Liquid crystal alignment agent and method for preparing high-hardness polyimide liquid crystal alignment film using the same

Abstract

The present invention belongs to the technical field of liquid crystal display materials, and particularly relates to a liquid crystal alignment agent and a method for preparing a high-hardness polyimide liquid crystal alignment film using the same. The liquid crystal alignment agent is composed of the following A component, B component and organic solvent: A component: polyamic acid polymerized from 1,3-bis(4-aminophenylethyl)urea, 4,4'-diaminodiphenylamine and tetracarboxylic dianhydride; B component: polyamic acid polymerized from diamines containing carboxyl and / or hydroxyl groups, p-phenylenediamine, 1,3,5-benzenetricarboxyl chloride and tetracarboxylic dianhydride; The present invention introduces a cross-linking agent having three reactive substituents into a linear polyamic acid chain, and when it is block-polymerized with an imide repeating unit having at least one carboxyl or hydroxyl group during the reaction, a polyamic acid block copolymer having a large molecular weight and cross-linking properties is formed, and the hardness of the formed liquid crystal alignment film is increased by increasing the degree of cross-linking.

Description

Technical Field

[0001] The invention belongs to the technical field of liquid crystal display materials, and in particular relates to a liquid crystal alignment agent and a method for preparing a high-hardness polyimide liquid crystal alignment film by using the same. Background Art

[0002] The liquid crystal alignment film is one of the key components in the manufacturing process of liquid crystal displays (LCDs). Its main function is to ensure that the liquid crystal molecules are aligned in a specific direction, thereby achieving precise control of the pixels. During the use of the LCD, the hardness of the liquid crystal alignment layer will affect the mechanical stability of the panel. For example, in a touch screen LCD, frequent touch operations will generate pressure and friction on the panel surface. If the alignment layer formed by the alignment agent is not hard enough, it is easy to cause scratches and wear on the surface, which will affect the display effect, and cause problems such as abnormal display at the scratches or decreased local contrast.

[0003] In the past, researchers have tried to improve the hardness of polyimide alignment agent systems by adding some inorganic fillers (such as nano-silica), but they often face problems such as poor dispersion of fillers and poor compatibility with organic matrices, which lead to decreased uniformity of the alignment layer, poor contrast due to poor black brightness of liquid crystal display elements, and poor afterimages caused by long-term AC drive. These phenomena affect the liquid crystal orientation effect and display performance, damage the electrical properties of the liquid crystal alignment agent, and result in reduced voltage holding rate and slow relief of residual charge accumulated due to DC voltage. Summary of the invention

[0004] In view of the shortcomings of the prior art, an object of the present invention is to provide a liquid crystal alignment agent, which can be used to prepare a liquid crystal alignment film with high hardness and high voltage holding rate.

[0005] The invention also provides a method for preparing a high-hardness polyimide liquid crystal alignment film by using the same, which is simple and easy to operate and suitable for large-scale production.

[0006] The liquid crystal alignment agent of the present invention is composed of the following component A, component B and an organic solvent:

[0007] Component A: polyamic acid prepared by polymerization of 1,3-bis(4-aminophenethyl)urea, 4,4'-diaminodiphenylamine and tetracarboxylic dianhydride;

[0008] Component B: polyamic acid obtained by polymerizing diamine containing carboxyl and / or hydroxyl groups, p-phenylenediamine, 1,3,5-benzenetricarboxylic acid chloride and tetracarboxylic dianhydride;

[0009] The diamine structure containing a carboxyl group is shown in Formula 1:

[0010]

[0011] Formula 1: 2-amino-5-[2-(4-amino-3-carboxyphenoxy)ethoxy]benzoic acid;

[0012] The structure of the diamine containing hydroxyl groups is shown in Formula 2:

[0013]

[0014] Formula 2: 2-amino-5-[2-(4-amino-3-hydroxyphenoxy)ethoxy]phenol.

[0015] The tetracarboxylic dianhydride is one of cyclobutanetetracarboxylic dianhydride and 3,3',4,4'-biphenyltetracarboxylic dianhydride.

[0016] The preparation method of the 2-amino-5-[2-(4-amino-3-carboxyphenoxy)ethoxy]benzoic acid is as follows:

[0017] (1) Add 5-hydroxy-2-nitrobenzoic acid to an aprotic solvent, then add 1,2-bis(tolyloxyethane), stir to obtain a mixed solution, add an acid binding agent, and heat to react. After the reaction is completed, add the reaction system to pure water, add an acid solution dropwise, precipitate a solid, adjust the pH of the solution, filter, and wash with pure water to obtain a dinitro product;

[0018] (2) Add 5 g of the dinitro product to a solvent, heat to dissolve, add a catalyst, react under a hydrogen atmosphere, filter while hot, rinse the filter cake with a hot solvent, and concentrate the filtrate to dryness to obtain a concentrated product;

[0019] (3) adding a poor solvent to the concentrated product, placing it in cold hydrazine for crystallization, filtering, washing, and drying to obtain 2-amino-5-[2-(4-amino-3-carboxyphenoxy)ethoxy]benzoic acid;

[0020] The preparation method of the 2-amino-5-[2-(4-amino-3-hydroxyphenoxy)ethoxy]phenol is:

[0021] A. Add 4-nitroresorcinol to an aprotic solvent, then add 1,2-dibromoethane, stir to obtain a mixed solution, add an acid binding agent, keep warm to react, add pure water to precipitate solids after the reaction is completed, filter, and rinse with solvent (methanol) to obtain a dinitro product;

[0022] B. adding the dinitro product to a solvent, heating to dissolve, adding a catalyst, reacting under a hydrogen atmosphere, filtering, and concentrating the filtrate to dryness to obtain a concentrated product;

[0023] C. Add a poor solvent to the concentrated product, place it in cold hydrazine, stir and crystallize, filter, wash and dry the filter cake to obtain 2-amino-5-[2-(4-amino-3-hydroxyphenoxy)ethoxy]phenol.

