A polymer A, preparation method thereof and applications thereof

Abstract

The present application discloses a polymer A, a preparation method thereof and an application thereof. In the synthesis process of this polyimide, a diamine compound containing a thiophene structure is introduced. Such polyimide materials can be used to prepare liquid crystal alignment agents and liquid crystal alignment films. Even when additives such as crosslinking agents or coupling agents are not added, the prepared liquid crystal display elements have excellent optoelectronic properties, high voltage holding ratio (VHR), less accumulation of direct current charge release (RDC), and fast release; due to the fact that the diamine compound of the present invention itself belongs to a special rigid fused ring structure, with a large conjugated system and strong electron transfer in its molecule, the polyimide material also has good thermal stability and excellent mechanical properties.

Description

Technical Field

[0001] The present application relates to a polymer A, a preparation method thereof and an application thereof, belonging to the field of liquid crystal alignment agents. Background Art

[0002] Polyimide is a special polymer material with excellent comprehensive properties, and its properties include resistance to high and low temperatures, high strength, high modulus, low dielectric constant, low thermal expansion coefficient and good chemical stability, etc. The source of these excellent properties is that one of the main repeating units contained in its polymer chain is an imide ring, and the electrons on this special chemical structure show highly conjugated characteristics. By cleverly utilizing this conjugation characteristic, the polymer chain segments can be "rigid and flexible", achieving a perfect integration of optical, electrical and mechanical properties. Therefore, polyimide materials have become the preferred materials for preparing liquid crystal alignment films.

[0003] The functional components of polyimide alignment agents are divided into two types: polyamic acid (PAA) and soluble polyimide (SPI). The process method of compounding PAA with SPI or PAAs with different resistivity is often used to develop high-performance PI alignment film materials, and this hybrid type of alignment film material can often provide good optoelectronic properties. In the prior art, the research on PAA-based alignment films is relatively sufficient, but the types of SPI are very limited, which greatly restricts the development of PI liquid crystal alignment films. In order to improve the display characteristics of liquid crystal display elements, various technologies have been proposed. As described above, by selecting the structures of polyamic acid and polyimide, mixing resins with different characteristics, etc., the liquid crystal alignment property can be further improved, the pretilt angle can be controlled and its stability can be improved, the voltage holding ratio can be increased, and at the same time, the disadvantages that it is difficult to accumulate and store charges for direct current voltage, and the stored charges are easy to disappear can be improved.

[0004] In recent years, with the continuous expansion of the application scope of LCDs, electrostatic interference often occurs. The static electricity generated during the most popular rubbing alignment process in the industry is likely to break down the alignment layer, resulting in short circuits or poor alignment of the liquid crystal cell, which has a great impact on the display picture quality and the yield of the production line. In addition, the high-quality operation of liquid crystal display devices requires a high voltage holding ratio (VHR), less accumulation and fast release of direct current charge (Relaxation of Direct Current, RDC), so as to ensure that the effective voltage obtained after charging in the frame period of the liquid crystal display element can be fully maintained until the next frame, reduce the flicker level of the picture, reduce the problem of image retention caused by charge accumulation, and improve its display quality.

[0005] Patent CN111971617B provides a specific diamine compound. When introduced into a polymer, the resulting liquid crystal alignment film can achieve rapid relaxation of accumulated charges, and the amount of charge accumulation is not easily changed even when irradiated by a backlight. However, there is no mention of improving friction, and the desired effect can only be achieved under the simultaneous action of multiple coupling agents or cross-linking agents. Summary of the Invention

[0006] In view of the above situation, the present invention introduces a diamine compound containing a thiophene structure to prepare a polyimide-based substance. Thiophene is a common heterocyclic structure with a special rigid fused-ring structure. The thiophene ring is relatively easy to form a relatively stable positive ion; it has a large conjugated system and strong electron transfer within the molecule; it has high thermal stability and photochemical stability; it is also easy to modify the structure to introduce various types of functional groups; it can be introduced into the polymer chain through different polymerization methods to form a polymer material; therefore, the polyimide prepared using this diamine has good thermal stability, optoelectronic properties, and excellent storage functions.

[0007] Through in-depth research, the present invention selects the key components in the liquid crystal aligning agent, that is, the liquid crystal aligning agent prepared from the polyimide of the present invention forms a liquid crystal alignment film with high VHR, low RDC, good thermal stability, high reliability, and can be aligned by ultraviolet light irradiation, avoiding problems such as electrostatic interference and friction debris caused by friction, effectively improving the yield of LCDs.

[0008] Thiophene is a common heterocyclic structure with a special rigid fused-ring structure. The thiophene ring is relatively easy to form a relatively stable positive ion; it has a large conjugated system and strong electron transfer within the molecule; it has high thermal stability and photochemical stability; it is also easy to modify the structure to introduce various types of functional groups; it can be introduced into the polymer chain through different polymerization methods to form a polymer material; therefore, the polyimide prepared using this diamine has good thermal stability, optoelectronic properties, and excellent storage functions.

[0009] In order to make the liquid crystal have high voltage holding characteristics, excellent liquid crystal alignment properties, and further reduce the effect of accumulated charges, the tetracarboxylic dianhydride includes at least one of an aliphatic tetracarboxylic dianhydride and an aromatic tetracarboxylic dianhydride;

[0010] According to the first aspect of the present application, a polymer A is provided.

[0011] The polymer A is a polyimide, a polyamic acid, or a composition thereof. The polyimide is a polymer formed by dehydrating the polyamic acid, and its structure is as shown in formula (1).

[0012]

[0013] In the above formula (1),

[0014] R1 is a tetravalent organic group of a tetracarboxylic dianhydride, and the tetracarboxylic dianhydride includes at least one of an aliphatic tetracarboxylic dianhydride and an aromatic tetracarboxylic dianhydride;

[0015] R2 is selected from derivatives obtained by removing terminal amino groups from diamine compounds, and the diamine compounds include diamine compound DA and diamine compound DN;

[0016] The diamine compound DA is selected from at least one of compounds (DA-1), (DA-2), (DA-3), (DA-4), and (DA-5);

[0017] The diamine compound DN is selected from at least one of compounds (DN-1), (DN-2), (DN-3), and (DN-4);

[0018] The structural formula of the diamine compound is shown as follows;

[0019] Among them, the diamine compound DN can not only make up for the deficiencies of the diamine compound DA, but also improve the stability of the polymer itself and the orientation of the liquid crystal alignment film;

[0020]

[0021]

[0022] The weight-average molecular weight (Mw) of the polymer A is 2,000 to 500,000.

[0023] Optionally, the polyamic acid is obtained by polycondensation of a tetracarboxylic dianhydride and a diamine compound;

[0024] Optionally, the polyimide is obtained by dissolving the polyamic acid in an organic solvent, heating and imidizing it under the action of a dehydrating agent and a basic catalyst to obtain a crude polyimide product, and finally purifying the crude polyimide product to obtain the polymer A;

[0025] Optionally, the aliphatic tetracarboxylic dianhydride is selected from at least one of 1,2,3,4-cyclobutanetetracarboxylic dianhydride, 1,3-dimethyl-1,2,3,4-cyclobutanetetracarboxylic dianhydride, 1,2,3,4-cyclopentanetetracarboxylic dianhydride, 1,2,3,4-cyclohexanetetracarboxylic dianhydride, 2,3,5-tricarboxycyclopentylacetic dianhydride, 3,4-dicarboxy-1-cyclohexyl succinic anhydride, 3,4-dicarboxy-1,2,3,4-tetrahydro-1-naphthalene succinic anhydride, bicyclo[3.3.0]octane-2,4,6,8-tetracarboxylic dianhydride, 1,2,3,4-butane tetracarboxylic dianhydride, 2,3,4,5-tetrahydrofuran tetracarboxylic dianhydride, bicyclo[2.2.2]oct-7-ene-2,3,5,6-tetracarboxylic dianhydride.

