ltd.) having a degree of saponification of 99% or more and having a thickness of 75 탆 was immersed in hot water at 40 캜 for 2 minutes and swelled. The swollen film was dipped in an aqueous solution at 45 캜 containing 0.05% by weight of the dye represented by the formula (4) and 0.1% by weight of sodium tripolyphosphate to adsorb the dye. The dye-adsorbed film was washed with water, washed and then treated with boric acid for 1 minute in an aqueous solution containing 2% by weight of boric acid at 40 캜. The film obtained by the boric acid treatment was subjected to a treatment for 5 minutes in an aqueous solution at 55 캜 containing 3.0% by weight of boric acid while being stretched 5.0 times. The film obtained by the boric acid treatment was subjected to cleaning with water at 30 캜 for 15 seconds while maintaining the tension of the film. The film obtained by the treatment was immediately dried at 70 캜 for 9 minutes to obtain a polarizing element having a film thickness of 28 탆 and used as a measurement sample.

Example  A-2

In the same manner as in Example A-1 except that 3-amino-4-methoxybenzoic acid was changed to 3-methoxy-4-aminobenzoic acid to prepare the dye represented by Formula (3) As a polarizing element, a measurement sample was used.

Example  A-3

The procedure of Example A-1 was repeated except that 3-amino-4-methoxybenzoic acid was changed to 3-methoxy-4-amino-5-chlorobenzoic acid to prepare the dye represented by Formula (7) In the same manner, a polarizing element was used as a measurement sample.

Comparative Example  A-1

The dye represented by the formula (4) used in Example A-1 was replaced with the dye represented by C.I. Direct 81 disazo dye was used in place of the disazo dye.

Comparative Example  A-2

A polarizing element was prepared in the same manner as in Example A-1, except that the dye represented by the formula (4) was changed to the disazo dye shown in Example 1 of Japanese Patent Publication No. 7-92531 .

Comparative Example  A-3

A polarizing element was prepared in the same manner as in Example A-1 except that the dye represented by the formula (4) was changed to the disazo dye shown in Example No. 16 of JP-A-63-189803. Respectively.

Comparative Example  A-4

A polarizing element was prepared in the same manner as in Example A-1 except that the dye represented by the formula (4) was changed to the copper dye shown in the compound example No. 8 of the Japanese Patent No. 2985408.

Comparative Example  A-5

In the same manner as in Example A-1 except that 3-amino-4-methoxybenzoic acid was changed to 3-nitro-4-methoxy-5-aminobenzene and a dye having a dicarboxylic acid represented by the following formula (11) Was prepared in the same manner as in Example 1 to prepare a polarizing element.

Comparative Example  A-6

32.5 parts of 2-aminonaphthalene-4,8-disulfonic acid (common name: C acid) was dissolved in 145 parts of water, and the mixture was added to 140 parts of water containing 26 parts of 35% hydrochloric acid, 6.9 parts of sodium nitrite was added at 15 to 20 ° C, Lt; / RTI > Subsequently, an aqueous solution consisting of 13.7 parts of paracresidine and 17.5 parts of 35% hydrochloric acid was added, and while the pH was kept at 3.0 to 3.5 with sodium acetate, the mixture was allowed to stand at 20 ° C for 4 hours until the paracetcid . Subsequently, 21.4 parts of 35% hydrochloric acid is added to the amino azo compound, 6.9 parts of sodium nitrite is added at 10 ° C, and the second diazotization is performed at 15-20 ° C for 2-3 hours. Subsequently, this was added to an aqueous solution composed of 31.5 parts of N, N-bis (1-hydroxy-3-sulfo-6-naphthyl) amine (common name: DIC), 125 parts of water and 11 parts of soda ash, The solution was kept at a pH of 8.5 to 9.5 while being poured, and subjected to a secondary coupling until a disazo compound was not identified by a spot test at 20 占 폚 over 3 hours to obtain a tetrakis compound. Subsequently, a copper complex salt prepared by adding 30.5 parts of monoethanolamine to 25 parts of copper sulfate was added, and the copperation reaction was carried out at 95 ° C for 10 hours until no unreacted product could be identified on the thin layer chromatography. To 25% by weight, followed by salting out with water, followed by evaporating to dryness at 60 ° C to prepare a dye having a dicarboxylic acid represented by the formula (12). A measurement sample was obtained in the same manner as in Example A-1 except that the dye represented by the following formula (12) was used instead of the dye represented by the formula (4), and the polarizing element was used.

Comparative Example  A-7

The procedure of Example A-1 was repeated except that 3-amino-4-methoxybenzoic acid was changed to 3-methoxy-4-aminobenzenesulfonic acid to prepare a dye having a dicarboxylic acid represented by the following formula (13) In the same manner as above, the same polarizing element was used as a measurement sample.

