CN102492430A

CN102492430A - Liquid crystal composition and liquid crystal display element containing the same

Info

Publication number: CN102492430A
Application number: CN2011103849755A
Authority: CN
Inventors: 李鹏飞; 吴凤; 宋晓龙; 季飞; 王盼盼; 游石枝
Original assignee: JIANGSU HECHENG CHEMICAL MATERIALS CO Ltd
Current assignee: JIANGSU HECHENG CHEMICAL MATERIALS CO Ltd
Priority date: 2011-11-28
Filing date: 2011-11-28
Publication date: 2012-06-13
Also published as: WO2013078766A1

Abstract

The invention discloses a liquid crystal composition having low viscosity, properly high optical anisotropy and dielectric anisotropy (delta epsilon) and a liquid crystal display element containing the composition. The liquid crystal composition comprises 2-25 wt% of compound of formula I, 3-40 wt% of compound of formula II, 5-60 wt% of compound of formula III, 0-45 wt% of compound of formula IV, 0-20 wt% of compound of formula V, and 0-30 wt% of compound of formula VI. The liquid crystal composition can be used in display members having a thin cell gap, has good low temperature intersolubility, and can be stored in a container for a long time without crystallization in a low temperature environment.

Description

Liquid crystal composition and liquid crystal display element comprising same

Technical Field

The present invention relates to a liquid crystal composition and a liquid crystal display device comprising the same, and particularly to a negative dielectric anisotropy liquid crystal composition and a liquid crystal display device. More specifically, the present invention relates to a liquid crystal composition having a relatively low viscosity and suitably high optical anisotropy (Δ n) and dielectric anisotropy (Δ ∈), and a liquid crystal display element containing the same.

Background

As the most important flat panel display device, in recent years, a liquid crystal display device (LCD) has been rapidly developed and increasingly used. The LCD has advantages of light weight, thin profile, low power consumption, etc. The liquid crystal display modes can be classified into a wide variety: phase change (hereinafter, abbreviated as PC), twisted nematic (hereinafter, abbreviated as TN), super twisted nematic (hereinafter, abbreviated as STN), electrically controlled birefringence (hereinafter, abbreviated as ECB), optically compensated bend (hereinafter, abbreviated as OCB), IPS, VA, and the like. With the increasing updating of the technology, the requirements of the liquid crystal display device for response become more and more strict. However, in the VA mode, insufficient response has been a difficult problem to solve. Especially, the requirements for response are more strict when the display device is applied to field sequential display.

The calculation formula for the opening and closing times is as follows:

time of opening

T_on＝C₁η/(εΔεV²-Kπ²/d²)

Closing time

T_off＝C₂ηd²/Kπ²

Wherein, C₁And C₂Is a constant, eta is a viscosity coefficient, Delta epsilon is a dielectric constant difference, K is an elastic coefficient, and d is a liquid crystal layer thickness. From the above formula, T_onAnd T_offBoth increase greatly with increasing η, so decreasing the viscosity coefficient increases the response speed. Also, reducing the thickness of the liquid crystal layer can greatly reduce the turn-on time of the response time.

From the above-mentioned relational expression, it is found that the response time can be shortened by lowering the viscosity coefficient or raising the elastic coefficient of the liquid crystal composition. However, if the viscosity is reduced to improve the response time, the elastic modulus and isotropic phase transition temperature of the liquid crystal will also be reduced accordingly. Also, if the elastic modulus increases, the threshold voltage and viscosity will tend to increase. Therefore, to improve response time, the trade-off between these two properties must be minimized.

In the VA mode, in order to obtain a large contrast ratio of the display, the product (Δ n.d) of the optical anisotropy (Δ n) of the composition and the cell gap (d) of the device must be designed to be a fixed value. The fixed value is in the range of 0.30 μm to 0.40 μm. Since the cell gap (d) is generally in the range of 2 μm to 6 μm, the optical anisotropy of the composition is mainly in the range of 0.05 to 0.20. The higher the polarity, the lower the threshold value, the lower the power consumption and the viscosity, so that in order to achieve faster response, the relationship among various parameters needs to be balanced, and the viscosity of the system is reduced on the basis of selecting proper refractive index and dielectric, so that fast response is achieved.