[0024] The temperature of the heat preservation reaction in step (1) is 100-140°C, and the time is 14-17h; the acid binding agent in step (1) is anhydrous sodium carbonate or anhydrous potassium carbonate; the molar ratio of the acid binding agent in step (1) to 5-hydroxy-2-nitrobenzoic acid is (3.85-4.2):1; the aprotic solvent in step (1) is one of N,N-dimethylformamide, N,N-dimethylacetamide, and acetonitrile; the pH of the solution in step (1) is adjusted to 3-4; the solvent in step (2) is one of tetrahydrofuran and ethanol; the temperature of the heating and dissolving in step (2) is 65-85°C, and the reaction time under hydrogen atmosphere is 16-21h; the poor solvent in step (3) is ethanol, and the temperature of the cold hydrazine is -5-5°C.

[0025] The temperature of the insulation reaction in step A is 105-135° C., and the reaction time is 8-12 hours; the acid binding agent in step A is anhydrous sodium carbonate or anhydrous potassium carbonate; the molar ratio of the acid binding agent in step A to 4-nitroresorcinol is (1.5-2.5):1; the aprotic solvent in step A is one of acetonitrile, N,N-dimethylformamide, and N,N-dimethylacetamide; the solvent in step B is one of tetrahydrofuran and ethanol; the temperature of the heating and dissolving in step B is 60-85° C., and the reaction time under hydrogen atmosphere is 14-16 hours; the poor solvent in step C is ethanol, and the temperature of the cold hydrazine is -10-0° C.

[0026] The molar ratio of the p-phenylenediamine, the diamine containing carboxyl and / or hydroxyl groups, the tetracarboxylic dianhydride and the 1,3,5-benzenetricarboxylic acid chloride is (0.1-0.5): (0.5-0.9): 1: (0.005-0.01).

[0027] The molar ratio of the 1,3-bis(4-aminophenethyl)urea, 4,4'-diaminodiphenylamine and tetracarboxylic dianhydride is (0.3-0.7):(0.3-0.7):1.

[0028] The method for preparing a high-hardness polyimide liquid crystal alignment film using a liquid crystal alignment agent according to the present invention comprises the following steps:

[0029] Step 1: 1,3-bis(4-aminophenethyl)urea and 4,4'-diaminodiphenylamine are mixed to obtain a diamine mixture, which is dissolved in an organic solvent, and tetracarboxylic dianhydride is added to react for 16 hours under a nitrogen environment to obtain a polyamic acid solution A having a solid content of about 15%, and the polyamic acid solution A is added to the organic solvent and mixed and stirred to obtain a polyamic acid solution a;

[0030] Step 2: dissolving a mixture of a diamine containing carboxyl and / or hydroxyl groups and p-phenylenediamine in an organic solvent, adding tetracarboxylic dianhydride and 1,3,5-benzenetricarboxylic acid chloride, reacting for 4 hours under a nitrogen environment, then adding a diamine containing carboxyl and / or hydroxyl groups, tetracarboxylic dianhydride, and an organic solvent, reacting for 12 hours under a nitrogen environment, to form a polyamic acid solution B having a solid content of about 15%; adding the polyamic acid solution B into an aprotic solvent and mixing and stirring to obtain a polyamic acid solution b;

[0031] Step 3: Mixing and stirring the polyamic acid solution a and the polyamic acid solution b to obtain a liquid crystal alignment agent;

[0032] Step 4: Filter the liquid crystal alignment agent through a filter and evenly coat it on the FFS substrate by a spin coating process. The spin coating process is 300 rpm for 10 seconds and then 2000 rpm for 60 seconds. After spin coating, place it on a hot plate and pre-bake it at 110°C for 80 seconds. After pre-bake, place it in an oven and burn it at 230°C for 20 minutes to obtain a high-hardness polyimide liquid crystal alignment film with a film thickness of 100 nm.

[0033] The organic solvent described in step 1 and step 2 can be any solvent capable of dissolving the generated polyamic acid, such as N,N-methylformamide, N,N-methylacetamide, N-methyl-2-pyrrolidone, N-methylcaprolactam, dimethyl sulfoxide, tetramethylurea, pyridine, dimethyl sulfone, hexamethyl sulfoxide or y-butyrolactone. These solvents can be used alone or in combination. The reaction temperature of the reaction described in step 1 and step 2 is 0-5°C.

[0034] The polyamic acid solution a and the polyamic acid solution b obtained after dilution have the same solid content and can be diluted as needed. The preferred solid content of the present invention is 5.5%.

[0035] The mass ratio of the polyamic acid solution a and the polyamic acid solution b in step three is (0.3-0.7): (0.4-0.6).

[0036] Compared with the prior art, the present invention has the following beneficial effects:

[0037] (1) The present invention introduces a crosslinking agent having three reactive substituents into the linear polyamic acid chain. During the reaction, it is block polymerized with an imide repeating unit having at least one carboxyl group or hydroxyl group to form a polyamic acid block copolymer with a large molecular weight and crosslinking properties. The hardness of the formed liquid crystal alignment film is improved by increasing the degree of crosslinking. The crosslinking agent having three reactive substituents can provide a stable network structure for the block copolymer, thereby improving the hardness of the film. In addition, the imide repeating unit having a carboxyl group or a hydroxyl group induces crosslinking coupling in the copolymer molecule, and the carboxyl group of the specific diamine monomer forms hydrogen bonds with the hydroxyl group and the imino group through interaction forces between the molecules to further consolidate the network structure.

[0038] (2) The specific diamine compound containing carboxyl and hydroxyl groups described in the present invention has carboxyl and hydroxyl groups in the structure that can act as electron jumping sites. The carboxyl group can be used as a part of the polyamic acid conjugated system and can provide a channel for electron transfer. The lone pair of electrons on the oxygen atom of the hydroxyl group can be conjugated with the π electron cloud of the benzene ring. This conjugation allows electrons to be transferred relatively easily between the hydroxyl group and the conjugated system. Therefore, the liquid crystal alignment film obtained from the polyamic acid using the specific diamine compound and / or the polyimide polymer obtained by imidizing the polyamic acid can promote the movement of charges in the liquid crystal alignment film. At this time, the obtained liquid crystal alignment agent has the effect of more quickly relieving the residual charge accumulated due to the DC voltage when the liquid crystal alignment film is made. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 is a synthetic route to 2-amino-5-[2-(4-amino-3-hydroxyphenoxy)ethoxy]phenol;

[0040] Figure 2 is the H NMR spectrum of 2-amino-5-[2-(4-amino-3-hydroxyphenoxy)ethoxy]phenol;

[0041] Figure 3 is a synthetic route to 2-amino-5-[2-(4-amino-3-carboxyphenoxy)ethoxy]benzoic acid;

[0042] Figure 4 This is the H NMR spectrum of 2-amino-5-[2-(4-amino-3-carboxyphenoxy)ethoxy]benzoic acid. DETAILED DESCRIPTION

[0043] The present invention will be further described below with reference to the embodiments.