[0026] Optionally, the aromatic tetracarboxylic dianhydride is selected from at least one of pyromellitic dianhydride, 3,3′,4,4′-biphenyltetracarboxylic dianhydride, 2,2′,3,3′-biphenyltetracarboxylic dianhydride, 2,3,3′,4′-biphenyltetracarboxylic dianhydride, 3,3′,4,4′-benzophenone tetracarboxylic dianhydride, 2,3,3′,4′-benzophenone tetracarboxylic dianhydride, bis(3,4-dicarboxyphenyl) ether dianhydride, bis(3,4-dicarboxyphenyl) sulfone dianhydride, 1,2,5,6-naphthalenetetracarboxylic dianhydride, 2,3,6,7-naphthalenetetracarboxylic dianhydride, 1,4,5,8-naphthalenetetracarboxylic dianhydride, 4,4'-(4,4'-isopropyl diphenoxy) diphthalic anhydride, 4,4′-(hexafluoroisopropylidene) diphthalic anhydride, 4,4'-isopropylidene-bis(phthalic anhydride).

[0027] Optionally, the diamine compound DA accounts for 10-100% of the total molar amount of the diamine compounds.

[0028] Optionally, the diamine compound DA accounts for 10-30% of the total molar amount of the diamine compounds.

[0029] Optionally, the diamine compound DN accounts for 10-100% of the total molar amount of the diamine compounds.

[0030] Optionally, the diamine compound DA accounts for 30-90% of the total molar amount of the diamine compounds.

[0031] Optionally, the organic solvent can be used as a dispersant or as a desiccant;

[0032] The dehydrating agent is selected from at least one of acetic anhydride, propionic anhydride, and trifluoroacetic anhydride.

[0033] Optionally, the dehydrating agent is acetic anhydride.

[0034] Optionally, the basic catalyst is selected from at least one of pyridine, collidine, lutidine, and triethylamine;

[0035] The imidization reaction temperature is -20°C to 140°C.

[0036] Optionally, the imidization temperature is 0°C to 100°C.

[0037] Optionally, the imidization reaction time is 1 to 100 h;

[0038] The amount of the basic catalyst is 0.5 to 30 times the molar amount of the polyamic acid.

[0039] Optionally, the basic catalyst is 2 to 20 times the molar amount of the polyamic acid;

[0040] The amount of the dehydrating agent is 1 to 50 times the molar amount of the polyamic acid.

[0041] Optionally, the amount of the dehydrating agent is 3 to 30 times the molar amount of the polyamic acid.

[0042] Optionally, the organic solvent is selected from at least one of N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, N-methylcaprolactam, N-methyl-2-pyrrolidone, γ-butyrolactone, methyl ethyl ketone, cyclohexanone, cyclopentanone, 4-hydroxy-4-methyl-2-pentanone, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, ethylene glycol methyl ethyl ether, ethylene glycol dimethyl ether, and dimethyl sulfoxide.

[0043] The purification process is to dissolve the obtained crude polyimide product in solvent B to precipitate polymer A, filter and recover it, redissolve the recovered product in the organic solvent, repeat the purification process multiple times, and dry to obtain purified polymer A;

[0044] The weight-average molecular weight (Mw) of polymer A is 5000 to 300000.

[0045] Optionally, the weight-average molecular weight (Mw) of polymer A is 10000 to 100000.

[0046] Optionally, solvent A is selected from 2-propanol, hexane, heptane, methyl ethyl ketone, methyl isobutyl ketone, water, methanol, ethanol, butyl cellosolve, acetone, toluene, etc., preferably at least one of methanol, ethanol, 2-propanol, and acetone.

[0047] In the second aspect of the present application, a liquid crystal aligning agent is provided, and the liquid crystal aligning agent includes polymer A, solvent B, and other polymers.

[0048] Optionally, the solvent B is selected from at least one of N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, N-methylcaprolactam, N-methyl-2-pyrrolidone, γ-butyrolactone, methyl ethyl ketone, cyclohexanone, cyclopentanone, 4-hydroxy-4-methyl-2-pentanone, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, ethylene glycol methyl ethyl ether, ethylene glycol dimethyl ether, and dimethyl sulfoxide.

[0049] Optionally, the other polymer is selected from at least one of acrylic polymers, methacrylic polymers, cellulose polymers, polystyrene, polysiloxane, and polyamide.

[0050] Optionally, the liquid crystal aligning agent further includes a solvent C;

[0051] Optionally, the solvent C is selected from at least one of ethanol, isopropanol, 1-butanol, 2-butanol, isobutanol, tert-butanol, ethyl cellosolve, butyl cellosolve, ethyl carbitol, butyl carbitol, ethyl carbitol acetate, 1-pentanol, 2-pentanol, 3-pentanol, ethylene glycol, 1-methoxy-2-propanol, 2-methyl-1-butanol, isopentanol, tert-pentanol, 1-ethoxy-2-propanol, 1-butoxy-2-propanol, 1-phenoxy-2-propanol, propylene glycol monoacetate, propylene glycol diacetate, propylene glycol-1-monomethyl ether-2-acetate, propylene glycol-1-monoethyl ether, 3-methyl-2-butanol, neopentyl alcohol, 1-hexanol, 2-methyl-1-pentanol, butyl cellosolve acetate, dipropylene glycol, 2-(2-ethoxypropoxy)propanol, furfuryl alcohol, diethylene glycol, propylene glycol monobutyl ether, methyl lactate, ethyl lactate, n-propyl lactate, n-butyl lactate, and isopentyl lactate.

[0052] Optionally, the weight ratio of the polymer A to the solvent B is 1:5 to 50.

[0053] Optionally, the weight ratio of the polymer A to the solvent B is 1:10 to 50.

[0054] Optionally, the content of the other polymer in the liquid crystal aligning agent is 1 to 30 wt%.

[0055] Optionally, the content of the other polymer in the liquid crystal aligning agent is 5 to 20 wt%.

[0056] Optionally, the content of the solvent C in the liquid crystal aligning agent is preferably 5 to 50 wt%.

[0057] Optionally, the content of the solvent C in the liquid crystal aligning agent is 10 to 30 wt%.

[0058] According to the third aspect of the present application, a liquid crystal alignment film is provided, which is prepared by coating the liquid crystal aligning agent on a substrate and then drying, baking, and performing an alignment treatment method.

[0059] Optionally, the substrate is selected from at least one of a glass substrate, an acrylic substrate, a silicon nitride substrate, a polycarbonate substrate, a polyurethane substrate, a trimethylpentene substrate, a cellulose triacetate substrate, and a cellulose acetate butyrate substrate.

[0060] Optionally, the coating method is selected from at least one of printing methods such as screen printing, offset printing, and flexographic printing, spraying methods, spin coating methods, and inkjet methods.

[0061] Optionally, the drying temperature is 50°C to 120°C, the drying time is 60 to 100 min, the curing temperature is 150 to 300°C, the curing time is 5 to 120 min, the thickness of the obtained liquid crystal alignment film is 5 nm to 300 nm, and the alignment treatment method is selected from at least one of a brush rubbing method and a photo-alignment method.

[0062] Optionally, the liquid crystal alignment film obtained from the liquid crystal aligning agent is made into a liquid crystal display element.

