JPH06247886A - Trifluorobenzene derivative - Google Patents

Abstract

PURPOSE:To obtain a new compound having low threshold voltage, broad liquid crystal phase temperature range and excellent compatibility, response speed and voltage-keeping ratio and useful as a liquid crystal material for active matrix display, etc. CONSTITUTION:The compound of formula I (R is H or 1-5C straight-chain alkyl; (m) is 0, 2 or 4; L and M are single bond or CH2CH2; ring A is 1,4- cyclohexylene or 1,4-phenylene), e.g. 1-[trans-4-(trans-4-vinylcyclohexyl) cyclohexyl]-3,4,5-trifluorobenzene. The compound of formula I can be produced e.g. by reacting a compound of formula II with a compound of formula III (Ph is phenyl).

Description

Detailed Description of the Invention

[0001]

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

[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 common, and the multiplex drive has become more common, and the simple matrix system, and recently the active matrix system has 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.

The liquid crystal material used in this active matrix display system is required to have various characteristics as in the case of a normal liquid crystal display. In particular, (1) it has a high specific resistance and an excellent voltage holding ratio, (2) Threshold voltage (V
_th ) is low, (3) the temperature range of the liquid crystal phase is wide,
(4) It is important to have excellent responsiveness.

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

Up to now, a substituent such as a cyano group has been introduced into a compound in order to increase the dielectric anisotropy of the liquid crystal compound. However, a compound having a cyano group has a high specific resistance value and a high voltage holding ratio. Tended to be difficult to obtain. Therefore, in order to increase the dielectric anisotropy, a compound having a fluorine atom instead of the cyano group, for example, 4-
Compounds having groups such as the fluorophenyl group 3,4-difluorophenyl group have been used.

However, the dielectric anisotropy of such a liquid crystal compound is considerably smaller than that of a compound having a cyano group, and it has been quite difficult to obtain a sufficiently low threshold voltage.

Apart from this, as a compound which is a fluorine-based compound and has a large dielectric anisotropy and can lower the threshold voltage, for example, a 3,4,5-trifluorophenyl group is used. Compounds having are known.
(Described in JP-A-2-233626) However, the maximum temperature of the liquid crystal phase of the liquid crystal compounds described in the examples of the above publications is not so high as less than 100 ° C. even for tricyclic compounds, Further, even if it is added to the liquid crystal composition, there is a problem that sufficient high speed response cannot be obtained.

[0010]

The problem to be solved by the present invention is that the maximum temperature of the liquid crystal phase is high, the dielectric anisotropy is large, the specific resistance and voltage holding ratio of the composition are increased, and It is intended to provide a compound having an effect of lowering a threshold voltage, and further to provide a liquid crystal composition containing the compound, having a wide temperature range, a low threshold voltage, and capable of high-speed response.

[0011]

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

[0012]

[Chemical 2]

(In the formula, R is a hydrogen atom or a carbon atom number 1 to
5 is a linear alkyl group, preferably a hydrogen atom or a linear alkyl group having 1 to 3 carbon atoms, and particularly preferably a hydrogen atom. m represents 0, 2 or 4, but preferably represents 0 or 2. L and M each independently represent a single bond or —CH ₂ CH ₂ —,
At least one of L and M represents a single bond, and preferably both L and M represent a single bond. Ring A represents a trans-1,4-cyclohexylene group or a 1,4-phenylene group, preferably a trans-1,4-cyclohexylene group. When R is a linear alkyl group having 1 to 5 carbon atoms, the double bond in the terminal alkenyl group preferably has a trans configuration. And a 3,4,5-trifluorobenzene derivative having an alkenyl group represented by

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

[0015]

[Chemical 3]

The compound represented by the formula (wherein R and m have the same meanings as in the general formula (I)) is preferable, and the compound represented by the general formula (Ia) is particularly preferable. The compound of the general formula (I) of the present invention can be produced, for example, as follows.