[0044] Unless otherwise specified, all raw materials used in the examples are commercially available.

[0045] Synthesis of 2-amino-5-[2-(4-amino-3-hydroxyphenoxy)ethoxy]phenol:

[0046] The synthetic route of 2-amino-5-[2-(4-amino-3-hydroxyphenoxy)ethoxy]phenol is as follows: Figure 1 shown.

[0047] Synthesis example 1

[0048] A. Add 8.670 g of 4-nitroresorcinol to 87 mL of N,N-dimethylformamide, then add 5 g of 1,2-dibromoethane, stir to obtain a mixed solution, then add 15.836 g of anhydrous potassium carbonate, and keep the mixture at 120°C for 10 h. After the reaction is completed, add pure water to precipitate solids, filter, and rinse with methanol to obtain 5.2 g of dinitro product with a yield of 58.1%;

[0049] B. Add 5 g of the dinitro product to 150 mL of ethanol, heat at 75 °C to dissolve, add 0.75 g of 5 wt.% Pd / C, react for 15 h under a hydrogen atmosphere, filter, rinse the filter cake with 50 °C ethanol, and concentrate the filtrate to dryness to obtain a concentrated product;

[0050] C. Add 50 mL of ethanol to the concentrated product, place it in cold hydrazine at 0°C and magnetically stir to crystallize for 2 h, filter, wash the filter cake with -5°C anhydrous ethanol, dry in a vacuum drying oven, replace nitrogen when taking out, and obtain 3.159 g of 2-amino-5-[2-(4-amino-3-hydroxyphenoxy)ethoxy]phenol, with a yield of 76.9%.

[0051] Synthesis example 2

[0052] A. Add 9.082 g of 4-nitroresorcinol to 73 mL of acetonitrile, then add 5 g of 1,2-dibromoethane, stir to obtain a mixed solution, then add 11.587 g of anhydrous potassium carbonate, and keep the mixture at 105°C for 11 hours. After the reaction is completed, add pure water to precipitate solids, filter, and rinse with methanol to obtain 4.224 g of dinitro product with a yield of 47.2%;

[0053] B. Add 5 g of the dinitro product to 125 mL of tetrahydrofuran, heat to dissolve at 60 °C, add 1 g of 5 wt.% Pd / C, react for 18 h under a hydrogen atmosphere, filter, wash the filter cake with 50 °C tetrahydrofuran, and concentrate the filtrate to dryness to obtain a concentrated product;

[0054] C. Add 40 mL of ethanol to the concentrated product, place it in -5°C cold hydrazine and magnetically stir to crystallize for 2 hours, filter, wash the filter cake with -10°C anhydrous ethanol, dry in a vacuum drying oven, replace nitrogen when taking out, and obtain 2.855 g of 2-amino-5-[2-(4-amino-3-hydroxyphenoxy)ethoxy]phenol, with a yield of 69.5%.

[0055] Synthesis example 3

[0056] A. Add 8.257 g of 4-nitroresorcinol to 99 mL of N,N-dimethylacetamide, then add 5 g of 1,2-dibromoethane, stir to obtain a mixed solution, then add 18.393 g of anhydrous potassium carbonate, and keep the mixture at 135°C for 8 hours. After the reaction is completed, add pure water to precipitate solids, filter, and rinse with methanol to obtain 4.108 g of dinitro product with a yield of 45.9%;

[0057] B. Add 5 g of the dinitro product to 175 mL of anhydrous ethanol, heat to dissolve at 80°C, add 0.5 g of 5 wt.% Pd / C, react for 14 h under a hydrogen atmosphere, filter, rinse the filter cake with 50°C tetrahydrofuran, and concentrate the filtrate to dryness to obtain a concentrated product;

[0058] C. Add 60 mL of ethanol to the concentrated product, place it in -10°C cold hydrazine and magnetically stir to crystallize for 2 h, filter, wash the filter cake with 0°C anhydrous ethanol, dry it in a vacuum drying oven, replace nitrogen when taking it out, and obtain 2.395 g of 2-amino-5-[2-(4-amino-3-hydroxyphenoxy)ethoxy]phenol, with a yield of 58.3%.

[0059] The 2-amino-5-[2-(4-amino-3-hydroxyphenoxy)ethoxy]phenol prepared in Synthesis Example 1 was tested using a nuclear magnetic resonance spectrometer. The nuclear magnetic hydrogen spectrum obtained by the test was as follows: Figure 2 As shown. Figure 2 It can be seen that 9.77ppm is the characteristic peak of hydroxyl hydrogen on the benzene ring, 6.58ppm is the characteristic peak of ortho-position hydrogen of amino group, 6.32ppm is the characteristic peak of ortho-position hydrogen and para-position hydrogen of hydroxyl group, 4.97ppm is the characteristic peak of amino hydrogen, 4.19ppm is the characteristic peak of hydrogen on ethoxy group, 3.36ppm is water peak, and 2.51ppm is deuterated DMSO solvent peak.

[0060] Synthesis of 2-amino-5-[2-(4-amino-3-carboxyphenoxy)ethoxy]benzoic acid:

[0061] The synthetic route of 2-amino-5-[2-(4-amino-3-carboxyphenoxy)ethoxy]benzoic acid is as follows Figure 3 shown.

