TW201704360A - Azo compound, dye-based polarizing film containing same, and polarizing plate - Google Patents

Abstract

The purpose of the present invention is to provide azo compounds that are useful as dichroic pigments for use in a polarizer plate that has excellent polarization properties and durability while also exhibiting minimal color leakage in the visible light spectrum, and for use in a neutral-gray polarizer plate that is for use in a vehicle and includes the polarizer plate. Specifically provided are azo compounds represented by formula (1) (therein, A is either A1, a substituted phenyl group, or A2, a naphthyl group having a hydrogen atom, a hydroxy group, a sulfo group and/or a C1-4 alkoxy group that has a sulfo group, and R1-R4 each independently represent a hydrogen atom, a C1-4 alkyl group or a C1-4 alkoxy group) and salts thereof.

Description

Azo compound, dye-containing polarizing film containing the same, and polarizing plate

The present invention relates to a novel azo compound, a dye-based polarizing film containing the same, and a polarizing plate.

A polarizing plate having a light transmission and a shielding function is a basic component of a display device such as a liquid crystal display (LCD) together with a liquid crystal having a light switching function. The application fields of this LCD are also from small computers such as computers and clocks in the early days, to notebook computers, word processors, liquid crystal projectors, LCD TVs, car navigation systems, and measurement devices inside and outside. It can also be applied to lenses having a polarizing function, such as sunglasses having improved visibility, or applications in polarized glasses such as 3D televisions in recent years. As the use of the above polarizing plate is gradually widened, the use conditions are also used under a wide range of conditions of low temperature to high temperature, low humidity to high humidity, low light amount to high light quantity, so high polarization performance is required and high. Durable polarizing plate.

Now, the polarizing plate is made by dyeing a polarizing film substrate using iodine or a dichroic dye or being contained in a polarizing film substrate, such as a polyvinyl alcohol or a derivative thereof which is extended and aligned. The film or a polyalkylene film obtained by dehydrating a polyvinyl chloride film or dehydrating a polyvinyl alcohol film to form a polyolefin. These are substances which have a large influence on the polarization characteristics or durability in the polarizing plate. Although the iodine-based iridium polarizing film is excellent in polarizing performance, water and heat are weak, and when it is used for a long period of time in a state of high temperature and high humidity, there is a problem in durability. In order to improve the durability, it is considered that there is a method in which a treatment with an aqueous solution containing boric acid or a boric acid is used, and a polymer film having a low moisture permeability is used as a protective film, but the effect is difficult. On the other hand, the dye-based polarizing film using a dye is superior in moisture resistance and heat resistance to an iodine-based polarizing film, but generally has insufficient polarizing performance.

In recent years, in order to improve the vividness of liquid crystal display images, image display is performed under high brightness. In order to reduce the driving time of the battery in a hybrid electric vehicle or a mobile terminal equipped with such a display, the liquid crystal display manufacturer needs to maintain the brightness of the image even if the brightness is lowered in order to reduce the power consumption. A polarizer with a sharpness of color and color.

However, in a polarizing film in which a plurality of dyes are adsorbed by a polymer film, light leakage at a specific wavelength (color leakage) occurs in a wavelength region of a visible light region, and the polarizing film is mounted on a liquid crystal panel, and is in a dark state. Below, there will be a change in the hue of the liquid crystal display. Therefore, after the polarizing film is loaded on the liquid crystal display device, in order to prevent the specific wavelength in the dark state The discoloration of the liquid crystal display caused by the color leakage, in the polarizing film which dyes the polymer film or contains a plurality of dyes and becomes an intermediate color, it is necessary to make the transmittance of the orthogonal position in the wavelength region of the visible light region (positive The cross penetration rate is similarly lowered. Further, in the in-vehicle liquid crystal display, since the summer car becomes a high-temperature and high-humidity environment, a polarizing plate having no change in polarization degree is also required. In the past, an iodine-based polarizing plate having a good polarizing property and exhibiting neutral ash was used. However, the iodine-based polarizing plate has a problem of insufficient light resistance, heat resistance, and moist heat resistance as described above. In order to solve this problem, it has become increasingly possible to use a dye-based neutral gray polarizing plate which is dyed or contains a plurality of kinds of dichroic dyes. The dye-based neutral gray polarizing plate is generally used in combination with the three primary colors of light, namely red, blue and yellow dyes. However, as previously described, the polarizing performance of the dye-based neutral gray polarizing plate is not sufficient. Therefore, it is necessary to develop a dichroic dye which is excellent in polarizing performance for each of the three primary colors.

The dye system is characterized in that, as previously described, in order to control the components of the three primary colors of light, the dyes are dyed or contain separate dyes corresponding thereto. In recent years, the light source used in the liquid crystal display panel has a cold cathode tube method or an LED method, but the wavelength of the light source emitted therefrom is different depending on the mode, and even in the same manner, many of them are manufactured according to the respective panels. The company is different. Therefore, in the development of dichroic dyes having good polarizing performance, it is extremely important to design a dichroic dye having an absorption wavelength in accordance with the wavelength of the light source.

The dye used in the production of the above-mentioned dye-based polarizing film is, for example, a water-soluble azo compound described in Patent Documents 1 to 5 and the like.

[Previous Technical Literature] [Patent Document]

[Patent Document 1] Japanese Patent No. 2622748

[Patent Document 2] Japanese Patent Laid-Open Publication No. 2001-33627

[Patent Document 3] Japanese Patent Laid-Open Publication No. 2009-132794

[Patent Document 4] Japanese Patent No. 4270486

[Patent Document 5] Japanese Patent No. 4360100

[Non-patent literature]

[Non-Patent Document 1] Dye Chemistry; Hosoda, Technology Report, 1957

One of the objects of the present invention is to provide a high-performance polarizing plate having excellent polarizing performance, moisture resistance, heat resistance and light resistance. Further, another object of the present invention is to provide a polarizing plate which exhibits neutral ash by adsorbing two or more kinds of dichroic dyes on a polymer film, and has no orthogonal color leakage in a wavelength region of a visible light region. High-performance polarizer with excellent polarizing performance, moisture resistance, heat resistance and light resistance.

A further object is to provide a dye-based neutral gray polarizing plate for a vehicle-mounted liquid crystal display, which is a high-performance polarizing plate which is excellent in brightness, polarization performance, durability, and light resistance.

In order to achieve the object, the inventors of the present invention have found that a polarizing film containing a specific azo compound or a salt thereof and a polarizing plate have excellent polarizing performance, moisture resistance, heat resistance, and light resistance, and have completed the present invention.

That is, the present invention relates to the following:

<1> an azo compound represented by the following formula (1) or a salt thereof, (wherein A is A ₁ : a phenyl group having a substituent, or A ₂ : a naphthyl group having a hydrogen atom, a hydroxyl group, an alkoxy group having a sulfonic acid group of 1 to 4 carbon atoms, and/or a sulfonic acid group; R ₁ to R ₄ each independently represent a hydrogen atom, an alkyl group having 1 to 4 carbon atoms or an alkoxy group having 1 to 4 carbon atoms).

