CN107699252A - A kind of novel polymerizable liquid-crystal compounds and preparation method and application - Google Patents

Abstract

The invention relates to the field of liquid crystal display materials, in particular to a novel polymerizable liquid crystal compound and its preparation method and application. The general structure of the liquid crystal compound of the present invention is: Wherein, R represents an alkyl or alkoxy group with 1-10 carbon atoms; ring A represents 1,4-phenylene in which 1-4 hydrogen atoms are replaced by fluorine atoms; m is 1 or 2. The present invention also provides a liquid crystal composition, which contains the above compound in a weight percentage of 0.05% to 20%. The liquid crystal composition added with the compound of the present invention has a high upper limit temperature of the nematic phase and a lower lower limit temperature of the nematic phase. , small viscosity, appropriate optical anisotropy, large dielectric anisotropy, appropriate elastic constant and appropriate pretilt angle and other physical properties, the application prospect is broad.

Description

A novel polymeric liquid crystal compound and its preparation method and application

technical field

The invention relates to the field of liquid crystal display materials, in particular to a novel polymerizable liquid crystal compound and its preparation method and application.

Background technique

The application of liquid crystal materials as environmental materials in information display materials, organic optoelectronic materials and other fields has great research value and bright application prospects. , Three-dimensional display technology has been born, and the importance of optically anisotropic bodies such as optical retarders, patterned retarders, and lenticular lenses that can be used in such liquid crystal displays is increasing day by day. For optically anisotropic products requiring high durability and high functionality, not only the optical properties, but also the polymerization rate, solubility, melting point, glass transition temperature, transparency, mechanical strength, surface hardness and durability of the compound Thermal properties and the like also become important factors.

The polymer-stabilized liquid crystal display technology uses the extra energy provided by the polymer to stabilize the orientation state or phase state of the liquid crystal molecules. The disclosed technologies such as polymer stabilized alignment mode (PSA) or polymer stabilized mode (PS), this mode A liquid crystal composition added with a polymerizable compound is injected into a display element, and ultraviolet rays are irradiated with a voltage applied between the electrodes to polymerize the polymerizable compound and generate polymers in the liquid crystal composition. By this method, a short response time, A liquid crystal display element that affects afterimages is improved. This method can be used for liquid crystal display elements in various operating modes. There are known modes such as PS-TN, PS-IPS, PS-FFS, PSA-VA, and PSA-OCB. Among the above In the technology, the polymer formed by curing the polymeric compound provides mechanical support to keep the liquid crystal molecules in a preset working state permanently, thereby improving the display effect, such as faster response speed, higher Contrast ratio, wider operating temperature range, etc.

The use of polymers in the elements of this mode improves the alignment ability of liquid crystal molecules, but the solubility of liquid crystal compositions is not greatly improved, and in the prior art, polymeric liquid crystal materials are used to make optically anisotropic bodies, but there are still problems Poor long-term stability, poor weather resistance, etc., so it is expected to develop a new type of polymerizability that has an appropriate balance between solubility and polymerization reactivity, and has better long-term stability and weather resistance for making optically anisotropic bodies. liquid crystal compound.

Contents of the invention

The first object of the present invention is to provide a new type of polymerizable liquid crystal compound, which has suitable polymerization reactivity, high conversion rate, high solubility to liquid crystal composition, stability and weather resistance of the optical anisotropic body produced. It has the advantages of better performance and has important application value.

The liquid crystal compound described in the present invention has the following general structure:

In general formula I, R represents an alkyl or alkoxy group with 1-10 carbon atoms; ring A represents 1,4-phenylene with 1-4 hydrogen atoms replaced by fluorine atoms; m is 1 or 2 .

Preferably, in the general formula I, R represents an alkyl or alkoxy group with 1-6 carbon atoms; ring A represents 1,4-phenylene with 1-4 hydrogen atoms replaced by fluorine atoms; m is 1 or 2.

As a more preferred technical solution, in general formula I, R represents an alkyl or alkoxy group with 1-6 carbon atoms; ring A represents 1,4-phenylene with 1-2 hydrogen atoms replaced by fluorine atoms basis; m is 1.

As a further preferred technical solution, R is methyl, ethyl, methoxy or ethoxy.

As a further preferred technical solution, the liquid crystal compound is selected from one or more of the following compounds:

In compounds of the general formulas I-1 to I-3, R represents an alkyl or alkoxy group having 1-6 carbon atoms; preferably, R represents a methyl, ethyl, methoxy or ethoxy group.