General formula (II)

[0018]

[Chemical 4]

(Wherein L, M and ring A have the same meanings as in formula (I)), the compound represented by formula (III)

[0020]

## STR00005 ## CH ₃ OCH═P (Ph) ₃ (III) (wherein Ph represents a phenyl group) is reacted with a Wittig reaction agent, followed by acid treatment, and, if necessary, cyclohexane. By isomerizing the ring to the trans form, the compound of the general formula (IV)

[0021]

[Chemical 6]

An aldehyde derivative represented by the formula (wherein L, M and ring A have the same meanings as in formula (I)) can be obtained. General formula (V)

[0023]

Embedded image A Wittig reagent represented by R—CH═P (Ph) ₃ (V) (wherein R has the same meaning as in formula (I) and Ph has the above-mentioned meaning). By reacting, a compound having m = 0 in the general formula (I) can be obtained. This time,
In the case of a compound in which R is an alkyl group, the double bond of the terminal alkenyl group has a cis configuration, but can be easily isomerized to the trans configuration by treating with a benzenesulfinic acid or the like.

Further, in the case of the compound of the general formula (I) in which m = 2 or m = 4, the reaction of the compound of the general formula (II) with the Wittig reagent of the general formula (III) is required a required number of times. After repeating, it can be easily obtained by similarly reacting with a Wittig reaction agent represented by the general formula (V).

Here, the general formula (I
The compound of I) is an important intermediate of various liquid crystal compounds including the compound of the general formula (I), and can be produced, for example, as follows.

[0026]

[Chemical 8]

1-Bromo-3,4,5-trifluorobenzene was used as a Grignard reagent, and this was mixed with bicyclohexane-4,4'-dione monoethylene acetal (4-
It is reacted with (4-oxocyclohexyl) cyclohexanone ethylene acetal) and then dehydrated to obtain a cyclohexene derivative of the general formula (VI). After hydrogenating this, the compound of the general formula (IIa) corresponding to the compound of the general formula (Ia) can be obtained by isomerizing the trans isomer, if necessary, and then deacetalizing it.

[0028]

[Chemical 9]

Further, the cyclohexene derivative of the general formula (VI) is converted into a biphenyl derivative with an oxidizing agent such as chloranil or dichlorodicyanobenzoquinone (DDQ),
Then, by deacetalization, a compound of the general formula (Id)
The compound of the general formula (IId) corresponding to the compound of can be obtained.

[0030]

[Chemical 10]

Further, the monoethylene acetal of bicyclohexane-4,4'-dione is reacted with the Wittig reagent of the general formula (III) two times repeatedly, and during the course, isomerization to the trans form is carried out, if necessary. The obtained aldehyde derivative is reacted with a Grignard reagent prepared from 1-bromo-3,4,5-trifluorobenzene, dehydrated, hydrogenated, and further deacetalized to give a compound represented by the general formula (I
Compounds of general formula (IIb) corresponding to compounds of b) can be obtained.

[0032]

[Chemical 11]

The compound of the general formula (IIc) corresponding to the compound of the general formula (Ic) is a monoethylene acetal of 4,4'-ethylenedicyclohexanone instead of the monoethylene acetal of bicyclohexane-4,4'-dione. Can be obtained in the same manner as the compound of the general formula (IIa).

The characteristics of the compounds of general formula (I) according to the invention are:
The number of carbon atoms in the terminal alkenyl group, especially in the methylene chain on the cyclohexane ring side is 0 or an even number, and such a compound exhibits excellent liquid crystallinity.

As shown in the examples below, the general formula (I)
Of the compounds of (3), for example, many compounds in which m is an odd number do not exhibit a liquid crystal phase and are often oily substances. Therefore, it can be easily understood that when such a compound is added to the liquid crystal composition, the temperature range of the liquid crystal phase of the composition is narrowed and there is a problem in compatibility. Therefore, it is very difficult to obtain a composition exhibiting a liquid crystal phase in a wide temperature range, a low threshold voltage, and a high-speed response by using a compound in which m is an odd number in the general formula (I). .

