HK1196669B - Polarizing element and polarizing plate - Google Patents

Abstract

[Problem] To provide a polarizing element and a polarizing plate which have improved optical characteristics and durability. [Solution] A polarizing element which is characterized by being formed of a stretched polyvinyl alcohol resin film that adsorbs, as a free acid, at least one dichroic dye that is a compound represented by formula (I) or a salt thereof and which is also characterized in that the polyvinyl alcohol resin has a polymerization degree of from 5,000 to 10,000. (In the formula, A represents a substituted phenyl group or a naphthyl group; each of R1-R6 independently represents a hydrogen atom, a hydroxyl group, a lower alkyl group, a lower alkoxy group, a sulfo group or a lower alkoxy group having a sulfo group; X represents an optionally substituted amino group, an optionally substituted benzoylamino group, an optionally substituted phenylamino group, an optionally substituted phenylazo group or an optionally substituted naphthotriazole group; and m represents 0 or 1.)

Description

Polarizing element and polarizing plate

Technical Field

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

Background

The polarizing element is generally manufactured by adsorbing iodine or a dichroic dye as a dichroic dye onto a polyvinyl alcohol resin film and aligning the same. A protective film made of triacetyl cellulose or the like is bonded to at least one surface of the polarizer via an adhesive layer to form a polarizing plate, which is used in 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 them, the dye-based polarizing plate has characteristics of high heat resistance, high humidity and heat durability, high stability, and high color selectivity by compounding, and on the other hand, when a polarizing plate having the same degree of polarization is compared, the dye-based polarizing plate has a problem of low transmittance, that is, low contrast, as compared with an iodine-based polarizing plate. Therefore, a dye-based polarizing plate is desired to have a higher transmittance and a high polarization characteristic while maintaining high durability and various color selectivities.

Documents of the prior art

Patent document

Patent document 1: japanese patent laid-open No. 2005-171231

Patent document 2: japanese laid-open patent publication No. 2007-238888

Patent document 3: japanese patent laid-open No. 2008-120868

Patent document 4: japanese laid-open patent publication No. 2009-14873

Patent document 5: japanese laid-open patent publication No. 1-105204

Patent document 6: japanese laid-open patent publication No. 3-175404

Patent document 7: japanese patent laid-open publication No. 2004-075719

Non-patent document

Non-patent document 1: dye chemistry; thin Tian Feng Ji (technical report hall)

Disclosure of Invention

Problems to be solved by the invention

In order to improve the optical properties of dye-based polarizing plates, patent documents 1 to 3 disclose techniques for improving the optical properties by using a structure of a dichroic dye. Patent document 4 discloses a technique for improving optical characteristics by using processing conditions of a polarizing element, and patent documents 5 and 6 disclose a technique for improving optical characteristics by using a polyvinyl alcohol film having a high polymerization degree or a substituent for a modified film. However, the above-disclosed technology is difficult to industrialize, and demands for a polarizing plate having a higher transmittance and a high contrast are high, and further improvement of optical characteristics thereof is desired. In order to industrially produce a polarizing film made of a polyvinyl alcohol resin having a high polymerization degree, it is necessary to optimize the physical properties of the polyvinyl alcohol resin film, the production conditions of the polarizing film, and the dichroic dye used in the polarizing element.

The present inventors have conducted extensive studies to solve the above problems, and as a result, have found that a polarizing element comprising an azo compound-based dichroic dye and a polyvinyl alcohol resin film having a specific molecular weight can improve optical characteristics and can improve durability against light, heat and humidity.

Namely, the present invention relates to:

(1) a polarizing element comprising a polyvinyl alcohol resin film, wherein the polyvinyl alcohol resin film is obtained by adsorbing and stretching at least one dichroic dye, the dichroic dye is a compound represented by formula (I) or a salt thereof in a free acid form, the polyvinyl alcohol resin has a polymerization degree of 5000 to 10000,

[ solution 1]

(wherein A represents a substituted phenyl group or naphthyl group, R₁～R₆Each independently represents a hydrogen atom, a hydroxyl group, a lower alkyl group, a lower alkoxy group, a sulfo group or a lower alkoxy group having a sulfo group, X represents an amino group which may or may not have a substituent, a benzoylamino group which may or may not have a substituent, an optionally substituted benzoylamino groupOr an unsubstituted phenylamino group, an unsubstituted phenylazo group, or an unsubstituted naphthotriazole group, and m represents 0 or 1. )

(2) The polarizing element according to (1), wherein in formula (I), when m =0, A is represented by formula (II),

[ solution 2]

(in the formula, R₇And R₈One of them is a sulfo group and the other represents a hydrogen atom, a sulfo group, a lower alkyl group, a carboxyl group or a lower alkoxy group. )

(3) The polarizing element according to (1), wherein in the formula (I), when m =0, X is a naphthotriazole group having or not having a substituent, and the dichroic dye is a transition metal complex of the compound represented by the formula (I) or a salt thereof,

(4) the polarizing element according to (1), wherein in the formula (I), when m =1, A is a naphthyl group having at least 1 substituent, at least 1 of which is a sulfo group, and the other substituents are a hydroxyl group or a lower alkoxy group having a sulfo group,

(5) the polarizing element according to (1), wherein in formula (I), when m =1, A is a phenyl group having at least 1 substituent, at least 1 of which is a sulfo group, and the other substituents are a sulfo group, a lower alkyl group, a lower alkoxy group having a sulfo group, a carboxyl group, a nitro group, an amino group, or a substituted amino group,

(6) the polarizing element according to any one of (1) to (5), wherein X is a benzoylamino group with or without a substituent, a phenylamino group with or without a substituent, a phenylazo group with or without a substituent, or a naphthotriazole group with or without a substituent, and the substituent is a lower alkyl group, a lower alkoxy group, a hydroxyl group, a carboxyl group, a sulfo group, an amino group or a substituted amino group,

(7) the polarizing element according to any one of (1) to (6), wherein the dichroic dye is a compound represented by the following formula (III) or a salt thereof,

[ solution 3]

(R₁～R₆Each independently a hydrogen atom, a methyl group, a methoxy group, a sulfo group, a lower alkoxy group having a sulfo group)

(8) The polarizing element according to any one of (1) to (7), which is obtained by using a green film (proto-trans フィルム) having a swelling degree of 200% to 240%,

(9) the polarizing element according to any one of (1) to (7), which is obtained by using a green film having a swelling degree of 200% to 210%,

(10) a polarizing plate comprising the polarizing element according to any one of (1) to (9) and a transparent protective layer provided on at least one surface of the polarizing element,

(11) a liquid crystal display device comprising the polarizing element according to any one of (1) to (9) or the polarizing plate according to (10),

(12) a liquid crystal projector comprising the polarizing element according to any one of (1) to (9) or the polarizing plate according to (10).

Effects of the invention

The polarizing element or polarizing plate of the present invention has improved optical characteristics and improved durability against light, heat, and humidity.

Detailed Description

The polarizing element of the present invention is characterized by comprising a polyvinyl alcohol resin film, wherein the polyvinyl alcohol resin film is formed by adsorbing and stretching at least one dichroic dye, the dichroic dye is a compound represented by formula (I) or a salt thereof in a free acid form, and the polymerization degree of the polyvinyl alcohol resin is 5000 to 10000.

[ solution 4]

(wherein A represents a substituted phenyl group or naphthyl group, R₁～R₆Each independently represents a hydrogen atom, a hydroxyl group, a lower alkyl group, a lower alkoxy group, a sulfo group or a lower alkoxy group having a sulfo group, X represents an amino group with or without a substituent, a benzoylamino group with or without a substituent, a phenylamino group with or without a substituent, a phenylazo group with or without a substituent, or a naphthotriazolyl group with or without a substituent, and m represents 0 or 1. )

The following describes a method for manufacturing a polarizing element according to the present invention.

the polyvinyl alcohol resin used in the present invention can be produced by a known method, for example, by saponifying a polyvinyl ester polymer obtained by polymerizing vinyl ester, and the polyvinyl ester polymer used in the present invention can be produced by a known method, and 1 or 2 or more of vinyl acetate can be selected from among vinyl acetate, vinyl formate, vinyl propionate, vinyl butyrate, vinyl pivalate, vinyl versatate, vinyl laurate, vinyl stearate, vinyl benzoate, and the like, and among these, vinyl acetate is preferably used, and the polymerization temperature is not particularly limited, but when methanol is used as a polymerization solvent, the polymerization temperature is preferably about 60 ℃ because the boiling point of methanol is in the vicinity of 60 ℃.

The saponification degree of the polyvinyl alcohol resin is preferably 99 mol% or more, and more preferably 99.5 mol% or more. When the saponification degree is less than 99 mol%, the polyvinyl alcohol is liable to be eluted, which may cause in-plane unevenness of optical properties, reduction in dyeing property in the dyeing step, and cutting in the stretching step, and may significantly reduce productivity, and therefore, it is not preferable that the saponification degree is less than 99 mol%.