<2> The azo compound or a salt thereof according to <1>, wherein in the above formula (1), R ₁ to R ₄ each independently represent a hydrogen atom, a methyl group or a methoxy group.

<3><1> or <2> The azo compound or a salt thereof is the above formula (1), A is A _1: The substituted phenyl group, and the substituent is at least one of a sulfonic acid having a a substituent other than a carboxyl group or a carboxyl group, a hydrogen atom, a sulfonic acid group, a carboxyl group, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, a halogen group, a nitro group, an amine group, and a carbon number of 1. The alkyl group of ~4 is substituted with an amine group or the alkyl group having 1 to 4 carbon atoms is substituted with a mercaptoamine group.

<4> an azo compound represented by the following formula (2) or a salt thereof, (wherein at least one of R ₃ and R ₄ is a sulfonic acid group, and the other represents a hydrogen atom, a sulfonic acid group, a carboxyl group, a methyl group or a methoxy group, and R ₅ to R ₈ each independently represent a hydrogen atom and a carbon number. Alkyl group of 1 to 4 or alkoxy group having 1 to 4 carbon atoms).

<5> The azo compound and the salt thereof according to <4>, wherein in the above formula (2), R ₅ to R ₈ each independently represent a hydrogen atom, a methyl group or a methoxy group.

<6> The azo compound of <1> or <2> or a salt thereof, wherein A is represented by the following formula (3), and A is represented by the following formula (3), (wherein R ₅ represents a hydrogen atom, a hydroxyl group, an alkoxy group having 1 to 4 carbon atoms having a sulfonic acid group, or a sulfonic acid group, and m represents an integer of 1 to 3).

<7> an azo compound represented by the following formula (4) or a salt thereof, (wherein R ₆ represents a hydrogen atom, a hydroxyl group or an alkoxy group having a sulfonic acid group having 1 to 4 carbon atoms, and R ₇ to R ₁₀ each independently represent a hydrogen atom, an alkyl group having 1 to 4 carbon atoms or a carbon number; 1 to 4 alkoxy groups, n represents an integer from 1 to 3).

<8> The azo compound or a salt thereof according to <7>, wherein in the above formula (4), R ₆ is a hydrogen atom, and n is 2.

<9> The azo compound of <7> or <8> or a salt thereof, wherein R ₇ to R ₁₀ each independently represent a hydrogen atom, a methyl group or a methoxy group in the above formula (4).

The azo compound or a salt thereof according to any one of <7> to <9>, wherein in the above formula (4), any one or two of R ₇ to R ₁₀ are a methoxy group.

<11> A dye-based polarizing film comprising a polarizing film substrate, wherein the polarizing film substrate contains the azo compound according to any one of <1> to <10> or a salt thereof.

<12> A dye-based polarizing film comprising a polarizing film substrate, wherein the polarizing film substrate contains the azo compound according to any one of <1> to <10> or a salt thereof, and one of the other types The above organic dyes.

<13> The dye-based polarizing film according to <11> or <12>, wherein the polarizing film substrate is a film composed of a polyvinyl alcohol resin or a derivative thereof.

<14> A dye-based polarizing plate which can be obtained by laminating a transparent protective layer on at least one surface of the dye-based polarizing film of any one of <11> to <13>.

<15> A polarizing plate for liquid crystal display, which is a dye-based polarizing film according to any one of <11> to <13> or a dye-based polarizing plate of <14>.

<16> A neutral gray polarizing plate for vehicle use, which uses a dye-based polarizing film according to any one of <11> to <13>, such as a dye of <14> A polarizing plate, such as a polarizing plate for liquid crystal display of <15>.

<17> A liquid crystal display device using a dye-based polarizing plate such as <14>, a polarizing plate for liquid crystal display such as <15>, or a neutral gray polarizing plate for automotive use as in <16>.

The azo compound of the present invention or a salt thereof is useful as a dye for a polarizing film. The polarizing film containing these compounds has high polarizing performance comparable to that of the polarizing film using iodine, and is excellent in durability. Therefore, it is suitable for use in various liquid crystal displays and liquid crystal projectors, and must have high-polarization performance and durability for automotive applications and display applications for industrial meters used in various environments.

The azo compound of the present invention is represented by the above formula (1). A in the above formula (1) is A ₁ : a phenyl group having a substituent, or A ₂ : a naphthalene having a hydrogen atom, a hydroxyl group, an alkoxy group having a sulfonic acid group of 1 to 4 carbon atoms or a sulfonic acid group The group R ₁ to R ₄ each independently represents a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, and an alkoxy group having 1 to 4 carbon atoms.

In the following, the compound of the above formula (1) is described. However, in the following substituents, the number of carbon atoms 1 to 4 is referred to as "lower".

In the present case, the "substituent" contains a hydrogen atom, but is simply described as a "substituent".

A ₁ in the above formula (1) represents a phenyl group having a substituent, and a substituent thereof is a hydrogen atom, a sulfonic acid group, a carboxyl group, a lower alkyl group, a lower alkoxy group, a halogen group, a nitro group, an amine group. a lower alkyl-substituted amine group or a lower alkyl-substituted mercaptoamine group is preferred. When two or more substituents are present, at least one of the substituents is a sulfonic acid group or a carboxyl group, and the other substituents are A sulfonic acid group, a hydrogen atom, a lower alkyl group, a lower alkoxy group, a carboxyl group, a chloro group, a bromo group, a nitro group, an amine group, a lower alkyl-substituted amine group, and a lower alkyl-substituted mercaptoamine group are preferred. Preferred is a sulfonic acid group, a hydrogen atom, a methyl group, an ethyl group, a methoxy group, an ethoxy group, a carboxyl group, a chloro group, a nitro group or an amine group, particularly preferably a sulfonic acid group, a carboxyl group, a hydrogen atom or a methyl group. Methoxy. The substitution position is not particularly limited, but a combination of a 2-position and a 4-position, or a 3-position and a 5-position is preferred.

A ₂ in the above formula (1) represents a naphthyl group having a substituent, and as the substituent thereof, a hydrogen atom, a sulfonic acid group, a hydroxyl group, a lower alkoxy group having a sulfonic acid group, or a sulfonic acid group is preferred. Preferably, A ₂ is a naphthyl group represented by the above formula (3), and R ₅ represents a hydrogen atom, a hydroxyl group, an alkoxy group having a sulfonic acid group having 1 to 5 carbon atoms, or a sulfonic acid group, and m is 1~3 is better. Further, the position of the sulfo group may be on any of the benzene nuclei of the naphthalene ring. As the lower alkoxy group having a sulfonic acid group, a linear alkoxy group is preferred, and a substitution position of the sulfonic acid group is preferably at the alkoxy end, preferably a 3-sulfonic acid propoxy group or a 4-sulfonate group. Acid butoxy group. The substitution position of the substituent of the naphthyl group is not particularly limited, and is represented by the following formula (5). When the substituent is two, the 5-position and the 7-position, or the 6-position and the 8-position and the 8-position are present. The combination of the bits is preferred. When the number of substituents is three, 3-position and 5-position and 7-position, 3-position and 6-position and 8-position are preferred.