[0062] Synthesis example 4

[0063] (1) Add 5.71 g of 5-hydroxy-2-nitrobenzoic acid to 85 mL of N,N-dimethylformamide, then add 5.5 g of 1,2-bis(tolueneoxy)ethane, stir to obtain a mixed solution, then add 17.453 g of anhydrous potassium carbonate, and keep the mixture at 120°C for 15.5 h. After the reaction is completed, add the reaction system to pure water, slowly add dilute hydrochloric acid solution dropwise, there is bubbling, and solids gradually precipitate. Adjust the solution to pH = 3-4, filter, and wash with pure water for several times to obtain 2.697 g of dinitro product with a yield of 46.3%;

[0064] (2) Add 5 g of the dinitro product to 125 mL of tetrahydrofuran, heat at 75 °C to dissolve, add 0.75 g of 5 wt.% Pd / C, react for 19 h under a hydrogen atmosphere, filter while hot, rinse the filter cake with 50 °C tetrahydrofuran, and concentrate the filtrate to dryness to obtain a concentrated product;

[0065] (3) Add 30 mL of anhydrous ethanol to the concentrated product, place it in cold hydrazine at 0°C and magnetically stir to crystallize for 2 h, filter it, wash the filter cake with anhydrous ethanol at -5°C, dry it in a vacuum drying oven, and replace nitrogen when taking it out to obtain 2.046 g of 2-amino-5-[2-(4-amino-3-carboxyphenoxy)ethoxy]benzoic acid, with a yield of 48.3%.

[0066] Synthesis example 5

[0067] (1) Add 5.981 g of 5-hydroxy-2-nitrobenzoic acid to 120 mL of acetonitrile, then add 5.5 g of 1,2-bis(tolueneoxy)ethane, stir to obtain a mixed solution, then add 18.961 g of anhydrous sodium carbonate, and keep the mixture at 105°C for 17 h. After the reaction is completed, add the reaction system to pure water, slowly add dilute hydrochloric acid solution dropwise, there is bubbling, and solids gradually precipitate. Adjust the solution to pH = 3-4, filter, and wash with pure water for several times to obtain 2.207 g of dinitro product with a yield of 37.9%;

[0068] (2) Add 5 g of the dinitro product to 150 mL of anhydrous ethanol, heat at 85 °C to dissolve, add 0.5 g of 5 wt.% Pd / C, react for 16 h under a hydrogen atmosphere, filter while hot, rinse the filter cake with 50 °C anhydrous ethanol, and concentrate the filtrate to dryness to obtain a concentrated product;

[0069] (3) Add 20 mL of anhydrous ethanol to the concentrated product, place it in -5°C cold hydrazine and magnetically stir to crystallize for 2 h, filter, wash the filter cake with -5°C anhydrous ethanol, dry it in a vacuum drying oven, and replace nitrogen when taking it out to obtain 1.817 g of 2-amino-5-[2-(4-amino-3-carboxyphenoxy)ethoxy]benzoic acid, with a yield of 42.9%.

[0070] Synthesis example 6

[0071] (1) Add 5.438 g of 5-hydroxy-2-nitrobenzoic acid to 55 mL of N,N-dimethylacetamide, then add 5.5 g of 1,2-bis(tolyloxy)ethane, stir to obtain a mixed solution, then add 15.801 g of anhydrous potassium carbonate, and keep the mixture at 130°C for 14 h. After the reaction is completed, add the reaction system to pure water, slowly add dilute hydrochloric acid solution dropwise, there is bubbling, and solids gradually precipitate. Adjust the solution to pH = 3-4, filter, and wash with pure water for several times to obtain 1.918 g of dinitro product with a yield of 32.93%;

[0072] (2) Add 5 g of the dinitro product to 100 mL of tetrahydrofuran, heat at 65°C to dissolve, add 0.75 g of 5 wt.% Pd / C, react under a hydrogen atmosphere for 21 h, filter while hot, rinse the filter cake with 50°C tetrahydrofuran, and concentrate the filtrate to dryness to obtain a concentrated product;

[0073] (3) Add 40 mL of anhydrous ethanol to the concentrated product, place it in cold hydrazine at 5°C and magnetically stir to crystallize for 2 h, filter it, wash the filter cake with anhydrous ethanol at -5°C, dry it in a vacuum drying oven, and replace nitrogen when taking it out to obtain 1.895 g of 2-amino-5-[2-(4-amino-3-carboxyphenoxy)ethoxy]benzoic acid, with a yield of 44.73%.

[0074] The 2-amino-5-[2-(4-amino-3-carboxyphenoxy)ethoxy]benzoic acid prepared in Synthesis Example 4 was tested using a nuclear magnetic resonance spectrometer. The nuclear magnetic hydrogen spectrum obtained by the test was as follows: Figure 4 As shown. Figure 4 It can be seen that 12.9ppm is the characteristic peak of carboxyl hydrogen on the benzene ring, 7.23ppm is the characteristic peak of ortho-position hydrogen of carboxyl, 6.84ppm is the characteristic peak of para-position hydrogen of carboxyl, 6.68ppm is the characteristic peak of ortho-position hydrogen of amino, 6.44ppm is the characteristic peak of amino hydrogen, 4.19ppm is the characteristic peak of ethyl in the middle of benzene ring, 3.43ppm is water peak, and 2.57ppm is deuterated DMSO solvent peak.

[0075] The raw materials and their code abbreviations used in the following examples are as follows:

[0076] A-1: p-phenylenediamine;

[0077] A-2: 2-amino-5-[2-(4-amino-3-carboxyphenoxy)ethoxy]benzoic acid (prepared by the method of Synthesis Example 4);

[0078] A-3: 2-amino-5-[2-(4-amino-3-hydroxyphenoxy)ethoxy]phenol (prepared by the method of Synthesis Example 1);

[0079] A-4: 1,3-bis(4-aminophenethyl)urea;

[0080] A-5: 4,4'-diaminodiphenylamine;

[0081] B-1: cyclobutanetetracarboxylic dianhydride;

[0082] B-2: 3,3',4,4'-biphenyltetracarboxylic dianhydride;

[0083] X: 1,3,5-benzenetricarboxylic acid chloride.

[0084] Example 1

[0085] (A-4) + (A-5) + (B-2)

[0086] The preparation of polyamic acid a1 comprises the following steps:

[0087] 1) 5.071 g of 1,3-bis(4-aminophenethyl)urea and 3.386 g of 4,4'-diaminodiphenylamine were mixed to obtain a diamine mixture, which was dissolved in 104.589 g of N-methylpyrrolidone, and 10 g of 3,3'4,4'-biphenyltetracarboxylic dianhydride was added. The mixture was reacted at a temperature of 0-5°C under a nitrogen environment for 16 hours to form a polyamic acid solution with a solid content of about 15%;

[0088] 2) 5 g of the polyamic acid solution prepared in step 1) was added to 4.545 g of N-methylpyrrolidone, and then added to 4.091 g of ethylene glycol monobutyl ether, and mixed and stirred to obtain a polyamic acid solution a1. The structural formula is shown in Formula 3 below.