In order to improve the optical properties of the present invention, it is necessary that the polymerization degree of the polyvinyl alcohol resin is 5000 to 10000, more preferably 5500 or more. When the polymerization degree of the polyvinyl alcohol resin is less than 5000, it is difficult to exhibit high polarization performance. When the polymerization degree exceeds 10000, the resin becomes hard, the film forming property and the stretchability are lowered, and the productivity is lowered, and therefore 10000 or less is preferable from the industrial point of view.

the degree of viscosity average polymerization can be determined by a method known in the art, for example, by dissolving 0.28g of a polyvinyl alcohol resin in 70g of distilled water at 95 ℃ to prepare a 0.4% polyvinyl alcohol aqueous solution, cooling the solution to 30 ℃ and cooling the solution in a constant-temperature water tank at 30 ℃ to prepare a sample for polymerization degree measurement, drying 10mL of the sample for polymerization degree measurement in an evaporation pan for 20 hours by a drier at 105 ℃, measuring the weight [ α (g) ] of the sample for polymerization degree measurement after drying, and calculating the concentration C (g/L) of the sample for polymerization degree measurement by the formula (i).

C =1000 × α/10 · formula (i)

The polymerization degree measurement sample or distilled water was put into an Ostwald viscometer using a 10mL pipette, and the mixture was stabilized in a constant temperature water bath at 30 ℃ for 15 minutes. The number of seconds of dropping t1 (sec) of the polymerization degree measurement sample and the number of seconds of dropping t0 (sec) of distilled water were measured, and the viscosity average polymerization degree E was calculated by the formulas (ii) to (iv).

η t = t1/t0 … formula (ii)

η =2.303 × Log (η t/c) … formula (iii)

Log (E) =1.613 XLog ([ η ] 104/8.29) · formula (iv)

A film blank (フィルム original product) was obtained by forming a film from the polyvinyl alcohol resin obtained above. The film-forming method can be obtained by the following method in addition to the method of melt-extruding the aqueous polyvinyl alcohol resin, but is not limited to these methods: a casting film formation method, a wet film formation method (discharging into a poor solvent), a gel film formation method (cooling and gelling the polyvinyl alcohol resin aqueous solution, and then extracting and removing the solvent), a casting film formation method (flowing the polyvinyl alcohol resin aqueous solution on a base and drying), and a method based on a combination thereof.

Examples of the solvent used for film formation include, but are not limited to, dimethyl sulfoxide, dimethylformamide, dimethylacetamide, N-methylpyrrolidone, ethylene glycol, glycerol, propylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, trimethylolpropane, ethylenediamine, diethylenetriamine, and water, and 1 type thereof may be used or 2 or more types thereof may be mixed and used. The amount of the solvent used for film formation is preferably 70 to 95% by mass based on the entire film-forming stock solution, but is not limited thereto. However, if the amount of the solvent is less than 50% by mass, the viscosity of the film-forming dope becomes high, filtration and defoaming during production are difficult, and it is difficult to obtain a film blank free from foreign matter and defects. When the amount of the solvent exceeds 95 mass%, the viscosity of the film-forming dope becomes too low to control the target thickness, and the surface shaking by wind during drying affects the film-forming dope, thereby increasing the drying time and lowering the productivity.

In the production of the film blank, a plasticizer may be used. Examples of the plasticizer include, but are not limited to, glycerin, diglycerin, ethylene glycol, propylene glycol, and low-molecular-weight polyethylene glycol. The amount of the plasticizer to be used is not particularly limited, and is usually preferably in the range of 5 to 15 parts by mass per 100 parts by mass of the polyvinyl alcohol resin.

Examples of the method for drying the film blank after film formation include, but are not limited to, drying with hot air, contact drying using a hot roll, and drying with an infrared heater. One of these methods may be used alone, or two or more methods may be used in combination to perform drying. The drying temperature is also not particularly limited, and is preferably in the range of 50 ℃ to 70 ℃.

The dried film blank is preferably subjected to a heat treatment in order to control the degree of swelling to a predetermined range described later. Examples of the method of heat treatment of the film blank after film formation include a method using hot air and a method of bringing the film blank into contact with hot rolls, and the method is not particularly limited as long as the film blank can be treated by heat. One of these methods may be used alone, or two or more of them may be used in combination. The heat treatment temperature and time are not particularly limited, but are preferably in the range of 110 ℃ to 140 ℃ and the treatment time is preferably approximately 1 minute to 10 minutes, but is not particularly limited.

The thickness of the film blank thus obtained is preferably 20 to 100. mu.m, more preferably 20 to 80 μm, and still more preferably 20 to 60 μm. When the thickness is less than 20 μm, film breakage easily occurs. When the thickness exceeds 100 μm, the stress applied to the film during stretching becomes large, and the mechanical load in the stretching step becomes large, and a large-scale apparatus is required to withstand the load.

Next, the green film obtained above was subjected to a swelling step.

The swelling step is performed by immersing the polyvinyl alcohol resin film in a solution at 20 to 50 ℃ for 30 seconds to 10 minutes. The solution is preferably water. When the time for producing the polarizing element is shortened, swelling occurs also in the dyeing treatment of the dye, and therefore the swelling step can be omitted.

The degree of swelling F of the film blank is preferably 200% to 240%, more preferably 200% to 230%, and still more preferably 200% to 210%. In particular, when the swelling degree is 200% to 210%, the durability of the obtained polarizing element is improved, which is preferable. When the swelling degree F is less than 200%, the elongation at stretching is small, and the possibility of breaking at a low magnification is high, and sufficient stretching is difficult. When the swelling degree F exceeds 240%, the swelling becomes excessive, and wrinkles or slacks occur, which causes breakage during stretching. In order to control the degree of swelling F, the degree of swelling F can be controlled to be appropriate by temperature and time at the time of heat treatment of the film blank after film formation.

As a method for measuring the degree of swelling F of the film blank, a method known in the art can be used, and the measurement can be performed, for example, as follows.

the film blank was cut into 5cm × 5cm, immersed in 1 liter of distilled water at 30 ℃ for 4 hours, the immersed film was taken out from the distilled water, the film was sandwiched by 2 sheets of filter paper to absorb water droplets on the surface, and then the weight [ β (g) ] of the film immersed in water was measured.

degree of swelling F =100 × β/γ (%). formula (v)

The dyeing step is performed after the swelling step. In the present invention, the dye represented by formula (I) can be adsorbed to the polyvinyl alcohol film in the dyeing step. In the dyeing step, there is no particular limitation as long as the pigment is adsorbed to the polyvinyl alcohol film, and for example, the dyeing step is performed by immersing the polyvinyl alcohol resin film in a solution containing a 2-color dye. The solution temperature in this step is preferably 5 to 60 ℃, more preferably 20 to 50 ℃, and particularly preferably 35 to 50 ℃. The time for immersing in the solution can be appropriately adjusted, and is preferably adjusted within a range of 30 seconds to 20 minutes, and more preferably 1 minute to 10 minutes. The dyeing method is preferably carried out by immersing the film in the solution, but dyeing can also be carried out by applying the solution to a polyvinyl alcohol resin film.

The solution containing the 2-color dye may contain sodium carbonate, sodium bicarbonate, sodium chloride, sodium sulfate, anhydrous sodium sulfate, sodium tripolyphosphate, etc. as a dyeing assistant. The content of these can be adjusted at any concentration according to the time and temperature based on the dyeing property of the dye, and each content is preferably 0 to 5 wt%, more preferably 0.1 to 2 wt%.

The coloring matter used in the dyeing step is an azo compound as a dichroic coloring matter represented by formula (I), and may be a salt of the compound.

In the formula (I), when m =0, that is, when the azo compound has a trisazo structure, the optical characteristics can be further improved by the structure represented by the formula (II), which is preferable. As a substituent thereof, it preferably has at least 1 sulfo group; when the substituent has two or more substituents, at least 1 of the substituents is a sulfo group, and the other substituents are preferably a sulfo group, a lower alkyl group, a lower alkoxy group having a sulfo group, a carboxyl group, a nitro group, an amino group, or a substituted amino group. More preferably methoxy, ethoxy, carboxyl, nitro, amino, particularly preferably lower alkyl, lower alkoxy; the lower alkoxy group having a sulfo group is preferably a linear alkoxy group, and the substitution position of the sulfo group is preferably an alkoxy terminal, more preferably 3-sulfopropoxy or 4-sulfobutoxy, and particularly preferably 3-sulfopropoxy. The number of substituents is preferably 2. The substitution position is preferably a combination of 2-position and 4-position, but is not particularly limited.

[ solution 5]

(in the formula, R₇And R₈One of them is a sulfo group and the other represents a hydrogen atom, a sulfo group, a lower alkyl group, a carboxyl group or a lower alkoxy group. )

In the formula (I), when m =0, that is, when a is an azo compound having a trisazo structure and a is a naphthyl group, a represents a naphthyl group having a substituent, and the substituent preferably has at least 1 sulfo group. The number of sulfo groups is not limited as long as it is 1 or more, and it is preferable that 2 or 3 sulfo groups are present. The other substituents are preferably a hydroxyl group, a carboxyl group, or a lower alkoxy group having a sulfo group.

In the formula (I), when m =1, that is, when m is an azo compound having a tetrazo structure and a is a naphthyl group, it is preferable that at least 1 substituent is present, and at least 1 of the substituents is preferably a sulfo group. The number of sulfo groups is not limited as long as it is 1 or more, and it is preferable that 2 or 3 sulfo groups are present. The other substituents are preferably a hydroxyl group, a carboxyl group, or a lower alkoxy group having a sulfo group.

