Trisazo compound or salt thereof, and polarizing film, polarizing plate, and display device containing same

Abstract

A trisazo compound represented by formula (0) or a salt thereof (in formula (0), X represents hydrogen or an alkoxy group, R1-R4 each independently represent hydrogen, an alkyl group, or an alkoxy group, where, if R1 or R2 has an alkoxy group, the other substituent represents hydrogen).

Description

Trisazo compounds or salts thereof, and polarizing films, polarizing plates, and display devices containing them.

[0001] The present invention relates to trisazo compounds or salts thereof, as well as polarizing films, polarizing plates, and display devices containing them.

[0002] Polarizing plates, which have light transmission and shielding functions, are fundamental components of display devices such as liquid crystal displays (LCDs), along with liquid crystals, which have light switching functions. Applications of LCDs range from small devices such as calculators and watches in the early days to laptop computers, word processors, LCD projectors, LCD televisions, car navigation systems, and indoor and outdoor measuring instruments. They can also be applied to lenses with polarizing functions, and have been used in sunglasses with improved visibility and, more recently, in polarized glasses for 3D televisions. Because the applications of polarizing plates are so widespread, they are used in a wide range of conditions, from low to high temperatures, low to high humidity, and low to high light intensity, so there is a demand for polarizing plates with high polarization performance and high durability.

[0003] Currently, polarizing plates are manufactured by dyeing or impregnating a film of polyvinyl alcohol or its derivatives with iodine or dichroic dyes, then stretching and oriented the film, or by generating polyenes through dehydrochlorination of polyvinyl chloride film or dehydration of polyvinyl alcohol-based film, and then oriented the polyenes. Generally, iodine-based polarizing films, while having excellent polarization performance, are weak against water and heat, and have durability issues when used for extended periods in high-temperature and high-humidity conditions. Methods to improve durability include treatment with aqueous solutions containing formalin or boric acid, and the use of polymer films with low moisture permeability as a protective layer, but these methods are not entirely effective. On the other hand, dye-based polarizing films, which use dyes, generally do not perform as well as iodine-based polarizing films.

[0004] Dye-based polarizing films are generally produced by using multiple dyes to create polarizing films with a wide variety of absorption bands suited to each purpose. For example, by mixing dyes from yellow to red, violet to blue, and blue-green to green, a polarizing film covering the entire visible light wavelength range can be obtained, which is suitable for polarizing plates used in display devices. Polarizing films used in display devices generally use three to four dyes, and it is obvious that a broad absorption band for each dye is preferable in order to produce a polarizing film that evenly absorbs the wavelength range of 380 nm to 780 nm, which is the visible light region, using three to four dyes. To obtain a polarizing film with higher optical properties, a broad wavelength range with a high degree of polarization is preferable.

[0005] For example, trisazo compounds are described in Patent Documents 1 to 13 as dichroic dyes that can provide polarizing films with excellent optical properties in the reddish-purple to blue-green region around 550 nm to 640 nm. However, Patent Document 1 only describes the degree of polarization at the maximum absorption wavelength, and makes no mention of the width of the absorption band or the wavelength range in which the degree of polarization is high at wavelengths other than the maximum absorption wavelength.

[0006] When creating a neutral gray polarizing film by combining multiple dichroic dyes, trisazo compounds are commonly used as the dichroic dye responsible for the reddish-purple to blue-green region around 550 nm to 640 nm. Trisazo compounds often have a second absorption band, and if the polarization characteristics of the second absorption band of the trisazo compound are poor, it can cause a decrease in the optical properties of the neutral gray polarizing film in the short-wavelength region, which would otherwise have absorption across the entire visible light region. Therefore, there is a need to develop dichroic dyes with good polarization characteristics in the second absorption band.

[0007] Patent document 8 describes a trisazo compound having a 3-sulfopropoxy group. However, trisazo compounds having a sulfoalkoxy group often have poor solubility in water, which is necessary for dyeing, resulting in poor dyeability and the inability to dye to the desired transmittance, leading to a problem of low polarization. As shown in Example 3 of Patent Document 2, there is a method of dyeing by raising the dyeing temperature, but raising the dyeing temperature carries the risk of melting the film used as the polarizing film substrate, such as a polyvinyl alcohol-based film. Furthermore, when creating a gray polarizing film by compounding with other dyes, it is difficult to balance the dyeability when compounding a dye that does not dye unless it is dyed at a high dyeing temperature with other dyes. Therefore, there is a need for the development of dichroic dyes with good dyeability.

[0008] Japanese Patent Publication No. 5-295281, Japanese Patent Publication No. 2002-155218, International Publication No. 2004 / 092282, International Publication No. 2021 / 015188, International Publication No. 2009 / 057676, International Publication No. 2007 / 145210, International Publication No. 2006 / 057214, International Publication No. 2009 / 142193, Japanese Patent Publication No. 3-12606, International Publication No. 2022 / 054786, International Publication No. 2024 / 043261, Japanese Patent Publication No. 8-67824, Japanese Patent Publication No. 6-122830

[0009] Dye Chemistry; by Yutaka Hosoda, Gihodo Publishing, 1957. Applications of Functional Dyes (CMC Publishing Co., Ltd., 1st edition, supervised by Masahiro Irie, pp. 98-100)

[0010] One object of the present invention is to provide a novel trisazo compound. Another object of the present invention is to provide a polarizing film and polarizing plate containing the trisazo compound having excellent polarizing performance.

[0011] To achieve this objective, the inventors diligently conducted research and, as a result, discovered a trisazo compound that can be used as a dichroic dye constituting polarizing films and polarizing plates, and that can realize polarizing films with excellent polarizing performance, thus completing the present invention.

[0012] That is, the present invention relates to the following [1] to [7], but is not limited thereto. [1] A trisazo compound represented by the following formula (0) or a salt thereof: (In formula (0), X represents hydrogen or an alkoxy group, R １ to R ４ each independently represent hydrogen, an alkyl group, or an alkoxy group, provided that when R １ or R ２ has an alkoxy group, the other substituent represents hydrogen). [2] The trisazo compound or a salt thereof according to [1], wherein the trisazo compound represented by formula (0) or a salt thereof is a trisazo compound represented by the following formula (1) or a salt thereof: (In formula (1), X represents hydrogen or a C1-10 alkoxy group, R １ to R ４ each independently represent hydrogen, a C1-10 alkyl group, or a C1-10 alkoxy group, provided that when R １ or R ２ has a C1-10 alkoxy group, the other substituent represents hydrogen). [3] A polarizing film comprising a base material, wherein the trisazo compound or a salt thereof according to [1] or [2] is contained in the base material. [4] A polarizing plate comprising a transparent protective film provided on one side or both sides of the polarizing film according to [3]. [5] A display device comprising the polarizing film according to [3] or the polarizing plate according to [4]. [6] A trisazo compound represented by the following formula (0) or a salt thereof, (In formula (0), X represents hydrogen or an alkoxy group, R １ to R ４ each independently represent hydrogen, an alkyl group, or an alkoxy group, provided that R １ or R ２(If the other substituent has an alkoxy group, the other substituent is hydrogen.) A polarizing film is made by dyeing a substrate with the trisazo compound or a salt thereof such that the transmittance of the element at the maximum absorption wavelength in the first absorption band is 44% ± 0.4%, stretching and oriented, wherein the trisazo compound or a salt thereof has multiple maximum absorption wavelengths, the wavelength range in the first absorption band where the degree of polarization is 90% or more is 105 nm or more, the wavelength range where the degree of polarization is 95% or more is 85 nm or more, and the degree of polarization at the wavelength with the greatest absorption in the visible light region in the second absorption band is 45% or more. [7] The trisazo compound or a salt thereof according to [6], wherein the trisazo compound or a salt thereof represented by formula (0) is the trisazo compound or a salt thereof represented by the following formula (1): (In formula (1), X represents hydrogen or a C1-C10 alkoxy group, R １ ~R ４ Each of these independently represents hydrogen, a C1-10 alkyl group, or a C1-10 alkoxy group, except R １ or R ２ (When the molecule has a C1-C10 alkoxy group, the other substituent is hydrogen.)

[0013] Furthermore, the present invention relates to, but is not limited to, the following [8] to

[10] . [8] A polarizing film containing a substrate, characterized in that the substrate contains the trisazo compound or a salt thereof described in [6] or [7]. [9] A polarizing plate comprising transparent protective films provided on one side and both sides of the polarizing film described in [8].

[10] A display device comprising the polarizing film described in [8] or the polarizing plate described in [9].

[0014] The present invention can provide a trisazo compound or a salt thereof that can be used as a dichroic dye to constitute polarizing films and polarizing plates and has excellent polarizing performance. In one embodiment, the trisazo compound or salt thereof of the present invention has a high degree of polarization, a wide wavelength range in which the degree of polarization is high, and good polarization characteristics even in the second absorption band. In another embodiment, the present invention can provide a trisazo compound or a salt thereof that has good dyeability to hydrophilic polymers. In another embodiment, the present invention can provide a trisazo compound having the above characteristics and a polarizing film and polarizing plate containing the same that have excellent polarizing performance.

[0015] In this specification and in the claims, unless it clearly refers to a free form, “trisazo compound or salt thereof” may be simply referred to as “trisazo compound.” In this specification and in the claims, since “substituents” may include hydrogen atoms, hydrogen atoms may also be described as “substituents” for convenience.

[0016] The trisazo compound or salt thereof of the present invention is represented by the following formula (0).

[0017] In the above formula (0), X represents hydrogen or an alkoxy group, and R １ ~R ４ Each of these independently represents a hydrogen atom, an alkyl group, or an alkoxy group, and R １ or R ２ If one of the substituents has an alkoxy group, the other substituent is hydrogen.

[0018] The alkyl group mentioned above is a linear, branched, or cyclic alkyl group, preferably C １ ~C １０ Alkyl alkyl group, comfortable C １ ~C ５ Alkyl groups are examples. C １ ~C １０ Specific examples of alkyl groups include linear C molecules such as methyl, ethyl, n-propyl, n-butyl, n-pentyl, n-hexyl, n-heptyl, n-octyl, n-nonyl, and n-decyl. １ ~C １０Alkyl groups; branched C such as isopropyl, isobutyl, sec-butyl, t-butyl, isoamyl, t-amyl, isohexyl, t-hexyl, isoheptyl, t-heptyl, isooctyl, t-octyl, 2-ethylhexyl, isononyl, and isodecyl. ３ ~C １０ Alkyl groups; or cyclic C such as cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, etc. ３ ~C ７ Examples include alkyl groups. Among these, linear or branched alkyl groups are preferred, C １ ~C ２ A linear alkyl group is more preferred, and a methyl group is even more preferred.