[0063] The beneficial effects that can be produced by the present application include:

[0064] After introducing the diamine monomer of the present invention into polyimide, preparing a liquid crystal aligning agent and curing it into a polyimide film, the 5% thermal weight loss temperature is greater than 400°C. The polyimide containing the diamine compound of the present invention has good thermal stability; at the same time, the liquid crystal unit has excellent orientation, and the DC charge residual voltage value is very small and can be quickly relaxed. Even under the condition of 60°C, a high voltage holding ratio can be maintained. The reliability and optoelectronic performance of the liquid crystal display element of the liquid crystal alignment film obtained from the liquid crystal aligning agent of the present invention are excellent, and it can be suitably used for large-screen and high-definition liquid crystal TVs, etc. Description of the Drawings

[0065] In order to ensure the reaction between the tetracarboxylic dianhydride and the diamine, infrared spectra were measured for the polyamic acid solutions in the synthesis examples. When the tetracarboxylic dianhydride reacts with the diamine, the tetracarboxylic dianhydride ring-opens and reacts with the amino group to form an amide group (-CONH-) and a carboxyl group (-COOH). The characteristic peaks of the amide group and the carboxyl group were observed through infrared spectra to prove the reaction between the two. It can be found from the spectra that at 1504 - 1510 cm -1 is the characteristic peak of C-N in the amide group, and at 1597 - 1622 cm -1 is the characteristic peak of C=O in the carboxyl group.

[0066] The data was measured using a Fourier transform infrared spectrometer (Bruker, Germany, Tensor-27). The specific spectra are shown in the appendix Figures 1 to 16 .

[0067] Figure 1 This is the infrared spectrum of Synthesis Example 1 of this application;

[0068] Figure 2 This is the infrared spectrum of Synthesis Example 2 of this application;

[0069] Figure 3 This is the infrared spectrum of Synthesis Example 3 of this application;

[0070] Figure 4 This is the infrared spectrum of Synthesis Example 4 of this application;

[0071] Figure 5 This is the infrared spectrum of Synthesis Example 5 of this application;

[0072] Figure 6 This is the infrared spectrum of Synthesis Example 6 of this application;

[0073] Figure 7 This is the infrared spectrum of Synthesis Example 7 of this application;

[0074] Figure 8 This is the infrared spectrum of Synthesis Example 8 of this application;

[0075] Figure 9 This is the infrared spectrum of Synthesis Example 9 of this application;

[0076] Figure 10 This is the infrared spectrum of Synthesis Example 10 of this application;

[0077] Figure 11 This is the infrared spectrum of Synthesis Example 11 of this application;

[0078] Figure 12 This is the infrared spectrum of Synthesis Example 12 of this application;

[0079] Figure 13 This is the infrared spectrum of Synthesis Example 13 of this application;

[0080] Figure 14 This is the infrared spectrum of Synthesis Example 14 of this application;

[0081] Figure 15 This is the infrared spectrum of Synthesis Example 15 of this application;

[0082] Figure 16 This is the infrared spectrum of Synthesis Example 16 of this application. Detailed implementation manners

[0083] The present application will be described in detail below in conjunction with the embodiments, but the present application is not limited to these embodiments.

[0084] Unless otherwise specified, the raw materials in the embodiments of the present application are all purchased through commercial channels;

[0085] The method for analyzing the solution viscosity of the polymer in the synthesis examples of the present application is as follows:

[0086] Viscosity analysis is carried out using an E-type rotational viscometer, that is, a polymer solution with a concentration of 6 wt% prepared with a good solvent for the polymer (for example, N-methyl-2-pyrrolidone, γ-butyrolactone, etc.), and the value measured with an E-type rotational viscometer at 25°C. The solution viscosity can be selected to be 20 - 300 mPa·s.

[0087] According to an embodiment of the present application, the preparation of the liquid crystal alignment film

[0088] The liquid crystal alignment film of the present invention is obtained from the above-mentioned liquid crystal aligning agent, and a method of performing alignment treatment on the film obtained by coating the liquid crystal aligning agent in the form of a coating solution on a substrate and drying and firing it by a brush treatment method or a photo-alignment treatment method.

[0089] As the substrate for coating the liquid crystal aligning agent of the present invention, as long as it is a substrate with high transparency, there are no other special limitations. Glass substrates, acrylic substrates, silicon nitride substrates, polycarbonate substrates, polyurethane substrates, trimethylpentene substrates, cellulose triacetate substrates, cellulose acetate butyrate substrates, etc. can be used. In addition, from the perspective of simplifying the process, it is preferred to use a substrate with an ITO electrode for driving liquid crystals, etc. In addition, in a reflective liquid crystal display element, if only one side of the substrate is used, an opaque substance such as a silicon wafer can be used, and at this time, an electrode that reflects light such as aluminum can also be used.

[0090] As the coating method of the liquid crystal aligning agent of the present invention, printing methods such as screen printing, offset printing, and flexographic printing, spraying methods, spin coating methods, inkjet methods, etc. can be cited. From the aspect of production efficiency, the printing method is often used in industrial production and can also be appropriately used in the present invention.

[0091] The liquid crystal aligning agent is coated using the above coating method, and the formed coating film is baked to become a cured film. The drying process after coating the liquid crystal aligning agent is not necessary, and the time from coating to baking for each substrate is not fixed. This drying only needs to remove the solvent until the shape of the coating film will not be deformed due to handling of the substrate, etc., and there are no special limitations on the drying means. For example, it can be cited to dry at 50 - 120°C, preferably 60 - 100°C for 1 minute - 10 minutes, preferably 2 - 5 minutes, and then cure at 150 - 300°C, preferably 200 - 240°C for 5 - 120 minutes, preferably 10 - 30 minutes. There is no special limitation on the thickness of the cured film. When the film thickness is too thin, the reliability of the liquid crystal display element may be reduced, so it is 5 - 300 nm, preferably 10 - 200 nm.

[0092] As a method for aligning a thin film, a rubbing method, a photo-alignment method, etc. can be cited, and the liquid crystal aligning agent of the present invention has better effects when used in the photo-alignment method.

[0093] According to an embodiment of the present application, the production of a liquid crystal display element.

[0094] Regarding the liquid crystal display element of the present invention, after obtaining a substrate with a liquid crystal alignment film obtained from the above liquid crystal aligning agent, a liquid crystal cell is produced by a known method, and an element is made using the liquid crystal cell.

[0095] Specific methods for producing a liquid crystal display element are listed as follows: First, prepare a pair of substrates with a liquid crystal alignment film. Then, scatter spacers on the liquid crystal alignment film of a single substrate, paste it on another substrate with the liquid crystal alignment film surface as the inner side, inject liquid crystal under reduced pressure and seal it. Alternatively, liquid crystal can be dropped onto the liquid crystal alignment film surface where spacers are scattered, and then the substrates are pasted and sealed. The thickness of the spacers at this time is preferably 1 to 30 μm, more preferably 2 to 10 μm.

[0096] The present invention will be further described below with reference to specific examples, but the present invention is not limited to the following examples. The methods are all conventional methods unless otherwise specified. The materials can all be obtained from publicly available commercial sources unless otherwise specified.

[0097] The molecular weights of the polyimide and polyamic acid obtained in the following examples were all measured by the GPC method (Shimadzu Corporation, Japan, gel permeation chromatography), the mobile phase was N-methylpyrrolidone, and the obtained molecular weights were all weight-average molecular weights (Mw).

