WO2013129171A1 - Dye-based polarizing element, and polarizing plate - Google Patents

Abstract

[Problem] To develop a polarizing element exhibiting excellent polarizing properties and high durability. [Solution] A polarizing element containing a polyvinyl alcohol resin or a derivative thereof, and a dichroic dye, and formed from a stretched film, wherein at least one of the dichroic dyes is characterized by being an azo compound represented by formula (1), or a copper complex of said azo compound. (In the formula, R₁ and R₂ each independently represent a hydrogen atom, a C_1-4 alkyl group, a C_1-4 alkoxy group, a sulfo group, a C_1-4 alkoxy group having a sulfo group, or a halogen atom.)

Description

Dye-type polarizing element and polarizing plate

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

A polarizing element is generally produced by adsorbing and orienting a dichroic dye, iodine or a dichroic dye, onto a polyvinyl alcohol resin film. A protective film made of triacetyl cellulose or the like is bonded to at least one surface of the polarizing element via an adhesive layer to form a polarizing plate, which is used for a liquid crystal display device or the like. A polarizing plate using iodine as a dichroic dye is called an iodine polarizing plate, while a polarizing plate using a dichroic dye as a dichroic dye is called a dye polarizing plate. Among these, dye-based polarizing plates have problems of low transmittance compared to iodine-based polarizing plates having the same degree of polarization, that is, low contrast, but have high heat resistance, high humidity heat durability, and high stability. In addition, dyes having various colors have been developed, and the color selectivity by blending is high.

Further, in recent years, the intensity of light sources has increased for optical applications, and there is a problem that the polarizing plate is discolored by the strong light and the heat generated therewith. Furthermore, the demand for polarizing plates used for liquid crystal displays such as digital signage, which is expected to be used outdoors, is also required for the degree of polarization and its light resistance, and the demand for improvement is high.

Patent Publication No. 3769140 JP2003-31451 Shoko 64-5623 JP 2004-075719

Patent Documents 1 and 2 disclose patents relating to polarizing plates that require light resistance and dyes used in polarizing plates. In Example 5 of Patent Document 3, a diJ acid obtained by diazotizing an aminoazo compound is disclosed.

However, although technologies such as Patent Document 1 and Patent Document 2 are disclosed, they do not meet market demands, and the dye disclosed in Patent Document 3 has relatively high durability. The polarization property of the thing was low. Therefore, development of a polarizing element having good polarization characteristics and high durability has been demanded.

As a result of intensive studies to solve the above problems, the present inventors are a polarizing element comprising a stretched film containing a polyvinyl alcohol resin or a derivative thereof and a dichroic dye, wherein the dichroic dye The polarizing element characterized by having at least one of the azo compound represented by the formula (1) or a salt thereof and having excellent polarization characteristics and high durability has been newly found. It was.

That is, “the present invention
(1) A polarizing element comprising a stretched film containing a polyvinyl alcohol resin or derivative thereof and a dichroic dye, wherein at least one of the dichroic dyes is in the form of a free acid in the formula (1) The polarizing element, which is an azo compound or a salt thereof shown

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

A polarizing element or polarizing plate containing a dichroic dye in the polyvinyl alcohol resin or derivative thereof of the present invention has high durability and good polarizing properties.

Hereinafter, the present invention will be described in detail.
The present invention relates to a polarizing element comprising a stretched film containing a polyvinyl alcohol resin or a derivative thereof and a dichroic dye, wherein at least one of the dichroic dyes is in the form of a free acid. The polarizing element characterized by being an azo compound represented by the formula (1) or a salt thereof, characterized by having good polarization characteristics and high durability. The feature can be achieved by being a film obtained by allowing a polyvinyl alcohol film to contain at least one dye represented by the formula (1) and stretching.

Wherein R ₁ and R ₂ are each independently a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, a sulfo group, or an alkoxy group having 1 to 4 carbon atoms having a sulfo group. Or a halogen atom.)

