CN116120551A

CN116120551A - Method for improving water tolerance and spraying effect of polyimide orientation agent

Info

Publication number: CN116120551A
Application number: CN202211702718.6A
Authority: CN
Inventors: 聂永惠; 王胜林; 黎厚明
Original assignee: Changsha Dalton Electronic Materials Co ltd
Current assignee: Changsha Dalton Electronic Materials Co ltd
Priority date: 2022-12-28
Filing date: 2022-12-28
Publication date: 2023-05-16

Abstract

The present invention discloses a polyimide which is modified polyimide and is prepared from at least one compound containing polyimide obtained by imidizing polyamide acid obtained by reacting diamine and tetracarboxylic dianhydride as polymers; the modified polyimide has obviously improved affinity or compatibility to water, is not easy to cause polyimide precipitation or hydrolysis, and can effectively solve the problem that spraying is not smooth or holes are blocked easily when a tank is used for switching PI liquid or idle in mass production, thereby achieving the aim of improving the Inkjet effect of the PI orienting agent. Has practical application value.

Description

Method for improving water tolerance and spraying effect of polyimide orientation agent

Technical Field

The invention relates to the technical field of material science, in particular to a method for improving water tolerance and spraying effect of a polyimide orientation agent.

Background

The TFT-LCD has the advantages of excellent performance, good mass production characteristics, high automation degree and wide development space, and is a main stream product in the display field. The TFT-LCD production process and the process are complicated, and a Layer of polymer organic film having an anchoring effect on liquid crystal, called Alignment Layer (Alignment Layer), is used as a liquid crystal Alignment film, which is an Alignment Layer obtained by coating and baking a solution of Polyimide precursor such as Polyamide acid (PAA) or soluble Polyimide (PI) as a main component, most widely used as a Polyimide material. Its function is to align the liquid crystal molecules in the designed direction. The film forming process in the TFT-LCD production box making process mainly comprises the following steps: wet cleaning before printing, cleaning, drying and cooling, dry cleaning before printing, PI film coating, PI pre-baking and solidifying, PI film printing quality inspection, substrate output and box forming process. PI film coating is a core process for PI film formation process, and a liquid crystal alignment film forming method is generally known as spin coating, dip coating, flexographic printing, and the like. However, these film forming methods are complicated and costly, and are not suitable for mass production. PI film coating is completed by adopting PI spraying (Inkjet) equipment in mass production, a PI spraying machine is provided with a row of printing spray heads (Head) to directly spray PI liquid onto a substrate, the realization mode is that piezoelectric ceramics in the spray heads deform to spray the PI liquid from small holes of the spray heads (nozzles), a high-density PI liquid drop array is formed by utilizing the movement of the spray heads or a glass substrate carrying platform, and finally PI liquid drops are connected in a diffusion mode to form a film under the action of surface tension, namely, a method of dripping fine liquid drops on the substrate and forming the film through the infiltration expansion of the liquid is adopted. Through debugging parameters such as machine voltage, frequency, coating speed and the like, PI alignment films with various film thicknesses can be prepared. The use of PI spray coating has the advantage of less waste of coating liquid, and can reduce the cost of the liquid crystal panel and improve the production efficiency.

The PI spraying coating equipment nozzle is very small, can accurately control liquid drops to ng level, and the tolerance of PI liquid can influence the spraying effect to a certain extent, and is mainly characterized in that the tolerance of PI to water and the volatilization of solvent are easy. Polyimide orientation agent is generally formed by condensing aromatic diamine and tetracarboxylic anhydride into five-membered imide ring to form molecular chain, which has high rigidity and strong acting force between molecular chains, thus the polyimide is relatively indissolvable, if PI is exposed in air for a long time, the PI is easy to absorb moisture and carbon dioxide in air to combine, and meanwhile, solvent volatilizes, thus PI is easy to be precipitated or hydrolyzed. During mass production, when the tank is used for switching PI liquid or idle, the spraying machine is easier to cause the situation of unsmooth spraying or hole blocking, thereby influencing the mass productivity and the yield. In order to improve the situation, a method for improving the water tolerance and the spraying effect of the polyimide aligning agent is invented, so that the aim of improving the Inkjet effect of the PI aligning agent is fulfilled.

Disclosure of Invention

In view of the drawbacks of the prior art, an object of the present invention is to provide a method for improving water tolerance and spraying effect of a polyimide aligning agent, so as to solve the problems set forth in the background art.

