CN107699252B

CN107699252B - A kind of polymerizable liquid crystal compound and its preparation method and application

Info

Publication number: CN107699252B
Application number: CN201610643392.2A
Authority: CN
Inventors: 高立龙; 谭小玉; 田会强; 储士红; 王杰; 陈海光; 姜天孟
Original assignee: Beijing Bayi Space LCD Technology Co Ltd
Current assignee: Beijing Bayi Space LCD Technology Co Ltd
Priority date: 2016-08-08
Filing date: 2016-08-08
Publication date: 2021-09-07
Anticipated expiration: 2036-08-08
Also published as: CN107699252A

Abstract

本发明涉及液晶显示材料领域，具体涉及一种聚合性液晶化合物及其制备方法与应用。本发明所述液晶化合物的通式结构为：

其中，R表示具有1‑10个碳原子的烷基或烷氧基；环A表示1‑4个氢原子被氟原子取代的1,4‑亚苯基；m为1或2。本发明还提供一种液晶组合物，其中包含重量百分比为0.05％～20％的上述化合物，加入了本发明化合物的液晶组合物，具有向列相的高上限温度、向列相的低下限温度、小的粘度、适当的光学各向异性、大的介电各向异性、适当的弹性常数以及适当的预倾角等物性，应用前景广阔。The invention relates to the field of liquid crystal display materials, in particular to a polymerizable liquid crystal compound and a preparation method and application thereof. The general structure of the liquid crystal compound of the present invention is:

wherein, R represents an alkyl or alkoxy group having 1-10 carbon atoms; Ring A represents a 1,4-phenylene group in which 1-4 hydrogen atoms are substituted by fluorine atoms; m is 1 or 2. The present invention also provides a liquid crystal composition, which contains 0.05% to 20% by weight of the above-mentioned compound, and the liquid crystal composition to which the compound of the present invention is added has a high upper limit temperature of the nematic phase and a low lower limit temperature of the nematic phase. , small viscosity, appropriate optical anisotropy, large dielectric anisotropy, appropriate elastic constant and appropriate pre-tilt angle and other physical properties, the application prospect is broad.

Description

Polymeric liquid crystal compound and preparation method and application thereof

Technical Field

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

Background

The application of liquid crystal materials as environmental materials in the fields of information display materials, organic optoelectronic materials and the like has great research value and good application prospect, in recent years, along with the rapid development of information-oriented society, more gorgeous and precise planar display technology and three-dimensional display technology are brought forward, and the importance of optical anisotropic bodies such as optical retarders, patterned retarders and cylindrical lenses which can be used for the liquid crystal displays is increasingly improved. In the case of an optically anisotropic body which requires high durability and high functionality, not only optical characteristics but also polymerization rate, solubility, melting point, glass transition temperature of a compound, transparency of a polymer, mechanical strength, surface hardness, heat resistance and the like become important factors.

The polymer stabilized liquid crystal display technology is a technology for stabilizing the alignment state or phase state of liquid crystal molecules using extra energy provided by a polymer, such as a polymer stabilized alignment mode (PSA) or a polymer stabilized mode (PS) in which a liquid crystal composition to which a polymerizable compound is added is injected into a display element, and the polymerizable compound is polymerized by irradiating ultraviolet light in a state where a voltage is applied between electrodes to form a polymer in the liquid crystal composition, and a liquid crystal display element having a short response time and improved image sticking is obtained by using the method, which can be used for liquid crystal display elements of various operation modes, such as PS-TN, PS-IPS, PS-FFS, PSA-VA, and PSA-OCB, in which the polymer formed by curing the polymerizable compound provides a mechanical support, the liquid crystal molecules are permanently kept in a preset working state, thereby improving the display effect, such as faster response speed, higher contrast ratio, wider working temperature range and the like.

In the device of this mode, although the ability to align liquid crystal molecules is improved by using a polymer, the solubility of the liquid crystal composition is not greatly improved, and the problems of the long-term stability and the weather resistance are still encountered in the conventional method of manufacturing an optically anisotropic body by using a polymerizable liquid crystal material, and therefore, it is desired to develop a polymerizable liquid crystal compound having a proper balance between the solubility and the polymerization reactivity and having excellent long-term stability and weather resistance for manufacturing an optically anisotropic body.