In the above formula (1), R ₁ to R ₄ may have a substituent, and the substituent thereof is not particularly limited. Preferably, R ₁ to R ₄ each independently represent a hydrogen atom, a lower alkyl group or a lower alkoxy group, more preferably a hydrogen atom, a methyl group, an ethyl group, and a lower alkoxy group such as a methoxy group or an ethoxy group. Particularly preferred are a hydrogen atom, a methyl group, an ethyl group, and a methoxy group. The substitution position is preferably a 2-position, a 5-position only, a 2-position and a 6-position combination, a 2-position and a 5-position, as described by the following formula (6). The combination, the combination of 3-bit and 5-bit is preferred, and more preferably only 2-bit, only 5-bit, 2-bit and 5-bit combination. Further, in the above, only the 2-position and only the 5-position system represent a substituent having one hydrogen atom only in the 2-position or the 5-position.

Next, specific examples of the azo compound represented by the above formula (1) used in the present invention are listed below. Further, the sulfonic acid group, the carboxyl group and the hydroxyl group in the formula are represented by the form of a free acid.

The azo compound or the salt thereof represented by the above formula (1) can be subjected to diazotization, coupling, and ureido group as described in Patent Document 3 by the method of producing the usual azo dye described in Non-Patent Document 1. It is easy to manufacture.

As a specific production method, a substituted phenylbenzene (benzene) having a substituent represented by the following formula (i) is produced by the same method as in Non-Patent Document 1. The amine or the aminonaphthalene (naphthylamine) is diazotized and coupled with an aniline of the following formula (ii) to obtain a monoazoamine group compound represented by the following formula (iii).

A-NH ₂ (i) (wherein A represents the same meaning as in the above formula (1).)

(wherein R ₁ and R ₂ have the same meanings as those in the above formula (1).)

(wherein, A, R ₁ and R ₂ have the same meanings as those in the above formula (1).)

Next, the monoazoamine-based compound (iii) is diazotized and subjected to secondary coupling with an aniline of the following formula (iv) to obtain a disazo represented by the following formula (v). Amino compound.

(wherein R ₃ and R ₄ have the same meanings as those in the above formula (1).)

(wherein, A, R ₁ to R ₄ have the same meanings as those in the above formula (1).)

The azo compound of the above formula (1) is obtained by reacting the bisazoamine group compound (v) with a phenyl chloroformate.

In the above reaction, the diazotization step is carried out by mixing the nitrite of sodium nitrite or the like with an aqueous solution or suspension of a mineral acid such as hydrochloric acid or sulfuric acid of a diazo component, or by a diazonium component. The aqueous solution of the sexual or weakly basic is preliminarily added with nitrite, and the reverse method of mixing the mineral acid is carried out. The temperature of the diazotization is suitably -10 to 40 °C. Further, in the coupling step with the aniline, an acidic aqueous solution such as hydrochloric acid or acetic acid is mixed with the above respective diazonium liquids, and the acidic conditions are carried out at a temperature of -10 to 40 ° C at a pH of 2 to 7.

The monoazoamine-based compound and the bis-azo-amine-based compound obtained by coupling are taken out by filtration or precipitation by acid precipitation or salting out, or can be further carried out in the state of solution or suspension to the next step. . When the diazonium salt is poorly soluble and is a suspension, it can also be filtered and used as a press cake for the subsequent coupling step.

A specific method for the urea group reaction of a bisazo-amine compound and a phenyl chloroformate, for example, by a method shown in Patent Document 3, pp57, at a temperature of 10 to 90 ° C and a pH of 7 to 11 from neutral to alkali Under sexual conditions. After completion of the reaction, it was precipitated by salting out and filtered, and taken out. Further, if purification is required, salting out may be repeated or an organic solvent may be used to precipitate out of water. The organic solvent to be used for the purification may, for example, be a water-soluble organic solvent such as an alcohol such as methanol or ethanol or a ketone such as acetone.

Further, in the present invention, in addition to the use as the free acid, the azo compound represented by the above formula (1) can also be used as a salt of an azo compound. Examples of such a salt include organic salts such as a lithium salt, a sodium salt, and a potassium salt, and an organic salt such as an ammonium salt or an amine salt. The sodium salt is generally used.

The starting material for synthesizing the water-soluble dye in which A of the above formula (1) is A ₁ is an aromatic amine (A ₁ -NH ₂ ). The substituent thereof may, for example, be a hydrogen atom, a sulfonic acid group, a lower alkyl group, a lower alkoxy group, a carboxyl group, a nitro group, a halogen group, an amine group, a lower alkyl group-substituted amine group or a lower alkyl group-substituted anthracene. Amino group. Preferred is a sulfonic acid group, a hydrogen atom, a methyl group, an ethyl group, a methoxy group, an ethoxy group, a carboxyl group, a chloro group, a bromo group, a nitro group, an amine group, a dimethylamino group or an ethyl fluorenyl group. It is a sulfonic acid group, a hydrogen atom, a methyl group, a methoxy group, a carboxyl group, a chlorine group, or an amine group. Further, at least one of the substituents is preferably a sulfonic acid group or a carboxyl group, and the aromatic amine having R ₃ to R ₄ represented by the above formula (2) has a substituent number of 2 or more. When A is a substituted phenyl group of A _1, the phenyl amines (A ₁ -NH _2), can include, for example, 4-amino-benzenesulfonic acid, 3-amino-acid, 2-aminobenzene Sulfonic acid, 4-aminobenzoic acid, 2-amino-5-methylbenzenesulfonic acid, 2-amino-5-ethylbenzenesulfonic acid, 2-amino-5-propylbenzenesulfonic acid, 2 -Amino-5-butylbenzenesulfonic acid, 4-amino-3-methylbenzenesulfonic acid, 4-amino-3-ethylbenzenesulfonic acid, 4-amino-3-propylbenzenesulfonic acid , 4-amino-3-butylbenzenesulfonic acid, 2-amino-5-methoxybenzenesulfonic acid, 2-amino-5-ethoxybenzenesulfonic acid, 2-amino-5-propyl Oxybenzenesulfonic acid, 2-amino-5-butoxybenzenesulfonic acid, 4-amino-3-methoxybenzenesulfonic acid, 4-amino-3-ethoxybenzenesulfonic acid, 4- Amino-3-propoxybenzenesulfonic acid, 4-amino-3-butoxybenzenesulfonic acid, 2-amino-4-sulfonic acid benzoic acid, 2-amino-5-sulfonic acid benzoin Acid, etc., 5-aminoisodecanoic acid, 2-amino-5-chlorobenzenesulfonic acid, 2-amino-5-bromobenzenesulfonic acid, 2-amino-5-nitrobenzenesulfonic acid, 2, 5-diaminobenzenesulfonic acid, 2-amino-5-dimethylaminobenzenesulfonic acid, 2-amino-5-diethylaminobenzenesulfonic acid, 5-acetamido-2-amine Benzobenzenesulfonic acid, 4-aminobenzene-1,3-disulfonic acid, 2-amino group 1,4-dicarboxylic acid and the like. 4-aminobenzenesulfonic acid, 2-amino-5-methoxybenzenesulfonic acid, 4-amino-2-methylbenzenesulfonic acid, 4-aminobenzene-1,3-disulfonic acid Very good.

