CN111718267B - Diamine compound and preparation method and application thereof - Google Patents

Abstract

The invention relates to the field of liquid crystal materials, in particular to a diamine compound and its preparation method and application. The structure of the diamine compound in the present invention is shown in formula I. When preparing the diamine compound, the raw material of compound I-a is reacted with ammonia gas to obtain compound I-b, and the compound I-b is reacted with a fluorinating reagent to obtain compound I. The present invention further provides the application of the diamine compound in the field of liquid crystal display. The diamine compound provided by the present invention can improve the performance of liquid crystal display elements, and the prepared polyamic acid, polyimide and liquid crystal alignment agent all have good properties such as chemical stability and thermal stability, and then make the formed The liquid crystal alignment film has a higher pretilt angle; the prepared liquid crystal display element has lower residual direct current charge, and thus has higher efficiency. The preparation method is stable and efficient, and the raw materials are easy to obtain, the preparation process is simple, and the popularization of the diamine compound is convenient.

Description

A diamine compound and its preparation method and application

Technical Field

The present invention relates to the field of liquid crystal materials, and in particular to a diamine compound and a preparation method and application thereof.

Background Art

Among liquid crystal displays, a typical example is a twisted nematic (TN) electric field effect liquid crystal display, which uses nematic liquid crystals with positive dielectric anisotropy. Generally speaking, liquid crystal molecules are placed between a pair of substrates containing electrodes, and the orientation directions of the two substrates are perpendicular to each other, and the arrangement of the liquid crystal molecules can be controlled by controlling the electric field. For this type of liquid crystal display, it is very important to make the long axis direction of the liquid crystal molecules form an alignment with a uniform tilt angle with the substrate surface. This material that arranges the liquid crystal molecules into a uniform pre-tilt angle alignment is generally called an alignment film.

There are currently two typical methods for preparing alignment films in the industry. The first method is to make an inorganic film from an inorganic substance by vapor deposition. For example, silicon dioxide is obliquely evaporated on a substrate to form a thin film, and the liquid crystal molecules are aligned in the direction of the evaporation. However, although the method can obtain uniform alignment, it does not have industrial benefits. The second method is to coat an organic film on the surface of a substrate, and then use a cotton, nylon or polyester soft cloth to rub the surface of the organic film so that the liquid crystal molecules are aligned in the rubbing direction. Since this method is relatively simple and it is quite easy to obtain uniform alignment, it is widely used on an industrial scale. In this method, polymers that can form alignment films such as polyvinylalcohol (PVA), polyethylene oxide (PEO), polyamide (PA) or polyimide, among which polyimide is most commonly used as an alignment film material due to its chemical stability and thermal stability.

In the prior art, when a voltage is applied to a liquid crystal display, the generated ionic charges will be absorbed by the liquid crystal alignment film, and even after the applied voltage is released, it is difficult for the ionic charges to be separated from the liquid crystal alignment film, thus causing the problem of afterimage on the screen. Therefore, the recent development of alignment film materials has focused on improving afterimage as the primary issue.

Summary of the invention

In order to solve the above problems, the present invention provides a diamine compound having the function of improving the performance of a liquid crystal display element, and a preparation method and application thereof.

The first object of the present invention is to provide a diamine compound, the structure of which is shown in Formula I:

Wherein, R ₁ and R ₂ are the same or different and independently represent -(CH ₂ )- or -(CH ₂ CH ₂ )-;

The L ₁ , L ₂ , L ₃ and L ₄ are the same or different, and independently represent H or F.

Preferably, in the general formula I, R ₁ and R ₂ both represent -CH ₂ -; and/or L ₁ and L ₃ are not H at the same time and L ₂ and L ₄ are not H at the same time;

As the best embodiment of the present invention, the compound is any one of the following:

This compound has the effect of improving the performance of liquid crystal display elements. The polyamic acid (polyamic acid), polyimide (PI) and liquid crystal alignment agent prepared using this diamine compound have good chemical stability and thermal stability, thereby making the formed liquid crystal alignment film have a higher pretilt angle.

The second object of the present invention is to provide a method for preparing the compound. To achieve the second object, the present invention adopts the following technical solution:

The synthetic route of the compound shown in Formula I is as follows:

The steps include:

1) Compound I-a is reacted with ammonia to obtain compound I-b;

2) The compound I-b is reacted with a fluorination agent to obtain compound I.

