Azo dichroic dye as well as preparation method and application thereof

Abstract

The invention discloses an azo dichroic dye and a preparation method and application thereof.The azo dichroic dye has high solubility, high dichroic ratio and high stability, shows excellent compatibility with a liquid crystal material, shows extremely high adaptability when used in cooperation with the liquid crystal material, and can be applied to liquid crystal display devices. And particularly, the application in a polaroid and a liquid crystal display is particularly prominent.

Description

Technical Field

[0001] The invention relates to the technical field of dichroic dyes, and in particular to an azo dichroic dye and a preparation method and application thereof. Background Art

[0002] With the rapid development of liquid crystal (LC) technology, liquid crystal displays have made significant progress in the past few years and are widely used in various electronic devices. Among them, dichroic dyes are widely used in guest-host liquid crystal materials, such as polymer dispersed liquid crystal (PDLC) or polymer network dispersed liquid crystal (PNLC) materials, which have shown great application potential in contrast enhancement films, reflective displays and other fields.

[0003] At present, almost all display screens cannot do without polarizers. For traditional liquid crystal displays (LCDs), two polarizers are usually required to display images; for emerging organic light-emitting diode (OLED) screens, although their structure is relatively simple and the backlight module is removed, a polarizer is still required to ensure the display effect. It can be seen that polarizers play a vital role in the operation of display technology and are an indispensable key component.

[0004] The core component of polarizer is dichroic dye. In order to prepare high-quality polarizer, a dichroic dye that can be easily dissolved and stored stably in solution for a long time is needed. Specifically, dichroic dyes with high dichroic ratio can more effectively control the polarization direction of light, thereby improving the contrast and color saturation of the display. At the same time, dichroic dyes with high stability can ensure that the polarizer maintains stable performance during long-term use and extend the service life of the display. However, existing dichroic dyes still have shortcomings in dichroic ratio and stability, and it is difficult to meet the growing application needs, especially in the field of liquid crystal display with extremely high requirements for image quality.

[0005] Therefore, developing dichroic dyes with high solubility, high dichroic ratio and high stability to meet the demand for high-quality polarizers in the liquid crystal display field has become a technical problem that needs to be solved urgently. Summary of the invention

[0006] In order to solve the above technical problems, the purpose of the present invention is to provide an azo dichroic dye and a preparation method and application thereof.

[0007] The above-mentioned purpose of the present invention is achieved through the following technical solutions:

[0008] An azo dichroic dye, the structural formula of the azo dichroic dye is shown in Formula A:

[0009]

[0010] Wherein, R is selected from one or more of trifluoromethyl, nitrile, ethoxycarbonyl and halogen.

[0011] Furthermore, the azo dichroic dye is selected from one of the following structural formulas:

[0012]

[0013]

[0014] The present invention provides a method for preparing the above-mentioned azo dichroic dye, comprising the following steps:

[0015] (1) Dissolve in a solvent, add sodium nitrite and a catalyst at 0-5°C to obtain solution A; add sodium phenylamino-N-methanesulfonate and a base to the solution A to react to obtain a compound shown in formula a; wherein R is selected from one or more of trifluoromethyl, nitrile, ethoxycarbonyl and halogen;

[0016] (2) dissolving the compound represented by formula a in an organic solvent, adding nitrosylsulfuric acid at 0-5° C., and then adding 1-naphthylamine to react to obtain the compound represented by formula b;

[0017] (3) dissolving the compound represented by formula b in an organic solvent, adding nitrosylsulfuric acid at 0-5° C., and then adding N-(2-ethylhexyl)naphthalene-1-amine to react to obtain the compound represented by formula A;

[0018] The structural formulas of the above formula a and formula b are as follows:

[0019]

[0020] Furthermore, in step (1), It is 4-trifluoromethylaniline, 2,4-difluoroaniline, 4-cyanoaniline, 4-ethoxycarbonylaniline or 3,4,5-trifluoroaniline.

[0021] Furthermore, in step (1), the solvent is aqueous hydrochloric acid solution.