[0019] The alkoxy group mentioned above may be a linear, branched, or cyclic alkoxy group, preferably C １ ~C １０ Alkoxy group, more convenient C １ ~C ５ An example is an alkoxy group. １ ~C １０ Specific examples of alkoxy groups include linear carbon atoms such as methoxy, ethoxy, n-propoxy, n-butoxy, n-pentoxy, n-hexyloxy, n-heptoxy, n-octyloxy, n-nonyloxy, and n-decyloxy. １ ~C １０ Alkoxy groups; branched C groups such as isopropoxy, isobutoxy, sec-butoxy, t-butoxy, isoamyloxy, t-amyloxy, isohexyloxy, t-hexyloxy, isoheptoxy, t-heptoxy, isooctyloxy, t-octyloxy, 2-ethylhexyloxy, isononyloxy, and isodecyloxy. ３ ~C １０ Alkoxy group; or cyclic C such as cyclopropoxy, cyclobutoxy, cyclopentoxy, cyclohexyloxy, cycloheptoxy, etc. ３ ~C ７ Examples include alkoxy groups. Among these, linear or branched alkoxy groups are preferred, C １ ~C ２A linear alkoxy group is more preferred, and a methoxy group is even more preferred.

[0020] A more favorable R １ ~R ４ For example, hydrogen atoms, C １ ~C ２ Alkyl alkyl group, C １ ~C ２ An example is an alkoxy group.

[0021] When the trisazo compound or salt thereof represented by formula (0) is the trisazo compound or salt thereof represented by formula (1) below, it is preferable because it can provide a polarizing film with a high degree of polarization over a wider wavelength range, and it is even more preferable when it is the trisazo compound or salt thereof represented by formula (2) below. (In formula (1), X represents hydrogen or a C1-10 alkoxy group, R １ ~R ４ Each of these independently represents hydrogen, a C1-10 alkyl group, or a C1-10 alkoxy group, except R １ or R ２ (When it has a C1-10 alkoxy group, the other substituent is hydrogen.) (In formula (2), R １ ~R ４ Each of these independently represents hydrogen, a C1-10 alkyl group, or a C1-10 alkoxy group, and R １ or R ２ If one of the substituents has a C1-10 alkoxy group, the other substituent is hydrogen.

[0022] The substituent R in formula (2) above １ ~R ４ Examples include the same substituents that may be present in formula (1). However, R １ ~R ４ Each substituent is selected independently. Preferred R １ ~R ４ Each is an independent hydrogen atom, C １ ~C ２ an alkyl group, or C １ ~C ２ It is an alkoxy group.

[0023] In formulas (0) to (2), “C１ ~C ２ Examples of alkyl groups include methyl and ethyl groups.

[0024] In formulas (0) to (2), “C １ ~C ２ Examples of "alkoxy groups" include methoxy groups and ethoxy groups.

[0025] The trisazo compound represented by formula (0) above, or a salt thereof, can be easily produced by known diazotization and coupling according to the conventional method for producing trisazo compounds as described in Non-Patent Document 1. The synthesis method is illustrated using the trisazo compound represented by formula (1) as an example.

[0026] First, 7-aminonaphthalene-1,3-disulfonic acid, represented by formula (A) below, is diazotized using a known method as described in Non-Patent Document 1, and then primary-coupled with aromatic amines of formula (B) below as a primary coupler to obtain a monoazoamino compound represented by formula (C) below. (In formulas (A) to (C), R １ ~R ２ These terms have the same meaning as those in equation (1).

[0027] Next, this monoazoamino compound (C) is diazotized by a known method as described in Non-Patent Document 1, and then secondary coupling with an aromatic amine of the following formula (D) as a secondary coupler to obtain a disazoamino compound represented by the following formula (E). (In equations (D) and (E), R １ ~R ４ These terms have the same meaning as those in equation (1).

[0028] Next, the compound of formula (E) is diazotized by a known method as described in Non-Patent Document 1, and then tertiarily coupled with a 6-phenylamino-1-naphthol-3-sulfonic acid of formula (F) below as a tertiary coupler to obtain the azo compound of formula (1).

[0029] In the above reaction, the diazotization step is carried out either by a forward method, in which a nitrite such as sodium nitrite is mixed with an aqueous solution of a mineral acid such as hydrochloric acid or sulfuric acid, or a turbidity of the diazo component, or by a reverse method, in which a nitrite is added to a neutral or weakly alkaline aqueous solution of the diazo component, and then mixed with the mineral acid. The appropriate temperature for diazotization is -10 to 40°C. Furthermore, the coupling step with aromatic amines is carried out by mixing an acidic aqueous solution such as hydrochloric acid or acetic acid with the above-mentioned diazo solutions, under acidic conditions at a temperature of -10 to 40°C and a pH of 2 to 7.

[0030] The monoazo and disazo compounds obtained by coupling can be used as is, precipitated by acid precipitation or salting out and filtered, or proceeded to the next step as a solution or turbidity. If the monoazo and disazo compounds obtained by coupling are sparingly soluble and form a turbidity, they can be filtered and used as a press cake in the next coupling step.

[0031] The coupling reaction between the diazotized disazo compound and naphthols represented by formula (F) is carried out under neutral to alkaline conditions at a temperature of -10 to 40°C and a pH of 7 to 10. This reaction yields the trisazo compound represented by formula (0). After the reaction is complete, the compound is precipitated by salting out and then filtered. If purification is required, salting out can be repeated or the compound can be precipitated from water using an organic solvent. Examples of organic solvents used for purification include water-soluble organic solvents such as alcohols like methanol and ethanol, and ketones like acetone.

[0032] When the aromatic amines represented by formulas (B) and (D) that serve as raw materials for synthesizing the trisazo compound represented by formula (0) or its salt are substituted phenylamine compounds, examples include, but are not limited to, aniline, 2-methylaniline, 2-ethylaniline, 2-propylaniline, 2-butylaniline, 3-methylaniline, 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-methoxy-5-methylaniline, 2,5-dimethoxyaniline, etc. Furthermore, the amino group of these aromatic amines may be protected. An example of a protecting group is the ω-methanesulfone group.

[0033] Specific examples of trisazo compounds or salts thereof represented by formula (0) are given below. Note that trisazo compounds are expressed in the form of free acids.

[0034] The trisazo compounds represented by formula (0) above may be in the form of free acids or salts, or they may be salts of metal ions or ammonium ions. Examples of metal ions include alkali metal ions such as lithium ions, sodium ions, and potassium ions, and alkaline earth metal ions such as calcium ions and magnesium ions. Examples of ammonium ions include ammonium ions in the narrow sense (NH₄). ４ ＋), methylammonium ion, dimethylammonium ion, triethylammonium ion, tetraethylammonium ion, tetra-n-propylammonium ion, tetra-n-butylammonium ion, monoethanolammonium ion, diethanolammonium ion, triethanolammonium ion, N-methyl-N-monoethanolammonium ion, etc. More specifically, for example, in the case of a free acid, it represents sulfonic acid (-SO ３ H), in the case of a sodium ion, it represents sodium sulfonate (-SO ３ Na), in the case of an ammonium ion, it represents ammonium sulfonate (-SO ３ NH ４ ). In the case of N-methyl-N-monoethanolammonium ion, it represents "-SO ３ － ・[MeNH ２ CH ２ CH ２ OH] ＋ ".

[0035] <Polarizing Film> The polarizing film of the present invention contains one or more trisazo compounds represented by formula (0) or salts thereof, and may optionally further contain one or more other organic dyes other than the trisazo compounds represented by formula (0). The other organic dyes are not particularly limited, but dyes that have absorption characteristics in a wavelength region different from the absorption wavelength region of the trisazo compound represented by formula (0) or salts thereof, and that have high dichroism are preferred. Examples of other organic dyes 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. Representative examples include Direct Red 81, C.I. Direct Red 247, C.I. Direct Blue 69, C.I. Direct Green 80, and C.I. Direct Green 59, as well as the dyes described in Non-Patent Literature 2. However, depending on the purpose, it is preferable to use dyes developed for polarizing plates, such as those described in International Publication No. 2017 / 146212, International Publication No. 2019 / 117131, International Publication No. 2020 / 050333, and International Publication No. 2021 / 015188. These organic dyes are used as free acids, alkali metal salts (e.g., Na salts, K salts, Li salts), ammonium salts, or amine salts.

[0036] In one embodiment of the present invention, the polarizing film produced using the trisazo compound represented by formula (0) or a salt thereof and other dichroic dyes is a neutral gray polarizing film, a color polarizing film, etc., which can be used depending on the application. Here, "neutral gray" means that when two polarizing films are superimposed so that their orientation directions are orthogonal to each other (hereinafter also referred to as "orthogonal position"), there is little light leakage (color leakage) of specific wavelengths in the visible light wavelength range.

[0037] When using a trisazo compound of formula (0) or a salt thereof in combination with multiple dichroic dyes, the types of organic dyes used will differ depending on whether the target polarizing film is a neutral gray polarizing film, a color polarizing film for liquid crystal projectors, or other color polarizing films. The blending ratio is not particularly limited, but generally, it is preferable to use a total of at least one of the other organic dyes in the range of 0.01 to 100 parts by weight per 1 part by weight of the trisazo compound of formula (0) or a salt thereof, and more preferably in the range of 0.1 to 10 parts by weight.

[0038] When the target polarizing film is a neutral gray polarizing film, the types and proportions of other organic dyes used in combination are adjusted so that the resulting polarizing film has minimal color leakage in the visible light wavelength range.

[0039] When the target polarizing film is a color polarizing film, the types and proportions of other organic dyes used in combination are adjusted so that the resulting polarizing film has a high single-plate average light transmittance in a specific wavelength range and a low average light transmittance at orthogonal positions.

