阅读说明：本技术 液晶化合物、由其组成的液晶组合物及应用 (Liquid crystal compound, liquid crystal composition composed of same and application ) 是由 史志兵 孙刚 于 2020-12-22 设计创作，主要内容包括：本发明涉及一种液晶化合物、由其组成的液晶组合物及应用,属于液晶材料领域。液晶化合物包含至少一个环结构,并且包通式I所示结构的尾链；-O(CH_2)_nCF＝CF(CH_2)_mOR I 其中,R表示1-12个碳的烷基或卤代烷基,一个或多个-CH_2-可各自独立地以氧原子不直接相连的方式被-O-、-CH＝CH-、-C≡C-、-CO-O-或-O-CO-卤素替代,-CH_2-上的氢可被卤素取代,n,m分别表示0-12的整数。本发明的化合物具有稳定的化学和物理性质,具有良好的低温互溶性,介电各向异性和折射率各向异性适中。本发明的化合物应用于液晶组合物中时,在提升响应速度的基础上,透过率也有明显提高。(The invention relates to a liquid crystal compound, a liquid crystal composition composed of the same and application thereof, and belongs to the field of liquid crystal materials. The liquid crystal compound comprises at least one ring structure and comprises a tail chain with a structure shown in a general formula I; -O (CH) 2 ) n CF＝CF(CH 2 ) m OR I wherein R represents an alkyl OR haloalkyl group of 1 to 12 carbons, one OR more-CH 2 -may each independently be replaced by-O-, -CH ═ CH-, -C ≡ C-, -CO-O-or-O-CO-halogen, with oxygen atoms not being directly attached, -CH 2 The hydrogen on the-radical may be replaced by halogen, and n and m each represent an integer from 0 to 12. The compound of the invention has stable chemical and physical properties and good performanceGood low temperature intersolubility, moderate dielectric anisotropy and refractive index anisotropy. When the compound is applied to a liquid crystal composition, the transmittance is obviously improved on the basis of improving the response speed.)

1. A liquid crystal compound characterized by: a tail chain comprising at least one ring structure and comprising a structure represented by formula I;

-O(CH₂)_nCF＝CF(CH₂)_mOR I

wherein R represents an alkyl group or a haloalkyl group having 1 to 12 carbon atoms, (CH)₂)_nOr (CH)₂)_mOne or more-CH of₂-may each independently be replaced by-O-, -CH ═ CH-, -C ≡ C-, -CO-O-or-O-CO-halogen, with oxygen atoms not being directly attached, -CH₂The hydrogen on the-radical may be replaced by halogen, and n and m each represent an integer from 0 to 12.

2. The liquid crystal compound according to claim 1, characterized in that: at least one ring structure is connected with the tail chain of the structure shown in the general formula I through a C-O single bond; the number of atoms of the skeleton structure of each independently present ring is 3 to 12.

3. The liquid crystal compound according to claim 2, characterized in that: the structure of the liquid crystal compound is shown as a general formula II:

R₁-(A₁-Z₁)_a-(A₂-Z₂)_b-(A₃-Z₃)_c-A₄·O(CH₂)_nCF＝CF(CH₂)_mOR II

in the compounds of the formula II, R₁Represents H, halogen, cyano or C1-15 alkyl, A₁、A₂、A₃、A₄Each independently represents a ring structure consisting of 3 to 12 atoms, hydrogen on the ring structure is optionally substituted by halogen or alkyl, and Z1, Z2 and Z3 each independently represents a C-C single bond, CH₂CH₂、CH₂O、OCH₂、CF＝CF、CF₂O、OCF₂、COO、OCO、CH＝CH、C≡C、CF₂CH₂、CH₂CF₂、(CH₂)₄、CF₂CF₂、OCH₂CH₂CH₂、CH₂OCH₂CH₂、CH₂CH₂OCH₂、CH₂CH₂CH₂O、OCH₂CH₂O、CH₂OCH₂O or OCH₂OCH₂A, b and c each independently represent an integer of 0 to 4, (CH)₂)_nOr (CH)₂)_mOne or more-CH of₂-each independently can be replaced by-O-, -CH ═ CH-, -C ≡ C-, -CO-O-, or-O-CO-in such a way that the oxygen atoms are not directly linked, -CH₂-the hydrogen in the radical may be substituted by halogen, R represents an alkyl or haloalkyl group having 1 to 12C atoms, n represents an integer from 0 to 12, m represents an integer from 1 to 12.