In the VA mode, the increase of the number of driving paths is also the direction of the development in the world, and the method commonly used at present is to increase the steepness by increasing the value of Δ n.d, and the increase of Δ n.d will bring about the increase of viscosity, so a low-viscosity liquid crystal mixture is urgently needed to meet the market demand.

Currently, none of the materials is able to satisfy the aforementioned properties as a single compound. All of these properties should be satisfied for the preparation of a liquid crystal composition, and thus there is a case where the aforementioned properties cannot be satisfied due to a small Δ n or a large viscosity. For example, in the negative liquid crystal composition disclosed in chinese patent publication No. CN101072847A, the viscosity can be made 17.6(mPa · s), but the refractive index is 0.076, the clearing point is 76 ℃, and the negative liquid crystal composition cannot be used in the small cell thickness in the VA mode; the negative liquid crystal composition disclosed in chinese patent No. CN101407719A had a refractive index of 0.186 and a viscosity of 49.1(mPa · s), but the threshold value was not sufficiently low.

It is an object of the present invention to provide a liquid crystal composition, in particular for VA-type displays, and in particular for liquid crystal displays, which should be free from the above-mentioned disadvantages, or only to a slight extent. Furthermore, the liquid crystal composition of the invention is required to have high specific resistance, wide viewing angle, high bright point and good low-temperature intersolubility, and particularly, the provided cell of the liquid crystal composition cannot be crystallized after being stored for 30 days at-30 ℃.

Disclosure of Invention

In order to achieve the above object, one aspect of the present invention provides a liquid crystal composition, comprising the following components in percentage by weight:

(1) 2-25% of a compound of the formula I

(2) 3-40% of a compound of formula II

(3) 5-60% of a compound of the formula III

(4) 0-45% of a compound of the formula IV

(5) 0-20% of a compound of the formula V

And

(6) 0-30% of a compound of the formula VI

Wherein,

in the compounds of formula I, R1 is alkyl of 1 to 12 carbon atoms, R2 is alkyl or alkoxy of 1 to 12 carbon atoms, ring a represents trans 1, 4-cyclohexane or 1, 4-phenylene, n represents the integer 0 or 1;

in the compound of formula II, R3 is an alkyl group of 1 to 12 carbon atoms, R4 is an alkyl or alkoxy group of 1 to 12 carbon atoms, ring B represents trans 1, 4-cyclohexane or 1, 4-phenylene, n represents an integer of 0 or 1;

r5 is an alkyl group of 1 to 12 carbon atoms in the compound of formula III; r6 is alkyl or alkoxy of 1-12 carbon atoms; ring C represents trans-1, 4-cyclohexane or 1, 4-phenylene, m represents an integer of 0 or 1;

in the compound of the formula IV, R7 and R8 are each independently alkyl or alkoxy of 1 to 12 carbon atoms, one or two non-adjacent-CH₂-may be substituted by-CH ═ CH-;

in the formula V, R9 and R10 are each independently an alkyl group of 1 to 12 carbon atoms, ring D represents a trans-1, 4-cyclohexane group or a1, 4-phenylene group, o, p represent an integer of 0 or 1;

in the compounds of formula VI, R11 is alkyl of 1 to 12 carbon atoms, R12 is alkyl or alkoxy of 1 to 12 carbon atoms, and k represents the integer 1 or 2.

The compounds of formula I of the present invention are preferably one or more of the compounds of the following structures:

wherein R1 is preferably an alkyl group of 1 to 5 carbon atoms, and R2 is preferably an alkyl or alkoxy group of 1 to 5 carbon atoms.

The compounds of the general formula I according to the invention are particularly preferably one or more of the compounds of the following structures:

most preferred are one or more of compounds I-A-5, I-A-6, I-A-7, I-A-8, I-B-5, I-B-6, I-B-7, I-B-8, etc.