[0022] Furthermore, in step (1), the catalyst is aminosulfonic acid.

[0023] Furthermore, in step (1), the base is sodium bicarbonate.

[0024] Furthermore, in step (1), the structural formula of the sodium phenylamino-N-methanesulfonate is

[0025] In a specific embodiment, in step (1), Dissolve in a solvent, add sodium nitrite at 0-5°C, stir for 1-2 hours, add a catalyst and stir for 10-20 minutes to obtain solution A; add sodium phenylamino-N-methanesulfonate and a base to the solution A, heat to 23-27°C to react for 10-12 hours, purify the obtained crude product, and finally obtain the compound shown in formula a.

[0026] Furthermore, the specific method of the purification treatment is: washing the obtained crude product and then dissolving it in water, adding an alkaline solution, stirring at 65-75° C. for 3-4 hours, filtering, washing, and drying to obtain the compound shown in formula a.

[0027] Furthermore, the alkaline solution is an aqueous solution of sodium carbonate.

[0028] Furthermore, in steps (2) and (3), the organic solvent is selected from one or more of N-methylpyrrolidone (NMP), dimethylformamide (DMF) and dimethylacetamide (DMAc).

[0029] Furthermore, step (2) further comprises the step of adding an acid while adding 1-naphthylamine.

[0030] Furthermore, the acid is selected from one or more of formic acid, acetic acid and propionic acid, and a small amount of the acid has a catalytic effect.

[0031] In a specific embodiment, in step (2), the compound represented by formula a is dissolved in an organic solvent, nitrosylsulfuric acid is added at 0-5°C, stirred for 1-2 hours, and then 1-naphthylamine is added. The reaction is carried out for 10-12 hours, and the obtained crude product is purified to finally obtain the compound represented by formula b.

[0032] Furthermore, the specific method of the purification treatment is: dissolving the obtained crude product in an alkaline solution, filtering and washing, adding n-hexane, stirring at 45-55° C. for 2-3 hours, filtering and drying to obtain the compound shown in formula b.

[0033] Furthermore, the alkaline solution is an aqueous solution of sodium carbonate.

[0034] Further, in step (3), the structural formula of the N-(2-ethylhexyl)naphthalene-1-amine is

[0035]

[0036] Furthermore, step (3) further comprises the step of adding an acid while adding N-(2-ethylhexyl)naphthalene-1-amine.

[0037] Furthermore, the acid is selected from one or more of formic acid, acetic acid and propionic acid, and a small amount of the acid has a catalytic effect.

[0038] In a specific embodiment, in step (3), the compound represented by formula b is dissolved in an organic solvent, nitrosylsulfuric acid is added at 0-5° C., stirred for 1-2 hours, and then N-(2-ethylhexyl)naphthalene-1-amine is added, and the reaction is carried out for 3-4 hours. The obtained crude product is purified to obtain the compound represented by formula A;

[0039] Furthermore, the specific method of the purification treatment is: dissolving the obtained crude product in an alkaline solution, filtering and washing, adding methanol, stirring at 45-55°C for 2-3h, filtering and drying to obtain the compound shown in formula b.

[0040] Furthermore, the alkaline solution is an aqueous solution of sodium carbonate.

[0041] The invention provides a liquid crystal material composition, comprising the above-mentioned azo dichroic dye.

[0042] The present invention protects the use of the azo dichroic dye or liquid crystal material composition in preparing a polarizer, and the polarizer can be used in a liquid crystal display.

[0043] Beneficial effects of the present invention:

[0044] The present invention provides an azo dichroic dye, which has high solubility, high dichroic ratio and high stability, exhibits excellent compatibility with liquid crystal materials, and exhibits extremely high adaptability when used in combination with liquid crystal materials, and is particularly outstanding in applications in polarizers and liquid crystal displays. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 This is the hydrogen nuclear magnetic resonance spectrum of the azo dichroic dye prepared in Example 1.