As the best embodiment of the present invention, the liquid crystal compound is selected from one or more of the following compounds:

The second object of the present invention is to provide the preparation method of above-mentioned liquid crystal compound, in order to realize this object, the present invention adopts following technical scheme:

The synthetic route of the compound of above-mentioned structural general formula (I) is as follows:

Preferably, it specifically includes the following steps:

(1) Reaction with organolithium reagents, followed by borate esters, gives

(2) and After Suzuki reaction, we get

(3) By hydrodebenzylation, the

(4) and By esterification reaction, the

Wherein, L ₁ represents H, Br; L ₂ represents Cl or Br; R, m, ring A in the compound involved in each step is corresponding to the group represented by R, m, ring A in the obtained liquid crystal compound product, specifically refers to The generation scope is the same as above (see the limitation of each substituent in general formula I).

In the step 1), The molar ratio of organolithium reagent to boric acid ester is 1:1.0～1.8:1.0～2.0;

Preferably, the reaction temperature can be at -50～-100°C;

Wherein, the organolithium reagent is selected from one or more of n-butyllithium, sec-butyllithium, tert-butyllithium or n-butyllithium and potassium tert-butoxide, and the borate is selected from borate tris One or more of methyl ester, triisopropyl borate, tributyl borate or triisobutyl borate.

In the step 2), and The feeding molar ratio is 1:0.9～1.2;

Preferably, the reaction temperature can be between 60°C and 120°C;

In the step 3), The mass ratio of feed to catalyst is 1:0.05～0.15;

Preferably, the reaction temperature can be between 10°C and 70°C;

Wherein, the catalyst is selected from one or more of Pd/C, Raney nickel, and Pt/C, preferably Pd/C.

In the step 4), and The feeding molar ratio is 1:2.0～3.0;

Preferably, the reaction temperature can be between -10°C and 30°C;

the above and All of them can be synthesized through open commercial channels or methods known in the literature.

The method of the present invention may involve conventional post-treatment if necessary, such as: extracting with dichloromethane, ethyl acetate or toluene, separating liquid, washing with water, drying, and evaporating with a vacuum rotary evaporator to obtain The product can be purified by vacuum distillation or recrystallization and/or chromatographic separation.

The liquid crystal compound described in the present invention can be obtained stably and efficiently by using the above preparation method.

In addition, the present invention also provides a liquid crystal composition containing any one or several polymerizable liquid crystal compounds represented by the general formula I above, wherein the addition ratio of the polymerizable compound accounts for 0.05% to 20% of the overall mixture. % weight ratio, according to different polymer-stabilized liquid crystal display modes, choosing an appropriate addition ratio can obtain a good display effect. For example, in polymer-stabilized vertical alignment technology, the selected addition ratio is 0.05% to 5% by weight. It is preferably 0.1%-1% by weight; in polymer stabilized blue phase technology, the selected addition ratio is 1%-20% by weight, preferably 2%-15% by weight.

The liquid crystal composition containing the polymerizable compound of the present invention has a high upper limit temperature of the nematic phase, a lower lower limit temperature of the nematic phase, a small viscosity, a suitable optical anisotropy, a large dielectric anisotropy, and a suitable elastic constant And proper pre-tilt angle and other physical properties.

The compound represented by any one of the above-mentioned general formula I and the above-mentioned liquid crystal composition containing any one of the compounds represented by the above-mentioned general formula I can be applied in liquid crystal display devices, and the liquid crystal display devices include but are not limited to PS-TN, PS-IPS, PS-FFS, PSA-VA or PSA-OCB LCD display. After the liquid crystal composition is applied to a liquid crystal display device, the liquid crystal display device has a wide temperature range, a short response time, a high voltage retention rate, a large contrast ratio and a long service life, and has broad application prospects.

detailed description

The following examples are used to illustrate the present invention, but are not intended to limit the scope of the present invention. The raw materials can be obtained from open commercial channels unless otherwise specified.