The invention solves the technical problems by adopting the following technical scheme:

the present invention provides an improved water resistance of a polyimide aligning agent, which is a modified polyimide composed of at least one compound containing polyimide obtained by imidizing a polyamic acid obtained by reacting a diamine and a tetracarboxylic dianhydride as a polymer;

the method for improving the water tolerance of the polyimide orientation agent comprises the following steps:

s1, preparing a polyimide acid (PAA) solution: dissolving diamine monomer in polar aprotic solvent, and then adding dianhydride monomer to react to obtain viscous transparent polyimide acid solution;

s2, preparing a Polyimide (PI) solution:

s21, synthesizing according to the step S1 to obtain a polyimide acid solution;

s22, adding a dehydrating agent and a catalyst into the polyimide acid solution obtained by the reaction in S21, performing imidization reaction by using a chemical imidization method, controlling the imidization rate of polyimide by adjusting the catalyst amount, the reaction temperature and the reaction time, removing a dehydrator and the catalyst by rotary evaporation, adding a proper amount of polar aprotic solvent, removing most of the solvent by rotary evaporation, repeating the above operation for three times, thus obtaining polyimide solution, controlling the final solid content to be more than 20%, and finally using a diluent to reach 5%wt, wherein a base solvent system is consistent with the S21;

s3, mixing P I with PAA solution: mixing P I obtained in the steps S1 and S2 with PAA solution in proportion, controlling the proportion of the PI solution to be 10-50%, and curing at 60-80 ℃ for 0.5-4 hours to obtain the mixed (P I/PAA) orientation agent;

s4, a modification method: and (3) continuously reacting the S1 or the S2 or the orientation agent synthesized by the S1, the S2 or the S3 with the modifier, gradually adding the modifier into the polyamic acid solution under the protection of nitrogen, stirring for 0.5-4h, and reacting at 0-80 ℃.

Preferably, the molar ratio of diamine to dianhydride in S1 is 100: (85-100), wherein the reaction temperature of the S1 is-15-100 ℃, the reaction time is 0.5-48h, and the reaction solid content of the polyimide solution is 5-50%.

Preferably, the diamine is one or more of alicyclic diamine, aromatic diamine, heterocyclic diamine, and aliphatic diamine.

Preferably, the solvent in the S1 is one or more of gamma-butyrolactone, N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, N-dimethylformamide, N-diethylformamide, N-dimethylacetamide, 2-pyrrolidone, N-vinyl-2-pyrrolidone, dimethyl sulfoxide and dimethyl sulfone.

Preferably, 1-30% wt of a leveling agent is also added in the S1, wherein the leveling agent is one or more of ethylene glycol monobutyl ether, diethylene glycol monomethyl ether and diethylene glycol diethyl ether.

Preferably, the dehydrating agent in the S22 is used in a proportion of 1-20 times of the mole number of the dianhydride, the catalyst is used in a proportion of 1-10 times of the mole number of the dianhydride, the reaction temperature of the chemical imidization is-20-200 ℃, and the reaction time is 0.5-48h.

Preferably, the dehydrating agent in S22 is one or more of acetic anhydride, propionic anhydride and trifluoroacetic anhydride, the catalyst is one or more of pyridine, collidine, lutidine and triethylamine, and the imidization rate of polyimide contained in the liquid crystal aligning agent in S22 is above 40%.

Preferably, the modifier in S4 has the following characteristics, and the structure is as follows:

ra and Rb are independently alkyl groups with 1-6 carbon atoms or hydroxyalkyl groups with 1-6 carbon atoms or Ra and Rb can be combined with each other to form a single ring, and Ra and Rb can be independent of each other and different in quantity and type, wherein Rc is alkyl with 1-6 carbon atoms;

the specific structure of the general formula is as follows:

preferably, the modifier in S4 reacts with polyimide as follows:

ra and Rb are independently alkyl groups of 1-6 carbon atoms or hydroxyalkyl groups of 1-6 carbon atoms or Ra and Rb can combine with each other to form a single ring, and Ra and Rb can be independent of each other and different in number and type, wherein Rc is alkyl of 1-6 carbon atoms.

