JPH06122636A - 4-fluoroalkyl benzene derivative - Google Patents

Abstract

PURPOSE:To provide a novel 4-fluoroalkylbenzene derivative capable of readily giving liquid crystal compositions having a wide liquid crystal temperature range, excellent in chemical stability and capable of being driven at a low voltage, and industrially readily be produced. CONSTITUTION:A compound of formula I (R<1> is 1-10C linear alkyl; the ring A is 1,4-phenylene, trans-1,4-cyclohexylene; R<2> is H, 1-5C linear alkyl; the cyclohexane ring has a trans configuration), e.g. 1-[trans-4-(trans-4propylcyclohexyl) cyclohexyl]-4-(4-fluorobutyl)benzene. The compound is readily obtained by fluorinating a 4-hydroxyalkylbenzene derivative of formula II with a fluorinating agent such as diethylaminosulfur trifluoride.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a novel compound which is a 4-fluoroalkylbenzene derivative useful as an electro-optical liquid crystal display material.

[0002]

2. Description of the Related Art Liquid crystal display devices have come to be used in watches, calculators, various measuring instruments, automobile panels, word processors, electronic notebooks, printers, computers, televisions and the like. Typical liquid crystal display methods are TN (twisted nematic) type, STN (super twisted nematic) type, DS (dynamic light scattering) type, GH (guest host) type, and FLC (ferroelectric liquid crystal). ) And the like are known, of which the TN type and the STN type are most widely used at present. Also as a drive system,
Multiplex drive has become commonplace from the conventional static drive, and the simple matrix system and recently the active matrix system have been put to practical use. Of these, the active matrix method can display the highest image quality, has a wide viewing angle, facilitates high definition and colorization, and can also display moving images. Is believed to be.

As a liquid crystal material used in this active matrix display system, as in a normal liquid crystal display,
Various characteristics are required, but in particular, (1) high specific resistance and excellent voltage holding ratio, (2) low threshold voltage (V _th ), (3) temperature of liquid crystal phase It is important that the range is wide.

Usually, the threshold voltage (V
_th ) is the formula (1)

[0005]

[Equation 1]

(In the formula, k is a proportional constant, K is an elastic constant, and Δε is a dielectric anisotropy.). As can be seen from this formula, the threshold voltage is lowered. Therefore, it is necessary to reduce the elastic constant of the liquid crystal material or increase the dielectric anisotropy.

[0007]

However, many liquid crystal compounds having a large dielectric anisotropy have a large polarity and tend to make it difficult to obtain a high specific resistance value or voltage holding ratio. Therefore, a liquid crystal material having a small elastic constant is required for such a purpose.

On the other hand, in order to extend the liquid crystal phase temperature range of the liquid crystal composition to a particularly high temperature range, it is necessary to add a compound having a high maximum liquid crystal temperature such as tricyclic or tetracyclic. However, such compounds having a high maximum temperature tend to have large elastic constants, and their addition tends to increase the threshold voltage of the liquid crystal material. Therefore, it is quite difficult to obtain a liquid crystal composition having a wide temperature range up to a high temperature range and a low threshold voltage without increasing the dielectric anisotropy of the liquid crystal material.

According to the above object, the problem to be solved by the present invention is to provide a compound having a relatively high maximum temperature of the liquid crystal phase and a small elastic constant, and using the compound, the temperature range is wide. And to provide a liquid crystal composition having a low threshold voltage.

[0010]

In order to solve the above-mentioned problems, the present invention has the general formula (I)

[0011]

[Chemical 2]

(In the formula, R ¹ represents a straight-chain alkyl group having 1 to 10 carbon atoms, preferably a straight-chain alkyl group having 1 to 5 carbon atoms, and ring A is 1,4-phenylene. Or a trans-1,4-cyclohexylene group,
R ² represents a hydrogen atom or a linear alkyl group having 1 to 5 carbon atoms, preferably a hydrogen atom, a methyl group or an ethyl group, and particularly preferably a hydrogen atom. The cyclohexane ring has a trans configuration. And a 4-fluoroalkylbenzene derivative represented by

The compounds represented by the general formula (I) according to the present invention have the corresponding general formula (II)

[0014]

[Chemical 3]

(Wherein R ¹ , rings A and R ² are represented by the general formula (I)
Has the same meaning as in. ) Can be easily obtained by fluorinating the 4-hydroxyalkylbenzene derivative represented by (4) with a fluorinating agent such as diethylaminosulfur trifluoride (DAST).

