JPH0967576A - Liquid crystalline composition and liquid crystalline display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liq. crystalline compsn., for AM-LCD, which possesses a particularly high clearing point while satisfying various property requirements for a liq. crystalline compsn. for AM-LCD used in the outdoors and in automobiles. SOLUTION: This liq. crystalline compd. comprises a first component of a compd. represented by formula I and a second component of at least one member selected from the group consisting of compds. represented by formulae II to III and the like (wherein R<1> and R<2> represent a 1-10C alkyl group, X<1> represents F, C1, OCF3 , CF3 , OCF2 H, OCF2 CF2 H, or OCF2 CFHCF3 , and Y<1> to Y<4> independently represent H or F.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal composition for a display device, more specifically, a liquid crystal composition suitably used for a display device using an active matrix system,
A liquid crystal display device using the same.

[0002]

BACKGROUND ART Liquid crystal display devices (LCDs) have lower power consumption, lower voltage drive, smaller size, lighter weight, and thinner size than cathode ray tubes (CRTs), so handy-type calculators and digital watches. Used for such purposes, it occupies the top position of flat displays. 2. Description of the Related Art In recent years, in order to meet the needs of advanced information technology, the application of LCDs to displays for personal computers, video cameras, televisions, outdoors and in-vehicle has been actively promoted. Since high-definition (high-contrast) display and good color display are expected, thin film transistors (TF
T) active matrix LCD (AM-L
CD) is expected as the favorite LCD display method. The AM-LCD operation method employs a TN display method in which the alignment directions of liquid crystal molecules on the upper and lower substrates of the cell are twisted at 90 °.

As a liquid crystal material for a display element, a material having characteristics suitable for the purpose of use must be appropriately selected. For example, when the above-mentioned outdoor or vehicle-mounted AM-LCD is used, the temperature change of the environment in which it is used is large, and therefore the liquid crystal material is also required to have a property capable of withstanding the temperature change. That is, it is strongly desired to exhibit a nematic liquid crystal phase in a temperature range as wide as possible centering on room temperature (in particular, a high clearing point). At present, no compound that satisfies these conditions has been found as a simple substance, and several kinds of liquid crystal compounds or non-liquid crystal compounds are mixed to prepare a liquid crystal composition having necessary properties. , L
It is used as a material for CDs.

In order to widen the nematic region of the liquid crystal composition, it is necessary to introduce a liquid crystal compound having a high clearing point and good compatibility with other liquid crystal compounds. Generally, in order to raise the clearing point, a compound having a high clearing point and having a large number of six-membered rings in terms of chemical structure may be used, but in this case, there is a tendency that a compatibility problem occurs in a low temperature range. ,
Since the viscosity of the liquid crystal composition obtained at the same time becomes large, its use is limited. Further, particularly in AM-LCDs, there is a demand for a so-called highly reliable liquid crystal composition having a high voltage holding ratio or a large specific resistance value in order to maintain a high contrast.

As a prior art aiming at high specific resistance and high reliability, there is a liquid crystal composition disclosed in JP-A-2-289682. This liquid crystal composition is an AM-LCD
However, the size of the nematic region (the height of the clearing point) is not sufficient for use outdoors and in vehicles.

As described above, although various investigations have been made on the liquid crystal composition, it is the present situation that the improvement of the characteristics is still required. Although many liquid crystal compounds having various characteristics are known as compounds that can be used in a liquid crystal composition, selection of compounds and design of composition ratio to satisfy the requirements at the same time are well-balanced. It is not easy for a person skilled in the art to know today as it is fragmented and sophisticated accordingly.

[0007]

The object of the present invention is to provide an AM
-To provide a liquid crystal composition having a particularly large nematic region (high clearing point) while satisfying various characteristics required for a liquid crystal material for LCD.

[0008]

[Means for Solving the Problems]

The first aspect of the present invention is to use a compound represented by the general formula (1) as the first component.

[Chemical 6] (R ¹ in the formula represents an alkyl group having 1 to 10 carbon atoms.)
Containing at least one compound represented by the formula (2) to (8) as the second component.