The invention also provides a method for improving the spraying effect of the water tolerance of the polyimide orientation agent, which comprises the following steps:

a1, filtering a synthesized polyimide solution orientation agent by a microporous filter membrane;

a2, spraying the orientation agent solution in a1 on ITO glass, then sequentially placing the ITO glass substrate at 70-110 ℃ for prebaking 10-20min, and then imidizing at 200-250 ℃ for 30-60min;

a3, rubbing the polyimide film on the ITO glass substrate in the a2 by using a rubbing machine, wherein the rubbing angle is 45 degrees;

and a4, bonding the two ITO glass substrates coated with the liquid crystal orientation film prepared in the step a3 into a box by using thermosetting glue containing 4um spacer particles, enabling friction surfaces of the two substrates to face each other and enabling friction directions to be orthogonal, filling liquid crystal, and sealing by using the thermosetting glue to obtain the liquid crystal box.

Compared with the prior art, the invention has the following beneficial effects:

the modified polyimide has obviously improved affinity or compatibility to water, is not easy to cause polyimide precipitation or hydrolysis, and can effectively solve the problem that spraying is not smooth or holes are blocked easily when a tank is used for switching PI liquid or idle in mass production, thereby achieving the aim of improving the Inkjet effect of the PI orienting agent. Has practical application value.

Drawings

FIG. 1 is a schematic diagram of the evaluation of PI water resistance test of the present invention.

Detailed Description

The following description of the embodiments of the present invention will be made clearly and fully with reference to the accompanying drawings, in which it is evident that the embodiments described are only some, but not all embodiments of the invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.

A typical liquid crystal aligning agent is a polymer resin solution. The polyamic acid is prepared by polycondensation of at least one dianhydride and at least one diamine, and the polyimide is prepared by dehydrative cyclization (i.e., imidization) of the polyamic acid. Types of liquid crystal aligning agents used may be classified as polyamic acid (PAA) resin solutions, polyimide (PI) resin solutions, or PI-mixed PAA resin solutions.

The preparation method comprises the steps of firstly dissolving diamine monomer in polar aprotic solvent, and then adding tetracarboxylic dianhydride monomer for reaction to obtain viscous transparent polyimide acid solution. Or conversely, a method of adding a diamine component to a solution obtained by dispersing or dissolving a tetracarboxylic dianhydride component in an organic solvent, a method of alternately adding a tetracarboxylic dianhydride component and a diamine component, or the like. The precursor PAA solution can be obtained, if the precursor PAA solution is required to be prepared into PI type, the PI type PAA solution is converted into polyimide solution through proper heat or chemical treatment (imidization or cyclodehydration), the chemical imidization treatment is usually used in a laboratory stage, the imidization rate is controlled to be lower than 60%, and if the control is not good, the problems of poor solubility, gel, afterimage during application and the like can be caused. The imidization process is schematically represented by the formula:

in the general formula of the structure, the structural formula,

represents a dianhydride residue;

Represents a diamine residue; n represents the number of repeating units.

No alignment agent, either a polyamic acid (PAA) resin solution, a Polyimide (PI) resin solution, or a P I mixed PAA type resin solution, is completely 100% imidized, and even if an alignment film is printed and cured at about 230 ℃ during LCD production, there is only 30 to 80% imidization, and thus, a large amount of non-imidized carboxylic acid groups are present in the polymer resin of the alignment film, and by utilizing this property, we can modify the polyimide-based alignment agent by a chemical modification method.

The present invention of this embodiment provides a polyimide having improved water resistance as an orientation agent, the orientation agent being a modified polyimide composed of at least one compound containing a polyimide obtained by imidizing a polyamic acid obtained by reacting a diamine and a tetracarboxylic dianhydride as a polymer;

s1, preparing a polyimide acid (PAA) solution:

diamine monomer is firstly dissolved in polar aprotic solvent, then dianhydride monomer is added for reaction to obtain viscous transparent polyimide acid solution, and the molar ratio of diamine to dianhydride is 100: (85-100), wherein the molar ratio of the dianhydride is in the range of-15 ℃ to 100 ℃, preferably 0 ℃ to 80 ℃, most preferably 20 ℃ to 60 ℃ as a viscosity parameter of the regulating system. The reaction time is 0.5 to 48 hours, preferably 1 to 24 hours, most preferably 2 to 12 hours. For the polyimide acid solution or polyimide solution used in the present invention, the reaction solid content is 5 to 50%, preferably 8 to 40%, and most preferably 10 to 30%. The initial stage is carried out at a high concentration, and then an organic solvent is added. After the reaction is finished, the mixture is diluted to 1 to 5 percent by weight by a diluent, and the solvent accounts for 95 to 99 percent by weight. When the content of the spray-type solvent is more than 99% by weight, the film thickness of the liquid crystal alignment film after drying after spraying becomes too small to obtain a good liquid crystal alignment film, and when the content of the solvent is less than 95% by weight, the ejection property of the head becomes poor. From the viewpoint of spraying, the viscosity is preferably 5 to 16 mPa.S, preferably 6 to 10 mPa.S;