Disclosure of Invention

The first object of the present invention is to provide a polymerizable liquid crystal compound which has advantages of appropriate polymerization reactivity, high conversion rate, high solubility in a liquid crystal composition, and excellent stability and weather resistance of the produced optically anisotropic body, and which has important application value.

The liquid crystal compound has the following general structure:

in the general formula I, 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.

Preferably, in formula I, R represents an alkyl or alkoxy group having 1 to 6 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.

As a more preferable embodiment, in the general formula I, R represents an alkyl group or an alkoxy group having 1 to 6 carbon atoms; ring A represents a 1, 4-phenylene group in which 1 to 2 hydrogen atoms are substituted with fluorine atoms; m is 1.

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

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

the second purpose of the present invention is to provide a method for preparing the liquid crystal compound, and to achieve the purpose, the present invention adopts the following technical scheme:

the synthetic route of the compound of the above general structural formula (I) is shown 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)

And

through a Suzuki reaction, obtaining

(3)

By hydrodebenzylation to give

(4)

And

through esterification reaction to obtain

Wherein L is₁Represents H, Br; l is₂Represents Cl or Br; r, m and ring A in the compound involved in each step correspond to groups represented by R, m and ring A in the obtained liquid crystal compound product, and the specific reference ranges are as above (see the definition of each substituent in the general formula I).

In the step 1) described above, the step of,

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 reaction temperature can be between-50 and-100 ℃;

the organic lithium 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.

In the step 2) of the said step,

and

the feeding molar ratio of (A) to (B) is 1: 0.9-1.2;

preferably, the reaction temperature can be 60-120 ℃;

in the step 3), the step of the method comprises the following steps,

the feeding mass ratio of the catalyst to the catalyst is 1: 0.05-0.15;

preferably, the reaction temperature can be 10-70 ℃;

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

In the step 4), the step of processing the first and second images,

and

the feeding molar ratio of (A) to (B) is 1: 2.0-3.0;

preferably, the reaction temperature can be-10 to 30 ℃;

as described above

And

can be synthesized by publicly available commercial methods or by methods known per se in the literature.

The method of the invention, if necessary, involves conventional post-treatment, such as: extracting with dichloromethane, ethyl acetate or toluene, separating liquid, washing with water, drying, evaporating with vacuum rotary evaporator, and purifying the obtained product by vacuum distillation or recrystallization and/or chromatographic separation.

The liquid crystal compound can be stably and efficiently obtained by the preparation method.

In addition, the invention also provides a liquid crystal composition containing any one or more of the polymeric liquid crystal compounds shown in the general formula I, wherein the addition ratio of the polymeric compounds accounts for 0.05-20% by weight of the total mixture, and good display effects can be obtained by selecting proper addition ratio according to different polymer stable liquid crystal display modes, for example, in the polymer stable vertical alignment technology, the selected addition ratio is 0.05-5% by weight, preferably 0.1-1% by weight; in the polymer stabilized blue phase technique, the addition ratio is selected to be 1 to 20% by weight, preferably 2 to 15% by weight.

The liquid crystal composition containing the polymerizable compound of the present invention has physical properties such as a high upper limit temperature of a nematic phase, a low lower limit temperature of a nematic phase, a small viscosity, an appropriate optical anisotropy, a large dielectric anisotropy, an appropriate elastic constant, and an appropriate pretilt angle.

Any of the compounds represented by the general formula I and the liquid crystal composition containing any of the compounds represented by the general formula I can be applied to liquid crystal display devices, including but not limited to PS-TN, PS-IPS, PS-FFS, PSA-VA or PSA-OCB liquid crystal displays. After the liquid crystal composition is applied to the liquid crystal display device, the liquid crystal display device has a wide temperature range, short response time, high voltage holding ratio, large contrast ratio, long service life and wide application prospect.

Detailed Description

The following examples are intended to illustrate the invention but are not intended to limit the scope of the invention. The starting materials are commercially available from the open literature unless otherwise specified.