The 4-hydroxyalkylbenzene derivative represented by the general formula (II) can be synthesized, for example, as follows. General formula (III)

[0017]

[Chemical 4]

(Wherein R ¹ and ring A have the same meanings as in formula (I)) and succinic anhydride are reacted in the presence of a Lewis acid such as aluminum chloride. General formula (IV)

[0019]

[Chemical 5]

4-oxo-in the formula, wherein R ¹ and ring A have the same meanings as in formula (I).
A 4-phenylbutanoic acid derivative can be obtained. This is reduced under alkaline conditions in the presence of hydrazine to give a compound of the general formula (V)

[0021]

[Chemical 6]

A 4-phenylbutanoic acid derivative represented by the formula (wherein R ¹ and ring A have the same meanings as in formula (I)) can be obtained. This compound can be directly or converted into a lower alkyl ester and then reduced with lithium aluminum hydride or the like to obtain a compound of the general formula (II) in which R ² is a hydrogen atom.
Next, this is oxidized to give a compound of the general formula (VI)

[0023]

[Chemical 7]

(Wherein R ¹ and ring A have the same meanings as in formula (I)), and then an aldehyde represented by formula (VII)

[0025]

Embedded image An organometallic compound represented by R ² —Z (VII) (wherein R ² has the same meaning as in formula (I), and Z represents Li, MgCl, MgBr, or MgI). By reacting, a compound in which R ² is an alkyl group in the general formula (II) can be obtained. Alternatively, when R ² is a methyl group, the carboxylic acid of general formula (V) may be reacted directly with methyllithium. Furthermore, the general formula (V
Aldehydes of I) can also be obtained by direct reduction of esters of carboxylic acids of general formula (V). Alternatively, the 4-hydroxyalkylbenzene derivative represented by the general formula (II) can be synthesized, for example, as follows.

General formula (VIII)

[0027]

[Chemical 9]

A halide represented by the formula (wherein R ¹ and ring A have the same meanings as in formula (I) and X represents a chlorine atom, a bromine atom or an iodine atom) is a Grignard compound. γ-butyrolactone or general formula (IX)

[0029]

[Chemical 10]

By reacting with a derivative represented by the formula (wherein R ² has the same meaning as in general formula (I)), general formula (X)

[0031]

[Chemical 11]

(Wherein R ¹ , rings A and R ² are represented by the general formula (I)
Has the same meaning as in. It is possible to obtain a 4-hydroxy-1-oxoalkylbenzene derivative represented by). This can be reduced in the presence of hydrazine under alkaline conditions to obtain the compound of general formula (II). Here, as the compound of the general formula (IX) which is γ-butyrolactone or a derivative thereof, a compound in which R ² is a hydrogen atom or a methyl group is commercially available, and other compounds are malonate and the general formula (XI).

[0033]

[Chemical 12]

It can be easily obtained from the epoxide represented by the formula (wherein R ² has the same meaning as in formula (I)). Table 1 shows typical examples of the compounds represented by formula (I) thus produced.

[0035]

[Table 1]

(In the table, Cr represents a crystalline phase, N represents a nematic phase, and Iso represents an isotropic liquid phase.)

The compound represented by the general formula (I) according to the present invention is used as a material for a field effect type display cell such as a TN type or STN type in the state of a mixture with another nematic liquid crystal compound. It can be used for the purpose of lowering the threshold voltage and is particularly suitable as a constituent component of a liquid crystal material for driving an active matrix.

As a preferred representative example of the nematic liquid crystal compound that can be used by mixing with the compound represented by the general formula (I), for example, 4-substituted benzoic acid 4-substituted phenyl ester, 4- Substituted cyclohexanecarboxylic acid 4-substituted phenyl ester, 4-substituted cyclohexanecarboxylic acid 4′-substituted biphenylyl ester, 4- (4-substituted cyclohexanecarbonyloxy)
Benzoic acid 4-substituted phenyl ester, 4- (4-substituted cyclohexyl) benzoic acid 4-substituted phenyl ester, 4
-(4-Substituted cyclohexyl) benzoic acid 4-substituted cyclohexyl ester, 4,4'-substituted biphenyl, 1-
(4-Substituted phenyl) -4-substituted cyclohexane, 4,
4 "-substituted terphenyl, 1- (4'-substituted biphenylyl) -4-substituted cyclohexane, 1- (4-substituted cyclohexyl) -4- (4-substituted phenyl) cyclohexane, 2- (4-substituted phenyl)- 5-substituted pyrimidines,
2- (4'-substituted biphenylyl) -5-substituted pyrimidine etc. can be mentioned.