s2, preparing a Polyimide (PI) solution:

s21, synthesizing according to the step S1 to obtain a polyimide acid solution;

s22, adding a dehydrating agent and a catalyst into the polyimide acid solution obtained by the reaction in S1, and performing imidization by using a chemical imidization method, wherein the imidization rate of polyimide can be controlled by adjusting the catalyst amount, the reaction temperature and the reaction time, and the dehydrating agent and the catalyst are not limited to acetic anhydride and pyridine. The dehydrating agent is used in a proportion of 1 to 20 times the mole number of the dianhydride, and the catalyst is used in a proportion of 1 to 10 times the mole number of the dianhydride, but the use proportion is not limited to 1 to 10 times. The reaction temperature for chemical imidization is-20 ℃ to 200 ℃, preferably 60 ℃ to 120 ℃, and most preferably 20 ℃ to 100 ℃. The reaction time is 0.5-48h. As the dehydrating agent, for example, an acid anhydride such as acetic anhydride, propionic anhydride, trifluoroacetic anhydride, etc., preferably acetic anhydride, can be used. The amount of dehydrating agent used depends on the desired imidization rate. In addition, as the dehydration ring-closing catalyst, for example, tertiary amines such as pyridine, collidine, lutidine, triethylamine, etc., preferably pyridine, can be used. The imidization ratio of the polyimide contained in the liquid crystal aligning agent of the present invention is not particularly limited, but is preferably 40% or more in view of electric characteristics, more preferably 50% or more in order to obtain a higher voltage holding ratio;

and (2) removing most of the solvent, pyridine and acetic acid from the polyimide solution obtained by the chemical imidization reaction in the step (S22) through rotary evaporation, adding a proper amount of aprotic solvent used in the step (I), removing most of the solvent through rotary evaporation, and performing cyclic operation for three times to remove most of the pyridine and acetic acid, thereby obtaining the polyimide solution, wherein the final solid content is controlled to be more than 20%. After the reaction is finished, a diluent is used for 5%wt, and a base solvent system is kept consistent with S1, so that a polyimide solution subjected to chemical imidization can be obtained;

s3, mixing with PI and PAA solution: mixing PI obtained in the step S1 and the step S2 with PAA solution in proportion, controlling the proportion of the PI solution to be 10-50%, preferably 30%, and curing at 60-80 ℃ for 0.5-4 hours, preferably 2-4 hours and most preferably 2 hours to obtain the mixed (PI/PAA) orientation agent;

s4, a modification method: s1 or S2 or the orientation agent synthesized by S1, S2 or S3 is continuously reacted with the modifier, the modifier is gradually added into the polyamic acid solution under the protection of nitrogen, the stirring reaction time is 0.5-4h, the reaction temperature is 0-80 ℃, preferably 10-50 ℃, all the modifiers can be one or more of the structural formulas, the addition mode is added according to the mole ratio, the total mole amount of diamine and dianhydride in the formula is 100 parts, the addition amount is 0-5%, the preferred addition amount is 1-2% of the total mole amount of diamine and dianhydride, and the maximum addition amount is required to ensure that the synthesized polyamic acid solution cannot precipitate. The modified polyamic acid solution is finally obtained by adding a modifying agent, and the method for preparing the polyimide aligning agent of the present invention is a method in which each component mainly comprising the polyimide is in a uniform state in the liquid crystal aligning agent.

The diamine of this embodiment is one or more of alicyclic diamine, aromatic diamine, heterocyclic diamine, and aliphatic diamine, and specific examples thereof are given below:

diamine compound:

dianhydride compound:

the solvent in S1 of this embodiment is one or more of gamma-butyrolactone, N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, N-dimethylformamide, N-diethylformamide, N-dimethylacetamide, 2-pyrrolidone, N-vinyl-2-pyrrolidone, dimethyl sulfoxide, and dimethyl sulfone, preferably gamma-butyrolactone or N-methyl-2-pyrrolidone.