Next, specific examples of the azo compound represented by the formula (1) used in the present invention will be given below. The sulfo group, carboxy group and hydroxy group in the formula are represented in the form of free acid.

Synthesis Method The azo compound represented by the formula (1) or a salt thereof can be easily produced by performing coupling in accordance with a usual production method of an azo dye as described in Non-Patent Document 2. As a specific production method, for example, an amino compound represented by the formula (10) is diazotized by a known method, and N, N-bis (1-hydroxy-3-sulfo-6-naphthyl) amine (common name) is used. : Di-J acid) at 10 to 20 ° C. to obtain a disazo compound. The obtained disazo compound is added with, for example, copper sulfate, aqueous ammonia, aminoalcohol and hexamethylenetetramine and subjected to a copperation reaction at 85 to 95 ° C. to obtain a solution containing the compound of the formula (1).

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

Next, this solution is evaporated to dryness or salted out, filtered and dried, and pulverized to obtain a compound of formula (1) of the present application. The compound of the formula (1) thus obtained is generally used as a sodium salt, but can also be used as a lithium salt, potassium salt, ammonium salt, alkylamine salt or the like.

The dye of formula (1) can be used in combination with other organic pigments to improve hue correction and polarization performance. The organic dye used in this case is a dye having absorption characteristics in a wavelength region different from that of the dye used in the present invention and having high polarization characteristics, and any dye may be used, and dichroism. The dye is not particularly limited as long as it dyes a hydrophilic polymer. Examples of the dye include dichroic dyes such as azo, anthraquinone, and quinophthalone, and examples of the dye described in the color index. Is done. For example, Sea. Ai. direct. Yellow 12, sea. Ai. direct. Yellow 28, Sea. Ai. direct. Yellow 44, Sea. Ai. direct. Orange 26, Sea. Ai. direct. Orange 39, sea. Ai. direct. Orange 107, sea. Ai. direct. Red 2, sea. Ai. direct. Red 31, sea. Ai. direct. Red 79, Sea. Ai. direct. Red 81, Sea. Ai. direct. Red 247, Sea. Ai. direct. Green 80, Sea. Ai. direct. Green 59, and JP 2001-33627, JP 2002-296417, JP 2003-215338, WO 2004/092822, JP 2001-056412, JP 2001-027708, JP 11-218611, JP 11-218610, Examples thereof include organic dyes described in JP-A-60-156759 and Non-Patent Document 1. These organic dyes can be used as free metal, alkali metal salts (for example, Na salt, K salt, Li salt), ammonium salts, or amine salts. However, the dichroic dye is not limited to these, and a known dichroic dye can be used, but an azo dye is preferable. Other than these dichroic dyes, other organic dyes can be used in combination as required.

Depending on whether the target polarizing element is a neutral color polarizing element, a color polarizing element for liquid crystal projectors, or other color polarizing elements, the types of organic dyes to be blended differ. The blending ratio is not particularly limited, and the blending amount can be arbitrarily set according to demands such as light source, durability, and required hue.

The dye of the formula (1) is impregnated in a film of polyvinyl alcohol resin or a derivative thereof. The manufacturing method of the polyvinyl alcohol resin which comprises a polarizing element is not specifically limited, For example, what is necessary is just to saponify a polyvinyl acetate resin. 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 copolymerized with vinyl acetate include unsaturated carboxylic acids, olefins, vinyl ethers, and unsaturated sulfonic acids. The saponification degree of the polyvinyl alcohol resin is usually preferably from 85 to 100 mol%, more preferably 95 mol% or more. This polyvinyl alcohol resin may be further 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, and more preferably from 1,500 to 6,000. Examples of the derivative of the polyvinyl alcohol resin that can be used in the present invention include the resin subjected to the modification treatment.