The effects of the compound of the general formula (I) are shown in the examples described later, but are clear as follows. Phenylcyclohexane-based host liquid crystal (A) currently widely used as a nematic liquid crystal material

[0040]

[Chemical 13]

(In the above, the cyclohexane ring represents the trans configuration and "%" represents "% by weight".) Was prepared. As a result, a nematic phase was exhibited at 54.5 ° C or lower, and the dielectric anisotropy (Δε ) Was 6.7, the refractive index anisotropy (Δn) was 0.092, and the threshold voltage (V _th ) of the TN cell manufactured using this was 1.60V.

80% by weight of the base liquid crystal (A) and No.
A liquid crystal composition (M-1) consisting of 20% by weight of the compound of 1 was prepared. The upper limit temperature of the nematic phase of (M-1) increased to 71.0 ° C. Δε was a little small at 6.6, and Δn was a little large at 0.109. A cell was similarly prepared using this composition and the threshold voltage (V _th ) thereof was measured. As a result, although the upper limit temperature of the nematic phase increased and Δε decreased, 1. 83
I was able to suppress V and its rise slightly. This is N
o. It is shown that the elastic constant (K) of the compound No. 1 is relatively low for a tricyclic compound. Elastic constant of the actually measured composition (M-1) is, K ₁₁ is 9.3, K ₃₃ 17.
It was 0.

On the other hand, in No. Instead of the compound of 1,
No. The compound of formula (R-1) which has a similar structure to the compound of 1 and has been used for the same purpose up to now.

[0044]

[Chemical 14]

20% by weight of the compound of and the host liquid crystal (A) 8
A liquid crystal composition (N-1) consisting of 0 wt% was prepared. The upper limit temperature of the nematic phase of (N-1) was 75.7 ° C, which was slightly higher than that of (M-1). The Δε was as small as 6.3, and the Δn was 0.111, which was not much different from (M-1). However, when a cell was prepared in the same manner and the threshold voltage (V _th ) thereof was measured, it was considerably high at 1.92V. This is the formula (R-
The elastic constant of the compound of 1) is no. It is believed that this is due to the fact that it is larger than the compound of No. 1. The elastic constants of the composition (N-1) actually measured were 10.5 for K _{11 and} 1 for K _33.
It was 7.5, which was larger than that of (M-1).

From the above results, the compound represented by the general formula (I) shows a nematic liquid crystal phase up to a high temperature and has a small elastic constant as a tricyclic compound. Therefore, a small amount should be added to the base liquid crystal (A). Thus, it is clear that the liquid crystal temperature range can be expanded to a high temperature range without _raising the threshold voltage (V _th ) so much.

[0047]

EXAMPLES The present invention will be further described below by showing Examples of the present invention. However, the invention is not limited to these examples.

The phase transition temperature was measured by using a polarizing microscope equipped with a temperature adjusting stage and a differential scanning calorimeter (DSC). Further, the structure of the compound has a nuclear magnetic resonance spectrum ( ¹ H-NMR) and an infrared absorption spectrum (I
R), mass spectrum (MS), etc. IR
(KBr) represents the measurement by tableting. N
CDCl _{3 in} MR represents a solvent, s is a singlet,
d is a doublet, t is a triplet, q is a quadruple, sixt is a sixt, and m is a multiplet. For example, dt is a doublet triplet. Further, J represents a coupling constant. M
M ^{+ in} S represents the parent peak.

Example 1 1- [trans-4- (trans-4-propylcyclohexyl) cyclohexyl] -4- (4-fluorobutyl) benzene (No. 1)
Compound)

[0050]

[Chemical 15]

(1-a) 4- [4- [trans-4-
Synthesis of (trans-4-propylcyclohexyl) cyclohexyl] phenyl] -4-oxobutanoic acid 7.7 g of succinic anhydride was dissolved in 50 ml of dichloromethane. 20.6 g of anhydrous aluminum chloride was added to this solution, and the mixture was stirred and dissolved, and then cooled to 0 ° C. To this, [trans-4- (trans-4-propylcyclohexyl) cyclohexyl] benzene 20 g dichloromethane 20 m
1 solution was added dropwise with stirring for 15 minutes, and further stirred at room temperature for 3 hours. After completion of the reaction, 50 ml of ethanol was added dropwise over 30 minutes, the mixture was stirred for 30 minutes and then dichloromethane was distilled off. To the resulting residue was added 3 ml of concentrated sulfuric acid, and the mixture was stirred for 3 hours.