[0040] The polarizing film of the present invention can be produced by incorporating a dichroic dye, which includes a trisazo compound represented by formula (0) or a salt thereof, and optionally other dyes, into a polarizing film substrate (also simply referred to as "substrate") in a known manner and oriented it.

[0041] The polarizing film substrate is preferably a polymer film, and more preferably a film made of polyvinyl alcohol resin or a derivative thereof. Specific examples of the polarizing film substrate include polyvinyl alcohol resin or polyvinyl alcohol resin modified with olefins such as ethylene and propylene, or unsaturated carboxylic acids such as crotonic acid, acrylic acid, methacrylic acid, and maleic acid. As the polarizing film substrate, a film made of polyvinyl alcohol resin or a derivative thereof is preferably used from the viewpoint of dye adsorption and orientation. The thickness of the polarizing film substrate is usually 10 to 100 μm, and preferably about 20 to 80 μm.

[0042] When the polarizing film substrate is a polymer film, a method of dyeing the polymer film is usually employed to incorporate the trisazo compound of formula (0) or a salt thereof. Dyeing is carried out, for example, as follows: First, a dye bath is prepared by dissolving the trisazo compound represented by formula (0) or a salt thereof, and optionally other organic dyes, in water. The dye concentration in the dye bath is not particularly limited, but is usually selected from a range of about 0.001 to 10% by weight. Dyeing aids may also be used if necessary; for example, it is preferable to use Glauber's salt at a concentration of about 0.1 to 10% by weight. The polymer film can be immersed in the dye bath prepared in this way for, for example, 1 to 10 minutes to perform dyeing. The dyeing temperature is preferably about 30 to 65°C.

[0043] The orientation of the trisazo compound or salt thereof represented by formula (0) above is performed by stretching a polymer film dyed with the trisazo compound. The stretching ratio is generally 2 to 9 times, preferably 3 to 8 times, and more preferably 4 to 7 times. Any known method may be used for stretching, such as a wet method or a dry method. Stretching of the polymer film may be performed before dyeing, if necessary. In this case, the orientation of the water-soluble dye is performed at the time of dyeing. The polymer film containing the water-soluble dye and oriented is subjected to post-treatment such as boric acid treatment by a known method as needed. Such post-treatment is performed to improve the transmittance and polarization degree of the polarizing film. The conditions for boric acid treatment vary depending on the type of polymer film and dye used, but generally the boric acid concentration of the boric acid aqueous solution is, for example, 0.1 to 15% by weight, preferably 1 to 10% by weight, the treatment temperature is 30 to 80°C, preferably 40 to 75°C, and the treatment is performed by immersion for 0.5 to 10 minutes. Furthermore, if necessary, a fixation treatment may be carried out in conjunction with an aqueous solution containing a cationic polymer compound.

[0044] A polarizing film containing the trisazo compound represented by formula (0) above or a salt thereof can be suitably used in applications requiring high optical properties. For example, in applications requiring high optical properties, the desirable optical properties are such that, at the maximum absorption wavelength in the first absorption band, when the single-layer transmittance is 44.0% ± 0.4%, the degree of polarization is preferably 98.5% or higher, more preferably 98.8%, and even more preferably 99.1% or higher.

[0045] A polarizing film containing the trisazo compound represented by formula (0) above or a salt thereof is characterized in that the wavelength range in which the degree of polarization is 90% or more when the transmittance of the single element is 44.0% ± 0.4% is 105 nm or more, and the wavelength range in which the degree of polarization is 95% or more is 85 nm or more. More preferably, the wavelength range in which the degree of polarization is 90% or more when the transmittance of the single element is 44.0% ± 0.4% is 108 nm or more, and the wavelength range in which the degree of polarization is 95% or more is 88 nm or more. Even more preferably, the wavelength range in which the degree of polarization is 90% or more when the transmittance of the single element is 44.0% ± 0.4% is 112 nm or more, and the wavelength range in which the degree of polarization is 95% or more is 92 nm or more. Most preferably, the wavelength range in which the degree of polarization is 90% or more when the transmittance of the single element is 44.0% ± 0.4% is 115 nm or more, and the wavelength range in which the degree of polarization is 95% or more is 95 nm or more. When a neutral gray polarizing film is fabricated by combining multiple dyes, it is possible to provide a polarizing film with excellent optical properties over a wide wavelength range by having high polarization characteristics over a wide wavelength range.

[0046] In a polarizing film containing the trisazo compound or a salt thereof of the present invention, if there are multiple maximum absorption wavelengths, the first absorption band refers to the absorption band containing the longest wavelength maximum absorption wavelength in the visible light region, and the second absorption band refers to the absorption band containing the next longest wavelength maximum absorption wavelength after the first absorption band. Furthermore, it is preferable that the first absorption band contains the absorption band with the largest maximum absorption wavelength. A polarizing film containing the trisazo compound or a salt thereof represented by the above formula (0) is characterized in that the degree of polarization in the second absorption band is 45% or more when the transmittance of the single component is 44.0% ± 0.4%. When a neutral gray polarizing film is made by combining multiple dyes, even if it has high polarization characteristics in the wavelength range covered by the first absorption band, if the polarization characteristics are low in the wavelength range covered by the second absorption band, the polarization characteristics of the polarizing film as a whole will be low. Therefore, by having high polarization characteristics in the second absorption band, it is possible to provide a polarizing film with excellent optical properties over a wide wavelength range.

[0047] <Polarizing Plate> The polarizing plate of the present invention (hereinafter also referred to as the "dye-based polarizing plate") can be obtained by using the compound of the present invention as a dichroic dye to control the transmittance in the long-wavelength region, and laminating a transparent protective film to one or both sides of the polarizing film produced. The material for forming the transparent protective film is preferably a material that is excellent in optical transparency, mechanical strength, thermal stability, moisture shielding properties, etc. Examples include, but are not limited to, cellulose acetate films, acrylic films, fluorine-based films such as tetrafluoroethylene / hexafluoropropylene copolymers, polyester resins, polyolefin resins, or polyamide resins. The transparent protective film is preferably a triacetylcellulose (TAC) film or a cycloolefin film, and the thickness of the protective film is usually preferably 10 to 200 μm. Furthermore, the transparent protective film is not limited to a film; a transparent protective layer may also be provided by forming a protective layer on the polarizing film made of an organic composition, an inorganic composition, or a mixed composition thereof, made of a material that is excellent in optical transparency, mechanical strength, thermal stability, moisture shielding properties, etc.

[0048] Furthermore, it can also be applied as a supported, integrated polarizing plate in which a transparent substrate thicker than the film is laminated to both or one side of the polarizing film. The support can be broadly divided into inorganic substrates and organic substrates, including inorganic substrates such as soda glass, borosilicate glass, quartz substrates, sapphire substrates, and spinel substrates, and organic substrates such as acrylic, polycarbonate, polyethylene terephthalate, polyethylene naphthalate, and polyolefins.

[0049] Adhesives or adhesives can be used to bond the polarizing film to the transparent protective film or protective substrate of a polarizing plate. Examples of adhesives include thermosetting adhesives and UV-curing adhesives, and include, but are not limited to, polyvinyl alcohol-based adhesives, urethane emulsion-based adhesives, acrylic-based adhesives, and polyester-isocyanate-based adhesives. Crosslinking agents, water-resistant agents, and other additives can be added to the adhesive to improve adhesive strength or water resistance. These are not particularly limited and can be selected as appropriate.

[0050] A transparent protective layer or functional layer may be provided on one or both sides of a polarizing plate on which a transparent protective film or the like has been formed. Examples of transparent protective layers include hard coat layers made of acrylic, polysiloxane, or urethane. As a functional layer, to further improve the transmittance of the single layer, an anti-reflective layer (anti-reflection layer, low-reflection layer, or a combination thereof), an anti-glare layer, an anti-fouling layer, etc., may be provided on the transparent protective film, transparent substrate, or transparent protective layer. The anti-reflection layer can be formed by vapor deposition or sputtering of a substance such as silicon dioxide or titanium dioxide, or by thinly coating a fluorine-based substance.

[0051] Optical components may be laminated on one or both sides of the polarizing plate, or optical components may be directly bonded to the polarizing film. Examples of optical components include cover glass, light diffusion film, and phase difference film.

[0052] For example, phase difference films include phase difference films made of transparent resins such as polycarbonate resin, and phase difference films made of liquid crystal coating. Polarizing plates and phase difference films can be bonded together using an adhesive or bonding agent. Polarizing plates to which phase difference films are bonded become elliptical polarizing plates or circular polarizing plates, which can be appropriately selected depending on the display device used to obtain effects such as viewing angle compensation and interfacial reflection prevention.

[0053] A support can be provided on one or both sides of the polarizing plate of the present invention, and it may be used as a polarizing plate with a support. The support preferably has a flat surface for attaching the polarizing plate, and since it is for optical applications, it is preferably a transparent substrate. Transparent substrates can be broadly divided into inorganic substrates and organic substrates, and examples of inorganic substrates include soda glass, borosilicate glass, quartz substrates, sapphire substrates, and spinel substrates, as well as organic substrates such as acrylic, polycarbonate, polyethylene terephthalate, polyethylene naphthalate, and cycloolefin polymers.

[0054] To bond the polarizing plate to optical components or supports, an adhesive layer may be formed on one or both sides of the polarizing plate. Adhesives and tacks can be used as the adhesive layer, but acrylic resins, polyester resins, polyurethane resins, and other tacks are preferred. The tacks used are not limited to these and can be appropriately selected depending on the application and components.

[0055] The polarizing plate of the present invention may be either a neutral gray polarizing plate or a color polarizing plate, depending on the application. Furthermore, these polarizing plates have excellent polarization performance, and discoloration and deterioration of polarization performance are suppressed even in high temperature and high humidity conditions, making them suitable for automotive or outdoor display applications.

[0056] <Display Device> The display device of the present invention comprises a polarizing film or polarizing plate of the present invention. Examples of display devices include known liquid crystal display devices, projector devices, or organic electronic display devices (OLEDs), and can be applied to, but are not limited to, calculators, watches, laptop computers, liquid crystal televisions, car navigation systems, and indoor and outdoor measuring instruments and displays. In particular, it is suitably used in various displays that require high polarization performance and durability, such as in-vehicle display devices or outdoor display devices (for example, for display applications in industrial instruments and wearable applications). The dye-based polarizing film or dye-based polarizing plate provided in the display device is preferably neutral gray.