The compounds of formula II of the present invention are preferably one or more of the compounds of the following structures:

wherein R3 is preferably an alkyl group of 1 to 5 carbon atoms, and R4 is preferably an alkyl or alkoxy group of 1 to 5 carbon atoms.

The compounds of the general formula II according to the invention are particularly preferably one or more of the compounds of the following structures:

most preferably one or more of the compounds II-A-2, II-A-4, II-A-6, II-B-2, II-B-4, II-B-6, etc.

The compounds of formula III of the present invention are preferably one or more of the compounds of the following structures:

wherein R5 is preferably an alkyl group of 1 to 5 carbon atoms; r6 is preferably an alkyl or alkoxy group of 1 to 5 carbon atoms.

The compounds of the general formula III according to the invention are particularly preferably one or more of the compounds of the following structures:

most preferred are one or more of the compounds III-A-1, III-A-2, III-B-1, III-B-2, III-C-1, III-C-2, etc.

The compound represented by the chemical formula IV has small rotational viscosity and low melting point, and can effectively reduce the viscosity of the mixed liquid crystal and improve the low-temperature intersolubility of the mixed liquid crystal. The compounds of formula IV of the present invention are preferably one or more of the compounds of the following structures:

wherein R7 and R8 are preferably alkyl or alkoxy groups of 1 to 5 carbon atoms.

The compounds of the general formula IV according to the invention are particularly preferably one or more of the compounds of the following structures:

most preferably one or more of compounds IV-A-2, IV-A-4, IV-B-2, IV-B-4, IV-C-6, etc.

The compounds of formula V of the present invention are preferably one or more of the compounds of the following structures:

wherein R9 and R10 are preferably alkyl groups of 2 to 5 carbon atoms.

The compounds of the general formula V according to the invention are particularly preferably one or more of the compounds of the following structure:

most preferred are one or more of the compounds V-A-1, V-A-2, V-B-1, V-B-2, V-B-3, V-B-4, etc.

The compounds of formula VI of the present invention are particularly preferably one or more of the compounds of the following structures:

wherein R11 and R12 are preferably alkyl or alkoxy groups of 1 to 5 carbon atoms.

most preferred are one or more of the compounds VI-A-2, VI-A-4, VI-B-2, VI-B-4, etc.

The liquid crystal composition disclosed by the invention particularly preferably comprises the following components in percentage by weight:

(1) 3-20% of a compound of formula I;

(2) 3-35% of a compound of formula II;

(3) 10-55% of a compound of formula III;

(4) 0-42% of a compound of formula IV;

(5) 0-15% of a compound of formula V;

(6) 0-27% of a compound of formula VI.

The refractive index of the liquid crystal composition obtained by optimally combining and proportioning a large amount of known liquid crystal compounds can be more than 0.150(20 ℃), so that the liquid crystal composition can be used on a display device with a thinner box thickness; the viscosity can be reduced to 22mm²·s^-1(20 ℃) below; delta epsilon is between-4.0 and-11.0 (25 ℃); the clearing point can reach more than 90 ℃, and the liquid crystal has better low-temperature intersolubility, and particularly, the liquid crystal does not crystallize after being stored in a container for a long time in a low-temperature environment.

The liquid crystal composition has wide dielectric coverage range and is suitable for products with different threshold sections; the liquid crystal display has a wider range of refractive indexes, and can be used in a thinner liquid crystal display, so that the response speed is improved; extremely low viscosity and thus has a fast response speed.

Another aspect of the present invention is to provide a liquid crystal display element comprising the liquid crystal composition of the present invention.

With the development of technology, people have higher requirements on the color and response of liquid crystal devices, and under the condition of more and more intense competition, the pressure from cost and the response requirement are more prominent and important. Particularly, in the field sequential display mode, the invention can meet the requirement of fast response in terms of improvement of liquid crystal performance under the requirement of fast response.