[0098] Synthesis Example 1

[0099] Introduce N into a 500 mL four-necked flask equipped with a stirring device 2, 2.0 g (0.009 mol) of DA-1, 7.95 g (0.037 mol) of DN-1, and 158.17 g of NMP were added in sequence. After dissolution, 14.51 g (0.032 mol) of CA-1 and 3.47 g (0.014 mol) of CA-2 were added. After reacting at room temperature for 24 hours, 10.92 g (0.138 mol) of pyridine and 23.48 g (0.230 mol) of acetic anhydride were added in sequence, and imidization reaction was carried out at 50 °C for 5 hours. Then the reaction solution was poured into ethanol for precipitation, and filtered by suction to obtain a pale yellow powdery solid. The obtained solid was washed with ethanol, then the solid was dissolved in NMP, and then precipitated in ethanol again, and filtered by suction to refine the polyimide. Finally, the refined polyimide was dried in vacuum for standby. The polyimide solid after vacuum drying was first dissolved in NMP, and then BC was added to prepare a solution with a polymer content of 6 wt%, NMP of 70 wt%, and BC of 24 wt% to obtain polyimide solution PI-1 with a viscosity of 45 mPa·s, and the molecular weight Mw measured by GPC was 69876 g / mol, and the viscosity measured was 46 mPa·s. The infrared spectrum of the product is shown in the appendix Figure 1 , it can be found from the spectrum that at 1504 cm -1 is the characteristic peak of C-N in the amide group, and at 1601 cm -1 is the characteristic peak of C=O in the carboxyl group, proving that the reaction generates an amide structure.

[0100] Synthesis Example 2

[0101] N was introduced into a 500 mL four-necked flask equipped with a stirring device 2 , 3.0 g (0.008 mol) of DA-2, 6.95 g (0.033 mol) of DN-1, and 145.79 g of NMP were added in sequence. After dissolution, 12.73 g (0.029 mol) of CA-1 and 3.05 g (0.012 mol) of CA-2 were added. After reacting at room temperature for 24 hours, 9.73 g (0.123 mol) of pyridine and 20.93 g (0.205 mol) of acetic anhydride were added in sequence, and imidization reaction was carried out at 50 °C for 5 hours. Then the reaction solution was poured into ethanol for precipitation, and filtered by suction to obtain a pale yellow powdery solid. The obtained solid was washed with ethanol, then the solid was dissolved in NMP, and then precipitated in ethanol again, and filtered by suction to refine the polyimide. Finally, the refined polyimide was dried in vacuum for standby. The polyimide solid after vacuum drying was first dissolved in NMP, and then BC was added to prepare a solution with a polymer content of 6 wt%, NMP of 70 wt%, and BC of 24 wt% to obtain polyimide solution PI-2, and the molecular weight Mw measured by GPC was 68956 g / mol, and the viscosity measured was 48 mPa·s. The infrared spectrum of the product is shown in the appendixFigure 2 As can be seen from the spectrogram, at 1504 cm -1 , there is a characteristic peak of C-N in the amide group, and at 1605 cm -1 , there is a characteristic peak of C=O in the carboxyl group, proving that the reaction generates an amide structure.

[0102] Synthesis Example 3

[0103] N₂ was introduced into a 500 mL four-necked flask equipped with a stirring device. 2 , 3.0 g (0.009 mol) of DA-3, 8.10 g (0.038 mol) of DN-1, and 167.11 g of NMP were added in sequence. After dissolution, 14.83 g (0.033 mol) of CA-1 and 3.55 g (0.014 mol) of CA-2 were added. After reacting at room temperature for 24 hours, 11.15 g (0.141 mol) of pyridine and 23.99 g (0.235 mol) of acetic anhydride were added in sequence, and imidization reaction was carried out at 50 °C for 5 hours. Then the reaction solution was poured into ethanol for precipitation, filtered by suction to obtain a pale yellow powdery solid. The obtained solid was washed with ethanol, then the solid was dissolved in NMP, and then precipitated in ethanol, filtered by suction to refine the polyimide. Finally, the refined polyimide was dried in vacuo for standby. The polyimide solid after vacuum drying was first dissolved in NMP, and then BC was added to prepare a solution with a polymer content of 6 wt%, NMP of 70 wt%, and BC of 24 wt% to obtain polyimide solution PI-3. The molecular weight Mw measured by GPC was 69143 g / mol, and the viscosity was measured to be 45 mPa·s. The reaction formula is as follows in Formula C. The infrared spectrum of the product is shown in the appendix Figure 3 As can be seen from the spectrogram, at 1504 cm -1 , there is a characteristic peak of C-N in the amide group, and at 1597 cm -1 , there is a characteristic peak of C=O in the carboxyl group, proving that the reaction generates an amide structure.

[0104] Synthesis Example 4

[0105] N₂ was introduced into a 500 mL four-necked flask equipped with a stirring device. 2, 3.0 g (0.009 mol) of DA-4, 7.95 g (0.037 mol) of DN-1, and 164.29 g of NMP were added successively. After dissolution, 14.56 g (0.032 mol) of CA-1 and 3.48 g (0.014 mol) of CA-2 were added. After reacting at room temperature for 24 hours, 10.92 g (0.138 mol) of pyridine and 23.48 g (0.230 mol) of acetic anhydride were added successively, and imidization reaction was carried out at 50 °C for 5 hours. Then the reaction solution was poured into ethanol for precipitation, filtered by suction to obtain a pale yellow powdery solid. The obtained solid was washed with ethanol, then the solid was dissolved in NMP and precipitated again in ethanol, and filtered by suction to refine the polyimide. Finally, the refined polyimide was dried under vacuum for standby. The polyimide solid after vacuum drying was first dissolved in NMP, and then BC was added to prepare a solution with a polymer content of 6 wt%, NMP of 70 wt%, and BC of 24 wt% to obtain polyimide solution PI-4. The molecular weight Mw measured by GPC was 66276 g / mol, the viscosity was measured to be 46 mPa·s, and the infrared spectrum of the product is shown in the appendix Figure 4 , it can be found from the spectrum that at 1504 cm -1 is the characteristic peak of C-N in the amide group, and at 1601 cm -1 is the characteristic peak of C=O in the carboxyl group, proving that the reaction generates an amide structure.

[0106] Synthesis Example 5

[0107] N was introduced into a 500 mL four-necked flask equipped with a stirring device 2 , 4.0 g (0.007 mol) of DA-5, 6.52 g (0.031 mol) of DN-1, and 143.53 g of NMP were added successively. After dissolution, 11.94 g (0.027 mol) of CA-1 and 2.86 g (0.011 mol) of CA-2 were added. After reacting at room temperature for 24 hours, 9.02 g (0.114 mol) of pyridine and 19.40 g (0.190 mol) of acetic anhydride were added successively, and imidization reaction was carried out at 50 °C for 5 hours. Then the reaction solution was poured into ethanol for precipitation, filtered by suction to obtain a pale yellow powdery solid. The obtained solid was washed with ethanol, then the solid was dissolved in NMP and precipitated again in ethanol, and filtered by suction to refine the polyimide. Finally, the refined polyimide was dried under vacuum for standby. The polyimide solid after vacuum drying was first dissolved in NMP, and then BC was added to prepare a solution with a polymer content of 6 wt%, NMP of 70 wt%, and BC of 24 wt% to obtain polyimide solution PI-5. The molecular weight Mw measured by GPC was 67746 g / mol, the viscosity was measured to be 44 mPa·s, and the infrared spectrum of the product is shown in the appendix Figure 5, it can be found from the spectrogram that at 1504 cm -1 is the characteristic peak of C-N in the amide group, and at 1594 cm -1 is the characteristic peak of C=O in the carboxyl group, proving that the reaction generates an amide structure.