[0057] For example, in the case of a liquid crystal display device, a dye-based polarizer is placed on either the incident side or the output side of the liquid crystal cell, or both. The dye-based polarizer may or may not be in contact with the liquid crystal cell, but from the viewpoint of durability, it is preferable that it is not in contact. If the dye-based polarizer is in contact with the liquid crystal cell on the output side of the liquid crystal cell, the liquid crystal cell can be used as a support for the dye-based polarizer. If the dye-based polarizer is not in contact with the liquid crystal cell, it is preferable to use a dye-based polarizer with a support other than the liquid crystal cell. Furthermore, from the viewpoint of durability, it is preferable to place the dye-based polarizer on both the incident and output sides of the liquid crystal cell, and it is even preferable to place the polarizer surface of the dye-based polarizer on the liquid crystal cell side and the support surface on the light source side. The incident side of the liquid crystal cell is the light source side, and the opposite side is called the output side.

[0058] The driving method for the liquid crystal display device can be any appropriate method from known technologies. For example, it is preferable to use an active matrix drive type in which liquid crystal is sealed between a transparent substrate on which electrodes and thin-film transistors are formed and a transparent substrate on which counter electrodes are formed. Light emitted from a light source such as a cold cathode lamp or white LED passes through a dye-based polarizing plate, then through a liquid crystal cell, a color filter, and another dye-based polarizing plate, and is projected onto the display screen.

[0059] The present invention will be described in more detail below with reference to examples, but these are illustrative and do not limit the present invention in any way. Unless otherwise specified, the percentages and parts by weight in the examples are based on weight.

[0060] [Example 1] (Step 1) 15.4 parts by weight of 7-aminonaphthalene-1,3-disulfonic acid was added to 200 parts by weight of water, and 9.8 parts by weight of 25% sodium hydroxide aqueous solution was added to dissolve the amino compound. 15.9 parts by weight of 35% hydrochloric acid was then added, followed by 9.1 parts by weight of 40% sodium nitrite aqueous solution, and the mixture was stirred at -10°C to 10°C for 1 hour to diazotize the amino compound. 6.5 parts by weight of 3-methoxyaniline was added dropwise as a primary coupler, and while stirring at 10 to 30°C, 15% sodium carbonate aqueous solution was added to adjust the pH to 2. Further stirring was performed to complete the coupling. Subsequently, salting out was performed with sodium chloride, the precipitate was filtered, and the obtained solid was dried to obtain 13.1 parts by weight of the monoazoamino compound represented by formula (100).

[0061] (Step 2) After adding 100 parts by weight of water to a container, 15.6 parts by weight of 35% hydrochloric acid was added and stirred at -10°C to 10°C to prepare a hydrochloric acid solution. In a separate container, 13.1 parts by weight of the monoazoamino compound represented by formula (100) was dispersed in 300 parts by weight of water, then 7.8 parts by weight of 40% sodium nitrite aqueous solution was added and stirred, and this was added dropwise to the aforementioned hydrochloric acid solution and stirred for 1 hour to diazotize the monoazoamino compound. Then, 5.5 parts by weight of 2,5-dimethylaniline was added as a secondary coupler, and while stirring at 20 to 30°C, 15% sodium carbonate aqueous solution was added to adjust the pH to 3. Further stirring was performed to complete the coupling. After that, salting out was performed with sodium chloride, the precipitate was filtered, and the obtained solid was dried to obtain 16.1 parts by weight of the disazoamino compound represented by formula (101).

[0062] (Step 3) After adding 100 parts by weight of water to a container, 14.6 parts by weight of 35% hydrochloric acid was added and stirred at 10°C to 20°C to prepare a hydrochloric acid solution. In a separate container, 16.1 parts by weight of the disazoamino compound represented by formula (101) was dispersed in 400 parts by weight of water, then 7.3 parts by weight of 40% sodium nitrite aqueous solution was added and stirred, and this was added dropwise to the aforementioned hydrochloric acid solution and stirred for 1 hour to diazotize the disazoamino compound. In a separate container, as a tertiary coupler, 25.6 parts by weight of 6-(4'-methoxyphenylamino)-1-naphthol-3-sulfonic acid was added to 60 parts by weight of water and dissolved with sodium carbonate to make it weakly alkaline to obtain a tertiary coupler solution. To this tertiary coupler solution, while maintaining its pH at 8 to 10, the diazotized disazoamino compound obtained earlier was injected and stirred to complete the coupling. Subsequently, the mixture was salted out with sodium chloride, the precipitate was filtered, and the resulting solid was dried to obtain 18.5 parts by weight of a trisazo compound represented by formula (102) (Compound Example 59).

[0063] [Example 2] (Step 1) 5.0 parts by weight of sodium bisulfite was added to 50 parts by weight of water and stirred at 40-50°C. 4.7 parts by weight of 36% formaldehyde solution was added, the pH was adjusted to 6-8 with sodium bisulfite, and the mixture was stirred at 50-70°C for 15 minutes. Then, 4.7 parts by weight of aniline was added and the mixture was stirred for 2 hours to prepare an aniline ω-methanesulfonic acid protective solution. In a separate container, 16.7 parts by weight of 7-aminonaphthalene-1,3-disulfonic acid was added to 200 parts by weight of water, and a 25% sodium hydroxide solution was added to adjust the pH to 8 and dissolve the amino compound. 17.6 parts by weight of 35% hydrochloric acid was added, followed by 14.8 parts by weight of 40% sodium nitrite aqueous solution. The mixture was stirred at -10°C to 10°C for 1 hour to diazotize the amino compound. The ω-methanesulfonic acid protective solution of aniline was then added dropwise, and the mixture was stirred at pH 7 for 2 hours to complete the coupling. A 25% sodium hydroxide solution was added to bring the pH to 11, and the mixture was stirred at 85°C to 95°C for 8 hours. After salting out with sodium chloride, the precipitate was filtered, and the resulting solid was dried to obtain 13.2 parts by weight of the monoazoamino compound represented by formula (103).

[0064] (Step 2) 12.6 parts by weight of the disazoamino compound represented by formula (104) was obtained by the same method as in Step 2 of Example 1, except that 13.1 parts by weight of the monoazoamino compound represented by formula (100) was replaced with 13.2 parts by weight of the monoazoamino compound obtained in Step 1 of Example 2.

[0065] (Step 3) 16.1 parts by weight of a trisazoamino compound represented by formula (105) (Compound Example 38) was obtained by the same method as in Step 3 of Example 1, except that 16.1 parts by weight of the disazoamino compound represented by formula (101) was replaced with 12.6 parts by weight of the disazoamino compound obtained in Step 2 of Example 2.

[0066] [Example 3] Except for substituting 6.5 parts by weight of 3-methoxyaniline for the primary coupler with 5.7 parts by weight of 3-methylaniline, and substituting 5.5 parts by weight of 2,5-dimethylaniline for 4.7 parts by weight of 3-methylaniline for the secondary coupler, 17.9 parts by weight of a trisazoamino compound represented by formula (106) (Compound Example 44) was obtained by the same method as in steps 1 to 3 of Example 1.

[0067] [Example 4] Except for substituting 5.5 parts by weight of 2,5-dimethylaniline with 7.0 parts by weight of 2,5-dimethoxyaniline as a secondary coupler, 18.1 parts by weight of a trisazoamino compound represented by formula (107) (Compound Example 42) was obtained by the same method as in steps 1 to 3 of Example 2.

[0068] [Example 5] Except for substituting 6.5 parts by weight of 3-methoxyaniline with 5.7 parts by weight of 3-methylaniline as the primary coupler, 18.7 parts by weight of a trisazoamino compound represented by formula (108) (Compound Example 45) was obtained by the same method as in steps 1 to 3 of Example 1.

[0069] [Example 6] Except for substituting 6.5 parts by weight of 3-methoxyaniline with 6.4 parts by weight of 2,5-dimethylaniline as the primary coupler, 17.9 parts by weight of a trisazoamino compound represented by formula (109) (Compound Example 52) was obtained by the same method as in steps 1 to 3 of Example 1.

[0070] [Example 7] Except that 6.5 parts by weight of 3-methoxyaniline was replaced with 5.7 parts by weight of 3-methylaniline as the primary coupler, and 25.6 parts by weight of 6-(4'-methoxyphenylamino)-1-naphthol-3-sulfonic acid was replaced with 23.4 parts by weight of 6-phenylamino-1-naphthol-3-sulfonic acid as the tertiary coupler, the same method as in steps 1 to 3 of Example 1 was used to obtain 17.6 parts by weight of a trisazoamino compound represented by formula (110) (Compound Example 10).

[0071] [Example 8] Except that 5.5 parts by weight of 2,5-dimethylaniline was replaced with 6.2 parts by weight of 2-methoxy-5-methylaniline as the secondary coupler, and 25.6 parts by weight of 6-(4'-methoxyphenylamino)-1-naphthol-3-sulfonic acid was replaced with 23.4 parts by weight of 6-phenylamino-1-naphthol-3-sulfonic acid as the tertiary coupler, the same method as in steps 1 to 3 of Example 2 was used to obtain 17.6 parts by weight of a trisazoamino compound represented by formula (111) (Compound Example 6).

[0072] [Example 9] Except that the primary coupler was replaced with 5.7 parts by weight of 3-methylaniline instead of 6.5 parts by weight of 3-methoxyaniline, the secondary coupler was replaced with 6.2 parts by weight of 2-methoxy-5-methylaniline instead of 5.5 parts by weight of 2,5-dimethylaniline, and the tertiary coupler was replaced with 23.4 parts by weight of 6-phenylamino-1-naphthol-3-sulfonic acid instead of 25.6 parts by weight of 6-(4'-methoxyphenylamino)-1-naphthol-3-sulfonic acid instead of 23.4 parts by weight of 6-phenylamino-1-naphthol-3-sulfonic acid, 17.9 parts by weight of a trisazoamino compound represented by formula (112) (Compound Example 13) was obtained by the same method as in steps 1 to 3 of Example 1.