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

[0037]

[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 of the general formula (I) of the present invention are relatively high. It is clear that it shows a nematic phase up to temperature.

On the other hand, the compound of formula (R-1) which has a similar structure to the compound of (No. 1), but whose terminal group is an alkyl group having the same number of carbon atoms as the compound of (No. 1).

[0040]

[Chemical 12]

The liquid crystal phase maximum temperature of the compound (4) is 44 ° C., which is lower than that of the compound (No. 1) by 30 ° C. or more. Therefore, it can be understood that the compound (No. 1) of the present invention can greatly expand the transition temperature of the composition to a higher temperature range.

The compound represented by the general formula (I) of the present invention is preferably used as a material for a field effect display cell such as a TN type or STN type in a state of being mixed with another nematic liquid crystal compound. it can. Moreover, since the compound of the general formula (I) does not have a strong polar group such as a cyano group or an ester bond in the molecule, a large specific resistance and a high voltage holding ratio can be easily obtained. Therefore,
It is particularly suitable as a constituent component of an active matrix driving liquid crystal material.

The present invention provides a liquid crystal composition containing at least one compound represented by the general formula (I). In the liquid crystal composition of the present invention, a preferable representative example of the nematic liquid crystal compound that can be used by mixing with the compound represented by the general formula (I) is, 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 bicyclohexyl, 4,4 "-substituted terphenyl, 1- (4'-substituted biphenylyl) -4-substituted cyclohexane, 1- (4-substituted cyclohexyl) -4
-(4-Substituted phenyl) cyclohexane, 4,4 "-substituted tercyclohexane, 1- (4-substituted phenyl) -2
-(4-Substituted cyclohexyl) ethane, 1- [4- (4
-Substituted phenyl) phenyl] -2- (4-substituted cyclohexyl) ethane, 1- [4- (4-substituted phenyl) cyclohexyl] -2- (4-substituted cyclohexyl) ethane, 1- [4- (4-substituted Cyclohexyl) cyclohexyl] -2- (4-substituted phenyl) ethane, 2- (4-
Substituted phenyl) -5-substituted pyrimidines, 2- (4′-substituted biphenylyl) -5-substituted pyrimidines and the like can be mentioned.

Among them, 4,4'-substituted biphenyl, 1- (4-substituted phenyl) -4-substituted cyclohexane, 4,4'-substituted bicyclohexyl, 4,4 "-substituted for active matrix driving. Terphenyl, 1-
(4′-Substituted biphenylyl) -4-substituted cyclohexane, 1- (4-substituted cyclohexyl) -4- (4-substituted phenyl) cyclohexane, 4,4 ″ -substituted tercyclohexane, 1- (4-substituted phenyl)- 2- (4-Substituted cyclohexyl) ethane, 1- [4- (4-substituted phenyl) phenyl] -2- (4-substituted cyclohexyl) ethane, 1- [4- (4-substituted phenyl) cyclohexyl]
-2- (4-substituted cyclohexyl) ethane, 1- [4-
(4-Substituted cyclohexyl) cyclohexyl] -2-
(4-Substituted phenyl) ethane and the like are preferable, and among these, 1- (4-substituted phenyl) -4-substituted cyclohexane, 1- (4′-substituted biphenylyl) -4-substituted cyclohexane, 1- (4- Substituted cyclohexyl) -4-
(4-substituted phenyl) cyclohexane, 1- (4-substituted phenyl) -2- (4-substituted cyclohexyl) ethane,
1- [4- (4-substituted phenyl) phenyl] -2- (4
-Substituted cyclohexyl) ethane, 1- [4- (4-substituted phenyl) cyclohexyl] -2- (4-substituted cyclohexyl) ethane, 1- [4- (4-substituted cyclohexyl) cyclohexyl] -2- (4-substituted) Phenyl) ethane is preferred.