Wherein, R ₁ , R ₂ , L ₁ , L ₂ , L ₃ , L ₄ in the compounds involved in each step correspond to the groups represented by R ₁ , R ₂ , L ₁ , L ₂ , L ₃ , L ₄ in the obtained compound product (same as above).

As a preferred embodiment of the present invention, in step 1), the reaction is carried out at 100°C to 300°C; preferably 150°C to 250°C.

As a preferred embodiment of the present invention, the reaction in step 1) is carried out at 0.1 MPa to 2.0 MPa; preferably 0.5 MPa to 1.5 MPa.

As a preferred embodiment of the present invention, the reaction time in step 1) is 3 to 8 hours.

As a preferred embodiment of the present invention, in step 2), the molar ratio of the compound I-b to the fluorination agent is 1:(2.0-5.0).

As a preferred embodiment of the present invention, in step 2), the reaction is carried out at -100°C to 30°C; preferably -75°C to -10°C.

As a preferred embodiment of the present invention, in step 2), the fluorination agent is one or a mixture of more than one selected from triethylamine hydrogen fluoride, pyridine hydrogen fluoride, diethylamino sulfur trifluoride, sulfur trifluoride, and hydrogen fluoride ether; preferably diethylamino sulfur trifluoride.

The raw material I-a can be synthesized through public commercial routes or methods known in the literature.

In addition, it is worth noting that in the preparation method described in the present invention, the solvents and their amounts used in each step, the separation and purification of the product, the drop rate of the reactants, etc., which are not particularly limited, are understood and mastered by those skilled in the art. As in the present invention, except for special instructions, the volume of the solvent is generally 5-15 times the mass of the reactants, and the specific amount can be appropriately adjusted according to the amount of the reaction substrate and the size of the selected reaction bottle; the drop rate of the reactants is usually combined with the specific reaction rate comprehensive control, etc. On the basis of the disclosure of the present invention, those skilled in the art can choose any available technical solution to implement the present invention according to the actual situation.

The preparation method of the present invention can stably and efficiently obtain the compound of the present invention.

The third object of the present invention is to provide application of the diamine compound in the field of liquid crystal display.

Preferably, the application is in one of the following aspects:

(1) Preparation of polyamic acid;

(2) Preparation of polyimide;

(3) Preparation of liquid crystal alignment agent;

(4) Preparation of liquid crystal protective agent;

(5) Preparation of liquid crystal alignment film;

(6) Preparation of liquid crystal display elements.

The present invention further provides a polyamic acid, which is prepared from raw materials including the diamine compound. The specific preparation process is as follows: the diamine compound and CBDA are dissolved in NMP (N-methylpyrrolidone), and reacted at room temperature to obtain the polyamic acid.

The present invention further provides a polyimide, which is prepared from a raw material including the diamine compound. The specific preparation process is as follows: the diamine compound and CBDA are dissolved in NMP (N-methylpyrrolidone), reacted at room temperature, and then diluted to obtain a polyamic acid solution; the polyamic acid solution is coated on the surface of a substrate, and heated at 200° C. for 30 minutes to form a polyimide film.

The present invention further provides a liquid crystal alignment agent, which contains the polyamic acid or polyimide.

In the polyimide, polyamic acid or liquid crystal alignment agent, the content of the diamine compound is at least 1%, preferably at least 10%, and more preferably at least 50%, by mole percentage.

Experiments have shown that by adding the diamine compound of the present invention during the preparation of a liquid crystal alignment agent, the resulting liquid crystal alignment agent not only has good chemical stability and thermal stability, but also the liquid crystal alignment film formed therefrom has a higher pretilt angle.

The present invention further provides a liquid crystal protective agent, which is prepared from raw materials including the diamine compound.

The present invention further provides a liquid crystal display element, wherein the liquid crystal alignment film contained in the liquid crystal display element is formed by the liquid crystal alignment agent. The liquid crystal display element has lower residual DC charge and thus has higher performance.

The beneficial effects of the present invention are as follows:

(1) The diamine compound provided by the present invention can improve the performance of liquid crystal display elements. The prepared polyamic acid, polyimide and liquid crystal alignment agent have good chemical stability and thermal stability, so that the formed liquid crystal alignment film has a higher pretilt angle; the prepared liquid crystal display element has a lower residual DC charge and thus has a higher performance.