[0108] Synthesis Example 6

[0109] N is introduced into a 500 mL four-necked flask equipped with a stirring device 2 , and 4.0 g (0.007 mol) of DA-5, 6.12 g (0.031 mol) of DN-2, and 141.26 g of NMP are added in sequence. After dissolution, 11.94 g (0.027 mol) of CA-1 and 2.86 g (0.011 mol) of CA-2 are added. After reacting at room temperature for 24 hours, 9.02 g (0.114 mol) of pyridine and 19.40 g (0.190 mol) of acetic anhydride are added in sequence, and the imidization reaction is carried out at 50 °C for 5 hours. Then the reaction solution is poured into ethanol for precipitation, filtered by suction to obtain a pale yellow powdery solid. The obtained solid is washed with ethanol, then the solid is dissolved in NMP, and then precipitated in ethanol and filtered by suction to refine the polyimide. Finally, the refined polyimide is dried in vacuo for standby. The polyimide solid after vacuum drying is first dissolved in NMP, and then BC is added to prepare a solution with a polymer content of 6 wt%, NMP of 70 wt%, and BC of 24 wt% to obtain a polyimide solution PI-6. The molecular weight Mw measured by GPC is 68132 g / mol, and the viscosity is measured to be 48 mPa·s. The infrared spectrum of the product is shown in the appendix Figure 6 , it can be found from the spectrogram that at 1508 cm -1 is the characteristic peak of C-N in the amide group, and at 1601 cm -1 is the characteristic peak of C=O in the carboxyl group, proving that the reaction generates an amide structure.

[0110] Synthesis Example 7

[0111] N is introduced into a 500 mL four-necked flask equipped with a stirring device 2, successively add 4.0 g (0.007 mol) of DA-5, 6.52 g (0.031 mol) of DN-3, and 143.52 g of NMP. After it is dissolved, add 11.94 g (0.027 mol) of CA-1 and 2.86 g (0.011 mol) of CA-2. After reacting at room temperature for 24 hours, successively add 9.02 g (0.114 mol) of pyridine and 19.40 g (0.190 mol) of acetic anhydride, and react at 50 °C for 5 hours for imidization reaction. Then pour the reaction solution into ethanol for precipitation, filter by suction to obtain a pale yellow powdery solid. After washing the obtained solid with ethanol, dissolve the solid in NMP again, and then precipitate it in ethanol and filter by suction to refine the polyimide. Finally, vacuum dry the refined polyimide for standby. First dissolve the vacuum-dried polyimide solid in NMP, and then add BC to prepare a solution with a polymer content of 6 wt% in the solution, 70 wt% of NMP, and 24 wt% of BC to obtain polyimide solution PI-7. The GPC test shows that the molecular weight Mw is 69674 g / mol, the viscosity test is 48 mPa·s, and the infrared spectrum of the product is shown in the appendix Figure 7 , it can be found from the spectrum that at 1504 cm -1 is the characteristic peak of C-N in the amide group, and at 1601 cm -1 is the characteristic peak of C=O in the carboxyl group, proving that the reaction generates an amide structure.

[0112] Synthesis Example 8

[0113] Introduce N 2 into a 500 mL four-necked flask equipped with a stirring device, successively add 4.0 g (0.007 mol) of DA-5, 6.89 g (0.031 mol) of DN-4, and 145.62 g of NMP. After it is dissolved, add 11.94 g (0.027 mol) of CA-1 and 2.86 g (0.011 mol) of CA-2. After reacting at room temperature for 24 hours, successively add 9.02 g (0.114 mol) of pyridine and 19.40 g (0.190 mol) of acetic anhydride, and react at 50 °C for 5 hours for imidization reaction. Then pour the reaction solution into ethanol for precipitation, filter by suction to obtain a pale yellow powdery solid. After washing the obtained solid with ethanol, dissolve the solid in NMP again, and then precipitate it in ethanol and filter by suction to refine the polyimide. Finally, vacuum dry the refined polyimide for standby. First dissolve the vacuum-dried polyimide solid in NMP, and then add BC to prepare a solution with a polymer content of 6 wt% in the solution, 70 wt% of NMP, and 24 wt% of BC to obtain polyimide solution PI-8. The GPC test shows that the molecular weight Mw is 67973 g / mol, the viscosity test is 46 mPa·s, and the infrared spectrum of the product is shown in the appendix Figure 8, it can be found from the spectrogram that at 1504 cm -1 is the characteristic peak of C-N in the amide group, and at 1601 cm -1 is the characteristic peak of C=O in the carboxyl group, proving that the reaction generates an amide structure.

[0114] Synthesis Example 9

[0115] N is introduced into a 500 mL four-necked flask equipped with a stirring device 2 , and 6.0 g (0.028 mol) of DN-1, 3.75 g (0.019 mol) of DN-2, and 158.15 g of NMP are added in sequence. After dissolution, 14.65 g (0.033 mol) of CA-1 and 3.51 g (0.014 mol) of CA-2 are added. After reacting at room temperature for 24 hours, 11.15 g (0.141 mol) of pyridine and 23.99 g (0.235 mol) of acetic anhydride are added in sequence, and the imidization reaction is carried out at 50 °C for 5 hours. Then the reaction solution is poured into ethanol for precipitation, filtered by suction to obtain a pale yellow powdery solid. The obtained solid is washed with ethanol, then the solid is dissolved in NMP, and then precipitated in ethanol, filtered by suction to refine the polyimide. Finally, the refined polyimide is dried under vacuum for standby. The polyimide solid after vacuum drying is first dissolved in NMP, and then BC is added to prepare a solution with a polymer content of 6 wt%, NMP of 70 wt%, and BC of 24 wt% to obtain a polyimide solution PI-9. The molecular weight Mw measured by GPC is 67452 g / mol, and the viscosity is measured to be 47 mPa·s. The infrared spectrum of the product is shown in the appendix Figure 9 , it can be found from the spectrogram that at 1508 cm -1 is the characteristic peak of C-N in the amide group, and at 1601 cm -1 is the characteristic peak of C=O in the carboxyl group, proving that the reaction generates an amide structure.

[0116] Synthesis Example 10

[0117] N is introduced into a 500 mL four-necked flask equipped with a stirring device 2, 6.0 g (0.028 mol) of DN-1, 3.99 g (0.019 mol) of DN-3, and 159.54 g of NMP were added successively. After dissolution, 14.65 g (0.033 mol) of CA-1 and 3.51 g (0.014 mol) of CA-2 were added. After reacting at room temperature for 24 hours, 11.15 g (0.141 mol) of pyridine and 23.99 g (0.235 mol) of acetic anhydride were added successively, and imidization reaction was carried out at 50 °C for 5 hours. Then the reaction solution was poured into ethanol for precipitation, and filtered by suction to obtain a pale yellow powdery solid. The obtained solid was washed with ethanol, then the solid was dissolved in NMP, and then precipitated in ethanol and filtered by suction to refine the polyimide. Finally, the refined polyimide was vacuum dried for standby. The vacuum-dried polyimide solid was first dissolved in NMP, and then BC was added to prepare a solution with a polymer content of 6 wt%, NMP of 70 wt%, and BC of 24 wt% to obtain polyimide solution PI-10. The molecular weight Mw measured by GPC was 69521 g / mol, the viscosity was measured to be 46 mPa·s, and the infrared spectrum of the product is shown in the appendix Figure 10 , it can be found from the spectrum that at 1504 cm -1 is the characteristic peak of C-N in the amide group, and at 1601 cm -1 is the characteristic peak of C=O in the carboxyl group, proving that the reaction generates an amide structure.

[0118] Synthesis Example 11

[0119] N was introduced into a 500 mL four-necked flask equipped with a stirring device 2 , 6.0 g (0.028 mol) of DN-1, 4.23 g (0.019 mol) of DN-4, and 160.82 g of NMP were added successively. After dissolution, 14.65 g (0.033 mol) of CA-1 and 3.51 g (0.014 mol) of CA-2 were added. After reacting at room temperature for 24 hours, 11.15 g (0.141 mol) of pyridine and 23.99 g (0.235 mol) of acetic anhydride were added successively, and imidization reaction was carried out at 50 °C for 5 hours. Then the reaction solution was poured into ethanol for precipitation, and filtered by suction to obtain a pale yellow powdery solid. The obtained solid was washed with ethanol, then the solid was dissolved in NMP, and then precipitated in ethanol and filtered by suction to refine the polyimide. Finally, the refined polyimide was vacuum dried for standby. The vacuum-dried polyimide solid was first dissolved in NMP, and then BC was added to prepare a solution with a polymer content of 6 wt%, NMP of 70 wt%, and BC of 24 wt% to obtain polyimide solution PI-11. The molecular weight Mw measured by GPC was 67884 g / mol, the viscosity was measured to be 45 mPa·s, and the infrared spectrum of the product is shown in the appendixFigure 11 As can be seen from the spectrogram, at 1504 cm -1 , there is a characteristic peak of C-N in the amide group, and at 1601 cm -1 , there is a characteristic peak of C=O in the carboxyl group, proving that the reaction produces an amide structure.