Example 1

The structural formula of the liquid crystal compound is:

The synthetic route for preparing compound BYLC-01 is as follows:

Specific steps are as follows:

(1) Synthesis of compound BYLC-01-1:

Under the protection of nitrogen, add 56.2g of 3-fluoro-4-benzyloxybromobenzene and 450ml of tetrahydrofuran to the reaction flask, add 0.25mol of n-butyllithium n-hexane solution dropwise at -70～-80°C under temperature control, and keep warm after dropping After reacting for 1 hour, 31.2 g of trimethyl borate was added dropwise under temperature control at -70 to -80°C, and then the temperature was naturally returned to -30°C. Add 300ml of 2M hydrochloric acid aqueous solution for acidification, carry out conventional post-treatment, and recrystallize petroleum ether to obtain 46.0g of light yellow solid (compound BYLC-01-1), HPLC: 93.5%, yield 84.5%;

(2) Synthesis of compound BYLC-01-2:

Under nitrogen protection, add 46.0g compound BYLC-01-1, 51.7g 2-methyl-4-benzyloxybromobenzene, 300ml N,N-dimethylformamide, 90ml deionized water, 38.5g to the reaction flask Anhydrous potassium carbonate, 0.7g tetrakistriphenylphosphine palladium, heated to reflux for 3 hours. After conventional post-processing and chromatographic purification, 61.3 g of light yellow solid (compound BYLC-01-2) was obtained, GC: 98.5%, yield: 82.6%.

(3) Synthesis of compound BYLC-01-3:

Add 40.0g of compound BYLC-01-2, 2.0g of palladium carbon, 120ml of toluene, 50ml of ethanol into the reaction flask, hydrogen replacement twice, hydrogenation reaction at a temperature of 10-30°C for 6h, conventional post-treatment, recrystallization of petroleum ether to obtain White solid (compound BYLC-01-3): 20.9 g, GC: 99.5%, yield: 95.8%.

(4) Synthesis of compound BYLC-01:

Under the protection of nitrogen, add 20.0g of compound BYLC-01-3, 40g of anhydrous sodium carbonate, 100ml of acetone to the reaction bottle, and add 28.8g of methacryloyl chloride dropwise under temperature control -10℃～0℃, and react at room temperature for 3 hours , TLC traced the reaction to be complete, carried out conventional post-processing, purified by chromatography, eluted with n-hexane, and recrystallized from ethanol to obtain 24.3 g of a white solid (compound BYLC-01), LC: 99.8%, yield 75.5%;

The obtained white solid BYLC-01 was analyzed by GC-MS, and the m/z of the product was 354.1 (M+).

¹ H-NMR (300 MHz, CDCl ₃ ): 1.15-2.10 (m, 6H), 2.15-2.95 (m, 3H), 5.25-6.10 (m, 4H), 6.55-7.60 (m, 6H).

Example 2

The structural formula of the liquid crystal compound is:

The synthetic route for preparing compound BYLC-02 is as follows:

Specific steps are as follows:

(1) Synthesis of compound BYLC-02-1:

Under nitrogen protection, add 37.0g compound BYLC-01-1, 44.0g 2-methoxy-4-benzyloxybromobenzene, 300ml N,N-dimethylformamide, 90ml deionized water to the reaction flask, 26.9g of anhydrous potassium carbonate and 0.6g of tetrakistriphenylphosphine palladium were heated under reflux for 3 hours. After conventional post-processing and chromatographic purification, 53.0 g of a light yellow solid (compound BYLC-02-1) was obtained, GC: 99.2%, yield: 85.4%.

(2) Synthesis of compound BYLC-02-2:

Add 41.0g of compound BYLC-02-1, 2.0g of palladium carbon, 120ml of toluene, 50ml of ethanol into the reaction flask, hydrogen replacement twice, hydrogenation reaction at a temperature of 10-30°C for 6 hours, conventional post-treatment, recrystallization of petroleum ether to obtain White solid (compound BYLC-02-2): 22.3 g, GC: 99.6%, yield: 96.5%.

(3) Synthesis of compound BYLC-02:

Under the protection of nitrogen, add 22.0g of compound BYLC-02-2, 39.8g of anhydrous sodium carbonate, 100ml of acetone to the reaction bottle, and add 24.6g of methacryloyl chloride dropwise at a temperature of -10°C to 0°C, and then react at room temperature 3 Hours, TLC tracked that the reaction was complete, carried out conventional post-processing, purified by chromatography, eluted with n-hexane, and recrystallized from ethanol to obtain 28.0 g of a white solid (compound BYLC-02), LC: 99.7%, yield 80.5%;

The obtained white solid BYLC-02 was analyzed by GC-MS, and the m/z of the product was 370.1 (M+).

¹ H-NMR(300MHz, CDCl ₃ ):1.15-2.10(m,6H),3.35-3.95(m,3H),5.25-6.10(m,4H),6.55-7.60

(m,6H).