4. The liquid crystal compound according to claim 3, characterized in that: in the compounds of the formula II, A₁、A₂、A₃、A₄Each is independentImmediately represents a benzene ring, cyclohexane, naphthalene ring, indene ring, tetralin, decahydronaphthalene, oxacyclohexane, cyclopropane, cyclobutane, cyclopentane, cycloheptane or bicyclo [2,2 ]]Octane, hydrogen of the ring structure optionally substituted by halogen or alkyl, CH of these ring structures₂Optionally substituted by O, -CH ═ CH-, -C.ident.C-, -CO-O-or-O-CO-.

5. The liquid crystal compound according to claim 3, characterized in that: in the general formula II, A4 is a six-membered ring, a naphthalene ring or a tetralin ring.

6. The liquid crystal compound according to claim 3, characterized in that: the structure of the liquid crystal compound is shown as a general formula II-1, II-2 or II-3:

in the compounds represented by the general formulae II-1 to II-3, the ring structures B1, B2, B3 and B4 each independently represent 1) cyclohexane, one or more CH of which₂May be substituted by O, or, 2) a phenyl ring in which one or more hydrogens may be substituted by F or methyl, Zb, Zc₁、Zc₂、Zd₁、Zd₂、Zd₃Each independently represents a C-C single bond, CH₂CH₂、CH₂O、OCH₂、CF₂CF₂、CF₂O、OCF₂COO, OCO or CH ═ CH, R₁Represents H, halogen, cyano or C1-15 alkyl, the tail chain being-O (CH)₂)_nCF＝CF(CH₂)_mOR is as defined for formula I.

7. The liquid crystal compound according to claim 6, characterized in that: in the general formulas II-1 to II-3, the structural formula of B1 is as follows:

wherein L1, L2, L3 and L4 are independently selected from H, F and CH₃。

8. The liquid crystal compound according to claim 7, wherein: the liquid crystal compound is a compound with structural formulas of III-1, III-2 and III-3:

wherein B2, B3 and B4 are respectivelyWherein CH on 1, 4-dicyclohexyl₂May be substituted by O, and H of 1, 4-diphenyl may be substituted by fluorine.

9. The liquid crystal compound according to claim 8, wherein: the liquid crystal compound of the general formula III-1 is one of the following compounds:

the liquid crystal compound of the general formula III-2 is one of the following compounds:

the liquid crystal compound of the general formula III-3 is one of the following compounds:

。

10. a liquid crystal composition comprising the liquid crystal compound according to any one of claims 1 to 9, and an electro-optical display device comprising the liquid crystal composition.

Technical Field

The invention relates to a liquid crystal compound, a liquid crystal composition composed of the same and application thereof, in particular to a liquid crystal composition containing a tail chain-O (CH)₂)_nCF＝CF(CH₂)_mThe invention relates to a compound of OR, a liquid crystal composition and application thereof, belonging to the field of liquid crystal materials.

Background

General physical properties required for a liquid crystal compound as a component of a liquid crystal composition are as follows:

(1) chemically stable and physically stable;

(2) has a high bright point (liquid crystal phase-isotropic phase transition temperature);

(3) a low lower limit temperature of a liquid crystal phase (optically isotropic liquid crystal phase such as a nematic phase, a cholesteric phase, a smectic phase, and a blue phase, etc.);

(4) excellent compatibility with other liquid crystal compounds;

(5) dielectric anisotropy with appropriate magnitude;

(6) with a suitably sized refractive index anisotropy.