(2) The preparation method of the present invention can stably and efficiently obtain the diamine compound of the present invention, and the raw materials are easily available and the preparation process is simple, which is convenient for the promotion of the diamine compound.

DETAILED DESCRIPTION

The following examples are used to illustrate the present invention but are not intended to limit the scope of the present invention.

Unless otherwise specified, the raw materials can be obtained from public commercial channels.

According to conventional detection methods in the art, various performance parameters of the compound are obtained by linear fitting, wherein the specific meanings of each performance parameter are as follows:

△n represents optical anisotropy (25°C);

△ε represents dielectric anisotropy (25°C, 1000Hz);

ε|| represents the dielectric constant parallel to the molecular axis (25°C, 1000Hz);

Cp stands for clearing point;

K represents the elastic constant (25°C).

The MDA used in the experimental examples and comparative examples is 4,4'-methylenedianiline, and the CBDA is 1,2,3,4-cyclobutanetetracarboxy lie dianhydride.

Example 1

A diamine compound, the structural formula of which is:

The synthetic route for preparing compound I-1 is as follows:

The specific steps are as follows:

(1) Synthesis of Compound I-b-1

28.8 g of compound I-a-1 and 200 ml of tetrahydrofuran were added to the reaction kettle, ammonia was introduced to a pressure of 0.5 MPa to 1.0 MPa at room temperature, the temperature was raised to 200 ° C and the reaction was carried out for 6 hours, the temperature was lowered and the pressure was reduced, and the reaction was quenched with a saturated sodium bicarbonate aqueous solution, and conventional post-treatment was performed, and n-heptane was recrystallized to obtain an off-white solid (compound I-b-1) 28.6 g, HPLC: 99.6%, yield 87.2%;

(2) Synthesis of Compound I-1

Under nitrogen protection, 25.0 g of I-b-1 and 200 ml of tetrahydrofuran were added to the reaction bottle, and 66.5 g of diethylaminosulfur trifluoride was added dropwise at a temperature of -70°C to -60°C. The reaction was carried out at a temperature of -70°C to -60°C for 1 hour, and the temperature was naturally returned to -30°C. A saturated aqueous sodium hydroxide solution was added to quench the reaction, and then conventional post-treatment operations were performed. The reaction was dissolved in ethyl acetate, separated, and purified by chromatography. The reaction was recrystallized with a mixed solution of n-heptane and toluene in a volume ratio of 3:1 to obtain 21.1 g of a white solid (compound I-1), HPLC: 99.5%, yield: 72.7%.

The obtained white solid compound I-1 was analyzed by GC-MS, and the m/z of the product was 318.1 (M+).

Elemental analysis: C: 60.35, H: 6.95, F: 23.87, N: 8.80.

Example 2

A diamine compound, the structural formula of which is:

The synthetic route for preparing compound I-3 is as follows:

(1) Synthesis of Compound I-c-1

55.0 g of compound I-b-1 and 250 ml of tetrahydrofuran were added to the reaction flask, and 13.5 g of potassium borohydride aqueous solution was added dropwise at a temperature of 10°C to 30°C. After the addition, the temperature was kept at 50°C to 60°C for 3 hours, and dilute hydrochloric acid was added to quench the reaction. Conventional post-treatment was performed, and 51.5 g of an off-white solid (compound I-c-1) was obtained by recrystallization from n-heptane, HPLC: 99.2%, yield 92.8%;

(2) Synthesis of Compound I-3

Under nitrogen protection, 50.0 g of I-c-1 and 300 ml of tetrahydrofuran were added to the reaction bottle, and 86.8 g of diethylaminosulfur trifluoride was added dropwise at a temperature of -70°C to -60°C. The reaction was carried out at a temperature of -70°C to -60°C for 1 hour, and the temperature was naturally returned to -30°C. A saturated aqueous sodium hydroxide solution was added to quench the reaction, and then conventional post-treatment operations were performed. The reaction was dissolved in ethyl acetate, separated, and purified by chromatography. The reaction was recrystallized with a mixed solution of n-heptane and toluene in a volume ratio of 3:1 to obtain 38.9 g of a white solid (compound I-3), HPLC: 99.8%, yield: 76.8%.

The obtained white solid compound I-3 was analyzed by GC-MS, and the m/z of the product was 282.1 (M+).

Elemental analysis: C: 68.05, H: 8.55, F: 13.45, N: 9.91.