Example 3

The structural formula of the liquid crystal compound is:

The synthetic route for preparing compound BYLC-03 is as follows:

Specific steps are as follows:

(1) Synthesis of compound BYLC-03-1:

Under nitrogen protection, add 42.1g of 2-fluoro-4-benzyloxybromobenzene and 300ml of tetrahydrofuran into the reaction flask, add 0.18mol of n-butyllithium n-hexane solution dropwise at -70～-80°C under temperature control, and keep warm after dropping After reacting for 1 hour, 22.2 g of trimethyl borate was added dropwise under temperature control at -70 to -80°C, and then the temperature was naturally returned to -30°C. Add 300ml of 2M hydrochloric acid aqueous solution for acidification, carry out conventional post-treatment, and recrystallize petroleum ether to obtain 30.4g of light yellow solid (compound BYLC-03-1), HPLC: 96.2%, yield 82.6%;

(2) Synthesis of compound BYLC-03-2:

Under nitrogen protection, add 30.0g compound BYLC-03-1, 33.7g 2-methyl-4-benzyloxybromobenzene, 210ml N,N-dimethylformamide, 70ml deionized water, 20.5g Anhydrous potassium carbonate and 0.6 g tetrakistriphenylphosphine palladium were heated under reflux for 3 hours. After conventional post-processing and chromatographic purification, 40.5 g of light yellow solid (compound BYLC-03-2) was obtained, GC: 99.5%, yield: 83.8%.

(3) Synthesis of compound BYLC-03-3:

Add 40.0g of compound BYLC-03-2, 2.0g of palladium carbon, 120ml of toluene, 50ml of ethanol into the reaction flask, hydrogen replacement twice, hydrogenation reaction at a temperature of 10-30°C for 6h, conventional post-treatment, recrystallization of petroleum ether to obtain White solid (compound BYLC-03-3): 19.8 g, GC: 99.6%, yield: 90.5%.

(4) Synthesis of compound BYLC-03:

Under the protection of nitrogen, add 15.0g of compound BYLC-03-3, 32.8g of anhydrous sodium carbonate, 100ml of acetone to the reaction bottle, and add 21.6g of methacryloyl chloride dropwise at a temperature of -10°C to 0°C, and then react at room temperature 3 Hours, TLC tracked that the reaction was complete, carried out conventional post-processing, purified by chromatography, eluted with n-hexane, and recrystallized from ethanol to obtain 19.6g of a white solid (compound BYLC-03), LC: 99.7%, yield 78.6%;

The obtained white solid BYLC-03 was analyzed by GC-MS, and the m/z of the product was 354.1 (M+).

¹ H-NMR (300 MHz, CDCl ₃ ): 1.15-2.10 (m, 6H), 2.15-2.95 (m, 3H), 5.25-6.10 (m, 4H), 6.55-7.60 (m, 6H).

Example 4

The structural formula of the liquid crystal compound is:

The synthetic route for preparing compound BYLC-04 is as follows:

Specific steps are as follows:

(1) Synthesis of compound BYLC-04-1:

Under nitrogen protection, add 38.5g compound BYLC-03-1, 44.8g 2-methoxy-4-benzyloxybromobenzene, 300ml N,N-dimethylformamide, 90ml deionized water to the reaction flask, 27.2g of anhydrous potassium carbonate and 0.6g of tetrakistriphenylphosphine palladium were heated under reflux for 3 hours. After conventional post-processing and purification by chromatography, 52.1 g of a light yellow solid (compound BYLC-04-1) was obtained, GC: 99.3%, yield: 80.5%.

(2) Synthesis of compound BYLC-04-2:

Add 40.0g of compound BYLC-04-1, 2.0g of palladium carbon, 120ml of toluene, 50ml of ethanol into the reaction flask, hydrogen replacement twice, hydrogenation reaction at a temperature of 10-30°C for 6h, conventional post-treatment, recrystallization of petroleum ether to obtain White solid (compound BYLC-04-2): 22.0 g, GC: 99.5%, yield: 97.6%.

(3) Synthesis of compound BYLC-04:

Under the protection of nitrogen, add 22.0g of compound BYLC-04-2, 38.5g of anhydrous sodium carbonate, 100ml of acetone to the reaction flask, and add 22.5g of methacryloyl chloride dropwise at a temperature of -10°C to 0°C, and then react at room temperature 3 Hours, TLC tracked that the reaction was complete, carried out conventional post-processing, purified by chromatography, eluted with n-hexane, and recrystallized from ethanol to obtain 27.3 g of a white solid (compound BYLC-04), LC: 99.8%, yield 78.6%;

The obtained white solid BYLC-04 was analyzed by GC-MS, and the m/z of the product was 370.1 (M+).