In the formula (I), when m =1, that is, when m is an azo compound having a tetrazo structure and a is a phenyl group, a represents a phenyl group having a substituent, and the substituent preferably has at least 1 sulfo group, and when two or more substituents are present, at least 1 of the substituents is a sulfo group, and the other substituents are preferably a sulfo group, a lower alkyl group, a lower alkoxy group having a sulfo group, a carboxyl group, a nitro group, an amino group, or a substituted amino group. More preferably sulfo, methyl, ethyl, methoxy, ethoxy, carboxyl, nitro, amino, particularly preferably sulfo, lower alkyl, lower alkoxy; the lower alkoxy group having a sulfo group is preferably a linear alkoxy group, and the substitution position of the sulfo group is preferably an alkoxy terminal, more preferably 3-sulfopropoxy or 4-sulfobutoxy, and particularly preferably 3-sulfopropoxy. The number of the substituents is preferably 2, the position of the substitution is not particularly limited, and a combination of 2-position and 4-position is preferred.

In the formula (I), X represents a substituted or unsubstituted benzoylamino group, a substituted or unsubstituted phenylamino group, a substituted or unsubstituted phenylazo group, or a substituted or unsubstituted naphthotriazole group, and when X is a substituted or unsubstituted benzoylamino group, a substituted or unsubstituted phenylamino group, or a substituted or unsubstituted phenylazo group, as a substituent thereof, a lower alkyl group, a lower alkoxy group, a hydroxyl group, a carboxyl group, a sulfo group, an amino group, or a substituted amino group is preferable; in the case where X is a naphthotriazolyl group which may or may not have a substituent, the substituent is preferably a sulfo group. When X is a phenylamino group which may or may not have a substituent, the substituent is preferably a methyl group, a methoxy group, an amino group, a substituted amino group, or a sulfo group, and the substitution position is not particularly limited, but is particularly preferably a para-position. When X is a substituted benzoylamino group, the substituent is preferably an amino group, a substituted amino group, or a hydroxyl group, and particularly preferably an amino group. The substitution position is not particularly limited, but the para position is particularly preferable. When X is a substituted phenylazo group, the substituent is preferably a hydroxyl group, an amino group, a methyl group, a methoxy group, or a carboxyl group, and particularly preferably a hydroxyl group. In any of the above cases, the number of substituents may be 2 or more, and may be the same or different types of substituents.

In order to further improve the optical properties, the dye represented by formula (I) preferably has a structure as shown in formula (III). R₁～R₆Each independently represents a hydrogen atom, a lower alkyl group, a lower alkoxy group, a sulfo group or a lower alkoxy group having a sulfo group, more preferably a hydrogen atom, a methyl group, an ethyl group, a methoxy group, an ethoxy group, a sulfo group; the lower alkoxy group having a sulfo group is a linear alkoxy group, and the substitution position of the sulfo group is an alkoxy end, and is more preferably a 3-sulfopropoxy group or a 4-sulfobutoxy group. Particularly preferred are a hydrogen atom, a methyl group, a methoxy group and a 3-sulfopropoxy group. As the substitution position, only the 2-position, only the 5-position, a combination of the 2-position and the 6-position, a combination of the 2-position and the 5-position, and a combination of the 3-position and the 5-position are preferable, and a combination of only the 2-position, only the 5-position, and the 2-position and the 5-position is particularly preferable.

[ solution 6]

The optical properties of the polarizing element using the dye represented by the above formulae (I) and (III) and using a polyvinyl alcohol resin film having a polymerization degree of 5000 to 10000 are greatly improved. In the lower alkyl group, the lower alkoxy group and the lower alkoxy group having a sulfo group, the lower group represents an alkyl group and an alkoxy group having 1 to 5 carbon atoms.

Next, specific examples of the azo compound represented by the above formula (I) used in the present invention are given below. In the formula, sulfo, carboxyl and hydroxyl groups are shown as free acids.

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The azo compound represented by the above formula (I) or a salt thereof can be easily produced by diazotization and coupling, which are well known in the production method of an azo dye in general described in non-patent document 1.

When a in the compound of formula (I) is a phenyl group having at least 1 sulfonic acid group, an aromatic amine or a phenol represented by formula (IV) is sulfoalkylated by a production method shown in patent document 7 (jp 2004-075719 a), the obtained sulfoalkoxyaniline is diazotized, and primary coupling is performed with an aniline represented by formula (a) to obtain a monoazo amino compound represented by formula (B).

[ solution 97]

(wherein, in the case where m =0, R₁₃And R₁₄One of them is a sulfo group, and the other represents a hydrogen atom, a sulfo group, a lower alkyl group, a carboxyl group or a lower alkoxy group; when m =1, at least 1 of the substituents is a sulfo group, and the other substituents represent a sulfo group, a lower alkyl group, a lower alkoxy group having a sulfo group, a carboxyl group, a nitro group, an amino group, or a substituted amino group. )

[ solution 98]

When a in the compound of formula (I) is a naphthyl group having at least 1 sulfonic acid group, a naphthylamine sulfonic acid group or an aminonaphthol sulfonic acid group represented by formula (a1) is sulfoalkylated, the obtained sulfoalkoxynaphthylamine sulfonic acid group is diazotized, and primary coupling is performed with an aniline of formula (a) by a production method shown on page 35 of patent document 7 to obtain a monoazo amino compound represented by formula (B) below.

[ solution 99]

(in the formula, R₁₁Represents a hydrogen atom, a hydroxyl group or a lower alkoxy group having a sulfo group, and n represents 1 to 3. )

[ solution 100]

(in the formula, A, R₁And R₂A, R in the above formula (I)₁And R₂The same meaning is used. )

Then, the monoazo amino compound represented by the formula (B) is diazotized and secondarily coupled with an aniline represented by the following formula (C) to obtain a disazo amino compound represented by the following formula (D).

[ solution 101]

(in the formula, R₃And R₄R in the formula (I)₃And R₄The same meaning is used. )

[ solution 102]

(in the formula, A, R₁、R₂、R₃And R₄A, R in the above formula (I)₁、R₂、R₃And R₄The same meaning is used. )

When m =1, the diazotization of the diazoamino compound represented by formula (D) and the three-time coupling with the aniline represented by formula (E) give a trisazo amino compound represented by formula (F).

[ solution 103]

(in the formula, R₅And R₆R in the formula (I)₅And R₆The same meaning is used. )

[ solution 104]

(in the formula, A, R₁、R₂、R₃、R₄、R₅And R₆A, R in the above formula (I)₁、R₂、R₃、R₄、R₅And R₆The same meaning is used. )

The azo compound as the compound of formula (I) is obtained by diazotizing formula (D) when m =0, diazotizing formula (F) when m =1, and coupling with a naphthol represented by the following formula (G).

[ solution 105]

(wherein X represents the same meaning as X in the above formula (I))

In the above reaction, the diazotization step may be carried out by a forward method of mixing a nitrite such as sodium nitrite in an aqueous solution or suspension of an inorganic acid such as hydrochloric acid or sulfuric acid as the diazotization component, or by a reverse method of adding a nitrite to a neutral or weakly alkaline aqueous solution of the diazotization component in advance and mixing it with an inorganic acid. The temperature of diazotization is proper between-10 ℃ and 40 ℃. In the coupling step with anilines, an acidic aqueous solution such as hydrochloric acid or acetic acid is mixed with each of the diazo solutions, and the coupling step is performed under acidic conditions of-10 ℃ to 40 ℃ and a pH of 2 to 7.

The monoazo compound, disazo compound and trisazo compound obtained by coupling may be removed by filtration as they are or by precipitation by acid precipitation or salting out, or may be directly subjected to the next step as a solution or suspension. When the diazonium salt is poorly soluble and becomes a suspension, the suspension can be filtered and used as a cake in the next coupling step.

For use in primary, secondary and tertiary couplings with R₁～R₆The aniline having a substituent(s) of (1) may be a specific process for producing an aniline having an alkoxy group containing a sulfo groupSulfoalkoxyanilines are obtained by sulfoalkylating and reducing phenols by a method disclosed on page 35 of patent document 7, and are used in a coupling step.

The fourth coupling reaction of the diazotized trisazo amino compound and the naphthol represented by the formula (G) is carried out under neutral to alkaline conditions at a temperature of-10 ℃ to 40 ℃ and a pH of 7 to 10. After the reaction, the salt is precipitated by salting out and removed by filtration. When purification is required, salting out may be repeated or precipitation from water may be performed using an organic solvent. Examples of the organic solvent used for purification include alcohols such as methanol and ethanol; water-soluble organic solvents such as ketones, e.g., acetone.