When a liquid crystal composition containing the chemically and physically stable liquid crystal compound according to (1) is used for a liquid crystal display device, the voltage holding ratio can be improved. In addition, if the liquid crystal composition contains the liquid crystal compound having a high clearing point or a low lower limit temperature of the liquid crystal phase as described in (2) and (3), the temperature range of the nematic phase or the optically isotropic liquid crystal phase can be expanded, and the liquid crystal composition can be used as a display element in a wide temperature range. Liquid crystal compounds are generally used as liquid crystal compositions prepared by mixing with many other liquid crystal compounds in order to exhibit properties that are difficult to be exhibited by a single compound. Therefore, the liquid crystal compound used in the liquid crystal display element is preferably excellent in compatibility with other liquid crystal compounds and the like as described in (4). In recent years, liquid crystal display elements having higher display performance, such as contrast, display capacity, response time characteristics, and the like, have been particularly demanded. Further, a liquid crystal composition having a low rotational viscosity and a low driving voltage is required for the liquid crystal material to be used. In addition, in order to drive an optical element driven in an optically isotropic liquid crystal phase at a low voltage, a liquid crystal compound having large dielectric anisotropy and refractive index anisotropy is preferably used.

Liquid crystal displays have a significantly better viewing angle dependence and are therefore mainly used in television sets and monitors, there is still a continuing need for improved response times, especially with respect to the use of displays having a viewing angle of more than 60 Hz. In addition, it is necessary to maintain good properties such as low temperature stability, and thus it is urgently required to provide a liquid crystal material which is fast in response and stable in low temperature properties.

Disclosure of Invention

Aiming at the problems in the prior art, the invention discloses a tail chain-O (CH)₂)_nCF＝CF(CH₂)_mThe compound of OR has fast response speed and good low-temperature performance when used as a liquid crystal material.

In order to achieve the purpose, the invention adopts the following technical scheme:

a liquid crystal compound comprises at least one ring structure and a tail chain with a structure shown in a general formula I,

-O(CH₂)_nCF＝CF(CH₂)_mOR I

wherein R represents an alkyl group having 1 to 12 carbons (unsubstituted) or a haloalkyl group, (CH)₂)_nOr (CH)₂)_mOne or more (e.g. 1-5, all of which may be substituted) -CH₂-may each independently be replaced by-O-, -CH ═ CH-, -C ≡ C-, -CO-O-or-O-CO-halogen, with oxygen atoms not being directly attached, -CH₂The hydrogen on-may be replaced by halogen, n, m each represent an integer of 0 to 12.

In the structure of the liquid crystal compound, at least one ring structure is connected with a tail chain structure of a structure shown in a general formula I by a C-O single bond.

In the structure of the liquid crystal compound, the number of atoms constituting the skeleton structure of each independently present ring is 3 to 12.

Further, the structure of the liquid crystal compound is shown as a general formula II:

R₁-(A₁-Z₁)_a-(A₂-Z₂)_b-(A₃-Z₃)_c-A₄·O(CH₂)_nCF＝CF(CH₂)_mOR II

in the compounds of the formula II, R₁Represents H, halogen, cyano or C1-15 alkyl, A₁、A₂、A₃、A₄Each independently represents a ring structure consisting of 3 to 12 atoms, the ringThe hydrogen in the structure is optionally substituted by halogen or alkyl (e.g. alkyl of 1-5 carbon atoms), Z1, Z2, Z3 each independently represent a C-C single bond, CH₂CH₂、CH₂O、OCH₂、CF＝CF、CF₂O、OCF₂、COO、OCO、CH＝CH、C≡C、CF₂CH₂、CH₂CF₂、(CH₂)₄、CF₂CF₂、OCH₂CH₂CH₂、CH₂OCH₂CH₂、CH₂CH₂OCH₂、CH₂CH₂CH₂O、OCH₂CH₂O、CH₂OCH₂O or OCH₂OCH₂A, b and c each independently represent an integer of 0 to 4, (CH)₂)_nOr (CH)₂)_mOne or more (e.g. 1-5, all of which may be substituted) -CH₂-may each be independently replaced by-O-, -CH ═ CH-, -C ≡ C-, -CO-O-, or-O-CO-, -CH₂-hydrogen in the group may be substituted by halogen, R represents an alkyl (unsubstituted) or haloalkyl group having 1 to 12C atoms, n represents an integer from 0 to 12, and m represents an integer from 1 to 12.