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

The polyvinyl alcohol resin film is first subjected to a swelling process. The swelling step is performed by immersing the polyvinyl alcohol resin film in a solution at 20 to 50 ° C. for 30 seconds to 10 minutes. The solution is preferably water. When the time for manufacturing the polarizing element is shortened, the swelling step can be omitted because the swelling occurs even during the dyeing process.

The dyeing process is performed after the swelling process. A dyeing | staining process is a process of impregnating a dye by immersing a polyvinyl alcohol-type resin film in the 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 dipping in the solution can be adjusted moderately, but is preferably adjusted from 30 seconds to 20 minutes, more preferably from 1 to 10 minutes. The dyeing method is preferably immersed in the solution, but can also be performed by applying the solution to a polyvinyl alcohol-based resin film.

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

The method for impregnating the dye may be carried out by immersing it in a solution containing a dichroic dye, but it may also be a method for containing the dye at the stage of molding the raw material of the polyvinyl alcohol-based resin film.

After the dyeing process, a cleaning process (hereinafter referred to as cleaning process 1) can be performed before entering the next process. The dyeing process 1 is a process of washing the dye solvent adhering to the surface of the polyvinyl alcohol resin film in the dyeing process. By performing the washing step 1, it is possible to suppress the migration of the dye into the liquid to be processed next. In the cleaning step 1, water is generally used.
The washing method is preferably immersed in the solution, but can be washed by applying the solution to a polyvinyl alcohol resin film. The washing time is not particularly limited, but is preferably 1 to 300 seconds, more preferably 1 to 60 seconds. The temperature of the solvent in the washing step 1 needs to be a temperature at which the hydrophilic polymer does not dissolve. Generally, it is washed at 5 to 40 ° C.

After the dyeing step or washing step 1, a step of adding a crosslinking agent and / or a water resistance agent can be performed. Examples of the crosslinking agent include boron compounds such as boric acid, borax or ammonium borate, polyvalent aldehydes such as glyoxal or glutaraldehyde, polyisocyanate compounds such as biuret type, isocyanurate type or block type, titanium oxy Titanium compounds such as sulfate can be used, but ethylene glycol glycidyl ether, polyamide epichlorohydrin, and the like can also be used. Examples of the water-resistant agent include succinic peroxide, ammonium persulfate, calcium perchlorate, benzoin ethyl ether, ethylene glycol diglycidyl ether, glycerin diglycidyl ether, ammonium chloride or magnesium chloride, preferably boric acid. Used. The step of containing a crosslinking agent and / or a water-resistant agent is performed using at least one kind of crosslinking agent and / or a water-resistant agent shown above. As a solvent in that case, water is preferable, but it is not limited. The concentration of the cross-linking agent and / or the water-proofing agent in the solvent in the step of adding the cross-linking agent and / or the water-proofing agent is 0.1 to 6.0 when boric acid is used as an example. % By weight is preferable, and 1.0 to 4.0% by weight is more preferable. The solvent temperature in this step is preferably 5 to 70 ° C, more preferably 5 to 50 ° C. Although it is preferable to immerse the polyvinyl alcohol-based resin film in the solution with a crosslinking agent and / or a waterproofing agent, the solution may be applied to or applied to 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-resistant agent, and if it is desired to shorten the time, this processing step may be omitted if a cross-linking treatment or a water-resistant treatment is unnecessary. .

After the dyeing step, the washing step 1, or the step of adding a crosslinking agent and / or a water resistance agent, the stretching step is performed. The stretching step is a step of stretching the polyvinyl alcohol film uniaxially. The stretching method may be either a wet stretching method or a dry stretching method.