The aromatic amine represented by the formula (A), which is a starting material for synthesizing the water-soluble dye represented by the formula (I), has a substituent (R) as the substituent₁、R₂) Examples thereof include a hydrogen atom, a sulfo group, a lower alkyl group, a lower alkoxy group having a sulfo group, a carboxyl group, a naphthotriazolyl group substituted with a sulfonic group or the like, a nitro group, an amino group, or an acetamido group, preferably a hydrogen atom, a sulfo group, a lower alkyl group, or a lower alkoxy group, more preferably at least 1 of the substituents thereof is a sulfo group, and further preferably the number of substituents is 2. The lower alkoxy group having a sulfo group is preferably a linear alkoxy group, and the substitution position of the sulfo group is preferably at the alkoxy terminal. Here, the lower alkoxy group preferably represents an alkoxy group having 1 to 5 carbon atoms, and among lower alkoxy groups having a sulfo group, any of 3-sulfopropoxy and 4-sulfobutoxy is preferable. When a in the formula (I) is a substituted phenyl group, examples of the compound of the formula (IV) as a raw material compound include: 4-aminobenzenesulfonic acid, 3-aminobenzenesulfonic acid, 2-aminobenzenesulfonic acid, 4-aminobenzoic acid, 2-amino-5-methylbenzenesulfonic acid, 2-amino-5-methoxybenzenesulfonic acid, 4-amino-2-methylbenzenesulfonic acid, 3-amino-4-methoxybenzenesulfonic acid, 2-amino-4-sulfobenzoic acid, 2-amino-5-sulfobenzoic acid and the like, 5-aminoisophthalic acid, 2-amino-5-nitrobenzenesulfonic acid, 5-acetamide-2-aminobenzenesulfonic acid, 2-amino-5- (3-sulfopropoxy) benzenesulfonic acid, 4-aminobenzene-1, 3-di-aminobenzeneSulfonic acid, 2-aminobenzene-1, 4-disulfonic acid, etc., and particularly preferably 4-aminobenzenesulfonic acid, 2-amino-5-methoxybenzenesulfonic acid, 4-amino-2-methylbenzenesulfonic acid, 4-aminobenzene-1, 3-disulfonic acid. Further, a naphthotriazolyl group may be contained as the substituent for the phenyl group, and examples thereof include a 6, 8-disulfo-naphthotriazolyl group, a 7, 9-disulfo-naphthotriazolyl group, a 7-sulfo-naphthotriazolyl group, a 5-sulfo-naphthotriazolyl group and the like, and in this case, it is particularly preferable that the substituent is in the para-position to the phenylazo group. The substituent of the naphthylamine sulfonic acid group includes, for example, a hydrogen atom, a sulfo group, a hydroxyl group, a tosylated hydroxyl group, an amino group, a substituted amino group, a nitro group, a substituted amido group, a lower alkoxy group having a sulfo group, and the like, and is preferably a hydrogen atom, a sulfo group, a lower alkoxy group having a sulfo group. The lower alkoxy group having a sulfo group is preferably a linear alkoxy group, and the substitution position of the sulfo group is preferably at the alkoxy terminal. Here, the lower alkoxy group preferably represents an alkoxy group having 1 to 4 carbon atoms, and among lower alkoxy groups having a sulfo group, any of 3-sulfopropoxy and 4-sulfobutoxy is preferable. The number n of substituents of the sulfo group is preferably 1 to 3, and the position of the sulfo group may have a sulfo group on any benzene nucleus of the naphthalene ring, but the position of the sulfo group is preferably any one of the 1-position, 3-position and 6-position, or when 2 or more sulfo groups are present, the position of the sulfo group is preferably any combination of the 1-position, 3-position, 6-position and 7-position. Examples of the group of compounds represented by a1 include: 2-aminonaphthalene-1-sulfonic acid, 8-aminonaphthalene-1-sulfonic acid, 5-aminonaphthalene-2-sulfonic acid, 8-aminonaphthalene-2-sulfonic acid, 3-aminonaphthalene-1-sulfonic acid, 6-aminonaphthalene-2-sulfonic acid, 4-aminonaphthalene-1-sulfonic acid, 7-aminonaphthalene-1, 3-disulfonic acid, 6-aminonaphthalene-1, 3-disulfonic acid, 3-amino-7-nitronaphthalene-1, 5-disulfonic acid, 4-aminonaphthalene-1, 6-disulfonic acid, 4-aminonaphthalene-1, 5-disulfonic acid, 5-aminonaphthalene-1, 3-disulfonic acid, 3-aminonaphthalene-1, 5-disulfonic acid, 2-aminonaphthalene-1, 5-disulfonic acid, 4-aminonaphthalene-1, 6-disulfonic acid, 7-aminonaphthalene-1, 3, 6-trisulfonic acid, 7-aminonaphthalene-1, 3, 5-trisulfonic acid, 8-aminonaphthalene-1, 3, 6-trisulfonic acid, 5-aminonaphthalene-1, 3, 6-trisulfonic acid, 7-amino-3- (3-sulfopropoxy) naphthalene-1-sulfonic acid, 7-amino-3- (4-sulfobutoxy) naphthalene-1-sulfonic acid, 7-amino-4- (3-sulfopropoxy) naphthalene-2-sulfonic acid, 7-amino-4- (4-sulfobutoxy) naphthalene-2-sulfonic acid, 6-ammoniaPhenyl-4- (3-sulfopropoxy) naphthalene-2-sulfonic acid, 6-amino-4- (4-sulfobutoxy) naphthalene-2-sulfonic acid, 2-amino-5- (3-sulfopropoxy) naphthalene-1, 7-disulfonic acid, 6-amino-4- (3-sulfopropoxy) naphthalene-2, 7-disulfonic acid, or 7-amino-3- (3-sulfopropoxy) naphthalene-1, 5-disulfonic acid, etc., preferably 7-aminonaphthalene-1, 3-disulfonic acid, 6-aminonaphthalene-1, 3-disulfonic acid, 7-aminonaphthalene-1, 3, 6-trisulfonic acid, 7-amino-4- (3-sulfopropoxy) naphthalene-2-sulfonic acid, etc, 6-amino-4- (3-sulfopropoxy) naphthalene-2-sulfonic acid, particularly preferably 7-aminonaphthalene-1, 3-disulfonic acid, 7-aminonaphthalene-1, 3, 6-trisulfonic acid, 7-amino-4- (3-sulfopropoxy) naphthalene-2-sulfonic acid.

Having substituents (R) for the primary, secondary and tertiary coupling components₁～R₆) The aniline of (1) shows a hydrogen atom, a lower alkyl group, a lower alkoxy group, or a lower alkoxy group having a sulfo group as a substituent, and is preferably a hydrogen atom, a methyl group, a methoxy group, or a 3-sulfopropoxy group, a 4-sulfobutoxy group, or a carboxyl group, and more preferably a hydrogen atom, a methyl group, a methoxy group, or a 3-sulfopropoxy group. 1 or 2 of these substituents may be bonded. The bonding positions thereof are preferably 2-position, 3-position and 2-position and 5-position, 3-position and 5-position, or 2-position and 6-position, preferably 3-position and 2-position and 5-position, with respect to the amino group. Examples of the aniline having a lower alkoxy group containing a sulfo group include: 3- (2-amino-4-methylphenoxy) propane-1-sulfonic acid, 3- (2-aminophenoxy) propane-1-sulfonic acid, 3- (2-amino-4-methylphenoxy) butane-1-sulfonic acid, and the like. Examples of the aniline other than these include aniline, 2-methylaniline, 3-methylaniline, 2-ethylaniline, 3-ethylaniline, 2, 5-dimethylaniline, 2, 5-diethylaniline, 2-methoxyaniline, 3-methoxyaniline, 2-methoxy-5-methylaniline, 2, 5-dimethoxyaniline, 3, 5-dimethylaniline, 2, 6-dimethylaniline and 3, 5-dimethoxyaniline. The amino groups of these anilines may be protected. Examples of the protecting group include an ω -methane sulfonic group thereof. The aniline used for the first coupling may be the same as or different from the aniline used for the second coupling.

X as the 3-time coupling component at m =0 and the 4-time coupling component at m =1 is a benzoylamino group with or without a substituent, a phenylamino group with or without a substituent, a phenylazo group with or without a substituent, or a naphthotriazolyl group with or without a substituent, and the substituents are preferably a hydrogen atom, a lower alkyl group, a lower alkoxy group, a hydroxyl group, a carboxyl group, a sulfo group, or an amino group with or without a substituent, respectively.

When X is a substituted or unsubstituted phenylamino group, the substituent (R) represented by the formula (H) is preferably a substituted group₉、R₁₀) The phenylamino group of (a). Substituent (R)₉、R₁₀) Each independently represents a hydrogen atom, a methyl group, a methoxy group, a sulfo group, an amino group or a substituted amino group, more preferably a hydrogen atom, a methyl group, a methoxy group or an amino group, and further preferably at least 1 substituent is in the para-position to the amino group. Examples thereof include phenylamino, 4-methylphenylamino, 4-methoxyphenylamino, 4-aminophenylamino, 4-amino-2-sulfophenylamino, 4-amino-3-sulfophenylamino, 4-sulfomethylaminophenylamino and 4-carboxyethylaminophenylamino.

[ solution 106]

When X is a substituted or unsubstituted benzoylamino group, the substituted group (R) represented by the formula (J) is preferably₁₁) The benzoylamino group of (1). Substituent (R)₁₁) Represents a hydrogen atom, an amino group or an amino group having or not having a substituent, and the substitution position is more preferably a para position. Examples of the benzoylamino group which may or may not have a substituent include a benzoylamino group, a 4-aminobenzoylamino group, a 4-hydroxybenzoylamino group, a 4-carboxyethylaminobenzamido group and the like.

[ solution 107]

When X is a substituted or unsubstituted naphthotriazolyl group, the naphthotriazolyl group having a sulfo group represented by the formula (K) is preferable. J represents 1 or 2, preferably 2, and examples thereof include a 6, 8-disulfo-naphthotriazolyl group, a 7, 9-disulfo-naphthotriazolyl group, a 7-sulfonaphthotriazolyl group, a 5-sulfonaphthotriazolyl group and the like. When X is a substituted or unsubstituted naphthotriazole group, the substituent (R) is a substituent(s) for the secondary coupling component when m =0₃～R₄) When the substituent in the aniline compound (2) has 1 or 2 methoxy groups, a copper complex compound can be formed with amino-3-sulfonic acid-1-naphthol. The copper complex salt compound may be treated with copper sulfate or the like by a known method to prepare a copper complex salt compound. When X is a substituted or unsubstituted naphthotriazole group, examples of the secondary coupling component in the case where m =0, which is capable of producing the copper complex salt compound, include 2-methoxyaniline, 2-methoxy-5-methylaniline, 2, 5-dimethoxyaniline, 3, 5-dimethylaniline, 2, 6-dimethylaniline, 3, 5-dimethoxyaniline, and the like. The amino groups of these anilines may be protected. Examples of the protecting group include an ω -methane sulfonic group thereof. The aniline used for the first coupling may be the same as or different from the aniline used for the second coupling.