[0120] Synthesis Example 12

[0121] N is introduced into a 500 mL four-necked flask equipped with a stirring device 2 . Then, 3.00 g (0.009 mol) of DA-4, 7.46 g (0.037 mol) of DN-2, and 161.52 g of NMP are added in sequence. After dissolution, 14.56 g (0.032 mol) of CA-1 and 3.49 g (0.014 mol) of CA-2 are added. After reacting at room temperature for 24 hours, NMP and BC are added in sequence to prepare a solution with a polymer content of 6 wt%, NMP of 70 wt%, and BC of 24 wt% to obtain a polyamic acid solution PAA-1. The molecular weight Mw measured by GPC is 68498 g / mol, the viscosity is 46 mPa·s, and the infrared spectrum of the product is shown in the appendix Figure 12 As can be seen from the spectrogram, at 1504 cm -1 , there is a characteristic peak of C-N in the amide group, and at 1601 cm -1 , there is a characteristic peak of C=O in the carboxyl group, proving that the reaction produces an amide structure.

[0122] Synthesis Example 13

[0123] N is introduced into a 500 mL four-necked flask equipped with a stirring device 2 . Then, 3.00 g (0.009 mol) of DA-4, 7.95 g (0.037 mol) of DN-3, and 164.28 g of NMP are added in sequence. After dissolution, 14.56 g (0.032 mol) of CA-1 and 3.49 g (0.014 mol) of CA-2 are added. After reacting at room temperature for 24 hours, NMP and BC are added in sequence to prepare a solution with a polymer content of 6 wt%, NMP of 70 wt%, and BC of 24 wt% to obtain a polyamic acid solution PAA-2. The molecular weight Mw measured by GPC is 69554 g / mol, the viscosity is 48 mPa·s, and the infrared spectrum of the product is shown in the appendix Figure 13 As can be seen from the spectrogram, at 1510 cm -1 , there is a characteristic peak of C-N in the amide group, and at 1622 cm -1 , there is a characteristic peak of C=O in the carboxyl group, proving that the reaction produces an amide structure.

[0124] Synthesis Example 14

[0125] N is introduced into a 500 mL four-necked flask equipped with a stirring device 2 , 3.00 g (0.009 mol) of DA-4, 8.40 g (0.037 mol) of DN-4, and 166.83 g of NMP are added in sequence. After dissolution, 14.56 g (0.032 mol) of CA-1 and 3.49 g (0.014 mol) of CA-2 are added. After reacting at room temperature for 24 hours, NMP and BC are added in sequence to prepare a solution with a polymer content of 6 wt%, NMP of 70 wt%, and BC of 24 wt% to obtain a polyamic acid solution PAA-3. The molecular weight Mw measured by GPC is 69152 g / mol, the viscosity is 47 mPa·s, and the infrared spectrum of the product is shown in the appendix Figure 14 , it can be found from the spectrum that at 1504 cm -1 is the characteristic peak of C-N in the amide group, and at 1601 cm -1 is the characteristic peak of C=O in the carboxyl group, proving that the reaction generates an amide structure

[0126] Synthesis Example 15

[0127] N is introduced into a 500 mL four-necked flask equipped with a stirring device 2 , 5.00 g (0.025 mol) of DN-2, 3.55 g (0.017 mol) of DN-3, and 139.80 g of NMP are added in sequence. After dissolution, 13.0 g (0.029 mol) of CA-1 and 3.11 g (0.013 mol) of CA-2 are added. After reacting at room temperature for 24 hours, NMP and BC are added in sequence to prepare a solution with a polymer content of 6 wt%, NMP of 70 wt%, and BC of 24 wt% to obtain a polyamic acid solution PAA-4. The molecular weight Mw measured by GPC is 67462 g / mol, the viscosity is 46 mPa·s, and the infrared spectrum of the product is shown in the appendix Figure 15 , it can be found from the spectrum that at 1504 cm -1 is the characteristic peak of C-N in the amide group, and at 1601 cm -1 is the characteristic peak of C=O in the carboxyl group, proving that the reaction generates an amide structure

[0128] Synthesis Example 16

[0129] N is introduced into a 500 mL four-necked flask equipped with a stirring device 2, successively add 5.00 g (0.025 mol) of DN-2, 3.75 g (0.017 mol) of DN-4, and 140.94 g of NMP. After it is dissolved, add 13.0 g (0.029 mol) of CA-1 and 3.11 g (0.013 mol) of CA-2. After reacting at room temperature for 24 hours, successively add NMP and BC to prepare a solution with a polymer content of 6 wt%, NMP of 70 wt%, and BC of 24 wt% to obtain a polyamic acid solution PAA-5. The molecular weight Mw measured by GPC is 68523 g / mol, the viscosity is 47 mPa·s, and the infrared spectrum of the product is shown in the appendix Figure 16 , it can be found from the spectrum that at 1504 cm -1 is the characteristic peak of C-N in the amide group, and at 1601 cm -1 is the characteristic peak of C=O in the carboxyl group, proving that the reaction generates an amide structure.

[0130] Example 1

[0131] Stir 40.00 g of the polyimide solution PI-1 obtained in Synthesis Example 1 and 60.00 g of the polyamic acid solution PAA-1 obtained in Synthesis Example 12 at room temperature for 3 hours to obtain a liquid crystal aligning agent 1.

[0132] Example 2

[0133] Stir 40.00 g of the polyimide solution PI-2 obtained in Synthesis Example 2 and 60.00 g of the polyamic acid solution PAA-1 obtained in Synthesis Example 12 at room temperature for 3 hours to obtain a liquid crystal aligning agent 2.

[0134] Example 3

[0135] Stir 40.00 g of the polyimide solution PI-3 obtained in Synthesis Example 3 and 60.00 g of the polyamic acid solution PAA-1 obtained in Synthesis Example 12 at room temperature for 3 hours to obtain a liquid crystal aligning agent 2.

[0136] Example 4

[0137] Stir 40.00 g of the polyimide solution PI-4 obtained in Synthesis Example 4 and 60.00 g of the polyamic acid solution PAA-1 obtained in Synthesis Example 12 at room temperature for 3 hours to obtain a liquid crystal aligning agent 4.

[0138] Example 5

[0139] Stir 40.00 g of the polyimide solution PI-5 obtained in Synthesis Example 5 and 60.00 g of the polyamic acid solution PAA-1 obtained in Synthesis Example 12 at room temperature for 3 hours to obtain a liquid crystal aligning agent 5.

[0140] Example 6

[0141] 40.00 g of the polyimide solution PI-6 obtained in Synthesis Example 6 and 60.00 g of the polyamic acid solution PAA-1 obtained in Synthesis Example 12 were stirred at room temperature for 3 hours to obtain a liquid crystal aligning agent 6.

[0142] Example 7

[0143] 40.00 g of the polyimide solution PI-7 obtained in Synthesis Example 7 and 60.00 g of the polyamic acid solution PAA-1 obtained in Synthesis Example 12 were stirred at room temperature for 3 hours to obtain a liquid crystal aligning agent 7.