[0046] Figure 2 This is the hydrogen nuclear magnetic resonance spectrum of the azo dichroic dye prepared in Example 3.

[0047] Figure 3 This is a graph showing the absorbance data of the azo dichroic dye prepared in Example 3 in the visible light range. DETAILED DESCRIPTION

[0048] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used herein in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more related listed items.

[0049] The present invention is further described below in conjunction with the accompanying drawings and specific embodiments so that those skilled in the art can better understand the present invention and implement it, but the embodiments are not intended to limit the present invention.

[0050] Unless otherwise specified, the experimental methods used in the following examples are all conventional methods, and the materials, reagents, etc. used are all available from commercial sources unless otherwise specified.

[0051] The structural formula of the liquid crystal LC242 in the following embodiment is:

[0052]

[0053] The structural formula of liquid crystal C11-3 in the following embodiment is:

[0054]

[0055] Example 1

[0056] A method for preparing an azo dichroic dye comprises the following steps:

[0057] (1) 33 g of 4-trifluoromethylaniline was dissolved in 42 mL of concentrated hydrochloric acid and 800 mL of water. At 5°C, 80 mL of an aqueous solution containing 15 g of sodium nitrite was added dropwise. The mixture was stirred at 5°C for 2 h. 2 g of aminosulfonic acid was added and stirred for 10 min. Solution A was obtained by filtration. 600 mL of an aqueous solution containing 42 g of sodium phenylamino-N-methanesulfonate and 42 g of sodium bicarbonate was added dropwise to solution A at 5°C. The mixture was gradually heated to about 25°C and reacted overnight. The mixture was filtered and the solid was washed with 20% brine. The crude product was transferred to 500 mL of water. 80 g of a sodium hydroxide (30%) solution was added dropwise within 10 min. The mixture was stirred at 70°C for 3 h. The reaction system was filtered while hot. The solid was washed with 500 mL of water and dried to obtain 55 g of an orange-yellow product, i.e., the compound shown in Formula 1a. The structural formula is as follows:

[0058]

[0059] (2) Dissolve 7 g of the compound of formula 1a in 150 mL of N-methylpyrrolidone, add 8.4 g of nitrosylsulfuric acid (40%) dropwise at 5°C and stir for 1 h. Add 50 mL of N-methylpyrrolidone solution containing 3.8 g of 1-naphthylamine and 1.6 g of acetic acid at 5°C and react overnight. Add 500 mL of 25% sodium carbonate aqueous solution to the system, filter to obtain a solid, wash with 250 mL of water and 100 mL of methanol to obtain a crude product. Add the crude product to 200 mL of n-hexane, stir at 50°C for 2 h, filter, and dry to obtain 6.3 g of a brown product, i.e., the compound of formula 1b, with the following structural formula:

[0060]

[0061] (3) 6 g of the compound of formula 1b was dissolved in 130 mL of N-methylpyrrolidone, and 4.6 g of nitrosylsulfuric acid (40%) was added dropwise at 5°C and stirred for 1 h. 50 mL of N-methylpyrrolidone solution containing 3.7 g of N-(2-ethylhexyl)naphthalene-1-amine and 0.9 g of acetic acid was added at 5°C and reacted for 3 h. 500 mL of 25% sodium carbonate aqueous solution was added to the system, and the solid was filtered to obtain a crude product, which was washed with 250 mL of water. The crude product was added to 200 mL of methanol, stirred at 50°C for 2 h, filtered, and dried to obtain 4.2 g of a black product, i.e., the compound of formula 1c, with the following structural formula:

[0062]

[0063] The δ(CDCl3) data of the hydrogen nuclear magnetic resonance spectrum (HNMR) of the compound represented by Formula 1c are: 0.97-1.07 (6H) 1.25-1.49 (8H), 1.8-1.9 (1H), 3.42 (2H), 5.21 (1H), 6.80 (1H), 7.63 (1H), 7.75-7.88 (7H), 8.10-8.33 (8H), 9.15-9.28 (3H). The hydrogen nuclear magnetic resonance spectrum is shown in Figure 1 shown.