[Chemical 7] (R ² in the formula represents an alkyl group having 1 to 10 carbon atoms,
X ¹ is F, Cl, OCF ₃ , CF ₃ , OCF ₂ H, OCF ₂
CF ₂ H and OCF ₂ CFHCF ₃ are shown, and Y ¹ to Y ⁴ are independently H or F. ) A liquid crystal composition containing one or more compounds selected from the group consisting of compounds represented by

As one embodiment of the present invention, the above-mentioned liquid crystal composition in which the mixing ratios of the first component and the second component are 3 to 30% and 50 to 97% of the total weight of the liquid crystal composition, respectively. You can

In another embodiment of the present invention, the general formula (9) or (10)

Embedded image (R ³ in the formula represents an alkyl group having 1 to 10 carbon atoms,
X ² represents F, Cl or OCF ₃ , and Y ⁵ and Y ⁶ independently represent H or F. And a liquid crystal composition further containing one or more compounds selected from the group consisting of compounds represented by the formula (1).

In still another embodiment of the present invention, the general formula (11) or (12)

Embedded image (R ⁴ in the formula represents an alkyl group having 1 to 10 carbon atoms,
Z ¹ represents a single bond or —CH ₂ CH ₂ —. And a liquid crystal composition further containing one or more compounds selected from the group consisting of compounds represented by the formula (1).

In still another embodiment of the present invention, the general formula (13) or (14)

Embedded image (In the formula, R ⁵ and R ⁶ independently represent an alkyl group having 1 to 10 carbon atoms, an alkoxy group or an oxaalkyl group,
Z ² represents a single bond, —CH═CH— or —C ♪ C—, A represents trans-1,4-cyclohexylene or 1,4-phenylene, and B represents trans-1,4-cyclohexylene or One H on the side position represents 1,4-phenylene which may be substituted with F, and n represents 0 or 1. The liquid crystal composition can further include one or more compounds selected from the group consisting of compounds represented by

A second aspect of the present invention relates to a liquid crystal display device using any of the above-mentioned liquid crystal compositions of the present invention as a liquid crystal material, and further to an AM-LCD utilizing the liquid crystal composition.

Next, the compounds constituting each component of the liquid crystal composition of the present invention will be described. The compounds represented by the general formulas (1) to (14) are all known and can be easily obtained by those skilled in the art.

In the present invention, the compound represented by the general formula (1) has high physical and chemical stability,
It makes the nematic region of the obtained liquid crystal composition large and plays an important role in the composition of the present invention.

As the compounds represented by the general formulas (2) to (8), the compounds represented by the following general formulas are preferably used.

[0018]

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[Chemical 12]

[0019]

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[Chemical 15]

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[0020]

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[0021]

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[Chemical 21]

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[0022]

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[0023]

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[0024]

[Chemical formula 26] In these formulas, R ² represents an alkyl group having 1 to 10 carbon atoms.

As the second component of the present invention, the above formula (2
-1), (2-2), (2-3), (2-4), (2-
7), (3-1), (3-2), (3-3), (3-
9), (3-30), (3-34), (3-35),
(3-36), (3-37), (3-38), (4-
2), (4-3), (4-5), (4-7), (5-
2), (5-3), (5-37), (6-3), (6-
7), (7-1), (7-3) (8-1) or (8
The compound represented by -3) is particularly preferably used.

The compounds represented by the general formulas (2) to (8) are compounds having a positive dielectric anisotropy, and are very excellent in thermal stability and chemical stability. For this,
In particular, these are indispensable compounds when preparing a liquid crystal composition for AM-LCD, which is required to have characteristics such as high voltage holding ratio or high specific resistance. These compounds are mainly used for the purpose of adjusting the clearing point and nematic range and / or adjusting the driving voltage, Δn, and viscosity.

As the compounds represented by the general formulas (9) to (10), the compounds represented by the following general formulas are preferably used.

[0028]

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[0029]

Embedded image In these formulas, R ³ represents an alkyl group having 1 to 10 carbon atoms.

Among these compounds, formula (9-1),
(9-2), (9-3), (9-4), or (10
The compound represented by -2) is particularly preferably used in the present invention.

The compounds represented by the general formulas (9) to (10) are compounds having positive dielectric anisotropy, and are very excellent in thermal stability and chemical stability. These compounds are mainly used for the purpose of adjusting the driving voltage and / or adjusting the viscosity.

As the compounds represented by the general formulas (11) to (12), the compounds represented by the following general formulas are preferably used.

[0033]

[Chemical 29] In these formulas, R ⁴ represents an alkyl group having 1 to 10 carbon atoms.