[0073] [Example 10] Except that the primary coupler was replaced with 6.4 parts by weight of 2,5-dimethylaniline instead of 6.5 parts by weight of 3-methoxyaniline, the secondary coupler was replaced with 6.2 parts by weight of 2-methoxy-5-methylaniline instead of 5.5 parts by weight of 2,5-dimethylaniline, and the tertiary coupler was replaced with 23.4 parts by weight of 6-phenylamino-1-naphthol-3-sulfonic acid instead of 25.6 parts by weight of 6-(4'-methoxyphenylamino)-1-naphthol-3-sulfonic acid instead of 6-phenylamino-1-naphthol-3-sulfonic acid, 17.6 parts by weight of a trisazoamino compound represented by formula (113) (Compound Example 20) was obtained by the same method as in steps 1 to 3 of Example 1.

[0074] [Example 11] Except that 6.5 parts by weight of 3-methoxyaniline was replaced with 5.7 parts by weight of 3-methylaniline as the primary coupler, and 5.5 parts by weight of 2,5-dimethylaniline was replaced with 7.0 parts by weight of 2,5-dimethoxyaniline as the secondary coupler, 18.8 parts by weight of a trisazoamino compound represented by formula (114) (Compound Example 49) was obtained by the same method as in steps 1 to 3 of Example 1.

[0075] [Example 12] Except that 6.5 parts by weight of 3-methoxyaniline was replaced with 6.4 parts by weight of 2,5-dimethylaniline as the primary coupler, and 25.6 parts by weight of 6-(4'-methoxyphenylamino)-1-naphthol-3-sulfonic acid was replaced with 23.4 parts by weight of 6-phenylamino-1-naphthol-3-sulfonic acid as the tertiary coupler, the same method as in steps 1 to 3 of Example 1 was used to obtain 16.8 parts by weight of a trisazoamino compound represented by formula (115) (Compound Example 17).

[0076] [Example A1] As a secondary coupler, 5.5 parts by weight of 2,5-dimethylaniline was replaced with 4.2 parts by weight of aniline, and an ω-methanesulfonic acid protective solution of aniline was prepared by the same method as in step 1 of Example 2 and used as a coupler. After completing the coupling, the pH was set to 11 and the mixture was treated at 85°C to 95°C. Except for these steps, 15.6 parts by weight of a trisazo compound represented by formula (A1) (Compound Example 36) was obtained by the same method as in steps 1 to 3 of Example 2.

[0077] [Example A2] Except for substituting 5.5 parts by weight of 2,5-dimethylaniline with 4.7 parts by weight of 3-methylaniline as a secondary coupler, 15.8 parts by weight of a trisazo compound represented by formula (A2) (Compound Example 37) was obtained by the same method as in steps 1 to 3 of Example 2.

[0078] [Example A3] Except for substituting 25.6 parts by weight of 6-(4'-methoxyphenylamino)-1-naphthol-3-sulfonic acid with 23.4 parts by weight of 6-phenylamino-1-naphthol-3-sulfonic acid as the tertiary coupler, 15.6 parts by weight of a trisazo compound represented by formula (A3) (Compound Example 3) was obtained by the same method as in steps 1 to 3 of Example 2.

[0079] [Example A4] Except for substituting 5.5 parts by weight of 2,5-dimethylaniline with 6.2 parts by weight of 2-methoxy-5-methylaniline as a secondary coupler, 16.4 parts by weight of a trisazo compound represented by formula (A4) (Compound Example 41) was obtained by the same method as in steps 1 to 3 of Example 2.

[0080] [Example A5] Except that 5.5 parts by weight of 2,5-dimethylaniline was replaced with 7.0 parts by weight of 2,5-dimethoxyaniline as the secondary coupler, and 25.6 parts by weight of 6-(4'-methoxyphenylamino)-1-naphthol-3-sulfonic acid was replaced with 23.4 parts by weight of 6-phenylamino-1-naphthol-3-sulfonic acid as the tertiary coupler, the same method as in steps 1 to 3 of Example 2 was used to obtain 16.1 parts by weight of the trisazoamino compound represented by formula (A5) (Compound Example 7).

[0081] [Example A6] Except for substituting 25.6 parts by weight of 6-(4'-methoxyphenylamino)-1-naphthol-3-sulfonic acid with 23.4 parts by weight of 6-phenylamino-1-naphthol-3-sulfonic acid as the tertiary coupler, 17.3 parts by weight of a trisazo compound represented by formula (A6) (Compound Example 9) was obtained by the same method as in Example 3.

[0082] [Example A7] Except that 6.5 parts by weight of 3-methoxyaniline was replaced with 5.7 parts by weight of 3-methylaniline as the primary coupler, and 5.5 parts by weight of 2,5-dimethylaniline was replaced with 6.2 parts by weight of 2-methoxy-5-methylaniline as the secondary coupler, 18.5 parts by weight of a trisazoamino compound represented by formula (A7) (Compound Example 48) was obtained by the same method as in steps 1 to 3 of Example 1.

[0083] [Example A8] Except for substituting 25.6 parts by weight of 6-(4'-methoxyphenylamino)-1-naphthol-3-sulfonic acid with 23.4 parts by weight of 6-phenylamino-1-naphthol-3-sulfonic acid as the tertiary coupler, 18.2 parts by weight of a trisazo compound represented by formula (A8) (Compound Example 14) was obtained by the same method as in Example 11.

[0084] [Example A9] Except for substituting 6.5 parts by weight of 3-methoxyaniline with 6.4 parts by weight of 2,5-dimethylaniline as the primary coupler, and substituting 5.5 parts by weight of 2,5-dimethylaniline with 6.2 parts by weight of 2-methoxy-5-methylaniline as the secondary coupler, 18.2 parts by weight of a trisazo compound represented by formula (A9) (Compound Example 55) was obtained by the same method as in steps 1 to 3 of Example 1.

[0085] [Example A10] Except that 6.5 parts by weight of 3-methoxyaniline was replaced with 6.4 parts by weight of 2,5-dimethylaniline as the primary coupler, and 5.5 parts by weight of 2,5-dimethylaniline was replaced with 7.0 parts by weight of 2,5-dimethoxyaniline as the secondary coupler, 19.1 parts by weight of a trisazoamino compound represented by formula (A10) (Compound Example 56) was obtained by the same method as in steps 1 to 3 of Example 1.

[0086] [Example A11] Except for substituting 25.6 parts by weight of 6-(4'-methoxyphenylamino)-1-naphthol-3-sulfonic acid with 23.4 parts by weight of 6-phenylamino-1-naphthol-3-sulfonic acid as the tertiary coupler, 18.5 parts by weight of a trisazo compound represented by formula (A11) (Compound Example 21) was obtained by the same method as in Example A10.

[0087] [Example A12] Except for substituting 5.5 parts by weight of 2,5-dimethylaniline with 4.7 parts by weight of 3-methylaniline as a secondary coupler, 18.2 parts by weight of a trisazoamino compound represented by formula (A12) (Compound Example 58) was obtained by the same method as in steps 1 to 3 of Example 1.

[0088] [Example A13] Except for substituting 25.6 parts by weight of 6-(4'-methoxyphenylamino)-1-naphthol-3-sulfonic acid with 23.4 parts by weight of 6-phenylamino-1-naphthol-3-sulfonic acid as the tertiary coupler, 17.6 parts by weight of a trisazo compound represented by formula (A13) (Compound Example 23) was obtained by the same method as in Example A12.

[0089] [Example A14] Except for substituting 25.6 parts by weight of 6-(4'-methoxyphenylamino)-1-naphthol-3-sulfonic acid with 23.4 parts by weight of 6-phenylamino-1-naphthol-3-sulfonic acid as the tertiary coupler, 17.9 parts by weight of a trisazo compound represented by formula (A14) (Compound Example 24) was obtained by the same method as in steps 1 to 3 of Example 1.

[0090] [Example A15] Except for substituting 5.5 parts by weight of 2,5-dimethylaniline with 7.0 parts by weight of 2,5-dimethoxyaniline as a secondary coupler, 19.1 parts by weight of a trisazoamino compound represented by formula (A15) (Compound Example 63) was obtained by the same method as in steps 1 to 3 of Example 1.

[0091] [Example A16] Except for substituting 6.5 parts by weight of 3-methoxyaniline for 6.5 parts by weight of 2-methoxyaniline as the primary coupler, 18.5 parts by weight of a trisazoamino compound represented by formula (A16) (Compound Example 66) was obtained by the same method as in steps 1 to 3 of Example 1.

[0092] [Example A17] Except for substituting 5.5 parts by weight of 2,5-dimethylaniline with 5.6 parts by weight of 3-methoxyaniline as a secondary coupler, 18.5 parts by weight of a trisazoamino compound represented by formula (A17) (Compound Example 60) was obtained by the same method as in steps 1 to 3 of Example 1.

[0093] [Example A18] Except for substituting 6.5 parts by weight of 3-methoxyaniline with 6.4 parts by weight of 2,5-dimethylaniline as the primary coupler, and substituting 5.5 parts by weight of 2,5-dimethylaniline with 4.7 parts by weight of 3-methylaniline as the secondary coupler, 18.2 parts by weight of a trisazoamino compound represented by formula (A18) (Compound Example 51) was obtained by the same method as in steps 1 to 3 of Example 1.

[0094] [Example A19] Except for substituting 25.6 parts by weight of 6-(4'-methoxyphenylamino)-1-naphthol-3-sulfonic acid with 23.4 parts by weight of 6-phenylamino-1-naphthol-3-sulfonic acid as the tertiary coupler, 17.6 parts by weight of a trisazo compound represented by formula (A19) (Compound Example 16) was obtained by the same method as in Example A18.

[0095] [Example A20] Except for substituting 6.5 parts by weight of 3-methoxyaniline with 5.7 parts by weight of 3-methylaniline as the primary coupler, and substituting 5.5 parts by weight of 2,5-dimethylaniline with 5.6 parts by weight of 3-methoxyaniline as the secondary coupler, 18.2 parts by weight of a trisazoamino compound represented by formula (A20) (Compound Example 46) was obtained by the same method as in steps 1 to 3 of Example 1.

