Azo compound or salt thereof, and polarizing element, polarizing plate and display device each containing the same

文档序号：1343070 发布日期：2020-07-17 浏览：4次中文

阅读说明：本技术 偶氮化合物或其盐、以及含有该化合物的偏光元件、偏光板及显示装置 (Azo compound or salt thereof, and polarizing element, polarizing plate and display device each containing the same ) 是由望月典明服部由侑樋下田贵大中村光则于 2018-12-11 设计创作，主要内容包括：本发明为一种偶氮化合物或其盐,该偶氮化合物为式(1)表示的偶氮化合物：<Image he="109" wi="700" file="DDA0002525484330000011.GIF" imgContent="drawing" imgFormat="GIF" orientation="portrait" inline="no"></Image>式中,Ay1及Ay2各自独立地表示可具有取代基的萘基、或可具有取代基的苯基,s、t各自独立地为0或1,而且s或t的任一者为1,Ry1至Ry8各自独立地表示氢原子或取代基。(The inventionAn azo compound represented by the formula (1) or a salt thereof: in the formula, Ay 1 And Ay 2 Each independently represents a naphthyl group which may have a substituent or a phenyl group which may have a substituent, s and t are each independently 0 or 1, and either s or t is 1, Ry 1 To Ry 8 Each independently represents a hydrogen atom or a substituent.)

1. An azo compound represented by the formula (1) or a salt thereof,

in the formula, Ay₁And Ay₂Each independently represents a naphthyl group which may have a substituent or a phenyl group which may have a substituent, s and t are each independently 0 or 1, and either s or t is 1, Ry₁To Ry₈Each independently represents a hydrogen atomA seed or a substituent.

2. The azo compound or salt thereof according to claim 1, wherein Ay is₁And Ay₂At least one of (a) and (b) is a phenyl group which may have a substituent.

3. The azo compound or a salt thereof according to claim 2, wherein the phenyl group which may have a substituent has at least one substituent selected from the group consisting of a sulfonic acid group, a carboxyl group, an alkoxy group having 1 to 4 carbon atoms and having a sulfonic acid group, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, a halogen atom, a nitro group, an amino group, an alkyl-substituted amino group having 1 to 4 carbon atoms, and an alkyl-substituted amide group having 1 to 4 carbon atoms.

4. The azo compound or a salt thereof according to claim 3, wherein the phenyl group which may have a substituent has at least one or more substituents selected from the group consisting of a sulfonic acid group, a carboxyl group, and an alkoxy group having 1 to 4 carbon atoms and having a sulfonic acid group.

5. The azo compound or salt thereof according to any one of claims 2 to 4, wherein the optionally substituted phenyl group is a phenyl group represented by the following formula (2),

in the formula, Ry₉And Ry₁₀One of them is a sulfonic acid group, a carboxyl group, or an alkoxy group having 1 to 4 carbon atoms and having a sulfonic acid group, and the other is a hydrogen atom, a sulfonic acid group, a carboxyl group, an alkoxy group having 1 to 4 carbon atoms and having a sulfonic acid group, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, a halogen atom, a nitro group, an amino group, an alkyl-substituted amino group having 1 to 4 carbon atoms, or an alkyl-substituted amide group having 1 to 4 carbon atoms, wherein ＊ in the formula represents a position bonded to the NH portion of the terminal amide group of the formula (1).

6. Azylation according to claim 5A compound or a salt thereof, wherein Ry₉And Ry₁₀One of them is a sulfonic acid group or a carboxyl group, and the other is a hydrogen atom, a sulfonic acid group, a carboxyl group, a methyl group, or a methoxy group.

7. The azo compound or salt thereof according to any one of claims 2 to 6, wherein Ay₁And Ay₂Each independently is a phenyl group which may have a substituent.

8. The azo compound or salt thereof according to claim 7, wherein Ay is excluded₁And Ay₂Each of which is a case of a phenyl group having 1 each of a carboxyl group, a sulfonic acid group and a hydroxyl group as a substituent and a phenyl group having a triazolyl group as a substituent.

9. The azo compound or salt thereof according to any one of claims 1 to 6, wherein Ay₁And Ay₂At least one of (a) and (b) is a naphthyl group which may have a substituent.

10. The azo compound or a salt thereof according to claim 9, wherein the optionally substituted naphthyl group is a naphthyl group which may have a substituent selected from the group consisting of a hydroxyl group, an alkoxy group having 1 to 4 carbon atoms and a sulfonic acid group.

11. The azo compound or salt thereof according to claim 10, wherein Ay is₁And Ay₂Each independently is a naphthyl group which may have a substituent selected from the group consisting of a hydroxyl group, an alkoxy group having 1 to 4 carbon atoms having a sulfonic acid group, and a sulfonic acid group.

12. The azo compound or salt thereof according to any one of claims 9 to 11, wherein the optionally substituted naphthyl group is a naphthyl group represented by the following formula (3),

in the formula, Ry₁₁Is a hydrogen atom, a hydroxyl group, an alkoxy group having 1 to 4 carbon atoms and a sulfonic acid group, k is an integer of 1 to 3, wherein x represents a position bonded to the NH site of the terminal amide group of the formula (1); in addition, provided that Ry₁₁And the substitution position of the sulfonic acid group is a substitution position other than the substitution position to be bonded to the NH site of the terminal amide group of the formula (1), and the substitution can be made at an arbitrary position on the naphthalene ring.

13. The azo compound or a salt thereof according to claim 12, wherein Ry in the formula (3) is₁₁Is a hydrogen atom and k is 2.

14. The azo compound or salt thereof according to any one of claims 1 to 13, wherein Ry₁、Ry₂、Ry₇、Ry₈Each independently is a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, Ry₃To Ry₆Each independently represents a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, or an alkoxy group having 1 to 4 carbon atoms and having a sulfonic acid group.

15. The azo compound or salt thereof according to claim 14, wherein Ry is₃To Ry₆Each independently is a group selected from the group consisting of a hydrogen atom, a methyl group, an ethyl group, a methoxy group and a 3-sulfopropoxy group.

16. The azo compound or a salt thereof according to any one of claims 1 to 15, wherein the formula (1) is an azo compound represented by the following formula (4),

in the formula, Ay₁、Ay₂、Ry₁To Ry₈S and t each have the same meaning as in the above formula (1).

17. A polarizing element comprising the azo compound or the salt thereof according to any one of claims 1 to 16.

18. The polarizing element according to claim 17, further comprising 1 or more kinds of organic dyes having a structure other than the formula (1).

19. The polarizing element according to claim 18, wherein the azo compound represented by formula (5) or a salt thereof and/or the azo compound represented by formula (6) or a salt thereof is contained,

in the formula, Ar₁Represents a substituted phenyl group or a substituted naphthyl group, Rr₁To Rr₄Each independently represents a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, or an alkoxy group having 1 to 4 carbon atoms and having a sulfonic acid group, Dr₁Represents an azo group or an amide group, j represents 0 or 1, Xr₁Represents an amino group which may have a substituent, an anilino group which may have a substituent, a phenylazo group which may have a substituent, a benzoyl group which may have a substituent, or a benzoylamino group which may have a substituent;

in the formula, Ag₁Represents a substituted phenyl group or a substituted naphthyl group, Bg and Cg are each independently a group represented by the following formula (7) or formula (8), one of which is a group represented by the formula (7), Xg₁Represents an amino group which may have a substituent, an anilino group which may have a substituent, a phenylazo group which may have a substituent, a benzoyl group which may have a substituent, or a benzoylamino group which may have a substituent:

in the formula, Rg₁Represents a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms or an alkoxy group having 1 to 4 carbon atoms and having a sulfonic acid group, p₁Represents an integer of 0 to 2;

in the formula, Rg₂And Rg₃Each independently represents a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, or an alkoxy group having 1 to 4 carbon atoms and having a sulfonic acid group.

20. The polarizing element according to claim 19, wherein the azo compound represented by the formula (5) or a salt thereof, and the azo compound represented by the formula (6) or a salt thereof are both contained.

21. The polarizing element according to claim 19 or 20, wherein Cg in the formula (6) is a group represented by the formula (7).

22. The polarizing element according to claim 21, wherein the azo compound represented by formula (6) or a salt thereof is an azo compound represented by formula (9) or a salt thereof,

in the formula, Ag₂Represents a substituted phenyl group or a substituted naphthyl group, Rg₄、Rg₅Each independently represents a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, or an alkoxy group having 1 to 4 carbon atoms and having a sulfonic acid group, Xg₂Represents an amino group which may have a substituent, an anilino group which may have a substituent, a phenylazo group which may have a substituent, a benzoyl group which may have a substituent, or a benzoylamino group which may have a substituent, p₂、p₃Each independently represents an integer of 0 to 2.

23. The polarizing element according to claim 22, wherein p is represented by formula (9)₂And p₃Each 1 or 2.

24. The polarizing element according to any one of claims 19 to 23, wherein Xr of the above formula (5)₁Is an anilino group which may have a substituent.

25. The polarizing element according to any one of claims 19 to 24, wherein Xg described in the above formula (6)₁Or Xg of the above formula (8)₂Is an anilino group which may have a substituent.

26. The polarizing element according to any one of claims 17 to 25, wherein 2 sheets of the polarizing element are stacked so that absorption axis directions thereof are parallel to each other, and a difference between an average transmittance at wavelengths of 420nm to 480nm and an average transmittance at wavelengths of 520nm to 590nm, which is obtained by measuring the difference, is 2.5% or less in absolute value, and a difference between an average transmittance at wavelengths of 520nm to 590nm and an average transmittance at wavelengths of 600nm to 640nm, which is obtained by measuring the difference, is 3.0% or less in absolute value.

27. The polarizing element according to any one of claims 17 to 26, wherein absolute values of a ＊ value and b ＊ value determined in accordance with JIS Z8781-4: 2013 in measurement of transmittance of natural light,

in the case of the above-mentioned polarizing element monomers, all of them are 1.0 or less (-1.0. ltoreq. a ＊ -s. ltoreq.1.0, -1.0. ltoreq. b ＊ -s. ltoreq.1.0),

in a state where 2 sheets of the above-described polarizing elements are arranged so that their absorption axis directions are parallel to each other, they are each 2.0 or less (-2.0. ltoreq. a ＊ -p. ltoreq.2.0, -2.0. ltoreq. b ＊ -p. ltoreq.2.0),

here, a ＊ -s represents a value of a ＊ in the case of a monomer, b ＊ -s represents a value of b ＊ in the case of a monomer, a ＊ -p represents a value of a ＊ in a parallel position, and b ＊ -p represents b ＊ in a parallel position.

28. The polarizing element according to any one of claims 17 to 27, wherein the polarizing element has a photosensitivity-corrected monomer transmittance of 35% to 45%,

in a state where the 2 polarizing elements are arranged so that the absorption axis directions thereof are parallel to each other, the average transmittance at each wavelength of 520nm to 590nm is 28% to 45%.

29. The polarizing element according to any one of claims 17 to 28, wherein the transmittance is determined in a state where 2 sheets of the polarizing elements are arranged so that the absorption axis directions thereof are orthogonal to each other,

the difference between the average transmittance at wavelengths of 420nm to 480nm and the average transmittance at wavelengths of 520nm to 590nm is 1.0% or less in absolute value, and the difference between the average transmittance at wavelengths of 520nm to 590nm and the average transmittance at wavelengths of 600nm to 640nm is 1.0% or less in absolute value.

30. The polarizing element according to any one of claims 17 to 29, wherein a transmittance at an orthogonal position of each wavelength in each wavelength of wavelength bands of 420nm to 480nm, 520nm to 590nm, and 600nm to 640nm is 1% or less, or a degree of polarization is 97% or more.

31. The polarizing element according to any one of claims 17 to 30, wherein absolute values of a ＊ value and b ＊ value obtained in measurement of transmittance of natural light in accordance with JIS Z8781-4: 2013 in a state where 2 sheets of the polarizing elements are arranged so that absorption axis directions thereof are orthogonal to each other are 2.0 or less (-2.0. ltoreq. a ＊ -c. ltoreq.2.0, -2.0. ltoreq. b ＊ -c. ltoreq.2.0), where a ＊ -c represents a ＊ value at an orthogonal position and b ＊ -c represents b ＊ at an orthogonal position.

32. The polarizing element according to any one of claims 17 to 31, wherein the polarizing element comprises a polyvinyl alcohol-based resin film as a base material.

33. A polarizing plate comprising the polarizing element according to any one of claims 17 to 32, and a transparent protective layer provided on one or both surfaces of the polarizing element.

34. A neutral gray polarizing plate provided with the polarizing element according to any one of claims 17 to 32 or the polarizing plate according to claim 33.

35. A display device provided with the polarizing element according to any one of claims 17 to 32 or the polarizing plate according to claim 33 or 34.

Technical Field

The present invention relates to a novel azo compound or a salt thereof, and a polarizing element, a polarizing plate and a display device containing the compound.

Background

The application field of L CD is from small-sized devices such as electronic computers and watches at the beginning to notebook personal computers, word processors, liquid Crystal projectors, liquid Crystal televisions, car navigation systems, and indoor and outdoor measuring devices, and also can be applied to lenses having a polarizing function, sunglasses with improved visibility, and in recent years, to polarizing glasses for 3D televisions.

The polarizing element is generally manufactured by adsorbing and aligning iodine and a dichroic dye on a substrate, such as a polyvinyl alcohol or a derivative thereof film that is stretched and aligned, or a polyene-based film in which polyenes are generated and aligned by dehydrochlorination of a polyvinyl chloride film or dehydration of a polyvinyl alcohol-based film. A polarizing plate obtained by bonding a protective film made of cellulose triacetate or the like to the polarizing element through an adhesive layer is used in a liquid crystal display device or the like. A polarizing plate using iodine as a dichroic dye is called an iodine-based polarizing plate, while a polarizing plate using a dichroic dye such as an azo compound having dichroism as a dichroic dye is called a dye-based polarizing plate. Among these polarizing plates, the characteristics of the dye-based polarizing plate are: has high heat resistance, high humidity and heat durability, and high stability, and has a high color selectivity by blending a dye, while the dye-based polarizing plate has a problem of low transmittance and contrast as compared with an iodine-based polarizing plate having the same polarization degree. Therefore, a polarizing element having a high transmittance and high polarization characteristics, in addition to maintaining high durability and diversifying color selectivity, is desired.

In recent years, liquid crystal displays have been used to display images with high brightness in order to improve the sharpness of the images. Since hybrid cars, mobile terminals, and the like that incorporate such displays are required to have longer battery driving times, manufacturers of liquid crystal displays are demanding polarizers that can maintain the brightness of images and the sharpness of colors even when the brightness is reduced due to power consumption.

However, in a polarizing element in which a plurality of dyes are adsorbed/oriented to a polymer film, when light leakage (discoloration) occurs at a specific wavelength in a wavelength region of a visible light region, when the polarizing element is mounted on a liquid crystal panel, the color phase of liquid crystal display may change in a dark state. Therefore, when a polarizing element is mounted on a liquid crystal display device, in order to prevent discoloration of the liquid crystal display due to discoloration of a specific wavelength in a dark state, in a polarizing element of a neutral color obtained by dyeing a polymer film or containing a plurality of dyes, it is necessary to uniformly reduce the transmittance at the orthogonal position in the wavelength region of the visible light region (orthogonal position transmittance). In addition, in the liquid crystal display for vehicles, since the interior of the vehicle becomes a high-temperature and high-humidity environment in summer, there is a demand for a polarizing plate that does not change the degree of polarization even in a severe environment. Conventionally, an iodine-based polarizing plate having excellent polarizing performance and exhibiting neutral gray color has been used. However, iodine-based polarizing plates have a problem that light resistance, heat resistance, and moist heat resistance are insufficient as described above. In order to solve this problem, a dye-based neutral gray polarizing plate dyed or containing several types of dichroic dyes has been used. The dye-based neutral gray polarizing plate is generally used by combining dyes of red/blue/yellow, which are three primary colors of light. However, as described above, the polarizing performance of the dye-based neutral gray polarizing plate is not sufficient. Therefore, development of dichroic dyes having good polarizing properties has been required depending on three primary colors.