Among these compounds, the formula (11-
The compounds represented by 1), (11-2) or (12-1) are particularly preferably used in the present invention.

The compounds represented by the general formulas (11) to (12) are compounds having a positive dielectric anisotropy and are very excellent in thermal stability and chemical stability. These compounds are mainly used for the purpose of adjusting the clearing point and nematic range.

As the compounds represented by the general formulas (13) to (14), the compounds represented by the following general formulas are preferably used.

[0037]

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[0038]

[Chemical 31] In these formulas, R and R ′ are independently C 1
And 10 to 10 alkyl groups.

In the above equation, equations (13-1) and (13
-3), (13-5), (14-1), (14-2),
(14-6), (14-8), (14-10), (14
The compound represented by formula (-11), (14-12) or (14-13) is particularly preferably used in the present invention.

The compound represented by the general formula (13) is a bicyclic compound having a negative or weakly positive dielectric anisotropy, and mainly reduces the viscosity and / or Δn of the obtained liquid crystal composition.
Used for adjustment purposes. The compound represented by the general formula (14) has a negative dielectric anisotropy or a weak positive 3
It is a cyclic compound or a tetracyclic compound, and is mainly used for the purpose of increasing the clearing point of the obtained liquid crystal composition to broaden the nematic match and / or for the purpose of adjusting Δn.

The amount of the first component used in the present invention is preferably 3% or more based on the total weight of the liquid crystal composition from the viewpoint of obtaining the effect of increasing the clearing point which is the subject of the present invention. From the viewpoint of keeping the viscosity at an appropriately low level, it is preferably 30% or less. More preferably, it is 3 to 20%.

The amount of the second component used in the present invention is preferably 50% or more based on the total weight of the liquid crystal composition from the viewpoint of ensuring a wide liquid crystal range, and the effect of increasing the clearing point of the present invention is obtained. From the viewpoint, 97% or less is preferable. It is more preferably 60 to 97%.

The use ratio of the compounds of the general formulas (9) to (10) is preferably 40% or less from the viewpoint of obtaining the effect of increasing the clearing point of the present invention. More preferably 30
% Or less. The use ratio of the compounds of the general formulas (11) to (12) is preferably 20% or less from the viewpoint of keeping the viscosity of the liquid crystal composition to be appropriately low. More preferably 10
% Or less. The use ratio of the compounds of the general formulas (13) to (14) is preferably 40% or less from the viewpoint of keeping the threshold voltage of the liquid crystal composition appropriately low. It is more preferably 30% or less.

The composition of the present invention can be used by mixing with a compound other than the compound represented by the above-mentioned general formula within the range not impairing the object of the invention. The liquid crystal composition of the present invention can be prepared by a conventional method per se. Generally, a method is used in which various component compounds are mixed at a predetermined ratio and then heated to a temperature higher than the clearing point thereof to be independently dissolved to form a uniform mixture. Further, the liquid crystal composition of the present invention is improved and optimized according to the intended use by adding an appropriate additive thereto.
Such additives are well known to those skilled in the art and are described in detail in the literature and the like. Normally, the spiral structure of liquid crystal is induced to adjust the required twist angle, and the reverse twist (reverse twist)
Add a chiral dopant to prevent ist).

In the liquid crystal composition of the present invention, a dichroic dye such as a merocyanine type, a styryl type, an azo type, an azomethine type, an azoxy type, a quinophthalone type, an anthraquinone type and a tetrazine type is added to a guest host. (G
It can also be used as a liquid crystal composition for H) mode. Alternatively, NCAP manufactured by encapsulating nematic liquid crystal or polymer network liquid crystal display device (PNL) in which a three-dimensional network polymer is manufactured in liquid crystal
Polymer dispersed liquid crystal display device (PD) represented by CD
It can also be used as a liquid crystal composition for LCD).
In addition, birefringence control (ECB) mode and dynamic scattering (D
It can also be used as a liquid crystal composition for S) mode.

[0046]

The present invention will be described in detail below with reference to examples and comparative examples, but the present invention is not limited to these examples. Also, the compositions in these examples are all given in weight percent. The voltage holding ratio was measured by Tatsuo Shimazaki and others,
Voltage holding characteristic of TFT-LCD I, p.78, according to the method described in Proceedings of 14th Liquid Crystal Conference (1988). In addition, a liquid crystal cell in which a polyimide-based alignment film was rubbed on a glass substrate on which an ITO pattern having a frame cycle of 60 Hz, a voltage of 5.0 V, an ON time of 60 μsec, a liquid crystal layer thickness of 7.0 μ, and an electrode area of 1 cm ² was rubbed. Was used to measure the voltage holding ratio.