Experimental Example 1

15.9 g (0.05 mol) of compound I-1 and 9.8 g (0.05 mol) of CBDA were dissolved in 92.8 g of NMP (N-methylpyrrolidone), reacted at room temperature for 12 hours, and then 348 g of NMP was added for dilution to obtain a polyamic acid solution (specific viscosity of 0.57 dl/g).

Then, the polyamic acid solution was spin-coated at 3000 rpm on a glass substrate having a transparent electrode.

Then, it was heated at 200°C for 30 minutes to form a polyimide film, and assembled into a parallel liquid crystal box using a 40-micron spacer. After the liquid crystal (model: BYLC-1000, manufactured by Bayi Spacetime Liquid Crystal Technology Co., Ltd.) was injected, the liquid crystal box rotated between the orthogonal Nicol prisms and presented a full dark state. The pre-tilt angle value obtained by the pre-tilt angle measuring machine was 87°; after testing, the residual DC charge was 93mV.

Experimental Example 2

14.1 g (0.05 mol) of compound I-3 and 9.8 g (0.05 mol) of CBDA were dissolved in 92.8 g of NMP (N-methylpyrrolidone), reacted at room temperature for 12 hours, and then 348 g of NMP was added for dilution to obtain a polyamic acid solution (specific viscosity of 0.57 dl/g).

Then, the polyamic acid solution was spin-coated at 3000 rpm on a glass substrate having a transparent electrode.

Then, it was heated at 200°C for 30 minutes to form a polyimide film, and assembled into a parallel liquid crystal box using a 40-micron spacer. After the liquid crystal (model: BYLC-1000, manufactured by Bayi Spacetime Liquid Crystal Technology Co., Ltd.) was injected, the liquid crystal box rotated between the orthogonal Nicol prisms and presented a full dark state. The pre-tilt angle value obtained by the pre-tilt angle measuring machine was 90°; after testing, the residual DC charge was 86mV.

Experimental Example 3

3.18 g (0.01 mol) of compound I-1, 14.8 g (0.04 mol) of MDA and 9.8 g (0.05 mol) of CBDA were dissolved in 110.2 g of NMP, reacted at room temperature for 12 hours, and then 413.4 g of NMP was added for dilution to obtain a polyamic acid solution (specific viscosity of 0.72 dl/g).

Then, the polyamic acid solution was spin-coated at 3000 rpm on a glass substrate having a transparent electrode.

Then, the film was heated at 200° C. for 30 minutes to form a polyimide film.

After the polyimide film was cooled, it was rubbed with a brush and assembled into a parallel liquid crystal box using a 40-micron spacer. After the liquid crystal (model: BYLC-1000, manufactured by BYLC Technology Co., Ltd.) was injected, the pre-tilt angle value obtained by the pre-tilt angle measuring machine was 6.1°; after testing, the residual DC charge was 292mV.

Experimental Example 4

2.82 g (0.01 mol) of compound I-3, 14.8 g (0.04 mol) of MDA and 9.8 g (0.05 mol) of CBDA were dissolved in 110.2 g of NMP, reacted at room temperature for 12 hours, and then 413.4 g of NMP was added for dilution to obtain a polyamic acid solution (specific viscosity of 0.72 dl/g).

Then, the polyamic acid solution was spin-coated at 3000 rpm on a glass substrate having a transparent electrode.

Then, the film was heated at 200° C. for 30 minutes to form a polyimide film.

After the polyimide film was cooled, it was rubbed with a brush and assembled into a parallel liquid crystal box using a 40-micron spacer. After the liquid crystal (model: BYLC-1000, manufactured by BYLC Technology Co., Ltd.) was injected, the pre-tilt angle value obtained by the pre-tilt angle measuring machine was 6.3°; after testing, the residual DC charge was 273mV.

Comparative Example

9.7 g (0.05 mol) of MDA and 9.8 g (0.05 mol) of CBDA were dissolved in 78 g of NMP, reacted at room temperature for 12 hours, and then 292.5 g of NMP was added for dilution to obtain a polyamic acid solution (specific viscosity: 0.81 dl/g).

The polyamic acid solution was then spin-coated at 3000 rpm on a glass substrate having a transparent electrode.

Then, the film was heated at 200° C. for 30 minutes to form a polyimide film.