[0096] [Example A21] Except for substituting 25.6 parts by weight of 6-(4'-methoxyphenylamino)-1-naphthol-3-sulfonic acid with 23.4 parts by weight of 6-phenylamino-1-naphthol-3-sulfonic acid as the tertiary coupler, 17.6 parts by weight of a trisazo compound represented by formula (A21) (Compound Example 11) was obtained by the same method as in Example A20.

[0097] [Example A22] Except for substituting 6.5 parts by weight of 3-methoxyaniline with 6.4 parts by weight of 2,6-dimethylaniline as the primary coupler, and substituting 5.5 parts by weight of 2,5-dimethylaniline with 4.7 parts by weight of 3-methylaniline as the secondary coupler, 18.2 parts by weight of a trisazoamino compound represented by formula (A22) (Compound Example 129) was obtained by the same method as in steps 1 to 3 of Example 1.

[0098] [Example A23] Except for replacing 6.5 parts by weight of 3-methoxyaniline with 6.4 parts by weight of 2,6-dimethylaniline as the primary coupler, and replacing 5.5 parts by weight of 2,5-dimethylaniline with 5.5 parts by weight of 2,6-dimethylaniline as the secondary coupler, 18.5 parts by weight of a trisazoamino compound represented by formula (A23) (Compound Example 119) was obtained by the same method as in steps 1 to 3 of Example 1.

[0099] [Example A24] Except for substituting 6.5 parts by weight of 3-methoxyaniline with 6.4 parts by weight of 3,5-dimethylaniline as the primary coupler, and substituting 5.5 parts by weight of 2,5-dimethylaniline with 4.7 parts by weight of 3-methylaniline as the secondary coupler, 18.2 parts by weight of a trisazoamino compound represented by formula (A24) (Compound Example 122) was obtained by the same method as in steps 1 to 3 of Example 1.

[0100] [Example A25] Except for substituting 25.6 parts by weight of 6-(4'-methoxyphenylamino)-1-naphthol-3-sulfonic acid with 23.4 parts by weight of 6-phenylamino-1-naphthol-3-sulfonic acid as the tertiary coupler, 17.6 parts by weight of a trisazo compound represented by formula (A25) (Compound Example 94) was obtained by the same method as in Example A24.

[0101] [Comparative Example 1] The compound described in Example 53 of Patent Document 1 was synthesized with reference to the method described in Patent Document 1. Its structure is shown by formula (116).

[0102] [Comparative Example 2] The compound described in Example 1 of Patent Document 2 was synthesized with reference to the method described in Patent Document 2. Its structure is shown by formula (117).

[0103] [Comparative Example 3] The compound described in Example 8 of Patent Document 3 was synthesized with reference to the method described in Patent Document 3. Its structure is shown by formula (118).

[0104] [Comparative Example 4] Except that 6.5 parts by weight of 3-methoxyaniline was replaced with 6.4 parts by weight of 2,5-dimethylaniline as the primary coupler, and 25.6 parts by weight of 6-(4'-methoxyphenylamino)-1-naphthol-3-sulfonic acid was replaced with 24.4 parts by weight of 6-benzylamino-1-naphthol-3-sulfonic acid as the tertiary coupler, 17.6 parts by weight of the trisazoamino compound described in Compound Example 119 of Patent Document 4, represented by formula (119), was obtained by the same method as in steps 1 to 3 of Example 1.

[0105] [Comparative Example 5] The compound described in Example 14 of Patent Document 5 was synthesized with reference to the method described in Patent Document 5. Its structure is shown by formula (120).

[0106] [Comparative Example 6] The compound described in Example 14 of Patent Document 6 was synthesized with reference to the method described in Patent Document 6. Its structure is shown by formula (121).

[0107] [Comparative Example 7] The compound described in Example 1 of Patent Document 7 was synthesized with reference to the method described in Patent Document 7. Its structure is shown by formula (122).

[0108] [Comparative Example 8] The compound described in Example 48 of Patent Document 8 was synthesized with reference to the method described in Patent Document 8. Its structure is shown by formula (123).

[0109] [Comparative Example 9] The compound described in Example 4 of Patent Document 9 was synthesized with reference to the method described in Patent Document 9. Its structure is shown by formula (124).

[0110] [Comparative Example 10] Except that the primary coupler was changed from 6.5 parts by weight of 3-methoxyaniline to 8.1 parts by weight of 2,5-dimethoxyaniline, the secondary coupler was changed from 5.5 parts by weight of 2,5-dimethylaniline to 7.0 parts by weight of 2,5-dimethoxyaniline, and the tertiary coupler was changed from 25.6 parts by weight of 6-(4'-methoxyphenylamino)-1-naphthol-3-sulfonic acid to 23.4 parts by weight of 6-phenylamino-1-naphthol-3-sulfonic acid, 19.4 parts by weight of the trisazoamino compound represented by formula (125) was obtained by the same method as in steps 1 to 3 of Example 1.

[0111] [Comparative Example 11] The compound described in Example F2 of Patent Document 10 was synthesized with reference to the method described in Patent Document 10. Its structure is shown by formula (126).

[0112] [Comparative Example 12] The compound described in Example 7 of Patent Document 11 was synthesized with reference to the method described in Patent Document 11. Its structure is shown by formula (127).

[0113] [Comparative Example 13] The compound described in Example 21 of Patent Document 12 is designated as Comparative Example 13, and the numerical values ​​described in Example 21 of Patent Document 12 are referenced. The structure of the compound is shown by formula (128).

[0114] [Comparative Example 14] The compound described in Example 18 of Patent Document 13 is designated as Comparative Example 14, and the numerical values ​​described in Example 18 of Patent Document 13 are referenced. The structure of the compound is shown by formula (129).

[0115] [Comparative Example 15] The compound described in Example 25 of Patent Document 1 is designated as Comparative Example 15, and the numerical values ​​described in Example 25 of Patent Document 1 are referenced. The structure of the compound is shown by formula (130).

[0116] (Examples 1-12, A1-A25 and Comparative Examples 1-12: Preparation of polarizing films) A 75 μm thick polyvinyl alcohol film was immersed for 2-4 minutes in an aqueous solution (dyeing bath) at 45°C containing 0.02% or 0.03% of the azo compound obtained in Examples 1-12, A1-A25 and Comparative Examples 1-12, and 0.1% of Glauber's salt. This film was stretched five times in a 3% boric acid aqueous solution at 55°C, a temperature preferred for production, and while maintaining tension, it was washed with water and dried to prepare a polarizing film. The prepared polarizing films were used as measurement samples for Examples 1-12, A1-A25 and Comparative Examples 1-12, respectively.

[0117] The polarizing films obtained in Examples 1-12, A1-A25 and Comparative Examples 1-12 were evaluated as follows: (a) Parallel polarization transmittance (Ky) and orthogonal polarization transmittance (Kz) The maximum absorption wavelength, parallel polarization transmittance (Ky), and orthogonal polarization transmittance (Kz) of the polarizing film were measured using a spectrophotometer (UH-4150, Hitachi High-Tech Science Corporation). Here, Ky is the transmittance when the absorption axis of the absolute polarizer and the absorption axis of the polarizing film are superimposed in parallel, and Kz is the transmittance when the absorption axis of the absolute polarizer and the absorption axis of the polarizing film are superimposed orthogonally. The parallel polarization transmittances Ky and Kz for each wavelength were measured at wavelength intervals of 1 to 10 nm in the range of 380 nm to 780 nm. (b) Single-layer transmittance (Ts) Single-layer transmittance (Ts) represents the spectral transmittance of a single polarizing film. The degree of polarization (ρ) was calculated from Ky and Kz at the maximum absorption wavelength obtained by measurement using the following formula (I): Ts (%) = (Ky + Kz) / 2 Formula (I) (c) Degree of polarization (ρ) The degree of polarization (ρ) at the maximum absorption wavelength in the first absorption band of each measurement sample, and the degree of polarization (ρ') at the wavelength with the greatest absorption in the second absorption band within the visible light region (380 nm to 780 nm) were calculated using the following formulas (II) and (III): ρ (%) = [(Ky - Kz) / (Ky + Kz)] × 100 Formula (II) ρ' (%) = [(Ky - Kz) / (Ky + Kz)] × 100 Formula (III) Furthermore, regarding the wavelength with the greatest absorption in the second absorption band, if there is no maximum absorption wavelength in the second absorption band within the visible light region (380 nm to 780 nm), the wavelength with the greatest absorption in the second absorption band within the visible light region is listed.

[0118] Table 1 shows the values ​​obtained by measurement and calculation of the polarizing films of Examples 1 to 12 and Comparative Examples 1 to 15. The values ​​for Comparative Examples 13 to 15 were taken from Patent Documents 12, 13, and 1, respectively.

[0119] Table 2 shows the values ​​obtained by measurement and calculation of the polarizing films of Examples 1 to 12 and Comparative Examples 1 to 12. For Comparative Examples 1, 9 to 12, since there was no maximum absorption wavelength of the second absorption band in the visible light region (380 nm to 780 nm), the wavelength with the greatest absorption in the second absorption band within the visible light region and the ρ' at that wavelength are listed.

[0120] As shown in Table 1, in Examples 1 to 12 and Comparative Examples 9 to 12, the polarizing films with a single-layer transmittance of 44% ± 0.4% had a wavelength range of 105 nm or more where the degree of polarization was 90% or higher. Furthermore, the wavelength range where the degree of polarization was 95% or higher was 85 nm or higher. On the other hand, in Comparative Examples 1 to 7, the polarizing films with a single-layer transmittance of 44% ± 0.4% did not have a wavelength range of 105 nm or more where the degree of polarization was 90% or higher. Also, in Comparative Examples 1 to 7, the wavelength range where the degree of polarization was 95% or higher was 85 nm or higher.

[0121] Furthermore, as shown in Table 1, in Examples 1 to 12, the polarization degree at the maximum absorption wavelength was 98.5% or higher in polarizing films with a single transmittance of 44% ± 0.4%. On the other hand, in Comparative Example 8, the single transmittance only reached 46.6%, and the polarization degree at the maximum absorption wavelength was also low at 90.4%. Comparative Examples 13 to 14 show a polarization degree of 98.5% or higher at the maximum absorption wavelength, but this is the value when the single transmittance is 41%, and they are not polarizing films adjusted to 44% ± 0.4%. Even if the polarization degree at the maximum absorption wavelength is 98.5% or higher in a polarizing film with a high single transmittance of 41%, when adjusted to a thin polarizing film with a single transmittance of 44% ± 0.4%, the polarization degree will be low, less than 98.5%. Comparative Example 15 had a single-layer transmittance of 43%, and even with a polarizing film denser than 44% ± 0.4%, it showed a polarization degree of 97.5%, which is less than 98.5%.