The starting material for synthesizing the water-soluble dye in which A of the above formula (1) is A ₂ is a naphthyl group having a hydrogen atom, a hydroxyl group, an alkoxy group having a sulfonic acid group having 1 to 4 carbon atoms, and/or a sulfonic acid group. Amines (A ₂ -NH ₂ ). Examples of the naphthylamine (A ₂ -NH ₂ ) having a hydrogen atom, a hydroxyl group or a sulfonic acid group include 4-aminonaphthalenesulfonic acid, 7-aminonaphthalene-3-sulfonic acid, and 1-amino group. Naphthalene-6-sulfonic acid, 1-aminonaphthalene-7-sulfonic acid, 7-aminonaphthalene-1,3-disulfonic acid, 6-aminonaphthalene-1,3-disulfonic acid, 7-amino group Naphthalene-1,5-disulfonic acid, 7-aminonaphthalene-1,3,6-trisulphonic acid and the like. Preferred are 7-aminonaphthalene-3-sulfonic acid, 6-aminonaphthalene-1,3-disulfonic acid, 7-aminonaphthalene-1,4-disulfonic acid, 7-aminonaphthalene-1, 5-disulfonic acid, 2-amino-8-hydroxy-naphthalene-6-sulfonic acid, 3-amino-8-hydroxynaphthalene-6-sulfonic acid, 1-aminonaphthalene-3,6,8-three Sulfonic acid, 2-amino-5-hydroxynaphthalene-1,7-disulfonic acid, 1-aminonaphthalene-3,8-disulfonic acid and the like. A is a compound represented by the above formula (3), and has a hydrogen atom, an alkoxy group having 1 to 4 carbon atoms and a sulfonic acid group, and a naphthylamine (A ₂ -NH ₂ ) having a sulfonic acid group. For example, 7-amino-3-(3-sulfonylpropoxy)naphthalene-1-sulfonic acid, 7-amino-3-(4-sulfobutoxy)naphthalene-1-sulfonate Acid, 7-amino-4-(3-sulfopropoxy)naphthalene-2-sulfonic acid, 7-amino-4-(4-sulfobutoxy)naphthalene-2-sulfonic acid, 6-Amino-4-(3-sulfonic acid propoxy)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-sulfonylpropoxy)naphthalene-2,7-disulfonate Acid, 7-amino-3-(3-sulfopropoxy)naphthalene-1,5-disulfonic acid and the like.

In the above formula (1), the substituents of R ₁ to R ₄ in the primary and secondary coupling components are not particularly limited, and preferably each independently represents a hydrogen atom, a lower alkyl group, a lower alkoxy group, and more preferably a hydrogen group. An atom, a methyl group, an ethyl group, a methoxy group, and an ethoxy group are particularly preferably a hydrogen atom, a methyl group, an ethyl group, a methoxy group, or a lower alkoxy group having a sulfonic acid group.

As the substitution position, it is preferably a combination of only 2-position, only 5-position, 2-position and 6-position, combination of 2-position and 5-position, and combination of 3-position and 5-position. Good, the best is only a combination of 2-bit, only 5-bit, 2-bit and 5-bit.

Examples of the aniline of the primary and/or secondary coupler include aniline, 2-methylaniline, 2-ethylaniline, 2-propylaniline, 2-butylaniline, 3-methylaniline, and 3 -ethylaniline, 3-propylaniline, 3-butylaniline, 2,5-dimethylaniline, 2,5-diethylaniline, 2-methoxyaniline, 2-ethoxyaniline, 2 -propoxyaniline, 2-butoxyaniline, 3-methoxyaniline, 3-ethoxyaniline, 3-propoxyaniline, 3-butoxyaniline, 2-methyl Oxy-5-methylaniline, 2,5-dimethoxyaniline, 3,5-dimethylaniline, 2,6-dimethylaniline or 3,5-dimethoxyaniline.

These amine groups of anilines can also be protected. The protective group may, for example, be an ω-methane fluorenyl group.

Further, in the dye-based polarizing film or the dye-based polarizing plate of the present invention, the azo compound represented by the above formula (1) or a salt thereof may be used singly or in combination, and one or more other organic dyes may be used in combination. The organic dye to be combined is not particularly limited, and a dye having an absorption property in a wavelength region different from the absorption wavelength region of the azo compound of the present invention or a salt thereof is preferred, and a high dichroic property is preferred. For example, CI Direct Yellow 12, CI Direct Yellow 28, CI Direct Yellow 44, CI Direct Orange 26, CI Direct Orange 39, CI Direct Orange 71, CI Direct Orange 107, CI Direct Red 2, CI Direct Red 31, CI Direct red 79, CI direct red 81, CI direct red 247, CI direct blue 237, CI direct blue 273, CI direct blue 274, CI direct green 80, CI direct green 59 and the dyes described in Patent Documents 1 to 5 are representative For the purpose of use, it is preferred to use a dye developed for a polarizing plate as described in Patent Documents 1 to 5. These pigments are used as a salt of a free acid or an alkali metal salt (for example, a Na salt, a K salt, or a Li salt), an ammonium salt, or an amine.

When it is necessary to use other organic dyes in combination, the polarizing film for the purpose is a type of a polarizing film of a neutral color, a color polarizing film for a liquid crystal projector, or another color polarizing film, and the type of the dye to be used is different. The blending ratio is not particularly limited, but is generally 0.1 to 10 parts by mass based on the total mass of at least one of the organic dyes based on the mass of the azo compound of the above formula (1) or a salt thereof. Within the scope Use is better.

If necessary, the azo compound represented by the formula (1) or a salt thereof can be contained in a polarizing film substrate (for example, a polymer film) together with other dyes to be aligned, or with a liquid crystal. The polarizing film having various colors or neutral colors is produced by mixing together or by aligning them by a coating method. The obtained polarizing plate is provided with a protective film, and is used as a polarizing plate, such as a protective layer, an AR (reflection preventing) layer, a support, etc., and is used for a liquid crystal projector, a computer, a clock, a notebook personal computer, a word processor, and the like. LCD TVs, car navigation and measuring instruments or displays inside and outside, lenses or glasses.