In the S1 of the embodiment, a leveling agent containing 1-30 wt% of one or more of ethylene glycol monobutyl ether, diethylene glycol monomethyl ether and diethylene glycol diethyl ether is also added.

The modifier in S4 of this embodiment has the following characteristics, and its structure is as follows:

the specific structure of the general formula is as follows:

the modifier in S4 of this example reacts with the polyimide as follows:

The method for improving the spraying effect of the water tolerance of the polyimide orientation agent in the embodiment comprises the following steps:

a2, spraying the orientation agent solution in a1 on ITO glass, then sequentially placing the ITO glass substrate at 70-110 ℃ for prebaking for 10-20min, and then imidizing for 30-60min at 200-250 ℃;

The kinds and mole percentages of the dianhydride compound and the diamine compound in the examples and comparative examples of the present invention are shown in Table 1:

TABLE 1

Example 1.

I. In a reactor equipped with nitrogen protection, 3.86g (10 mmol) of A-6, 3.18g (15 mmol) of A-5, 4.96g (25 mmol) of A-2, 2.16g (20 mmol) of A-1, 6.01g (30 mmol) of A-3 and 168.09g of NMP were successively added at room temperature, and stirred at room temperature for 30 minutes to confirm complete dissolution. Then, 3.92G (20 mmol) of G-1 and 17.93G (80 mmol) of G-2 were added in this order. Stirring and reacting for 4 hours at room temperature to obtain the viscous polyamic acid solution with the solid content of 20 weight percent. After the reaction, 487.46gNMP,201.71g GBL,151.18g BC was added and diluted to 4.0% by weight with stirring to obtain a polyamic acid solution having a solvent ratio of NMP/GBL/bc=65/20/15.

II. Under the protection of nitrogen, the modifier N-1 is gradually added into the polyamic acid solution in a dropwise manner, wherein the addition amount is 0.1783g, and is 1 percent of the total molar amount (0.2 mol) of diamine and dianhydride, the stirring reaction time is 2 hours, the reaction temperature is 60 ℃, the mixture is filtered by a microporous filter membrane, and then the spraying effect test is carried out. And after coating, preparing a box by a subsequent process, and then testing the inclination angle and the electrical property of the liquid crystal box.

Example 2.

I. In a reactor equipped with nitrogen protection, 3.86g (10 mmol) of A-6, 2.99g (15 mmol) of A-4, 5.95g (30 mmol) of A-2, 2.16g (20 mmol) of A-1, 5.01g (25 mmol) of A-3 and 144.46g of NMP were successively added at room temperature, and stirred at room temperature for 30 minutes to confirm complete dissolution. Then, 4.36G (20 mmol) of G-4 and 15.69G (80 mmol) of G-1 were added in this order. Stirring and reacting for 4 hours at room temperature to obtain the viscous polyamic acid solution with the solid content of 20 weight percent.

II. Then, 10.2g (100 mmol) and 15.82g (200 mmol) of pyridine were added thereto, and 30.24g of NMP was added thereto, and the mixture was reacted at room temperature for 2 hours to effect chemical imidization. The polyimide solution is prepared by removing most of pyridine and solvent by rotary evaporation at 100 ℃, adding 120g of NMP solvent, and circularly operating for 3 times, wherein most of pyridine and acetic acid can be removed, and the final solid content is controlled to be more than 20%. After the completion of the reaction, the solid content was measured by a hot plate method and was found to be 21.69%, and NMP 479.74g,201.71g GBL,151.18g BC was added thereto and diluted to 4.0% by weight with stirring to obtain a polyimide solution having a solvent ratio of NMP/GBL/BC=65/20/15.

And III, gradually dropwise adding a modifier N-1 into the polyamic acid solution under the protection of nitrogen, wherein the addition amount is 0.1783g, which is 1 percent of the total molar amount (0.2 mol) of diamine and dianhydride, stirring and reacting for 2 hours, the reaction temperature is 60 ℃, filtering by a microporous filter membrane, and then performing a spraying effect test. And after coating, preparing a box by a subsequent process, and then testing the inclination angle and the electrical property of the liquid crystal box.