Further, in the compound represented by the general formula II, A₁、A₂、A₃、A₄Each independently represents a benzene ring, cyclohexane, naphthalene ring, indene ring, tetralin, decahydronaphthalene, oxacyclohexane, cyclopropane, cyclobutane, cyclopentane, cycloheptane or bicyclo [2,2 ]]Octane, optionally substituted with halogen or alkyl (e.g. 1-5 carbon atoms) hydrogen in these ring structures, CH in these ring structures₂Optionally substituted by O, -CH ═ CH-, -C.ident.C-, -CO-O-or-O-CO-.

Further, in formula II, a4 is a six-membered ring, a naphthalene ring, or a tetralin ring.

Further, the structure of the liquid crystal compound is shown as a general formula II-1, II-2 or II-3:

in the compounds represented by the general formulae II-1 to II-3, the ring structures B1, B2, B3 and B4 each independently represent 1) cyclohexane, one or more (for example, 1 to 5, or all of them may be substituted) CH₂May be substituted by O in such a way that oxygen atoms are not directly bonded, i.e., oxygen atoms-O-are not directly bonded when substituted by a plurality of-O-, or, 2) a benzene ring in which one or more (e.g., 1 to 5, or all) hydrogen may be substituted by F or methyl, Zb, Zc₁、Zc₂、Zd₁、Zd₂、Zd₃Each independently represents a C-C single bond, CH₂CH₂、CH₂O、OCH₂、CF₂CF₂、CF₂O、OCF₂COO, OCO or CH ═ CH, R₁Represents H, halogen, cyano or C1-15 alkyl, the tail chain being-O (CH)₂)_nCF＝CF(CH₂)_mOR is as defined for formula I.

Further, in the general formulae II-1 to II-3, the structural formula of the ring structure B1 is:

wherein L1, L2, L3 and L4 are independently selected from H, F and CH₃。

Further, the liquid crystal compounds represented by the general formulae II-1 to II-3 are preferably compounds having the structural formulae III-1, III-2 and III-3:

wherein B2, B3 and B4 are respectivelyWherein CH on 1, 4-dicyclohexyl₂May be substituted by O, and H of 1, 4-diphenyl may be substituted by fluorine.

Further, the liquid crystal compound of the formula III-1 is preferably one of the following compounds:

the liquid crystal compound of the formula III-2 is preferably one of the following compounds:

the liquid crystal compound of the formula III-3 is preferably one of the following compounds:

the invention also provides a composition containing the tail chain-O (CH)₂)_nCF＝CF(CH₂)_mOR, and an electro-optical display device including the same. The above-mentioned compound containing the tail chain-O (CH)₂)_nCF＝CF(CH₂)_mThe compound of OR is applied to the liquid crystal composition, and has high response speed and high transmittance.

The invention has the advantages that:

the compound provided by the invention has stable chemical and physical properties, good low-temperature intersolubility, and moderate dielectric anisotropy and refractive index anisotropy. When the compound provided by the invention is applied to a liquid crystal composition, the transmittance is obviously improved on the basis of improving the response speed. In addition, the compound provided by the invention has good solubility and wide applicability.

The present invention is further illustrated by the following specific embodiments, which are not meant to limit the scope of the invention.

Detailed Description

For convenience of expression, in the following examples, the group structure of the liquid crystal composition is represented by the code listed in table 1:

TABLE 1 radical structural code of liquid crystal compounds

The following compounds are exemplified:

the code of Table 1 is 3CWO4,3 represents cyclohexyl, C represents cyclohexane, W represents 2, 3-difluorobenzene and 4 represents butyl.

The abbreviated codes of the test items in the following examples are as follows:

cp (. degree. C.): clearing point (nematic-isotropic phase transition temperature);

Δ n: refractive index anisotropy (589nm, 25 ℃);

Δ ε: dielectric anisotropy (1KHz, 25 ℃);

t (ms): response time (25 ± 0.5 ℃);

wherein, Delta Epsilon ═ Epsilon_||-ε_⊥Wherein | | | is the dielectric constant parallel to the molecular axis, ∈ | | is the dielectric constant perpendicular to the molecular axis, the test conditions are as follows: 25 ℃ and 1 KHz;

γ₁: represents the rotational viscosity [ mPas ] measured at 25 DEG C]Measured in a magnetic field by the rotational method.