[0122] In Table 2, Examples 1-12 and Comparative Examples 2-7, with a single-color transmittance of 44% ± 0.4%, exhibited a polarization degree of 45% or higher at the wavelength with the greatest absorption in the visible light region within the second absorption band. On the other hand, Comparative Examples 1, 8-12, with a single-color transmittance of 44% ± 0.4%, exhibited a polarization degree of less than 45% at the wavelength with the greatest absorption in the visible light region within the second absorption band. In applications where neutral gray polarizing films are produced by mixing with other colors, a low polarization degree in the second absorption band results in poor polarization characteristics for the polarizing film as a whole. Therefore, dichroic dyes that exhibit a high polarization degree even in the second absorption band are preferred.

[0123] The results in Tables 1 and 2 show that Examples 1 to 12 exhibited high polarization at the maximum absorption wavelength, a wide absorption wavelength range showing high polarization, and high polarization in the second absorption band. On the other hand, none of the Comparative Examples 1 to 15 exhibited high polarization at the maximum absorption wavelength, a wide absorption wavelength range showing high polarization, or high polarization in the second absorption band. Therefore, by using the compounds of the present invention, an excellent polarizing film can be provided.

[0124] Next, based on the results in Table 1, the properties of the polarizing films and the structures of the compounds will be described in detail. Comparing Examples 1 to 12 with Comparative Example 1, the major structural difference is in the structure of the right end, where the substituent substituted at the 6th position of 3-sulfo-1-naphthol is either a phenylamino group or a 4-methoxyphenylamino group in Examples 1 to 12, but a methylamino group in Comparative Example 1, indicating a difference in the type of substituent. With a single-component transmittance of 44% ± 0.4%, the polarizing film of Comparative Example 1 showed low values, with a wavelength range of 95 nm for polarization degree of 90% or more and a wavelength range of 70 nm for polarization degree of 95% or more. The polarizing films of Examples 1 to 12, with a single-component transmittance of 44.0% ± 0.4%, showed a wide wavelength range of 105 nm or more for polarization degree of 90% or more and a wavelength range of 85 nm or more for polarization degree of 95% or more, indicating that the trisazo compounds of Examples 1 to 12 have excellent polarization properties. Comparing Example 3 with Comparative Example 2, in the structure at the right end, the substituent substituted at the 6th position of 3-sulfo-1-naphthol is a 4-methoxyphenylamino group in Example 3, while it is a 4-aminobenzamide group in Comparative Example 2, indicating a difference in the type of substituent. With a single-component transmittance of 44% ± 0.4%, the polarizing film of Comparative Example 2 showed low values, with a wavelength range of 91 nm for polarization degree of 90% or more and a wavelength range of 71 nm for polarization degree of 95% or more. The polarizing film of Example 3, with a single-component transmittance of 44.0% ± 0.4%, showed a wide wavelength range of 110 nm for polarization degree of 90% or more and a wavelength range of 87 nm for polarization degree of 95% or more, demonstrating that the trisazo compound of Example 3 has superior polarization properties. Comparing Example 5 with Comparative Example 3, in the structure at the right end, the substituent substituted at the 6th position of 3-sulfo-1-naphthol is a 4-methoxyphenylamino group in Example 5, while it is a 4-aminobenzamide group in Comparative Example 3, indicating a difference in the type of substituent. Furthermore, in the structure of the leftmost terminal, Example 5 is naphthalene-1,3-disulfonic acid, while Comparative Example 3 is a benzotriazole represented by formula (200), and therefore has a different structure. With a single-component transmittance of 44% ± 0.4%, the polarizing film of Comparative Example 3 showed low values, with a wavelength range of 93 nm for polarization degree of 90% or more and a wavelength range of 73 nm for polarization degree of 95% or more.The polarizing film of Example 5 had a single-component transmittance of 44.0% ± 0.4, and the wavelength range with a polarization degree of 90% or higher was 124 nm, and the wavelength range with a polarization degree of 95% or higher was 105 nm, indicating that the trisazo compound of Example 5 has excellent polarization properties.

[0125] Comparing Example 6 with Comparative Example 4, in the structure at the right end, the substituent substituted at the 6th position of 3-sulfo-1-naphthol is a 4-methoxyphenylamino group in Example 6, while it is a benzylamino group in Comparative Example 4, indicating a difference in the type of substituent. With a single-component transmittance of 44% ± 0.4%, the polarizing film of Comparative Example 4 showed low values, with a wavelength range of 91 nm for polarization degree of 90% or more and a wavelength range of 67 nm for polarization degree of 95% or more. The polarizing film of Example 6, with a single-component transmittance of 44.0% ± 0.4%, showed a wide wavelength range of 109 nm for polarization degree of 90% or more and a wavelength range of 86 nm for polarization degree of 95% or more, demonstrating that the trisazo compound of Example 6 has superior polarization properties. Comparing Example 7 with Comparative Example 5, in the structure at the left end, Example 7 is naphthalene-1,3-disulfonic acid, while Comparative Example 5 is a phenol having naphthotriazoles represented by formula (201) as substituents, indicating a difference in structure. With a single-component transmittance of 44% ± 0.4%, the polarizing film of Comparative Example 5 showed low values, with a wavelength range of 99 nm for polarization degree of 90% or more and a wavelength range of 79 nm for polarization degree of 95% or more. The polarizing film of Example 7, with a single-component transmittance of 44.0% ± 0.4%, showed a wide wavelength range of 106 nm for polarization degree of 90% or more and a wavelength range of 91 nm for polarization degree of 95% or more, indicating that the trisazo compound of Example 7 has excellent polarization properties.

[0126] Comparing Example 11 and Comparative Example 6, in the structure at the right end, the substituent substituted at the 6th position of 3-sulfo-1-naphthol in Example 11 is a 4-methoxyphenylamino group, while Comparative Example 6 has a structure represented by formula (202) with a substituent of naphthotriazole, indicating a difference in the type of substituent. With a single-component transmittance of 44% ± 0.4%, the polarizing film of Comparative Example 6 showed low values, with a wavelength range of 99 nm for polarization degree of 90% or more and a wavelength range of 70 nm for polarization degree of 95% or more. The polarizing film of Example 11, with a single-component transmittance of 44.0% ± 0.4%, showed a wide wavelength range of 126 nm for polarization degree of 90% or more and a wavelength range of 105 nm for polarization degree of 95% or more, demonstrating that the trisazo compound of Example 11 has excellent polarization properties.

[0127] Comparing Example 12 and Comparative Example 7, the structure differs in the left-end structure: Example 12 is naphthalene-1,3-disulfonic acid, while Comparative Example 7 is 3-methoxybenzenesulfonic acid. With a single-component transmittance of 44% ± 0.4%, the polarizing film of Comparative Example 7 showed low values: the wavelength range with a polarization degree of 90% or more was 98 nm, and the wavelength range with a polarization degree of 95% or more was 80 nm. The polarizing film of Example 12, with a single-component transmittance of 44.0% ± 0.4%, showed a wide wavelength range with a polarization degree of 90% or more was 105 nm, and the wavelength range with a polarization degree of 95% or more was 88 nm, indicating that the trisazo compound of Example 12 has excellent polarization properties. Comparing Example 8 and Comparative Example 13, the major structural difference is in the left-end structure: Example 8 is naphthalene-1,3-disulfonic acid, while Comparative Example 13 is a phenyl group with benzothiazoles represented by formula (203) as substituents, indicating a structural difference. At a single-component transmittance of 41%, the polarizing film of Comparative Example 13 showed a polarization degree of 99.0%. However, as mentioned above, even when the single-component transmittance was adjusted to 44.0% ± 0.4, the polarization degree is expected to remain below 98.5%. The polarizing film of Example 8 showed a polarization degree of 99.7% at a single-component transmittance of 44.0% ± 0.4, demonstrating that the trisazo compound of Example 8 exhibits excellent polarization properties.

[0128] When comparing Example 8 and Comparative Example 14, the significant structural difference lies in the structure of the left terminal: Example 8 has naphthalene-1,3-disulfonic acid, while Comparative Example 14 is a stilbene compound represented by formula (204), and the structures are different. When the single transmittance is 41%, the polarizing film of Comparative Example 14 exhibits a degree of polarization of 99.1%. As described above, it is considered that even if the single transmittance is adjusted to 44.0%±0.4%, the degree of polarization will still be less than 98.5%. The polarizing film of Example 8 exhibited a degree of polarization of 99.7% at a single transmittance of 44.0%±0.4%, thus demonstrating that the trisazo compound of Example 8 has excellent polarizing properties.

[0129] When comparing Example 10 and Comparative Example 15, regarding the structure of the left terminal: Example 10 has an azo group at the 7-position of naphthalene-1,3-disulfonic acid, while Comparative Example 15 has an azo group at the 6-position of naphthalene-1,3-disulfonic acid, so the substitution position of the azo group is different. When the single transmittance is 43%, the polarizing film of Comparative Example 15 exhibits a degree of polarization of 97.5%. As described above, it is considered that even if the single transmittance is adjusted to 44.0%±0.4%, the degree of polarization will still be less than 98.5%. The polarizing film of Example 10 exhibited a degree of polarization of 99.2% at a single transmittance of 44.0%±0.4%, thus demonstrating that the trisazo compound of Example 10 has excellent polarizing properties.

[0130] Next, based on the results in Table 2, the characteristics of the polarizing film and the structure of the compound will be specifically described.