¹ H-NMR (300 MHz, CDCl ₃ ): 1.15-2.10 (m, 6H), 3.35-3.95 (m, 3H), 5.25-6.10 (m, 4H), 6.55-7.60 (m, 6H).

According to the technical solutions of the above embodiments, the following liquid crystal compounds can be synthesized by simply replacing the corresponding raw materials without changing any substantive operations. After structural characterization, the following structural compounds were indeed obtained:

Experimental example

The liquid crystal compounds used in the following compositions were all provided by Beijing Bayi Space-Time Liquid Crystal Technology Co., Ltd. Unless otherwise specified, the contents of each component in the examples represent mass percentages.

According to conventional detection methods in this field, various performance parameters of the liquid crystal 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); γ1 represents rotational viscosity (mPa.s, 25°C); Cp represents clearing point (°C); τ is τon+τoff (response time) (ms); V ₁₀ is the threshold voltage, which is the characteristic voltage when the transmittance changes by 10% (V, 20°C).

The preparation method of compound BYLC-02 used below is the same as that in Example 2; compound DJ-1 is a known compound.

Experimental example 1

Compound BYLC-02 was dissolved in cyclohexanone to prepare a solution with a solid content of 30%. Spin-coat the solution on glass with polyimide, and irradiate it with a high-pressure mercury lamp for 120 seconds. The ultraviolet light intensity is 30mW/cm ² , and the compound BYLC-02 is polymerized while maintaining a uniform orientation state to obtain an optical Anisotropic body Y1.

Compound DJ-1 was prepared into optically anisotropic body Y2 in the same manner as above.

The above-mentioned optical anisotropic bodies Y1 and Y2 were subjected to high-low temperature cycle treatment (high temperature 150°C, low temperature -30°C) 50 times, and the optical retardation before the treatment was set to 100%.

The optical retardation analysis and comparison of Y1 and Y2 obtained from BYLC-02 and DJ-1 respectively, the results are shown in Table 1-1:

Table 1-1: Test results of optical retardation of optical anisotropy body

As can be seen from the test results in Table 1-1, compared with the compound (DJ-1) of Comparative Example 1, the optical retardation reduction rate of the optical anisotropic body prepared in Example 2 BYLC-02 is lower, indicating that it is stable Better performance and better weather resistance.

Experimental example 2

The liquid crystal composition BYHJ-1 is selected, its components and parts by weight are shown in Table 2-0, prepared by conventional methods in the field, and its performance parameters are: Cp: 91.0°C, Δn: 0.100, Δε: -2.2, γ1: 79.

Table 2-0

Based on the above composition BYHJ-1, the following compounds were added in proportions of 0.3% by weight:

Obtain liquid crystal composition BYHJ-11;

The liquid crystal composition BYHJ-22 was obtained.

The solubility of the above-mentioned liquid crystal compositions BYHJ-11 and BYHJ-22 were tested respectively, and the test results are shown in Table 2-1:

Table 2-1: Solubility Test Results of Liquid Crystal Compositions

It can be clearly seen from the test results in Table 2-1 that the liquid crystal compound provided by the present invention has better solubility in liquid crystal compositions than conventional compounds with similar chemical structures.

Experimental example 3

Will contain the same as experimental example 2 Composition BYHJ-11 and containing The comparison of the composition BYHJ-22, the change of the pretilt angle before and after UV (ultraviolet) and the content of the residue as the polymerization time prolongs, the results are shown in Table 3-1 and Table 3-2:

Table 3-1: Pretilt angle detection results

Weight composition ratio UV front pretilt UV rear pretilt BYHJ-11 99.7% BYHJ-1+0.3% BYLC-02 89.7 86.5 BYHJ-22 99.7% BYHJ-1+0.3% DJ-1 89.6 87.1

Table 3-2: Polymer residue test results

From the comparative data in Table 3-1 and Table 3-2, it can be seen that compared with the polymerizable liquid crystal compound DJ-1, the polymerizable liquid crystal compound BYLC-02 of the present invention has a better alignment effect, a faster polymerization rate, and a faster Completely, the residue is lower, which improves the display.