In recent years, a cold cathode tube system, an L ED system, or the like is used as a light source for a liquid crystal display panel, but the wavelength of the light source emitted therefrom varies depending on the system, and even in the same system, it is often different from each company of the panel manufacture.

Examples of dyes used for producing such dye-based polarizing elements include water-soluble azo compounds described in patent documents 20, 16, 13, 21, and 22.

There is a problem that a dye-based polarizing plate having a variety of color selectivity has a yellowish white color even when 2 conventional polarizing elements are arranged one on top of another so that their absorption axes are in a positional relationship parallel to each other (hereinafter, also referred to as "parallel positions") to display a white color (hereinafter, also referred to as "white display time" or "bright display time"). Even in a polarizing plate manufactured to suppress the yellow sensation by improving the problem of the yellowish white color, when black is displayed (hereinafter, also referred to as "black display state" or "dark display state") by superimposing 2 polarizing plates in a conventional polarizing plate so that the absorption axis directions are orthogonal to each other (hereinafter, also referred to as "orthogonal position"), black appears blue. Therefore, a polarizing plate which displays achromatic white in white display and black in black display is required. In particular, it is difficult to obtain a polarizing plate having a high quality level of white color in white display, which is commonly called paper white (white). In order to make the polarizing plate colorless, the transmittance of each wavelength must be approximately constant regardless of the wavelength at the parallel position and the orthogonal position, but such a polarizing plate has not been obtained in the past.

The reason why the hues are different between the white display and the black display is due to the difference in wavelength dependence of the transmittance between the parallel position and the perpendicular position, and particularly, the transmittance of each wavelength in the visible light region is not constant. Further, it is difficult to realize a non-colored polarizing plate because dichroism is not fixed in the visible light region. When an iodine-based polarizing plate is described as an example, an iodine-based polarizing plate using polyvinyl alcohol (hereinafter, also referred to as "PVA") as a base material and iodine as a dichroic dye generally has absorption around 480nm and 600 nm. It is believed that the absorption at 480nm is due to polyiodide I₃ ^-Complex with PVA, and the absorption at 600nm is due to polyiodide I₅ ^-A complex with PVA. The degree of polarization (dichroism) at each wavelength is comparable to that based on polyiodide I₃ ^-The degree of polarization (dichroism) of the complex with PVA based on polyiodide I₅ ^-The degree of polarization (dichroism) of the complex with PVA is high. That is, when the transmittance at the orthogonal position is to be kept constant at each wavelength, the transmittance at the parallel position is higher at 600nm than at 480nm, and a phenomenon occurs in which white is colored yellow in white display. On the contrary, when the transmittance at each wavelength in the parallel position is to be kept constant, the transmittance at the orthogonal position is lower at 600nm than at 480nm, so that the black color is blue in black display. When white appears yellow in white display, becauseOften resulting in a sustained impression of degradation and is not considered suitable. In addition, when blue is dropped in black display, the black is not clear black, and therefore, the impression of no high-quality feeling is created. In addition, in the iodine-based polarizing plate, it is difficult to control the color phase because there is no complex based on the wavelength mainly in the vicinity of 550nm where the sensitivity (luminance factor) is high.

In this way, since the polarization degree (dichroism) of each wavelength is not fixed, the polarization degree is wavelength-dependent. Further, since only two kinds of dichroic dyes of 480nm and 600nm are absorbed by a complex of iodine and PVA, the hue cannot be adjusted in an iodine-based polarizing plate composed of iodine and PVA. Methods for improving the hue of an iodine-based polarizing plate are described in patent document 1 and patent document 2. Patent document 1 describes a polarizing plate whose neutral coefficient is calculated and whose absolute value is 0 to 3. Patent document 2 describes a polarizing film in which iodine, a direct dye, a reactive dye, or an acid dye is added to adjust and color the transmittance at each wavelength of 410nm to 750nm to within ± 30% of the average value. Further, patent document 3 also discloses a technique of a colorless dyed polarizing plate.

[ Prior art documents ]

[ patent document ]

[ patent document 1] Japanese patent application laid-open No. 2002-

[ patent document 2] Japanese patent application laid-open No. 10-133016

[ patent document 3] WO2014/162635 publication

[ patent document 4] Japanese patent application laid-open No. 8-291259

[ patent document 5] Japanese patent application laid-open No. 2002-275381

[ patent document 6] Japanese WO2015/152026 publication

[ patent document 7] Japanese patent application laid-open No. 1-161202

[ patent document 8] Japanese patent application laid-open No. 1-172907

[ patent document 9] Japanese patent application laid-open No. 1-183602

[ patent document 10] Japanese patent application laid-open No. 1-248105

[ patent document 11] Japanese patent application laid-open No. 1-265205

[ patent document 12] Japanese examined patent publication No. 7-92531

[ patent document 13] Japanese patent laid-open No. 2009-132794

[ patent document 14] WO2006/057214 publication

[ patent document 15] Japanese patent application laid-open No. 11-218611

[ patent document 16] Japanese patent application laid-open No. 2001-033627

[ patent document 17] Japanese patent application laid-open No. 2004-251962

[ patent document 18] Japanese patent application laid-open No. 8-291259

[ patent document 19] Japanese patent application laid-open No. 2008-065222

[ patent document 20] Japanese patent application laid-open No. 3-12606

[ patent document 21] Japanese patent application laid-open No. 2001-240762

[ patent document 22] Japanese patent application laid-open No. 2001-108828

[ patent document 23] Japanese patent application laid-open No. Sho 60-156759

[ non-patent document 1] application of functional pigment (CMC (stock) publication, No.1 brush issue, Jiangzhining, and inspection and repair, pages 98 to 100)

[ non-patent document 2] dye chemistry; the Toyobo, the Chunzhengtang, 1957.

Disclosure of Invention

[ problems to be solved by the invention ]

An object of the present invention is to provide a high-performance polarizing plate having excellent polarizing performance and moisture resistance/heat resistance/light resistance. Another object of the present invention is to provide a polarizing plate in which 2 or more kinds of dichroic dyes are adsorbed/aligned to a polymer film and which exhibits a neutral gray color, and a high-performance polarizing plate which is not discolored at a position orthogonal to a wavelength region in a visible light region and which has excellent polarizing performance, moisture resistance, heat resistance, and light resistance.

Another object of the present invention is to provide a dye-based neutral gray polarizing plate for a liquid crystal display of a vehicle, and a high-performance polarizing plate having excellent brightness, polarizing performance, durability and light resistance.

Further, the polarizing film of patent document 1 is known from example 1 thereof that even if the neutral coefficient (Np) is low, the hue at the parallel position determined from JIS Z8729 shows yellowish green color in the white display because the a ＊ value is-1.67 and the b ＊ value is 3.51, and the polarizing film of patent document 2 shows a blue color in the black display because the a ＊ value is 0.69 and the b ＊ value is-3.40 in the hue at the orthogonal position, and the polarizing film of patent document 2 shows no hue in both the white display and the black display because the a value and the b value of the UCS color space measured using only 1 polarizing film are set to be an absolute value of 2 or less, and the average value of the single transmittance of the polarizing film of patent document 2 is not simultaneously shown in both the white display and the black display because the polarizing film of patent document 2 is overlapped with each other, 31.95% in example 1, 31.41% in example 1, and shows a low value because the transmittance of the polarizing film of patent document 2 is low, and the polarizing film is required to have a high transmittance and a high relative humidity, and a relatively durable color of the polarizing film is not used as a long time, and a long life test, and a long time, and a long life test is not particularly, and a long life test is carried out, and a long time.

On the other hand, although dye-based polarizing plates have excellent durability, the wavelength dependence is different between the parallel position and the orthogonal position as in the iodine-based polarizing plate. Azo compounds showing dichroism, which show the same hue at parallel and orthogonal positions, are almost absent, and even if present, azo compounds having low dichroism (polarization characteristics). Depending on the type of the azo compound having dichroism, there are azo compounds having completely different wavelength dependencies at orthogonal positions and parallel positions, such as white color in white display and black color in black display. Further, since human sensitivity to color varies depending on the light intensity, even if color correction of the dye-based polarizing plate is performed, color correction suitable for the light intensity of each light is necessary by controlling polarization in a range from the orthogonal position to the parallel position. The achromatic polarizing plate must have a transmittance of a substantially constant value at each wavelength and have no wavelength dependence at each parallel position and at each orthogonal position. In order to obtain a polarizing element having high transmittance and high contrast, the polarization degree (dichroic ratio) of each wavelength must be high and constant, in addition to satisfying a certain transmittance at both the parallel position and the orthogonal position. When 1 azo compound is applied to a polarizing element, the wavelength dependence of the transmittance is different between the orthogonal position and the parallel position, but in order to obtain a constant transmittance at each wavelength by blending 2 or more azo compounds, the relationship between the two-color ratio of 2 or more must be accurately controlled in consideration of the transmittance at each of the 1 parallel position and the orthogonal position.

On the other hand, even if the relationship of the dichroic ratio of the transmittance of the parallel position and the orthogonal position is accurately controlled and the transmittance of each wavelength can be individually fixed, a high transmittance and a high contrast have not been achieved. That is, the higher the transmittance or the higher the polarization degree, the more difficult it is to make the color-less polarizing plate, and the color-less polarizing plate with high transmittance or high polarization degree cannot be realized. It is very difficult to obtain a colorless polarizing plate having high transmittance and/or high contrast, which is not realized by using dichroic pigments of three primary colors of color. In particular, it is very difficult to achieve both a constant transmittance and high dichroism at each wavelength in parallel. White color does not exhibit a high quality level even if only a few colors are mixed. In addition, white in the bright state is important because of high luminance and high sensitivity. Therefore, a polarizing element is required which displays achromatic white as paper of high quality level in white display and achromatic black in black display, and has a high degree of polarization with a monomer transmittance of 35% or more after the correction of the visual sensitivity. Patent document 3 also describes a polarizing plate which is colorless in white display and black display, but further improvement in performance is desired.

Accordingly, an object of the present invention is to provide a high-performance achromatic polarizing element having high transmittance and high polarization degree and being achromatic both in white display and black display, particularly white color at a high quality level in white display, and an achromatic polarizing plate and a liquid crystal display device using the achromatic polarizing element.

[ means for solving the problems ]

As a result of intensive studies to achieve the above object, the present inventors have found that a polarizing element and a polarizing plate containing a specific azo compound or a salt thereof have excellent polarizing performance, moisture resistance, heat resistance, light resistance and the like, and have completed the present invention.

The present inventors have also found that by blending azo compounds of formulae (5), (6) and (1), a polarizing element can be produced which has no wavelength dependence in dichroism, no coloration in the parallel and orthogonal positions, and a higher degree of polarization than conventional polarizing elements. The present inventors have first found that wavelength independence in the visible light region can be achieved even with a high transmittance, and developed a polarizing element having a high polarization degree which can achieve a high-quality level of white color, commonly called as paper white, on a paper-like level.

That is, the present invention relates to the following inventions 1 to 35.

Invention 1

An azo compound represented by the formula (1) or a salt thereof,

Invention 2

The azo compound of the invention 1 or a salt thereof, wherein Ay₁And Ay₂At least one of (a) and (b) is a phenyl group which may have a substituent.

Invention 3

The azo compound or a salt thereof according to claim 2, wherein the phenyl group which may have a substituent has at least one or more substituents selected from the group consisting of a sulfonic acid group, a carboxyl group, an alkoxy group having 1 to 4 carbon atoms and having a sulfonic acid group, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, a halogen atom, a nitro group, an amino group, an alkyl-substituted amino group having 1 to 4 carbon atoms, and an alkyl-substituted amide group having 1 to 4 carbon atoms.

Invention 4

The azo compound of the invention 3 or a salt thereof, wherein the optionally substituted phenyl group has at least one substituent selected from the group consisting of a sulfonic acid group, a carboxyl group, and an alkoxy group having 1 to 4 carbon atoms and having a sulfonic acid group.

Invention 5

The azo compound or a salt thereof according to any one of inventions 2 to 4, wherein the above-mentioned phenyl group which may have a substituent(s) is a phenyl group represented by the following formula (2),

Invention 6

The azo compound of the invention 5 wherein Ry or a salt thereof₉And Ry₁₀One of them is a sulfonic acid group or a carboxyl group, and the other is a hydrogen atom, a sulfonic acid group, a carboxyl group, a methyl group, or a methoxy group.

Invention 7

The azo compound or a salt thereof according to any one of inventions 2 to 6, wherein Ay₁And Ay₂Each independently is a phenyl group which may have a substituent.

Invention 8

The azo compound of the invention 7 or a salt thereof, wherein Ay is excluded₁And Ay₂Each of which is a case of a phenyl group having 1 each of a carboxyl group, a sulfonic acid group and a hydroxyl group as a substituent and a phenyl group having a triazolyl group as a substituent.

Invention 9

The azo compound or a salt thereof according to any one of inventions 1 to 6, wherein Ay₁And Ay₂At least one of (a) and (b) is a naphthyl group which may have a substituent.

Invention 10

The azo compound of the invention 9 or a salt thereof, wherein the optionally substituted naphthyl group is a naphthyl group optionally substituted by a substituent selected from the group consisting of a hydroxyl group, an alkoxy group having 1 to 4 carbon atoms and a sulfonic acid group.

Invention 11

The azo compound of the invention 10 or a salt thereof, wherein Ay₁And Ay₂Each independently is a naphthyl group which may have a substituent selected from the group consisting of a hydroxyl group, an alkoxy group having 1 to 4 carbon atoms having a sulfonic acid group, and a sulfonic acid group.

Invention 12

The azo compound or a salt thereof according to any one of inventions 9 to 11, wherein the above-mentioned naphthyl group which may have a substituent(s) is a naphthyl group represented by the following formula (3),

in the formula, Ry₁₁Is a hydrogen atom, a hydroxyl group, an alkoxy group having 1 to 4 carbon atoms and a sulfonic acid group, k is an integer of 1 to 3, ＊ in the formula represents a position bonded to the NH site of the terminal amide group of the above formula (1), provided that Ry is₁₁And the substitution position of the sulfonic acid group is a substitution position other than the substitution position to be bonded to the NH site of the terminal amide group of the formula (1), and the substitution can be made at an arbitrary position on the naphthalene ring.

Invention 13

As described in invention 12An azo compound or a salt thereof, wherein in the above formula (3), Ry₁₁Is a hydrogen atom and k is 2.

Invention 14

The azo compound or a salt thereof according to any one of claims 1 to 13, wherein Ry₁、Ry₂、Ry₇、Ry₈Each independently is a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, Ry₃To Ry₆Each independently represents a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, or an alkoxy group having 1 to 4 carbon atoms and having a sulfonic acid group.

Invention 15

The azo compound of the invention 14 wherein Ry or a salt thereof₃To Ry₆Each independently is a group selected from the group consisting of a hydrogen atom, a methyl group, an ethyl group, a methoxy group and a 3-sulfopropoxy group.

Invention 16

The azo compound or a salt thereof according to any one of inventions 1 to 15, wherein the aforementioned formula (1) is an azo compound represented by the following formula (4),

in the formula, Ay₁、Ay₂、Ry₁To Ry₈S and t each have the same meaning as in the above formula (1).

Invention 17

A polarizing element comprising the azo compound or the salt thereof according to any one of claims 1 to 16.

Invention 18

The polarizing element according to invention 17, further comprising 1 or more kinds of organic dyes having a structure other than the formula (1).

Invention 19

The polarizing element according to invention 18, which comprises an azo compound represented by formula (5) or a salt thereof and/or an azo compound represented by formula (6) or a salt thereof,

Invention 20

The polarizing element according to invention 19, which comprises both the azo compound represented by the above formula (5) or a salt thereof and the azo compound represented by the above formula (6) or a salt thereof.

Invention 21

The polarizing element according to claim 19 or 20, wherein Cg in the formula (6) is a group represented by the formula (7).