[0064] Example 2

[0065] A method for preparing an azo dichroic dye comprises the following steps:

[0066] (1) Dissolve 10 g of 2,4-difluoroaniline in 8.3 mL of concentrated hydrochloric acid and 100 mL of water, add 10 mL of an aqueous solution containing 2.8 g of sodium nitrite at 5°C, stir at 5°C for 2 h, add 0.4 g of aminosulfonic acid and stir for 10 min, and filter to obtain solution A. Add 60 mL of an aqueous solution containing 8 g of sodium phenylamino-N-methanesulfonate and 8 g of sodium bicarbonate to solution A at 5°C, gradually heat to about 25°C and react overnight, filter, and wash the solid with 20% brine. Transfer the crude product to 500 mL of water, add 15 g of sodium hydroxide (30%) solution within 10 min, and stir at 75°C for 3.5 h. Filter the reaction system while hot, wash the solid with 500 mL of water, and dry to obtain 6.4 g of an orange-yellow product, i.e., the compound shown in formula 2a, with the following structural formula:

[0067]

[0068] (2) Dissolve 4 g of the compound of formula 2a in 80 mL of N-methylpyrrolidone, add 5.45 g of nitrosylsulfuric acid (40%) dropwise at 5°C and stir for 1 h. Add 12 mL of N-methylpyrrolidone solution containing 2.5 g of 1-naphthylamine at 5°C and react overnight. Add 250 mL of 50% sodium carbonate aqueous solution to the system, filter to obtain a solid, wash with 250 mL of water, and wash with 250 mL of methanol to obtain a crude product. Add the crude product to 200 mL of toluene, stir at 50°C, slowly add 300 mL of n-hexane, stir for 2 h, filter, and dry to obtain 3.7 g of a dark blue product, i.e., the compound of formula 2b, with the following structural formula:

[0069]

[0070] (3) 3 g of the compound of formula 2b was dissolved in 80 mL of N-methylpyrrolidone, and 2.7 g of nitrosylsulfuric acid (40%) was added dropwise at 5°C and stirred for 1 h. 10 mL of N-methylpyrrolidone solution containing 2.1 g of N-(2-ethylhexyl)naphthalene-1-amine was added at 5°C and reacted for 3 h. 250 mL of 50% sodium carbonate aqueous solution was added to the system, and a solid was filtered to obtain a crude product, which was washed with 250 mL of water. The crude product was added to 100 mL of methanol, stirred at 50°C overnight, filtered, and dried to obtain 2.6 g of a reddish brown product, i.e., the compound of formula 2c, with the following structural formula:

[0071]

[0072] The δ(CDCl3) data of the hydrogen nuclear magnetic resonance spectrum (HNMR) of the compound represented by Formula 2c are: 0.97-1.07 (6H), 1.25-1.49 (8H), 1.8-1.9 (1H), 3.42 (2H), 5.21 (1H), 7.60-7.64 (1H), 6.79-6.81 (1H), 7.71-7.90 (5H), 8.09-8.12 (4H), 8.19-8.21 (2H), 8.28-8.34 (3H), 9.16-9.28 (3H).

[0073] Example 3

[0074] A method for preparing an azo dichroic dye comprises the following steps:

[0075] (1) Dissolve 10 g of 4-cyanoaniline in 17 mL of concentrated hydrochloric acid and 300 mL of water, add 30 mL of an aqueous solution containing 6 g of sodium nitrite at 5°C, stir for 2 h at 5°C, add 0.8 g of aminosulfonic acid and stir for 10 min, and filter to obtain solution A. Add 160 mL of an aqueous solution containing 17 g of sodium phenylamino-N-methanesulfonate and 17 g of sodium bicarbonate to solution A at 5°C, gradually raise the temperature to about 25°C and react overnight, filter, and wash the solid with 20% brine. Transfer the crude product to 500 mL of water, add 15 g of sodium hydroxide (30%) solution within 10 min, and stir at 75°C for 3 h. Filter the reaction system while hot, wash the solid with 500 mL of water, and dry to obtain 11.2 g of an orange-yellow product, i.e., the compound shown in formula 3a, with the following structural formula:

[0076]

[0077] (2) 8 g of the compound of formula 3a was dissolved in 130 mL of N-methylpyrrolidone, and 11.5 g of nitrosylsulfuric acid (40%) was added dropwise at 5° C. and stirred for 1 h. 12 mL of N-methylpyrrolidone solution containing 5.1 g of 1-naphthylamine was added at 5° C. and the reaction was allowed to proceed overnight. 250 mL of 50% sodium carbonate aqueous solution was added to the system, and the solid was filtered to obtain a solid, which was washed with 100 mL of methanol to obtain a crude product, which was washed with 500 mL of water, filtered, and dried to obtain 11.3 g of a dark blue product, i.e., the compound of formula 3b, with the following structural formula:

[0078]

[0079] (3) 5 g of the compound of formula 3b was dissolved in 120 mL of N-methylpyrrolidone, and 4.3 g of nitrosylsulfuric acid (40%) was added dropwise at 5° C. and stirred for 1 h. 15 mL of N-methylpyrrolidone solution containing 3.4 g of N-(2-ethylhexyl)naphthalene-1-amine was added at 5° C. and reacted for 3 h. 250 mL of 50% sodium carbonate aqueous solution was added to the system, and extracted with ethyl acetate. The ethyl acetate liquid was removed by rotary evaporator to obtain a solid, and 3.1 g of a reddish brown product was obtained by column chromatography, i.e., the compound of formula 3c, with the structural formula as follows:

[0080]

[0081] The δ(CDCl3) data of the hydrogen nuclear magnetic resonance spectrum (HNMR) of the compound represented by formula 3c are: 0.97-1.07 (6H), 1.25-1.49 (8H), 1.8-1.9 (1H), 3.42 (2H), 5.21 (1H), 7.60-7.64 (1H), 6.79-6.81 (1H), 7.71-7.90 (6H), 8.09-8.12 (4H), 8.19-8.21 (2H), 8.28-8.34 (3H), 9.16-9.28 (3H). The hydrogen nuclear magnetic resonance spectrum is as follows: Figure 3 shown.

[0082] Example 4

[0083] A liquid crystal material composition comprises, by weight, 8 parts of the azo dichroic dye prepared in Example 1, 43 parts of liquid crystal LC242, 43 parts of liquid crystal C11-3 and 6 parts of photoinitiator 369.

[0084] Example 5

[0085] A liquid crystal material composition comprises, by mass, 8 parts of the azo dichroic dye prepared in Example 2, 43 parts of liquid crystal LC242, 43 parts of liquid crystal C11-3 and 6 parts of photoinitiator 369.

[0086] Example 6

[0087] A liquid crystal material composition comprises, by weight, 7 parts of the azo dichroic dye prepared in Example 3, 44 parts of liquid crystal LC242, 43 parts of liquid crystal C11-3 and 6 parts of photoinitiator 369.

[0088] Comparative Example 1

[0089] A liquid crystal material composition, comprising 5 parts by weight of an azo dichroic dye 46 parts of liquid crystal LC242, 45 parts of liquid crystal C11-3 and 6 parts of photoinitiator 369.

[0090] Application Examples

[0091] The alignment agent SD1 (Mordinal Yellow 26) was dissolved in ethylene glycol monomethyl ether to prepare a SD1 solution with a concentration of 1 mg / mL; the liquid crystal material composition of Examples 4-6 and Comparative Example 1 was dissolved in 400 parts of a mixed solvent of cyclohexanone and cyclopentanone (the mass ratio of cyclohexanone to cyclopentanone was 1:4) to obtain a liquid crystal material composition solution.