In the case of the dry stretching method, the stretching heating medium is preferably from room temperature to 180 ° C., and in the case of the air medium, the temperature of the air medium is preferably stretched from room temperature to 180 ° C. The treatment is preferably performed in an atmosphere of 20 to 95% RH. Examples of the heating method include an inter-roll zone stretching method, a roll heating stretching method, a pressure stretching method, an infrared heating stretching method, and the like, but the stretching method is not limited. The stretching step can be performed in one step, but can also be performed by two or more multi-step 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 perform the stretching treatment while being immersed in a solution containing a crosslinking agent and / or a water resistance agent. Examples of the crosslinking agent include boron compounds such as boric acid, borax or ammonium borate, polyvalent aldehydes such as glyoxal or glutaraldehyde, polyisocyanate compounds such as biuret type, isocyanurate type or block type, titanium oxy Titanium compounds such as sulfate can be used, but ethylene glycol glycidyl ether, polyamide epichlorohydrin, and the like can also be used. Examples of water-proofing agents include succinic peroxide, ammonium persulfate, calcium perchlorate, benzoin ethyl ether, ethylene glycol diglycidyl ether, glycerin diglycidyl ether, ammonium chloride, and magnesium chloride. Stretching is performed in a solution containing at least one or more crosslinking agents and / or waterproofing agents as described above. The crosslinking agent is preferably boric acid. The concentration of the crosslinking agent and / or waterproofing agent in the stretching step is preferably, for example, 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 ° C, more preferably 45 to 58 ° C. The stretching time is usually from 30 seconds to 20 minutes, more preferably from 2 to 5 minutes. The wet stretching step can be performed in one step, but can also be performed by two or more steps.

After performing the stretching step, the film surface may be subjected to a cleaning step (hereinafter referred to as a cleaning step 2) because the cross-linking agent and / or waterproofing agent may precipitate or foreign matter may adhere to the film surface. it can. The washing time is preferably 1 second to 5 minutes. The washing method is preferably immersed in a washing solution, but the solution can be washed on the polyvinyl alcohol resin film by coating or coating. The cleaning process can be performed in one stage, and the multi-stage process of two or more stages can be performed. The solution temperature in the washing step is not particularly limited, but is usually 5 to 50 ° C., preferably 10 to 40 ° C.

As the solvent used in the treatment steps so far, for example, water, dimethyl sulfoxide, N-methylpyrrolidone, methanol, ethanol, propanol, isopropyl alcohol, glycerin, ethylene glycol, propylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol or triethylene glycol Examples of the solvent include, but are not limited to, alcohols such as methylolpropane, and amines such as ethylenediamine or diethylenetriamine. A mixture of one or more of these solvents can also be used. The most preferred solvent is water.

After the stretching process or washing process 2, a film drying process is performed. The drying process can be performed by natural drying, but in order to further improve the drying efficiency, the surface can be removed by compression with a roll, an air knife, a water absorption roll, etc., and / or blow drying is performed. You can also. The drying treatment temperature is preferably 20 to 100 ° C., more preferably 60 to 100 ° C. A drying treatment time of 30 seconds to 20 minutes can be applied, but 5 to 10 minutes is preferable.

By the above method, a polyvinyl alcohol-based resin film polarizing element with improved durability according to the present invention can be obtained. Even if the film for adsorbing the dichroic dye in the polarizing element is not a polyvinyl alcohol resin, a film obtained from an amylose resin, starch resin, cellulose resin, polyacrylate resin, etc. A similar polarizing element can be produced by containing and orienting a hydrophilic resin by stretching, shear orientation, etc., but a polarizing element film made of a polyvinyl alcohol-based resin film is most preferable.

The obtained polarizing element is made into a polarizing plate by providing a transparent protective layer on one side or both sides thereof. The transparent protective layer can be provided as a polymer coating layer or as a film laminate layer. The transparent polymer or film forming the transparent protective layer is preferably a transparent polymer or film having high mechanical strength and good thermal stability. As a substance used as a transparent protective layer, for example, cellulose acetate resin such as triacetyl cellulose or diacetyl cellulose or film thereof, acrylic resin or film thereof, polyvinyl chloride resin or film thereof, nylon resin or film thereof, polyester resin or film thereof A film, a polyarylate resin or a film thereof, a cyclic polyolefin resin having a cyclic olefin such as norbornene or a film thereof, polyethylene, polypropylene, a polyolefin having a cyclo or norbornene skeleton or a copolymer thereof, a main chain or a side chain Examples include imide and / or amide resins or polymers or films thereof. In addition, a resin having liquid crystallinity or a film thereof can be provided as the transparent protective layer. The thickness of the protective film is, for example, about 0.5 to 200 μm. A polarizing plate is produced by providing one or more layers of the same or different types of resins or films on one side or both sides.