The effects of the compounds of the general formula (I) are shown in the examples described below, but are clear from the following examples, for example. A matrix liquid crystal (A) currently widely used as a nematic liquid crystal material

[0046]

[Chemical 13]

(In the above, the cyclohexane ring represents the trans configuration and "%" represents "% by weight."), A nematic phase was exhibited at 54.5 ° C or lower, and the dielectric anisotropy (Δε) ) Was 6.7, and the threshold voltage (V _th ) of the TN cell manufactured using this was 1.60V. The response time was 39.2 milliseconds and the applied voltage at that time was 3.2V.

Here, the response time is the rise time (τ _r ) from the state in which no voltage is applied to the state in which light is applied and the state in which light is transmitted, and the light is no longer transmitted except for the voltage in the voltage applied state. Is the time (milliseconds) when the fall times (τ _d ) up to (τ _r = τ _d ) are equal.

This matrix liquid crystal (A) 80% by weight and (N
o. A liquid crystal composition comprising 20% by weight of the compound of 1) (M-
When 1) was prepared, the maximum temperature of the nematic phase was 59.
It became considerably higher at ℃. Moreover, when a cell was similarly prepared using this composition, the threshold voltage (V _th )
Is 1.54V, which is considerably lower than that of (M-1). The response time was 41 milliseconds, and the applied voltage at that time was 3.3V.

On the other hand, in place of the compound (No. 1), a compound of the formula (R-1) described in the above-mentioned publication, in which the side chain is an alkyl group.

[0051]

[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 52.5 ° C., which was considerably lower than that of (M-1) and lower than that of the base liquid crystal (A). When a cell was prepared in the same manner, V _th
Was 1.52 V, which was slightly lower than (M-1), but the response time was considerably slow at 50 ms. The applied voltage at that time was 3.2V.

Then, instead of the compound of (No. 1), a compound of the formula (R-2) which is different only in the position of the double bond.

[0054]

[Chemical 15]

20% by weight of the compound of and the host liquid crystal (A) 8
A liquid crystal composition (N-2) consisting of 0 wt% was prepared. Since the compound of the formula (R-2) did not show a liquid crystal phase and was oily (under supercooling) even at room temperature, the upper limit temperature of the nematic phase of the composition (N-2) was lowered to 45 ° C.

From the above results, the compound represented by the general formula (I) raises the upper limit temperature of the liquid crystal phase of the host liquid crystal exhibiting the nematic liquid crystal phase and the threshold voltage (V _th ).
Can be reduced, and high-speed response can be easily obtained.

[0057]

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, m represents a multiplet, and J represents a coupling constant. M ^{+ in} MS represents the parent peak. (Example 1) 1- [trans-4- (trans-4-
Vinylcyclohexyl) cyclohexyl] -3,4,5
-Synthesis of trifluorobenzene (compound of general formula (Ia))

[0059]

[Chemical 16]