[0144] Example 8

[0145] 40.00 g of the polyimide solution PI-8 obtained in Synthesis Example 8 and 60.00 g of the polyamic acid solution PAA-1 obtained in Synthesis Example 12 were stirred at room temperature for 3 hours to obtain a liquid crystal aligning agent 8.

[0146] Example 9

[0147] 40.00 g of the polyimide solution PI-5 obtained in Synthesis Example 5 and 60.00 g of the polyamic acid solution PAA-2 obtained in Synthesis Example 13 were stirred at room temperature for 3 hours to obtain a liquid crystal aligning agent 9.

[0148] Example 10

[0149] 40.00 g of the polyimide solution PI-5 obtained in Synthesis Example 5 and 60.00 g of the polyamic acid solution PAA-3 obtained in Synthesis Example 14 were stirred at room temperature for 3 hours to obtain a liquid crystal aligning agent 10.

[0150] Comparative Example 1

[0151] 40.00 g of the polyimide solution PI-9 obtained in Synthesis Example 9 and 60.00 g of the polyamic acid solution PAA-2 obtained in Synthesis Example 13 were stirred at room temperature for 3 hours to obtain a liquid crystal aligning agent 11.

[0152] Comparative Example 2

[0153] 40.00 g of the polyimide solution PI-10 obtained in Synthesis Example 10 and 60.00 g of the polyamic acid solution PAA-2 obtained in Synthesis Example 13 were stirred at room temperature for 3 hours to obtain a liquid crystal aligning agent 12.

[0154] Comparative Example 3

[0155] 40.00 g of the polyimide solution PI-11 obtained in Synthesis Example 11 and 60.00 g of the polyamic acid solution PAA-2 obtained in Synthesis Example 13 were stirred at room temperature for 3 hours to obtain a liquid crystal aligning agent 13.

[0156] Comparative Example 4

[0157] 40.00 g of the polyimide solution PI-5 obtained in Synthesis Example 5 and 60.00 g of the polyamic acid solution PAA-4 obtained in Synthesis Example 15 were stirred at room temperature for 3 hours to obtain a liquid crystal aligning agent 14.

[0158] Comparative Example 5

[0159] 40.00 g of the polyimide solution PI-5 obtained in Synthesis Example 5 and 60.00 g of the polyamic acid solution PAA-5 obtained in Synthesis Example 16 were stirred at room temperature for 3 hours to obtain a liquid crystal aligning agent 15.

[0160] Comparative Example 6

[0161] 40.00 g of the polyimide solution PI-9 obtained in Synthesis Example 9 and 60.00 g of the polyamic acid solution PAA-4 obtained in Synthesis Example 15 were stirred at room temperature for 3 hours to obtain a liquid crystal aligning agent 16.

[0162] Comparative Example 7

[0163] 40.00 g of the polyimide solution PI-9 obtained in Synthesis Example 9 and 60.00 g of the polyamic acid solution PAA-5 obtained in Synthesis Example 16 were stirred at room temperature for 3 hours to obtain a liquid crystal aligning agent 17.

[0164] (1) Fabrication of FFS-driven liquid crystal cell

[0165] On a glass substrate with electrodes, a liquid crystal aligning agent was coated by spin coating. On the substrate used, an ITO electrode having a dense pattern and constituting a counter electrode was formed as the first layer. On the counter electrode of the first layer, a SiN (silicon nitride) film formed by CVD (chemical vapor deposition) was formed as the second layer. The film thickness of the SiN film of the second layer was 500 nm, which functioned as an interlayer insulating film. On the SiN film of the second layer, a comb-shaped pixel electrode (electrode width: 3 μm, electrode pitch: 6 μm, electrode height: 50 nm) formed by patterning an ITO film was disposed as the third layer.

[0166] The liquid crystal aligning agent filtered through a filter with a pore size of 1.0 μm was spin-coated on the surface of the above-mentioned glass substrate. After drying for 2 minutes on a hot plate at 80°C, it was cured in a hot air circulation oven at 230°C for 14 minutes to form a coating film with a film thickness of 100 nm. The coating film surface was subjected to photo-alignment treatment by irradiating ultraviolet light with a wavelength of 254 nm through a polarizing plate at 500 mJ / cm 2 2.

[0167] Taking the above two substrates as a group, a sealant was printed on the substrates, and another substrate was attached so that the liquid crystal alignment film surfaces faced each other and the brushing directions were anti-parallel. The sealant was cured to produce an empty cell with a gap of 4 μm. Liquid crystal MLC-7028 (Merck) was injected into the empty cell by a vacuum injection method, and the injection port was sealed. In order to remove the flow alignment during liquid crystal injection, it was heated at 120°C and then slowly cooled to room temperature, and polarizers were attached to both outer sides of the substrate to fabricate an FFS-driven liquid crystal cell.

[0168] (2) Evaluation of thermal decomposition temperature

[0169] The thermal decomposition temperature (T 5％ ), which represents the 5% thermal weight loss temperature here, refers to the temperature corresponding to when the mass of the substance decreases by 5% during the heating process of the substance. This temperature can usually be used to represent the thermal stability of the substance.

[0170] The prepared polyimide film was placed in a thermogravimetric analyzer (TGA55 series of TA Instruments, USA). The heating program was: from 10°C / min to 600°C, and held at a constant temperature for 1.0 min. The evaluation results are shown in Table 1.

[0171] (3) Evaluation of liquid crystal alignment

[0172] The liquid crystal aligning agents 1 to 20 were respectively made into the FFS-driven liquid crystal cells described in the above (1). Using a microscope at a magnification of 50 times, the presence or absence of abnormal regions where light and dark changes occurred when a voltage of 5 V was turned on and off was observed. The case where no abnormal region was observed was set as "excellent" in terms of alignment, and the case where an abnormal region was observed was set as "poor". The evaluation results are shown in Table 1.

[0173] (4) Evaluation of residual direct current charge (RDC)

[0174] The liquid crystal display cell was placed in an oven at 60°C, and a DC voltage of 5 V was applied to the liquid crystal display cell for 1 hour. After short-circuiting for 1 second, the voltage value of the liquid crystal display cell was measured, and the voltage value after 10 minutes was used as the RDC of the liquid crystal display cell. The test results are shown in Table 1.

[0175] (5) Evaluation of voltage holding ratio (VHR)

[0176] After applying a voltage of 5 V to the fabricated FFS-driven liquid crystal cell with an application time of 60 microseconds and a span of 167 milliseconds, the voltage holding ratio 167 milliseconds after the application release was measured. During the measurement, the temperature of the liquid crystal cell was set to 25 °C and 60 °C respectively for the measurement. The evaluation results are shown in Table 1.

[0177] Table 1

[0178]

[0179] From the above results, it can be seen that after introducing the diamine monomer of the present invention into the polyimide and preparing the liquid crystal aligning agent and curing it into a polyimide film, the 5% thermal weight loss temperature is greater than 400 °C. It can be seen that the polyimide containing the diamine compound of the present invention has good thermal stability; at the same time, the liquid crystal cell has excellent orientation, and the DC charge residual voltage value is very small and can be quickly relaxed. Even under the condition of 60 °C, a high voltage holding ratio can be maintained.

[0180] Therefore, the reliability and optoelectronic performance of the liquid crystal display element having the liquid crystal alignment film obtained from the liquid crystal aligning agent of the present invention are excellent, and it can be suitably used for large-screen and high-definition liquid crystal TVs, etc.

[0181] As described above, only several embodiments of the present application are presented, and no form of limitation is imposed on the present application. Although the present application is disclosed with preferred embodiments, it is not intended to limit the present application. Any person skilled in the art, without departing from the scope of the technical solution of the present application, making some changes or modifications using the disclosed technical content is equivalent to equivalent implementation cases and all belong to the scope of the technical solution.