Example 3.

The steps I and II are the same as in example 2.

And III, gradually dropwise adding a modifier N-3 into the polyamic acid solution under the protection of nitrogen, wherein the addition amount is 0.2103g, which is 1 percent of the total molar amount (0.2 mol) of diamine and dianhydride, stirring and reacting for 2 hours, the reaction temperature is 60 ℃, filtering by a microporous filter membrane, and then performing a spraying effect test. And after coating, preparing a box by a subsequent process, and then testing the inclination angle and the electrical property of the liquid crystal box.

Example 4.

I. 3.24g (30 mmol) of A-1, 14.02g (70 mmol) of A-4 and 147.50g of NMP were successively added to a reactor equipped with nitrogen protection at room temperature, and stirred at room temperature for 30 minutes, to confirm complete dissolution. 19.61G (100 mmol) of G-1 were then added in succession. Stirring and reacting for 4 hours at room temperature to obtain the viscous polyamic acid solution with the solid content of 20 weight percent. After the reaction, NMP 427.74g,177.00g GBL,132.75g BC was added and diluted to 4.0% by weight with stirring to obtain a polyamic acid solution A having a solvent ratio of NMP/GBL/BC=65/20/15.

II. 3.86g (10 mmol) of A-6, 6.37g (30 mmol) of A-5, 11.90g 60 mmol) of A-2 and 178.14g of NMP were successively added to a reactor equipped with nitrogen protection at room temperature, and stirred at room temperature for 30 minutes to confirm complete dissolution. 22.42G (100 mmol) of G-2 was then added in sequence and stirred at room temperature for reaction for 4 hours to give a transparent viscous polyamic acid solution having a solid content of 20% by weight. Then, 10.2g (100 mmol) and 15.82g (200 mmol) of pyridine were added thereto, and 48.21g of NMP was added thereto, and the mixture was reacted at 60℃for 2 hours to effect chemical imidization. The polyimide solution is prepared by removing most of pyridine and solvent by rotary evaporation at 100 ℃, adding 120g of NMP solvent, and circularly operating for 3 times, wherein most of pyridine and acetic acid can be removed, and the final solid content is controlled to be more than 20%. After the reaction, the solid content was 22.38% by a hot plate method, and NMP 540.29g,213.77g GBL,160.33gBC was added thereto and diluted to 4.0% by weight with stirring to obtain a polyimide solution B having a solvent ratio of NMP/GBL/BC=65/20/15.

And III, taking 800g of the solution A and 200g of the solution B obtained in the two steps, stirring and curing at 60 ℃ for 1h, dropwise adding the modifier N-1 into the polyamic acid solution under the protection of nitrogen, wherein the addition amount is 0.1783g, is 1% of the total molar amount (0.2 mol) of diamine and dianhydride, stirring for 2h, filtering by a microporous filter membrane at the reaction temperature of 60 ℃, and then testing the spraying effect. And after coating, preparing a box by a subsequent process, and then testing the inclination angle and the electrical property of the liquid crystal box.

Example 5.

II. 1.11g (10 mmol) of A-7, 3.86g (10 mmol) of A-6, 4.24g (20 mmol) of A-2, 11.90g (60 mmol) of A-2 and 174.09g of NMP were successively added to a reactor equipped with nitrogen protection at room temperature, and stirred at room temperature for 30 minutes to confirm complete dissolution. 22.42G (100 mmol) of G-2 was then added in sequence and stirred at room temperature for reaction for 4 hours to give a transparent viscous polyamic acid solution having a solid content of 20% by weight. Then, 10.2g (100 mmol) and 15.82g (200 mmol) of pyridine were added thereto, and 46.52g of NMP was added thereto, and the mixture was reacted at 60℃for 2 hours to effect chemical imidization. The polyimide solution is prepared by removing most of pyridine and solvent by rotary evaporation at 100 ℃, adding 120g of NMP solvent, and circularly operating for 3 times, wherein most of pyridine and acetic acid can be removed, and the final solid content is controlled to be more than 20%. After the reaction, the solid content was 23.65% by a hot plate method, and NMP538.46g,208.91g GBL,156.69g BC was added thereto and diluted to 4.0% by weight with stirring to obtain a polyimide solution B having a solvent ratio of NMP/GBL/bc=65/20/15.