[0089]

[0090] Formula 3.

[0091] Example 2

[0092] (A-4) + (A-5) + (B-2)

[0093] The preparation of polyamic acid a2 comprises the following steps:

[0094] 1) 3.043 g of 1,3-bis(4-aminophenethyl)urea and 4.741 g of 4,4'-diaminodiphenylamine were mixed to obtain a diamine mixture, which was dissolved in 100.77 g of N-methylpyrrolidone, and 10 g of 3,3',4,4'-biphenyltetracarboxylic dianhydride was added. The mixture was reacted at a temperature of 0-5°C under a nitrogen environment for 16 hours to form a polyamic acid solution with a solid content of about 15%;

[0095] 2) Take 5 g of the polyamic acid solution prepared in step 1) and add it to 4.545 g of N-methylpyrrolidone, then add it to 4.091 g of ethylene glycol monobutyl ether, mix and stir to obtain polyamic acid solution a2. The structural formula is shown in Formula 3 above:

[0096] Example 3

[0097] (A-4) + (A-5) + (B-2)

[0098] The preparation of polyamic acid a3 comprises the following steps:

[0099] 1) 7.099 g of 1,3-bis(4-aminophenethyl)urea and 2.032 g of 4,4'-diaminodiphenylamine were mixed to obtain a diamine mixture, which was dissolved in 108.408 g of N-methylpyrrolidone, and 10 g of 3,3',4,4'-biphenyltetracarboxylic dianhydride was added. The mixture was reacted at a temperature of 0-5°C under a nitrogen environment for 16 hours to form a polyamic acid solution with a solid content of about 15%;

[0100] 2) 5 g of the polyamic acid solution prepared in step 1) was added to 4.545 g of N-methylpyrrolidone, and then added to 4.091 g of ethylene glycol monobutyl ether, and mixed and stirred to obtain a polyamic acid solution a3. The structural formula is shown in Formula 3 above.

[0101] Example 4

[0102] (A-1)+(A-2)+X+(B-1)+(A-3)+(B-1)

[0103] The preparation of polyamic acid b1 comprises the following steps:

[0104] 1) 2.757 g of p-phenylenediamine and 4.236 g of 2-amino-5-[2-(4-amino-3-carboxyphenoxy)ethoxy]benzoic acid were mixed to obtain a diamine mixture, which was dissolved in 82.896 g of N-methylpyrrolidone, and 0.135 g of 1,3,5-benzenetricarboxylic acid chloride and 7.5 g of cyclobutanetetracarboxylic dianhydride were added, and the reaction was carried out at 2°C for 4 h under a nitrogen environment. 3.522 g of 2-amino-5-[2-(4-amino-3-hydroxyphenoxy)ethoxy]phenol, 2.5 g of cyclobutanetetracarboxylic dianhydride, and 34.125 g of N-methylpyrrolidone were added, and the reaction was carried out at 2.5±2.5°C for 12 h under a nitrogen environment to form a polyamic acid solution with a solid content of about 15%;

[0105] 2) 5 g of the polyamic acid solution prepared in step 1) was added to 4.545 g of N-methylpyrrolidone, and then 4.091 g of ethylene glycol monobutyl ether was added, and the mixture was mixed and stirred to obtain a polyamic acid solution b1, the structural formula of which is shown in Formula 4 below:

[0106]

[0107] Formula 4.

[0108] Example 5

[0109] (A-1)+(A-2)+X+(B-1)+(A-3)+(B-1)

[0110] The preparation of polyamic acid b2 comprises the following steps:

[0111] 1) 0.551 g of p-phenylenediamine and 7.625 g of 2-amino-5-[2-(4-amino-3-carboxyphenoxy)ethoxy]benzoic acid were mixed to obtain a diamine mixture, which was dissolved in 77.885 g of N-methylpyrrolidone, and 0.068 g of 1,3,5-benzenetricarboxylic acid chloride and 5.5 g of cyclobutanetetracarboxylic dianhydride were added, and the reaction was carried out at 2°C for 4 h under a nitrogen environment. 6.340 g of 2-amino-5-[2-(4-amino-3-hydroxyphenoxy)ethoxy]phenol, 4.5 g of cyclobutanetetracarboxylic dianhydride and 61.426 g of N-methylpyrrolidone were added, and the reaction was carried out at 2.5±2.5°C for 12 h under a nitrogen environment to form a polyamic acid solution with a solid content of about 15%;

[0112] 2) 5 g of the polyamic acid solution prepared in step 1) was added to 4.545 g of N-methylpyrrolidone, and then 4.091 g of ethylene glycol monobutyl ether was added, mixed and stirred to obtain a polyamic acid solution b2, the structural formula of which is shown in Formula 4:

[0113] Example 6

[0114] (A-1)+(A-2)+X+(B-1)+(A-3)+(B-1)

[0115] The preparation of polyamic acid b3 comprises the following steps:

[0116] 1) 1.654 g of p-phenylenediamine and 5.931 g of 2-amino-5-[2-(4-amino-3-carboxyphenoxy)ethoxy]benzoic acid were mixed to obtain a diamine mixture, which was dissolved in 80.352 g of N-methylpyrrolidone, and 0.095 g of 1,3,5-benzenetricarboxylic acid chloride and 6.5 g of cyclobutanetetracarboxylic dianhydride were added, and the reaction was carried out at 2°C for 4 h under a nitrogen environment. 4.931 g of 2-amino-5-[2-(4-amino-3-hydroxyphenoxy)ethoxy]phenol, 3.5 g of cyclobutanetetracarboxylic dianhydride and 47.776 g of N-methylpyrrolidone were added, and the reaction was carried out at 2.5±2.5°C for 12 h under a nitrogen environment to form a polyamic acid solution with a solid content of about 15%;

[0117] 2) 5 g of the polyamic acid solution prepared in step 1) was added to 4.545 g of N-methylpyrrolidone, and then 4.091 g of ethylene glycol monobutyl ether was added, and the mixture was mixed and stirred to obtain a polyamic acid solution b3, the structural formula of which is shown in Formula 4:

[0118] Example 7

[0119] (A-1)+(A-3)+X+(B-1)

[0120] The preparation of polyamic acid b4 comprises the following steps:

[0121] 1) 2.206 g of p-phenylenediamine and 8.453 g of 2-amino-5-[2-(4-amino-3-hydroxyphenoxy)ethoxy]phenol were mixed to obtain a diamine mixture, which was dissolved in 117.834 g of N-methylpyrrolidone, and 0.135 g of 1,3,5-benzenetricarboxylic acid chloride and 10 g of cyclobutanetetracarboxylic dianhydride were added. The mixture was reacted at 2.5±2.5°C under a nitrogen environment for 16 h to form a polyamic acid solution having a solid content of about 15%;

[0122] 2) 5 g of the polyamic acid solution prepared in step 1) was added to 4.545 g of N-methylpyrrolidone, and then 4.091 g of ethylene glycol monobutyl ether was added, mixed and stirred to obtain a polyamic acid solution b4, the structural formula of which is shown in Formula 5:

[0123]

[0124] Formula 5.

[0125] Example 8

[0126] (A-1)+(A-2)+X+(B-1)

[0127] The preparation of polyamic acid b5 comprises the following steps:

[0128] 1) 1.103 g of p-phenylenediamine, 13.556 g of 2-amino-5-[2-(4-amino-3-carboxyphenoxy)ethoxy]benzoic acid were mixed to obtain a diamine mixture, which was dissolved in 140.271 g of N-methylpyrrolidone, and 0.095 g of 1,3,5-benzenetricarboxylic acid chloride and 10 g of cyclobutanetetracarboxylic dianhydride were added. The mixture was reacted at 2.5±2.5°C under a nitrogen environment for 16 h to form a polyamic acid solution having a solid content of about 15%;

[0129] 2) Take 5 g of the polyamic acid solution prepared in step 1) and add it to 4.545 g of N-methylpyrrolidone, then add 4.091 g of ethylene glycol monobutyl ether, mix and stir to obtain a polyamic acid solution b5, the structural formula of which is shown in Formula 6:

[0130]

[0131] Formula 6.

[0132] Comparative Example 1

[0133] (A-1) + X + (B-1)

[0134] The preparation of polyamic acid c1 comprises the following steps:

[0135] 1) Dissolve 5.514 g of p-phenylenediamine in 88.681 g of N-methylpyrrolidone, add 0.135 g of 1,3,5-benzenetricarboxylic acid chloride and 10 g of cyclobutanetetracarboxylic dianhydride, and react for 16 hours at a temperature of 2.5±2.5°C under a nitrogen environment to form a polyamic acid solution with a solid content of about 15%;

[0136] 2) 5 g of the polyamic acid solution prepared in step 1) was added to 4.545 g of N-methylpyrrolidone, and then 4.091 g of ethylene glycol monobutyl ether was added, and the mixture was mixed and stirred to obtain a polyamic acid solution c1, the structural formula of which is shown in Formula 7:

[0137]

[0138] Formula 7.

[0139] Comparative Example 2

[0140] (A-1)+(A-2)+(A-3)+(B-1)

[0141] The preparation of polyamic acid C2 comprises the following steps:

[0142] 1) 2.757 g of p-phenylenediamine, 4.236 g of 2-amino-5-[2-(4-amino-3-carboxyphenoxy)ethoxy]benzoic acid, and 3.522 g of 2-amino-5-[2-(4-amino-3-hydroxyphenoxy)ethoxy]phenol were mixed to obtain a diamine mixture, which was dissolved in 116.255 g of N-methylpyrrolidone, and 10 g of cyclobutanetetracarboxylic dianhydride was added. The mixture was reacted at 2.5±2.5°C under a nitrogen environment for 16 h to form a polyamic acid solution having a solid content of about 15%;

[0143] 2) 5 g of the polyamic acid solution prepared in step 1) was added to 4.545 g of N-methylpyrrolidone, and then 4.091 g of ethylene glycol monobutyl ether was added, mixed and stirred to obtain a polyamic acid solution c2, the structural formula of which is shown in Formula 8:

[0144]

[0145] Formula 8.

[0146] Comparative Example 3

[0147] (A-1) + (B-1)

[0148] The preparation of polyamic acid C3 comprises the following steps:

[0149] 1) Dissolve 5.514 g of p-phenylenediamine in 87.914 g of N-methylpyrrolidone, add 10 g of cyclobutanetetracarboxylic dianhydride, and react for 16 h at a temperature of 2.5±2.5°C under a nitrogen environment to form a polyamic acid solution with a solid content of 15%;

[0150] 2) 5 g of the polyamic acid solution prepared in step 1) was added to 4.545 g of N-methylpyrrolidone, and then 4.091 g of ethylene glycol monobutyl ether was added, mixed and stirred to obtain a polyamic acid solution c3, the structural formula of which is shown in Formula 9:

[0151]

[0152] Formula 9.

[0153] Preparation of liquid crystal alignment agent:

[0154] 1) 5 g of the polyamic acid solution a1 prepared in Example 1 and 5 g of the polyamic acid solution b1 prepared in Example 4 were mixed and stirred to obtain a liquid crystal alignment agent D1;

[0155] 2) 5 g of the polyamic acid solution a2 prepared in Example 2 and 5 g of the polyamic acid solution b1 prepared in Example 4 were mixed and stirred to obtain a liquid crystal alignment agent D2;

[0156] 3) 5 g of the polyamic acid solution a3 prepared in Example 3 and 5 g of the polyamic acid solution b1 prepared in Example 4 were mixed and stirred to obtain a liquid crystal alignment agent D3;

[0157] 4) 5 g of the polyamic acid solution a1 prepared in Example 1 and 5 g of the polyamic acid solution b2 prepared in Example 5 were mixed and stirred to obtain a liquid crystal alignment agent D4;

[0158] 5) 5 g of the polyamic acid solution a1 prepared in Example 1 and 5 g of the polyamic acid solution b3 prepared in Example 6 were mixed and stirred to obtain a liquid crystal alignment agent D5;