(1-a) 4- [4-hydroxy-4-
Synthesis of (3,4,5-trifluorophenyl) cyclohexyl] cyclohexanone ethylene acetal 1-Bromo-3,4,5-trifluorobenzene 89 g
90 ml of THF solution of THF of 10.3 g of magnesium
It was added dropwise to the F330 ml suspension in 30 minutes. A 220 ml THF solution of monoethylene acetal of bicyclohexane-4,4′-dione was added dropwise to the prepared Grignard reactant at 10 ° C. for 15 minutes. After reacting for 1 hour at room temperature, the reaction solution is poured into a saturated aqueous solution of ammonium chloride,
The reaction product was extracted with ethyl acetate. After the extract was washed with water and dried over anhydrous sodium sulfate, the solvent was distilled off to give 4- [4-hydroxy-4- (3,4,5-trifluorophenyl) cyclohexyl] cyclohexanone ethylene acetal. 172 g of crude crystals were obtained. (1-b) Synthesis of 4- [4- (3,4,5-trifluorophenyl) -3-cyclohexenyl] cyclohexanone ethylene acetal 4- [4-hydroxy-4-obtained in (1-a) above.
To a solution of 170 g of (3,4,5-trifluorophenyl) cyclohexyl] cyclohexanone ethylene acetal in 170 ml of xylene, 5.2 g of potassium hydrogen sulfate was added, and the mixture was refluxed for 10 hours while removing water. After completion of the reaction, water was added and the reaction product was extracted with toluene, then the extract was dried over anhydrous sodium sulfate, the solvent was distilled off, and 4-
120 g of white crystals of [4- (3,4,5-trifluorophenyl) -3-cyclohexenyl] cyclohexanone ethylene acetal were obtained. (1-c) Synthesis of 4- [trans-4- (3,4,5-trifluorophenyl) cyclohexyl] cyclohexanone ethylene acetal 4- [4- (3,4,5) obtained in (1-b) above -Trifluorophenyl) -3-cyclohexenyl] cyclohexanone ethylene acetal 120 g toluene 1.5 l
100 ml of triethylamine and 24 g of palladium carbon were added to the solution, and the mixture was reacted in an autoclave at a hydrogen pressure of 5 kg / cm ² for 3 hours. After completion of the reaction, the catalyst was filtered off, the filtrate was concentrated, and the obtained crude product was purified by silica gel column chromatography (hexane / ethyl acetate = 4) and recrystallized from ethanol to give 4 38 g of white crystals of-[trans-4- (3,4,5-trifluorophenyl) cyclohexyl] cyclohexanone ethylene acetal were obtained. (1-d) Synthesis of 4- [trans-4- (3,4,5-trifluorophenyl) cyclohexyl] cyclohexanone (Compound of the general formula (IIa)) 4- [trans obtained in the above (1-c) -4- (3,4
5-trifluorophenyl) cyclohexyl] cyclohexanone ethylene acetal 38 g toluene 380 m
150 g of formic acid was added to the 1-solution and stirred at room temperature for 4 hours. After completion of the reaction, water was added to separate the organic layer, and the organic layer was washed with an aqueous sodium hydrogen carbonate solution and dried over anhydrous magnesium sulfate, the solvent was distilled off, and the residue was recrystallized from ethanol to give 4- [ 32.7 g of white crystals of trans-4- (3,4,5-trifluorophenyl) cyclohexyl] cyclohexanone were obtained. Melting point: 86 ° C. IR (KBr): 1715, 1610, 1525, 14
45, 1340, 1235, 1035, 1025, 85
5,780 cm ^-1 NMR: δ = 1.0 to 1.9 (m, 14H), 2.2
2.4 (m, 5H), 6.7 to 7.3 (m, 2H) MS: m / e = 310 (M ⁺ ) (1-e) trans-4- [trans-4- (3,
Synthesis of 4,5-trifluorophenyl) cyclohexyl] cyclohexanecarbaldehyde Methoxymethyltriphenylphosphonium chloride 35.4
g was suspended in 80 ml of THF and cooled to -5 ° C. To this suspension, 11.6 g of potassium t-butoxide was added and stirred at room temperature for 1 hour to prepare a Wittig reaction agent. In addition to this, 4- [trans-4- (3, obtained in (1-d) above]
4,5-trifluorophenyl) cyclohexyl] cyclohexanone 24.7 g in a solution of 25 ml of THF at -5 ° C.
At 5 minutes. After stirring at room temperature for 5 hours, the reaction solution was poured into water, and hexane was added to this to separate an organic layer. The precipitate of triphenylphosphine oxide was filtered off,
After washing with water, it was dried over anhydrous sodium sulfate. The solvent was distilled off, and the obtained crude product was purified by silica gel column chromatography (hexane / ethyl acetate = 9) to give 4- [trans-4- (3,4,5-trifluorophenyl). 21.8 g of white crystals of cyclohexyl] cyclohexanecarbaldehyde were obtained. This is a diastereomeric mixture of cis and trans configurations of the cyclohexane ring to which the formyl group is attached. This was dissolved in 100 ml of ethanol, 2 ml of 20% aqueous sodium hydroxide solution was added, and the mixture was stirred at room temperature for 3 hours. After the reaction,
After adding water and neutralizing with 1N hydrochloric acid, the reaction product was extracted with ethyl acetate. The extract was washed with water and dried over anhydrous sodium sulfate. The solvent was distilled off, and the obtained crude product was purified by silica gel column chromatography (hexane / ethyl acetate = 9) and further recrystallized from hexane to purify it, and then trans-4- [trans-4 -(3
White crystals of 3.2 g of 4,5-trifluorophenyl) cyclohexyl] cyclohexanecarbaldehyde were obtained. (1-f) 1- [trans-4- (trans-4-vinylcyclohexyl) cyclohexyl] -3,4,5-
Synthesis of trifluorobenzene THB was added with 1.62 g of methyltriphenylphosphonium chloride.
The suspension was suspended in 2 ml of F and 8 ml of toluene and cooled to 15 ° C. 0.52 g of potassium t-butoxide was added to this suspension and stirred at room temperature for 1 hour to prepare a Wittig reaction agent. 1.0 g of trans-4- [trans-4- (3,4,5-trifluorophenyl) cyclohexyl] cyclohexanecarbaldehyde obtained in (1-e) above
3 ml of toluene solution of was added dropwise at 15 ° C. over 5 minutes. After stirring at room temperature for 1.5 hours, the reaction solution was poured into water and toluene was added to separate the organic layer. After concentrating the organic layer, hexane was added, the precipitate of triphenylphosphine oxide was filtered off, washed with a water / methanol mixed solvent (1/1), and then dried over anhydrous sodium sulfate. The crude product obtained by distilling off the solvent was purified by silica gel column chromatography (hexane) to give 1- [trans-4.
0.86 g of white crystals of-(trans-4-vinylcyclohexyl) cyclohexyl] -3,4,5-trifluorobenzene was obtained.

Further, it was recrystallized from ethanol for purification, and its phase transition temperature was measured. The melting point was 59.5.
It showed a nematic phase up to 75.5 ° C at 0 ° C, and became an isotropic liquid phase at higher temperatures. NMR: δ = 1.0 to 1.8 (m, 18H), 2.1 to
2.6 (m, 2H), 4.8-5.1 (m, 2H),
5.5-6.1 (m, 1H), 6.6-6.9 (m, 2
H) IR: 1640, 1615, 1530, 1345, 12
30,1030,915,845 cm ^-1 MS: m / e = 322 (M ⁺ ) (Example 2) 1- [trans-4- [trans-4-
Synthesis of (trans-1-butenyl) cyclohexyl] cyclohexyl] -3,4,5-trifluorobenzene In (1-f) of Example 1, butyltriphenylphosphonium chloride was used instead of methyltriphenylphosphonium chloride. The same as Example 1 except that 1-
[Trans-4- [trans-4- (cis-1-butenyl) cyclohexyl] cyclohexyl] -3,4,5-
Trifluorobenzene was obtained.

2.0 g of this compound was dissolved in 6 ml of toluene, 10 ml of 9% hydrochloric acid and 0.2 g of sodium benzenesulfinate were added, and the mixture was heated under reflux for 8 hours. After allowing to cool, toluene was added to remove the aqueous layer and insoluble matter, and the organic layer was washed with diluted hydrochloric acid, saturated aqueous sodium hydrogen carbonate solution and water. After dehydration over anhydrous sodium sulfate, the mixture was concentrated to give the starting material and 1- [trans-4- [trans-4- (trans-1-butenyl) cyclohexyl] cyclohexyl]-.
Weight ratio of 3,4,5-trifluorobenzene of about 75/2
A mixture of 5 was obtained. This was recrystallized from ethanol and purified to give white crystals of 1- [trans-4- [trans-4- (trans-1-butenyl) cyclohexyl] cyclohexyl] -3,4,5-trifluorobenzene. 3 g was obtained. The phase transition temperature is shown in Table 1. (Reference example) 1- [trans-4- [trans-4-
(2-Propenyl) cyclohexyl] cyclohexyl]
Synthesis of -3,4,5-trifluorobenzene [compound of formula (R-2)]

[0063]

[Chemical 17]

18.1 g of methoxymethyltriphenylphosphonium chloride was suspended in 50 ml of THF and cooled to -5 ° C. To this was added 6.9 g of potassium t-butoxide,
The Wittig reaction agent was prepared by stirring at room temperature for 1 hour.
A solution of trans-4- [trans-4- (3,4,5-trifluorophenyl) cyclohexyl] cyclohexanecarbaldehyde (13.2 g) obtained in Example (1-e) in THF (20 ml) was added thereto at -5 ° C for 5 minutes. Dropped. After stirring at room temperature for 3 hours, the reaction solution was poured into water and hexane was added to separate the organic layer. The precipitate of triphenylphosphine oxide was filtered off, washed with water, 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 trans-4- [trans-
White crystals of 4- (3,4,5-trifluorophenyl) cyclohexyl] cyclohexylacetaldehyde 1
0.4 g was obtained.

Next, 3.11 g of methyltriphenylphosphonium iodide was suspended in 3 ml of THF and 10 ml of toluene and cooled to 10 ° C. To this, 0.99 g of potassium t-butoxide was added and stirred at 20 ° C. for 1 hour to prepare a Wittig reaction agent. To this, a solution of 2.0 g of trans-4- [trans-4- (3,4,5-trifluorophenyl) cyclohexyl] cyclohexylacetaldehyde in 10 ml of toluene was added dropwise at 10 ° C over 10 minutes.
After stirring at room temperature for 1 hour, the reaction solution was poured into water and hexane was added to separate the organic layer. The precipitate of triphenylphosphine oxide was filtered off, washed with water, and dried over anhydrous sodium sulfate. The crude product obtained by distilling off the solvent was purified by silica gel column chromatography (hexane) to give 1- [trans-4- [trans-4-].
(2-Propenyl) cyclohexyl] cyclohexyl]
White crystal of 3,4,5-trifluorobenzene 1.8
3 g was obtained.

Further, it was recrystallized from ethanol for purification,
When its phase transition temperature was measured, it had an isotropic liquid phase with a melting point of 31 ° C., and even under supercooling it did not show a nematic phase below room temperature. NMR: δ = 1.0 to 1.8 (m, 19H), 2.0 to
2.3 (m, 3H), 4.8 to 5.1 (m, 2H),
5.5-5.9 (m, 1H), 6.7-6.9 (m, 2
H) IR: 1615, 1530, 1450, 1445, 13
45,1235,1035,910,845,690cm
^-1 (Example 3) Preparation of liquid crystal composition

[0067]

[Chemical 18]

(Among the above, the cyclohexane ring represents a trans configuration and "%" represents "% by weight") to prepare a base liquid crystal (A). This matrix liquid crystal (A) is 5
It showed a nematic (N) phase at 4.5 ° C or lower. Also, 2
Physical property value at 0 ° C., threshold voltage (V _th ) and rise time (τ _r ) of TN cell manufactured using the same
Falling and time (tau _d) and was as applied voltage response time of less than a moment of time equal.

Dielectric anisotropy (Δε) 6.7 Threshold voltage (V _th ) 1.60 V Response time 39.2 msec (Applied voltage: 3.2 V) 80% by weight of this host liquid crystal (A) and A liquid crystal composition (M-1) containing 20% by weight of the compound of (No. 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 ) 59.0 ° C. Dielectric anisotropy (Δε) 7.3 Threshold voltage (V _th ) 1.54 V Response time 41.0 msec (Applied voltage: 3 .3V) As described above, by adding the compound of (No. 1), the temperature range of the N phase is expanded to a high temperature range, and the threshold voltage is significantly lowered, and the speed is sufficiently high. It shows responsiveness. (Comparative Example 1) In Example 3, in place of the compound of (No. 1), a compound of the formula (R-1) having a similar structure to the compound of (No. 1) and having an end group of an alkyl group.