[0131] When comparing Example 9 and Comparative Example 9, in the structure represented by formula (0), in Example 9, R １ is hydrogen, and R ２ has a methyl group, while in Comparative Example 9, R １ is a methoxy group, and R ２ has a methyl group. In Comparative Example 9, R １ or R ２When one substituent has an alkoxy group, the other substituent has a structure other than hydrogen. With a single-component transmittance of 44% ± 0.4%, the polarizing film of Comparative Example 9 showed a low polarization degree of 41.0% at the wavelength with the greatest absorption in the second absorption band. The polarizing film of Example 9 showed a high polarization degree of 55.2% at the wavelength with the greatest absorption in the second absorption band, with a single-component transmittance of 44% ± 0.4%, indicating that the trisazo compound of Example 9 has excellent polarization properties. Comparing Example 10 with Comparative Example 10, in the structure shown by formula (0), Example 10 has R １ A methyl group, R ２ Although it has a methyl group, Comparative Example 10 is R １ A methoxy group, R ２ It has a methoxy group, and Comparative Example 10 is R １ or R ２ When one substituent has an alkoxy group, the other substituent has a structure other than hydrogen. With a single-component transmittance of 44% ± 0.4%, the polarizing film of Comparative Example 10 showed a low polarization degree of 37.9% at the wavelength with the greatest absorption in the second absorption band. The polarizing film of Example 10 showed a high polarization degree of 47.5% at the wavelength with the greatest absorption in the second absorption band, with a single-component transmittance of 44% ± 0.4%, indicating that the trisazo compound of Example 10 has excellent polarization properties. By comparing Example 9 with Comparative Example 9, and Example 10 with Comparative Example 10, it was found that in the structure of formula (0), R １ or R ２ It was shown that if one of the substituents has an alkoxy group, the other substituent must be hydrogen.

[0132] Comparing Example 4 and Comparative Example 11, the left-end structure of Example 4 is naphthalene-1,3-disulfonic acid, while that of Comparative Example 11 is 1,8-dihydroxynaphthalene-3,6-disulfonic acid, indicating a structural difference. With a single-component transmittance of 44% ± 0.4%, the polarizing film of Comparative Example 11 showed a low polarization degree of 29.6% at the wavelength with the greatest absorption in the second absorption band. The polarizing film of Example 4, with a single-component transmittance of 44% ± 0.4%, showed a high polarization degree of 57.5% at the wavelength with the greatest absorption in the second absorption band, demonstrating that the trisazo compound of Example 4 has superior polarization properties. Comparing Example 2 and Comparative Example 12, the major structural difference is in the right-end structure, where the substituent substituted at the 6-position of 3-sulfo-1-naphthol is a 4-methoxyphenylamino group in Example 2, while it is an isoindolyl group in Comparative Example 12, indicating a difference in the type of substituent. With a single-component transmittance of 44% ± 0.4%, the polarizing film of Comparative Example 12 showed a low polarization degree of 39.7% at the wavelength with the greatest absorption in the second absorption band. The polarizing film of Example 2, with a single-component transmittance of 44% ± 0.4%, showed a high polarization degree of 63.0% at the wavelength with the greatest absorption in the second absorption band, indicating that the trisazo compound of Example 2 has excellent polarization properties.

[0133] Table 3 shows the values ​​obtained from measurements and calculations of the polarizing films in Example 7 and Comparative Example 8.

[0134] Table 3 shows the feasibility of producing a polarizing film with a single-color transmittance of 44% ± 0.4% when using a dye concentration of 0.2 g / L. Example 7 successfully produced a polarizing film with a single-color transmittance of 44% ± 0.4%. In contrast, Comparative Example 8 did not achieve a single-color transmittance of 44% ± 0.4% even after dyeing for more than three times the time of Example 7, and the degree of polarization at the maximum absorption wavelength was 90.4% lower than shown in Table 1. Considering actual manufacturing and assuming dyeing in a production machine, there are limits to the dyeing time, and dyes with poor dyeability are not suitable for practical use. Furthermore, regarding dye concentration, in applications where it is used in combination with other colors, there are limits to how high the concentration can be depending on the concentration of the other dyes, and dyes that can be dyed at lower concentrations are superior. Comparative Example 8 is R in formula (0). １It has a sulfopropoxy group, and it is thought that this has increased the size of the molecule, making it difficult to penetrate into the polymer chains in the film, thus worsening the staining performance. Therefore, from the viewpoint of staining performance, the sulfoalkoxy group is R of formula (0) １ ~R ４ It was shown that the substituents were unsuitable, and that the substituents of the present invention were suitable. Furthermore, as shown in Table 1, the polarizing film of Example 7 had a single-unit transmittance of 44.0% ± 0.4, with a wide wavelength range of 106 nm for polarization degree of 90% or more and 91 nm for polarization degree of 95% or more, indicating that the trisazo compound of Example 7 has excellent polarization properties.

[0135] Tables A1 and A2 show the values ​​obtained from measurements and calculations of the polarizing films of Examples A1 to A25.

[0136] As shown in Table A1, in Examples A1 to A25, the polarizing films with a single-layer transmittance of 44% ± 0.4% had a wavelength range of 105 nm or more where the degree of polarization was 90% or higher. Furthermore, the wavelength range where the degree of polarization was 95% or higher was 85 nm or higher.

[0137] Furthermore, as shown in Table A1, in Examples A1 to A25, the polarizing films with a single-layer transmittance of 44% ± 0.4% had a polarization degree of 98.5% or higher at the maximum absorption wavelength.

[0138] In Table A2, Examples A1 to A25, with a single-component transmittance of 44% ± 0.4%, exhibited a polarization degree of 45% or higher at the wavelength with the greatest absorption in the visible light region within the second absorption band. In applications where neutral gray polarizing films are produced by mixing with other colors, a low polarization degree in the second absorption band results in poor polarization characteristics for the polarizing film as a whole. Therefore, trisazo compounds that exhibit a high polarization degree even in the second absorption band are preferred.

[0139] The results from Tables A1 and A2 show that Examples A1 to A25 exhibited high polarization at the maximum absorption wavelength, a wide absorption wavelength range showing high polarization, and high polarization in the second absorption band. Therefore, by using the compound of the present invention, an excellent polarizing film can be provided.

[0140] <Example 13: Dye-based polarizing plate> A dye-based polarizing plate was prepared by laminating a triacetylcellulose film (TG-60UL, manufactured by Fujifilm Corporation) to both sides of the polarizing film obtained in Example 1 via a polyvinyl alcohol-based adhesive. One side of the obtained polarizing plate was laminated to glass using an adhesive and used as the observation sample for Example 13.

[0141] <Comparative Example 16: Iodine-based polarizing plate> As a general iodine-based polarizing plate, an iodine-based polarizing plate manufactured by Nippon Kayaku Co., Ltd. (product name: SKN-18243P) was bonded to glass using an adhesive on one side and used as the observation sample for Comparative Example 16.

[0142] The polarizing plates of Example 13 and Comparative Example 16 were observed for visual hue changes after 500 hours under heat-resistant conditions at an ambient temperature of 105°C, or under high-temperature and high-humidity conditions at an ambient temperature of 80°C and relative humidity of 90%. The observations were performed by five experts, and the consensus of the observation results was determined. The results are shown in Table 4 (○: no or almost no hue change; △: slight hue change; △, ×: significant hue change).

[0143] As shown in Table 4, the dye-based polarizer of Example 13 showed almost no hue change even under high temperature and high humidity conditions. On the other hand, the iodine-based polarizer of Comparative Example 16 showed a very large hue change. In other words, the dye-based polarizer of the present invention has high environmental resistance and is suitable for use in display devices used in harsh environments.

[0144] Polarizing films or polarizing plates made using the trisazo compound of the present invention can be optionally equipped with a protective or functional layer and a transparent support such as glass, quartz, or sapphire, and are applicable to liquid crystal projectors, calculators, watches, laptop computers, liquid crystal televisions, polarizing lenses, polarizing glasses, car navigation systems, and indoor and outdoor measuring instruments and displays. In particular, the polarizing films or polarizing plates of the present invention can be suitably used in liquid crystal display devices, such as reflective liquid crystal display devices, semi-transparent liquid crystal display devices, and organic electronic luminescence, even in applications other than liquid crystal display devices.

Claims

1. A trisazo compound represented by the following formula (0) or a salt thereof: (In formula (0), X represents hydrogen or an alkoxy group, R １ ~R ４ Each of these independently represents a hydrogen atom, an alkyl group, or an alkoxy group, except R １ or R ２ If one of the substituents has an alkoxy group, the other substituent will be hydrogen.

2. The trisazo compound or salt thereof represented by formula (0) is the trisazo compound or salt thereof represented by the following formula (1) according to claim 1: (In formula (1), X represents hydrogen or a C1-10 alkoxy group, R １ ~R ４ Each of these independently represents hydrogen, a C1-10 alkyl group, or a C1-10 alkoxy group, except R １ or R ２ (When the molecule has a C1-10 alkoxy group, the other substituent is hydrogen.) 3. A polarizing film containing a substrate, characterized in that the substrate contains the trisazo compound or a salt thereof described in claim 1 or 2.

4. A polarizing plate comprising transparent protective films provided on one and both sides of the polarizing film described in claim 3.

5. A display device comprising the polarizing film described in claim 3 or the polarizing plate described in claim 4.

6. A trisazo compound represented by the following formula (0) or a salt thereof, (In formula (0), X represents hydrogen or an alkoxy group, R １ to R ４ each independently represent hydrogen, an alkyl group or an alkoxy group, provided that R １ or R ２ has an alkoxy group, the other substituent represents hydrogen) In a polarizing film obtained by dyeing a substrate with the trisazo compound or a salt thereof, stretching and orienting the substrate such that the single transmittance at the maximum absorption wavelength in the first absorption band is 44% ± 0.4%, the trisazo compound or a salt thereof has a plurality of maximum absorption wavelengths, a wavelength range where the degree of polarization is 90% or more in the first absorption band is 105 nm or more, a wavelength range where the degree of polarization is 95% or more is 85 nm or more, and the degree of polarization at the wavelength with the largest absorption in the visible light region in the second absorption band is 45% or more, the trisazo compound or a salt thereof.

7. The trisazo compound or salt thereof according to claim 6, wherein the trisazo compound or salt thereof represented by formula (0) is the trisazo compound or salt thereof represented by the following formula (1): (In formula (1), X represents hydrogen or a C1-C10 alkoxy group, R １ ~R ４ Each of these independently represents hydrogen, a C1-10 alkyl group, or a C1-10 alkoxy group, except R １ or R ２ (When the molecule has a C1-C10 alkoxy group, the other substituent is hydrogen.)

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