The polarizing film substrate (polymer film) used in the dye-based polarizing film of the present invention is preferably a film composed of a polyvinyl alcohol resin or a derivative thereof, and specific examples thereof include polyvinyl alcohol or a derivative thereof. And any one of these is obtained by denaturation of an olefin such as ethylene or propylene or an unsaturated carboxylic acid such as crotonic acid, acrylic acid, methacrylic acid or maleic acid. From the viewpoint of the adsorptivity and the alignment property of the dye, a film composed of polyvinyl alcohol or a derivative thereof is also suitably used. The thickness of the substrate is usually from 30 to 100 μm, preferably from 50 to 80 μm.

When such a polarizing film substrate (polymer film) contains the azo compound of the above formula (1) or a salt thereof, a method of using a color polymer film is usually employed. The dyeing is carried out, for example, by the following operations. First, the azo compound of the present invention or a salt thereof and, if necessary, a dye other than necessary are dissolved in water to prepare a dyebath. The concentration of the dye in the dyebath is not particularly limited and is usually selected from the range of 0.001 to 10% by mass. Also, use it if necessary Dyeing aids, for example, are suitable for use in the concentration of 0.1 to 10% by mass of Glauber's salt. The polymer film was immersed in the dye bath prepared thereby for 1 to 10 minutes for dyeing. The dyeing temperature is preferably about 40 to 80 °C.

The alignment of the azo compound of the above formula (1) or a salt thereof is carried out by stretching the polymer film dyed by the above operation. As a method of extending, any known method such as a wet method or a dry method can be used. The extension of the polymer film can also be carried out before dyeing, as the case may be. In this case, the alignment of the water-soluble dye is carried out at the time of dyeing. The polymer film containing the water-soluble dye and aligned is subjected to a treatment such as boric acid treatment by a known method. Such post-treatment is carried out for the purpose of improving the light transmittance and the degree of polarization of the polarizing film. The conditions of the boric acid treatment vary depending on the type of the polymer film to be used or the type of the dye to be used. However, the boric acid concentration of the boric acid aqueous solution is generally 0.1 to 15% by mass, preferably 1 to 10% by mass, and is preferably treated. It is carried out by immersing in a temperature range of 30 to 80 ° C, preferably 40 to 75 ° C for 0.5 to 10 minutes. Further, if necessary, an aqueous solution containing a cationic polymer compound may be used together for a fix treatment.

The dye-based polarizing film of the present invention thus obtained is obtained by laminating a transparent protective film having excellent optical transparency and mechanical strength on one surface or both surfaces thereof to form a polarizing plate. As the material for forming the protective film, for example, a cellulose acetate film or an acrylic film may be used, and a fluorine film such as a tetrafluoroethylene/hexafluoropropylene copolymer, a polyester resin, or a polyolefin may be used. A film made of a resin or a polyamide resin. A triethylenesulfonyl cellulose (TAC) film or a cycloolefin film is preferably used. The thickness of the protective film is usually 40~200μm.

Examples of the adhesive which can be used for bonding the polarizing film and the protective film include a polyvinyl alcohol-based adhesive, a urethane emulsion-based adhesive, an acrylic adhesive, and a polyester-isocyanate adhesive. Suitable as a polyvinyl alcohol-based adhesive.

Further, a transparent protective layer may be further provided on the surface of the dye-based polarizing plate of the present invention. Examples of the protective layer include a hard coat layer of an acrylic or polyoxyalkylene system, a protective layer of an urethane type, and the like. Moreover, in order to further improve the light transmittance of the single plate, it is preferable to provide an AR layer on the protective layer. The AR layer can be formed by, for example, vapor deposition or sputtering treatment of a substance such as cerium oxide or titanium oxide, and can be formed by coating a fine fluorine-based substance. Further, the dye-based polarizing plate of the present invention can also be used as an elliptically polarizing plate to which a phase difference plate has been attached.

The dye-based polarizing plate of the present invention thus constituted is characterized in that it has a neutral color, has no orthogonal color leakage in a wavelength region of a visible light region, and has excellent polarizing performance even under high temperature and high humidity conditions. Without causing discoloration or a decrease in polarizing performance, light leakage under the orthogonal position in the visible light region is small.

The neutral gray polarizing plate for vehicle-mounted use of the present invention contains the azo compound represented by the above formula (1) or a salt thereof, and further contains the other organic dye as a dichroic molecule as necessary. Further, the polarizing film used in the color polarizing plate for a liquid crystal projector of the present invention can also be produced by the above-described manufacturing method. In addition, a polarizing plate is added to the protective film, and a protective layer, an AR layer, a support, etc. are required, and it is used as a vehicle. Use a neutral gray polarizer.

As a color polarizing plate for liquid crystal projectors, the necessary wavelength range of the polarizing plate (A. When using an ultrahigh pressure mercury lamp; 420 to 500 nm for blue channel, 500 to 580 nm for green channel, 600 to 680 nm for red channel, B. 3 primary colors) The peak wavelength of the LED lamp; the average light transmittance of the single plate in the blue channel is 430~450nm, the green channel is 520~535nm, and the red channel is 620~635nm), and the average light transmittance of the orthogonal bit is 0.4. Preferably, the average light transmittance of the single plate in the necessary wavelength range of the polarizing plate is 41% or more, and the average light transmittance of the orthogonal position is 0.3% or less, preferably 0.2% or less. More preferably, the average light transmittance of the single plate in the necessary wavelength range of the polarizing plate is 42% or more, and the average light transmittance of the orthogonal dots is 0.1% or less. The color polarizing plate for a liquid crystal projector of the present invention has brightness and excellent polarizing performance as described above.

In addition, the average light transmittance of the veneer is a specific wavelength region when natural light is incident on one of the polarizers which are not provided with the AR layer and the transparent glass plate (the following is the same meaning when used simply as a polarizing plate). The average value of the light transmittance. The average light transmittance of the orthogonal bits is an average value of light transmittance in a specific wavelength region when natural light is incident on two polarizing plates in which the alignment directions are arranged in orthogonal positions.

The neutral gray polarizing plate for vehicle-mounted use of the present invention is preferably a polarizing plate having an AR layer provided on a polarizing plate comprising a polarizing film and a protective film, and is attached to a transparent resin or the like. A polarizing plate with an AR layer and a support on the support is preferred.

The neutral gray polarizing plate for vehicle use of the present invention is generally used. As a polarizer with a support. Since the support is attached with a polarizing plate, it is preferable to have a flat portion, and since it is used for optical purposes, a transparent substrate is preferred. The transparent substrate is roughly classified into an inorganic substrate and an organic substrate, and examples thereof include an inorganic substrate such as soda glass, borosilicate glass, a crystal substrate, a sapphire substrate, or a spinel substrate, or acrylic, polycarbonate, or polypyrene. An organic substrate such as ethylene glycol diester, polyethylene naphthalate or a cycloolefin polymer, but an organic substrate is preferred. The thickness or size of the transparent substrate can be the desired size. Further, in order to increase the light transmittance of the single plate, the polarizing plate with the transparent substrate is preferably provided with an AR layer on one or both sides of the supporting body surface or the polarizing plate surface.