An adhesive is required to bond the transparent protective layer to the polarizing element. Although it does not specifically limit as an adhesive agent, A polyvinyl alcohol-type adhesive agent is preferable. Examples of the polyvinyl alcohol-based adhesive include, but are not limited to, Gohsenol NH-26 (manufactured by Nihon Gosei Co., Ltd.), EXEVAL RS-2117 (manufactured by Kuraray Co., Ltd.), and the like. A cross-linking agent and / or a waterproofing agent can be added to the adhesive. 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. As maleic anhydride-isobutylene copolymers, for example, isoban # 18 (manufactured by Kuraray), isoban # 04 (manufactured by Kuraray), ammonia-modified isoban # 104 (manufactured by Kuraray), ammonia-modified isoban # 110 (manufactured by Kuraray) ), Imidized isoban # 304 (manufactured by Kuraray), imidized isoban # 310 (manufactured by Kuraray), and the like. A water-soluble polyvalent epoxy compound can be used as the crosslinking agent at that time. Examples of the water-soluble polyvalent epoxy compound include Denacol EX-521 (manufactured by Nagase Chemtech) and Tetrat-C (manufactured by Mitsui Gas Chemical Co., Ltd.). Moreover, as adhesives other than polyvinyl alcohol-type resin, well-known adhesives, such as urethane type, an acrylic type, and an epoxy type, can also be used. Further, for the purpose of improving the adhesive strength of the adhesive or improving the water resistance, additives such as zinc compounds, chlorides, iodides and the like can be simultaneously contained at a concentration of about 0.1 to 10% by weight. The additive is not limited. After laminating the transparent protective layer with an adhesive, the polarizing plate is obtained by drying or heat treatment at a suitable temperature.

In some cases, when the obtained polarizing plate is bonded to a display device such as a liquid crystal or organic electroluminescence, various functional layers for improving the viewing angle and improving the contrast on the surface of the protective layer or film that will be an unexposed surface later. In addition, a layer or a film having brightness enhancement can be provided. In order to bond the polarizing plate to these films and 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, and a hard coat layer on the other surface, that is, the exposed surface of the protective layer or film. A coating method is preferable for producing the layer having various functions, but a film having the function can be bonded through an adhesive or a pressure-sensitive adhesive. The various functional layers can be a layer or a film for controlling the phase difference.

By the above method, the polarizing element and the polarizing plate of the present invention can be obtained. The display using the polarizing element or polarizing plate of the present invention is a display having high reliability, high contrast over the long term, and high color reproducibility.

The polarizing element of the present invention thus obtained is provided with a protective film as a polarizing plate, provided with a protective layer or a functional layer and a support as necessary, a liquid crystal projector, a calculator, a watch, a notebook computer, a word processor, a liquid crystal television, Used for polarized lenses, polarized glasses, car navigation, indoor and outdoor measuring instruments and displays.

Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited thereto. In addition, the transmittance | permeability and polarization degree which are shown to an Example were performed as follows. In the following, “part” means “part by weight”.

Each transmittance was measured using a spectrophotometer [“U-4100” manufactured by Hitachi, Ltd.].