Invention 22

The polarizing element according to invention 21, wherein the azo compound represented by the above formula (6) or a salt thereof is an azo compound represented by the following formula (9) or a salt thereof,

Invention 23

The polarizing element according to invention 22, wherein p is represented by the above formula (9)₂And p₃Each 1 or 2.

Invention 24

The polarizing element according to any one of inventions 19 to 23, wherein Xr of (5)₁Is an anilino group which may have a substituent.

Invention 25

The polarizing element according to any one of inventions 19 to 24, wherein Xg is represented by the formula (6)₁Or Xg of the above formula (8)₂Is an anilino group which may have a substituent.

Invention 26

The polarizing element according to any one of inventions 17 to 25, wherein 2 sheets of the polarizing element are stacked so that absorption axis directions thereof are parallel to each other, and a difference between a determined average transmittance at wavelengths of 420nm to 480nm and an average transmittance at wavelengths of 520nm to 590nm is 2.5% or less in absolute value, and a difference between an average transmittance at wavelengths of 520nm to 590nm and an average transmittance at wavelengths of 600nm to 640nm is 3.0% or less in absolute value.

Invention 27

The polarizing element according to any one of inventions 17 to 26, wherein absolute values of a ＊ value and b ＊ value obtained in measurement of transmittance of natural light according to JIS Z8781-4: 2013,

in the case of the above-mentioned polarizing element monomers, all of them are 1.0 or less (-1.0. ltoreq. a ＊ -s. ltoreq.1.0, -1.0. ltoreq. b ＊ -s. ltoreq.1.0),

Invention 28

The polarizing element according to any one of inventions 17 to 27, wherein the monomer transmittance after the visibility correction of the above polarizing element is 35% to 45%,

Invention 29

The polarizing element according to any one of inventions 17 to 28, wherein the transmittance is determined in a state where 2 sheets of the polarizing elements are arranged so that the absorption axis directions thereof are orthogonal to each other,

Invention 30

The polarizing element according to any one of inventions 17 to 29, wherein a transmittance at an orthogonal position of each wavelength in each wavelength of wavelength bands of 420nm to 480nm, 520nm to 590nm, and 600nm to 640nm is 1% or less, or a degree of polarization is 97% or more.

Invention 31

The polarizing element according to any one of inventions 17 to 30, wherein absolute values of a ＊ value and b ＊ value obtained in measurement of transmittance of natural light in accordance with JIS Z8781-4: 2013 in a state where 2 sheets of the above polarizing elements are arranged so that respective absorption axis directions thereof are orthogonal to each other (-2.0. ltoreq. a ＊ -c. ltoreq.2.0, -2.0. ltoreq. b ＊ -c. ltoreq.2.0),

here, a ＊ -c represents the value of a ＊ at the orthogonal position, and b ＊ -c represents b ＊ at the orthogonal position.

Invention 32

The polarizing element according to any one of inventions 17 to 31, wherein the polarizing element comprises a polyvinyl alcohol-based resin film as a substrate.

Invention 33

A polarizing plate comprising the polarizing element according to any one of claims 17 to 32, and a transparent protective layer provided on one or both surfaces of the polarizing element.

Invention 34

A neutral gray polarizing plate comprising the polarizing element according to any one of claims 17 to 32 or the polarizing plate according to claim 33.

Invention 35

A display device comprising the polarizing element according to any one of claims 17 to 32 or the polarizing plate according to claim 33 or 34.

[ Effect of the invention ]

The azo compound or a salt thereof of the present invention is useful as a dye for a polarizing element. Further, a polarizing element containing these compounds has high polarizing performance comparable to that of a polarizing element using iodine and excellent durability. Therefore, the liquid crystal display device is suitable for various liquid crystal displays and liquid crystal projectors, and is suitable for vehicle applications requiring high polarization performance and durability, and display applications of industrial instruments used in various environments.

In one aspect, the present invention can provide a high-performance achromatic polarizing element having high transmittance and high polarization degree and exhibiting a high quality level of white in white display, particularly a polarizing element achromatic in both white display and black display, and an achromatic polarizing plate and a display device using the achromatic polarizing element.

Detailed Description

In the specification and claims of the present application, the "azo compound or a salt thereof" may be simply referred to as "azo compound" in some cases, except for the case where the free form is clearly indicated.

In the specification and claims of the present application, "lower carbon number" of the lower alkyl group, lower alkoxy group, and lower alkylamino group means that the carbon number is 1 to 4, more preferably 1 to 3. In the present specification, for convenience, the "substituent" includes a hydrogen atom. The phrase "may have a substituent" means that the substituent is not present. For example, "phenyl group which may have a substituent" includes an unsubstituted simple phenyl group and a phenyl group having a substituent.

Examples of the "aliphatic hydrocarbon group having a low carbon number (having 1 to 4 carbon atoms)" include a straight-chain alkyl group such as a methyl group, an ethyl group, an n-propyl group, or an n-butyl group, a branched-chain alkyl group such as a sec-butyl group or a tert-butyl group, and an unsaturated hydrocarbon group such as a vinyl group.

Examples of the "alkoxy group having a low carbon number (having 1 to 4 carbon atoms)" include methoxy, ethoxy, propoxy, n-butoxy, sec-butoxy and tert-butoxy groups.

Examples of the "aryloxy group" include a phenoxy group, a naphthoxy group and the like.

< azo Compound >

The azo compound of the present invention is an azo compound represented by the above formula (1).

Description of the inventionThe above formula (1). In the above formula (1), Ay₁And Ay₂Each independently a naphthyl group which may have a substituent, or a phenyl group which may have a substituent, s and t are each independently 0 or 1, and either s or t is 1, Ry₁To Ry₈Each independently represents a hydrogen atom or a substituent.

In one embodiment, Ay₁Or Ay₂Any of (a) and (b) is naphthyl which may have a substituent.

In one embodiment, Ay₁And Ay₂Each independently is a naphthyl group which may have a substituent, and more preferably, each independently is a naphthyl group which may have a substituent selected from the group consisting of a hydroxyl group, an alkoxy group having 1 to 4 carbon atoms and a sulfonic acid group.

In one embodiment, Ay₁And Ay₂Each independently is a phenyl group which may have a substituent.

In one aspect, Ay is excluded from the azo compound of the present invention or a salt thereof₁And Ay₂Each of which is a case of a phenyl group having 1 each of a carboxyl group, a sulfonic acid group and a hydroxyl group as a substituent and a phenyl group having a triazolyl group as a substituent.

The substituent of the phenyl group which may have a substituent is not particularly limited, and examples thereof include an aliphatic hydrocarbon group having 1 to 4 carbon atoms which may have a substituent, an alkoxy group having 1 to 4 carbon atoms which may have a substituent, an aryloxy group which may have a substituent, a hydroxyl group, a sulfonic acid group, a carboxyl group, a substituted or unsubstituted amino group, an amide group and the like, and a substituent selected from the group consisting of an alkoxy group having 1 to 4 carbon atoms which may have a substituent, a sulfonic acid group and a carboxyl group is preferable.

Examples of the "substituted or unsubstituted amino group" include a primary substituted amino group such as an amino group, a methylamino group, an ethylamino group, a n-propylamino group, a n-butylamino group, a monoanilino group, a naphthylamino group and the like, and a secondary substituted amino group such as a dimethylamino group, a diethylamino group, a diphenylamino group and the like. These substituted amine groups may further have a substituent.

The "substituent" in the above aliphatic hydrocarbon group having 1 to 4 carbon atoms which may have a substituent and the alkoxy group having 1 to 4 carbon atoms which may have a substituent is not particularly limited, and examples thereof include a hydroxyl group, a sulfonic acid group, a carboxyl group, a substituted or unsubstituted amine group, and an amide group. The "substituent" of the aryloxy group which may have a substituent and the "substituent" which may be further contained in the substituted amino group are not particularly limited, and examples thereof include aliphatic hydrocarbon groups having 1 to 4 carbon atoms which may have a substituent.

Ay in the above formula (1)₁And Ay₂More preferably, the phenyl group has 1 or more substituents selected from the group consisting of a sulfonic acid group, a carboxyl group, a lower alkoxy group having a sulfonic acid group, a lower alkyl group, a lower alkoxy group, a halogen atom, a nitro group, an amino group, a lower alkyl-substituted amino group, and a lower alkyl-substituted amide group.

Ay in the above formula (1)₁And Ay₂Preferably, the phenyl group may further have a hydrogen atom, a sulfonic acid group, a carboxyl group, an alkoxy group having 1 to 4 carbon atoms and having a sulfonic acid group, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms and having a sulfonic acid group, a halogen group, a nitro group, an amino group, an alkyl-substituted amino group having 1 to 4 carbon atoms, or an alkyl-substituted amide group having 1 to 4 carbon atoms.

When the phenyl group has 2 or more substituents, at least one of these substituents is a sulfonic acid group, a carboxyl group, or a lower alkoxy group having a sulfonic acid group, and the other substituents are preferably a sulfonic acid group, a hydrogen atom, a lower alkyl group, a lower alkoxy group having a sulfonic acid group, a carboxyl group, a chlorine group, a bromine group, a nitro group, an amino group, a lower alkyl-substituted amino group, or a lower alkyl-substituted amide group. The other substituent is preferably a sulfonic acid group, a hydrogen atom, a methyl group, an ethyl group, a methoxy group, an ethoxy group, a carboxyl group, a sulfoethoxy group, a sulfopropoxy group, a sulfobutoxy group, a chlorine group, a nitro group, or an amine group, more preferably a sulfonic acid group, a carboxyl group, a hydrogen atom, a methyl group, a methoxygroup, a sulfoethoxy group, a sulfopropoxy group, or a sulfobutoxy group, and particularly preferably a sulfonic acid group, a carboxyl group, a hydrogen atom, a methyl group, a methoxy group, or a.

The substitution position in the above-mentioned phenyl group which may have a substituent is not particularly limited, but is preferably 2-position alone, 4-position alone, a combination of 2-position and 6-position, a combination of 2-position and 4-position, or a combination of 3-position and 5-position, and particularly preferably 2-position alone, 4-position alone, a combination of 2-position and 4-position, or a combination of 3-position and 5-position. The 2-position alone and the 4-position alone mean that only the 2-position or the 4-position has a substituent other than 1 hydrogen atom.

The substituted phenyl group is preferably a phenyl group represented by the formula (2).

In the above formula (2), Ry₉Or Ry₁₀One of them is a sulfonic acid group, a carboxyl group, or an alkoxy group having 1 to 4 carbon atoms and having a sulfonic acid group, and the other is a hydrogen atom, a sulfonic acid group, a carboxyl group, an alkoxy group having 1 to 4 carbon atoms and having a sulfonic acid group, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, a halogen atom, a nitro group, an amino group, an alkyl-substituted amino group having 1 to 4 carbon atoms, or an alkyl-substituted amide group having 1 to 4 carbon atoms ＊ in the formula represents a position bonded to the NH moiety of the terminal amide group of the formula (1).

More preferably Ry₉Or Ry₁₀One is a sulfonic acid group or a carboxyl group, and the other is a hydrogen atom, a sulfonic acid group, a carboxyl group, a methyl group, or a methoxy group.

Examples of the naphthyl group in the above-mentioned naphthyl group which may have a substituent include a 1-naphthyl group and a 2-naphthyl group, and a 2-naphthyl group is preferable.

The substituent in the optionally substituted naphthyl group is not particularly limited, and examples thereof include an aliphatic hydrocarbon group having 1 to 4 carbon atoms which may have a substituent, an alkoxy group having 1 to 4 carbon atoms which may have a substituent, an aryloxy group which may have a substituent, a hydroxyl group, a sulfonic acid group, a carboxyl group, a substituted or unsubstituted amine group, an amide group and the like, and an alkoxy group having 1 to 4 carbon atoms which may have a substituent, and a sulfonic acid group are preferable.

The above-mentioned naphthyl group which may have a substituent is more preferably a naphthyl group which may have 1 or more substituents selected from the group consisting of a hydroxyl group, a lower alkoxy group having a sulfonic acid group and a sulfonic acid group.

The above naphthyl group which may have a substituent is more preferably a naphthyl group represented by the above formula (3).

In the above formula (3), Ry₁₁Is a hydrogen atom, a hydroxyl group, an alkoxy group having 1 to 4 carbon atoms and a sulfonic acid group, and k is an integer of 1 to 3, ＊ in the formula represents a position bonded to the NH site of the terminal amide group of the above formula (1)₁₁And the substitution position of the sulfonic acid group is a substitution position other than the substitution position to be bonded to the NH site of the terminal amide group of the formula (1), and the substitution can be made at an arbitrary position on the naphthalene ring.

In the above formula (3), Ry₁₁Preferably, a hydrogen atom is used, and k is preferably 2.

In the above formula (3), the sulfonic acid group may be located at any benzene nucleus of the naphthalene ring. The lower alkoxy group having a sulfonic acid group is preferably a linear alkoxy group, and the substitution position of the sulfonic acid group is preferably an alkoxy terminal. The lower alkoxy group having a sulfonic acid group is preferably a 3-sulfopropoxy group and a 4-sulfobutoxy group. The position of the substituent of the naphthyl group is not particularly limited, and when the substitution position of the azo group is 2 positions, a combination of 4 and 8 positions, 5 and 7 positions, or 6 and 8 positions is preferable when the substituent is 2, and 3 and 5 and 7 positions, 3 and 6 and 8 positions are preferable when the substituent is 3.

In the above formula (1)，Ry₁To Ry₈Each independently represents a hydrogen atom or a substituent. The substituent is not particularly limited, and may be the same as described in the above item of the phenyl group which may have a substituent or the naphthyl group which may have a substituent.

Ry in the above formula (1) is more preferable₁、Ry₂、Ry₇、Ry₈Each independently represents a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, or an alkoxy group having 1 to 4 carbon atoms, and more preferably a hydrogen atom, a methyl group, an ethyl group, a methoxy group, or an ethoxy group. Ry₃To Ry₆Each independently preferably represents a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, or an alkoxy group having 1 to 4 carbon atoms and having a sulfonic acid group. More preferably Ry₃To Ry₆Each independently is a hydrogen atom, a methyl group, an ethyl group, a methoxy group, an ethoxy group, a 3-sulfopropoxy group, or a 4-sulfobutoxy group, and more preferably a hydrogen atom, a methyl group, an ethyl group, a methoxy group, or a 3-sulfopropoxy group. As Ry₃To Ry₆When the position of the ureido skeleton is the 1-position, the substitution position(s) is preferably the 2-position alone, the 5-position alone, the combination of the 2-position and the 6-position, the combination of the 2-position and the 5-position, or the combination of the 3-position and the 5-position, more preferably the 2-position alone, the 5-position alone, or the combination of the 2-position and the 5-position. The 2-position or 5-position alone represents a substituent other than 1 hydrogen atom at only the 2-position or 5-position.

When s and t in the above formula (1) are both 0, the polarization characteristics are not preferable because of low polarization characteristics.

The azo compound represented by the formula (1) is preferably an azo compound represented by the above formula (4).

Ay in the above formula (4)₁、Ay₂、Ry₁To Ry₈S and t each have the same meaning as in formula (1).