[ solution 108]

The compound represented by formula (I) of the present invention may exist in the form of a free acid, or may exist in the form of a salt thereof. Examples of the salt include an alkali metal salt, an alkaline earth metal salt, an alkylamine salt, an alkanolamine salt, and an ammonium salt. When dyeing a substrate for a polarizing film, a salt of sodium, potassium or ammonium is preferable. The salt of the compound represented by formula (I) can be isolated as a free acid by adding an inorganic acid after the coupling reaction, and then washed with water or acidified water to remove the inorganic salt. The acid-type pigments thus obtained with a low salt content can then be prepared as solutions of the corresponding salts by neutralization in an aqueous medium with the desired inorganic or organic bases. Alternatively, a desired salt can be prepared by preparing a sodium salt using, for example, sodium chloride or the like at the time of salting out after the coupling reaction, or by preparing a potassium salt using, for example, potassium chloride. Further, a copper complex salt compound can be produced by treatment with copper sulfate or the like.

In the dye-based polarizing element or dye-based polarizing plate of the present invention, the azo compound represented by the above formula (I), a salt thereof, or a transition metal complex thereof may be used alone or in combination with 2 or more kinds thereof, and one or more kinds of other organic dyes may be used in combination as necessary. The organic dye to be used in combination is not particularly limited, but is preferably an organic dye that dyes a hydrophilic polymer, and the dye has absorption characteristics in a wavelength region different from the absorption wavelength region of the azo compound or salt thereof of the present invention, and is highly dichroic. Typical examples thereof include the following dyes: examples thereof include c.i. direct yellow 12, c.i. direct yellow 28, c.i. direct yellow 44, c.i. direct orange 26, c.i. direct orange 39, c.i. direct orange 71, c.i. direct orange 107, c.i. direct red 2, c.i. direct red 31, c.i. direct red 79, c.i. direct red 81, c.i. direct red 247, c.i. direct green 80, and c.i. direct green 59, and these dyes can be selected according to the purpose and are not limited thereto. These pigments are used in the form of free acids, or salts of alkali metal salts (e.g., Na salt, K salt, Li salt), ammonium salts, and amines.

When other organic dyes are used in combination as necessary, the types of dyes to be mixed with the objective polarizing element are different depending on the neutral-color polarizing element, the color polarizing element for a liquid crystal projector, and the other color polarizing element. The mixing ratio is not particularly limited, and generally, the total amount of at least one of the organic dyes is preferably in the range of 0.1 to 10 parts by weight based on the weight of the azo compound of the formula (I) or a salt thereof.

After the dyeing step and before proceeding to the next step, a washing step (hereinafter referred to as washing step 1) can be performed. The cleaning step 1 is a step of cleaning the dye solvent adhering to the surface of the polyvinyl alcohol resin film in the dyeing step. By performing the washing step 1, the transfer of the dye into a liquid to be treated later can be suppressed. In the cleaning step 1, water is usually used. The cleaning method is preferably performed by immersing the polyvinyl alcohol resin film in the solution, but the cleaning method may be performed by applying the solution to the polyvinyl alcohol resin film. The cleaning time is not particularly limited, but is preferably 1 second to 300 seconds, and more preferably 1 second to 60 seconds. The temperature of the solvent in the cleaning step 1 needs to be a temperature at which the hydrophilic polymer is not dissolved. The washing treatment is usually carried out at 5 to 40 ℃.

The dyeing step or the washing step 1 may be followed by a step containing a crosslinking agent and/or a water-resistant agent. As the crosslinking agent, for example, a boron compound such as boric acid, borax, or ammonium borate; polyaldehydes such as glyoxal and glutaraldehyde; polyisocyanate-based compounds such as biuret-type, isocyanurate-type and blocked-type compounds; titanium compounds such as titanyl sulfate, etc., and ethylene glycol glycidyl ether, polyamide epichlorohydrin, etc. can also be used. Examples of the water-resistant agent include succinic peroxide, ammonium persulfate, calcium perchlorate, benzoin ethyl ether, ethylene glycol diglycidyl ether, glycerol diglycidyl ether, ammonium chloride, and magnesium chloride, and boric acid is preferably used. The step of containing a crosslinking agent and/or a water-resistant agent is performed using at least one of the crosslinking agent and/or the water-resistant agent described above. The solvent in this case is preferably water, but is not limited thereto. In the step of containing the crosslinking agent and/or the water-resistant additive, when boric acid is used as an example of the concentration of the crosslinking agent and/or the water-resistant additive in the solvent, the concentration is preferably 0.1 to 6.0% by weight, more preferably 1.0 to 4.0% by weight, based on the solvent. The temperature of the solvent in this step is preferably 5 to 70 ℃ and more preferably 5 to 50 ℃. The method of incorporating the crosslinking agent and/or the water-resistant agent into the polyvinyl alcohol resin film is preferably a method of immersing in the solution, but the solution may be coated or coated on the polyvinyl alcohol resin film. The treatment time in this step is preferably 30 seconds to 6 minutes, more preferably 1 minute to 5 minutes. However, the crosslinking agent and/or the water-resistant agent are not essential, and when the time is to be shortened, the crosslinking treatment or the water-resistant treatment is not necessary, the 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-resistant chemical, the stretching step is performed. The stretching step is a step of uniaxially stretching the polyvinyl alcohol film. The stretching method may be either a wet stretching method or a dry stretching method, and the present invention can be achieved by stretching at a stretching ratio of 3 times or more. The stretching ratio may be 3 times or more, preferably 5 to 7 times.

In the case of the dry stretching method, when the stretching heating medium is an air medium, the stretching is preferably performed at a temperature of the air medium of from room temperature to 180 ℃. The treatment is preferably performed in an atmosphere having a humidity of 20% RH to 95% RH. Examples of the heating method include, but are not limited to, an inter-roll zone stretching method, a roll heating stretching method, a pressure stretching method, an infrared heating stretching method, and the like. The stretching step may be performed by 1-stage stretching, or may be performed by 2-stage or more stretching.

In the wet stretching method, stretching is performed in water, a water-soluble organic solvent, or a mixed solution thereof. The stretching treatment is preferably performed while being immersed in a solution containing a crosslinking agent and/or a water-resistant agent. As the crosslinking agent, for example, a boron compound such as boric acid, borax, or ammonium borate; polyaldehydes such as glyoxal and glutaraldehyde; polyisocyanate-based compounds such as biuret-type, isocyanurate-type and blocked-type compounds; titanium compounds such as titanyl sulfate, etc., and ethylene glycol glycidyl ether, polyamide epichlorohydrin, etc. can also be used. Examples of the water-resistant agent include succinic peroxide, ammonium persulfate, calcium perchlorate, benzoin ethyl ether, ethylene glycol diglycidyl ether, glycerol diglycidyl ether, ammonium chloride, and magnesium chloride. Stretching is performed in a solution containing at least one or more of the crosslinking agents and/or the water-resistant agents shown above. The crosslinking agent is preferably boric acid. The concentration of the crosslinking agent and/or the water resistance improver in the stretching step is, for example, preferably 0.5 to 15 wt%, more preferably 2.0 to 8.0 wt%. The stretching ratio is preferably 2 to 8 times, and more preferably 5 to 7 times. The treatment is preferably carried out at a stretching temperature of 40 to 60 ℃ and more preferably 45 to 58 ℃. The stretching time is usually 30 seconds to 20 minutes, and more preferably 2 minutes to 5 minutes. The wet stretching step may be performed by 1-stage stretching, or may be performed by 2-stage or more stretching.

After the stretching step, precipitates or foreign matters of the crosslinking agent and/or the water-resistant agent may adhere to the film surface, and therefore, a cleaning step (hereinafter referred to as cleaning step 2) of cleaning the film surface can be performed. The washing time is preferably 1 second to 5 minutes. The cleaning method is preferably a method of immersing in a cleaning solution, but cleaning can also be performed by coating or applying the solution on a polyvinyl alcohol resin film. The cleaning treatment may be performed in 1 stage, or a multi-stage treatment of 2 stages or more may be performed. The temperature of the solution in the washing step is not particularly limited, but is usually 5 to 50 ℃ and preferably 10 to 40 ℃.

Examples of the solvent used in the treatment step include water; dimethyl sulfoxide; n-methyl pyrrolidone; alcohols such as methanol, ethanol, propanol, isopropanol, glycerol, ethylene glycol, propylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, and trimethylolpropane; and amines such as ethylenediamine and diethylenetriamine, but not limited thereto. Also, a mixture of 1 or more of these solvents may be used. The most preferred solvent is water.

After the stretching step or the cleaning step 2, a film drying step is performed. The drying treatment can be performed by natural drying, but in order to further improve the drying efficiency, the surface may be dehydrated by compression with a roller, an air knife, a water suction roller, or the like, and/or may be dried by air blowing. The drying temperature is preferably 20 to 100 ℃ and more preferably 60 to 100 ℃. The drying treatment time can be applied for 30 seconds to 20 minutes, preferably 5 minutes to 10 minutes.

The polyvinyl alcohol resin film polarizing element of the present invention having improved optical characteristics and durability can be obtained by the above method.