The reaction solution was poured into water and the organic layer was separated.
The reaction product was extracted from the aqueous layer with toluene, combined with the organic layer, washed with water and then with saturated saline, and dehydrated and dried over anhydrous sodium sulfate. The crude crystals obtained by distilling off the solvent were recrystallized from hexane and purified to give 4- [4- [trans-4- (trans-4-propylcyclohexyl) cyclohexyl] phenyl] -4-oxobutanoic acid. 24 g of white crystals were obtained. IR (KBr): 1735, 1680, 1600, 13
20,1180,980,820cm ^-1

(1-b) 4- [4- [trans-4-
Synthesis of (trans-4-propylcyclohexyl) cyclohexyl] phenyl] butanoic acid 12 g of potassium hydroxide was added to 90 m of triethylene glycol.
It was dissolved in 1. 4 in the solution obtained in (1-a) above
24 g of ethyl [-[4- [trans-4- (trans-4-propylcyclohexyl) cyclohexyl] phenyl] -4-oxobutanoate and 12 g of hydrazine hydrate were added, and the mixture was heated with stirring at 180 ° C. for 3 hours. After allowing to cool, diluted hydrochloric acid was added to make the mixture acidic, and the reaction product was extracted three times with ethyl acetate. The organic layers of the extracts were combined, washed with water, and dehydrated and dried over anhydrous sodium sulfate. The crude crystals obtained by distilling off the solvent were purified by column chromatography (hexane / ethyl acetate = 9) to give 4- [4
16 g of white crystals of-[trans-4- (trans-4-propylcyclohexyl) cyclohexyl] phenyl] butanoic acid were obtained. NMR: δ = 0.9 (d, J = 6 Hz, 3H), 1.0
-2.0 (m, 26H), 2.1-2.6 (m, 5
H), 7.1 (s, 4H)

(1-c) 4- [4- [trans-4-
Synthesis of ethyl (trans-4-propylcyclohexyl) cyclohexyl] phenyl] butanoate 4- [4- [trans-4-] obtained in the above (1-b)
16 g of (trans-4-propylcyclohexyl) cyclohexyl] phenyl] butanoic acid was added to 120 m of ethanol.
It was dissolved in 1 l, 5 ml of sulfuric acid was added, and the mixture was heated under reflux for 3 hours. After most of the ethanol was distilled off, toluene was added and dissolved, and the mixture was washed with an aqueous sodium hydrogen carbonate solution and then with water. After dehydration and drying with anhydrous sodium sulfate, the solvent was distilled off and the obtained crude product was purified by silica gel column chromatography (hexane / ethyl acetate = 20) to give 4- [4- [trans-4 19.5 g of white crystals of ethyl- (trans-4-propylcyclohexyl) cyclohexyl] phenyl] butanoate were obtained. NMR: δ = 0.9 (t, J = 6 Hz, 3H), 1.2
(T, J = 7 Hz, 3H), 1.0 to 2.0 (m, 25
H), 2.1 to 2.6 (m, 5H), 4.1 (q, J =
7Hz, 2H,), 7.1 (s, 4H)

(1-d) 4- [4- [trans-4-
Synthesis of (trans-4-propylcyclohexyl) cyclohexyl] phenyl] butanol 1.8 g of lithium aluminum hydride was suspended in 30 ml of tetrahydrofuran (THF). 4- [4- [trans-4-] obtained in the above (1-c) was added to this suspension.
Ethyl (trans-4-propylcyclohexyl) cyclohexyl] phenyl] butanoate 19.5 g THF2
The 0 ml solution was added dropwise at room temperature over 30 minutes. After completion of the dropwise addition, the mixture was stirred for an additional hour, an aqueous solution of ammonium chloride was added to decompose excess hydride, and diluted hydrochloric acid was further added to precipitate an inorganic substance. The organic layer was dried over anhydrous magnesium sulfate and the crude product obtained by distilling off the solvent was subjected to silica gel column chromatography (hexane / ethyl acetate = 4).
And purified using 4- [4- [trans-4- (trans-4-propylcyclohexyl) cyclohexyl]
15.1 g of phenyl] butanol was obtained. IR (KBr): 3420, 1500, 1440, 13
50, 1045, 1000, 810 cm ^-1 NMR: δ = 0.9 (t, J = 6 Hz, 3H), 1.0
-2.0 (m, 28H), 2.4-2.7 (m, 3)
H), 3.6 (t, J = 6 Hz, 2H), 7.1 (s,
4H)