In one embodiment, in the formula (4), Ay is more preferable₁And Ay₂Each independently a phenyl group which may have a substituent selected from the group consisting of an alkoxy group having 1 to 4 carbon atoms, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, a carboxyl group, a halogen group, a nitro group, a sulfonic acid group, a substituted or unsubstituted amino group, and an amide group,s and t are each independently 0 or 1, and either s or t is 1, Ry₁、Ry₂、Ry₇And Ry₈Each independently is a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, or an alkoxy group having 1 to 4 carbon atoms, Ry₃To Ry₆Each independently is a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, or an alkoxy group having 1 to 4 carbon atoms having a sulfonic acid group. More preferably Ay₁And Ay₂Each independently a phenyl group which may have a substituent selected from the group consisting of a carboxyl group, a halogen group and a sulfonic acid group, s and t each independently 0 or 1, and either s or t is 1, Ry₁、Ry₂、Ry₇And Ry₈Each independently is a hydrogen atom, a methyl group, or a methoxy group, Ry₃To Ry₆Each independently is a hydrogen atom, a methyl group, a methoxy group, or a 3-sulfopropoxy group. More preferably Ay₁And Ay₂Each independently is 4-sulfophenyl, 4-carboxyphenyl, 4-chloro-4-carboxyphenyl, or 2, 4-disulfonylphenyl, s and t are each independently 0 or 1, and either s or t is 1, Ry₁、Ry₂、Ry₇And Ry₈Each independently is a hydrogen atom, a methyl group, or a methoxy group, Ry₃To Ry₆Each independently is a hydrogen atom, a methyl group, a methoxy group, or a 3-sulfopropoxy group. Particularly preferred is Ay₁And Ay₂Each of which is any one of a combination of 4-sulfophenyl and 4-carboxyphenyl, a combination of 4-carboxyphenyl and 4-chloro-3-carboxyphenyl, a combination of 4-sulfophenyl and 4-chloro-3-carboxyphenyl, or a combination of 4-carboxyphenyl and 2, 4-disulfonylphenyl, s and t are each independently 0 or 1, and either s or t is 1, Ry₁、Ry₂、Ry₇And Ry₈Each independently is a hydrogen atom, a methyl group, or a methoxy group, Ry₃To Ry₆Each independently is a hydrogen atom, a methyl group, a methoxy group, or a 3-sulfopropoxy group.

In one embodiment, in the formula (4), Ay is more preferable₁And Ay₂Each independently a naphthyl group which may have a substituent selected from the group consisting of an alkoxy group having 1 to 4 carbon atoms and a sulfonic acid group, or a naphthyl group having a sulfonic acid groupAlkoxy group having 1 to 4 carbon atoms, alkyl group having 1 to 4 carbon atoms, alkoxy group having 1 to 4 carbon atoms, carboxyl group, halogen group, nitro group, sulfonic acid group, substituted or unsubstituted amino group, phenyl group which may have an amide group, and Ay₁Or Ay₂Is naphthyl which may have a substituent selected from the group consisting of an alkoxy group having 1 to 4 carbon atoms having a sulfonic acid group and a sulfonic acid group, s and t are each independently 0 or 1, and either s or t is 1, Ry₁、Ry₂、Ry₇And Ry₈Each independently is a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, or an alkoxy group having 1 to 4 carbon atoms, Ry₃To Ry₆Each independently is a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, or an alkoxy group having 1 to 4 carbon atoms having a sulfonic acid group. More preferably Ay₁And Ay₂Each independently a naphthyl group which may have a substituent selected from the group consisting of an alkoxy group having 1 to 4 carbon atoms and a sulfonic acid group, or a phenyl group which may have a substituent selected from the group consisting of a carboxyl group, a halogen group, and a sulfonic acid group, and Ay₁And or Ay₂Is naphthyl which may have a substituent selected from the group consisting of an alkoxy group having 1 to 4 carbon atoms having a sulfonic acid group and a sulfonic acid group, s and t are each independently 0 or 1, and either s or t is 1, Ry₁、Ry₂、Ry₇And Ry₈Each independently is a hydrogen atom, a methyl group, or a methoxy group, Ry₃To Ry₆Each independently is a hydrogen atom, a methyl group, a methoxy group, or a 3-sulfopropoxy group. More preferably Ay₁And Ay₂Each independently a naphthyl group which may have a substituent selected from the group consisting of a 3-sulfopropoxy group and a sulfonic acid group, s and t are each independently 0 or 1, and either s or t is 1, Ry₁、Ry₂、Ry₇And Ry₈Each independently is a hydrogen atom, a methyl group, or a methoxy group, Ry₃To Ry₆Each independently is a hydrogen atom, a methyl group, a methoxy group, or a 3-sulfopropoxy group. Particularly preferred is Ay₁And Ay₂Each is 6, 8-disulfonated naphthalene or 6-sulfonic-8- (3-sulfopropoxy) naphthalene, s and t are each independently 0 or 1, and either s or t is 1, Ry₁、Ry₂、Ry₇And Ry₈Each independently is a hydrogen atom, a methyl group, or a methoxy group, Ry₃To Ry₆Each independently is a hydrogen atom, a methyl group, a methoxy group, or a 3-sulfopropoxy group. Very preferably Ay₁And Ay₂Each of 6, 8-disulfonylnaphthalene or 6-sulfonic-8- (3-sulfopropoxy) naphthalene, s and t each of 1, Ry₁、Ry₂、Ry₇And Ry₈Each independently is a hydrogen atom, a methyl group, or a methoxy group, Ry₃To Ry₆Each independently is a hydrogen atom, a methyl group, a methoxy group, or a 3-sulfopropoxy group.

Next, specific examples of the azo compound represented by the formula (1) are shown below. In the formula, the sulfonic acid group, the carboxyl group, and the hydroxyl group are represented as free acids.

First, Ay is mentioned below₁And Ay₂Specific examples of the azo compound are phenyl groups which may have a substituent.

Next, Ay is mentioned below₁And Ay₂Specific examples of the azo compound in which at least one of the groups is a naphthyl group which may have a substituent.

The azo compound represented by the above formula (1) may be in the form of a free acid or a salt. Examples of such salts include organic salts such as alkali metal salts, ammonium salts, and amine salts of lithium salts, sodium salts, and potassium salts, and sodium salts are more preferable.

The azo compound represented by the above formula (1) or a salt thereof can be produced by diazotization and coupling according to a general method for producing an azo dye as described in non-patent document 2, and further by reaction with a ureido agent as described in patent document 13.

As a specific example of the production method, anilines having a substituent represented by the following formula (a) can be reacted with an acid chloride represented by the following formula (B) in the same manner as in patent document 18, and then subjected to a reduction reaction to obtain aminobenzoylanilines represented by the following formula (C).

In the above formulae, Ay₁、Ry₁、Ry₂Each represents Ay same as that of the above formula (1)₁、Ry₁、Ry₂Are meant to be the same.

Next, the substituted aminobenzoylanilines represented by the above formula (C) are disazo-converted and coupled with anilines represented by the following formula (D) by the same method as that of non-patent document 2 to obtain a monoazo amino compound represented by the following formula (E).

In the above formulae, Ay₁、Ry₁To Ry₄Represents Ay same as that in the above formula (1)₁、Ry₁To Ry₄Are meant to be the same.

Then, the substituted anilines represented by the following formula (F) are reacted with an acid chloride represented by the following formula (G) by the same method as in patent document 1, followed by a reduction reaction to obtain aminobenzoylanilines represented by the following formula (H).

In the above formulae, Ay₂、Ry₇And Ry₈Each represents Ay same as that of the above formula (1)₂、Ry₇And Ry₈Are meant to be the same.

Next, the substituted aminobenzoylanilines represented by the above formula (H) are disazo-converted and coupled with anilines represented by the following formula (I) by the same method as that of non-patent document 2 to obtain a monoazo amino compound represented by the following formula (J).

In the above formulae, Ay₂、Ry₅To Ry₈Represents Ay same as the above formula (1)₂、Ry₅To Ry₈Are meant to be the same.

To obtain a compound in which s and t are each 1 in the above formula (1), the monoazo amino compound (E) and the monoazo amino compound (J) are reacted with phenyl chloroformate of a ureidoing agent.

In order to obtain a compound represented by the above formula (1) wherein s and t are each 0, anilines having a substituent represented by the following formula (K) are disazo-converted by the same method as that of non-patent document 2 and coupled with anilines of the above formula (I) to obtain a monoazo amino compound represented by the following formula (L).

In the above formulae, Ay₂、Ry₅And Ry₆Each represents Ay same as that of the above formula (1)₂、Ry₅And Ry₆Are meant to be the same.

Next, the monoazo amino compound (E) and the monoazo amino compound (L) are reacted with phenyl chloroformate of a ureidoing agent to obtain the azo compound of the formula (1).

In order to obtain a compound in which s is 0 and t is 1 in the formula (1), anilines having a substituent represented by the following formula (M) are disazo-converted by the same method as that of non-patent document 2 and coupled with anilines of the formula (D) to obtain a monoazo amino compound represented by the following formula (N).

In the above formulae, Ay₁、Ry₃、Ry₄Each represents Ay same as that of the above formula (1)₁、Ry₃、Ry₄Are meant to be the same.

In the above formula (M), Ay₁Represents Ay same as that in the above formula (1)₁Are meant to be the same. In the above formula (N), Ay₁、Ry₃To Ry₄Represents Ay same as the above formula (1)₁、Ry₃To Ry₄Are meant to be the same.

Next, the monoazo amino compound (J) and the monoazo amino compound (N) are reacted with phenyl chloroformate of a ureidoing agent to obtain the azo compound of the formula (1).

The diazotization step is carried out by a cis method of mixing a nitrite such as sodium nitrite in an aqueous solution or suspension of a mineral acid such as hydrochloric acid or sulfuric acid of the diazotization component, or by a reverse method of adding a nitrite in advance to a neutral or weakly alkaline aqueous solution of the diazotization component and then mixing it with a mineral acid. The temperature of the diazotization is suitably from-10 to 40 ℃. In addition, the step of coupling with anilines is preferably carried out under acidic conditions of-10 to 40 ℃ and a pH of 2 to 7 by mixing an acidic aqueous solution such as hydrochloric acid or acetic acid with each of the disazo solutions.

The monoazo amino compound (E), the monoazo amino compound (J), the monoazo compound (L), and the monoazo compound (N) obtained by the coupling can be removed by acid precipitation and salting out, and filtration, or the next step can be carried out in the state of a solution or suspension.

Specific conditions for the urethanization reaction using phenyl chloroformate are, for example, a method of the production described in patent document 13, page 57, and the temperature is preferably 10 to 90 ℃ and the pH3 to 11, more preferably 20 to 80 ℃, and the pH4 to 10, particularly preferably 20 to 70 ℃, and the pH6 to 9. As the ureidoing agent, phenyl chloroformate, phosgene, triphosgene, ethyl chloroformate, butyl chloroformate, isobutyl chloroformate, 4-nitrophenyl chloroformate, 4-fluorophenyl chloroformate, 4-chlorophenyl chloroformate, 4-bromophenyl chloroformate, diphenyl carbonate, bis (2-methoxyphenyl) carbonate, bis (pentafluorophenyl) carbonate, bis (4-nitrophenyl) carbonate, and 1, 1' -carbonyldiimidazole can be used, but are not limited thereto. The ureidoing agent is preferably phenyl chloroformate, 4-nitrophenyl chloroformate, 4-chlorophenyl chloroformate, diphenyl carbonate or bis (4-nitrophenyl) carbonate, and more preferably phenyl chloroformate or 4-nitrophenyl chloroformate.

After completion of the urethanization reaction, the azo compound of formula (1) obtained is precipitated by salting out and removed by filtration. When purification is required, salting out may be repeated or precipitation from water may be performed by using an organic solvent. Examples of the organic solvent used for purification include water-soluble organic solvents such as alcohols such as methanol and ethanol, and ketones such as acetone.

The starting material, Ay, for the synthesis of the azo compound represented by formula (1)₁-NH₂And Ay₂-NH₂The aromatic amines are naphthylamines or anilines.

Examples of the aniline include 4-aminobenzenesulfonic acid, 3-aminobenzenesulfonic acid, 2-aminobenzenesulfonic 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-propoxybenzenesulfonic acid, and the like, 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-sulfobenzoic acid, 2-amino-5-sulfobenzoic acid, 4-amino-3-sulfobenzoic acid, 5-amino-2-chlorobenzoic acid, 5-aminoisophthalic acid, 2-amino-5-chlorobenzenesulfonic acid, 2-amino-5-bromobenzenesulfonic acid, 2-amino-5-nitrobenzenesulfonic acid, 2, 5-diaminobenzenesulfonic acid, 2-amino-3-methoxybenzenesulfonic acid, 4-amino-3-ethoxybenzenesulfonic acid, 4-amino-3-propoxybenzenesulfonic acid, 2-amino-5-dimethylaminobenzenesulfonic acid, 2-amino-5-diethylaminobenzenesulfonic acid, 5-acetamido-2-aminobenzenesulfonic acid, 4-aminobenzene-1, 3-disulfonic acid, 2-aminobenzene-1, 4-disulfonic acid, 4-amino-2-methylbenzenesulfonic acid, 2- (4-aminophenoxy) ethane-1-sulfonic acid, 3- (4-aminophenoxy) propane-1-sulfonic acid, 4- (4-aminophenoxy) butane-1-sulfonic acid, 2- (3-aminophenoxy) ethane-1-sulfonic acid, 3- (3-aminophenoxy) propane-1-sulfonic acid, and mixtures thereof, 4- (3-aminophenoxy) butane-1-sulfonic acid, 2-amino-5- (2-sulfoethoxy) benzenesulfonic acid, 2-amino-5- (3-sulfopropoxy) benzenesulfonic acid, 2-amino-5- (4-sulfobutoxy) benzenesulfonic acid, 2-amino-5- (2-sulfoethoxy) benzoic acid, 2-amino-5- (3-sulfopropoxy) benzoic acid, 2-amino-5- (4-sulfobutoxy) benzoic acid, 4-amino-3- (2-sulfoethoxy) benzenesulfonic acid, 4-amino-3- (3-sulfopropoxy) benzenesulfonic acid, N-hydroxyimino-5-butenyloxy) benzenesulfonic acid, N, 4-amino-3- (4-sulfobutoxy) benzenesulfonic acid, 4-amino-3- (2-sulfoethoxy) benzoic acid, 4-amino-3- (3-sulfopropoxy) benzoic acid, 4-amino-3- (4-sulfobutoxy) benzoic acid, 2- (4-amino-3-methylphenoxy) ethane-1-sulfonic acid, 3- (4-amino-3-methylphenoxy) propane-1-sulfonic acid, 4- (4-amino-3-methylphenoxy) butane-1-sulfonic acid, 2- (4-amino-3-ethylphenoxy) ethane-1-sulfonic acid, and mixtures thereof, 3- (4-amino-3-ethylphenoxy) propane-1-sulfonic acid, 4- (4-amino-3-ethylphenoxy) butane-1-sulfonic acid, 2- (4-amino-3-propylphenoxy) ethane-1-sulfonic acid, 3- (4-amino-3-propylphenoxy) propane-1-sulfonic acid, 4- (4-amino-3-propylphenoxy) butane-1-sulfonic acid, 2- (4-amino-3-butylphenoxy) ethane-1-sulfonic acid, 3- (4-amino-3-butylphenoxy) propane-1-sulfonic acid, 4- (4-amino-3-butylphenoxy) butane-1-sulfonic acid, and mixtures thereof, 2- (4-amino-3-methoxyphenoxy) ethane-1-sulfonic acid, 3- (4-amino-3-methoxyphenoxy) propane-1-sulfonic acid, 4- (4-amino-3-methoxyphenoxy) butane-1-sulfonic acid, 2- (4-amino-3-ethoxyphenoxy) ethane-1-sulfonic acid, 3- (4-amino-3-ethoxyphenoxy) propane-1-sulfonic acid, 4- (4-amino-3-ethoxyphenoxy) butane-1-sulfonic acid, 2- (4-amino-3-propoxyphenoxy) ethane-1-sulfonic acid, and mixtures thereof, 3- (4-amino-3-propoxyphenoxy) propane-1-sulfonic acid, 4- (4-amino-3-propoxyphenoxy) butane-1-sulfonic acid, 2- (4-amino-3-butoxyphenoxy) ethane-1-sulfonic acid, 3- (4-amino-3-butoxyphenoxy) propane-1-sulfonic acid, 4- (4-amino-3-butoxyphenoxy) butane-1-sulfonic acid, and the like. The amine groups of these aromatic amines may be protected. Examples of the protective group include an ω -methanesulfonic acid group.