When measuring the transmittance using a spectrophotometer ("U-4100" manufactured by Hitachi, Ltd.), the transmittance after the visibility correction based on JIS-Z8701 (C light source 2 ° field of view) is provided on the light exit side. An iodine polarizing plate (SKN-18043P manufactured by Polatechno Co., Ltd.) having a polarization degree of 99.99% at 43% was installed so that absolute polarized light could be incident on the measurement sample. In this case, the protective layer of the iodine-based polarizing plate is triacetyl cellulose having no ultraviolet absorbing ability.

Absolutely polarized light is incident on the polarizing plate of the present invention, and the vibration direction of the absolute polarized light is orthogonal to the absorption axis direction of the polarizing plate of the present invention (the absolute polarizer and the absorption axis of the polarizing plate of the present invention are parallel). The absolute parallel transmittance obtained by the measurement is Ky, the vibration direction of the absolute polarized light and the absorption axis direction of the polarizing plate of the present invention are parallel (absorption of the absolute polarizer and the polarizing plate of the present invention). The absolute orthogonal transmittance obtained by measuring so that the axes were orthogonal) was defined as Kz.

The single body transmittance Ts was determined from the absolute parallel transmittance Ky and the absolute orthogonal transmittance Kz by the following calculation formula (i).

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

The degree of polarization ρ was determined by the following calculation formula (ii) from the absolute parallel transmittance Ky and the absolute orthogonal transmittance Kz.

ρ = (Ky−Kz) / (Ky + Kz) (ii)

Example A-1
<Preparation of dye>
17.9 parts of 3-amino-4-methoxybenzoic acid is dissolved in 145 parts of water, added to 140 parts of water containing 26 parts of 35% by weight hydrochloric acid, and 6.9 parts of sodium nitrite is added at 15 to 20 ° C. for 1 hour. To diazotize. This was then added to an aqueous solution consisting of 31.5 parts of N, N-bis (1-hydroxy-3-sulfo-6-naphthyl) amine (common name: di-J acid), 125 parts of water, and 11 parts of soda ash. Further, while adding a soda ash solution, the pH was kept at 8.5 to 9.5 and coupling was carried out at 20 ° C. for 3 hours until no disazo compound was observed in the speckle test to obtain a disazo compound. Next, a copper complex salt prepared by adding 30.5 parts of monoethanolamine to an aqueous solution of 25 parts of copper sulfate is added, and the copperation reaction is carried out at 95 ° C. for 10 hours until no unreacted substances are observed on the thin layer chromatography. The resulting solution was added with 25% by weight of sanuki salt, salted out, filtered, and evaporated to dryness at 60 ° C. to prepare a dye represented by the formula (4) of the present application.

<Production of polarizing element>
A polyvinyl alcohol resin film (VF series, manufactured by Kuraray Co., Ltd.) having a saponification degree of 99% or more and a film thickness of 75 μm was immersed in warm water at 40 ° C. for 2 minutes for swelling treatment. The film subjected to the swelling treatment was immersed in an aqueous solution at 45 ° C. 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 film on which the dye was adsorbed was washed with water. After washing, the film was treated with boric acid for 1 minute with a 40 ° C. aqueous solution containing 2% by weight of boric acid. The film obtained by the boric acid treatment was treated for 5 minutes in an aqueous solution at 55 ° C. containing 3.0% by weight of boric acid while stretching 5.0 times. While maintaining the tension of the film obtained by the boric acid treatment, the film was washed with water at 30 ° C. for 15 seconds. The film obtained by the treatment was immediately dried at 70 ° C. for 9 minutes to obtain a polarizing element having a thickness of 28 μm as a measurement sample.

Example A-2
In the same manner as in Example A-1, except that 3-amino-4-methoxybenzoic acid was replaced by 3-methoxy-4-aminobenzoic acid to prepare a dye represented by the formula (3) of the present application, An element was used as a measurement sample.

Example A-3
The same as Example A-1, except that 3-amino-4-methoxybenzoic acid was replaced with 3-methoxy-4-amino-5-chlorobenzoic acid to prepare a dye represented by the formula (7) of the present application. Thus, a polarizing element was obtained as a measurement sample.