Example 1

The structural formula of the liquid crystal compound is as follows:

the synthetic route for the preparation of compound BYLC-01 is shown below:

the method comprises the following specific steps:

(1) synthesis of Compound BYLC-01-1:

under the protection of nitrogen, 56.2g of 3-fluoro-4-benzyloxy bromobenzene and 450ml of tetrahydrofuran are added into a reaction bottle, 0.25mol of n-hexane solution of n-butyllithium is dripped into the reaction bottle at the temperature of minus 70 ℃ to minus 80 ℃, the reaction is kept for 1 hour after dripping, 31.2g of trimethyl borate is dripped into the reaction bottle at the temperature of minus 70 ℃ to minus 80 ℃, and then the reaction bottle is naturally cooled to minus 30 ℃. Acidification was carried out by adding 300ml of 2M aqueous hydrochloric acid solution, and conventional workup was carried out, and recrystallization from petroleum ether gave 46.0g of a pale yellow solid (compound BYLC-01-1), HPLC: 93.5%, yield 84.5%;

(2) synthesis of Compound BYLC-01-2:

under the protection of nitrogen, 46.0g of the compound BYLC-01-1, 51.7g of 2-methyl-4-benzyloxy bromobenzene, 300ml of N, N-dimethylformamide, 90ml of deionized water, 38.5g of anhydrous potassium carbonate and 0.7g of palladium tetratriphenylphosphine were added to a reaction flask, and the mixture was heated under reflux for 3 hours. After the conventional workup, purification was carried out by chromatography to obtain 61.3g of a pale yellow solid (compound BYLC-01-2), GC: 98.5%, yield: 82.6 percent.

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

adding 40.0g of compound BYLC-01-2, 2.0g of palladium carbon, 120ml of toluene and 50ml of ethanol into a reaction bottle, performing hydrogen replacement twice, controlling the temperature to be 10-30 ℃, performing hydrogenation reaction for 6 hours, performing conventional post-treatment, and recrystallizing petroleum ether to obtain a white solid (compound BYLC-01-3), wherein the weight ratio of the compound BYLC-01-3 to GC: 99.5%, yield: 95.8 percent.

(4) Synthesis of Compound BYLC-01:

under the protection of nitrogen, 20.0g of compound BYLC-01-3, 40g of anhydrous sodium carbonate and 100ml of acetone are added into a reaction bottle, the temperature is controlled to be minus 10 ℃ to 0 ℃, 28.8g of methacryloyl chloride is dripped, the reaction is carried out for 3 hours at room temperature after dripping, TLC tracking reaction is complete, conventional post-treatment is carried out, and the white solid (compound BYLC-01)24.3g is obtained through chromatographic purification, normal hexane elution and ethanol recrystallization, wherein LC: 99.8 percent and the yield is 75.5 percent;

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

¹H-NMR(300MHz,CDCl₃):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 as follows:

the synthetic route for the preparation of compound BYLC-02 is shown below:

the method comprises the following specific steps:

(1) synthesis of Compound BYLC-02-1:

37.0g of a compound BYLC-01-1, 44.0g of 2-methoxy-4-benzyloxy bromobenzene, 300ml of N, N-dimethylformamide, 90ml of deionized water, 26.9g of anhydrous potassium carbonate and 0.6g of palladium tetratriphenylphosphine were added to a reaction flask under the protection of nitrogen, and the mixture was heated under reflux for 3 hours. After the conventional workup, the product was purified by chromatography to give a pale yellow solid (Compound BYLC-02-1)53.0g, GC: 99.2%, yield: 85.4 percent.

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

adding 41.0g of compound BYLC-02-1, 2.0g of palladium carbon, 120ml of toluene and 50ml of ethanol into a reaction bottle, performing hydrogen replacement twice, controlling the temperature to be 10-30 ℃, performing hydrogenation reaction for 6 hours, performing conventional post-treatment, and recrystallizing petroleum ether to obtain a white solid (compound BYLC-02-2), wherein 22.3g of white solid is obtained, and GC: 99.6%, yield: 96.5 percent.