Claims

1. A liquid crystal alignment agent, characterized in that: The liquid crystal alignment agent includes polymer A, solvent B and other polymers; The polymer A is a composition of polyimide and polyamic acid, wherein the polyimide is one or more components of a polymer obtained by dehydrating polyamic acid, and has a structure as shown in formula (1): In the above formula (1), R1 is a tetravalent organic group of tetracarboxylic dianhydride, wherein the tetracarboxylic dianhydride includes at least one of aliphatic tetracarboxylic dianhydride and aromatic tetracarboxylic dianhydride; R2 is selected from the derivatives of diamine compounds without terminal amine groups, and the diamine compounds include diamine compounds DA and diamine compounds DN; The diamine compound DA is selected from at least one of compounds (DA-1), (DA-2), (DA-3), (DA-4), and (DA-5); The diamine compound DN is selected from at least one of (DN-1), (DN-2), (DN-3), and (DN-4); The diamine compound DA accounts for 10-100% of the total molar amount of the diamine compound; The structural formula of the diamine compound is shown below: The preparation method of the polyimide comprises the following steps: Mixing raw materials containing polyamic acid, an organic solvent, a dehydrating agent and an alkaline catalyst, and reacting them to obtain a product containing polyimide; The weight average molecular weight (Mw) of the polyimide is 2,000 to 500,000.

2. The liquid crystal alignment agent according to claim 1, characterized in that: The aliphatic tetracarboxylic dianhydride is selected from at least one of 1,2,3,4-cyclobutanetetracarboxylic dianhydride, 1,3-dimethyl-1,2,3,4-cyclobutanetetracarboxylic dianhydride, 1,2,3,4-cyclopentanetetracarboxylic dianhydride, 1,2,3,4-cyclohexanetetracarboxylic dianhydride, 2,3,5-tricarboxycyclopentylacetic dianhydride, 3,4-dicarboxy-1-cyclohexylsuccinic dianhydride, 3,4-dicarboxy-1,2,3,4-tetrahydro-1-naphthalenesuccinic dianhydride, bicyclo[3.3.0]octane-2,4,6,8-tetracarboxylic dianhydride, 1,2,3,4-butanetetracarboxylic dianhydride, 2,3,4,5-tetrahydrofurantetracarboxylic dianhydride, and bicyclo[2.2.2]oct-7-ene-2,3,5,6-tetracarboxylic dianhydride; The aromatic tetracarboxylic dianhydride is selected from at least one of pyromellitic dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride, 2,2',3,3'-biphenyltetracarboxylic dianhydride, 2,3,3',4'-biphenyltetracarboxylic dianhydride, 3,3',4,4'-benzophenonetetracarboxylic dianhydride, 2,3,3',4'-benzophenonetetracarboxylic dianhydride, bis(3,4-dicarboxyphenyl)ether dianhydride, bis(3,4-dicarboxyphenyl)sulfone dianhydride, 1,2,5,6-naphthalenetetracarboxylic dianhydride, 2,3,6,7-naphthalenetetracarboxylic dianhydride, 1,4,5,8-naphthalenetetracarboxylic dianhydride, 4,4'-(4,4'-isopropyldiphenyloxy)phthalic anhydride, 4,4'-(hexafluoroisopropylene)phthalic anhydride, and 4,4'-isopropyl-bis(phthalic anhydride).

3. The liquid crystal alignment agent according to claim 1, characterized in that: The diamine compound DA accounts for 10-30% of the total molar amount of the diamine compounds.

4. The liquid crystal alignment agent according to claim 1, characterized in that: The dehydrating agent is selected from at least one of acetic anhydride, propionic anhydride and trifluoroacetic anhydride; The alkaline catalyst is selected from at least one of pyridine, colidine, lutidine and triethylamine; The reaction temperature is between -20°C and 140°C; The reaction time is 1 to 100 hours.

5. The liquid crystal alignment agent according to claim 1, characterized in that: The amount of the alkaline catalyst is 0.5 to 30 times the mole of the polyamic acid; The amount of the dehydrating agent is 1 to 50 times the mole of the polyamic acid; The organic solvent is selected from at least one of N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, N-methylcaprolactam, N-methyl-2-pyrrolidone, γ-butyrolactone, methyl ethyl ketone, cyclohexanone, cyclopentanone, 4-hydroxy-4-methyl-2-pentanone, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, ethylene glycol methyl ethyl ether, ethylene glycol dimethyl ether, and dimethyl sulfoxide; The weight average molecular weight (Mw) of the polyimide is 5,000 to 300,000.

6. The liquid crystal alignment agent according to claim 1, characterized in that: The alkaline catalyst is 2 to 20 times the mole of the polyamic acid.

7. The liquid crystal alignment agent according to claim 1, characterized in that: The amount of the dehydrating agent is 3 to 30 times the mole of the polyamic acid.

8. The liquid crystal alignment agent according to claim 1, characterized in that: The weight average molecular weight (Mw) of the polyimide is 10,000 to 100,000.

9. The liquid crystal alignment agent according to claim 1, characterized in that: The solvent B is selected from at least one of N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, N-methylcaprolactam, N-methyl-2-pyrrolidone, γ-butyrolactone, methyl ethyl ketone, cyclohexanone, cyclopentanone, 4-hydroxy-4-methyl-2-pentanone, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, ethylene glycol methyl ethyl ether, ethylene glycol dimethyl ether, and dimethyl sulfoxide; The other polymer is at least one selected from acrylic polymers, methacrylic polymers, cellulose polymers, polystyrene, polysiloxane, and polyamide.

10. The liquid crystal alignment agent according to claim 1, characterized in that: The liquid crystal alignment agent also includes a solvent C; The solvent C is selected from ethanol, isopropanol, 1-butanol, 2-butanol, isobutanol, tert-butanol, ethyl cellosolve, butyl cellosolve, ethyl carbitol, butyl carbitol, ethyl carbitol acetate, 1-pentanol, 2-pentanol, 3-pentanol, ethylene glycol, 1-methoxy-2-propanol, 2-methyl-1-butanol, isopentanol, tert-pentanol, 1-ethoxy-2-propanol, 1-butoxy-2-propanol, 1-phenoxy-2-propanol, propanol At least one of glycol monoacetate, propylene glycol diacetate, propylene glycol-1-monomethyl ether-2-acetate, propylene glycol-1-monoethyl ether, 3-methyl-2-butanol, neopentyl alcohol, 1-hexanol, 2-methyl-1-pentanol, butyl cellosolve acetate, dipropylene glycol, 2-(2-ethoxypropoxy)propanol, furfuryl alcohol, diethylene glycol, propylene glycol monobutyl ether, methyl lactate, ethyl lactate, n-propyl lactate, n-butyl lactate, and isoamyl lactate.

11. The liquid crystal alignment agent according to claim 1, characterized in that: The weight ratio of the polymer A to the solvent B is 1:5-50; The content of the other polymer in the liquid crystal alignment agent is 1 to 30 wt %; The content of the solvent C in the liquid crystal alignment agent is preferably 5 to 50 wt %.

12. The liquid crystal alignment agent according to claim 1, characterized in that: The weight ratio of the polymer A to the solvent B is 1:10-50.

13. The liquid crystal alignment agent according to claim 1, characterized in that: The content of other polymers in the liquid crystal alignment agent is 5 to 20 wt %.

14. The liquid crystal alignment agent according to claim 1, characterized in that: The content of the solvent C in the liquid crystal alignment agent is 10-30 wt %.

15. A liquid crystal alignment film, characterized in that: A liquid crystal alignment film prepared from the liquid crystal alignment agent according to any one of claims 1 to 14.

16. A liquid crystal display element, characterized in that: The liquid crystal alignment film according to claim 15 is used as a liquid crystal display element.

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