After the polyimide film was cooled, it was rubbed with a brush and assembled into a parallel liquid crystal box using a 40-micron spacer. After the liquid crystal (model: BYLC-1000, manufactured by BYLC Technology Co., Ltd.) was injected, the pre-tilt angle value obtained by the pre-tilt angle measuring machine was 2.1°; after testing, the residual DC charge was 533mV.

Table 1 Comparison of pretilt angles of experimental examples and comparative examples

It can be seen from Table 1 that when the diamine compound of the present invention is added during the preparation of the liquid crystal alignment agent, the pretilt angle of the formed liquid crystal alignment film is significantly improved.

Table 2 Comparison of residual DC charge between experimental example and comparative example

It can be seen from Table 2 that when the diamine compound of the present invention is added during the preparation of the liquid crystal alignment agent, the obtained liquid crystal display element has a lower residual DC charge.

In summary, the liquid crystal alignment agent contains polyimide or polyamic acid obtained by polymerization reaction of the diamine compound of the present invention and tetracarboxylic acid or its dianhydride compound. The liquid crystal alignment film formed by this liquid crystal alignment agent has a higher pretilt angle, and the obtained liquid crystal display element has a lower residual DC charge, thereby improving the performance of the liquid crystal display element.

Although the present invention is disclosed as above by embodiments, it is not intended to limit the present invention. Any technical personnel in this field may make any changes or equivalent substitutions without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention shall be based on the scope defined by the claims of this application.

Claims (13)

1. A diamine compound, characterized in that the structure is as shown in Formula I:

In the general formula I, R ₁ and R ₂ both represent -CH ₂ -; L ₁ and L ₃ are not H at the same time, and L ₂ and L ₄ are not H at the same time; the compound is any one of the following:

2. The method for preparing the diamine compound according to claim 1, characterized in that: The synthetic route for preparing compound I-1 is as follows:

The steps include: 1) Compound I-a-1 is reacted with ammonia to obtain compound I-b-1; 2) reacting the compound I-b-1 with a fluorination agent to obtain compound I-1; The synthetic route for preparing compound I-3 is as follows:

The steps include: 1') Compound I-b-1 is used as the starting material to obtain compound I-c-1 through reduction reaction; 2') reacting the compound I-c-1 with a fluorination agent to obtain compound I-3; Wherein, the fluorination agent is one selected from triethylamine hydrogen fluoride, pyridine hydrogen fluoride, diethylamino sulfur trifluoride, sulfur trifluoride, and hydrogen fluoride ether, or a mixture of more than one. 3. The method according to claim 2, characterized in that in step 1), the reaction is carried out at 100°C to 300°C; And/or, the reaction is carried out at 0.1 MPa to 2.0 MPa. 4. The method according to claim 3, characterized in that in step 1), the reaction is carried out at 150°C to 250°C. 5. The method according to claim 3, characterized in that in step 1), the reaction is carried out at 0.5 MPa to 1.5 MPa. 6. The method according to any one of claims 2 to 5, characterized in that the molar ratio of the compound I-b-1 to the fluorination agent is 1:(2.0-5.0); And/or, in step 2) or step 2'), the reaction is carried out at -75°C to -10°C. 7. The method according to claim 6, characterized in that the fluorination agent is diethylaminosulfur trifluoride. 8. Use of the diamine compound according to claim 1 or the diamine compound prepared by the method of any one of claims 2 to 7 in the field of liquid crystal display. 9. The application according to claim 8, characterized in that the application is an application in one of the following aspects: (1) Preparation of polyamic acid; (2) Preparation of polyimide; (3) Preparation of liquid crystal alignment agent; (4) Preparation of liquid crystal protective agent; (5) Preparation of liquid crystal alignment film; (6) Preparation of liquid crystal display elements. 10. A polyamic acid, characterized in that it is prepared from a raw material comprising the diamine compound according to claim 1 or a diamine compound prepared by the method of any one of claims 2 to 7. 11. A polyimide, characterized in that it is prepared from a raw material comprising the diamine compound according to claim 1 or a diamine compound prepared by the method of any one of claims 2 to 7. 12 . A liquid crystal alignment agent, characterized in that it contains the polyamic acid according to claim 10 or the polyimide according to claim 11 . 13 . A liquid crystal display element, characterized in that a liquid crystal alignment film contained therein is formed by the liquid crystal alignment agent according to claim 12 .