In the obtained polarizing element, a transparent protective layer is provided on one surface or both surfaces thereof to prepare a polarizing plate. The transparent protective layer can be provided in the form of a coating layer using a polymer or in the form of a laminate layer of films. 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. Examples of the substance used as the transparent protective layer include cellulose acetate resins such as triacetyl cellulose and diacetyl cellulose, and films thereof; an acrylic resin or a film thereof; a polyvinyl chloride resin or a film thereof; nylon resin or a film thereof; polyester resins or films thereof; a polyarylate resin or a film thereof; a cyclic polyolefin resin or film thereof using a cyclic olefin such as norbornene as a monomer; polyethylene, polypropylene, polyolefins having a cyclic or norbornene skeleton or copolymers thereof; a resin or polymer having an imide and/or amide as a main chain or a side chain, a film thereof, or the like. Further, as the transparent protective layer, a resin having liquid crystallinity or a film thereof may be provided. The thickness of the protective film is, for example, about 0.5 μm to 200 μm. The polarizing plate is produced by providing 1 or more layers of the same or different resins or films on one or both surfaces.

As described above, an adhesive is required to bond the transparent protective layer to the polarizing element. The binder is not particularly limited, and a polyvinyl alcohol-based binder is preferable. Examples of the polyvinyl alcohol-based adhesive include, but are not limited to, Gohsenol NH-26 (manufactured by Nippon synthetic Co., Ltd.), Exceval RS-2117 (manufactured by KURARAAY Co., Ltd.). A cross-linking agent and/or a water resistance agent may be added to the cement. The polyvinyl alcohol-based adhesive uses a maleic anhydride-isobutylene copolymer, but if necessary, an adhesive mixed with a crosslinking agent can be used. Examples of the maleic anhydride-isobutylene copolymer include Isobam # 18 (manufactured by KURAAY corporation), Isobam # 04 (manufactured by KURAAY corporation), ammonia-modified Isobam # 104 (manufactured by KURAAY corporation), ammonia-modified Isobam # 110 (manufactured by KURAAY corporation), imidized Isobam # 304 (manufactured by KURAAY corporation), and imidized Isobam # 310 (manufactured by KURAAY corporation). In this case, a water-soluble polyepoxy compound may be used as the crosslinking agent. Examples of the water-soluble polyvalent epoxy compound include Denacol EX-521 (manufactured by Nagase ChemteX) and Tetoratto-C (manufactured by Mitsui gas Chemicals). As the adhesive other than the polyvinyl alcohol resin, known adhesives such as urethane, acrylic, and epoxy adhesives can be used. In addition, in order to improve the adhesion of the adhesive or to improve the water resistance, an additive such as a zinc compound, chloride, or iodide may be added at a concentration of about 0.1 to 10 wt%. The additive is not limited either. After the transparent protective layer is bonded with an adhesive, the resulting laminate is dried or heat-treated at an appropriate temperature to obtain a polarizing plate.

In the case where the obtained polarizing plate is bonded to a display device such as a liquid crystal display or an organic electroluminescence display in some cases, various functional layers for improving a viewing angle and/or a contrast, or a layer or a film having a luminance improving property may be provided on the surface of a protective layer or a film which is not exposed later. In order to bond the polarizing plate to the film or the display device, an adhesive is preferably used.

The other surface of the polarizing plate, i.e., the exposed surface of the protective layer or the film, may have various known functional layers such as an antireflection layer, an antiglare layer, and a hard coat layer. In order to produce the layers having various functionalities, a coating method is preferred, but a film having such a function may be bonded via an adhesive or a pressure-sensitive adhesive. In addition, various functional layers may be made into a layer or a film that controls the phase difference.

By the above method, optimization of film physical properties and an optimum dye structure can be designed in the polyvinyl alcohol resin film having a polymerization degree of 5000 to 10000 of the present invention, and thus a polarizing element and a polarizing plate having improved optical characteristics and improved durability against light, heat and humidity can be obtained. A liquid crystal display device using the polarizing element or the polarizing plate of the present invention has high reliability, high contrast for a long period of time, and high color reproducibility.

The polarizing element or polarizing plate of the present invention thus obtained is provided with a protective layer, a functional layer, a support, and the like as necessary, and is used for a liquid crystal projector, a desktop computer, a timepiece, a notebook computer, a word processor, a liquid crystal television, a polarizing lens, polarizing glasses, a satellite navigation, an indoor/outdoor meter, a display, and the like.

As a method of applying the polarizing plate of the present invention, it can be used in the form of a polarizing plate with a support. For attaching the polarizing plate, the support preferably has a flat surface portion, and for optical use, the support is preferably a glass molded product. Examples of the glass molded article include a glass plate, a lens, and an optical prism (e.g., a triangular optical prism and a cubic optical prism). The lens to which the polarizing plate is attached can be used as a condenser lens with a polarizing plate in a liquid crystal projector. In addition, the optical prism to which the polarizing plate is attached can be used as a polarizing beam splitter with a polarizing plate or a dichroic prism with a polarizing plate in a liquid crystal projector. In addition, the film can also be attached to a liquid crystal box. Examples of the material of the glass include inorganic glasses such as soda glass, borosilicate glass, an inorganic mount made of crystal, and an inorganic mount made of sapphire; organic plastic plates such as acrylic and polycarbonate, and inorganic glass are preferred. The thickness and size of the glass plate may be set to desired dimensions. In the polarizing plate with glass, in order to further improve the single-plate light transmittance, it is preferable to provide an AR layer on one or both of the glass surface and the polarizing plate surface. For such a support, for example, a transparent adhesive (tacky) is applied to the flat surface of the support, and then the polarizing plate of the present invention is attached to the applied surface. Alternatively, a transparent adhesive (pressure-sensitive adhesive) may be applied to the polarizing plate, and then a support may be attached to the applied surface. The adhesive (pressure-sensitive adhesive) used herein is preferably an acrylate-based adhesive, for example. When the polarizing plate is used as an elliptically polarizing plate, the retardation plate side is usually attached to the support side, but the polarizing plate side may be attached to the glass molded article.

Examples

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples. The transmittance shown in the examples was evaluated in the following manner.

The respective transmittances were measured using a spectrophotometer ("U-4100" manufactured by Hitachi Ltd.).

When the transmittance was measured using a spectrophotometer ("U-4100" manufactured by Hitachi Ltd.), an iodine-based polarizing plate (SKN-18043P manufactured by Polatechno) having a transmittance of 43% and a degree of polarization of 99.99% after visual sensitivity correction in accordance with JIS-Z8701 (a 2 ℃ visual field from a C light source) was provided on the light emission side so that absolute polarized light could be incident on the measurement sample. The protective layer of the iodine-based polarizer in this case was triacetyl cellulose having no ultraviolet absorption ability.

The polarization plate of the present invention is subjected to incidence of absolute polarized light, and the vibration direction of the absolute polarized light is measured to be orthogonal to the absorption axis direction of the polarization plate of the present invention (the absorption axis of the absolute polarizer is parallel to the absorption axis of the polarization plate of the present invention), and the obtained absolute parallel transmittance at each wavelength is represented by Ky; the vibration direction of the absolute polarized light was measured in parallel to the absorption axis direction of the polarizing plate of the present invention (the absorption axis of the absolute polarizer was perpendicular to the absorption axis of the polarizing plate of the present invention), and the obtained absolute perpendicular transmittance for each wavelength was Kz.

From Ky and Kz of each wavelength, the monomer transmittance Ts of each wavelength is calculated by the formula (L), and the degree of polarization ρ of each wavelength is calculated by the formula (M).

Monomer transmittance Ts = (Ky + Kz)/2 · · formula (L)

Degree of polarization ρ = (Ky-Kz)/(Ky + Kz) · · equation (M)

The azo compounds used in the following examples were synthesized by the following methods, respectively.

Synthesis example 1 Synthesis of Compound example 12

20.3 parts of 2-amino-5-methoxybenzenesulfonic acid is added to 500 parts of water, dissolved with sodium hydroxide, cooled to 10 ℃ or below, added with 32 parts of 35% hydrochloric acid, then added with 6.9 parts of sodium nitrite, and stirred at 5 ℃ to 10 ℃ for 1 hour. To this solution, 13.7 parts of 2, 5-dimethylaniline dissolved in dilute hydrochloric acid water was added, and while stirring at 30 to 40 ℃, sodium carbonate was added to adjust the pH to 3, and further stirring was performed to complete the coupling reaction, followed by filtration to obtain a monoazo compound. To the obtained monoazo compound, 32 parts of 35% hydrochloric acid was added, followed by 6.9 parts of sodium nitrite, and the mixture was stirred at 25 to 30 ℃ for 2 hours. To this, 12.1 parts of 2, 5-dimethylaniline dissolved in dilute hydrochloric acid water was added, and while stirring at 20 to 30 ℃, sodium carbonate was added to adjust the pH to 3, and further stirring was performed to complete the coupling reaction, followed by filtration to obtain a diazo compound. 15 parts of the obtained diazo compound was dispersed in 600 parts of water, and then 32 parts of 35% hydrochloric acid and 6.9 parts of sodium nitrite were added, followed by stirring at 25 ℃ to 30 ℃ for 2 hours to conduct diazotization. On the other hand, 35.8 parts of 6- (4' -aminobenzoyl) amino-3-sulfonic acid-1-naphthol (common name: aminobenzoyl J acid) was added to 250 parts of water, dissolved by adjusting the pH to weak alkalinity with sodium carbonate, and the solution was poured with the diazo compound of the diazo compound obtained previously so that the pH was maintained at 7 to 10, and stirred to complete the coupling reaction. Salting out with sodium chloride, and filtration were carried out to obtain the trisazo compound shown in compound example 12 of the present invention as a sodium salt.