(1-e) 1- [trans-4- (trans-4-propylcyclohexyl) cyclohexyl]
Synthesis of 4- (4-fluorobutyl) benzene 4- [4- [trans-4- obtained in (1-d) above.
7.6 g of (trans-4-propylcyclohexyl) cyclohexyl] phenyl] butanol was dissolved in 22 ml of dichloromethane. The solution is cooled to 0 ° C. and DAS
T5.2 g was added dropwise over 10 minutes. 1 hour at 0 ° C
Stir at room temperature for 5 hours. The reaction mixture was poured into saturated aqueous sodium hydrogen carbonate solution, the organic layer was separated, and washed with water. The solvent was distilled off after drying over anhydrous sodium sulfate,
The obtained crude product was purified by silica gel column chromatography (hexane / toluene = 9) to give 1-
[Trans-4- (trans-4-propylcyclohexyl) cyclohexyl] -4- (4-fluorobutyl)
5.8 g of white crystals of benzene were obtained. This was further recrystallized from ethanol and purified, and its phase transition temperature was measured. As a result, the melting point was 133 ° C., which showed a nematic phase up to 154 ° C., and became an isotropic liquid phase at a temperature higher than that. . IR (KBr): 1500, 1445, 1390, 10
45,1000,810 cm ^-1 NMR: δ = 0.9 (t, J = 6 Hz, 3H), 1.0
-2.0 (m, 27H), 2.2 (m, 1H), 2.6
(T, J = 7 Hz, 2H), 4.4 (dt, J = 47H
zand 5 Hz, 2H), 7.1 (s, 4H) MS: m / e = 352 (M ⁺ ).

Example 2 1- [trans-4- (trans-4-propylcyclohexyl) cyclohexyl] -4- (4-fluoropentyl) benzene (No.
Compound 2)

[0058]

[Chemical 16]

(2-a) 5- [4- [trans-4-
Synthesis of (trans-4-propylcyclohexyl) cyclohexyl] phenyl] pentan-2-one 4- [4- [trans-4-] obtained in the above (1-b)
1.1 g of (trans-4-propylcyclohexyl) cyclohexyl] phenyl] butanoic acid was dissolved in 10 ml of THF. This solution was cooled to 0 ° C., and 5.5 ml of methyllithium (1.1M ether solution) was added dropwise over 10 minutes. After stirring at 0 ° C. for 1 hour, the mixture was returned to room temperature, poured into ice water, and the reaction product was extracted with ethyl acetate. The organic layer was washed with water and dehydrated and dried over anhydrous sodium sulfate. The crude product obtained by distilling off the solvent was purified by silica gel column chromatography (hexane / ethyl acetate = 9) to give 5- [4- [trans-4- (trans-4-propylcyclohexyl)). 0.5 g of white crystals of cyclohexyl] phenyl] pentan-2-one were obtained.

(2-b) 5- [4- [trans-4-
Synthesis of (trans-4-propylcyclohexyl) cyclohexyl] phenyl] pentan-2-ol 80 g of sodium borohydride was added to 2 m of isopropanol.
It was dissolved in 1. To this solution, 0.5 g of 5- [4- [trans-4- (trans-4-propylcyclohexyl) cyclohexyl] phenyl] pentan-2-one obtained in (2-a) above in 2 ml of isopropanol was added,
It was added dropwise at room temperature over 5 minutes. After completion of dropping, the mixture was further stirred for 1 hour, diluted hydrochloric acid was added to decompose excess hydride, and the reaction product was extracted with ethyl acetate three times. The organic layers were combined, washed with water and saturated saline, and dehydrated and dried over anhydrous sodium sulfate. The crude product obtained by distilling off the solvent was purified by silica gel column chromatography (hexane / ethyl acetate = 9) to give 5- [4- [trans-
0.47 g of white crystals of 4- (trans-4-propylcyclohexyl) cyclohexyl] phenyl] pentan-2-ol was obtained. NMR: δ = 0.9 (t, J = 6 Hz, 3H), 1.0
~ 2.6 (m, 34H), 3.8 (q, J = 6Hz, 1
H), 7.1 (s, 4H)