[0092] At room temperature, SD1 solution was evenly scraped on a glass substrate with a 10-micron wire rod. After being kept in an oven at 120°C for 3 minutes, a polarizer was placed on top of the film with the direction of the polarizer parallel to the scraping direction. The film was irradiated with a UV lamp at 25°C for 1 minute for orientation to form an SD1 layer.

[0093] At room temperature, the surface of the SD1 layer was evenly coated with the liquid crystal material composition solutions of Examples 4-6 and Comparative Example 1 using a 30-micron wire rod, and then placed in a 120°C oven for 20 seconds, transferred to a 75°C hot stage and kept warm for 10 minutes. The hot stage temperature was set to 65°C and kept warm for 15 minutes. The layer was then transferred to a 30°C hot stage and irradiated with an ultraviolet lamp for 5 seconds in a nitrogen atmosphere to cure the layer, thereby obtaining a polarizer covered with a polarizing film.

[0094] Test Case

[0095] The dichroic ratio is measured on a UV spectrophotometer with the aid of a polarizer. The test method is as follows: a polarizer is placed in front of the light path, and the maximum absorbance D of the film dye to polarized light parallel to and perpendicular to the liquid crystal director is measured respectively. ⊥ and D ∥ , through D ⊥ and D ∥ Calculate the dichroic ratio D A =D / / / D ⊥ The solubility refers to the mass percentage of the azo dichroic dye in the liquid crystal material composition (Examples 4-6 and Comparative Example 1 are both at the maximum solubility).

[0096] The test results are shown in Table 1 and Figure 3 As shown:

[0097] Table 1

[0098]

[0099] Figure 3 This is a graph showing the absorbance data of the azo dichroic dye prepared in Example 3 in the visible light range.

[0100] Obviously, the above embodiments of the present invention are only examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. Those skilled in the art should understand that other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the embodiments here. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the claims of the present invention.

Claims

1. An azo dichroic dye, characterized in that: The structural formula of the azo dichroic dye is shown in Formula A: Wherein, R is selected from one or more of trifluoromethyl, nitrile, ethoxycarbonyl and halogen.

2. The azo dichroic dye according to claim 1, characterized in that The azo dichroic dye is selected from one of the following structural formulas:

3. A method for preparing the azo dichroic dye according to claim 1, characterized in that: The following steps are involved: (1) Dissolve in a solvent, add sodium nitrite and a catalyst at 0-5°C to obtain solution A; add sodium phenylamino-N-methanesulfonate and a base to the solution A to react to obtain a compound shown in formula a; wherein R is selected from one or more of trifluoromethyl, nitrile, ethoxycarbonyl and halogen; (2) dissolving the compound represented by formula a in an organic solvent, adding nitrosylsulfuric acid at 0-5° C., and then adding 1-naphthylamine to react to obtain the compound represented by formula b; (3) dissolving the compound represented by formula b in an organic solvent, adding nitrosylsulfuric acid at 0-5° C., and then adding N-(2-ethylhexyl)naphthalene-1-amine to react to obtain the compound represented by formula A; The structural formulas of the above formula a and formula b are as follows:

4. The preparation method according to claim 3, characterized in that: In step (1), It is 4-trifluoromethylaniline, 2,4-difluoroaniline, 4-cyanoaniline, 4-ethoxycarbonylaniline or 3,4,5-trifluoroaniline.

5. The preparation method according to claim 3, characterized in that: In step (1), the catalyst is aminosulfonic acid.

6. The preparation method according to claim 3, characterized in that: The step (2) further comprises the step of adding an acid while adding 1-naphthylamine.

7. The preparation method according to claim 6, characterized in that: The acid is selected from one or more of formic acid, acetic acid and propionic acid.

8. The preparation method according to claim 3, characterized in that: In steps (2) and (3), the organic solvent is selected from one or more of N-methylpyrrolidone, dimethylformamide and dimethylacetamide.

9. A liquid crystal material composition, characterized in that: The invention comprises the azo dichroic dye according to claim 1.

10. Use of the azo dichroic dye according to claim 1 or the liquid crystal material composition according to claim 9 in preparing a polarizer.

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