[0159] 6) 5 g of the polyamic acid solution a1 prepared in Example 1 and 5 g of the polyamic acid solution b4 prepared in Example 7 were mixed and stirred to obtain a liquid crystal alignment agent D6;

[0160] 7) 5 g of the polyamic acid solution a1 prepared in Example 1 and 5 g of the polyamic acid solution b5 prepared in Example 8 were mixed and stirred to obtain a liquid crystal alignment agent D7;

[0161] 8) 5 g of the polyamic acid solution a1 prepared in Example 1 and 5 g of the polyamic acid solution c1 prepared in Comparative Example 1 were mixed and stirred to obtain a liquid crystal alignment agent D8;

[0162] 9) 5 g of the polyamic acid solution a1 prepared in Example 1 and 5 g of the polyamic acid solution c2 prepared in Comparative Example 2 were mixed and stirred to obtain a liquid crystal alignment agent D9;

[0163] 10) 5 g of the polyamic acid solution a1 prepared in Example 1 and 5 g of the polyamic acid solution c3 prepared in Comparative Example 3 were mixed and stirred to obtain a liquid crystal alignment agent D10;

[0164] 11) 2 g of the polyamic acid solution a1 prepared in Example 1 and 8 g of the polyamic acid solution b1 prepared in Example 4 were mixed and stirred to obtain a liquid crystal alignment agent D11;

[0165] 12) 8 g of the polyamic acid solution a1 prepared in Example 1 and 2 g of the polyamic acid solution b1 prepared in Example 4 were mixed and stirred to obtain a liquid crystal alignment agent D12;

[0166] The liquid crystal alignment agent prepared above was used to prepare a liquid crystal alignment film for performance testing, and the preparation method was as follows:

[0167] The liquid crystal alignment agents D1~D10 were filtered through a 0.45μm filter, and then 1.5g was taken and evenly coated on an FFS substrate with a size of 50mm×50mm×0.7mm by a spin coating process. The spin coating process was 300rpm for 10s and then 2000rpm for 60s. After spin coating, it was placed on a hot plate and heated at 110℃ for 80s for pre-baking. After pre-baking, it was placed in an oven and fired at 230℃ for 20min to obtain a liquid crystal alignment film with a film thickness of 100nm.

[0168] The liquid crystal alignment film prepared above was used to prepare a liquid crystal box for performance testing, and the preparation method was as follows:

[0169] The liquid crystal alignment film was treated with LPUV at a wavelength of 254 nm and an irradiation energy of 500 mJ / cm 2 . Then put the FFS substrate into an oven and heat it at 230°C for 30 minutes. Then drop 0.175±0.025g of liquid crystal in the middle of the FFS substrate coated with the liquid crystal alignment film, and apply frame glue around the other FFS substrate coated with the liquid crystal alignment film. Then vacuum bond the two FFS substrates in the opposite order of UV irradiation. After pressing for 30 seconds, put it into a UV irradiator with a wavelength of 365nm for UV curing, and finally put it into an oven and heat it at 120°C for 40 minutes to finally obtain a liquid crystal box.

[0170] Detection method:

[0171] Evaluation of pencil hardness:

[0172] The sample for pencil hardness evaluation was prepared as follows. The liquid crystal alignment agent was applied to a 50 mm × 50 mm FFS substrate by spin coating. It was dried on a hot plate at 80°C for 2 minutes, and the coating surface was irradiated with ultraviolet light with a wavelength of 254 nm and an extinction ratio of 10:1 or more through a polarizing plate. It was then calcined in a hot air circulation oven at 230°C for 20 minutes to obtain a substrate with a liquid crystal alignment film. The substrate was measured using the pencil hardness test method (JIS K5400).

[0173] Determination of residual DC voltage (RDC, V):

[0174] A 10V DC voltage was applied to the liquid crystal box for 30 minutes, and the voltage of the liquid crystal box was measured after it was short-circuited for 1 second. The voltage values ​​after 50 seconds and 1000 seconds were measured as the RDC of the liquid crystal box. The test results are shown in Table 1 below:

[0175] Table 1 Test results

[0176]

[0177] Through the test data, it was found that by comparing D1~D10, when carboxyl-containing diamine and / or hydroxyl-containing diamine and a cross-linking agent are simultaneously present in the liquid crystal alignment agent, the liquid crystal alignment film prepared by the liquid crystal alignment agent can obtain a higher pencil hardness. By comparing D1 and D8, since D8 only contains a cross-linking agent but does not contain carboxyl-containing diamine and / or hydroxyl-containing diamine, the pencil hardness of the liquid crystal alignment film is reduced; and by comparing D1 and D9, since D9 only contains carboxyl-containing diamine and / or hydroxyl-containing diamine but does not contain a cross-linking agent at the same time, the hardness of the liquid crystal alignment film prepared by the liquid crystal alignment agent is reduced.

[0178] At the same time, the present invention compares D6~D7 and finds that when there is only one carboxyl-containing diamine or hydroxyl-containing diamine in the liquid crystal alignment agent, the prepared liquid crystal alignment film can still obtain good hardness. This may be because the hydroxyl or carboxyl group in the molecular chain can form a hydrogen bond with the imine group -NH- in the liquid crystal alignment agent, thereby improving the intermolecular stability and the hardness of the liquid crystal alignment film.

[0179] Through the test data, it was found that by comparing D1~D7 and D9, it was found that when carboxyl-containing diamine and / or hydroxyl-containing diamine existed in the liquid crystal alignment agent, the liquid crystal box prepared by the liquid crystal alignment agent showed a good residual current dissipation effect, indicating that the specific diamine compound in the invention has a significant effect on the relief of residual charge, indicating that the liquid crystal alignment agent prepared by using carboxyl-containing diamine and / or hydroxyl-containing diamine and a cross-linking agent has excellent quality.