Comparative Example  A-8

In the same manner as in Example A-1 except that 3-amino-4-methoxybenzoic acid was changed to 3-methoxy-4-amino-5-chlorobenzenesulfonic acid, A polarizing element was prepared in the same manner as in Example 1 except that a dye was prepared.

Using the spectrophotometer U-4100, the obtained polarizing elements were measured Ky and Kz at intervals of 1 nm at 380 nm to 780 nm. With respect to the degree of polarization ρ calculated from the obtained Ky and Kz, the wavelength having the highest degree of polarization was defined as λmax. Table 1 shows the degree of polarization? max at? max when the unitary transmittance Ts at? max is set to about 40.5% to 41.5%.

Comparing the polarization degree ρmax at λmax of the obtained polarizing element, it can be seen that Examples A-1 to A-3 have a degree of polarization equal to or higher than that of Comparative Examples A-1 to A-8. In particular, it can be understood that a polarizing element having a degree of polarization of about 4% to 6% can be obtained as compared with Comparative Examples A-5 to A-8 having a similar diacid.

Example  B-1

≪ Light resistance test &

A triacetylcellulose film (TD-80U, manufactured by Fuji Photo Film Co., Ltd., hereinafter abbreviated as TAC) having a thickness of 80 탆 and subjected to alkali treatment of the polarizing element obtained in Example A-1 was coated with a polarizing element / / TAC, and laminated to obtain a polarizing plate.

The resulting polarizing plate was cut into 40 mm x 40 mm and bonded to a 1 mm transparent glass plate through a pressure-sensitive adhesive PTR-3000 (manufactured by Nippon Kayaku Co., Ltd.) with a polarizing element / adhesive layer / TAC / adhesive layer / transparent glass plate, Respectively.

The light resistance test was conducted for 70 hours from the side of the polarizing element at 100 W with a xenon arc tester (SX-75 manufactured by Suga Seikisha Co., Ltd.), at a black panel temperature of 89 캜 and at an environmental humidity of 30% Kz, and the contrast CR calculated from the following formula (iii) was calculated to compare the durability with respect to light.

CR = Ky / Kz (iii)

Comparative Example  B-1

A durability test on light was conducted in the same manner as in Example B-1 except that the polarizing element A-1 used in Example B-1 was changed to the polarizing element obtained in Comparative Example B-1.

Comparative Example  B-2

A durability test on light was conducted in the same manner as in Example B-1 except that the polarizing element A-1 used in Example B-1 was changed to the polarizing element obtained in Comparative Example B-2.

Comparative Example  B-3

A durability test for light was conducted in the same manner as in Example B-1 except that the polarizing element A-1 used in Example B-1 was changed to the polarizing element obtained in Comparative Example B-3.

Table 2 shows Ky, Kz and CR at? Max after the durability test and the light resistance test of the polarizing plate obtained in Example B-1 and Comparative Examples B-1 to B-3.

As can be seen from Table 2, the dyes of the present invention were remarkably superior in light resistance to light as compared with Comparative Examples B-1 to B-3, and the reduction of contrast was remarkably suppressed.

As can be seen from Tables 1 and 2, the dyes of the present invention have a high polarizing property and a polarizing element having a degree of polarization equal to or higher than conventionally used dyes for a polarizing plate, It is possible to obtain a polarizing plate having a low contrast lowering than that of the polarizing plate and having a high light resistance against light. From this point of view, the polarizing plate of this example had a high polarization ratio and was also excellent in light resistance at a high temperature and long time exposure (exposure). By using the polarizing element or the polarizing plate of the present invention for a liquid crystal projector, an electronic tabletop calculator, a clock, a notebook personal computer, a word processor, a liquid crystal television, a polarizing lens, a polarizing glasses, a car navigation system, It is possible to obtain a liquid crystal display device and a lens which have high stability even without using a dye corresponding to a specific compounding substance such as a dye,

Claims (4)

A polarizing element comprising a film comprising a polyvinyl alcohol resin or a derivative thereof and a dichroic dye, wherein at least one of the dichroic dyes is an azo compound represented by the formula (1) in the form of a free acid or a salt thereof Polarized light.

Wherein R ₁ and R ₂ each independently represent a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, a sulfo group, an alkoxy group having 1 to 4 carbon atoms having a sulfo group, . A polarizing plate provided with a protective layer on one side or both sides of the polarizing element according to claim 1. A liquid crystal display device having the polarizing element according to claim 1 or the polarizing plate according to claim 2. The polarizing element according to claim 1, or the polarizing plate having the polarizing plate according to claim 2.