Synthesis example 2 Synthesis of Compound example 14

The trisazo compound shown in compound example 14 was obtained as a sodium salt in the same manner as in synthesis example 1 except that 6- (4 '-aminobenzoyl) amino-3-sulfonic acid-1-naphthol (common name: aminobenzoyl J acid) in synthesis example 1 was changed to 6- (4' -benzoylphenyl) amino-3-sulfonic acid-1-naphthol (common name: benzoyl J acid).

Synthesis example 3 Synthesis of Compound example 17

The trisazo compound shown in compound example 17 was obtained as a sodium salt in the same manner as in synthesis example 1 except that 6- (4 '-aminobenzoyl) amino-3-sulfonic acid-1-naphthol (common name: aminobenzoyl J acid) in synthesis example 1 was changed to 6- (4' -methoxyphenyl) amino-3-sulfonic acid-1-naphthol.

Synthesis example 4 Synthesis of Compound example 18

A trisazo compound shown in compound example 18 was obtained as a sodium salt in compound example 17 of [ synthetic example 3] except that the 1 st coupling agent was changed from 2, 5-dimethylaniline to 3- (2-amino-4-methylphenoxy) propane-1-sulfonic acid.

Synthesis example 5 Synthesis of Compound example 20

The trisazo compound shown in compound example 20 was obtained as a sodium salt in the same manner as in synthesis example 1 except that 6- (4' -aminobenzoyl) amino-3-sulfonic acid-1-naphthol (common name: aminobenzoyl J acid) in synthesis example 1 was changed to 6- (4-amino-3-sulfophenyl) amino-3-sulfonic acid-1-naphthol.

Synthesis example 6 Synthesis of Compound example 22

A trisazo compound shown in compound example 22 was obtained as a sodium salt in the same manner as in synthesis example 5 except that 2-amino-5-methoxybenzenesulfonic acid as a raw material compound was changed to 36.1 parts of 7-amino-3- (3-sulfopropoxy) naphthalene-1-sulfonic acid.

Synthesis example 7 Synthesis of Compound example 36

Adding 38.3 parts of 7-aminonaphthalene-1, 3, 6-trisulfonic acid to 500 parts of water, cooling to below 10 ℃, adding 31.3 parts of 35% hydrochloric acid, then adding 6.9 parts of sodium nitrite, stirring at 5-10 ℃ for 1 hour, and diazotizing. To this solution, 10.7 parts of 3-methylaniline dissolved in dilute hydrochloric acid water was added, and while stirring at 10 to 30 ℃, sodium carbonate was added to adjust the pH to 3, and further stirring was performed to complete the coupling reaction, followed by filtration to obtain 40.1 parts of a monoazo amino compound. The obtained monoazo amino compound was added to 400 parts of water, dissolved with sodium hydroxide, added with 25.0 parts of 35% hydrochloric acid at 10 to 30 ℃ and then with 5.5 parts of sodium nitrite, stirred at 20 to 30 ℃ for 1 hour, and diazotized. To this solution, 8.6 parts of 3-methylaniline dissolved in dilute hydrochloric acid water was added, and while stirring at 20 to 30 ℃, sodium carbonate was added to adjust the pH to 3, and further stirring was performed to complete the coupling reaction, followed by filtration to obtain 39.7 parts of a bisazo amino compound. The obtained diazoamino compound was added to 250 parts of water, dissolved with sodium hydroxide, added with 20.0 parts of 35% hydrochloric acid at 20 to 30 ℃ and then with 4.4 parts of sodium nitrite, stirred at 20 to 30 ℃ for 1 hour, and diazotized. To this solution, 7.7 parts of 2, 5-dimethylaniline dissolved in dilute hydrochloric acid water was added, and while stirring at 20 to 30 ℃, sodium carbonate was added to adjust the pH to 3.5, and further stirring was performed to complete the coupling reaction, followed by filtration to obtain 38.5 parts of a trisazo amino compound. The obtained trisazo amino compound was added to 200 parts of water, dissolved with sodium hydroxide, added with 16.0 parts of 35% hydrochloric acid at 20 to 30 ℃, then added with 3.5 parts of sodium nitrite, stirred at 20 to 30 ℃ for 1 hour, and diazotized. On the other hand, 16.1 parts of 6-aminophenyl-3-sulfonic acid-1-naphthol (conventional name: phenyl J acid) was added to 50 parts of water, dissolved by adjusting the pH to weak alkalinity with sodium carbonate, and the diazotized product of the trisazo amino compound obtained previously was poured into this solution so as to maintain the pH at 8 to 10, followed by stirring to complete the coupling reaction. Salting out with sodium chloride and filtration were carried out to obtain a tetrazo compound shown in compound example 36.

Synthesis example 8 Synthesis of Compound example 43

A tetrazo compound shown in Compound example 43 was obtained in the same manner as in Synthesis example 7 except that 6-aminophenyl-3-sulfonic acid-1-naphthol (common name: phenyl J acid) used in Synthesis of Compound example 36 was changed to 6- (6, 8-disulfo-naphthotriazole) -3-sulfonic acid-1-naphthol.

Synthesis example 9 Synthesis of Compound example 67

A tetrazo compound shown in Compound example 67 was obtained in the same manner as in Synthesis example 7 except that 7-aminonaphthalene-1, 3, 6-trisulfonic acid used in Synthesis of Compound example 36 in Synthesis [ Synthesis example 7] was changed to 4-aminobenzene-1, 3-disulfonic acid, and 6-aminophenyl-3-sulfonic acid-1-naphthol (common name: phenyl J acid) was changed to 6- (4-methoxyphenyl) amino-3-sulfonic acid-1-naphthol.

Synthesis example 10 Synthesis of Compound example 71

A tetrazo compound shown in Compound example 71 was obtained in the same manner as in Synthesis example 7 except that 7-aminonaphthalene-1, 3, 6-trisulfonic acid used in Synthesis of Compound example 36 in Synthesis [ Synthesis example 7] was changed to 4-aminobenzene-1, 3-disulfonic acid, and 6-aminophenyl-3-sulfonic acid-1-naphthol (common name: phenyl J acid) was changed to 6- (6, 8-disulfo-naphthotriazole) -3-sulfonic acid-1-naphthol.

Synthesis example 11 Synthesis of Compound example 72

A tetrazo compound shown in Compound example 72 was synthesized in the same manner as in Synthesis example 7 except that 7-aminonaphthalene-1, 3, 6-trisulfonic acid used in Synthesis of Compound example 36 was changed to 4-aminobenzene-1, 3-disulfonic acid and 6-aminophenyl-3-sulfonic acid-1-naphthol (common name: phenyl J acid) was changed to 6- (4' -aminobenzoyl) amino-3-sulfonic acid-1-naphthol (common name: aminobenzoyl J acid).

[ example 1]

A polyvinyl alcohol resin film (VF series manufactured by KURARAAY corporation) having a film thickness of 40 μm and a degree of saponification of 99% or more, a polymerization degree of 5500, and a swelling degree of 232% was immersed in warm water at 30 ℃ for 3 minutes to carry out a swelling treatment. The swollen membrane was immersed in a 35 ℃ aqueous solution containing 0.3 wt% of the dye of compound example 12, 0.1 wt% of sodium tripolyphosphate, and 0.1 wt% of sodium sulfate, and the dye was adsorbed. The film after the adsorption of the dye was washed with water, and after washing, boric acid treatment was performed for 1 minute with an aqueous solution at 20 ℃ containing 2% by weight of boric acid. The film obtained by the boric acid treatment was treated in an aqueous solution containing 3.0 wt% of boric acid at 58 ℃ for 5 minutes while being stretched 5.0 times. The film obtained by this boric acid treatment was treated with water at normal temperature for 5 seconds while maintaining the tension state. The film obtained by the treatment was immediately dried at 60 ℃ for 5 minutes to obtain a polarizing element having a monomer transmittance of 44% and a film thickness of 15 μm. A polarizing element using a polyvinyl alcohol film having a polymerization degree of 5500 was produced by the above method.

A polyvinyl alcohol-based adhesive was used for the polarizing element, and triacetyl cellulose films (TD-80U manufactured by Fuji photo film Co., Ltd., hereinafter abbreviated as TAC) having a film thickness of 80 μm after alkali treatment were laminated in such a configuration as TAC/adhesive layer/polarizing element/adhesive layer/TAC, and laminated to obtain polarizing plates, thereby obtaining measurement samples.

Similarly, a polarizing element was produced using a polyvinyl alcohol resin film having a film thickness of 75 μm and a polymerization degree of 2400 (VF-PS, manufactured by KURARAAY corporation), and a polarizing element using a polyvinyl alcohol film having a polymerization degree of 2400 was produced, and used for comparison of optical characteristics due to polymerization degrees. A polarizing plate using this polarizing element was also produced by laminating TAC films, and a measurement sample for comparison was prepared.

[ example 2]

A sample was prepared and a measurement sample was prepared in the same manner as in example 1, except that compound example 14 was used instead of compound example 12 used in example 1.

[ example 3]

A sample was prepared and a measurement sample was prepared in the same manner as in example 1, except that compound example 17 was used instead of compound example 12 used in example 1.

[ example 4]

A sample was prepared and a measurement sample was prepared in the same manner as in example 1, except that compound example 18 was used instead of compound example 12 used in example 1.