As the naphthylamine, 1 or more naphthylamines having a group selected from the group consisting of a hydrogen atom, a hydroxyl group, a lower alkoxy group having a sulfonic acid group, and a sulfonic acid group are preferably used. Examples of the naphthylamines include 4-aminonaphthalenesulfonic acid, 7-aminonaphthalene-3-sulfonic acid, 1-aminonaphthalene-6-sulfonic acid, 1-aminonaphthalene-7-sulfonic acid, 7-aminonaphthalene-1, 3-disulfonic acid, 6-aminonaphthalene-1, 3-disulfonic acid, 7-aminonaphthalene-1, 5-disulfonic acid, and 7-aminonaphthalene-1, 3, 6-trisulfonic acid. Preferred examples of the sulfonic acid include 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-trisulfonic acid, 2-amino-5-hydroxynaphthalene-1, 7-disulfonic acid, and 1-aminonaphthalene-3, 8-disulfonic acid.

Examples of the naphthylamines having a sulfonic acid group and a lower alkoxy group having a sulfonic acid group include 7-amino-3- (3-sulfopropoxy) naphthalene-1-sulfonic acid, 7-amino-3- (4-sulfobutoxy) naphthalene-1-sulfonic acid, 7-amino-4- (3-sulfopropoxy) naphthalene-2-sulfonic acid, 7-amino-4- (4-sulfobutoxy) naphthalene-2-sulfonic acid, 6-amino-4- (3-sulfopropoxy) naphthalene-2-sulfonic acid, 6-amino-4- (4-sulfobutoxy) naphthalene-2-sulfonic acid, 2-amino-5- (3-sulfopropoxy) naphthalene-1, 7-disulfonic acid, 6-amino-4- (3-sulfopropoxy) naphthalene-2, 7-disulfonic acid, 7-amino-3- (3-sulfopropoxy) naphthalene-1, 5-disulfonic acid, and the like.

Examples of the aromatic amines (D) and (I) as the primary conjugate include 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, 3, 5-dimethylaniline, 2, 6-dimethylaniline, 2-ethylaniline, 2-methylaniline, 2-ethylaniline, 2-propylaniline, 3-methylaniline, 3-, 3, 5-dimethoxyaniline, 3- (2-amino-4-methylphenoxy) propane-1-sulfonic acid, 3- (2-aminophenoxy) propane-1-sulfonic acid, 4- (2-amino-4-methylphenoxy) butane-1-sulfonic acid, 4- (2-aminophenoxy) butane-1-sulfonic acid, 2- (2-amino-4-methylphenoxy) ethane-1-sulfonic acid, 2- (2-aminophenoxy) ethane-1-sulfonic acid, 3- (3-amino-4-methylphenoxy) propane-1-sulfonic acid, 3- (3-aminophenoxy) propane-1-sulfonic acid, and mixtures thereof, 4- (3-amino-4-methylphenoxy) butane-1-sulfonic acid, 4- (3-aminophenoxy) butane-1-sulfonic acid, 2- (3-amino-4-methylphenoxy) ethane-1-sulfonic acid, 2- (3-aminophenoxy) ethane-1-sulfonic acid, 3- (2-amino-4-methoxyphenoxy) propane-1-sulfonic acid, 4- (2-amino-4-methoxyphenoxy) butane-1-sulfonic acid, 2- (2-amino-4-methoxyphenoxy) ethane-1-sulfonic acid, 3- (3-amino-4-methoxyphenoxy) propane-1-sulfonic acid, and mixtures thereof, 4- (3-amino-4-methoxyphenoxy) butane-1-sulfonic acid, 2- (3-amino-4-methoxyphenoxy) ethane-1-sulfonic acid, 3- (2-amino-4-ethoxyphenoxy) propane-1-sulfonic acid, 4- (2-amino-4-ethoxyphenoxy) butane-1-sulfonic acid, 2- (2-amino-4-ethoxyphenoxy) ethane-1-sulfonic acid, 3- (3-amino-4-ethoxyphenoxy) propane-1-sulfonic acid, 4- (3-amino-4-ethoxyphenoxy) butane-1-sulfonic acid, and mixtures thereof, 2- (3-amino-4-ethoxyphenoxy) ethane-1-sulfonic acid, and the like. The amine groups of these aromatic amines may be protected. Examples of the protective group include an ω -methanesulfonic acid group.

Examples of the acid chlorides (B) and (G) include 4-nitrobenzoyl chloride, 3-methyl-4-nitrobenzoyl chloride, 2-methyl-4-nitrobenzoyl chloride, 3-ethyl-4-nitrobenzoyl chloride, 2-ethyl-4-nitrobenzoyl chloride, 3-propyl-4-nitrobenzoyl chloride, 2-propyl-4-nitrobenzoyl chloride, 3-butyl-4-nitrobenzoyl chloride, 2-butyl-4-nitrobenzoyl chloride, 3-methoxy-4-nitrobenzoyl chloride, 3-ethoxy-4-nitrobenzoyl chloride, 3-propoxy-4-nitrobenzoyl chloride, 3-butoxy-4-nitrobenzoyl chloride, 3-nitro-benzoyl chloride, 2-methoxy-4-nitrobenzoyl chloride, 2-ethoxy-4-nitrobenzoyl chloride, 2-propoxy-4-nitrobenzoyl chloride, 2-butoxy-4-nitrobenzoyl chloride, and the like.

< polarizing element >

The polarizing element of the present invention comprises an azo compound represented by formula (1) or a salt thereof and a base material.

In one aspect, the polarizing element of the present invention may be either a neutral gray polarizing element or a color polarizing element, and is preferably a neutral gray polarizing element. Here, "neutral gray" means that light leakage (discoloration) at a specific wavelength in a wavelength region of the visible light region is small in a state where 2 polarizing elements are stacked such that their alignment directions are orthogonal to each other (hereinafter, also referred to as "orthogonal positions").

The polarizing element of the present invention contains 1 or more types of azo compounds represented by formula (1) or salts thereof alone or in combination as dichroic dyes, and may optionally further contain 1 or more types of other organic dyes, the other organic dyes are not particularly limited, but dyes having absorption characteristics in a wavelength region different from the absorption wavelength region of the azo compounds represented by formula (1) or salts thereof and having high dichroism are preferable, and examples of the other organic dyes include c.i.direct Red 2, c.i.direct Red 31, c.i.direct Red 79, c.i.direct Red 81, c.i.direct Red 247, c.i.direct Violet 9, c.i.direct Blue 202, c.i.direct Green 80, and c.i.direct Green 59, and dyes described in patent documents 20, 16, 13, 21 to 23 as representative examples, and dyes described in patent documents 20, 16, 13, 21 to 23 as examples, and salts of organic acids such as salts of the polarizing plate can be developed as organic acid salts, such as salts described in patent documents 20, 16, 13, 21 to 23, and salts of the organic acids described in patent documents 20, 23 as preferable examples.

When other organic dyes are used in combination, the kind of the organic dye to be blended is different depending on the neutral gray color polarizer, the color polarizer for liquid crystal projector, and the other color polarizers. The blending ratio is not particularly limited, and usually, the total amount of at least one of other organic dyes is preferably in the range of 0.01 to 100 parts by mass, more preferably in the range of 0.1 to 10 parts by mass, based on 1 part by mass of the azo compound of formula (1) or a salt thereof.

When the target polarizer is a neutral-gray polarizer, the kind and blending ratio of other organic dyes used in combination are adjusted so as to reduce discoloration when the absorption axis of the polarizer is orthogonal in the wavelength region of the visible light region of the obtained polarizer, whereby a polarizer generally called neutral-gray can be obtained.

When the target polarizing element is a color polarizing element, the kind and blending ratio of the other organic dyes used are adjusted so that the obtained polarizing element has a high single-plate average light transmittance in a specific wavelength band and the average light transmittance at the orthogonal position is low, for example, so that the polarizing element has a single-plate average light transmittance of 39% or more in a specific wavelength band and the average light transmittance at the orthogonal position is 0.4% or less.

The polarizing element of the present invention can be produced by causing a substrate (for example, a polymer film) to contain a dichroic dye containing an azo compound represented by formula (1) or a salt thereof and optionally other dyes and aligning them, mixing them with a liquid crystal, or aligning them by a coating method using a well-known method.

In one embodiment, the polarizing element of the present invention contains an azo compound represented by the above formula (5) or a salt thereof and/or an azo compound represented by the above formula (6) or a salt thereof in addition to the azo compound represented by the above formula (1) or a salt thereof.

In one aspect, the polarizing element of the present invention contains both the azo compound represented by the above formula (5) and/or the azo compound represented by the above formula (6) or a salt thereof in addition to the azo compound represented by the above formula (1) or a salt thereof, whereby a polarizing plate having higher transmittance and higher polarization degree than the conventional achromatic polarizing plate can be realized, while realizing, for example, high-quality paper white, that is, commonly known as paper white, at the time of white display, and achromatic black, particularly clear black having a high-quality feeling at the time of black display, and having higher contrast than the conventional dye-based polarizing plate can be realized.

The azo compound represented by the above formula (5) will be described.

In the above formula (5), Ar₁Represents a substituted phenyl group or a substituted naphthyl group, Rr₁To Rr₄Each independently represents a hydrogen atom, a lower alkyl group, a lower alkoxy group, or a lower alkoxy group having a sulfonic acid group, Dr₁Represents an azo group or an amide group, j represents 0 or 1, Xr₁Represents an amino group which may have a substituent, an anilino group which may have a substituent, a phenylazo group which may have a substituent, a benzoyl group which may have a substituent, or a benzoylamino group which may have a substituent.

The above-mentioned substituted phenyl group or substituted naphthyl group is illustrated. Ar (Ar)₁In the case of a phenyl group having a substituent, it is preferable that the substituent has at least one sulfonic acid group or carboxyl group. When the phenyl group has 2 or more substituents, at least one of these substituents is a sulfonic acid group or a carboxyl group, and as another substituent, a sulfonic acid group, a carboxyl group, a lower alkyl group, a lower alkoxy group having a sulfonic acid group, a nitro group, a benzoyl group, an amino group, an acetamido group, or a lower alkylamino group-substituted amino group is preferable, and as another substituent, a sulfonic acid group, a methyl group, an ethyl group, a methoxy group, an ethoxy group, a carboxyl group, a nitro group, a benzoyl group, or an amino group is more preferable, and a sulfonic acid group, a methyl group, a methoxy group, an ethoxy group, a benzoyl group, or a carboxyl. The lower alkoxy group having a sulfonic acid group is preferably a linear alkoxy group, and the substitution position of the sulfonic acid group is preferably an alkoxy end, more preferably a 3-sulfopropoxy group and a 4-sulfobutoxy group, and particularly preferably a 3-sulfopropoxy group. The number of sulfonic acid groups in the phenyl group is preferably 1 or 2, the substitution position is not particularly limited, and when the substitution position of the azo group or the amide group is the 1-position, the 4-position alone, the combination of the 2-position and the 4-position, and the combination of the 3-position and the 5-position are preferable.

Ar above₁In the case of a naphthyl group having a substituent, at least one of an alkoxy group having 1 to 4 carbon atoms and having a sulfonic acid group, a hydroxyl group and a sulfonic acid group is usedWhen 2 or more substituents are present, at least one of the substituents is a sulfonic acid group, and the other substituent is preferably a sulfonic acid group, a hydroxyl group, a carboxyl group, or a lower alkoxy group having a sulfonic acid group. The lower alkoxy group having a sulfonic acid group is preferably a linear alkoxy group, and the substitution position of the sulfonic acid group is preferably an alkoxy terminal, more preferably a 3-sulfopropoxy group and a 4-sulfobutoxy group, and particularly preferably a 3-sulfopropoxy group. When the number of sulfonic acid groups is 2, the position of the sulfonic acid group on the naphthyl group is preferably a combination of the 4-position and the 8-position, and a combination of the 6-position and the 8-position, more preferably a combination of the 6-position and the 8-position, when the substitution position of the azo group or the amide group is the 2-position. When the number of sulfonic acid groups in the naphthyl group is 3, the substitution position of the sulfonic acid group is particularly preferably a combination of the 3-position and the 6-and 8-positions.

Rr mentioned above₁To Rr₄Each independently represents a hydrogen atom, a lower alkyl group, a lower alkoxy group, or a lower alkoxy group having a sulfonic acid group. Rr₁To Rr₄Each independently preferably represents a hydrogen atom, a lower alkyl group or a lower alkoxy group, and more preferably a hydrogen atom, a methyl group or a methoxy group. The lower alkoxy group having a sulfonic acid group is preferably a linear alkoxy group, and the substitution position of the sulfonic acid group is preferably an alkoxy terminal, more preferably a 3-sulfopropoxy group and a 4-sulfobutoxy group, and particularly preferably a 3-sulfopropoxy group.

When j is 0 or 1. j is 0, color control is easy, and when the absolute values of the a ＊ value and b ＊ value obtained in the measurement of the transmittance of natural light according to JIS Z8781-4: 2013 are overlapped with each other in the state where the polarizing elements 2 are arranged so that the absorption axis directions thereof are parallel to each other, the absolute values are easily adjusted to 2.0 or less (-2.0. ltoreq. a ＊ -p. ltoreq.2.0, -2.0. ltoreq. b ＊ -p. ltoreq.2.0) at the same time, so that one of the more preferable forms for color adjustment is 1, which shows a high degree of polarization, and when j is 1, Dr is one of the more preferable forms for high performance₁Represents an azo group or an amide group, but Dr₁When the compound is an amide group, it is particularly excellent in that it exhibits a high polarizing propertyAnd (4) selecting.

The above-mentioned Xr₁Represents an amino group which may have a substituent, an anilino group which may have a substituent, a phenylazo group which may have a substituent, a benzoyl group which may have a substituent, or a benzoylamino group which may have a substituent. The amino group which may have a substituent is preferably an amino group having 1 or 2 substituents selected from the group consisting of a hydrogen atom, a lower alkyl group, a lower alkoxy group, a sulfonic acid group, an amino group and a lower alkylamino group, and more preferably an amino group having 1 or 2 substituents selected from the group consisting of a hydrogen atom, a methyl group, an ethyl group, a methoxy group, an ethoxy group, an amino group and a lower alkylamino group. The anilino group which may have a substituent is preferably an anilino group having 1 or 2 substituents selected from the group consisting of a hydrogen atom, a lower alkyl group, a lower alkoxy group, a sulfonic acid group, an amino group, and a lower alkylamino group, and more preferably an anilino group having 1 or 2 substituents selected from the group consisting of a hydrogen atom, a methyl group, a methoxy group, a sulfonic acid group, and an amino group. The benzoyl group which may have a substituent is preferably a benzoyl group having 1 atom selected from the group consisting of a hydrogen atom, a hydroxyl group, a sulfonic acid group, an amino group, and a carboxyethylamino group. The benzoylamino group which may have a substituent is more preferably 1 benzoylamino group selected from the group consisting of a hydrogen atom, a hydroxyl group, an amino group, and a carboxyethylamino group. The phenylazo group which may have a substituent is preferably a phenylazo group having 1 to 3 groups selected from the group consisting of a hydrogen atom, a hydroxyl group, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, an amino group and a carboxyethylamino group. Xr (x of X)₁The amino group which may have a substituent, the benzoylamino group which may have a substituent, and the anilino group which may have a substituent are preferable, and the amino group which may have a substituent and the anilino group which may have a substituent are more preferable. The position of the substituent is not particularly limited, and Xr₁In the case of a group having a phenyl group, it is particularly preferable that one of the substituents is substituted at the para-position with respect to the bonding position indirectly bonded to the naphthalene skeleton represented by the formula (5), and in the case of an anilino group, it is preferable that the substituent is at the para-position with respect to the amino group.

Examples of the method for obtaining the azo compound represented by the above formula (5) include the methods described in patent documents 4 to 6, etc., but the method is not limited to these methods.

Further specific examples of the azo compound represented by the above formula (5) are shown below as a free acid.

Next, the compound of the above formula (6) will be described.