In the case of producing a color polarizing plate with a support for vehicle use, for example, a transparent adhesive (adhesive) agent is applied to the flat surface of the support, and then the dye-based polarizing plate of the present invention may be attached to the coated surface. Further, a transparent adhesive (adhesive) may be applied to the polarizing plate, and then the support may be attached to the coated surface. The adhesive (adhesive) used herein is preferably, for example, an acrylate. When the polarizing plate is used as an elliptically polarizing plate, the phase difference plate side is usually attached to the support side, but the polarizing plate side may be attached to the transparent substrate.

In other words, in the liquid crystal display for vehicle use using the dye-based polarizing plate of the present invention, the dye-based polarizing plate of the present invention is disposed on either or both of the incident side and the exit side of the liquid crystal cell. The polarizing plate may or may not be in contact with the liquid crystal cell, but it is preferably not contacted from the viewpoint of durability. On the exit side, when the polarizing plate is in contact with the liquid crystal cell, the dye-based polarizing plate of the present invention using the liquid crystal cell as a support can be used. Polarizer does not work with liquid When the crystal unit is brought into contact, it is preferred to use the dye-based polarizing plate of the present invention using a support other than the liquid crystal cell. Moreover, it is preferable to arrange the dye-based polarizing plate of the present invention on either the incident side or the exit side of the liquid crystal cell from the viewpoint of durability, and to arrange the polarizing plate surface of the dye-based polarizing plate of the present invention on the liquid crystal. On the unit side, it is preferable to arrange the support body surface on the light source side. Further, the incident side of the liquid crystal cell refers to the light source side, and the opposite side is referred to as the exit side.

In the liquid crystal display for vehicle-mounted use using the dye-based polarizing plate of the present invention, the liquid crystal cell used is, for example, an active matrix type and sealed between a transparent substrate on which an electrode and a TFT have been formed and a transparent substrate on which a counter electrode has been formed. Liquid crystal formation is preferred. Light emitted by a light source such as a cold cathode tube lamp or a white LED passes through a neutral gray polarizing plate, and is then projected onto a display screen by a liquid crystal cell, a color filter, and a neutral gray polarizing plate.

The neutral gray polarizing plate for vehicle-mounted use is characterized in that it has excellent polarizing performance and does not cause discoloration or a decrease in polarizing performance even in a high-temperature, high-humidity state in a vehicle.

[Examples]

In the following, the present invention will be described in more detail by way of examples, but these are not to be construed as limiting. The % and parts in the examples are quality benchmarks unless otherwise defined.

(Example 1)

25.3 parts of 4-aminobenzene-1,3-disulfonic acid was added to 500 parts of water, and cooling was carried out. 31.3 parts of 35% hydrochloric acid was added at 10 ° C or lower, followed by adding 6.9 parts of sodium nitrite, and stirring at 5 to 10 ° C. Diazotization was carried out for 1 hour. Thereafter, 10.7 parts of 3-methylaniline was added, and the mixture was stirred at 10 to 30 ° C, and sodium carbonate was added thereto to prepare pH 3. The mixture was stirred and the coupling reaction was completed, and filtration was carried out to obtain the following formula (M1). The monoazoamine compound was 33.4 parts.

33.4 parts of the monoazoamine-based compound obtained was added to 400 parts of water, dissolved in sodium hydroxide, and 28.2 parts of 35% hydrochloric acid was added at 10 to 30 ° C, and then 6.2 parts of sodium nitrite was added thereto at 20 to 30. The mixture was stirred at ° C for 1 hour for diazotization. Thereafter, 9.6 parts of 3-methylaniline was added, and the mixture was stirred at 20 to 30 ° C, and sodium carbonate was added thereto to prepare pH 3, and the mixture was stirred to complete the coupling reaction, followed by filtration to obtain the following formula (M2). The bisazoamine compound was 46.1 parts.

Adding 35.2 parts of the obtained bisazoamine compound to water 250 parts were dissolved in sodium hydroxide, and 5.6 parts of phenyl chloroformate was stirred at 30 to 70 ° C for 2 hours for urea formation. Salting out with sodium chloride and filtering were carried out to obtain 28.9 parts of the azo compound (hereinafter also referred to as a urea-based compound) of the present invention represented by the above formula (7). The maximum absorption wavelength in this 20% aqueous pyridine solution of this compound was 462 nm.

(Example 2)

In addition, the first-order coupler of the above formula (7) was changed from 10.7 parts of 3-methylaniline to 12.1 parts of 2,5-dimethylaniline, and the second coupler was changed from 9.6 parts of 3-methylaniline to 2 parts. In the same manner as in Example 1, except that 12.3 parts of methoxy-5-methylaniline was used, 31.5 parts of the ureido compound of the present invention represented by the above formula (8) was obtained. The maximum absorption wavelength in this 20% aqueous pyridine solution of this compound was 469 nm.

(Example 3)

30.3 parts of 7-aminonaphthalene-1,3-disulfonic acid was added to 400 parts of water, and dissolved with sodium hydroxide. 10.4 parts of 35% hydrochloric acid was added, followed by 6.9 parts of sodium nitrite, and stirred for 1 hour. To this, 12.1 parts of 2,5-dimethylaniline was added, and the mixture was stirred at 30 to 40 ° C, and sodium carbonate was added thereto to prepare pH 5, and the mixture was stirred to complete the coupling reaction, and a single sample represented by the following formula (M3) was obtained. The azoamine compound was 39.2 parts.

After dispersing 50.4 parts of the monoazo compound of the above formula (65) in 600 parts of water, 9.4 parts of 35% hydrochloric acid was added, followed by 6.2 parts of sodium nitrite, and the mixture was stirred at 25 to 30 ° C for 2 hours to carry out diazotization. To this, 12.3 parts of 2-methoxy-5-methylaniline was added, and the mixture was stirred at 30 to 40 ° C, and sodium carbonate was added thereto to prepare pH 3, followed by stirring to complete the coupling reaction, and the following formula (M4) was obtained. The bisazoamine compound shown was 46.6 parts.

46.6 parts of the obtained bisazoamine-based compound was added to 250 parts of water, and dissolved with sodium hydroxide, and 6.2 parts of phenyl chloroformate was subjected to urea formation at 30 to 70 ° C for 2 hours. Salting out with sodium chloride and filtering to obtain 35.2 parts of the azo compound of the present invention represented by the above formula (31). The maximum absorption wavelength of this compound in a 20% aqueous pyridine solution was 455 nm.

(Example 4)

In addition to the modification of 2,5-dimethylaniline to 2,5-dimethoxy in Example 3. Other than the aniline, 31.4 parts of the azo compound of the present invention represented by the above formula (32) was obtained in the same manner as in Example 3. The maximum absorption wavelength in this 20% aqueous pyridine solution of this compound was 492 nm.