Claims

1. A liquid crystal alignment agent, characterized in that: It is composed of the following A component, B component and organic solvent: Component A: polyamic acid prepared by polymerization of 1,3-bis(4-aminophenethyl)urea, 4,4'-diaminodiphenylamine and tetracarboxylic dianhydride; Component B: polyamic acid obtained by polymerizing diamine containing carboxyl and / or hydroxyl groups, p-phenylenediamine, 1,3,5-benzenetricarboxylic acid chloride and tetracarboxylic dianhydride; The diamine structure containing a carboxyl group is shown in Formula 1: Formula 1: 2-amino-5-[2-(4-amino-3-carboxyphenoxy)ethoxy]benzoic acid; The diamine structure containing hydroxyl groups is shown in Formula 2: Formula 2: 2-amino-5-[2-(4-amino-3-hydroxyphenoxy)ethoxy]phenol; The tetracarboxylic dianhydride is one of cyclobutanetetracarboxylic dianhydride and 3,3',4,4'-biphenyltetracarboxylic dianhydride; The molar ratio of the p-phenylenediamine, the diamine containing carboxyl and / or hydroxyl groups, the tetracarboxylic dianhydride, and 1,3,5-benzenetricarboxylic acid chloride is (0.1-0.5): (0.5-0.9): 1: (0.005-0.01); The molar ratio of the 1,3-bis(4-aminophenethyl)urea, 4,4'-diaminodiphenylamine and tetracarboxylic dianhydride is (0.3-0.7):(0.3-0.7):

1.

2. The liquid crystal alignment agent according to claim 1, characterized in that: The preparation method of the 2-amino-5-[2-(4-amino-3-carboxyphenoxy)ethoxy]benzoic acid is as follows: (1) Add 5-hydroxy-2-nitrobenzoic acid to an aprotic solvent, then add 1,2-bis(tolyloxyethane), stir to obtain a mixed solution, add an acid binding agent, and heat to react. After the reaction is completed, add the reaction system to pure water, add an acid solution dropwise, precipitate a solid, adjust the pH of the solution, filter, and wash with pure water to obtain a dinitro product; (2) adding the dinitro product to a solvent, heating to dissolve, adding a catalyst, reacting under a hydrogen atmosphere, filtering while hot, eluting the filter cake with a hot solvent, and concentrating the filtrate to dryness to obtain a concentrated product; (3) adding a poor solvent to the concentrated product, placing it in cold hydrazine for crystallization, filtering, washing, and drying to obtain 2-amino-5-[2-(4-amino-3-carboxyphenoxy)ethoxy]benzoic acid; The preparation method of the 2-amino-5-[2-(4-amino-3-hydroxyphenoxy)ethoxy]phenol is: A. Add 4-nitroresorcinol to an aprotic solvent, then add 1,2-dibromoethane, stir to obtain a mixed solution, add an acid binding agent, and heat to react. After the reaction is completed, add pure water to precipitate a solid, filter, and rinse with a solvent to obtain a dinitro product; B. adding the dinitro product to a solvent, heating to dissolve, adding a catalyst, reacting under a hydrogen atmosphere, filtering, and concentrating the filtrate to dryness to obtain a concentrated product; C. Add a poor solvent to the concentrated product, place it in cold hydrazine, stir and crystallize, filter, wash and dry the filter cake to obtain 2-amino-5-[2-(4-amino-3-hydroxyphenoxy)ethoxy]phenol.

3. The liquid crystal alignment agent according to claim 2, characterized in that: The temperature of the heat preservation reaction in step (1) is 100-140°C, and the time is 14-17h; the acid binding agent in step (1) is anhydrous sodium carbonate or anhydrous potassium carbonate; the molar ratio of the acid binding agent in step (1) to 5-hydroxy-2-nitrobenzoic acid is (3.85-4.2):1; the aprotic solvent in step (1) is one of N,N-dimethylformamide, N,N-dimethylacetamide, and acetonitrile; the pH of the solution in step (1) is adjusted to 3-4; the solvent in step (2) is one of tetrahydrofuran and ethanol; the temperature of the heating and dissolving in step (2) is 65-85°C, and the reaction time under hydrogen atmosphere is 16-21h; the poor solvent in step (3) is ethanol, and the temperature of the cold hydrazine is -5-5°C.

4. The liquid crystal alignment agent according to claim 2, characterized in that: The temperature of the insulation reaction in step A is 105-135° C., and the reaction time is 8-12 hours; the acid binding agent in step A is anhydrous sodium carbonate or anhydrous potassium carbonate; the molar ratio of the acid binding agent in step A to 4-nitroresorcinol is (1.5-2.5):1; the aprotic solvent in step A is one of acetonitrile, N,N-dimethylformamide, and N,N-dimethylacetamide; the solvent in step B is one of tetrahydrofuran and ethanol; the temperature of the heating and dissolving in step B is 60-85° C., and the reaction time under hydrogen atmosphere is 14-16 hours; the poor solvent in step C is ethanol, and the temperature of the cold hydrazine is -10-0° C.

5. A method for preparing a high-hardness polyimide liquid crystal alignment film using the liquid crystal alignment agent according to any one of claims 1 to 4, characterized in that: The following steps are involved: Step 1: 1,3-bis(4-aminophenethyl)urea and 4,4'-diaminodiphenylamine are mixed to obtain a diamine mixture, which is dissolved in an organic solvent, and tetracarboxylic dianhydride is added to react to obtain a polyamic acid solution A, and the polyamic acid solution A is added to the organic solvent and mixed and stirred to obtain a polyamic acid solution a; Step 2: dissolving a mixture of a diamine containing carboxyl and / or hydroxyl groups and p-phenylenediamine in an organic solvent, adding tetracarboxylic dianhydride and 1,3,5-benzenetricarboxylic acid chloride to react, and then adding a diamine containing carboxyl and / or hydroxyl groups, tetracarboxylic dianhydride, and an organic solvent to react to obtain a polyamic acid solution B; adding the polyamic acid solution B to the organic solvent and mixing and stirring to obtain a polyamic acid solution B; Step 3: Mixing and stirring the polyamic acid solution a and the polyamic acid solution b to obtain a liquid crystal alignment agent; Step 4: Filter the liquid crystal alignment agent through a filter, spin-coat it on the FFS substrate, pre-bake and sinter it to obtain a high-hardness polyimide liquid crystal alignment film.

6. The method for preparing a high-hardness polyimide liquid crystal alignment film according to claim 5, characterized in that: The reaction temperature of the reaction described in step 1 and step 2 is 0-5°C.

7. The method for preparing a high-hardness polyimide liquid crystal alignment film according to claim 5, characterized in that: The mass ratio of the polyamic acid solution a and the polyamic acid solution b in step three is (0.2~0.8): (0.2~0.8).

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