Comparative Example A-1
The dye represented by the formula (4) used in Example A-1 is the same as C.I. I. A polarizing element was obtained in the same manner except that the disazo dye of Direct81 was used, and a measurement sample was obtained.

Comparative Example A-2
A polarizing element was obtained in the same manner as the measurement sample except that the dye represented by the formula (4) used in Example A-1 was replaced with the disazo dye shown in Example 1 of JP-B-7-92531.

Comparative Example A-3
The dye represented by the formula (4) used in Example A-1 was prepared in Example No. 63 of JP-A-63-189803. A polarizing element was obtained in the same manner except that the disazo dye shown in FIG.

Comparative Example A-4
A polarizing element was obtained in the same manner as the measurement sample except that the dye represented by the formula (4) used in Example A-1 was replaced with the copperated dye represented by Compound Example No. 8 in Japanese Patent No. 2985408.

Comparative Example A-5
In Example A-1, a dye having a di-J acid represented by the following formula (11) was prepared by replacing 3-amino-4-methoxybenzoic acid with 3-nitro-4-methoxy-5-aminobenzene. In the same manner as described above, a polarizing element and a measurement sample were obtained.

Comparative Example A-6
Dissolve 32.5 parts of 2-aminonaphthalene-4,8-disulfonic acid (common name: C acid) in 145 parts of water, add it to 140 parts of water containing 26 parts of 35% hydrochloric acid, and add sodium nitrite 6 at 15-20 ° C. Add 9 parts and diazotize over 1 hour. Next, an aqueous solution consisting of 13.7 parts of paraclecidin and 17.5 parts of 35% hydrochloric acid was added, and paraclecidin was not observed in a spot test over 4 hours at 20 ° C. while maintaining pH 3.0 to 3.5 with sodium acetate. Coupling up to Next, 21.4 parts of 35% by weight hydrochloric acid are added to the aminoazo compound, 6.9 parts of sodium nitrite is added at 10 ° C., and secondary diazotization is carried out at 15 to 20 ° C. over 2 to 3 hours. This was then added to an aqueous solution consisting of 31.5 parts of N, N-bis (1-hydroxy-3-sulfo-6-naphthyl) amine (common name: di-J acid), 125 parts of water, and 11 parts of soda ash. Further, while adding a soda ash solution, the pH was maintained at 8.5 to 9.5, and secondary coupling was carried out at 20 ° C. for 3 hours until no disazo compound was observed in the speckle test to obtain a tetrakis compound. . Next, a copper complex salt prepared by adding 30.5 parts of monoethanolamine to an aqueous solution of 25 parts of copper sulfate is added, and the copperation reaction is carried out at 95 ° C. for 10 hours until no unreacted substances are observed on the thin layer chromatography. The resulting solution was added with 25% by weight of sanuki salt, salted out, filtered, and evaporated to dryness at 60 ° C. to prepare a dye having a di-J acid represented by the following formula (12). . In Example A-1, a measurement sample was prepared in the same manner as in Example A-1, except that a dye represented by the following formula (12) was used instead of the dye represented by the formula (4).

Comparative Example A-7
In Example A-1, except that 3-amino-4-methoxybenzoic acid was replaced by 3-methoxy-4-aminobenzenesulfonic acid, a dye having a di-J acid represented by the following formula (13) was prepared. Was similarly used as a polarizing element and a measurement sample.

Comparative Example A-8
In Example A-1, 3-amino-4-methoxybenzoic acid was replaced with 3-methoxy-4-amino-5 chlorobenzenesulfonic acid to prepare a dye having a di-J acid represented by the following formula (14) In the same manner as described above, a polarizing element and a measurement sample were obtained.

The obtained polarizing element was measured for Ky and Kz at 1 nm intervals from 380 nm to 780 nm using a spectrophotometer U-4100. In the polarization degree 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 ρmax at λmax when the single transmittance Ts at λmax is about 40% to 41%.