Comparative Example 1 The following liquid crystal composition disclosed in JP-A-2-289682 was prepared.

Embedded image The clearing point (T _NI ) of this liquid crystal composition is 78.9 ° C. and 20 ° C.
Viscosity (η) at 26.2 mPa · s, refractive index anisotropy (Δn) at 25 ° C. is 0.080, dielectric anisotropy (Δε) at 20 ° C. is 6.7, threshold value at 20 ° C. The voltage (V _th ) was 1.97 V, and the voltage holding ratio at 25 ° C. was 98.1%.

Comparative Example 2

[Chemical 33] A liquid crystal composition was prepared. The clearing point of this liquid crystal composition is 100.2 ° C, and the viscosity at 20 ° C is 25.3 mP.
a · s, refractive index anisotropy at 25 ° C. is 0.093, 2
The dielectric anisotropy at 0 ° C. was 5.1, the threshold voltage at 20 ° C. was 2.20 V, and the voltage holding ratio at 25 ° C. was 98.3%.

Example 1 The following compounds were mixed with 95 parts by weight of the liquid crystal composition prepared in Comparative Example 2 to prepare a liquid crystal composition.

Embedded image The clearing point of this liquid crystal composition is 107.5 ° C., the viscosity at 20 ° C. is 27.8 mPa · s, the refractive index anisotropy at 25 ° C. is 0.093, and the dielectric anisotropy at 20 ° C. is 5.
Threshold voltage at 4, 20 ℃ is 2.23V, 25 ℃
The voltage holding ratio was 98.4%. The clearing point is higher than that of the liquid crystal compositions of Comparative Example 1 and Comparative Example 2.

Example 2

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Embedded image A liquid crystal composition was prepared. The clearing point of this liquid crystal composition is 114.9 ° C, and the viscosity at 20 ° C is 39.7 mP.
a · s, refractive index anisotropy at 25 ° C. is 0.094, 2
The dielectric anisotropy at 0 ° C. was 12.2, the threshold voltage at 20 ° C. was 1.55 V, and the voltage holding ratio at 25 ° C. was 98.8%.

Example 3

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Embedded image A liquid crystal composition was prepared. The clearing point of this liquid crystal composition is 108.4 ° C, and the viscosity at 20 ° C is 31.3 mP.
a · s, refractive index anisotropy at 25 ° C. is 0.122, 2
The dielectric anisotropy at 0 ° C. was 7.7, the threshold voltage at 20 ° C. was 1.95 V, and the voltage holding ratio at 25 ° C. was 98.5%.

Example 4

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[Chemical 40] A liquid crystal composition was prepared. The clearing point of this liquid crystal composition is 110.5 ° C, and the viscosity at 20 ° C is 27.8 mP.
a · s, refractive index anisotropy at 25 ° C. is 0.107, 2
The dielectric anisotropy at 0 ° C. was 7.3, the threshold voltage at 20 ° C. was 2.04 V, and the voltage holding ratio at 25 ° C. was 98.5%.

Example 5

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Embedded image A liquid crystal composition was prepared. The clearing point of this liquid crystal composition is 106.6 ° C., and the viscosity at 20 ° C. is 27.3 mP.
a · s, refractive index anisotropy at 25 ° C. is 0.090, 2
The dielectric anisotropy at 0 ° C. was 5.5, the threshold voltage at 20 ° C. was 2.16 V, and the voltage holding ratio at 25 ° C. was 98.4%.

Example 6

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Embedded image A liquid crystal composition was prepared. The clearing point of this liquid crystal composition is 107.2 ° C, and the viscosity at 20 ° C is 33.1 mP.
a · s, refractive index anisotropy at 25 ° C. is 0.087, 2
The dielectric anisotropy at 0 ° C. was 9.7, the threshold voltage at 20 ° C. was 1.70 V, and the voltage holding ratio at 25 ° C. was 98.8%.