Experimental example 4

The liquid crystal composition BYHJ-11 (same as Experimental Example 2) added with the polymerizable liquid crystal compound of the present invention and the liquid crystal composition BYHJ-1 without the polymer of the present invention (same as Experimental Example 2) were prepared respectively. Polymerize under UV light for 3 minutes, and test the threshold voltage and response time respectively; the test results are as follows in Table 4-1:

Table 4-1:

Threshold voltage (V) response time (ms) BYHJ-1 (without adding the polymer of the present invention) 2.44 15.2 BYHJ-11 (plus the polymer of the present invention) 2.09 7.8

It can be seen from Table 4-1 that after the alignment of the polymeric liquid crystal compound of the present invention, the threshold voltage is lowered, the response time is shortened, and the problem of energy consumption is greatly improved.

In addition to the compositions listed in the experimental examples, other liquid crystal compositions added with other liquid crystal compounds provided by the present invention can obtain the same excellent optical and electrical properties.

Although the present invention has been described in detail with general descriptions and specific embodiments above, it is obvious to those skilled in the art that some modifications or improvements can be made on the basis of the present invention. Therefore, the modifications or improvements made on the basis of not departing from the spirit of the present invention all belong to the protection scope of the present invention.

Claims (10)

1. A novel polymerizable liquid crystal compound characterized by having the following general structure:

wherein R represents an alkyl group or an alkoxy group having 1 to 10 carbon atoms; ring A represents a 1, 4-phenylene group in which 1 to 4 hydrogen atoms are substituted with fluorine atoms; m is 1 or 2.

2. The liquid crystal compound according to claim 1, wherein in the general formula I, R represents an alkyl group or an alkoxy group having 1 to 6 carbon atoms.

3. The liquid crystal compound according to claim 2, wherein ring a represents a 1, 4-phenylene group in which 1 to 2 hydrogen atoms are substituted with fluorine atoms; m is 1.

4. The liquid crystal compound according to claim 1, wherein the liquid crystal compound is selected from one or more of the following compounds:

wherein R represents an alkyl group or an alkoxy group having 1 to 6 carbon atoms.

5. The liquid-crystal compound according to any one of claims 1 to 4, wherein R represents a methyl group, an ethyl group, a methoxy group or an ethoxy group.

6. The liquid crystal compound according to claim 1, wherein the liquid crystal compound is selected from one of the following compounds:

7. a process for producing a liquid crystal compound according to any one of claims 1 to 6, characterized in that the synthetic route is as follows:

preferably, the method specifically comprises the following steps:

(1)reacting with organic lithium reagent and then reacting with boric acid ester to obtain

(2)Andthrough a Suzuki reaction, obtaining

(3)By hydrodebenzylation to give

(4)Andthrough esterification reaction to obtain

Wherein L is₁Represents H, Br; l is₂Represents Cl or Br; r, m, Ring A is specifically referred to within the scope of any one of claims 1 to 5.

8. The production method according to claim 7,

in the step 1), the step (A) is carried out,the feeding molar ratio of the organic lithium reagent to the boric acid ester is 1: 1.0-1.8: 1.0-2.0; preferably, the organolithium reagent is selected from one or more of n-butyllithium, sec-butyllithium, tert-butyllithium or n-butyllithium and potassium tert-butoxide, and the borate is selected from one or more of trimethyl borate, triisopropyl borate, tributyl borate or triisobutyl borate; and/or the presence of a gas in the gas,

in the step 2), the step (c) is carried out,andthe feeding molar ratio of (A) to (B) is 1: 0.9-1.2; and/or the presence of a gas in the gas,

in the step 3), the step (c),the feeding mass ratio of the catalyst to the catalyst is 1: 0.05-0.15;

preferably, the catalyst is selected from one or more of Pd/C, Raney nickel and Pt/C; and/or the presence of a gas in the gas,

in the step 4), the step of mixing the raw materials,andthe feeding molar ratio of (A) to (B) is 1: 2.0-3.0.

9. A liquid crystal composition comprising the liquid crystal compound according to any one of claims 1 to 6 or the liquid crystal compound prepared by the method according to any one of claims 7 to 9, wherein the liquid crystal compound is present in an amount of 0.05 to 20% by weight;

preferably, the weight percentage content of the liquid crystal compound is 0.05-5%, and more preferably 0.1-1%; or,

preferably, the weight percentage of the liquid crystal compound is 1-20%, and more preferably 2-15%.

10. Use of a liquid crystal compound according to any one of claims 1 to 6 or a liquid crystal compound prepared by a process according to any one of claims 7 to 9 or a liquid crystal composition according to claim 9 in a liquid crystal display device; preferably, the liquid crystal display is a PS-TN, PS-IPS, PS-FFS, PSA-VA or PSA-OCB liquid crystal display.