Example 1: synthesis of LDT-1

The preparation process comprises the following steps:

(1) synthesis of LDT-1-1

Adding 24.6g of 4-pentylcyclohexylphenol and 500ml of N, N-dimethylformamide into a 1L reaction bottle, dissolving, adding 8.2g of sodium hydride under the protection of nitrogen, heating to 55 ℃ under stirring, reacting for 7h, cooling to room temperature, dropwise adding 32g of tetrafluorodibromoethane, reacting for 11 h at room temperature, adding 300ml of ethyl acetate and 200ml of water, extracting a liquid layer, extracting a water layer with ethyl acetate, washing with water, drying, concentrating, recrystallizing, and purifying by column chromatography to obtain 36.1g of a crude product, and performing gas chromatography GC: 98.9%, yield: 85 percent.

(2) Synthesis of LDT-1-2

21.2g of LDT-1-1, 6.2g of zinc powder and 200ml of acetonitrile are added into a 500ml reaction bottle, reflux is carried out under nitrogen for llh, the temperature is reduced to room temperature, suction filtration and spin drying are carried out, thus obtaining a crude product, and the crude product is subjected to column chromatography and spin drying to obtain 13.9g of a product. Yield 85% GC 90.2%.

(3) Synthesis of LDT-1

29.4g of sodium ethoxide, 1-28.2 g of LDT-1 and 100ml of tetrahydrofuran are added into a 250ml reaction bottle, and the temperature is raised to 60 ℃ for reaction for 6 hours. Cooling to room temperature, acidifying, extracting with ethyl acetate, washing with water, drying, concentrating to obtain crude product, and performing column chromatography to obtain product LDT-17.3 g with yield of 80%. The content GC 99% MS: m/z 298.2.

The obtained product is analyzed by nuclear magnetic resonance hydrogen spectrum, and the result is as follows:¹H NMR(300MHz,CDCl₃)δ7.22–6.97(m,2H),6.90–6.71(m,2H),4.72(t,J＝1.0Hz,2H),4.12(t,J＝1.0Hz,2H),3.34(s,2H),2.62(dd,J＝6.4,5.5Hz,1H),2.01–1.12(m,18H),1.00–0.78(m,3H)。

example 2: synthesis of LDT-2

The specific preparation process comprises the following steps:

(1) synthesis of intermediate LDT-2-1

Adding 21g of 2, 3-difluoro-4-bromophenol and 500ml of N, N-dimethylformamide into a 1L reaction bottle, dissolving, adding 8.2g of sodium hydride under the protection of nitrogen, heating to 55 ℃ under stirring for reaction for 7 hours, cooling to room temperature, dropwise adding 32g of tetrafluorodibromoethane, reacting for 11 hours at room temperature, adding 300ml of ethyl acetate and 200ml of water, extracting and separating liquid, extracting a water layer with ethyl acetate, washing with water, drying, concentrating, recrystallizing, and purifying by column chromatography to obtain 31g of crude product, wherein GC content is 98.5%, and yield is as follows: 80 percent.

(2) Synthesis of LDT-2-2

19.5g of LDT-2-1, 6.2g of zinc powder and 200ml of acetonitrile are added into a 500ml reaction bottle, l0h is refluxed under nitrogen, the temperature is reduced to room temperature, the filtration and the spin drying are carried out to obtain a crude product, and the crude product is subjected to column chromatography and the spin drying to obtain 11.5g of a product. The yield was 80% by GC 90.8%.

(3) Synthesis of LDT-2-3

29.4g of sodium ethoxide, 2-27.9 g of LDT-2 and 100ml of tetrahydrofuran are added into a 250ml reaction bottle, and the temperature is raised to 60 ℃ for reaction for 6 h. Cooling to room temperature, acidifying, extracting with ethyl acetate, washing with water, drying, concentrating to obtain crude product, and performing column chromatography to obtain product 7.3g LDT-2-3 with yield of 80%. The content GC 95%.