(Example 5)

In addition to the change of 2,5-dimethylaniline to 2,5-dimethoxyaniline in Example 3, and the conversion of 2-methoxy-5-methylaniline to 2,5-dimethylaniline In the same manner as in Example 3, 30.6 parts of the azo compound of the present invention represented by the above formula (33) was obtained. The maximum absorption wavelength of this compound in a 20% aqueous pyridine solution was 491 nm.

(Example 6)

The present invention of the above formula (34) was obtained in the same manner as in Example 3 except that 2,5-dimethylaniline was changed to 2-methoxy-5-methylaniline in Example 3. The azo compound was 35.7 parts. The maximum absorption wavelength of this compound in a 20% aqueous pyridine solution was 483 nm.

(Example 7)

In addition to Example 3, 2,5-dimethylaniline was changed to 2-methoxy-5-methylaniline, and 2-methoxy-5-methylaniline was changed to 2,5-dimethyl Other than the aniline, 35.3 parts of the azo compound of the present invention represented by the above formula (35) was obtained in the same manner as in Example 3. The maximum absorption wavelength of this compound in a 20% aqueous pyridine solution was 463 nm.

(Example 8)

The same procedure as in Example 3 was carried out except that 7-aminonaphthalene-1,3-disulfonic acid was changed to 7-aminonaphthalene-1,3,6-trisulphonic acid in Example 3. (36) 33.8 parts of the azo compound of the present invention shown. The maximum absorption wavelength of this compound in a 20% aqueous pyridine solution was 453 nm.

(Example 9)

Other than Example 7 except that 7-aminonaphthalene-1,3-disulfonic acid was changed to 6-amino-4-(3-sulfopropoxy)naphthalene-2-sulfonic acid in Example 3. 3 The same operation was carried out to obtain 32.7 parts of the azo compound of the present invention represented by the above formula (37). The maximum absorption wavelength in this 20% aqueous pyridine solution of this compound was 457 nm.

(Embodiment 10)

The present invention of the above formula (38) was obtained in the same manner as in Example 3 except that 2-methoxy-5-methylaniline was changed to 2,5-dimethylaniline in Example 3. The azo compound was 29.0 parts. The maximum absorption wavelength in this 20% aqueous pyridine solution of this compound was 441 nm.

(Example 11)

In addition to the change of 2,5-dimethylaniline to 3-methylaniline in Example 3, and the conversion of 2-methoxy-5-methylaniline to 3,5-dimethylaniline, Example 3 The same operation was carried out to obtain 29.0 parts of the azo compound of the present invention represented by the above formula (39). 20% pyridine of this compound The maximum absorption wavelength in the aqueous solution is 433 nm.

(Embodiment 12)

Except that in Example 3, 2,5-dimethylaniline was changed to 2-methylaniline, and 2-methoxy-5-methylaniline was changed to 2,5-dimethylaniline. Example 3 The same operation was carried out to obtain 34.0 parts of the azo compound of the present invention represented by the above formula (63). The maximum absorption wavelength of this compound in a 20% aqueous pyridine solution was 449 nm.

(Example 13)

0.1% aqueous solution of Glauber's salt and a concentration of 0.03% compound of the above formula (7) in the creation of Example 1 was immersed in 45 ℃ made of 75 μ m thickness of the polyvinyl alcohol for 4 minutes. This film was extended five times in a 3% boric acid aqueous solution at 50 ° C, washed with water and dried under a state of tension to obtain a polarizing film of the present invention.

The obtained polarizing film has a maximum absorption wavelength of 482 nm, a polarization ratio of 99.9%, and a high polarization ratio.

(Example 14)

A polyvinyl alcohol having a thickness of 75 μm was immersed in an aqueous solution of 0.03% of the compound of the above formula (31) and a concentration of 0.1% of sodium sulfate in Example 4 to give a polyvinyl alcohol having a thickness of 75 μm for 4 minutes. This film was extended five times in a 3% boric acid aqueous solution at 50 ° C, and washed with water and dried to maintain the polarizing film of the present invention.

The obtained polarizing film has a maximum absorption wavelength of 502 nm, a polarization ratio of 99.9%, and a high polarization ratio.

Further, the test methods are described below.

The measurement of the maximum absorption wavelength of the polarizing film and the calculation of the polarization ratio were carried out by using a spectrophotometer (U-4100 manufactured by Hitachi, Ltd.) to measure the parallel transmittance at the time of incident polarized light and the orthogonal transmittance.

Here, the parallel transmittance (Ky) is the transmittance when the absorption axis of the absolute polarizer is parallel to the absorption axis of the polarizing film, and the orthogonal transmittance (Kz) is the absorption axis of the absolute polarizer and the absorption axis of the polarizing film. Transmittance when orthogonal.

The parallel transmittance and the orthogonal transmittance of each wavelength were measured at intervals of 1 nm at 380 to 780 nm. Using the values of the individual measurements, the polarization ratio of each wavelength was calculated by the following formula (i), and the polarizing ratio at the highest at 380 to 780 nm and its maximum absorption wavelength (nm) were obtained.

Polarization rate (%) = [(Ky-Kz) / (Ky + Kz)] × 100 (i)

(Example 15)

The polarizing film of the present invention was obtained in the same manner as in Example 13 except that the compound of the above formula (8) obtained in Example 2 was used instead of the compound of the above formula (7). The maximum absorption wavelength and the enthalpy ratio of the obtained polarizing film are shown in Table 1.

(Examples 16 to 19)

Further, in place of the compound of the above formula (31), the azo compounds described in Example 4, Example 6, Example 7, and Example 12 were used instead (the above formulas (32), (34), (35), (63). The compound of the present invention was obtained in the same manner as in Example 14 to obtain the polarizing film of the present invention. The maximum absorption wavelength and polarization ratio of the obtained polarizing film are shown in Table 1.

As shown in Table 1, the polarizing films formed using these compounds have high polarizing ratios.

(test example)

As an indicator of image quality, there is a contrast between the white display and the black display, and the maximum absorption wavelengths of the polarizing films obtained in Examples 12 and 14 and 13 and 15 to 17 are compared at this time. exhibition Shown in Table 2. In this comparison, the ratio of the parallel transmittance to the orthogonal transmittance is shown (contrast = parallel transmittance at the maximum absorption wavelength (Ky) / straight transmission at the maximum absorption wavelength (Kz)), and the larger the value, the polarization The better the polarizing performance of the board. Further, the evaluation of the polarizing performance was performed by comparing the parallel transmittances of the maximum absorption wavelengths of the polarizing films. As shown in Table 2, the polarizing films made using these compounds have high contrast.

(Comparative Example 1)

In place of the compound of the present invention, a compound (II-5) synthesized in the same manner as in the method described in Example 1 of Patent Document 5 was used, and a polarizing film was produced in the same manner as in Example 12 of the present invention, and a comparison was calculated. As shown in Table 2, the compounds of the present invention showed high contrast with respect to Comparative Example 1, and were excellent in polarizing performance.