In the above formula (6), Ag₁Represents a substituted phenyl group or a substituted naphthyl group. Ag₁In the case of a substituted phenyl group, it is preferable to have at least one sulfonic acid group or carboxyl group as a substituent. When the phenyl group has 2 or more substituents, at least one of the substituents is a sulfonic acid group or a carboxyl group, and the other substituent is preferably a sulfonic acid group, a carboxyl group, a lower alkyl group, a lower alkoxy group having a sulfonic acid group, a nitro group, an amino group, an acetamido group, or a lower alkylamino group-substituted amino group. The other substituent is preferably a sulfonic acid group, a methyl group, an ethyl group, a methoxy group, an ethoxy group, a carboxyl group, a nitro group, or an amine group, and particularly preferably a sulfonic acid group, a methyl group, a methoxy group, an ethoxy group, or a carboxyl group. The lower alkoxy group having a sulfonic acid group is preferably a linear alkoxy group, and the substitution position of the sulfonic acid group is preferably an alkoxy terminal, more preferably a 3-sulfopropoxy group and a 4-sulfobutoxy group, and particularly preferably a 3-sulfopropoxy group. The number of substituents of the phenyl group is preferably 1 or 2, the substitution position is not particularly limited, and when the position of the azo group is the 1-position, the 4-position alone, the combination of the 2-position and the 4-position, and the combination of the 3-position and the 5-position are preferable. Ag₁In the case of a substituted naphthyl group, it is preferable to have at least one sulfonic acid group as a substituent. When the naphthyl group has 2 or more substituents, at least one of these substituents is a sulfonic acid group, a hydroxyl group, or an alkoxy group having 1 to 4 carbon atoms and having a sulfonic acid group, and as the other substituent, a sulfonic acid group, a hydroxyl group, a carboxyl group, or a lower alkoxy group having a sulfonic acid group is preferable. The naphthyl group particularly preferably has 2 or more sulfonic acid groups as substituents. The lower alkoxy group having a sulfonic acid group is preferably a linear alkoxy group, the substitution position of the sulfonic acid group is preferably an alkoxy terminal, and a 3-sulfopropoxy group and a 4-sulfobutoxy group are more preferable, and a 3-sulfopropoxy group is particularly preferable. When the number of sulfonic acid groups in the naphthyl group is 2, the substitution position of the sulfonic acid group is preferably a combination of the 4-position and the 8-position, and the 6-position and the 8-position in the case where the position of the azo group is the 2-positionThe combination of bits is preferable, and the combination of 6 bits and 8 bits is more preferable. When the number of sulfonic acid groups contained in the naphthyl group is 3, the substitution position of the sulfonic acid group is more preferably a combination of the 3-position and the 6-and 8-positions, provided that the substitution position of the azo group is the 2-position.

In the formula (6), Bg and Cg are each independently a group represented by the formula (7) or the formula (8), and either Bg or Cg is a group represented by the formula (7).

In the above formula (7), Rg₁Represents a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, or an alkoxy group having 1 to 4 carbon atoms and having a sulfonic acid group, and is preferably a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, or an alkoxy group having 1 to 4 carbon atoms, and more preferably a hydrogen atom, a methyl group, or a methoxy group. Particularly preferably in Rg₁Is preferably a hydrogen atom or a methoxy group. The alkoxy group having a sulfonic acid group and having 1 to 4 carbon atoms is preferably a linear alkoxy group, and the substitution position of the sulfonic acid group is preferably an alkoxy terminal, more preferably a 3-sulfopropoxy group and a 4-sulfobutoxy group, and particularly preferably a 3-sulfopropoxy group. In formula (7) substituted in Ag₁The side azo group being in the 1-position, Rg₁The substitution position (2) or (3) is preferably the 2-or 3-position, more preferably the 3-position. p is a radical of₁Represents an integer of 0 to 2. When having a sulfonic acid group (p)₁1 or 2), the substitution position of the sulfonic acid group is preferably the 6-position or the 7-position, more preferably the 6-position.

In the above formula (8), Rg₂And Rg₃Each independently represents a hydrogen atom, a lower alkyl group, a lower alkoxy group, or a lower alkoxy group having a sulfonic acid group, and a hydrogen atom, a lower alkyl group, a lower alkoxy group, or a lower alkoxy group having a sulfonic acid group is preferable, and a hydrogen atom, a methyl group, a methoxy group, a 3-sulfopropoxy group, or a 4-sulfopropoxy group is more preferable. As Rg₂Or Rg₃Will be substituted at the substitution position of Ag of the above formula (6)₁The azo group on the side is 1-position, and a combination of 2-position alone, 5-position alone, 2-position and 5-position, 3-position and 5-position, 2-position and 6-position, or 3-position and 6-position can be applied, and 2-position alone, 5-position alone, 2-position and 5-position alone are more preferable. Furthermore, 2 bits alone and 5 bits alone indicate that only 2 bits are presentOr a substituent other than 1 hydrogen atom at the 5-position.

Xg in the above formula (6)₁Represents an amino group which may have a substituent, an anilino group which may have a substituent, a phenylazo group which may have a substituent, a benzoyl group which may have a substituent, or a benzoylamino group which may have a substituent. Xg₁The amino group which may have a substituent or the anilino group which may have a substituent is preferable, and the anilino group which may have a substituent is more preferable. The amino group which may have a substituent is preferably an amino group having 1 or 2 amino groups selected from the group consisting of a hydrogen atom, a methyl group, a methoxy group, a sulfonic group, an amino group, and a lower alkylamino group, more preferably an amino group having 1 or 2 hydrogen atoms, a methyl group, and a sulfonic group. The anilino group which may have a substituent is preferably an anilino group having 1 or 2 substituents selected from the group consisting of a hydrogen atom, a lower alkyl group, a lower alkoxy group, a sulfonic acid group, an amino group, and a lower alkylamino group, and more preferably an anilino group having 1 or 2 substituents selected from the group consisting of a hydrogen atom, a methyl group, a methoxy group, a sulfonic acid group, and an amino group. The phenylazo group preferably has 1 to 3 phenylazo groups selected from the group consisting of a hydrogen atom, a hydroxyl group, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, an amino group, a hydroxyl group and a carboxyethylamino group. The benzoyl group which may have a substituent is preferably a benzoyl group having 1 substituent selected from the group consisting of a hydrogen atom, a hydroxyl group, an amino group, and a carboxyethylamino group. The benzoylamino group which may have a substituent is more preferably a benzoylamino group having 1 substituent selected from the group consisting of a hydrogen atom, a hydroxyl group, an amino group, and a carboxyethylamino group. The position of the substituent is not particularly limited, Xg₁In the case of a group having a phenyl group, 1 of the substituents is particularly preferably para to the bonding position indirectly bonded to the naphthalene skeleton represented by the formula (6), and in the case of an anilino group as a specific example, it is preferably para to the amino group.

The azo compound represented by the above formula (6) or a salt thereof is preferably an azo compound represented by the above formula (9) or a salt thereof because of particularly improved performance.

In the above formula (9), Ag₂To representAnd Ag in the formula (6)₁The same meaning is used. Rg (Rg)₄And Rg₅Each independently represents Rg in the formula (7)₁The same meaning is used. Xg₂Xg in the formula (6)₁The same meaning is used. p is a radical of₂And p₃Each independently represents the same meaning as p1 in (7). In particular p₂And p₃Each independently is 1 or 2, which is preferable because the polarization characteristics are improved.

In the above polarizing element, the content of the azo compound represented by the above formula (6) or a salt thereof is preferably 0.01 to 5000 parts by mass, more preferably 0.1 to 3000 parts by mass, even more preferably 10 to 1000 parts by mass, and even more preferably 40 to 400 parts by mass, relative to 100 parts by mass of the content of the azo compound represented by the above formula (5).

The azo compound represented by the above formula (6) or a salt thereof can be synthesized, for example, by the methods described in patent documents 7 to 12, etc., but is not limited thereto.

Specific examples of the azo compound represented by the formula (6) include azo compounds such as c.i.direct Blue 34, c.i.direct Blue 69, c.i.direct Blue 70, c.i.direct Blue 71, c.i.direct Blue 72, c.i.direct Blue 75, c.i.direct Blue 78, c.i.direct Blue 81, c.i.direct Blue 82, c.i.direct Blue 83, c.i.direct Blue 186, c.i.direct Blue 258, benzofast ChromeBlue FG (c.i.34225), benzofast Blue BN (c.i.34120), and c.i.direct Green 51.

Specific examples of the azo compound represented by the above formula (6) are shown below as a free acid.

In the above polarizing element, the content of the azo compound represented by the above formula (1) or a salt thereof is preferably 0.01 to 300 parts by mass, more preferably 0.1 to 200 parts by mass, and still more preferably 30 to 200 parts by mass, based on 100 parts by mass of the content of the azo compound of the formula (5).

The azo compound represented by the above formula (1) particularly exerts an influence on the transmittance of 400 to 500 nm. In the polarizing element, transmittance and polarization degree (dichroism) on the short wavelength side of 400 to 500nm affect blue color separation in black display and yellowing of white color in white display. The azo compound represented by formula (1) can suppress a decrease in transmittance of the polarizing element on the short wavelength side of the parallel position, improve the polarizing properties (dichroism) of 400 to 500nm, and further reduce yellowing in white display and blue separation in black display. The polarizing element further contains an azo compound represented by formula (1), and thus the monomer transmittance after the visibility correction is in the range of 35 to 45%, and further exhibits a high-quality level of paper white in white display and further improves the degree of polarization, which is more preferable.

The azo compounds represented by the above formulae (1), (5) and (6) may be in the form of a free form or a salt. The salt may be, for example, an alkali metal salt such as a lithium salt, a sodium salt, and a potassium salt, or an organic salt such as an ammonium salt and an alkylamine salt. The salt is preferably a sodium salt.

The above-mentioned polarizing element can have the performance of higher transmittance and higher polarization degree in the transmittance after the correction of the visibility and the polarization degree by containing the azo compound represented by the formula (1), the formula (5) and/or the formula (6), and the above-mentioned polarizing element can have the chromaticity in a more preferable range described later, that is, the a ＊ value and the b ＊ value, the transmittance of the monomer after the correction of the visibility, and the average transmittance in a specific wavelength band.

The blending ratio of the azo compounds in the polarizing element is preferably adjusted so that the transmittance and chromaticity are in more preferable ranges described below, among the contents of the azo compounds. The performance of the polarizer varies not only depending on the blending ratio of the azo compounds of the polarizer but also depending on various factors such as the degree of swelling of the substrate to which the azo compounds are adsorbed, the stretching ratio, the dyeing time, the dyeing temperature, the pH during dyeing, and the influence of salts. Therefore, the blending ratio of each azo compound can be determined according to the swelling degree of the base material, the temperature, time, pH, the kind of salt, the concentration of the salt, and the draw ratio at the time of dyeing.

(substrate)

The substrate is preferably a film formed from a hydrophilic polymer capable of adsorbing a dichroic dye, particularly an azo compound. The relatively hydrophilic molecule is not particularly limited, and examples thereof include polyvinyl alcohol-based resins, amylose-based resins, starch-based resins, cellulose-based resins, and polyacrylate-based resins. From the viewpoint of the dyeing properties, processability, crosslinkability and the like of the dichroic dye, the relatively hydrophilic molecule is most preferably a polyvinyl alcohol resin or a derivative thereof. The polarizing element can be produced by adsorbing the azo compound or a salt thereof to the base material and applying alignment treatment such as stretching.

(penetration after visibility correction)

The transmittance after the visual sensitivity correction is a transmittance according to JIS Z8722: 2009 the calculated visibility of the human eye is corrected to obtain the penetration rate. The transmittance for each wavelength to be corrected can be measured by using a C light source (2 degree viewing angle) for a measurement sample (e.g., a polarizing element or a polarizing plate) and measuring the spectral transmittance for each wavelength of 400 to 700nm at 5nm or 10nm, respectively, in accordance with JIS Z8722: 2009 and obtains the visual acuity through correction. The penetration after the visual acuity correction was: the monomer transmittance after the visual sensitivity correction when the polarized light element or the polarized light plate is measured by the monomer; a parallel position transmittance after visibility correction in which the transmittance when 2 polarizing elements or polarizing plates are used and the respective absorption axes are parallel is subjected to visibility correction; and a transmittance at an orthogonal position after the visibility correction by performing the visibility correction on the transmittances when the respective absorption axes are orthogonal by using 2 polarizing elements or polarizing plates.

(I) Difference in average transmittance of 2 wavelength bands

The difference in average transmittance between the specific wavelength bands of the polarizer is preferably equal to or less than a predetermined value. The average transmittance is an average value of the transmittance of each wavelength in a specific wavelength band.

Wavelength bands of 420nm to 480nm, 520nm to 590nm, and 600nm to 640nm, based on the wavelength bands of JIS Z8781-4: 2013 shows the dominant wavelength band of the matching function (matching function) used in the calculation of color. Specifically, the molecular weight distribution is determined in JIS Z8781-4: 2013, wherein each wavelength band of wavelengths of 420nm to 480nm, 520nm to 590nm, and 600nm to 640nm shows a value of 20 or more, assuming that each maximum value of x (λ) having a maximum value of 600nm, y (λ) having a maximum value of 550nm, and Z (λ) having a maximum value of 455nm is 100.

In the above-described polarizer, the transmittance measured AT each wavelength in a state where 2 polarizers are arranged one on top of another so that the absorption axis directions thereof are parallel (in the case of bright display or white display) is also referred to as "parallel position transmittance" for each wavelength, and the average transmittance AT each wavelength from ○ nm to △ nm is also referred to as "AT_○-△"in the following. Transmittance AT parallel position for each wavelength of the polarizing element of the present invention_420-480And AT_520-590The difference in (b) is preferably 2.5% or less, more preferably 1.8% or less, still more preferably 1.5% or less, and particularly preferably 1.0% or less in absolute value. And, for parallel position transmittance of each wavelength, AT_520-590And AT_600-640The difference in (b) is preferably 3.0% or less, more preferably 2.0% or less, still more preferably 1.5% or less, and particularly preferably 1.0% or less in absolute value. Such a polarizing element is capable of displaying white as a high quality level of paper in a parallel position.

The transmittance measured at each wavelength in a state where 2 polarizing elements are arranged so that the absorption axis direction is orthogonal (in the case of black display or in the case of dark display) is also referred to as "orthogonal position transmittance" at each wavelength. Transmittance AT orthogonal position for each wavelength of the polarizing element of the present invention_420-480And AT_520-590The difference of (A) is 1.0% or less in absolute value, and AT_520-590And AT_600-640The absolute value of the difference of (a) is preferably 1.0% or less. Such a polarizing element is capable of displaying achromatic black at orthogonal positions. Also, for orthogonal position penetration, AT_420-480And AT_520-590The absolute value of the difference (c) is preferably 0.6% or less, more preferably 0.3% or less, and still more preferably 0.1% or less. For orthogonal position penetration, AT_520-590And AT_600-640The difference in (b) is preferably 1.0% or less, more preferably 0.6% or less, still more preferably 0.3% or less, and particularly preferably 0.1% in absolute terms.

Further, the average transmittance at each wavelength of the monomer transmittance, the parallel position transmittance and the orthogonal position transmittance in the wavelength bands of 380nm to 420nm, 480nm to 520nm and 640nm to 780nm is preferably adjusted to some extent, although the average transmittance in the wavelength bands of 420nm to 480nm, 520nm to 590nm and 600nm to 640nm is not largely affected by the hue of the polarizing element. Transmittance of monomer for each wavelength, AT_380-420And AT_420-480The absolute value of the difference of (A) is preferably 15% or less, AT_480-520And AT_420-480The difference of (A) is preferably 15% or less in absolute value, AT_480-520And AT_520-590The difference of (A) is preferably 15% or less in absolute value, AT_640-780And AT_600-640The absolute value of the difference of (b) is preferably 20% or less.

(II) monomer penetration after Vision sensitivity correction

The monomer transmittance after the correction of the visibility of the polarizing element is preferably 35% to 66%. The monomer transmittance after the sensitivity correction was measured for 1 sheet of a measurement sample (for example, a polarizing element or a polarizing plate) in accordance with JIS Z8722: 2009, penetration after visual acuity correction. In terms of the performance of the polarizing plate, a polarizing plate having a high transmittance is required, but if the transmittance of the monomer after the visibility correction is 35% to 60%, the polarizing plate does not have a sense of incongruity even when used in a display device and can exhibit brightness. Since the higher the transmittance, the lower the degree of polarization tends to be, the monomer transmittance after the correction of the visibility is more preferably 37% to 50%, more preferably 38% to 50%, and most preferably 38% to 45%, from the viewpoint of balance with the degree of polarization. When the transmittance of the monomer after the visibility correction is more than 65%, the polarization degree may be low, but when the polarizing element is required to have a bright transmittance or a specific polarizing performance and contrast, the transmittance of the monomer after the visibility correction may be more than 65%.