Example 7

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Embedded image A liquid crystal composition was prepared. The clearing point of this liquid crystal composition is 101.5 ° C., and the viscosity at 20 ° C. is 23.4 mP.
a · s, refractive index anisotropy at 25 ° C. is 0.116, 2
The dielectric anisotropy at 0 ° C. was 5.9, the threshold voltage at 20 ° C. was 2.21 V, and the voltage holding ratio at 25 ° C. was 98.5%.

Example 8

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Embedded image A liquid crystal composition was prepared. The clearing point of this liquid crystal composition is 104.9 ° C, and the viscosity at 20 ° C is 27.9 mP.
a · s, refractive index anisotropy at 25 ° C. is 0.093, 2
The dielectric anisotropy at 0 ° C. was 6.9, the threshold voltage at 20 ° C. was 2.04 V, and the voltage holding ratio at 25 ° C. was 98.4%.

Example 9

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Embedded image A liquid crystal composition was prepared. The clearing point of this liquid crystal composition is 116.2 ° C., and the viscosity at 20 ° C. is 26.9 mP.
a · s, refractive index anisotropy at 25 ° C. is 0.095, 2
The dielectric anisotropy at 0 ° C. was 4.5, the threshold voltage at 20 ° C. was 2.55 V, and the voltage holding ratio at 25 ° C. was 98.6%.

Example 10

[Chemical 51]

Embedded image A liquid crystal composition was prepared. The clearing point of this liquid crystal composition is 122.4 ° C, and the viscosity at 20 ° C is 30.2 mP.
a · s, refractive index anisotropy at 25 ° C. is 0.132, 2
The dielectric anisotropy at 0 ° C. was 5.4, the threshold voltage at 20 ° C. was 2.40 V, and the voltage holding ratio at 25 ° C. was 98.5%.

Example 11

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Embedded image A liquid crystal composition was prepared. The clearing point of this liquid crystal composition is 110.8 ° C., and the viscosity at 20 ° C. is 28.9 mP.
a · s, refractive index anisotropy at 25 ° C. is 0.100, 2
The dielectric anisotropy at 0 ° C. was 6.3, the threshold voltage at 20 ° C. was 2.02 V, and the voltage holding ratio at 25 ° C. was 98.5%.

Example 12

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Embedded image A liquid crystal composition was prepared. The clearing point of this liquid crystal composition is 105.2 ° C, and the viscosity at 20 ° C is 25.1 mP.
a · s, refractive index anisotropy at 25 ° C. is 0.081, 2
The dielectric anisotropy at 0 ° C. was 6.2, the threshold voltage at 20 ° C. was 2.06 V, and the voltage holding ratio at 25 ° C. was 98.4%.

Example 13

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Embedded image A liquid crystal composition was prepared. The clearing point of this liquid crystal composition is 103.5 ° C, and the viscosity at 20 ° C is 23.9 mP.
a · s, refractive index anisotropy at 25 ° C. is 0.094, 2
The dielectric anisotropy at 0 ° C. was 4.4, the threshold voltage at 20 ° C. was 2.39 V, and the voltage holding ratio at 25 ° C. was 98.6%.

Example 14

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Embedded image A liquid crystal composition was prepared. The clearing point of this liquid crystal composition is 116.7 ° C., and the viscosity at 20 ° C. is 25.3 mP.
a · s, refractive index anisotropy at 25 ° C. is 0.096, 2
The dielectric anisotropy at 0 ° C. was 5.6, the threshold voltage at 20 ° C. was 2.33 V, and the voltage holding ratio at 25 ° C. was 98.6%.

Example 15

[Chemical formula 61]

Embedded image A liquid crystal composition was prepared. The clearing point of this liquid crystal composition is 115.0 ° C, and the viscosity at 20 ° C is 27.7 mP.
a · s, refractive index anisotropy at 25 ° C. is 0.134, 2
The dielectric anisotropy at 0 ° C. was 5.7, the threshold voltage at 20 ° C. was 2.31 V, and the voltage holding ratio at 25 ° C. was 98.7%.

Example 16

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Embedded image A liquid crystal composition was prepared. The clearing point of this liquid crystal composition is 115.2 ° C, and the viscosity at 20 ° C is 24.8 mP.
a · s, refractive index anisotropy at 25 ° C. is 0.085, 2
The dielectric anisotropy at 0 ° C. was 5.0, the threshold voltage at 20 ° C. was 2.37 V, and the voltage holding ratio at 25 ° C. was 98.4%.