In the context of the present invention, all temperatures are degrees celsius and all percentages are percentages by weight, unless otherwise indicated.

Detailed Description

It should be noted that the examples are for illustrating the present invention and do not represent a limitation.

For convenience of expression, in the following examples, the group structures of liquid crystal compounds are represented by codes listed in Table 1.

TABLE 1 radical structural code of liquid crystal compounds

Compounds of the following formula are exemplified:

the structural formula is represented by the code listed in Table 1, and can be expressed as: 3 in the 3CWO2, wherein 3 in the code represents the number of C atoms in the left alkyl group, i.e., the alkyl group is-C₃H₇(ii) a C in the code represents cyclohexane; w in the code represents a benzene plus two lateral F substituted structures, and O in the code represents an oxygen atom; 2 in the code represents the number of C atoms of the alkyl group at the right end, that is, the alkyl group is-C₂H₅。

The various liquid-crystalline components contained in the liquid-crystalline compositions according to the invention are all compounds known in the art, of which compounds of the formula I and of the formula II are referred to in DE2937700A1/EP0675188A, compounds of the formula III are referred to in CN1911888, compounds of the formula V are referred to in EP0087102A1 and compounds of the formula VI are referred to in DE3807957A 1. The synthesis method of the compound in the general formula IV is simple, and the compound in the general formula IV can be synthesized by a conventional method by a person skilled in the art.

The abbreviations of the parameters tested in the examples and the test conditions are as follows:

cp clearing Point (nematic- > transition temperature of Isotropic phase)

S- > N Low temperature phase transition point (smectic phase- > transition temperature of nematic phase)

Eta volume viscosity (mm)²/s，20℃)

Delta epsilon dielectric anisotropy (25 ℃, 1KHZ)

Δ n optical anisotropy (20 ℃, 589nm)

Vth threshold voltage (V, 25 deg.C)

The flow viscosity Visc was measured using a cone and plate viscometer;

the refractive index and the refractive index anisotropy were measured using an Abbe refractometer under a sodium lamp (589nm) light source at 20 ℃.

The test cartridges used in the above tests were all 6 μm negative cartridges.

Comparative example 1

Table 2 lists the weight percentages of the components of the commercial MERCK product of the comparative liquid crystal composition. The comparative example liquid crystal composition was filled in a test cell for performance testing, and the test results are also shown in the table corresponding to the tables.

TABLE 2 weight percent of commercially available MERCK product components and their performance test data

Component code	Weight percent (wt.%) of	Results of performance parameter testing
			3CCEPC4	4％	Cp＝101℃
3CCEPC3	4％	Δn＝0.091
			3CCEPC5	4％	Δε＝-4.1
3CCEC3	3％	Vth＝2.17
			4CCEC5	3％	η＝40
5CWO2	15％
			2CPWO2	6％
3CWO4	15％
			5CWO4	15％
3CCWO2	6％
			5CCWO2	6％
4CCWO2	5％
			3CCWO3	7％
5CC3	7％

Example 1

The nematic liquid crystal compositions of the present invention were prepared by using the compounds and weight fractions listed in tables 3 and 4, and filled in test boxes for performance tests, and the test data are also listed in tables 3 and 4, respectively.

Examples 1 to 1

TABLE 3 weight percents of Components of liquid Crystal composition of example 1-1 and their Performance test data

Component code	Weight percent (wt.%) of	Results of performance parameter testing
			3CCEPC4	2％	Cp＝96℃
3CCEPC3	1％	Δn＝0.091
			3CCEC3	3％	Δε＝-4.1
4CCEC5	3％	Vth＝2.17
			2CEP(2N)O4	3％	η＝29
3CEP(2N)O4	3％
			3CPTWO1	3％
3CPTWO2	3％
			5CWO2	10％
2CPWO2	7％
			3CWO4	5％
5CWO4	5％
			3CCWO2	6％
5CCWO2	5％
			4CCWO2	5％
3CCWO3	5％
			5CC3	13％
3CCV	18％