(III) average transmittance in a specific wavelength band

AT measured in parallel position of polarizing element_520-590Can be 25% to 50%. When the polarizing element is provided in a display device, the display device can be bright and high-brightness and clear. The transmittance of each wavelength in the wavelength band of 520nm to 590nm is based on a transmittance in the range of JIS Z8781-4: 2013 shows one of the main wavelength bands of the matching function used in the calculation of the color. In particular, each wavelength band of 520nm to 590nm is a wavelength band having the highest visibility based on the matching function, and the transmittance in this range is a transmittance close to that which can be visually confirmed. Therefore, it is important to adjust the transmittance of each wavelength in the wavelength band of 520nm to 590 nm. AT measured in parallel position_520-590More preferably 28% to 45%, still more preferably 30% to 40%, and the polarizing element in this case may have a degree of polarization of 80% to 100%, preferably 80% to 100%Is 90% to 100%, more preferably 97% to 100%, still more preferably 99% or more, and particularly preferably 99.5% or more. The degree of polarization is preferably high, but in the relationship between the degree of polarization and the transmittance, the transmittance and the degree of polarization can be adjusted to be appropriate in accordance with importance placed on brightness or importance placed on the degree of polarization (or contrast).

(chroma a ＊ value and b ＊ value)

The chromaticity a ＊ value and b ＊ value are values obtained in accordance with JIS Z8781-4: 2013 in the measurement of the transmittance of natural light, the method of expressing an object color specified in JIS Z8781-4: 2013 corresponds to the method of expressing an object color specified by the international commission on illumination (abbreviated as CIE), the measurement of the chromaticity a ＊ value and b ＊ value is performed by irradiating natural light to a measurement sample (for example, a polarizing element or a polarizing plate), and in the following, the chromaticity a ＊ value and b ＊ value obtained for the measurement sample 1 sheet are shown as a ＊ -s and b ＊ -s, and the chromaticity a ＊ value and b ＊ value obtained in the state where the measurement sample 2 sheets are arranged with their absorption axis directions parallel to each other (in the white display) are shown as a ＊ -p and 46b 84-p, and the chromaticity b ＊ -p are obtained in the state where the measurement sample 2 sheets are arranged with their absorption axis directions orthogonal to each other (in the black display) are shown as a 8945-36 c and b-8284-p.

The absolute values of a ＊ -s and b ＊ -s of the above-described polarizing elements are preferably 1.0 or less, the absolute values of a ＊ -p and b ＊ 1-p are preferably 2.0 or less, such polarizing elements are neutral colors when they are single bodies, and can display high quality white when displayed in white, the absolute values of a ＊ 2-p and b ＊ 3-p of the polarizing elements are preferably 1.5 or less, and more preferably 1.0 or less, and the absolute values of a ＊ -c and b ＊ -c of the polarizing elements are preferably 2.0 or less, and 1.0 or less, such polarizing elements are more preferably black when displayed in black, the absolute values of a 856 and b ＊ are only 0.5 different, human beings can perceive a difference in color, and human beings have a great perception of color difference in color perception even if they are capable of displaying achromatic black when they are displayed in black, the absolute values of polarization control, a ＊ and b ＊ are only 0.5 difference in absolute values of 0, even if they are capable of displaying black when they are displayed in black, even if they are not more than 0% in black, they are capable of being displayed in a black, even if they are capable of being displayed in a high, they are capable of being displayed in a perpendicular, they are not only a black, they are not only when they are not more than a, and are not capable of being displayed in a, and are not only a high, and are not capable of being displayed in perpendicular, and are not only a, and are not capable of being displayed in a high, and are not capable of being displayed in a white, and are not capable of being displayed in a high, and no, and are not capable of being displayed in a, and no more than 2, and no, even if they are not more than a, preferably no, no more than 2, no more than 2, no more than 2, no more than 2, no more than 2 when no more than 2, no more than 2, no more preferably no more than 2 when.

As is clear from the above, when the 2-plate polarizers are arranged so as to be superimposed with the absorption axis direction orthogonal to each other, a preferable method of providing black color by the hue thereof can be realized by satisfying any one of the following items 1) to 3).

1) AT is a transmittance (hereinafter, also referred to as "orthogonal position transmittance") of each wavelength measured in a state where 2-plate polarizers are arranged in a superimposed manner so that the absorption axis direction is orthogonal (in black display or dark display), and the transmittance is measured_420-480And AT_520-590The difference of (A) is 1.0% or less in absolute value, and AT_520-590And AT_600-640The difference of (d) is 1.0% or less in absolute value.

2) The absolute values of a ＊ -c and b ＊ -c are 2.0 or less.

3) A transmittance of 1% or less or a degree of polarization of about 97% or more at an orthogonal position in each wavelength of wavelength bands of 420nm to 480nm, 520nm to 590nm, and 600nm to 640 nm.

The polarizing element of the invention has high contrast and high transmittance, and simultaneously has the colorlessness and high polarization degree of the monomer. Further, the polarizing element of the present invention is capable of exhibiting a white color (paper white) such as paper of a high quality level in white display and capable of exhibiting a colorless black color, particularly a clear black color having a high-grade feeling in black display. Such a polarizing element having high transmittance and achromatic properties has not been known in the past. Further, the polarizing element of the present invention has high durability, particularly durability against high temperature and high humidity.

Further, the polarizing element of the present invention has an advantage that the absorption of light having a wavelength of 700nm or more is small as compared with a commonly used iodine-based polarizing plate and patent document 3, and therefore, heat generation is small even after irradiation with light such as sunlight. For example, when a liquid crystal display is used outdoors, sunlight is irradiated on the liquid crystal display, and as a result, the sunlight is also irradiated on the polarizer. Sunlight also has a wavelength of 700nm or more and contains near infrared rays having a heat-generating effect. For example, although a polarizing element using an azo compound described in example 3 of Japanese patent publication No. Hei 02-061988 absorbs light of near infrared rays having a wavelength of about 700nm and generates some heat, the polarizing element of the present invention generates little heat even when exposed to sunlight outdoors because the absorption of near infrared rays is very small. The polarizing element of the present invention is excellent in that it generates less heat and thus suffers less deterioration.

(method for manufacturing polarizing element)

Hereinafter, a method for producing a polarizing element will be specifically described by taking as an example a case where an azo compound is adsorbed on a polyvinyl alcohol resin substrate to produce the polarizing element. The method for manufacturing the polarizing element of the present invention is not limited to the following manufacturing method.

(preparation of blank film)

The green film can be produced by forming a polyvinyl alcohol resin film. The polyvinyl alcohol resin is not particularly limited, and commercially available products can be used, or the polyvinyl alcohol resin can be synthesized by a known method. The polyvinyl alcohol resin can be obtained by, for example, saponifying a polyvinyl acetate resin. Examples of the polyvinyl acetate resin include polyvinyl acetate which is a homopolymer of vinyl acetate, and a copolymer of vinyl acetate and another monomer copolymerizable therewith. Examples of the other monomer copolymerizable with vinyl acetate include unsaturated carboxylic acids, olefins, vinyl ethers, and unsaturated sulfonic acids. The saponification degree of the polyvinyl alcohol resin is usually preferably about 85 to 100 mol%, and more preferably 95 mol% or more. The polyvinyl alcohol resin may be further modified, and for example, polyvinyl formaldehyde, polyvinyl acetal, or the like modified with aldehydes may be used. The polymerization degree of the polyvinyl alcohol resin means a viscosity-average polymerization degree, and can be determined by a method well known in the art, and is usually preferably about 1,000 to 10,000, more preferably about 1,500 to 6,000.

The method for forming the film of the polyvinyl alcohol resin is not particularly limited, and a known method can be used to form the film. In this case, the polyvinyl alcohol resin film may contain glycerin, ethylene glycol, propylene glycol, low molecular weight polyethylene glycol, or the like as a plasticizer. The amount of plasticizer is preferably 5 to 20 mass%, more preferably 8 to 15 mass%, in the total amount of the film. The film thickness of the green film is not particularly limited, but is, for example, about 5 μm to 150 μm, and more preferably about 10 μm to 100 μm.

(swelling step)

The green film obtained as described above is subjected to swelling treatment. The swelling treatment is preferably performed by immersing the green film in a solution at 20 to 50 ℃ for 30 seconds to 10 minutes. The solution is preferably water. The draw ratio is preferably adjusted to 1.00 to 1.50 times, more preferably adjusted to 1.10 to 1.35 times. In the case of shortening the time for producing the polarizing element, the blank film swells even in the dyeing process described later, and therefore the swelling process can be omitted.

(dyeing step)

In the dyeing step, the resin film obtained by swelling the green film is adsorbed and impregnated with an azo compound. When the swelling step is omitted, the swelling treatment of the green film can be performed simultaneously with the dyeing step. The treatment of adsorbing and impregnating the azo compound is a step of coloring the resin film, and is therefore a dyeing step.

As the azo compound used in the dyeing step, an azo compound represented by formula (1) or a salt thereof can be used, and the color can be adjusted by arbitrarily using an azo compound represented by formula (5) and/or formula (6) or a salt thereof, and/or a dichroic dye exemplified in non-patent document 1 or the like, that is, an azo compound, to the extent that the performance of the polarizing element of the present application is not impaired. These azo compounds may be used in the form of free acids, and salts of the compounds may also be used. Examples of such salts include alkali metal salts such as lithium salts, sodium salts, and potassium salts, and organic salts such as ammonium salts and alkylamine salts, with sodium salts being more preferred.

The dyeing step is not particularly limited as long as the resin film is adsorbed and impregnated with the dye, and is preferably performed by, for example, immersing the resin film in a dyeing solution, and can also be performed by applying the dyeing solution to the resin film. Each azo compound in the dyeing solution can be adjusted, for example, in the range of 0.001 to 10 mass%. The solution temperature in this step is preferably 5 to 60 ℃, more preferably 20 to 50 ℃, particularly preferably 35 to 50 ℃. The time of immersion in the solution can be suitably adjusted, but is preferably adjusted at 30 seconds to 20 minutes, more preferably 1 to 10 minutes.

The dyeing solution may optionally further contain a dyeing assistant in addition to the azo compound. Examples of the dyeing assistant include sodium carbonate, sodium bicarbonate, sodium chloride, sodium sulfate, anhydrous sodium sulfate, and sodium tripolyphosphate. The content of the dyeing assistant can be adjusted to any concentration depending on the time and temperature of the dyeing property of the dye, and each content is preferably 0.01 to 5% by mass, more preferably 0.1 to 2% by mass in the dyeing solution.

(washing step 1)

After the dyeing step, a washing step (hereinafter, also referred to as "washing step 1") can be performed before proceeding to the next step. The washing step 1 is a step of washing the dyeing solution attached to the surface of the resin film in the dyeing step. By performing the washing step 1, the dye can be inhibited from moving into the liquid to be treated later. In the washing step 1, water is usually used as a washing liquid. The cleaning method is preferably immersion in a cleaning liquid, and the resin film can be cleaned by applying the cleaning liquid thereto. The washing time is not particularly limited, but is preferably 1 to 300 seconds, more preferably 1 to 60 seconds. The temperature of the washing liquid in the washing step 1 must be a temperature at which a material constituting the resin film (for example, a relatively hydrophilic molecule, in this case, a polyvinyl alcohol resin) is not dissolved. The washing treatment can be carried out usually at 5 to 40 ℃. However, since there is no problem in performance even if the step of the washing step 1 is not provided, the washing step can be omitted.

(step containing crosslinking agent and/or Water-resistant agent)

After the dyeing step or the washing step 1, a step containing a crosslinking agent and/or a water-resistant agent can be performed. The method of containing the crosslinking agent and/or the water-resistant agent in the resin film is preferably a method of immersing the resin film in the treatment solution, and the treatment solution may be applied or coated on the resin film. The treatment solution contains at least one of a crosslinking agent and/or a water-resistant agent, and a solvent. The temperature of the treatment solution at this step is preferably 5 to 70 ℃, more preferably 5 to 50 ℃. The treatment time at this step is preferably 30 seconds to 6 minutes, more preferably 1 to 5 minutes.

As the crosslinking agent, for example, there can be used: boron compounds such as boric acid, borax, or ammonium borate, polyaldehydes such as glyoxal or glutaraldehyde, polyisocyanate-based compounds such as biuret-based, isocyanurate-based, or blocked-type, titanium-based compounds such as titanyl sulfate, etc., and ethylene glycol glycidyl ether, polyamide epichlorohydrin, etc. can also be used. Examples of the water-resistant agent include succinic peroxide, ammonium persulfate, calcium perchlorate, benzoin ethyl ether, ethylene glycol diglycidyl ether, glycerol diglycidyl ether, ammonium chloride, and magnesium chloride, and boric acid is preferably used. The solvent for the crosslinking agent and/or the water-resistant agent is preferably water, but is not limited thereto. The concentration of the crosslinking agent and/or the water-resistant agent to be contained can be appropriately determined by those skilled in the art according to the kind thereof, and boric acid is exemplified as an example, and the concentration in the treatment solution is preferably 0.1 to 6.0 mass%, more preferably 1.0 to 4.0 mass%. However, it is not necessary to contain a crosslinking agent and/or a water-resistant agent, and if a crosslinking treatment or a water-resistant treatment is not required in the case of shortening the time, the treatment step can be omitted.

(elongation step)

After the dyeing step, the washing step 1, or the step containing a crosslinking agent and/or a water-resistant agent is performed, the extension step is performed. The stretching step is performed by uniaxially stretching the resin film. The stretching method may be either a wet stretching method or a dry stretching method. The draw ratio is preferably 3 times or more, more preferably 4 to 8 times, particularly preferably 5 to 7 times.

In the wet stretching method, the resin film is preferably stretched in water, a water-soluble organic solvent, or a mixed solution thereof. It is preferable to perform the stretching treatment while immersing the sheet in a solution containing at least one of a crosslinking agent and a water-resistant agent. As the crosslinking agent and the water-resistant additive, the same crosslinking agent and water-resistant additive as those described in the step of containing a crosslinking agent and/or a water-resistant additive can be used. The concentration of the crosslinking agent and/or the water resistant agent in the solution in the extension step is, for example, preferably 0.5 to 15 mass%, more preferably 2.0 to 8.0 mass%. The stretching temperature is preferably 40 to 60 ℃ and more preferably 45 to 58 ℃. The extension time is usually 30 seconds to 20 minutes, preferably 2 to 5 minutes. The wet stretching step may be performed in 1-stage stretching, or may be performed by multi-stage stretching in 2 or more stages.

In the dry drawing method, when the drawing heating medium is an air medium, the resin film is preferably drawn at a temperature of from room temperature to 180 ℃. The humidity is preferably set to 20 to 95% RH in an environment. Examples of the heating method include an inter-roll zone stretching method, a roll heating stretching method, a rolling stretching method, and an infrared heating stretching method, and the stretching method is not limited. The extension step can be performed by 1-stage extension, or by multi-stage extension in 2 or more stages.

(washing step 2)

After the stretching step, the crosslinking agent and/or the water resistance agent or the foreign matter may be deposited on the surface of the resin film, and therefore, a washing step (hereinafter, also referred to as "washing step 2") of washing the surface of the resin film can be performed. The washing time is preferably 1 second to 5 minutes. The washing method is preferably a method in which the resin film is immersed in a washing liquid, and the resin film can be washed by applying or coating the resin film with the solution. The washing liquid is preferably water. The washing treatment can be performed in 1 stage, and the multi-stage treatment can be performed in 2 or more stages. The temperature of the solution in the washing step is not particularly limited, and is usually 5 to 50 ℃ and more preferably 10 to 40 ℃.