(4) Synthesis of LDT-2

Adding 16.5g of intermediate LDT-2-3, propylcyclohexylphenylboronic acid 14.7, 100ml of toluene, 50ml of ethanol, 50ml of water and 20g of anhydrous sodium carbonate into a 500ml reaction bottle, adding 0.5g of tetrakis (triphenylphosphine) palladium under the protection of nitrogen, heating and refluxing for 6 hours under stirring, cooling to room temperature after the reaction is finished, performing aftertreatment, recrystallization and column chromatography purification to obtain 18.0g of white solid, namely a compound LDT-2, GC 99.3%, yield: 80 percent. MS: m/z: 436.5.

The obtained product is analyzed by nuclear magnetic resonance hydrogen spectrum, and the result is as follows:¹H NMR(300MHz,CDCl₃)δ7.48(dd,J＝9.2,5.0Hz,1H),7.37–7.12(m,4H),6.96(dd,J＝9.3,5.0Hz,1H),4.75(t,J＝1.0Hz,2H),4.12(t,J＝1.0Hz,2H),3.34(s,2H),2.94–2.46(m,1H),1.94–1.15(m,13H),0.90(t,J＝7.6Hz,3H)。

example 3: synthesis of LDT-3

The specific preparation process comprises the following steps:

(1) synthesis of intermediate LDT-3-1

Adding 17.3g of p-bromophenol and 500ml of N, N-dimethylformamide into a 1L reaction bottle, dissolving, adding 8.2g of sodium hydride under the protection of nitrogen, heating to 55 ℃ under stirring, reacting for 7 hours, cooling to room temperature, dropwise adding 32g of tetrafluorodibromoethane, reacting for 11 hours at room temperature, adding 300ml of ethyl acetate and 200ml of water, extracting and separating liquid, extracting a water layer with ethyl acetate, washing with water, drying, concentrating, recrystallizing, and purifying by column chromatography to obtain 27.8g of crude product, 99.0% of GC, wherein: 85 percent.

(2) Synthesis of LDT-3-2

17.5g of LDT-3-1, 6.2g of zinc powder and 200ml of acetonitrile are added into a 500ml reaction bottle, reflux is carried out for 12h under nitrogen, the temperature is reduced to room temperature, suction filtration and spin drying are carried out to obtain a crude product, and the crude product is subjected to column chromatography and spin drying to obtain 12.6g of a product. The yield was 80% by GC 91.5%.

(3) Synthesis of LDT-3-3

30.4g of sodium n-propoxide, 3 to 210 g of LDT-3 and 100ml of tetrahydrofuran are added into a 250ml reaction bottle, and the temperature is raised to 60 ℃ for reaction for 6 hours. Cooling to room temperature, acidifying, extracting with ethyl acetate, washing with water, drying, concentrating to obtain crude product, and performing column chromatography to obtain product 11.6g LDT-3-3 with yield of 80%. The content GC 95%.

(4) Synthesis of LDT-3

Adding 7.3g of intermediate LDT-3-3, 8.3 g of propylcyclohexylphenylboronic acid, 50ml of toluene, 25ml of ethanol, 25ml of water and 10g of anhydrous sodium carbonate into a 250ml reaction bottle, adding 0.2g of tetrakis (triphenylphosphine) palladium under the protection of nitrogen, heating and refluxing for 6 hours under stirring, cooling to room temperature after the reaction is finished, performing aftertreatment, recrystallization and column chromatography purification to obtain 8.88g of white solid, namely a compound LDT-3, GC 99.2%, yield: 80 percent. MS: m/z: 444.4.

The obtained product is analyzed by nuclear magnetic resonance hydrogen spectrum, and the result is as follows:¹H NMR(300MHz,CDCl₃)δ7.72–7.29(m,6H),7.24–6.84(m,4H),4.72(t,J＝1.0Hz,2H),4.12(t,J＝1.0Hz,2H),3.34(s,2H),2.61(tt,J＝6.4,1.0Hz,2H),1.66(dt,J＝7.7,6.3Hz,2H),0.96(t,J＝7.5Hz,3H)。

EXAMPLE 4 Synthesis of LDT-4 Compound

The preparation process comprises the following steps:

(1) synthesis of LDT-4-1

Adding 25.4g of 4-propyl-cyclohexyl 2, 3-difluorophenol and 500ml of N, N-dimethylformamide into a 1L reaction bottle, dissolving, adding 8.2g of sodium hydride under the protection of nitrogen, heating to 55 ℃ under stirring for reaction for 7 hours, cooling to room temperature, dropwise adding 33g of tetrafluorodibromoethane, reacting for 10 hours after adding the room temperature, adding 300ml of ethyl acetate and 200ml of water, extracting and separating liquid, extracting a water layer with ethyl acetate, washing with water, drying and concentrating, recrystallizing, and purifying by column chromatography to obtain 37.2g of crude product, GC: 99.2%, yield: 86 percent.