Examples 1 to 2

TABLE 4 weight percents of Components of liquid Crystal compositions of examples 1-2 and their Performance test data

Component code	Weight percent (wt.%) of	Results of performance parameter testing
			3CCEPC4	2％	Cp＝96℃
3CCEPC3	1％	Δn＝0.092
			3CCEC3	3％	Δε＝-4.0
4CCEC5	3％	Vth＝2.11
			2CEP(2N)O4	3％	η＝27
3CEP(2N)O4	2％
			3CPTWO1	4％
3CPTWO2	3％
			5CWO2	10％
2CPWO2	7％
			3CWO4	5％
5CWO4	5％
			3CCWO2	5％
5CCWO2	5％
			4CCWO2	5％
3CCWO3	5％
			5CC3	13％
3CCV	19％

From the data of the above examples, it can be seen that the use of the liquid crystal composition of the present invention can reduce the viscosity by 30% or more from the original viscosity while maintaining the equivalent refractive index, dielectric anisotropy and clearing point.

Comparative example 2

Table 5 lists the weight percentages of the components of the commercial MERCK product of the comparative liquid crystal composition. The comparative example liquid crystal composition was filled in a test cell for performance testing, and the test results are also shown in the table corresponding to the tables.

TABLE 5 weight percent of commercially available MERCK product components and their performance test data

Component code	Weight percent (wt.%) of	Results of performance parameter testing
			3CCEPC4	2％	Cp＝95℃
3CCEPC3	2％	Δn＝0.101
			3CCEPC5	2％	Δε＝-4.2
3CCEC3	3％	Vth＝2.14
			4CCEC5	3％	η＝35.5
3CPTWO1	2％
			3CPTWO2	4％
5CWO2	15％
			2CPWO2	9％
3CWO4	11％
			5CWO4	11％
3CC(N)5	1％
			3CCWO2	5％
5CCWO2	5％
			4CCWO2	5％
3CCWO3	7％
			5CC3	7％
3CCV	6％

Example 2

The nematic liquid crystal compositions of the present invention were prepared by using the compounds and weight fractions listed in tables 6 and 7, and filled in test boxes for performance tests, and the test data are also listed in tables 6 and 7, respectively.

Example 2-1

TABLE 6 weight percents of Components of the liquid crystal composition of example 2-1 and their performance test data

Component code	Weight percent (wt.%) of	Results of performance parameter testing
			3CCEC3	3％	Cp＝96℃
4CCEC5	3％	Δn＝0.101
			2CEP(2N)O4	2％	Δε＝-4.1
3CEP(2N)O4	2％	Vth＝2.14
			3CPTWO1	5％	η＝28.8
3CPTWO2	6％
			5CWO2	8％
2CPWO2	6％
			3CWO4	7％
5CWO4	7％
			3CCWO2	5％
5CCWO2	5％
			4CCWO2	5％
3CCWO3	5％
			5CC3	10％
VCCP1	4％
			3CCV	17％

Examples 2 to 2

TABLE 7 weight percents of Components of liquid Crystal composition of example 2-2 and their Performance test data

Component code	Weight percent (wt.%) of	Results of performance parameter testing
			3CCEPC4	2％	Cp＝95℃
3CCEC3	1％	Δn＝0.101
			4CCEC5	2％	Δε＝-4.0
2CEP(2N)O4	2％	Vth＝2.16
			3CEP(2N)O4	2％	η＝22.0
3CPTWO1	6％
			3CPTWO2	6％
5CWO2	8％
			2CPWO2	6％
3CWO4	8％
			5CWO4	8％
3CCWO2	5％
			5CCWO2	5％
4CCWO2	5％
			3CCWO3	5％
5CC3	12％
			3CCV	17％

As can be seen from the data of the above examples and comparative examples, the use of the liquid crystal composition of the present invention reduced the viscosity by 20% or more from the original level while ensuring comparable refractive index, dielectric anisotropy and clearing point.