(3) Synthesis of Compound BYLC-02:

under the protection of nitrogen, 22.0g of compound BYLC-02-2, 39.8g of anhydrous sodium carbonate and 100ml of acetone are added into a reaction bottle, 24.6g of methacryloyl chloride is dropwise added at the temperature of-10-0 ℃, the reaction is carried out for 3 hours after the dropwise addition, the TLC tracking reaction is complete, the conventional post-treatment is carried out, and the compound BYLC-02 is obtained by chromatographic purification, normal hexane elution and ethanol recrystallization, wherein the weight of white solid (compound BYLC-02) is 28.0g, LC: 99.7 percent and the yield is 80.5 percent;

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

¹H-NMR(300MHz,CDCl₃):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 as follows:

the synthetic route for the preparation of compound BYLC-03 is shown below:

the method comprises the following specific steps:

(1) synthesis of Compound BYLC-03-1:

under the protection of nitrogen, 42.1g of 2-fluoro-4-benzyloxy bromobenzene and 300ml of tetrahydrofuran are added into a reaction bottle, 0.18mol of n-hexane solution of n-butyllithium is dripped into the reaction bottle at the temperature of minus 70 to minus 80 ℃, the reaction is kept for 1 hour after dripping, 22.2g of trimethyl borate is dripped into the reaction bottle at the temperature of minus 70 to minus 80 ℃, and then the reaction bottle is naturally cooled to minus 30 ℃. Acidification was carried out by adding 300ml of 2M aqueous hydrochloric acid solution, and conventional workup and recrystallization from petroleum ether gave 30.4g of a pale yellow solid (compound BYLC-03-1), HPLC: 96.2 percent and the yield is 82.6 percent;

(2) synthesis of Compound BYLC-03-2:

30.0g of a compound BYLC-03-1, 33.7g of 2-methyl-4-benzyloxy bromobenzene, 210ml of N, N-dimethylformamide, 70ml of deionized water, 20.5g of anhydrous potassium carbonate and 0.6g of palladium tetratriphenylphosphine were added to a reaction flask under the protection of nitrogen, and the mixture was heated under reflux for 3 hours. After the conventional post-treatment, the product was purified by chromatography to obtain a pale yellow solid (compound BYLC-03-2)40.5g, GC: 99.5%, yield: 83.8 percent.

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

adding 40.0g of compound BYLC-03-2, 2.0g of palladium carbon, 120ml of toluene and 50ml of ethanol into a reaction bottle, performing hydrogen replacement twice, controlling the temperature to be 10-30 ℃, performing hydrogenation reaction for 6 hours, performing conventional post-treatment, and recrystallizing petroleum ether to obtain a white solid (compound BYLC-03-3), 19.8g of which is shown in the specification, and GC: 99.6%, yield: 90.5 percent.

(4) Synthesis of Compound BYLC-03:

under the protection of nitrogen, 15.0g of compound BYLC-03-3, 32.8g of anhydrous sodium carbonate and 100ml of acetone are added into a reaction bottle, 21.6g of methacryloyl chloride is dropwise added at the temperature of-10-0 ℃, the reaction is carried out for 3 hours after the dropwise addition, the TLC tracking reaction is complete, the conventional post-treatment is carried out, and the mixture is subjected to chromatographic purification, n-hexane elution and ethanol recrystallization to obtain 19.6g of white solid (compound BYLC-03), LC: 99.7 percent and the yield is 78.6 percent;

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

Example 4

The structural formula of the liquid crystal compound is as follows:

the synthetic route for the preparation of compound BYLC-04 is shown below:

the method comprises the following specific steps:

(1) synthesis of Compound BYLC-04-1:

under the protection of nitrogen, 38.5g of the compound BYLC-03-1, 44.8g of 2-methoxy-4-benzyloxy bromobenzene, 300ml of N, N-dimethylformamide, 90ml of deionized water, 27.2g of anhydrous potassium carbonate and 0.6g of palladium tetratriphenylphosphine were added to a reaction flask, and the mixture was heated under reflux for 3 hours. After the conventional post-treatment, the product was purified by chromatography to obtain 52.1g of a pale yellow solid (Compound BYLC-04-1), GC: 99.3%, yield: 80.5 percent.