Examples of the treatment solution or the solvent thereof used in the conventional treatment step include, but are not limited to, water, alcohols such as dimethyl sulfoxide, N-methylpyrrolidone (Methyl pyrrolidone), methanol, ethanol, propanol, isopropanol, glycerol, ethylene glycol, propylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, trimethylolpropane, and amines such as ethylenediamine and diethylenetriamine. The treatment liquid or its solvent is most preferably water. These treatment solutions or solvents thereof may be used alone in 1 kind, or may be used in a mixture of 2 or more kinds.

(drying step)

After the extension step or washing step 2, a drying step of the resin film is performed. The drying treatment can be performed by natural drying, but for further improvement of drying efficiency, it can be performed by removing moisture and the like on the surface by compression using a roll, a doctor blade, a water suction roll or the like, and/or by air drying. The drying treatment temperature is preferably 20 to 100 ℃ and more preferably 60 to 100 ℃. The drying treatment time is, for example, 30 seconds to 20 minutes, preferably 5 to 10 minutes.

In the method for producing a polarizer, the degree of swelling of the base material in the swelling step, the blending ratio of the azo compounds in the dyeing step, the temperature of the dyeing solution, the pH, the type and concentration of salts such as sodium chloride, sodium sulfate, and sodium tripolyphosphate, the dyeing time, and the draw ratio in the drawing step are preferably adjusted so that the polarizer satisfies at least one of the following conditions (i) to (v), and more preferably so that the polarizer further satisfies the conditions (vi) and (vii).

(i) For parallel position penetration, AT_420-480And AT_520-590The difference in absolute value of (A) is 2.5% or less, AT_520-590And AT_600-640The absolute value of the difference of (A) is 3.0% or less.

(ii) For orthogonal position penetration, AT_420-480And AT_520-590The difference of (A) is 1.0% or less in absolute value, AT_520-590And AT_600-640The absolute value of the difference of (A) is 1.0% or less.

(iii) The monomer transmittance after the visibility correction becomes 35% to 45%.

(iv) The absolute values of the a ＊ value and the b ＊ value are 1.0 or less in the case of the polarizer alone, and 2.0 or less in the case of the parallel position.

(v) The absolute values of the a ＊ value and the b ＊ value measured at the orthogonal positions are both 2 or less.

(vi) For parallel position penetration, AT_520-590Becomes 28 to 45%.

(vii) AT in the single body transmittance or orthogonal position transmittance of each wavelength_380-420And AT_420-480The difference of (A) is 15% or less in absolute value, AT_480-520And AT_420-480The difference of (A) is 15% or less in absolute value, AT_480-520And AT_520-590The difference of (a) is 15% or less in absolute value, and/or AT_640-780And AT_600-640The absolute value of the difference in (c) is 20% or less.

By the above method, a polarizing element containing a combination of at least the azo compounds represented by formula (5) and/or formula (6) and formula (1) can be produced. Such a polarizing element has a higher transmittance and a higher degree of polarization than conventional polarizing elements, and when 2 polarizing elements are arranged one on top of another so that the absorption axis directions thereof are parallel to each other, it can exhibit a high-quality level of paper white, for example, and when used alone, it has a neutral color (neutral gray). When the 2-plate polarizers are arranged so that the absorption axis directions are orthogonal to each other, the polarizer displays a high-quality achromatic black color. In addition, the polarizing element has high durability against high temperature and high humidity.

< polarizing plate >

The polarizing plate of the present invention has excellent polarizing performance and excellent moisture resistance, heat resistance and light resistance because it includes the polarizing element of the present invention.

The polarizing plate of the present invention includes a polarizing element and a transparent protective layer provided on one or both surfaces of the polarizing element. The transparent protective layer is provided for the purpose of improving the water resistance and operability of the polarizing element.

The transparent protective layer is a protective film formed using a transparent material. The protective film is preferably a film having a layer shape capable of maintaining the shape of the polarizer, and is preferably a plastic having excellent transparency, mechanical strength, thermal stability, moisture-shielding properties, and the like. The same function can be provided by forming the same layer. Examples of the plastic constituting the protective film include films obtainable from: examples of the polyolefin-based resin include thermoplastic resins such as polyester-based resins, acetate-based resins, polyether sulfone-based resins, polycarbonate-based resins, polyamide-based resins, polyimide-based resins, polyolefin-based resins, acrylic-based resins, and fluorine-based resins such as tetrafluoroethylene-hexafluoropropylene-based copolymers, thermosetting resins such as acrylic-based resins, urethane (urethane) based resins, acrylic urethane-based resins, epoxy-based resins, and silicone-based resins, and ultraviolet-curable resins. In general, it is preferable to select a protective film that does not hinder the performance of the polarizing element after the protective film is laminated, and cellulose Triacetate (TAC) and norborene composed of a cellulose acetate-based resin are particularly preferable as such a protective film. In addition, the protective film may be subjected to hard coating treatment, antireflection treatment, treatment for the purpose of anti-sticking, diffusion, anti-glare, or the like, as long as the effects of the present invention are not impaired. The thickness of the transparent protective layer is usually preferably 10 to 200 μm.

The polarizing plate preferably further includes an adhesive layer for bonding the transparent protective layer and the polarizing element. Examples of the adhesive constituting the adhesive layer include a polyvinyl alcohol adhesive, a urethane emulsion adhesive, an acrylic adhesive, and a polyester-isocyanate adhesive, and a polyvinyl alcohol adhesive is preferable.

The polyvinyl alcohol-based adhesive may include, for example, Gohsenol NH-26 (manufactured by japan synthesis corporation) and Exceval RS-2117 (manufactured by KURARAY corporation), but is not limited thereto, a crosslinking agent and/or a water resistant agent may be added thereto, the polyvinyl alcohol-based adhesive may preferably use a maleic anhydride-isobutylene copolymer, and an adhesive containing a crosslinking agent may optionally be used, the maleic anhydride-isobutylene copolymer may include, for example, ISOBAM #18 (manufactured by KURARAY corporation), ISOBAM #04 (manufactured by KURARAY corporation), ammonia-modified ISOBAM #104 (manufactured by KURARAY corporation), ammonia-modified ISOBAM #110 (manufactured by KURARAY corporation), imide-ISOBAM #304 (manufactured by KURARAY corporation), and imide-ISOBAM #310 (manufactured by KURARAY corporation), the crosslinking agent may use a water-soluble multi-epoxy compound, the epoxy-based adhesive may include, for example, epoxy-L (manufactured by KURARAY corporation), and the polyvinyl alcohol-based adhesive may be used alone, and the crosslinking agent may be used as a water resistant adhesive, and the polyvinyl alcohol-based adhesive may be used, and the adhesive may be used may be a polyvinyl alcohol-based adhesive may be a resin may be a polyvinyl alcohol-based adhesive, and may be used, and may be a polyvinyl alcohol-based adhesive, and may be a resin obtained by a suitable heat treatment, and may be a transparent adhesive, and may be a resin such as a resin, and may be a resin such as a resin, a.

The polarizing element or the polarizing plate may be provided with various well-known functional layers such as an AR layer (anti-reflection layer), an antiglare layer, and a hard coat layer on the exposed surface of the transparent protective layer or the film. The layer having these various functionalities is preferably produced by a coating method, and a film having these functionalities can be bonded to each other with an adhesive or a pressure-sensitive adhesive (pressure-sensitive adhesive).

Examples of the hard coat layer include acrylic and silicone hard coat layers, and urethane protective layers. In addition, the AR layer can be expected to further improve the transmittance. The AR layer can be formed by, for example, vapor deposition or sputtering of a substance such as silicon dioxide or titanium oxide, or by thinly applying a fluorine-based substance.

When a polarizing element or a polarizing plate is attached to a display device such as a liquid crystal display or an organic electroluminescence (also referred to as O L ED or OE L) as the case may be, various functional layers for improving a viewing angle and/or improving a contrast, a layer or a film having a luminance improving property may be provided on the surface of a transparent protective layer or a film which is a non-exposed surface, and the various functional layers may be, for example, a layer or a film for controlling a retardation (hereinafter, also referred to as "retardation plate").

In a liquid crystal display device, the polarizing plate of the present invention is disposed on either or both of the incident side and the emission side of a liquid crystal cell. The polarizing plate may be in contact with the liquid crystal cell or not in contact with the liquid crystal cell, and is preferably not in contact with the liquid crystal cell from the viewpoint of durability. When the polarizing plate is in contact with the liquid crystal cell on the emission side of the liquid crystal cell, the liquid crystal cell can be used as a support for the polarizing plate. When the polarizing plate is not in contact with the liquid crystal cell, a polarizing plate provided with a support other than the liquid crystal cell is preferably used. In addition, from the viewpoint of durability, it is preferable that the polarizing plate is disposed on both the incident side and the emission side of the liquid crystal cell, and it is more preferable that the polarizing plate surface of the polarizing plate is disposed on the liquid crystal cell side and the support surface is disposed on the light source side. The incident side of the liquid crystal cell is referred to as a light source side, and the opposite side is referred to as an emission side.

The liquid crystal cell provided in the liquid crystal display device is, for example, of an active matrix type, and is preferably a liquid crystal cell formed by sealing liquid crystal between a transparent substrate on which electrodes and TFTs are formed and a transparent substrate on which a counter electrode is formed, and light emitted from a light source such as a cold cathode tube lamp or white L ED is projected on a display screen through a polarizing plate, and then the liquid crystal cell, a color filter, and the polarizing plate are connected.

The polarizing plate may be either a neutral gray polarizing plate or a color polarizing plate depending on the application.

The neutral gray polarizing plate has a neutral color, is less discolored at an orthogonal position in a polarization region in a visible light region, has excellent polarization properties, can suppress discoloration and deterioration in polarization properties even in a high-temperature and high-humidity state, and has high durability, and thus is suitable for a display device for a vehicle or a display device for an outdoor display.

Since the polarizing plate of the present invention has brightness, excellent polarizing performance, and polarizing and light-resistance properties, the liquid crystal display device is less likely to suffer discoloration and deterioration in polarizing performance even in a high-temperature and high-humidity state such as in a vehicle interior or in an outdoor environment, and has high reliability.

As in the case of the neutral gray polarizing plate, the polarizing element used for the color polarizing plate of the display device for vehicles or the display device for outdoor use may be provided with a protective layer, an AR layer, a support, and the like. The color polarizing plate with a support is obtained by, for example, applying a transparent adhesive (pressure-sensitive adhesive) to the flat surface of the support and then attaching a polarizing plate to the applied surface. Alternatively, a transparent adhesive (pressure-sensitive adhesive) may be applied to the polarizing plate, and then the support may be attached to the applied surface. The adhesive is preferably an acrylate adhesive. In the case of using the polarizing plate as an elliptical polarizing plate, the polarizing plate/retardation plate/support are generally laminated by attaching the retardation plate side of the polarizing plate with a retardation plate to the support, but the retardation plate/polarizing plate/support may be laminated by attaching the retardation plate-free side to the support.

The neutral gray polarizing plate for vehicle or outdoor display preferably has an AR layer in addition to the polarizer and the transparent protective layer to further increase the transmittance, and is preferably a polarizing plate having an AR layer and a support, both of which are attached to the AR layer and the support such as a transparent resin. The AR layer can be provided on one or both sides of the polarizing plate. The support is preferably provided on one surface of the polarizing plate, and may be provided directly on the polarizing plate or the AR layer may be provided on the support. The polarizing plate having the AR layer and the support is preferably provided with the AR layer, the polarizing plate, and the support having the AR layer in this order. The support is preferably provided with a flat surface portion for attaching the polarizing plate, and is preferably a transparent substrate because of its optical use. The transparent substrate is roughly classified into an inorganic substrate and an organic substrate, and examples thereof include: inorganic substrates such as soda-lime glass, borosilicate glass, crystal substrates, sapphire substrates, and spinel (spinel) substrates; and organic substrates such as acrylic, polycarbonate, polyethylene terephthalate, polyethylene naphthalate, and cycloolefin polymers, and organic substrates are preferable. The thickness and size of the transparent substrate may be the desired dimensions.

The color polarizing plate has excellent polarizing performance, and is less likely to cause discoloration or deterioration in polarizing performance even in a high-temperature and high-humidity state, and therefore, is suitable for use in display devices such as liquid crystal projectors, vehicles, and outdoor displays.

A color polarizing plate for a liquid crystal projector having brightness and excellent polarizing performance, wherein the polarizing plate has an average light transmittance of 39% or more for each wavelength in a necessary wavelength band (A. when an extra-high pressure mercury lamp is used; 420 to 500nm for a blue Channel (Channel), 500 to 580nm for a green Channel, 600 to 680nm for a red Channel, B. when a 3-primary color L ED lamp is used; 430 to 450nm for a blue Channel, 520 to 535nm for a green Channel, 620 to 635nm for a red Channel), and an average light transmittance of 0.4% or less for each orthogonal position of each wavelength, and more preferably, the polarizing plate has an average light transmittance of 41% or more for each wavelength in the necessary wavelength band, and an average light transmittance of 0.3% or less, more preferably 0.2% or less for each wavelength in the orthogonal position, and still more preferably, the polarizing plate has an average light transmittance of 42% or more for each wavelength in the necessary wavelength band, and an average light transmittance of 0.1% or less for each wavelength in the orthogonal position.

The average transmittance of a single plate is an average value of transmittances in a specific wavelength range when natural light is incident on 1 polarizing plate (hereinafter, also simply referred to as "polarizing plate") which is not provided with a support such as an AR layer or a transparent glass plate. The average transmittance at the orthogonal position is an average value of the transmittance of light in a specific wavelength region when natural light is incident in a state where 2 polarizing plates are stacked so that the alignment directions thereof are orthogonal to each other.

In one aspect, the polarizing plate of the present invention has a high transmittance and a high degree of polarization, while being capable of realizing colorlessness, and particularly capable of exhibiting a high level of paper-like white color in white display, and capable of exhibiting a neutral black color in black display.

< display device >

The polarizing element or the polarizing plate of the present invention, which has no wavelength dependence at a single body, a parallel position, or even at an orthogonal position and has almost constant transmittance at each wavelength, can be suitably used for improving the reproducibility of display colors of a display device because the color hue does not change even when used in each state at a single body, a parallel position, or even at an orthogonal position. By utilizing the characteristics thereof, a protective layer or a functional layer and a transparent support such as glass, crystal, sapphire and the like are optionally provided, and the liquid crystal display device can be suitably applied to a liquid crystal projector, a computer, a watch, a notebook personal computer, a word processor, a liquid crystal television, a polarizing lens, polarizing glasses, a car navigation device, an indoor and outdoor meter, a display and the like.

In one aspect, the polarizing element or the polarizing plate of the present invention can be suitably used in a liquid crystal display device such as a reflective liquid crystal display device, a transflective liquid crystal display device, and a transmissive liquid crystal display device, in particular, and can improve high color reproducibility even with ambient light without requiring color correction even in a state without a backlight. In the conventional polarizing plate, since the transmittance of short wavelengths is low at the parallel position when the contrast is high, the parallel position is colored yellow in ambient light (natural light). Therefore, it is necessary to correct the color using a backlight and a color filter, and there is a problem that, when the color correction is performed in a parallel position, blue discoloration occurs in an orthogonal position. Such a liquid crystal display device has high color reproducibility because the polarizing element or the polarizing plate is not colored even when ambient light is displayed (even when a backlight is not used), and can be suitably used in a liquid crystal display device such as a reflective liquid crystal display device, a transflective liquid crystal display device, and a transmissive liquid crystal display device by utilizing the advantage that the color does not change when ambient light is displayed or when a backlight is used. The liquid crystal display device can be suitably used particularly in a reflective liquid crystal display device and a transflective liquid crystal display device by utilizing the characteristic. That is, a liquid crystal display device using the polarizing element or the polarizing plate of the present invention can exhibit white and neutral black as high quality level of paper. The liquid crystal display device has high durability and high reliability, and has high contrast and high color reproducibility over a long period of time. The polarizing element or the polarizing plate of the present application can be suitably used for organic electroluminescence or the like for the purpose of preventing reflection of ambient light in addition to a liquid crystal display device.

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Azo compound or salt thereof, and polarizing element, polarizing plate and display device each containing the same

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