Example 3

The individual compounds and weight fractions listed in table 8 were formulated into nematic liquid crystal compositions of the present invention, which were filled in test cells for performance testing, and the test data are also listed in table 8.

Table 8 weight percent of the components of the liquid crystal composition of example 3 and the performance test data thereof

Component code	Weight percent (wt.%) of	Results of performance parameter testing
			3CEWO1	11％	Cp＝96℃
3CCEW1	7％	Δn＝0.150
			2CEP(2N)O4	2％	Δε＝-8.0
3CEP(2N)O4	2％	η＝94.0
			5CEP(2N)O4	3％
3PTWO1	13％
			3PTWO2	7％
3CPTWO1	8％
			3CWO2	7％
2CPWO2	5％
			3CPWO2	5％
3CC(N)5	10％
			3CCWO2	14％
5CCWO2	2％
			4CCWO2	4％

Example 4

The individual compounds and weight fractions listed in table 9 were formulated into nematic liquid crystal compositions of the present invention, which were filled in test cells for performance testing, and the test data are also listed in table 9.

TABLE 9 weight percent of liquid crystal composition of example 4 and its performance test data

Component code	Weight percent (wt.%) of	Results of performance parameter testing
			3CEWO1	11％	Cp＝96℃
3CCEW1	5％	Δn＝0.151
			2CEP(2N)O4	2％	Δε＝-7.9
3CEP(2N)O4	2％	Vth＝1.60
			5CEP(2N)O4	2％	η＝85.0
3PTWO1	13％
			3PTWO2	7％
3CPTWO1	8％
			3CWO2	10％
2CPWO2	5％
			3CPWO2	5％
3CC(N)5	9％
			3CCWO2	14％
5CCWO2	3％
			4CCWO2	4％

Example 5

The individual compounds and weight fractions listed in table 10 were formulated into nematic liquid crystal compositions of the present invention, which were filled in test cells for performance testing, and the test data are also listed in table 10.

TABLE 10 weight percent of the components of the liquid crystal composition of example 5 and the performance test data thereof

Component code	Weight percent (wt.%) of	Results of performance parameter testing
			3CEWO1	12％	Cp＝103℃
3CCEW1	7％	Δn＝0.146
			2CEP(2N)O4	6％	Δε＝-11.0
3CEP(2N)O4	6％	η＝148.0
			5CEP(2N)O4	5％
3PTWO1	5％
			3PTWO2	6％
3CPTWO1	8％
			3CPTWO2	8％
3CWO2	5％
			2CPWO2	5％
3CPWO2	5％
			3CC(N)5	7％
3CCWO2	5％
			5CCWO2	5％
4CCWO2	5％

Example 6

The individual compounds and weight fractions listed in table 11 were formulated into nematic liquid crystal compositions of the present invention, which were filled in test cells for performance testing, and the test data are also listed in table 11.

TABLE 11 weight percent of liquid crystal composition of example 6 and its performance test data

Component code	Weight percent (wt.%) of	Results of performance parameter testing
			3CEWO1	9％	Cp＝90℃
3CCEW1	4％	Δn＝0.150
			2CEP(2N)O4	5％	Δε＝-11.0
3CEP(2N)O4	5％	Vth＝1.30
			5CEP(2N)O4	6％	η＝136.0
3PTWO1	9％
			3PTWO2	9％
3CPTWO1	6％
			3CPTWO2	6％
3CWO2	10％
			2CPWO2	5％
3CPWO2	5％
			3CC(N)5	6％
3CCWO2	5％
			5CCWO2	5％
4CCWO2	5％

The composition of the invention can also be used in a low threshold system, such as a system with a refractive index of 0.15 and a dielectric of-11, the viscosity can be within 137, and the viscosity of similar products of other companies sold in the market is more than 200.

Example 7

The liquid crystal compositions prepared in examples 1 to 6 were used for liquid crystal display elements according to a conventional method.

The above-described preferred embodiments of the present invention are not intended to be limiting, and all other equivalent changes and modifications that do not depart from the spirit of the invention are intended to be included within the scope of the appended claims.