When the polarization degree ρmax at λmax of the obtained polarizing element was compared, Examples A-1 to A-3 had a polarization degree equal to or higher than that of Comparative Examples A-1 to A-8. I understand that. In particular, it can be seen that a polarizing element having a high degree of polarization of about 4% to 6% is obtained as compared with Comparative Examples A-5 to A-8 having the same di-J acid.

Example B-1
<Light resistance test>
A polarizing element obtained by subjecting the polarizing element obtained in Example A-1 to an alkali treatment with a triacetyl cellulose film having a thickness of 80 μm (TD-80U manufactured by Fuji Photo Film Co., Ltd., hereinafter abbreviated as TAC) using a polyvinyl alcohol adhesive. A laminate of / adhesive layer / TAC was laminated and laminated to obtain a polarizing plate.

The obtained polarizing plate is cut into 40 mm × 40 mm, and a polarizing element / adhesive layer / TAC / adhesive layer / transparent glass plate is formed on a 1 mm transparent glass plate via an adhesive PTR-3000 (manufactured by Nippon Kayaku Co., Ltd.). To obtain an evaluation sample for light resistance test.

The light resistance test was conducted with a xenon arc tester (manufactured by Suga Seiki Co., Ltd .; SX-75) at 100 W, black panel temperature of 89 ° C and environmental humidity of 30% for 70 hours from the polarizing element side. The changes in Ky and Kz were confirmed, and the contrast CR calculated from the formula (iii) was calculated to compare the durability against light.

CR = Ky / Kz Formula (iii)

Comparative Example B-1
A light durability test was conducted in the same manner except that the polarizing element A-1 used in Example B-1 was replaced with the polarizing element obtained in Comparative Example B-1.

Comparative Example B-2
A light durability test was conducted in the same manner except that the polarizing element A-1 used in Example B-1 was replaced with the polarizing element obtained in Comparative Example B-2.

Comparative Example B-3
A light durability test was conducted in the same manner except that the polarizing element A-1 used in Example B-1 was replaced with the polarizing element obtained in Comparative Example B-3.

Table 2 shows Ky, Kz, and CR at λmax before and after the durability test of the polarizing plates 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 application were significantly more light-resistant to light than Comparative Examples B-1 to B-3, and the reduction in contrast was drastically suppressed.

As can be seen from Table 1 and Table 2, the dye of the present application has a high polarization property from Table 1, and a polarizing element having a polarization degree equal to or higher than that of conventionally used polarizing plate dyes can be obtained. It can be seen from 2 that a polarizing plate having a high light resistance to light with less contrast reduction than the conventional polarizing plate is obtained. Also from this fact, the polarizing plate of this example had a high degree of polarization, and was excellent in light resistance when exposed to high temperature for a long time. By using the polarizing element or polarizing plate of the present invention for a liquid crystal projector, a calculator, a watch, a notebook computer, a word processor, a liquid crystal television, a polarizing lens, polarized glasses, a car navigation system, an indoor / outdoor measuring instrument or a display, etc., dianisidine It can be seen that a liquid crystal display device having high stability, a lens, and the like can be obtained without using a dye corresponding to the specific chemical substance.

Claims (4)

1. A polarizing element comprising a stretched film containing 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 The polarizing element, which is a compound or a salt thereof.
   

   

   Wherein R ₁ and R ₂ are each independently a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, a sulfo group, or an alkoxy group having 1 to 4 carbon atoms having a sulfo group. Or a halogen atom.)
2. The polarizing plate in which the protective layer is provided in the single side | surface or both surfaces of the polarizing element of Claim 1.
3. A liquid crystal display device comprising the polarizing element according to claim 1 or the polarizing plate according to claim 2.
4. A polarizing lens having the polarizing element according to claim 1 or the polarizing plate according to claim 2.