And III, taking 700g of the solution A and 300g of the solution B obtained in the two steps, stirring and curing at 60 ℃ for 1h, dropwise adding the modifier N-1 into the polyamic acid solution under the protection of nitrogen, wherein the addition amount is 0.1783g, is 1% of the total molar amount (0.2 mol) of diamine and dianhydride, stirring for 2h, filtering by a microporous filter membrane at the reaction temperature of 60 ℃, and then testing the spraying effect. And after coating, preparing a box by a subsequent process, and then testing the inclination angle and the electrical property of the liquid crystal box.

Comparative example 1.

I. In a reactor equipped with nitrogen protection, 3.86g (10 mmol) of A-6, 3.18g (15 mmol) of A-5, 4.96g (25 mmol) of A-2, 2.16g (20 mmol) of A-1, 6.01g (30 mmol) of A-3 and 168.09g of NMP were successively added at room temperature, and stirred at room temperature for 30 minutes to confirm complete dissolution. Then, 3.92G (20 mmol) of G-1 and 17.93G (80 mmol) of G-2 were added in this order. Stirring and reacting for 4 hours at room temperature to obtain the viscous polyamic acid solution with the solid content of 20 weight percent. After the reaction, 487.46gNMP,201.71g GBL,151.18g BC was added and diluted to 4.0% by weight with stirring to obtain a polyamic acid solution having a solvent ratio of NMP/GBL/bc=65/20/15. Filtering with microporous membrane, and testing spraying effect. And after coating, preparing a box by a subsequent process, and then testing the inclination angle and the electrical property of the liquid crystal box.

Comparative example 2.

II. Then, 10.2g (100 mmol) and 15.82g (200 mmol) of pyridine were added thereto, and 30.24g of NMP was added thereto, and the mixture was reacted at room temperature for 2 hours to effect chemical imidization. The polyimide solution is prepared by removing most of pyridine and solvent by rotary evaporation at 100 ℃, adding 120g of NMP solvent, and circularly operating for 3 times, wherein most of pyridine and acetic acid can be removed, and the final solid content is controlled to be more than 20%. After the completion of the reaction, the solid content was measured by a hot plate method and was found to be 21.69%, and NMP 479.74g,201.71g GBL,151.18g BC was added thereto and diluted to 4.0% by weight with stirring to obtain a polyimide solution having a solvent ratio of NMP/GBL/BC=65/20/15. Filtering with microporous membrane, and testing spraying effect. And after coating, preparing a box by a subsequent process, and then testing the inclination angle and the electrical property of the liquid crystal box.

Comparative example 3.

And III, taking 800g of the solution A and 200g of the solution B obtained in the two steps, stirring and curing at 60 ℃, wherein the curing time is 1h, and then uniformly mixing, filtering by a microporous filter membrane and then testing the spraying effect. And after coating, preparing a box by a subsequent process, and then testing the inclination angle and the electrical property of the liquid crystal box.

Comparative example 4.

And III, taking 700g of the solution A and 300g of the solution B obtained in the two steps, stirring and curing at 60 ℃, wherein the curing time is 1h, and then uniformly mixing, filtering by a microporous filter membrane and then testing the spraying effect. And after coating, preparing a box by a subsequent process, and then testing the inclination angle and the electrical property of the liquid crystal box.

The polyimide solutions obtained in the following examples were evaluated for their post-cartridge properties as follows:

(1) Water resistance test:

the evaluation method comprises the following steps: 10g of PI sample was weighed by a precision analytical balance, and the grams of water added when the PI became turbid was visually observed and recorded by dropping water. To better illustrate this evaluation method, a schematic diagram is shown in fig. 1.

The water resistance test results are shown in Table 2.

TABLE 2

(2) Evaluation of spray effect

Spray test of synthetic polyimide solutions using a spray coater

The printing mode is as follows: i nkjet

Equipment model: i J-1011-A2FS-M0

Head specification: 50 μm

The discharge process comprises the following steps: TC3 (20.77V), 128 mm/s.times.43.5 ng/dot.times.1 times

Liquid drop: conventional: 43.5ng/dot

The spray effect evaluation results are shown in Table 3.

TABLE 3 Table 3

(3) Pretilt angle test conditions of liquid crystal cell:

pretilt angle test conditions of liquid crystal cell:

test equipment: shintech Optitro-STD (3 STN 11)

Test wavelength: 591.4nm

Test mode: TN mode

HAV parameters: the results of the pretilt angle and pretilt angle stability test of the cell at a temperature of 60℃under illumination of 313nm for 125s in DC program 20V are shown in Table 4.

