JPH0733702A - 4-(2,2,2-trifuluoroethoxy)-3,5-difluorobenzene derivetive - Google Patents

Abstract

PURPOSE:To obtain a new liquid crystal compound usable as an additive capable of lowering the threshold voltage of a liquid crystal composition and increasing the upper limit temperature of the liquid crystal phase of the composition. CONSTITUTION:A 4-(2,2,2-trifluoroethoxy)-3,5-difluorobenzene derivative of formula I (R<1> is a 1-10C straight-chain alkyl or straight-chain alkenyl; L and M are single bound or CH2CH2; at least one of L and M is single bond), e.g. 1-[trans-4-(trans-4-propylcyclohexyl) cyclohexyl]-3,5-difluoro 4-(2,2,2- trifluoroethoxy) benzene. The compound of formula I wherein L and M are single bond and R is a 1-5C alkyl (R<a>) (the compound of formula Ia) can be produced by reacting a compound of formula IV with magnesium to obtain a Grignard reaction agent, reacting the agent with a compound of formula V, subjecting the reactional product to dehydration and hydrogenation to obtain a mixture of isomers having different steric configurations of the central cyclohexane ring and resolving the isomer mixture or isomerizing with a base.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a novel compound which is a 4- (2,2,2-trifluoroethoxy) -3,5-difluorobenzene derivative useful as an electro-optical liquid crystal display material, and a compound containing the same. Liquid crystal composition.

[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 the drive system, the conventional static drive has become more common, and the multiplex drive has become more common, and the simple matrix system and recently the active matrix system have been put into 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 range of liquid crystal phase Is important.

Normally, the threshold voltage in liquid crystal display is expressed by the equation (1)

[0005]

[Equation 1]

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

In order to reduce the elastic constant of the liquid crystal composition, it is necessary to add a liquid crystal compound having a small elastic constant. Many of the bicyclic compounds have a small elastic constant, but most of them add a large amount to the composition and significantly lower the maximum temperature of the liquid crystal phase of the composition.
In addition, many tricyclic or tetracyclic liquid crystal compounds have a high maximum temperature of the liquid crystal phase, and the temperature range of the liquid crystal phase can be expanded to a high temperature range. Many of these compounds have large elastic constants. Therefore, it is quite difficult to reduce the elastic constant of the liquid crystal phase while ensuring a wide temperature range of the liquid crystal phase (hereinafter, referred to as liquid crystal temperature range) especially in a high temperature range.

On the other hand, in order to increase the dielectric anisotropy of the liquid crystal compound, a cyanobenzene compound is usually used in a general liquid crystal display device for TN and STN.
However, in the liquid crystal compound having this cyano group,
It is difficult to obtain a high specific resistance value and a high voltage holding ratio, and therefore it cannot be used for active matrix display. Therefore, fluorobenzene-based liquid crystal compounds are mainly used for such applications. However, in such a compound, the polarization due to fluorine is much smaller than that due to the cyano group, so it is necessary to introduce two or more fluorine atoms into the benzene ring in order to increase the dielectric anisotropy.

As a compound capable of lowering the threshold voltage of the composition by adding it to the base liquid crystal,
General formula (II)

[0010]

[Chemical 2]

A 3,4,5-trifluorobenzene compound represented by the formula (wherein R represents an alkyl group) is known (described in JP-A-2-233626). However, since the liquid crystal phase maximum temperature of the liquid crystal compound described therein is not so high as 100 ° C. or lower, when an attempt is made to obtain a composition having a wide liquid crystal temperature range up to a high temperature range, the addition amount thereof is considerably limited, It was difficult to sufficiently reduce the threshold voltage of the composition.

In order to make up for the drawbacks of the compounds of the general formula (II) as described above, the present inventors have proposed the general formula (III)

[0013]

[Chemical 3]

(In the formula, R and R'represent an alkyl group respectively), 4-alkoxy-3,5-
Difluorobenzene compounds have already been developed. With this compound of general formula (III), the liquid crystal temperature range was greatly improved, and it became easy to obtain a liquid crystal composition with a wide temperature range, but the dielectric anisotropy of the compound was reduced and the threshold voltage Also, the effect of reducing the above was not sufficient.

As described above, almost no liquid crystal compound has been known in which the liquid crystal temperature range is wide up to a high temperature range and the threshold voltage of the composition can be lowered by addition.

[0016]

The problem to be solved by the present invention is to reduce the threshold voltage of the liquid crystal composition and increase the upper limit temperature of the liquid crystal phase of the composition by addition according to the above-mentioned object. A liquid crystal compound capable of being produced, and containing the compound, the liquid crystal temperature range is wide,
Another object is to provide a liquid crystal composition having a low threshold voltage.

[0017]

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

[0018]

[Chemical 4]

(In the formula, R ¹ represents a linear alkyl group or a linear alkenyl group having 1 to 10 carbon atoms, preferably a linear alkyl group having 1 to 10 carbon atoms, and Preferably, it represents a straight-chain alkyl group having 1 to 5 carbon atoms, and L and M each independently represent a single bond or —CH ₂ CH ₂ —, but at least one represents a single bond, and preferably both. Represents a single bond, R ² represents a linear alkyl group having 1 to 10 carbon atoms, preferably a linear alkyl group having 1 to 5 carbon atoms, and the cyclohexane ring has a trans configuration. .) Represented by 4- (2,2,2-trifluoroethoxy)-
Provided is a 3,5-difluorobenzene derivative.

Among the compounds represented by the general formula (I) of the present invention, the following general formulas (Ia) to (Id)

[0021]

[Chemical 5]

A compound represented by the formula (wherein R ^a represents a straight-chain alkyl group having 1 to 5 carbon atoms and R ^b represents a straight-chain alkenyl group having 1 to 5 carbon atoms), The compound represented by formula (Ia) is particularly preferable.

The compounds of the general formulas (Ia) to (Id) can be prepared, for example, by using commercially available 2,6-difluorophenol.
It can be manufactured as follows.

[0024]

[Chemical 6]

4-Bromo-2,6-difluorophenol obtained by brominating 2,6-difluorophenol was treated with CF ₃ CH ₂ X (X is chlorine, bromine, iodine or p-toluenesulfonyl group) in the presence of a base. And a leaving group such as p-toluenesulfonyl group is preferred.
It can be obtained by reacting 2,2,2-trifluoroethanol with p-toluenesulfonyl in the presence of pyridine. ), 1- (2,2,2- of the formula (IV)
Trifluoroethoxy) -4-bromo-2,6-difluorobenzene can be obtained.

[0026]

[Chemical 7]

Next, the compound of the formula (IV) is reacted with magnesium to obtain a Grignard reactant, which is represented by the formula (V).
By reacting with 4- (trans-4-alkylcyclohexyl) cyclohexanone, followed by dehydration and hydrogenation to obtain an isomer mixture due to the difference in the configuration of the central cyclohexane ring. These can be separated or isomerized with a base to obtain the compound of the general formula (Ia).

[0028]

[Chemical 8]

Here, instead of the compound of formula (IV), 1
1- [trans-4- (trans-4-alkylcyclohexyl) cyclohexyl] -3,5-difluoro-4 obtained by reacting with -methoxy-4-bromo-2,6-difluorobenzene in the same manner as above. -Methoxybenzene is demethylated with hydrobromic acid or trimethylsilyl iodide to give 4- [trans-4- (trans-4-alkylcyclohexyl) cyclohexyl]
2,6 and difluorophenol, which also reacted similarly with a base and the aforementioned CF ₃ CH ₂ X, to give compounds of general formula (Ia).

Also, instead of the compound of the formula (V), 4- (trans-4-alkylcyclohexyl) cyclohexaneethanal of the following general formula (VI) is reacted in the same manner to give the compound of the general formula (Ib). Can be obtained.

[0031]

[Chemical 9]

The compound of the general formula (VI) can be easily prepared by, for example, repeating the step of reacting the compound of the general formula (V) with the Wittig reagent of the formula (VII) and then performing an acid treatment twice. Can be obtained.

Further, in place of the compound of the general formula (V), 4- [2- (trans-4-alkylcyclohexyl) ethyl] cyclohexanone of the following general formula (VIII) is used to obtain the compound of the general formula (Ic). The compound can be obtained.

[0034]

[Chemical 10]

Here, the compound of the general formula (VIII) is
For example, using trans-4-alkyl-1- (2-bromoethyl) cyclohexane as a Grignard reagent, reacting this with monoethylene acetal of cyclohexane-1,4-dione, dehydration, hydrogenation, and removal of acetal Etc. can be easily obtained.

[0036]

[Chemical 11]

Further, in place of the compound of the general formula (V), the same reaction is carried out by using the monoethylene acetal of the bicyclohexane-4,4'-dione of the formula (IX), and finally the acetal is removed. 4- [trans-4- [4- (2,2,2-trifluoroethoxy) of the formula (X)
-3,5-Difluorophenyl] cyclohexyl] cyclohexanone is obtained.

[0038]

[Chemical 12]

(In the formula, n and m each represent an integer of 1 or more, and n + m ≦ 10.) The compound of the formula (X) may be added with a Wittig reagent of the formula (VII), if necessary. The compound of the general formula (Id) having a double bond at any position of the side chain can be obtained by reacting once and further reacting with the Wittig reagent of the formula (XI).

In the above formula, when m ≧ 2, cis isomers are mainly obtained, which can be isomerized to trans isomers by a usual method such as irradiation with light in the presence of a catalyst or a sensitizer. Is.

Representative examples of the compound represented by the general formula (I) thus produced are shown in Table 1.

[0042]

[Table 1]

(In the table, Cr represents a crystalline phase, N represents a nematic phase, and I represents an isotropic liquid phase.) From Table 1, the compounds represented by the general formula (I) of the present invention are high. It exhibits a nematic liquid crystal phase up to temperature. Therefore, when it is added to a normal nematic host liquid crystal, its transition temperature can be expanded to a high temperature range.

Therefore, the compound represented by the general formula (I) can be used as T in a state of being mixed with another nematic liquid crystal compound.
It can be suitably used as a material for an N-type or STN-type field effect display cell. In addition, since the compound represented by the general formula (I) does not have a strong polar group such as a cyano group or an ester bond in its molecule, addition of the compound facilitates a liquid crystal composition having a high specific resistance and a high voltage holding ratio. Obtainable. Therefore, it is particularly suitable as a constituent component of an active matrix driving liquid crystal material.

The present invention also provides a liquid crystal composition containing as a constituent at least one compound represented by formula (I). In the liquid crystal composition of the present invention, preferred representative examples of the nematic liquid crystal compound that can be used as a mixture with the compound represented by the general formula (I) are, 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)
Examples thereof include -5-substituted pyrimidine and 2- (4'-substituted biphenylyl) -5-substituted pyrimidine.

Particularly for active matrix, 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 and the like are preferable.

The effects of the liquid crystal composition of the present invention are apparent from the following examples. Among nematic liquid crystal materials, a base liquid crystal (A) particularly suitable for active matrix

[0048]

[Chemical 13]

(Wherein the cyclohexane ring represents the trans configuration and the composition "%" represents "% by weight"). The base liquid crystal (A) exhibits a nematic phase at 116.7 ° C. or lower, and the dielectric anisotropy (Δε) is 4.7, and a TN cell (cell thickness 8.0 μm) manufactured using this liquid crystal (A) is used.
The threshold voltage (V _th ) of m) was 2.43V.

A liquid crystal composition (M-1) comprising 70% by weight of the base liquid crystal (A) and 30% by weight of the compound (No. 1) in Table 1 was prepared, and the maximum temperature of the nematic phase was 119. It greatly rose to ℃. In addition, Δε increased to 6.4. Extrapolating from this value, the Δε of the compound (No. 1) itself is about 10.4. Similarly, TN
A cell (cell thickness: 8.2 μm) was prepared, and V _th was measured.
It dropped to 2V.

From the above results, the addition of the compound represented by the general formula (I) lowers the threshold voltage (V _th ) of the nematic host liquid crystal, and effectively expands the liquid crystal temperature range particularly to a high temperature range. It is clear that you can.

On the other hand, the compound of the formula (R-1) which is a compound represented by the general formula (II)

[0053]

[Chemical 14]

30% by weight of the compound of and the host liquid crystal (A) 7
A liquid crystal composition (M-2) consisting of 0% by weight was prepared. This
TN cell (cell thickness 8.5 μm produced using the composition of
m) V _thWas significantly low at 2.10V, but the liquid crystal phase
Has a maximum temperature of 109 ° C, which is lower than that of the composition (M-1).
The total temperature was 10 degrees lower.

Further, the compound represented by the general formula (III) is represented by the formula (R-2)

[0056]

[Chemical 15]

30% by weight of the compound of and the host liquid crystal (A) 7
A liquid crystal composition (M-3) consisting of 0 wt% was prepared. Although the maximum temperature of the liquid crystal phase of this composition was 124 ° C., which was extremely high, a TN cell (cell thickness of 7.7 μm) prepared in the same manner was used.
_Vth of m) has risen to 2.7V.

From the above, the compound of the general formula (I) of the present invention has an excellent effect which the conventional compounds listed as a comparison do not have, that is, it can raise the nematic phase maximum temperature of the liquid crystal composition. It can be understood that it has the effect of lowering the threshold voltage at the same time.

[0059]

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). The structure of the compound was confirmed by nuclear magnetic resonance spectrum ( ¹ H-NMR), mass spectrum (MS) and the like. In NMR, CDCl ₃ represents a solvent, s represents a singlet, d represents a doublet, t represents a triplet, q represents a quartet, m represents a multiplet, and J represents a coupling constant. M ^{+ in} MS represents the parent peak. In addition, "%" in a composition means the "weight%." Reference Example 1 1- [trans-4- (trans-4-
Propylcyclohexyl) cyclohexyl] -3,5-
Synthesis of difluoro-4-methoxybenzene (1-a) Synthesis of 4-bromo-2,6-difluoroanisole

[0061]

[Chemical 16]

Commercially available 2,6-difluorophenol 1
8.0 g of dichloromethane 100 ml and pyridine 1
It was dissolved in 1.0 g and cooled to 5 ° C. While stirring this solution, 27 g of bromine was added dropwise over 30 minutes. Then, an aqueous sodium hydrogen sulfite solution was added to decompose excess bromine, and the organic layer was separated. The aqueous layer was extracted with dichloromethane, the organic phases were combined, washed with water and saturated saline, and dried over anhydrous sodium sulfate. The solvent was distilled off and 4-bromo-
28.6 g of crude crystals of 2,6-difluorophenol were obtained.

Next, the whole amount was dissolved in 150 ml of acetone, and 28 g of potassium carbonate was added. After adding 29.1 g of methyl iodide thereto, the mixture was heated and stirred under reflux for 1 hour. After dilute hydrochloric acid was added to make the mixture acidic, acetone was distilled off under reduced pressure, and the reaction product was extracted with ethyl acetate. The organic layer was washed with water and saturated saline and dehydrated with anhydrous sodium sulfate,
After drying, the solvent was distilled off to give oily 4-bromo-2,
26.9 g of 6-difluoroanisole was obtained. (1-b) Synthesis of 1- [trans-4- (trans-4-propylcyclohexyl) cyclohexyl] -3,5-difluoro-4-methoxybenzene

[0064]

[Chemical 17]

4-bromo-obtained in the above (1-a)
26.9 g of 2,6-difluoroanisole was dissolved in 140 ml of tetrahydrofuran (THF). This solution was added dropwise to 10 ml of THF and 3.5 g of magnesium, keeping the temperature at which gentle reflux continued. After completion of the dropping, the mixture was heated and stirred for another hour. After allowing to cool to room temperature, a solution of 4- (trans-4-propylcyclohexyl) cyclohexanone (26.8 g) in THF (140 ml) was added dropwise over 0.5 hour. After stirring for a further 3 hours, dilute hydrochloric acid was added and the reaction product was extracted with ethyl acetate. After distilling off the solvent of the extract, it was dissolved in 200 ml of toluene, 1 ml of sulfuric acid was added, and the mixture was stirred at 110 ° C. for 1 hour. After allowing to cool at room temperature, the mixture was washed successively with saturated aqueous sodium hydrogen carbonate solution, water and saturated brine. After dehydration over anhydrous sodium sulfate and drying, the solvent was distilled off to give 1- [4- (trans-4-propylcyclohexyl) cyclohexen-1-yl]-.
Crude crystal of 3,5-difluoro-4-methoxybenzene 3
9.6 g was obtained. The total amount was dissolved in 400 ml of ethyl acetate, 4.0 g of palladium-carbon was added, and catalytic reduction was carried out at room temperature for 4 hours under a hydrogen atmosphere at normal pressure. After the catalyst was filtered off, the solvent was distilled off to give 1- [4-
(Trans-4-propylcyclohexyl) cyclohexyl] -3,5-difluoro-4-methoxybenzene was obtained. It was recrystallized from ethanol and purified to give 1
-[Trans-4- (trans-4-propylcyclohexyl) cyclohexyl] -3,5-difluoro-4-
37.4 g of white crystals of methoxybenzene were obtained. NMR: δ = 0.84 to 0.95 (t, 3H), 1.0
~ 2.34 (m, 14H), 3.88 (s, 3H),
7.26 (d, J = 8 Hz, 2H) MS: m / e = 350 (M ⁺ ) (1-c) 2,6-difluoro-4- [trans-4
Synthesis of-(trans-4-propylcyclohexyl) cyclohexyl] phenol

[0066]

[Chemical 18]

27.2 g of 1- [trans-4- (trans-4-propylcyclohexyl) cyclohexyl] -3,5-difluoro-4-methoxybenzene obtained in the above (1-b) was dissolved in 560 ml of acetic acid. . To this solution, 800 ml of 48% hydrobromic acid was added, and the mixture was heated under reflux for 8 hours. After allowing to cool, the reaction solution was poured into water, and the reaction product was extracted with toluene. The aqueous layer was washed with water until it became neutral, then dried over anhydrous sodium sulfate and dried. The crude crystal obtained by distilling off the solvent was recrystallized from hexane and purified to give 18.4 g of 2,6-difluoro-4- [trans-4- (trans-4-propylcyclohexyl) cyclohexyl] phenol. Got (Example 1) 1- [trans-4- (trans-4-
Propylcyclohexyl) cyclohexyl] -3,5-
Synthesis of difluoro-4- (2,2,2-trifluoroethoxy) benzene

[0068]

[Chemical 19]

(In the formula, Ts represents a p-toluenesulfonyl group.) 2,6-difluoro-4- [trans-4- (trans-4-propylcyclohexyl) cyclohexyl] obtained in the above (Reference Example) Phenol 0.7g
Was dissolved in 3 ml of N, N-dimethylformamide (DMF), and this was added dropwise to 90 mg of sodium hydride dissolved in 3 ml of THF. After stirring for 1 hour at room temperature,
A solution of 0.62 g of 2,2,2-trifluoroethyl p-toluenesulfonate in 2 ml of THF was added dropwise, and the mixture was further heated under reflux for 5 hours. After allowing to cool, water was added to the reaction solution, and the reaction product was extracted with ethyl acetate. After washing with water and saturated saline, the solvent was distilled off, and the residue was purified by silica gel column chromatography (hexane / ethyl acetate = 9/1) and further purified by recrystallization from ethanol to give 1-
[Trans-4- (trans-4-propylcyclohexyl) cyclohexyl] -3,5-difluoro-4-
0.38 g of white crystals of (2,2,2-trifluoroethoxy) benzene were obtained. Phase transition temperature: 69.2 ° C (Cr → N), 138.1 ° C
(N-I) NMR :? = 0.40 to 2.83 (m, 27H), 4.
60 (q, 2H), 6.79 (d, 2H) MS: m / e = 418 (M ⁺ ) (Example 2) Preparation of liquid crystal composition Base liquid crystal composed of a fluorine-based compound suitable for active matrix ( A)

[0070]

[Chemical 20]

(Wherein the cyclohexane ring represents the trans configuration) was prepared and showed a nematic (N) phase at 116.7 ° 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) 4.7 Refractive index anisotropy (Δn) 0.090 Threshold voltage (V _th ) 2.43 V 70% by weight of this host liquid crystal (A) and in Example 1 A liquid crystal composition (M-1) comprising 30% by weight of the obtained (No. 1) compound 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 ) 119.0 ° C. Dielectric anisotropy (Δε) 6.4 Refractive index anisotropy (Δn) 0.090 Threshold voltage (V _th ) 2.32 V From this, it is clear that the compound (No. 1) raises the upper limit temperature of the nematic phase of the liquid crystal composition, and at the same time lowers the threshold voltage by about 0.1V. The specific resistance of this composition (M-1) was as large as 10 ¹³ Ω · cm or more, and the voltage holding ratio of the cell prepared using this composition was very high. (Comparative Example 1) 70% by weight of host liquid crystal (A) and formula (R-1)

[0074]

[Chemical 21]

A liquid crystal composition (M-2) comprising 30% by weight of the compound of (3) was prepared. The maximum temperature (T _NI ) of the nematic phase of this composition (M-2) and the threshold voltage (V _th ) similarly measured were as follows.

Upper limit temperature of N phase (T _NI ) 109.0 ° C. Threshold voltage (V _th ) 2.10 V From this, the compound of formula (R-1) changes the threshold voltage of the liquid crystal composition. Although it significantly lowers, the maximum temperature of the nematic phase is significantly lowered, and it is clear that it is lower than the composition (M-1) by 10 degrees. (Comparative Example 2) 70% by weight of base liquid crystal (A) and formula (R-2)

[0077]

[Chemical formula 22]

A liquid crystal composition (M-3) containing 30% by weight of the compound of the above was prepared. The maximum temperature (T _NI ) of the nematic phase of this composition (M-3) and the threshold voltage (V _th ) measured in the same manner were as follows.

Maximum temperature of N phase (T _NI ) 124.3 ° C. Threshold voltage (V _th ) 2.70 V From this, the compound of formula (R-2) has a maximum temperature of nematic phase of the liquid crystal composition. Although it greatly increases, it is clear that the threshold voltage also greatly increases at the same time.

[0080]

INDUSTRIAL APPLICABILITY The compound represented by the general formula (I) according to the present invention can be easily produced industrially as shown in Examples and is chemically stable against heat, light, water and the like. is there. Further, it is also excellent in compatibility with the host liquid crystal that is currently widely used as a nematic liquid crystal. Moreover, by adding it to the host liquid crystal, the temperature range of the nematic phase can be expanded to a high temperature range and the threshold voltage (V _th ) can be lowered.

Further, since the compound of the general formula (I) does not have a polar group such as a cyano group or an ester bond in the molecule,
Addition makes it possible to easily obtain a liquid crystal composition having a large specific resistance and a high voltage holding ratio. Therefore, it is very useful as various liquid crystal display elements which have a wide liquid crystal temperature range and are required to be driven at a low voltage, particularly as a liquid crystal material for driving an active matrix.

Claims (3)

[Claims] 1. A compound represented by the general formula (I): (In the formula, R ¹ represents a linear alkyl group or a linear alkenyl group having 1 to 10 carbon atoms, L and M each independently represent a single bond or —CH ₂ CH ₂ —, At least one of them represents a single bond). 2. The compound according to claim 1, wherein R ¹ represents a linear alkyl group having 1 to 10 carbon atoms, and L and M both represent a single bond. 3. A liquid crystal composition containing the compound represented by the general formula (I) according to claim 1.