(2) Synthesis of LDT-4-2

22.0g of LDT-4-1, 6.2g of zinc powder and 200ml of acetonitrile are added into a 500ml reaction bottle, reflux is carried out under nitrogen for llh, the temperature is reduced to room temperature, suction filtration and spin drying are carried out, thus obtaining a crude product, and the crude product is subjected to column chromatography and spin drying to obtain 14.5g of a product. Yield 87% GC 93.5%.

(3) Synthesis of LDT-4

29.4g of sodium ethoxide, 4-28.4 g of LDT-4 and 100ml of tetrahydrofuran are added into a 250ml reaction bottle, and the temperature is raised to 60 ℃ for reaction for 6 h. Cooling to room temperature, acidifying, extracting with ethyl acetate, washing with water, drying, concentrating to obtain crude product, and performing column chromatography to obtain LDT-47.6 g with yield of 83%. The content GC 99.2% MS: m/z 306.1.

The obtained product is analyzed by nuclear magnetic resonance hydrogen spectrum, and the result is as follows:¹H NMR(300MHz,C)δ7.35–6.74(m,2H),4.28(q,J＝6.4Hz,2H),2.95(td,J＝5.8,0.7Hz,1H),1.99–1.11(m,17H),0.90(t,J＝7.6Hz,3H)。

comparative example 1: a mixture LCM-D1 filled between two substrates of a liquid crystal display was prepared according to the compounds and weight percentages listed in Table 2, and the composition and test data of the mixture LCM-D1 are shown in Table 2 below:

TABLE 2

Application example 1

The compound LDT-1 is used for replacing 5CPO2 in the mixture LCM-D1, the proportion of other components is unchanged, and the mixture LCM-1 is filled between two substrates of a liquid crystal device for performance test, and the composition and the test data of the mixture LCM-1 are shown in the following table 3:

TABLE 3

Components	Percentage of	Performance of
				2CPWO2	9	Cp	74.4
3CPWO2	7	Δn	0.09
				3CWO4	22	Δε	-3.0
3CCWO2	9	γ1	73
				3CCWO3	5	t(ms)	15
4CCWO2	6
				5CCWO2	8
LDT-1	9
				3CC2	11
4CC3	4
				5CC2	8
3CPP2	2
				Total of	100

Application example 2

The compound LDT-4 is used for replacing 3CWO4 in the mixture LCM-D1, the content of each component is unchanged, the mixture LCM-2 is obtained and filled between two substrates of a liquid crystal display to carry out performance tests, and the composition and the test data of the mixture LCM-2 are shown in Table 4.

TABLE 4

Components	Percentage of	Performance of
				2CPWO2	9	Cp	74.8
3CPWO2	7	Δn	0.09
				LDT-4	22	Δε	-3.0
3CCWO2	9	γ1	72
				3CCWO3	5	t(ms)	13
4CCWO2	6
				5CCWO2	8
5CPO2	9
				3CC2	11
4CC3	4
				5CC2	8
3CPP2	2
				Total of	100

Application example 3

The compound LDT-2 is used for replacing 3CPWO2 in the mixture LCM-D1, the content of each component is unchanged, and a mixture LCM-3 filled between two substrates of a liquid crystal display is subjected to performance test, and the composition and the test data of the mixture LCM-3 are shown in the following table 5.

TABLE 5

As can be seen by comparing the above application comparative example 1 with application examples 1 to 3, however, the compound of the general formula I has a very low rotational viscosity and a high absolute value of dielectric anisotropy. Liquid-crystal mixtures having short response times, simultaneously good phase properties and good low-temperature properties can thus be prepared.