(Comparative Example 2)

In place of the compound of the present invention, the compound (4) of Patent Document 4 synthesized in the same manner as the method described in Example 2 of Patent Document 4 was used, and a polarizing film was produced in the same manner as in Example 13 of the present invention, and was calculated. Compared. As shown in Table 2, the compounds of the present invention exhibited high contrast and excellent polarizing performance with respect to Comparative Example 2.

(Comparative Example 3)

Substituting the compound of the present invention and using it in Patent Document 5 The compound (I-3) which was synthesized in the same manner as in the method described in 0077, and a polarizing film was produced in the same manner as in Example 13 of the present invention, and the comparison was calculated. As shown in Table 2, the compounds of the present invention exhibited high contrast and excellent polarizing performance with respect to Comparative Example 3.

(Embodiment 20)

Except that the compound of the above formula (7) obtained in Example 1 was used as an aqueous solution of a dye of 0.2%, C.I. direct orange 39 0.07%, C.I. direct blue 274 0.02%, and thenardite 0.1% concentration, and other examples. 12 The same operation was carried out to form a polarizing film. The obtained polarizing film has a maximum absorption wavelength of 557 nm, an average transmittance of a single plate of 380 to 600 nm of 42%, an average light transmittance of 0.02% of orthogonal positions, and a high degree of polarization.

A triethylenesulfonated cellulose film (TAC film; manufactured by Fujifilm Co., Ltd.; trade name: TD-80U) was laminated on both surfaces of the polarizing film via an adhesive of a polyvinyl alcohol aqueous solution, and an AR support was obtained using an adhesive. The dye of the present invention is a polarizing plate (neutral gray polarizing plate). The polarizing plate of the present invention has a high polarizing ratio and exhibits long-term durability even in a state of high temperature and high humidity. It is also excellent for long-term exposure to light.

(Example 21)

The same as Example 2 except that the compound of the above formula (31) obtained in Example 4 was used as an aqueous solution of a dye of 0.2%, CI Direct Orange 39 0.07%, CI Direct Blue 274 0.02%, and Glauber's nitrate 0.1% concentration. The same operation was carried out to prepare a polarizing film. The obtained polarizing film has a maximum absorption wavelength of 555 nm, a single plate average transmittance of 42% at 380 to 600 nm, an average light transmittance of 0.02% in the orthogonal position, and a high degree of polarization.

A triethylenesulfonated cellulose film (TAC film; manufactured by Fujifilm Co., Ltd.; trade name: TD-80U) was laminated on both surfaces of the polarizing film via an adhesive of a polyvinyl alcohol aqueous solution, and an AR support was obtained using an adhesive. The dye of the present invention is a polarizing plate (neutral gray polarizing plate). The polarizing plate of the present invention has a high polarizing ratio and exhibits long-term durability even in a state of high temperature and high humidity. It is also excellent for long-term exposure to light.

Claims (17)

An azo compound represented by the following formula (1) or a salt thereof; In the formula, A is A ₁ : a phenyl group having a substituent, or A ₂ : a naphthyl group having a hydrogen atom, a hydroxyl group, an alkoxy group having a sulfonic acid group of 1 to 4 carbon atoms, and/or a sulfonic acid group. R ₁ to R ₄ each independently represent a hydrogen atom, an alkyl group having 1 to 4 carbon atoms or an alkoxy group having 1 to 4 carbon atoms. The azo compound of the claim 1 or a salt thereof, wherein R ₁ to R ₄ each independently represent a hydrogen atom, a methyl group or a methoxy group in the above formula (1). The azo compound according to claim 1 or 2, wherein, in the above formula (1), A is A ₁ : a phenyl group having a substituent, at least one of which is a sulfonic acid group or a carboxyl group, and The substituent other than the substituent is a hydrogen atom, a sulfonic acid group, a carboxyl group, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, a halogen group, a nitro group, an amine group, and an alkyl group having 1 to 4 carbon atoms. Substituted amine groups or alkyl groups having 1 to 4 carbon atoms are substituted for mercaptoamine groups. An azo compound represented by the following formula (2) or a salt thereof; In the formula, at least one of R ₃ and R ₄ represents a sulfonic acid group, and the other represents a hydrogen atom, a sulfonic acid group, a carboxyl group, a methyl group or a methoxy group, and R ₅ to R ₈ each independently represent a hydrogen atom and have a carbon number of 1; ~4 alkyl or alkoxy having 1 to 4 carbon atoms. The azo compound of claim 4, wherein R ₅ to R ₈ are each independently a hydrogen atom, a methyl group or a methoxy group, and a salt thereof in the above formula (2). The azo compound or a salt thereof according to claim 1 or 2, wherein in the above formula (1), A is represented by the following formula (3); In the formula, R ₅ represents a hydrogen atom, a hydroxyl group, an alkoxy group having 1 to 4 carbon atoms having a sulfonic acid group, or a sulfonic acid group, and m represents an integer of 1 to 3. An azo compound represented by the following formula (4) or a salt thereof; Wherein, R ₆ represents a hydrogen atom, a hydroxyl group or a sulfonic acid group having a carbon number of alkyl group of 1 to 4, R ₇ ~ R ₁₀ each independently represent a hydrogen atom-based, or alkyl having 1 to 4 carbon atoms of 1 ~4 alkoxy, n represents an integer from 1 to 3. The azo compound according to claim 7 or a salt thereof, wherein R ₆ is a hydrogen atom and n is 2 in the above formula (4). The azo compound according to claim 7 or 8, or a salt thereof, in the above formula (4), each of R ₇ to R ₁₀ is independently a hydrogen atom, a methyl group or a methoxy group. The azo compound or a salt thereof according to any one of claims 7 to 9, wherein in the above formula (4), any one or two of R ₇ to R ₁₀ are a methoxy group. A dye-based polarizing film comprising a polarizing film substrate, wherein the polarizing film substrate contains the azo compound according to any one of claims 1 to 10 or a salt thereof. A dye-based polarizing film comprising a polarizing film substrate, the polarizing film substrate comprising the azo compound according to any one of claims 1 to 10 or a salt thereof, and one or more other organic dyes. The dye-based polarizing film according to claim 11 or 12, wherein the polarizing film substrate is a film composed of a polyvinyl alcohol resin or a derivative thereof. A dye-based polarizing plate which can be obtained by laminating a transparent protective layer on at least one surface of the dye-based polarizing film according to any one of claims 11 to 13. A polarizing plate for liquid crystal display, which uses the dye-based polarizing film of any one of claims 11 to 13 or the dye-based polarizing plate of claim 14. A neutral gray polarizing plate for use in a vehicle, which is a dye-based polarizing film according to any one of claims 11 to 13, a dye-based polarizing plate according to claim 14, or a polarizing plate for liquid crystal display according to claim 15 . A liquid crystal display device using the dye-based polarizing plate of claim 14, the polarizing plate for liquid crystal display of claim 15, or the neutral gray polarizing plate for automotive use according to claim 16.