(2-c) 1- [trans-4- (trans-4-propylcyclohexyl) cyclohexyl]
Synthesis of 4- (4-fluoropentyl) benzene 5- [4- [trans-4- obtained in (2-b) above]
From (470 mg of (trans-4-propylcyclohexyl) cyclohexyl] phenyl] pentan-2-ol, 1- [trans- was prepared in the same manner as in Example (1-e).
4- (trans-4-propylcyclohexyl) cyclohexyl] -4- (4-fluoropentyl) benzene 1
90 mg was obtained. NMR: δ = 0.9 (t, J = 6 Hz, 3H), 1.0
~ 2.6 (m, 33H), 5.7 (d sixtet,
J = 49 Hz and 4 Hz, 1 H), 7.1 (s, 4)
H) MS: m / e = 372 (M ⁺ ).

Example 3 Preparation of Liquid Crystal Composition Phenylcyclohexane base liquid crystal (A) having the following composition

[0063]

[Chemical 17]

(In the above, the cyclohexane ring represents the trans configuration and "%" represents "% by weight".) Was prepared and showed a nematic (N) phase at 54.5 ° C or lower. The physical properties and the threshold voltage (V _th ) of the TN cell manufactured using the same were as follows.

Dielectric anisotropy (Δε) 6.7 Refractive index anisotropy (Δn) 0.092 Threshold voltage (V _th ) 1.60 V

80% of the base liquid crystal (A) and No. 1 obtained in Example 1 were used. A liquid crystal composition (M-1) consisting of 20% of the compound of 1 was prepared. The upper limit temperature (T _NI ) of the N phase of (M-1) and its physical properties were as follows.

Maximum temperature of N phase (T _NI ) 71.0 ° C. Dielectric anisotropy (Δε) 6.6 Refractive index anisotropy (Δn) 0.109 Threshold voltage (V _th ) 1.83 V

Thus, although the upper limit temperature of the N phase has risen by 15 degrees or more, its threshold voltage is only slightly high. Although the dielectric anisotropy (Δε) is slightly small, considering No. 1 in consideration of the above formula (1). The elastic constant (K) of the compound No. 1 is considered to be quite small.

When this composition was left at a low temperature for a long time, no precipitation or the like was observed. Therefore, No. 1
It can be understood that the compound (1) is also excellent in compatibility with conventional liquid crystal compounds.

(Comparative Example) In Example 3, No. The compound of formula (R-1) which has been used for the same purpose up to now instead of the compound of formula (1)

[0071]

[Chemical 18]

20% by weight of the compound of and the host liquid crystal (A) 8
A liquid crystal composition (N-1) consisting of 0 wt% was prepared. The upper limit temperature (T _NI ) of this N phase of (N-1) and its physical properties were as follows.

Maximum temperature of N phase (T _NI ) 75.7 ° C. Dielectric anisotropy (Δε) 6.3 Refractive index anisotropy (Δn) 0.111 Threshold voltage (V _th ) 1.92 V In this way, the upper limit temperature of the N phase rises to 75.7 ° C, and (M
Although it was higher than that of (-1), the threshold voltage (V _th ) was considerably higher than that of (M-1).

From this result, No. The compound of 1 has the formula (R
-1), although the dielectric anisotropy (Δε) of the host liquid crystal (A) is made smaller, the threshold voltage (V _th ) is not increased so much and the maximum temperature of the nematic liquid crystal is increased. It is clear that it has the effect of increasing

[0075]

The compound represented by the general formula (I) according to the present invention exhibits a liquid crystal phase up to a high temperature and is excellent in compatibility with a host liquid crystal which is currently widely used as a nematic liquid crystal. Therefore, even though the nematic liquid crystal temperature range is expanded to a high temperature range and the dielectric anisotropy (Δε) is rather reduced by adding a small amount to the composition, the threshold voltage (V _th ) is not too high.

Further, the compound of the general formula (I) can be easily produced industrially and is chemically stable to heat, light, water, etc., so that it is very useful as a material for various liquid crystal display devices. It is useful.

Claims (3)

[Claims] 1. A compound represented by the general formula (I): (In the formula, R ¹ represents a linear alkyl group having 1 to 10 carbon atoms, and ring A is a 1,4-phenylene group or trans-
It represents a 1,4-cyclohexylene group, R ² represents a hydrogen atom or a linear alkyl group having 1 to 5 carbon atoms, and the cyclohexane ring represents a trans configuration. ) The compound represented by. 2. The compound according to claim 1, wherein R ² is a hydrogen atom. 3. A liquid crystal composition containing the compound represented by the general formula (I) according to claim 1.