Example 17

Embedded image A liquid crystal composition was prepared. The clearing point of this liquid crystal composition is 139.3 ° C., and the viscosity at 20 ° C. is 27.9 mP.
a · s, refractive index anisotropy at 25 ° C. is 0.117, 2
The dielectric anisotropy at 0 ° C. was 5.8, the threshold voltage at 20 ° C. was 2.46 V, and the voltage holding ratio at 25 ° C. was 98.5%.

Example 18

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Embedded image A liquid crystal composition was prepared. The clearing point of this liquid crystal composition is 110.5 ° C, and the viscosity at 20 ° C is 22.5 mP.
a · s, refractive index anisotropy at 25 ° C. is 0.106, 2
The dielectric anisotropy at 0 ° C. was 5.4, the threshold voltage at 20 ° C. was 2.45 V, and the voltage holding ratio at 25 ° C. was 98.5%.

Example 19

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Embedded image A liquid crystal composition was prepared. The clearing point of this liquid crystal composition is 130.6 ° C., and the viscosity at 20 ° C. is 24.6 mP.
a · s, refractive index anisotropy at 25 ° C. is 0.110, 2
The dielectric anisotropy at 0 ° C. was 5.6, the threshold voltage at 20 ° C. was 2.67 V, and the voltage holding ratio at 25 ° C. was 98.8%.

Example 20

Embedded image A liquid crystal composition was prepared. The clearing point of this liquid crystal composition is 107.2 ° C, and the viscosity at 20 ° C is 22.4 mP.
a · s, refractive index anisotropy at 25 ° C. is 0.113, 2
The dielectric anisotropy at 0 ° C. was 5.7, the threshold voltage at 20 ° C. was 2.22 V, and the voltage holding ratio at 25 ° C. was 98.7%.

[0069]

As shown in Examples and Comparative Examples, according to the present invention, a liquid crystal composition having a wide nematic range (in particular, a high clearing point) can be prepared while maintaining the voltage holding ratio. By using this liquid crystal composition, it becomes possible to provide outdoor and vehicle-mounted AM-LCDs.

Claims (6)

[Claims] 1. A compound represented by the general formula (1): (R ¹ in the formula represents an alkyl group having 1 to 10 carbon atoms.)
Containing at least one compound represented by the general formula (2) to (8) (R ² in the formula represents an alkyl group having 1 to 10 carbon atoms,
X ¹ is F, Cl, OCF ₃ , CF ₃ , OCF ₂ H, OCF ₂
CF ₂ H and OCF ₂ CFHCF ₃ are shown, and Y ¹ to Y ⁴ are independently H or F. ) A liquid crystal composition comprising one or more compounds selected from the group consisting of the compounds represented by 2. The mixing ratio of the first component and the second component is 3 to 30% and 50 to 50% of the total weight of the liquid crystal composition, respectively.
It is 97%, The liquid crystal composition of Claim 1 characterized by the above-mentioned. 3. In addition to the liquid crystal composition according to claim 1 or 2, a compound represented by the general formula (9) or (10): (R ³ in the formula represents an alkyl group having 1 to 10 carbon atoms,
X ² represents F, Cl or OCF ₃ , and Y ⁵ and Y ⁶ independently represent H or F. ) A liquid crystal composition further comprising one or more compounds selected from the group consisting of compounds represented by 4. In addition to the liquid crystal composition according to any one of claims 1 to 3, a compound represented by the general formula (11) or (12): (R ⁴ in the formula represents an alkyl group having 1 to 10 carbon atoms,
Z ¹ represents a single bond or —CH ₂ CH ₂ —. ) One or more compounds selected from the group consisting of compounds represented by
A liquid crystal composition further comprising: 5. In addition to the liquid crystal composition according to any one of claims 1 to 4, a compound represented by the general formula (13) or (14): (In the formula, R ⁵ and R ⁶ independently represent an alkyl group having 1 to 10 carbon atoms, an alkoxy group or an oxaalkyl group,
Z ² represents a single bond, —CH═CH— or —C ♪ C—, A represents trans-1,4-cyclohexylene or 1,4-phenylene, and B represents trans-1,4-cyclohexylene or One H on the side position represents 1,4-phenylene which may be substituted with F, and n represents 0 or 1. ) A liquid crystal composition further comprising one or more compounds selected from the group consisting of the compounds represented by 6. A liquid crystal display device comprising the liquid crystal composition according to claim 1.