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

adding 40.0g of compound BYLC-04-1, 2.0g of palladium carbon, 120ml of toluene and 50ml of ethanol into a reaction bottle, performing hydrogen replacement twice, controlling the temperature to be 10-30 ℃, performing hydrogenation reaction for 6 hours, performing conventional post-treatment, and recrystallizing petroleum ether to obtain a white solid (compound BYLC-04-2), 22.0g of which, GC: 99.5%, yield: 97.6 percent.

(3) Synthesis of Compound BYLC-04:

under the protection of nitrogen, 22.0g of compound BYLC-04-2, 38.5g of anhydrous sodium carbonate and 100ml of acetone are added into a reaction bottle, the temperature is controlled to be minus 10 ℃ to 0 ℃, 22.5g of methacryloyl chloride is dripped, the reaction lasts for 3 hours at room temperature after dripping, TLC tracking reaction is complete, conventional post-treatment is carried out, and 27.3g of white solid (compound BYLC-04) is obtained through chromatographic purification, n-hexane elution and ethanol recrystallization, wherein the mass ratio of LC: 99.8 percent and the yield is 78.6 percent;

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

According to the technical scheme of the embodiment, the following liquid crystal compounds can be synthesized only by simply replacing corresponding raw materials without changing any substantial operation. Through structural characterization, the following structural compounds are indeed obtained:

examples of the experiments

The liquid crystal compounds used in the following compositions are all supplied by the company of the Beijing eight billion space-time liquid Crystal technology, Inc. Except for special description, the contents of each component in the examples represent mass percentages.

According to the conventional detection method in the field, various performance parameters of the liquid crystal compound are obtained through linear fitting, wherein the specific meanings of the performance parameters are as follows:

Δ n represents optical anisotropy (25 ℃); Δ ε represents the dielectric anisotropy (25 ℃, 1000 Hz); γ 1 represents rotational viscosity (mpa.s, 25 ℃); cp stands for clearing Point (. degree. C.); τ is τ on + τ off (response time) (ms); v₁₀Is a threshold valueThe voltage is a characteristic voltage (V, 20 ℃) when the transmittance is changed by 10%.

The following preparation method of BYLC-02, a compound used in the present invention, was the same as in example 2; the compound DJ-1 is a known compound.

Example 2(BYLC-02)

COMPARATIVE EXAMPLE 1(DJ-1)

Experimental example 1

Compound BYLC-02 was dissolved in cyclohexanone to make a 30% solids solution. The solution was spin-coated on a glass with polyimide, and irradiated with a high-pressure mercury lamp for 120 seconds at an ultraviolet intensity of 30mW/cm²The compound BYLC-02 was polymerized while maintaining a uniform orientation, to obtain an optically anisotropic body Y1.

An optically anisotropic body Y2 was prepared from compound DJ-1 in the same manner as described above.

The optically anisotropic bodies Y1 and Y2 were subjected to high/low temperature cycle treatment (high temperature 150 ℃ C., low temperature-30 ℃ C.) for 50 times, and the optical retardation before the treatment was 100%.

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

tables 1 to 1: optical anisotropic body optical retardation amount detection result

As is clear from the results of measurement in Table 1-1, the optically anisotropic body obtained in example 2BYLC-02 had a lower decrease in the optical retardation, and demonstrated better stability and weather resistance, as compared with the compound (DJ-1) of comparative example 1.

Experimental example 2

Selecting a liquid crystal composition BYHJ-1, wherein the components and the parts by weight are shown in the following table 2-0, preparing by adopting a conventional method in the field, and the performance parameters are as follows: cp: 91.0 ℃, Δ n: 0.100, Δ ε: -2.2, γ 1: 79.

TABLE 2-0

The following compounds were added in a proportion of 0.3% by weight, based on the above composition BYHJ-1, respectively:

BYLC-02 to obtain a liquid crystal composition BYHJ-11;

DJ-1 to obtain a liquid crystal composition BYHJ-22.

The solubility of the liquid crystal compositions BYHJ-11 and BYHJ-22 was measured, respectively, and the measurement results are shown in Table 2-1:

table 2-1: solubility detection result of liquid crystal composition

As is apparent from the test results in Table 2-1, the solubility of the liquid crystal compound provided by the present invention in the liquid crystal composition is better than that of the conventional compound having a similar chemical structure.