Claims

1. A liquid crystal composition comprises the following components in percentage by weight:

(1) 2-25% of a compound of the formula I

(2) 3-40% of a compound of formula II

(3) 5-60% of a compound of the formula III

(4) 0-45% of a compound of the formula IV

(5) 0-20% of a compound of the formula V

And

(6) 0-30% of a compound of the formula VI

Wherein,

in the compounds of the formula IV, R7 and R8 are each independently alkyl or alkoxy of 1 to 12 carbon atoms, one or two of which are not adjacent-CH₂-may be substituted by-CH ═ CH-;

2. The liquid crystal composition of claim 1, wherein the compound of formula I is selected from one or more of the following compounds:

wherein R1 is an alkyl group of 1 to 5 carbon atoms and R2 is an alkyl or alkoxy group of 1 to 5 carbon atoms.

3. The liquid crystal composition of claim 1, wherein the compound of formula II is selected from one or more of the following compounds:

wherein R3 is an alkyl group of 1 to 5 carbon atoms and R4 is an alkyl or alkoxy group of 1 to 5 carbon atoms.

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

wherein R5 is an alkyl group of 1 to 5 carbon atoms and R6 is an alkyl or alkoxy group of 1 to 5 carbon atoms.

5. A liquid crystal composition according to claim 1, wherein the compound of formula IV is preferably one or more of the compounds of the following structures:

wherein R7 and R8 are each independently an alkyl or alkoxy group of 1 to 5 carbon atoms.

6. The liquid crystal composition of claim 1, wherein the compound of formula V is selected from one or more of the following compounds:

wherein R9 and R10 are each independently an alkyl group of 2 to 5 carbon atoms.

7. The liquid crystal composition of claim 1, wherein the compound of formula VI is selected from one or more of the following compounds:

wherein R11 and R12 are each independently an alkyl or alkoxy group of 1 to 5 carbon atoms.

8. The liquid crystal composition according to any one of claims 1 to 7,

the compound of the general formula I is selected from one or more of the following compounds:

the compound of the general formula II is selected from one or more of the following compounds:

the compound of the general formula III is selected from one or more of the following compounds:

the compound of the general formula IV is selected from one or more compounds of the following structures:

the compound of the general formula V is selected from one or more of the following compounds:

the compound of formula VI is selected from one or more of the compounds of the following structures:

9. the liquid crystal composition according to claim 8,

the compound of the general formula I is one or more of compounds of chemical formulas I-A-5, I-A-6, I-A-7, I-A-8, I-B-5, I-B-6, I-B-7 and I-B-8;

the compound of the general formula II is one or more compounds of chemical formulas II-A-2, II-A-4, II-A-6, II-B-2, II-B-4 and II-B-6;

the compound of the general formula III is one or more compounds of chemical formulas III-A-1, III-A-2, III-B-1, III-B-2, III-C-1 and III-C-2;

the compound of the general formula IV is one or more of compounds of chemical formulas IV-A-2, IV-A-4, IV-B-2, IV-B-4, IV-C-4 and IV-C-6;

the compound of the general formula V is one or more of compounds of chemical formulas V-A-1, V-A-2, V-B-1, V-B-2, V-B-3 and V-B-4; and

the compound of the general formula VI is one or more of compounds of chemical formulas VI-A-2, VI-A-4, VI-B-2 and VI-B-4.

10. The liquid crystal composition of claim 1, wherein the compound of formula I comprises 3-20% of the total weight of the composition; the compound of the general formula II accounts for 3-35% of the total weight of the composition; the compound of the general formula III accounts for 10-55% of the total weight of the composition; the compound of the general formula IV accounts for 0-42% of the total weight of the composition; the compound of the general formula V accounts for 0-15% of the total weight of the composition; and, the compound of formula VI comprises 0-27% of the total weight of the composition.

11. A liquid crystal display element comprising the liquid crystal composition according to any one of claims 1 to 10.