[0071]

[Chemical 19]

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.

Upper limit temperature of N phase (T _NI ) 52.5 ° C. Threshold voltage (V _th ) 1.52V Response time 50.0 milliseconds (applied voltage: 3.2V) The temperature was considerably lower than that of (M-1) and also lower than that of the base liquid crystal (A).
Although the threshold voltage was slightly lower than (M-1), the response time was considerably slow. (Comparative Example 2) In Example 3, in place of the compound of (No. 1), the compound of formula (R) having a similar structure of the compound of (No. 1) and different double bond positions in the terminal alkenyl group −
2)

[0074]

[Chemical 20]

20% by weight of the compound of and the host liquid crystal (A) 8
A liquid crystal composition (N-2) consisting of 0 wt% was prepared. The maximum temperature (T _NI ) of the N phase of (N-2) and its physical properties were as follows.

Upper limit temperature of N phase (T _NI ) 45.0 ° C. In this way, the upper limit temperature of N phase is greatly lowered,
Compared with (M-1), it was 14 ° C lower. Therefore, it is apparent that it is difficult to raise the liquid crystal maximum temperature of the composition even by using the compound of the formula (R-2). (Example 4) Preparation of liquid crystal composition (2)

[0077]

[Chemical 21]

(In the above, the cyclohexane ring represents a trans configuration and "%" represents "% by weight"), and a fluorine-based host liquid crystal (B) particularly suitable for an active matrix was prepared.

This host liquid crystal (B) showed a nematic (N) phase at 116.7 ° C. or lower. The physical properties, the threshold voltage (V _th ) and the response time of the TN cell manufactured using the same were as follows.

Dielectric anisotropy (Δε) 4.7 Threshold voltage (V _th ) 2.43V Response time 28.4 milliseconds (applied voltage: 5.9V) 80% by weight of this host liquid crystal (B) and A liquid crystal composition (M-2) containing 20% by weight of the compound of (No. 1) was prepared. The upper limit temperature (T _NI ) of the N phase of (M-2) and its physical properties were as follows.

Maximum temperature of N phase (T _NI ) 108.0 ° C. Dielectric anisotropy (Δε) 5.8 Threshold voltage (V _th ) 2.21 V Response time 30.3 milliseconds (applied voltage: 5 As described above, the upper limit temperature of the nematic phase is slightly lowered, but the threshold voltage (V _th ) is significantly lowered, and it is clear that the nematic phase has a high-speed response.

Further, the specific resistance of this composition (M-2) is 1
It was as large as 0 ¹² Ω · cm or more, and the voltage holding ratio of the cell manufactured using this was as high as 98% or more.

[0083]

INDUSTRIAL APPLICABILITY The compound represented by the general formula (I) of the present invention can be easily produced industrially, is chemically stable to heat, light, water and the like, and is widely used as a nematic liquid crystal at present. It also has excellent compatibility with the base liquid crystals. Moreover, the threshold voltage (V _th ) of the composition can be lowered, the response can be accelerated, and the nematic phase temperature range can be expanded to a high temperature range.

Further, since the compound of the general formula (I) does not have a strong polar group in the molecule, a large specific resistance and a high voltage holding ratio can be easily obtained. Therefore, it is very useful as various liquid crystal display elements that require a wide temperature range of the liquid crystal phase and low voltage driving, especially as a liquid crystal material for active matrix driving.

Claims (3)

[Claims] 1. A compound represented by the general formula (I): (In the formula, R represents a hydrogen atom or a linear alkyl group having 1 to 5 carbon atoms, m represents 0, 2 or 4, and L and M are each independently a single bond or -CH ₂ CH. _2- , but at least one of L and M represents a single bond, and ring A represents a 1,4-cyclohexylene group or a 1,4-phenylene group.). 2. The compound according to claim 1, wherein L and M are both single bonds, and ring A is a trans-1,4-cyclohexylene group. 3. A liquid crystal composition containing the compound represented by the general formula (I) according to claim 1.