Experimental example 3

The same contents as those in Experimental example 2

Composition BYHJ-11 and composition containing

The composition BYHJ-22, the pretilt angle change before and after UV (ultraviolet) and the content of residue as a function of polymerization time were compared, and the results are shown in tables 3-1 and 3-2:

table 3-1: pretilt angle detection results

	Proportion of the components by weight	Pretilt angle before UV	Pretilt angle after UV
				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

Tables 3-2: polymer residue test results

As is clear from the comparative data in tables 3-1 and 3-2, the polymerizable liquid crystal compound BYLC-02 of the present invention has better alignment effect, faster and more complete polymerization rate, and lower residue, compared to the polymerizable liquid crystal compound DJ-1, thereby improving the display effect.

Experimental example 4

A liquid crystal composition BYHJ-11 to which a polymerizable liquid crystal compound of the present invention was added (same as Experimental example 2) and a liquid crystal composition BYHJ-1 to which a polymer of the present invention was not added (same as Experimental example 2) were added, respectively. Polymerizing for 3min under UV light, and respectively testing threshold voltage and response time; and the test results are shown in the following table 4-1:

table 4-1:

	threshold voltage (V)	Response time (ms)
			BYHJ-1 (without addition of the Polymer of the invention)	2.44	15.2
BYHJ-11 (plus Polymer of the invention)	2.09	7.8

As is clear from Table 4-1, the threshold voltage is lowered and the response time is shortened after the alignment of the polymerizable liquid crystal compound of the present invention, so that the problem of energy consumption is well improved.

Other liquid crystal compositions to which other liquid crystal compounds provided by the present invention were added, in addition to the compositions listed in the experimental examples, could give equally good optical and electrical properties.

Although the invention has been described in detail hereinabove with respect to a general description and specific embodiments thereof, it will be apparent to those skilled in the art that modifications or improvements may be made thereto based on the invention. Accordingly, such modifications and improvements are intended to be within the scope of the invention as claimed.

Claims

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

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

2. The liquid crystal compound according to claim 1, wherein R represents a methyl group, an ethyl group, a methoxy group, or an ethoxy group.

3. A method for producing a liquid crystal compound according to claim 1 or 2, wherein the synthetic route is as follows:

wherein L is₁Represents H or Br; l is₂Represents Cl or Br; r is specifically defined in the scope of claim 1 or 2; m is 1 and ring A is 2-fluoro-1, 4-phenylene.

4. The method for preparing a liquid crystal compound according to claim 3, comprising the steps of:

(1)

(2)

And

through a Suzuki reaction, obtaining

(3)

By hydrodebenzylation to give

(4)

And

through esterification reaction to obtain

5. The production method according to claim 4,

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; and/or the presence of a gas in the gas,

in the step 2), the step (c) is carried out,

and

the 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; and/or the presence of a gas in the gas,

in the step 4), the step of mixing the raw materials,

and

the feeding molar ratio of (A) to (B) is 1: 2.0-3.0.

6. The preparation method of claim 5, wherein in the step 1), 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 3), the catalyst is selected from one or more of Pd/C, Raney nickel and Pt/C.

7. A liquid crystal composition comprising the liquid crystal compound according to claim 1 or 2 or the liquid crystal compound prepared by the method according to any one of claims 3 to 6, wherein the liquid crystal compound is present in an amount of 0.05 to 20% by weight.

8. The liquid crystal composition according to claim 7, wherein the liquid crystal compound is present in an amount of 0.05 to 5% by weight.

9. The liquid crystal composition according to claim 8, wherein the liquid crystal compound is present in an amount of 0.1 to 1% by weight.

10. The liquid crystal composition according to claim 7, wherein the liquid crystal compound is present in an amount of 1 to 20% by weight.

11. The liquid crystal composition according to claim 10, wherein the liquid crystal compound is present in an amount of 2 to 15 wt%.

12. Use of a liquid crystal compound according to claim 1 or 2 or a liquid crystal compound prepared by the method according to any one of claims 3 to 6 or a liquid crystal composition according to any one of claims 8 to 11 in a liquid crystal display device.

13. Use according to claim 12, wherein the liquid crystal display device is a PS-TN, PS-IPS, PS-FFS, PSA-VA or PSA-OCB liquid crystal display.