[ example 5]

A sample was prepared and a measurement sample was prepared in the same manner as in example 1, except that compound example 20 was used instead of compound example 12 used in example 1.

[ example 6]

A sample was prepared and a measurement sample was prepared in the same manner as in example 1, except that compound example 22 was used instead of compound example 12 used in example 1.

[ example 7]

A sample was prepared and a measurement sample was prepared in the same manner as in example 1, except that compound example 36 was used instead of compound example 12 used in example 1.

[ example 8]

A sample was prepared and a measurement sample was prepared in the same manner as in example 1, except that compound example 43 was used instead of compound example 12 used in example 1.

[ example 9]

A sample was prepared and a measurement sample was prepared in the same manner as in example 1, except that compound example 67 was used instead of compound example 12 used in example 1.

[ example 10]

A sample was prepared and a measurement sample was prepared in the same manner as in example 1, except that compound example 71 was used instead of compound example 12 used in example 1.

[ example 11]

A sample was prepared and a measurement sample was prepared in the same manner as in example 1, except that compound example 72 was used instead of compound example 12 used in example 1.

[ example 12]

A sample was prepared and a measurement sample was prepared in the same manner as in example 1, except that the swelling degree of the PVA having a polymerization degree of 5500 used in example 1 was 208%.

[ example 13]

A sample was prepared and a measurement sample was prepared in the same manner as in example 9 except that the degree of swelling of the PVA having a polymerization degree of 5500 used in example 9 was changed from 232% to 208%.

Comparative example 1

A sample was prepared in the same manner as in example 1, except that compound example 12 used in example 1 was prepared by changing the dye to a dye represented by the following formula (B1).

[ solution 109]

Comparative example 2

A sample was prepared in the same manner as in example 1, except that compound example 12 used in example 1 was prepared by changing the dye to a dye represented by the following formula (B2).

[ solution 110]

Comparative example 3

A sample was prepared in the same manner as in example 1, except that compound example 12 used in example 1 was prepared by changing the dye to a dye represented by the following formula (B3).

[ solution 111]

Comparative example 4

A sample was prepared in the same manner as in example 1, except that compound example 12 used in example 1 was prepared by changing the dye to a dye represented by the following formula (B4).

[ solution 112]

Table 1 shows the polarization characteristics of the samples obtained in examples 1 to 13 and comparative examples 1 to 4. The polarization characteristics show the degree of polarization ρ at which Ts is 44% at a wavelength (hereinafter abbreviated as λ max) at which each polarizing plate sample exhibits the maximum polarization characteristics. The polarization degrees at a polymerization degree of 5500 and a polymerization degree of 2400 are shown for the PVAs of examples and comparative examples.

[ Table 1]

From examples 1 to 13 and comparative examples 1 to 4, it was confirmed that the polarizing element and the polarizing plate of the present invention have improved characteristics and improved polarization characteristics when a polyvinyl alcohol resin having a polymerization degree of 5500 is used, compared to when a polyvinyl alcohol resin having a polymerization degree of 2400 is used. In contrast, in comparative examples 1 to 4, even when a polyvinyl alcohol resin having a polymerization degree of 5500 was used, the improvement in the characteristics was small, and particularly, the deterioration in the characteristics was observed in comparative example 4.

As is clear from examples 1 to 13 and comparative examples 1 to 4, polarizing plates having improved optical properties were obtained by using the polarizing element of the present invention. The polarizing plate thus obtained can be a polarizing element and a polarizing plate having improved durability against light, heat and humidity, and a liquid crystal display device and a polarizing lens using the polarizing element and the polarizing plate can have excellent polarization characteristics and durability.

[ example 14]

A polarizing plate obtained by using the PVA having a polymerization degree of 5500 and a swelling degree of 232% obtained in example 1 was cut into a 40mm square, and the polarizing plate was bonded to a 40X 40mm thick transparent plate glass with a thickness of 1mm via an adhesive (product name: AD-ROC manufactured by Polatechno) to prepare a sample for light resistance test.

[ example 15]

A polarizing plate obtained by using the PVA having a polymerization degree of 5500 and a swelling degree of 208% obtained in example 12 was cut into a 40mm square, and the polarizing plate was bonded to a 40X 40mm thick transparent plate glass with a thickness of 1mm via an adhesive (product name: AD-ROC manufactured by Polatechno) to prepare a sample for a light resistance test.

Using the samples obtained in examples 14 and 15, a light irradiation test was performed at 85 ℃ for 480 hours using a high-pressure mercury lamp light resistance tester (2000W, extra-high pressure mercury lamp manufactured by usioinc corporation). The irradiation light was set in such a manner as to be incident from the TAC face and was tested. The change in the degree of polarization at 555nm was confirmed before and after the test, and as a result, the degree of polarization was changed to 96.51% in example 14, whereas the degree of polarization was changed to 97.43% in example 15.

[ example 16]

A polarizing plate obtained by using PVA having a polymerization degree of 5500 and a swelling degree of 232% obtained in example 9 was cut into a 40mm square, and the polarizing plate was bonded to a 40X 40mm thick transparent plate glass with a thickness of 1mm via an adhesive (product name: AD-ROC manufactured by Polatechno) to prepare a sample for light resistance test.

[ example 17]

A polarizing plate obtained by using the PVA having a polymerization degree of 5500 and a swelling degree of 208% obtained in example 13 was cut into a 40mm square, and the polarizing plate was bonded to a 40X 40mm thick transparent plate glass with a thickness of 1mm via an adhesive (product name: AD-ROC manufactured by Polatechno) to prepare a sample for light resistance test.

Using the samples obtained in examples 16 and 17, a light irradiation test was performed at 85 ℃ for 480 hours using a high-pressure mercury lamp light resistance tester (2000W, extra-high pressure mercury lamp manufactured by usioinc corporation). The irradiation light was set in such a manner as to be incident from the TAC face and was tested. The change in the degree of polarization of 585nm was confirmed before and after the test, and as a result, the degree of polarization was changed to 97.19% in example 16, whereas the degree of polarization was changed to 98.19% in example 17.

From the results of examples 14 to 17, it is understood that the polarizing element comprising at least one 2-color dye and a polyvinyl alcohol resin film having a polymerization degree of 5000 to 10000 has a small change in the degree of polarization in the light resistance test and high durability when the degree of swelling is 208% as compared with the case where the degree of swelling of the polyvinyl alcohol resin film is 232%. That is, this indicates that a polarizing plate formed of a polyvinyl alcohol resin film having a degree of polymerization of 5000 to 10000 and a degree of swelling of 210% or less shows little change in the degree of polarization in a light resistance test of light having an intensity such as an ultrahigh pressure mercury lamp, and further, it is found that a liquid crystal projector using a polarizing element or a polarizing plate of the present invention can maintain stable performance even when used for a longer period of time by using a polyvinyl alcohol resin film having a degree of polymerization of 5000 to 10000 and a degree of swelling of 200% to 210%.

Claims (9)

1. A polarizing element comprising a polyvinyl alcohol resin film obtained by adsorbing and stretching at least one dichroic dye, which is a compound represented by formula (I) or a salt thereof in the form of a free acid, wherein the degree of polymerization of the polyvinyl alcohol resin is 5000 to 10000, the degree of swelling of a base film of the polyvinyl alcohol resin film is 200 to 240%,

[ solution 1]

Wherein A represents a substituted phenyl group or naphthyl group, R₁～R₆Each independently represents a hydrogen atom, a hydroxyl group, a lower alkyl group, a lower alkoxy group, a sulfo group or a lower alkoxy group having a sulfo group, X represents a benzoylamino group with or without a substituent, a phenylamino group with or without a substituent, a phenylazo group with or without a substituent, or a naphthotriazolyl group with or without a substituent, and m represents 1.

2. The polarizing element according to claim 1, wherein in the formula (I), when m is 1, a is a naphthyl group having at least 1 substituent, at least 1 of which is a sulfo group, and the other substituents are a hydroxyl group or a lower alkoxy group having a sulfo group.

3. The polarizing element according to claim 1, wherein in formula (I), when m is 1, a is a phenyl group having at least 1 substituent, at least 1 of which is a sulfo group, and the other substituents are a sulfo group, a lower alkyl group, a lower alkoxy group having a sulfo group, a carboxyl group, a nitro group, an amino group, or a substituted amino group.

4. The polarizing element according to any one of claims 1 to 3, wherein X is a benzoylamino group with or without a substituent, a phenylamino group with or without a substituent, a phenylazo group with or without a substituent, or a naphthotriazole group with or without a substituent, and the substituent is a lower alkyl group, a lower alkoxy group, a hydroxyl group, a carboxyl group, a sulfo group, an amino group or a substituted amino group.

5. The polarizing element according to any one of claims 1 to 3, wherein the dichroic dye is a compound represented by the following formula (III) or a salt thereof,

[ solution 3]

R₁～R₆Each independently is a hydrogen atom, a methyl group, a methoxy group, a sulfo group, a lower alkoxy group having a sulfo group.

6. A polarizing element as claimed in any one of claims 1 to 3, wherein the swelling degree of the green film is 200% to 210%.

7. A polarizing plate comprising the polarizing element according to any one of claims 1 to 6 and a transparent protective layer provided on at least one surface of the polarizing element.

8. A liquid crystal display device comprising the polarizing element according to any one of claims 1 to 6 or the polarizing plate according to claim 7.

9. A liquid crystal projector comprising the polarizing element according to any one of claims 1 to 6 or the polarizing plate according to claim 7.