TABLE 4 Table 4

(4) Conditions for testing electrical properties of liquid crystal cell:

test equipment: 6254CVHR measurement conditions: voltage 5V, pulse width 60 us/frame, period 1667ms, measurement temperature 23 deg.C/90 deg.C

Ion Density measurement conditions: voltage 5V, pulse width 60 us/frame, period 1667ms, measurement temperature 23 deg.C/90 deg.C

The results of the electrical properties are shown in Table 5.

TABLE 5

The innovation point of the invention is that:

It will be evident to those skilled in the art that the invention is not limited to the details of the foregoing illustrative embodiments, and that the present invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.

Furthermore, it should be understood that although the present disclosure describes embodiments, not every embodiment is provided with a separate embodiment, and that this description is provided for clarity only, and that the disclosure is not limited to the embodiments described in detail below, and that the embodiments described in the examples may be combined as appropriate to form other embodiments that will be apparent to those skilled in the art.

Claims

1. A method for improving the water tolerance and spraying effect of a polyimide orientation agent, characterized in that the orientation agent is modified polyimide, which is composed of at least one compound containing polyimide obtained by imidizing polyamide acid obtained by reacting diamine and tetracarboxylic dianhydride as polymer;

s2, preparing a Polyimide (PI) solution:

s21, synthesizing according to the step S1 to obtain a polyimide acid solution;

s3, mixing with PI and PAA solution: mixing the PI obtained in the step S1 and the step S2 with the PAA solution in proportion, controlling the proportion of the PI solution to be 10-50%, and curing at 60-80 ℃ for 0.5-4 hours to obtain the mixed (PI/PAA) orientation agent;

2. The method for improving the water tolerance and the spraying effect of the polyimide aligning agent according to claim 1, wherein the molar ratio of diamine to dianhydride in the S1 is 100: (85-100), wherein the reaction temperature of the S1 is-15-100 ℃, the reaction time is 0.5-48h, and the reaction solid content of the polyimide solution is 5-50%.

3. The method for improving the water resistance and the spraying effect of the polyimide aligning agent according to claim 1, wherein the diamine is one or more of alicyclic diamine, aromatic diamine, heterocyclic diamine and aliphatic diamine.

4. The method for improving water tolerance and spraying effect of polyimide aligning agent according to claim 1, wherein the solvent in S1 is one or more of γ -butyrolactone, N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, N-dimethylformamide, N-diethylformamide, N-dimethylacetamide, 2-pyrrolidone, N-vinyl-2-pyrrolidone, dimethylsulfoxide, dimethylsulfone.

5. The method for improving the water tolerance and the spraying effect of the polyimide orientation agent according to claim 1, wherein the leveling agent containing 1-30% by weight of the polyimide orientation agent is added in the S1, and the leveling agent is one or more of ethylene glycol monobutyl ether, diethylene glycol monomethyl ether and diethylene glycol diethyl ether.

6. The method for improving the water tolerance and the spraying effect of the polyimide aligning agent according to claim 1, wherein the dehydrating agent in the step S22 is used in a proportion of 1-20 times of the mole number of the dianhydride, the catalyst is used in a proportion of 1-10 times of the mole number of the dianhydride, the reaction temperature of the chemical imidization is-20-200 ℃, and the reaction time is 0.5-48h.

7. The method for improving water tolerance and spraying effect of polyimide aligning agent according to claim 1, wherein the dehydrating agent in S22 is one or more of acetic anhydride, propionic anhydride and trifluoroacetic anhydride, the catalyst is one or more of pyridine, collidine, lutidine and triethylamine, and imidization rate of polyimide contained in the liquid crystal aligning agent in S22 is above 40%.

8. The method for improving the water tolerance and the spraying effect of the polyimide aligning agent according to claim 1, wherein the modifying agent in the S4 has the following characteristics:

the specific structure of the general formula is as follows:

9. the method for improving water tolerance and spraying effect of polyimide aligning agent according to claim 1, wherein the modifying agent in S4 reacts with polyimide as follows:

10. The method for improving the spray effect of water resistance of a polyimide orientation agent according to claim 1, comprising the steps of: